Re: Op-Ed in International Herald Tribune

[ROBBARISH@AOL.COM]

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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