In the course of five years of research and writing, I discovered a cultural crime which should not be possible in a free society: a complex corruption of science and a prolonged deception of the public. The crime emerged from the sciences of environmental cancer and cancer prevention, and it has all the superficial characteristics of "The Purloined Letter": It has been committed under our very eyes, its details are publicly recorded in documents which are within hand's reach, and yet it remains invisible to most of the people of this country who are its victims. It is rendered invisible by one thing above all: the phenomenon of "the two cultures"-the dangerous barrier which separates the scientific and the humanist cultures and which may leave even the most educated layman incapable of differentiating between serious science and ideology in a white smock.
One of the realms in which one discovers this complex corruption of science is cancer prevention based exclusively on animal tests. The layman's understanding of this science is severely limited and is usually dominated by the approach to laboratory carcinogens adopted by the press. Shaped by the regulatory process, that approach is to present every announcement that a substance is "suspected" of causing cancer as high drama involving a battle between the regulators and an incriminated industry. My research into animal-man extrapolation, however, turned up an entirely different set of controversies-the extraordinarily large number of theoretical controversies in the academic world that lie concealed behind the regulatory facade. If one does not know these theoretical controversies, if one interprets the science of cancer prevention in purely economic-regulatory terms, one can never judge the nature of that science.
In the course of my investigation I found every reason to believe that the root of the many theoretical battles in the world of cancer research is politics-specifically, warring attitudes toward the American industrial system. One cannot put scientists into rigid boxes, but there do tend to be opposing factions that show up on one side or the other of every one of the specific and interlocking controversies in this field-and the sides are usually determined by whether the position enhances or diminishes the case for stringent regulatory action.
The most fundamental and most dramatic of these politicized academic controversies revolves, inevitably, around that theory in the cancer-prevention repertoire which justifies the most stringent regulatory action: the no-threshold, or no-safe-dose, or one-molecule theory. This theory holds that the most minute amount of a carcinogen, even a single molecule, might give someone cancer and, consequently, that the only safe dose or exposure is zero. The no-threshold theory is the premise of the process by which American citizens are sheltered from carcinogenic risk by American "regulatory" science, whose purpose, unlike that of basic science, is not to understand the biological mechanisms of cancer but to eliminate "suspected" substances from the environment whether biological understanding exists or not.
The no-threshold theory is a remarkable premise, however, for while it is the rock on which the temple of cancer prevention has been built, nobody has any idea if it is true. As Marvin Schneiderman of the National Cancer Institute (NCI) put it at hearings held by the Occupational Safety and Health Administration (OSHA) in 1978:
Another problem and one which unfortunately is not amenable to scientific solution, is the existence of a threshold. Is there a lower limit of exposure below which normal repair and recuperative processes will prevent cancer? This is perhaps one of the most pernicious questions that confront the regulatory agencies. It is the refuge of the apologist for industry and has support from traditional toxicology. [Emphasis added]
A premise that "is not amenable to scientific solution" is a problem in a scientific endeavor, and it does generate hostility to regulators who impose it coercively-not only from "apologists for industry" but from "traditional toxicology," which is to say that a substantial number of "regulatory" scientists are as antagonized by the no-threshold theory as others are devoted to it. In fact, although regulators are loathe to inform citizens that anyone but industrialists condemns their policies, this is by far the most intense battle within the world of "regulatory" science itself.
The academic conflict over the no-threshold theory is so profound that it has caused certain institutions and people to adopt a position of cautious neutrality. In 1978, the Office of Science and Technology Policy circulated an early draft of its guidelines for the control of carcinogens. The draft was "widely" circulated among scientists, and responses were received from several dozen, including Joseph Fraumeni of the National Cancer Institute (NCI), Philip Handler of the National Academy of Sciences, David Rail of the National Institute of Environmental Health Sciences (NIEHS), Joseph Rodricks of the Food and Drug Administration (FDA), and Arthur Upton of the NCI and the NCI staff. On the basis of the response, the OSTP decided to leave the subject of thresholds out of its policy report: "Most comments made reference to lack of consensus among scientists regarding this issue. Since a full presentation of the debate is beyond the scope of this paper, we have elected to omit explicit reference to thresholds from the paper."
In the same year, Thomas Maugh of Science magazine, who did try to review the debate, also preferred to remain neutral. Acknowledging the intensity of the conflict in the scientific world, Maugh, who is not normally given to hyperbole, said: "Debate between those who think carcinogens can be detoxified and those who do not has raged for years with all the intensity of a jihad. The analogy to religion is not inappropriate, moreover, since there is little hard scientific evidence to support either point of view.... Arguments on both sides of the question often seem to be little more than articles of faith, and it is exceptionally difficult for an impartial observer to decide which faith is more deserving of support."
