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Sediment toxicity

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Description of key information

The 28-day NOEC for Chironomus riparius exposed to cloquintocet-mexyl via the water column in an OECD 219 study was 8.0 mg/L (nominal), the highest concentration tested (Grade, 1998). A sediment NOEC of 93.4 mg/kg dwt is proposed.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
93.4 mg/kg sediment dw

Additional information

Grade (1998) investigated the toxicity of cloquintocet-mexyl to the sediment-dwelling larvae of the midge Chironomus riparius in a GLP compliant 28-day study performed according to OECD Guideline 219 (Sediment-Water Chironomid Toxicity Test Using Spiked Water). The study is considered to be reliable without restriction. There were no significant effects of exposure, relative to the untreated control, on the timing of the hatch of winged adults or on the emergence of male and female midges. The 28 -day NOEC was therefore 8.0 mg/L, the highest concentration tested.

Combined measurements of the concentration of the test substance cloquintocet-mexyl (CGA185072) and metabolite CGA153433 in sediment in this study were also taken at day 0, 7 and 28. At day 0, where minimal metabolite is likely to have formed, the measured concentration in sediment was 20.3 mg/kg wwt. After 28 days this value was 27.1 mg/kg wwt. Therefore a sediment NOEC of 20.3 mg/kg wwt is proposed, or 93.4 mg/kg dwt (conversion factor= 4.6, EUSES v2.1.1).