No RERF Report No.7-17

A research paper published in the Journal of Radiation Research§“Typical doses and dose rates in studies pertinent to radiation risk inference at low
doses and low dose rates”
Werner Rühm, Tamara Azizova, Simon Bouffler, Harry M. Cullings, Bernd Grosche, Mark P. Little,Roy E. Shore, Linda Walsh, and Gayle E. Woloschak
J Radiat Res 2018 Apr 1;59(suppl_2):ii1-ii10.
(doi: 10.1093/jrr/rrx093)
Study Findings
This review paper examined the radiation doses and dose rates in various experimental studies inradiobiology and radioepidemiological studies of exposed human populations and compared them tothose of the Japanese atomic bomb survivors in the RERF Life Span Study (LSS).
Explanation
To estimate risk from radiation exposures that are of interest in radiation protection, which
generally occur at low dose rates (<1 mGy/minute averaged over 1 hour) and amount to low doses(<100 mGy), it is necessary to extrapolate downward from results obtained at higher doses and dose
rates. This paper reviews the doses and dose rates in a variety of relevant studies in experimental
radiobiology (cell cultures, animals) and exposed human populations, and compares them to the doses
and dose rates experienced by the atomic bomb survivors studied by RERF, as the latter are often
considered to be a “gold standard” in radiation risk estimation. Dr. Cullings, Chief, Department ofStatistics, RERF, collaborated in this study by providing and explaining relevant details of the doses
received by the atomic bomb survivors as estimated by the dosimetry system, DS02, used at RERF.
Results
The experimental studies in cells and animals often involved doses and dose rates much higher
than those of interest for radiation protection of human populations, and it was advised that theradiation-induced effects seen in such studies need to be extrapolated with care for use in radiation
protection at lower doses and dose rates. On the other hand, the low-dose-rate epidemiological studies
in human populations that were reviewed for this paper were found to have dose rates directly relevant
to radiation protection and therefore to provide a valuable complement to the A-bomb survivor studies,
which involve very high dose rates.
Study SignificanceThis study was put together by Task Group 91 of the International Commission on Radiation
Protection (ICRP) to provide information to researchers around the world about the doses and dose
rates of the studies that the said ICRP task group is considering in its new review, which is aimed atreconsidering the “dose and dose-rate effectiveness factor” (DDREF) that the ICRP previously
recommended for use in radiation protection to “extrapolate radiation risks at high doses and high dose
rates, where an abundance of data are available, down to low doses and low dose rates, where there ismuch less human data.” That extrapolation is a key step in using the information from the higher-doseand higher-dose-rate studies to establish standards for radiation protection at lower doses and doserates.
The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring in Hiroshima
and Nagasaki for around 70 years. RERF’s research achievements are considered the principal scientific basis
for radiation risk assessment by the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) and for recommendations regarding radiation protection standards by the International
Commission on Radiological Protection (ICRP). RERF expresses its profound gratitude to the A-bomb survivors
and survivors’ offspring for their cooperation in our studies.
The Journal of Radiation Research is a fully open-access multidisciplinary journal that publishes articles inradiation science in the fields of biology, chemistry, physics, epidemiology, environmental sciences andoncology. (Impact factor in 2017/2018: 2.031)

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