Association between indoor air pollution and risk of oesophageal cancer: a Chinese population-based case–control study

Introduction: Oesophageal cancer is a highly lethal malignancy with geographic disparity and a heavy burden in developing countries. While smoking and alcohol are established risk factors, emerging evidence suggests that indoor air pollution (IAP) may also play a role through the inhalation of aerosols along the aerodigestive tract, but its relationship with oesophageal cancer remains poorly understood. Previous studies have focused on how IAP is associated with lung cancer, and evidence on oesophageal cancer is sparse, underpowered and inconclusive. Methods: This population-based case-control study was conducted in the Jiangsu Province, China, from 2003 to 2010. We analysed 2969 cases and 8019 controls using unconditional logistic regression, adjusting for potential confounders. In addition to the six individual household air pollution sources, we also studied their combined effect by calculating the unweighted and weighted sum of these IAP sources to improve comparability. Furthermore, we conducted subgroup analyses by sex and smoking status, as well as by sex exclusively among non-smokers. Results: In both the overall sample and subgroups, higher exposure to various individual or combined IAP sources was associated with a dose-response increase in oesophageal cancer risk (weighted risk score (WRS) semi-Bayesian (SB)-adjusted OR (aOR): 2.70; 95% CI 2.36 to 3.07). Solid fuels appeared to have the strongest association (SB-aOR: 1.76; 95% CI 1.56 to 1.98), followed by coal used for cooking, passive smoking and poor ventilation in the kitchen and bedrooms. The vulnerability to different sources varied by sex and smoking status, and females among non-smokers consistently experienced a more profound impact from combined IAP exposure using WRS. Conclusions: Exposure to common IAP is associated with an increased risk of oesophageal cancer among the Chinese population, with variations in susceptibility observed across sex and depending on smoking status.