United States
Environmental Protection
Agency
Air and Radiation
(6604J)
402-R-93-055
September 1993
4>EPA EPA's Map of Radon Zones
OHIO
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EPA'S MAP OF RADON ZONES
OHIO
RADON DIVISION
OFFICE OF RADIATION AND INDOOR AIR
U.S. ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER, 1993
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ACKNOWLEDGEMENTS
This document was prepared by the U.S. Environmental Protection Agency's (EPA's)
Office of Radiation and Indoor Air (ORIA) in conjunction with the U.S. Geological Survey
(USGS). Sharon W. White was the EPA project manager. Numerous other people in ORIA
were instrumental in the development of the Map of Radon Zones, including Lisa Ratcliff,
Kirk Maconaughey, R. Thomas Peake, Dave Rowson, and Steve Page.
EPA would especially like to acknowledge the outstanding effort of the USGS
radon team — Linda Gundersen, Randy Schumann, Jim Otton, Doug Owen, Russell
Dubiel, Kendell Dickinson, and Sandra Szarzi — in developing the technical base for the
Map of Radon Zones.
ORIA would also like to recognize the efforts of all the EPA Regional Offices in
coordinating the reviews with the State programs and the Association of American State
Geologists (AASG) for providing a liaison with the State geological surveys. In addition,
appreciation is expressed to all of the State radon programs and geological surveys for their
technical input and review of the Map of Radon Zones.
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TABLE OF CONTENTS
I. OVERVIEW
II. THE USGS/EPA RADON POTENTIAL
ASSESSMENTS:INTRODUCTION
III. REGION 5 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF OHIO
V. EPA'S MAP OF RADON ZONES - OHIO
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OVERVIEW
Sections 307 and 309 of the 1988 Indoor Radon Abatement Act (IRAA) direct EPA to
identify areas of the United States that have the potential to produce elevated levels of radon
A A^X\ Geol°Slcal Survey (USGS), and the Association of American S.ate Geologists
(AASG) have worked closely over the past several years to produce a series of maps and
documents which address these directives. The EPA Map of Radon Zones is a compilation of
that work and fulfills the requirements of sections 307 and 309 of IRAA. The Map of Radon
Zones identifies, on a county-by-county basis, areas of the U.S. that have the highest potential
tor elevated indoor radon levels (greater than 4 pCi/L).
The Map of Radon Zones is designed to assist national, State and local governments
and organizations to target their radon program activities and resources. It is also intended to
help building code officials determine areas that are the highest priority for adopting radon-
resistant building practices. The Map of Radon Zones should not be used to determine if
individual homes in any given area need to be tested for radon. EPA recommends that all
homes be tested for radon, regardless of geographic location or the zone designation of
the county in which they are located.
™ r? 1S, d°CUment Provides background information concerning the development of the
Map of Radon Zones. It explains the purposes of the map, the approach for developing the
n 5 °f
norH , USGS)' the data sources used> *« conclusions
and confidence levels developed for the prediction of radon potential, and the review process
that was conducted to finalize this effort.
BACKGROUND
Radon (Rn222) is a colorless, odorless, radioactive gas. It comes from the natural
decay of uranium that is found in nearly all soils. It typically moves through the ground to
the air above and into homes and other buildings through cracks and openings in the
foundation. Any home, school or workplace may have a radon problem, regardless of
whether it is new or old, well-sealed or drafty, or with or without a basement. Nearly one out
of every 15 homes in the U.S. is estimated to have elevated annual average levels of indoor
Radon first gained national attention in early 1984, when extremely high levels of
indoor radon were found in areas of Pennsylvania, New Jersey, and New York along the
Reading Prorig-physiographic province. EPA established a Radon Program in 1985 to assist
States and homeowners in reducing their risk of lung cancer from indoor radon.
Since 1985, EPA and USGS have been working together to continually increase our
understanding of radon sources and the migration dynamics that cause elevated indoor radon
levels. (Early efforts resulted in the 1987 map entitled "Areas with Potentially High Radon
Levels. This map was based on limited geologic information only because few indoor radon
measurements were available at the time. The development of EPA's Map of Radon Zones
and its technical foundation, USGS1 National Geologic Radon Province Map, has been based
on additional information from six years of the State/EPA Residential Radon Survey a
independent State residential surveys, and continued expansion of geologic and geophysical
information, particularly the data from the National Uranium Resource Evaluation project
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Purpose of the Map of Radon Zones
EPA's Map of Radon Zones (Figure 1) assigns each, of the 3141 counties in the
United States to one of three zones:
o Zone 1 counties have a predicted average indoor screening level > than
4 pCi/L
o Zone 2 counties have a predicted average screening level > 2 pCi/L and
< 4 pCi/L
o Zone 3 counties have a predicted average screening level < 2 pCi/L
The Zone designations were determined by assessing five factors that are known to be
important indicators of radon potential: indoor radon measurements, geology, aerial
radioactivity, soil parameters, and foundation types.
The predictions of average screening levels in each of the Zones is an expression of
radon potential in the lowest liveable area of a structure. This map is unable to estimate
actual exposures to radon. EPA recommends methods for testing and fixing individual homes
based on an estimate of actual exposure to radon. For more information on testing and fixing
elevated radon levels in homes consult these EPA publications: A Citizen's Guide to Radon,
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide to
Radon.
EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to high radon potential
areas. Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates and policies and building codes, etc.) in such areas
addresses the greatest potential risks first.
EPA also believes that the use of passive radon control systems in the construction of
new homes in Zone 1 counties, and the activation of those systems if necessitated by follow-
up testing, is a cost effective approach to achieving significant radon risk reduction.
The Map of Radon Zones and its supporting documentation establish no regulatory
requirements. Use of this map by State or local radon programs and building code officials is
voluntary. The information presented on the Map of Radon Zones and in the supporting
documentation is not applicable to radon in water.
Development of the Map of Radon Zones
The technical foundation for the Map of Radon Zones is the USGS Geologic Radon
Province Map. In order to examine the radon potential for the United States, the USGS
began by identifying approximately 360 separate geologic provinces for the U.S. The
provinces are shown on the USGS Geologic Radon Province Map (Figure 2). Each of the
geologic provinces was evaluated by examining the available data for that area: indoor radon
measurements, geology, aerial radioactivity, soil parameters, and foundation types. As stated
previously, these five factors are considered to be of basic importance in assessing radon
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potential and some data are available for each of these factors in every geologic province. The
province boundaries do not coincide with political borders (county and state) but define areas
of general radon potential. The five factors were assigned numerical values based on an
assessment of their respective contribution to radon potential, and a confidence level was
assigned to each contributing variable. The approach used by USGS to estimate the radon
potential for each province is described in Part II of this document.
EPA subsequently developed the Map of Radon Zones by extrapolating from the
province level to the county level so that all counties in the U.S. were assigned to one of
three radon zones. EPA assigned each county to a given zone based on its provincial radon
potential. For example, if a county is located within a geologic province that has a predicted
average screening level greater than 4 pCi/L, it was assigned to Zone 1. Likewise, counties
located in provinces with predicted average screening levels > 2 pCi/L and < 4 pCifL, and
less than 2 pCi/L, were assigned to Zones 2 and 3, respectively.
If the boundaries of a county fall in more than one geologic province, the county was
assigned to a zone based on the predicted radon potential of the province in which most of
the area lies. For example, if three different provinces cross through a given county, the
county was assigned to the zone representing the radon potential of the province containing
most of the county's land area. (In this case, it is not technically correct to say that the
predicted average screening level applies to the entire county since the county falls in
multiple provinces with differing radon potentials.)
Figures 3 and 4 demonstrate an example of how EPA extrapolated the county zone
designations for Nebraska from the USGS geologic province map for the State. As figure 3
shows, USGS has identified 5 geologic provinces for Nebraska. Most of the counties are
extrapolated "straight" from their corresponding provinces, but there are counties "partitioned"
by several provinces ~ for example, Lincoln County. Although Lincoln county falls in
multiple provinces, it was assigned to Zone 3 because most of its area falls in the province
with the lowest radon potential.
It is important to note that EPA's extrapolation from the province level to the
county level may mask significant "highs" and "lows" within specific counties. In other
words, within-county variations in radon potential are not shown on the Map of Radon
Zones. EPA recommends that users who may need to address specific within-county
variations in radon potential (e.g., local government officials considering the
implementation of radon-resistant construction codes) consult USGS' Geologic Radon
Province Map and the State chapters provided with this map for more detailed
information, as well as any locally available data.
Map Validation
The Map of Radon Zones is intended to represent a preliminary assessment of radon
potential for the entire United States. The factors that are used in this effort -indoor radon
data, geology, aerial radioactivity, soils, and foundation type ~ are basic indicators for radon
potential. It is important to note, however, that the map's county zone designations are not
"statistically valid" predictions due to the nature of the data available for these 5 factors at the
county level. In order to validate the map in light of this lack of statistical confidence, EPA
conducted a number of analyses. These analyses have helped EPA to identify the best'
situations in which to apply the map, and its limitations.
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Figure 3
Geologic Radon Potential Provinces for Nebraski
Lincoln County
lifl Uoieritc Low
Figure 4
NEBRASKA - EPA Map of Radon Zones
Lincoln County
Zote I Zoae 2 Zone 3
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One such analysis involved comparing county zone designations to indoor radon
measurements from the State/EPA Residential Radon Surveys (SRRS). Screening avera^
for counties with at least 100 measurements were compared to the counties' predicted radon
potential as indicated by the Map of Radon Zones. EPA found that 72% of the county
screening averages were correctly reflected by the appropriate zone designations on the Map
In all other cases, they only differed by 1 zone.
Another accuracy analysis used the annual average data from the National Residential
Radon Survey .(NRRS). The NRRS indicated that approximately 6 million homes in the
United States have annual averages greater than or equal to 4 pCi/L. By cross checking the
county location of the approximately 5,700 homes which participated in the survey, their
radon measurements, and the zone designations for these counties, EPA found that'
approximately 3.8 million homes of the 5.4 million homes with radon levels greater than or
equal to 4 pCi/L will be found in counties designated as Zone 1. A random sampling of an
equal number of counties would have only found approximately 1.8 million homes greater
than 4 pCi/L. In other words, this analysis indicated that the map approach is three times
more efficient at identifying high radon areas than random selection of zone designations.
Together, these analyses show that the approach EPA used to develop the Map of
Radon Zones is a reasonable one. In addition, the Agency's confidence is enhanced by results
of the extensive State review process -- the map generally agrees with the States' knowledge
of and experience in their own jurisdictions. However, the accuracy analyses highlight two
important points: the fact that elevated levels will be found in Zones 2 and 3, and that there
will be significant numbers of homes with lower indoor radon levels in all of'the Zones For
these reasons, users of the Map of Radon Zones need to supplement the Map with locally
available data whenever possible. Although all known "hot spots", i.e., localized areas of
consistently elevated levels, are discussed in the State-
specific chapters, accurately defining the boundaries of the "hot spots" on this scale of map is
not possible at this time. Also, unknown "hot spots" do exist.
The Map of Radon Zones is intended to be a starting point for characterizing radon
potential because our knowledge of radon sources and transport is always growing. Although
this effort represents the best data available at this time, EPA will continue to study these
parameters and others such as house construction, ventilation features and meteorology factors
in order to better characterize the presence of radon in U.S homes, especially in high risk
areas. These efforts will eventually assist EPA in refining and revising the conclusions of the
Map of Radon Zones. And although this map is most appropriately used as a targeting tool
by the aforementioned audiences -- the Agency encourages all residents to test their homes
for radon, regardless of geographic location or the zone designation of the county in
which they live. Similarly, the Map of Radon Zones should not to be used in lieu of
testing during real estate transactions.
Review Process
The Map of Radon Zones has undergone extensive review within EPA and outside the
Agency. The Association of American State Geologists (AASG) played an integral role in
this review process. The AASG individual State geologists have reviewed their State-specific
information, the USGS Geologic Radon Province Map, and other materials for their geologic
content and consistency.
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In addition to each State geologist providing technical comments, the State radon
offices were asked to comment on their respective States' radon potential evaluations. In
particular, the States were asked to evaluate the data used to assign their counties to specific
zones. EPA and USGS worked with the States to resolve any issues concerning county zone
designations. In a few cases, States have requested changes in county zone designations. The
requests were based on additional data from the State on geology, indoor radon
measurements, population, etc. Upon reviewing the data submitted by the States, EPA did
make some changes in zone designations. These changes, which do not strictly follow the
methodology outlined in this document, are discussed in the respective State chapters.
EPA encourages the States and counties to conduct further research and data collection
efforts to refine the Map of Radon Zones. EPA would like to be kept informed of any
changes the States, counties, or others make to the maps. Updates and revisions will be
handled in a similar fashion to the way the map was developed. States should notify EPA of
any proposed changes by forwarding the changes through the Regional EPA offices that are
listed in Part H Depending on the amount of new information that is presented, EPA will
consider updating this map periodically. The State radon programs should initiate proper
notification of the appropriate State officials when the Map of Radon Zones is released and
when revisions or updates are made by the State or EPA.
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THE USGS/EPA RADON POTENTIAL ASSESSMENTS: AN INTRODUCTION
by
Line/a C.S. Gimdersen and R. Randall Schumann
U.S. Geological Survey
and
Sharon W. White
U.S. Environmental Protection Agency
BACKGROUND
The Indoor Radon Abatement Act of 1988 (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify areas of the United States that have the
potential to produce harmful levels of indoor radon. These characterizations were to be based
on both geological data and on indoor radon levels in homes and other structures. The EPA
also was directed to develop model standards and techniques for new building construction
that would provide adequate prevention or mitigation of radon entry. As part of an
Interagency Agreement between the EPA and the U.S. Geological Survey (USGS), the USGS
has prepared radon potential estimates for the United States. This report is one of ten
booklets that document this effort. The purpose and intended use of these reports is to help
identify areas where states can target their radon program resources, to provide guidance in
selecting the most appropriate building code options for areas, and to provide general
information on radon and geology for each state for federal, state, and municipal officials
dealing with radon issues. These reports are not intended to be used as a substitute for
indoor radon testing, and they cannot and should not be used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts. Elevated
levels of indoor radon have been found in every State, and EPA recommends that all homes
be tested for indoor radon.
