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Short-term toxicity to fish

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Description of key information

Exposure of rainbow trout to the test item gave LL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF. It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L (OECD 203 and EU Method C.1).

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Additional information

GUIDELINE

A study was performed to assess the acute toxicity of the test item to rainbow trout (Oncorhynchus mykiss). The method was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No 203 "Fish, Acute Toxicity Test" referenced as Method C.1 of Commission Regulation (EC) No. 440/2008.

METHOD

Due to the low aqueous solubility and complex nature of the test item, the test medium was prepared as a Water Accommodated Fraction (WAF).

In accordance with the recommendations of REACH, the test was conducted according to the threshold approach recommended by ECHA. Using this approach the lowest EL50 value from either the algal growth inhibition study or acute toxicity to Daphnia magna study is set as the threshold loading rate and a "limit test" is conducted at this threshold loading rate. If no mortalities are observed this indicates that fish are not the most sensitive species and that the LL50 is greater then the loading threshold rate. The EL50 value obtained from the acute toxicity to Daphnia magna study was the lower of the two applicable EL50 values and hence the test was conducted at a single loading rate of 100 mg/L.

Seven fish were exposed to a Water Accommodated Fraction (WAF) of the test item at a single nominal loading rate of 100 mg/L for a period of 96 hours at a temperature of 14°C to 15°C under semi-static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

RESULTS

Chemical analysis of the freshly prepared 100 mg/L loading rate WAF test preparations at 0 and 72 hours (fresh) showed measured test concentrations of 0.97 and 0.75 mg/L respectively were obtained. The 24 hour old sample saw an increase in measured concentration from 0 hours to 1.46 mg/L. The duplicate sample for the 24 hour old sample was also analysed and confirmed an increase in the measured concentration to 1.28 mg/L. A decline in measured test concentration was observed at 96 hours to 0.055 mg/L.

Given that the toxicity cannot be attributed to a single component or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

CONCLUSION

Exposure of rainbow trout to the test item gave LL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF. It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L.