Long-term associations between ambient PM₂.₅ and PM₁₀ and lung cancer hospital admissions.

e20092 Background: Air pollution is a significant environmental health threat worldwide and an important modifiable risk factor for respiratory diseases. This study investigated the association between ambient concentrations of air pollutants (PM₂.₅ and PM₁₀) and hospital admissions with a primary diagnosis of lung cancer, used as an indicator of severe disease burden over a 17-year period. Methods: Air quality data for PM₂.₅, PM₁₀, and Air Quality Index was gathered from up to 38 fixed monitoring stations in Tehran from January 2009 to January 2026, according to the Tehran Municipality's website. Information on lung cancer patients was obtained from Masih Daneshvari Hospital (a referral center for respiratory diseases in Tehran). During this timeframe, 3321 patients of lung cancer were documented. The research population included 2033 individuals diagnosed with lung cancer and residing in Tehran. Pollutant concentrations at the city level were derived from daily station readings; sensitivity analyses were conducted for determining the robustness of exposure estimates to the inclusion criteria for monitoring stations. Associations between air pollutants and lung cancer admissions were evaluated using negative binomial regression with distributed lag models. Results: Over the 17-year study period, there was a significant association between increased PM₂.₅ and lung cancer hospital admissions, suggesting that fine particulate matter may play a more important role in severe lung cancer burden than coarser particles. Among other characteristics, it is highly probable that these hospitalizations were typically higher among males, reflecting their higher smoking and occupational exposures. The most common months with high AQI are December, January, and November. The month with the greatest patient count is often not the same as the month with the highest AQI. A delayed effect is a more reasonable explanation because lung cancer develops gradually over time. Significant associations were observed between PM₂.₅ (IRR = 1.077, p < 0.03) and lung cancer hospitalizations, whereas PM₁₀ (IRR = 0.991) and AQI (IRR = 0.976) showed weak inverse, non-significant associations. Air pollution peaked in winter, with strongest lagged effects 6–8 years post-exposure (peak at 7 years). Sensitivity analyses indicated that annual exposure estimates were robust to monitoring station inclusion, with variations generally within ±10% across pollutants and years. Conclusions: This 17-year study provides evidence that air pollution may affect the timing or severity of clinical presentations in lung cancer patients; however, it does not establish a causal effect on lung cancer incidence. Nonetheless, these findings underscore the importance of monitoring and mitigating fine particulate pollution to reduce the health impacts of lung cancer and reinforce PM₂.₅ as a key target for public health interventions.