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Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
96 hours + 96 hour recovery
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The concentrations in fish were extremely variable most probably by ingestion of particulate precipitated test substance.
Qualifier:
no guideline followed
Principles of method if other than guideline:
A group of 12 bluegill sunfish were maintained in water containing 283 dpm/ml radiolabeled Dechlorane Plus. 3 fish each were killed at 48 and 96 hours of exposure, and the remaining 6 fish were transferred to water without substance after 96 hours of exposure and were killed at 48 and 96 hours post-exposure. The concentration of Dechlorane Plus in all fish and in water during the exposure period was determined by liquid scintillation.
GLP compliance:
no
Radiolabelling:
yes
Details on sampling:
sampling of fish after 48 and 96 hours of exposure and at 48 and 96 hours after exposure, sampling of water after 48 and 96 hours of exposure.
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
Dechlorane Plus was solubilized in hexane before adding it to the water
Test organisms (species):
Lepomis macrochirus
Details on test organisms:
No details reported.
Route of exposure:
aqueous
Test type:
static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
48 - 96 h
Total depuration duration:
48 - 96 h
Hardness:
not reported
Test temperature:
not reported, presumably room temperature
pH:
not determined
Dissolved oxygen:
not determined, water aerated
TOC:
not reported
Salinity:
not reported
Details on test conditions:
no further details reported
Nominal and measured concentrations:
Nominal 283 dpm/ml radioactivity, measured 256 dpm/ml after 48 hours and 311 dpm/ml after 96 hours.
Reference substance (positive control):
no
Details on estimation of bioconcentration:
Radioactivity in fish divided by radioactivity in water
Type:
BCF
Value:
7.02 dimensionless
Basis:
whole body w.w.
Remarks:
radioactivity in dpm/g wet tissue
Calculation basis:
other: concentration after 48 hours exposure
Remarks on result:
other: Conc.in environment / dose:256 dpm/ml
Type:
BCF
Value:
1.97 dimensionless
Basis:
whole body w.w.
Remarks:
radioactivity in dpm/g wet tissue
Calculation basis:
other: concentration after 96 hours exposure
Remarks on result:
other: Conc.in environment / dose:311 dpm/ml
Details on kinetic parameters:
not determined
Metabolites:
not determined
Results with reference substance (positive control):
none
Details on results:
The bioconcentration factor was determined at 7.02 after 48 hours of exposure and at 1.97 after 96 hours of exposure. After transferring the fish to water without test substance, high and highly variable concentrations were found in fish tissue at 48 and 96 hours postexposure. No conclusion on the elimination from fish tissues could be drawn.
Reported statistics:
none

Uptake                     Fish                            Water                     Bioconc. factor

48 hours              1,798 dpm/ml                  256 dpm/ml              7.02

96 hours              614 dpm/ml                     311 dpm/ml              1.97

Depuration

48 hours              25,843 dpm/ml               -                                   -

96 hours              1,299 dpm/ml                     -                                -

Validity criteria fulfilled:
yes
Remarks:
for uptake phase only, not for depuration phase
Conclusions:
No relevant bioconcentration during 96 hours of exposure in fish.
Executive summary:

A total of 12 bluegill sunfish were exposed to 283 dpm/ml radiolabeled Dechlorane Plus. Groups of 3 fishes each were killed after 48 and 96 hours of exposure, the remaining fish were transferred after 96 hours of exposure to water without test substance. Groups of 3 fishes each were killed at 48 and 96 hours postexposure. The bioconcentration factors were calculated at 7.02 after 48 hours exposure and at 1.97 after 96 hours exposure. No depuration could be observed due to oral intake of particulate precipitates by the fish leading to increasing concentrations of test substance in fish tissues after the end of exposure.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
96 hours and 42 days
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Methods and results and the interpretation of results are not described in sufficient detail.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Groups of 3 juvenile salmons were exposed to a mixture of chemicals including Dechlorane Plus 25 in water for 96 hours followed by 192 hours observation in water without test substance. Concentrations in water and fish were determined at regular intervals during both phases. Other groups of fish were fed with food pellets coated with the same mixture for 42 days followed by an observation phase of 71 days. The concentration in fish tissues was determined at regular intervals.
GLP compliance:
no
Radiolabelling:
no
Details on sampling:
time points of water sampling not reported, concentrations in fish exposed via water were determined after 12, 24, 48, and 96 hours of exposure and after 25.5, 102, and 192 hours postexposure. Food was spiked with a mixture of different chemicals and contained 9.12 µg/g nominal and 8.88 µg/g by analysis Dechlorane Plus 25. Fish from food exposure experiments were analyzed on days 15, 28, and 42 during exposure and on days 16, 32, 49, and 71 after the end of exposure.
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
A mixture of compounds in hexane containing a small amount of toluene was applied to flasks, and the solvent was completely evaporated. Then water and fish were added. Food was contaminated by coating a suspension of food in hexane by a mixture of the compounds.
Test organisms (species):
Salmo salar
Details on test organisms:
Atlantic salmon, juvenile, no further details reported.
Route of exposure:
other: in water or food
Test type:
static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
96 h
Total depuration duration:
192 h
Hardness:
not reported
Test temperature:
10 °C
pH:
not reported
Dissolved oxygen:
not reported
TOC:
not reported
Salinity:
not reported
Details on test conditions:
Groups of 3 juvenile salmons were exposed to a mixture of chemicals including Dechlorane Plus 25 in water for 96 hours followed by 192 hours observation in water without test substance. Concentrations in water and fish were determined at regular intervals during both phases. Other groups of fish were fed with food pellets coated with the same mixture for 42 days followed by an observation phase of 71 days. The concentration in fish tissues was determined at regular intervals.
Nominal and measured concentrations:
In water: nominal 76.15 µg/l, measured 6.06 µg/l, in food nominal 9.12 µg/G, measured 8.88 µg/g
Reference substance (positive control):
no
Type:
other: analytical determination of concentration in tissue
Value:
0 other: not detected in fish tissue analytically
Basis:
whole body w.w.
Remarks on result:
other: not detected in fish tissue analytically
Remarks:
Conc.in environment / dose:6.06 µg/l
Type:
other:
Value:
>= 44.2 - <= 176 other: ng/g wet weight of fish tissues
Basis:
whole body w.w.
Calculation basis:
other: analysis on days 15, 28, and 42 of exposure
Remarks on result:
other: Concentration in fish decreased steadily
Remarks:
Conc.in environment / dose:8.88 µg/g food
Elimination:
yes
Parameter:
other: analysis of fish tissue on days 16, 32, 49, and 71 post-exposure after administration in food
Depuration time (DT):
71 d
Details on kinetic parameters:
not determined
Metabolites:
not determined
Details on results:
After exposure in water, Dechlorane Plus 25 was not detected in fish tissue during the exposure time and during the depuration time. After exposure via food, Dechlorane Plus 25 was detected in fish tissue at a maximum concentration of 176 ng/g wet weight at the first time point of analysis. The concentration decreased thereafter steadily to 44.2 ng/g at the end of exposure on day 42 and to 18.7 ng/g at the end of the depuration time on day 71 postexposure. No complete elimination was reached, but no accumulation was seen during 42 days of exposure.

Day                     Dechlorane Plus 25 (ng/g wet weight, whole body)

Exposure              

15                                   176

28                                   61.8

42                                   44.2

Postexposure

16                                   34.6

32                                   26.8

49                                   23.1

71                                   18.7

Validity criteria fulfilled:
yes
Conclusions:
Dechlorane Plus 25 was not absorbed from water but was absorbed from food. It did not accumulate in fish tissue. After absorption and distribution into fish tissues, Dechlorane Plus 25 was very slowly eliminated. No complete elimination was achieved within 71 days after the end of exposure.
Executive summary:

Groups of 3 juvenile atlantic salmons were exposed to Dechlorane Plus 25 in water at a nominal concentration of 76.15 µg/l corresponding to an analytical concentration of 6.06 µg/l for 96 hours followed by a postexposure observation period of 192 hours. Other groups were exposed via food coated with Dechlorane Plus 25 at a nominal concentration of 9.12 µg/g corresponding to an analytical concentration of 88.8 µg/g for 42 days followed by a postexposure observation period of 71 days. Samples of water and fish tissues (whole body) were analyzed at regular intervals. Dechlorane Plus 25 was not absorbed from water and was not detected in the water-exposed fish during the exposure and the postexposure period. The substance was absorbed from food reaching a maximum concentration of 176 ng/g wet tissue in fish at the first sampling time on day 15 of food exposure. Thereafter the concentration in fish tissue declined steadily during the following exposure period and the postexposure period to a minimum of 18.7 ng/g wet weight on day 71 postexposure. No accumulation was observed, but the elimination from tissues was very slow, and no complete elimination from fish tissues could be achieved.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1975
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Although no standard guideline was followed (none were available in 1975) the study followed basic scientific principles available at that time. However, using 1% acetone in water as vehicle to maintain a dechlorane plus concentration of 0.1 ppm is uncommon and not realistic, but almost certainly has increased bioavailability above natural levels and maybe also absorption. In addition no steady state was observed and thus the results may be seen with caution.
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
one group of 36 bluegill sunfish weighing each about 2-4 g was exposed to Dechlorane Plus 25 at a concentration of 0.1 ppm for 30 days in a dynamic system. The fish were observed for mortality and behavioural changes, and samples of fish and water were analysed for test substance concentration at regular intervals.
GLP compliance:
no
Remarks:
pre-dates GLP
Radiolabelling:
no
Details on sampling:
At 0 (6 hours), 6, 12, 18, 24 and 30 days, samples of fish were taken from the bioassay vessel. At each interval, 6 fish were taken and killed with a sharp hit on the head. The fish were rinsed in deionized water twice, blotted dry, and then rinsed in acetone twice and blotted dry. Each sampling of fish was then held frozen for analysis.
Water samples were siphoned from the test vessel at 0 (6 hours), 6, 18, 24 and 30 days. Each water sample was collected in a 500 milliliter glass bottle and refrigerated until all samples were available for analysis.
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
The test water for the dynamic bioassay was double charcoal filtered Decatur city water contained in a 100 gallon constantly aerated reservoir. The reservor temperature was controlled by a Honeywell mixing valve and proportioning electronic controller which mixed charcoal filtered cold water and 82 °C hot water heated in a Reemglas water heater. As a water quality check, bluegills, channel catfish, fathead minnows, goldfish and daphnia are maintained in flow-through systems using this water exclusively.
The test apparatus consisted of a flow-through system delivering 300 milliliters of water every 90 seconds below the water surface of a glass covered bioassay vessel having a capacity of 150 liters. Overflow pipes removed water at the same rate as it flowed into the vessel. The turnover time (time of continuous flow of water to fill the 150 liter vessel) was 12.5 hours. The equipment running the flow-through system was monitored with a time clock. During each 90-second interval, a calculated amount of Dechlorane Plus 25 in the form of a 0.001% (w/v) solution in acetone was injected beneath the surface of the water with a Harvard Apparatus Company peristaltic pump. Due to the low water solubility of the test material, the 0.001% solution of Dechlorane Plus 25 in acetone could not be mixed with the incoming water prior to entering the bioassay vessel.
Test organisms (species):
Lepomis macrochirus
Details on test organisms:
36 Bluegill sunfish (Lepomis macrochirus) were used as test animals.
Healthy bluegill sunfish (Lepomis macrochirus) with an average weight of 2 to 4 grams were used as test animal. The fish were obtained from Fenders Fish Hatchery in Ohio and were kept under observation for general health and suitability as test animals for a period of not less than 21 days prior
to experimental use. The fish were held in stock tanks at a temperature of 20 - 22 °C and fed Purina Trout Chow #2 supplemented with live freshwater cladocerans (Daphnia magna). When the test began, only the Purina Trout Chow was fed to the fish once each day.
Fish were acclimated in a similar flow-through system to the high concentration of solvent used in the bioassay, 1.0% (v/v) acetone in water (8,000 ppm acetone), for a period of 28 days. After the 28-day acclimation period, a total of 36 fish was introduced into the bioassay vessel at 0 day. A sample of the remaining fish was taken and served as the background value for the fish tissue analysis. At this time, a water sample was taken from the flow through system reservoir and served as the background value for the water analysis.
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
30 d
Hardness:
Hardness was monitored every 3 days and results were in the range of 106 - 144 ppm as CaCO3
Test temperature:
Test temperature was monitored daily and ranged from 19.0 - 21.8 °C
pH:
pH was monitored daily ranging from 7.8 - 8.7
Dissolved oxygen:
dissolved oxygen was monitored daily ranging from 7.4 - 8.3 ppm
TOC:
no data
Salinity:
Alkalinity was measured every third day ranging from 56 - 67 ppm as CaCO3
Nominal and measured concentrations:
A 0.1 ppm concentration of Dechlorane plus was targeted for based on pre-test results. The actual concentration in water/acetone was measured every six days. At 12 days the peristaltic pump was recalibrated in order to insure correct delivery of 0.001% (w/v) solution of Dechlorane Plus 25 in acetone. The pH increase recorded at 10, 11 and 12 days indicates a change in the rate of flow of stock solution. The decreased flow of stock solution containing Dechlorane Plus 25 would correspond with a lower level of test material being found through analysis in the 12-day water sample.
Reference substance (positive control):
no
Details on estimation of bioconcentration:
Magnification factors were calculated by dividing the concentration of DP found in fish (mean of 6 fish) through the concentrations found in water at the same time of measurement.
Type:
BMF
Value:
5.58 dimensionless
Basis:
whole body w.w.
Time of plateau:
30 d
Calculation basis:
other: steady state not reached
Remarks on result:
other: Magnification factors increased steadily with a peak of 25.9 at day 18 considered to be unreliable. At day 30 a steady state was not reached and a BMF of 5.58 was measured.
Remarks:
Conc.in environment / dose:0.1 ppm
Elimination:
not specified
Details on kinetic parameters:
no data
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
Results on DP concenntrations in water and fish:
Day 0 (6 hours): Water conc. 0.102 ppm, fish conc. 0.111 ppm, BMF: 1.09
Day 6: Water conc. 0.095 ppm, fish conc. 0.181 ppm, BMF: 1.91
Day 12: Water conc. 0.074 ppm, fish conc. 0.130 ppm, BMF: 1.76
Day 18: Water conc. 0.083 ppm, fish conc. 2.15 ppm, BMF: 25.9
Day 24: Water conc. 0.085 ppm, fish conc. 0.320 ppm, BMF: 3.76
Day 30: Water conc. 0.069 ppm, fish conc. 0.385 ppm, BMF: 5.58
Reported statistics:
no statistics performed

The test data showed the fish accumulated Dechlorane Plus immediately after introduction into the test vessel (6 hours) and the concentration increased slowly, but steadily thereafter. The fish sample for day 18 is suspected to have been contaminated because the value obtained is not consistent with the amounts of Dechlorane accumulated by the other fish. The amount of Dechlorane Plus in the water decreased slightly during the study from an initial value of 0.104 ppm to 0.069 ppm at day 30.

The magnification factors presented are computed by dividing the concentration found in each fish sample by the concentration of the corresponding water sample. The data show that Dechlorane Plus does accumulate slightly in the fish. The presence of 1.0% (v/v) acetone in the water was required to maintain the concentration of Dechlorane Plus at the 0.1 ppm level for the duration of the study.

Recovery data for Dechlorane Plus from fortified fish and water samples were recorded. The recoveries were 80% and 83% at the 0.1 ppm and 1.0 ppm levels in fish respectively. In water recoveries were 109% and 101% at the 0.1 ppm level.

None of the fish exposed to 0.1 ppm Dechlorane Plus 25 died during the 30-day test period. Quiescence, dark discoloration of the integument, rapid respiration and passive feeding were noted among the test animals. These reactions were considered to be attributed to the high concentration of solvent (acetone) in the water. The reactions were first noted in the fish during the 28-day solvent acclimation period in which the concentration of acetone was increased from 0.1 to 1.0% (v/v) acetone in water. The reactions were first observed at a concentration of 0.7%.

Validity criteria fulfilled:
not applicable
Remarks:
no standard test model at that time available
Conclusions:
At a conc. of 0.1 ppm Dechlorane plus in water (with 1% acetone to maintain DP conc.) concentration of DP in fish steadily increased during the exposure period whereas the conc. in water could be maintained relatively constant. No steady state was achieved during 30 days of exposure and biomagnification steadily increased to a factor of 5.58 at day 30.
Executive summary:

No deaths or unusual behavioral reactions were noted that could be attributed to the 0.1 ppm test concentration of Dechlorane Plus. Using the procedure applied it was found that the test material did accumulate in the bluegill fish from a level of 0.111 ppm to 0.385 ppm at 0 (6-hours) and 30-day intervals, respectively. The Dechlorane Plus water concentration stayed relatively constant throughout the study with a starting concentration of 0.102 ppm at Day 0 dropping to only 0.069 ppm at Day 30. The use of a 1% (v/v) solution of acetone was needed to keep the chemical in solution at the 0.1 ppm level. Biomagnification did not reach a steady state and a value of 5.58 was eeen at the end of exposure period (day 30).

Endpoint:
bioaccumulation in sediment species, other
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
October - December 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: reliable publication in peer-reviewed journal with standard analytical setup and proper documentation.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Water, sediment and oyster samples were collected at 15 sampling sites near the Bohai and Huanghai Sea shore area of northern China in 2008. Samples were analysed for contaminants including Dechlorane Plus by GC/MS. From the results, the biota-sediment accumulation factor (BSAF) of DP could be derived.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
Between October and December of 2008, water, sediment, and oyster samples were collected at 15 sites (1 industrial, 2 urban, and 12 rural) in proximity to the shore around Dalian, Northeast China. Among the 15 sampling sites, 8 were from Bohai Sea (R01-R08) and 7 were from Huanghuai Sea (the rest sampling sites). All samples (water, sediment, and oyster) were packed in solvent-rinsed glass bottles with Teflon-lined caps. Surface sediment (0 - 5 cm) was collected using a bucket grab. An acetone rinsed bistoury was used to harvest edible parts from oyster shells and at least 15 individual samples were thus collected from each. Each water or sediment sample was composed of well-mixed five subsamples collected from different locations at each site. After collection, samples were sent to the laboratory of the International Joint Research Center for Persistent Toxic Pollutants (IJRC-PTS), Dalian Maritime University, Dalian, China, for processing and analysis. Sediment and oyster samples were stored at -20 °C and 1 L seawater samples were mixed with 100 mL dichloromethane (DCM) for storage at 4 °C until extraction.
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
Extraction and Analyses: Samples were extracted and analyzed according to the methods established at the National Laboratory for Environmental Testing (NLET), Environment Canada. After spiking with CB 155 surrogate, water samples were extracted with 100 mL dichloromethane (DCM) in a separatory funnel with agitation followed by a 1 h settling time. Extraction was thrice repeated, followed by DCM collection and rotary-evaporation to 1 mL.
Ten grams of sediment and 10 g anhydrous sodium sulfate were measured into a pre-cleaned extraction thimble and spiked with a CB155 surrogate standard. After mixing, samples were Soxhlet extracted for 24 h with 100 mL mixed solvent (hexane/acetone, 1:1 v/v). Following extraction, the extract was added to a separatory funnel and washed 3 times using 98% H2SO4, which was subsequently discarded. Extracts were then rotary evaporated to 1 mL. The extraction method for oyster was similar with the additional step of gravimetric lipid determination for 10% of the extract after Soxhlet extraction.
The 1 mL extracts were passed through a 5.5 g silica gel column after a 25 mL hexane pre-rinse and eluted with 40 mL of hexane/DCM mixture (1:1, v/v). The extract was rotary-evaporated to 2 mL, then solvent-exchanged into isooctane and reduced to 1 mL under nitrogen. The internal standard OCN was added to correct volume difference prior to GC-MS analysis.
Test organisms (species):
other: oysters (not further specified)
Route of exposure:
sediment
Test type:
field study
Water / sediment media type:
natural sediment: marine
Hardness:
not reported as field study
Test temperature:
not reported as field study
pH:
not reported as field study
Dissolved oxygen:
not reported as field study
TOC:
not reported as field study
Salinity:
not reported as field study
Details on test conditions:
In a field study, oysters were caught and analysed together with sediment samples taken from the same area in the Chinese Bohai Sea and Huanghai Sea, in the area of Dalian city.
Nominal and measured concentrations:
background concentrations in the habitat of the oysters (field study)
Reference substance (positive control):
no
Lipid content:
>= 0.97 - <= 4 %
Time point:
end of exposure
Remarks on result:
other: mean fraction of lipid was 2.0 ±0.76 in oysters
Type:
BSAF
Value:
>= 1 - <= 7.9 dimensionless
Basis:
whole body w.w.
Calculation basis:
other: natural habitat
Remarks on result:
other: mean value of 4.6
Remarks:
Conc.in environment / dose:natural level in Bohai and Huanghai Sea
Details on kinetic parameters:
not applicable as field study
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
Bioaccumulation Indication: The biota-sediment accumulation factor (BSAF) has been suggested as a simple approach to the prediction and estimation of the bioaccumulation potential of HOCs in aquatic biota. BSAF is based on equilibrium partitioning, which assumes that HOCs partition between the carbon pools of biotic tissue lipids and sediment organic carbon. This approach also assumes that there is no chemical transformation, mass transfer resistance, differential biotic uptake or depuration. Under these conditions, bioaccumulation can be assessed using the BSAF which is defined as
BSAF = (C b / f lip) / (C s / f OM ) (eq. 1)
where C b is the biota HOC concentration (ng/g ww), f lip is the organism lipid content, C s is the sediment HOC concentration (ng/g dw), and f OM is the sediment organic carbon content. A theoretical BSAF value of 1.7 has been estimated based on partitioning of nonionic organic compounds between tissue lipids and sediment organic carbon. A value of less than 1.7 indicates less partitioning of an organic compound into lipids than predicted and a value greater than 1.7 indicates more uptake of the pollutant. In the present study, BSAFs were calculated for a total of 64 paired sediment and oyster samples that have both measurement values above IDL (15 for Dec 602, 26 for total DP and 23 for Mirex). Figure 2 describes the range, mean, and median of the BSAF values for total DP, Dec 602, and Mirex depending on compounds. Individual compound BSAF values (mean and range in parentheses) are in the order: Mirex (9.1, 2.3 - 23) > Dec 602 (5.6, 2.1 - 12) > DP (4.6, 1.0 - 7.9). This sequence is contrary to the order of logarithm of octanol – water partition coeffcients (log K ow), which is DP (11.3) > Dec 602 (8.05) > Mirex (7.01) and indicates that chemicals with higher log K ow are likely to be retained in sediment and that Mirex and Dec 602 have a higher accumulation potential in biota than DP. Interestingly, this trend is consistent with that found in PBDEs and PAHs.
Reported statistics:
no data

Dechloranes in Water, Sediment, and Oyster: Concentrations of Dechloranes in seawater, sediment, and oyster samples are presented in Figure 1 with statistics listed in Table 1. Dec 604 was not detectable in any water, sediment, and oyster samples, and thus is not shown in either Figure 1 or Table 1. While Dec 602 and Dec 603 were not detected in all seawater samples, DP (syn- and anti-isomer) and Mirex were detected in most seawater samples. In general, seawater concentrations of DP isomers in this study were higher than those at an e-waste recycling plant in South China (syn-DP: 0.27 ng/L, anti-DP: 0.53 ng/L), and much higher than those in the fresh water (mean total DP = 0.03 ng/L) of the Songhua River, China, and in seawater (syn-DP: ND - 0.0009 ng/L, anti-DP: ND - 0.0004 ng/L) from East Greenland Sea and in the Northern and Southern Atlantic toward Antarctica. A further investigation has been arranged to understand the source of this high DP level in seawater in the area. DP concentrations in sediments have been widely reported for the Great Lakes, as well as the Songhua River. Dec 602, Dec 603, Dec 604, and Mirex concentrations have also been reported in Great Lake sediments. These chemicals, however, have never been reported in marine sediments. In this study, DP was detected in most sediment samples, Mirex and Dec 602 were detected in half of the samples, whereas Dec 603 in only two samples (Frequency of detection is 13%, Table 1). Mirex and DP concentrations in this study were higher than those in Lake Superior, Lake Michigan, Lake Huron, and Lake Erie, but lower than those in Lake Ontario, and concentrations of DP were a factor of magnitude lower than those measured in Lake Winnipeg sediments and much higher than those in the Songhua River. In general, Dec 602 and Dec 603 in sediment were relatively low, similar to those in sediments from Lakes Superior, Michigan, Huron, and Erie, but much lower than that in Lake Ontario.Recent studies have indicated that DP can bioaccumulate in biota, for example, in lake food webs, fish, and herring gull eggs, as well as freshwater food webs in south China. Shen et al. reported DP, Dec 602, Dec 603, Dec 604, and Mirex in fish samples from Great Lakes. In the present study, Dechloranes were widely detected in oyster samples and frequencies of detection were from 22% to 78% (Table 1). The mean concentrations of syn-DP, anti-DP, and Mirex were very similar, 1.9, 2.2, and 2.0 ng/g ww respectively. Much lower concentrations were observed for Dec 602 and Dec 603 in oyster samples. It is worthwhile to compare concentrations of Dechloranes in seawater, sediment, and oyster among samples collected in Bohai and Huanghai areas. SI Figure SI-2 depicts the results of comparison, showing that, in general, concentrations of Dechloranes in rural areas in Bohai Sea were higher than those in Huanghai Sea. This is not surprising since the Bohai Sea is half closed internal sea of China, surrounded by the City of Tianjin, and three provinces of Shangdong, Hebei, and Liaoning, with an average residence time of about 580 days, while Huanghai Sea is an open sea directly connects the Pacific Ocean. The former areas receive pollutants from many other urban centers around the Bohai Sea. Therefore, the contamination status in Bohai Sea is much severer than that in Huanghai Sea. In fact, the mean DP concentration for water at rural sites along the Bohai Sea (1.7 ng/L) was 10 times higher than that along the Huanghai Sea (0.17 ng/L). Previous studies have associated high DP air concentrations with urban and industrial regions, which holds true in the present study. DP concentrations in water, sediment and oyster samples are higher in urban and industrial areas than in surrounding area for the samples along Huanghai Sea, indicating that the urban region of Dalian is a potential source of DP along the shore area of Huanghai Sea.

Regression Analysis: Pearson correlation was performed for Dechlorane compounds and significant correlations were only found between total DP and Mirex concentrations in water, sediment and oyster samples (r = 0.81, p < 0.001 for water, 0.75, p < 0.001 for sediment, and r = 0.70, p < 0.005 for oyster), which possibly suggest that DP and Mirex have the similar sources in the study area. While the source of DP in Dalian is still not fully understood, the source of Mirex seems clear. China started to produce Mirex in the 1960s, but production was low and ceased in 1975 due to the compound’s toxicity. It resumed however in 1997 after a serious termite disaster in southern China. Subsequent production until 2002 totalled 151 t. Mirex is used as a termicide for termite control in China, as is chlordane. A gridded usage inventory was produced based on the assumption of a use pattern similar to chlordane. A total of 106 kg of Mirex was used in the city of Dalian from 1997 to 2002, possibly forming the sources of Mirex in the area.

