UV EFFECTS ON HUMAN HEALTH 



MARGARET L. KRIPKE 



Department of Immunology 



The University of Texas 



M.D. Anderson Cancer Center 



1515 Holcombe Boulevard 



Houston, Texas 77030 



ABSTRACT: The major consequence of stratospheric ozone depletion is to increase 

 the amount of UV-B (280-320 nm) radiation in sunlight reaching the earth's 

 surface. There is considerable evidence that repeated exposure of light-skinned 

 individuals to the UV-B radiation in sunlight leads to the development of basal 

 and squamous cell cancers of the skin. Around 500,000 new cases of skin cancer 

 are diagnosed each year in the United States, making this the most common type of 

 cancer in the United States. The majority of these cancers are thought to be 

 caused by UV-B exposure. Thus an increase in the amount of UV-B radiation in 

 sunlight would further increase the incidence of these skin cancers, which are 

 associated with a low level of mortality (between 1 and 2%) but significant 

 morbidity. 



There is growing indirect evidence that UV-B radiation also contributes to the 

 incidence of cutaneous melanoma. This cancer of the pigment cells in skin is 

 much less common than the other forms of skin cancer (approximately 25,000 new 

 cases per year in the United States), but causes lethal disease in around 25% of 

 persons affected. The role played by UV-B radiation in the incidence of 

 cutaneous melanoma is not well understood, and it is clear that factors other 

 than sunlight exposure are also involved. Because UV-B radiation is thought to 

 contribute to the development of at least some cutaneous melanomas, an increase 

 in the UV-B radiation in sunlight is expected to increase the incidence of these 

 cancers as well . 



Other effects of UV-B radiation on human health include ocular changes leading to 

 the formation of cataracts and other abnormalities and perturbations of the 

 immune system. Studies on laboratory animals have shown that exposure to UV-B 

 radiation interferes with several immune responses, including those directed 

 against skin cancers. 



Exposing animals to low doses of UV-B radiation interferes with the function of 

 immune cells in the skin, leading to a decreased immune response, and exposure to 

 higher doses of UV-B impairs certain immune responses occurring at distant, 

 unexposed sites. Evidence for similar immunologic changes in humans is growing, 

 which raises the question of whether exposure to an increased amount of UV-B 

 radiation might interfere with the body's immune defenses against certain 

 infectious diseases. This possibility is currently under investigation in 

 several laboratories using various animal models of infectious diseases. 



REFERENCES: 



Hoffman, J.S., 1987. Assessing the Risks of Trace Gases That Can Modify the 

 Stratosphere, Vol. 1: Executive Summary. United States Environmental Protection 



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