Booklets detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the geologic radon potential booklets. Each
booklet consists of several components, the first being an overview to the mapping project
(Part I), this introduction to the USGS assessment (Part II), including a general discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used. The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain EPA's map of radon zones for each state and an
accompanying description (Part V).
Because of constraints on the scales of maps presented in these reports and because the
smallest units used to present the indoor radon data are counties, some generalizations have
been made in order to estimate the radon potential of each area. Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
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tracts. Within any area of a given geologic radon potential ranking, there are likely to be
areas where the radon potential is lower or higher than that assigned to the area as a whole,
especially in larger areas such as the large counties in some western states.
In each state chapter, references to additional reports related to radon are listed for the
state, and the reader is urged to consult these reports for more detailed information. In most
cases the best sources of information on radon for specific areas are state and local
departments of health, state departments responsible for nuclear safety or environmental
protection, and U.S. EPA regional offices. More detailed information on state or local
geology may be obtained from the state geological surveys. Addresses and telephone
numbers of state radon contacts, geological surveys, and EPA regional offices are listed in
Appendix C at the end of this chapter.
RADON GENERATION AND TRANSPORT IN SOILS
Radon (M5Rn) is produced from the radioactive decay of radium (~6Ra), which is, in turn,
a product of the decay of uranium (:3SU) (fig. 1). The half-life of :"Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron ("°Rn), which occurs in
concentrations high enough to be of concern in a few localized areas, they are less important
in terms of indoor radon risk because of their extremely short half-lives and less common
occurrence. In general, the concentration and mobility of radon in soil are dependent on
several factors, the most important of which are the soil's radium content and distribution,
porosity, permeability to gas movement, and moisture content. These characteristics are, in
turn, determined by the soil's parent-material composition, climate, and the soil's age or
maturity. If parent-material composition, climate, vegetation, age of the soil, and topography
are known, the physical and chemical properties of a soil in a given area can be predicted.
As soils form, they develop distinct layers, or horizons, that are cumulatively called the
soil profile. The A horizon is a surface or near-surface horizon containing a relative
abundance of organic matter but dominated by mineral matter. Some soils contain an E
horizon, directly below the A horizon, that is generally characterized by loss of clays, iron, or
aluminum, and has a characteristically lighter color than the A horizon. The B horizon
underlies the A or E horizon. Important characteristics of B horizons include accumulation of
clays, iron oxides, calcium carbonate or other soluble salts, and organic matter complexes. In
drier environments, a horizon may exist within or below the B horizon that is dominated by
calcium carbonate, often called caliche or calcrete. This carbonate-cemented horizon is
designated the K horizon in modern soil classification schemes. The C horizon underlies the
B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
or B horizons; that is, it is generally not a zone of leaching or accumulation. In soils formed
in place from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
bedrock overlying the unweathered bedrock.
The shape and orientation of soil particles (soil structure) control permeability and affect
water movement in the soil. Soils with blocky or granular structure have roughly equivalent
permeabilities in the horizontal and vertical directions, and air and water can infiltrate the soil
relatively easily. However, in soils with platy structure, horizontal permeability is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have dominantly vertical permeability. Platy and
prismatic structures form in soils with high clay contents. In soils with shrink-swell clays, air
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and moisture infiltration rates and depth of wetting may be limited when the cracks in the
surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platy
structure, can form a capping layer that impedes the escape of soil gas to the surface
(Schumann and others, 1992). However, the shrinka^" of clays can act to open or widen
cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
Radon transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
1964). Diffusion is the process whereby radon atoms move from areas of higher
concentration to areas of lower concentration in response to a concentration gradient. Flow is
the process by which soil air moves through soil pores in response to differences in pressure
within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
tends to dominate in highly permeable soils (Sextro and others, 1987). In low-permeability
soils, much of the radon may decay before it is able to enter a building because its transport
rate is reduced. Conversely, highly permeable soils, even those that are relatively low in
radium, such as those derived from some types of glacial deposits, have been associated with
high indoor radon levels in Europe and in the northern United States (Akerblom and others,
1984; Kunz and others, 1989; Sextro and others, 1987). In areas of karst topography formed
in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
increase soil permeability at depth by providing additional pathways for gas flow.
Not all radium contained in soil grains and grain coatings will result in mobile radon
when the radium decays. Depending on where the radium is distributed in the soil, many of
the radon atoms may remain imbedded in the soil grain containing the parent radium atom, or
become imbedded in adjacent soil grains. The portion of radium that releases radon into the
pores and fractures of rocks and soils is called the emanating fraction. When a radium atom
decays to radon, the energy generated is strong enough to send the radon atom a distance of
about 40 nanometers (1 nm = 10'9 meters), or about 2x10"* inches—this is known as alpha
recoil (Tanner, 1980). Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain. Because water is more dense than air, a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil
Concentrations of radon in soils are generally many times higher than those inside of
buildings, ranging from tens of pCi/L to more than 100,000 pCi/L, but typically in the range
of hundreds to low thousands of pCi/L. Soil-gas radon concentrations can vary in response to
variations in climate and weather on hourly, daily, or seasonal time scales. Schumann and
others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
radon concentrations between seasons in Colorado and Pennsylvania. The most important
factors appear to be (1) soil moisture conditions, which are controlled in large part by
precipitation; (2) barometric pressure; and (3) temperature. Washington and Rose (1990)
suggest that temperature-controlled partitioning of radon between water and gas in soil pores
also has a significant influence on the amount of mobile radon in soil gas.
Homes in hilly limestone regions of the southern Appalachians were found to have higher
indoor radon concentrations during the summer than in the winter. A suggested cause for this
phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface
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solution cavities in the carbonate rock into houses. As warm air enters solution cavities that
are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others,
1993). In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the winter, caused by cooler outside air entering the
cave, driving radon-laden air into cracks and solution cavities in the rock and soil, and
ultimately, into homes (Gammage and others, 1993).
RADON ENTRY INTO BUILDINGS
A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points must exist for radon to enter a building from'the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold winter months are
common driving forces. Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
Radon levels in the basement are generally higher than those on the main floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes. The term "nonbasement" applies to
slab-on-grade or crawl space construction.
METHODS AND SOURCES OF DATA
The assessments of radon potential in the booklets that follow this introduction were
made using five main types of data: (1) geologic (lithologic); (2) aerial radiometric; (3) soil
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data; and (5) building architecture (specifically, whether homes in each area are built
slab-on-grade or have a basement or crawl space). These five factors were evaluated and
integrated to produce estimates of radon potential. Field measurements of soil-gas radon or
soil radioactivity were not used except where such data were available in existing, published
reports of local field studies. Where applicable, such field studies are described in the
individual state chapters.
GEOLOGIC DATA
The types and distribution of lithologic units and other geologic features in an
assessment area are of primary importance in determining radon potential. Rock types that
are most likely to cause indoor radon problems include carbonaceous black shales, glauconite-
bearing sandstones, certain kinds of fluvial sandstones and fluvial sediments, phosphorites,
chalk, karst-producing carbonate rocks, certain kinds of glacial deposits, bauxite, uranium-rich
granitic rocks, metamorphic rocks of granitic composition, silica-rich volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks.
Rock types least likely to cause radon problems include marine quartz sands, non-
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and
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igneous rocks, and basalts. Exceptions exist within these general lithologic groups because of
the occurrence of localized uranium deposits, commonly of the hydrothermal type in
crystalline rocks or the "roll-front" type in sedimentary rocks. Uranium and radium are
commonly sited in heavy minerals, iron-oxide coatings on rock and soil grains, and organic
materials in soils and sediments. Less common are uranium associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
Although many cases of elevated indoor radon levels can be traced to high radium and
(or) uranium concentrations in parent rocks, some structural features, most notably faults and
shear zones, have been identified as sites of localized uranium concentrations (Deffeyes and
MacGregor, 1980) and have been associated with some of the highest reported indoor radon
levels (Gundersen, 1991). The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a; Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991; Muessig and Bell
1988).
NURE AERIAL RADIOMETRIC DATA
Aerial radiometric data are used to quantify the radioactivity of rocks and soils.
Equivalent uranium (eU) data provide an estimate of the surficial concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by a gamma-ray detector from the 1.76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (214Bi), with the assumption that uranium and
its decay products are in secular equilibrium. Equivalent uranium is expressed in units of
parts per million (ppm). Gamma radioactivity also may be expressed in terms of a radium
activity; 3 ppm eU corresponds to approximately 1 picocurie per gram (pCi/g) of radium-226.
Although radon is highly mobile in soil and its concentration is affected by meteorological
conditions (Kovach, 1945; Klusman and Jaacks, 1987; Schery and others, 1984; Schumann
and others, 1992), statistical correlations between average soil-gas radon concentrations and
average eU values for a wide variety of soils have been documented (Gundersen and others,
1988a, 1988b; Schumann and Owen, 1988). Aerial radiometric data can provide an estimate
of radon source strength over a region, but the amount of radon that is able to enter a home
from the soil is dependent on several local factors, including soil structure, grain size
distribution, moisture content, and permeability, as well as type of house construction and its
structural condition.
The aerial radiometric data used for these characterizations were collected as part of the
Department of Energy National Uranium Resource Evaluation (NURE) program of the 1970s
and early 1980s. The purpose of the NURE program was to identify and describe areas in the
United States having potential uranium resources (U.S. Department of Energy, 1976). The
NURE aerial radiometric data were collected by aircraft in which a gamma-ray spectrometer
was mounted, flying approximately 122 m (400 ft) above the ground surface. The equivalent
uranium maps presented in the state chapters were generated from reprocessed NURE data in
which smoothing, filtering, recalibrating, and matching of adjacent quadrangle data sets were
performed to compensate for background, altitude, calibration, and other types of errors and
inconsistencies in the original data set (Duval and others, 1989). The data were then gridded
and contoured to produce maps of eU with a pixel size corresponding to approximately 2 5 x
2.5 km (1.6 x 1.6 mi).
II-6 Reprinted from USGS Open-File Report 93-292
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FLIGHT LINE SPACING OF NUKE AERIAL SURVEYS
2 KV (1 VILE)
5 Ik (3 HUES)
2 t 5 IU
10 IU (6 HUES)
5 I 10 KM
MO DATA
Figure 2. Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (from Duval and others, 1990). Rectangles represent I°x2° quadrangles.
-------
Figure 2 is an index map of NUKE 1° x 2° quadrangles showing the flight-line spacing
for each quadrangle. In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
States was actually measured by the airborne gamma-ray detectors (Duval and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing between areas (fig. 2). This suggests that some localized uranium anomalies may not
have been detected by the aerial surveys, but the good correlations of eU patterns with
geologic outcrop patterns indicate that, at relatively small scales (approximately 1:1,000,000
or smaller) the National eU map (Duval and others, 1989) gives reasonably good estimates of
average surface uranium concentrations and thus can assist in the prediction of radon potential
of rocks and soils, especially when augmented with additional geologic and soil data.
The shallow (20-30 cm) depth of investigation of gamma-ray spectrometers, either
ground-based or airborne (Duval and others, 1971; Durrance, 1986), suggests that gamma-ray
data may sometimes underestimate the radon-source strength in soils in which some of the
radionuclides in the near-surface soil layers have been transported downward through the soil
profile. In such cases the concentration of radioactive minerals in the A horizon would be
lower than in the B horizon, where such minerals are typically concentrated. The
concentration of radionuclides in the C horizon and below may be relatively unaffected by
surface solution processes. Under these conditions the surface gamma-ray signal may indicate
a lower radon source concentration than actually exists in the deeper soil layers, which are
most likely to affect radon levels in structures with basements. The redistribution of
radionuclides in soil profiles is dependent on a combination of climatic, geologic, and
geochemical factors. There is reason to believe that correlations of eU with actual soil
radium and uranium concentrations at a depth relevant to radon entry into structures may be
regionally variable (Duval, 1989; Schumann and Gundersen, 1991). Given sufficient
understanding of the factors cited above, these regional differences may be predictable.
SOIL SURVEY DATA
Soil surveys prepared by the U.S. Soil Conservation Service (SCS) provide data on soil
characteristics, including soil-cover thickness, grain-size distribution, permeability, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use. The
reports are available in county formats and State summaries. The county reports typically
contain both generalized and detailed maps of soils in the area.
Because of time and map-scale constraints, it was impractical to examine county soil
reports for each county in the United States, so more generalized summaries at appropriate
scales were used where available. For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics, depth to seasonal high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil types is the "Soils" sheet of the National Atlas (U.S. Department
of Agriculture, 1987).
II-8 Reprinted from USGS Open-File Report 93-292
-------
Soil permeability is commonly expressed in SCS soil surveys in terms of the speed, in
inches per hour (in/hr), at which water soaks into the soil, as measured in a soil percolation
test. Although in/hr are not truly units of permeability, these units are in widespread use and
are referred to as "permeability" in SCS soil surveys. The permeabilities listed in the SCS
surveys are for water, but they generally correlate well with gas permeability. Because data
on gas permeability of soils is extremely limited, data on permeability to water is used as a
substitute except in cases in which excessive soil moisture is known to exist. Water in soil
pores inhibits gas transport, so the amount of radon available to a home is effectively reduced
by a high water table. Areas likely to have high water tables include river valleys, coastal
areas, and some areas overlain by deposits of glacial origin (for example, loess).
