EPA-520/4-76-018
A PRELIMINARY EVALUATION
OF THE
CONTROL OF INDOOR
RADON DAUGHTER LEVELS
IN NEW STRUCTURES
THE UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RADIATION PROGRAMS
WASHINGTON, D.C. 20460
NOVEMBER 1976
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A PRELIMINARY EVALUATION OF THE CONTROL OF INDOOR
RADON DAUGHTER LEVELS IN NEW STRUCTURES
Joseph E. Fitzgerald, Jr.
Richard J°. Guimond
Roger A. Shaw
November 1976
U.S. Environmental Protection Agency
Office of Radiation Programs
Criteria § Standards Division
Washington, D.C. 20460
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PREFACE
The Office of Radiation Programs of the Environmental Protection
Agency carries out a national program designed to evaluate public
health impact from ionizing and nonionizing radiation, and to promote
development of control necessary to protect the public health and the
environment. In response to this latter mandate, this preliminary
evaluation of the control of indoor radon daughter levels in new
structures was prepared. Readers of this report are encouraged to
inform the Office of Radiation Programs of any omissions or errors.
Comments or requests for further information are also invited.
W. D. Rowe, Ph.D.
Deputy Assistant Administrator
for Radiation Programs (AW-458)
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This report has been reviewed by the Office of
Radiation Programs, U.S. Environmental Protection
Agency, and approved for publication. Mention of
trade names or commercial products does not consti-
tute endorsement or recommendation for use.
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CONTENTS
I. Summary and Conclusions 1
II. Introduction 6
III. Radon Control Technology 10
IV. Identification of Parameters Used in
Evaluation 39
V. Cost Analysis 41
VI. Model for Decision-Making 53
References 59
APPENDIX A; Effectiveness of Air Cleaning in the Removal of
Radon Daughter Participates: A Model
APPENDIX B: Florida Indoor Radon Daughter Levels -
February 1976
APPENDIX C: Federal Register Notice of Interim Recommendations
for Radiation Levels for Florida Phosphate Lands
APPENDIX D: Experimental Effectiveness of Selected Commercial
Polymeric Sealants in Stopping Radon Diffusion
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FIGURES
1. Phosphate Deposits in Florida 7
2. Uranium-238 Decay Series 8,
3. Calculated Effect of Ventilation on Radon/Radon
Daughter Equilibrium 12
4. Particle Diameters of Typical Particles
(Including Radon Daughter Particulates) and Gas
Disperoids, and Types of Cleaning Equipment
Effective for such Particles and Disperoids 17
5. Capacity-Efficiency Chart for Honeywell Electronic
Air Cleaner Models F50, F51, and F52 22
6. Fractional Reduction in the Radon Emanation Rate
as a Function of Overlying Fill Material 32
7. Fractional Reduction in the Radon Exhalation Rate
as a Function of Concrete Slab Thickness 35
8. Decision-Making for the Control of Indoor Radon
Daughter Levels in New Structures Due to Emanation
Through the Foundation 54
TABLES
1. Control Measures: Advantages and Disadvantages 37
2. Estimated Average Cost of Radon Daughter
Control Measures 43
3. Average Cost per Percent Reduction of Radon
Daughter Levels 45
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ABSTRACT
As part of its assessment of the radiological impact of the
phosphate industry in Florida, the U.S. Environmental Protection
Agency has surveyed residences built atop uraniferous reclaimed
phosphate mining land. These surveys have shown elevated radon
daughter levels to exist in structures built on this land. In
order to allow safer use of this land for residential construc-
tion, various state-of-the-art radon daughter control technologies
were evaluated by the Agency. These included forced ventilation,
polymeric sealants, excavation, crawl space construction, and
improved slab quality. From a cost-effectiveness evaluation,
crawl space construction was determined to best satisfy the
criteria for "optimal" radon daughter control. These criteria
were established as: (1) operative passivity (i.e., requiring
no occupant responsibilities); (2) uniform effectiveness over
the lifetime of a structure; (3) a one-time reasonable cost upon
implementation; and (4) not having a significant impact on the
lives of future occupants.
Presented at the Health Physics Society Tenth Midyear Topical
Symposium on Natural Radioactivity in Man's Environment,
Saratoga'Springs, New York (October 10-13, 1976).
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I. SUMMARY AND CONCLUSIONS
An evaluation is presented on state-of-the-art radon daughter
control measures for proposed structures which have radon exhalation
through the foundations. This evaluation is largely based on a liter-
ature survey, preliminary field studies by the U.S. Environmental
Protection Agency in central Florida, and communications with private
industry concerning control technology. Five technologies are evaluated
for cost-effectiveness: ventilation, polymeric sealants, excavation,
ventilated crawl space construction, and improved slab construction.
The implementation of these control measures by the builder through
interaction with local health authorities is also evaluated.
From the data the Environmental Protection Agency has collected
and data provided in this report, the following conclusions can be
drawn concerning the implementation of control measures in new struc-
tures built on phosphate land in Florida:
1. The potential for construction of structures on reclaimed
phosphate land is high.
The amount of reclaimed phosphate mining land in Florida has
been estimated at approximately 25,000 acres. Of the 20,000 reclaimed
acres in Polk County, the County Health Department estimates that about
29 percent of the land has residential structures and 8 percent has
commercial structures. The remainder consist of undeveloped land and
land being utilized for parks, farming, and grazing. At the current
rate of mining, 4,700 acres per year, assuming that 40-50 percent of
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the mined area may be reclaimed and that phosphate mining in Florida
will continue at the current rate for at least 30 years, there could be
as much as 70,000 additional acres open to reclamation. Because a
large portion of this land is located adjacent to several large cities
and towns, as well as major highways, the potential for further residen-
tial or commercial construction is high (1). In addition, a large area
of land may exist that naturally contains phosphate deposits near the
surface. This land may also pose a potential hazard for occupants.
2. Surveys to date have shown elevated radon daughter working
*
levels in conventionally-built structures located on reclaimed land.
The Surgeon General of the U.S. Public Health Service in making
recommendations to the State of Colorado, established the following
indoor radon daughter working level guidelines for the Grand Junction
remedial action program (all values have background subtracted):
>.05 WL Remedial action indicated
.01 - .05 WL Remedial action may be suggested
<.01 WL No action indicated.
Although these recommendations were written for dwellings con-
structed on or with uranium mill tailings, they are relevant as a tool
for evaluating levels measured in structures built on phosphate land.
Data from Appendix B are provided in the following table and indicate
that, as a group, structures on reclaimed land have greater radon
daughter levels than structures not on reclaimed land.
^Working Level (WL) - the potential alpha energy from the short-lived
daughters of radon which will produce 1.3xl05 MeV in one liter of air
(applied originally as a unit of lung exposure for uranium miners).
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*
Percentage Range of Radon Daughter Levels
February 1976
Reclaimed Land (n=12) Nonreclaimed Land (n=9)
>0.5 WL : 33.3% >0.05 WL : -0-
0.05 - 0.01 WL : 33.3% 0.05 - 0.01 WL : 22.2%
<0.01 WL : 33.3% <0.01 WL : 77.8%
3. Control technologies do exist which should substantially
reduce radon daughter levels.
The technologies discussed in this report have been shown,
theoretically or in actual use, to have radon daughter reduction effi-
ciencies ranging from 40 percent to greater than 80 percent. At this
time there is an uncertainty as to the long-term effectiveness of these
measures, since they have not been assessed in actual field use. It
is expected that as experience is gained from the use of these
and other control measures, their selection will become a more refined
process with less uncertainties over the actual efficiencies to be
realized.
4. There will be a cost, significant with some control measures,
associated with the implementation of these measures in structures.
A particular control measure or combination of measures may be
selected for implementation based on desired working level reduction,
*A11 working level measurements have "background" subtracted out.
Background radon daughter activity for unmined land in the phosphate
deposit area is assumed to be 0.003 WL based on an average of measure-
ments made in structures built on such land (see Appendix B). It
should be stressed that this value was chosen to facilitate comparison
with existing guidelines and cannot be deemed representative until
more extensive background radiation surveys are conducted.
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builder preferences, and cost. The total cost (capital and operational)
projected for implementation of a few control measures, such as exca-
vation and forced ventilation, could prove to be a significant fraction
of the capital and maintenance cost of a structure.
5. The optimal control measure is one that is "passive" in its
operation (i.e., requiring no occupant responsibilities), uniformly
effective over the lifetime of a structure, involving a one-time
reasonable cost upon implementation and not having a significant
impact on the lives of future occupants.
Although what constitutes a "reasonable" cost is open to debate,
this definition of an optimal radon daughter control measure contains
the elements by which criteria can be established not only for the
selection of measures, but also the development of innovative control
technologies. At this time, it is difficult to determine which of the
control measures discussed would meet these criteria. As Table 3
details, however, a few could approach such optimality if radon exhala-
tion through the slab is the primary pathway. For example, if a high
effectiveness for ventilated crawl spaces and improved slab construction
can be supported by actual field application, they would provide a
favorable cost-effective means to effect a working level reduction.
Likewise, if the durability of polymeric sealants under normal residen-
tial conditions can be proven, then it too would be favorably cost-
effective if applied properly. It should be kept in consideration,
though, that conditions at some sites may cause control measures other
than these to be preferred.
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6. There is need for further research, coupled with field studies^
to develop and improve radon control measures and their attendant
cost-effectiveness.
The basis for much of the effectiveness and cost estimates for
the control measures evaluated are theoretical modeling and calculations.
What data is available, on control measures applicable to radon daughter
control, concerns applications for other purposes (except for the
studies performed by Culot, et al., and Auxier, et al., on polymeric
sealant effectiveness). There is a need for further research, coupled
with field studies, to develop and improve radon control measures and
their attendant cost-effectiveness. As part of this effort, the Office
of Radiation Programs, U.S. Environmental Protection Agency, is contin-
uing its assessment program involving structures built on reclaimed
phosphate land. A part of this assessment will encompass field studies
of newly built slabs and unoccupied homes in order to quantify more
precisely the effect of variables such as ventilation and slab
construction on radon working levels.
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II. INTRODUCTION
A recent study by the Office of Radiation Programs (ORP), U.S.
Environmental Protection Agency, has found that elevated radon daughter
levels exist in a number of structures built on reclaimed phosphate
mining land in Florida as compared to unmined land (see Figure 1) (1).
These daughter products result from the decay of radon-222, an inert
gas which may diffuse into a structure from the underlying ground.
Radon and its daughters are members of the uranium decay series which
is illustrated in Figure 2. Uranium is a natural constitutent of phos-
phate rock. Throughout the world it ranges in concentration from a few
ppm to a few hundred ppm depending upon the particular deposit. In the
marine phosphate formations of central Florida, uranium concentrations
of about 150 ppm have been noted (2). In the natural state, the uranium
is approximately in secular equilibrium with its daughters through
radium-226.
In the process of strip-mining, the overburden is removed and piled
adjacent to the pit. After the ore is extracted, a common reclamation
practice in preparation for future residential or commercial development
has been to fill these mined pits with the overburden to obtain a flat
plane. Another technique involves regrading the mined overburden so as
to permit multi-purpose utilization of the land. These mining and
reclamation methods lead to mixing of the overburden layers, uraniferous
leach zone material and other high activity material with "normal"
activity soil. As a result, elevated concentrations of radionuclides
may be distributed near the surface and thus allow radon to migrate into
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LEGEND
Northern land-pebble district
Hardrock district
Central land-pebble district
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FIGURE 2
URANIUM - 238 DECAY SERIES
ATOMIC WOT.
ELEMENT
ATOMIC NO.
HALF-LIFE
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9
the atmosphere. Without several feet of overburden acting as a barrier,
a large fraction of the radon gas produced by the decay of radium-226
can diffuse to the surface and into the atmosphere. Due to the gen-
erally high mixing and dilution characteristics of the lower atmosphere,
radon and its progeny do not build up in the open air as they can in a
confined space. When structures.are built over these phosphate areas,
radon seeps into the structures and as a result of the buildup of decay
products, increased radiation exposure to the occupants may occur.
The Environmental Protection Agency, as part of its role in pro-
viding radiation protection guidance on this potential health hazard,
has reviewed various radon progeny control measures for their cost-
effectiveness. The purpose of this report is to provide an evaluation
of the most practicable technologies based on present data and infor-
mation that may be used to control radon daughter levels in proposed
structures to be built on phosphate lands. It is emphasized that this
report does not provide new field data on the effectiveness of the
control technologies, but represents an evaluation of applicable
existing studies and data. Further, although the subject of reclamation
of phosphate mining areas is outside the scope of this report, it is
recognized that with proper management of reclaimed land, no radon
control measures for structures may be necessary.
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10
III. RADON CONTROL TECHNOLOGY
Although the potential radiation exposure problems associated with
residential construction on phosphate land may be known to a builder,
he may choose to initiate construction for a number of reasons. First,
gamma surveys (as outlined in Appendix C) may show the site to be below
the interim guideline of 10 yR/hr average gamma exposure. Second, even
though the land may survey greater than 10 yR/hr, due to the desirability
of the site (e.g., for economic or zoning reasons), the builder may
decide to implement some type of control measure to reduce the indoor
radon daughter working level.
