Allegheny Front: The largest chemical hub in the Americas courses through this city in a seemingly unending line of plants that produce about a quarter of the countrys petrochemicals.
These plants have helped fuel the citys economic rise. But they also have added to its poor air quality, with emissions that have been linked to asthma, cancer, and heart attacks.
In recent years, Houston has found ways to reduce air pollution, in part by zeroing in on chemical plant emissions. Experts say Houstons experience...