If one examines the no-threshold/one-molecule debate by itself, one must inevitably end up perched on the fence, for "it is not amenable to scientific solution." If, however, one examines it within the context of the goal of cancer prevention, it becomes luminously clear that the "articles of faith" of one camp-the no-threshold camp-have necessarily been triumphant and that the dissenters against this position have necessarily been defeated in the battle.
The stated goal of the cancer prevention program in the United States is, quite simply, to protect-in advance-every one of the 226,000,000 citizens from the real or potential effects of carcinogens. The goal is stated in slightly different terms by different scientists, although they all mean the same thing. According to one group of scientists at the government's National Cancer Institute, including Charles C. Brown, Thomas R. Fears, and Marvin A. Schneiderman, "all members of a heterogeneous population must be protected at all times," and thus a regulatory agency "must consider the lowest threshold for an individual over his exposure period, as well as the lowest thresholds in the entire population." And Umberto Saffiotti of the NCI expresses the same idea more economically: "A prudent policy of cancer prevention requires protection of the most sensitive individuals in the population." This goal is resonant with good intentions, but it poses very peculiar problems. On the face of it, it is obvious that no one can possibly know the identity of all the individuals in a nation of 226,000,000 or any random portion thereof who will be "most sensitive" to a disease that has not yet occurred as a response to a particular substance in question and that is not in general understood. All that can be known is that individual reactions are very different. Many scientists have testified to OSHA that, as OSHA puts it, there is a "wide variability in susceptibility to cancer within a population." Science is not presently capable of identifying the degree of "susceptibility" of every individual in the nation, particularly in a "heterogeneous" population.
The simplest way for the layman to understand the problem of varied susceptibility to cancer of a "heterogeneous" population is to consider the observation of David Rail of the government's NIEHS. "Man," he has observed, "is among the most heterogeneous systems on earth." In fact, "if sufficient effort were exerted, one could find that metabolically some man would exhibit a pattern like a rat, another man would exhibit a characteristic of a dog, and so forth." The "and so forth," however, is more important than the rest, because Rail only mentioned laboratory animals; but his statement, at a minimum, means that any given man may metabolize a carcinogen like any given mammal-that is, that somewhere a citizen of the United States may be metabolizing carcinogens like a gorilla, a leopard, a zebra, or an aardvark. The ultimate goal of cancer prevention in a heterogeneous species, then, is to protect that unknown susceptible citizen living somewhere on this gigantic continent who may, unknown to him or anyone else, metabolize carcinogens like an aardvark; and the aardvark, for all we know-since "sufficient effort" has not been exerted-may be helplessly vulnerable to carcinogens.
For the sheer pleasure of naming things, we will call this the Aardvark Principle. This "principle" is merely a symbolic restatement of the goal of cancer prevention as defined with greater solemnity by the above-quoted scientists at the NCI. Accordingly, OSHA, one of the government's leading regulators of environmental carcinogens, defines a threshold in the manner most appropriate to the Aardvark Principle: For scientific or regulatory purposes, threshold would be a dosage level below which an effect (cancer) could not and never would occur, not merely a point below which an effect would be infrequent, no matter how very infrequent. [Emphasis in original]
It must now be observed that the Aardvark Principle, all the more formal definitions of the goal of cancer prevention by NCI scientists, and OSHA's definition of a threshold as a dose that "could not" and "never would" cause a carcinogenic response in a single citizen have one unusual thing in common: To establish a threshold dose, all require the proof of a negative, which is impossible in logic. There is no way of demonstrating that an unknown individual in a population of 226,000,000 is not unusually susceptible to a disease whose mechanism is unknown; there is no way of demonstrating that an unknown individual does not metabolize carcinogens like an aardvark; there is no way to identify any metabolic response that "could not" and "never would" occur. The goal of cancer prevention may be resonant with good intentions, but a student of Logic I who presented a comparable proposition would receive a resonant F. Assuming, however, that one accepts a public health goal that sets forth the need for a set of logically impossible calculations, one must thereafter conclude that one cannot perform those calculations-which is to say that one cannot calculate a threshold dose for man for any carcinogen.
In fact, a great many scientists have understood perfectly well that there is no way on earth to calculate a threshold dose for a population. Some scientists simply say forthrightly that the calculations cannot be performed and, short of challenging the logic of the goal, explain why. For example, Harold Stewart of the National Institutes of Health, chairman of the Ad Hoc Committee on Testing for Environmental Carcinogens, was quoted by OSHA as follows: