Looking through the particles: a narrative review of air pollution and lung cancer

Air pollution, particularly fine particulate matter ≤2.5 µm (PM_2.5), has emerged as a significant public health concern with established carcinogenic properties. Lung cancer incidence among patients who have never smoked cigarettes has doubled from 8% to 15% of cases since the 1990s, with stronger correlations observed between poor air quality and cancer development. This review synthesizes epidemiological evidence linking PM_2.5 exposure to lung cancer development, focusing on molecular mechanisms and clinical outcomes in those who have never smoked.

A systematic literature search was conducted in PubMed and Scopus using search terms related to PM_2.5 epidemiology and lung cancer in never-smokers. Articles were limited to original research, reviews, and meta-analyses published in English between 2004 and 2024. Of 198 articles identified, 45 were selected as relevant.

PM_2.5 particles penetrate into alveoli, triggering inflammatory pathways including PI3K/Akt, NF-κB, JAK/STAT, and MAPK signaling, leading to oxidative stress, DNA damage, and oncogenic mutations. Non-tobacco user lung cancers demonstrate higher rates of epidermal growth factor receptor (EGFR) mutations, with PM_2.5 promoting carcinogenesis by acting on cells with pre-existing EGFR mutations through interleukin-1β release and macrophage activation. Post-treatment outcomes are significantly impacted by continued PM_2.5 exposure, particularly in populations with higher proportions of non-white patients, with higher exposure levels associated with increased mortality risk following surgical resection.

There has been an increased incidence of lung cancer in patients who have never smoked and can be associated with the increase in air pollution, particularly PM_2.5. Furthermore, PM_2.5 exposure is associated with worse outcomes after treatment of lung cancer. Because of this linkage between PM_2.5 and lung cancer, further research is needed to identify PM_2.5 exposure reduction strategies and improve post-treatment outcomes.