Wildland Fires: Toward Improved Understanding and Forecasting of Air Quality Impacts: Proceedings of a Workshop (2022)
Chapter: Wildfires and Human Health - An Overview
Wildfires and Human Health—An Overview
John Balmes, University of California, San Francisco and Berkeley, opened the workshop by providing an overview of wildfires in California and their effects on air quality and human health. Wildland fires have increased in frequency and area burned in recent years in California as well as other locations, with further increases anticipated in the future. The state typically receives snow and rain in the winter and spring, followed by hot and dry summers when fires occur; then rains begin again in October, which end the fire season. Climate change is now shifting this pattern, causing hotter and drier summers and later arrival of the rainy season, thereby extending the fire season. At the same time, drought conditions have killed hundreds of millions of trees, which serve as fuel when fires occur. A long legacy of fire suppression in the state has also contributed to a buildup of fuels, meaning that fires have much to consume once ignited.
The 2020 fire season, which was ongoing at the time of this workshop, was poised to be a record-setting year for California. Four of the five largest fires in the state’s history were active, more than 3.6 million acres had burned, more than 7,000 structures were damaged or destroyed, and at least 26 fatalities had occurred. Residents had also been exposed to smoke for many weeks, compared to previous years when exposures were typically on the order of days in a single fire season.
Wildland fire emissions contain a variety of pollutants of concern for human health. Primary pollutants released directly from fire include PM, carbon monoxide (CO), nitrogen dioxide (NO2), polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). Balmes said that wildland fire emissions are “much like tobacco smoke without the nicotine” because both are produced by burning plant biomass. Secondary pollutants form when emissions react in the atmosphere and include PM and ozone (O3).
Balmes explained that there is robust evidence of acute respiratory health effects from wildfire smoke exposure (e.g., Reid et al., 2016), and, more recently, links to an increase in acute cardiovascular events, including strokes, have been identified (e.g., Wettstein et al., 2018). There are also health outcomes of possible concern that researchers are examining based on what is known about exposure to PM2.5.1 These include effects on pregnant mothers, birth outcomes, effects on child development, metabolic outcomes like diabetes, cognitive decline in older people, and mental health concerns.
Part of protecting the public from these possible outcomes is to have those communicating with the public provide a consistent, simple message. Balmes noted that at-risk communities can be made more resilient by preparing for both the fires themselves as well as the smoke. Preparing for fires can include actions like bulldozing fuel breaks around neighborhoods, removing vegetation from around homes, and improving escape routes. To mitigate smoke exposure, residents can stay indoors and install filtration equipment while those in outdoor occupational settings and vulnerable populations can benefit from respiratory protection gear. Many of these potential actions were discussed in more detail during this workshop and are captured throughout this proceedings.
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1 PM2.5 is commonly measured in research studies and is regulated by the U.S. Environmental Protection Agency through the National Ambient Air Quality Standards.
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