Hannan M A, Paul M, Amer M H, Al-Watban F H
Cancer Res. 1984 May;44(5):2192-7.
Sunlight-related biological effects such as skin cancer, sunburning, and synthesis of vitamin D in the body have been found to be very low in people in the midregion of Saudi Arabia. The present studies were undertaken to measure the sunburning-carcinogenic ultraviolet light (UV) radiation (UV-B) in natural sunlight in the city of Riyadh (25 degrees north latitude). The average noontime incidence of UV-B, measured with a sunburn UV-meter, was found to be between 1.9 and 3.4 sun units/hr in the months of March to May. Concomitantly with the UV measurements, a bioassay using a wild-type and an excision repair-deficient diploid strain of the yeast, Saccharomyces cerevisiae, was carried out to detect both lethal and genotoxic effects (mutation and mitotic gene conversion) of the sunlight. Exposure of the yeast cells to sunlight 30 to 180 min resulted in a significant level of cell death and a dose-dependent induction of mutations and mitotic gene conversion. The use of a Mylar filter cutting off virtually all of the wavelengths below 312 nm greatly reduced the lethal and genotoxic effects of sunlight. The results of UV measurements and biological studies suggest that an appreciable amount of potentially carcinogenic short UV wavelengths is present in sunlight in the Riyadh area. Therefore, factors other than the lack of biologically significant UV radiation in sunlight appear more likely to be responsible for the reduced incidence of sunburning and skin cancer in this geographical area.
在沙特阿拉伯中部地区的人群中，已发现诸如皮肤癌、晒伤以及体内维生素D合成等与阳光相关的生物效应非常低。本研究旨在测量利雅得市（北纬25度）自然阳光中导致晒伤的致癌紫外线（UV-B）辐射。在3月至5月期间，使用晒伤紫外线计测量的UV-B平均正午发生率为每小时1.9至3.4个阳光单位。在进行紫外线测量的同时，利用酿酒酵母的野生型和切除修复缺陷二倍体菌株进行了生物测定，以检测阳光的致死和遗传毒性效应（突变和有丝分裂基因转换）。将酵母细胞暴露于阳光30至180分钟会导致显著水平的细胞死亡以及剂量依赖性的突变和有丝分裂基因转换诱导。使用几乎能切断所有低于312纳米波长的聚酯薄膜滤光片可大大降低阳光的致死和遗传毒性效应。紫外线测量和生物学研究结果表明，利雅得地区的阳光中存在相当数量的潜在致癌短紫外线波长。因此，除了阳光中缺乏具有生物学意义的紫外线辐射之外，其他因素似乎更有可能是导致该地理区域晒伤和皮肤癌发病率降低的原因。
