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The Hiroshima/Nagasaki Survivor Studies: Discrepancies Between Results and General Perception

Chris Busby published an answering to this paper. As soon as I am getting it, I will add it here below this paper.

By Bertrand R. Jordan – Unité Mixte de Recherche 7268 ADÉS, Aix-Marseille Université/Etablissement Français du Sang/Centre National de la Recherche Scientifique, Espace éthique méditerranéen, Hôpital d’Adultes la Timone, 13385 Marseille Cedex 05, France

ABSTRACT The explosion of atom bombs over the cities of Hiroshima and Nagasaki in August 1945 resulted in very high casualties, both immediate and delayed but also left a large number of survivors who had been exposed to radiation, at levels that could be fairly precisely ascertained. Extensive follow-up of a large cohort of survivors (120,000) and of their offspring (77,000) was initiated in 1947 and continues to this day. In essence, survivors having received 1 Gy irradiation ( 1000 mSV) have a significantly elevated rate of cancer (42% increase) but a limited decrease of longevity ( 1 year), while their offspring show no increased frequency of abnormalities and, so far, no detectable elevation of the mutation rate. Current acceptable exposure levels for the general population and for workers in the nuclear industry have largely been derived from these studies, which have been reported in more than 100 publications. Yet the general public, and indeed most scientists, are unaware of these data: it is widely believed that irradiated survivors suffered a very high cancer burden and dramatically shortened life span, and that their progeny were affected by elevated mutation rates and frequent abnormalities. In this article, I summarize the results and discuss possible reasons for this very striking discrepancy between the facts and general beliefs about this situation.

THE first (and only) two A-bombs used in war were deto-nated over Hiroshima and Nagasaki on August 6 and 9, 1945. Casualties were horrendous, approximately 100,000 in each city including deaths in the following days from severe burns and radiation. Although massive bombing of cities had already taken place with similar death tolls (e.g., Dresden, Hamburg, and Tokyo, the latter with 100,000 casualties on March 9, 1945), the devastation caused by a single bomb was unheard of and remains one of the most horrifying events in the past century. The people who had survived the explosions were soon designated as Hibakusha and were severely discrim-inated against in Japanese society, as (supposedly) carriers of (contagious?) radiation diseases and potential begetters of malformed offspring. While not reaching such extremes, the dominant present-day image of the aftermath of the Hiroshima/ Nagasaki bombings, in line with the general perception of radiation risk (Ropeik 2013; Perko 2014), is that it left the sites heavily contaminated, that the survivors suffered very serious health consequences, notably a very high rate of cancer and other debilitating diseases, and that offspring from these sur-vivors had a highly increased rate of genetic defects. In fact, the survivors have been the object of massive and careful long-term studies whose results to date do not support these conceptions and indicate, instead, measurable but limited det-rimental health effects in survivors, and no detectable genetic effects in their offspring. This Perspectives article does not provide any new data; rather, its aim is to summarize the results of the studies undertaken to date, which have been published in more than 100 papers (most of them in interna-tional journals), and to discuss why they seem to have had so little impact beyond specialized circles.

Bombings and Implementation of Cohort Studies

Characteristics of the bombs and the explosions



Figure 1 Number of solid cancers ob-served up to 1998 in the exposed group; the white portion indicates the excess cases associated with radiation (compar-ison with the unexposed group). Data are from Preston et al. (2007).

The device used at Hiroshima was based on enriched uranium and exploded at an altitude of 600 m with an estimated yield equivalent to 16 kilotons of high explosive. The bomb at Nagasaki was based on plutonium and exploded at 500 m with a yield of 21 kilotons. The major effect of both bombs was an extreme heat and pressure blast accompanied by a strong burst of gamma radiation and a more limited burst of neutrons. The heat blast set the (mostly wooden) buildings on fire in a radius of several kilometers and resulted in an extensive fire-storm centered on the explosion site (also called the hypocen-ter). People were exposed to the combined heat and radiation blasts, with little shielding from the buildings; most of those located within 1.5 km of the hypocenter were killed. The contribution of fallout from these explosions, which occurred mostly as “black rain” in the following days, is not precisely known: few measurements were taken due to scarcity of equipment, and investigations in the first months were per-formed by the US army and subsequently classified. It was probably limited: the bombs exploded at a significant altitude, the resulting firestorm carried the fission products into the high atmosphere, and the eventual fallout was spread over a large area. In addition, a strong typhoon occurred 2 weeks after the bombings and may have washed out much of the materiel. The major health effects (other than the heat blast and accompanying destruction) were almost certainly due to the gamma and neutron radiation from the blasts themselves, and these doses can be quite reliably estimated from the dis-tance to the hypocenter. Thus studies on the survivors can ascertain the health effects of a single, fairly well-defined dose of gamma radiation with a small component from neutrons.

The Atomic Bomb Casualty Commission and the Radiation Effects Research Foundation

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November 4, 2017 Posted by | radiation | , , , | 6 Comments