EPA/600/8-90/041
June 1990
Indoor Air - Assessment
Methods of Analysis for
Environmental Carcinogens
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park. NC 277ii
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DISCLAIMER
This document has been reviewed in accordance with U.S. Environmental Protection
Agency policy and approved for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
11
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PREFACE
In October 1986 Congress passed the Superfund Amendments and Reauthorization Act
(SARA, PL 99-499) that includes Title IV - The Radon Gas and Indoor Air Quality Research
Act. The Act directs that EPA undertake a comprehensive indoor air research program.
Research program requirements under Superfund Title IV are specific. They include
identifying, characterizing, and monitoring (measuring) the sources and levels of indoor air
pollution; developing instruments for indoor air quality data collection; and studying high-
risk building types. The statute also requires research directed at identifying effects of indoor
air pollution on human health. In the area of mitigation and control the following are
required: development of measures to prevent or abate indoor air pollution; demonstration of
methods to reduce or eliminate indoor air pollution; development of methods to assess the
potential for contamination of new construction from soil gas, and examination of design
measures for preventing indoor air pollution. EPA's indoor air research program is designed
to be responsive in every way to the legislation.
In responding to the requirements of Title IV of the Superfund Amendments, EPA-
ORD has organized the Indoor Air Research Program around the following categories of
research: A) Sources of Indoor Air Pollution; B) Building Diagnosis and Measurement
Methods; C) Health Effects; D) Exposure and Risk (Health Impact) Assessment; and
E) Building Systems and Indoor Air Quality Control Options.
EPA is directed to undertake this comprehensive research and development effort not
only through in-house work but also in coordination with other Federal agencies, state and
local governments, and private sector organizations having an interest in Indoor air pollution.
The ultimate goal of SARA Title IV is the dissemination of information to the public.
This activity includes the publication of scientific and technical reports in the areas described
above. To support these research activities and other interests as well, EPA publishes its
results in the INDOOR AIR report series. This series consists of five subject categories:
Sources, Measurement, Health, Assessment, and Control. Each report is
quantity. Copies may be ordered while supplies last from:
printed in a limited
in
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U.S. Environmental Protection Agency
Center for Environmental Research Information
26 West Martin Luther King Drive
Cincinnati, OH 45268
When EPA supplies are depleted, copies may be ordered from:
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
IV
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ABSTRACT
This monograph describes, in a general way, published sampling procedures and
analytical approaches for known and suspected carcinogens. The primary focus is upon
carcinogens found in indoor air, although the methods described are applicable to other media
or environments. In cases where there are no published methods for a particular pollutant in
indoor air, methods developed for the workplace and for ambient air are included since they
should be adaptable to indoor air.
Known and suspected carcinogens have been grouped into six categories for the purposes
of this and related work. The categories are radon, asbestos, organic compounds, inorganic
species, particles, and non-ionizing radiation. Some methods of assessing exposure that are
not specific to any particular pollutant category are covered in a separate section.
This report is the fifth in a series of EPA/Environmental Criteria and Assessment Office
Monographs. The series includes the following titles:
I. DEVELOPMENT OF A RISK CHARACTERIZATION FRAMEWORK
H. A REVIEW OF INDOOR AIR QUALITY RISK CHARACTERIZATION STUDIES
m. USE OF BENZENE MEASUREMENT DATA IN RISK CHARACTERIZATION
ESTIMATES: A PRELIMINARY APPROACH
IV. INDOOR CONCENTRATIONS OF ENVIRONMENTAL CARCINOGENS
V. METHODS OF ANALYSIS FOR ENVIRONMENTAL CARCINOGENS
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CONTENTS
Page
PREFACE iii
ABSTRACT v
TABLES ix
AUTHORS AND REVIEWERS X
INTRODUCTION 1
RADON 2
OVERVIEW 2
SAMPLING 2
ANALYSIS 3
ASBESTOS 9
OVERVIEW 9
PHASE CONTRAST MICROSCOPY 9
SCANNING ELECTRON MICROSCOPY (SEM) 10
TRANSMISSION ELECTRON MICROSCOPY (TEM) 11
FIBROUS AEROSOL MONITOR (FAM-1) 11
ORGANIC COMPOUNDS
OVERVIEW
GENERAL ANALYTICAL METHODS FOR GAS
PHASE ORGANIC COMPOUNDS 12
FORMALDEHYDE 15
POLYCYCLIC AROMATIC HYDROCARBONS 18
PESTICIDES 18
INORGANIC SPECIES 19
OVERVIEW 19
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CONTENTS (continued)
Page
INORGANIC ARSENIC (SALTS, ARSENATES,
AND ARSENTTES 19
BERYLLIUM 19
CADMIUM (OXIDE, BROMIDE, AND CHLORIDE) 21
CHROMIUM (HEXAVALENT) 21
NICKEL (CARBONYL AND SUBSULFIDE) 21
SELENIUM (SULFIDE) 22
PARTICLES 23
OVERVIEW 23
ENVIRONMENTAL TOBACCO SMOKE 23
NON-IONIZING RADIATION 26
OVERVIEW 26
RADIOMETRIC MEASUREMENTS 26
INTERACTION COEFFICIENTS 27
DOSIMETRY 27
OTHER APPROACHES TO ASSESSING EXPOSURE 28
BIOLOGICAL MARKERS 28
QUESTIONNAIRES 29
EXPOSURE MODELING 29
REFERENCES 30
VTM
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TABLES
Number Page
1 Radon-222 decay series 4
2 Applications and sensitivities of some radon measurement
devices 5
3 Results from round 5 of the Radon Measurement
Proficiency Program 8
4 Comparison of PCM, SEM, and TEM 10
5 Classification of organic pollutants 13
6 Properties of some common sorbents 14
7 Common gas chromatography detectors 16
8 Sampling and analysis approaches for inorganic species 20
9 Sampling devices and analysis methods for particles 25
IX
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AUTHORS AND REVIEWERS
This report was written by Drs. Max R. Peterson and Dennis F. Naugle, Research
Triangle Institute; and Dr. Michael A. Berry, Environmental Criteria and Assessment Office,
U.S. Environmental Protection Agency, Research Triangle Park, N.C. Reviewers were
Charles H. Ris, Human Health Assessment Group, and Richard Walentowicz, Exposure
Assessment Group, U.S. Environmental Protection Agency, Washington, D.C., and Dr.
Cynthia Sonich-Mullin, Environmental Criteria and Assessment Office, Cincinnati, OH.
