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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The substance is gaseous and the primary environmental compartment to which it partition is air. Chloromethane is not harmful to microorganisms and the inhibition of the degradation activity of activated sludge is also not anticipated

Key value for chemical safety assessment

Additional information

Chloromethane is a gaseous substance and primary environmental compartment to which it partition is air. Therefore, the substance will evaporate from the water body. As such significant toxicological effects on activated sludge is not expected and if chloromethane that finds its way into a bio-oxidation wastewater treatment system is likely to volatilize directly to the air. Based on the fugacity model STPWIN® (USEPA 2000), 77% of the chloromethane that enters the model treatment facility is volatilized directly to the air and 22% released with the final effluent (SIDS, 2002).

But one study is available for bacteria (Bringmann and Kühn, 1976; 1979), the reported TTC (comparable to EC3) values were 500 mg/L for Pseudomonas putida but it is unclear from the description of the available studies if vessels were closed or not. Because all results are based on nominal concentrations, a validity score of 3 is assigned (not valid). Results on methanogenic bacteria (Blum et al, 1991a and 1991b) were EC 50 values of 39 mg/L after 24h and 50 mg/L after 48 h, but the results are inconsistent and the documentation is insufficient for assessment. Additionally a Nitrobacter test (Tang, 1992) shows a IC50 of 2010 mg/L after 24 h (inhibition of NO2-N production). Because all results are based on nominal concentration all test results should be evaluated with caution because optimum test conditions (i. e. measured concentrations, closed system) were not met.

Nevertheless, the cell multiplication inhibition test with the standard single organismsPseudomonas putidashowed a only a low toxicity far above 100 mg/L (EC3 of 500 mg/L). Therfore, chloromethane is not harmful to microorganisms and the inhibition of the degradation activity of activated sludge is also not anticipated.