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Long-term toxicity to aquatic invertebrates

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Description of key information

The chronic toxicity of CBS to aquatic invertebrates (Dapnia magna) was tested according to OECD TG 211 "Daphnia magna Reproduction test". After 21 days of exposure an EC50 of 0.12 mg/L and a NOEC of 0.058 mg/L were obtained (National Institute of Technology and Evaluation, 1996).
No data are available regarding the hydrolysis products from CBS, such as BT and BTon, but some are available from other relevant metabolites of CBS such as MBT. The chronic toxicity of MBT to Daphnia magna was investigated in a flow-through system (CMA, 1989). The NOEC-21d and EC50 -21d was reported as 0.24 mg/l (measured) and >0.47 mg/l (measured), respectively.
Regarding the data summarized here, the long-term toxicities of the described metabolites of CBS to aquatic invertebrate are lower than the one of CBS itself.

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Additional information

A hydrolysis half-life time of CBS of 12.5 h and a complete hydrolysis of CBS in 24.9 h were observed in deionized water buffered at pH 7.0 and at 25°C (Monsanto, 1984). 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 CBS and its hydrolysis products. The reported effective concentrations are lower than water solubility of CBS (i.e. 0.32 mg/l).