Wildfire Smoke: Air Quality Concerns and Management

INSIGHTi

Wildfire Smoke: Air Quality Concerns and

Management

Updated February 10, 2021

Wildfire smoke can temporarily degrade air quality and harm human health. Some Members of Congress

have expressed concern about wildfire health risks, including potential interactions with COVID-19. This

Insight provides background, discusses federal air quality requirements related to wildfires, and identifies

wildfire smoke response programs.

Background

The Clean Air Act (CAA) requires the U.S. Environmental Protection Agency (EPA) to establish

minimum national standards for air quality to protect human health and the environment from emissions

that pollute ambient (outdoor) air. EPA has set and periodically revised national ambient air quality

standards (NAAQS) for six “criteria” air pollutants—ozone, particulate matter, sulfur dioxide, carbon

monoxide, nitrogen dioxide, and lead. Under the CAA, states have primary responsibility for assuring

compliance with the standards, and for establishing and incorporating procedures in state implementation

plans to attain and maintain the NAAQS.

Wildfire smoke is a complex mixture of air pollutants that can travel long distances. The chemical

composition of smoke depends on various factors including burn conditions (e.g., fire temperature), type

of biomass burned (e.g., vegetation), and weather-related influences (e.g., wind). Particles (particulate

matter) are the principal pollutant of concern from wildfire smoke. Additional pollutants of concern from

wildfire smoke include carbon monoxide, hazardous air pollutants, and emissions that contribute to the

formation of ground-level ozone.

Particulate matter is a mixture of solid particles and liquid droplets in the atmosphere. Particle size can

range from those visible only through high-power microscopes to larger particles (e.g., soot). EPA’s

National Emissions Inventory (NEI) identifies wildfires as a major contributor of particulate matter

(2002-2019 data and 2014 NEI Report), though quantifying the precise contribution remains an active

area of research.

Smoke particles are typically very small and can be inhaled deeply into the lungs. Research has linked

short-term exposure to fine particles with a range of health effects, including eye irritation, sore throat,

coughing, breathing difficulties, worsening of preexisting heart and lung disease, and increased premature

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mortality. While smoke may affect the health of any individual exposed, sensitive populations—children,

pregnant women, and the elderly—are more vulnerable to the exposure. Also, studies show wildland

firefighters are exposed to particles and other smoke constituents, including carcinogens. Less is known

about cumulative and long-term exposure to wildfire smoke.

Air Quality Requirements and Wildfires

Wildfire smoke can temporarily increase ambient levels of particulate matter and other criteria pollutants

regulated under the CAA. These increases may be measured by air monitoring stations comprising a

national network, which informs determinations about NAAQS compliance. Congress authorized EPA to

treat emissions from certain natural events differently than those from anthropogenic sources. The CAA

allows EPA to exclude air quality data from regulatory decisions if such data were demonstratively

influenced by “exceptional events” such as certain natural events (42 U.S.C. §7619(b)). EPA described

conditions under which states and tribes can demonstrate that air quality impacts from wildfires (or

prescribed fires) should be excluded from NAAQS compliance determinations.

Wildfire smoke may also affect implementation of CAA visibility requirements. The CAA established a

national visibility goal and authorized a regional haze program to protect visibility in national parks and

wilderness areas (42 U.S.C. §7491). For more information, see CRS In Focus IF10496, Protecting Clean

Air in National Parks and Wilderness Areas.

State-level regulations may also apply to wildfire smoke. Many states have developed programs to

manage and control smoke from prescribed burns. Smoke management plans seek to minimize smoke

entering populated areas, prevent public safety hazards, and maintain CAA compliance.

Wildfire Smoke Response

Wildfire response strategies rely on air quality monitoring, smoke forecasting, and timely communication

of air quality conditions and related health risks to the public. Various federal, tribal, state, and local

agencies contribute to these tasks.

EPA and other agencies have developed tools to measure air quality conditions and alert the public. For

example, EPA manages AirNow, a multiagency website that reports air quality based on monitoring data

received on a regular basis from state, local, and federal agencies. AirNow compiles the data in a

consistent format and displays it through interactive maps.

AirNow reports air quality information using the Air Quality Index (AQI), a nationally uniform index.

EPA calculates the AQI for a criteria pollutant based on the ambient concentration of that pollutant. AQI

values range from 0 to 500. The higher the AQI, the greater the level of air pollution. EPA describes AQI

values of 100 or lower as satisfactory.

The Interagency Wildland Fire Air Quality Response Program (IWFAQRP) contributes to air quality

monitoring and communication. Led by the U.S. Forest Service (USFS), this interagency program “was

created to directly assess, communicate, and address risks posed by wildland fire smoke to the public as

well as fire personnel.” The program has a national cache of smoke monitoring equipment and deploys

technical specialists—Air Resource Advisors (ARAs)—during large smoke events. ARAs may provide,

install, and operate monitors, develop smoke forecasts, and share information with wildfire response

teams, air quality regulators, and the public.

The need for real-time air quality information is critical during wildfire events. The frequency of air

quality reporting varies, however, depending on the equipment used. In addition, permanent monitors may

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not be located near the areas affected by smoke. While temporary monitors may be deployed, specialists

also use computer modeling to estimate pollution levels.

EPA, USFS, other agencies, and stakeholders are exploring emerging technologies to improve air quality

monitoring during wildfire events. For example, the AirNow Sensor Data Pilot adds air pollution data

from “low-cost sensors” to the Fire and Smoke Map. Federal agencies caution that such data should be

considered supplemental to existing resources, given uncertainties about the “precision, accuracy, and

reliability” of sensors.

As Congress deliberates on wildfire legislation, it may consider which monitoring strategies effectively

inform smoke management and public health responses. Monitoring strategies may include some

combination of stationary monitors, mobile sensors, or models. Congress may also consider monitoring

costs, which may vary by location, along with public health benefits.

Author Information

Kate C. Shouse

Analyst in Environmental Policy

Disclaimer

This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff

to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of

Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of

information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.

CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United

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