United States

Environmental Protection

Agency

Air And

Radiation

(ANR-464)

EPA 400-R-92-011

May 1992

&EPA Technical Support Document

for the 1992 Citizen's Guide

to Radon

@ Printed on Recycled Paper

TECHNICAL SUPPORT DOCUMENT FOR THE

1992 CITIZEN'S GUIDE TO RADON

Radon Division

Office of Radiation Programs

U.S. Environmental Protection Agency

May 20,1992
ACKNOWLEDGEMENTS

This document was prepared by the U.S. Environmental Protection Agency's (EPA's)

Office of Radiation Programs (ORP) within the Office of Air and Radiation. Mr. Frank

Marcinowski in ORP's Radon Division was the Project Director.

The efforts of several additional key contributors within ORP were instrumental in the

development of this document, including Mike Walker (Project Director of the 1992 Citizen's

Guide), Jerry Puskin, Chris Nelson, Anita Schmidt, Marion Ceraso, Dennis Wagner, Mark

Dickson, Lisa Ratcliff, Stacy Greendlinger, Jed Harrison, Kirk Maconaughey, Dave Rowson, and

Steve Page.

Mr. Bruce Henschel within EPA's Office of Research and Development provided critical

input related to radon mitigation. He supplied important information on the effectiveness of

different mitigation technologies and played a key role in developing the cost model discussed in

Chapter 5 and supporting appendices.

Several individuals outside of EPA also provided key input on a variety of topics. Mr.

Harry Chmelynski with Sandy Cohen & Associates supplied statistical analyses of radon testing

options. Valuable input on radon mitigation was provided by a number of mitigators who are also

instructors at EPA's Regional Radon Training Centers and who have conducted research for

EPA's radon demonstration program. These individuals included Terry Brennan, Doug Kladder,

William Brodhead, Jim Fitzgerald, Terry Howell, John Anderson, and Jack Bartholomew.

Finally, ICF Incorporated assisted ORP in preparing this document. The ICF project

team was directed by Sam Napolitano and Steve Wyngarden, and included Kerry Bashes, FreddiJo Eisenberg, Sarah Stafford, and John Trever.
TABLE OF CONTENTS

1. INTRODUCTION AND BACKGROUND 1-1

2. ESTIMATION OF RISKS 2-1

3. ANALYSIS OF EPA RADON TESTING OPTIONS 3-1

4. MITIGATION TECHNOLOGY 4-1

5. COST-EFFECTIVENESS ANALYSIS 5-1

6. RISK COMMUNICATION 6-1

7. RATIONALE FOR 1992 CITIZEN'S GUIDE 7-1

REFERENCES R-1

APPENDIX A - RADON CONCENTRATIONS IN AMBIENT AIR A-1

APPENDIX B - BACKGROUND INFORMATION ON RADON B-1

APPENDIX C - COMMONLY USED RADON MEASUREMENT DEVICES C-1

APPENDIX D - COVERAGE OF RADON TESTING POLICY D-1

APPENDIX E - RISK ANALYSIS METHODOLOGY E-1

APPENDIX F - RADON MITIGATION COST MODEL F-l

APPENDIX G - SENSITIVITY ANALYSIS OF THE COST-EFFECTIVENESS G-l

OF THE REVISED CITIZEN'S GUIDE

APPENDIX H - COST-EFFECTIVENESS OF RADON ACTION LEVELS H-1

GREATER THAN 4 pCi/L

CHAPTER 1

INTRODUCTION AND BACKGROUND

This document presents the wide range of technical analyses, radon risk communication

research, legislative directives, and other information that the U.S. Environmental Protection Agency

(EPA) used to shape the policies that are set forth in the 1992 A Citizen's Guide to Radon. The

document summarizes extensive technical analyses of the data that have been gathered over the past

SIX years.

Background on the 1986 Citizen's Guide

In late 1984, the discovery of extremely high indoor radon in the Reading Prong area of

Pennsylvania, New Jersey, and New York thrust radon into the national spotlight as a major public

health problem. The government quickly responded to this problem by creating the Radon Program

in 1985 to help States and homeowners reduce the health risks of indoor radon. EPA's Radon

Program is non-regulatory, designed to provide public information and technical assistance to enable

citizens to make informed decisions on how they should protect themselves.

A Citizen's Guide to Radon has played a major role in the overall strategy of the Radon

Program. It serves as both EPA's core policy statement and primary public information brochure on

radon in homes, as well as the Federal government's principal guidance document on indoor radon.

Published jointly with the U.S. Department of Health and Human Services (HHS) in 1986, the

original Citizen's Guide provided basic background information on indoor radon and its associated

health risks, explained how radon levels in homes should be measured, and advised homeowners on

when they need to take action to reduce radon levels in their homes.

When EPA and HHS issued the 1986 Citizen's Guide, there was less information on indoor

radon than is available now. The recommendations in 1986 were based primarily on limited

experience with homes whose indoor air had been contaminated with radon from uranium mill

tailings. Research in these homes showed that most could be mitigated consistently to an average

indoor radon level of 4 picocuries per liter (pCiIL). Based on this technology limitation, EPA

established 4 pCiIL as the action level at which people should fix their homes.

Since little information was availahle from many homes on the relationship between shortterm and annual average radon concentrations, and because the scientific community agreed that

long-term measurements provided a better estimate of a home's annual average radon level, it was

important to stress the need for long-term measurements before decisions on the need for mitigation

were made. The Agency also wanted to provide States and homeowners with the means to gauge

worst-case radon levels existing in their home or area, so that, the need for further aCtion could be

determined without waiting 11' months for tne results of the measurement. These two cOhsiderations

led to the development of a two-step strategy of measuring radon: (1) a short-term screening

measurement in the lowest livable level during the wintertime, intended to measure the highest

concentration to which occupants could be exposed; and (2) if the results of the screening

measurement were above 4 pCiIL, a confirmatory measurement in lived-in levels, designed to provide

an estimate of the average radon levels to which the occupants were exposed. The recommended

duration of the confirmatory measurement depended on the results of the screening measurement

and ranged from less than one week to one year.

Chapter 1: Introduction and Background Page 1-1
Factors Influencing Revisions to the Guide

Many factors influenced the development of the revised Citizen's Guide. These factors

included:

• The Indoor Radon Abatement Act, passed by Congress in 1988, which requires EPA

to issue a revised Citizen's Guide, and contains specific requirements for the new

Guide;

• Advancements in the understanding of the health risks associated with exposure to

residential radon;

• Improved understanding of the accuracy of measurements made under different

conditions for purposes of determining the need for mitigation;

• Advancements in the understanding of mitigation technology;

• Analyses of the costs and benefits of alternative action levels and testing strategies;

and

• Risk communication research findings.

These factors are brietly reviewed in the following sections and are covered in detail in the remaining

chapters of this document.

Indoor Radon Abatement Act (lRAA)

This amendment to the Toxic Substances Control Act endorses the non-regulatory strategy

of the Radon Program and provides EPA with funding and a legislative mandate for a variety of

additional activities designed to further reduce the risks of indoor radon exposure. Section 301 of

the Act establishes the national long-term goal that indoor air be as free of radon as ambient air

outside of buildings. This goal reflects the Congressional direction contained in Report language that

EPA be more protective of public health. Results from EPA's Ambient Radon Field Study, initiated

to comply with this requirement and confirm reported outdoor radon levels, are summarized in

Appendix A.

Congress provided specific guidance on the scope of the revised Citizen's Guide in section 303,

requiring EPA to provide a "series of action levels with a description of the associated health risks"

to ensure that the public understands that 4 pCi/L is not a safe level of exposure and that a

significant health risk exists at levels below 4 pCi/L. The Act also requires EPA to address health

risks to special populations, i.e. children and smokers. In addition, Congress specified that EPA

present an analysis of the relationship between short- and long-term measurement results and their

relative impacts on alternative action levels.

Updated Radon Risk Information

The Biological Effects of Ionizing Radiation (BEIR IV) Committee of the National Academy

of Sciences issued a report (NAS 1988) on the effects of exposure to alpha radiation that includes

extensive information on the results of studies of underground miners exposed to radon decay

Chapter 1: Introduction and Background Page 1-2
products. National radiation risk experts comprising the BEIR IV Committee prepared and reviewed

a radon risk projection model (the BEIR IV model). EPA used the BEIR IV model to estimate

radon risk, making slight adjustments to the model to account for background radon and to

incorporate the most recent information on dose per unit exposure in mines and homes (NAS 1991).

The Agency also (1) used new data on residential radon levels collected through EPA's National

Residential Radon Survey (U.S. EPNOffice of Radiation Programs 1991a); (2) assembled an

independent panel of experts on radiation risk (the Agency's Science Advisory Board), who reviewed

the Agency's risk calculation methods and provided EPA with further suggestions for refinements;

and (3) conducted a detailed analysis of uncertainty associated with the radon risk estimates. EPA's

revised risk estimates fall within the ranges established by national and international scientific

organizations, including the National Academy of Sciences, the International Commission on

Radiological Protection, the National Council on Radiation Protection and Measurement, and the

United Nations Scientific Committee on the Effects of Atomic Radiation. Chapter 2 discusses EPA's

risk assessment methodology and risk estimates in detail. Appendix B provides basic background

information on radon and its decay products.

Analysis of Measurement Options

Since publishing the 1986 Citizen's Guide, EPA has conducted extensive research to determine

how well various radon testing options meet the basic purpose of testing -- to enable homeowners

to make the right decision on whether to mitigate radon levels. The Agency drew from the wealth

of radon testing data and experience gained since 1986 to develop a number of testing options, each

defined by a given action and "trigger level," a certain testing location, appropriate ventilation

conditions, and different measurement durations. Using a statistical model, data on the magnitude

of measurement errors caused by various sources, and the distribution of annual average radon levels

developed from the National Residential Radon Survey, EPA then evaluated each testing option in

terms of how frequently it would result in homeowners making a correct mitigation decision (i.e., how

well a testing procedure provides a reasonably accurate basis for determining whether a home is

above the action level). EPA considered this information on the effectiveness of testing options,

together with real-world information on public acceptability, in order to select a revised testing

protocol for the 1992 Citizen's Guide. Chapter 3 provides the details of this analysis and Appendix

C provides background information on commonly used radon measurement devices.

Advancements in the Understanding of Mitigation Technologv

There has been progress in the understanding of radon measurement and mitigation

technology since 1986, with a wide variety of methods now available to prevent radon entry into

homes and to reduce indoor radon concentrations after entry. A radon mitigation industry also has

emerged to provide homeowners throughout the country with the ability to reduce their radon levels.

Research by EPA's Office of Research and Development and a recently completed survey of radon

mitigation contractors (U.S. EPA/Radon Division 1990a) have shown that radon mitigation in the vast

majority of cases should leave homes with an annual average level of less than 4 pCilL. It also will

be very common for homes to have post-mitigation levels of 2 pCi/L or less. Chapter 4 describes

current mitigation technology and its overall effectiveness and cost.

Analysis of Costs and Benefits

Additional data collected since the Citizen's Guide was first published have enabled the

Agency to conduct a detailed analysis of the costs and risk reductions (benefits) for the public if it

Chapter 1: Introduction and Background Page 1-3
-followed the Guide's testing and mitigation advice. Based on this analysis, EPA has estimated (1) the

costs ofthe different testing and mitigation options considered for inclusion in the revised Guide (i.e.,

the total annualized costs of testing and mitigation); (2) the risk reductions provided by the different

options (i.e., the annual lives saved by testing and mitigation); and (3) the cost-effectiveness of

alternate approaches (i.e., the cost per lung cancer death averted). EPA also has evaluated the costeffectiveness results by relating them to the public's willingness to pay to save a statistical life and by

comparing the estimated cost per life saved for radon reduction to the cost per life saved for other

health-related programs. The methods and results of this analysis are described in Chapter 5 and in

Appendices D, E, F,' G, and H.

Risk Communication Research

Substantial information is now available on risk communication and, in particular, how the

public responds to radon risk messages. Researchers and public health officials report that

homeowners do not overreact or panic after receiving information on radon. Instead, the public

remains largely apathetic about radon, as evidenced by the small proportion of homes that have been

measured and fixed. Radon risk communication research has provided useful insight into why this

apathy exists and identified six key ways for public information materials to help overcome it. One

of the most important findings has been that the guidelines on testing and mitigation presented in

the 1986 Guide need to be streamlined in order to minimize barriers to public action. Homeowners

often drop out of the two-step testing process, especially if it means having to wait for an entire year

to get the results of the recommended long-term follow-up measurement. A 1990 telephone survey

(Johnson 1990), for example, found that only 9 percent of the participants were willing to conduct

a one-year radon test. In fact, it appears that those homeowners who do mitigate are acting on the

basis of short~termmeasurements in the lowest livable area of their home. Current research on radon

risk communication and a summary of how that research has been incorporated into the revised

Guide is provided in Chapter 6.

Chapter 1: Intmduction and Background Page 1-4
CHAPTER 2

ESTIMATION OF' IUSKS

Section I: Overview

Radon has been classified as a known human carcinogen based on extensive data from

epidemiologic studies of underground miners. 1 The carcinogenicity of radon has been well

established by the scientific community, including the World Health Organization's International

Agency for Research on Cancer (IARC 1988), the Biological Effects of Ionizing Radiation (BEIR

IV) Committee of the National Academy of Sciences (NAS 1988), the International Commission on

Radiological Protection (ICRP 1987), and the National Council on Radiation Protection and

Measurement (NCRP 1984). In addition, the Centers for Disease Control, the American Lung

Association, the American Medical Association, and the American Public Health Association have

recognized radon as a significant public health problem. Radon has been characterized as "a

potentially important cause of lung cancer in the general population, which is exposed through

contamination of indoor air by radon from soil, water, and building materials" (Samet 1989).

To assess the risk of lung cancer

associated with residential exposure to radon,

EPA currently uses the risk projection model

developed by the BEIR IV Committee (NAS

1988) with minor modifications by EPA. EPA

adjusted the BEIR IV relative risk model to

incorporate the most recent information on

dose per unit of exposure in mines and homes

from the report: Comparative DosimetlY of

Radon in Mines and Homes (NAS 1991), and to

account for background radon. EPA's current

estimate of risk incorporates the estimate of the

average national residential radon level from

the recently completed EPA National

Residential Radon Survey (U.S. EPNOffice of

Radiation Programs 1991a). Additionally, the

Agency has included in this radon risk assessment a detailed analysis of the uncertainty associated

with the lung cancer risk estimates, based on the approach employed in the National Institutes of

Health report on the development of radioepidemiological tables (NIH '1985):'

Using the modified BEIR IV model, EPA estimates that the number of lung cancer deaths

per year in the U.S. due to residential radon exposures is approximately 14,000, with an uncertainty

range of 7,000 to 30,000. This estimate is based on the Census Bureau's estimate of 250 million

people for the residential U.S. population as of October 1, 1990 (Bureau of the Census 1992a).

1 The term radon when used in this chapter refers to radon-222 and its decay products. Of the short-lived radon decay

products (polonium-2IS, lead-2I4, bismuth-2I4, and poloniulll-214), the polonium isotopes contribute most of the

radiologically significant dose to the lung. The risk from inhaled radon-222 is small compared to the risk from inhaled radon222 decay products.

Chapter 2: Estimation ofRisks Page 2-1
EXHIBIT 2-1

ESTIMATES OF LUNG CANCER RISK FROM EPIDEMIOLOGICAL

STUDIES OF UNDERGROUND MINERS EXPOSED TO RADON

Average Relative

Study Population Exposure Risk Reference

(WLM) Coefficient

(%/WLM)g/

Czech Uranium 313 1.92 Thomas et al. 1985

Miners 226 1.5 Sevc et al. 1988

Ontario Uranium 40-90 0.5-1.3 Muller 1984

Miners 1.42/ NAS 1988

New Mexico 111.4 1.8 Samet et al. 1991

Uranium Miners

Swedish Iron Miners 81.4 3.6 Radford & St. Clair Renard 1984

(Malmberget) 1.42/ NAS 1988

Colorado Plateau 834 .45 Thomas et al. 1985

Uranium Miners 0.62/ NAS 1988

Eldorado 20.2 3.28 Howe et al. 1986

(Beaverlodge) 2.62/ NAS 1988

Uranium Miners

Newfoundland 382.2 0.9 Morrison et a1. 1988

Fluorospar Miners

~The relative risk coelJicient is the fractional increase above the baseline lung cancer incidence or mortality

rate per WLM.

lYEstimate based on reanalysis of the data by the NAS with the cooperation of the principal investigators.

• When cumulative exposures were equal, low exposures over longer periods produced greater

lung cancer risk than high exposures over short periods.

• Increased lung cancer risk with radon exposure has been observed even after controlling for,

or in the absence of, other mine exposures such as asbestos, silica, diesel fumes, arsenic,

chromium, nickel and ore dust.

Chapter 2: Estimation otRisks Page 2-4
• Increased lung cancer risk has been observed in miners at relatively low cumulative exposures

(e.g., 40-70 working level months2 (WLM) in the study of Ontario uranium miners).

• Non-smoking miners exposed to radon have been observed to have an increased risk of lung

cancer.

In their review of five of the major studies of underground miners, Samet and Hornung

(1990) noted that although there were significant differences in the studies, all demonstrated an

exposure-response relationship between exposure to radon and excess lung cancer, and excess relative

risk per WLM estimates that were "remarkably homogeneous." The following sections review findings

from eight major studies, including those reviewed by Samet and Hornung. This is not meant to be

an exhaustive review, but rather represents an overview of the findings from a number of the

prominent studies of miners. The studies reviewed here were conducted in Czechoslovakia, Ontario

(Canada), New Mexico (U.S.), Sweden, the Colorado Plateau (U.S.), Australia, Northern

Saskatchewan (Canada), and Newfoundland (Canada). The miners in these studies continue to be

followed over time, and updated analyses are conducted as new data become available.

The Czechoslovakian study included four large cohorts, with a total of 9,403 uranium miners

(Samet and. Hornung 1990). Average cumulative exposures for the cohorts ranged from 3.2-303

WLM, and average length of follow-up varied from 6-30 years. Excess lung cancer mortality was

found largely in the cohorts with the highest cumulative exposures and the longest follow-up periods.

However, the study also detected a significant increase in the risk of lung cancer from levels of

cumulative exposure as low as 50-99 WLM. The attributable risk of lung cancer was observed to

increase with age at initial exposure, and the overall attributable risk was estimated to be 20 per

WLM per 106 person-years. When cumulative exposures were equal, low exposures over long periods

were found to produce higher risk than high exposures over short periods. The combined effect of

cigarette smoking and exposure to radon progeny was observed to be approximately additive.

Strengths of this study include the extensive exposure data and long follow-up periods (25-30 years

for two of the four cohorts). The study is limited by incomplete smoking information for the cohorts

that had the highest exposure and the longest follow-up, and by the use of analytical methods that

did not readily allow for comparison with other studies.

The Ontario, Canada study included 15,984 uranium miners, a large number of whom were

exposed at relatively low levels (Samet and Hornung 1990). The mean cumulative exposures of the

miners in this study were 40 WLM and 90 WLM, depending upon the method used to estimate

exposure, and the mean period of follow-up was 15 years. At exposure levels of 40-70 WLM, lung

cancer mortality was found to be significantly increased. The attributable risk of lung cancer was 7

or 3 per WLM per 106 person-years, again depending upon the exposure estimate. The excess

relative risk was calculated to be 1.3% per WLM. The study also showed a decrease in risk with time

since exposure. Strengths of this study are the large number of miners exposed to radon progeny at

relatively low levels, and the consideration of exposures received in other types of hard-rock mining.

The study is currently limited by the fact that the members of the cohort were stilI too young at the

end of the follow-up period (median age was 49 years) for observation of the complete temporal

2A working level is defined as any combination of short-lived radon decay products in 1 liter of air that will result in the

ultimate emission of 1.3 x 105 MeV of potential alpha energy. A working level month is defined as the exposure to 1 working

level for 170 hours (1 working month).

Chapter 2: Estimation ofRisks Page 2-5
expression of excess tung cancer risk from exposure to radon progeny. There was also a lack of

smoking information for study subjects.

The New Mexico study included 3,469 uranium miners who had worked at least one year

underground in New Mexico uranium mines prior to December 31, 1976 (Samet et a1. 1991b). The

follow-up period extended through 1985, and the mean cumulative exposure level for the cohort was

111.4 WLM. The risk of lung cancer in this cohort was increased for exposure categories above 100

WLM; the excess relative risk increased by 1.8% per WLM. The study data were consistent with a

multiplicative interaction between radon and smoking. Additionally, lung cancer risk was observed

to increase more steeply for those less than 55 years of age. The authors noted that the study may

suffer from random misclassification of radon exposure, and possible systematic bias in exposure

estimates. However, the authors cite the extensive database on which exposure estimates were based

as one of the strengths of the study.

The Swedish study included 1,415 iron miners, with an average cumulative exposure of 81

WLM (Samet and Hornung 1990). This study had the longest follow-up period of the eight studies;

the average time in the study was 44 years. Of the 1,415 miners, 1,294 were observed between 1951

and 1976, during which time 50 lung cancer deaths occurred. Based on Swedish national mortality

rates, 14.6 lung cancer deaths were expected. The study found significant excess risk for cumulative

ex~osures above 80 WLM, and attributable risk of lung cancer was estimated to be 19 per WLM per

10 person-years. Through an analysis that required many assumptions, the combined effect of

smoking and exposure to radon progeny was estimated to be additive. Silica, diesel exhaust, arsenic,

chromium, and nickel were discounted as potential confounding exposures because they were present

in small concentrations in the mines. The strengths of this study are the length of the follow-up

periods and the thorough confirmation of cause of death. The study is limited by uncertainty in the

accuracy of exposure estimates, by the lack of smoking information for all subjects, and by the use

of different methods of exposure assignment for lung cancer cases and non-cases.

The U.S. Public Health Service Colorado Plateau study included 4,127 uranium miners

working in Colorado, New Mexico, Arizona, and Utah (Samet and Hornung 1990). Of these, 3,346

were included in the risk assessment conducted by the National Institute of Occupational Safety and

Health. The average cumulative exposure level of this cohort was 821 WLM. The average length

of follow-up was 22 years. In the range of exposure below 600 WLM, excess relative risk of lung

cancer was found to be 1.2% per WLM, and attributable risk of lung cancer was 6.3 per WLM per

106 person-years. Relative risk was observed to decrease with time since cessation of exposure, and

miners first exposed at older ages were at increased risk of lung cancer compared to those exposed

at younger ages. As in the Czech study, low exposures over long periods of time were found to be

more hazardous than high exposures for short periods of time, when cumulative exposures were

equaL The relationship between smoking and exposure to radon progeny was estimated to be slightly

submultiplicative. Strengths of this study are the large number of miners in the study, the close and

lengthy follow-up, and the availability ofsmoking information for most study subjects. The high levels

of exposure that characterize this study may limit its applicability to risk estimation at lower levels of

exposure. Consequently, in their analysis of these data for the development of a radon risk model,

the BEIR IV Committee excluded these very high exposure levels (above 2,000 WLM). In addition,

although the most recent complete data analysis was based on smoking information collected in 1969,

smoking histories have recently been updated and are being incorporated into a new analysis of the

radon-lung cancer relationship in this miner cohort (Roscoe 1991).

Chapter 2: Estimation ofRisks Page 2-6
The Colorado Plateau cohort was also the data source for a study of lung cancer risk in nonsmokers exposed to radon (Roscoe et a1. 1989). For this study, a sub-cohort of 516 male uranium

miners who never smoked cigarettes, pipes, or cigars was selected from the original cohort of 4,127

miners, and was followed from 1950-1984. When the non-smoking miners were compared to nonsmoking U.S. veterans, the miners were 12.7 times more likely to have died of lung cancer than were

the veterans. When compared to male non-smokers in the general U.S. population, the miners were

9.3 times more likely to have died of lung cancer. No lung cancer deaths were found among nonsmoking miners with less than 465 WLM of cumulative radon exposure. However, the limited

number of non-smoking miners in the study who were exposed at lower levels severely restricted the

statistical power of the study to detect risks at these lower exposures relevant to residential levels.

The authors of this study concluded that: "exposure to radon daughters in the absence of cigarette

smoking is a potent carcinogen that should be strictly controlled" (Roscoe et a1. 1989).

The Australian study included 2,574 uranium miners (1,433 underground workers, 1,141

surface workers) at the Radium Hill mine which operated in eastern South Australia from 1952-1961

(workers were followed through 1987). Compared to other mines of that period worldwide,

cumulative exposures of underground workers were low, with a mean of 7.0 WLM and a median of

3.0 WLM. When compared with the surface workers, lung cancer risk was significantly increased in

the underground workers with exposures above 40 WLM. The authors concluded that it was unlikely

that the increase in risk was due to differences in smoking habits or other confounders (such as

asbestos, dust levels, diesel fumes). Strengths of the study include low exposure levels, a long followup period (more than 30 years for most workers) and relatively detailed historical information on

radon gas concentrations at the mine. However, the authors noted that assumptions and

approximations were necessary to estimate personal radon-daughter exposures. Additionally,

according to the authors, the study was limited by the small size of the workforce and their inability

to trace over one-third of the workers beyond the end of employment at Radium Hill.

The Eldorado (Beaverlodge) study included 8,487 workers employed at the Eldorado

Resources Limited Beaverlodge Uranium Mine in Northern Saskatchewan (Howe et a1. 1986).

Follow-up was carried out from 1950-1980. The average cumulative exposure, weighted by personyears at risk was 20.2 WLM (NAS 1988). A highly significant linear relationship between dose and

increased lung cancer risk was observed, with an estimated relative risk coefficient of 3.28% per

WLM. This study is notable for the low cumulative exposure levels and for the low silica exposures

and the absence of any diesel machinery in the mines. The authors note that the study was limited

by the lack of any smoking information on the miners, and by incomplete information on the cohort's

work experience at mines other than Beaverlodge where exposure to radon daughters may have

occurred.

Subsequent to this study, a case-control study was undertaken within this cohort to examine

the potential contribution of smoking and non-Beaverlodge work experience to the relative risk

coefficients from the original Beaverlodge study (L'Abbe et a1. 1991). The study included 46 lung

cancer cases and 95 controls that were enrolled in the Beaverlodge uranium mine cohort study

between 1950 and 1980. The authors concluded that cigarette smoking and other mining experience

were unlikely to have made an important contribution to the relative risk coefficients reported in the

original study. The study did not definitively distinguish between a multiplicative or an additive

relationship between radon exposure and cigarette smoking, although the authors suggest that their

data offer limited support for the multiplicative relationship.

Chapter 2: Estimation ofRisks Page 2-7
The Newfoundland study included 1,772 Newfoundland underground t1uorspar miners with

an average cumulative exposure of 382.8 WLM, followed from 1950-1984 (Morrison et aI. 1988). The

study reported significantly elevated numbers of cancers of the lung, salivary gland and buccal cavity

and pharynx. A highly significant association was observed between radon exposure and the risk of

death from lung cancer. The relative risk coefficient was estimated at 0.9% per WLM, and those first

exposed before age 20 had the highest relative risk coefficients. Smoking miners were observed to

have relative and attributable risk coefficients comparable to those of non-smoking miners. The

strengths of this study include the collection of information on cigarette smoking status for 48% of

the cohort, and a long follow-up period (1950-1984). Study limitations include the lack of any radon

measurements prior to 1960, and an inability to trace a large number of the workers (approximately

16% of the underground cohort as originally defined was excluded because of a lack of adequate

personal identifying information).

Occupational data on exposure to radon and lung cancer risk continue to be made available

through ongoing follow-up of existing miner cohorts, and through newly reported studies. The

National Cancer Institute has acquired data from 11 cohort studies and in collaboration with the

various principal investigators is undertaking a joint analysis. These studies represent all major

cohorts of radon exposed miners currently available, and will include 2,300 lung cancer cases. The

analysis is expected to be completed in 1992 (Lubin 1991).

Residential Studies

There is uncertainty associated with the projection of lung cancer risk from occupational

radon exposures to the general population for residential exposures (see Section V for discussion of

uncertainty). Residential studies have been undertaken in an attempt to directly define and examine

the association between lung cancer incidence and exposure to radon progeny in the home.

There are a wide variety of residential radon epidemiologic studies that are already completed,

ongoing, or being planned. Residential studies conducted to date can be divided into two basic

categories, those that examine the association between radon and lung cancer based on group

characteristics (e.g., ecologic studies), and those that examine the association based on individual

characteristics (e.g., case-control studies).

Ecologic studies compare frequencies of exposure and diseasehetween groups, rather than

between individuals, or assess changes in disease frequency and exposure frequency over time for one

or more groups. Selection of the group ~s often based on geographic parameters. Ecologic studies

are relatively inexpensive and convenient, and are useful for generating hypotheses; however, they

are not recommended for identifying the cause of a disease as they cannot: (1) determine the joint

distribution of the disease (e.g., lung cancer) and the study factor (e.g., radon exposure) within each

group, or (2) separate the effects of two or more variables (KIeinbaum et aI. 1982). The use of

ecologic (group) data to draw conclusions about effects in individuals (e.g., development of lung

cancer) may yield causal inferences that suffer from an "ecological fallacy;" an association or the lack

of an association between a study factor and disease that is observed at the level of the group may

not hold at the individual level. The study groups being compared may differ in many factors other

those being considered in the study, and anyone of these may be the underlying cause of the

difference in their disease states.

For ecologic studies of radon risk, the average radon exposure and average lung cancer

incidence or mortality for each group can be identified. However, there is no way to relate the level

Chapter 2: Estimation ofRisks Page 2-8
of radon exposure for an individual to that individual's health status. The number of lung cancer

patients with a history of elevated radon exposure or the number of individuals with elevated radon

exposure who develop lung cancer is not determined. Because the unit of analysis is the group, this

type of study is incapable of assessing individual smoking history or mobility, both of which are very

important variables in radon risk assessment.

Completed ecologic studies have generally used characteristics of a geographical region, such

as geology or radon in water, as surrogates for radon exposure and correlated them with lung cancer

rates in the same area. Most of these studies showed associations between lung cancer incidence or

mortality and exposure to radon. However, since individual exposures were not considered, results

can only suggest that residential exposure to radon progeny increases lung cancer risk (Samet 1989).

The 1989 International Workshop on Residential Radon Epidemiology endorsed the use of

case-control studies for residential radon research, and specifically recommended against the further

use of ecologic studies because of their limitations for testing causal hypotheses (U.S. DOE/Office

of Energy Research 1989).

Case-control studies involve the comparison, with respect to exposure, of individuals who

have the disease of interest (cases) and those who do not (controls). Case-control studies are useful

for testing causal hypotheses for specific diseases. They do not require extensive follow-up, and have

a greater ability to control for potentially confounding variables (e.g., smoking, diet) than ecologic

studies, since they collect information on study subjects individually.

Case-control studies have been used to more directly test the relationship between lung

cancer incidence or mortality and residential radon exposure (Samet 1989). Early case-control

studies, conducted in Sweden, the United States, and Canada, generally used housing characteristics

as surrogates for radon exposure. A number of these studies found associations between the radon

exposure surrogates and increased lung cancer incidence or mortality.

Four case-control studies of residential radon exposure and lung cancer risk have been

completed recently. Unlike most of the earlier studies that used surrogates for exposure, these

studies took measurements in the homes ofstudy subjects to determine radon exposure. The results

of these studies were mixed, with one study showing a statistically significant trend of increasing lung

cancer risk with increasing radon concentration (Schoenberg et a1. 1990), one study showing a

borderline significant increase in lung cancer risk with estimated radon exposure (Pershagen in press

1992), and two studies showing no statistically significant association between radon exposure and

lung cancer risk (Ruosteenoja 1991, Blot ct a1. 1990). The following is a brief review of findings from

these four studies conducted in the U.S. (New Jersey), Sweden, Finland, and China.

A study of radon and lung cancer in New Jersey women with 480 lung cancer cases and 442

controls (Schoenberg et a1. 1990) has reported a statistically significant trend of increasing lung cancer

risk with increasing residential radon concentration. This trend was observed even after adjusting for

smoking, age, and occupational history. Additionally, the observed increase in relative risk (3.4% per

WLM), although associated with considerable uncertainty, is consistent with the increases reported

in the studies of underground miners, supporting the extrapolation of data from the miner studies to

the residential setting. However, the estimates of risk for the different categories of radon

concentration, when taken individually, were not statistically significant. Furthermore, the authors

of the study cite the small number of subjects with high radon exposures, the possibility of selection

Chapter 2: Estimation ofRisks Page 2-9
biases, and the incomplete cumulative exposure assessments as reasons for exercising caution in

interpreting the study results.

A study of Swedish women with 210 lung cancer cases and 400 controls has found a

borderline significant increase in lung cancer risk with estimated radon exposure in women whose

average radon level exceeded 4 picocuries per liter (pCi/L). Positive trends were observed correlating

the relative risk oflung cancer with the estimated cumulative residential radon exposure. Adjustment

for the percentage of time actually spent in the home reduced the evidence for a dose-response

relationship. The authors state that their findings suggest that radon exposure is of importance for

the risk of developing lung cancer, particularly in the younger age groups. However, they cautioned

that the small sample size limited the ability of the study'to discriminate between various models in

describing the association between estimated radon exposure and lung cancer risk (Pershagen et a1.

in press 1992).

A study of Finnish men with 291 lung cancer cases and 495 controls found no statistically

significant relationship between indoor radon exposure and the risk of lung cancer (Ruosteenoja

1991). The exposure-response curve initially showed an increase but then deviated downward at the

higher exposure levels (above 7.4 pCi/L). The authors postulated that this may have been due to

random variation or systematic bias. The authors also noted that the final sample size was too small

to detect the risk that was expected based on findings from the miner studies.

A study of Chinese women, which included 308 lung cancer cases and 356 controls, showed

no statistically significant association between radon exposure and lung cancer risk, regardless of

cigarette smoking status (Blot et a1. 1990). A non-significant trend of increased lung cancer risk with

increased radon exposure was observed among residents that were exposed to high levels of radon.

The authors of the study advised cautious interpretation of these results, however, given the

potentially important confounding effect of high indoor air pollution in the study area. Another issue,

in light of the ethnic and cultural differences between China and the U.S., is the applicability of these

results to the U.S. population.

A number of residential radon case-control studies that are presently in progress were

presented at the International Workshop on Residential Radon Epidemiology in July of 1989 in

Alexandria, VA (Samet et al. 1991a). The principal investigators of these studies as well as other

scientists discussed a variety of issues at the workshop, including the issue ofsample size. Workshop

attendees concluded that the majority of the residential radon studies, when taken individually, have

samples too small to characterize the exposure-response relationship between radon and lung cancer.

As indicated in an analysis conducted by Lubin et al. (199o), the number of lung cancer cases needed

to characterize the exposure-response relationship between indoor exposure to radon and lung cancer

risk may be in the thousands. For this reason, the study investigators have decided to undertake a

pooling of results from the international case-control residential radon studies as they are completed.

By pooling the data and thus increasing sample size, the investigators hope to characterize the

exposure-response relationship. The Second International Workshop on Residential Radon

Epidemiology, held in Alexandria, VA in July of 1991, determined that an initial pooling effort would

not be possible until 1994. Exhibit 2-2 summarizes 11 ongoing case-control studies of residential

radon exposure and lung cancer risk.

Chapter 2: Estimation of Risks Page 2-10
Q

&

§'.

I::> ,... g'

<Q,

fr

IV,

.......

.......

EXHlHIT 2-2

ONGOING CASE-CONTROL STUDIES OF RESIDENTIAL RADON EXPOSURE AND LUNG CANCER RISK

Study Site Principal Funding Agency Estimated # Lung Duration of

Investigator ComlJletion Cancer Radon

Cases Measurement

U.S./CN Jan Stolwijk National Institute of Environmental Health 1993 1000 1 year

Sciences

U.S.JFL Hellther Stockwell NlItionlll ClIncer Institute 1992 300 1 yellr

U.S.JMO Michllel AhlVlmjll NlItionlll ClIncer Institute 1993 600 1 yellr

U.S./NJ WiIIillln Nicholson NlItionlll Institute of Environmentlll Helllth 1994 500 1 yearJ4 days

Sciences

U.S.JUT & So. ID Joseph Lyon NlItionlll Institute of Environmental Health 1994 750 I yellrJ6 months

Sciences

Belgium Andre Poffyn National Fund for Science Research 1994-96 tOO 6 months

ClInada Eo G. Letourneau ClInadian Health and Welfare 1993 750 6 months

"'ranee Margot Tirmarche University of Uresl/National Institute of Health and 1994-96 600 3 months

Medical Research

Sweden Goran Pershllgen Nationlll Institute of RlIdiation Protection and the 1992 1500 3 months

Swedish ClIncer Society

U.K. Sarah DlIrby Imperial Cancer Research FundiNationlll 1994 600 6 months

Radiological I'rotection Board

West Germany H. Erich Wichmann Federal Ministry of Environment 1996 3200 1 year

Source: Second International Workshop on Residential Radon El'iddlliolog.v, Alexandria, VA, 1991.

A coordinated case-control study involving France. Germllny, Luxembourg, the United Kingdom and Belgium is being sponsored by the Commission of EUCOI)ean Communities.

The coordinator is Dr. A. I'offyn at the State University of Ghent ill lkl~illm.
Animal Studies

Further information on the deleterious health effects associated with exposure to radon has

been provided by experimental studies of animals. According to the BEIR IV Committee, animal

experiments conducted in both the United States and in France have confirmed the carcinogenicity

of radon, and have provided insight into the nature of the exposure-response relationship, as well as

the modifying effects of exposure rate (NAS 1988). The following is a summary of relevant findings

to date from animal studies:

•

•

•

•

•

•

Section III:

Health effects observed in animals exposed to radon and radon decay products

include lung carcinomas, pulmonary fibrosis, emphysema, and a shortening of lifespan (U.S. DOE/Office of Energy Research 1988a).

The incidence of respiratory tract tumors increased with an increase in cumulative

exposure and with a decrease in rate of exposure (NAS 1988).

Increased incidence of respiratory tract tumors was observed in rats at cumulative

exposures as low as 20 WLM (NAS 1988).

Exposure to ore dust or diesel fumes simultaneously with radon did not increase the

incidence of lung tumors above that produced by radon progeny exposures alone

(DOE/Office of Energy Research 1988a).

Lifetime lunftumor risk coefficients that have been observed in animals (between

1 and 5 x 10- /WLM) are similar to the lifetime lung-cancer risk coefficients observed

in human studies (DOE/Office of Energy Research 1988a).

In a study of rats exposed to radon progeny and uranium ore dust simultaneously,

it was observed that the risk of lung cancer was elevated at exposure levels similar

to those found in homes. The risk decreased in proportion to the decrease in radonprogeny exposure (Cross et a1. 1991).

Exposure Assessment

EPA estimates annual U.S. lung cancer deaths due to radon by extrapolating risks observed

in miners to the general public based on estimated cumulative radon exposures, expressed in terms

of WLM. Exposure is often estimated indirectly, using assumptions or mathematical models. For

radon, EPA has directly estimated exposures to the public based on the results of the National

Residential Radon Survey (NRRS) (U.S. EPNOffice of Radiation Programs 1991a). The NRRS

included approximately 6,000 randomly selected homes that were statistically representative of all

residential structures across the fifty United States. Alpha track detectors were placed in each home

for a period of one year, and a questionnaire was used to gather information on occupant living

patterns, smoking habits, house construction, weatherization, and heating, ventilation, and air

conditioning characteristics. The survey was implemented in 1989 and 1990 and completed in 1991.

An estimate of average exposure in the general population must include information on both

the magnitude and duration of exposure. Based on results of EPA's NRRS, the current estimate of

the average national residential radon concentration (i.e., magnitude of e~posure) is 1.25 pCiIL (based

Chapter 2: Estimation ofRisks Page 2-12
on the average of all lived-in levels) (U.S. EPNOffice of Radiation Programs 1991a). Using this

concentration, EPA has calculated the average annual U.S. cumulative exposure to radon to be 0.242

WLM. This estimate assumes that, on average, 75% of a person's day is spent in the home (i.e.,

duration of exposure), and the equilibrium factor is 0.5 (see section Y.2.b for definition of the

equilibrium factor).

The primary source of residential radon concentrations is soil gas which enters the house

through cracks or openings in the foundation. However, radon can also enter the home through

ground water sources, and be released into indoor air during household water use such as showering

and washing clothes. It is estimated that this source accounts for approximately 5% of the total

indoor air concentration in houses served by ground-water sources. On average every 10,000 pCiIL

of radon in water contributes about 1 pCiIL of radon to indoor air. Generally, the contribution to

lung cancer risk from radon that enters the home through water is small compared to the risk from

radon that enters the home through soil gas. In addition, certain building materials and, to a lesser

degree, natural gas may occasionally make a small contribution to indoor radon concentrations. This

document focuses on the lung cancer risk associated with inhalation exposures to radon. Although

the ingestion of drinking water contaminated with radon may add some minor risk of developing

stomach or other internal organ cancer, this risk is small compared to the risks from breathing indoor

air containing radon (U.S. EPA/Radon Division 1991).

There is some uncertainty associated with the estimate of the U.S. population's average

annual cumulative radon exposure. The average residential radon level, the occupancy factor, and

the equilibrium factor all contribute to the uncertainty in the estimation of average residential

exposure. This uncertainty has been factored into EPA's overall estimate of risk as discussed in

Section Y.

Section IV: Characterization of Exposure and Response

The purpose of exposure-response assessment is to describe the relationship between

exposure to the substance of interest and the occurrence of an effect or response (e.g., cancer).

Subsequently, an estimate of the potential response at various levels of exposure can be made based

on this relationship. Usually this means extrapolating from the effects observed at high levels of a

substance administered to experimental animals, or at occupational exposures noted in epidemiologic

studies, down to the generally lower levels of exposure to the general population.

Data on the relationship of exposure and response from human epidemiologic studies arc

clearly preferable to animal data when predicting risks to human populations. Uncertainties

associated with applying a pattern of exposure and response observed in animals to humans are due

to obvious differences, including differences in genetic makeup, size, life span, metabolism,

absorption, and excretion of a substance.

EPA's estimates of lung cancer risks to the general population due to radon are based on

human exposure-response data from epidemiologic studies of underground miners. Unlike many

other environmental pollutants, therefore, special procedures for extrapolating from animals to

humans (with their associated uncertainties) are not needed for radon. Further, although it is

necessary to extrapolate from the risk observed in miners at occupational levels of exposure to

estimate the risk from residential exposure, the extrapolation is not large. Average cumulative

lifetime radon exposures to the general public are only slightly below those for which excess risk can

Chapter 2: Estimation ofRisks Page 2-13
be demonstrated in miners (about 40-70 WLM). For example, exposure to the annual average U.S.

cumulative radon exposure of 0.242 WLM over a lifetime (74 years) is equivalent to a cumulative

exposure of approximately 18 WLM, and exposure to a concentration of 4 pCilL over a lifetime is

equivalent to a cumulative exposure of approximately 57 WLM, assuming that the equilibrium factor

is 0.5 and the fraction of time spent indoors is 75% (see Exhibit 2-13 for more comparisons of WLM

and pCilL based on these assumptions).

Assumption of Linear Exposure-Response Relationship

In assessing residential radon risk, EPA assumes that the exposure-response relationship is

linear at low exposures and exposure rates. This assumption is consistent with the evidence for

linearity at a wide range of cumulative exposures in the radon epidemiologic studies of underground

miners. There is no evidence of a threshold for lung cancer response from radon exposure, that is,

a level of radon exposure below which no increased risk of lung cancer would exist. It is generally

recognized that even low doses of alpha radiation produce DNA damage that cannot always be

repaired. Research further indicates that at low doses of alpha radiation the dose-response

relationship for cell transformation and tumorigenesis is linear and independent of dose rate (NCRP

1980; NAS 1988).

The BEIR IV Committee has stated that "linear models are adequate for extrapolation to low

doses of high linear energy transfer (LET) radiations" (NAS 1988). The Committee noted that the

only significant evidence against linearity in their analysis was the observation of a decrease in risk

per WLM at very high exposure levels (above 2,000 WLM), and these levels were excluded from their

primary analysis (NAS 1988). Significant increases in lung cancer mortality have been observed. in

miners at a wide range of cumulative exposures, including low levels comparable to a lifetime

residential exposure at 4 pCilL. In developing their radon risk projection models, both the ICRP 50

and BEIR IV Committees assumed that the relationship between cumulative radon progeny exposure

and lung cancer risk is linear at low exposures. The EPA's Science Advisory Board (SAB)

recommended that the Agency continue to assume a linear exposure-response relationship when

extrapolating risks from miners to estimate the risks from residential exposures (U.S. EPA 1988).

