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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

In a guideline study performed by Chemex (2010), an endpoint of ‘not biodegradable’ was concluded under the test conditions. This value was taken as the key study, although due to the stringency of the test conditions, the result does not necessarily mean that 4-chloro-o-cresol does not biodegrade under environmental conditions.

A number of papers relating to biodegradability in water were referenced in the European Risk Assessment report reviewed by the Danish Rapporteur. A study performed by Milner and Goulder (1986), observed that 4-cloro-o-cresol inhibited the growth of microorganisms in the water, however no conclusions appeared to be drawn relating to the biodegradability.

A modified MITI (I) test (MITI, 1992) showed 4-chloro-o-cresol to not readily biodegrade. Biodegradation of 0% was observed at concentrations of 100mg/L, however as other studies using lower concentrations of the test substance show some biodegradation it was considered that the result might be a consequence of the toxicity of the test substance to the microorganisms. 

In a pilot plant study on activated sludge (Buisson et al. 1998) the test substance appeared to be removed by adsorption and biodegradation, however the levels removed were low under the study conditions. The study suggests that biodegradation may be possible but data from the study was not sufficient to allow calculation of a degradation rate.

The shake flask die away test (Lingaard-Jorgensen, 1989) defined a half-life in seawater of 3 days at 1.8-micrograms/L test substance. In the same study, a half-life of 45 days was obtained in wastewater at a test substance concentration of 3.6 micrograms/L. It was suggested that either the higher test substance concentration had an inhibitive effect on the microorganisms present or that other organic compounds present were transformed to 4-chloro-o-cresol.

Overall the studies presented in the European risk assessment do not provide conclusive evidence relating to the biodegradability of the test substance in the environment. For this reason robust summaries of the studies are not provided in this dossier.

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