Public Information Officers Incident Management Response Roundtable

March 16, 2022

Jason Sacks

Senior Epidemiologist

Center for Public Health and Environmental Assessment

Office of Research and Development

US EPA

Health Effects of Wildfires

Chiwaukum Creek Wildfire 2014

Okanogan-Wenatchee National Forest

Photo Credit: https://ecology.wa.gov/
Disclaimer

The views expressed during this presentation are those 

of the author and do not necessarily reflect the views or 

policies of the U.S. EPA. 

2
Outline

• Wildfire smoke and air quality

• Health effects & research needs

• Mitigating wildfire smoke exposure

• Information for public health officials, 

healthcare professionals, and the public

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Source: Brianna Paciorka, Knoxville 

News Sentinel
Wildland Fire Smoke

4

Complex mixture

– Particulate matter

– Carbon dioxide

– Carbon monoxide

– Hydrocarbons

– Organic chemicals

– Oxides of nitrogen

– Trace minerals

– Water vapor Lands End San Francisco, CA

Camp Fire November 2018

Picture by Wayne Cascio
What is Particulate Matter?

5

Source: https://www.epa.gov/pm-pollution

• Mixture of solid and liquid droplets

• Primary particles emitted directly from a 

source (e.g., smokestacks, fires, construction 

sites)

• Secondary particles produced through 

complex atmospheric reactions of chemicals 

(e.g., NO2, SO2) emitted by sources such as 

power plants, automobiles, etc. 

• Particles defined by aerodynamic diameter

• Fine particles (PM2.5), aerodynamic diameter 

≤ 2.5 μm

• Coarse particles (PM10-2.5), aerodynamic 

diameter > 2.5 μm and ≤ 2.5 μm

• Ultrafine particles (UFPs), aerodynamic 

diameter ≤ 0.1 μm
Wildfire Smoke Emissions and PM2.5

6

Source: Prichard et al. (2020). Int. J. Wildland Fire, 

29, 132-147. Table 3. 

Agriculture

14%

Commercial 

Cooking

2%

Dust

16%

Fires

44%

Fuel 

Combustion

11%

Industrial 

Processes

5%

Miscellaneous

0%

Mobile Sources

5%

Waste Disposal

3%

Total PM2.5 Emissions in 2017 NEI

(5.7 million tons)

Source: https://www.epa.gov/air-emissionsinventories/2017-national-emissionsinventory-nei-data

Pollutants in Wildfire Smoke

n = # observations; EF = emissions factor
Wildfire smoke

Where There is Smoke There is Illness

Organic

species

Reactive

metals

Volatile

liquids

Gases

Particles

Wildfires

Health 

effects

Inhaled particle deposition in the lung

>10 μm

2.5 – 10 μm

(Ultrafine PM)

(Coarse PM)

(Fine PM)

< 0.1 μm 0.1 – 2.5 μm 

Larynx

Trachea

Bronchi

Alveoli

Nasal 

Cavity

7
8

Health Effects of Wildfire Smoke

Decades of research on 

the health effects of 

ambient PM2.5 exposures

• Studies provide extensive 

scientific evidence 

demonstrating a range of 

health effects due to both 

short-term (i.e., 1-hour to 

a month) and long-term 

(i.e., 1 month to years) 

exposures 

https://www.epa.gov/isa/integratedscience-assessment-isa-particulate-matter
Health Effects Associated with Wildland 

Fire Smoke

9

Source: Liu et al 2015; Reid et al. 2016; Cascio 2018

• All-cause mortality

• Asthma & chronic obstructive pulmonary

disease (COPD) exacerbations 

• Bronchitis & pneumonia

• Childhood respiratory disease

• Cardiovascular outcomes

• Adverse birth outcomes

• Symptoms such as eye irritation, sore throat,

wheeze and cough
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Health Effects of Wildfire Smoke:

