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Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well-documented peer-reviewed article.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Twenty grams (wet weight) of the prepared sediment was added to clean 60 mL glass vessels followed by 30 mL of groundwater drawn from an aquifer. After 24 hours of equilibration, 10 mature Lumbriculus (ca. 15 mm in length, 8 mg dry weight) were added to each vessel. Vessels were aerated for 5 minutes every day and the overlying water replenished with distilled water every two days. Each test concentration was replicated 6 times. LAS concentrations were measured at 0 and 28 days. After 28 days the sediment was removed and all live worms counted, blotted dry, and wet weighed prior to air drying for 48 hours to a constant dry weight.
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Liquid scintillation monitoring with and without HPLC.
Vehicle:
yes
Details on sediment and application:
Natural sediment was collected on Nov. 21, 1997 from ARC Study Centre, UK. The composition was 44% sand, 48% silt, and 8% clay. Total organic carbon content was 1.7%. Dried sediment samples were mixed with wet sediment for 1 hr. 10 +/-1 g samples of sediment were spiked with aliquots of LAS in dichloromethane (100 mg LAS/ml dichloromethane) and radiolabeled LAS. Samples were left overnight so the vehicle could evaporate. Unspiked sediment was used for control.
Test organisms (species):
Lumbriculus variegatus
Study type:
laboratory study
Test type:
semi-static
Water media type:
freshwater
Type of sediment:
natural sediment
Duration:
28 d
Exposure phase:
total exposure duration
Hardness:
250 mg/L CaCO3
pH:
8.0
Nominal and measured concentrations:
nominal: 50, 75, 100, 150 300 and 600 mg/kg dry weight
Details on test conditions:

Twenty grams (wet weight) of the prepared sediment was added to clean 60 mL glass vessels followed by 30 mL of groundwater drawn from an aquifer. After 24 hours of equilibration, 10 mature Lumbriculus (ca. 15 mm in length, 8 mg dry weight) were added to each vessel. Vessels were aerated for 5 minutes every day and the overlying water replenished with distilled water every two days. Each test concentration was replicated 6 times. LAS concentrations were measured at 0 and 28 days. After 28 days the sediment was removed and all live worms counted, blotted dry, and wet weighed prior to air drying for 48 hours to a constant dry weight.




EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : survival, reproduction, and biomass measurements at end of study
The mode of reproduction (architomy) necessitates the treatment of survival and reproduction as a single endpoint, i.e., number of organisms at test termination.

Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
>= 105 mg/kg sediment dw
Basis for effect:
mortality
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
81 mg/kg sediment dw
Basis for effect:
mortality
Details on results:
LAS half-life in aerobic sediment was approximately 20 days. This is shorter than studies conducted in the same sediment without worms (half-life of 38 days), most likely due to increased bioturbation due to worm activity.

There was a loss of between 15 and 78% of the LAS radioactivity over the duration of the test, which was attributed to mineralization of LAS by the worms and microorganisms present in the sediment (biodegradation).  Results are therefore based on the average of day 0 and day 28 measured sediment concentrations.  All results are shown in the following table.

                                    

Sediment Concentration (mg/kg dw)

Survival/Reproduction Endpoint

NOEC

LOEC

EC20

EC50

Based on nominal values

100

150

90

136

Based on measured day 0 values

136

170

131

164

Based on mean of days 0 & 28 values

81

110

73

105

Biomass Endpoint

Based on nominal values

100

150

108

144

Based on measured day 0 values

136

170

146

166

Based on mean of days 0 & 28 values

82

110

102

109

Validity criteria fulfilled:
yes
Conclusions:
The 28-day EC50 is >= 105 mg/kg sediment dw.
Executive summary:

This study determined the toxicity to sediment dwelling organisms. Samples of natural sediment were spiked with test substance at concentrations of 50, 75, 100, 150, 300, and 600 mg/kg/dry weight. 10 test organisms of species Lumbriculus variegatus were then added. Exposure lasted 28 days, at which time the organisms were observed for survival and biomass. The test substance half-life in aerobic sediment was approximately 20 days. The EC50 was >= 105 mg/kg sediment dw.

Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well-documented peer-reviewed article.
Qualifier:
no guideline followed
Principles of method if other than guideline:
A 3-day chronic study was conducted using sediment spiked with cold-material LAS.
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
Liquid scintillation monitoring with and without HPLC.
Vehicle:
yes
Details on sediment and application:
The test sediment contained 44% sand, 48% silt, and 8% clay, with 2% organic matter.
Test organisms (species):
Caenorhabditis elegans
Details on test organisms:
The test species is an infaunal bacterial feeder with a short life cycle, so 72 hrs (3 days) is considered a chronic test.
Study type:
laboratory study
Test type:
semi-static
Water media type:
freshwater
Type of sediment:
artificial sediment
Duration:
72 h
Exposure phase:
total exposure duration
Hardness:
250 mg/L CaCO3
pH:
8.0
Nominal and measured concentrations:
Nominal concentrations were in the range of 10-1000 mg/kg dw. The nominal concentrations were 10, 50, 100, 200, 300, 400, 500, 750 and 1000 mg/kg dw and controls.
Details on test conditions:
At the start of the test, ten juvenile worms of the first stage (270 ± 16 µm body length) were transferred to each test vial containing 0.75 g wet weight of spiked sediment mixed with 0.25 mL of a bacterial suspension. Five replicates were set up for each treatment, and the samples were incubated on a shaker at 20°C. After 72 hours the test was stopped by heat-killing the worms at approximately 50°C. The samples were mixed with an aqueous solution of rose Bengal to stain the worms for easier recovery. Sublethal toxicity endpoints were determined for growth based on the body length of the organisms, and fecundity by counting the number of eggs in the body of the test organism (egg production).
Duration:
3 d
Dose descriptor:
other: EC10
Effect conc.:
275 mg/kg sediment dw
Basis for effect:
growth rate
Duration:
3 d
Dose descriptor:
NOEC
Effect conc.:
200 mg/kg sediment dw
Basis for effect:
growth rate
Details on results:
The test was regarded as valid as the fertility of the test organisms in the control was ¿ 80%.

Nominal Sediment Concentration (mg/kg dw)

Test Parameter

NOEC

LOEC

EC10

EC30

Growth

200

300

275

Fertility

200

300

258

Egg Production

100

200

125

Validity criteria fulfilled:
yes
Conclusions:
The 3-day EC10 was 275 mg/kg sediment dw based on growth rate.
Executive summary:

This study determined the toxicity to sediment dwelling organisms. Samples of natural sediment were spiked with concentrations of 10, 50, 100, 200, 300, 400, 500, 750 and 1000 mg/kg dw mg/kg dw and controls. 10 test organisms of species Caenorhabditis elegans were then added. Exposure lasted 3 days, at which time the organisms were observed for survival and reproduction. The EC10 was 275 mg/kg sediment dw based on growth rate.

Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not reported
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Followed guideline with minor deviation, well documented, non GLP
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
Surfactant levels in sediment, OW, and IW were measured during the hatchability and chronic tests. A detailed description of the analytical procedures is not available in either the publication or the study report.

SEDIMENT
- Sorbed levels of LAS were measured at the beginning and twice during the sediment-spiking experiment. A 3 ml syringe with the narrow end removed was used to collect sediment cores from each chamber.

PORE WATER (INTERSTITIAL WATER) (IW)
- Sampling interval: Upon completion of each test, IW was collected by decanting overlying water, centrifuging the wet sediment at 10,000 rpm for 40 min, and collecting the supernatant as IW.

OVERLYING WATER (OW)
- Sampling interval: Sampled every 2 to 3 d throughout the tests by pipetting duplicate 10 mL aliquots directly from test chambers.
Vehicle:
no
Details on sediment and application:
PREPARATION OF SPIKED SEDIMENT
- Natural stream sediment was collected from a pristine site in Rapid Creek, South Dakota, and contained no detectable levels of LAS, pesticides, or heavy metals as determined by GC and AA analyses.
- Pooling or mixing of different substrates: Not applicable
- Method of mixing: Mechanical stirring
- Details of spiking: Test material was added to sediment slurry and mechanically stirred overnight. Then the sediment was poured into each test chamber and allowed to settle.
- Equilibration time: overnight, with mechanical mixing
- Equilibration conditions: Not reported
- Controls: Control was maintained from the sediment without the addition of test material

