Re: Radon Exposure Assessment for Cases

[BERNARD L COHEN <blc+@PITT.EDU>]

On Sat, 26 Jan 2002, Michael Ford wrote:



> I would maintain that as houses age, they tend to settle and and the

> structure loosens up and allows more exchange with outside air (i.e., less

> energy efficient).



	--My studies (Health Phys.60:631-642;1991) show that radon levels

in houses, on average, decrease slowly as they age from 1 year to 80 years

ending up with 64% of the original radon. But that is "on average". Much

more important is the fact that the radon level in a particular house can

change drastically if a crack opens up or becomes sealed, if ventilation

conditions change as by changing the furnace type or using exhaust fans or

dryer vents, if something is done to change the air exchange between

basement and upper floors, etc. Note that changes in the particular houses

used in case-control studies would be much more likely than changes in the

average radon level of a county.





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