United States Air and Energy Engineering
Environmental Protection Research Laboratory
Agency Research Triangle Park NC 27711
April 1991
Research and Development
«>EPA The 1991 International
Symposium on Radon
and Radon Reduction
Technology:
Preprints - Additional Papers
Sessions I - X
April 2-5, 1991
Adam's Mark Hotel
Philadelphia, Pennsylvania
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The 1991 International Symposium on Radon
and Radon Reduction Technology
Additional Papers
Table of Contents
Opening Session Paper
Comparative Dosimetry of Radon in Mines and Homes: An Overview
of The NAS Report
Jonathan M. Samet, University of New Mexico Medical Center 0-1
Session I Government Programs and Policies Relating to Radon
The Need for Coordinated International Assessment of the Radon
Problem - The IAEA Approach
Frederick Steinhausler, International Atomic Energy,
Austria 1-1
Session I Posters
EPA Radon Policy and Its Effects on the Private Industry
David Saum and Marc Messing, INFILTEC IP-2
Session II. Radon-Related Health Studies
Review of Radon Risk & Lung Cancer
Jonathan M. Samet, University of New Mexico and
Richard Hornung, NIOSH II-3
Estimating Levels of Radon from Polonium-210 in Glass
Hans Vanmarcke, Belgium II-6
Session III Panel: Detection of Radon Measurement Tampering
Guidelines for Radon/Radon Decay Product Testing in Real
EBtate Transactions of Residential Dwellings
William P. Brodhead, WPB Enterprises III-ll
Session XII Posters
Unit Ventilator Operation and Radon Concentrations in a
Pennsylvania School
William P. Brodhead, WPB Enterprises IIIP-6
Session IVi Radon Reduction Methods
Pressure Field Extension Using a Pressure Washer,
Bill Brodhead, WPB Enterprises IV-4
Session XV Posters
A Laboratory Test of The Effects of Various Raincaps on
Sub-slab Depressurization Systems
Mike Clarkin, Camroden Associates IVP-3
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Session V: Radon Entry Dynamics
A Modeling Examination of Parameters Affecting Radon and Soil
Gas Entry Into Florida-Style Slab-on-Grade Houses
R. G. Sextro, Lawrence Berkeley Laboratory V-l
Radon Dymanics in Swedish Dwellings: A Status Report
Lynn M. Hubbard, Swedish Radiation Protection Institute V-4
Session VII: State Programs and Policies Relating to Radon
New Jersey Program
Jill A. Lapoti, NJ Department of Environmental Protection VII-4
Session VIII: Radon Prevention in New Construction
Radon Reduction in New Construction: Double-Barrier Approach
C. Kunz, NY Department of Health VIII-3
Session IX: Radon Occurrence in the Natural Environment
Technological Enhancement of Radon Daughter Exposures Due
to Non-Nuclear Energy Activities
J. Kovac, University of Zagreb, Yugoslavia IX-4
Session Z: Radon in Schools and Large Buildings
Extended Heating, Ventilating and Air Conditioning Diagnostics
in Schools in Maine
Terry Brennan, Camroden Associates X-3
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Opening Session Paper
COMPARATIVE DOSIMETRY OF RADON
IN MINES AND HOMES: AN OVERVIEW
OF THE NAS REPORT
by: Jonathan M. Samet, M.D.
Department of Medicine,
and New Mexico Tumor Registry
University of New Mexico Medical Center
Albuquerque, NM 87131
ABSTRACT
The findings of the recent report by a National Academy of
Science* panel on radon dosimetry are reviewed. The committee was
charged with comparing exposure-dose relations for the circumstances of
exposures in mines and homes. The community fl.rst obtained data on the
various parameters included in dosimetric lung models and then selected
values that it Judged to be best supported by the available evidence.
Dosimetric modeling was used to calculate the ratio of exposure to radon
progeny to dose of alpha energy delivered to tArget cells for various
scenarios. The committee's modeling shows that exposure to radon
progeny in homes delivers a somewhat lower dose co target cells Chan
exposure In mines; this pattern was found for infants, children, men,
and women.
The work described In this paper was not funded by the U.S.
Environmental Protection Agency end therefore the contents do not
necessarily reflecc the views of the Agency and no official endorsement
should be lnferrsd.
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INTRODUCTION
Radon, an inert gas, is a naturally occurring decay product of
radiua*226, the fifth daughter of uranium-238. Radon decays with a
half-life of 3.82 day* into a series of solid, shore-lived progeny; two
of these progeny, polonium-218 and polonium-214, emit alpha particles.
When radon progeny are inhaled and these alpha emissions occur within
the lungs, the cells lining the airways may be injured and damage to the
genetic material of th« cells may lead to the development of cancer.
Radon has been linked to excess cases of lung cancer in
underground miners since the early decades of the twentieth century.
Epidemiologic evidence on radon and lung cancer, as well as other
diseases is now available from about 20 different groups of underground
miners <1,2). Many of these studies include information on the miners'
exposure to radon progeny and provide estimates of the quantitative
relation between exposure to progeny and lung cancer risk (2,3); the
range of excess relative risk coefficients, describing the Increment In
risk per unit of exposure is remarkably narrow in view of the differing
methodologies of these studies (2).
As Information on air quality in indoor environments was collected
during the last 20 years, It quickly became evident that radon is
ubiquitous indoors and that concentrations vary widely and may be as
high as levels in underground mines in some homes. The well-documented
and causal association of radon with lung cancer in underground miners
appropriately raised concern that radon exposure might also cause lung
cancer in the general population. The risk of Indoor radon has been
primarily assessed by using risk assessment approaches that extend the
risks found In the studies of miners to the general population. Risk
models that can be used for this purpose have been developed by
committees of the National Council on Radiation Protection and
Measurements (NCR?) (4), the International Commission on Radiological
Protection (5) (1987)! and the National Academy of Sciences (Biological
Effects of Ionizing Radiation (BEIR) IV Alpha Committee) (1).
Extrapolation of Che lung cancer risks in underground miners to
the general population is subject to uncertainties related to the
differences between the physical environments of homes and mines, the
circumstances and temporal patterns of exposure in the two environments,
and potentially significant biological differences between miners and
the general population (Table 1). A number of these factors may affect
the relation between exposure to radon progeny and the dose of
alpha-particle energy delivered to target cells in the tracheobronchial
epithelium; these factors Include the activity-aerosol size distribution
of the progeny, the ventilation pattern of the exposed person, the
morphometry of the lung, the pattern of deposition and the rate of
clearance of deposited progeny, And the thickness of the mucous layer
lining the airways.
The activity-aerosol size distribution refers to the physical size
distribution of the particles containing the alpha activity. The term
"unattached fraction" has historically been applied to progeny existing
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as ions, molecules, or small clusters; Che "Attached fraction"
designates progeny attached to ambient particles (6). Using newer
methods for characterizing activity-aerosol size distributions, the
unattached fraction has bean Identified as ultrafine particles in the
size range of 0,5 to 3.0 nm (6). Typically, mines have higher aerosol
concentrations than homes and the unattached fraction would be expected
co be higher in homes than in mines. Because of differing sources of
particles in the two environments, aerosol size distributions could also
plausibly differ between homes and mines.
The physical work involved in underground mining would be expected
to increase the amount of air inhaled in comparison with the generally
sedentary activities of time spent at home. The greater minute
ventilation of miners would result in a higher proportion of the Inhaled
air passing through the oral route, in comparison with ventilation
during typical activities in residences. The physical characteristics
of the lungs of underground miners, almost all adult males, differ
significantly from those of infants, children and thickness of the
epithelial layer could also plausibly differ, comparing miners with the
general population, because of the chronic Irritation by dust and fumes
in the mines.
Methods are available for characterizing the effects of these
factors on the relation between exposure to radon progeny and the dose
of alpha energy delivered to target cells In the respiratory tract.
Using models of the respiratory tract, the dose to target cells in the
respiratory epithelium can be estimated for the circumstances of
exposure In the mining and indoor environments. One of the
recommendations of the 1968 BEIR IV Report (1) was that "Further studies
of dosimetric modeling in the indoor environment and in mines are
necessary to determine the comparability of risks per WLM [working level
month] In domestic environments and underground mines". The BEIR IV
Report had included a qualitative assessment of the dosimetry of progeny
in homes and in mines, but formal modeling was not carried out.
Consequently, the U.S. Environmental Protection Agency asked the
National Research Council to conduct a study addressing the comparative
dosimetry of radon progeny in homes and in mines. This paper reviews
the findings of the recently published report of the committee (Panel on
Dosimetric Assumptions Affecting the Application of Radon Risk
Estimates). The panel was constituted with the broad expertise,
covering radon measurement and aerosol physics, dosimetry, lung biology,
epidemiology, pathology, and risk assessment, needed for this task.
THE COMMITTEE'S APPROACH
To address the charge of undertaking further dosimetric modeling,
the committee obtained data on the various parameters Included in
dosimetric lung models that contributed to uncertainty in assessing the
risk of Indoor radon. The committee not only reviewed the literature,
but obtained recent and unpublished information from several
investigators involved in relevant research. After completing this
review, the committee selected values for parameters in dosimetric
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model* that It Judged to be best supported by the available evidence.
The committee then utilized a dosimetric model, developed In part by the
Task Group of the International Commission for Radiological Protection,
to compare exposure-dose relations for exposure to radon progeny in
homes and In mines. While the report provides the exposure-dose
figures, the committee expressed Its principal findings as a ratio,
termed K in the BEIR IV report (1). K, a unltless measure, represents
the quotient of the dose of alpha energy delivered per unit of exposure
in a hone to the dose per unit exposure for a male miner exposed In a
mine. If the K factor exceeds unity, the delivered dose per unit
exposure 1s greater Indoors whereas if it is less than unity, the
delivered dose per unit exposure is less Indoors.
Factors other than lung dosimetry of radon progeny also introduce
uncertainty in extrapolating risks from the studies of underground
miners to the general population. The committee briefly reviewed the
evidence on cigarette smoking, tissue damage, age at exposure, sex, and
exposure pattern. These sources of uncertainty were considered In a
qualitative rather than a quantitative fashion.
THE COMMITTEE'S FINDINGS
The committee selected several different sets of exposure
conditions in hones and in mines (Table 2,3). The mining environment
includes the areas of active mining, the haulage drifts, and less active
and dusty areas such as lunch rooms. In some analyses, the values for
active mining and haulage ways were averaged to represent typical
conditions. Separate mlcroenvlronments considered in the home included
the living room and the bedroom. Parameters for the living room and the
bedroom were averaged to represent a typical scenario for the home. The
effects of cooking and cigarette smoking on radon progeny aerosol
characteristics were also considered. While the contrast between the
home and mining environments was somewhat variable across the scenarios,
homes were characterized as having greater unattached fractions and
smaller particles. Higher average minute volumes were assumed for the
mining environment (Table 2,3).
The committee also examined uncertainties associated with other
assumptions in the dosimetric model. Doses to basal and secretory cells
in the tracheobronchial epithelium were calculated separately, because
all types of cells with the potential to divide were considered to be
potential progenitor cells for lung cancer. The committee also compared
the consequences of considering: lobar and segmental bronchi rather than
all bronchi as the target; radon progeny as insoluble or partially
soluble in the epithelium; of breathing through the oral or nasal route
exclusively; of varying the thickness of the mucus lining the epithelium
and the rate of mucociliary clearance; and cellular hyperplasia leading
to thickening or injury causing thinning of the epithelium.
Across the wide range of exposure conditions and exposed persons
considered by the committee, most values of K were below unity (Table
4), For both secretory and basal cells, K values indicated lesser doses
of alpha energy per unit exposure, comparing exposures of Infants,
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children, aen and women in homes with exposures of male miners
underground. While the highest values of K were calculated for
children, the values for children did not exceed unity, suggesting that
children exposed to radon progeny are not at greater risk for lung
cancer on * dosimetric basis.
The committee explored the sensitivity of the K factors to
underlying assumptions in the dosimetric model. The general pattern of
the findings was comparable for secretory and basal cells. The K
factors remained below unity regardless of whether the radon progeny
were assumed to be insoluble or partially soluble in the epithelium.
The K factor was also not changed substantially with the assumption that
lobar and segmental bronchi, rather than *11 bronchi, are the target.
Assumptions regarding breathing route also had little impact, After the
committee had completed Its principal analysis, new data became
available suggesting that recent higher values for nasal deposition
reported by Cheng et al. (7) might be preferable to lower values from
the 1969 report of George and Breslin (8); other new evidence suggested
that a value of 0.15 um should be used for aerosol size in the haulage
drifts. Inclusion of these two modifications of the committee's
preferred parameter values in the dosimetric model reduced the values of
K by about 20 percent.
The committee did not attempt to reach quantitative conclusions
concerning sources of uncertainty not directly addressed by the
dosimetric modeling. It noted the paucity of data on such factors as
cigarette smoking, age at exposure and particularly the effect of
exposure during childhood, and exposure pattern. The evidence on these
factors received detailed review in the BEIR IV raport (1) and the
present committee did not reach any new conclusions on these sources of
uncertainty. The committee also commented on the potential effects of
the miners' exposures to dust and fumes while underground. Increased
cell turnover associated with these exposures may have increased the
risk of radon exposure for the miners.
SUMMARY
The Panel on Dosimetric Assumptions Affecting the Application of
Radon Risk Estimates comprehensively reviewed the comparative dosimetry
of radon progeny in homes and in mines. The committee's modeling shows
that exposure to radon progeny In homes delivers a somewhat lower dose
to target cells than exposure in mines; this pattern was found for
Infants, children, men, and women. This finding was not sensitive to
specific underlying assumptions in the committee's modeling. Assuming
that cancer risk is proportional to dose of alpha energy delivered by
radon progeny, the committee's analyses suggests that direct
extrapolation of risks from the mining to the home environment may
overestimate the numbers o£ radon•caused cancers.
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REFERENCES
1. National Research Council (NRC). 1988. Health Risks of Radon and
Other Internally Deposited Alpha•Emitters . BEIR IV. Committee on
the Biological Effects of Ionising Radiation. Washington, D.C.:
National Academy Press.
2. Samet, J.M. Radon and lung cancer. J Natl Cancer Inst. 81:
745-757, 1989.
3. Lubin, J.H. Models for the analysis of radon-exposed populations.
Yale J Biol Med. 61: 195-214m 1988.
4. National Council on Radiation Protection and Measurements (NCKP).
1984b. Evaluation of Occupational and Environmental Exposure co
Radon and Radon Daughters in the United States. NCRP Report 78.
fiethesda, MD: National Council on Radiation Protection and
Measurements.
5. International Commission on Radiological Protection (ICRP). 1987.
Lung Cancer Risk from Indoor Exposures to Radon Daughters. ICRP
Publ. No. 50. Oxford: Pergsmon Press,
6. National Research Council. Comparative dosimetry of radon in mines
and homes, Panel on dosimetric assumptions affecting the
application of radon risk estimates. National Academy Press,
Washington, D.C., 1991.
7. George, A.C. and Breslin, A.J. Deposition of radon daughters in
humans exposed to uranium mine atmospheres. Health Phys. 17:
115-124, 1969.
8. Cheng, Y.S., Swift, D.L., Su, Y.F. and Yeh, H.C. Deposition of
radon progeny in human head airways. In: Inhalation Toxicology
Research Institute Annual Report 1988-89. Lovelace Biomedical and
Environmental Research Institute. Albuquerque, NM, 1989. LMF-126.
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TABLE 1. POTENTIALLY IMPORTANT DIFFERENCES BETWEEN EXPOSURE TO
RADON IN THE MINING AND HOME ENVIRONMENTS
Physical Factors
Aerosol characteristics: Greater concentrations in mines;
differing size distributions
Attached/unattached fractions: Greater unattached fraction in
homes
Equilibrium of radon/decay products: Highly variable in homes and
mines
Activity Factor*
Amount of ventilation: Probably greater for working miners than
for persons indoors
Pattern of ventilation: Patterns of oral/nasal breathing not
characterized, but mining possibly associated with greater oral
breathing
Biological Factory
Age: Miners have been exposed during adulthood; entire spectrum
of ages exposed indoors
Gender: Miners studied have been exclusively male; both sexes
exposed Indoors
Exposure pattern; Miners exposed for variable intervals during
adulthood; exposure is lifelong for the population
Cigarette smoking: The majority of the miners studied have been
smokers; only a minority of U.S. adults are currently smokers
*Taken from Table 1-2 in reference (6).
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TABLE 2. ASSUMPTIONS FOR EXPOSURE SCENARIOS ASSUMED
FOR MINES AND HOMES
SUMMARY OF RADON PROGENY AEROSOL CHARACTERISTICS ASSUMED TO
REPRESENT EXPOSURE CONDITIONS IN MINES AND HOMES
Exposure Scenario f_ AMD of Room AMD of Aerosol
Aerosol (urn) in respiratory
trace (urn)
Mine
Mining 0.005 0.2S 0,5
Haulage drifts 0.03 0.25 0.5
Lunch room 0.08 0.25 0.5
UyIpk R°9W
Normal 0.08 0.15 0.3
Smoker • average 0.03 0.25 0.5
- during smoking 0.01 0.25 0.5
Cooking/vacuuming 0.05 0.02/0.15* 0.02/0.3
(15*/80%) (l5%/80%)
Beflggpn
Normal 0.08 0,15 0.3
High 0.16 0.15 0.3
*Based on Tables 3-1 and 3-2 in reference 6.
*The radon progeny aerosol produced by cooking/vacuuming has
three size nodes; 5% of potential alpha energy is unattached,
15% ha* an AMD of 0.02 n, and 80% has an AMD of 0.15 um.
The 0.02 y® AMD mode Is hydrophobic and does not Increase in
size within th« respiratory trace.
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TABLE 3. ASSUMPTIONS FOR EXPOSURE SCENARIOS ASSUMED
FOR MINES AND HOMES
LEVELS OP PHYSICAL EXERTION AND AVERAGE MINUTE VOLUMES
ASSUMED FOR UNDERGROUND MINERS AND FOR ADULTS IN THE HOME
Exposure Scenario Level of Exertion Average $E
(liters/coin)
Man Woman
Underground Mine
Mining
Haulage way
Lunch room
25% heavy work/75% light work
100% light work
50% light work/50% rest
Home-Living Room
Normal and smoker 50% light work/50% rest
Cooking/vacuuming 75% light work/25% rest
Home-Bedroon
Normal and high 100% sleep
31
25
17
17
21
7.5
14
17
5.3
*Based on Tables 3*1 and 3-2 in reference 6.
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TABLE 4. SUMMARY OF K FACTORS FOR BRONCHIAL DOSE CALCULATED FOR
NORMAL PEOPLE IN THE GENERAL ENVIRONMENT RELATIVE
TO HEALTHY UNDERGROUND MINERS
K Factor for Target Cells
« , „ _ Secretory Basal
Subject Category
Infant, age 1 month
0.74
0.64
Child, age 1 year
1.00
0.87
Child, age 5-10 years
0.83
0.72
Female
0.72
0.62
Kale
0.76
0.66
Taken from Table 5-1 in reference 6,
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1-1
THE NEED FOR A COORDINATED
INTERNATIONAL ASSESSMENT OF THE
RADON PROBLEM
F. Steinhausler
International Atomic Energy Agency
Vienna
INTERNATIONAL SYMPOSIUM ON
RADON AND RADON REDUCTION TECHNOLOGY
"A New Decade of Progress"
April 2-5, 1991
Philadelphia, Pennsylvania, USA
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7695t
The Weed for a Coordinated International Assessment
of the Radon Problem
F. Steinhausler
International Atomic Energy Agency
Division of Nuclear Safety
P.O. Box 100, A-1400 Vienna, Austria
1. The radon problem - an issue of growing awareness
Radon is a natural pollutant which has been part of the
human environment through all stages of evolution. However,
the level of Rn-exposure has undergone various "technological
enhancements" from the pre-historic days of taking up a habitat
inside a cave dwelling, to the present day energy-efficient
dwellings with ventilation rates below 0.3 air changes/hour.
As early as in the 1950's and 1960's individual
scientists have emphasized the overriding dose contribution
from radon (Rn) and its short-lived decay products (Rn-d) in
comparison to those doses that the majority of their colleagues
were dealing with at the time, i.e. resulting from the nuclear
fuel cycle or nuclear weapon testing programmes (Hu 56, Po 65).
In the 1970* s and the 1980' s two series of scientific
meetings stressed increasingly the importance of the radon
issue, published in the form of proceedings of the US-DOB
sponsored International Symposium Series "The natural Radiation
Environment", Houston (USA) and of the International Specialist
Meetings held in Pocos de Caldas (Brazil), Bombay (India), Rome
and Capri (Italy). During this period the first large scale
national Rn surveys were conducted and regulatory guidelines
issued in Scandanavia and Canada.
At the international level the Organization for Economic
Cooperation and Development, Nuclear Energy Agency (OECD-NEA,
Paris, France) and the Commission of the European Communities
(CEC, Brussels, Belgium) reviewed all available Rn related
information on metrology and dosimetry in the first half of the
1980's (OE 83, OE 85). Furthermore, CEC-NEA jointly initiated
the International Intercomparison and Intercalibration
Programme (HIP), which has now been taken under the auspices
of the IAEA. The CEC took a leading role in European research
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related to the Natural Radiation Environment (NRE) in general
and in the Rn-issue in particular and supported several
national programmes among its Member States (CE 80). In the
second half of the 1980's the largest national Rn-research and
survey programme so far has been undertaken in the USA (Co89)
under the leadership of the Department of Energy (DOE) and the
Environmental Protection Agency (EPA).
All internationally available information has been
compiled regularly in the UNSCEAR reports. Over the past
thirty years the previously seemingly invariable "constant" of
1 mSv for the average annual effective dose from all NRE
sources was increased to 2.4 mSv (UN 88).
In view of the above 30+ years of evidence it is
difficult to understand the statement made by the Health
Physics Society in 1991, itself a most valuable source for
radon-related data, ... "it was not until recently that it was
realized that the largest radiation exposures received by most
individuals come from the natural sources of radiation,
primarily radon and its radioactive decay products " (HP91).
2. The global dimension of the radon problem
At all times everybody is exposed to radon (Rn) and its
decay products (Rn-d) anywhere on earth. Therefore this topic
warrants a global approach on the research and the regulatory
level. In the following section some of the major
international and national activities in response to the
increasing significance of the Rn-problem are discussed.
2.1. IAEA—CEC coordinated research
In response to the requests from Member States of the
International Atomic Energy Agency (IAEA, Vienna, Austria) and
in recognition of the global concern over the Rn issue the
IAEA, jointly with the CEC, initiated the Coordinated Research
Programme (CRP) on "Radon in the Human Environment". The World
Health Organization (WHO, Geneva, Switzerland) and the
International Cancer Research Agency (IARC, Lyon, France)
agreed to provide logistic support in all areas related to the
assessment of potential health effects. The potential for
US-EPA and US-DOE involvement in Quality Assurance Programmes
and risk assessment studies of this CRP is currently being
explored.
Altogether 111 projects from five continents have been
recommended for a phase-wise inclusion in the CRP. In
addition, 25 CEC-approved projects are part of the CRP.
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The objective of the CRP is to coordinate international
research efforts aimed at the quantification of the impact of
environmental Rn on man. Four areas are emphasized:
a) international intercalibration and intercomparison
of Rn-measurement technology;
b) standardization of large scale Rn-survey
techniques;
c) institutionalised exchange of information on
Rn-levels, dosimetric methods and associated risk
assessment, and mitigation techniques through
Research Coordination Meetings under the auspices
of the IAEA;
d) establishment of an international databank on Rn.
This databank would enable members of the
international scientific community and national
regulatory agencies to obtain structured access to
the results obtained from the multiple large scale
Rn-surveys, which will be performed over the next
five years mainly in the USA, Canada, Africa,
Europe and Asia, Provided that the input data have
fulfilled certain criteria, these data sets can be
used for follow-up research, ranging from
optimisation of technical remedial measures to
improved lung cancer risk assessment. Finally
such a database facilitates the exchange of
scientific and technical know—how from developed
to developing countries.
The implementation of the first phase of the CRP started
in 1990 by awarding 12 Research Contracts and 37 Research
Agreements (Fig. 1). The Becond phase, concerning the
acceptance of the remaining projects, is scheduled for 1992.
The CRP-Oualitv Assurance Programme (QAP) is an
essential element of the CRP (Fig. 2). For this purpose it is
intended to invite the participants in the former OECD-NEA/CEC
International Intercalibration and Intercomparison Programme
(HIP), as they are: ARL (Melbourne, Australia), NRPB (Didcot,
UK), EML (New York, USA) and US-BM (Denver, USA). These
laboratories, well-renowned in Rn metrology, are able to act as
"Reference Centres" for designated "Regional Coordinated
Centres": Ministry of Public Health (Beijing, China P.R.) for
the Asian-Pacific region; Institute of Radiation Protection and
Dosimetry (Rio de Janerio, Brazil) for the South American
region; Ghana Atomic Energy Commission (Legon, Ghana) for the
African region; institute of Atomic Physics (Sofia, Bulgaria)
for the Eastern European region and Middle East; Centre of
Radiation Hygiene (Prague, CSFR) for the remaining European
regions.
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Quality control is maintained by the interchange of
Rn-detectors between Regional Coordination Centres and
Reference Centres. This will involve an initial calibration
and subsequent qualifying tests. The aim of the initial
calibration is the establishment of calibration factors, lower
limit of detection, reproducibility, accurance and linearity of
the detectors used in the CRP. An exposure test regime in a
Rn-chamber will include blanks, low-, medium- and high level
Rn-exposure of the detectors, taking into account different
climatic exposure conditions. The analysing laboratory will be
informed of the actual exposure values. For the qualifying
tests CRP-participants provide detectors to a Reference Centre
as above, but the analysing laboratory is not informed of the
exposure levels prior to the reporting of their results. This
test will be repeated annually. Pre-defined criteria for
passing the test will be used, e.g. the mean value for each
group of exposure category would be within ± 25% of the
calibration exposure (except blanks).
Surveys will be carried out in two stages. In a pilot
Rn-survey all logistic and technical components for the
follow-up large scale Rn-survey are tested. Secondary aims are
the training of survey personnel and the establishment of the
necessary national and regional programme infrastuctures. A
follow-up large scale Rn-survey is aimed at determining yearly
averaged indoor Rn-values using a standardized survey
protocol. Since these surveys are carried out in areas with
largely different climatic and socio-economic characteristics,
it is necessary for the standardized format to be adopted to
the local needs.
Each participant who does not already have an
established integrating Rn-detection system, is provided with:
passive open-faced track-etch detectors (material:
LR 115) for short-term integrating screening
measurements (exposure period: 1 week);
passive electric-based ion chambers (material:
permanently charged Teflon material) and/or
passive track-etch detectors (material: CR-39) for
repeated long-term integrating measurements
(exposure period: 6 months).
In the pilot-type surveys, sites are selected on a
pseudo-random method, based on population distributions, in one
urban and one rural community each. Detectors are distributed
and collected after exposure either by mail or survey teams,
following the guidelines of a standardized experimental
protocol. The large scale-type surveys are population-based,
with statistically chosen sampling of dwellings within each
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Member State. The detailed sampling method is country-specific
and takes into consideration different approaches to
approximate optimal randomization. The preferred method
consists of a questionnaire being mailed to randomly selected
individuals, together with a pre-paid, pre-addressed envelope.
Upon return of the completed questionnaires, detectors are sent
to those interested parties. This approach should improve the
rate of active participation and maximize detector return.
Optionally, the questionnaire can be completed individually by
the survey team at the time of distribution of the detector in
the randomly selected dwelling.
The results of the CRP are planned to be summarized in
1995 in the form of joint IAEA/CEC publications in the IAEA
Safety Series and will include a summary of: a) the practical
implications of the findings of the CRP, with the emphasis on
international guidance on Rn control; and, b) the results of
the nip on Quality Control organized prior to and under this
CRP.
2.2. International research activities
The international research community is currently
carrying out intensive Rn-ralated research. The main
activities involve about 30 European research teams
collaborating within the framework of the CEC Rn-programme (si
91), approximately 50 US-institutions engaged in Federal Rn
activities in the USA and worldwide additionally approximately
100 laboratories among the other IAEA-Member States. In this
section some of the main Rn-related research activities outside
the USA are described (the corresponding contact persons are
listed in the Appendix).
a) Research in detectand analytical methods
Development of a device for continuous Rn-measurements
in water, based on an integrated Rn-deemanation device and
scintillation counter (A-Pi); the use of Po 210-activity on
glass surfaces as an estimator for past Rn indoor exposure
(A-Sa); optimisation of passive/open alpha track etch detectors
for the short and long term estimation of the Potential Alpha
Energy Concentration (PAEC), including thoron (Rn 220)
daughters (A-An1); development of a low-level continuous Rn-
and thoron- PAEC monitor, using o-spectroscopic analysis of
Po 218 Po 214 and Po 212 (A-Ku); optimisation of a low level
environmental thoron monitor, "sing Po 210-deposition on a
surface barrier detector in a high tension field (A—Ke); thoron
detection based on flow-through scintillation cells and
multiple time analysis of recorded pulse events (A-Pa);
simulation of rapidly changing environmental Rn/Rn-d levels
with a walk-in type test facility (A-Sc); optimisation of
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- 6 -
quality assurance programmes for national indoor Rn-surveys
(A-Bo); accuracy tests of integrating Rn-detectors (A-Me).
b) radon dynamics and aerosol science
behaviour of the unattached fraction in underground
environments with variable aerosol concentration (A-Bu); the
effect of mechanical air filtration and electrostatic
precipitators on the unattached fraction and the equilibrium
fraction of Rn-d indoors (A-Ko); sub-micron sized Rn-d particle
size distributions in mines (A-Bol); modelling of atmospheric
diffusion of Rn and thoron, describing the relationship between
atmospheric concentration and the vertical diffusion
coefficient (A-Cu); indoor behaviour of Rn-d in dependence of
aerosol attachment, nuclide desorption from the aerosol and
Rn-d plate-out on surfaces (A-Po); the effects of seasonal
differences on indoor Rn (A-Pa); determination of the Rn and
thoron exhalation rate and its dependence on surface cover and
material temperature (A-Le, A-Al); development of rapid
diagnostic techniques for determining Rn entry rates into
dwellings (A-Ra); in situ-determination of Rn exhalation,
combining time-dependent Rn and Rn-d measurements (A-Al); in
situ-determination of gas permeability in soil with miniature
probes (A-Da); temporal RaA-variability indoors, using
continuous measurements (A-Ni); measurement of Rn-d equilibrium
activity deposited on surfaces by analysis of the spatial
distribution of alpha tracks on CR-39 (A-La); Rn diffusion
characteristics through hydrocarbons for application in oil
exploration (A-Ra^);
c) outdoor studies
airborne surveys in order to correlate outdoor-, indoor
Bn levels and geology (A-Gr); ship-based atmospheric studies on
the Rn- and Rn-d distribution trend over the equatorial Pacific
Ocean (A-Ho); model validation describing the temporal
variation and horizontal distribution of Rn in the atmosphere
(A-Ik); wash-out effects on atmospheric Rn-d (A-Fu); temporal
variation of the specific activity of Rn-d in rainwater (A-Yo);
multi-parameter correlation of the Rn concentration with the
variation of the atmospheric boundary layer (A-Ka); enhancement
of outdoor Rn-levels due to uranium mining (A-Kr); optimisation
of radon potential mapping, using airborne-, ground surveys and
borehole radiometric procedures (A-Ba);
d) indoor studies
influence of fly-ash containing construction materials
on indoor Rn levels (A-St); thoron and thoron decay products
indoors due to building materials (A-Cl); survey of workplaces
with elevated Rn levels (A-Oi); Rn-levels in dwellings built on
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- 7 -
uranium deposits and phosphate rocks (A-Si); identification of
dwellings with high Rn-levels due to wall constructions using
soil (A-Do); atmospheric Rn concentration in underground subway
transport systems (A-An); identification of sources in
dwellings with extremely high Rn-levels situated in former
uranium mining communities (A-Th); thoron decay product
exposure assessment for inhabitants of volcanic tuff-made
dwellings (A-Sc1); correlation of Rn-d levels with the
unattached fraction in houses with anomalous Rn-levels (A-Ro);
Rn-levels in tourist caves, show mines and historical monuments
(A-Ro, A-Hu).
e) dosimetry and risk assessment
microdosimetry of inhaled Rn-d by simulating randomized
energy deposition at different cells (A-Ho); low dose
extrapolation of Rn-related dose-effect curves with a
hypothetical threshold (A-Ci); lung cancer risk assessment
based on case-control studies in normal and coal
brick-dwellings (A-De, A-Wa).
3. International regulatory approaches to radon control -
a mosaic of options
Over the past 25 years the International Commission on
Radiological Protection (ICRP) has drastically changed its
approach to Rn control. In 1966 the ICRP categorically declared
that its dose limitations referred only to exposures from
technical practices that added to the natural background
radiation (IC 66). In 1991, however, the proposed revised
recommendations acknowledge that "....radon in dwellings needs
special attention" (IC 91). For existing dwellings the ICRP
discriminates between the recommendation of a vague "guidance"
for owner-occupied dwellings and an "action level" for rented
properties, without specifying any numerical values. Also the
advice provided on the choice of action level is rather
philosophical, i.e. it should be such that the number of houses
in need of remedial work should not be "unmanagable". From the
view point of the ICRP a recommendation for a "new building" is
not really warranted because the concentration of radon cannot
be determined with confidence until its completion and having
been occupied for about a year. By then it is an existing
dwelling Finally the ICRP admits it is proceeding
"cautiously" and recommends to continue using its
Recommendation no. 39, i.e. an equilibrium equivalent
concentration (EEC) of 200 Bq/n»3 as a "reference level" for
new dwellings. This would result in an effective dose of 12
mSv/yr with the present lung model. However, "revised
recommendations in due course" are already announced.
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- 8 -
The World Health Organization (WHO) recognizes in 1989
that "...radon and its daughter products remain a matter of
concern due to widespread occurrences and the total delivered
dose" (WH 89) . Using a different approach, it accounts for the
extent of mitigation required in the case of existing buildings
(Ah 90): if the annual average EEC exceeds 100 Bq/m3,
remedial actions should only be taken, provided they are simple
to implement. This caveat does not apply if an annual average
of EEC > 400 Bq/m3 is prevailant and then prompt actions
should be taken. WHO recognizes "new buildings" as being a
different situation than already existing dwellings and
recommends that an annual average EEC of 100 Bq/m3 should not
be exceeded.
The Commission of the European Communities (CEC)
recommends to use a dose-related "reference level". If an
effective dose of 20 mSv/y is exceeded, this should be "cause
for consideration" of "simple, but effective" countermeasures
(CE 90). Applying presently available dosimetry this
corresponds to an annual average EEC of 200 Bq/m^ (F = 0.5).
Also the CEC recognizes the difference between existing and new
buildings and recommends in the latter case a "design level" of
10 mSv/yr (= EEC: 100 Bq/m^; F = 0.5). It is emphasized by
the CEC that a) all decisions should be based on annual
averages of Rn or Rn-d, using integrating techniques;
b) adequate Quality Assurance Programmes should be in effect.
In the following two examples for national regulatory
actions are discussed. In Austria the total radiation exposure
indoors resulting from building materials is regulated, i.e.
the sum resulting from external gamma radiation and exhalation
of Rn (ON 88). Different equations apply for single component-
or multiple-compound building materials. The materials are
considered suitable if the resulting effective dose from the
total indoor exposure does not exceed the average national
value of 2 mSv/yr. Contributions from cosmic rays, Rn from
drinking water, etc. are excluded in this recommendation on
building materials.
In 1980 the Swedish government took the lead worldwide
to introduce a system of comprehensive limits and
recommendations for decreasing Rn concentrations in all
dwellings (MB 80). At present a Rn- "action level" of 200
Bq/m3 is used for existing dwellings, provided simple
measures can be taken; otherwise 800 Bq/m3 are recommended.
For new dwellings a Rn- "design level" of 140 Bq/m3 is in
effect. In 1985 Rn has been recognized officially as an urgent
health problem requiring action (SG 85). Therefore, the
government recommended each municipality to take appropriate
measures to ensure via building permit that in new buildings
the average collective exposure to Rn-d and to gamma radiation
is decreased as far as it is practical and economically
reasonable (Fa 90).
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- 9 -
4. Recommendations for a unified approach
Radon represents a multidisciplinary issue on an
international scale. Therefore it appears advantageous to use a
unified approach to its solution. Such an internationally
coordinated approach should address the following areas:
A.1 Research needs
In the following areas further research is needed in
order either to overcome actual lack of data or to improve
existing databases.
a) Source Term Characterisation:
Radon 220 (Thoron, Tn) and its decay products
(particularly ThB) may represent a non-negligible
component of the indoor environment in some areas; more
measurements are needed to characterize occurrence and
dynamics of these nuclides; Rn-related
convective/advective/diffusive/ transport phenomena need
quantification for a variety of environmental boundary
conditions, such as under the influence of
meteorological parameters; interaction of
pressure-driven flow with subsoil; multizone transport
and interzone flow; quantification of Rn-entry into
spaces; Rn/Tn generation and mobility in soil and rocks
as a function of: soil moisture, -porosity, -type,
-depth, weathering; emanation process into gas and
vapour phases dependent on pore space, grain size,
permeability; microdistribution of radium 226 within
grains.
b) Aerosol Sciences:
Chemical and physical characteristics of Rn/Tn and their
decay products, e.g.: formation of cluster ions and
their reaction products; dynamics of Rn-d/Tn-d
interactions with indoor aerosol (size distribution,
diffusion coefficient, recoil phenomena, plateout rate);
Rn-d/Tn-d interaction with other indoor pollutants:
generation rate of free radicals, ions, neutral
products; long-term measurements of unattached fraction
in a variety of environments, including size
distribution studies and humidity effects.
c) Dosimetry:
Microdosimetric calculations to obtain values for the
quality factor and RBE for Rn-d; biological dosimetry
for evaluating prior Rn-d/Tn-d-exposure, using samples
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- 10 -
of bone, teeth, blood, hair, etc; refined dosimetric modelling
for infants, children, sick and older people using actual
morphological and physiological data rather than scaling
factors only; development of species-specific physical models
of different regions in the respiratory tract.
d) Radiobiology
Molecular approach to mechanisms of Rn/Tn-induced injury:
Rn/Tn-in vitro exposure of human cell cultures; biophysical and
biochemical modelling for the identification of cellular
markers for pre-malignant or malignant cells; use of molecular
probes of genes cloned as recombinant DMA molecules to study
Rn/Tn-induced DNA changes; activation of oncogenes;
Cellular approach:
quantification of the changes of parameters indicative for
transformation processes, such as:
anchorage-independent growth, immortalization, growth
enhancement; abnormal expression of growth factors; adaption
studies to ultra-low levels of Rn-d exposure (hormesis); Tn-d
distribution in different organs after inhalation; interaction
of Rn-d/Tn-d smoke and other irritants known to occur indoors
and underground;
A.2 Logistic requirements and aspects of programme design
Over the next few years a large number of Rn-progranunes
will be carried out worldwide. In order to achieve optimal
cost-effectiveness and comparability of results international
coordination is desirable also in the implementation of these
programmes, addressing logistic requirements and programme
design:
a) standardisation of the data collection-methods for
describing the Rn exposure indoors and outdoors in
different types of exposure situations (homes, schools,
offices, factories, public buildings, recreational
areas, health spas, mines) and reflecting the subsequent
use of the data (real estate transaction, design of
mitigation procedures, epidemiological research);
b) definition of minimum criteria to be fulfilled by
quality assurance programmes concerning different
measurement programmes (short-term integration,
long-term integration; measurements of Rn-, Rn-d, thoron
daughters and unattached fraction; Rn determination
methods for soil gas, water, exhalation rates);
c) establishment of an international Rn-databank
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- 11 -
d) harmonization of the international regulatory approach
to risk limitation from Rn-exposure, differentiating
between the residential-use of owner occupied buildings,
rented accomodations, public buildings and work places;
e) provision of information material (graphical,
audio-visual) for specific target groups, such as public
health services, scientific-technical community, real
estate agents, Rn-testing companies and contractors, and
the media. This material should be scientifically sound,
presented but also sufficiently interesting to reach the
target audience. It should assist in obtaining a
positive response from the public, thereby adding to
improved control of the exposure situation.
f) development of durable Rn-mitigation techniques for
different architectural styles and geo-climatic regions,
taking into account the cost-effectiveness of achievable
dose-reductions;
Summarizing it appears advantageous to find an
international agreement on a unified approach to view the
issues of "Radon in indoor air" and related public health risks
from individual and collective exposures in a consistent manner
with risks from other radiation sources but also from all other
contaminants occurring indoors, such as microorganisms,
organics, combustion products and passive cigarette smoke.
