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E.10
E.4 SPECIFIC CONSIDERATION OF HEALTH EFFECTS FROM TRANSURANICS
Data relevant for predicting specific health effects from transuranics have been con-
sidered elsewhere, in great detail (USAEC 1974, Bair 1974 and MRC 1975). Only the kinds of
data available and the approaches that might be taken if specific transuranic health effect
predictions were desired are considered here.
E.4.1 Experience with Transuranic Elements in Man
No serious health effects attributable to transuranic elements have been reported in
man. There are extensive data, however, on exposure of man to transuranic elements. Such
exposures arise from two main sources: the worldwide plutonium fallout from atmospheric
testing of nuclear weapons and other devices, and the accidental exposure of persons working
with transuranics. Since these exposures have produced no effects distinguishable from
effects caused by other causes, the information is useful in health effects prediction only
as an indication that unusual or unexpectedly severe effects are not to be anticipated;
i.e., such negative data can be used only to set an upper limit on possible effects.
E.4.2 Experience with Natural Radiation in Man
Alpha-emitting elements are a natural part of the human environment. Humans have
lived with these internally deposited radioelements and with radiation from other natural
sources throughout the history of the species. It is of some relevance to note that inhaled
naturally occuring alpha-emitting radionuclides contribute an average annual dose of about
0.1 rem to the lung, and that naturally occurring alpha emitters in bone contribute an aver-
age annual dose at bone surfaces of about 0.04 rem (NCRP 1975). While these doses cannot
be related to any measure of specific effects, they have been at least "tolerable" on the
evolutionary scale, and therefore slight increases can hardly have catastrophic effects.
E.4.3 Data from Experiments with Animals
Direct information on the toxicity of transuranic elements is available only from stud-
ies in experimental animals. The radiobiological literature suggests that the biological
effects observed in such animal experiments will at least qualitatively approximate those
that would occur in man exposed under the same conditions. Based on extensive data from
several animal species, it is concluded that the most probable serious effects of long-term,
low-level exposure to transuranics are lung, bone, and possibly liver tumors. Most of these
data are from experiments with plutonium, but can probably be applied to other transuranics
with less error than is involved in many other necessary assumptions. While quantitative
extrapolation from animal to man involves considerable uncertainty, the animal data suggest
tumor risks per million organ-rem of 60 to 200 for lung (Bair and Thomas 1976), and 10
to 100 for bone (Bair 1974, Mays et al. 1976). These estimates are compared with others in
Table E.4.1.