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Re: AW: Denver, BEWARE!
Since background radiation levels increase with increasing altitude, if one
believes in LNT,
cancer incidence should also increase so that any decrease in cancer occurs
despite the
increased radiation levels. If you believe in hormesis, the decreasing
cancer incidence
with altitude might be due either to increasing radiation, or decreasing
oxygen, or both.
Jerry
----- Original Message -----
From: Kai Kaletsch <eic@shaw.ca>
To: jjcohen <jjcohen@PRODIGY.NET>; <radsafe@list.vanderbilt.edu>
Sent: Monday, December 20, 2004 12:51 PM
Subject: Re: AW: Denver, BEWARE!
> I wonder if the inverse relationship between altitude and cancer incidence
> survives after stratifying by background radiation or radon.
>
> The inverse relationship between altitude and cancer as well as the
inverse
> relationship between background radiation and cancer are factual
> observations. The question of the cause seems to still be open.
>
> Kai
>
> ----- Original Message -----
> From: "jjcohen" <jjcohen@PRODIGY.NET>
> To: "Bradshaw, Keith" <keith.bradshaw@niras.co.uk>;
> <radsafe@list.vanderbilt.edu>
> Sent: Monday, December 20, 2004 12:36 PM
> Subject: Re: AW: Denver, BEWARE!
>
>
> > Several years ago, Daniel Koshland, chairman of AAAS & editor of
> > SCIENCE,
> > published an article implicating oxygen as a mild carcinogen. In this
> > article, he noted the inverse relationship between altitude and cancer
> > incidence and postulated that increased oxygen tension increased levels
of
> > free radicals which tend to have carcinogenic effects.[That is why
> > dietary
> > anti-oxidants, such as vitamin E are recommended for avoiding cancer).
Of
> > course, OTOH, oxygen is necessary for life. Many people have trouble
with
> > the concept that the same substance can simultaneously cause both
> > beneficial
> > and harmful effects. That is likely that is why Radiation Hormesis has
> > such
> > problems gaining acceptance.
> >
> >
> > ----- Original Message -----
> > From: Bradshaw, Keith <keith.bradshaw@niras.co.uk>
> > To: <radsafe@list.vanderbilt.edu>
> > Sent: Monday, December 20, 2004 9:02 AM
> > Subject: RE: AW: Denver, BEWARE!
> >
> >
> >> >>When I'm a mile high, I breathe harder than at sea level, so I
> >> >>naturally
> >> >>thought that the body makes up for the thinner air by trying to
inhale
> >> >>more of it.
> >>
> >> >I hear people say the body makes up for the thinner air by making more
> > red
> >> >blood cells. (It takes a few days to adapt.) The implication is: we
> >> >don't
> >> >inhale a larger volume, but I have never seen any data. I would
> > appreciate
> >> >a reference to real data, if anyone can provide it.
> >>
> >> My theory:
> >> The haemoglobin oxygen saturation stays pretty constant down to about
14%
> >> oxygen, or the equivalent in altitude, then it falls away quickly.
Once
> > you
> >> are in this steeply falling region of the curve, the actual tissue
> >> concentration of oxygen will be significantly reduced. The haemoglobin
> > acts
> >> as a buffer for oxygen concentration in the tissues.
> >>
> >> I think the real issue is the oxygen tension or partial pressure. I
> > suppose
> >> you could argue any increased number of red blood cells, as a result of
> >> adaptation at altitude, would deliver the same oxygen to the tissues,
but
> >> perhaps that only happens when the tissues demand it. Irrespective of
> >> the
> >> actual amount of haemoglobin, the saturation curve is the same shape.
> >>
> >> If this is the correct way of looking at it, that means there is
> >> significantly less oxygen-generated free radical damage at altitude.
> >> This
> >> more than makes up for the increased cosmic ray dose, possibly
explaining
> >> the longevity of people who live up mountains.
> >>
> >> Perhaps we need a proper physiologist to comment !!
> >>
> >> Personal views only
> >>
> >> keith.bradshaw@niras.co.uk
> >>
> >>
> >> web: www.niras.co.uk
> >>
> >>
> >>
> >> NNC's UK Operating Companies : NNC Holdings Limited (no. 3725076), NNC
> > Limited (no. 1120437), National Nuclear Corporation Limited (no.
2290928),
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> > The
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head
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is
> > 01565 633800. The NNC website is www.nnc.co.uk
> >>
> >> Any request, advice, information or opinion in this message which does
> >> not
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