Re: LNT models -Constancy of Radon levels over time??

[FIELDRW@aol.com]

In a message dated 00-03-08 13:41:10 EST, Tom Mohaupt writes:

Radon is not constant. The concentration has been changing over the years due 
to buttoning up homes and filtering air. This point can easily applied to 
residential radon studies. It also applies to the Iowa study, which does not 
correct for  this effect. See "Residential Radon and Lung Cancer Case-Control 
Study" at  http://www.cheec.uiowa.edu/misc/radon.html. The paper describes 
the Iowa radon study methodology for those of you who are interested.
 
Tom,
--------------------------------
Tom,  

Your statement above is incorrect.  The report you reference above is our 
findings for the "radon gas phase" of the Iowa Radon Lung Cancer Study.  The 
paper will be published in the May issue of the American Journal of 
Epidemiology.   There is less radon gas variation over time in the Iowa Study 
than other studies, because the study was limited to individuals who lived in 
the same house for 20 years (median 32 years).  One of the predominant 
factors that affect temporal variation of indoor radon concentrations is 
occupant behavior (opening windows, etc.) with new homeowners.  The occupant 
behavior in the Iowa study is less of a concern, since at least one of the 
occupants have stayed in the same home for extended periods (>20 years).  

We have examined the temporal radon gas variation in a subset of the homes 
over time and can assess how that affects our risk estimates.  We also looked 
at factors that may have affected radon concentrations over time (furnace 
change, addition of window or central air, etc.).  We can stratify the homes 
that may have had changes to see if it affects the risk analyses.  This can 
not be done with an ecologic study.  

Let me ask you this.  Do you think you would get a better idea of the radon 
concentration in your home from a measurement performed in your home five 
years ago or using the county average radon concentration (as used in 
ecologic studies)?

In addition, we performed retrospective determination of radon progeny 
exposure using glass-based detectors (I would be glad to provide references 
on these devices), which minimizes the problems associated with temporal 
radon variation.  if you would like to call me, I would be glad to discuss 
this is more detail.

How would you design a study to examine the risk posed by residential radon?

How would you test the validity of the LNT?

Bill Field
College of Public Health
University of Iowa
bill-field@uiowa.edu       


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