Effects of Terrain Shielding on Cancer Mortality among Nagasaki A-Bomb Survivors

Abstract

We compared cancer mortality between two groups of Nagasaki A-bomb survivors; one group was bombed in areas shielded by mountains located east and east-south at about 2.5 km from the hypocenter, while the other was bombed in unshielded areas in the south at a similar distance from the hypocenter. Cancer mortality from 1 January 1970 to 31 December 2000 in 1541 survivors bombed in the unshielded area was 1.36-fold (95%CI: 0.95-1.93, P=0.09) higher than that in 1627 bombed in the shielded area after adjustment for sex, age at the time of the bombing and attained age. The results suggest that shielding effects by mountain should be taken into account in the evaluation of cancer mortality in Nagasaki A-bomb survivors.