Effective Dose Equivalent

[Al Tschaeche <xat@inel.gov>]

 The concept of total effective dose equivalent or TEDE requires addition of
external dose to internal dose.  The internal dose is calculated by
multiplying the organ committed dose equivalent by an appropriate weighting
factor.  The weighting factor is chosen so that the risk of fatal cancer or
hereditary effects or non fatal cancer hypothetically caused by the
committed organ dose equivalent would be the same as the hypothetical risk
from exposure of the whole body to a dose equal to that of the organ
multiplied by the weighting factor.  However, I have a conceptual problem
with that idea, particularly for large doses.

For example:  Suppose the testicles receive a dose of 40 Sv and the rest of
the body receives zero dose (remember this is hypothetical).  The equivalent
dose is 10 Sv (weighting factor of 0.25 in 10 CFR 835).  10 Sv will almost
certainly result in death.  40 Sv to the testicles will result in sterility,
but probably nothing else (at least I can't find any risk numbers for fatal
testicular cancer as a function of dose).  So, how are the 10 Sv and the 40
Sv equivalent in risk?

A similar problem appears if the testicles are exposed to 4 Sv (equivalent
dose of 1 Sv).  4 Sv could cause sterility.  1 Sv could have a significant
risk of cancer.  Are those two risks equivalent?  Even worse: the DOE
Radiological Control Manual requires establishing special control levels for
individuals whose total lifetime dose in rem exceeds their age in years
(based on an NCRP recommendation).  Would it make sense to establish such a
level for such a person?

What am I missing here?

Is there an upper limit of dose above which the concept of equivalent dose
does not apply?  Maybe 50 mSv per year?