Biomedical Engineering Reference
In-Depth Information
Table 14.3
Probability Coefficients for Stochastic Effects (per Sv effective dose)
Adult Workers
Whole Population
(
10
-2
Sv
-1
)
(
10
-2
Sv
-1
)
Detriment
Fatal cancer
4.0
5.0
Nonfatal cancer
0.8
1.0
Severe genetic effects
0.8
1.3
Total
5.6
7.3
Source: ICRP Publication 60 and NCRP Report No. 116.
lower than before. According to the latest ICRP pronouncement (Section 14.8),
the Commission continues to endorse the numerical dose limits recommended in
Publication 60 as providing an appropriate level of protection.
14.6
Current Exposure Limits of the NCRP and ICRP
The exposure limits of the NCRP and ICRP embrace the following philosophy, as
stated in NCRP Report No. 116 (p. 9):
The specific objectives of radiation protection are:
(1)
to prevent the occurrence of clinically
significant radiation-induced
deterministic effects by adhering to dose
limits that are below the apparent
threshold levels and
(2)
to limit the risk of stochastic effects,
cancer and genetic effects, to a reasonable
level in relation to societal needs, values,
benefits gained and economic factors.
The Council goes on to include the principle of ALARA in its philosophy. It states,
further, that for radiation-protection purposes, the risk of stochastic effects is as-
sumed to be proportional to dose without threshold throughout the dose range of
relevance in routine radiation protection.
Occupational Limits
The Council states that the total lifetime detriment incurred each year from radi-
ation by a worker exposed near the limits over his or her lifetime should be no
greater than the annual risk of accidental death in a “safe” industry. The annual
rate of fatal accidents in 1991 varied from about
0.2
10
-4
, being lowest
for trade, manufacturing, and service industries and highest for mining and agri-
culture. The Council cites the 1980 average annual dose equivalent of 2.1 mSv for
10
-4
to
5
×
×
