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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
>>
>>
>>
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