Gallagher Richard P, Lee Tim K, Bajdik Chris D, Borugian Marilyn
Cancer Control Research Program, British Columbia Cancer Agency, British Columbia.
Chronic Dis Can. 2010;29 Suppl 1:51-68.
The major source of ultraviolet radiation is solar radiation or sunlight. However, exposure to artificial sources particularly through tanning salons is becoming more important in terms of human health effects, as use of these facilities by young people, has increased. The International Agency for Research on Cancer has noted that there is sufficient evidence from studies in animals and in man to establish ultraviolet radiation as a human carcinogen. Skin cancer has been the most commonly studied cancer site with respect to UV radiation. The nature and timing of sun exposure appear to be important determinants of both the degree of risk and the type of skin cancer. Cutaneous malignant melanoma and basal cell cancer are much more strongly related to measures of intermittent ultraviolet exposure (particularly those of childhood or adolescence) than to measures of cumulative exposure. In contrast, squamous cell cancer is more strongly related to constant or cumulative sun exposure. Lip cancer is causally related to lifetime sun exposure. It has been estimated that solar ultraviolet radiation accounts for approximately 93 percent of skin cancers and about half of lip cancers. This translates to approximately 4,500 life-threatening cancers (cutaneous malignant melanoma) per year in Canada, as well as 65,000 less serious cancers (basal cell cancer, squamous cell cancer and lip cancer). Appropriate clothing use, care not to sunburn and judicious use of sunscreens could prevent at least half of these and save approximately 450 lives per year. In addition, physician and public education programs can significantly increase the proportion of melanomas diagnosed early. Lesions that have not yet penetrated deeply are associated with a mortality rate of less than five percent. Several recent studies suggest a possible inverse relationship between ultraviolet radiation exposure and risk of non-Hodgkin lymphoma, colon, breast and prostate cancer, and investigators have speculated that this might be due to the higher serum levels of vitamin D stimulated by high lifetime sun exposure. Further, studies conducted within cohorts using stored pre-diagnostic serum suggest that those with high levels of vitamin D have lower incidence rates of a number of malignancies, particularly colon cancer. However, since serum vitamin D levels can be raised through the use of supplements without increasing risk for skin lip and other known UV-related cancers, changes to health policy with regard to exposure are not merited at this point. Further research is needed in this area.
紫外线辐射的主要来源是太阳辐射或阳光。然而，就对人类健康的影响而言，接触人工光源，尤其是通过晒黑沙龙接触，正变得越来越重要，因为年轻人对这些设施的使用有所增加。国际癌症研究机构指出，动物和人体研究中有充分证据表明紫外线辐射是一种人类致癌物。皮肤癌是紫外线辐射方面研究最为普遍的癌症部位。日晒的性质和时间似乎是风险程度和皮肤癌类型的重要决定因素。皮肤恶性黑色素瘤和基底细胞癌与间歇性紫外线暴露（尤其是儿童期或青春期的暴露）的关联，比与累积暴露的关联更为密切。相比之下，鳞状细胞癌与持续或累积日晒的关联更为密切。唇癌与终生日晒有因果关系。据估计，太阳紫外线辐射导致了约93%的皮肤癌和约一半的唇癌。这意味着在加拿大每年约有4500例危及生命的癌症（皮肤恶性黑色素瘤），以及65000例不太严重的癌症（基底细胞癌、鳞状细胞癌和唇癌）。适当穿着衣物、注意不被晒伤以及明智使用防晒霜至少可以预防其中一半的癌症，每年挽救约450条生命。此外，医生和公众教育项目可以显著提高早期诊断出的黑色素瘤的比例。尚未深度浸润的病变的死亡率低于5%。最近的几项研究表明，紫外线辐射暴露与非霍奇金淋巴瘤、结肠癌、乳腺癌和前列腺癌的风险之间可能存在负相关关系，研究人员推测这可能是由于终生高日晒刺激血清维生素D水平升高所致。此外，在队列研究中使用储存的诊断前血清进行的研究表明，维生素D水平高的人多种恶性肿瘤的发病率较低，尤其是结肠癌。然而，由于可以通过补充剂提高血清维生素D水平而不增加皮肤唇癌和其他已知紫外线相关癌症的风险，目前在暴露方面改变健康政策并不合适。这一领域需要进一步研究。
