- 39 were, & person with 0.0] microcurie would be getting approximately 4
rads per year to the bame and one with one microcurie would get approximately 40 rade per year.
Since radium distribution tends to be spotty
one must think in terms of localized areas receiving 10 or more times
this average exposure.
On the other hand, Sr-90 tends to be much more
evenly distributed in bone.
This would be especially true in growing
bone. The radiation from Sr-90 is:a moderately energetic beta ray ag
opposed to the princimlly very short range alpha radiation from redium.
The dose to the bone then will be ich more uniform. There is experimental
work in mice (14) indicating that at higher dose levels the more uniform
the distribution of the radiation 4n bone the more tumors are produced.
One hundred puc of radiostrontium/gm caloium, the presently considered
permissible body burden for the pogululation as a whole, would give about
0.28 rad per year or 20 rad in 60 years, i.e., three times the exposure
rate to bone from naturally occurring radioactivity or from 4 to 28
times that from the Sr.90 body burden estimates for 1975 referred to on page
eenmeeremeae ©
Experimental work in mice and dogs at low body burden levels is
incomplete, but the evidence to date seems quite clear that the curve
for bone tumor formation in mice is either steeply sigmoidal with much
less relative effect at low doses orthat there 1s actually a threshold
at about 10 microcuries per kilogram at body weight.
In other words,
very few if any bone arcomas will result from 100 uuc Sr-90/gram of
calcium (14).