Re: Radon and smoking

[AndrewsJP@AOL.COM]

In a message dated 2/13/2002 2:51:39 PM Eastern Standard Time, bill-field@UIOWA.EDU writes:



> 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. 


This information is new to me and very interesting.  However, it does not discuss the fraction of the radon daughters attached to the various particle sizes and the distribution of those sized in a typical atmosphere.  Seems to me that the particulate size distibution in air in a smokers house, for example, will be quite different than that of a non-smoker.  Also there are a number of causes of dust in a home or workplace that will cause the particle size distribution to vary widely.  Perhaps this is a significant confounder in any study of the effects of radon.  The mind boggles at the thought of trying to characterize the dust patterns in a home over a lifetime.




John Andrews

Knoxville, Tennessee