The quality of the air you breathe is on the line in this year's election. And the purity of your drinking water. And whether polluters will have to pay to clean up the cancer-causing chemicals they've left in the Hudson River, the Great Lakes and waters across America.

That's because the next President will likely appoint several Justices to the Supreme Court, which, depending on the wisdom of those choices, could imperil the environmental progress we have achieved.

Over the past 30 years, our nation has substantially cleaned up our air and water--thanks to citizen enforcement lawsuits, tough federal laws that regulate interstate pollution and the ability of Congress and executive agencies to employ modern, innovative solutions to environmental problems as our society grows more complicated. However, conservative Justice Antonin Scalia has been leading an effort on the Supreme Court to revive obscure legal doctrines that restrict the ability of the government and citizens to protect our environment. If the next President appoints more Justices in the mold of Justice Scalia, our environmental standards are at grave risk.

And a conservative Scalia Court is not just a doomsday prediction: Texas Gov. George W. Bush publicly stated on "Meet the Press" one year ago yesterday that Justice Scalia is his model for a Supreme Court Justice.

While scholarly and accomplished, Justice Scalia advocates a judicial philosophy that looks backwards into the 19th century and that seeks to roll back years of environmental progress.

Leading legal scholars consider Justice Scalia the most anti-environmental Justice ever to sit on the Supreme Court. Even other conservative Justices, such as Justice Sandra Day O'Connor, often disagree with Justice Scalia in environmental cases because of his failure to acknowledge scientific progress.

The Scalia philosophy would slam the courthouse door shut on citizens bold enough to seek to enforce environmental laws that safeguard our air and water, defend our wildlife heritage and protect communities from toxic pollution. When Congress passed the Clean Water Act, Clean Air Act and Endangered Species Act, these laws gave people the power to file lawsuits to prevent environmental crimes and protect their families' health without having to wait on the slow grind of government's gears. But Justice Scalia would strip citizens of the power to protect their families from pollution.

For example, in a case decided earlier this year, Justice Scalia expressed horror that a person who lives near a polluting plant would be able to hold the company accountable for violating the law. Justice Scalia argued that the Court was making it too easy for people to fight environmental threats in their own neighborhoods. Never mind that the factory in question had poisoned a river by dumping toxic mercury into the water 489 separate times.

The good news is that Justice Scalia was in the minority and that his views did not prevail that time. But that could change if the next President were to add more like-minded Justices to the Supreme Court.

It's not only citizen enforcement suits authorized by Congress that draw Justice Scalia's anger. He also opposes efforts to enact uniform national laws to address nationwide problems. Air and water pollution respect no borders. People in downstream states have no ability to protect themselves from upstream pollution without strong federal protective laws. But, for the first time in generations, federal courts and the Supreme Court in particular are on the brink of turning the clock back to a time when the citizenry--including industries--was at the mercy of a crazy quilt of inconsistent and often grossly inadequate state laws.

Additionally, this year the Supreme Court faces the question whether a long-dead legal doctrine will prevent Congress from protecting the nation from air pollution. And it is widely anticipated that Justice Scalia will side with the 19th century, preventing the Environmental Protection Agency from applying scientific data to tackle our complex air pollution problems. Last year, a lower federal court struck down new, greatly improved soot and smog standards. Will the Supreme Court allow us to keep our air clean? While the question hangs in the air, pollution burns the lungs of people suffering from asthma.

The environment will suffer profoundly if the next President packs the Supreme Court with members who share Justice Scalia's disdain for the legal means Americans have used to clean up our air and water. While the next President will only be in office four to eight years, his legacy on the Supreme Court could harm our environment and our communities for more than a generation.

Robert Cox is president of the Sierra Club and professor of communication studies at the University of North Carolina at Chapel Hill.