Re: Question on low-dose rad effects

["Philippe Duport" <pduport@home.com>]

Good question!

Why elephants, who live tens of years and weigh tons don't have more cancers
than mice who live 36 months and weigh tens of grams?  The same can be said
for different organs in the human body.  The ICRP tissue weighting factors
wT have little relation with the mass of the organs.

The quantity of energy delivered per unit per mass is not the only factor in
cancer induction.  It seems that the cell sensitivity to radiation and the
effectiveness of cell repair mechanisms are different for each tissue,
species and strain, age at exposure, ...   Perhaps other RADSAFERs can tell
us why.

Animal experiments (on  mice) have shown that low doses of low LET radiation
and even of neutrons have increased the life span of the animals and reduced
the risk of spontaneous cancer.  This is not true in all experiments, but
this is observed with strong statistical significance in some experiments.
I will provide references if required.

Philippe Duport
University of Ottawa
personal e-mail address: pduport@uottawa.ca

----- Original Message -----
From: "Jerry Cohen" <jjcohen@prodigy.net>
To: "Multiple recipients of list" <radsafe@romulus.ehs.uiuc.edu>
Sent: Thursday, October 12, 2000 6:25 PM
Subject: Fw: Question on low-dose rad effects


>
>
>
>
>      Perhaps someone could enlighten me on something that has puzzled me
for
> a long time. Why is the degree of harm, detriment, etc. from low-level
> radiation  expressed in terms of rad, rem, sieverts, etc. which are
> functions of absorbed energy per unit mass (i.e. ergs/gm)?
>  Isn't the probability of a mutation, or other adverse effect a direct
> function of the total number of ionizing events occuring in the vicinity
of
> suseptible DNA molecules and isn't that ,in turn, a function only of total
> absorbed energy?
>      For example, consider two individuals of the same age, sex, and
general
> state of health with the only difference between the two being that one
> weighs twice as much as the other.  Given that both recieve a radiation
dose
> of say 1.0 rem, have they both experienced an equal degree of harm? Due to
> his/her larger mass, the heavier individual gets twice as many ionizing
> events occuring near twice as many DNA molecules any one of which might
> result in an adverse mutation.  Why doesn't the individual with twice the
> mass, get twice the risk???     Jerry Cohen
> jjcohen@prodigy.net
>
> >
> >
>
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