Organic matter fraction (f OM ) in sediment is an important variable that influences the concentration of hydrophobic organic compounds (HOCs). In this study, the values of f OM were measured for each sediment sample and ranged from 3.20% to 10.23%. It shows a statistically significant and strong correlation (r = 0.91, p < 0.001) between total Dechloranes and f OM in sediment. This finding indicates that f OM plays an important role in sediment absorption of Dechloranes. A statistically significant correlation (r = 0.64, p < 0.001) was observed between concentrations of total DP in oyster and oyster sample lipid content (f lip) (n = 45) and a less significant relationship (r = 0.44, p < 0.01) was observed between Mirex concentrations and lipid content. No significant correlation between Dec 602, Dec 603 in oyster and lipid content was found, probably due to the relatively low concentrations of Dec 602 and Dec 603.

Fractional Abundances of DP Isomers: The stereoisomer ratios of DP can be described by the fractional abundance given by

f syn = ([syn – DP] + [anti – DP]) (eq. 2)

Several previous studies have reported f syn values of technical DP: 0.20, 0.20 - 0.25, 0.25, 0.28, 0.34, and 0.36. Recently Wang et al. measured f syn in technical DP produced in China, and the value of 0.41 was found, which was higher than all reported f syn values of technical DP. The f syn values were calculated using eq 2 for water, sediment, and oyster samples in our study, and the mean values are shown in Table 1 and Figure 3. The mean values of f syn were 0.34 (0.10, 0.44 ±0.086, and 0.45 ±0.11 for water, sediment, and oyster samples respectively. Mean f syn in surface seawater is significantly lower (p < 0.05) than the value of Chinese technical DP and similar to values found in Chinese air (0.34). An extraordinarily high f syn value (0.55) in water samples of relatively low DP concentration (0.35 ng/L) was observed at R06 sampling sites. Values of f syn higher than that of technical mixtures were observed in sea sediment and oyster samples, indicating an enrichment of syn-DP in these two matrices. Similar pattern was also found in fish in Great Lakes water. Fresh water and sediment f syn data were usually lower than that found in technical DP. Values of f syn higher than that of technical mixtures were also observed in both air and seawater in Arctic and Antarctica, possibly indicating different mechanism that affects the depletion/enrichment of syn- and anti-DP in seawater versus fresh water, but further studies are needed to achieve a full understanding of the phenomenon. Previous air measurements in China showed higher f syn values (0.34 ±0.11) than in Chinese soil (0.29 ±0.08), which indicated the stronger depletion of syn-DP relative to anti-DP isomer in soil than in air. A similar pattern was observed for the water and sediment samples in the Songhua River in northeastern China. The mean f syn (0.31 ±0.15) for all water samples in the urban section of the river was higher than that for sediment samples in the same section of the river (0.29 ±0.03) and that in the rural section of the river (0.21 ±0.04), showing higher depletion of syn-DP relative to anti-DP isomer in sediments than water. Ma et al. also measured DP in multimedia, including air, water, soil, and sediment in Harbin, a city in Northeast China. DP was detected in all media except water. The lower f syn was also found in soil and sediment than in air. This result is in agreement to the depletion of syn-DP relative to anti-DP isomer in sediment samples from North America. It is interesting to note that f syn values of marine sediment decline with the increase in f syn values of seawater at sampling sites. At this point, very little information exists on the transport and exchange of DP in water and sediment, and whether this finding is a reflection of the different transport and biodegradation process of DP isomers is still unclear. Further research is needed to investigate the physical and chemical properties of DP stereoisomers to obtain a full understanding of their behavior in the environment.

Validity criteria fulfilled:
not applicable
Conclusions:
For dechlorane plus, BSAF value for sediment / oyster was determined being 4.6 (range of 1.0 - 7.9) based on 15 sediment samples and 45 oyster samples, analyzed in groups of 15 sampling sites in Bohai Sea (R01 - R08) and Huanghuai Sea (R09 - R15).
Executive summary:

Dechloranes, including Dechlorane Plus (DP), Mirex (Dechlorane), Dechlorane 602 (Dec 602), Dechlorane 603 (Dec 603), and Dechlorane 604 (Dec 604), were determined using GC-MSD for water, sediment and oyster samples collected at 15 sampling sites near the Bohai and Huanghai Sea shore area of northern China in 2008. DP and Mirex were detected in most water, sediment, and oyster samples, which indicated widespread distribution of these two compounds. The mean concentrations in water, sediment and oyster samples, respectively, were 1.8 ng/L, 2.9 ng/g dry weight (dw) and 4.1 ng/g wet weight (ww) for total DP, and 0.29 ng/L, 0.90 ng/g dw, and 2.0 ng/g ww for Mirex. Dec 602 and Dec 603 were not detected in water but in small portions of the sediment and oyster samples, showing a low level of contamination by these two chemicals in the region. Strong and significant correlations were found between total DP and Mirex concentrations in water, sediment and oyster samples, probably suggesting similar local sources of these two chemicals. Dec 604 was not found in any samples. The biota-sediment accumulation factor (BSAF) of DP, Mirex, and Dec 602 declined (Mirex (9.1, 2.3 - 23) > Dec 602 (5.6, 2.1 - 12) > DP (4.6, 1.0 - 7.9).) along with the increase of their logarithm of octanol - water partition coeffcients (log K ow) (DP: 11.3 > Dec 602: 8.05 > Mirex: 7.01), possibly indicating that compounds with lower log K ow (like Mirex and Dec 602) accumulated more readily in biota. The mean fractional abundance of syn-DP (f syn) was 0.34 in water samples, a value lower than that in Chinese commercial mixture (0.41), while the mean f syn for surface sediment (0.44) and oyster (0.45) samples were higher than technical values. Enrichment of syn-DP in oyster was in agreement with previously reported findings in Great Lakes fish. Enrichment of syn-DP in marine surface sediments, however, is contrary to data reported for fresh water sediments.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1979 - 2004
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Niagara River suspended sediments and lake trout were sampled from Lake Ontario north of Main Duck Island as part of long-term monitoring by the Great Lakes Laboratory for Fisheries and Aquatic Sciences (GLLFAS, now part of Environment Canada) and samples were analysed for DP (and other Dechloranes) content by GC/MS. Seasonal variations were investigated.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
Sample Collection: Niagara River suspended sediments were collected near the river mouth at Niagara-on-the-Lake, Ontario using a large-volume 24 h time-integrated dissolved/particulate phase sampling protocol detailed elsewhere. Pumped water was passed through a Westphalia centrifuge assembly to collect suspended sediment followed by a Goulden extractor for dissolved analytes. Weekly/biweekly suspended sediment samples were freeze-dried and archived, and the temporal study was conducted on spring composites of these prepared from April and/or May samples from 1980 to 2002. Samples collected over the period April 2006 to March 2007 were combined into monthly composites to examine seasonal variation.
Lake trout were sampled from Lake Ontario north of Main Duck Island as part of long-term monitoring by the Great Lakes Laboratory for Fisheries and Aquatic Sciences (GLLFAS, now part of Environment Canada). Fish were collected every four to six years (1979, 1983, 1988, 1993, 1998, and 2004), with four or five individuals per time point. Individual whole fish were homogenized then stored frozen in glass jars at -80 °C in the Great Lakes Specimen Bank until analysis. The sediment core was collected from Lake Ontario using a mini-box core sampler from aboard the Canadian Coast Guard Ship (C.C.G.S.) Limnos, followed by subsampling using push cores and extrusion and sectioning on board into 1 cm (for first 15 cm) and 2 cm intervals. A replicate core from the same box was dated by determining the 210Pb activity as a function of the chronological age of the sediments. Data were calculated using both the Constant Initial Concentration (CIC) model (assumes a constant sedimentation rate) and the Constant Rate of Supply (CRS) model (assumes a variable sedimentation rate). Porosity and density analyses indicated changes in sediment composition that could indicate a variable accumulation rate, thus the CRS chronology was considered most accurate.
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
Sample Preparation: This study utilized sample extracts previously prepared for determination of mono-ortho dioxin-like polychlorinated biphenyls (DLPCBs) according to previously described extraction and cleanup procedures for sediment and fish. Briefly, frozen homogenized fish tissue samples were thawed, and sediment samples were air-dried, ground, and homogenized. Fish samples ( ∼ 5 g, wet weight (wt)) were digested with hydrochloric acid and extracted with hexane. Sediment samples (5 - 10 g, dry wt) were Soxhlet-extracted with toluene. Sample extracts were processed using a 2 stage column procedure (multilayer silica and Amoco PX21 carbon/silica) for fish and 3 stages for sediment (multilayer silica, alumina, and Amoco PX21 carbon/silica), resulting in 2 fractions in nonane. Fraction A from each of these methods (the mono-ortho PCB fraction) contained the target norbornenes Chemical Analysis.
Test organisms (species):
Salvelinus namaycush
Details on test organisms:
Salvelinus namaycush, Lake Ontario lake trout, predator fish
Route of exposure:
aqueous
Test type:
field study
Water / sediment media type:
natural water: freshwater
Hardness:
not reported as field study
Test temperature:
not reported as field study
pH:
not reported as field study
Dissolved oxygen:
not reported as field study
TOC:
not reported as field study
Salinity:
not reported as field study
Details on test conditions:
in a field study, fish were caught and analysed together with sediment samples taken from the same area in the western part of Lake Ontario, close to mouth of the Niagara river.
Nominal and measured concentrations:
background concentrations in the habitat of the test fish (field study)
Reference substance (positive control):
no
Type:
BSAF
Value:
0.8 dimensionless
Basis:
whole body w.w.
Calculation basis:
other: natural habitat
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in Lake Onario
Type:
BSAF
Value:
0.3 dimensionless
Basis:
whole body w.w.
Calculation basis:
other: natural habitat
Remarks on result:
other: anti-DP
Remarks:
Conc.in environment / dose:natrual level of Lake Ontario
Details on kinetic parameters:
not applicable as field study
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
Bioaccumulation of Dechloranes: Bioaccumulation of chemicals in apex species such as lake trout is a key element in considering if chemicals are an environmental concern. The octanol / water partition coefficient (Kow) is one indicator of bioaccumulation potential. Kow values have been estimated for DP and have not been otherwise measured. Empirically derived indicators, such as the trophic magnification factor (TMF) and the predator / prey biomagnification factor (BMF) also provide indications of bioaccumulation potential in aquatic food webs. anti-DP was found to biomagnify in a Lake Winnipeg, Canada foodweb (TMF = 2.5), but no significant biomagnification was found in the Lake Ontario foodweb. In foodweb samples from a source-influenced reservoir in China, TMFs for both syn- and anti-DP (11.3 and 6.6, respectively) indicated biomagnification. BMFs determined for some predator / prey relationships in Lake Ontario and in exposure studies also indicated bioaccumulation potential for DP. However, no foodweb accumulation or BMF studies to date have included Dec 602, 603, 604 or CP. The biota-sediment accumulation factor (BSAF) is a common empirical measure that also provides an indication of bioaccumulation in aquatic systems and a means of comparing accumulation potential between compounds in that system, especially in the absence of more direct information. The BSAF is calculated by:
BSAF = C(B)/C(S)
where C(B) is the contaminant concentration in biota (wet weight) and C(S) is the corresponding concentration in sediment (dry weight). Lipid- (C(BL)) and organic carbon-normalized (C(SOC)) BSAFs (BSAF’) are also a common means of expressing BSAFs. Using data from this and our previous study reported on a dry weight (sediment) and wet weight (biota) basis, BSAFs were estimated for Mirex, Dec 602, 603, 604, CP, syn- and anti-DP for lake trout relative to sediments from Lake Ontario (Table 1). Estimates of log Kow are also listed for comparison as determined using EPI Suite, SPARC, and ABSOLV-ppLFER estimation programs. Mirex was found to have the highest BSAF (7400) followed by Dec 602 (270) and CP (91). The DP isomers had the lowest BSAFs. For comparison, the corresponding BSAF for total PCBs for Lake Ontario lake trout is 5, 30 and calculated BSAFs for BDE 47, 99, 153, 154, and 183 are 58, 20, 22, 35, and 0.3 respectively using average lake trout data (wet weight) from 2000 and average surface sediment concentrations (dry weight). The results were consistent with log Kow estimates, with the lowest Kow values associated with the higher BSAFs. Very high log Kow values ( >= 8) have been shown to have lower BMFs and assimilation effciencies. The BSAFs and log Kow estimates suggest that Dec 602, Dec 603, and Dec 604 have a greater potential for bioaccumulation than DP in the environment. There is little information available regarding the production history and current use of these compounds globally. Sediment cores and environmental trends in Lake Ontario and the Niagara region indicate that there may not be current production of at least Dec 602 and Dec 603 in the region, but they have been widely detected in environmental samples in the Great Lakes region and in China.
Reported statistics:
no data

Concentrations of Dechloranes in Sediments and Fish: Mirex, Dec 602, 603, 604, CP, and DP were detected in all Niagara River suspended sediment samples and in the top 10 cm of the sediment core from LO4. In general, the relative concentration pattern of these dechloranes in suspended sediments and sediments cores was total DP > Mirex > Dec 602 and 604 > Dec 603 > CP. Total DP concentrations (5.4 - 9.5 ng/g dry wt) were similar to those of BDE 209 (9.5 - 14 ng/g dry wt) in suspended sediments collected since 2000. The average DP concentration (110 ng/g dry wt) in the top 3 cm of sediments of the Lake Ontario sediment core was greater than that of BDE 209 (3 - 29 ng/g dry wt), and the average Dec 602 concentration (12 ng/g dry wt) was also similar to BDE 209. After Mirex, Dec 602 and 604 were the next most abundant dechloranes found in sediment samples. Production and use information for Dec 602 and 604 is limited, but Dec 602 has been used in Fiberglass-reinforced Nylon-6 at 18% and is listed as having been a commercially used flame retardant. Dec 604 is listed as an ingredient in Molykote AS-810 Silicone Grease (10 - 30%) produced by Dow Corning Corp. Dec 602 and Dec 604 may be used together in wire insulation (U.S. Patent 3900533). Dec 603 and CP had much lower concentrations in suspended sediments and sediment cores. Although Dec 603 and CP appeared in U.S. patents of flame retardant polymer compositions, there is no information available on their actual use. Dec 603 is reported to be an impurity in technical Aldrin and Dieldrin products and CP in technical Chlordene and Chlordane, and their environmental occurrence is consistent with historical pesticide usage. Mirex, Dec 602, 603, and syn- and anti-DP isomers were detected in all lake trout between 1979 and 2004. CP was not detected in half of the fish samples due to matrix effects, and Dec 604 was not found in any fish samples in this study. As expected, Mirex, listed for elimination on the United Nations Environment Program Stockholm Convention on Persistent Organic Pollutants, had elevated concentrations (83 - 4300 ng/g lipid) compared to other dechloranes because of its ability to bioaccumulate. In contrast to DP in sediments, DP concentrations in fish (180 - 1900 pg/g lipid) were much lower than those of Dec 602 (8000 - 180 000 pg/g lipid), indicating Dec 602 may be more bioavailable and/or more likely to bioaccumulate in fish compared to DP.

Temporal Trends of Dechloranes in Niagara River Suspended Sediments: Concentration trends of dechloranes in suspended sediments collected between 1980 and 2006 are shown in Figure 1. Both Dec 602 and 603 declined significantly over the study period (Pearson correlation, R = -0.86, p < 0.01 for Dec 602 and R = -0.72, p < 0.01 for Dec 603) (part a of Figure 1). The trend for CP (R = -0.86, p < 0.01) was similar to Dec 602 and 603, whereas Dec 604 concentrations fluctuated since 1980 (R = 0.31, p > 0.05) (part b of Figure 1). Mirex does not show any decline until the late 1990s (part c of Figure 1), which indicates that Mirex continued to leach from chemical production facility properties and/or waste storage sites along the Niagara River long after use of Mirex was prohibited in 1978. The declines since the late 1990s might reflect remediation efforts at several sites in the region through the 1990s. A declining concentration trend for DP was reported previously for Niagara River suspended sediments and confirmed in this study (R = -0.60, p < 0.01), with results consistent with declines observed in a sediment core collected near the river mouth on the Niagara River bar. It is not clear if the decline in DP represent changes in production volumes at the manufacturing site or whether it reflects emission controls adopted over the past 20+ years at the site. The suspended sediment trends were also reflected in open lake sediment core trends, which generally decline since 1980 in the Niagara basin (this study, discussed below) and in the Mississauga basin. DP, Dec 602, and Dec 604 were found to be higher in tributary sediments from the Niagara River area and Lake Ontario than Lake Erie tributaries, and higher in lake sediments and fish from Lake Ontario than Lake Erie, suggesting similar sources for these compounds. Concentration ratios of these compounds in suspended sediments with year were compared to further assess relative contributions to the Niagara River and Lake Ontario. The ratio of DP/Dec 602 shows a considerable increase to present (R = 0.66, p < 0.01), indicating that Dec 602 concentrations are declining more rapidly than for DP. This is consistent with continued manufacture, emissions, and/or use of DP and possibly reduced or ceased production of Dec 602 in the area. The ratio of Dec 602/Dec 604 was more variable (R = -0.41, p > 0.05), and there was no trend in the DP/Dec 604 ratio(R = -0.06, p > 0.05). It is diffcult to interpret these results in terms of source contributions without more knowledge of production history and use. The periodic manufacture in the area of Dec 602 and/or Dec 604 at different times could account for the more variable results, or the relative influence of uses and sources (i.e., ongoing use and emissions in certain applications compared to manufacture and emissions in the region), could influence concentrations and occurrence patterns. The use of Dec 604 individually compared to the use of Dec 602 and Dec 604 together (noted above) could account for the greater variability in the Dec 602/Dec 604 ratios and in the concentration trend for Dec 604 (part b of Figure 1).

Seasonal Variation of Dechloranes in Niagara River Suspended Sediments: The dechloranes varied seasonally over the period of April 2006 to March 2007 with some distinct patterns observed as illustrated by Dec 602, 603, 604, and DP (Figure 2). Total organic carbon (TOC)-normalized concentrations of Dec 602 and 604 were highest in late summer (August-September) and in late winter (February-March) (part a of Figure 2). Mirex exhibited a similar seasonal pattern to Dec 602 and 604. Relatively higher TOC-normalized concentrations of DP were observed in August-September, similar to Dec 602 and 604, but the March 2007 composite had the highest TOC-adjusted DP concentration (part b of Figure 2). The seasonal pattern of Dec 603 differed from those of Dec 602, 604, and DP, with the highest TOC-adjusted concentrations observed in January - February (part c of Figure 2). CP did not exhibit a clear pattern. TOC concentrations were highest during late summer (part d of Figure 2) when Dec 602, 604, DP and Mirex concentrations also increased. However, normalization to TOC did not fully account for the observed trends (parts a and b of Figure 2), consistent with the influence of localized sources, and that these compounds are not strongly associated with sorption to algal matter, which increases throughout summer in upstream Lake Erie (the main source of Niagara River water). Lake Erie is also stratified during this period resulting in relatively lower suspended sediment concentrations (part d of Figure 2). Possible explanations for the trends may include the mobilization of sediments/soils from the local Niagara region that may contain higher chemical concentrations during summer rain events, contributing to the sediment load of the river in addition to upstream lake sediments. Similarly, during late winter rain and melt events, sediment/soil particles with elevated concentrations may be washed into the river. DP may additionally have emissions occurring at different times of the year depending on when batches are manufactured. The Dec 603 trend showing higher winter concentrations is consistent with a greater proportion of suspended particles from Lake Erie during winter. The lake is no longer stratified in winter when storms and ice scour increases particle concentrations, and elevated Dec 603 concentrations were observed in Lake Erie tributary sediments relative to Lake Ontario and the Niagara area. There was no trend apparent in the f syn of DP (fraction of syn-DP relative to the sum of syn-DP + anti-DP) to aid interpretation.

Temporal Trends of Dechloranes in Lake Ontario Sediment Cores: Figure 3 shows the concentration trends for Mirex, Dec 602, 603, 604, CP, and total DP in the sediment core from the Niagara basin of Lake Ontario. Downward concentration trends were observed in the upper slices since 1980 and were generally consistent with trends in Niagara River suspended sediments over the same period. However, core results were more variable and had lower resolution as each core slice integrates inputs over 5 - 7 years compared to annual values for the Niagara River suspended sediments. The Niagara basin is also influenced by other inputs (industrial, municipal, tributary, and atmospheric) to the western end of Lake Ontario. Smaller declines in the core for DP and Dec 604 compared to Dec 602 are consistent with observations in the suspended sediments. The lowest concentrations (post-1980) in both suspended sediments and the sediment core occurred since 2000. There was a more substantial decline in Mirex in the core that differed from the suspended sediment trends for reasons which are unclear. Sediment cores provide an indication of input trends for the target compounds prior to the 1980s when detailed monitoring programs were established. For example, Mirex concentrations gradually increased from the early 1950s, peaked in the early 1980s, and declined considerably since then (part a of Figure 3). Dec 603 had a temporal trend similar to Mirex (part b of Figure 3) as Mirex, Aldrin, and Dieldrin were manufactured beginning in the late 1940s and/or early 1950s and their registered uses were limited by the mid-1970s in North America. Concentrations of CP also increased between the mid-1950s and early 1980s, but declined only since the mid-1990s (part c of Figure 3). Most uses of Chlordane were limited by the mid-1970s and the U.S. EPA banned all approved uses in 1988, but manufacture for export still continued until 1997. There are 23 Chlordane-contaminated hazardous waste sites located in the Great Lakes Basin, and the Niagara River area is on the list of Areas of Concern (AOC), with Chlordane listed as one of the pesticides which is a Chemical of Concern. Dec 602, 604, and DP concentrations increased in sediments between the early and mid-1960s (parts d - f of Figure 3, respectively), approximately 10 years after Mirex. The maximum concentration of Dec 602 occurred in the mid-1990s followed by a subsequent decline. Dec 604 peaked around the late 1980s, but concentrations have not dropped as rapidly as Dec 602, with 2/3 of the maximum concentration found in the top 1 cm. The maximum DP concentration was observed around 1980, but appreciable declines did not occur until recently. No trend was observed for the f syn in sediment cores. Sediment core profiles for the dechlorane compounds in the Niagara basin were similar to those observed in a core from the Mississauga basin, consistent with the broad influence of Niagara River inputs to Lake Ontario depositional basins. Both exhibited bimodal peaks for most analytes around 1980 and again in the mid-1990s. Without knowledge of the production history for these compounds, it is difficult to relate production and use to core observations. Observed trends in the Niagara basin core may be influenced by production changes, but also industrial emission abatement efforts and remedial actions at contaminated locations which have impacted other historical contaminant levels in the area.

Temporal Trends of Dechloranes in Lake Ontario Lake Trout: Mirex was found at the highest concentrations in the lake trout, followed by Dec 602 and DP, similar to results reported previously for a small number Lake Ontario lake trout. Peak concentrations for each compound studied occurred in the early or late 1980s with subsequent declines to 2004 (Figure 4). Mean concentrations declined 6-fold, 5-fold, and 4.5-fold from peak year to 2004 for Mirex, Dec 602, and Dec 603 respectively, but only 2.5-fold for total DP. Consistent with observations in the sediment core and suspended sediments, the lowest concentrations occurred in recent years (1998/2004). syn-DP bioaccumulates to a greater extent or is more bioavailable than anti-DP in fish, but this may vary depending on the foodweb studied. In this study, the measured f syn in lake trout were all above the reported f syn of technical DP products (0.2 - 0.36) ranging from 0.42 to 0.56, consistent with previous observations in fish, and were greater than sediment f syn values. A decreasing trend in f syn was found with time (R = -0.81, p << 0.001) with lower f syn values in fish collected in 1998 and 2004. This was in contrast to the sediment core and suspended sediments where no trends were noted. Modulations of f syn by trophic interactions in the foodweb at different times would need to be considered to understand this trend. For example, a major perturbation of the Lake Ontario foodweb occurred in the mid-1990s with the dreissenid mussel invasion. Although remediation of contaminated sites along the Niagara River occurred in the late 1990s that may have contributed to reduced concentrations, changing f syn values resulting from such efforts were not noted in suspended sediments. It is important to note that the relatively high concentrations of Dec 602 in fish compared to other dechloranes indicate that it is more amenable to bioaccumulation, similar to Mirex. For example, in suspended sediments of the Niagara River, the DP concentrations were 20 to 120 times greater than those of Dec 602; while the Dec 602 concentrations were 50 to 380 times greater than those of DP in Lake Ontario lake trout.

Validity criteria fulfilled:
yes
Conclusions:
Biota-sediment-Accumulation Factors (BSAF) for syn-DP and anti-DP were 0.8 and 0.3, respectively. With a BSAF of less than 1 bioaccumulation in lake trout of Lake Ontario is considered low in contrast to Mirex and Dechlorane 602, having BSAFs of 7400 and 270, respectively, being considered strongly bioaccumulating in the food web of Lake Ontario.
Executive summary:

The relative concentration patterns observed were total DP > Mirex > Dec 602 and Dec 604 > Dec 603 > CP in suspended sediments and sediment cores, whereas Mirex was highest in lake trout, followed by Dec 602 and DP. Dec 602 concentrations were 50 to 380 times greater than those of DP in lake trout, indicating Dec 602 has a greater bioaccumulation potential. The estimated biota-sediment accumulation factor (BSAF) for Dec 602 (270) was much greater than for DP (0.8 for syn-DP and 0.3 for anti-DP) in Lake Ontario, and was greater than those calculated for PBDEs. syn-DP bioaccumulates to a greater extent or is more bioavailable than anti-DP in fish, but this may vary depending on the foodweb studied. In this study, the measured f syn in lake trout were all above the reported f syn of technical DP products (0.2 - 0.36) ranging from 0.42 to 0.56, consistent with previous observations in fish, and were greater than sediment f syn values.

