Trends in gaseous pollutant emissions and their effects on lung cancer incidence: an analysis using mixed-effects models and the difference-in- differences approach

Gaseous pollutant emissions (GPEs) have become a significant environmental risk factor. However, the specific contribution of GPEs to lung cancer incidence remains underexplored. This study aimed to evaluate global emissions of gaseous pollutants and assess their impact on lung cancer incidence worldwide. Using data from 220 countries (1990–2022), we analyzed GPEs (N₂O, NOₓ, SO₂, CO₂, and others) from the Community Emissions Data System (CEDS) and lung cancer incidence rates from the Global Burden of Disease (GBD) database. Joinpoint regression assessed annual emission trends, mixed-effects models quantified pollutant-health associations adjusted for covariates (e.g., particulate matter (PM _2.5 ), human development index (HDI), forest coverage), and difference-in-differences (DID) approach evaluated causality and the attributable fractions. Global GPEs increased annually by 1.51%, with stark disparities: high-HDI countries showed stable/declining emissions, while low- and middle-HDI countries experienced significant rises (e.g., Kosovo: +18.48% annually). Mixed-effects models revealed that each 1,000-kiloton increase in total GPEs elevated lung cancer incidence by 0.002 cases per 100,000 population (P < 0.01). N₂O exhibited the strongest association (+ 6.013 cases per 100,000 population; P < 0.01), whereas CH₄ showed no effect. Higher HDI and forest coverage reduced lung cancer risk (P < 0.01). The DID approach attributed 9.7% (95% CI: 8.63–10.76) of global lung cancer incidence to GPEs, excluding SO₂ and CH₄. Gaseous pollutants, particularly N₂O, significantly contribute to lung cancer burden, with disproportionate impacts in regions undergoing rapid industrialization. Strengthening air quality policies to target GPEs, alongside promoting afforestation and socioeconomic development, is critical to mitigating global lung cancer incidence.