Scientists at NASA’s Environment and Climate Change Canada and researchers at University of Maryland, College Park and Dalhousie University discovered 39 unreported “major” sources of toxic air pollution. Using the space agency’s satellite imaging, the group located the man-made sources where toxic sulfur dioxide is being emitted. Sulfur dioxide (SO2) is a contributor to acid rain and is regulated on the ground by the EPA. However, to properly police the emissions, the government agency has to know the location of the pollutants.