EPA 560/5-85-001
July 1985
METHODS FOR ASSESSING EXPOSURE
TO CHEMICAL SUBSTANCES
Volume 1
Introduction
by
Michael A. Callahan, G1na L. D1xon, Stephen H. Nacht,
Douglas A. D1xon, John J. Dorla
EPA Contract No. 68-02-3968
Project Officer
Michael A. Callahan
Exposure Evaluation Division
Office of Toxic Substances
Washington, D.C. 20460
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDES AND TOXIC SUBSTANCES
WASHINGTON, D.C. 20460
U.S. Environmental Protection Agsncy
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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DISCLAIMER
This document has been reviewed and approved for publication by the
Office of Toxic Substances, Office of Pesticides and Toxic Substances,
U.S. Environmental Protection Agency. The use of trade names or
commercial products does not constitute Agency endorsement or
recommendation for use.
111
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FOREWORD
This document 1s one of a series of volumes, developed for the U.S.
Environmental Protection Agency (EPA), Office of Toxic Substances (OTS),
that provides methods and Information useful for assessing exposure to
chemical substances. The methods described 1n these volumes have been
Identified by EPA-OTS as having utility 1n exposure assessments on
existing and new chemicals 1n the OTS program. These methods are not
necessarily the only methods used by OTS, because the state-of-the-art 1n
exposure assessment 1s changing rapidly, as 1s the availability of
methods and tools. There 1s no single correct approach to performing an
exposure assessment, and the methods 1n these volumes are accordingly
discussed only as options to be considered, rather than as rigid
procedures.
Perhaps more Important than the optional methods presented 1n these
volumes 1s the general Information catalogued. These documents contain a
great deal of non-chem1cal-spedf1c data which can be used for many types
of exposure assessments. This Information 1s presented along with the
methods 1n Individual volumes and appendices. As a set, these volumes
should be thought of as a catalog of Information useful 1n exposure
assessment, and not as a "how-to" cookbook on the subject.
The definition, background, and discussion of planning exposure
assessments are discussed 1n the Introductory volume of the series
(Volume 1). Each subsequent volume addresses only one general exposure
setting. Consult Volume 1 for guidance on the proper use and
Interrelations of the various volumes and on the planning and Integration
of an entire assessment.
The titles of the nine basic volumes are as follows:
Volume 1 Methods for Assessing Exposure to Chemical Substances
(EPA 560/5-85-001)
Volume 2 Methods for Assessing Exposure to Chemical Substances 1n the
Ambient Environment (EPA 560/5-85-002)
Volume 3 Methods for Assessing Exposure from Disposal of Chemical
Substances (EPA 560/5-85-003)
Volume 4 Methods for Enumerating and Characterizing Populations
Exposed to Chemical Substances (EPA 560/5-85-004)
Volume 5 Methods for Assessing Exposure to Chemical Substances 1n
Drinking Water (EPA 560/5-85-005)
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Volume 6 Methods for Assessing Occupational Exposure to Chemical
Substances (EPA 560/5-85-006)
Volume 7 Methods for Assessing Consumer Exposure to Chemical
Substances (EPA 560/5-85-007)
Volume 8 Methods for Assessing Environmental Pathways of Food
Contamination (EPA 560/5-85-008)
Volume 9 Methods for Assessing Exposure to Chemical Substances
Resulting from Transportation-Related Spills
(EPA 560/5-85-009)
Because exposure assessment 1s a rapidly developing field, Its
methods and analytical tools are quite dynamic. EPA-OTS Intends to Issue
periodic supplements for Volumes 2 through 9 to describe significant
Improvements and updates for the existing Information, as well as adding
short monographs to the series on specific areas of Interest. The first
four of these monographs are as follows:
Volume 10 Methods for Estimating Uncertainties 1n Exposure Assessments
(EPA 560/5-85-014)
Volume 11 Methods for Estimating the Migration of Chemical Substances
from Solid Matrices (EPA 560/5-85-015)
Volume 12 Methods for Estimating the Concentration of Chemical
Substances 1n Indoor A1r (EPA 560/5-85-016)
Volume 13 Methods for Estimating Retention of Liquids on Hands
(EPA 560/5-85-017)
Michael A. Callahan, Chief
Exposure Assessment Branch
Exposure Evaluation Division (TS-798)
Office of Toxic Substances
v1
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ACKNOWLEDGEMENTS
This report was prepared by Versar Inc. of Springfield, Virginia, for
the EPA Office of Toxic Substances, Exposure Evaluation Division,
Exposure Assessment Branch (EAB) under EPA Contract No. 68-01-6271 (Task
42) and Contract No. 68-02-3968 (Task 9). The EPA-EAB Program Manager
was Michael A. Callahan; his support and guidance 1s gratefully
acknowledged.
A number of Versar personnel have contributed to this task over the
three-year period of performance as shown below:
Program Management - Gayaneh Contos
Task Management - G1na D1xon
Technical Support - John Dorla
Douglas D1xon
Editing - Juliet Crumrlne
Secretarial/Clerical - Shirley Harrison
Lucy Gentry
Donna Barnard
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1
1.1 Background 2
1.2 Purpose and Scope 2
2. PLANNING AN EXPOSURE ASSESSMENT 5
2.1 Purpose of Exposure Assessments 6
2.2 Scope 7
2.3 Depth 9
2.4 Approach 11
2.5 Summary 14
3. ORGANIZATION AND CONTENTS OF AN EXPOSURE ASSESSMENT .. 15
3.1 General Information 17
3.2 Sources 17
3.3 Exposure Pathways and Environmental Fate 18
3.4 Monitoring or Estimated Concentrations 19
3.5 Exposed Populations 20
3.6 Integrated Exposure Analysis 20
4. OVERVIEW AND INTEGRATION OF SETTINGS 23
4.1 Exposure to Chemical Substances 1n the
Ambient Env1ronment 23
4.2 Exposure from Disposal of Chemical Substances 27
4.3 Populations Exposed to Chemical Substances 29
4.4 Exposure to Chemical Substances 1n Drinking Water 32
4.5 Occupational Exposure 34
4.6 Consumer Exposure 36
4.7 Environmental Pathways of Food Contamination 38
4.8 Exposure from Transportation-Related Spills 39
5. TYPES OF EXPOSURE ASSESSMENTS 41
5.1 Screening Level Assessments 41
5.2 Intermediate Level Exposure Assessments 43
5.3 Detailed Exposure Assessments 44
5.4 Special Exposure Assessments 45
IX
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TABLE OF CONTENTS (continued)
Page No.
6. GLOSSARY 47
7. ABBREVIATIONS 59
8. REFERENCES 63
APPENDIX 65
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LIST OF TABLES
Page No.
Table 1. Suggested Outline for an Exposure Assessment 16
Table 2. Exposure Assessment Needs for Various
Exposure Settings 24
XI
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1.
INTRODUCTION
This volume 1s the first of a series of 9 volumes addressing methods
for assessing exposures to chemical substances. The reports are being
developed for the U.S. Environmental Protection Agency (EPA), Office of
Toxic Substances (OTS). This volume presents Information on planning and
performing exposure assessments for chemical substances and provides an
overview of the other eight volumes 1n the series. The following
companion volumes provide methods and supporting Information for
assessing exposures 1n each of the following exposure categories or
settings:
• Volume 2 - Methods for Assessing Exposure to Chemical Substances
1n the Ambient Environment
• Volume 3 - Methods for Assessing Exposure From Disposal of
Chemical Substances
• Volume 4 - Methods for the Enumerating and Characterizing
Populations Exposed to Chemical Substances
• Volume 5 - Methods for Assessing Exposure to Chemical Substances
1n Drinking Water
• Volume 6 - Methods for Assessing Occupational Exposure to
Chemical Substances
• Volume 7 - Methods for Assessing Consumer Exposure to Chemical
Substances
• Volume 8 - Methods for Assessing Environmental Pathways of Food
Contamination
• Volume 9 - Methods for Estimating Exposure to Chemical Substances
Resulting from Transportation-Related Spills
The purpose and scope of this volume and the entire methods series
are discussed 1n this section. Section 2 of this volume discusses the
planning of an exposure assessment; Section 3 discusses the components of
an exposure assessment; Section 4 provides an overview of the methods
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for assessing exposure 1n each exposure category; and Section 5 discusses
the different types of exposure assessments that may be performed
(depending on the level of detail required and the Information
available). A glossary of the terms used 1n exposure assessments 1s
presented 1n Section 6. An appendix presents the Table of Contents from
each of the other methods volumes.
1.1 Background
Under the Toxic Substances Control Act (TSCA) of 1976 (P.L. 94-469),
the U.S. Environmental Protection Agency (EPA) must evaluate the risks to
human health and the environment from the manufacture, processing,
distribution 1n commerce, use, and disposal of new and existing chemical
substances. An evaluation of risk Includes, by definition, exposure
assessment; OTS 1s responsible for performing all TSCA exposure
assessments.
1.2 Purpose and Scope
Performing an exposure assessment may be fairly simple, or 1t may be
an extremely complicated task. Exposure assessments can be very
different from one another 1n scope, depth, or approach. This can
complicate any attempt to develop exposure assessment methods or
procedures that apply to all (or at least most) situations. The goal of
this series of reports 1s to attempt to make the job manageable. In
doing so, the task of exposure assessment has been divided Into the seven
exposure settings listed previously (occupational, consumer, and so on).
Methods and procedures were then developed or Identified to aid
assessment for each setting. Some of the methods apply to more than one
setting, and some of the settings are related to one another or may be
considered subcategorles of others.
OTS performs a large number of exposure assessments 1n support of
Sections 4, 5, and 6 of TSCA. This methods series Is a collection of
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Information sources, generic data, and methods that are being used by OTS
to perform exposure assessments efficiently and consistently. Other
methods may be currently used effectively by other organizations; these
OTS methods are not meant to automatically replace all other exposure
assessment methods. Because of the large amount of Information collected
1n these volumes, however, they are being published as a source of
Information for others doing exposure assessments. Other assessors may
find this catalog of methods useful as a model to guard against
significant oversights or omissions when performing their own assessments.
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2. PLANNING AN EXPOSURE ASSESSMENT
Planning should be the first step of any complex task. This 1s
certainly the case with exposure assessment, which can be bewllderlngly
complex unless one has a clear Idea of the purpose, scope, depth, and
approach to be used. This section discusses these four areas of planning
*
an exposure assessment using concepts developed by Callahan (1982) .
Every exposure assessment Is based upon certain explicit or Implicit
assumptions. Limitations Imposed by these assumptions affect the final
form of the assessment and hence the comparability of different
assessments. For example, one assessment may cover routes of exposure,
such as 1ngest1on of food, that another does not; one assessment may be 3
pages long, while another 1s 300 pages 1n length. Some simple arithmetic
concerning the combinations of answers to the questions presented In this
section show that there are easily hundreds of different ways to plan an
exposure assessment, and hence many "different kinds" of assessments.
An exposure assessment cannot easily be regimented Into a set format
or protocol; there are many legitimate reasons for differences 1n
purpose, scope, depth, and approach. Rather than 1n the format or
protocol, the primary point of common understanding 1n exposure
assessment must be 1n the use of a common set of questions to define the
purpose, scope, depth, and approach, I.e., a common set of planning
questions. By addressing these questions explicitly 1n the planning
stage, the assessor will be better able to consolidate his approach and
control the final form of the assessment. This will help save resources
by eliminating unnecessary or unproductive work. It will also help the
reader recognize the boundaries of the assessment and will facilitate
comparison with other assessments.
*Th1s section 1s abstracted from an unpublished presentation "Planning
an Exposure Assessment", by M.A. Callahan, EPA-OTS-EED.
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The planning of an exposure assessment actually comes down to a very
manageable number of questions, which are discussed Individually 1n the
following subsections.
2.1 Purpose of Exposure Assessments
The purpose of an exposure assessment 1s often stated as Its Intended
use, for example, "In support of Section 6 of TSCA." While this may be
accurate, 1t Is not a sufficient guide for planning the form or content
of the assessment. The question of purpose should be: "What will be
done with the assessment after 1t Is finished?"
Most exposure assessments are done as part of a risk assessment. In
risk assessment, the exposure levels found for Individuals or populations
will be combined with effects data (hazard, toxicology) to estimate
risk. If the exposure assessment 1s going to be used 1n a risk
assessment, this usually requires that a quantitative or
semi-quantitative level of exposure be assigned to Individuals or
populations.
Some exposure assessments, especially 1n regulatory agencies, are
also used as a risk reduction evaluation tool. In other words, one
calculates the exposure as 1t exists today, and then Imposes certain
proposed or hypothetical "controls" or "actions" and uses the assessment
to evaluate the effects of those actions on exposure levels (and,
subsequently, risk levels). Exposure assessments can thereby become
powerful tools for predicting consequences of a variety of optional
actions.
The latter type of exposure assessment requires a very different
approach than the former. In the former case, monitoring data alone (1f
they exist) may provide much of the needed Information. In the latter
case, an effort must be made to understand the causes of exposure In
addition to collecting data. These considerations will arise In
questions under "Approach," below.
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A third purpose of an exposure assessment would be to answer the
question of whether there 1s significant exposure, Independent of a risk
assessment. In this case, the exposure assessment 1s an end In Itself.
This purpose arises Infrequently compared to the first two purposes. An
example of such an exposure assessment would be that required by
section 4(a)(l)(B) of TSCA, where the Agency 1s directed to require
testing of a chemical based on substantial exposure.
In summary, 1t Is Important that the assessor clearly define the
purpose of the assessment 1n the sense of "what will be done with the
assessment when 1t 1s finished?" The answer(s) to this question will
have a significant Impact on the scope, depth, and approach, where the
questions about "what 1s needed to accomplish the end purpose" and "how
to get there" are addressed.
2.2 Scope
Scoping questions limit the broadness of the assessment. These
questions, more than any other, determine the general outline of the
exposure assessment. They also play a critical part 1n potential
resource expenditure, since unclear answers to these questions may result
1n much unnecessary effort. Scoping questions are of the nature of,
"What should be Included or excluded from the assessment?" They need to
be addressed as a group, rather than sequentially, since they are
Interrelated. Note that they do not address the detail 1n which the
topics are covered, but merely whether they are to be covered at all.
The question listed below also need to be thought of 1n the context of
the hazard of concern, 1f 1t 1s known, which can serve to focus the
assessment somewhat.
Humans vs. Non-humans
Should the assessment Include exposures to humans only, non-humans
only, or a combination of the two?