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- 12 -
References
(Ah 90) AHMED, J.U, Radon Overview in Natural Environment
and Dwellings, Proc. Int. Conf. High Levels of
Natural Radiation, Ramsar, Iran, 3-7 November 1990
(in press).
(CE 80) Proc. CEC-Seminar on the "Radiological Burden of
Man from Natural Radioactivity in the Countries of
the European Communities", Le Vesinet, Paris,
1979, CEC Publ., Luxembourg (1980).
(CE 90) CEC, Recommendation of the Commission, Doc. no.
90/143/Euratom (1990).
(Co 89) Committee on Indoor Air Quality (CIAQ) Radon Work
Group, Federal Radon Activities Inventory,
US-DOE/EPA Rep. no. DOE/ER-0409, Washington D.C.,
USA (1989).
(Fa 90) FALK, R., Management of the Radon Problem in
Sweden, Proc. First Int. Sem. "Managing the Indoor
Radon Problem", Mol, Belgium (1990).
(HP 91) Health Physics Society (HPS) Position Statement,
Perspectives and Recommendations on Indoor Radon,
The HPS Newsletter, Vol. XIX, No. 1, p. 3 (1991).
(Hu 56) HULTQUIST, B. , Studies on Naturally Occuring
Ionizing Radiations, Kungl. Svenska
Vetenskapsakademiens Handligar, Fjarde Ser. Vol.6,
No. 3 (1956).
XIC 66) ICRP, Recommendations no. 9 (1966).
(IC 91) ICRP, Recommendations of the Commission (1991).
(NB 80) National Board of Health and Welfare, Ordinance
SOSFS (M) 71, Stockholm, Sweden (1980).
(OE 83) 0ECD-NEA Group of Experts, Dosimetry Aspects of
Exposure to Radon and Thoron Daughters, Report
ISBN 92-64-12520-5, Paris, France (1983).
(OE 85) OECD-NEA Group of Experts, Metrology and
Monitoring of Radon, Thoron and their Daughter
Products, Report ISBN 92-64-12767-4, Paris, France
(1985).
(Po 65) POHL, E., Biophysikalische Untersuchungen iiber die
Inkorporation der natiirlichen radioaktiven
Emanationen und deren Zerfallsprodukte,
Sitzungsber. Oesterr. Akad. Wise. II, Vol. 174,
pp. 309 (1965).
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(Si 91) SINNAEVE, J., The European Research Programme and
the Commission of the European Communities, (this
symposium).
(SG 85) Swedish Government, Proposition 1984/85:181,
Stockholm, Sweden (1985).
(UN 88) United Nations Scientific Committee on the Effects
of Atomic Radiation, Sources, Effects and Risks of
Ionizing Radiation, UNSCEAR Report to the General
Assembly (1988).
(Wa 90) WALKINSHAW, D.S., Proc. 5th Int. Conf. on "Indoor
Air Quality and Climate", Toronto, Canada (1990).
(WH 89) WHO, Report on the Twelfth Intersecretarial
Meeting on Air Pollution Problems in Europe,
Geneva, Doc. no. EUR/ICP/CEH 199 (1989).
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Appendix
(A-Al) ALDENKAMP, P.J., University, Groningen, The
Netherlands.
(A-An) ANNANMAEKI, K. , Centre f. Rad. and Nucl. Safety,
Helsinki, Finland.
(A-Anl) ANDRU, J., Kodak Pathe, Sevran, France.
(A-Ba) BALL, T.K., Geological Survey, Nottingham, United
Kingdom.
(A-Bo) BOCHICCHIO, F., National Institute of Health,
Rome, Italy.
(A-Bol) BOULAUD, D., CEA/IPSN, Fontenay-aux-Roses, France.
(A-Bu) BUTTERWECK, G., University, Gottingen, Germany.
(A-Ci) CIGNA, A., ENEP, Saluggia, Italy.
(A-Cl) CLIFF, K.D., NRPB, Chilton, United Kingdom.
(A-Da) DAMKJAER, A., University, Lyngby, Denmark.
(A-De) DERI, Zs., Inst, of Nuclear Research, Debrecen,
Hungary.
(A-Di) DIXON, D.W., NRPB, Chilton, United Kingdom.
(A-Do) DOI, M., Nat. Inst, of Rad. Sciences, Chiba, Japan.
(A-Fa) FALK, R., Radiation Protection Institute,
Stockholm, Sweden.
(A-Fu) FUJITAKA, K., Nat. Institute of Rad. Sciences,
Chiba, Japan.
(A-Gr) GRASTY, R.L., Geological Survey, Canada.
(A-Ho) HOFMANN, W., University, Salzburg, Austria.
(A-Hu) HUSSEIN, M.I., Atomic Energy Authority, Cairo,
Egypt.
(A-Ik) IKEBE, Y., University, Nagoya, Japan.
(A-Ka) KATAOKA, T., Inst, of Public Health and Env.
Sciences, Okayama, Japan.
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(A-Ke) KESTEN, J., University Gottingen, Germany.
(A-Ko) KOJIMA, H., Science University of Tokyo, Japan.
(A-Kr) KRIZMAN, M., University, Ljubljana, Yugoslavia.
(A-Ku) KUROSAWA, R., Waseda University, Tokyo, Japan.
(A-Le) LETTNER, H., University, Salzburg, Austria.
(A-La) MCLAUGHLIN, J.P., University College, Dublin,
Ireland.
(A-Me) MELLANDER, H. , Radiation Protection Institute,
Stockholm, Sweden.
(A-Mo) MOCHIZUKI, S.t Institute of Technology, Muroran,
Japan.
(A-Ni) NISHIMURA, K., Science University, Tokyo, Japan.
(A-Pa) PAPASTEFANOU, C. , University, Thessaloniki, Greece.
(A-Pi) PILLER, G., Bundesamt f. Gesundheitswesen,
Fribourg, Switzerland.
(A-Po) PORSTENDOERFER, J., University, Gottingen, Germany.
(A-Ra) RANNOU, A. , CEA/IPSN, Fontenay-aux-Roses, France.
(A-Ral) RAMOLA, University, Salzburg, Austria.
(A-Ro) ROX, A., Staatl. Materialpriifungsamt, Dortmund,
Germany.
(A-Sa) SAMUELSSON, C., University Hospital, Lund, Sweden.
(A-Sc) SCHULER, Ch., Paul Scherrer Institute, Villigen,
Switzerland.
(A-Scl) SCIOCCHETTI, G., ENEA, Cassacia, Italy.
(A-Si) SImgH, J., University, Amritsar, India.
(A-St) STEGNAR, P., University, Ljubljana, Yugoslavia.
(A-Th) THOMAS, J., Inst, of Hygiene and Epidemiology,
Prague, Czechoslovakia.
(A-Wa) WANG, Z., Ministry of Public Health, Beijing,
China.
(A-Yo) ^OshIOKA, K. , Inst, of Public Health and Env.
Sciences, Shimane, Japan.
-------
Fig. 1: Participants in the IAEA Co-ordinated Research Programme
"Radon in the Human Environment"
(Status: February 1991)
Mexico
«0Q
Sweden
Norway
tP NL
Belgium
Ireland
embourg
Poland
Germany
CSFR —Austria
H
Canada
France
Switzerland
Portugal
Spain
X
i^iJapan
Korea
Vietnam
Singapore
Italy
Tunesia
China
Algeria
Greece
Iran
Israel
Egypt
Pakistan
Kuwait
Kenia Thailand
Indonesia
Ghana
Bulgaria
Sudan
Brazil
d
Australia
Costa Rica
5TEIN6B/HI-02-25,FL/LP
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Fig. 2: Implementation of Quality Assurance Programme within the
Framework of the IAEA-CRP "Radon in the Human Environment"
China,P.R.
IAEA-SECRETARIAT
Algeria
Egypt
Sudan
Tunesia
Regional
Coord.
"America"
(Brazil)
Regional
Coord.
"Africa"
(Ghana)
Regional
Coord.
¦Europe"
(CSFR)
Regional
Coord.
Eastern Europe
& Middle East1
(Bulgaria)
(China,P.R.)
Regional
Coord.
'Asia-Pacific'
Argentina
Canada
Costa Rica
Ecuador
Mexico
USA
Reference
Centre
USA
Reference
Centre
Europe
Reference
Centre
Australia
Reference
Centre
China
Hungary
Iran
Israel
Kuwait
Poland
Syria
Turkey
Indonesia
Japan
Korea
Pakistan
Singapore
Thailand
Vietnam
Austria
Belgium
France
Germany
Greece
Italy
Netherlands
Norway
Portugal
Spain
Switzerland
5TE INBVI I -02-25 , FL/LP
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I P - 2
EPA RADON POLICY AND ITS EFFECTS ON THE RADON INDUSTRY
by: David Saum
Infiltec
Falls Church, VA 22041
Although the EPA has always stated a goal of solving the indoor radon problem through
private sector testing and mitigation, EPA programs may be impeding the development of a
viable private radon industry. Several possibilities for modification of the EPA programs are
discussed: 1) "sunset" provisions for EPA programs that would schedule their termination so that
the private sector could plan for privatization, 2) increased utilization of voluntary consensus
standards organizations such as ASTM and ASHRAE to replace EPA protocols and guidelines,
3) cost/benefit analyses of impact of past and future EPA programs on the radon industry, 4) an
EPA ombudsman to serve as a contact point for radon industry comments to the EPA, 5)
increased radon industry participation in future development of EPA programs and guidelines to
prevent surprises and allow for longer term planning, 6) a revision of the EPA authority to issue
guidelines, protocols, examinations, etc. so that this de facto rulemaking would be subject to the
same review as formal EPA rule making.
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INTRODUCTION
What is the proper response of the federal government to the indoor radon problem? This
paper will briefly consider policy approaches, outline the problems with the current EPA indoor
radon programs, and offer suggestions for a change in direction current federal policy that should
offer better services to the public by allowing market forces to operate more efficiently.
Under our constitutional republic, all governmental authority must be authorized by the
constitution which makes no mention of indoor radon. We must assume that the current
activities are authorized under the "general welfare" clause in the preamble. This phrase allows
for broad interpretation which varies with the vision of the current executive, legislative and
judicial branches. The EPA, as a member of the executive branch, appears to be following
President Bush's vision (last stated in The State-of-The-Union address) of relying on the private
sector whenever possible and returning power to the states and localities. Congress appears to
have agreed by authorizing the EPA to assist the states in developing and regulating radon
activities, and the most recent legislation is the Indoor Radon Abatement Act (IRAA) of 1988.
All of this activity has been characterized the EPA and Congress as "non regulatory" since radon
is naturally occurring and its primary exposure has been in private residences where the
government does not want to intrude. Tie EPA has issued radon guidelines and has provided
"voluntary" proficiency demonstration programs to assist the states in determining who is capable
of measuring and mitigating radon problems. The EPA has also provided extensive public
information, and it has often stated that it wants private industry to provide a solution to the
indoor radon problem through a non regulatory program.
Unfortunately, this non regulatory approach has resulted in a highly regulated
marketplace from the point of view of private industry participants. More and more states have
enacted regulation to make it impossible to perform radon related work without full compliance
with all the latest EPA "voluntary" programs. Mandatory state regulation through the use of
voluntary EPA programs appears to be an ideal situation to state regulators since they can rely on
the authority of the EPA to legitimize the state programs at little or no expense. But it presents
an increasing burden to those in the industry who face increased competition from competitors
trained by EPA developed courses and certified by EPA developed examinations,
increased costs to private industry from fees mandated to support these programs, and an
increased paperwork burden from an ever increasing "voluntary" protocols and revisions to these
programs. The EPA has no attempted to justify these programs by offering proof that these
programs offer the public a higher quality and more cost effective service.
These programs each appear to be well intentioned, but in their sum they are creating an
industry that is focussed around the lowest common denominator. The only standard of quality is
whether a firm has the required EPA "certification". These programs were created without
significant industry input, they are completely controlled and managed by the EPA without
continuing industry input, there is no plan for eventual privatization of these programs, an
increasing bureaucracy is being created to support these programs, and Congress has directed the
EPA to support these programs through the imposition of user fees on the industry but not the
States who are the prime beneficiaries. Many persons who have remained in the industry despite
the current severe recession are discussing whether to hold on a little while longer in the hope
that the competition will succumb before they do, or whether to begin a strike against die
increasing governmental regulations on the industry.
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POSSIBLE EPA APPROACHES
What approaches could the federal government have used in dealing with the indoor
radon problem? Within the current federal economic and political constraints at least three
approaches can be imagined:
Laissez-faire Approach
Although true laissez-faire would involve no governmental programs, we can imagine
approaching laissez-faire by limiting the federal government to the conduct of limited research to
identify the problem, issuing recommendations, and leaving the market place to develop
solutions. This approach assumes the indoor radon problem is not an immediate emergency of
such complexity that emergency measures are called for, and that the complexity of society
requires the variety of solutions that can best be offered by relying on individual initiative rather
than a bureaucracy. The primary disadvantage of this approach is that it might have taken longer
for a significant market solution to have developed, given what we now know about the public
apathy and the extraordinary amount of education that it has taken to generated even today's
marginal response. Possible advantages of this approach include low cost to the federal
government, and the potential for the development of a "Sears or McDonalds" approach to radon
where some large, well financed company would have the incentive to devote the resources
necessary to develop a high quality radon service firm. In today's market where anyone can get
EPA "certification" there is little advantage to offering a well established, brand-name, quality
service. One disadvantage is that the states would have to develop their own programs for
certifying competent firms, such as they currently do for home improvement contractors.
Bootstrap-Sunset Approach
Under a bootstrap-sunset approach, the federal government assumes that the problem is
serious enough to justify the development of programs for training and proficiency demonstration
to get the industry started, but the government realizes that this bureaucracy can never be able to
deal with the evolving complexities of the situation and so each program would have a sunset
provision so that they could be taken over by industry groups or private firms. In this way, the
EPA could prevent the heavy hand of bureaucracy from becoming a permanent burden on the
industry and determining every aspect of its future. One disadvantage is that the states would
eventually have to develop their own programs to identify the competent members of the
profession. This approach would not require continuing expenditures by the federal government
and the imposition of user fees to pay for them.
Bureaucratic Approach
Under the bureaucratic approach, the federal government assumes that the problem is so
complex that a permanent federal bureaucracy should be developed to control all aspects of the
radon industry through "voluntary" guidelines and programs that are offered to the states as the
basis for their non-voluntary regulation. One disadvantage of this plan is that it is expensive,
even if it is financed by mandatory user fees, because in any case the funding will come from the
public. Another hidden cost of the program is that it stifles new market solutions to the problems
because the heavy hand of bureaucracy drives out the best services, reducing everything to a
common denominator. The primary advantages are that the states will have a simple solution to
the problems of providing lists of competent "EPA certified" firms. This appears to be the
approach that the EPA has selected.
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EVALUATION OF CURRENT EPA PROGRAMS
When the indoor radon problem was first identified in the mid 1980s, EPA researchers
provided contractors with vital information on radon mitigation and testing, and the EPA policy
office provided much needed public information material. This activity seemed to be an
excellent marriage between public and private interests that served to bootstrap a market solution
to the problem. However, now that the radon industry is maturing, it is time to consider the
potential benefits of returning as much of the EPA radon program as possible to the private
sector. Many of the services now being provided by the EPA are in areas such as training,
certification, and calibration are not special types of services (such as law enforcement and court
systems) that can only be provided by the government. Privately provided services are generally
acknowledged to be more efficient, and this privatization of indoor radon will certainly provide a
welcome reduction of government expenditures in this time of budget deficits. An orderly
transition to private services should provide services that are more responsive to the
marketplace, and the alternative to privatization is a permanent government bureaucracy which
has never been the stated intention of the EPA or Congress.
RMP Program
Consider, for example, the EPA's Radon Measurement Proficiency (RMP) Program.
Certainly everyone wants to have accurate measurements, and RMP initially provided a valuable
service when no private sector services were available. Unfortunately, the current program may
actually be impeding the development of private sector efforts to provide calibration and quality
assurance services. Wouldn't it be preferable to have many private calibration facilities,
conveniently located, offering competitive services; rather than a few of EPA laboratories in
distant locations offering very limited services? The presence of the "implied EPA certification"
provided by RMP makes it difficult for anyone to take the private labs seriously. The private
sector can not compete with the authority of EPA pronouncements, even if the private service is
demonstrably better.
A second problem with RMP is that it is a proficiency demonstration program that does
not certify contractors, but everyone who uses the program (contractors, states, and local
governments, etc.) treats it as a certification of calibration. Private labs find it impossible to sell
real calibration services since they do not have the EPA authority, and why should anyone go to
the extra expense of going through two programs (RMP and private) when all anyone asks for is
the RMP seal of authority). The net result is that RMP has resulted in a low level of calibration in
the industry because it has monopolized the calibration business and then offered very infrequent
services (approximately every 2 years).
A simple privatization plan for the EPA RMP program would begin with an
announcement by EPA of a date (e.g. June 1,1992) after which the EPA would no longer provide
laboratory services for the RMP program. The EPA would also announce conditions under
which private laboratories could provide the equivalent laboratory service in lieu of the EPA labs.
This would allow the private laboratories to make plans to take over this service. The EPA might
initially provide an intercalibration service to certify these new labs, and it might even work with
the National Institute of Standards and Technology (NIST) to develop improved radon
calibration standards. Currently there does not appear to be any EPA effort to assist private labs
in taking over the RMP role. In addition, EPA literature would be modified to indicate that the
public should look for testing firms that can "demonstrate fulfillment of a plan to provide
accurate measurements either through private calibration facilities or though the temporary EPA
RMP". Ultimately the EPA could turn the remainder of the RMP program (record keeping,
publishing lists, etc.) over to the highest bidder or an industry trade group.
RCP Programs
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In contrast to RMP, the EPA Radon Contractor Proficiency (RCP) Program is an example
of an EPA program where some consideration has been given to privatization. In order to
stimulate and guide the radon mitigation industry, the EPA developed training courses and exams
on radon mitigation, and these courses were originally given by the EPA. To protect its
investments in this program, and guarantee geographic distribution of these services, the EPA
competitively selected regional training centers where the courses and exams are given from the
EPA prepared materials. In addition to these centers, private firms can apply to give the courses
if they met specified criteria.
Ideally, the entire RCP program would be turned over to the private sector. This includes
updates to the courses and exams, and will require a number of changes since the program was
developed without significant industry input or control. Today the radon industry does not have
a formal role in revising the examinations or courses, there is no formal plan to phase out EPA
control, there is no appeals process for RCP examination results, no grading criteria have been
published, and there is no EPA response to comments submitted after completion of the
examination or course. The RCP exam also diminishes the possibility of competition among
radon mitigation companies. Home owners do not want to hear about a contractor's years of high
quality work and innovative solutions, they just want to know "Are you EPA certified?".
De Facto Rulemaking
All the EPA guidelines, recommendations, and proficiency demonstrations quickly
become de facto rules because the states are quick to incorporate them into law or local
regulations. But the EPA is not required to subject these de facto rules to the same level of
public scrutiny as their other formal rule making activity. All of these activities should be open
to public scrutiny, and anyone who submits written comments should have a response in writing
as to the disposition of the comments. An EPA indoor radon ombudsman is recommended as a
contact point for comments on current EPA programs. The industry has lost confidence that any
of its comments are taken seriously unless they are made though congress.
User Fees for EPA Programs
The EPA was authorized by the IRAA to implement user fees with the goal of recovering
costs in programs like RMP and RCP. Again this appears to be an excellent idea in these days of
budget deficits and "pay as you go". Since RCP and RMP are voluntary and provide valuable
services, why shouldn't the users pay for them.
The case for user fees would be stronger if the programs were truly voluntary and the
programs had not made it impossible for the private sector to provide equivalent services. Much
of the industry does not have any choice, they must participate in RCP and RMP or the State will
not allow them to stay in business. For this reason, the EPA should consider privatization of
these services as an alternative to user fees for cost recovery.
It is well known that the demand for free or underpriced services/items of value is very
large, and I think that the EPA has proven this again at great expense, especially in the RMP
program. Some sort of price (not necessarily money) must be imposed in order to avoid wasting
money on applications that come from companies that are not serious about providing radon
services. But this does not mean that the proposed fees must be related to cost recovery.
Let's take cost recovery to its logical extreme. There is only one ultimate "payer" in
business and that is the customer. If there are increased costs to the industry, then the customer is
ultimately going to have to pay for it In todays radon mature market, the consumer has largely
decided to ignore the problem, and the radon business is primarily related to a small percentage
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house sales. I estimate that in this market approximately 10,000 mitigation jobs and about
100,000 testing jobs are done every year, and a mitigation job costs about ten times more than a
test I also estimate that the EPA is spending about $10 million per year on indoor radon, and if
this was allocated to each test and mitigation and test proportional to their present cost, then
simple algebra shows that we would have to add $500 to the cost of each mitigation and $50 to
each test in order to provide full cost recovery for the EPA radon program. Would the public put
up with this surcharge or even a fraction of it?
Quality Assurance Programs
A Quality Assurance (QA) Program has been suggested as part of RMP for all radon test
companies. This could be considered as a response to the realization that RMP has become the
primary radon industry calibration program, even though it was never meant to provide that
service, and it is a very poor substitute. Privatization of this aspect of RMP is somewhat
confusing because the marketplace would probably not recognize the artificial distinction that is
being made between "demonstrating proficiency" and running a measurement QA program.
Again we see an apparently good idea that could result in all companies offering "EPA certified
QA Plans", making it impossible for die consumer to determine which companies have a serious
commitment to QA. A more effective approach to accurate measurements might be to encourage
"double blind" evaluations of testing companies where testers would be evaluated without their
knowledge, and the results would be published for all to see. Then there would be a real
premium on QA - not just a paper requirement
RMP Examinations
A "voluntary" examination for radon testers is under development that would require that
all test personnel attend EPA approved training courses. Again, no cost/benefit or industry
impact studies have been offered by the EPA to justify this program to the industry, but it will
certainly give the states an easy way to recommend test companies. Again, the radon industry
has had no part in this development, and no plan for its ultimate privatization has been suggested.
RCP Mitigation Protocols
The next step in the RCP program appears to be the promulgation of EPA protocols for
radon mitigation. It seems that when radon mitigators signed up for the voluntary RCP exam,
they agreed to adhere to EPA mitigation guidelines. The draft protocols contain valuable
material, and they would malm a useful technical resource document that might replace or
supplement the aging 1987 EPA Technical Guidance document on radon mitigation.
Unfortunately, the new document was produced without formal industiy input, without a
cost/benefit analysis, and without plans for consensus approval and periodic updates. The IRAA
directed the EPA to work with consensus standards groups such as ASTM, an this should be
expedited by EPA. During the extensive open review necessary to arrive at a consensus
document, all substantive comments must be dealt with in writing, and there is an automatic
provision for periodic updates. The EPA is currently under no such restrictions for developing its
current "voluntary" guidance and recommendations. Under current EPA policy, we can expect a
cursory review period for the EPA mitigation protocols, after which the states will pick them up
as gospel, and create an increased level of regulation for the radon industry.
Redraft of "Citizen's Guide to Radon"
The EPA recently asked for comment on a new draft of the "Citizens Guide to Radon"
which contained major shocks for the radon industry. Since this draft was prepared in response
to the IRAA which directed EPA to recommend that home owners reduce their indoor radon
levels as close to ambient as possible, few in the radon industiy expected new EPA guidance that
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would effectively raise the radon action level that the radon industry is currently implementing.
The technical arguments in this debate are outside the scope of this paper, but I think it is safe to
say that if the industry had understood that the EPA was heading in this direction, then many in
the industry would have reconsidered their commitment to the radon business. As you can
understand, business people have to make long range plans, and it would be very helpful if they
knew as early as possible about major policy shifts that might radically alter the economics of
their business. Preliminary EPA response to industry comments suggests that the EPA did not
anticipate the negative industry response to the draft Guide. This misunderstanding might have
been avoided if the EPA had performed a cost/benefit analysis on the radon industry in addition
to their study of the impact on the U.S. population. The radon industry could provide valuable
input in these matters if there was a partnership between EPA and industry that allowed for
continuing communication during the development of these guidelines, protocols, examinations,
etc. Although the Citizens Guide contains only recommendations and guidance, it has an impact
on the U.S. population and the radon industry that is comparable to any EPA rule making.
Therefore, this guidance should be subject to the same full public review as formal EPA rule
making.
RECOMMENDATIONS
It appears that Congress did not direct the EPA to work as a partner in assisting the
private sector to create a high quality radon industry with a planned rapid transition to a fully
private sector effort Rather, it has effectively directed the EPA to create programs that have
taken over the management of the industry with no plans for future privatization. It is no wonder
that there are few signs from the industry of increasing self management, since the burden of
EPA regulation increases daily.
It's ironic that these problems are taking place as Eastern Europe throws off the shackles
of central planning and acknowledges that most problems are more efficiently solved by the free
market. Well meaning controls that stifle innovative market solutions must be guarded against
with constant vigilance. Sometimes we forget that the radon industry is a trade that is closer to
home improvement contracting than it is to brain surgery, and radon industry regulation should
be consistent with that fact.
DISCLAIMER
The work described in this paper was not funded by the U.S. Environmental Protection
Agency and therefore the contents do not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
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11-3
REVIEW OF RADON AND LUNG CANCER RISK
By: Jonathan M. Samet
University of New Mexico Medical Center
Albuquerque, NM 87131
Richard W. Hornung
National Institute for Occupational
Safety and Health
Cincinnati, OH 45226
ABSTRACT
Radon, a long-established cause of lung cancer in uranium
and other underground miners, has recently emerged as a potentially
important cause of lung cancer in the general population. The
evidence for widespread exposure of the population to radon and the
we11-documented excess of lung cancer among underground miners
exposed to radon decay products have raised concern that exposure
to radon progeny might also be a cause of lung cancer int he
general population. To date, epidemiological data on the lung
cancer risk associated with environmental exposure to radon have
been limited. Consequently, the lung cancer hazard posed by radon
exposure in indoor air has been addressed primarily through risk
estimation procedures. The quantitative risks of lung cancer have
been addressed primarily through risk estimation procedures. The
quantitative risks of lung cancer have been estimated using
exposure-response relations derived from the epidemiological
investigations of uranium and other underground miners. We review
five of the more informative studies of miners and recent risk
projection models for excess lung cancer associated with radon.
The principal models differ substantially in their underlying
assumptions and consequently in the resulting risk projections.
The resulting diversity illustrates the substantial uncertainty
that remains concerning the most appropriate model of the temporal
pattern of radon-related lung cancer. Animal experiments, further
follow-up of the miner cohorts, and well-designed epidemiological
studies of indoor exposure should reduce this uncertainty.
Further information regarding the paper may be found in:
J. M. Samet and R. W. Hornung, "Review of Radon and Lung Cancer
Risk", Risk Analysis, Vol. 10, No. 1, 1990, pp. 65-75.
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Risk Analysis, Vol 10, No. 1, 1990
Workshop on Indoor Air Quality
Review of Radon and Lung Cancer Risk
Jonathan M. Samet^and Richard W. Hornung2
Received March 7, 1989; revised October 25, 1989
Radon, a long-established cause of lung cancer in uranium and other underground miners, has
recently emerged as a potentially important cause of lung cancer in the general population. The
evidence for widespread exposure of the population to radon and the well-documented excess of
lung cancer among underground miners exposed to radon decay products have raised concern that
exposure to radon progeny might also be a cause of lung cancer in the general population. To
date, epidemiological data on the lung cancer risk associated with environmental exposure to radon
have been limited. Consequently, the lung cancer hazard posed by radon exposure in indoor air
has been addressed primarily through risk estimation procedures. The quantitative risks of lung
cancer have been estimated using exposure-response relations derived from the epidemiological
investigations of uranium and other underground miners. We review five of the more informative
studies of miners and recent risk projection models for excess lung cancer associated with radon.
The principal models differ substantially in their underlying assumptions and consequently in the
resulting risk projections. The resulting diversity illustrates the substantial uncertainty that remains
concerning the most appropriate model of the temporal pattern of radon-related lung cancer. Animal
experiments, further follow-up of the miner cohorts, and well-designed epidemiological studies of
indoor exposure should reduce this uncertainty.
KEY WORDS: Radon; radon decay products; lung cancer; indoor air pollution.
1. INTRODUCTION
As information on air quality in indoor environ-
ments accumulated during the 1970s, it became apparent
that radon and its decay products were invariably present
indoors, and that concentrations reach unacceptably high
levels in some dwellings.'1* The evidence for widespread
exposure of the population to radon and the well-docu-
mented excess of lung cancer among underground min-
ers exposed to radon decay products(Z) have raised concern
> Department of Medicine, and The New Mexico Tumor Registry,
Cancer Center, University of New Mexico Medical Center, Albu-
querque, New Mexico 87131.
2 National Institute for Occupational Safety and Health, 4676 Colum-
bia Parkway, Mail Stop R-4, Cincinnati, Ohio 4S226.
1 To whom all correspondence shoul be addressed.
that exposure to radon decay products might also cause
lung cancer in the general population.
Radon is an inert gas which is a naturally occurring
decay product of radium-226, the fifth daughter of ura-
nium-238. After radon forms from decay of radium-226,
some of the radon molecules leave the soil or rock and
enter the surrounding air or water.(3) As a result, radon
is ubiquitous in indoor and outdoor air. Radon decays
with a half-life of 3.82 days into a series of solid, short-
lived radioisotopes. Two of these decay products emit
alpha particles, high-energy and high-mass particles, which
are highly effective in damaging tissues. When these
alpha emissions take place within the lung as inhaled
radon progeny decay, cells lining the airways may be
damaged and lung cancer may result.
The measure of occupational exposure to alpha ra-
diation from radon decay products is the "Working Level
65
0272-4332ftV03(XK>063S06.00/l C 1990 Society for Riik Anilyiii
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66
Samet and Hornung
Month" (WLM). One Working Level (WL), a concen-
tration unit, is any combination of short-lived radon de-
cay products in 1 L of air which results in the release of
1.3 x 105 MeV of potential alpha energy. The WLM,
a cumulative measure of exposure, is the product of ra-
don decay products concentration in WL and duration in
working months of 170 hr.
Concentrations in homes are most often reported as
pCi/L; a curie is a measure of the rate of radioactive
decay. An indoor concentration of 100 pCi/L is approx-
imately 0.5 WL, assuming a 50% equilibrium of radon
with its decay products. Thus, the Environmental Pro-
tection Agency's guideline of 4 pCi/L translates to 0.02
WL; annual occupancy of a home at this concentration
for 75% of time results in exposure of 0.8 WLM.
Epidemiological methods have been used to assess
directly the lung cancer risk associated with exposure to
radon decay products indoors. However, the available
data on environmental radon are limited and preliminary,
and the findings of epidemiological investigations cannot
yet be used to characterize the risks of indoor radon.
Consequently, the lung cancer hazard posed by radon
exposure in indoor air has been addressed primarily
through risk estimation procedures. The quantitative risks
have been estimated using risk projection models incor-
porating exposure-response relationships derived from
the epidemiological investigations of underground min-
ers.
This presentation reviews currently applied risk
projection models for lung cancer resulting from radon
exposure. We initially consider the investigations of un-
derground miners, and discuss the methodology and lim-
itations of the principal studies. We then describe and
compare the most widely used risk projection models.
2. INVESTIGATIONS OF MINERS
2.1. Introduction
Occupational lung disease associated with the min-
ing of radioactive ores was documented as early as the
fifteenth century among miners in the Erz Mountains of
eastern Europe. In 1879, Harting and Hesse(4) reported
that miners in this area developed cancer of the lung.
During the twentieth centuiy, it was recognized that these
and other underground mines were contaminated with
radon, and that the decay products of radon were the
agents directly associated with the production of lung
cancer.
At present, the health risk associated with exposure
to radon decay products can be best characterized by
examining the more informative epidemiologic studies
of underground miners. We describe the methods and
findings of five major studies. About 15 additional pop-
ulations of radon-exposed miners have been investi-
gated. The report of the Biological Effects of Ionizing
Radiation Committee (BE1R) IV provides a comprehen-
sive review.<2i
2.2. Czechoslovakian Uranium Miners
The latest update of the Czechoslovakian study re-
ported on four cohorts of uranium miners with follow-
up ending December 31, 1980 (Table I).(5) The groups
had exposures to radon decay products ranging from an
average of 3.2-303 WLM, and varying follow-up, rang-
ing from 6-30 years. To date, excess lung cancer mor-
tality has been found principally in the cohorts with highest
exposure and longest follow-up.
The most recent follow-up has detected signifi-
cantly elevated risk of lung cancer from exposures as
low as 50-99 WLM.(5) Risk estimates were reported as
either attributable or absolute risks, and are therefore
difficult to compare to studies reporting estimates as rel-
ative risks. The overall attributable risk of lung cancer
was estimated to be 20.0 per WLM/106 person years.
The Czech study also identified several factors that
modify the exposure-response relationship of lung can-
cer risk with cumulative exposure. The attributable risk
of lung cancer was found to increase with age at initial
exposure, although lung cancers were found at young
ages (before 40 years). An exposure rate effect was iden-
tified; low exposures for long duration produced higher
risk than high exposures for short duration when cu-
mulative exposure was equal. The joint effect of ciga-
rette smoking and exposure to radon decay products was
approximately additive. Finally, the investigators ex-
amined mortality for other causes of death and found a
T»ble I. Czechoslovakian Uranium Miners Study
Study group
A
B
C
D
No. of miners
2194
1849
3799
1561
Mean exposure (WLM)
303
134
6.1
3.2
Mean length of
follow-up (yrs)
30
25
10
6
Attributable risk
(per WLM per 10" PYRS*)
23.0
19.1
20.9
NA
" PYRS -= person-years.
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Radon and Lung Cancer Risk
67
statistically significant risk of basal cell carcinoma of the
skin.
One of the strongest features of the Czech study is
the large size of the cohorts (Table 1). The exposure
data for these miners are also very extensive. The av-
erage number of measurements in each mine ranged from
101-690 per year. The follow-up period was also quite
long (25-30 years) for two of the four groups. The low
exposure groups may be informative in the future. Since
over 5000 miners have average exposures below 10 WLM,
further follow-up of this group could provide invaluable
information concerning the effects at levels that are near
the average lifetime exposure in the U.S. homes.
Interpretation of the Czech study has been made
difficult by the analytical methods employed and the
manner in which the results have been presented; as a
result, comparison with other studies has been difficult.
While methodology used in early analyses of the Czech
data was apparently different from that used in other
studies of miners, the latest analysis was based on an
approach comparable to the widely used modified life
table approach.
The exposure databases are also limited by the mea-
surement, before 1960, of radon rather than decay prod-
ucts. Accurate estimates of concentrations of radon decay
products can only be obtained if the equilibrium ratio of
radon to its decay products is known. Smoking infor-
mation was also incomplete on the cohorts with the high-
est exposures and the longest follow-up.
2 .3. Ontario Uranium Miners
The study includes 15,984 uranium miners who had
no known asbestos exposure.'75 Requirements for entry
into the study included receiving a miner's physical exam
between 1955-1977 and working at least 1 month un-
derground. Exposure estimates were made by combining
WL measurements with work history information for ex-
perience before 1968. After 1968, exposure was ob-
tained directly from the mining companies. The exposure
estimates were made in two ways: "Standard" WL val-
ues were obtained by averaging quarterly measurements
in each year; "special" WL values were obtained by
weighing the measurements toward the highest levels
found. The "special" WL values were regarded as upper
bounds of the actual exposures experienced by the min-
ers. The mean cumulative exposure levels in this cohort
were about 40 WLM for "standard" values and 90 WLM
for "special" values (Table II).
Lung cancer mortality was analyzed using a mod-
ified life table approach and found to be significantly
Table II. Ontario Uranium Miners Study
No. of miners 15,984
Mean length of follow-up (yrs) 15.1
Mean exposure
Standard WLM 40
Special WLM 90
Percent excess relative risk/
WLM
Standard WLM 1.3
Special WLM 0.5
Attributable risk (per WLM per 10* PYRS)
Standard WLM 7
Special WLM 3
increased for exposures in the categories of 40-70 WLM
(mean = 53 standard WLM) and higher. A linear dose-
response model was employed; the model estimated the
excess lung cancer risk to be 1.3% per WLM for the
"standard" values. The latest analyses also showed a
decrease in risk with time since last exposure to radon
decay products.
This study is important because of the large number
of miners with relatively low exposures, and for the con-
sideration given to exposures received in other types of
hard-rock-mining. In addition, appropriate analytical
methods have been used, and the dose-response rela-
tionship has been estimated.
At the end of follow-up in 1981, the cohort was
relatively young, with median age of 49 years. Since
lung cancer mortality rates increase sharply in the fifth
and sixth decades, this cohort has not yet been followed
for sufficient time for description of the full temporal
expression of excess lung cancer risk associated with
exposure to radon decay products. Information on cig-
arette smoking is not available for cohort members; how-
ever, the investigators are addressing this potential
limitation by conducting a case-control study within the
cohort. The exposure database may be limited by reli-
ance on the opinions of mining engineers for exposure
estimates for some mines in the years before 1968.
2.4. New Mexico Uranium Miners
This cohort consists of approximately 3500 under-
ground uranium miners who had worked at least 1 year
underground prior to December 31, 1976 (Table 1II).(8)
This study group includes only about 100 members of
the Colorado Plateau cohort; in comparison with the ear-
lier Colorado Plateau cohort, its members are younger
and received lower cumulative exposures. At the most
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68
Samet and Hornung
Table III. New Mexico Uranium Miners Study, Colorado Plateau
Uranium Miners Study, Swedish Iron Miners Study
New Mexico
Swedish
uranium
Colorado Plateau
iron
miners
uranium miners
miners
No. of miners
3500
3346
22
821
430
1415
44
81
Mean follow-up (yrs)
18
Mean exposure (WLM)
113
Median exposure (WLM)
36
Attributable risk
6.3
19.0
(per WLM per 10" PYRS)
—
% excess relative
1.1
1.2
3.6
risk/WLM
recent follow-up, which extended through 1985, the mean
exposure was 113 WLM and the mean follow-up interval
was 17.7 years. The latest analysis was a nested case-
control study involving 65 lung cancer cases and 230
controls. A proportional hazards model was used to es-
timate relative risk. The effect of cumulative exposure
was found to be curvilinear downward at the highest
exposure interval. Subsequent analyses were restricted
to total cumulative exposures less than 1000 WLM. A
linear model fit the data well in this range, with a relative
risk increase of 1.1% per WLM. A multiplicative rela-
tionship between cigarette smoking and exposure to ra-
don decay products was also found. Relative risk was
estimated to decline with increasing age at risk. In con-
trast to the Ontario and Colorado Plateau studies, relative
risk did not vary significantly during the first 15 years
after ceasing to work in the mine, but was found to
increase 15 years or more after cessation of exposure.
