A suffocating layer of pollution-bound smog settled over Minneapolis last month, blanketing the city in its worst air quality since 2005. A temperature inversion acted like a ceiling, trapping tiny particles released by idling engines and overworked heaters in a mesh that enveloped the skyline. That haze came amid the warmest winter on record for the Midwest. Warmer temperatures melted what little snow had fallen and released moisture that helped further trap pollution.
Although summer pollution of wildfire smoke and ozone getting more attention, climate change is making these kinds of winter inversions increasingly common – with alarming results. One in four Americans are now exposed to unhealthy air, according to a report by First Street Foundation.
Jeremy Porter, head of research on climate implications at the non-profit climate research firm, calls it increase in air pollution a “climate penalty,” roll back improvements made over four decades. On the West Coast this tipping point was passed about 10 years ago; air quality across the region has consistently deteriorated since 2010. Now a wider swath of the country is beginning to see worsening conditions. During Canada’s boreal wildfires last summer, for example, millions of people from Chicago to New York suffered some of the the worst air pollution in the world. It was an unprecedented wave that saw the average person exposed to more small particles than at any time since the detection started in 2006.
This is a preview of more to come.
Since Congress passed the Clean Air Act in 1970, federal legislation regulated all sources of emissions, successfully reducing pollution. Between 1990 and 2017, the number of particles smaller than 2.5 micrometres, known as PM2.5, fell 41 percent. These particles form a significant threat because they can burrow into the lungs and enter the bloodstream. Exposure can cause heart disease, strokes, respiratory diseases such as lung cancer and premature death. Such concerns have the Environmental Protection Agency to tighten pollution limits for the first time in a decade, lower the limit from 12 micrograms per cubic meter of air to 9 earlier this month.
But a stricter standard probably won’t solve the problem, said Marissa Childs, a postdoctoral researcher at Harvard University’s Center for the Environment. That’s because the agency considers wildfires an “exceptional event,” and that’s why exempt from the regulation. Yet about one-third of all particulate pollution in the United States now comes from here wildfire smoke. “The Clean Air Act is challenged by smoke,” she said, both because wildfires defy the EPA’s traditional enforcement mechanisms, and because capacity to travel long distances. “Are we going to start saying that New York is out of compliance because there was a fire in California?”
To get a better idea of how growing exposure to air pollution could affect the public, First Street used wildfire and climate models to estimate what the air might look like in the future. (Although his researchers relied on Childs’ national database of PM2.5 concentrations(were she not otherwise involved in First Street’s report.) They found that by 2054, 50 percent more people, or a total of 125 million, will experience at least one day of “red” air quality with an air quality index of 151-200, a level considered risky enough that everyone should reduce their exposure. “We’re essentially adding additional premature deaths, adding additional heart attacks,” Porter said during a meeting about the report. “We lose productivity in the economic markets by losing additional working days outside.”
First Street now has its air quality forecasts at a online tool enabling anyone to search for climate risks by home address. As extreme heat increases ozone and changing conditions exacerbate wildfires, it shows just how uneven the impact will be. While New York City is expected to see eight days a year with the air quality index at an unhealthy orange, which is a in the range of 101 to 150, a two-day increase, the Seattle metropolitan area is expected to see nearly two additional weeks of poor air. “That’s two weeks out of only 52,” said Ed Kearns, First Street’s chief scientific officer. “Twelve more days of being stuck in your house, not being able to go outside – worrying about the health consequences.”
Just as the sources of pollution are unevenly distributed, so is people’s ability to respond. “People across the board are looking for air quality information,” Childs said, for example by searching online about pollution levels on particularly smoky days. But not everyone has the same ability to make choices to protect themselves. Childs co-wrote a 2022 Nature Human Behavior paper who found behavioral responses to smoking—for example, staying indoors or driving to work rather than waiting for the bus—were strongly correlated with income. If it’s left up to individuals, she says, “the people who have the most resources will be the most protected, and we’re going to leave a lot of people behind.”
In a collaboration with real estate company Redfin, First Street found early signs that people are already leaving areas with poor air quality. Tarik Benmarhnia, an environmental epidemiologist at the University of California, San Diego, disputes these conclusions, but says many variables affect both air quality and residential mobility, such as income and home prices. Air pollution is a notoriously complex subject—difficult to predict even a week out, much less speculate on what might happen in three decades. “I think the most critical problem is a total absence of any discussion of uncertainty,” he said.
He also worries that First Street’s risk index may inadvertently magnify these distinctions of privilege. If potential homeowners use the database to avoid areas based on the report’s predictions, property values in those regions could drop accordingly, reducing tax bases and reducing the ability to provide services such as common clean-air rooms during smoking events. “It can act like a self-fulfilling prophecy.”
Benmarhnia notes that traditional sources of air pollution, such as factory emissions, show a very consistent relationship between socioeconomic status, race, and higher pollution levels, a pattern that repeats itself across the country. Smoke and ozone do not tend to follow these social gradients because they spread so widely. “But smoke from wildfires doesn’t come on top of anything, it’s on top of existing inequities” such as access to health care, or jobs that increase exposure to the outdoors, he said. “Not everyone starts from the same place.” Benmarhnia recently published a paper finding that wildfires, in conjunction with extreme heat, exacerbate the risk to cardiovascular systems. But the people most likely to be harmed by these synergies live in low-income communities of color.
“The thing about air pollution is that there’s only so much you can do at the individual or civil society level,” says Christa Hasenkopf, the director of the Clean Air Program at the Energy Policy Institute at the University of Chicago. “This is a political and social issue that needs to be tackled at the national level.” The university’s Air Quality Life Index measure how air pollution contributes to early deaths around the world, with the aim of providing a clearer picture of the health gaps. “The size of the impact on life expectancy in two relatively geographically close areas can be surprising,” she says, such as between Eastern and Western Europe.
For her part, Hasenkopf is enthusiastic about First Street’s air quality report, hoping it will help highlight some of these disparities. Although 13 people die every minute of air pollution, funding for cleaner air solutions remains limited. “The disconnect between the magnitude of the air pollution issue and the resources we devote to it is quite staggering,” Hasenkopf said.
