Respiratory risks from wildfire-specific PM2.5 across multiple countries and territories

Under a warming climate, wildfires are becoming more frequent and severe. Multicountry studies evaluating associations between wildfire fine particulate matter (PM2.5) and respiratory hospitalizations are lacking. Here we evaluate the short-term effects of wildfire-specific PM2.5 on respiratory hospitalizations from 1,052 communities across Australia, Brazil, Canada, Chile, New Zealand, Vietnam, Thailand and Taiwan, during 2000–2019. A 1 µg m−3 increase in wildfire-specific PM2.5 was associated with increased hospitalization risks for all-cause respiratory, asthma, chronic obstructive pulmonary disease, acute upper respiratory infection, influenza and pneumonia by 0.36%, 0.48%, 0.38%, 0.42%, 0.79% and 0.36%, respectively. Higher risks were observed among populations ≤19 or ≥60 years old, from low-income or high non-wildfire PM2.5 communities, and residing in Brazil, Thailand, Taiwan and Vietnam. Australia and New Zealand exhibited a greater hospitalization risk for asthma associated with wildfire-specific PM2.5. Compared with non-wildfire PM2.5, wildfire-specific PM2.5 posed greater hospitalization risks for all respiratory diseases and a greater burden of asthma. Wildfire-specific PM2.5 contributed to 42.4% of PM2.5-linked respiratory hospitalizations, dominating in Thailand. Overall, the substantial contribution of wildfire-specific PM2.5 to respiratory hospitalizations demands continued mitigation and adaptation efforts across most countries. Intervention should be prioritized for influenza, children, adolescents, the elderly and populations in low-income or high-polluted communities. Wildfires are becoming increasingly frequent in several regions around the world due to climate change, posing serious health risks, especially for respiratory diseases. This study examines the respiratory health risk and burden of wildfire-specific PM2.5 pollution across eight countries and territories.