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INTRODUCTION
Indoor air compounds with carcinogenic activity in animals, humans, or both include
radon, asbestos, organic compounds, inorganic compounds, particles (including environmental
tobacco smoke or ETS), and non-ionizing radiation (NIR). Some of the pollutants in this list
exist as vapors, some as fibers or paniculate material, some are adsorbed onto suspended
particulate material, and some are distributed between a vapor-phase and a particle-bound
state. Some classes contain a large number of compounds (ETS and organics), one is
associated with a single parent element (radon); and one is not a chemical species at all
(NIR). Most are dangerous in themselves but one (radon) is a precursor to even more deadly
progeny. Because of these differences in physical and chemical states and properties, each
carcinogen class generally requires different sampling and analysis approaches.
As a further complication, a single indoor environment may contain a wide variety of
air pollutant mixtures. No single best approach currently exists for assessing the composition
and concentrations of such complex mixtures. There are many uncertainties inherent in
characterizing the pollutant mix of indoor environments and there is great difficulty in
predicting the severity and nature of lexicological interactions.
Identical mixtures of pollutants from different sampling sites are rarely, if ever,
encountered in indoor air. Similar mixtures may be found in a variety indoor environments,
but with concentrations of individual components differing significantly. For example, ETS
may contain 4,500 individual compounds, each present at a concentration that depends upon a
wide variety of factors. Therefore, from a practical sampling and analysis point of view,
only the most toxic of the compounds or the pollutants making up the largest portions of the
mixture can be measured.
The analytical methods presented below are classified by pollutant category with
sub-categories added as deemed appropriate. The purpose of this monograph is to present an
overview of some common methods for each category of pollutant or, in some cases, for
specific pollutants. While the list of methods for each category is not exhaustive, significant
effort was expended to include at least one or two workable methods for each category.
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RADON
OVERVIEW
Sampling and analysis of radon and radon progeny (decay products) in indoor air are
complicated by both spatial and temporal changes in concentration. An acceptable
measurement scheme must also take into account diurnal and seasonal variations.
In addition, analysis is complicated by dramatic changes in composition of a collected
sample with time. The change in composition is due to the radioactive decay of both radon
and its progeny. Radon decays more slowly (half-life 3.83 days) than any of its progeny but
still at a fast enough rate to require that analyses be made very soon after samples are taken
(Cothern and Smith, 1987). New methodologies to measure time-integrated radon
concentrations on indoor glass surfaces (such as picture glass) are under development and
appear promising for long term human exposure studies (Samuelsson, 1988).
SAMPLING
Collection of samples may be accomplished by grab sampling, continuous sampling, or
integrative sampling. Grab sampling involves the taking of essentially an instantaneous
sample and allows determination of the concentration at the specific time the sample was
taken. Continuous sampling involves the taking of many measurements at closely spaced time
intervals and allows the determination of patterns in the variation of concentration over the
entire sampling time. Integrative sampling involves the taking of a single sample over a long
time interval and allows determination of a single average concentration over the sampling
period (Cothern and Smith, 1987).
Radon may be separated from its progeny during sampling, and the concentration of
either or both determined by analysis. The separation is typically accomplished by allowing
radon to diffuse through a passive barrier (e.g., foam rubber). Radon progeny, which rapidly
adsorb onto the surfaces of airborne particulates and other solids, cannot pass through such
barriers.
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ANALYSIS
Most of the analytical methods for radon and radon progeny actually measure emitted
radiation and not concentration of the target species, although the two are directly related in
the absence of other radioactive material. The decay chain for radon and its progeny is
summarized in Table 1. The decay sequence includes the emission of three fundamental kinds
of radioactivity: Alpha particles, beta particles, and gamma rays. The emission rate of any
or all of these may be measured with appropriate instrumentation (Cothern and Smith, 1987).
Concentrations of radon are usually expressed in bequerels per cubic meter (Bq/m^) or
in picocuries per liter (pCi/L). One bequerel equals 1 event per second (decay/s) and one
picocurie equals 0.037 bequerel.
Radon progeny concentrations are usually expressed in working level months (WLM).
One working level equals the quantity of short-lived progeny that will result in 1.3 x 10^
MeV of potential alpha energy per liter of air. Potential alpha energy is used to relate
atmospheric concentration of radon progeny to dose delivered to the human lung. It
represents the total alpha energy an atom can emit as it decays through its entire radioactive
series, and it must be calculated from measurements (or estimates) of the concentrations of the
progeny.
Although a large number of devices are available, the actual analysis for radon and/or
its progeny is typically accomplished using a scintillation phosphor mounted on a
photomultiplier, an ionization chamber, a thermoluminescent dosimeter (TLD), or a visual or
automatic image-processing method. Table 2 provides a summary of currently available
radon measurement devices based on instrument type.
Scintillation devices include cells for gaseous and liquid samples and plates for samples
of radon progeny collected on filters. Gas scintillation cells and scintillation plates are
typically coated with zinc sulfide; in liquid scintillation cells, the liquid contains both the
radioactive material and the scintillator. In all cases, the intensity of the light pulses
generated by the impingement of radioactive particles (alpha, beta, and/or gamma) on the
scintillating material is measured with the aid of a photomultiplier tube (Cothern and Smith,
1987; Henschel, 1988).
An ionization chamber may be used to measure radon in air. The current in the
chamber is directly proportional to the radon concentration (Cothern and Smith, 1987).
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TABLE 1. RADON-222 DECAY SERIES
Isotope
Radon-222
Polonium-218*
Lead-214*
Bismuth-214*
Polonium-214*
Lead-210
Bismuth-210
Polonium-210
Lead-206
Symbol
222Rn
86
1
218Po
84
i
214Pb
82
4
214Bi
83
;
214Po
84
i
210pb
82
i
210B1
83
1
210p0
84
1
206Pb
82
Decay Mode
Alpha $He)
Alpha (^He)
Beta (_^e)
Beta (_?e)
Alpha ^He)
Beta (_?e)
Beta (_?e)
Alpha (^He)
Half-Life
2.82 days
30.5 min
26.8 min
19.7 min
0.000164 sec
21 years
5 days
138 days
Stable
Radon progeny of primary concern.
A thermoluminescent dosimeter (TLD) may be used to provide an integrated
measurement of radon or radon progeny activity. The TLD chip is typically lithium fluoride
or calcium fluoride (Cothern and Smith, 1987).
