Wildfire Smoke Is More Damaging to Respiratory Health Than Other Sources of Air Pollution

Smoke exposure was associated with more hospital admissions than equivalent amounts of non-wildfire emissions

A satellite image shows wildfire smoke over the west coast of the United States
A satellite image captured in September of 2020 shows how wildfire smoke blanketed the West Coast. Image by the European Space Agency under CC BY-SA 3.0 IGO via Wikimedia Commons

Pollution from wildfires has a greater impact on people’s health than similar levels of pollution from other sources, according to a study published on March 5 in the journal Nature Communications.

The study analyzed hospital admissions data in Southern California from 1999 to 2012 and found that air pollution from wildfires has a ten times greater impact on health than a similar amount of pollution from other sources. The 2020 fire season was California’s worst yet, with 4.1 million acres burned, and five of its six largest fires on record. One-in-seven Americans faced dangerous levels of pollution for at least a day, and smoke from 20 major fires turned the Bay Area’s skies eerily orange for days. The new research raises concerns about whether wildfire smoke should be treated differently than other pollution.

“We know wildfires are going to become more extreme, due to climate change,” says University of California San Diego environmental health scientist Rosana Aguilera, who co-authored the new research, to Dani Anguiano at the Guardian. “And it’s important that we start to reckon with the health effects of that.”

Aguilera and the research team focused on levels of PM2.5 pollution, which refers to extremely small particles of pollution that are the main component of wildfire smoke. The particles are dangerous because they are so small. When a person inhales the tiny particles, the pollutants can slip through the natural defenses of the nose and lungs and enter the bloodstream, eventually damaging vital organs, according to a statement.

Previous studies have shown in laboratory settings that PM2.5 pollution from wildfires is more dangerous than other pollution on an individual level, but the new study shows evidence of its effects in a real-world setting.

The study focused on Southern California, where the Santa Ana winds carry wildfire smoke and other pollutants over densely populated areas. They found that hospital admissions for respiratory problems, like asthma and pneumonia, rose by ten percent during periods when the region was covered by wildfire smoke. During periods when similar pollution levels came from other causes, hospital admissions rose by less than one percent.

“There’s no question it’s a huge air quality problem that has major health impacts,” says John Balmes, an expert in occupational and environmental medicine at the University of California San Francisco, to Paul Rogers at the Mercury News. “There was a ring of fire last year around the Bay Area. We are going to have to spend billions of dollars to maintain our forests better. It is going to take years. It can’t be done overnight.”

Research published last month showed that wildfire-related pollution accounts for half of the PM2.5 across the western United States, Kevin Stark reported for KQED at the time. Climate change has increased wildfire risk in the United States and extended California’s wildfire season. At the same time, aggressive wildfire repression has allowed dry undergrowth to pile up, which fuels stronger fires.

In addition to managing climate change, experts have recommended reintroducing controlled burns to forest management in order to prevent catastrophic, uncontrolled fires. (Native Americans in California have long practiced controlled burns to manage underbrush growth, and state officials are looking to learn from them, Lauren Sommer reported for NPR in August.)

Study co-author Tom Corringham, an economist at the University of California, San Diego, tells NPR’s Nathan Rott that the research highlights the need for better air monitoring systems and public health programs, like subsidies for the cost of air filters. But as the Guardian reports, the people who are most at-risk from the effects of dangerous smoke pollution are the people who work outdoors. Often this disproportionately affects low-wage farm workers and people of color in the state.

“In our region, the majority of workers have asthma. Their kids have asthma, their parents have asthma. This has been an ongoing crisis,” says Luz Gallegos, the executive director of Todec, which offers legal resources to immigrant workers in Southern California, to the Guardian. Gallegos adds that people who work on farms regularly breathe smog that is full of pesticides, and that they worked outdoors throughout the dangerous, smoke-saturated wildfire season last year.

“One woman in our community just collapsed in the field, as she was working,” says Gallegos to the Guardian. The woman not only has asthma, but also tested positive for Covid-19 at the hospital. “Thank God, she survived. These stories are very, very common.”