As the EPA has slowly been crafting its new rules to regulate global-warming emissions, one of the crucial first steps has involved getting a basic sense of where the pollution’s actually coming from.

Back in 2009, the agency required all large greenhouse-gas emitters — any power plant, refinery, or other facility that puts out more than 25,000 metric tons per year — to report their emissions. And today the EPA has unveiled a interactive online map that lets people check out the major polluters in their area (the emissions data are all from 2010). For instance, here’s a map for downtown Washington:

The city’s biggest emitters, not surprisingly, are its power plants, particularly the Benning Road Generating Station (219,199 metric tons), which burns distillate fuel oil for electricity, as well as the GSA Central Heating Plant, which powers most federal buildings. But there are also a few unexpected smaller emitters that make the list, such as the Walter Reed Army Medical Center and the Naval Research Laboratory, both of which have on-site combustion.

I also narrowed the search down here to locate the 10 largest sources of greenhouse gases in the United States. The top two, as it happens, are both large coal-fired power plants in Georgia, with the Robert W. Scherer Power Plant in Juliette, Ga., taking top honors, putting 22.9 million metric tons of greenhouse gases into the air in 2010.