Re: Editorial on EPA Proposed Federal Guidance -Reply

["H.B. Knowles" <hbknowls@ix.netcom.com>]

At 07:02 PM 5/18/98 -0500, you wrote:
>Ken,
>
>Am I missing something or shouldn't more attention be paid to dose rate?
When
>the NCRP tried to find data for or against a dose rate reduction factor,
they could
>find no effects to compare for exposures where the dose rate was below 8.3
rad per
>day.  Considering the biological repair processes, it seems reasonable
that dose
>rate could be important, perhaps even having a threshold effect.
>
>Charlie Willis
>caw@nrc.gov
>
Mr. Willis:

There IS a dose rate effect, and it's rather important, Some 25 years back,
Harald Rossi  measured the induction of cataracts on the eyes of (I believe
guinea pigs) by thermal neutrons. It was found that for the same total
dose-equivalent, that the RBE (equals quality factor equals now, I guess,
weighing factor) INCREASED as the dose rate was reduced.. I believe that
there are other data that support this finding. This observatuion is
consistent with (a) The fact that quality factors for radiation protection
are high (like, 10) for radiation protection (low rate of rxposre) compared
, let us say, to  what is observed in cancer radiation therapy (high dose
rate) where quality factors closer to 1.0 are observed, and also to the
fact that in an extreme radiation overdose, quality factors of 1 are indeed
used.  It tends to go against  seem illogical at first. How ever, data
tends to support it.


H.B. Knowles, PhD, Physics Consulting
4030 Hillcrest Rd, El Sobrante, CA 94803
Phone\Fax (510)758-5449
hbknowls@ix.netcom.com