How clean is each form of power? The US EPA has updated its database of the environmental characteristics of almost all electric power generated in the United States. These environmental characteristics include air emissions for nitrogen oxides, sulfur dioxide, carbon dioxide, methane, and nitrous oxide; emissions rates; net generation; resource mix; and many other attributes, plus summary charts and tables. The eGrid database (Emissions & Generation Resource Integrated Database) now includes data from 2007.Like Canadian provinces, the US states vary dramatically in their sources of electricity, which are directly reflected in both their air quality and their politics. Iowa, for example, has a rapidly growing wind sector, which last year provided more than 15% of the state’s electricity. In 2007, Nevada was the US leader in geothermal. Kentucky and North Dakota relied almost entirely on coal; Washington DC burned only oil; Connecticut was half powered by nuclear; Idaho had 79% hydropower.