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

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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.
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atmosphere
Review
A Review of Community Smoke Exposure from
Wildfire Compared to Prescribed Fire in the
United States
Kathleen M. Navarro 1, *, Don Schweizer 2,3, John R. Balmes 4and Ricardo Cisneros 2
1United States Department of Agriculture Forest Service, Pacific Southwest Region, Fire and Aviation
Management, 1600 Tollhouse Rd., Clovis, CA 93611, USA
2School of Social Sciences, Humanities and Arts, University of California, Merced, CA 95340, USA;
donaldwschweizer@fs.fed.us (D.S.); rcisneros@ucmerced.edu (R.C.)
3United States Department of Agriculture Forest Service, Pacific Southwest Region, Fire and Aviation
Management, Bishop, CA 93514, USA
4Division of Environmental Health Sciences, School of Public Health, University of California,
Berkeley, CA 94720, USA; jbalmes@ucsf.edu
*Correspondence: kathleennavarro@fs.fed.us; Tel.: +1-408-644-0186
Received: 30 March 2018; Accepted: 9 May 2018; Published: 12 May 2018
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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 (PM
2.5
) 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. PM
2.5
concentrations from wildfire smoke were found to be significantly
lower than reported PM
2.5
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.
Keywords: wildfire; prescribed fire; smoke; particulate matter; public health; exposure
1. 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
]. Native Americans historically used wildfire as a vegetation
management tool to increase density of edible plants, provide material for basketry, and control insects
and plant diseases [
3
]. Historically, 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
]. In California,
Atmosphere 2018,9, 185; doi:10.3390/atmos9050185 www.mdpi.com/journal/atmosphere
Atmosphere 2018,9, 185 2 of 11
Stephens et al. (2007) estimated that during the prehistoric period wildland fires emitted 47 billion
kilograms of fine particulate matter (PM2.5) annually [5].
Prescribed fire; planned and intentionally ignited low-intensity fires, and managed wildfires;
wildfires that are allowed to burn for land management benefit, could be used to treat the abundance of
fuel in forests and restore fire-adapted landscapes across a larger area [
2
]. However, 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
]. Wildfire smoke can contain fine to inhalable particulate matter (PM
2.5
–PM
10
),
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].
Past health studies of wildfire exposure have generally examined the relationship between
exposure to PM
2.5
from wildfire smoke and associated adverse health outcomes [
9
,
10
]. Fine particulate
matter is derived primarily from combustion and can absorb and retain toxic substances, such as
volatile and semi-volatile organics (PAHs and quinones), transition metals, reactive gases (ozone and
aldehydes), and sulfate and nitrate particles [
11
,
12
]. Particulate matter can be deposited in the human
respiratory tract through three main mechanisms—impaction, sedimentation, and diffusion [
13
].
Inhalable particles with diameters of 0.5 to 2
µ
m are deposited in the respiratory tract through
sedimentation. Larger particles, usually up to 10
µ
m in diameter, are deposited in the respiratory
tract through inertial impaction, whereas smaller particles <0.5
µ
m are deposited though diffusional
deposition [
14
]. Fine particulate matter can be deposited in respiratory bronchioles and alveolar regions
where gas exchange occurs in the human lung [
13
,
14
]. There is evidence that PM
2.5
can cause adverse
health outcomes through multiple biological mechanisms, such as increased local lung oxidative stress
and inflammation, leading to acute and chronic respiratory effects; the lung inflammatory responses
can spill over into systemic circulation contributing to acute and cardiovascular effects [1518].
Although there are many epidemiological studies that have provided evidence of adverse health
outcomes associated with long and short-term exposure to PM
2.5
in urban environments, there are
fewer studies examining health outcomes and exposures to PM
2.5
from wildfire smoke. It is important
to study exposures to PM
2.5
from wildfire smoke, as the chemical composition of PM
2.5
in wildfire
smoke can differ from that of urban sources of PM
2.5
[
8
,
9
]. Previous studies have suggested that PM
2.5
from wildfire smoke causes adverse respiratory health effects and possibly increased mortality and
cardiovascular health effects [
19
22
]. A recent systematic review of health impacts from wildfire smoke
by Reid et al. (2016) found evidence that wildfire smoke was associated with respiratory morbidity,
including exacerbations of symptoms of asthma and chronic obstructive pulmonary disease. There was
some evidence, not conclusive, that wildfire smoke exposure is associated with respiratory infections
and all-cause mortality [
10
]. Additionally, there are a few studies that found associations between
wildfire smoke exposure and adverse birth outcomes, such as low-birth weight; however, these studies
were limited and do not provide conclusive evidence. Holstius et al. (2012) demonstrated that average
birth weight was slightly reduced among infants that were in utero during the 2003 Southern California
wildfires [
23
]. Fann et al. (2018), estimated that wildfire events affected additional premature deaths
and respiratory hospital admissions in Louisiana, Georgia, Florida, northern California, Oregon and
Idaho. Additionally, the short and long term economic value of exposure to wildfire events were $63
and $450 billion (in present value), respectively [24].
Smoke from wildfire is inevitable, particularly in fire prone ecosystems. Exposure to smoke can
to some extent be controlled by suppression and other anthropogenic actions. Historically, in the
United States, full suppression has been utilized in an attempt to eliminate smoke and fire from the
landscape [
25
]. The understanding that this practice is unsustainable has led to increased interest in
using fire on the landscape to improve ecological health [
26
]. Human health is intrinsically coupled to
Atmosphere 2018,9, 185 3 of 11
ecological health, but this relation is confounded by smoke exposure [
27
]. Understanding relative risk
from fire management actions is essential to informed protection of public health.
The objective of this synthesis is to examine the differences in ambient community-level exposures
from smoke in the United States from two smoke exposure scenarios—wildfire and prescribed fire.
Several key questions will be addressed: (1) What are the PM
2.5
concentration differences between
prescribed fire and wildfire smoke exposures? (2) How do PM
2.5
concentrations from each exposure
scenario compare to the National Ambient Air Quality Standards (NAAQS)? (3) How long are
communities exposed to PM
2.5
during each exposure scenario? This synthesis will provide public
health practitioners, air quality regulators, and natural resource managers with more information on
the exposure differences of smoke exposure from wildfire compared with prescribed fire. Ultimately,
this information can be used to understand and quantify the health risks associated with smoke
exposure from wildfire compared with prescribed fire.
2. Materials and Methods
A systematic search was conducted to identify scientific papers from peer-reviewed journals to be
included in this review. The systematic search followed the Guidelines for Systematic Review and
Evidence Synthesis in Environmental Management [28].
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. The search strategy used
the following search terms—wildfire, wildland fire, prescribed fire, grass fire, peat fire, prescribed
managed fire, prescribed natural fire and smoke, exposure assessment, air quality. For each search that
was performed, we recorded the search date, search terms that were used, database that was searched,
and titles that were returned from the search.
The synthesis was restricted to scientific papers that met the following inclusion criteria: (1) studies
that were conducted in the United States and (2) reported PM
2.5
concentrations during specific
wildfire or prescribed fire events. Studies were appraised for the quality of the methods used for
air monitoring or modeling used for concentration estimation. Studies that reported only PM
2.5
occupational exposures during a wildfire or prescribed fire event were not included.
