The carcinogenic risks of modern tanning equipment: Is UV-A safer than UV-B?
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An animal experiment is presented in which three groups of albino hairless mice (Skh-hr 1) were exposed to daily doses of either UV-B or UV-A to study carcinogenesis. The UV-A was filtered carefully so as to eliminate contaminating UV-B. The doses required for acute effects (erythema and edema) were also determined for the two radiation modalities. In order to study the relative carcinogenic risks of exposures to UV-A and to UV-B, for both modalities, the doses causing skin tumors were compared to the doses required for eliciting acute effects in the skin.
In the experiment on carcinogenesis all animals developed tumors, the ones exposed to UV-A as well as the ones exposed to UV-B. A striking difference, however, was that the induction times of the first tumors showed a larger spread in the mice exposed to UV-A than in the UV-B groups. Also, the development of successive tumors in each individual mouse was more spread in time in the UV-A group. A second difference between the effects on the skin was that in the animals exposed to UV-B no skin reactions were seen until the tumors developed. However, in most UV-A exposed animals, a marked scratching, probably caused by severe itching, and hyperkeratosis preceded the development of the tumors.
Histologically at least 60% of the larger tumors induced by UV-A appeared to be squamous cell carcinomas. This finding is very similar for UV-B induced tumors. The elastic fibers in the UV-A exposed animals were also examined and actinic elastosis was observed.
Experience has proven that the doses for acute affects in man and mouse are at least proportional to human tanning doses. Comparison of the doses of UV-A and UV-B required for the induction of tumors and for acute reactions of the skin, therefore, leads to the conclusion that the carcinogenic risks of tanning by UV-A and of tanning by UV-B are in the same order of magnitude.
Key wordsUV-radiation Erythema Tanning Carcinogenesis
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