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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP; Non-guideline; published in peer reviewed literature; minor restrictions in design and/or reporting but otherwise adequate for assessment.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
not specified
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data reported
Analytical monitoring:
no
Details on sampling:
No data reported
Vehicle:
not specified
Details on test solutions:
No data reported
Test organisms (species):
Daphnia magna
Details on test organisms:
Saturated solutions prepared using double distilled water and allowed to settled for 48 hours at room temperature before bioassay. Solutions diluted just before use.
Test type:
static
Water media type:
freshwater
Total exposure duration:
48 h
Post exposure observation period:
No data reported
Hardness:
Distilled water
Test temperature:
23± 2°C
pH:
7 - 6
Dissolved oxygen:
9 - 5 mg/l
Salinity:
Not applicable
Nominal and measured concentrations:
No analysis was done since it was assumed that there was negligible loss of the compound from the saturated solution by volatilisation. Amounts of saturated solutions added were determined by the differences in mass before and after addition. Concentrations were calculated from available literature solubility of compounds and from the extent of dilution.
Details on test conditions:
Daphnia bioassays were performed in 24mL glass vials with teflon lined screw-on caps, 10 animals per vial, 2-4 replicates per test concentration and at least 5 test concentrations and controls. Daphnia were placed in the glass vials of known mass with a known amount of distilled water. The saturated aqueous solution was then added to the vials and the final mass determined. Solution was added to the point of overflow and the vials were immediately closed tightly and shaken gently for a few minutes. Vials had no air spaces, were not aerated and the animals were not fed during the bioassays. Control tests were conducted by placing animals in diluent water with no toxicant. A toxicity test was valid if the average control mortality did not exceed 10% (death was defined as immobility). If av control mortality did exceed 10% , the test was repeated.
Reference substance (positive control):
yes
Remarks:
Phenol
Key result
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 95% CL 2.6 - 13.2 mg/L
Details on results:
LC50 = 50 mmol/m3 ( 6.0 mg/L). 95% confidence interval = 22-110 mmol/m3 (2.6 - 13.2 mg/L). Based on water solubility of 474 mmol/m3 and 5 test concentrations.
Results with reference substance (positive control):
Phenol (LC50 319 mmol/m3 or 30mg/L)
Reported statistics and error estimates:
95% confidence interval = 22-110 mmol/m3 (2.6 - 13.2 mg/L).
Validity criteria fulfilled:
yes
Remarks:
Toxicity test considered valid if average control mortality did not exceed 10%. Dissolved oxygen > 3 mg/L during test.
Conclusions:
The reported experimental 48 hour LC50 for Daphnia magna was determined to be 50 mmol/m3 (6.0 mg/L). The result does not indicate that mesitylene (1,3,5-trimethylbenzene) would meet the criteria for toxic in the PBT assessment. This endpoint in conjunction with the predicted non-biodegradability of the substance will result in a classification of a category Aquatic Chronic 2 toxicity to the environment and the hazard statement 'Toxic to aquatic life with long lasting effects'.
Executive summary:

In the absence of any other study, this can be considered the key study. This robust summary has a reliability rating of 2 because it is a non-GLP; non-guideline study, published in peer reviewed literature with minor restrictions in design and/or reporting but otherwise adequate for assessment. There is otherwise no information in the article to suggest that the data are invalid. The reported experimental 48 hour LC50 for Daphnia magna was determined to be 50 mmol/m3 (6.0 mg/L). The result does not indicate that mesitylene (1,3,5-trimethylbenzene) would meet the criteria for toxic in the PBT assessment. This endpoint in conjunction with the predicted non-biodegradability of the substance will result in a classification of a category Aquatic Chronic 2 toxicity to the environment and the hazard statement 'Toxic to aquatic life with long lasting effects'.

Description of key information

The reported experimental freshwater 48 hour LC50 for Daphnia magna exposed to 1,3,5-trimethylbenzene was determined to be 50 mmol/m3 (6.0 mg/L).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
6 mg/L

Additional information

Based on the information available, the study by Bobra et al. (1983) is considered to be the key study. The study has a reliability rating of 2 because it is a non-GLP, non-guideline study, published in peer reviewed literature with minor restrictions in design and/or reporting but otherwise adequate for assessment. There is otherwise no information in the article to suggest that the data are invalid. The reported experimental 48 hour LC50 for Daphnia magna was determined to be 50 mmol/m3 (6.0 mg/L).

A supporting QSAR calculation using the ECOSAR model gives an estimated 48 hour LC50 for Daphnia of 3.63 mg/L.