The systematic search resulted in 271 journal articles from PubMed, with 229 unique titles,
and 2023 journal articles from Web of Science, with 1093 unique titles (Figure 1). Once merged,
there were 1449 unique scientific journal articles. Next, we reviewed the journal titles and selected
79 relevant articles. During the title review, reasons for articles to be excluded included: (1) were not
conducted in the United States; (2) indicated a focus on developing models to estimate PM
2.5
emissions,
source apportionment, or plumes; (3) conducted an occupational exposure study; (4) measured other
air contaminants; (5) indicated that they were conducted in a laboratory. Of the selected articles,
we reviewed their abstracts for extractable information that was relevant to the synthesis objectives.
Based on the information provided in the abstracts, such as study methods and results, we selected
the article to be further reviewed by reading the full article (N= 34). Sixteen peer-reviewed scientific
journal articles met the study criteria and were included in this synthesis.
From each selected journal article, information was extracted and inputted into a table for
comparison and analysis (Table 1). Extracted data from each article included: information on the
wildfire or prescribed fire event name and date range, reported concentration mean and range, number
of reported days that exceeded the NAAQS 24-h standard (PM
2.5
concentration
35
µ
g m
3
) [
29
],
number of days sampled, the data source of the reported concentrations, and what type of average
concentration average or sampling time was used for each study.
Atmosphere 2018,9, 185 4 of 11
Figure 1. Flow diagram of study selection.
Atmosphere 2018,9, 185 5 of 11
Table 1. Characteristics of included studies and answers to synthesis objectives.
Study Event Location and Name, (Dates) Fire Size
(ha) a
PM2.5 Concentration (µg m3)NAAQS
Exceedance b
# of Days
Sampled Data Source Sampling Time
Range
Mean Range
Wildfire Events
Ward and Smith 2005 [30] Montana Missoula Fire Season (8/13 and 8/25/2000) - 39.9 and 42.2 Not Reported 2 days 2 Monitor 24 h Average
Ward et al. 2006 [31]cMontana Missoula Wildfires (8/14–8/18/2003) - 87.5 46–136.8 7 days 4Monitor 24 h Average
Montana Missoula Wildfires (8/31–9/2/2003) - 54 37–69 3
Viswanathan et al. 2006 [32] California Cedar, Paradise and Otay Fires (10/26–11/4/2003)
113,424
22,945
18,988
Not reported Max-104.6,
170 2 days 10 Monitor 24 h Average
Herron-Thorpe et al. 2010 [33]Pacific Northwest Wildfires (7/3–8/22/2007) - 16.8 Not reported 10 days 51 Model 24 h Average
Pacific Northwest Wildfires (6/22–8/27/2007) - 15.9 Not reported 19 days 67
Strand et al. 2011 [34]d
Idaho Frank Church Fire (8/11–9/14/2005) 22,194 2–22 8–244 3 days
13–77 Monitor Hourly Average
Washington Tripod Fire (7/24/2006–Mid Oct/2006) 70,820 3–69 49–1659 47 days
Region-fire wide event Western MT (8/2007–Mid Oct/2007) - 3–57 21–575 11 days
Region-fire wide event Northern CA(6/21/2008–9/2007) - 4–95 28–472 40 days
Schweizer and Cisneros 2014 [35] California Lion Fire (7/8–9/7/2011) 8370 7.7–20.1 Max-166.7 0 days 62 Monitor 24 h Average
Burley et al. 2016 [36]
California Aspen Fire (7/22–8/11/2013) 9227 41.5 11.7–92.7 13 days 20
Monitor 24 h Average
California Rim Fire (8/17–10/24/2013) 104,131 8.7 1.3–69.9 2 days 49
California French Fire (7/28–8/17/2014) 5202 14.4 7.9–21.9 0 days 20
California King Fire (9/13–10/9/2014) 39,546 6.6 1.6–27.8 0 days 26
Navarro et al. 2016 [37] California Rim Fire (8/17–10/24/2013) 104,131 6–121 1–450 Not Reported 49 Monitor 24 h Average
Zu et al 2016 [38]Quebec Wildfires-Impacts in Boston (7/7–7/16/2002) - 23 4.1–64.5 Not Reported 28 Monitor 24 h Average
Quebec Wildfires-Impacts in New York City (7/7–7/16/2002) - 25.2–27.3 4.8–84.2 Not Reported 28
Prescribed Fire Events
Robinson et al. 2004 [39]Arizona (Flaming Phase Samples) Oct/Nov 2001–2002 20–80 Not reported 523–6459 Not Reported 6Monitor 1.5–2 h Samples
Arizona (Smoldering Phase Samples) Oct/Nov 2001–2002 155–904 6 4–51 h Samples
Lee et al. 2005 [40] Georgia Prescribed Burn (4/15 and 16, 4/28 and 29/2004) 82–154 1810 Not Reported Not Reported 4 Monitor Total Average
Naeher et al. 2006,
Achtemeier et al. 2006 [41,42]
Georgia Non-chipped plot (2/13/2003) 1 519.9 13.6–805.7 Not Reported 1 Monitor 12 h Average
Georgia Chipped plot (2/12/2003) 1 198.1 94.3–300.3 Not Reported 1 Monitor 12 h Average
Hu et al. 2008 [43] Prescribed Fire impacts on Atlanta (2/28/2007) 1200 37.8 NA 1 day 1 Model 24 h Average
Robinson et al. 2011 [44]Northern Arizona Broadcast Burns (2001–2007) 10–40 2800 523–8357 Not Reported 15 Monitor 1–3 h Samples
Northern Arizona Pile Burns (2001–2007) 3000 Not Reported 6
Pearce et al. 2012 [45] South Carolina Savannah River Site Burns (2003–2007) 10–1111 74.01 5.69–1415.96 Not Reported 55 Monitor 22 h Average
a
Fire size is reported for studies that examined specific fire events;
b
Days that were reported to be above the US EPA NAAQS for PM
2.5
(35
µ
g m
3
) [
29
];
c
Ward et al., (2006) [
31
] used
PM
10
monitoring concentration data to estimate PM
2.5
concentrations;
d
Strand et al. (2011) [
33
] reported hourly median and maximum concentration, and these values are used in place of
the concentration mean and range, respectively. PM: particulate matter; NAAQS: National Ambient Air Quality Standards.
Atmosphere 2018,9, 185 6 of 11
3. Results
The systematic review identified 16 studies that characterized exposures to PM
2.5
from wildfire
and prescribed fire events (Table 1). Generally, studies directly measured PM
2.5
concentrations
with existing air monitoring networks or temporary monitoring stations placed in communities
that were deployed specifically for fire events. Although there were studies that attempted to model
concentrations of PM
2.5
from wildfire or prescribed fire smoke, they did not report PM
2.5
concentrations
associated with a specific fire event and did not meet the inclusion criteria.
The systematic search identified nine scientific studies that examined exposure to PM
2.5
from
wildfire smoke. The studies covered a wide geographic area and were focused on wildfires that
occurred in California, Montana, the Pacific Northwest, and Canada that impacted major cities in
the United States. The selected papers reported PM
2.5
concentrations from several large wildfires
(region-wide events), occurring at one period or during specific wildfire events. For example,
Ward et al. (2006)
measured PM
2.5
concentrations in Missoula, Montana, while 298,172 ha burned
throughout all of Montana [31].
