LANSING, Mich. (AP) _ The U.S. Supreme Court is expected to release a decision this week about new mercury and toxic air emissions standards for power plants, but Michigan’s utility companies have already been working toward compliance.

The case against the U.S. Environmental Protection Agency is led by Michigan, which was joined by 20 other states.

The main issue is whether the EPA was required to take $9.6 billion in compliance costs into account when it first decided to regulate air pollutants from power plants or if health risks are the only consideration under the Clean Air Act.

Michigan’s two largest utility companies, Consumers Energy and DTE Energy, say they’ve already been working toward compliance with the air pollution rule, regardless of the outcome of the case.