The case heard Wednesday could put a rule on hold that reduces smog-forming pollution from states like Ohio that wafts downwind to states like Pennsylvania.
How the latest news about a new soot standard, a settlement with U.S. Steel and EPA's rejection of the company's air permit could impact Pittsburgh's air.
EPA has ordered Allegheny County to revise its air permit for U.S. Steel’s Edgar Thomson plant to include stronger testing and monitoring requirements.