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RE: Op-Ed in International Herald Tribune



Title: RE: Op-Ed in International Herald Tribune

Food for thought:

I will suggest that perhaps in the first weeks of pregnancy, there is little awareness of the condition on the part of the mother.  Further, it has been suggested (Mettler and Upton, Medical Effects of Ionizing Radiation, 2 ed 1995) that spontaneous abortion background rates may be as high as 30-50%- the probable outcome of adverse radiation effects during pre-implantation.  I believe this suggests that the discussion, at least with regard to this stage of pregnancy, becomes purely academic.

Respectfully,

Andrew L. Scott

-----Original Message-----
From: ROBBARISH@AOL.COM [mailto:ROBBARISH@AOL.COM]
Sent: Friday, June 08, 2001 1:05 AM
To: andrew_mcewan@nrl.moh.govt.nz
Cc: radsafe@list.vanderbilt.edu
Subject: Re: Op-Ed in International Herald Tribune


Hi Folks

Andrew McEwan quotes from ICRP 84:

"When the number of cells in the conceptus is small and their nature is not
yet specialised, the effect of damage to these cells is most likely to take
the form of failure to implant or of an undetectable death of the conceptus;"

I think that I'll simply state that Andrew has provided a pretty sound reason
why a woman might not want to be exposed to a large fluence of flare-induced
high-energy neutrons if she could avoid it. Failure to implant and death of
the conceptus is not what most women want as an outcome of their pregnancy.

I think that my comment in a newspaper (not a scientific journal) about women
in early stage pregnancy considering postponing a trip for a few hours in
circumstances that only occur a handful of times in an eleven-year solar
cycle is a reasonable one. I'll live with my inability to provide a sound
scientific justification for a position that is, I believe, compatible with a
community consensus, i.e. that an exposure of 100-200 mGy (10-20 rad) in the
first few weeks of pregnancy might best be avoided when all that's required
is taking the next flight.

Rob Barish

>In Rob Barish's article he states
>Such a decision could be of great importance
>during a woman's first few weeks of pregnancy, a time when a human embryo is
>particularly sensitive.

>What is the basis for this statement?

>ICRP Publication 84 paragraph 24 states
>"The effects of exposure to radiation  on the conceptus depend on the time
of >exposure relative to conception and the amount of absorbed dose.  When
>the number of cells in the conceptus is small and their nature is not yet
>specialised, the effect of damage to these cells is most likely to take the
>form of failure to implant or of an undetectable death of the conceptus;
>malformations are unlikely or very rare.  Exposure of the embryo in the first
>two weeks following conception is not likely to result in malformation or
fetal death, >despite the fact that the central nervous system and heart are
>beginning to develop in the third week.  During the rest of the period of
major >organogenesis, conventionally taken to be from the third week after
>conception, malformations may be caused especially in the organs under
>development at time of exposure.  These effects have a threshold of 100-200
mGy
>or higher."

>Andrew McEwan
>_______________________
>Andrew C McEwan PhD
>National Radiation Laboratory
>PO Box 25-099
>Christchurch, New Zealand
>
>Ph 64 3 366 5059
>Fax 64 3 366 1156
>Andrew_McEwan@nrl.moh.govt.nz
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