SEATTLE -- With thick wildfire smoke covering the Puget Sound region, residents are experiencing the worst air quality in the 21st Century so far -- even worse than the smoky days of last summer.
But air quality has been worse if you go back farther in Seattle's history -- a lot worse.
Historical data from the Puget Sound Clean Air Agency going back to 1980 shows several winter days in the mid 1980s with far worse numbers. In fact, December 13, 1985 had an estimated 24-hour air quality particulate measurement (155) that was nearly double the reading Seattle had on Tuesday (80).
Several other dates from December 1985 are high on the list. Many more from winters in 1982 and 1983. Tuesday's air quality ranks somewhere around 55th on the list of worst days since 1980. Wednesday's numbers will likely rank higher than 80, but still short of 155.
Certainly no wildfires in the middle of winter, so what gives?
Usually, Seattle's worst air quality days are not from wildfire smoke, but from wintertime inversions that trap particulates near the ground. Clear skies at night allow temperatures to drop, colder air is denser than warm air, the sun comes up and warms the upper layers but light winds keep the cold air near the ground, acting like a lid. The city generates pollution and it has nowhere to go.
Back then, we didn't have any good program to regulate home heating, and dirty wood burning stoves ran rampant, dumping smoke particulate into the skies in massive quantities. The overnight temperatures dropped into the mid 20s for six straight nights (colder in the outlying areas) around Dec. 13. But any kind of similar cold stretch in the 80s produced similarly bad air quality.
In addition, cars and trucks ran dirtier, especially diesel semi trucks which polluted at 50-60 times the rates of today's trucks, according to Erik Saganic with the Puget Sound Clean Air Agency. And skies were a bit dustier due to fewer paved roads and more gravel-type roads -- especially in the industrial valleys where the monitors are located, Saganic said.
But as cars' emission standards became better, fuels and wood stoves became cleaner, stricter standards were placed on industrial emissions, and burn bans were implemented by the Puget Sound Clean Air Agency when winter weather conditions led to inversions, air quality has drastically improved in the Puget Sound region. Even the worst air quality numbers in the modern day winters are about 25-40 on the particle measurement scale -- about 75-85 percent cleaner than those gunky numbers in the mid 1980s.
Yet as far as summers go? You could say this is likely the worst summer air quality day in Seattle in decades....
We should see some improvement later this week and into the weekend, but low level smoke may again be a factor early next week.