Desmedipham

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2002-06-14 to 2004-02-11

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)

Version / remarks:

June 14, 1996

Deviations:

not specified

GLP compliance:

yes

Radiolabelling:

yes

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION

Two concentrated stock solutions were prepared by the following procedure: 57.6 mg of a defined mixture of labeled (specific activity: 6.497 MBq/mg) and unlabeled test substance was dissolved in 19.2 L of dilution water resulting in a stock solution of 3 mg/L the day before the start of the study.
Due to the 5fold higher need of stock solution at the higher dose level, 5 volumes were prepared. The pH was adjusted to 4.5 -5.0 by using 100% acetic acid: 1 m KOH (1:5). The stock solution and dilution water (pH 8 - 8.5) was pumped continuously into mixing beakers from where the test solutions flowed into the test vessels. The actual flow rates were controlled by measurements of radioactivity. They varied by less than ± 20% at the lower concentration for the first 48 h of the test. The stock solutions as well as the test solutions in the mixing beakers were stirred using magnetic stirrers. The pH in the test vessels was adjusted to 6.5 -7.0 by continuously adding phosphoric acid by a tube pump.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trout (Oncorhynchus mykiss)
- Mean body length: 8.0 ± 4.0 cm
- Mean body weight: 1.3 - 1.4 g
- Biological loading: 0.8 g/L
- Health status: Only healthy fish free from observable diseases and abnormalities were used in the study.
- Feeding: No feeding during the uptake phase, moderate daily feeding (1-2% of body weight) during the depuration phase with pulverized trout food.

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

other: Purified drinking water

Total exposure / uptake duration:

3 d

Total depuration duration:

>= 5 - <= 6 d

Test temperature:

13.2 - 15.2°C.

pH:

6.3 - 7.1

Dissolved oxygen:

> 60 %

Details on test conditions:

TEST SYSTEM
- Test vessel: glass aquaria
- Size, fill volume: 23.5 x 40.5 x 26.5 cm h x I x w), 25 L
- Biomass loading rate: At the start of the test fish loadings were between 117 g and 125 g, the loading rate was always equal to lower than 0.8 g/(L *d).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Purified drinking water was used according to the OECD-Guideline. The purification includes filtration with charcoal, aeration and passage through a lime stone column.
- Intervals of water quality measurement: characteristics of the dilution water are measured routinely on a monthly basis

OTHER TEST CONDITIONS
- Photoperiod: The light/dark cycle were adjusted to 8/16 hours (darkness from 6 pm to 2 am)

Nominal and measured concentrations:

Nominal test concentrations: 100 µg/L and 500 µg/L

Details on estimation of bioconcentration:

Calculation of the steady state BCFss
According to OECD 305 the steady state is reached if "three successive analyses of Cf taken at intervals of at least two days are within ±20% of each other, and there are no significant differences between the values. When pooled samples are analysed at least four successive analyses are required."
Due to the fast uptake of the test substance, sampling intervals of 2 days were not appropriate. Thus, in this study it was assumed that the steady state was reached if three successive C, values varied by less than 20%.
The BCFss was calculated by dividing the mean of the selected three values for desmedipham in fish (µg/kg) by the mean of the corresponding concentration in water (µg/L).

Calculation of kinetic BCFk
The kinetic BCF is given by
Eq. 5: BCFk = k1/k2 (for the one compartment model, respectively)
Eq. 6: BCFk = k1/ (a*ka +(1-a)*kb) (for the two-compartment model)

Conc. / dose:

500 µg/L

Type:

BCF

Value:

66 dimensionless

Basis:

whole body d.w.

Calculation basis:

kinetic

Details on results:

Mortality and other signs of intoxication
At a nominal concentration of 500 µg test item/L, after 50 hours four fish were tumbling. To avoid stronger toxic effects, all fish at that test concentration were transferred into substance-free dilution water. Thus, the depuration phase started after 55 hours of exposure. After 72 hours, 6 fish were dead. In the further depuration phase, no signs of intoxication could be observed any more. The number of affected fish at nominally 500 µg test item/L was in total 10 of 85 (12%).
At 100 µg/L, the fish showed no behavioral effects during uptake, and the uptake phase was stopped as planned after 72 hours.
After 96 hours, 6 of 85 fish (7%) were dead in the control vessel. At 100 µg/L, 18 fish (21%) were dead. Because there were absolutely no signs of intoxication of fish in both vessels until the evening of the fourth day (82 h), it is assumed that a temporary dosing problem of phosphoric acid or dilution water in the night was responsible for the mortality. However, the pH measurement after 96 h did not indicate a dosing problem (any longer).

