Chronic toxicity and oncogenicity of inhaled methyl acrylate and n-butyl acrylate in Sprague-Dawley rats.

No exposure-related clinical signs or lesions of systemic toxicity and no oncogenic responses were observed in male and female Sprague-Dawley rats exposed by inhalation to methyl acrylate (MA) or n-butyl acrylate (BA) vapours, at concentrations of 0, 15, 45 and 135 ppm. The rats were whole-body-exposed 6 hr/day, 5 days/wk, for 24 consecutive months. There was a 6-month post-exposure observation period for subgroups of BA-exposed rats. Atrophy of the neurogenic epithelial cells and hyperplasia of reserve cells were observed in the nasal mucosa of all MA- and BA-exposed groups. These changes were dose related and mainly affected the anterior part of the olfactory epithelium. Opacity and neovascularization of the cornea were seen in all MA-exposed groups and in the group exposed to 135 ppm BA. These toxic effects of the olfactory epithelium and cornea were attributed to the known irritancy of MA and BA. In the BA subgroups kept for a 6-month post-exposure observation, reconstructive effects, such as replacement of altered olfactory epithelium with respiratory epithelium, and partial regression of corneal neovascularization were observed.