皮膚砷癌之流行病學特徵與危險因子

Research on the epidemiologic characteristics and risk factors of arsenic-induced skin cancer were reviewed in detail. Arsenic-induced skin cancers are nonmelanoma skin cancers. Nonmelanoma skin cancers are much more common in white than in black or other dark-skinned populations. The incidence of nonmelanoma skin cancer is greater in males than in females. It occurs mostly on the face, head and neck, while the trunk and upper extremities are the next most common sites. The risk of nonmelanoma skin cancer is asscciated with the sunlight exposure in a dose-response relationship. Ultraviolet radiation, chemicals, ionizing radiation, immunologic and other host factors are risk factors for nonmelanoma skin cancer. Arsenic is a metalloid element, contaminating the environment through leaching from mineral ores, copper smelting, and other industrial and agricultural sources. Inorganic arsenic is much more toxic than organic arsenic compounds. It induces gastrointestinal disturbance, cardiovascular diseases, neurological disorders, liver and kidney damage, skin lesions and cancers. Inorganic arsenic has been documented as a human carcinogen of the skin and lung. Exposure to inorganic arsenic from medicinal, environmental and occupational sources has been found to be associated with the development of skin cancer. In contrast with nonmelanoma cancers of other etiologies, arsenic-induced skin cancers occur on every part of the body, especially marked in areas unexposed to sunlight, such as the palms, soles, extremities and trunk. They are multifocal and randomly distributed epidermal carcinoma lesions. A dose-response relationship between the prevalence and mortality of skin cancer and the arsenic concentration of artesian well water has been well documented in a black-foot disease endemic area on the southwest coast of Taiwan. A significant dose-response relation has recently been reported between skin cancer prevalence and chronic arsenic exposure, indexed by duration of living in the endemic area, duration of consuming high-arsenic contaminated artesian well water, average arsenic in artesian well water and cumulative arsenic exposure. Salt field working, chronic HBsAg carrier status with liver dysfunction, and high consumption of dried sweet potatoes have been found to be significantly associated with an increased prevalence of arsenic-induced skin cancer in those living in the blackfoot disease endemic area. Arsenic metabolism capacity, distribution of urinary arsenic species, serum level of micronutrients and immunologic profiles need to be explored for their associations with arsenic-induced skin cancer. Skin cancer has been considered as a biological marker for chronic inorganic arsenic exposure. Both standardized mortality ratio and cumulative mortality of skin cancer and various internal cancers have been reported to be significantly higher among residents in the blackfoot disease endemic area than in the general population in Taiwan. The mechanism of arsenic-induced skin cancer as well as the association between skin cancer and internal cancers deserve further investigation.