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Key value for chemical safety assessment

Additional information

Bacteria:

Methyl formate was negative in four independent valid tests which were all conducted according to OECD 471, with and without metabolic activation. All tests included negative and positive controls, which performed as predicted. The experimental details are described in the following paragraphs.

BASF AG (1989) tested 20 to 5000 µg methyl formate/plate in the standard plate and the preincubation test using Salmonella typhimurium TA1535, TA100, TA1537, and TA98. There was no indication of gene mutations and no bacteriotoxicity at any concentration.

The negative result is supported by other studies:

JETOC (1997) tested 1,000, 5,000, 10,000, 50,000, 100,000 and 500,000 ppm methyl formate in filtered air with Salmonella typhimurium TA100 and TA1535 both with and without metabolic activation. There was no indication of gene mutations. Bacteriotoxicity was seen at 50,000 ppm.

Methyl formate was tested in the preincubation test using Salmonella typhimurium TA98, TA100, TA1535, TA1537, and TA1538 at concentrations of 667, 1000, 3333, 6667, and 10000 µg/plate. The incubation period was 48 hours and the incubation system was sealed during the first 24 hours. There was no indication of gene mutations and no bacteriotoxicity at any concentration (Microbiological Associates, 1989; TSCATS, 1989).

Zeiger et al. (1992) reported that methyl formate (100, 333, 1000, 3333, 10000 µg/plate) was negative in the Ames preincubation test using Salmonella typhimurium TA97, TA98, TA100, and TA1535 both in the presence and absence of metabolic activation. Slight bacteriotoxicity was seen at 3333-10000 µg/plate. This result was obtained in two independent laboratories.

Chromosome aberration

No data were located for methyl formate but for formic acid and methanol which are rapidly formed.

Formic acid: In a mammalian cell cytogenetics assay (Chromosome aberration, conducted similar to OECD Test Guideline No. 473) CHO cell cultures were exposed to formic acid dissolved in F12 cell culture medium at concentrations of 6 to 14 mM, i.e. 0, 276, 368, 460, 552, and 644 µg/mL with and without metabolic activation. In a series of subsequent experiments the influence of confounding factors, i.e. pH and osmolality) on the incidence of aberrant cells (%) was examined at concentrations of 20, 25, 27.5, and 30 mM, i.e. at 920, 1150, 1266, and 1380 µg/mL. Formic acid was negative in this assay (Morita, 1990).

Methanol: Data on methanol were used for the chromosomal aberrations endpoint. Of four in vitro micronucleus and cytogenetic assays and ten in vivo micronucleus and cytogenicity assays, all were negative for chromosomal aberrations except one cytogenetic assay, which was positive for aneuploidy, sister chromatid exchange, and micronuclei. Thus, most studies indicate that methanol does not have the potential to induce chromosomal aberrations. 

Mammalian cell mutations

No data were located for methyl formate but for formic acid and methanol which are rapidly formed.

Formic acid: in a mammalian cell gene mutation assay (HPRT locus), Chinese Hamster ovary cells cultured in vitro were exposed to formic acid (85.3%) at concentrations of 0, 31.25, 62.5, 125, 250, and 500μg/mL in the presence, and of 0, 25, 50, 100, 200, and 400μg/mL in the absence of mammalian metabolic activation. Formic acid was negative in this assay (BASF, 2002).

Moreover, potassium diformate, a supporting substance that liberates formic acid in a 1:1 molar ratio, showed no carcinogenic potential in a 104-week rat study, and in a 80-week mouse study.

Methanol: Of four in vitro micronucleus and cytogenetic assays and ten in vivo micronucleus and cytogenicity assays, all were negative for chromosomal aberrations except one cytogenetic assay, which was positive for aneuploidy, sister chromatid exchange, and micronuclei. Thus, most studies indicate that methanol does not have the potential to induce chromosomal aberrations.

In addition, there was no evidence of a carcinogenic potential when methanol was tested in two valid long-term whole body inhalation studies in rats (24 months) and mice (18 months) at exposure concentrations up to 1.3 mg/L, 19 or 20 hours per day.



Short description of key information:
Methyl formate did not induce gene mutations in an Ames test (OECD TG 471), with and without metabolic activation.
No methyl formate data exist for chromosome aberration and mutations in mamlian cells. However, a multitude of assays was conducted with formic acid and methanol (supporting substances) in vitro and in vivo. Both substances failed to induce chromsosome aberrations, mutations in mammalian cells, or carcinogenicity in the rat or mouse.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

No classification. Negative results were obtained almost exclusively with methyl formate, or formic acid and methanol, in vitro (mutations in bacterial and mammalian cells; chromosome aberration, micronucleus assays) and in vivo (micronucleus assays, cancer studies).