Epidemiological and Clinical Evidence on the Association Between Wildfire PM2.5 and Pulmonary Health Outcomes

As climate change accelerates the frequency and severity of wildfires worldwide, the pulmonary consequences of wildfire smoke exposure have emerged as an important yet under-recognized public health concern. Wildfire-related fine particulate matter (PM2.5) possesses distinct toxicologic properties compared to urban PM2.5 and disproportionately affects vulnerable populations, including children, older adults, and individuals with chronic respiratory diseases. This narrative review synthesizes current epidemiological, mechanistic, and clinical evidence on the impact of wildfire PM2.5 on exacerbations and progression of asthma, chronic obstructive pulmonary disease (COPD), and interstitial lung disease (ILD), drawing from recent large-scale meta-analyses and international cohort studies. We reviewed data from over 30 peer-reviewed sources, including longitudinal cohorts, systematic reviews, environmental modeling studies, and public health guidelines. Special attention was given to pediatric populations, the elderly, and patients with pre-existing pulmonary conditions. Wildfire PM2.5 is consistently associated with significant increases in emergency department visits and hospitalizations for asthma and COPD, with relative risks often exceeding those of urban PM2.5. Pediatric asthma-related visits may increase by over 30% during wildfire events, while elderly COPD patients face heightened hospitalization and mortality risks. ILD patients, especially those with idiopathic pulmonary fibrosis (IPF), exhibit higher rates of acute exacerbations and accelerated disease progression with PM2.5 levels as low as 8-10 μg/m³. Mechanistically, wildfire PM2.5 promotes oxidative stress, epithelial injury, and immune dysregulation, contributing to disease exacerbation and chronic progression. Preventive interventions such as high-efficiency particulate air (HEPA) filtration, indoor sheltering, and respiratory protection significantly reduce PM2.5 exposure and related morbidity. Wildfire PM2.5 is a potent and growing contributor to pulmonary morbidity, with a higher toxicity profile than other ambient air pollutants. While acute impacts are well-documented, long-term consequences remain understudied. Urgent research is needed to define chronic health outcomes, develop interventions, and inform public health policy. As wildfires become more frequent and intense globally, clinicians must be prepared to recognize and manage the growing burden of wildfire-related pulmonary disease.