Word: ultraviolet
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Some scientists, Soviet and American alike, have still not abandoned hope of finding life or its remnants deeper in the Martian soil. There life forms might have access to water and be protected from the fierce solar ultraviolet radiation that rains down on the surface, virtually unobstructed by the Martian atmosphere. Sedimentary rocks in the ancient riverbeds would be an ideal place to hunt for fossils of organisms that may have lived when Mars was more benign, with a thicker atmosphere, warmer climate and running water on its surface...
That is now difficult to do, and the consequence may be costly: prolonged exposure to invisible ultraviolet beams of sunlight may permanently damage the eyes. Ultraviolet-B is thought, for example, to be a major factor in the formation of cataracts, in which the normally transparent lens of the eye becomes cloudy or opaque. About 15% of people over 65 suffer reduced vision from cataracts; many eventually undergo surgery to have the lens replaced. Some ophthalmologists also believe that decades of absorbing ultraviolet-A may lead to destruction of cells in the center of the retina. The condition, known...
...divides sunglasses into three categories: fashion spectacles that shield eyes from only 70% of UV-B and less than 60% of UV-A; everyday eyewear that screens out 95% of UV-B and between 60% and 92% of UV-A; and special-purpose glasses that absorb almost 99% of ultraviolet rays...
...information, however, is not included on all the tags. Says a spokesman for the Food and Drug Administration: "If you're a consumer and there's a rack of sunglasses, you usually have no way of telling the amount of ultraviolet transmission." The agency is now considering proposals to establish mandatory labeling standards for the sunglass industry. Ultimately, say experts, the best solution may be a simple rating system similar to the numerical system now used with sunscreens...
...recent trials of the tan enhancer, Norman Levine, a University of Arizona dermatologist, confirmed that it produces a fast tan for all skin types by increasing melanin, the skin pigment that absorbs the sun's ultraviolet rays. The black mark against Bergasol, say other doctors, is that it contains the chemical psoralen, extracted from citrus oil. In animal tests at Harvard Medical School, high doses of psoralen caused skin cancer. Still, says Harvard Dermatologist Madua Pathak, Bergasol also contains sunscreen, which reduces UV absorption and cuts the risk to humans to acceptable levels. Harvard Colleague Robert Stern...