Lung adenocarcinoma risk in an area with seasonal high PM2.5 exposure: a population-based study in upper northern Thailand

Background Air pollution exposure has been associated with increased lung cancer risk globally. However, evidence linking fine particulate matter with an aerodynamic diameter of ≤2.5 micrometers (PM 2.5 ) to adenocarcinoma, the most common histological subtype of lung cancer, using the real-world data remains limited in Southeast Asia populations where air pollution levels are rising. This study aimed to investigate the association between average daily PM 2.5 exposure and lung adenocarcinoma incidence in upper northern Thailand. Methods A population-based study was conducted across eight upper northern provinces (103 districts) of Thailand. Daily PM 2.5 exposure data were linked with lung adenocarcinoma incidence rates obtained from population-based cancer registries during 2013–2017 using patients’ residential areas at the district level. Generalized estimating equations were employed to estimate adjusted incidence rate ratios (IRRs), adjusting for individual-level characteristics (gender and age <65 years) and geographical-level characteristics (urbanization and smoking prevalence). Results Among 12,484 lung cancer cases, cell type was identified in 5,465 cases, of which 3,318 (60.7%) were lung adenocarcinoma, with a median age of 64 years (IQR: 57–71). A significant positive association was observed between 10 μg/m 3 increment in average daily PM 2.5 exposure and lung adenocarcinoma incidence (adjusted IRR = 1.022, p = 0.013). Additional significant associations were found for female (aIRR = 1.126, p < 0.001), age <65 years (aIRR = 1.105, p < 0.001), and smoking prevalence in the patient’s residing district (aIRR = 0.991, p = 0.001). Conclusion This finding highlights PM 2.5 as an important environmental risk factor for lung adenocarcinoma in the region, regardless of smoking prevalence. Our findings support the need for targeted air pollution control policies to reduce incidence of related cancers.