Some cigarettes now have so little tar, nicotine and other harmful elements that they can be called "less hazardous" and can even be smoked in "tolerable" numbers without "appreciable" ill effects on the average smoker, a leading federal cancer scientist said yesterday.

Cigarettes in recent years have been found guilty beyond reasonable doubt of causing lung cancer, heart disease and several other illnesses.

But Dr. Gio Batta Gori, deputy director of cancer prevention at the National Cancer Institute, and Dr. Cornelius J. Lynch said yesterday there has been huge progress "in the last year and year and a half" in removing toxins - or poisons - from some brands. They expect to report this soon in the Journal of the American Medical Association.

"I am not calling any cigarette 'safe'," Gori emphasized. "The only cigarette that is safe is the cigarette that is not lit.

"I am not talking about what might happen to any individual. I am talking about averages. There may be a risk that still may be there even though we might not see it in overall, large population studies."

Still he said, there has been so much progress in removing toxins that "we can now begin to talk about 'tolerable' levels of smoking from an overall, public health standpoint. I think we will begin to see some beneficial effect in this country" - that is, some abatement in this nation's lung cancer epidemic - "in five or six years."

Gori said one brand - Carlton Menthols - is so low in the toxins that most persons could smoke 23 a day, mor than a pack, with no measurable risk beyond a nonsmoker's.

He said the average smoker might similarly consumer 18 Now Menthols, 17 Nows or Strides or 16 Caltons without any problems beyond a nonsmoker's so far as large-scale statistical studies could detect.

A cancer institute spokesman yesterday said Gori "probably represents the best expertise we have on smoking and health. "Until two weeks ago he headed the institute's program in that field, including the effort to learn to make less hazardous cigarettes. Dr, Arthur Upton, cancer institute director, nonetheless issued a more cautious statement yesterday saying your present knowledge does not permit us to establish" any levels "below which smoking might be safe."

"It is the firm position of the National Cancer Institute, the National Heart, Lung and Blood Institute and the Public Health Service that no cigarette now on the market can be considered wholly without risk to health," he said.

He said Gori's figures cannot indicate whether the risk to any single individual is large or small, only that it is "not demonstrable" in epidemoilogic or population studies. Upton said "you might double your own risk of cancer," for example, "with no appreciable effect" on large-scale population studies."

Gori also said there are many "high risk" individuals who should "never" smoke. These include present or former workers exposed to asbestos or the families of such workers, women using oral contraceptives, pregnant women, and persons with any of the heart, lung or breathing disorders linked to cigarettes.

Some scientists would also caution anyone exposed to any potentially cancer-causing chemical, since many harmful chemicals add to each others' effects in ways that are still little understood.

"What I am saying," Gori explained, is that the average effect of smoking "tolerable" levels of certain "less hazardous" cigarettes today would be as small as the ill effect on persons who smoked only two cigarettes a day before 1960. Virtually all cigarettes then were loaded with poisons like tar and nicotine far beyond present levels.

Gori disclosed his estimates first in an interview with Associated Press reporter Michael Putzel. The Washington Post then obtained a copy of the Gori-Lynch report.

Lynch is manager of the smoking and health program at Enviro Control Inc. of Rockville, the cancer institute's main contractor in the effort.

The five leading brands of less hazardous cigarettes on the Gori-Lynch list - Carlton Menthols, Now Menthols, Nows, Strides and Carltons - represented just under 2 percent of all cigarettes sold last year. Lynch estimated. But 22 more brands - with 17 to 18 percent of the market - are low enough in toxins so the average smoker might use between three and eight a day without appreciable added risk, Lynch said.

The cancer institute program to remove or minimize the effect of the main toxins found in cigarettes or cigarette smoke - tar or "total particulate matter," nicotine, carbon monoxide, nitrogen oxides an acrolein - began in 1970. At the most it has cost $4 million a year, a drop in the bucket compared to the cost of smoking's huge toll in death and disease.

Still, it is a program that has often been flayed by some critics of smoking who have argued that efforts should be concentrated on halting smoking altogether.

"I think ours has been a worthwhile program," Gori replied. "We are not trying to endorse cigarettes or smoking in any way. We are only trying to put the facts before the public.

"If we could go from 100,000 cases of lung cancer a year to, say, 2,000 or 3,000 by the development of less hazardous cigarettes, I would still regret the 2,000 or 3,000 deaths but I would think we would have made a tremendous public health gain."