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Re: AW: Denver, BEWARE!
Hi Richard,
Added anecdotal information-- Starting with 21% O2 concentration at mean
sea level (STP). Concentration remains the same as pressure altitude
decreases, but molecules of air decrease. Commercial aircraft use
pressurization to keep cabin pressure altitude at or below about 8,000
ft. At 12,000 ft for example, there are 40% fewer molecules per breath;
thus, we breathe more rapidly -- unless you have an O2 bottle to suck
on. <g> All of this simply confirms Ruth's comments. Also note that
apparently the thickness of your "8,000 ft package of air" in the
passenger cabin is not sufficient to offset the loss of shielding from
flight at 30,000 ft.
I did a cursory internet search to see what might be found about
hyperoxia. Found nothing to suggest that O2 might be carcinogenic. It
seems, however, that in terms of corrections for confounding in
research, distinctions probably should be made between pressure altitude
and O2 concentration. There are situations in which hyperoxia has
untoward physiological effects even in normal animals. These can be
observed also in emphysema cases using supplemental O2.
Surely the shielding effects of altitude from ionizing radiation must be
a function of air density rather than the concentration of O2 -- though
this could be an easy empirical question. Ionizing radiation does not
become a practical flight issue until one reaches pressure altitudes of
30,000 ft or thereabouts. Then the flight industry unions begin to chirp
....
Cheers and Merry Christmas to all,
Maury maurysis@ev1.net
===================
Richard L. Hess wrote:
> At 05:54 PM 12/19/2004 -0500, RuthWeiner@AOL.COM wrote:
>
>> Richard et al:
>>
>> I think "correcting for oxygen" means correcting for the fact that
>> the atmospheric pressure is less at 5280 feet than at sa leve, so
>> there is less oxygen available. This is a well known phenomenon (we
>> are a mile high here in Albuq. also). I don't think the idea was
>> that oxygen is a carcinogen, but that metabolism, breathing rate,
>> saturation of hemoglobin, etc are affected
>>
>> Ruth
>>
>
> Thanks, Ruth and Franz,
>
> I'm still confused, because Franz reminded me of the graph I made on
> an airplane a few years ago--and at altitude (IIRC about 41,000 feet)
> we were up at about 250µR per hour (as measured on an Aware RM-70
> pancake G-M tube)--and I understood from RADSAFE at the time, that the
> G-M tube under-reports the high-energy. For the graph, please see
> http://www.richardhess.com/rad/lax_chi.jpg
>
> 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.
>
> So we have Cohen's data for Radon, Wes's data for altitude, and then
> Franz throwing in the reduced shielding aspect. Even with Wes
> correcting for altitude I'm not sure I understand the effect that he's
> discussing. I took the data from Table 2 of Van Pelt's paper and did a
> simple graph in Excel. I even added a 2nd order polynomial trend line.
> See http://www.richardhess.com/rad/cohen_binned_by_van_pelt.jpg
>
> I still don't see a correlation between the slope "B" of the overall
> data and altitude. I see changes, I don't see a correlation--but I
> never was very good at statistics. Several years ago, I worked on a
> project with a Caltech statistician and he and I kept trying to get
> the other to explain, in simple terms, what was going on. I think we
> both saw the light that it was hard to reduce our own practice to
> simple terms the other could understand--but we got through it.
>
> Cheers,
>
> Richard
>
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