Wildfires in Canada led to dangerous air quality in parts of the US for the first time. See the affected areas

By Annette Choi and Krystina Shveda, CNN

(CNN) — Cities across the US, particularly those in California where wildfires are common, are often exposed to lower air quality due to a mix of urban pollution and weather effects. But even some rural areas of the country known for their pristine air reached dangerous pollution levels this summer.

So far in 2023, 19 counties in 11 states had days with “very unhealthy” and “hazardous” air quality — given at least a “code purple” alert on the US Environmental Protection Agency’s Air Quality Index — for the first time, a CNN analysis of EPA data shows.

The EPA advises everyone — including healthy people — avoid outdoor activities and close windows and doors when air quality is deemed a code purple, or worse, maroon.

Code red, an alert level below purple, is when air quality may cause serious health effects for sensitive groups, including children and the elderly.

More than a third of Americans — 119.6 million people — live in places with deteriorating levels of ozone or particle pollution, according to a recent report by the American Lung Association. Nearly 8.7 million adults and 1.7 million children with asthma and more than 6.6 million people with cardiovascular disease live in counties with the most air pollution, the report found.

Hazardous air from intense Canadian wildfires

This summer, Canadian wildfire smoke extended to the United States, causing widespread and alarming levels of air pollution.

“The increased purple air days that you saw this year, probably 100% of those were attributable to the [Canadian] wildfires,” Chet Wayland, director of the Air Quality Assessment Division, told CNN.

Seven of the eight North Dakota counties that have ever recorded code purple status or higher over a 24-hour period did so for the first time this May, the start of this year’s Canadian wildfire season, a CNN analysis of the EPA data found.

On the morning of May 17, the AQI was so high that Ryan Mills, manager of ambient air monitoring at the North Dakota Department of Environmental Quality, thought the air quality analyzers were malfunctioning.

“We had seen numbers like I’ve never seen before on our monitors, and it just progressively got worse,” Mills told CNN.

North Dakota residents don’t have to worry about bad air quality under normal circumstances, he said.

“North Dakotans enjoy some of the cleanest air in the nation. And we pride ourselves on that,” Mills said.

At least 195 counties in 25 states had code purple or maroon air quality days in 2023 through the end of August. Nineteen experienced those levels for the first time, according to the same data.

A majority of the 19 counties affected are located in states that aren’t typically impacted by unhealthy air conditions, including those in Idaho, Illinois, Indiana, Iowa, Montana, North Dakota, Oklahoma and Wisconsin, the CNN analysis found.

Because air quality can shift throughout the day, and EPA data captures a 24-hour air quality average, counties where air quality was dangerous for shorter bursts of time were not counted.

On June 8, when smoke from the Canadian wildfires rolled into the US capital, Washington, DC was under its first-ever code purple alert. But because the code purple alert did not last long enough over a 24-hour average, DC was not included in the EPA dataset.

By mid-September, more than 42 million acres of the country had burned, which is comparable to the size of Florida, according to Canadian Interagency Forest Fire Centre data. More acres have burned so far in 2023 than in any of the past 40 years of available data.

Wildfires are spreading so much that national resources available to fight them have until recently been officially declared “inadequate” and are still insufficient now.

The intense wildfire season resulted in a record 410 megatonnes of carbon dioxide emitted into the atmosphere, nearly a third of this year’s emissions from wildfires globally, according to an analysis by the Copernicus Atmosphere Monitoring Service.

Climate change-driven wildfires threaten to stall progress on air quality

In the years before the Clean Air Act Amendments of 1990, a renewed nationwide effort to address urban smog, ozone pollution caused frequent code purple days.

1988 was a particularly bad year for air pollution, especially in the Northeast, with more than 2,500 code purple days logged across the nation.

“That was one of the premier ozone episodes in the country,” Wayland told CNN.

The combination of stagnant air, warm temperatures and pollution from loosely regulated motor vehicles “cook[ed ozone] like on a stove,” he said.

Although ozone-driven air pollution fell dramatically across much of the United States, thanks to local and international regulation, smoke from wildfires has undone some of that progress.

As climate change intensifies, exposure to higher air pollution levels from wildfires coupled with urban pollution — both in the United States and Canada — will not only lead to short-term health effects but also reduce life expectancy, according to Christa Hasenkopf, director of air quality programs at the Energy Policy Institute at the University of Chicago (EPIC).

“In regions where we expect more wildfires, local plans for dealing with them are going to be important,” Hasenkopf told CNN.

This includes how schools are preparing indoor air quality and whether public spaces are adequately prepared for these scenarios.

Research by the American Lung Association found that people of color and those with lower incomes are at a disproportionately higher risk for illness from air pollution.

Earlier this year, the EPA proposed strengthening air quality standards by lowering the allowed annual concentration of PM 2.5 – the tiniest and most insidious air pollutant — closer to the latest, lower WHO guidelines. This could gain a combined 3.2 million life years across the United States, according to calculations by EPIC.

“Ultimately, it comes down to reducing carbon emissions if we want to reduce the number of wildfires caused by climate change, and that’s a collective action,” Hasenkopf said.

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