Hack, hack! If you want to track emissions from places like cement factories, Google Earth--via the EPA--now provides such useful information. As Inhabitat points out, the data is displayed in graph form, so you can compare each emitter. And then decide if you'd rather live next to a petroleum refinery or a paper factory.
· Google Earth [Official Site]
· Where You Live [EPA]
· Google Earth Shows Air Pollution! [Inhabitat]