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Radon gas may enter groundwater, become stuck
in pockets of gas in the earth's soil, or rise to the
surface where it enters the air or buildings
through cracks in foundations, drains and other
means. Radon levels in outdoor air, indoor air,
soil air and groundwater can all be very different,
with outdoor air raging from one pCi/L to about
3,000 pCi/L, with an average about one to two
pCi/L, according to the United States Geological
Survey. Radon in soil air is usually between 200
and 2,000 pCi/L.
While most buildings draw less than one percent of their indoor air from the
soil, those with low indoor air pressures, poorly sealed foundations and
several entry points for soil air may draw a much higher percentage of air
from soil. Even if soil air has only moderate levels of radon, levels inside a
building may be high. Water systems also may allow radon to enter a
building.
Radon levels may be higher in areas where there are higher concentrations
of uranium, such as granite and shale. High levels of radon discovered in
Pennsylvania coincide with the uranium-rich Reading Prong formation, while
the uranium-rich Ohio Shale formation extends into southern Michigan.
While state lawmakers have passed laws regarding radon testing for
homes in counties with a high risk for radon, as well as daycare facilities,
there has been almost no efforts to increase radon testing in schools.
"You can find trace amounts of uranium associated with black shale,"
Redmond said. "In Pennsylvania, there is the famous Marcellus formation,
which they are fracking now for natural gas. Michigan has a similar black
shale, Antrim Shale. I never tested for radon in Michigan, but I wouldn't be
surprised that in some areas where you have a structure over shale, you
could have higher radon levels. I don't think there's any granite in the lower
peninsula, but you certainly have black shale."
While state lawmakers have passed laws regarding radon testing for homes
in counties with a high risk for radon, as well as daycare facilities, there has
been almost no efforts to increase radon testing in schools.
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