EPA-600/R- 96-107
September 1996
Contributions of Building Materials
to Indoor Radon Levels in Florida Buildings
Final Report
by
Kirk K. Nielsen, Rodger B. I lolt, and Vern C. Rogers
Rogers & Associates Engineering Corporation
P.O. Box 330
Salt Lake City, I T 84110-0330
EPA Interagency Agreement RWFL 933783
DC A Agreement 95RD-30-13-00-22-001
EPA Project Officer: David C. Sanchez
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
DCA Project Officer: Mohammad Madani
Florida Department of Community Affairs
2740 Centerview Drive
Tallahassee, FL 32399
University of Florida Project Directors: John F. Alexander and Paul D. Zwick
Department of Urban and Regional Planning
431 ARCH, University of Florida
Gainesville, FL 32611
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
-------
NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse
ment or recommendation for use.
-------
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
i i i
-------
ABSTRACT
The Florida Standard for Radon-Resistant Residential Building Construction originally
contained a provision to limit the concentration of radium in concrete. The provision was
designed to prevent concrete from causing elevated indoor radon concentrations. It was
removed from the October 1994 version of the standard, however, because concrete from
commercial sources had not been shown tc be a major radon contributor in Florida. This
report documents follow-up work aimed at identifying one or more Florida buildings whose
source of indoor radon is suspected to come from building materials, and at recommending
related changes to the building materials radium standard.
A mathematical model is presented to estimate the contributions of building materials
to indoor radon concentrations. The model computes radon flux from concrete surfaces using
typical Florida concrete properties, and multiplies the flux by corresponding concrete areas
to determine their radon contribution to a building. A simplified expression is given that
accounts for building ventilation in estimating the radon source to a building from building
materials. Published radon data from houses and large buildings are used to calculate indoor
radon sources from building materials.
Past and present radium and radon emanation measurements for Florida concretes
and their constituents are presented and analyzed to characterize typical Florida concrete
properties. Radium distributions in residential floor slabs had a geometric mean of 1.3
pCi g1 and a geometric standard deviation (GSD) of 1.62. Radon emanation coefficients for
the slabs averaged 0.10 ± 0.04. Radium measurements in concretes with potentially elevated
radon sources had a similar geometric mean of 1.4 pCi g"1, but a much greater GSD of 3.0,
owing to occasional elevated-radium samples. Radon emanation coefficients for these samples
were also slightly higher and more variable, averaging 0.14 ± 0.07. Radium and radon
emanation were also measured in concrete aggregate materials. They showed similar
distributions, with occasionally elevated radium concentrations consistent with the concrete
measurements.
A concrete and block building in Lake City was found to contain both elevated concrete
radium levels and elevated indoor radon. Gamma ray surveys suggested elevated radium
levels, and subsequent concrete analyses showed 33 pCi g"1 radium in one slab. Indoor radon
concentrations averaged 5.0 ± 0.8 pCi L"1, and radon source calculations suggested a
ventilation rate of 0.43 h"1 during the elevated radon period. The radon source calculations
suggested that approximately 93% of the radon came from the ceiling slab, while only 3%
came from the floor slab and block walls. The remaining 4% of the radon was estimated to
have diffused through the floor slab from foundation soils. The calculated radon source
strengths were also consistent with the gamma ray trend identified from published data.
A revised building material radium standard was developed that accounts for the
areas and radium concentrations of concretes exposed to building interiors. The standard
would limit the indoor radon increment from building materials to no more than 2 pCi L'1.
It would limit concrete radium concentrations to 7 to 9 pCi g"1 if only a single slab or walls
contain elevated radium. However it could limit radium to approximately 3 pCi g"1 if floor,
ceiling, and walls all utilize concrete with elevated radium.
i v
-------
TABLE OF CONTENTS
Chapter Page
Abstract
List of Figures
List of Tables
IV
v^fi
1. INTRODUCTION 1-1
1.1 Background 1-1
1.2 Objective and Scope 1-2
2. THEORETICAL EFFECT OF CONCRETE RADON SOURCES 2-1
2.1 Mathematical Model 2-1
2.2 Comparison with Gamma Ray Intensity 2-3
3. RADIUM AND RADON EMANATION MEASUREMENTS 3-1
3.1 Measurements in Concretes 3-1
3.2 Measurements in Concrete Aggregates 3-7
4. ASSOCIATION OF CONCRETE RADIUM WITH INDOOR RADON 4-1
4.1 Empirical Measurements 4-1
4.2 Calculated Effects 4-5
5. BUILDING MATERIALS RADIUM STANDARD 5-1
5.1 Technical Basis 5-1
5.2 Proposed Standard 5-2
6. LITERATURE REFERENCES 6-1
v
-------
LIST OF FIGURES
Number Page
2-1 Regression of radon sources (CX) on gamma activity 2-3
using data from Kah83.
4-1 Locations of gamma ray measurements in the study building. 4-2
4-2 Indoor radon measurements in the Lake City study building 4-4
vi
-------
LIST OF TABLES
Number Page
3-1 Radium and radon emanation measurements in Florida house concretes 3-2
3-2 Radium and radon emanation measurements in dry-mix materials 3-4
3-3 Radium and radon emanation measurements in concretes 3-6
from Florida buildings with potentially elevated radon
3-4 Radium and radon emanation measurements in Florida aggregate 3-8
materials
4-1 Calculated contributions of building materials to indoor radon 4-5
5-1 Limiting concrete radium concentrations for contributing 2 pCi L"1 5-2
of radon to a 140 m2 residence using equation (6).
vi i
-------
1. INTRODUCTION
1.1 BACKGROUND
Radon (222Rn) gas enters buildings primarily from radium (z26Ra) in foundation soils.
However, significant radon contributions can also come from radium in building materials
and from radon dissolved in water if the source strengths in these media are sufficiently
elevated. If the total radon entry rate is elevated and the building is not well ventilated,
radon can accumulate to levels that can significantly increase the occupants' risks of lung
cancer with chronic exposure. The degree of health risk is proportional to the long-term
average level of radon exposure. The U.S. Environmental Protection Agency (EPA) attributes
7,000 to 30,000 lung cancer fatalities annually to radon, and recommends remedial action if
indoor radon levels average 4 picocuries per liter (pCi L"1) or higher (EPA92a; EPA92b).
The Florida Department of Community Affairs (DCA), under the Florida Radon
Research Program (FRRP), has developed radon-protective building standards. These
standards are incorporated in proposed rule 9B-52, the Florida Standard for Radon-Resistant
Residential Building Construction (DCA94), which is primarily aimed at controlling radon
by blocking its entry from foundation soils. The standards require passive radon barriers and
active sub-slab ventilation in regions with elevated soil radon potentials, as identified by a
statewide radon protection map.