In the five studies that examined the impacts of specific wildfire events, the wildfires ranged in
size from 5202 to 113,424 ha for the French and Cedar fires in California, respectively. Only three studies
reported where the PM
2.5
monitors were located in relation to the fire events. Strand et al. (2011) [
34
]
deployed monitors in local communities and small towns, at a minimum of 12 to 36 km from the
fire locations in Idaho, Washington, Western Montana, and Northern California.
Navarro et al. (2016)
and Schweizer et al. (2014) [
35
,
37
] both used permanent and temporary monitors that were located
7–189 km from the Rim Fire and 16.6–242.8 km from the Lion Fire, respectively.
Eight studies that were selected used direct air monitoring methods to assess PM
2.5
exposures,
while Herron-Thorpe et al. (2010) [
33
] used a modeling approach to estimate PM
2.5
concentrations
from specific wildfire events during 2007 in the Pacific Northwest. From the data extracted from
the studies, we focused on comparing studies that used the same averaging time (24 h average) to
calculate a mean and range of PM
2.5
concentrations. Mean PM
2.5
concentrations from wildfires ranged
from 8.7 to 121
µ
g m
3
, with a 24 h maximum concentration of 1659
µ
g m
3
. The 2013 Rim Fire
and 2003 Montana Fires reported the highest mean PM
2.5
concentrations of 121 and 86.5
µ
g m
3
,
respectively [
31
,
37
]. On average, PM
2.5
concentrations from wildfires were sampled and reported for
30 days; events ranged from 2 to 77 days. During wildfire events, the number of days that exceeded
the NAAQS ranged from 2 to 47 days and averaged 11 days. The PM
2.5
concentrations from the Tripod
Fire smoke in Eastern Washington resulted in 47 days that were above the NAAQS [34].
Seven scientific studies were identified that measured exposure to PM
2.5
at prescribed fires
in Arizona, Georgia and South Carolina. Six studies used air monitoring equipment to measure
PM
2.5
concentrations, while one study Hu et al. (2008) [
43
] simulated PM
2.5
concentrations using
fire and atmospheric conditions from a specific prescribed fire event. Almost all sampled prescribed
fires were performed as broadcast burns, where fire was applied directly across a predetermined
area and was confined to that space. One sampled prescribed fire was conducted as a pile burn
operation, where only piles of cut vegetation are ignited and burned [
44
]. Naeher et al. (2006) and
Achtemeier et al. (2006) [40,41]
reported PM
2.5
concentrations from the same prescribed fire event
where researchers examined the effects of mechanical chipping on smoke measurements. The size of
the prescribed fires ranged from 1 to 1200 ha, with the largest event being two adjacent prescribed fires
in the Southeast United States, outside of Atlanta (Hu et al., 2008) [43].
Generally, the prescribed fire air sampling occurred during the burn operation and monitors were
placed inside or next to the fire perimeter. For example, Robinson et al. (2011) [
43
] placed monitors next
to the fire perimeter on Day 1 of sampling and inside the fire perimeter on Day 2 to capture emissions
during the smolder phase of the fire. Naeher et al. (2006) and Achtemeier et al. (2006) [
41
,
42
] also
placed monitors inside the prescribed fire and along the fire perimeter on the downwind side of the
prescribed fire burn unit. Pearce et al. (2012) [
45
] measured concentrations using a grid of 18 monitors
that were placed 10–12 km on the downwind side of the prescribed fire burn unit.
Hu et al. (2008) [42]
Atmosphere 2018,9, 185 7 of 11
was the only study to report PM
2.5
concentrations from a prescribed fire in an urban center—Atlanta,
Georgia—which was 80 km from the prescribed fire.
Reported mean concentration of PM
2.5
from the selected studies ranged from 37.8
µ
g m
3
,
in Atlanta, Georgia, to 3000
µ
g m
3
at a prescribed fire in Arizona [
43
,
44
]. Additionally, the same
prescribed fire in Arizona during the flaming phase produced the highest maximum PM
2.5
concentration of 8357
µ
g m
3
[
44
]. Only Hu et al. (2008) [
43
] examined the impacts of a prescribed fire
on NAAQS exceedances and reported that one day exceeded the NAAQS (24 h mean =
37.8 µg m3
)
during the prescribed fire event. Unlike the wildfire studies that generally used a consistent averaging
time (24 h), prescribed fire studies averaged concentration over many different time periods. Averaging
times ranged from 1.5–2 h samples to a four-day total average.
4. Discussion
Due to differences in study objectives and methodology, PM
2.5
concentrations from wildfire smoke
were found to be lower than reported PM
2.5
concentrations from prescribed fire smoke. Although the
acres burned on wildfires was up to 100 times larger, monitoring location, distance and concentration
averaging time was shown to have an impact on the reported PM
2.5
concentrations. Wildfire studies
focused on assessing air quality impacts to communities that were close to the fire (for example
12–36 km) and urban centers that were far from the wildfire. However, prescribed fire studies used
air monitoring methods that focused on characterizing PM
2.5
exposures and emissions directly from,
and next to, the burns site.
Wildfire and prescribed fire smoke exposure, similar to other emissions, is dependent on proximity
to the source. Wildfire studies that were examined measured smoke at locations that ranged from
7 to 242.8 km from the wildfires, while prescribed locations ranged from next to the burn perimeter
(0 km) and up to 80 km away from the burn. The dependence on proximity and smoke direction
was demonstrated by Burley et al. (2016) [
36
], showing that megafires, such as the Rim and King
fires, largely missed their monitoring site due to smoke plume direction, while the smaller and closer
Aspen Fire transported more directly and had the highest exposure impacts at Devils Postpile National
Monument. Hu et al. (2008) [
43
] was the only prescribed fire study identified that assessed the air
quality impact from PM
2.5
to a large urban area. The 24-h PM
2.5
concentration in an urban area (Atlanta,
Ga) that was estimated from this prescribed burn was 37.8
µ
g m
3
and in the range of the measured
wildfire concentrations. In addition, the distance of the burn (80 km) was also similar to the monitor
distance for wildfires.
The selected wildfire studies largely reported PM
2.5
mean concentrations that were generally
averaged over a 24 h time period. However, the prescribed fire studies reported mean concentrations
that were sampled over time periods ranging from 1–96 h. The short duration prescribed fire sampling
events resulted in mean concentrations (198.1–3000
µ
g m
3
) that were higher than the prescribed fires
that reported 22–24 h average PM
2.5
concentrations (37.8–74.01
µ
g m
3
). The shorter prescribed fire
sampling events captured the periods of higher smoke emissions, while the longer averaging time for
wildfire studies resulted in lower mean PM2.5 concentrations.
Wildfire exposures are often episodic and short-term, but if they happen often, over a course
of a fire season over many years, they could be considered long-term exposures. From the studies
that were reviewed, the wildfire events that were included occurred over multiple weeks and months,
while the prescribed fire events occurred over a few days. The duration of an event is important
to consider because the longer exposure durations can lead to higher cumulative exposures to air
contaminants [46].
