Acute toxicity, genotoxicity, and dermal carcinogenicity assessment of isooctyl acrylate

Isooctyl acrylate (IOA) monomer is a complex mixture comprised predominantly of isomeric, eight-carbon alkyl esters of acrylic acid. Limited evidence from animal studies suggests that certain acrylate esters may be carcinogenic by the dermal route of exposure. The following studies were performed with IOA monomer: acute oral toxicity limit test in rats, primary dermal and ocular irritancy in rabbits, Ames Salmonella microsome assay, Saccharomyces cerevisiae D3 recombinogenicity assay, L5178Y TK +/- mouse lymphoma cell assay, and C3H/10T1/2 mouse embryo cell transformation assay. Finally, a limited dermal carcinogenicity bioassay was performed in which aliquots (25 microliters) of IOA monomer (5% v/v in acetone), IOA polymer (19% w/v in 70:30 acetone/heptane), or acetone (vehicle control) were applied to the shaved backs of male C3H/HeJ mice three times per week for the animals' lifetimes. IOA monomer had an acute oral LD50 in rats greater than 5000 mg/kg, was slightly irritating to the eyes and skin of rabbits on single exposures, and exhibited no genotoxic or cell-transforming potential. In the dermal carcinogenicity bioassay, no significant difference in mean survival times was observed between either treatment group and the control group. Animals treated with IOA monomer exhibited moderate dermatitis, surface crusting, hyperkeratosis, epidermal hyperplasia, diffuse melanosis, and one benign melanoma at the treatment size. Animals treated with IOA polymer exhibited varying degrees of dermatitis, surface crusting, and hyperkeratosis. Neither IOA monomer nor IOA polymer was carcinogenic under the conditions of the study.