Air quality from wildfire smoke expected to worsen in Seattle

Data: First Street Foundation; Note: Maximum count of days with unhealthy air quality from anywhere within each county; Map: Axios Visuals

King County residents are likely to get three full weeks of poor air quality days this year — a trend that's expected to get even worse in the coming decades, according to a new report. Why it matters: An increase in severe heat waves and large wildfires is dragging down air quality in Washington state and across the western U.S.

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• Unhealthy air limits people's ability to safely go outside or even open their windows, especially if they're children or have a medical condition like asthma .

By the numbers: King County is predicted to have 21 days this year with an air quality index over 100, a level deemed unhealthy for sensitive groups, per new research from the nonprofit First Street Foundation.

• That's on par with what the county saw in 2022, the most recent year of data posted by the Puget Sound Clean Air Agency . That year, local air quality ranked as the world's worst for multiple days because of wildfire smoke .
• By 2054, King County's number of days with unhealthy air could rise to 27, First Street predicts. That would be almost 30% more unhealthy air days.

Zoom in: Within Seattle city limits, the number of poor air quality days isn't expected to rise nearly as much over time. But in recent years, the Emerald City has already seen a large increase.

• First Street estimated that 15 years ago, Seattle's air quality reached "orange" levels that are unhealthy for sensitive groups only one day of the year.
• This year, the organization is predicting the city will see 10 of those days. That's expected to rise to 11 by 2054.

Data: First Street Foundation; Note: Maximum count of days with unhealthy air quality from anywhere within each county; Map: Axios Visuals

The big picture: Climate change is increasing the prevalence of two of the air pollutants most harmful to human health: particulate matter, commonly referred to as PM2.5 , and tropospheric ozone , the report finds.

• First Street's researchers found that the West will be hit particularly hard by increasing amounts of PM2.5 emissions as wildfires become more frequent and severe.

Threat level: Washington, Oregon and California are projected to see some of the worst air quality impacts, with Seattle flagged as one of several hot spots.

Of note: The report's conclusions flow from methods contained in peer-reviewed studies published by the coauthors. The report itself is not peer-reviewed, however.

What they're saying: The growing "climate penalty" of worsening air quality "is perhaps the clearest signal we've seen regarding the direct impact climate change is having on our environment," Jeremy Porter, head of climate implications at First Street, told Axios in an interview.

What we're watching: Projections suggest that PM2.5 levels will increase by nearly 10% over the next 30 years, Porter said.

• This would "completely" erase air quality gains made in the last two decades, he said.

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