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Long-term toxicity to aquatic invertebrates

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Description of key information

Due to the high reactivity of the category substances with water, long-term aquatic studies are not deemed meaningful. Immediate hydrolysis leads to the formation of inert polyurea. The further (minor) common degradation product MDA has been adequately characterized with respect to its short- and long-term toxicity to aquatic organisms. For the reasons stated above, a long-term environmental impact of the category substances is not to be expected. Supporting evidence is available from a chronic (21 days) D. magna study (Caspers et al., 1986). The test substance was dispersed in water using a glass rod followed by magnetic stirring for one hour. The testing media were renewed three times per week. Likely due to the addition of activated sludge extract, the maximum DOC of 2 mg/L allowed by the current OECD Guideline 211 was exceeded (5 mg/L). The study has been performed without analytical monitoring. No long-term effects on survival, growth, and reproduction were observed after 21 days exposure to 10 mg/L, which was the highest concentration tested (NOEC ≥ 10 mg/L). The test was carried out according to OECD Guideline 211. 


Studies performed with substances added to the test media above the water solubility limit (heterogeneous conditions) do not really describe the effect of the substance itself. Experiences with hydrolysis studies according to OECD TG 120 and with acute aquatic studies have shown that the formation of polyureas and MDA is difficult to control. It depends on several parameters such as stirring conditions, size of particles and of vessels and composition of the media.


Therefore to make the endpoint more robust, the registrant will perform additional OECD 211 studies. The data will be generated on the boundary substances of the category 4,4'-MDI/DPG/HMWP, pMDI as well as the other representative substance of the category: 2,4'-MDI. 


Testing proposals for the OECD 211 studies with these three substances are added to the respective dossiers. A category approach will be used to fulfill the data requirement for the registered substance.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
NOEC
Effect concentration:
10 mg/L

Additional information

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