Answer to the comments by Eric J. Grant et al. in “Radiation unlikely to be responsible for high cancer rates among distal Hiroshima A-bomb survivors”

Table 1 Standardized mortality ratio by colon doses and solid cancers; LSS people in Hiroshima, both sexes, aged 0–34 years at time of bombing, 1971–1990

Solid cancers; standard population	Dose categories (Sv)
	VLD group: <0.005 Sv (very low); 2.5–10.0 km			LD group: 0.005–0.1 Sv (low); 1.4–2.5 km			HD group: ≥0.1 Sv (high); 1.1–1.4 km			Total
	O^a	E^b	SMR^c (95% CI) P ^d VLD: Baseline	O^a	E^b	SMR^c (95% CI) P ^d SMR (LD)/SMR (VLD)	O^a	E^b	SMR^c (95% CI) P ^d SMR (HD)/SMR (VLD)	O^a	E^b	SMR^c (95% CI) P ^d
Hiroshima
Males	218	184.6	1.181 (1.035–1.343)^* 1.0	250	208.6	1.198 (1.059–1.351)^** 1.015	147	104.6	1.406 (1.196–1.642)^*** 1.190	615	497.7	1.236 (1.142–1.335)^***
Females	228	220.3	1.035 (0.909–1.174) NS 1.0	269	244.9	1.099 (0.975–1.234) NS 1.061	226	137.5	1.644 (1.443–1.865)^*** 1.588	723	602.6	1.200 (1.116–1.289)^***
Okayama
Males	218	169.8	1.284 (1.123–1.458)^*** 1.0	250	192.6	1.298 (1.145–1.461)^*** 1.011	147	96.2	1.528 (1.303–1.788)^*** 1.190	615	458.6	1.341 (1.238–1.448)^***
Females	228	211.5	1.078 (0.949–1.225) NS 1.0	269	234.8	1.146 (1.016–1.285)^* 1.063	226	131.8	1.714 (1.503–1.942)^*** 1.591	723	578.1	1.251 (1.163–1.344)^***

*P < 0.05, **P < 0.01, ***P < 0.001; NS, not significant
LSS, Life Span Study; O, observed number of deaths; E, expected number of deaths; SMR, standardized mortality ratio; VLD, very low dose; LD, low dose; HD, high dose; CI, confidence interval
^aThe observed number of deaths (O) due to solid cancer was calculated according to follow-up interval (1971–1990), sex, age at exposure (0–34 years old), and colon radiation dose (three levels based on DS86; see below), using the data on exposed survivors of the Hiroshima bombing included in LSS 12 (LSS-H group). We then calculated the mortality rate by cause of death for people in the Hiroshima and Okayama prefectures, respectively, according to follow-up interval, sex, and age in 1945
^bThe expected number of deaths (E) was calculated for each category (sex, age at exposure, colon radiation dose, and cause of death) of the LSS group using an indirect method based on observed persons. This expected number of deaths was calculated in two ways: (1) with the population of Hiroshima prefecture as the standard (upper row); (2) with the population of Okayama prefecture as the standard (lower row)
^cThe O and E values were used to calculate the SMR. The colon radiation dose was divided into three categories: <0.005 Sv (VLD), ≥0.005 and <0.1 Sv (LD), and ≥0.1 (but <4.0 Sv) (HD), respectively
^dThe test of significance was done using the chi-square test

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