The five basic control measures which will be discussed and
analyzed in this report are: 1) improved effective ventilation,
2) ventilated crawl space construction, 3) polymeric sealants, 4) site
excavation and fill, and 5) improved slab construction. These technol-
ogies were selected because they have been shown to be technically
feasible, applicable to residential situations and are reasonably
cost-effective.
A. Improved Effective Ventilation
The function of improved effective ventilation is to lower the
indoor radon daughter exposure to occupants through dilution with out-
side air and/or physical removal of the daughter products by a filter
"Effective" ventilation is the replacement of air within a structure
with air containing background radon concentrations through either
movement of air through an air cleaner or natural infiltration of
outside air.
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11
or electronic air cleaner.* As Figure 3 shows, with no ventilation or
filtration, radon and its daughter products are assumed to be in "sec-
ular" equilibrium, that is, having the same activities. When both the
radon and its decay products are removed through ventilation or when
the latter is removed by filtration, the ratio of the parent to each
daughter becomes something less than 1:1. This effect is most obvious
at ventilation rates of one air change per hour or more. As the rate
of ventilation increases, the activity of the fresh makeup air becomes
more critical because there is less time for radon daughter in-growth
in the room air. For the purpose of the report, though, ventilation
rates of this magnitude (>4 air changes per hour) will not be consid-
ered and makeup air will be assumed to have background levels of radon
(0.5 - 1.0 pCi/1 for phosphate land) (3).
When polonium-218, a daughter product of radon, is formed, it
occurs as a single charged ion which remains suspended in the air until
collision with an aerosol or macro-surface (including larger particu-
lates) whereupon attachment occurs (4,5). The attachment rate for these
ions to aerosols has been found to be proportional to the surface area
of the aerosol itself (5). Thus, the number and particle size distri-
bution of dust particles, and condensation nuclei in home atmospheres
are critical in determining the behavior of these radon daughters.
*
Improved ventilation at high air exchange rates or selective removal
of aerosols by high efficiency filters may actually lead to an
increased radiation dose to the lungs. This effect, due to an
increase in the "free ion fraction" of the radon daughters, is dis-
cussed iii subsequent sections dealing with this parameter and with
air cleaners.
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o
cc
cc
Ul
H-
O
O
O
O
oc
6
P
o
01
o
o
o
FIGURE 3
CALCULATED EFFECT OF VENTILATION
ON RADON/RADON DAUGHTER EQUILIBRIUM
(from modeling calculations - see Appendix A)
456
AIR CHANGES PER HOUR
8
10
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13
The average aerosol concentration for homes in the United
States was found to be approximately 3x10** particles per cc with parti-
cle sizes ranging from 0.012 to 0.2 micron, with a mean value of 0.05
micron. This concentration and size range is supported in studies
performed by Haque and Collinson (6), who concludes that 60 percent of
in-house daughter product activity is associated with particles between
0.012 and 0.08 micron; by Mercer and Stowe (7), who found that the mean
aerodynamic diameters approximated 0.2 micron; and by Jacobi (4), who
estimates that 50 percent of the daughter product activity is associated
with particles with less than 0.1 micron diameter. For centrally air-
conditioned and heated homes, such as those in the Florida study area,
though, aerosol concentrations less than 101* particles per cc are more
likely..
The free ion fraction, the fraction of daughter ions which
remain unattached to surfaces or aerosols, is of particular concern in
lung deposition of daughter particulates. Harley and Pasternack (8)
note that unattached RaA ions deposit with 100 percent efficiency in
the tracheobronchial region. Subsequent decay of these particulates
give rise to a substantial fraction of the total alpha dose to this
region of the lung. Jacobi (9) indicates that the uncombined fraction
(that fraction of the ions which are free ions) of the total potential
alpha energy fp (for RaA + RaC1) provides a better measure of the dosi-
metry of the inhaled ions deposited in this region. He also indicates
(10) that fp is a function of aerosol concentration and the ventilation
rate of a' volume. With decreasing aerosol concentrations and an
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14
increasing ventilation rate, the ratio of the absorbed alpha energy or
integral alpha energy in the bronchial and pulmonary region to the
inhaled potential alpha energy increases for the former and decreases
for the latter. This effect may lead to higher dose levels to lung
tissue than would normally be associated with radon daughter working
levels. Because of the complexities in estimating this parameter
quantitatively under various control conditions, for the purposes of
this report, it will be considered a constant with working levels
assumed to be proportional to dose.
Particle distribution and concentration is largely dependent
upon the ventilation rate. Typical residential structures have some
degree of air infiltration through the walls and ceiling. The magni-
tude of this infiltration is a function of the "tightness" of construc-
tion, insulation, and outside weather conditions. In addition to these
factors, others, such as room occupancy, and the number of windows and
doors will significantly affect radon daughter levels in various rooms
of the house. A survey by Handley and Barton (11) indicates that
average single family housing units in the United States have ventila-
tion (or infiltration) rates ranging from 0.5 to 1.5 air changes per
hour. This is in general agreement with studies performed by Kaye (12)
and Johnson, et al. (13,14).
The "effective" ventilation rate for homes with elevated radon
daughter particulate concentrations is the rate at which the in-house
atmosphere is replaced with air containing background levels of radon
daughter products. In order to increase the effective ventilation
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15
rate, either the natural infiltration rate must be enhanced or the
internal air must be cycled through an air cleaner. These two
approaches will be discussed further in the following sections.
1. Utilization of Natural Ventilation
Although continuous natural ventilation through open
doors and windows is effective in reducing indoor radon progeny
levels (1), such external ventilation is not always desirable because
of climate conditions. In Florida, a majority of new homes being built
(approximately 65 percent in 1973) have central air-conditioning which
is installed primarily because of the prevalent warm weather conditions
(15). Another underlying consideration is that individual preference
governs the degree to which such natural ventilation is used, therefore,
introducing a significant variability in the overall effectiveness of
such control when considered on a large population basis.
Another technique makes use of outdoor makeup air in an
air exchange system which is coupled with the central air-conditioning
and heating unit. This system maintains a continuous influx of outdoor
air to add to the normal complement of internal air being recirculated.
Although the use of fresh makeup air is effective in increasing the
number of air changes per unit time, it may decrease to some degree,
the natural air infiltration through leakage into the house by creating
a positive pressure differential (16)- This effect can be overcome by
increasing the amount of makeup air accordingly until the desired
equilibrium makeup fraction is achieved. From modeling calculations
(to be discussed later), a theoretical working level reduction of about
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16
45 percent could be obtained with 25 percent makeup air. Of course,
this method of control would involve larger capacity air refrigeration
and heating systems than would normally be used and require higher
energy consumption, which would make it energy intensive for areas
with generally warm climates, such as Florida.
2. Utilization of Air Cleaners
Air cleaners are designed to remove particulates from the
circulating air of building interiors. The type of air cleaner used
depends upon the particle size and shape, specific gravity, concentra-
tion of the particulates, and the efficiency of removal desired. The
particle size is the most important characteristic by which an air
cleaner is chosen. Figure 4, from Chapter 10 of the 1972 ASHRAE Hand-
book of Fundamentals, gives data on the sizes and characteristics of
airborne particulates and the cleaning equipment effectiveness range
for a wide range of particulate size (17).
The three operating characteristics that distinguish the
different types of air cleaners are: 1) efficiency, 2) air flow resis-
tance, and 3) life- or dust-holding capacity (18). Efficiency is a
measure of the ability of an air cleaner to remove particulates from
an air stream. Air flow resistance is the static pressure drop across
the filter at a given air flow rate. Dust-holding capacity is the
amount of a particular dust which an air cleaner can hold when operated
at a certain flow rate to some maximum resistance value. The air
cleaners are tested for these various characteristics and are rated
accordingly.
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FIGURE 4.
DIAMETERS OF TYPICAL PARTICLES (INCLUDING RADON DAUGHTER
PARTICULATES) AND GAS DISPEROIDS, AND APPLICABLE EFFECTIVE
CLEANING EQUIPMENT
Typical Particles
and
Gas Dispersoids
t
Types of
Gas Cleaning
Equipment
0> CO:
Hi F] CI,
CO H,0 HCI
'Molecular diame
from viscosity dat
C.H.
Gas
Molecules' '
SO, |
ers calculated
a at O'C.
N — — Vi
•« Rosin Smoke »
•* Tobacco
Mrtilli
•* Carbon Bla
•« — Zinc Oxide Ft
taloidd
Aitken
Nuclei
i*- Sea S
Combustion
Nuclei
Radon Daught
< Products—
•uses *\
jrgical Dusts and
••-Ammonium Chloridf
ck »i« C™1
K-r-Fertilizer, Ground Limestone— »•
Flu Ach ... . -•
Fume-»M Cement Dust »•
Sulfuric ' ^.
^Concentrator Mi
act
• Sulfuric Mist "~
•* Paint Pigments H
jme — H \*— Insecticide Dusts->
< Spray D
« Alkali Fu
— H
alt Nuclei -H
Lung
iorl Mill/ k.
me H
-< MilloH
« — Nebulizer Dro
Damaging^.
Dust " }
!!»._. Red Blood Cell Diameter (At
" \* o — »«-:*
1
Ultrasonics
(very limited indi
stnal application)
fin
Ccntrif
Thermal Precipitation
(used only
for sampling)
-Electrical Precipit
>t
•* — Flotation Ore1
,i
Plant
Spores
•* — Pollens *•
Tlniir hi
r--»
ps-»i n —
^ Pneumatic t
Nozzle Drops
dults): 7.5/i ±0.3/i
-<- Common Air Filters — *
ators
t Beach Sand
Hydraulic Nozzle
Hairn
oettling Lnan
parators — H
234568 234568 234568 234568 234568 234568 234568
0.0001 0.001 0.01 0.1 1 10 100 1,C
(lm/0 (In
/Particle Diameter, microns (/i)
Drops — *•
1
ibers •
2 34568
XX) 10
im.) (1
2 :
000
cm.)
(Adapted from original table prepared by C.E. Lapple, Stanford Research Institute)
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18
Three major types of air cleaners are in general use at
the present (18):
1. Fibrous media unit filters in which accumulating dust
load causes the pressure drop to increase (and thereby the efficiency)
up to some maximum permissible value. This category includes both
viscous impingement and dry type air filters.
2. Renewable media filters in which fresh media is intro-
duced into the air stream as needed to maintain constant resistance.
This filter system also maintains essentially constant efficiency.
3. Electronic air cleaners, which have essentially
constant pressure drop and efficiency, unless their precipitating
elements become severely dust-loaded.
These air cleaners can be used in tandem in numerous com-
binations to improve overall efficiency and operating life. For
example, a renewable media filter may be used upstream of a HEPA (High
Efficiency Particulate Air) -filter in order to prolong its effectiveness.
Fibrous media filters can be divided into two major types:
1) viscous impingement filters, and 2) dry type air filters. The
former, utilizing a viscous media coating, 'is characterized by a low
pressure drop, low cost, good efficiency on lint, but low efficiency
on normal atmospheric dust. Because of the particle size limitation,
such a filter would not be effective for removing radon daughter
particulates. Dry type air filters use a medium composed of random
fiber mats or blankets of varying thicknesses, fiber sizes, and
densities. Media of bonded glass fiber, cellulose fibers, wood felt,
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19
asbestos, synthetics, and other materials have gained commercial and
residential application. This type of filter is characterized by a
generally higher efficiency produced by the smaller fiber size and
inter-fiber spacing. The higher the efficiency of the filter, the
greater the operating resistance against which the air must flow. With
HEPA filters, resistance may reach 2.0 inches of water at duct velocities
of 200 feet per minute, necessitating the use of backup fans. HEPA
filters have been in standard use in hospital clean rooms and in radio-
active and toxic-particulate applications. They are unsurpassed in
filter efficiency (99%+) and are effective at particulate size ranging
down to 0.03 micron (18).
The advantages of the HEPA filter include its low initial
installation cost and lack of mechanical moving parts. Disadvantages
include the cost of replacing spent filters, the lower efficiency
realized at higher air flow rates and the electrical cost associated
with fan operation. A particular disadvantage of concern is the
increased free ion fraction (fp) resulting from a decreased aerosol
concentration due to their selective removal by the filter. As has
been discussed, a higher effective dose to the tracheobronchial region
of the lung is associated with such an increase. The magnitude of the
increase is dependent on numerous variables including the infiltration
rate, the air cleaner pass-through rate, and the equilibrium concentra-
tion of indoor aerosols. This effect would predominate at the higher
effective ventilation rates (2-3 air changes per hour) (10).
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20
The renewable media filters make use of moving rolls of
either viscous fiber or dry fiber media to trap particulates. When the
media roll is exhausted, the entire roll is disposed of, and a new roll
is installed. As this type of filter is less than 30 percent efficient
for dust-sized particulates (>1.0 micron diameter), it will have little
application for radon daughter particulate removal.
