EPA-600/R-96-022
March 1996
Technical Basis for a Candidate
Building Materials Radium Standard
Final Report
by
Vern C. Rogers and Kirk K. Nielson
Rogers & Associates Engineering Corporation
P.O. Box 330, Salt Lake City, UT 84110-0330
EPA1 Interagency Agreement RWFL 933783
-Florida DCA Contract 94RD-30-13-00-22-003
DCA Project Officer: Mohammad Madani
Florida Department of Community Affairs
2740 Centerview Drive
Tallahassee, FL 32399
University of Florida Project Officer: Paul D. Zwick
Department of Urban and Regional Planning
431 ARCH, University of Florida
Gainesville, FL 32611
U.S. EPA Project Officer: David C. Sanchez
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
Prepared for:
State of Florida
Florida Department of Community Affairs
2740 Centerview Drive
Tallahassee, FL 32399
and
U. S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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1 ^ TECHNICAL REPORT DATA
| . _ _ ^ {Please read Instructions on the reverse before comp-
[l. REPORT NO. 2.
EPA-600 ,/R-96-022
4. TITLE AND SUBTITLE
Technical Basis for a Candidate Building Materials
Radium Standard
5. REPORT DATE
March 1996
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Vern C. Rogers and Kirk K. Nielson
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING OROANIZATION NAME AND ADDRESS
Rogers and Associates Engineering Corporation
P. C. Box 330
Salt Lake City. Utah 84110-0330
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA IAG RWFL 933783
DCA S4RDr30~-13-0"0~22-003 :
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 4-11/93
14. SPONSORING AGENCY CODE
EPA/600/13
15.supplementary notes projeot officer is David C. Sanchez, Mail Drop 54, 919/
541-2979. DCA project officer is M. Madani. FL Dept. of Community Affairs, 2740
Centerview Dr., Tallahassee, FL 32399.
i6vABSTRACT^ jhe report summarizes the technical basis for a candidate building mater-
ials radium standard. It contains the standard and a summary of the technical basis
for the standard.' (NOTE: The Florida Radon Research Program (FRRP), sponsored
by the Environmental Protection Agency and the Florida Department of Community
Affairs, is developing the technical basis for a radon-control construction standard.
Results of the research conducted under1 the FRRP are presented in severaljechni-
cal reports.)
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.identifiers/open ended terms
c. cosati Field/Group
Pollution
Construction Materials
Design Standards
Radium
Pollution Control
Stationary Sources
13 B
13 C
14G
07B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)'
Unclassified
21. NO. OF PAGES
12
20. SECURITY CLASS fThis page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions lead-
ing to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research
program is providing data and technical support for solving environmental pro-
blems today and building a science knowledge base necessary to manage our eco-
logical resources wisely, understand how pollutants affect our health, and pre-
vent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks
from threats to human health and the environment. The focus of the Laboratory's
research program is on methods for the prevention and control of pollution to air,
land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites and groundwater; and prevention and
control of indoor air pollution. The goal of this research effort is to catalyze
development and implementation of innovative, cost-effective environmental
technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and infor-
mation transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Re-
search and Development to assist the user community and to link researchers
with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161.
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ABSTRACT
The Florida Radon Research Program (FRRP), sponsored by the Environmental
Protection Agency and the Florida Department of Community Affairs, is developing the technical
basis for a radon-control construction standard. Results of the research conducted under the
FRRP are presented in several technical reports. This report is a summary of the technical basis
for a candidate building materials radium standard. The report contains the standard and a
summary of the technical basis for the standard.
ii
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TABLE OF CONTENTS
Section Page No.