Soil permeabilities greater than 6.0 in/hr may be considered high, and permeabilities less
than 0.6 in/hr may be considered low in terms of soil-gas transport. Soils with low
permeability may generally be considered to have a lower radon potential than more
permeable soils with similar radium concentrations. Many well-developed soils contain a
clay-rich B horizon that may impede vertical soil gas transport. Radon generated below this
horizon cannot readily escape to the surface, so it would instead tend to move laterally,
especially under the influence of a negative pressure exerted by a building.
Shrink-swell potential is an indicator of the abundance of smectitic (swelling) clays in a
soil. Soils with a high shrink-swell potential may cause building foundations to crack,
creating pathways for radon entry into the structure. During dry periods, desiccation cracks in
shrink-swell soils provide additional pathways for soil-gas transport and effectively increase
the gas permeability of the soil. Soil permeability data and soil profile data thus provide
important information for regional radon assessments.
INDOOR RADON DATA
Two major sources of indoor radon data were used. The first and largest source of data is
from the State/EPA Residential Radon Survey (Ronca-Battista and others, 1988; Dziuban and
others, 1990). Forty-two states completed EPA-sponsored indoor radon surveys between 1986
and 1992 (fig. 3). The State/EPA Residential Radon Surveys were designed to be
comprehensive and statistically significant at the state level, and were subjected to high levels
of quality assurance and control. The surveys collected screening indoor radon measurements,
defined as 2-7 day measurements using charcoal canister radon detectors placed in the lowest
livable area of the home. The target population for the surveys included owner-occupied
single family, detached housing units (White and others, 1989), although attached structures
such as duplexes, townhouses, or condominiums were included in some of the surveys if they
met the other criteria and had contact with the ground surface. Participants were selected
randomly from telephone-directory listings. In total, approximately 60,000 homes were tested
in the State/EPA surveys.
The second source of indoor radon data comes from residential surveys that have been
conducted in a specific state or region of the country (e.g. independent state surveys or utility
company surveys). Several states, including Delaware, Florida, Illinois, New Hampshire, New
Jersey, New York, Oregon, and Utah, have conducted their own surveys of indoor radon. The
quality and design of a state or other independent survey are discussed and referenced where
the data are used.
H-9 Reprinted from USGS Open-File Report 93-292
-------
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Data for only those counties with five or more measurements are shown in the indoor
radon maps in the state chapters, although data for all counties with a nonzero number of
measurements are listed in the indoor radon data tables in each state chapter. In total, indoor
radon data from more than 100,000 homes nationwide were used in the compilation of these
assessments. Radon data from State or regional indoor radon surveys, public health
organizations, or other sources are discussed in addition to the primary data sources where
they are available. Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes. Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.
RADON INDEX AND CONFIDENCE INDEX
Many of the geologic methods used to evaluate an area for radon potential require
subjective opinions based on the professional judgment and experience of the individual
geologist. The evaluations are nevertheless based on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods and conceptual framework used by the U.S. Geological Survey to evaluate areas for
radon potential based on the five factors discussed in the previous sections. The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area, and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination. This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones (state/county boundaries) in which
the geology may vary across the area.
Radon Index. Table 1 presents the Radon Index (RI) matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively ranked (using a point value of 1, 2, or 3) for their respective contribution to
radon potential in a given area. At least some data for the 5 factors are consistently available
for every geologic province. Because each of these main factors encompass a wide variety of
complex and variable components, the geologists performing the evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections of this introduction.
Indoor radon was evaluated using unweighted arithmetic means of the indoor radon data
for each geologic area to be assessed. Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys and other carefully selected sources were used, as
described in the preceding section. To maintain consistency, other indoor radon data sets
(vendor, state, or other data) were not considered in scoring the indoor radon factor of the
Radon Index if they were not randomly sampled or could not be statistically combined with
the primary indoor radon data sets. However, these additional radon data sets can provide a
means to further refine correlations between geologic factors and radon potential, so they are
II-11 Reprinted from USGS Open-File Report 93-292
-------
TABLE 1. RADON INDEX MATRIX, "ppm eU" indicates parts per million of equivalent
uranium, as indicated by NURE aerial radiometric data. See text discussion for details.
INCREASING RADON POTENTIAL
, ^
FACTOR
INDOOR RADON (average)
AERIAL RADIOACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECrURE TYPE
POINT VALUE
1
<2pCi/L
< 1.5 ppm eU
negative
low
mostly slab
2
2-4pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
>4pCi/L
> 2.5 ppm eU
positive
high
mostly basement
*GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for specific, relevant geologic field studies. See text for details.
Geologic evidence supporting: HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
SCORING:
Radon potential category Point range
T nw -3_« nn;nfo
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 pouits
12-17 points
Probable average screening
indoor radon for area
<2pCi/L
POSSIBLE RANGE OF POINTS = 3 to 17
^ 4t* fc/ ^-"/ -"-^
2-4pCi/L
>4pCi/L
TABLE 2. CONFIDENCE INDEX MATRIX
INCREASING CONFIDENCE
FACTOR
INDOOR RADON DATA
AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY
POINT VALUE
1
sparse/no data
questionable/no data
questionable
questionable/no data
2
fair coverage/quality
glacial cover
variable
variable
3
good coverage/quality
no glacial cover
proven geol. model
reliable, abundant
SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10-12 points
POSSIBLE RANGE OF POINTS = 4 to 12
11-12 Reprinted from USGS Open-File Report 93-292
-------
included as supplementary information and are discussed in the individual State chapters. If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned 1 point, if it was between 2 and 4 pCi/L, it was scored 2 points, and if
the average screening indoor radon level for an area was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NURE aerial gamma-ray surveys (Duval and
others, 1989). These data indicate the gamma radioactivity from approximately the upper 30
cm of rock and soil, expressed in units of ppm equivalent uranium. An approximate average
value of eU was determined visually for each area and point values assigned based on
whether the overall eU for the area falls below 1.5 ppm (1 point), between 1.5 and 2.5 ppm
(2 points), or greater than 2.5 ppm (3 points).
The geology factor is complex and actually incorporates many geologic characteristics. In
the matrix, "positive" and "negative" refer to the presence or absence and distribution of rock
types known to have high uranium contents and to generate elevated radon in soils or indoors.
Examples of "positive" rock types include granites, black shales, phosphatic rocks, and other
rock types described in the preceding "geologic data" section. Examples of "negative" rock
types include marine quartz sands and some clays. The term "variable" indicates that the
geology within the region is variable or that the rock types in the area are known or suspected
to generate elevated radon in some areas but not in others due to compositional differences,
climatic effects, localizeddistribution of uranium, or other factors. Geologic information
indicates not only how much uranium is present in the rocks and soils but also gives clues for
predicting general radon emanation and mobility characteristics through additional factors
such as structure (notably the presence of faults or shears) and geochemical characteristics
(for example, a phosphate-rich sandstone will likely contain more uranium than a sandstone
containing little or no phosphate because the phosphate forms chemical complexes with
uranium). "Negative", "variable", and "positive" geology were assigned 1, 2, and 3 points,
respectively.
In cases where additional reinforcing or contradictory geologic evidence is available,
Geologic Field Evidence (GFE) points were added to or subtracted from an area's score
(Table 1). Relevant geologic field studies are important to enhancing our understanding of
how geologic processes affect radon distribution. In some cases, geologic models and
supporting field data reinforced an already strong (high or low) score; in others, they provided
important contradictory data. GFE points were applied for geologically-sound evidence that
supports the prediction (but which may contradict one or more factors) on the basis of known
geologic field studies in the area or in areas with geologic and climatic settings similar
enough that they could be applied with full confidence. For example, areas of the Dakotas,
Minnesota, and Iowa that are covered with Wisconsin-age glacial deposits exhibit a low aerial
radiometric signature and score only one RI point in that category. However, data from
geologic field studies in North Dakota and Minnesota (Schumann and others, 1991) suggest
that eU is a poor predictor of geologic radon potential in this area because radionuclides have
11-13 Reprinted from USGS Open-File Report 93-292
-------
been leached from the upper soil layers but are present and possibly even concentrated in
deeper soil horizons, generating significant soil-gas radon. This positive supporting field
evidence adds two GFE points to the score, which helps to counteract the invalid conclusion
suggested by the radiometric data. No GFE points »r~ awarded if there are no documented
field studies for the area.
"Soil permeability" refers to several soil characteristics that influence radon concentration
and mobility, including soil type, grain size, structure, soil moisture, drainage, slope, and
permeability. In the matrix, "low" refers to permeabilities less than about 0.6 in/hr; "high"
corresponds to greater than about 6.0 in/hr, in U.S. Soil Conservation Service (SCS) standard
soil percolation tests. The SCS data are for water permeability, which generally correlates
well with the gas permeability of the soil except when the soil moisture content is very high.
Areas with consistently high water tables were thus considered to have low gas permeability.
"Low, "moderate", and "high" permeability were assigned 1, 2, and 3 points, respectively.
Architecture type refers to whether homes in the area have mostly basements (3 points),
mostly slab-on-grade construction (1 point), or a mixture of the-two. Split-level and crawl
space homes fall into the "mixed" category (2 points). Architecture information is necessary
to properly interpret the indoor radon data and produce geologic radon potential categories
that are consistent with screening indoor radon data.
The overall RI for an area is calculated by adding the individual RI scores for the 5
factors, plus or minus GFE points, if any. The total RI for an area falls in one of three
categories—low, moderate or variable, or high. The point ranges for the three categories were
determined by examining the possible combinations of points for the 5 factors and setting
rules such that a majority (3 of 5 factors) would determine the final score for the low and
high categories, with allowances for possible deviation from an ideal score by the other two
factors. The moderate/variable category lies between these two ranges. A total deviation of 3
points from the "ideal" score was considered reasonable to allow for natural variability of
factors—if two of the five factors are allowed to vary from the "ideal" for a category, they
can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2 points
different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate, and
high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
possible variability allows a maximum of 8 points in the low category. Similarly, an ideal
high score of 15 points minus 3 points gives a minimum of 12 points for the high category.
Note, however, that if both other factors differ by two points from the "ideal", indicating
considerable variability in the system, the total point score would lie in the adjacent (i.e.,
moderate/variable) category.
Confidence Index. Except for architecture type, the same factors were used to establish a
Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
National Association of Home Builders, U.S. Department of Housing and Urban
Development, and the Federal Housing Administration; thus it was not considered necessary
11-14 Reprinted from USGS Open-File Report 93-292
-------
to question the quality or. validity of these data. The other factors were scored on the basis of
the quality and quantity of the data used to complete the RT matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random sampling (State/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States arid for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated. In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score. Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points. Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only one point, if
the data were considered questionable'or if coverage was poor.
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point).
The soil permeability factor was also scored based on quality and amount of data. The
three categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor. Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate. Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
11-15 Reprinted from USGS Open-File Report 93-292
-------
significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the soil permeability factor when assigning the RI score, but
may have less certainly in some cases and thus would be assigned a lower CI score.
The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing radon generation and transport in
rocks and soils, and thus, of the potential for elevated indoor radon levels to occur in a
particular area. However, because these reports are somewhat generalized to cover relatively
large areas of States, it is highly recommended that more detailed studies be performed in
local areas of interest, using the methods and general information in these booklets as a guide.
11-16 Reprinted from USGS Open-File Report 93-292
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and indoor radon with geology in glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-91/026b, p. 6-23-6-36.
11-18 Reprinted from USGS Open-File Report 93-292
-------
Schumann, R.R., Owen, D.E., and Asher-Bolinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
Gundersen, L.C.S., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Term., U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith, R.C., H, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, LL, University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment HI, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal kinds of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Aflas of the United States of America, sheet
38077-BE-NA-07M-00, scale 1:7,500,000.
U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
prepared by the U.S. Energy Research and Development Administration, Grand Junction
Colo.: GJO-11(76).
Wanty, Richard B., and Schoen, Robert, 1991, A review of the chemical processes affecting the
mobility of radionuclides in natural waters, with applications, in Gundersen, Linda C.S.,
and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water: U.S.
Geological Survey Bulletin no. 1971, p. 183-194.
Washington, J.W., and Rose, A.W., 1990, Regional and temporal relations of radon in soil gas to
soil temperature and moisture: Geophysical Research Letters, v. 17, p. 829-832.
White, S.B., Bergsten, J.W., Alexander, B.V., and Ronca-Battista, M., 1989, Multi-State
surveys of indoor 222Rn: Health Physics, v. 57, p. 891-896.
11-19 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Ph«neroioic2
Proterozoic
(Pi
Archean
/ At
l«J
Era or
Erathem
Cenozoic2
(CD
Mesozoic2
M»n (pA) *
Age estimates
of boundaries
in mega-annum
(Ma)1
5 (A. Q- K 1\
-570 3
reflect uncertainties of botopic and btostrstionphic age tssiflnmenu. Age boundaries not dotely bracketed by existing
dtt« shown by •* Decay constants and Isotopic ratios employed are cited in Steiger and Jlger (1877). Designation m.y. used for an
Interval of time.
"Modlfienj (towtr, middle, upper or early, middle, late) when used with these Hems are informal divisions of the larger unit: the
first toner of the modifier is lowercase.
'Rocks older than 570 Ma also called Precambrian (p€). a time term without specific rank.
'Informal time term without specific rank.
USGS Open-File Report 93-292
-------
APPENDIX B
GLOSSARY OF TERMS
Units of measure
pCi/L (picocuries per liter)- a unit of measure of radioactivity used to describe radon
concentrations in a volume of air. One picocurie (1(H2 curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.
Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One becquerel is equal to one radioactive disintegration per
second. One pO/L is equal to 37 Bq/m3.
ppm (parts per million)- a unit of measure of concentration by weight of an element in a
substance, in this case, soil or rock. One ppm of uranium contained in a ton of rock corresponds
to about 0.03 ounces of uranium. The average concentration of uranium in soils in the United
States is between 1 and 2 ppm.
in/hr (inches per hour)- a unit of measure used by soil scientists and engineers to describe the
permeability of a soil to water flowing through it It is measured by digging a hole 1 foot (12
inches) square and one foot deep, filling it with water, and measuring the time it takes for the water
to drain from the hole. The drop in height of the water level in the hole, measured in inches, is
then divided by the time (in hours) to determine the permeability. Soils range in permeability from
less than 0.06 in/hr to greater than 20 in/hr, but most soils in the United States have permeabilities
between these two extremes.
Geologic terms and terms related to the study of radon
aerial radiometric, aeroradiometric survey A survey of radioactivity, usually gamma rays,
taken by an aircraft carrying a gamma-ray spectrometer pointed at the ground surface.
alluvial fan A low, widespread mass of loose rock and soil material, shaped like an open fan
and deposited by a stream at the point where it flows from a narrow mountain valley out onto a
plain or broader valley. May also form at the junction with larger streams or when the gradient of
the stream abruptly decreases.
alluvium, alluvial General terms referring to unconsolidated detrital material deposited by a
stream or other body of running water.
alpha-track detector A passive radon measurement device consisting of a plastic film that is
sensitive to alpha particles. The film is etched with acid in a laboratory after it is exposed. The
etching reveals scratches, or "tracks", left by the alpha particles resulting from radon decay, which
can then be counted to calculate the radon concentration. Useful for long-term (1-12 months)
radon tests.
amphibolite A mafic metamorphic rock consisting mainly of pyroxenes and(or) ampnibole and
plagioclase.
n-21 Reprinted from USGS Open-File Report 93-292
-------
argillite, argillaceous Terms referring to a rock derived from clay or shale, or any sedimentary
rock containing an appreciable amount of clay-size material, i.e., argillaceous sandstone.
arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
amount of precipitation.
basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
such as volcanic basalt flows, or intrusive origin, such as basalt dikes.
batholith A mass of plutonic igneous rock that has more than 40 square miles of surface
exposure and no known bottom.
carbonate A sedimentary rock consisting of the carbonate (CO3) compounds of calcium,
magnesium, or iron, e.g. limestone and dolomite.
carbonaceous Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
matter.
charcoal canister A passive radon measurement device consisting of a small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.
clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.
day A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm.
day mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.
concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center, such as
a leaf, shell, bone, or fossil, within a sedimentary or fractured rock.
conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.
cuesta A hill or ridge with a gentle slope on one side and a steep slope on the other. The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
1-22 Reprinted from USGS Open-File Report 93-292
-------
delta, deltaic Referring to a low, flat, alluvial tract of land having a triangular or fan shape,
located at or near the mouth of a river. It results from the accumulation of sediment deposited'by a
river at the point at which the river loses its ability to transport the sediment, commonly where a
nver meets a larger body of water such as a lake or ocean.
dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
across the bedding or foliation of the rock it intrudes.
diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor
quartz.
dolomite A carbonate sedimentary rock of which more than 50% consists of the mineral dolomite
(CaMg(CO3)2), and is commonly white, gray, brown, yellow, or pinkish in color.
drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
Also refers to the water features of an area, such as lakes and rivers, that drain it
eolian Pertaining to sediments deposited by the wind.
esker A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
by streams beneath a glacier and left behind when the ice melted.
evapotranspiration Loss of water from a land area by evaporation from the soil and
transpiration from plants.
extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
fault A fracture or zone of fractures in rock or sediment along which there has been movement
fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
may be formed during deformation or metamorphism.
formation A mappable body of rock having similar characteristics.
glacial deposit Any sediment transported and deposited by a glacier or processes associated
with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
gneiss A rock formed by metamorphism in which bands and lenses of minerals of similar
composition alternate with bands and lenses of different composition, giving the rock a striDed or
"foliated" appearance. - *
granite Broadly applied, any coarsely crystalline, quartz- and feldspar-bearing igneous plutonic
52J- Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
65% of the total feldspar.
gravel An unconsolidated, natural accumulation of rock fragments consisting predominantlv of
particles greater than 2 mm in size.
heavy minerals Mineral grains in sediment or sedimentary rock having higher than average
specific gravity. May form layers and lenses because of wind or water sorting by weight and size
n-23 Reprinted from USGS Open-File Report 93-292
-------
and may be referred to as a "placer deposit" Some heavy minerals are magnetite, garnet, zircon,
monazite, and xenotime.
igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
one of the three main classes into which rocks are divided, the others being sedimentary and
metamorphic.
intermontane A term that refers to an area between two mountains or mountain ranges.
intrusion, intrusive The processes of emplacement or injection of molten rock into pre-existing
rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock".
kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
dissolution of the rock by water, forming sinkholes and caves.
lignite A brownish-black coal that is intermediate in coalification between peat and
subbituminous coal.
limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
primarily in the form of the mineral calcite (CaCOa).
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural
changes in response to changes in temperature, pressure, stress, and the chemical environment
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, imbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4.
11-24 Reprinted from USGS Open-File Report 93-292
-------
physiographic province A region in which all parts are similar in geologic structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.
placer deposit See heavy minerals
residual Formed by weathering of a material in place.
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (tithification) of clay or mud.
shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.
shrink-swell clay See clay mineral.
siltstone A fine-grained clastic sedimentary rock composed of silt-sized rock and mineral
material and more or less firmly cemented. Silt particles range from 1/16 to 1/256 mm in size.
sinkhole A roughly circular depression hi a karst area measuring meters to tens of meters in
diameter. It is funnel shaped and is formed by collapse of the surface material into an underlying
void created by the dissolution of carbonate rock.
slope An inclined part of the earth's surface.
solution cavity A hole, channel or cave-like cavity formed by dissolution of rock.
stratigraphy Hie study of rock strata; also refers to the succession of rocks of a particular area.
surflcial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent
n-25 Reprinted from USGS Open-File Report 93-292
-------
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment.
till Unsorted, generally unconsolidated and imbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by meltwater. Size of grains varies greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
11-26 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
EPA Regional Offices
State
EPA Reeion
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-4502
EPA Region 2
(2AIR:RAD)
26 Federal Plaza
New York, NY 10278
(212) 264-4110
Region 3 (3AH14)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
EPA Region 5 (5AR26)
77 West Jackson Blvd.
Chicago, TL 60604-3507
(312) 886-6175
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7604
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303) 293-1713
EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202) 442-7660
Alabama 4
Alaska 10
Arizona 9
Arkansas 6
California 9
Colorado 8
Connecticut 1
Delaware 3
District of Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho 10
Illinois 5
Indiana 5
Iowa 7
Kansas : 7
Kentucky 4
Louisiana 6
Maine 1
Maryland 3
Massachusetts 1
Michigan 5
Minnesota 5
Mississippi 4
Missouri 7
Montana 8
Nebraska 7
Nevada 9
New Hampshire 1
New Jersey 2
New Mexico 6
New York 2
North Carolina 4
North Dakota 8
Ohio 5
Oklahoma 6
Oregon 10
Pennsylvania 3
Rhode Island 1
South Carolina 4
South Dakota 8
Tennessee 4
Texas 6
Utah 8
Vermont 1
Virginia „ 3
Washington 10
West Virginia 3
Wisconsin 5
Wyoming 8
H-27 Reprinted from USGS Open-File Report 93-292
-------
STATE RADON CONTACTS
May, 1993
California
Colorado
James McNees
Division of Radiation Control
Alabama Department of Public I. .Jth
State Office Building
Montgomery, AL 36130
(205)242-5315
1-800-582-1866 in state
Charles Tedford
Department of Health and Social
Services
P.O. Box 110613
Juneau, AK 99811-0613
(907)465-3019
1-800-478-4845 in state
John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St.
Phoenix, AZ 85040
(602)2554845
LeeGershner
Division of Radiation Control
Department of Health
4815 Markham Street, Slot 30
Little Rock, AR 72205-3867
(501)661-2301
J. David Quinton
Department of Health Services
714 P Street, Room 600
Sacramento, CA 94234-7320
(916)324-2208
1-800-745-7236 in state
LindaMartin
Department of Health
4210 East llth Avenue
Denver, CO 80220
(303)692-3057
1-800-846-3986 in state
Connecticut Alan J. Siniscalchi
Radon Program
Connet ..cut Department of Health
Services
150 Washington Street
Hartford, CT 06106-4474
(203) 566-3122
Delaware MaraiG. Rejai
Office of Radiation Control
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302)736-3028
1-800-554-4636 Li State
District Robert Davis
of Columbia DC Department of Consumer and
Regulatory Affairs
614 H Street NW
Room 1014
Washington, DC 20001
(202)727-71068
Florida N. Michael Gilley
Office of Radiation Control
Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, EL 32399-0700
(904)488-1525
1-800-543-8279 in state
Richard Schreiber
Georgia Department of Human
Resources
878 Peachtree St., Room 100
Atlanta, GA 30309
(404) 894-6644
1-800-745-0037 in state
Hawaii Russell Takata
Environmental Health Services
Division
591 Ala Moana Boulevard
Honolulu, HI 96813-2498
(808) 5864700
H-28 Rejirinted from USGS Open-File Report 93-292
-------
Idato
Illinois
Indiana.
Iowa
Kansas
Kentucky
PatMcGavarn
Office of Environmental Health
450 West State Street
Boise, ID 83720
(208)334-6584
1-800-445-8647 in state
Richard Allen
Illinois Department of Nuclear Safety
1301 Outer Park Drive
Springfield, IL 62704
(217)524-5614
1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317)633-8563
1-800-272-9723 In State
Donald A. Plater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515)281-3478
1-800-383-5992 In State
Harold Spiker
Radiation Control Program
Kansas Department of Health and
Environment
109 SW 9th Street
6th Floor Mills Building
Topeka, KS 66612
(913)296-1561
JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
(502)564-3700
Louisiana. Matt Schlenker
Louisiana Department of
Environmental Quality
P.O. Box 82135
Baton Rouge, LA 70:84-2135
(504)925-7042
1-800-256-2494 in state
Maine Bob Stilwell
Division of Health Engineering
Department of Human Services
State House, Station 10
Augusta, ME 04333
(207)289-5676
1-800-232-0842 in state
Maryland LeonJ. Rachuba
Radiological Health Program
Maryland Department of the
Environment
2500 Broening Highway
Baltimore, MD 21224
(410)631-3301
1-800-872-3666 In State
Massachusetts William J. Bell
Radiation Control Program
Department of Public Health
23 Service Center
Northampton, MA 01060
(413) 586-7525
1-800-445-1255 in state
Michigan SueHendershott
Division of Radiological Health
Bureau of Environmental and
Occupational Health
3423 North Logan Street
P.O. Box 30195
Lansing, MI 48909
(517) 335-8194
Minnesota Laura Oatmann
Indoor Air Quality Unit
925 Delaware Street, SE
P.O. Box 59040
Minneapolis, MN 55459-0040
(612)627-5480
1-800-798-9050 in state
n-29 Reprinted from USGS Open-File Report 93-292
-------
Mississippi Silas Anderson
Division of Radiological Health
Department of Health
3150 Lawson Street
P.O. Box 1700
Jackson, MS 39215-1700
(601)354-6657
1-800-626-7739 in state
Missouri Kenneth V. Miller
Bureau of Radiological Health
Missouri Department of Health
1730 East Elm
P.O. Box 570
Jefferson City, MO 65102
(314)751-6083
1-800-669-7236 Instate
Montana Adrian C. Howe
Occupational Health Bureau
Montana Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406)444-3671
Nebraska Joseph Milone
Division of Radiological Health
Nebraska Department of Health
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509
(402)471-2168
1-800-334-9491 In State
Nevada Stan Marshall
Department of Human Resources
505 East King Street
Room 203
Carson City, NV 89710
(702)687-5394
New Hampshire David Chase
Bureau of Radiological Health
Division of Public Health Services
Health and Welfare Building
Six Hazen Drive
Concord, NH 03301
(603)271-4674
1-800-852-3345 x4674
New Jersey Tonalee Carlson Key
. Division of Environmental Quality
Department of Environmental
Protection
CN415
Trenton, NJ 08625-0145
(609)987-6369
1-800-648-0394 in state
New Mexico William M. Floyd
Radiation Licensing and Registration
Section
New Mexico Environmental
Improvement Division
1190 St. Francis Drive
Santa Fe,NM 87503
(505) 827-4300
New York William J. Condon
Bureau of Environmental Radiation
Protection
New York State Health Department
Two University Place
Albany, NY 12202
(518)458-6495
1-800-458-1158 in state
North Carolina Dr. Felix Fong
Radiation Protection Division
Department of Environmental Health
and Natural Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 571-4141
1-800-662-7301 (recorded info x4196)
North Dakota Arlen Jacobson
North Dakota Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701)221-5188
Ohio Marcie Matthews
Radiological Health Program
Department of Health
1224 Kinnear Road - Suite 120
Columbus, OH 43212
(614)644-2727
1-800-523-4439 in state
n-30 Reprinted from USGS Open-File Report 93-292
-------
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
Gene Smith .