Electronic air cleaners use electrostatic precipitation
principles to collect particulate matter. Unlike their industrial
counterparts, residential electronic air cleaners operate on standard
house current and with normal operation use electricity at the same
rate as a 50-watt lightbulb (19). There are two general types of elec-
tronic air cleaners: 1) charged media filters (single-stage electronic
air cleaners) and 2) the two-stage electronic air cleaners.
In the charged media filter, either a dielectric media
consisting of glass, cellulose fibers or other material, or a series
of charged plates are utilized to form the electrostatic field. The
field, produced by a voltage of up to 12,000 volts, polarizes particu-
lates and attracts them to the charged fiber media or metal plates.
Cleaning of the plates or fiber media is necessary periodically to
remove excess particulate loading.
The two-stage electrostatic precipitator makes use of a
two-stage electronic cell. The first stage forms an electric field
that ionizes particulates as they enter the system, ..ile the second
stage contains an alternating series of grounded and positive plates.
The grounded plates attract and hold the ionized particulates, while
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21
positively charged plates repel particulates toward the grounded ones.
Normally, molecular adhesion and interparticle cohesion are sufficient
to maintain particulate adhesion to the plates. However, when exces-
sive loading with fine dry particles takes place, some type of prepared
adhesive may be necessary. As with the charged media filter, periodic
cleaning of the plates is necessary in order to maintain efficiency (18).
The performance of electronic air cleaners depends upon the
*
rate of air flow and the quality of installation. A number of commer-
cially available models are designed to meet these performance para-
meters, as well as others such as the volume of air to be cleaned and
the size of the heating or cooling unit. Figure 5 illustrates particle
removal efficiencies as a function of flow rate for typical residential
electronic air cleaners (20).
Installation of an electronic air cleaner into the central
heating or cooling system of a residence requires care in order to
insure efficient operation. Generally, the air cleaner must be situated
so that there exists an even air flow through the plates. This require-
ment will sometimes necessitate alterations in the feed duct work.
Location of humidifiers, if present, are critical in that excess
humidity lowers the effectiveness of the cleaner significantly.
Although no field or experimental studies have been
performed as yet to determine the effectiveness of this air cleaner on
free radon daughter ions, from its operating characteristics it can be
assumed that as many, if not more, free ions will be proportionally
removed as -will particulates (21). This assumption is based on the
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22
FIGURE 5
CAPACITY-EFFICIENCY CHART FOR HONEYWELL
ELECTRONIC AIR CLEANER MODELS F50, FBI
AND F52. '
F50 (20 IN.)
F51 (20 IN.)
F52B (2 CELL)
500 1000 1500
CUBIC FEET PER MINUTE (CFM)
I I I
2000
50 100 150 200
FURNACE OUTPUT BTUH (IN THOUSANDS-APPROXIMATE)
I | | | |
12345
TONS OF COOLING (APPROXIMATE)
a AS MEASURED BY THE NATIONAL BUREAU OF STANDARDS
DUST SPOT METHOD USING ATMOSPHERIC DUST.
5647
(From Electronic Air Cleaner —
Application and Installation,
Honeywell Corporation, i¥ 70-9723.)
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23
basic operation of the electronic air cleaner, which involves the
formation of a "corona" of positively charged ions in the first stage
in order to enhance the removal of the attached particulates by the
oppositely charged plates in the second stage. It is extremely doubtful
that a charged ion would be able to escape from this charged field.
Therefore, it is unlikely that the utilization of an electronic air
cleaner for radon daughter level control will have a significant effect
on the equilibrium value of the free ion fraction in a structure.
The advantage of the electronic air cleaner lies in its
high efficiency over a wide range of particulate sizes, down to sub-
micron diameters, as well as its ease of maintenance. The disadvantages
are its relatively high initial cost and the discharge of ozone which,
at moderate concentrations (0.003 to 0.10 ppm), is perceivable by the
average person as an odor and at higher levels (0.3 ppm) can lead to
such symptoms as nausea, headaches, and pulmonary edema. The concen-
tration of ozone produced in a home by an electronic air cleaner ranges
from 0.005 to 0.02 ppm (20). These levels are several factors lower
than those found in many cities and are also lower than the Food and
Drug Administration (FDA) concentration standard of 0.05 ppm for elec-
trical devices (21 CFR 3.96 (1975), 21 CFR 801.415 (1976)).
As no data is available concerning the efficiency of air
cleaners in reducing the concentration of radon daughters, modeling
was performed to make such an estimation. These calculations, provided
in Appendix A, show that most of the radon daughter level reduction
occurs at effective ventilation rates of less than two air changes per
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24
hour (approximately 70 percent). Therefore, assuming that natural
infiltration accounts for one air change per hour, air cleaners, which
can effectively handle ventilation rates of about one to two air changes
per hour, would have a relatively marginal effect on working level
reduction. For HEPA and electronic air cleaners, a 38 percent reduction
in the equilibrium radon daughter working levels was calculated. For
HEPA filters, though, increased effective ventilation rates could lead
to an increased tracheobronchial dose (and therefore, a potentially
higher total lung dose), due to the resulting increase in the free ion
fraction of radon daughters (10).
For a combined electronic air cleaner and outside air
exchange system, an efficiency of 62 percent was calculated for working
level reduction. This model assumes a flow rate through the system of
1.5 air changes per hour and about 25 percent makeup air (see Appendix A).
B. Ventilated Crawl Space Construction
The function of building a crawl space for radon progeny
control is to provide a highly ventilated space between the soil sur-
face and the overlying structure in which the emanating radon gas can
be diluted or removed before diffusion into the structure. The degree
to which such ventilation is effective is dependent upon the number of
air changes per unit time within the enclosure below the floor.
Assuming that a wooden floor would allow radon gas to diffuse readily,
the fractional reduction of radon gas diffusion into the structure
would be proportional to the reduction in partial pressure of the radon
in the crawl space due to ventilation. There are two means by which
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25
the ventilation characteristics of a crawl space can be enhanced,
involving respectively, passive and nonpassive measures. First, the
crawl space can be constructed utilizing oversized, properly spaced
vents on all sides of the structure. Second, a fan could be set up
for forced ventilation of the crawl space, thereby establishing a
lower limit of ventilation. Although there is no readily available
data concerning the magnitude or range of the ventilation rate achiev-
able by these means, with proper construction it could compare favorably
with a well-ventilated house (2-4 air changes per hour). Assuming such
ventilation rates, radon daughter working level reductions of 80 percent
or more would be possible. The level of reduction achievable could be
increased, if desired, through the use of a radon impervious barrier
in the floor. Such a barrier, possibly in the form of a polymeric
sealant underlying a seamless tile floor, would have side advantages
such as moisture proofing and a reduction in heating and air-conditioning
infiltration loss.
The advantages of nonmechanical crawl space construction as a
control technique are that it is passive, permanent, maintenance-free,
effective, and easily constructed. The advantage of mechanical con-
struction lies in its use of forced ventilation, from which a minimum
effectiveness can be selected and maintained. Disadvantages would be
its nonpassivity, inconvenience, and expense (maintenance and electri-
cal) . Disadvantages for both types are the additional cost such
construction would entail as compared to a slab-on-grade construction
and the greater natural infiltration rate through the floor which would
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26
necessitate either additional insulation, or greater heating and cooling
capacity. There is also the expense and effort involved in changing
blueprints and construction specifications on the part of the builder.
In turn, the prospective purchasers may object to the crawl space on
aesthetic grounds, or on grounds that it may attract insects or a
rodent population.
C. Polymeric Sealants
Ideally, if one could completely seal all of the floor and
wall space below ground level for a structure with radon diffusing
through the floor, the problem would be largely alleviated. The radon
gas that would normally diffuse through the floor would be trapped by
this barrier so that it would decay in the structural material and not
enter the structure's atmosphere. Polymeric sealants, having low
permeability to radon gas, have been proven to be effective in reducing
in-house radon progeny when properly applied. An EPA funded study by
Culot, et al. (22), showed that radon diffusion into a structure could
be reduced by more than one-half utilizing an epoxy sealant. An impor-
tant finding of this study was that a significant reduction of radon
diffusion into structures could be obtained only in a situation free
of other major pathways for radon. From past analyses with test struc-
tures on slabs, as well as experience with remedial action in structures
*There is a whole-body gamma exposure related to such decay, although
in regard to potential health effect it is insignificant in compar-
ison to radon daughter alpha exposure in the lung. From past field
studies (22), fractional gamma increases of 2 to 20 percent were
measured for a 4-inch concrete slab after sealant application.
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27
in Grand Junction, Colorado, it was determined that such pathways do
exist and are common in typical residential structure. One such path-
way is minute cracks in the concrete slab at the juncture of the slab
and wall. Another is the channel through which pipes and drains enter
the slab. These analyses and field experience have shown that with
incomplete sealing of these pathways with a radon-impermeable base,
only a relatively small working level reduction could be obtained.
The thoroughness of sealant application, then, is of prime importance
in this control measure. Sealants must be applied at a thickness
appropriate for the expected wear in an area.. The applied sealant
should be protected from such wear (e.g., by a floor covering such as
quartz seamless) whenever possible, although multi-layer application of
newly developed wear-resistant epoxy may be durable enough to withstand
such wear. All wiring and piping junctures in the slab should be
sealed thoroughly to prevent radon seepage.
The Bureau of Mines has been active in the development of
effective radon sealant barriers for use in uranium mines to reduce the
emanation of radon gas from uranium ore. In a recent lab analysis, 46
different single-coat polymers and 14 two-coat applications were tested
on uranium rock samples. Franklin, et al. (23), reported reduction
efficiencies of up to 100 percent (see Appendix D). Subsequent field
studies conducted at Grants, New Mexico, have shown radon gas emanation
reductions of up to 62 percent. The Bureau's Spokane Mining Research
Center has developed these criteria for a good radon gas barrier (23):
1. Material must stop at least 50 percent of gas emitted
from ore samples.
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28
2. Material must be easily applied.
3. Material must not emit toxic or noxious vapors during
application or curing.
4. Material must be flame resistant (not readily burnable and
not emitting toxic vapors should heat be applied).
5. Material must cure in a mine environment (45° to 60° F,
40 to 100 percent relative humidity).
6. Material should be cost competitive.
7. Material must adhere to wet or dry, dusty, porous rock.
Although these criteria were developed for polymer application in mines,
they would also apply to a large degree in residences.
Lawrence Livermore Laboratory (LLL) of the University of
California conducted further investigations into1 the properties of
available commercial polymers in order to identify the best overall
sealants (24). The sealants evaluated by LLL were selected from ones
already tested at the Bureau of Mines, SMRC, with the exception of a
few polymers obtained from the chemical industry through a survey.
Radon permeability coefficients for each polymer were determined by the
use of two similar noble gases, krypton and argon, and a conversion
factor derived from the molecular diameters of these gases. Besides
permeability, the polymers were tested for fire resistance and toxic
properties. The results showed that virtually all coatings with per-
meation constants lower than 10~10 cm3 (STP)»cm/s«cm2*cm Hg and thick-
ness between 5 and 10 mils will provide nearly 100 percent radon
exhalation reduction. As many of the polymers did, in fact, meet this
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29
criteria, the research staff recommends that selection should be based
on factors other than efficiency, such as cost, vapor toxicity during
application and binding properties. The authors ranked the nine
polymers that were analyzed and commented on their potential short-
comings (see Appendix D).
An efficiency range of 70-90 percent radon progeny reduction
for polymeric sealants was derived from test data by Culot, et al. (22).
Their experiments involved the use of sealed tanks above a sealed
concrete slab with uranium tailings underneath. Assuming an equilibrium
radon progeny concentration over the slab equal to 10 percent of the
source term under the slab, which they had previously determined, the
range of reduction was approximately 75-99 percent using polyester
*
styrene, polyester resin, and Omnitech polymers. From a similar
experimental analysis, Auxier, et al., suggests that an 88 percent
reduction in airborne radon progeny could be obtained (25). As these
reductions were achieved in an experimental lab situation, the reduc-
tion range of 70-90 percent was chosen as a conservative approximation
of actual residential application. Again, the degree of reduction
achievable would be dependent upon the method and thoroughness of
application.
Application of polymeric sealants in new home construction
would involve much less effort and expense than would the same proce-
dures in an existing residence. In fact, one innovative technique
which may prove effective at increasing the durability of the polymer
*0mnitech Industries, Inc.
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30
is to "sandwich" it between two layers of concrete in the slab. This
would be done by applying a water-based polymer after half of the slab
(by depth) has been poured and then pouring the other half. The water-
based polymer would then form a bond with the cement which would be
extremely durable (26). However, cracking of the slab itself would be
just as detrimental in this application as in a conventional application
if the integrity of the sealant is breached.
Another innovative sealant application would involve its use
as a ground surface preparation before slab pour. This would require
careful ground preparation (leveling and rolling) and a heavy-duty
sealant application. The durability of such an arrangement has not
been tested under field conditions and, therefore, would be in question.
If its long-term efficiency can be shown, though, it could prove valu-
able as both an adjunct to conventional application and as a control
measure in itself.