This review highlights the lack of consistent information about exposures to PM
2.5
from fire
smoke, especially from prescribed fires. Monitoring for prescribed fire was more focused on capturing
the smoke emission directly next to the fire and not downstream from the burn, while wildfire
studies either used existing urban sites and/or monitored for sensitive receptors. There were many
studies identified during the initial search that have assessed smoke from wildfires or prescribed fires,
Atmosphere 2018,9, 185 8 of 11
but there were few studies that directly reported concentrations of PM
2.5
to meet the inclusion criteria.
Characterization of PM
2.5
air quality impacts to communities from prescribed fire smoke is needed to
better understand how PM
2.5
exposures are different compared to those of wildfires. Prescribed fire
exposure studies should be designed to examine emissions directly from the burn but also consider
and measure the impacts on downwind communities. Additionally, one could use an area of the
United States that is prone to frequent wildfires and estimate exposure through modeling from recent
specific wildfires and prescribed fires to examine exposure differences. This approach was suggested
by Baker et al. (2016), as it would lead to better model inputs for fire size and emissions, and could be
validated against an existing monitoring network [
47
]. An additional approach that could be used
would be a health impact assessment used by Fann et al (2018) [
24
] to estimate the incidence and
economic value of human health impacts attributable to wildfire smoke compared to prescribed fire
smoke [24]. Lastly, improved exposure estimates could be used to quantify the risk of adverse health
effects from each of these different exposure scenarios [48].
5. 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 prescribed
fire 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 PM
2.5
concentrations 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.
Funding:
This research was funded by United States Department of Agriculture Forest Service Pacific Southwest
Research Station: #A17-0121-001.
Acknowledgments:
We would like to thank Penny Morgan for feedback on an earlier draft of this review.
This work was supported by the United States Department of Agriculture Forest Service Pacific Southwest
Research Station (#A17-0121-001). The manuscript reflects solely the opinion of the authors and not of the
funding source.
Conflicts of Interest: The authors declare no conflicts of interest.
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Anderson, K. Tending the Wild: Native American knowledge and the Management of California’s Natural Resources;
University of California Press: Berkeley, CA, USA, 2005; ISBN 0-520-23856-7.
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... 10 Although PM 2·5 emissions tend to be lower following prescribed burning, population exposure to air pollution can be substantial because of the closer proximity of the fires, the more frequent exposure, and weather conditions that generally favour accumulation rather than dispersal of smoke. [11][12][13] To better under stand the existing trade offs and effectiveness of fire management tools, such as prescribed burning, the relative public health burden attributable to wildfire and prescribed fire smoke exposure needs to be considered. 11,14 An improved under standing of the public health burden is especially important in the context of a changing climate in which extreme wildfires might increase both in magnitude and frequency 15 and the availability of suitable days for prescribed burning might be restricted or changed in seasonality. ...
... A systematic review of studies from the USA found that PM 2·5 exposure from wildfires was significantly lower than prescribed burns, but these findings were attributed to differences in the methods between studies, because particulate matter was measured further away for wildfires and closer for prescribed burns. 12 These results were not in keeping with our findings or those of other studies. Jaffe and colleagues 35 found that for 2017, maximum daily PM 2·5 values were higher for wildfires (125-550 µg/m³) compared with prescribed burns (29-49 µg/m³) for the top five states for annual area burned, with both fire types having a similar magnitude of area burned (260-640 thousand hectares per year). ...
... This can be due to various reasons, including the larger magnitude of wildfire surface, proximity to people, or because prescribed burns tend to occur in weather more conducive to produce smoke accumulation. 11,12 Prescribed burns are usually done at interfaces between rural and urban environments; the aim of these burns is to protect the built environ ment. Therefore, prescribed burns probably produce a substantial population exposure to air pollution. ...
Article
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Background Smoke from uncontrolled wildfires and deliberately set prescribed burns has the potential to produce substantial population exposure to fine particulate matter (PM2·5). We aimed to estimate historical health costs attributable to smoke-related PM2·5 from all landscape fires combined, and the relative contributions from wildfires and prescribed burns, in New South Wales, Australia. Methods We quantified PM2·5 from all landscape fire smoke (LFS) and estimated the attributable health burden and daily health costs between July 1, 2000, and June 30, 2020, for all of New South Wales and by smaller geographical regions. We combined these results with a spatial database of landscape fires to estimate the relative total and per hectare health costs attributable to PM2·5 from wildfire smoke (WFS) and prescribed burning smoke (PBS). Findings We estimated health costs of AU$ 2013 million (95% CI 718–3354; calculated with the 2018 value of the AU$). $1653 million (82·1%) of costs were attributable to WFS and $361 million (17·9%) to PBS. The per hectare health cost was of $105 for all LFS days ($104 for WFS and $477 for PBS). In sensitivity analyses, the per hectare costs associated with PBS was consistently higher than for WFS under a range of different scenarios. Interpretation WFS and PBS produce substantial health costs. Total health costs are higher for WFS, but per hectare costs are higher for PBS. This should be considered when assessing the trade-offs between prescribed burns and wildfires. Funding None.
... The long-term respiratory health effects of severe or repeated exposures to wildfire smoke are largely unknown [109]. However, both short-and long-term occupational exposures to smoke are well-documented among wildland firefighters [110][111][112]. Similar to other comparisons between occupational and ambient exposures, wildland firefighters typically have far greater exposure than the general public due to factors such as closer proximity to the source, different compositional exposure, and longer periods of exposure [113,114]. ...
... To date, there has been little research on the tradeoffs between wildfires and dry forest restoration practices on the pollutants emitted [119] and subsequent health effects. Very few studies have examined health effects of exposure to PM 2.5 specific to prescribed fire smoke [112,[120][121][122]. A preliminary study from Prunicki et al. [122] collected data from children in Fresno, California, who were living within a 70-mile range of a wildfire, a prescribed fire, or no fire during the spring and fall of 2015. ...
... Another study in Australia examining asthma symptoms in both children and adults suggested that the lower and shorter exposures to PM associated with prescribed burning led to less severe health effects than exposure to wildfire smoke [123]. In these studies that compare wild and prescribed fires, there is a lack of consistent study objectives and methodologies to make adequate comparisons between the two scenarios [9,112,122]. ...
Article
Full-text available
Purpose of Review Increasing wildfire size and severity across the western United States has created an environmental and social crisis that must be approached from a transdisciplinary perspective. Climate change and more than a century of fire exclusion and wildfire suppression have led to contemporary wildfires with more severe environmental impacts and human smoke exposure. Wildfires increase smoke exposure for broad swaths of the US population, though outdoor workers and socially disadvantaged groups with limited adaptive capacity can be disproportionally exposed. Exposure to wildfire smoke is associated with a range of health impacts in children and adults, including exacerbation of existing respiratory diseases such as asthma and chronic obstructive pulmonary disease, worse birth outcomes, and cardiovascular events. Seasonally dry forests in Washington, Oregon, and California can benefit from ecological restoration as a way to adapt forests to climate change and reduce smoke impacts on affected communities. Recent Findings Each wildfire season, large smoke events, and their adverse impacts on human health receive considerable attention from both the public and policymakers. The severity of recent wildfire seasons has state and federal governments outlining budgets and prioritizing policies to combat the worsening crisis. This surging attention provides an opportunity to outline the actions needed now to advance research and practice on conservation, economic, environmental justice, and public health interests, as well as the trade-offs that must be considered. Summary Scientists, planners, foresters and fire managers, fire safety, air quality, and public health practitioners must collaboratively work together. This article is the result of a series of transdisciplinary conversations to find common ground and subsequently provide a holistic view of how forest and fire management intersect with human health through the impacts of smoke and articulate the need for an integrated approach to both planning and practice.