Radiation Protection Division
Oklahoma State Department of
Health
P.O. Box 53551
Oklahoma City, OK 73152
(405)271-5221
George Toombs
Department of Human Resources
Health Division
1400 SW5th Avenue
Portland, OR 97201
(503) 731-4014
Michael Pyles
Pennsylvania Department of
Environmental Resources
Bureau of Radiation Protection
P.O. Box 2063
Harrisburg, PA 17120
(717)783-3594
1-800-23-RADON In State
David Saldana
Radiological Health Division
GJP.O. Call Box 70184
Rio Piedras, Puerto Rico 00936
(809)767-3563
Edmund Arcand
Division of Occupational Health and
Radiation
Department of Health
205 Cannon Building
Davis Street
Providence, RI02908
(401)277-2438
Bureau of Radiological Health
Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803)734-4631
1-800-768-0362
South Dakota MikePochop
. Division of Environment Regulation
Department of Water and Natural
Resources
Joe Foss Building, Room 217
523 E. Capitol
Pierre, SD 57501-3181
(605)773-3351
Tennessee Susie Shimek
Division of Air Pollution Control
Bureau of the Environment
Department of Environment and
Conservation
Customs House, 701 Broadway
Nashville, TN 37219-5403
(615) 532-0733
1-800-232-1139 in state
Texas Gary Smith
Bureau of Radiation Control
Texas Department of Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 834-6688
Utah John Hultquist
Bureau of Radiation Control
Utah State Department of Health
288 North, 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801)536^250
Vermont Paul demons
Occupational and Radiological Health
Division
Vermont Department of Health
10 Baldwin Street
Montpelier, VT 05602
(802) 828-2886
1-800-640-0601 in state
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region n
in New York
(212)264-4110
11-31 Reprinted from USGS Open-File Report 93-292
-------
Virginia Shelly Ottenbrite
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804)786-5932
1-800-468-0138 in state
Washington KaleColeman
Department of Health
Office of Radiation Protection
Airdustrial Building 5, LE-13
Olympia,WA 98504
(206)753-4518
1-800-323-9727 In State
West Virginia Beanie L.DeBprd
Industrial Hygiene Division
West Virginia Department of Health
151 llth Avenue
South Charleston, WV 25303
(304) 558-3526
1-800-922-1255 In State
Wisconsin. Conrad Weiffenbach
Radiation Protection Section
Division of Health
Department of Health and Social
Services
P.O. Box 309
Madison, WI53701-0309
(608)267-4796
1-800-798-9050 in state
Wyoming Janet Hough
Wyoming Department of Health and
Social Services
Hathway Building. 4th Floor
Cheyenne, WY 82002-0710
(307)777-6015
1-80O458-5847 in state
II-32 Reprinted from USGS Open-File Report 93-292
-------
STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Ernest A. Mancini
Geological Survey of Alabama
P.O. Box 0
420 Hackberry Lane
Tuscaloosa, AL 35486-9780
(205)349-2852
Alaska Thomas E. Smith
Alaska Division of Geological &
Geophysical Surveys
794 University Ave., Suite 200
Fairbanks, AK 99709-3645
(907)479-7147
Arizona Larry D. Fellows
Arizona Geological Survey
845 North Park Ave., Suite 100
Tucson, AZ 85719
(602)882-4795
Arkansas Norman F. Williams
Arkansas Geological Commission
Vardelle Parham Geology Center
3815 West Roosevelt Rd.
Little Rock, AR 72204
(501)324-9165
James F. Davis
California Division of Mines &
Geology
801 K Street, MS 12-30
Sacramento, CA 95814-3531
(916)445-1923
Colorado Pat Rogers (Acting)
Colorado Geological Survey
1313 Sherman St., Rm 715
Denver, CO 80203
(303)866-2611
Connecticut Richard C. Hyde
Connecticut Geological & Natural
History Survey
165 Capitol Ave., Rm. 553
Hartford, CT 06106
(203)566-3540
Delaware Robert R. Jordan
Delaware Geological Survey
University of Delaware
101 Penny Hall
Newark, DE 19716-7501
(302)831-2833
Florida Walter Schmidt
Florida Geological Survey
903 W. Tennessee St
Tallahassee, FL 32304-7700
(904)488^191
William H. McLemore
Georgia Geologic Survey
Rm. 400
19 Martin Luther King Jr. Dr. SW
Atlanta, GA 30334
(404)656-3214
Hawaii Manabu Tagomori
Dept of Land and Natural Resources
Division of Water & Land Mgt
P.O. Box 373
Honolulu, HI 96809
(808)548-7539
EariH. Bennett
Idaho Geological Survey
University of Idaho
Morrill Hall, Rm. 332
Moscow, ID 83843
(208) 885-7991
Illinois Morris W.Leighton
Illinois State Geological Survey
Natural Resources Building
615EastPeabodyDr.
Champaign, IL 61820
(217)333^747
Indiana Norman C. Hester
Indiana Geological Survey
611 North Walnut Grove
Bloomington, IN 47405
(812)855-9350
Lffla Donald L.Koch
Iowa Department of Natural Resources
Geological Survey Bureau
109 Trowbridge Hall
Iowa City, IA 52242-1319
(319)335-1575
Kansas LeeC. Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence, KS 66047
(913)864-3965
11-33 Reprinted from USGS Open-File Report 93-292
-------
Kentucky Donald CHaney
Kentucky Geological Survey
University of Kentucky
228 Mining & Mineral Resources
Building
Lexington, KY 40506-0107
(606)257-5500
Louisiana William E. Marsalis
Louisiana Geological Survey
P.O. Box 2827
University Station
Baton Rouge, LA 70821-2827
(504) 388-5320
Maine Walter A. Anderson
Maine Geological Survey
Department of Conservation
State House, Station 22
Augusta, ME 04333
(207)289-2801
Maryland Emery T. Cleaves
Maryland Geological Survey
2300 St Paul Street
Baltimore, MD 21218-5210
(410) 554-5500
Massachusetts Joseph A. Sinnott
Massachusetts Office of
Environmental Affairs
100 Cambridge St, Room 2000
Boston, MA 02202
(617)727-9800
Michigan R. Thomas Segall
Michigan Geological Survey Division
Box 30256
Lansing, MI 48909
(517) 334-6923
Minnesota Priscilla C. Grew
Minnesota Geological Survey
2642 University Ave.
St Paul, MN 55114-1057
(612)627-4780
Mississippi S. Cragin Knox
Mississippi Office of Geology
P.O. Box 20307
Jackson, MS 39289-1307
(601) 961-5500
Missouri James H. Williams
. Missouri Division of Geology &
Land Survey
111 Fairgrounds Road
P.O. Box 250
Rolla, MO 65401
(314)368-2100
Montana Edward T.Ruppel
Montana Bureau of Mines & Geology
Montana College of Mineral Science
and Technology, Main Hall
Butte,MT 59701
(406)4964180
Nebraska Perry B. Wigley
Nebraska Conservation & Survey
Division
113 Nebraska Hall
University of Nebraska
Lincoln, ME 68588-0517
(402)472-2410
Nevada Jonathan G. Price
Nevada Bureau of Mines & Geology
Stop 178
University of Nevada-Reno
Reno, NV 89557-0088
(702) 784-6691
New Hampshire Eugene L. Boudette
Dept of Environmental Services
117 James Hall
University of New Hampshire
Durham, NH 03824-3589
(603) 862-3160
New Jersey Haig F. Kasabach
New Jersey Geological Survey
P.O. Box 427
Trenton, NJ 08625
(609)292-1185
New Mexico Charles E. Chapin
New Mexico Bureau of Mines &
Mineral Resources
Campus Station
Socorro,NM 87801
(505) 835-5420
New York Robert ELFakundiny
New York State Geological Survey
3136 Cultural Education Center
Empire State Plaza
Albany, NY 12230
(518)474-5816
11-34 Reprinted from USGS Open-File Report 93-292
-------
North Carolina Charles H. Gardner
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919)733-3833
North Dakota John P. Bluemle
North Dakota Geological Survey
600 East Blvd.
Bismarck, ND 58505-0840
(701)224-4109
.Qhip Thomas M. Berg
Ohio DepL of Natural Resources
Division of Geological Survey
4383 Fountain Square Drive
Columbus, OH 43224-1362
(614)265-6576
Oklahoma Charles J. Mankin
Oklahoma Geological Survey
Room N-131, Energy Center
100E.Boyd
Norman, OK 73019-0628
(405)325-3031
Donald A. Hull
Dept of Geology & Mineral Indust.
Suite 965
800 NE Oregon SL #28
Portland, OR 97232-2162
(503)731-4600
Pennsylvania Donald M. Hoskins
Dept. of Environmental Resources
Bureau of Topographic & Geologic
Survey
P.O. Box 2357
Harrisburg,PA 17105-2357
(717)787-2169
Puerto Ricn Ram6n M. Alonso
Puerto Rico Geological Survey
Division
Box 5887
Puerta de Tierra Station
San Juan, PJL 00906
(809)722-2526
Rhode Island J.Allan Cain
Department of Geology
University of Rhode Island
315 Green Hall
Kingston, RI 02881
(401)792-2265
Utah
South Carolina Alan-Jon W. Zupan (Acting)
. South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-9998
(803)737-9440
South Dakota CM. Christensen (Acting)
South Dakota Geological Survey
Science Center
University of South Dakota
Vermfflion, SD 57069-2390
(605)677-5227
Tennessee Edward T.Luther
Tennessee Division of Geology
13th Floor, L & C Tower
401 Church Street
Nashville, TN 37243-0445
(615)532-1500
William L. Fisher
Texas Bureau of Economic Geology
University of Texas
University Station, Box X
Austin, TX 78713-7508
(512)471-7721
M. Lee Allison
Utah Geological & Mineral Survey
2363 S. Foothill Dr.
Salt Lake City, UT 84109-1491
(801)467-7970
Vermont Diane L. Conrad
Vermont Division of Geology and
Mineral Resources
103 South Main SL
Waterbury.VT 05671
(802)244-5164
Virginia Stanley S. Johnson
Virginia Division of Mineral
Resources
P.O. Box 3667
Charlottesville, VA 22903
(804)293-5121
Washington Raymond Lasmanis
Washington Division of Geology &
Earth Resources
Department of Natural Resources
P.O. Box 47007
Olympia, Washington 98504-7007
(206)902-1450
11-35 Reprinted from USGS Open-File Report 93-292
-------
, West Virginia Larry D.Wopdfoik
West Virginia Geological and
Economic Survey
Mont Chateau Research Center
P.O. Box 879
Morgantown.WV 26507-0879
(304) 594-2331
Wisconsin James Robertson
Wisconsin Geological & Natural
History Survey
3817 Mineral Point Road
Madison, WI 53705-5100
(608)263-7384
Wyoming Gary B. Glass
Geological Survey of Wyoming
University of Wyoming
Box 3008, University Station
Laramie, WY 82071-3008
(307)766-2286
11-36 Reprinted from USGS Open-File Report 93-292
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EPA REGION 5 GEOLOGIC RADON POTENTIAL SUMMARY
by
R. Randall Schumann, Douglass E. Owen, and Sandra L. Szarzi
U.S. Geological Survey
EPA Region 5 comprises the states of Illinois, muiana, Michigan, Minnesota, Ohio, and
Wisconsin. For each state, geologic radon potential areas were delineated and ranked on the
basis of geologic, soil, housing construction, and other factors. Areas in which the average
screening indoor radon level of all homes within the area is estimated to be greater than 4 pCi/L
were ranked high. Areas in which the average screening indoor radon level of all homes within
the area is estimated to be between 2 and 4 pCi/L were ranked moderate/variable, and areas in
which the average screening indoor radon level of all homes within the area is estimated to be
less than 2 pCi/L were ranked low. Information on the data used and on the radon potential
ranking scheme is given in the introduction chapter. More detailed information on the geology
and radon potential of each state in Region 5 is given in the individual state chapters. The
individual chapters describing the geology and radon potential of the six states in EPA Region 5,
though much more detailed than this summary, still are generalized assessments and there is no '
substitute for having a home tested. Radon levels, both high and low, can be quite localized, and
within any radon potential area homes with indoor radon levels both above and below the
predicted average will likely be found.
Radon potential in EPA Region 5 is controlled by three primary factors. Bedrock
geology provides the source material for the overlying glacial deposits, and in areas with no
glacial cover, directly provides the parent material for the soils. Glacial geology (fig. 1) is an
important factor because glaciers redistributed the bedrock and glacially-derived soils have
different soil characteristics from soils developed on bedrock. Climate, particularly precipitation
and temperature, in concert with the soil's parent material, controls soil moisture, the extent of
soil development and weathering, and the types of weathering products that form in the soils.
The following is a brief, generalized discussion of the bedrock and glacial geology of EPA
Region 5 as they pertain to indoor radon. More detailed discussions may be found in the
individual state geologic radon potential chapters.
Western and southern Minnesota are underlain by deposits of the Des Moines and Red
River glacial lobes. Des Moines lobe tills are silty clays and clays derived from Upper
Cretaceous sandstones and shales, which have relatively high concentrations of uranium and high
radon emanating power. Deposits of the Red River lobe are similar to those of the Des Moines
lobe, but also contain silt and clay deposits of glacial Lake Agassiz, a large glacial lake that
occupied the Red River Valley along the Minnesota-North Dakota border. The Upper
Cretaceous Pierre Shale provides good radon source material because, as a whole, it contains
higher-than-average amounts of uranium (average crustal abundance of uranium is about 2.5
parts per million). Glacial deposits of the Red River and Des Moines lobes generate high
(> 4 pCi/L) average indoor radon concentrations (fig. 2) and have high geologic radon potential
(fig. 3). Northern Wisconsin, the western part of the Upper Peninsula of Michigan, and part of
northern Minnesota are underlain by glacial deposits of the Lake Superior lobe. Parts of northern
Minnesota are also underlain by deposits of the Rainy and Wadena lobes (fig. 1). The
underlying source rocks for these tills are Precambrian volcanic rocks, metasedimentary and
metavolcanic rocks, and granitic plutonic rocks of the Canadian Shield. The volcanic,
metasedimentary, and metavolcanic rocks have relatively low uranium contents, and the granitic
rocks have variable, mostly moderate to high, uranium contents. The sandy tills derived from the
ffl-l Reprinted from USGS Open-File Report 93-292-E
-------
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volcanic, metasedimentary, and metavolcanic rocks have relatively high permeability, but
because of their lower uranium content of and lower emanating power, they have mostly
moderate to locally high radon potential (fig. 3). Sandy, granite-rich tills in northern Minnesota
generally have high radon potential. Granites and granite gneisses, black slates and graphitic
schists, and iron-formation are associated with anomalous uranium concentrations and locally
high radon in northern Wisconsin and adjacent northwestern Michigan. In central Wisconsin,
uraniferous granites of the Middle Proterozoic Wolf River and Wausau plutons are exposed at
the surface or covered by a thin layer of glacial deposits and cause some of the highest indoor
radon concentrations in the State. An area in southwestern Wisconsin and adjacent smaller parts
of Minnesota, Iowa, and Illinois, is called the "Driftless Area" (fig. 1). It is not covered by
glacial deposits but parts of the area were likely overran by glaciers at least once. The Driftless
Area is underlain by Cambrian and Ordovician limestone, dolomite, and sandstone with
moderate to high radon potential.
