[Ultraviolet radiation as a risk factor on the Earth and outer space]

UVR effects on human health are considered. The critical organs for UVR are skin, eye, and the immune system. In the skin, UVR can induce erythema, tanning, vitamin D photosynthesis, premature aging, and cancer. UVR has a specific immunosuppressive effect on the skin secondary to altered lymphoid cells function. It results in inhibition of the anti-neoplastic activity and suppression of contact hypersensitivity and delayed hypersensitivity to various antigens. UV can induce photokeratoconjunctivitis and play an active role in etiology of cataracts, corneal and retinal degeneration, pterigium and uveal melanoma. Action spectra and biologically effective doses for the effects are presented. Measured UV energy spectra naturally occurring at the Earth's surface and in space were used to calculate the effective time of UV exposure to produce these effects. Data obtained and modulation of the UV effects by other space flight factors are discussed. Quantitative analysis of maximum permissible UV levels in the production area established in Russia, USA, and the Netherlands was performed. As a result, substantive differences in the approaches of these countries to setting limits and permissible ranges were stated. Applicability of the UV limits to regulation of natural UV exposures is considered.