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In 1991, the Michigan Indoor Radon Program conducted
a survey of radon in Michigan schools. More than 13,000 measurement
devices were placed in 288 randomly selected school buildings across the
state. About 2.3 percent of the samples at that time exceeded the EPA's
guidelines of four pCi/L.
The EPA has also assigned risk categories to each county across the nation,
with "Zone 1" counties having the highest potential to test higher than four
pCi/L; "Zone 3" the lowest potential; and "Zone 2," between the two zones.
The EPA ranks Oakland County as a Zone 2 county, while Macomb and
Wayne Counties are Zone 3. Also listed as Zone 2 counties are Lapeer and
Genesee counties to the north, and Livingston County to the west.
Washtenaw County, to the southwest of Oakland County, is considered one
of eight Zone 1 counties.
Radon levels reported to Air Check tend to follow the EPA's zone rankings of
radon risk, with Oakland's average of 3.6 pCi/L higher than Wayne (2.5 pCi/
L) and Macomb (2.0 pCi/L); and lower than Washtenaw County's average of
4.9 pCi/L.
In 2011, the Ann Arbor News published an investigation of elevated radon
levels in the basement of the former police department. The report detailed
instances of radon levels as many as seven times the EPA's action level, with
tests showing elevated levels from the 1990s when a mitigation system was
installed.
Air Check lists the percent of test results above four pCi/L in Washtenaw
County to be 37.3 percent, with 60.6 percent above two pCi/L.
Although the ranking system and news reports give an idea of where higher
risks may be, the amount of radon exiting the soil depends upon several
factors, one of the greatest being geology.
"It all starts with uranium," Redmond said. "It goes through a series of
decays and ultimately ends up as lead."
All rocks contain at least a small amount of uranium, typically between one
and three parts per million. As the uranium breaks down over millions of
years, it decays into radium, which then decays into radon gas. In gas form,
radon may be breathed in, where it further continues to decay into
polonium, another radioactive decay product, and can damage lung tissue
and lead to lung cancer over time. Thus, it's the radioactive decay process
that may occur in one's body that ultimately leads to harm.
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