n ‐Butyl acrylate [MAK Value Documentation, 2017]

Abstract

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of 2 ml/m 3 for n‐butyl acrylate. The critical effect in a two‐year inhalation study with rats was reserve cell hyperplasia with loss of ciliated or olfactory cells at the lowest concentration of 15 ml/m 3 . The lower confidence limit of the benchmark dose for an extra risk of 5% increase of the critical effect incidence (BMDL 05 ) of about 3 ml/m 3 , which had been calculated in the previous evaluations, was confirmed. 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. Based on this approach, the equivalent concentration at the workplace is 1.5 ml/m 3 . However, studies in humans to investigate the sensory irritation of n‐butyl acrylate are lacking. As the structurally related ethyl acrylate possesses a RD 50 value as well as subchronic and chronic NOAECs similar to those of n‐butyl acrylate, the NOAEC of 2.5 ml ethyl acrylate/m 3 for sensory irritation in volunteers was used as a read‐across. As the MAK value for ethyl acrylate has been set at 2 ml/m 3 , the MAK value of 2 ml/m 3 for n‐butyl acrylate could be confirmed. In analogy to ethyl acrylate, the assignment of n‐butyl acrylate to Peak Limitation Category I and the excursion factor of 2 were confirmed. The NOAECs for developmental toxicity in rats and mice are sufficiently high so that damage to the embryo or foetus is unlikely when the MAK value is observed. Thus, n‐butyl acrylate continues to be classified in Pregnancy Risk Group C. The substance is marginally clastogenic in vitro but not in vivo and was not carcinogenic in a 2‐year inhalation study in rats. There are only a few cases of contact sensitization in humans but there are positive results in local lymph node assays. Data on airway sensitization are still not available. n‐Butyl acrylate continues to be designated with “Sh”. Skin absorption was calculated to contribute significantly to the systemic toxicity and n‐butyl acrylate is designated with an “H”.