Desmedipham concentrations in the water
At the nominal test concentration of 100 µg/L, desmedipham concentrations in the water stayed within the range of 100 to 125 µg/L within the first 48 h (Figure 1). During the third day the concentration dropped down to 60 µg/L, although the concentration of radioactivity was maintained (Table 6). The trend of decreasing desmedipham concentrations during the third day was even stronger at nominally 500 µg/L in spite of slightly increasing radioactivity. Thus, maintenance of constant desmedipham concentrations was disturbed by degradation rather than by flow-through conditions. Therefore, for the calculation of the uptake kinetics of desmedipham, only the first 48 hours were considered. Within this time, the concentrations at nominally 100 µg/L stayed within ± 20% of the mean measured concentration of 11 0 µg/L. At nominally 500 µg/L, the validity criterion ± 20% was slightly missed by one value exceeding the mean of 315 µg/L by 21.8%.

Desmedipham concentrations in fish
The maximum concentration of desmedipham in fish was reached after 48 h with 7.7 mg/kg (exposed at 100 µg/L) respectively 24.7 mg/kg (exposed at mean measured 315 mg/L) (Figure 2). After transferring the fish into clean water, the concentration decreased by more than 99% within less than six days.

Steady State Bioconcentration Factors BCFss
Maximum and minimum values of the three last measurements before and including 48 h varied by less the 20% of the maximum values, which is in correspondence to the definition of the steady state in the OECD Guideline 305. Thus, the BCFss was calculated by dividing the mean of the 26, 36, and 48 h values for desmedipham in fish (µg/kg) by the mean of the corresponding concentrations in the water (µg/L). The results were similar at both nominal concentrations:
BCFss(100 µg/L) = 64
BCFss(500 µgL) = 65

Uptake and elimination rates and BCFk
The log-linear plots of desmedipham concentrations in fish during the depuration phase suggest a two-compartment model for the elimination process. During the first 8 respectively 16 hours, a fast decrease can be described by first order kinetics (one-compartment fit in Figure 3 and Figure 4 ), but later on, elimination seems to be much slower.
The fit of eq. 2 (two-compartment model) at nominally 100 µg/L attributed more than 95% of desmedipham to the fast compartment A. The data set for the higher test concentration was not suited for the full 4-parameter model fit, and therefore the ratio between the two compartments was set as derived from the other test concentration. Because of the problems with fitting the 4 parameter model and because of the apparently low importance of the compartment B, calculations of the rates and the resulting BCFk were done using both, the one and the two compartment model. The one compartment model was applied only to the data of the first 8 respectively 16 hours of the depuration phase, while the two compartment model was fitted to the whole data set. The results for the rate constants and the BCF values are summarized in Table 2.

Relation of desmedipham to total radioactivity
With respect to total radioactivity, two trends were observed:
1. Fixation of radioactivity as non-extractable residue (NER) in fish. Even after one hour of exposure, already 42 - 48% of the total radioactivity in fish could not be extracted. Accumulation of NER increased faster and more steadily than of extractable radioactivity, resulting in an increase of the part of NER to 70% after 48 h (Figure 7) and more than 90% until the end of the depuration phase. Due to the physico-chemical properties of desmedipham it is evident that NER is formed by metabolism of desmedipham or its degradates to more polar metabolites or structural components.
2. Decreasing percentage of desmedipham in the extracts (Figure 8). During the uptake phase, the percentage of desmedipham in the extractable part of radioactivity decreased from 89% after 1 h to 60% after 48 h and to 41% after 72 h (at 100 µg/L). This is well reflecting the part of desmedipham in the radioactivity in water (Table 6). Within the first 8 to 16 h of depuration, desmedipham decreased to below 10%.

Validity criteria

The validity criterion that mortality or other adverse effects should be less than 10% at the end of the study, was not fulfilled for the exposure vessels. Nevertheless, the study is regarded as viable for the assessment of the BCF and the uptake and depuration rate constants.

 

The following validity criteria were met;

• Water parameters of the test medium throughout the study fulfilled the validity criteria listed in OECD Guideline 305 within the first 48 h of the study.