A criterion was developed under the FRRP to limit radon sources in building materials
(Rog96). The criterion was included in early drafts of the Florida Standard for Radon-
Resistant Residential Building Construction (RAE-9226/4-2, May 1994, Sec. 403.4.1), and
required that:
No material used in concrete for the construction of habitable structures shall
have a radium concentration that exceeds 10 pCi g"1, as measured in
accordance with approved procedures.
1-1
-------
This criterion was removed from the October 1994 version of the standard, when
proposed for public hearing, after comments from the Florida Concrete and Products
Association indicated that the criterion was unnecessary because: (a) concrete from
commercial sources had not been shown to be a major radon contributor in Florida; (b) testing
and related cost impacts were not defined; and
-------
measurements with gamma ray activity. Chapter 3 summarizes the results of FRRP radium
and radon emanation measurements in various concrete and aggregate samples. Chapter 4
presents measurements and analyses linking elevated indoor radon measurements in a
concrete building with elevated radium concentrations. Chapter 5 presents a technical basis
and draft text for a revised building material radium standard.
1-3
-------
2. THEORETICAL EFFECT OF CONCRETE RADON SOURCES
Radon generated by concrete or other building materials cannot be distinguished from
soil-generated radon once it has entered a structure and mixed with indoor air. Radon from
concrete therefore must be measured directly as a flux exiting a slab or wall surface to
characterize it separately from other sources. Although radon fluxes from building materials
have been measured in several studies (Smi80; Nie95b; Obr95), the procedures are often
difficult and expensive, making alternative approaches such as modeling preferable whenever
possible. This chapter describes a simple modeling approach that is used to estimate indoor
radon contributions from concrete and other building material sources (Smi80; Nie94). This
chapter also compares published indoor radon data with gamma ray measurements to suggest
a simple empirical approach for estimating radon source strengths.
2.1 MATHEMATICAL MODEL
Indoor radon concentrations reflect a balance between the rate of radon entry into a
structure and the rate of radon loss by decay and dilution by ventilating air. The rate of
radon entry is the sum of radon coming from foundation soils, building materials, and in
unusual cases, water supplies, natural gas combustion, and any other potential sources.
Radon loss rates are invariably dominated by the building ventilation rate, which is
commonly expressed in air changes per hour. The simple equation expressing the indoor
radon concentration under these conditions is:
IJi'Ai
Cnel = Cin - « L (1)
V(-J^+kRn)
3,600
where = net indoor radon from non-airborne sources (pCi L"1)
Cin = measured indoor radon concentration (pCi L'1)
Cout = outdoor radon concentration in ventilating air (pCi L"1)
2 „•!>,
J, = radon flux from surface t (pCi m' s" )
2-1
-------
Ai = area of radon-emitting surface i (m2)
V = interior volume of the structure (L)
X = rate of ventilation by outdoor air (h"!)
3,600 = unit conversion (s h"1)
^Rn = rate of radon decay (2.1 x 10"6 s"1).
The expression for indoor radon concentration can be simplified even further by
neglecting the C0ut and XRn terms. Hie outdoor radon concentration, seldom approaches
the 4-pCi L"1 level at which becomes a concern, so ^oui can be generally ignored.
Similarly, the value of XRn is only 2.1 x 10"6 s"\ which is less than 8% of the common lower
limit of A/3,600 = 2.8 x 10*6 s"1 for ventilation rates in most occupied buildings. With these
simplifications, equation (1) can be rearranged by grouping X with (hereafter called C) to
isolate the most variable building properties from the more constant ones, giving the
following expression:
The radon flux for a concrete surface can be calculated from the radium concentration,
density, emanation coefficient, diffusion coefficient, and thickness of the concrete as:
R = concrete radium concentration (pCi g"1)
p = concrete bulk dry density (g cm"3)
E = concrete radon emanation coefficient (dimensionless fraction)
D = radon diffusion coefficient for the concrete (cm2 s"1)
x = concrete thickness (cm).
CX = 3'60Q j Jj-Aj
V i 1 1
(2)
J = 104RpE\jxRnD tanh(
unit conversion (cm2 m"2)
where 10'
(3)
2-2
-------
2.2 COMPARISON WITH GAMMA RAY INTENSITY
Using the simplified relationship in equation (2), published (Kah83) radon
concentrations calculated for building materials in houses and large buildings are compared
with corresponding calculations of gamma ray intensity. The CX grouping from equation (2)
is used to obtain a lumped parameter that is less subject to time and variations caused by
changes in building ventilation rate. The radon source strengths (CX) are plotted versus
gamma ray activity in Figure 2-1 to obtain the following relationship by least-squares linear
regression:
CX = 0.0127y - 0.081 <4>
where y = gamma ray activity (pR h'1).
0.8
° Houses
• Large buildings
— y = -0.081 + 0.0127 x (rA2=0.96)
0.7
0.6
0.5
O 0.4
Q.
o 0.3
0.2
a.
0.1
0.0
0
10
20
30
40
50
60
70
Gamma ray intensity (ptR/h)
Figure 2-1. Regression of radon sources (CX) on gamma activity
using data from Kah83.
2-3
-------
The empirical correlation of radon source strength with indoor gamma ray intensity
in equation (4) could potentially offer a simple, inexpensive test for radon sources in building
materials. However, actual gamma ray measurements are subject to several potential biases,
including natural background gamma activity, 232Th and 40K gamma activity from the
building materials, and source-measurement geometry biases. The effects of background
gamma activity should be avoidable by simply subtracting an appropriate background value
from the indoor measurements.
Contributions from 232Th activity should generally be small and predictable, since
thorium concentrations in most of Florida's natural earthen materials are on the order of 1
pCi g"1 or less. Although exceptions in certain mineralized areas could lead to elevated
gamma ray measurements, the exceptions would be conservative. This means that the
possible 230Th anomalies could lead to unnecessary testing of building materials in a few
cases, but that they would not lead to unknowingly incorporating materials with elevated
radon sources into new buildings. Contributions from 40K would be similar in nature to those
from 230Th, except that they would be much smaller and less frequent.
Possible biases from different source-measurement geometries could generally be made
conservative by utilizing maximum readings where the gamma distribution is non-uniform.
Although the gamma distribution is relatively uniform if elevated radium levels are present
in large concrete floor or ceiling slabs, elevated radium in smaller structures causes a more
localized gamma anomaly. Since the smaller structures would cause proportionately less
indoor radon, the maximum gamma measurements close to a small structure would
overestimate total building radon if attributed to a slab geometry. Therefore, indoor gamma
ray measurements could conservatively screen building materials for elevated radon sources.
Sampling and laboratory analysis could then be used only where a confirmatory measurement
is required.
