Allegheny County is ramping up its air quality monitoring in the aftermath of a deadly explosion at the Clairton Coke Works plant. The health department began deploying mobile air units Thursday provided by Pennsylvania’s Department of Environmental Protection and Carnegie Mellon University. The units will travel around Clairton to test for dozens of hazardous air pollutants.
Monday’s explosion — which happened as workers were preparing two coke batteries for maintenance — sent plumes of black smoke above the Mon Valley, prompting concerns among clean air advocates about the release of toxic pollutants into the community. While county health officials have found no signs of fine particulate matter or sulfur dioxide that exceed federal limits since the explosion, the mobile units will be able to test for a wider range of toxic pollutants closer to the plant.
Clairton Coke Works, site of Monday’s explosion, has a history of problems
“We can take this unit lots of different places and get instantaneous readings,” said David Good, director of air quality monitoring at the Allegheny County Health Department. “Here we can [track] a host of different pollutants that we don’t even currently measure for” at the county’s monitoring stations, he added.
The health department’s air quality team joined scientists from Pennsylvania’s Department of Environmental Protection to take air samples around the plant Thursday. The team set up a weather station on top of a truck and an air quality analyzer to begin taking samples in a parking lot near the plant.
Inside the truck is a mobile laboratory, where chemists point an infrared beam toward a mirror set up outside, about 50 yards away. The mirror reflects that beam back to the analyzer, allowing it to detect dozens of “chemical fingerprints,” according to Matt Kundrat, DEP’s special operations and mobile lab unit manager.
“The computer will search for more than 100 [pollutants] at the same time,” he said. “So whatever happens to show up in front of the mirror, if there’s enough of it there, we’ll find it.”
On Thursday, the mobile unit detected pollutants including methane, carbon monoxide, nitrous oxide and o-Xylene in the parking lot near the plant. But according to Anthony Friedline, a DEP chemist manning the beam, it’s too soon to tell whether the amount of pollutants detected in the sample are at a dangerous level or whether they’re coming from the plant itself.
“We don’t know if that’s the plant or the train that passed by a few minutes ago or if it’s something from the road just on the other side of the beam,” he said. Weather conditions can also factor into how concentrated a pollutant is.
In addition to hazardous air pollutants such as methane and o-Xylene, DEP is also tracking volatile organic compounds like benzene, which is highly volatile and associated with severe health impacts including cancer and blood disorders.
The team will continue to monitor air samples around the plant Friday before sending their data back to Harrisburg for a more in-depth analysis. According to a statement from the DEP, a final report will be presented “in a few weeks.”
In addition to sampling different locations, Good said the team needs to sample the air at different times of the day.
Early morning air quality can be worse in the Mon Valley during temperature inversions when warm air sits on top of cooler air near the ground, trapping pollutants. Still, Good said monitoring during the afternoon — while the hot sun rises, warm air to mix and disperse pollutants — is just as important as monitoring during the morning — when temperature inversions are more likely — to create a full picture.
“We want to get every condition possible and as many different locations as possible,” Good said. “[Friday] we’re going to go as early as we can so that we can get [samples when] we know it’s going to be among the poorest air quality.”
When finding a location to set up the unit, Good said the team is looking for an open space that aligns with the direction of the wind. But perhaps more importantly, the right location will have a strong odor.
“Following our nose is really the way to go,” he said.
On Friday, Good and the DEP will be joined by a team from Carnegie Mellon University to do additional monitoring around the plant. Good said CMU’s air monitor van uses similar technology to the county’s monitoring stations, but it can collect samples on the go.
“They’ll be able to drive around and take … samples all across the perimeter [of the plant] and even back into the community,” he said. The teams will compare readings from the DEP’s stationary truck laboratory to the van operated by CMU.
The DEP and county health officials have assured the public that pollutants tracked by the county’s stationary air quality monitors have remained within the limit set by the U.S. Environmental Protection Agency during and after the explosion. One reason for that was the absence of an inversion during the time of the blast.
“Through conversations with our meteorologists and specialists in this area, we know that the event happened in the middle of a late summer morning, and the plume was able to rise out of the valley without the presence of an inversion in place,” said Dr. Iulia Vann, director of the Allegheny County Health Department, during a press conference this week.
In a statement announcing the mobile units, the county described them as going “beyond the normal and rigorous regulatory air quality monitoring” already conducted by the health department.
Allegheny County Executive Sara Innamorato touted the collaboration among the county, the state Department of Environmental Protection and Carnegie Mellon University.
“We deeply appreciate the partnership between PA DEP, CMU, and our county health department so we can make the best public health decisions possible, informed by data and science,” she said.
Compared to U.S. Steel’s other two facilities in the Mon Valley — the Irvin plant in West Mifflin and the Edgar Thompson plant in Braddock — the Clairton plant emits the highest measurements of hazardous air pollutants, according to Allegheny County’s emissions inventory.
In 2022 — the most recent year for which data is available — the plant emitted 232 tons of hazardous air pollutants such as benzene and arsenic. Both cause serious health effects above certain concentration levels, including cancer.
One reason why the Clairton plant emits higher levels of pollutants is due to its “coking” process. The facility turns coal into coke by heating it to extremely high temperatures in sealed ovens to remove impurities that would otherwise weaken steel. The process produces coke oven gas, a mixture of toxic chemicals.
The additional monitoring comes as the investigation into what caused the explosion continues.
In a statement, U.S. Steel said the company is “fully cooperating with all local, state, and federal agencies investigating the cause of the explosion and conducting air quality monitoring in and around our facility.”
“This is a time when industry and government must work cooperatively,” the statement continued. “U.S. Steel will continue to monitor environmental performance at all of our Mon Valley facilities, as we do around the clock.”
Gov. Josh Shapiro pledged to provide every resource at the state level to assist Allegheny County’s investigation. Shapiro said at a press conference earlier this week that he would support a fully transparent investigation aimed at providing clarity to the families of the two victims as well as the workers back on the job at the plant.
“We owe them an answer for what happened,” he said. “We owe them the answers to their questions, and we owe them to never forget the sacrifices that occurred here.”
Susan Scott Peterson contributed to this report.