PREPARATION OF SPIKED WATER
- Details of spiking: The test materials were combined in known proportions in aqueous stock solutions.
- Controls: Dilution water without test materials.
Test organisms (species):
Chironomus riparius
Details on test organisms:
TEST ORGANISM
- Common name: Midge
- Strain/clone: Not reported
- Source: from P&G ESD (environmental safety department) stock. Original source not provided.
- Age of parental stock: Not reported
- Breeding conditions: Midges used in this study were reared in 10-gallon tanks, with screened tops, containing 4 gallons of aerated well water replenished at a rate of 2 L/hr. Two inches of natural stream sediment served as substrate in culture chambers. Midge cultures (and test organisms) were fed a mixed diet of Ralston-Purina trout chow-dehydrated alfalfa (5:1, w/w). This was supplemented with commercial dog treats at a rate adjusted to prevent fouling. Cultures were maintained at 22 ± 2 °C. Water hardness was 150 mg/L as CaCO3, pH ranged 7.8 to 8.4, and there was a 16:8 hr photoperiod (400 ft-c).
- Handling of egg masses and larvae: Not reported
- Age of animals at beginning of exposure: 1-2 d
- Feeding during test: Yes
- Food type: Same as culture. Feeding was discontinued upon emergence of the first adult in each test chamber.
- Amount: Not reported
- Frequency: Not reported

ACCLIMATION
- Acclimation period: Not reported. However, midge were obtained in-house, cultured under the same conditions as the test.
- Acclimation conditions: Same
- Type and amount of food: See description of culture above.
- Feeding frequency: Not reported
- Health during acclimation (any mortality observed): Not reported
Study type:
laboratory study
Test type:
other: Semistatic (Egg hatchability) & Flow through (Chronic assay)
Water media type:
freshwater
Type of sediment:
natural sediment
Limit test:
no
Duration:
24 d
Exposure phase:
total exposure duration
Remarks:
72 h (Egg hatchability) was also done
Post exposure observation period:
Not reported
Hardness:
150 mg/L as CaCO3
Test temperature:
22±2°C
pH:
7.8-8.4
Dissolved oxygen:
Details not provided in publication. However, the chronic test was flow-through, and the acute test was static renewal, and low DO was not anticipated.
Salinity:
Not reported
Ammonia:
Not reported
Nominal and measured concentrations:
Egg hatchability (acute tes): Nominal concentrations not provided in publication. Measured concentrations were 0.0, 1.0, 4.7, 9.4, and 18.9 mg/L.

Chronic assay (test a): Nominal concentrations not provided in publication. The measured concentrations provided in the report were 0, 2.4, and 3.7 mg/L.

Chronic assay (test b): Nominal concentrations were 0, 1.5, 3, 6, and 12 mg/L. Measured concentrations not available for test b.

Chronic assay (sediment-spike LAS): Nominal concentrations not provided in publication. Measured concentrations were 0.0, 8±2, 42±5, 146±18, 319±23, 993±225 mg/kg sediment (dry weight).

All results are based on measured concentrations, except for test b. Details on measured concentrations are in "any other information on results" below (Tables 1,2,3,4).
Details on test conditions:
TEST SYSTEM- Test container (material, size): 13 W x 25 L x 18 H cm dimensions chamber (chronic assay); 50 ml Cylindrical test chamber with Nitex® bottom ( Egg hatchability);
- Sediment volume: 350 g (note: chronic tests were conducted with and without sediment)
- Weight of wet sediment with and without pore water: 350 g sediment (dry weight equivalent) per test chamber (Chronic assay); Wet sediment was autoclaved for 40 to 60 min before testing to reduce microbial populations and minimize initial rates of surfactant biodegradation.
- Overlying water volume: Not reported
- Depth of sediment and overlying water: Not reported
- Aeration: No (chronic test was flow-through; acute test was semi-static)

EXPOSURE REGIME (Egg hatchability)
- No. of organisms per container (treatment): 20 eggs in a loop
- No. of replicates per treatment group: Duplicate
- No. of replicates per control / vehicle control: Duplicate
- Feeding regime: Fed each day following water replenishment
- Type and preparation of food: Not reported
- Amount of food: Not reported

EXPOSURE REGIME (Chronic assay)
- No. of organisms per container (treatment): 2 0 larvae per chamber
- No. of replicates per treatment group: Duplicate
- No. of replicates per control / vehicle control: Duplicate
- Feeding regime: Each food formulation daily
- Type and preparation of food: Not reported
- Amount of food: 1 mL

RENEWAL OF OVERLYING WATER
- Details on volume additions: Egg hatchability test: Replenished daily by trickling 150 mL directly into each test chamber and allowing excess volume from the overflow beaker to drain. Chronic test: flow-through design; details on renewal not provided.
- Flow-rate: Not reported

