Where There’s Fire, There’s Smoke

Examining the effects of climate change on lung health

By Matthew Carr
March 5, 2024

2023 was the hottest year in recorded history.

For the first time, the earth’s land and ocean surface temperatures were at least 1 °C warmer than preindustrial levels. Nearly half of the days were 1.5 °C warmer or more, with the highest temperatures reaching 2 °C higher. Unfortunately, 2024 isn’t faring much better.

Globally, extreme heat waves are now nearly 5 times more likely to occur than they were 150 years ago. And summers are getting longer. Extreme heat presents the dangerous reality of an increasing threat of wildfires, drought, severe weather, rising sea levels, and air pollution.

For millions of people around the world, the chain reaction from climate change is personal. “The lungs interact with the outside world from the day of birth, hence any detrimental environmental change is important,” said Priya Balakrishnan, MD, MS, FCCP, a staff physician at the Respiratory Institute of the Cleveland Clinic.

Priya Balakrishnan, MD, MS, FCCP

Priya Balakrishnan, MD, MS, FCCP
Staff Physician, Respiratory Institute, Cleveland Clinic

Spreading like wildfire

The last 2 decades have seen a record-breaking number of wildfires, leaving historic amounts of devastation and unbreathable air in their wake. “Emissions from wildfires not only cause local issues but have far-reaching consequences, [as we saw with the] Canadian wildfires and NY haze last year,” Dr. Balakrishnan said.

Smoke doesn’t need a passport—nor does it respect the authority of border patrol. As the wildfires in northwest Canada blazed on in June and July of 2023, the skies in many major US cities, from Minneapolis to Chicago to New York, were transformed. The red and orange haze produced when sunlight hits the particles of ash created a deadly beauty for many.


55 M
acres burned

5.4 M
acres burned

3.7 M
acres burned

8.5 M
acres burned

42 M
acres burned

4 M
acres burned

46 M
acres burned

When it comes to natural disasters such as wildfires, a local crisis can quickly turn into a global one, broadening the potential at-risk zone and affecting billions of people.

“The global risk of climate change affects all patients (and everyone),” Dr. Balakrishnan said. “The scale is very concerning.”

Health effects of wildfires particularly problematic

Wildfires emit large amounts of CO2 and fine particulate matter (PM), specifically PM2.5 (particles smaller than 2.5 micrometers in diameter). That’s 20 times smaller than the width of a human hair.

“The lungs interact with the outside world from the day of birth, hence any detrimental environmental change is important.”

Particulate matter is a heterogeneous mixture of volatile organic and nonorganic compounds in the air and is classified by size. PM2.5 is the most significant because these particles deposit in any area of the respiratory tract and translocate into the circulatory system.

Breathing PM2.5 is extremely dangerous, and exposure is linked to a variety of health problems, including COPD, pneumonia, idiopathic pulmonary fibrosis, rheumatoid arthritis-associated interstitial lung disease, incidental interstitial lung abnormality, OSA, and more.

“Ambient concentrations of PM2.5 increase significantly within the vicinity of wildfires and have been associated with increased ED, ambulatory visits, and hospitalizations for patients with asthma and COPD exacerbations,” according to a journal CHEST® article written by Dr. Balakrishnan; Sean J. Callahan, MD, FCCP; Sujith V. Cherian, MD, FCCP; Abirami Subramanian, MD, MPH; Sauradeep Sarkar, MD; Nitin Bhatt, MD; and Mary-Beth Scholand, MD, FCCP—most of whom are members of CHEST’s Occupational & Environmental Health Section within the Diffuse Lung Disease and Lung Transplant Network.

As PM2.5 concentrations increase, the relative risk—the ratio of risk in an exposed to unexposed population—of pulmonary and respiratory threats does as well.

During the San Francisco wildfire in 2018 and the Sydney fire in 2019, the relative risk of exacerbated COPD due to PM2.5 exposure saw a 75% to 100% increase. Meanwhile, the relative risk for lower respiratory infections more than doubled. And when smoke from Canada blanketed New York City last summer, PM2.5 concentrations increased 590% to 1,229% over the 10-year baseline.

More than just asthma and COPD

PM2.5 is a threat that our lungs can’t ignore.

