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DOSE RATE CRAD/DAY)
Figure XVI.
A comparison of radtation-specitfie death rate in dogs and mice
under duration-of-life exposure, as a funetion of the daily dose-rate in rad.
Data from Norrts et al.
(c)
[NT].
the ratio of slopes or the slope displacement has an identical relationship
to the reduction of life expectancy in both species.
250 rad (i.e.
They thus calculated that
5 rem/year which is the present limit of dose equivalent for wor-
kers x 50 years of working life) given chronically over a very long time would
produce 15 days of life-shortening for an average 100 day-old mouse and about
15 months for the average 20 years-old man.
237.
At the same time Sacher, Tyler and Trucco [S50] extended their observa-
tions to 15 species of mammals from the orders of Carnivora, Arctiodactyla and
Rodentia, exposed for the duration of life to gamma rays.
The survival data
analysed in terms of the radiation-specific death rate showed that all species
(with the exception of the black rat) had a “death rate to dose-rate" relation
where the death-rate increased as the square of the dose-rate up to a break
point above which death-rate increased linearly with dose-rate.
A log-log
plot of the coordinates of the breaking points showed a linear relationship,
indiciating that the species variation to chronic irradiation is due to a sin-