October 04, 2015

Puget Sound Winter Air Quality Has Greatly Improved

These days there is a lot of talk about environmental problems, but there is one great success story we should not forgot: the substantial improvement in air quality around the nation, and specifically here in the Puget Sound region.

Here is a plot of the levels of small particles (PM2.5, smaller than 2.5 microns), capable of moving deep into the lungs, at Kent, Washington (provided to me by Nick Bond, state climatologist) from 1990 to now during the winter.  You will note a big drop during the 1990s, with levels now a quarter of what they had been.
What about larger particles at Kent (PM 10)?  Major decreases!

Want to know about Seattle?  Huge drops in PM10 (see below).  The red lines shows the warming level of the national air quality standards.   Seattle exceeded in in the late 80s and early 90s.  Now we are well below.

Live in Tacoma?  Big improvements there as well.

Or consider the number of days of moderate or worse air quality over King County:  a big decline in the 1990s

I could show you many more statistics, but you get the picture: the concentration of small particles has radically lessened in our region.  A boon to the health of Puget Sound residents, particularly those that are sensitive to poor air quality.

So why has air quality gotten better?  There are many reasons.

Probably the most important is the reduction in wood burning by our local residents and better wood stoves.   We are simply burning less wood and fireplaces and wood stoves have been a huge source of particles and toxics.

Back in the 80s, the Seattle Times was FULL of ads for wood stoves.   Many new homes had wood fireplaces.   The situation is very different today.  The ads are gone.  Wood burning is less popular, and many homes have gas fireplaces.   Just as important, Federal and local regulations have required that new wood stoves are far less polluting.

A lot of credit should be given to local  and Federal air quality agencies such as Puget Sound Clean Air Agency (PSCAA), the State Dept. of Ecology, and EPA, who have worked aggressively to reduce emissions.   Only low-emission wood stoves are now sold as result of their actions.  When the meteorology is poor for dispersion of pollutants (weak winds, strong and low level inversion), agencies such as PSCAA call burn bans that restrict burning wood other than for primary heating.

Local, state, and Federal  agencies have also worked to reduce emissions from cars, trucks, and large vessels, in addition to lessening emissions from industrial sources.

Getting back to wood.  In general, it is a very dirty and polluting way to heat a home (see graphic from PSCAA).   Natural gas is hugely better and inexpensive natural gas has encouraged folks to use this fuel.

Meteorologically, we are now moving into the worst air quality season for home fireplace/stove smoke.   Nights are getting longer and cooler, so folks want to get the wood burning.  But this is also the season of strongest, low-level inversions, as relatively clear skies allow the surface to radiate heat to space, producing an inversion---warming of air with height.   Inversions are very stable and tend to act as atmospheric caps that keep pollutants, like smoke, near the surface.  Winds are also relative light this time of year, before the big storms approach.

Want a good example of a low-level inversion?   Consider this morning!  Here is the temperature plots with height at the Sand Point (Seattle) vertical profiler, run by the Puget Sound Clean Air Agency.  Large increase in temperature with height in the lowest several hundred meters of the atmosphere.  Pollutants will be trapped near the surface.  And air quality has declined at some locations around the Puget Sound region.
Some folks in rural neighborhoods love burning wood.   But during inversion situations, they end of seriously polluting their own air and that of their neighbors.  I can't tell you how many times I have seen situations like this, with dense smoke coming out of a fireplace that does not loft because of an inversion.  Not good.

The worst wood smoke air quality tends to be in valleys, where the smoke and low-level cool air below the inversion tends to pool.   Some of the low areas of Lake Forest Park, north of Seattle, are notorious.  What is happening there this morning with the strong inversion?  (see graphic of small particle levels).  Oh oh....bad news.  A spike in particle concentrations.

So the bottom line is that regional air quality has greatly improved, particularly in reducing small particle pollution.   But wood smoke is still a serious issue, particularly during inversion conditions and in valley areas.


  1. Same story in the lower mainland of SW BC. But it would be interesting to see NOX trends(especially in regions with high VW concentrations :)

  2. Any idea what caused the number of moderate air quality days to begin trending upwards after '98?

  3. I wouldn't consider electric heat clean as much of the electricity in our nation comes from burning coal.

  4. 60% of our electricity up here is hydro, and there's very little coal. The best way to heat in the PNW right now is heat pump, powered by electricity.