Since average exposures in the New Mexico study
were approximately 20% of the mean exposures in the
Colorado Plateau study, extension of risk estimates from
this study to the indoor environment requires less ex-
trapolation than from studies with substantially higher
exposures. Also, because the Mew Mexico miners worked
more recently than the Colorado Plateau miners, the ex-
posure levels for the New Mexico study tend to be better
documented. Cigarette smoking histories are available
for most of the subjects.
The case-control analysis must be interpreted with
caution until results from the full cohort are available.
By contrast, the Colorado Plateau analysis used the en-
tire cohort of 3346 miners, including 256 lung cancer
cases. Given the high relative risks seen in both of these
groups, a case-control design with less than four controls
per case might not produce risk estimates with the same
degree of precision as estimates from analysis of data
from the full cohort.
2.5 Swedish Iron Miners
This is a study of 1415 Swedish iron miners born
between 1890 and 1919, who were alive in 1930 and
worked at least 1 year underground between 1897 and
1976 (Table III).(9) Exposures ranged from 2-300 WLM
with an average exposure rate of 4.8 WLM per year.
The average cumulative exposure was reported to be
81.4 WLM, which was calculated with a lag of exposure
by 5 years to account for cancer latency. The average
total cumulative exposure without discarding any expo-
sure was 93.7 WLM.
Of the 1415 miners, 1294 were observed between
1951 and 1976, and 50 lung cancer deaths occurred dur-
ing this period. The expected number of deaths based
upon Swedish national mortality rates was calculated to
be 14.6 (standardized mortality ratio [SMR] = 342 for
lung cancer). With control for cigarette smoking, the
SMR increased to 391. Significant excess risk was shown
for exposures above 80 WLM. The attributable risk was
estimated as 19.0 per 106 person-years per WLM (Table
III).
An attempt was made to consider the confounding
effects of such co-carcinogens as cigarette smoking, die-
sel exhaust, arsenic, chromium, and nickel. On the basis
of an informal statistical analysis that required many as-
sumptions, the joint effect of cigarette smoking and ex-
posure to radon decay products was considered to be
additive. The effects of the other potential confounding
exposures were discounted because of the small concen-
trations found to be present in the mines in this study.
Indoor radon exposures were not considered to be of
consequence because of low lung cancer rates in the
surrounding communities.
This cohort has the most lengthy follow-up of the
five studies considered here. The average time in the
study was 44 years, with 99.5% ascertainment of vital
status. The confirmation of cause of death was thorough,
since approximately one half of all deaths in Sweden are
followed by autopsy. Also, the exposures were relatively
low with an average rate of 4.8 WLM per year.
This study is potentially limited by the sparse data
from which cumulative exposures of individual miners
were assigned. Reconstruction of past concentrations of
radon was based upon measurements first taken in 1968,
information on ventilation conditions in prior years, and
consistency of radon measurements in groundwater be-
tween 1915 and 1975. Although the investigators con-
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Radon and Lung Cancer Risk
69
sider that exposures were accurate to ±30%, the exposure
estimates could not be validated and their accuracy is
uncertain.
Analyses related to smoking are potentially flawed
because smoking histories were not available for all sub-
jects. A sample of the responses to a 1972-1973 survey
of active miners and surface workers and from a 1977
survey of retirees were considered. Smoking histories
for the lung cancer cases were obtained primarily from
surrogate sources.
Differential exposure misclassification may have been
introduced by the method used to assign exposure. Ex-
posure assignment for lung cancer cases was apparently
done differently from that for noncases. A detailed his-
tory of each mine area worked was obtained for lung
cancer cases only, whereas noncases were assigned ex-
posure based upon a weighted average of annual mine
exposure levels. Any differential treatment of cases and
noncases can potentially introduce a bias into the risk
estimates.
2.6 Colorado Plateau Uranium Miners
The U.S. Public Health Service conducted a study
of 4127 underground uranium miners with at least 1
month of underground exposure between 1950 and 1964.
These miners worked in the four-state area of Colorado,
New Mexico, Arizona, and Utah. The risk assessment
conducted by the National Institute for Occupational Safety
and Health (NIOSH) was confined to 3346 white male
miners.(10) As shown in Table III, the average exposure
was 821 WLM (median of 430 WLM), the highest of
the five studies considered. Follow-up began as early as
1950 and ended December 31, 1982, with an average
length of 22 years.
The NIOSH risk assessment used a generalized ver-
sion of the Cox proportional hazards model to estimate
relative risk and to identify factors potentially influenc-
ing the risk estimates. Over the full range of exposure
(1-10,000 WLM), the dose-response function was found
to be nonlinear, with a decreasing trend at the higher
exposure levels. However, in the range of current inter-
est in relation to indoor air (below 600 WLM), the risk
model was essentially linear with excess risk estimated
as 1.2% per WLM.
Other factors found to influence the exposure-risk
relationship included'age at initial exposure, time since
last exposure, exposure rate, and cigarette smoking.
Miners first exposed at older ages were at increased risk
of lung cancer compared to those first exposed at younger
ages. Relative risk was found to decrease with time since
cessation of exposure. Exposures received at low ex-
posure rates over long duration were more hazardous
than high exposure levels for short duration, cumulative
exposure being equal. Finally, cigarette smoking had a
synergistic relationship with exposure to radon decay
products. The relationship appeared to be closer to mul-
tiplicative, with the most likely estimate being slightly
submultiplicative.
The Colorado Plateau and New Mexico studies are
only large studies of underground miners with cigarette
smoking information for most cohort members. The co-
hort is relatively large and has been followed closely
since the study's initiation in 1950.
The primary weakness of this study in relation to
current risk assessment needs is the high cumulative ex-
posures received by most subjects. Risks estimated at
lower levels therefore depend to some degree upon trends
found at higher levels of exposure. Some of the exposure
data may be biased on the high side due to the use of
exposure measurements for years after 1960 that were
made by mine inspectors who usually oversampled high
exposure areas. Smoking data were obtained on all min-
ers, but the last update of this data was in 1969. There-
fore, the cumulative cigarette consumption of mineis who
quit smoking after this date will be overestimated by
extrapolation of the smoking histories.
2.7 Discussion
Although the five studies were conducted on dif-
ferent cohorts of miners, using different analytical ap-
proaches and varying amounts of data, the findings
demonstrate several consistent patterns. Each study
showed an exposure-response relationship between the
lung cancer excess and cumulative exposure to radon
decay products. Table IV presents the relative risk es-
timates for each study in relation to cumulative expo-
sure. The excess relative risk per WLM ranges from
3.6% per WLM for the Swedish miners to 1.1% per
WLM in the New Mexico uranium miners. These esti-
mates are not strictly comparable since they are based
upon different analytical techniques, different treatment
of the exposure data, and varying degrees of adjustment
for cigarette smoking. However, considering the differ-
ences among the five studies, the risk estimates are re-
markably homogeneous. In fact, the BEIR IV Committee
analyzed data from three of these five cohorts (Sweden,
Ontario, and Colorado Plateau) and found that the rel-
ative risk in the Swedish cohort was approximately 1.6%
per WLM.<2) In addition, BEIR IV found no significant
differences among the risk coefficients derived from the
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70
Samet and Hornung
Table IV. Comparison of Relative Risk Coefficients for Lung
Cancer Among Five Studies of Underground Miners
Excess relative
Study
risk/100 WLM
Czechoslovakian uranium miners
1.5
Ontario uranium miners
1.3"
New Mexico uranium miners
1.1
Swedish iron miners
3.6"
Colorado Plateau uranium miners
1.2
" Based upon "standard" WLM values.
* This estimate was calculated by discarding the first 10 years of
exposure and lagging by 5 years. When the first 10 years exposure
was included, RR dropped to 1.6 as estimated by BEIRIV Committee.
four cohorts for which data were analyzed. The Com-
mittee concluded that the overall relative risk coefficient
from the four studies was approximately 1.5% per WLM.
Several factors other than cumulative exposure ap-
pear to influence the risk of lung cancer. The Czech and
Colorado Plateau studies demonstrated an increasing risk
with older age at initial exposure. A decrease in relative
risk with time since last exposure was found in the Col-
orado Plateau and Ontario studies. The Colorado Plateau
and Czech studies showed an exposure-rate effect in which
lower exposure rates for longer duration were more haz-
ardous than higher exposure rates for shorter duration
when cumulative exposure was equal. A similar dose-
rate effect has been found in a number of animal studies
of exposure to radon decay products although at very
high exposures.Finally, all five studies found an
increased risk of lung cancer among smoking miners
compared to nonsmoking miners, at least to the degree
that the data permitted. The joint effect of radon decay
products exposure and cigarette smoking ranged from
additive in the Swedish and Czech studies to approxi-
mately multiplicative in the Colorado Plateau and New
Mexico studies.
3. RISK ASSESSMENT MODELS
3.1 Introduction
Protection of the health of underground miners and
of the general population has provided a strong rationale
for making quantitative estimates of the lung cancer risk
posed by radon. A risk projection model describes the
temporal expression of the radon-associated lung cancer
as well as the effects of potentially important cofactors,
such as cigarette smoking, age at exposure, and age at
risk. The two most widely applied models are the rela-
tive risk and attributable risk models; the relative risk
model assumes that the background risk is multiplied by
the risk of radon, whereas the attributable risk model
assumes that the excess risk is additive to the background
risk. A model may also describe the risk as varying with
time since exposure. The manner in which radon expo-
sure and cigarette smoking are assumed to interact strongly
influences the results of risk estimation models for ra-
don. If a multiplicative interaction is assumed, then the
risks for smokers, already much greater than for non-
smokers, are multiplied by the risk from radon exposure.
If an additive interaction is assumed, then the same ex-
cess risk is added to the background rates for smokers
and for nonsmokers. The interaction between the two
agents might plausibly take some form other than purely
additive or purely multiplicative.
Diverse risk projection models have been devel-
oped.(2,13~l6> Models for environmental radon were re-
cently published by the National Council for Radiation
Protection and Measurements (NCRP),(13) the Interna-
tional Commission on Radiological Protection (1CRP),(U>
the Environmental Protection Agency (EPA),(16) the Na-
tional Institute for Occupational Safety and Health
(NIOSH),<1S) and the Biological Effects of Ionizing Ra-
diation Committee (BEIR IV) of the National Research
CounciI(2) (Table V). Each of the models estimates lung
cancer risk on the basis of the epidemiological evidence
from underground miners, but the assumptions under-
lying the models and the resulting risk projections differ.
In this paper, we focus on the NCRP, ICRP, and BEIR
IV models because these models are most widely used
for assessing the risks of environmental radon. The EPA
and NIOSH models are briefly described.
3.2 NCRP Model
NCRP Report No. 78 describes an attributable risk
model adapted from an earlier report by Harley and Pas-
ternack.<17> The annual attributable risk is calculated as:
A (t/t0) = R (.Pt/Pt0) e-^'-'o'
where A (tit J is the attributable annual lung cancer rate
at age t for 40 years and above due to a single annual
exposure at age t0; R is the risk coefficient; PJP,. is the
Iifetable correction and X(X = ln2/20 yr_1) describes
the decrease in risk with time since exposure. The risk
coefficient (R), 10 x 10~6 per year per working level
month (WLM), represents the arithmetic average of
coefficients available when the report was prepared.
-------
Radon and Lung Cancer Risk
71
Table V. Recent Risk Projection Models for Radon and Lung Cancer
Agency
Type of model
Source of risk estimate
National Council on
Radiation Protection
and Measurements'13'
International Comm-
ission on Radiological
Protection"4'
Environmental Protec-
tion Agency* ">
Attributable risk,
time-dependent
Constant relative
risk
Constant relative
risk
Average risk coeffi-
cient from principal
studies of miners
Adjusted risk coeffi-
cient from 3 studies
of miners
Range of coefficients
based on studies of
National Institute for
Occupational Safety
and Health""
National Research
Council0'
Relative risk,
time-dependent
Relative risk,
time-dependent
Risk based on
Colorado Plateau
uranium miners
Risk based on analysis
of 4 studies of miners
The absolute risk model was selected by the NCRP
committee as appropriate for describing the appearance
of lung cancer in uranium miners; additionally, the com-
parability of additive risks in smoking and nonsmoking
Swedish miners employed at the Malmberget mines and
studied by Radford and Renard was cited. The term
g-^c-'o) was included to describe loss of transformed
cells by repair, cell death, or other mechanisms. Because
lung cancer is infrequent before age 40 years, the model
did not project cancers until age 40. In this model, cor-
rection for higher bronchial doses in children did not
greatly change risk projections, and, accordingly, a sin-
gle dose conversion factor was use for males and females
of all ages.
For an average annual exposure of 0.2 WLM, the
model estimates the increment in lifetime risk as 0.18%.
If expressed uniformly over a 45-year period (ages 40
through 85 years), then the model projects 9000 radon-
attributable lung cancer deaths annually in the U.S.
3.3 ICRP Model
ICRP Publication 50 details a constant relative risk
model for lung cancer resulting from radon, and applies
this model to a reference population with lung cancer
mortality and activity patterns representative of more de-
veloped countries. The ICRP committee justified the
choice of the constant relative risk approach on data from
studies of miners and the atomic bomb survivors. The
best estimate of the relative excess risk was derived from
the studies of Colorado Plateau uranium miners, Czech-
oslovakian uranium miners, and Ontario uranium min-
ers. The average from these studies, 1.0% per WLM,
was adjusted to 0.64% to account for contributions from
carcinogens other than radon in the mining environment
and for differing dosimetry in homes and mines. For
exposure received before age 20 years, a threefold in-
crease in effect was assumed on the basis of the pattern
of age-dependence in the atomic bomb survivors and of
the increased bronchial dose in children.
The model was then used to estimate the lung can-
cer risk associated with constant lifetime exposure. The
reference population for this analysis was assumed to be
in a steady state with lung cancer frequency of 60 per
100,000 among males and 12 per 100,000 among fe-
males. The analysis assumed that 65% of time was spent
indoors at home, 20% in other indoor locations, and 15%
outdoors. For this population at exposure rates less than
3 WLM annually, the attributable relative risk was 0.5
per WLM per year. Assuming an indoor exposure of
about 1 pCi/L, approximately 10% of the lung cancer in
the reference population was attributable to indoor ra-
don.
BEIR IV Model
The BEIR IV Committee obtained data from four
studies of underground miners: U.S. uranium miners in
the Colorado Plateau; underground uranium miners in
Saskatchewan and in Ontario, Canada; and underground
metal miners in Sweden. The committee first carried out
separate but parallel analyses of the four data sets and
-------
72
Samet and Homung
then a formal analysis of the combined data. The analy-
sis used relative risk models for the age-specific lung
cancer mortality rates that incorporated terms for poten-
tial modifying factors, such as age at first exposure and
age at risk, as well as for exposure to radon decay prod-
ucts.
The models were fit to the individual studies and
then to the combined data set using Poisson regression.
In analyzing the data sets, the committee used a form of
relative risk model which was termed the Time-Since-
Exposure model. Rather than considering cumulative ex-
posure prior to age at observation, this model estimates
the effects of exposures received in distinct time win-
dows before the age at risk. The version of the model
used by the committee estimated the effects during three
windows: exposures received from the fifth through the
ninth year before age at risk, from the tenth through the
fourteenth year, and from the fifteenth year and beyond.
The general form of this model is
Hfl) = r0(a) (1 + (3 7 (a) (dj + M2 + Ms)]
where dlf d2, d3 are the exposures received during the
three windows, and 02 and 03 represent variation in the
effects of exposure among the windows.
The analyses showed reasonable consistency among
the cohorts; the final model was
r{a) = r0(a) [1 + 0.0257(a) (W, + 0.5W2))
where r0(a) is the age-specific baseline rate; 7(0) is 1.2
for (a) less than 55 years, 1.0 for (a) 55-64 years, and
0.4 for (a) 65 years or more; Wt is WLM of exposure
received 5—15 years before age (a) and W2 is WLM
received 15 years or more before age (a). This model
departs from the widely used constant relative risk model,
in which the increase in relative risk associated with a
given exposure is constant over time after exposure. The
BEIR IV Time-Since-Exposure model implies that the
effect of exposure wanes as the interval since exposure
lengthens.
3.5 EPA Model
The EPA used a constant relative risk model to
predict that radon causes 5000-20,000 lung cancer deaths
annually. Based on the studies of miners, a range of
relative risks from 1-4% per WLM was assumed. The
model also adjusted for differences in breathing rates of
miners (30 1 per minute) and of average adults (15.3 1
per minute), assuming that dose varies directly with min-
ute ventilation.
3.6 NIOSH Model
NIOSH used a generalized form of the Cox pro-
portional hazards model to account for possible depar-
tures from a constant relative risk.(15) The NIOSH
modeling approach described lung cancer mortality pat-
terns as a function of cumulative exposure to radon de-
cay products, exposure rate, age, cigarette smoking, and
time since last exposure without making assumptions
about exposure effects regarding nonmining populations.
The NIOSH model showed a decreasing effect of ex-
posure above 2000 WLM, but the model was essentially
linear below that level with a relative risk coefficent of
1.2% per WLM. An exponential decrease in relative risk
after cessation of exposure was found with relative risk
reduced by 50% 14 years after leaving the mines.
4. COMPARISON OF THE NCRP, ICRP, AND
BEIR IV MODELS
Although each uses risk coefficients which are de-
rived from the studies of miners, the three models differ
substantially in describing the expression of excess risk
associated with radon exposure (Tables VI and VII). The
NCRP model generally projects the lowest excess risk
because it is an additive model, and the radon-associated
excess declines over time. The ICRP model, a constant
relative risk model, projects the highest risks. Exposures
received by age 20 years lead to a particularly large
excess because of the threefold higher risk assumed up
to age 20 years than in subsequent ages. In the BEIR IV
model, the percent excess risk varies with both age and
time since exposure.
When smokers and nonsmokers are considered sep-
arately, the substantial difference between assuming an
additive or a multiplicative interaction between smoking
and radon exposure is evident (Table VIII). The additive
NCRP model projects small increments for smokers in
comparison with the multiplicative ICRP and BEIR IV
models. Lifetime excess lung cancer risks for smokers
estimated by the models are markedly different. For ex-
ample, Land (18) has calculated the excess lung cancer
risk per 100,000 smokers exposed to 1 WLM at age 15
as: NCRP—7.4, ICRP-278.7, BEIR IV-114.5; for
exposure to 1 WLM at age 35 years, the corresponding
estimates are 15.5, 94.3. and 129.4.
5. CONCLUSIONS
For some dimensions of the radon problem, the de-
gree of uncertainty is minimal. The causal association
-------
Radon and Lung Cancer Risk
73
Table VI. Features of Selected Risk Projection Models for Radon and Lung Cancer
NCRP
ICRP
BEIR IV
Form of model
Time-dependent
Lag interval
Age at exposure
Age at risk
Dosimetry
adjustment
Risk
coefficient
Attributable risk
Yes; risk declines
exponentially after
exposure
5 years
No effect of age
at exposure
Risk commences
at age 40 years
Increased risk
for indoor expo-
sure
10 x lO-'/year/WLM
Relative risk
No
10 years
3-fold in-
creased risk
for exposures
before age 20
years
Constant rela-
tive risk with
age
Decreased risk
for indoor
exposure
Excess rela-
tive risks:
1.9%/WLM at
ages 0-20
years and
0.64%/WLM
for ages
21 years
and above
Relative risk
Yes; risk
declines as
time since expo-
sure lengthens
5 years
No effect of age
at exposure
Lower risks for
ages 55 years
and older
No adjustment
Excess relative
risk of 2.5%/
WLM but modified
by time since
exposure
of radon with lung cancer has been amply documented
by studies of underground miners and by complementary
animal studies.(2) Both the epidemiological and the an-
imal data show that lung cancer risk increases with in-
creasing exposure to radon or its decay products. The
epidemiological evidence also indicates synergism be-
tween exposure to radon decay products and cigarette
smoking, although the extent of the synergism is uncer-
tain.(2) Epidemiological studies have not yet empirically
demonstrated that radon in indoor environments causes
lung cancer, but current understanding of the dosimetiy
of radon decay products in the respiratory tract indicates
that radon should have approximately equivalent carcin-
ogenic potency in homes and in mines.(2>
Substantial uncertainties remain, however, with re-
gard to other facets of the radon problem. The quanti-
tative relationship between exposure to radon and radon
decay products and lung cancer risk has not been pre-
cisely described, and uncertainties about the effects of
age, gender, cigarette smoking, and other factors on this
relationship await resolution. Extrapolation of risk esti-
mates based on studies of miners to the general public
requires assumptions in areas of uncertainty. We also
lack exposure information based on a large and repre-
sentative sample of the nation's homes.
The studies of uranium and other underground min-
ers have provided a relatively extensive database for es-
timating the exposure-response relationship between
exposure to radon decay products and lung cancer risk.
Although the populations of miners studied to date have
been diverse and methodology has varied among the epi-
demiological studies, the risk coefficients derived from
the miners are remarkably consistent (Table IV).(2) The
range of the coefficients covers approximately one order
of magnitude, in spite of potential bias from differential
and nondifferential misclassification of exposure to ra-
don decay products and of the diagnosis of lung cancer.
Recently published risk projection models for lung
cancer associated with environmental radon have incor-
porated risk coefficients based on the studies of miners.
-------
74
Samet and Hornung
Table VII. Increments* in Lung Cancer Risks for One WLM
Projected by NCRP, ICRP, and BEIR IV Models
Exposure at age 15 years
Increment
NCRP"
BEIR IV
a( age
(*)
ICRP
(years)
Male
Female
{%)
{%)
35
0
0
1.9
1.5
50
0.3
0.7
1.9
1.5
65
0.05
0.2
1.9
0.5
85
0.02
0.1
1.9
0.5
Exposure at age 35 years
50
0.6
1.4
0.6
3.0
65
0.1
0.4
0.6
0.5
85
0.05
0.2
0.6
0.5
' The excess is additive for the NCRP model. The percent excess
relative risk was calculated for illustration using sex-specific lung can-
cer mortality rates for the U.S., 1980-1984. The additive increments
are 3.0 x 10"6, 1.8 x 10~\ and 0.9 x 10"* for ages 50, 65, and
85 years, respectively, for exposure at age 15 years; and 6.0 x 10-",
3.5 x 10-#, and 1.8 x 10-6, respectively, for exposure at age 35
years.
Table VIII. Lung Cancer Mortality Rates per 100,000 Projected for
Nonsmoking and Smoking Males at Age 65 Years by NCRP, ICRP,
and BEIR IV Models'
NCRP ICRP BEIR IV
Exposure to 10 WLM
at age 15 years
Nonsmoking
Smoking
59.8
698.3
69.0
828.8
60.9
731.3
Exposure to 10 WLM
at age 35 years
Nonsmoking
Smoking
61.5
700.0
61.5
738.3
60.9
731.3
' Background lung cancer mortality rates estimated as 58.0 x 10''
for nonsraokers and 696.5 x 10-' for smokers.®
The principal models differ substantially in their under-
lying assumptions and consequently in the resulting risk
projections (Tables VI-VIII). The committees that de-
veloped these models offered rationales for the assumed
pattern of temporal expression of excess risk that were
based on biological mechanisms and epidemiological
evidence. The resulting diversity illustrates the substan-
tial uncertainty that remains concerning the most appro-
priate model of the temporal pattern of radon-related
lung cancer. Animal experiments and further follow-up
of the miner cohorts should reduce this uncertainty.
At present, however, risk modeling remains the
principal approach for quantifying the hazard of envi-
ronmental radon. Which risk model should be chosen
for this task? While we cannot justify the choice of a
particular model, we consider that the epidemiological
data from miners are not consistent with an additive model,
such as that published by the NCRP.(13) The largest data
set, which is based on the Colorado Plateau uranium
miners, indicates synergism between smoking and ex-
posure to radon decay products, and the data reject an
additive model for the two exposures.'10) The evidence
from a Tecent study of New Mexico uranium miners is
consistent.® The epidemiological data also support a
declining effect as the time since exposure length-
ens.(2,10) Thus, a constant relative risk model, such as
that published by the ICRP,<14) may not be biologically
appropriate. The BEIR IV model describes the effect of
radon exposure on lung cancer risk as varying with time
since exposure; the BEIR IV model also assumes a mul-
tiplicative interaction between smoking and radon ex-
posure. Use of the BEIR IV model for environmental
radon, however, requires the extrapolation of risks from
four cohorts of adult male miners observed over partic-
ular age and time spans to the general population. New
epidemiological and experimental data should provide
more refined risk models with less uncertainty.
ACKNOWLEDGEMENT
Supported in part at the University of New Mexico
by the U.S. Department of Energy, Office of Energy
Research, under grant no. DE-FG04-86ER60452.
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-------
DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service
Centers for Disease Control
National Institute for
Occupational Safety & Health
Robert A. Taft Laboratories
4676 Columbia Parkway
Cincinnati OH 45226
March 14, 1991
Mr. Timothy Dyess
U.S. Environmental
Protection Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Dear. Mr. Dyess:
I was contacted by Ms. Sharon Thompson, who asked me to send you
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for receipt is Monday, March 18, please contact Julie Krafft at
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The enclosed paper is a published copy of my presentation, which
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that this is not a violation. I am certain that the presentation
cannot be republished from this copy. If there is a problem,
please contact Julie Krafft as soon as possible.
Thank you for your assistance.
Richard W. Hornung
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11-6
ESTIMATING RADON LEVELS FROM Po-210 IN GLASS
by : J. Cornells*, H. Vanmarcke**, C. Landsheere* and
A. Poffijn*
* Nuclear Physics Laboratory, State University of Gent
Proeftuinstraat 86, B-9000 Gent, Belgium
** Radiation Protection, Nuclear Research Center,
S.C.K./C.E.N.
Boeretang 200, B-2400 Mol, Belgium
ABSTRACT
The ct-decay of Po-210 may become a useful indicator of the radon
exposure during the last decades. The uncertainties associated with this
technique were studied both experimentally and theoretically.
The depth distribution of absorbed Pb-214 and Pb-210 in glass is
calculated using the theory of Lindhard for low energy heavy ions. It is
found that 29.8 % of the absorbed Po-214 reappears at the glass surface
after a-decay. The surface layer in which the decay products are absorbed
is less than 100 nm. Measurements of the a-activity of Po-214 show that
cleaning the glass once removes 85Z of the deposited activity.
Room model calculations indicate that the ratio of the Po-210 surface
activity to the radon air activity is about equally dependent on the
deposition constant of the unattached decay products and on the attachment
rate. The presence of aerosol sources, for instance, lowers the surface
activity by a factor of two. Experimental investigations prove this
finding.
INTRODUCTION
Lively in 1987 (1) and Samuelsson in 1988 (2) put up the idea of using
the a-activity of Po-210, absorbed in vitreous glass, to determine the long
term radon exposure in the living environment. The technique may be used as
a retrospective exposure measure, for instance, in epidemiological studies.
The parameters influencing the absorbed and deposited Po-210 activity
are indicated in figure 1. A fraction of the airbone Po-218, Pb-214,
Bi-214, Po-214 and Pb-210 deposits on macroscopic surfaces. Half of the
deposited activity recoils into the surface, upon a-decay, forming a thin
absorbed layer. Subsequent a-decay makes a fraction of the absorbed
activity to reappear at the surface. Household cleaning largely wipes away
-------
the deposited activity. The values of the transfer probabilities will be
assessed in the next sections.
Airborne
J . .
218 d d
Po
214Pb d d
214Bi *d +
Deposited
on the surface
| Absorbed
Lass
29.8%
70.2% a
wiped away in
housecleaning
Stable
Figure 1. Decay-product deposition and absorption mechanisms
and associated transfer probabilities.
Aj is the deposition constant of the unattached decay
products and is the deposition constant of the
attached decay products.
-------
DEPTH DISTRIBUTION OF Pb-214 AND Pb-210
The theory of Lindhard (3) provides a framework to determine the range
of low energy heavy ions in amorphous media. Two recoil nuclei have to be
considered, Pb-214 with a recoil energy of 112 keV and Pb-210 with a recoil
energy of 146 keV. The details of the calculation are beyond the scope of
this paper. They are published in dutch by Landsheere (A). A description in
english is available on request.
The depth distributions of Pb-214 and Pb-210 are shown in figure 2.
The full line and the broken line are calculated from Pb-214 and Pb-210
nuclei deposited on the surface of vitreous glass and recoiling into the
glass.
The dot and dash line is the depth distribution of Pb-210 from Po-214
absorbed in the glass. The diffusion of the radon decay products in glass
is negligable so that Pb-214 and Po-214 have the same distribution just as
Pb-210 and Po-210. The depth distribution of Po-210 will always be a
mixture of the two Pb-210 lines. The contribution of each line depends on
the values of the transfer probabilities of the room model (see figure 2).
100
Po)
Pb (a-DECAY OF DEPOSITED
Po)
Pb (a-DECAY OF DEPOSITED
Po)
Pb Ia-DECAY OF ABSORBED
M
M
Pb
Pb
Pb
DEPTH (I0"9m)
Figure 2. The penetration depth distributions of Pb-214 from decaying
Po-218 deposited on the surface and of Pb-210 from deposited
Po-214 and from absorbed Po-214.
-------
The probability for recoiling Pb-210 to reappear at the surface of the
glass is calculated from the depth distribution of absorbed Pb-2K. The
resulting probability is 29.8%.
CLEANING EFFECTS ON DEPOSITED DECAY PRODUCTS
An experimental arrangement was setup to investigate wether cleaning
removes the deposited activity (see figure 3). A radon chamber of 1 m3 was
filled with radon laden air having a relative humidity of 50%. NaCl aerosol
was produced with an atomiser and supplied to the chamber at least 4 hours
before performing a measurement.
RADON
SOURCE
50% HUMIDITY
LUCAS
CELL
i
i
AEROSOL
GENERATOR
1Og/1 Na CI
CONDENSATION
NUCLEUS COUNTER
A
1
RADON CHAMBER 1 m*
RADON CONCENTRATION 180-300 kBq/m*
ATTACHMENT RATE 6-500 h
-1
RESISTOR WIRE
43.5 W
awn
—©~
FILTER OR
GLASS SHEET
J
SAMPLING CIRCUIT (FILTER)
PLATE-OUT (GLASS SHEET)
Figure 3. Experimental setup.
-------
The aerosol concentration was measured with a condensation nucleus counter.
Turbulence was standardised with a resistor wire dissipating continuously
A3.5 W in the radon chamber. A glass sheet was exposed until steady state
activities for the shortlived decay products were reached. The Po-218 and
Po-214 a-activity of the glass sheet was measured outside the radon chamber
for 20 min. Then the glass was cleaned with a cloth containing alcohol and
the remaining Po-214 was registered.
Cleaning removes activity from the glass. The number of counts if no
cleaning would have taken place was obtained from a filter measurement. The
details of the procedure are given by Cornells (5). The non-wiped fraction
is shown in figure 4 as a function of the attachment rate. The indicated
error is one standard deviation. The attachment rate was calculated from
the particle concentration using the formula of Bricard (6). The diameter
distribution was measured a few times with an electrostatic classifier.
About 35% of the activity remains on the glass after cleaning. The scatter
at high attachment rates is due to counting statistics caused by low
plate-out. The lines are the calculated ratios of the absorbed activity to
the total activity (absorbed + deposited). They are assessed from the room
model using two sets of deposition constants for the unattached decay
products. The dashed line was calculated with the same value for the three
shortlived decay products (11 1/h, 11 1/h, 11 1/h). Recent experiments (7)
indicate that the unattached deposition constant of Po-218 has a higher
value than the one of Pb-214. Different values were taken to calculate the
full line (11 1/h, 5.5 1/h, 5.5 1/h). A higher deposition constant for
Po-218 gives less deviation between theory and experiment (see figure 4).
Cleaning the glass once doesn't remove all of the deposited activity.
From the difference between the experimental and the theoretical values
(see figure 4) it is concluded that about 15Z of the deposited activity
remains on the glass.
CALCULATION OF THE Po-210 SURFACE ACTIVITY
The fraction of the Po-210 activity remaining on vitreous glass
depends on the values of the parameters of the room model. Most of the
variability is due to the deposition constant of the unattached decay
products and due to the attachment rate. The surface activity of Po-210 is
given in table 1 assuming a radon air activity of 1 Bq/m9 during 50 years.
During this period the following conditions are assumed to be present on an
average.
- Ventilation rate 1.0 1/h.
- Surface to volume ratio 3 1/m (a typical value for a furnished room).
- 15% of the deposited activity is not cleaned away.
- Deposition constant of the unattached decay products 10 1/h or 20 1/h or
30 1/h. The same value is taken for all of the decay products.
- Deposition constant of the attached decay products is 1/100 of the
deposition constant of the unattached decay products.
- Attachment rate 20 1/h or 40 1/h or 100 1/h.
-------
001 0.1 1 10
ATTACHMENT RATE (h~1)
100 1000
Figure A. The remaining Po-214 activity after cleaning the glass sheet with
a cloth containing alcohol versus the attachment rate. The lines
are calculated from the room model using two sets of deposition
constants for the unattached decay products. Only the absorbed
fraction is assumed to withstand cleaning.
The surface activity of Po-210 is only 3 to 13% of the radon air act ivity.
The attachment rate and the deposition constant are about equally
important. The lower and the higher values of the attachment rate are
typical for rooms without and with aerosol sources. The surface activity is
about a factor of two lower if aerosol sources are present in the room.
Turbulence influences the deposition constant. The presence of a convection
heater near the vitreous glass, for instance, will enhance the surface
deposition.
-------
These considerations indicate that an accurate determination of the
cumulated radon activity involves an estimation of the time averaged
attachment rate and of the time averaged deposition constant of the
unattached decay products.
TABLE 1. THE DEPOSITED AND ABSORBED SURFACE ACTIVITIES OF Po-214 AND Po-2I0
ASSUMING A RADON AIR CONCENTRATION OF 1 Bq/m3 DURING 50 YEARS
Without
cleaning
With regular
u
cleaning
X
A
Deposited
Absorbed
Deposited Absorbed
Absorbed +
d
15% deposited
Po-214
Po-214
Po-210
Po-210
Po-210
1/h
1/h
Bq/m2
Bq/m2
Bq/m2
Bq/m2
Bq/m2
20
10
0.12
0.04
0.07
0.07
0.08
20
20
0.16
0.06
0.09
0.10
0.11
20
30
0.18
0.08
0.10
0.11
0.13
40
10
0.08
0.03
0.05
0.05
0.06
40
20
0.13
0.05
0.08
0.08
0.09
40
30
0.15
0.06
0.09
0.09
0.10
100
10
0.05
0.01
0.04
0.03
0.03
100
20
0.09
0.03
0.06
0.05
0.06
100
30
0.11
0.04
0.07
0.06
0.07
DISCUSSION
The depth distributions of Pb-214 and Pb-210 in glass were calculated
from recoiling surface activity arid from recoiling Pb-210 already absorbed
in the glass, using the theory of Lindhard (3) (see figure 2). Diffusion of
the radon decay products in glass is negligable so that Pb-210 and Po-210
have the same distribution. In practice the depth distribution of Po-210 is
composed of the two Pb-210 distributions. The importance of each
distribution depends mainly on the aerosol and plate-out conditions in the
room.
The probability for absorbed Po-214 to reappear at the surface of the glass
upon ct-decay is 29.8%.
The absorbed decay products are found in a thin layer of less than
100 nm, see figure 2. It should be investigated if decades of household
cleaning doesn't remove this layer.
Another problem arises when the vitreous glass is not regularly cleaned.
Dust will cover the glass so that a fraction of the recoil nuclei will be
stopped in the dust and will be wiped away when the glass is eventually
cleaned.
These considerations indicate the need for some tedious experimental work.
-------
Experimental investigations indicate that 15% of the deposited
activity remains on the surface of vitreous glass when cleaned once with a
cloth containing alcohol. This may be due to radon decay products forming
chemical bonds to the glass or to deposition of the decay products into
microcracks present on the surface of glass.
ACKNOWLEDGMENT
This work is partly funded by the Commission of the European
Communities under contract BI7*-0047-C(JR).
It is not funded by the U.S. Environmental Protection Agency and
therefore the contents do not necessarily reflect the views of the Agency
and no official endorsement should be inferred.
REFERENCES
1. Lively, R.S. and Ney, E.P. Surface radioactivity resulting from the
deposition of Rn-222 daughter products. Health Phys. 52 : 411-415,
1987.
2. Samuelsson, C. Retrospective determination of radon in houses. Nature.
334 : 338-340, 1988.
3. Lindhard, J., Nielsen, V. and Scharff, M. Approximation method in
classical scattering by screened coulomb fields. Mat. Fys. Medd. Dan.
Vid. Selsk. 36 : 10, 1968.
4. Landsheere, C. ExpeTimentele en theoretische studie van de fraktie van
de Po-210 aktiviteit geabsorbeerd in glas. Student thesis, State Univ.
Gent, Nucl. Phys. Lab., 1989.
5. Cornells, J. Experimented studie van de invloed van aerosolen op de in
glas geabsorbeerde fractie van de Po-210 activiteit. Student thesis,
State Univ. Gent, Nucl. Phys. Lab., 1990.
6. Bricard, J. Physique des aerosols II, nucleation, condensation, ions,
electrisation, proprietes optiques. Report Commisariat a l'Energie
Atomique, R-4831, 1977.
7. Vanmarcke, H., Landsheere, C., Van Dingenen, R. and Poffijn, A.
Influence of turbulence on the deposition rate constant of the
unattached radon decay products. Accepted for publication in Aer.
Science and Techn. 14, 1991.
-------
111-11
GUIDELINES FOR
RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS
OF RESIDENTIAL DWELLINGS
PREPARED BY
AMERICAN ASSOCIATION OF RADON SCIENTISTS AND TECHNOLOGISTS
REAL ESTATE TESTING COMMITTEE
This document has come about from the hard work over the past two
years of many talented individuals who are professionally involved in
radon. The document started in a real estate testing committee of the
Eastern Pennsylvania Chapter of AARST. The committees year and a half
work was completed and turned over to a special sub-committee of the
National AARST Technical Committee in October of 1990. This national
committee is presently composed of the following individuals:
Co-Chairs - Bill Brodhead & Richard Roth, Rich Tucker, Jack Dempsey,
Dan Cutler, John Sykes, Ian Thompson, Bill Belanger.
This draft document is the most recent version and although
close to a final version is still open to revision and comments. The
intent of the committee is to have a final version approved for
presentation to the National AARST membership for a vote at the EPA
Symposium during the first week of April.
Todate there have been many inquires for the most recent version
of this document from state agencies in order to help guide them in
setting state policies. It is anticipated that this will be the first
such document to address real estate testing directly and thus be
influential in the direction that testing regulations take in this
critical area.
