"The scientific case has been building for how a smoggy summer afternoon in North Texas might harm a child playing outdoors, a person with asthma or, on the worst days, perhaps even a healthy adult."

"President Obama could leave office with the most aggressive, far-reaching environmental legacy of any occupant of the White House. Yet it is very possible that not a single major environmental law will have passed during his two terms in Washington."

"The U.S. Supreme Court on Tuesday agreed to weigh a challenge by industry groups and some states to an Obama administration regulation intended to limit emissions of mercury and other hazardous pollutants mainly from coal-fired power plants."

"The Obama administration is expected to release on Wednesday a contentious and long-delayed environmental regulation to curb emissions of ozone, a smog-causing pollutant linked to asthma, heart disease and premature death."

"The Environmental Protection Agency on Monday rejected parts of a key Texas clean-air plan, setting up a conflict with deep implications both for the state’s electricity mix and air quality across much of the country."

"After failing to rid Beijing’s skies of pollution before a gathering of world leaders this week, Chinese officials took a different approach to smog control -- limit the data."

"COLUMBIA, SC — Hazardous chemical vapors are leaking through the top of an industrial waste dump along Lake Marion and are suspected of contaminating shallow groundwater near the surface of the 36-year-old site."

"Residents of parts of the Russian capital Moscow have been urged by the emergencies ministry to stay indoors because of a noxious gas that is spreading through the city."

"Potash Corp of Saskatchewan Inc agreed to spend more than $52 million on plant improvements and pay a $1.3 million civil penalty to resolve U.S. charges that it violated the Clean Air Act over the emission of harmful pollutants such as sulfur dioxide, U.S. authorities said."

"An ozone-destroying chemical long thought to be on the decline in Earth’s upper atmosphere is making an unexpected comeback, an international team of scientists has found."