The justices ruled in the face of a vigorous challenge from the state of Nebraska and several water systems represented by a conservative advocacy group.
"This is a big victory for public health and for all Americans who want safe drinking water," said Erik Olson, a senior attorney with the Natural Resources Defense Council (NRDC) who argued the case after the group intervened on behalf of EPA to defend the law and the arsenic rule.
According to a 1999 study by the National Academy of Sciences, arsenic in drinking water causes bladder, lung, and skin cancer and may cause kidney and liver cancer.
The study also found that arsenic harms the central and peripheral nervous systems, as well as heart and blood vessels, and causes serious skin problems. It also may cause birth defects and reproductive problems.
The court rejected the arguments of the advocacy group Competitive Enterprise Institute and the state of Nebraska that the arsenic rule and Safe Drinking Water Act are unconstitutional.
The panel of judges held that Congress has the power under the Commerce Clause of the U.S. Constitution to regulate poisonous chemicals like arsenic in water systems that sell water across state lines.
The court ruling confirmed that the Safe Drinking Water Act is consistent with the 10th Amendment of the U.S. Constitution, which restricts federal government regulation of states, because the law does not compel states to regulate arsenic in tap water, though they may cede that authority to the federal EPA.
Judge Raymond Randolph, a George H.W. Bush appointee, wrote the decision, and was joined by Judges Harry Edwards, a Carter appointee, and David Tatel, a Clinton appointee.
This was the third time Nebraska politicians have unsuccessfully challenged the constitutionality of the Safe Drinking Water Act in court.
"State officials, siding with industry, keep insisting that it is OK for the people of Nebraska to drink water containing more arsenic than in the rest of the country," Olson added. "It's three strikes, and they're out."
