The possible impact of passive smoke exposure on radiationrelated risk estimates for lung cancer among women:
the Life Span Study of atomic bomb survivors
Previous analyses by RERF of the Life Span Study (LSS)1 of A-bomb survivors have shown agender difference in excess relative risk (ERR)2 of lung cancer due to radiation exposure, withwomen having about four times the risk of men. The reason for this difference is not completely
understood, but one possibility is that the effects of passive smoke exposure were not taken into
consideration in the previous analyses of LSS members. Such passive smoke exposure is now
thought by many to increase risk of lung cancer. Like other Japanese populations of the samegeneration, the smoking rate among men in the LSS population tended to be high, whereas therate among women was low. With that, the percentage of women exposed to passive smoking islarger and therefore analysis of only active smoking (direct exposure) effects, without including
passive smoke exposure, might be one reason why a high ERR of lung cancer was observed
among women in the LSS population following radiation exposure.
RERF scientists investigated the extent of decrease in this sex difference in the ERR of lungcancer due to radiation exposure after passive smoke exposure effects were taken into
consideration. Since no data have been collected regarding the issue of passive smoke exposurein the LSS, the assumption was made, based on the smoking habits of men in the LSS, that
passive smoke exposure effects on non-smoking women would be equivalent to a range of 0–
50% of active smoking effects. When the effect was increased from no passive smoke exposureeffects (in other words, when passive smoke exposure effects were equivalent to 0% of activesmoking effects) to passive smoke effects estimated to be 50% of active smoking effects, the ERR
of lung cancer following radiation exposure in women decreased, from 1.54 at 0% to 0.78 at 50%,
and the risk difference between men and women also decreased in the same way, from 5.30 to
2.69.
The study results suggest that the lack of consideration of passive smoke exposure might havebeen one factor in the high ERR of lung cancer due to radiation exposure in women previously
observed in LSS analyses.
Notes
1Life Span Study (LSS):
The main purpose of this study is to investigate the long-term effects of atomic bombradiation on the cause of death and cancer incidence. At the time of the 1950 national
population census in Japan, about 94,000 atomic bomb survivors were selected from among
those who were confirmed to be in Hiroshima and/or Nagasaki at the time of the atomic
bombings and about 27,000 who were not in city at the time. This study has tracked overmany years about 120,000 subjects.

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Excess relative risk (ERR):
The increase or decrease of a certain health risk in an exposed group compared with a control
group. An excess relative risk of 0 means that radiation exposure did not affect risk. An excess
relative risk of 1 in the exposed group would indicate a rate of disease that is double the rate in
the unexposed, or control, group.

doi.10.1080/09553002.2021.1976863(Doi are permanent, content-specific numbers assigned to most digital information and, in this case, canbe used to link to published abstracts and/or full papers.)

RERF’s objective with this brief outline is to succinctly explain our research for the laypublic. Much of the technical content of the original paper has been omitted. For further
details about the study, please refer to the full paper published by the journal.