Fire season is only a few months away in the western United States, bringing smoky skies and recommendations to stay inside. Wildfires send plumes of smoke into the air, carrying fine particulate matter hundreds of kilometers away.
These small air pollutants, which scientists call PM2.5, or particles smaller than 2.5 micrometers, are highly hazardous to human health. Most PM2.5 pollution comes from burning fossil fuels and industry and environmental sources (such as dust), and the particulates can lead to cardiovascular and pulmonary diseases.
Now researchers are delving into what kind of health havoc is created from wildfire particulates.
In a paper in Environmental Health Perspectives, researchers used 3 years of air quality data and Medicare health records to see just how hazardous smoky days can be to people. They found clear links between wildfire smoke and cardiopulmonary health effects on older adults (65 years and older), including an increase in hospitalizations.
Consider the Source
To understand the connections between wildfires and health, scientists collected air quality data between 2008 and 2010 all around the United States in areas that experienced smoky days. During that time, more than 120 wildfires burned, and each fire was large, charring around 4,050 hectares. The researchers concentrated on air quality in communities located within 200 kilometers of wildfires—well within the limits of drifting smoke.
The team measured short-term PM2.5 values directly with U.S. Environmental Protection Agency (EPA) air monitoring sites scattered throughout the country. They also estimated particulate levels using the Community Multiscale Air Quality (CMAQ) model to fill in gaps between monitoring stations.
“One challenge to studying wildfires is that there are not air pollution monitors in all locations where we want to assess smoke exposure,” says Colleen Reid, a geographer at the University of Colorado Boulder who was not involved in the study.
She says that CMAQ estimates are made using an understanding of the chemistry and physics of air pollution emissions and transport. And although CMAQ helped broaden the air quality data, Reid notes that models don’t always get the exposures completely correct.
Looking at the air quality data, the researchers considered days when concentrations of PM2.5 were more than 5 micrograms per cubic meter “smoke days.” In total, the researchers found that about 4% of the days over the 3-year period were smoke days.
Smoke Sick Days
Researchers investigated the health effects of wildfire particulates and focused on the older population (more than 65 years old) in nearby communities.
“We had an opportunity to study a population of older individuals which we have found are at a higher risk,” says Ana Rappold, a researcher at the EPA’s National Health and Environmental Effects Research Laboratory in Research Triangle Park, N.C.
Rappold says that this age demographic provides a rich data set for U.S. populations because people are eligible for Medicare at age 65, and their health is well documented.
Using hospital inpatient data from Medicare Provider Analysis and Review (MEDPAR) files, the team collected information on admissions for respiratory and cardiovascular issues. During smoke days—which carry fine particulates common in wildfire smoke—the researchers found there was a 1% increase in cardiovascular hospitalizations for older adults. Asthma-related hospitalizations were even higher, with an increase of almost 7% compared to nonsmoke days.
“When you’re exposed to that level of concentration of particles and gases, your first [interaction] is with the breathing mechanism,” says Rappold. She adds that their research shows wildfire smoke, and the particular combination of particles and gases that it contains, can create a pretty high health risk for older people.
And more smoke equals more hospitalizations. “For every 10-microgram increase, the respiratory risk increases by 7%,” says Rappold.
Reid points out that the current study shows an increased risk for Medicare-age people. “Would we expect to find similar impacts of fine particulate matter both during and outside of wildfires on the respiratory health of working age adults and children?”
She says that at the moment there is less understanding about minor health impacts from smoke such as experiencing more coughing or other symptoms that don’t require a trip to the doctor.
The prevalence of wildfire smoke days is bound to increase, says Reid, and increases in air pollution are happening in areas affected by the fires. But it’s not just people in the western United States who are at risk. “We also know that air pollution from wildfires in the West can reach population centers on the East Coast, thus affecting all Americans to some extent,” says Reid. “As we go forward…wildfire smoke is going to [be] a larger and larger part of the air pollution we are exposed to.”
—Sarah Derouin (@Sarah_Derouin), Science Writer