Scott Pruitt speaks on election night 2010, after his successful campaign for Oklahoma attorney general. When Pruitt assumed office, he also took control of the state's case against the poultry industry.
This month, The state of Maryland announced a $4 million pilot program to dredge behind the Conowingo Dam. The dam has been holding back pollution for nearly a century, but recent research shows it has filled up with sediment faster than expected.
Will Parson/Chesapeake Bay Program/Flickr
Pollution has driven some families to leave Beijing. A group of Chinese lawyers is suing the governments of Beijing and its surrounding areas for not doing enough to get rid of the smog.
California is looking into ways to reduce the use of gas-powered lawn and gardening equipment because they will soon surpass cars as the biggest polluters in the state.
Some environmental justice advocates say California's cap-and-trade program hasn't done anything to clean up the air in low-income communities like Wilmington, where refineries are located near residential neighborhoods.
Face masks were placed on stone monkeys at the Beijing Zoo on Dec. 19 to protest heavy air pollution in northeast China. A week earlier, riot police cracked down after artists put similar masks on human figures in Chengdu.