In the two-filter method, a small tube, 30-100 cm long, is equipped with two filters:
An entrance filter, which removes progeny from the sample as it is drawn into the tube, and
an exit filter, which traps the polonium-218 formed by the decay of some of the radon atoms
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TABLE 2. APPLICATIONS AND SENSmVITIES OF SOME RADON
MEASUREMENT DEVICES
Instrument type
Application
Sensitivity*
Purpose1
Direct measurement
Scintillation cell
lonization chamber
Passive barrier method**
Scintillator
TLD chip
Two-filter method
Passive sampling devices
Activated charcoal
Alpha track
Grab or
continuous
Grab or
continuous
Continuous
Integrating
Grab or
continuous
Integrating
Integrating
3.7 Bq/m3c
3.7 Bq/m3c
3.7 Bq/m3c
0.08-8. IBq/m3
3.7 Bq/m3c
7.4 Bq/m3 for
100-hour exposure
18.5 Bq/m3 for
30-day exposure0
Screening,
diagnostic
Screening,
diagnostic
Screening,
diagnostic
Screening, large
scale survey
Diagnostic
Screening, large
scale survey
Screening, large
scale survey
aWith collection of progeny on (or in close proximity to) a scintillator or thermoluminescent detector (TLD)
chip.
bAdapted from Cothern & Smith (1987). 1 pCi/L = 37 Bq/m3.
CA sensitivity less than the value shown is generally achievable depending on the specific instrument used.
'Three typical purposes are illustrated:
• Screening: The aim of a screening method is to evaluate rapidly and inexpensively where high radon
concentrations may occur.
• Diagnostic: Designed to measure specific parameters for detailed radon analysis such as:
- short-term spatial and temporal variations,
- relationship with other factors (such as ventilation rate),
- equilibrium fraction of each of the radon daughters,
- effect of remedial actions.
• Large-scale survey: A national, regional or other large study aimed at evaluating the exposure of the
public. A large number of time-averaged measurements are needed.
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as they move through the tube. After sampling, the filter is removed and counted by
measurement of the alpha decays. The method has been adapted to continuous and integrative
monitoring through the use of a TLD chip at the exit filter (Cothern and Smith, 1987).
Radon may be collected from air by adsorption onto the surface of activated charcoal.
It may be analyzed by de-emanation of the radon from the charcoal into a scintillation cell
and alpha-counting; by heating the charcoal and counting gamma emissions from the desorbed
radon using a sodium iodide system; or by dissolving the charcoal in liquid scintillation fluid
and counting in a liquid scintillation detector (Cothern and Smith, 1987).
In an alpha track detector, a thin piece of an appropriate plastic is placed in a holder and
exposed to air containing radon (and perhaps its progeny) for an extended period of time (up
to a year). During the exposure period, alpha particles, emitted by decaying nuclei, strike the
surface of the plastic making microscopic gouge marks or alpha tracks. The exposed plastic
is removed from its holder and chemically etched to enlarge the tracks. The alpha tracks,
now appearing as small holes on the surface, are then visually counted using a wide-screen
microscope (Cothern and Smith, 1987) or some other counting system (e.g., spark counter,
CCD camera, etc.).
The principles used for the measurement of radon progeny are similar to those used to
measure radon, but the sampling and analysis approach must be altered significantly. Radon
progeny may be removed by passing the air sample through a filter. Radon gas passes
through such a barrier while the progeny, which are adsorbed onto suspended paniculate
material, are collected on the filter.
The early methods for measuring radon progeny were based on the method originally
reported by Kusnetz (1956) and Tsviglou et al. (1953). The progeny, which are largely
attached to aerosols, are collected on a filter and subsequently analyzed by alpha-particle
spectroscopy. This allows the determination of the activity of each progeny on the filter and
the subsequent computation of the potential alpha energy or working level concentration.
Both passive and active alpha track detection have been applied to the measurement of
radon progeny. Unfortunately, while progeny are easily excluded from the analysis for radon
by this method, radon is not easily excluded from the analysis for progeny. The typical
approach is to measure radon-plus-progeny, then radon only, and subtract to get the
progeny-only value.
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Programs designed to assist commercial firms offering radon measurement services have
been established in many countries. In the United States, the Environmental Protection
Agency (U.S. Environmental Protection Agency) supports a National Radon Measurement
Proficiency (RMP) Program (U.S. Environmental Protection Agency, 1988). Each company
participating in the National RMP Program submits passive detectors for exposure in a
chamber containing a known concentration of radon or, in the case of continuous or active
monitors, carries the device(s) to the chamber and samples the contaminated air directly
through a port. After exposure, the passive detectors are returned to the company for
analysis. The company reports its measured values for all detectors and/or monitors to the
RMP Program Coordinator. The RMP Program currently uses the mean of the absolute value
of the relative error (MARE) to evaluate the company's performance with a particular device
or type of detector. The company is judged proficient at measurement if its MARE is 0.25 or
less. The results of the RMP Program provide useful information on the relative accuracy of
methods used to sample and measure radon and radon progeny in indoor air. Table 3
summarizes the results of the most recent proficiency measurement round for which published
data are available (Singletary, 1988).
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TABLES. RESULTS FROM ROUND 5 OF THE RADON
MEASUREMENT PROFICIENCY PROGRAM*
Relative
Median standard
Species
Method
Numberb
of sets
Range of
target values
error0 deviatioi
Alpha track detectors
Charcoal canisters
Continuous monitors
Grab sampling
Electret-PERM
Radon progeny
Continuous working-level
monitors
Grab working-level
sampling
Radon progeny integrating
sampling unit (RPISU)
9 170 to 2000 Bq/m3
223 160 to 1900 Bq/m3
88 220 to 1400 Bq/m3
60 420 to 3700 Bq/m3
97 170 to 2000 Bq/m3
70 0.02 toO. 15 WLd
48 0.01 to 0.21 WL
4 0.04 to 0.07 WL
18
12
11
13
18
11
19
14
24
18
12
12
20
171e
13
36
&Based on Gearo et al. (1988) and Research Triangle Institute (1988).
"Each set consists of 4 separate measurements.
cMedian of the Absolute Relative Error
°1 Working level, WL, («2.08xlO"^J/M3) = The potential alpha energy concentration of progeny in
equilibrium with a radon concentration of 3700 Becquerels per cubic meter (Bq/m ).
eLarge standard deviation was primarily due to two sets of data with enormous absolute relative error.
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ASBESTOS
OVERVIEW
Very few studies have been made of asbestos in homes. This section contains analytical
methods used to measure airborne asbestos in the workplace and in post-abatement situations.
The same methods can, in principle, be applied to asbestos in homes.
Because of their small size, airborne asbestos fibers are difficult to distinguish from
other man-made and natural fibers. Fibers are usually collected on either a cellulose ester
filter or a polycarbonate filter and measured visually under relatively high magnification,
using phase contrast microscopy (PCM), scanning electron microscopy (SEM), or
transmission electron microscopy (TEM). All three methods require the visual counting of
fibers in randomly selected grid sections of slides prepared from the collected material. The
key features of PCM, SEM, and TEM are shown in Table 4.
