Lung cancer risk and solid fuel smoke exposure: a systematic review and meta-analysis.

The aim of this systematic review was to quantify the impact of biomass fuel and coal use on lung cancer and to explore reasons for heterogeneity in the reported effect sizes. A systematic review of primary studies reporting the relationship between solid fuel use and lung cancer was carried out, based on pre-defined criteria. Studies that dealt with confounding factors were used in the meta-analysis. Fuel types, smoking, country, cancer cell type and sex were considered in sub-group analyses. Publication bias and heterogeneity were estimated. The pooled effect estimate for coal smoke as a lung carcinogen (OR 1.82, 95% CI 1.60-2.06) was greater than that from biomass smoke (OR 1.50, 95% CI 1.17-1.94). The risk of lung cancer from solid fuel use was greater in females (OR 1.81, 95% CI 1.54-2.12) compared to males (OR 1.16, 95% CI 0.79-1.69). The pooled effect estimates were 2.33 (95% CI 1.72-3.17) for adenocarcinoma, 3.58 (1.58-8.12) for squamous cell carcinoma and 1.57 (1.38-1.80) for tumours of unspecified cell type. These findings suggest that in-home burning of both coal and biomass is consistently associated with an increased risk of lung cancer.