Factors Governing the Individual Response of Humans to Ionising Radiation

Abstract

The current system for radiological protection of humans is largely based on populations rather than individuals – ICRP risk estimates for cancers are provided as age-, sex- and population averages, for example. In this publication an extensive review of the literature has been undertaken to consider which factors influence individual response to radiation in terms of normal tissue reactions following radiotherapy, circulatory diseases, cataract, cognitive impairment, and cancers. These include individual intrinsic such as sex, age, and genetic attributes, or extrinsic factors such as co-exposures to other agents or co-morbidities. While the literature related to individual factors is extensive, robust evidence exists for only a few factors. Age influences risk of cancer, cognitive impairment, and other normal tissue reactions; biological sex influences cancer risk; some genetic factors influence normal tissue reaction risk (inherited monogenic disorders) and possibly cancer risk; concurrent chemotherapy influences risk of normal tissue reactions and possibly circulatory disease risk; some underlying conditions/comorbidities influence normal tissue reaction risk and possibly cataract risk; and smoking influences cancer risk (with most evidence available from studies of radon exposure related lung cancer risk). While investigations have considered other factors such as alcohol consumption, body mass index, and the immune system, only limited and often conflicting evidence is available. While some studies suggest that individual risk of normal tissue reactions may be predicted by use of simple cellular or genetic tests, the overall evidence base is mixed, and no clear consensus exists that risk can be predicted. The situation is similar in terms of prediction of cancer risk.