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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The 3h-EC10 of 89.9 mg Na2S2O4/L (endpoint: respiration of activated sludge) that was determined by ECT (2010) wase put forward for the effects assessment of sodium dithionite for micro-organisms.  

Key value for chemical safety assessment

EC50 for microorganisms:
187.6 mg/L
EC10 or NOEC for microorganisms:
89.8 mg/L

Additional information

Two different studies reported on the effect of sodium dithionite on micro-organisms in the aquatic environment.

A growth inhibition tests with the bacteria Pseudomonas putida was conducted (BASF, 1988) which resulted in a 17h-EC50 and EC10 value of 106.5 mg Na2S2O4/L and 61.6 mg Na2S2O4/L, respectively.

 

Secondly, an OECD No. 209 respiration inhibition test (under GLP) was conducted with sodium dithionite (Na2S2O4) as test substance (ECT, 2010). The activated sludge originated from the sewage treatment works in Frankfurt/Main Niederrad treating predominantly domestic sewage. The 3h-EC50and 3h-EC10– expressed as Na2S2O4, were 187.6 mg/L and 89.8 mg/L, respectively.

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 sodium dithionite for micro-organisms.