Please call or fax comments tos
Bill Brodhead Co-Chair of AARST Testing Committee
2844 Slifer Valley Rd.
Riegelsville, Pa. 18077
(215) 346-8004 Fax (215) 346-8575
DRAFT
Version 14B
March 1991
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
TABLE OF CONTENTS
INTRODUCTION
PURPOSE
SCOPE
DEFINITIONS
1.0 TESTING GUIDELINES
1.1 Guidelines vs State Regulations or Federal Protocols
1.2 Radon Survey by Certified Testing Technician
1.3 Detector Non-interference
1.4 Number and Location of Measurements
1.5 Closed House and Other Test Conditions
1.6 Post Mitigation Testing
1.7 Long Term Measurements
1.8 New Construction Testing Conditions
2.0 QUALITY ASSURANCE
2.1 Quality Assurance and Operating Procedures
2.2 Primary Calibration Requirements
2.3 Inter-Calibrating other Active Detectors
2.4 Daily Source Checks
2.5 Active Detector Identification
2.6 Calibration Record Keeping
3.0 REPORTING TEST RESULTS
3.1 Test Result Report
3.2 Reporting all Information
3.3 Mitigation Systems Status
3.4 Reporting Structural Openings
3.5 Reporting Test Variations
3.6 Converting Measurements
3.7 Retesting Recommendations
Appendix A. Radon Test Agreement Example
Appendix B. Radon Test Agreement Example
Appendix C. Non-interference Examples
Appendix D. Radon Survey Notification Form Example
Page 1
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
This is a living document that is not intended to limit
innovative techniques or research, inhibit or prevent consumer choices
or prevent positive changes in the industry and, as such, will be
reviewed for content, applicability and new developments in the field
on a periodic basis.
DEFINITIONS
Terms used in this document are defined as follows:
Action Guidelines - The level of radon or radon decay products in a
home above which the EPA recommends taking corrective action and below
which the EPA recommends that the occupant should decide if they should
take corrective action to further reduce their exposure.
Active Detector - A radon or radon decay product detector that includes
electronics or an active pump.
ARE - The absolute value of the relative error as defined by the EPA.
ARE = | ( MV - AV ) / AV J where MV = Measured Value, and
AV = Actual Value.
Attic Ventilator - An exhaust fan installed in the roof or gable of a
dwelling that is used to ventilate the attic space.
Average - The number obtained by dividing the sum of a set of
quantities by the number of quantities in the set.
Citizen's Guide - EPA Document OPA-86-004 "A Citizen's Guide To Radon",
or any revision, amendment or substitution to this document. The
Citizen's Guide is an explanation for homeowners of what radon is, how
to test their own house for it, and what action would be appropriate
based on the test results.
Client - Person, persons or businesses who have contracted with a radon
testing company to perform a radon survey in a dwelling involved in a
real estate transfer.
Closed-House Conditions - Those conditions defined in the EPA
Measurement Protocols and this document for the limiting of building
ventilation.
Coefficient of Variation (COV) - The percentage of variation of one
measurement to another measurement. /, a, .
The formula is: ~
First measurement = Ml
Second measurement = M2
(n, 1- Hi.yx
Combustion Appliance - A unit designed for heating that burns a fuel
inside a dwelling that should have the exhaust gases vented to the
outside. Examples of this are wood/coal stoves, fireplaces, oil and
gas furnaces, boilers and water heaters. A heat pump or a freestanding
kerosene stove is not included in this definition.
Page 3 Version 14B 3/15/91
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
INTRODUCTION
The American Association of Radon Scientists and Technologists
(AARST) is a national, non-profit professional and trade association
devoted to benefiting the public health and to formulating measurement
and remediation guidelines that assist its members in maintaining a
high level of integrity, among other objectives.
Scientific studies since the 1950's have shown a direct
relationship between elevated radon and radon decay product
concentrations and an increased probability of the incidence of lung
cancer. In view of the potential increased risk from lung cancer
associated with elevated radon and radon decay products, we, as a
professional association, recommend that every occupied dwelling be
tested for radon or radon decay products as outlined in the EPA
pamphlet, "A Citizen's Guide To Radon" or this guideline.
We further recommend in situations where a dwelling is involved in
a real estate transfer, with its many complicating and demanding
factors, that it be tested by a professional radon testing technician
who is EPA proficient and/or state certified and that the test, as a
minimum be conducted according to the guidelines given in this
document.
We also recommend that after the installation of a radon mitigation
system, a short term test or tests be performed by a testing
technician. If the results of this test are below EPA action
guidelines, a long term test or several short term tests in different
seasons should be done to better define the average concentration of
the locations tested and insure that the levels have been adequately
reduced.
PURPOSE
This document provides voluntary guidelines for AARST members
and other radon testing professionals to follow when conducting radon
and radon progeny measurements in residential dwellings involved in the
process of a real estate transaction. The purpose of this document is
to prescribe procedures and actions which will ensure that accurate
measurements are made with a high level of quality assurance and in a
manner that is ethical and professional.
Compliance with these guidelines requires that all applicable
provisions be completely followed. Exceeding these guidelines is
encouraged when doing so is compatible with the purpose of this
document.
The Appendices that follow this guideline are listed strictly as
examples and are not a part of the this guideline. The use of the
information or examples in the Appendices is not required to comply
with this guideline.
SCOPE
This guideline applies to measurements of indoor radon and radon
decay products made in conjunction with real estate transactions of
residential dwellings as defined within this document.
Page 2 Version 3/15/91
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
Detector - Any radon or radon decay product measuring device that is
used by a testing company and with which the company has successfully
passed the most recent EPA RMPP round for that type of detector and/or
has met any government or government recognized certification
requirements of the state in which the detector is used.
Diagnostic Measurements - Measurements used to help diagnose radon
entry routes, radon flux and building conditions. They may or may not
follow this guideline or the EPA Measurement Protocols.
Dwelling - A permanent residential structure that is or could be
occupied at least 10 hours per week. Excluded are dwellings that are
situated above livable spaces over which the occupant of the dwelling
has no control. It does not include commercial, industrial, or
institutional buildings.
EPA - The United States Environmental Protection Agency.
EPA Measurement Protocols - The following EPA documents: "Interim
Indoor Radon and Radon Decay Product Measurement Protocols" (EPA 520/1-
86-04, April 1986); "Interim Protocols for Screening and Follow-up
Radon and Radon Decay Product Measurements" (EPA 520/1-86-014-1,
February 1987); and "Indoor Radon and Radon Decay Product Measurement
Protocols" (February 1989) or any revision, amendments, or replacements
to these documents that describe how a radon measurement is to be made.
Any reference to EPA Protocols refers to those in effect at the time of
testing.
Equilibrium Ratio - The ratio of the potential alpha energy
concentration in the air to that which would exist if all short lived
radon decay products were in equilibrium with the radon present. A
formula for determining the equilibrium ratio is: ER = ( WL X 100 ) /
pCi/L.
Follow-up Measurements - Radon measurements that are made to confirm
whether the average yearly radon levels, indicated from previous
measurements, are above the EPA recommended action level.
Fresh Air Supply - An air duct or air intake that routes outside air to
a heating or cooling air handling system to add fresh air to the
dwelling.
Lived-in Area - A habitable space within a dwelling that is used for
cooking, dining, eating, sleeping or living in. It does not include
areas used for closets, storage, hallways, utility rooms, laundry rooms
or bathrooms.
Long Term Testing - Any radon or radon decay product measurement that
is acknowledged as appropriate and acceptable in the EPA measurement
protocols and has a duration of more than three months.
Lowest Livable Area - The lowest level of the house that is a lived-in
area or could be converted into a lived-in area without major
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
structural changes such as lowering the floor to create necessary head
room.
Make-up Air - Fresh air that is routed directly from the outside to a
combustion appliance to supply combustion air that would otherwise be
drawn from indoor air.
HARE - The mean absolute value of the relative errors as defined by
the EPA, MARE = the average of the ARE's.
Mitigation System - The permanent installation of materials, equipment
or an apparatus that is specifically designed to reduce radon or radon
decay product levels in a dwelling.
Non-interference Agreement - A written agreement that is signed by
both a representative of the testing company and by the party or
parties responsible for maintaining the required conditions of the
radon survey at the dwelling being tested, wherein the parties state
that they understand and will maintain the necessary conditions for a
proper test to be conducted.
Normal Occupied Temperature - Typically this is between 65 and 75
degrees in the lived in portions of the dwelling. It can however be
different in rooms that are occupied irregularly, such as an unfinished
basement or an attached green house.
Occupant - A person living in a dwelling who may or may not be the
owner of the dwelling, and is responsible for the dwelling.
Parties - Owner(s) of the dwelling, buyer(s) of the dwelling, anyone
acting as an authorized agent for the buyer(s) or owner(s), any person
who is responsible for maintaining the dwelling to be tested on behalf
of the owner.
Passive Detector - A radon or radon decay product measuring device that
contains no energized electronic parts or pumps. Examples of passive
detectors are charcoal canisters and vials, electret ion chambers, or
alpha track detectors.
pCi/L - A unit of measurement of the concentration of radioactivity in
a fluid, usually a gas. One pCi/L corresponds to 0.037 radioactive
disintegrations per second in a liter of air. One pCi/L is the
equivalent of 37 Bq/m3.
Primary Measurements - Radon or radon decay product measurements that
provide an averaged concentration over the exposure period. The
detector shall be located as specified in the EPA Measurement
Protocols. The detector shall be exposed in accordance with the
recommendations of the detector manufacturer or supplier. The detector
exposure time shall not be less than the recommended time as specified
in the EPA Measurement Protocols, the Citizen's Guide or any future EPA
Real Estate Testing Protocols. The detector shall not be exposed for
fewer than 48 continuous hours.
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
Radon - When used in this guideline without modification, the terms
"radon" or "radon measurement" refer to the radioactive elements radon
(222Rn) and/or its short-lived decay products. If this document states
"radon gas", the term refers only to 222Rn, a naturally occurring
radioactive element which is a gas and is measured in units of
picocuries per liter (pCi/L) or in units of Becquerels per cubic meter
(Bq/m3).
Radon Decay Products - Refers to the first four decay products of
radon gas, Polonium 218, Lead 214, Bismuth 214, and Polonium 214.
Radon Decay Products are also referred to as radon progeny or radon
daughters. The concentration of these products is a combined
measurement that is reported in units of working level (WL).
Radon Survey - The process of a testing company following these
guidelines in the placing of detectors to sample and analyze the air of
a dwelling, either passively or actively, to measure the radon or radon
decay product concentration during the test period.
Real Estate Transactions - This refers to the refinancing of a dwelling
or the transfer of the title of a dwelling to a new owner and preparing
for such actions.
Responsible Individual - This refers to the person or persons who
is/are responsible for assuring that closed house conditions are being
maintained at a dwelling during a radon survey. This responsible
individual does not necessarily have to be the owner of the dwelling.
RMPP - Radon Measurement Proficiency Program sponsored by the EPA to
determine the proficiency of testers testing for radon gas and radon
decay products
Severe Storm - A period of at least two hours during a test period when
the outside winds average at least 25 miles per hour greater than the
normal wind speed or there has been over 3/10" of rainfall greater than
a typical rainfall for that area in 24 hours.
Shall - indicates a requirement that is necessary to fully adhere to
the provisions of this document.
Short Term Testing - Any radon or radon decay product measurement that
is a primary measurement and has a duration of from two days to three
months.
Should - indicates an advisory recommendation that is to be applied
whenever practical.
Structural Area - Each area of a dwelling located directly above a
distinct foundation type. Examples of distinct foundation types are a
basement, crawl space or slab on grade.
Structural Openings - These are openings from the livable and lived-in
portions of the dwelling to the outside that allow a significant
exchange of air between the inside and the outside. Examples of these
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GUIDELINES FOR RADON/RADON DECAY PRODUCT TESTING
IN REAL ESTATE TRANSACTIONS OF RESIDENTIAL DWELLINGS
openings would be large air spaces around pipes that penetrate above
grade, windows that are broken or will not fully close, large gaps
around cellar doors, and crawl space foundation vents.
Test Period - This includes the continuous sampling time of the radon
or radon decay product detector. If the detector sampling period is
four days or fewer in duration, then the test period must be
immediately preceded by 12 hours of closed house conditions. The
detector exposure period shall be in increments of 24 hours, plus or
minus 2 hours for each day of exposure length. This means that a three
day test can be exposed from 66 to 7 8 hours. The exceptions to this
are: An exposure period cannot be fewer than 48 hours; an exposure
period cannot be less than the minimum exposure time recommended in the
EPA Measurement Protocols, future EPA Real Estate Testing Protocols,
the Citizen's Guide or regulations of the state in which the test is
being carried out; an exposure period shall be in accordance with the
manufacturer or supplier recommendations.
Testing Company - A company or an individual who provides a radon
survey for a dwelling involved in a real estate transfer.
Testing Technician - The person responsible for placing and retrieving
the radon or radon decay product detector. This person may be the
owner, an employee or a sub-contractor of the testing company. This
technician shall abide by all the requirements of the state in which
the test is being conducted. The technician shall be under the
supervision of the testing company. The technician shall have, as a
minimum, attended a state or federally approved radon testing course
that fulfills any necessary educational requirements for state
certification in the state in which the test is being performed, or
shall have been continually employed for one year as a testing
technician under the supervision of a state certified company.
Whole House Fan - A large exhaust fan used to ventilate the whole
house. Typically the fan is installed the ceiling or attic of the
dwelling and draws air from the ceilin9 the highest floor of the
dwelling.
Working Level ( WL ) - A measurement unit of the energy that is
released by the successive disintegrations of the four short term decay
products that follow radon gas in a measured volume of air over a
specified amount of time.
1.O TESTINGGUlDELINES
1.1 The guidelines of this document shall be followed unless
superseded by the EPA Measurement protocols °r any regulations or
certification requirements of the state in which the radon survey is
being performed. The testing require1®6^8 of any state shall be
followed for measurements performed in that state. The existing laws,
ordinances and regulations of all govearnxng bodies shall be complied
with in any location in which busineS® 18 being conducted, if any
state or Federal regulations has mini®11111 re(juirements and these
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guidelines exceed the state or federal regulations, then, these
guidelines should be followed.
1.2 Real estate transfer radon tests in a state which has a
certification program shall only be conducted by a state certified
testing technician or certified testing company. In all cases the
placement and retrieval of the detector for the primary measurement of
a radon survey shall only be performed by a testing technician.
1.3 A radon survey shall have a minimum of one primary measurement in
each lowest livable structural area of the residential dwelling. The
same type or a combination of different types of detectors exposed
concurrently can be implemented. The testing technician may make any
number of additional or diagnostic measurements to obtain additional
information. The measurement placement shall conform to the current
EPA measurement protocols for screening and follow-up measurements.
1.4 The testing device shall not be moved, covered or have its
performance altered during the radon survey by anyone.
1.5 Dwellings that are being tested with short term measurements
shall have emphasis placed on maintaining closed-house conditions
during the measurement period.
1.5.1 The testing company shall determine who is the
responsible individual for the dwelling during the test period.
The testing company shall inform the responsible individual of
the requirements of and the need for closed-house conditions as
well as all other conditions of the test before the detector is
exposed.
1.5.2 When the radon survey is four days or fewer in duration,
the testing technician shall inquire to determine if closed house
conditions have been maintained for the twelve hours prior to the
start of the test. If the testing technician discovers that
closed house conditions were not maintained or discovers
strutural openings that are due to disrepair or structural
defects and these openings allow a significant amount of
ventilation, the radon survey shall not be initiated until such
structural openings have been corrected and twelve hours of prior
closed house conditions have been maintained including the repair
of the openings mentioned. Closed house conditions prior to the
start of the radon survey do not need to be maintained if the
exposure period extends to at least four days with an appropriate
detector.
1.5.3 Closed house conditions require that all the windows
shall be kept closed and external doors shall be closed except
for normal momentary entering and exiting during the test period.
All windows and exterior doors shall be inspected by the testing
technician at the placement and retrieval of the detector.
Heating, air conditioning, and heat recovery ventilators
can be operated normally. Operation of dryers, range hoods, and
bathroom fans should be kept to a minimum. The responsible
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individual, however, should be warned that over-use of an exhaust
appliance may effect the final readings. Whole house fans shall
not be operated. Portable window fans shall be removed from the
window or sealed in place. Window air conditioning units shall
only be operated in a recirculating mode. Fireplaces or
combustion appliances that are not primary heat sources shall not
be operated. No ceiling fans, portable dehumidifiers, portable
humidifiers, portable air filters portable room air conditioners
to operate in the same room as the detector. If the dwelling '
contains an air handling system, the air handling system shall
not be set for continuous operation.
1.5.4 For short term testing, a notification that a radon survey
is in progress, with the conditions of the test stated on the
notification, shall be posted in a conspicuous location at the
dwelling so that all occupants shall have access to information
about the test and the conditions of the test. Appendix D is an
example of a testing notification form.
1.5.5 The responsible individual shall be requested to sign a
non-interference agreement that indicates a knowledge of the
testing conditions of this guideline and a willingness to co-
operate in maintaining the required test conditions. If such an
agreement cannot or will not be signed by the responsible
individual, the testing company shall indicate why the signature
was not obtained. Appendix A and B are examples of Non-
interference Agreements.
This signed agreement, along with an inspection of the
dwelling at the placement and retrieval of the detector, the
informing of the responsible individual, and the posting of a
testing notification, shall fulfill a test company's minimum
requirements for verifying closed house conditions. This guide
does not require the testing technician to be responsible for
inspecting for closed house conditions 12 hours before the start
of the test or between placement and retrieval.
1.6 Test periods that are four days or less and are made immediately
following the installation of a radon mitigation system shall not begin
the exposure period for a minimum of 24 hours after the system is
completed and operating. Closed house conditions shall be maintained
for the 24 hours preceding the start of this test. Test periods that
are greater than four days can, however, be started immediately after
completing the radon installation.
1.7 If the radon survey is to be a long term measurement, closed
house conditions do not have to be maintained. The testing individual
or testing company shall, however, recommend to the owner or occupant
of the dwelling that at least half the test period should be during the
season that the home will most likely be operated with closed house
conditions and that reasonable closed house conditions should be
maintained during the test period so that the results of the test are
more accurate indicators of the yearly average.
1.8 New construction shall not be tested unless the test complies
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with EPA testing protocols and the following items, if such items are
part of the completed dwelling, are installed and completed before the
radon survey is initiated: all insulation, all exterior doors, all
windows, all fireplaces and fireplace dampers, all ceiling coverings,
all interior coverings and interior trim for the exterior walls, all
exterior siding, weatherproofing and caulking. If the testing
technician or testing company knows work is to be done inside the
dwelling during the test period which will interfere with the
performance of the test, the testing company shall re-schedule the
test.
2 . O QUALITY ASSURANCE
2.1 The testing individual or testing company shall have and abide by
a written Quality Assurance Plan (QAP) and a written Standard Operating
Procedures (SOP). The QAP and SOP shall be prepared in accordance with
the EPA Measurement Protocols and ANSI N323-1978 as well as any
relevant EPA, ANSI and detector manufacturers documents.
2.2 All detectors shall only be used according to manufacturers
specifications for all primary measurements.
2.3 At least one or a minimum of 20% of all active detectors shall be
calibrated at least once a year in a radon chamber that is inter-
compared with an EPA or DOE radon chamber or shall calibrate with a
source that is traceable to the National Institute of Standards and
Technology (NIST). Calibrations shall be according to the
manufacturers protocols and shall include all necessary checking of
equipment functions.
If the calibration test "ARE" for any active detector or the
"MARE" of a group of similar passive detectors is greater than 25%,
then the testing company shall make any necessary corrections and
repeat the comparison test as specified above, or discontinue testing
service with the detector or detectors until its accuracy is confirmed
by the test specified above.
2.4 All other active detectors used by the testing company will be
inter-compared at least 5% of their usage with a detector calibrated
according to the procedures listed in 2.3. If any of these testing
company inter-comparisons produce an "ARE" greater than 10% from the
calibrated detector, then the deviant detector or detectors shall be
recalibrated to match the chamber calibrated detector and recompared to
the chamber calibrated detector to verify accuracy before being used
again.
2.5 To assure proper operation of active instruments between
calibrations, the instrument should be tested with a check source prior
to each measurement survey. Ambient background radiation readings
and/or blank samplers or detectors shall be obtained at the sampling
frequency specified by the manufacturer.
2.6 Each active detector shall have its identification code and its
latest calibration date written on the outside of the detector.
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2.7 All calibration and check source data shall be recorded and
maintained by the testing company.
2.8 QAP's for testing companies that utilize passive detectors shall
include a minimum of approximately 5% of each type of passive detector
deployed or 25 each month, whichever is smaller, set aside as blanks.
These blanks will be treated identically as similar field detectors
except they will be kept sealed in a low radon environment, less than
0.5 pCi/1, during the exposure period of the field detectors and
returned for analysis along with the field detectors. If one or more
of the field blanks produces a measurement result that is significantly
greater than the LLD or other standard specified by the manufacturer
for that detector then additional blanks will be returned for analysis.
If any of these blanks also have measurement results greater than the
LLD commercial use of this detector type will be discontinued until
correction can be made and verified by the processing laboratory.
2.10 QAP's for testing companies shall include a minimum of
approximately 10% of each type of detector deployed or 50 each month,
whichever is smaller, exposed as a duplicate with another detector,
side by side exposure. Each duplicate shall be treated identically.
If possible the duplicates shall not be identified as such to the
processing laboratory. These duplicates shall be distributed
throughout the radon surveys conducted during the month. If any of
these duplicate measurements have greater COV than 25% from each other
at radon concentrations greater then 4 pCi/1 than duplicate
measurements will be made with the next radon exposure of the same
detector. If this duplicate measurement also produces a COV more than
25% from the duplicate detectors, then commercial use of this detector
will be discontinued until the precision of the detector is verified to
be within the above standard.
3 . O REPORTING TEST RESULTS
3.1 The test report shall be in writing and either mailed, faxed or
handed to the client within five business days after the results are
available to the testing company. All reporting statements required by
this document shall be included in the test report. The client should
be informed of any reporting of results to persons other than the
client.
3.2 The test report shall contain all individual primary measurement
results and their locations. The test report shall contain a
description of the type of detector used, its manufacturer, model or
type and the detector identification numbers. No average of any
measurements made throughout the dwelling shall be reported. Any
diagnostic measurements shall be reported as such.
3.3 If there is a visible active radon mitigation system installed in
the dwelling, the testing company shall include a statement in the test
report indicating the presence and operation of a mitigation system at
the time of placement and retrieval of the detector. The testing
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company should include a statement that the testing company makes no
claims as to the proper operation of the system.
3.4 Any readily visible structural openings shall be noted on the
test report as to their presence and condition.
3.5 Any Known variation from the required test conditions during the
test period that the testing company or testing technician discovers
shall be included in the test report. If the testing technician or
testing company discovers that the test area is not maintained at
normal occupied temperatures during any portions of the test period at
the time of placement or retrieval of the detector, the test report
shall report this condition.
3.6 The test report should describe the general limitations of the
test such as the following statements: the testing company cannot be
assured that the necessary conditions of the test were interfered with
or that any interference would influence the radon or radon decay
product measurement; there is an uncertainty with any measurement
result due to statistical variation and other factors; there are daily
and seasonal variations in radon concentrations due to changes in the
weather and operation of the dwelling; if a severe storm occurred
during a short term test period, it may raise or lower the radon levels
of the building, and it may be necessary to repeat the test.
3.7 The measurements shall be reported in units that are appropriate
to the measurement method. Any test results that convert the
measurements to the unit of another product shall include a statement
similar to the following:
Any conversions from WL to pCi/L or pCi/L to WL are only
approximate conversions and are not likely to be the true
concentration of the converted value.
3.8 All test results shall include a statement which recommends that
the dwelling be retested for each of the following situations whether
the dwelling has or has not been mitigated:
a) Occupancy by a new owner
b) A period of six months since a short term test
c) A period of three years since a long term test
d) A new addition to the dwelling
e) An alteration is made to the dwelling which could change the
ventilation pattern of the dwelling
f) Major cracks occur in the foundation walls or slab
g) An unsealed penetration is made in a foundation wall or slab
h) Significant construction blasting or earthquakes
i) Changes are made or happen to an installed mitigation system*
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APPENDIX A
EXAMPLE OF A NON-INTERFERENCE RADON TEST AGREEMENT
FOR RESIDENTIAL DWELLINGS
REQUIRED CONDITIONS OF THE RADON SURVEY
Radon and radon decay product concentrations in a dwelling fluctuate.
The following test recommendations were developed by the USEPA to provide
standardized conditions under which a short term radon test is to be
performed in order to reduce the variation in radon levels in a dwelling.
These conditions will tend to maximize the radon measurement in order to"
determine if a dwelling has the "potential" to have an elevated radon
level. If the result is elevated, the EPA recommends further testing to
better determine the yearly average concentration.
The radon technician has my permission to install and retrieve radon
testing devices at the property listed below. AGREE DISAGREE
I/WE will not move, cover or try to alter or effect the performance""
of the test devices. AGREE DISAGREE
I/WE will not touch, and/or remove any non-interference controls
which may be used. AGREE DISAGREE
I/WE will not operate equipment, other than a HRV, which brings
fresh air directly into the building. AGREE DISAGREE
I/WE will not use any whole house ventilating fans, wood stoves or
fireplaces unless they are primary heaters. AGREE DISAGREE
I/WE will keep all windows closed and external doors closed except
for normal momentary entering and exiting. AGREE DISAGREE
I/WE agree that the normal occupied operating temperature be
maintained at the test location. AGREE DISAGREE
I/WE will notify the testing co. during or at the test conclusion if
any conditions of the agreement are violated. AGREE DISAGREE
I/WE agree that the above conditions have been or will be maintained
by all persons at the test location during the testing period. If the
measurement period is four days or less I/WE verify and agree that these
conditions have been or will be maintained for the 12 hours before the
detector is exposed. AGREE DISAGREE
Property Location:
Testing
Detector Type & Locations Technician
1st Owner
2nd Agent
3rd Signing Date
Installed Date/Time Retrieval Date/Time
Comments:
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APPENDIXB
EXAMPLE OF A NON-INTERFERENCE RADON SURVEY AGREEMENT
FOR RESIDENTIAL DWELLINGS
REQUIRED CONDITIONS OF THE RADON SURVEY
Radon and radon decay product concentrations in a dwelling fluctuate
from hour to hour, from day to day and from season to season. The
following test recommendations were developed by the EPA to provide
standardized conditions under which a short term radon test is to be
performed in order to reduce the variation in radon levels in a dwelling.
These conditions will tend to maximize the radon measurement in order to
determine if a dwelling has the "potential" to have an elevated radon
level. If the result is elevated, the EPA recommends further testing to
better determine the yearly average concentration.
If the test conditions below are not adhered to, the test results
may be deemed invalid. The following conditions must be read, understood
and followed:
All windows must be kept closed. All doors must be kept closed
except for normal, momentary entering and exiting.
The radon detector cannot be moved, covered or altered in any way.
Heating, air conditioning, dryers, range hoods, bathroom fans and
attic ventilators can be operated normally. If any heating, air
conditioning or ventilating equipment has a built in fresh air supply, it
shall be turned off or the inlet closed. Fireplaces or wood stoves shall
not be operated, unless they are a primary heat source. Whole house fans
shall not be operated. Window fans shall be removed or sealed shut.
The dwelling shall be maintained at its normal operating temperature.
These test conditions shall be maintained for 12 hours prior to the
start of the radon detector being exposed, unless the test is longer than
four days in duration.
If there are any questions, or the test conditions are not met,
please contact the testing company at (Co. Phone Number )
I/We the occupant or building custodian understand and will inform all
parties in this dwelling of the above conditions of the test. I/we agree
to maintain these conditions during the test period.
Property Location:
Technician Owner
Installed Date/Time Retrieval Date/Time
Detector Locations
Date Comments s
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APPENDIXC
NON-INTERFERENCE CONTROLS
INTRODUCTION
The following are examples of non-interference controls which may or
may not be used to help deter or determine that interference has occurred
during a radon survey. These examples do not provide complete assurance
that a radon survey has or has not been interfered with.
This appendix is provided for reference purposes only and are not
required by the guidelines to verify closed house conditions unless these
examples are directly specified in the guidelines.
EDUCATION
Before the radon survey is begun, educate all parties responsible
for the dwelling to be tested about the conditions of the radon survey
and the necessity to adhere to these conditions or the test results may
be deemed invalid. This includes the owner and occupants of the dwellina
as well as the real estate brokers or any individuals responsible for the
dwelling during the test.
Inform all individuals who may or will enter the dwelling about the
conditions of the test by prominently displaying a notification of a
radon survey in progress and the conditions of the test, on or near all
exterior doors that are normally used for entrance into or out of the
dwelling or in another prominent location.
AGREEMENTS
Have the owner or the person responsible for the dwelling read and
sign a non-interference agreement.
WINDOWS & DOOR SEALS
Windows, especially those in the same room as the detector, can be
marked with seals placed between the window sash and the jambs to
identify any movement. Some seals should be visible to help deter anyone
from attempting to open the window during the test period. The window
could also have invisible seals installed to reduce the chance of someone
removing all the seals and later replacing the removed seals when the
window is closed. Some of the possible seal materials include clear
double stick tape, white paper seals, and removable non-staining adhesive
caulk. The seals can be further altered to avoid tampering by using
color coded tape or coloring it at the test site, initialing or coding
white paper seals or slicing the seal to make it difficult to remove or
open the window without tearing the seal.
Exterior doors that are not the primary entrance into the dwelling
could be sealed in a similar manner as the windows or with seals on the
door hinges.
DETECTORS
A continuous radon or radon decay product detector can be used that
gives interval measurements. An unusual variation in concentrations
might indicate that the dwelling was ventilated or the performance of the
equipment was altered or that severe weather conditions took place during
the exposure period.
To determine if a detector is moved during a test period the
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detectors can be installed in a noted position or on top of a paper with
a coded grid or light sensitive paper. The paper would first be
installed with double stick tape to secure it in place. The detector
would then be placed in a noted location on the grid so that any movement
of the detector could be determined at the time of retrieval. The
movement of the detector can then be documented by drawing a circle
around the detector in its changed position.
The radon entry location into the detector could have a loop of
double stick tape installed in such a manner that it does not obstruct
the entry of radon into the detector but reduces the possibility of the
entry location being covered.
The detector could be placed in or on a motion detector that does
not interfere with the performance of the detector but detects any
movement.
The detector could be placed to overhang the edge of its stand so
that any attempt to cover it up would be difficult.
If the detector stand is portable, the stand could be taped to the
floor in a manner that would indicate any attempt to move the stand.
VENTILATION EQUIPMENT
Switches which control ventilation equipment could be held in place
with a double stick tape or white initialed tape. This may include the
fresh air supply control for a window air conditioner. In an unoccupied
home, a seal could also be placed on the electrical control panel to
indicate changes in the power supply to the heating equipment.
GRAB SAMPLES
Grab samples taken of radon and/or radon decay products at the
beginning and/or end of the test period can be compared to the average
test results from the whole exposure period. If there is a significant
difference in the readings, it might indicate the building had been
ventilated either before or during the exposure period. Grab samples can
be used to locate the measurement device in the highest radon location
that still falls within the protocols placement location.
MEASUREMENTS of RADON and RADON DECAY PRODUCTS
If both radon and radon decay product measurements are made at the
same time at the beginning and/or end of a measurement period, the
equilibrium ratio between the readings can be obtained. If there is
significant variation in the readings or the reading is significantly low
it may indicate that excessive ventilation has taken place.
TEMPERATURE MEASUREMENTS
Temperature readings of the outdoor and the indoor testing area
taken at the beginning and end or throughout the measurement period might
indicate excessive ventilation if the indoor temperature is significantly
closer to the outdoor temperature as compared to the normal occupied
temperature of the dwelling.
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APPENDIXD
EXAMPLE OF RADON SURVEY IN PROGRESS NOTIFICATION FORM
RADON SURVEY IN PROGRESS
DO NOT REMOVE THIS NOTIFICATION
The following conditions must be maintained:
1) Do not open any windows. Do not open any doors except
for normal momentary entering and exiting.
2) Do not touch, cover, move or alter the performance of
any radon detectors or non-interference controls.
3) Do not operate any whole house fan(s). Do not use any
fireplace(s) or wood stove(s) unless they are the primary heat
source.
4) Operate heating and air conditioning normally. Turn off any
equipment which supplies fresh air to the house unless it is
vented supply air to a combustion appliance.
5) The testing locations must be maintained at their
normal occupied temperature.
NOTE:
Exhaust fans such as the dryer, range hood, bathroom fan or attic
ventilating fan can be operated. This equipment should only be
operated normally because any exhaust fan or any combustion appliance
may increase the negative pressure in the dwelling, which can raise or
lower the radon concentration. Windows must be kept closed because
they can create negative pressure in the lower portions of the house
due to the warm air escaping or the direction of the wind, which can
raise or lower the radon levels From:
Responsible Party: To:
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IIIP-6
UNIT VENTILATOR OPERATION AND RADON CONCENTRATIONS
IN A PENNSYLVANIA SCHOOL
By: Norm Grant
Quoin Partnership, Architects & Engineers
Trappe, Pa.
Bill Brodhead
WPB Enterprises, Inc.
Riegelsville, Pa.
ABSTRACT
An elementary school in Pennsylvania was tested in the
spring of 1990 and discovered to have elevations ranging from
5.5 to 76 pCi/1 in 25 different rooms. The school is divided
between an older wing that is a slab on grade with an access
tunnel around the perimeter and a newer wing that has half
the classrooms over a slab and the other half over a walk out
multipurpose room, kitchen and maintence room. Although
typically the operation of a univent heater will reduce radon
concentrations in a room because of the introduction of
outside air, it was discovered however that in the older wing
of the school, the heaters were responsible for a significant
portion of the radon entering the classrooms. This paper is
a review of the operation of the univent heaters and
alterations to the units and the operation of the building in
order to determine the radon pathways and how they might be
controlled.
-------
EXECUTIVE SUMMARY:
Diagnostic testing was conducted over several days from December 22,1990 through January 14, 1991,
It included radon detection utilizing sampling techniques at specified intervals, as welt as, averaging
monitors. Additional types of measurements were made to determine building and radon behavior under
various operating and potential remediation conditions.
Radon exists in varying concentrations (from near 0 to approximately 1700 pCi/l) beneath the floors in
contact with the ground in virtually all areas of the school. This radon is migrating into the building and then
diffuses through the building, following normal air currents In the structure. The diffusing process tends to
dilute the radon to levels from about 2 to 90 pCi/l within the occupied areas of the building.
The mechanical systems of the building, both wings, are presently not operating as designed. For example,
in the old wing' there is far less outside air being introduced than necessary for Pennsylvania Department
of Education requirements. This contributes to higher interior radon concentrations (and may also contribute
to a higher transmission of communicable diseases). The apparent lack of operation of a portion of the
mechanical system to relieve pressure in the new wing may be forcing radon to migrate to the old wing.
Radon can be remediated by using the following techniques and/or combinations thereof:
1. Subslab deoressurization - Creating a slightly lower pressure under the floor(slab) of a
structure to intercept or "vacuum off" the radon before It has an opportunity to penetrate
any openings on the foundations and/or floor.
2. Sealing - Effective blocking of entry routes for any subslab gas.
3. Building pressurization - Creating a slightly greater interior pressure than exists below the
building slab so that the building effectively resists the entry of any gas from below.
4. Dilution - Introducing sufficient outside air to reduce interior radon concentrations to
acceptable levels.
5. Conducive condition avoidance - Removing operational conditions which enhance radon
entry into a structure.
The greatest success with radon remediation has historically been achieved with a combination of the first
two approaches. Each method has its advantages and disadvantages, none is effective forever," without
some attention/maintenance. It should be clearly understood that because of environmental conditions
(expansion, contraction, settling, mechanical wear, deterioration, weathering, etc.), once a building is
remediated, it should be regularly retested to insure that the system is functioning as intended. The US
Environmental Protection Agency suggests annual retesling. There are maintenance procedures that may
be involved in the system implemented.
OLD WING:
Remediation can be most cost-effectively achieved by subsiab depressurization in the old wing by utilizing
the existing subslab utility tunnel as part of that depressurization system. This has been effectively
demonstrated by the temporary system in operation. That temporary system should be made permanent
and be supplemented by additional appropriate sealing techniques to reduce radon concentrations to within
acceptable levels. The asbestos-containing materials In the tunnel should be removed and new insulation
applied to the piping In the tunnel to minimize energy loss.
Since evidence Indicates Inadequate and Improper operation of various functions of the mechanical system,
that entire system should be tuned-up" to insure proper functioning of all components and outside air
introduction Unit ventilators should be Installed in normally-occupied rooms which do not have them.
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There was a "conducive condition" which clearly increased the potential for radon entry from the tunnel to
the classrooms: When the unit ventilator fans operated, they virtually "inhaled" any radon that existed in the
tunnel below. The unit then distributed that radon-laden air to the classroom. The solution to that problem
has been identified and implemented, namely, reducing the tunnel pressure beyond the capability of the unit
ventilator to draw on It, reducing the capability of the unit to "inhale" from the tunnel, and sealing
penetrations between the unit and the tunnel, all without affecting unit ventilator performance.
Since the utility tunnel was an integral part of the old wing mechanical system, and Is now excluded from
that use by its functioning as the plenum for a subslab depressurization system, new provisions for proper
operation of the mechanical system must be Implemented. This will Involve providing grilles In each of the
classroom doors.
NEW WING-
The mechanical system on the Main Level should be returned to its intended mode of operation. A unit
ventilator should be provided in the special education classroom.
On the Main Level, a subslab depressurization system, which could be integrated with the Lower Level
system, should be designed and implemented.
On the Lower Level, a subslab depressurization system should be designed and partially implemented to
address those areas of highest subslab concentrations. That system should include provision for addressing
the lack of porosity of the subslab material so that adequate, relatively-consistent, depressurization can be
achieved. The design should also incorporate sealing apparent cracks and construction joints in the floor,
as well as, the cores of the block walls, at or near, the floor of the Storage Corridor and the Faculty Dining
Room.
The design should commence so that implementation of the Lower Level remediation could occur over a
few weekends or during Spring vacation.
RELOCATABLES:
Since radon detected in this area is significantly lower that most other parts of the school and it is
speculated that radon may be migrating from the old wing, it would be appropriate to wait until the
remainder of the building is remediated before undertaking a campaign to relieve a problem that may not
exist.
TIMING:
Since levels well in excess of 20 pCi/l have been confirmed by multiple tests, the US EPA recommends that
action be taken within several weeks to implement remediation.
PROCEDURE:
1. Design and specify the radon remediation system incorporating all appropriate techniques outlined
herein, the necessary mechanical system redesign elements, the mechanical system "tune-up," the
terms and conditions of all contracts, and the bid package(s)/documents.
2. Advertise for bids when appropriate.
3. Evaluate bids.
4. Select contractor.
5. Implement remediation.
Page X
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DISCUSSION - OBSERVATIONS ("Old" Wing):
Heating /Ventilating System:
Classrooms:
The heating system consists of steam-supplied unit ventilators manufactured by Herman Nelson (no longer
in business) in each classroom. The unit ventilators include provision for outside air and return air mixing
to respond individually to room conditions. Return air Is delivered to each unit by means of a plenum
chamber built behind integral bookcases/storage shelving. There is no direct opening for return air through
the front of the enclosure from the room to the return air chamber (lowest portion) of the unit ventilator.
