In 2015, when Karen Grzywinski heard that the Shenango Coke Works near Pittsburgh was closing after 54 years in operation, she didn’t believe it. Neither did her neighbors, some of whom had joined her in fighting a long battle for the plant to better control its pollution. “A number of us thought it was a joke,” she said. “We were really, really surprised.”

Shenango, which produced coke, a concentrated form of coal used to manufacture steel, was then a major source of air pollution in the region. After years of suffering from respiratory symptoms triggered by bad air days, Grzywinski said she noticed a change soon after the closure. “You could look across the river and not see this perpetual haze,” she said. “It was astounding, the difference.”

Since Shenango closed in 2016, researchers

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