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RE: Po-210 in tobacco
Radsafers, Ray, Kjell, Franz,
If rock phosphate is used unprocessed, you are probably right.
Concerning the radon impact of phosphate fertilizer, according to a
chemist, the uranium separates with the phosphate and the radium with
the calcium (gypsum) in the manufacture of fertilizer, so that radon in
the field from this source would be delayed by the slow growing back of
the radium (halflife 1600 y). In the meantime, the soluble uranium
would also tend to be taken up by the crops. The radium content of
phospho-gypsum containing insoluble radium sulphate restricts its
potential uses in e.g. buildings due to radon emanation.
The dose rate from radon inhalation is taken as proportional to the
equilibration factor times the radon concentration, i.e. the latter
hardly contributes. Only daughters down to Po-214 are considered (which
reach the 0.4 equilibrium within minutes). Due to the 22.2y halflife of
Pb-210, it must have about a 100% chance of plating out before decay.
Remember, the radon concentration below ground is about 1000 times that
above, and there the whole decay chain has a chance to be in equilibrium
(several decades, due to the slow decays near the end). The only
long-lived alpha-decay is Po-210, going to Pb-206, with a halflife long
enough to be seen in the processed leaf, so the uptake by tobacco
through the roots need not be particularly selective to be registered.
Am I missing something?
Regards, Chris Hofmeyr.
chofmeyr@nnr.co.za
-----Original Message-----
From: Raymond Shadis [mailto:shadis@ime.net]
Sent: Monday, July 02, 2001 6:47 AM
To: Franz Schoenhofer; Kjell A. Johansen; radsafe
Subject: Re: Po-210 in tobacco
HelloFranz,Kjell, et al,
Am I missing something? I have long understood the level of Polonium
content
in most American tobacco products corresponded directly to the
application
of Florida rock phosphate [high in radium and daughters] in tobacco
fields.
On a related note: just a few years back, EPA found an apparent
synergistic
effect when smoking was combined with residential radon exposure.
Ray
----- Original Message -----
From: Franz Schoenhofer <franz.schoenhofer@CHELLO.AT>
To: Kjell A. Johansen <kajohans@powercom.net>; radsafe
<radsafe@list.vanderbilt.edu>
Sent: Sunday, July 01, 2001 6:32 PM
Subject: Re: Po-210 in tobacco
> Dear Kjell,
>
> I disagree with your disagreement....,..
>
> -----Ursprüngliche Nachricht-----
> Von: Kjell A. Johansen <kajohans@powercom.net>
> An: radsafe <radsafe@list.vanderbilt.edu>
> Datum: Sonntag, 01. Juli 2001 02:17
> Betreff: Po-210 in tobacco
>
>
> >Franz,
> >I have to disagree. The Po-210 in tobacco does come from the air.
The
> >mechanism is as follows:
> >Radon diffuses from the ground. As the radon decays it becomes
> >charged. The charged atom is attached to small airborne particles
> >called Aiken particles. The particle assumes the charge of the
charged
> >atom. Now, the underside of the tobacco leaf has many fine, hair
like
> >appendages which results in a large surface area for charged particle
> >attachment. The charged Aiken particles become attached to this
"fuzz."
> >
> >Sorry, but I do not remember the reference from which I got the
> >mechanism.
>
> No reference necessary, because the fact that radon decay products
will be
> attached to leafy vegetables (of which tobacco might be one....) as
well
as
> to any other surfaces like the walls in ones home is a fact, which
needs
not
> be discussed.
>
> O.K., now we are in the situation of "attobequerels of plutonium per
cubic
> square kilometer have been measured in air; plutonium is the most
deadly
> (!!!!) element in the world, therefore breathing this air will result
in
the
> extinction of the human race."
>
> Let me return to science. Radon-222 emanating from soil will be to
some
> extent in equilibrium with its short lived daughter products.
> "Equilibium-factor" probably int he range of 0.5. The short lived
daughters
> of interest are Po-218 and Po-214 with half lifes of 3 minutes and
165*10E-6
> seconds. They are responsible for the possible damage of lung tissue.
> Pb-210 has a half life of 22.2 years and its daugher Po-210 a half
life
of
> 138.4 days. Pb-210 is present in ambient air in an extremely low
> concentration. Unfortunately I have to use for my RADSAFE
communications
my
> private e-mail address, so I do not have the ambient Po-210
concentrations
> by hand, but qualitatively speaking it will be extremely low, if not
> negligible from the point of radiation protection. I know very well
that
> data are used in research for air masses displacements and research of
> transfer of air masses. Due to the extremely low concentrations of
Pb-210
in
> air the foliar uptake can be only extremely small.
>
> Oh, sorry, I made a mistake. You are talking about Po-210 uptake and
not
> Pb-210, the long lived radionuclide, as I did. Anything known about
the
> concentrations of Pb-210 compared to Po-210 in air?
>
> What about removal of this incredibly low Po-210 (Pb-210????) -amount
from
> the plant by rain or irrigation?
>
> Once again I can only refer to common sense and the many orders of
magnitude
> I have experience. If there is a hard challenge I might go deeper into
the
> question,. In the meantime I would remind every smoker that he or she
is
> subject to highly enhanced risk of dying from lung cancer - induced by
tar
> and policyclic constituents, Po-210 being a contributor.
>
> Happy smoking!
>
> Franz
>
>
>
>
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