Smoky air hanging over Clark County may begin to circulate today but probably not for long, so you may want to postpone stoking flames in your fireplace out of courtesy for sensitive neighbors.
Particulate pollution spikes during inversions, when cold air is trapped near the ground and households burn wood for warmth.
About 50 percent of the particulate comes from wood burning, said Randy Peltier, operations manager for Southwest Clean Air Agency in Vancouver. The fine particles can cause breathing problems for vulnerable people.
That’s why the agency imposed a ban on outdoor burning, as well as the use of fireplaces and older wood stoves, after the National Weather Service’s Portland office issued an air stagnation advisory earlier this week. The advisory and burn ban are expected to be lifted today.
Inversions are “fairly common here,” said Beth Burgess, a weather service meteorologist. “It’s just the way the weather patterns work in the Pacific Northwest.”
So far this year, the air has been bad enough that the Southwest Clean Air Agency has banned burning four times: Jan. 16 through 23; Nov. 22 through Dec. 2; Dec. 10 through 16; and Tuesday until today.
The burn bans are an attempt to keep pollution within standards set by the U.S. Environmental Protection Agency under the Clean Air Act.
The EPA’s standard for so-called PM 2.5 — particulate matter 2.5 microns in diameter and smaller, or 100 times thinner than a human hair — is 35 micrograms per cubic meter.
That pollutant has exceeded the standard 15 times this year, with measurements ranging from 35.6 to 67.8 micrograms per cubic meter in a 24-hour period, Peltier said.
Fine particles are a concern because they can penetrate to the deepest part of the lungs.
“They carry chemicals and toxins that can pass into blood and affect lung tissue,” Peltier said.
The clean air agency’s index at http://www.swcleanair.org rates current air quality from green (good) to red (bad).
Children, the elderly, and people with asthma and heart disease will feel the effects of elevated particle pollution first.
“During the orange and red days, we would recommend that they stay inside and limit their physical activity,” Peltier said.
Portland-Vancouver air violated standards for ozone and carbon monoxide so frequently in the 1990s that the EPA labeled this region a Clean Air Act “nonattainment area” for those pollutants, but never for particulate matter.
“We’re coming close — by the skin of our teeth — for this year,” Peltier said.
The nonattainment designation is determined by a formula that takes into account the number of times the standard is exceeded each year, averaged over three years.
The EPA labeled Tacoma a nonattainment area for particle pollution in 2009. The Tacoma-Pierce County Clean Air Task Force and the state Department of Ecology are working with the EPA to bring the region into compliance with the Clean Air Act, in part by increasing enforcement of burn bans and requiring removal of uncertified wood stoves.
Stagnant air here may begin to mix today, but the relief isn’t predicted to last.
“We have a little weak front coming through that’s going to improve things, but the inversion comes right back on Saturday. It’s going to be around, with varying degrees of strength,” Burgess said. “We’re going to be basically stuck in this pattern.”
