喫煙習慣を考慮した日本人集団に対する放射線被ばくの生涯肺がんリスク

Lifetime lung cancer risk due to radiation exposure considering smoking history for Japanese people

嶋田 和真 ; 甲斐 倫明*

Shimada, Kazumasa; Kai, Michiaki*

これまでの放射線の健康リスク評価は、年齢・性別は考慮していたが、喫煙等の生活習慣は考慮しておらず、高リスク集団である喫煙者を含んだ混合集団に対してリスク評価を行っていたため、非喫煙者集団に対するリスクを過大評価していると考えられる。そこで、放射線の健康リスクの高精度化を図るためには生活習慣を考慮したリスク評価が重要である。近年、原爆被爆者の疫学調査より、肺がんリスクにおいて放射線と喫煙の相乗効果が観測され、一回被ばくに対するリスクモデルが開発された。本研究では、放射線と喫煙の相乗効果モデルを慢性被ばくに改良し、日本人集団の非喫煙者及び喫煙者に対して放射線被ばくによる生涯肺がんリスクを算出した。

This paper describes lung cancer mortality risks due to radiation exposure considering the history of smoking in Japanese people. In this study, we calculated the DALY of lung cancer mortality for Japanese males considering the joint effects of radiation and smoking using the generalized multiplicative excess relative risk interaction model (GM model). First, we estimated the lung cancer baseline risk for non-smokers to divide the risk of smoking for mixed population groups that include smokers and non-smokers. Second, we developed a radiation risk model from single to chronic exposure to be able to evaluate the risk of cancer in existing and control exposure situations. Forth, the maximum relative risks of lung cancer mortality for smokers and non-smokers induced by a radiation exposure of 20 mGy/y for Japanese smokers between the age of 20 and 60 years were calculated using the GM model to be 22.2 for men and 15.7 for women, respectively. Therefore, our calculations show that only considering radiation risks strongly underestimate the real risk of lung cancer when the smoking history is not taken into account. Our study indicates that estimations of the health risk due to radiation exposure should consider not only age and gender but also the history of smoking for deriving an occupational exposure limit.