Wildfire Smoke Is Smothering the US—Even Where You Don't Expect It

America is on fire … again. More than a million and a half acres are burning in 15 states, from Arizona to Alaska. More than 3,000 firefighters are working to contain the Mendocino Complex Fire 100 miles north of San Francisco, now the largest in California history, and over the weekend, lightning strikes sparked dozens of new wildfires across the state of Washington. Near Mount Shasta, the deadly Carr Fire has so far incinerated 1,077 homes, forced mass evacuations, and killed eight.

Putting a few hundred miles between you and combustion country certainly confers some measure of safety. But not as much as you might think. While wildfires are geographically limited by nearby fuel sources, wildfire smoke goes wherever the wind takes it. Carried on eastward-flowing air currents, dangerous particulate matter from wildfires is increasingly smothering large swathes of the US, causing health scares wherever these air pollution spikes hit. Welcome to the United States of Smoke.

“Minnesota actually gets just about the most smoke days of any state in the US, you just don’t notice it,” says Nolan Miller, an economist at the University of Illinois at Urbana-Champaign who studies the deadly health impacts of temperature and weather extremes on the elderly. In new research, his group discovered that smoke shocks can also kill. More than 1,000 people die each year from downwind exposure, according to Nolan’s analysis, which is detailed in a working paper. Smoky days also sent more people to emergency departments and doctor’s offices than on days without smoke, especially folks with cardiovascular or respiratory conditions. “The key message of our research is that the bulk of the health burden of wildfires is not felt by people living really near the fire, but rather, on people hundreds or even thousands of miles away from the source,” says Eric Zou, an economist who led the satellite data analysis.

Historically, it’s been difficult for researchers to conclusively connect wildfire smoke with specific health outcomes because of patchy data—fires tend to occur in rural areas that often lack air pollution monitoring coverage and where few people live. But satellites are beginning to change that.

Using smoke plume image data from the National Oceanic and Atmospheric Administration, Miller’s group derived a daily smoke exposure status for every zip code in the US for every day between August 2005 and December 2013. By linking this geographic smoke score to air pollution monitoring data and deidentified billing records for every Medicare beneficiary over the same time period, they were able to construct an eight-year, day-by-day look at how the country’s elderly fared during smoke shocks—sometimes down to a few square miles. Miller says it’s the first national-scale study of wildfire smoke health impacts using satellite data, though he stresses that the results are just preliminary.

But other scientists have found evidence that the wildfire smoke public health problem is only going to get worse as the west gets hotter and drier. A 2016 study predicts that climate change will drive almost 60 percent more “smoke waves”—or multiple days of high particulate pollution from wildfires—across much of the US by 2050.

Demographic shifts are also raising the stakes. More people are living at the wildland-urban interface, where wildfires are deadliest. A recent analysis of US Census data found that 43 percent of all new houses built between 1990 and 2010 were constructed in the WUI. Then there’s the aging Boomers. By 2050, an estimated 83.7 million people over the age of 65 will call the US home, nearly doubling the current population—and a paper published in April found that bad smoke days during California’s 2015 wildfire season caused spikes in emergency room visits, with the most pronounced impact on patients over 65. “It was the older population that was really driving that effect,” says Ana Rappold, an epidemiologist at the Environmental Protection Agency and an author on the study.

Most of those ER visits were made by people with cardiovascular conditions. And unlike folks who suffer from respiratory ailments like asthma and COPD, people with pre-existing heart issues aren’t particularly aware of how bad the smoke can be for them, as a recent study by researchers at the Centers for Disease and Control concluded. To combat these and other gaps in public understanding, Rappold is leading up a citizen science project at the EPA to teach people about the dangers of wildfire smoke.

Last August, her team released an app called Smoke Sense, which asked users to answer questions about conditions in their zip code, any symptoms they might be feeling—runny nose, coughing, chest pain, anxiety—and what they’re doing to reduce their exposure. In the 2017 pilot season about 5,000 people launched the app more than 50,000 times, according to Rappold. Her team is making that data available to teachers, as part of a STEM curriculum to help kids learn about smoke and health.

They also expect to release a newer, slicker version in the next few weeks, which will provide information about local air pollution and a 24-hour smoke prediction forecast. “The hope is that a user would be able to use the Smoke Sense app in the same way that we use weather maps,” says Rappold. “You can see what the air quality is now and what it is likely to be in the near future so it can help you plan your day.” So far, Smoke Sense has revealed an unsurprising truth; that people only take action to stay out of the smoke once it starts to make them feel really crappy. With the 2018 fire season already outpacing last year by 500,000 blazing acres, it’s never too early—and you’re never too far away—to stock up on those N95 masks.