Objective To investigate the effects of indoor air pollution and lifestyle on the risk of non-smoking female lung cancer (NFLC).

Methods New cases of NFLC aged 18 to 79 years, who were collected in Jiangyin and Xinyi, Jiangsu province, China from December 2020 to November 2024, were enrolled in the study group, and age-matched non-lung cancer patients who attended the same hospital were enrolled in the control group. Information such as demographics, exposure factors, and living habits was collected through structured questionnaires. Indoor air pollution exposure scores were constructed using random forests and multivariate Logistic regression, while lifestyle scores were based on alcohol consumption, physical activity, diet, and body mass index. Subgroup analysis and interaction models were used to evaluate the effects of indoor air pollution and lifestyle on the risk of NFLC.

Results A total of 336 cases were enrolled in the study group and 352 cases were enrolled in the control group, with M (P₂₅, P₇₅) of indoor air pollution exposure scores being 0.17 (-0.05, 0.25) and 0.11 (-0.06, 0.21), respectively, and the numbers of participants with an unhealthy lifestyle being 213 (63.4%) and 193 (54.8%), respectively. Based on random forest and multivariate Logistic regression analysis, the risk of NFLC was significantly higher in individuals with higher indoor air pollution exposure scores (odds ratio OR=1.40, 95% confidence interval CI: 1.03-1.91) and those with unhealthy lifestyles (OR=1.55, 95%CI: 1.12-2.15). Subgroup analysis revealed that the indoor air pollution exposure scores had a greater impact on the risk of NFLC among individuals without a first-degree family history of cancer, those who cooked, those with occupational chemical exposure, and those with passive smoking exposure. Similarly, lifestyle had a greater impact on the risk of NFLC among individuals with lower education levels (below junior high school), those without a first-degree family history of cancer, those with occupational chemical exposure, and those with passive smoking exposure. Multivariate Logistic regression analysis showed no additive or multiplicative interaction between indoor air pollution and lifestyle on the risk of NFLC.

Conclusion Both indoor air pollution and lifestyle are associated with an increased risk of NFLC. However, no interaction between indoor air pollution and lifestyle factors was found in their impact on the risk of NFLC.