2-year carcinogenicity study in the male NMRI mouse with 2-ethylhexyl acrylate by epicutaneous administration.

A 2 yr carcinogenicity study of 2-ethylhexyl acrylate (2-EHA) was conducted by applying 25 microliters 21.5, 43 or 85% 2-EHA or 0.015% benzo[a]pyrene (B[a]P) in acetone, three times/wk, to the clipped dorsal skin of male NMRI mice (80 per group). A further group received acetone and served as the vehicle control. After about 7 months of treatment, half of each group was rested from treatment for a period of 2 months, then treated with the promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) for 20 wk followed by observation until termination of the study. The other half of each group received continuous treatment with 2-EHA, B[a]P or acetone, respectively, for 2 yr. Signs signs of skin irritation were apparent in all groups treated with 2-EHA [hyperkeratosis, hyperplasia (acanthosis), crust formation and ulceration]. In the group treated with B[a]P alone or B[a]P with TPA, 79% and 67% of the mice, respectively, bore squamous cell carcinomas. None of the mice treated with acetone or 2-EHA alone developed a skin tumour at the application site. One squamous cell papilloma occurred in each of the groups treated with 2-EHA and TPA, an incidence matched by the single squamous cell papilloma in an untreated area of an acetone control mouse. Thus, 2-EHA proved not to be carcinogenic in the skin of male NMRI mice by epicutaneous administration.