2-YEAR CARCINOGENICITY STUDY IN THE MALE NMRI MOUSE WITH 2-ETHYLHEXYLACRYLATE BY EPICUTANEOUS ADMINISTRATION

A 2 yr carcinogenicity study of 2-ethylhexyl acrylate (2-EHA) was cond ucted by applying 25 mu l 21.5, 43 or 85% 2-EHA or 0.015% benzoapyre ne (BaP) in acetone, three times/wk, to the clipped dorsal skin of m ale NMRI mice (80 per group). A further group received acetone and ser ved 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 t reated with the promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) fo r 20 wk followed by observation until termination of the study. The ot her half of each group received continuous treatment with 2-EHA, BaP or acetone, respectively, for 2 yr. Signs of skin irritation were app arent in all groups treated with 2-EHA hyperkeratosis, hyperplasia (a canthosis), crust formation and ulceration. In the group treated with BaP alone or BaP 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 sq uamous cell papilloma occurred in each of the groups treated with 2-EH A and TPA, an incidence matched by the single squamous cell papilloma in an untreated area of an acetone control mouse. Thus, 2-EHA proved n ot to be carcinogenic in the skin of male NMRI mice by epicutaneous ad ministration.