The health impacts and economic value of wildland fire episodes in the U.S.: 2008–2012
Graphical abstract
Introduction
The increasing frequency and intensity of large wildfires deteriorates air quality and adversely affects human health (Crimmins et al., 2016, Henderson et al., 2009, Liu et al., 2015, Liu et al., 2016, Westerling et al., 2006). These events in turn both promote, and are exacerbated by, long-term changes to the climate; current trends in these events are expected to continue (Crimmins et al., 2016, Stavros et al., 2014). While the level and type of pollutants emitted during wildfires vary according to region and fuel type, all fires release directly emitted particulate matter (PM) as well as precursors to fine particles (PM2.5) and can contribute to downwind formation of ozone (Knorr et al., 2012).
While risks to human health from exposure to PM are especially well characterized in the epidemiological, toxicological and controlled human exposure literature (US EPA, 2009), health impacts from PM stemming from wildland fires have been less extensively studied, though epidemiological literature has consistently observed adverse human health impacts attributable to wildfire-related PM2.5 (Liu et al., 2015). For example, Rappold et al., 2012, Rappold et al., 2011 found that a peat fire episode in eastern North Carolina was associated with increasing numbers of Emergency Department visits for cardiopulmonary and respiratory outcomes. Similarly, Delfino et al. (2009) observed increasing rates of respiratory and cardiovascular hospital admissions resulting from a month-long wildland fire episode in southern California. Epidemiological studies conducted in other countries, including Australia, have observed similar affects (Johnston et al., 2007, Morgan et al., 2010). A systematic review of literature from the U.S., Australia and elsewhere by Liu et al. (2014) found that wildland fire-related coarse particles (PM10) were most consistently associated with respiratory outcomes.
Despite the growing body of epidemiological studies, there are a relatively small number of air pollution risk assessments that attribute the number of premature deaths and illnesses and the economic value of health impacts to wildfire episodes. The risk assessments performed thus far have been limited in their temporal scope, using a single (2005) and projected (2016) year (Fann et al., 2013), or have been limited to examining one fire at a time (Jones et al., 2015, Kochi et al., 2012, Rappold et al., 2014, Rittmaster et al., 2006). This paper builds upon this literature to estimate the number and economic value of wildland fire PM2.5-related premature deaths and illnesses in the contiguous United States using chemical transport model predictions of PM2.5 from wildland fire episodes over a 5-year period beginning in 2008. Considering a national scope allows us to more fully capture the impact that wildland fires may have on human health.
Section snippets
Materials and methods
In this study we characterized the overall magnitude and distribution of adverse health impacts by age and race that were associated with exposure to fire-PM2.5 during wildfire smoke episodes. We used health impact functions derived from epidemiological studies that assessed the relationship between fire-PM2.5 and expected incidence of health outcomes. We also performed a systematic literature review and meta-analysis; however, using results from the meta-analysis in a health impact function
Air quality
The median of the predicted annual mean wildland fire-attributable PM2.5 concentrations across all model grid cells ranges from between 0.3 μg/m3, in 2009 and 0.8 μg/m3 in 2012, while the population-weighted annual mean PM2.5 concentration ranges from between 0.6 μg/m3 in 2009 to 1.1 μg/m3 in 2008 (Table 1). In general, the distribution of wildfire attributable PM2.5 concentrations are greatest in the year 2008 and lowest in the years 2009 and 2010 of the years included in this analysis.
A small
Discussion and conclusions
To our knowledge, this is the first manuscript to characterize the PM2.5-related incidence and economic value of wildland fire impacts in the continental United States across an extended time period. The number of wildland fire-attributable PM2.5-related hospital admissions, emergency department visits and other outcomes we estimated in this analysis are comparable to those reported in Fann, Fulcher and Baker (2013) for the year 2016. That analysis, like this one, employed photochemical
Disclaimer
The research described in this article has been reviewed by the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency, nor does the mention of trade names of commercial products constitute endorsement or recommendation for use.
Competing financial interests
The authors declare no competing financial interests.
Acknowledgements
We gratefully acknowledge the comments received from Bryan Hubbell and Karen Wesson, who reviewed early versions of this manuscript.
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