Reanalysis of cancer mortality risk in association with organ absorbed dose forJapanese nuclear workers 1991-2010
Hiroshige Furuta1,*, Akemi Nishide1, Shin’ichi Kudo1, Keiko Yoshimoto1, Shin Saigusa1
1

Radiation Effects Association,1-9-16, Kajicho, Chiyoda-ku, Tokyo, 101-0044, Japan*
furuta@rea.or.jp

ABSTRACT
Background: Japanese Epidemiological Study on Low-Dose Radiation Effects (J-EPISODE) has analyzed
health effects in association with photon exposure assessed in Hp(10) since 1990. However, it is under way
to estimate cancer morbidity and mortality risk evaluated in organ absorbed dose, which is recommended
by ICRP.
Aim: To reconstruct organ absorbed dose during 1957 to 2010, and reanalyze cancer mortality risk for
J-EPISODE 1991-2010.
Materials and methods: The reconstruction method of organ dose principally followed the approach
adopted in the IARC 15-Country Collaborative Study. However, the method was modified considering
recent usage practice of dosimeters in Japan and body size of Japanese. Despite the IARC’s framework withHp(10) being the common quantity, it was simplified using air kerma as common quantity (Figure 1).
[1] The preceding studies on
Japanese NPPs in 1980s werefound to confirm that theassumptions of distribution ofenergy and geometry ofphoton exposure in IARC
study were applicable for
J-EPISODE.
[2] Dosimeter response data ,defined as readings per air
kerma, under combinations ofa specific photon energy; 119,207 and 662 keV, and a specific geometry; antero-posterior geometry and isotropic geometry, were newly
experimented in the same way as IARC study for recently used three types of dosimeters; glass badge (GB),electronic personal dosimeter (EPD) and optically stimulated luminescence (OSL) dosimeter, while thosefor film badge (FB) and thermoluminescence dosimeter (TLD) referred IARC study data.
[3] Conversion coefficients from air kerma to organ absorbed dose were developed for Japanese adult malevoxel phantom (JM-103) in order to compare with Caucasoid phantom.
[4] Finally, conversion coefficients from readings to organ absorbed dose were computed using the above
data on dosimeter response as well as coefficients from kerma to organ absorbed dose for each year andeach site where workers were exposed to photon, followed by reconstruction of organ absorbed dose forsubjects of J-EPISODE during 1957 to 2010. Then, Poisson regression method was applied for estimating
ERR (Excess Relative Risk) for cancer mortality.
Results: 1) The IARC assumptions of energy and geometry distribution were applicable.
2) Dosimeter response among dosimeter types demonstrated small differences.
3) Conversion coefficients for JM-103 revealed small differences from Caucasoid.
4) Conversion coefficients from readings to organ absorbed dose (Gy/Sv) were around 0.7 to 0.8.
5) Organ absorbed dose for several tissues was reconstructed from the recorded dose during 1957 to 2010.
6) ERRs for cancer mortality were estimated in terms of organ absorbed dose.
Conclusion: Evaluation method of cancer morbidity and mortality risk in association with organ absorbed
dose, which is recommended by ICRP, became applicable for Japanese nuclear workers.
Keywords: Epidemiology, Organ absorbed dose, Nuclear worker
ACKNOWLEDGMENTS: This work was funded by Nuclear Regulation Authority, Japan.