PHASE CONTRAST MICROSCOPY
The standard protocol for measuring exposure to airborne asbestos in the industrial
workplace adopted by the Occupational Safety and Health Administration (OSHA) specifies
PCM as the analytical method. The method (NIOSH 7400) specifies a 25-mm diameter, 0.8
to 1.2 /im pore size cellulose ester membrane filter for collection. Microscope slides are
prepared from the collected material and the fibers in randomly chosen regions of each slide
are counted using a positive phase contrast microscope with a 100 /im diameter graticule.
One of two sets of counting rules are used to define which fibers are counted. The "A" Rules
require that only fibers longer than 5 /im and with an aspect ratio (length to diameter) greater
than or equal to 3:1 be counted. The "B" Rules require that only the ends of fibers longer
than 5 /im and less than 3 /im in diameter and with an aspect ratio equal to or greater than 5:1
be counted. The final fiber count for the B Rules is determined by dividing the number of
ends by 2. Fiber density on the filter is reported in fibers/mm^; fiber concentration in the
original air sample is reported in fibers/mL (Eller, 1984).
There are two serious limitations in the protocols described above. The first limitation is
that PCM cannot distinguish between asbestos and non-asbestos fibers; all fibers or elongated
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TABLE 4. COMPARISON OF PCM, SEM, AND TEMS
PCM SEM TEM
Specificity for Not specific (all More specific but Definitive (with
asbestos fibers > 5 jim not definitive options)
long are counted)
Magnification 400 1000-2000 20000
Sensitivity 0.15 /*m (best) 0.05 jun (best) 0.0002/zm (best)
(thinnest fiber 0.25 /*m (typical) 0.20 pm (typical) 0.0025 /im (typical)
visible)
aFrom U.S. Environmental Protection Agency (1985b). See text for definitions of PCM, SEM, TEM.
particles that meet the length, diameter, and aspect ratio criteria are counted. The second
limitation is a result of the optical magnification used in PCM: Only fibers or particles
0.25 urn in diameter or larger can be seen (U.S. Environmental Protection Agency, 1985b).
SCANNING ELECTRON MICROSCOPY (SEM)
Scanning electron microscopy (SEM) is more sensitive to thin fibers and has a better
specificity for asbestos than PCM. Fibers are typically collected on a 0.4 to 0.8 /zm pore size
polycarbonate (or cellulose ester) filter, carbon-coated directly on the filter, and transferred to
an EM grid. The fiber substrate is relatively thick and the electrons bombarding the specimen
during visual analysis are scattered and reflected rather than transmitted. These electrons are
detected as noise by the microscope and restrict the visual range to fibers with a diameter of
about 0.20 /im or larger (Environmental Protection Agency, 1985b).
At present, there is no standard method, no quality assurance laboratory testing, and no
National Institute of Science and Technology (NIST, formerly NBS) reference materials for
SEM. In spite of this, SEM is still more available and much less expensive than TEM.
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TRANSMISSION ELECTRON MICROSCOPY (TEM)
Transmission electron microscopy (TEM) is considered the better of the two types of
electron microscopy used for measuring airborne asbestos. There are two methods for
collecting fibers and preparing slides for TEM analysis. One method requires the collection
of fibers on a 0.4 /zm pore size polycarbonate filter. A strip of the polycarbonate filter is
carbon coated, placed on a TEM grid, and cleared by Jaffe washer or condensation washer.
The second method requires the collection of fibers on a 0.45 jum pore size cellulose ester
filter. A wedge of the cellulose ester filter is collapsed on a glass slide, etched in a low
temperature plasma asher, carbon coated, and transferred to a TEM grid using a Jaffe washer.
By both methods, the mounted fibers are identified as asbestos (from fiber morphology,
selected area electron diffraction (SAED) patterns, and energy dispersive x-ray analysis
(EDXA), measured, and counted at 20,000x magnification (U.S. Environmental Protection
Agency, 1985b; Federal Register, 1987).
The major disadvantages of TEM are the cost and the time required for analysis. It is
also less available than the other two methods. The analysis can be broken down into three
levels to reduce cost and time for analysis: (1) identification of asbestos (for screening
purposes), (2) elemental analysis of selected fibers (for regulatory action), and (3) quantitative
analysis of a few representative fibers (for confirmatory analysis) (Yamate et al., 1984;
Federal Register, 1987).
FIBROUS AEROSOL MONITOR (FAM-1)
The fibrous aerosol monitor (FAM-1) is a real-time direct reading instrument for
measuring airborne fibers. The detectability of fibers depends on both length and diameter.
For example, fibers 5 pm long can be detected down to a diameter of about 0.75 /mi; fibers
10 /im long can be detected down to a diameter of about 0.6 /im (Lilienfeld, 1987). The
FAM-1 induces fibers to oscillate by means of an electric field and detects the light scattering
signature resulting from the oscillation of the fibers under illumination by a helium-neon laser
beam (Monitoring Instruments for the Environment, no date). This approach allows the
counting of fibers in the presence of nonfibrous particles but does not discriminate between
asbestos and non-asbestos fibers.
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ORGANIC COMPOUNDS
OVERVIEW
A large number of organic compounds are typically present in indoor air. They range
from compounds that are gases at ambient conditions to non-volatile compounds adsorbed
onto suspended particulate material. Table 5 may be used to classify individual compounds
on the basis of boiling point and provides information on typical sampling methods for each
class. Most gas phase organic compounds may be measured by one or more of the general
analytical methods described in the next section. More detailed information for specific
compounds may be found in the literature (e.g., Riggin and Purdue, 1984; Riggin et al.,
1986). Because of the emphasis placed upon them in the literature, formaldehyde, polycyclic
aromatic hydrocarbons, and pesticides are covered in separate sections of this chapter.
GENERAL ANALYTICAL METHODS FOR GAS PHASE ORGANIC
COMPOUNDS
Little is currently known about the concentrations and health risks of most organics in
indoor air (Seifert and Ullrich, 1987). The Total Exposure Assessment Methodology
(TEAM) Studies (Wallace, 1987; Pellizzari et al., 1987a,b; Handy et al., 1987), under the
sponsorship of the U.S. EPA, represent the most in-depth studies of indoor pollutants to date.
Personal air, fixed-site air, drinking water, and breath samples from individuals and homes in
several states were analyzed for twenty selected organic chemicals, several of them
carcinogenic. The methods used in the TEAM studies are rapidly becoming standard.
