"In a bid to clean up one of the nation’s dirtiest coal-fired power plants without causing economic harm to the Navajo Nation that surrounds it, the Environmental Protection Agency indicated on Friday that it would give the plant’s owners five extra years, until 2023, to install expensive state-of-the art emissions reduction equipment."

"GENEVA -- A new and legally binding international treaty to reduce harmful emissions of mercury was adopted Saturday by more than 140 nations, capping four years of difficult negotiations but stopping short of some of the tougher measures that proponents had envisioned."

"Crisis-weary developed countries' reluctance to help finance a ground-breaking international treaty to rein in the use of health-hazardous mercury is threatening the accord, UN officials warned Thursday."

"Opponents of the Keystone XL pipeline and the heavy Canadian crude oil that it would carry released two reports on Thursday asserting that the environmental impacts of the project are worse than previously estimated, and urged the Obama administration to veto it."

"The U.S. Environmental Protection Agency said Wednesday that total toxic air releases in 2011 declined 8 percent from 2010. In the mid-Atlantic region, which includes Pennsylvania and Delaware, the agency recorded a decline of 13.8 percent or 32.5 million pounds. Among the hazardous air pollutants showing declines were hydrochloric acid and mercury, which EPA attributed to improved pollution control technologies at coal-fired power plants and a shift to other fuel sources."

"Citgo Petroleum Corp. reached an agreement with New Hampshire to be dismissed from an $816 million trial over groundwater contamination while a settlement is completed, as a witness testified that 2 percent of the state’s private wells are polluted with hazardous levels of the chemical MTBE."

"CHEYENNE, Wyo. -- Gov. Matt Mead has joined those expressing disappointment that the U.S. Environmental Protection Agency has extended for a third time a public comment period on a report on groundwater pollution in a Wyoming gas field rather than moving toward wrapping up the study."

"Black carbon, the soot produced by burning fossil fuels and biomass, is a more potent atmospheric pollutant than previously thought, according to a four-year international study released on Tuesday."

"WEATHERFORD, Texas -- When a man in a Fort Worth suburb reported his family's drinking water had begun "bubbling" like champagne, the federal government sounded an alarm: An oil company may have tainted their wells while drilling for natural gas. At first, the Environmental Protection Agency believed the situation was so serious that it issued a rare emergency order in late 2010 that said at least two homeowners were in immediate danger from a well saturated with flammable methane. More than a year later, the agency rescinded its mandate and refused to explain why."