Re: Inflight radiation exposure -Reply

[Mutty Sharfi <SHARMM@doe-md.gov>]

Julian,

I just want to clarify my point about exposure to unborn embryo.  It is not
about dose consequence, but about the fact that the airlines would say
one thing to the passengers and have a completely separate and
conflicting policy for their employees.

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The opinions expressed above are mine alone and my not represent the
opinions of my employer of the DOE.
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Mutty Sharfi
Internal Dosimetry
Mound Site 
BWXT of Ohio
sharmm@doe-md.gov 

>>> "Gibbs, S Julian" <s.julian.gibbs@vanderbilt.edu> 11/16/99 02:37pm
>>>
I agree that we are discussing a non-problem here.  Doses 
are very small.  However, I cannot let one comment pass 
without issuing a rebuttal.  The timing of radiation risk 
to an unborn embryo depends on the end point:
1.  Exposure preimplantation (days 1-10 post coitus) leads 
to prenatal death in studies of rodents.  These data are 
presumed to apply to humans.  No other effects have been 
observed from exposure in this period.  This is a 
deterministic effect with a threshold generally accepted as 
about 10 rem.  A few studies suggest 5 rem.  The NCRP 
states no statistically significant effect below 15 rem.
2.  Exposure during major organogenesis (about days 10-50 
p.c.) leads to congenital anomalies and neonatal death in 
rodents, again a deterministic effect with a threshold 
about 10 rem. Growth and mental retardation may also follow 
exposure during this period.
3.  Exposure during the fetal period (after day 50 p.c.) 
leads to growth and mental retardation.  The period of 
maximum sensitivity to mental retardation in the Japanese 
survivors irradiated in utero was 8-15 weeks p.c.

Note that most of these effects occur from exposure in the 
first trimester with only growth and mental retardation 
carrying over into early second trimester.
***********************************************************
S. Julian Gibbs, DDS, PhD               Voice: 615-322-3190
Professor of Radiology                    FAX: 615-322-3764 
Dept. of Radiology & Radiological Sciences
Vanderbilt University Medical Center
Nashville TN 37232-2670        Email:j.gibbs@vanderbilt.edu
***********************************************************
Tell me and I forget; teach me and I remember; involve me
and I learn.
                       --Chinese proverb

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