AP According to PennEnvironment, U.S. Steel's Clairton plant was the third most toxic active industrial facility in Allegheny County in 2019. The 10 biggest industrial polluters in Allegheny County released more toxic pollution into the air in 2019 than they did in previous years, according to a report PennEnvironment released Tuesday. But while overall emissions were higher, there are signs that several sites will pollute less in the future. “Collectively, we found that the ‘Toxic 10’ combined released more than 1 million pounds of pollution in 2019,” said PennEnvironment’s Zachar...