EP A/600/A-94/264
The U, S. Environmental Protection Agency's National Strategy for Radon Remediation
Timothy M. Dyess1 and Stephany DeSciscioio2
1 U, S. Environmental Protection Agency, Air and Energy Engineering Research Laboratory,
Research Triangle Park, NC 27711 USA
2 U. S. Environmental Protection Agency, Office of Radiation and Indoor Air,
Washington, DC 20460 USA
ABSTRACT
During the past 10 years the U.S. Environmental Protection Agency (EPA) has pursued a national
strategy to address radon remediation in buildings to meet its goals of radon risk reduction.
Initially the approach developed and demonstrated remediation methods and techniques in existing
residences with specific attention to the effect of regional climate variations and the differences in
housing construction. A number of studies and demonstrations were undertaken to accurately
characterize and evaluate the effectiveness of several remediation methods and techniques. This
knowledge was then later expanded through research on radon control for newly constructed
houses with the subsequent development of model standards and techniques. Additionally, other
research was initiated to gain a better understanding of remediation approaches in existing and
newly constructed non-residential buildings such as schools, commercial office buildings, and
hospitals. This paper provides an historical summary of the evolution of EPA's national strategy
for indoor radon remediation, recent developments, and anticipated future directions.
KEYWORDS
Radon, mitigation, research, soil gas, technology
BACKGROUND
Indoor radon is recognized as one of the most significant environmental health problems in the
United States. Radon is the main source of exposure of individuals to ionizing radiation. The EPA
predicts that 1 in 15 U.S. houses may have elevated radon levels, and exposure to increased levels
of radon is believed to cause between 7,000 and 30,000 deaths per year in the U.S. (USEPA,
1992a). EPA's risk estimates for indoor radon arc based on extensive epidemiological evidence
from 20 different studies of lung cancer in occupationally exposed miners. This evidence is
among the strongest that has been assembled on the carcinogenicity of an environmental
contaminant. EPA's risk estimates are also based on the work of the National Academy of
Sciences and have been peer reviewed by the Agency's Science Advisory Board. Independent
evaluations by the International Agency for Research on Cancer, the International Commission on
Radiological Protection, and the National Council on Radiation Protection and Measurement have

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reached comparable conclusions on the significance of the indoor radon problem (Marcinowski and
Napolitano, 1993).
Indoor radon drew national attention when, in December 1984, a house in northeastern
Pennsylvania was discovered to have indoor radon levels in excess of 74,000 Bq m"3. Investigators
attributed the high indoor radon concentration to the uranium-rich soil and rock on which the
house was built. In 1986 the U.S. Congress authorized EPA to conduct surveys to determine the
extent of the hazard, and to develop and demonstrate measurement and mitigation technologies.
Legislation followed in 1988 with the Indoor Radon Abatement Act (IRAA) which further
expanded the efforts to include development of technologies to achieve indoor radon levels as low
as the ambient air outside of buildings for existing houses, new houses, schools, and day care
centers. Proposed legislation, if passed, would require disclosure of radon information during a
real estate transaction, accelerate the adoption of radon-resistant building codes, and create a
mandatory certification program for radon measurement and mitigation contractors.
Development of radon mitigation technology has been a coordinated effort between two EPA
organizations, the Office of Research and Development (ORD) and the Office of Radiation and
Indoor Air (ORIA). ORD has focused on development and demonstration of mitigation
technologies, including fundamental studies and innovative mitigation technology development.
ORIA has complemented these efforts by demonstrating field applicability of various mitigation
techniques, as well as providing policy guidance to states and to homeowners based on research
findings. EPA's research efforts are also augmented by the U.S. Department of Energy which is
conducting basic research in radon fundamentals.
PROGRAM RESULTS
EPA' s initial efforts in radon mitigation targeted existing residential construction. Mitigation
techniques were demonstrated in numerous houses with varying radon levels, foundation types, and
architectural designs. Since the application of radon mitigation techniques by homeowners is
largely voluntary (except when required by a real estate transaction), the EPA targeted mitigation
technologies that were reliable, durable, and low in cost. This effort resulted in development of
soil depressurization techniques that have effectively lowered radon levels to below the EPA action
level of 148 Bq m'3 in a variety of residential structures. The most commonly applied radon
reduction method in existing U.S. houses is the active soil depressurization (ASD) system. EPA
has found ASD to be the most consistently effective radon reduction method in existing houses,
and it is the technique most widely used by commercial mitigators (Henschel, 1993). Radon
mitigation techniques for existing houses have been found to be very effective, reducing indoor
radon levels to below 148 Bq m"J in 97 percent of houses and to below 74 Bq m'3 in about 70
percent of houses studied (Hoornbeek and Lago, 1991). The cost of a subslab depressurization
system will range between $500 and $2,500 (US) (USEPA, 1992b).