Endpoint:
bioaccumulation: aquatic / sediment
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2000 - 2003
Reliability:
2 (reliable with restrictions)
Qualifier:
no guideline followed
Principles of method if other than guideline:
From data derived in a field study in the food web of Lake Ontario and Lake Winnipeg biomagnification factors (BMF) of Dechlorane Plus for different sets of predator/prey in Lake Winnipeg and Lake Ontario were established based on quantitative concentrations found in samples taken between 2000 and 2003.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
Samples for both studies were collected between 2000 and 2003. Additional sediment samples from the central basin of Lake Ontario collected by Environment Canada (EC) in 1990 were also analyzed. All samples were processed at the Freshwater institute (FWI) laboratory. Biological samples were homogenized with dry ice, spiked with a suite of recovery internal standards, and extracted using accelerated solvent extraction (ASE), lipid removal by gel permeation chromatography (GPC), and further cleanup using Florisil. Sediment samples were first freeze-dried and extracted in a manner identical to that of biota with the exception of GPC. Stable isotope analysis of nitrogen was previously determined on biota to define trophic levels (TL).
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
An interlaboratory comparison (EC and FWI) on the technical mixture gave excellent agreement: the respective contributions of the syn- and anti-isomers in the mixture were estimated to be 36 and 64% by EC laboratory and 34 and 66% by FWI laboratory. Four sediment extracts were also analyzed in both laboratories and showed good agreement (63 to 86%) between the measured DP isomer values and suggested good precision between laboratories.
Method detection limits (MDLs) were estimated from the procedural blanks which consisted of Ottawa sand. Trace amounts of both isomers (syn, 0.6 pg; anti, 2.6 pg) were present in the blanks Using an average sample mass of 15 g, MDLs of 0.3 and 1.5 pg/g for syn- and anti-isomers, respectively, were determined. The linear dynamic range of the instruments was 10-2500 pg on column (r² =- 0.995) for both isomers. The ratio of the quantitation and confirmation ions in samples was within 15% of measured standard values in all cases.
Test organisms (species):
other: burbot, zooplankton, mussels, walleye, goldeye, whitefish, emerald shiner, white sucker, sediment
Route of exposure:
feed
Test type:
field study
Water / sediment media type:
natural water: freshwater
Hardness:
not mentioned
Test temperature:
not mentioned
pH:
not mentioned
Dissolved oxygen:
not mentioned
TOC:
not mentioned
Salinity:
not mentioned
Nominal and measured concentrations:
Fish, mussels and zooplancton were not exposed to a defined concentration of DP but were caught from lake Winnipeg and lake Ontario in their natural habitat and analysed for Dechlorane plus (DP) content. For comparission, sediment samples were collected and analysed too.
Reference substance (positive control):
no
Details on estimation of bioconcentration:
throphic level adjusted biomagnification factors (BMF TL) were determined based on fish samples of different species (and trophic levels) corrected based on lipid content of species analysed. BMF TL = [(predator)/(prey)]/[(TL predator)/(TL prey)]
Stable isotope analysis of nitrogen was previously determined on biota to define trophic levels.
Lipid content:
1.15 %
Time point:
end of exposure
Remarks on result:
other: for walleye, Lake Winnipeg
Lipid content:
8.78 %
Time point:
end of exposure
Remarks on result:
other: for whitefish, Lake Winnipeg
Lipid content:
2.27 %
Time point:
end of exposure
Remarks on result:
other: for whitesucker, Lake Winnipeg
Lipid content:
2.34 %
Time point:
end of exposure
Remarks on result:
other: for goldeye, Lake Winnipeg
Lipid content:
13.67 %
Time point:
end of exposure
Remarks on result:
other: for zooplankton, Lake Winnipeg
Lipid content:
13.4 %
Time point:
end of exposure
Remarks on result:
other: for trout, Lake Ontario
Lipid content:
3.51 %
Time point:
end of exposure
Remarks on result:
other: for alewife, Lake Ontario
Lipid content:
1.32 %
Time point:
end of exposure
Remarks on result:
other: for smelt, Lake Ontario
Type:
other: BMF TL
Value:
0.3 dimensionless
Basis:
normalised lipid fraction
Remarks:
walleye/whitefish
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
11 dimensionless
Basis:
normalised lipid fraction
Remarks:
walleye/whitefish
Calculation basis:
other: natural environment
Remarks on result:
other: anti-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
0.6 dimensionless
Basis:
normalised lipid fraction
Remarks:
walleye/whitesucker
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
0.4 dimensionless
Basis:
normalised lipid fraction
Remarks:
walleye/goldeye
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
0.8 dimensionless
Basis:
normalised lipid fraction
Remarks:
walleye/goldeye
Calculation basis:
other: natural environment
Remarks on result:
other: anti-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
< 0.1 dimensionless
Basis:
normalised lipid fraction
Remarks:
goldeye/zooplankton
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Winnipeg
Type:
other: BMF TL
Value:
1 dimensionless
Basis:
normalised lipid fraction
Remarks:
trout/alewife
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Ontario
Type:
other: BMF TL
Value:
0.9 dimensionless
Basis:
normalised lipid fraction
Remarks:
trout/alewife
Calculation basis:
other: natural environment
Remarks on result:
other: anti-DP
Remarks:
Conc.in environment / dose:natural level in lake Ontario
Type:
other: BMF TL
Value:
12
Basis:
normalised lipid fraction
Remarks:
trout/smelt
Calculation basis:
other: natural environment
Remarks on result:
other: syn-DP
Remarks:
Conc.in environment / dose:natural level in lake Ontario
Type:
other: BMF TL
Value:
11 dimensionless
Basis:
normalised lipid fraction
Remarks:
trout/smelt
Calculation basis:
other: natural environment
Remarks on result:
other: anti-DP
Remarks:
Conc.in environment / dose:natural level in lake Ontario
Details on kinetic parameters:
not assessed
Metabolites:
none reported
Results with reference substance (positive control):
no positive control used
Details on results:
Lake Winnipeg. Concentrations of DP isomers in the Lake Winnipeg food web was investigated. The syn-isomer was consistently detected in all samples while the anti-isomer was less frequently detected (~ 45% of samples). In biota, concentrations of the syn-isomer were greatest in burbot (range, 67 - 773 pg/g, median, 415 pg/g), zooplankton (range, 469 - 647 pg/g, median, 542 pg/g), and mussels (range, 76 - 823 pg/g, median, 504 pg/g), while the anti-lsomer was greatest in walleye (range, 608 - 883 pg/g, median, 714 pg/g) and goldeye (range, 594 - 932 pg/g; median, 763 pg/g). Concentrations of both isomers were similar in whitefish but varied considerably in walleye and goldeye; respective concentrations of the anti-isomer were 25 and 14 times greater than that of the syn-isomer in these species. Sediments contained small pg/g (dry weight) concentrations (syn, 11.7 pg/g; anti, 10.3 pg/g dry wt) of both isomers.
Lake Ontario. Concentrations of the isomers in the Lake Ontario food web were also assessed. Both isomers were detected in all samples with anti-DP consistently greater than that of the syn-isomer. Similar concentrations of both isomers were observed in trout (median, syn = 44.3, anti = 47.2 pg/g), smelt (median, syn = 5.5, anti = 6.5 pg/g), alewife (median, syn =48.3, anti = 54.2 pg/g) and sculpin (median, syn = 626, anti = 777 pg/g). Concentrations of the anti-isomer were approximately 2.5 times greater than the syn-isomer in Diporeia, 3 times greater in Mysis, and 2 times greater in plankton. In sediments, the anti-isomer comprised approx.. 85% of the total DP concentrations (mean Sum of DP = 206 ng/g dry wt], which were orders of magnitude greater than those from Lake Winnipeg.
In sediments, Sum of DP concentrations were only slightly less than Sum of HBCD concentrations supporting the hypothesis that reduced bioavailability of the DP-isomers may be a contributing factor to the small concentrations of DP compared to HBCD observed in biota.
Biomagnification: Two measures of trophic transfer were calculated for the DP-isomers. The first method calculated trophic level (TL) adjusted biomagnification factors (BMF TL) and was based on the ratio of the lipid-corrected concentrations in the predator - prey relationship given by Fisk et al. (Fisk, A. T.; Hobson, K. A.: Norstrom, R. I. influence of chemical and biologial factors on trophic transfer of persistent organic pollutants in the Northwater Polynya food web. Environ. Sci. Technol. 2001, 35, 732- 738)
BMF TL = [(predator)/(prey)]/[(TL predator)/(TL prey)]
Trophic magnification factors (TMFs) can also be used as a descriptor for biomagnification and are derived from the slope of the regression between an organism’s lipid-normalized contaminant concentrations and trophic position, as determined by stable isotopes of nitrogen. TMFs represent the average increase in contaminant concentration in food webs rather than the variability shown between species in BMF TL, calculations, which represent only specific predator-prey relationships.
There are a few interesting features of the BMF TL, values for the isomers in both food webs. In the walleye/whitefish feeding relationship, only the anti-isomer had a BMF TL >1; the large BMF TL, for the anti-isomer suggests that either there is a stereoselective elimination of the syn –isomer in preference to the anti-isomer by walleye or that walleye can metabolize the syn-isomer more readily. In Lake Ontario, only the trout/smelt feeding relationship showed BMF TL values >1. Similar BMF TL values between DP-isomers suggest that lake trout, unlike walleye from Lake Winnipeg, are not stereoselectively accumulating or metabolizing the isomers. Taken together, these results support the hypothesis that interspecies differences in bioaccumulatinn and biotransformation are likely.
Regressions of the TL against concentrations were statistically significant for both isomers only in the Lake Winnipeg food web. For Lake Ontario, plots were constructed using wet weight {not presented) and lipid weight concentrations but neither plot yielded significant relation-ships for either isomer. Regression analysis for the Lake Winnipeg food web suggested that with a lipid weight TMF value of 2.5 (r²: = 0.12. p = 0.04). the anti-isomer was biomagnifying throughout the entire food web while the syn-isomer with a lipid weight TMF value of 0.45 (r² = 0.17. p = 0.01] was being diluted with increasing TL. The lack of biomagnification potential of the syn-isomer in the Lake Winnipeg food web is consistent with the other data presented in this study. TMF values for the same Lake Winnipeg food web for Sum of HBCD of 6.3 and for perflourooctane sulfonate (PFOS) in the Lake Ontario food web of 6.1 were greater than that of the anti-isomer.
Reported statistics:
Statistical treatment of the data was done using SigmaStat (Version 9.01, Systat Software lnc.).
Validity criteria fulfilled:
not applicable
Conclusions:
Biomagnification factors (BMF) of Dechlorane plus for different sets of predator/prey in Lake Winnipeg and Lake Ontario were established based on samples taken between 2000 and 2003. Whereas in Lake Winnipeg for most predator/prey sets no biomagnification was seen (BMF TL < 1) in one case (walleye/whitefish) a BMF TL of 11 was found for the anti-isomer whereas for the syn-isomer the BMF TL was only 0.3.
In sample taken from Lake Ontario the differences between syn- and anti-isomer were not particularly relevant and BMF TL were also mainly less or equal to 1. However, for the set trout/smelt BMF TLs of 12 and 11 were found for the syn- and anti-isomer, respectively.
Executive summary:

Biomagnification factors (BMF) of Dechlorane plus for different sets of predator/prey in Lake Winnipeg and Lake Ontario were established based on samples taken between 2000 and 2003. Whereas in Lake Winnipeg for most predator/prey sets no biomagnification was seen (BMF TL < 1) in one case (walleye/whitefish) a BMF TL of 11 was found for the anti-isomer whereas for the syn-isomer the BMF TL was only 0.3.

In sample taken from Lake Ontario the differences between syn- and anti-isomer were not particularly relevant and BMF TL were also mainly less or equal to 1. However, for the set trout/smelt BMF TLs of 12 and 11 were found for the syn- and anti-isomer, respectively.

The reasons for these differences is not fully understood currently.

Endpoint:
bioaccumulation in sediment species, other
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
August - October 2010
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Fifty four samples were collected in a river in northeastern China and analyzed for DP (and other Dechloranes) by gas chromatography/mass spectrometry. The average concentrations of total DP (syn- and anti-) in water, sediment, air, reed (Phragmites australis), and fish (E. elongatus) were analysed and biota-sediment accumulation factor (BSAF) derived.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
A total of 54 samples, including 16 water, 16 sediment, 2 air, 5 reed (P. australis) and 15 fish (Eelpout, or E. elongatus) samples, were collected from the Daling River in August 2010. Among the 16 sampling sites of water and sediment, 10 (R01-R10) were along the Daling River, 5 in wetland (WL01-WL05) and 1 in urban sewage (SW) which was secondary treatment wastewater. Two passive air samples using polyurethane foam (PUF) disk were deployed in the mouth of river (A01) and near urban sewage (A02) for approximately three months (90 day) between August and October, 2010. Five reed samples were collected at 5 wetland sites (WL01-WL05). An original plan was made to sample fish at every sampling site, but the fish samples (15 in total) were collected only at R09, an estuary area of Daling River. Sites R01-R04 and SW are located in the city of Linghai with a population of 533,000 and the others are in remote area, approximately 50 - 70 km away to the south from the city and close to the Bohai Sea. Water samples collected at sampling sites were placed into acetone-rinsed brown glass bottles and one liter of water sample was mixed with 100 mL dichloromethane (DCM) for storage at 4 °C. Sediment samples were collected using a grab sampler. Reed samples were composed of five subsamples collected from different locations at each site and mixed completely. All samples were stored in prewashed glass bottles with Teflon-lined caps and stored at -20 °C until extraction. After collection, samples were sent to the laboratory of the International Joint Research Center for Persistent Toxic Pollutants (IJRC-PTS), Dalian Maritime University, Dalian, China, for processing and analysis. The Daling River is an important water supply and irrigation
resource in Liaohe River Delta in northeastern China which is 397 km long and has a drainage area of 23,500 km² catchments. The river originates in the north and enters to the Bohai Sea in the south. Recently, coast ecological environment of Bohai Sea was damaging and estuary wetland of Liaohe River Delta was seriously degenerating as development of industry and agriculture in surrounding area.
Vehicle:
no
Test organisms (species):
other: Enchelyopus elongatus
Route of exposure:
sediment
Test type:
field study
Water / sediment media type:
natural sediment: freshwater
Hardness:
not mentioned, field study
Test temperature:
not mentioned, field study
pH:
not mentioned, field study
Dissolved oxygen:
not mentioned, field study
TOC:
not mentioned, field study
Salinity:
not mentioned, field study
Details on test conditions:
Fish (Eelpout, or Enchelyopus elongatus) were not exposed to a defined concentration of DP but were caught from Daling River in August 2010 in their natural habitat and analysed for Dechlorane plus (DP) content. For comparission, sediment samples were collected and analysed too.
Nominal and measured concentrations:
not mentioned, field study
Reference substance (positive control):
no
Type:
BSAF
Value:
0.88 dimensionless
Basis:
whole body w.w.
Calculation basis:
other: natural habitat
Remarks on result:
other: syn-DP (range: 0.33 - 2.8)
Remarks:
Conc.in environment / dose:natural level in Daling river
Type:
BSAF
Value:
0.33 dimensionless
Basis:
whole body w.w.
Calculation basis:
other: natural habitat
Remarks on result:
other: anti-DP (range: 0.086 - 1.0)
Remarks:
Conc.in environment / dose:natural level in Daling river
Type:
other: BSAF'
Value:
0.75 dimensionless
Basis:
normalised lipid fraction
Calculation basis:
other: natural habitat
Remarks on result:
other: syn-DP, BSAF' is BSAF normalized to fish lipid and sediment organic carbon content
Remarks:
Conc.in environment / dose:natural level in Daling river
Type:
other: BSAF'
Value:
0.28 dimensionless
Basis:
normalised lipid fraction
Calculation basis:
other: natural habitat
Remarks on result:
other: anti-DP, BSAF' is BSAF normalized to fish lipid and sediment organic carbon content
Remarks:
Conc.in environment / dose:natural level in Daling river
Details on kinetic parameters:
not assessed
Metabolites:
none reported
Results with reference substance (positive control):
none applied
Details on results:
Bioaccumulation of Dechloranes: Bioaccumulation is a process where chemical concentration in an aquatic organism achieves a level exceeding that in the water as a result of chemical uptake through all routes of chemical exposure. Chemical bioaccumulation in aquatic systems can be quantified using two parameters: biota-sediment accumulation factor (BSAF) and bioaccumulation factor (BAF). BSAF is equal to C(B) / C(S), where C(B) is chemical concentration in biota (wet weight) and C(S) is chemical concentration in sediment (dry weight) (Gobas and Morrison, 2000). BAF is calculated as C(B) / C(W), where C(W) is chemical concentration freely dissolved in water (ng/mL) (Streets et al., 2006). In this study, BSAF values were estimated as 4.7 (1.2 - 9.2) for Dec 602, 0.88 (0.33 - 2.8) for syn-DP, and 0.33 (0.086 - 1.0) for anti-DP. Shen et al. (2011) also reported that the BSAF values of syn-DP and anti-DP were, respectively 0.8 and 0.3 in the Lake Ontario, very well consistent with the results from the present study. However, the BSAF value of Dec 602 in present study was much lower than that in the Lake Ontario (270 ng/mL). The low BSAF for Dec 602 in present fish may be associated with the lower contamination of Dec 602 in sediment (0.033 ng/g dw) in the estuary area of Daling River in comparison to those in Lake Ontario (5.7 - 12 ng/g dw) (Shen et al., 2011). Another parameter, BSAF’, has been also used as biota-sediment accumulation factor, which is defined as (C(B) / f(L)) / (C(S) / f(SOC)), where f(L) is the organism lipid content and f(SOC) is the sediment organic carbon content (Zhang et al., 2011; Jia et al., 2011). Bioaccumulation is implied when a BSAF’ is greater than one. A theoretical value of 1.7 has been estimated based on partitioning of non-ionic organic compounds between tissue lipids and sediment carbon (ASTM, 1997). The value of BSAF’ less than 1.7 indicates less partitioning of an organic compound into lipids than predicted, and a value greater than 1.7 indicates more uptake of the pollutant (Jia et al., 2011; Ozkoc et al., 2007). The value of BSAF’ in our study were 4.0 (1.1 - 10), 0.75 (0.27 - 2.5) and 0.28 (0.070 - 0.89) (mean and range in parentheses) for Dec 602, syn-DP and anti-DP, respectively. BSAF’ of total DP were at least 1 order higher than previous research in an e-waste recycling plant fish in south China (0.003, 0.004, and 0.025 in northern snakehead, crucian carp, and mud carp) (Zhang et al., 2011), which indicates higher bioaccumulation potential of DP isomers in the fish in our study than those fishes in Zhang et al. (2011). The differences in BSAF’ may be attributed to difference in fish species or ecosystem conditions. Higher BSAF for syn-DP compared to anti-DP were found in this study, as well as Lake Ontario fish (Shen et al., 2011), e-waste recycling plant fish (Zhang et al., 2011) and oyster in China (Jia et al., 2011). Tomy et al. (2008) reported that the uptake rate for syn-DP was significantly greater than that for anti-DP and a significantly smaller depuration rate constant was found for syn-DP compared to anti-DP. The LogK OW of Dec 602, syn-DP, anti-DP were 7.06, 9.03, 9.03, respectively (Sverko et al., 2011). It was found that the sequence of BSAF values for these Decs is opposite to the order of LogK OW , and the higher BSAF values associated with the lowest LogKOW . Similarly, Zhang et al. (2011) have reported significantly negative correlations between LogKOW and BSAF of DP, polychlorinated biphenyls (CBs 199, 203, 207, 208) and decabromodiphenyls ether (BDE 209) despite of their different chemical structures. BAF for DP are difficult to measure because water concentrations in the environment are usually close to or below detection limits, and concentrations of dissolved DP in water is even much more lower (Sverko et al., 2011). Wu et al, (2010) estimated the average log BAF of total DP ranged from 2.13 to 4.40 for different fishes in a reservoir in the vicinity of electronic waste recycling workshops in South China. Although syn- and anti-DP were measured in both water and fish at Site R09, but we were not able to separate the dissolved and particulate phases for DP in the present study. A further study to find the value of BAF for DP will be carried out in our future plan.

Water: DPs (syn- and anti-DP) were detected in water samples at Sites SW and R01-R10, but not in wetland (Sites WL01-WL05). Water concentrations of DP in Daling River ranged from 0.25 to 0.72 ng/L with a mean of 0.40 ng/L. The highest concentrations of DP appeared around the sampling sites at urban sewage (Site SW). In comparison with data reported for other places, water concentration of DP was 10 times higher than those in fresh water in Songhua River (with a mean of 0.030 ng/L) (Qi et al., 2010), similar to those in urban water in Harbin City (0.55 ng/L) (Qi et al., 2010), and in north China Sea (1.7 ng/L) (Jia et al., 2011). None of Dec 602, Dec 603 and 604 was detected in any water samples. Very high concentrations were found in water in the vicinity of electronic waste recycling workshops in South China, 0.80 ng/L in dissolved phase, and 3800 ng/g dw in suspend particulate phase (Wu et al., 2010). Assuming 1 L water has 0.05 g particles (dry weight), than the DP in water should be 190 ng/L, 4 orders of magnitude higher than that in our study.

Sediment: DPs were detected in all sediment surface samples at Sites SW, river (Sites R01-R10), and wetland (Sites WL01-WL05). Average DP concentrations (ng/g dw) in river sediment samples at sites in the river (R01-R10) and wetland (WL01-WL05) were 1.3 and 0.76, respectively. These DP levels are much lower than those near an e-waste recycling plant (7550 ng/g dw) (Wu et al., 2010), in the Lake Ontario (150 ng/g dw) (Sverko et al., 2008) and in the Lake Winnipeg (30 ng/g dw) (Tomy et al., 2007), but much higher than those in the Songhua River (0.040 ng/g dw) (Qi et al., 2010). As the case for water, the highest concentrations of DP appeared at Site SW (3.3 ng/g dw), followed by those at Sites (R02, R03 and R04), which are in town and near the urban sewage drainage outlet. The tendency of DP concentrations in sediment decreased with increasing distance from Site SW, possibly indicating the sewage drainage is the source of DP in the sediment. Dec 602, 603, and 604 concentrations in sediments were reported in the Great Lakes (Shen et al., 2010; Sverko et al., 2008; Tomy et al., 2007) and in northern China (Jia et al., 2011). In this study, Dec 602 was detected in most samples and Dec 603 was found in one sample (Site SW, 0.027 ng/g dw), while no Dec 604 was detected in any sediment samples. The mean sediment concentrations of Dec 602 (in ng/g dw) were 0.027 and 0.019 in river and wetland, respectively, less than or comparable to those reported for the north China Sea (Dec 602: 0.11, Dec 603: 0.028) (Jia et al., 2011), Lake Erie (Dec 602: 0.043, Dec 603: 0.029) and Lake Huron (Dec 602: 0.196, Dec 603: 0.058) (Shen et al., 2010).

Air: Atmospheric DP was first reported in Great Lakes in 2006 (Hoh et al., 2006). The concentration of DP in the vicinity of manufacturer was significantly higher than surrounding areas (Wang et al., 2010; Venier and Hites, 2008). In this study, only DP was detected in air at Sites A01 and A02, with concentrations of 0.13 and 0.38 ng/m, respectively if we adopt 0.35 (m³/day) as the effective volume (Ren et al., 2008). DP concentration in town area (A02) was higher than that in the remote area (A01). This is consistent with those reported in previous studies. For example, Ren et al. (2008) reported that local rather than trans-boundary sources were found to be primarily responsible for higher DP concentration in urban areas than rural areas. Similar findings were also reported by Qi et al. (2010) and Venier and Hites (2008).

Reed (Phragmites australis): Tree bark is an easy and inexpensive monitor for semivolatile organic compounds (Zhu and Hites, 2006; Simonich and Hites, 1997; Hermanson and Hites, 1990). In this research, reed was chosen to reflect pollution of Decs in wetland plant. DP was detected in all reed samples and concentrations of total DP (in ng/g ww) were 0.53 - 0.88 with a mean of 0.63 ±0.18, comparable to those in tree barks in Tianjing (0.18 ±0.12), Hangzhou (0.23 ±0.02) and in Shenzheng (0.30 ±0.16) (Qiu and Hites, 2008). Dec 603, detected in two out of five samples, ranged from BDL to 0.024 ng/g ww with a mean of 0.0090 ±0.010 ng/g ww. None of Dec 602 and Dec 604 was detected in any reed samples.

Fish (Enchelyopus elongatus): Fifteen fish samples were collected at R09, an estuary area of Daling River. Dec 604 was not detected in any fish sample. Concentrations (in ng/g lipid weight (lw)) of DP, Dec 602 and 603 were, respectively in the range of 8.7 - 93 (mean ±SD: 29 ±20), 2.2 - 20 (8.0 ±4.5), and BDL-7.3 (3.8 ±2.1). The concentrations of DP in the estuary area of Daling River fish were much greater than those collected in the Lake Erie (in the range of 0.14 - 0.91 ng/g lw) (Hoh et al., 2006), Lake Ontario (0.015 - 1.55 ng/g lw) and Lake Winnipeg (0.035 - 0.82 ng/g lw) (Tomy et al., 2007), similar to those in South Korea (0.61 - 126, with a mean of 24.5 ng/g lw) (Kang et al., 2010), but at least 1 order of magnitude less than the most fish samples previously reported near an e-waste recycling plant in south China (20.2, 190, 171, 277, 255, and 1970 in Chinese mysterysnail, prawn, mud carp, crucian carp, northern snakehead, and water snake) (Wu et al. 2010).

Further implications: A comparison was made for water and sediment concentrations of DP among urban, remote and wetland areas. It is interesting to note that, DP levels in wetland waters were all below IDL (0.063 ng/L), at least 1 order lower (P < 0.01) than those in urban (0.45 ng/L) and remote area (0.42 ng/L). The reason for the much lower concentration of DP in wetland water could be related to the natural cleansing functions that wetland performs (the ‘‘kidney function’’). The sediments with high portion of organic carbon in the wetland can absorb more toxic pollutants from water, and wetland plants, such as reeds, can also assimilate pollutants from water and sediments. There was no significant difference (P > 0.05) in the levels of DP in waters between urban and remoter sites, suggesting DP released from the city of Linghai can easily enter Bohai Sea. Similar comparison was also carries out for DP in two Chinese rivers and two lakes in North America (NA. While DP concentrations in sediment in two Chinese rivers are much lower than those in the 2 NA lakes (by 1 - 2 orders), DP in fish in the estuary area of Daling River are much higher than those in these lakes (Water concentrations are not available). The higher DP concentration in sediment in these 2 NA lakes may be caused by history use of DP. Indeed, while DP (and other Decs) was produced in the USA in the late 1960s by Hooker Chemical (now known as OxyChem) (Shen et al., 2010), DP production in China started less than 10 years ago in 2003 (http://www.anpon.com/English/Main.asp). The higher DP concentrations in Daling River possibly indicating that, although the historical release of DP in Daling River much less than that in Lake Ontario and Lake Winnipeg, indicated by much lower DP concentrations in surface sediments in Daling River than these two Lakes, the current DP levels in fish (or most likely in water too) in Daling River are much higher than those in NA lakes, possibly due to the release of DP through waste waters emitted from the urban cities and industrial centers along the river. However, it is also arguable that the high concentration of DP in fish in Daling River was also affected by factors in many ways, such as species, age, tissues and biochemical parameters, which are the crucial impact factors needed to be investigated in further research.

