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Tests with fish invertebrates and algae

Reliable short-term toxicity data are available for freshwater fish, invertebrates and algae. 96 h, 48 h and 72 h L(E)C50 values of >100 mg/l (nominal concentrations) for all three trophic levels and >71, >59 and >53 mg/l (geometric mean measured concentrations) have been determined for the effects of the hydrolysis product of the registered substance with Danio rerio (tested as Brachydanio rerio), Daphnia magna and Desmodesmus subspicatus (tested as Scenedesmus subspicatus) respectively.

Data waivers are applicable for long-term toxicity to fish and aquatic invertebrate endpoints.

The nature of the substance that the organisms were exposed to in the short-term tests and the results of analysis of the test media are given further consideration below and in the subsections relating to each of the endpoints.

The hydrolysis half-life of the registered substance is 12 – 36 hours at pH 7 and 25°C. However the pH of the test medium was 8 and at this pH the hydrolysis rate is expected to be 5-10 times faster. In addition, the use of static and semi-static exposure regimes do not maximise the exposure to the parent substance. As a consequence it is therefore likely that the organisms were exposed to a mixture of the parent substance and the hydrolysis product of the registered substance. Inspite of this the studies are still considered to be representative of the effects of the substance because:

·        no mortalities or effects were recorded at the start of the study when exposure to the parent substance will have been at its highest;

·        invertebrates are considered to be the most susceptible taxonomic group to the effects of epoxides and data are available with a supporting study indicating no effects at the highest concentration tested;

·        the retention time in WWTP is sufficiently long and the conditions in the WWTP are such that organisms in the environment would be exposed predominantly to hydrolysis product (further considerations are presented below);

·        while pH values in freshwater environments are variable the pH in the marine environment is approximately 8 (ECHA 2010c, R.16) and therefore closer to the pH of the media in the reported tests.

The results of the short-term tests are presented in terms of both geometric mean-measured and nominal concentrations.The analysis of the test media in all three studies has been further reviewed. In the opinion of the reviewer it is likely that because of the poor thawing protocol, the extraction method and the pH of the test media that the results relate to hydrolysis product. The presence of only one peak in the chromatogram also indicates that this is likely to be the case. It is not possible to determine which intermediate hydrolysis product the analysis relates to.

Inspite of the above it is still considered appropriate to base the assessment of the hazards and risks of the registered substance to fish, invertebrates and algae on the results of the available studies.

WWTP considerations

The average retention time of a substance in the WWTP is approximately 12-24 hours. The presence of metals in sludge is likely to catalyse the rate of hydrolysis resulting in the hydrolysis product being the substance organisms will be exposed to in the environment.