Risk Projection Models

1. I-Iistory

Several models have been developed to characterize the lung cancer risk associated with

exposure to radon daughters in the residential environment, based on studies of miners exposed to

radon. EPA has relied primarily on relative risk projection models to estimate radon risks to the

public. This section reviews the models that EPA used in the past to calculate radon risk estimates.

Section 2 that follows describes EPA's current approach to the estimation of radon risks.

In general terms, the relative risk models assume that the rate of excess lung cancer due to

radon increases with the baseline rate of lung cancer in the population due to all other causes. This

means that the estimated number of deaths due to radon w.iIl vary depending on the baseline lung

cancer mortality rate, which varies with age, sex, and other factors such as the prevalence of smoking

in the population. Since smoking accounts for most of the baseline lung cancer risk, this approach

is consistent with the assumption that radon and smoking act multiplicatively in causing lung cancer

(Puskin and Yang 1988). A multiplicative relationship exists when the relative risk associated with

Chapter 2: Estimation ofRisks Page 2-14
combined exposure to both factors is approximately equal to the product of the relative risks

associated with exposure to either of the factors alone.

Prior to 1988, EPA used a constant relative risk model to project radon-induced lung cancer

risk in the general population. The model was of the form:

(1)

where:

rea) represents the lung cancer mortality rate at age a from all causes including radon

exposure,

ro(a) is the age-specific baseline lung cancer mortality rate,

B is the relative risk coefficient, and

W* is the cumulative "exposure equivalent" up to age a-1O.

EPA's SAB recommended assuming a range of 1 to 4%/WLM for B. The "exposure

equivalent" was an adjustment to the cumulative exposure estimate (WLM) to account for agespecific differences in airway dimensions and surface area, respiratory frequency, and tidal volume.

EPA assumed that the dose per WLM was 40% lower for residential exposures than for exposures

received in underground mines.

The constant relative risk model was used in conjunction with a lifetable analysis governed

by 1980 US. vital statistics, to project a risk factor of 460 fatal cancers/106 person-WLM with an

uncertainty range of 230-920 fatal cancers/106 person-WLM. EPA's estimate of annual lung cancer

deaths was 5,000-20,000 lung cancer deaths per year (US. EPNOffice of Radiation Programs 1987).

In May 1988, EPA reviewed its risk assessment methodology in response to the publication

of the BEIR IV report (NAS 1988) and the issuance of a draft risk assessment for the National

Emission Standards for Hazardous Air Pollutants (NESHAPS) rulemaking on radionuclides under

the Clean Air Act (U.S. EPA/Office of Radiation Programs 1989). The SAB recommended that EPA

use both the BEIR IV and the ICRP 50 reports to determine a range of radon risk estimates, and

suggested using the average of the central values calculated with these two risk projection models to

derive EPA's risk estimate (US. EPA 1988). The SAB did not recommend use of the NCRP 78

model, which is an absolute risk model. Absolute risk models have been described as less appropriate

for the estimation of lifetime radon risk, as they do not assume a temporal correlation with the

baseline lung cancer rate (ICRP 1987). Moreover, the NCRP model presumes that the effects of

radon and cigarette smoke are additive, contrary to evidence from the Colorado Plateau Study. The

SAB also recommended that EPA assume that indoor and mining exposures give the same dose per

WLM of cumulative radon exposure. This was also the assumption used by the BEIR IV Committee.

For assessing the risks due to childhood exposures, the SAB recommended that EPA rely on the

ICRP 50 model. This model assumes a three-fold higher risk coefficient for exposures to people

under 20 years of age. EPA used the BEIR IV and the ICRP 50 models in conjunction with a

lifetable analysis and 1980 mortality data to estimate risk factors (lung cancer deaths/106 personWLM) and annual deaths from lung cancer.

Chapter 2: Estimation ofRisks Page 2-15
In deriving these rates with both models, EPA adjusted the age-specific baseline rates of lung

cancer mortality, ro(a), by eliminating deaths due to average background radon exposure. Relative

risk is normally used to determine the excess cases of a disease in an exposed population compared

to an unexposed population. But in the case of radon, exposure is universal. The 1980 age-specific

baseline rates of lung cancer include a radon contribution to lung cancer deaths. Therefore, EPA

derived "radon free" background lung cancer rates, that is, reduced to reflect the removal of the agespecific radon contribution to these rates. EPA assumed that the average background radon exposure

was 0.25 WLM/year. The net effect of this adjustment was to reduce the lifetime risk estimates given

by the BEIR IV model by approximately 15% (U.S. EPA/Office of Radiation Programs 1989). In

this way, the relative risk models do not project higher rates of excess radon-induced lung cancer

based on lung cancer rates that already include lung cancers due to background radon. In their

calculation of lifetime population risks from indoor radon exposure, the ICRP 50 Committee

corrected the baseline lung cancer rate assuming an average exposure rate of 0.2 WLM/year (ICRP

1987). The BEIR IV Committee did not incorporate this correction in their risk estimates (NAS

1988). EPA adjusted both models assuming an average exposure rate of 0.25 WLM/year.

EPA's calculations using the adjusted BEIR IV model yielded a risk factor of 305 lung cancer

deaths per 106 person-WLM, and an estimated 18,300 annual lung cancer deaths. The calculations

using the adjusted ICRP 50 model yielded a risk factor of 420 lung cancer deaths per 106 personWLM, and an estim~ted 25,200 annual lung cancer deaths. EPA then averaged the values calculated

using each of these models separately. This gave a risk factor of 360 lung cancer deaths per 106

person-WLM and an estimated 21,600 annual lung cancer deaths.

The following sections discuss the ICRP 50 and the BEIR IV models and the adjustments

made by EPA.

a. ICRP 50 Model

The ICRP 50 Committee developed their constant relative risk model based on the lung

cancer incidence observed in three of the miner cohorts (U.S., Ontario, and Czechoslovakian uranium

miners) and on information from the studies of the atomic bomb survivors (ICRP 1987). The model

assumes a constant rate of excess lung cancer risk due to radon over time and age; that is, the

increase in relative risk for a given exposure is constant over time after exposures end. The ICRP

50 model is written:

(2)

where:

rea) represents the rate of lung cancer mortality from all causes (including radon) at a specific

attained age a,

ro(a) is the age-specific baseline lung cancer mortality rate (corrected for background radon

exposure),

Pis the relative risk coefficient for radon-induced lung cancer,

Chapter 2: Estimation of Risks Page 2-16
WcalO) is the cumulative radon progeny exposure up to age a except for the previous 10

years.. The 10 years represent the assumed minimum latency period between exposure and

cancer development, and

ro(a)~Wca_lO) represents the age-specific rate of excess lung cancer risk due to radon.

The ICRP 50 model does not assume that the excess risk oflung cancer in miners due to

radon can be directly transferred (extrapolated) to the general population. To adapt a relative risk

model derived from studies of miners for use in estimating risks to the general population, the ICRP

made certain adjustments. The radon relative risk coefficient from the miner data (~) was modified

by the ICRP Committee to ret1ect presumed differences between mine and indoor radon exposures.

First, because of potential co-carcinogenic int1uences that may be present in the mines but

not indoors (e.g., exposures to vapors, dust, and other forms of radiation), the ICRP assumed that

the risk coefficient for indoor exposures would be only 80% of that from mine exposures.

Second, due to potential differences between indoor and mine exposure conditions, the ICRP

Committee assumed that the absorbed dose of alpha radiation per unit of cumulative radon exposure

(WLM) for the general population is only 80% of that for miners.

Third, based on findings from studies of the atomic bomb survivors, the ICRP Committee

assumed a three-fold higher risk coefficient for exposures to people under 20 years of age. This had

the effect of increasing overall lifetime risk by approximately 40% (Puskin and Nelson 1989).

When these correction factors are applied to the miner relative risk coefficient, the ICRP

Committee's risk coefficients for indoor exposures to radon are:

= 1.9% per WLM for exposures at ages < 20 years

= 0.64% per WLM for adult exposures> 20 years

When EPA used the ICRP 50 model to estimate lung cancer risks to the general population,

a slight modification was made to these ICRP Committee risk coefficients (U.S. EPNOffice of

Radiation Programs 1989). EPA eliminated the assumption that the absorbed dose of alpha radiation

per unit of cumulative radon exposure (WLM) for the general population is only 80% of that for

miners, and assumed instead that there was a 1:1 relationship between dose per unit exposure in

mines and in homes. This was based upon a recommendation from the SAB and evidence considered

by the BEIR IV Committee. The recalculated risk coefficients are then:

= 2.4% per WLM for exposures at ages < 20 years

j} = 0.8% per WLM for adult exposures > 20 years.

b. BEIR IV Model

The BEIR IV Committee developed their relative risk projection model based on detailed

analyses of four major cohort studies of underground miners (NAS 1988). These were the U.S.,

Ontario, and Saskatchewan (Beaverlodge) uranium miners and the Swedish (Malmberget) iron

miners. The Committee reviewed both the original study data as well as unpublished material, and

conducted a reassessment of the data using new statistical methods.

Chapter 2: Estimation of Risks Page 2-17
The Committee found a pattern of increased risk of lung cancer that was very consistent·

among the four groups. In the U.S. uranium miners, a decline in relative risk with age and with time

since exposure was observed. There was no consistent effect on relative risk from age at first

exposure or from rate of exposure. As additional data are collected from ongoing follow-up of the

miner cohorts, the lifetime pattern of risk from radon exposure may be further clarified.

The BEIR IV modified relative risk model departs from a constant relative risk model (such

as the earlier EPA model and the ICRP 50 model) by including additional assumptions about the

effects of time since exposure (TSE) and of age. The BEIR IV preferred TSE model can be written

as:

where:

rea) = ro(a)[1 + 13y(a) (WI + 0.5W2)] (3)

r(a) is the lung cancer mortality at attained age a due to all causes including radon exposure,

roea) is the age-specific baseline lung cancer mortality rate,

y(a) is the age-specific adjustment to the relative risk coefficient for radon (~ = 0.025), with

yea) = 1.2 when a < 55 years

= 1.0 when a is 55-64 years

= 0.4 when a > 65 years. .

The yea) adjustment decreases the radon-induced lung cancer risk with age. This

incorporates the Committee's finding that excess relative risk in the miners decreased with

age at risk.

(WI + 0.5W2) represents cumulative lifetime exposure up to age a modified as follows:

WI = cumulative exposure occurring from 5-15 years before age a, and

W2 = cumulative exposure up to age a-15 years.

Since W2 is reduced by 50%, the model gives less weight to exposures more distant in time

since exposure. This reflects the Committee's conclusion that risk decreases with time since exposure

as modeled for the four cohort studies of miners. Hence, the relative risk coefficient (~ = 0.025)

effectively varies from 0.5%/WLM to 3.0%/WLM, depending upon age at risk and time since

exposure (Puskin and Nelson 1989). According to the model, 0.025y (a)r()(a)(WI + 0.5W2) represents

the rate of excess lung cancer due to radon.

2. Current Risk Projection Approach - Adjusted BEIR IV Model

In 1991, the Office of Radiation Programs requested that the SAB review proposed revisions

to EPA's radon risk assessment methodology. The SAB recommended that the Agency use only the

BEIR IV model for assessment of risk from residential exposure to radon. The recommendation to

use only the BEIR IV model and discontinue use of the ICRP 50 model was based on several new

pieces of information. The first was evidence from epidemiologic studies of a decrease in lung cancer

Chapter 2: Estimation ofRisks Page 2-18
risk with time since exposure, which had been incorporated into the BEIR IV model, but not the

ICRP 50 model. The second was the publication of the BEIR V report (NAS 1990) and a study of

Chinese miners exposed to radon gas (Lubin et al. 1990). These publications found no evidence of

dependence on age at exposure for lung cancer. This was not consistent with the increased risk to

children assumed in the ICRP 50 model (for further discussion of age dependence of risk see Section

V).

EPA has made two adjustments to the BEIR IV model in estimating radon risks. The first

modification was an adjustment of the age-specific baseline lung cancer mortality rate by eliminating

deaths due to an average background exposure of 0.242 WLM/year, reducing the lifetime risk

estimates by about 10%. The second modification was based on findings in the NAS' report,

completed under a grant from EPA, Comparative DosimetlY of Radon in Mines and Homes (NAS

1991). The purpose of this report was to compare the dose to the bronchial epithelium per unit of

radon progeny exposure in mines and homes, based upon a number of physical and biological factors

which are expected to differ in the two environments. Among the factors considered in the report

are the following: age, sex, aerosol size distribution, the unattached fraction of radon progeny, the

breathing rate and route (oral vs. nasal), the pattern and efficiency of deposition of radon progeny,

the solubility of radon progeny in mucus, and the growth of aerosols in the respiratory tract (for

further discussion of this report see Section V.l.d.). This comparison of exposure-dose relations in

the mining and home environments indicated that the dose per unit of exposure to radon progeny

is approximately 30% lower in the home environment. This finding was expressed in terms of a Kfactor (K = 0.7).

Risk is presumed to be proportional to the dose received by target cells in the bronchial

epithelium. Therefore, in calculating the risks for residential exposures, it is appropriate to multiply

the risk coefficient in the BEIR IV model by a factor of K.

Taking K = 0.7 for both sexes and all ages, the modified BEIR IV model becomes:

rea) = ro(a)[1 + 0.0175 yea) (W t + 0.5W2)] (4)

where the parameters are as described in equation 3, with the difference that = 0.0175 as a result

of the adjustment for the factor K = 0.7.

The most recent estimates of the deaths/person-WLM and annual U.S. lung cancer deaths

calculated using the BEIR IV model are discussed in Section V of this chapter.

3. Lifetable Derivation: Rate of Radon-Induced Excess Lung Cancer Death

Because data are not available on the actual incidence rate oflung cancer death due to radon

for the general population, the risk projection models are used to calculate a rate. (Although death

certificates may identify cause of death, it is not possible to differentiate between the lung cancer due

to radon and that due to smoking, or any other cause.)

To calculate a lifetime, age-averaged rate for radon-induced lmig cancer in the general

population, EPA has used a standard lifetable analysis in conjunction with the BEIR IV model as

adjusted by EPA (US. EPNOffice of Radiation Programs 1989). The lifetable approach was used

to account for the effect of competing causes of death. For each year of the lifetable calculation, the

rate of age-specific death due to all causes competes with the rate of age-specific radon-induced lung

Chapter 2: Estimation ofRisks Page 2-19
cancer death. This is important because of the inherent delay between radon exposure and the

occurrence of lung cancer. During and after the period of radon exposure and before cancer appears,

a potential lung cancer victim is exposed to other causes of death (e.g., auto accidents, cardiovascular

disease). When people die from these other causes, they are no longer in the "pool" of people at risk

of dying from lung cancer due to radon.

EPA uses a lifetable for a general population that reflects the 1980 U.S. age-specific mortality

rates and vital statistics. The lifetable starts out with the "birth" of 100,000 hypothetical persons who

are followed from birth to death, with no member living longer than 110 years. Therefore, in each

year of the lifetable, all members of the "birth cohort" (minus those that have died from various

causes in the previous year, including radon-induced lung cancer) are the same age.

Using the BEIR IV model, the lung cancer deaths due to a given cumulative radon exposure

(person-WLM) can be calculated for each year of the lifetable over a full lifespan, from birth to 110

years. The deaths for each year are calculated based on the cumulative radon exposures for that year

and for the preceding years as determined by the model. The age-specific rate of lung cancer death

due to radon derived with the BEIR IV model is 0.0175y (a)ro(a)(W1 + .5W2) (see previous

discussion of the BEIR IV model).

In deriving the risk per unit exposure, EPA assumes each member of the lifetable receives

a constant low level of radon exposure (0.001 WLM/year) from birth to death. (A constant low level

of exposure over 110 years is used because the lifetime risk estimate would no longer increase linearly

if there were high cumulative radon exposures.) Thus, from the beginning of the lifetable, 100,000

persons are subjected year after year to the age-specific mortality rates of the 1980 U.S. population

and to an increased age-specific lung cancer mortality rate due to low level radon exposure

experienced up to that year.

As each age-specific radon-induced lung cancer mortality rate is calculated (e.g., for age lO11), it is applied to the surviving lifetable population for that year. This generates the excess deaths

that year for the cumulative radon exposure experienced by the lifetable population up to that year

(i.e., Y excess lung cancer deaths per Z person-WLM). These deaths are then reflected in the

overall mortality rate from all causes for the next year (e.g., for age 11-12). Therefore, due to deaths

from all causes, each year there are fewer and fewer of the original 100,000 members of the lifetable

population still alive and at risk from radon exposure. The lung cancer mortality for cumulative

radon exposure is recalculated each year of the lifetable based on the revised population and

cumulative radon exposure for that next year.

After this has been done for each of the 110 years in the lifetable, the excess radon-induced

lung cancer deaths for each year can be summed to give a total lifetime number of deaths for the

population. The collective exposures to the cohort from each year (i.e., over all ages) are also

summed to give the lifetime population exposure.

4. Applying the Rate of Radon-Induced Lung Cancer to the U.S. Population

EPA's estimation of annual deaths due to radon (see Section V) is based on a steady-state

population, i.e., one that does not change from year to year. The steady-state population is

constructed to have people of all the same age groups, and in the same proportion, as those in each

year of the lifetable cohort (i.e., covering newborns to 110 year-olds). For each year of exposure, the

population will have the same proportion of exposure (person-WLM) by age as a birth cohort

Chapter 2: Estimation ofRisks Page 2-20
receiving a constant lifetime exposure. This is essentially the population that would result from a

constant birth rate of 100,000 per year (birth cohort) with the age-specific mortality rates of each

cohort defined by the 1980 mortality rates and vital statistics. Therefore, the number of radoninduced lung cancer deaths per person-WLM for constant lifetime exposure to the single birth cohort

is the same as that for an annual exposure to all members (at various ages) of the stationary

population (U.S. EPNOffice of Radiation Programs 1989).

Because these estimates of annual lung cancer deaths due to radon were derived using a

lifetable defined by 1980 statistics, they are specific to the 1980 population. Since a relative risk

approach is used, the estimated number of excess lung cancer deaths due to radon exposure will

change as these background rates of lung cancer mortality change. As new mortality rates and vital

statistics become available, EPA will revise its estimates of radon risk.

Section V: Risk Characterization

EPA's characterization of the risk associated with residential exposure to radon has two

primary components: calculation of the numerical estimates of risk, and presentation of the

information needed to judge the overall significance of the risk estimates.

In addition to deriving estimates of risk from low-level residential radon exposures and the

number of lung cancers induced by radon each year using the BEIR IV model, EPA has identified

and quantified, to the extent possible, the major sources of uncertainty in these estimates and has

made a quantitative estimate of overall uncertainty. This includes a discussion of the uncertainty

associated with both the risk factor and the estimate of average residential radon exposure. Since

the uncertainty analysis is critical to the interpretation of the risk estimates, this analysis is presented

first, followed by EPA's current estimates of risk.

Uncertainty Issues

In the past, EPA has quantified uncertainty using the ICRP uncertainty range which

represents a range of risk coefficients from the miner studies (ICRP 1987). The Agency's current

uncertainty analysis is based on the methodology used in the National Institutes of Health report on

the development of radioepidemiological tables (NIH 1985). According to this approach, each

component of uncertainty is treated as independently affecting risk by a multiplicative factor, and the

upper and lower bounds for each component of uncertainty are treated as the limits of a 90%

"confidence interval." These are referred to as "credibility intervals" by NIH to emphasize the

element of subjectivity involved in their estimation. In estimating the overall uncertainty, each

component is further assumed to be distributed lognormally on each side of the nominal geometric

mean (G) of the upper and lower bounds. The lower and upper bounds are then defined by

multiplicative factors Land U, such that the limits of a 90% confidence interval are given by LxG

and UxG, respectively. The selection of a lognormal distribution is somewhat arbitrary, and much

of the justification is one of practicability and mathematical tractability.

Sources of uncertainty that do not readily lend themselves to quantification were not included

in the uncertainty analysis, but were addressed qualitatively.

Chapter 2: Estimation ofRisks Page 2-21
1. Risk Factor and Associated Uncertainty

The following are sources of uncertainty associated with the estimate oflifetime risk that were

addressed in the uncertainty analysis: (a) statistical variability in the miner data, (b) projection ofrisk

beyond period of epidemiologic follow-up (projection of risk over time), (c) age dependence of risk,

(d) extrapolation from mines to homes, (e) intluence of mine exposures other than radon, (f)

exposure-rate effect, (g) extrapolation to females, and (h) relationship between radon risk and

smoking.

Of the eight sources of uncertainty that were addressed, four were included in the quantitative

analysis. These were: variability in the miner data, time projection, age sensitivity, and extrapolation

from mines to homes based on bronchial dose.

a. Statistical Variability in the Miner Data

As discussed in the BEIR IV Report, the statistical variability in the miner data is most readily

addressed in terms of a constant relative risk model. It is recognized that this is not the model

preferred by the BEIR IV Committee for describing the temporal and age dependence of the risk;

however, the uncertainty in the time and age projections can be treated separately.

The BEIR IV Committee analyzed four cohorts of miners. Exhibit 2-3 shows the risk

coefficient derived from each study, assuming a constant relative risk model, and, in parentheses, the

respective multiplicative standard error (MSE).

EXHIBIT 2-3

BEIR IV ESTIMATES OIi' RISK COEFFICIENTS FOR

A CONSTANT RELATIVE RISK MODEI.J!I

Cohort % Increase in Relative Risk/WLM

P (MSE)

Eldorado (Beaverlodge) 2.6 (1.5)

Ontario 1.4 (1.6)

Malmberget 1.4 (2.6)

Colorado Plateau 0.6 (1.5)

oj Source: NAS 1988.

The values in Exhibit 2-3 are based on an internal analysis in which the miner cohort

effectively served as its own control (NAS 1988). Results from an external analysis of each cohort

Chapter 2: Estimation ofRisks Page 2-22
differ only slightly from these values. Treating the errors as lognormally distributed, the combined

estimate of the risk coefficient and standard error from the four studies is calculated to be:

In P =

where:

'LiOn p/ln2 Sj)

Li(l/ln2 SD

1/(ln2 S) = Li(1/ln2 Sj)

the Pi values are the respective risk coefficients estimated for the individual studies, and

the Sj values are the corresponding multiplicative standard errors.

(5)

Substituting from Exhibit 2-3 above, the combined estimate for Pis 1.30%/WLM (S = 1.27).

This compares with the BEIR IV combined estimate of 1.34%/WLM and an MSE of about 1.3. The

small difference between the estimates given in BEIR IV and those given here (calculated by EPA)

may reflect rounding errors or a difference in method for arriving at the combined estimate (the

BEIR IV report does not describe its calculation).

As noted in BEIR IV, agreement among the studies is quite good and, on statistical grounds,

there is no reason to reject any of the four studies as an outlier. Further support for the reliability

of the estimate is provided by other studies not included in the BEIR IV analysis. A noteworthy

example is a recent analysis of the Czechoslovakian uranium miner data that derived the estimate of

1.5%/WLM (Sevc et a1. 1988). In addition, based on an analysis of 8 miner cohorts, Lubin (1988)

obtained a combined estimate for Pof 1.5%/WLM with an MSE of 1.2. It was noted that none of

the four studies considered by BEIR IV can be regarded as a statistical outlier. It is nonetheless

instructive to examine the sensitivity of the combined estimate for Pto possible bias in a single study.

If, on the one hand, the cohort yielding the highest estimate (Eldorado) is removed from the analysis,

the estimate of Pis reduced from 1.30 to 0.90%/WLM. On the other hand, removing the Colorado

cohort, which yields the lowest estimate, increases the combined estimate to 1.93%/WLM. Thus, the

risk factor is fairly robust with respect to potential systematic error in anyone study.

Upper and lower confidence limits on Passociated with the statistical variability in the miner

data are readily obtained from the estimated MSE of 1.3: U = L- 1 c(1.3)1.64 c 1.5. That is,

considering only statistical variability in the miner data, the 90% confidence interval for p is (0.013/1.5

- 0.013 x 1.5), or about 0.0087 to 0.0195.

It is important to emphasize that this estimate of uncertainty in the miner data docs not

include uncertainty associated with systematic errors in the assignment of exposure to individual

miners, and the possible influence of mine exposures other than radon.

b. Projection of Risk Over Time

When data from all four of the BEIR IV miner cohorts were combined, the resulting risk

coefficient was 1.3%/WLM. This value represented a best estimate for the limited period of followup in the cohorts, assuming a constant relative risk model and a 5-yr minimum latency. Further

statistical analysis, however, revealed an apparent decrease in the relative risk with (1) age at risk and

(2) time since exposure. Consequently, the BEIR IV Committee preferred model incorporates ageat-risk and time-since-exposure dependent parameters. The net effect of these model changes was

Chapter 2: Estimation ofRisks Page 2-23
to reduce the estimated lifetime risk due to lifetime exposure by about one-third. In the preferred

model, the risk coefficient effectively varies from 0.5 to 3%/WLM, and the lifetime risk estimate is

about the same as would be projected using a constant relative risk model with = 0.9%/WLM.·

Although there is statistically significant evidence of a temporal fall-off in risk in the data for

four cohorts, much uncertainty remains as to the rate and eventual degree of the fall-off. Some of

the observed decline may be due, at least in part, to changes in miner smoking habits over time or

other unknown confounding factors. However, the BEIR IV Committee concluded that it was

unlikely that the decrease could be accounted for ·simply by changes in the smoking habits of the

miner cohorts. Additional follow-up on temporal changes in the smoking habits of the miners may

help settle this issue.

To obtain a reasonable bound on the possible underestimate in risk due to uncertainty over

the time projection, a constant relative risk model was assumed. As indicated above, this assumption

increased the risk estimate by about a factor of U = (1.3%/WLM)/(0.9%/WLM) '" 1.5.

An estimate of the corresponding lower bound was obtained using an approach suggested in

the BEIR IV Report (NAS 1988). Although the preferred model assumes an excess risk projection

over a full lifetime, useful follow-up on the miners extends only for 30-40 y after their first exposure.

To obtain a reasonable lower bound estimate, therefore, it was assumed that the excess risk ends

completely about 40 y subsequent to exposure. As pointed out in BEIR IV, this is equivalent to

stipulating that W2' in the preferred model, includes only exposure accrued 15-40 y before the age

at risk. Quantitatively, the effect of such a postulated cut-off would be to reduce the general

population risk estimate by about 33%, i.e., by a factor of L = 1/1.5 (see Exhibit 2-4).

As shown in Exhibit 2-4, most of the effect of such a cut-off is associated with childhood

exposures. The estimated risk due to exposures at age 0 and 10 is reduced by a factor of 100 and

10, respectively. For all exposures between ages 0 and 20, the average risk is decreased by a factor

of 7.5; by comparison, for all exposures above age 20, the average risk is decreased by only 10%.

EXHIBIT 2-4

AVERAGE LUNG CANCEH MOHTALITY RISK PER 106 WLM BY EXPOSUI{E GROUP,

WITH AND WITHOUT 40-Yn. CUTOFF IN EXPRESSION OF RISKQI

Exposure Group by Age (y)

Projection 0 10 0-20 +20 All Limit

None 322 328 328 294 304

40 Yr 3.4 32 44 264 205

WSource: Calculated using the BEIR IV model (uncorrected for difference between dosimetry in homes and

mines). The baseline lung cancer rate was corrected for the contribution of background radon exposure, which was

assumed to be 0.25 WLM/y for this calculation.

Chapter 2: Estimation ofRisks Page 2-24
c. Age Dependence of Risk

The BEIR IV Committee "did not find an effect of age at first exposure, after controlling for

other correlates of age" (NAS 1988). However, their study population was comprised entirely of

adults. Direct evidence on the sensitivity of children to radon is very limited. The only such

information currently available is from a study of Chinese tin miners that included some individuals

who started mining before age 13 (Lubin et al. 1990). No enhancement in the risk per unit exposure

was seen in these individuals as compared to the rest of the cohort. However, given the sparseness

of the data and the lack of control for smoking, no definite conclusions can be drawn from this study.

Atomic bomb survivors irradiated before age 20 show a highly statistically significant greater

relative risk for radiogenic induction of cancer than those irradiated after age 20. Also, for lung

cancer, a higher relative risk is observed for those irradiated before age 20, but the increase in risk

is not statistically significant (Shimizu et al. 1988). Guided by the results obtained on the atomic

bomb survivors (through 1978), the authors of the ICRP 50 report on radon risk assigned a 3 times

higher relative risk coefficient to exposures received before age 20 (ICRP 1987).

The data on atomic bomb survivors are suggestive of a higher risk of radiogenic lung cancer

in children, but epidemiologic follow-up is still too short for those exposed as children to express

many lung cancers; consequently, no firm conclusions can be drawn. Additional follow-up should

settle the question, but the applicability of the findings to the case of chronic radon daughter

exposures would remain an issue.

As an upper limit on the possible effect of age at exposure on the BEIR IV risk estimate, the

lifetime risk for a constant exposure rate was calculated using the preferred BEIR IV model revised

to incorporate a 3 times higher risk coefficient for all exposures before age 20. The net effect of the

modification was to increase the general population risk by about 60%. Accordingly, for this source

of uncertainty, U is taken to be 1.6.

While there is no basis for postulating that the lungs of children are inherently less sensitive

to the carcinogenic effects of radon daughters, a temporal fall-off in risk could effectively make the

lifetime risk from childhood exposures very small. This possibility has already heen addressed in the

previous section and incorporated into the uncertainty relating to the temporal projection. Thus, with

respect to age sensitivity, L is taken to be 1.0.

d. Extrapolation from Mines to Homes

As discussed previously, the risk coefficients used in the BEIR IV risk model were adjusted

by a factor K = 0.7 to correct for an estimated lower hronchial dose per WLM in homes as compared

to mines, hased on information contained in the recent report, Comparative Dosimetry ofRadon in

Mines and Homes (NAS 1991). The NAS' report did not attempt to quantify the overall uncertainty

in K, but it did indicate how much change would occur under some alternative sets of assumptions.

That information was used here to develop an estimate of the uncertainty in K.

It is important, in this connection, to distinguish uncertainty from variability. The value of

K appropriate to an individual will vary widely across the population, depending on personal

characteristics (e.g., age) and on conditions in the home. For example, Tahle 3-4 of the NAS' report

shows large standard deviations on K (typically, about 30%). In large part, these reUect calculated

Chapter 2: Estimation ofRisks Page 2-25
changes in K due to variability in the aerosol conditions that people are exposed to, not uncertainties

in the value of K most characteristic of average exposure conditions.

Numerous assumptions have to be made in calculating the dose to target cells in the lung

from a given radon exposure, and each of these assumptions is associated with some uncertainty. For

example, the NAS' Committee considered various alternative classes of target cells: primarily,

secretory vs. basal cells, and the whole bronchial tree vs. the upper (lobar/segmental) bronchi only.

No preference was expressed regarding the type of cell; estimates were generally given for secretory

and basal types separately or as the mean of the two. Assuming that secretory or basal cells alone

are the target cells would increase or decrease the estimate of K by 6%, respectively, relative to the

mean. The preferred estimates were based on target cells being distributed over the whole bronchial

tree; if only the upper bronchi were to be considered, K would have been decreased by 5%.

Much of the uncertainty in K pertains to the dose contributed by unattached radon decay

products in the home. According to estimates endorsed by the NAS' Committee, it was considered

that about 2/3 of the total dose in homes comes from the unattached fraction. However, subsequent

to the publication of new dosimetric information, the Committee presented revised estimates based

on a modified set of assumptions. The modifications included a higher nasal deposition of unattached

daughters and a smaller particle size in some mine locations. With the higher nasal deposition, the

contribution of the unattached fraction in homes fell to roughly 50% (James 1991), and the estimate

of K for each age group was reduced by about 20%.

The fraction (fp) of radon daughter alpha-energy which is "unattached" (Le., present as an

ultrafine fraction) varies considerably between houses and, over time, even within a single house. The

NAS' report adopted a value of 8% as typical for the indoor environment, and cited a range of 7%

to 10% for indoor measured values in the absence ofsmoking. However, given differences in heating

and cooking methods, air cleaning equipment, ventilation, etc., this range would seem to be too

narrow. In this connection, the report noted that fp may exceed 16% in houses with low aerosols.

Tobacco smoke provides additional attachment sites for radon decay products; consequently,

f

p is expected to be lower in houses with a smoker present. The NAS' Committee assumed that, on

average, f

p is reduced from 8% to 3% during waking hours in houses with a smoker, and to 1%

during actual smoking. As a consequence, for waking hours, K is reduced by about 40% in houses

with a smoker present. Taking into account sleeping hours, the reduction in average K is roughly

20%. The reduction would be less under the assumptions discussed above (higher nasal deposition

of unattached daughters and smaller particle size in mines), since the contribution to dose from the

unatlached fraction would be less. Another aspect that should be considered in this connection is

the higher equilibrium factor (defined in Section Y.2.h.) expected in homes with tobacco smoke

(Vanmarcke et a\. ]988). Thus, for a given radon concentration, smoking will increase radon

daughter concentration but decrease the unattached fraction. These changes will have opposite

effects on dose and it is unclear whether the average dose, at a given radon concentration, would

actually be higher or lower in homes with a smoker.

A critical assumption made by the NAS' Committee, which substantially reduced their estimate

of K, pertains to the hygroscopic growth (by taking up and retaining moisture) of aerosols inside the

respiratory tract. Except for certain nonhygroscopic aerosols produced by cooking and vacuuming,

the Committee assumed a doubling of the aerosol particle size in the respiratory tract. Due to

differences in the initial size distribution of the aerosols, assuming hygroscopic growth led to a

reduction in calculated dose for homes but an increase for mines, especially during heavy exercise.

Chapter 2: Estimation ofRisks Page 2-26
With no hygroscopic growth, K would be increased by about a factor of 1.6 (1.5, with modified

assumptions on nasal deposition and particle size).

Summarized in Exhibit 2-5 are the average adult values calculated for K by the NAS' panel,

with and without the modifications in nasal deposition and particle size, with and without growth

(doubling) of aerosol size in the respiratory tract (NAS 1991). For children, the values of K would

typically be increased by about 10%.

EXHIBIT 2-5

AVERAGE ADULT VALUES FOR K ADJUSTED FOR

NASAL DEPOSITION AND HYGROSCOPIC GROWTH~/

Assumptions on Nasal

Deposition and Particle Growth No Growth

Size

Unmodified 0.70 1.1

Modified 0.58 0.88

<Y Source: NAS 1991.

Another source of uncertainty in K is associated with uncertainty over the activity-weighted

size distributions of radon progeny, both in mines and in homes. However, this uncertainty is not

quantified in the NAS' Radon Dosimetry report.

In view of the recent data indicating higher nasal deposition of the unattached fraction and

the expectation of at least some hygroscopic growth of particles in the respiratory tract, it would

appear that the dose/WLM is, on average, higher in mines than in homes (i.e., K < 1). Taking into

account possible enhanced nasal deposition of unattached daughters in conjunction with an assumed

size doubling of hygroscopic particles, as well as some allowance for additional sources of uncertainty

inherent in the NAS' analysis, K = 0.5 is assumed to be a reasonable lower bound. These

conclusions must be regarded as tentative and subject to change in light of better information on

aerosol conditions in mines and homes. Accordingly, a symmetric multiplicative uncertainty range U

= L-1 = 1.4 is taken around the central value of K = 0.70.

e. Other Mine Exposures

Uncertainty associated with the presence of agents such as ore dust, arsenic, fluorides, silica

and diesel fumes in the mining environment has been considered but not quantified in this analysis.

It has been suggested that these other mine exposures may have enhanced the risk of lung

cancer in the miners by increasing cell turnover (NAS 1991). It is important to note, however, that

the potential effects of other mine exposures have been taken into consideration in many of the

miner studies. Sevc et a1. (1984) reported that in the Czech uranium mines, a comparison of areas

with similar radon levels but different arsenic levels showed no variation in lung cancer incidence.

Chapter 2.' Estimation ofRisks Page 2-27
Archer et ai. (1985) conducted an analysis offive mining or milling groups and found that lung cancer

rates correlated with radon exposure regardless of silica dust levels. Animal studies have shown that

exposure to ore dust or diesel fumes simultaneously with radon does not increase the incidence of

tumors produced by radon daughter exposures (Cross et a1. 1991). The miner studies were conducted

in different types of mines where environmental pollutants other than radon were present to varying

degrees, and radon was the common exposure. The similarity in the estimates of lung cancer risk per

WLM of radon exposure provides evidence of the role of radon as the primary carcinogen.

Further analysis of the potential effect of other exposures on lung cancer risk in the

underground miners will be undertaken in the previously described joint analysis of 11 miner cohorts

(Lubin 1991), which proposes to critically evaluate the variation of the exposure-response relationship

with age, time after exposure, cigarette smoking, and other mine exposures.

f. Exposure-Rate Effect

Exposure levels in homes are generally lower than those the miner cohorts experienced.

Laboratory studies indicate that the risk per unit dose from alpha irradiation, in general, and from

radon daughters in the lung, specifically, is maximal at low dose rates. The same trend has been

found in human studies (NAS 1988, Sevc et a1. 1988, Howe et a1. 1986). If risk decreases with

increasing exposure rate, then the estimate of the risk coefficient derived from miner studies may in

some cases be biased low relative to what is appropriate for use at the lower exposure rates in

residences. In particular, it often has been suggested that the high exposure rates prevailing in the

Colorado mines may be responsible for the comparatively low risk coefficient derived from the

Colorado Plateau cohort study. A quantitative estimate of possible bias in the BEIR IV analysis

associated with exposure rate might then be obtained by excluding the Colorado Plateau cohort from

the analysis. As discussed in the previous section, this exclusion would increase the combined

estimate of 13 by about a factor of 1.5, i.e., from 1.30%/WLM to 1.93%/WLM.

g. Extrapolation to Females

The BEIR IV Committee assumed that the same age-specific relative risks found for men

could be applied to women. However, U.S. male lung cancer rates are substantially higher than

female rates. As a result, the BEIR IV model projects a much higher risk of lung cancer attributable

to radon for men than for women. There is, however, no evidence that males arc inherently more

susceptible to the disease; rather, most of the difference in baseline rates seems to be explained by

differences in smoking habits. It follows that a great deal of the uncertainty regarding dependence

of radon risk on gender revolves around the question of the radon-smoking interaction.

h. Relationship Betwecn Radon Risk and Smoking

Issues surrounding the possible form of the radon-smoking interaction and its possible effcct

on radon risk arc complex and rather intractable given the limitcd information available. No attempt

is made hcrc to quantify thc uncertainty due to this source, but rather to outline what appear to be

the major problems.

Information on the interaction between smoking and ionizing radiation in causing lung cancer

is somewhat contlicting. Data on the atomic bomb survivors suggest additivity but are also consistent

with a supra-additive or even a multiplicative interaction (Prentice et a1. 1983). According to BEIR

Chapter 2: Estimation of Risks Page 2-28
V, despite lower smoking exposures, women have about the same excess risk of lung cancer

attributable to radiation as ,men; thus, women appear to have higher relative risks.

The most important data currently available on the interaction between radon and smoking

come from the Colorado Plateau miners, for which there is individual smoking information on all

miners (changes in smoking habits in the cohort subsequent to 1968 have not yet been reported for

the entire cohort however). Statistical analyses of this cohort yield results that are consistent with

a multiplicative but not an additive model; however, a wide range of supra-additive and even supramultiplicative models also give acceptable fits (NAS 1988). Other human data are rather limited,

including support for everything from a multiplicative to a protective effect ofsmoking on radon risk

(Lubin 1988, L'Abbe et al. 1991, Samet et al. 1991b, Sevc et al. 1988, Radford and St. Clair Renard,

1984). Animal studies, too, are conflicting: one study showing a synergism with tobacco smoke

(Chameaud et al. 1980); another, a protective effect (Cross et al. 1982).

The EPA model of radon risk is based on the BEIR IV assumption that radon and smoking

act multiplicatively in causing lung cancer. According to this model, the radon risk is proportional

to the baseline lung cancer rate, so that as the baseline rate varies over time (due largely to changes

in smoking habits), the projected rate of radon-induced lung cancers varies in parallel. Therefore,

neglecting possible changes in average exposure rates, it is, according to the model, the proportion

of all lung cancers attributable to radon that remains constant over time, not the absolute rate of

radon-induced lung cancers. Thus, for past years when lung cancer rates were much lower than they

have been recently, the model also projects much lower rates of radon-induced lung cancers.

An important element of uncertainty concerns the temporal dependence ofthe smoking-radon

interaction. Young children are not generally smokers, but some of them will smoke when they get

older. By employing a relative risk model in which the risk of lung cancer due to childhood exposure

increases with the baseline rate at the age at risk, EPA effectively assumes that the risks from

childhood radon exposure and adult smoking multiply. This may not be unreasonable since animal

data suggest that tobacco smoke exposure acts synergistically with prior radon exposure in causing

lung cancer (Chameaud et al. 1980). Moreover, such an assumption is consistent with the widely held

view that radiation is primarily an initiator of carcinogenesis while tobacco smoke acts both as an

early and late stage carcinogen (Doll 1978). Another issue concerns risks to former smokers, either

due to radon exposures received prior to cessation of smoking or afterward. Additional follow-up

on the U.S. miners may shed light on this question.

Finally, it should be noted that the risks calculated here are based on 1980 lung cancer

mortality rates. These rates are continually changing in response to changes in smoking patterns. This

limits the ability of the current risk estimates to predict future radon-induced lung cancers.

I. Overall Uncertainty in the Risk Factor

Summarized in Exhibit 2-6 are the upper and lower multiplicative uncertainties due to the

sources of error that could be estimated reasonably. With regard to the epidemiologic studies of

miner cohorts, there is additional uncertainty not addressed in this analysis associated with systematic

errors in the assignment of exposures to individual miners based on area radon and radon decay

product monitoring and, in some cases, highly questionable extrapolations over space and time. Also

not included is the possible effect of other mine exposures. In extrapolating the miner data to the

situation of radon in homes, additional uncertainty exists regarding the dependence of radon risk on

exposure rate, gender, and smoking. These also are not addressed quantitatively here.

Chapter 2: Estimation ofRisks Page 2-29
EXHIBIT 2-6

QUANTITATIVE ESTIMATES OF UNCERTAINTIES IN RADON RISKW

Source of Uncertainty U (LJl 1

Statistical Variability in Miner Data 1.5 1.5

Projection of Risk Over Time 1.5 1.5

Age Dependence of Risk 1.6 1.0

Extrapolation from Mines to Homes 1.4 1.4

fl./ Source: Calculated in text.

Following, in outline, the calculations presented in the National Institutes of Health report

on the development of radioepidemiological tables (NIH 1985), each source of uncertainty (i) is

characterized by a lognormal probability distribution where the geometric mean Gj = (Uj xLD'12 and

where the geometric standard deviation (GSD) Sj is given by U/Lj = S?·Z9. The latter equation is

equivalent to the assumption that the 90% "confidence interval" of the respective distribution is

(GjxLj

, GixUJ The combined uncertainty distribution due to all four sources is then lognormal with

a geometric mean G given by

and a GSD given by

lnz S = lnz SJ + lnz Sz + lnz S3 + lnz S4

(6)

(7)

Substituting from Exhibit 2-6 then, G = 1.26(5). The 90% "confidence interval" encompassing all

four sources of uncertainty is then (GxL, GxU) where U2 = 1/L2 = S3.29. Solving, U = IlL = 2.02.

The four components of uncertainty were defined relative to a central estimate of risk based

on the BEIR IV model, adjusted to correct for an assumed 30% lower dose per WLM in homes

compared to mines. Upper and lower bound estimates that reflect the combined uncertainty are then

obtained by multiplying the central estimate by GxU = 2.56 and G/U = 0.625, respectively. Thus,

according to this analysis, the actual risk could be about 2.6 times higher than estimated by the

adjusted BEIR IV model or about 1.6 times lower.

The adjusted BEIR IV model, used in a lifetable calculation in conjunction with U.S. 1980

vital statistics, yields a risk factor of 224 lung cancer deaths per 106 person-WLM, for constant

lifetime exposure. Multiplying this value by G, the geometric mean risk estimate is 283 lung cancer

deaths per 106 person-WLM. The estimated uncertainty range is then found to be 140 to 570 lung

cancer deaths per 106 person-WLM.

