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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August - September 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This robust summary has a reliability rating of 1 because the study followed a standard guideline, followed GLP guidelines, and was conducted without deviations that would invalidate the study.
Qualifier:
according to guideline
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Samples for analysis of new and old test solutions and controls were taken on days 1, 2, 3, 7, 10, 14, 17, and 21.
Vehicle:
no
Details on test solutions:
The water accommodated fraction (WAF) of the test material was prepared by stirring the test material in the exposure solution for approximately 2 days with a 1 to 3 hour settling period, after which the aqueous phase was removed and added to the test system. An equilibration study was conducted over a period of 96 hours prior to the definitive study to determine the approximate length of time needed to stir the test substance in the test media to acheive a saturated solution. Results suggested that a stirring period of approximately 2 days would be sufficient to reach equilibrium. The stirring period to develop WAFs used through the study ranged from 44.5 to 46.5 hours.
Test organisms (species):
Daphnia magna
Details on test organisms:
Organisms used in the test were from a laboratory culture were less than 24 hour old. The source of the culture was from Zeneca Brixham Laboratory from I.R.Ch.A., France.
Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
21 d
Post exposure observation period:
None
Hardness:
154 to 170 mg/L CaCO3
Test temperature:
20.1 to 20.5 degrees C
pH:
8.3 to 9.0
Dissolved oxygen:
7.8 to 9.1 mg/L
Nominal and measured concentrations:
The nominal treatment levels of the test substance included a control and 1000 mg/L, which measured <0.002 (the limit of detection, with the exception of the day 10 control sample, which measured 0.003 mg/L) and 0.036 mg/L, respectively. The measured data represent the mean test substance concentration of samples taken from new and 24-hour old treatment solutions from days 1, 2, 3, 7, 10, 14, 17, and 21. The mean concentration of the test substance in new and old WAFs was 0.047 and 0.025 mg/L, respectively. The percent decrease in concentration of test material in solution from new to old WAFs on the sampling days ranged from 41 to 54%.
Details on test conditions:
The study was conducted in closed test systems that were renewed daily during the study. The test systems used were 150 ml glass Erlenmeyer flasks that were completely filled with media so as not to leave any headspace. The control and treatment level were each evaluated in 10 replicate test systems. One organism, less than 24 hours old, was added to each control and treatment solution flasks and were fed each day of the study. The feed was chlorella vulgaris at a rate of 0.3 mg carbon/daphnid/day. This rate was greater than that suggested in the OECD guideline (0.2 mg carbon/daphnid/day) because the test vessels were larger than specified by the guideline (50 to 100 ml). Light intensity was 505 lux.
Reference substance (positive control):
no
Key result
Duration:
21 d
Dose descriptor:
EL50
Effect conc.:
> 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
immobilisation
Key result
Duration:
21 d
Dose descriptor:
NOELR
Effect conc.:
< 1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
Adult immobility: control - 10%; 1 mg/L - 10%
Total live young produced: control - 1245; 1 mg/L - 841
Mean number of live young produced per surviving adult: control - 138; 1 mg/L - 93
Mean number of dead young produced per surviving adult: control - 0; 1 mg/L - 13

Reduction in fecundity in 1 mg/L treatment relative to control:
Brood 1 - 88%
Brood 2 - 73%
Brood 3 - 39%
Brood 4 - ca.0%
Brood 5 - (-46%) the treatment solution produced a greater number of live young (31) than the control (16 live young)
Reported statistics and error estimates:
The significance of differences in the mean number of live young produced by adults in 21 days between the control and treatment solutions was assessed using a two-sample T-test.
Validity criteria fulfilled:
yes
Remarks:
The results show that survival of the adult control daphnids (90%) and the mean number of living offspring produced per surviving control parent (138) fulfilled the test validity criteria of >/= 80% and >/= 60 young/daphnia.
Conclusions:
During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.
Executive summary:

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

Description of key information

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

Key value for chemical safety assessment

Additional information

Hydrocarbon solvents are UVCBs formed by homologous series of different classes of hydrocarbons. As these test substances are complex petroleum substances comprising large numbers of poorly water soluble hydrocarbons, it has been recommended that only ecotoxicity data generated using a “water accommodated fraction” (WAF) approach will be suitable for the purposes of classifying and labelling for environmental hazard. In the WAF methodology, test substances are typically equilibrated with water at each "concentration" or loading rate in sealed test vessels and the water phase ("WAF") tested for toxicity. Test data generated using other approaches, like gas phase loading or Water Soluble Fraction (WSF) testing, are not considered appropriate due to methodological issues which will impact hydrocarbon exposure concentrations.

 

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

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