Abstract ii
1 INTRODUCTION 1-1
1.1 Purpose of the Candidate Standard 1-1
1.2 Candidate Building Materials Radium Standard 1 -1
1.3 Why the Standard Limits Radium 1 -1
2 TECHNICAL ANALYSIS SUPPORTING THE
CANDIDATE STANDARD 2-1
2.1 Performance Objectives 2-1
2.2 Indoor Radon Calculations 2-2
2.3 External Gamma Radiation Measurements 2-3
3 CONCLUSIONS FROM TECHNICAL ANALYSIS 3-1
4 LITERATURE REFERENCES 4-1
iii
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Section 1
INTRODUCTION
1.1 PURPOSE OF THE CANDIDATE STANDARD
Residential building materials, principally concrete, can contain small amounts of radium,
which generates radon gas that can migrate into residences. Furthermore, radon daughters
trapped in concrete emit gamma radiation that can cause exposures to building occupants.
This portion of the standard defines acceptable limits for the concentration of radium in
building materials.
1.2 CANDIDATE BUILDING MATERIALS RADIUM STANDARD
The candidate building materials radium standard is:
No material used in concrete for the construction of habitable structures shall
have a total radium concentration that exceeds 10 pCi/g, as measured in
accordance with procedures contained in "Standard Measurement Protocols,
Florida Radon Research Program" (Williamson and Finkel 1991). The radium
concentration in concrete used in the construction of habitable structures shall
not have a total radium concentration that exceeds 5 pCi/g.
1.3 WHY THE STANDARD LIMITS RADIUM
Radiation exposures from building materials to people can occur either from indoor radon or
from external gamma radiation. Both the concentration of indoor radon and the level of
gamma radiation from the building materials depend primarily on the total radium
concentration in the materials. Thus, limiting the radium concentration in the building
material limits the amount of potential exposure to building occupants from both indoor
radon and gamma radiation. For typical concrete thicknesses (tens of centimeters), the
1-1
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gamma radiation exposures yield about the same radium concentration limits in building
materials as do exposures to indoor radon from the materials.
1-2
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Section 2
TECHNICAL ANALYSIS SUPPORTING THE CANDIDATE STANDARD
The technical analysis supporting the building materials standard consists of the following three
steps:
1. Determine building material performance objectives for potential radon and
gamma exposures.
2. Calculate radium limit for indoor radon exposures.
3. Calculate radium limit for external gamma radiation exposures.
2.1 PERFORMANCE OBJECTIVES
Performance objectives were selected according to their consistency with other Florida Radon
Research Programs. Specifically, the performance objectives are a selected fraction of the U. S.
Environmental Protection Agency's (EPA) indoor radon (as radon-222) concentration guideline
of 4 pCi/L (EPA 1992a) and the EPA's external gamma radiation criterion of 20 ^R/hr for
cleanup of off-pile lands associated with uranium milling (EPA 1992b).
Indoor radon and gamma exposures to occupants of residences can come from many sources in
addition to the building materials. Soils under building structures constitute the major source.
Accordingly, a reasonably conservative value of 0.25 has been selected as the fraction of the
radon guidance and gamma radiation criterion attributed to building materials. Thus, the
building material performance objectives are:
1. Indoor radon-222 concentration limit - 1 pCi/L.
2. External gamma radiation limit - 5 uR/hr.
2-1
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22 INDOOR RADON CALCULATIONS
The calculations of indoor radon concentration from a concrete slab use the procedure and
equation from Rogers et al. (1994). Rearranging Equation (5-6) of that reference gives
Ra = 1 ; , (l)
pE s/XD tanh (/£/fT xc)
where
Ra = radium-226 concentration limit in the concrete (pCi/g)
F = radon flux (pCi/cm2 s)
p = concrete density (g/cm3)
E = radon emanation coefficient (unitless)
X = radon decay constant (2.06xl0'6/s)
D = radon diffusion coefficient of concrete (cm2/s)
Xc = thickness of concrete slab (cm).