Chapter 2: Estimation ofRisks Page 2-30
As discussed previously, this range does not include several potentially important sources of

uncertainty, such as errors in miner dosimetry and the effects of exposure rate, gender, and smoking,

which cannot be quantified at present. In general, these uncertainties could produce underestimates

or overestimates of the risk. Also, it should be emphasized that the uncertainties in risk to specific

subpopulations - including children, never smokers, and former smokers - are considerably higher.

2. Average Residential Radon Exposure and Associated Uncertainty

The average residential exposure is estimated to be:

E = C [F x O.OlWL/(pCiIL)][ Q x 51.6 WLM/WL-y] (8)

where C is the average radon concentration in homes, F is the average equilibrium factor, and Q is

the average occupancy factor. Based on a review of available information, EPA has determined that

the previously employed values of F = 0.5 and Q =0.75 are still appropriate for estimating exposure

and risk, but the estimate of C is revised slightly downward from 1.29 to 1.25 pCiIL (a discussion of

the estimates for these parameters and their uncertainties is provided below). Substituting into the

equation above, the estimated average exposure is 0.242 WLM/y.

a. Estimate of Average Radon Concentration

EPA's National Residential Radon Survey (NRRS) of U.S. residences estimates that the

annual average radon concentration to which people are exposed in their homes is about 1.25 pCilL.

This value reflects an average over all frequently occupied areas for each home, averaged over all

homes. The standard error in the measurement is 0.07, implying a 90% statistical confidence interval

of about 1.14 to 1.36 pCiIL.

The radon level in each house, as determined by the NRRS, represents year-long

measurements taken at one or two locations on each tloor defined as a frequently occupied area.

Frequently occupied areas are defined as any level of the home, including basements, which contain

a family room, living room, playroom, den, or bedroom. Also included as frequently occupied areas

are basements which may not contain one of the previously mentioned room types, but are occupied

by a resident for more than four hours per day, such as a frequently utilized workshop. The annual

average radon concentration estimate of 1.25 pCi/L does not reflect the time spent on tloors not

classified as frequently occupied ares. Occupancy data, which retlect the total time each individual

spent in the house and on each floor of that house, were collected in the NRRS, but they primarily

reUect summertime activity patterns, which are likely to be atypical; consequently, they were not used

to adjust the estimate of the average indoor radon concentration. Had floor occupancy data been

used to weight the Hoor measurements, the estimate of the annual average radon concentration

would have been diminished only slightly - by about 6%.

In order to allow for these additional uncertainties discussed in the preceding paragraph, an

estimate is adopted of the overall uncertainty in the average radon concentration to which people

are exposed in their homes, a range of 1.1 to 1.4 pCi/L, which is slightly wider than the statistical 90%

confidence interval from the NRRS cited above.

Chapter 2: Estimation ofRisks Page 2-31
b. Estimate of Average Equilibrium Factor (F)

The equilibrium factor (F) is defined as the ratio of the potential alpha energy concentration

in the existing mixture to that which would exist if all short-lived daughters were in equilibrium with

the radon present (NCRP 1988). Measured values of F are highly variable between houses (or even

within a single house), depending on ventilation rates, aerosol concentrations, and other factors. The

equilibrium factor rises with increasing aerosol concentration because the radon decay products attach

more rapidly, reducing plate-out onto walls and other surfaces. Consequently, F will be increased in

the presence of a smoker. From a risk standpoint, the situation is less clear, however, since

concomitant with the increase in F will be a decrease in the unattached fraction, f

p; the changes in

F and f

p are predicted to have opposite effects on lung dose.

Based primarily on measurements in 21 houses reported by George and Breslin (1980), EPA

has used a value of 0.5 for F. The NAS' radon dosimetry report suggests that the average value is

more likely to lie between 0.3 and 0.4, but that conclusion seems to rest on measurements carried out

in a relatively small number of houses - mostly European. Recently, two large surveys of houses in

the U.S. have been completed. The first was a survey of 200 houses conducted by the State of New

Jersey that gave a mean equilibrium factor of 0.45 (NJ Department of Environmental Protection

1989). The second, a multi-state survey of 113 homes conducted by Radonics, yielded an average

value of 0.51 (Radonics 1991). The data from the latter were found to be approximately lognormally

distributed; the geometric and arithmetic means of the distribution were 0.54 and 0.56, respectively.

Exhibit 2-7 summarizes various measurements of F. For the most part, they represent "grab

sample" measurements and/or measurements taken in a small number of houses. Only the Radonics

study (1991) seems to ret1ect measurements taken over several days in a large number of houses. In

EXHIBIT 2-7

MEASURED VALUES OF THE EQUILIBRIUM FRACTION, F, IN HOMES

Location F Rcferencc

Austria 0.60 Steinhausler et al. 1980

Finland 0.47 Makelainen 1980

Norway 0.50 Stranden et al. 1979

Sweden 0.44 Swedjcmark 1983

nonsmoker 0.4(, Jonassen and Jensen 1989

smoker OS! Jonassen and Jensen 1989

United States

cellars 0.52 George and Breslin 1980

living areas OBi George and Breslin 1980

0.33 Israeli 1985

0.45 NJ Dept. of Environ. Protection 1989

0.51 Radonics, Inc. 1991

West Germany 0.37 Wicke and Porstendorfer 1982

0.34 Keller and Folkerts 1984

no smoke 0.30 Porstendorfer 1987

smoke 0.50 Porstcndorfcr 1987

Chapter 2: Estimation ofRisks Page 2-32
light of the available information, F = 0.5 will continue to be employed as a nominal point estimate;

an uncertainty range of 0.35 to 0.55 will be adopted.

c. Estimate of Average Occupancy Factor (0)

The occupancy factor, which is the percent of time spent in the home, naturally varies with

lifestyle. For example, a study sponsored by the Electric Power Research Institute and conducted

by GEOMET found values of 61.6%, 91.5%, and 86.2% for fully employed persons, housewives, and

elderly individuals, respectively (GEOMET 1981). Exhibit 2-8 summarizes estimates of occupancy

from the literature. For the most part, these estimates reflect analyses of detailed reports by

individuals as to their activities over a fixed time period. However, it should be cautioned that several

of the U.S. estimates are based on identical or overlapping data sets.

EXHIBIT 2-8

PERCENTAGE OF TIME SPENT AT HOME

Reference Date Country Avg. Occupancy

(%)

Oakley 1972 US 79.5

Moeller & Underhill 1976 US 74.4

GEOMET 1981 US 75.3

New Jersey 1989 US 71

U.S. EPNOHEA 1989 US 64-73

U.S. EPNORP 1991b US 61.5

Brown 1983 UK 75

Francis 1987 UK 77

Roy & Courtay 1990 France 76.7

The estimates for 0 vary from about 60% to 80%. The lowest value is the National

Residential Radon Survey finding of 61.5%; this estimate is highly questionable, however, given the

lack of detail obtained in the data acquisition and the concentration on summertime activity patterns.

Based on the data in Exhibit 2-8, EPA will continue to employ an occupancy factor of 75%, as a

nominal point estimate for calculating exposure and risk, with an uncertainty range of 65% to 80%.

d. Overall Uncertainty in the Estimate of Exposure

The estimated annual radon progeny exposure is proportional to the radon concentration (C),

the equilibrium factor (F), and the occupancy factor (0). As discLlssed above, the average values for

these parameters and the associated uncertainty ranges (in parentheses) are estimated to be: C =

Chapter 2: Estimation ofRisks Page 2-33
1.25 pCiIL (1.1-1.4 pCilL), F = 0.5 (0.35-0.55), and Q = 0.75 (0.65-0.8). The geometric means of the

uncertainty ranges are CG = 1.24, FG = 0.439, and QG = 0.721. From Equation 8 it follows that the

geometric mean of the uncertainty range for exposure is:

GE = (0.242 WLM/y) (1.24/1.25)(0.439/0.5)(0.721/0.75) (9)

Hence, GE = 0.203 WLM/y. Treating the uncertainty distribution for each factor above as lognormal

and the respective ranges as 90% confidence intervals, the corresponding 90% confidence interval

for the uncertainty in exposure will be (GxL, GxU), where

In2 UIL = In2(1.4/1.1) + In2(0.55/0.35) + In2(0.8/0.65) (10)

Solving this equation, U/L = 1.76. By symmetry of the lognormal distribution, U = l/L = 1.32.

Thus, the annual exposure is estimated to be between 0.203/1.32 and 0.203 x 1.32 WLM/y; i.e., from

0.154 to 0.268 WLM/y.

Numerical Estimates of Lung Cancers Induced by Residential Radon Exposures

Based on an average annual exposure of 0.242 WLM, the estimated number of radon-induced

lung cancer deaths (led), per year, according to the modified BEIR IV model is:

N = (224 led per 106 person-WLM)(0.242 WLM)(250x106 persons)

'" 13,600

An uncertainty range for N can be estimated from the caleulated uncertainty distributions for

the risk factor and for the annual exposure. The former was approximated by a lognormal

distribution with geometric mean GR = 283 led per 106 person-WLM and upper and lower 90%

confidence bounds equal to 2.02xGR and GR/2.02 (140 and 570). Similarly, for the latter, GE was

0.203 WLM/y and the corresponding uncertainty bounds were 1.32xGE and GE/1.32 (0.154 and 0.268

WLM/y). The upper and lower uncertainty bounds on N are then given by NT = 250x106

(GRxGExL) and Nu = 250x106 (GRxGEXU), where:

In2 U = In2 IlL = In2 2.02 + In2 1.32, or

U = IlL = 2.13.

(11)

(12)

The uncertainty distribution for N is then lognormal with geometric mean GN = 250xl06,

(GR xGE) = 14,400 lcd/y, and "90% confidence limits," GN/2.13 and 2.13xGN. Thus, it is projected

that for the general population, 6,740 to 30,600 lcd/y are attributable to residential radon exposures.

EPA has continued to update its estimates of radon risk as exposure estimates have been

refined and as new information has become available on the radon risk projection models and

comparative dosimetry in mines and homes. Exhibit 2-9 shows the evolution of radon risk estimates

over time, including the current estimate of approximately 7,000 to 30,000 lung cancer deaths per year

due to residential radon exposure.

Chapter 2: Estimation ofRisks Page 2-34
EXHIBIT 2·9

EPA'S RADON RISK ESTIMATES

ModellApproach Date of Range of Estimated Annual

Estimate Lung Cancer Deaths

EPA Model 1986 5,000 - 20,000

Average of ICRP 50 and BEIR IV 1988 8,000 - 43,000

BEIR IV Model (as adjusted by EPA) 1992 7,000 - 30,000

Section VI: The Effect of Smoking Status on Radon Risk

The revised Citizen's Guide includes charts on the risk of radon exposure for smokers and

never smokers. The charts present risks in terms of lung cancer deaths/LOOO persons and also in

comparison to the risk of death from different types of accidents. This section presents the approach

used to estimate the lifetime lung cancer risk/person from radon for smokers and never smokers.

EPA estimates of annual lung cancer deaths due to radon presented earlier in this chapter

are calculated for the general population, consisting ofsmokers and non-smokers. Since the risk of

lung cancer from radon exposure appears to be enhanced by cigarette smoking, it is of interest to

estimate the variation in radon risk by smoking category (current, former, and never smoker).

The assumption underlying the estimation of radon risk by smoking category is that radon risk

varies in proportion to smoking risk. Therefore, for example, if lung cancer risk is more than twice

as great in a current smoker compared to a person in the general population, then the radon risk for

a current smoker also would be more than twice as great as that of a person in the general

population. This assumption is consistent with the BEIR IV Committee conclusion that radon and

smoking act multiplicatively in causing lung cancer (NAS 1988). For further discussion of the

relationship between radon and smoking in causing lung cancer, see Section V of this chapter.

1. Smoking Risk Data

The data source for the prevalence and relative risks of smoking was the Surgeon General's

Report, Reducing the Health Consequences of Snwking (DHHS 1989), which included the Cigarette

Smoking Supplement to the 1985 National Health Interview Survey (NHIS 1985), and the American

Cancer Society's Cancer Prevention Study II (American Cancer Society 1988). The National Health

Interview Survey provided information on the prevalence ofsmoking in the U.S., and the American

Cancer Society's CPS II study provided the relative risks for current and former smokers (see Exhibit

2-10).

To date, only the female data for CPS-II have been analyzed in detail; hence, estimates of

risk for specific smoking levels (packs per day) or time since cessation cannot be made for males or

the general population. For this reason, this analysis considers only the broad categories of current

smokers and former smokers, with no further breakdown of smoking by subgroup.

Chapter 2: Estimation ofRisks Page 2-35
It should be cautioned that the relative risks by smoking category derived in the CPS-II study

may not accurately retlect the effect of smoking on lung cancer risk in the U.S. population. Subjects

in CPS-II are more representative of middle-class white Americans than of the U.S. population as

a whole. As a result, exposures to occupational and environmental carcinogens in the CPS-II group

are likely to be lower than average. So, for example, non-smokers in the CPS-II group may have a

lower incidence of lung cancer than non-smokers in general. In the case of current or former

smokers, the study group may differ from the general population with regard to their smoking

patterns, as well as other relevant factors.

2. Average Relative Risk

Exhibit 2-10 summarizes data from the Surgeon General's Report on smoking prevalence

(proportion of the population in each smoking category) and relative risks of lung cancer by sex and

by smoking category (current, former, and never smokers). These data were used to calculate a

separate average relative risk of lung cancer for all males and for all females (see "All" under each

gender in Exhibit 2-10). The relative risk of smoking is usually calculated as the ratio of the lung

cancer mortality rate of a smoker group to that of a never smoker group. The average relative risk

calculated here differs in that it is given by the ratio of the lung cancer mortality rate in the total

EXHIBIT 2-10

'PREVALENCE AND LUNG CANCER RISKS OF CIGARETTE SMOKING

Category Prevalence0' Relative Lung Cancer

RiskQ/ Deaths/105persons~/

Males

Current smoker 0.327 22.36 14,118

Former smoker 0.291 9.36 5,909

Never smoked regularly 0.382 1.0 631.4

All (averageyJ/ 1.0 10.429 6,579

Females

Current smoker 0.275 11.92 5,593

Former smoker 0.171 4.69 2,200

Never smoked regularly 0.554 1.0 469.2

AU (averageyJ/ 1.0 4.64~/ 2,177

9./ Proportion of popUlation in each smoking category; data from Surgeon General's Report (DIU-IS 1989).

Q/ Defined as the ratio of the age-adjusted lung cancer mortality rate in the current and former smoker category to

(divided by) the age-adjusted lung cancer mortality rate in the never smoker category; data from Surgeon General's

Report (m-IRS 1989).

9 Calculated by EPA, as described in text.

'::Y Includes current, former, and never smokers.

Chapter 2: Estimation of Risks Page 2-36
male or female population (including never smokers) to the lung cancer mortality rate in the never

smokers for each respective gender. This approach to the calculation of relative risk is based on the

methodology employed in the National Institutes of Health report on the development of

radioepidemiological tables (NIH 1985).

Thus the average relative risk for all males is:

(13)

where Pi and RRi are the prevalences and relative risks for all smoking categories including those

persons who never smoked regularly. Thus, the average relative risk for all males is

RR = 0.327x22.36 + 0.291x9.36 + 0.382x1.0 = 10.42

relative to males who never smoked regularly. Similarly, for all females, the average relative risk is

RR = 0.275x11.94 + 0.171x4.69 + 0.554x1.0 = 4.64

relative to females who never smoked regularly.

3. Lung Cancer Mortality Calculations

The average relative risks calculated in Section 2 were used in conjunction with 1980 vital

statistics and decennial life tables (NCHS 1983, NCHS 1985) to calculate lung cancer deaths in male

and female birth cohorts (all smoking categories combined) of 100,000. The number of lung cancer

deaths yielded by these calculations was 6,579 and 2,177 per 100,000 males and per 100,000 females,

respectively (see Exhibit 2-10).

The number of lung cancer deaths in cohorts of 100,000 of each smoking category of males

and of females was then calculated. The lung cancer death rate for each category was assumed to

be proportional to the relative risk for that smoking catcgory of males or fcmales. For example, the

lung cancer death rate in male current smokers (M,CS) was given by:

Icd(M,CS) = (22.36/10.42) (6579 lcd/100,0(0)

= 14,118 lcd/100,000.

The estimated lung cancer deaths/100,000 for all smoking categories and both sexes are listed in

Exhibit 2-10.

For the general population (defined as males and females combined), the number of lung

cancer deaths was subsequently estimated by adjusting the number of lung cancer deaths calculated

for males and for females according to the sex distribution of the birth cohort (1.051 male: 1 female).

Thus, the number of lung cancer deaths for the general population would be (1.051x6579 +

2177)/2.051 = 4433 lung cancer deaths (see Exhibit 2-11). To calculate the number of lung cancer

deaths in each smoking category of the general population, the male and female lung cancer rates

Chapter 2: Estimation ofRisks Page 2-37
were combined. As an example, consider the case of current smokers. The fraction of the current

smokers birth cohort that is male was estimated to be:

f(M,CS) = 1.051 p(M,CS)

1.051 p(M,CS) + p(F,CS)

(14)

where p(M,CS) and p(F,CS) are the prevalences of current smokers among males and females,

respectively. From Exhibit 2-10, p(M,CS) = 0.327 and p(F,CS) = 0.275. Solving, f(CS,M) = 0.5555.

The fraction of current smokers that is female is then given by:

1'(CS,F) = 1-1'(CS,M) = 0.4445 (15)

In a birth cohort of 100,000 (male and female) current smokers, therefore, the number of lung cancer

deaths would be:

lcd(CS) = (0.5555)(14,118)+(0.4445)(5593) = 10,329

Lung cancer deaths in birth cohorts of 100,000 (male and female) former smokers and 100,000 (male

and female) never smokers were calculated following the same approach, and are presented in Exhibit

2-11.

EXHIBIT 2-11

LUNG CANCER RISK OF CIGARETTE SMOKING

IN THE GENERAL POPULATION~I

Category Lung Cancer Deaths/105persons

Current Smoker 10,329

Former Smoker 4,579

Never Smoked Regularly 537.4

All (Average) 4,433

Combined male and female data from Exhibit 2-10. Sex ratio at birth, M:F = 1.051:1.

The lung cancer death rates in each smoking category in the general population were

compared to the average lung cancer death rate for the general population to obtain the radon risk

multipliers presented in Exhibit 2-12. For example, the number oflung cancer deaths/100,000 current

smokers in the general population is 10,329. This is a factor of 2.33 times the 4,433 lung cancer

deaths expected in the general population, averaging over all smoking categories. It follows from the

presumed multiplicative interaction between radon and smoking that the radon risk among current

Chapter 2: Estimation ofRisks Page 2-38
smokers also would be about 2.33 times the radon risk for the general population. Risk multipliers

were derived for former and never smokers as well, using this approach. As shown in Exhibit 2-12,

the lung cancer risk (and thus the radon risk) for never and former smokers in the general population

are estimated, respectively, to be 0.121 and 1.03 times that of the general population.

EXHIBIT 2-12

RISK MULTIPLIERS BY SMOKING CATEGORY

IN THE GENERAL POPULATION~

Category Risk Multiplier

Current Smoker 2.33

Former Smoker 1.03

Never Smoked Regularly 0.121

All (Average) 1.00

Calculated in text.

4. Lifetime Radon Risk by Smoking Category

The above risk multipliers were used in conjunction with a standard lifetable analysis, 1980

decennial vital statistics and the EPA-adjusted BEIR IV relative risk model (K =0.7) to estimate the

lung cancer risk for never smokers and for current smokers at several radon levels. As before, in

using the BEIR IV model, the lung cancer baseline risk was adjusted for an annual background radon

exposure of 0.242 WLM.

For a more rigorous calculation of the excess risk due to radon, the baseline lung cancer risk

for current smokers and for never smokers would be multiplied by the risk multipliers 2.33 and 0.121,

respectively. This would mean constructing new lifetables for both groups. However, there are a

number of difficulties with this approach. For example, age-specific death rates are generally not

available for smokers and never smokers separately. A simpler approach is to multiply the excess

lung cancer risks (not the baseline risks) due to radon for never smokers and for current smokers by

their respective risk multipliers. For example, in the case of current smokers, the excess risk R(a)

is estimated as:

R(a) = 2.33 x [rea) - ro(a)] (16)

where rea) is the age dependent total lung cancer risk and ro(a) is the age dependent baseline lung

cancer risk. Simplifying the calculation gives risk estimates that are within 10% of the values

calculated using the same approach described in the BEIR IV report (NAS 1988), without requiring

changes to the lifetables.

Chapter 2: Estimation ofRisks Page 2-39
Exhibit 2-13 shows the risks for never smokers and current smokers along with the risks for

the general population, for selected exposure levels. Levels are expressed in both pCifL and WLM/y.

The relationship between the two is as follows:

where:

WLM/y = [F x 0.01 WL/(pCifL)] x [0 x 51.6 WLM/WL-y] pCi/L

F, the equilibrium factor, is assumed to be 0.5, and

0, the fraction of time spent indoors, is assumed to be 0.75.

(17)

For further discussion of the average equilibrium factor and average occupancy factor, see Section

V.

EXHIBIT 2-13

LU'ETIME LUNG CANCER RISK FOR NEVER SMOKERS,

CURRENT SMOKERS, AND THE GENERAL POPULATION

Radon Level Lifetime Lung Cancer Risk (per person)

pCifL WLM/y Never Smokers Current Smokers General Population

20 3.87 7.72xl0·3 1.35xl0-1 6.15xl0-2

10 1.94 3.87xl0-3 7.llx1O-2 3.14x1O-2

8 1.55 3.1Oxl0-3 5.74xl0-2 2.52x1O-2

4 0.774 1.55x1O-3 2.93xlO-2 1.27x1O-2

2 0.387 7.76xl0-4 1.48xl0-2 6.39xl0-3

1.25 0.242 4 9.29xlO-3 4.00xlO-3 4.85xlO0040 0.077 1.55xlO-4 2.98xlO-3 1.28x1O-3

5. Discussion

The approach used here for calculating the risks for various smoking categori~s is

approximate. It does not account for life-shortening due to smoking, which reduces the relative

contribution of smoking-attributable lung cancer deaths. An analysis of the effect of smoking

presented in BEIR IV only partly corrected for life-shortening because it neglected all smokingrelated causes of death other than lung cancer. EPA calculations show that use of the BEIR IV

methodology would produce a difference of less than 10% in the risk multipliers presented here. In

light of the larger potential sources of error associated with the calculation, these differences would

appear to be insignificant. The chief sources of error and uncertainty associated with the analysis of

the effects of smoking on radon risk are the uncertainty over the actual form of the interaction (e.g.,

multiplicative or submultiplicative); the variations in the relative risk of smoking by age and gender;

Chapter 2: Estimation ofRisks Page 2-40
the changes in age-specific relative risks for smokers as smoking habits and types of cigarettes change

over time; and the int1uence of environmental and passive cigarette smoke on radon risk.

Section VII: Conclusions

For most pollutants, the assessment of human risk is based on data from animals exposed to

very high levels of a given substance. The large and obvious uncertainty associated with this

extrapolation is usually compounded by the fact that the substance may be administered to laboratory

animals in a way that is different from human exposure (e.g., oral versus inhalation). In addition, the

animals are often exposed to levels of a substance several orders of magnitude greater than typical

human exposures.

Radon is a known human carcinogen. Estimates of lung cancer risk for the general

population from inhalation of radon and radon progeny are derived using human data on the

occurrence of lung cancer in underground miners due to inhalation exposures. Furthermore, the

average lifetime cumulative radon exposures to the general population are only slightly below those

for which increased risk can be demonstrated in underground miners. Hence, low-exposure

extrapolation is less of an issue for radon risk assessment than it is for the assessment of risk for most

other environmental carcinogens.

There is extensive evidence supporting the classification of radon as a known human

carcinogen. There is some uncertainty associated with the projection of lung cancer risk from

occupational radon exposures to the general population for residential exposures. Although the

epidemiologic data on increased risk from indoor exposures are limited, some of the studies suggest

that the relative risk coefficients for the general population and for underground miners are

comparable.

Uncertainty is always present to some extent in risk assessment for environmental pollutants.

However, as more data become available for radon, the uncertainties associated with estimation of

lung cancer risk may diminish. Follow-up of the underground miners will continue to clarify the

relationship of radon and smoking and the nature of the exposure-response relationship for radon

exposure and lung cancer risk over a lifetime. The results of epidemiologic studies of indoor radon

exposure may help to further define the relationship at low exposure levels. Advances in dosimetric

modeling and the findings of the NAS' report on comparative radon dosimetry (NAS 1991) have

improved the extrapolation of risks from miners to the public. As new information becomes available,

EPA will continue to update its estimates of lung cancer risk from residential radon exposure.

Chapter 2: Estimation ofRisks Page 2-41

CHAPTER 3

ANALYSIS OF EPA RADON TESTING OPTIONS

EPA recommends that individuals living in the following types of housing test their homes for

radon: single family homes, apartment units within multi-unit structures (if they are below the third

floor), mobile homes with permanent foundations, and units in ·group quarters below the third floor

(e.g., college dormitories). Among other changes, the proposed revision of the Citizen's Guide

recommends a new procedure for testing home radon levels. EPA narrowed the options down to six

and chose a final testing procedure from among

those six approaches. 1 This chapter describes

the six options and explains the process the

Agency used to analyze all of them before

recommending one for the public to use.

This chapter is organized into two major

parts. The first provides background

information, reviews the major considerations

important to developing testing procedures, and

summarizes the results of an analysis of the

effectiveness of the testing options (Sections I,

II, and III). The second part of the chapter

presents the details of the analysis and closes

with general conclusions drawn from the

analytic results (Sections IV, V, and VI). This

second part describes the analytic process, but does not replicate the analysis. Therefore, EPA has

cited rather than included technical background information. Finally, Appendix C supports this

chapter by providing basic background information on commonly used measurement devices.

Section I: Background

The original Citizen's Guide recommended that individuals perform (1) a short-term

(screening) measurement in the lowest livable level of the home under "closed-house" conditions

during the winter months, and (2) confirmatory long-term tests in the lived-in levels of the home if

the result of the short-term test was above 4 picocuries per liter (pCiIL). The recommended duration

of the confirmatory tests depended on the short-term test results and varied from less than one week

to a full year. The short-term test was designed to obtain the most reproducible estimate of the

highest (worst-case) radon concentration likely to be found in that particular house at any time. The

long-term measurement was intended to be an estimator of the annual average concentration in livedin levels of the home, being made over an entire year under normal ventilation conditions. An

exception to this process was when the short-term result was so elevated as to necessitate a more

rapid confirmation. Descriptions of short-term and long-term tests are given below.

lEPA originally considered more than six options. However, for reasons discussed in Section II (Appropriate Testing

Location), EPA focused this analysis on the six options that recommend testing on the lowest lived-in level.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-1
Short-term measurements, which last from 2 to 90 days, aim to give a quick assessment of

the level of radon in a home. Short-term screening measurements, which EPA recommended be

taken in the winter months in the "lowest livable" level of homes (the bottom-most inhabitable

space) under "closed-house" conditions, tend to produce conservative (i.e., high) estimates of annual

average radon levels. Short-term tests also can be conducted in the lowest lived-in level of homes

(a room that is used regularly) to produce estimates that more closely represent the annual average

radon concentration.

Long-term measurements are usually taken over the course of an entire year under normal

ventilation conditions. Because long-term measurements take into account seasonal fluctuations in

radon levels, and because they are performed under the ventilation conditions normally encountered

by homeowners, they tend to be better indicators of the actual radon concentrations to which

individuals in a home are exposed.

While long-term measurements tend to be better indicators of the average radon

concentration in a house over the course of a year, short-term measurements are simpler to make

and provide faster results. In cases where radon concentrations are extremely high, fast results are

desirable in order for mitigation to begin quickly.

An individual's risk of getting lung cancer from radon is directly proportional to his or her

integrated exposure, and the annual average concentration in lived-in levels of the home is the most

readily measurable quantity that approximates that exposure. However, it is not necessary to know

the actual risk in order to act to reduce it; a homeowner only needs to know that the radon

concentration is above some action level. Since the public seemed willing to take action based only

on short-term tests (see Chapter 6), EPA needed to adopt a recommended testing protocol for the

revised Guide that would allow homeowners to make the best possible mitigation decision based on

short-term test results.

In revising the Citizen's Guide, EPA has focused on how well options meet the basic purpose

of testing -- to enable homeowners to make the right decision on whether to mitigate radon levels.

When analyzing those options utilizing short-term measurements, the primary concern was not on

how well short-term measurements could estimate long-term averages. Rather, the central issue was

how well a testing option provides a reasonably accurate basis for determining whether there is a

need to reduce radon levels in a home. Errors could result when (1) a test indicated that mitigation

should occur when actual radon levels were below the action level (false positive), or (2) a test

indicated that mitigation should not occur when actual radon levels were above the action level (false

negative). Combining the percentages of both types of errors provides an estimate of the rate to

which each option might misclassify homes for mitigation. As discussed in the next section, the

misclassification rate for various testing schemes was one of five major factors that was important to

EPA in evaluating testing options.

Section II: Major Considerations in Developing Testing Procedures

EPA's goal is to recommend a radon testing procedure in homes that will lead the public to

decisions about radon reduction that are timely, simple, cost-effective, and protective of human

health. Before developing possible testing procedures, EPA identified five major factors that were

important to consider in developing and evaluating options. These considerations are listed in

summary form in Exhibit 3-1. The first factor is the action level used to determine whether a home

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-2
EXHIBIT 3-1

CONSIDERATIONS IN DEVELOPING RADON TESTING OPTIONS

• Appropriate Action Level

• Appropriate Testing Location

• Appropriate Ventilation Conditions

• Acceptability to Potential Users

• Effectiveness of Short-Term and Long-Term Measurements

requires mitigation. The second concern is the location inthe home where testing occurs. The third

factor is the ventilation condition (i.e., "open-house condition" versus "closed-house condition")

under which tests are performed. The fourth concern is the acceptability of the procedure to

potential users, and the final factor is the effectiveness of relying on short-term measurements. Each

of these factors is explained in more detail in the text that follows.

Appropriate Action Level - EPA is recommending an action level of 4 pCilL for several

reasons. First, the Office of Research and Development's (ORD's) research on mitigation

effectiveness and the Office of Radiation Programs' mitigator survey suggest that elevated levels of

radon can be reduced to 4 pCiIL more than 95 percent of the time. Results from the mitigator

survey indicate that 2 pCiIL can be achieved about 70 percent of the time, while the ORD research

suggests this estimate may be even higher (U.S. EPAIORD 1989; U.S. EPAIRadon Division 1990a).

Reducing the action level to 2 pCiIL, therefore, could result in perhaps as many as 30 percent of

homes with elevated levels being unable to achieve the action level. Second, lower action levels

introduce more uncertainty in the measurement results. Measurement device error increases to

approximately 50 percent at 2 pCi/L. This device error in conjunction with the larger fraction of

homes (of total homes testing) that have radon levels around 2 pCilL would result in a threefold

increase in false negatives and a twofold increase in false positives over those expected at a 4 pCi/L

action level.

Appropriate Testing Location - In the 1986 Citizen's Guide, EPA recommended that, for

screening purposes, a short-term measurement be taken on the "lowest livable" level, i.e., the lowest

area of a home that is used or has the potential to be used as a living space during the winter

months. This definition would include an unfinished basement that is in a condition such that it could

be converted to a bedroom, playroom, den, etc. For a confirmatory test (if the short-term test result

was above 4 pCilL), the 1986 Guide recommended a follow-up test in the lived-in levels of the home.

Lived-in level is defined as a level of a house that is used regularly, such as a living room, playroom,

den, or bedroom, but not a kitchen or bathroom, where high humidity conditions or the operation

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-3
of an exhaust fan could affect the validity of the test. EPA considered both "lowest livable" and

"lowest lived-in" testing locations in formulating the testing protocol in the revised Guide.

The choice between "lowest livable" and "lowest lived-in" level affects where homes with

basements will place radon detectors. Roughly 50 percent of homes nationwide have basements; only

half of !hese homes, or almost 25 percent of the national total, have basements that are used as a

lived-in level (U.S. EPNOffice of Radiation Programs 1991a). Accordingly, a recommendation that

devices be placed in the "lowest livable" level would result in 50 percent of the devices being placed

in the basement. A recommendation that devices be placed in the "lowest lived-in" level would

result in only 25 percent of devices being placed in the basement, and the remaining 75 percent being

placed on the first floor. A difference in the testing location therefore would affect 50% of homes

with basements that are not presently lived-in; this is 25% of all U.S. homes.

Keeping the short-term test in the lowest livable area as compared to moving it to the lowest

lived-in area would reduce false negative results by a factor of 1.5; however, the number of false

positive results would increase by a factor of 2. Measurements taken in the lowest lived-in area strike

a more equitable balance between false positives (public money spent with more limited benefits in

many cases) and false negatives (public health protection) than do livable area measurements.

Additionally, recent research (Harleyet a1. 1991) suggests that basement short-term measurements

overstate personal exposure by a factor of 3 to 5, while first floor short-term measurements are, on

average, only 30 percent greater than occupant exposure. Since the goal of radon measurement on

which a mitigation decision relies is to assess occupant exposure (U.S. EPA 1991a), lived-in level

measurements are better predictors than livable level measurements. Based on this finding and the

recommendation of EPA's Science Advisory Board (SAB) (U.S. EPA 1992b), short- or long-term

measurements that are to be used for the purpose of making mitigation decisions should be made on

the lowest lived-in level since it more closely approximates that concentration to which inhabitants

are exposed. Therefore, only lived-in level testing is considered in the various testing options

discussed below.

Appropriate Ventilation Conditions - EPA examined whether tests should be made under

"open-house" or "closed-house" conditions. In open-house conditions, tests are made with windows

and other ventilating passageways either closed or open as they would be when a test is not being

conducted. In closed-house conditions, all windows and other ventilated passageways are closed, to

the extent possible. Overall, EPA stresses the value of closed-house conditions in the final revised

Guide. Specifically, the final Guide recommends keeping windows and outside doors closed "as much

as possible" during short-term testing. For short-term tests lasting just 2 or 3 days, the final Guide

recommends closing windows and outside doors at least 12 hours before beginning the test.

Acceptability to Potential Users - EPA realized that, in real terms, the testing procedure

recommended in the original Citizen's Guide was technically sound, but was not viable because many

individuals dropped out before obtaining long-term measurements of the radon level in their homes.

Current Radon Program experience indicates that long-term tests are a deterrent to action and that

few people take long-term follow-up tests (see Chapter 6). In fact, the majority of people who

mitigate their homes are currently doing so based on a single short-term measurement.

Effectiveness of Short-Term and Long-Term Tests - Long-term tests are more indicative of

annual exposure than are short-term tests. Although a few of the testing procedures incorporate the

use of long-term tests, experience indicates that people are unwilling to take such tests. (Please refer

to Chapter 6 for more details on the public's unwillingness to use long-term tests.) Because shortChapter 3: Analysis ofEPA Radon Testing Options Page 3-4
term tests are completed in a short period of time, they are much more appealing to the public. A

procedure that does not incorporate long-term testing may be more effective in actual risk reduction.

Therefore, EPA assessed the feasibility of testing procedures utilizing short-term tests. Before

recommending a testing procedure not based on long-term testing, EPA sought to examine the

implications of relying on short-term tests as indicators of whether or not mitigation is necessary.

From knowledge of the relationship between short-term measurements and annual averages

gained from EPNState Residential Radon Surveys (SRRS), the Agency believed that although shortterm measurements are imperfect indicators of annual averages, they could potentially serve

effectively in the intended use EPA was considering. EPA reasoned that people measuring radon

levels in their homes do not require an accurate measurement of the annual average; instead,

homeowners require only a reasonably accurate basis for determining whether they need to mitigate.

Testing options need to have low misclassification rates for mitigation decisions to be acceptable.

EPA recognized that the distribution of radon levels in homes that is believed to exist would work

in the Agency's favor in using short-term tests. Exhibit 3-2 shows the distribution of annual average

radon concentrations suggested by EPA's National Residential Radon Survey (NRRS) for homes that

should be tested according to EPA's recommendations. Over 82 percent of the homes have radon

levels below 2 pCi/L. Another 7 percent of the homes have levels between 2 and 3 pCi/L. (These

estimates are based on lived-in level averages.) Therefore, errors in the use of short-term testing for

nearly 90 percent of the homes would have to be very substantial for these homes to be misclassified

as above the action level. The largest chances for problems exist in the range of 3 to 5 pCi/L, where

there are roughly 6 percent of all houses. The skewed distribution of radon levels towards the lower

end of the range could serve as a strong moderating force to any potential misclassification errors.

EPA was able to assess how short-term measurements could be used to make radon mitigation

decisions, as it had carefully tested large numbers of homes and compiled data to enable such an

evaluation. Beginning in 1987, EPA and States had cooperatively conducted 40 state-wide surveys

of radon levels in homes. For these surveys, which were designed to eliminate bias using standard

statistical techniques, EPA collected short-term radon measurements from nearly 60,000 homes and

paired short-term/long-term measurements from over 1,000 homes. EPA used testing protocols and

maintained a strong quality assurance and control program to ensure that the radon testing data

collected could be relied on in EPA evaluations of the significance of the radon problem and in

determining recommendations for public action.

As explained in more detail later in this chapter, EPA used both the SRRS and NRRS results

in a variety of ways in the analysis of radon testing options. For example, the Agency used the SRRS

results to analyze the relationship between short- and long-term measurements. The Agency used

the NRRS results to determine the distribution of annual average radon concentrations in homes

across the nation.

EPA initially considered the implications of a single, short-term test that people would

conduct in the lowest lived-in level of their homes. This simple approach did not offer enough

confidence that homes would be correctly classified in relation to the action level. Therefore, EPA

concentrated on analyzing options that relied on multiple tests. One of the options was very similar

to the short-term/long-term testing approach in the original Citizen's Guide, except the test would

occur in the lowest lived-in level (as opposed to the lowest livable level). This option is a reliable

approach that can be compared to options using short-term confirmatory tests. EPA evaluated five

other options that relied on multiple tests in a shorter time interval than the first option. All six

options were analyzed to estimate their rate of misclassification of homes for mitigation.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-5
EXHIBIT 3-2

DISTRIBUTION OF RADON LEVELS IN U.S. HOMES FOR WHICH EPA RECOMMENDS RADON TESTING

70% r-------------------------------..,

0- 1 1-2 2-3 3-4 4-5 5 - 10 >10

Annual Average Radon Concentration (pCilL)

-- Average over All Living Levels--

Source: U.S. EPNoffice ofRadiation Programs 1991a

Section III: Summary of the Misclassification Analysis Results for EPA's Testing Options

This section describes the six testing options that the Agency considered in developing a

testing protocol for the revised Citizen's Guide. It then describes the criteria used to judge the

effectiveness of each option, and presents the results of the Agency's analysis in summary form. The

options considered are diagrammed in Exhibit 3-3. For this document, EPA labeled the six options

in the order that makes their presentation most comprehensible. The Agency did not necessarily

create or evaluate options in the order in which they are described in this chapter.

When describing testing alternatives, the Agency made a distinction between action level and

trigger level. The action level was the level above which EPA recommended that a home be

mitigated. It also could be the same point where additional testing should occur. In contrast, the

trigger level was the level above which the Agency recommended in Option D that an individual

conduct further long-term or short-term testing to determine if a home was above the action level.

The action level was fixed at 4 pCi!L. The trigger levels in Option D were fixed at 2 pCi!L

(additional long-term testing required) and 10 pCi!L (additional short-term testing required).

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-6
EXHIBIT 3-3

ILLUSTRATION OF TESTING OPTIONS CONSIDERED

Initial Short-Term Test

f

Below 2pCilL:

No Further Action

Required

-

Initial Short-Term Test

fl.

Below 4pCilL: &I[§)@w@ [FJ©Mb:

No Further Action ILu ©@[1i)~~1l'1JiJil

Required + [M]~~~@@\l@ ~~

ILU o@) &l1l»@w@

~[FJ©~

\ J

-

t

&I[§)@\\7® 11 @ [FJ©~:

~U©@[1i)@Il'IJiJil~

[M]~~@@\l@ ~~ &lw@o @~

~U@ [FJ©Mb • lli)@@AIr@@[1i) @[1i)@] 11 @ [FJ©~

lLu ©@[1i)~~1l'1JiJil I

f ,

No Action If [M]olW@@~@ ~~ ILu ~@)

Below 4 pCilL &l1l»@w@ [FJ©M'IL J

11111 II1111 I11111111111111111111111111111111111111111!IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII111111111~lll Initial Short-Term Test

t I •

Below 4pCilL: &l1l»@w@ [FJ©Mb:

No Further Action ~u ©@[1i)~~1l'1JiJil

Required +

[M]o~o@@\l@ ~~

&lw@Il'@@@ 00

~U@) ~@) &I[§)@w@

[pJ©M'1L

\ J

-

Initial Short-Term Tests

On All Living Levels in Home

t I •

Average of All STs [M]o~o@@\l@

Below 4pCilL: &lw@Il'@@@ @~

No Further Action &I~~ ~U@) ~@)

Required &l1l»@w@ [FJ©M'IL

\ J

-

Initial Short-Term Test

fl.

Below 4pCilL: &I[§)@\\7® [FJ©Mb:

No Further Action ILu @Il' ~u ©@[1i)@1l'IJiJil

Required l

ILu: [M]o~~@@~@ ~~ ~u: [M]/K(o@@\l@ ~~

ILu ~@) &I[§)@w@ &lw@Il'@@@ 00 ~u

[FJ©M'IL u @@)~ o@) &l1l»@w@

, [FJ©0fl1L J

111111111111111111111111111111111111111111111111111111IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII~IIIIIIIIIIIIII'I!:

Initial Short-Term Test

t

Follow-Up Short-Term Test

t I •

Either ST [M]o~@@\l@

Below 4pCilL: lli)@~1liJ ~IF@) &l1l'@

No Further Action &l1l»@w@ [FJ©M'IL

Required

\ J

ST = Short-Term Test LT =Long-Term Test
•

•

•

•

•

•

Option A

Option B

Option C

Option D

Option E

Option F

Individuals would· make an initial short-term measurement in the

lowest lived-in level. Ifthe measurement exceeded the action level set

by EPA, the individual would be advised to make a long-term (i.e.,

year-long) measurement. If this measurement exceeded the action

level set by EPA, the Agency would recommend mitigation. [Note:

The original Citizen's Guide recommended a testing procedure similar

to Option A, except that short-term tests were conducted on the

lowest livable level, and the recommended duration of the

confirmatory test was not necessarily one full year.]

Individuals would make an initial short-term measurement in the

lowest lived-in level. If the measurement exceeded the action level,

the individual would be advised to make a confirmatory short-term

measurement. If the average of the two short-term measurements

exceeded the action level set by EPA, the Agency would recommend

mitigation. [Note: EPA proposed this testing procedure in the

revised draft of the Citizen's Guide, published in 1990.]

Individuals would make an initial short-term measurement in the

lowest lived-in level. If the result exceeded the action level, the

individual would make either a confirmatory long-term or short-term

measurement. This essentially gives individuals the choice of Options

A and B. If a confirmatory long-term measurement were made, the

results would be compared to the EPA action level, as in Option A.

If a confirmatory short-term measurement were made, the average of

the two short-term tests would be compared t,o the EPA action level,

as in Option B. If either method resulted in a value which exceeded

the action level, the Agency would recommend mitigation.

Individuals would make an initial short-term measurement in the

lowest lived-in level of their home. If the measurement exceeded a

trigger level of 10 pCiIL, the individual would be advised to make a

short-term test to confirm that the home required mitigation. If the

measurement was below 10 pCiIL but above a second trigger level of

2 pCi/L, the individual would be asked to make a confirmatory longterm measurement. If the average of the two short-term tests (for

homes above 10 pCi/L) or the result of the long-term measurement

exceeded the action level, the Agency would recommend mitigation.

Individuals would make simultaneous short-term measurements on all

lived-in levels of their home, one measurement device per level. For

single level homes, the Agency would recommend that individuals

perform two tests in different rooms. If the average of all test results

indicated that the radon level in the home exceeded the action level,

the Agency would recommend mitigation.

