Wildfire smoke worsens coronavirus risk, putting firefighters in extra danger

Researchers found that wildfire smoke exposure can lead to an increase of other pathogens in lungs.

Norbeck prescribed fire Wind Cave National Park
A firefighter at the end of the day, igniting the Norbeck prescribed fire in Wind Cave National Park in the Black Hills of South Dakota, Oct. 20, 2014. Photo by Bill Gabbert.

By Luke Montrose, Assistant Professor of Community and Environmental Health, Boise State University

(This article first appeared at The Conversation)

As summer approaches, two forces of nature are on a collision course, and wildland firefighters will be caught in the middle.

New research suggests that the smoke firefighters breathe on the front lines of wildfires is putting them at greater risk from the new coronavirus, with potentially lethal effects.

At the same time, firefighting conditions make precautions such as social distancing and hand-washing difficult, increasing the chance that, once the virus enters a fire camp, it could quickly spread.

As an environmental toxicologist, I have spent the last decade expanding our understanding of how wood smoke exposure impacts human health. Much of my current research is focused on protecting the long-term health of wildland firefighters and the communities they serve.

‘Camp crud’ and the dangers of air pollution

People have long understood that the air they breathe can impact their health, dating back more than 2,000 years to Hippocrates in his treatise on Air, Water, and Places. Today, there is a growing consensus among researchers that air pollution, specifically the very fine particles called PM2.5, influences risk of respiratory illness. These particles are a tiny fraction of the width of a hair and can travel deep into the lungs.

Italian scientists reported in 2014 that air pollutants can increase the viral load in the lungs and reduce the ability of specialized cells called macrophages to clear out viral invaders.

Researchers in Montana later connected that effect to wood smoke. They found that animals exposed to wood smoke 24 hours before being exposed to a pathogen ended up with more pathogen in their lungs. The researchers showed that wood smoke exposure decreased the macrophages’ ability to combat respiratory infection.

Now, new evidence suggests that long-term exposure to PM2.5 air pollution, which is produced by sources such as wildfirespower plants and vehicles, may make coronavirus particularly deadly.

Researchers from the Harvard T.H. Chan School of Public Health conducted a nationwide study of county-level data and found that even a small increase in the amount of PM2.5 from one U.S. county to the next was associated with a large increase in the death rate from COVID-19. While small increases in PM2.5 also raise the risk of death from other causes for older adults, the magnitude of the increase for COVID-19 was about 20 times greater. The results were released last week, before the usual peer review process was conducted, to help warn people of the risks.

Taken together, these findings suggest that air pollution, including wood smoke, could increase the risk that wildland firefighters will develop severe COVID-19 symptoms.

That probably doesn’t surprise seasoned firefighters.

They’re already familiar with “camp crud,” a combined upper and lower respiratory illness accompanied by cough and fatigue that has become common in firefighting camps.

The National Wildfire Coordinating Group, in its guidance on infectious disease, has pointed out that “the close, overlapping living conditions of an incident command post lends itself to rapid spreading of contagious microorganisms, as witnessed by the common outbreaks of ‘camp crud.’ Outbreaks also have a history of spreading from incident to incident as people are reassigned.”

How to protect wildland firefighters

So, what can be done to avoid the spread of COVID-19 among wildland firefighters and prevent them from being vectors in the communities they serve?

In some areas, officials have been delaying firefighter training sessions and brush-clearing operations that would normally be underway now. But while that might protect firefighters from exposure right now, it can be put off for only so long. Wildfires have already broken out in several states, and delaying controlled burns leaves more fuel when fires get out of control.

The National Wildfire Coordinating Group’s guidance on infectious disease encourages planning ahead so personal protective equipment is available and maintaining records of symptoms so illnesses can be tracked and stopped from spreading.

The guidance also calls for better camp hygiene, providing access to medical care, making isolation possible and coordinating cross-agency communication about the public health risks.

Firefighter camps are not typically well outfitted to promote good personal hygiene. Improving those conditions could help prevent a virus’s spread, such as by adding hand-washing stations and possibly mobile shower units. Single-person tents would allow for more effective social distancing.

