LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
termination. Sediment concentrations were monitored using LSC and
verified with HPLC.
GLP: Yes [X] No [ ] ? [ ]
Test substance: LAS (Procter & Gamble), average alkyl chain length C11.4. The radiolabelled
LAS was 3-dodecylbenzene sulfonate (DOBS; 95% purity)
Results: 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 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
Biomass Endpoint
81 110 73 105
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
Remarks: LAS half-life in aerobic sediment was approximately 20 days. This is
shorter than studies conducted in the same sediment without worms (halflife
of 38 days), most likely due to increased bioturbation due to worm
activity. No specific endpoint was particularly sensitive to LAS.
Reference: Comber, S.D.W., Conrad, A.U., Hurst, K., Hoss, S., Webb, S., and Marshall,
S. 2004. Chronic toxicity of sediment-associated linear alkylbenzene
sulphonates (LAS) to freshwater benthic organisms. Manuscript in
preparation.
Reliability: 2 Valid with restrictions
(s)
Type : Artificial soil [ ]; Filter paper [ ]; Other [X] Spiked Sediment
Species: Caenorhabditis elegans (Nematode)
Endpoint: Mortality [ ]; Weight [ ]; Other [X] Survival, Fertility, Egg Production
Exposure period: 3 days
Results: LC50 (3 d) > 100 mg/kg soil dry weight
NOEC = 100 mg/kg soil dry weight (egg production)
Method: A 3 day chronic study was conducted using sediment spiked with coldmaterial
LAS. Nominal concentrations were in the range of 10 to 1,000
mg/kg/dw. The test species is an infaunal bacterial feeder with a short life
cycle, so 72 hours (3 days) is considered a chronic test. The nominal
concentrations were 50, 75, 100, 150, 300, 600 mg/kg/dry weight and
controls. The test sediment contained 44% sand, 48% silt, and 8% clay,
with 2% organic matter. 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). The test
was regarded as valid as the fertility of the test organisms in the control was
≥ 80%.
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