APPLICATION OF THE HSEF TO ASSESSING RADIATION RISES IN THE PRACTICE OF RADIATION PROTECTION

The primary risk coefficients upon which exposure limits for radiation protection purposes are currently based are derived almost exclusivel y from cancer-induction data obtained from human populations exposed t o radiations of low linear energy transfer. The question of higher lin ear energy transfer radiations is handled by means of quality factors derived from values for relative biological effectiveness obtained fro m animal data. However, the advent of microdosimetry has made it possi ble to establish hit size effectiveness functions from single-cell sys tems, both in vitro and in vivo. This type of function can substitute completely for the concept of relative biological effectiveness, Q and equivalent dose. A common basis for risk coefficients and the hit siz e effectiveness function lies in the fact that human cancers are monoc lonal and thus single cell in origin. The present communication utiliz es this common base as a means of extending the present low-linear ene rgy transfer based risk coefficients to include carcinogenic responses from exposure in radiation fields of any one or mixed qualities, exte nding from the smallest to the largest linear energy transfers of prac tical consequence. In doing so, risks from ionizing radiations of any linear energy transfer may be predicted more accurately than at presen t.