A natural gas-fired power station in Long Beach, Calif. The EPA said the decline in power plant emissions is due in part to a switch from coal to natural gas. David McNew/Getty Images

The amount of harmful greenhouse gas pollution spewed into the atmosphere by large U.S. power plants has declined 10 percent since 2010, the Obama administration said Wednesday.

The results came from the third year of carbon pollution emissions data that the Environmental Protection Agency (EPA) collects from nearly 8,000 facilities including power plants, oil refineries and steel mills.

In all, these operations, which make up 85 to 90 percent of total U.S. greenhouse gas production, reported direct carbon emissions of 3.13 billion metric tons in 2012.

The decline in power plant emissions is "due to a switch from coal to natural gas for electricity generation and a slight decrease in electricity production," the EPA said in a statement.

The decline from 2011 to 2012 was 4.5 percent, it added.

"Fossil-fuel fired power plants remain the largest source of US greenhouse gas emissions," said the EPA, noting that just under 1,600 facilities had emitted over 2 billion metric tons of carbon dioxide, or 40 percent of the U.S. total, in 2012.

The EPA mandate to report on greenhouse gases from U.S. sources that emit 25,000 metric tons or more of carbon dioxide per year began under President Barack Obama in 2009.

In June, the Obama administration set strict limits for carbon pollution generated by any newly constructed power plants. The focus on greenhouse gas emissions comes as Obama continues to weigh whether to greenlight the controversial Keystone XL pipeline, which would carry carbon-intensive tar sands oil from Canada to refineries in Texas. The president has said he will approve the pipeline only if its construction would not result in a net increase in the climate-warming gases.