More than 20 years after the Exxon Valdez ran aground and dumped hundreds of thousands of barrels of oil into Alaska's Prince William Sound, Exxon Mobile Corp. has come under fire again from environmental groups, except this time, it's for polluting another of the classical Greek elements.

Federal Judge David Hitner ruled Tuesday that he will allow a pair of environmental groups to pursue a lawsuit accusing the company and two subsidiaries of repeated air pollution over the past five years.

Sierra Club and Environment Texas teamed to bring suit against the refiner last December, alleging that Exxon violated the Clean Air Act thousands of times at its Baytown, Texas-based oil refinery and chemical plant complex. The groups say 8 million pounds of pollutants, including cancer-causing toxins, have been diffused into the air as a result of these violations.

Exxon had asked that the court throw out the suit, arguing that, among other things, citizens cannot sue to enforce the Clean Air Act because the Texas Commission on Environmental Quality and the U.S. Environmental Protection Agency already oversee the complex. However, the environmental groups countered by saying that the government's failure to stop Exxon's violations had opened the door to direct enforcement of the law by citizen groups.

“Congress specifically allowed for citizen enforcement suits because sometimes government agencies fall down on the job, and this case is a perfect example of that,” Luke Metzger, director, Environment Texas, said in a statement.

This is the groups' third federal lawsuit since 2008 targeting illegal air emissions in the Houston area following successful cases against Shell Oil Co. and Chevron Phillips Chemical Co.

No trial date has been set for the Exxon suit.

More than 20 years after the Exxon Valdez ran aground and dumped hundreds of thousands of barrels of oil into Alaska's Prince William Sound, Exxon Mobile Corp. has come under fire again from environmental groups, except this time, it's for polluting another of the classical Greek elements.

Federal Judge David Hitner ruled Tuesday that he will allow a pair of environmental groups to pursue a lawsuit accusing the company and two subsidiaries of repeated air pollution over the past five years.

Sierra Club and Environment Texas teamed to bring suit against the refiner last December, alleging that Exxon violated the Clean Air Act thousands of times at its Baytown, Texas-based oil refinery and chemical plant complex. The groups say 8 million pounds of pollutants, including cancer-causing toxins, have been diffused into the air as a result of these violations.

Exxon had asked that the court throw out the suit, arguing that, among other things, citizens cannot sue to enforce the Clean Air Act because the Texas Commission on Environmental Quality and the U.S. Environmental Protection Agency already oversee the complex. However, the environmental groups countered by saying that the government's failure to stop Exxon's violations had opened the door to direct enforcement of the law by citizen groups.

“Congress specifically allowed for citizen enforcement suits because sometimes government agencies fall down on the job, and this case is a perfect example of that,” Luke Metzger, director, Environment Texas, said in a statement.

This is the groups' third federal lawsuit since 2008 targeting illegal air emissions in the Houston area following successful cases against Shell Oil Co. and Chevron Phillips Chemical Co.

No trial date has been set for the Exxon suit.