In conventional applications, the concrete slabs or basements
should be treated before any other structure or flooring is built over
them. Once the concrete slab is set, its surface should be ground
smooth as with a wire brush, and all cracks should be sealed with an
epoxy caulk. Quartz seamless flooring or other such similar flooring
can then be installed (assuming that wall-to-wall carpeting is not
being considered). The sealants are applied in five coats:
1. 60 percent solid, water resistant epoxy primer at
approximately 3 mils thickness.
2. 100 percent solid, pigmented epoxy, no less than 15 mils
thickness.
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31
3. 100 percent solid, clear epoxy, at no less than 15 mils
thickness, with ceramic coated quartz granules broadcast at no less
than one-half pound per square foot of floor.
4. 100 percent solid, clear epoxy, glaze coat at approximately
10 mils thickness.
5. 100 percent solid, clear epoxy, glaze coat at approximately
6 mils thickness.
The preceding appliation technique for Omnitech epoxy sealant
was utilized by Culot, et al. (22), in their experimental analysis of
the product. They found that radon diffusion through the slab had been
reduced to -background levels for the 15 days after treatment.
The advantage of using polymeric sealants is that it is rela-
tively effective and does not impact on the lives of residents. The
major disadvantage is that the longevity of the seal provided by the
sealant is untested. Therefore, it is conceivable that sometime
during the lifetime of the structure either a reapplication or some
type of maintenance will be required on the sealed slab. As many new
homes have wall-to-wall carpeting installed, such a procedure could
entail some expense and inconvenience to the homeowner. Likewise,
hardwood floors and tile surfaces would have to be removed for slab
resealing.
D. Site Excavation and Fill
As Figure 6 shows, a ten-foot layer of soil with a relaxation
length of ,4.9 feet (for moist packed earth and dry packed uranium
*The depth of a uniform layer of material of the same density in which
a diffusing gas (radon in this case) is reduced in concentration by a
factor of "e" (2.703).
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32
O
I
111
DC
<
O
FIGURE 6
FRACTIONAL REDUCTION IN THE RADON EMANATION
RATES AS A FUNCTION OF OVERLYING FILL MATERIAL
(assuming relaxation of distance*
of 4.9ft. (1.5 m) for fill material)
0.01
•SEE DEFINITION, PAGE 31.
8 12 16
DEPTH OF FILL (FT.)
20
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33
tailings with a diffusion coefficient of 5xlO~2 cm2/s) (22) can be as
much as 80 percent effective at reducing radon emanation from the
ground surface. Such data indicates that by removing this depth of
reclaimed phosphate soil and replacing it with non-uraniferous soil of
the same density and porosity, approximately 80 percent of the radon
would be retained in the ground. If such a procedure were done for a
home site on phosphate land, the diffusion rate of radon into the
structures to be built would then be proportionally less, assuming
*
negligible lateral radon diffusion.
Such an operation would involve the use of earth-moving equip-
ment to excavate the soil at the site to a suitable depth. This soil
would then be dumped or spread at a location owned and approved by the
county or State for such purpose (such land could be zoned to disallow
residential and commercial construction). A gravel or soil replacement
fill would be trucked in, dumped at the excavation site and packed
thoroughly. A slab would then be poured on-grade.
The advantages of such a control measure are that it is rela-
tively simple, efficient, and permanent. Disadvantages would be the
cost involved in the excavation, the purchase of material and the
expense in hauling it to the site.
E. Improved Slab Construction
Another technique by which the overall effectiveness of radon
daughter control measures could be enhanced would be improving the
*Although no field studies have been performed concerning lateral
diffusion, the cost-effectiveness calculations in Section V allow
for excavation to a distance of 3 feet from the foundation.
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34
quality control of slab pour (quality, reinforcement and thickness).
As the pore size present in the cement has a large influence on its
radon stopping ability, utilizing concrete with a low water to cement
ratio by weight (W/C) and dense aggregate material (such as granite or
marble) will decrease radon permeability.
Increasing the thickness of the concrete slab will, likewise,
reduce the radon diffusion rate, assuming this is the major pathway.
As radon gas has a relaxation distance of about 5 cm (2 inches) in a
standard concrete (density = 2.35 g/cm3), by doubling the thickness of
a normal 4-inch slab to 8 inches, 80 percent reduction in exhalation
is possible (see Figure 7). This technique is advantageous in that it
represents a passive control measure, thereby not permitting any occu-
pant interaction, and also because it does not require any major changes
in structural specifications. A disadvantage is the likelihood of
cracking in the slab which would provide a conduit for the underlying
radon. Also, if the piping should prove to be a major pathway for
seepage, much of the effectiveness of this measure would be negated.
Another innovative technique which may prove effective in
reducing radon diffusion is the laying of a perforated tile field under
a slab construction. The field would tie into a number of surface vents
which would permit the radon to bypass the slab and be diluted in the
open air. Although a reduction in indoor working levels is likely with
this technique, the lack of field work makes it impossible to estimate
the magnitude of such reduction and the cost involved with installation.
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35
FIGURE 7
FRACTIONAL REDUCTION IN THE RADON EXHALATION
RATE AS A FUNCTION OF CONCRETE SLAB THICKNESS
(assuming relaxation distance*
of 2 in. (5 cm) for concrete)
o.oi
DEPTH OF CONCRET SLAB (IN.)
*SEE DEFINITION, PAGE 31.
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36
The advantages and disadvantages of the control measures
discussed are summarized in Table 1. There are three major pathways
identified for radon exhalation into a structure. They are: 1) exhala-
tion through the concrete slab and/or flooring; 2) exhalation through
the walls of the structure; and 3) seepage in and around piping entering
the slab and flooring.
The first has been well-documented in experimental studies by
Culot, et al. (22), and Auxier, et al. (25). The second has also been
documented by Culot, et al., in their study of structures built on or
adjacent to uranium mill tailings in Grand Junction, Colorado. The
third pathway is under study at present by the Environmental Protection
Agency's Eastern Environmental Radiation Facility. Preliminary findings
to date indicate that this pathway could be a potentially significant
source of radon in structures (27). As this piping would be buried at
depths of at least several feet under the slab, it may serve as a path-
way for radon gas into the house. This potential radon pathway will be
studied further by EPA to determine the magnitude of the influx.
Some of the control measures discussed will have efficiencies
that are pathway-dependent. For example, sealing a concrete slab would
be effective for radon exhalation through the slab and possibly around
the piping (if applied properly), but not for any exhalation through
the walls. A crawl space, likewise, would be effective for the floor
and walls, and possibly the piping pathways. Excavation wouxd similarly
be effective at posing a barrier for the floor and wall pathways, but
probably not the piping pathway, if it should exist. Ventilation,
-------
TABLE 1
CONTROL MEASURES: ADVANTAGES AND DISADVANTAGES
CONTROL MEASURE
ADVANTAGES
DISADVANTAGES
FULL MEASURES
VENTILATED CRAWL SPACE
1-PASSIVE, LIFE-OF-HOUSE MEASURE
2-HIGH EFFECTIVENESS WITH PROPER
VENTILATION
1-EXPENSE ASSOCIATED W/CHANGES IN
HOME'S STRUCTURAL SPECIFICATIONS
2-BUYER'S OBJECTIONS ON AESTHETIC
OR OTHER GROUNDS
3-HIGHER ELECTRICAL COST FROM
INFILTRATION
POLYMERIC SEALANT
1-PASSIVE MEASURE
2-WITH PROPER APPLICATION, HIGH
EFFECTIVENESS ACHIEVED AT
RELATIVELY LOW COSTS
3-SEALANT PROVIDES ADDITIONAL
WATER-PROOFING
1-UNCERTAINTY AS TO LONGEVITY OF
SEALANT EFFECTIVENESS
2-THOROUGH APPLICATION NECESSARY
FOR EFFICIENT RADON REDUCTION
EXCAVATION AND
FILL (W/NOMINAL
FILL COST)
1-PASSIVE, LIFE-OF-HOUSE MEASURE
2-NO ALTERATION IN HOUSE PLANS OR
CONSTRUCTION PROCEDURES
NECESSARY
1-EFFECTIVENESS BASED ON THEORY ALONE
2-PROBLEMS ASSOCIATED WITH IMPROPER
COMPACTION OF FILL
3-RADON INFILTRATION ALONG PIPING
LAID UNDER SLAB
EXCAVATION AND FILL
(AT COMMERCIAL RATES!
SAME AS ABOVE
SAME AS ABOVE EXCEPT FOR HIGH COST
ASSOCIATED WITH FILL
ELECTRONIC & AIR EXCHANGER
1-SYSTEM DURABLE
2-LITTLE MAINTENANCE REQUIRED
3-PARTICULATE CONCENTRATION
REDUCED IN HOME
1-NON-PASSIVE
2-HIGH COST INVOLVED WITH OPERATION
3-OZONE RELEASED BY PRECIPITATOR
IMPROVED SLAB CONSTRUCTION
(8" SLAB!
1-PASSIVE, LIFE-OF-HOUSE MEASURE
2-VERY LITTLE ALTERATION IN CON-
STRUCTION PLANS REQUIRED
1-CRACKING IF IT OCCURS, WOULD NEGATE
MUCH OF EFFECTIVENESS
LIMITED MEASURES
ELECTRONIC AIR CLEANER
1-MINIMAL ELECTRICAL COST AND
MAINTENANCE NECESSARY
2-PARTICULATE CONCENTRATION
REDUCED IN HOME
1-NON-PASSIVE
2-OZONE RELEASED BY PRECIPITATOR
HEPA FILTERS
1-EFFECTIVE AT SMALL PARTICLE
SIZE RANGE
2-NON MECHANICAL PARTS, NO MAIN-
TENANCE NECESSARY
1-NON-PASSIVE
2-HIGH COST OF FILTERS
3-HIGH PRESSURE DROP (AS AIR FLOW
RATE INCREASES, EFFICIENCY DECREASES)
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38
however, would be uniformly effective for any pathway, as it removes
radon daughters after they are already present in the structure's
atmosphere.
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39
IV. IDENTIFICATION OF PARAMETERS USED IN EVALUATION
In order to facilitate an objective comparison and ranking of the
control measures that were reviewed, two parameters were chosen by which
each measure could be assessed. The two, cost and effectiveness, were
determined separately, but combined in the cost per percent reduction
ranking of the control measures. It should be stressed that although
this ranking is largely based on cost-effectiveness, there may be other
factors of importance to the builder or developer which may play a role
in the selection of a control measure. These may include building
costs and availability of equipment and labor. Whatever the method of
selection, the control measure chosen should achieve and maintain the
level of radon daughter reduction pursuant to existing guidance at the
time of implementation.
A. Cost
The cost associated with implementing control measures for
reducing radon progeny levels in homes is a combination of several
factors:
1. Capital Investment in Equipment or Structural Alterations
For air cleaners, this would include the cost of HEPA
filters and backup fans, or an electronic air cleaner, as well as any
duct work alteration needed. For crawl space construction, it would be
the additional expense inherent in building a house in this manner.
With polymeric radon barriers, the cost of the polymer and its
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40
application would be included. With excavation, costs would include
removal of the reclaimed phosphate soil and replacement with gravel or
soil fill.
2. Maintenance and Replacement Costs
These costs would largely apply to mechanical equipment,
such as air cleaners. HEPA filters, for example, would require periodic
replacement, while electronic air cleaners would require occasional
servicing and parts replacement. Other costs are intangible, such as
those involved with maintenance activities by the homeowner, while
others are unpredictable, such as reapplying a polymeric sealant. These
costs, although potentially significant, cannot be quantified definitively.
3. Cost of Electricity
This cost would be associated with the use of electronic
air cleaners, backup fans for HEPA filters, and for any additional
heating or cooling necessary to balance the additional infiltration or
makeup air used in some control measures.
B. Effectiveness
The effectiveness of control measures in reducing the activity
level of radon daughter products in a structure is measured in percent
reduction from levels which would exist without any control technology.
As many of the techniques discussed in this report have not been field
tested in residential structures for verification, the efficiencies
used are rough estimates which would be expected to vary accordingly.
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41
V. COST ANALYSIS
A cost analysis on the utilization of radon daughter control
technology is critical to any decision-making process in this area.
As with pollution control equipment in industry, the cost of radon
daughter control measures would probably be passed on to the consumer,
or the homeowner in this case (except when government subsidization is
involved). In order to minimize expenses, the builder must first deter-
mine, from available data, which control measures reduce the radon
progeny concentrations down to acceptable residential levels, and
second, which of these measures can be implemented and maintained at
the 'least cost.
The cost figures utilized in this analysis are best average esti-
mates based on data derived from literature, government, and private
industry. Because of their different sources, a degree »f variability
is to be expected for the actual cost of application in specific local-
ities of the country. Another source of variability is inherent in the
use of an average value. Such an estimate is applicable only for an
average site and, therefore, cannot be generally applied. The "plus"
(+) sign is utilized in Table 2 to permit more flexibility in estimating
cost values. It signifies that one or more components of the total
cost represent minimum values that are likely to be higher based on
nonquantitative information. All cost figures utilized in this analysis
are present dollar values and are discounted at rates of 0 and 6 percent.
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42
There are numerous components of the total cost, both tangible and
intangible, which will be considered. The capital cost is the most
important component to the prospective builder. This expenditure would
be made by him to implement the control measure. With mechanical equip-
ment, such as air cleaners, maintenance and replacement costs also become
important in calculating the total cost. As most equipment of this type
has a useful life of roughly ten years (19), some maintenance and possi-
bly replacement will be required on this equipment over the average life
span of a building. Another component is electrical cost which is,
again, primarily associated with the use of mechanical air cleaning
equipment. Due to probable increased air infiltration in homes with
crawl spaces, there would be additional electrical costs as a result of
the corresponding increase in the use of air-conditioners or electrical
heating units.
A. Ventilation Costs
Table 2 shows that the capital cost for the installation of a
HEPA filter is about $350. This cost includes the cost of the filter,
filter holder, backup fan, and actual installation into the residential
heating/cooling system (28). If an optional prefilter is installed
upstream of the HEPA filter, an additional $50 cost will be accrued.
As this system has no mechanical parts, the maintenance costs would
consist of replacing the filter periodically. The length of time
between replacement will vary according to the particulate concentration
in the house, the air flow characteristics of the ventilation equipment,
-------
TABLE 2 4
ESTIMATED AVERAGE COST OF RADON DAUGHTER CONTROL MEASURES
CONTROL MEASURE
AIR CLEANERS:
HEPA
ELECTRONIC
ELECTRONIC &
AIR EXCHANGE
VENTILATED CRAWL SPACE
POLYMERIC SEALANT
EXCAVATION AND FILL
(TO 10' DEPfHJ:
COMMERCIAL FILL RATE
W/NOMINAL FILL COST
(TO 5' DEPTH):
COMMERCIAL FILL RATE
W/NOMINAL FILL COST
IMPROVED SLAB CONSTRUCTION
CAPITAL
COST
$ 350
300
800+
450
400-1300
2100-3700
1575-1850
1100-1900
800- 950
450
ANNUAL
MAINTENANCE &
REPLACEMENT
COST
$ 100
20+**
20+
NONE
UNDEFINED**
NONE
NONE
NONE
NONE
NONE
ANNUAL
ELECTRICAL
COST
UNDEFINED
17
140+
UNDEFINED
NONE**
NONE
NONE
NONE
NONE
NONE
ANNUAL AVG.
OPERATING
COST
$100
37+
160+
NONE**
NONE**
NONE
NONE
NONE
NONE
NONE
TOTAL COST
DISCOl
0%
$3250-5250
1400-2200
5600-8800
450
400-1300
2100-3700
1575-1850
1100-1900
800- 950
450
[30 - 50 YRS)
NT RATE
6%
$1725-1925
800- 900
3000-3325
450
400-1300
2100-3700
1575-1850
1100-1900
800- 950
450
.p-
u>
•ASSUMING 1000 SO. FT. FLOOR AREA AND PRESENT DOLLAR VALUE.
**SEE TEXT FOR EXPLANATION;"+" SIGNIFIES THAT THE ESTIMATE IS GIVEN MOST LIKELY A MINIMAL ONE, ALTHOUGH THE
ACTUAL AVERAGE IS UNDEFINABLE USING AVAILABLE COST DATA.
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44
*
and whether a prefliter is installed. Assuming a replacement rate of
once a year and a unit cost per filter of $100 (28), the expense to the
homeowner per year and the total over the range of 30-50 years (the
assumed life span of the structure) would be approximately $100 and
$1725-$1925, respectively (assuming a 6 percent discount rate, and
neglecting price increases and electrical consumption by the fan). The
average total cost ($1825) coupled with an approximate lifetime reduc-
tion efficiency of 40 percent for radon progeny results in an average
$45 cost per percent reduction (see Table 3).
A capital cost estimate of $300 is given for electronic air
cleaners. This figure includes the estimated cost of the air cleaning
unit ($250), and the cost of a prefilter ($50) (29). This estimate is
probably an upper limit one, as in many cases (especially in new home
construction) the cost of installing a prefilter and special duct work
to improve air flow into a unit can be minimized through standardization
and large volume purchases. The maintenance cost for an installed
electronic air cleaner would include filter changes for the prefilter
(assumed to be once a quarter at $5 a filter), and parts replacement or
repair for the electrostatic unit. The former comes to $275-$315 (dis-
counted at 6 percent) over 30-50 years while the latter is difficult to
quantify. It would be expected, though, that a warranty would be in
effect for the first few years after installation. The cost of the
electricity needed to operate the air cleaner on a 24-hour basis is
*The replacement rate would decrease through the use of a renewable or
cleanable prefilter, although the tradeoff would be the additional
cleaning maintenance and initial capital cost.
-------
TABLE 3
AVERAGE COST PER PERCENT REDUCTION OF RADON DAUGHTER LEVELS
CONTROL MEASURE
AIR CLEANERS:
HEPA
ELECTRONIC
ELECTRONICS
AIR EXCHANGE
VENTILATED CRAWL SPACE
POLYMER 1C SEALANT
EXCAVATION AND FILL
(TO 10' DEPTH):
COMMERCIAL FILL RATE
W/NOMINAL FILL COST
(TO 5' DEPTH):
COMMERCIAL FILL RATE
W/NOMINAL FILL COST
IMPROVED SLAB CONSTRUCTION
ESTIMATED
PERCENT
RADON PROGENY
REDUCTION
40%
40%
60%
80%+
80%
80%
80%
40%
40%
80%+
TOTAL
COST
(30-50 YRS) *
$1725-1925
800- 900
3000-3325
450
400-1300
2100-3700 *
1595-1850
1100-1900
800- 950
450
AVERAGE
COST/PERCENT
REDUCTION
$43-48($45)
20-23($21)
50-55($52)
6($ 6)
5- 16($ 10)
26- 46($ 36)
20- 23($ 22)
28- 48($ 38)
20- 24($ 22)
6($ 6)
RANK
FULL LIMITED
MEASURE**MEASURES
5
2
5 6
1 . 1
2 3
4
3
4
2
1 1
•WITH 6% DISCOUNT RATE.
** MEASURES WITH ESTIMATED REDUCTION OF EFFICIENCIES OF 50% OR MORE.
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46
difficult to project. With an electrical consumption rate of
50 watts over a one-year period (440 kwh) and an electrical cost of
$.03711/kwh (present rate charged in the Polk County area by Florida
Power and Light Co. (30)), the annual cost would be approximately $17.
The total discounted cost thus comes to about $800-$900 over a 30-50
year period which results in a cost/percent reduction of $21 (assuming
a 40 percent efficiency).
An electronic air cleaner can be utilized in combination with
an air exchange vent in order to obtain a substantial reduction in radon
daughter activity (upwards of 60 percent at 25 percent air exchange).
Because larger capacity aAr-conditioning units are necessary to handle
the continuous influx of warm air, the capital cost largely would be
the cost-differential between the normal 2-ton unit (24,000 BTU) and a
3-ton unit (36,000 BTU), which would be needed to compensate for the
air exchange. As Table 2 shows, this cost is approximately $500 (31)
assuming that the cost of the exchange vent is minimal. The total
capital cost is the sum of this value and the capital cost for the
electronic air cleaner.
The annual electrical cost is estimated at $120 using an
electrical consumption differential of about 3000 kwh/yr between the
2-ton and 3-ton units and a charge of $0.04/kwh (37). The total cost
for electrical power shown is again, a combination of this value and
that for the electronic air cleaner.
As it is probable that the maintenance and replacement costs
associated with the use of the larger air-conditioning unit will not be
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47
significantly higher, the costs represented are those of the air
cleaner alone. The "plus" beside the cost figure represents the addi-
tional capital cost which would be associated with the use of special
dehumidifying equipment. Because an air exchanger of this magnitude
will introduce a large moisture load on the air-conditioning system,
the normal dehumidifying cycle may not be sufficient to treat the air.
As electronic air cleaning efficiency decreases with an increase in
humidity, such equipment would be necessary. No cost estimates were
possible because such equipment is not normally applied to residential
structures. However, such a unit because of its sophistication, would
likely increase the capital and electrical power cost significantly.
Disregarding the dehumidifier cost, the total discounted cost
for the application of this system is projected at $3000-$3325 for a
30-50 year .period at a cost per percent reduction of $52.
B. Cost for Ventilated Crawl Space Construction
The capital cost for constructing a crawl space of standard
dimensions for a single story detached home is approximately $450 over
the cost for a slab-on-grade construction (32). The total cost of $450
was derived from these projected costs which results in a $6 per percent
reduction (assuming 80 percent reduction).
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48
C. Excavation Costs
The capital cost for the excavation and filling of a 14,260
cubic foot (46' x 31' x 10') pit on a 1000 square foot single home site
(40* x 25') would consist of the following cost components:
Commercial Rates -
Excavation (32,33): $ 475 ($0.90/yd3)
Hauling and fill cost (33):
dirt/sand fill, or 1635 ($3.10/yd3)
limerock fill 3225 ($7.62/yd3)
TOTAL * $2100 or $3700
W/Nominal Fill Cost -
Hauling and fill cost: $1100 - $1375 ($2.10-$2.60/yd3)
TOTAL = $1575 - $1850
The estimate of $0.90/yd3 for excavation is taken from the 1974
HUD Regional Costs Data Handbook for Region IV (including Florida).
This figure, although not adjusted for inflationary increases, does
compare favorably with estimates of $0.70/yd3 and $1.00/yd3 from exca-
vating contractors in the Polk County area. The cost of the replacement
fill and the hauling needed to transport it to the site (assuming a
15-mile distance) was determined from estimates made by private con-
tractors. The figure of $3.10/yd3 for dirt/sand and $7.62/yd3 for lime-
rock were the lowest estimates received. Limerock is considerably
cheaper due to its availability in the central Florida area while gravel
must be shipped by rail from out-of-State. These two types of fill were
used in making the cost estimate because they were found to be the least
expensive. Their density and porosity characteristics have not been
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49
determined so that relaxation distances for radon diffusion could not
be ascertained. If these fills should show relaxation distances less
than 4.9 feet, then less excavation would be necessary. Of course,
the reverse would also be true for longer relaxation distances. If
less excavation is found to be necessary because of either less radon
emanation at the site or use of fills with shorter relaxation distances
for radon, total costs can be reduced considerably. Because basic
costs are generally related to the volume excavated, transported, and
filled, excavation to a depth of only five feet halves the cost while
excavation of only three feet reduces the cost by a factor of about
three.
As a properly excavated and filled pit should not require any
later maintenance, the total cost would merely be the capital cost.
Thus, with a total cost of $2100-$3700, the cost per percent reduction
would be $26-$46 per percent (assuming 80 percent radon level reduction).
If the contractor has access to fill which can be obtained at
a nominal cost, total costs can be reduced considerably. As no data is
available on what the cost range would be in such a situation, $2.10-
$2.60 was chosen as a representative range for the cost of the fill and
the hauling involved (assuming a fill cost of $0-$0.50/yd3). The total
cost arrived at then, is $1575-$1850 leading to a cost per percent
reduction of $20-$23.
D. Polymeric Sealant Cost
The,cost range for polymeric sealants, $400-$1300, shown in
Table 2, is based on a square footage cost range of $0.40-$1.30 assuming
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50
a 1000 square foot home. The upper range of this estimate is derived
from field studies performed by Culot, et al. (22), at Colorado State
University in 1972. In their study, Omnitech epoxy sealant was
utilized at a cost of $1.30 per square foot of multi-coat application
(as described previously in this report).
As the CSU procedure applies to an existing structure, the
actual cost should be less for a new structure as no flooring would
have been built over the slab before sealing. The application process
itself, should also be easier, not being hindered by any obstructions
such as walls and woodwork. An "integral coverbase" is not included in
this cost estimate, although it was in the'original as many of the new
polymers commercially available can be applied directly to a properly
prepared slab. Although these factors would probably reduce the total
cost to below a dollar a square foot, inflationary increases over the
past four to five years would probably negate much of these savings.
Thus, a cost of $1.30 per square foot has been retained as the upper
limit for polymeric sealant use.
The Lawrence Livermore Laboratory (24) analysis of nine poly-
meric sealants being tested by the Bureau of Mines showed that Hydrepoxy
300, manufactured by the Acme Chemicals and Insulation Company, showed
the best results in permeability, fire, and other laboratory tests.
Communications with Acme (34) provided us with a cost estimate of approx-
imately $0.41/ft.2 assuming application of three layers (.006" thickness)
*
Omnitech Industries, Inc.
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51
of Hydrepoxy 300 with proper slab preparation and labor charge included
as outlined below:
1. The application of two coats of Hydrepoxy 300 at .006" dry
thickness each coat to most masonry surfaces will cost approximately
$0.10 per square foot to the construction trade, and approximately
$0.15 per square foot to the do-it-yourself homeowner. Application to
rough or porous cement block can increase this cost by some 25 percent.
2. Preparation is generally done by wire brushing, sand-
blasting, or acid etching to clean and rough up smooth surfaces.
3. A typical family house (assumed to be 1000 sq. ft. in area)
would probably have the following requirements to coat a poured concrete
slab:
a. Materials - assuming 1000 square feet of floor @
$0.15 for 3 coats = approximately $150.
b. Equipment - $25 (includes rollers, brushes, etc.).
c. Labor - Preparation - 5 to 10 hours
Application - 12 hours
Cleanup - 1 hour.
Total labor required = 18-23 hours at .$10/hr.
Total labor cost = $18 - $230
Total cost = $350 - $400 ($0.35 - $0.40/sq. ft.).
This cost range of $0.40 - $1.30 square foot is also supported
by estimates made in the 33rd Annual Edition for 1975 of "Building
Construction Cost Data" (Robert Snow Means Co., Inc.). A range of
$0.50 - $1.50 per square foot was -ascribed to polymeric sealant appli-
cation by the editors of this reference manual (35). Actual costs of
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52
materials and labor, however, will vary widely according to locality,
polymer type, and manufacturer.
The costs for maintenance and replacement are listed as
"undefined" because the durability and long-term effectiveness of
polymeric sealants under normal residential usage has not yet been
determined. .Without proper protection, such as the use of a protective
overcoat and substrate, the manufacturers of Hydrepoxy 300 project a
minimal five-year life without cracking or peeling. In a number of
homes, a monolithic (nonfooted) slab is utilized which tends, over the
years, to settle and crack. Application of sealants over such surfaces
will probably be only a temporary measure and reapplication will be
necessary.
E. Cost of Improved Slab Construction
The cost for increasing the slab thickness of a 1000 square
foot structure from 4 inches to 8 inches, listed as $450 in Table 2, is
based on an estimated $1 cost per square foot (32). The differential
between this figure and that for a conventional slab ($0.55 per square
foot) results in a cost of $0.45 per square foot or $450 for a 1000
square foot structure. This cost includes the poured concrete (2500
Ibs), reinforcement wire (6" x 6", #10) and trowel finish. With a
projected radon daughter reduction efficiency of about 80 percent, a
cost per percent reduction of $6 results, as Table 3 shows.
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53
VI. MODEL FOR DECISION-MAKING
In order to address the implementation of the control measures
discussed, a model for decision-making is presented. This model pre-
sumes the interaction of local and State health and housing agencies
in the decision-making process. This situation, in fact, does not
exist in the State of Florida, neither the State nor the counties
involved having the authority to regulate construction on affected land
at the present. However, notwithstanding the lack of governmental
interaction, the decision-making process described could be of use to
prospective developers in these areas.
In Figure 8, a flow diagram is presented which describes the
options which would be available for a builder or developer when a
potential radon diffusion problem is identified. The diagram is based
on data in Tables 2 and 3, as well as survey experience from field
studies. The outdoor gamma levels utilized in the decision process are
based on the interim guidelines, issued by the Office of Radiation
Programs, EPA, in January 1976 and amended in June 1976 for publication
in the Federal Register (41FR26066) (36). These interim recommendations
are subject to change at a later date through the development of more
discriminating measurement techniques or through additional data
collection.
A. Decision Process Summary
PICK HOMESITE - Prerogative of builder or developer.
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54
FIGURE 8a
MODEL FOR DECISION MAKING FOR THE CONTROL OF
INDOOR RADON DAUGHTER LEVELS IN NEW STRUCTURES
DUE TO EMANATION THROUGH THE FOUNDATION
IS SITE
ON PHOSPHATE
LAND?
DECISIO
BY BUILDER OR
DEVELOPER
CONVENTIONAL
CONSTRUCTION
RELOCATE HOUSE
SITE AS FAR AWAY
AS PRACTICABLE
FROM SUCH AREA
CONVENTIONAL
CONSTRUCTION
-------
55
FIGURE 8b
MODEL FOR DECISION MAKING FOR THE CONTROL OF INDOOR RADON DAUGHTER
LEVELS IN NEW STRUCTURES DUE TO EMANATION THROUGH THE FOUNDATION (CONT.)
LEVEL SIGNIFICANTL
HIGHER THAN ..
CONSIDER LIMITED
CONTROL MEASURES
CONSIDER FULL CONTROL
ASURES OR COMBINATIONS
THERE OF
CONSIDER PROBABLE
WORKING LEVEL MAGNITUDE
(AS DERIVED FROM INTERIM
GUIDELINE GRAPH
CONSTRUCT OR ADAPT
HOME W/CONTROL
MEASUREIS)
FULL CONTROL
MEASURE
PRACTICABLE?
AREALTERNA
SITES AVAILABLE
* PRACTICABLE?
HEALTH DEFT. FOR
DECISION
STATE OR COUNTY
HEALTH DEPT. FOR
DECISION
CONSIDER
COMBINATION OF
CONTROL MEASURES
IS SUCH
A COMBINATION
PRACTICABLE?
IS THERE
ANY OTHER TECH.
BY WHICH WL CAN
BE REDUCED?
CONSTRUCT OR ADAPT
HOME W/CONTROL
MEASUREIS)
NO FURTHER CONTROL
MEASURE NECESSARY
NO FURTHER CONTROL
MEASURE NECESSARY
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56
IS SITE ON PHOSPHATE LAND?* - This information should be
obtained from State and county authorities. If the site is determined
definitely not to be on phosphate land, normal construction can be
initiated. If the site is on phosphate.land or if there is any uncer-
tainty (due to missing records, poor filing, etc.) as to this question,
an on-site gamma radiation survey is recommended.
ON-SITE GAMMA SURVEY - To be performed as outlined in EPA's
Interim Recommendations for Gamma Exposure Levels at New Structure
Sites on Florida Phosphate Lands (36). (See Appendix B.)
ARE "HOT SPOTS" PRESENT? - This information would be obtained
from the preceding gamma survey of the site. Because the interim guide-
lines are based on an average of the gamma levels measured on-site,
anomalous elevated readings at a few points may raise the average
reading so that it exceeds the recommended average gamma exposure level
of 10 yR/hr. If such a situation does exist, the builder or developer
should choose another site on the lot which would locate the proposed
residence as far from these locations as practicable, or remove surface
or near surface materials, such as phosphate slag, which may cause
anomalous readings. The new or altered site would then be surveyed.
ARE OUTDOOR GAMMA EXPOSURE LEVELS AT THE SITE WITHIN ACCEPTABLE
LIMITS? - If the average gamma exposure level is below the interim
guideline of 10 yR/hr and no significant hot spots are present, conven-
tional construction is suggested. Should the average level be equal to
*For this report, phosphate land is defined as land which contains
reclaimed mining overburden at or near the surface, and outcroppings
of phosphate matrix material where it occurs.
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57
or above this recommended guideline, the builder, developer, and/or
appropriate county and State health agencies should decide whether:
1) control measures should be considered, 2) construction should be
delayed pending further study, or 3) an alternate site should be found
for construction. The first possibility, which this report addresses,
is diagrammed fully in Figure 8b and is discussed further in the
following section. It should be emphasized that the interim guidelines
are subject to change as more data becomes available.
B. Control Measures
IS ON-SITE GAMMA LEVEL SIGNIFICANTLY HIGHER THAN GUIDELINE? -
In order to introduce a degree of flexibility into the selection of
control measures, an allowance needs to be made for the use of limited
measures (efficiencies less than 50 percent). Because marginally
elevated gamma readings (e.g., in the 10-20 mR/hr range) iiay be reduced
effectively by these measures, their use could be justified. Conversely,
with significantly elevated gamma readings, more efficient control
measures are necessary to reduce potential indoor working levels to
acceptable values. Such measures, termed full measures, have reduction
efficiencies of at least 60 percent. With a working level approximation
derived from the interim guidelines using outdoor gamma data, the pro-
spective builder should first, determine what reduction efficiency he
will need to reduce in-house radon daughter activities to acceptable
levels, and second, what control measure or combination of control
measures will, provide this level of efficiency. Once such a decision
has been made, a test home, incorporating these measures, should be
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58
built to allow for an actual survey. For single home construction, an
acceptable in-house survey measurement would permit normal occupancy.
Likewise, for multi-home construction, continued construction could be
permitted if measured activities were low enough. If a survey still
showed elevated levels, the responsible State or county agency would
make the decision as to whether to grant a waiver or instruct the
builder to institute an improved control program. There is also an
option that allows the builder to develop innovative technologies by
which radon working levels can be reduced in homes. Should acceptable
daughter activities still be unattainable, an effort should be made to
find another site for the structure(s). In the case of single home
construction, a possible approach on the part of local government would
be to allow the structure to be occupied pending further study of con-
trol measures. This type of flexibility on the part of the local
government agencies is integrated into this decision process in order
to allow them to be better able to handle cases on an individual basis.
It is expected that situations will arise where such flexibility will
serve to improve the performance and results of a control program such
as this one.
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59
REFERENCES
1. "Preliminary Findings - Radon Daughter Levels in Structures
Constructed on Reclaimed Florida Phosphate Land," Office of
Radiation Programs, U.S. Environmental Protection Agency,
Technical Note ORP/CSD-75-4 (September 1975).
2. Guimond, R.J. and S.T. Windham, "Radioactivity Distribution in
Phosphate Products, By-Products, Effluents, and Waste," Office
of Radiation Programs, U.S. Environmental Protection Agency,
Technical Note ORP/CSD-75-3 (August 1975).
3. Private communication with Sam T. Windham, Eastern Environmental
Radiation Facility, Montgomery, Alabama, Office of Radiation
Programs, U.S. Environmental Protection Agency.
4. Jacobi, W., "The Dose to the Human Respiratory Tract by
Inhalation of Short-Lived Rn-222 and Rn-220 Decay Products,"
Health Physios 10:1163-1174 (1964).
5. Raabe, O.G., "Concerning the Interactions that Occur Between
Radon Decay Products and Aerosols," Health Physios 17:177-185
(1969).
6. Haque, A.K.M.M. and A.J.L. Collinson, "Radiation Dose to the
Respiratory System Due to Radon and its Daughter Products,"
Health Physios 13:431-443 (May 1967).
7. Mercer, T.T. and W.A. Stowe, "Radioactive Aerosols Produced by
Radon in Room Air, in Inhaled Particles-Ill," Proceedings of an
International Symposium organized by the British Occupational
Hygiene Society, London, edited by W.H. Walton, Unwin Brothers
Ltd., Surrey, England (September 14-23, 1970).
8. Harley, N.H. and B.S. Pasternack, "Alpha Absorption Measurements
Applied to Lung Dose from Radon Daughters," Health Physios
23:771-782 (1972).
9. Jacobi, W., "Relation Between Cumulative Exposure to Radon
Daughters, Lung Dose and Lung Cancer Risk," Preceedings of
Noble Gases Symposium, Las Vegas, Nevada (September 24-28, 1973).
10. Jacobi, W., "Relations Between the Inhaled Potential a-Energy of
Rn-222 and Rn-220 Daughters and the Absorbed a-Energy in the
Bronchial and Pulmonary Region," Health Physios ^3:3-11, No. 7
(1972)..
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60
11. Handley, T.H. and C.J. Barton, "Home Ventilation Rates: A
Literature Survey," ORNL-TM 4318 (September 1973).
12. Kaye, S.V., "Plowshare Research and Development Progress Report
for the Period January 1, 1973 - May 31, 1973: Evaluation of
Radiological Exposure to Population," Memorandum to Distribution,
ORNL (April 19, 1973).
13. Johnson, R.H., Bernhardt, D.E., Nelson, N.S., and H.W. Galley, Jr.,
"Assessment of Potential Radiological Health Effects from Radon
in Natural Gas," Office of Radiation Programs, U.S. Environmental
Protection Agency, EPA-520/1-73-004 (November 1973).
14. Johnson, R.H., Bernhardt, D.E., Nelson, N.S., and H.W. Galley, Jr.,
"Radiological Health Significance of Radon in Natural Gas,"
Proceedings of the Noble Gases Symposium, Las Vegas, Nevada
(September 24-28, 1973).
15. Department of Housing and Urban Development, Federal Housing
Administration, Sarasota Regional Office, Publication RR-250.
16. Private communication with representative, Bryant-Clary, Inc.,
Tampa, Florida.
17. American Society of Heating, Refrigeration and Air-Conditioning
Engineers' Handbook of Fundamentals, "Air Contaminants,"
Chapter 10, pp.177-185 (1972).
18. American Society of Heating, Refrigeration and Air-Conditioning
Engineers' Equipment Handbook, "Air Cleaners," Chapter 10,
pp. 10.1-10.11 (1975).
19. Private communications with William Galagher, Honeywell Corporation,
McLean, Virginia, and Honeywell Laboratories, Minneapolis, Minnesota.
20. Honeywell Corporation, "Electronic Air Cleaner-Application and
Installation," #70-9723.
21. Private communication with Frank Simon, Honeywell Corporation,
Minneapolis, Minnesota.
22. Culot, M.V.J., Olson, H.E., and K.J. Schiager, "Radon Progeny
Control in Buildings," Colorado State University, EPA RO 1 EC0015.3
and AEC AT (ll-l)-22733 (May 1973).
23. Franklin, J.C. and L.T. Nuzman, "Polymeric Materials for Sealing
Radon Gas into the Walls of Uranium Mines," Spokane Mining
Research Center, U.S. Bureau of Mines, RI 8036, HO-220006, and
HO-230007 (1975).