Fractional abundances of DP isomers Several f syn (=syn-DP/(syn-DP + anti-DP)) values were reported for technical DP products, from 0.2 to 0.25 by Hoh et al. (2006), 0.35 by Tomy et al. (2007), and 0.36 by Sverko et al. (2008) for technical DP produced in the USA, and 0.40 - 0.41 by Wang et al. (2010) for technical DP produced in China. The f syn value of 0.41 in technical DP product is adapted here. Fig. 2 shows that the mean values of f syn were 0.28, 0.25, 0.27 and 0.47 in water, sediment, reed and fish, respectively. The fish value of f syn was significant (P < 0.01) different from other media by Duncan’s multiple range test. Most of f syn value was below 0.41 except for fish, indicating that enrichment of syn-DP, possibly due to that the syn-isomer appears to have a higher biomagnification factor than the anti- isomer (Tomy et al., 2008). Previous work has shown that photo-decomposition (Moeller et al., 2010), microbial degradation (Sverko et al., 2008), bio-accumulation (Wu et al., 2010) and long range atmospheric transport (Hoh et al., 2006) will lead to change in the f syn value.

Validity criteria fulfilled:
yes
Conclusions:
It was found that biota-sediment accumulation factor (BSAF) was 0.88 for syn-DP, and 0.33 for anti-DP. Thus, neither syn- nor anti-DP was considered bioaccumulating, although significant differences were seen for syn- and anti-DP.
Executive summary:

The average concentrations of total DP (syn- and anti-) in water, sediment, air, reed (Phragmites australis), and fish (E. elongatus) were 0.30 ±0.24 (mean ±SD) ng/L, 1.3 ±0.69 ng/g dry weight (dw), 0.25 ±0.18 ng/m³, 0.63 ±0.18 ng/g wet weight (ww), and 29 ±20 ng/g lipid weight (lw), respectively. The mean ratio of syn-DP to total DP (f syn ) in water, sediment, reed, and fish were 0.28, 0.25, 0.27 and 0.47, suggesting depletion in abiota and enrichment in biota for syn-DP. It was found that biota-sediment accumulation factor (BSAF) was 0.88 for syn-DP, and 0.33 for anti-DP.

Endpoint:
bioaccumulation in aquatic species, other
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2006
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Field study determining DP in the food web in the vicinity of electronic waste recycling workshops in South China, based on quantified data from water, sediment and biota samples. From these data, trophic magnification factors (TMFs) were derived as outlined below.
GLP compliance:
not specified
Remarks:
no indication of GLP consideration was provided in the publication
Radiolabelling:
no
Details on sampling:
Sample Collection: The samples analyzed in this study are the same as those reported in our previous papers (see Wu, J. P.; Luo, X. J.; Zhang, Y.; Luo, Y.; Chen, S. J.; Mai, B. X.; Yang, Z. Y. Bioaccumulation of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in wild aquatic species from an electronic waste (e-waste) recycling site in South China. Environ. Int. 2008, 34, 1109 – 1113 and Wu, J. P.; Luo, X. J.; Zhang, Y.; Yu, M.; Chen, S. J.; Mai, B. X.; Yang, Z. Y. Biomagnification of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls in a highly contaminated freshwater food web from South China. Environ. Pollut. 2009, 157, 904 - 909). Briefly, a total of 88 wild aquatic biota samples, 6 water samples, and 6 surficial sediment samples were concurrently collected from a reservoir near the e-waste recycling plants, South China (23.6021 N, 113.0785 E) in 2006. Biota samples included two invertebrates, i.e., Chinese mystery snail (Cipangopaludina chinensis) and prawn (Macrobrachium nipponense), four fish species, i.e., mud carp (Cirrhinus molitorella), crucian carp (Carassius auratus), common carp (Cyprinus carpio), and northern snakehead (Ophicephalus argus), and one reptile, water snake (Enhydris chinensis). In addition, mud carp (Cirrhinus molitorella) were collected from another pond 5 km away from the e-waste recycling plant, as reference samples.
Vehicle:
not specified
Details on preparation of test solutions, spiked fish food or sediment:
study performed in natural environment (real life), no laboratory setup for exposure
Test organisms (species):
other: Chinese mystery snail (Cipangopaludina chinensis), prawn (Macrobrachium nipponense), mud carp (Cirrhinus molitorella), crucian carp (Carassius auratus), common carp (Cyprinus carpio), northern snakehead (Ophicephalus argus), watersnake (Enhydris chinensis
Details on test organisms:
Invertebrates: Chinese mystery snail (Cipangopaludina chinensis), n = 43, and prawn (Macrobrachium nipponense), n = 7
Fish: mud carp (Cirrhinus molitorella), n = 12, crucian carp (Carassius auratus), n= 18, common carp (Cyprinus carpio), northern snakehead (Ophicephalus argus), n = 6, water snake (Enhydris chinensis), n = 2
Route of exposure:
aqueous
Test type:
field study
Water / sediment media type:
natural water: freshwater
Hardness:
not reported as field study
Test temperature:
not reported as field study
pH:
not reported as field study
Dissolved oxygen:
not reported as field study
TOC:
not reported as field study
Salinity:
not reported as field study
Details on test conditions:
in this field study, invertebrates, fish and snake were caught and analysed together with sediment and water samples taken from the same area.
Nominal and measured concentrations:
background concentrations in the habitat of the test fish (field study)
Reference substance (positive control):
no
Details on estimation of bioconcentration:
Bioaccumulation factors (BAFs) for the DP-isomers were calculated by dividing the concentrations of DP in biota (ng/g wet wt) by the mean concentrations of DP in the dissolved phase of water (ng/mL). The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake). Chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70.
The food web biomagnification potential of DP was evaluated via estimation of trophic magnification factors (TMFs), defined mathematically as the slope of the regression model obtained from a plot of lipid-normalized contaminant concentrations in organisms versus trophic levels.
Lipid content:
ca. 0.59 %
Time point:
end of exposure
Remarks on result:
other: Chinese mysterysnail
Lipid content:
ca. 2.39 %
Time point:
end of exposure
Remarks on result:
other: Prawn
Lipid content:
ca. 2.87 %
Time point:
end of exposure
Remarks on result:
other: Mud carp
Lipid content:
ca. 3.63 %
Time point:
end of exposure
Remarks on result:
other: Crucian carp
Lipid content:
ca. 1.49 %
Time point:
end of exposure
Remarks on result:
other: Northern snakehead
Lipid content:
ca. 1.06 %
Time point:
end of exposure
Remarks on result:
other: Water snake
Type:
other: log BAF
Value:
ca. 2.1 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Chinese mysterysnail
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: log BAF
Value:
ca. 3.7 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Prawn
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: log BAF
Value:
ca. 4 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Mud carp
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: log BAF
Value:
ca. 3.8 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Crucian carp
Remarks:
Conc.in environment / dose:0.80 ng/L
Type:
other: log BAF
Value:
ca. 4.4 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Water snake
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: log BAF
Value:
ca. 3.3 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: Northern snakehead
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: trophic magnification factor (TMF)
Value:
11.3 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: TMF for syn-DP
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: trophic magnification factor (TMF)
Value:
ca. 6.5 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: TMF for anti-DP
Remarks:
Conc.in environment / dose:0.80 ng/L water
Type:
other: trophic magnification factor (TMF)
Value:
ca. 10.2 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks on result:
other: TMF for sum of DP
Remarks:
Conc.in environment / dose:0.80 ng/L water
Details on kinetic parameters:
not applicable as field study
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
DP Levels: Concentrations of DP in biota, water, and sediments are given in Table 1. The total DP concentrations in the collected aquatic species varied from 19 to 9630 ng/g lipid wt. The highest average concentration was found in water snake (1970 ng/g), followed by mud carp (1710 ng/g), crucian carp (277 ng/g), northern snakehead (255 ng/g), prawn (190 ng/g), and Chinese mysterysnail (20.2 ng/g). The average concentrations of DP were 0.80 ng/L, 3930 ng/g dry wt (dw), and 7590 ng/g dw in the dissolved phase of water, suspended particles, and surficial sediments, respectively.
The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake). Chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70. In our study, all species, except for Chinese mysterysnail and northern snakehead, showed log BAF values higher than 3.70, suggesting significant bioaccumulation of DP was occurring in these species.
The calculated trophic magnification factors (TMFs) of syn-, anti- and total DP were 11.3, 6.5, and 10.2, respectively. This indicated that DP, no matter whether the syn-DP or anti-DP isomer, was significantly biomagnified throughout the entire food web. The TMF of syn-DP was almost two times greater than that of anti-DP, suggesting that the biomagnification potential of syn-DP was higher than that of anti-DP in the present food web (Figure 3).

DP Levels: Concentrations of DP in biota, water, and sediments are given in Table 1. The total DP concentrations in the collected aquatic species varied from 19 to 9630 ng/g lipid wt. The highest average concentration was found in water snake (1970 ng/g), followed by mud carp (1710 ng/g), crucian carp (277 ng/g), northern snakehead (255 ng/g), prawn (190 ng/g), and Chinese mysterysnail (20.2 ng/g). The average concentrations of DP were 0.80 ng/L, 3930 ng/g dry wt (dw), and 7590 ng/g dw in the dissolved phase of water, suspended particles, and surficial sediments, respectively (Table 1).

DP was detected in all mud carps from the e-waste recycling site, whereas it was detected in only one of the five reference mud carp, at concentrations 3 - 159 times lower than in the study sample mud carp. These results revealed the heavy DP pollution of the aquatic species from the e-waste recycling site, due to the primary recycling process. To date, few studies have reported DP levels in aquatic species. Hoh et al. analyzed DP in archived fish (walleye) from Lake Erie and found levels of DP ranging from 0.14 to 0.91 ng/g lipid wt. Tomy et al. reported mean concentrations of 0.035 - 0.82 ng/g lipid wt in fish from Lake Winnipeg and 0.015 - 4.41 ng/g lipid wt in Lake Ontario. These concentrations were 1 - 4 orders of magnitude lower than those in our samples. DP levels in sediments were only reported within the Northern American Great Lakes region. Levels of DP in the sediment of the present study were more than one order of magnitude higher than the highest concentration reported in sediment (586 ng/g dw) from Lake Ontario. The elevated levels of DP in the environmental media from the e-waste recycling site also indicated that release from the e-waste may be an important source of DP in South China, as assumed by Ren et al.

Isomeric Ratios: The isomer composition of DP in the environmental samples may vary from that of the technical product, due to the stereospecific photodegradation, biodegradation, and biota isomer-selective uptake or elimination. The fraction of anti-DP (f anti), defined as the concentration of the anti-DP divided by the sum of concentrations of syn- and anti-DP, were calculated for the abiotic samples and aquatic species. Sediments had mean f anti values of 0.72 ±0.01, which were close to the reported values in the DP commercial product (f anti) 0.75 - 0.80) and the measured value (f anti = 0.70 ±0.003) in three commercial products bought from a Chinese producer. It was interesting to find that the f anti values (mean of 0.72) in sediments were apparently intermediate between those in water (mean of 0.66) and the suspended particles (mean of 0.84). One likely explanation for this observation was that, compared to anti-DP, more fractions of syn-DP entered into the dissolved phase of water during partition process, due to the different octanol-water partition coefficients of the two isomers. The two isomers were reported to have different aqueous solubility, at 207 ng/L and 572 ng/L (source Oxychem), but no information was provided as to which isomer exhibited which solubility. On the other hand, other factors such as isomer-selective microbial degradation and biota uptake might also result in the different f anti values in water, suspended particles, and sediment. For example, the lower f anti values in surficial sediment than in suspended particles might also reflect that the microbial degradation of anti-isomer in the surficial sediment is more significant, although anti-isomer in suspended particles might experience both photo- and microbial degradation. With the exception of two Chinese mystery snail samples, in which syn-DP was below the LOQ, all of the samples had smaller f anti values than those in surficial sediments, indicating an enrichment of syn-DP. This was in line with observations in several fish species from the Great Lakes region. The higher assimilation efficiency and lower depuration rate of syn-DP relative to anti-DP, as documented in juvenile rainbow trout (Oncorhynchus mykiss) administrated DP isomers, may account for the low f anti values. The f anti values (0.65 - 0.74) in the prawn were close to those in surficial sediment, which might be related to its benthic habitat and polyphagic feeding habit. In addition, the absence of biotranformation for anti-DP in prawns may also contribute to this observation as prawns were thought to have low metabolic capabilities for xenobiotic pollutants, such as PBDEs and PCBs. In contrast, northern snakehead occupied the highest trophic level in the present food web had the lowest lower f anti values (0.09 - 0.20), which were much lower than those in sediments. Interestingly, a significant negative correlation was found between f anti values and trophic level of the species (r = -0.86, p < 0.05). This finding indicated that organisms with higher trophic positions might have higher metabolic capacities for anti- DP, and/or have higher uptake efficiencies for the syn-isomer compared to anti-isomer. Higher f anti values in species with higher trophic positions were also found in aquatic organisms from Lake Winnipeg, but no clear trends between f anti values and TL were observed in these biota. At this point, very little information exists on the biodegradation (metabolism) of DP in organisms. A photodegradation of DP conducted by Sverko et al. has demonstrated that anti-DP degrades more readily than does syn-DP. The relatively low anti-DP fraction observed in the present study and other reports implied that anti-DP might be metabolized more readily than the syn-DP in biota. The structure of anti-DP, in which the four interior carbons on the cyclooctane are less blocked by chlorines than are those of syn-DP, makes it more susceptible to biological attack than syn-DP, as noted by Hoh et al.

Bioaccumulation Factors and Trophic Magnification Factors: Bioaccumulation factors (BAFs) for the DP-isomers were calculated by dividing the concentrations of DP in biota (ng/g wet wt) by the mean concentrations of DP in the dissolved phase of water (ng/mL). The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake). Chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70. In our study, all species, except for Chinese mysterysnail and northern snakehead, showed log BAF values higher than 3.70, suggesting significant bioaccumulation of DP was occurring in these species. The low log BAF values in Chinese mysterysnail were not surprising, as it lies at the lowest trophic level in the present food web. However, the low log BAF in northern snakehead was unexpected since it occupied the highest trophic level in the present food web. Combined with the lowest f anti in the northern snakehead, it is suggested that this species might have higher metabolic capacity for DP than other species, and/or have lower uptake rates of anti-DP compared to other species. The log BAF values of the syn-isomer were significantly greater than those of the anti-isomer in the each aquatic species (paired samples t-test, p < 0.05). This is expected, considering that fish may have higher assimilation efficiency and stronger biomagnification power for the syn-isomer than for the anti- isomer. The food web biomagnification potential of DP was evaluated via estimation of trophic magnification factors (TMFs), defined mathematically as the slope of the regression model obtained from a plot of lipid-normalized contaminant concentrations in organisms versus trophic levels. The regressions between trophic levels and the lipid-normalized concentrations (ln-transformed) of syn-, anti-, and total DP in the aquatic species are presented in Figure 3. Northern snakehead had an a typical pattern with respect to its trophic level, possibly due to higher metabolic capacity for DP, as discussed above. Its presence significantly distorted the general relationship for DP (Figure 3). For example, its inclusion changed the R-squared from 0.89, 0.82, and 0.89 to 0.49, 0.05, and 0.36 for syn-DP, anti-DP, and total DP, respectively. Thus, this species was excluded when calculating the TMF. The calculated TMFs of syn-, anti- and total DP were 11.3, 6.5, and 10.2, respectively. This indicated that DP, no matter whether the syn-DP or anti-DP isomer, was significantly biomagnified throughout the entire food web. The TMF of syn-DP was almost two times greater than that of anti-DP, suggesting that the biomagnification potential of syn-DP was higher than that of anti-DP in the present food web (Figure 3). A more ready metabolism of anti-DP over syn-DP in biota could partly explain this finding. The higher assimilation efficiency for the syn-isomer in species in higher trophic levels, such as fish, might also result in the higher TMF of syn-DP compared to anti-DP. Trophic transfer of DP has been reported previously in food webs from Lake Ontario and Lake Winnipeg, but the results were different from those of the present study. No significant relationships between trophic level and concentration were found for either isomer in the Lake Ontario food web. The anti-isomer was observed to have undergone biomagnification in the Lake Winnipeg food web with a TMF of 2.54 (p = 0.04). This value was two times lower than the value determined in the present study (6.5). In addition, syn-DP was found to be diluted in the food web with increasing trophic levels in Lake Winnipeg, a result entirely opposite to our findings. It is very difficult to explain these discrepancies between the two studies based on the present data. Various factors including the food web composition, the assimilation efficiency of DP in the food web components, and even extrinsic conditions such as water temperature and environmental DP levels may have led to different trophic biomagnification potentials of DP isomers among the food webs. For example, the same Lake Winnipeg study also demonstrated that isomer-selective accumulation or metabolism of the isomers was likely among different species. Further studies, especially for the metabolism of DP in organisms, are warranted to investigate mechanisms of DP biomagnification in different food webs.

Comparing the Bioaccumulation Behavior of DP with PCBs and PBDEs: Our earlier work reported the bioaccumulation potentials of PCBs and PBDEs in the same food web as studied here. This provided an opportunity to compare the bioaccumulation behavior of DP isomers with those of PCBs and PBDEs. Comparing the DP levels with BDE 47 and PCB 153, the most abundant congeners found in those species, DP concentrations were found to be 1 - 2 orders of magnitude lower than those for BDE 47 and PCB 153. The syn-DP was found to be significantly correlated with PCBs and PBDEs in the biota samples (p < 0.001), after removal of an outlier - a mud carp containing the highest level of DP. However, this was not the case for anti-DP. This observation suggested that syn-DP may have bioaccumulation behavior similar to that of PBDEs and PCBs, while anti-DP may have an entirely different behavior in biota. The stereoselective metabolism of anti-DP throughout the entire food web may lead to the different behavior observed in the biota. Significant food web biomagnification of BDEs 47, 100, and 154 and most of the PCB congeners was observed in the present food web. To make an identical food web composition, the TMFs for BDEs 47, 100, 154 and total PBDEs and seven indicator PCBs (PCBs 28, 52, 101, 118, 138, 153, and 180) and total PCBs were recalculated after removal of the northern snakehead from the food web. The TMF of total DP was 10.2, which was approximately 5 times higher than that of total PBDEs (2.3), while it was similar to the value of total PCBs (11.1). These results suggested that the trophic biomagnification potential of total DP was greater than that of the total PBDEs, but it was comparable to that of the total PCBs. A comparison of the TMFs of DP isomers with those of individual congeners of PCBs and PBDEs in the same food web showed that TMFs of syn-DP and anti-DP were 2 - 4 times greater than most of the PBDE congeners, but were generally lower than those highly recalcitrant PCB congeners (Figure 5). The greater food web biomagnification potentials of DP isomers relative to PBDEs was likely due to the fact that PBDEs were much more readily metabolized compared to DP isomers in the species of high trophic positions. Metabolism of PBDEs has been demonstrated in several fish species. However, none of the possible metabolites of DP was found in lake trout exposed to DP, although metabolism of anti-DP is suspected in certain fish species. On the other hand, the log Kow of DP may also influence their trophic transfer. Most PCB congeners have log Kow in the range of 5 and 8, while DP had a log Kow of 9.43. This much higher Kow is likely to account for the lower food web biomagnification potentials of DP compared to PCBs, because chemicals with log Kow between 5 and 8 generally have the highest biomagnification potentials in top-level predatory fish, while the biomagnification potentials of compounds with log Kow greater than 8 are dramatically decreased. Our results demonstrated that both syn- and anti-DP had significant biomagnification potentials in aquatic food webs and that a stereospecific metabolism of anti-DP and/or isomer-selective residence of syn-DP occurred in organisms. The food web biomagnification potential of DP was higher than that of PBDEs but was lower than that of PCBs.

Validity criteria fulfilled:
not applicable
Conclusions:
The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake) in this study, equivalent to BAFs of 135 to 25.100, respectively. The calculated trophic magnification factors (TMFs) of syn-, anti- and total DP were 11.3, 6.5, and 10.2, respectively. This indicated that DP, no matter whether the syn-DP or anti-DP isomer, was significantly biomagnified throughout the entire food web. However, interesting is that the top predator in this web, the northern snakehead, showed significantly lower bioaccumulation and therefore was not considered for the assessment of trophic magnification factors.
Executive summary:

The results demonstrated that both syn- and anti-DP had significant biomagnification potentials in aquatic food webs and that a stereospecific metabolism of anti-DP and/or isomer-selective residence of syn-DP occurred in organisms. The food web biomagnification potential of DP was higher than that of PBDEs but was lower than that of PCBs. The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake). Chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70. In this study, all species, except for Chinese mysterysnail and northern snakehead, showed log BAF values equal or higher than 3.70, suggesting significant bioaccumulation of DP was occurring in these species. The low log BAF values in Chinese mysterysnail were not surprising, as it lies at the lowest trophic level in the present food web. However, the low log BAF in northern snakehead was unexpected since it occupied the highest trophic level in the present food web. Combined with the lowest f anti in the northern snakehead, it is suggested that this species might have higher metabolic capacity for DP than other species, and/or have lower uptake rates of anti-DP compared to other species. Northern snakehead had an atypical pattern with respect to its trophic level, possibly due to higher metabolic capacity for DP, as discussed above. Its presence significantly distorted the general relationship for DP (Figure 3). For example, its inclusion changed the R-squared from 0.89, 0.82, and 0.89 to 0.49, 0.05, and 0.36 for syn-DP, anti-DP, and total DP, respectively. Thus, this species was excluded when calculating the TMF. The calculated TMFs of syn-, anti- and total DP were 11.3, 6.5, and 10.2, respectively. This indicated that DP, no matter whether the syn-DP or anti-DP isomer, was significantly biomagnified throughout the entire food web.

