Management of Commercially Generated Radioactive Waste - U.S. ...

56
RADIOLOGICAL ISSUES
The EPA risk for thyroid listed in Table E.1, 25 thyroid cancer death/106 personrem,
is referenced to EPA 520/4-76-017 (Reference 6, draft Appendix G). That risk estimate can-
not be found in the cited.reference. However, on p. 96, ibid., it states"..., a population
age weighted value of 60 thyroid cancers per million rems to the thyroid was used." A sim-
ilar risk estimate is shown in Tables 45 and 46 of EPA report 520/9-73-003-C, Environmental
Analysis of the Uranium Fuel Cycle. Part II--Nuclear Power Reactors, 1973. Note that these
thyroid risk estimates refer to cases, not fatalities, and so do not fit into Table E.1
(113-EPA)
Response
In-this comment the EPA notes certain qualifications on its risk factors as quoted in
draft Table E.1 (p. E.4). The only substantive comment related to the value for the thyroid
risk factor, which, as the EPA correctly observes, does not appear in the reference given.
The number included in draft Table E.1 represented an attempt to translate the EPA "case
estimate" as given in the quoted reference, to a "fatality estimate". In retrospect this-
seems ill-advised and the thyroid risk factor has been deleted, since EPA has not given such
a factor in terms of fatal cancers.
Draft p. E.7 and p. E.8, Table E.3
Issue
Newcombe's estimate of ten genetic effects based on a normal incidence rate of 0.1% for
autosomal/dominant disorders has not been supported by other studies. Current incidence
estimates are about 1% autosomal dominant and X-linked disorders, the estimate in
UNSCEAR 1977. (113-EPA)
Response
The genetic effects estimates attributed to the BEIR report and EPA in draft Table E.3
are not comparable to those given in the 1977 UNSCEAR report since they assume a 30-yr
reproductive generation time. To compare the BEIR and EPA estimates with those of UNSCEAR,
the BEIR and EPA estimates should be multiplied by a factor of about 0.6 to adjust for a
30-yr population generation versus the current, approximately, 50-yr population generation.
More recent EPA estimates have been adjusted for the current population generation (Feldmenn
1976), to yield 200 genetic effects, close to the UNSCEAR 1977 estimate.
EPA notes that some of the bases for Newcombe's estimate of a genetic risk factor, as
included in draft Table E.3 (p. E.8), are not supported by other studies and have not been
accepted by UNSCEAR. The fact that Newcombe's value "has not been generally accepted" is
noted, as quoted, in the sentence on overlapping draft pp. E.7 and E.8. Newcombe's argu-
ments still carry weight, however, and deserve to be noted as a responsible view, albeit one
which is not employed in the Statement. The EPA also notes in this comment that the BEIR