  5. All I can say is I'm glad for fewer migraine triggers floating around in the air (fine particulates are a trigger for me).

  6. Why the heck is burning wood still allowed? Particularly in summer, when my firebug neighbor thinks his outdoor fire pit is the duckiest thing on the planet earth?

    PS: He enjoys lighting fireworks on the fourth of July in Seattle...

    what a t*rd!!!

  7. Cliff, thank you for speaking to the health concerns of wood smoke. So many people still have a romantic view of burning wood.

  8. I agree that the wood burning situation has improved, both in terms of better stoves and more people being aware that a wood stove should be used for dry firewood, not green, wet wood or trash.
    It is interesting that you say that "probably" the improvement is caused by changes in wood burning. However, if you had a chart similar to the one you showed, but that also included the impact of the generation of the firewood, electricity, and oil; and also included the impact that vehicle emissions and industrial emissions have on our air quality; then I think that you would find that homeowner wood burning has very little impact compared to other polluters.

  9. Also included in any discussion on air quality should be the burning in our National forests by the forest service. BLM also burns slash piles. Once the burning bans are lifted huge brush piles are ignighted. Areas that have had forest fires are being cleaned up and burned. These fires put out huge volumes of wood smoke during times of inversion. These fires emit far more pollutant into the air than any wood stove. It all happens all at once as soon as burn bans are lifted every single year.

  10. I have several neighbors who burn trash in the fall and winter, which is choking and eyewatering and no doubt full of toxins. Wood smoke is an asthma trigger for me but is a deeply emotional comfort for most people. But what to do about the trash burners? Surely nobody likes the smell of burning plastic?

  11. Wood burning still needs to be allowed because some people, mostly in rural areas, don't have good heating or insulation in their homes, but have easy access to wood.

  12. Electric heat is probably the cleanest option here in terms of particulates, but until it's all from pollution-free sources (and it is not, coal is still at least part of the picture) it's dishonest to characterize it as "zero pollution" as that clean air agency graphic does.

  13. Ryan,

    I think the EPA lowered the level for "Moderate" in 1999 when they replaced the Pollutant Standards Index with the Air Quality Index. That's why there are more "Moderate" days.

  14. What about pellet stoves? I have been using one since 2002.

  15. I'm old enough to remember a polluted Lake Washington, and Lake Sammamish, accompanied by days when dread "smog" obscured the region, some days, and sometimes as dramatically, if not nearly as often, or severely, as it did L.A.

    Our air, and water, have definitely greatly improved.

    Long term forecast may show a mild storm on Columbus Day, Cliff.

    I'm old enough to remember 1962, too; Issaquah was a small town at that time, with remnants from the Great Depression, employment projects scattered around, including Memorial Stadium in downtown. The Columbus Day storm destroyed it. Compared to other damage it seemed irrelevant, but for this then boy who watched the entire roof of what was to me a real stadium, lifed up, and torn, from its posts, like an umbrella, and carried, and dropped, on the other side of the football field, the storm was made all the more memorable, and impressive.

  16. It is unfair to characterize all wood burning as bad. We heat our large home with our wood stove; we never have large smoke plumes as seen in the pictures in this post. We use a certified wood stove, only burn dry wood (no trash). We don't consider wood heat to be "romantic"; it's really a lot of work. But it is economical, and really not horrible environmentally if done correctly.

  17. Yes, it is ironic- and unfortunate- that the worst inversions all happen on the coldest nights.

    Not what I remember in New England. The wind howls all winter. Usually.

    But this year, Mother Nature gets the booby prize for pollution. I visited Lake Chelan in August. What a disaster! Couldn't see across the lake and the sun was barely visible at times.

  18. I'm sure the free market would have magically achieved the same thing without any stupid government regulations in the same timeframe, achieving the same benefits. Because the free market magically regulates itself, and people would have just spent their money on the stoves that didn't pollute as much. Because magic.

  19. I do miss seeing the "Split Wood Not Atoms" bumper sticker.

  20. Don't forget that extracting natural gas from the earth messes up the environment & climate (air AND water) in the places where that is occurring, and can't go on forever. Humans in cold places will be back to burning wood eventually, hopefully not the dining table & chairs!

    Passive solar heating should be maximized in our buildings to reduce the burning of all heating fuels.

  21. keep in mind that burning wood is using current carbon, and most of the other sources of heating out there are using fossil fuels. These are only adding to higher levels of co2 in the atmosphere = climate change.


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