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Individuals vs. Subpopulatlons vs. Populations
Should the assessment Include all humans (1f appropriate) 1n a
defined area, or just some of them? For example, an assessment may cover
everyone 1n the U.S. (population), only pipefitters (subpopulatlon), or
only the pipefitters 1n a particular plant (several Individuals). If
non-humans are to be assessed, which species (populations) or other
divisions (subpopulatlons) are to be considered?
Geographic Boundaries
Will this assessment cover people exposed to a certain plant or
dump site (site-specific), a city or town (local), a state or similar
area (regional), the entire country (national), or the world (global)?
Although the same things must be addressed in each case, the approach to
these assessments may need to differ widely from one another. One may
also define the geographic boundaries as a series of sites, regions,
etc., as when assessing "all the plants that make chemical Z," which may
fall Into three specific regions.
Route of Exposure
The route of exposure Is the means by which the chemical or agent
enters an organism. For humans, the normal routes are 1ngest1on (e.g.,
food, drinking water), Inhalation, and dermal absorption, although other
routes are possible (direct contact with blood through an Injury, medical
treatment, etc.).An assessment may be limited to one or more of these
routes.
Media
The exposure media are the vehicles that transport the chemical or
agent to contact the receptor. These could Include air, surface water,
drinking water, food, or others. The assessment may be limited to the
exposures occurring through certain media. This has often been the case
with exposure assessments done 1n the past by regulatory groups with
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authority over only one medium. More recently there has been a tendency
to do more detailed assessments 1n a single medium, but also to do
rudimentary assessments 1n other media In order to maintain perspective.
(Remember, the scoping question asks only 1f the media are to be
addressed, not 1n what depth). An assessment 1n a single medium may also
want to consider sources In a different medium. For example, 1f one were
hypothetlcally assessing air exposure to chemical A, one could also be
Interested 1n water discharges which result 1n air pollution (but not
necessarily all water discharges) 1f one were planning to evaluate
control strategies.
Exposure Settings
One of the common ways of limiting an exposure assessment 1s by
limiting exposure settings. One can break out the total exposure to a
chemical agent Into several general categories for convenience. In the
case of the seven settings that are the subjects of these methods
reports, one can define boundaries around each setting and use these
boundaries to limit the assessment. Although the seven settings are
somewhat arbitrary, they do tend to allow exposures within each setting
to be addressed Independently from the others. Once the boundaries are
established, subdividing exposure assessment Into categories or settings
provides both a structure for organizing the assessment and a framework
for data collection.
One of the most common differences, 1f not the most common
difference, among exposure assessments today Is a difference 1n the
exposure settings covered by the assessment. OSHA/NIOSH tend to be
Interested 1n the occupational setting only; CPSC concentrates on
consumer use, FDA on food, and so on.
2.3 Depth
Another critical area 1n planning an exposure assessment 1s the depth
of detail. This 1s another reason for diversity In exposure assessments
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and why one assessment can be three pages long while another 1s 300 pages
long.
Exposure assessments are usually used as support for decision
making. How much effort 1s expended 1n refining the accuracy and detail
of an assessment needs to be commensurate with the Importance of the
decision being made.
The overall question guiding the planning for how detailed the
exposure assessment must be, after considering the Importance of the
decision to be made, 1s, "What degree of accuracy and precision 1s needed
to make the decision?" The answer, "the most accurate degree possible"
1s usually not a good answer for at least two reasons. First, 1f the
exposures are to be used 1n a risk assessment (and most are), the risk
assessment will be no more accurate than the least accurate of the two
components, hazard and exposure. It may be wasteful of resources to plan
an exposure assessment which 1s orders-of-magn1tude more accurate than
the toxlcologlcal Information with which 1t will be combined. On the
other hand, one may want to be more detailed on the exposure side because
the assessment will be used to evaluate control options. In any case,
the matching of accuracy of the hazard and exposure data must be
carefully considered.
Second, "the most accurate answer possible" 1s rarely the most
accurate answer feasible. Once one reaches a given level of accuracy
(I.e., plus or minus an order of magnitude; plus or minus a factor of
two; etc.), additional Improvements become far more resource-Intensive.
Although 1t 1s possible 1n many cases to Improve the accuracy and
precision of the assessment, one may run out of resources long before
reaching the "most accurate assessment possible," with marginal
additional benefits 1n the quality of decisions derived from the
assessment.
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Another consideration 1n planning for depth of detail Is that the
assessment need not have the same level of detail 1n all areas. For
example, an assessor 1n EPA's Office of Water may want a detailed
assessment of exposure through surface water. In addition, the assessor
may want to put this waterborne exposure Into perspective by comparing
Its magnitude with exposures through air, food, etc. The result would be
a detailed assessment on water and a much less detailed estimate 1n the
other exposure settings. This "mixed" level of detail Is becoming
Increasingly common with the push toward multimedia exposure assessments.
Exposure assessments usually have five components: sources, fate,
monitoring, populations, and Integration (see Section 3). In planning
the depth of detail, simplifying assumptions are often made 1n these
components. For example. In doing an assessment on pollutants from
vehicular exhaust, one can assume a number of vehicles, each with an
average emission rate. One may then look 1n much more detail at the fate
of the pollutant, or examine extensive monitoring data. On the other
hand, one might do an extensive materials balance on the sources of a
chemical 1n widespread use, and make certain simplifying assumptions
about the populations exposed (e.g., all U.S. population exposed to some
average level). Often the depth of detail In the five exposure
components are dictated by resource limitations and lack of data. (The
components themselves will be discussed 1n more detail 1n Section 3.)
2.4 Approach
The answers to the scope and depth questions above have a large
Influence on the approach taken. The exposure assessment field has many
useful tools, and In planning an approach, one 1s deciding which tools to
use. The following questions are useful 1n directing the assessor to the
proper tools.
• Will this assessment be qualitative ("1s there exposure or not?"),
semi-quantitative ("are exposure levels high or low?"), or quantitative
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("what 1s the exposure level?")? The answer will be especially
Influenced by how purpose and depth are defined.
• What mix of measurement techniques vs. predictive/theoretical
techniques 1s desired? A purely measurement-oriented assessment would
Involve measuring the exposures to each of the members of a population
(or some statistically representative subset) over a period of time.
While this practice may sometimes be feasible, 1t 1s usually expensive
due to sampling and analysis costs. A purely measurement-oriented
assessment also may not allow geographic Interpolation between data
points, which can be a drawback 1n complicated exposure distributions.
A purely predictive/theoretical assessment, on the other hand,
Involves modeling and predicting of exposures on a theoretical or
empirical basis. This type of exposure assessment may be much less
expensive than one using monitoring, but may yield results that are
widely at variance with actual exposures. However, this approach does
provide a basis for understanding how a chemical behaves and how the
exposure 1s taking place.
Neither pure technique Is used very often; rather, a mix of
monitoring data and predictive tools are usually used. In planning the
assessment, the considerations here are resources available (lower
resources drive the assessment toward predictive techniques or more
narrow scope), and accuracy of exposure required (more accurate
assessments require a greater mix of monitoring as a verification of the
predictive tools).
• What period of exposure 1s to be covered? An assessment of
carcinogenic risk often considers exposure over 70-year lifetimes, but
the toxlcologlcal Information may dictate the need for yearly exposures,
dally exposures, hourly exposures, or even continuous exposures. The
answer to this question should reflect a match between the exposure and
hazard Information.
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• How should exposure be defined for the purposes of this
assessment? Generally, "exposure" has been viewed at least three
different ways 1n past assessments. First, some assessments look only at
concentrations of a chemical or agent 1n the media of concern. This
approach requires a set of assumptions (e.g., breathing rates, or food
Intake rates) 1f an actual exposure assessment 1s to be made, since
without considering populations, no exposure can be evaluated. Second,
many assessments look at the contact between the chemical and the
Individual with such concerns as how It 1s Ingested, applied to skin, or
Inhaled. This 1s a very common treatment of exposure, and matches much
of the animal toxicology studies where a dose-response curve 1s set up In
terms of Inhaled amount vs. effect or Ingested amount vs. effect or
amount rubbed on skin vs. effect. A third way of treating exposure 1s to
look at absorbed dose, such as amount absorbed through dermal contact,
1ngest1on, or Inhalation. More recently the "absorbed dose" treatment of
exposure has been gaining popularity, mainly due to additional
Information and understanding which can be added to the assessment.
• What types of scenarios will be set up? Scenarios are tools to
estimate exposure levels when conditions are those listed 1n the
scenario's assumptions. Conditions, however, may change significantly so
that In the actual situation, a given scenario only applies for a part of
the time. Is this assessment looking at "worst-case" scenarios? These
are good for determining when exposure (risk) 1s not a problem, but not
for determining the extent of a problem 1f one does exist. "Reasonable
worst case" scenarios look at the worst case that Is likely to occur with
a frequency that would cause concern. "Typical" case scenarios depict
average or widespread conditions. One may also want to view the likely
range of exposures, or even the distribution of exposures over a
population (the latter 1s particularly resource-Intensive). The
scenarios one chooses are dependent on the purpose, scope, and depth
questions.
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• Is the assessment concerned with a single chemical, a number of
chemicals, or a mixture or other substance? The tools one chooses to
perform the risk assessment will vary, sometimes widely, according to the
answer to this question.
2.5 Summary
Planning 1s a critical step 1n preparation of an exposure
assessment. Planning Involves answering a relatively small number of
specific questions on purpose, scope, depth, and approach. Once the
purpose, scope, depth, and approach are defined, the assessor will have a
much better Idea of the tools needed to do the work. If the planning
assumptions, decisions, and definitions are clearly stated 1n the
exposure assessment, the reader will be able to quickly determine what
type of assessment 1t 1s, what 1s Included, and whether 1t 1s likely to
meet his or her needs.
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3. ORGANIZATION AND CONTENTS OF AN EXPOSURE ASSESSMENT
A suggested outline for an exposure assessment document 1s given In
Table 1. The actual order 1n which topics appear 1s somewhat arbitrary.
However, the document most often Includes some discussion of all five
major topics listed below and proceeds In a logical order from sources to
exposure estimates.
The major topics that are usually addressed are: sources, fate and
pathways, exposed populations, monitoring (or estimated concentrations),
and Integrated exposure analysis. Examples of subheadings within each of
these topics are presented 1n Table 1. The extent to which any
assessment discusses these subtopics depends on the purpose, scope, and
depth of the assessment as well as on the quantity and quality of
available Information. A given topic may be covered by a single
statement proposing a broad assumption, or by a detailed analysis of each
piece of Information. The outline 1s simply a guide for organizing
whatever data are developed for each assessment. In Its general
structure, this outline 1s appropriate for assessments of any scope
(Including site-specific assessments) or depth (Including screening level
assessments), and for both new and existing chemicals.
The sections from "Sources" through "Monitoring" may each have
several subsections for each setting or for each chemical of a
multi-chemical (e.g., Industry-wide or site-specific) assessment. The
different settings are combined 1n the "Integrated Exposure Analysis"
section.
The components of an exposure assessment report will be described
below, based on recommendations In EPA's Interim Guidance for Exposure
*
Assessment (USEPA 1984) ; consult this guidance, published 1n the
Federal Register (November 23, 1984), for more detailed Information.
*Th1s section 1s abstracted and adapted from the EPA's proposed
guidelines (49FR227:46304).
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Table 1
SUGGESTED OUTLINE FOR AN EXPOSURE ASSESSMENT
1. EXECUTIVE SUMMARY
2. INTRODUCTION
2.1 Background
2.2 Purpose and Scope
3. GENERAL INFORMATION
3.1 Identity
Molecular formula and structure, CAS number, TSL number
Description of technical grades, contaminants, additives
Other identifying characteristics
3.2 Chemical and Physical Properties
4. SOURCES
4.1 Production and Distribution
Production quantities and process
Distribution in commerce
4.2 Uses
4.3 Disposal
4.4 Summary of Environmental Releases
5. EXPOSURE PATHWAYS AND ENVIRONMENTAL FATE
5.1 Transport and Transformation
5.2 Identification of Principal Pathways of Exposure
6. MONITORING OR ESTIMATED CONCENTRATIONS
6.1 Summary of Monitoring Data
6.2 Estimation of Environmental Concentrations
7. EXPOSED POPULATIONS
7.1 Human Populations (Size, Location, and Habits)
Population size and characteristics
Population location
Population habits
(often arranged by the seven exposure categories in Table 2)
7.2 Non-human Populations (where appropriate)
Population size and characteristics
Population location
Population habits
8. INTEGRATED EXPOSURE ANALYSIS
8.1 Development of Exposure Profiles
Identification and characterization of the exposed
populations and critical elements of the ecosystem
Pathways of exposure
8.2 Human Dosimetry and Monitoring
8.3 Calculation of Exposures
8.4 Evaluation of Uncertainty
Source: Adapted from USEPA (1984)
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3.1 General Information
This section should contain background Information on the
chemlcal(s). Each chemical should be Identified by at least the
following characteristics (where appropriate): molecular formula and
structure; synonyms; Chemical Abstracts Service (CAS) number; description
of technical grade, contaminants, and additives; and radioactive halfUfe
(1f applicable). Chemical and physical properties should be summarized,
emphasizing those features that affect the chemical's behavior 1n the
environment. These properties may Include molecular weight, density,
boiling point, melting point, vapor pressure, water solubility, vapor
density, partition coefficients, and chemical halfUfe, among others.
Data may be obtained by following the procedures described 1n
Volume 2. Therefore, an assessor may wish to consult Volume 2 even when
preparing an assessment that excludes the ambient scenario.
3.2 Sources
Any points at which the chemical may enter the environment should be
Identified 1n this section, together with any known or estimated rates of
entry. A detailed exposure assessment will Include or be based on a
previous "materials balance". A materials balance 1s a study of sources,
production, uses, destruction/disposal, and environmental release of a
substance which quantifies the mass made, Incorporated Into products, and
lost to the environment.
The source chapter as a whole will consist of Information derived
from Volumes 2, 3, 6, 7, and 9 of this series. In the sources section,
the quantities of the chemical released to each environmental medium
should be estimated as best as possible. An extremely detailed
assessment may attempt to specify the following for each significant
source: location, quantity of the chemical released to each medium as a
function of time, physical characteristics of the source, and the
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physical and chemical form of the substance being released. The assessor
should evaluate the level of uncertainty associated with the estimates
and remain aware of uncertainties through the rest of the exposure
assessment.