Epidemiologic Evidence

Study

Gan et al. (2017)a

Gan et al. (2017)b

Gan et al. (2017)c

Stowell et al. (2019)d,e

Tinling et al. (2016) 

Tinling et al. (2016) 

Hutchinson et al. (2018)

Delfino et al. (2009)

Reid et al. (2016)

Reid et al. (2019)

Deflorio-Barker et al. (2019)f

Deflorio-Barker et al. (2019)g

Deflorio-Barker et al. (2019)h

Alman et al. (2016)

Reid et al. (2016)

Reid et al. (2019)

Gan et al. (2017)a

Gan et al. (2017)b

Gan et al. (2017)c

Stowell et al. (2019)d,e

Gan et al. (2020)i

Gan et al. (2020)j

Gan et al. (2020)

Tinling et al. (2016) 

Tinling et al. (2016) 

Hutchinson et al. (2018)

Gan et al. (2020)k

Delfino et al. (2009)

Reid et al. (2016)

Reid et al. (2019)

Deflorio-Barker et al. (2019)f

Deflorio-Barker et al. (2019)g

Deflorio-Barker et al. (2019)h

Alman et al. (2016)

Reid et al. (2016)

Reid et al. (2019)

Location

Washington Washington Washington

Colorado

North Carolina (28 counties)

North Carolina (28 counties)

San Diego, CA

S. California

N. California (781 ZCTA)

N. California (753 zip codes)

692 U.S. counties

692 U.S. counties

692 U.S. counties

Colorado

N. California (781 ZCTA)

N. California (753 zip codes)

Washington Washington Washington

Colorado

Oregon

Oregon

Oregon

North Carolina (28 counties)

North Carolina (28 counties)

San Diego, CA

Oregon

S. California

N. California (781 ZCTA)

N. California (753 zip codes)

692 U.S. counties

692 U.S. counties

692 U.S. counties

Colorado

N. California (781 ZCTA)

N. California (753 zip codes)

Lag

0

0

0

0-2

0-2DL

0-2DL

0-2 (72-h MA)

0-1

1-2

1-2

0

0

0

0-2

1-2

1-2

0

0

0

0-2

0

0

0

0-2DL

0-2DL

0-2 (72-h MA)

0

0-1

1-2

1-2

0

0

0

0-2

1-2

1-2

Age

All

All

All

All

<18

18+

0-64

All

All

All

65+

65+

65+

All

All

All

All

All

All

All

All

All

All

<18

18+

0-64

All

All

All

All

65+

65+

65+

All

All

All

All Respiratory 

Asthma

0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25

Odds Ratio/Relative Risk

Legend:

= studies that used smoke/wildfire 

PM2.5 as the exposure indicator

= studies that used ambient PM2.5

measurements as the exposure 

indicator

Solid circles = hospital admissions

Open circles = ED visits

Note: All risk estimates are for a 10 

μg/m3increase in PM2.5 concentrations, 

except for Stowell at al. (2019), which 

are for a 1 μg/m3increase. U.S.-based Epidemiologic Studies Examining the Relationship Between Short-term Wildfire Smoke Exposure 

and Combinations of Respiratory-Related Diseases and Asthma Hospital Admissions and Emergency 

Department Visits

• Exposure Assessment: Different exposure indicators used across studies (e.g., wildfire-specific PM2.5, smoke plume density)

• Associations generally consistent across studies regardless of exposure indicator

• Most studies focus on daily (24-h avg) exposures

• Consistent, positive associations across studies examining respiratory-related and asthma hospital admissions and ED visits

• Fewer studies examining cardiovascular outcomes and mortality

Source: U.S. EPA (2021) – CAIF Report, 

https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=352824
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Who’s At-Risk from Wildland Fire Smoke? 