“We historically recognized on an individual level the environmental ‘triggers’ that worsened control of chronic conditions like COPD and asthma. There were also associations of environmental and occupational exposures that increased risk of cancers,” Dr. Balakrishnan said. “We are used to thinking of these issues as abstract and minimal. It only affected an ‘unfortunate’ and ‘minor’ number of patients.”

This is no longer the case.

Research shows that wildfire exposure can result in a decline in adult lung function even 10 years after the initial exposure. New evidence also indicates that higher levels of PM2.5 are associated with more severe disease at diagnosis, greater disease progression, and higher mortality—regardless of which respiratory disease presents.

Major damage to minority groups

In addition to the health damage from PM2.5 exposure and smoke inhalation, wildfires leave immense physical damage in their wake. Minority groups are often hit the hardest. Black, Hispanic, and Native American populations experience 50% greater vulnerability to wildfires compared with primarily White communities.

“We are used to thinking of these issues as abstract and minimal. It only affected an ‘unfortunate’ and ‘minor’ number of patients.”

Rural communities are 3 times more prone to wildfires, as they tend to be in more heavily wooded areas with more “fuel” for the flames, like crop fields and dry vegetation. There is a long history in the US of forced relocation onto reservations—mostly rural, remote areas—which is why Native Americans are 6 times more likely than other groups to live in areas prone to wildfires.

Additionally, rural areas tend to have a higher proportion of residents over age 65. This age group is disproportionately vulnerable due to a lack of mobility and preexisting health conditions that are exacerbated by smoke.

The reality of this data is that the communities most likely at risk for wildfires from a geographic perspective also have higher rates of poverty, have fewer resources, and are less likely to recover from a natural disaster, further exacerbating socioeconomic inequities. They also take the brunt of the health impact, as seen from studies on smoke inhalation in Aboriginal and non-Aboriginal populations after wildfires in Australia.

Minoritized communities are similarly at a disadvantage. Immigrant populations are generally underserved and marginalized both before and after a natural disaster. Emergency agencies have historically struggled to release timely and correct bilingual information. Plus, the fear of deportation can hinder individuals from seeking out needed care.

Low socioeconomic circumstances—and the potential geographical vulnerabilities that correlate with those circumstances—put poorer, ethnic communities directly in the path of wildfires and all that comes with them.

Lighting a fire under the medical community

The science is conclusive: Climate change is causing more wildfires, negatively impacting lung health. So what can be done? Recognition of the direct impact of climate change on health is growing among the health care community, yet 62% of pulmonary clinicians still do not feel adequately knowledgeable about climate change and its health consequences, according to a survey from the American Thoracic Society.

“Major work is needed in terms of awareness, education, and prevention.”

“Medical education and training have not adapted fast enough to address these challenges,” Dr. Balakrishnan said. “A lot of us [in the health care community] simply lack the ability to counsel patients on ways to reduce harmful environmental exposures. These have increased due to climate change.”

She noted that some small but impactful ways clinicians can help patients are by:

  • Recognizing local environmental changes and tailoring advice to patients with heightened risk
  • Being aware of and prepared to provide remediation methods for harmful environmental exposure (DIY home air filters, how to clear mold at home, access to methods on determining local air quality index, etc)
  • Getting involved in advocacy at the local (hospital) and national (governing bodies) levels to reduce harmful activities that perpetuate climate change

An infographic from the journal CHEST provides several other helpful suggestions for clinicians, patients, and health care entities alike.

“Patients do rely on physicians for guidance,” Dr. Balakrishnan said. “So major work is needed in terms of awareness, education, and prevention.”

Explore infographics on climate-related disaster response

Check out an article and accompanying infographic by the Chest Infections and Disaster Response Network on the health effects of wildfire smoke, including how symptoms present, possible long-term effects, and treatment strategies for pulmonologists. “Wildfire smoke and resultant poor air quality is associated with an increase in inpatient and outpatient health care utilization and can strain limited resources,” the authors wrote. Be prepared to act and help your patients.



Another piece by the Chest Infections and Disaster Response Network focuses on the health effects of hyperthermia, heat injury, and heatstroke. The infographic explains how to identify heat injuries, know which tests to run, and understand treatment options.