3.3 Exposure Pathways and Environmental Fate
This section should describe how the chemical gets from the source to
the receptor population. Broad generalizations on environmental fate may
suffice for less detailed assessments. In the absence of data, as for
new (PMN) substances, fate may be predicted by reference to data on
analogous substances. Fate may also be predicted using models or
experimental data. At any level of detail, a given pathway may be judged
Insignificant and excluded from further consideration. Pathways, sites,
and media may also be limited by Initial scoping decisions.
For more detailed assessments Involving environmental fate, the
source analysis described above should provide not only the rate of
emissions but the location of emission sources. Fate analysis tracks the
substance from Its Initial point of release through the environment to
Its ultimate fate. It may provide an estimate of Its geographic
concentration distribution and changes 1n levels with time within the
media of concern.
Guidance 1n performing the fate analysis may be found 1n Volume 2.
Volume 6 and Volume 5 discuss models of particular relevance to
assessments of occupational and drinking water exposure respectively;
both, however, refer back to Volume 2 for necessary background
Information.
The fate chapter Includes discussions of the following:
• Transport and transformation. It 1s essential to evaluate the
environmental behavior of a substance, since chemical and physical
processes may yield an ultimate environmental distribution quite
different from the Initial distribution at the point of release.
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-- Transport Includes hydrologlcal, atmospheric, or other physical
processes that convey the mass of a pollutant through and
across media from source to receptor. They may also serve to
concentrate or dilute the pollutant.
-- Transformation 1s the chemical alteration on a compound by
processes such as blodegradatlon, hydrolysis, photodegradatlon,
reaction with other compounds, etc.
Environmental partitioning. Models may be used to estimate
relative concentrations of a substance 1n difference environmental
media.
Identification of principal pathways of exposure. Once the
environmental media containing the chemical are Identified,
potential pathways of exposure can be listed. Significant
pathways are often defined by the chemical's load Into a medium
and Its physical and chemical properties.
3.4 Monitoring or Estimated Concentrations
Monitoring data are used throughout the exposure assessment to
estimate releases and environmental concentrations. These data should be
evaluated for accuracy, precision, and representativeness. Evaluating,
selecting, and Interpreting monitoring data for each scenario are
discussed In the corresponding methods volume. Unless environmental
monitoring data are known to be complete and accurate, concentrations are
often estimated as well, either by models or by analogy with better-known
chemicals.
Concentration estimates should be compared (when possible) with
monitoring data. However, one must keep 1n mind that monitoring data are
often not comparable to modeling results. For example, measured
atmospheric concentrations usually represent Instantaneous or short-term
average levels (e.g., over several days or weeks), whereas models may
predict annual averages at different locations. Therefore, great care
must be exercised when comparing estimates with monitoring data.
Monitoring data should not be considered a de facto substitute for
environmental pathways and fate analysis, at least 1n the following
situations:
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• when monitoring data are limited 1n scope;
• when analysis of monitoring data alone sheds little light on the
relationships between materials balance data and ultimate
environmental concentration distributions; or
• when fate analysis 1s required to trace measured concentrations
back to Individual sources that can be regulated.
Environmental concentration estimates should be presented 1n a format
consistent with the purpose and depth of the assessment. An estimate of
annual average concentration may be sufficient for a general assessment.
More detailed assessments may require an estimate of the temporal and
geographic concentration distribution. It may also be useful, If
regulatory options are being analyzed, to project future environmental
concentrations resulting from controlled releases.
3.5 Exposed Populations
Populations to be studied may be defined at the outset of the
assessment, or else selected later on the basis of sources and fate
studies. Subpopulatlons of high sensitivity may be studied separately.
Subpopulatlons may be defined on the basis of geographical area, age,
sex, etc. For example, one may wish to enumerate women of child-bearing
age If the chemical 1s a known or suspected teratogen.
Guidance 1n Identifying exposed populations within each exposure
setting may be found 1n the "Exposed Populations" section of the
appropriate methods volume. Enumeration and characterization of all
populations 1s discussed 1n Volume 4.
3.6 Integrated Exposure Analysis
In this section, estimates of environmental concentrations are
combined with data on exposed populations to yield exposure profiles and
pathway analyses. This entails Integrating the settings for a total
exposure picture (assuming the scope of the assessment Includes more than
one scenario).
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A population may be exposed to a chemical from several different
sources and through several exposure routes. Ideally, total exposure for
a population Is determined by summing exposures from all sources within
an exposure route. In reality, exposures are usually not summed because
(1) 1t Is not known, for example, whether the people exposed
occupatlonally are the same as those who are exposed via drinking water,
and (2) EPA's regulatory purposes require separate estimates. Exposures
through different routes are usually kept separate for at least the
following reasons:
• Different exposure routes are often associated with different
rates of absorption and different types of toxldty;
• Target organs may differ;
• Keeping routes separate will facilitate formulation and evaluation
of control options.
Exposure estimates may be compared with results of any available human
doslmetry, personal monitoring, or body burden analyses.
Exposure calculations and results should be presented 1n a format
consistent with available dose-response data 1n order to facilitate
ultimate risk assessment. For example, results can be expressed as
annual average exposures, peak exposures, exposures 1n excess of a given
threshold value, etc.
An Integrated analysis should Include the size of the exposed
population; duration, frequency, and Intensity of exposure; and route of
exposure. Exposures should be related to source, since 1t 1s ultimately
sources that are regulated. The assessor should also evaluate the
associated level of uncertainty by analyzing the uncertainties In each
step of the assessment.
More detailed assessments may consider such factors as the geographic
distribution of receptor populations, or their relevant behavioral and
biological characteristics. Scenarios may be constructed to Illustrate
exposure via multiple settings; for example, a worker who lives near a
21
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plant and 1s exposed occupatlonally, by breathing ambient air, and by
drinking contaminated water. Subpopulatlons exposed to different
concentration ranges may be enumerated separately. Results may be
presented 1n tabular or graphic form.
It can be seen that the form and contents of the "Integrated Exposure
Analysis" section depend on the purpose of the assessment and on other
considerations discussed 1n Section 2 of this volume. The Individual
methods volumes do not provide specific guidance on this subject.
Section 5 of this volume does provide examples of assessments with
various levels of detail. However, two different assessments of the same
general type may still require slightly different treatment. Each
assessment will have a unique set of problems which must be solved on a
case-by-case basis, and It 1s not possible to provide detailed rules for
dealing with every conceivable alternative.
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4. OVERVIEW AND INTEGRATION OF SETTINGS
Each of the seven settings 1n which exposure may occur 1s the subject
of an Individual volume 1n this methods series. An additional volume
discusses the populations exposed 1n each setting. Recall that the
division between settings, as defined below, 1s largely for the sake of
convenience:
ambient exposure
exposure resulting from disposal
occupational exposure
exposure resulting from transportation spills
exposure from 1ngest1on of drinking water
consumer exposure
exposure from 1ngest1on of food
This section summarizes the contents of each volume. The subject matter
In the methods series may be seen 1n Table 2, which lists the major data
needs 1n each exposure setting. To avoid redundancy, some data needs
common to all settings (such as chemical properties) 1s addressed only In
one volume, and the reader 1s referred between reports as necessary.
4.1 Exposure to Chemical Substances In the Ambient Environment
Volume 2 of this series describes methods for assessing exposure of
humans (and, to a lesser extent, non-humans) to chemicals 1n the ambient
environment. In this case, the ambient environment refers primarily to
outside air and surface waters. Ambient exposure 1s unique 1n that
Individuals are exposed to chemicals simply 1n the normal course of their
dally routine, rather than as a direct consequence of their activities
(occupation, use of a product, etc.). In other words, the exposed
populations have little or no choice or control over their exposure. The
chemicals are 1n the ambient environment as a result of someone else's
activities. Estimating exposure 1n this environment can be difficult
because the presence of a chemical may be a result of a large number of
activities (I.e., production, various uses, etc.). This Is further
complicated by the
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transport and transformation processes that occur 1n the environment
following a chemical's release.
As discussed 1n Section 2, exposure assessments can be performed for
several purposes. Among the most common are to determine the risk posed
by the chemical and to Identify possible methods to reduce the risks.
There are many tools, techniques, and Information sources available to
help an assessor accomplish either or both of these purposes. Some of
the most useful of these are described 1n Volume 2 of this series.
The tools and techniques described In Volume 2 Include estimation
techniques, mathematical models, and monitoring data. Each has strengths
and weaknesses. Volume 2 describes the specific limitations and provides
guidance on the appropriate use of each tool. The tools used together
(when appropriate) may help present a more complete picture of exposure.
The most significant routes of exposure described 1n Volume 2 are
Inhalation of ambient air and dermal contact via swimming 1n contaminated
surface waters. Calculation of Inhalation exposure Involves combining
the air concentration, breathing rates, frequency, and duration of
exposure. This results In an estimate of the quantity of chemical taken
Into the lungs. If Information 1s available on the rate at which the
chemical 1s absorbed through the lung tissue, this can be used to
calculate the dose, or the quantity taken Into the body. However, this
type of Information 1s usually not available. Therefore, 1t 1s Important
that the assessor be aware of this and understand that neglecting the
absorption rate may cause calculated exposures to be somewhat higher than
the amount actually taken Into the body. Tox1colog1cal data often take
absorption Into account; 1f that 1s the case for the chemical substance
being assessed, and the exposure assessment 1s 1n support of a risk
assessment, no attempt to quanltlfy absorption need be made.
Dermal exposure 1n the ambient environment can be somewhat more
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difficult to quantify. For Inhalation, a known volume of material 1s
taken Into the lungs. This volume 1s used to determine the exposure
levels. However, when all or part of the body 1s Immersed 1n
contaminated water (as may be the case while swimming), 1t 1s very
difficult to determine the quantity of material which a person contacts.
Under these circumstances, the following factors determine exposure:
• ambient concentration
• area of skin exposed
• frequency and duration of exposure
• diffusion rate of chemical through the skin
Calculation of aquatic concentrations 1s relatively straightforward, and
can be used to assess ecosystem exposure as well as human exposure.
Unfortunately, Information on diffusion rates of most chemicals through
skin are not available. However, methods have been developed that allow
this to be estimated for many substances. Although a detailed
description of these methods 1s beyond the scope of this report, Volume 2
shows where this Information may be found.
As an alternative, assumptions may be made regarding the quantity of
chemical In contact with the skin. These assumptions Involve estimating
the thickness of the layer of material on the skin and the surface area
of skin exposed. This Information can be used to determine the volume of
material on the skin. Multiplying this by the density of the material
yields a quantity of material on the skin. More guidance on doing this
1s provided 1n Volume 2.
Much of Volume 2 Involves discussion of methods to calculate the
concentration of chemicals 1n the air and water. The use of models such
as UNAMAP and ATM for estimating ambient air concentrations and EXAMS for
water concentrations Is described. The report goes on to describe how
these model outputs are used 1n the exposure assessment process.
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The use of monitoring data 1s also described 1n the report. These
data represent measured concentrations of a chemical at a specific
location at a particular time. They must be used with caution, as
described 1n the report. Sources of this Information Include a number of
computerized data bases maintained by several agencies of the U.S.
Government. Some of the data bases described Include AEROS and SAROAD
for air data and STORET for water, sediment, and blotlc data.
The report also Includes Information for determining activity
patterns of exposure populations. This Information Is used to define the
frequency and duration of exposure. The activity patterns show how often
an Individual 1s located 1n a contaminated environment and for how long.
Volume 2 also provides some guidance on estimating the size of the
exposed population. A more complete discussion of this can be found 1n
Volume 4.
Estimating ecosystem exposure (I.e., exposure of non-human
populations) 1s very similar to the process described above, as far as
estimating environmental concentrations. Population characteristics such
as size, frequency and duration at the exposure site, and Inhalation
rates are usually unavailable (or often Irrelevant). However, Volume 4
of this series describes some of the sources of this type of Information.
4.2 Exposure from Disposal of Chemical Substances
Volume 3 of the exposure assessment methods series presents methods
for assessing exposures resulting from disposal of chemicals. These
exposures result from releases of the chemical Into the ambient
environment; this report guides the user 1n estimating the magnitude and
frequency of these releases. The user 1s then referred to the ambient
exposure methods volume to estimate the resultant concentration 1n the
environment and subsequent exposure, or to the drinking water methods
report 1f releases to water are expected as a result of the disposal
methods.
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This report on assessing exposures relating to disposal Is
essentially a mass-balance technique. The six most common disposal
methods are addressed: landfllUng, land treatment, surface Impoundment,
Incineration, sewage treatment, and Injection Into deep wells. A series
of decision trees guides the user through the steps of the technique, and
at each step where data are required, the potential sources of the data
are listed. A great deal of data that apply to a disposal method or
pattern, regardless of the chemical substance being disposed of, are also
presented.
This methods report 1s arranged 1n a fashion unlike the others; the
framework Is a series of stages. There are five stages, as described
below:
• Stage 1 takes a basic materials balance and determines the total
amount of waste to be disposed of from each manufacturing process
or end use.
• Stage 2 lists the Individual wastestreams for which data have been
compiled.
• Stage 3 allocates the wastestreams to the most likely disposal
method of the six listed above.
• Stage 4 allows one to determine the geographic distribution of
treatment sites.
• Stage 5 estimates emissions from disposal; when disposal results
1n additional waste (like Incinerator ash), the method allows for
that waste to be dealt with In Stage 3 and subsequently.
Accurately assessing exposures resulting from disposal practices
requires Information on the location of waste production and the location
of waste disposal. This report leads the user to sources of such data on
the state, local, regional, and national level. Often, however, these
data will not be adequate; this subject 1s one for which generic national
data have been developed.
This methods report 1s geared to a very detailed assessment of
disposal related exposures. In many cases, the procedure requires that
28
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loops through the framework be repeated a number of times. Such 1s the
case 1f a chemical may be disposed by more than one of the six methods (a
common occurrence), or 1f a treatment scheme generates a new waste to be
disposed of. The report does, however, present guidance 1n simplifying
the assessment. Methods for determining which treatment modes may be
relatively Insignificant (and thus disregarded) and a number of other
simplifying procedures are discussed. The circumstances under which an
assessment 1s best made qualitative or semi-qualitative are briefly
addressed.
4.3 Populations Exposed to Chemical Substances
The fourth volume 1n this series 1s the report on enumerating and
characterizing the populations exposed to chemical substances In each of
the seven exposure settings. As 1n the other reports, a great many
methods are presented that may depend either on generic data Included 1n
the report or on sources of specific data that the reader can be directed
to. Unlike the other methods volumes, however, the methods are presented
as a series of steps to be performed; more guidance 1s provided In choice
of methods as well.
