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CAUSALITY OF A GIVEN CANCER AFTER KNOWN RADIATION EXPOSURE 25 original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. accidental harm in the context of public health and its subdisciplines of epidemiology and accident statistics. This discussion is followed by consideration of the infrequent casualties that result from such exposure. In particular, the question of whether causality and the kinds of harm can be addressed adequately only by one with medical knowledge and experience is examined. Finally, the single-cell origin of many cancers and of genetic defects is discussed, as well as the probabilistic nature of the induction of many types of cancer. It is concluded that, for these diseases, the traditional medical approach must be replaced by a probabilistic approach to address adequately the questions of causality. ACCIDENTAL HARM IN POPULATIONS OF EXPOSED PERSONS Randomly induced (accidental) harm is dealt with in the discipline of public health, which is concerned primarily with the health and well-being of populations. The common characteristic of such populations, which are usually constituted on geographical or occupational bases, is that they are or may be exposed directly to infectious or chemical agents present in the environment or to carriers or vehicles for such agents. They may also be exposed to the common agent, energy, present as an integral property of energy carriers, which are physical objects in the environment potentially in motion relative to the individual. An exposure results in random encounters or collisions of agents or energy carriers with individuals, which produce direct transfers of the agent. As a consequence of these transfers, a small and usually more or less constant percentage of exposed individuals may become ill or injured during any equivalent exposure period. The concern of the professional public health officer must be for the population as a whole, without regard to the identity of any individual. Thus the public health officer, who often has an M.D. degree, must be knowledgeable in epidemiology and statistics and must be aware of trends in disease incidence, accident statistics, changes in exposure conditions, and possible unusual susceptibilities in segments of the population (see Bingham, in this volume). Whereas a person who becomes a casualty immediately becomes an identified patient of a physician, the casualty is important to the public health officer primarily as a statistic (if the person dies, as a death statistic). Should the question of single versus multiple causation arise with respect to any casualty, the public health professional might be asked about the exposure conditions under which the accidental encounter and agent transfer occurred, causing the harm and its consequent probability of a quantal response. However, he or she would probably be unable to provide an