2-4
-------
3. RADIUM AND RADON EMANATION MEASUREMENTS
A review of radium and radon emanation measurements in Florida concretes gives
insight into their typical radon source properties. Radium concentrations in concrete floor
slabs from Florida houses were directly measured in two previous FRRP studies, one dealing
with new houses (Rog94) and the other with older houses (Rog95). Additional concrete
analyses were performed in connection with anomaly investigations for the statewide
mapping study (Nie95a), and in connection with this study. Together, the concrete analyses
give an approximate characterization of the range of radium concentrations and radon
emanation coefficients in Florida residential concretes. Additional data on rock aggregate
materials are also summarized here from separate FRRP measurements as a possible
explanation of the radium distributions observed in Florida concretes.
3.1 MEASUREMENTS IN CONCRETES
In the two previous studies that focused on concrete floor slabs in Florida houses,
samples were obtained from cores drilled from the floor slabs of residential structures (Rog94;
Rog95). The structures were chosen to represent typical single-family dwellings without
regard to indoor radon levels; in fact, indoor radon data were not available for these houses.
The radium and emanation measurement procedures and supporting quality assurance (QA)
data were reported previously (Rog94). The results of the analyses are presented in Table
3-1.
The data from the first study (first seven rows in Table 3-1) show a geometric mean
radium concentration of 1.4 pCi g'1 and a geometric standard deviation (GSD) of 1.38, while
the data from the second study (remaining rows of Table 3-1) show a geometric mean radium
concentration of 1.3 pCi g"1 and a GSD of 1.76. Although the variations are larger among the
older homes, the means are not significantly different, and both sets are represented here by
a single distribution for the 19 slabs with a geometric mean of 1.3 pCi g"1 and a GSD of 1.62.
Radon emanation averaged 0.069 ± 0.008 in the first study and 0.116 ± 0.042 in the second
study, with an overall average of 0.101 ± 0.041 for all 18 slabs in Table 3-1.
3-1
-------
Table 3-1. Radium and radon emanation measurements
in Florida house concretes.
Concrete
Radium®
Radon6
Sample
Age
Slab
Concentration
Emanation
Identification
(years)
Location
(pCi g"1)
(fraction)
C002F
1
Jacksonville
1.6 ± 0.1
(not measured)
C003F
1
Jacksonville
1.3 ±0.1
0.063 ± 0.012
C004C
1
Florida*
2.4 ± 0.1
0.057 ± 0.002
C005C
1
Florida0
1.7 ± 0.1
0.072 ± 0.003
TC1-1
1
Bartow
1.0 ±0.1
0.075 ± 0.007
TC1-C
1
Bartow
1.1 ± 0.1
0.078 ± 0.007
TC2-4
1
Bartow
1.0 ± 0.1
0.070 ± 0.007
A-l
12
Boca Raton
1.7
0.085
B-l
1
Boca Raton
2.6
0.13
C-l
25
Pompano Beach
O.S
0.13
D-l
18
Miami
2.1
0.03
E-l
20
Boca Raton
0.9
0.19
F-l
14
Boca Raton
1.5
0.11
G-l
45
Delray Beach
1.0
0.06
H-l
20
Miami
0.6
0.13
1-1
15
Boca Raton
1.8
0.13
J-l
40
Delray Beach
0.4
0.15
K-l
21
Boca Raton
1.3
0.14
L-l
36
Miami
2.2
0.11
First study mean ± s.d.
1 ±0
1.4 (1.38)^
0.069 ± 0.008
Second study mean ± s.d.
22 ± 13
1.3 (1.76)d
0.116 ± 0.042
Overall mean ± s.d.
14 ± 14
1.3 a.md
0.101 ± 0.041
°Dry mass basis mean ± standard deviation (based on Poisson counting statistics).
^Mean ± standard deviation (based on Poisson counting statistics).
^Florida samples from unspecified locations.
dGeometric mean and geometric standard deviation in parentheses.
3-2
-------
The radium concentrations in Table 3-1 are 40% to 80% higher than typical U.S. or
worldwide concrete radium levels, while the radon emanation coefficients are slightly lower
than previously reported values (Rog94). Thus, further insight was sought on radium and
radon emanation distributions in Florida concretes from analyses of dry-mix concrete
materials sampled from four diverse Florida locations. Portions of these samples were
separated by sieving to isolate the aggregate, sand, and cement fractions so that each fraction
could be analyzed separately. Additionally, bulk analyses were performed on concretes
prepared from the dry mixes. The results of these analyses are presented in Table 3-2.
The geometric mean radium concentration for concretes mixed from the four samples
was 0.6 pCi g"1 (GSD=2.3), nearly identical to the geometric mean of 0.5 pCi g"1 (GSD=2.2)
among the mass-weighted component means. Interestingly, the geometric mean radium in
the cement components was highest (1.2 pCi g"1, GSD=1.4), followed by the highly variable
aggregate radium concentrations (0.5 pCi g'1, GSD=4.1) and the uniformly low sand radium
concentrations (0.1 pCi g"1, GSD=1.4). Although the average dry-mix radium concentration
is only about half the average for the 19 slabs in Table 3-1, both distributions are so variable
that this difference is not statistically significant.
The average radon emanation coefficient for concretes mixed from the four samples
was 0.19 ± 0.14, nearly identical to the 0.18 ± 0.09 average of the mass-weighted component
means that utilized the moist-paste cement emanation coefficients. The average emanation
for the moist cement paste (0.31 ± 0.06) was much greater than for the dry cement powder
(0.02 ± 0.01); however, the average 18% composition of cement in the concretes minimizes the
effect of this moisture dependence in the mass-weighted means. The average emanation of
the sand was lower (0.14 ± 0.05), and that for the aggregate was lower yet (0.07 ± 0.07). The
average emanation coefficient for the dry-mix concretes is nearly 90% higher than the
average for the slabs in Table 3-1, probably as a result of the higher moisture in the dry-mix
samples. The potentially strong moisture dependence of emanation in concretes, as suggested
by the cement paste data in Table 3-2, suggests a potential bias in using air-dry concrete
samples for laboratory emanation measurements. If concretes, particularly slabs contacting
soil surfaces, have elevated moisture, their radon emanation may be significantly higher than
would be measured from an air-dry laboratory specimen.
3-3
-------
Table 3-2. Radium and radon emanation measurements in dry-mix materials.
