| Risk Assessment for the Harmful Effects of UVB Radiation on the Immunological Resistance to Infectious Diseases Wim Goettsch,
1
Johan Garssen,
1
Wout Slob,
1
Frank R. de Gruijl,
2
and Henk Van Loveren
1
1
National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands
2
Department of Dermatology, University of Utrecht, Utrecht, The Netherlands Abstract
Risk assessment comprises four steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization. In this study, the effects of increased ultraviolet B (UVB, 280-315 nm) radiation on immune functions and the immunological resistance to infectious diseases in rats were analyzed according to this strategy. In a parallelogram approach, nonthreshold mathematical methods were used to estimate the risk for the human population after increased exposure to UVB radiation. These data demonstrate, using a worst-case strategy (sensitive individuals, no adaptation) , that exposure for approximately 90 min (local noon) at 40°N in July might lead to 50% suppression of specific T-cell mediated responses to Listeria monocytogenes in humans who were not preexposed to UVB (i.e., not adapted) . Additionally, a 5% decrease in the thickness of the ozone layer might shorten this exposure time by approximately 2.5%. These data demonstrate that UVB radiation, at doses relevant to outdoor exposure, may affect the specific cellular immune response to Listeria bacteria in humans. Whether this will also lead to a lowered resistance (i.e., increased pathogenic load) in humans is not known, although it was demonstrated that UVB-induced immunosuppression in rats was sufficient to increase the pathogenic load. Epidemiology studies are needed to validate and improve estimates for the potential effects of increased UVB exposure on infectious diseases in humans. Key words : immunosuppression, immune system, Listeria, risk assessment, UVB radiation. Environ Health Perspect 106: 71-77(1998) . [Online 21 January 1998] http://ehpnet1.niehs.nih.gov/docs/1998/106p71-77goettsch/ abstract.html Address correspondence to J. Garssen, National Institute of Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands. This work was supported by the National Research Program Global Change grant 850017 from the ministry of Public Housing and Environmental Protection and by the Environmental Program of the European Community grant PL 910034. We are obliged to J.G. Vos, M. Norval, H. Slaper, and J.C. van der Leun for reviewing this manuscript. Received 4 February 1997 ; accepted 6 October 1997.
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