Like Option B, this option requires that individuals make an initial

short-term measurement in the lowest lived-in level. If the

measurement exceeded the action level, the individual would be

Chapter 3: AnaLysis ofEPA Radon Testing Options Page 3-8
advised to make a follow-up short-term measurement. If the

confirmatory measurement also exceeded the action level, the Agency

would recommend mitigation.

EPA used the following six quantitative measures to evaluate the simplified testing

procedures. Each measure was expressed as a percentage of the total homes tested, except the fifth

and sixth measures, which are explained further below.

Correct classification percentage - the percentage of homes tested for which the testing procedure

came to the correct conclusion (i.e., that homes with high radon levels should be mitigated

and all others left alone).

Error rate - homes for which the testing procedure came to the incorrect conclusion (i.e., either

false negative or false positive). This is the misclassification rate.

False negatives - homes tested in which the procedure incorrectly concluded that mitigation was not

required. False negatives can be presented as a percent of all homes or as a percent of actual

positives (i.e., homes that actually have radon levels greater than 4 pCi/L regardless of test

results).

False positives - homes tested in which the procedure incorrectly concluded that mitigation was

required. False positives can be presented as a percent of all homes or as a percent of all

positive tests.

False positives with quantifiable benefits - homes with false positive test results with actual annual

radon levels between 2 and 4 pCi/L (i.e., homes that have low starting radon concentrations,

but will still receive significant risk reduction through mitigation). False positives with

quantifiable benefits are presented as a percent of all positive tests.

False positives with non-quantifiable benefits - homes with false positive test results with actual

annual radon levels below 2 pCiIL. These homes also will also receive risk reduction through

mitigation, though the risk reduction will be less than that in homes with actual annual radon

levels between 2 and 4 pCi/L. Because the cost-effectiveness analysis presented in Chapter

5 assumes that mitigation only lowers homes to an average of 2 pCi/L, the actual benefits of

fixing homes with initial levels below 2 pCiIL is left unquantified. False positives with these

"nono.quantifiable" benefits are presented as a percent of all positive tests.

Exhibit 3-4 schematically shows how misclassification rates depend on the annual average

lived-in area radon concentration, the result of the testing procedure, and the action level. Among

other items, the exhibit shows that the inaccuracies in testing procedures matter only when they

produce results on the opposite side of the action level from the correct annual average (i.e.,

misclassifications). The exhibit also shows that the correct classification percentage and the error rate

are complementary, and that the false negative percentage and the false positive percentage add up

to the error rate. In the remainder of this chapter, EPA refers to the error rate as the

misclassification rate.

To determine the effectiveness of testing procedure options, EPA performed statistical

analyses of the misclassification rates associated with each option. EPA was interested in how

frequently a given test procedure correctly indicated whether a home should be mitigated. Exhibit

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-9
EXHIBIT 3-4

THE ACCURACY OF MITIGATION DECISIONS

BASED ON SHORT-TERM MEASUREMENTS

Short-Term

Measurement

< Action Level

Short-Term

Measurement

Action Level

Annual Average < Action Level

CORRECT CLASSIFICATION

Although the short-term

measurement may vary from the

annual average, both are below

the action level. The short-term

test correctIv indicates that

mitigation is unnecessary.

Annual Average Action Level

Although the short-term

measurement may vary from the

annual average, both are at or

above the action level. The

short-term test correctly indicates

that mitigation is necessary.

Correct Classification Percentage

(corresponds to total unshaded cells)

EITor Rate

(corresponds to total shaded cells)

Number of times testing led to a correct conclusion

total homes tested

Number of times testing led to an incorrect conclusion

total homes tested

Note: Often home mitigations will reduce radon levels to 2 pCi/L or lower. Consequently, mitigations undertakcn due to false

positive short-term testing results where the annual average radon concentration is above 2 pCi/L (but less than 4 pCiIL)

may result in significant risk reduction.

3-5 summarizes the results of EPA's statistical analysis of the six testing procedures it considered.

As recommended by the SAB (U.S. EPA 1992b), all results are based on the true radon levels being

equal to the annual average radon levels in homes, across all lived-in levels, as determined by EPA's

National Residential Radon Survey (U.S. EPNOffice of Radiation Programs 1991a). Results are

based on an action level of 4 pCi/L (the level used in both the original and revised Citizen's Guide).

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-10
EXHIBIT 3-5

TESTING PROCEDURES EPA CONSIDERED

AND THEIR MISCLASSIFICATION RATES

(Action Level = 4 pCilL)

Test Accuracy Option A Option B Option C Option D Option E Option F

Correct 98.1% 93.7% 94.1% 98.5% 94.7% 94.8%

Classification

Error Rate 1.9% 6.3% 5.9% 1.5% 5.3% 5.2%

False Negatives 1.9% 2.3% 2.3% 0.5% 1.5% 2.8%

as a Percent of

All Tests

False Negatives 30.2% 36.5% 36.5% 7.9% 23.8% 44.4%

as a Percent of

Actual Positives

False Positives 0.0% 4.0% 3.6% 1.0% 3.8% 2.4%

as a Percent of

All Tests

False Positives 0.0% 49.9% 47.4% 15.2% 44.3% 40.4%

as a Percent of

All Positive

Tests

False Positives 0.0% 28.9% 27.4% 8.2% 30.9% 26.5%

with

Quantifiable

Benefit

False Positives 0.0% 21.0% 20.0% 7.0% 13.4% 13.9%

with NonQuantifiable

Benefit

The accuracy of the testing procedure options also can be expressed in terms of the annual

lung cancer deaths that would be averted (i.e., the annual lives that would be saved) and the annual

deaths from lung cancer that would not be prevented (i.e., the number of lung cancer deaths in

homes that received a false negative test result). For the purposes of these calculations, EPA

assumed that 100 percent of the population followed the testing procedures and mitigated their

homes when results were above the action level (see Appendix E for a more detailed explanation).

Exhibit 3-6 presents the annual lives saved due to mitigations (where risk reductions were

quantifiable) under each of the testing procedure options. The exhibit also shows the lives not saved

due to false negative testing results.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-11
EXHIBIT 3-6

ANNUAL LIVES SAVED AND NOT SAVED

UNDER TESTING PROCEDURE OPTIONS~

Annual Lives Annual Lives Annual Lives Not

Saved in Homes Saved in Homes Total Lives Saved in Homes

Testing with True Positive with False Positive Saved with False Negative

Option Results Results Annually Results

A 2,160 0 2,160 620

B 2,040 200 2,240 750

C 2,050 180 2,230 740

D 2,630 50 2,680 160

E 2,330 240 2,570 450

F 1,820 140 1,960 970

~I Estimates assume 100% testing and mitigation.

Section IV: Approach for Analyzing Misclassification Rates of Each Testing Procedure Option

To help determine which testing procedure option to recommend to the public, EPA focused

on how well testing options provided a reasonably accurate basis for determining whether there was

a need to mitigate radon levels in a home. EPA wanted to estimate the misclassification rates

associated with each option. Misclassifications result from the inaccuracies of test measurements in

estimating the annual average with respect to the action level.

Because even Option A, which relies only on long-term tests for confirmatory purposes, relies

on a short-term test for initial screening, all of the options EPA considered have misclassifications

resulting from short-term testing. To analyze the misclassification rates that result from the shortterm testing components of each of the options, the Agency used a statistical approach that relied

to some extent on empirical data. The six steps involved in this statistical approach are summarized

in Exhibit 3-7. These steRs are explained in more detail in the text that follows according to the step

numbering in the exhibit.2

2 The development of EPA's statistical approach is further documented in two reports. The tirst report describes the

Agency's empirical analysis of existing radon measurement data (Marcinowski 1990). The second report details EPA's

development of a quantitative approaCh to predict short-term misclassification rates (Chmelynski 1992).

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-12
EXHIBIT 3-7

STEPS INVOLVED IN EPA'S

STATISTICAL ANALYSIS OF TESTING OPTIONS

(1) EPA developed a statistical model that explained a short-term test's inaccuracy

in estimating the annual average.

(2) For each option, EPA determined what test procedure outcomes were possible,

depending on the results of the initial and confirmatory tests.

(3) EPA considered the misclassifications resulting from all possible outcomes for

a given option separately.

(4) To determine how many homes would not require a confirmatory test and how

many false negatives there would be among homes not retesting, EPA modeled

the outcome of the initial test by developing a joint probability distribution of

short-term measurements and annual average radon concentrations.

(5) Given the joint probability distribution developed above, EPA modeled the

outcome ofsubsequent tests by developing conditional probability distributions

based on the annual averages in homes that would be required to retest.

(6) EPA determined the overall misc1assification rates for each option by summing

the probabilities of misclassification under all possible outcomes for the option.

Step 1 - EPA's first step was to develop a statistical model that could explain how short-term

measurements could deviate from annual averages. EPA's model is presented in Equation 1. After

starting with the annual average as an expected value for a short-term measurement, EPA's model

includes components that could contribute to deviations from annual averages. The model includes

components for three error types - measurement error, temporal error, and spatial error - as well

as the bias of radon concentration on the testing floor level, compared to the overall house annual

average. EPA developed upper and lower bound estimates for all three error types used in its model.

Lowest Living Level

Short-Term

Measurement

(

Annual Lowest Living Level)

Average x Floor Bias

x (emeasurement x etemporaJ x espatiaJ)

(1)

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-13
An annual average is the mean radon level over time for a particular house. It reflects an

average of the radon concentrations in all lived-in levels of a home. To calculate the

misclassifications associated with each option, EPA needed to know the distribution of annual

averages, since these determine what short-term measurements will be observed. For its analysis,

EPA assumed that nationwide annual average radon levels had the distribution suggested by the

Agency's National Residential Radon Survey (U.S. EPA/Office of Radiation Programs 1991a) for

homes that EPA recommends test.

Measurement error is the error associated with either a testing device itself or in the reading

of an exposed device by a laboratory technician. EPA's analysis covered only two types of

measurement devices, charcoal canisters and alpha track detectors. Other commonly used

measurement devices, such as electrets and continuous monitors, would perform similarly, if not

better. If the latter were the case, then the misclassification rates listed in Exhibit 3-5 would be

reduced slightly. A description of commonly used measurement devices is included in Appendix C.

For its analysis, EPA assumed that there was an equal likelihood of using charcoal canisters

and alpha track detectors. Initially, EPA intended to model the measurement device error associated

with charcoal canisters and alpha track detectors separately. For this purpose, EPA obtained data

on charcoal canisters from EPNState surveys (U.S. EPAlRadon Division 1990c) and data on alpha

track detectors from a New York State survey commissioned by the State government (Perritt 1990).

The EPNState surveys provided paired charcoal canister and alpha track detector data on over 1,000

homes. The New York State survey had information on over 2,000 homes. After comparing these

two sources of data, EPA concluded that no significant difference in measurement error existed

between these two types of devices. EPA data show that typical measurement device error for both

charcoal canisters and alpha track detectors is approximately 15 percent in the lab and 30 percent in

the field, in the vicinity of 4 pCilL (U.S. EPAlNational Air and Radiation Laboratory 1991). The

percentage measurement error is higher at lower radon levels, and lower at higher radon levels.

Temporal error is the error associated with the time of year a short-term measurement was

taken. EPA assumes that the annual average is constant, but that within any day, month, or year

there will be fluctuations in the radon level. At any time in the year, therefore, the exact relationship

of a short-term measurement to the annual average will not be known exactly. This inexactness is

the temporal error.

Since there are seasonal differences in the radon level of a home, the false positive rate could

be greater in the winter than in the summer, or the false negative rate could be greater in the

summer than in the winter (Marcinowski 1990; Condon et aI. 1990). However, Radon Program

Experience indicates that measurements are currently being conducted during all seasons of the year.

This indicated the need for a testing protocol that could be used throughout the entire year, so the

analysis focused on testing occurring equally during all seasons.3

Research indicates that temporal errors are the biggest contributor to the overall error

associated with short-term measurements. EPA simulated charcoal canister and alpha track device

measurements separately in its analysis because of the difference in temporal errors associated with

3It is unreasonable to assume that closed-house conditions would be maintained for a 90-day test. Because there is a

lack of data on compliance with closed-house conditions, EPA assumed both open-house and closed-house conditions would

occur with equal frequency for testing periods of this duration.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-14
these devices due to their different recommended durations of exposure. Because of the significance

ofseasonal variation in radon levels, EPA estimates that a measurement is subject to a temporal error

ranging from as low as 40 percent, for certain tests made under closed-house conditions using alpha

track detectors, to as high as 80 percent, for certain tests made under open-house conditions using

charcoal canisters. These estimates have been based on an EPA study comparing short-term

measurements to annual averages (U.S. EPNRadon Division 1990d). Because data in this study are

from a cold climate area with a long heating season and since the seasonal variability is greater in

areas with long heating seasons, the estimate of temporal error is conservative (i.e., high).

Chmelynski (1992) provides more detail on the methods used to estimate temporal error.

Spatial error is the error associated with the relationship between the radon concentration

on the lowest lived-in floor, where short-term tests are made, and the overall radon concentration

in a house. Spatial error does not account for the entire difference between the radon level on a

particular floor and the overall home average, but only the unpredictable component of this

difference. EPA estimates that short-term measurements are subject to spatial error that is about

40 percent of a measurement. This estimate has been based on data gathered for a study comparing

basement radon levels to first floor radon levels (Ronca-Battista 1989).

Since annual averages in most cases take into account the radon levels on more than one

floor within a house, short-term measurements may be inaccurate if the floor on which they are taken

does not tend to have the same radon level as the home as a whole. EPA identified the predictable

difference between the radon level on a given floor and the overall home average as the floor bias.

When radon measurements (short-term or long-term) on all lived-in levels in a home are considered

together, the resulting aggregate has no floor bias, since it would be expected to approach the house

overall average. Houses with only one lived-in level would not have any floor bias, since the lived-in

level average would be the same as the overall house average.

Research indicates that for 75 percent of homes, the lowest lived-in level is the first tloor

(Sterling et ai. 1985). Research also indicates that for most homes, the first tloor average is roughly

retlective of the overall home annual average (Peake 1990). Accordingly, the Agency assumed for

its modeling that there would be no floor bias associated with lowest lived-in level measurements.

The components of Equation 1 are multiplicative (retlecting how lowest lived-in floor bias and

error components affect the annual average) rather than additive. To make this equation more

conducive to statistical analysis, EPA applied a logarithmic transformation to both sides of the

equation. Equation 2 shows that the log of a single short-term measurement can be modeled using

five additive components.

[

Lowest Living LeVel)

log Short-Term

Measurement

[

10 (Annual) + 10 (Lowest Livin/f Level)]

g Average g Floor Bias

+ [log emeasurement+ log etemporaz+ log eSpalial]

(2)

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-15
Steps 2 and 3 - To make its calculation of the overall misc1assification rates for an option, EPA

needed to calculate separately the misclassification rates associated with each possible outcome ofthe

option (i.e., what type of confirmatory test, if any, would be required based on the measurement

observed in the initial test). In Exhibit 3-8, the different outcomes possible under each option are

graphically separated into different boxes. The types of error associated with each possible outcome

are also indicated. In this exhibit, unshaded areas for each option indicate the range of initial shortterm measurements for which no confirmatory tests are required. Shading indicates areas where

errors are dependent on the combination of initial short-term and confirmatory tests. Option E is

completely unshaded, unlike other options, because for this option no confirmatory tests are

performed.

Step 4 - For each option, EPA began its analysis of misclassification rates by focusing on the

possible outcomes of the initial test. Based on the statistical model shown in Equation 2, EPA

developed a joint probability distribution of annual average radon concentrations and expected shortterm measurements. A joint probability distribution indicates the probability with which certain shortterm measurements can be expected to be observed at a given annual average. EPA needed to

develop a joint probability distribution of annual averages and short-term measurements to determine

the proportion of homes in which a confirmatory test would be required under each option, assuming

the national distribution of annual average radon levels.

Because a joint probability distribution indicates the distribution ofshort-term measurements

that will occur for a given distribution of annual averages, it can be used to calculate the

misclassification rates attributed to testing outcomes not requiring a confirmatory test. Options A,

B, C, and F all require one initial short-term test with an action level of 4 pCilL. Exhibit 3-8

indicates that the initial short-term test components in these options will produce false negatives in

the same way, since all four options have one initial measurement and the same action level. The

overall misclassification rates of these four options vary due to differences in the confirmatory test

required when the initial measurement is above the action level. Since Option D requires further

testing if the initial measurement is above 2 pCilL, this option has fewer false negatives associated

with the initial testing. Option E, unlike other options, bases mitigation decisions on the average of

several initial short-term tests. This option requires no further testing regardless of the radon level

observed using short-term testing. Consequently, Steps 5 and 6 are not required for this option.

Step 5 - Using the joint probability distribution of annual averages and short-term testing that it

developed for Options A, B, C, D, and F, EPA developed conditional probability distributions to

model the outcome of the possible subsequent tests required under each option. Conditional

probability distributions indicate the expected frequency of results considering only the subset of a

population that has already met a given condition.

In EPA's analysis, the subset of the population being considered was only those homes that

had short-term measurements above the action level (Options A, B, C, and F) or the trigger level

(Option D). For each possible outcome in an option, EPA developed a separate conditional

probability distribution. In all cases, the conditional distributions took into account the subpopulation

required to retest and whether a long-term or short-term test was required. As part of its analysis

of conditional distributions, EPA focused on the probabilities of false positives occurring at homes

with annual average radon levels between 2 pCilL and 4 pCilL. If these homes are mitigated, it is

likely that the radon levels in them will decrease and the occupants will receive some benefits from

lowering their exposure to radon.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-16
EXHIBIT 3-8

COMPARISON OF FALSE NEGATIVES AND FALSE POSITIVES UNDER

RADON TESTING OPTIONS THAT EPA CONSIDERED

Option A

IfST test is below action level, no retest

is required. False negatives may result.

Option B

If ST test is below action level, no retest

is required. False negatives may result.

Option C

If ST test is below action level, no retest

is required. False negatives may result.

: 4 pCiJL Action Level For Options

: A-C. Initial Test Above This Level

• Leads to Confirmatory Testing.

•

-

•

•

•

-

•

•

•

•

·

-

Option D

IfSTis below 2 pCi/L,

no retest is required.

False negatives may result.

•

• 2 pC11I. 10 pCilL

: TriggerLev~ : TrlggerLevel

Option E

~-.

• ·

•

·

••

If average of ST measurements is below

action level, false negatives may result.

Option F

IfST test is below action level, no retest

is required. False negatives may result.

ST =Short-Term Test

LT =Long-Term Test

:If average of ST measurements

• is above action level,

: false positives may result. •

•

•

•

•

-

: 4 pC11I. Action Level

•

Note: Shaded areas indicate results dependent on both Initial and confirmatory tests.
Step 6 - To determine the overall misclassification rates for each option, EPA summed probabilities

in the joint probability distribution of annual averages and initial short-term tests and in the

conditional probability distributions of houses required to retest. To calculate the total of false

negatives, EPA summed probabilities that a testing outcome would classify a home as being below

the action level when the annual average was actually above the action level. To calculate the total

of false positives, EPA summed probabilities that a testing outcome would classify a home as being

above the action level when the annual average was actually below the action level. EPA aggregated

false negatives and false positives for possible outcomes under each option to generate the results

presented in Exhibit 3-5. Because EPA's analysis in essence is a comparison between the accuracy

of the option relying on a confirmatory long-term test and the accuracies of options relying to varying

degrees on confirmatory short-term tests, the Agency simplified its analysis by assuming that long-term

tests did not result in any misclassifications. This is because temporal variation is the largest

contributor to the misclassification rate and for year-long tests, this error term is negligible. The

misclassification for those options utilizing a long-term confirmatory test is insignificant and is

represented as resulting in no misclassifications in the results.

Section V: Analysis of Options

Options A, B, C, and F begin with a single short-term test, followed by a confirmatory longterm or short-term test if the result of the initial test is above the action level. Because these four

options begin with the same procedure, they share the same rate of false negatives among homes not

requiring a subsequent test. The difference in misclassification rates among these four options is due

strictly to differences in the procedures they use for follow-up testing. To determine the

misclassification rates associated with follow-up tests under each option, EPA developed conditional

probability distributions for the subset of homes expected to need confirmatory testing.

Like Options A, B, C, and F, Option D also begins with a single short-term test. Option D,

however, has a trigger level of 2 pCi/L, and an additional trigger level at 10 pCiIL that is discussed

further below in the documentation of EPA's analysis of Option D. Option D's lower trigger level

of 2 pCiIL for initiating confirmatory testing leads to a lower rate of false negatives than Options A

through C since homes with measurements between 2 to 4 pCiIL are subject to long-term tests. Only

false positives happen in measurements above 10 pCiIL, since in the interval of 2 to 10 pCi/L longterm testing is done.

Option E, unlike other testing alternatives, consists of multiple initial tests and does not

require confirmatory testing. Accordingly, for this option EPA analyzed only the misclassification

rates due to initial testing. EPA's approaches for determining the misclassification rates for the six

options are discussed in more detail below.

OPTION A - This alternative recommends a confirmatory long-term test whenever the

results of the short-term measurement are above the action level. As discussed above, the

misclassifications for long-term measurements are insignificant and, therefore, all long-term tests were

represented as resulting in correct classifications of homes concerning the need for mitigation.

Accordingly, to compute the misclassification rates associated with this option, EPA needed only to

consider the probabilities that false negatives would occur with the initial short-term test. These

probabilities were obtained from a joint probability distribution of annual averages and expected

results of the initial short-term test. This joint probability distribution was based on Equation 2,

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-18
which states the assumed relationship between short-term measurements and long-term annual

averages. See Steps 1 through 3 of Exhibit 3-9 for the derivation of the joint distribution.

OPTION B - This option is similar to Option A, except that it requires a confirmatory

short-term test when the initial short-term measurement exceeds 4 pCilL. Some false negatives result

from this testing procedure when the initial short-term measurement is below the action level. Both

false negatives and false positives are associated with the option when the initial short-term

measurement is above 4 pCiIL, depending on the outcome of the second test. Exhibit 3-9 illustrates

the key steps in determining false positives for Option B.

To analyze the misclassification rates associated with Option B, EPA separately considered

the range of initial short-term measurements below the action level and above the action level. For

its analysis of Option A, it already had analyzed the probability of obtaining false negatives associated

with short-term measurements below 4 pCilL.

To calculate the misclassification rates associated with the average of two short-term

measurements with a 30-day waiting period between them, EPA modified its statistical model. When

EPA was analyzing the misclassifications associated with only one short-term test, as in Option A, it

took into account the temporal error associated with a radon measurement made at one given time

of the year. If a second short-term measurement were made at the same time as the first (as in the

case of Option E, described below), the Agency would still be dealing with the same amount of

temporal error. In statistics, the strength of the relationship between sequential samples is called

serial correlation. In the absence ofserial correlation, the averaging of two measurements would lead

to a 1//2 reduction of the temporal error associated with short-term measurements, and hence to a

large reduction in the misclassification rate. To determine the degree to which a second sample

would reduce temporal error, EPA needed to take serial correlation into account in its statistical

model. In considering Option B, the Agency did this at a point in its analysis corresponding to Step

5 in Exhibit 3-7.

To determine how much serial correlation there is between two short-term measurements,

EPA studied the variations in radon levels in homes over time in the course of its Butte, Montana

study (U.S. EPA/Radon Division, 1990d). The reduction in uncertainty obtained using a second,

serially correlated short-term measurement was determined by computing the serial correlation of

various short-term averages separated by a set number of days using data on daily radon levels in

these homes. When the short-term measurements are made under closed-house conditions, a serial

correlation of approximately 0.4 was obtained for 2- to 7-day tests separated by 30 days. For 90-day

tests separated by 90 days, the serial correlation was lower, approximately 0.1. Variance reduction

factors were then computed, and these factors were then applied to the temporal error term in

Equation 2. The reduction in temporal error due to seasonal variation resulting from a second,

uncorrelated measurement would be approximately 30 percent (1 - [1//2]). The estimated reduction

in temporal error for 2- to 7-day tests separated by 30 days was 16 percent, compared to 26 percent

for back-to-back 90-day tests.

After estimating the amount of reduction in uncertainty that a confirmatory short-term

measurement would bring, EPA developed a conditional probability distribution of the average of two

sequential short-term tests among houses with an initial short-term test above 4 pCilL. Evaluation

of the required conditional distribution was based on the joint (trivariate) distribution of two serially

correlated short-term tests and the long-term annual average, as described in Step 5 of Exhibit 3-9.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-19
EXHIRrr 3-9

HOW FAIBE POSITIVE MISClASSIFICATION RATES WERE CALCUlATED FOR OPTIONS

Step (1) - EPA Developed a Model for Expressing Short-Term Measurements

in Terms of the Long-Term Annual Average and Several Components

Contributing to Deviations from this Average (See Equation 2 in Text)

2.4%

1.9%

1.9%

2 - 3 pCi/L

1 - 2 pCi/L

o- 1 pCilL

Step (4) - EPA Analyzed the Percentages ofInitial Short·Term Measurements

Above 4 pCilL for Certain Ranges of Annual Averages (percentages are

expressed as proportion of homes testing)

11·······l'rlle~lll111aFAve..ageJ1allJ~e I

+ flog e + log e + log e .] r' measurement tf!mporal spatill.!

[

10 (Annual) + 10 (Lowest Livin~ Level)]

g Average g Floor Bzas

(

Lowest Living Level

log Short-Term

Measurement

3 - 4 pCi/L 1.6%

Step (2) - EPA Assumed Values or Ranges of Values for All Additive

Components Based on EPA Studies

Lowest Living Floor Bias - none

Measurement Error - 30% at 4 pCilL

Temporal Error - 40% to 80%

Spatial Errol' - 40%

Step (5) - EPA Developed a Conditional Probability Distribution for the

Average of Two Short-Tel'm Tests, Taking into Account Serial Correlation,

Given the Distribution of Annual Averages and the Initial Measurement

I

Prob fSTAVG> 4pCi/L I ST. > 4 pCi/L, AA < 4pCi/Ll = J..:., f,~, ... f;,"~<T, f(AA, ST" ST,) dAA dST. dST,

f~... f:r.... f<AA, ST.) dAA dST.

where STI , ST'Z = Short-Term Measurements, AA = Anntud Averagl

Step (3) - EPA Developed a Joint Probahility Distrihution to Predict the

Homes Requiring Confirmatory Testing. The model in Step (1) estimates the

conditional distribution of S1\ given the annual average, f(STl'AA).

Step (6) - EPA Estimated the Percentage of Short-Term Measurements above

4 pCi/L and Summed Them to Get Total False Positives

Probability {STt > 4pCi/L, AA < 4pCi/L} '" f- f4 feST]' AA) dSTt dAA

ST,=4 AA=O o- 1 pCi/L I 0.4%

where ST1 == Initial Short-Tenn Measurement, AA == Annual Average 1 - 2 pCi/L I 0.9%

2 - 3 pCi/L I 1.1%

3 - 4 pCilL I 1.2%

I 0 - 4 pCi/L .--- I 3.6% I
To obtain the overall misclassification rate for Option B, EPA aggregated the probabilities of

obtaining false negatives when follow-up testing was not required with the probabilities of obtaining

false negatives and false positives when a confirmatory test was required. (In addition to leading to

a false positive by confirming an initial short-term test, the confirmatory test can lead to a false

negative if it does not agree with an initial test when the radon level is actually high,) These results

are presented in Exhibit 3-5.

OPTION C - To analyze the misclassification rates associated with Option C, EPA viewed

this testing procedure as a combination of Options A and B. Those options, respectively, require

initial short-term measurements to be followed by a confirmatory long-term or short-term

measurement.

Since Option C allows individuals to use either a confirmatory long-term or short-term test,

EPA's first task in analyzing the misclassification rates associated with this option was to determine

the frequencies with which each type of test would be used. EPA relied on a study it had done of

the public's willingness to use long-term tests. This study indicated that only 9 percent of the public

was willing to use long-term tests (Johnson 1990). Accordingly, EPA assumed for its analysis of

Option C that for initial short-term measurements that were above the action level, 9 percent would

be followed by confirmatory long-term measurements and that the remaining 91 percent would be

followed by confirmatory short-term tests.

Once EPA had assumed how the public would respond to the tlexibility in the testing

procedure offered under Option C, it could determine the misclassification rate of the option by

combining its analytical approaches for Options A and B. The Agency weighted the results of these

two options with factors of 0.1 and 0.9, respectively, to simulate the choice of long-term and shortterm testing procedures by the public. The results are presented in Exhibit 3-5.

OPTION D - Like Option C, this option can be viewed for analytical purposes as a

combination of Options A and B. Option D, however, does not give the public the choice between

long-term and short-term tests, but rather specifies which type of confirmatory test will be used, based

on the concentration of the initial short-term measurement. For measurements between 2 pCilL and

10 pCi/L, a confirmatory long-term test is required. For measurements above 10 pCiIL, only a

confirmatory short-term test is required. Of course, for measurements below 2 pCi/L, no

confirmatory test is required at all.

To determine the total amount of misclassification associated with Option D, EPA considered

the three possible outcomes of the initial short-term test separately. Exhibit 3-8 illustrates what types

of misclassification errors are associated with these three outcomes. Because initial short-term

measurements below the lower trigger level of 2 pCiIL do not include any scenarios leading to

mitigation, some false negatives occur. Roughly 93 percent of all homes in the population considered

did not require a confirmatory measurement. Initial short-term measurements above the lower trigger

level (2 pCilL), but below the higher trigger level (10 pCilL), were represented as not resulting in

any misclassifications at all, since the misclassifications for long-term measurements were insignificant.

Roughly 4 percent of all homes that should test had this outcome. Results above the higher trigger

level always indicated that mitigation was necessary, since the average of the two short-term tests was

always at least 5 pCilL. In practice, however, if there is a large disparity between the results of the

first and second test, additional evaluation may be necessary to determine the need for mitigation.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-21
Less than 3 percent of all homes in the population had initial short-term tests with measurements

above 10 pCilL.

Based on its analysis of Options A through C, EPA had already obtained a joint probability

distribution of annual averages and initial short-term measurements. From this joint probability

distribution, EPA determined the probability of false negatives due to initial short-term tests

incorrectly providing measurements of less than 2 pCilL.

Since EPA assumed that no misclassifications would be associated with long-term

measurements, it determined that all initial short-term measurements at least equal to 2 pCi/L but

below 10 pCilL would result in correct final classifications, regardless of the accuracy of the initial

short-term test.

EPA knew that all initial short-term measurements above 10 pCilL would require mitigation.

To determine the number of false positives associated with this outcome, EPA aggregated the

probabilities of having a false positive above 10 pCilL from the joint probability distribution. (EPA

did not have to take into account the serial correlation between the two short-term tests under this

option, since it assumed that the outcome would always resultin an assessment that mitigation was

necessary.)

To determine the overall misclassification rate associated with Option D, EPA combined the

probabilities that false negatives would occur due to initial short-term measurements below 2 pCilL

with the probabilities that false positives would occur due to initial short-term measurements above

10 pCiIL. The results are presented in Exhibit 3-5.

OPTION E - Unlike Options A through D, Option E requires that short-term tests be

conducted on all levels of a home that are lived-in levels (i.e., floors on which individuals spend more

than 4 hours of their time). Because this testing procedure would result in a number of different

testing patterns based on home type and lifestyle, EPA repeated its analysis of this option for three

different housing situations that could occur. The summarized results presented in Exhibit 3-5 reflect

a weighted average of the misclassifications for the different housing situations. The first situation

EPA considered was an individual living on one level. In this case, the individual would make two

tests on the same level, in different locations. The second situation EPA considered was an individual

living on two levels, either basement and first Hoor or first Hoor and second tloor. The third situation

EPA considered was an individual living on three levels.

After the Agency had determined the reduction in error components in Equation 1 under all

three scenarios, EPA derived three separate joint probability distributions for this option. All of

these distributions differed slightly from the single short-term measurement/annual average joint

probability distribution developed for Options A through D. Because each of the three scenarios had

a different joint probability distribution, each also had a different misclassification rate.

OPTION F - Like Option B, this option required a confirmatory short-term test when the

initial short-term measurement exceeded 4 pCi/L. As Exhibit 3-8 illustrates, some false negatives

resulted from this testing procedure when the initial short-term measurement was below the action

level. Both false negatives and false positives were associated with the option when the initial shortterm measurement was above 4 pCi/L, depending on the outcome of the second test. Unlike Option

B, however, this option does not average test results.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-22
To analyze the misclassification rates associated with Option F, EPA modified the approach

that it had taken for the analysis of Option B. After estimating the amount of reduction in

uncertainty that a confirmatory short-term measurement would bring given the serial correlation

between two sequential·measurements, EPA developed a conditional probability distribution of the

probability of outcomes for a second short-term among houses with an initial short-term test above

4 pCiIL. To obtain the overall misclassification rate for Option F, EPA aggregated the probabilities

of obtaining false negatives when follow-up testing was not required with the probabilities of

obtaining false negatives and false positives when a confirmatory test was required. (In addition to

leading to a false positive by confirming an initial short-term test, the confirmatory test could lead to

false negatives if it does not agree with an initial test when the radon level is actually high.)

Section VI: General Conclusions

Analysis of options that rely on short-term tests to decide whether to mitigate existing radon

levels shows that these tests can be used effectively. For the action level of 4 pCiIL, the Agency

found that short-term testing procedures can lead to a reasonably low level of misclassification of

homes with respect to the action level. EPA found that the skewed distribution of radon levels

towards the lower end of the distribution served as a strong countervailing factor to any

misclassifications created by short-term testing errors. The results are based on examination of the

most commonly used radon measurement devices and consideration of testing throughout the year.

Option A, which requires a single short-term measurement followed by a confirmatory longterm test, parallels the testing procedure recommended in the original Citizen's Guide, except that

testing would be conducted on the lowest lived-in level. Under Option A, 98 percent of homes were

correctly classified with regard to the need for mitigation. To determine how testing procedures

relying on a short-term confirmatory test would compare to this option, EPA developed and analyzed

five other options (Options B through F). EPA found that all of these options produced results

yielding at least 94 percent correct classifications. Similarly, each option has the potential to save a

significant number of lives, although there is some variation in the potential number of lives saved

and the number of lives not saved under each testing procedure.

Given these results, the Agency determined that on the basis of misclassification, none of the

options should be rejected. EPA decided that other factors, such as procedure simplicity, should be

weighed with the trade-off of increased levels of proper classification in making the decision on the

testing option to recommend in the revised Citizen's Guide. As stated previously, current experience

indicates that few people are actually taking long-term follow-up tests, and that most people who

mitigate do so based on a single short-term measurement. This is supported by risk communication

research that indicates that only 9 percent of the population is willing to conduct annual tests (see

Chapter 6 for a more detailed discussion). This suggests that a testing protocol that relies exclusively

on long-term confirmatory tests is unlikely to be followed by most of the public. Therefore, although

Options A and D have more desirable error rates than other options, it is likely that compliance with

these options would be low. Selection of either of these two options is apt to result in a situation

in which decisions are most often made based on a single short-term measurement when homeowners

do not complete the testing process. By explicitly providing homeowners a process that calls for more

than one short-term test, all of the other options considered would be more likely to result in people

having better information to use in reaching a mitigation decision.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-23
On the other hand, since long-term measurements are more desirable than short-term

measurements and since there are some individuals who are willing to conduct long-term tests, the

use of long-term tests should not be precluded from the testing protocol. As a result, Options B, E,

and F, which do not include long-term tests, are also undesirable.

Option C offers an effective compromise between these different approaches. It promotes

long-term testing by people who are willing to conduct long-term tests and recommends an effective

short-term test as an alternative for people who are not willing to conduct a long-term test.

Therefore, consistent with the advice from EPA's SAB, the revised Guide recommends Option C

because it should maximize the total risk reduction the public would gain through future testing and

mitigation.

Chapter 3: Analysis ofEPA Radon Testing Options Page 3-24
CHAPTER 4

MITIGATION TECHNOLOGY

This chapter explains different types of

available and emerging radon mitigation

techniques, their effectiveness, and costs. The

chapter is based primarily on research that

EPA's Office of Research and Development

(ORD) has conducted and results from a survey

of commercial radon mitigators that EPA's

Office of Radiation Programs (0RP) conducted

in 1989.

Section I: Mitigation Methods

Preventing radon entry and reducing radon concentrations after entry are two common

mitigation strategies. Preventing entry is often the best strategy since it has a high probability of

success, even in locations with very high radon levels. Techniques that reduce radon after entry are

most appropriate for buildings with relatively low radon levels, where radon entry cannot be

prevented, or in which increased ventilation could provide valuable benefits in addition to radon

reduction.

Regardless of the strategy considered, any mitigation plan must take into account a number

of considerations. In addition to controlling radon, the mitigation system should be unobtrusive,

quiet, and capable of indicating system failure. It should be economical and easy to maintain and

operate. Mitigation systems also must be a permanent part of the building rather than portable or

window-mounted devices that can be removed when the building is sold.1

Methods that Prevent Radon Entrv

Gaseous elements contained beneath the earth's surface can migrate through openings in soil

or rock and be released from the ground, depending on a number of factors. Soil gas is drawn

indoors by the differential between relatively low air pressure in a house and the higher air pressure

in the soil. Depressurization of the surrounding soil and foundation can prevent radon-bearing soil

gas from entering a house. Experience also shows that depressurization may be made more effective

by sealing cracks and other openings in floors and walls. Sub-slab depressurization is the preferred

approach because of its effectiveness, applicability, and ease of installation. Whenever any active

system is installed, the mitigator should test the house for combustion backdrafting.

Sub-slab depressurization (also called sub-slab suction) is a popular mitigation technology.

Once soil gas accumulates in the soil and aggregate underlying the concrete slab in a basement or

slab-on-grade house, it can migrate indoors through any openings in the slab. Active sub-slab

depressurization systems use pipes running down through the slab and up to a fan that vents the gas

lAccording to the Interim Mitigation Standards for the EPA Radon Contractor Proficiency Program.

Chapter 4: Mitigation Technology Page 4-1
outdoors. The fan reduces air pressure in the soil, thereby reversing the pressure gradient and

causing air to flow out of the house and into the soil through any openings in the slab. Passive subslab depressurization systems also can be used, but are less effective than active sub-slab

depressurization. Soil depressurization under a plastic or rubber membrane, or sub-membrane

depressurization, is used in buildings with earth-floored crawlspaces or basements (Hubbard et al.

1987). Its function is essentially the same as sub-slab depressurization, except that the mitigator

constructs a barrier as a collection cover rather than using the existing slab as a barrier.

If a perforated drain tile is present, drain-tile depressurization can be used to create a

negative pressure field surrounding the foundation walls to draw soil gas away from possible entry

routes. Block-wall depressurization consists of using a fan and duct work to draw suction on the

hollow interior cavities of a concrete block wall. By maintaining a lower pressure in the void network

within the block wall than in the basement, this technique forces the flow of soil gas to be outward

rather than into the basement. In a baseboard depressurization system, a "baseboard" is installed

around the entire perimeter ofthe basement and fans are used to depressurize the block wall cavities.

This system evenly distributes the pressure field and may simultaneously handle wet foundation

problems (Fowler et al. 1988; Henschel 1987).

Sub-slab and block-wall pressurization have been tested as alternatives to depressurization

in a number of government research projects. Essentially, these techniques reverse the fan in a soil

depressurization system, creating a positive shield of diluted air around a building. These methods

have had mixed results (Henschel and Scott 1987; Hubbard et al. 1987; Pyle et a1. 1988; Turk et al.

1986). In certain conditions, they perform better than soil depressurization. (The selection of these

techniques requires caution when pesticides have been applied nearby.)

Basement pressurization prevents soil gas from entering the building and reduces radon

concentrations by dilution (Nitschke et al. 1985; Turk et al. 1986). It can be accomplished by using

a fan to pull indoor air from the upstairs lived-in area and blow it into the basement. This process

creates a higher air pressure in the basement than outside, causing indoor air to flow through cracks

and holes in the basement out into the soil. Basement pressurization should be considered an

alternative for houses that are not compatible with soil depressurization techniques. Adequate longterm data are not available to determine the effect of basement pressurization on energy costs or

whether condensation will occur as basement air is forced out through cracks above grade.

Sealing openings to the soil is helpful as a supplementary activity to other methods as it

closes radon entry pathways and can improve the extension of depressurization on the soil. However,

the results of sealing are unpredictable when it is used alone as the primary mitigation method.

Success seems to be based on the number of cracks and holes in the slab or foundation, as well as

their connection to radon transport mechanisms. If the house is situated in a permeable soil with

elevated radon concentrations in the soil gas, it is very difficult to make a sealing-only technique

work. If there is only one primary transport mechanism connected to a single entry point, sealing

could make a difference, assuming the entry route could be sealed.

Isolation is another form of sealing that can be used to prevent radon entry. This technique

closes the openings between a large area of the substructure and the adjacent lived-in space, thereby

isolating exposed soil and rock under, around, or within a house that can be both a major source and

entry route for radon (Nitschke et al. 1985; Turk et al. 1986). When used in combination with

ventilation, isolation can be a very effective mitigation approach. Unfortunately, many spaces cannot

be easily isolated from the lived-in space and ventilated without causing winter freezing problems or

Chapter 4: Mitigation Technology Page 4-2
summer moisture problems. ·Crawlspaces lend themselves to isolation and ventilation, unless they

contain air distribution duct work that makes isolation difficult. Lived-in space radon concentrations

can be reduced by passively ventilating a crawlspace, depressurizing the crawlspace, pressurizing the

crawlspace, or creating a balanced flow. The two primary goals are to (1) decouple the lived-in area

from the soil, and (2) reduce concentrations in the crawlspace by dilution.

Radon entry also can be deterred by reducing negative pressure in the lowest level of the

house, since this pressure is the main driving force for infiltrating soil air. Negative pressure can be

reduced by sealing thermal bypasses at the ceiling level or supplying makeup (combustion or exhaust)

air to appliances such as furnaces, boilers, and bath fans that depressurize a house by using and

exhausting air to the outside. Currently, reducing negative pressure is not a primary mitigation

technique, but is used to enhance the performance of other mitigation efforts or to prevent a radon

problem in new construction (very little research has been done to evaluate it as a primary mitigation

approach). This technique also may reduce a home's heating needs.

Methods that Remove Radon from a Building

Once radon has entered a building, a variety of mitigation techniques can be used to reduce

the radon concentrations. Any radon problem can be reduced to some extent by blowing air through

the house. However, the use of increased ventilation is usually limited to homes in mild climates with

less than 20 pCiIL of radon because of the energy costs and comfort problems that would be

associated with the addition of large amounts of ventilation air. Best results are obtained when

basement areas are ventilated. Ventilation also can provide additional benefits such as the dilution

of other indoor air contaminants.

Mechanically powered ventilation is used either to blow air into the house or to supply and

exhaust air simultaneously. The indoor air pressure is increased (i.e., negative pressure is reduced)

if air is blown into the house, possibly leading to higher radon reductions than would be expected

from dilution alone. However, in climates where heating is necessary, blowing unconditioned air into

the house also would tend to increase energy usage and may increase the risk of moisture problems

in the building shell. If one fan is blowing in the same amount of air that another fan is removing,

the indoor pressure level will not be affected. Therefore, if other factors such as wind and

temperature remain constant, the influx of radon will remain the same and the radon concentration

will go down in proportion to the increase in the ventilation rate. Ifmechanically powered ventilation

is used only to exhaust air from the house, radon may be increased due to the negative pressure

induced inside (Hubbard et al. 1987; Lencheck et al. 1987).

Ventilation systems can be designed with or without a heat recovery system. A typical system

without heat recovery can employ a duct that draws outdoor air into the cold-air return of a forcedair furnace when the furnace is operating (Pyle et al. 1988). When the furnace fan is not operating,

fresh air enters only in response to pressure differentials between outside and inside air, thereby

reducing pressure differentials. The furnace heats this air and distributes it to the house. This small

amount of air will probably not move the house from negative pressure to positive pressure, but it

will reduce the negative pressure in the basement.

Heat recovery ventilators (HRVs or air-to-air heat exchangers) are designed to bring in the

same amount of air that the system is exhausting. The incoming air stream is preheated by the

outgoing airstream (Fowler et a1. 1988; Henschel and Scott 1987; Lenchek et a1. 1987; Nitschke et

a1. 1988). This process reduces the energy costs and associated discomfort. Because the balanced

Chapter 4: Mitigation Technology Page 4-3
now should have no impact on basement pressure, radon gas reduction will occur only through

dilution. The radon concentration will be reduced by the inverse of the ventilation increase. If a

basement is large, leaky, or has greatly elevated radon levels, it will be very difficult to make a

significant difference with ventilation.

Another radon removal ·device circulates interior air through alternating charcoal filtration

beds. As interior air circulates through one bed that accumulates radon and· its decay products,

exterior air is circulated through the second bed and exhausted outside. Thus, the beds collect radon

and its decay products from the indoor air which are then transported outside by the now of outside

air. The airnows alternate between beds to maintain radon removal efficiency.

Passive ventilation is achieved by opening windows while ensuring that the house is not

depressurized. Passive ventilation works by diluting the indoor radon concentration and by

neutralizing the pressure differentials between the inside and the outside. In one study, by opening

all the windows the leakage area of the house was increased by a factor of 10 to 20, and radon

concentrations in the house were reduced by a factor of 4 to 10 (Hubbard et a1. 1987). Because this

method can be used only when the outside weather permits, it is not an adequate permanent solution.

Other Methods under Development

There are several other methods that have not yet been shown to reduce radon health risks,

but which are still the subject of research and may prove to be significant after further improvement.

These alternate methods include air cleaners and space ionization. EPA does not recommend the

use of these techniques. because they can be easily removed from the structure.

Air cleaners that are commonly used to remove airborne particulates and condition indoor

air undoubtedly remove some radon decay products. However, many questions remain concerning

the relative health effects of the decay products that are not removed (the unattached fraction).

Space ionization removes radon decay products from indoor air by ionizing and circulating

the air. Many units may be needed to treat an entire house effectively. Also, no easy way currently

exists to monitor the performance of units that remove decay products without affecting radon gas

concentrations. Use of these devices should be considered only where preventative techniques are

not feasible, or as a temporary technique until other controls are implemented.

Section II: Effectiveness and Cost

This section summarizes the effectiveness and cost of various radon mitigation techniques.

Effectiveness is measured by the reduction in initial radon levels, and cost includes all the associated

costs of employing each technique. There are two primary sources of information on mitigation

effectiveness and cost: EPA research and demonstration projects and the Private Sector Radon

Mitigator Survey (U.S. EPAIRadon Division 1990a). Each one of the sources is summarized

individually. (The Office of Radiation Programs also has constructed a mitigation cost model that

uses the information summarized here along with additional information supplied by private mitigators

to estimate costs. That model is explained in Chapter 5.)

Chapter 4: Mitigation Technology Page 4-4
Effectiveness

Several research projects on the reduction in radon levels achieved by various mitigation

techniques have been conducted by EPA's ORD. Pre- and post-mitigation radon concentrations were

measured in the basement for houses with basements, and in the lived-in area for houses with slabon-grade and crawlspaces. Various measurement methods were used in the different projects (e.g.,

alpha track detectors, charcoal canisters, continuous monitors). ORD's program was designed to

reduce radon levels in homes with very high initial radon levels and often was conducted in houses

that had been identified as difficult to fix.

Through this research, ORD has found that radon levels in almost all homes can be reduced

to less than 4 pCilL (U.S. EPAlORD 1989). In fact, radon levels very often were reduced to less

than 2 pCilL, even though the mitigation efforts were only trying to reach an action level of 4 pCilL.

EPA believes that radon reduction to 2 pCilL or lower would have been even more common if it

were not for the fact that many of the homes examined had very high initial radon levels. Based on

this experience, the data suggest that available mitigation technologies are able to reduce radon levels

in homes above 4 pCilL down to 2 pCiIL, on average. Such reductions can be expected in houses

with different foundation types, including basement, slab-an-grade, and crawlspace homes.

Similar evidence of the ability of mitigation techniques to reduce radon levels was compiled

in ORP's Private Sector Radon Mitigator Survey, a nationwide survey of about 340 private sector

radon mitigators in the fall of 1989. Exhibit 4-1 summarizes the final results from this survey for

detached houses.2

EXHIBIT 4-1

PERCENT OF PRE- AND POST-MITIGATION RADON LEVELS

CITED IN PRIVATE SECTOR UADON MITIGATOR SURVEY

(U.S. EPAlRadon Division 1990a)

PRE-MITIGATION })OST-MITIGATION

pCi/L Percent Homes pCilL Percent Homes

<4 1% < 1 41%

4 - 10 23% 1 - 2 28%

10 - 20 37% 2-3 18%

20 - 50 29% 3-4 10%

> 50 10% >4 3%

1'he question asked of private mitigators was "What were the radon concentrations in the last building you mitigated

of each of the following types: detached house, school, workplace?" The answers for detached houses were used to

develop Exhibit 4-1.

Chapter 4: Mitigation Technology Page 4-5
The exhibit shows mitigators reporting that they have reduced radon levels to below 4 pCiIL

in 97 percent of the cases reported. Mitigators have also reduced radon levels to 2 pCilL, or less in

69 percent of the cases reported. Examination of the pre-mitigation radon levels in these homes

suggests that the private mitigator survey is reporting results from a set of homes that have a higher

proportion of units with elevated radon levels (above 10 pCiIL) than will exist nationally in the homes

that remain above the action level (i.e., 4 pCilL) and therefore need to be mitigated. Also, although

mitigators were trying to get radon concentrations below EPA's action level, they were not necessarily

trying to reduce radon levels to 2 pCilL or less. Therefore, EPA expects even better results for the

owners of the remaining homes that follow EPA's advice and have mitigators try to reduce radon

levels as much as possible. EPA believes that it is reasonable to assume that mitigators should be

able to get all homes above 4 pCilL down to an overall average of 2 pCilL (with some homes still

above 4 pCiIL and many homes attaining levels below 2 pCilL).3

Based on the findings of ORD's own research and the mitigator survey, the Agency concludes

that radon mitigation in the vast majority of cases (more than 95% of the time) should lead to radon

reductions that leave homes with an annual average level of less than 4 pCilL. It also will be very

common for homes to have post-mitigation levels of 2 pCilL or less. Results from the mitigator

survey indicate that 2 pCi/L can be achieved approximately 70 percent of the time, while the ORD

research suggests this estimate may be even higher. ORD's research shows that, on average, homes

above 4 pCilL can be mitigated to 2 pCi/L. In the fraction of homes where this lower level can be

reached, reductions to 2 pCilL or less should occur without inordinate effort, as the private sector

survey results are based on mitigation experience when radon mitigators were trying to bring homes

down to an action level of 4 pCiIL. Therefore, homeowners should expect that mitigators can provide

radon reductions at, or well below EPA's action level.

Lowering high radon levels often requires considerable technical knowledge and special skills.

As a result, the revised Citizen's Guide recommends that homeowners use mitigation contractors who

have passed the EPA Radon Contractor Proficiency (RCP) Program tests. Research indicates that

remedial actions taken by homeowners themselves are generally less effective than mitigation by

contractors, and often are not followed by retesting to verify their effectiveness (Doyle et al. 1990).

Nevertheless, EPA recognizes that some homeowners may want to mitigate their homes themselves

and has produced several publications to help guide "do-it-yourself' efforts. The revised Citizen's

Guide also recommends that homeowners contact their State radon office for further information on

do-it-yourself mitigation.

Cost

The cost of a mitigation technique depends primarily on two factors: the cost of installing

the system and the cost of operating and maintaining the system. Installation costs vary depending

on foundation type, size and structure of the home, and initial radon level. Operating costs vary

depending primarily on whether there is an energy penalty resulting from the loss of conditioned air,

the price of electricity to operate active systems, and various maintenance requirements. Therefore,

operating costs are usually presented as a range.

3Additionally, when EPA considered setting the action levels as low as 2 pCiIL, the Agency recognized that over 60

percent of the homes that should be fixed when the action level was 2 pCiIL would be between 2 and 4 pCiIL. These

homes would only need to achieve a 50 percent reduction, or less, to meet that action level. Often they would probably

have reductions well beloVl' 2 pCiIL.

Chapter 4: Mitigation Technology Page 4-6
From EPA's Private Sector Radon Mitigator Survey, the mean of the average reported

mitigation cost in 1989 was approximately $1,200 and the median was $1,100.4 Cited average costs

ranged from $50 to $5,000, but about 85 percent of the average costs reported were between $500

and $2,000. More recent EPA research (U.S. EPA 1991b) suggests that it may be more appropriate

to consider $2,500 as the upper end of the range.

Exhibit 4-2 presents estimated ranges of installation and operating costs for various dominant

mitigation techniques. This exhibit is a result of the collaborative effort of EPA's ORP and ORD,

and is based largely on the results of past research. The costs shown are typical ranges for most

homes, although the actual cost of installing and operating a mitigation system in a home may be

more or less than the range indicated in the exhibit. For active sub-slab depressurization, the exhibit's

figures are further backed by a detailed study of the installation and operating costs of soil

depressurization techniques (U.S. EPA 1991). More details on different aspects of radon mitigation

are provided in Appendix F, which supports Chapter 5.

As shown in Exhibits 4-2, typical installation costs for radon mitigation techniques range from

$100 to $3,000. However, depending on the type of house, installation costs can be above the upper

end of this range. In addition to installation costs, most mitigation systems (except sealing) will have

annual operating costs ranging from around $70 to $700. The effectiveness of each system will

depend on the characteristics of the house to be mitigated.

4The question asked in the survey was "What are the average charges for the mitigation techniques you use in

detached houses?" EPA then calculated the mean and median of the responses.

Chapter 4: Mitigation Technology Page 4-7
EXHIBIT 4-2

ESTIMATED INSTALLATION AND OPERATING COSTS FOR

VARIOUS RADON MITIGATION TECHNIQUES (1991 $)~/

o- 50% $200 - 500 if

additional vents

are installed; $0

if no additional

vents

80 - 99% $800 - 2,500

90 - 99% $800 - 1,700

50 - 99% $1,500 - 3,000

90 - 99% $800 - 2,500

80 - 99% $1,000 - 2,500

Technique

Sub-slab Suction

(Sub-slab

Depressurization)

Drain-tile

Suction

Block-wall

Suction

Sump Hole

Suction

Sub-membrane

Depressurization

in Crawlspace

Natural

Ventilation in a

Crawlspace

Typical

Radon

Reductions

Typical Range of

Installation

Costs

(Contractor)

Typical Operating Cost

Range for Fan

Electricity and

Heated/Cooled Air

Loss (Annual)

$75 - 175

$75 - 175

$150 - 300

$100 - 225

$50 - 175

May be some energy

penalties

Comments

Works best if air can move easily in

the material under the floor slab.

Works best if drain-tiles form

complete loop around the house.

Only in houses with hollow blockwalls; requires sealing job of major

openings.

Works best if air can move easily to

sump under slab, or if drain-tiles form

complete lOop.

Less heat loss than natural ventilation

in cold winter climates.

Costs are variable

Sealing of Radon

Entry Routes

House

,(Basement)

Pressurization

Natural

Ventilation

Heat Recovery

Ventilation

o- 50% $100 - 2,000

50 - 99% $500 - 1,500

Variable $200 - 500 if

additional vents

installed; $0 if no

adclitional vents

25 - 50% if $1,200 - 2,500

used for

full house;

25 - 75% if

used for

basement

None

$150 - 500

$100 - 700

$75 - 500 for

continuous operation

Normally used in combination with

other techniques. Requires proper

materials and careful installation.

Works best with tight basement that

can be isolated from outdoors and

upper floors.

Significant heat and conditioned air

loss; operating cost dependent upon

utility rates and amount of ventilation.

Limited use; works best in a tight

house and when used for basement;

less conditioned air loss than natural

ventilation.

~The costs provided in this exhibit represent the range of typical costs for reducing radon levels in homes above 4 pCiIL down

to radon levels below 4 pCiIL. In most cases homes are reduced to an average of about 2 pCiIL.

Chapter 4: Mitigation Technology Page 4-8
CHAPTER 5

COST-EFFECTIVENESS ANALYSIS

This chapter presents an analysis of the

risk reductions and costs for the public if it

followed the radon testing and mitigation advice

that EPA offers in the revised Citizen '8 Guide to

Radon. The first section of the chapter

provides an initial overview of the analysis. This

overview is followed by a section that describes

the testing and mitigation options that the

Agency considered in revising the Guide as well

as the portion of housing stock and residential

population that would be targeted by each. The

next two sections analyze, in turn, the risk

reductions and costs for the public that result

from the options that EPA considered. The

final section examines the cost-effectiveness of

each alternative.

Section I: Overview of the Analysis

This analysis estimates the annual risk reductions that would occur if the public followed the

program prescrihed in the revised Citizen '8 Guide to Radon, the annualized costs the public would

incur, and the overall cost-effectiveness of the prescribed program as reflected by the cost per life

saved. The analysis considers three options, with each consisting of the basic testing approach

recommended in the revised Guide (Option C as defined in Chapter 3) coupled with different action

levels for triggering the mitigation of a home. EPA recognized that the other testing options

discussed in Chapter 3 also could he cost-effective in providing large risk reductions if the public

followed the advice it had provided, but believed that these options had other weaknesses as outlined

earlier that ruled out their selection. Following EPA's Science Advisory Board's concurrence on

using Option C, the Agency focused its cost-effectiveness analysis on the action levels it should chose

rather than on testing approaches.

The first option includes an action level of 4 pCiIL, which is the action level recommended

in the revised Citizen '8 Guide. However, as stated in several places in the revised Guide, EPA

recognizes that mitigation down to lower levels may be appropriate because radon levels less than

4 pCi/L still pose a health risk. Also, most homes today can be reduced to 2 pCiIL or below, and

Congress has set a long-term goal that indoor radon levels be no more than outdoor levels, which are

typically below 2 pCi/L. As a result, the cost-effectiveness analysis also considers two other options

with lower action levels, 2 pCiIL and 3 pCiIL. 1

lThe Agency also examined action levels of 8 pOlL and 20 pOlL These action levels are discussed in Appendix H.

Chapter 5: Cost-Effectiveness Analysis Page 5-1
The results for each option are compared to the figures that EPA's Guidelines for PelfOlming

Regu.latOlY Impact Analysis (1983) suggest that the public is willing to pay to save "statistical lives."

The figures presented in these guidelines represent the value the public places on reducing risks of

death from all types of causes, given empirical evidence of the public's willingness to either pay to

reduce small risks or receive payments for accepting those risks. The results also are compared to

the cost-effectiveness of EPA's prior testing and mitigation advice in the original Guide and to the

cost-effectiveness of other health and safety programs.

The analysis examines seven major components for each option: (1) the population of homes

and people covered by the advice; (2) radon distributions in the affected homes; (3) the number of

homes that should mitigate given the effectiveness of radon testing; (4) the risk reduction associated

with lower radon exposure due to mitigation; (5) the unit costs associated with testing and mitigating

homes; (6) the total costs of testing and mitigation for the group covered; and (7) the costs per life

saved. The major steps in the analysis are summarized in Exhibit 5-1.

EXHIBIT 5-1

MAJOR STEPS IN THE COST-EFFECTIVENESS ANALYSIS

Step 1:

Step 2:

Step 3:

Step 4:

Step 5:

Step 6:

Step 7:

Determine the Universe Covered by the Testing and Mitigation Advice Option

Estimate the Radon Distribution in Affected Housing Units2/

Calculate the Number of Housing Units that Should Mitigate Given the

Estimated Accuracy of Radon Testing

Analyze the Annual Risk Reductions Resulting from Mitigation

Determine the Unit Costs of Testing and Mitigation

Develop the Total Annualized Costs of Testing and Mitigation

Calculate the Cost per Life Saved

!!/See Appendix D for a description or the affected housing units.

Throughout the analysis, a 100 percent public compliance rate with EPA's advice on testing

and mitigation is assumed. There is no consideration of actions the public already has taken in

response to the 1986 Citizen's Guide and independent State programs.

Section II: EPA's Approach to Reducing Residential Radon

This section provides a brief description of the residential radon problem, which, as opposed

to radon problems in schools and other buildings, is the focus of the revised Citizen's Guide. It also

describes EPA's advice to the public in the revised Citizen's Guide on how to reduce the risks from

Chapter 5: Cost-Effectiveness Analysis Page 5-2
radon exposure and defines the residential population (and housing stock) that the Guide is trying

to convince to take action to reduce radon exposures.

Residential Radon Problem

Radon can pose a significant health problem in any building where it can accumulate. Its

greatest risk to the public appears to result from its accumulation in homes, where the public is

estimated to spend about 75 percent of its time. Radon can emanate from certain building materials

or be released at harmful levels in the home from water taken from ground-water sources, but it

usually reaches elevated levels in homes due to soil gas entry through the home foundation. EPA's

revised Citizen's Guide focuses on testing for radon in homes and taking actions to reduce radon entry

or mitigate its effects. The Agency estimates that radon levels in the United States housing stock

lead to 7,000 to 30,000 lung cancer deaths in the residential population annually. EPA's central

estimate is that about 14,000 lung cancer deaths result each year from residential radon levels. The

vast majority of the exposure occurs in single-family homes, mobile homes with permanent

foundations, and the lower levels of apartment buildings and group quarters, such as college

dormitories. Chapter 2 describes EPA's risk estimates for residential radon in more detail and

Appendix B provides basic background information on radon.

Revised Citizen ~\' Guide~" Approach

In the revised Citizen's Guide, EPA advises homeowners initially to conduct a short-term test

in the lowest lived-in level of their homes. If the results of the test are above the established action

level of 4 pCilL, homeowners are advised to obtain a follow-up measurement using either a shortterm or long-term test. The higher the initial short-term result, the greater the certainty that the

long-term average is also above the action level. With this in mind, and to keep homeowners from

being unduly exposed to extremely elevated levels, EPA recommends that a short-term follow-up test

be used if the results of the first short-term test are above 10 pCilL. If homeowners conduct a longterm follow-up test, they are advised to mitigate their homes if the results of the long-term test are

at or above the action level. If homeowners conduct a short-term follow-up test, they are advised

to consider mitigating their homes if the average of the results of the two short-term tests is 4 pCilL

or more. The revised Guide also notes that homeowners can further reduce their lung cancer risk

by mitigating homes that are below 4 pCi/L.

Homeowners are advised to mitigate their homes as quickly as possible. The mitigation

technology that a person chooses to install will depend on the type of housing unit, the number of

floors in the unit, the foundation type, and its interior space use. Most people will probably use one

of the major technologies such as active subslab depressurization, sealing/plugging, natural ventilation,

and heat recovery ventilation. Chapter 4 contains a more detailed discussion of these technologies.

In the revised Citizen's Guide to Radon, EPA establishes an action level of 4 pCilL. The

action level, i.e., the radon level at which homeowners are advised to mitigate, effectively determines

the number of homes that should mitigate. Lowering the action level increases the number of homes

that should mitigate and thus increases the scope of the radon program as well as the national risk

reductions and total costs associated with the program. As described in the overview, this analysis

also examines two alternative action levels, 2 pCiIL and 3 pCiIL.

Chapter 5: Cost-Effectiveness Analysis Page 5-3
Coverage of Revised Citizen xGuide

Exhibit 5-2 presents the total number of housing units and the total population that would

be affected by EPA's advice to test and fix homes for radon. In the revised Citizen's Guide to Radon,

all single-family homes, apartment units that are below the third floor, mobile homes with permanent

foundations, and units in group quarters (e.g., college dormitories, military barracks) that are below

the third floor should test for radon. EPA took the numbers of single-family homes, apartments in

multi-unit structures, and mobile homes that were used in the analysis of the radon testing population

from initial releases of 1990 Census data provided by the Bureau of the Census.2 EPA's radon

testing policy would lead to the testing of about 83 million housing units that are occupied by about

215 million people. This represents almost 83 percent of the housing stock that is regularly used and

about 87 percent of the residential population. Appendix D provides greater explanation of how the

estimates in Exhibit 5-2 were derived.

Section III: Risk Reduction

The risk analysis calculated the risk reductions resulting from the mitigation of homes with

elevated radon. EPA estimated the annual risk reduction that occurred from each option examined

in terms of annual lung cancer deaths averted, i.e., annual lives saved. The Agency also calculated

annual deaths from lung cancer that are not prevented because of false negative test results (i.e.,

negative test results for a home that actually has a radon level above 4 pCilL). The number of homes

mitigated, and thus the risk reductions that occur, depends on (1) the action level established by EPA

in each option, (2) the distribution of radon in housing units that test, and (3) the effectiveness of

the radon tests. It also critically depends on the effectiveness of mitigation techniques that reduce

radon levels.

This section initially describes the analyses conducted to determine how effective EPA's

testing approach would be in classifying homes correctly using testing Option C (defined in Chapter

3) at various action levels. This description is followed by a summary of the assumptions made about

the effectiveness of mitigation actions in lowering radon levels. The section closes with a explanation

of how EPA calculated risk reductions based on this information and provides the results.

Results of Radon Testing

According to EPA's testing advice, an initial short-term screening test should be conducted

in the lowest lived-in level of a home. If the results of the initial test are above the action level

established by EPA, either a short-term or long-term follow-up test should be conducted. To

determine the frequencies with which each type of test would actually be used by the public to make

the follow-up measurement, EPA conducted a study of the public's willingness to use long-term tests.

The study concluded that only 9 percent of the public were willing to use long-term tests (Johnson

1990). Accordingly, this analysis assumes that 9 percent of all follow-up tests will be long-term tests

and 91 percent will be short-term tests.

2EPA used 1990 Census data released in June 1991 (from Summary Tape File 1A) that provided official Census

disaggregated estimates of population characteristics and types of structures as of April 1990. The Census Bureau's

residential population estimate at that time was 248.7 million people, which by October 1990 was estimated to have grown

to 250 million people (the basis of Chapter 2's risk calculation). As of May 1992, the residential population is 255 million

people (Bureau of tne Census, 1992b).

Chapter 5: Cost-Effectiveness Analysis Page 5-4
EXllllUT 5-2

1990 HOUSING UNITS AND RESIDENTIAL POI'ULATION

COVEREI> BY EPA'S RADON TESTING POLICY

(in 1000s)

100% 83%

Total Units Total

Intended for Units that Should Coverage Criteria from Residential Radon Testing

Regular Use~! Test for Radon!! Radon Testing I'olicy I'opulation!!! Population

62,461 62,461 All single family homes 174,891 174,891

26,569 I 17,801 All units below 3rd Ooor 52,596 35,239

I

All units on permanent

8,067 403 foundation 14,526 I 726

3,383 2,267 All units below 3rd Ooor 6,698 I 4,487

100,480 82,932

95% 78%

3,383

8,521

100%

27,981

65,762

105,647

Total Units~!

Mobile Homes

Multi-Units

Percent of All Units

Group Quarters

HOUSING UNITS

Percent of Units Intended

for Regular Use{

Percent Population

TOTAL

Single-I<'amily

Q

~.

;::

:::.

'?

""

0:;'

Note: Totals may not sum due to rounding.

All estimates, except group quarters are from 1990 Census data. Number of group quarters estimate based on assumed OCCUpaIK), of about two persons per unit and

1990 Census estimate of persons living in group quaners. Mobile homes also include relatively small numbers of trailers and "other" units that could not easily be removed

from the estimate.

21 All estimates derived from available 1990 Census data on numbers of total units and excluding units with vacancies that were due to seasonal, occasional,and "other"

(undefined) uses. All these cases were assumed to be situations in which owners would not test their units since they were not intended to have regular usage. Vacant

units for rent or sale for year-round use wcre covered and used in estimating the units that should test in the next column.

Estimates of units that should test based on EPA testing policy (i.e., that anyone living in detached houses, including mobile homes with permanent foundations should

test for radon (U.S. EPNOffice of Public A11airs J988)). Applicable criteria appear in the next column.

Occupancy rates were derived from published and unpublished Census data and assumptions about similarities in unit usage between structures that did and did not

"'t:1 I have data available for direct computations uf occupancy rates. These rates were used to estimate the population residing in each type of unit.

:::.

Yt

v,
EPA generated distribution tables for each action level based on testing devices used, number

of home floors, and testing conditions.3 (For a more detailed explanation of radon tests, please refer

to Chapter 3.) Based on 1990 Census data and data from the Characteristics ofNew Housing: 1990

Cun"ent Constntction RepOlts (Bureau of the Census 1991), the weights for single floor vs. multi-floor

homes were determined to be 46 and 54 percent, respectively. The same approach that was uSyd to

derive the mitigation classification rates in Chapter 3 was also used here, except the focus was on

options that had different action levels combined with the same Option C testing approach.

Exhibit 5-3 presents the weighted testing distribution for the action level of 4 pCi/L. The

distribution is based on the actual annual average radon level in the home and the radon level

EXHIBIT 5-3

JOINT PROBABILI1Y DISTRIBUTION OF RADON TESTING RESULTS

FOR AN ACTION LEVEL OF 4 pCi/L

4-6 >20 TOTAL~

FALSE POSITIVES - 3.6%

0.0012 0.0005 0.0004 0.0000 0.6198

0.0021 (W008 0.0006 0.0000 0.2074

0.0025 0.0010 0.0009 (WOOl 0.0717

0.0382

3-4

Radon Level According to Test Results (pCi/L)

2-3

1-2

0-1

3-4

Intervals of

Actual Annual

Average Radon Level 0-1

(pCiIL)

4-6 0.0007 0.0036 0.0061 0.0075 0.0373

6-8 <>.0001 0.0005 0.0011 0.0121

8-10 0.0000 0.0001 0.0003 0.0005 0.0067

10-20 0.0000 0.0000 0.0001 0.0062

>20 0.0000 0.0000 0.0000 0.0006

TOTAU' 0.5493 0.1899 0.1114 0.0726 1.0000

2

/

Totals may not sum due to rounding. Very small values rounded to zero in the exhibit.

3The Agency generated distribution tables using information in a report entitled 'An Evaluation of the Performance of

Alternative Short-Term Radon Testing Procedures in Homes with Pending Real Estate Transactions'. Chmelynski, H. 1992.

Chapter 5: Cost-Effectiveness Analysis Page 5-6
indicated by the test results.4 From this exhibit, it is apparent that close to 8 percent of the housing

stock should mitigate their homes based on their test results (Le., 3.6 percent with false positive

results plus 4.0 percent with true positive results). About 53 percent of these houses have actual true

positive results; 47 percent of the homes actually have false positive results. Very often homes with

false positive results also will receive risk reductions when mitigated and, therefore, substantial

benefits are still derived from fixing homes below the action level. (This is discussed further in the

next section on mitigation effectiveness.) The Agency also prepared unique distributions for the

other action levels. From these distributions, EPA calculated the fractions of the population that

obtain false positive, true positive, false negative, and true negative test results.

Exhibit 5-4 presents estimates of the homes testing, retesting, and mitigating at various action

levels, as well as the population in each set of these homes. Of the 83 million homes that should

initially test, about 10 million homes (12 percent) would be expected to retest using EPA's selected

action level of 4 pCiIL. About 6 million of these homes will have results above the action level 30d

should mitigate (8 percent of homes initially testing). Close to 17 million people live in the homes

that should mitigate. This is about 8 percent of the occupants in homes that should test and close

to 7 percent of the residential population of the U.S.

EXHIBIT 5-4

ESTIMATES OF HOMES TESTING AND MITIGATING

AT SELECTED ACTION LEVELS AND RESIDENTS IN THOSE HOMES (in 1000s)

HOUSING UNITS Initial Testing Retesting Mitigating

i/ '1~2--' ......./ ................< \ .» // ....................... ........ ./

." .',\ » ../ y..\ » .•••• ......y ...>.y.

2 82,900 21,900 16,000

3 82,900 14,400 9,700

4 82,900 10,000 6,400

RESIDENTS Initial Testing Retesting Mitigating

/a···· <).> ..•• IT.). •••.••• .\/ y y •...• < •••• ....... // /y ..... / sr/ •.•••••• ••••••• < ........ ............... ..

• ••••••••••••••

2 215,300 57,000 41,600

3 215,300 37,300 25,200

4 215,300 26,000 16,500

"This distribution retlects the results expected to be obtained using the testing advice in the 1992 Citizen'~ Guide.

Therefore, it includes homes that have tested once and received a result below the action level and homes that have tested

twice. Homes that retest with a short-term test average the results of the two tests. I-Iomes that retest with a long-term test

use only the results of the long-term test since long-term tests are assumed to always result in correct classification of homes.

Chapter 5: Cost-Effectiveness Analysis Page 5-7
Effectiveness of Mitigation

For the purposes of estimating the benefits (risk reduction) of various policy decisions, this

analysis assumes that homes with annual average radon levels above 2 pCi/Lthat mitigate will reduce

radon levels to a post-mitigation annual lived-in area level of 2 pCi/L.5 This is a level of radon

mitigation that EPA believes most homes can achieve on average, as discussed in Chapter 4.6

Homes with average radon levels below 2 pCi/L that mitigate (due to false positive test results) are

likely to receive some reduction in radon levels, but the amount cannot be quantified. Therefore,

the Agency conservatively assumed no reduction in risks. The Agency estimated radon exposure for

the testing population using results from EPA's National Residential Radon Survey (U.S. EPNOffice

of Radiation Programs 1991a). EPA also derived the mean radon exposure for each interval in the

testing population distribution using data from the Survey. The exposure reduction achieved in each

interval from mitigation was then calculated using Equation 1.

Radon Exposure

Reduction in

pCilL Interval

Calculation of Risk Reductions

Mean Rodon

Exposure in Interval

Post

Mitigation Level (1)

This analysis assumes that the reduction in risk associated with a reduction in radon exposure

.of 1 pCi/L was 43.2 lives saved annually per million people receiving the reduction. This risk factor

was derived from EPA's risk assessment methodology that is explained in Chapter 2.7 The central

estimate of the radon risk factor is used in this analysis, rather than the upper bound risk estimate.

The upper bound estimate would have increased all the risk estimates by about 2.5 times and

improved later cost-effectiveness estimates by about 60 percent. Using the central risk factor, the

number of radon deaths averted per million people was calculated for each radon concentration

interval as shown in Equation 2.

Radon Deaths Averted

in Interval

Per Million People

Radon Exposure Risk Reduction = Reduction in pCilL Interval x Factor

(From (1»

(2)

5Mitigation is assumed to lower homes to an average of 2 pCi/L, regardless of the action level.

&rhis assumption is based on review of the results from post-mitigation testing, which is often conducted in the lowest

lived-in level in a home. Therefore, it could potentially lead to a conservative estimate of the average reduction of radon

throughout the home (i.e., it could lead to an underestimate of the risk reduction). In Appendix G, the sensitivity of this

assumption is examined.

7EPA converted its central risk factor (2.24 x 10-4 lifetime risk) into an annual risk reduction factor for homes based on

a conversion of 0.193 working level months per pCiIL and assuming an average life expectancy of 74. years.

Chapter 5: Cost-Effectiveness Analysis Page 5-8
Annual lives saved (due to both true positive and false positive test results) and annual lives

lost (due to false negative test results) were then calculated for each radon concentration interval

using the weighted testing distribution and the testing population as shown in Equation 3.8

Annual Lives

Saved (Lost)

in pCilL Interval

Testing

Population x

(in Millions)

Fraction

of Population

in pCilL Interval

x

Radon Deaths Averted

in Interval

Per Million People

(From (2))

(3)

Exhibit 5-5 presents the results of the risk analysis for all three action levels and provides an

estimation of the percentage of risk that is above each action level.9 The estimated 2,200 lives saved

annually with an action level of 4 pCi/L is roughly 17 percent of the lives that could potentially be

lost due to residential radon exposure. lO The action levels of 2 pCilL and 3 pCilL would reduce

the estimated number of lung cancer deaths by 23 percent and 19 percent, respectively. More detail

on how the risk assessment was conducted is provided in Appendix E.

EXHIBIT 5-5

ANNUAL LIVES SAVED AND NOT SAVED

UNDER ALTERNATIVE ACTION LEVELS FOR MITIGATION

Percentage of PreMitigation Risk Annual Lives Saved

Above the Action (Due to True and False Annual Lives Not Saved

Action Level Level Positive Test Results) (Due to False Negatives)

2 pCiIL 55% 3,100 460

3 pCiIL 42% 2,600 750

4 pCilL 32% 2,200 740

8Equation 3 is used to calculate both annual lives saved and annual lives lost. If the test results arc [rue or false positives,

lives are saved due to the reduction in radon exposure. If the results are false negatives, lives are lost due to no reduction

in radon exposure.

'The results in Exhibit 5-5 are based on a central estimate of 13,430 radon-induced lung cancer deaths per year. This

estimate was developed using the Census Bureau's residential population figure of 248.7 million people as of April 1990,

which is lower than the figure of 250 million people as of October 1990 used in Chapter 2.

lOoyhe rel1uction is lower than the percentage of risk that exists in homes above 4 pCi/L because mitigation will, on

average, lower homes to 2 pCi/L, and because false negative results prevent mitigation from fixing all homes above 4 pCi/L.

(Additionally, fixing many homes with false positive results does lead to significant levels of risk reduction.)

Chapter 5: Cost-Effectiveness Analysis Page 5-9
Section IV: Costs

EPA estimated the costs of testing and the costs of mitigating of homes based on the most

recent information available, and employed basic assumptions that are consistent witp. those used in

the risk analysis. The Agency calculated all costs as total present value costs. Annualized costs were

then derived to show the total costs of each alternative in annual constant dollars over the time

period of the analysis. All testing and installation of mitigation systems were assumed to occur

immediately. The time period used for the analysis to estimate operating and maintenance (O&M)

expenses was 74 years. This is actually the average life expectancy of the U.S. population today and

a time period representative of at least thc avcrage life of a home.!1 The Agency chose this time

period as an analytic convention to make the analysis comparable to other EPA analyses that estimate

cancer cases averted based on an assessment of the lifetime risks and then convert those estimates

into annual rates of cancer incidence avoided. A three percent discount rate was used to calculate

both the present value of the total costs and the annualized costs. 12

Testing Costs

The analysis assumes that the average initial homeowner testing cost is $28. This is based on

the assumption that half of the homeowners would use charcoal canister tests (ap~roximately $20 per

test) and half would use alpha track detectors (approximately $35 per test). b For homes that

retest, the cost of a second short-term test was again assumed to be $28. Long-term tests were

estimated to cost homeowners $100 per test.14 Based on a study conducted by EPA on the public's

willingness to use long-term tests (Johnson 1990), this analysis assumes that short-term tests are used

in follow-up testing 91 percent of the time and long-term tests are used 9 percent of the. time.15

The number of homes that test initially is assumed to be all homes covered by the revised Citizen's

Guide advice, i.e., approximately 83 million homes. The number of homes that retest was calculated

from the distribution of radon in the affectcd population using Equation 4.

Fraction of Number of Number of Homes That Retest = Homes That Initially Test x Affected

Above Action Level Homes

llExamination of housing data on demolition rates suggests that the average home life is longer than 74 years.

(4)

12The three percent discount rate is based on the opportunity cost of money to the homeowner recognizing that most

of the expenses will result from yearly operating and maintenance expenses.

13Some homeowners will use more expensive devices, especially during real estate transactions. The assumption here is

that the vast majority of homeowners will use charcoal canisters or alpha track detectors, since CRMs and electrets aren't

"do-it-yourselt" devices.

14This assumption is based on homeowners using an alpha track detector over a long period of time in a single location

or multiple locations; using charcoal canisters over several seasons; or having tests conducted by a contractor. This estimate

is meant to be an overall average cost of fOllOW-Up by the 9 percent of homes retesting with a long-term test, which is a very

modest percentage of total costs. The testing costs cover actions of homeowners and do not include additional tests mitigators

may perform on site while they fIx a home.

15The sensitivity analysis presented in Appendix G looks at the annual lives saved and cost incurred if 100% of the public

used long-term confIrmatory. tests.

Chapter 5;· Cost-Effectiveness Analysis Page 5-10
Total initial testing and retesting costs were calculated as shown in Equation 5 and Equation 6.

Total Initial

Testing Cost

Number of Cost of

Homes That xl· . 1 "..

Initially Test nztla.l. est

(5)

Total

Retesting Cost

Mitigation Costs

Number of Homes x ( Cost of x 91 % + Cost of x 9%) Short-term Test Long-term Test That Retest

(6)

The costs of radon mitigation were calculated using a model developed by EPA. The model

includes both upfront costs of system installation and operating and maintenance costs. The model

provides a weighted average cost of mitigation based on characteristics of the housing stock such as

foundation type, radon levels in the homes to be mitigated, and mitigation methods employed. The

model produces different weighted average costs for each action level. For an action level of 4 pCiIL,

the model produces a lifetime (74 years) weighted average cost of about $6,550 per home. About

$1,500 of this expense (close to 25 percent), is for upfront costs of correctly installing systems. Close

to $1,250 of this upfront cost is direct installation of the system and the remainder is for price

estimation and post-mitigation activities conducted to ensure proper system operation. The largest

portion of mitigation costs results from O&M costs and is roughly $5,050, or about 75 percent of the

total costs. The majority of this cost comes from active systems that use electricity and require

homeowners to pay for increased ventilation in the home or additional space conditioning because

of exhalation of air beneath the foundation due to depressurization efforts in subslab systems.

A similar upfront and O&M cost relationship exists in the costs for the lower action levels.

The total weighted average costs in those cases are $6,150 and $6,350 for 2 pCi/L and 3 pCi/L,

respectively. The lower costs are due to an increasingly larger percentage of homes at lower radon

levels that enter into the calculation of the weighted average costs. In the majority of situations

(especially in homes using ASD), the costs of reducing radon levels in homes above all three action

levels down to 2 pCi/L is about the same. However, mitigations in the smaller set of homes that use

sealing and ventilation technologies cost less at the lower action levels, because the mitigation systems

need to provide lower percentage reductions in radon levels.

An explanation of how the model works is provided in Appendix F. The model was designed

to estimate costs for mitigation contractors for single-family detached homes (nearly 69 percent of

the homes covered). This analysis assumes that mitigation costs for other types of housing units are

the same as for single-family detached homes. This may overestimate the costs for these other units,

since it fails to recognize economies of scale and other factors in mitigating single-family attached

homes, multi-units, group quarters, and mobile homes. Of the housing stock that should be tested

for radon, these units represent 7 percent, 21 percent, 3 percent, and 0.5 percent, respectively. The

analysis assumes that all radon mitigation system installations occur immediately and that the

mitigation systems operate over the 74-year period of the analysis. In addition to routine annual

operating costs, biennial testing and repair and replacement costs are considered in developing

lifetime home costs (U.S. EPA/Radon Division, 1991). The cost model does not make a distinction

Chapter 5: Cost-Effectiveness Analysis Page 5-11
between homes that are mitigated due to true positive test results and homes that are mitigated due

to false positive results. The number of homes that are mitigated was calculated using Equation 7.

Fraction of • Number of Homes H Th t R t st = omes a e e x

That Mitigate Above Action Level

Total mitigation costs were calculated using Equation 8.

Number of

Affected

Homes

(7)

Total Costs

Total

Mitigation Costs

Number of

Homes x

Mitigated

Weighted Average

Cost of

Mitigation

(8)

Exhibit 5-6 presents the results of the cost analysis for all three action levels for testing and

mitigation. It shows that if the public fully followed EPA's advice with an action level of 4 pCiIL, the

annualized cost is about $1.5 billion. About 6 percent of the cost would be for testing and about 94

percent cost would be for mitigation. About 87 percent of the testing costs is incurred in the initial

round of testing.

EXHIBIT 5-6

NATIONAL COSTS OF ALTEllNATIVE ACTION LEVELS FOR MITIGATION

(1000s of 1991 $)

Action Level Initial Testing Cost Retesting Cost Mitigation Cost Total Cost

Total Present Value of Costs

2 pCi/L 2,322,000 757,000 98,171,000 101,250,000

3 pCi/L 2,322,000 495,000 61,726,000 64,542,000

4 pCilL 2,322,000 346,000 41,839,000 44,507,000

Annualized Costs

2 pCilL 78,000 26,000 3,317,000 3,421,000

3 pCi/L 78,000 17,000 2,086,000 2,181,000

4 pCiIL 78,000 12,000 1,414,000 1,504,000

Chapter 5: Cost-Effectiveness Analysis Page 5-12
Section V: Cost-Effectiveness

EPA has used cost per life saved (cost per death averted) as a measure of effectiveness of

the revised Citizen's Guide in reducing risks to the public. This section discusses how EPA calculated

cost-effectiveness and provides the results for the alternative action levels considered in revising the

Citizen's Guide. The section then evaluates these results in three different ways, by (1) relating the

results to the public's willingness to pay to save a statistical life, (2) comparing the cost per life saved

of radon reduction to the cost per life saved of other safety and health-related programs, and (3)

comparing the cost-effectiveness of the approach taken in the revised Citizen's Guide to that of the

1986 (original) Guide. The section also analyzes the sensitivity of the results to major assumptions

and parameters used in the analysis.

Cost per Life Saved of Selected Approaches to the Revised Guide

The average cost per life saved for each alternative was calculated using Equation 9.

Average Cost per

Life Saved

Total

Annualized Cost

Annual Lives

Saved

(9)

Exhibit 5-7 presents the average cost per life saved for all three action levels. The exhibit also

presents the incremental cost per life saved. 16 The incremental cost per life saved is the added cost

per life saved of each increment of risk reduction that can be gained when a lower action level is

selected.I7 The results of the cost per life saved calculations for each action level are best

evaluated in relationship to the value the public places on risk reductions. It is also helpful to look

at the cost-effectiveness of other health and safety programs. Simply comparing one action level

against another in the analysis can lead to misleading conclusions. For example, although an action

level of 2 pCiIL is the least cost-effective option analyzed here, an EPA radon program based on that

level could be more cost-effective in protecting public health than other governmental actions to

reduce other forms of risk. It could also be providing a risk reduction at a cost the public is generally

willing to pay for safety and health measures. Therefore, it is important to evaluate the results in

Exhibit 5-7 in the broader context of what government can do overall to reduce risks.

In addition, the incremental cost per life saved is a very valuable tool in evaluating the costeffectiveness of an option because it clearly assesses the value of the additional cost incurred by

expanding the program to gain additional risk reduction. In evaluating the cost-effectiveness of the

options analyzed here, the incremental cost per life saved for each option is best compared to the

value the public places on saving a statistical life.

l<1'he cost per life saved of additional action levels is provided in Appendix H.

17For example, the incremental cost per life saved of an action level of 3 pCiIL is the increased annual cost of moving

from an action level of 4 pCiIL to 3 pCiIL ($677 million) divided by the increased annual risk reduction (about 400 lives

saved) -- an incremental cost per life saved of $1.7 million. Alternatively, the average cost per life saved is the direct division

of the annualized cost of a 3 pCi/L action level ($2.18 billion) by the annual lives saved (2,600 lives saved) -- an average cost

per life saved of $0.8 million.

Chapter 5: Cost-Effectiveness Analysis Page 5-13
EXHIBIT 5-7

COST PER LIFE SAVED

UNDER ALTERNATIVE TESTING AND MITIGATION PROGRAMS

Average Cost Incremental Cost

Number of Lives Annualized Cost per Life Saved per Life Saved

Action Level Saved Annually (1000s of 1991$) (1000s of 1991$) (1000s of 1991$)

2 pCi/L 3,100 $3,421,000 $1,100 $2,400

3 pCi/L 2,600 2,181,000 800 1,700

4 pCi/L 2,200 1,504,000 700 700~1

~/Based on assumption that "no action" was the alternative EPA had to this action level.

Note: The central estimate aUhe radon risk factor is used in this analysis, rather than the upper bound risk estimate. The

upper bound estimate would have increased all the risk estimates by about 2.5 times and reduced the cost-effectiveness

estimates by about 60 percent.

Public Willingness to Pay to Reduce Risks

The cost per life saved indicates how cost-effective an alternative is in providing health

benefits to the public. It should be compared to the public's willingness to pay to save a "statistical

life," Le., buy risk reductions. In the past, EPA's 1983 Regulatory Impact Analysis (RIA) Guidelines

(U.S. EPA 1983) have indicated that the public appears to value a risk reduction that saves a life (in

statistical terms) for between $600,000 to $9,900,000 in 1991 dollars. A more recent study (Fisher

et a1. 1989) suggests that the public places the value of a statistical life between $2,000,000 and . 18 $10,500,000 III 1991 dollars.

All three alternatives analyzed here have average cost per life saved values well below the

upper end for the value of a statistical life. In fact, when compared to the most recent study's results

of the public's willingness to pay, all three options provide an average cost per life saved that is well

below the lower end of the range.