Sample Location
Material
Percent
of Mix
(wt. %)
Radium0
Concentration
(pCi g'1)
Radon
Emanation
(fraction)
Mixed Concrete
100
1.2 ± 0.2b
0.09 ± 0.016
Cement (moist paste)
16
1.1
0.32
Cement (dry powder)
0.02
Sand
45
0.1
0.14
Aggregate
39
1.8
0.04
Calculated Weighted Mean
100
0.9 ± 0.2C
0.10^
Mixed Concrete
100
1.1 ± 0.16
0.13 ± 0.026
Cement (moist paste)
18
2.0
0.26
Cement (dry powder)
0.02
Sand
45
0.1
0.19
Aggregate
37
1.3
0.03
Calculated Weighted Mean
100
0.9 ± 0.3C
0.13rf
Mixed Concrete
100
0.5 ± 0.26
0.15 ± 0.056
Cement (moist paste)
15
0.9
0.39
Cement (dry powder)
0.04
Sand
77
0.1
0.16
Aggregate
8
0.1
0.17
Calculated Weighted Mean
100
0.2 ± 0.3°
0.30rf
Mixed Concrete
100
0.2 ± 0.16
0.39 ± 0.266
Cement (moist paste)
22
1.0
0.29
Cement (dry powder)
0.01
Sand
43
0.2
0.08
Aggregate
35
0.2
0.04
Calculated Weighted Mean
100
0.3 ± 0.2°
0.19'^
Mixed Concrete
100
0.6 (2.3)
0.19 ± 0.14
Cement (moist paste)
y-x
00
1+
CO
1.2 (1.4)
0.32 ± 0.06
Cement (dry powder)
0.02 * 0.01
Sand
52 ± 16
Aggregate
30 ± 15
0.5 (4.1)
0.07 ± 0.07
Calculated Weighted Mean
100
0.5 (2.2)
0.18 ± 0.09
M-l
Lakeland
M-2 Tampa
M-3 Jacksonville
M-4 Pensacola
M-l to
M-4
Average6
°Dry mass basis.
^Means of three measurements ± std. deviations calculated from Poisson counting statistics.
cStandard deviation calculated from Poisson counting statistic uncertainty of components.
dUsing moist-paste emanation for cement.
"Mean ± s.d. for percents and emanation; geometric mean (geometric s.d.) for radium.
3-4
-------
Additional concrete analyses were performed in connection with the radon map
anomaly investigations (Nie95a) and with this study. The samples for these analyses were
obtained from various locations throughout Florida by commercial concrete suppliers, radon
mitigators, and Rogers & Associates Engineering Corp. (RAE) personnel. The samples
represented both single-family dwellings and multi-story apartment buildings. Although
most samples consisted of cores drilled from floor slabs, some were also taken from
foundation footings, poured concrete walls, and concrete blocks. The analyses, summarized
in Table 3-3, utilized the laboratory and QA procedures described previously (Rog94).
The measurements in Table 3-3 may be less representative of all Florida concretes
than those in Table 3-1 because the Table 3-3 samples were sought from buildings with
potentially elevated indoor radon (>4 pCi L"1). The radium concentrations in Table 3-3 have
only a slightly higher geometric mean (1.4 pCi g"1 compared to 1.3 pCi g'1) than those in
Table 3-1, but their GSD is significantly higher (3.0 compared to 1.6). The radon emanation
coefficients in Table 3-3 average 0.14 ± 0.07, somewhat higher than the 0.10 ± 0.04 average
from Table 3-1, but lower than the average in Table 3-2. Although the radon sources (the
product of radium concentration and radon emanation coefficient) in Table 3-3 are expectedly
higher, they are not high enough to suggest a consistent correlation of building materials
with indoor radon. The comparisons are more consistent with the usual trend of indoor radon
concentrations that are dominated by foundation soils rather than by building materials.
Despite the usual trend of soil-dominated radon levels, some of the radium
concentrations in Table 3-3 are sufficiently high to contribute to or cause elevated indoor
radon if sufficient concrete is used in the buildings. Although radon levels dominated by
building materials are expected less frequently than levels dominated by soils, the data in
Table 3-3 show the possibility for significant radon problems in buildings where concrete
components may contain elevated radon sources.
3-5
-------
Table 3-3. Radium and radon emanation measurements in concretes
from Florida buildings with potentially elevated radon.
Radium Radon
Sample
Latitude
Longitude
Sample
Concentration
Emanation
Location
(North)
(West)
Material
(pCi g'1)
(fraction)
Florida"
b
6
Concrete floor slab
1.2 ± 0.4
0.12
±
0.04
Florida"
b
6
Concrete floor slab
0.4 ± 0.3
c
Florida"
b
6
Concrete floor slab
1.3 ± 0.4
0.14
±
0.05
Florida"
b
6
Concrete floor slab
1.6 ± 0.4
0.09
0.02
Florida"
b
b
Concrete floor slab
1.8 ± 0.4
0.11
0.02
Florida"
b
b
Concrete floor slab
2.0 ± 0.4
0.09
±
0.02
Florida"
b
b
Concrete floor slab
0.6 ± 0.4
0.31
±
0.20
Ft. Myers
26.492°
81.820°
Concrete floor slab
3.8 ± 0.3
0.04
±
0.01
Gainesville
6
6
Concrete floor slab
0.3 ± 0.4
c
Gainesville
b
b
Concrete floor slab
1.0 ± 0.3
0.15
±
0.05
Gainesville
b
b
Concrete floor slab
0.6 ± 0.4
0.02
±
0.01
Gainesville
b
b
Concrete floor slab
0.6 ± 0.3
0.14
0.08
Lake City
30.179°
82.692°
Concrete floor slab
32.8 ± 1.7
e
Lake City
30.179°
82.692°
Concrete floor slab
0.6 ± 0.4
c
Naples
26.18°
81.75°
Concrete floor slab
2.7 ± 0.2
0.11
+
0.01
Tallahassee
b
b
Concrete floor slab
0.2 ± 0.2
c
Ft. Myers
26.491°
81.820°
Concrete foundation
4.0 ± 0.3
0.16
±
0.01
Naples
26.234°
81.813°
Concrete foundation
4.8 ± 0.3
c
Naples
26.234°
81.813°
Concrete foundation
1.2 ± 0.2
c
St. Petersburg
27.720°
82.691°
Concrete foundation
1.1 ± 0.9
c
Naples
26.232°
81.813°
Concrete wall
4.0 ± 0.3
0.16
0.01
St. Petersburg
27.720°
82.691°
Concrete wall
0.7 ± 0.2
0.30
±
0.11
Ft. Myers
26.493°
81.836°
Concrete block
0.6 ± 0.3
0.13
0.06
Lakeland
b
6
Concrete block
1.2 ± 0.4
0.18
±
0.05
Naples
26.234°
81.813°
Concrete block
5.1 ± 0.2
c
Naples
26.18°
81.75°
Concrete block
4.9 * 0.2
0.08
±
0.01
St. Petersburg
27.720°
82.691°
Concrete block
2.1 ± 0.2
0.11
0.03
Mean — poured concrete
1.3 (3. IT*
0.14
±
0.08
Mean — concrete block
2.1 (2.5)^
0.13
0.04
Mean —
all
1.5 (3.0)*
0.14
±
0.07
"Florida samples provided without location details.
^Latitude and longitude not measured.
Tladon emanation not measured.
^Geometric mean and geometric standard deviation in parentheses.