Endpoint:
bioaccumulation in aquatic species, other
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2006
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Biota-sediment accumulation factors (BSAFs) for Dechlorane Plus (DP) were determined in three bottom fish species, i.e., crucian carp, mud carp, and northern snakehead from an electronic waste recycling site in South China, by measuring concentrations of DP in sediment and fish using GC-MS technique. Results were compared to known bioaccumulating substances (brominated flame retardants).
GLP compliance:
not specified
Details on sampling:
Fish samples selected in this study: Three bottom fish species were selected, i.e., crucian carp (Carassius auratus) (n=17), mud carp (Cirrhinus molitorella) (n=12), and northern snakehead (Ophicephalus argus) (n=6) to calculate the BSAFs for DP isomers. These fish samples were concurrently collected with the surficial sediment samples from a natural pond in an e-waste recycling site, South China in 2006. Detailed information on these samples and the sampling site has been described in our previous publications (Wu et al., 2008, 2009) and the feeding habits, body mass, body length, and trophic levels of these fish were generally summarized as follows:
Mud carp: Feeding habit: omnivore, body mass 2.9 – 122.4 g; body length: 5.8 – 18.1 cm; δ15N 9.2 – 13.9 ‰; trophic level: 2.85 – 4.22
Crucian carp: Feeding habit: omnivore, body mass 9.6 – 20.6 g; body length: 5.5 – 8.7 cm; δ15N 9.8 – 12.3 ‰; trophic level: 3.01 – 3.75
Northern snakehead: Feeding habit: carnivore, body mass 43.2 – 80.3 g; body length: 14.1 – 16.7 cm; δ15N 11.9 – 15.2 ‰; trophic level: 3.64 – 4.60.
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
study performed in natural environment (real life), no laboratory setup for exposure
Test organisms (species):
other: mud carp (Cirrhinus molitorella), crucian carp (Carassius auratus) and northern snakehead (Channa argus)
Details on test organisms:
Mud carp: Feeding habit: omnivore, body mass 2.9 – 122.4 g; body length: 5.8 – 18.1 cm; δ15N 9.2 – 13.9 ‰; trophic level: 2.85 – 4.22
Crucian carp: Feeding habit: omnivore, body mass 9.6 – 20.6 g; body length: 5.5 – 8.7 cm; δ15N 9.8 – 12.3 ‰; trophic level: 3.01 – 3.75
Northern snakehead: Feeding habit: carnivore, body mass 43.2 – 80.3 g; body length: 14.1 – 16.7 cm; δ15N 11.9 – 15.2 ‰; trophic level: 3.64 – 4.60.
Route of exposure:
aqueous
Test type:
field study
Water / sediment media type:
natural water: freshwater
Hardness:
not reported as field study
Test temperature:
not reported as field study
pH:
not reported as field study
Dissolved oxygen:
not reported as field study
TOC:
not reported as field study
Salinity:
not reported as field study
Details on test conditions:
in a field study, fish were caught and analysed together with sediment samples taken from the same area.
Nominal and measured concentrations:
background concentrations in the habitat of the test fish (field study)
Reference substance (positive control):
no
Details on estimation of bioconcentration:
Calculation of BSAF: The BSAF has been defined (Burkhard et al., 2004) as
BSAF = (Co /f l ) / (Cs /f soc)
where Co is the chemical concentrations in the organism, f l is the lipid fraction of the organism, Cs is the corresponding chemical concentration in surficial sediment, and f soc is the fraction of sediments as organic carbon. Measured concentrations of DP isomers, the extremely hydrophobic PCBs (CBs 199, 203, 207, and 208), and BDE 209 in sediment, crucian carp, mud carp, and northern snakehead were summarized in Table 2.
Table 2: Levels (mean ±SE) of DP isomers, the extremely hydrophobic PCBs, and BDE 209 in the sediment (ng/g organic carbon) and bottom fish (ng/g lipid) from an e-waste recycling site, South China.
Sediment (n=3) Mud carp (n=7) Crucian carp (n=6) Northern snakehead (n=6)
syn-DP 13100±2880 496±310 134±47 225±106
anti-DP 55300±7140 1210±842 142±68 30±12
total DP 77140±9300 1950±1300 299±133 255±117
CB 199 1570±66 1600±232 816±177 3110±653
CB 203 1530±131 1850±293 878±201 3500±763
CB 207 102±13 83±17 51±16 143±28
CB 208 231±9 151±27 101±27 236±49
BDE 209 1130000±107000 10100±4430 1430±1100 81±21
Type:
BSAF
Value:
0.004 dimensionless
Basis:
total lipid content
Remarks:
/ total DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: crucian carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.007 dimensionless
Basis:
total lipid content
Remarks:
/ syn-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: crucian carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.003 dimensionless
Basis:
total lipid content
Remarks:
/ anti-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: crucian carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.025 dimensionless
Basis:
total lipid content
Remarks:
/ total DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: mud carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.01 dimensionless
Basis:
total lipid content
Remarks:
/ syn-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: mud carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.025 dimensionless
Basis:
total lipid content
Remarks:
/ anti-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: mud carp (omnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.003 dimensionless
Basis:
total lipid content
Remarks:
/ total DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: northern snakehead (carnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.06 dimensionless
Basis:
total lipid content
Remarks:
/ syn-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: northern snakehead (carnivore)
Remarks:
Conc.in environment / dose:field study
Type:
BSAF
Value:
0.001 dimensionless
Basis:
total lipid content
Remarks:
/ anti-DP
Calculation basis:
other: not applicable as field study
Remarks on result:
other: northern snakehead (carnivore)
Remarks:
Conc.in environment / dose:field study
Details on kinetic parameters:
not applicable as field study
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
BSAFs for DP isomers: The calculated BSAFs for syn-DP, anti-DP, and total DP (sum of the syn- and anti-isomers) in the three bottom fish species were shown in Fig. 1. The BSAFs for CBs 199, 203, 207, and 208 and BDE 209, compounds with similar physiochemical properties with DP and have been documented as bioaccumulative chemicals, were also shown for comparison. Both fish species showed very low BSAFs for total DP, with average values of 0.004, 0.025, and 0.003 in crucian carp, mud carp, and northern snakehead, respectively. According to the equilibrium partitioning theory, when in conditions of equilibrium and no metabolism of the chemical, the BSAF for the hydrophobic organic chemicals (HOCs) is equal to the partitioning relationship of the chemical between organic carbon in the sediment and lipids of the organism, that is, the BSAFs should be 1 - 2 (Burkhard et al., 2004). The low BSAFs for DP isomers in the present fish indicated that DP may be in non-equilibrium conditions between sediment and fish. This is reasonable for fish because wide ranges of factors including sediment/water column chemical disequilibrium, chemical bioavailability, and dietary uptake efficiencies would influence the concentrations of HOCs between sediment and fish (Burkhard et al., 2004; Wong et al., 2011). Another explanation for the low BSAFs is that chemical metabolism within the investigated bottom fish and/or their underlying food web may occur. DP was assumed to be metabolized in northern snakehead (Wu et al., 2010) and other fish species (Tomy et al., 2007) in field investigations, although no direct evidence has been found to support the assumption so far. These low BSAFs indicated the low bioaccumulation potential of DP in the present fish species. However, the BAFs determined previously in the same samples showed that both DP isomers were highly bioaccumulative (BAFs >5000) in most of the samples (Wu et al., 2010). With a very high K OW value (log K OW ~9.3) (OxyChem, 2010), DP is super-hydrophobic and highly sorptive to the sediment, resulting in high values for BAF and the low for BSAF. This implied that BSAF may be not an appropriate bioaccumulation parameter for DP in highly contaminated site such as e-waste recycling site in South China. The BSAFs for syn-DP are significantly greater than those for the anti-isomer in all the three fish species (p ≤0.05), suggesting that the retention of syn-DP is greater than the anti-isomer in the present fish. Higher BSAFs for syn-DP compared to anti-DP were also found in Lake Ontario fish (Shen et al., 2011). The observed differences in BSAFs between the two DP isomers may be attributed to the differences in their physiochemical properties (e.g., K OW and the stereo structure conformation), resulting in different dietary uptake rates, depuration rates, and rates of metabolism in the fish. The results of dietary exposure to DP isomers using juvenile rainbow trout showed that the uptake rate for syn-DP was significantly greater than that for anti-DP (the calculated average uptake rates were 0.045 and 0.018 nmol/day for syn- and anti-DP, respectively) (Tomy et al., 2008). On the other hand, a significantly smaller depuration rate was found for syn-DP compared to anti-DP (the average depuration rate constants were 0.013 and 0.023 for syn- and anti-isomer, respectively) (Tomy et al., 2008). These two aspects may result in the higher assimilation efficiency of the syn-DP compared to anti-DP in fish, leading to the greater BSAFs for the former isomer. Furthermore, because of the configuration of the pendant chlorocyclopentene moieties, anti-DP would be more susceptible to biological attack (Hoh et al., 2006), which may also result in the relatively smaller BSAFs for anti-DP compared to syn-DP. To our knowledge, only two studies have reported field determined BSAFs for DP isomers. Based on concentrations (wet weight) in fish and corresponding concentrations in sediment (dry weight) collected from Lake Ontario, Shen et al. calculated average BSAFs of 0.8 and 0.3 for syn- and anti-DP, respectively (Shen et al., 2011). Jia and co-works reported an average BSAF of 4.6 for DP in oyster sampled form coastal environment of Northern China (Jia et al., 2011). These BSAFs are several orders (generally 2 – 3) of magnitude greater than those in our fish. We cannot explain the much lower BSAFs observed in the present study based on current data, however, differences in ecosystem conditions (e.g., concentrations of DP in the sediment, distribution of DP between the sediment and water column, and bioavailability of DP due to amounts and types of organic carbon in the ecosystems), biochemical parameters such as species type, trophic level, body size and metabolism capacity for DP, diet of the organism, etc., may result in the observed discrepancies among these studies. The much lower BSAFs in our fish compared to other studies (Jia et al., 2011; Shen et al., 2011) also suggest that the current BSAFs may have underestimated the bioaccumulation potential of DP in the e-waste recycling site.
Reported statistics:
Data analysis: The Kolmogorov/Smirnov one-sample test with Lilifor's transformation was used to assess whether BSAF values were normally distributed in certain species. The two-group t-test or the Mann/Whitney U-test was used if the data was normally distributed or non-normally distributed, respectively, for comparing BSAFs values for syn- and anti-DP isomers in certain species, and BSAFs for the investigated chemicals among species. Linear regression analyses were performed between the BSAF values and logarithm of octanol-water partition coefficients (log K OWs) of DP, PCBs, and BDE 209. The criterion for significance that was used in all statistical tests was p < 0.05.

Comparison with extremely hydrophobic PCBs and BDE 209: The average BSAFs for CBs 199, 203, 207, and 208 are 0.52 - 1.98, 0.57 - 2.28, 0.50 - 1.39, and 0.43 - 1.92, respectively, with significantly higher values in northern snakehead (p <0.05). Northern snakehead is a predatory fish feeding on small fish species including crucian carp and mud carp, biomagnification of PCBs in northern snakehead may account for the relatively higher BSAFs compared those in crucian carp and mud carp. Our BSAFs are consistent with those reported in grass shrimp, striped mullet, and sea trout from coastal Georgia, USA, which showed mean BSAFs of 0.28 - 2.1, 0.18 - 2.4, and 0.14 - 1.5 for CBs 199, 207, and 208, respectively (Maruya and Lee, 1998). The BSAFs calculated in northern snakehead in the present study are also similar to those (1.68 - 3.0) determined in 2 - 3 years age lake trout from southern Lake Michigan, but are about 2 times lower than the BSAFs (2.58 - 5.28) computed in 4 - 9 years age lake trout (Burkhard et al., 2004). The body length of our northern snakehead ranged 14.1 to 16.7 cm, corresponding to 1 - 2 years age (Yu et al., 2008). The different exposure time and other factors such as different diet composition may account for the different BSAFs observed between the two fish species. BSAF ranges of 1.92 - 28.3, 2.32 - 57.3, and 2.32 - 19.8 for CBs 203, 207, and 208, respectively were found in marine mussels from the coastal British Columbia, Canada (Debruyn et al., 2009), which are several (generally 5) times higher than our values, possibly due to the direct intact with and ingestion sediment of the mussels. The mean BSAFs for BDE 209 were 0.001, 0.009, and 0.0001 in crucian carp, mud carp, and northern snakehead, respectively. These values were consistent with those (0.0002 - 0.002) determined in mudsnails from another e-waste recycling site in South China (Yang et al., 2009). However, the calculated BSAFs for BDE 209 in the present study are generally 1 - 2 orders magnitude lower than our earlier reported values (averages of 0.02 - 0.11) in several marine fish and shrimp species collected from the Pearl River Estuary, South China (Xiang et al., 2007). The much lower BSAF values in the present fish may, at least in part attribute to the great metabolic capacity for BDE 209 in these fish species. All of these fish investigated in the present study are from the carp family, who has been documented to have high metabolic capacity for PBDEs including BDE 209 (Stapleton et al., 2004, 2006). The BSAFs for BDE 209 estimated in the present study are also several orders of magnitude less than those (0.52 - 3.53) reported in marine mussels from coastal British Columbia, Canada (Debruyn et al., 2009). The direct intact with and ingestion sediment, and the generally low metabolic capacity for xenobiotics in invertebrates may account for the much higher BSAFs for BDE 209 in these mussels compared to our fish. The calculated BSAFs for DP in the present fish are smaller than those for the extremely hydrophobic PCBs by a factor of two in the same sample set. However, the BSAFs for DP isomers are comparable to those for BDE 209. Bioaccumulation of HOCs is driven by the hydrophobicity of the chemicals. For HOCs without metabolism, the bioaccumulation potential increases with increasing K OW , but subsequently declines at certain K OW value (e.g., log K OW =7 for PCBs) (Burkhard et al., 2004). Thus, the smaller BSAFs for DP and BDE 209 were partly attributed to the greater K OW s of these chemicals (the log K OW s are 9.3 and 9.7 for DP and BDE 209, respectively) (Li et al., 2008; OxyChem, 2010) compared to those of the investigated PCBs (log K OW of 7.2 - 7.74) (Hawker and Connell, 1988). Further, compared to highly chlorinated PCBs, BDE 209 and DP seem to be more susceptible to enemy attack in fish (Stapleton et al., 2004, 2006; Wu et al., 2010), which may also be attributable, in part, to their reduced BSAFs. The BAFs, defined as the field-observed ratios of the concentration of a given chemical in biota to the concentration in corresponding water, calculated for total DP (in averages of 12200, 7170, and 2000 for mud carp, crucian carp, and northern snakehead, respectively) (Wu et al., 2010) are also lower than those (in averages of 17100 - 531000, 26700 - 940000, and 26500 - 914000 for crucian carp, mud carp, and northern snakehead, respectively) for the extremely hydrophobic PCBs (Wu et al., 2008). This is consistent with the present finding that the bioaccumulation potential of DP is less than PCBs in the three bottom fish species.

Relationship between BSAFs and K OW values of the chemicals: The K OW is one indicator of bioaccumulation potential of HOCs (Fisk et al., 1998). To investigate the influence of K OW of the chemicals on the BSAFs in the investigated fish, linear regression analysis was carried out for relationships between the log K OW values and the BSAFs for DP, the extremely hydrophobic PCBs, and BDE 209. The log K OW values for DP (9.3), the extremely hydrophobic PCBs (7.2 - 7.74), and BDE 209 (9.7) are from OxyChem (2010), Hawker and Connell (1988), and Li et al. (2008), respectively. Despite of the different chemical structures of the three compound classes, a significantly negative correlation between log K OW s and BSAFs was found in crucian carp (r² = 0.94, p = 0.001), mud carp (r² = 0.87, p = 0.007), and northern snakehead (r² = 0.81, p = 0.012). A log K OW value of 11.3 for DP is generated by the US EPA modeling program EPI Suite (Sverko et al., 2011). When the correlation analysis was performed using this value, the BSAFs are also significantly correlated to the log K OW of the investigated chemicals (r² >0.75, p <0.05). The strong correlations between K OW s and BSAFs indicate that hydrophobicity is a key factor conditioning the bioaccumulation of these chemicals in the present fishes. The negative correlations between BSAFs and log K OW s have been also found for very hydrophobic chemicals, e.g., PCBs with log K OW s exceeding seven, due to the decreased bioavailability of these chemicals from water, as well as growth dilution and/or biodegradation by the organism (Burkhard et al., 2004; Wu et al., 2008).

Validity criteria fulfilled:
yes
Conclusions:
Biota-sediment accumulation factors (BSAFs) for DP were found being 0.007, 0.01, and 0.06 for syn-DP, and 0.003, 0.025, and 0.001 for anti-DP in crucian carp, mud carp, and northern snakehead, respectively, suggesting low bioaccumulation potential of DP isomers in these fish.
Executive summary:

The current BSAFs suggest low bioaccumulation potential of DP isomers in bottom fish from the e-waste recycling site. However, field determined BAFs for DP in the same sample set indicated that DP isomers were highly bioaccumulative (BAFs >5000) in most of the samples (Wu et al., 2010). This implies that BSAF may be not a suitable bioaccumulation indicator for DP isomers in highly contaminated site. The syn-DP presents greater BSAFs than the anti-isomer. Compared to the extremely hydrophobic PCBs, both DP isomers showed approximately two orders of magnitude lower BSAF values in the same sample set. However, the BSAFs for DP isomers are comparable to those for BDE 209. The differences in the physiochemical properties (typically K OW ) of the chemicals and metabolism capacity in organisms may contribute to the different BSAFs between the DP isomers, and among the three compound classes (DP, PCBs, and BDE 209).

Endpoint:
bioaccumulation: aquatic / sediment
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
In this field study, birds (five different species) were collected near an e-waste recycling area and muscle, liver and kidney tissue was analyzed for content of flame retardants (including DP). Trophic level of birds was estimated by 15N and 13C analysis.
GLP compliance:
not specified
Details on sampling:
Sampling: Specimens (n = 29) from five bird species, including Ardeidae (Chinese-pond heron, Ardeola bacchus; n = 5), Rallidae (white-breasted waterhen, Amaurornis phoenicurus, n = 11; slaty-breasted rail, Gallirallus striatus, n = 5; ruddy-breasted crake, Porzana fusca, n = 5), and Scolopacidae familes (common snipe, Gallinago gallinago, n = 3), were collected between 2005 and 2007 from Qingyuan County, the second largest e-waste recycling region in the Pearl River Delta. Detailed information about the sampling site and collected bird species is provided in our previous publication. Pectoral muscle, liver, and kidney were excised from the aforementioned birds, which were found dead or dying from various causes (hunting, poisoning, and distress, etc). All tissues were stored at -20 °C until analysis.
Vehicle:
no
Test organisms (species):
other: 5 bird species: Ardeidae (Chinese-pond heron, Ardeola bacchus), Rallidae (white-breasted waterhen, Amaurornis phoenicurus); slaty-breasted rail, Gallirallus striatus); ruddy-breasted crake, Porzana fusca), Scolopacidae familes (common snipe, Gallinago)
Details on test organisms:
Birds were collected between 2005 and 2007 from Qingyuan County, the second largest e-waste recycling region in the Pearl River Delta. Pectoral muscle, liver, and kidney were excised from the birds, which were found dead or dying from various causes (hunting, poisoning, and distress, etc). All tissues were stored at -20 °C until analysis.
Route of exposure:
feed
Test type:
field study
Water / sediment media type:
not specified
Hardness:
not applicable
Test temperature:
no data
pH:
not applicable
Dissolved oxygen:
not applicable
TOC:
not applicable
Salinity:
not applicable
Details on test conditions:
in this field study, birds were collected and analysed for content of flame retardants (including DP) in muscle, liver and kidney tissue. Trophic level of the birds was estimated by 15N and 13C analysis. Birds were living in their natural habitat and found dead or were hunted.
Nominal and measured concentrations:
not applicable, as field study; background concentrations in the habitat of the test birds
Reference substance (positive control):
no
Details on kinetic parameters:
not assessed
Metabolites:
not assessed
Results with reference substance (positive control):
not applicable
Details on results:
Stable Carbon and Nitrogen Isotopic: The stable carbon and nitrogen isotope composition of collected birds was recorded and graphically analysed. The relative trophic status of collected birds, defined by δ 15N, increases in the following order: slaty- breasted rail (7.0‰) < ruddy-breasted crake (8.4 ‰) < common snipe (9.2‰) and white-breasted waterhen (9.2‰) < Chinese-pond heron (10.7‰). This trophic status is consistent with the different feeding habits of bird species. The Chinese pond heron is a piscivorous bird feeding primarily on fish. The white-breasted waterhen eats mainly seeds, insects, and small fish, and they also often forage above ground in low bushes and small trees. The common snipe feeds mainly on aquatic insect and invertebrates in wetland areas. The ruddy-breasted crake feeds mostly on tender shoots, berries, and some aquatic insects. In a given food web, δ 15N and δ 13C are often correlated because foods enriched in δ 15N are often also enriched in δ 13C. In the present study, a positive correlation between δ 15N and δ 13C was found except for the slaty-breasted rail, which has a relatively high δ 13C but low δ 15N, diverging the regression line. This indicates that this bird species has a primary food source different from that of other bird species.
Levels and Profiles of Contaminants: The levels and congener profiles of PBDEs in the muscle of collected birds have been described in detail in our previously published paper. Table 1 presents the reported PBDE concentrations in the muscle samples of these birds, accompanying the data in liver and kidney measured in this study (Table 1). PBDE profile differences between tissues were investigated using ANOVA, which showed no differences. The PBDE congener profiles in the birds in the present study could be classified into three groups according to the predominant congeners. The Chinese pond heron and ruddy-breasted crake are in one group, in which BDE 47 is the predominant congener, similar to the previously acquired results for aquatic birds. The common snipe and seven of the eleven white-breasted waterhens (denoted as WBW1) are in another group, in which BDE 153 is a major contribution congener to the total PBDEs, followed by BDE 183, 99, 154, and 100. The slaty-breasted rail and four other white-breasted waterhens (denoted as WBW2) are in the third group, where BDE 209 is dominant. Interestingly, the white-breasted waterhens have two completely different PBDE profiles. Four of the white-breasted waterhens (WBW2) show similar PBDE profiles to the slaty-breasted rail, which has a completely different diet exposure from other species as revealed by the stable carbon and nitrogen isotope composition data (Figure 1a). We hypothesize that the diet source of the four white-breasted waterhens (WBW2) in which BDE 209 dominated is different from that of the other seven white-breasted waterhens (WBW1). Thus, we reanalyzed the relationship between δ 15N and δ 13C after dividing the white-breasted into two groups. Figure 1b shows that the composition of δ 15N and δ 13C in the four white-breasted waterhens (WBW2 in the Figure 1b), as in the slaty-breasted rail, obviously diverges from the regression line. The correlation coefficient increased from 0.81 to 0.96 and p value decreased from 0.19 to 0.039 after removing WBW2. Compared with WBW1, the δ 13C in WBW2 increased while δ 15N decreased although no significant difference exists. This composition of δ 13C and δ 15N is similar with that of slaty-breasted rail which also show relatively high δ 13C and low δ 15N. Birds in the present study were collected from two adjacent towns in which e-waste recycling activities were conducted. It is very likely that some birds directly consume food items containing BDE 209 at e-waste dumping sites. These BDE 209 containing materials might have different δ 13C and δ 15N (e.g., high δ 13C but low δ 15N) from other food, and they may make a minor contribution to total consuming food by bird. This is a plausible explanation for that the PBDE congener profile in WBW1 is completely different from that of WBW2, but no significant differences were found between WBW1 and WBW2 in δ 13C and δ 15N. Newsome et al. reported that the different PBDE congeners in urban and nonurban peregrine falcons can be attributed to their different dietary compositions. Our results are consistent with their findings, confirming that diet plays a key role in determining PBDE congener profile. Both syn- and anti-DP were detectable in all birds, except for one Chinese pond heron. The DP concentrations ranged from nd - 610, nd - 2200, and nd - 1830 ng/g lw in muscle, kidney, and liver, respectively. The highest DP level was observed in slaty-breasted rail (muscle 14 - 610; liver 55 - 920; kidney 21 - 830 ng/g lw). Generally, the DP concentrations in the studied birds were 1 - 2 orders of magnitude lower than their corresponding concentrations of ΣPBDEs, except for the ruddy-breasted crake, whose DP concentrations were comparable to those of ΣPBDEs (Table 1). DPs have been widely detected in air, dust, sediment, fish, bird, and human serum. DP was detected with the median of 2.4 ng/g ww in herring gull eggs from colonies in the Laurentian Great Lakes. However, there has no report concerning the concentrations of DP in muscle, liver, or kidney. Thus a comparison with the same tissue is impossible in the present study. The fraction of anti-DP (f anti ), defined as the concentration of anti-DP divided by the sum of concentrations of syn- and anti-DP, was 0.70 for DP in commercial products bought from the chemical market. No difference in the f anti between tissues was found in a given bird species (ANOVA). Thus, an overall f anti, not accounting for the tissues, was calculated for the five bird species. The mean f anti for the Chinese pond heron, white-breasted waterhen, common snipe, ruddy-breasted crake, and slaty-breasted rail were 0.34, 0.36, 0.43, 0.46, and 0.61, respectively. These values are all lower than 0.70, indicating a preferential accumulation of syn-DP in biota samples, in line with the reports for DPs in fish samples. Of the three non-PBDE BFRs, PBEB was detected in all samples; PBT was detected in 79% of samples; and BTBPE was detected only in the slaty-breasted rail, ruddy-breasted crake, one white-breasted waterhen, and one common snipe with a detection frequency of 37%. Up to now, litter information was obtained on these non-PBDE BFRs in bird tissues. Gauthier et al. reported that the concentrations of PBEB, PBT, and BTBPE in eggs of herring gulls from the Laurentian Great Lakes were in the range from 0.03 to 1.4, from 0.04 to 0.02, and from 0.04 to 0.26 ng/g ww, respectively. PBEB was used as a FR in the 1970s and 1980s, while PBT has been, and currently is, used as a flame retardant in textiles, polyester resins, and paint emulsions. Information on the current production of PBT and PBEB is not publicly available, but recent studies showed that they are distributed in the environment and are bioavailable in organisms. Although BTBPE has been widely detected in air, sediment, fish, and birds, the low detection frequencies indicate that the environment of the study area might be less subject to this compound contamination. Simple linear correlation analysis revealed that DP significantly correlated with BTBPE and PBDEs, and PBT significantly correlated with PBEB (Table 2). This suggested that DP, BTBPE, and PBDEs may have the same source and/or environmental behavior but different from those of PBT and PBEB. The syn-DP was found to significantly correlate with PBDEs, but this was not the case for anti-DP. This observation is consistent with that in fish collected from a contaminated pond in the study area, confirming that anti-DP has a different behavior from syn-DP in biota.
Tissue Distribution: The ratios of muscle concentration to liver concentration (M/L) and kidney concentration to liver concentration (K/L) were used to analyze the tissues difference of contaminants in bird species. Regardless of whether the concentration was expressed on a wet weight base or a lipid weight base, no significant difference (t-test, p > 0.05) in the concentration of contaminants between kidney and liver was found in all species, except for common snipe, although the K/L ratio varied greatly between less than 1 to larger than 1. In common snipe, the level of PBT was obviously higher in the liver than in the kidney. Based on wet weight, the M/L ratio was less than 1 for all contaminants in all bird species except for PBDEs which have M/L ration larger than 1 in three bird species: Chinese pond heron, slaty-breasted rail, and ruddy-breasted crake. The lipid contents in liver were higher than those in muscle (Table 1) which can partially explain the high concentration in liver. When the concentrations were expressed on lipid weight, the ratios of M/L for PBDEs were larger than 1 in four of the five bird species. Whereas the M/L ratios for PBT and PBEB were less than 1 for all bird species and so were the M/L ratios for syn-DP and anti-DP, except the ruddy-breasted crake. This observation suggested that PBDEs have high accumulation ability in muscle compared with other BFR. This result is consistent with laboratory exposure and field studies, which both reported that the PBDE concentrations in muscle were higher than those in liver for birds.
Correlation with Trophic Level: The relationship between trophic level of the birds and monitored BFRs and DP was examined by regressing the log-normalized concentration of the individual compounds in muscle against δ 15N, with the exception of BTBPE due to its low detection frequencies. The layouts of the biplot of the δ 15N and Ln-normalized concentration of the target compounds were similar to those of the biplots of the δ 15N and the δ 13C (Figure 2, Figure 1b). The slaty-breasted rail and WBW2 diverges the regression line of δ 15N and δ 13C. They also show a different PBDE congener pattern from other birds. These results suggested that the sources of pollutants in these birds are different from other bird. Therefore, slaty-breasted rail and WBW2 were excluded from the analysis. A significant positive correlation between the δ 15N and concentrations of ΣPBDEs, PBEB, and PBT (p < 0.05 in three cases) was found. Trophic magnification of ΣPBDEs and BDE congeners had been reported in both freshwater and marine food webs. The biomagnification of PBDEs and BDE congeners were also observed in a small terrestrial food web composed of birds with different trophic levels. In the present study, the concentrations of ΣPBDEs, BDE47, BDE99, and BDE100 were found to have a significant positive linear correlation with trophic level. Highly brominated congeners such as BDE153, BDE154, BDE183, and BDE196 also showed an increasing trend with increasing trophic level, but the regression was not significant (p-value larger than 0.05). This was due to the decrease in concentration of highly brominated congeners in the Chinese pond heron. These results indicate that most BDE congeners biomagnify with increased trophic level. To the best of our knowledge, there is no information available on the biomagnification of PBT and PBEB through the food web. The significant positive correlations between the concentrations of these two compounds and the δ 15N implied that both PBT and PBEB could be biomagnified through the food web as PBDEs. Therefore, further studies on the ecotoxicology of PBT and PBEB for wildlife or humans are needed. Both syn-DP and anti-DP did not correlated well with the δ 15N (p > 0.05, Figure 2), indicating that no biomagnifications occurred. Only two studies have thus far reported on the trophic transfer of DP in food webs. Biomagnification for anti-DP, but biodilution for syn-DP, was observed in the aquatic food web from Lake Winnipeg. In the food web from Lake Ontario, no statistically significant correlation between the concentrations of both isomers and trophic level was found, which is consistent with the present study. However, both anti-DP and syn-DP have been found to be biomagnified in the food web from a highly contaminated pool in the presently studied region after the removal of the highest trophic-level fish species. The confounding data regarding the trophic transfer of DP can be attributed to many factors, such as the composition of the food web, the contaminated levels of DPs, and the metabolism of DP in the biota. Anti-DP is more susceptible to biological attack than syn-DP due to the fact that the four interior carbons of anti- DP on the cyclooctane are less blocked by chlorines than those of syn-DP. In this way, it has been suggested that the f anti could be related to the biota’s metabolic capacity for DP. The decrease in f anti up the trophic ladder was found in aquatic organisms, indicating that the ability of metabolizing DP increases with trophic level. A same trend for f anti was also observed for the avian species in the present study (Figure 3). The high metabolism of DP in high trophic-level birds may mask the biomagnifications of DP. However, it should be kept in minds that no direct evidence to support the hypothesis that the f anti can reflect the metabolism of DP in biota. Selective uptake and excretion can also result in the change of f anti. Thus, more research on the biodegradation of DP is urgently needed to garner an understanding of the bioaccumulation and trophic transfer of DP.
Reported statistics:
For samples with contaminant concentrations below LOQ, zero was used for the calculations. Concentrations were expressed on a lipid weight basis (LW). To depict the tissue distribution of targets in birds, the concentration ratios of targets in muscle-versus-liver and kidney-versus-liver were calculated and compared with one by t-test. A linear regression analysis between trophic levels and concentrations of target compounds were performed. Data analysis was performed using SPSS for Windows Release 11.5 (SPSS Inc.). Statistical significance was set at p < 0.05 throughout the manuscript.
Validity criteria fulfilled:
yes
Conclusions:
Both syn-DP and anti-DP did not correlated well with the δ 15N (p > 0.05, Figure 2), indicating that no biomagnifications occurred, as no statistically significant correlation between the concentrations of both isomers and trophic level was found. The decrease in f anti up the trophic ladder was found, indicating that the ability of metabolizing DP increases with trophic level. The high metabolism of DP in high trophic-level birds may mask the biomagnifications of DP.
Executive summary:

The present study is primarily designed to examine the role played by dietary sources on polybrominated diphenyl ethers (PBDE) congener profiles in waterbirds collected in an e-waste recycling region in South China. Some emerging halogenated flame retardants (HFRs), such as dechloraneplus (DP), 2,3,4,5,6-pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), were also quantified. Stable isotopes (δ 15N and δ 13C) were analyzed to assess the trophic levels and dietary sources of the birds. PBDEs were found to be the predominant HFRs, followed by DP, PBT, PBEB, and BTBPE. The birds in which BDE209 was predominant have differential δ 13C and δ 15N signatures compared with other birds, suggesting that dietary source is one of the important factors in determining the PBDE congener profile in birds. The levels of ΣPBDEs, PBEB, and PBT were significantly correlated with the trophic level (δ 15N) for avian species which are located in a food chain, indicating the biomagnification potential of these compounds. No correlation was found between DP concentrations and trophic level of the birds and hence no biomagnification. There is a significantly negative correlation between the fraction of anti-DP and δ 15N, suggesting that the metabolic capability of DP in birds increases with the trophic level of the birds.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2013
Reliability:
1 (reliable without restriction)
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was designed to explore the gastrointestinal absorption and tissue-specific bioaccumulation of DP and its dechlorinated analogues in common carp. Therefore, the main objective of the present study was to improve the understanding of the bioaccumulation process of DP. Thus, no BCF or BAF values were reported but tissue specific measurements were undertaken to exploit the tissue specific uptake and depuration pattern while carps were exposed via feed to Dechlorane Plus (DP).
In the present study, common carp (Cyprinus carpio) was exposed to contaminated food pellets for 50 days. The contaminated food was made by known amounts of commercial DP-25 dissolved in cod liver and then mixed with fish food pellets. After the exposure period, a depuration period lasting a further 40 days was designed for the carp, during which the carp were fed with non-spiked food. The purposes of the present study were (1) to investigate gastrointestinal absorption by comparing the concentration and congener profile of DP between spiked food and feces and (2) to investigate the uptake and depuration behaviours of the DP congeners in different carp tissues after exposure to high doses of DP-25 mixtures.
GLP compliance:
not specified
Remarks:
no indication of GLP consideration was provided in the publication
Radiolabelling:
no
Details on sampling:
In March, 2013, forty common carps, approximately 12 cm in length, were purchased from an aquarium market in Guangzhou, China. Four carps were randomly collected as the control group and kept in one glass tank (80 cm x 35 cm x 50 cm). The remaining carp (n = 36) were kept in another glass tank (120 cm x 40 cm x 60 cm) as the treated group. Air stones were placed in the tank to maintain oxygen saturation in the water. The water in each tank was heated to a constant temperature of 22 ±1 °C and circulated using a submersible pump at a rate of 1.5 L/min. Fish were acclimated to the non-spiked diet for a period of 7 days prior to exposure.
Details on preparation of test solutions, spiked fish food or sediment:
Fish were fed food at a rate of 1 percent of their body weight/day based on their weight. Commercial DP-25 (>99 percent purity, particle diameter ≤6 μm, Chlorine content of 65.1 percent and density of 1.8 g/cc) was acquired from Jiangsu Anpon Co., Ltd and cod liver oil was obtained from Peter Moller (Norway). DP-25 was delivered in artificially contaminated food. The DP dose of fish exposed was approximately 1.5 mg per day for each fish. DP-25 mixtures were first dissolved in isooctane and then diluted to the desired concentration with cod liver oil. Then, 1 mL of cod liver oil was mixed with 10 g of fish food pellets (Yangzhou Five-Star Aquatic Products Co., LTD, PR China). Non-spiked food was prepared by mixing food with solute-free cod liver oil. Food was homogenized by mixing in a shaking incubator (24 h, 25 °C). The spiked and non-spiked food was stored in amber containers in a cool, dark place throughout their use. The treated group (36 common carps) was exposed to spiked food for 50 days, followed by non-spiked food for 40 days. The control group was fed a non-spiked diet throughout the experiment. The food was collected on days 5 and 45 (spiked food in uptake period) and on days 55 and 90 (non-spiked food in depuration period).
Test organisms (species):
Cyprinus carpio
Details on test organisms:
Common carp is a kind of freshwater and omnivorous fish. The carp reach sexual maturity in 1 to 3 years and lay eggs.
Route of exposure:
feed
Test type:
static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
50 d
Total depuration duration:
40 d
Hardness:
not described
Test temperature:
22 ±1 °C
pH:
not described
Dissolved oxygen:
kept at saturation
TOC:
not described
Salinity:
not described
Details on test conditions:
Air stones were placed in the tank to maintain oxygen saturation in the water. The water in each tank was heated to a constant temperature of 22 ±1 °C and circulated using a submersible pump at a rate of 1.5 L/min. Fish were acclimated to the non-spiked diet for a period of 7 days prior to exposure. Fish were fed food at a rate of 1 percent of their body weight/day based on their weight. Commercial DP-25 (>99 percent purity, particle diameter ≤6 μm, Chlorine content of 65.1 percent and density of 1.8 g/cc) was acquired from Jiangsu Anpon Co., Ltd and cod liver oil was obtained from Peter Moller (Norway). DP-25 was delivered in artificially contaminated food. The DP dose of fish exposed was approximately 1.5 mg per day for each fish. DP-25 mixtures were first dissolved in isooctane and then diluted to the desired concentration with cod liver oil. Then, 1 mL of cod liver oil was mixed with 10 g of fish food pellets (Yangzhou Five-Star Aquatic Products Co., LTD, PR China). Non-spiked food was prepared by mixing food with solute-free cod liver oil. Food was homogenized by mixing in a shaking incubator (24 h, 25 °C). The spiked and non-spiked food was stored in amber containers in a cool, dark place throughout their use. The treated group (36 common carps) was exposed to spiked food for 50 days, followed by non-spiked food for 40 days. The control group was fed a non-spiked diet throughout the experiment.
Nominal and measured concentrations:
The DP dose of fish exposed was approximately 1.5 mg per day for each fish.
Reference substance (positive control):
no
Details on kinetic parameters:
Uptake and depuration kinetics of DP in fish tissues: The uptake and depuration kinetics of DP in the serum, muscle, liver, and gonad were investigated. The four chemicals (anti-DP, syn-DP, anti-Cl11-DP and syn-Cl11-DP), except for syn-Cl11-DP in the serum, were detected in all target tissues. All chemicals exhibited linear accumulation kinetics in serum (r² = 0.88, r² = 0.84 and r² = 0.69 for anti-DP, syn-DP and anti-Cl11-DP, respectively) and muscle (r² = 0.84, r² = 0.81, r² = 0.84 and r² = 0.81 for anti-DP, syn-DP anti-Cl11-DP and syn-Cl11-DP, respectively) samples during the uptake period (Fig. 2a and b) and reached the highest concentrations at the end of the uptake period (50th day). No steady state was observed in the serum or muscle for any chemical during the 50-day exposure. Depuration of the chemicals in both muscle and serum showed an initial rapid depuration for the first 10 days followed by a fluctuating depuration over the remainder of the experiment. No obvious trend towards a decrease was found in the last 30 days of the depuration.
The uptake kinetics of DP and their dechlorinated analogs in the liver and gonad were not linear (Fig. 2c and d). The concentrations in the gonad showed co-variation with those in the liver with the 5-day hysteresis during the uptake period. This hysteresis in the gonad might be attributed to maternal transfer of DP in fish. The depuration curves of DP in the liver showed 2-stage elimination kinetics, with an initial decrease to day 70, followed by a slight increase. The concentrations of DP and their analogs fluctuate and follow a zigzag pattern in the depuration. This unique accumulation pattern of DP in the gonad of carp could be because gonads collected in different individuals may be in different stages of embryonic development as some of the DP was determined in fish ovaries and some was determined in fish eggs. It remains unclear as to why no linear uptake occurred in the liver in the uptake period and accumulation in the liver was still occurring at the end of the experiment.
Metabolites:
To evaluate whether dechlorination occurred in fish, the concentration ratios of dechlorinated analogues to their parent compound were calculated for muscle (the predominant tissue for DP deposition). This result indicated that the ratio for syn-isomer and anti-isomer showed a decreasing trend in the depuration period and suggested that dechlorinated analogues are eliminated more rapidly than their corresponding parent chemicals. This result did not support the dechlorination metabolism of the 2 DP isomers in fish. However, f anti and f anti-Cl11 in fish were lower than those in the commercial DP mixture, and the uptake efficiency of anti-isomer was higher than those of the syn-isomer, thereby strongly suggesting the selective degradation of anti-isomers in fish. Thus, a metabolic pathway other than dechlorination, such as hydroxylated metabolism, may occur and more studies are needed to investigate this issue.
Results with reference substance (positive control):
not applicable
Reported statistics:
All statistical analyses were conducted using PASW Statistics 18.0 to test for the inter-tissues variability of DP levels and isomer compositions. DP concentrations determined in fish tissues were not normalized to total lipid content, due to higher variations of these concentrations when normalized to lipid content.

Background levels and quality control: After the 90-d experiment, the length of common carp was 12.4 ±0.8 cm, which did not change significantly compared to days 1 (12.1 ±0.6 cm) (p <0.05). No mortality was observed during the experiment. Procedural blanks covering the whole procedure were performed in parallel with the samples at each batch extraction. Anti-DP was detected in the blanks, but syn-DP, anti-Cl10-DP, syn-Cl11-DP, and anti-Cl11-DP were not detected in the blanks. The method detection limit (MDL) was defined as the mean value plus 3-fold standard deviation for anti-DP detected in the procedural blanks (n = 7). For syn-DP, anti-Cl10-DP, syn-Cl11-DP, and anti-Cl11-DP, which were not detected in blanks, a signal-to-noise ratio of 10 was set as the MDL. The MDLs for syn-DP, anti-DP, anti-Cl10-DP, syn-Cl11-DP, and anti-Cl11-DP were between 0.02 and 0.11 ng/g wet weight (ww) in fish tissues, and between 0.18 and 0.47 ng/g dry weight (dw) in food and feces. The recoveries of BDE 181 for all samples (n = 112) ranged from 80 percent to 128 percent. During the 90-day experiment, no anti-Cl 10-DP, syn-Cl11- DP, or anti-Cl11-DP were detected in the control fish tissues or the non-spiked food. Both anti-DP and syn-DP were detected in control fish tissues and the non-spiked food. The average concentrations of syn-DP and anti-DP in control fish tissues were 19 ±12 pg/g and 34 ±26 pg/g (ww) and 0.52 ±0.38 ng/g and 1.5 ±1.1 ng/g (dw) in non-spiked food, respectively. These levels were several orders of magnitude lower than those of the dosed fish and the spiked food.

Gastrointestinal absorption and fecal excretion of DP congeners: Syn-DP, anti-DP, syn-Cl11-DP, and anti-Cl11-DP were detected in 100 percent of the food and fecal samples while no anti-Cl10-DP was detected. The average concentrations of syn-DP, anti-DP, syn-Cl11-DP, and anti-Cl11-DP in the spiked food were 2071 ±24, 7826 ±1031, 4.0 ±0.3, and 33.5 ±0.4 ng/g (dw), respectively. The concentrations of DP congeners in feces collected in the uptake period were in the range of 1.5 - 8.2-fold compared to that in the administered food. A ratio of the chemical concentration in the feces to that in the food is directly related to the chemical absorption and excretion in the gut if the chemicals are not metabolized by endogenous enzymes in the gastrointestinal system. The higher the ratio, the lower the absorption efficiency or the higher excretion efficiency is. The concentration ratios of feces to food in the uptake period were in the range of 1.55 - 4.98 for syn-DP, 1.53 - 4.31 for anti-DP, 1.86 - 8.26 for syn-Cl11-DP and 1.53 - 6.31 for anti-Cl11-DP. The ratios of feces to food for syn-DP were slightly higher than those for anti-DP in each sampling in the uptake period except for the 50-day sampling (p <0.05). Similar results were also seen between syn-Cl11-DP and anti-Cl11-DP (p <0.05). These phenomena imply that the absorption efficiencies of anti-isomers in the gastrointestinal system were higher than those of the syn-isomers. In the study of Tomy et al., 2008, accumulation rate of syn-DP was found to be faster than that of anti-DP in juvenile rainbow trout. Obviously, the difference in gastrointestinal absorption rate between the two isomers cannot be responsible for stereoselective accumulation of syn-DP in fish given that anti-DP rather than syn-DP were absorbed more efficiently through the gut. The concentrations of four chemicals in the feces collected in the 60-day (the first feces sample for the depuration period) sharply decreased by 1 order of magnitude compared to the feces in the uptake period. An exponential decrease trend of concentration of target chemicals over the depuration period was observed (Fig. 1b). To evaluate the differences in excretion rate between syn- DP and anti-DP, a ratio of feces to food (non-spiked food) was calculated (Fig. 1b). The calculated result indicated that there were no systematic differences in the ratio of feces to food between syn-DP and anti-DP (p <0.05), indicating no stereoselective excretion for DP in common carp. The congener profile of DP can be expressed by the fractions of the anti-isomer (f anti : ratio of anti-DP concentration to total concentration of anti-DP and syn-DP; f anti-Cl11 : ratio of anti-Cl11-DP concentration to total concentration of anti-Cl11-DP and syn-Cl11-DP). f anti in the spiked food was 0.791 ±0.02, which was slightly higher than those in feces collected in the uptake period (range: 0.765 - 0.787; mean, 0.775) except for at 50 days (0.850). The f anti-Cl11 in the spiked food was 0.893, which was also higher than that in feces in the uptake period (range: 0.853 - 0.873; mean, 0.866) except for at 50 days (0.920). These results further confirm that syn-isomers have lower absorption efficiencies or higher elimination efficiencies than anti-isomers in the gut. f anti and f anti-Cl11 were significantly lower in feces in the depuration period than in feces in the uptake period and in the spiked food (p <0.05), indicating anti-isomers have been selectively metabolized in common carps.

Uptake and depuration kinetics of DP in fish tissues: The uptake and depuration kinetics of DP in the serum, muscle, liver, and gonad were investigated. The four chemicals (anti-DP, syn-DP, anti-Cl11-DP and syn-Cl11-DP), except for syn-Cl11-DP in the serum, were detected in all target tissues. All chemicals exhibited linear accumulation kinetics in serum (r² = 0.88, r² = 0.84 and r² = 0.69 for anti-DP, syn-DP and anti-Cl11-DP, respectively) and muscle (r² = 0.84, r² = 0.81, r² = 0.84 and r² = 0.81 for anti-DP, syn-DP anti-Cl11-DP and syn-Cl11-DP, respectively) samples during the uptake period (Fig. 2a and b) and reached the highest concentrations at the end of the uptake period (50th day). No steady state was observed in the serum or muscle for any chemical during the 50-day exposure. Depuration of the chemicals in both muscle and serum showed an initial rapid depuration for the first 10 days followed by a fluctuating depuration over the remainder of the experiment. No obvious trend towards a decrease was found in the last 30 days of the depuration. There are no previous studies regarding DP uptake and clearance curves in the fish serum, but the DP uptake and clearance curves in the muscle observed in the present study were similar to results reported by other researchers during bioaccumulation studies of hydroponic contaminants in fish (Fisk et al., 1998; Tomy et al., 2004). The uptake kinetics of DP and their dechlorinated analogs in the liver and gonad were not linear (Fig. 2c and d). The concentrations in the gonad showed co-variation with those in the liver with the 5-day hysteresis during the uptake period. This hysteresis in the gonad might be attributed to maternal transfer of DP in fish. The depuration curves of DP in the liver showed 2-stage elimination kinetics, with an initial decrease to day 70, followed by a slight increase. The concentrations of DP and their analogs fluctuate and follow a zigzag pattern in the depuration. This unique accumulation pattern of DP in the gonad of carp could be because gonads collected in different individuals may be in different stages of embryonic development as some of the DP was determined in fish ovaries and some was determined in fish eggs. It remains unclear as to why no linear uptake occurred in the liver in the uptake period and accumulation in the liver was still occurring at the end of the experiment. Enterohepatic circulation and redistribution of lipophilic contaminants can affect liver concentrations and ultimately give rise to complex uptake and depuration kinetics (Roberts et al., 2002). Additionally, the potential metabolism of DP and analogs in the liver and the high variation in the concentrations between individual fish could also contribute to the complex uptake and depuration kinetics. Moreover, during the experimental period, the undulating tissue concentrations of DP isomers and Cl11-DP isomers could be partly due to the individual variation. Meanwhile, based on the research of Tomy et al., 2008, which reported half-lives of DP in the 40 to 50 day length, so the depuration phase (40 d) of the present experiment was not long enough. This is probably a major contributor to the inability for us to find a significant elimination rate. The mean assimilation efficiencies of syn-DP, anti-DP, syn-Cl11-DP, and anti-Cl11-DP calculated from days 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 were estimated to be 3.8 percent, 3.2 percent, 20.4 percent, and 14.8 percent, respectively. These assimilation efficiencies of DP isomers were comparable to those (6.0 percent for syn-DP and 3.9 percent for anti-DP) determined in juvenile rainbow trout (Tomy et al., 2008). Meanwhile, the assimilation efficiencies of syn-isomers were significantly higher than those of anti-isomers (p <0.05). However, the ratios of feces to food indicate that the uptake efficiencies of syn-isomers were lower than those of the anti-isomers. Therefore, the relatively low assimilation efficiencies of anti-isomers could be attributed to stereoselective metabolism of anti-isomers in carp. This is also consistent with the structural conformation of the isomers as it has been suggested that because of the configuration of the pendant chlorocyclopentane moieties, the anti-isomer would be more susceptible to biological attack (Tomy et al., 2008).

Dynamic tissue distribution and isomer composition: The concentrations of DP and the analogs in the liver were higher than those in the muscle, serum, and gonad throughout the experiment (p <0.1) (Fig. 3). Lipid content is not a cause for this tissue distribution because the lipid contents in the liver (1.70 ±1.56 percent) were significantly lower than those in the muscle (3.39 ±1.69 percent) and the gonad (3.71 ±1.96 percent). This result indicates that DP and analogs prefer to accumulate in the liver than in other tissues, which is consistent with that reported by Li et al., 2013a and is also in line with reports on other highly halogenated flame retardants (Guvenius et al., 2002; Iwata et al., 2004). In Chinese sturgeon, liver also showed higher dechlorane concentrations than muscle and adipose tissue (Peng et al., 2012). Sequestration of DP isomers by hepatic proteins could be a cause for their disposition in the liver although this was not identified (Li et al., 2013b). Exposure to xenobiotic pollutants such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzo-furans, and coplanar PCBs may induce hepatic binding proteins leading to hepatic sequestration of the compounds (Kubota et al., 2004). A dynamic tissue distribution for DP and its analogs among tissues was observed. At the start of exposure, the concentration ratios of the liver to other tissues were the highest, and then the ratio exponentially decreased over time to close to or slightly lower than 1 at the end of the experiment (Fig. 3). This result indicated that the liver is the first organ to which contaminants deposit after absorption from the gastrointestinal tract in fish. This result was consistent with a study on the tissue distribution of PBDEs in 2 predatory fish species (Zeng et al., 2013). In that study, the liver was found to readily achieve equilibrium with the serum while the muscle did not until the end of the experiment, using a tissue fugacity comparison. The muscle is the main organ for contaminant deposition. The percentage of DP and analogs in the muscle was greater than 60 percent during the entire experimental period. This is because the muscle is the largest tissue in volume in fish, despite its low concentration. The percentage in the muscle increased over time and reached the maximum at the 75th day (95 percent), and then a decreasing trend was seen until the end of the experiment. A concomitant decrease in the liver from 23 percent at the 5th day to 3 percent at the 75th day was observed. The gradual accumulation of contaminants occurring in the muscle was the main reason for the above observation. The decreased proportion in the muscle along with a corresponding increase in the liver in the last 15 days of the experiment implies a redistribution of DP and analogs among tissues. A non-regular trend was found for the gonadal proportion during the whole experiment, and this may be due to the variations in the number of gonads between individual fish. DP and analogs in the gonad accounted for 2 percent to 20 percent of the total amount in fish with most cases being greater than 5 percent. Meanwhile, the concentration of DP and analogs in the gonad was higher than that in the muscle (p <0.05), which is consistent with the report of Peng et al. (2012), where the ratio of the chemical concentration in the eggs to those in the maternal tissues was greater than 1. These results indicate that DP and analogs readily underwent maternal transfer. Considering the fact that a high content of the pollutant usually exhibits a significant development toxicity to naturally hatched larvae (Abdelouahab et al., 2009), such a high accumulation of DP and Cl11-DP in the gonad suggests that the maternal transfer of DP congeners and the corresponding adverse effects for larvae should be elucidated further. The isomer composition of DP and analogs also showed tissue-specific and dynamic changes over time (Fig. 4). In the early stage of the uptake experiment (from day 0 to the 20th day), f anti and f anti-Cl11 values in tissues were lower than those in the commercial DP mixtures, indicating a preference for syn-isomers. f anti and f anti-Cl11 values then increased over time until they were close to those in commercial DP mixtures, especially f anti in the serum. Serum accumulated more syn-DP than anti-DP compared with other tissues while the liver showed a preference for anti-DP to syn-DP compared with other tissues in the early stage of the experiment. The fact that the liver preferred anti-DP to syn-DP was in line with the results of a rat exposure experiment (Li et al., 2013a). The greatest deviation of f anti between the serum and liver reached 0.09 (0.70 vs. 0.79). However, in the late stage of the experiment, the larger deviation of f anti between different tissues disappeared and no significant differences were found between different tissues (p >0.1). These results indicate that the isomer-specific accumulation of DP is a very complex and multi-factorial process. In the current state, it was not possible to provide a detailed mechanism for this accumulation. Using rats exposed to different doses of DP, Li et al., 2013a found that no stereoselective accumulation was seen in the low dose exposure group, whereas a selective accumulation of syn-DP was observed in the high dose exposure group. This result indicates that the f anti value in rat was dose-dependent. Tissue-specific f anti has been reported in several previous studies. Zhang et al., 2011 reported that the brain of mud carp has a high affinity for anti-DP. Peng et al., 2012 recently reported the tissue distribution of DP in Chinese sturgeon. They found that the f anti in maternal tissues was significantly higher than that in eggs, while f anti-Cl11 in maternal tissue was significantly lower than that in eggs. Meanwhile, f anti in heart, intestine, and gonad were lower than those in the muscle and liver. Combining these results with our finding, the factors determining the isomer composition of DP in biota were DP concentration, different affinity for isomers in different tissues, and reaching equilibrium between the biota and the environment. To evaluate whether dechlorination occurred in fish, the concentration ratios of dechlorinated analogs to their parent compound were calculated for muscle (the predominant tissue for DP deposition). This result indicated that the ratio for syn-isomer and anti-isomer showed a decreasing trend in the depuration period and suggested that dechlorinated analogs are eliminated more rapidly than their corresponding parent chemicals. This result did not support the dechlorination metabolism of the 2 DP isomers in fish. However, f anti and f anti-Cl11 in fish were lower than those in the commercial DP mixture, and the uptake efficiency of anti-isomer was higher than those of the syn-isomer, thereby strongly suggesting the selective degradation of anti-isomers in fish. Thus, a metabolic pathway other than dechlorination, such as hydroxylated metabolism, may occur and more studies are needed to investigate this issue.

Conclusion: In summary, dynamic tissue-specific accumulation of DP isomers was observed in common carp under laboratory conditions. The higher absorption efficiencies but the lower assimilation efficiencies of anti-isomers indicated a stereoselective metabolism of anti-isomer in common carp. A dynamic tissue distribution with an increasing proportion in the muscle along with a decreasing proportion in the liver over time was observed. The isomer composition of DPs and their dechlorinated analogs also exhibited tissue specificity and dynamic changes over the experimental period. Our result suggests that isomer-specific accumulation of DPs and their dechlorinated analogs in fish is a complex and multi-factorial process.

