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Key value for chemical safety assessment

Additional information

Reaction mass of methyl chloroacetate and chloroacetic acid:

1.- Chloroacetic acid:

a) Genetic toxicity in vitro:

Monochloroacetic acid was not mutagenic in Salmonella typhimurium strains (TA 98, TA100, TA 102, TA 104, TA1535, TA1537, and TA1538) and E coli strains (WP2uvrA and WP2uvrA/pKM101) with or without exogenous metabolic activation (S9).

In Chinese hamster V79 ovary cells, a dose-related increase in sister chromatid exchanges was observed without S9 although no induction of chromosome aberrations was observed after treatment with or without S9, (Galloway et al., 1987).

Monochloroacetic acid caused no induction of 8-azaguanine- and ouabain-resistant mutants in an in vitro HGPRT assay with Chinese hamster V79 cells (Huberman et al., 1975). Monochloroacetic acid did not induce DNA strand breaks in primary cultures of rat and mouse hepatocytes or in human CCRF-CEM cells (Chang, 1992).

At cytoxic concentrations, a positive response was obtained in the mouse lymphoma L5178Y cell assay for the induction of trifluorothymidine resistance, with and without S9 activation (Amacher and Turner, 1982; McGregor et al., 1987). Below cytotoxic concentrations, the response was negative and in general, an acidic pH shift was noted at cytotoxic concentrations. It is well known that changes in pH may lead to increased mutation frequencies, but neither of the two mutation assays with mouse lymphoma cells included appropriate controls for the possible influence of changes in pH under the test conditions used, thereby hampering the evaluation of the relevance of the positive test results.

It is well established that genotoxic irrelevant effects might occur under culture conditions resulting in cytotoxicities and pH shifts (Berly and Garriott, 1996; Clive et al., 1995; Cifone et al., 1987). Consequently, taking this, the negative findings in the bacterial mutagenicity assays and the fact that a positive mouse lymphoma assay respons occurs only at cytotoxic concentrations into consideration, the mutagenic activity observed in the mouse lymphoma assays is questionable.

b) Genetic toxicity in vivo: There is one publication on the induction of cytogenetic abnormalities in bone marrow in Swiss mice exposed intraperitoneal, oral, or subcutaneous. It is concluded that dose- and route-dependent variaties of bone marrow chromosome anomalies were induced. However, the results of these experiments cannot be evaluated, due to the very limited description of the experiment and the results.

In a second publication, micronuclei induction and chromosomal aberrations in rat after intraperitoneal administration are studied. For the chromosomal aberration results, the most significant impact was observed at 24 h post administration, when the recorded mean frequency of chromosomal aberrations was maximum for test substance. This result is observed when gaps are included in the total aberration frequency. However, according to the recommended guideline, gaps are recorded but generally not included in the total aberration frequency. When gaps are not included in the total aberration frequency, no significant differences are observed. For the micronuclei induction, the intraperitoneal administration of chloroacetic acid displayed an induction of micronuclei that was significant at 24 hours by 0.012 mg/g bw (highest concentration). However, the frequency of micronuclei formation 24 h post administration declined and significantly low incidences were observed at 48 hours.

In a third publication, monochloroacetic acid did not induce DNA strand breaks in spleen, duodenum, and stomach of mice, or livers of mice and rats treated orally in vivo.

2.- Methyl chloroacetate:

a) Genetic toxicity in vitro: In the Ames test, the test compound did not cause a significant increase in the number of revertant colonies with any of the tester strains neither in the absence nor presence of S9-mix. It is concluded that the test substance is not mutagenic in this bacterial test system neither in the absence nor in the presence of metabolic activation.

b) Genetic toxicity in vivo: micronucleus assay: The incidence of micronucleated polychromatic erythrocytes in the treated animals was within the normal range of the negative control. The number of normochromatic erythrocytes containing micronuclei was not increased. The ratio of polychromatic/normochromatic erythrocytes in both male and female animals remained unaffected by the treatment. It can be stated that, under the conditions described, administration of methyl chloroacetate did not lead to a substantial increase of micronucleated polychromatic erythrocytes. It is concluded that the methyl chloroacetate is not mutagenic in the micronucleus test.


Short description of key information:
Genetic toxicity in vitro:
Monochloroacetic acid: weight of evidence: experimental results. Data is provided on bacterial tests and in vitro studies in mammalian cells (gene mutation, chromosomal aberrations and sister chromatid exchanges).

Methyl chloroacetate: Key studies: experimental results. OECD guideline 471.

Genetic toxicity in vivo:
Monochloroacetic acid: supporting studies: experimental results: one publication (poorly documented) on cytogenetic abnormalities in bone marrow in Swiss mice exposed intraperitoneal, oral, or subcutaneous. A second publication (no data on individual animals is provided) on micronuclei induction and chromosomal aberrations in rat after intraperitoneal administration. In a third publication, on induction of DNA strand breaks in spleen, duodenum, and stomach of mice, or livers of mice and rats treated orally in vivo.

Methyl chloroacetate: Key study: Experimental results: micronucleus test, OECD 474.

Endpoint Conclusion:

Justification for classification or non-classification

Based on the results from the genetic toxicity assays both in vitro and in vivo, neither the substance chloroacetic acid nor the substance methyl chloroacetate are classified for genetic toxicity. Therefore, the reaction mass of chloroacetic acid and methyl chloroacetate is not classified for genetic toxicity.