At-risk populations include:

• Older adults (i.e., > 65 years of age)

• Children

• People with respiratory disease

• People with cardiovascular disease

• Pregnant women and fetuses

• People of low socioeconomic status

• Outdoor workers

More recent evidence:

• Minority populations 

• Populations with chronic inflammatory diseases (e.g., diabetes, obesity)

~30% of the 

U.S. 

population 

is at-risk

Source: U.S. EPA (2019), Wildfire Smoke: A Guide for Public Health Professionals

Source: U.S. EPA (2020), Integrated Science Assessment for Particulate Matter (PM ISA)
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Exposures < 24-hour average

• Potentially important from the standpoint of public health messaging

• Limited number of studies examining ambient PM2.5, with most consisting of panel studies and 

controlled human exposure studies

• Primarily examining subclinical effects (e.g., markers of inflammation), changes in heart and lung function

• Recent wildfire study focusing on emergency ambulance dispatches reports an association with 1-h 

PM2.5 exposure and respiratory and cardiovascular outcomes

(Yao et al. 2020. Environ Health Perspect 128,6)

Exposures > 1 week

• Examined in firefighters (Adetona et al. 2016, Inhalation Tox 28:3, 95-139)

• Focus on respiratory-related health effects

• Some evidence that cumulative exposures (> 1 week) can lead to changes in lung function

• Increased risk of mortality in hemodialysis patients as cumulative exposures increase up to 30 days

(Xi et al. 2020, JASN 31)

Health Effects of Wildfire Smoke: 

Uncertainties
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Repeated high exposures over a few days

Long-term health consequences of high exposure

• Initial evidence of a relationship between high wildfire smoke exposure:

• Reductions in lung function in subsequent years (Orr et al. Toxics, 2020, 8, 53)

• Increased risk of influenza during the following winter influenza season (Landguth et al. 2020, Environ 

Int. 139:105668)

• COVID-19 cases and deaths (Zhou et al. 2021, Sci Adv. Aug 13;7(33))

Exposures over multiple fire seasons

• Particularly in communities that experience wildfire smoke exposure on a recurring basis

Changing wildfire smoke mixture and exposures

• Wildland-urban interface (WUI)

Health Effects of Wildfire Smoke: 

Uncertainties
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• In studies examining wildfire smoke exposure there is 

high variability between studies, and within studies 

(between homes/filters) on the effectiveness of 

different actions

• Studies examined whether people took actions 

to reduce exposures, not if health responses 

changed

Mitigation of Wildfire Smoke Exposure

Source: U.S. EPA (2021) – CAIF Report 

(https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=352824) 
Main Actions that Individual People can 

Take to Reduce Wildfire Smoke Exposure

Source: Xu et al. (2020). N Engl J Med 2020; 383:2173-2181

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• Public health outreach: helping the public 

understand how fires impact their health, including 

providing real-time information during fire events.

• AirNow

• Wildfire Smoke: A Guide for Public Health 

Officials

• Smoke Sense App

• Preparedness resources

• Clean Air Spaces

• Respirator Use

• Information Clearinghouse: Smoke Ready Toolbox

• Continuing Medical Education (CME) Courses 

• Particle Pollution and Your Patients’ Health

• Wildfire Smoke and Your Patients’ Health

• Research 

• How to improve community capacity and 

resiliency around smoke events

• Community Health Vulnerability Index

• How fires impact air quality

• Monitoring Needs

EPA Plays a Supportive Role

Courtesy of Erika Sasser, OAR 16
Summary

• Extensive scientific evidence demonstrating the health effects of PM2.5

• While uncertainties remain with respect to the health effects of wildfire smoke for some exposure 

durations, clear evidence that PM2.5 can lead to adverse health effects

• Actions and interventions can be instituted to reduce wildfire smoke exposure with 

proper health messaging and/or availability 

• AQI, and other similar indices, can provide information to inform the public on wildfire 

smoke
Thank you

Jason Sacks

Senior Epidemiologist

Center for Public Health and Environmental Assessment

Office of Research and Development

U.S. Environmental Protection Agency

Email: sacks.jason@epa.gov 

Questions

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