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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

In the 21-d long term toxicity study to fathead minnows (Pimephalespromelas) under static-renewal conditions of the test substance (Diflufenzopyr sodium salt), the LOEC for the study, based on dry weight, was 10 mg a.i./L. and the NOEC was 5.0 mg a.i./L.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
5 mg/L

Additional information

A long term toxicity to fish study with the test substance (Diflufenzopyr sodium salt) was performed according to the EPA guideline OPPTS 850.1400 (Fish Early-life Stage Toxicity Test). The 33 -day key study, was to evaluate the influence of the test item on Pimephales promelas. Fathead minnow embryos were exposed to a geometric series of six test concentrations and a negative (dilution water) control under static-renewal conditions. Four replicate test chambers were maintained in each treatment and the control group, with one incubation cup in each test chamber. Each incubation cup contained 20 embryos, resulting in a total of 80 embryos per treatment. The exposure period included a 5-day embryo exposure period, and a 28-day post-hatch juvenile growth period. Nominal test concentrations were selected based on the results of an exploratory range-finding test. Nominal test concentrations selected were 0.63, 1.3, 2.5, 5.0, 10 and 20 mg active ingredient (a.i.)/L. Test solutions were renewed three times per week (i.e., Monday, Wednesday and Friday). Water samples were collected at test initiation, at the beginning and end of the longest renewal cycle each week and at test termination to measure concentrations of the test substance. At test initiation, embryos 2 to 24 hours old were collected from Wildlife International, Ltd. cultures and groups of 1 to 3 individuals were impartially distributed among incubation cups until each cup contained 20 embryos.One cup was then placed in each treatment and control test chamber. Dead embryos were counted and removed from the cups daily. After hatching, the larvae were counted and released into the test chambers, where exposure continued until test termination (28 days post-hatch). Fathead minnows (Pimephalespromelas) exposed to the read across substance at a concentration of 5 .0 mg a.i./L. for 28 days post-hatch showed no significant reductions in time to hatch, hatching success, post hatch survival or growth. Fathead minnows exposed to 10 and 20 mg a.i./L showed treatment-related reductions in dry weight. In addition, fathead minnows exposed to 20 mg a.i./L showed a statistically significant reduction in total length.. The LOEC for the study, based on dry weight, was 10 mg a.i./L. The NOEC was 5.0 mg a.i./L and the MATC (maximum acceptable toxicant concentration) was calculated to be 7.1 mg a.i./L.