MAK Value Documentation for Methacrylic acid
The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the work place (MAK value) of methacrylic acid of 5 ml/m3, considering all toxicity endpoints. Available unpublished study reports and publications are described in detail. The critical effects of methacrylic acid are goblet cell hyperplasia/hypertrophy in the respiratory epithelia and reduced body weight gain in rats, which is probably a secondary effect of the irritation at 350 ml/m3 in a 90‐day study. Since 2014 the Commission uses an empirical approach to set MAK values for substances with critical effects on the upper respiratory tract or the eyes. According to this approach, the NOAEC of 100 ml/m3 corresponds to a work place air concentration of 33 ml/m3. As the goblet cell hyperplasia is judged to be adaptive and its incidence is not significantly increased, the MAK value is elevated to 50 ml/m3. Since local effects are critical, the assignment to Peak Limitation Category I and the excursion factor 2 are confirmed. Studies with the read‐across methyl methacrylate which is cleaved to methacrylic acid show that damage to the embryo or foetus is unlikely when the MAK value for methacrylic acid is observed, and the assignment to Pregnancy Risk Group C is confirmed. Methacrylic acid and methyl methacrylate are not genotoxic. Carcinogenicity studies with methacrylic acid are lacking but methyl methacrylate is not carcinogenic. Skin contact does not contribute significantly to systemic toxicity and sensitization is not expected.