Validity criteria fulfilled:
not applicable
Conclusions:
The higher absorption efficiencies but the lower assimilation efficiencies of anti-isomers indicated a stereoselective metabolism of anti-isomer in common carp. A dynamic tissue distribution with an increasing proportion in the muscle along with a decreasing proportion in the liver over time was observed. The isomer composition of DPs and their dechlorinated analogs also exhibited tissue specificity and dynamic changes over the experimental period. The result suggests that isomer-specific accumulation of DPs and their dechlorinated analogs in fish is a complex and multi-factorial process. No BCF or BMF values were derived in the publication, as no steady-state conditions were achieved after 50 days exposure period.
Executive summary:

In the present study, common carp (Cyprinus carpio) was exposed to known amounts of commercial Dechlorane plus (DP) DP-25 under laboratory conditions. The gastrointestinal absorption and tissue-specific bioaccumulation of DP and its dechlorinated analogs in common carp were investigated. The higher absorption efficiencies but lower assimilation efficiencies of anti-isomers indicated isomer-selective metabolism of anti-isomers in fish. Linear uptake curves were seen in serum and muscle, but the depuration curves for all the four tissues (muscle, serum, liver and gonad) did not follow the first-order kinetics. The liver exhibited a high affinity for anti-isomers during the experiment. Other tissues, such as serum, muscle, and gonad, showed a selective accumulation of syn-DP in the early stages of the experiment, particularly the serum. However, the deviation of f anti between different tissues disappeared at late stages of the experiment, and the f anti values in all tissues were close to that in commercial mixtures. The results suggest that the bioaccumulation of DP is a complex and multi-factorial process.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1973
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Although no standard guideline was followed (none were available in 1973) the study followed basic scientific principles available at that time. However, using 1% acetone in water as vehicle to maintain a dechlorane plus concentration of 0.1 ppm is uncommon and not realistic, but almost certainly has increased bioavailability above natural levels and maybe also absorption. In addition no steady state was observed and thus the results may be seen with caution.
Qualifier:
no guideline followed
Principles of method if other than guideline:
20 healthy juvenile bluegill sunfish of 2 - 6 grams weight were exposed to Dechlorane Plus 515 at a nominal concentration of 1 ppm in a static system for 30 days. Mortality and behavioural changes were recorded. Samples of fish and water were analysed for test substance concentration at regular intervals.
GLP compliance:
no
Remarks:
pre-dates GLP
Radiolabelling:
no
Details on sampling:
At 0, 7, 14, 21, and 30 days, samples of fish were taken from the bioassay vessel. At each interval, 4 fish were taken and killed with a sharp blow to the skull, blotted dry, rinsed in deionized water for a period of 10 seconds, blotted dry, then rinsed in acetone for a period of 10 seconds, and blotted dry again. Each sampling of fish was then held frozen for analysis.
Water samples were taken at same times and refrigerated until all samples were available for analysis.
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
Bioassay vessels were filled with 125 liters reconstituted water and a calculated amount of each test material (0.125 gms) was slowly dispensed into the respective bioassay vessel while the water was stirred vigorously. Dechlorane Plus 515 was added in the form of 1.0% (w/v) suspensions in acetone. A group of 20 fish was then added to each bioassay vessel. Following the introduction of the fish, each bioassay vessel was observed for a period of 30 days during which time any mortalities and/or untoward behavioral reactions were recorded. Throughout the entire 30-day test period, the water in each bioassay vessel was aerated.
All stock tanks and bioassay vessels contained reconstituted water. The following compounds were added in the amounts stated per liter of deionized water: 30 mg calcium sulfate, 30 mg magnesium sulfate, 48 mg sodium bicarbonate, 2 mg potassium chloride.
Test organisms (species):
Lepomis macrochirus
Details on test organisms:
Bluegill sunfish (Lepomis macrochirus) with an average weight of 2 to 6 grams were used as test species. All of the fish were kept under observation for general health and suitability as test animals for a period of not less than 28 days prior to experimental use. The fish were held in stock tanks at
a temperature of 18 °C and fed live daphnia or Purina Trout Chow #2. The stock tanks and bioassay vessels contained reconstituted water. The following compounds were added in the amounts stated per liter of deionized water: 30 mg calcium sulfate, 30 mg magnesium sulfate, 48 mg sodium bicarbonate, 2 mg potassium chloride.
Route of exposure:
aqueous
Test type:
static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
30 d
Hardness:
no data available in report
Test temperature:
18 °C in tanks
pH:
no data available in report
Dissolved oxygen:
not measured but tanks were aerated throughout exposure period. Thus oxygen saturation is assumed.
TOC:
no data available in report
Salinity:
no data available in report
Details on test conditions:
A 1 ppm concentration of Dechlorane plus was targeted for based on pre-test results, by adding 0.125 grams Dechlorane plus as 1% suspension in acetone to the reconstituted water (bioassay vessels with 125 liters), while the water was stirred vigorously. The actual concentration in water/acetone was measured prior to addition of test substance, and 7, 14, 21 and 30 days after addition of the fish.
Reference substance (positive control):
no
Details on estimation of bioconcentration:
Magnification factors were calculated by dividing the concentration of DP found in fish (mean of 4 fish) through the concentrations found in water at the same time of measurement.
Key result
Type:
BMF
Value:
2 907
Basis:
whole body w.w.
Time of plateau:
30 d
Calculation basis:
steady state
Remarks on result:
other: only two measured fish conc. values (at days 21 and 30) were in the same range and thus the steady state condition is not absolutely confirmed.
Remarks:
Conc.in environment / dose:1 ppm (nominal)
Elimination:
not specified
Details on kinetic parameters:
no data
Metabolites:
not investigated
Results with reference substance (positive control):
not applicable
Details on results:
Results on DP concenntrations in water and fish:
Day 0: Water conc. <0.0001 ppm, fish conc. <0.010 ppm (blank, prior to addition of test substance)
Day 7: Water conc. 0.046 ppm, fish conc. 6.03 ppm, BMF: 131
Day 14: Water conc. 0.014 ppm, fish conc. 7.80 ppm, BMF: 557
Day 21: Water conc. 0.001 ppm, fish conc. 8.78 ppm, BMF: 8780
Day 30: Water conc. 0.003 ppm, fish conc. 8.72 ppm, BMF: 2907
Reported statistics:
no statistics performed

No deaths or untoward behavioral reactions were noted among the fish that were exposed to 1.0 ppm Dechlorane Plus 515.

An algal bloom occurred in each bioassay vessel during the second week on test. This was due in part to the fact that the tanks were set up beneath a combination of Durotest (Optima) and wide spectrum Grow-lux fluorescent bulbs. This light source stimulated the algal bloom in each tank. The results of the Dechlorane Plus determinations in water and fish are presented in details on results section. The limit of sensitivity of the method for water was determined to be 0.0001 ppm and for the fish, 0.010 ppm. The test data showed that the fish accumulated Dechlorane Plus rapidly such that equilibrium was reached after 7 days of exposure. The accumulated concentrations remained within 7-9 ppm for Dechlorane Plus over the additional 21 days of exposure. The magnification factors presented in each table are computed by dividing the concentration found in each fish sample by the concentration of the corresponding water sample. Although the initial water concentration was 1.0 ppm for each Dechlorane, the experimentally determined concentrations were below that value. The reason for this could be due to the fact that the solubility of these compounds in water is less than 1 ppm and that the values obtained are representative of the amount of each compound actually dissolved in the water. Also, adsorption to the organic matter such as the algae could have decreased the experimental concentration.

Although it was indicated by Hooker that Dechlorane Plus was considered to be 100% pure, two GC peaks were observed from chromatographing the material. The reason given for this behavior was hypothesized by Hooker to be due to thermal degradation of the compound at GC temperatures. Application of thin layer chromatography (TLC) and alternate column gas chromatography, however, proved that two discreet components were present. Using thin layer chromatography it was possible to obtain two spots on the TLC plate. Isolation of each portion followed by solvent elution gave two solutions which contained a single component as determined by GC. The retention time of each component matched exactly the retention time of the respective component in the Standard Dechlorane Plus. Using a 6‘ x 0.25" 1.5% OV-17/1.95% QF-1 it was possible to separate the peaks completely. Infrared analysis of each component was also obtained, but due to the small amount of material isolated, definitive differences could not be obtained. However, the evidence gathered suggests the presence of a synthesis by-product or contaminant and not a GC decomposition product or other artifact (comment: meanwhile it is known that the two peaks observed are due to the syn- and anti-conformer of Dechlorane Plus).

Recovery data for the Dechloranes from fortified fish samples were 96% for Dechlorane Plus 25. Fortification levels were at 0.01, 0.10, and 1.00 ppm. The limit of sensitivity of the method was determined to be 0.01 ppm for each Dechlorane.

Validity criteria fulfilled:
not applicable
Remarks:
no standard test model at that time available
Conclusions:
At a conc. of 1 ppm Dechlorane plus in water (nominal, using acetone as dispenser) concentration of DP in fish rapidly increased during the exposure period whereas, stabilising in the range of 7.8 - 8.8 ppm from day 14 on til day 30 (end of exposure period). However, the conc. in water significantly decreased durig the exposure period. A steady state was achieved strictl spoken only at the last two time points of measurement and thus can't be considered reliable. The biomagnification reached 2907 at day 30.
Executive summary:

No deaths or untoward behavioral reactions were noted among the fish that were exposed to the Dechloranes. All three test materials showed a significant increase in total body concentrations. Dechloranes Plus increased from less than 0.010 ppm to 8.8 ppm respectively during the test period. Concentration in fish appeared rather stable from day 14 on with 7.80 ppm on day 14, 8.78 ppm on day 21 and 8.72 ppm on day 30. However, fluctuation of DP conc. in water (due to measurement at concentrations much higher than water solubility) led to a high variation in biomagnification factors calculated (557, 8780 and 2907, respectively).

The procedure developed for the determinaton of Dechlorane residues in fish included a solvent extraction followed by a sulfuric acid cleanup of the extract. An additional florisil column cleanup was found necessary. Quantitation was made by EC-GLC.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2007 - 2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
method for BMF calculation not described but other than that in line with OECD 305 protocol.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)
Deviations:
no
Principles of method if other than guideline:
Method for BMF calculation not described but other than that in line with OECD 305 protocol.
GLP compliance:
not specified
Remarks:
not reported in publication
Radiolabelling:
no
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
Three batches of food were prepared in this study: two of the batches (1.9 kg each) were spiked with a known amount of syn- and anti-DP (3.6 mL of 50 µg/mL). whereas no isomer was added to the third batch (control). Food was stored in the dark at -4 °C to limit the possibility of light-induced degradation of DP. Using the analytical techniques described below, control corrected lipid based concentrations of (arithmetic mean ±1 x standard error) of syn- and anti-DP in the food were determined to be 0.79 ±0.03 (n = 3), 1.17 ±0.12 µg/g (n = 3), respectively. Small amounts of the syn-DP were detectable in the unfortified food (1.5 ng/g). Average percent lipid in the food was determined to be 14.3 ±0.3%. Concentrations of neither DP isomer declined in the food from the start of the exposure experiment (day = 0) to the end of the clearance phase (day = 161). A control group was fed unfortified food (however, small amounts of 1.5 ng syn-DP/g feed were detected therein). Four fish were sampled on days 0, 7, 14, 21, 35, and 49 of the uptake and on days 7, 22, 35, 49, 70, and 112 of the depuration period and analytical determined concentrations were corrected for lipid content and recovery (using BDE-77, -126, -197, and -207). Biomagnification factors of 5.2 and 1.9 were determined for syn- and anti-DP, respectively.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
Juvenile rainbow trout (initial mean weights, 50 ±5 g) were fed spiked food for 49 days, followed by untreated food for 112 days. The daily feeding rate was equal to 1.0% of the mean weight of fish, adjusted after each sampling period based on the mean weight of the subsample of fish that were sacrificed. Feed was presented by sprinkling at the surface of the water and was generally consumed by each group offish within 1 min. Sixty fish were used for each treatment and each treatment was held in separate 200 L fiberglass aquaria receiving 0.3 L UV and carbon dechlorinated Winnipeg city tap water/min (12 °C. pH 7.9 - 9.1). The dissolved oxygen was always at the level of saturation. A 12 h light:12 h dark photoperiod was maintained throughout the experiment. Four fish were sampled from each tank on days 0, 7, 14, 21, 35, and 49 of the uptake period and on days 7, 22, 35, 49, 70, and 112 days of the depuration period. Fish were always sampled 24 h after the previous feeding. Sampled fish were euthanized with an overdose (0.8 g/L) of pH buffered MS-222. After fin movement ceased (<3 min), liver was dissected from each fish. Livers were frozen immediately on dry ice and later held at -90 °C until analysis. Whole body minus the liver was used for calculation of bioaccumulation parameters.
Route of exposure:
feed
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
49 d
Total depuration duration:
112 d
Hardness:
not reported
Test temperature:
12 °C
pH:
7.9 - 9.1
Dissolved oxygen:
at level of saturation
TOC:
not reported
Salinity:
not reported
Details on test conditions:
Fish were maintained in a 12h light/12h dark period throughout the entire period of the experiment.
Nominal and measured concentrations:
0.79 µg/g lipid in food for syn-form of DP and 1.17 µg/g lipid in food of anti-form of DP.
A third control group received unfortified food.
The lipid content of food was determined as 14.3 ±0.3%.
Daily feeding rate was 1% of fish mean weight.
Reference substance (positive control):
no
Lipid content:
6.9 %
Time point:
end of exposure
Remarks on result:
other: measured on day 49 for anti-DP exposure
Lipid content:
7.5 %
Time point:
end of exposure
Remarks on result:
other: measured on day 49 for syn-DP exposure
Lipid content:
7.3 %
Time point:
other: end of depuration
Remarks on result:
other: measured on day 161 for syn- and anti-DP
Key result
Type:
BMF
Value:
5.2 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks:
not reached
Remarks on result:
other: syn-form of DP
Remarks:
Conc.in environment / dose:0.79 ± 0.03 µg/g, lipid weight, of syn-Dechlorane Plus
Key result
Type:
BMF
Value:
1.9 dimensionless
Basis:
whole body w.w.
Calculation basis:
steady state
Remarks:
not reached
Remarks on result:
other: anti-form of DP
Remarks:
Conc.in environment / dose:1.17 ± 0.12 µg/g, lipid weight, of anti-Dechlorane Plus
Key result
Elimination:
yes
Parameter:
other: half-life of syn-form
Depuration time (DT):
53.3 d
Key result
Elimination:
yes
Parameter:
other: half-life of anti-form
Depuration time (DT):
30.4 d
Details on kinetic parameters:
The uptake and clearance kinetics of the DP isomers were also assessed in the liver. Regression analysis suggested that the uptake for both isomers in the liver was linear (syn-: r²= 0.7145, p= 0.03; anti-: r²=0.7119, p= 0.03) . Respective uptake rates of the syn- and anti-isomers in the liver were 0.065 ±0.020 and 0.024 ±0.008 nmoles per day. Similar uptake rates were observed in the carcass.
Depuration of the isomers from the liver did not follow first order kinetics. That the isomers of DP have similar chemical properties to other highly halogenaled bioaccumulative flame retardants i.e., high Kow, potentiates the retention of the isomers in lipid rich tissues. Enterohepatic circulation and redistribution of lipophilic contaminants can affect liver concentrations and ultimately give rise to complex deputation kinetics. This may partly explain the deputation profiles of the isomers we observe in the liver.
Metabolites:
Although a purposely large dosing regime was employed in the study, no DP-metabolites were detected in the liver.
Results with reference substance (positive control):
no positive control used
Details on results:
Bioaccumulation Parameters in Fish Carcass: Bioaccumulation parameters of DP-isomers from dietary exposure using juvenile rainbow trout are shown in the followig table:

uptake rates (mmol/day) depuration rate constant (kd) x 0.01/d half-life t1/2 (d) BMF
syn- 0.045 ± 0.005 0.013 ± 0.003 53.3 ± 13.1 5.2
anti- 0.018 ± 0.002 0.023 ± 0.004 30.4 ± 5.7 1.9

Both isomers were detectable in the fish after 7 days of exposure. The appearance of both uptake curves suggests that neither isomer reached steady state in fish even after 49 days of exposure. Only the syn-isomer accumulated in the fish in a linear manner throughout the duration of the uptake phase (r² = 0.8845, p <0.0001). The appearance of a nonlinear uptake of the anti-isomer is driven by the large increase in the amount of this isomer accumulated during the first seven days of exposure. After that time the uptake of this isomer was linear (r² = 0.9560, p <0.005); as such, uptake rates for the anti-isomer were therefore calculated over the period of days 7 to 49. Based on the regression analysis, the average uptake rate, calculated as the slope of nmoles versus time, for syn- and anti-DP was statistically different at the 95% confidence level and were calculated to be 0.045 ±0.005 and 0.018 ±0.002 nmol/day, respectively.
The elimination of DP isomers from the fish followed first order deputation kinetics. While plots of the log transformed nmoles versus time were linear for both isomers the slopes were statistically different (95% confidence level). Depuration rate constants, kd, derived from the slope, of 0.013 ±0.003 (syn-) and 0.023 ±0.004 (anti-) were obtained. Based on the calculated kd respective t1/2's were derived for both syn- and anti-DP giving 53.3 ±13.1 and 30.7 ±5.7 days, respectively.
The mean assimilation efficiencies of the syn- and anti-isomer, calculated from days 7, 14, 29, 35, and 49, were estimated to be 6 and 3.9%, respectively. Using the equation described in our other studies, an average EMF of 5.2 for the syn- and 1.9 for anti- was calculated.

The BMFs of the two DP-isomers were re-calculated based on the data published by Tomy et al. (2008). The respective concentrations of the DP-isomers during the depuration phase (whole body minus liver in [nmol of isomer per fish]) were estimated from the graphs in Figures 1 (page 5565) and Figure 2 (page 5566) and fitted to a single first-order (SFO) model (Table 1 below and Figure1) using the statistical program R (R v 3.3.2,R Core Team; 2016).

Regarding the first-order-elimination function, the concentration at the start of the depuration phase (C0) was either fixed as reported in Table1 (2.25 nmol and 1.70 nmol of syn- and anti-DP per fish, respectively) or estimated by the model (Figure1, attached pictures). The latter approach produced higher coefficients of determination (R² of 0.35 and 0.7 for syn and anti-DP, respectively) and was thus applied for the recalculation of BMFs by us based on the data published by Tomy et al. (2008).

Depuration rate constants of 0.001 day-1and 0.023 day-1were determined for the syn- and anti-DP isomer, respectively. Whereas the depuration rate constants of 0.023 day-1 for the anti-DP isomer is identical to value reported by Tomy et al. (2008), the depuration rate constants of 0.001 day-1for the syn-DP isomer is more than 10-fold lower than the value reported by Tomy et al. (2008). All recalculated values are summarised in Table2 below.

Table1 Concentration of syn- and anti-DP per fish estimated from Figures 1 & 2 in Tomy et al.(2008)

Day

depuration / test

Concentration [nmol]**

ln (concentration)

syn-DP

anti-DP

syn-DP

anti-DP

0 / 49

2.25

1.70

0.81

0.53

7 / 56

0.75

0.60

-0.29

-0.51

22 / 71

0.90

0.85

-0.11

-0.16

35 / 84

1.00

0.50

0.00

-0.69

49 / 98

1.65

0.60

0.50

-0.51

70 / 119

0.90

0.35

-0.11

-1.05

112 / 161

0.25

0.10

-1.39

-2.30

** Concentration per fish, i.e. whole body (minus liver), control- and lipid-corrected; estimated from Figure 1 (syn-DP) and Figure 2 (anti-DP) in Tomy et al. (2008)

Table2: Comparison of biomagnification data in Tomy et al. (2008) with respective recalculations

Bioaccumulation parameter

Tomy et al. (2008)

Data recalculated from Tomy et al. (2008) by Arnot and Quinn (2015)

Fact sheet on DP (Annex XV report, UK, 2017)

Data recalculated from Tomy et al. (2008), present document

syn-DP

anti-DP

syn-DP

anti-DP

syn-DP

anti-DP

syn-DP

anti-DP

Mean depuration rate constant (kd) [day-1]

0.013a)

0.013× 10-2 a)

0.023a)

0.023 × 10-2 a)

0.013

0.017

0.012

0.019

0.010

0.023

Half-life (t1/2) [days]

53.3 ± 13.1

30.4 ± 5.7

53.3

40.3

58

36

70.0

30.4

assimilation coefficient(α) [%]

6.0

3.9

6.0b)

3.9b)

1.6e)

0.8e)

6.0b)

3.9b)

Food ingestion rate (I)

[g food/gfish × day]

0.01

0.01b)

0.01b)

0.01b)

Average lipid content fish [%]c)

7.4

7.4b)

7.4b)

7.4b)

Average lipid content of food [%]

14.3 ± 0.3

14.3 ± 0.3b)

14.3 ± 0.3b)

14.3 ± 0.3b)

Lipid correction factord)

n.d.

0.5

0.5

0.5

BMF (growth corrected)

5.2

1.9

0.046

0.023

0.06

0.01

0.06

0.02

BMFL(lipid corrected)

n.d.

n.d.

0.089

0.046

0.12

0.02

0.12

0.03

a)    The depuration rate constants (kd) reported in the text (i.e. 0.013 and 0.023 day-1for syn- and anti-DP, respectively; 2ndparagraph on page 5565) is 100-fold lower than the values listed in Table 2 (i.e.0.013× 10-2and 0.023 × 10-2day-1for syn- and anti-DP, respectively; on page 5565) of the publication;

b)   adopted from Tomy et al. (2008);

c)    Average lipid content of fish samples (n = 4) from day 49 and 161 of the experiment (i.e. start and end of the depuration phase);

d)   lipid content in food divided by lipid content in fish;

e)    )to re-calculate (α),the authors transformed the nanomoles syn- and anti-DP per fish - as estimated from the graphs given in Tomy et a. (2008) – to µg/g (lipid?) concentration, since it is unclear how the lipid-correction was applied, (α) needs to be treated with caution; n.d. = not determined

 

Validity criteria fulfilled:
yes
Conclusions:
Based on the study results it is concluded that the syn-Dechlorane plus is more biomagnifying (BMF 5.2) than the corresponding anti-isomer (BMF 1.9). With BMF of >1 the substance is sufficiently bioavailable when absorbed via food and will biomagnify in fish.
Based on BMF values re-calculated from the data of Tomy et al. (2008) which are clearly below 1, Dechlorane Plus cannot be considered to be a vB substance. Contrary to the conclusion drawn by Tomy et al. (2008), results do not indicate a biomagnification, but may rather point to a relatively slow depuration of DP isomers.
Executive summary:

The results of our study indicate that there are clear differences in the bioaccumulation potentials of the two isomers of DP. The syn-isomer had a statistically significant greater uptake rate, t½ and BMF than the anti-isomer in the whole-body (minus liver) of the fish. These disparities were thought to be due to differences in the lipophilicity between the isomers. Liver-specific uptake kinetics were similar to those observed in the carcass suggesting that uptake rates of the isomers are not tissue-specific. Interpretation of the depuration kinetics of the isomers from the liver was complicated; enterohepatic recirculation and reabsorption of the isomers by the liver during clearance from other tissues may partly explain these observations. Although a purposely large dosing regime was employed in the study, no DP-metabolites were detected in the liver. It is difficult to ascribe this observation solely to the recalcitrant nature of the isomers; other factors like biotransformation rates of the parent compound and clearance rates of the metabolites in trout need to be considered.

Bio magnification factors (BMF) of 5.2 and 1.9 were determined for the syn- and anti-isomer of Dechlorane plus, respectively.

Description of key information

The highest values found for Dechlorane Plus from all studies assessed were:

BCF: 2907 (Boudreau, 1973 using acetone as vehicle and thus of limited relevance)

Half-lifes in fish: 53.3 days and 40.4 days for the syn- and anti-isomer, respectively (Tomy, 2008, exposure via feeding of rainbow trouts under flow-through conditions).

BMF: 12 and 11 for syn- and anti-DP, respectively (Tomy, 2007 for trout/alewife set in Lake Ontario, whereas other predator/prey sets showed values ≤1)

log BAF: 4.4 (Wu, 2010 for water snake)

BSAF (freshwater sediment): 0.88 (0.33 - 2.8) for syn-DP, and 0.33 (0.086 - 1.0) for anti-DP (Wang, 2012)

BSAF (marine sediment): 4.6, ranging from 1.0 to 7.9 (Jia, 2011)

Key value for chemical safety assessment

BCF (aquatic species):
2 907 dimensionless

Additional information

Dechlorane Plus is very poorly soluble in water (water solubility < 1.67 ng/L).

Bioaccumulation has been assessed in company owned reports but also in various publications.

Bioaccumulation studies by aqueous exposure:

Chou et al. assessed accumulation in bluegill sunfish upon exposure to radiolabelled Dechlorane Plus (DP) dissolved in water. 12 fish were used and 3 each were killed and analysed following 48 hours exposure, 96 hours exposure, 48 hours depuration and 96 hours depuration. Bioconcentration factors of 7.02 (48 hours exposure and 1.97 (96 hours exposure) were found. Data from depuration phase were very variable, which may have been caused by oral uptake of particulates during the exposure phase, thus not suitable for interpretation. No steady state was seen and thus the data are of limited value.

Zitko (1980) had published his finding from exposure of groups of 3 juvenile salmons to DP in water over 96 hours followed by a 192 hours depuration phase. Upon exposure to DP via the aqueous phase no DP concentration was found in fish (water conc. 6.06 µg/L, hexane and toluene used as solubilizer). Thus, no bioaccumulation was seen. Exposure via food was also investigated and is described below.

In a study by Gara et al. (1975) bluegill fish were exposed to extraordinarily high concentrations of DP in water, which were achieved by adding 1% acetone to water at static conditions. Thus, 0.1 ppm DP concentration could be achieved and kept almost constant during the 30 days exposure period. A magnification factor of 5.58 (whole body, wet weight) was seen and concentrations in fish stabilized as of day 24. However, only two measurements showed fish concentration stability (0.320 ppm at day 24 and 0.385 ppm at day 30), indicative of a beginning steady state concentration.

In a similar experiment, performed 2 years before by Boudreau et al. (1973), much higher nominal concentrations (1 ppm) were applied in water to bluegill sunfish and less excessive acetone amounts were applied; consequently, the measured concentrations dropped down to 0.003 ppm in water within 30 days. The significant decline in DP-water concentration from 0.046 ppm to 0.003 ppm from day 6 to day 30 mainly led to a significant bio-magnification of 2907 finally, whereas concentrations in fish showed to reach steady state as of day 14 (7.80 ppm on day 14, 8.78 on day 21 and 8.72 on day 30).

Bioaccumulation studies by feed exposure:

Zitko (1980) also investigated DP accumulation in fish exposed via feed, applying a 42 days exposure and 71 days depuration period. Measured feed concentrations were 8.88 µg/g feed (using hexane as vehicle in feed preparation). The substance was absorbed from food reaching a maximum concentration of 176 ng/g wet tissue in fish at the first sampling time on day 15 of food exposure. Thereafter, the concentration in fish tissue declined steadily during the following exposure period and during post-exposure period to a minimum of 18.7 ng/g wet weight on day 71 of post-exposure. No accumulation was observed, but the elimination from tissues was very slow, and no complete elimination from fish tissues was achieved.

Tomy et al. (2008) published his finding from a flow-through bioaccumulation study using juvenile rainbow trouts (Oncorhynchus mykiss) that were exposed for 49 days with DP-spiked feed and non-spiked feed for a further 112 days (depuration period). Syn- and anti-DP was run in parallel experiments and a third group (control) was treated with plain feed. Concentrations in feed were 0.79 µg/g lipid weight of syn-DP and 1.17 µg/g lipid weight of anti-DP. BMF values found were 5.2 for syn-DP and 1.9 for anti-DP. The results of study indicate that there are clear differences in the bioaccumulation potentials of the two isomers of DP. The syn-isomer had a statistically significant greater uptake rate, t½ and BMF than the anti-isomer in the whole-body (minus liver) of the fish. These disparities were thought to be due to differences in the lipophilicity between the isomers. Liver-specific uptake kinetics was similar to those observed in the carcass suggesting that uptake rates of the isomers are not tissue-specific. Interpretation of the depuration kinetics of the isomers from the liver was complicated. Although a purposely large dosing regime was employed in this study, no DP-metabolites were detected in the liver. It is difficult to ascribe this observation solely to the recalcitrant nature of the isomers; other factors like biotransformation rates of the parent compound and clearance rates of the metabolites in trout need to be considered.

The uptake and clearance kinetics of the DP isomers were also assessed in the liver. Regression analysis suggested that the uptake for both isomers in the liver was linear (syn-: r²= 0.7145, p= 0.03; anti-: r²=0.7119, p= 0.03). Respective uptake rates of the syn- and anti-isomers in the liver were 0.065 ±0.020 and 0.024 ±0.008 nmoles per day. Similar uptake rates were observed in the carcass. The half-lifes were assessed by the authors as 53.3 days and 40.4 days for the syn- and anti-isomer, respectively.