OVERLYING WATER CHARACTERISTCS: Not reported
- Type of water: Blend of deionized, reverse osmosis water and well water with a hardness of approximately 150 mg/L as CaCO3. This ¿blended¿ water, a mixture of deionized and well water, is often used in environmental testing at P&G. The details are not provided in the publication, but this water has been well characterized.
- Filtration: Not reported
- Alkalinity: Not reported
- Conductivity: Not reported
- Particulate matter: Not reported
- Total organic carbon: Not reported
- Chemical oxygen demand: Not reported
- Unionized ammonia: Not reported
- Residual chlorine: Not reported
- Total organic chlorine compounds and PCBs: Not reported
- Total organophosphorous compounds: Not reported
- Total organic chlorine: Not reported

SOURCE OF NATURAL SEDIMENT
- Location and description of sampling site: Pristine site in Rapid Creek, South Dakota
- Contamination history of site: Contained no detectable levels of test materials, pesticides or heavy metals

HANDLING OF NATURAL SEDIMENT
- Time of collection: Not reported
- Core depth: Not reported
- Water depth: Not reported
- Storage conditions: Not reported
- Storage duration (prior to test): Not reported


CHARACTERIZATION OF SEDIMENT
- Particle size distribution:
% fine sand: 6 %
%medium sand: 4%
% fine silt : 19 %
% clay: 71 %
- Colour/texture: Not reported
- Moisture: Not reported
- Presence of macrophytes/animals: Not reported
- Metals: Not reported
- Sulfides: Not reported
- Organic compounds: Not reported
- Total volatile solids: Not reported
- Acid volatile sulfides: Not reported
- Oil and grease: Not reported
- Petroleum hydrocarbons: Not reported
- Sediment sieved: Not reported
- pH pore water: Not reported
- pH dry matter and/or whole sediment: Not reported
- Ammonia content of pore water: Not reported
- Total organic carbon (%): 4.2% prior to testing; 8.8% reanalysis following the test
- Total inorganic carbon (%): Not reported
- BOD: Not reported
- COD: Not reported
- CEC: Not reported
- Proof of absence of chemical contaminants: Yes

OTHER TEST CONDITIONS
- Light quality: Not reported
- Photoperiod: 16 h light : 8 h dark
- Light intensity: 400 ft-c at the water surface

EFFECT PARAMETERS MEASURED: Acute test - egg hatching and survival of newly hatched larvae. Chronic test - midge larval and pupal development was measured by % emergence as winged adults (daily observations).

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Egg hatchability test: 2.0 to 4.7. Chronic test: 2.2 to 5.3. These spacing factors are based on the measured concentrations.
- Range finding study: Static acute (48 hr) tests with 72-hr, posthatch larvae were used to target concentration ranges for the initial chronic test with nonspiked sediment. (No details of the range finding study are provided in the publication.)
- Results used to determine the conditions for the definitive study: Yes

CHRONIC ASSAY PROCEDURE
-Test materials were cycled through the chambers for at least 3 d to equilibrate exposure conditions before introducing organisms.
- Water flow was turned off for 24 h to allow larvae to settle to the bottom. Before continuous cycling was restarted, overflow water from a single cycle was collected from each chamber and examined for larvae. If larvae were present, water flow was suspended an additional 24 h. In most cases, the larvae settled during the initial static period. Tests were continued until all live midges emerged as adults.
- The average test duration was 24 d. Numbers of winged adults were recorded daily; typically, they first emerged 12 to 14 d after hatching.
Reference substance (positive control):
no
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
2.4 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test a (no sediment present)
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
4.5 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test a (w/sediment). Estimated from graph.
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
3 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test b (no sediment present)
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
3 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test b (w/sediment: sand-silt)
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
6 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test b (w/sediment: sand)
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
6 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: test b (w/sediment: silt)
Duration:
24 d
Dose descriptor:
NOEC
Effect conc.:
319 mg/kg sediment dw
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: sediment spiked with LAS
Duration:
24 d
Dose descriptor:
LOEC
Effect conc.:
993 mg/kg sediment dw
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Remarks on result:
other: Sediment spiked with LAS
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
> 1 - < 4.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
mortality
Remarks on result:
other: survival of newly hatched larvae
Details on results:
- Mortality of test animals at end of exposure period: In the egg hatchability assay, at the lowest exposure level 1.5 % mortality was observed. At 4.7 mg/L and above, 100% mortality was observed. For details see Table 1 under `Any other information on results incl. tables¿
- Total mass of test animals at beginning of test: Not reported
- Changes in body weights of live adults: Not reported
- No. of offspring produced: Not reported
- No. of emerged male and female midges (per vessel and per day): Not reported
- No. of pupae failing to emerge (per vessel and per day): Not reported
- Percent emergence per test concentration: See Tables 2,3,4 under `Any other information on results incl. tables¿
- Mean development rate of fully emerged midges: Not reported
- Mean individual dry weight of larvae: Not reported
- Morphological abnormalities: Not reported
- Behavioural abnormalities: Not reported
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Chi-square analyses used for significant differences among treatments and variance homogeneity were applied to numbers of larvae and unhatched egg - Probit analysis used to calculate EC50 values for each data set in chronic assay