In 1987 EPA began to develop model standards for the construction of radon-resistant housing.
By working directly with the housing industry, EPA was able to develop methods to prevent the
entry of radon into a new house based on construction practices that are common to U.S. builders.
These methods are based on a passive subslab depressurization system which enables the radon to
be vented from under the slab and exhausted above the roof line of a house. The passive system
relies on natural air currents to assist in drawing the radon from underneath the slab. If, after
construction, the house is found to have radon levels above 148 Bq m3, a fan can be easily
installed to upgrade the passive system to an active one, thereby ensuring that radon levels stay
below EPA's action level. The cost of including a passive radon control system in a new house is
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between $350 and $500 (US) (USEPA, 1992c).
Elevated radon levels have been found in a number of U.S. school buildings, and a national survey
of schools released in 1991 predicted that about 19 percent of U.S. public schools may have
elevated radon levels (above 148 Bq m3 ) in one or more classrooms (USEPA, 1993).
Development and demonstration of radon mitigation technologies for schools began in 1988 with
existing school buildings. Initially, research in schools focused on ASD since it was the most
successful radon control technique in houses. In a follow-up study of 14 schools conducted in
1992, it was found that ASD systems were effective in maintaining low radon levels in the
schools, with only 4 percent of the 409 tested locations exceeding 148 Bq m1 (Dehmel, et al.,
1993). A study of the cost of mitigating existing school buildings found the average cost to be
about $5.40 per nr (1991 US dollars) (Leovic, et al.,1992).
Complicated subslab structures and subslab fill materials can make ASD expensive to install
because of an increased number of suction points, so EPA concentrated part of its research efforts
in schools on the use of the heating, ventilating, and air-conditioning (HVAC) system for radon
reduction. Research found that a school's HVAC system could be used to control radon levels if it
allowed for the introduction of sufficient amounts of outdoor air. If the HVAC system could
provide sufficient outdoor air, p re-mitigation radon levels below 370 Bq m'J could be reduced
successfully. In most of the 40 schools visited by researchers, the HVAC systems were found to
be operating improperly, often the result of neglect and poor maintenance practices. In some cases
the introduction of outdoor air had been compromised. Researchers also measured carbon dioxide
concentrations in 15 of the schools and found 14 of them with levels above 1,000 parts per million
(Ligman, 1994).
Low cost and effective radon mitigation technology has been demonstrated in the construction of
large buildings, including schools. An ASD system for inclusion in large building construction has
been designed and demonstrated by EPA. This system consists of a 1.2 x 1.2 x 0.2 m void area
created by a wire cage placed centrally underneath the poured slab. ASTM #5 crushed aggregate
(ASTM, 1986) is recommended for the subslab . A suction pipe is routed from the wire cage to
the rooftop, where a blower is installed to activate the system. In demonstrations of this pit
design, slab areas as large as 5,574 m2 have been successfully mitigated with one suction pit and a
suction fan rated for 240 L s"1 (at no head pressure), using a 15 cm diameter vent pipe. Radon
levels were lowered from 1,950 Bq nr5 (highest reading) to levels that were not measurable with
open faced charcoal canisters. The construction cost of this ASD system was around $0.90 per m2
(1991 US dollars) (Craig, et al., 1993).
A variety of technology transfer products have been generated by EPA that directly impact the
public and the radon mitigation industry, including a number of public information booklets and
brochures that cover such topics as basic information on radon to aid consumers in their quest to
mitigate their homes. EPA has also produced technical manuals, brochures, special reports,
articles in peer reviewed journals, and unique information pieces for selected audiences. The
regular development and distribution of these technology transfer products keeps the variety of
users aware of the latest developments in radon mitigation technology and allows them to achieve
long term maximum radon reductions at minimum cost for labor and resources.
PROGRAM PLANS
The future of EPA's research program includes the development of the next generation of radon
mitigation technologies capable of lowering indoor concentrations to near-ambient levels. A
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program of innovative research focused on achieving ambient levels of radon has been undertaken
at EPA. This research will emphasize unique barrier technologies to prevent the entry of soil gas
into houses and the feasibility of using removal techniques to lower the dose from radon progeny.
EPA also plans to direct more future mitigation research to multi-story buildings since these
buildings pose unique mitigation challenges and may require innovative mitigation approaches
more dependent on HVAC control to prevent the entry of radon (via pressurization of the building
interior) and to dilute radon and other indoor air pollutants.