Glacial deposits in southern Wisconsin, northern and central Illinois, and western Indiana
are primarily from the Green Bay and Lake Michigan lobes. The Green Bay and Lake Michigan
lobes advanced from their source in the Hudson Bay region of Canada and moved southward
terminating in Illinois and Iowa. These tills range from sandy to clayey and are derived
primarily from shales, sandstones, and carbonate rocks of southern Wisconsin, the western
Michigan Basin, and the northern Illinois Basin. A small part of eastern Illinois and much of
western Indiana are covered by deposits of the Huron-Erie lobe, and west-central Illinois is
covered by glacial deposits of pre-Wisconsinan, mostly niinoian, age. The Huron-Erie lobe
entered Illinois from the east and moved westward and southwestward into the State. Huron-Erie
lobe and pre-Wisconsinan glacial deposits are derived from Paleozoic shale, sandstone, siltstone
carbonate rocks, and coal of the Illinois Basin, and they are commonly calcareous due to the
addition of limestones and dolomites of northern Indiana and Ohio and southern Ontario In
contrast, Lake Michigan lobe deposits contain significant amounts of dark gray to black
Devonian and Mississippian shales of the Michigan Basin, accounting for the high clay content
of Lake Michigan lobe tills. Unglaciated southernmost Illinois is part of the Mississippi
Embayment of the Coastal Plain and has low geologic radon potential.
Wisconsin-age glacial deposits in Indiana were deposited by three main glacial lobes—
the Lake Michigan lobe, which advanced southward as far as central Indiana; the Huron-Erie
lobe; and the Saginaw sublobe of the Huron lobe (labeled Huron lobe on fig. 1), which advanced
from the northeast across northern Ohio and southern Michigan, respectively. Michigan lobe
deposits are clayey near Lake Michigan, sandy and gravelly in an outwash and morainal area in
northwestern Indiana, and clayey to loamy in west-central Indiana. Saginaw sublobe deposits are
loamy and calcareous and are derived primarily from carbonate rocks and shale. The Huron-Erie
lobe advanced from the northeast and covered much of northern and central Indiana at its
maximum extent Eastern Indiana and western Ohio are underlain by tills of the Huron-Erie lobe
that are derived in part from black shales of the Devonian Ohio Shale and Devonian-
Mississippian New Albany Shale, but also include Paleozoic limestone, dolomite, sandstone
siltstone, and gray shale. Black shales and carbonates underlie and provide source material for
glacial deposits in a roughly north-south pattern through central Ohio, including the Columbus
area, and extend south of the glacial limit, where the black shales form a prominant arcuate
pattern in northern Kentucky that curves northward into southern Indiana and underlies glacial
deposits in east-central Indiana. The overall radon potential of this area is high. Eastern Ohio is
underlain by Devonian to Permian shales and limestones with moderate to high radon potential
m-5 Reprinted from TJSGS Open-File Report 93-292-E
-------
The Michigan Basin covers all of the Southern Peninsula and the eastern half of the
Northern Peninsula of Michigan, as well as parts of eastern Wisconsin and northeastern Illinois,
northern Indiana, and northwestern Ohio. Glacial deposits include silty and clayey tills of the
Lake Michigan, Huron, and Huron-Erie lobes (fig. 1). Huron lobe tills are sandy to gravelly and
calcareous, containing pebbles and cobbles of limestone, dolomite, and some sandstone and
shale, with boulders of igneous and metamorphic rocks and quartzite. Tills of the Huron-Erie
and Lake Michigan lobes are derived from similar source rocks but are more silty and clayey in
texture. Source rocks for these tills are sandstones, gray shales, and carbonate rocks of the
Michigan Basin, which are generally poor radon sources. In the Southern Peninsula, the
Devonian Bell, Antrim, and Ellsworth Shales, and Mississippian Sunbury Shale locally contain
organic-rich black shale layers with higher-than-average amounts of uranium, except for the
Antrim Shale, which is organic rich throughout These shales underlie and constitute source rock
for glacial deposits in the northern, southeastern, and southwestern parts of the Southern
Peninsula, and are locally exposed at the surface in the northern part of the Southern Peninsula.
Because of generally moist soils, soils developed on tills derived from black shales in Michigan
generate moderate to locally high radon, with higher values more common in the southern part of
the State (fig. 2).
Glaciated areas present special problems for radon-potential assessment because bedrock
material in the central United States was commonly transported hundreds of km from its source.
Glaciers are quite effective in redistributing uranium-rich rocks; for example, in Ohio, uranium-
bearing black shales have been disseminated over much of western Ohio and eastern Indiana,
now covering a much larger area than their original outcrop pattern, and display a prominent
radiometric high. The physical, chemical, and drainage characteristics of soils formed from
glacial deposits vary according to source bedrock type and the glacial features on which they are
formed. For example, soils formed from ground moraine deposits tend to be more poorly
drained and contain more fine-grained material than soils formed on kames, moraines, or eskers,
which are generally coarser and well-drained. In general, soils developed from coarser-grained
tills are poorly structured, poorly sorted, and poorly developed, but are generally more highly
permeable than the bedrock from which they are derived.
Clayey tills, such as those underlying parts of western and southern Minnesota, have
relatively high emanation coefficients and usually have low to moderate permeability, depending
on the degree to which the clays are mixed with coarser sediments. Tills consisting of mostly
coarse material tend to emanate less radon because larger grains have lower surface area-to-
volume ratios, but because these soils have generally high permeabilities, radon transport
distances are generally longer. Structures built in these materials are thus able to draw soil air
from a larger source volume, so moderately to highly elevated indoor radon concentrations may
be achieved from comparatively lower-radioactivity soils. In till soils with extremely high
permeability, atmospheric dilution may become significant, and if the soils have low to moderate
radium contents, elevated indoor radon levels would be less likely to occur. Soil moisture has a
significant effect on radon generation and transport and high levels of soil moisture generally
lower the radon potential of an area. The main effect of soil moisture is its tendency to occlude
soil pores and thus inhibit soil-gas transport. Soils in wetter climates from northern Minnesota to
northern Michigan generally have lower radon potential than soils derived from similar tills in
the southern parts of those states or in Indiana and Illinois, in part because of higher soil moisture
conditions to the north.
m-6 Reprinted from USGS Open-FUe Report 93-292-E
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PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF OHIO
by
Douglass E. Owen
U.S. Geological Survey
INTRODUCTION
Ohio is one of the Great Lakes States and is located south of Lake Erie. Ohio is highly
industrialized, but also has significant agricultural activity. The State is subdivided into 88
counties (fig. 1). The population distribution by county is shown on figure 2. All 88 counties in
Ohio have more than 10,000 residents, 20 counties have between 100,000 and 500,000 residents,
and 5 counties have more than 500,000 residents.
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Ohio. The scale of this assessment is such that it is inappropriate for use in identifying
the radon potential of small areas such as neighborhoods, individual building sites, or housing
tracts. Any localized assessment of radon potential must be supplemented with additional data and
information from the locality. Within any area of a given radon potential ranking, there are likely
to be areas with higher or lower radon levels than characterized for the area as a whole. Indoor
radon levels, both high and low, can be quite localized, and there is no substitute for testing
individual homes. Elevated levels of indoor radon have been found in every state, and EPA
recommends that all homes be tested. For more information on radon, the reader is urged to
consult the local or State radon program or EPA regional office. More detailed information on state
or local geology may be obtained from the State geological survey. Addresses and phone numbers
for these agencies are listed in chapter 1 of this booklet
GEOGRAPHIC SETTING OF OHIO
Approximately the eastern third of Ohio is part of the Allegheny Plateau. The remainder of
the State is part of the Interior Lowlands physiographic province (fig. 3). The Allegheny Plateau,
which is drained by the Ohio River, is much more dissected than the Interior Lowlands. The
Allegheny Plateau is subdivided into two physiographic sections, the unglaciated plateau and the
glaciated plateau (fig. 4). Valleys in the unglaciated section tend to be deeper and steeper sided
than in the glaciated section. The Interior Lowlands are subdivided into three physiographic
sections-the Till Plains, the Lake Plains, and the Lexington Plain (fig. 4). The Till Plains formed
during the glaciation of the Pleistocene Epoch and are either flat or gently undulating. The
undulations are due either to variations in the underlying bedrock or to other glacial deposits such
as moraines, kames, and eskers. Water trapped between the retreating ice of the last continental ice
sheet and the glacial deposits of west-central Ohio produced lakes. The Lake Plains resulted when
these lakes drained, exposing the flat lake bottoms. The Lexington Plain is unglaciated and was
formed by stream erosion of limestone bedrock. The areas between stream dissections in the
Lexington Plain are flat-topped and also contain a large number of sinkholes.
IV-1 Reprinted from USGS Open-File Report 93-292-E
-------
Fig. 1. Counties
-------
POPULATION (1990)
0 0 to 25000
0 25001 to 50000
0 50001 to 100000
H 100001 to 500000
• 500001 to 1412140
Figure 2. Population of counties in Ohio (1990 U.S. Census data).
-------
Interior Lowlands
Allegheny Plateau
(modified from Wright, 1953)
FIfl. 3. Physical Settinfl (modified from Noble and Kor.ok. 1975}
| | Tm Plain* «,-" (Southern limit of
Wlsconainan glaciatlon)
Lake Plain*
Glaciated Plateau
Lexington Plain
I**]
[AA! Unglaciated Plateau
Fig. 4. Physiographic Sections
-------
GEOLOGIC SETTING OF OHIO
The bedrock in Ohio ranges in age from Ordovician to Permian. (Note-a Geologic Time
Scale is presented in the appendix to the introduction.) Only rocks of sedimentary origin crop out
in Ohio; however, igneous and metamorphic material is present in the deposits left behind by the
continental glaciers. In general, rocks become younger from west to east in Ohio (fig. 5). A
generalized section of rocks of Ohio, listing formation names, member names, and other geologic
information for each of the geologic time periods can be found in Stout (1947). The stratigraphy
of western Ohio is dominated by carbonate rocks, and numerous thin limestones are present in
eastern Ohio along with shales, sandstones, and coals (fig. 6). The abundance of carbonates is
also reflected in the soils. Devonian shales crop out in a north-south band in the center of the State
and along Lake Erie (fig. 5).
About two-thirds of Ohio was glaciated during the Pleistocene Epoch. Deposits left behind
by three of the four major glacial advances have been identified in Ohio. The oldest, pre-Elinoian
(formerly called Kansan), is of limited extent and is only found in the southwest corner of the
State. The next oldest, Dlinoian, is exposed in a band just below the furthest advance of the
youngest glacial deposits, the Wisconsinan (fig. 7). Wisconsinan lake deposits, kames and
eskers, ground moraine, and end moraines are shown on figure 7.
SOILS
The soil regions found in Ohio are shown on figure 8 and the drainage characteristics of the
soils are shown on figure 9. Drainage characteristics give an indication of the soil permeability,
which influences radon migration. Because the amount of moisture available to soils affects both
emanation and transport of radon, a map showing annual precipitation has been included (fig. 10).
INDOOR RADON DATA
Figure 11 presents screening indoor radon data from the State/EPA Residential Radon
Survey graphically, and Table 1 presents the data from which figure 11 was derived, including
data from those counties with less than 5 measurements (which are not shown on figure 11).
Figure 1 shows the Ohio counties and can be used in conjunction with the indoor radon maps
shown in figure 11. Forty-two of the counties in Ohio had average radon concentrations greater
than 4 pCi/L (fig. 11 & Table 1). Five counties had greater than 60 percent of the homes with
radon concentrations greater than 4 pCi/L (fig. 11, Table 1). Twenty-five counties had between 40
and 60 percent of the homes with radon concentrations greater than 4 pCi/L (fig. 11, Table 1).
In general, counties with average radon concentrations greater than 4pCi/L seem to be
associated with the north-south trending Ohio Shale outcrop band that has been redistributed by
glaciers, with limestone glacial soils, and with some residual limestone soils (figs. 5,7, 8,11). In
a study of Franklin County (located over the N-S outcrop band of Ohio Shale), Grafton (1990)
found that 92 percent of the homes in a random survey using screening indoor radon
measurements had indoor radon concentrations greater than 4 pCi/L. The counties around the
precipitation high in the northeastern corner of the State (fig. 10) in general have a low percentage
of homes with radon concentrations exceeding 4 pCi/L. This may partially be due to inhibited
radon transport caused by the precipitation.
IV-5 Reprinted from USGS Open-File Report 93-292-E
-------
KJ\\\\Ma\V(ii. v\\\YiVi
'Ww^1 i
'V.Aii^WS'.nM'M
from Ohio Geological Survey Map)
m'Afc*
-Shale.
sandstone, and coal
Pennsylvanian -Shale.
sandstone, coal, and
limestone
!• •_ IMI s s I s s'l p p I a n -Shale.
l*« I sandstone, and
limestone
Devonian -Shale and
limestone
Tfl Silurian -Limestone
Ml and shale
|rz| Ordovlclan -Shale
and limestone
Fig. 5. Geologic Map
-------
(modified from Wright. 1963)
|g| Numerous thin und.fferenti.ted lime.tone.
