Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Description of key information

a study conducted under the auspices of the US EPA looked at the effect of 1,1,1-trichloroethane and other materials of national interest on the biological degradation of the sewage in  pseudo commercial  treatment plants.  The results of this study showed that the EC50 for trichloroethane was 360mg/L. 

Key value for chemical safety assessment

EC50 for microorganisms:
360 mg/L

Additional information

The UK1996 review considers that bacteria are the most sensitive organisms to 1,1,1-trichloroethane and reviews the data on single and mixed species. The results of this review are to say the least confusing as they do not entirely agree with the published studies reported in the biodegradation section of this dossier. It is acknowledged that individual species of bacteria differ in the sensitivity to 1,1,1-trichloroethane. It has already been adequately demonstrated that the degradation of 1,1,1-trichloroethane only takes place under anaerobic conditions and that any studies conducted other than in sealed vessels must be considered unreliable. It is also acknowledged that 1,1,1-trichloroethane possesses only basic activity rather than specific activity against bacteria. In practice the most important requirement, after taking into account the fact that this material does not naturally occur in the environment, of the potential adverse effects relating to release is to determine at what contamination level effects on sewage treatment will occur. It is for this reason that the American study has been selected as the key study as it is conducted to a recognise guideline ( with modification to reduced volatilisation) namely OECD209 and meets the basic quality criteria set for this guideline. It should be noted that this study was not considered by the UK government reviewers which in the opinion of the applicant is surprising.