Final report of the Advisory Committee on Human Radiation Experiments.

  • United States. Advisory Committee on Human Radiation Experiments.
Date:
1996
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Licence: Public Domain Mark

Credit: Final report of the Advisory Committee on Human Radiation Experiments. Source: Wellcome Collection.

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    raised by these developments, radiation research- ers would be on the front line in having to deal with them. The burgeoning government-funded biomedical research, including human radiation research, required a reexamination of the tradi- tional doctor-patient relationship. At the same time, the evolving role of medical researchers as government officials and advisers also posed questions about the place of doctors, and more generally of scientists, in service to government. THE BASICS OF RADIATION SCIENCE The ethical and historical issues of human radia- tion experiments cannot be understood without a basic grasp of the underlying science. This re- quires more than a glossary defining technical terms. At least an intuitive understanding of the natural laws and scientific techniques of radia- tion science is necessary. Obviously, acquiring a professional level of knowledge would require far more time than most readers can afford; indeed, entire careers are devoted to studying just one aspect of the field. To serve the inter- ests of democracy in a technological world, however, we must provide sufficient technical background for all citizens to become active par- ticipants in considering the ethical and political dimensions of scientific research. What follows is an attempt to provide such a background for the events and issues discussed in this report, directed toward those readers less familiar with “the basics” of radiation science. This task was deemed important enough to de- serve a distinct section of this Introduction. What Is Ionizing Radiation? What is radiation? Radiation is a very general term, used to describe any process that transmits energy through space or a material away from a source. Light, sound, and radio waves are all examples of radiation. When most people think of radiation, however, they are thinking of sonizing radiation—tradia- tion that can disrupt the atoms and molecules within the body. While scientists think of these emissions in highly mathematical terms, they can be visualized either as subatomic particles or as rays. Radiation’s effects on humans can best be understood by first examining the effect of radiation on atoms, the basic building blocks of matter. What 1s ionization? Atoms consist of comparatively large particles (protons and neutrons) sitting in a central nucleus, orbited by smaller particles (electrons): a miniature solar system. Normally, the num- ber of protons in the center of the atom equals the number of electrons in orbit. An zon is any atom or molecule that does not have the normal number of electrons. lonizing radiation is any form of radiation that has enough energy to knock electrons out of atoms or molecules, cre- ating ions. How 1s tonizing radiation measured? Measurement lies at the heart of modern science, but a number by itself conveys no information. Useful measurement requires both an instru- ment for measurement (such as a stick to mark off length) and an agreement on the uzits to be used (such as inches, meters, or miles). The units chosen will vary with the purpose of the measure- ment. For example, a cook will measure butter in terms of tablespoons to ensure the meal tastes good, while a nutritionist may be more con- cerned with measuring calories, to determine the effect on the diner’s health. The variety of units used to measure radiation and radioactivity at times confuses even scien- tists, if they do not use them every day. It may be helpful to keep in mind the purpose of vari- ous units. [here are two basic reasons to mea- sure radiation: the study of physics and the study of the biological effects of radiation. What cre- ates the complexity is that our instruments mea- sure physical effects, while what is of interest to some are biological effects. A further complica- tion is that units, as with words in any language, may fade from use and be replaced by new units. Radiation is not a series of distinct events, like radioactive decays, which can be counted indi- vidually. Measuring radiation in bulk is like