Oeleware and Columbus Limestones
,.,and and Detrolt Rlver
(dolomite8)
Nl«0ra Group (dolomite)
. „.„.„,„.
Fig. 6. Limestone and Dolomite Resources
-------
Fig. 7. Glacial Deposits
Wlsconelnan
^B End Moraine
I I Ground Moraine
Lake Deposits
(modified from Noble and Koraok. 1075)
o %o Ho
Illlnolan
|^| Undlflerentieted
III
111
Kanean
I77T
|"«V;| Kamee and Eekere
Ground Moraine
-------
Bottom, terrace, and outwash soil*
I j Glacial limestone soils
Glacial and lacustrine soils over limestone
|^.~| Glacial sandstone and shale soils
JV»~VI
j..;| Lacustrine sandstone and shale soils
Residual limestone soils
Residual sandstone and shale soils
(modified from Noble and Korsok. 1876)
Fig. 8. Soils
-------
["~] Generally poorly drained
Jr.".J Moderately well drained
Generally well drained
(modified from Noble and Korsok.1976)
Fig. 9. Soil Drainage Characteristics
-------
Hi
"II
(modified from Noble and Korsok. 1075)
Fig. 10. Mean Annual Precipitation (inches)
-------
Bsmt. & 1st Floor Rn
OtolO
11 to 20
21 to 40
41 to 60
61 to 80
81 to 100
Missing Data
(< 5 measurements)
100 Miles
Bsmt & 1st Floor Rn
Average Concentration (pCi/L)
27ESS3
3M
3U
0.0 to 1.9
2.0 to 4.0
4.1 to 10.0
10.1 to 26.1
Missing Data
(< 5 measurements)
100 Miles
Figure 11. Screening indoor radon data from the EPA/State Residential Radon Survey of Ohio,
1988-89, for counties with 5 or more measurements. Data are from 2-7 day charcoal canister tests.
Histograms in map legends show the number of counties in each category. The number of samples
in each county (see Table 1) may not be sufficient to statistically characterize the radon levels of the
counties, but they do suggest general trends. Unequal category intervals were chosen to provide
reference to decision and action levels.
-------
TABLE 1. Screening indoor radon data from the EPA/State Residential Radon Survey of
Ohio conducted during 1988-89. Data represent 2-7 day charcoal canister measurements
from the lowest level of each home tested.
COUNTY
ADAMS
ALLEN
ASHLAND
ASHTABULA
ATHENS
AUGLAIZE
BELMONT
BROWN
BUTLER
CARROLL
CHAMPAIGN
CLARK
CLERMONT
CLINTON
COLUMBIANA
COSHOCTON
CRAWFORD
CUYAHOGA
DARKE
DEFIANCE
DELAWARE
ERIE
FAIRFIELD
FAYETTE
FRANKLIN
FULTON
GEAUGA
GREENE
GUERNSEY
HAMILTON
HANCOCK
HARDEST
HARRISON
HENRY
HIGHLAND
HOCKING
HOLMES
HURON
JACKSON
JEFFERSON
" NO. OF
MEAS.
10
28
20
15
14
10
12
5
33
7
12
15
12
9
13
18
14
120
15
8
20
19
31
6~
170
6
11
6
13
90
15
17
7
16
8
9
9
14
15
7
MEAN
1.9
7.2
6.0
1.9
1.9
2.8
3.3
1.2
4.0
8.6
26.1
7.8
2.6
1.6
2.7
9.7
5.3
2.0
1.9
6.2
4.5
19.9
1.7
7.4
2.5
2.2
1.1
4.0
1.8
2.1
5.6
6.0
4.5
2.5
2.4
4.7
10.4
3.7
1.3
L9I
GEOM.
F MEAN
1.1
3.6
3.4
1.2
1.0
1.5
2.3
0.9
2.6
4.7
3.2
3.3
1.2
1.
i.r
4.3
4.0
1.0
2.6
1.6
4.1
2.8
6.1
1.0
5.3
1.9
1.4
0.8
2.5
1.2
1.4
3.6
3.2
3.5
1.5
1.7
3.6
4.4
2.2
1.0
1.2
MEDIAN
2.1
3.9
2.7
0.9
1.2
1.6
22
1.1
3.0
3.5
4.3
2.0
1.5
2 1
1.9
3.4
5.3
1.1
2.9
1.9
5.6
2.5
8.1
1.3
5.4
2.3
1.2
1.2
2.7
1.4
1.4
3.0
3.7
2.7
22
1.7
5.4
4.4
3.4
1.1
1.5
STD.
DEV.
1.5
12.9
8.8
22
2.0
2.6
2.9
0.8
3.6
10.2
75.4
10.6
3.
1.2
2.3
14.0
3.1
6.8
4.6
1.0
5.5
4.9
45.0
1.6
6.9
1.6
2.5
0.8
3.5
1.6
5.4
6.7
3.8
1.9
2.9
15.7
3.3
0.9
2.1
MAXIMUM
4.8
62.6
36.6
7.5
6.4
7.9
10.1
2.1
14.9
277
265.2
33.7
10.7
3.4
7.8
56.9
11.6
74.5
13.0
3.9
21.7
21.1
238.5
4.5
46.0
4.8
92
2.4
11.1
4.9
16.2
16.1
26.2
10.1
6.1
7.3
8.2
50.5
11.8
3.4
6,4
%>4pCi/L
10
50
30
13
14
30
33
0
42
43
50
40
17
0
23
50
41
40
0
37
61
17
64
17
9
0
40
15
14
47
41
29
13
13
56
56
36
0
14
%>20pCi/L
0
7
10
0
0
0
0
0
0
14
8
13
0
0
0
11
0
1
0
0
5
0
0
o
0
0
0
0
o
o
o
o
11
o
o
0
-------
TABLE 1 (continued). Screening indoor radon data for Ohio.
COUNTY
KNOX
LAKE
LAWRENCE
LICKING
LOGAN
LORAIN
LUCAS
MADISON
MAHONING
MARION
MEDINA
MEIGS
MERCER
MIAMI
MONROE
MONTGOMERY
MORGAN
MORROW
MUSKINGUM
NOBLE
OTTAWA
PAULDING
PERRY
PICKAWAY
PIKE
PORTAGE
PREBLE
PUTNAM
RICHLAND
ROSS
SANDUSKY
saoTO
SENECA
SHELBY
STARK
SUMMIT
TRUMBULL
TUSCARAWAS
UNION
VANWERT
VINTON
WARREN
WASHINGTON
NO. OF
MEAS.
14
28
9
29
19
21
71
10
20
17
9
9
12
22
6
67
2
8
24
6
9
8
12
7
8
6
4
18
29
10
11
13
21
9
50
60
34
13
6
18
2
15
16
MEAN
7.2
3.9
1.0
8.0
5.4
2.7
2.6
2.4
2.1
4.9
1.4
1.1
5.6
8.3
3.5
4.3
9.2
6.3
4.6
3.2
5.4
1.3
3.8
4.5
8.5
4.1
4.1
5.7
5.4
6.9
5.7
2.5
6.0
8.3
5.5
3.2
2.2
6.5
1.5
3.8
2.2
4.5
7.6
GEOM.
MEAN
4.5
1.6
0.9
5.1
2.5
1.4
1.8
1.7
1.6
3.1
1.1
0.9
2.4
4.9
2.6
2.5
1.0
5.3
3.1
3.0
0.9
0.9
1.9
3.3
2.6
2.0
3.1
4.1
3.5
3.5
4.4
1.7
3.9
4.6
3.5
2.0
1.5
3.4
0.9
2.8
2.1
3.3
2.3
MEDIAN
5.2
1.5
0.8
5.3
2.4
1.4
1.8
1.6
1.9
2.9
1.3
1.0
3.0
5.4
2.8
2.5
9.2
5.9
2.9
2.9
1.0
0.8
1.8
4.6
2.7
1.8
2.7
4.1
2.7
4.0
4.0
1.5
5.4
3.8
3.8
2.1
1.6
3.5
1.6
3.8
2.2
3.6
2.1
STD.
DEV.
7.4
6.7
0.5
6.8
6.8
4.0
2.9
1.9
1.4
5.2
1.0
0.9
9.9
10.3
2.7
6.8
12.9
3.8
4.6
1.3
7.9
1.3
5.3
3.2
9.9
6.3
3.6
4.9
6.6
7.7
4.5
2.5
4.4
8.4
5.5
4.0
2.0
7.5
1.1
2.8
0.4
3.7
21.4
MAXIMUM
28.8
31.2
1.7
28.9
24.1
17.1
15.8
5.9
5.1
20.8
3.3
3.2
36.5
46.8
8.2
46.8
18.3
12.7
19.4
4.8
19.5
3.5
18.8
8.2
22.8
16.8
9.3
20.2
32.7
26.7
17.0
9.5
15.3
21.7
25.0
22.7
7.9
26.2
2.9
9.6
2.4
14.8
87.6
%>4pCi/L
57
21
0
72
37
19
17
20
10
41
0
0
42
55
33
28
50
63
38
33
33
0
25
57
38
17
25
50
41
50
45
15
62
44
46
20
12
46
0
44
0
40
19
%>20j)Ci/L
7
4
0
7
5
0
0
0
0
6
0
0
8
9
0
3
0
0
0
0
0
0
0
0
25
0
0
6
3
10
0
0
0
11
4
3
0
8
0
0
0
0
6
-------
TABLE 1 (continued). Screening indoor radon data for Ohio.
COUNTY
WAYNE
WILLIAMS
WOOD
WYANDOT
NO. OF
MEAS.
12
8
18
10
MEAN
4.2
3.5
4.9
7.0
GEOM.
MEAN
2.0
1.8
2.8
4.8
MEDIAN
2.2
2.2
2.5
4.8
STD.
DEV.
6.3
5.3
6.5
7.6
MAXIMUM
22.8
16.4
27.3
27.4
%>4pCi/L
25
13
28
50
%>20pCi/L
8
0
6
10
-------
The American Lung Association of Ohio (address in Bibliography) tested a total of 1,148
homes in the State, of which 48.9 percent had less than 4 pCi/L, 27.4 percent had 4 to 10 pCi/L,
12.7 percent had 10 to 20 pCi/L, 5.4 percent had 20 to 100 pO/L, and 5.7 percent had greater than
100 pQ/L indoor radon. Their data appears to compare reasonably well with the State/EPA data.
GEOLOGIC RADON POTENTIAL
The first rock units to be investigated as potential source rocks of radon in Ohio were the
organic-rich marine shales of the Devonian. The Upper Devonian Ohio Shale averages 30 ppm
uranium and is the largest source of uranium in Ohio (Belisto and others, 1988). Stout (1947)
divides the Ohio Shale into three members, in ascending order: the Huron, the Chagrin, and the
Cleveland. Ghahremani (1981) found higher soil-gas radon concentrations associated with thicker
portions of the Cleveland and Huron Members in northeast Ohio. Hume and others (1989) found
radon levels as high as 3,000 pCi/L in ground water associated with the Huron Member in Erie,
Huron, and Seneca counties. In northeastern Ohio, Ghahremani (1988) found a good correlation
among the bedrock type (Cleveland or Huron Members of Ohio Shale), the amount of fracturing in
the rock, and the migration of soil-gas radon to the surface and into structures.
Harrcll and others (1991) found a strong positive correlation among uranium, indoor
radon, and organic carbon content in the Ohio Shale. They discovered that radon escaping from
the shale varies in direct proportion to the uranium content; the uranium content increases with the
organic content, and because the organic carbon content of the shale increases from east to west, so
does the radon emanating from the Ohio Shale. They predicted that high indoor radon values will
be found along the north-south Ohio Shale outcrop. They further state that a thick layer of glacial
material would serve to retard or act as a barrier to radon migration provided that the glacial
material does not contain clasts of Ohio Shale. They also believe that large-scale advective
transport is occurring because of the abundant vertical fractures in the Ohio Shale.
Limestones and dolomites generally do not contain much uranium (i.e. they are below the
crustal average of 2.5 ppm [Carmichael, 1989]) unless they are rich in phosphate. However,
Harrell and others (1991) found higher radon in basements over the phosphate-poor limestones
and dolomites of the Columbus and Delaware Limestones (Middle Devonian) and the "Monroe
Formation" [A name replaced by the Bass Islands (Upper Silurian) and Detroit River (Lower
Devonian) Groups, fig. 6.] than they did in basements over the Ohio Shale in the same area.
When carbonate rocks weather, the uranium and other metals that were widely dispersed in the
rock can be concentrated in the iron-rich soils that form as a result of the weathering. This
phenomenon may explain the higher radon values observed by Harrell and others (1991). Much of
Ohio is underlain by limestones and dolomites (fig. 6) and approximately 2/3 of the soils present in
Ohio are described as glacial limestone soils or as residual limestone soils (fig. 8). Because
uranium may have been concentrated in these soils formed from carbonate rocks, they represent a
potential radon source material.
Approximately two-thirds of Ohio is covered by glacial material (fig. 7). Smith and Mapes
(1989) found that the permeability of the glacial sediment appears to be the most important physical
attribute controlling surface radon concentrations, regardless of sediment thickness (see fig. 9 for
estimates of soil permeabilities). They found that the influence of bedrock is twofold: (1) the rocks
may be producing radon themselves, and (2) they may contribute radon-producing materials to
glacial sediments derived from them. Smith and Mapes (1989) also found that, as a general rule,
areas underlain by end moraines had the lowest indoor radon measurements and that areas
IV-16 Reprinted from USGS Open-File Report 93-292-E
-------
Figure 12 .Aenal radiometric map of Ohio (after Duval and others, 1989). Contour lines at 1 5 and
2.5 ppm equivalent uranium (eU). Pixels shaded from 0 to 6.0 ppm eU at 0.5 ppm eU
increments; darker pixels have lower eU values; white indicates no data.