There is a continued need to further refine known mitigation techniques, and to make them more
efficient, less costly, and more durable. New techniques need to be demonstrated for reducing
radon levels in large, multi-story buildings. We should look for opportunities to share research
experiences with other indoor air investigators and continue technology transfer of information that
is useful to homeowners, mitigators, and researchers around the world.
REFERENCES
American Society for Testing Materials (1986), Standard Specifications for Concrete Aggregate,
ASTM-33-86, Philadelphia, PA .
Craig, A.B., D.B. Harris, and K.W. Leovic (1993). Radon prevention in construction of schools
and other large buildings - status of EPA's program. In: Proceedings: The 1992 International
Symposium on Radon and Radon Reduction Technology, vol. 2, EPA-600/R-93-083b (NTIS
PB93-196202), 10-151 - 10-171.
Dehinel, J-C., P.L. McCloskey, and G. Mollyn (1993). Follow-up radon measurements in 14
mitigated schools. United States Environmental Protection Agency, EPA-600/R-93-197 (NTIS
PB94-1147JB).
Henschel, D.B. (1993). Radon reduction techniques for existing detached houses, technical
guidance for active soil depressurization systems (third edition). United States Environmental
Protection Agency, EPA/625/R-93/011.
Hoombeek, J. and J. Lago (1991). Private sector radon mitigation survey. In: Proceedings:
The 1990 International Symposium on Radon and Radon Reduction Technology, vol. 3, EPA-
600/9-91-026c (NTIS PB91-234468), 4-17 - 4-30.
Leovic, K.W., H.E. Rector, and N.L. Nagda (1992). Costs of radon diagnostics and mitigation in
school buildings. Presented at the Air and Waste Management Association 85th Annual
Meeting and Exhibition, Kansas City, MO, June 21-26, 1992.
Ligman, Bryan K., United States Environmental Protection Agency, Office of Air and Radiation,
Washington, D C. Personal communication, December 13, 1994.
Marcinowski, F. and S. Napolitano (1993). Reducing the risks from radon. Air and Waste, 43:7.
955-962.
United States Environmental Protection Agency (1992a). A Citizen's Guide to Radon (Second
Edition}, EPA 402-K92-001. Office of Air and Radiation, Washington, DC.
United States Environmental Protection Agency (1992b). Consumer's Guide to Radon Reduction,
EPA 402-K92-003, Office of Air and Radiation, Washington, DC.
United States Environmental Protection Agency (1992c). Analysis of Options for EPA's Model
Standards for Controlling Radon in New Homes. Office of Air and Radiation, Washington,
DC.
United State Environmental Protection Agency (1993). National school radon survey: report to
congress. Office of Air and Radiation, Washington, DC.
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e
TECHNICAL REPORT DATA
A E J jlI L" P~ 1244 (i'lcasc read Inslruetions on the reverse before con


1 . fU POUT NO. 2.
EPA/600/A-94/264


A. T 1 TLf AND SUBTITLE
rJ"he U.S. Environmental Protection Agency's
National Strategy for Radon Remediation
5.	REPORT DATE
6.	PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
T.M.Dyess (EPA/CRD) and S. DeScisciolo (EPA/
ORIA)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
See Block 12
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
NA (Inhouse)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper;
14. SPONSORING AGENCY CODE
EPA/600/13
is.supplementary notes /\jt;eRL project officer is Timothy M. Dyess, Mail Drop 54, 919/
541-2802. For presentation at International Workshop, Indoor Air—An Integrated
Approach. 11/27-12/1/94. Gold Coast. Australia.
i6. "abstract T" hi e paper provides an historical summary of the evolution of the U.S.
EPA's national strategy for indoor radon remediation, recent devlopments, and anti-
cipated future directions. During the past 10 years, EPA has pursued a national
strategy to address radon remediation in buildings to meet its goals of radon risk re-
duction. Initially, the approach developed and demonstrated remediation methods and
techniques in existing residences with specific attention to the effect of regional cli-
mate variations and the differences in housing construction. A number of studies and
demonstrations were undertaken to accurately characterize and evaluate the effec-
tiveness of several remediation methods and techniques. This knowledge was then
later expanded through research on radon control for newly constructed houses with
the subsequent development of model standards and techniques. Additionally, other
research was initiated to gain a better understanding of remediation approaches in
existing and newly constructed non-residential buildings such as schools, commer-
cial office buildings, and hospitals.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATi Field/Group
Pollution
Radon
Research
Buildings
Soils
Gases
Pollution Control
Stationary Sources
Soil Gas
Indoor Air
13 B
07B
14F
13 M
08G.08M
07D
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICf:
EPA Form 2220-1 (9-73)

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