41Ca in tooth enamel. part II: A means for retrospective biological neutron dosimetry in atomic bomb survivors

W. Rühm*, A. Wallner, H. Cullings, S. D. Egbert, N. El-Faramawy, T. Faestermann, D. Kaul, K. Knie, G. Korschinek, N. Nakamura, J. Roberts, G. Rugel

*Corresponding author for this work

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11 Citations (Scopus)


41Ca is produced mainly by absorption of low-energy neutrons on stable 40Ca. We used accelerator mass spectrometry (AMS) to measure 41Ca in enamel of 16 teeth from 13 atomic bomb survivors who were exposed to the bomb within 1.2 km from the hypocenter in Hiroshima. In our accompanying paper (Wallner et al., Radiat. Res. 174, 000000, 2010), we reported that the background-corrected 41Ca/Ca ratio decreased from 19.5 × 10-15 to 2.8 × 10-15 with increasing distance from the hypocenter. Here we show that the measured ratios are in good correlation with γ-ray doses assessed by electron paramagnetic resonance (EPR) in the same enamel samples, and agree well with calculated ratios based on either the current Dosimetry System 2002 (DS02) or more customized dose estimates where the regression slope as obtained from an errors-in-variables linear model was about 0.85. The calculated DS02 neutron dose to the survivors was about 10 to 80 mGy. The low-energy neutrons responsible for 41Ca activation contributed variably to the total neutron dose depending on the shielding conditions. Namely, the contribution was smaller (10) when shielding conditions were lighter (e.g., outside far away from a single house) and was larger (26) when they were heavier (e.g., in or close to several houses) because of local moderation of neutrons by shielding materials. We conclude that AMS is useful for verifying calculated neutron doses under mixed exposure conditions with γ rays.

Original languageEnglish
Pages (from-to)146-154
Number of pages9
JournalRadiation Research
Issue number2
Publication statusPublished - Aug 2010
Externally publishedYes


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