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Short-term toxicity to aquatic invertebrates

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Description of key information

Nominal concentrations: 48-h EL50 (reported as “EC50” in the report) >1,000 mg/L. 48-h NOELR (reported as “NOEC” in the report)  < 100 mg/L based on WAF loading rates.
Effect concentrations based on nominal loading rates. Test results reported in original study as “effect concentrations” (EC) are reported in this summary as “effective loading” (EL), because test results are based on WAF loading rates and not measured concentrations. Similarly, the “no observed effect concentration (NOEC) in the report is presented as “no observed effect loading rate” (NOELR) in this summary.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
1 000 mg/L

Marine water invertebrates

Marine water invertebrates
Effect concentration:
40 mg/L

Additional information

In the key study, the acute toxicity of the water accommodated fraction (WAF) of 100, 300, and 1,000 mg/L mixtures of the test material and water to the daphnid, Daphnia magna was investigated during a study conducted at T.R. Wilbury Laboratories, Inc. The test, which was designed to determine the toxicity of the test substance, was performed from 6th to 8th August, 1991 and was conducted according to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test).

This study is presented as the key information as the reliability rating for this study is 1, according to the criteria of Klimisch, 1997. This study was conducted under freshwater conditions which is the preferred system and was also tested at the lower concentrations than the supporting study and therefore is considered the most reliable study.

Marine conditions:

- The Exxon, 1993 study was not considered the key study as it was conducted under marine conditions which are not the preferred conditions for this endpoint. However for chemical safety assessment purposes, the LC50 from this study will satisfactory fulfil the marine key study endpoint.

The study was conducted according to US EPA guideline, comparable to OECD guideline, however there were no details on dose concentration analysis and so a reliability rating of 2 was assigned.

Result: The 96-hour LC50 was > 40mg/L, the highest treatment level tested.

- The Douglas M.T. and Sewell I.G., 1988 study (HRC report number: CMA 2(1)/88923) was not considered the key study as it was considered to be unreliable. The study was also conducted less recently than the above key study and was conducted under marine conditions which are not the preferred conditions for this endpoint.

Due to the test substance forming a very poor dispersion in the water column and adhering to the mesh screens around the propeller shield the study was not considered to be reliable and has been assigned a reliability rating of 3, according to the criteria of Klimisch, 1997.

From the cumulative mortality data over 96 hours it is probable that the 48 - 96-hour LC50 values lie between 100 - 500 mg/L although it should be stressed that much of the adverse effects of this material are due to its physical rather than chemical properties and that the true toxicity is lower than is indicated by these values.