The first chapter 1n this report 1s an extensive discussion on
quantifying and characterizing populations exposed to chemical substances
1n the ambient environment. Most of the methods rely on data collected
by the Bureau of the Census, regardless of the source of the chemical 1n
the environment. Recall that the distinction between the sources
discussed 1n the ambient, transportation spills, and disposal exposure
reports Is a somewhat arbitrary one used largely for organizational
purposes 1n these reports. This chapter, though titled Populations
Exposed 1n the Ambient Environment, deals with all three types of sources,
Choosing the best method for enumerating a population exposed 1n the
ambient environment depends not only on the route of exposure but also on
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the characteristics of the chemical source. Different methods apply to
point sources, area sources, and line sources and the methods may differ
according to the number of similar sources to be dealt with. A point
source release 1s easily defined, and Us position can be accurately
determined; the population consequently exposed 1s described 1n terms of
distance from the source. The report discusses the use of a program
called SECPOP, part of EPA-OTS1 computerized GEMS system. SECPOP uses
data from the Census Bureau to accurately perform population enumeration,
along with an atmospheric dispersion/exposure model (ATM) 1f desired.
Generic data are provided for use In exposure assessments that cannot,
for any reason, deal with Individually-defined point sources.
Area sources are usually much more numerous within any
geographically-defined area and are therefore dealt with on a non-source
specific basis. This report guides the user to the appropriate Census
Information methods that rely on population densities along with source
densities to estimate exposed populations.
Line sources are often associated with transportation emissions,
either from spills or releases of exhaust. The exposed population may
therefore live along a corridor: a road or rail line. Populations may
also be exposed at corridors along a river from which a chemical 1s
volatilizing. Both site-specific methods that use actual Census data for
a locale and methods based on generic population densities are presented.
The methods discussed above are for Inhalation exposures, the primary
topic of Interest 1n ambient exposure assessments. Other types of
exposures that can be Important are dermal contact with waterborne
pollutants during recreation and more Incidental exposures like pica, the
child's habit of eating dirt. These potentially exposed populations
receive less attention 1n this report.
Some exposure assessments require that the exposed populations be
exceptionally well-defined. The methods report on populations presents
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age and sex distributions for the U.S. as a whole and lists Census
publications that go to various levels of geographic resolution with such
data.
The second chapter of the populations report presents methods to deal
with occupatlonally-exposed populations. The preferred methods use data
from the Bureau of Labor Statistics (part of the Department of Labor) and
the Commerce Department's series of census reports - the Census of
Manufactures, Censuses of Retail and Wholesale Trade, etc. The methods
are presented step by step, with guidance 1n choosing the most
appropriate method 1n each case. A small section 1s devoted to finding
site-specific data when a limited number of manufacturing facilities are
of Interest. The final portion of the report guides the user 1n
determining the age and sex distribution of an occupational group.
Populations exposed via food 1ngest1on are the subject of the next
chapter. The methods are keyed to the source of contaminant:
agricultural practices, processing or packaging, other sources, and
unknown sources (when contamination 1s demonstrated by monitoring data).
Data from national surveys of food consumption, such as those performed
by the USDA, are referred to throughout and are the basis of the methods
to characterize the exposed populations.
Persons using consumer products containing chemicals for which
exposure assessments may be required can be enumerated and characterized
by the methods 1n the next chapter of this volume. The primary source of
data Is market research reports, such as the Simmons Market Research
Bureau studies. They present data not only on the number of users of
numerous types of consumer products but also on frequency of use and
demographic characteristics of users. Though use of marketing data
probably serve the majority of exposed assessment needs 1n this setting,
supplemental methods are presented for predicting exposed populations
from production data, use data, and from data on common hobby activities.
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The final major section deals with populations exposed via the
consumption of drinking water. Data maintained by EPA are the basis for
most of the methods. One method relies on EPA files like the HLDF and
the WSDB; user access to those files 1s explained and contact persons
within EPA are listed. Also discussed are data needed to enumerate
persons exposed to chemicals that may be Introduced by a treatment
practice or 1n the distribution system. It may be necessary to
extrapolate results of monitoring that do not specify a contamination
source to estimate populations exposed nationally, so an estimation
procedure 1s provided to fulfill that need.
The final part of Volume 4 Is an appendix Illustrating the
application of each method presented.
4.4 Exposure to Chemical Substances 1n Drinking Water
Methods for assessing exposure to chemical substances 1n drinking
water are discussed 1n Volume 5 of this series. Only exposure derived
from Ingestlon of the water 1s addressed In detail; exposure that may
occur as a result of bathing or other dermal contact, or Inhalation of
chemicals that volatilize from drinking water, are only briefly discussed,
This methods report 1s linked by logic to the methods volumes that
deal with quantifying chemical concentrations 1n surface and
groundwater: the ambient, disposal, and transportation spills methods
reports. This volume assumes that the exposure assessor has one of the
following components with which to begin:
• The site of release of the chemical to the environment and
sufficient Information to predict the concentration.
• One or more measurements of the concentration 1n the drinking
water (either before or after treatment).
The assessment proceeds upon paths defined by the type of data available-
suggestive evidence resulting from the presence of nearby sources, or
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positive evidence of contamination as shown by monitoring, whether or not
the source 1s readily determined.
Exposure to chemicals via drinking water Involves the major exposure
route not yet discussed 1n this section of this report: 1ngest1on. The
framework for that exposure calculation 1s very straightforward.
Exposure 1s a function of the concentration of chemical 1n water and the
1ngest1on rate. The methods report discusses how to best assign values
to each of these parameters.
The report begins with an overview of drinking water systems,
Including the characteristics basic to all as well as some specific
differences between treatment plants that produce water from groundwater
versus surface water sources. The sections that follow that overview are
keyed to taking a release and turning 1t Into a concentration at a raw
water Intake. Numerous models are discussed; the application of the most
commonly-used models (like SESOIL and EXAMS) 1s emphasized. Also
Included 1s a fairly detailed discussion of the use of data bases
maintained by EPA, such as HLDF. Those useful sources of Information
enable the exposure assessor to perform tasks systematically and
effectively, such as determining the spatial orientation of suspected
sources of drinking water contamination and potentially affected drinking
water treatment plants.
A relatively large portion of the volume on drinking water deals with
estimating the removal effectiveness of various water treatment schemes.
Both treatment on a large scale, 1n a municipal system, and the effects
of home treatments, such as water softeners and filters, are discussed.
The report summarizes the most pertinent literature and translates much
of 1t Into readily-applied removal factors. Within that section 1s
guidance 1n predicting the type of treatment expected for a particular
source of water. Exposure may also result from addition of chemicals
during treatment or distribution through pipes, either Intentionally or
as a result of a reaction between a trace contaminant 1n the water and a
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chemical added during treatment (notably chlorinated organlcs formed as a
result of chlorlnatlon). Techniques to predict the chemistry and fate of
substances during drinking water treatment are presented.
As 1n many of the other assessment methods volumes, a brief section
addresses the Identification and enumeration of populations exposed to
chemical substances 1n drinking water. Most of the methods discussed
rely on data maintained by EPA and kept 1n files such as the Water Supply
Data Base and the Federal Reporting Data System. Generic data that can
be used to predict the populations exposed as a result of treatment
practices themselves are presented; they are based on such factors as the
national use of various types of water treatment chemicals and the
relative amount of water drawn from surface and groundwater. The details
of assessing population exposure are In the Volume 4 report on
populations.
The exposure calculation procedure 1s the subject of the final
section. The commonly-used Intake factor 1s supplemented with a listing
of water Intake rates by age and sex of the Individual.
4.5 Occupational Exposure
Volume 6 describes methods for assessing exposure 1n the workplace.
Inhalation and dermal contact are the most Important routes of exposure
1n that setting, and they are the only ones considered 1n this volume.
The basic methods and data needs for dealing with Inhalation exposure 1n
the occupational setting are very similar to those discussed previously
for the ambient environment. Dermal exposure 1s significantly different
1n that, unlike the dilute concentrations of contaminant encountered 1n
the ambient environment, dermal exposure 1n the workplace usually means
contact with a concentrated Industrial waste stream or handling the
chemical Itself.
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There are a variety of sources of chemical exposure 1n the workplace,
most of which are best described by the type of operation being
performed: manufacturing of the chemical, production of Intermediate or
final products, commercial use, sales, or other operations. Volume 6
discusses many of the specific activities that are expected to lead to
worker exposure.
Though the terms "pathways" and "fate" are commonly construed as a
set of processes that occurs outdoors, 1n air or water, some transport
and transformation of a chemical also occurs 1n the occupational
environment. This report discusses the fate processes that are likely to
affect worker exposure to chemical substances Indoors: the
characteristics of the chemical that define Its fate Indoors are also
discussed, with reference materials for obtaining chemical property
Information presented with estimation techniques for use when data are
unavailable.
A quantitative exposure assessment requires, by definition, some
knowledge of the concentration of the chemical; 1n this case, 1n the
Indoor work environment. The concentration can be estimated by using
models that Incorporate release amounts and fate process Information.
This report provides guidance 1n selecting and applying predictive models
to describe worker exposure.
Monitoring data are often available (through regulatory agencies like
OSHA and NIOSH or from chemical manufacturers themselves) that can be
used to quantify exposure. In some cases, when data are plentiful and
appear valid, they may form the basis of the assessment. In other cases,
the monitoring data may be used 1n conjunction with model predictions to
provide estimates of long-term average worker exposure. The occupational
exposure methods report guides the user 1n obtaining relevant monitoring
data and then assessing the data for validity and applicability. The
sorts of questions the report leads the reader to ask about data are:
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• Are the measurement techniques correct?
• Were a sufficient number of samples taken so that the data are
representative?
• Are the data reported as short-term or long-term averages?
As with all the scenario-based methods reports, there 1s a brief
discussion of Identifying, quantifying, and describing the potentially
exposed populations. The details of that subject comprise a section In
Volume 4. This report simply describes the types of employment data
available from the Bureau of Labor Statistics, the Department of
Commerce, and other agencies and organizations. The format of the data
are described relative to the needs of an exposure assessor and guidance
for matching the two provided as needed.
There are two appendices to this report that bear mentioning. The
first Is a compilation of data on expected release amounts and
characteristics. This appendix is very detailed; there are 23 chapters
with titles such as Chlorinatlon, Hydrolysis, and similar unit process
descriptors.
The second appendix 1s a matrix of Information sources, followed by
pages from each referenced book, data base, or journal publication. A
similar appendix was also prepared for many of the other methods volumes.
4.6 Consumer Exposure
The seventh volume 1n the exposure assessment methods series presents
methods for assessing exposure resulting from use of consumer products.
Inhalation and dermal contact are the routes of most Interest 1n this
setting; as in the other volumes, methods for fulfilling the data needs
for exposure calculations are the bulk of the report. Not considered 1n
this report are consumer products and consequent exposures that are not
under EPA's regulatory jurisdiction: foods, drugs, commercial
pesticides, tobacco, firearms and explosives, and a few other
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categories. The difference between active exposure, which occurs while a
person actually uses a product, and passive exposure that can be
experienced afterward or by bystanders, 1s noted; there are some
ramifications In calculation of exposure that depend on whether 1t 1s an
active or passive process.
Following the Introduction, this report lists the chemical properties most
Important to a consumer exposure assessment. Sources of data and some general
Information are listed.
The most significant limitation to assessments of exposure to chemicals In
consumer products has In the past been defining the formulation of the
product. Such data are carefully guarded as proprietary; only Imprecise
Information provided for poison control and similar applications has been
available. This methods report lists sources of pertinent Information, and
summarizes formulary data for twenty common household products 1n an appendix.
The amount of chemical released as a result of use can range from nearly
100 percent, as In the case of aerosol sprays, to a small fraction
quantifiable only through use of complex migration equations. The full gamut
of releases 1s addressed, and simplified release models are presented for use
1n assessments when time Is limited or results are primarily for screening
purposes. The methods presented serve as Input to calculations of Indoor air
contaminant levels, which are usually the only available way of estimating
Inhalation exposures (monitoring data are especially rare 1n this setting).
Other data needed for that exposure estimate, such as room volume, are also
presented.
A summary of the methods to Identify, enumerate, and characterize exposed
populations comprises the next section. As 1n the entire methods series,
detailed Information 1s not presented; the user 1s referred to Volume 4.
The final section of the report explains the complete logic and
calculation train of a consumer exposure assessment. Frameworks for
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calculating Inhalation and dermal exposure are discussed and some data on
Incidental pathways that may occasionally be significant are presented. The
Information on Inhalation exposure calculation 1s much like that presented 1n
the other assessment methods volumes. The Information on dermal exposure
estimation 1s more detailed than that contained 1n the volumes for other
settings 1n which dermal exposure may occur (the ambient and occupational
environments). Those data on skin surface area, thickness of films remaining
on the skin after contact with a solution, and dust adhesion factors are
applicable to the ambient and occupational settings as well.
The final sections of this volume are appendices that Illustrate the
methods outlined throughout; valuable additional data are presented and
exposure scenarios for many consumer product uses are set up. Information
resources summaries comprise the last appendices.
4.7 Environmental Pathways of Food Contamination
Exposure to Ingested chemicals Is the product of the amount of (1n
this case) food Ingested and the concentration of chemical substance 1n
the food. This report concentrates on Identifying pathways by which food
can become contaminated and presenting methods to estimate levels of
chemical contaminants 1n foods. The report also discusses calculation of
total dietary Intake of contaminants.
Following the Introductory material, which Includes an overview of
the methods and the framework 1n which they are presented, a discussion
of pathways by which foods may come Into contact with and become
contaminated with chemicals Is presented. A chemical's uses, Its
physical chemical properties, and the nature of the food Itself are the
major determinants of pathways of contamination. For any exposure
assessment, the assessor can perform a systematic evaluation of the
likelihood of food contamination with the use of this 11st. A scoring
exercise that takes Into account both the magnitude and severity of
potential contamination 1s then presented; use of the scoring will
prioritize pathways for quantitative treatment.
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Two approaches to food exposure evaluation are discussed. The
approach that comprises the bulk of this methods volume 1s geared toward
predicting the level of food contamination resulting from each pathway;
this approach 1s necessary when no monitoring data are available or when
the assessor must be able to relate particular sources of contamination
to the presence of a chemical 1n food. The use of monitoring data alone
to calculate exposure 1s more straightforward. Predictive methods to
estimate the level of the chemical substance 1n a food are presented 1n
these groups of pathways:
- B1oconcentrat1on by livestock or fish of chemicals 1n their
environment or food;
- Uptake by crops;
- Post-harvest contamination (storage or processing 1n the presence
of a contaminant);
- Direct addition (Including Inadvertent addition, such as 1n
process water).
