North Dakota, South Dakota, Texas and Nevada are suing the Environmental Protection Agency, alleging it has failed to determine the states' compliance with a new federal clean air requirement that limits sulfur dioxide emissions.
Attorneys general said in court papers that the states meet the new standard under the Clean Air Act, and that the EPA's inaction "will lengthen and complicate the overall permitting process, or even make permitting impossible."
The states allege the EPA is in violation federal law by missing its deadline to make the required determinations. Their lawsuit was filed last week in federal district court in Bismarck.
"(The states) and the sources they regulate live in great uncertainty," court papers said.
EPA officials did not immediately return telephone calls from The Associated Press on Thursday.
Sulfur dioxide smells like rotten eggs and is a major emission from coal-fired power plants. The gas has been linked to acid rain and various respiratory ailments.
The EPA in 2010 issued the new standard for sulfur dioxide based on a one-hour measurement of gas concentration, instead of the 24-hour measurement used previously. The EPA required states to submit air quality data.
North Dakota Attorney General Wayne Stenehjem said the EPA had until June 2012 to determine whether the states met the new standard.
"The EPA has failed to do its part to make the required designations for the states," Stenehjem said. "It appears that the EPA is holding itself to a different standard than the states that are complying with the Clean Air Act."
Stenehjem said the states gave the EPA more than 60 days' notice before filing the lawsuit.
Attorney General Marty Jackley said in a statement that "EPA's failure to act is inhibiting small business growth in our state while not protecting air quality."