Two-year carcinogenicity study on three aromatic epoxy resins applied cutaneously to CF1 mice

The cutaneous and systemic carcinogenic potentials of pure and two technical diglycidyl ethers of bisphenol A, DGEBPA, EPON 828 and EPIKOTE 828, respectively, have been investigated in six groups each of 50 male and 50 female CF1 mice. Twice weekly over a period of 2 yr, 0.2 ml of a 1 or 10% (w/v) solution of one of the epoxy resins in acetone was applied to the dorsal skin. A group of 50 male and 50 female CF1 mice was similarly treated treated with 2% (w/v) beta-propiolactone in acetone (the positive control) while a group of 100 male and 100 female mice was treated with acetone alone (negative control). Survival of the CF1 mice to 2 yr was unaffected by cutaneous exposure to each epoxy resin. The compounds proved to be mildly irritant to murine skin, the response in males being greater than in females. There was a very low incidence of benign and malignant tumours of the skin and subcutis after exposure to any of these compounds. The number of systemic lymphoreticular/haematopoietic tumours was increased only in females treated with EPIKOTE 828 or DGEBPA. In male mice, treated with 10% EPON 828, there was a slight increase in the number of renal tumours. The incidence of other systemic tumours in either sex was not increased following cutaneous application of the purified or the two technical DGEBPA resins (1 to 10% in acetone). The significance of all these findings is fully discussed.