... There is a need for an observational evidence base of the dispersion of prescribed burning smoke, but as yet, there have been few such studies. Indeed Navarro, Schweizer [12] reviewed observational studies in the USA and found only seven empirical studies of prescribed burning. These reported higher levels of particulates than studies of wildfire, but they were not directly comparable because the measurements were closer to the exposed communities. ...
... Atmosphere 2021, 12, 1389 ...
Article
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Prescribed burns produce smoke pollution, but little is known about the spatial and temporal pattern because smoke plumes are usually small and poorly captured by State air-quality networks. Here, we sampled smoke around 18 forested prescribed burns in the Sydney region of eastern Australia using up to 11 Nova SDS011 particulate sensors and developed a Generalised Linear Mixed Model to predict hourly PM2.5 concentrations as a function of distance, fire size and weather conditions. During the day of the burn, PM2.5 tended to show hourly exceedances (indicating poor air quality) up to ~2 km from the fire but only in the downwind direction. In the evening, this zone expanded to up to 5 km and included upwind areas. PM2.5 concentrations were higher in still, cool weather and with an unstable atmosphere. PM2.5 concentrations were also higher in larger fires. The statistical model confirmed these results, identifying the effects of distance, period of the day, wind angle, fire size, temperature and C-Haines (atmospheric instability). The model correctly identified 78% of hourly exceedance and 72% of non-exceedance values in retained test data. Applying the statistical model predicts that prescribed burns of 1000 ha can be expected to cause air quality exceedances over an area of ~3500 ha. Cool weather that reduces the risk of fire escape, has the highest potential for polluting nearby communities, and fires that burn into the night are particularly bad.
... The effect of wildfires on human physical and psychological health has been documented by several review articles, including those of occupational (Groot et al., 2019;Koopmans et al., 2020) and non-occupational (Liu et al., 2015) exposure as well as natural and prescribed fires (Burhan and Mukminin, 2020;Navarro et al., 2018). The dominant theme is understandably the effect of smoke exposure on respiratory health and lung function (Kondo et al., 2019;Reid et al., 2016), however, other topics are addressed, including mortality rate (Reid et al., 2016), hypertension (Groot et al., 2019), cardiovascular diseases (Liu et al., 2015;Reid et al., 2016), psychological effects (Boylan and Lawrence, 2020;Reid et al., 2016), perinatal health (Reid et al., 2016) and psychosocial impacts of wildland fires on children, adolescents and family functioning (Kulig and Dabravolskaj, 2020). ...
Article
Along with the increase in the frequency of disastrous wildfires and bushfires around the world during the recent decades, scholarly research efforts have also intensified in this domain. This work investigates divisions and trends of the domain of wildfire/bushfire research. Results show that this research domain has been growing exponentially. It is estimated that the field, as of 2021, it has grown to larger than 13,000 research items, with an excess of 1,200 new articles appearing every year. It also exhibits distinct characteristics of a multidisciplinary research domain. Analyses of the underlying studies reveal that the field is made up of five major divisions. These divisions embody research activities around (i) forest ecology and climate, (ii) fire detection and mapping technologies, (iii) community risk mitigation and planning, (iv) soil and water ecology, and (v) atmospheric science. Research into the sub-topics of reciprocal effects between climate change and fire activities, fire risk modelling/mapping (including burned area modelling), wildfire impact on organic matter, biomass burning, and human health impacts currently constitute trending areas of this field. Amongst these, the climate cluster showed an explosion of activities in 2020 while the human health cluster is identified as the most recent emerging topic of this domain. On the other hand, dimensions of wildfire research related to human behaviour—particularly issues of emergency training, risk perception and wildfire hazard education—seem to be notably underdeveloped in this field, making this one of its most apparent knowledge gaps. A scoping review of all reviews and meta-analysis of this field demonstrates that this sub-topic is also virtually non-existent on the research synthesis front. This meta-synthesis further reveals how a western, deductive view excludes socioecological and traditional knowledge of fire.
... Operator "×" is used to indicate 116 multiplication of scalars, vectors or matrices depending on the context in this article. The 117 second equation that describes the dynamic linear modelling is related to the term θ #$ ; its 118 name is the system equation, and it describes a dynamic autoregressive first-order model, 119 shown as: 120 θ #$ = a × θ #,$9: + w #$ (2) where w #$ is the temporal and spatial error; it has a normal distribution and a variance, 121 σ < 6 /(1 − a 6 ). The temporal and spatial variance (σ < 6 ) is based on the correlation between 122 monitoring stations and their Euclidean spatial distance using a Gaussian-Mattern field, 123 and is parameterized by the empirically derived correlation range (r). ...
Article
Full-text available
Wildfires are natural ecological processes that generate high levels of fine particulate matter (PM2.5) that are dispersed into the atmosphere. PM2.5 could be a potential health problem due to its size. Having adequate numerical models to predict the spatial and temporal distribution of PM2.5 helps to mitigate the impact on human health. The compositional data approach is widely used in the environmental sciences and concentration analyses (parts of a whole). This numerical ap-proach in the modelling process avoids one common statistical problem: the spurious correlation. PM2.5 is a part of the atmospheric composition. In this way, this study developed an hourly spa-tio-temporal PM2.5 model based on the dynamic linear modelling framework (DLM) with a compositional approach. The results of the model are extended using a Gaussian–Mattern field. The modelling of PM2.5 using a compositional approach presented adequate quality model indices (NSE = 0.82, RMSE = 0.23, and a Pearson correlation coefficient of 0.91); however, the correlation range showed a slightly lower value than the conventional/traditional approach. The proposed method could be used in spatial prediction in places without monitoring stations.
... This trend is obvious when comparing the mean PM 2.5 of all US stations (black line with no markers) and the mean PM 2.5 of all WA stations (grey line with no markers). Ground-level PM 2.5 reaches (Navarro et al., 2018). Table 3 shows relevant statistics for 15 states that have at least one daily record of non-attainment of EPA standards (> 35 µg m −3 ). ...
Article
Full-text available
Frequent and widespread wildfires in the northwestern United States and Canada have become the “new normal” during the Northern Hemisphere summer months, which significantly degrades particulate matter air quality in the United States. Using the mid-visible Multi Angle Implementation of Atmospheric Correction (MAIAC) satellite-derived aerosol optical depth (AOD) with meteorological information from the European Centre for Medium-Range Weather Forecasts (ECMWF) and other ancillary data, we quantify the impact of these fires on fine particulate matter concentration (PM2.5) air quality in the United States. We use a geographically weighted regression (GWR) method to estimate surface PM2.5 in the United States between low (2011) and high (2018) fire activity years. Our results indicate an overall leave-one-out cross-validation (LOOCV) R2 value of 0.797 with root mean square error (RMSE) between 3 and 5 µg m−3. Our results indicate that smoke aerosols caused significant pollution changes over half of the United States. We estimate that nearly 29 states have increased PM2.5 during the fire-active year and that 15 of these states have PM2.5 concentrations more than 2 times that of the inactive year. Furthermore, these fires increased the daily mean surface PM2.5 concentrations in Washington and Oregon by 38 to 259 µg m−3, posing significant health risks especially to vulnerable populations. Our results also show that the GWR model can be successfully applied to PM2.5 estimations from wildfires, thereby providing useful information for various applications such as public health assessment.
