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Long-term toxicity to aquatic invertebrates

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Description of key information

Data are available in an OECD guideline study conducted under GLP conditions.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
172 µg/L

Additional information

In a 21-day, flow through OECD TG 211 study, Daphnia magna were exposed to mean measured concentrations of 11, 35, 53, 111 and 172 µg/L.  The 21 day mean measured EC50 was > 172 µg/L (0.17 mg/L) and the NOEC was >= 172 µg/L (mean measured, highest concentration tested.) (Springborn Smithers Laboratories, 2004). It is important to note that due to 172 µg/L being the highest concentration tested; this value is considered to be conservative.  The EC50 and NOEC values are anticipated to be higher, thus indicating lower toxicity. In the study, the actual concentration was set to be 400 µg/l as a nominal. However, the actual concentration declined to 172 µg/l (40% of the nominal) although flow-through test conditions were employed.

In order to investigate the causality of this dissipation another 7 -day flow-through stability experiment was conducted at the testing facility (Springborn Smithers Laboratories, 2003). Four different test conditions were set, 1A=test substance only, 1B=with daphnids, food and brushing the test vessel, 1C=with daphnids, food and exchanging the test vessel daily, 1D=with daphnids, food, and without brushing the test vessel. The concentration of resorcinol was set to be 400 µg/l and the renewal rate was 7.8 test vessel volumes per 24 hour period. As a result, during a 7 -day testing period, the concentrations of resorcinol in the test vessels were declined to be from 74 µg/l (1D, 19% of the nominal) to 149 µg/l (1A, 37% of the nominal) suggesting that microbes may have quickly developed an affinity for resorcinol resulting in even faster degradation rates that cannot be compensated under flow-through conditions. This shows that the test chemical is fairly unstable in the aquatic environment.