Re: Question on low-dose rad effects

["Otto G. Raabe" <ograabe@ucdavis.edu>]

October 21, 1999
Davis, CA

Dear Jerry:

You asked why the cancer risk from radiation exposure does not depend on
the total energy deposited in a body or organ so that bigger people or
animals or organs should have bigger risk from a sievert of irradiation
than smaller people or animals or organs. The simple answer is that the net
effect from exposure to radiation (and potentially toxic chemicals) depends
on the energy (or toxic chemical) concentration in an organ rather than the
number of cells in the organ. This has been empirically observed in animal
and human studies. In addition, he net effect is not stochastic even though
the individual interactions are stochastic, so the simple model that
visualizes ionization events in DNA or a chemical events in DNA as
representing a specific cancer risk that is proportional to the average
cancer risk per event is wrong. Also wrong, then, is the corollary concept
which is called the linear no-threshold dose-response model.

Otto

		*****************************************************
		Prof. Otto G. Raabe, Ph.D., CHP
              Institute of Toxicology & Environmental Health (ITEH)
		   (Street address: Building 3792, Old Davis Road)
		University of California, Davis, CA 95616
		Phone: 530-752-7754  FAX: 530-758-6140
		E-mail ograabe@ucdavis.edu
              *****************************************************
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