In recent years, wildfires have grown more frequent and intense across the United States as climate conditions have become hotter and drier. Wildfire smoke contains a complex mixture of chemical components that undergo atmospheric reactions and condensation, forming particulate matter that suspends in the air. Among air pollutants, fine particulate matter with diameters of less than 2.5 micrometers in size (PM2.5) can penetrate deep into the lungs and enter the bloodstream, leading to systemic health effects. This study, published by the Society of Actuaries, sought to quantify the impact of PM2.5 exposure during the wildfire season and its lagged effects on the prevalence of four sets of disease conditions: circulatory conditions (CIR), mental and behavioral disorders (MBD), neoplasms (NEO), and respiratory conditions (RSP). Machine learning and statistical methods were applied to a combination of healthcare claims data, climate data, and community-level socioeconomic data for 2017 to 2023. Three major health insurance coverage types were included in the data: commercial, Medicare, and Medicaid.

Key findings

• Clinical risks and demographic factors explained approximately 68% to 92% of prevalence rates in the four sets of disease conditions studied.
• PM2.5 exposure during wildfire season and its lagged effects accounted for 11% to 26% of the environmental and socio-contextual domain.
• Extreme heat and its lagged effects accounted for 2.3% to 8.6% of disease prevalence, or 26% to 56% of the total environmental and socio-contextual influence.
• The combined effects of exposure from PM2.5 and extreme heat accounted for 6.7% to 7.8% of the total MBD prevalence rate, or 50% to 56% of the prevalence contribution from environmental and socio-contextual factors.
• The effects of PM2.5 exposure during wildfire season extended for months and sometimes years after the exposure event, particularly for CIR and MBD.
• RSP exhibited immediate increases in prevalence following PM2.5 exposure during wildfire season, while CIR and MBD displayed delayed responses, often peaking several months after exposure.
• Communities with limited healthcare access, higher social vulnerability, or preexisting chronic conditions tended to experience greater health burdens during wildfire and heat events.

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