EVERETT — The Puget Sound Clean Air Agency on Wednesday called for a stage 2 burn ban for Darrington.
In addition, the U.S. Environmental Protection Agency has called for a burn ban on several Indian reservations in the state, including those of the Tulalip and Stillaguamish tribes.
Snohomish County has been operating under a stage 1 burn ban since Tuesday. A stage 1 ban prohibits outdoor fires and most indoor burning except for pellet stoves and inserts or wood-burning stoves certified by the EPA.
A stage 2 ban, the highest level of alert, prohibits all burning, under penalty of a $1,000 fine, unless a wood stove has been previously approved by the state because it is the home’s only source of heat.
This is the second time this month that the Clean Air Agency has singled out Darrington.
That’s an experiment the agency started conducting this year, said Philip Swartzendruber, an air quality scientist with the agency.
“We feel like we’ve got a clearer handle on the differences between Darrington and the rest of the county,” Swartzendruber said.
While the agency’s air quality monitors are set up to detect a number of pollutants, in Darrington wood smoke far and away is the dominant pollutant.
A big part of the problem is that Darrington is in a basin in the upper Stillaguamish Valley, which traps stagnant air and pollutants. There is also a proportionally higher use of wood-burning stoves in the upper valley than down on the coast.
Normally, the Puget Sound region’s prevailing winds keep air moving, and the rain tends to wash pollutants out of the air, said Cliff Mass, a meteorologist and professor of atmospheric sciences at the University of Washington.
“Then we get these situations where high pressure systems build over the regions — that’s when the trouble occurs,” Mass said.
A lack of clouds leads to cooling at the surface, prompting people to start trying to warm up with a fire. But air also tends to sink and compress near the ground, trapping the smoke there.
“The whole thing is even worse if you live in a valley,” he said. “Darrington is famous, Darrington is like disaster land.”
There are a number of different factors and pollutants that go into measuring air quality. The Air Quality Index is a scale that wraps all the various criteria into one number that can be used to make decisions about burn bans.
An index of 50 or below is considered “good,” while 51-100 is considered “moderate” and 101-150 is “unhealthy for sensitive groups,” meaning that air quality is bad enough that the elderly, children and people with asthma or other respiratory problems are at greater risk to experience health problems.
At 11 a.m. Wednesday, when the stage 2 ban was called for Darrington, the local index for the town was at about 101. Elsewhere in Snohomish County the index hovered in the 50-55 range.
It could be worse in Darrington. There are three higher levels of pollution on the air quality index: “unhealthy” for everyone, “very unhealthy” and “hazardous.”
Beijing, famous for its opaque ground-level smog, saw its air quality index shoot above 500 in January 2014, not just into the “hazardous” zone but off the upper end of the scale.
But you don’t have to have the sun blocked for there to be negative effects.
“You’re getting health effects at any level, and the risk goes up as the concentrations go up,” Swartzendruber said.
That’s why the threshold for action is set low by state law. The Clean Air Agency calls for a stage 1 ban in Snohomish County when the forecast is for the index to reach 30, still within in the “good” range.
Stage 2 burn bans are called when the measured index hits 25.
Chris Winters: 425-374-4165; cwinters@ heraldnet.com. Twitter: @Chris_At_Herald.
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