High-precision European satellites have detected a 38 percent decrease in compounds such as nitrogen dioxide and nitric oxide in the valley between 1999 and 2005, the study found.
During the same period, electricity demand in the region increased, the study noted.
"The reduction in NOx emissions from these large eastern power plants is dramatic," Greg Frost, the lead author of the study, said in a prepared statement. Nitrogen oxides come from burning fossil fuels. When combined with other gases and sunlight, they can form ozone. While ozone is a component of the outer atmosphere, ozone is also a key component of smog when closer to the earth.
Results of the study were released at anmeeting taking place this week in San Francisco.
Coal-burning power plants are more common in Ohio and Pennsylvania than other parts of the country and are a major contributor to air pollution. In those states, a plug-in hybrid car, which mostly runs on electricity and can get up to 100 miles a gallon, can as a standard hybrid, according to advocates of hybrid cars. This is because the power plants those cars draw electricity from tend to be coal-burning.
Several politicians and researchers have called for regulations to curb greenhouse gas emissions, and some states, such as California, have already passed such laws. Some businesses claim that those regulations can hurt the economy. Many investment bankers and scientists, however, have countered that history does not necessarily bear that out. Energy efficiency, they assert, could in fact help kick off an economic boom.
In the 1970s in California, manufacturers fought regulations requiring more energy-efficient appliances, claiming that appliance prices would skyrocket.
Instead, refrigerator prices have declined (after adjusting for inflation) while. Refrigerators are also larger than they were in 1973.
"They all claimed it was the...end of civilization as we knew it," said Art Rosenfeld, a researcher who helped kick off the campaign for energy efficiency in the 1970s.