Poll after poll shows that the public believes the nation’s air is getting dirtier. That’s flat wrong, of course. Every major form of air pollution – carbon monoxide, sulfur dioxide, nitrogen oxide, even particulate matter, or dust – is down dramatically from two or three decades ago.

But in politics, perception is often what counts, and the press has by and large abnegated its role of skeptical reporting. So even the supposedly anti-environmental President Bush has been pushing a “Clear Skies” proposal, first proposed in 2003, aimed at reducing the remaining air pollution by 70% by the year 2018. Mr. Bush included a strong pitch for Clear Skies in his State of the Union speech last week.

The proposal includes a market-oriented trading system that would produce the reductions far more efficiently than the old command-and-control approach favored by the environmental left. But the tighter standards will yield only diminishing returns, according to most studies. If the administration isn’t careful, the new trading system could simply be a more efficient route to a very bad end.

Mr. Bush needs to use the bully pulpit to make clear that things, far from getting worse, actually have been getting significantly better. Air pollution has been cut in half in recent decades even as the economy has more than doubled. This was achieved not just because of government regulation but because of the natural process of replacing older, polluting technology, with newer, more efficient – and thus less polluting – technology.

And precisely because the low-hanging fruit have already been picked, further reductions will be far more difficult and expensive. That’s why it would make sense in any case to shift to a system that sets clear, enforceable – but realistic – targets and lets industry figure out how – and how fast – to get there.

Similarly, Clear Skies would allow industry to upgrade plants and equipment without triggering the inflexible “new source review” mechanism that the Clinton administration had used to bludgeon power-plant operators and others into installing state-of-the-art pollution controls before the old equipment had worn out. This requirement was a classic case of allowing the best to become the enemy of the good. Not only did it drive up electricity prices, it gave many companies incentives to leave the old, polluting equipment in place.

The problem is that the environmental left is using Clear Skies to push for even more draconian standards. Clear Skies would require a 70% reduction in mercury emissions. Environmentalists, predictably, are demanding a 90% reduction, a Utopian goal that would be fantastically expensive and yield no measurable extra health benefit.

Worse, environmental lobbying groups are insisting that Clear Skies include limits on carbon dioxide emissions. This would be a backdoor means of hitching America to the disastrous Kyoto Protocol negotiated by the former vice president, Al Gore, in 1997 to combat the supposed danger of global warming. But Co2 isn’t toxic, so it has no place in this bill. And even when the Democrats controlled the Senate, they blocked the Kyoto agreement by a vote of 95-0, recognizing it would be disastrous for the nation’s economic health.

The administration may be kidding itself if it thinks Clear Skies will bring an end to the extensive litigation over Clean Air issues, often setting state against state, which has characterized the last decade. But by clarifying the standards, setting tangible goals, and providing a market mechanism for rational action – companies that exceed the standards could sell credits to those that don’t, giving the latter time to get into compliance – individual states would have less incentive to be at each other’s throats.

This is particularly important for the industrial heartland, which otherwise faces a possible economic meltdown at the hands of the environmental crazies over ever shifting standards and unpredictable court rulings. Democrats like Michigan’s Senators Carl Levin and Deborah Stabenow may be tempted to oppose Clear Skies on partisan grounds. But if they and their colleagues continue to stand on the sidelines, the industrial heartland, and in particular the American auto industry, will continue its long, painful slide – eventually followed by the country as a whole.

Mr. Bray is a Detroit News columnist.