Brief examples of methods applications are presented throughout. A
discussion of potential loss of pollutant during consumer preparations,
such as washing and cooking, completes that portion of the methods
report. Though not quantitative, a similar subject briefly dealt with 1s
accidental contamination of food.
The final portion of this volume summarizes the methods and provides
example calculations for a variety of scenarios, often combining methods
dealing with different pathways of food contamination.
4.8 Exposure from Transportation-Related SpHls
Methods for assessing exposures from transportation-related spills
are presented 1n the ninth volume of this series. Much like the disposal
exposure methods report, this Is not a stand-alone report but one that 1s
to be used 1n conjunction with the ambient and drinking water exposure
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methods reports. This report presents Information on tracking the routes
along which chemicals are transported and discusses some methods for
predicting the volume and frequency of spills from three types of
transportation: trucking, rail, and barges.
The heart of the report 1s an adaptation of probability theory that
allows the assessor to rapidly apply accident statistics and chemical-
specific Information to estimate spill releases. Methods are presented
1n the report to assign values to each of the parameters 1n the
calculation scheme: the expected number of accidents, the probability of
a spill when an accident occurs, the number of accidents per mile, miles
per shipment, and number of shipments. This Iteration 1s repeated for
each transportation mode, and followed by calculation of the amount of
chemical released to the environment. At this point, the user may begin
applying the results to an assessment of exposure 1n the ambient
environment.
This volume does not touch on the number of people potentially
exposed as a result of transportation related spills. The report on
population enumeration (Volume 4) devotes an entire section to exposed
populations along transportation corridors.
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5. TYPES OF EXPOSURE ASSESSMENTS
An exposure assessment may be defined either by Its level of detail.
Its accuracy, or Its completeness 1n assessing various exposure
scenarios. This document earlier described the planning steps during
which the scope and purpose of the assessment are determined; that 1n
large part dictates the type of exposure assessment to be performed.
This chapter provides a discussion of five general types of assessments
to Illustrate how differences 1n scope and purpose can affect the effort
and direction of the assessment. Several of the types of exposure
assessments done 1n OTS are noted as examples.
5.1 Screening Level Assessments
Almost all screening level exposure assessments are performed to
determine If there 1s sufficient exposure potential to warrant further
Investigation. They usually employ "conservative" assumptions (I.e.,
"worst-case" or "worst reasonable case"), with the Intention of screening
out from further concern those situations where worst case estimates
would appear to cause little or no concern. Screening level assessments
usually roughly estimate exposure to a chemical about which little Is
known, or prioritize numerous chemicals 1n terms of predicted exposure.
Estimates are often used 1n Heu of chemical-specific or site-specific
data.
Screening level exposure assessments are usually Inexpensive and
fast, but not necessarily precise. Limited time, dollar, and manpower
resources (e.g., assessments must be done on many chemicals, or 1n a very
short time) usually dictate the use of screening level assessments.
Because of resource constraints, only relatively easy to find data are
usually available to do the assessments. The following types of data may
constitute the universe of knowledge about a new or little-known existing
chemical to be assessed on a screening level:
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• production volume (total annual)
• locations where the chemical 1s produced
• a brief 11st of the chemical's uses
• the chemical's formula, structure, and selected physical-chemical
properties.
To supplement these basic data, an assessor may also employ
estimation techniques that relate chemical properties to one another 1n
order to obtain the parameters essential to determining the chemical's
behavior. The solubility, vapor pressure, octanol-water partition
coefficient, and similar chemical characteristics can be calculated from
a minimum of Input data; computerization of the system enables rapid
estimation.
These chemical property estimates can then be used, along with other
estimation techniques, to determine the magnitude of releases to the
environment resulting from production and use. A typical approach might
be to apply emission factors (for example, 0.4 percent of production
volume 1s released via wastewater) to estimate releases. The volume of
wastewater flow, 1f unknown, might be assumed to be equal to the average
flow rate for the Industry.
A screening level fate analysis combines the estimated chemical
properties and knowledge about the fate of structurally-similar chemicals
to qualitatively address environmental fate. The resulting assessment
might make such statements as "the high octanol-water partitioning
coefficient Indicates that the chemical would adsorb to sediments In an
aquatic environment." In keeping with the conservative nature of this
type of assessment, however, the approach to calculating aquatic
concentrations relies often on assuming dilution, but no removal
processes. If the actual location of waterborne discharges 1s not known,
the mean or low-flow rate of streams and rivers receiving this Industry
sector's wastewater may be assumed.
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Human exposure to chemicals In screening assessments 1s evaluated
through the use of scenarios. A scenario combines chemical and product
characteristics with use patterns (frequency and duration of use) and
Intake parameters (breathing rates, etc.) to estimate typical or
worst-case exposure. An examination of the chemical's uses may lead to a
11st of consumer products that could contain the substance. For
Instance, 1f the chemical Is a fragrance, scenarios of consumer use of
cosmetics, soaps, shampoos, and similar products may be constructed.
A screening assessment that Indicates potentially significant
exposure can lead to more 1n-depth assessment. Two examples are OTS1
Chemical Hazard Information Profile screening assessment of existing
chemicals, and the Exposure Assessment Meeting (EXAM) report, the OTS
screen for new (premanufacture notice) chemicals.
5.2 Intermediate Level Exposure Assessments
Intermediate level exposure assessments combine the predictive tools
described previously with more sophisticated analytic procedures, and
Involve considerably more detail than a screening level assessment. If
worst-case assumptions 1n a screening level assessment Indicate that
significant exposure may occur. It 1s usually 1n the Intermediate level
assessment that the assumptions are refined to bring them closer to
real-world conditions. Intermediate level assessments are usually
considerably more costly than screening level assessments. Where a
screening level assessment might be accomplished 1n hours or days, an
Intermediate level assessment usually takes weeks or months.
In a typical Intermediate level assessment, the source evaluation
often Includes a materials balance with all points of potential release
to the environment quantified; emission factors are supplemented by
monitoring data obtained through a literature search. All sources,
Including Inadvertent production, and all Identifiable uses are
addressed. The fate analysis may combine estimates and analogies with
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Information derived from the published literature. Where possible, the
fate analysis 1s quantitative, providing rate constants for environmental
processes to more precisely define the environmental fate of the
substance 1n all relevant media. All available monitoring data are
collected and evaluated for quality and completeness. The results of
that review of the monitoring data often dictate whether modeling 1s
performed, and 1f so, what modeling techniques are necessary. The
population analysis 1s geared toward Identifying all potentially exposed
Individuals and determining the size of specific subpopulatlons. In
support of accurate exposure estimates, the Integrated assessment section
presents the basis of the exposure estimates: frequency and duration of
exposure and physiologic parameters like Intake rates. Exposure
estimates may be characterized as "typical," "worst-case," or other
scenarios.
An Important component of this type of exposure assessment 1s a
discussion of the uncertainty of the exposure analysis and a listing of
significant data gaps. This section 1s used to guide planning and to
determine the necessity for further action. The chemical may be
determined to be of no concern; the data gaps may be substantial enough
to warrant field studies; or the data may show enough exposure so that
concern for significant potential hazard 1s raised. OTS performs a
number of Intermediate level assessments each year, known as Preliminary
Existing Chemical Exposure Assessments. Either the need for field
studies to gather additional data or the Initiation of a regulatory
review can prompt OTS to begin a detailed exposure assessment.
5.3 Detailed Exposure Assessments
Detailed exposure assessments often require a significant effort to
generate new exposure data, usually to Improve the accuracy of the
assessment. Field studies and surveys are often the tools used to
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generate these new data, so the assessment can be quite expensive.
Normally, the field studies will be focused on certain narrow areas of
Interest, such as a specific occupational setting, consumer use of a
specific product, or monitoring exposures at a certain site. The scope,
depth, and approach of a detailed assessment make 1t a very specific
document, with a level of accuracy that may be necessary for regulations.
The sources, fate, monitoring, and population studies sections 1n a
detailed exposure assessment would be at least as comprehensive as 1n an
Intermediate level assessment. Field studies, surveys, or other data
collection activities would be developed for the purpose of filling data
gaps and reducing uncertainty. Models used might be verified, and there
may be Investigation of the accuracy and appropriateness of the scenarios
used. Extensive QA/QC measures and analysis of uncertainty 1s usually
done. Because of the complexity usually accompanying field studies, a
detailed exposure assessment may often take months to years to complete.
5.4 Special Exposure Assessments
5.4.1 Assessments Limited to Specific Settings
Exposure assessments are often limited to specific settings either by
choice of the assessor or by the legislative mandate of the regulatory
agency Involved; for example, CPSC 1s concerned only with consumer
exposure, and OSHA with occupational exposure. Sometimes settings are
limited by the nature of the chemical or Its use, as 1n the case of a
captive Intermediate (I.e., a consumptive use), where occupational
exposure 1s the only category likely to be significant.
Restricting the assessment to certain settings may automatically
narrow the scope 1n other ways as well by eliminating Irrelevant
populations, media, and routes from consideration. Nevertheless, all
five major components are still typically addressed and limiting the
scope to one setting does not preclude the possibility that more than one
volume of this series of methods reports may need to be consulted.
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5.4.2 Generic Assessments
A generic assessment 1s one where the non-chem1cal-spec1f1c factors
are gathered for the exposure scenarios, but the chemical-specific data
are left for future chemical-specific work. The specific chemical data
can later be "plugged Into" the generic framework, 1f needed.
In addition to providing a framework for future chemical-specific
assessments, generic assessments are also useful for estimating exposure
to an entire category of chemicals for screening purposes. The main
feature of this type of assessment, as far as planning 1s concerned, 1s
the emphasis on semi-quantitative predictive methods for estimating
environmental concentrations. Results are usually based on the average
phys1cochem1cal properties of the chemical group and generic release
rates.
Analysis of exposed populations can proceed as for other
assessments. Scenarios are constructed according to the exposure
categories, taking Into account frequency and duration of exposure.
Generic assessments are particularly useful for evaluating PHN
chemicals, the bulk of which tend to fall Into a limited number of
well-defined categories (e.g., lubricant additives, AZO dyes). The
Information contained 1n the volumes of this series 1s particularly
useful 1n doing generic exposure assessments.
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6. GLOSSARY
Active exposure: Exposure of the user of a consumer product resulting
from Initial use or application of the product, (cf. "Passive Exposure.")
Aeration: In water treatment, the process by which a gaseous phase,
usually air, and water are brought Into Intimate contact for the purpose
of transferring volatile substances to or from the water.
AEROS: Aerometrlc Emission Reporting System; a data base containing
Information on point-source atmospheric discharges.
AGRICOLA: The cataloging and Indexing base of the National Agricultural
Library.
Area source: An emission source defined only by broad geographic
boundaries (e.g. urban areas as a source of automotive exhaust).
AT123D: A model for estimating transport 1n saturated and unsaturated
soil zones. See Volume 5.
ATM: Atmospheric Transport Model, used to model point-source atmospheric
emissions; see Volume 2. The model may be Interfaced with Census Bureau
data to allow direct computation of the number of people exposed to
various concentrations of a pollutant; see Volume 4.
Atmospheric Box Model: A model used for modeling atmospheric area-source
emissions; see Volume 2.
Av, Availability: In dermal exposure calculation, the total amount of
skin surface area available for contact with a pollutant during a given
activity.
Best Available Technology Review Studies: An Industry-specific data base
containing Information on point-source aquatic discharges.
Block: A Census block 1s a well-defined piece of land, bounded by
streets, roads, railroad tracks, streams, or other features on the
ground. Blocks do not cross census tract boundaries, but may cross other
boundaries such as city limits. Blocks are the smallest areas for which
census data are tabulated.
Block Group (BG): A combination of contiguous blocks having an average
population of about 1,100. BGs are subdivisions of census tracts.
Breathing losses: Emissions vented from fixed-roof and floating-roof
tanks used for storing volatile liquids.
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6. GLOSSARY (continued)
Census County Division (CCD): A modification of the Census-defined
category "Minor C1v1l Division". In 21 states, MCDs were found to be
unsuitable for presenting statistics due to area's small population size,
frequent boundary changes, etc. CCDs are defined with boundaries that
seldom change and can be easily located (e.g., roads, railroads, power
lines, and bridges).
Census-Designated Place: A densely settled population center without
legally defined limits or corporate powers.
Census Tracts: Small, relatively permanent areas Into which metropolitan
and certain other areas are divided. An average tract contains about
4,000 residents. All SMSAs are completely tracted.
Central city (of an SMSA): The largest city of an SHSA. One or two
additional cities may be added to the SMSA title and Identified as
central cities providing they meet certain criteria.
CFEST: The Coupled Fluid Energy and Solute Transport model for
estimating contaminant concentrations 1n groundwater; see Volume 5.
Clarification: In water treatment, the process of allowing solids to
settle out of the water 1n a basin.
Coagulation: In water treatment, a process to reduce the net repulsive
forces between electrolytes 1n solution 1n order to aggregate
contaminants associated with turbidity; these are subsequently removed by
settling.
Compliance Data System: A data base containing Information on
point-source atmospheric emissions; see Volume 2.
Consumptive use: In manufacturing, consumptive use occurs when a
chemical undergoes a reaction to form a new chemical.
Data Collection Portfolios: A data base containing Industry-specific
aquatic point-source discharge data.
DIALOG: A computerized data search system.
Direct discharge: The direct release of wastewaters to surface waters
without treatment at a POTW.
Disposal: The discharge, deposit, dumping, or placing of any waste Into
or on land or water.
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6. GLOSSARY (continued)
Division: A group of states; a subdivision of a Census region. There
are nine divisions: New England, Hlddle Atlantic, South Atlantic, East
South Central, West South Central, East North Central, West North
Central, Mountain, and Pacific.
Dust: Airborne solid particles, generated by physical processes such as
handling, crushing, or grinding of solids, ranging 1n size from 0.1 to
25 p.
EADS: Environmental Assessment Data Systems, a data base containing
Information on point-source atmospheric and aquatic discharges.
Economic Information System: A computerized data base listing
Information on facility location and number of employees for companies In
the U.S.
Electrostatic predpltator: An air pollution control device.
ENPART: A model for evaluating environmental partitioning; see Volume 2.
Enumeration Districts (EDs): Areas within census tracts, MCDs, and CCDs
with an average of about 800 people or 250 housing units. EDs are
generally used when block groups are not defined for an area.
