AARST 2004 SYMPOSIUM PROCEEDINGS

LUNG CANCER PREVENTION THROUGH RADON MITIGATION:
URGENCY AND EFFECTIVENESS FROM A
LOCAL PERSPECTIVE
L. Moorman, Ph.D.
Radon Home Measurement and Mitigation, Inc.
Fort Collins, Colorado
USA

ABSTRACT
A realistic estimate, incorporating radon concentration distributions, is given of the total number
of local lung cancer incidences attributable to radiation from radon and its decay products in the
residential environment in a community with an increased average indoor-air radon
concentration. An estimate of the currently prevented lung cancer incidences due to past
mitigations is presented. Finally we present the expected residual lung cancer death rates due to
radon exposure for this community during the next decade. The purpose of this presentation is to
provide information to educators and mitigators in order to aid in the process for legislative
action and to demonstrate the effectiveness of small to medium sized companies. Finally, the
presented information could serve as an example in the broader national discussion.

MOTIVATION AND GOAL
There is a need for realistic data of the number of local lung cancer incidences that are
attributable to radiation from radon and its decay products in the residential environment and
lung cancer incidences prevented as a consequence of current mitigation efforts in local
communitiesi. At the heart of the discussion in one such community is the question whether to
adapt a new City Building Code to include mandatory radon mitigation systems in new home
construction for the prevention of lung cancerii. This community near the foothills of the Rocky
Mountains with a substantially higher than average indoor-air radon concentration compared to
the national average could serve as an example in a broader national discussion for other
communities after careful comparison of available local radon concentration data with the data
presented in this study.
The goal of this study is to calculate local average yearly lung cancer risk rates, to
calculate various aspects of the lung cancer risk reduction already achieved due to radon
mitigation, and to use these data to predict the residual lung cancer death rates for the community
in the next decade. In addition, the purpose of this manuscript is to provide information to other

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communities that have an increased average indoor-air radon concentration compared to the
national average in order to aid in the process whether legislative action is needed or desirable.
Finally we want to demonstrate the effectiveness of small to medium sized companies in this
context.

STATISTICAL DISTRIBUTION OF RESIDENTIAL RADON CONCENTRATION
MEASUREMENTS IN THE AREA.
This manuscript uses in situ radon concentrationiii reductions obtained with radon
mitigation systems that were installed in accordance with the recommendations of the EPA radon
mitigation standardsiv to calculate radon cancer rate reductions, using the committees’ two
preferred dose-response models presented in BEIR VI, in a community that has a larger average
radon concentration in residential structures than the national average. Our datav on homes that
were not previously tested in the City of Fort Collins, indicate that on the average three out of
four tested residential structures have a test result above 4.0 pCi/L. The sample average of our
distribution is 6.4 pCi/L with a strongly asymmetric distribution.
All mitigated homes by RHMM with pre-mitigation levels above 4.0 pCi/L were reduced
to below 4.0 pCi/L after mitigation. The data does not show a correlation between the final
radon concentration values and pre-mitigation levels. Post mitigation radon concentration levels
were measured following the EPA protocol including a 24 hour open house waiting period and
closed house conditions during and at least 12 hours before the start of the test. After analysis a
correlation was found between the final radon concentration and certain details of the building
construction that consequently allows for a diversification of mitigation types. The three
distinguished types of mitigations are “Phase I-”, “Complete-” and “Ideal Mitigation Systems”.
An increasing degree of success was obtained in reaching a lower radon concentration as is
indicated by the average values of measured concentrations in Table 1. The shape and width of
the data show nevertheless that neighboring distributions overlap.

SAMPLE STATISTICAL DATA FROM MITIGATED HOMES
Radon concentrations, ρi(n), before and after mitigation (n=1,2) for an indiviual house, i,
were measured via EPA radon measurement protocols partially during real estate transactions
and partially for home owners. In total 267 homes are included in this study over the period
1998-2003 that were mitigated by means of active soil depressurization of the sub-slab, a submembrane, or mitigated by a combination of the two methods. Using the dose-response factors
vi
for the two preferred models of the Committee, a Lung Cancer risk rate was
m from BEIR VI
calculated for each residential structure that was mitigated and multiplied with the number of the
occupants living in the home Ni at the time of, or immediately before or after the mitigation:

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j

L(jm n ) = 1.936 ⋅ α ( m ) ∑ N i ρ i( n ) .
i =1

Fig. 1 shows, cumulatively, the Lung Cancer risk rate attributable for the number of
homes mitigated for every ten year period in the future. The significance of this curve is the
large difference of its slope and the slope of the curve that indicates the calculated residual lung
cancer death rate after mitigation. The difference, Lj(m1) - Lj(m2), of the slopes represents the
eliminated average lung cancer deaths per home for every period of 10 years in the future. The
ratio of the two slopes Lj(m1)/Lj(m2), indicates that an 8.2-fold reduction of lung cancer risk on the
average is accomplished due to the combined mitigation effort as measured by the accomplished
radon reductions.
The data can be viewed in a different way by calculating the average lung cancer risk
reduction for the occupants in each mitigated home
Ri = ρ i(1) / ρ i( 2 )
and generating the frequency distribution of all individual data.
A mathematical fit to the resulting distribution is shown in Figure 2 which has a strongly
asymmetric shape with its maximum near a factor 5 reduction and with 6% of the data indicating
a lung cancer risk reduction of more than 40 times. The average of the distribution is 17.5,
which is larger than the factor 8.2 mentioned previously because the distribution is strongly
asymmetric.

TOTAL AND RADON/RDP CONFOUNDED
LOCAL LUNG CANCER RATES
Lung cancer incidence age adjusted rates for Larimer County are available from the
county . Since the survival rate of lung cancer is small the mortality rate after initial diagnosis
is only slightly lower. In the calculations presented in this manuscript we have not taken the
specific age distribution of the Fort Collins population into account which is a relatively young
population because it is a university town. Therefore we have assumed this distribution to be
equal to the national age distribution and our results should be compared to the county rates that
are age adjusted to the national age distribution. The population in the community is estimated
using 1990 data to be 87,941 occupants and in this report we will normalize the resulting data to
this number o foccupants by assuming a no-growth scenarioviii. The age adjusted lung cancer
incidence rates reported by the county scaled to the Fort Collins population size is in the bracket
33 to 51 lung cancer incidence per year for the rates reported from 1990-2000.
The most simple model to calculate the Radon/RDP confounded lung cancer rates would
be a proportionally scaled population model, ignoring any radon concentration exposure
differences to the local compared to the national population , which results in the bracket 5 to 7
lung cancer instances per year. This however underestimates the true rate because the average of
the radon concentrations in this community are larger than the nations’ average. The Fort Collins
data based on the average, 6.4 pCi/L, indicates an increased health risk for its population
compared to the national health risk by a factor 5, which we could name the lung cancer risk
vii

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enhancement factor. Taking this difference in radon concentration averages into account results
in 26 to 36 expected radon related lung cancer deaths every year in this community.ix
A more accurate value for the lung cancer risk enhancement factor from radon for this
City can be calculated by comparing the local measured radon distribution (f( )), to the national
distribution (g( )) in the BEIR VI report. When assuming a linear dose-response relationship,
H(  
with
the dose-response factor and assuming an average occupation per residence,
following any of the linear no-threshold models in BEIR VI the lung cancer risk enhancement
factor can be calculated using the accumulative risk enhancement factor:
r

r)

∫

f ( ρ ) H ( ρ ) dρ

0
r

∫ g ( ρ ) H ( ρ ) dρ
0

r

  ∫0

f ( ρ )ρdρ



r

∫ g ( ρ )ρdρ
0

This means that the lung cancer risk enhancement factor can be calculated universally and
depends only on the distributions f and g and more specifically is independent of the exact
value of the dose-response factor in the linear model.
The lung cancer risk enhancement factor was calculated as a function of the radon
concentration, ρ. The saturation of this curve for large radon concentrations indicates that the
lung cancer risk enhancement by radon for the Fort Collins Community is 3.2 larger than the
national average. Comparing this to the calculated national rate our calculation shows that this
most realistic radon/RDP confounded lung cancer rate is in the 17 to 24 bracket. This rate
represents the maximum mitigatable lung cancer death rate under a no-growth scenario and this
is the rate that should be recognized as the target for this community to put methods in place to
help reduce it.
The three calculated Radon/RDP confounded lung cancer incidences per year in this
section for this community are summarized in Fig. 3 and compared with the County lung cancer
incidences for all causes scaled for this City. In this comparison the most accurate and relevant
calculation includes the radon concentration distributions.