Emissions of specific organics from building materials and consumer products have been
evaluated in the laboratory by various methods (Merrill et al., 1987; Wallace et al., 1987;
Girman et al., 1987). Emissions from indoor combustion of fuels has also been studied
(Traynor, 1987; Traynor et al., 1982; Spengler and Cohen, 1985).
As a rule, it is quite difficult to accurately measure a specific organic compound directly
within the matrix of other components normally present in indoor air. The determination
usually involves collection of a sample by some appropriate means, separation by gas
chromatography, and measurement with an appropriate detector.
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TABLE 5. CLASSIFICATION OF ORGANIC POLLUTANTS1
Description
Boiling Range*
Sampling Methods
Used in Field Studies
Very
Volatile
Organic
Compounds
Volatile
Organ
Compounds
Semi-
Volatile
Organic
Compounds
Particulate
Organic
Material0
<0to 50-100
50-100 to 240-260
240-260 to 380-400
>380
Batch sampling, adsorption on charcoal
Adsorption on tenax, carbon molecular
black, or charcoal
Adsorption on polyurethane foam (PUF)
or XAD-2
Collection on filters
aAdapted from World Health Organization (1987).
kpolar compounds tend to boil near the higher end of the range; less-polar compounds, near the lower end.
clncludes organic compounds associated with particulate matter.
Collection. Samples may be collected on a sorbent, in an impinger solution, or in an
evacuated canister. Sorbent and impinger collection are more selective than canister
collection although all methods have inherent disadvantages (Jayanty, 1989).
Ideally, a sorbent used for sample collection will have a strong affinity for the
compound(s) of interest and little or no affinity for other species (H2O, CO2, etc.) in the
matrix. Properties of several common sorbents are given in Table 6 (Sheldon et al., 1985;
Raymer and Pellizzari, 1987; Levins, 1979; Krost et al., 1982; Piecewicz et al., 1979;
Sanchez et al., 1987; Raymond and Guiochon, 1975; Riggin, 1984).
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TABLE 6. PROPERTIES OF SOME COMMON SORBENTS
Sorbent
Properties
Tenax GC Resin
XAD-2 Resin
Activated Charcoal
Graphitized Carbon Black
Carbon Molecular Sieves
Porous polymer of 2,6-diphenyl-p-phenylene oxide;
hydrophobic; not suitable for very light organics; lower capacity
than XAD-2 but may be thermally desorbed.
A polystyrene-divinylbenzene porous polymer; hydrophobic; not
suitable for very light organics; higher capacity than Tenax GC
but requires solvent desorption.
Typically a coconut charcoal; relatively high retention of water;
organics are very strongly adsorbed; requires solvent desorption.
Obtained by heating thermal carbon blacks at 3000 °C under an
inert gas; nonselective; low retention of water and light gases;
may be thermally desorbed.
Pyrolyzed porous beads of polyvinylidene chloride; low capacity
for water but organics are very strongly adsorbed; higher
capacity for organics than graphitized carbon blacks; better than
Tenax GC for highly volatile compounds; very light, volatile
compounds may be thermally desorbed.
Sorbents offer the advantage of concentrating the sample as it is collected but require a
desorption step prior to measurement. Desorption may be accomplished thermally or with a
suitable solvent.
Impinger collection concentrates the analyte of interest through use of an absorbing
solution. Impinger collection may also be used to stabilize very reactive substances, perhaps
through derivatization.
Alternatively, samples may be collected in evacuated canisters. The inside walls of the
canister must be chemically and physically inert to the species of interest. Stainless steel
canisters with specially treated interior walls are available. Samples may also be collected in
glass bulbs or bags made of an appropriate material (Jayanty, 1989).
14
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Separatipn. Separation of organic gases and vapors is generally accomplished by gas
chromatography (OC). Typically, an open-bore capillary column is used for the separation.
The method is simple and relatively fast, and the species of interest can be measured as it
exits the GC column by use of an appropriate detector. Cryogenic focusing or sorbent
trapping may be used in the inlet of the OC to concentrate the sample and lower the detection
limit for the species of interest.
MesKui-emffnt. Gas chromatography detectors represent the most commonly used
measurement method for airborne organics. Mass spectrometry, often associated with gas
chromatography (GC-MS), is also used. A more recent approach involves the use of an array
of sensors to selectively detect and measure a specific compound within the matrix (i.e.,
without separation).
Choice of an appropriate GC detector depends upon response to the compound(s) of
interest, response to other species in the sample matrix, and desired sensitivity. Table 7
summarizes key features of some commonly used GC detectors.
Mass spectrometry (MS) provides one of the most powerful tools of chemical analysis.
Every vaporizable compound gives a unique, often complex mass spectrum. Mass
spectrometers used to measure components of complex mixtures must be used either
(1) downstream from a gas chromatograph or (2) in conjunction with a sophisticated data
system. Chemical ionization, rather than electron impact ionization, may be used to reduce
fragmentation and simplify the mass spectrum, but the quantity of data acquired from a single
analysis of a mixture is quite large.
An array of piezoelectric quartz crystals, each coated with a different partially selective
material, may be used for direct analysis of multicomponent mixtures (Carey and Kowalski,
1986, 1988; Carey et al., 1987). The response of the array to a particular analyte resemble
a typical absorption or emission spectrum with the resolution dependent on the number of
sensors in the array. The pattern of the response is used to identify the analyte; analyte
concentration is calculated from the magnitude of the response.
FORMALDEHYDE
Formaldehyde, because of its reactivity, is often collected in an impinger containing
water. Formaldehyde reacts on contact with water to form methylene glycol. The water
15
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TABLE 7. COMMON GAS CHROMATOGRAPHY DETECTORS
Detector
Detection
Limit
Applications
Argon
lonization
Detector
Electron
Capture
Detector
Flame
lonization
Detector
Flame
Photometric
Detector
Far
Ultra-
violet
Detector
Hall
Electrolytic
Conductivity
Detector
Helium
lonization
Detector
Mass
Selective
Detector
sub ppm
to
ppb
Pg
sub ppm
sub ng
sub ppb
low ng
sub ppm
to ppb
10 pg
Responds to compounds with an ionization
potential < 11.8eV
Responds to electron-capturing species,
especially to halogenated compounds
Responds to all combustible substances
Responds to compounds containing sulfur or
phosphorus
Responds to all substances except the
noble gases
50-100 pg Responds to compounds containing a halogen,
nitrogen or phosphorus
Responds to compounds with an ionization
potential < 19.8 eV
Responds to all substances; may be used to
identify as well as measure individual
components of a mixture
16
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TABLE 7 (cont'd). COMMON GAS CHROMATOGRAPHY DETECTORS
Detector
Detection
Limit
Applications
Nitrogen
Phosphorus
Detector
Photo-
lonization
Detector
Redox
Chemiluminescence
Detector
Thermal
Conductivity
Detector
10 pg
10 pg
>ppb
sub ng
Responds to compounds containing nitrogen or
phosphorus
Responds to compounds with an ionization potential
< 11.7 eV
Responds to compounds containing oxygen, sulfur,
nitrogen or phosphorus and to unsaturated
hydrocarbons
< 100 ppm Responds to all compounds
solution is then treated with either chromotropic acid or pararosaniline and the resulting
solution analyzed spectrophotometrically (National Research Council, 1981; Hawthorne and
Matthews, 1987; Georghiou etal., 1987).
