A Review of Community Smoke Exposure from Wildfire Compared to Prescribed Fire in the United States

Kathleen Navarro,John Balmes,Ricardo Cisneros,Don Schweizer

doi:10.3390/atmos9050185

Abstract

Prescribed fire, intentionally ignited low-intensity fires, and managed wildfires—wildfires that are allowed to burn for land management benefit—could be used as a land management tool to create forests that are resilient to wildland fire. This could lead to fewer large catastrophic wildfires in the future. However, we must consider the public health impacts of the smoke that is emitted from wildland and prescribed fire. The objective of this synthesis is to examine the differences in ambient community-level exposures to particulate matter (PM2.5) from smoke in the United States in relation to two smoke exposure scenarios—wildfire fire and prescribed fire. A systematic search was conducted to identify scientific papers to be included in this review. The Web of Science Core Collection and PubMed, for scientific papers, and Google Scholar were used to identify any grey literature or reports to be included in this review. Sixteen studies that examined particulate matter exposure from smoke were identified for this synthesis—nine wildland fire studies and seven prescribed fire studies. PM2.5 concentrations from wildfire smoke were found to be significantly lower than reported PM2.5 concentrations from prescribed fire smoke. Wildfire studies focused on assessing air quality impacts to communities that were nearby fires and urban centers that were far from wildfires. However, the prescribed fire studies used air monitoring methods that focused on characterizing exposures and emissions directly from, and next to, the burns. This review highlights a need for a better understanding of wildfire smoke impact over the landscape. It is essential for properly assessing population exposure to smoke from different fire types.

Highlights

Wildfire has long been an important ecological process of our natural world, only requiring three ingredients—fuel, oxygen, and heat [1]
Smoke-caused air quality impacts and compliance to air quality regulations can be an impediment to the use of prescribed fire, and the public health impacts of the smoke that is emitted from wildfire and prescribed fire must be considered [2,6]
There were studies that attempted to model concentrations of PM2.5 from wildfire or prescribed fire smoke, they did not report PM2.5 concentrations associated with a specific fire event and did not meet the inclusion criteria

Summary

Introduction

Wildfire has long been an important ecological process of our natural world, only requiring three ingredients—fuel, oxygen, and heat [1]. Prior to European settlement, many forests in the United States were historically shaped by wildfires [2]. In the Western US, frequent fires of low severity burned on the forest floor and resulted in coniferous forests that are more vulnerable to the effects of fire [4]. Stephens et al (2007) estimated that during the prehistoric period wildland fires emitted 47 billion kilograms of fine particulate matter (PM2.5 ) annually [5]. Wildfire smoke can contain fine to inhalable particulate matter (PM2.5 –PM10 ), acrolein, benzene, carbon dioxide, carbon monoxide, formaldehyde, crystalline silica, total particulates, and polycyclic aromatic hydrocarbons (PAHs) [7,8]. Individuals can be exposed occupationally, if they work as wildland firefighters, or from ambient air that is contaminated with smoke from a nearby or distant wildfire [9]

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