An "on-off, and three-position fan speed control is readily accessible at the unit. There is a centralized
pneumatic temperature control system which controls outside air introduction, steam delivery and day-night
temperature selection and fan operation (entirely dependent on the position of the local fan controls) via day
thermostats in each classroom and night setback thermostats in two classrooms (Rooms 2 and 6).
During school-day operation, each unit ventilator responds to the thermostat and fan controls manually-set
in its respective classroom. During the night mode, the unit ventilator fans are disengaged and the unit
ventilators respond to the night thermostats by adjusting steam application to all units.
As part of the original heating and ventilating design, the school is provided with a utility tunnel containing
steam supply piping, steam condensate return piping, hot and cold water piping, sink drain piping, and
electrical conduits. Some of these pipes are insulated with seriously-deteriorating asbestos-containing
insulation. This tunnel also served as relief for fresh air introduced by the unit ventilators. Each classroom
contains grilles (18 in X 16 in) open to the tunnel. Originally, a normally-running fan was provided at the
accumulated end of the tunnels in the boiler room to continually withdraw air from each classroom via the
utility tunnel, discharging that air into the boiler room where It would become combustion air for the boiler
and/or would be forced to the outside through a large louver above the exterior double door. According
to maintenance personnel, the relief fan has not operated "in years." However, because of the tunnel
configuration, heating of tunnel air, and the higher temperature level in the boiler room, there is air
movement occurring in the tunnel caused by convection, from the tunnel extremities to the boiler room.
It is Important to note that the positions of the indoor and outdoor dampers in the unit ventilators is a
function of mechanical adjustments, and these adjustments varied significantly from classroom to classroom.
Because of this, the percentage of damper opening and closing could not be ascertained by the damper
mechanism indicator. It was demonstrated that the dampers in half of the classrooms did respond to
thermostat settings by automatically adjusting the dampers accordingly, but the exact ratio of outside to
return air could not be visually determined. In one case (Room #3), the return air damper was "caught" on
pneumatic control tubing and could not move. [We extricated lt-l
In classrooms 2, 4, 6, and 8 the outside air dampers remained closed regardless of the operating mode.
In three classrooms the Honeywell air stream control device is disconnected. In classroom 4, there is a
steam leak and also, the steam to the unit ventilator does not shut off, even though the thermostat is
satisfied. In classroom 5, the damper modulated inconsistently.
Day thermostats were set between 60 and 75 degrees Fahrenheit. Night thermostats were set at 64 and 70
degrees Fahrenheit.
Paae 3
-------
DISCUSSION - OBSERVATIONS ("Old" Wing):
Other Spaces:
The office areas, health room, lobby, corridor, boys and girts rooms are heated by means of
thermostatically-controlled steam-supplied cabinet unit heaters and convectors. In these cases, there are
no automatic provisions for outside air supply. Whereas the office, health, and lobby have operable
windows, the interior office, corridor, faculty (snack), and boiler rooms have non-operable windows. The
girls and boys rooms have no windows.
It was observed behind some exterior wall convectors that there are direct openings Into the exterior wall
wythes and block cavities.
The flooring above steam pipe routing in the lobby area was hot (as opposed to warm) to the touch. Actual
temperature measurements revealed that this floor was maintained at 112 degrees Fahrenheit, when the
building was in the heating mode, (note: Water above 110 degrees F is generally considered to be
scalding.)
DISCUSSION - EXISTING DRAWING ANALYSIS ("Old" wing):
Structure:
Interior and exterior wall footings are constructed of porous concrete masonry units (blocks) which, on the
interior continue as walls up through the floor slabs.
There is indication that there should be 4 in. of stone directly below the floor slabs.
The tunnel volume is approximately 6800 cubic feet
The energy-saving retrofits were designed to reduce both heat loss by the reduction in glass window
surfaces and exfiltration by providing "tighter" construction details.
Heating and Ventilating:
The boiler(steam generator) is specified as 60 bHp.
The unit ventilators are specified as 1000 cfm, 450 cfm outside air, 43.0 MBH total, with a 1/12 Hp motor.
The boiler room tunnel exhaust fan Is specified as 4210 cfm at 1/4 in. static pressure, with a 1/2 Hp motor.
The unit heater in the lobby and the convector in the faculty room are supplied by steam piped in terra cotta
sleeves under the floor from the tunnel to the units.
The boys and girls rooms have a common exhaust fan. The private lavatory in the office area has an
exhaust fan.
-------
DISCUSSION - POTENTIAL RADON ENTRY ROUTES ("Old" wing);
The initial building audit revealed several conditions that could contribute to radon infiltration into the
occupied spaces. The extent, size, configuration, and construction materials[porous block footings and
walls and dirt/shale floor) of the utility tunnel present a natural path for any subslab radon to accumulate
and/or move. There are several direct openings from the tunnel to each room for air relief, heating pipe
sleeves, and electrical conduits. In addition, five rooms (Rooms 1, 3, 4, 7 and the Health Room) have
loosely-fitting tunnel access doors with holes at the handles, built into the floor.
The hollow cores of interior wall blocks, because of temperature variations within the cavity, cause an air
flow from below the floor to the Interior of the building and to above the ceiling. This could be radon-laden
air, which depending on a number of conditions could be Infiltrating the building.
There is a significant crack in the terrazzo floor of the corridor in the vicinity of the office area. This breach
will allow passage of subfloor gases.
It was indicated that classroom doors are normally kept open during the school day unless noise control
is necessary. This tends to equalize radon levels.
It is possible, because the pressure relief dampers are closed in the new wing, that radon may be migrating
between the "old* and "new" wings, as well as, between the old wing and the relocatables.
Page S
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DISCUSSION - TESTING METHODOLOGY
Appendix A contains previous test data made available by the School District and the Pennsylvania
Department of Environmental Resources to Quoin Partnership.
In the process of building analysis, consideration was given to potential radon remediation techniques, the
most successful of which has proven to be subslab depressurlzation (the interception of radon gas below
the slab by creating a slight vacuum in the space below the slab and safely exhausting the gas to the
exterior).
The Initial effort concentrated on a detailed audit of the building, Its systems, and the existing operation of
those systems under various conditions. Secondly, It was intended to prepare the building to operate as
it would during school conditions during the winter, since this would result in the probable worst case
scenario, under which minimum Introduction of outside air occurs therefore radon concentrations would be
expected to be the highest.
In the worst case operating mode the building would then be tested, based on previous screening and
confirmatory radon measurements. Testing included determining whether or not the building was
pressurized (working against radon entry) or depressurized (enhancing radon entry) relative to the exterior
and the ground beneath the structure. To make these pressure measurements it was necessary to drill
through the structural slabs (floors) in selected rooms which are in contact with the ground.
Under those same conditions, pressure measurements were made between various locations within the
structure and components of the building to ascertain potential radon infiltration routes and radon behavior
within the building, and to identify any building systems operations which might be contributing to radon
infiltration.
Visual chemical smoke tests were conducted to determine the behavior of the air (and other gases, including
radon) at selected locations within the structure. These tests could indicate radon entry points, radon
transmission (communication) within the building and its structural elements, and potential success of
remediation techniques.
At most floor slab penetrations, radon sampling was done to obtain a profile of apparent subslab radon
concentrations.
In the original (1956) wing of the school, a sub-floor utility tunnel which extends virtually around the entire
perimeter offered a high probability of subslab radon distribution to various parts of the building. Radon
measurements were taken at various locations In this "tunnel."
Very short term(less than one minute) radon sampling measurements were taken by "Pylon" radon monitors
for relative comparison between tested points. Longer-term (hours and days) radon measurements were
taken utilizing electret devices and "Pylon" monitors, the latter set to record levels In desired increments of
time (hourly and in some cases every 15 minutes), so that radon levels under different operating conditions
of the building could be compared.
Additional environmental parameters (temperature and air flow) were measured under various conditions
as needed.
Page 6
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RESULTS/CONCLUSIONS - OLD WING
Conclusions
The subslab Pylon sampling indicates that radon exists and/or migrates to varying degrees
throughout the area below the building.
Radon concentrations in the tunnel were as high as 436 pCi/l. Entry to that space should only be
done by personnel with the proper radon protective equipment.
There are multiple Intentional (pipe sleeves, relief grilles, etc.) and unintentional openings (normal
construction situations) between the tunnel and occupied spaces and the subslab areas and
occupied spaces which allow radon entry.
All walls with hollow cores represent potential radon infiltration routes, because they are supported
by hollow core foundation walls which extend several feet below the floor slabs.
The spaces without unit ventilators or exhaust fans, and consequently, with no fresh air introduction
have no means of diluting or exhausting any radon that enters the space.
Operation of the unit ventilator fans, at any speed, results In a negative pressure at the base of each
unit. That negative pressure is sufficient to cause any gas, including radon, which exists in the
tunnel to be drawn into the unit ventilator return air chamber, and from there, to be distributed to
the classroom.
The automatic response and mechanical linkage adjustment of the unit ventilator outside air
introduction is inconsistent. Air flow data indicates that some units provide no outside air
Introduction while others provided far less than the original design criteria and consequently, far less
than the current Pennsylvania Department of Education requirements. Therefore, there is, in some
cases, no dilution for radon entering a classroom, and in others, less than adequate outside air
introduction.
Depressurizing the tunnel by means of a HEPA negative air unit, without sealing slab penetrations
providing significant leakage points, would have resulted in unsatisfactory depressurization of the
areas below the slab. Once obvious/major openings from the rooms to the tunnel had been sealed,
depressurization was achieved, therefore this demonstrates adequate subslab communication, and
a satisfactory long-term subslab pressure reduction method.
Attempting a potential interim method of flushing the building with outside air and then operating
under normal interior conditions without subslab depressurization resulted in unacceptable radon
build-ups in a matter of a few hours. Therefore, flushing only, is not an acceptable interim measure
to reduce radon.
Subslab depressurization by exhausting tunnel air to reduce tunnel pressure to -0.020 relative to the
rooms, is, in itself, insufficient to reduce radon concentrations in all areas to 4 pCi/l or less.
Tunnel depressurization does not reduce subslab pressures In the interconnecting corridor between
the wings.
Page 7
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RESULTS/CONCLUSIONS - OLD WING
Recommendations:
1. All asbestos-containing materials in the tunnels should be removed. This will allow subslab
depressurization utilizing the existing tunnel for the exhaust plenum without addressing the hazards
of asbestos: There will be no maintenance and disposal of any asbestos filters. Radon remediation
workers requiring access to the tunnel will only require radon protective breathing apparatus rather
than full protective clothing (and the associated disposal costs), as well. Removal of the
deteriorating pipe insulation will allow complete and proper insulation of the steam and hot water
pipes with the resultant energy savings. Lastly, maintenance personnel can have access to the
tunnels for maintenance and repair with only breathing precautions (for radon) rather than complete
body and breathing protection for asbestos.
NOTE: Radon remediation can be undertaken without removing asbestos-containing materials in
the utility tunnel. Such remediation will significantly increase radon remediation costs
because of the expense associated with reduction in remediation worker efficiency
associated with the necessary asbestos protective required for workers and the building;
as well as, the costs associated with disposal of contaminated clothing.
2. All openings between the tunnel and the exterior, and the tunnel and the occupied spaces, should
be sealed against radon infiltration. Any existing openings in the interior tunnel walls should remain
to aid in subslab depressurization. Exterior tunnel wall penetrations, if any, should be similarly
sealed. All existing classroom pressure relief grilles should be permanently sealed. Mechanical
system design-compatible pressure relief louvers should be provided in all classroom doors such
that during outside air introduction the room remains slightly pressurized relative to the subslab
area.
3. A code-compliant tunnel depressurization system should be provided to create a minimum negative
pressure of -0.020 at all subslab locations. The system should include a roof-mounted fan, (with
appropriate air-flow annunciation) above the boiler room, interconnected to the existing tunnel duct
in the boiler room. All existing and new duct work should be designed to prevent and/or sealed
against, any radon leakage into the boiier room. The system shall be provided with all code-
required smoke detection and interlocked, if necessary, with the exhaust fan.
4. The lower front panel enclosure for each classroom unit ventilator should be perforated to reduce
the negative pressure in the lower portion of the unit, immediately above the floor and tunnel below
iL (This recommendation has been implemented by SGASD staff.)
5. The mechanical heating and ventilating system should be "tuned-up" to insure proper control and
mechanical operation, including appropriate outside air introduction per the Pennsylvania
Department of Education Piancon requirements. Unit ventilators should be provided in occupied
spaces presently without outside air introduction.
6. Potential additional measures which could be implemented to help alleviate radon infiltration include:
A. Drilling and sealing the hollow cores of the masonry units of the uppermost row of the
exterior wall of the tunnel.
6. Removal (and subsequent replacement) of bookshelves and storage shelves adjacent to the
unit ventilators to seal any potential infiltration routes not observable without their removal.
C. install an independent subslab system for the interconnecting corridor between the wings.
Page 9
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SPRING GROVE AREA SCHOOL DISTRICT
RADON DIAGNOSTIC TESTING DATA
December 26, 1990, 6:00 PM
Pressure Differentials - Room #1 Unit Ventilatorflnches H20] (Main Level-Old Wing)
[Both top control access doors closed during measurements]
Room to exterior: +0.010
Room to tunnel: -0.020
Lower
left Side
Lower
Center
Lower
Rioht Side
Not Accessible Not measured
Not Accessible -0.038
Not Accessible -0.043
Not Accessible -0.048
Front of enclosure in place:
Fan Speed Off +0.001
Low -0.034
Medium -0.040
High -0.044
Front of enclosure removed:
Fan Speed Off Not measured Not measured Not measured
Low -0.002 -0.005 -0,002
Medium -0.002 -0.006 -0.003
High -0.002 -0.007 -0.004
Page 9
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I V - 4
PRESSURE FIELD EXTENSION
USING A
PRESSURE WASHER
NEW JERSEY DEP SPONSORED PROJECT
INNOVATIVE MITIGATION RESEARCH AWARDS
BILL BRODHEAD
2844 SLIFER VALLEY RD.
RIEGELSVILLE, PA., 18077
215-346-8004
ABSTRACT
This project was delayed because of contract negotiations and is
presently in the preliminary stages. Although only a limited amount
of data is available, the technique was successful done.
Radon remediation is typically done with sub-slab ventilation
systems. Sub-slab ventilation installation failures are often
due to an incomplete pressure field extension that allows radon to
continue to enter the building. Over half the homes we mitigate do
not have a good gravel base under the slab. This project
investigated a technique for extending the pressure field in tight
soils from a single suction point by the creation of sub-floor
tunnels using commonly available high pressure washers. Two
buildings with the appropriate tight non-rocky soil were tested for
pressure field extension before and after tunneling with the high
pressure washer.
The tunneling under the slab was an effective method for
extending the pressure field. This technique holds good promise for
mitigators dealing with tight soils and limited choices for
suction hole locations.
-------
PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
PROBLEM STATEMENT:
If we are to achieve levels as low as reasonably possible,
techniques must be developed that are simple and effective for all
types of housing and soil. New data is showing that even levels as
low as the 4 pCi/1 guideline may still result in a substantial
relative risk of developing lung cancer. This makes it more critical
to optimize the mitigation systems to produce the maximum benefit
while still being cost effective.
This project addresses a technique to be used with buildings
that have a problem with sub-slab ventilation systems. The problem
building addressed in this project is partially finished and built
without any gravel under the concrete floor with no significant
settling of the sub-soil. It is what we refer to in the industry as
a soil with poor communication. This condition can be revealed in
the initial site visit if a diagnostic communication test is done.
The test requires an approximate 1" hole to be drilled through the
concrete floor and a shop vac set up to suck on the hole. Small test
holes are drilled at varying distances from the shop vac hole and the
pressure change with the shop vac on versus off is measured along
with the total amount of air flow. A tight soil is indicated if the
results of the test reveal limited air coming out of the vacuum
cleaner and very limited pressure field extension. If their is a lot
of air flow but limited pressure field extension then this indicates
good communication but significant leaks or porosity in the soil.
This project addresses the tight soil condition, especially in
situations where the finished condition of the space makes it costly
or impossible to practically add additional suction holes. A goal of
this project is to determine if it is more practical in unfinished
spaces to add suction holes than to use this technique.
HRV's - Mitigators in the past have often had to fall back
on using air to air heat exchangers in houses with finished areas and
poor sub-soil communication. This, however, has not been a
satisfactory solution. Ventilators increase the heating load and add
excess humidity in the summer. The performance of ventilators often
deteriorates when maintenance is not performed on a regular basis.
With ventilators, homeowners have no easy way to determine if the
system is operating properly, other than to continually test for
radon. Sub-slab systems are preferred over HRV's because they
require very little maintence, there is less deterioration of
performance over time, their is less operating cost, the system can
be monitored with a pressure gauge and generally costs less to
install.
FAILED SUB-SLAB SYSTEMS - The present industry standard for
radon action is 4 pCi/1. There are, however, many sub-slab systems
that are installed which fail to reduce the radon levels below 4
pCi/1. Often this failure is due to incomplete pressure field
extension of the sub-slab vacuum system. This incomplete vacuum or
pressure field is often due to a tight sub-soil without any stone
base. Most newer buildings have a stone base although some basement
PAGE 1
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PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
concrete floors are poured directly on packed sand or screenings.
Older buildings often had the concrete floor poured on the dirt and
the basement space is now finished. A finished basement complicates
the situation because it is difficult to add extra suction points.
SUCTION PITS - Some mitigators will dig a pit to enhance the
pressure field in poor communication soils. Digging a pit, however,
beyond what can be dug out of a single five inch hole, will typically
only extend the pressure field the distance that the pit is dug out.
This is because hole size enlargement produces diminishing reductions
in pressure loss due to the limited amount of air flowing through the
tight soil. There will actually be little pressure drop reduction
once the hole has a few gallons of sub-soil dug out of it. Other
mitigators have tried digging long ditches and filling the ditch with
gravel and then replacing the floor. This would be more effective
than a suction pit, but is very labor intensive, produces a lot of
dust, and requires additional equipment to open up the floor, haul
the dirt out and replace with gravel and new concrete.
WATER JET ALTERNATIVE - Poor communication soils can be
effectively mitigated with sub-slab suction systems, but we need to
develop more good techniques for dealing with this situation. If the
same effect as trenching could be obtained by tunneling under the
concrete floor through the existing 5" suction hole, a large cost
savings could be realized without all the drawbacks and could give
better results than a pit suction. Pressure washer equipment that
can produce from 800 to 3000 psi pressure is readily available. The
cost of these units runs from $450 to $2500. The smaller units are
powered by an electric motor. The larger units use a gas powered
motor. One component of the study is to determine if the less
expensive and troublesome electric powered pressure washer is
adequate or is it necessary to use the larger more bothersome gas
powered unit. Both of these units are within the cost of other
equipment used by the mitigators, such as hammer and core drills.
HOUSE SELECTION - The ideal house to use this technique on
would have one or more of the following characteristics: a soil that
is free from rocks larger that an inch or two; the requirement for
additional pressure field extension but difficult and expensive
because of the finished condition of the basement or obstructions
preventing easy pipe routing; a source of water; an outside
entrance to the basement near the unfinished section to make hauling
and adjustment of power equipment easier; a work area around the
suction hole; a place that the water and sludge used in this
technique can be discarded as the work is being done.
PRESSURE WASHING EQUIPMENT - The equipment used in this
project was purchased through Grainger's which has warehouses
throughout the US. The electric power washer is model # 3Z829. It
uses a 1 1/2 horsepower electric motor and produces 1000 psi with a
flow 2 gallons per minute. Its retail cost is $840.91. This unit
can be set up to run in the basement.
The gasoline powered unit has 11 horse power and produces 2900
psi with a flow rate of 3 1/2 gallons per minute. The model # is
PAGE 2
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PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
5Z169 and presently retails for $1711.20. Both units require an
additional 25 feet of 1/4" hydraulic hose that will handle the water
jet pressure. A solid cap is installed on the end of the hydraulic
hose and it is installed in the wand spray trigger handle that comes
with the units. A 1/32" hole is drilled in the hose cap. This unit
must be run outside or in an open garage with the hoses run between
the basement and the unit. One concern if you live in a northern
climate is the possibility that the water left in the pressure washer
will freeze if the unit is left in the truck at night.
FIRST TRY - We had begun a mitigation of a school dormitory
building and had not been able to do initial diagnostic communication
tests. The center suction hole revealed a clay soil and limited
pressure field extension with a F150 fan pulling directly on the dug
out suction hole. The gasoline power pressure washer was used with a
two man crew. One man controlled the trigger and the other held the
hose in the suction hole and slowly pushed the spray head through the
soil. Occasionally the hose would get stuck as it was pushed away
from the hole or in trying to retrieve it out of the hole. it also
took two hands to force the hose to tunnel away from the hole as the
water pressure pushed back. The shop vac did a good job of sucking
up the muck but you often mistakenly fill the shop vac container full
of water. Carrying a shop vac full of water up a set of basement
stairs will either put hair on your chest or give you a hernia.
Having a place to dump the slurry at the job site will save a lot of
hauling of sloshing buckets. Digging the hole out, although a muddy
job, is fairly easy.
Protective gloves are critical as the kick of the hose upon
start up would forces your hands into the jagged concrete which in
this case also contained broken wire mesh. Protective equipment
including eye goggles is a good idea to prevent what could be a
serious injury.
We were able to get at least 10 gallons of clay out of the hole
and the pressure hose extended about five feet in several directions.
When we tested the pressure field extension we were surprised to
find that the readings were about 20% weaker than before we had used
the water jet. Three days later when we recheck the same test holes
we found that we now had approximately doubled the original vacuum
readings. Two of the readings reversed from .001" and .003" positive
to .001" and .002" negative. It seems that the water temporarily
clogs up the pores of the soil until it has a chance to dry.
We continued to use the pressure hose on three other suction
holes and the final pressure readings under the slab were excellent
and the radon concentrations fell to below 2 pCi/1.
FIRST HOUSE - The first house in the study is a thirty year old
two story colonial that has a partially finished basement, a small
dirt floor crawl space, an attached garage, and a slab on grade patio
that has been converted into an enclosed spa room. The basement has
a set of stairs leading to the garage as well as a standard set of
stairs between the basement and the first floor. The foundation is
block walls that are capped on top. The radon levels measured 20.8
pCi/1 in the basement.
A communication test revealed that their was screenings, which
PAGE 3
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PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
is a fine crushed rock, under the concrete floor. The soil
communication in the stretched half way across the unfinished portion
of the basement. A two hole suction system was installed in the
basement and a rubber EPDM barrier was sealed on top of the dirt
floor of the crawl space. A dampered suction pipe was install
through the crawl space barrier. The pipe was routed through a hall
closet in a single story portion of the house into the attic and out
the roof. A F150 fan was installed in the attic.
INITIAL SYSTEM PERFORMANCE - All pressure readings were taken
with a EDM digital micromanometer. Airflow measurements were taken
with the digital micromonometer and a pitot tube.
The vacuum in the two basement suction pipes was 1.2" and the
floor vacuum ranged from .040 negative to .013 positive in the far
end of the finished area. The air flow in the basement suction pipes
was about 10 CFM while the crawl space suction pipe was moving 67 CFM
even with the damper partially closed.
RADON LEVELS - The first followup radon measurements before
the high pressure water jet was tried were 9.4 in the finished area
and 9.3 in the unfinished area near the crawl space entrance.
Although the primary reason for developing this technique is to
reduce the radon levels, the success of this technique is more
quantitatively measured with pressure changes in the surrounding sub-
soil, rather than radon measurements. Radon can vary so much from
day to day that, changes in the concentration are more difficult to
interpret. Failure to reduce the levels significantly may be due to
other radon sources in the building that are not part of the area
that the pressure field is being extended to. This source could be
the block walls that are adjacent to the slab on grade spa room or
the garage slab.
WATER JET PROCEDURE - All of the following procedures were done
with one person. The center hole in the basement was opened up and
enlarged to 6" to allow more room to work. This took about 15
minutes. An additional eight gallons of screenings and soil was
removed from the hole. This took about 30 minutes. The pipe was
then replaced and the pressure field extension test holes remeasured.
There was no change in the pressure reading in the finished area and
about a 10 to 20% increase in the test holes in the same room. These
holes are twelve and eighteen feet from the suction hole. This took
about 30 minutes to set up the pipe and remeasure the test holes.
The hole was then opened again and the water jet set up. The
end cap of the hydraulic hose was modified with two additional 1/32"
drilled holes that slanted to the back. This was done to reduce the
back pressure of trying to push the hose through the soil, to cause a
larger tunnel to be formed and to assist removal of the hose when it
becomes stuck.
About five tunnels were dug approximately six feet through the
screenings that were just below the slab. The screenings were only
an inch or two thick so the tunneling more than likely went through
the soil. In this case, there was no accumulation of water compared
to the commercial job done previously as it must have soaked into the
screenings. An additional four to six gallons of soil and screenings
PAGE 4
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PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
was removed from the hole. If the tunnels traveled in a straight
line , which is hard to determine, then the suction hole was actually
enlarged to a diameter of over ten feet. This procedure took about
30 minutes.
WATER JET FOLLOW MEASUREMENTS - The sub-slab pipes were hooked
back up and the pressure field extension measurements were repeated
and once again there seemed to be a reduction in vacuum readings of
about 10% for the test holes that were relatively close to the
suction pipe. The air flow and pressure measurements in the pipe did
not change significantly. These final measurements took about 30
minutes to do again and clean up took about 15 minutes.
Three days later I repeated the floor pressure measurements and
was surprized that they had not changed. Upon opening the pipe into
the floor to inspect the suction hole I discovered that most of the
pipe inlet had become blocked by loose plastic that was used as a
backer rod around the pipe in the enlarged hole. Once the barrier
was removed and the pipe resealed into the hole the pressure field
extension measurements improved dramatically. The percentage
increase was from no increase in the far end of the finished area to
a 10%, 25%, 50%/ 175%, and 250% increase in negative pressure under
the floor.
POST WATER JET RADON LEVELS - Followup radon measurements
after the high pressure water jet were 7.1 in the finished area and
8.1 in the unfinished area near the center suction hole. Because the
back room measured slightly higher than the finished area it was
decided that a suction should be installed into the slab on grade spa
room sub floor from the basement. Although this would lessen the
amount of available suction to the sub- floor it might eliminate a
major source of the remaining radon. The suction point was installed
so that it would draw from the soil and not directly from the block
wall and a damper was installed to control excessive air flow. A
followup radon test however indicated that this extra suction had
little effect on the radon levels. It appears that the remaining
problem is still due to the lack of vacuum in the finish area and an
additional suction point will have to added with pipes run across the
finish ceiling or a third suction hole might be installed in the
unfinished area with a repeat of the water jet procedure.
PAGE 5
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PRESSURE FIELD EXTENSION
USING A HIGH PRESSURE WATER JET
FIRST HOUSE PRESSURE FIELD EXTENSION MEASUREMENTS
ALL MEASUREMENTS DONE WITH BASEMENT TO OUTSIDE DOOR OPEN
SUB-SLAB
HOLE DUG
FRESH
3 DAYS
ONLY
OUT
WATER JET
LATER
T2 -.064
T2 -.053
T2 -.053
T2 -.059
T3 -.020
T3 -.020
T3 -.016
T3 -.050
T4 +.002
T4 +.001
T4 +.002
T4 +.001
T5 +.000
T5 -.000
T5 +.000
T5 -.000
T6 -.025
T6 -.027
T6 -.027
T6 -.041
T7 -.038
T7 -.045
T7 -.042
T7 -.056
T8 -.092
T8 -.091
T8 -.080
T8 -.159
PAGE 6
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IVP-3
A LABORATORY TEST OF THE EFFECTS VARIOUS RAIN CAPS ON SUB-SLAB
DEPRESSURIZATION SYSTEMS
By: Mike Clarkin
Terry Brennan
David Fazikas
Camroden Associates, Inc.
R.D. #1 Box 222 East Carter Road
Oriskany, NY 13424
ABSTRACT
Many sub-slab depressurization systems are installed with some type of rain
cap intended to keep rain water from entering the exhaust pipe. There is some
question among researchers and radon mitigators whether a rain cap in necessary,
and what effects a rain cap has on the sub-slab depressurization system. This paper
makes no effort to explore the necessity of a rain cap, only the effect that certain rain
caps have on the system. To help answer that question, a series of tests were
performed to determine: 1. the additional resistance the caps place on a pipe, and, 2.
the effect of wind on the system with the various rain caps installed. The results of
those tests are presented in this paper.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency and therefore the contents do not necessarily reflect the views of
the Agency and no official endorsement should be inferred.
1
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INTRODUCTION
Many radon mitigation contractors routinely install some type of cap on the end
of a sub-slab depressurization system to prevent rain from entering the exhaust pipe.
While the use of a rain cap may or may not be necessary, this paper takes neither side
of the argument. The objectives of the tests described herein were to explore the effect
that various types of hardware that are often used as rain caps have on sub-slab
depressurization systems. To reach those objectives, a series of measurements were
made to determine the backpressures the rain caps induced on the system. Additional
tests were made to determine the draft generated by each rain cap on a passive sub-
slab depressurization system.
TYPE OF CAPS TESTED
OPEN PIPE
The open pipe was a length of 4 inch, schedule 20, PVC plastic pipe.
CAP A
This cap is manufactured for the purpose of preventing rain from entering a sub-
slab depressurization system. The cap consists of a PVC plastic collar which slips
over the end of the exhaust pipe, a PVC plastic cover to keep rain out, and a PVC grill
on each end to keep other objects out of the exhaust pipe.
Air, flowing vertically up the SSD exhaust pipe, strikes the cover, and is diverted
horizontally through the grills. This cap is designed to slide over the end of the SSD
exhaust pipe, therefore the area available for exhausting air is not reduced by the cap.
DRYER VENT CAP
This type of cap is manufactured for the purpose of capping a horizontal clothes
dryer exhaust pipe. The cap is constructed of plastic and has movable louvers which
remain normally closed until an airflow of sufficient volume and velocity opens the
louvers. The cap is designed to fit on the inside of the 4 inch exhaust pipe, which
decreases the exhaust pipe area from to 12.7 to 10.3 square inches. The louvers,
depending on the degree of opening, causes a change in exhaust area that ranges
from nearly nothing when closed, to approximately 9.7 square inches when fully open.
DRAFT INDUCER
The draft inducer tested was a 6 inch diameter stainless steel unit. The inducer
was connected to the test system with a 6 in. to 4 in. rubber reducing fitting.
Draft inducers are designed to be placed on the end of a chimney to increase
the amount of draft and assist in the proper exhaust of combustion gases. The draft
inducer is designed to fit over the end of the exhaust pipe, therefore exhaust pipe area
is not reduced. Air, flowing vertically up the SSD exhaust pipe, strikes the top of the
inducer and is diverted horizontally. The draft inducer, when used in radon control
systems, is usually used to provide additional suction in a passive SSD system, and is
2
-------
not normally installed for the purpose of keeping rain from entering the system.
TURBINE VENT
The turbine vent tested was a 4-inch diameter, galvanized steel unit. The
turbine rotates on bearings with passing breezes, and creates an upward draft of air.
The bearing assembly reduces the exhaust pipe area to approximately 10 square
inches.
Turbine ventilators are designed for removing hot air from a building in summer
and moisture-laden air in the winter. The turbine vent, when used in radon control
systems, is usually used to provide additional suction in a passive SSD system, and is
not normally installed for the purpose of keeping rain from entering the system.
Figure 1 illustrates each type cap tested.
Figure 2 illustrates the areas available for the exhausting of air for an open pipe,
and each cap tested.
3
-------
t
AIRFLOW
/ffTTn\
CAP A
HINGED
FLAPS
\
ATTACHES TO
EXHAUST PIPE
AIRFLOW
DRYER VENT
CUT-AWAY VIEW
\
1
AIRFLOW
TOP VIEW
DRAFT INDUCER
Figure 1. Types of caps tested.
TURBINE VENT
4
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Dryer Vent 9.7 sq in.
Turbine Vent 10 sq in.
Open Pipe, Cap A, Draft Inducer
12.6 sq in.
Figure 2. Relative exhaust areas. Drawings are approximately to scale.
5
-------
TEST PROCEDURES
BACKPRESSURES CAPS PLACE ON THE PIPE
The objective of a sub-slab depressurization system is to create an air pressure
field beneath the floor slab that is less than the air pressure in the building. This is
commonly referred to as the "negative pressure". To maintain the negative pressure
beneath the slab the system must overcome conditions which tend to equalize the
pressure differences between the sub-slab and the interior of the building. Air,
exhausted from the house by temperature differences, wind effects, and the
exhausting of inside air by ventilation fans all tend to create a low pressure in the
house. Restrictions in the sub-slab depressurization system tend to create a high
pressure in the system. .
Techniques that can be used to lessen the negative pressures in the home are
often out of the scope of the radon mitigation contractor. This is not to say the
mitigation contractor is not able to perform those techniques. In fact, many mitigation
contractors were insulating, weatherproofing, or performing HVAC work long before
they got into the radon business. However, as a mitigation contractor, they are at a
clients home to fix a radon problem. One of the primary methods is with a sub-slab
depressurization system, therefore, the SSD designer normally is concerned with the
sub-slab depressurization system only.
There are chiefly two issues of concern to the sub-slab depressurization system
designer The first concern is the amount of air that will flow through the system. The
second is the amount of backpressure that is resisting the flow of air.
As air flows through the exhaust pipe, obstructions, changes in airflow direction
(elbows) and even air friction inside the pipe create a resistance to the flow of air.
This resistance in turn creates a backpressure in the pipe. An increase in
backpressure can decrease the strength of the negative pressure field beneath the
slab to a point where the negative pressure field no longer exists, or is not sufficiently
strong or extensive enough to prevent radon from entering the building.
To determine the effect that different rain caps had on the airflow and
backpressures, the cap under test was placed on the end of a length of 4 inch PVC
pipe Airflow through the pipe was produced by an in-line fan. A micromanometer
was used to measure the pressure differentials between the inside and outside of the
exhaust pipe. The micromanometer and flow grid was used to measure the pitot
pressure in the pipe from which the volume of air flowing through the pipe was
determined. A variac was used to change the speed of the fan to provide several data
points at different airflows and pressure differences. Figure 3 illustrates the equipment
configuration for this test.
6
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flow grid
fan
rain caps placed
micromanometer
to measure pressure
differential
micromanometer
to measure pitot
pressure
variac to adjust
fan speed
AIRFLOW
~
~
AIRFLOW
Figure 3. Equipment layout for system backpressure tests.
INDUCED DRAFT TESTS
Passive sub-slab depressurization systems rely on means other than an
electrically powered fan to develop the desired negative pressure field beneath the
floor slab. Natural forces, such as the stack and wind effects, if the conditions are
correct, can produce an upward movement of air within a sub-slab depressurization
system. The negative pressure field can be rather weak in a passive system, therefore
rain caps that increase the backpressures may have a serious detrimental effect on a
passive system. Conversely, a cap that is designed to induce airflow may have a
positive effect on the system.
To determine the draft that the cap induced on a passive sub-slab
depressurization system, pressure differences between the interior of the pipe and the
outside air were measured at various wind speeds. A wind tunnel was constructed to
direct the flow or air across the cap. The cap to be tested was placed on a length of 4
in. PVC pipe within the wind tunnel. A large blower door fan was used to draw air from
the open end of the tunnel and across the cap. A vaned anemometer was used to
measure the windspeed at different locations within the tunnel, and the average
7
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windspeed was calculated. The pressures induced in the pipe by the wind were
measured with a micromanometer. Curves representing pressure differences at those
windspeeds were generated for each cap tested.
Figure 4 illustrates the equipment configuration.
AIRFLOW
1
~ZD
LJ X
^ anemometer
micromanometer
Figure 4. Equipment layout for induced draft tests.
RESULTS
BACKPRESSURE TESTS
As illustrated on Figure 5, all caps tested developed an additional resistance
within the exhaust pipe when compared to an open ended pipe. The best performer
was the draft inducer, which resulted in the least amount of backpressure across the
entire operating range of the fan. The worst performer was the dryer vent. Note that
the curve for the dryer vent is inverted when compared to the other caps tested and the
open ended pipe. The inversion is due to the vanes on the vent cap opening wider at
the higher airflows. All caps resulted in a backpressure that could cause a marginally
operating sub-slab depressurization system to fail to reduce indoor radon
concentrations.
8
-------
o
(A
CO
a
ui
oc
3
(/)
(f)
ill
a:
a
*
o
<
OQ
CAP A
TURBINE
OPEN PIPE
DRYER VENT
DRAFT INDUCER
500
1000
1500
2000
AIRFLOW (Ipm)
Figure 5. Backpressure in pipe due to caps.
INDUCED DRAFT TESTS
All caps, and the open ended pipe, produced a negative pressure in the pipe
when air was flowing across the cap, however, Cap A, which produced a fairly strong
negative pressure within the pipe when the airflow was perpendicular to the cap,
produced a backpressure in the pipe when the open end of the cap was parallel to the
airflow. Perhaps a modification to Cap A, which moved the cap so that the open end
was always parallel to the wind would improve the overall performance of this cap.
The best performer, when all windspeeds are considered, was the turbine ventilator,
which produced a negative pressure in the pipe that ranged from -3 pascals at 11 kph
(-0.01 in. at 6.5 mph) to -31 pascals at 27 kph (-0.12 in. WC at 17 mph). Figure 6
shows the results of the tests performed.
9
-------
1 0
-10
-20
-30
-40 H
OPEN PIPE
TURBINE
CAP A PARALLEL
CAP A PERPENDICULAR
DRAFT INDUCER
-50
10
20
T-|—>
30
¦ ! ¦
40
50
WINDSPEED (kph)
Figure 6. Induced pressure results.
CONCLUSIONS
Caps, when placed on the end of a sub-slab depressurization system can
increase the amount of backpressure in the system. In order of increased
backpressures, the open pipe results in the least backpressure, followed by the draft
inducer, Cap A, the turbine vent, and finally, with the greatest amount of backpressure,
the dryer vent. This comes as no great surprise. If we had considered the open
exhaust area of each cap with regard to a resistance to airflow, and the diversion of the
flow of air from the vertical to the horizontal as another resistance to airflow, we
Drobablv could have predicted quite accurately how each cap would rank However,
that would have resulted in a very short paper. The test results indicate that
backpressures created by the caps amount to 10 to 12 pascals at most, and, are more
likely to be 2 to 5 pascals at the airflows encountered in most SSD installations. This
is not a significant backpressure when the air pressure induced under a slab is 50 to
200 pascals However, when the pressure under the slab is only 5 to 10 pascals, as It
may be in a passive SSD, or on very permeable soils, or in spots where there is fine
10
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sand or clays under the slab, the backpressure from the caps becomes significant.
The best recommendation is when considering whether to use a cap is to measure the
sub-slab pressures with the pipe uncapped, and with the cap temporarily installed. If
the cap seems to make a significant difference in the sub-slab pressure, don't use it.
A substantial draft can be induced on a passive sub-slab depressurization
system when wind blows across the end of the exhaust pipe. Of all the caps tested,
the turbine ventilator created the strongest draft at high windspeeds. The worst
performer was the dryer vent. Notice that there is very little difference between open
pipe and other caps until a wind speed of greater than 12 kph is reached. This makes
caps most useful in windy sites, but it must be understood that windspeeds are
extremely variable, and the prudent mitigation contractor should not count on the wind
to be of much help.
