Good thoughts but lets not rely on those EPA county zone maps anymore--they are "broken" in many instances. What  I mean is that, for example in southeast Michigan , you have a thin hot zone band running through in area of lower risk. The averaging of the few highs and the many lows presents a meaningless measure of risk. EPA Zone maps only seem to be useful where the geology is fairly uniform across the county.

The radon data are out there--someone needs to start publishing the data superimposed on geological maps--then we can start getting a better handle on the high risk areas and they won't get lost from being averaged into the lower risk areas.

Larry,

THe EPA "action" level is 4.0 pCi/l and the "consider action" level of 2.0 pCi/l are advisory, not law, so why can't lenders set their own standards?  Over a span of 20 years I wotked with [residential] buyers who often demanded levels below the EPA action levels.  Even in cases where sellers had contract provisions tied to the EPA action level buyers countered to get what they wanted.

Regardless of what level a lender or buyer is willing to accept it's important to be specific about where measurements are taken.  Where I live and work radon tests are almost always done in basements.  In my experience except in the case of a high rise building with a convoluted HVAC system a basement level of 4.0 pCi/l translates to less than 2 pCi/l on the first floor and only trace levels above that.  Likewise, a basement level of 2.0 pCi/l translates to trace levels on the first and higher floors.  Whether you accept EPA's recommendations or set your own standards it would be prudent to adopt a standard that applies specifically to finished living space and require testing only on living levels.

It seems to me that the incentive for testing and abatement should be according to the Golden Rule:  He who has the gold (in this case, the lender) makes the rules.       

I don't argue with what you say although I'm wondering how much loan shopping is going on right now...

I would like to clarify/amplify two technical points for you to respond to:

1.  There is theoretical risk at every radon level but it's in outdoor and indoor air and it's not possible to avoid exposure so any standard must tolerate at least "trace" amounts.

2.  Even if a lender is loathe to going beyond the law (if this was a law) the lender could still be specific about where measurements are taken and I think the lender would find less loans to be worried about.

And finally, one additional question for you:

Since Mike is hypothetically concerned with properties that test in the 1 - 3 pCi/L range, would it be reasonable for him to tighten up his standards by adopting the "consider action" level, rather than the action level?  I raise the question especially because in my experience living spaces above a 4.0 pCi/L basement are most likely to be lower than that:  If the lender currently uses the "action" level of 4.0 pCi/l basement reading the 2.0 upper limit for living spaces above is virtually automatic.  Also, specifically requiring testing in living spaces negates the risk of the odd circumstance of higher levels on higher floors.

In central Ohio this is typically a building-code issue.  New homes are required to incorporate radon control via sealed sumps and either active (blower) or passive (non-blower) vent systems serving the sub-slab space, whether basement or slab-on-grade.  In my opinion this is the most appropriate mechanism to deal with radon mitigation.  It should be possible to require mitigation whenever property transfers occur, via a similar mechanism.