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CHERYL GLASER: The Justice Department is expected to weigh in today on a Supreme Court case over how to interpret the Clean Air Act. On one side: Duke energy, one of the biggest electricity providers in the country. On the other: Environmental Defense, a non-profit group. There's a lot at stake. Some are calling the case the biggest challenge to the Clean Air Act to come before the high court. Shia Levitt has more.
SHIA LEVITT: At debate here is a part of the Clean Air Act that dictates when power plants have to update pollution control technology.
Currently, controls have to be modernized when plant renovations cause a boost in emissions. But industry and public health advocates differ on what constitutes an "increase" in pollution. Whether it's tons released per year or average hourly emission rates.
It might sound like semantics, but it's an important difference says Scott Segal. He directs the Electric Reliability Coordinating Council, a group of power companies including Duke Energy that works on interpreting and reforming the Clean Air Act.
SCOTT SEGAL: "If you're measuring the total annual pollution out of a power plant, that's a function of how much demand there was for power in that particular year, and frankly that's not something the power plant has control over. If you measure the hourly rate of emissions, you're saying 'how little pollution can you make to produce the same unit of electricity?' That's a real measurement of how effective environmental controls are at a plant."
Segal says requiring expensive pollution control technologies might run some power companies out of business, or force them to pass higher costs on to consumers.
Instead, he advocates what he calls a more flexible approach to the Clean Air Act, such as cap and trade policies. He says that would give industry incentives to bring emissions down.
But environmental and public health advocates say the law is meant to regulate annual pollution levels.
John Walke directs the Clean Air program at the National Resources Defense Council. He says there are health costs in the communities near power plants when overall emissions go up.
JOHN WALKE: "Kids go to the hospitals with asthma and the elderly get sick from heart disease when pollution goes up. They are increasing pollution where we live by tens of thousands of tons per year and trying to escape responsibility for cleaning it up."
Walke says measuring hourly pollution means plants could operate longer hours and increase overall smog and soot in surrounding areas.
WALKE: "What you're talking about here are some companies that don't want to spend the money to protect the public and to deliver their electricity services in the clean manner that their competitors are doing."
The Duke Energy versus Environmental Defense case is being watched closely by several states and public health groups. Craig Oren is an environmental law professor at Rutgers University.
CRAIG OREN:"This same issue of what constitutes a change in emissions has come up and in fact a number of courts are waiting for the Supreme Court's decision in order to decide what to do in other cases."
If the Supreme Court decides in favor of an annual rate, it could mean hundreds of millions of dollars in upgrades for power plants. The case will be argued in the High Court's November session.
In Washington, I'm Shia Levitt for Marketplace.