Allegheny County has issued an air pollution watch for the Mon Valley after it said levels of fine particles increased Tuesday evening and remain elevated on Wednesday.

The readings were taken at the Liberty Monitor and showed an increase of PM2.5 particulates.

The county Health Department said the elevated levels were “unusual and unexpected” due to the atmospheric conditions at the time.

The Health Department said it contacted U.S. Steel, one of the county’s largest polluters, which has been cited repeatedly for failing to meet air quality standards. The Health Department said in a news release Wednesday morning it was told that the company took three of its oldest batteries offline sometime in the past 12 hours. The department is requesting additional information from the company “to understand the situation.”

“The forecast for the next 24 hours indicates that the PM2.5 levels will likely exceed the 24-hour standard for the Mon Valley,” the county said in the release.

The fine airborne particles, less than 2.5 micrometers across or one-40th the size of a human hair, are emitted in vehicle exhausts, industrial and power plant emissions and fires and are so dangerous because they can be inhaled deep into lungs and contain hundreds of chemicals.

Young children, the elderly and those with respiratory problems — such as asthma, emphysema and bronchitis — are vulnerable to air pollution and should limit outdoor activities during this time, the county said.

“We have requested that U.S. Steel delay bringing the batteries online until air quality improves and we have a better understanding of what caused the unhealthy situation,” the county said.

The Breathe Project, a collaborative project represented by people who work as environmental advocates, public health professionals, academics and concerned citizens, monitors and provides information about air pollution in southwestern Pennsylvania, said the region has had poor air for at least nine days since the start of spring.

“Residents in SWPA shouldn’t have to endure nine days of having the worst air quality in the country,” said Matt Mehalik, Breathe Project’s executive director, in a statement.

On Tuesday, about 200 people joined a town hall hosted by the Facebook group North Braddock Residents for Our Future. During the meeting, titled “Our Right to Clean Air” and attended by people from across Allegheny County, participants took aim at U.S. Steel’s Clairton Coke Works, railroads and other manufacturers as major polluters.

Some of the speakers also expressed concern about the Shell petrochemical plant being built in Potter Township, Beaver County.

But they all had something in common: “They are fed up with the air pollution and failure of county officials to robustly combat it,” said Howard Rieger, a resident of Squirrel Hill and one of the speakers.

“We must carry forward this simple message: The status quo that allows unhealthy and toxic air in our region is no longer acceptable,” he said.

In late January, Allegheny County announced that it was meeting all federal air quality standards for the first time, based on preliminary monitoring measurements reported by the county Health Department.

The announcement marked a historic milestone in the county’s long-standing pollution control efforts, as the county was in attainment of limits for carbon monoxide, nitrogen oxide, ozone and both fine and coarse airborne particles — or soot — at all eight of its monitors.

Mr. Rieger said the county took a victory lap, “but it took a pandemic” that included cutbacks in industrial production, “closed business, massive unemployment, dramatically reduced road traffic” to get to those levels. 

“It took a disaster,” he said, “not the stewardship of county officials empowered to oversee and protect our air quality.”

First Published: April 7, 2021, 3:48 p.m.
Updated: April 8, 2021, 10:51 a.m.