Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

In the up-to-date assessment, results from MITI online are used mostly as key studies for aquatic toxicity, because they are more sensitive than the results from either Monsanto or Bayer AG. The most sensitive acute toxicity is to aquatic algae (Selenastrum capricornutum) tested according to OECD TG 201 "Alga, Growth Inhibition Test". After 72 hours of exposure, an ECr50 of 0.15mg/L and a NOEC of 0.0084 mg/L were obtained. A long-term study is available for aquatic invertebrates (Dapnia magna) 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. For the assessment of microorganisms in biological treatment plants, an EC50 value of > 10000 mg/l after 3 hours exposure at a pH 7.2 - 8.1 and temperature of 20.6 - 22.8 °C was observed.

It was concluded in chapter 5.1 that dissolved CBS can be rapidly degraded by hydrolysis and photolysis, the hydrolysis half-life was determined to be 12.5 h and complete degradation was observed over 24.9 h. It is expected that in static aquatic toxicity tests the observed effects were caused by the parent substance and the degradation products. Analytical measurements reveal that in a flow-through system the influence of hydrolysis and photolysis could be minimized.

If the present quality criteria are strictly applied, the static acute tests, where no monitoring of the test concentrations occurred, should be regarded as not valid. The main degradation products appearing during the time frame of acute tests are benzothiazole (BT) and benzothiazolone (BTon). BT and BTon are more than one order of magnitude less toxic than CBS. Thus the results of the static tests with nominal concentrations can be considered as the upper limit for the actual effect value.