As the outermost layer of the skin, the stratum corneum is exposed to environmental oxidants. To investigate putative synergisms of environmental oxidative stressors in stratum corneum, hairless mice were exposed to ultraviolet radiation (UV) and ozone (O3) alone and in combination. Whereas a significant depletion of α-tocopherol was observed after individual exposure to either a 0.5 minimal erythemal dose of UV or 1 ppm O3 for 2 h, the combination did not increase the effect of UV alone. However, a dose of 0.5 ppm O3×2 h, which had no effect when used alone, significantly enhanced the UV-induced depletion of vitamin E. We conclude that concomitant exposure to low doses of UV and O3 at levels near those that humans can be exposed to causes additive oxidative stress in the stratum corneum.