11
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Paper V -1
A MODELING EXAMINATION OF PARAMETERS AFFECTING RADON AND
SOIL GAS ENTRY INTO FLORIDA-STYLE SLAB-ON-GRADE HOUSES
R.G. Sextro, K.L. Revzan and W.J. Fisk
Indoor Environment Program
Lawrence Berkeley Laboratory
University of California
Beikeley, CA 94720
ABSTRACT
This paper discusses the use of a finite-difference numerical model to examine the influence of soil,
fill, and construction characteristics on convective entry of radon and soil gas into slab-on-grade houses.
Such houses, built with a perimeter, hollow-core concrete block stem wall and an above-grade floor slab
resting on fill, are typical of a portion of the Florida housing stock. When the building is depressurized
with respect to the ambient pressure, radon-bearing soil air will flow through various combinations of
soil, fill, and blockwall components, entering the house through perimeter slab-stem wall gaps or interior
cracks or other openings in the floor slab. At a constant building depressurization, the model predicts the
steady-state pressure, flow, and radon concentration fields for a soil block 10 m deep and extending 10 m
beyond the 7-m-radius slab. From the concentration and pressure fields, radon and soil gas entry rates are
then estimated for each entry location. Under base case conditions, approximately 93 percent of the soil
gas entry is through the exterior section of the stem wall, 5 percent is through the interior section of the
stem wall, 2 percent through an interior slab opening, and less than 1 percent through gaps assumed to
exist between the stem wall and footing or the stem wall and floor slab. In contrast, 57 percent of the
radon entry rate occurs through the interior section of the stem wall, 22 percent through the interior slab
opening, 20 percent through the exterior section of the stem wall, and less than 0.5 percent through the
gaps. Changes in fill permeability have significant effects on radon entry, while changes in blockwall
permeability are largely offset by increased flow and entry through structural gaps. These results, along
with those from other model configurations, will be discussed.
This work has been supported, in part, by the U.S. Environmental Protection Agency. This paper
has been reviewed in accordance with the U.S. EPA peer and administrative review policies and has been
approved for presentation and publication.
-1-
-------
INTRODUCTION
The role of convective flow of soil gas in transporting radon into buildings is widely acknowledged;
however, the factore that affect radon entry can be complex. These flows will depend upon the driving
pressure, the type and location of the openings connecting the building interior with the surrounding soil
environment, and upon the characteristics of the soil medium (1,2). The nature of these openings is
strongly influenced both by the type of building substructure and by the specific construction details. The
driving pressure, which is the pressure difference between the surface of the soil surrounding the building
and the building interior, is caused by the stack effect (due to temperature differences between the inside
of the building and the outdoors), wind loading on the building shell, and the operation of heating and/or
air conditioning systems.
In response to the discovery of elevated radon concentrations in a fraction of the Florida housing
stock (3), the State of Florida and the U.S. Environmental Protection Agency have established the Florida
Radon Research Program, with the broad goals of conducting research on radon entry into housing typical
of that built in Florida and to investigate and develop techniques that limit radon entry into existing build-
ings or new construction (4). One objective of the research is to understand how indoor radon concentra-
tions are influenced by details of the building substructure and the adjacent soils and fill materials.
We have developed and refined several detailed numerical models of radon transport through soil
and entry into buildings (5,6,7) in order to investigate factors influencing soil gas and radon migration,
including characteristics of the building and the surrounding soil. In the present study, a two-
dimensional, steady-state finite-difference numerical model, utilizing cylindrical symmetry, has been
assembled, with boundary conditions appropriate for one form of the slab-on-grade construction used in
Florida housing. The model has been used to explore the influence of soil and building parameters on soil
gas and radon entry. This paper summarizes the results of these simulations and discusses their implica-
tions for possible methods of limiting soil gas and radon entry. Greater detail is presented in reference
(8).
MODEL DESCRIPTION AND APPROACH
MODEL OVERVIEW
The model used in this study is based upon a finite-difference numerical code in which the soil is
assumed to be isothermal and the relationship between gas flow and driving pressure is assumed to be
linear (Darcy's law) (5,6). We have used a form of the model in which the Cartesian coordinates are
transformed into a cylindrical coordinate system. This, in effect, reduces the model to two dimensions for
computing purposes. Since many of the structural elements of interest to our analysis are at the perimeter
of the house or can be chosen to have cylindrical symmetry, there is Utile loss of generality in using
cylindrical coordinates. This approach permits increased resolution and/or more rapid convergence with
-2-
-------
only modest loss in realism in moving from a fully three-dimensional treatment (6). Because we are
interested in a parametric analysis, the benefit of greater speed outweighed the slight loss in accuracy
compared with a fully three-dimensional configuration.
Details of the model, including the appropriate governing equations, are presented in references
(6,8). We discuss here some of the major features and assumptions of the model. Boundaries for the soil
block have been chosen to be 10 m from the footing in both the radial (r) and vertical (z) directions, as
indicated in Figure 1. The bottom surface of the slab and the outer surfaces of the footing are assumed to
be no-flow boundaries. Thus the model does not explicitly account for radon entry by diffusion through
the concrete slab; rather, this entry rate is calculated separately (9). The model does, however, include
migration of radon in the soil and fill by diffusion.
A static pressure difference is applied between the surface of the soil exterior to the building and the
floor slab (top) surface, the mouth of the interior slab gap and the opening between the slab edge and the
outer element of the stem wall (subsequently referred to as the slab edge opening). These geometries are
illustrated in Figures 1 and 2, and are discussed in greater detail in the next section. In the general case
we have assumed that the slab edge opening is sufficiently large so there is no pressure drop associated
with flow through this opening. Thus, the static pressure difference is effectively between the inner sur-
faces of the stem wall, the mouth of any of the gaps, and the exterior soil surface. We have also modeled
two cases where this general picture is altered. In the first case, the stem wall is assumed to be filled with
impermeable concrete, so that the only gap is between the top of the interior element of the stem wall and
the bottom of the floor slab. In the second case, we reduce the size of the slab edge opening so that pres-
sure drop does occur across it, reducing the pressure difference between the exterior soil surface and the
stem wall interior.
We assume that all air and radon entering the stem wall interior also passes through the slab edge
opening into the house. Soil gas and radon can also enter the house through the interior floor slab gap. In
order to compute the static pressure at the soil or fill surface located at the bottom of the various gaps, we
use an algorithm (10) to compute the pressure drop across a gap, APg:
|AP»l=^|V|*P(1'2*n>v2, (1)
where t is the length of the gap in the flow direction, w is the gap width perpendicular to the flow, n is the
number of bends in the gap, and v is the average air velocity in the gap (i.e., the flow rate through the gap
divided by the gap area). The constants and p are the dynamic viscosity and density of air, respec-
tively.
The model computes the pressure field throughout the soil and fill region by solving the Laplace
equation. Soil gas transport is then calculated, from Darcy's law, which assumes a linear relation
between applied pressure and fluid velocity. The mass balance equation describing radon migration,
including radon generation, radioactive decay, and both convective and diffusive radon transport, is
solved to determine the radon concentration field. The model then yields soil gas and radon entry rates at
each entry point. This paper presents only the soil gas and radon entry rates at selected entry locations
and, for the base case, the radon concentration in the fill adjacent to the entry locations.
-3-
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BUILDING SUBSTRUCTURE AND SOIL GEOMETRY
A large fraction of houses built in Honda are constructed with a slab-on-grade substructure, of
which there several variants (11,12). For this work, we have modeled an above-grade concrete slab floor
which rests on a perimeter hollow-core concrete block stem wall. The slab edge rests on a chair block,
which is the top course of blocks in the stem wall. There is an opening between the edge of the floor slab
and the outer section of the stem wall, as noted earlier. Hie floor is also supponed by fill matenal placed
within the boundaries of the stem wall and elevated above the natural grade. A vertical section of the
substructure is shown in Figure 1. As indicated in Figure 2, where the floor and stem wall are shown in
2reater detail gaps are assumed to exist between both the inner and outer elements of the stem wall and
L footing, and between the inner portion of the stem wall and the bottom of the floor slab. The gap
dimensions are chosen as an input parameter. We also examined the effect on soil gas and radon entry of
eliminating the gaps at the bottom of the stem wall.
The inner and outer elements of the concrete blocks that comprise the stem wall are assumed to be
permeable to air flow; this permeability is another input parameter for the model. These wall elements
are modeled as vertically homogeneous; that is, no provision is made for differences due to mortar joints
between the blocks. In order to simplify the model, we have not included the block webs - sections of
the block that connect the inner and outer wall elements. In the general case, the interior of the block is
open and flow through the webs themselves should be not significantly affect our results. In the cases
where the stem wall is filled with concrete, we also assume that these webs are not present and thus no
flow path is provided. The concrete footing and floor slab are assumed to be impenneable to gas flow.
An interior gap in the slab floor is included in the model, with radial location and gap width as model
inputs. The length of this gap is defined by the radial location.
As can be seen in Figure 2, the fill below the slab and on top of the footing is defined as a separate
region to enable us to specify fill properties that may differ from those of the natural soil. The two
parameters of greatest interest here are both the air permeability and the radium content of the soil or fill.
BASE CONFIGURATION
We have chosen a set of parameters that constitute a base case for our modeling. These have been
selected based on reviews of the available data on Florida housing (11,12) and on soil and fill properties
(13 14) Because we were interested in evaluating the effects of varying several of the soil and/or build-
ing substructure features on soil gas and radon entry, we also established a range over which each param-
eter was varied The base case values and ranges are summarized in Table 1. As noted earlier, the fixed
dimensions for the slab, soil block, and the stem wall details arc indicated in Figure 2
and
with a radium concentration w hu.j 04 -o
respectively. The pressure difference between the top of the slab and the top of the soil outside the build-
ing was chosen to be -2.4 Pa.
The parametric investigation was earned out using two approaches. First, each parameter was
varied individually, with the remaining parameters held fixed at their respective base case values.
Second, in some cases we varied more than one parameter at the same time in order to explore more fully
the effects of the parameters of interest. In these cases we varied:
-4-
-------
-9 2 ,K 2
1) the soil permeability for high (10 m ) and low (10 m ) fill permeabilities;
2) independently the soil and fill permeabilities when the slab gap is the only soil gas entry path;
3) the soil, fill, and stem wall permeabilities independently when the core of the concrete blocks mak-
ing up the stem wall is filled with impermeable concrete;
4) the stem wall permeability when both gaps between the bottom of the stem wall and the concrete
wall footing are completely closed; and
5) the size of the slab edge opening.
RESULTS AND DISCUSSION
A
In the base case, the predicted soil gas and radon entry rates due to convective flow are 5.1 xlO
m"3 s'1 and 1.6 Bq s~*, respectively. The distribution of soil gas and radon flows through the various
entry points shown in Figure 2 are summarized in Table 2. The model simulations predict that 93 percent
of the total soil gas entry occurs through the exterior side of the stem wall, while about 6 percent proceeds
through the interior surface of the stem wall. Most of the gas flow is through the sides of the stem wall,
rather than through the 3 mm wide gaps at the top and bottom of the stem wall. Only 1.6 percent of the
total soil gas entry is predicted to occur at the interior slab gap, which in the base case is located at 3 m
radius. This corresponds to a crack length of 18.8 m. These relative entry rates are consistent with the
path length of the flow lines - and therefore the resistance to flow - connecting the exterior soil surface
and the specific entry point.
The distribution of the radon entry rates associated with this air flow is different, with almost 59
percent predicted to occur through the interior side of the stem wall, 21 percent through the exterior side
of the stem wall, and 20 percent through the interior slab crack. The predicted radon concentrations at
each of the entry points, shown in Table 2, indicate that, although the largest fraction of gas flow occurs
through the exterior side of the stem wall, the radon concentration in the adjacent soil is low due to diffu-
sion to the atmosphere and to dilution by the atmospheric air entering the soil through a short flow path.
In contrast, the radon concentrations are much higher in the fill materials located adjacent to the interior
side of the stem wall and below the interior of the slab.
In comparison with the convective radon entry rate, the diffusive entry rate, based on a radon diffu-
sion coefficient for concrete of 5 xlO m s"1 and a concrete porosity of 0.2, is 0.5 Bq s"1 (9). Thus, for
a single-story house with a volume of 500 m and an average air exchange rate of 0.5 h , the total indoor
radon concentration would be 31 Bq m for this base case soil and substructure.
Results of selected model runs in which the effects of different parameters are evaluated are shown
in Table 3 and in Figure 3. We extensively investigated the effects of changes in permeability of the soil,
both alone and in conjunction with variations in other parameters or assumptions. Changes in soil per-
meability alone had a somewhat modest effect on radon entry in the base case, since flows at the higher
soil permeabilities are then limited by the fill permeability. The role of the fill in determining flows is
demonstrated bv comparing the predicted radon entry rates when the fill permeability is chosen to be
either high (10* m^) or low (10" m ). For high fill permeability, radon entry is limited by the permea-
bility of the underlying soil. When both are high, the increased radon entry rate is significant, almost 30
times the base case. On the other hand, if the fill has a low permeability, total radon entry is quite low
-5-
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and is essentially unaffected by changes in soil penneability.
Another effect that arises when soil permeability is varied is the change in the importance of the
various radon entry locations. As soil permeabilities are reduced below that of the base case, radon entrv
through the exterior of the stem wall changes only slightly as soil permeabilities range from 10"12 to 10
m2. However, entry through the interior side of the stem wall is reduced as the soil permeability is
reduced below the base case, and increases as the soil penneability increases. Radon entry at the interior
slab gap behaves in a similar fashion, though it does not increase as much with increasing soil permeabil-
ity. Thus at the low end of the range of soil permeabilities modeled here, radon entry through the exterior
side of the stem wall is the largest single component; as soil permeability increases, the relative impor-
tance of this entry pathway decreases. At the high end of the soil permeability range, approximately 88
percent of the radon entry occurs through the interior side of the stem wall, almost 10 percent is through
the interior slab gap, and about 2 percent occurs through the exterior side of the stem wall.
If the soil is layered, the effects on radon entry of variations in the penneability of the layer depend
upon the location of the layer. We modeled two different layered soil cases in which the permeability of
the soil layer was varied while those of the fill and the remaining soil were held fixed at the base case
values. In the first configuration, the soil layer began at grade level (i.e., in direct contact with the fill
material) and extended 1 m deep. In the second case, the soil layer began at 0.5 m below grade (which is
the depth of the bottom of the footing) and extended to 1.5 m below grade. As shown by the results in
Table 3, when the layer is in contact with the fill (assuming the fill has the base case permeability), the
layer has a larger effect on radon entry than when the soil layer is deeper.
Interestingly, filling the stem wall interior with impermeable concrete has only a modest effect on
total radon entry. In this case, we assume that there is still a gap between the top of the concrete-filled
stem wall and the bottom of the floor slab. As shown in Table 3 and Figure 3, total radon entry still
increases with increasing soil penneability, though for a given penneability the radon entry rate is lower
than in the base case. One can also see that the effects on radon entry of changing the fill penneability
when the stem wall is filled with concrete are also modest. These results can, in general, be explained by
the fact that the pressure field distribution in the adjacent fill is altered when the stem wall interior is
impermeable. The larger pressure gradient at the remaining entry point, which compensates somewhat
for the reduced number of entry points, results in a higher soil gas and radon entry rate.
Similarly, changing the penneability of the stem wall itself has very little effect on total radon
entry, as can be seen from Figure 3. Again, this is due to compensating effects. As long as the wall per-
meability is greater than that of the adjacent fill, flow through the wall is the most important. As the wall
permeability decreases below that of the fill, the gaps between the wall and the footing and between the
wall and the floor slab become increasingly important flow pathways as the pressure field is altered due to
the changing wall permeability.
We also parametrically examined the effect of the size of the slab edge opening on the radon entry
rate. In our initial problem definition, we assumed that this opening was sufficiently large so that no pres-
sure drop occurred at this point - effectively applying the full -2.4 Pa static pressure difference between
the exterior soil surface and the inner surfaces of the stem wall. In actual construction practice this open-
ing may in fact be much smaller, in effect reducing die driving force for convective flow into the stem
wall interior. Holding all the soil and wall parameters at their base case values, the effect of closing this
opening to 1 mm reduced the total radon entry by about 40 percent Radon entry via this opening drops
-6-
-------
by about a factor of 4 in this case, but the predicted entry via the interior slab gap increases by almost a
factor of 2, compensating somewhat for the reduction at the stem wall. This increased entry rate at the
interior slab gap arises because the pressure gradient in the fill region near the stem wall is reduced, thus
more of the air flow through the soil is directed toward this interior opening.
In addition to the flow of soil gas into the stem wall, via the wall material itself or through the gaps
indicated in Figure 2, there is air flow through that portion of the exterior wall that is above grade. In
fact, in the base case, this flow is 6.3 x 10"^ m^ s"*, which is about 12 times the total predicted soil gas
flow from the soil into the house (we have not included this entering outdoor air as a source of radon, just
as we have not included infiltration through the house superstructure as a radon source). In order to
investigate the effects of changing the flow balance between the inner and outer stem wall elements we
increased the permeability of the above-grade portion of the exterior stem wall element to 10*9 m and
fixed the permeability of the remainder of the wall at 10"^ m^ (as might be achieved with a wall coating
or sealant). With the slab edge opening reduced to 1 mm, the the radon entry rate through the stem wall is
reduced dramatically to 0.01 Bq s"1 from 0.9 Bq s'1 in the base case. Total radon entry predicted for the
entire substructure is not reduced as much, to about 37 percent of the base case rate, because radon entry
through the intejrior slab gap increases in response to the changes in the pressure field distribution, as
described earlier.
The effect of water table depth on the predicted radon entry rate was found to be small. For a water
table (modeled as a change in the position of the no-flow boundary at the bottom of the soil block) depth
between 2.5 and 10.5 m below grade, the radon entry rate was essentially unchanged. At depths less than
2.5 m, the entry rate reduction was small; at 0.5 m deep, the radon entry rate was predicted to be 0.88 Bq
s .
Finally, we investigated the effect on predicted radon entry of changes in the radium content of the
soil and fill. First, it should be noted that, if the radium content (and thereby the soil gas radon concentra-
tion) was increased uniformly in both the soil and fill, the radon entry rate would increase proportionately
(except for minor reductions due to the slight increase in diffusive losses from the soil surface). If the fill
radium content is changed from the base case, the radon entry rate does not change proportionately, as
can be seen from Table 3. Larger changes in radon entry can occur if the radium content of the soil below
1.5 m were to increase, as might be the case where a high radium soil layer was close to the surface. The
effects of similar changes in radium content of soil below 5 J m are diminished, reflecting die fact that
any additional radon from the enhanced radium content is transported through the soil by means of diffu-
sion into the soil and fill region where convective transport into the structure becomes important
CONCLUSIONS
Application of our finite-difference models, incorporating key features of the soil, fill, and substruc-
ture, has provided additional insight into transport of soil gas and radon through the soil and into a build-
ing. The model results have also shown that changes in the characteristics of various entry locations or
pathways can impact radon migration and entry at other locations, leading to compensating effects. As
one example of this, a reduction in the permeability of the stem wall elements reduces flow through the
wall materials, but soil gas and radon entry increases through the gaps at the top and bottom of the stem
wall in response to the changes in die pressure field in the adjacent fill. Thus the total radon entry rate is
-7-
-------
not significantly affected. Similariy. a reduction in the sire of the opemng at the dab edge to 1 mm or
ZtTZZZ, to effect an, significant reduction in the total radon entry rate. If the imenor opening in
Ae LTdab^eUminated (but the stem wall entty is unchanged), the total radon entty rate is reduced by
ortv W ireent over the base case rate. If. on the other hand, all entty points at the stem wall an: elim-
imted (a^might be accomplished by use of a solid, one-piece wall arri floor slab) the total radon entty
race is reduced by 66 percent (assuming that the floor-slab gap is present).
in the air petmeability of the soil andI fill can have the most significant effect on radon
entry tacreased soil petmeability (above the 10"U tn2 value assumed tn the base case) wtll mcrease total
tZ «mv- if accompanied by an increase in fill petmeability. the increase in radon enny rate is more
drama"" On the o J hand, if the fill petmeability alone is reduced below the base case value (4 x 10
mT radon entry is reduced substantially. At very low fill permeabilities, conveef ve a„„ of radon from
rte »« is esseSally negligible, and is laraely invariant with regard to changes in other parameters^ Even
* a mire modest M permeability of 10'ft m2. total radon em, is reduced by 80 percent from the base
case It should be noted that these results assume that the fill matenal maintains its u«egr.ty; that ts.
bracks or gaps develop in the fill or in those regions of the fill penetrated by utility pipes or conduit.
Changes in radium content of the fill have some effect on total radon entty. though the more
significant effects occur for fill radium contents more than 3 times the base c«e. Ganges in the soil
radium concentration can have a more impotent effect, depending upon the deptt of the rad.um-beanng
C in the case where the radium content of the soil below 1.5 m is a factor of 5 tmes that of the base
radon entry increases by more than 3 times the base case value, wlule a 10-fold mcrease in radium
providesa radon entty rate that is 6 times greater than in the base case. For a whim™* sod layer below
will Bie changesare less pronounced, with only a 25 percent increase in radon enoy ansing from a 10-
fold increase in the radium content.
ACKNOWLEDGEMENTS
This work was supported by the U.S. Environmental Protection Agency through Interagency Agree-
ment DW89934620-0 with the U.S. Department of Energy. The woric was also supported by the Assis-
Lt Secretary for Conservation and Renewable Energy. Office of Building Technologies. Building Sys-
tems and Materials Division, and by the Director, Office of Energy Research, Office of Health and
Environmental Research, Human Health and Assessments Division and Ecological Research Dwision of
DOE, under contract DE-AC03-76SF00098.
REFERENCES
i Nazaroff W W Moed, B.A., and Sextro, R.G. (1988). Soil as a Source of Indoor Radon: Genera-
' tion, Migration, and Entry. In Radon and Its Decay Products Indoors, Nazaroff. W.W. and Nero.
A.V., eds., pp 57-112. Wiley. New Yoik.
2. Nero, A.V. and Nazaroff, W.W. (1984). Characterizing the Source of Radon Indoors. Radiation
Protection Dosimetry 7,23-29.
3. Geomet Technologies Inc. (1988). Honda Statewide Radiation Survey. Geomet Report IE-1808.
Germantown, MD.
-8-
-------
4. Sanchez, D.C., Dixon, R., and Williamson, A.D. (1990). The Florida Radon Research Program:
Systematic Development of a Basis for Statewide Standards. Presented at the 1990
International Symposium on Radon and Radon Reduction Technology, Atlanta, GA., Paper A-1 -
3, U. S. EPA.
5. Loureiro, C. 0., Abriola, L. M.( Martin, J. E., and Sextro, R. G. (1990). Three Dimensional
Simulation of Radon Transport into Houses Under Constant Negative Pressure. Environ. Sci.
Techno!. 24, 1338-1348.
6. Revzan, K. L.( Fisk, W. J., and Gadgil, A. J. (1990). Modeling Radon Entry into Houses with
Basements: Model Description and Validation. Lawrence Berkeley Laboratory Report LBL-
27742. Berkeley, CA.
7. Narasimhan, T. N., Tsang, Y. W., and Holman, H. Y. (1990). On the Potential Importance of
Transient Air Flow in Advective Radon Entry Into Buildings. Geophysical Research Letters 17,
821-824.
8. Revzan, K. L., Fisk, W. J., and Sextro, R. G. (1990). Modeling Radon Entry into Florida Houses
with Concrete Slabs and Concrete-block Stem Walls. Lawrence Berkeley Laboratory Report
LBL-30005, Berkeley, CA.
9. Zapalac, G. H. (1983). A Time-Dependent Method for Characterizing the Diffusion of Radon-
222 in Concrete, Health Phys., 45(2), 377-283.
10. Baker, P. H., Sharpies, S., and Ward, I. C. (1989). Air Flow Through Cracks. Building and
Environment, 22(4), 293-304.
11. Scott, A. G., and Findlay, W. O. (1983). Demonstration of Remedial Techniques Against
Radon in Houses on Florida Phosphate Lands. Report EPA-520/5-83-009 (NTIS PB84-156157),
U. S. EPA, Montgomery, AL.
12. Acres International Corporation (1990). Radon Entry Through Cracks in Slabs-on-Grade, Vol.
2, Sealants for Cracks and Openings in Concrete Slabs-on-Grade. Acres Report P09314.
Amherst, NY.
13. Nielson, K. K., and Rogers, V. C. (1990). Correlation of Florida Soil-Gas Permeabilities with
Grain Size, Moisture, and Porosity. Rogers and Associates Report RAE-8945-1. Salt Lake City,
UT.
14. Roessler, C. E., Smith, D. L., Bolch, W. E., Hintenlang, D. E.( and Furman, R. A. (1990). Gas
Permeabilities and Radon Content of Florida Fill Materials and Soils. University of Florida
Report, Gainesville, FL.
-9-
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TABLE 1. BASE CASE VALUE AND RANGE FOR MODEL PARAMETERS
Parameter Base Case Value Range
Soil air permeability:
a. total soil block ] q?
b. soil layer 0-1 m deep* r 10" m 10" -10" m
c. soil layer 0.5-1.5 m deep* J
Fill air permeability:
'¦"""J , , „ ) 4X10-1V 10-15-10"9m2
b. extenor to stem wall J
Stem wall air permeability:
a. both vertical wall elements ]
b. inner wall element ?¦ 10" m 10" -10 m
c. outer wall element J
Slab opening:
a. width 3 mm 1 mm -10 cm
b. radial distance 3 m 0 - 7 m
Radium content (relative to base case):
a. fill "]
b. soil below 0.6 m depth* >• 1 0.1-10
c. soil below 4.6 m depth* J
Water table:
a. depth below surface 10 m 0.5 -10 m
~Depth with respect to grade level
-10-
-------
TABLE 2. BASE CASE SOIL GAS AND RADON ENTRY AT VARIOUS ENTRY POINTS
Fraction of
Radon
Fraction of
Soil Gas Entry*
Concentration
Radon Entryt
Entry Location
(percent)
(percent of C^)
(percent)
Interior side of the stem wall:
a. top gap
0.06
88
0.65
b. bottom gap
0.06
87
0.65
c. side of wall
5.0
88
53.
d. bottom of wall
0.23
87
2.5
e. top of wall
0.24
88
2.6
Exterior side of the stem wall:
a. bottom gap
0.98
5
0.67
b. side of wall
88.
3
18.
c. bottom of wall
4.
5
2.7
Slab opening
1.6
98
20.
* Total base case soil gas entry = 5.1 xlO"4 s"1
T Total base case radon entry = 1.6 Bq s"1
-11-
-------
Parameter
Radon Entry (Bq s *)
2
Soil air permeability (m ):
a. all other parameters =£as^case
b. fill permeability = 2
c. fill permeability = 10 m
d. filled stem wall
e. soil layer 0 to 1 m deep*
f. soil layer 0.5 to 1.5 m deep*
g. slab opening only
2
Fill air permeability (m ):
a. all other parameters = base case
b. filled stem wall
c. slab opening only
10"12
10"11
10"IU
10"9
0.4
0.63 .
5. x lO"4
0.16
0.64
0.74
0.14
10*15
1.6
21 -4
5. x 10^
1.2
1.6
1.6
0.55
10"13
6.6
13 -4
5. x 10^
3.8
4.2
2.5
1.1
10"11
13
47 .4
5. x 10^
5.1
7.9
3.3
1.2
10*9
5.3x10^
6. x 10":
3. x 10*5
5. x 10"2
4.8 x 10"2
3. x 10"3
1.1
0.8
0.2
2.1
1.6
1.6
Radium content (relative to base case):
a. fill
b. soil below 0.6 m*
c. soil below 4.6 m*
0.1
1
5
10
1.3
0.75
1.5
1.6
1.6
1.6
2.6
5.1
1.7
4
9.3
2.0
Width of slab edge opening (cm):
a all other parameters = base case:
0.1
0.2
1
5
0.88
1.5
1.6
1.6
* Depth with respect to grade level
-12-
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7 m
3 m
Slab
opening
10 m
Soil surface
10 m
Figure 1: Vertical cross-section of the region modeled showing the dimensions of the soil block
and the location of the slab gap for the base case. Greater detail for the stem wall is
presented in Figure 2.
-------
- 0.19 m
028 m
Concrete
Block wall
/
House
side
gaps
0.4 m
Backfill
0.2 m
- N\\
0.45 m
Figure 2: Detail of the stem wall, showing the fixed dimensions for the wall height, dimensions
of the footing, and fill depth and location with respect to the footing. The size of the
gaps at the top and bottom of the stem wall is exaggerated in this diagram. In the
base case, their widths are 3 mm. The floor slab thickness if 10 cm.
-------
T 1 I I I I II
in
cr
go
-------
V-4
RADON DYNAMICS IN SWEDISH DWELLINGS:
A STATUS REPORT
Lynn M. Hubbard, Nils Hagberg, Anita Enflo, Gun Astri Svedjemark
Swedish Radiation Protection Institute
Box 60204
S-10401 Stockholm, Sweden
ABSTRACT
A status report of a long term study on radon entry into Swedish
dwellings is given. Both physical modelling and continuous measurements
of radon and other relevant parameters in real home environments are being
used in the investigation. Building characteristics typical of Swedish
dwellings and geological factors typical of Swedish ground are discussed
with regard to their relevance to radon entry. The research homes used in
this study are described and factors affecting .radon entry are compared to
similar factors in the New Jersey Piedmont research houses. Current
results of the measurements in the research homes are presented and the
dynamic modelling being developed to study the temporal behavior of radon
indoors is introduced.
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INTRODUCTION
Several researchers in recent years have begun to focus on
understanding the various mechanisms driving radon entry into dwellings,
and to what extent these mechanisms cause indoor radon concentrations to
vary with time. Driving forces such as temperature differences between
the indoors and outdoors, the wind, and the effects of indoor ventilation
systems have been observed in relationship to temporal variations in
indoor radon concentrations (1). Understanding these mechanisms driving
radon entry will ultimately be useful in designing more effective ways to
mitigate homes with high indoor radon concenrations, and in constructing
better protocols for measuring radon indoors.
Our own research focuses on understanding the behavior of some basic
parameters associated with radon entry and movement indoors. The quantity
of main interest is the amount of air infiltrating a dwelling from the
radon-containing soil gas versus the relatively radon-free outdoor air.
We hope to understand how the amount of air infiltrating a dwelling from
these two different sources changes with relation to each other, with
time, and with environmental driving forces such as temperatures inside
and outside the dwelling and the wind. We are using both theoretical
modelling and measurements in real houses to obtain a better understanding
of these processes.
This report is organized as follows. We begin with a brief
description of building characteristics which are typical in Sweden, which
is intended to provide a background for understanding the types of radon
problems which exist in Sweden. This discussion is followed by a
description of our current data collection procedures in two research
houses, and the houses are described and compared to the houses in the
Piedmont Project (1). We conclude with a report on our ongoing efforts at
modelling indoor radon concentrations.
BUILDING CHARACTERISTICS OF SWEDISH HOUSES
THE SOIL
The radon concentration in the soil gas in Swedish soil has always
been found to be at least 5000 Bq/m1 at a depth of 1 meter. It is usually
between 20,000-40,000 Bq/m3 in moraine and 30,000 - 150,000 Bq/m3 in
gravel. When the soil contains some alum-shale the radon concentration
can be as high as 1-2x10^ Bq/m3. Moraine is very common in Sweden and
other glaciated terrains such as in Canada and the northern United States.
In addition, eskers are very common in Sweden, which are long ridges or
mounds of sand, gravel, and boulders deposited from flows under or around
stagnated glaciers from the last ice age, and the soil is very permeable.
The combination of the rather high radon concentration in the soil air and
-------
the permeability of the soil give most of Sweden a rather high potential
for radon ingress into houses.
BUILDING MATERIALS AND BUILDING FOUNDATION
Most Swedish one-family houses are built of wood, with the exception
of the Skane landscape in the south of Sweden, where most houses are built
of stone materials. During the last decade brick and concrete have been
more common in the whole country. In about 102 of the 1976 building
stock, (which includes both one-family houses and apartments in multi-
family houses), alum-shale based concrete had been used. Alum-shale based
226
concrete contains enhanced levels of Ra of between 600 - 4300 Bq/kg,
and was produced between 1929 and 1974. The alum-shale materials give
radon levels in many houses in the range of 400-800 Bq/m3. Most multi-
family houses are built of concrete or brick.
Houses built with basements (or cellers) are the most common in
Sweden. Before 1940, houses built with crawlspaces were about equally
common as those built with basements. During the 1970s, houses built with
a slab-on-grade became increasingly more popular. The proportion of the
housing stock, as a function of year when built, with either slab-on-
grade, crawlspace, or basement (celler) can be seen in figure 1.
~
proportion of the number
OF HOUSES PER GROUP («)
100
SLAB ON THE GROUND
CRAWL SPACE
CELLAR
I
m
iH
saw
vXsv
mz
m
mi
8BBS
ms:¦
¦k;*v
K-5SK
YEAR WHEN BUILT .40 41-
iO
TYPE OF BUILDING DETACHED HOUSES
41-
75
74-
ei
-40
41-
40
41-
75
74-
81
MULTI-FAMILY HOUSES
OFFICES INST
SHOPS EDUCAT
NON-RESIOENTIAL
TOTAL
NUMBER
OF HOUSES
Figure 1. Type of building foundation in Swedish buildings.
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VENTILATION
The most common ventilation system in Swedish detached houses is
natural draught ventilation combined with a kitchen fan. An increasing
number of houses built during the 1970's used mechanical exhaust
ventilation, which began to be changed to mechanical inlet and outlet
ventilation with some kind of heat recovery during the 1980's.
The older multi-family houses have natural draught ventilation and an
increasing ratio of those built since 1945 have mechanical exhaust
ventilation. Since 1980 mechanical ventilation has been required in
multi-family houses.
Our current research program on radon dynamics in Swedish homes
concentrates on understanding radon entry in two houses which are somewhat
typical in design. We describe them next, and discuss how they differ
from houses one of us has studied in a previous research project called
the Piedmont Project, which was funded by the USEPA (1).
MEASUREMENTS IN RESEARCH HOUSES
We currently have two houses for study which are of somewhat typical
Swedish design. During the past year we have instrumented the two houses
for collecting continuous data, which includes environmental temperatures
in a variety of locations indoors and outdoors, pressure differences
across the building shell in a variety of locations, and radon gas
concentrations in differenct indoor or subfloor zones. The data are
recorded electronically and hourly averaged data are stored in a computer
located at the house. The two houses both have indoor radon
concentrations which average between 100-200 Bq/m3 in the living level and
the source of the radon is the soil gas.
The first house, (labeled 901), was instrumented in March, 1990, and
data collection began at that time. This house was built in I960, and the
substructure consists of a basement with two attached crawlspaces, and a
single living level floor above the substructure. The basement is a
finished working space vith a poured concrete slab. Both crawlspaces,
which can be accessed from the basement through small doors vith vents,
have dirt floors. The house is of wood construction with a concrete block
substructure. It is heated by hot water radiators with the water heated
by an oil burner located in an attached room adjacent to the house. The
house contains a natural draught ventilation system. This house will be
the more difficult to model of the two research homes, because of its more
complicated substructure.
The second house, (labeled 902), was instrumented in October, 1990,
and data collection began Nov. 1. This house was built in 1907, and is
entirely of wood construction. It is located on an esker and thus the
soil is rather sandy and permeable. The structure of 902 is simple,
consisting of a rectangular two-storied house on top of a small crawlspace
on top of the ground. The house is heated with electrical radiators and
contains a natural draught ventilation system. We hope the simplicity of
the structure, shown in figure 2, will be useful in our modelling efforts.
-------
w
F1oor A
cs
crow1spoce
cs
Figure 2. Research house 902, which is located on an esker. The Q's
label air inflows and outflows needed for modelling.
Radon Concentrations
House 902, LJeek 3, 1991
250
200
150
100
- • Dounstairs
— Upstairs
0
14
17
20
Julian Date, 1991
Figure 3. Hourly averaged radon concentrations.
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Despite the fact that House 902 is a two-story house, the two levels
are connected by considerable open space, and it acts very much like a
single indoor zone. Figure 3 shows the radon concentrations upstairs and
downstairs during one week in January, 1991, and the close agreement
between the two indicates good mixing of the indoor air. The pressure
difference between the downstairs and upstairs has also been continuously
measured and is never larger than a few tenths of a Pascal. We thus treat
House 902 as a single indoor zone in our radon flow model.
Both homes have natural draught ventilation, which is the most common
type of ventilation system in Swedish detached houses. Natural draught
ventilation does not work very well in the summer season when the outdoor
temperature is about the same as the indoor temperature and the house has
a low air exchange rate, as do most houses in Sweden. However, in the
fall, winter, and spring natural draught is a rather efficient means of
ventilating. Also, natural draught ventilation does not add any
perturbing pressure differences across the building shell, as have been
observed before in the New Jersey Piedmont homes due to unbalanced air
handlers, which greatly complicates the modelling of the airflows and
infiltration. Figure A shows the daily radon concentration varying nicely
with the outdoor-indoor pressure difference and temperature difference in
research house 901, showing that during non-windy days infiltration should
be veil described in a model using stack pressures alone.
The most significant factor affecting the daily dynamics of radon
entry which differs in the current research from the Piedmont Project is
the type of ventilation in the homes. All seven of the Princeton/ORNL
research homes had forced air ventilation. The difference between the
daily variations in the radon concentrations when the forced air
ventilation system was in use versus when electric heaters were brought in
to heat the home was quite large in the one home where this experiment was
performed (2). In most cases the pressure differences across the building
shell created by the air handler use were dominant over the effect of the
indoor-outdoor temperature differences in their effect on the hourly
variations of the radon.
Other differences between these research houses and the Piedmont
research houses are the following. The Piedmont homes generally had
unfinished basements with hollow block vails, a poured concrete slab with
either a perimeter drain or a perimeter crack, and a sump. The hollov
block vails played a role in radon entry because of their extremely porous
nature, as did the perimeter drains and sumps with their direct connection
to soil gas. These obvious entry routes usually make mitigation
straightforward, by enough sealing of the entry routes to make
depressurizing the area beyond the barrier created by the slab and vails
possible. As is generally knovn nov, this can usually be accomplished by
sealing of perimeter drains and sumps and applying suction vith a fan to
the subslab. These methods are not suitable in the current Swedish
research homes because of the exposed dirt floors in the crawlspaces.
Either basement or crawlspace ventilation or soil ventilation using a
radon veil, especially in house 902 vhich has such permeable soil, vill be
applied here, if mitigation is desired by the homeovners.
-------
Radon Concern t ra t i ons and
Temperature and Pressure Differences
Betueen the Outdoors and the Basement
House 901
Normalized Units
1
0.5
• • • DP(out-b)
- * T in-T out
— Radon in
Craulspace
~
150 151
156 157 158
Julian Date, 1990
Figure 4. The curves vere normalized to facilitate comparison. Maximum
and minimum values for each curve are: 1) radon concentrations, 670 and
3
326 Bq/m , 2) temperature differences, 16 and -12 °C, and 3) pressure
differences, 1.7 and -1.1 Pa.
