An obituary notice should not be the occasion of controversy, but neither should it be the means of spreading a common -- and dangerous -- misconception. Fortunately, the quarrel I have to pick with The Post's obituary of Dr. Wilhelm Heuper (Jan. 1) has to do, not wirh dr. Hueper's accomplishments, which were notable, but rather with the obituary's evaluation of them.

Writing of Dr. Heuper's conviction that most cancers are environmental in origin, the obituary writer concluded, "Although many considered him an alarmist at the time, authorities now acknowledge that 70 to 90 percent of all cancer is related to environmental factors." Even though this "70 to 90 percent" figure is passing into common belief in a manner akin to the folk myth that aspirin mixed with Coca Cola renders a young lasy incapable of sexual discretion, its pooular acceptance does not make it true. There are two fundamental problems with The Post's unequivocal statement that, "Authorities now acknowledge...." First, by no means all authorities acknowledge anything of the kind. Second, even those who do delieve it use the word "environmental" in a manner that has nothing to do with the popular sense of the word.

The figure of "70 to 90 percent" was initially derived not from any direct evidence or even epidemiologic data, but by a rather ingenious and unusual statistical construct. Statisticians at the World Health Organization examined the incidence of different cancers in the various nations of the world. Taking the country with the lowest incidence of a paricular cancer as the baseline, they suggested that this rate indicated the rock-bottom genetic susceptibility to a particular tumor, and that any mortality rate above it was due to environmental factors.

This is a valid approach to cancer epidemiology, but it's by no means without problems. Quite obviously, the reliability of death certificates varies from country to country, and few people claim that the "cause of death" in El Salvador or Indonesia is as well authenticated as it is in Sweden. Furthermore, the method depends on the assumption that the genetic susxeptibility to various cancers is the same for all races and population groups. This, too, is a rather over-reaching assumption; The high rate of stomach cancer in Japan may be due to dietary factors or it may be due to genetic susceptibility, or it may be due to an interaction of the two.

This, however, is certain -- the "70 to 90 percent" figure is a hypothesis, and one which many authorities in the field of carcinogenesis dispute. Assessing the evidence, the editorial board of the respected English medical journal Lancet in 1977 referred to the 90 percent figure as a "rumor," and concluded that the figure was unsubstantiated. Just last month Lancet reviewed the controversy on occupational-environmental carcinogenesis. In words unusually sharp for a scientific journal it called a recent National Institutes of Health estimate of occupationally-related cancers "insubstantial" and concluded that, "It is sad to see such a fragile report under such distinguished names."

At this point it is important to clear up a serious misconception about the word "environmental" as it is used by some cancer epidemiologosts. Rather than using it to mean factors in air, food and water over which the individual has no control, cancer epidemiologists have used it to mean everything other than heredity. Personal habits are therefore considered an "environmental" factor and, in carcinogenesis, foremost among these is cigarette smoking. Since cigarette smoking is associated not only with cancer of the lung, but also cancer of the bladder, larynx, and mouth, its contribution to "environmental" tumors is enormous -- some authorities estimate that 25 percent of all cancers are cigarette-related. Cigarettes appear to have a synergistic effect on many occupational carcinogens -- thus, it's bad to smoke, it's danderous to work with asbestos, but it's several times more dangerous to do both.

Many cancers besides cigarette-associated tumors are "environmental" if the wors is used (as it is used in the 90 percent estimate) to refer to personal habits. Cancer of the esophagus and liver are virtually unknown in our society among non-drinkers. One of the most obvious "environmental" cancers is cancer of the cervix, the one in which the Pap smear is used as a detection device. The environmental offender here is sexual intercourse. Cervical cancer is almost never found in virgins, and its incidence is most directly linked to early onset of intercourse, frequent intercourse, and multiple partners. Basal cell and squamous cell cancers of the skin (among the most common of all cancers) are strongly associated with another essentially individual "environmental" factor -- exposure to the sun.

Confusion also results from a tendency to confuse statistics about "environmental" cancer with those relating to "occupational" cancer -- indeed, the recent Lancet editorial progresses imperceptibly from a discussion of the former to an examination of the latter. In his book "The Politics of Cancer" Dr. Samuel Epseein does not always make the distinction clear. Sir Richard Doll, Who believes that 90 percent of cancers are "preventable," feels that only "a very small percentage" are occupational.

Still, even if one realizes that the word "environmental" is used to include personal habits, it is clear that for many of our most serious cancers we have only the faintest glimmerings about causation. The epidemiology of colon cancer, for example, seems associated with fat in the diet, but the association is so tenuous, so interwoven with a dozen other individual and social factors, that no reputable scientist considers it other than a hypothesis. With cancer of the prostate, the third most common cancer in men, even a hypothesis barely exists. The viral theory of carcinogenesis, everyone's favorite 10 years ago, still is strong, particularly in reference to Hodgkin's disease, other lymphomas and some leukemias.

The reason it is important to challenge the "70 to 90 percent" figure is that not only is it misleading and far-from-universally accepted, but also that it leads to an air of fatalism in the general public, expressed in the bumper sticker, "Life Causes Cancer." After all, if 90 percent of cancer is "environmental," why should the individual stop smoking or cut down on his drinking? The unquestioned truth is that, of those cancers in which we have a pretty good idea of the cause, the individual has control over exposure. Placing responsibility on the individual has been derided by some sociologists as "blaming the victim." I'm no great fan of haranguing the public about its habits, but truth is truth. As the French scientist Lucien Israel says in his book, "Conquering Cancer," "It is still better to be a nonsmoker in Paris than to smoke 40 cigarettes a day in the mountain pastures of Lozere." This is not "blaming the victim" -- it is a statement of epidemiologic fact. It is just as true that, as our laboratory methods get more precise, some genuine environmental contaminants -- both industrial and non-industrial -- will be identified as significant carcinogens. Many occupational carcinogens are already known, and some may be dangerous, not merely to the people who make them, but also to those who use them. "Blaming the victim" by no means excludes "blaming the polluter" -- it merely depends on the kind of cancer. In the field of carcinogenesis, there is responsibility enough for everyone.