PREVENTED AND PREVENTABLE LUNG CANCER RATES
The need for an ongoing community effort may be judged by the accomplished residual
lung cancer death rate due to radon/RDP inhalation. If the residual lung cancer death rate is high
a larger effort may be encouraged through the legislative process as through Code changes in
new home construction. If the residual lung cancer death rate is low the need for implementation
of Code changes may not be appropriate.
In the City of Fort Collins a steady increase of mitigation systems has been accomplished
since 1986. Data of the Cityx during the period 1998 to 2000 indicate that approximately 351
homes were mitigated each year. In an effort to make a best estimate it is assumed here that a
linear increase of mitigated homes from 1986 until now has been accomplished and will continue

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in the near future and that the systems installed by all mitigation companies have a similar
success in their effectiveness of radon removal. An elementary calculation of which the result is
displayed in Fig 4 for the two models shows that in 2003, approximately 6 to 8 lung cancer
deaths are prevented every year depending on the BEIR VI model chosen in this community by
past mitigations. This is indicated by the cross shaded shape in order to show that even if there
was an immediate freeze on all future mitigations, the mitigations in the past would continue to
save lives among the occupants in the mitigated homes. The shape of the distribution shows that
if a linearly increasing number of homes are mitigated every year, a quadratically increasing
number of lives will be saved in each future year. Following this scenario the preventable rate
would be in the bracket 16 to 21 lung cancer deaths prevented per year in the year 2013. The
true rate will be smaller because the average of the pre-mitigation radon concentrations of the
mitigated homes in the future will decrease when more homes have been mitigated.
Extrapolation beyond 2013 is not realistic because of these and other unknown parameters. For
example the rate increases if currently discussed legislative requirements of new home
construction are implemented and will show a saturation at large values. A similar calculation
based on the averages of the known radon concentration distributions results in 14 to 20
preventable lung cancer deaths per year. Both values for 2003 and 2013 are shown in Fig 3.

RESIDUAL RADON/RDP LUNG CANCER RATES
The analysis in this study shows that the expected residual lung cancer death rate with radon as a
confounding factor, given the measured radon distribution in homes in Fort Collins compared to
the national distribution, is currently estimated in the bracket 11 to 16 lung cancer deaths per
year. The expected residual lung cancer death rate in 2013 can be calculated by using the data
presented in Fig 1 and by dividing the preventable radon lung cancer rate by the factor 8.2 that
was extracted from these data. The result will be in the bracket 2 to 3 lung cancer deaths per
year in the year 2013. This reduction from the current 11 to 16 lung cancer deaths per year
means that in this small community by a continued effort on the average one additional lung
cancer death can be prevented at least every five weeks. Formulated this way may best help to
illustrate the urgency for the ongoing radon mitigation effort. Based on the data presented here
this effort is also expected to result in a lowering of the current total lung cancer death rate in this
community by a substantial fraction of 30%.

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ACKNOWLEDGMENTS: The presented data could have not been measured without the many
who helped to load and unload the trailer, fight the spiders and seal the radon barriers
meticulously in those 4- and 2-foot crawl spaces, those who caulked all expansion joints, control
grooves and cracks in basement slabs and spend time in those sauna-like attics in the summer. I
am indebted to Heather Fleck, Shaun McDonnell, Juan Moreno and others for their assistance
and to all home owners who cleaned up their crawl spaces and basements before the start of our
mitigation work.
REFERENCES

i

Fort Collins City Council meeting, July 2002, and May 2003.
On July 20, 2004 the Council of the City of Fort Collins adopted the IRC 2000 building code to
be effective January 1, 2005, with an amendment requiring passive mitigation systems in New
Home Construction.
iii
The term “Radon concentration” which is measured in terms of the “radon (radio-) activity
density” and is defined as the rate of decay by radon atoms per unit of volume, often
measured in units pCi/L or Bq/m3, in which 1 pCi/L=37 Bq/m3.
iv
Radon Mitigation Standards EPA 402-R-93-078, Oct 1993, Rev. April 1994
v
Data gathered by the City of Ft. Collins shows that of more than 10,000 tests gathered
approximately 75% had a radon concentration larger than 4.0 pCi/L.
vi
National Academy of Sciences: The Commission on Biological Effects of Ionizing Radiation
(BEIR) VI “ The health effects of exposure to Indoor Radon.”
vii
Larimer County, with Fort Collins as seat, has a population of 221,725 (1996) World
Almanac, 1998. The yearly Lung Cancer Incidence rates for Larimer County during the decade
1990-2000 are available via the Larimer County website and vary from a low 37.6 to a high of
57.7 lung cancer incidences per year per 100,000 occupants. Source: Colorado Department of
Public Health and Environment - Colorado Central Cancer Registry.
viii
Resulting rates will have to be scaled with future population changes.
ix
Weighed risk factor for public includes smokers and no-smokers.
x
Radon Program Review 2001: City of Fort Collins Natural Resources Department (CPES),
March 2001
ii

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