Today, in a unanimous decision, the United States Supreme Court ruled in favor of environmental groups in an enforcement case against Duke Energy Corp. for failing to upgrade its air pollution controls when it renovated eight aging coal-fired power plants.

At issue are the Clean Air Act’s “New Source Review” (“NSR”) provisions, which require installation of the most current air pollution control technologies at power plants, refineries, and other industrial polluters whenever they are changed in a way that increases air pollution.

“This is a solid win for the environment and for public health,” said Earthjustice attorney Keri Powell. “For more than a generation, power companies have delayed cleaning up their dirtiest plants. The public paid the price for this delay in terms of unnecessary deaths, more hospital visits, higher asthma rates and unhealthy air.”

Though renovations to Duke’s plants caused them to release more air pollution each year, a lower court ruled that the changes did not trigger NSR because they did not increase the maximum amount of pollution the plants could emit each hour.  The Supreme Court overruled the lower court, concluding that under federal regulations, NSR plainly applies to any physical or operational change that increases a plant’s actual air pollution levels, measured on a yearly basis.

Earthjustice assisted attorneys for the environmental group petitioners in the Duke case, and represented some of the same groups in two closely related cases litigated in the D.C. Circuit Court of Appeals.

“This decision should come as a wake up call for power companies and their shareholders,” Powell added. “When it comes to clean air, delay and inaction are losing strategies.”

In addition, the Supreme Court also decided in favor of environmentalists, public health groups and states challenging the EPA’s decision to not regulate harmful global warming pollution from motor vehicles. Learn more about that victory here.