Emissions of two air pollutants from the U.S.'s largest electricity generators have fallen since 1990, while emissions of carbon dioxide, the most significant human-caused greenhouse gas, have been steadily rising, according to new research. A report [1] issued by the environmental nonprofit NRDC [2], the sustainable investment group Ceres [3], and the utility Public Service Enterprise Group (PSEG) [4], found that government regulation of nitrogen oxides (NOx) and sulfur dioxide (SO2) helped significantly reduce emissions of the pollutants. CO2 is not subject to government regulation.

NOx and SO2 are regulated under the Clean Air Act [5]. According to the report, NOx emissions decreased by 36 percent from 1990 to 2004, while SO2 emissions fell by 44 percent. Nitrogen oxides and sulfur dioxide cause smog and haze, asthma and lung problems, and other environmental harms.

The report found a large disparity in the amount of emissions released by power plants generating similar amounts of electricity, based on the type and mix of fuels used and the pollution controls in place. The report also found that a relatively small number of power plants use available emission-control technologies.

Interest is growing among businesses and industry groups for national-level regulation of carbon dioxide emissions. Emissions-reduction programs are currently either local or regional in scale, or voluntary. New proposed changes [6] to rules and procedures of the Clean Air Act could, according to environmental groups, weaken scores of air pollution standards and allow power plants to increase their emissions.

Photo credit: DOE [7]