April 25, 2019

Is Washington State Air Quality Getting Better or Worse?

Has air quality in Washington State gotten better or worse during the past 15  years?  

The answer:  generally better except during wildfire smoke periods during the summer.

Let me show you the data.  I started at a wonderful web site run by the Puget Sound Clean Air Agency that allows one to plot all kinds of air quality indices.   I plotted PM2.5 concentrations--the concentrations of particles below 2.5 microns (millionths of a meter).  These particles are the kind that can move deep into your lungs, causing all kinds of problems.  And high concentrations are associated with poor visibility.

Here is the plot of maximum daily values in Seattle from August 2001 to yesterday.  The vertical lines are on January 1st of each year.  The first thing you notice is that August 2018 had the biggest peak on record (about 150)--that was the terribly smoky period of August 21-22.   Next came the wildfire smoke period in 2017. 

Look closer and you will notice that earlier in the period, the worst air pollution was generally during the winter--often when we had high pressure and low-level inversions.  The source of the pollutants were mainly from combustion (trucks, cars, ships) and wood-burning in stoves and fireplaces.

Look even closer and you will notice that the pollution levels were generally HIGHER earlier in the century.   So our air has gotten generally better except for some wildfire spikes during summer. 

A good way to see this is to plot the monthly small particle values at Seattle (below).  The general levels are clearly lower after approximately 2007, with the sole exceptions of two summer months in 2017 and 2018....which included the few days of wildfire smoke in Seattle.

The annual average concentrations, which include everything, suggest a similar pattern, including a minimum during the economic slowdown in 2008!  Less trucks and cars on the road, I assume. 

Even with the wildfire smoke incidents, our air is overall better now than before 2007.  As Mr. Spock would say...fascinating.

What about Spokane, in the eastern part of our state?  A similar story.  They had an additional wildfire smoke spike in 2015 (a big year for wildfires).    They are closer to more of the wildfire sites than Seattle.

Spokane's monthly pattern is similar--general improvement over the years except for the transient smoke periods during summer.  But their annual amounts (not shown) have gotten worse because they are more exposed to the summer wildfire smoke.

An excellent paper examining this issue was completed by Dr. Crystal McClure and Professor Dan Jaffe of UW Bothell.  They compared the trends of small particles in the air for the Pacific Northwest and the rest of the country and plotted this (see below) for various concentrations (that is what the quantile business is below....the high concentrations are in the high quantiles) 

For the rest of the U.S. the particles are declining at ALL concentrations.   But this is NOT true for the Northwest!   We ARE getting better for low and moderate concentrations of particles, but are having more days of the HIGHEST concentrations--that is the influence of the wildfires.

They even plotted a map of the change in the trend of very large concentrations of small particles (the top 2%  each year) for 1988-2016, which is shown below (note they did not include 2017 and 2018).   Most of the nation has shown a decline in high concentrations of the small particles (blue and green colors), except for a broad area of the Northwest, where increased wildfire smoke is having an impact.

Finally, why is our air quality getting much better, with the exceptions of the summer wildfires? I talked this over with Eric Saganic, an air quality expert at Puget Sound Clean Air Agency.   He told me there are several reasons: 

1.   Trucks have become MUCH cleaner (starting around 2007-2008), with new ones emitting about 1/50th the amount of particulates.
2.    Car emissions have declined as gas mileage has improved, more hybrid vehicles have hit the road, and engine technology has been enhanced.
3.   Ships in our harbor are using much cleaner, lower-sulfur fuels
4.  Wood burning for heat has declined and wood stoves have improved.
5.  More aggressive and effective burn bans by his organization and others when poor air quality situations threaten.

A huge advance in cleaning our air. 

Be we have to deal with the wildfire smoke, which means making the investments in dealing with our disastrously mismanaged forests east of the Cascade crest that have become overgrown and susceptible to large catastrophic fires due to nearly a century of fire suppression.  That means thinning, select harvesting, and prescribed fires during the spring and autumn to clear out the small stuff.  Such forest management has been terribly underfunded during the past decades, but some folks in DNR are starting to talk about it seriously.   It is time for an aggressive program to restore our forests to be like they were 150 years ago, which frequent fires east of the Cascades crest were the rule.


  1. Thank you, Cliff.

    Disastrously mismanaged forests, you can't say that often enough. There seems to be no zoning in place keeping home and landowners away from areas that are the domain of the forests where fires have always happened naturally. There are a number of business interests that profit from that mismanagement. The same goes for many locations in the country which have been terribly impacted by hurricanes and landslides. It so happens that prior to the disasters in Oso, Wa, and hurricanes Sandy in NY and Harvey
    in Texas, I read reports from scientists warning about the absence of any management regarding these locations.

  2. Twinkle, spot - on in your assessment. However, other than a few lonely outposts like this one, these subjects are rarely covered. It doesn't help matters when the government steps in to insure properties being built in high - risk areas, when regular insurers won't go near them.

  3. Cliff,

    I'm looking forward to your workshop next week!

    It's forest management's moment to garner funding for forest management improvements. Your blog provides justification. We'll see what happens. Keep up the good work.

  4. What I still marvel at, is how they allow private tree farm owners, like Pork Blakely, Hemphil-Oneil, Weyerhaeuser et al to do these MASSIVE slash burns. What is up with that? Last year, was awful for those down in the valley below me. The only thing that saved me from weeks of heavy smoke was wind direction and altitude.


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