Table 1. Effects of LAS upon Chironomus egg hatching success and survival of newly hatched larvae

Average measured concentration

(mg/L)

Egg hatching success

(%)

Survival

(%)

0.0

100

91

1.0

100

88.5

4.7

100

0a

9.4

100

0a

18.9

100

0a

a Significantly  different from control value (p < 0.05)

72 hr (acute) test.

Table 2. Chronic toxicity of LAS to Chironomus: Effect of sediment

Details of this experiment are in a graph in the publication.

Table 3. Chronic toxicity of LAS to Chironomus: Effect of substrate

Overlying water concentration (mg/L; nominal)

Emergence of winged adults (%)

No substrate

Sand

Sand-silt

Silt

0

80

100

100

100

1.5

80

100

100

85

3

75

95

100

85

6

40a

95

75a

75

12

5a

0a

20a

0a

a Significantly different(p< 0.05) from respective control value

Table 4. Partitioning and chronic effects of LAS to Chironomus: Sediment-spiked experiment

Surfactant sediment

Concentrations (ppm; mean ± SE)

Interstitial water (lW)

overlying water (OW)

% Emergence

993±225

15.2 ± 2.7

1.69±0.12

73a

319 ± 23

15.0 ± 1.4

1.05 ± 0.Q7

90

146 ± 18

7.7±1.1

0.59 ± 0.05

90

42 ± 5

1.5 ± 0.3

0.35 ± 0.01

90

8 ± 2

0.2 ± 0.0

0.32 ± 0.01

95

0(control)

0

0

98

a Significantly different(p< 0.05) from control value

 

Validity criteria fulfilled:
yes
Conclusions:
The effect of C12 LAS (linear alkylbenzene sulfonate) on midge was evaluated in acute and chronic tests. The 24-day chronic NOEC was 2.4 mg/L, based on emergence. The 72-hour acute LC50 was between 1.0 and 4.7 mg a.i./L, based on survival of newly hatched larvae.
Executive summary:

A sediment toxicity test of LAS (linear alkylbenzene sulfonate) was conducted following the OECD 218 guideline, using the midge Chironomus riparius.  All results are based on the measured concentration of the test substance. The LAS had an average alkyl chainlength of 11.9, and was comprised of C10 -C14 alkyl chains.

In an egg hatchability semi-static assay (acute test), midge eggs were exposed to a range of LAS concentrations in water and were monitored for hatching success and posthatch survival. No significant reduction in egg hatching was observed at the highest concentration tested (18.9 mg/L). However, significant reduction in the survival of the newly hatched larvae occurred at 4.7 mg/L. The 72h LC50 was between 1.0 and 4.7 mg/L, based on survival of newly hatched larvae.

In the partial life cycle bioassay in a flow-through sediment/water test system (chronic test), percentages of winged adults emerging after continuous exposure of larvae and pupae to a range of LAS concentrations were determined. Exposure concentrations in sediment, interstitial water and overlying water were monitored by 14C liquid scintillation counting. The effect of LAS level in the water column was determined in a total of 6 chronic toxicity tests. The NOECs from these tests were 2.4 -3.0 (without sediment), and 3.0 -6.0 (with sediment). The effect of LAS on Chironomus was also evaluated in an experiment using sediment spiked with LAS. In this test, the NOEC of sediment-spiked LAS was 319 mg/kg sediment (dry weight basis). The normalized NOEC is 2.87 mg/L for C11.6 LAS (van de Plassche et al., 1999).

