66
N-10
Studies on intake by inhalation concentrated on
plutonium-239,-240 at Bikini Island (Shinn et al 1980).
In
calculating the results, it was assumed that a person would He
exposed to maximurz dust conditions for 5 hours per day throughout
life (tilling fields), an unrealistic assumption bound to gife very
high exposures (tilling deposits 1.5 x 10-3 picocuries per hgur in
the lungs).
To obtain the Rongelap dose, it was assumed by Robison @t al
(1982b) that the distribution of particle sizes and of radioguclides
was practically the same on Bikini and Rongelap Islands. Thérefore,
the inhalation dose on Rongelap would be to that on Bikini ag the
transuranic specific activity of Rongelap soil (0-5 cm) was fo that
of Bikini Island.
Island
Specific activity in
top 5 ca of soil
in 1978
Bikini
a/
plutonium-239,-240
americiua-241
Rongelap b/
plutoniun-239,-240
anericius~241
a/
b/
c/
pci/g
Inhalation 30-yemr
dose to
bone marrow
ren
ij
8.7
033
035
3.2
-010
1.0
-005
Robison et al (1982a, pp. 8, 12, 44, 56).
Robison et al (1982p, pp. 12, 14, 47, B10, B13).
The dose throughout the bone would be about 4 times as great
The dose is greater for a growing child.
Robison et al (1992a) used
a factor of 2.8 to convert the adult inhalation dose to that forjthe age
period 0-30 years (.042 rem). The dose to the adult lung is congidered
to be about 2.5 times that to the narrow.
Dr. Robison (personal communication, 1988) has reviewed thege dose
estimates according to the more recent ICRP factors. He has rediced dust
consumption by a factor of 3.5, which would reduce the dose
proportionally. This is still a liberal allowance for every dayfof life
from birth to death, but in any case a much more reasonable one.] The net
result is a reduction in dose for plutonium by a factor of about] 3, and
for americium by a factor of 4.