• The maintenance criterion of the test substance concentrations during the uptake phase was clearly met by the lower dosing level, and nearly met by the higher dosing level (maximum +21.8% of mean measured concentration instead of 20 %).


• No mortality or any signs of intoxication occurred at any dose level.


• The BCFss according to OECD Guideline 305 was reached.

Thus, the uptake phase was conducted under viable conditions.

Validity criteria fulfilled:

yes

Remarks:

See "Any other information on results incl. tables" for the validity criteria.

Conclusions:

The study was generally in line with the old OECD test guideline 305. The validity criteria for the updated OECD TG 305 (2012) were met: the water temperature variation was less than ± 2°C, the concentration of dissolved oxygen did not fall below 60% saturation. However, 6 of 85 fish (7%) were dead in the control vessel and 18 fish ((21%) at 100 µg/L were dead. Because there were absolutely no signs of intoxication of fish in both vessels until the evening of the fourth day (82 h), it is assumed that a temporary dosing problem of phosphoric acid or dilution water in the night was responsible for the mortality. However, the pH measurement after 96 h did not indicate a dosing problem (any longer). The concentrations of the active substance were within ± 20 % of nominal hence, the results represent the bioaccumulation potential of desmedipham. The results were calculated over the period where the validity criteria were met. Hence the results can be used to assess the bioaccumulation potential. The calculated BCF was 66.

Executive summary:

The rainbow trouts (Oncorynchus mykiss) were maintained for 3 days in in a flow-through system dosed with ¹⁴C-labelled DESMEDIPHAM at two target dose levels of 100 and 500 µg/L (accumulation period) and then maintained in purified drinking water for 5-6 days (depuration period). The fish were analysed individually for total radioactivity by LSC and pooled per sampling date for analysis of the parent compound (and known metabolites when exceeding 10% of total radioactivity) by HPLC. The calculated BCF was 66.

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-08-10 to 1994-12-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 E (Bioaccumulation: Flow-through Fish Test)

Version / remarks:

May 12, 1981

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Vehicle:

yes

Remarks:

14C-DESMEDIPHAM: acetone; Unlabelled DESMEDIPHAM: acetonitrile

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION

Initially, 14C-DESMEDIPHAM (about 5 mCi) was quantitatively dissolved in 20 ml acetone (stock solution I). After LSC (liquid scintillation counting) the actual amount proved to be 4515.3 µCi at a specific radioactivity of 50.17 µCi/mg. The radiochemical purity amounted to > 99.9% .

For the low dose (target concentration 6.2 µg/L), based on a total volume of 3375 litres (a flow-through volume of 3001 per day during 7 days, 4 reserve portions and a tank volume of 75 I), an amount of 10.44 mg 14C-DESMEDIPHAM (2.32 ml of the stock solution I) was given into a vial and the acetone was evaporated under nitrogen. To the vial 10.48 mg unlabelled DESMEDIPHAM were given and the volume was made up to 25 mL by adding acetonitrile. After LSC, the amount of 14C-DESMEDIPHAM proved to be 21.21 mg in 25 mL at a specific radioactivity of 25.37 µCi/mg (stock solution II, low dose).

Similarly, for the high dose (target concentration 62 µg/L), based on a total volume of 3375 litres (a flow-through volume of 300 I per day during 7 days, 4 reserve portions and a tank volume of 75 L), an amount of 10.44 mg 14C-DESMEDIPHAM (2.32 mL of the stock solution I) was given into a vial and the acetone was evaporated under nitrogen. To the vial 198.90 mg unlabelled DESMEDIPHAM were given and the volume was made up to 25 ml by adding acetonitrile. After LSC, the amount of 14C-DESMEDIPHAM proved to be 209.68 mg in 25 mL at a specific radioactivity of 2.578 µCi/mg (stock solution III, high dose).

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trouts (Oncorynchus mykiss)
- Feeding: The fish were fed once daily (Kliba "Forellenfutter", diet of known lipid and total protein content), initially based on about 4% of the average fish body weight during acclimation and 4% of the fish body weight during the study, taking into account increasing body weights (assuming 25% increase/week) and the decreasing number of fish per sampling interval, i.e. ranging from 0.9 -1.1 g for the control tank and from 0.5 - 4.2 g for the treated tanks.
- Additional information: For the study, a total of 173 fish was used, taking into account accidental fish mortality. Additionally, 10 fish were used for a 96 hours pre-test on toxicity. Before starting the experiments, the fish were acclimized for at least one week to the laboratory environment.

