Population: 2,447,393
Cardiovascular cases: 702,228
Rank in most ozone-polluted cities: 20
It's been decades since Pittsburgh's nickname, Smoky, was appropriate. As big steel exited the city's industrial landscape, the pollutants belching forth from the city's coke ovens and blast furnaces have almost all disappeared.
Nowadays, the economy is driven by the service and tech industries. Yet, it still remains a major transportation hub and diesel engines power much of the truck, train and boat traffic that moves through the area.
As a result, harmful emissions are a particular problem. The city has a high rate of lung diseases, especially emphysema with nearly 43,000 cases and cardiovascular disease with more than 700,000 cases, according to the American Lung Association.
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