U.S. Air Quality Slips After Decades of Improvement

After decades of improvement, America's air may not be getting any cleaner.

Over the last two years the nation had more polluted air days than just a few years earlier, federal data shows. While it remains unclear whether this is the beginning of a trend, health experts say it's troubling to see air quality progress stagnate.

After decades of improvement, America's air may not be getting any cleaner. Over the last two years the nation had more polluted air days than just a few years earlier, federal data shows. While it remains unclear whether this is the beginning of a trend, health experts say it's troubling to see air quality progress stagnate.