Estimating Risk and NCRP's Commentary 27

Abstract

The National Council on Radiation Protection (NCRP) chose the six epidemiological cancer studies that they felt provided strong evidence for Linear No Threshold (LNT) as a basis for radiation protection. LNT maintains that any level of radiation is harmful and consequently the public and workers are at some risk from very low levels of radiation.

The six studies included two on the long-term effects of Hiroshima/Nagasaki (H/N), two on nuclear workers, and two that combined medical and H/N cohorts. NCRP Commentary 27 used these studies to reaffirm LNT as the most prudent and practical basis for radiation protection. This paper examines the six studies to determine if they are consistent with a radiation dose threshold of 100 milli-Gray (mGy) below which there is no harm. This paper calls into question radiation risks below 100 mGy.

LNT tells the public that they are at risk from tens of micro-Gray of dose annually from, for example, the Near Surface Disposal Facility (NSDF) planned for construction at Chalk River Laboratories. By contrast, if there is no significant evidence that 100 mGy poses a risk, then we must assume that dose from the NSDF is well below a risk threshold and so is safe. The psychology of this difference in viewpoint is profound.