Climate change is reversing previous gains in air quality; fires are most to blame for this

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

“The air quality really shows how the changing climate is felt by individuals.”

A hotter planet sets the stage for more wildfire smoke and amplifies the chemical reactions that lead to smog. That means the game is changing when it comes to preventing pollution in the future. After decades of success in reducing pollution from smokestacks and tailpipes, climate change is wiping out some of these gains.

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

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The group’s latest work shows that about 10 percent of U.S. properties (approximately 14.3 million) have been experiencing days when air quality is considered “unhealthy” for a week or more due to particulate matter pollution. particles, also called soot. Nearly half of these properties fare much worse, experiencing two weeks of unhealthy air quality days.

To find out, First Street looked back at data from the Environmental Protection Agency’s network of air quality sensors across the country. 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 over 30 years, the length of an average mortgage. According to First Street, air quality could return to 2004 levels by 2054 on its current trajectory, “wiping out 20 years of air quality improvements.” A further 1.7 million properties are expected to experience ten or more days of poor air quality each year from both soot and smog – an increase of 15 per cent from today.

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

Hot, dry conditions also cause the land to burn. Fire is the leading cause of air quality deterioration due to climate change, the report finds. It’s especially egregious in the western US, where the number of days with poor air quality increased by a whopping 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 when the index value is considered at least “unhealthy for sensitive groups” — an orange day. Red days are ‘unhealthy’, purple is ‘very unhealthy’ and maroon is considered ‘dangerous’. Based on the highest daily soot levels in the US, the researchers found that the average highest value has increased from orange to red since 2000.

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That generally explains the peak levels of particulate pollution during specific events such as forest fires. The health risks of sudden, short periods of pollution are different from those of persistent exposure to pollution from, for example, living along a busy highway. Health risks, including problems related to respiratory and cardiovascular disease, increase with chronic exposure.

“For example, if you have more fires but less pollution the rest of the year, you will see these acute effects increase, but they will be offset by a decrease in chronic effects,” said Drew Shindell, a professor of earth sciences at the University of California. Duke University, which studies climate change and air quality but was not involved in the First Street report.

Shindell also points out that there is still the possibility of changing the trajectories set out in the report. Just as the Clean Air Act led to major improvements in air quality between the 1970s and 1990s, the U.S. now has an opportunity to take action. Cleaning up pollution will simply have to look different for policymakers than it used to, both Shindell and Porter say.

“The job of someone as an air quality regulator is changing because it used to be that 100 percent of your focus was on emissions from human activities – so you would be concerned about power plants, industry and motor vehicles,” says Shindell. “We have kept a lot of these things under control. But we have not done a good job of controlling greenhouse gases.”

In other words, to get soot and smog under control, regulators will also have to prioritize reducing other pollutants – the carbon dioxide and methane emissions that cause climate change. They will also have to think about issues such as forest management to better control forest fires. All of which links the local effects of air pollution to what’s happening in the wider world, in addition to concerns about your neighbours’ emissions. Last year, wildfires in Canada sent a plume of smoke into the northeastern US, briefly giving New York City the title of worst air quality in the world.

To view historical data and forecasts for future air quality in your area, consult First Street’s online tool at It uses First Street’s peer-reviewed models to predict risks related to flooding, fire, heat and now air quality. It will show how a property compares to others in the US when it comes to local air quality, what sources of pollution are nearby, and how many days of poor air quality you can expect in the area now and in the future.

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