Exposure to indoor wood-burning stoves and fireplaces and risk of lung cancer among Sister Study participants

Abstract

Background and Aim: Epidemiological evidence from case-control studies has identified exposure to household combustion of biomass fuel (primarily wood) as a probable lung carcinogen. However, few studies have been conducted in the United States, where indoor wood-burning and usage patterns differ. We examined the association of exposure to indoor wood smoke from fireplaces and stoves with incident lung cancer in U.S. women. Methods: 50,399 women were studied in the U.S.-based prospective Sister Study cohort (recruited 2003-2009) who answered baseline exposure information and did not have lung cancer before enrollment. At baseline, women reported their frequency of use of wood-burning stoves and/or fireplaces in their longest-lived adult residence. Cox regression was used to estimate adjusted hazard ratios (HRadj) and 95% confidence intervals (CI) for the association between indoor wood-burning fireplace/stove use and incident lung cancer. Results: During an average of 11.3 years of follow-up, 520 lung cancer cases were diagnosed. Overall, 62.2% of the study population reported the presence of an indoor wood-burning fireplace/stove at their longest-lived adult residence. Compared to those without a wood-burning fireplace/stove, an elevated risk of lung cancer was observed in women who used their wood-burning fireplace/stove ≥30 days/year (HRadj = 1.20; 95% CI = 0.94, 1.52; p-for-trend=0.09). Associations were more pronounced in never smokers, with elevated HRs observed in women reporting use both 1-29 days/year (HRadj = 1.87; 95% CI = 1.07, 3.28) and ≥30 days/year (HRadj = 1.69; 95% CI = 0.92, 3.11). Findings were stronger among women who were younger, had less educational attainment and lived in urban settings. Conclusions: Our prospective analysis of a cohort of U.S. women found that frequent use of wood-burning indoor fireplaces/stoves was associated with incident lung cancer, consistent with earlier findings. Keywords: Wood Smoke; Lung Cancer; Women; Respiratory Diseases