Opinion The wildfire smoke may be gone. But the health threat remains.

The primary pollutants of concern are the fine particles that wildfires release into the air. Such “particulate matter” is microscopic; those 2.5 microns or smaller are referred to as “PM 2.5.” If inhaled, PM 2.5 can infiltrate deep in our lungs. From there, it can enter the bloodstream and affect other organs. It can also trigger the body’s immune system, just as invading viruses or bacteria would. But because our immune system can’t neutralize particulate matter, the body produces an inflammatory response, with both short- and long-term implications.

The immediate impact of wildfire smoke is evident to anyone who breathed it last week and experienced hoarseness, coughing and shortness of breath, but it can also lead to more severe illness. One study of wildfires in California found that pediatric emergency room visits for asthma increased 112 percent in the days after exposure. For infants younger than 1, emergency room visits for asthma spiked 243 percent. Another study found a 7.2 percent increase in the risk of hospitalization for respiratory conditions among adults 65 years or older during the days when PM 2.5 concentrations exceeded the safety limit.

Guest Opinion: People who never had to think about wildfire before need to start

The respiratory system is not the only affected part of the body. Smoke exposure from wildfires is also correlated with cardiac arrest and heart attacks, as scientists believe that the inflammatory response constricts blood vessels and increases heart rate and blood pressure.

For people with existing cardiovascular conditions, this could be life-threatening. As one study published in the Journal of the American Heart Association shows, ER visits for heart attacks increased 42 percent within a day of exposure to dense wildfire smoke. In a separate study, researchers found that being around heavy smoke raised the likelihood of out-of-hospital cardiac arrest for several days after inhaling smoke, with the highest increase — 70 percent — occurring on the second day after exposure.

The lasting effects of wildfire smoke can persist for months. According to an analysis of Montana communities, higher PM 2.5 concentrations during wildfire season in the summer were associated with influenza in the subsequent winter flu season. After a bad wildfire season in 2012, flu rates were three to five times as high as normal. Montanans affected by hazardous PM 2.5 levels still had decreased lung function a year later.

High PM 2.5 levels might also increase susceptibility to the coronavirus. A 2021 study in the journal Science examined 92 western U.S. counties affected by 2020 wildfires. Overall, an increase of 10 micrograms of PM 2.5 per cubic meter was associated with a nearly 12 percent increase in coronavirus infections and an 8.4 percent increase in deaths.

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