The scientific jigsaw puzzle: Fitting the pieces of the low-level radiation debate

摘要

Quantitative risk estimates from exposure to ionizing radiation are dominated by analysis of the one-timenexposures received by the Japanese survivors at Hiroshima and Nagasaki. Three recent epidemiologic studiesnsuggest that the risk from protracted exposure is no lower, and in fact may be higher, than from singlenexposures. There is near-universal acceptance that epidemiologic data demonstrates an excess risk of delayedncancer incidence above a dose of 0.1 sievert (Sv), which, for the average American, is equivalent to 40 years ofnunavoidable exposure from natural background radiation. Model fits, both parametric and nonparametric, tonthe atomic-bomb data support a linear no-threshold model, below 0.1 Sv. On the basis of biologic arguments,nthe scientific establishment in the United States and many other countries accepts this dose-model down tonzero-dose, but there is spirited dissent. The dissent may be irrelevant for developed countries, given thenincrease in medical diagnostic radiation that has occurred in recent decades; a sizeable percentage of thisnpopulation will receive cumulative doses from the medical profession in excess of 0.1 Sv, making talk of anthreshold or other sublinear response below that dose moot for future releases from nuclear facilities or andirty bomb. The risks from both medical diagnostic doses and nuclear accident doses can be computed usingnthe linear dose-response model, with uncertainties assigned below 0.1 Sv in a way that captures alternativenscientific hypotheses. Then, the important debate over low-level radiation exposures, namely planning fornaccident response and weighing benefits and risks of technologies, can proceed with less distraction. One ofnthe biggest paradoxes in the low-level radiation debate is that an individual risk can be a minor concern, whilenthe societal risk裻he total delayed cancers in an exposed population裞an be of major concern