Compound Exposure to Extreme Heat and Substantial Landscape Fire-Sourced Air Pollution on Cardiovascular Mortality
Bo Wen1, Yao Wu2, Eric Lavigne3
1Climate Air Quality Research unit, School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.
Journal of the American College of Cardiology
|July 29, 2026
Summary
Combined exposure to heat waves and wildfire smoke increases cardiovascular death risk more than single exposures. This highlights the need to consider these co-occurring climate change impacts together to accurately assess health risks.
Area of Science:
- Environmental Health
- Cardiovascular Epidemiology
- Climate Change Impacts
Background:
- Climate change intensifies co-occurring extreme heat and wildfire smoke events.
- Limited evidence exists on the combined cardiovascular impacts of these concurrent environmental hazards.
Purpose of the Study:
- To investigate the association between combined heat waves and substantial fire-sourced air pollution (SFAP) exposure and cardiovascular disease (CVD) mortality risk.
- To determine if this combined exposure poses a greater risk than single exposures and to assess additive interactions.
Main Methods:
- A multicountry time-series study analyzed CVD mortality data from 6 countries.
- Daily exposure was categorized into: no hazard, heat wave-only, SFAP-only, and compound exposure.
- Quasi-Poisson regression estimated relative risks (RRs), and additive interaction was evaluated using RERI and attributable proportion.
Main Results:
- Compound exposure showed an 11.5% increase in CVD mortality (RR: 1.115), higher than heat wave-only (RR: 1.083) or SFAP-only (RR: 1.014) exposures.
- A modest positive additive interaction was observed for overall CVD mortality (RERI: 0.018).
- Heart failure (HF) mortality exhibited the largest additive interaction (RR: 1.245), with 7.7% of HF deaths attributable to combined exposure.
Conclusions:
- Combined exposure to heat waves and SFAP is linked to elevated cardiovascular mortality, exceeding risks from single exposures.
- Stronger additive interaction signals for heart failure suggest this condition is particularly vulnerable.
- Current risk assessments may underestimate mortality by treating these hazards independently.
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