Diffusion badges containing a water solution may also be used to sample formaldehyde
in air. After exposure, the badge solution is analyzed colorimetricaUy. A comparison of
impinger and diffusion badge collection (Stock, 1987) indicates close agreement of the two
sampling methods.
Silica gel coated with acidified 2,4-dinitrophenylhydrazine may be used to sample
aldehydes and ketones in air (Tejada, 1986). Analysis of the sample, which contains the
hydrazone derivatives of any aldehydes and ketones collected, is typically accomplished by
high performance liquid chromatography (HPLC).
17
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POLYCYCLIC AROMATIC HYDROCARBONS
Polycyclic aromatic hydrocarbons (PAHs) in air may (1) exist as a vapor, (2) be
adsorbed onto atmospheric paniculate material, or (3) be distributed between the vapor and
adsorbed states. Sampling usually involves the collection of particulate-bound material on a
filter and the collection of vapors on an adsorbent or in an impinger (Davis et al., 1987, and
Otsonetal., 1987).
The particulate-bound PAHs are typically extracted with a liquid solvent or a
supercritical fluid (Hawthorne and Miller, 1987). Recovery is complicated by the
vaporization of loosely bound PAHs from the paniculate material after collection and by the
difficulty of desorbing very tightly bound PAHs (Engelbach et al., 1987). Spitzer (1982) has
shown that XAD-2 resin will separate PAHs from polar and non-polar contaminants in air
paniculate material. Extracts are usually analyzed by ultraviolet absorptiometry, fluorescence
spectrometry, or gas chromatography/mass spectrometry, but a number of other methods have
also been reported (Davis et al., 1987).
PESTICIDES
Carcinogenic species used in pesticides and frequently found in indoor air include
chlordane, heptachlor/heptachlor epoxide, aldrin, and dieldrin (Cavender et al., 1986 and
1987). These and similar species are typically collected on polyurethane foam (PUF) or
PUFin combination with some granular sorbent (e.g., XAD-2, Tenax GC, or Florisil PR).
Following Soxhlet extraction and concentration, the samples are analyzed by GC-ECD,
GC-MS, or GC-MS-MID (multiple ion detection) (Hsu et al., 1988; Lewis and Jackson,
1982; Lewis and MacLeod, 1982; Lewis et al., 1986).
18
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INORGANIC SPECIES
OVERVIEW
In addition to asbestos, a number of inorganic pollutants, especially some of the heavy
metals, have been classified as carcinogens. The inorganic species of most concern are
inorganic arsenic (salts, arsenates, and arsenites); beryllium; cadmium (oxide, bromide, and
chloride); chromium (hexavalent); nickel (carbonyl and subsulfide); and selenium (sulfide).
Table 8 summarizes sampling and analysis approaches that are currently used to measure
concentrations of individual metals in workplace atmospheres. They should also be
appropriate for indoor air. In most instances, more accurate methods of collection and
analysis are available, but they have not yet been accepted as standard methods.
INORGANIC ARSENIC (SALTS, ARSENATES, AND ARSENITES)
National Institute for Occupational Safety and Health Method 7300 (Eller, 1984) is
appropriate for 29 elements including arsenic. By this method, the sample is collected on a
cellulose ester membrane filter and, after preparation, analyzed by inductively coupled argon
plasma, atomic emission spectroscopy.
NIOSH Method 7900 is designed to measure arsenic and its compounds as arsenic. By
this method, the sample is again collected on a cellulose ester membrane but, after
preparation, is analyzed by atomic absorption, flame arsine generation. The estimated limit
of detection for this method is 0.02 /ig per sample (Eller, 1984).
BERYLLIUM
Beryllium occurs in air as a component of suspended particulate matter and may be
collected on a membrane filter. Analysis by gas chromatography (Ross and Sievers, 1972) or
atomic absorption spectroscopy (AAS) (Owens and Gladney, 1975) appears to offer adequate
sensitivity, but both require pretreatment to remove interfering species (U.S. Environmental
Protection Agency, 1987). Beryllium may also be measured by inductively coupled plasma
emission.
19
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TABLE 8. SAMPLING AND ANALYSIS APPROACHES
FOR INORGANIC SPECIES
Species
Arsenic *
(salts,
arsenites,
arsenates)
Beryllium
Cadmium
(oxide,
bromide,
chloride)
Chromium(VI)
Nickel
carbonyl
Nickel
subsulfide
Selenium
sulfide
Sampling
Cellulose ester
membrane
Membrane filter
Cellulose ester
membrane
Cellulose ester
membrane
Filter
Cellulose ester
membrane
PVC filter
Impinger
Filter
Cellulose ester
membrane
Cellulose ester
membrane
Analysis
ICAP-AES
AA-Flame Arsine
Generation
GC
AAS
ICAP-AES
AA-Graphite
Furnace
ICAP-AES
AAF
1C
Effect on Oxid.
of r by H2O2
ICAP-AES
VAS
Chemiluminescence
AAF
AAS, XRF, ICAP,
colorimetry,
SSMS, NAA, FES
ICAP-AES
ICAP-AES
LOD Ref.
a
0.02 /ig a
d,e
d,f
a
0.05 ng a
a
a
b
0.001 ng g
a
0.05 /ig a
ppb h
0.005 /ig/mL i j
c
1/ig a
1 /*g a
aEller (1984) eRoss and Sievers (1972) ^ickett and Koirtyohann (1969)
^U.S. Environmental Protection Agency (1984) fOwens and Gladney (1975) JSachdev and West (1970)
°U.S. Environmental Protection Agency (1985a) &Kneebone and Freiser (1975)
dU.S. Environmental Protection Agency (1987b) nStedman et al. (1979)
20
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Beryllium concentration may also be determined by NIOSH Method 7300, described
above for arsenic, or by NIOSH Method 7102. Method 7102 requires collection on a
cellulose ester membrane filter and, after sample preparation, analysis by atomic absorption,
graphite furnace. The estimated limit of detection is 0.005 /ig per sample (Eller, 1984).
