Researchers compare smoke emissions from prescribed and wild fires

DC-10 drop North Park Fire
A DC-10 comes out of the smoke dropping retardant on the North Park Fire in Southern California, October 12, 2018. Screen grab from @ABC7Leticia video.

Four researchers, in a study funded by the U.S. Forest Service, evaluated data collected in 25 previous studies to compare exposure to particulate matter (PM2.5) created by prescribed fires and wildfires. The authors were Kathleen Navarro, Don Schweizer, John Balmes, and Ricardo Cisneros. Titled, A Review of Community Smoke Exposure from Wildfire Compared to Prescribed Fire in the United States, it is published under Open Access guidelines.

Below are excerpts from the study — the abstract and conclusions. And, information about a March 21 webinar featuring Ms. Navarro about the health effects of vegetation smoke.


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. TheWeb 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.

Conclusions

Destructive wildfires have higher rates of biomass consumption and have greater potential to expose more people to smoke than prescribed fires. Naturally ignited fires that are allowed to self-regulate can provide the best scenario for ecosystem health and long-term air quality. Generally, prescribed fire smoke is much more localized, and the smoke plumes tend to stay within the canopy, which absorbs some of the pollutants, reducing smoke exposure. Land managers want to utilize prescribed fire as a land management tool to restore fire-adapted landscapes. Thus, additional work is needed to understand the differences in exposures and public health impacts of smoke of prescribedfire compared to wildfire. One way to do this would be for managers to collaborate with air quality departments (internal to agency or external) to monitor PM2.5concentrations in communities near a prescribed fire.

Consistent monitoring strategies for all wildland fires, whether prescribed or naturally occurring, are needed to allow the most robust comparative analysis. Currently, prescribed fire monitoring is often focused on capturing the area of highest impact or characterizing fire emissions, while wildfire monitoring often relies on urban monitors supplemented by temporary monitoring of communities of concern. A better understanding of smoke impact over the landscape and related impacts is essential for properly assessing population exposure to smoke from different fire types.

(end of excerpt)


In a webinar March 21 at 11 a.m. CDT, Ms. Navarro will describe information from a different smoke study. She will present on a recent Joint Fire Science Program study estimating the lifetime risk of lung cancer and cardiovascular disease from exposure to particulate matter (PM) from smoke. This analysis combined measured PM exposures on wildfires, estimated wildland firefighter breathing rates, and an exposure disease relationship for PM to estimate mortality of lung cancer and cardiovascular disease mortality from lifetime exposure to PM.

Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire. Google+

3 thoughts on “Researchers compare smoke emissions from prescribed and wild fires”

  1. According to a Congressional Research Service Report, “…prescribed fires may produce more pollution (because of less efficient burning) than wildfires burning the same area.” The impact of smoke from prescribed fires and “managed” wildfires causes the most damage to health.

  2. Our study published here (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016JD026315, not open access sorry) found that wildfires produce 2-4 times more mass of smoke particles per ton of fuel burned than prescribed fires. Previous work we cited therein had already indicated that wildfires consume about 5 times more fuel per acre than prescribed fires. Thus, on average, about 17 times more pollution per unit area burned comes from wildfires. This makes sense because much more fuel is available during fire season and the increase is in “smoky” fuels. The public exposure is a separate issue that depends case by case on where the smoke goes and who lives there. Land managers can at least attempt to burn prescribed fires when public exposure is minimized. Therefore, it is perhaps not surprising that in Missoula over the last 20 years the overwhelming majority of smoke impacts were due to wildfires. E.g., in 2017 > 20 smoke impacts from wildfires and none from prescribed fires (https://www.atmos-chem-phys-discuss.net/acp-2018-1063/, open access, in revision as indicated). In 2018 we had one prescribed fire impact and about a dozen from wildfires.

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