In vitro and in vivo estrogenicity of UV screens

Ultraviolet (UV) screens are increasingly used as a result of growing conce rn about UV radiation and skin cancer; they are also added to cosmetics and other products for light stability. Recent data on bioaccumulation in wild life and humans point to a need for in-depth analyses of systemic toxicolog y, in particular with respect to reproduction and ontogeny. We examined six frequently used UVA and UVB screens for estrogenicity in vitro and in vivo . In MCF-7 breast cancer cells, five out of six chemicals, that is, benzoph enone-3 (Bp-3), homosalate (HMS), 4-methyl-benzylidene camphor (4-MBC), oct yl-methoxycinnamate (OMC), and octyl-dimethyl-PABA (OD-PABA), increased cel l proliferation with median effective concentrations (EC50) values between 1.56 and 3.73 muM, whereas butyl-methoxydibenzoylmethane (B-MDM) was inacti ve. Further evidence for estrogenic activity was the induction of pS2 prote in in MCF-7 cells and the blockade of the proliferative effect of 4-MBC by the estrogen antagonist ICI 182,780. In the uterotrophic assay using immatu re Long-Evans rate that received the chemicals for 4 days in powdered feed, uterine weight was dose-dependently increased by 4-MBC (ED50 309mg/kg/day) , OMC (ED50 935 mg/kg/day), and weakly by Bp-3 (active at 1,525 mg/kg/day). Three compounds were inactive by the oral route in the doses tested. Derma l application of 4-MBC to immature hairless (hr/hr) rats also increased ute rine weight at concentrations of 5 and 7.5% in olive oil. Our findings indi cate that UV screens should be tested for endocrine activity, in view of po ssible long-term effects in humans and wildlife.