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Long-term toxicity to aquatic invertebrates

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Description of key information

The chronic toxicity of MBT to aquatic invertebrates (Dapnia magna) was tested according to OECD TG 211 "Daphnia magna Reproduction test". After 21 days of exposure, an EC50 of 0.33 mg/L and a NOEC of 0.08 mg/L were obtained (National Institute of Technology and Evaluation, 1999).
No experimental data available regarding the chronic toxicity of the described metabolites of MBT to aquatic invertebrates, such as BT, BTon, MBTS and MeSBT. According to the acute toxicity of them to aquatic invertebrates, they are expected to be less toxic than MBT.

Key value for chemical safety assessment

Additional information

MBT can be rapidly degraded by direct photolysis with a half-life time of ca. 30 mins (CMA, 1989). MITI online did not provide detailed information, whether the effect concentrations were nominal concentrations or from analytical monitoring. The observed effect is most probably a combined effect from both MBT and its hydrolysis products like BT, however BT has a much lower acute toxicity to aquatic invertebrates than MBT.