EXAMS: Exposure Assessment Modeling System, which considers the fate and
transport of a chemical as 1t passes through a series of water
compartments and associated sediment and blotlc compartments; see
Volume 2 and Volume 5.
Fate: The combined transport and transformation of a pollutant.
FEMWASTE: A mass transport model for soil; combined with FEMWATER, 1t
can predict groundwater flow. See Volume 5.
Flocculatlon: In drinking water treatment, a process whereby slow mixing
of the water and chemicals causes formation of large particles ("floe")
by both physical and chemical means.
Fly ash: Combustion residue entrained 1n the exhaust gases leaving an
Incinerator.
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6. GLOSSARY (continued)
FRDS: Federal Reporting Data System; a data base by the EPA Office of
Drinking Water containing Inventory data on each public water supply 1n
the U.S.
Fugitive releases: Emissions that occur during manufacturing from leaks
1n the process equipment and from defective, Inadequate, or worn seals 1n
pumps, valves, and compressors; they occur as a result of normal plant
operations due to thermal and mechanical stress.
Fume: Solid particles generated by condensation from the gaseous state,
generally after volatilization from the molten state. Their formation 1s
often accompanied by oxidation or other chemical reaction. Particles
range 1n size from 0.1 to 5yi.
FURS: The Federal Underground Injection Reporting System, a data base to
contain detailed site-specific Information on each Injection well 1n the
U.S.
GAGE: The Stream Gaging Inventory File, a data base containing the'
locations of all stream gaging (sampling) stations 1n the U.S., together
with stream flows at those locations and other related Information.
Gas: Formless fluids occupying space that can be changed to the liquid
or solid state by Increased pressure and decreased temperature.
GEMS: Graphical Exposure Modeling System, an Interactive computer
program managed by OTS, containing models and data bases for assessing
exposure; these Include ATM-SECPOP, ENPART, EXAMS, etc.
GEOECOLOGY: A computerized data base for environmental data.
GIOAP: The GEOMET Indoor/Outdoor A1r Pollution Model for estimating
Indoor concentrations of toxic chemicals emitted by an outdoor source;
see Volume 2.
Hardness: The presence 1n drinking water of divalent cations,
principally calcium and magnesium. If present 1n excess, hardness 1s
removed by specific treatment processes.
HATREMS: Hazardous and Trace Emissions System, a data base containing
Information on atmospheric area sources.
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6. GLOSSARY (continued)
Hazardous waste: Hazardous waste, as defined 1n Title 40 of the Code of
Federal Regulations, 1s a legal rather than a scientific term. To be
considered hazardous, a waste must be 1n the 11st of specific hazardous
wastestreams or chemicals, or else 1t must exhibit one or more of certain
specific characteristics Including 1gn1tab1l1ty, corroslvlty, reactivity,
and toxldty. The definition excludes household waste, agricultural
waste returned to the soil, and mining overburden returned to the mine
site. It also excludes all wastewater discharged directly or Indirectly
to surface waters. However, hazardous waste may be physically 1n the
liquid state.
HAZHAT: A data base of the U.S. Department of Transportation, containing
Information on hazardous materials spills 1n Interstate commerce.
HLDF: The Hydrologlcally Linked Data File System, a comprehensive group
of aquatic data bases useful 1n the evaluation of drinking water quality,
and Including the REACH, IFD, WSDB, GAGE, and STORET files, as well as
the Pollution-Caused F1shk1ll File.
HWDMS: Hazardous Waste Data Management System; a computerized system for
tracking permit applications for the treatment/storage/dlsposal of
hazardous waste.
HYDRO: An Interactive program for accessing data 1n the HLDF (q.v.).
Incineration: A waste treatment method that Involves the controlled
burning of wastes resulting 1n their thermal destruction.
Indirect discharge: The release of wastewater to a POTW for treatment
prior to ultimate release to surface waters.
Industrial Facilities Discharge File: A data base containing Information
on direct and Indirect aquatic dischargers within each major Industrial
category.
Industrial Incinerator: Any combustion unit used 1n the process of
burning a nongaseous Industrial wastestream which does not recover heat
for any useful purpose. (An Industrial wastestream 1s here defined as
one composed of more than 50% by weight of waste generated at a
manufacturing establishment or collected by a resource recovery
establishment).
Industrial solid waste: Any waste generated by a manufacturing process
and not disposed of with wastewater; this Includes some waste that Is
physically 1n the liquid state.
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6. GLOSSARY (continued)
Injection well: A waste disposal facility where liquid wastes are
Injected Into a permeable rock layer below the surface.
1-0 Matrix: The Industry-Occupation Matrix, a compilation of employment
data.
IW1S: The Injection Well Inventory System, a data base containing
Inventory Information on Injection wells.
Lagoon: A surface Impoundment.
Land treatment: A disposal technique by which wastes are mixed with
surface soil and allowed to be degraded through natural processes.
Landfill: A waste disposal site where wastes are placed on the ground
and covered with soil; see "Sanitary Landfill" and "Open Dump".
Landspreadlng: Same as land treatment.
Leachate: Liquid released Into soil from a land disposal facility.
Leachate 1s generated when water enters a landfill, migrates through 1t
picking up soluble materials, and seeps Into the soil.
Line source: An emission source that 1s mobile, following a pathway such
as a road, railway, or river.
LOMA: The Leachate Organic Migration and Alternation Model for
predicting the transport of organic solutes 1n soil; see Volume 5.
Maximum Contaminant Levels: A set of standards for public drinking water
set by the Safe Water Drinking Act.
Medium: The environmental vehicle by which a pollutant 1s carried to the
receptor (e.g., air, surface water).
Metric ton: Same as kkg.
M1croenv1ronment: A region of local variability within an environment.
The microevlronments discussed 1n Volume 2 Include the Indoor, outdoor,
and 1n-veh1cle microenvlronments.
Minor C1v1l Divisions (MCDs): These are the primary poltlcal and
administrative subdivisions of counties, most frequently known as
townships, but 1n some states Including towns, precincts, and magisterial
districts.
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6. GLOSSARY (continued)
M1st: Suspended liquid droplets generated by condensation from the
gaseous to the liquid state or by dispersion of a liquid, ranging 1n size
from 0.5 to 1,000»i.
MMT: The Multlcomponent Mass Transport model for predicting movement of
radioactive contaminants 1n the soil; see Volume 5.
Municipal Incinerator: Any Incinerator that burns at least 50% municipal
solid waste.
Municipal landfill: Any landfill, publicly or privately owned and
operated, that accepts municipal waste; as defined 1n Volume 3,
"municipal landfills" Include off-site Industrial landfills.
National Occupational Hazard Survey: A 2-year field study Initiated by
NIOSH 1n 1972 to describe the health and safety conditions 1n the
American work environment.
National Pollutant Discharge Elimination System: This 1s a permit
Issuing program designed to monitor and control the discharge of
pollutants Into the nation's surface waters. The NPDES compliance files
contain aquatic point-source discharge monitoring data.
NAWDEX: National Water Data Exchange; an Interagency data base managed
by USGS to assist 1n Identifying, locating, and acquiring water data.
NEDS: National Emissions Data System, a data base containing Information
on atmospheric area source emissions.
NEEDS: A computerized data base containing Information collected 1n
annual surveys conducted by the EPA Office of Water Programs Operations.
It Includes design and operating characteristics for all municipal sewage
treatment facilities In the U.S.
Open dump: Any landfill not meeting the criteria for a sanitary landfill
(q.v.).
ORBIT: A computerized data search system.
Partitioning: The relative distribution of a substance among
environmental compartments (e.g. air, surface water, sediment, biota,
soil).
Passive exposure: Exposure arising subsequent to the Initial use or
application of a consumer product, usually affecting persons 1n addition
to the Initial user. (cf. "Active Exposure.")
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6. GLOSSARY (continued)
PATHS: A model for estimating contaminant flow 1n soil; see Volume 5.
Pathway: A history of the flow of a pollutant from source to receptor,
Including qualitative descriptions of emission type, transport, medium,
and exposure route.
Periodicity: In exposure calculation, the product of frequency and
duration of exposure; 1n emission characterization, a monitored or
estimated schedule of emissions from the source.
PEST: A dynamic simulation model that evaluates the fate of toxic
organic compounds 1n freshwater environments; see Volume 5.
PESTAN: A screening model that evaluates a chemical's potential for
groundwater contamination; see Volume 5.
PIRS: The Pollution Incident Reporting System for collecting Coast Guard
reports on hazardous materials spills from barges.
PLUME: A steady-state analytical model for estimating contaminant
transport 1n the saturated zone of soil; see Volume 5.
PMS: The Pollutant Movement Simulator, a model that describes air-water
flow 1n a coupled unsaturated-saturated porous medium; see Volume 5.
Point source: A known location of emissions Identifiable by geographic
coordinates (e.g., Industrial dischargers, disposal sites.)
Preliminary treatment: Wastewater treatment Involving only commun1t1on,
screening, and/or grit removal.
Premanufacturlng notice (PMN): A notification of Intent to produce or
Import a new chemical substance. It 1s submitted to EPA by the
manufacturer or Importer, and 1s required to contain Information on
proposed production amounts, uses, occupational exposure levels, disposal
methods, etc.
Primary producer: The Industry that extracts or starts the manufacturing
process with raw material and modifies 1t to produce an Intermediate or a
finished product.
Primary treatment: Wastewater treatment producing effluent that does not
meet regulatory standards for secondary treatment. Conventional primary
treatment provides preliminary treatment plus primary sedimentation to
remove settlable solids; advanced primary treatment Includes some
biological treatment as well.
54
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6. GLOSSARY (continued)
Process releases: Emissions that occur during a manufacturing process,
and are Inherent 1n the unit operations that make up the process.
Publicly-owned treatment works: Municipal sewage treatment plant.
REACH File: A series of Il-d1g1t numerical codes that uniquely Identify
every major stream, river, or lake segment 1n the U.S. Each REACH number
combines the 8-d1g1t USGS hydrologlc unit with a 3-d1g1t EPA segment
number.
Reduction: Any waste treatment method that decreases waste volume, such
as wet oxidation or Incineration.
Region: A large, geographically contiguous group of states (with the
exception of the region that Includes Alaska and Hawaii). There are four
Census regions (Northeast, North Central, South, and West) and 10 EPA
Regions.
Route: The means by which a pollutant 1n a given medium contacts or
enters the receptor (e.g., Inhalation, 1ngest1on).
Rural Area: By Census definition, any area not classified as urban
(q.v.).
Sanitary landfill: Any landfill meeting the criteria set forth 1n Sec.
4004 of RCRA, as opposed to "open dump". Sanitary landfills must meet
stringent siting and operational standards.
SAROAD: Storage and Retrieval of Aerometrlc Data, a data base for
atmospheric ambient monitoring Information.
Scenario: A set of assumptions about how exposure takes place.
Scenarios are usually constructed 1n the "Integrated Exposure Analysis"
section of an exposure assessment, and are usually specific to an
exposure setting.
Secondary producer: The Industry that processes and uses an Intermediate
to form other products.
Secondary releases: Emissions which result from the handling, treatment,
and disposal of aqueous, liquid, and solid wastes generated by an
Industry.
55
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6. GLOSSARY (continued)
Secondary treatment: Wastewater treatment comprising preliminary plus
biological processes (I.e. trickling filter, activated sludge, rotating
biological contactors) with no additional process except disinfection.
Advanced secondary treatment consistently provides effluents with low BOD
and the removal of nutrients, phosphorus, and ammonia.
SECPOP: A computerized population distribution model; see "ATM" and
Volume 4.
SESOIL: The Seasonal Soil Compartment Model, a mathematical model for
long-term environmental pollutant fate simulations that describes water
transport, pollutant transport/transformation, and soil quality. It may
be used to predict leachate contamination of groundwater as well as gas
emissions to the atmosphere.
Setting: One of seven OTS-deflned exposure categories; see Volume 1,
Table 3.
Severity: In Inhalation exposure calculation, the product of ambient
concentration and ventilation rate; 1n dermal exposure calculation, the
product of concentration and availability.
Sewage sludge Incinerator: An Incinerator that burns more than 5054
sewage sludge.
SITEHELP: An Interactive program for accessing data 1n the HLDF (q.v.).
SRI data base: A computerized data base that offers statistical analysis
and retrieval of human t1me-d1ary data.
Stabilization: Treatment of sludge by digestion of organic solids.
Standard Consolidated Statistical Area (SCSA): A census region composed
of two or more contiguous SMSAs which meet certain criteria of population
size, urban character, social and economic Integration, and contiguity of
urbanized areas,.
Standard Industrial Classification (SIC): A comprehensive series of 2-
to 4- digit codes used by the U.S. Department of Commerce to designate
segments of Industry, commerce, and agriculture.
Standard Metropolitan Statistical Area (SMSA): As defined by the Census
Bureau, an Integrated economic and political unit with at least one
densely populated central city. Generally, each SMSA consists of one or
more entire counties, or county equivalents, that meet standards
pertaining to population and metropolitan character.
56
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6. GLOSSARY (continued)
STAR: The Stability Array Program, which provides data on atmospheric
stability, wind direction, and wind speed, based on National Weather
Service data, for Input to air models; see Volume 2.
STOM: The Solute Transport and Dispersion Model for predicting the
movement of contaminants 1n soil; see Volume 5.
STF: Summary Tape Files, a computerized source of Census Information.
STORET: Storage and Retrieval of Water Quality and Related Data, a data
base containing Information on ambient water quality monitoring.
Surface Impoundment: A waste handling facility where liquid wastes are
treated, stored, or disposed of 1n a natural or manmade topographical
depression.
Surface Impoundment Assessment: An Inventory of surface Impoundments In
the U.S., together with data on their potential effects on groundwater
quality.
SWIFP: A model for predicting the movement of contaminants In soil, see
Volume 5.
SWIP: The Survey Waste Injection Program, a model for Investigating
contaminant movement associated with Injection wells.
Tertiary treatment: Wastewater treatment producing effluent with a BOD
less than 10 mg/1 and capable of removing more than 50% total nitrogen
from the Influent wastewater.
Transformation: The chemical alteration of a pollutant 1n the
environment via blodegradatlon, photolysis, hydrolysis, or other means.
(see "Transportation.")
Transport: The mass movement of a pollutant via hydrologlcal,
meteorological, or other physical processes, Including Intermedia
transfer, (see "Transformation.")
Treatment: Any process designed to change the physical, chemical, or
biological character or composition of a waste for the purpose of making
1t safer for transport, amenable for recovery or storage, or reduced In
volume.