A simple approximation for F is obtained from Nielson et al. (1994):
F - ChV(3.6xl06) , (2)
where
C = indoor radon concentration (pCi/L)
h = average indoor height of building (cm)
= dwelling ventilation rate (air changes/hour)
3.6xl06 = units conversion (cm3 s/L hr)
Combining Equations (1) and (2) gives
ChXv
Ra c (3)
(3.6x10 s pE vftD tanh Xc)
The following values were used in the calculations:
C =1 pCi/L (performance objective)
h = 240 cm
\ = 0.25 air changes/hour
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p =2.1 g/cm3
E = 0.11
Xc = 10 cm
D = 2xl0"3 cm2/s
Substituting these values into Equation (3) gives a radium Jimit of 4 pCi/g in the concrete.
This is rounded to 5 pCi/g in the Standard.
The radium concentration limit in concrete readily converts to radium concentration limits
in concrete constituents. Table 1 presents typical weight percentages of concrete constituents
(Snoddy 1992):
Table 1. Typical weight percentages of concrete constituents.
Constituent Weight Percent
aggregate 49
sand 39
cement 8
fly ash 4
Total 100
Since Table 1 shows that aggregate comprises about 49% of concrete, the concrete aggregate
radium limit can be estimated as 4 pCi/g/0.49, or 8 pCi/g in the aggregate. A similar limit
for sand is 10 pCi/g.
2.3 EXTERNAL GAMMA RADIATION MEASUREMENTS
Exposures from gamma-emitting radionuclides in the concrete were estimated by a slab with
the same characteristics as given in Section 2.2. A 6x6-m area was assigned to the slab, and
the gamma-radiation exposures were calculated with the MICROSHIELD computer code
(Grove 1993).
2-3
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The MICROSHIELD calculations gave a value of 0.95 pR/hr per pCi/g of total radium in the
concrete. Thus, a radium limit of about 5 pCi/g for the concrete gives a potential exposure
of 5 jiR/hr. The corresponding total radium limit in the aggregate is 10 pCi/g, and that for
the sand is approximately 13 pCi/g.
2-4
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Section 3
CONCLUSIONS FROM TECHNICAL ANALYSIS
Potential exposures from building materials to occupants of dwellings occur from external
gamma radiation and from indoor radon. The extent of these potential exposures is mainly
determined by the radium concentration in the materials. Both indoor radon exposure limits
and external gamma exposure limits yield a 5 pCi/g radium concentration limit in concrete
and a 10 pCi/g radium limit in the aggregate for the concrete.
3-1
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Section 4
LITERATURE REFERENCES
Environmental Protection Agency, 1992a, "A Citizen's Guide to Radon," Second Edition,
Washington, D.C.: Y. S. Environmental Protection Agency, USDHHS, and USPHS report 402-
K92-001, May 1992.
Environmental Protection Agency, 1992b, "Health and Environmental Protection Standards fro
Uranium and Thorium Mill Tailings," Code of Federal Regulations, Title 40, Part 192.
Grove Engineering, 1993, "MICROSHIELD Users Manual," Version 4.10, Grove Engineering
Inc., Rockville. MD.
Nielson, K.K., Rogers, V.C., Rogers, V., and Holt, R.B., 1994, "The RAETRAD Model of
Radon Gas Generation, Transport, and Indoor Entry," Research Triangle Park, NC: U.S.
Environmental Protection Agency report EPA-600/R-94-198 (NTIS PB95-142030), November
1994.
Rogers, V.C., Nielson, K.K., Lehto, M.A., and Holt, R.B., 1994, "Radon Generation and
Transport Through Concrete Foundations," Research Triangle Park, NC: U.S. Environmental
Protection Agency report EPA-600/R-94-175 (NTIS PB95-101218), September 1994.
Snoddy, R., 1994, "Laboratory Assessment of the Permeability and Diffusion Characteristics of
Florida Concretes, Phase I. Methods Development and Testing, EPA-600/R-94-053 (NTIS
PB94-162781).
Williamson, A.D., and Finkel, J.M., 1991, "Standard Measurement Protocols, Florida Radon
Research Program," Research Triangle Park, NC: U. S. Environmental Protection Agency report
EPA-600/8-91-212 (NTIS PB92-115294), November 1991.
4-1
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