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Documents > RSH Data Doc > 1.2 > 1.2.1 > 1.2.1.2 Okumura 1997 References |
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"Low Level Revision 1 by Radiation, Science, and Health, Inc., 1.2.1 1.2.1.1 |
Dr. Y. Okumura and Dr. M. Mine of
the Atomic Bomb Disease Institute, Nagasaki University School of Medicine, report (1997)
on survivor death rates that: "Among about 100,000 A-bomb survivors registered at Nagasaki University School of Medicine, male subjects exposed to 31 - 40 cGy showed significantly lower mortality from non-cancerous diseases than age-matched unexposed males. And the death rate for exposed male and female was smaller than that for unexposed. It was presented that the low doses of A-bomb radiation increased lifespan of A-bomb survivors. "The hypothesis that radiation is hazardous even at small doses without threshold has been widely accepted. Based on this hypothesis, radiation protection practices have presumed low-dose risk estimates by linear extrapolation from observed high dose-effects. However, the validity of the no-threshold model has seldom been critically assessed with actual data on humans exposed to low doses.
"The relative risk of death from all causes, cancer and non-cancer was analyzed. For deaths from all causes, the relative risk did not show significant increase with dose. The relative risk of deaths from cancer increased with a dose threshold at about 50 cGy. However, for non-cancer deaths, the relative risk at 31-40 cGy range was below unity for males, statistically significant (p<0.05) as shown in Figure 1.
"Figure 2 shows the death rate for male and female. Closed symbols are of A-bomb survivors whose exposed radiation dose was less than 0.5 cGy and was assumed as non-exposed. Open symbols are of A-bomb survivors whose exposed radiation dose was more than 1 cGy and was assumed as exposed. The average dose of exposed population was 125 cGy. The death rate was lower for exposed A-bomb survivors than for non-exposed survivors. "It is clear that A-bomb radiation causes cancer in survivors dependent on
radiation dose. The above data suggest that small doses of A-bomb radiation decreased
death rate and relative risk and that increased lifespan of A-bomb survivors (Kondo
1993)." |
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