Betty Marsee tried to convince her son, Sean, of the dangers of using snuff.

But the high school track star always responded, "Mom, there's no warning label and athletes wouldn't advertise it if it was bad for you."

He died of oral cancer in 1984.

A $142.9 million lawsuit against U.S. Tobacco Co. charges that six years of using Copenhagen snuff caused the Ada, Okla., boy's death. The case has yet to come to trial.

Concerns about "smokeless tobacco" -- snuff and chewing tobacco -- are growing as use of the products increases, says Dr. Joseph Cullen, chairman of the surgeon general's panel studying smokeless tobacco use and health problems.

"Nobody used the stuff in quantity when we began studying smoking," says Cullen. "Back in 1975, fewer than 3 percent of adult males used snuff, and fewer than 5 percent used chewing tobacco."

Smokeless tobacco was considered a regional problem, confined to southern states, he says.

In recent years, use of moist snuff has zoomed.

About 22 million persons, or 10 percent of Americans, now use smokeless products, says Cullen. Snuff, which is not chewed, is either inhaled or tucked between the cheek and mouth. Salivia distributes the tobacco taste throughout the mouth, and is then spit out.

Chewing tobacco is chewed, with the user spitting out the juice, until the flavor is gone.

Sales of the fine-cut tobacco used to make snuff and chewing tobacco rose from 15.2 million pounds to 39.2 million pounds in 10 years. Sales of moist and fine cut snuff, the largest share of smokeless tobacco sales, were estimated at $500 million last year.

A further cause for concern is that most growth is from sales to youth, says Cullen.

Earlier this year, the increased sales sparked the Federal Trade Commission to ask the Surgeon General to name a panel to study addiction and diseases related to smokeless tobacco. The Surgeon General's report is not expected before spring, after the National Institutes of Health holds a Concensus Development Conference on snuff and chewing tobacco in January.

The action came after Ralph Nader's Public Citizen Health Research Group petitioned the FTC to require health warnings similiar to those on cigarettes.

While investigation of addiction to smokeless tobacco is sketchy, much research points to links between smokeless tobacco and cancer.

Some research has tied dental problems such as periodontal disease, abrasive tooth wear, gum recession and leukoplakia, a callous in the mouth that is often precancerous.

The International Agency for Research Against Cancer (IARC) found "significant evidence" that snuff causes oral cancer. The IARC, an arm of the World Health Organization, also found some evidence linking chewing tobacco to oral cancer, Cullen says.

"I would be very surprised if our cancer conclusions were any different," says Cullen. His scientists will review the IARC data.

One frequently cited cancer study done in North Carolina in 1981 found women using snuff were four times as likely as nonusers to get oral cancer. And the risk increased 50-fold for women who used snuff for more than 50 years.

On the average, a person with oral cancer has a 40 percent chance of living five years, according to the National Cancer Institute.

Industry officials say warning labels are unneeded because health dangers are unproven.

However, the president of the Smokeless Tobacco Council, Michael Kerrigan, testified at a Congressional hearing that snuff and chewing tobacco should not be sold to children younger than 18 years old.

"We think it's an adult product," says Gail Balph, a spokeswoman for the council. The industry code bars anyone under 25 or an active professional athlete from promoting smokeless tobacco, although former athletes do promote it. Charges of wooing youngsters, she says, are "baloney."

"It can be an alternative to cigarettes. A lot of smokeless tobacco users are people who work in jobs where they can't light up," she says.

Industry ads are aimed at 18- to-25-year old males, not teen-agers, she says.

Despite this, Cullen and others contend industry advertising campaigns target the youth market.

Ads featuring athletes and musicians pushing a "pouch instead of a puff" imply unlit tobacco is a safe alternative to smoking, says Allen Greenburg, a lawyer for Public Citizen.

Cullen says a young person in high school is "looking to the 25-year-old as a peer." And teens who start using snuff may later turn to cigarettes for a quicker nicotine fix, he says.

Many experts agree television advertising influences new users. While cigarette ads are banned from the airwaves, smokeless tobacco ads are unregulated.

"It fits the macho western cowboy image that's fashionable," says Dr. Elbert Glover of East Carolina University, Greenville, N.C. Sales began rising at the same time movies like "Urban Cowboy" sparked the popularity of western culture.

Glover began research on snuff and chewing tobacco after finding a high number of cigarette quitters in Houston high schools switched to snuff or chewing tobacco.

He found that as many as 7 percent of third graders in an Oklahoma school used smokeless tobacco. And 22 percent of high schoolers used the products.

The products are so popular among college students that many colleges have spitting and chewing clubs and contests.

Another study in Arkansas found that 21 percent of kindergarten children -- one in five -- used moist snuff, says Dr. Arden Christen, chairman of Indiana University's department of preventative dentistry.

All warning label advocates agree teen-age peer pressure is a big reason high school and college students chew tobacco.

"Kids in Texas will put the can in their pocket and wash their jeans three or four times so a circular pattern will show through," says Glover. Greenberg says the development of "Skoal Bandits" -- snuff in a pouch -- means youngsters get a "nicotine high" with less danger of nausea from chewing.

Ample research supports nicotine addiction to cigarettes, and a UCLA study found users of smokeless tobacco had blood levels of nicotine and continine -- a metabolic breakdown of nicotine -- as high or higher than smokers.

That may forecast future smoking when users get jobs where spitting is socially unacceptable, Cullen and Greenberg say.

Many users are athletes who would never touch a cigarette, says Greenberg.

That description fit her son, says Betty Marsee.

"He always nagged his sister about smoking, and I quit when he asked me to," she says.

"There's no doubt in my mind he died because of using snuff," says Marsee. Before his death, her son had agreed to lecture with his surgeon on the link between his cancer and snuff.

"I didn't file the suit for money. I did it for the public, for the kids," she says. Some Oklahoma teen-agers have stopped using smokeless tobacco because of her son's death.

Vicki Brown, a reporter for Knight Ridder Financial News Wire, lives in Washington.