[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: radon and smoking
Ruth,
Radon-222 progeny is another name for the
222Rn decay products
or 222Rn daughters.
Radon-222 progeny rather than
222Rn gas deliver the
actual radiation dose to lung tissues. The solid airborne
222Rn progeny,
particularly 218Po,
214Pb, and
214Bi, are of health
importance because they can be inspired and retained in the lung. The
radiation released during the subsequent decay of the alpha-emitting
decay products 218Po
and 214Po delivers a
radiologically significant dose to the respiratory epithelium. The ratio
of progeny to 222Rn
gas ranges from 0.2-0.8 with a typical value of 0.4. The ratio between
progeny and 222Rn gas
is called the equilibrium factor.
After decay of the
222Rn gas, a high
percentage of the decay products attaches to ambient aerosols. A small
percentage of the decay products remains unattached; others increase
their diameter through chemical and physical processes. The percent
attachment depends on numerous factors, including the size and
concentration of the airborne particles. The size and density of a
particle determine its behavior in the respiratory tract. The unattached
particle fraction with a 1-nm diameter is generally removed in the nose
and mouth during breathing and has limited penetration of the bronchi.
Maximal deposition occurs as the particles with diameters ranging from
3-10 nm increase their rate of penetration through the mouth and nose,
ultimately depositing in the bronchial region. The deposition rate
decreases for particles as their diameter increases toward 100 nm and
larger because the particles are less able to diffuse to the airway
surface. However, particle deposition into the respiratory tract through
impaction starts to increase again for particles above 500 nm. Larger
particles with a diameter exceeding 3.5 µm deposit predominantly in the
nose and mouth during inhalation and do not reach the sensitive
respiratory epithelium.
SEE ALSO:
http://www.vh.org/Providers/Textbooks/Radon/HealthRisk.html
Regards, Bill
At 01:33 PM 2/13/2002 -0500, you wrote:
In
a message dated 2/13/02 9:57:34 AM Mountain Standard Time,
bill-field@UIOWA.EDU writes:
In your email below, you did not
mean to imply that the radon GAS
concentrations increased did you? I would expect the aerosols and
airborne
radon progeny to increase, but not the radon gas concentrations.
I do not understand this question. Radon is chemically
inert. If damage to the lung alveoli is from the radon alpha, what
difference does it make if it is carried into the lung as a gas on
loosely bound to a particle. Is the difference in the residence
time in the lung? Is the difference that radon progeny would be
more likely to stay in the lung if the radon is on a particle?
Ruth Weiner, Ph. D.
ruthweiner@aol.com
************************************************************************
You are currently subscribed to the Radsafe mailing list. To unsubscribe,
send an e-mail to Majordomo@list.vanderbilt.edu Put the text "unsubscribe
radsafe" (no quote marks) in the body of the e-mail, with no subject line. You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/