| An estimated 800,000 inhabitants are consuming groundwater that is geologically contaminated with inorganic arsenic in West Bengal, India. Early manifestations of long-term arsenic exposure include skin keratoses and hyperpigmentation. These skin lesions pose a serious public health problem because advanced forms of keratoses are painful, and may increase susceptibility to respiratory effects and later cancer risks. Gaps of information in the literature include the following: the magnitude of people affected; whether the skin lesions are markers for other adverse health outcomes; and the dose-response relation at low doses.;As a part of the dissertation, an analysis was published of the largest cross-sectional survey to assess individuals' exposure, and to establish the prevalence of arsenic-induced skin lesions in West Bengal. The prevalence of hyperpigmentation was 3.1% in females and 6.4% in males. Clear exposure-response patterns were found. Surprisingly, a number of individuals with skin lesions consumed low arsenic levels (<100 mug/L). This paper was published in the International Journal of Epidemiology, 1998, 27:871--877.;Further analyses of non-smokers in the same population revealed new evidence that respiratory effects largely occurred in individuals with arsenic-induced skin lesions. In participants with skin lesions, the age-adjusted prevalence odds ratios for cough were 7.8 for females (95% CI: 3.1--19.5) and 5.0 for males (95% CI: 4.0--22.9). This report appeared in the International Journal of Epidemiology, 2000, 29:1047--1052.;A case-control study was designed, conducted, and analyzed as another integral component of the dissertation. This was the first investigation of skin lesions to assess exposures from past decades, and the first to confirm cases with photographs. The proportion of cases confirmed by photograph was high (87%). Using those exposed to peak levels of <50 mug/L as the referent group, the odds ratio rose from a two-fold increase in the second category (50--99.9 mug/L) to a 25-fold increase in the highest peak category (>300 mug/L). These trends remained after adjusting for sex, age, smoking, and body mass index. Analyses restricted to confirmed cases with complete exposure histories since 1980 suggested stronger trends. For the first time, the dose-response relation of skin lesions and arsenic ingestion at low doses was characterized using a detailed exposure assessment. |