... Our results provide reference information for the PM 2.5 concentration caused by real forest fires, and the PM 2.5 data observed from our test can be included in the national fire database for the fire smoke management in China. PM 2.5 inhalable particles threats the health and safety of fire fighters seriously, and the PM 2.5 released from natural forest burnings is even more danger to fire fighters than the PM 2.5 from prescribed burnings (Navarro et al., 2018). To deeply understand the regular of PM 2.5 released from forest burning under a variety of meteorological and fuel impactors, we use laboratory burning to simulate prescribed burns to study PM 2.5 concentration; hopefully, our work can act as a pilot project to lead to the development of PM 2.5 prediction for field natural fires. ...
Article
A B S T R A C T High concentration particulate matter 2.5 released from forest fires, in addition to direct burns and asphyxia, PM2.5 is one of the main pollutants which threaten the safety of forest fire fighter. Therefore, to assess spatial distribution of PM2.5, a simulation study was conducted. Fuel beds with different moisture contents and loads were constructed. 144 times burning experiments were carried out under different wind speeds by using wind tunnel device. PM2.5 particles at different spatial points were collected and calculated. The results show that, in the two of three variables interaction between wind speed, fuel load, and, except fuel moisture content, wind speed and fuel load are positively correlated with the PM2.5 concentrations. From PM2.5 concentration which collected at each point in the horizontal and vertical directions, the overall trend is that PM2.5 concentration increases along the horizontal downwind direction (C and D higer than A and B) and the vertical upward direction (A and C higer than B and D) Based on BP neural network, the spatial distribution model of PM2.5 concentration with single hidden layer was established. The prediction accuracy of modeling samples and validation samples is balanced when hidden layer node is 5. This study will help to make reference for PM2.5 occupational exposure standards, forest fire smoke management and forest fire management in China.
... Prescribed fires tend to burn at lower temperatures with more smolder than wildfires, likely producing a different smoke profile. However, smoke exposure assessment studies have used different sampling periods at different proximities to the fire, which complicates efforts to directly compare pollutant exposures from prescribed fires and wildfires (6). It remains unknown how the toxicity of smoke from different types of fires compares (7). ...
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Wildland fires are diminishing air quality on a seasonal and regional basis, raising concerns about respiratory health risks to the public and occupational groups. This American Thoracic Society (ATS) workshop was convened in 2019 to meet the growing health threat of wildland fire smoke. The workshop brought together a multi-disciplinary group of 19 experts, including wildland fire managers, public health officials, epidemiologists, toxicologists, and pediatric and adult pulmonologists. The workshop examined four major topics: (1) the science of wildland fire incidence and fire management, (2) the respiratory and cardiovascular health effects of wildland fire smoke exposure, (3) communication strategies to address these health risks, and (4) actions to address wildland fire health impacts. Through formal presentations followed by group discussion, workshop participants identified top priorities for fire management, research, communication and public policy to address health risks of wildland fires. The workshop concluded that short-term exposure to wildland smoke causes acute respiratory health effects, especially among those with asthma and chronic obstructive pulmonary disease (COPD). Research is needed to understand long-term health effects of repeated smoke exposures across fire seasons for children, adults and highly exposed occupational groups (especially firefighters). Other research priorities include fire data collection and modeling, toxicology of different fire fuel sources, and the efficacy of health protective measures to prevent respiratory effects of smoke exposure. The workshop committee recommends a unified Federal response to the growing problem of wildland fires, including investment in fire behavior and smoke air quality modeling, research on the health impacts of smoke, and the development of robust clinical and public health communication tools.
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Background: Preharvest burning of sugarcane is a common agricultural practice in Florida, which produces fine particulate matter [particulate matter (PM) with aerodynamic diameter ≤2.5μm (PM2.5)] that is associated with higher mortality. Objectives: We estimated premature mortality associated with exposure to PM2.5 from sugarcane burning in people age 25 y and above for 20 counties in South Florida. Methods: We combined information from an atmospheric dispersion model, satellites, and surface measurements to quantify PM2.5 concentrations in South Florida and the fraction of PM2.5 from sugarcane fires. From these concentrations, estimated mortalities attributable to PM2.5 from sugarcane fires were calculated by census tract using health impact functions derived from literature for six causes of death linked to PM2.5. Confidence intervals (CI) are provided based on Monte Carlo simulations that propagate uncertainty in the emissions, dispersion model, health impact functions, and demographic data. Results: Sugarcane fires emitted an amount of primary PM2.5 similar to that of motor vehicles in Florida. PM2.5 from sugarcane fires is estimated to contribute to mortality rates within the Florida Sugarcane Growing Region (SGR) by 0.4 death per 100,000 people per year (95% CI: 0.3, 1.6 per 100,000). These estimates imply 2.5 deaths per year across South Florida were associated with PM2.5 from sugarcane fires (95% CI: 1.2, 6.1), with 0.16 in the SGR (95% CI: 0.09, 0.6) and 0.72 in Palm Beach County (95% CI: 0.17, 2.2). Discussion: PM2.5 from sugarcane fires was estimated to contribute to mortality risk across South Florida, particularly in the SGR. This is consistent with prior studies that documented impacts of sugarcane fire on air quality but did not quantify mortality. Additional health impacts of sugarcane fires, which were not quantified here, include exacerbating nonfatal health conditions such as asthma and cardiovascular problems. Harvesting sugarcane without field burning would likely reduce PM2.5 and health burdens in this region. https://doi.org/10.1289/EHP9957.
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Prescribed fire is an increasingly important tool in restoring ecological conditions and reducing uncontrolled wildfire. Prescribed burn techniques could reduce public health impacts associated with wildfire smoke exposure. However, there have been few assessments of the health impacts of prescribed burning, and potential vulnerabilities among populations exposed to smoke from prescribed fires. Our study area focused on counties in and near U.S. National Forests - a set of lands distributed across the U.S. In county-level analyses, we compared the sociodemographic and health characteristics of areas that were exposed with those that were not exposed to prescribe burns during the years 2010-2019 on a national level and within three regions. In addition, using spatial error regression models, we looked for associations between prescribed fire exposure and health behaviors and outcomes while controlling for spatial autocorrelation. On a national level, we found disproportionate prescribed fire exposure in rural counties with higher percentage mobile home and vacant housing units, and higher percentage African-American and white populations. Regionally, we found evidence of disproportionate exposure to prescribed burns among counties with lower percentage white population, higher percentage Hispanic population and mobile homes in the southern region, and to high poverty counties with high vacancy in the western region. These findings could indicate that vulnerable populations face potential health risks from prescribed burning smoke exposure, but also that they are not missing out on the benefits of prescribed burning, which could involve considerably lower smoke exposure compared to uncontrolled wildfire. In addition, in regression analyses, we found no evidence of disproportionate health burden in exposed compared to unexposed counties. Awareness of these patterns could influence both large-scale or institutional polices about prescribed burning practice, and could be used to build decision-making factors into modeling tools and smoke management plans, as well as community-engagement around wildfire risk reduction.