Cost per Life Saved of Other Programs

The cost per life saved calculations for the alternatives examined in this analysis can be

compared to the cost per life saved of other health-related programs in order to evaluate how costeffective the radon program is in protecting public health relative to other governmental actions

taken to reduce risk. Its value as an aid to decisionmaking is based on the premise that given the

limited availability of resources, public agencies should try to use societal resources to purchase the

greatest risk reductions possible for the public. The lower the cost per life saved of actions taken,

the more risk reduction the government could provide for the resources society can spend for health

and safety protection.

l&rhis study was conducted by the same researchers who provided EPA with the range in the 1983 RIA Guidelines.

Chapter 5: Cost-Effectiveness Analysis Page 5-14
Exhibit 5-8 shows the cost-effectiveness of other health and safety programs that has been

reported in various sources. The effectiveness measures are cost per life saved. Another similar

measure that is often used to evaluate the cost-effectiveness of government programs is the cost per

cancer case avoided, when there is less certainty about the percentage of the time the cancer cases

involved will lead to fatalities. 19 EPA has calculated this latter measure for many of its regulatory

decisions because Agency risk estimates routinely report cases avoided, rather than fatalities. An

'EPA-sponsored review of EPA decisions over the last decade shows that the Agency has often

decided on regulatory controls that cost several million dollars per cancer case avoided (Travis et a1.

1987).

EXHIUIT 5-8

COST-EFFECTIVENESS ESTIMATES FOR SELECTED

HEALTH AND SAFETY PROGRAMS~/

Range of Cost Per Life

Saved/Case Avoided

Federal Program Area (lOOOs of 1991$) Source

Medical Screening/Care 63 - 510 per life saved Cohen 1987

Highway Safety 100 - 3,300 per life saved OMB 1991

Air Transportation Safety 100 - 1,600 per life saved OMB 1991

Occupational Safety 100 - 74,000 per life saved OMB 1991

;!!These values represent the ranges for regulatory decisions and health programs that have been reported in the literature

from the most authoritative sources found. They are not all inclusive and other sources may provide different ranges because

of differences in analytic approaches and year in which studies were completed.

The studies that have provided these estimates could have significant differences in their

methodologies for calculating risk reductions and costs. Therefore, care must be taken in comparing

these results to each other and to the results for the radon program. For instance, most assessments

of the benefits from EPA rules are based on estimates of risk reductions that use conservative risk

factors analogous to the upper hound estimate for radon. If the upper bound estimate for the risk

factor had been used in this analysis, the average cost per life saved would have been reduced by

about 60 percent.

However, simple direct comparisons of the range of results in Exhibit 5-8 and the review of

EPA's own past regulatory experience to the results for the revised Citizen's Guide provide a general

sense of how cost-effective the radon program is. For example, the average cost per life saved for

190ften in occupational health, food safety, and environmental protection analyses, only the incidence of cancer cases

rather than death is calculated, because the target site and specific cancer mortality rate are unknown. In general, one in

every two cases of cancer results in a fatality.

Chapter 5: Cost-Effectiveness Analysis Page 5-15
an action level of 4 pCiIL is approximately $700,000. This falls well within the range of the cost per

life saved of highway safety, air transportation safety, and occupational safety programs and

regulation. It is slightly higher than the upper bound cost per life saved of medical screening and

health care. The $700,000 cost per life saved also compares favorably to the expenditures that EPA

has been willing to see incurred for risk reductions in the past.20

Comparisons to the 1986 Citizen's Guide

EPA also examined the risk reductions, costs, and cost-effectiveness of the 1986 Citizen's

Guide and compared its findings to what could be expected under the revised Citizen's Guide. The

original Guide called for a short-term test in the lowest "livable space" and general follow up with a

long-term test. If the long-term test results were greater than the action level of 4 pCiIL, mitigation

was recommended.

EPA believes that about six percent of homes that should be tested had actually been tested

as of July 1991. EPA estimates that this has led to the saving of about 40 lives per year, with an

annualized cost of close to $40 million. The cost per life saved, therefore, has been close to $900,000.

The cost per life saved under the revised Guide is about 25 percent less. The main reason for this

reduction is that following the new EPA testing advice reduces the chances of false positive results.

Homes with false positive results often will install mitigation systems that could provide only relatively

small, if any, risk reductions.

Sensitivity Analysis and Examimition of' Higher Action Levels

EPA examined the sensitivity of the results ofits cost-effectiveness analysis to the assumptions

it used for major parameters of the analysis. This analysis covered the action level that EPA selected

for the revised Citizen's Guide (action level of 4 pCi/L.) The results of changing major parameters

within the reasonable range of potential values that they could have still suggest that the radon

program should be cost-effective. The results of the analysis are provided in Appendix G.

In keeping with the Congressional mandate in IRAA to consider lowering the action level for

radon mitigation, the Agency has focused its attention on action levels of 4 pCi/L and lower. This

also is in keeping with EPA's mission as a public health agency to reasonably minimize risks to the

public. EPA believes it is reasonable to focus on these lower action levels since higher action levels

would remove a relatively smaller portion of the public's residential radon risk. Furthermore, having

an action level of at least 4 pCi/L was determined to be incrementally cost-effective early in the

Agency's deliberations on the Citizen's Guide. Appendix H provides a summary of the analytic results

on which EPA has based its conclusions.

2~e cost-effectiveness of environmental controls is in terms of cancer cases avoided and not in terms of lives saved.

Any comparison of cost-effectiveness between the radon program and other environmental programs should take this

difference into consideration.

Chapter 5: Cost-Effectiveness Analysis Page 5-16
CHAPTER 6

RISK COMMUNICATION

Section I: Introduction

Two conditions must be met for any successful voluntary public health program: (1) the

public must believe that the behavior or substance in question poses a significant personal threat, and

(2) the solution must be simple enough for the public to be willing to adopt. The goal of the

Citizen's Guide is to stimulate public action by convincing people that radon poses a serious health

threat that can be mitigated relatively easily. Public action entails testing for the presence of radon

and mitigating if necessary. Because it is

difficult to persuade people to take voluntary

action, it is critical to find and use the best

possible risk communication strategies. Risk

communication research has helped EPA

develop and refine the communication strategies

used in the Citizen's Guide to ensure its success

in educating the public and stimulating testing.

Risks associated with high radon levels

in homes began receiving national publicity

about six years ago. Since then, a number of

researchers have studied risk communication

issues associated with radon (e.g., the reactions

of homeowners to information about radon

risks). Most of this growing body of research has been sponsored by EPA's Office of Policy, Planning

and Evaluation (OPPE) in cooperation with universities, States, and others. These studies include

risk communication testing of the Fall 1990 draft Guide.

When the original (1986) Citizen's Guide was prepared, a major concern was avoiding public

panic. Accordingly, the tone of the Guide was factual and informative. This approach, however,

resulted in public apathy, not panic. EPA estimates that about SA million homes have been tested

for radon as of July 1991.1 This figure represents approximately six percent of the occupied homes

in the United States that should test (including single family homes, mobile homes with permanent

foundations, apartment units below the third tloor, and units in group quarters such as college

dormitories that are below the third tloor). Furthermore, of the sma)) percentage of those who test

for radon, many do not mitigate. EPA estimates that between 140,000 and 170,000 homes in the U.S.

have been mitigated by contractors as of July 1991.2 These estimates represent less than three

percent of the occupied homes believed to have radon levels above 4 pCi/L.

lThis estimate is based on an update of the National Residential Radon Survey (NRRS) June 1989 results. To update

the NRRS estimate, EPA conducted a telephone survey of large primary measurement firms to obtain information on the

number of tests performed since June 1989.

2This estimate is based on an update of the Radon Division's Private Sector Radon Mitigator Survey finding that almost

100,000 homes had been mitigated by contractors as of February 1990. The estimate as ofJuly 1991 is based on information

collected by EPA staff in informal discussions with mitigation firms, the Regional Radon Training Centers, and States.

Chapter 6: Risk Communication Page 6-1
Radon risk communication has provided useful insight into why public "apathy exists and

suggests directions for overcoming it. Six key findings, listed in Exhibit 6-1, have emerged from the

available research that can be applied to the revision of the Citizen's Guide.

EXHIBIT 6-1

KEY RISK COMMUNICATION FINDINGS

1. Be prescriptive as well as informative.

2. Streamline guidelines on testing and mitigation to minimize barriers to public action.

3. Overcome public denial through the use of persuasive appeals such as concern for the

family.

4. Provide an appropriate level of radon information, since too much or too little

information may result in an undesired effect.

5. Personalize the radon threat with tangible, relevant comparisons to familiar risk.

6. Stress that radon problems can be corrected but do not overstate the ease of fixing

them.

The remainder of this chapter discusses the evolution of the current Citizen's Guide from the

standpoint of risk communication research and issues. The first section (Section II) reviews the major

research results as they relate to the six key findings above. The next section (Section III) describes

how this research was incorporated into the Fall 1990 draft Guide. The following section (Section

IV) discusses the major public reactions to the Fall 1990 draft Guide and what changes were made

to incorporate public comments into the final revised Guide. The concluding section (Section V)

reiterates the main themes of the chapter.

Section II: Research Findings and Implications

This section provides a brief summary of the research that supports each of the key findings

listed in Exhibit 6-1.

1. Be Prescriptive

The original Citizen's Guide was informative, emphasizing what was known about radon risks

in order to help the citizen make an educated decision to reduce risks by testing and mitigating if

necessary. Research has shown, however, that people are more responsive to information brochures

Chapter 6: Risk Communication Page 6-2
that tell them exactly what they should do. A study of different radon information formats (Smith

et aI. 1987), for example, found that, of several approaches tested, the "command/quantitative

approach" that combined clear directions for action with precise information seemed to perform best

overall. "Messages" that tell people clearly what to do are the most satisfactory, and when required

actions are not emphasized, the resulting uncertainty can delay or even prevent action. Smith et al.

(1987) also found that "people dislike uncertainty and may use it as an excuse for disregarding a

radon risk message that indicates a lack of complete understanding of a risk or disagreement among

experts." Similarly, Fisher and Johnson (1990) concluded that brochures that told people what to do

rather than asked them to make their own decisions resulted in greater satisfaction with the message

received.

2. Streamline Guidelines

As outlined in Chapter 3, the original Citizen's Guide recommended that individuals perform

(1) a short-term measurement in the lowest livable level of the home under "closed-house" conditions,

and (2) confirmatory tests in the lived-in levels if the result of the short-term test was above 4 pCiIL.

The recommended duration of the confirmatory test depended on the result of the short-term

measurement and varied from less than one week to a full year. The original Guide then provided

guidance on whether and how quickly citizens should take action to fix their homes based on the

confirmatory test results. This "test-test-fix" strategy is comprised of several steps that provide

multiple opportunities for homeowners to "drop out" of the process. Compared to actions required

to protect against other household risks, such as fire and theft, radon-related protective action

recommended in the original Guide was a "multi-faceted, technical, multi-person, multi-skilled,

.recursive process" (Doyle et aI. 1990) that deters action to reduce exposure.

Research has shown that it is very difficult to convince people to take even the first step to

test their home. Weinstein, Sandman, and Klotz (1987), for example, investigated a random sample

of homeowners living in or near the Reading Prong area in New Jersey and their responses to the

radon threat. The researchers found that few people in the sample had tested or planned to test

their homes for radon, even though they lived in a known high risk area. In accordance with the

recommendations in the original Guide, this hurdle essentially had to be overcome twice -- once for

the initial test and again for the confirmatory test.

Research also indicates that people are especially unwilling to take a second measurement

if it means having to wait for long-term test results. For example, the Wirthlin Group's February

1990 telephone survey found that only 9 percent of the participants were willing to conduct a oneyear radon test and that 27 percent were willing to wait no more than two days for test results

(Johnson 1990). Fifty-five percent of respondents preferred a two-day test to longer-term tests. In

a similar study, researchers found that 60 percent of all respondents preferred a two-day test to

longer-term tests, 37 percent of all respondents stated that two days is the longest time that they

would be willing to wait for test results, and only 20 percent were willing to wait for one year

(Bruskin Associates 1991).

Other data confirm that long-term follow-up testing protocols are ignored by the public.

Radon industry representatives maintain that despite EPA's recommendations, people are not

conducting long-term tests. According to a senior representative from the American Association of

Radon Scientists and Technologists, less than 5 percent of all testing devices sold are used for longterm testing (Walker 1991). People who have the initiative to begin a long-term test often misplace

the measuring device, lose the mailer, or forget about the test altogether over the course of the year.

Chapter 6: Risk Communication Page 6-3
The experiences of State radon programs also demonstrate the public's lack of interest in long-term

testing. For example, the Pennsylvania Department of Environmental Resources actively advertises

free long-term follow-up tests for all citizens with screening test results of 20 pCiIL or higher, yet

virtually no one requests the free tests (Walker 1991).

In addition, informal telephone surveys ofmeasurement companies have found that most longterm testing devices are purchased for government studies, not by private citizens. Due to the lack

of demand for long-term testing devices, only a small percentage of testing companies offer them for

sale. As of July 9, 1991, only 120 testing firms out of 711 applying to the latest round of the Radon

Measurement Proficiency Program market devices that can be used for long-term testing, and many

of the devices sold by these firms may also be used for short-term testing (Walker 1991).

Finally, there is contlicting evidence about whether people who have tested for radon are

inclined to fix their home. Some studies indicate that some people may drop out of the process

before taking this final step. Doyle et a1. (1989), for example, analyzed the effectiveness of the mass

media radon information and testing campaign conducted in Washington, D.C. in 1988. A grocery

store chain that teamed up with a Washington, D.C. TV station in its "Radon Watch" campaign could

not keep monitors in stock at a bargain price of $4.75. However, only about half of the buyers

actually performed the test and only a fraction with elevated levels did any credible mitigation.

Researchers estimated that, of those people in the target population that tested their homes and

needed to mitigate, only about 8 percent actually mitigated.

Other studies, however, provide evidence that once people have tested their home, they are

likely to mitigate if necessary. Weinstein et a1.. (1988), for example, surveyed 123 New Jersey

homeowners who discovered at least two years in advance of the study that they had elevated radon

levels in their home. Of those whose initial first-floor readings were 20 pCilL or more, 93 percent

made home modifications. Seventy-one percent of those with readings between 8 and 20 pCiIL and

62 percent of those with readings between 4 and 8 pCilL also modified their homes. Additionally,

a June 1990 survey of 300 people who had tested their homes found that, of the 135 who had radon

levels above 4 pCilL, 24 percent had acted to reduce radon levels and the remaining 76 percent

indicated that they planned to act, either by mitigating or by doing a follow-up test (Wagner and

Dickson 1991).

3. Use I)ersnasive Appeals to Overcome Denial

Like many other public health and safety issues (e.g., seat belts) the radon issue suffers from

people's belief that "it can't happen to me." There is a significant amount of research supporting the

principle that people tend to deny that radon could be a problem in their home or their community

(e.g., Desvousges and Kollander 1986, Smith et al. 1987, Weinstein et al. 1987, Weinstein et al. 1989,

Leferman Associates, Inc. 1989, and TBWA 1990). Smith et al. (1987) evaluated how homeowners

in New York State responded to different informational brochures. The researchers found that

participants believed that their personal radon risks were lower than general population risks of

radon. Weinstein et al. (1989) evaluated the responses to two public opinion surveys conducted in

1988 and 1989. Respondents to these surveys claimed that radon was less likely to be a problem in

their own homes than in a home selected at random in their community. Even in high risk areas,

residents tended to see a radon problem in their homes as fairly unlikely.

Research also shows that people use information about radon to rationalize why they do not

have a problem and to create excuses for inaction. For example, when told that radon is caused by

Chapter 6: Risk Communication Page 6-4
uranium in soil, people hypothesize that their soil does not contain uranium. Told that a certain

percentage of homes are likely to have a radon problem, they assume their home does not. If people

learn that radon problems are related to housing characteristics, such as age or construction type, they

assume that the characteristics of theirs is such that it is not likely to be affected. Finally, if they

learn that radon problems may be more prevalent in certain geographical areas, they hypothesize that

their area is not likely to have a problem.

Research has found that this tendency to deny that high radon levels can affect "me" can best

be overcome by using a "persuasive appeal" that affects people on an emotional level and provides

a powerful risk message. TBWA focus groups found that focusing on concern for family members

was a highly effective persuasive approach.

In communications testing of the 1990 draft Citizen's Guide, Leferman Associates, Inc. (1990)

assessed consumer response to two different appeals used in radon information brochures: "protect

your family" and "dangerous intruder." Both of these themes were developed from TBWA and other

research suggesting the need to emphasize family protection, perhaps through an unsettling approach,

in order to stimulate action quickly before barriers are built in people's minds. In this

communications testing, both approaches were successful in conveying the risks of radon as the

brochures were found to be clear, easy to understand, and believable. Overall, more than half of the

participants claimed that they would be likely to test their home after studying either brochure.

Positive responses were higher, however, among those exposed to the "dangerous intruder" brochure

than among those evaluating the "protect your family" brochure. The "dangerous intruder" brochure

also evoked a higher level of immediate action. The researchers believed that the "danger" expressed

in that theme evoked a stronger need to do something than the, perhaps, more passive suggestion

to "protect."

4. Provide an Appropriate Level of Radon Information

Several risk communication studies have evaluated the success of providing various levels of

information in radon brochures. The most successful level of information is a difficult parameter to

evaluate because other variables (e.g., the way in which the information is presented) complicate the

issue. Also, "success" can be measured in terms of "success in promoting testing" or "success in

communicating accurate information." While no study has identified the "perfect" level of

information, the available risk communication studies suggest that too little information can cause

confusion and unnecessary concern and too much information can be overwhelming or create excuses

for inaction.

Smith et a1. (1987), for example, examined alternative radon information formats and found

that homeowners who received a brief fact sheet (ather than an informational brochure showed lower

levels of learning and were sometimes unnecessarily concerned over low radon readings. They were

also more likely to ask for more information and more willing to demand the services of a radon

diagnostician (Fisher and Johnson 1990). In a later study by Smith et a1. (1990), homeowners

received one of six types of radon information material along with the result of their radon test.

Although the study did not identify anyone format as being more effective than the others, it again

found that the brief fact sheet is ineffective. The fact sheet created concern about risk from radon

when it was not warranted. '

Other research, in contrast, has found that readers can use additional information to create

excuses for inaction. Results offocus group testing conducted by TBWA (1989), for example, suggest

Chapter 6: Risk Communication Page 6-5
3. Use Persuasive Appeals to Overcome Denial

As summarized in Section II, two "persuasive appeals" designed to affect people on an

emotional level, "protect your family" and "dangerous intruder," were found to be successful in

conveying the risks of radon. EPA used both of these themes in the draft revised Guide. For

example, the draft overview to the Guide included a number of references to "keeping your family

safe." EPA focused heavily on the "dangerous intruder" theme throughout the Fall 1990 draft Guide

because it was believed, based on the research summarized above, that a strong message was needed

to overcome the public apathy that was met by the original Citizen's Guide.

4. Provide an Appropriate Level of Radon Information

The Fall 1990 draft Guide sought to strike an appropriate balance between too little

information, which can result in confusion and unwarranted concern, and too much information,

which can result in greater denial of radon risks and a greater tendency toward inaction.

5. Personalize the Radon Threat

To personalize radon risks, the Fall 1990 draft Guide included charts comparing radon risks

to an annual number of chest x-rays. In addition, EPA attempted to tailor the Guide to people in

different smoking categories by separating information on smokers and never smokers. The risks to

former smokers were addressed in a footnote to the charts. The Fall 1990 draft Guide also provided

quantitative information on risks and the number oflung cancer deaths attributable to radon to help

people fully understand and appreciate the threat.

6. Stress that Radon Problems Can Be Corrected without Overstating the Ease of

Fixing

EPA recognizes that while emphasizing the ease of corrective action may stimulate more

people to test and/or mitigate, overstating the ease of such action could cost the program some

credibility. Therefore, the 1990 draft Guide emphasized that radon problems in homes can be

remedied without overstating the ease, or understating the cost of corrective action. For example,

the Guide stated "the cost of repairing a radon problem in the home will vary from home to home.

Most homes can be fixed for about the same cost as other common home repairs. A lot depends on

the way the home is built." In a later section the Guide stated "the costs of making repairs to reduce

radon will vary depending on how your home was built. And the extent of the radon problem. But

in most cases, homes can be fixed for between $500 and $2,000."

Section IV: Reactions to the Fall 1990 Draft Guide and Changes Made in Response to

Comments

Recognizing the significance of the proposed changes in the Fall 1990 draft Guide, EPA took

direct steps to solicit input from the public, States, and other government agencies, and to carefully

weigh all comments in preparing the final version. EPA announced the availability of the draft Guide

in the Federal Register on September 24, 1990 and distributed 700-800 copies of the Guide and its

TSD for external review and comment. Although the comment period officially closed at the end of

October 1990, EPA continued to receive and accept comments well beyond that time and ultimately

Chapter 6: Risk Communication Page 6-8
received 143 individual comment letters totalling over 700 pages. Virtually all sectors were

represented by the comments, including 33 States, Congress, 14 Federal agencies, numerous medical

and building associations, universities, the real estate industry, the radon testing and mitigation

industry, and private citizens. A large fraction of the public comments centered on risk

communication issues.

The final revised Citizen's Guide attempts to strike a balance between what the risk

communication research indicates is necessary and additional information provided by public

commenters. The final Guide addresses the concerns of the commenters, without sacrificing all of

its persuasive strength. This section summarizes the major concerns expressed by commenters as they

relate to each of the six key findings and describes how these concerns were incorporated into the

final version of the Guide.3

1. Be Prescriptive

Several commenters found the testing recommendations in the draft Guide to be confusing,

and many misinterpreted the guidelines to be advocating a "test-fix" strategy. In addition, there was

significant confusion among the commenters caused by the draft Guide's suggestion to "consider fixing

between 2 and 4 pCiIL." The commenters thought that this suggestion makes the final action level

unclear, and that in effect, it sets a de facto action level of 2 pCiIL.

The recommendations on the inside cover of the draft Guide were designed to encourage

public action by being brief, clear and easy to follow. The misinterpretation of the recommendations

by some of the commenters indicated to the Agency that the format or brevity of the

recommendations may have caused some confusion. Therefore, EPA revised its testing

recommendations to be much more explicit. The recommendation to fix, printed in bold at the very

beginning of the final Guide, is essentially the same as that in the draft version; only the wording has

been revised slightly to make the Guide more clear. The testing recommendations in a later section

of the Guide have been expanded and clarified, and a new section, "What your test results mean," has

been added. EPA believes that the recommendations are now very clear, and that there is no room

for misinterpretation.

With regard to the recommended action level, the 1992 Guide maintains 4 pCi/L as the level

for triggering home mitigation (see Chapters 3 and 7 for EPA's specific reasons for choosing this

action level). For example, the front inside cover the Guide states in bold: "Fix your home if your

radon level is 4 picocuries per liter (pCiIL) or higher." The final Guide also explains that there is

some health risk at levels below 4 pCilL and that most homes today can be reduced to 2 pCiIL or

below. However, based on its risk communication research, EPA believes that this explanation simply

provides homeowners with added factual information to help them make informed decisions and will

not result in significant confusion.

2. Streamline Guidelines

Several commenters objected tathe draft Guide's testing strategy, which allowed homeowners

to reach a mitigation decision based on short-term tests. The commenters believed that short-term

3EPA has prepared a separate response-to-comments document (Response to Public Comments on EPA's Draft "A

Citizen's Guide to Radon") that summarizes these and other issues in more detail and provides direct Agency responses.

Chapter 6: Risk Communication Page 6-9
test results are not reliable and do not adequately approximate average annual radon levels, especially

at lower radon concentrations. Several commenters stated that short-term measurements may differ

from annual average results by a very large amount and could, therefore, lead the homeowner to

make the wrong mitigation decision.

EPA recognizes that short-term tests are not as representative as long-term tests of average

annual radon levels. However, as summarized above, research has shown that people are much more

likely to conduct short-term tests than long-term tests. Also, it is usually infeasible to conduct longterm tests during a real estate transaction. Based on these practical limitations, the 1992 Guide

discusses the relative accuracy ofshort-term vs. long-term tests, emphasizing the benefits of long-term

testing, but allowing people to choose to conduct either a long- or a short-term follow-up test. This

approach represents the best balance between obtaining radon measurements that closely

approximate average year-round radon levels and ensuring that people do not drop out of the testing

process. In this sense, EPA believes that the approach recommended in the final Guide will result

in the greatest amount of radon risk reduction.

3. Use Persuasive Appeals to Overcome Denial

Many commenters addressed the degree to which EPA should attempt to stimulate the public

to test and fix their homes. A few commenters believed that the persuasive approach was effective

and/or appropriate, with at least one risk communication expert commenting that the tone should be

even more persuasive. A majority of commenters, however, believed that the approach was too

alarmist. Although the severity of this concern among the commenters varied, most believed that the

approach could confuse or alarm the public. Commenters focused their critique on the use of the

"intruder" strategy, stating that it was patronizing and misleading.

As discussed above, it was EPA's intent that the revised Citizen's Guide function more as a

persuasive brochure than as an informational document, prompting people to test their homes rather

than educating them fully on the technical aspects of radon. After weighing these comments, EPA

revised the Guide to be more informational and less "startling," while still striving to stimulate public

action. EPA also abandoned the "intruder" concept in favor of the "protect your family" theme. This

theme is displayed on the cover of the final Guide as well as being referred to throughout.

4. Provide an Appropriate Level of Radon Information

The many commenters who addressed the level of technical information in the Guide agreed

almost unanimously that more general and/or technical information should be added. The

commenters differed, however, in their suggestions ofwhat additional information should be included.

Several commenters, for example, suggested that the Guide should provide more information on

testing and mitigation systems and techniques. Other commenters recommended that the Guide list

references for more information and indicate how these references can be obtained. Finally, several

commenters advised that the assumptions, estimates, and uncertainties regarding risk should be better

covered in the Guide. Many of the commenters addressing this issue represented State radon offices

that were concerned that the release of the draft 1990 Guide would cause them to be inundated with

telephone calls requesting more radon information.

In response to these concerns, EPA added a significant amount of information to the Guide.

Because the Agency recognized that the inclusion of additional technical information risked sacrificing

Chapter 6: Risk Communication Page 6-10
the effectiveness of the Guide as a persuasive tool, EPA sought to strike a balance in deciding how

much information to add. The Agency believes that the final revised Guide contains a sufficient level

of information while sacrificing as little as possible of the clarity, accessibility, and persuasive strength

of the draft 1990 Guide.

EPA added several new sections to the Guide, such as how to use a test kit (including

appropriate sampling locations and procedures), options for short-term and long-term testing, what

to do with test and retest results, radon and home sales, radon and home renovations, and radon

myths. Several sections also have been clarified and/or expanded, such as how radon enters a home

(including radon in building materials), radon in water, how to test, how to mitigate, and the health

risks associated with radon. The Guide does not include what would be an extremely long list of

radon contractors but suggests that the reader call his or her State radon office for a list of EPAapproved contractors in the State. The Guide also includes a list of State radon office phone

numbers and hotline numbers, and references additional EPA materials and indicates how they can

be obtained. Also, in revising the Guide, an effort was made to address the assumptions and

uncertainties associated with radon risk in such a way that informs homeowners but does not present

a barrier to action. Based on recommendations made by EPA's SAB, the Guide includes several

statements acknowledging uncertainty in the risk estimates. More specific information on uncertainty

was not included because it was considered too technical. Instead, the Guide references this TSD,

which contains a detailed and expanded discussion of uncertainty in Chapter 2.

5. Personalize the Radon Threat

The commenters agreed that the use of comparative risk charts was an effective way of

conveying personal risks. Several commenters suggested that measures should be taken to decrease

the chance of alienating nonsmokers or allowing smokers to discount their risk due to radon. In

addition, many commenters suggested that the x-ray comparison is misleading and frightening and

should be replaced by a more tangible analogy, such as the risks associated with accidents in homes

or cars, or radiation doses from airplane flights.

The Agency's primary goal in designing a risk chart for the updated Guide was that it

characterize risk as accurately as possible without alienating either smokers or nonsmokers or allowing

them to deny their risk. To do this, the final version of the Guide presents two separate risk charts.

The Agency believes that this approach allows both smokers and never smokers to accurately

characterize their risk without alienating either group.

EPA had spent a considerable amount of effort prior to the release of the draft revised Guide

identifying an effective and appropriate comparison to the health risks associated with radon. The

Agency found in extensive communications tests that the comparison to x-rays did not frighten

people. In fact, the risk communication research showed that people found the x-ray comparison

clear and easy to understand. Nevertheless, in response to the concerns expressed by commenters,

the Agency conducted additional communication studies on four possible comparisons: x-rays,

illnesses, accidents (e.g., airplane crashes, home fires, etc.), and an approach that combined several

comparisons. EPA found in this later research that none of the sets of risk comparisons was clearly

better than another at producing appropriate responses to the risks from radon (Weinstein and

Sandman 1991). In light of this finding and the concerns of commenters, EPA chose to compare

radon risk to the risk of being killed in different types of accidents.

Chapter 6: Risk Communication Page 6-11
6. Stress that Radon Problems Can Be Corrected without Overstating the Ease of

Fixing

Several commenters addressed the costs of mitigation as an issue in the draft revised Guide.

Most of these commenters recommended that the Guide should be more explicit and provide specific

remediation costs for different remediation methods, rather than just provide a range. A few

commenters suggested the Guide provide examples of home repairs that are of comparable costs to

radon mitigation, with one believing that the draft Guide exaggerated its claim that a home can be

mitigated for the same cost as other home repairs.

The final Guide discusses remediation techniques and costs in the "How to Lower the Radon

Level in Your Home" section. The Agency revised the range of $500-$2,000 estimated to fix a home

to $500-$2,500, based on data collected by EPA's Office of Research and Development. These data

augmented the Private Sector Radon Mitigator Survey that surveyed 340 radon mitigation firms on

their radon reduction activities (U.S. EPAIRadon Division 1990a). The survey found that, within this

range, approximately $1,200 (in 1989 $) was the average charge to mitigate a detached house. The

Guide also provides examples of home repairs (i.e., painting or installing a new water heater) that are

comparable to the costs of radon mitigation.

Section V: Summary and Conclusion

Risk communication research has made an extremely important contribution in the evolution

of the Citizen's Guide. Over the past six years, a number of researchers have analyzed key issues

relating to radon risk communication, and their findings were incorporated into the Fall 1990 draft

Guide. Studies of the Fall 1990 version of the Guide showed the document to be extremely effective

in terms of risk communication. When the draft Guide was distributed for review, commenters were

able to identify areas in which they believed that other concerns should be considered and factored

in with the risk communication findings. Commenters noted, for example, that while the "intruder"

concept may be effective in stimulating testing, some people may find it offensive. Also, as State

representatives pointed out, an effective level of information from a risk communication standpoint

may result in State radon offices being inundated with calls from people asking for more information.

Thus, the commenters helped EPA refine its use of the six key risk communication findings and

develop a final version of the Citizen's Guide that both incorporates the main findings of risk

communication and addresses the commenters' practical concerns.

Chapter 6: Risk Communication Page 6-12
CHAPTER 7

RATIONALE FOR 1992 CITIZEN'S GUIDE

This chapter summarizes the main conclusions from the previous chapters and brietly describes

how those conclusions were used to develop the 1992 Citizen's Guide. It outlines the rationale

underlying EPA's approach in the revised Guide for accomplishing two main goals: (1)

communicating radon risks to the public; and (2) recommending a radon testing and mitigation

strategy for homeowners. The chapter also discusses the interrelationship of these two goals and how

EPA considered them together in shaping the 1992 Guide.

Section I: Risk Communication

Developing the final approach for risk communication in the revised Citizen's Guide required

the consideration of two distinct issues: what to tell the public about radon risks and how to

communicate that information. The rationale for the revised Guide's approach with respect to each

of these issues is outlined in separate sections below.

What to Tell the Public about Radon Risks

As presented in Chapter 2, radon is one of the most extensively studied pollutants in the

world. Radon risks have been well documented by numerous scientific and public health authorities,

and are based on extensive studies of thousands of underground miners. This research provides

strong scientific evidence that exposure to radon can cause lung cancer in humans. Further research

since the original Citizen's Guide was published in 1986 has helped to improve EPA's projection of

lung cancer risk to the general population due to radon exposures in the home. EPA now estimates

that the number of lung cancer deaths per year in the U.S. due to residential radon exposure is

approximately 14,000, with an uncertainty range of 7,000 to 30,000. Even using the lower end of this

uncertainty range, this makes indoor radon the second leading cause of lung cancer in the U.S., after

smoking. Continuing scientific evaluation of radon hazards serves primarily to refine EPA's estimate

of the annual number of radon-induced lung cancer deaths, not to determine whether indoor radon

exposure poses a serious public health problem.

In addition, in order to understand the risks of indoor radon, the public needs information

on the relationship between radon and smoking risks and the radon risks to children. Key findings

related to each of these issues are summarized below:

• Although the risk of lung cancer from radon exposure appears to be enhanced by

smoking tobacco, a person does not have to be a smoker to be at risk from radon.

EPA estimates that the radon risk for current smokers is close to 20 times the risk for

never smokers and the risk to former smokers may be over 8 times greater than the

risk for never smokers.

• Although there is information that indicates that children may be at greater risk than

adults from some kinds of radiation exposure, there is no direct evidence that children

are at greater risk than adults from radon.

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-1
Based on these conclusions, the revised Guide warns that an individual's lung cancer risk is especially

high if he or she is a smoker, and provides risk charts that allow readers to identify their radon risk

according to what smoking category they fall into. The revised Guide also clarifies that "children have

been reported to have greater risk than adults of certain types of cancer from radiation, but there

are currently no conclusive data on whether children are at greater risk than adults from radon."

How to Commnnicate Radon Risk Information

As discussed in Chapter 6, extensive risk communication research since the 1986 Guide was

published has provided useful insight into why the public remains largely apathetic about indoor radon

and suggestions for overcoming that apathy. In developing the revised Guide, EPA applied six key

findings that have emerged from this research: (1) be prescriptive rather than simply informative; (2)

streamline guidelines on testing and mitigation so they do not present barriers to public action; (3)

overcome public denial through the use of "persuasive appeals" such as concern for the family; (4)

provide an appropriate level of radon information, since too much or too little information can result

in an undesired effect; (5) personalize the radon threat with tangible, relevant comparisons to familiar

risks; and (6) stress that radon problems can be corrected but do not overstate the ease of fixing

them.

In updating the Citizen's Guide, it was important for EPA to balance the results of this risk

communication research with other practical considerations. For example, some of the risk

communication research suggested that the revised Guide should provide only a minimal amount of

technical information on radon, since readers can use additional information to create excuses for

inaction. This finding, however, had to be balanced against concerns that State offices could be

inundated with public requests for more information if the Guide did not provide enough detail to

answer homeowners' questions. This balancing of the risk communication research with practical

limitations led to the following design features with respect to the six key findings listed above:

• The 1992 Citizen's Guide was designed to be prescriptive. It provides brief, clear, and

easy to follow directions on what to do (e.g., how to test and when to mitigate), rather

than simply providing information and allowing readers to come to their own

conclusions.

• EPA's Radon Program experience and risk communication research indicate that

many people drop out of the testing and mitigation process before they fully comply

with the 1986 Guide's recommendation to conduct a long-term follow-up

measurement prior to reaching a mitigation decision. Based on this finding and EPA's

detailed analysis of various testing options, the revised Guide attempts to streamline

the testing guidelines by: (1) emphasizing the benefits of long-term testing; but also

(2) allowing people to choose to conduct either a long- or short-term follow-up test.

• The 1992 Guide was designed to function more as a persuasive document than the

1986 version. It utilizes the "protect your family" theme found to be effective in risk

communication testing, while avoiding other emotional appeals that might compromise

the scientific credibility of the message.

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-2
•

•

•

Section II:

The revised Guide contains a sufficient level of technical information to educate

homeowners, while sacrificing as little as possible in terms of clarity, accessibility, and

incentive to test.

EPA designed the revised Guide to help personalize the radon threat by providing

tangible, relevant comparisons to familiar risks. Specifically, the revised Guide

provides risk charts for smokers and never smokers that characterize each group's risk

as accurately as possible without alienating them or allowing them to deny their risk.

The Guide also compares radon risk to other risks, such as drunk driving, drowning,

fires, airline and car crashes, and violent crimes.

The revised Guide puts radon mitigation in proper perspective by describing

remediation techniques, providing realistic estimates of remediation costs based on

EPA's Private Sector Radon Mitigator Survey and research by EPA's Office of

Research and Development, and providing examples of other home repairs that are

of a comparable cost.

Testing and Mitigation Advice

The Citizen's Guide provides specific advice to homeowners on how to test for radon and

when they should mitigate. EPA's rationale for this advice, drawing on the main conclusions from

the previous chapters of this document, is summarized below.

How to Test

Chapter 3 identifies several major attributes that are used to define the recommended radon

testing strategy, including: (1) a testing location, (2) ventilation conditions, and (3) a testing duration

before reaching a mitigation decision. EPA's recommendations and rationale with respect to each

of these attributes are summarized below, followed by an explanation of the basis for the overall

testing strategy recommended in the revised Citizen's Guide.

1. Testing Location

EPA is revising the recommended test location for the initial short-term radon measurement

from the "lowest livable" level, recommended in the 1986 Guide, to the "lowest lived-in" level. There

is a difference between these two locations. The lowest livable level is the lowest area of a home that

is used or has the potential to he used as a living space, whereas the lowest lived-in level is the lowest

level of a house that is used regularly. In both the original and revised Guide, however, the

recommended location for decision-making tests (i.e., tests on which to base a mitigation decision)

is the lowest lived-in level.

Roughly 50 percent of the homes nationwide have basements; however, only about half of

these homes, or almost 25 percent of the national total, have basements that are used as a lived-in

level (U.S. EPA/Office of Radiation Programs 1991a). Accordingly, a recommendation that devices

be placed in the lowest livable level would result in 50 percent of the devices being placed in the

basement. A recommendation that devices be placed in the lowest lived-in level would result in only

25 percent of devices being placed in the basement, and the remaining 75 percent being placed on

the first floor.

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-3
Keeping the short-term test in the lowest livable area as compared to moving it to the lowest

lived-in area would reduce false negative results by a factor of 1.5; however, the number of false

positive results would increase by a factor of 2. Measurements taken in the lowest lived-in area strike

a more equitable balance between false positives (public money spent with more limited benefits in

many cases) and false negatives (public health protection) than do lowest livable area measurements.

Most importantly, lowest lived-in measurements are the most representative of human exposure to

radon. Recent research by Harley et a1. (1991) suggests that basement measurements overstate

personal exposure by a factor of 3 to 5, while first noor measurements are, on average, only 30

percent greater than occupant exposure (for short-term measurements). Since the goal of radon

measurement on which a mitigation decision relies is to assess occupant exposure (U.S. EPA 1991a),

lived-in level measurements are better predictors of risk than livable level measurements. Based on

this finding and the recommendation of the EPA Science Advisory Board (U.S. EPA 1992b), shortor long-term measurements that are to be used for the purpose of making mitigation decisions should

be made in the lowest lived-in level because it more closely approximates the radon concentration

to which inhabitants are exposed.

2. Ventilation Conditions

EPA examined whether tests should be made under "open-house" or "closed-house"

conditions. In open-house conditions, tests are made with windows and other ventilating passageways

either closed or open as they would be when a test is not being conducted. In closed-house

conditions, windows and other ventilated passageways are closed to the extent possible. EPA stresses

the value of closed-house conditions in the revised Guide, because these conditions provide more

consistent radon measurements. However, the revised Guide makes allowances for practical

limitations in maintaining these conditions. Specifically, the Guide recommends keeping windows and

outside doors closed "as much as possible" during short-term testing.

3. Testing Duration

The 1986 Citizen's Guide recommended that homeowners perform (1) a short-term

measurement, and (2) a confirmatory measurement if the result of the short-term test was above 4

pCiIL. The recommended duration of the confirmatory measurement depended on the result of the

short-term test and varied from less than one week to a full year. Mitigation decisions were to be

based on the results of the longer-term confirmatory measurement. Since the original Guide was

published, however, EPA's Radon Program experience and risk communication research have

indicated that many people drop out of this process before obtaining the long-term measurements

needed to reach a mitigation decision. Short-term tests are much more appealing to the public

because they are simpler to make and provide faster results. Therefore, it became apparent that a

recommended testing procedure that' does not rely solely on long-term testing may be more effective

in actual risk reduction by removing an existing barrier to radon mitigation.

EPA examined the implications of relying on short-term tests as indicators of annual average

radon levels in developing the 1992 Guide. From knowledge of the relationship between short-term

measurements and annual averages gained from EPNState Residential Radon Surveys, the Agency

recognized that short-term measurements are imperfect indicators of annual averages, but believed

they potentially could provide homeowners with a reasonably accurate basis for determining whether

they need to mitigate. EPA thus constructed various testing options, including different test durations

prior to reaching a mitigation decision, and analyzed the effectiveness of each option in terms of

misclassification rates and public acceptability. Based on the results of this analysis, described in

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-4
detail in Chapter 3 and summarized in the following section, EPA concluded that a testing strategy

that allows homeowners to reach a mitigation decision based on short-term test results would

maximize public health protection.

4. Rationale for Recommended Testing Strategy

EPA began its analysis of radon testing options by considering a strategy that requires a single

short-term measurement followed by a confirmatory long-term test. This option, defined as Option

A in Chapter 3, parallels the testing procedure recommended in the 1986 Citizen's Guide, except that

both tests would be conducted on the lowest lived-in level. Under Option A, 98 percent of homes

were correctly classified with regard to the need for mitigation. To determine how testing procedures

relying on a short-term confirmatory test would compare to this option, EPA developed and analyzed

five other options, defined as Options B through F in Chapter 3. EPA found that all of these options

produced results yielding at least 94 percent correct classifications.

Given these results, the Agency determined that on the basis of misclassification, none of the

options should be rejected. EPA decided instead that other factors, such as procedure simplicity,

should be weighed with the trade-offs for increased levels of correct classification in selecting the

testing option to recommend in the revised Guide. As noted above, current Radon Program

experience indicates that few people are actually taking long-term follow-up measurements prior to

reaching a mitigation decision, and that most people who do mitigate do so based on a single shortterm test. This finding is supported by EPA's risk communication research that indicates that as little

as 9 percent of the population is willing to conduct year-long tests. These conclusions suggest that

a testing protocol that relies exclusively on long-term confirmatory tests is unlikely to be followed by

most of the public. Therefore, although Options A and D have more desirable error rates than the

other options, compliance with these options is likely to be low. Also, selection of either of these

two options is apt to result in a situation in which decisions are most often made based on a single

short-term measurement. By explicitly providing homeowners a process that calls for more than one

short-term test, all of the other options considered would be more likely to result in people having

better information to use in reaching a mitigation decision.

On the other hand, since long-term measurements are more desirable than short-term

measurements and since there are some individuals who are willing to conduct long-term tests, the

use of long-term tests should not be precluded from the testing protocol. As a result, Options B, E,

and F, which do not include long-term tests, are also undesirable.

Option C offers an effective compromise between these different approaches. It promotes

long-term testing by people who are willing to conduct long-term tests and recommends an effective

short-term test as an alternative for people who are not willing to conduct a long-term test. . . Therefore, consistent with the advice from EPA's Science Advisory Board, the revised Guide

recommends Option C because it should maximize the total risk reduction the public would gain

through future testing and mitigation while minimizing error. The Guide also explains the trade-otIs

between short-term and long-term testing. It acknowledges that long-term testing is more

representative of annual exposures, but enables the public to have a short-term measurement process

that is sound.

Chapter 7: RationaLe for 1992 Citizen's Guide Page 7-5
When to Mitigate

EPA is recommending that the action level of 4 pCilL established in the 1986 Guide be

maintained for several reasons. First, lower action levels introduce more uncertainty in the

measurement results. Measurement device error increases to approximately 50 percent at 2 pCiIL.

This device error in conjunction with the larger fraction of homes (of total homes testing) that have

radon levels around 2 pCiIL would result in a threefold increase in false negatives and a twofold

increase in false positives over those expected at a 4 pCiIL action level. In addition, as outlined in

detail in Chapter 4, the Office of Research and Development's (ORD's) research on mitigation

effectiveness and the Office of Radiation Programs' Private Sector Radon Mitigator Survey suggest

that elevated levels of radon can be reduced to 4 pCilL more than 95 percent of the time. Results

from the mitigator survey indicate that 2 pCiIL can be achieved about 70 percent of the time, while

the ORD research suggests this estimate may be even higher (U.S. EPA/ORD 1989; U.S. EPNRadon

Division 1990a). Reducing the action level to 2 pCilL, therefore, could result in perhaps as many as

30 percent of homes with elevated levels being unable to achieve the action level.