Tomy et al (2007) published their findings from environmental sampling (burbot, zooplankton, mussels, walleye, goldeye, whitefish, emerald shiner, white sucker, sediment) in Lake Winnipeg and Lake Ontario Food Webs (samples were collected between 2000 and 2003) and based on these data trophic level adjusted biomagnification factors (BMF TL) were determined based on fish samples of different species (and trophic levels) corrected based on lipid content of species analysed. BMF TL = [(predator)/(prey)]/[(TL predator)/(TL prey)]; stable isotope analysis of nitrogen was previously determined on biota to define trophic levels. Lipid content of biota samples were measured and taken into account for biomagnification factor assessment, which was performed based on normalized lipid fraction.

Biomagnification factors (BMF) of Dechlorane Plus for different sets of predator/prey in Lake Winnipeg and Lake Ontario were established. Whereas in Lake Winnipeg for most predator/prey sets no biomagnification was seen (BMF TL < 1) in one case (walleye/whitefish) a BMF TL of 11 was found for the anti-isomer whereas for the syn-isomer the BMF TL was only 0.3. In Lake Ontario the BMF for trout/alewife was found being 1 and 0.9 for syn- and anti-DP, and for trout/smelt was 12 and 11 for syn- and anti-DP, respectively.

Thus, the potential for biomagnification appears to be very much depending on the predator/prey set analysed and most predator/prey sets investigated showed no biomagnification whereas only a few did show biomagnification (walleye/whitefish, anti-DP only and trout/smelt, syn- and anti-DP) in the range of a factor 10. Apparently, only top predators in the food web showed biomagnification of syn- and anti-DP. The reasons for these differences is not fully understood currently.

Zeng et al. (2014) investigated in a study common carp (Cyprinus carpio) that were exposed to contaminated food pellets for 50 days. The contaminated food was made by known amounts of commercial DP-25 dissolved in cod liver and then mixed with fish food pellets. After the exposure period, a depuration period lasting a further 40 days was designed for the carp, during which the carp were fed with non-spiked food. The purpose of the present study was (1) to investigate gastrointestinal absorption by comparing the concentration and congener profile of DP between spiked food and feces and (2) to investigate the uptake and depuration behaviours of the DP congeners in different carp tissues after exposure to high doses of DP-25 mixtures.

The uptake and depuration kinetics of DP in the serum, muscle, liver, and gonad were investigated. The four chemicals (anti-DP, syn-DP, anti-Cl11-DP and syn-Cl11-DP), except for syn-Cl11-DP in the serum, were detected in all target tissues. All chemicals exhibited linear accumulation kinetics in serum (r² = 0.88, r² = 0.84 and r² = 0.69 for anti-DP, syn-DP and anti-Cl11-DP, respectively) and muscle (r² = 0.84, r² = 0.81, r² = 0.84 and r² = 0.81 for anti-DP, syn-DP anti-Cl11-DP and syn-Cl11-DP, respectively) samples during the uptake period and reached the highest concentrations at the end of the uptake period (50th day). No steady state was observed in the serum or muscle for any chemical during the 50-day exposure. Depuration of the chemicals in both muscle and serum showed an initial rapid depuration for the first 10 days followed by a fluctuating depuration over the remainder of the experiment. No obvious trend towards a decrease was found in the last 30 days of the depuration.

The uptake kinetics of DP and their dechlorinated analogues in the liver and gonad were not linear. The concentrations in the gonad showed co-variation with those in the liver with the 5-day hysteresis during the uptake period. This hysteresis in the gonad might be attributed to maternal transfer of DP in fish. The depuration curves of DP in the liver showed 2-stage elimination kinetics, with an initial decrease to day 70, followed by a slight increase. The concentrations of DP and their analogues fluctuate and follow a zigzag pattern in the depuration. This unique accumulation pattern of DP in the gonad of carp could be because gonads collected in different individuals may be in different stages of embryonic development as some of the DP was determined in fish ovaries and some was determined in fish eggs. It remains unclear as to why no linear uptake occurred in the liver in the uptake period and accumulation in the liver was still occurring at the end of the experiment. To evaluate whether dechlorination occurred in fish, the concentration ratios of dechlorinated analogues to their parent compound were calculated for muscle (the predominant tissue for DP deposition). This result indicated that the ratio for syn-isomer and anti-isomer showed a decreasing trend in the depuration period and suggested that dechlorinated analogues are eliminated more rapidly than their corresponding parent chemicals. This result did not support the dechlorination metabolism of the 2 DP isomers in fish. However, f anti and f anti-Cl11 in fish were lower than those in the commercial DP mixture, and the uptake efficiency of anti-isomer was higher than those of the syn-isomer, thereby strongly suggesting the selective degradation of anti-isomers in fish. Thus, a metabolic pathway other than dechlorination, such as hydroxylated metabolism, may occur and more studies are needed to investigate this issue.

The higher absorption efficiencies but the lower assimilation efficiencies of anti-isomers indicated a stereoselective metabolism of anti-isomer in common carp. A dynamic tissue distribution with an increasing proportion in the muscle along with a decreasing proportion in the liver over time was observed. The isomer composition of DPs and their dechlorinated analogues also exhibited tissue specificity and dynamic changes over the experimental period. The result suggests that isomer-specific accumulation of DPs and their dechlorinated analogues in fish is a complex and multi-factorial process. No BCF or BMF values were derived in the publication, as no steady-state conditions were achieved after 50 days exposure period.

Wu et al. (2010) assessed in a field study DP in the food web in the vicinity of electronic waste recycling workshops in South China, based on quantified data from water, sediment and biota samples. From these data, trophic magnification factors (TMFs) were derived. A total of 88 wild aquatic biota samples, 6 water samples, and 6 surficial sediment samples were concurrently collected from a reservoir near an e-waste recycling plants in South China in 2006. Biota samples included two invertebrates, i.e., Chinese mystery snail (Cipangopaludina chinensis) and prawn (Macrobrachium nipponense), four fish species, i.e., mud carp (Cirrhinus molitorella), crucian carp (Carassius auratus), common carp (Cyprinus carpio), and northern snakehead (Ophicephalus argus), and one reptile, water snake (Enhydris chinensis). In addition, mud carp (Cirrhinus molitorella) were collected from another pond 5 km away from the e-waste recycling plant, as reference samples.

Bioaccumulation factors (BAFs) for the DP-isomers were calculated by dividing the concentrations of DP in biota (ng/g wet wt) by the mean concentrations of DP in the dissolved phase of water (ng/mL). The food web biomagnification potential of DP was evaluated via estimation of trophic magnification factors (TMFs), defined mathematically as the slope of the regression model obtained from a plot of lipid-normalized contaminant concentrations in organisms versus trophic levels.

The total DP concentrations in the collected aquatic species varied from 19 to 9630 ng/g lipid wt. The highest average concentration was found in water snake (1970 ng/g), followed by mud carp (1710 ng/g), crucian carp (277 ng/g), northern snakehead (255 ng/g), prawn (190 ng/g), and Chinese mysterysnail (20.2 ng/g). The average concentrations of DP were 0.80 ng/L, 3930 ng/g dry wt (dw), and 7590 ng/g dw in the dissolved phase of water, suspended particles, and surficial sediments, respectively.

The average log BAF of total DP ranged from 2.13 (Chinese mysterysnail) to 4.40 (water snake). Chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70. In this study, all species, except for Chinese mystery snail and northern snakehead, showed log BAF values higher than 3.70, suggesting significant bioaccumulation of DP was occurring in these species.

The calculated trophic magnification factors (TMFs) of syn-, anti- and total DP were 11.3, 6.5, and 10.2, respectively. This indicated that DP, no matter whether the syn-DP or anti-DP isomer, was significantly biomagnified throughout the entire food web. The TMF of syn-DP was almost two times greater than that of anti-DP, suggesting that the biomagnification potential of syn-DP was higher than that of anti-DP in the present food web. However, interesting is that the top predator in this web, the northern snakehead, showed significantly lower bioaccumulation and therefore was not considered for the assessment of trophic magnification factors.

The study was designed to explore the gastrointestinal absorption and tissue-specific bioaccumulation of DP and its dechlorinated analogues in common carp. Therefore, the main objective of the present study was to improve the understanding of the bioaccumulation process of DP. Thus, no BCF or BAF values were reported but tissue specific measurements were undertaken to exploit the tissue specific uptake and depuration pattern while carps were exposed via feed to Dechlorane Plus (DP).

Biota sediment accumulation

Zhang et al (2011) published their findings, when investigating the bottom fish species crucian carp, mud carp, and northern snakehead from an electronic waste recycling site in South China, by measuring concentrations of DP in sediment and fish using GC-MS technique.

The investigated fish species showed very low BSAFs for total DP <= 0.025, with average values of 0.004, 0.025, and 0.003 in crucian carp, mud carp, and northern snakehead, respectively. According to the equilibrium partitioning theory, when in conditions of equilibrium and no metabolism of the chemical, the BSAF for the hydrophobic organic chemicals (HOCs) is equal to the partitioning relationship of the chemical between organic carbon in the sediment and lipids of the organism, that is, the BSAFs should be 1 - 2 (Burkhard et al., 2004). The low BSAFs for DP isomers in the present fish indicated that DP may be in non-equilibrium conditions between sediment and fish. This is reasonable for fish because wide ranges of factors including sediment/water column chemical disequilibrium, chemical bioavailability, and dietary uptake efficiencies would influence the concentrations of HOCs between sediment and fish. Another explanation for the low BSAFs is that chemical metabolism within the investigated bottom fish and/or their underlying food web may occur. DP was assumed to be metabolized in northern snakehead (Wu et al., 2010) and other fish species (Tomy et al., 2007) in field investigations, although no direct evidence has been found to support the assumption so far. These low BSAFs indicated the low bioaccumulation potential of DP in the present fish species. With a very high K OW value (log K OW ~9.3), DP is super-hydrophobic and highly sorptive to the sediment, resulting in low values for BSAF. This implied that BSAF may be not an appropriate bioaccumulation parameter for DP in highly contaminated site such as e-waste recycling site in South China.

Compared to the extremely hydrophobic PCBs, both DP isomers showed approximately two orders of magnitude lower BSAF values in the same sample set. However, the BSAFs for DP isomers are comparable to those for BDE 209. The differences in the physiochemical properties (typically K OW ) of the chemicals and metabolism capacity in organisms may contribute to the different BSAFs between the DP isomers, and among the three compound classes (DP, PCBs, and BDE 209).

Wang et al. (2012) published their results on investigation performed on 54 samples that were collected in a river in north eastern China (Daling River in August 2010) and analysed for DP (and other Dechloranes) by gas chromatography/mass spectrometry. The average concentrations of total DP (syn- and anti-) in water, sediment, air, reed (Phragmites australis), and fish (E. elongatus) were analysed and biota-sediment accumulation factors (BSAF) derived. In this study, biota-sediment accumulation factor (BSAF) were estimated as 4.7 (1.2 - 9.2) for Dec 602, 0.88 (0.33 - 2.8) for syn-DP, and 0.33 (0.086 - 1.0) for anti-DP. Thus, neither syn- nor anti-DP were considered bioaccumulating, although significant differences were seen for syn- and anti-DP.

Shen et al. (2011) investigated suspended sediments and lake trout from Niagara River sampled from Lake Ontario north of Main Duck Island as part of long-term monitoring by the Great Lakes Laboratory for Fisheries and Aquatic Sciences (GLLFAS) and samples were analysed for DP (and other Dechloranes) content by GC/MS. Seasonal variations were investigated. BSAFs were estimated for syn- and anti-DP for lake trout relative to sediments from Lake Ontario. Biota-Sediment-Accumulation Factors (BSAF) for syn-DP and anti-DP were 0.8 and 0.3, respectively. With a BSAF of less than 1 bioaccumulation in lake trout of Lake Ontario is considered low in contrast to Mirex and Dechlorane 602, having BSAFs of 7400 and 270, respectively, being considered strongly bioaccumulating in the food web of Lake Ontario. The relative concentration patterns observed were total DP > Mirex > Dec 602 and Dec 604 > Dec 603 > CP in suspended sediments and sediment cores, whereas Mirex was highest in lake trout, followed by Dec 602 and DP. Dec 602 concentrations were 50 to 380 times greater than those of DP in lake trout, indicating Dec 602 has a greater bioaccumulation potential. The estimated biota-sediment accumulation factor (BSAF) for Dec 602 (270) was much greater than for DP (0.8 for syn-DP and 0.3 for anti-DP) in Lake Ontario, and was greater than those calculated for PBDEs. Syn-DP bioaccumulates to a greater extent or is more bioavailable than anti-DP in fish, but this may vary depending on the foodweb studied. In this study, the measured f syn in lake trout were all above the reported f syn of technical DP products (0.2 - 0.36) ranging from 0.42 to 0.56, consistent with previous observations in fish, and were greater than sediment f syn values.

Jia et al. (2011) collected water, sediment and oyster samples at 15 sampling sites near the Bohai and Huanghai Sea shore area of northern China in 2008 (October – December). Samples were analysed for contaminants including Dechlorane Plus by GC/MS. From the results, the biota-sediment accumulation factor (BSAF) of DP could be derived.

The biota-sediment accumulation factor (BSAF) has been suggested as a simple approach to the prediction and estimation of the bioaccumulation potential of hydrophobic organic compounds (HOC) in aquatic biota. BSAF is based on equilibrium partitioning, which assumes that HOCs partition between the carbon pools of biotic tissue lipids and sediment organic carbon. This approach also assumes that there is no chemical transformation, mass transfer resistance, differential biotic uptake or depuration. Under these conditions, bioaccumulation can be assessed using the BSAF which is defined as BSAF = (C b / f lip) / (C s / f OM ) , where C b is the biota HOC concentration (ng/g ww), f lip is the organism lipid content, C s is the sediment HOC concentration (ng/g dw), and f OM is the sediment organic carbon content. A theoretical BSAF value of 1.7 has been estimated based on partitioning of non-ionic organic compounds between tissue lipids and sediment organic carbon. A value of less than 1.7 indicates less partitioning of an organic compound into lipids than predicted and a value greater than 1.7 indicates more uptake of the pollutant. In the present study, BSAFs were calculated for a total of 64 paired sediment and oyster samples that have both measurement values above instrument detection limits (IDL). Individual compound BSAF values (mean and range in parentheses) are in the order: Mirex (9.1, 2.3 - 23) > Dec 602 (5.6, 2.1 - 12) > DP (4.6, 1.0 - 7.9). This sequence is contrary to the order of logarithm of octanol / water partition coefficients (log K ow), which is DP (11.3) > Dec 602 (8.05) > Mirex (7.01) and indicates that chemicals with higher log K ow are likely to be retained in sediment and that Mirex and Dec 602 have a higher accumulation potential in biota than DP. Interestingly, this trend is consistent with that found in PBDEs and PAHs. The mean fractional abundance of syn-DP (f syn) was 0.34 in water samples, a value lower than that in Chinese commercial mixture (0.41), while the mean f syn for surface sediment (0.44) and oyster (0.45) samples were higher than technical values. Enrichment of syn-DP in oyster was in agreement with previously reported findings in Great Lakes fish. Enrichment of syn-DP in marine surface sediments, however, is contrary to data reported for fresh water sediments.

Field studies

In this field study, reported by Zhang et al. (2011), birds (five different species) were collected near an e-waste recycling area and muscle, liver and kidney tissue was analysed for content of flame retardants (including DP). Trophic level of birds was estimated by 15N and 13C analysis.

The present study was primarily designed to examine the role played by dietary sources on polybrominated diphenyl ethers (PBDE) congener profiles in waterbirds collected in an e-waste recycling region in South China. Some emerging halogenated flame retardants (HFRs), such as Dechlorane Plus (DP), 2,3,4,5,6-pentabromo ethylbenzene (PBEB), pentabromo toluene (PBT), and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), were also quantified. Stable isotopes (δ 15N and δ 13C) were analysed to assess the trophic levels and dietary sources of the birds. PBDEs were found to be the predominant HFRs, followed by DP, PBT, PBEB, and BTBPE. The birds in which BDE209 was predominant have differential δ 13C and δ 15N signatures compared with other birds, suggesting that dietary source is one of the important factors in determining the PBDE congener profile in birds. The levels of ΣPBDEs, PBEB, and PBT were significantly correlated with the trophic level (δ 15N) for avian species which are located in a food chain, indicating the biomagnification potential of these compounds. No correlation was found between DP concentrations and trophic level of the birds and hence no biomagnification. There is a significantly negative correlation between the fraction of anti-DP and δ 15N, suggesting that the metabolic capability of DP in birds increases with the trophic level of the birds. Both syn-DP and anti-DP did not correlated well with the δ 15N (p > 0.05), indicating that no biomagnification occurred, as no statistically significant correlation between the concentrations of both isomers and trophic level was found.

Summary

In summary, results on bioaccumulation of DP are not clear and consistent.

Studies performed with exposure to DP in water showed only low accumulation of DP in fish and Bioconcentration factors (BCF) found were far below 500. However, given the extremely low solubility of Dechlorane Plus in water, the studies were of limited value as

a)     in some of them significant amounts of solubility enhancers were used to achieve concentrations in water far above the water solubility of DP

b)     when using solubility enhancers, concentrations were not easily maintained and declined during exposure period, indicating super-saturated solutions with particulate matter

c)      steady state conditions could not be achieved, respectively were seen to begin but only at the end of exposure period.

For substances with extremely low water solubility as Dechlorane Plus, feed exposure studies appear more appropriate. Zitko (1980) exposed fish through spiked feed and DP was absorbed rapidly at the beginning of exposure, but thereafter fish tissue concentration declined. During post exposure period of 71 days no full elimination of DP from fish was seen, although concentration in tissue decreased. However, no accumulation of DP was observed.

Tomy (2008) investigated bioaccumulation through a feeding study with juvenile rainbow trouts under flow-through conditions. Although a purposely large dosing regime was employed in this study, no DP-metabolites were detected in the liver. BMF values found were 5.2 for syn-DP and 1.9 for anti-DP, indicating clear differences in the bioaccumulation potential of the two isomers of DP. The syn-isomer had a statistically significant greater uptake rate, t½ and BMF than the anti-isomer in the whole-body (minus liver) of the fish. The half-lifes were assessed by the authors as 53.3 days and 40.4 days for the syn- and anti-isomer, respectively.

In a very recent publication Zeng et al. (2014) fed common carp with DP-spiked food pellets for 50 days, followed by a depuration period of 40 days. Syn- and anti-DP was detected in serum, muscle, liver, and gonads. Whereas in serum and muscle accumulation kinetics was linear, no steady state was achieved; at the beginning of depuration, concentrations decreased rapidly but then only slowly, if at all. In liver and gonads accumulation kinetics was not linear and decreased in the depuration period was only observed in the first three weeks after which a slight increase was observed again. The result suggests that isomer-specific accumulation of DPs and their dechlorinated analogues in fish is a complex and multi-factorial process. No BCF or BMF values were derived in the publication, as no steady-state conditions were achieved after 50 days exposure period.

Results from environmental sampling in Lake Winnipeg and Lake Ontario reported by Tomy (2007) had shown that biomagnification in a natural food web of the lakes was very much dependent of the predator/prey pair assessed. Biomagnification factors (BMF) for most predator/prey sets were less than one (e.g. trout/alewife, walleye/whitesucker, walleye/goldeye, goldeye/zooplancton), indicating no potential for bioaccumulation but one predator/prey set showed significantly higher BMF values (trout/smelt with BMF of 12 and 11 for syn- and anti-DP, respectively). Very peculiar was the predator/prey set walleye/whitefish in Lake Winnipeg that showed a BMF of 0.3 for syn-DP and 11 for anti-DP. Thus, the potential for biomagnification appears to be very much depending on the predator/prey set analysed and most predator/prey sets investigated showed no biomagnification whereas only a few did show biomagnification (walleye/whitefish, anti-DP only and trout/smelt, syn- and anti-DP) in the range of a factor 10. Apparently, only top predators in the food web showed biomagnification of syn- and anti-DP, and the reason for this difference is not fully understood.

Wu et al. (2010) sampled biota, water and sediment in vicinity to an e-waste recycling area in China for analysis and therefrom derived Bioaccumulation factors (BAF) and trophic magnification factors (TMF). The average log BAF of total DP ranged from 2.13 (Chinese mystery snail) to 4.40 (water snake) and chemicals are considered to be bioaccumulative if the BAF is greater 5000, corresponding to a log BAF of 3.70. In this study, all species, except for Chinese mystery snail and northern snakehead, showed log BAF values higher than 3.70, suggesting significant bioaccumulation of DP was occurring in these species. However, when deriving trophic magnification factors, the results with northern snakehead were omitted, which led to a TMF of 11.3 and 6.5 for syn- and anti-DP, respectively, indicative for biomagnification through the food web.

Thus, the results from Tomy (2007) indicated the top-predator in the food web of Lake Ontario and Lake Winnipeg accumulated DP more efficiently than prey fish, the results of Wu (2010) showed the opposite (northern snakehead is the top-predator in the food web in the investigated vicinity to the e-waste recycling area in China).

Current results do indicate that bioaccumulation of DP via feed exposure, either under natural conditions or in wild life, is very much depending on species assessed and might be influenced by several factors such as metabolism, concentration in environment (feed/sediment) and eventually also degradation pathways, although no dechlorination of DP was observed so far in biota. Whereas some species do appear to bioaccumulate DP strongly, others, even in the same food web, do not. Even following 50 days exposure to feed did not result in a stead state condition and thus it is questionable, whether further studies would give a better framework to assess bioaccumulation under laboratory conditions. Field studies appear thus more appropriate but results are inconclusive over an entire food web and do vary rather strongly.

When assessing studies published on sediment / biota accumulation, Zhang et al. (2011) found rather low biota sediment accumulation factors (BSAF) of less than 0.025 investigating crucian carp, mud carp, and northern snakehead, respectively. The authors concluded that DP is super-hydrophobic and highly sorptive to the sediment, resulting in low values for BSAF. This implied that BSAF may be not an appropriate bioaccumulation parameter for DP in a highly contaminated site such as the e-waste recycling site in South China investigated. Another explanation for the low BSAFs is that chemical metabolism within the investigated bottom fish and/or their underlying food web may occur. DP was assumed to be metabolized in northern snakehead (Wu et al., 2010) and other fish species (Tomy et al., 2007) in field investigations, although no direct evidence has been found to support the assumption so far. Compared to the extremely hydrophobic PCBs, both DP isomers showed approximately two orders of magnitude lower BSAF values in the same sample set.

Wang et al. (2012) derived biota-sediment accumulation factors (BSAF) from 54 samples that were collected in a river in north eastern China (Daling River in August 2010) and analysed for DP (and other Dechloranes) by gas chromatography/mass spectrometry. The BSAF found were 4.7 (1.2 - 9.2) for Dec 602, 0.88 (0.33 - 2.8) for syn-DP, and 0.33 (0.086 - 1.0) for anti-DP and hence neither syn- nor anti-DP were considered bioaccumulating, although significant differences were seen for syn- and anti-DP.

Also Shen et al. (2011) derived BSAF values from samples taken from Lake Ontario north of Main Duck Island as part of long-term monitoring. Biota-sediment-Accumulation Factors (BSAF) for syn-DP and anti-DP were 0.8 and 0.3, respectively. With a BSAF of less than 1 bioaccumulation in lake trout of Lake Ontario was considered low in contrast to Mirex and Dechlorane 602, having BSAFs of 7400 and 270, respectively, being considered strongly bioaccumulating in the food web of Lake Ontario. syn-DP bioaccumulates to a greater extent or is more bioavailable than anti-DP in fish, but this may vary depending on the foodweb studied. In this study, the measured f syn in lake trout were all above the reported f syn of technical DP products (0.2 - 0.36) ranging from 0.42 to 0.56, consistent with previous observations in fish, and were greater than sediment f syn values.

Jia et al. (2011) collected marine water, sediment and oyster samples at 15 sampling sites near the Bohai and Huanghai Sea shore area of northern China in 2008 analysing them for contaminants including Dechlorane Plus by GC/MS. From the results, the biota-sediment accumulation factor (BSAF) of DP could be derived. Individual compound BSAF values (mean and range in parentheses) are in the order: Mirex (9.1, 2.3 - 23) > Dec 602 (5.6, 2.1 - 12) > DP (4.6, 1.0 - 7.9). This sequence is contrary to the order of logarithm of octanol / water partition coefficients (log K ow), which is DP (11.3) > Dec 602 (8.05) > Mirex (7.01) and indicates that chemicals with higher log Kow are likely to be retained in sediment and that Mirex and Dec 602 have a higher accumulation potential in biota than DP. Interestingly, this trend is consistent with that found in PBDEs and PAHs.

Thus, biota sediment accumulation factors (BSAF) for Dechlorane Plus are mainly not indicative of bioaccumulation potential except of in marine oysters, where BSAF values greater 1 were observed.

In a field study, reported by Zhang et al. (2011), five birds different species were collected near an e-waste recycling area and muscle, liver and kidney tissue was analysed for content of flame retardants (including DP). Trophic level of birds was estimated by 15N and 13C analysis.

The levels of ΣPBDEs, PBEB, and PBT were significantly correlated with the trophic level (δ 15N) for avian species which are located in a food chain, indicating the biomagnification potential of these compounds. No correlation was found between DP concentrations and trophic level of the birds and hence no biomagnification. There is a significantly negative correlation between the fraction of anti-DP and δ 15N, suggesting that the metabolic capability of DP in birds increases with the trophic level of the birds. Both syn-DP and anti-DP did not correlated well with the δ 15N (p > 0.05), indicating that no biomagnification occurred, as no statistically significant correlation between the concentrations of both isomers and trophic level was found.

From all publications assessed so far no consistent findings on accumulation of DP in the food chain can be derived. Bioconcentration studies using fish did not show high levels of bioaccumulation, but their relevance to highly insoluble substances such as Dechlorane Plus is limited. In some freshwater predator/prey sets and also in marine oysters, bioaccumulation was observed that could be considered very bioaccumulative. However, the results mainly reported in peer-reviewed literature did not indicate strong bioaccumulation, or even indicated no accumulation in the food webs investigated in many predator/prey sets. Whenever different flame retardants were assessed by authors it was stated, that bioaccumulation of DP was lower than for example for mirex, polychlorinated biphenyl ethers or Dechlorane 602.

The highest values found for Dechlorane Plus from all studies assessed were:

BCF: 2907 (Boudreau, 1973 using acetone as vehicle and thus of limited relevance)

Half-lifes in fish: 53.3 days and 40.4 days for the syn- and anti-isomer, respectively (Tomy, 2008, exposure via feeding of rainbow trouts under flow-through conditions).

BMF: 12 and 11 for syn- and anti-DP, respectively (Tomy, 2007 for trout/alewife set in Lake Ontario, whereas other predator/prey sets showed values ≤1)

log BAF: 4.4 (Wu, 2010 for water snake)

BSAF (freshwater sediment): 0.88 (0.33 - 2.8) for syn-DP, and 0.33 (0.086 - 1.0) for anti-DP (Wang, 2012)

BSAF (marine sediment): 4.6, ranging from 1.0 to 7.9 (Jia, 2011)