Lung cancer and arsenic exposure in rural Bangladesh

Abstract

Background: Arsenic is a known carcinogen but no estimate has been made of the risk of lung cancer from the widespread contamination of drinking water in rural areas of Bangladesh.

Objectives: To determine whether estimated exposure to arsenic in drinking water used by villagers in Bangladesh differed between cases of lung cancer and those found to have non-malignant lesions

Methods: Data were obtained from 7286 subjects with lung biopsy 2003-2006 at a single diagnostic centre that took referrals from throughout Bangladesh. Analysis was limited to 5372 living in villages for the last 10 years who reported using tube well water. Of these, 3223 with a primary lung tumour were cases and 1588 with non-malignant lesions referents in an unmatched analysis. Arsenic exposure was estimated by average concentrations for each of 64 districts. Logistic regression was used to test the effects of age, arsenic and smoking on risk and to investigate relation to cell type.

Results: Male cases were older than referents and more likely to smoke, to smoke more than 20 units/day and to smoke bidi. Odds ratios for lung cancer increased steadily with mean arsenic concentration but the confidence interval excluded 1.0 only at concentrations >100 µg/L (OR=1.45, 95%CI 1.16-1.80). This trend was seen only in smokers where the increased risk at >100 µg/L was 1.65 (95%CI 1.25-2.18). A similar trend was seen in women smokers. Squamous cell type was more frequent in smokers and, having adjusted for smoking, in districts with arsenic concentrations above100 µg/L

Conclusions: Among Bangladeshis who smoke, those whose drinking water is contaminated with arsenic at concentrations > 100 µg/L are at increased risk of lung cancer. With high levels of exposure misclassification and short latency of exposure, the study cannot estimate or exclude likely long term risk in non-smokers and at lower arsenic concentrations.