However, EPA recognizes that mitigation down to lower radon levels may be appropriate

because levels below 4 pCi/L still pose a health risk. Furthermore, as mentioned above, mitigation

technology available today permits most homes to be reduced to 2 pCilL or below, and Congress has

set a long-term goal that indoor radon levels be no more than outdoor levels, which are typically less

than 2 pCilL. As a result, EPA also closely examined the costs and benefits of selecting an action

level of 2 pCilL and 3 pCilL.

The results of this cost-effectiveness analysis, detailed in Chapter 5, show that setting the

action level at 4 pCilL would result in a cost of roughly $700,000 per lung cancer death averted (i.e.,

per life saved). Lowering the action level would incrementally increase this cost to $1,700,000 per

life saved if 3 pCiIL was used, and to $2,400,000 per life saved if 2 pCiIL was used instead of 3 pCiIL.

All three of the action levels have cost per life saved values that are at the lower end of, or below,

the values that the public is willing to pay to save a statistical life, according to EPA's 1983 Regulat01Y

Impact Analysis Guidelines. Based on these findings, EPA believes any of the three action levels

considered would provide cost-effective results.

At the selected action level, the Radon Program would be as or more cost-effective than many

other government programs for personal safety and environmental protection. EPA also believes the

recommended testing protocol combined with an action level of 4 pCiIL in the 1992 Guide will be

more cost-effective than that recommended in the 1986 Guide - $700,000 per life saved now versus

the $900,000 per life saved that EPA calculates from program experience based on the 1986 Guide.

EPA's decision to keep 4 pCiIL as the action level in the revised Citizen's Guide is supported

by the cost-effectiveness analysis. However, the revised Guide also notes, although not with the same

weight as the recommended action level, that homeowners can further reduce their lung cancer risk

by mitigating homes that are below 4 pCiIL. As long as the revised Guide clearly establishes 4 pCilL

as the recommended action level to avoid confusion and the other problems mentioned above, EPA

believes this discussion of reducing radon below the action level helps to fully inform the reader and

is justified based on: (1) the health risk involved; (2) the effectiveness of available mitigation

technology; (3) cost-effectiveness; and (4) Congressional intent.

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-6
Section III: Conclusions

In developing the 1992 Citizen's Guide, EPA had to balance the findings of its technical

analyses on risk, testing accuracy, mitigation technology, and cost-effectiveness with the information

it was collecting from its risk communication research. For example, EPA and the scientific

community had amassed and analyzed in depth a considerable amount of information on the level and

significance of indoor radon risk since the original Guide was published in 1986. EPA had to convey

that risk in the updated Guide with a message that was strong enough to persuade homeowners to

act, while being careful not to provide too much detail, which could sacrifice accessibility, or make

it too startling, which might compromise scientific credibility and support. Furthermore, although

EPA recognized the technical superiority of long-term versus short-term testing after extensive

evaluation of the issue, it had to accept the compelling practical limitation that the public at large is

more likely to use short-term testing. A lot of "good" testing, after all, will provide greater public

health protection than a more limited amount of "perfect" testing. Finally, emphasis on an action

level that is achievable by the vast majority of homes is better than recommending a lower action

level that pushes the limit of technology. EPA's ultimate objective was to advance a technically wellsupported 1992 Citizen's Guide that takes a pragmatic step in better communicating radon's risks to

the public and promoting broader public action in response to the problem.

Chapter 7: Rationale for 1992 Citizen's Guide Page 7-7
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1986, Final Report. Rutgers, The State University of New Jersey, Cook College.

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Cancer Rates Among Former Workers, 1952-87. Cancer Causes and Control. 2: 213-220.

References Page R-10
APPENDIX A

RADON CONCENTRATIONS IN AMBIENT AIR

According to Section 301 of the Indoor Radon Abatement Act, "The national long-term goal

of the United States with respect to radon levels in buildings is that the air within buildings in the

United States should be as free of radon as the ambient air outside of buildings." To ensure that

EPA program goals are consistent with the·requirements of this legislation and to confirm reported

outdoor ambient concentrations, EPA reviewed available literature on outdoor radon measurements

and conducted the Ambient Radon Field Study (Hopper 1991).

Individually measured radon concentrations vary widely in the reviewed literature -- from 0.1

to 1.2 picocuries per liter (pOlL) -- while the average concentrations range from about 0.1 to 0.8

pCiIL. In general, concentrations appear to be higher in the western States than in the eastern

States. Articles describing measurements of ambient radon-222 concentrations obtained within one

mile of a uranium mill tailings pile or phosphogypsum stack were not used in this analysis.

The first consideration when measuring the very low radon concentrations expected in

outdoor air is the reliability of the measurement method at such low levels. The methods used to

measure ambient radon concentrations include alpha track detectors, continuous radon monitors,

continuous flow-through monitors (scintillation cells), pump/collapsible bag devices, and electret ion

chambers (EICs). There are very few data establishing accuracy and precision of these methods at

levels of 0.1 to 1 pCiIL. Because of this uncertainty, the data quality objectives for the EPA Ambient

Radon Field Study were:

1. To determine if the majority of the ambient radon levels are < 0.6, < 1.0, or > 1.0

pCilL;

2. To maintain a preCISIon in the measurement that will allow EPA to distinguish

between an ambient air level of 0.2 pCilL and 0.6 pCilL; and

3. To assure that the 2-standard deviation error will be no greater than 0.25 pOlL, at

an ambient radon concentration of 0.25 pOlL.

The study was designed to measure selected outdoor radon levels across the country. Since

EPA's Office of Radiation Programs (ORP) has Environmental Radiation Ambient Monitoring

System (ERAMS) stations in every State, these stations were selected as the sample sites for making

quarterly outdoor radon measurements. The study was limited in scope and not designed to

statistically represent the distribution of ambient radon concentrations for the United States.

However, estimates of annual average ambient radon concentration and associated error estimates

can be derived at each site since the radon samples were stratified by quarter.

ORP's Las Vegas, Nevada facility (ORP-LVF) conducted the study, but ERAMS station

operators were responsible for deployment and retrieval of detectors. ORP generally relies on State

personnel to operate and maintain these stations. ORP-LVF selected the short-term EIC paired with

a thermoluminescent dosimeter (TLD) for this study. The short-term EIC deployed for 90 days

provided adequate sensitivity to meet the data quality objectives to and from the ERAMS stations.

Appendix A Page A-I
Since ·EICs respond to ionizations both from radon decay within the detector chamber and from

external gamma radiation, TLDs were used to measure and correct for background gamma radiation.

At each ERAMS station, three EICs and three TLDs were placed in ventilated shelters

located approximately one meter from ground level to provide uniformity. The devices were left in

place for 90 days and exchanged each quarter by station operators. The quarterly results were

compared and have been combined into an average annual radon concentration for each site.

The primary goal of the study, to measure outdoor ambient radon concentrations at different

geographic locations in the United States, has been met with good results. For the sites examined,

the mean annual outdoor concentrations ranged from a low of 0.16 at one site to a high of 0.57 pCilL

at another. The individual concentrations used to calculate mean concentrations ranged from 0.0 to

1.11 pCilL, with a median of 0.39 pCilL. In the study to date, field measurements using short-term

EICs have been made with acceptable errors and the devices have exhibited sufficient sensitivity for

measuring ambient levels of radon.

Appendix A PageA-2
APPENDIX B

BACKGROUND INFORMATION ON RADON

Radon is a naturally-occurring, chemically inert, radioactive gas. Because radon is chemically

unreactive with most materials, it is free to travel as a gas. It can move easily through very small

spaces such as those between particles of soil and rock. Radon is odorless, invisible, and without

taste; thus, it cannot be detected with the human senses. Radon is also moderately soluble in water

and, therefore, can be absorbed by water flowing through rock or sand. Its solubility depends on the

water temperature; the colder the water, the greater radon's solubility.

The two natural sources of radon, thorium and uranium, are common, naturally-occurring

elements that are found in low concentrations in rock and soil. Through radioactive decay, both are

constant sources of radon. Radon is produced from the radioactive decay of the element radium,

which is itself a decay product of either uranium or thorium. Radioactive decay is a process in which

an unstable atomic nucleus undergoes spontaneous transformation, by emission of particles or

electromagnetic radiation, to form a new nucleus (decay product), which mayor may not be

radioactive. The level of radioactivity is measured in curies, where 1 curie equals 37 billion

disintegrations per second. The time required for a given specific activity of an isotope to be reduced

by a factor of two is called its half-life. A picocurie (pCi) is equal to one-trillionth of a curie.

Specific activity concentrations are typically measured in picocuries per gram (in a solid) or picocuries

per liter (in a gas, such as air).

Uranium-238 decays in several steps to radium-226, which decays into radon-222. Radon-222

has a half-life of 3.8 days and, therefore, has enough time to diffuse through dry, porous soils or to

be transported in water for a considerable distance before it decays. Similarly, thorium-232 decays

into radon-220 (a different radon isotope, also called thoron), which has a half-life of only 55 seconds.

Because of its short half-life and limited ability to migrate into residences, radon-220 is usually a less

important source of radon exposure to humans. The United Nations Scientific Committee on the

Effects of Atomic Radiation has estimated the average exposure from indoor radon-220 decay

products to be about 25 percent of that from radon-222. Only radon-222 is addressed specifically in

the Citizen's Guide because it is the radon isotope of most concern to the public. Although radon220, or thoron, has not been measured separately in most homes, radon mitigation will also reduce

exposure to thoron.

Radon-222 is preceded in the uranium-238 decay series by radium-226, which has a half-life

of 1,600 years. Radon-222 decays in several steps to form radioactive isotopes with short half-lives:

polonium-2I8, lead-2I4, bismuth-214, and polonium-2I4. These isotope particles are commonly

referred to as radon decay products, daughters, or progeny. Radon decay products are chemically

reactive and can attach themselves to walls, floors, or airborne particles that are inhaled into the

lungs. Unattached radon decay products also can be inhaled and, subsequently, can become deposited

on lung tissue.

The four radon-222 decay products just mentioned all have half-lives of less than 30 minutes.

This short half-life is significant since, once deposited on lung tissue, the radon decay products can

undergo considerable decay before the action of mucus in the bronchial tubes can clear these

radioactive particles. Two of the short-lived decay products, polonium-2I8 and polonium-2I4, emit

Appendix B Page B-1
alpha particles during the decay process. An alpha particle is a subatomic particle that has two

protons and two neutrons and has a double positive electrical charge. It is identical to a helium

nucleus.

Radon-222 is found virtually everywhere in at least small amounts because its predecessor,

radium-226 (or, more distantly, uranium-238), is found in all rock and soil. In outdoor air, radon

concentrations are usually less than onepicocurie per liter (pCiIL) (see Appendix A for a summary

of the results of EPA's Ambient Radon Field Study). Higher concentrations of radon outdoors may

be observed during brief periods, such ·as during a temperature inversion, when a warm air mass traps

a colder one beneath it. The highest individual concentration measured outdoors in EPA's Ambient

Radon Field Study was 1.11 pCiIL. Indoor air concentrations, in contrast, can vary from around 0.5

pCilL to over 2,000 pCiIL, with results from EPA's National Residential Radon Survey indicating that

over 6 percent of all homes nationwide have average annual indoor radon levels above 4 pCiIL. Most

indoor radon comes from the rocks and soil around a home, although other, usually less significant,

sources of indoor radon are water and some construction materials.

Appendix B Page B-2
APPENDIX C

COMMONLY USED RADON MEASUREMENT DEVICES

Activated Charcoal Adsorption Devices - Activated charcoal adsorption devices (AC) are

passive devices requiring no power to function. The passive nature of the activated charcoal allows

continual adsorption and desorption of radon. During the measurement period, the adsorbed radon

undergoes radioactive decay. Therefore, the technique does not uniformly integrate radon

concentrations during the exposure period. As with .all devices that store radon, the average

concentration calculated using the mid-exposure time is subject to error if the ambient radon

concentration adsorbed during the first half of the sampling period is substantially higher or lower

than the average over the period. For a 2- to 7-day exposure period, the lower level of detection

(LLD) should be 0.5 PcilL or less (U.S. EPA!Radon Division 1989). This level of sensitivity can

normally be achieved with a counting time of up to 30 minutes. This LLD should be calculated using

the results of charcoal background determinations. The coefficient of variation should not exceed

10 percent (1 sigma) at radon concentrations of 4 pCilL or greater (U.S. EPAlRadon Division 1989).

This precision should be monitored using the results of duplicate canister analyses. ACs can achieve

an average coefficient of variation of less than 5 percent at concentrations of 4 pCiIL or greater.

Alpha Track Detectors - An alpha track detector (AT) consists ot a small piece of plastic or

film enclosed in a container with a filter-covered opening. Radon diffuses through the filter into the

container and alpha particles emitted by radon and its decay products strike the detector and produce

submicroscopic damage tracks. At the end of the measurement period, the detectors are returned

to a laboratory. Plastic detectors are placed in a caustic solution that accentuates the damage tracks

so they can be counted using a microscope or an automated counting system. The number of tracks

per unit area is correlated to the radon concentration in air, using a conversion factor derived from

data generated at a calibration facility. The number of tracks produced per unit time is proportional

to the radon concentration, so an AT functions as a true integrating detector and measures the

average concentration over the measurement period. The LLD (sensitivity) and precision of an AT

system is dependent upon the tracks counted, and therefore, the area of the detector that is analyzed.

With present ATs, routine counting can achieve an LLD of 1 pCiIL-month, and an LLD of 0.2

pCi/L-month may be achieved by counting additional area. The coefficient of variation (precision)

should be monitored using the results of duplicate detectors. The coefficient of variation should not

exceed 20 percent (1 sigma) at radon concentrations of 4 pCilL or greater (U.S. EPA Measurement

Protocols 1989).

Electret Ion Chamber Radon Detectors - Electret ion chamber radon detectors (EICs) require

no power and function as true integrating detectors, measuring the average concentration during the

exposure period. EICs contain a permanently charged electret (an electrostatically charged disk of

Tef]onr), which collects ions formed in the chamber by radiation emitted from radon decay products.

When the device is exposed, radon diffuses into the chamber through filtered openings. Ions that

are generated continuously bythe decay ofradon and radon decay products are drawn to the surface

of the electret and reduce its surface voltage. The amount of voltage reduction is directly related to

the average radon concentration present during the exposure period. There are both short-term (2-

to 7-day) and long-term (1- to 12~month) EICs that are currently marketed. The thickness of the

electret affects the usable measurement period. For a 7-day exposure period using a short-term EIC,

as well as for a long-term EIC, the LLD (sensitivity) is about 0.3 pCilL (U.S. EPA!Radon Division

1989). The coefficient of variation should not exceed 10 percent (1 sigma) at radon concentrations

Appendix C Page C-l
of 4 pCiIL or greater (U.S. EPAlRadon Division 1989). This precision should be monitored by using

results of duplicate detector analyses.

Continuous Radon Monitors - There are three types of continuous radon monitors (CRs).

In the first type, ambient air is sampled for radon in a scintillation cell after passing through a filter

that removes radon decay products and dust. Alpha particles (produced by radon decays) strike the

zinc sulphide coating of the cell, yielding scintillations that are detected by a photo-multiplier tube

in the detector. A second type of CR operates as an ionization chamber. Radon in the ambient air

diffuses into the chamber through a filtered area so that the radon concentration in the chamber

follows the radon concentration in the ambient air with some small time lag. The third type of CR

functions by allowing ambient air to diffuse through a filter into a detection chamber. As radon

decays, the alpha particles are counted using a solid state silicon detector. Most CRs are capable of

an LLD (sensitivity) of 0.5 pCiIL or less (U.S. EPAlRadon Division 1989). Special cells are available

for some CRs that have LLDs of 0.1 pCilL. The precision of most CRs can achieve a coefficient of

variation of less than 10 percent (1 sigma) at 4 pCilL or greater (U.S. EPAlRadon Division 1989).

Appendix C Page C-2
APPENDIX D

COVERAGE OF RADON TESTING POLICY

EPA's estimation of the housing stock and residents covered by its radon testing policy

required the determination of how many units were covered in each category of structures (e.g.

single-family homes) and the occupancy rates of these units. It was assumed that the units covered

would be homes that were intended for regular (year-round) use. Units that were seasonally or

occasionally used (by Census definitions), or could not be linked to regular usage (the Census

classifies them as "other" vacancies) were assumed to not be covered by EPA's testing policy.

The coverage estimates are based on 1990 Census data. Many of these data were available

through 1991 Census press releases. The remainder was made available to EPA from internal Census

documents that are normally used to answer specific inquiries.

Adjustments of the Census data were necessary because the specific statistics needed were

not available (e.g., number of group quarters units), or because EPA's testing policy only covered a

segment of a housing group (e.g., units below the third floor in multi-unit structures.) Some statistics

were available nationally; others had to be constructed from State-level data. The results of the

analysis appear in Exhibit D-l. A summary of how the estimates of housing units and residents

covered for each major housing group were developed follows.

Housing Units

• Single-Family Homes: The 1990 Census collected data on the number of single-family

homes. This figure was then adjusted to reflect only homes intended for year-round use. 1

• Mobile Homes: The number of mobile homes placed on permanent foundations was assumed

to be five percent of all mobile homes. This assumption was based on a review of new

construction reports published by the Census and information collected from trade

associations.

• Multi-Units: The 1990 Census collected data on the number of multi-units. This figure was

then adjusted to reflect only multi-units intended for year-round use, using the same approach

used for single-family homes. The number of apartments in multi-unit structures that are

below the third floor was assumed to be two-thirds of the total number of apartments in

multi-unit structures. This was derived from an assessment of the relationship between multiunit structures and numbers of stories in these buildings.

• Group Quarters: The number of group quarters was calculated by dividing the number of

people living in group quarters (also taken from the 1990 Census data) by the national

lA vacancy adjustment factor was calculated by dividing the number of housing units used occasionally by the total

number of housing units and adding that figure to the adjustment factor for homes occupied by residents that "usually

reside elsewhere" (URE) (e.g., travellers). The Census Bureau provided a national URE factor of approximately 2

percent. The vacancy adjustment factor was then used to determine the number of units that were not intended for

regUlar use.

Appendix D Page D-l
vvcupancy rate for multi-units.2 An assumption was made that these structures have

comparable occupancy rates given their similarity. The number of group quarters below the

third noor was assumed to be two-thirds the total number of group quarters.

Residents in Housing Units

The population affected by the testing and mitigation program includes all residents ofsinglefamily homes, multi-units, mobile homes, and group quarters that should test.

• Single-Family Homes: Based on information from the Census Bureau, the average occupancy

rate of single-family homes that are intended for year-round use was determined to be about

2.8 persons per home. This occupancy rate was then multiplied by the number of singlefamily homes intended for year-round use.

• Mobile Homes and Multi-Units: The occupancy rate for mobile homes and multi-units was

calculated by taking the total nationaI.population, subtracting out the number of people living

in single-family homes and group quarters, and dividing the remainder by the number of

mobile homes and multi-units. This occupancy ra te was then multiplied by the number of

mobile homes and multi-units that should test.

• Group Quarters: The number of people residing in group quarters was taken from State-byState results from the 1990 Census. The number was multiplied by two-thirds to calculate the

number of residents in group quarters that should test. This was done based on the

assumption that group quarters have the same distribution of stories and building geometry

as multi-unit structures.

2The national occupancy rate of multi-units was assumed to be comparable to the occupancy

rate of group quarters.

Appendix D Page D-2
EXHIBIT 0-1 ESTIMATION OF 1990 U.S. POPULATION IN DIFFERENT TYPES OF HOUSING

REQUIRING RADON TESTING AND POTENTIAL MITIGATION BY STATE

(IN THOUSANDS)

STATE

SINGLE-FAMILY

POPULATION HOMES

RESIDENTS OF

SINGLE-FAMILY

HOMES

MOBILE

HOMES

RESIDENTS OF

MOBILE

HOMES

MOBILE HOMES

WITH

PERMANENT

FOUNDATIONS

RESIDENTS OF

MOBILE HOMES

WITH PERMANENT

FOUNDATlONS MULTI-UNITS

Alabama 4,041 1,117 3,128 230 389 11 19 254

I:Alaska.,.:.. : . :. :.;.:'.:.. '\.::::'::'. ::: .:.,,'::: .'5<;(j ::. ;.127 ~5!l' :. \::::::::::.::22.....;.:< .':.' .:.:::=::=':- 46 .: ::"":: ::" .1....' .: 2 ..' 61>:

TOTALS

Appendix D

248,710 62,461 174,891 8,067 14,526 403 726 26,569

Page D-3
EXHIBIT D-l ESTIMATION OF 1990 U.S. POPULATION IN DIFFERENT TYPES OF HOUSING

REQUIRING RADON TESTING AND POTENTIAL MITIGATION BY STATE

(IN THOUSANDS)

STATE

MULTI-UNITS

RESIDENTS OF THAT SHOULD

MULTI-UNlTS TEST

RESIDENTS OF

MULTI-UNITS

THAT SHOULD

TEST

GROUP

QUARTERS

RESIDENTS

OF GROUP

QUARTERS

GROUP

QUARTERS

THAT SHOULD

TEST

RESIDENTS OF

GROUP QUARTERS

THAT SHOULD

TEST

RESIDENTS OF

ALL UNITS ALL UNITS

THAT SHOULD THAT SHOULD

TEST TEST

Alabama 431 170 289 47 92 31 62 1.330 3,498

AI;!SKa=': ..::. . 12~ . 41. . 85 .. H). .. . :" .)H . 1: 14'176 457

Arizona 633 251 424 41 81 27 54 1,192 3.023

IN:~~ri~(:':' ·1~2..·as. .::: 1Q$' :. .:. Sif)!Q :. $.$. 8n ~,113

~r~;~r::j: :~~} ...': :'l~;: ·:r!t~:lt:f}:::;;:::::;::::.::::}J.::.:J:::::~·# ..~F:;·:f;:::?:.··; :.:n::::::J;··::)lg~~l; ·..l·{.:··· f··:f:::·.·::::;:.f;'::~.71

4

jff::::f:::. f: ··f.j: ~.g'~f.j=.: (n· .{: l.

H

·g~;~gj:f..·:jffJ·'0;:.:.•. ::::;:2::·§~7i9j~~:j:. District of Columbia 272 111 182 21 42 14 28 228 499

fW!i,l:a:.:\::: :'. 2~j~$, .. j.;~~6::::.::.. :::. ::l:892:>j~~: 3l1.7; . .:194 .. 296 4;377:J9,'152

Georgia 1.078 388 722 88 174 59 116 2.118 5.504

Ba.~~lf:t::::· '.'...: '::::::'::::::::::ij;2~: .:.:~;t ::·:·:·::::;:::::#~i#4·::.t: :ff·{··:..:f'::)l)9W:t::; ::::g~lija::1 r:m:;:f ::·)?lr·~~!:·:J I'H'U' I: :m:H:i':g2'~sw'l:; H':" :.(31~3'i90 k: :::n:'~'lm~:"~:"~:i:::>l Id,~~.~ 110 36 74 11 21 7 14 318 855

mlf.lOlS·.:: :·: ··a.,34~. ". ·.<.))'i4If ::::\.::::\~~M':I}.r:;:::jl.~.:··.:2S:1:: '~7 ::' .' :192 .. 3;'100 '9,857

Montana 69 35 46 12 24 8 16 273 701

N~br~.;:. '147.. .::' ....: ::~O ?::::::::::::::::::;;~::: U}:::::::::·gKf::;:::::/:::::::;:::::mrr!::::::::::-;:r::::J:::A:iiiij'.=f::·l';r.:n:·:·m:·:n·:·:··:·.;·.::,,{.{:.. /'.:@16MI::.. :.m.m. ::::.:.{::::::}::::::::::: ..::S2;~::: 1:. W·: ::)..:.,§~7t~1r..:·II:· :: i:.1=j1.';.:'M.~~..tT:

Nevada 333 116 223 12 24 8 16 379 951

NElWHamf.!Sfiir~ "23~: :: :: '\/:·.:'82'.: .:' :(:·::::15;1' ::::::::::::(::::i~:.:::'::::::::::?\:=3.2·:ill.· '.. 22. . ;: '373. '.<:'95S

TOTALS

Appendix D

52.596 17.801 35.239 3.383 6.698 2.267 4,487 82.932

Page D-4

215,344
APPENDIX E

RISK ANALYSIS METHODOLOGY

The assessment of reductions in risks that result from the public following the testing

procedure advice in the final revised Citizen's Guide ("Testing Option C" in Chapter 3) for

alternative action levels of 2 pCi/L, 3 pCi/L, and 4 pCi/L had two major components:

• Estimation of the number of residents in homes that have testing results above the

action level and should mitigate their radon levels.

• Calculation of the risk reductions that should result when these mitigations occur.

Each of these components of the analysis is discussed in the sections that follow.

Residential Population that Should Mitigate

To determine the size of the residential population that would be mitigating their homes, it

was necessary to (1) estimate the residential coverage of EPA's radon testing policy and (2) predict

the testing results that this group would have if it followed EPA's advice in the revised Citizen's

Guide. Appendix D explains how the Agency estimated the population covered by EPA's testing

policy. Based on 1990 Census data, EPA estimates that about 215 million people are covered by the

testing policy. The remainder of this discussion explains how EPA predicted the results of this

group's radon testing (using Option C).

The public is advised to conduct an initial short-term test. If the results are above the action

level, Option C gives the public the choice of (1) conducting a follow-up long-term test and fixing

the house if the results are above the action level (like Option A); or 2) conducting a second shortterm test and fixing the house if the average of the two results is above the action level (like Option

B). EPA believes that under Option C, the public will actually pursue Option A testing about 9

percent of the time and Option B testing about 91 percent of the time. EPA used a statistical model

to predict the radon test results from using Testing Option C for alternative action levels by

independently looking at the predicted outcomes for Option A and Option B for each action level

(Chmelynski 1990). EPA weighted the results by the expected usage of each testing approach by the

public and then combined them to provide Option C results.

The statistical model used to predict testing results provided the joint probability distribution

for the results of short-term testing given the actual long-term radon levels houses were likely to

have. Exhibits E-1 through E-3 show these distributions for each action level examined. Each exhibit

provides results of Option A, Option B, and Option C, which is the combination of the preceding two

options. Summations of the appropriate portions of each of these distributions leads to estimates of

the fraction of homes that will need to be fixed. Multiplying these fractions by the residential

population covered in EPA's testing policy yields the number of persons affected. For instance, the

fraction of homes that have less than 1 pCi/L of radon and that will have false positive radon testing

results under Option B is the summation of the exhibit entries in the row "0_1" that begins from "4_6"

to ">20." This fraction multiplied by 215 million people provides the population that lives in homes

that are below 1 pCi/L and that would get false positive results, if all homeowners used Option B to

test their homes for radon.

Appendix E Page E-1
EPA generated the distribution tables for each action level based on testing devices used,

number of home floors, and testing conditions. 1 EPA assumed there was an equal chance of

homeowners using short-term devices like charcoal canisters and alpha track detectors. For charcoal

canisters, EPA assumed that all tests were done under closed~house conditions.2 For alpha track

detectors (ATDs), EPA assumed that 50 percent of tests would occur under open-house conditions

and that 50 percent would occur under closed-house conditions. Based on data from the 1990 Census

Data and the Charactelistics of New Housing: 1990 Current Construction Reports, the weights for

single floor vs. multi-floor homes were determined to be 46 and 54 percent, respectively. (The same

approach that EPA used to derive the mitigation dassification rates in Chapter 3 was also used here,

except the focus was on options that had different action levels using the same Option C testing

approach.)

Risk Reductions Due to Mitigation

EPA assumed for the Chapter 5 analysis that all homeowners of houses testing above the

action levels in long- or short-term testing installed and operated mitigation systems. The Agency

used the radon testing results shown in the first three exhibits to develop estimates of homes at

various radon levels that mitigated, as well as the exposure reductions they would receive, for each

of the selected pCi/L intervals in these exhibits. To estimate the exposure reductions received in

each interval, EPA subtracted the level of radon existing after mitigation from the radon levels

estimated to exist within each interval before mitigation. The average pre-mitigation radon levels in

the intervals were taken from results of the EPA National Residential Radon Survey. Exhibit E-4

provides these average levels. Based on the mitigation research and experience that is summarized

in Chapter 4, EPA assumed that homes that were above 2 pCi/L would have their levels reduced to

2 pCi/L (on average) and homes below that level would not have any radon reductions.3 The same

type of approach was used to estimate the risk reductions that were not gained ("lives lost") when

mitigation of homes above the action levels did not occur due to false negative testing results.

To facilitate the assessment of risk reductions that result from exposure reductions, EPA

developed multipliers that provided the lung cancer deaths averted per million persons receiving the

exposure reduction in each interval. The multipliers were based on EPA's central estimate of the

risk factor (i.e., that there will be 43.2 lung cancer deaths annually per million persons annually

exposed to one pCi/L). Exposure reductions (in pCi/L) for each interval were multiplied by the risk

factor to arrive at each interval's own multiplier. Exhibit E-4 shows the multipliers that were used

in all the analyses of the action levels.

EPA independently calculated risk reductions gained (or lost) for homes that had f~lse

positive test results, true positive test results, and false negative test results. Exhibjts E-5 through E-7

show these results for each action level. The final results that appear in Chapter 5 are the Option

C results in each exhibit. The intermediate results for Options A and B are also shown in the

exhibits. These results assume that the entire testing population (215 million people) follows that

IDistribution tables were generated using An evaluation of the performance of alternative shorHerm radon testing

procedures in homes with pending real estate transactions. Chmelynski, H. 1990. Submitted to EPA.

2por a more detailed explanation of radon tests, please refer to Chapter 3.

3There will often be some risk reduction that will occur for homes below 2 pCiIL. Due to the lack of data on exactly how

much reduction, however, EPA made a conservative assumption that there :would be no reduction.

Appendix E Page E-2
testing option. The results from Options A and B are then weighted by the portion of the population

that follows· each option to derive the results for Option C. Exhibit E-8 helps explain the reasons

for the differences in the levels of risk reduction that can occur given the exposure distribution that

exists in the U.S. housing stock.

Appendix E Page E-3
Exhibit E-l

Weighted Testing Distributions

at Action Level 4pCi/L

OPTION A

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

OPTION B

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 > 20 TOTAL

0.46289731 0.09305886 0.03151984 0.01374314 0.01085996 0.00384689 0.00168459 0.00187647 0.00031058 0.61979767

0.07260808 0.06399632 0.03126357 0.01589892 0.01373066 0.00507591 0.00221464 0.00232588 0.00028592 0.20739993

0.00935460 0.01951012 0.01472083 0.00945063 0.00979078 0.00421989 0.00201153 0.00231958 0.00032199 0.07169998

0.00196702 0.00694166 0.00740183 0.00588678 0.00734195 0.00372795 0.00196585 0.00254703 0.00041995 0.03820005

0.00068686 0.00364974 0.00532080 0.00529788 0.00824628 0.00515586 0.00312115 0.00480042 0.00102097 0.03730000

0.00005831 0.00047387 0.00095279 0.00121286 0.00245525 0.00197302 0.00142079 0.00274733 0.000805720.01209997

0.00001098 0.00011760 0.00028938 0.00043318 0.00106341 0.00103796 0.00086413 0.00206755 0.00081574 0.00669997

0.00000251 0.00003546 0.00010599 0.00018565 0.00055858 0.00068153 0.00068512 0.00231919 0.00162592 0.00619998

o 0.00000019 0.00000091 0.00000217 0.00000943 0.00001679 0.00002330 0.00015659 0.00039030 0.00059971

0.54758572 0.18778386 0.09157597 0.05211125 0.05405634 0.02573583 0.01399113 0.02116006 0.00599713 0.99999731

Two rounds of testing for positives (one round of testing for negatives)

Average Short-term Measurement (pCi/L)

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

OPTION C

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

0-1 1-2 2-3 3-4 4-6 6-8 8~ 10 10-20 > 20 TOTAL

0.46289731 0.09305886 0.03930476 0.01827882 0.00393081 0.00132012 0.00051290 0.00045174 0.00004232 0.61979768

0.07260808 0.06399632 0.03809300 0.02211290 0.00664640 0.00236203 0.00087742 0.00066808 0.00003566 0.20739994

0.00935460 0.01951012 0.01772150 0.01379046 0.00636274 0.00278552 0.00114636 0.00096730 0.00006135 0.07169998

0.00196702 0.00694166 0.00874512 0.00871796 0.00570512 0.00314840 0.00146495 0.00139973 0.00011005 0.03820005

0.00068686 0.00364974 0.00613777 0.00771167 0.00703149 0.00529483 0.00297480 0.00344802 0.00036477 0.03729999

0.00005831 0.00047387 0.00106081 0.00165693 0.00199744 0.00224083 0.00164993 0.00256784 0.00039391 0.01209996

0.00001098 0.00011760 0.00031517 0.00055988 0.00075293 0.00113674 0.00106112 0.00225052 0.00049497 0.00669995

0.00000251 0.00003546 0.00011330 0.00022744 0.00031344 0.00062719 0.00077200 0.00278277 0.00132583 0.00619996

o 0.00000019 0.00000094 0.00000241 0.00000277 0.00000856 0.00001597 0.00016090 0.00040793 0.00059972

0.54758572 0.18778386 0.11149240 0.073058510.032743170.01892425 0.01047548 0.01469695 0.003236900.99999728

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 >20 TOTAL

0.46456937 0.09305886 0.03860412 0.01787061 0.00357704 0.00120131 0.00046674 0.00041108 0.00003851 0.61979768

0.07260808 0.06612329 0.03747835 0.02155364 0.00604823 0.00214945 0:00079846 0.00060795 0.00003245 0.20739994

0.00935460 0.01951012 0.01913118 0.01339987 0.00579009 0.00253482 0.00104318 0.00088024 0.00005582 0.07169998

0.00196702 0.00694166 0.00862422 0.00990340 0.00519166 0.00286504 0.00133310 0.00127375 0.00010015 0.03820005

0.00068686 0.00364974 0.00606425 0.00749443 0.00840968 0.00481829 0.00270707 0.00313769 0.00033194 0.03729999

0.00005831 0.00047387 0.00105109 0.00161697 0.00181767 0.00288534 0.00150144 0.00233673 0.00035851 0.01209996

0.00001098 0.00011760 0.00031285 0.00054848 0.00068517 0.00103444 0.00149201 0.00204798 0.00045042 0.00669996

0.00000251 0.00003546 0.00011264 0.00022367 0.00028523 0.00057074 0.00070252 0.00306066 0.00120650 0.00619997

o 0.00000019 0.00000093 0.00000239 0.00000252 0.00000779 0.00001453 0.00014642 0.00042490 0.00059972

0.54925778 0.18991083 0.11137967 0.07261350 0.03180731 0.01806726 0.01005908 0.01390256 0.00299925 0.99999728

Appendix E Page E-4
Exhibit E-2

Weighted Testing Distributions

at Action Level 3pCi/L

OPTION A

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

OPTION B

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 > 20 TOTAL

0.46289731 0.09305886 0.03151984 0.01374314 0.01085996 0.00384689 0.00168459 0.00187647 0.00031058 0.61979767

0.07260808 0.06399632 0.03126357 0.01589892 0.01373066 0.00507591 0.00221464 0.00232588 0.00028592 0.20739993

0.00935460 0.01951012 0.01472083 0.00945063 0.00979078 0.00421989 0.00201153 0.0023195& 0.00032199 0.07169998

0.00196702 0.00694166 0.00740183 0.00588678 0.00734195 0.00372795 0.00196585 0.00254703 0.00041995 0.03820005

0.00068686 0.00364974 0.00532080 0.00529788 0.00824628 0.00515586 0.00312115 0.00480042 0.00102097 0.03730000

0.00005831 0.00047387 0.00095279 0.00121286 0.00245525 0.00197302 0.00142079 0.00274733 0.00080572 0.01209997

0.00001098 0.00011760 0.00028938 0.00043318 0.00106341 0.00103796 0.00086413 0.00206755 0.00081574 0.00669997

0.00000251 0.00003546 0.00010599 0.00018565 0.00055858 0.00068153 0.00068512 0.00231919 0.00162592 0.00619998

o 0.00000019 0.00000091 0.00000217 0.00000943 0.00001679 0.00002330 0.00015659 0.00039030 0.00059971

0.54758572 0.18778386 0.09157597 0.05211125 0.05405634 0.02573583 0.01399113 0.02116006 0.00599713 0.99999731

Two rounds of testing for positives (one round of testing for negatives)

Average Short-term Measurement (pCi/L)

(pCi/L) 0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 >20 TOTAL

0-1 0.46289731 0.10153744 0.04280681 0.00575363 0.00445658 0.00136478 0.00050742 0.00043364 0.00003993 0.61979758

1-2 0.07260808 0.06937046 0.04403728 0.00917330 0.00812751 0.00251395 0.00088221 0.00065262 0.00003448 0.20739994

2-3 0.00935460 0.02100491 0.02111349 0.00693803 0.00806765 0.00302242 0.00117354 0.00096456' 0.00006072 0.07169996

3-4 0.00196702 0.00739270 0.01041371 0.00467816 0.00729849 0.00342878 0.00150674 0.00140473 0.00010969 0.03820005

4-6 0.00068686 0.00384442 0.00716892 0.00401302 0.00893349 0.00574629 0.00306243 0.00347800 0.00036654 0.03730000

6-8 0.00005831 0.00049249 0.00119839 0.00074225 0.00251960 0.00241887 0.00169167 0.00258330 0.00039505 0.01209997

8-10 0.00001098 0.00012124 0.00034771 0.000211l3 0.00094417 0.00122360 0.00108561 0.00225984 0.00049565 0.00669997

10-20 0.00000251 0.00003631 0.00012226 0.00006876 0.00038884 0.00067140 0.00078679 0.00279025 0.00133281 0.00619996

>20 0 0.00000020 0.00000097 0.00000038 0.00000343 0.00000920 0.00001633 0.00016108 0.00040808 0.00059970

TOTAL 0.54758572 0.20380020 0.12720958 0.03157871 0.04073978 0.02039933 0.01071278 0.01472806 0.00324298 0.99999718

OPTION C

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 >20 TOTAL

0.46580626 0.10077437 0.04179098 0.00523581 0.00405548 0.00124195 0.00046175 0.00039461 0.00003633 0.61979759

0.07260808 0.07244466 0.04288765 0.00834770 0.00739603 0.00228769 0.00080281 0.00059389 0.00003138 0.20739994

0.00935460 0.02087038 0.02306845 0.00631361 0.00734156 0.00275040 0.00106792 0.00087775 0.00005525 0.07169996

0.00196702 0.00735210 0.01014264 0.00622718 0.00664162 0.00312018 0.00137113 0.00127831 0.00009982 0.03820005

0.00068686 0.00382690 0.00700259 0.00365185 0.01061731 0.00522912 0.00278681 0.00316498 0.00033355 0.03730000

0.00005831 0.00049081 0.00117629 0.00067544 0.00229283 0.00315652 0.00153942 0.00235081 0.00035950 0.01209997

0.00001098 0.00012092 0.00034246 0.00019213 0.00085920 0.00111348 0.00155328 0.00205645 0.00045104 0.00669997

0.00000251 0.00003623 0.00012080 0.00006257 0.00035384 0.00061098 0.00071597 0.00308416 0.00121285 0.00619996

o 0.00000020 0.00000096 0.00000035 0.00000312 0.00000837 0.00001486 0.00014658 0.00042523 0.00059970

0.55049467 0.20591660 0.12653285 0.03070668 0.03956104 0.01951874 0.01031401 0.01394758 0.00300498 0.99999719

Appendix E Page E-5
Exhibit E-3

Weighted Testing Distributions

at Action Level 2pCi/L

OPTION A

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

OPTlON B

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8

0.46289731 0.09305886 0.03151984 0.01374314 0.01085996 0.00384689

0.07260808 0.06399632 0.03126357 0.01589892 0.01373066 0.00507591

0.00935460 0.01951012 0.01472083 0.00945063 0.00979078 0.00421989

0.00196702 0.00694166 0.00740183 0.00588678 0.00734195 0'.00372795

0.00068686 0.00364974 0.00532080 0.00529788 0.00824628 0.00515586

0.00005831 0.00047387 0.00095279 0.00121286 0.00245525 0.00197302

0.00001098 0.00011760 0.00028938 0.00043318 0.00106341 0.00103796

0.00000251 0.00003546 0.00010599 0.00018565 0.00055858 0.00068153

o 0.00000019 0.00000091 0;00000217 0.00000943 0.00001679

0.54758572 0.18778386 0.09157597 0.05211125 0.05405634 0.02573583

8-10

0.00168459

0.00221464

0.00201153

0.00196585

0.00312115

0.00142079

0.00086413

0.00068512

0.00002330

0.01399113

10-20 >20 TOTAL

0.00187647 0.00031058 0.61979767

0.00232588 0.00028592 0.20739993

0.00231958 0.00032199 0.07169998

0.00254703 0.00041995 0.03820005

0.00480042 0.00102097 0.03730000

0.00274733 0.00080572 0.01209997

0.00206755 0.00081574 0.00669997

0.00231919 0.00162592 0.00619998

0.00015659 0.00039030 0.00059971

0.02116006 0.00599713 0.99999731

Two rounds of testing for positives (one round of testing for negatives)

Average Short-term Measurement (pCi/L)

(pCilL)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

OPTION C

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20

0.46289731 0.12680067 0.01613261 0.00694534 0.00476502 0.00133799 0.00048029 0.00040174

0.07260808 0.08653552 0.02265543 0.01235090 0.00916006 0.00255170 0.00086859 0.00063603

0.00935460 0.02569338 0.01237851 0.00971940 0.00923427 0.00311838 0.00117925 0.00096163

0.00196702 0.00877038 0.00597427 0.00659872 0.00831560 0.00353820 0.00151918 0.00140689

0.00068686 0.00441416 0.00364563 0.00561705 0.01005635 0.00591306 0.00309478 0.00350249

0.00005831 0.00054525 0.00048325 0.00103758 0.00281113 0.00247601 0.00170199 0.00259007

0.00001098 0.00013130 0.00011404 0.00029464 0.00104921 0.00125052 0.00109080 0.00226217

0.00000251 0.00003855 0.00003140 0.00009533 0.00042971 0.00068433 0.00078908 0.00279173

o 0.00000020 0.00000012 0.00000053 0.00000379 0.00000941 0.00001640 0.00016107

0.54758572 '0.25292944 0.06141529 0.04265953 0.04582517 0.02087963 0.01074041 0.01471386

>20 TOTAL

0.00003646 0.61979747

0.00003357 0.20739993

0.00006051 0.07169997

0.00010977 0.03820007

0.00036960 0.03730000

0.00039636 0.01209999

0.00049627 0.00669998

0.00133729 0.00619997

0.00040815 0.00059970

0.00324803 0.99999711

Average

(pCi/L)

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

>20

TOTAL

Short-term Measurement (pCi/L)

0-1 1-2 2-3 3-4 4-6 6-8 8-10 10-20 > 20 TOTAL

0.46864304 0.12376390 0.01468067 0.00632026 0.00433617 0.00121757 0.00043707 0.00036559 0.00003318 0.61979749

0.07260808 0.09087859 0.02061644 0.01123932 0.00833566 0.00232205 0.00079042 0.00057879 0.00003055 0.20739993

0.00935460 0.02513689 0.01511961 0.00884466 0.00840318 0.00283772 0.00107312 0.00087508 0.00005507 0.07169997

0.00196702 0.00860579 0.00543659 0.00864105 0.00756720 0.00321976 0.00138245 0.00128027 0.00009989 0.03820007

0.00068686 0.00434537 0.00331752 0.00511152 0.01211798 0.00538088 0.00281625 0.00318726 0.00033633 0.03730000

0.00005831 0.00053883 0.00043975 0.00094420 0.00255813 0.00329427 0.00154881 0.00235697 0.00036069 0.01209998

0.00001098 0.00013007 0.00010378 0.00026812 0.00095478 0.00113797 0.00158405 0.00205857 0.00045161 0.00669998

0.00000251 0.00003827 0.00002858 0.00008675 0.00039103 0.00062274 0.00071806 0.00309506 0.00121693 0.00619997

o 0.00000020 0.00000011 0.00000048 0.00000345 0.00000856 0.00001492 0.00014658 0.00042537 0.00059970

0.55333145 0.25343794 0.05974308 0.04145639 0.04466761 0.02004156 0.01036520 0.01394420 0.00300966 0.99999713

Appendix E Page E-6
Exhibit E-4

Radon Exposure and Deaths Per Million

In Each Interval

Appendix E

pCi/l

Interval

0-1

1-2

2-3

3-4

4-6

6-8

8-10

10-20

> 20

Arithmetic

Mean Exposure

In Interval

0.440

1.400

2.440.

