Conflicting infornation on radon maps

[jcampbell3]

EPA Maine radon map http://www.epa.gov/radon/states/images/maine.gif does not come close to agreeing with the University of Maine radon map. http://www.physics.umaine.edu/radiation/radmap1.htm I'm wondering which to believe. What do you think of this? If you do radon testing, how would you explain the discrepancy to your clients? Of course, not everyone will be aware of the conflict, but, I imagine that some people who are concerned about radon will have done a good amount of research on the subject. And also, there will be those who may use the discrepancies to discredit, or at least mistrust, other information concerning radon.

[Jeffrey R. Jonas]

Two different sources, two different ways of determination. Most likely, one uses geographic data to determine areas "prone" to Radon. The other uses "reported" test results. Or... other methodology... or any combination thereof. JMHO.

[Douglas Wall]

I may have been missing something over the years. After 10 years and thousands of radon test I really can't remember when I last looked at one of those radon maps. A few years ago, I do remember that one or two zip codes I looked up had 65 or so tests having been done there and we had performed over a couple hundred there ourselves. The information must be terribly outdated. Florida DOH is a joke and we are one of the states that is regulated.

No one thought there was much elevated radon in SW Florida when we started, 1999. In 2008 the EPA gave Florida a grant to study Collier and Lee Counties (SW FL) because so many high rise condos come back elevated. Now the DOH says one out of two homes in "some areas" has elevated radon levels.

You don't know unless you test. Don't put to much stock in the maps.

[David A. Andersen]

Way back when (about 10 years ago) I radon testing and then radon mitigation courses with the EPA, the maps that you described were taught in class as being inaccurate cause of the way data was available, collected and reported. We were instructed to ignore these maps.

If you go back and read your EPA stuff, there is no way to predict radon levels at any time. One house in a 100 home subdivision could have a problem and the rest do not, and vice versa.

It is my suggestion that you just don't worry about it. If you're trying use these maps to induce someone to perceive they may have a problem, you're barking up the wrong tree anyway.

[Russel Ray]

You have to look deeper than the maps. Last time I was digging through radon maps, I found several counties that had high levels of radon. Unfortunately, they only had one or two tests from the whole county. Not statistically relevant.

[David A. Andersen]

Exactly what EPA put out.

A lot of counties that do not have a high radon rating on the map could be because they are located where little or no radon testing had been conducted and reported. It doesn't mean the radon levels are low.

This is all about the results of known tests.
In order to create a map you must have a sample number of tests conducted in every county of a sufficient quantity to formulate an average that can be compared in one county to another.

Just look upon the map as a historical reference of where high radon testing results occurred (if testing was conducted in that location at all).

[Joseph Burley]

The EPA radon maps average data on a county wide basis. So if your local geology and (therefore radon risk) is very consistent across the whole county, the maps are reasonably accurate. However, as is usually the case, especially here in southern Mich, you have bands of hot spots crossing through a county that otherwise has low risk. This screws up the average and makes the EPA county radon classification relatively worthless for local purposes. The same problem can happen with radon data by city or zip code. Radon data really needs to be mapped geographically by address to provide meaningful data for mapping.