Background: Arsenic is a well-documented human carcinogen, and studies on urinary and skin cancers have shown that the carcinogenicity of ingested arsenic has cell-type specificity. To evaluate whether this is also true for lung cancers, we conducted a study on 243 townships in Taiwan. Methods: The arsenic levels were assessed using measurement reports from a previous survey, and the incidence of lung cancer was assessed using the data gathered by the National Cancer Registry Program. We analyzed data by regression models with multiple variables to describe exposure levels; each variable denoted the proportion of people in a specific exposure category in each township. An urbanization index and variables denoting the distribution of age in each township were also included in the model to adjust for effects of urbanization and age. Results: Among the three major cell types of lung cancer, squamous cell carcinoma appeared to be associated with arsenic level in drinking water, and the association was more prominent at exposure level above 0.64 mg/L in both men and women. A 1% increase in the proportion of wells in this category was associated with an increase of 0.27 per 100,000 per year in the incidence of squamous cell lung cancer in men and 0.13 per 100,000 per year in women. Adenocarcinoma and small cell carcinoma were not associated with arsenic level in drinking water. Conclusions: The results suggested that the carcinogenicity of arsenic on lungs is cell-type specific, which is compatible with observations on urinary and skin cancers. Whereas data in the literature were limited, the association between adenocarcinoma and arsenic exposures through inhalation appeared to be stronger than that of squamous cell carcinoma. Therefore, different exposure routes may give rise to different mechanisms in the carcinogenicity of arsenic.
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