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Ambient concentrations of O 3 , PM 2.5 , NH 3 , NO, NO 2 , HNO 3 , SO 2 and VOCs were measured at Devils Postpile National Monument (DEPO) during the summer seasons of 2013 and 2014. The measurements were impacted by the Aspen and Rim Fires in 2013, and the French and King Fires in 2014. While O 3 concentrations were not discernibly perturbed by the fire events, the 70 ppb threshold (8-hour average) corresponding to both the current California Ambient Air Quality Standard (CAAQS) and the new National Ambient Air Quality Standard (NAAQS) was exceeded on five days during 2013, and on 16 days during 2014. The older NAAQS of 75 ppb (8-hour average) was exceeded once in 2013, and six times in 2014. Exceedances of the CAAQS or NAAQS occurred when background sources of O 3 were augmented by regional-scale transport, at higher altitudes, of polluted air masses that had passed through the San Joaquin Valley before arriving at the DEPO site. The 2013 Aspen Fire elevated PM 2.5 to a maximum hourly concentration of 214 µg m –3 and a maximum 24 h mean of 92.7 µg m –3 , and resulted in 13 exceedances of the 35 µg m –3 (24 h average) NAAQS for PM 2.5. The 2013 Rim Fire increased PM 2.5 to a maximum hourly concentration of 132 µg m –3 and a maximum 24 h mean of 69.6 µg m –3 , and resulted in two exceedances of the 24 h NAAQS. Concentrations of NH 3 increased during all fires, as did those of NO 2 during the Aspen and Rim Fires. Concentrations of benzene increased substantially during the French Fire.
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Background: Wildfire activity is predicted to increase in many parts of the world due to changes in temperature and precipitation patterns from global climate change. Wildfire smoke contains numerous hazardous air pollutants and many studies have documented population health effects from this exposure. Objectives: We aimed to assess the evidence of health effects from exposure to wildfire smoke and to identify susceptible populations. Methods: We reviewed the scientific literature for studies of wildfire smoke exposure on mortality and on respiratory, cardiovascular, mental, and perinatal health. Within those reviewed papers deemed to have minimal risk of bias, we assessed the coherence and consistency of findings. Discussion: Consistent evidence documents associations between wildfire smoke exposure and general respiratory health effects, specifically exacerbations of asthma and chronic obstructive pulmonary disease. Growing evidence suggests associations with increased risk of respiratory infections and all-cause mortality. Evidence for cardiovascular effects is mixed, but a few recent studies have reported associations for specific cardiovascular endpoints. Insufficient research exists to identify specific population subgroups that are more susceptible to wildfire smoke exposure. Conclusions: Consistent evidence from a large number of studies indicates that wildfire smoke exposure is associated with respiratory morbidity with growing evidence supporting an association with all-cause mortality. More research is needed to clarify which causes of mortality may be associated with wildfire smoke, whether cardiovascular outcomes are associated with wildfire smoke, and if certain populations are more susceptible.
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Introduction: Wildland fires degrade air quality and adversely affect human health. A growing body of epidemiology literature reports increased rates of emergency departments, hospital admissions and premature deaths from wildfire smoke exposure. Objective: Our research aimed to characterize excess mortality and morbidity events, and the economic value of these impacts, from wildland fire smoke exposure in the U.S. over a multi-year period; to date no other burden assessment has done this. Methods: We first completed a systematic review of the epidemiologic literature and then performed photochemical air quality modeling for the years 2008 to 2012 in the continental U.S. Finally, we estimated the morbidity, mortality, and economic burden of wildland fires. Results: Our models suggest that areas including northern California, Oregon and Idaho in the West, and Florida, Louisiana and Georgia in the East were most affected by wildland fire events in the form of additional premature deaths and respiratory hospital admissions. We estimated the economic value of these cases due to short term exposures as being between $11 and $20B (2010$) per year, with a net present value of $63B (95% confidence intervals $6-$170); we estimate the value of long-term exposures as being between $76 and $130B (2010$) per year, with a net present value of $450B (95% confidence intervals $42-$1200). Conclusion: The public health burden of wildland fires-in terms of the number and economic value of deaths and illnesses-is considerable.
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Wildland fire is an important ecological process in the California Sierra Nevada. Personal accounts from pre-20th century describe a much smokier environment than present day. The policy of suppression beginning in the early 20th century and climate change are contributing to increased megafires. We use a single particulate monitoring site at the wildland urban interface to explore impacts from prescribed, managed, and full suppression wildland fires from 2006 to 2015 producing a contextual assessment of smoke impacts over time at the landscape level. Prescribed fire had little effect on local fine particulate matter (PM2.5) air quality with readings typical of similar non-fire times; hourly and daily good to moderate Air Quality Index (AQI) for PM2.5, maximum hourly concentrations 21–103 μg m⁻³, and mean concentrations between 7.7 and 13.2 μg m⁻³. Hourly and daily AQI was typically good or moderate during managed fires with 3 h and one day reaching unhealthy while the site remained below National Ambient Air Quality Standards (NAAQS), with maximum hourly concentrations 27–244 μg m⁻³, and mean concentrations 6.7–11.7 μg m⁻³. The large high intensity fire in this area created the highest short term impacts (AQI unhealthy for 4 h and very unhealthy for 1 h), 11 unhealthy for sensitive days, and produced the only annual value (43.9 μg m⁻³) over the NAAQS 98th percentile for PM2.5 (35 μg m⁻³). Pinehurst remained below the federal standards for PM2.5 when wildland fire in the local area was managed to 7800 ha (8–22% of the historic burn area). Considering air quality impacts from smoke using the NAAQS at a landscape level over time can give land and air managers a metric for broader evaluation of smoke impacts particularly when assessing ecologically beneficial fire. Allowing managers to control the amount and timing of individual wildland fire emissions can help lessen large smoke impacts to public health from a megafire.
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Rationale: Epidemiologic evidence indicates that exposures to fine particulate matter air pollution (PM2.5) contribute to global burden of disease, primarily as a result of increased risk of cardiovascular morbidity and mortality. However, mechanisms by which PM2.5 exposure induces cardiovascular injury remain unclear. PM2.5-induced endothelial dysfunction and systemic inflammation have been implicated, but direct evidence is lacking. Objective: To examine whether acute exposure to PM2.5 is associated with endothelial injury and systemic inflammation. Methods and results: Blood was collected from healthy, non-smoking, young adults over three study periods that included episodes of elevated PM2.5 levels. Microparticles and immune cells in blood were measured by flow cytometry, and plasma cytokine/growth factors were measured using multiplexing laser beads. PM2.5 exposure was associated with elevated levels of endothelial microparticles (annexin V(+)/CD41-/CD31(+)) including subtypes expressing arterial-, venous-, and lung-specific markers, but not microparticles expressing CD62(+) These changes were accompanied by suppressed circulating levels of pro-angiogenic growth factors (EGF, sCD40L, PDGF, RANTES, GROα, and VEGF), and an increase in the levels of anti-angiogenic (TNFα, IP-10) and proinflammatory cytokines (MCP-1, MIP-1α/β, IL-6, and IL-1β), and markers of endothelial adhesion (sICAM-1 and sVCAM-1). PM2.5 exposure also was associated with an inflammatory response characterized by elevated levels of circulating CD14(+), CD16(+), CD4(+), and CD8(+), but not CD19(+) cells. Conclusions: Episodic PM2.5 exposures are associated with increased endothelial cell apoptosis, an anti-angiogenic plasma profile, and elevated levels of circulating monocytes, and T, but not B, lymphocytes. These changes could contribute to the pathogenic sequelae of atherogenesis and acute coronary events.
