MOSES LAKE — While there is a chance the air quality over the Columbia Basin will improve toward the end of the week, the smoke from western wildfires is likely to hang around for a while.

According to Charlotte Dewey, a meteorologist with the National Weather Service in Spokane, a cold front is expected to arrive on Thursday and may provide some relief from smoke enveloping much of the region.

“It should kick up some wind, and maybe even some rain,” Dewey said. “But there’s not a high confidence of that.”

According to data available from both the Washington State Department of Ecology’s air quality monitoring network, the air quality in Moses Lake as measured by an Ecology monitoring station at the Moses Lake Civic Center was moderate, while Ecology monitoring stations in Quincy and Ritzville listed air quality as unhealthy for everyone.

Separate private sensors streaming data to the federal Environmental Protection Agency’s online fire and smoke map reported very unhealthy air near Moses Lake High School and unhealthy air near the Mid-Columbia Library branch in Othello.

While the sensors and monitoring stations track a number of pollutants — including oxides of nitrogen, ozone, carbon monoxide and sulfur dioxide — the main pollutant being tracked during fire season are small particles of soot 2.5 microns or less in diameter, or PM2.5.

A micron is one-millionth of a meter long, and a typical human hair is roughly 75 microns around.

The soot particles come from the many large and small wildfires in Oregon, California, Idaho and Canada, and have been carried by slow moving air over eastern Washington where a high pressure cell responsible for much of the recent heat is keeping them trapped, Dewey said.

According to Stephanie Shopbell, environmental health manager and emergency response coordinator for the Grant County Health District, the tiny particles are a danger because they can get lodged deep in the lungs and even get into the blood.

Because of that, the soot can aggravate underlying conditions like asthma or chronic obstructive pulmonary disease (COPD) and can cause sore throats and make it harder to breathe.

“The best thing is for people to stay inside in a space with recirculated air,” Shopbell said.

If you have to work outside, Shopbell said it also helps to reduce physical activities and wear an N-95 mask to filter out the particles.

Air quality was unhealthy to hazardous across much of eastern Washington, with some of the worst air quality in western Okanogan County near Winthrop, site of the Cub Creek Fire — which has burned nearly 59,000 acres as of mid-Monday — and the Cedar Creek Fire, which burned nearly 49,000 acres as of mid-Monday, according to the U.S. Forest Service’s online Incident Information Center, which tracks wildfires across the United States.

Shopbell said the health district will make recommendations to organizations hosting outdoor activities on whether the air quality should prompt closing the event.

The city of Moses Lake canceled the police department’s National Night Out at the city’s McCosh Park on Tuesday and closed the Surf ‘n Slide Water Park on Saturday because the air quality was unhealthy.

“We wish the circumstances could be different,” City Manager Allison Williams said in a press release. “We need to ensure residents are safe and the air quality is at healthy levels for outdoor public events to occur.”

According to the smoke forecast from the Department of Ecology, air quality around Moses Lake is expected to hover between unhealthy for sensitive groups and generally unhealthy for the rest of the week, though the same forecast expects some clearing for the Quincy area by Friday.

“Right now, this is going to stick around for the rest of the week,” Shopbell said.

Charles H. Featherstone can be reached at cfeatherstone@columbiabasinherald.com.