MODELLING RADON ENTRY
Ve have previously described a model for calculating the time
dependent radon concentration in different indoor zones, called the radon
flow model (1). It takes as its input the airflows between indoor zones
and between the indoors and the outdoors, at each time period At, and the
initial radon concentration in each zone. It gives as its output the
modelled (or predicted) radon concentration in each zone as a function of
time. The equations for predicted radon in zone i, neglecting the radon
decay term because for our research houses it is insignificant compared to
the flow terms, are the following.
IRn(t)]j(predicted)-[Rn(t-l)Jj+[Rn(t)]j(inflow)-[Rn(t)Jj(outflov) (1)
-------
where
[Rn( t) ] ^ i nf low) = At x rr.Q(t-l)_. ,.x[Rn(t-l)l ,+ Rn£]
1
(2)
[Rn(t)].(outflow) - [Rn(t-l)]. x At ZjQ( t-1)^
vol.
1
(3)
and where
i» j
index the different indoor zones and the outdoors;
is the flow from zone i to zone j during the time period
[Rn(t-l)].
volj
At
from t-1 to t;
is the predicted radon concentration in zone i at t-1;
is the volume of zone i;
Rn£
is the short time period during which radon
concentrations in each zone are held constant; and
is a radon entry rate from outdoors, which is 0 except in
the zone or zones which have flow directly from the soil
gas.
The tricky part in implementing this model is obtaining the airflows
between indoor zones and between indoor zones and the outside. In our
previous application of this model we used as input airflows in a research
home which were measured using a multi-tracer gas system. That system
measured time-varying airflows at the same time we were measuring time
varying radon concentrations, which gave us the ability to check the
modeled radon concentrations. The agreement between the modelled and the
measured radon in the two indoor zones was quite good, indicating how well
the measured airflows represented the true situation (1). It is not
always possible to have a multi-tracer gas system available in research
houses, however. In fact only a few such systems exist in the world.
The next best alternative to measuring the airflows is to model them.
In fact modelled airflows are more desirable than measured ones from a
pedagogical viewpoint because, once the airflows are properly modelled, we
can use the model to learn more about radon entry by altering the input
parameters.
Our current modelling efforts have been concentrated on developing a
simple formulism for modelling the airflows, treating the air infiltrating
from the soil gas separately from the air infiltrating from the outdoor
air. There exists several indoor airflow and infilration models vhich
could be adapted for use in indoor pollution transport models, such as the
radon flow model. However, they require detailed house specific knowledge
on leakage characteristics, such as the location and type of flow paths
beween zones and around the building shell, and they are often cumbersome
and difficult to use.
Our initial goal is t0 see h°v simple we can make an infiltration
model and retain enough of the physics to learn something from the model.
Consider the simplest case for modelling and for predicting the airflows
-------
and the radon concentration. That would consist of simply one indoor zone
connected to both the outdoors and to a source of radon in the soil gas.
We have been fortunate enough to obtain just this type of house for one of
our research homes; as mentioned earlier in connection with figure 3,
House 902 can be treated as a single indoor zone. This has made it rather
easy to begin our effort at modelling airflows and predicting radon and
check the predictions on a simple, but real, home environment. The flows
labeled in figure 2 are the relevent airflows to model for a single indoor
zone. Qfioor *s airflow which will carry the radon into the house
from the crawlspace. For modelling radon entry during the winter months
we assume the flow from the indoors to the crawlspace is negligible.
We have begun by considering only the temperature difference between
the indoors and the outdoors as the driving force for air infiltration.
Because of the large number of days in Sweden during the fall, winter, and
spring months which have significant temperature differences between the
indoors and the outdoors, stack effect pressure differences caused by
differences in the indoor and outdoor temperatures are an important
driving force for air infiltration in Swedish houses.
The stack pressure is the difference in pressure difference between
the indoors and the outdoors at one level, or height, on the building
versus another level on the building. But the pressure difference must be
known at one of the heights to know it at any other, which is why the
stack pressure is often referenced to a neutral pressure plane, labeled
0Q, where the pressure difference is zero. We also use the neutral
pressure plane as a point of reference, and find that often one can solve
the continuity equations exactly for 0Q.
The stack pressure difference between the outdoors and a single
indoor zone is given (in Pascals) by:
aps
where pQUt is the density of the outdoor air, g is the acceleration due to
2
gravity, (m/sec ), T^n and TQut are indoor and outdoor temperatures, (K),
0 is a dimensionless height, z - H 6, (and 0 refers to the height z
SO o
where the indoor pressure equals the outdoor pressure), and H is the
s
height dimension of the building over vhich the stack pressure is being
calculated, (m). The sign convention for equation (4) and all pressure
differences reported in this paper is the pressure outdoors minus (-) the
pressure indoors.
We have chosen a week in January, 1991, during which there was little
wind, to compare the measured pressure difference between the indoors and
the crawlspace, recorded hourly from a transducer measuring in the center
of the floor area, with the calculated stack pressure difference at the
floor level, (0-0), using equation (A). The hourly measured indoor and
-------
outdoor temperatures and the stack height of house 902 are the input to
equation (A). This comparison is shown in figure 5, and it is encouraging
how well the stack pressure reproduces the measured pressure difference
during this non-windy week. The bimp on day 20 in the measured pressure
difference and also in the radon concentrations shown if figure 3
correspond to a time when the homeowner aired the house.
Pressure Differences
Betueen Craulspace CCS) and Indoors
Measured versus Calculated
House 902, Ueek 3, 1991
Pascals
6
5
4
3
DP cs-in
measured
2
1
~
DP out-in
floor lvl
-1
19
20
16
18
14
Julian Date, 1991
CONCLUSION
Ve are currently modelling airflows using the stack pressures alone
to determine infiltration. The stack pressures are modelled using
temperatures measured at the research house. Ve will check the modelled
radon concentrations using data measured at the research house during non-
vindy days or weeks. Pressure differences modelled from the effect of
wind are intended to be added separately to the model. Our ultimate goal
is to determine to what approximation we can model indoor radon
concentrations using a simple formalism based on temperature differences
and the wind. Once we have determined that, we can use the model to learn
more about the radon dynamics as a function of parameters, such as the
leakiness to the soil gas versus the leakiness to the outdoor air. A
future report will present details of the model formalism and results.
-------
Acknowledgments. The authors thank Leif Nyblom and Hans More for
crucial help with the instrumentation and data loggers.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not
necessarily reflect the views of the Agency and no official endorsement
should be inferred. The work described in this paper was, however,
partially funded by the the CEC/NRPB Association Agreement contract No.
B.16.347 UK (H), which we gratefully acknowledge.
REFERENCES
1. Dudney, C.S., Hubbard, L.M., Matthews, T.G., Socolow, Gadsby, K.J.,
Bohac, D.L., Hawthorne, A.R., Harrje, D.T., Wilson, D.L., Investigation of
Radon Entry and Effectiveness of Mitigation Measures in Seven Houses in
New Jersey, Final Report ORNL-6487, NTIS TN 37831, August, 1989.
2. Hubbard, L.H., B. Bolker, R.H. Socolow, D. Dickerhoff, and R.B.
Mosley, "Radon Dynamics in a House Heated Alternately by Forced Air and by
Electric Resistance," in Proceedings of The 1988 Symposium on Radon and
Radon Reduction Technology, Volume 1, EPA-600/9-89-006a (NTIS PB89-
167480), P. 6-1, March, 1989.
3. Tolstoy, N. and Svennerstedt, B.f Repair requirements in the Swedish
building stock. Report M84:10, National Institute for Building Research,
Gavle, 1984 (in Swedish).
-------
VI1-4
NEW JERSEY RADON PROGRAM, 1991
Background
Early in 1985, the Pennsylvania Department of Environmental
Resources contacted the New Jersey Department of Environmental
Protection (NJDEP) and described finding high indoor radon levels
in homes along the geologic formation known as the Reading Prong.
Since the Reading Prong extends from Pennsylvania, through northern
New Jersey, and into southern New York State, it was likely that
a similar hazard existed in homes in New Jersey. A few months
after this initial notification, a greater sense of urgency was
added to the situation as a result of an article about radon and
the Reading Prong which appeared in the New York Times. As a
result of the article, the State received a large number of phone
calls from concerned citizens.
Early on the NJDEP identified two major issues: 1) there was
a potential indoor radon exposure problem in the State which
required testing and remediation whenever necessary, and 2) the
extent of the problem needed to be identified. It would not have
been enough to assume that only the Reading Prong area was
affected, but that was the natural starting place to begin studying
and testing.
A review of available geologic data showed that uranium, of
which radon is a natural decay product, was commonly present in a
greater geographic area of the State than the Reading Prong. Based
on this data, the NJDEP estimated that 1.6 million homes could
potentially be affected. That meant as many as 4 million people
or more might be affected, greater than one half of New Jersey's
population. Two facts were apparent; indoor radon posed an
extremely large potential environmental hazard and no single state
agency had the resources to deal with a problem of such magnitude.
In late 1985, planning began on what actions to take and how to
involve all levels of government, as well as the private sector
wherever possible.
The New Jersey Legislature also recognized the magnitude of
the situation and enacted two separate pieces of legislation
providing $4.2 million and mandating specific activities. The
NJDEP was designated the lead agency and required to develop an
information outreach program to educate New Jersey residents about
the problem and methods of testing and remediation. Additionally
the NJDEP was to institute a program of confirmatory monitoring for
residents whose initial radon tests showed 4 picoCuries per liter
(4 pCi/1) or higher and to also conduct a statewide scientific
study to identify areas at risk for residential exposure to high
levels of radon. Finally the legislation required the NJDEP to
develop a certification program for companies offering radon
testing and mitigation services. The New Jersey Department of
Health (NJDOH) was required to conduct an epidemiologic study to
identify potential risk of lung cancer associated with residential
exposure and also to develop a voluntary registry of residents with
-------
a radon exposure history.
Activities
The information outreach program that the NJDEP developed,
centers around a toll-free "800" number that is open to callers
every work day from 8:00 a.m. to 5:00 p.m. Since July of 1985 when
the information phone line was first set up, more than 125,000
calls have been logged. Many callers want information about
testing and remediation, so brochures were prepared and a standard
information packet is sent to callers upon request. To date over
60,000 of these packets have been sent out. More than 350
presentations by Radon Program staff have been made to audiences
including homeowners and local officials, realtors, health
professionals, educators and students, testers and mitigators, and
a number of professional groups at conferences convened for the
purpose of information exchange. Other public awareness and
education outreach activities include production of a radon slide
show, which was also converted to a video. Three billboards were
put up along roadways in high exposure areas in an attempt to
generate more awareness about radon testing. Radon Program staff
worked with representatives from New Jersey Transit on a project
to put placards in buses, so as people rode to work or went
shopping they would repeatedly see the radon testing message. a
mass mailing to almost a half million households in the Tier 1
area, resulted in about 40,000 inquiries about radon, its health
effects, and testing and mitigation programs. More recently, an
insert was included in energy bills, which the participating
utility company estimates goes to about 2,000,000 customers. it
generated over 1,000 telephone inquiries, which is a small
percentage, but calls are still coming in and the mailing was at
no cost to the NJDEP. An article about radon, its identification
hazards, and control was prepared by Radon Program staff and is
scheduled to appear in a real estate magazine and also in a New
Jersey Transit publication which is available to commuters.
As important as it was and is to promote public awareness
about the hazard of radon and the importance of testing, the NJDEP
knew it could not offer every potentially affected homeowner a free
test kit. Some communities, where an initial few high readings
were found, did make radon test canisters available for free or at
greatly reduced prices. Instead, the NJDEP established a program
offering free confirmatory testing to any homeowner who requests
it because their initial test results are equal to or above 8
pci/l. Up to and including October 1988, the confirming test was
offered if the initial result was equal to or above 4 pCi/1. This
program has now been expanded to include followup measurements on
homes which have been mitigated. The confirmatory and followup
programs were an effective means to monitor the growing industry
providing radon testing services and home mitigation services.
From October 1985 through October 1988, when confirmatory
testing was offered for a test result equal to or greater than 4
-------
pci/l, 7,223 tests were conducted. Since the level was raised to
8 pCi/1 in November 1988, an additional 1,909 tests have been
performed, making a total of 9,132 confirmatory tests conducted
through December 1990. From October 1985 through December 1990,
2,389 followup remediation tests have been conducted.
Perhaps the most significant undertaking in the beginning of
the New Jersey Radon Program was determining the extent of the
potential radon exposure problem.
To start, the NJDEP delineated the geographic area of the
Reading Prong that ran through the State in order to make an
initial evaluation of the number of potentially affected homes.
The number exceeded 250,000. Then a review of available geologic
data for the State was conducted. It showed uranium deposits
extended beyond the Reading Prong formation. Additionally, an
examination of a New Jersey Geological Survey literature review
showed that "radioactive mineralizations" were present throughout
northern New Jersey. This meant the potential geographic area was
any part of the State north of Trenton, and that approximately 1.6
million homes were affected. Further the number of homes was
increasing in that area as more people were building in the
northwestern portion of the State during the 1980*s. This initial
review of available geologic data gave New Jersey officials a sense
of the magnitude of the radon problem in the State. However
officials were aware that an extensive statewide radon study needed
to be conducted to determine where elevated radon levels were most
likely to be found and to better understand how environmental and
structural factors contribute to radon entry in homes.
Work on the legislatively mandated Statewide Study of Radon
was begun in the summer of 1986 when a contractor for the project
was selected. The study was to prepare a risk assessment of
contracting lung cancer as a result of exposure to indoor radon and
radon progeny. Almost 6,000 homes were tested in different
geologic areas of the State over the course of the study. In order
to estimate an annual exposure rate, the contractor took the
average of radon readings based on a six month heating season and
a six month non-heating season. Residency periods and smoking
history were major factors in the risk assessment. Statistics
showing risk of contracting lung cancer were compiled on both
county and selected municipal levels. The findings confirmed, and
further defined, the initial areas of concern identified by the
State.
In the autumn of 1987, using information from both the initial
NJDEP geologic data review and data already collected during the
statewide study, the voluntary certification program, and the
Cluster Study Program, the NJDEP released the first "Tier" map
entitled, "Preliminary Recommendations for Radon Testing". The map
outlined three tiers: Tier 1 was "test as soon as practical", Tier
2 was "test within one year", and Tier 3 was "test if concerned".
Municipalities were categorized as Tier 1, 2, or 3 based on the
percentage of homes measured with radon levels greater than or
-------
equal to 4 pci/l. Data on 25 homes was required to classify a
municipality into a particular tier. If there was insufficient
data, then classification of the municipality was based on the
geological province data in which the municipality was located.
The tiers are drawn on municipal boundaries because these were
considered the smallest workable political and geographic
subdivisions on which to identify radon potential.
Both a press release and a direct mailing to every homeowner
in Tier 1 were done in conjunction with the map release. The
mailing was sent to almost a half million home and resulted in
approximately 40,000 inquiries about the radon issue and testing
recommendations.
The Tier map continues to be periodically updated based on
data submitted to the NJDEP by radon testing firms currently
participating in the "Interim Voluntary Certification Program"
Over the past four years the Tier boundaries have altered. The
reported test results have shown that although the initial
designated areas were on track further identification and
definition are possible and necessary. Recently the tiers ceased
to be defined as recommendations for testing. Instead, they are
defined as radon potential. The current criteria used to classify
municipalities into a particular Tier are outlined in Table l.
Tier
TABLE 1
Criteria for Tier Designation
Municipality*
Tier 1 -
Tier 2 -
Tier 3 -
High Radon
Potential
Moderate Radon
Potential
Low Radon
Potential
>25% of homes
tested have
radon levels
>4.0 pci/l
5-24% of homes
tested have
radon levels
>4.0 pci/l
0-4% of homes
tested have
radon levels
>4.0 pci/l
Geologic
Province**
>25% of homes
tested have
radon levels
>4.0 pCi/1
5-24% of homes
tested have
radon levels
>4.0 pCi/1
0-4% of homes
tested have
radon levels
>4.0 pCi/1
- . criteria used if there are at least 25 homes that have been
tested in the municipality.
** rriteria used only when municipality data is insufficient
/ less than 25 hemes tested for radon) and at least 100 homes have
been tested in the province.
-------
The New Jersey Legislature had also mandated requirements for
the NJDOH. An epidemiological study of radon and lung cancer based
on actual radon measurements in homes and detailed smoking
histories for individual subjects was conducted by the NJDOH. It
was an extension of a previously conducted lung cancer study among
New Jersey women. Residence criterion was established and both
year-long alpha track detector measurements for estimating subject
exposure as well as four-day canister quick screening for current
residents were done. The entire study group, cases and controls
combined, was 835 women. Detailed smoking histories were taken for
the subjects. The findings reported by the NJDOH suggested "the
trend for increasing risk with increasing radon exposure was
statistically significant". Consequently, "the study suggests that
the findings of radon-related lung cancer in miners can be applied
to the residential setting. Excess radon exposures typical of
homes may increase risk of lung cancer; extremely high residential
exposures would be associated with very serious lung cancer risks."
The NJDOH reported that the study findings supported the State's
initiatives for technical information and services, citizen
education, and research studies, and that smoking avoidance
education for the public should also be included and emphasized in
any radon reduction program.
The NJDOH was also charged with establishing and operating a
Voluntary Radon Exposure Registry. Residents who were found to
have high indoor radon levels which they had been exposed to for
some time, could be listed on the registry. They are to receive
follow-up information about hazard reduction, risk, and medical
treatments. The registry is also a source for background
information about exposures and exposure areas.
Current Program Activities
Two major programs are currently underway which should improve
radon protection efforts in New Jersey. The first is the
legislatively required certification program for testers and
mitigators. The second is the federal State Indoor Radon Grant
program.
The New Jersey Legislature enacted a law requiring that the
NJDEP develop a mandatory certification program for all radon
testers and mitigators who want to operate in the State.
Initially, the NJDEP established a voluntary program in which
testers and mitigators voluntarily submitted proof to the NJDEP
that they met certain requirements. These companies were included
on an "Interim Voluntary Certification" list. These companies have
been the major source of information about home testing done in the
State. To date they have supplied data for more than 140,000 tests
conducted statewide.
Final regulations have been adopted, and as of May 13, 1991,
no tester or mitigator may continue to operate in New Jersey, if
he or she has not applied for and met the State's certification
-------
requirements. The certification process begins with a tester or
mitigator taking a training course that is given by the NJDEP or
that is NJDEP-approved. Then the applicant must take an
examination. There are four exams, each given for a particular
title, and they are Radon Measurement Specialist, Radon Measurement
Technician, Radon Mitigation Specialist, and Radon Mitigation
Technician. Finally, there is an application form on which the
applicant reports his or her qualifications and experience, and
this form must be submitted to and reviewed by Radon Program staff.
Applicants may choose to submit their certification forms for
review prior to taking the examination.
However, it is not sufficient to simply await data that is
supplied by testers and mitigators. There remain large portions
of the homeowning population who know about radon and its
associated risk but still do not test. And there is also a large
population group that may be unaware of radon problems although
they might very well be at risk. With funds from the United States
Environmental Protection Agency's State Indoor Radon Grant program
the NJDEP is working to increase awareness and educate the public
about radon issues.
One project is the development of school activities to teach
children about radon and also about the concept of risk, using
radon as an example. The intent is that these children will grow
up being more aware of potential hazards in life and how to make
rational risk based decisions regarding them. it is also hoped
that the children will carry the message home to their parents.
Somehow, adults find it hard to ignore information that is
presented to them by a child who has just learned a new and
interesting lesson in school. Especially, when that lesson has
direct bearing on all their lives.
Another project that received funding is training local health
officials to evaluate elevated radon areas. This creates a
valuable working resource, lessening the burden on Radon Program
staff in conducting labor intensive radon evaluation studies.
Evaluations of elevated radon areas are needed when a home test
result is at or above 200 pCi/1 because it has been found in a
number of communities that as many as three quarters of the
surrounding homes will have readings exceeding 4pCi/l. A protocol
was developed for State employees to conduct area evaluations and
recently, with grant funding, local health officers are being
trained in the protocol. It consists of confirmatory testing
public meetings to explain the situation and plan of action'
selection of candidate homes for radon testing based on geologic
data, house structure and a gamma survey, radon canister placement
and pickup by evaluating staff, and a public report of findings and
recommendations. In the first year of the project, 28 local health
officers were trained and others have expressed interest.
Contacting and communicating with low income residents and
residents of metropolitan areas (urban environments) about radon
presents a unique challenge. Currently, two grant projects are
-------
being funded to identify and assess the radon exposure, testing,
and remediation needs of low income and disabled persons, and also
urban populations especially focusing on multifamily dwellings.
Many of the standard means for informing and educating the public
are not applicable to these population groups. Additionally,
questions such as testing and remediation expenses and building
owner responsibility and liability must be dealt with.
A fifth grant project is to survey real estate transactions
in New Jersey. This project has four objectives: 1) to assess the
current radon knowledge and information needs of buyers, realtors,
bankers, and real estate attorneys? 2) to assess the assistance and
notification that current home buyers are receiving about radon?
3) to develop additional information pieces for all of these
groups; and 4) to develop guidelines and policies on radon testing
and real estate transactions.
Since the New Jersey Radon Program began work in the spring
of 1985, the direction of the program has been identifying the
extent of the radon problem in the State, educating the public
about radon, and assuring that the latest and most effective means
for control and mitigation are available. The NJDEP believes that
residential exposure to radon is the most serious environmental
health threat facing New Jersey citizens today. The NJDEP has
taken steps to make each State resident aware of the hazards of
radon exposure by providing information about potential radon
occurrence in local areas via the Tier map, advertising the toll-
free Radon hotline number, and preparing and distributing
informational materials.
-------
VI11-3
RADON REDUCTION IN NEW CONSTRUCTION: DOUBLE-BARRIER APPROACH
by: C. Kunz
Wadsworth Center for Laboratories and Research
New York State Department of Health
Albany, New York 12201-0509
ABSTRACT
A double-barrier design with the space between the barriers having
little resistance to gas flow is described for those parts of homes and
buildings that interface with the soil or surficial rock to reduce soil-gas
(radon) entry into structures. The outside or soil-side barrier interfaces
with the soil. A barrier placed on the soil under the subslab aggregate is
an important element in this design. This forms the outer barrier for the
floor. The subslab aggregate forms a permeable layer, while a plastic
membrane above the aggregate, the slab, and caulking form the inner barrier.
If hollow block are used, barrier coatings can be placed on both the soil
side and interior wall of the blocks, while the hollow space in the blocks
forms the permeable space. The hollow-block walls are connected to the
subslab aggregate to form a small interconnected permeable volume that can be
managed in the following ways to reduce soil-gas entry into the structure.
1. Sealed.
2. Passively vented to outdoor air.
3. Passively depressurized using an internal stack.
4. Actively depressurized.
5. Actively pressurized.
In addition to basements with hollow-block walls, the double-barrier
technique can be adapted to solid vail, crawl space and slab-on-grade
construction including various combinations.
-------
INTRODUCTION
In the long term, substantial reduction in radon exposure can result
from improved new home and building construction techniques that reduce radon
entry. In addressing this approach to reducing radon exposure, the EPA has
published a report "Radon-Resistant Residential New Construction" (1) in
which construction techniques to minimize radon entry in new structures and
to facilitate its removal after construction are described. This report is
the first edition of technical guidance for constructing radon-resistant
structures to be issued by the EPA, and they anticipate future editions as
additional experience and approaches become available. The EPA report
includes a section on barriers to reduce radon entry including wall coatings,
sub-slab membranes, caulking, sealing and prevention of slab cracking.
Another section discusses designs for post-construction active or passive
sub-slab ventilation. A primary element in these designs is a minimum of 4
in. of aggregate under the slab. The preferred material is crushed aggregate
with a minimum of 80% of the aggregate at least 3/4 in. in diameter. This
highly permeable bed under the slab is necessary for good communication in
the event that sub-slab ventilation is needed. The aggregate is placed
directly on the soil and represents a large permeable volume into which radon
can diffuse or flow from the soil and rock under and around the foundation.
The radon that accumulates in the permeable aggregate can then flow with
little resistance to any penetrations in the barriers above the aggregate.
These barriers include the membrane placed over the aggregate, the slab and
any caulking and sealing of the wall floor joint, cracks and penetrations.
Having a permeable volume between the soil and the barriers reduces the
effectiveness of the barriers. Barriers are most effective when interfacing
with the soil. A similar situation occurs when hollow blocks are used to
construct the foundation walls. Radon that infiltrates through the outer
wall and into the hollow cavity of the block walls can then flow with little
resistance to any penetrations of the inside wall barriers. Again, barriers
to radon entry are most effective on the outside or soil-side of the wall.
An indication that aggregate under the slab increases radon entry into
structures was obtained in a survey of over 6,000 homes in New Jersey (2).
The data collected in this study show a definite relationship between age and
radon concentration. On average, houses built since World War II tend to
have higher indoor radon concentrations than houses built between 1900 and
about 1945. Initially, it was suspected that newer houses had higher indoor
radon concentrations because newer houses tend to be tighter and have lower
air exchange rates. However, closer examination of the data indicated that
the differences in radon concentrations associated with tightness did not
fully account for the decline in radon concentration with increasing age in
20th-century houses. The authors speculated that the use of sub-slab
aggregate, which increased in the post-World War II era, could also
contribute to the higher indoor radon observed in newer homes.
It is difficult to determine the effectiveness of the barriers to radon
entry suggested by the EPA, when used in the passive mode, since it is not
possible to know vhat the indoor radon concentrations would be for a house if
the radon-resistant techniques were not employed. The initial results,
hovever, have led the EPA to conclude "that in the presence of a moderate-to-
high radon source, radon prevention techniques that are passive only may not
produce indoor radon levels consistently below 4 pCi/1." In a study of 15
-------
full-basement homes in New York State which were built employing radon-
resistant techniques in an area vith above-average levels of indoor radon,
most of the hones required active sub-slab ventilation systems (3). The
results from the New Jersey survey and the initial results of the homes built
with radon-resistant construction indicate that sub-slab aggxegate
interfacing directly with the soil or rock under a home can increase radon
entry into the home and decrease the effectiveness of barriers placed above
the aggregate.
DOUBLE-BARRIER CONSTRUCTION
It is the purpose of this paper to suggest a design for new home
construction that is more effective in reducing radon entry in the passive
mode but one that can be readily adapted to active mitigation systems if
needed. The design proposes to reduce soil-gas entry by using double-barrier
construction for the sub-grade structure of homes and buildings. A primary
element in this approach is to have a radon barrier under the subslab
aggregate at the soil interface.
The double-barrier approach is illustrated in Figure 1 for a basement
with block walls and a sump. The hollow space in the block walls is
connected to the subslab aggregate via weeping holes or some other low
resistance pathway for air flow, to form an interconnected permeable space
that surrounds the entire subgrade structure. Barriers to radon transport
such as membranes, coatings, caulking, sealing, etc., are placed on both the
soil side and inside of the permeable space. Since radon barriers are most
effective at the soil interface, most of the barrier effort should be
concentrated on the sub-aggregate and outside wall barriers. The barrier
below the aggregate may be a composite of materials such as cement, tar,
plastic film, fine sand, and clay. Barriers at the soil interface should be
resistant to both diffusive and convective flow. A special effort should be
made to seal the outside vail barrier at the wall-footing joint and the
barrier below the aggregate at the footing-aggregate and aggregate-sump
joints.
The double-barrier subgrade construction creates a reasonably small
volume between the inside and outside barriers that can be managed in several
ways to reduce radon entry. Without a barrier below the aggregate, the soil
and rock under and around the house will be directly connected to any
mitigation system used to reduce radon entry. The double-barrier approach
works toward decoupling this direct connection. For the double-barrier
system shown in Figure I, passively venting the hollow-block walls to outdoor
air will allow outdoor air to flow vith little resistance into the permeable
space. As gas from the permeable space is drawn through any penetrations in
the interior or upper barriers into the basement by indoor-outdoor pressure
differentials, outdoor air can flov into the permeable space vith little
resistance. The outside air flov reduces the drav on soil-gas at any
penetration in the outer or belov barriers and thereby reduces the flov of
¦oil-gas radon into the permeable space. Alternatively, the permeable space
could be treated by depressurization (passive or active) or pressurization
(active). For these approaches it vould be best to not vent the block vails
to outside air. Radon entry reduction can then be accomplished by creating
•ither a reduced pressure or increased pressure in the permeable space.
Having created a reasonably small interconnected permeable space vith sealing
-------
VENT TO
OUTDOOR AIR
OUTSIDE WALL
BARRIER AT —5
SOIL INTERFACE
CHANNELS
IN FOOTING
SOLID ROCK
INSIDE WALL
BARRIER
DEPRESSURIZATION
OR
PRESSURIZATION
SUMP
DISCHARGE
SUBSLAB
AGGREGATE
SEALS
SUMP
BELOW SUBSLAB AGGREGATE
BARRIER AT SOIL INTERFACE
Figure 1. Double-barrier construction for a basement with sump.
-------
on both the soil side and inside, it is expected that, if passive venting
(using a stack through the house interior), active suction, or positive
pressure flow is necessary to reduce indoor radon to acceptable
concentrations, then relatively low flow rates would be successful.
An example for an active pressurization system would be to draw air from
ceiling vents in the highest level of the house and blow this air into the
permeable space between the double barriers (Figure 2). The fan could be
located in the basement and relatively low flow rates ("20 cfm) should
suffice. In this manner, heated air from the highest interior level of the
house would be used to pressurize the double-barrier system heating the floor
and walls of the basement while reducing heat loss via exfiltration from the
higher levels of the house.
It is of primary importance to ensure that water effectively drains from
the permeable substructure space between the double barriers. This can be
accomplished with a sump as shown in Figure 1. It may be necessary to grade
the soil forming the base of the subslab aggregate toward the drain tiles and
the sump to aid in preventing the accumulation of water in the subslab
aggregate. If it is possible to drain the subslab aggregate to grade or to a
sewer, then this drainage option could be used instead of or with a sump.
Solid pipe should be used and it should be sealed at the outside or soil-side
barrier.
Exterior footing drainage of gravel and/or perforated piping is used by
many builders and presents a problem to the double-barrier design approach.
The gravel and/or perforated piping of the exterior drainage system runs
around the outside perimeter of the wall-footing joint. It represents a
permeable volume in which radon can accumulate and flow to any penetrations
in the wall and wall-footing joint. To minimize radon entry, the exterior
drainage system should be drained to daylight or to a sewer and not connected
to the subslab aggregate and sump via weeping holes or other methods.
Connecting the exterior drainage system to the subslab aggregate would
provide a pathway for soil-gas radon to enter the permeable zone of the
double-barrier system. Exterior perimeter drainage systems increase the need
for careful sealing at the exterior wall-footing joint.
The double-barrier approach is illustrated for slab-on-grade and crawl
space construction in Figure 3. Drainage of water that might accumulate in
the sub-slab-on-grade aggregate can be accomplished using a sealed sump as
shown in Figure 1 or by drainage to grade or a sewer using solid pipe. If
the double-barrier system is not effective in the passive mode (sealed,
vented to outdoor air, or passively depressurized using stack ventilation),
then active pressurization or depressurization can be employed. When a
barrier is placed directly on the soil of a crawl space and the floor of the
house is sealed, one obtains a double-barrier system with the space between
the soil barrier and the floor being the permeable space. The crawl space
can then be vented to outdoor air or the crawl space can be sealed and
passively depressurized, or actively pressurized or depressurized. To reduce
the volume of air to be pressurized or depressurized, a permeable layer of
aggregate or other construction to form a permeable space with barriers on
both the soil side and house side can be used as shown in Figure 3. Sealing
the floor and using a double barrier at the soil surface results in a triple-
barrier system where the two permeable spaces could be treated independently.
-------
SUMP
BARRIER AT
SOIL INTERFACE
Double-barrier pressurization using interior air.
-------
VENT TO
OUTDOOR AIR"
A 666
6 A4&
itit
DEPRESSURIZATION
OR
PRESSURIZATION
tttt
BARRIER AT SOIL
INTERFACE
TTTKl
A4A4
ittt
4 446A4A&444
SLAB-ON-GRADE
t
EST
SiH
VENT TO
OUTSIDE AIR
DEPRESSURIZATION
OR
PRESSURIZATION
BARRIER AT SOIL
INTERFACE
CRAWL SPACE
Figure 3. Double-barrier systems for slab-on-grade and crawl space
construction.
-------
For example, the aggregate could be passively depressurized and the space
below the floor could be vented to outdoor air.
SUMMARY
Radon-resistant construction designed to decouple houses from the soil
has been suggested and used in various forms. The EPA refers to constructing
a pressure break between the foundation and the soil. Brennan and Osborne
(A) suggested that a drainage mat be used to form an air curtain around the
foundation. A Denver builder excavates to a depth of 10 ft. and constructs a
crawl space under a wood basement floor (1). The crawl space is then
actively ventilated. Walkinshaw (5) constructs a shell inside the basement
and then ventilates the space between the interior shell and the basement
floor and walls.
The double-barrier approach described in this paper attempts to modify
normal building practices to be more radon-resistant at moderate cost.
Barriers under the aggregate and on the outside of hollow-block walls
interfacing with the soil and rock will be the most effective barriers in
reducing radon entry. The double-barrier construction creates a relatively
small permeable volume between the inside and outside barriers that can be
managed in several ways, either passively or actively, to reduce radon entry.
A key element in this design is to maintain water drainage from the permeable
space between the barriers and from around the foundation. There are many
types and variations of house and foundation construction. Very often these
variations are dictated by the local and regional surficial geology. It is
not possible to describe a radon-resistant design readily applicable to all
types of construction and water drainage conditions. However, a better
understanding of how water drainage systems around foundations can increase
the potential for radon entry will enable builders to make water drainage and
radon-resistant construction more compatible. Double-barrier construction is
such an attempt to make water drainage and radon resistance work together.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not necessarily
reflect the views of the agency and no official endorsement should be
inferred.
-------
REFERENCES
Osborne, M.C., Radon-Resistant Residential New Construction, United
States Environmental Protection Agency, EPA/600/8-88/087, July 1988.
Task 3 Final Report, Sampling Design, Data Collection and Analysis,
Statewide Scientific Study of Radon, Prepared for the New Jersey
Department of Environmental Protection, Prepared by Camp Dresser and
McKee Inc., April 1989.
Demonstration of Mitigative Techniques in Existing Houses and New House
Construction Techniques to Reduce Indoor Radon, Prepared for New York
State Energy Research and Development Authority and the U.S.
Environmental Protection Agency, Prepared by W.S. Fleming and
Associates, Inc. (NYSERDA report in publication).
Brennan, T. and Osborne, M.C., Overview of Radon-Resistant New
Construction, In Proceedings of the EPA 1988 Symposium on Radon and
Radon Reduction Technology, Denver, CO, Oct. 1988.
Walkinshaw, D.S., The Enclosure Conditioned Housing (ECHO) System: A New
Approach to Basement Design, In Proceedings of The Fifth International
Conference on Indoor Air Quality and Climate, Toronto, Canada, Aug.
1990, Vol 3, p. 257.
-------
I X - 4
TECHNOLOGICAL ENHANCEMENT OF RADON DAUGHTER
EXPOSURES DUE TO NON-NUCLEAR ENERGY ACTIVITIES
by: J. Kovac, D. Cesar and A. Bauman
Institute for Medical Research and
Occupational Health
University of Zagreb
Ksaver 158, P.O.Box 291
41000 Zagreb, Yugoslavia
ABSTRACT
Natural radioactivity is a part of our natural surrounding and concentra-
tions of natural radionuclides in the environment increase with the development
of technologies. This is the case with phosphate ore processing in fertilizer
industry and during coal combustion in coal-fired power plants. A major source
of exposure to the population in the vicinity of non-nuclear industries results
from inhalation of Rn-222 daughters. Exposure to radon daughters has been also
associated with lung disorders that include cancer among workers. For that rea-
son the radon daughter concentrations in different atmospheres are discused in
this paper.
Working levels were measured as "grab samples" for several years at seve-
ral stations on-site and off-site of the coal-fired power plant as well as the
phosphate fertilizer plant, both located in Croatia. The average mean values
of working levels are presented, and measurement techniques are reviewed.
-------
INTRODUCTION
The exposure from man-made natural sources is called "technologicaly enhan-
ced natural radiation" (TENR)(1). One of the first sourcesof uranium and thori-
um which was detected not being connected with the nuclear industry, was found
during energy production using fossil fuels.
Uranium is widely distributed in nature and is a minor contaminant in all
rocks, sand, and soil. Typical values for uranium are in the domain of 12 - 50
Bq/kg. Hence in ordinary back-yard soil there is of the order of 30 tons of
uranium and 10 g of radium per square mile to a depth of 5 ft. Each cubic yard
of ordinary soil or rock contains the order of 74 kBq of radium. This radium
transforms at a constant rate into its daughter product, radon (222Rn), and
maintains a constant activity of about 74 kBq of radon per cumic yard of rock.
Because all rock and soil is slightly porous some radon diffuses out of any
exposed rock or soil surface. A typical value for the flow of radon from ordi-
nary surface soils into the atmosphere is 3.7/UBq/sec.cm2, or about 3.7 kBq/day
per square yard (2). This radon is diluted in the atmosphere so that typical
values for the radon concentration in outdoor air are in the domain of 3.7 - 37
Bq per cubic meter of air. Radon levels will build up near the surface under
still, inversion conditions when mixing is minimal. The actual volume of radon
in an uranium orebody is extremely small. 37 GBq of radon occupies only 0.66
mm3 at normal conditions of pressure and temperature. Thus in the 1000 tonnes
of ore, with 11 GBq of Ra-226, and therefore also 11 GBq of Rn-222, there is
only about 0.2 mm3 of radon.
EXPERIMENTAL PROCEDURES
MEASUREMENTS TECHNIQUES
The radon or radon daughter measurement techniques vary considerably from
modified film badge type detectors (3) to highly elaborate alpha or beta coun-
ting equipment and even solid state alpha spectrometry (4). It is desirable,
for the long-term monitoring of an atmosphere, that the measurement techniques
be simple, accurate and require a minimum of equipment. The techniques in this
paper allow direct evaluation of the working level value which is ultimately
the quantity correlated with biological hazard.
The working level (WL) is defined as any combination of short-lived radon
daughters in one liter of air that will result in the emission of 1.3 x 10 MeV
of potential alpha energy. Under conditions of secular equilibrium 3.7 kBq/m3
(100 pCi/1) of Rn-222 produces 1 WL (5). The definition is given in Table 1.
-------
TABLE 1. DEFINITION OF THE "WORKING LEVEL" UNIT (WL)
Radionuclide
Alpha
energy
(MeV)
Half-life
Number of
atoms per
100 pCi
Ultimate
alpha energy
per atom
(MeV)
Total ultimate
alpha energy
(MeV/100 pCi)
Ra-222
5.49
3.8
d
1,770,000
excluded
-
Po-218
6.00
3.05
m
977
6.00 + 7.68
0.134 x 105
Pb-214
-
26.8
m
8,580
7.68
0.659 x 105
Bi-214
-
19.7
m
6,310
7.68
0.485 x 105
Po-214
7.69
0.0027
m
0.0008
7.68
0.000 x 105
1.278 x 105
or
1.3 x 105
Measurements of radon daughters can be converted to working levels by an
exact calculation if the state of daughter equilibrium is known. Several aut-
hors (6) have developed methods to determine the state of radon daughter equ-
librium relative to Po-218, by alpha counting a filtered air sample. The most
widely applied measurement technique in the uranium mines is that of Tsivoglou,
than Kusnetz.
