Re: EPA, risk and dose

[BLHamrick@AOL.COM]

In a message dated Thu, 29 Mar 2001  2:40:11 PM Eastern Standard Time, "Frohmberg, Eric" <Eric.Frohmberg@state.me.us> writes:



<<I don't think they are saying any of what you suggest below (except maybe 

that they don't like NRC dosimetry assumptions) - all of what you say are 

taken into account in their estimates of the cancer slope factor - eg all 

dosimetry type questions - the RBE, competing causes of death, etc. the 

model for absorption and distribution of various radionuclides - just as 

they are taken into account in the dose conversion factor.>>



I think you may have misunderstood me.  I agree that all these factors are built into the dosimetric models (EPA's as well as NRC's), so they cannot be the reasons EPA uses to justify their claim that they can't convert dose to risk and vice versa.



If they simply mean that a dose to the thyroid will not present the same overall risk as the same dose to the lungs, that would make sense, but it would also mean they were rejecting the idea that one can normalize those doses via the weighting factors to arrive at an effective dose equivalent, and then talk about risk.  But, based on their written guidance they don't appear to be doing that.



Ultimately, a bigger problem is that their slope factors are in units of risk per intake, implying that somehow the activity taken in can be directly converted to risk, but that the computed dose from that intake cannot, and that's where it gets a little Alice in Wonderlandish for me.



Barbara

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