Environmental groups sue the EPA to enforce air quality laws in Oklahoma, Missouri and several other states

Several of the largest conservation nonprofits in the U.S. claim in a federal lawsuit that the Environmental Protection Agency has failed to enforce air quality standards.As part of the Clean Air Act, every state must submit a detailed plan to the EPA every 10 years for reducing air pollution in national parks and wilderness areas. Nearly three dozen states, including Oklahoma Missouri, Illinois, Iowa and Nebraska, have not submitted updated plans to the EPA — and environmental advocates hope to compel the federal agency to take action.