--All of this discussion ignores the difference between a short term charcoal adsorption test with a diffusion barrier and a short
term charcoal adsorption test without a diffusion barrier. The
former gives a much longer time averaging (3-5 day vs 1-2 day
average) at very little extra cost. Another issue is whether windows
were kept closed for the short term measurement. Our recommendation
was to add 30% to a Summer measurement to estimate the annual
average. With attention to these matters, our studies have shown
that a charcoal adsorption measurement with a diffusion barrier and
with closed windows gives much better results than those described
here. Why not make those simple steps standard?
On 6/17/2011 11:05 AM, Steck, Daniel wrote:
My thanks to those who continue to think that this is an
important issue worthy of discussion. I have been reluctant
to respond to the numerous recent posts since I feel that this
discussion list is an inadequate forum for a debate of the
complex issue of the performance of the current EPA screening
protocol. However, it is an important issue that deserves a
thorough, fact-based discussion before a large audience. I am
trying to organize such a discussion.
In the meantime I do want to respond to some of the
statements using as a basis my research and the current
scientific literature on the performance of short-term
screening tests in (a) making mitigation derisions and (b) the
related issue of predicting the annual average radon
concentration in living spaces. (The latter is usually taken
as an adequate standard for judging long-term radon exposure
even though year-to-year variations can be substantial.) I
don’t claim to have all the answers but I have spent almost 30
years trying to establish some scientific information about
the situation in the Upper Midwest to compare with other
research and experience.
Rest assured that I want the fragile radon industry to
survive and expand but I also want their customers and clients
to be well served. Shot-tem measurements can be useful and I
often recommend them for certain applications or to supplement
long-tem measurements (two seasonal). Short-term measurements
can provide temporary relief from radon anxiety, catch a few
of those extreme cases that Phil J described and also may be
fine for post-mitigation tests. (based on ~100 cases).
However, SHORT-TERM SCREENING TESTS correlate poorly with
ANNUAL AVERAGE RADON CONCENTRATION IN LIVING SPACES , not just
in the Upper Midwest, but in national surveys conducted for
the EPA (look at the 1994 publications from White et al.),
ANNUAL AVERAGE RADON CONCENTRATION IN LIVING SPACES
predictions based on SHORT-TERM SCREENING TESTS are no better
than about
a multiplicative factor of 2 to 3.
Is this good enough for a mitigation decision? If the house
has a ANNUAL AVERAGE RADON CONCENTRATION IN LIVING SPACES
below 1 pCi/l (as many US houses do) then a factor of two
uncertainty will not lead to many poor mitigation decisions.
But, in a radon prone region many people who should mitigate
don’t because their SHORT-TERM SCREENING TESTS came back under
4 pCi/L when their ANNUAL AVERAGE RADON CONCENTRATION IN
LIVING SPACES was above 4 pCi/L. In my 2005 study, reported at
the AARST conference, ONLY SHORT-TERM SCREENING TESTS BELOW
about 1 pCi/L reliably predicted (95%) ANNUAL AVERAGE RADON
CONCENTRATION IN LIVING SPACES below 4 pCi/L. It took
SHORT-TERM SCREENING TEST result of around 6 pCi/L to reliably
predict ANNUAL AVERAGE RADON CONCENTRATION IN LIVING SPACES
above 4 pCi/L. If you look at the national data (table 2
White 1994) you see a similar pattern of increasing failure
rates of SHORT-TERM SCREENING TESTS as the house measurements
approach 4 pCi/L. So SHORT-TERM SCREENING TESTS may only fail
a few percent of the time when applied to a national sample
but fails at a an unacceptable rate in radon regions and for
homes whose ANNUAL AVERAGE RADON CONCENTRATION IN LIVING
SPACES is near the action level. Depending on your values,
you may be more tolerant of a false positive failure
(mitigating a house whose ANNUAL AVERAGE RADON CONCENTRATION
IN LIVING SPACES is less than 4 pCi/L) than a false negative
failure (not mitigating a house with ANNUAL AVERAGE RADON
CONCENTRATION IN LIVING SPACES greater than 4 pCi/L). We
need to find a way to incorporate uncertainty to reduce the
decision-making failure rate for homes “near” the action
level.
I think that we, as a professional community, can improve
mitigation decision making without great economic damage to
measurement companies or unnecessary disruption of consumer
confidence. However, progress will require effort,
resources, and respectful cooperation of researchers,
industry, and (hopefully) government agencies. I hope you
think it is a worthwhile task.
Sincerely
Dan
Daniel J. Steck, PhD.
Professor, Physics Department, St. John's University
Director: Schaefer Environmental Radiation Laboratory
109 PENGL Science Center
Collegeville, MN USA 56321
320-363-3186 or 800-820-3209 FAX 320-363-3202
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