Camp personnel should also have access to thermometers and coronavirus test kits. Protocols for quarantining and removing infected firefighters from the field should not only be implemented but practiced.

Also missing from the National Wildfire Coordinating Group’s guidance are policies on traveling to and from training sites, working within communities and traveling from camp. Social distancing may not always be possible, so protective gear, such as face masks, should be made available and their use encouraged.

firefighters crew Whitetail Fire 3-8-2017 Photo by Bill Gabbert
Firefighters on the Whitetail Fire in the Black Hills of South Dakota, March 8, 2017. Photo by Bill Gabbert.

A recent paper from Belgium suggests that even some of the ways firefighters operate in the field should be reconsidered to protect against the virus’s spread. It shows how droplets released when a person exhales can travel farther than six feet during heavy activity. For firefighters, that could mean walking farther apart and in a V-shaped delta formation, rather than a traditional line, to reach the fire.

It is also important to consider that frontline firefighters are often younger and could be asymptomatic but still able to spread the virus, so their contact with with rural community members, such as volunteer firefighters and ranchers, should be considered.

Finally, a system for cross-state communication should be engaged to facilitate sharing of best practices and lessons learned. It also could help track the movement of firefighters across the region.

The safety of rural western communities depends on the wildland firefighters and their ability to respond to emergencies. Protecting their health helps protect public health, too.

National Firefighter Registry releases time line toward implementation

UPDATED at 10:45 a.m. MDT Nov. 21, 2019

On November 21 the National Firefighter Registry that is being created by the National Institute for Occupational Safety and Health (NIOSH), a division of the Centers for Disease Control and Prevention, released information about their accomplishments. We are updating this article originally published November 17, 2019 to include the new data.


Milestones from this Quarter
Much of the work this quarter focused on creating the NFR protocol, filling staffing needs, and meeting with firefighters and stakeholders about the NFR. Some of our key milestones for this quarter include:

  • Reviewed Federal Register comments made on the NFR’s Request for Information (RFI). Thank you to those that were able to provide feedback. These comments are very helpful in guiding the development of the NFR.
  • Began development of the protocol, informed consent document, and enrollment questionnaire.
  • Started gathering details on record keeping systems at fire departments to better understand what data are available and potential mechanisms for importing the data.
  • Made progress on developing requirements for the registration web portal.
  • Held discussions with representatives from select state cancer registries and related organizations to better understand cancer surveillance on a national level.
  • Hired a new health scientist, Andrea Wilkinson, formerly of the First Responder Health & Safety Laboratory at Skidmore College.
    Created the NFR webpage https://www.cdc.gov/niosh/firefighters/registry.html
  • Began formation of the NFR Advisory Committee. This committee will include at least 10 members with various backgrounds, expertise, and experience related to firefighter health and research.

Next Steps

  • Finalize protocol and consent form
  • Begin Office of Management and Budget (OMB) clearance process for enrollment questionnaire
  • Hire Health Communications Specialist
  • Continue conversations with stakeholders and obtain their support
  • Continue conversations with select fire departments throughout the country.

(Originally published at 9:54 a.m. MDT Nov. 17, 2019)

The National Firefighter Registry, originally called the Firefighter Cancer Registry in the authorizing legislation, has released very broad time-based goals for implementing a system which hopefully can identify any relationships between cancer and occupational exposure to toxicants.

Earlier this year the National Institute for Occupational Safety and Health (NIOSH), a division of the Centers for Disease Control and Prevention, asked firefighters for input on how to maximize participation in the Registry (perhaps working on the first goal in the timeline chart). That comment period ended May 28, 2019.

From the time line, it appears that NIOSH hopes to begin enrolling firefighters sometime between 2019 and 2022.

firefighters smoke
Firefighters in a smoky environment on the White Tail Fire, March 8, 2019, Black Hills National Forest.

Previous studies, including one completed by NIOSH in 2014, have highlighted firefighters’ increased risk for certain cancers compared to the general population. However few previous studies have collected data about wildland firefighters, volunteer firefighters, or sufficient numbers of female and minority firefighters in order to draw conclusions regarding their risk of cancer.

