United States
Environmental Protection
Agency
Office of Exploratory
Research
Washington DC 20460
Research and Development
EPA-600/S6-84-002 Jan. 1984
<&EPA Project Summary
Mini-Assessment: Total
Exposure Assessment and
Exposure-Dose Relationships
William M. Mendez, Jr., Kenneth B. Kolsky, and Michael J. Gibbs
This report briefly examines recent
research in the areas of total exposure
assessment and research concerning
the relationship between patterns of
exposure to environmental pollutants
and dose levels received by exposed
individuals and populations. This assess-
ment is intended to provide policy
makers with a concise discussion of
important trends in recent research; it is
not meant to be a comprehensive litera-
ture review.
This Project Summary was developed
by EPA's Office of Exploratory Re-
search, Washington. DC. to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
This mini-assessment is intended to
provide a brief examination of recent
research in the areas of total exposure
assessment and research concerning the
relationship between patterns of expo-
sure to environmental pollutants and dose
levels received by exposed individuals
and populations. Because the major focus
of the study is on the use of exposure
assessment as a tool in the analysis of
environmental policies, emphasis is
placed on studies directly relevant to the
assessment of such policies, rather than
on more basic research. An annotated
bibliography in the final report will enable
the reader to obtain more in-depth infor-
mation. Much of the research on which
this assessment is based was completed
in August, 1982.
The final report identifies areas where
further research on total exposure assess-
ment and exposure-dose relationships is
needed. This compilation of research
priorities was developed from several
sources, i.e., from the scientific literature
and personnel directly involved in re-
search in exposure and exposure-dose
assessment. When discussing possible
research priorities, the report emphasizes
those areas of research most relevant to
environmental policy assessments.
Discussion
Chapter 1 of the report develops a
framework for evaluating research in
exposure and dose assessment and ex-
plaining howthe assessment of exposure
and exposure-dose relationships influ-
ences the quality of environmental risk
assessment and environmental policy.
Often in the past, the relationship be-
tween exposure and dose has been
neglected. Only in the relatively recent
past have studies been made of total
exposure; e.g., identification of important
sources of pollutant exposure and assess-
ment of the relative importance of differ-
ent routes of exposure for individuals and
populations.
Also briefly reviewed in Chapter 1 are
the important distinctions between popu-
lation and individual exposure. These
distinctions, along with the framework
for the use of exposure and dose assess-
ment in environmental policy analysis,
provide the structure for the remainder of
the report.
Chapter 2 discusses techniques for the
measurement and assessment of individ-
ual exposure to pollutants. Two different
but complementary approaches to meas-
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uring total exposure to air pollutants, i.e.,
personal exposure monitoring and micro-
environmental characteristics, are de-
scribed, as are recent advances in
personal monitoring devices. Also dis-
cussed are the relative strengths and
limitations of devices for measuring
exposures to specific pollutants. Current
knowledge about microenvironmental
characterization of indoor air quality is
presented.
Chapter 3 of the report addresses
methods for assessing and measuring
population exposures to environmental
pollutants, both directly and by general-
izing results from individual monitoring
or microenvironmental characterization.
A survey of exposure estimation tech-
niques based on the use of ambient
monitoring results reveals the need for
better models of human behavior. Recent
efforts to apply studies of population
behavior (commuting or time use pat-
terns, etc.) to the assessment of popula-
tion exposures are discussed.
Chapter 4 deals with the determinants
of relationships between exposure pat-
terns and dose levels in individuals and
populations exposed to pollutants. The
chapter begins with a short review of
recent studies of the properties of individ-
ual pollutants (solubility and particle size
distribution, for exa mple) which affect the
dose absorbed by exposed individuals.
This is followed by a discussion of how
primary demographic variables, socio-
economic factors, and abnormal physio-
logical states can affect exposure-dose
relationships for environmental pollu-
tants. The chapter also discusses mathe-
matical models for absorption and trans-
port of pollutants in the body, and models
for integrating and comparing exposures
by differing routes. Recent studies of
physiologic indicators of pollutant expo-
sure and dose and their potential applica-
tions in characterizing total exposures
conclude this chapter.
At the end of each chapter of the final
report is a brief discussion of recom-
mendations for important research. A
summary of these findings is presented
below.
Recommendations and
Research Needs
Individual Exposure
• Improved personal monitoring devices
for a number of pollutants (NO,, par-
ticulates) are required. Such devices
need to be more sensitive, lighter, and
capable of more or less continuous
recording of pollutant levels if personal
exposures are to be characterized
adequately.
• Characterization of trace organic con-
taminants in food and of metals and
pesticides in individually prepared
foods is needed.
• Characterization of aerosols such as
asbestos and particle-bound polycyclic
hydrocarbons should be improved.
• Studies to further characterize impor-
tant pollutant microenvironments,
when possible, validated by personal
sampling procedures, should continue.
Population Exposure
• EPA should develop a consensus on its
exposure assessment needs and de-
velop procedures to allow the most
efficient use of resources devoted to
exposure assessment.
• Existing data sources on environmen-
tal exposure (emission inventories,
monitoring network results) need to be
improved and updated to facilitate
better characterization of population
exposures.
• Approaches to selection of population
samples should be refined.
• Theoretical criteria for selection of
microenvironments should be devel-
oped.
• Intercity and geographic variations in
activity patterns should be analyzed
and microenvironments defined.
• Pollutant concentrations in microenvi-
ronments and their variability over
time should be characterized.
• Predictive exposure assessment
models should be developed and vali-
dated.
• Alternatives for dealing with subjects
about recording exposure dates, food
intake, and activities during the day
should be analyzed.
Exposure-Dose Relationships
• An understanding of the physiological
variables affecting individual exposure-
dose relationships should be refined in
order to allow more accurate identifica-
tion of high risk groups.
Pharmacokinetic models of pollutant
uptake and metabolism can be applied
to the clarification of exposure-dose
and dose-response relationships. More
emphasis should be placed on assump-
tions regarding pollutant uptake as
inputs to these models.
Efforts must be continued to develop
models which allow the assessment of
contribution to total exposure from
multiple sources and by multiple routes
of exposure.
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William M. Mendez. Kenneth B. Kolsky, and Michael C. Gibbs are with ICF
Incorporated, Washington, DC 20006.
Marvin Rogul was the EPA Project Officer ffor present contact see below).
The complete report, entitled "Mini-Assessment: Total Exposure Assessment and
Exposure-Dose Relationships." (Order No. PB 84-128 032; Cost: $16.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For information contact John W. Reuss at:
Office of Exploratory Research
Office of Research and Development
U.S. Environmental Protection Agency
Washington, DC 20460
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