There's a ton of information here, including interactive maps, EPA data, stories of specific towns, and more. Here's how NPR introduces the project:
Two decades ago, Democrats and Republicans together sought to protect Americans from nearly 200 dangerous chemicals in the air they breathe. That goal remains unfulfilled. Today, hundreds of communities are still exposed to the pollutants, which can cause cancer, birth defects and other serious health issues. A secret government 'watch list' underscores how much government knows about the threat — and how little it has done to address it.
An interactive map shows all the data for Montana, as well as more than 17,000 facilities throughout the United States that have emitted hazardous chemicals into the air. There's info on which sites count as a "high priority violator" and links to full EPA reports. You'll find many of the usual local suspects, including Smurfit-Stone, Plum Creek, Columbia Falls Aluminum and Knife River.
Poynter has more on how NPR and CPI put this together. There's a full Q&A, but here's a taste:
The EPA didn’t want the list made public out of fear it would appear to be a sort of “Most Wanted” list. The list shows that the government recognizes the level of chronic pollution in hundreds of communities yet does not seriously enforce laws to address it.
In one case, an entire town is covered in a sort of black mist until citizens, not the government, force action.
CPI Senior Reporter Jim Morris read about the list in an EPA Inspector General’s report last spring. In June, CPI and NPR joined forces and filed a FOIA request. In late August, the team got the most recent data and began plowing through it.