In one study that collected data from wildland firefighters in the field, a group of researchers concluded that firefighters’ exposure to smoke can increase the risk of mortality from lung cancer, ischemic heart disease, and cardiovascular disease by 22 to 39 percent. The project only looked at the wildland fire environment, and was not a long term study of firefighters’ health.

The ultimate goal of the Registry is to better understand the link between workplace exposures and cancer among firefighters. The Registry will include all U.S. firefighters, not just those with a cancer diagnosis. The Registry also has the potential to provide a better understanding of cancer risk among subgroups such as women, minorities, and volunteers, and among sub-specialties of the fire service like instructors, wildland firefighters, and arson investigators.

From the Registry information, CDC/NIOSH will estimate an overall rate of cancer for firefighters. They might find certain groups of firefighters are at a higher risk of cancer than others based on level of exposure, geography, gender, or other factors. They may also find that certain protective measures are associated with a reduced risk for cancer, which could provide additional evidence and support for specific control interventions.

The Registry will be completely voluntary, and no one can force a person to join.

All active and retired as well as volunteer, paid-on-call, and career firefighters will be encouraged to join the Registry, regardless of their current health status.

CDC/NIOSH promises that they will always maintain participants’ privacy and will never share personal information with an outside organization including fire departments, unions, or other researchers without permission of the individual.

Researchers find prescribed fire smoke to be less harmful than that from wildfires

Therefore, prescribed fires to protect communities can protect residents in more ways than one

Wolf Trap National park prescribed fire
Prescribed fire at Wolf Trap National Park, April, 2018. NPS photo by Nathan King.

Researchers studying the effects of smoke on children found prescribed fire smoke to be less harmful than smoke from wildfires. The Stanford University study looked at three groups of children:

  • Those who were exposed to smoke from a prescribed fire;
  • Children exposed to smoke from a wildfire in which no structures burned; and,
  • Children that were not exposed to smoke.

Sometimes fire personnel refer to a prescribed fire as “good fire”. Now they may call smoke from a planned burn as “good smoke”. A way to look at this research is that removing hazardous fuels near a community is a way to reduce the threat of a wildfire spreading into the town and burning structures or entrapping and killing people. And, removing the fuels with good fire rather than allowing a wildfire to burn the same area, exposes residents to less harmful smoke. For fire-prone areas, it is not IF it burns, it’s WHEN. Do you want your smoke now under controlled conditions or later, possibly under extreme conditions?

From Stanford University:


…The study was published May 30 in the European Journal of Allergy and Clinical Immunology. It was conducted in Fresno, California, a city with high air pollution levels due to its topography and other sources, including traffic and agriculture.

“This study suggests that exposure to wildfire smoke is detrimental above and beyond poor air quality,” said the lead author, Mary Prunicki, MD, PhD, an instructor of medicine.

The study’s senior author is Kari Nadeau, MD, PhD, professor of medicine and of pediatrics and director of the Sean N. Parker Center for Allergy & Asthma Research at Stanford.

Native Americans traditionally used controlled burns to manage California’s forests, but throughout the early 20thcentury, wildfires were widely suppressed. This began to change in the 1960s and 1970s, when scientists recognized fire as a normal part of forest ecology. Recent wildfires have brought more attention to the possible benefits of prescribed burns as a way to reduce fuel levels and wildfire risk, but not everyone is enthusiastic.

Opposition to controlled burns
“We know that there’s some public opposition to doing prescribed burning,” Prunicki said. “It’s our feeling that prescribed burning, because it’s so controlled, may expose people to fewer health effects than wildfires.” Prescribed burns are of lower intensity and are permitted only when weather conditions allow the fire to be contained.

In the study, the researchers compared blood samples from three groups of children, all of whom were 7 or 8 years old. One group of 32 children had been exposed to smoke from a 553-acre prescribed burn that occurred in March 2015; a second group of 36 children had been exposed to smoke from a 415-acre wildfire in September 2015. Both fires were about 70 miles away from Fresno, and blood samples were collected from the children within three months of each fire.

