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Environ Health Prev Med (2009) 14:247249 DOI 10.1007/s12199-009-0087-8
COMMENTARY
Radiation unlikely to be responsible for high cancer rates among distal Hiroshima A-bomb survivors
Eric J. Grant Yukiko Shimizu Fumiyoshi Kasagi Harry M. Cullings Roy E. Shore
Received: 4 March 2009 / Accepted: 8 April 2009 / Published online: 2 May 2009 The Japanese Society for Hygiene 2009
Watanabe et al. [1] (hereafter referred to as WMHY) used A-bomb survivor data from the Radiation Effects Research Foundation (RERF) Life Span Study (LSS) Report 12 (available online at http://www.rerf.or.jp
Web End =http://www.rerf.or.jp ) and mortality rates for Hiroshima and Okayama Prefectures [2] to create standardized mortality ratios (SMR) for LSS cohort members residing in Hiroshima at the time of the bombing. WMHY divided cohort members into three radiation dose categories: very low dose (\0.005 Gy, VLD), low dose(0.0050.1 Gy, LD), and high dose ([0.1 Gy, HD). At issue are the men in the VLD category, who experienced higher than expected deaths due to cancers compared with prefectural rates (note that, for brevity, we discuss only the solid cancer results). WMHY concluded that the increased cancer deaths among the VLD were due to underestimated neutron doses and/or unaccounted-for residual radiation exposures. We nd their conclusions to be implausible and believe that the data show it is far more likely that the observed risks among the VLD are due to nonradiation factors. The reasons are briey summarized below.
Implausible sex-specic risks
If there were unaccounted-for radiation exposures, it is reasonable that they would have exposed men and women alike. However, the SMR values for VLD women were very close to 1.0; only those for men were elevated. In a related observation, previous studies have shown that the excess relative risk (ERR) per gray (Gy) of cancer mortality after radiation exposure is consistently higher for women compared with men [3, 4]. Thus, if radiation were responsible for the high SMR levels, we would expect to see higher SMRs in women compared with men. Using the estimates from Table 1 in WMHY [1], the sex ratio of excess risks for solid cancer is greater than unity in the HD group (female/male = 0.64/0.41 = 1.56) as expected, but is less than unity for the LD group (0.10/0.20 = 0.50) and even...