Re: Radon Exposure Assessment for Cases

["Rad health" <healthrad@HOTMAIL.COM>]

Kia wrote:>

>I think when you assume LNT, averaged data is quite important because

>average risk is supposed to be proportional to average exposure. If the

>categorical analysis disagrees with the analysis on averages, it is likely

>due to the choices in picking the categories. (It doesn't matter if these

>were chosen a priory or not.)



Kai,



First, the average concentration does not equal the average exposure.  

Concentration and exposure are two different things. The Iowa case control 

study has nothing what so ever to do with the LNT.  Unless, you want to use 

it to show they did not find a threshold effect but did find a linear 

effect.  Yes it does matter when the categories were chosen.  They could be 

chosen after the fact to either maximize or minimize the association by 

arbitrarily choosing endpoints that would support a specific finding.  I 

think Iowa's choice of equal categories based on exposure make a lot of 

sense. By using mean radon concentration data to predict risk you are 

falling into the ecologic fallacy by assuming grouped findings = risk to an 

individual.



The cause you are concerned about is likely as simple as these cases 

developed lung cancer because the radon level was higher in their living 

area as compared to controls.  You really have to study the linkage of 

concentration with time.





Don





_________________________________________________________________

Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.



************************************************************************

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/