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职称英语卫生类考试考前每日一练 Sunbath and Skin Cancer In the summer, millions of Americans will offer up their bodies to the sun rays. A tan indicates health and beauty, and most sun worshippers will sacrifice a lot to achieve it, in-eluding themselves. With each hour，the suns ultraviolet radiationproduces irreversibledamage，hastening the development of unsightly wrinkles.And with each year OII the beach or rooftop，the sunbather increases his risk of getting skin cancer.Skin cancer is by far the most common form of cancer.An estimated 400，00 new cases will be blamed this year in the United States.and almost all of them can be blamed on over-exposure to the sun. Fortunately，most of these cancers are highly curable.I3ut they can he disfiguring arm take time to treat.For that reason，sun worshippers should treat deity with a good deal of awe.Sunburn，of course，is the initial hazard posed by UV radiation.Prolonged exposure to UV，however，interferes with the production of collagen fibersin the dermis，causing the skin to lose elasticityand creating premature wrinkles.Further deteriorationof the dermis deprives t he epidermisof nutrition and causes it to become thin and dry. Cancer is UVs final result.Shortwave radiant energy，especially from the UV B band，breaks the strandsof DNA.Enzymeswork constantly trearrange the DNA into proper sequence.but with repeated UV exposure，the repair process may eventually break down.Then the mutantDNA may produce a colony of cancer cells.But skin cancer may be avoided with a good dose of common sense.People with fair skin and blue eyes who burn easily stand the highest risk.Special danger spots are the parts of the body most constantly exposed to the sun，such as the cheeks，nose，lower lip and the ears.People who have already developed precancerouslesionsor had one skin-cancer growth stand a greatly increased chance of developing others. | 
