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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The 3h-EC10 of 1000 mg (NH4)2S2O3/L (endpoint: respiration of activated sludge) that was determined by ECT (2010) wase put forward for the effects assessment of thiosulfate substances for micro-organisms.  

Key value for chemical safety assessment

EC50 for microorganisms:
757 mg/L

Additional information

An OECD No. 209 respiration inhibition test (under GLP) was conducted with ammonium thiosulfate ((NH4)2S2O3) as test substance (ECT, 2010). The activated sludge originated from the sewage treatment works in Frankfurt/Main Niederrad treating predominantly domestic sewage. No effects on repiration rate were observed at the highest test concentration of 1000 mg test substance/L. The 3h-EC50 and 3h-EC10– expressed as (NH4)2S2O3, were >1000 mg/L and ≥1000 mg/L, which corresponds to ≥757 mg S2O32-/L or ≥1079 mg SO32-/L.

As respiration tests with activated sludge is a more relevant test design for evaluating effects of a substance on micro-organisms, and taking into account that the ECT (2010) study was an OECD Guideline GLP-study, the data reported by ECT (2010) are put forward for the effects assessment of thiosulfates on micro-organisms.