‘Unhealthy’ Air Quality in Portland Caused by an Industrial Fire, Experts Say

Air quality levels in Portland, Ore., reached “unhealthy” levels and were among the worst in the nation on Wednesday. Although wildfires in the region and beyond have been behind some of the recent spikes in air quality levels, this time the culprit was a factory fire an hour north of the city.

A paper mill, Nippon Dynawave Packaging in Longview, Wash., caught fire on Tuesday night and was still burning as of Wednesday afternoon, according to the Longview Fire Department.

“The plume of smoke from that has been pointed at the metro area since last evening,” said Paul C. Loikith, a meteorologist and associate professor in the geography department at Portland State University.

For a few hours during the middle of the day on Wednesday, the Air Quality Index in Portland passed 170, placing it within the “unhealthy” range. While wildfires have recently been the cause of air quality issues across the United States, experts said the fire at the paper mill was the reason the A.Q.I. spiked in the Portland area.

Paper mills often have a great deal of wood chips on site to make paper, which may have contributed to the large amount of smoke from the fire, said Dylan Darling, a spokesman for the Oregon Department of Environmental Quality.

Nippon Dynawave Packaging makes an array of paper products, some of which eventually become milk cartons or to-go coffee cups.

The fire occurred primarily at the wood chip facility, which is mainly outdoors. Several wood chip piles caught on fire, and each pile is about the diameter of a football field, said Brian Wood, the company’s director of support services.

The initial call about the fire came in at 6:39 p.m. on Tuesday night, and firefighters were still working to extinguish it as of Wednesday afternoon, said Jon Dunaway, the Longview fire marshal.

“We are expecting to be putting out this fire for the next couple of hours, and possibly into the morning,” Mr. Dunaway said.

It is unclear why the fire started, he said. No one was injured during the blaze.

Even as crews work to extinguish the fire, there is still a great deal of smoke because the fire is reaching the “smoldering” phase, Mr. Dunaway said. As firefighters apply water to the fire, the smoke cools, which causes it to linger closer to the ground.

The smoke has shifted east of the central city as of Wednesday morning and the air quality is improving across most of the metro area, Mr. Loikith said.

It’s unclear how long the degraded air quality will last. It will likely depend on how long it takes to extinguish the fire, he said.

Clark and Cowlitz Counties in Washington, both north of Portland, are under an air pollution advisory through Friday because of the smoke, according to the Southwest Clean Air Agency.

The Health Department in Multnomah County, where Portland is, also issued an advisory Wednesday, citing “poor air quality from structure fires.”

Under the advisory, residents may not burn wood, including through the use of fireplaces, wood stoves and outdoor devices. The department did not give a timeline for when the advisory would be lifted.

There was also a large structure fire at a vacant former Kmart in Northeast Portland that impacted air quality Wednesday morning, but the effects of the ongoing paper mill fire will likely last longer, Oregon’s Department of Environmental Quality said in an email.