On Jan. 1 the Ottawa Citizen, the only English-language daily in the Canadian capital, will become the fifth Ontario newspaper to refuse to carry tobacco advertising.

The five newspapers account for about 45 percent of the weekday circulation in the province and for 20 percent throughout Canada. By year's end other Canadian newspapers are expected to follow their lead, according to Garfield Mahood, the executive director of the Non-Smokers Rights Association.

The NSRA has been credited with keeping alive the debate -- which has engaged publishers in the United States as well -- over whether newspapers ought to ban advertising for a product that poses a known health risk. Those who oppose a ban say it would violate an advertiser's basic rights.

The move to ban tobacco ads in Canada started at two small and independently owned papers, The Whig-Standard in Kingston, Canada's oldest daily, which acted in November 1984, and The Recorder and Times in Brockville, in April 1985. Two of the nation's largest papers followed: The Globe and Mail, the Toronto-based national newspaper and the third-ranking in daily circulation, which announced its tobacco ban in August 1986, and The Toronto Star, the largest daily, which followed in February 1987.

By contrast, in the United States 11 dailies refuse tobacco ads, but their combined weekday circulation of about 390,000 is 0.6 percent of the national total.

In both countries tobacco advertising accounts for a slim share of total newspaper ad revenue -- an average of one-half of 1 percent.

The 11 U.S. dailies include several that also turn down ads for alcoholic beverages, and the two largest -- the Christian Science Monitor (150,800), and the Deseret News of Salt Lake City (63,100) -- have ties to churches that oppose use of tobacco.

Another sharp Canadian-U.S. contrast involves pending bills to ban all print tobacco advertising and promotion.

In Ottawa, Conservative Prime Minister Brian Mulroney's government introduced a bill so tough it would bar tobacco companies that sponsor athletic and cultural events from using their brand names and trademarks. The five Ontario papers -- along with many other Canadian dailies that continue to take tobacco ads -- have endorsed the bill, and it is expected to pass.

In Washington, Reps. Mike Synar (D-Okla.) and Bob Whittaker (R-Kan.) have introduced similar legislation. The Reagan administration and the American Newspaper Publishers Association -- whose members account for about 90 percent of daily and Sunday circulation -- oppose it, on First Amendment grounds, and it is given little chance of passage.

In interviews, Canadian publishers cited unparalleled pressures from the NSRA, described by a U.S. trade publication as "one of the fiercest {lobbies} in the world."

NSRA, in a campaign begun in May 1984, argued that tobacco ads violated the Code of Advertising Standards, which newspaper industry organizations endorse, and which -- like NSRA itself -- has no precise U.S. equivalent. The code's clause 11 prohibits advertising that encourages "unsafe or dangerous practices."

Among the U.S. papers that do accept tobacco ads, many have carried editorials calling smoking a danger to health, while saying that refusing ads for tobacco could set a bad precedent under which commercial speech protected by the First Amendment would be denied to other legal products alleged to be harmful, such as cholesterol-rich eggs and ice cream.

Washington Post Publisher Donald E. Graham said, "Our policy is, we allow advertising of lawful products within certain well-defined limits, and we don't allow that to inhibit our news coverage. As a newspaper, our job is to see to it that readers know what reputable people think are the harmful effects of various products."

"If it is legal to sell a product, it should be legal to advertise it," senior executives of the American Newspaper Publishers Association and the Magazine Publishers Association said in a letter to the American Medical Association. Reflecting the view of the Tobacco Institute as well as of many U.S. newspapers and columnists, the letter also said, "This 'commercial speech' is constitutionally protected."

In Ottawa, Citizen Publisher Russell A. Mills rejects the argument. He said in an interview that "the First Amendment should be preserved for more significant issues than this," and that whether to take tobacco ads "is an ethical issue."

Journalism professor Tom Goldstein, in a 1986 study for the Twentieth Century Fund, argued that "there is no such thing as a constitutionally guaranteed 'right to advertise.' " Goldstein said "the almost universal response" to a questionnaire he sent to 110 publishers "was that they accept advertising for all lawful products."

However, he found that papers routinely decline ads for a wide range of legal products, including X-rated movies, "Happy Hours," Planned Parenthood services, academic papers written by agencies for students, a union's plea for reduced imports of foreign clothing, liquor -- even coffee and tea -- envelope stuffing and home sewing.

Citizen Publisher Mills called tobacco "a product that would not be legal if it came along today," partly because it has been shown to be "powerfully addictive" and "a carcinogen." Tobacco "should not be legal," but is so "only because 25 percent or 30 percent of the population is addicted to it," he said.

Whig-Standard Publisher Michael L. Davies, in a Whig-Standard news story, said he had first considered banning tobacco ads in 1981, when a severe recession spurred his entire work force to make a desperate effort to prop up falling ad and circulation revenue to avoid layoffs.

He said in an interview that he held off the ban because only tobacco-ad income -- about $50,000 a year -- prevented the layoffs. But he vowed a fresh look when business improved. "The time has come," he said in the 1984 story.

The prestigious Globe and Mail published an editorial, "No tobacco promotion," that said, " ... tobacco is legal only because it was introduced before its full effects were known. If a manufacturer were to propose today to market a product which produced addiction, disease and death in epidemic proportions ... it would have no more chance than a request to add a known carcinogen to baby food.

"The logic of this, of course, is that tobacco should be banned. But we must live in the real world. However desirable a ban might be in theory, in practice it would simply be unenforceable. ...

"Why single put tobacco? Because, unlike even alcohol, whose abuse can destroy the lives of drinkers and create other victims, tobacco is unsafe when used precisely the way the manufacturer intends. Society has an interest, both in human and financial terms -- smoking costs an estimated $6 billion a year in health costs in Canada -- in trying to prevent further addiction."

The independent Toronto Star, announcing its decision on its front page, said tobacco advertising had provided about $1 million in annual revenue.

David Jolley, company president, said in an interview, "I didn't want to profit any longer from tobacco advertising. I don't think anybody can argue any longer with the harm that's done by smoking."

He said an especially vexing issue was the "advertiser's right to advertise." But in the end, he said, the conclusion was that the situation had reached "the point where I think I didn't want to make money out of it."