Understanding nuclear power/ICRP: RBE of alphas

["Bjorn Cedervall" <bcradsafers@HOTMAIL.COM>]

From: "John Johnson" <idias@interchange.ubc.ca>

Date: Thu, 22 Nov 2001 07:30:00 -0800



----- Original Message -----

From: Bjorn Cedervall <bcradsafers@HOTMAIL.COM>

To: <radsafe@list.vanderbilt.edu>



 >The weighting factor (RBE) for

 > alpha may be reduced considerably (probably to make it more consistent

with various endpoints) - as a preliminary standpoint a factor of 10 rather

than 20 has been mentioned.



Bjorn and Radsafers;



Lowering the W(sub r) for alphas would make sense. Many of us thought that

it should have been lowered to five (instead of being raised to 20) the last

time ICRP reviewed it.

------

John,



I think that 10 for alphas - if that becomes the next step - is a deliberate

conservative standpoint (to be on the "safe side"). I agree that a lower

value than 10 may be a better estimate - but this is my personal statement

that only is a vague guess work considering various informations that I

looked at a few years ago so don't take it as a formal reference.



Even stepping down from 20 to 10 will have an important impact on some

earlier lung cancer studies (the fraction of deaths due to smoking).



RBE (alphas) in cell biology/DNA experiments is a complicated issue

that is very dependent on the endpoint. If we discuss cell survival there

is a difficulty measuring below 0.5 Gy with statistical certainty and we

are dealing with single (or no) hits per cell. The RBE (cell surival)

is probably highest at the lowest doses - but this is also dependent

on the model used for describing the data.



Please comment or correct: Best is of course if someone has solid

reasoning and hard facts/data behind any bottom line for a best RBE

estimate (endpoint: cancer).



Best regards,



Bjorn Cedervall    bcradsafers@hotmail.com





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