3-6
-------
3.2 MEASUREMENTS IN CONCRETE AGGREGATES
The occasionally elevated radon sources in concrete may be caused by any of its
constituents. However, the radium and emanation measurements in dry-mix materials
(Table 3-2) gave little insight on which constituent dominates, since none of the four samples
analyzed contained elevated radon sources. A brief survey of concrete aggregate materials
was therefore conducted because aggregate is the least-characterized major concrete
constituent. Sand, the other major constituent, is widely distributed throughout most of
Florida, and its radium distribution is already characterized by aeroradiometric data and
other data summarized by the Florida radon map (Nie95a). Radium distributions in sand are
log-normal, extending into ranges that could readily contribute to elevated radon
concentrations if sands are not judiciously selected in areas containing elevated-radium soils.
The survey of concrete aggregate materials involved collecting and analyzing aggregate
samples from sources throughout Florida. The samples were collected opportunistically
during various field investigations and map validation studies. They consisted of aggregate
materials from active quarries, rock samples from U.S. Geological Survey investigations in
Dade and Broward Counties, and road aggregate samples from various sites. The results of
the radium and radon emanation measurements on the aggregate samples are presented in
Table 3-4.
3-7
-------
Table 3-4. Radium and radon emanation measurements
in Florida aggregate materials.
Sample Radium Radon
Location Latitude Longitude Sample" Concentration Emanation
(County) (North) (West) Material (pCi g"1) (fraction)
Broward
b
Potential aggregate
0.7 ± 0.3
0.10
0.04
Broward
b
b Potential aggregate
0.7 ± 0.2
0.14
±
0.05
Broward
b
6 Potential aggregate
0.5 ± 0.2
0.13
±
0.06
Broward
b
b Potential aggregate
<0.3
C
Dade
b
6 Potential aggregate
<0.3
c
Dade
b
6 Potential aggregate
1.9 ± 0.5
0.55
±
0.16
Dade
b
b Potential aggregate
4.1 ± 0.3
0.66
±
0.04
Dade
b
6 Potential aggregate
4.9 ± 0.3
0.49
3:
0.03
Dade
b
6 Potential aggregate
1.1 ± 0.3
0.26
±
0.06
Dade
b
6 Potential aggregate
3.4 ± 0.3
0.29
±
0.03
Dade
b
b Potential aggregate
1.3 ± 0.3
0.09
±
0.02
Dade
b
6 Potential aggregate
3.1 ± 0.3
0.51
0.05
Dade
b
b Potential aggregate
0.8 ± 0.3
0.16
dfc
0.06
Dade
b
6 Potential aggregate
2.9 ± 0.4
0.86
0.13
Dade
b
b Potential aggregate
1.0 ± 0.3
0.33
HK
0.09
Dade
b
6 Potential aggregate
1.1 ± 0.3
0.05
±
0.01
Dade
b
6 Potential aggregate
11.3 ± 0.4
0.50
±
0.02
Dade
b
6 Potential aggregate
2.0 ± 0.3
0.38
+
0.06
Dade
b
6 Potential aggregate
<0.2
c
Dade
b
b Potential aggregate
4.1 ± 0.3
0.62
±
0.05
Dade
b
6 Potential aggregate
1.2 ± 0.3
0.23
±
0.06
Dade
25.690°
80.487° Aggregate
1.7 ± 0.3
0.02
±
0.01
Lake
28.814°
81.627° Road aggregate
0.7 ± 0.5
0.25
0.19
Lee
26.491°
81.820° Aggregate
3.8 ± 0.3
0.05
0.01
Lee
26.498°
81.694° Aggregate
5.0 ± 0.3
0.04
±
0.01
Lee
26.497°
81.825° Aggregate
5.1 ± 0.3
0.04
±
0.01
Lee
26.491°
81.760° Aggregate
3.1 ± 0.3
0.05
±
0.01
Polk
27.886°
82.022° Road aggregate
56.9 ± 0.5
0.02
0.01
Collier
26.234°
81.813° Aggregate
1.3 ± 0.3
c
Collier
26.234°
81.813° Aggregate
3.1 ± 0.3
c
Nassau
30.569°
81.445° Road aggregate
0.3 ± 0.3
c
Sumter
28.651°
82.008° Aggregate
1.5 ± 0.3
0.10
±
0.02
Hillsborough
27.977°
82.402° Road aggregate
49.7 ± 0.6
0.20
±
0.02
Hillsborough
27.982°
82.403° Road aggregate
43.0 ± 0.6
c
Geometric mean (GSD) or mean ± s.d.
2.1 (4.0)
0.26
±
0.23
"Potential aggregate is not from a developed quarry; road aggregate includes asphalt.
^Latitude and longitude not measured.
Tladon emanation not measured.
3-8
-------
Radium measured in the five samples from active gravel quarries was distributed most
closely, ranging from 1.7 pCi g"1 to 5.1 pCi g"1, and having a geometric mean of2.7 pCi g'1 and
a GSD of 1.7. These samples may overestimate the typical radium concentration in Florida
aggregates, since they would lead to slightly higher concrete radium concentrations than
those listed in Table 3-1. They also fall into the upper range of the radium distribution
measured for Florida soils (geometric mean - 0.6 pCi g"1; GSD - 3.5) (Nie95a). Radium in
the 21 "potential aggregate" rock samples in Table 3-4 ranged from <0.2 pCi g'1 to 11.3 pCi g*
\ and had a lower geometric mean of 1.4 pCi g"1, but a higher GSD of 2.8. Radium in the five
road aggregate samples ranged from 0.7 pCi g"1 to 57 pCi g"1, with a geometric mean of 13
pCi g'1 and a GSD of 13.2. The overall geometric mean of the 34 radium measurements in
Table 3-4 is 2.1 pCi g"1, and its GSD is 4. Although the rock materials described in Table 3-4
may over-estimate typical radium concentrations in Florida concrete aggregate materials,
they show a potential for elevated radium concentrations in concretes.
Radon emanation coefficients for the gravels from active quarries averaged 0.05 ± 0.03,
significantly less than the 0.35 ± 0.23 for the potential aggregate rocks and the 0.16 ± 0.12
for the road aggregate samples. These differences are probably dominated by differences in
ambient moisture levels, since the emanation measurements were conducted at ambient
moisture. Surface samples from gravel piles were dry, while the "potential aggregate" rock
samples were collected at significant depths below the soil surface. Road aggregates probably
had intermediate moisture, since they were in contact with shallow soils, but were mixed
with or covered by asphalt materials. In general, the potential and road aggregate samples
suggest emanation coefficients comparable to the "wet paste" values in Table 3-2 unless
materials are completely dry.
3-9
-------
4. ASSOCIATION OF CONCRETE RADIUM WITH INDOOR RADON
Several radium and radon emanation measurements in Chapter 3 are high enough to
associate with elevated indoor radon concentrations using the equations in Chapter 2.
However, this study also seeks to determine if actual Florida buildings can be found in which
elevated indoor radon levels are caused by building materials. This objective requires
measurement of elevated indoor radon in buildings that have elevated radium levels in their
building materials.
