Threshold (was Re: DOSE RATES AND RAD. EFFECTS)

[liselin@planetx.bloomu.edu (Louis H Iselin)]

In article  "John Moulder" <jmoulder@post.its.mcw.edu> writes:

>- the magnitude and shape of the dose-rate relationship is not known
>- there is essentially no data (perhaps none at all) at the dose rates that 
>are really of interest for radiation protection

>Agreed, but I don't think that the "high dose" dose rate studies done in 
>radiotherapy-oriented radiobiology are of much relevance to the debate.

They may be relevant in that they are available, repeated data.  Since the 
question often arises as to the additive or multiplicitive nature of radiation 
effects, That answer might come from a comparison of low dose rate effects to 
high dose rate effects -- do they add together or multiply together?

>In fact, I'm not sure that laboratory radiobiology is much of any real use in 
>the LNT debate, because most of the argument is about the shape of the dose 
>response curve at dose and dose rates at which no effects can be demonstrated 
>in the laboratory.  Remember, that in the laboratory is is extremely 
>difficult to demonstrate any low-LET radiation effects below a total dose 
>of about 10 rad.

>Maybe those who would debate the LNT vs no-LNT need to be reminded 
>periodically that they are arguing about the shape of the dose-response 
>curves for doses below which it is possible to directly detect 
>statistically significant biological effects.

I believe that you have adequately defined a threshold unless an "indirect yet 
statistically significant AND causal" approach is found.

(tongue pressed firmly in cheek)
That eliminates most health physics as we know it.  What's next?

Louis

_____________________________________________________________________
Louis H. Iselin, Ph.D.           * Go Gators! *                   <*>
Assistant Professor of Physics (Health Physics Program)
Bloomsburg University of Pennsylvania
Bloomsburg PA  17815-1399                          liselin@bloomu.edu