ANS National
 Meetings/
 Sessions

November 1995

A. N. Tschaeche

(INEL/LITCO)

4. The Linear Hypothesis - An Idea Whose Time Has Passed

                 “The linear no-threshold hypothesis is the basis for radiation protection standards in the United States. In the words of the National Council on Radiation Protection and Measurements (NCRP), the hypothesis is: ‘In the interest of estimating effects in humans conservatively, it is not unreasonable to follow the assumption of a linear relationship between dose and effect in the low dose regions for which direct observational data are not available.’¹ The International Commission on Radiological Protection (ICRP) stated the hypothesis in a slightly different manner: ‘One such basic assumption ...is that ... there is ... a linear relationship without threshold between dose and the probability of an effect.’²  The hypothesis was necessary 50 yr ago when it was first enunciated because the dose-effect curve for ionizing radiation for effects in humans was not known. The ICRP and NCRP needed a model to extrapolate high-dose effects to low-dose effects. So the linear no-threshold hypothesis was born. Certain details of the history of the development and use of the linear hypothesis are presented. In particular, use of the hypothesis by the U.S. regulatory agencies is examined. Over time, the sense of the hypothesis has been corrupted. The corruption of the hypothesis into the current paradigm of ‘a little radiation, no matter how small, can and will harm you’ is presented. The reasons the corruption occurred are proposed. The effects of the corruption are enumerated, specifically, the use of the corruption by the antinuclear forces in the United States and some of the huge costs to U.S. taxpayers due to the corruption. Examples are given of how and why those costs have been created. Players in the creation of the costs have been the regulators, Congress, the antinuclear forces, the nuclear industry itself, and the public. The interrelation and communications among those groups that resulted in creating the costs are examined. A pessimistic future for the nuclear industry and lost benefits to society are forecast if the hypothesis continues to be the basis for radiation protection standards in the United States.

                “Analternative basis for radiation protection standards to assure public safety, based on the weight of scientific evidence  on radiation health effects, is proposed. The basis is a numerical value for annual permissible dose. If an individual's dose remains below that value, no cost would be justified to reduce it further. If it were anticipated that the dose would significantly exceed the standard, the concept of ALAP, or keeping the dose as low as practicable, taking into account economic and social considerations and individual circumstances, would be applied. The same value is proposed for both radiation workers and the general public. It is proposed that studies of groups of individuals who are exposed near the limit be funded by the federal government to verify that no harm is observed.  It is further proposed that other standards be developed to prevent the spread of radioactive material into industrial processes that are particularly sensitive to the presence of such material.  Examples of such processes are photographic film and paper manufacture, computer chip manufacture, radiation measuring equipment manufacture, and research laboratories that use radioactive material. These latter standards are not safety standards. With this two-tiered set of standards, one to assure health and safety purposes, the other for industrial and research purposes, comparable to industrial ‘clean room’ standards, members of the public would be informed that a little radiation would not hurt them, and that radioactive material may otherwise need to be controlled so that it will not be deleterious to certain manufacturing and research activities. The evils and unwarranted costs of the linear hypothesis would then be eliminated. The nuclear industry will then be able to continue to provide the enormous benefits to society that it is uniquely capable of providing.

1.‘Basic Radiation Protection Criteria,’ NCRP-39, p. 55 (1971).

2.‘Recommendations of the International Commission on Radiological Protection,’ 1CRP-26, Para. 27 (1977).