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

other: Tap water

Total exposure / uptake duration:

7 d

Total depuration duration:

14 d

Test temperature:

15.3 - 16.5°C

pH:

7.7 to 8.0

Dissolved oxygen:

7.0 - 9.2 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Tank
- Type: open
- Fill volume: 75 L
- Aeration: yes
- No. of organisms per vessel: control – 25; low dose (6.2 µg/L) – 75; high dose (62 µg/L) – 73+
- No. of vessels per concentration: 1
- No. of vessels per control: 1
- Biomass loading rate: control – 0.13 g/L; low dose (6.2 µg/L) – 0.35 g/L; high dose (62 µg/L) – 0.32 g/L

OTHER TEST CONDITIONS
- Photoperiod: Twilight for 16 hours daily
- Light intensity: 500 lux

Nominal and measured concentrations:

Nominal test concentrations: 6.2 and 62 µg/L

Details on estimation of bioconcentration:

The average plateau levels in fish and fish parts including standard deviation were calculated by the non-linear parameter estimation program MINSQ (MicroMath Scientific Software, Salt Lake City, Utah 84121). The bioconcentration factor (BCF) was calculated from the concentration of radioactivity in the fish or fish parts at plateau level (Cf) related to the average concentration of parent equivalents in the water (Cw) during exposure:

BCF = Cf / Cw

Additionally, the uptake rate constants (k1) and the depuration rate constants (k2) with corresponding standard deviations of radioactivity in edibles, non-edibles and whole fish were calculated by the non-linear parameter estimation method using the program MINSQ .

Conc. / dose:

6.2 µg/L

pH:

4

Type:

BCF

Value:

157

Basis:

whole body d.w.

Time of plateau:

120 h

Remarks on result:

other: Initial BCF

Key result

Conc. / dose:

6.2 µg/L

pH:

4

Type:

BCF

Value:

333.9 L/kg

Basis:

whole body d.w.

Time of plateau:

120 h

Remarks on result:

other: Re-evaluated BCF

Details on results:

Observations
No mortality was observed during accumulation, justifying the choice of the selected concentrations.

Level of radioactivity in water during exposure and depuration
The levels of radioactivity found in the water of the respective tanks during the accumulation phase are shown in Table 4. The application solutions during the exposure period of 7 days were based on the target concentrations of 6.2 µg/L (tank 2) and 62 µg/L (tank 3). Actual concentrations ranged from 5.94 to 7.92 µg/L and from 57.14 to 65.61 µg/L for tank 2 and tank 3, respectively. Mean values amounted to 6.46 ± 0.71 µg/L (tank 2) and 61.33 ± 3.10 µg/L (tank 3). During depuration, radioactivity levels in the treated tanks were below background. The values in the water of the untreated tank 1 were always below background (Table 4).

Residual radioactivity in fish during exposure (Bioaccumulation)
Residual radioactivity in whole fish and in the edible and non-edible parts of fish during exposure to two dose levels during 7 days are presented in Tables 6 and 7 and in Figures 6 and 7. Corresponding background levels are presented in Table 5. The residues were calculated as parent equivalents according to the radioactivity found in fish or fish parts, and are based on the fresh weight of the respective material.

Depuration of residual radioactivity in fish
Depuration of radioactivity from rainbow trout during 14 days after 7 days of exposure to two different concentrations of 14C-DESMEDIPHAM is shown in Tables 6, 7 and 9 and in Figures 6 and 7.

Calculation of the bioconcentration factors
The bioconcentration factors (BCF) were calculated from the plateau levels of total radioactivity reached in fish or fish parts during exposure (calculated by MINSQ) and the concentration in the fish water expressed as µg parent equivalents per liter. BCF values and corresponding rate constants (k.,) including standard deviations are presented in Table 8. For the low dose, low BCF-values of 45.20, 290.7 and 157.3 for edibles, non-edibles and whole fish, respectively, were obtained. For the 10 times higher dose level, similar BCF-values were found, amounting to 37.83 (edibles), 228.1 (non-edibles) and 147.7 (whole fish).
According to report M-578715-01-1, from the original report, desmedipham has a logPow of 2.7 (pH 4-9, HPLC method). However, a new study performed at pH 4 according to the shake flask method, has been made available and the new logPow (3.5) is considered more reliable than the existing one. In the original study, the concentration of the parent substance was analysed in the medium over the course of the exposure phase, for both exposure concentrations. The results are provided in tables 12 and 13.

The bioconcentration factor (BCF) was calculated from the concentration of radioactivity in the fish or fish parts at plateau level (Cf) related to the average concentration of parent equivalents in the water (Cw) during exposure: BCF = Cf / Cw. Cw were 6.46 and 61.33 µg/L. However, desmedipham accounted for only 47.1 to 78.3% of the radioactivity in the low exposure concentration and for only 46.5 to 79.9% in the high exposure concentration. In order to reflect more accurately the bioconcentration potential of desmedipham, the BCF should be based on the measured concentration of the parent substance in water. As a worst case, the lowest measured amount of desmedipham was considered for further calculation (See "Attachments" in "Overall remarks, attachments" ), i.e. 47.1 and 46.5% for the low and high concentrations, respectively.

The available information on bioconcentration of desmedipham in fish has been re-assessed (documented in report M-578715-01-1) in order to consider the hydrolytic behaviour of the substance. New BCF values were derived on the basis of the amount of parent substance in water, with worst case assumptions. Steady state BCF are in the range 317.7 – 333.9 L/kg in whole fish.

See "Attachments" in "Overall remarks, attachments" for the tables.

Validity criteria fulfilled:

yes

Remarks:

The water temperature variation was less than ± 2°C, the concentration of dissolved oxygen did not fall below 60% saturation and no mortality was reported in any test group or control.

Conclusions:

After exposure to DESMEDIPHAM, low plateau levels were reached at about 120 hours (5 days) at both dose levels for non-edibles and whole fish and at 29 to 55 hours for edibles. After the exposure period, depuration from fish and fish parts during 336 hours (14 days) occurred with half-lives of 10.6 - 24.5 hours for non-edibles and whole fish and 69.3 - 95.0 hours for edibles, indicating that initial uptake of DESMEDIPHAM in fish was highly reversible. After 14 days of depuration the remaining residual radioactivity in fish and fish parts decreased to about 4 to 20 % of the accumulated radioactivity. The bioaccumulation study on rainbow trout of DESMEDIPHAM at concentrations of 6.46 µg/L (low dose) and 61.33 µg/L (high dose) during an exposure period of 7 days showed low BCF values of 37.83 - 45.20 in edibles, 228.1 - 290.7 in non-edibles and 147.7 -157.3 in whole fish. However, the available information on bioconcentration of desmedipham in fish has been re-assessed (documented in report M-578715-01-1) in order to consider the hydrolytic behaviour of the substance. New BCF values were derived on the basis of the amount of parent substance in water, with worst case assumptions. Steady state BCF are in the range 317.7 (high dose) – 333.9 L/kg (low dose) in whole fish.

Executive summary:

The rainbow trouts (Oncorynchus mykiss) were maintained for 7 days in tap water dosed with 14^C-labelled DESMEDIPHAM in two separate tanks at two target dose levels of 6.2 μg/L and 62 μg/L (accumulation period) and then maintained in untreated tap water for 14 days (depuration period). Radioactivity levels in whole fish, edible and non-edible parts and water were determined at various time intervals during the entire study (21 days). The calculated BCF from the original report was 157.3, while the re-evaluted BCF given was 333.9 L/kg (low dose) in whole fish.

Description of key information

In the table below all available studies are listed. For some studies only the results are presented since they are not considered relevant due to the reasons given under “Assessment”. All available studies have been evaluated within the scope of Plant Protection Regulation in the respective Draft Renewal Assessment Report (DAR) under Regulation (EC) 1107/2009.

Test species	Result	Assessment	Reference
Oncorhynchus mykiss (rainbow trout)	BCF = 333.9 (whole fish)	Key study	Burri (1994); amended by Herno (2017)
Oncorhynchus mykiss (rainbow trout)	BCF = 66	Supporting study	Schäfers (2004)
Lepomis macrochirus (bluegill sunfish)	BCF = 98	This study is not considered valid. Also, the re-evaluation by Herno (2017) concludes that the study is not valid.	Blakemore (1993); amended by Herno (2017)

Key value for chemical safety assessment

BCF (aquatic species):

334 dimensionless