Automated screening method identifies recent probable wildland fire exceptional events for ozone and PM_2.5 across...

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Public Health

Background:

• Wildfire events increasingly cause seasonal air quality degradation.
• The Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for public health.
• Exceptional event demonstrations can exclude wildfire-impacted data from air quality attainment calculations.

Purpose of the Study:

• To develop and validate a nationwide screening methodology for identifying PM2.5 and ozone concentration enhancements due to wildfire emissions.
• To evaluate the scale and regional trends of wildfire smoke impacts on air quality across the United States.

Main Methods:

• Combined NOAA's Hazard Mapping System data, PM2.5 and ozone monitor data, modeled smoke PM2.5 results, and Generalized Additive Modeling.
• Developed a nationwide screening methodology to identify probable exceptional events caused by wildfire smoke.

Main Results:

• Identified regional wildfire trends, including year-round agricultural burning smoke in the Southeast and significant Canadian wildfire impacts in the Northeast (2021, 2023).
• Confirmed the screening method's efficacy through case studies in high- and low-frequency wildfire-impacted areas.
• Found that over one-third of days during recent design value periods (2020-2022, 2021-2023) experienced ozone or PM2.5 smoke events nationwide.

Conclusions:

• Wildfire smoke substantially contributes to national air pollution levels.
• The developed screening methodology effectively identifies probable wildfire exceptional smoke events.
• This tool aids air agencies in managing air quality standards during wildfire events.