This holiday season, we at iWatch News wanted to revisit some of our best stories and investigations of 2011. We'll feature a different investigation each day, through the start of 2012.

One of the best takeaways from the collaborative "Poisoned Places" project is the NPR/iWatch-developed map showing more than 17,000 facilities that emit hazardous chemicals into the air.

Check your community for possible air polluters.