Acetic acid

Endpoint summary

Additional information

Non-human information

 

In vitro data

The key studies are considered to be bacterial mutation assays (Zeiger et al., 1992; Ishidate et al., 1984) and a mammalian cell cytogenetic assay (Morita et al., 1990).  These are two recognised core assay types for investigating mutation in vitro.

Glacial acetic acid (99.7 %) was tested in the Salmonella mutation assay using four strains of Salmonella typhimurium (TA1537, TA97, TA98, TA100) with and without metabolic activation from hamster and rat liver S9 (10% and 30% S9). The pre-incubation assay was used with a 20 minute pre-incubation time before plating, and with doses up to 10mg/plate (Zeiger et al., 1992). A similar evaluation of glacial acetic acid including additional Salmonella strains was undertaken in a pre-incubation assay (20 minute), with and without rat liver S9, and up to doses of 10 mg/plate. Salmonella strains TA1535, TA1537, TA92, TA98, TA100, and TA94 were used. Both assays gave negative results for acetic acid. Other evaluations in bacterial genotoxicity assays have given confirmatory negative results, including mutagenicity assays and an SOS assay, but one positive result was reported in 1951 for a non-guideline study of streptomycin dependence in strains of E coli. Contradictory results have been reported in bacterial DNA repair assays (EU DAR, 2008). 

Overall, the data indicate that acetic acid is not mutagenic in bacterial test systems.

Acetic acid has been examined for cytogenetic activity in the absence and presence of S9 in Chinese hamster ovary K1 cells (Morita et al., 1990). The evaluation included an examination of the relationship between the pH of the medium and clastogenic activity. A dose-dependent increase in chromosomal aberrations was observed in CHO cells exposed to acetic acid, beginning at a concentration of 10 mM in the absence of S9 and at 8 mM in the presence of S9. These concentrations were close to the cytotoxic limit at which cells could no longer be evaluated. This activity was removed when the pH of the medium was maintained near neutral through the use of media with increased buffering capacity, or by neutralisation with sodium hydroxide. This activity, observed at or near the limit dose for this assay type (10 mM), and which is removed when the pH is maintained at near neutral, is considered to be a function of the pH change induced by acetic acid at very high concentrations, and not due to genotoxicity of the chemical itself. This is supported by negative findings in other cytogenetic assays using standard dose levels, or positive results only when the pH is once again reduced through excessively high concentrations of acetic acid (EU DAR, 2008).

It is concluded that acetic acid has no significant clastogenic activity in vitro.

Small increases in sister chromatid exchanges were observed in isolated human lymphocytes treated in vitro but only under the same conditions of high acetic acid concentrations where a reduction in pH was seen (EU DAR, 2008). Acetic acid is considered to have no significant cytogenetic activity under conditions of biological relevance.

Acetic acid has not been examined in an in vitro mammalian cell gene mutation assay. However, there are data available that indicate that acetic acid would not show any significant genotoxic activity in this assay. Acetic acid has been examined in a number of studies with different endpoints and concluded to have no significant genotoxic activity, including bacterial mutation, SOS chromotest, and cytogenetic assays in mammalian cells. In the cytogenetic assays (chromosomal damage and sister chromatid exchange), effects were only seen at very high doses (non-physiological doses and ones exceeding the guideline limit doses for the assays) and these were due to the induced pH changes in the cell culture systems. These data indicate that were acetic acid to be examined in a mammalian cell gene mutation assay such as the L5178Y TK+/- assay, it would show no genotoxic activity at standard dose levels, but would follow the cytogenetic assays and at excessively high doses, the pH of the cell culture system would be altered, and effects may be seen. However, any such effects would be (as with the cytogenetic assays), of no relevance for any meaningful hazard assessment of acetic acid. This phenomenon of irrelevant effects at reduced pH levels in mammalian cell gene mutation assays has already been reported (Cifone et al, 1987) [see comment in table above], including reference to the effect being induced by several short chained aliphatic acids.

Acetic acid has been shown to have no significant genotoxic activity in a number of endpoints, and acetate is a normal component of cellular metabolism. It is considered that there are sufficient data to be able conclude that acetic acid has no significant genotoxic activity in vitro, and that the conduct of a mammalian cell gene mutation assay would not change this conclusion.

Acetic anhydride hydrolyses rapidly in aqueous media to release 2 molecules of acetic acid per mole of acetic anhydride and so provides an equivalent test material exposure to testing using acetic acid.

Acetic anhydride has been examined for mutagenic activity in mammalian cells in vitro using the mouse lymphoma L5178Y assay (Seifried et al., 2006: HSE, 2002).  In the presence of S9, no increase in mutant frequency was observed. In the absence of S9, an increase in mutant frequency was observed, but only at a dose level inducing excessive toxicity (6% relative total growth, cf a limit of 10%). This is effectively a no-test. The assay was repeated, but again three out of four dose levels produced excessive toxicity (6% or less). The remaining dose level produced toxicity of 21% relative total growth, with just a two-fold increase in mutant frequency over controls. The observed increase in mutant frequency was small and appears to be associated with the increasing cytotoxicity induced by the treatment. Although the data can be formally regarded as equivocal, they do not indicate any significant genotoxic activity for acetic anhydride in mammalian cells in vitro. A recent evaluation of these data has reported them as inconclusive (Seifried et al., 2006). These data in the mouse lymphoma assay further support the conclusion that acetic acid can be considered to have no significant mutagenic activity in mammalian cells.

  

In vivo data

No data from in vivo regulatory studies for genotoxicity are available. 

An abstract containing limited details and data reported that acetic acid applied dermally in acetone at doses of 25 and 30 mg produced increased mutant frequencies in the skin of transgenic mice (MUTA™mouse) killed on day 7 postdose (EU DAR, 2008). However, these doses also caused focal ulceration and eschar formation. No increase in mutations was seen at lower doses inducing mild irritation. It is likely that any mutagenic effects were secondary to the severe toxicity induced. These data are considered insufficient to indicate any significant genotoxic activity for acetic acid in vivo.

Acetate is a systemic metabolite of acetic anhydride. Since acetic anhydride did not cause any substantial increase in the incidence of micronucleated immature erythrocytes or any substantial decrease in the proportion of immature erythrocytes, it is concluded that acetic anhydride and its systemic metabolite acetate, did not show any evidence of causing chromosome damage or bone marrow cell toxicity following subchronic inhalation exposure of rats in this in vivo test procedure (HRC, 1996).

 

Human information

 

There is no information indicating any adverse effects of acetic acid.

 

Summary and Discussion of Mutagenicity

 

Acetic acid has been examined for mutagenicity in vitro in recognised core assays. It has shown negative results for mutagenicity in vitro, and with no indications for likely mutagenicity in vivo. It is concluded that the available data indicate that acetic acid has no significant genotoxicity. The available data from in vitro studies suggest that at excessive and unphysiological concentrations of acetic acid, the pH of the test system is significantly reduced and positive results can be induced as a result of this. However, these results are at doses exceeding the limit dose for the assays, which cause circumstances that are now accepted in the literature as being artificial and of no value for contributing to an evaluation of the genotoxicity of a chemical (EU DAR, 2008). There are limited data indicating that this may also be the case in vivo.

It is concluded that the available data indicate that acetic acid has no significant genotoxic activity.

Citation:

HSE(2002): Acetic anhydride Risk Assessment Document. EH72/16. ISBN 0 7176 2364 5

Short description of key information:
The available data indicate that acetic acid has no significant genotoxic activity.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Available data indicate no genotoxic activity, therefore acetic acid does not warrant classification for genotoxicity.