The Thomas-Tsivoglou method for calculation of radon daughter concentra-
tions is inconvenient for field use. The irregular counting times require
manual control of the scaler with consequent probabilities of error, and an
error renders the complete data set useless. The 30-min counting period limits
the processing rate to two samples an hour, so at least two scalers are requ-
ired if rapid changes in daughter concentrations are to be measured. With the
method developed by Scott (7) and our equipment it is possible to transfer a
filter from air pump to portable scaler within 40 sec, and next 15 sec is
ample time to note down the scaler reading and restart. Our procedure is there-
fore to take an air sample from 0 to 5 min, and then count the filter from 6
to 11 minutes (the M count), and from 11.25 to 16.25 min (the R count). These
are the only fixed counting times. The third 5-min count (K count) is made on
the filter at a time between 45 and 90 min. The rapid estimation of WL is:
^ = 5550 x V x E (1)
where "R" is the total number of alpha counts, "V" is the sample flow rate
(liters/min), and "E" is the counting efficiency. The value for the average
daughter ratio is 5539 counts, which is rounded to 5550 for convenience.
The radon monitor consists of an alpha scintillator (ZnS/Ag), photomulti-
plier tube, a light-tight outer housing for the detector with passive air entry
and an electronic package to convert the measured pulses to a digitally recor-
-------
ded signal, all battery operated for field use.
For estimating WLs, paralel with alpha counting we used for a long time a
single beta-counting of air sampler filters, using the method developed by
Holmgreen (8), based on the Eberline Air Particulate Monitor and total low-
level beta counting sistem, battery operated for field use. Since the method is
unjustly forgotten, here is a reminder of the basis for WL calculation.
The method for calculation of WLs from total beta activity concentrations
is based upon Table 1, using two simplifying assumptions:
1. Since at equilibrium Pb-214 and Bi-214 account for 90% of the total
ultimate alpha energy, a WL estimation based on Pb-214 and Bi-214 concentrati-
ons would approximate 90% of the actual value, so a factor "F" may be introdu-'
ced to compensate for the exclusion of the Po-218 contribution as a result of
counting only beta activity.
2. The radon daughter concentration ratios 1:0.65:0.35 (Po-218:Pb-214:
Bi-214) are employed in the model.
The ultimate energy assigned to an atom of Po-218 is 13.68 MeV, the energy
of its own alpha plus the alpha energy of Po-214, its great-granddaughter.
Also, Pb-214 and Bi-214, although only beta emitters, are assigned the alpha
energy of Po-214, as Po-214 will ultimately be produced from either of these
atoms. The energy contribution of Po-214 present in the 1 litre volume is near-
ly zero, because of the small population of the extremely short-lived Po-214
atoms. Equation |2| defines the WL unit:
(13.68MeV/atomA)(NA) + ^^MeV/atomg^KNg+N^,)
1.3 x 105 MeV/WL
where "N^" is number of atoms of Po-218, "N " number of atoms of Pb-214, and
"Nr" is number of atoms of Bi-214. The numBers of atoms of each daughter can
be determined from Table 1. Substitution of numbers of atoms of each daughter
into equation |2| yields:
WL = 0.001028(pCiA/l.) + 0.005069(pCig/1.) + 0.003728(pCic/l.) (3)
Based upon two assumptions given above, equation |3| may be modified to become:
WL = F|0.005069(pCig/l.) + 0.003728(pCic/l.)| (4)
Also: pCig/1. = 0.65 Ca (5)
and pCic/l. = 0.35 Ca (6)
where C is the total measured beta activity concentration (pCi/1.). Substitu-
tion into equation |4| of equations |4| and 151 and factoring, and taking into
account that parameter "F" has an empirically determined value of 1.25, substi-
tution into equation |4| gives:
WL = C (0.00575)
a
(7)
-------
In all our measurements we used glass fiber filters (General Electric),
even we tried with molecular filters, but they were not convinient in very
dusty atmosphere.
WL IN COAL-FIRED POWER PLANT
As the combustion of coal increases, so will the magnitude of environmen-
tal and human health hazards associated with trace elements and radionuclides
mobilized by the coal fuel cycle. The large fraction of coal ash that does not
find a commercial application is usually dumped in the vicinity of the coal-
fired power plant (CFPP). When the dumping is finished, most dry ash dumps are
covered by topsoil and converted into areas for agricultural or recreational
use, but not yet in Yugoslavia (9).
The coal ash may contain enhanced levels of the natural radionuclides in
the uranium and series, especially fly ash. Among the decay products are the
radon isotopes, Rn-222, Rn-220 and Rn-219, which are noble gases and thereby
pose special problems in assessing the radiological hazard of fly ash. The
fractional amount of radon lost from the parent-containing material is called
the emanation coefficient or emanating power. It is important to stress the
difference between radon which escapes the physical confines of the parent-
containing material (emanation) and that which occurs in a gas atmosphere which
may be sampled (emanation + diffusion). Beck measured the emenation coeffici-
ents of coal ash obtained from three different power plants (10). For all sam-
ples he studied, the emenation coefficients were less than 0.1. Gamma radiation
from a tailings dump is in general not a serious problem. Radiation levels 1 m
from the pile surface tend to be less than 0.01 mGy/h and average around 0.005
mGy/h though "hot spots" with much higher dose rates have been reported (9).
As with radon emenation, higher surface dose rates are to be expected over the
tailings from higher grade coal, such as in the investigated case.
For all that reasons, investigations of the hazards were undertaken in the
CFPP in Croatia, because the anthracite coal used for combustion has an average
10% sulphur and a variation of uranium. In the seventies the uranium content in
coal was between 500 - 1200 Bq/kg. After 1980 it declined to an average 250
Bq/kg due to opening of an different vein in the coal mine. This requested a
thorough monitoring programme which included measurements of activity concen-
tration of radionuclides in coal and ash samples, and measurements of WL. First
measurements of WL were carried out at 1977. In the CFPP seven locations have
been chosen, because of long-time occupational exposure, and five on-site in
places with natural air flow. Measurements have been repeated in 1983, when
CFPP used coal with lower uranium content. In 1977 we used only Holmgreen's
method, and in 1983 we used both, Holmgreen's and Scott's method. Tables 2 and
3 summarize the estimated WL values, together with occupancy time limit.
-------
TABLE 2. WL OF OCCUPATIONALLY EXPOSED PERSONS INSIDE THE CFPP
Work place
mWL *
(1977)
Occupancy
time limit
mWL
(1983)
Occupancy
time limit
1. Conveyour belt (coal)
I
CO
o
42 h/week**
unlimited
7.0
42 h/week
unlimited
2. Conveyour belt (coal)
15.0
24-42 h/week
6.0
42 h/week
unlimited
3. Below the automatic
control (ash hooper)
80.0
21 h/week
12.0
24-42 h/week
4. Below the automatic
control (ash hooper)
60.0
42 h/week
12.0
24-42 h/week
5. Waste pile fresh
80.0
21 h/week
-
-
6. Waste pile old
-
-
60.0
42 h/week
7. Bottom ash
80.0
21 h/week
20.0
24-42 h/week
TABLE 3. WL ON-SITE IN PLACES WITH NATURAL AIR FLOW
Work place
mWL*
(1977)
Occupancy
time limit
mWL
(1983)
Occupancy
time limit
1. Area around the steam
generator building
6.0
unlimited
6.0
unlimited
2. Under the stack
5.0
unlimited
6.0
unlimited
3. Near the furnice
5.0
unlimited
6.0
unlimited
4. Office building
(500 m from the CFPP)
3.0
unlimited
.
5. 10 km from the CFPP
3.0
unlimited
6.0
unlimited
* -3
mWL = 1 x 10 WL. All WL values are an arithmetic mean of 3 measurements.
**
42 h/week was taken as the occupancy time limit to comply with the US
general population standards, since the workers in the CFPP were never
considered as people occupationally exposed to radiation.
The WLs have shown great variations between two measurements depending on
the radioactivity of the coal and combustion products present at the time of
the measurements in the CFPP. Places on-site with good ventilation had 3-6
mWL. The highest WL was besides the bottom ash and fresh waste pile where even
an occupancy time limit should be considered. The values for the WL are chan-
ging, so that the new data are lower than these presented in Table 2 and 3.
Table 4 summarizes the estimated WL values measured in 1990f when we used only
Scott*s method.
-------
TABLE 4. WL MEASURED ON-SITE AND OFF-SITE CFPP IN 1990.
Location
mWL
1.
Coal storehouse
6.0
2.
Below the automatic
control (ash hooper)
11.0
3.
Area around the steam
generator building
6.0
4.
Slag and ash pile
6.0
5.
Strmac
6.0
6.
Vozilici
5.0
7-
Stepcici
5.0
8.
Luka Plomin
4.0
9.
Rabac
3.0
There were no differences in WLs between measurements done by one or the
other method. As we expected, the highest values were obtained on-site of the
CFPP. Locations 5-9 were at different directions and distances from the CFPP,
chosen in dependency on the wind-rose (Table 5).
TABLE 5. ALTITUDES, DISTANCES AND DIRECTIONS FROM THE CFPP
Location
Altitude (m)
Distance (km)
Direction
Strmac
120
3
SW
Vozilici
100
5
NW
Stepcici
80
2
W
Luka Plomin
10
1
SE
Rabac
0
20
S
The most interesting case is the location Strmac, where a hamlet was built
on a ninety years old tailing site, where already the second and even the third
generation of same families are dweling in the same houses.
At the location Rabac, which is at the sea shore the WL is slightly lower,
since the radon levels over the sea and the ocean are much lower than over the
land, due to the lower Ra-226 content of the sea. For this reason, radon levels
in the atmosphere at coastal sites are very dependent on whether the wind is
blowing from the land or the sea.
-------
WL IN FERTILIZER INDUSTRY
Three years after the beguining of the WL measurements at the CFPP, the
same type of investigations has started in a fertilizer plant.
The activity mass concentrations of natural radionuclides in phosphate ore
for a given radionuclide and type of fertilizer vary markedly from one country
to another, depending on the origin of the components. General features are that
the activity mass concentrations of K-40 and Th-232 and its decay products are
always low and that the activity mass concentrations of the radionuclides of the
U-238 decay series are 5-50 times higher than in normal soil. The degree of
radioactive equilibrium between U-238 and its decay products in a given type of
fertilizer depends essentially on the relative contribution of phosphoric acid,
since phosphoric acid usually has a very low Ra-226 concentration. For the pur-
pose of this, it is assumed that Th-230 and U-234 are in radioactive equilibrium
with U-238 and that Pb-210 and Po-210 are in radioactive equilibrium with Ra-226
A typical concentrations of U-238 and Ra-226 in sedimentary phosphate depo-
sits are 1500 Bq/kg, which are generally found to be in radioactive equilibrium.
When these rocks are processed into fertilizer most of the uranium and some of
the radium accompanies the fertilizer, and than in the fields through crops
enters the food chain.
In the production of fertilizers, phosphate rocks are used in two different
ways. The first method, the acidulation of phosphate rocks was ensured by sul-
phuric acid, where phosphoric acid and gypsum result as normal superphosphate.
The second method, where the phosphate rock is treated by nitric acid, the final
product is phosphoric acid and gypsum as residue, which contains most of the
radium (11).
Almost all of Ra-226 originally in the phosphate ore is discharged in the
piles. The concentration of Ra-226 in piles is about 700 Bq/kg. Since the rate
of radon production equals the rate of radium decay, the rate of radon produc-
tion can be readily calculated. The answer is, 1 g of Ra-226 (this is also 1 Ci
or 37 GBq of Ra-226) produces 74 kBq/sec of Rn-222. Thus the radon production
rate in piles containing 700 Bq/kg od Ra-226 is 1.4 raBq/kg/sec. The density of
dry piles is about 0.7 g/cm3, which means that the production rate of radon per
unit volume is about 1 mBq/m3/sec.
The highest occupational radiation exposure during the process are to be
expected in the fertilizer production or in the fertilizer storehouse. To check
the level of radiation dose, a monitoring programme was introduced, including
the determination of specific activities of natural radionuclides in ambient
air, phosphate ore, phosphate fertilizers, waste products, trickling and well
waters. Measurements of WLs were carried out at ten locations, twice a year for
the last ten years. Five of them were inside the phosphate fertilizer plant,
one on the gypsum's pile. The off-site locations were at four different direc-
tions and distances, chosen on the basis of the wind-rose. Results are presented
in Table 6.
-------
TABLE 6. WL MEASURED ON-SITE AND OFF-SITE THE FERTILIZER PLANT
Location
mWL
1. Phosphate ore storehouse
12.0
2. KC1 storehouse
4.6
3. Fertilizer package store (NPK)
21.0
4. Inside the fertilizer production
9.4
5. Phosphoric acid production
4.4
6. Gypsunfs pile
3.0
7. Off-site locations
1.2
All values are an arithmetic mean of ten years measurements performed in
summer and winter, always three times on each location. During the first year
only beta measurements (Holmgreen) were done, and later only alpha measure-
ments (Scott)(7,8). There were no significant differences observed during the
years. For the comparison in Table 7 one year data are presented measured once
by alpha and once by beta measurement.
TABLE 7. WL MESURED BY DIFFERENT METHODS
Location
Holmgreen
Scott
mWL
1.
Phosphate ore storehouse
3.1
3.2
2.
KC1 storehouse
2.5
1.1
3.
Fertilizer package store (NPK)
3-5
4.2
4.
Off-site locations
1.4
1.2
The WL rate differs slightly not because of different measuring methods,
but also due to different phosphate ore origin.
CONCLUSION
This paper introduces WL measurements in industries where TENR is present.
The CFPP is a specific case with the appearance of natural radioactivity which
was very similar to open pit uranium mining, where WL measurements are routi-
nelly done. For that reaso WL measurements were applied also in this case. When
some places of occupational exposure in the CFPP were detected, the authors
have tried to find out if the same problem also exists in the fertilizer indus-
try. The appearence of places with an increase of natural radioactivity in non-
nuclear industries have left the legislator, at present without a ready soluti-
-------
on in Yugoslavia, how to systematize occupationally exposed workers, especially
after the Chernobyl accident, when the public become sensitive to radiation of
any origin.
The work described in this paper was not funded
by the U.S. Environmental Protection Agency and
therefore the contents do not necessarily reflect
the views of the Agency and no official endorsement
should be inferred.
REFERENCES
1. Gesell, T.F. and Pritchard, H.M. The technologically enhanced natural radi-
ation environment. Health Physics. 28: 361, 1976.
2. Fry, R.M. Radiation hazards in uranium mining and milling. Atomic Energy in
Australia. 18(4): 1, 1975.
3. Costa-Ribeiro, C., Thomas, J., Drew, R.T., Wrenn, M.E. and Eisenbud, M.
A radon detector suitable for personnel or aera monitoring. Paper presented
at the Uranium Mining Health Physics Workshop, Denver, Colorado. June
21-22, 1970.
4. Lasseur, C. Apparatus for selective continuous measurements of each solid
short-lived daughter products of radon. Paper presented at the Journess
d'Electronique de Toulouse, France. March 4-8, 1968.
5. Evaluation of occupational and environmental exposures to radon and radon
daughters in the united states. NCRP Report No. 78. National Council on
Radiation Protection and Measurements, Bethesda, Md, 1985. 83 pp.
6. Manual on radiological safety in uranium and thorium mines and mills. IAEA.
Safety series No. 43. International Atomic Energy Agency, Vienna, Austria,
1976. 16 pp.
7. Scott, A.G. A field method for measurement of radon daughters in air.Health
Physics. 41: 403, 1981.
8. Holmgreen, R.M. Working levels of radon daughters in air determined from
measurements of RaB + RaC. Health Physics. 27: 141, 1974.
9. Bauman, A., Horvat, D., Kovac, J. and Lokobauer, N. Technologically enhanced
natural radioactivity in a coal-fired power plant. In: K.G. Vohra, K.C.
Pillai, U.C. Mishra and S. Sadasivan (ed.), Natural Radiation Environment.
Wiley Eastern Limited, Bombay , 1982. p. 401.
10. Beck, H.L., Gogolak, C.V., Miller, K.M. and Lowder, W.M. Perturbations on
the natural radiation environment due to the utilization of the coal as an
energy source. Paper presented at the DOE/UT Symposium on the Natural Radi-
ation Environment III, Houston, Tx. 1978.
11. Kovac, J., Cesar, D. and Bauman, A. Natural radioactivity in a phosphate
fertilizer plant. In: Proceedings of the XIV Regional Congress of IRPA.
Current Problems and Concerns in the Field of Radiation Protection.
Yugoslav-Austrian-Hungarian Radiation Protection Meeting, Kupari, Yugosla-
via, 1987. p. 69.
-------
X-3
EXTENDED HEATING. VENTILATING AND AIR CONDITIONING
DIAGNOSTICS IN SCHOOLS IN MAINE
BY - Terry Brennan
Camroden Associates
RD#1 Box 222
Oriskany, New York 13424
Gene Fisher
Robert Thompson
USEPA
Office Of Radiation Programs
Washington, Dc
William Turner
H.L. Turner Group
Harrison, Maine
ABSTRACT
An extensive effort to assess the effects of HVAC system operation on the indoor
radon levels was conducted. Many schools in the EPA School Evaluation Program
have been found to have disabled or malfunctioning outside air on the ventilation
system. The outside air in the Maine schools had been disabled. This condition was
corrected using professional HVAC and control contractors. Measurements were
made of radon levels, total and outside airflows, pressure differentials across the
building shell and sub-slab radon levels. Exhaust ventilation, built up air handlers and
unit ventilators were investigated. A heat recovery ventilator was added to a room that
had leaky window sash as the outside air supply for a passive roof vent system. The
passive vents have been blocked off.
1
-------
INTRODUCTION
In August, 1990, extended radon diagnostics were performed in two Maine
Schools. The purpose was to assess the effects of returning the heating, ventilation
and air conditioning (HVAC) system to the original operating specifications would
have on indoor radon levels. This effort was part of the 1990 School Evaluation
Program[1]. Measurements of radon, air pressure differences across the building shell
and carbon dioxide levels[2] were made to help judge the system changes. While a
large amount of data was collected, these measurements were open to a number of
interpretations because the radon levels found in the schoolrooms during the
extended diagnostics week were much lower than were found by the screening
measurements made in April, 1990.
In December of 1990, followup measurements were made at the Gray High
School and Russell Elementary School in Gray, Maine. The purpose of these
measurements was to provide a basis upon which to judge the effect of the HVAC
improvements on radon levels, air pressure relationships and carbon dioxide
concentrations in occupied rooms. December was a good time to make this
assessment because it represented a worst case scenario. That is, the outside air
dampers in the unit ventilators and built up air handlers were closed to minimum and
the competing stack effect was at the maximum. Both conditions are the result of the
low outdoor temperatures found in Maine at that time of year. The measurements were
carried out by a team of people. The team included : Gene Fisher and Bob Thompson
USEPA Office of Radiation Programs, Washington, D.C. ; Bruce Harris, USEPA,
AEERL, Radon Branch, Research Triangle Park, NC; Bill Turner, Fred McKnight, H.L.
Turner Group, Harrison, Maine; Terry Brennan, Camroden Associates, Oriskany, New
York; and Gene Moreau, Bob Stillwell, Maine Department of Health Engineering,
Augusta, Maine.
A special note of thanks is extended to the Maine Department of Health for their
active participation in this evaluation.
PROCEDURE
The evaluation consisted of a visual inspection and measurement of key
performance related variables in the Gray High School and the Russell Elementary
School.
2
-------
An extensive set of measurements were made in the High School.
The following measurements were made :
continuous radon (pulse ionization and semi-conductor)
continuous air pressure differences (variable capacitance)
carbon dioxide survey (infrared spectrometer)
Continuous radon monitors were placed in rooms 2, 7, 17, 31, 32, 33, the
Guidance Office and the Conference Room. The monitors used were eight Honeywell
continuous radon monitors and two femto-Tech continuous radon monitors (room 33
and room 7). The Honeywell units provide mean radon levels for 4 hour intervals and
the femto-Techs for 1 hour intervals. Air pressure differences were monitored across
the floor slab in rooms, 33, 7, the Conference Room and the Guidance Office. Variable
capacitance chambers manufactured by Setra were connected to a data logger
provided by EPA to collect pressure difference data. Calibration curves were made for
each sensor using a micromanometer. Ventilation rates, outside air fractions and
ventilation effectiveness were estimated by making a survey of carbon dioxide levels
in the occupied classrooms. These could then be compared to carbon dioxide
measurements made in the same rooms at the end of the previous school year. Data
was collected from 12/18/90 until 1/16/91. This afforded the opportunity to see the
classrooms operated both normally and with school in recess for the Christmas
Vacation.
Additionally, measurements of sub slab radon were made in the High School and
the nearby Middle School. A carbon dioxide survey was also made in the Middle
School. The Middle School is very close to the High School but does not seem to have
nearly the elevated radon levels that the High School does. These measurements
were made to determine whether the Middle School radon levels were lower due to
lower source term, construction characteristics or HVAC operation and design. The
radon levels under both schools were in the range of 2000 to 4000 pCi/L. There is no
evidence that the source strength is the variable causing the large difference in the
radon levels in the two schools.
RESULTS
Overview Of Results
The results of this investigation can be briefly summarized in a few lines. The
evidence supporting these conclusions are then presented.
1) average radon levels that do not distinguish between occupied and unoccupied
3
-------
conditions can be misleading
2) the operation of the air handlers, both outside air and exhaust only, has a definite
reducing effect on the radon concentrations in the rooms
3) the decay rate of the radon after the air handler turns on is less than would be
expected given the amount of outside air that is introduced because the radon is still
entering due to negative building air pressure
4) repairing the outside air functions of the air handler made dramatic improvements in
the carbon dioxide levels in the rooms where outside air was introduced.
5) while effective and reliable at solving radon problems, soil depressurization in
rooms with inadequate ventilation leaves children sitting in high concentrations of C02
and other indoor air contaminants for which C02 levels are an indicator.
Effect Of Outside Air Improvements On Radon Levels And Dynamics
Introduction-
Continuous radon levels were monitored in eight rooms of the High School.
Rooms 33 and 7 are going to be used to illustrate the effects of the air handler
operation on radon levels in classrooms. The resolution of the femto-Tech units in
these rooms allows one hour radon levels to be used in the analysis. These rooms are
representative of the two different air handling systems - exhaust fans only and unit
ventilators with passive relief. Room 33 is in the new wing of the high school, contains
a unit ventilator and has repeatedly shown the highest average radon levels and
spikes. Room 7 is in the old wing, which has exhaust only ventilation and has shown
high radon levels. The only fan powered outside air that can potentially enter Room 7
is from the gym air handlers, when they are running. Otherwise, outside air to Room 7
consists of whatever is drawn in through leakage in the building shell, window wall
and corridor.
The next two major sections will examine first Room 33, the unit ventilator room
and then Room 7, the exhaust only room, in detail.
Room 33 - Unit Ventilator Ventilation-
The results of the continuous monitoring in Room 33 are shown in Figure 1.
Notice that the "rain spike" in this room on Christmas eve rises from 8 to 90 pCi/L and
4
-------
drops again to 16 pCi/L in a 24 hour period. This is far more severe than in other
monitored rooms, indicating that a substantial amount of radon is available to enter
this room. As in Room 7, the radon levels in this room drop quickly when the ventilation
turns on. This can be seen at the points labeled "Air Handler On" in Figure 1. Notice
that on Christmas eve during a rain storm there is large spike in the radon
concentration. This spike is seen in every room monitored and is interpreted as a rain
spike.
The dynamics of the drop in radon that occurs when the unit ventilator comes on
is illustrated by Figure 2. This graph shows the 24 hour period of December 19, 1991.
Between midnight and 6 AM the radon level hovers around 17 pCi/L. At 6 AM when
the unit ventilator is turned on by a timeclock control, the radon level drops in an
exponential decay until it reaches a minimum of around 2 pCi/L in the late afternoon.
An exponential decay of contaminant level is expected when dilution air is introduced
into the room. After the unit ventilator is turned off, the radon levels begin to climb until
they reach a level of 7 pCi/L again at midnight. The mean radon concentration for this
24 hour period is 8.9 pCi/L and for the occupied time it is 6 pCi/L. However, for the
lowest nine hour period the mean radon level is 3.8 pCi/L. This means that the dose
delivered to the occupants could be reduced 37% by starting the unit ventilator three
hours earlier.
NOTE : A correction for built up radon decay products in the continuous monitor is not
required for the pulse ionization device used because the decay products are
collected using an electric field without being counted. However, due to diffusion lag
into and outof the sensitive volume, a one hour time delay is observed in the radon
dynamic.
5
-------
Radon vs. Time Rm 33
CD
i_
13
CT>
Li-
Spike to 90 pCi/L
Air Handler On
Air
Handler
On
t?
if
Air Handler Off
Christmas Vacation
576 Sat 648
0 ' 72 Saf^ 216
Dec 18,1990
288 Mon360
Dec 31
Time (Hours)
720
-------
Figure 2 - Radon Dynamics in Unit Ventilator Room 33
25 —
Unit Ventilator on
20
7 AM
o
Q.
c
o
TS
(0
cc
24 hour mean = 8.9 pCi/L"
Mean occupied
time = 6 pCi/L
Lowest 9 hour
mean = 3.8 pCi/L
PM
24 ' 28 32 36 40 44 48
Time (Hours)
7
-------
While for this one day, the 19th of December the mean radon level for the
occupied time period was 6 pCi/L, it was not so for other occupied days. In fact, the
average occupied time radon level for the entire monitored period shown in Figure 1 is
a higher 7.8 pCi/L. This is still 28% lower than the 10.8 pCi/L mean for the entire time
period.
Another approach to understanding this dynamic is to apply tracer decay theory.
This has been done in the analysis shown in Figure 3. Figure 3 was created by taking
the decay curves for all the occupied days during the monitoring period and plotting
them on a single graph. The time scale has been changed from consecutive hours to
hours after the unit ventilator turns on. The result is a scattergram that plots all the
decay data for all the occupied days on top of each other.
If a given amount of contaminant is released into a room and then allowed to be
removed by dilution with ventilation air, it is expected that the concentration of the
contaminant will decay exponentially with time[3]. The rate at which it decays is
described by the solution to the continuity equation. This is given as the following :
1) C(t) = C(0) x eNt
where : C(t) = concentration at time t
C(0) = concentration at the start of the decay
N = airchange rate in air changes per hour
t = time in hours
By fitting an exponential decay curve to the data in Figure 3, the decay rate and
the air exchange rate for the average day during this monitoring period can be
determined. It is obvious from this curve that if the radon level at the start of the day is
greater than about 8 pCi/L, the mean level during the day would not get below 4 pCi/L.
The curve fit yields an air exchange rate of 0.13 air changes per hour (ACH). By direct
measurement of outside air, it is known that the air exchange rate in the room is 1
ACH. This discrepancy is explained in the following way. In order for equation 1) to
describe radon concentrations, the entry rate of radon after the start of the decay must
be zero. The introduction of outside air has not stopped radon from entering the room.
This is easily verified by a glance at the air pressure difference between the room air
and the sub slab air. The room air was at a lower pressure than the sub slab air during
the entire monitoring period. When the unit ventilator turned on, this difference became
smaller, but the room was still negative relative to the sub slab. The radon
8
-------
Figure 3 - Reduction Rate of Radon in Room 33
Air Handler On - All Days Combined
y = 15.416 * eA(-0.13157x) R= 0.83454
- - - y = 15.416 * e*(-1x) R= 1
0 6
^ ' d i
r; o
2 0 2 4 6 8 10 12
Time After Air Handler Comes On (Hours)
—o- Measured Decay-all days
- Decay Curve if radon entry were stopped
9
-------
entry rate may have been reduced but it certainly was not stopped. If the room was
pressurized by the unit ventilator then the radon concentration would have dropped
according to the lower curve in Figure 3. The radon concentration would be below 4
pCi/L in a matter of an hour.
In fact, it is likely that this is the case in this room during the spring and fall when
the outside temperature is warmer than in January. This is expected for two reasons.
One, warmer outside air means a reduction in the air pressure differences induced by
the stack effect. Two, when the outside air is warm enough gains from body heat will
overheat the room and cause the outside air dampers to open more. This will increase
the outside air volume and contribute to pressurizing the room.
Lastly, the room could potentially be pressurized even under the worst case
condition represented by these test results. This could be accomplished by air sealing
the room so that the minimum outside air flow rate would pressurize the room. Not only
would this control the indoor radon but it also would result in energy savings by
reducing air infiltration.
Room 7 - Exhaust Only Ventilation-
Figure 4 shows the continuous radon data in Room 7. The data begins on
December 18, 1990. Christmas vacation began on December 20, 1990 and ended
January 2, 1991. The radon levels in this room plummet whenever the rooftop exhaust
fans turn on (see the points labeled "Air Handlers On" in Figure 1). This effect is
repeatable. The radon levels drop in spite of the fact that operation of the exhaust fans
drives the air pressure difference between room 7 air and the sub slab air 3 pascals
lower. It is likely that the amount of radon entering the room increases when the fans
turn on. Although more soil air is being drawn in by the operation of the fans, the
dilution effect of the increased ventilation from above grade overwhelms the increased
radon entry. Unfortunately, the increased entry is not overwhelmed enough so that the
occupied radon levels are below 4 pCi/L, but are instead 7.1 pCi/L.
Figure 5 shows the agglomerated radon data for the occupied days in Room 7.
This graph was generated in the same way that Figure 3 was for Room 33. The
general trend of decreasing radon levels after the exhaust fan turns on is obvious.
There is a great deal more scatter in this data than there was in the data from Room 33
(the unit ventilator room). The curve fit to this data shows an effective ventilation rate of
only 0.065 ACH, while the measured exhaust rate informs us that there is actually 0.63
ACH (shown as the theoretical curve in Figure 5). The data from Figure 3 and Figure 5
are combined in a single graph in Figure 6. This figure highlights the similarities and
differences between the dynamics of the two rooms. Notice that the theoretical curves
for the two rooms almost coincide, even though the fan powered air exchange rates
10
-------
Radon vs. Time Rm. 7
N- %
e c
° 5
O ^
«- CO
DC tr
«
(D
>
(D
_l
C
0
"O
(0
DC
1
-------
Figure 5 -Reduction Rate of Radon in Room 7
Exhaust Fan On-All Days
Rm 7
Theory rm 7
(. ;
§
i
H 1
£ 0
©
D Q
0 ~
o
* © ~)
0
w (J
¦
¦
o 8
^5
e
o
o 0
t^
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-c _
o $-
8
i
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f * ¦
8
10 12
I 2 4 6
Time
y = 9.6569 * eA(-0.065616x) R= 0.4982
y = 9.67 * eA(-0.63x) R= 1
12
-------
Figure 6 - Reduction Rate of Radon
Air Handlers On - Rms. 7 & 33
25
20
15
o
a
§
3
* 10
-2
Rm 33
Theory rm 33
Rm 7
Theory rm 7
©
¦ «
> 1 + 1 ¦ 1 !
4 6
Time
8
10 12
y =
y =
15.416 * eA(-0.13157x) R= 0.83454
- y = 15.416 * eA(-1x) R= 1
9.6569 * eA(-0.065616x) R= 0.4982
y = 9.67 * eA(-0.63x) R= 1
13
-------
are quite different (1 and 0.63 ACH). This is largely due to the difference in source
terms. Room 7 begins the average occupied day at around 10 pCi/L while Room 33
begins the average occupied day at just over 15 pCi/L
It is tempting to attribute the differences in radon dynamics in these two rooms to
the difference between exhaust only and fan powered outside air ventilation. But, two
rooms, no matter the depth of study provide anecdotal, not conclusive evidence. The
results of these measurements do support the current model of radon entry and control
as follows :
• entry is dominated by air pressure driven mechanisms
• exhaust ventilation can lower radon concentrations, but not as effectively
as powered outside air ventilation
To these two basics we can add a further hypothesis :
• unless fan powered outside air ventilation stops radon entry, the reduction
rate of radon will not be as great as expected from dilution alone
and a corollary :
• exhaust only ventilation will never lower radon concentrations as quickly
as would be expected from dilution alone because it does not stop the
entry of radon
It is important to understand that these two suggestions apply only to dynamic
radon behavior and not to steady state conditions. This only applies to the rate at
which radon levels change.
Effect Of Outside Air Improvements On Carbon Dioxide Measurements
Introduction--
The reason we breathe is to get oxygen to the cells in our bodies and to remove a
number of the byproducts of respiration. Carbon dioxide and water vapor are the most
plentiful products of respiration. Carbon dioxide levels in outgoing breath are several
thousand parts per million. Carbon dioxide measurements made in occupied rooms
can be used as a surrogate for levels of indoor air contaminants that are produced by
the occupants themselves and routine activities of occupants. If a simplifying
assumption is made about the generation rate of C02 being constant then they also
can be used to estimate the outside air ventilation rate [4]. The ventilation guidelines of
14
-------
15 cfm/person in the publication ASHRAE 62-1989 Ventilation for Acceptable Indoor
Air Quality should result in a steady state 1000 ppm of carbon dioxide in an occupied
classroom.
Carbon Dioxide Measurements-
Carbon dioxide measurements were made in the High School and the Russell
School (pre and post radon control) and in the Middle School. The pre radon control
measurements were made in early June of 1990 and the post measurements were
made in December of 1990.
Carbon Dioxide Measurements in the High School--
A histogram is shown in Figure 7 that differentiates between the pre and post
carbon dioxide measurements. Only measurements from occupied rooms with closed
windows are shown. The distribution of C02 levels has been very clearly pushed to
the lower levels by the repairs made to the ventilation system. The pre radon control
C02 levels had a mean of 1402 ± 450 ppm and the post level mean was 1042 ± 394
ppm. This represents a 33% decrease in the mean. From a health, comfort and
alertness perspective, this is a great improvement over the situation before the
ventilation equipment- was repaired. Although the mean is now nearly the level
recommended in the ASHRAE guidelines[4], half the rooms in the post control sample
would still be considered underventilated by the current guideline. Eight percent of
them (2 rooms) are above 1700 ppm, which would reflect an outside air exchange rate
of 5 cfmiperson. By contrast, all the rooms in the pre mitigation set of measurements
were above the current guidelines (1000 ppm) and 27% of them (3 rooms) were above
1700 ppm.
15
-------
Figure 7 - Pre and Post Control C02 Histogram for High School
W
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n in
in in
i i' '»iI) n tii]iif i i i r i r
Post Ventilation
Pre ventilation
JJ^.
JUJL
UL
400 800 1200160020002400280032003600
Carbon Dioxide (ppm)
Carbon Dioxide Measurements in the Russell School-
A bar graph is shown in Figure 8 that differentiates between the pre and post
carbon dioxide measurements and between ventilation and radon control type.
Measurements are from occupied rooms with closed windows except the pre control
measurements in the exhaust only ventilation - soil depressurization rooms. These
rooms had open windows during the June measurements. The number of open
windows is shown on the bar graph.
The C02 levels have been very clearly lowered by the repairs made to the unit
ventilators (rooms 5, 9, and 6) and by the installation of the heat recovery ventilator
(located in room 1, with no powered ventilation). Pre control C02 levels were not
available for some rooms with unit ventilators (rooms 7, 8, 10 and 11) but post control
measurements were. The mean post control C02 levels for all the rooms in which unit
ventilators were repaired (5, 6, 7, 8, 9, 10, and 11) was 1350 ± 408 ppm.
Rooms 1, 2a, 2b, 3 and 4 are in the oldest wing, where there is no fan powered
ventilation. Rooms 2a and 2b show slight increases in C02 levels, averaging 1500
ppm C02, as compared to Room 1 which has dropped from over 1250 ppm to 925
16
-------
i 1 1 1 1 1 i r i
Number of windows open during pre test*
1 wo
4 wo
3 wo
2 wo
4 wo
4 wo
Exhaust ventilation
with Soil Oepressurization
Unit Ventilators
No
Powered
Ventilation
One
window
open
Pre C02
Post C02
5 9 6 1 13 2 2 20 22 24 26 25 23 21
Room Number
*Note No windows were open in the Unit Ventilator rooms during the C02 tests
-------
ppm. This is expected considering that no changes in the ventilation of rooms 2a
and 2b have taken place, but a heat recovery ventilator has been added to Room 1.
Rooms 20, 21, 22, 23, 24, 25, and 26 are in the exhaust only wing, in which soil
depressurization has been used to control the radon. The radon levels in these rooms
(except for the library, which is around 7 pCi/L) are averaging between 1.4 and 3.5
pCj/L. The pre control C02 levels in these rooms must be interpreted cautiously
because at least one window was open in each room when these measurements were
made. The post control C02 levels had a mean of 1857 ± 376 ppm.
None of the exhaust only rooms meet the current ASHRAE guideline for
ventilation rates. In fact, none of them meets the ASHRAE ventilation guideline for the
year in which they were constructed. While it is clear that soil depressurization will
control indoor radon, it is also clear that it has little impact on other indoor air
contaminants.
Histograms of the C02 data from the Russell School are not presented because
there is so little pre control data that did not have windows open.
CONCLUSIONS
Conclusions for this work contribute to interpretation of radon measurements
made in school rooms (and other non-residential settings) where a wide range of
occupant activities and the operation of air handlers can have important effects on
radon measurements. Radon measurements in the Maine Schools show that average
radon levels that do not distinguish between occupied and unoccupied conditions can
be misleading when the effect of air handlers is unknown.
The operation of both types of air handlers, outside air and exhaust only, has a
definite reducing effect on the radon concentrations In the rooms. Unless radon is
prevented from entering, the radon concentration does not drop as quickly as
expected given the known amount of outside air that is being introduced. Only fan
powered outside air has the chance of doing this. In the High School it is not doing so
during the coldest months. It is likely that there are times during the spring and fall
when the outside air dampers are open wider and the stack effect is reduced that the
unit ventilator rooms are pressurized enough to prevent radon entry. Exhaust only
ventilation can have reducing effects, but will always be drawing some soil air into the
building. It is possible that for given source strengths and slab/building shell leakage
characteristics exhaust ventilation could be good enough to control radon, but that is
not so in the Gray High School.
Clearly many, if not all the classrooms investigated, were underventilated for the
number of occupants. The carbon dioxide data gives plenty of evidence for this
contention. Repairing the outside air functions of the air handler made dramatic
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improvements in the carbon dioxide levels in the rooms where outside air was
introduced. However, while effective and reliable at solving radon problems, soil
depressurization in rooms with inadequate ventilation leaves children sitting in high
concentrations of C02 and other indoor air contaminants for which C02 levels are an
indicator.
1. Fisher, G., Brennan, T.B., Turner, W. The School Evaluation Program, in The
1990 International Symposium on Radon and Radon Reduction Technology : Volume
V. Preprints. 1990. Atlanta: EPA.
2. Brennan, T., Turner, W., Fisher, G. Building HVAC/Foundation Diagnostics For
Radon Mitigation in Schools and Commercial Buildings : Part 1. in Indoor Air '90 The
Fifth International Conference on Indoor Air Quality and Climate. 1990. Toronto,
Canada
3. Charlesworth, P., Air Exchange Rate and Airtightness Measurement Techniques
- An Applications Guide. 1988, Coventry, Great Britain: Air Infiltration and Ventilation
Centre.
4. ASHRAE, 62-89 Ventilation For Acceptable Air Quality. 1989, American Society
of Heating Refrigeration and Air Conditioning Engineers.
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