- 37 effect of a large single exposure to radiation (18).
One of the problems
in attempting to estimate the leukemogenic effects of relatively low
doses of radiation is that we do not know the proportion, if any, of the
present incidence of leukemia which may be the result of natural radio~
activity.
Undoubtedly, hereditary factors play a role.
Carcinogenic
hydrocarbons are know leukemogens (29) while in experimental studies
susceptibility to radiation induced leukemia can be appreolably altered
by artificially induced endocrine imbalances (19).
It is logical to
assum that endocrine factors as well as chemical and hereditary ones all
play mijor roles in determining the "natural incidence” of leukemia.
It appears then that if leukemia in general or even one type of
leukemia can be the result simply of a radiation-induced somtic mutation untempered by homeostatic factors, fallout at the present rate of
weapons testing could, on the tasis of certain assumptions as to the
number of cases of leukemia due to background radiation, result in this
country in some 30-40 additional cases per year or about 1000 per gen-
eration.
The same assumptions lead to a figure of 900 cases per year
as the result of medical x-rays (27,000 per generation).
If small
amounts of Sr-90 relatively uniformly distributed in bone can indeed
produce leukemia in the manner postulated by Lewis, fallout from con-
tinued weapons testing "at the present rate” could eventually lead to
35 to 250 additional cases per year (1000 to 7000 per generation).
To
complete the story, one must keep in mind that co-carcinogenic factors
and additive factors may in certain susceptible individuals prepare the
way for a smll dose of radiation to trigger a case of leukemia,