Description of key information

Three sediment toxicity studies are available using LAS. The first study (Comberet al. 2006) determined the toxicity to sediment dwelling worms. Samples of natural sediment were spiked with test substance at concentrations of 50, 75, 100, 150, 300, and 600 mg/kg/dry weight. Ten test organisms of species Lumbriculus variegatus were then added. Exposure lasted 28 days, at which time the organisms were observed for survival and biomass. The test substance half-life in aerobic sediment was approximately 20 days. The EC50 was ≥ 105 mg/kg sediment dry weight. The NOEC was 81 mg/kg sediment dry weight.

The second study (Comberet al. 2006) consisted of samples of natural sediment spiked with concentrations of 10, 50, 100, 200, 300, 400, 500, 750 and 1000 mg/kg dw and controls. Ten test organisms of the nematode species Caenorhabditis elegans were then added. Exposure lasted 3 days, at which time the organisms were observed for survival and reproduction. The NOEC for egg production was 100 mg/kg sediment dw, the NOEC for fertility was 200 mg/kg sediment dw and the EC10 for growth was 275 mg/kg sediment dw.

In the final toxicity study (Pittinger et al. 1989; The Procter & Gamble Company 1986; van de Plassche et al 1999), which was conducted following the OECD 218 guideline, the midge Chironomus riparius, was exposed to C11.9LAS for 24 days. This actually consisted of a series of separate tests. In an egg hatchability semi-static assay (acute test), midge eggs were exposed to a range of LAS concentrations in water and were monitored for hatching success and posthatch survival. No significant reduction in egg hatching was observed at the highest concentration tested (18.9 mg/L). However, significant reduction in the survival of the newly hatched larvae occurred at 4.7 mg/L. The 72 hour LC50 was between 1.0 and 4.7 mg/L, based on survival of newly hatched larvae. In the partial life cycle bioassay in a flow-through sediment/water test system (chronic test), percentages of winged adults emerging after continuous exposure of larvae and pupae to a range of LAS concentrations were determined. Exposure concentrations in sediment, interstitial water and overlying water were monitored by14C liquid scintillation counting. The effect of LAS level in the water column was determined in a total of six chronic toxicity tests. The NOECs from these tests ranged from 2.4 to 3.0 (without sediment), and 3.0 to 6.0 (with sediment). The effect of LAS on Chironomus was also evaluated in an experiment using sediment spiked with LAS. In this test, the NOEC of sediment-spiked LAS was 319 mg/kg sediment (dry weight basis). The normalized NOEC is 2.87 mg/L for C11.6LAS.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
81 mg/kg sediment dw

Additional information

Three toxicity studies are available for sediment organisms. Test materials are considered to represent the materials in the category. As summarized in the Table below, the average alkyl chain lengths of tested materials ranged from C11.4 to C11.8, similar to C11.6 for the LAB Sulfonic Acids/LAS typically used in European detergent formulations. The C14 homologue content of tested materials was not reported for the C11.4 LAS (and likely to be <=1%) while the C14 content for the C11.8 LAS was 8.7%, compared to <1% for the LAS used in European detergent formulations.  The lowest sediment data point is a 28 day NOEC = 81 mg/kg sediment dw for the earthworm Lumbriculus variegates using C11.4 LAS.

 

Table: Alkyl Chain Lengths and C14 Content of LAS Used in Sediment Toxicity Tests*

Test

Average Alkyl Chain Length

C14 Homologue Content

Results

.001 Earthworm (Lumbriculus variegates)

C11.4

N/A

28 day NOEC = 81 mg/kg sediment dw

.002 Nematode (Caenorhabditis elegans)

C11.4

N/A

72 hour NOEC (egg production) = 100 mg/kg sediment dw

.003 (midge,Chironomus riparius), water only test

C11.8

8.7%

24 day NOEC = 319 mg/kg sediment dw

* N/A = not available, dw = dry weight.

 

Based on the availability of toxicity data on three sediment organisms, the assessment factor (AF) method was used to determine the PNECsediment in accordance with R.10.5.2.2. Based on the lowest NOEC value from the three studies (81 mg/kg sediment dw) and an AF = 10 (in accordance with Table R.10-7), the final calculated PNECsediment-freshwater value is 8.1 mg/kg sediment dw. Applying an additional assessment factor of 10 for marine systems results in the final calculated PNECsediment-marine value of 0.81 mg/kg sediment dw.