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61
24. Hammon, H.G., Ernst, K., Gaskill, J.R., Newton, J.C., and
C.J. Morris, "Development and Evaluation of Radon Sealants for
Uranium Mines," UCRL-51818, Lawrence Livermore Laboratory,
USBM H0232047 (May 29, 1975).
25. Auxier, J.A., Shinpaugh, W.H., Derr, G.D., and D.J. Christian,
"Preliminary Studies of the Effects of Sealants on Radon Emanation
from Concrete," Health Physios _27_:390-392, No. 4 (1974).
26. Private communication with Donald F. Hubert, Acme Construction
Company, New Haven, Connecticut.
27. Field Study Report, Eastern Environmental Radiation Facility,
Montgomery, Alabama, Office of Radiation Programs, U.S.
Environmental Protection Agency (March 1976).
28. Private communications with:
Bryant-Clary, Inc., Tampa, Florida
Air Guard Industries, Inc., Louisville, Kentucky
Cambridge Air Filters, Syracuse, New York
American Air Filer Co., Louisville, Kentucky
Continental Air Filter Co., Louisville, Kentucky
29. Private communications with:
Lennox Industries, Inc., Decatur, Georgia
Airtemp Corporation, Dayton, Ohio
Bryant-Clary, Inc., Tampa, Florida
Honeywell Corporation, Minneapolis, Minnesota
30. Private communication with Public Information Department, Florida
Power and Light Company.
31. Private communication from Harry Allen, Public Information
Department, Florida Power and Light Company.
32. Department of Housing and Urban Development, Regional Cost Data
Handbook, Region IV, Atlanta, Georgia (1974).
33. Private communications with:
American Crane Co., Tampa, Florida
Blue Fill Paving and Asphalt, Lakeland, Florida
Cams Contracting, Bartow, Florida
Windgate Co., Tampa, Florida
Colorock Co., Tampa, Florida
34. Private communication from Donald F. Hubert, Sales Engineer,
Acme Chemicals and Insulation Company to Richard L. Immerman,
Research Assistant, Harvard University Kresge Center for
Environmental Health (February 12, 1976).
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62
35. Godfrey, R.S., Editor-in-Chief, "Building Construction Cost
Data, 1975," 33rd Annual Edition, Robert Snow Means Company,
Inc., 100 Construction Plaza, Duxbury, Massachusetts (1975).
36. "Interim Recommendations for Radiation Levels," Office of
Radiation Programs, U.S. Environmental Protection Agency,
Federal Register 4-1:26066 (June 24, 1976).
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APPENDIX
EFFECTIVENESS OF AIR CLEANING IN THE REMOVAL
OF RADON DAUGHTER PARTICULATES: A MODEL
-------
EFFECTIVENESS OF AIR CLEANING IN THE REMOVAL
OF RADON DAUGHTER PARTICULATES: A MODEL
Because little experimental work has been performed on the
effectiveness of radon daughter particulate removal by air cleaners in
residential settings, modeling was chosen as a technique by which a
rough approximation of effectiveness could be determined. These approx-
imations of effectiveness are used in this report to compare relative
working level reductions between various air cleaners and various
ventilation rates. The function of the model is to determine what effect
air cleaners will have on the equilibrium actiyity level of the daughter
particulates. Air cleaning efficiencies approximating those found in
HEPA filters and electronic air cleaners were used as they have been
found to be critical for radon daughter particulates. The various para-
meters used, the assumptions made and the calculations performed are
discussed in the following annotated calculations.
Determination of Radon Daughter Activities and Equilibrium Ratios With
and Without Air Cleaners
Assumptions:
1. Natural air infiltration rate = 1 air change/hour.
2. Electronic and HEPA air cleaners 80 percent efficient for
removal of radon daughter particulates with once-through cleaning.
3. The plateout factor, the fraction of the radon daughters
removed by adhesion to macro-surfaces (walls, flooring, furniture, etc.),
will be ignored in calculations as it has not been well-defined for
residential situations and because it will be substantially the same for
-------
A-2
structures with or without air cleaners. Evans (1) indicates that in
mine shafts, a deposition factor of 0.7 h"1 was measured. He indicates,
however, that lower deposition rates would be expected in structures
due to lower air flow rates and lower particulate concentration (not-
withstanding the possibility that this could be offset somewhat by
electrostatic attraction for particles than the ribs, floors, and walls
of a mine shaft) .
Calculations ;
1. To determine radon daughter activities and equilibrium ratios
without air cleaners -
A,= A, N
1"-« A, + A
1 d- v
where,
A, = Activity of RaA
A_ = Radon activity/structure volume (1.0 or unity)
N, = Atoms of RaA in structures
a
\L = Decay constant for RaA (3.85x10"3 s"1)
A = Infiltration constant (2.8x10""* s"1)
0.93
Al Xd
A0 = V " - 2
*2 "2 "d2 d2
where,
A- = Activity of RaB
N, = Atoms of RaB
d2
-------
A-3
A, = Decay constant for RaB (4.27X10-1* s l)
d2
= 0.56
where,
A., =
N.
Activity of RaC
Atoms of RaC
= Decay constant for RaC (5.8x10 ** s"1)
= 0.38
RADON:RADON
Daughter Activity Equilibrium Ratios
Radon
RaA
RaB
RaC
Ratio
Rn
Daughters
1
.93
.56
.38
Ratio
Rn
Daughters
(Haque and Collison
1
.9
.5
.35
(2))
As the Table shows, the equilibrium ratios of the radon daughter
activities to the radon activity for these calculations correspond to
values calculated by Haque and Collison (2) for a structure with
"adequate" ventilation. By determining these daughter/parent ratios
for a structure with an air cleaner, a measure of the reduction in
daughter product activity can be determined.
-------
A-4
2. To determine radon daughter activities and equilibrium ratios
with air cleaners:
Al = V Hd. = X. - X, - X (AR = 1'° or
11 d- f v
where far electronic and HEPA air cleaners,
Aj = Filtration constant corresponding to an 80 percent
efficiency for radon daughter particulates removal
(3.
= 0.84
AiV,
X£
A2 = 0.34
A3
= 0.17
Ratio of daughter activities to radon activity - li .84: .34:.17
Table A-l provides calculations for determining working levels
for daughter activities in structures with and without the use of air
clearners.
-------
A-5
Table A-l
Determination of Working"Level
Reductions With and Without Air Cleaners*
Radionuclide
Rn
RaA
RaB
RaC
Air
Cleaner
None
Electronic &
HEPA
None
Electronic &
HEPA
None
Electronic &
HEPA
None
Electronic &
HEPA
Concentrations
pci/1
1
1
.93
.84
.56
.34
.38
.17
Atoms /I
1.77xl04
9.08
8.20
48.05
29.17
24.86
11.12
Alpha
Energy per
Atom (MeV)
—
13.68
7.68
7.68
Total Potential
Alpha Energy
per liter (MeV)
—
124
112
369
224
190
85
Total None
Electronic &
HEPA
683 MeV
421 MeV
As total alpha energy is directly proportional to working levels (1 WL
defined as 1.3 x 105 MeV alpha/1) then:
421
% reduction w/electronic & HEPA air cleaners = 100% - (—5- x 100) - 38%
boJ
^Assuming attached and unattached ions are ventilated and removed at the
same rate. For HEPA filters utilizing a high effective ventilation rate
(>2-3 air changes Air), though, an increased tracheo-bronchial dose would
be realized from the elevated free ion fraction. For electronic air
cleaners the opposite would be more likely with almost complete removal of
RaA free ions to be expected in the electric field.
-------
A-6
Utilization of Graphic Representation;
The curves in Figures A-l and A-2 are derived from the preceding
A
calculations. Figure A-l provides a radon-222 "equilibrium value" in
pCi/m for known emanation and ventilation rates. An equilibrium con-
centration (pCi/m3) can be calculated for the structure assuming a
known volume or height. The graph has primarily been utilized in this
report to determine radon daughter reduction efficiencies, an example
of which is provided at the end of this section.
Figure A-2 provides a measure of the radon daughter level (WL/100
pCi liter radon-222) as a function of effective ventilation rate. By
comparing the working level measurement for a conventional residential
situation against one with air cleaning equipment, a reduction effi-
ciency for the air cleaner can be approximated. As an example, a
reduction efficiency determination encompassing both graphs is provided
below for the hypothetical utilization of a combination air exchanger
and electronic air cleaner.
Determination of Radon Daughter Reduction Efficiency from Combined
Electronic Air Cleaner and Outside Air Exchange System
Assumptions;
Air flow rate through ventilation system - 1.5 air changes/hr.
Percentage makeup air - 25 percent.
Efficiency of electronic air cleaner - 80 percent.
Natural air infiltration rate - 1.0 ac/h.
Air changes per hour - 1.4 (radon only).
Total effective air changes per hour - 2.3 (radon and daughters).
*In this case, the equilibrium value denotes the equilibrium concen-
tration of radon-222 in the air volume of the structure overlying a
square meter of floor space.
-------
A-7
9
8
7
6
5
4
CM
O
a.
LJJ
cn
CO
1x104
9
8
7
6
5
4
3
a
111
CM
CM
CM
1x103
9
8
7
6
1x102
FIGURE A—1
EFFECT OF NATURAL VENTILATION ON
RADON CONCENTRATION IN STRUCTURES
(FOR RADON DIFFUSION RATES NOTED)
I
I
12345
NATURAL VENTILATION (AIR CHANGES/HR.)
-------
FIGURE A—2
WORKING LEVELS (WL) PER 100 pCi PER LITER OF
RADON-222 VS EFFECTIVE VENTILATION RATE
CM
z
o
Q
<
tc
cc
Ul
oc
Ul
a.
I
j
a
w
UJ
O
DC
i
00
234567
EFFECTIVE VENTILATION RATE (AIR CHANGES PER HOUR)
8
10
-------
A-9
From Figure A-2 an increase of 0.4 ac/hr from a total effective
ventilation of 1.0 to 1.4 ac/yr gives an approximate reduction of
17 percent in the number of working levels per 100 pCi/1 of radon-222.
As Figure A-l shows, 1.4 air changes per hour also leads to a radon
source term reduction of 26 percent, using 1.0 ac/h, again, as a base-
line. Because the radon source term reduction and the working level
reduction are additive (Figure A-2 relates only to the effect of ventil-
ation and air cleaning on radon daughters while Figure A-l relates to
the radon source term itself), a combined reduction in the working
level of 43 percent is calculated for the air change system.
In order to determine the combined efficiency of the electronic
air cleaner and an outside air exchange system, the effective ventil-
ation rates of each are summed, and then added to the radon source
term already calculated. From Figure A-2, a combined effective
ventilation rate of approximately 2.3 ac/hr results in a 36 percent
working level reduction which added to the 26 percent reduction of
radon source term gives a total reduction of 62 percent.
-------
A-10
REFERENCES
1. Evans, R.D., "Engineers' Guide to the Elementary Behavior of
Radon Daughters," Health Physios 17:229-252 (reprint 1969).
2. Haque, A.K.M.M. and A.J.L. Collinson, "Radiation Dose to the
Respiratory System Due to Radon and its Daughter Products,"
Health Physics 13:431-443 (May 1967).
-------
APPENDIX B
FLORIDA INDOOR RADON
DAUGHTER LEVELS - FEBRUARY 1976
-------
Table Bl
Florida Indoor Radon Levels Data - February 1976
**
Location No.
ORP/CSD 75-4
(No. of
Avg. WL Measurements)
New Data
Avg. WL
(No. of
Measurements)
98R
110R
107R
105R
94R
76R
172
103R
169
51R
118R (No A/C)
50R
170
175
84R (No A/C)
112R
134
176
180
135
136
137*
200*
203*
204*
0.205
0.111
0.101
0.051
0.031
0.030
0.025
0.023
0.022
0.011
0.010
0.007
0.006
0.005
0.005
0.004
0.004
0.004
0.004
0.0002
0.0002
1
(2)
(2)
(1)
(2)
(3)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(3)
(1)
(1)
(1)
(1)
(1)
0.105
0.075
0.067
0.037
0.023
0.058
0.027
0.023
0.020
0.013
0.006
0.006
0.005
0.002
0.007
0.002
0.001
0.003
0.002
0.0002
0.0005
0.0006
0.005
0.003
0.005
(4)
(4)
(2)
(5)
(5)
(4)
(4)
(4)
(4)
(4)
(4)
(5)
(4)
(4)
(2)
(6)
(4)
(4)
(4)
(4)
(4)
(4)
(4)
(3)
(4)
**
Elemental Phosphorus facilities.
*
Preliminary Findings Radon Daughter Levels in Structures Constructed on
Reclaimed Florida Phosphate Land, Office of Radiation Programs, U.S.
Environmental Protection Agency, Technical Note ORP/CSD-75-4 (Sept. 1975)
R — Believed to be on reclaimed phosphate land.
