Health Impacts of Wildfire Smoke Exposure

Wildfire smoke contains a complex mixture of gases and particles, notably fine particulate matter (PM2.5) and black carbon, alongside organic compounds, nitrogen oxides and volatile organic compounds. These constituents penetrate deeply into the respiratory tract and enter the systemic circulation, triggering inflammation, oxidative stress and impaired lung function. Acute exposure is linked to exacerbations of asthma and chronic obstructive pulmonary disease, increased respiratory infections and emergency department visits. Evidence for cardiovascular effects is mixed but suggests associations with arrhythmias, heart failure and hypertension. Chronic exposure may elevate risks of all-cause mortality, reduced birth weight and adverse perinatal outcomes. Vulnerable groups include the very young, older adults and individuals with pre-existing cardiopulmonary conditions. Transboundary transport extends impacts far from source regions, posing a growing global health challenge under climate-driven increases in wildfire incidence. Effective mitigation and adaptation measures encompass emission reduction, early warning systems and targeted health advisories.

Research from Nature Portfolio

Multicountry analyses spanning Australia, Brazil, Canada and parts of Asia have demonstrated that incremental rises in wildfire-specific PM2.5 are associated with consistent increases in hospitalisation risks for asthma, chronic obstructive pulmonary disease and pneumonia, with the greatest vulnerability observed among children and older adults. Comparative studies isolating wildfire-derived particles indicate higher relative toxicity than PM2.5 from other sources, with respiratory admissions rising by up to 10 % per 10 µg/m3 of wildfire PM2.5, compared with lower rates for non-wildfire PM2.5. These findings emphasise the need for source-specific air quality management and tailored public health interventions during fire events.

Health Impacts of Wildfire Smoke Exposure publication trend

The graph below shows the total number of articles in health impacts of wildfire smoke exposure across all publications each year (not limited to Nature Index journals).

Technical terms

PM2.5: Fine particulate matter with an aerodynamic diameter of 2.5 µm or less that can penetrate deep into the lungs.

Black carbon: Carbonaceous component of PM2.5 formed by incomplete combustion, associated with high oxidative potential and toxicity.

Wildfire-specific PM2.5: Fraction of ambient fine particles directly attributable to biomass burning, isolated from other emission sources.

References

1. Long-term mortality burden trends attributed to black carbon and PM2·5 from wildfire emissions across the continental USA from 2000 to 2020: a deep learning modelling study. The Lancet Planetary Health (2023).
2. Respiratory risks from wildfire-specific PM2.5 across multiple countries and territories. Nature Sustainability (2025).
3. Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California. Nature Communications (2021).
4. Health impact analysis of PM2.5 from wildfire smoke in Canada (2013–2015, 2017–2018). The Science of The Total Environment (2020).
5. Critical Review of Health Impacts of Wildfire Smoke Exposure. Environmental Health Perspectives (2016).
6. Birth Weight following Pregnancy during the 2003 Southern California Wildfires. Environmental Health Perspectives (2012).