Measurement opportunities were sought in buildings where elevated concrete radium
levels had already been measured. However, access to these buildings was limited because
the concrete samples were mostly provided by concrete suppliers or construction workers who
could not also provide access for indoor sampling of the completed buildings. Therefore, only
one building was studied in sufficient detail to show a link between its concrete radium level
and the indoor radon concentration. This chapter describes the measurements made in the
study building and the calculated contributions of its concrete radium to the indoor radon
level.
4.1 EMPIRICAL MEASUREMENTS
The study building was located at 30.179° N latitude and 82.692° W longitude, in the
vicinity of Lake City, Florida, which is entirely within a green (low radon potential) area of
the Florida radon protection map (Nie95a). The building was a two-story structure with a
concrete floor slab, concrete block walls, and a 20-cm concrete slab separating the first and
second stories. The building was initially identified by gamma ray surveys, which showed
gamma ray intensities exceeding 60 pR h'1 in some locations. Gamma ray surveys in the
vicinity of the building showed no elevated soil radium sources, with typical soil gamma
intensities in the 2-pR h"1 to 4-pR h"1 range. Radon flux measurements from the bare
surfaces of surrounding soils averaged 0.2 ±0.1 pCi m"2 s"1, also indicating that the site soils
should not contribute to elevated indoor radon concentrations.
4-1
-------
A detailed gamma ray survey was conducted in the accessible first-floor portion of the
building, as shown in Figure 4-1. The survey was designed to identify the relative
radioactivity of different structural parts of the building. As illustrated, the gamma activity
near the floor was consistently lower than corresponding gamma ray measurements at the
ceiling of the first level. The floor measurements averaged 25.9 ± 3.2 pR h"1, while the ceiling
measurements averaged 50.7 ± 4.2 pR h*1. Gamma measurements along the block walls were
intermediate, as shown in Figure 4-1, while gamma activity at a single accessible location on
the floor of the second level was slightly higher than the measurements from the ceiling of
the first level. Because of the relative uniformity of the gamma ray distributions over the
survey area, it appeared that the concretes were causing the elevated gamma activity.
41.2 wall
Building
survey area
• level 1 location
o level 2 location
X sampling location
ceiling (pR/h)
floor <|iR/h)
m51.8 54.0
25.2 29.4
46.4 51.7
•23.3 o 21.1®
47.8 50.8
'27.3 31.4
53.5
28.1
51.5
31.5
55.0
24.6
54.8
23.6
51.1
30-1 28.6
53.9
53.9 _ 23-0
23.5 •*
42.0
26.5
42.7
25.1
22.9
23.0
63.8 38.8 wall
Figure 4-1. Locations of gamma ray measurements in the study building.
4-2
-------
Sampling within the building consisted of making triplicate radon flux measurements
from the floor slab, taking single concrete samples from the floor slab and the ceiling slab,
and making indoor radon measurements in the first level of the building. The radon flux
measurements utilized the small charcoal canister method described and used previously for
the statewide radon flux sampling (Nie95a). The flux cans were sealed to concrete surfaces
with rope caulk. The concrete samples were obtained by drilling several 1.6-cm-diameter, 5-
cm-deep holes in the slabs and collecting the drill cuttings on plastic sheets for analysis. The
concrete cuttings were analyzed by the same gamma assay procedure used previously for soil
samples (Nie95a).
Indoor radon measurements utilized a continuous radon monitor (Model AB-5, Pylon
Electronics Inc., Ottawa, Ontario, Canada) that circulated approximately 2 L min"1 of room
air through its scintillation cell (Pylon, Model 110A) while continually recording alpha
activity over 20 min intervals. Radon concentrations were computed from the continuously
measured alpha counts using the calibration method and equations of Thomas and Countess
(Tho79). The efficiency of the scintillation was determined previously from calibration
analyses at the U.S. Department of Energy's Technical Measurement Center radon chamber
at Grand Junction, Colorado.
The radon flux measurements from the building floor slab averaged 0.083 ± 0.049
pCi m"2 s"1, typical of the range that may be expected from ordinary diffusion of radon
through a slab from underlying soils. The concrete radium concentrations were more
surprising, however, indicating 0.6 ± 0.4 pCi g'1 of radium in the floor slab and 32.8 ± 1.7
pCi g"1 in the ceiling slab. Based on these assays, most of the gamma activity at the floor
surface was hypothesized to come from the ceiling. The intermediate values along the walls
are consistent with this gamma shine interpretation, suggesting that any radium activity in
the concrete block walls is too low to significantly affect the gamma measurements.
The indoor radon measurements are presented in Figure 4-2. The concentrations
increased at an initial rate of approximately 0.24 pCi L"1 h"1 during the first 10 h of
measurements. The concentrations reached the 3 to 4-pCi L'1 range, and then decreased
during a period when outdoor gusty winds were observed. The outside door was briefly
4-3
-------
opened four times during the measurement period, as shown in Figure 4-2, for entry or exit
of personnel. The increased ventilation from door openings may also have contributed to the
declines observed during the 10 to 16-h and 22 to 26-h periods.
Door opened
->i i
Noticeable wind
i i
5/13/95
-><— 5/14/95—>
' 1 ' ' * *
12 16 20 24
Elapsed time (hours)
28
32
Figure 4-2. Indoor radon measurements in the Lake City study building.
Radon concentrations increased at a higher rate of about 1.2 pCi L"1 h"1 during the
period from 18 to 22 h. They reached the 4 to 6-pCi L"1 range and then decreased to levels
that were mostly below 4 pCi L'1. The data in Figure 4-2 demonstrate that the building had
sufficient radon potential to exceed 4 pCi L'1 for sustained periods of several hours when
perturbing effects such as winds or mechanical openings were not increasing its natural
ventilation rate. For calculation purposes, the indoor radon concentration was estimated
from an average of 13 points during the 19 to 23-h period to be 5.0 ± 0.8 pCi L"1.
4-4
-------
4JS CALCULATED EFFECTS
The contributions of various building materials in the study building to indoor radon
levels were calculated using the equations presented in Chapter 2. Table 4-1 presents the
results of these calculations. Radon fluxes from the ceiling slab were calculated from its
32.8-pCi g"1 radium concentration using equation (3), assuming typical density, emanation,
and diffusion properties for concretes as measured in the previous studies (Rog94; Rog95).
The values used for these parameters are shown in footnotes of Table 4-1. The indoor radon
source resulting from this flux was computed from equation (2) using the 25.4-m2 slab area
and 61.9-m3 volume of the study room. Contributions from the block walls were estimated
similarly, assuming a radium concentration equal to that of the floor slab, 0.6 pCi g"1. The
wall area used to calculate Ck was estimated to be 40.9 m2. The radon flux and resulting
source from radium in the floor slab were calculated from the measured slab radium
concentration in the same way as the corresponding values were calculated for the ceiling.
Table 4-1. Calculated contributions of building materials to indoor radon.
Radon
Source Material
Radon Flux
(pCi m"2 s"1)
CX
Radon Source
(pCi L"1 h'1)
Contribution to
Indoor Radon
Ceiling Slab
1.353°
1.996
92.9 %
Wall Blocks
0.0136
0.031
1.4 %
Floor Slab
0.025°
0.037
1.7 %
Foundation Soil
o.oss*
0.086
4.0%
Total
2.15
100.0 %
"Calculated from measured radium concentration, 10% emanation, 2.1 g cm"3 density, and
0.001 cm2 s"1 radon diffusion coefficient.
6Same as a, but assuming 0.6 pCi g'1 radium.
"Difference between measured flux and floor flux calculated from measured radium.
4-5
-------
The flux of radon diffusing through the floor slab from foundation soils was estimated
from the difference between the total measured floor flux and the portion that was explained
by radium in the slab. The measured floor flux of 0.083 pCi m"2 s"1 was strongly dominated
by underlying soils when compared to the flux of 0.025 pCi m'"2 s"1 calculated to result from
radium in the concrete. The soil contribution to the total radon source strength was also
estimated using equation (2). The last column in Table 4-1 shows the relative contributions
of each of the four components to the total indoor radon concentration.
The indoor radon concentration expected from the calculations in this section is equal
to the total value of CX =2.15 pCi L"1 h"1 from Table 4-1 divided by the ventilation rate of the
room. Although the ventilation rate was not directly measured, previous estimates of
ventilation in Florida residential structures have usually been in the 0.25-h"1 to 0.50-h*1 range
(Nie94). This range of ventilation rates corresponds to a radon concentration range of 4.3
pCi L'1 to 8.6 pCi L"1 for the calculated radon source potential. The measured concentration
of 5.0 ± 0.8 pCi L'1 is within this range, and corresponds to a ventilation rate of X = 0.43 h"1.
This ventilation rate is higher than values estimated for many Florida buildings, suggesting
that the measured radon source could potentially cause higher indoor radon levels in a more
tightly sealed building. Ventilation rates as low as 0.1 h"1 have been measured in Florida
(Nie94), and rates as low as 0.04 h'1 have been reported for unoccupied buildings when
ventilation systems were not operating (Smi80).
The indoor radon source strength was also estimated independently, using the
empirical relationship in equation (4). The average gamma ray intensity of 50.7 pR h"1
measured near the ceiling gives a radon source estimate of 0.56 pCi L"1 h"1, which is within
the measurement uncertainty of the 0.52-pCi L"1 h'1 value estimated in Table 4-1.
The study building satisfies the objective of identifying a Florida building whose
source of indoor radon is suspected to be from building materials. Based on the building
material contributions demonstrated in Table 4-1, the indoor radon is clearly dominated by
radium in the ceiling slab. The long-term average radon concentration in the study building
remains unclear because of the short duration of the radon measurements and the lack of
4-6
-------
information on its average ventilation rate. However, the short-term radon measurements
and ventilation estimates for Florida buildings (A. ~ 0.25 - 0.50 h"1) both suggest the potential
for long-term radon concentrations exceeding 4 pCi L"1. The consistency of the calculated
radon potential with that estimated from the gamma ray correlation in equation (4) suggests
a potential for screening buildings for building-material radon sources using gamma ray
surveys.
4-7
-------
5. BUILDING MATERIALS RADIUM STANDARD
5.1 TECHNICAL BASIS
The present empirical measurements and model analyses show that building materials
can and do contribute significantly to indoor radon concentrations in some instances. To
protect the public against unknowingly incorporating harmful radon sources into building
materials, a standard is proposed for limiting radium concentrations in the building
materials. The standard is based on the typical concrete properties used in the analyses in
Table 4-1, from which equation (3) gives the following relationship between concrete radium
concentration Cft in pCi g'1) and radon flux (J in pCi m'2 s"1) for a 20 cm concrete wall:
J = 0.04LR. <5>
Substituting equation (5) into equation (2) then gives a relationship that expresses indoor
radon concentration as a function of concrete radium concentration, concrete area, ventilation
rate, and occupied volume. Assuming a ventilation rate of X = 0.25 h"1, as in previous
modeling of Florida residences (Nie95a), the resulting equation can be simplified to give:
C = RtAi <«>
V i 1 1
where C = indoor radon concentration caused by concrete materials (pCi L"1)
Ri - concrete radium concentration in slab i (pCi g"1)
A, = area of interior concrete surface i (m2)
V = interior occupied volume (L).
Equation (6) can be used to predict indoor radon contributions from concrete building
materials under various construction scenarios. For example, a 140-m2 (1,500-ft2) residence
could have 140 m2 of floor slab area plus another 140 m2 of ceiling slab area if it were part
of a multi-story building separated by concrete slabs. In addition, concrete or block perimeter
walls could comprise an additional 115 m2 of concrete area exposed to the occupied space.
5-1
-------
If all of the concrete contained background radium at the 0.5-pCi g"1 level, the concrete would
contribute a total of only 0.35 pCi L'1 to the indoor radon concentration. However, if the
concrete contained elevated radium concentrations, it would cause higher radon levels, as
shown by the limiting radium concentrations in Table 5-1. These concentrations are the
calculated limits for the total concrete to contribute no more than 2 pCi L*1 to the indoor
radon levels.
Table 5-1. Limiting concrete radium concentrations for contributing 2 pCi L"1 of
radon to a 140-m2 residence using equation (6).
Concrete Structures with a
Background Radium
Concentration of 0.5 pCi g"1
Concrete Structures with
Elevated Radium
Concentrations
Limiting Elevated Radium
Concentration
(pCi g1)
2 Slabs
Walls + 1 Slab"
Walls
None
Walls
1 Slab0
2 Slabs
2 Slabs + Walls
8.6
7.2
3.8
2.9
"Either floor or ceiling slab.
5.2 PROPOSED STANDARD
The standard proposed for limiting radium concentrations in building materials is
designed to permit no more than 2 pCi L"1 of indoor radon to be caused by the building
materials. The 2-pCi L"1 limit is purposely defined lower than the 4-pCi L'1 standard
addressed by the Florida legislature to accommodate radon contributions from other sources,
such as soil gas from foundation soils. The proposed standard gives specific guidance for
concrete products, since concrete presently appears to be the dominant building material
contributing to indoor radon levels. The standard is also formulated to give credit for
different occupied volumes, for different surface areas of concrete components, and for
different radium concentrations in concrete components. The standard is based on equation
5-2
-------
(6), which is explicitly stated in the standard for clarity. Radium concentrations specified by
the standard and by equation (6) are intended to be measured by protocols accepted by the
FRRP (Wil91). The following standard is therefore proposed for avoiding elevated indoor
radon concentrations caused by radium in building materials:
Building materials used in the construction of habitable structures shall
not contain quantities of radium that increase the indoor radon concentration
by more than 2 pCi L"1. The contribution of concrete materials toward the
2-pCi L*1 limit shall be defined as:
c = ">
where C = radon concentration from concrete materials (pCi L"1)
V = volume of the habitable space (L)
Rf = radium concentration in the floor slab(s) (pCi g"1)
Af = area of the concrete floor slab{s) (m2)
Rc - radium concentration in the ceiling slab(s) (pCi g"1)
Ac = area of the concrete ceiling slab(s) (m2)
Rw = radium concentration in the concrete walls (pCi g'1)
Aw = area of concrete walls facing the interior volume (m2).
