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Long-term toxicity to fish

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The long-term toxicity of cloquintocet-mexyl to fish was investigated in a GLP-compliant study conducted to OECD 204 guideline (extended to 21 days). However, in accordance with ECHA R.7b guidance it has been assumed, as a worst-case, that the long-term toxicity to fish endpoint is not fulfilled.
Based on the chemical safety assessment no long-term toxicity testing on fish is needed.

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Additional information

One study investigated the long-term study toxicity of cloquintocet-mexyl to rainbow trout (Oncorhynchus mykiss) (Vial, 1990). However, this study was conducted according to OECD guideline 204. The ECHA R.7b guidance expresses some reservations concerning the OECD guideline 204 (fish extended mortality test) because mortality is the only endpoint covered, and the exposure duration may only be 14 days.  Furthermore, the developmental stage tested is not particularly sensitive. However, studies which have been conducted in accordance with this guideline in recent years usually include exposure for 21 days, with mortality, growth and behaviour as endpoints.  In addition, the developmental stage of the rainbow trout to be tested is the same as recommended in the OECD guideline 215 for the ‘Juvenile Growth Test’, given that the weight of a 5 cm long rainbow trout (OECD 204) is in the range of 1 - 5 g (OECD 215).  A combination of both guidelines is therefore considered most appropriate.  Hence, the study should have a 28 day exposure duration and include survival, growth and behaviour as endpoints. However, it is suggested that in order to avoid unjustified animal testing, existing valid studies conducted in accordance with OECD 204 but lasting only 21 days should really be acceptable to fulfill the long-term toxicity to fish endpoint. Despite this, as a worst-case, the assessment presented here follows the ECHA R.7b guidance that "tests performed according to OECD 204 (Fish, Prolonged Toxicity Test: 14-Day Study (OECD 1984)) or similar guidelines cannot be considered suitable long-term tests". Therefore, it is assumed that the long-term toxicity to fish endpoint is not fulfilled (the Vial, 1990 study is therefore reported as a short-term test).