PHILADELPHIA (WPVI) -- It's good news for Pennsylvania, New Jersey, Delaware and Maryland because all have made progress in cleaning up air pollution.
In fact, we had fewer high ozone days, meaning there's less smog in the air.
But, there is some bad news too. The Philadelphia-metro area made the list for the top 25 most polluted cities.
Across the nation, about 40-percent of people still live in areas with unhealthy air.
It can trigger asthma attacks and other problems.
But, overall the particle pollution levels have dropped due to shutting down coal-fired power plants and retiring old diesel engines.
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Report: Delaware Valley making progress cleaning up air pollution