The study also included blood samples from a control group of 18 children who lived in the San Francisco Bay Area and had not been exposed to wildfire or prescribed-burn smoke.

The researchers measured air pollution levels recorded at four monitoring stations in Fresno and estimated pollution levels at the children’s homes during the fires based on how far they lived from the stations.

Pollutant exposures were higher in the wildfire group compared to the prescribed-burn group.  The air pollutants measured included nitrogen dioxide, polycyclic aromatic hydrocarbons, elemental carbon, carbon monoxide and particulate matter.

Wildfire smoke exposure was associated with lower blood levels of type-1 T helper cells, a group of immune cells that are involved in the immune response. Among children exposed to wildfire smoke, the researchers also saw increased methylation of the Foxp3 gene, indicating reduced activity of this gene, which is broadly involved in modulating allergic and other immune responses. The finding of greater Foxp3 methylation is congruent with earlier studies of the effects of air pollution on the immune system, Prunicki noted.

Significance of particulate matter
One important aspect of the study was that the September 2015 wildfire was confined to forested areas and did not burn any structures.

“Particulate matter from wildfires is different from region to region and depends on what is burning,” Prunicki said. “When a wildfire is going through a town, there are a lot of concerns about what happens to the chemicals in people’s homes and cars when they go up in flames.” Smoke from wildfires that burn inhabited areas almost certainly has worse health effects than those found in the current study, she said.

The researchers plan to conduct larger, more detailed studies of the effects of wildfire smoke on health. They will be enrolling healthy people in a trial at Stanford later this summer to collect baseline data from blood samples. When future wildfires affect Bay Area air quality, the participants will be asked to provide follow-up blood samples.

The scientists also plan to research the health effects of using home air purifiers during wildfires, as well as measure the protection offered by N95 masks, with the aim of developing recommendations for when masks should be used by different populations, such as healthy adults, elderly people, children and people with chronic illnesses.

The study’s other Stanford co-authors are biostatistician Justin Lee; life science researcher Xiaoying Zhou, PhD; Francois Haddad, MD, clinical associate professor of medicine; and Joseph Wu, MD, PhD, professor of medicine and of radiology.

Over 2 million acres burned in Flint Hills in 28 days

map Flint Hills burning
Map showing heat detected by satellites during the last seven days. Updated at 1 p.m. CDT April 19, 2019.

The Kansas Department of Health and Environment (KDHE) says the average annual acreage burned in the Flint Hills during the prescribed fire season was almost matched over the past month. Most of the burning is related to agriculture, improving pastures or preparing crop lands.

map flint hillsAlmost 2.1 million acres of grassland were treated with fire between March 15 and April 12. KDHE said roughly 2.5 million acres are burned annually.

The reporting time period includes 21 counties in Kansas and Oklahoma.

KDHE said burns from April 8-9 caused six air quality exceedances across parts of Kansas, Missouri and Oklahoma. There were no air quality exceedances due to burns last year.

acres burned county flint hills

Thanks and a tip of the hat go out to Matt. Typos or errors, report them HERE.

Establishment of firefighter cancer registry is progressing

The next step is to collect input from firefighters and stakeholders on an approach to the Registry including potential enrollment methods

A firefighter works a blaze in Northern California. Photo courtesy CAL FIRE.
A firefighter works a blaze in Northern California during the fires in Wine Country in 2017. Photo courtesy of CAL FIRE.

(UPDATED at 10 a.m. MDT March 28, 2019)

The Request for Information about the new National Firefighter Registry described below was published today. The National Institute for Occupational Safety and Health (NIOSH), an agency within the Centers for Disease Control and Prevention (CDC), is requesting input about three possible enrollment strategies. Specifically, NIOSH is asking for input on how to maximize participation for the Registry. The comment period will close on May 28th, 2019.

The process for leaving a comment is convoluted. They ask you to click on this link and then you have to search for the appropriate issue. I searched for “National Firefighter Registry” which brought up 208 results. When I checked today it was the first one.

When found, you have to click in the search results on “Comment Now”(over on the right)  Maybe THIS will take you directly to the comment form.

