"Drilling for shale gas through hydraulic fracturing, or fracking, appears to cause smaller leaks of the greenhouse gas methane than the federal government had estimated, and considerably smaller than some critics of shale gas had feared, according to a peer-reviewed study released on Monday."

"Truckers want tougher enforcement and point to competitors who violate state rules to install filters or upgrade to cleaner engines."

"Something peculiar is happening to rivers and streams in large parts of the United States — the water's chemistry is changing. Scientists have found dozens of waterways that are becoming more alkaline. Alkaline is the opposite of acidic — think baking soda or Rolaids."

"This month, the Environmental Protection Agency will propose standards that will establish stricter pollution limits for gas-fired power plants than coal-fired power plants, according to individuals who were briefed on the matter but asked not to be identified because the rule was not public yet."

"WASHINGTON -- House Republicans scouring for evidence of overreaching environmental regulations are taking aim at a two-decade-old, taxpayer-funded scientific study by Harvard researchers that linked air pollution to disease and death."

"Emissions from battery recycler Exide pose a 'chronic hazard' to more than 250,000 people in surrounding areas, air district officials say. Risks include neurological changes in children."

"More than half a century has elapsed since the Seattle School Board — with nary a raised eyebrow, records indicate — voted to allow one of the nation's biggest and busiest highways to be built cheek-by-jowl with John Marshall Junior High, trading away the school's playground for a larger plot of land nearby."

"Federal regulators have reached a tentative deal with Carnival Corp. on a plan to reduce air pollution from nearly a third of its cruise ships, but the accord comes too late to reverse at least a temporary loss of lucrative cruise business for Baltimore."

"CAMBRIDGE, Mass. -- Polluted air causes roughly 200,000 early deaths each year across the United States, researchers from the Massachusetts Institute of Technology conclude after tracking emissions from industrial smokestacks, vehicle tailpipes, marine and rail transport, and commercial and residential heating."

"The World Bank said on Tuesday it was planning 'aggressive action' to help developing nations cut emissions of soot and other air pollutants blamed for causing climate change, in a shift also meant to protect human health and aid crop growth."