Wildfires are sinking Spokane air quality over the last decade

October 1, 2021 6:11 PM

Matt Gray,

Posted: October 1, 2021 6:11 PM

by Matt Gray

SPOKANE, Wash. — Wildfire season is coming to an end in the Northwest. While there’s plenty of mop-up remaining for fire crews this October, wildfire smoke and poor air quality are largely in the rearview until next summer. The Spokane Regional Clean Air Agency said on Friday that the city had eight days with unhealthy air because of wildfire smoke this year. Air quality has to average at least 100 on the Air Quality Index for 24 hours to be considered an unhealthy day.

Modern air quality measurements (PM2.5) go back to 1999. 2021 had the fourth-highest number of unhealthy days in the 22-year record. Before 1999, less accurate standards of measurement were in place. Even so, the Spokane Regional Clean Air Agency says there were no significant wildfire smoke events in Spokane dating back to the 1970s. Perhaps then the last period of significant fire in the region’s history was over 100 years ago. This includes the Great Fire of 1889 and the Big Burn of 1910.

If we just look at the modern data, there is a stark difference between the last two decades when it comes to wildfire smoke. In the past 10 years, smoke is hanging around Spokane longer and is leading to more days with unhealthy air. Research shows hospitalizations for respiratory issues can rise up to 7 percent during and after days with unhealthy air quality.

From 1999 to 2011 there were zero days where wildfire smoke kept air unhealthy for 24 hours. In 2012 there were two and there was a single day in 2014. Things changed dramatically beginning in 2015 when thirteen days reached the unhealthy threshold because of wildfires. Since 2015, Spokane averaged eight unhealthy smoke days per year. Looking across the Northwest as a whole, air quality got 6 percent worse between 2000 and 2020 according to the EPA.

24 hour periods of unhealthy air quality are much higher in Spokane since 2011

Unhealthy air quality days because of smoke are increasing in Spokane.

Acres burned and unhealthy air quality days because of wildfire are both increasing

Acres burned in WA and unhealthy air quality days due to smoke in Spokane have both increased in the 2010s

While many factors play into where wildfire smoke goes and how long it lingers, more fires mean more opportunities for smoke and unhealthy air. In the state of Washington, acres burned by wildfires are going up too.

washington state acres burned by wildfire last 20 years

The average acres burned in WA is 3x higher the past 10 years than the decade prior.

Some of the reasons why fires and smoke trended up over the past decade are due to natural variations and bad luck. Like most things in the natural world though, climate change also plays a role. Rising average temperatures and drying weather in the summers are helping to create more fire weather days which leads to more fire growth and smoke production. This isn’t just an Inland Northwest problem either. Parts of five western states now see a significant number of smoky days each fire season.