Risks Associated with Low Doses and Low Dose Rates of Ionizing Radiation: Why Linearity May Be (Almost) the Best We Can Do

In contrast to the arguments of Tubiana et al, we judge that there is little epidemiologic or biologic evidence for these for cancer

Mark P. Little

2009

Scholarcy highlights

  • In the parallel editorial, evidence is presented for possible real thresholds or “hormetic” effects of low doses of ionizing radiation
  • The arguments are of three forms: assessment of the degree of curvature in the cancer dose response within the Japanese atomic bomb survivors and other exposed groups, consistency of risks between the Japanese and other moderate- and low-dose cohorts, and assessment of biologic data on mechanisms
  • The International Commission on Radiological Protection’s survey of the epidemiologic data indicates that there are a number of groups exposed at low doses and dose rates that exhibit excess risk, compatible with extrapolations from risks observed at moderate to high doses and dose rates, and these we discuss
  • Direct epidemiologic evidence exists of excess cancer risk in a number of groups exposed at low doses or low dose rates
  • Excess cancer risks observed in the Japanese atomic bomb survivors and in many medically and occupationally exposed groups exposed at low or moderate doses are generally statistically compatible
  • The International Agency for Research on Cancer 15-country study risk for leukemia, an excess relative risk of 1.93 per sievert, was similar to that in an age-matched subset of the Life Span Study, with the linear coefficient being 1.54 per sievert, for solid cancers there were indications of higher relative risks than in the LSS: an ERR of 0.97 per sievert compared with an ERR of 0.32 per sievert in an agematched subset of the LSS
  • The dose response in these groups is compatible with linearity over the range observed
  • This large body of evidence does not suggest, and is not statistically compatible with, any very large threshold in dose or with possible hormetic effects

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