CADMIUM (OXIDE, BROMIDE, AND CHLORIDE)
Cadmium may be analyzed by NIOSH Method 7300, described above for arsenic, or by
NIOSH Method 7048. By Method 7048, the sample is collected on a cellulose ester
membrane filter and, after preparation, analyzed by atomic absorption with flame. The
estimated limit of detection by this method is 0.05 /ig per sample (Eller, 1984).
CHROMIUM (HEXAVALENT)
Chromium occurs in air as a component of suspended particulate matter and may be
collected on a filter. Filters are typically composed of cellulose, polyethylene, polystyrene,
PVC, or glass (U.S. Environmental Protection Agency, 1984). Chromium(VI) may be
separated from matrix materials by ion chromatography.
Chromium(VI), collected on filters, may be measured by a catalytic method developed
by Kneebone and Freiser (1975). The measurement is based on the catalytic effect of
chromium(VI) on the oxidation of iodide by hydrogen peroxide. The sensitivity of the
method is 0.001 /*g Cr(VI).
Chromium may also be measured by NIOSH Method 7300 as described previously for
arsenic. Hexavalent chromium may be measured using NIOSH Method 7600 which requires
sample collection on a PVC membrane filter and, after preparation, analysis by visible
absorption spectrophotometry. The estimated limit of detection for this method is 0.05 /Jg per
sample (Eller, 1984).
NICKEL (CARBONYL AND SUBSULFIDE)
Trace amounts of nickel in ambient air are almost always present as a component of
suspended particulate matter. As a result, nickel is usually collected, along with other
particulate material, on a filter. Unfortunately, nickel carbonyl, because of its volatility,
21
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cannot be collected in this fashion. In sampling nickel from flue gases, an impinger is
typically used to trap gaseous species (U.S. Environmental Protection Agency, 1985a).
The most commonly used analytical method for nickel in air is atomic absorption
spectrophotometry with flame (AAF). The detection limit for nickel by this method is
0.005 /Jg/mL (Pickett and Koirtyohann, 1969; Sachdev and West, 1970). Other methods
include atomic absorption spectrophotometry without flame, x-ray fluorescence spectrometry
(XRF), inductively coupled argon plasma (ICAP) spectroscopy, colorimetry, spark source
mass spectrometry (SSMS), neutron activation analysis (NAA), and flame emission
spectrophotometry (FES) (U.S. Environmental Protection Agency, 1985a).
Analysis for specific nickel compounds in ambient air is quite difficult due to induced
chemical changes inherent in the analytical techniques and to the very low concentrations of
nickel compounds in ambient air. A variety of techniques for identifying compound form
have been attempted on flyash samples (U.S. Environmental Protection Agency, 1985a).
Vapor-phase inorganic nickel compounds (e.g., nickel carbonyl) are easily separated
from other nickel compounds on the basis of their volatility. The chemiluminescence
analytical method is quite specific for nickel carbonyl and has a detection limit in the
parts-per-billion range (Stedman et al., 1979).
Nickel may also be measured by NIOSH Method 7300 as described previously for
arsenic. The estimated instrumental limit of detection for nickel is 1 jig per sample (Eller,
1984).
SELENIUM (SULF1DE)
Selenium may be measured by NIOSH Method 7300 as described previously for arsenic.
The estimated instrumental limit of detection for selenium is 1 ^g per sample (Eller, 1984).
22
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PARTICLES
OVERVIEW
Participate matter is made up of solid aerosols (e.g., dusts and smokes) and liquid
aerosols (e.g., mists and fogs). Table 9 gives brief descriptions of devices used to collect and
measure particles. Environmental tobacco smoke is perhaps the most notorious of the
pollutants containing paniculate material that may be present in indoor air.
ENVIRONMENTAL TOBACCO SMOKE
Environmental tobacco smoke (ETS) is a complex mixture of gaseous substances and
suspended particulates and is quite difficult to measure in indoor air. More than
4,500 compounds have been identified in tobacco smoke: Some exist completely in the vapor
phase, others are adsorbed onto particulate material, and still others are distributed between
the vapor and adsorbed phases. As a result of adsorption onto and desorption from suspended
particles, and even some chemical changes in the more reactive compounds, the components
of ETS show a pronounced spatial and temporal distribution in indoor environments. In
addition, background indoor air is a complex mixture containing a number of the chemical
species also found in ETS. Even though body burden of specific components of ETS can be
determined, there are no direct measures of total dose. However, there are several methods
for assessing exposure.
Respirable suspended particle concentrations have been determined using personal
monitors in order to estimate exposure to ETS (Spengler et al., 1985). In addition, personal
and indoor space monitoring have been used to measure concentrations of specific compounds
or classes of compounds and these (e.g., nicotine) may be used to indicate exposure to ETS
(Hammond et al., 1987; Muramatsu et al., 1984). Two recent studies on the chemical
composition of ETS suggests potential gas-phase (Eatough et al., 1989) and particulate phase
(Benner et al., 1989) tracers based on environmental chamber experiments.
Sampling of ETS components may be active or passive. Active samplers utilize filters
and/or vapor traps to collect material; passive samplers utilize diffusion and permeation to
concentrate collected gases and vapors. In both cases, the samples are subsequently analyzed
in the laboratory. Particles are typically measured by light-scattering principles or frequency
23
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changes induced in piezoelectric quartz crystals. Gases are typically measured using infrared
absorption, electrochemical reactions, or gas chromatography with appropriate detection
(National Research Council, 1986; Hammond et al., 1987). Studies found in the literature
(described in Guerin et al., 1987) suggest that determination of a specific compound
(nicotine, for example) in ETS should include measurements of the quantity/concentration of
the compound in both particle-bound and vapor- phase material (Hammond et al., 1987)
since, as cigarette smoke ages some compounds change from particulate to vapor phase and
vice versa.
Other approaches used to assess exposure to ETS include measuring air and body
nicotine and cotinine, and nitrosamines: questionnaires; and exposure modeling. These
topics are described in a later section of this work.
24
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TABLE 9. SAMPLING DEVICES AND ANALYSIS METHODS FOR PARTICLES*
Device or Method
Description
Sampling Devices:
settling chamber
centrifugal device
impinger
impactor
filter
electrostatic precipitator
thermal precipitator
Analysis Methods:
microscopy
piezoelectric
optical
electrical
Particles from a trapped sample of air settle by gravity onto a
microscope slide.
