Wildfire Smoke
Airborne particulate matter and gases produced by wildfires, now the leading source of hazardous air quality events in the western United States.
Detailed Explanation
Wildfire smoke is a complex mixture of fine particles, gases, and volatile organic compounds produced by the combustion of vegetation and structures during wildfires. The primary health concern in wildfire smoke is PM2.5, which can reach concentrations hundreds of times above normal during major fire events. Wildfire smoke can travel thousands of miles from its source, affecting air quality far from the actual fire — smoke from Canadian wildfires in 2023 caused hazardous air quality readings in New York City and across much of the eastern United States. Over the past decade, wildfire smoke has become the single largest factor disrupting air quality progress in the United States. While human-caused emissions of most pollutants have steadily declined due to regulation and cleaner technology, wildfire emissions have increased dramatically due to climate change, decades of fire suppression creating excess fuel loads, and expanding development into wildfire-prone areas. AirHistory data reveals this trend clearly: many western cities that showed improving air quality trends from 2014-2018 have seen those gains erased or reversed in recent years due to severe wildfire seasons. Cities in California, Oregon, Washington, and Colorado are most affected, though smoke events now regularly impact cities in the Mountain West and even the Midwest and East Coast.
Related Terms
PM2.5 (Fine Particulate Matter)
Airborne particles smaller than 2.5 micrometers in diameter — small enough to penetrate deep into the lungs and enter the bloodstream.
Particulate Matter (PM)
A mixture of solid particles and liquid droplets suspended in the air, ranging in size from visible dust to microscopic particles.
Unhealthy Air Days
Days when the AQI exceeds 100, meaning air quality may pose health risks for sensitive groups or the general population.
Air Quality Forecast
Predictions of future AQI levels issued by state and local agencies, typically covering 1-2 days ahead.
Frequently Asked Questions
Airborne particulate matter and gases produced by wildfires, now the leading source of hazardous air quality events in the western United States.
Wildfire smoke is a complex mixture of fine particles, gases, and volatile organic compounds produced by the combustion of vegetation and structures during wildfires. The primary health concern in wildfire smoke is PM2.5, which can reach concentrations hundreds of times above normal during major fire events. Wildfire smoke can travel thousands of miles from its source, affecting air quality far from the actual fire — smoke from Canadian wildfires in 2023 caused hazardous air quality readings in New York City and across much of the eastern United States.