For decades, public health advocates have championed harm reduction for people who cannot stop taking health risks ­ or do not want to. Needle exchange is a classic example. Intravenous drug users get clean needles because, the reasoning goes, contracting and spreading AIDS is worse than making heroin use a little easier.

But harm reduction for hard-core smokers is another matter.

At issue is a form of smokeless tobacco, a popular Swedish product called snus (rhymes with loose) that satisfies smokers' nicotine addiction with negligible health risks of its own. But to many foes of smoking, it is not a lifesaver, but the devil's instrument.

Snus, moist oral tobacco, comes in a tiny tea bag. It sits discreetly between lip and gum. Because it does not stimulate saliva production, there is no spitting. Even better, there is no smoke.

"It is the tobacco smoke, with its thousands of toxic agents, that leads to cancer, heart disease and emphysema," said Dr. Brad Rodu, a pathologist at the University of Alabama at Birmingham.

Eliminate the smoke, and you significantly reduce the risk.

Snus, a Swedish version of snuff, is especially attractive to smokers because it produces nicotine levels comparable to smoking. Gum and the patch administer too little nicotine to reliably prevent craving and withdrawal symptoms.

The health benefits are impressive. Forty percent of Swedish men use tobacco products. Yet Sweden has the lowest rate of lung cancer by far. Why? Largely because of snus, which represents half of all the tobacco that Swedish men use. (The other half smoke.) Snus has not caught on with women.

Smoking opponents should herald snus. But instead, the very notion of harm reduction inflames them.

"It's like trying to play God trading oral cancer for lung cancer," said Dr. Gregory Connolly of the Massachusetts Tobacco Control Program.

Over 20 epidemiological studies show that smokeless tobacco is far safer for mouth cancer than cigarettes. Even traditional smokeless products bring one-third to one-half the risk. Users of snus, which contains low levels of tobacco-specific nitrosamines, a carcinogen, incur a risk of developing oral cancer no greater than nonsmokers, the journal Tobacco Control reported last year.

What about gateway effects? Clearly, if using smokeless tobacco turns people on to nicotine and they "graduate" to smoking, it fails as a public health strategy. But Sweden has the best record of smoking reduction in Europe. Moreover, the proportion of current smokers who are former snus users is far less than the proportion of snus users who once smoked.

In short, snus has largely been a pathway away from smoking, not vice versa. Dr. Lynn T. Kozlowski of the biobehavioral health department at Penn State, found that more than three-fourths of men from 18 to 34 who used smokeless tobacco never went beyond it to cigarettes or had used cigarettes before using smokeless products.

Swedish snus and brands of compressed tobacco like Ariva, Exalt and Revel are available in this country but are hard to find. Most smokers have never heard of them, and many doctors are unfamiliar with the products.

The government, rather than clearing the air, is muddying it. Last year, the surgeon general, Dr. Richard H. Carmona, told Congress, "There is no significant scientific evidence that suggests smokeless tobacco is a safer alternative to cigarettes." This is simply wrong in the case of smokeless tobacco in general, and snus in particular.

"Tips for Teens" from the Department of Health and Human Services answers the question, "Isn't smokeless tobacco safer to use than cigarettes?" with an emphatic ­ and erroneous ­ "no."

"I suppose you could argue that shooting yourself in the leg poses less of a health risk than shooting yourself in the head," a former president of the American Dental Association, Dr. D. Gregory Chadwick, said. "But do we really need to have that discussion?"

Yes, we do. Experts have for years endorsed harm reduction as a pragmatic last resort for addicts, because they are convinced of the relative safety that accrues to the user and society.

No one disputes that quitting is optimal. But that is not practical in every case. Snus in particular, and smokeless tobacco in general, provide clear, lifesaving advantages over smoking that antitobacco activists refuse to acknowledge.

Sally Satel is a psychiatrist and a resident scholar at the American Enterprise Institute.