Is Any Radiation Too Much Radiation?

More thoughts on the question of thresholds


Nuclear energy has come under increasing attack in recent months from some people who line up on the side of individual liberty. They argue that, since nuclear power generation necessarily involves the emission of some amount of radiation, "by its very nature" it causes "premeditated random injury or murder" of innocent, nonconsenting persons and threatens "genetic damage for generations to come." And they conclude that it thus violates the "libertarian rule of law" by depriving people of life "without due process of law." (The representative quotes are from John Gofman, Libertarian Review, Sept./Oct. 1979, and John Gofman and Egan O'Connor, Inquiry, Feb. 18, 1980.)

In reply, Bernard Cohen has written an excellent defense of nuclear power (REASON, Mar. 1980), but his arguments fall short of supporting its safety completely, especially since he agrees with Gofman on the scientific acceptability of the so-called linear hypothesis, which assumes that radiation is harmful at low doses since we know that it is at high doses. They differ only on the questions "How harmful?" and "Is this harm acceptable?"


Gofman argues that no amount of risk and harm is acceptable, just like the "Delaney clause" allows food producers to use no amount of an additive shown to cause cancer at high doses. Cohen replies that Gofman's estimates of harmful effects from low doses are much exaggerated and that the actual risks are far less than those we commonly take and "accept" everyday in other areas. But they both fail to see the scientific and legal merits of the contrary "threshold hypothesis," which assumes that there is no harm below a certain dose until and unless proven otherwise.

Scientifically, there are plenty of things that are harmful at high doses but required for human survival at low doses. Water, salt, and vitamins A and D are common examples. These cases dictate against making the "linear hypothesis" a general assumption, even for a cancer-causing substance, since it assumes that the human body does not have any defenses. Surgeons obviously make the "threshold" assumption when they remove most of a large malignant tumor in the belief that the body's natural defenses can then handle the small amount left.

Again, animal studies show "negative" (lack of harm) effects at low levels of radiation. This, however, does not "absolutely prove" that there is a threshold, since this is an impossible task, requiring the testing of all animals and humans (past, present, and future) to show that none of them is harmed at low levels. On the other hand, it is possible to show harm below a presumed threshold, simply by producing one animal or human, or a group of them, harmed at a lower dose. Thus, the legal burden of proof must be placed on those who claim that these are "false negatives"—on Gofman and others who say that we are mistaken in believing that radiation is safe below a certain threshold, that it is in fact harmful (and that someday we will have the resources to prove this).

This placement of the burden of proof also conforms with the libertarian principle that all persons have the right to do as they want so long as they do not violate the rights of others. That is, this principle entails the legal presumption that a person is not violating another's rights unless it is proven otherwise. This is the difference between living in a statist society where an "environmental impact statement" has to be filed before one acts, and a libertarian society where one is free to act until one has infringed or threatened to infringe upon others' rights. Both "libertarian rule of law" and "constitutional due process of law" presume innocence, not "premeditated random murder."


Nonetheless, the "linear hypothesis" has at least two nonlegal uses. Insurance companies can use it to estimate their maximum liabilities and to calculate premiums for insuring nuclear plants and medical uses of radiation. Second, since it can be expensive for an individual to prove harm from a particular source of radiation, one can, in effect, insure oneself for this eventuality by paying a scientific organization (like the National Academy of Sciences) to conduct further research into the possible truth of the "linear hypothesis." To figure out how much to spend, the "linear hypothesis" can be used to do a "cost-benefit analysis." The costs are what one spends for the research, while the benefits are stopping or preventing the harm, which is calculated by multiplying the amount of harm to be stopped (based on the linear hypothesis) by the probability that there is harm (that the linear hypothesis is true).

So these two debated hypotheses each has a proper place. The threshold hypothesis should be adopted as a legal presumption until proven otherwise, while the linear hypothesis should be used by Gofman and others "to put their money where their mouth is," to come up with the evidence required to return a verdict of guilty for nuclear power.

Bruce Bell recently completed an appointment as a resident fellow at the Reason Foundation and is continuing work applying philosophical, legal, and public policy considerations to the issue of food additives, drugs, and environmental pollution.