Fallout blamed for thyroid cancer -Reply -Reply -Reply -Reply

[Charles Willis <CAW@nrc.gov>]

Michael,

I did not intend to argue for the validity of the risk-population dose relationship.  I
do believe that the use of the relationship is conventional.  Thus, while it seems
appropriate to disagree with someone or some group that uses the risk-population
dose estimates, it does not seem proper to castigate that person or group for being
wild-eyed extremists.

I find the numbers interesting.  BEIR-V suggests a relative risk value of 0.083 per
rem.  The "natural" thyroid cancer rate is about 6.4 E-5 per person-year or about
0.0045 per person (lifetime).  This yields 0.00037 thyroid cancers per person-rem. 
Thus, the production of 225,000 thyroid cancers would require a population dose of
about 6 E8 person-rems.  (With the 1960 US population, this would be an average
dose of a little over 3 rems.)  According to FGR-11 (ICRP 30), the ingestion of 1
microcurie of I-131 gives a thyroid dose of about 1.76 person-rem.  To get the 6 E
8 person-rems, the intake would have to be about 3.45 E 8 microcuries, i.e. 345 Ci.
 The I-131 released in atmospheric weapons tests is estimated to be about 2.7 E 10
curies.  It does not seem unreasonable to think that Americans might have
ingested 1.3 E -6 percent of that I-131.

In reality, of course, fallout was highly non-uniform, life styles differ dramatically
from place to place, the risk probably is almost exclusively to the children, etc. 
Any attempt to get realistic makes the problem very difficult.  I would not claim to
have a good estimate of the risk, but I do conclude that this does not seem to have
been a Sternglass-type assessment.

Charlie Willis
caw@nrc.gov
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