If you want a single example that captures why so many people no longer believe in the good intentions of the Bush administration, look at the case of mercury pollution.

Mercury can damage the nervous system, especially in fetuses and infants -- which is why the Food and Drug Administration warns pregnant women and nursing mothers against consuming types of fish, like albacore tuna, that often contain high mercury levels. About 8 percent of American women have more mercury in their bloodstreams than the Environmental Protection Agency considers safe.

During the 1990's, government regulation greatly reduced mercury emissions from medical and municipal waste incineration, leaving power plants as the main problem. In 2000, the E.P.A. determined that mercury is a hazardous substance as defined by the Clean Air Act, which requires that such substances be strictly controlled. E.P.A. staff estimated that enforcing this requirement would lead to a 90 percent reduction in power-plant mercury emissions by 2008.

A few months ago, however, the Bush administration reversed this determination and proposed a ''cap and trade'' system for mercury that it claimed would lead to a 70 percent reduction by 2018. Other estimates suggest that the reduction would be smaller, and take longer.

For some pollutants, setting a cap on total emissions, while letting polluters buy and sell emission rights, is a cost-efficient way to reduce pollution. The cap-and-trade system for sulfur dioxide, which causes acid rain, has been a big success. But the science clearly shows that cap-and-trade is inappropriate for mercury.

Sulfur dioxide is light, and travels long distances: power plants in the Midwest can cause acid rain in Maine. So a cap on total national emissions makes sense. Mercury is heavy: much of it precipitates to the ground near the source. As a result, coal-fired power plants in states like Pennsylvania and Michigan create ''hot spots'' -- chemical Chernobyls -- where the risks of mercury poisoning are severe. Under a cap-and-trade system, these plants are likely to purchase pollution rights rather than cut emissions. In other words, the administration proposal would perpetuate mercury pollution where it does the most harm. That probably means thousands of children born with preventable neurological problems.

So how did the original plan get replaced with a plan so obviously wrong on the science?


E.P.A. experts normally study regulations before they are issued, but they were bypassed. According to The Los Angeles Times: ''E.P.A. staffers say they were told not to undertake the normal scientific and economic studies called for under a standing executive order. . . . E.P.A. veterans say they cannot recall another instance where the agency's technical experts were cut out of developing a major regulatory proposal.''

Mercury is just a particularly vivid example of what's going on in environmental protection, and public policy in general. As a devastating article in Sunday's New York Times Magazine documented, the administration's rollback of the Clean Air Act has gone beyond the polluters' wildest dreams.

And the corruption of the policy process -- in which political appointees come in with a predetermined agenda, and technical experts who might present information their superiors don't want to hear are muzzled -- has infected every area I know anything about, from tax cuts to matters of war and peace.

A Yawngate update: CNN called me to insist that despite what it first said, the administration really, truly wasn't responsible for the network's claim that David Letterman's embarrassing video of a Bush speech was a fake. I still don't understand why the network didn't deny White House involvement until it retracted the charge. But the main point of Friday's column was to highlight the way CNN facilitated crude administration smears of Richard Clarke.