3.430

···4.942

6.900

8.950

·12.890

29.250

Deaths per

Million in

Interval

NONE

NONE

19

62

127

212

·300

470

1,177

Page E-7
Exhibit E-5

Risk Calculations for Existing Homes Using

Distribution for All Homes that Should Test

Option A at Action Level 4pCi/L

Radon Radon Annual Deaths Annual Lives

pCill Test Fraction of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0

1-2 FP/TN 0.2074 NONE NONE 0

2-3 FP/TN 0.0717 NONE NONE 0

3-4 FP/TN 0.0382 NONE NONE 0

4-6 TP 0.0223 2 127 612

6-8 TP 0.0094 2 212 429

8-10 TP 0.0058 2 300 378

10-20 TP 0.0059 2 470 595

>20 TP 0.0006 2 1,177 151

4-6 FN 0.0150 NONE 127 (409)

6-8 FN 0.0027 NONE 212 (123)

8-10 FN 0.0009 NONE 300 (55)

10-20 FN 0.0003 NONE 470 (33)

>20 FN 0.0000 NONE 1,177 (1)

Option B

Radon Radon Annual Deaths Annuai Lives , i

pCi/1 Test Fraction of Reduction Averted per Saved .,.

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 01 False

1-2 FP/TN 0.2074 NONE NONE 0 Positive·

2-3 FP/TN 0.0717 2 19 46 204

3-4 FP/TN 0.0382 2 62 157 ... ,

4-6 TP 0.0191 2 127 523

6-8 TP 0.0089 2 212 403 .. ,..True . ..

8-10 TP 0.0057 2 300 368 .....

Positive

10-20 TP 0.0058 2 470 590 2,036

>20 TP 0.0006 2 1,177 151

4-6 FN 0.0182 NONE 127 (498)

6-8 FN 0.0032 NONE 212 (148) .False ,.....

8-10 FN 0.0010 NONE 300 (65) Negative

10-20 FN 0.0004 NONE 470 (38) ...... (750)

>20 FN 0.0000 NONE 1,177 (1) .... ' ....... ,

Appendix E Page E-8
Exhibit E-5 (continued)

Option C

Radon Radon Annual Deaths Annual Lives

pCifl Test Fraction of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FPfTN 0.6198 NONE NONE 0 > ... •••.•• r<u:,c

1-2 FPfTN 0.2074 NONE NONE o I···· L v,,"'<''"'

2-3 FPfTN 0.0717 NONEI2** 17 42 I 185

3-4 FPITN 0.0382 NONEI2** 56 143

4-6 TP 0.0194 2 127 531

6-8 TP 0.0089 2 212 406 True

8-10 TP 0.0057 2 300 369 Positive

10-20 TP 0.0058 2 470 590 ... 2,047

>20 TP 0.0006 2 1,177 151

4-6 FN 0.0179 NONE 127 (490)

6-8 FN 0.0032 NONE 212 (146) False

8-10 FN 0.0010 NONE 300 (64) .. Negative ....

10-20 FN 0.0004 NONE 470 (38) (738)

>20 FN 0.0000 NONE 1,177 (1)

*True Positive (TP), False Positive (FP), True Negative· (TN), and False Negative (FN). Assumes 100% testing

and mitigation. Column entries may not sum due to rounding of estimates.

**There is no radon reduction level for TN homes, there is a radon reduction level of 2 for homes that test FP.

Appendix E Page E-9
Option A

Exhibit E-6

Risk Calculations for Existing Homes Using

Distribution for All Homes that Should Test

at Action Level 3pCifL

Radon Radon Annual Deaths Annual Lives ...

pCifl Test Fraction of Reduction Averted per Saved ,

Interval Status* Population Level Million Persons (Lost)

0-1 FPfTN 0.6198 NONE NONE 0 False

1-2 FPfTN 0.2074 NONE NONE 0 Positive

2-3 FP/TN 0.0717 NONE NONE 0 0

3-4 TP 0.0219 2 62 291

4-6 TP 0.0276 2 127 757 .... ,

6-8 TP 0.0106 2 212 484· True

8-10 TP 0.0063 2 300 406 Positive

10-20 TP 0.0061 2 470 614 2,703

>20 TP 0.0006 2 1,177 152

3-4 FN 0.0163 NONE 62 (217) '.' ..

4-6 FN 0.0097 NONE 127 (264)

6-8 FN 0.0015 NONE 212 (68) False

8-10 FN 0.0004 NONE 300 (27) Negative

10-20 ·FN 0.0001 NONE 470 (15) (591)

>20 FN 0.0000 NONE 1,177 (0)

Option B

Radon Radon Annual Deaths Annual Lives

pCi/l Test Fraction of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0 False

1-2 FP/TN 0.2074 NONE NONE 0 Positive

2-3 FP/TN 0.0717 2 19 83 83

3-4 TP 0.0184 2 62 245

4-6 TP 0.0256 2 127 701

6-8 TP 0.0096 2 212 438 True

8-10 TP 0.0060 2 300 389 Positive

10-20 TP O.OO~O 2 470 60S 2,529

>20 TP 0.0006 2 1,177 152

3-4 FN 0.0198 NONE 62 (263)

4-6 FN 0.0117 NONE 127 (320)

6-8 FN 0.0025 NONE 212 (114) False

8-10 FN 0.0007 NONE 300 (45) Negative

10-20 FN 0.0002 NONE 470 (23) (765)

>20 FN 0.0000 NONE 1,177 (0)

Appendix E Page E-10
Exhibit E~6 (continued)

Radon Radon Annual Deaths Annual Lives

pCi/1 Test Fraction of Reduction Averted per Saved .> .. ..........

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0 False

1-2 FP/TN 0.2074 NONE NONE 0 Positive

2-3 FP/TN 0.0717 NONE/2** 17 75 75

3-4 TP 0.0187 2 62 249

4-6 TP 0.0258 2 127 706

6"':8 TP 0.0097 2 212 442 True

8-10 TP 0.0060 2 300 390 Positive

10-20 TP 0.0060 2 470 606 2,544

>20 TP 0.0006 2 1,177 152 ....

3-4 FN 0.0195 NONE 62 (259)

4-6 FN 0.0115 NONE 127 (315)

6-8 FN 0.0024 NONE 212 (109) False

8-10 FN 0.0007 NONE 300 (43) Negative

10-20 FN 0.0002 NONE 470 (23) (750)

>20 FN 0.0000 NONE 1,177 (0)

Option C

*True Positive (TP), False Positive (FP), True Negative (TN), and False Negative (FN). Assumes 100% testing

and mitigation. Column entries may not sum due to rounding of estimates.

**There is no radon reduction level for TN homes, there is a radon reduction level of 2 for homes that test FP.

Appendix E Page E-11
Exhibit E-7

Risk Calculations for Existing Homes Using

Di.stribution for All Homes that Should Test

Option A at Action Level 2pCiIL

Radon Radon Annual Deaths Annual Lives

pCi/1 Test Fraction of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0

1-2 FP/TN 0.2074 NONE NONE 0

2-3 TP 0.0428 2 19 175

3-4 TP 0.0293 2 62 390

4-6 TP 0.0330 2 127 902

6-8 TP 0.0116 2 212 527

8-10 TP 0.0066 2 300 425

10-20 TP 0.0062 2 470 624

>20 TP 0.0006 2 1,177 152

2-3 FN 0.0289 NONE 19 (1l8)

3-4 FN 0.0089 NONE 62 (1l9)

4-6 FN 0.0043 NONE 127 (1l9)

6-8 FN 0.0005 NONE 212 (24) False

8-10 FN 0.0001 NONE 300 (8) Negative

10-20 FN 0.0000 NONE 470 (4) (392)

>20 FN 0.0000 NONE 1,177 (0)

Option B

Radon Radon Annual Deaths Annual Lives

pCi/1 Test F!"action of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0 False

1-2 FP/TN 0.2074 NONE·· NONE 0

2-3 TP 0.0367 2 19 150 0

3-4 TP 0.0275 2 62 365

4-6 TP 0.0322 2 127 881

6-8 TP 0.01l5 2 212 524 True

8-10 TP 0.0066 2 300 424 .. Positive

10-20 TP 0.0062 2 470 624 3,121

>20 TP 0.0006 2 1,177 152

2-3 FN 0.0350 NONE 19 (143)

3-4 FN 0.0107 NONE 62 (143)

4-6 FN 0.0051 NONE 127 (140)

6-8 FN 0.0006 NONE 212 (28)

8-10 FN 0.0001 NONE 300 (9)

10-20 FN 0.0000 NONE 470 (4)

>20 FN 0.0000 NONE 1,177 (0)

Appendix E Page E-12
Exhibit E-7 (continued)

Option C

Radon Radon Annual Deaths Annual Lives

pCill Test Fraction of Reduction Averted per Saved

Interval Status* Population Level Million Persons (Lost)

0-1 FP/TN 0.6198 NONE NONE 0

1-2 FP/TN 0.2074 NONE NONE 0

2-3 TP 0.0372 2 19 152

3-4 TP 0.0276 2 62 368

4-6 TP 0.0323 2 127 883

6-8 TP 0.OIl5 2 212 524

8-10 TP 0.0066 2 300 424

10-20 TP 0.0062 2 470 624

>20 TP 0.0006 2 1,177 152

2-3 FN 0.0345 NONE 19 (141)

3-4 FN 0.0106 NONE 62 (141)

4-6 FN 0.0050 NONE 127 (138)

6-8 FN 0.0006 NONE 212 (27)

8-10 FN 0.0001 NONE 300 (9)

10-20 FN 0.0000 NONE 470 (4)

>20 FN 0.0000 NONE 1,177 (0)

*True Positive (TP), False Positive (FP), Tru~ Negative (TN), and False Negative (FN). Assumes 100% testing

and mitigation. Column entries may not sum due to rounding of estimates.

**There is no radon reduction level for TN homes, there is a radon reduction level of 2 for homes that test FP.

Appendix £ Page £-13
[

~.

t'1] 70

DISTRIBUTION OF HOMES AND TOTAL EXPOSURE AT SELECTED

RADON LEVELS FOR ALL HOMES

64%

20%

ToIaJs lIIIill no' llUm '0 '00% due 10 rounding _01S.

> 20

10' 0.06% 70

11 %

8-20

1%

1_--1 Percentage of Homes

D Percentage of Exposure

2-3 3-4 4-8

PicoCuries Per Liter

0-1 1-2

o

10

40

20

50

30

60

+-'

c

Q)

e

Q)

a..

;t'

t;'1

......

-l:..
APPENDIX F

RADON MITIGATION COST MODEL

EPA has a cost model for estimating the total system costs for radon mitigation in singlefamily detached homes. For any specified action level, the model can predict the total costs of

reducing radon levels for homes above that level down to a specified "target level," an average level

all homes will reach when mitigation systems are installed. The model calculates a weighted average

cost (WAC) of mitigation, which can be multiplied by the number of housing units that EPA

estimates will require radon mitigation to arrive at total mitigation costs. The costs are for

contractor-installed systems (versus homeowner efforts). The estimates are provided as present value

estimates--all unit costs are summed and presented in 1991 dollars based on a 3 percent discount rate.

Background

When the model was first built in 1987, the overall average target level of radon reduction

was 4 pCi/L (equal to EPA's action level). For ease of development, the model's unit costs were

developed using 4 pCiIL as a reference level for overall reduction. Scalers were devised to multiply

against the reference unit costs for achieving a reduction down to 4 pCi/L to consider higher, or

lower mitigation target levels. For instance, in some cases installing a mitigation system that would

get homes above 4 pCiIL down to 2 pCiIL was estimated to be twice as expensive as a system that

gets homes above 4 pCiIL down to 4 pCiIL. The model has been updated over time as EPA has

learned more about mitigation experiences through the U.S., but it has kept this reference cost and

scaler (multiplier) approach to estimating individual unit costs of various mitigation activities.

Recent Model Update

The model was updated in the Fall of 1991. EPA reviewed recent radon mitigation literature

and consulted mitigation experts throughout the United States during its revision of the model.

EPA's recently completed Parametric Analysis of the Installation and Operating Costs ofActive Soil

Depressurization Systems for Residential Radon Mitigation (EPA, October 1991) was relied on quite

heavily for updating the costs of active subslab depressurization, which is the technology that EPA's

expects the vast majority of homeowners to use. To a lesser degree, EPA's Private Sector Radon

Mitigator Swvey (June 1991) which reports on data collected in 1989 was also used.

Radon mitigation has been an active business for less than 10 years. There is not extensive

published information on the usage rates of different systems and cost differences geographically.

To overcome this lack of data, EPA consulted with expert radon mitigators throughout the country

to develop information on what types of systems were being used and the costs of their usage in

different parts of the country. These experts had significant experience and were mitigation

instructors at EPA's Regional Radon Training Centers. They had substantial knowledge of practices

in the Northeast, South, West, Pacific Northwest, and Central U.S. Additionally, a senior EPA

mitigation expert, who has directed its extensive mitigation research activities for existing homes, and

the principal developer of EPA's radon mitigation training course, who has substantial national

experience in reducing radon levels in homes, were also consulted. From these experts' input and

Appendix F Page F-l
recognition of where most mitigation activity in the country would be occurring1, cost functions and

estimates of technology usage throughout the nation were prepared.

Model Components

The model has two major components. The first combines unit costs of different aspects of

radon mitigation to derive total upfront and lifetime system costs for selected mitigation technologies

that are most prevalently used in the U.S. The second component uses estimates of how often

various technologies are used to provide weighted average costs of radon mitigation for upfront and

lifetime expenditures. Each of these components is explained below.

Unit and Total Costs of Mitigation Systems

The model examines unit costs in five major cost categories: (1) diagnosis, (2) installation,

(3) post-mitigation, (4) regular operation, and (5) repairs. It is supplied unit costs at a level of detail

that is sensible to consider cost variations for four major factors: (1) foundation type, (2) mitigation

technology, (3) initial radon levels, and (4) degree of difficulty in installing a system (i.e., whether

homes are easy or hard to fix). For installation, it makes sense to provide unit costs for each

combination of these factors. Therefore, average unit costs for all appropriate situations were

developed (see Exhibit F-2). For diagnosis and post-mitigation, the best way to examine unit costs

was on the basis of whether the home was easy or hard to fix (see Exhibit F-3). For regular

operation costs (shown in Exhibit F-4) and repairs (shown in Exhibit F-5), the best way to examine

unit costs was on the basis of the mitigation technology used.

Each of the cost categories used in the analysis is discussed below.

• Diagnosis - This category covers the average costs for a radon mitigator to provide

a limited assessment of the extent of a radon problem in a home and to estimate the

cost to fix it -- it is essentially the cost of a price estimate. It is delineated by whether

the home will be easy or difficult to fix (see Exhibit F-3).

• Installation - This category covers the costs of materials and labor for initially

installing the system (see Exhibit F-2). Unit costs were estimated for every mitigation

situation (i.e., combination of factors) that the Agency believed should occur at levels

that are not insignificant. It was assumed that any practice that would be used less

than 5 percent of the time was insignificant. Note that the unit costs for homes.

between 2 and 4 pCi/L only apply if the action level considered in the cost analysis

is either 2 or 3 pCilL. For all technologies, it is assumed some sealing occurs in areas

of the foundation where it makes sense to do so. (Sealing/Plugging as a mitigation

technology category here means that its the only method used.)

• Post-mitigation - This category covers the contractor returning to the home shortly

after system installation to check its operation and make any necessary adjustments.

It is delineated by whether the home was easy or difficult to fix (see Exhibit F-3).

lExhibit F-l shows by EPA Region the percentage of homes that are above EPA's action level (4 pCiIL) based on

EPA's report on the National Residential Radon Survey.

Appendix F Page F-2
• Regular Operation - This category estimates the normal operating expenses incurred

by homeowners during mitigation system operation (see Exhibit F-4). For all

technologies, it is assumed to be at least $35 every 2 years (or about an average of

$18 a year) based on the assumption that all homes will biennially test their radon

levels (as recommended in the Rep Interim Radon Mitigation Standards, 1991) using

an alpha track detector. Additional annual operating costs for each technology

include:

Active subslab depressurization - there are costs for fan electricity and

heating/cooling .losses of conditioned air.

Simple ventilation - for this cost category, there are averaged costs of using

ventilation fans with open windows and simply opening windows. The costs

are for fan electricity (where a fan is used) and heating/cooling losses.

Heat recovery ventilation - this technology has added costs for fan electricity,

heat loss, annual filter replacement, and annual unit inspection.

Depressurization in crawl space - there are costs for fan electricity and the

added space heating requirements resulting from this system.

• Repairs - This cost category gives the costs of labor and materials for repairing

mitigation systems, or replacing materials over time (see Exhibit F-5). The repair

costs vary by mitigation technology:

Active subslab depressurization - For all foundations, it is assumed that cracks

will be resealed in years 2 and 20 after system installation to fix problems

caused by caulks degrading or house settling. This resealing is estimated to

cost $100 each time. Fans are replaced every 10 years at a cost of $150 each

time and the alarm device that indicates fan failure is replaced for $95 in year

37 (half way through system life.) For crawl space homes, the membrane

liner is replaced in year 37 (halfway through system life.)

Sealing/plugging - initial sealing is repaired every five years at 40 percent of

the original cost of installation.

Simple ventilation - repair and replacement is averaged between using fans

with open windows and open windows only. For all foundations, assumes

cracks will be resealed in years 2 and 20. Basement and slab-on-grade homes

that use fans replace them every 20 years for $230 each time. There are no

replacement costs associated with open windows other than sealing foundation

cracks.

Heat recovery ventilation - costs are twice the ASD costs above, since the

systems use two fans.

The unit costs are meant to retlect national average unit costs. This is after compiling the

unit cost estimates mitigators provided from different regions of the country and considering where

Appendix F Page F-3
in the country certain mitigation practices in certain types of houses (by foundation) were likely to

occur. As mentioned earlier, there was also consideration of areas of the country that will have the

largest percentages of homes to fix.

In each case, the "average" size house that was considered had 1,900 square feet. Only major

mitigation technologies that would often be used were considered -- active subslab depressurization

(ASD), sealing/plugging, simple ventilation (using fans with open windows or just properly opened

windows), heat recovery ventilation (HRV), and space depressurization for crawl space homes.

Whether a house was easy or hard to fix related to its structural design, materials the home

foundation rested on, and interior space use. The definition reflected the level of effort (and'

materials to some degree) a mitigator would spend on installing a system. Effort was always linked

to whether areas in the house that required mitigator attention were readily accessible or not. For

instance, whether cracks in the foundation that needed sealing were easy to reach or not. Often it

would also depend on how much effort and materials were needed to install a system that would be

fully effective in a particular situation. For example, where the area under a foundation does not

provide for easy passage of soil gas, the resulting "poor communication" will lead to the placement

of more than one suction pipe in an active subslab depressurization system. A house such as this

would be "hard" to fix.

Initial radon levels, in pCiIL, were selected based on radon ranges that could lead to different

selections of various types of mitigation systems and different overall levels of effort (although to a

lesser degree). It is important to recognize that although mitigators are fixing homes with levels

above 4 pCiIL, it is uncommon for homes initially testing between 2 to 4 pCilL to be mitigated.

Therefore, the expenses for mitigating homes in this ran~e are based on theoretical assumptions of

what the costs should be and not practical experience. The housing foundation types selected

represent the three dominant types that exist (note that partial and full basement homes are simply

considered as basement homes). It was assumed that 47 percent of the homes have basements, 26

percent have slab-on-grade, and 27 percent have crawl space. These estimates were taken from the

American Housing Survev for 1989 published bY,the Census Bureau.

The costs are estimated from the vantage point ofthe homeowner. For diagnosis, installation,

post-mitigation, and repairs, the costs are the amounts homeowners would pay commercial contractors

to perform the work. For the operating expenses, the costs reflect what homeowners would pay

testing companies and utilities for electricity and space conditioning. It is important to consider that

the first three costs elements together (diagnosis, installation, and post-mitigation) should sum to the

total price mitigators would charge for mitigation system installation. It is assumed that mitigators

are using practices EPA recommends for installing mitigation systems in its guidance materials and

training programs. It is also important to recognize that the costs in each category are meant to

provide average unit costs that can be combined to provide overall system costs. The costs considered

in the analysis are for 74 years, the assumed average lifetime of a house.

The total costs for upfront expenses and system life are calculated for each type of mitigation

system. The estimates are the summation of the appropriate unit cost components as shown in

~he expert mitigators were queried on whether it was reasonable to assume that the costs of getting the average

house between 2 and 4 pCiIL down to 2 pC/I was the same as getting the average house between 4 and 8 pCiIL down to

4 pCiIL. They all believed such an assumption was reasonable.

Appendix F Page F-4
Exhibits F-2 through F-5. Exhibit F-7 shows the total lifetime costs. An example of how these unit

costs are combined is provided below:

For basement homes that are greater than 20 pCiIL and easy to fix, their average cost is the

summation of diagnosis ($80), installation ($1,000), post-mitigation ($70), annual operation

($110 per year, or $3,265 in present value terms), and repairs ($565 in present value terms),

or $4,971. The initial costs that a mitigator would want to charge someone, $1,150, are

captured by diagnosis, installation, and post-mitigation.

Mitigation Technology Usage

For each set of homes that is expected to exist in various pCiIL intervals, the model uses

estimates of the percentage of time various technologies would be used in easy and hard situations.

Exhibit F-6 shows the assumptions made by each type of home foundation. These percentages were

arrived at by using the judgments of the expert mitigators mentioned above.

The left-hand portions of Exhibit F-7 show the cost results of the total lifecycle analysis in

present value dollars for the case of all homes with an annual average level above 4 pCiIL reducing

their radon levels to an overall annual average of 2 pCiIL. These initial results are used to develop

a weighted average cost (WAC) for each foundation type and ultimately a WAC for the whole

housing stock. This is calculated using information on the percentages of homes that are found in

each range of initial radon levels and the percentages of homes with each foundation type.

Exhibit F-8 shows for each action level examined in Chapter 5 what percentage of homes

were in different initial radon ranges. (EPA assumed an even distribution of range levels by

foundation type.) In the cases where the action level is 4 pCiIL, the system costs for 2-4 pCiIL homes

would not enter the analysis. The right-hand portion of Exhibits F-6 and F-7 show the case where

the action level could be 2 or 3 pCiIL and homes between 2 to 4 pCiIL reduce their overall annual

average to 2 pCiIL. As Exhibit F-8 shows, each of the action levels that was examined has different

WACs for the upfront and total lifetime costs due to the variability in percentages of homes that are

fixed at different levels. The lower WACs for lower action levels are due to an increasingly larger

percentage of homes at lower radon levels that enter into the calculation of the WAC. In the

majority of situations (especially in homes using ASD), the costs of reducing radon levels down to

2 pCiIL is about the same. However, mitigations in the smaller set of homes that use sealing and

ventilation technologies cost less at the lower action levels because the mitigation systems need to

provide lower percentage reductions in radon levels.

Appendix F Page F-5
EXHIBIT F-1

ESTIMATED NUMBER OF HOUSING UNITS WITH

RADON LEVELS ABOVE 4pCi/L. 1989-1990

I

IREGIONS

REGION 1

·B~IONgU••/······

REGION 3

agGIOO4.•····./···

REGION 5

.RI5GI()N~ .•·.·•••·

REGION 7

a:~GiON::~:·}?·

REGION 9

AI$IONtij>··

TOTAL

SINGLE-FAMILY

HOMES

ABOVE 4PCi/L'

124

%OF

TOTAL

MOBILE

HOMES

ABOVE 4pCi/L'

8

i

% OF I MULTI-UNITS

TOTAL iABOVE 4pCi/L'

TOTAL

% OF UNITS

TOTAL ABOVE 4pCi/L'

212

:/: OF

TOTAL

4%

•Number of homes in thousands.

Source: National Residential Radon Survey

Appendix F Page F-6
EXHIBIT F-2

RADON MITIGATION SYSTEM INSTALLATION COSTS BY BUILDING FOUNDATION,

SOURCE STRENGTH, AND DEGREE OF DIFFICULTY TO FIX

REDUCING HOMES REDUCING HOMES

ABOVE 4 pCi/L TO 4 pCi/L BElWEEN 2-4 pCi/L TO 2 pCi,

SOURCESTRENGTH(PCiIl);..:> .</ ..:.....« ...,,~m· ....:..:....:........... .....~.< ... ...•:i/ ""'>

DIFFICULTY

TO FIX

EASY $1,000 $1,000 $1,000 $1,000

HARD 1,500 1,300 1,300 1,300

EASY 1,250 1,100 500 500

HARD a 3,000 2,750 2,750

0 0 115 115

a 2,000 2,000 a

SIMPLE VENTILATION'

HEAT RECOVERY VENTILATION"

BASEMENT

ACTIVE SUBSLAB DEPRESSURIZATION

SEALING/PLUGGING

EASY $1,200 $1,200 $1,200 $1,200

HARD 1,700 1,600 1,600 1,600

EASY 0 600 600 600

HARD 0 3,000 1,250 1,250

0 0 115 115

0 0 0 0

SIMPLE VENTILATION"

HEAT RECOVERY VENTILATION"

SLAB-aN-GRADE

ACTIVE SUBSLAB DEPRESSURIZATION

SEALING/PLUGGING

EASY $1,300 $',300 $1,300 $1,300

HARD 1,650 ',650 1,650 1,650

EASY 0 ',250 500 500

HARD 0 0 1,250 1,250

0 0 0 400

450 450 450 450

CRAWLSPACE

ACTIVE SUBMEMBRANE DEPRESSURIZATION

SIMPLE VENTILATION'

DEPRESSURIZATION'

ISOLATION

MULTlPLlERS FOR HOMES ABOVE 4 pCilL ACHIEVING 2PCi/L LEVELS (MULTlPLlED AGAINST COSTS FOR REACHING 4 pCi/L)

ACT.SUBSL. DEPPRESURIZATION - EASY:

ACT.SUBSL. DEPPRESURIZATION - HARD:

SEALING/PLUGGING - EASY AND HARD:

SIMPLE VENTILATlON (BASEMENTAND S-O-G):

SIMPLE VENTILATION (CRAWLSPACE):

HEAT RECOVERY VENTILATION:

DEPRESSURIZATION:

1.00

1.25

1.50

2.00

1.00

1.75

1.00

HOMES BETWEEN 2-4 pCi/L REACH 2 WITH SAMEASSUMED COSTAS HOMES BETWEEN 4-8 pCilL REACHING 4 pCi/L

• Simple ventilation and depressurization (in the crawlspace) are auumed to be easy and heat recovery ventilation is assumed to be hard to do.

Note: Zero entries in the installation table indicates that the technology shown would not be applied in that particular situation.

Appendix F Page F-7
EXHIBIT F-3

COMMON COSTS ASSOCIATED WITH PROPER MITIGATION SYSTEM INSTALLATION

FOR ALL FOUNDATIONS BY DEGREE OF DIFFICULTY TO FIX*

FOR HOMES REDUCED TO 4 PCi/L

EASY HARD

MULTIPLIERS FOR ACHIEVING 2 PCi/L

FOR HOMES (NITIALLY ABOVE 4 pCi/L* "

DIAGNOSTICS

(PRICE ESTIMATE)

$80 $140 1.0 - Same cost for homes

going down to 2 pCi/L

POSTMITIGATION $70 $280 Multiply by 1.0 for easy homes

and 1.5 for hard homes going

down to 2 pCi/L

*Note that simple ventilation and crawlspace depressurization is always considered easy to install and heat recovery is always

considered hard to install.

"Homes between 2 and 4 pCilL that reduce to 2 pCilL are assumed to have the same costs as homes above 4 pCilL reducing down

to 4 pCilL (I.e., the multiplier is 1.0).

Appendix F Page F-B
EXHIBIT F-4

ANNUAL OPERATING COSTS FOR RADON MITIGATION SYSTEMS

All Foundations

SEALING/PLUGGING COSTS (FOR BIENNIAL TESTING)

FOR HOMES TO REACH 4 OR 2 pCi/L $35 (or $18 per year)

FOR HOMES INITIALLY ABOVE 4 pCi/L

Basement &

Slab-on-grade Crawlspace

ACTIVE SUBSLAB DEPRESSURIZATION

FOR HOMES AT 4 PCilL: $110 $110

FOR HOMES AT 2 PCi/L: 110 110

(Includes annual testing, energy penalty, and fan electricity)

SIMPLE VENTILATION

FOR HOMES AT 4 PCilL: $335 $120

FOR HOMES AT 2 PCi/L: 670 120

(Includes annual testing, energy penalty, and fan electricity)

DEPRESSURIZATION

FOR HOMES AT 4 PCi/L: - $185

FOR HOMES AT 2 PCi/L: - 185

(Includes annual testing, energy penalty, and fan electricity)

HEAT RECOVERY VENTILATION

FOR HOMES AT 4 PCilL: $240 -

FOR HOMES AT 2 PCilL: 480 -

(Includes annual testing, energy penalty, and fan electricity)

FOR HOMES BETWEEN 2 AND 4 pCi/L REACHING TARGET LEVEL OF 2 pCi/L

Assumed that costs are the same as homes above 4 pCi/L reaching 4 pCi/L target level (Le., multiplier of 1.0)

Note: Operating costs are assumed constant across homes with different source strengths (i.e., initial radon levels) and degree of difficulty to fix.

Appendix F Page F-9
EXHIBIT F-5

REPAIR COSTS FOR COMPONENTS OF RADON MITIGATION SYSTEMS

REDUCING HOMES ABOVE 4 pCi/L DOWN TO ALTERNATIVE TARGET LEVELS

FOR HOMES ACHIEVING 4 pCi/L

ACTIVE SUBSLAB DEPRESSURIZATION:

SUBMEMBRANE DEPRESSURIZATION IN CRAWLSPACE:

SEALING:

SIMPLE VENTILATION:

HEAT RECOVERY VENTILATION:

REPLACING FANS EVERY 10 YEARS

AT A COST OF $150 EACH TIME

WARNING DEVICE FAILURE AT YEAR 37: $95

1/2 INSTALLATION (EASY) AT YEAR 37

WARNING DEVICE FAILURE AT YEAR 37: $95

RESEALING EVERY 5 YEARS AT

40% OF INSTALLATION COST

REPLACING FANS EVERY 10 YEARS FOR $230

DOUBLING THE COST OF ASD ABOVE

(SYSTEMS USETWO FANS)

FOR HOMES ACHIEVING 2 pCi/L

REPLACEMENT COST MULTIPLIERS FOR HOMES ACHIEVING 2 pCi/L LEVELS

(MULTIPLY THEM AGAINST ABOVE COSTS OF GETTING HOMES DOWN TO A TARGET LEVEL OF 4 pCill)

ACTIVE SUBSLAB DEPRESSURIZATION - EASY:

ACTIVE SUBSLAB DEPRESSURIATION - HARD:

SEALING/PLUGGING:

SIMPLE VENTILATION (NON-CRAWLSPACE):

HEAT RECOVERY VENTILATION:

CRAWLSPACE DEPRESSURIZATION:

CRAWLSPACE SIMPLE VENTILATION (Only 2-4 Range):

FOR HOMES BETWEEN 2 TO 4 pCi/L ACHIEVING· 2 pCi/L

COSTS ARE THE SAME AS HOMES FROM 4 TO 8 pCi/L REACHING 4 pCi/L

(Le.• the multiplier is 1.0)

1.00

1.25

1.50

2.00

1.75

1.00

1.00

Note: Replacement costs are assumed constant across homes with different source strengths (Le.• initial radon levels) and degrees of difficulty to fix.

Appendix F Page F-10
EXHIBIT F-6

MITIGATION TECHNOLOGY USE BY BUILDING FOUNDATION TYPE,

SOURCE STRENGTH, AND DEGREE OF DIFFICULTY TO FIX

DIFFICUL1Y

BASEMENT

ACTIVE SUBSLAB DEPRESSURIZATION EASY 65% 65% 500

Al 45%

HARD 35% 30% 20% 15%

SEALING/PLUGGING EASY 0% 0% 10% 15%

HARD 0% 0% 5% 5%

SIMPLE VENTILATION (EASY) 0% 0% 10% 20%

HEAT RECOVERY VENTILATION (HARD) 0% 5% 5% 0%

SLAB-ON-GRADE

ACTIVE SUBSLAB DEPRESSURIZATION EASY 65% 65% 60% 60%

HARD 35% 35% 30% 30%

SEALING/PLUGGING EASY 0% 0% 5°Al 5%

HARD 0% 0% 0% 0%

SIMPLE VENTILATION (EASY) 0% 0% 5% 5%

HEAT RECOVERY VENTILATION (HARD) 0% 0% 0% 0%

CRAWLSPACE

ACTIVE SUBMEMBRANE DEPRESSURIZATION EASY 55% 55% 55% 35%

HARD 35% 35% 300Al 15%

ISOLATION EASY 0% 0% 5% 5%

HARD 0% 0% 0% 10%

DEPRESSURIZAT!ON (EASY) 10% 10% 10% 10%

SIMPLE VENTILATION (EASY) 0% 0% 0% 25%

Note: Technologies with less than 2.5% usage were given 0%; all %'s rounded to nearest 5%.

Appendix F Page F-ll
EXHIBIT F-7

SAMPLE MODEL OUTPUT

RADON MITIGATION SYSTEM COSTS BY PICOCURIE/UTER RANGE

(PRESENT VALUE 1991$)

REDUCING HOMES

TO 2pCi/L

DIFFICULTY

TO FIX

BASEMENT

ACTIVE SUBSLAB DEPRESSURIZATION

SEALING/PLUGGING

31MPLE VENTILATION

HEAT RECOVERY VENTILATION

SLAB-ON-GRADE

ACTIVE SUBSLAB DEPRESSURIZATION

SEALING/PLUGGING

SIMPLE VENTILATION

HEAT RECOVERY VENTILATION

CRAWLSPACE

ACTIVE SUBSLAB DEPRESSURIZATION

ISOLATION

DEPRESSURIZATION

SIMPLE VENTILATION

EASY $4,971 $4,971 $4,971 $4,971

HARD 6,377 6,127 6,127 5,521

EASY 0 0 3,078 2,280

HARD 0 0 14,249 9,717

0 0 21,091 10,620

0 19,840 19,840 0

EASY $5,171 $5,171 $5,171 $5,171

HARD 6,627 6,502 6,502 5,821

EASY 0 0 3,557 2,599

HARD 0 0 0 0

0 0 21,091 10,620

0 0 0 0

EASY $5,509 $5,509 $5,509 $5,509

HARD 6,862 6,862 6,862 6,109

EASY 0 0 3,078 2,280

HARD 0 0 0 4,925

6,640 6,640 6,640 6,640

0 0 0 4,539

EXHIBIT F-8

DISTRIBUTION OF HOMES INITIALLY TESTING ABOVE SELECTED ACTION LEVELS

AND WEIGHTED AVERAGE COSTS OF MITIGATION

DISTRIBUTION OF HOMES ABOVE THE ACTION LEVEL IN pCi/L' WEIGHTED AVERAGE COST (1991$)

ACTION LEVEL >20 8-20 4-8 2-4 TOTAL UPFRONT LIFETIME

2 pCilL 0.0156 0.1258 0.3349 0.5237 1.00 $1,366 $6,126

3 pCi/L 0.0257 0.2073 0.5047 0.2623 1.00 1,442 6,359

4 pCi/L 0.0390 0.3119 0.6491 0.0000 1.00 1,520 6,566

•Rows may not sum due to rounding.

Appendix F PageF-12
APPENDIX G

SENSITIVITY ANALYSIS OF THE

COST-EFFECTIVENESS OF THE REVISED CITIZEN'S GUIDE

This appendix presents the results of a sensitivity analysis of the most significant parameters

used in the cost-effectiveness analysis in Chapter 5. It only examines the option that EPA has

decided to adopt in the revised Citizen's Guide. which recommends that the public fix all homes with

radon levels above 4 pCilL. Exhibit G-l shows the results of the analysis for this option or Base

Case. To facilitate evaluation of the sensitivity of the cost-effectiveness results to the assumptions

that were used for the most critical parameters. the base case results appear at the top of the exhibit.

Each major parameter that EPA used was analyzed independently with regard to the relevant

range of values it potentially could have. All the other values remained as they were in the base case

(i.e.. were held constant) while each parameter was examined. In the base case. the critical

assumptions were:

• radon's risk factor is equal Lo EPA's central estimate;

• 100 percent of the public will follow EPA's testing and mitigation advice;

• 91 percent of the public will conduct a short-term follow-up test. and the rest

will conduct a long-term follow-up test;

• the time period of analysis is 74 years;

• on average. all homes installing radon mitigation systems will reduce radon

levels to 2 pCiIL;

• the radon testing policy covers all single family homes. multi-unit and group

quarters below the third tloor. and mobile homes on permanent foundations;

• the social discount rate 1 is 3 percent;

• mitigation systems have an average present value cost of $6.566 (about 25

percent of the total expenses are initial costs and about 75 percent of the

costs are operating.and maintenance (O&M) costs); and

• smoking habits will continue unchanged.

The following assumptions were analyzed in the sensitivity analysis.

• Risk factor - Used EPA's lower and upper bound estimates of the radon risk

factor. (See Chapter 2 for values used.)

IThc opportunity cost of money used by homeowners to test, fi-x, and operate their homes.

Appendix G Page G-l
Appendix G

•

•

•

•

•

•

•

•

•

Public Response rates - Examined changes in the expected level of radon

testing and the expected level of mitigation that would occur after testing.

Testing choices - Analyzed the public's use of a long-term follow-up test

(Option A) in all cases or use of a short-term follow-up test (Option B) in all

cases. EPA recommends in the 1992 Guide that the public use either test.

Time period of analysis - Examined shorter time periods for the analysis that

reflect other relevant time periods EPA could have considered. Five years

represents the lowest available estimate of how often homes are sold on

average. Thirty years is the life of a typical mortgage.

Effectiveness of svstems - Selected a level of 3 pCiIL and 1 pCiIL as

alternatives to EPA's assumption that radon mitigation will attain an annual

average reduction to 2 pCiIL. Alternatively, it was assumed that homes

between 1 and 2 pCiIL that have false positive results could get down to 1

pCiIL and homes above 2 pCiIL would get down to that level. In a

subsequent run, it was assumed that homes with false positives between 1 and

2 pCiIL could get down to 1 pCi/L and homes between 0 and 1 pCiIL could

reduce their radon levels by 50 percent if mitigation systems are installed

while homes above 2 pCiIL are still reduced down to 2 pCiIL.

Coverage of testing policv - Excluded from consideration' all hQusing units that

were not single family homes. Single family homes were assumed to average

2.8 residents per unit as opposed to 2 residents per home in other types of

housing units.

Discount rate - Examined other discount rates that have been used by the

federal governmenC in preparing cost analyses.

Initial mitigation svstem costs - Varied by 50 percent the upfront costs of

installing radon mitigation systems (including the costs of diagnosis,

installation, and post mitigation follow-up).

Mitigation O&M cost - Varied by 30 percent the costs of operating and

repairing radon mitigation systems over their entire lives.

Smoking Habit Changes - Analyzed two types of changes in smoking patterns.

First, EPA examined changes in habits that reduced the level of current

smokers (by 20 to 50 percent) and assumed that this share of people entered

the "former smoker" category. Second, EPA analyzed changes in smoking

habits that altered the distribution of "current smokers" and "never smokers."

In this case, assumed that 20 to 50 percent of today's current smokers are

instead persons who have never smoked.

Page G-2
EXHIBIT "G-l

SENSITIVITY ANALYSIS OF THE

COST-EFFECTIVENESS OF THE REVISED CITIZEN'S GUIDE

Cost Per

Annual Annualized Cost Life Saved

Case Lives Saved (Million 1991$) (Thousand 1991$)

Ii rHc"; ...''''''> --> " : ......:

...... :....,. ::::.::::::::::::

RISK FACTOR

EPA Lower Bound Risk Factor 1,400 1,500 1,070

EPA Upper Bound Risk Factor 5,900 1,500 260

PUBLIC RESPONSE RATE

50% Testingl100% Mitigation 1,120 750 670

10% Testingl100% Mitigation 220 . 150 670

100% Testing/25% Mitigation 560 440 800

100% Testing/1O% Mitigation 220 230 1,040

TESTIN(; CHOICES

100% Option A 2,160 930 430

100% Option B 2,240 1,560 700

TIME PERIOD OF ANALYSIS

5 Years 2,230 3,930 1,760

30 Years 2,230 1,730 780

EFFECTNENESS OF SYSTEMS

Average Reduction to 3 pCiIL 1,710 1,500 880

Average Reduction to 1 pCi/L 3,000 1,500 490

Homes Between 1 and 2 Can Reduce to 1 pCiIL 2,270 1,500 660

Homes Between 1 and 2 Can Reduce to 1 pCiIL 2,280 1,500 660

and Homes Below lean Reduce by 50%

COVERAGE OF TESTING POLICY

Single-Family Homes Only 2,120 1,240 590

ASSUMED DISCOUNT RATE

0% DiscQunt Rate 2,230 1,240 560

5% Discohnt Ratc 2,230 1,730 780

7% Discount Rate 2,230 1,980 890

10% Discount Rate 2,230 2,360 1,060

INITIAL MITIGATION SYSTEM COSTS

50% Cost Reduction 2,230 1,340 600

50% Cost Increase 2,230 1,670 750

MITIGATION SYSTEM O&M COSTS

30% Cost Reduction 2,230 1,180 530

30% Cost Increase 2,230 1,830 820

DIFFERENCES IN SMOKING HABITS

20% Current Smokers Quit 2,060 1,500 730

50% Current Smokers Quit 1,790 1,500 840

20% of Current Smokers Never Smoked 1,930 1,500 780

50% of Current Smokers Never Smoked 1,490 1,500 1,010

Appendix G Page G-3
APPENDIXH

COST-EFFECTIVENESS OF RADON ACTION

LEVELS GREATER THAN 4 pCi/L

EPA initially examined five different action levels for the revised Citizen's Guide. It quickly

became apparent that the higher action levels did not reduce nearly as much of the risk from radon

as did the lower action levels. Also, the· lower action levels were found to be incrementally costeffective. Reducing radon levels in the additional homes covered by lower action levels appeared to

be a good risk reduction purchase for the public to make if practical programs for doing so could be

offered.

Exhibit H-l provides a summary of the results of EPA's analysis of action levels greater than

and lower than 4 pCilL. The same approach that is explained in Chapter 5 and supporting

appendices was used to provide these results. For the action levels of 8 and 20 pCilL, EPA estimates

that 2.1 million homes and 0.2 million homes, respectively, would be mitigated if a 100 percent public

response rate were obtained. This compares with 6.4 million homes that would be mitigated when

the action level is 4 pCiIL.

EXHIBIT H-l

COST PER LIFE SAVED

UNDER ALTERNATIVE TESTING AND MITIGATION PROGRAMS

Average Cost Incremental Cost

Number of Lives Annualized Cost per Life Saved per Life Saved

Action Level Saved Annually (1000s of 1991$) (1000s of 1991$) (1000s of 1991$)

2 pCiIL 3,100 3,421,000 $1,100 $2,400

3 pCi/L 2,600 2,181,000 800 1,700

4 pCi/L 2,200 1,504,000 700 900

8 pCilL 1,100 501,000 400 400

20 pCilL 220 116,000 500 500W

Based on assumption that "no action" was the alternative EPA had to this action level.

Note: The central estimate of the radon risk factor is used in this analysis, rather than the upper bound risk estimate.

The upper bound estimate would have increased all the risk estimates by about 2.5 times and reduced the costeffectiveness estimates by about 60 percent.

Appendix H Page H-I

Ot:t'A

United States

Environmental Protection Agency

(ANR-464)

Washington, DC 20460

Official Business

Penalty for Private Use

$300

EPA/400-R-92-011

May 1992