ABSTRACT

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 10.2 Animal Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 10.3 Cellular Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 10.4 Summary of Human Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 10.5 Bystander and Abscopal Effects Measured in Cellular Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 237 10.6 Conclusions Regarding Cancer Risk from Radiation Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

This chapter is concerned with the biology of radiation-induced carcinogenic events in animal and in vitro cellular studies. In particular, studies are presented to demonstrate the consensus view of the present state of science on the probability of a cancer event occurring when an organism is exposed to radiation and also that there is a dose-response function for such an exposure. The chapter also shows studies that demonstrate the importance of the time-line of exposure, the type of exposure, and the long-term effects of exposure to ionizing radiation. The risk or probability arising from an exposure rests on the biological knowledge that science has accumulated on radiation effects. Unlike the law profession where evidence is presented and a judge or jury makes a definite determination of truth or falsehood, science relies on an accumulation of data, which is often inconsistent when viewed in isolation, to build a consensus that can then be framed as a theory. Theories or hypotheses only hold as long as the data support them. Often new data do not support a hypothesis or theory and science designs newer ones. In biology there are few theories and many hypotheses.