Wildfire and prescribed burning impacts on air quality in the United States

Abstract

Air quality impacts from wildfires have been dramatic in recent years, with millions of people exposed to elevated and sometimes hazardous fine particulate matter (PM 2.5) concentrations for extended periods. Fires emit particulate matter (PM) and gaseous compounds that can negatively impact human health and reduce visibility. While the overall trend in U.S. air quality has been improving for decades, largely due to implementation of the Clean Air Act, seasonal wildfires threaten to undo this in some regions of the United States. Our understanding of the health effects of smoke is growing with regard to respiratory and cardiovascular consequences and mortality. The costs of these health outcomes can exceed the billions already spent on wildfire suppression. In this critical review, we examine each of the processes that influence wildland fires and the effects of fires, including the natural role of wildland fire, forest management, ignitions, emissions, transport, chemistry, and human health impacts. We highlight key data gaps and examine the complexity and scope and scale of fire occurrence, estimated emissions, and resulting effects on regional air quality across the United States. The goal is to clarify which areas are well understood and which need more study. We conclude with a set of recommendations for future research. Implications: In the recent decade the area of wildfires in the United States has increased dramatically and the resulting smoke has exposed millions of people to unhealthy air quality. In this critical review we examine the key factors and impacts from fires including natural role of wildland fire, forest management, ignitions, emissions, transport, chemistry and human health.

Field Evaluation of Low-Cost Particulate Matter Sensors for Measuring Wildfire Smoke

“…A uniform smoke calibration for optical sensors may be reasonable given the mostly invariant particle properties of aged smoke. PM from most wildfires is almost entirely composed of organic carbon (>90% by mass), although certain combustion conditions (e.g., flaming) and fuel types (e.g., grasses) can have larger fractions of black carbon (or elemental carbon) and inorganic species that would impact optical properties [ 3 ]. Freshly emitted smoke has a lognormal particle size distribution with a median diameter in the range of 100–150 nm and geometric standard deviation of 1.6−1.9 [ 35 ], which is below the limit of detection of most optical sensors.…”

“…However, rural areas with more frequent wildfires also tend to have few to no regulatory monitors. Additionally, during smoke events, the nearest monitoring site may not accurately represent local pollution concentrations due to complex topography, localized smoke plumes, and drainage patterns that result in large spatial gradients in smoke concentrations [ 3 ]. During wildfire smoke episodes, state or local air quality agencies and the United States Forest Service (USFS) will often augment the stationary monitoring network with temporary monitoring sites [ 4 ].…”

Wildfire-Induced CO Plume Observations From NAST-I During the FIREX-AQ Field Campaign

“…The fire influence on regional to global environments and air quality (FIREX-AQ) of August 2019 is the first joint field campaign conducted by NOAA and NASA addressing wildfire emissions and their impact on air quality and climate. It is dedicated to the sampling and characterization of fires and their impact on air quality and weather from the point of trace species emissions [ 2 ], [ 3 ]. Carbon monoxide (CO) is one of the major pollutants due to combustion; air particles downwind of combustion often show elevated CO resulting from photochemical production [ 4 ].…”

Wildfire and prescribed burning impacts on air quality in the United States

“…The 2020 Critical Review (CR) by Jaffe et al (2020a) provides an in-depth examination of large-scale outdoor biomass burning locations and intensities throughout the United States. It documents remote and ground-based measurement technologies and data bases that are used to examine these fires both in near real-time and historically, observing an increasing annual trend in the areas burned.…”

“…Fires are also large contributors to the Earth's carbon dioxide (CO 2 ) load. The CR summary (Jaffe et al 2020b) is supplemented with articles on wildfire and air quality management, data bases, and health effects (Baker et al 2020; DeMerritt 2020; Freeburn 2020; Kinsman 2020; Lahm and Larkin 2020; Sasser and Lahm 2020) in the June issue of EM magazine. Herein, expert discussants provide additional perspectives and information on the topic.…”