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Additional information

A number of Ames tests have been performed on 4 -chloro-o-cresol: BASF (1988), Teknologisk Institut (1982) and Rananen at al (1977) all of which gave negative results and have been reported individually.

A further study was performed by Strobel and Grummt (1987), which showed a 4.4 fold dose related increase with the TA97 strain and a 5.4 fold dose related increase in the TA98 strain. A high dose toxic effect was observed in all strains. The reporting of these results in the literature leaves open questions with regard to interpretation of the results.

A further study was performed by Binderup (1996). This study (reported separately) performed using Salmonella typhimurium strains TA97 and TA98 showed no mutagenic effect in either strain.

In addition to the Ames tests, a mouse micronucleus study was performed (Proudlock, 1997). This study showed no damage to chromosomes or bone marrow cells. This report substantiates the negative results obtained in the Ames tests reported.

PCOC cannot be considered a mutagen based on 4 negative Ames tests and a negative mouse micronucleus test.

Short description of key information:
4-Chloro-o-cresol is not considered to cause any mutagenic effects based on the Ames test and a mouse micronucleus test.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

It is considered that based on the results from 4 negative Ames tests and a negative mouse micronucleus test, the substance cannot be considered a mutagen and therefore no classification with respect to mutgenicity is required.