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Long-term toxicity to aquatic invertebrates

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Description of key information

OECD Guideline 211, GLP, key study, validity 2:
- The 21-day EC10 value for reproduction was 69 µg a.i./L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
69 µg/L

Additional information

One study is available to assess the effects of the test substance on the survival, growth and reproduction of Daphnia magna during a 21 -day exposure period under flow-through test conditions. This study was performed according to the OECD Guideline 211, the US EPA OPPTS 850.1300 and ASTM E 1193-97, with GLP statement.

Daphnids (neonates < 24 hours old at initiation) were exposed to a geometric series of five test concentrations, a negative control (dilution water) and a solvent control (0.1 mL/L HPLC-grade dimethylformamide (DMF)). Two replicate test chambers were tested for each treatment and control group. Each replicate contained two compartments with five daphnids, resulting in a total of 20 daphnids in each treatment and control group. 

The mean measured concentrations test concentrations were 3.8, 12, 25, 63 and 157 µg a.i./L, which represented 59, 75, 63, 63 and 63% of nominal concentrations, respectively. The results of the study were based on the mean measured concentrations.

First-generation daphnids were observed daily during the test for mortality, the onset of reproduction, and clinical signs of toxicity. Following the onset of reproduction, the numbers of second-generation daphnids were counted three times per week and at test termination (Day 21). Body lengths and dry weights of the surviving first-generation daphnids were measured at the end of the exposure period. 

There were no statistically significant treatment-related effects on survival, reproduction or growth at concentrations ≤ 63 µg a.i./L. Growth, measured as length and dry weight, and reproduction were the most sensitive biological endpoints measured in this study. Daphnids exposed to the test substance at a concentration of 157 µg a.i./L had statistically significant reductions in growth and reproduction in comparison to the pooled control. 

Consequently, the 21-day EC10 value for adult immobility was 107 µg a.i./L and the 21-day EC10 value for reproduction was 69 µg a.i./L. The 21-day EC50 value for adult immobility and the 21‑day EC50 value for reproduction were >157 µg a.i./L, the highest concentration tested.