Replies to items from Aug.22 -Reply

[FRAMEP@ORAU.GOV]

BLC wrote; 	.Reply to Loesch on Paul Frame message:
>The experiments you refer to are examples of "Adaptive response".
>There are dozens of results of the type you mention and they are
>well accepted. They are reviewed in an Annex to the 1994 UNSCEAR
>Report.

My comments were geared to low doses and, by implication, chronic
exposures.  I believe that the adaptive response referred to involved
a high dose acute exposure, greater than 100 rad, and did not involve
the type of stochastic risks that are of concern at low doses. I have
no doubt that such adaptive responses exist, I do question their
relevance in the low dose chronic exposure arena however. Even then,
the comment I made (that Loesch referred to) implied that a mechanism
can indeed be proposed for hormesis - something a little out of place
if I was defending the linear no threshold approach. 

>Other evidence that the simple defense of linear-no threshold
>offered by Paul Frame is far too simple

Boy, I'd hate to call what I did "a defense" of the linear no
threshold approach. "Simple", I'll agree with. I was pointing out
that the LNT approach does not require ignoring the existence of
repair mechanisms (a question had been stated to that effect). In
fact, I pointed out that the use of the DDREF (which I have no
problem with) implies that the repair mechanisms are more effective
at low doses and that we should reduce the risks seen at the high
doses accordingly.

> it is well established that low level radiation stimulates the
>immune response; it changes the timing in the cell cycle, extending
>the time in the cycle available for repair; and the time delay
>between irradiation and development of cancer increases as dose
>decreases so natural death has a better chance of occuring before
>the cancer develops from low level radiation.

It has always been my understanding that very little was "well
established" with "low level radiation" except uncertainty. What do
you mean by low level? Under 20 rad? Are you really saying, for
example, that it is "well established" "that the time delay between
irradiation and the development of cancer increases as dose
decreases"  "at low levels" from, for example, 10 rad to 5 rad?	

Fun stuff

Paul Frame
Professional Training Programs
Oak Ridge Institute for Science and Education
framep@orau.gov