"WASHINGTON — A federal appeals court on Tuesday overturned a federal rule that laid out how much air pollution states would have to clean up to avoid incurring violations in downwind states.

 The decision sends the Environmental Protection Agency, and perhaps even Congress, back to the drawing board in what has become a long and paralyzing argument over how to mesh a system of state-by-state regulation with the problem of industrial smokestacks pumping pollutants into a single atmosphere.

"RANJIT NAGAR, India -- When the United Nations wanted to help slow climate change, it established what seemed a sensible system. Greenhouse gases were rated based on their power to warm the atmosphere. The more dangerous the gas, the more that manufacturers in developing nations would be compensated as they reduced their emissions. But where the United Nations envisioned environmental reform, some manufacturers of gases used in air-conditioning and refrigeration saw a lucrative business opportunity."

"In the Olympics of pollution, an environmental group has given Kentucky a gold medal of sorts for spewing the most toxic air emissions from its power plants, most of them fueled by coal."

"FLAGSTAFF, Ariz. -- The U.S. Environmental Protection Agency has issued its final rule aimed at cleaning up the largest single source of haze-causing pollutants in the country."

"Americans could breathe more smog and toxic chemicals on summer days if regulators fail to get a handle on companies that use diesel-burning generators as a last line of defense against power outages, a coalition of state officials from the Northeast says in a new report."

"CHEYENNE, Wyo. -- A federal judge has dismissed a legal challenge from environmental groups that sought to block federal coal leases in Wyoming's Powder River Basin on the grounds that burning the coal would contribute to global warming."

"U.S. Steel violated the Clean Air Act numerous times — in one case, more than 15,000 times — at its Gary Works facility and two other plants in Michigan and Illinois, according to a lawsuit filed by the federal government Wednesday in the U.S. District Court in Hammond."

"A byproduct of the ongoing heat wave, increased smog, may ultimately bring more and longer-lasting annoyance than the heat itself. The heat wave will eventually break, but Wichita’s smog reports probably already have been damaged to the extent of triggering some mandatory -- and potentially costly and inconvenient -- pollution controls like those in other big cities."

"Athletes completing their final pre-Olympics training, and members of the public gathering in London for the final stages of the Olympic torchrelay, have been warned of high levels of pollution in the UK capital on Thursday, ahead of the opening ceremony on Friday night."