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The 2013 Rim Fire was the third largest wildfire in California history and burned 257,314 acres in the Sierra Nevada Mountains. We evaluated air quality impacts of PM2.5 from smoke from the Rim Fire on receptor areas in California and Nevada. We employed two approaches to examine the air quality impacts, (1) an evaluation of PM2.5 concentration data collected by temporary and permanent air monitoring sites and (2) an estimation of intake fraction (iF) of PM2.5 from smoke. The Rim Fire impacted locations in the central Sierra nearest to the fire and extended to northern Sierra Nevada Mountains of California and Nevada monitoring sites. Daily 24-hr average PM2.5 concentrations measured at 22 air monitors had an average concentration of 20 ?g/m3 and ranged from 0 to 450 ?g/m3. iF for PM2.5 from smoke during the active fire period was 5 per million, which is slightly higher to representative iF for PM2.5 in rural areas and much lower than for urban areas. This study is an unique application of intake fraction to examine emissions-to-exposure for wildfires and emphasizes that air quality cannot only be localized to communities near large fires but can extend long distances and impact larger urban areas.
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Two specific fires from 2011 are tracked for local to regional scale contribution to ozone (O3) and fine particulate matter (PM2.5) using a freely available regulatory modeling system that includes the BlueSky wildland fire emissions tool, Spare Matrix with Operation Kernel Emissions (SMOKE) model, Weather and Research Forecast (WRF) meteorological model, and Community Multiscale Air Quality (CMAQ) photochemical grid model. The modeling system was applied to track the contribution from a wildfire (Wallow) and prescribed fire (Flint Hills) using both source sensitivity and source apportionment approaches. The model estimated contributions to primary and secondary pollutants are comparable using source sensitivity (brute-force zero out) and source apportionment (Integrated Source Apportionment Method) approaches. Model estimated O3 enhancement relative to CO is similar to values reported in literature indicating the modeling system captures that range of O3 inhibition possible near fires and O3 production both near the fire and downwind. O3 and peroxyacetyl nitrate (PAN) are formed in the fire plume and transported downwind along with highly reactive VOC species such as formaldehyde and acetaldehyde that are both emitted by the fire and rapidly produced in the fire plume by VOC oxidation reactions. PAN and aldehydes contribute to continued downwind O3 production. The transport and thermal decomposition of PAN to nitrogen oxides (NOX) enables O3 production in areas limited by NOX availability and the photolysis of aldehydes to produce free radicals (HOX) causes increased O3 production in NOX rich areas. The modeling system tends to overestimate hourly surface O3 at routine rural monitors in close proximity to the fires when the model predicts elevated fire impacts on O3 and Hazard Mapping System (HMS) data indicates possible fire impact. A sensitivity simulation in which solar radiation and photolysis rates were more aggressively attenuated by aerosol in the plume reduced model O3 but does not eliminate this bias. A comparison of model predicted daily average speciated PM2.5 at surface rural routine network sites when the model predicts fire impacts from either of these fires shows a tendency toward overestimation of PM2.5 organic aerosol in close proximity to these fires. The standard version of the CMAQ treats primarily emitted organic aerosol as non-volatile. An alternative approach for treating organic aerosol as semi-volatile resulted in lower PM2.5 organic aerosol from these fires but does not eliminate the bias. Future work should focus on modeling specific fire events that are well characterized in terms of size, emissions, and have extensive measurements taken near the fire and downwind to better constrain model representation of important physical and chemical processes (e.g. aerosol photolysis attenuation and organic aerosol treatment) related to wild and prescribed fires.
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Wildland fire smoke is inevitable. Size and intensity of wildland fires are increasing in the western USA. Smoke-free skies and public exposure to wildland fire smoke have effectively been postponed through suppression. The historic policy of suppression has systematically both instilled a public expectation of a smoke-free environment and deferred emissions through increased forest fuel loads that will lead to an eventual large spontaneous release. High intensity fire smoke is impacting a larger area including high density urban areas. Policy change has largely attempted to provide the avenue for increased use of ecologically beneficial fire but allows for continued reliance on suppression as a primary tool for a smoke averse population. While understanding the essential role of suppression in protection of life and property, we dispute the efficacy of attempting to eliminate smoke exposure through suppression in a fire prone area to protect human health at the population level. Sufficient consideration to future negative health outcomes needs to be considered in fire management decisions. It is likely that long term air quality is inextricably linked to ecosystem health in the Sierra Nevada. We contend that landscape use of ecological fire is essential to forest and human health. Radical change is needed where beneficial wildland fire smoke is treated as natural background and exempted from much of the regulation applied to anthropogenic sources. Tolerance of the measured release of routine smoke emissions from beneficial fire is needed. Using present air quality standards in the more remote areas will provide an opportunity to increase burning in many forests while protecting public health.
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Each year, the general public and wildland firefighters in the US are exposed to smoke from wildland fires. As part of an effort to characterize health risks of breathing this smoke, a review of the literature was conducted using five major databases, including PubMed and MEDLINE Web of Knowledge, to identify smoke components that present the highest hazard potential, the mechanisms of toxicity, review epidemiological studies for health effects and identify the current gap in knowledge on the health impacts of wildland fire smoke exposure. Respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with community level exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. These cardiopulmonary effects were mostly observed in association with ambient air concentrations of fine particulate matter (PM2.5). However, research on the health effects of this mixture is currently limited. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after the firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits and help determine the types of exposure controls that may be applicable to the occupation.
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John Muir was an early proponent of a view we still hold today-that much of California was pristine, untouched wilderness before the arrival of Europeans. But as this groundbreaking book demonstrates, what Muir was really seeing when he admired the grand vistas of Yosemite and the gold and purple flowers carpeting the Central Valley were the fertile gardens of the Sierra Miwok and Valley Yokuts Indians, modified and made productive by centuries of harvesting, tilling, sowing, pruning, and burning. Marvelously detailed and beautifully written, Tending the Wild is an unparalleled examination of Native American knowledge and uses of California's natural resources that reshapes our understanding of native cultures and shows how we might begin to use their knowledge in our own conservation efforts.M. Kat Anderson presents a wealth of information on native land management practices gleaned in part from interviews and correspondence with Native Americans who recall what their grandparents told them about how and when areas were burned, which plants were eaten and which were used for basketry, and how plants were tended. The complex picture that emerges from this and other historical source material dispels the hunter-gatherer stereotype long perpetuated in anthropological and historical literature. We come to see California's indigenous people as active agents of environmental change and stewardship. Tending the Wild persuasively argues that this traditional ecological knowledge is essential if we are to successfully meet the challenge of living sustainably.