An epidemiologic study of arsenic-related skin disorders and skin cancer and the consumption of arsenic-contaminated well waters in Huhhot, inner Mongolia, China

Well-use histories were obtained and dermatological examinations were conducted for 3,179 of the 3,228 (98.5%) residents of 3 villages in Inner Mongolia with well water arsenic levels as high as 2,000 ppb (ug/L). Eight persons were found to have skin cancer, 172 had hyperkeratoses, 121 had dyspigmentation, 94 had both hyperkeratoses and dyspigmentation, and, strikingly, none had Blackfoot disease. All 8 subjects with skin cancer also had both hyperkeratoses and dyspigmentation. Arsenic levels were measured for 184 wells and individual well-use histories were obtained. Arsenic exposure histories were summarized as both highest arsenic concentration (highest exposure level for at least 1-year duration) and cumulative arsenic exposure (ppb-years). Sixty-nine percent of the participants had highest arsenic concentrations below 100 ppb; 71% had cumulative arsenic exposures below 2,000 ppb-years. Exposure-response analyses included frequency-weighted, simple linear regression, and most-likely estimate (hockey-stick) models. Skin cancer cases were only found for those with a highest arsenic concentration greater than 150 ppb, and those with exposure less than 150 ppb had a statistically significant deficit. A frequency-weighted model showed a threshold at 150 ppb, and a hockey-stick model showed a threshold at 122 ppb. Considerations of duration, age, latency, and misclassification did not appear to markedly affect the analysis. The non-malignant skin findings showed thresholds of 40-50 ppb in the hockey-stick models. Application of these analytic models to the data from other epidemiological studies of arsenic ingestion and malignant and non-malignant skin disorders can be used to examine patterns of arsenic carcinogenicity.