Centrifugal force, inside a small cyclone or curved surface
trap, is used to separate particles on the basis of size.
A glass nozzle submerged in a liquid is used to collect
particles.
Particles are collected from an aerosol stream by impaction
onto a surface.
Particles are collected by passing an air sample through a
filter.
An ionizing electrode and a collection (or grounded) electrode
are used to collect particles.
Particles are removed from an aerosol on the basis of response
to a temperature gradient.
Allows previously collected dust particles to be counted, sized,
and/or identified.
Allows real-time monitoring of particulate mass concentration
by deposition of particles onto a quartz crystal.
Allows a direct measurement of particles in air on the basis of
particle interactions with light.
Allows direct measurement of particles in air on the basis of
the tendency of airborne particles to acquire electrical charge.
beta attenuation
The collected mass of airborne particles is measured by its
attenuation of beta radiation passing through it.
aBased on Lioy and Lioy (1983).
25
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NON-IONIZING RADIATION
OVERVIEW
Non-ionizing radiation (NIR) refers to electromagnetic radiation with wavelengths longer
than 100 nm. It includes ultra-violet (UV); visible; infrared (IR); radiofrequency (RF),
including microwaves (MW); and extremely low frequency (ELF) fields, including power
frequencies of 50-60 Hz. Pressure waves (e.g., infrasound and ultrasound) are also included
(International Radiation Protection Association, 1985).
All electromagnetic radiation consists of an electric field and a magnetic field. Either or
both, or their effects on living tissues, may be measured. The analytical approach used to
measure NIR depends upon the purpose of the measurement. Radiometry deals with
quantities (e.g., field intensity) associated with radiation fields; interaction coefficients deal
with the interaction of radiation and matter; and dosimetry deals with quantities used to
determine the specific absorption rate (SAR) of biological tissue (International Radiation
Protection Association, 1985).
RADIOMETRIC MEASUREMENTS
Electric and magnetic fields associated with radiation of a particular wavelength oscillate
at the same frequency, typically 50 or 60 cycles per second from alternating-current (AC)
power lines. The fields have both a magnitude and a direction. The field intensity, or field
strength, of an electric field is typically measured in volts per meter; the field intensity of a
magnetic field, in teslas or gauss (Shepard et al., 1987).
The Electric Power Research Institute (EPRI) has funded the development of EMDEX
(Electric and Magnetic Field Digital Exposure), a compact, lightweight instrument used to
monitor personal exposure to electromagnetic radiation. Exposure assessments are obtained
by combining the field intensity measurements and computer models which can extrapolate
measured values to a wide variety of environments (Sussman, 1988; Shepard et al., 1987).
Cahill and Elder (1984) have described several other instruments, both developmental
and commercial, for measuring the intensity of electric and magnetic fields.
26
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INTERACTION COEFFICIENTS
Interactions of NIR with matter include attenuation, absorption, scattering, and
reflection and related phenomena. An interaction coefficient may be calculated for each type
of interaction (e.g., a scattering coefficient). The term "coefficient" generally refers to the
relative decrease of a radiometric quantity due to an interaction phenomenon during passage
through a thin layer of medium divided by the thickness of the layer. Interaction coefficients
are expressed in reciprocal meters (m"1) (International Radiation Protection Association,
1985).
DOSIMETRY
Dosimetry is the quantification of the specific absorption rate (SAR) of a biological
entity. The SAR is dependent on the configuration of the source, the physical characteristics
of the exposed subject, the orientation of the exposed subject with respect to the source, and
the frequency of the electromagnetic radiation. Determination of the SAR of tissues requires
measurements with electric field probes, thermocouples, thermistors, fiber optic probes,
thermography, and calorimetry. The appropriate method for a particular application depends
upon the frequency range of the radiation, the type of subject or biological preparation, and
whether distributive or whole-body average SAR is desired (Guy, 1987).
27
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OTHER APPROACHES TO ASSESSING EXPOSURE
BIOLOGICAL MARKERS
The assessment of exposure to some pollutants may be made by analysis of physiological
fluids. Biochemical methods may be used to obtain estimates of exposure based on the uptake
of specific agents in body fluids.
Biological markers have been used to estimate exposure to environmental tobacco smoke
(ETS). For example, The presence of nicotine and its major metabolite, cotinine, in
biological fluids is entirely due to exposure to tobacco, tobacco smoke, or environmental
tobacco smoke. The determination of nicotine and cotinine in the saliva, blood, or urine of
active or passive smokers is done primarily by gas chromatography (GC) with a
nitrogen-sensitive detector, or by radioimmunoassay (RIA). The GC method can be used to
measure concentrations of nicotine as low as 1 ng/mL and concentrations of cotinine as low as
6 ng/mL in biological fluids. The radioimmunoassays for nicotine and cotinine represent a
newer analytical method. The sensitivity of these assays is about 0.5 ng/mL for both nicotine
and cotinine and has inter- and intra-assay variation of ±5% (Langone et al., 1973; Hill
et al., 1983). The RIA method has been used by only a limited number of laboratories
because it requires the synthesis of specific nicotine and cotinine derivatives for the generation
of serum albumin conjugates and the raising of antibodies to these conjugates (Langone et al.,
1973). The RIA method also requires careful drawing and handling of samples to avoid
contamination.
Cotinine, the major metabolite of nicotine, offers several advantages as a biological
marker for ETS exposure. Cotinine is specific for tobacco and its quantitation can be useful
in gathering information from large populations of both smokers and non-smokers.
The use of cotinine as an indicator of side-stream smoke exposure in children has been
studied by Greenberg et al. (1984). The study revealed a high correlation between the
exposure of children at home to side-stream smoke and the levels of cotinine in their urine.
28
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QUESTIONNAIRES
Questionnaires can be useful for the assessment of exposure to some pollutants (e.g.,
ETS). A questionnaire may be used, for example, to determine the physical characteristics of
microenvironments within a home and the activity patterns of those living there. From this
information, individuals may be classified with regard to broad categories of exposure
(National Research Council, 1986). It is not a simple matter, however, to design questions
which will elicit unambiguous replies and permit quantitative estimates of individual
exposures.
EXPOSURE MODELING
Exposure modeling requires knowledge of the concentrations of air contaminants in all
the microenvironments within a residence or work area and the time individuals spend in each
of those microenvironments. Typically, a model must take into account generation rate,
ventilation, infiltration, mixing, removal by adsorption onto surfaces, and volume of space in
which exposure occurs. Models are particularly useful in making exposure estimates in
situations where measured concentrations are not available.
29
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