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Long-term toxicity to aquatic invertebrates

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Description of key information

Diuron is a chronic (long-term) effect to aquatic invertebrates

Key value for chemical safety assessment

Additional information

Two long term toxicity tests with Daphnia magna, according to OECD guideline 211 (cited as OECD guideline 202, part 2) with GLP, are available for Diuron. The key study is based on measured concentrations of the test substance and calculated the NOEC (21d) to be 0.56 mg/L, with a LOEC of 0.97 mg/L. Further to this the NOEC and LOEC values for effects on the parent animals were calculated at 0.1 and 0.17 mg/L respectively (Heimbach, 1996). The supporting study could determine no significant effects up to the highest concentration of Diuron tested, therefore the NOEC was determined as =1 mg/L and the LOEC as > 1 mg/L in this case (Ritter, 1989). Based on these findings, the results from the key study (Heimbach, 1996) should be used to determine that the test substance is a chronic toxicity hazard to aquatic invertebrates, evidenced by the NOEC/LOEC values of < 1 mg/L.

Discussion on endocrine disruption:

As at the current stage there is still no agreed approach and guidance on how to evaluate endocrine disruption in various EU legislations the OECD Conceptual framework for Testing and Assessment of Endocrine Disruptors might be used. Comparing available data with the Framework`s level concept allowed to rank Heimbach et al. (1996) and Ritter (1989) in OECD level 5, which means both studies allow final conclusion on endocrine disruption properties of diuron. Both studies investigated on effects to reproduction of Daphnia magna according to GLP standard and formerly OECD test guideline No. 202, part II, which mainly translated into the current OECD test guideline 211 on reproduction of D. magna. Both studies reported of no effect to daphnia reproduction which is the endpoint of OECD test guideline 211. There is, thus, no indication that diuron could be an endocrine disruptor. See also the document on the ad hoc assessment on endicrine disruption properties of diuron attached in chapter 13 of IUCLID.