Re: EPA, risk and dose

[BLHamrick@AOL.COM]

Eric,



Your explanation below makes sense, because that amounts to choosing a different set of units to express the limits, but that does not jive with the EPA written guidance, which states, e.g., "No simple and direct conversion between radiation dose and radiogenic cancer risk is available...a given dose from one radionuclide via a given exposure pathway may present a much 

greater cancer risk than the same dose from another radionuclide and/or exposure pathway...Therefore, any conversion between dose and risk must be performed on a radionuclide-and pathway-specific basis."



It seems to me, they are saying that the energy imparted to a given organ by one radionuclide being inhaled will not have the same effect as the same total energy imparted to the same organ by a different radionuclide that is ingested.  And, that's where they lose me.  The different effects of high-LET vs. low-LET radiation are built in via the quality factors to dose calculations, so that does not help the EPA's argument any.



If, instead, they are meaning to say that a different pathway and/or different radionuclide will impact different organs, that doesn't help their argument either, because that information also goes into the dose calculations.



Finally, they may be saying, without ever saying it, that the NRC's use of the CEDE does not adequately characterize the overall cancer risk, because the ICRP's normalization of the doses and effects is inadequate, but their own guidance contradicts that  possibility.



The only thing they can possibly be saying is that 100 rem to the thyroid from the inhalation of I-131 will not create the same risk of cancer as 100 rem to the thyroid from the ingestion of I-125, and that means they have some other idea about just what is causing the damage and/or risk.



Barbara L. Hamrick

BLHamrick@aol.com



In a message dated Thu, 29 Mar 2001 12:54:44 PM Eastern Standard Time, "Frohmberg, Eric" 

<Eric.Frohmberg@STATE.ME.US> writes:



<< As I understand it, EPA's cancer slope factor has all the dosimetry

assumptions built into it.  There are some differences in the dosimetry

(which version of ICRP is used, etc.), but instead of taking an intake

(pCi/lifetime) and calculating a dose, they are simply calculating risk.

 And, of course, the risk estimates would change over time just as the dose

estimates would.>>









************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.



------------------------------