137Cs into food crops and/or el
it from the
soil column would substantially] reduce the
Similarly, the mean 30-y integral effective
dose of 0.0059 Sv (0.59 rem) estimated for
Rongelap Island is only 12% of the 0.05 Sv
potential exposure of the Rongelap
peopleliving
on RongelapIsland.
The external gamma exposur€ is next in
significance and contributes about] 40% of the
30-y integral effective dose. The p
source
of exposure from the external
pathwayis
(5 rem) Federal guidance for the general public
for a 30-y period (EPA, 1987; FRC, 1960a,b). It is
20% of 0.03 Sv (3 rem), which is the equivalent
of 1 mSv y-! (100 mrem y-!) summed over 30 y.
In view of the fact that there is some
question as to whether such guidanceis really
relevant for a situation such as the Marshall
Islands, it is useful to develop other reference
criteria. For perspective, the annualeffective
background dose in the United States is
137Cs. In the first year, 1995, 137Csl contributes
more than 99% of the 0.11 mSv y-1 (1 mrem y-!)
external gamma dose rate; °Co a
than 0.08%.
ts for less
By the year 2000,[137Cs will
essentially accountforall of the ext
gamma
dose rate. The annual external effective dose
rates, the cumulative effective ddse, and the
compared in Table 15 to the total maximum
annual effective dose, including natural and
contributions of 137Cs and 69Co
man-made sources, at Rongelap Island. Thetotal
maximum annual effective dose at Rongelap
Island of 2.66 mSv (266 mrem) is 89% of the
annual background effective dose of 3 mSv
(300 mrem)in the United States.
Appendix C.
The inhalation pathway is
age listed in
ntially the
most significant exposure pathway for the
transuranic radionuclides. For
this pathway,
239+240Py and 241Am are about 3 t@ 4 orders of
magnitude more significant than 7Cs, 90Sr, or
Relative Contributions of Exposure
Pathways
60Co. The transuranic radionuclidés contribute
less through the ingestion pathway
The ingestion dose calculation fq@r Pu and Am
includes a 100 mg d-! consumption surface soil
The relative contribution of each of the
exposure pathwaysis presented in Table 16. The
dose from the terrestrial food-chain pathway
accounts for about 60% of the total estimated 30-
every day of one's life.
We feef this model
probably overestimates the ann
soil, but chose it as a conservativ
y integral effective dose; 137Cs accounts for about
96% of this dose and %Sr for about 2%. Any
the problem.
We also used
recommended ICRP gut-transfer fa
organically bound transuranic r
procedure that would either block the uptake of
Table 16. The 30-, 50-, and 70-y integral effective dose for the various exposure pathwayA)
Effective integral equivalent dose, Sv (rem
Exposure pathway
Oy
Oy
ny
Terrestrial food
External gamma
Marine food
0.0034 (0.34)
0.0024 (0.24)
1.6 x10-5 (0.0016)
0.0047 (0.47)
0.0033 (0.33)
3.5 x10-5 (0.0035)
0.0056 (¢.56)
0.0039 (9.39)
6.0 x10-¥
(0.0060)
Inhalation
Totala
4.8 x 10-5 (0.0048)
0.0059 (0.59)
1.2 x 10+ (0.012)
0.0082 (0.82)
2.0 x 10-F
(0.020)
0.097 (07)
Cistern and ground water
5.1 x 10- (0.00051)
7.8 x 10-6 (0.00078)
a The total dose mayvary in the second decimal place due to rounding.
33
1.0 x 10-
(0.0010)