Keep in mind that any information (e.g., personal or contact) you provide on the comment form may be publicly disclosed and searchable on the Internet and in a paper docket. But you don’t have to leave your name or email address.


(Originally published at 2:41 p.m. MDT March 27, 2019)

In April, 2017 a bill was introduced in Congress that would establish a registry to track the occurrence of cancer among firefighters. A version of the bill was finally signed into law on July 7, 2018. Now, eight months later it appears that the creation of the registry is some distance from becoming a reality, but we can report some progress.

The legislation called it a Firefighter Cancer Registry, but it appears that the name has changed to National Firefighter Registry — a vague term which does not provide a clue about the purpose.

Kenny Fent is the Team Lead for what will become the National Firefighter Registry Program. Mr. Fent is a Research Industrial Hygienist with the National Institute for Occupational Safety and Health, a division of the Centers for Disease Control and Prevention. He told us that soon the agency will post a Request for Information (RFI) to the Federal Register regarding the Registry. During a 60-day period they will seek input on an approach to the Registry including potential enrollment methods. All stakeholders, including firefighters, will be encouraged to review the document and respond with comments.

NIOSH-CDC logoOnce the Registry design is finalized, CDC/NIOSH will begin enrollment. Where possible, CDC/NIOSH will collect work history and exposure records to explore the relationship between exposures and cancer. They will also link with state cancer registries to confirm diagnoses. Findings will be shared through scientific publications and communications to stakeholders and the public.

Previous studies, including a study completed by the National Institute for Occupational Safety and Health (NIOSH) in 2014, have highlighted firefighters’ increased risk for certain cancers compared to the general population. However, few previous studies have collected data about wildland firefighters, volunteer firefighters, or sufficient numbers of female and minority firefighters in order to draw conclusions regarding their risk of cancer.

In one study that collected data from wildland firefighters in the field, a group of researchers concluded that firefighters’ exposure to smoke can increase the risk of mortality from lung cancer, ischemic heart disease, and cardiovascular disease by 22 to 39 percent. The project only looked at the wildland fire environment, and was not a long term study of firefighters’ health.

The ultimate goal of the Registry is to better understand the link between workplace exposures and cancer among firefighters. The Registry will include all U.S. firefighters, not just those with a cancer diagnosis. The Registry also has the potential to provide a better understanding of cancer risk among subgroups such as women, minorities, and volunteers, and among sub-specialties of the fire service like instructors, wildland firefighters, and arson investigators.

From the Registry information, CDC/NIOSH will estimate an overall rate of cancer for firefighters. They might find certain groups of firefighters are at a higher risk of cancer than others based on level of exposure, geography, gender, or other factors. They may also find that certain protective measures are associated with a reduced risk for cancer, which could provide additional evidence and support for specific control interventions.

The Registry will be completely voluntary, and no one can force a person to join.

All active and retired as well as volunteer, paid-on-call, and career firefighters will be encouraged to join the Registry, regardless of their current health status.

CDC/NIOSH promises that they will always maintain participants’ privacy and will never share personal information with an outside organization including fire departments, unions, or other researchers without permission of the individual.

Resources for learning about effects of exposure to wildland fire smoke

wildland fire smoke exposure
Cover of USFS publication.

Last week the Northern Rockies Fire Science Network conducted a live webinar titled,  “Smoke Exposure Health Effects and Mitigations for Wildland Fire Personnel: Current Research and Recommendations.” The one-hour presentation was very informative and heavily emphasized how smoke from burning vegetation can be hazardous to your health, especially for firefighters. Below is the recorded version, and following that is a list of resources identified in the webinar that provide more information about the effects of wildland fire smoke. I suggest that firefighters make the video a part of their annual refresher training.

We have written dozens of times about smoke and the research efforts directed toward evaluating the effects on humans. Articles that describe the effects are all tagged “smoke & health” on Wildfire Today. At this writing there are 17 of them. This article is the 18th.

In addition to those resources, here are others that were listed in last week’s webinar. Where possible, we downloaded them to the Wildfire Today web site in order to preserve the documents.