-------
underlain by glacial outwash and alluvium had the highest radon measurements (probably a
permeability influence). •
Figure 12 is an aerial radiometric map of Ohio produced from the NURE data (Duval and
others, 1989). The north-south-trending Ohio Shale belt and several of the terminal moraines can
be distinguished by their equivalent uranium (eU) signature on the map (see figs. 5,7, and 12). A
series of 1:500,000 aerial radiometric contour maps showing eU, eTh, and percent K are available
for Ohio (Duval, 1985). A series of color aerial radiometric maps (scale of 1:1,000,000) are also
available for Ohio (Duval, 1987). Overall, the radiometric map corresponds well with the geology.
SUMMARY
Ohio has a moderate to high radon potential in general. Its radon potential has been
summarized using the Radon Index (RI) Matrix and the Confidence Index (CI) Matrix, which are
discussed and described in the introduction to this volume. Table 2 presents the Radon Index and
Confidence Index scores for the generalized radon potential areas shown on figure 13.
Area 1 has a moderate radon potential (RI=11) and comprises those parts of both the
glaciated and unglaciated plateau that in general have less than 2.5 ppm eU (fig. 12). The rocks in
Area 1 are dominantly Mississippian through Permian in age and have a diversity of lithologies
(Le. shale, sandstone, coal, and limestone). Area 2 has a high radon potential (RI=12) and
comprises those parts of the glaciated and unglaciated plateau that in general have more than 2.5
ppm eU (fig. 12). Area 3, the Till Plains of Wisconsinan age, has a high radon potential (RI=14).
The bedrock in Area 3 is dominantly Ordovician through Devonian in age, with the exception of
the northwestern corner of the State, where it is Mississippian. The lithology of these rocks is
dominantly limestone and shale. Area 3 was given 2 GFE points for the known high radon
potential of the Devonian shales and glacial limestone soils (Harrell and others, 1991). Area 4, the
Lake Plains, has a moderate radon potential (RI=10) and has generally poorly drained clayey soils.
Area 5, the Lexington Plain, has a high radon potential (RI=13). Area 5 has generally well-drained
limestone and shale soil soils developed on Ordovician and Silurian-age bedrock. Area 6, the Pre-
Wisconsinan Till Plains (i.e. Till Plains south of the southern limit of Wisconsinan glaciation on
figure 4), has a moderate radon potential (RI=11). Area 6 in general has a lower eU than the
Wisconsinan Till Plains to the north.
This is a generalized assessment of the State's geologic radon potential and there is no
substitute for having a home tested. The conclusions about radon potential presented in this report
cannot be applied to individual homes or building sites. Indoor radon levels, both high and low,
can be quite localized, and within any radon potential area there will likely be areas with higher or
lower radon potential that assigned to the area as a whole. Any local decisions about radon should
not be made without consulting all available local data. For additional information on radon and
how to test, contact your State radon program or EPA regional office. More detailed information
on state or local geology may be obtained from the State geological survey. Addresses and phone
numbers for these agencies are listed in chapter 1 of this booklet.
IV-18 Reprinted from USGS Open-File Report 93-292-E
-------
TABLE 2. Radon Index (RI) and Confidence Index (CI) scores for generalized radon potential
areas of Ohio shown on figure 13.
AREA
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
1
RI
2
2
2
2
3
0
11
CI
3
2
2
2
9
RI
2
3
2
2
3
0
12
2
CI .
3 -
2
2
2
9
3
RI
2
3
3
1
3
+2
14
a
3
2
2
2
Q
RANKING MOD MOD
HIGH MOD
HIGH MOD
4
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
RI
2
2
2
1
3
0
10
MOD
CI
3
2
2
2
—
—
9
MOD
5
RI
2
3
3
3
3
0
14
HIGH
CI
3
2
2
2
_^
—
9
MOD
6
RI
2
2
2
2
3
0
11
MOD
a
3
2
2
2
9
MOD
RADON INDEX SCORING:
Radon potential catepnrv
LOW
MODERATE/VARIABLE
HIGH
Point range
•^^M—IMHiAAA^^^Kl^0_&
3-8 points
9-11 points
> 11 points
Probable screening indoor
radon average for area
^ T ^rTj/r
<2pCi/L
2-4pCi/L
>4pCi/L
Possible range of points = 3 to 17
CONFIDENCE INDEX SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
,4-6 points
7-9 points
10 - 12 points
Possible range of points = 4 to 12
IV-19 Reprinted from USGS Open-File Report 93-292-E
-------
Fig. 13. Generalized Radon Potential Areas
CDescrlbed in Table 2)
-------
REFERENCES CITED IN THIS REPORT
AND GENERAL REFERENCES PERTAINING TO RADON IN OHIO
American Lung Association of Ohio, 1700 Arlingale Lane, P.O. Box 16677, Columbus Ohio
43216
Banks, P.O. and Ghahremani, D.T., 1983, Detection of Gas Seeps in Northeastern Ohio-
Potential Strategy for Developing Devonian Shale Gas: Ohio Journal of Science, v. 83 no
2, p. 24. .
Bates, R.G., 1965, Natural Gamma Aeroradioactivity Map of Central Ohio and East-Central
Indiana: U.S. Geological Survey Map GP-524.
Belisto, M.E., Harrell, J.A., Kumar, A., and Akkari, J., 1988, Radon Hazards Associated with
Outcrops of the Devonian Ohio Shale: GS A Abstracts with Programs, v. 20, no. 5, p. 334.
Bownocker, J.A., 1981, Geologic Map of Ohio: State of Ohio Department of Natural Resources
Division of Geological Survey.
Carmichael, R.S., 1989, Practical Handbook of Physical Properties of Rocks and Minerals: CRC
Press, Inc., 741 p.
Dotson, G.K. and Smith, T.R., 1958, Our Ohio Soils: Ohio Department of Natural Resources
Division of Lands and Soil, 95 p.
Durrance, E.M., 1986, Radioactivity In Geology, Principles and Applications: John Wiley &
Sons, 441 p.
Duval, J.S., 1985, Aerial Radiometric Contour Maps of Ohio: U.S. Geological Survey Map GP-
968. v
Duval, J.S., 1987, Aerial Radiometric Color Contour Maps and Composite Color Map of Regional
Surface Concentrations of Uranium, Potassium, and Thorium in Ohio: U.S. Geological
Survey Map GP-966.
Duval, J.S., 1989, Radioactivity And Some Of Its Applications In Geology in Proceedings of the
Symposium on the Application of Geophysics to Engineering and Environmental
Problems: Society of Engineering and Mineral Exploration Geophysicists, p. 1-61.
Eisenbud, M., 1987, Environmental Radioactivity From Natural, Industrial, and Military Sources:
Academic Press Inc., 475 p.
Ghahremani, D.T., 1981, Radon Prospecting for Shale Gas in Northeastern Ohio: GSA Abstracts
with Programs, v. 13, no. 6, 278 p.
Ghahremani, D.T. and Banks, P., 1982, Radon and Hydrocarbons in Soil Gases of Northeastern
Ohio: AAPG Bulletin, v. 66, no. 2, p. 244.
IV-21 Reprinted from USGS Open-File Report 93-292-E
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Ghahremani, D.T. and Banks, P., 1984, Detection of Light Hydrocarbons in Soil Gases of
Northeastern Ohio: Ohio Journal of Science, v. 84, no. 2, p. 13.
Ghahremani, D.T., 1987, Radon Occurrences in Northeast Ohio-An Environmental Hazard?:
Ohio Journal of Science, v. 87, no. 2, p. 11.
Ghahremani, D.T., 1988, Radon Technology~A Scientific Review and Hazard Analysis in Ohio:
Ohio Journal of Science, v. 88, no. 2, p. 13.
Grafton, H.E., 1990, Indoor Radon Levels in Columbus and Franklin County, Ohio Residences,
Commercial Buildings, and Schools in The 1990 International Symposium on Radon and
Radon Reduction Technology: EPA/600/9-90/005a, v. 1-Preprints, A-I-1,14 p.
Hansen, M.C., 1986, Radon: Ohio Geology Newsletter- Fall 1986, Ohio Department of Natural
Resources Division of Geological Survey, p. 1-6.
Harrell, J.A. and Kumar, A., 1988, Radon Hazards Associated With Outcrops Of The Devonian
Ohio Shale: Ohio Air Quality Development Authority, 83 p.
Harrell, J.A., Belsito, M.E., and Kumar, A., 1991, Radon Hazards Associated With Outcrops Of
The Ohio Shale In Ohio: Environmental Geology and Water Sciences, v. 18, p. 17-26.
Hoover, K.V., 1960, Devonian-Mississippian Shale Sequence in Ohio: Ohio Department of
Natural Resources, Division of Geological Survey, Information Circular No. 27, 154 p.
Hume, D.S., Dean, S.L., and Harrell, J.A., 1989, Radon Occurrence Along Upper Devonian-
Upper Middle Devonian Outcrop Belt In Erie, Huron and Seneca Counties, Ohio: GS A
Abstracts with Programs, v. 21, no. 4, p. 15.
Lewis, T.L. and Schwietering, J.F., 1971, Distribution of the Cleveland Black Shale in Ohio:
GSA Bulletin, v. 82, p. 3477-3482.
Nobel, A.G. and Korsok, A.J., 1975, Ohio- An American Heartland: Ohio Department of Natural
Resources Division of Geological Survey Bulletin 65,230 p.
Roen, J.B., Wallace, L.G., and De Witt, W., 1978, Preliminary Stratigraphic Cross Section
Showing Radioactive Zones of the Devonian Back Shales in Eastern Ohio and West-
Central Pennsylvania: U.S. Geological Survey Oil and Gas Investigations Chart OC-82.
Smith, G.W. and Mapes, R.H., 1989, Radon Hazards Associated With Glacial Deposits In Ohio:
Report to The Ohio Air Quality Development Authority, 60 p.
Seller, D.R., 1986, Preliminary Map Showing the Thickness of Glacial Deposits in Ohio: U.S.
Geological Survey Miscellaneous Field Studies Map MF-1862.
State of Ohio, 1958, The Story of Ohio's Mineral Resources: Ohio Department of Natural
Resources Division of Geological Survey Information Circular No. 9,14 p.
IV-22 Reprinted from USGS Open-File Report 93-292-E
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State of Ohio, 1958, Our Ohio Soils: Ohio Department of Natural Resources, Division of Lands
and Soil, 95 p.
State of Ohio, 1983, Geologic Map and Cross Section of Ohio: State of Ohio Department of
Natural Resources Division of Geological Survey.
State of Ohio, 1983, Glacial Deposits of Ohio: State of Ohio Department of Natural Resources
Division of Geological Survey.
State of Ohio, 1982, Physiographic Sections of Ohio: State of Ohio Department of Natural
Resources Division of Geological Survey.
State of Ohio, 1982, Map Showing County Outlines: State of Ohio Department of Natural
Resources Division of Geological Survey.
Stout, W., 1947, Generalized Section of Rocks of Ohio: Geological Survey of Ohio Information
Circular No. 4.
Tanner, A.B., 1988, Rock And Soil As Sources Of Indoor Radon In Ohio: Proceedings of the
Northeastern Ohio Radon Conference, October 27,1988, Youngstown State University,
(Abstract).
Wallace, L.G., Roen, J.B., and De Witt, W., 1977, Preliminary Stratigraphic Cross Section
Showing Radioactive Zones in the Devonian Black Shales in the Western Part of the
Appalachian Basin: U.S. Geological Survey Oil and Gas Investigations Chart OC-80.
Wright, A.J., 1953, Economic Geography of Ohio: State of Ohio Department of Natural
Resources Division of Geological Survey Bulletin 50,217 p.
IV-23 Reprinted from USGS Open-Hie Report 93-292-E
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EPA's Map of Radon Zones
The USGS1 Geologic Radon Province Map is the technical foundation for EPA's Map
of Radon Zones. The Geologic Radon Province Map defines the radon potential for
approximately 360 geologic provinces. EPA has adapted this information to fit a county
boundary map in order to produce the Map of Radon Zones.
The Map of Radon Zones is based on the same range of predicted screening levels of
indoor radon as USGS1 Geologic Radon Province Map. EPA defines the three zones as
follows: Zone One areas have an average predicted indoor radon screening potential greater
than 4 pCi/L. Zone Two areas are predicted to have an average indoor radon screening
potential between 2 pCi/L and 4 pCi/L. Zone Three areas are predicted to have an average
indoor radon screening potential less than 2 pCi/L.
Since the geologic province boundaries cross state and county boundaries, a strict
translation of counties from the Geologic Radon Province Map to the Map of Radon Zones
was not possible. For counties that have variable radon potential (i.e., are located in two or
more provinces of different rankings), the counties were assigned to a zone based on the
predicted radon potential of the province in which most of its area lies. (See Part I for more
details.)
OHIO MAP OF RADON 7DNFS
The Ohio Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Ohio geologists and radon program experts. The
map for Ohio generally reflects current State knowledge about radon for its counties. Some
States have been able to conduct radon investigations in areas smaller than geologic provinces
and counties, so it is important to consult locally available data.
Two counties do not strictly follow the methodology for adapting the geologic
provinces to zones. EPA and the Ohio Department of Health have designated Hamilton and
Summit counties as Zone 1. Although these counties demonstrate moderate radon potential
overall, they are prone to have locally high radon potential areas. This determination has
been made based on the geology of these counties and on indoor radon data that was
submitted by the Ohio Department of Health.
Although the information provided in Part IV of this report -- the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Ohio" - may appear to be quite
specific, it cannot be applied to determine the radon levels of a neighborhood, housing tract,
individual house, etc. THE ONLY WAY TO DETERMINE IF A HOUSE HAS
ELEVATED INDOOR RADON IS TO TEST. Contact the Region 5 EPA office or the
Ohio radon program for information on testing and fixing homes. Telephone numbers and
addresses can be found in Part II of this report.
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