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

57
RADIOLOGICAL ISSUES
and EPA genetic risk factors are not derived on the same basis as the UNSCEAR factors and
that corrections can be made to eliminate this discrepancy. The same comment could be made
for nearly every risk factor quoted in this appendix, but it seemed more appropriate to list
the factors as originally reported. The corrections,.in any case, would not alter the
selection of values in draft Table E.2 and employed in the Statement.
Draft p. E.9, Table E.4
Issue
The column titled "Mays (19)" may-contain an error. Mays, et al. (Reference 19, draft
Appendix E) estimated 200 bone cancer deaths/10 6 person-rads. Using a Q of 10, this would
be equivalent to 20 bone cancer deaths/10 6 person-rem.- In a contemporary paper
(C. W. Mays, Estimated Risk from 23 9 Pu to Human Bone. Liver and Lung, pp. 373-384 in Bio-
logical and Environmental Effects of Low-Level Radiation, Vol. II, IAEA, Vienna, 1976), Mays
estimated (again assuming a Q of 10) 20 lung cancer deaths, 20. .bone cancer deaths and
10 liver cancer deaths per 106 person-rem.
EPA in its guidance on transuranium elements (EPA 520/4-77-016) provided an analysis
of the health impact of exposure to transuranium elements in the environment which includes
both risk and dose-rate estimates for a cohort of 100,000 exposed since birth. This guid-
ance is supplemented by technical reports, Technical Report EPA 520/4-78-010 and Technical
Note CSD-78-1, which provide background information for the basic guidance document. Since
the health impact calculated in these reports is based on lifetime exposure and risk coeffi-
cients for specific organs, the results are not indirectly comparable with Table E.4 but
they are a more realistic estimate of health impact from transuranium elements in the
environment. (113-EPA)
Response
The EPA suggests that the bone cancer risk factor of four bone cancer deaths/10 6
organ rem, attributed to Mays, in draft Table E.4 (p. E.9), may be in error. They note that
the Mays reference gives a value of 200 bone cancer deaths/10 6 person-rads; and dividing
by a quality factor of 10, the EPA suggests that the equivalent factor is 20 bone cancer
deaths/10 6 person-rem. They neglect however, to apply the additional "distribution fac-
tor", n, which has a value of 5, and reduces the risk factor to four bone cancer deaths/10 6
person-rem, as listed in draft Table E.4. For surface-seeking alpha emitters in bone, 1 rad
is equivalent to 50 rem, all doses being considered on an average-dose-to-bone basis. The
later-Mays paper referenced by the EPA gives the same estimate of 200 bone cancer deaths/10 6
person-rad.
The EPA also calls attention in this comment to its own risk factor for transuranics
in bone, as developed for their Proposed Guidance on Dose Limits for Persons Exposed to