-------
APPENDIX
NOTICE OF INTERIM RECOMMENDATIONS
FOR RADIATION LEVELS ON
FLORIDA PHOSPHATE LANDS
-------
2GOGG
NOTICES
ENVIRONMENTAL PROTECTION
AGENCY
FLORIDA PHOSPHATE LANDS
Interim Recommendations for Radiation
Levels
In June 1975, the Environmental Pro-
tection Agency initiated a study to deter-
mine the radiological impact of living
and working In structures constructed
on reclaimed phosphate mine land in
Central Florida. Prom data acquired by
this study, the Environmental Protec-
tion Agency issued a report entitled,
"Preliminary Findings Radon Daughter
Levels in Structures Constructed on Re-
claimed Florida Phosphate Land," (ORP/
CSD 75-4. September 1975) showing ele-
vated indoor radon daughter levels in
some structures built on reclaimed lands
as compared to structures built on un-
mlned soil. On September 22. 1975, the
Administrator of the Environmental Pro-
tection Agency informed the Governor
of Florida by letter that a potential pub-
lic health problem appears to exist due
to exposure to j elevated radon daughter
concentrations' in some of these struc-
tures. The primary public health con-
sideration is the potential risk of in-
creased lung cancer. As a result of these
findings, the Administrator recom-
mended to the Governor that "as a pru-
dent interim measure that the start of
construction of new buildings on land
reclaimed from phosphate mining areas
be discouraged."
Since this initial study, the Agency In
cooperation with the Florida Department
of Health and Rehabilitative Services.
and the Polk County Health Department
has been acquiring additional Informa-
tion necessary for liic development of ap-
propriate radiation protection guides.
These guides will be used to determine
the extent of any remedial action neces-
sary to reduce radon daughter concen-
trations.
However, because of the Agency's cau-
tion to the State of Florida to discourage
the start of construction of new build-
ings, some delays in new • construction
have resulted on land sites which do not
represent a threat to health. Conse-
quently, the Agency developed recom-
mendations which would allow construc-
tion on such land areas with minimal risk
of significant radiation exposure. By let-
ter of January 22, 1976, the Agency pro-
vided the Director of the Florida Division
of Health an interim recommendation
to be used for screening of land sites for
construction of new structures on Florida
phosphate areas. The recommendations
are considered not applicable for any
situation other than the one specified.
The interim recommendations are
based .on the findings presented in the
noted EPA report, additional radon
daughter^level data from the same struc-
tures identified in the report, information
obtained from investigations of the po-
tential hazard associated with the use of
uranium mill tailings in several Western
States, and consideration of the Surgeon
General's Guidelines for remedial action
in Grand Junction. Colorado (Code of
Federal Regulations, Title 10, Fart 12).
While these recommendations do not
-onstitute hew formal Federal Radiation
'rotection Guidance on this subject un-
der 42 USC 2021 (h), they are consistent
with the basic principles of present Fed-
eral guidance for radiation protection of
the public (25 FR 4402, May 18.1960).
The Agency believes that implementa-
tion of these recommendations would
provide public health protection to the
extent necessary to minimize the health
risk to individuals or populations. The
interim recommendations to the State
of Florida are as follows:
INTERIM RECOMMENDATIONS FOR GAMMA
EXPOSURE LEVELS AT NEW STRUCTURE
SITES ON FLORIDA PHOSPHATE LANDS
Average External
Gamma Radiation
. Level Recommendations
Equal to or greater Construction should be
than 10 /iR/hr. delayed pending ad-
ditional study or ac-
ceptable control tech-
nology should be In-
stituted to preclude
Indoor radon daugh-
ter problems.'
Less than 10 A&/ Construction may be
nr. Initiated.
RATIONALE AND EXPLANATORY NOTES
1. The external gamma radiation level
recommended Includes background
which varies throughout Central Florida
but is generally 5 to 7 nR/hr In the re-
gions of concern (ORP/fcSD 75-4, Sep-
tember 1975).
2. The purpose of these interim recom-
mendations is to limit radon daughter
exposures in structures constructed on
Florida phosphate lands in the absence
of both an acceptable criterion for radon
daughter exposures in the subject situ-
ation and a definitive radon daughter
level to gamma exposure level correla-
tion.
3. Figure 1 is a plot of Indoor radon
daughter levels as a function of outside
average gamma levels for the structures
sampled through January 1976. The
curve represents a multiple regression fit
to the data. The points identified by an
"x" were not included in the fit because
they are high ventilation locations
which lowers radon daughter levels but
does not effect gamma measurements. Al-
though this data is limited in number
and period of collection, it suggests a
positive relationship between gamma
levels and indoor radon daughter levels.
4. Based on uranium mill tailing ex-
periences and the data presented in Fig-
ure 1, it is possible to observe indoor ra-
don daughter levels two or more times
the normal background level, which
ranges from about .0002 WL to .005 WL
in Central Florida, at gamma levels a few
microroentgens per hour above the nor-
mal gamma-background. However, dif-
ferences in ventilation, construction, and
use may create wide variations in the
observed indoor radon daughter levels in
structures constructed on land exhibit-
ing the same gamma level.
5. At gamma radiation levels less than
10 /iR/hr, the observed indoor radon
daughter levels in structures constructed
on this land should be substantially less
than .05 WL (the upper limit of the
Surgeon General's Guidelines for re-
medial action in Grand Junction, Colo-
.rado) and generally comparable to
background.
6. A Working Level (WL) is the term
used to describe radon daughter product
activities in air. Tills term is defined as
any combination of short-lived radon
daughter products in one liter of air that
will result in the ultimate emission of
1.3 x 103 MeV of potential alpha energy.
If 100 pCi of randon-222 per liter of air
are present in equilibrium with its short-
lived daughter products through RaC',
the ultimate alpha energy released will
be 1.3 x 10" MeV or one Working Level.
7. In evaluating proposed construction
sites, gamma radiation level measure-
ments should be made by a competent
technician using properly calibrated
equipment. The site external gamma ra-
diation levels should be determined by
averaging at least ten or more measure-
ments made within a perimeter of two
feet around the proposed structure as
Illustrated by Figure 2. All measurements
should be made at a height of three feet
above the ground surface.
FEDERAL REGISTER VOL. 41, NO.- 123—THURSDAY, JUNE 24, 1976,
-------
NOTICES
2COG7
8. IT the exact proposed structure loca-
tion on a building site is not known, then
the entire area of the site suitable for
structure construction should be eval-
uated with one measurement made
within each 500 square feet. These meas-
urements should be averaged to obtain
an overall site value.
Any comments on the.se recommenda-
tions should be sent to the Director,
Criteria & Standards Division, Office of
Radiation Programs, Environmental Pro-
1.0 i-
tcction Agency (AW-460), 401 M Street.
SW., Washington, D.C. 20460. Copies of
the cited September 1975 EPA Report
entitled, "Preliminary Findings Radon
Daughter Levels in Structures Con-
structed on Reclaimed Florida Phosphate
Land* are available at the above address.
Dated: June 16, 1976.
ROGER STRELOW,
Assistant Administrator
/or Air and Waste Manaegcment.
.1
3
UJ
Ul
3
^
O
o
a
cc
cc
o
0.01
0.001
0.0001
X-HIGH VENTILATION
LOCATIONS
10 20 30
OUTSIDE AVERAGE GAMMA LEVELS (/uR/hr)
40-
FIGURE 1 OBSERVED INDOOR RADON DAUGHTER LEVELS AS A FUNCTION
OF OUTDOOR AVERAGE GAMMA RADIATION LEVELS FOR DATA
COLLECTED AS OF FEBRUARY 1976.
FEDERAL IEGISTU. VOL 41. NO. 123—THURSDAY, JUNE 24. 1976
-------
26068
NOTICES
tVPICAl SITE EVALUATION FOR A PROPOSED STRUCTURE
LOCATION OP
T
EMENT 1
1
1
1
*--
4
*
STRUCTURE
rw*M *
'*" t
i
j.
*
DRIVEWAY
... ?
1
1
1
~*
STREET .
[FR Doc.76-18173 Filed 6-23-76:8:45 ank]
-------
APPENDIX D
EXPERIMENTAL EFFECTIVENESS OF SELECTED
COMMERCIAL POLYMERIC. SEALANTS IN STOPPING RADON
DIFFUSION
-------
D-l
EXPERIMENTAL EFFECTIVENESS OF SELECTED COMMERCIAL
POLYMERIC SEALANTS IN STOPPING RADON DIFFUSION
Table D-l — Various Coatings Tested in the Laboratory
Company
Product Identification
Effectiveness
Percent
Acme Chemical
Do
Do
Do
Do
American Cyanamid
Do
Do
BF Goodrich
Gallery
Celanese Coatings Co.
Do
Devcon Corp.
Dev-Cote
Dow Chemical
Do
Do
Do
Do
Essex Chemical Corp.
Do
Fraley's modified system
Hercules
Morton Chemical
Do
Preserv-0-Paints
Do
Quaker Koat
Rustreat
Sika Chemical
Southwest Research
Staley Chemical
Do
Swift Co.
Do
Tra-Con
Do
HydrEpoxy 101 water-base epoxy
HydrEpoxy 260
HydrEpoxy 156
HydrEpoxy 300 (modified 1)
HydrEpoxy 300 epoxy
Aerospray 52
Reflecto-0-Seal
Aerospray 70
Vinyl latex Geon 652
Urethane
EpiRez WD 510 epoxy
EpiR^z WE 3520
Epoxy U.W.
Intumescent
Saran Resin F-310
Saran Resin F-300
Latex XD 4624
Latex XD 7151
Latex XD 7828
Unsaturated polyester
Liquid Envelope 65-24
Inorganic
Chlorinated rubber
Serfene 432X
Latex FR 103
Polythane
El-Stretch-0
Asphalt
Latex metal primer
Colma-Kote
Sulfur
P-961
P-930HT
4517
Adcote
Tra-Bond 2106T
Tra-Bond FS91
38
4
94
18
87
0
0
99
0
56
100
73
73
82
0
0
89
64
0
95
0
0
85
5
0
71
0
0
44
99
100
0
0
0
0
100
95
From Franklin, J.C. and L.T. Nuzman, "Polymeric Materials for Sealing Radon
Gas into the Walls of Uranium Mines," Spokane Mining Research Center,
Washington, U.S. Bureau of Mines, RI 8036, HO-220006, and HO-230007 (1975).
-------
D-2
Table D-l — CONTINUED
Company
Product Identification
Effectiveness
Percent
United Paint
Do
Do
Ventron Corp.
Do
Do
Do
Michael Walters Ind.
Washington State University
Butyl rubber
— do —
Chlorinated rubber
Resitron I furan resin
Resitron II furan resin
Resitron II modified 14,500 cp
Resitron II modified 7,800 cp
Inorganic
Modified epoxy
38
32
11
50
97
91
0
0
100
i
1Three samples were widely scattered and will be recoated and retested.
Figure given is for one of the three samples tested.
Table D-2 — Two-Coat Systems Tested in the Laboratory
Prime Coat
HydrEpoxy 156 *
Do
Resitron II
Latex XD 4624
HydrEpoxy 156 2
Latex XD 4624
Resitron II
Do
Latex XD 4624
Resitron II3
Do3
Do
Do3
Do
•
Top Coat
HydrEpoxy 156
HydrEpoxy 300
— do —
HydrEpoxy 156
— do —
HydrEpoxy 300
Resitron II, 14,500 cp
Resitron II, 7,800 cp
Unsaturated polyester
Resitron II, 14,500 cp3
HydrEpoxy 156
Unsaturated polyester
EpiRez WD 510
Washington State University
modified epoxy
Effectiveness
Percent
77
79
70
95
75
86
100
100
0
100
100
77
99
65.
xDiluted by 75 percent water.
2Diluted by 50 percent water.
3Diluted with water.
-------
D-3
Development and Evaluation
of Radon Sealants for Uranium Mines
by
H.G. Hammon, K. Ernst, J.R. Gaskill,
J.C. Newton, and C.J. Morris
(Excerpt from summary and conclusions)
Ranking of sealants studied:
Name and Type *
1. HydrEpoxy 300, pigmented water-dispersed epoxy
2. Resitron II, furan (catalyzed furfuryl alcohol
polymer)
3. Essex Polyester, pigmented one-component
styrenated polyester
4. Aerospray 70, plasticized polyvinyl acetate
latex
5. Saran XD-7151, vinylidene chloride copolymer
6. EpiRez WD-510/EpiCure 872, unpigmented water-
dispersed epoxy
7. WSU-118, modified epoxy
8. Promulsion 200, unidentified composition
9. Hydro Seal, acrylic emulsion
Comments
Bad odor
Flammable;
contains styrene
Possible smoke
problem
Liberates hydrogen
chloride in
possible fire
Possible smoke
problem
Possible smoke
problem
Possible smoke
problem
Possible smoke
problem
The authors note that the coatings ranked here only represent a few of
such commercial coatings available, that other manufacturers may make
similar coatings. The ranking gives little weight to permeability, as
all of the sealants were adequate in stopping radon exhalation. Thus,
much emphasis was placed on application and safety problems. They
conclude that the selection of a suitable sealant should be based on
cost/m2, vapor toxicity during application and the ability to bind to
surface without the formation of pinholes.
------- |