UIC: The Underground Injection Control program, by which states are
required to develop programs to prevent groundwater contamination brought
about by deep well Injection of wastes.
57
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6. GLOSSARY (continued)
UNAMAP: User's Network for Applied Modeling of A1r Pollution, a series
of atmospheric line-source models; see Volume 2.
UNSATIO: The One-Dimension Saturated Flow model for predicting flow 1n
the saturated zone of soil; see Volume 5.
Urban area: By Census definition, an urbanized area or a place of 2,500
habitants or more outside urbanized areas.
Urbanized area: By Census definition, an area containing a central city
(or twin cities) meeting the same criteria as an SMSA, plus the
surrounding closely settled Incorporated and unincorporated areas which
meet certain criteria of population size of density.
Vapor: Gaseous form of a substance normally 1n the liquid or solid state
at normal temperature and pressure.
WAS: Waste Age Survey, an Inventory of landfills conducted on roughly an
annual basis by Waste Age magazine.
WATSTORE: Water Data Storage and Retrieval System; a data bank for all
Information collected by USGS at Its water sampling sites throughout the
U.S.
WHTM: Wisconsin Hydrologlc Transport Model, which simulates the movement
of a chemical through an Inland watershed; see Volume 5.
WSDB: The Water Supply Data Base, which contains Information on the
locations of surface-water-derived drinking water utilities, Including
locations of treatment plants, Intakes, and sources, populations served,
and average and maximum dally production.
58
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7. ABBREVIATIONS
BAT: Best Available Technology
BG: Block Group.
BMCS: The Bureau of Motor Carrier Safety of the U.S. Department of
Transportation.
BOD: Biological oxygen demand.
CAS: Chemical Abstracts Service.
CCD: Census County Division
COP: Census-Designated Place.
CDS: Compliance Data System.
CPSC: Consumer Products Safety Commission.
DOT: U.S. Department of Transportation.
ED: Enumeration District.
EGD: (USEPA) Effluent Guidelines Division.
EIS: Economic Information System.
ESP: Electrostatic predpltator.
FWPCA: Federal Water Pollution Control Act (P.L. 95-217).
GPO: U.S. Government Printing Office.
HLDF: Hydrologlcally Linked Data File
HO: Halogenated organic.
IFD: Industrial Factllltles Discharge.
MCD: Minor C1v1l Division.
MCL: Maximum Contamination Level.
MDSD: (USEPA) Monitoring and Data Support Division.
mgd: Millions of gallons per day.
59
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7. ABBREVIATIONS (continued)
HSW: Municipal solid waste.
HTB: The Materials Transportation Bureau of the U.S. Department of
Transportation.
NEMC06: Northeast Michigan Council of Governments.
NIOSH: National Institute for Occupational Safety and Health.
NOAA: U.S. National Oceanic and Atmospheric Administration.
NOHS: National Occupational Hazard Survey.
NPDES: National Pollutant Discharge Elimination System.
NPTOC: Nonpurgeable total organic carbon.
NTA: N1tr1lotr1acet1c add.
NTIS: National Technical Information Service.
OSHA: U.S. Occupational Safety and Health Administration.
OSW: (USEPA) Office of Solid Waste.
OTS: (USEPA) Office of Toxic Substances.
PMN: Premanufacturlng notice.
POTW: Publicly-owned treatment works.
RCRA: Resource Conservation and Recovery Act of 1976 (P.L. 94-580)
RDF: Refuse-derived fuel.
SCSA: Standard Consolidated Statistical Area.
SDF: Stream dilution factor.
SIA: Surface Impoundment Assessment.
SIC: Standard Industrial Classification.
SL: Sanitary landfill.
60
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7. ABBREVIATIONS (continued)
SMRB: Simmons Market Research Bureau.
SMSA: Standard Metropolitan Statistical Area.
SOCMI: Synthetic organic chemicals manufacturing Industry (SIC 28)
THM: Trlhalomethane.
TOC1: Total organic chlorine.
TRY: tons per year.
TSCA: The Toxic Substances Control Act of 1976 (P.L. 94-469).
TSD: Treatment/storage/dlsposal.
USDI: U.S. Department of the Interior.
USDW: Underground source of drinking water.
USGS: U.S. Geological Survey.
USACE: U.S. Army Corps of Engineers.
VOC: Volatile organic carbon.
WAS: Waste Age Survey.
WMT: Wet metric tons.
61
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8. REFERENCES
Callahan MA. 1982. Planning an exposure assessment. Draft.
Washington, DC: Office of Toxic Substances, U.S. Environmental
Protection Agency.
USEPA. 1984. Proposed guidelines for exposure assessment; request for
comments. Federal Register 49:227 (23 November 1984), p. 46304.
63
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Appendix
Table of Contents from Each
Volume 1n the Exposure Assessment
Methods Series
65
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VOLUME 2 - METHODS FOR ASSESSING EXPOSURE TO CHEMICAL SUBSTANCES IN THE
AMBIENT ENVIRONMENT
67
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Report Organization 2
1.3 Framework for Calculation 2
1.3.1 Inhalation Exposure of Humans 4
1.3.2 Dermal Exposures of Humans 4
1.3.3 Exposure of Aquatic Biota 7
2. SOURCES 8
3. ENVIRONMENTAL PATHWAYS 13
3.1 Phys1cochem1cal Properties 13
3.1.1 General Properties 13
3.1.2 Particle Size Analysis for Airborne Pollutants 17
3.2 Partitioning 17
3.2.1 Analogy with Other Compounds 17
3.2.2 Mathematical Models 20
3.2.3 Empirical Methods 24
3.3 Envlronmental Pathway Models 25
4. MONITORING DATA 27
4.1 Sources 27
4.1.1 A1r Emissions 27
4.1.2 Water Discharges 31
4.2 Ambient 32
4.2.1 A1r 33
4.2.2 Water 33
4.3 Background 34
4.3.1 A1r 34
4.3.2 Water 36
69
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TABLE OF CONTENTS (continued)
Page No.
4.4 Personal Monitoring 36
4.5 Analytical Techniques 40
4.5.1 Organlcs 41
4.5.2 Inorganics 41
5. EXPOSED POPULATIONS 46
6. CALCULATING EXPOSURES 48
6.1 Identification of Exposed Populations 48
6.1.1 Ambient A1r 48
6.1.2 Ambient Water 49
6.1.3 Aquatic Biota 50
6.2 Inhalation Exposures 50
6.2.1 Periodicity 55
6.2.2 Ventilation Rate 56
6.2.3 Ambient Air Concentrations 64
6.3 Dermal Exposure 86
6.3.1 Frequency and Duration 86
6.3.2 Availability 87
6.3.3 Ambient Aqueous Concentration 87
6.4 Exposure of Aquatic Biota 104
7. REFERENCES 105
70
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VOLUME 3 - METHODS FOR ASSESSING EXPOSURE FROM DISPOSAL OF CHEMICAL
SUBSTANCES
71
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Limitations 2
1.3 Overview - Potential for Exposure to Chemical
Substances from Waste 01sposal 3
2. GENERAL METHODOLOGICAL APPROACH 6
2.1 Integration with Other Exposure Scenarios 7
2.2 Framework for Estimating Releases 7
2.3 General Decision Trees for Stages 1 through V 10
2.3.1 Stage I Decision Tree - Estimating Releases
to Disposal 11
2.3.2 Stage II Decision Tree - Characterizing Waste
Stream Releases and Concentrations 13
2.3.3 Stage III Decision Tree - Allocating Waste
Streams to Disposal Practices 14
(1) Incinerator residues 19
(a) Background Information 19
(b) Stage III decision tree 23
(2) POTW sludge 25
(a) Background Information 25
(b) Stage III decision tree 27
(3) Wastewater 29
(a) Background Information 30
(b) Stage III decision tree 31
(4) Hazardous Waste 35
(a) Background Information 35
(b) Stage III decision tree 38
(5) Nonhazardous Industrial solid waste 41
(a) Background Information 41
(b) Stage III decision tree 45
(6) Municipal Solid Waste (MSW) 46
(a) Background Information 46
(b) Stage III decision tree 49
2.3.4 Stage IV Decision Tree - Allocating Waste Streams
Streams to Individual Disposal Sites 50
2.3.5 Stage V Decision Tree - Estimating Environmental
Releases from Disposal Sites 53
73
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TABLE OF CONTENTS (continued)
Page No.
3. LANDFILLS 56
3.1 Background Information 56
3.1.1 Landfill Types and Operation 56
3.1.2 Environmental Releases from Landfills 57
3.1.3 Predicting Environmental Releases 60
3.1.4 Model Input Data 62
3.1.5 Additional Considerations for Modeling Chemical
Releases from Landfills 74
3.1.6 Estimating Emissions from Broad Geographical
Regions 82
3.1.7 Monitoring 82
3.2 Allocating Waste Streams to Landfill Sites - Stage IV
Decision Tree 83
3.2.1 Municipal Landfills 83
3.2.2 Industrial Nonhazardous Landfills 84
3.2.3 Hazardous Waste Landfills 85
3.3 Estimating Environmental Releases from Landfills -
Stage V Dec 1 s 1 on Tree 86
3.3.1 Municipal Landfills 87
3.3.2 Industrial Landfills 89
4. LAND TREATMENT 91
4.1 Background Information 91
4.1.1 Types of Waste Treated 92
4.1.2 Environmental Impacts and Environmental Releases 95
4.1.3 Location of Sites 97
4.1.4 Estimating Environmental Releases 98
4.1.5 Model Input Data 100
4.1.6 Monitoring 104
4.2 Allocating Waste Streams to Land Treatment Sites -
Stage IV Decision Tree 104
4.3 Estimating Environmental Releases from Land Treatment -
Stage V Dec 1 s 1 on Tree 106
74
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TABLE OF CONTENTS (continued)
Page No.
5. SURFACE IMPOUNDMENTS 110
5.1 Background Information 110
5.1.1 Types of Impoundments Ill
5.1.2 Environmental Releases from Surface Impoundments 115
5.2 Allocating Waste Streams to Surface Impoundments -
Stage IV Decision Tree 118
5.3 Estimating Environmental Releases from Surface
Impoundments - Stage V Decision Tree 127
6. PUBLICLY OWNED TREATMENT WORKS (POTWs) 134
6.1 Background Information 134
6.1.1 General 134
6.1.2 Chemical Substances 1n POTW Effluent and Sludge 136
6.1.3 Predicting Releases of Chemical Substances
from POTWs 136
6.2 Allocating Wastewater to Individual POTWs - Stage IV
Dec 1 s 1 on Tree 140
6.3 Estimating Releases from POTWs - Stage V Decision Tree 142
7. INCINERATION 145
7.1 Background Information 145
7.1.1 General 145
7.1.2 Information Resources 147
7.1.3 Emissions and Products of Incineration 149
7.1.4 Estimating Emissions from Incineration 153
7.2 Allocating Waste Streams to Individual Incinerators -
Stage IV Decision Tree 154
7.3 Estimating Emissions from Incineration - Stage V
Decision Tree 157
75
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TABLE OF CONTENTS (continued)
Page No.
8. DEEP-WELL INJECTION 161
8.1 Background Information 161
8.1.1 General 161
8.1.2 Information Resources Useful 1n Assessing the
Potential for Exposure from Injection Wells 166
8.1.3 Modeling Releases to Groundwater 166
8.2 Allocating Waste Streams to Individual Injection Wells-
Stage IV Decision Tree 167
8.3 Estimating Releases from Injection Wells - Stage V
Decision Tree 169
REFERENCES 172
76
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VOLUME 4 - METHODS FOR ENUMERATING AND CHARACTERIZING POPULATIONS EXPOSED
TO CHEMICAL SUBSTANCES
77
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1
1.1 Purpose and Scope 1
1.2 Report Organization 1
1.3 Framework of Methods 2
2. POPULATIONS EXPOSED TO CHEMICAL SUBSTANCES IN THE AMBIENT
ENVIRONMENT 5
2.1 Introduction 5
2.2 Identification of Exposed Populations 5
2.3 Methods for the Enumeration of Exposed Populations... 9
2.3.1 Census of Population 9
2.3.2 Enumeration of Populations Exposed via
Inhalation 35
2.3.3 Enumeration of Populations Exposed via Dermal
Contact 56
2.3.4 Enumeration of Non-Human Populations 59
2.4 Characterization of Exposed Populations 61
2.4.1 Populations Exposed via Inhalation 61
2.4.2 Population Exposed via Dermal Contact 63
2.5 References 66
3. POPULATIONS EXPOSED TO CHEMICAL SUBSTANCES IN THE
OCCUPATIONAL ENVIRONMENT 69
3.1 Introduction 69
3.2 Identification of Exposed Populations 69
3.3 Methods for the Enumeration of Exposed Populations... 72
3.3.1 Enumeration of Populations Identified by SIC
Code 73
3.3.2 Enumeration of Populations Defined by
Occupation and Industry 77
3.3.3 Enumeration of Site-Specific Populations 79
3.4 Characterization of Occupatlonally Exposed Populations 82
3.5 References 87
79
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TABLE OF CONTENTS (Continued)
Page No.
4. POPULATIONS EXPOSED TO CHEMICAL SUBSTANCES VIA THE
INGESTION OF FOOD 89
4.1 Introduction 89
4.2 Identification of Exposed Populations 89
4.3 Methods for the Enumeration of Exposed Populations... 91
4.3.1 Enumeration of Populations Exposed as a Result
of Agricultural Practices 93
4.3.2 Enumeration of the Populations Exposed as a
Result of Processing and Packaging 94
4.3.3 Enumeration of Populations Exposed as a Result
of Releases from Other Sources 98
4.3.4 Enumeration of Exposed Populations by the Use
of Monitoring Data 106
4.4 Characterization of the Exposed Population Ill
4.5 References 115
5. POPULATIONS EXPOSED TO CHEMICAL SUBSTANCES VIA THE USE OF
CONSUMER PRODUCTS 117
5.1 Introduction 117
5.2 Identification of Exposed Populations 117
5.3 Methods for the Enumeration of Exposed Populations 120
5.3.1 Enumeration of Exposed Populations via Simmons
Market Research Bureau Reports 120
5.3.2 Enumeration of Exposed Populations via
Production and Sales Data 138
5.3.3 Enumeration of Exposed Populations via
Chemical-Specific Information 138
5.3.4 Enumeration of Consumers Performing Amateur or
Hobbyist Activities 141
5.4 Characterization of Exposed Populations 142
5.5 References 146
80
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TABLE OF CONTENTS (Continued)
Page No.