Radium concentrations used to compute radon contributions shall be measured
in accordance with "Standard Measurement Protocols, Florida Radon Research
Program" (Wil91), or other procedures accepted by the Department.
5-3
-------
6. LITERATURE REFERENCES
DCA94 Florida Department of Communilv Affairs, Florida Standard for Radon-Resistant Residenlial
Building Construction, Tallahassee PL: Florida Department of Community Affairs, proposed Rule
9B-52. amended December 1994.
EPA92a U.S. Environmental Protection Agency, A Citizen's Guide to Radon, second edition. Washington,
DC: U.S. Environmental Protection Agency report ANR-464, May 1992.
EPA92b U.S. Environmental Protection Agency. Technical Support Document for the 1992 Citizen's Guide
to Radon, Washington D.C.. U.S. Environmental Protection Agency report EPA-4QQ-R-92-01L
(NTiS PB92-218395), May 1992.
Ing83 Ingersoll. J.G., A Survey of Radionuclide Contents and Radon Emanation Rates in Building
Materials Used in the U.S., Health Physics 45. 363-368, 1983.
Kah83 Kahn, B.. G.G. Eichholz, and F.J. Clarke, Search for Building Materials as Sources of Elevated
Radiation Dose, Health Physics 45. 349-361, 1983.
Naz88 Nazarolf. W.W. and A.V. Nero, Radon and Its Decay Products in Indoor Air, New York: Wiley
& Sons, 1988.
Nie94 Nielson. K.K., V.C. Rogers, and R.B. Molt. Development of a I .umped-Parametcr Model of indoor
Radon Concentrations, Research Triangle Park. NC: U.S. Environmental Protection Agency report
EPA-600/R-94-201 (NTIS PB95-142048), November 1994.
Nie95a Nielson, K.K., R.B. Holt, and V.C. Rogers, Statewide Mapping of Florida Soil Radon Potentials,
Volumes 1 and 2, Research Triangle Park, NC: U.S. Environmental Protection Agency report
EPA-600/R-95- 142a,b, (NTIS PB96-10435 i, -104369), September 1995.
6-1
-------
Nie95b
Nielson, K.K., R.B. Holt, and V.C. Rogers, Site-Specific Characterization of Soil Radon Potentials,
Research Triangle Park, NC: U.S. Environmental Protection Agency report EPA-600/R-95-16I
(NTISPB96-140553), November 1995.
Ohr95 O'Brien, R.S., J.R. Peggie, and I.S. Leith, Estimates of Inhalation Doses Resulting from the
Possible Use of Phospho-gypsum Plaster-board in Australian Homes, Health Physic,v 68, 561-570.
1995.
Rog94 Rogers, V.C., K.K. Nielson, M.A. Lehto, and R.B. Holt, Radon Generation and Transport through
Concrete Foundations, Research Triangle Park, NC: U.S. Environmental Protection Agency report
EPA-600/R-94-175 (NTLS PB95-I012I8). September 1994.
Rog95 Rogers, V.C., K.K. Nielson, and R.B. Holt. Radon Generation and Transport in Aged Concrete,
Research Triangle Park, NC: U.S. Environmental Protection Agency report EPA-600/R-95-032,
1995.
Rog96 Rogers. V.C. and K.K. Nielson, Technical Basis for a Candidate Building Materials Radium
Standard. Research Triangle Park, NC: U.S. Environmental Protection Agency report EPA-600/R-
96-022 (NTIS PB96-157565), March 1996.
Smi80 Smith, D. and A. Scott, Elevated Radon and Thoron Concentrations from Natural Radioactivity
in Building Materials, 25th Annual Meeting. Health Physics Society, Seattle, WA, 1980.
Tho79 Thomas, J.W. and R.J. Countess, Continuous Radon Monitor, Health Physics 36, 734-738, 1979.
Wil9l Williamson, A.D. and J M. Finkel, 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.
6-2
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before compl
1. REPORT NO.
EPA-600/R-96-107
2.
4. TITLE AND SUBTITLE
Contributions of Building Materials to Indoor Radon
Levels in Florida Buildings
5. REPORT DATE
September 1996
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Kirk R. Nielson, Rodger R. Holt, and Vern C. Rogers
8. PERFORMING ORGANIZATION REPORT NO.
RAE-9226/7-5R1
9. PERFORMING ORGANIZATION 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 RWFL933783
DCA 95RD-30-13-00-22-01
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; 7/94-6/95
14. SPONSORING AGENCY CODE
EPA/6Q0/13
15. SUPPLEMENTARY NOTESAppCD roject officer ig Dayid Q
541-2979.
Sanchez, Mail Drop 54, 919/
16. abstract rep0rj- documents work to characterize potential radon sources in con-
cretes and recommend related chages to Florida's building materials radium stand-
ard. (NOTE: The Florida Standard for Radon-resistant Residential Building Construc-
tion originally contained a provision to limit the concentration of radium in concrete.
The provision was designed to prevent concrete from causing elevated indoor radon
concentrations. It was removed from the October 1994 version of the standard, how-
ever, because concrete from commercial sources had not been shown to be a major
radon contributor in Florida.) A mathematical model is presented to estimate the
contributions of building materials to indoor radon levels. The model computes radon
flux from concrete surfaces using typical Florida concrete properties, and multiplies
the flux by concrete surface areas to estimate their contribution to indoor radon. The
model also accounts for building ventilation by outdoor air. A revised building mater-
ial radium standard was developed to account for the areas aJid radium concentra-
tions of concretes exposed to building interiors. The standard would limit the indoor
radon increment from building materials to 2 pCi/JIt would limit concrete radium
concentrations to 7-9 pCi/g if only a single slab or walls contain elevated radium.
However, it could limit radium to about 3 pCi/g if floor, ceiling, and walls are high.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Gioup
Pollution Slabs
Radon Soils
Construction Materials
Concretes Residential Buildings
Radium Mathematical Models
Ventilation
Pollution Control
Stationary Sources
Indoor Air
13B 13 M
07B 08G.08M
13 C
12 A
13 A
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
35
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73) 6_3
------- |