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RE: AW: Denver, BEWARE!
Jerry, Keith et al
I agree with the statement that "increased levels of free radicals which
tend to have carcinogenic effects" but I'm not sure if there is a change in
"oxygen tension" with altitude. In addition food is both necessary for life
but too much of the wrong kind causes fat deposited that can result in death
due to cardiovascular diseases.
John
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-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of jjcohen
Sent: December 20, 2004 10:36 AM
To: Bradshaw, Keith; radsafe@list.vanderbilt.edu
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
>
>
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