Re: LNT, regs and lives

[Bernard L Cohen <blc+@pitt.edu>]

On Tue, 7 Sep 1999, Otto G. Raabe wrote:

> 
> Prof. Cohen says:
> 
> "	-Pierce et al assume that the high dose and low dose effects are
> due to the same dominant process. If different effects are important at
> low dose, such as stimulation of the immune system, adaptive response,
> etc, their analysis is irrelevant. There is good evidence that these
> effects are important only at low dose."
> 
> Could you cite a few key references that show this "good evidence" of
> effects that could alter carcinogenesis and are known to occur at low dose.
> It is known that high acute doses stimulate DNA repair, but I haven't seen
> any evidence at low dose (less than 0.05 Sv).

	A clear demonstration is in Makinodan and James, Health
Physics 59:29-34;1990 which shows a large increase in immune response up
to about 20 cSv followed by a rapid decrease at higher exposures. But all
that is necessary for my argunent is that biological defense mechanisms do
not increase linearly with dose up to high doses. There are many
demonstrations that these at least level off as doses increase for
adaptive response and for immune system activity. The book "Low dose
irradiation and biological defense mechanisms" edited by Sugihara, Sagan,
and Aoyama (1992) has lots of such data. I am sure the UNSCEAR Report on
Adaptive response also has this type of data. Surely no one expects these
effects to continue to increase linearly with dose up to the high dose
region. Any one of the many dozens of adaptive response studies would show
that not to be the case.

	As for evidence below 5cSv (5 rad), Cai and Liu in Int. J. Radiat.
Biol. 58:187-194;1990 show an important reduction of chromosome
aberrations at 0.2cSv, Kelsey et al in Mutat. Res.263:197-201;1991 show an
important reduction in genetic mutations at 1cSv, Liu in the book cited
above by Sugihara et al show an important effect on immune function at 2.5
cSv, etc. Even I could cite several more examples and I make no pretense
at keeping up with these fields. 

> 
Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu



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