Household air pollution and lung cancer risk among never-smokers in Nepal.

More than half of the global population relies on biomass fuels (wood, charcoal, crop residue, dung) for cooking and/or heating purposes. Household air pollution (HAP) resulting from the use of these solid fuels is of particular concern, given the overall prevalence as well as the intensity of exposure and the range of potential adverse health outcomes. Long term exposure to HAP is a major public health concern, particularly among women and children in low and middle income countries. In this study, we investigated the association between exposure to HAP resulting from combustion of biomass and lung cancer risk among Nepalese population. Using a hospital-based case-control study (2009-2012), we recruited 606 lung cancer cases and 606 healthy controls matched on age (±5 years), gender, and geographical residence. We used unconditional logistic regression to compute odds ratios (ORs) and 95% Confidence Intervals (95% CI) for lung cancer risk associated with HAP exposures, adjusting for potential confounders (tobacco use, TB status, SES, age, gender, ethnicity, and exposure to second hand smoke. In our overall analysis, we observed increased risk of lung cancer among those who were exposed to HAPs (OR: 1.77, 95% CI: 1.00-3.14). A more detailed analysis stratified by smoking status showed considerably higher risk of lung cancer associated with increasing duration of exposure to HAP from biomass combustion, with evidence of a borderline exposure-response relationship (Ptrend=0.05) that was more pronounced among never-smokers (Ptrend=0.01). Our results suggest that chronic exposure to HAP resulting from biomass combustion is associated with increased lung cancer risk, particularly among never-smokers in Nepal.