Lung cancer and arsenic concentrations in drinking water in Chile

Cities in northern Chile had arsenic concentrations of 860 mug/liter in dri nking water in the period 1958-1970. Concentrations have since been reduced to 40 mug/liter. We investigated the relation between lung cancer and arse nic in drinking water in northern Chile in a case control study involving p atients diagnosed with lung cancer between 1994 and 1996 and frequency-matc hed hospital controls. The study identified 152 lung cancer cases and 419 c ontrols. Participants were interviewed regarding drinking water sources, ci garette smoking, and other variables. Logistic regression analysis revealed a clear trend in lung cancer odds ratios and 95% confidence intervals (CIs ) with increasing concentration of arsenic in drinking water, as follows: 1 , 1.6 (95% CI = 0.5-5.3), 3.9 (95% CI = 1.2-12.3), 5.2 (95% CI = 2.3-11.7), and 8.9 (95% CI = 4.0-19.6), for arsenic concentrations ranging from less than 10 mug/liter to a 65-year average concentration of 200-400 mug/liter. There was evidence of synergy between cigarette smoking and ingestion of ar senic in drinking water; the odds ratio for lung cancer was 32.0 (95% CI = 7.2-198.0) among smokers exposed to more than 200 mug/liter of arsenic in d rinking water (lifetime average) compared with nonsmokers exposed to less t han 50 mug/liter. This study provides strong evidence that ingestion of ino rganic arsenic is associated with human lung cancer.