Climate change is erasing previous gains in air quality — fires are mostly to blame

Air quality in the United States is expected to decline in coming decades, returning to mid-2000s levels due to climate change, according to a new report. The report is accompanied by an online tool that allows users to zoom in on individual properties to see what type of air quality residents might experience there in the future. It paints a picture of a changing landscape for regulators, who will have to adapt to evolving threats.

“Air quality really highlights how climate change is experienced by people. »

A warmer planet paves the way for more wildfire smoke and speeds up the chemical reactions that lead to smog. This means that the game is changing when it comes to how to prevent pollution in the future. After decades of success in combating pollution from smokestacks and tailpipes, climate change is erasing some of those gains.

“Air quality really highlights how climate change is experienced by individuals,” says Jeremy Porter, lead author of the report published by the nonprofit research organization First Street Foundation. “Very severe flooding and very severe forest fires are relatively rare, [although] we see them more and more often. But something like poor air quality, it doesn’t just affect the low-lying houses on the street, it affects everyone in the community,” Porter says. First Street has previously published research and online tools to assess flood, fire and heat risks for individual properties.

As anthropogenic emissions decline, climate impacts such as concentrations of fine particle pollution will worsen.
Image: First Street, EPA: non-FRM/FEM PM2.5 hourly mass

The group's latest work shows that about 10% of properties in the United States (about 14.3 million) already face a week or more of days where air quality is considered “unhealthy” due to pollution by fine particles, also called soot. Nearly half of these properties are far worse, experiencing two weeks of poor air quality days.

To learn more, First Street examined data from the Environmental Protection Agency's network of air quality sensors across the country. Porter and his colleagues were then able to combine this 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 life of a typical mortgage. On its current trajectory, air quality in 2054 could return to being as bad as it was in 2004, according to First Street, “wiping out 20 years of air quality improvement.” An additional 1.7 million properties are expected to experience 10 or more days of poor air quality per year due to soot and smog, an increase of 15% from today. today.

This upward trend reflects a “climate penalty”, indicates the report. Smog, or ground-level ozone, in technical terms, is produced by a photochemical reaction in which nitrogen oxides and volatile organic compounds react with each other under sunlight. As a result, smog can be worse on hot, sunny days. Climate change causes heat waves longer and more intense, and pollution is part of this problem.

Hot and arid conditions also encourage land to burn. According to the report, fire is the main driver of air degradation linked to climate change. This is particularly evident in the western United States, where the number of days with poor air quality increased by up to 477% between 2000 and 2021.

This figure is based on the EPA's color-coded Air Quality Index and counts the number of days the index value is at least considered “unhealthy for sensitive groups” – one day orange. Red days are “unhealthy,” purple days are “very unhealthy,” and brown is considered “dangerous.” By averaging the highest daily soot levels in the United States, the researchers found that the highest average value has changed from orange to red since 2000.

Average maximum values ​​of fine particle pollution between 2000 and 2001.
Image: First Street, EPA: non-FRM/FEM PM2.5 hourly mass

This generally explains peak levels of particle pollution during specific events like wildfires. The health risks from sudden, brief periods of pollution are different from those from persistent exposure to pollution from living near a busy highway, for example. Health risks, including problems related to respiratory and cardiovascular diseases, increase with chronic exposure.

“If there are, say, more fires but less pollution the rest of the year, you will see an increase in these acute effects, but they will be offset by a decrease in the chronic effects,” says Drew Shindell, professor in Earth Sciences at New York University. Duke University which studies climate change and air quality but was not involved in the First Street report.

Shindell also emphasizes that it is still possible to modify the trajectories laid out in the report. Just as the Clean Air Act led to significant improvements in air quality between the 1970s and 1990s, the United States has an opportunity to act now. According to Shindell and Porter, the fight against pollution will have to be different than it has been before for policymakers.

“The job of an air quality regulator is changing, because previously all your focus was on emissions from human activities – so you worry about power plants, industry and motor vehicles,” says Shindell. “We've done a good job of controlling a lot of these things. But we haven't done a good job controlling greenhouse gases.

In other words, to get soot and smog under control, regulators will also need to prioritize reducing other pollutants – the carbon dioxide and methane emissions that cause climate change. They will also need to think about things like forest management to better control wildfires. All of this connects the local effects of air pollution to what's happening around the world, plus worrying about what your neighbors might be emitting. Last year, wildfires in Canada sent a plume of smoke toward the northeastern United States, allowing New York City to briefly hold the title for worst air quality in the world. world.

To view historical data and forecasts of future air quality in your area, you can visit First Street's online tool at It uses First Street's peer-reviewed models to predict flood, fire, heat and, now, air quality risks. It will show how a property ranks compared to others in the United States when it comes to local air quality, what pollution sources are nearby, and how many days of poor air quality there are in the region is to be expected now and in the future.

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