A new report came out on how healthy our air is.
Just after the U.S. Supreme Court issued a key ruling on pollution.
Overnight we learned the air we're breathing is getting better in some areas, worse in others.
The American Lung Association's annual "state of the air" report finds particle pollution is down thanks to cleaner diesel fuel and power plants
But ozone pollution is up, meaning there's less stuff floating around, but smog is worse.
The Lung Association blames warmer weather. "Which is bad news for public health[.] It shows we need to take the threat of climate change very seriously," said Paul Billings of the American Lung Association.
The Association says polluted air can lead to more asthma, heart attacks and stroke.
In all, they count 147 million people - almost half the country - living in unhealthy air.
And there were stark differences: Los Angeles saw record low particle pollution last year, but had more high ozone days than the year before.
In fact, all but three of the top 25 cities saw ozone levels increase.
The report comes just hours after the U.S. Supreme Court ruled 6 to 2 that the federal government can police particle pollution that floats across state lines. "This is about people's basic health, and about a level playing field," said Gov. Jack Markell, (D) Delaware.
It's a big defeat for coal, mining and other industries that fought the rule.
The decision limits emissions from plants in more than two dozen states.
Tracie Potts, NBC News.