|
This map, representing the yearly averages of radon levels in
the main floor, is from the Wisconsin Department of Health and Family Services. This map is derived from 87,000 basement test
results obtained from companies that sell radon detectors.
The conversion to the main-floor average shown on the
map is based on a random survey of 1100 houses, in which one-year follow-up measurements were done on the first floors in
200 houses where basement 2-day screening levels were over 4 pCi/L (picoCuries per liter). Year-average main-floor radon levels
for individual houses were typically 40% of the corresponding basement short-term levels. They ranged from 10% to 100% of
the basement short-term results, with the distribution peaking at 40%, the average. For the map, basements with short-term
test results over 10 pCi/L were taken to correspond statistically (though not for any particular house) to main-floor year
averages higher than the EPA 4 pCi/L guideline. The more measurement results there are for a given zip code, the better this
estimating procedure is.
|
