methyl acrylate; methyl propenoate

Endpoint summary

Additional information

In-vitro studies: Bacterial systems

Methyl acrylate was not mutagenic in the Ames test in Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98, TA97 and TA100, both in the presence and in the absence of S-9 mix from Aroclor 1254 induced rats when tested up to cytotoxic doses (BASF AG 1977, Waegemaekers 1984; Zeiger 1987). In addition, a modified Ames assay (plate gradient assay) was performed in ten tester strains (Salmonella typhimurium G 46, TA 1535, TA 100, C 3076, TA 1537, D 3052, TA 1538,TA 98, E. coli WP2, E. coli WP2uvrA-) with and without metabolic activation. Methyl acrylate was reported to be negative (McMahon 1979)

In-vitro studies: Mammalian cell gene mutation test

Methyl acrylate did not induce increases in mutant frequencies in the Chinese Hamster Ovary (CHO) HGPRT test performed in the absence of metabolic activation (Moore 1991), and no mutagenicity was demonstrated in AS52/XPRT Chinese hamster cells in which the hgprt gene has been largely deleted and replaced by a single copy of the functional xanthine-guanine phosphoribosyl transferase (XPRT) gene from E. coli. This test was also performed only in the absence of metabolic activation (Oberly 1993).

In contrast, methyl acrylate was active at clearly cytotoxic concentrations (≤ 50% cell survival) in the Mouse Lymphoma TK+/- mutation assay using L5178Y cells in the absence of metabolic activation (Moore 1988, 1989). The majority of the mutant colonies were small colonies, suggesting that methyl acrylate did act via a clastogenic mechanism (Moore 1988, 1989, Amtower 1986).

Moore et al have described a mutagenic effect of Methylacrylate in the TK assay. The induction of mutant colonies was also closely associated with the induced cytotoxicity. It has been previously reported, that Glutathione has a high affinity for Methylacrylate. This could lead to a depletion of the intracellular levels of Glutathione. In the study by BAMM (2019) the cultures were treated with the same levels of the test substance as previously described to be cytotoxic and mutagenic. Furthermore, a group of the cultures were replenished with Glutathione in order to assess the impact of Glutathione supplementation on mutagenicity and cytotoxicity. The results in the absence of supplementary Glutathione confirmed the data from Moore et al. However, the addition of 1 mM Glutathione abrogated this observed cytotoxicity. Furthermore, according to the results of the present in vitro study, the test substance Methylacrylate did not lead to a relevant increase in the number of mutant colonies after the addition of 1 mM Glutathione The mutant frequencies at any concentration were close to the range of the concurrent vehicle control value and within the range of historical negative control data without S9 mix.

In-vitro studies: Genotoxicity tests

There is a number of chromosome aberration tests in vitro available for MA (Ishidate 1981, Moore et al. 1988, 1989). Assays were performed with CHL cells, L5178Y mouse lymphoma cells and CHO cells with (Ishidate 1981) and without metabolic activation (Ishidate 1981, Moore et al. 1988, 1989). All assays gave positive or equivocal results at doses which reduced cell survival to 50 % or lower. There were no doses tested for chromosome aberrations which resulted in 60 % cell survival or more. Thus, there is no experimental evidence that MA might cause chromosome aberrations at non-cytotoxic doses.

More recent studies have indicated that there is an association between chromosomal aberrations and cytotoxicity at exposure concentrations which reduce cell growth to less than 50% of the control value (Galloway, 2000 and references cited therein). These data suggest that the increase in mutagenicity reported in the cytogenicity assays with methyl acrylate may be an artifact of the experimental method.

Conclusion-In vitro studies

In vitro, methyl acrylate was negative in a variety of studies for point mutation both in the presence (Ames test only) and in the absence of metabolic activation, but induced chromosome aberrations in Chinese hamster cells, Chinese ovary cells and L5178Y mouse lymphoma cells in the absence of metabolic activation. Further studies by BAMM (2019) clearly indicate that the genotoxic effects in vitro are associated with glutathione depletion and cytotoxicity since supplimentation of glutathione completed negated the observed cytotoxicity and did not lead to a relevant increase in the number of mutant colonies.

In vivo studies

Methyl acrylate has been tested in three in vivo micronucleus assays. It did not induce micronuclei in bone marrow cells of male ddY mice exposed for 3 hours to atmospheres containing 1300 or 2100 ppm (4.64 or 7.50 mg/L) methyl acrylate. Bone marrow samples were taken at 18, 24, 30, 48 or 72 hours after exposure. (The group size was not specified) (Sofuni 1984).

No induction of micronuclei was also found in male ddY mice after single oral doses (62.5, 125 or 250 mg/kg bw; 6 mice per group) or repeated dosing (125 mg/kg bw/d for 4 consecutive days; 4 mice). Bone marrow cells were sampled 24 hours after the last dose (Hachiya 1982).

In contrast, exposure of Balb/C mice to 37.5, 75, 150 or 300 mg/kg bw (4 mice/dose; 2 injections, 24 hours apart) by the intraperitoneal route, induced a not clearly dose-dependant increase in micronuclei at toxic dose levels as evidenced by significant reductions in the ratio of polychromatic to normochromatic erythrocytes. Only a short summary of the results is available (Przybojewska 1984). The validity of the results of this study is questionable. In the available publication methyl and ethyl acrylate were tested in parallel and both are described to be positive in the mouse micronucleus test (i.p.). In the case of ethyl acrylate, different laboratories tried to reproduce the positive results reported in Przybojewsla et al. In these well conducted and documented studies the results were negative (Ashby 1989, Kligerman 1991, Hara 1994). Therefore, based on the data available and the questionability of the findings in the Przybojewska et al. study, the weight of evidence indicates that methyl acrylate is negative in vivo in mouse micronucleus studies.

Conclusion-in vivo studies

In vivo, two micronucleus tests using the inhalation and oral route in ddY mice were negative.

Galloway SM (2000). Environmental and Molecular Mutagenesis 35:191-201.

Short description of key information:
Methyl acrylate was negative in bacterial mutation tests. In gene mutation assays in mammalian cells, i.e. HGPRT and XPRT assays, MA was clearly negative. MA seems to have some potential for genotoxicity in mammalian cells, presumably by a clastogenic mechanism. Further in vitro studies confirm genotoxicity in vitro is clearly associated with significant glutathione depletion and cytotoxicity since such effects are completely abrogated when glutathione supplimentation is employed. Since this effect is limited to doses with moderate to strong cytotoxicity, it is highly unlikely that this potential will be expressed in vivo. Methyl acrylate was negative in several in vivo mouse micronucleus assays. Thus, taking the negative test results in vivo for MA into consideration, it can be assumed that MA will not cause any DNA damage, i.e. genotoxicity in vivo. Furthermore, in carconogeicity studies conducted via the inhalation route (the most relevant route for MA) histopathological data demonstrated toxicity (decreased body weight gain and olfactory epithelial degeneration) in the absence of mutagenicity (i.e. tumors) in either somatic cell or germ cells in wide array of tissues. This comprehensive in vivo study provides strong weight of evidence to indicate that methyl acrylate is not a mutagen in vivo.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

EU classification according to Regulation (EC) No. 1272/2008: no classification required