Air quality in the US is projected to backslide in the coming decades, landing back where it was in the mid-2000s as a result of climate change, according to a new report. The report comes with an online tool for users to zoom in on individual properties to see what kind of air quality residents might experience there in the future. It paints a picture of a changing landscape for regulators, who are going to have to adapt to evolving threats.

A hotter planet sets the stage for more wildfire smoke and supercharges the chemical reactions that lead to smog. That means the game is changing when it comes to how to prevent pollution in the future. After decades of success reining in pollution from smokestacks and tailpipes, climate change is erasing some of those gains.

“Air quality really highlights how the changing climate is being felt by individuals,” says Jeremy Porter, lead author of the report published by the nonprofit research organization First Street Foundation. “Really bad floods and really bad wildfires are relatively rare, [although] we see them more and more often. But something like poor air quality, it doesn’t just affect the low houses on the street, it affects everybody in the community,” Porter says. First Street has previously released research and online tools for assessing flood, fire, and heat risks for individual properties.

The group’s latest work shows that around 10 percent of properties in the US (roughly 14.3 million) already have to cope with a week or more of days when air quality is considered “unhealthy” due to fine particle pollution, also called soot. Nearly half of those properties have it much worse, experiencing two weeks of unhealthy air quality days.

To suss that out, First Street looked back on data from the Environmental Protection Agency’s network of air quality sensors across the nation. Porter and his colleagues were then able to combine that data with First Street’s existing peer-reviewed fire and heat models to make predictions about the future.

First Street modeled air quality 30 years from now, the length of a typical mortgage. On its current trajectory, air quality in 2054 could revert back to how bad it was in 2004, according to First Street, “wiping away 20 years of air quality improvements.” An additional 1.7 million properties are expected to face 10 or more poor air quality days a year from both soot and smog — a 15 percent rise from today.

That upward trend reflects a “climate penalty,” the report says. Smog, or ground-level ozone, in technical terms, is produced through a photochemical reaction where nitrogen oxides and volatile organic compounds react with each other in sunlight. As a result, smog can be worse on hot, sunny days. Climate change is making heatwaves longer and more intense, and pollution is part of that problem.

Hot, arid conditions also prime the land to burn. Fire is the primary driver of worsening air with climate change, the report finds. It’s particularly egregious in the Western US, where the number of poor air quality days grew by as much as 477 percent between 2000 and 2021.

That figure is based on the EPA’s color-coded air quality index and counts the number of days in which the index value is at least considered “unhealthy for sensitive groups” — an orange day. Red days are “unhealthy,” purple are “very unhealthy,” and maroon is considered “hazardous.” Averaging the highest daily soot levels across the US, the researchers found that the average highest value has risen from orange to red since 2000.

That generally accounts for peak levels of particle pollution during specific events like wildfires. The health risks from sudden, brief periods of pollution are different than those linked to persistent exposures to pollution from living next to a busy freeway, for example. Health risks including problems related to respiratory and cardiovascular disease increase with chronic exposure.

“If you have, say, more fires but less pollution in the rest of the year, you’d see these acute effects increase, but they will be offset by decreases in chronic effects,” says Drew Shindell, a professor of earth science at Duke University who studies climate change and air quality but was not involved in the First Street report.

Shindell also points out that there’s still the opportunity to change the trajectories laid out in the report. Just like the Clean Air Act led to big improvements in air quality between the 1970s and 1990s, the US has the opportunity to act now. Cleaning up pollution is just going to have to look different than it used to for policymakers, both Shindell and Porter say.

“The job of somebody like an air quality regulator is changing because it used to be 100 percent of your attention would be on emissions from human activities — so you’d worry about power plants, and industry, and motor vehicles,” Shindell says. “We’ve done a good job of controlling many of these things. But we haven’t done a good job of controlling greenhouse gases.”

In other words, to get soot and smog under control, regulators will also have to prioritize slashing other pollutants — carbon dioxide and methane emissions that cause climate change. They’ll also have to think about things like forest management to better keep wildfires under control. That all links the local effects of air pollution to what’s going on in the wider world, on top of worrying about what your neighbors might be emitting. Last year, wildfires in Canada sent a plume of smoke down to the Northeastern US, causing New York City to briefly hold the title for worst air quality in the world.

To see historical data and forecasts for future air quality in your region, you can check out First Street’s online tool at RiskFactor.com. It uses First Street’s peer-reviewed models for forecasting flood, fire, heat, and now, air quality risk. It’ll show how a property ranks compared to others in the US when it comes to local air quality, which sources of pollution are nearby, and how many days of poor air quality in the area to expect now and in the future.