"Greenhouse gas emissions from U.S. power plants fell 4.6 percent in 2011 as more generators were switched to cleaner-burning natural gas and renewable sources from coal, according to new data from the Environmental Protection Agency."

"BRUSSELS -- Long-term exposure to fine particles of pollutants in the air can trigger adverse birth outcomes, childhood respiratory diseases and atherosclerosis, the World Health Organization warned today.

"Dawn Morrow is not allowed to go outside. The brown soupy mix hanging over the Grand Valley spells disaster for her lungs, which already are compromised by a rare lung disease with a long name, lymphangioleiomyomatosis."

"SALT LAKE CITY -- A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem."

"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."

"Bicycles, pedestrian-friendly plazas and walkways, new bus lines, and parking meters are combining to transform parts of Mexico City from a traffic nightmare to a commuter's paradise. The Mexican capital, one of the world's most populated urban areas, has captured this year's Sustainable Transport Award, the Institute for Transportation and Development Policy (ITDP) announced Tuesday."

"BEIJING — One Friday more than two years ago, an air-quality monitoring device atop the United States Embassy in Beijing recorded data so horrifying that someone in the embassy called the level of pollution 'Crazy Bad' in an infamous Twitter post. That day the Air Quality Index, which uses standards set by the United States Environmental Protection Agency, had crept above 500, which was supposed to be the top of the scale."

"GENEVA -- Mercury pollution in the top layer of the world's oceans has doubled in the past century, part of a man-made problem that will require international cooperation to fix, the U.N.'s environment agency said Thursday."

"Utahns have choice words for the ugly, unhealthy clouds that periodically shroud its valleys in winter -- like the one we can expect to endure through Thursday."

"The Environmental Protection Agency has granted California a Clean Air Act waiver allowing the state to set new standards to control emissions of various pollutants, including greenhouse gases, for passenger vehicles through 2025."