6. POPULATIONS EXPOSED TO CHEMICAL SUBSTANCES VIA THE INGESTION
OF DRINKING WATER 147
6.1 Introduction 147
6.2 Identification of Exposed Populations 149
6.3 Methods for the Enumeration of Exposed Populations 149
6.3.1 Enumeration of Populations 1n Specific
Geographic Areas 151
6.3.2 Enumeration of Populations Exposed via
Treatment Methods 160
6.3.3 Enumeration of Exposed Populations by Type of
Distribution System 163
6.3.4 Enumeration by Use of Monitoring Data 165
6.4 Characterization of Exposed Populations 168
6.5 References 169
APPENDIX A: APPLICA1ION OF METHODS TO EXAMPLE PROBLEMS 171
Introduction 173
A-l. Populations Exposed to Chemical Substances
In the Ambient Environment 174
A-2. Populations Exposed to Chemical Substances
1n the Occupational Environment 200
A-3. Populations Exposed to Chemical Substances
via the Ingestlon of Food 208
A-4. Populations Exposed to Chemical Substances
via the Use of Consumer Products 214
A-5. Populations Exposed to Chemical Substances
via the Ingestlon of Drinking Water 225
APPENDIX B: EXAMPLES OF DATA BASES USED IN OCCUPATIONAL
POPULATIONS METHODS SECTION 233
81
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VOLUME 5 - METHODS FOR ASSESSING EXPOSURES TO CHEMICAL SUBSTANCES IN
DRINKING WATER
83
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1-1
1.1 Purpose and Scope 1-1
1.2 Methodological Framework 1-2
2. DRINKING WATER SYSTEMS AND EXPOSURE PATHWAYS 2-1
2.1 Sources of Contamination 2-1
2.2 Drinking Water Supplies 2-1
2.3 Water Treatment Processes 2-6
2.4 Distribution Systems 2-8
2.5 Uses of Finished Water 2-9
2.6 Water Quality Requirements 2-9
3. IDENTIFICATION OF CONTAMINATED WATER SUPPLIES 3-1
3.1 Identification of Surface Water Supplies 3-1
3.1.1 Hydrologlcally Linked Data File
(HLDF) System 3-2
3.1.2 Federal Reporting Data System (FRDS) 3-22
3.2 Identification of Ground Water Supplies 3-24
3.2.1 Identifying Site-Specific Ground
Water Supplles 3-25
3.2.2 Identifying Nons1te-Spec1f1c
Ground Water Supplies 3-27
4. QUANTIFICATION OF RAW WATER CONCENTRATIONS
OF CHEMICAL SUBSTANCES 4-1
4.1 Monitoring Data 4-1
4.2 Estimation of Concentration 1n Surface Water 4-5
4.2.1 Conservative Estimate 4-5
4.2.2 Chemical Fate Models 4-11
4.3 Estimation of Concentration 1n Ground Water 4-22
4.3.1 Release Rate Models 4-23
4.3.2 Solute Transport Models 4-26
4.3.3 Practical Model Application 4-33
85
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TABLE OF CONTENTS
Page No.
5. CONCENTRATION OF CHEMICAL SUBSTANCES IN FINISHED WATER 5-1
5.1 Public Water Systems 5-1
5.1.1 Unit Processes 1n Water Treatment 5-1
5.1.2 Addition of Contamination during Water
Treatment and Distribution 5-28
5.1.3 Calculation of Finished Water
Contaminant Concentrations 5-33
5.2 Pr1 vate Systems 5-39
5.2.1 Guidelines for Selection of Suitable
Private Drinking Water Sources 5-40
5.2.2 Home Drinking Water Treatment Systems 5-40
6. EXPOSED POPULATIONS 6-1
6.1 Identification of Exposed Populations 6-1
6.2 Enumeration of Exposed Populations 6-2
6.3 Characterization of Exposed Populations 6-5
7. CALCULATION OF EXPOSURE 7-1
8. REFERENCES 8-1
86
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION
1.1 Purpose and Scope 1
1.2 Methodology Framework 1
1.3 Organization of the Report 4
2. Sources
2.1 Determining Chemical Manufacturing, Processing, and
Use Locations 8
2.2 Identifying Production and Use Processes and
Activities 8
2.2.1 Manufacturing 8
2.2.2 Processing 13
2.2.3 General Industrial Worker Activities 16
2.2.4 Activities of Wholesale and Retail Trade 19
3. MONITORING DATA 20
3.1 QA/QC Considerations 21
3.1.1 Sample Design 22
3.1.2 Sample Collection 22
3.1.3 Analytical Measurement Systems 22
3/1/4 Data Entry and Processing 23
3.2 Types of Monitoring 23
3.2.1 Personal/Breathing Zone Monitoring 24
3.2.2 Workplace or Area Monitoring 24
3.2.3 Biological Monitoring 24
3.3 Sample Collection Techniques 24
3.3.1 Types of Samples 25
3.3.2 Employees Sampled 25
3.4 Exposure Measurement Strategies 26
3.4.1 Sample Measurement 27
3.4.2 Length and Duration of Measurement 27
89
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TABLE OF CONTENTS (continued)
Page No.
3.5 Available Information on Occupational Exposure 29
3.5.1 National Institute of Occupational Safety and
Health 31
3.5.2 Occupational Safety and Health
Administration 35
3.6 Summary 37
4. ESTIMATING CONTAMINANT RELEASES IN THE OCCUPATIONAL
SETTING 39
4.1.2 The Mass Balance Approach 40
4.1.3 Estimating Releases 42
5. ENVIRONMENTAL FATE AND EXPOSURE PATHWAYS 60
5.1 Workplace Air Contaminant Fate Processes 60
5.1.1 Indoor Transport Processes 60
5.1.2 Indoor A1r Contaminant Removal Mechanisms 62
5.1.3 Outdoor Airborne Contaminant Fate Processes... 68
5.2 Estimating A1r Concentrations 1n the Indoor
Occupational Setting 70
5.3 Estimating A1r Concentrations 1n the Outdoor
Occupational Setting 77
5.3.1 Ground Level Releases 78
5.3.2 Vent Releases 80
6. EXPOSED POPULATIONS ANALYSIS 82
6.1 Identification and Enumeration of Exposed
Populations 82
6.1.1 Generic Identification and Enumeration Data ... 83
6.1.2 Specific Identification and Enumeration
Data 84
6.2 Population Characterization 85
6.3 Frequency and Duration of Occupational Exposure 85
6.3.1 Frequency and Duration 85
6.3.2 Workllfe 89
90
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TABLE OF CONTENTS (continued)
Page No.
CALCULATING EXPOSURE 96
7.1 Introduction 96
7.2 Inhalation Exposure 97
7.3 Dermal Exposure 101
7.3.1 Exposure to a Film of Liquid Deposited on
the Skin 101
7.3.2 Immersion 1n Liquids 102
7.3.3 Exposure to Dusts and Powders 102
7.4 Ingestlon Exposure 106
91
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1-1
1.1 Background and Purpose 1-1
1.2 Federal Regulatory Authority over Consumer Products 1-2
1.3 Consumer Products Considered by This Methods Report 1-6
1.4 Overview of Methodological Approach 1-15
2. PHYSICAL-CHEMICAL PROPERTIES 2-1
2.1 General Property Information 2-1
2.2 Data Gathering 2-1
2.2.1 Sources of Experimental Data 2-5
2.2.2 Methods for Estimating Physical-Chemical Properties.. 2-9
2.3 Summary 2-9
3. IDENTIFICATION OF CONSUMER PRODUCTS AND FORMULATIONS 3-1
4. METHODS FOR ESTIMATING RELEASE OF CHEMICALS FROM CONSUMER
PRODUCTS AND EXPOSURE CONCENTRATIONS 4-1
4.1 Overview of Exposure Pathways, Chemical Release Processes,
and Factors Affecting Exposure Concentrations 4-2
4.1.1 Chemical Release Processes 4-3
4.1.2 Factors Affecting Exposure Concentrations 4-5
4.2 Consumer Environment Monitoring Data 4-6
4.3 Methods to Estimate Contaminant Release from Consumer
Products 4-7
4.3.1 Release of Aerosols from Consumer Products 4-7
4.3.2 Chemical Release from Liquid Films 4-8
4.3.3 Chemical Release from Liquids and Solids 4-12
4.4 Methods for Calculating Exposure Concentrations 4-19
4.4.1 Concentrations Resulting from Instantaneous
Release of Chemicals 4-19
4.4.2 Concentrations Resulting from Continuous Release
of Chemicals 4-27
4.4.3 Direct Contact with Contaminant Source 4-30
4.5 Potential Refinements to Existing Methods 4-31
95
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TABLE OF CONTENTS (Continued)
Page No.
5. EXPOSED POPULATIONS 5-1
5.1 Identification of Exposed Populations 5-1
5.2 Enumeration of the Exposed Population 5-2
5.2.1 Enumeration of Exposure Populations via Simmons
Market Research Bureau Reports 5-2
5.2.2 Enumeration of Exposed Populations via Production
and Sales Data 5-4
5.2.3 Enumeration of Exposed Populations via Chemical-
Specific Information 5-4
5.3 Characterization of Exposed Populations 5-5
6. EXPOSURE ANALYSIS 6-1
6.1 Exposure Pathways and Routes 6-1
6.1.1 Inhalation Pathways 6-2
6.1.2 Dermal Pathways 6-3
6.1.3 Ingestlon Pathways 6-5
6.1.4 Other Pathways 6-7
6.2 Exposure Calculation 6-8
6.2.1 Frequency and Duration 6-8
6.2.2 Inhalation Exposure 6-11
6.2.3 Dermal Exposure 6-28
6.2.4 Ingestlon 6-35
6.3 Absorbed Dose 6-36
6.3.1 Inhalation 6-36
6.3.2 Dermal 6-36
6.3.3 Ingestlon 6-42
6.4 Exposure Scenarios 6-47
6.4.1 Inhalation Exposure Scenarios 6-48
6.4.2 Dermal Exposure Scenarios 6-49
6.4.3 Ingestlon Scenarios 6-49
7. REFERENCES 7-1
96
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TABLE OF CONTENTS (Continued)
Page No.
APPENDIX A. Consumer Exposure Scenarios
APPENDIX B. Exposure Assessment Data Sheets
APPENDIX C. Information Resource Summaries
APPENDIX D. Simmons Market Research Bureau (SMRB) Reports
97
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VOLUME 8 - METHODS FOR ASSESSING ENVIRONMENTAL PATHWAYS OF FOOD
CONTAMINATION
99
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1-1
1.1 Purpose and Scope 1-1
1.2 Organization of the Report 1-1
2. EXISTING METHODOLOGIES 2-1
2.1 U.S. EPA Office of Radiation Programs 2-1
2.2 U.S. EPA Office of Pesticide Programs 2-2
2.3 FDA 2-3
2.4 Summary 2-4
3.. OVERALL METHODOLOGICAL FRAMEWORK 3-1
3.1 Approach 3-1
3.1.1 General Discussion 3-1
3.1.2 Step by Step Approach 3-9
3.1.2.1 Step 1 Determine the Scope of the
Assessment 3-10
3.1.2.2 Step 2 Collect Available Residue for
Food 3-13
3.1.2.3 Step 3 Pathways Approach 3-13
3.1.2.4 Step 4 Estimate Concentrations 1n Food 3-13
3.1.2.5 Step 5 Compile Food Concentration Data 3-14
3.1.2.6 Step 6 Collect Appropriate Consumption
Data 3-14
3.1.2.7 Step 7 Estimate Individual Dietary
Intake 3-15
3.1.2.8 Step 8 Consider Population Exposed ... 3-15
3.2 Data Sources 3-16
3.2.1 Concentration Data 3-17
3.2.2 Consumption Data 3-17
3.2.3 Population Data 3-20
4. SUMMARY AND EXAMPLE 4-1
5. REFERENCES 5-1
101
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TABLE OF CONTENTS
Page No.
APPENDIX A - PATHWAYS OF FOOD CONTAMINATION A-l
APPENDIX B - QUANTITATIVE METHODS B-l
APPENDIX C - EXAMPLE OF PATHWAYS APPROACH AND QUANTITATIVE
METHODS C-l
102
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VOLUME 9 - METHODS FOR ESTIMATING EXPOSURE TO CHEMICAL SUBSTANCES
RESULTING FROM TRANSPORTATION-RELATED SPILLS
103
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TABLE OF CONTENTS
Page No.
1. INTRODUCTION 1
2. GENERAL METHODOLOGY 2
2.1 Probability of a Spill 3
2.2 Quantity Spilled 4
2.3 Extent of Exposure 5
2.4 Environmental Releases 6
2.5 Spill Exposure Assessment Methodology 7
2.6 Conclusions 8
3. DETERMINATION OF COMMODITY SHIPPING PATTERNS 9
3.1 Importation of Commodities 9
3.1.1 Major Ports of Entry for Imported Goods 9
3.1.2 Domestic Transportation of Imported Goods 13
3.2 Estimation of Shipping Distance 15
3.2.1 Sources of Information for Average Shipping Distances
of Commodities by Mode of Transportation 15
3.2.2 Methods for Estimating Average Shipping Distances . 21
4. SPILLS FROM BARGES 31
4.1 Spill Risks from Barges 31
4.1.1 Barge Design 32
4.1.2 Barge Accident Statistics 32
4.2 Quantity Spilled from Barges 35
4.2.1 Amount of Material Shipped by Barge 35
4.2.2 Average Quantity Released 1n Each Barge 35
4.3 Human Exposure to Spills from Barges 40
4.4 Environmental Releases from Barge Spills 40
5. SPILLS FROM HIGHWAY TRUCKS 41
5.1 Accident Type and Frequency 44
5.2 Quantity Spilled from Trucks 50
5.3 Human Exposure to Spills from Trucks 52
5.4 Environmental Release of Chemicals Spilled from Trucks ... 53
105
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TABLE OF CONTENTS (Continued)
Page No.
6. SPILLS FROM RAILROAD CARS 54
6.1 Sp111 Occurrences from Rail road Cars 54
6.2 Quantity Spilled from Railroad Cars 59
6.3 Human Exposure from Railroad Spills 59
6.4 Environmental Release of Chemicals from Railroad Spills .. 60
7. DEMONSTRATION OF METHODOLOGY 61
7.1 Transportation Spills of D1-(2-ethylhexyl) Phthalate 61
7.1.1 Spills of DEHP from Railroad Tank Cars 61
7.1.2 Spills of DEHP from Trucks 63
7.1.3 Summary 66
7.2 Transportation Spills of Formaldehyde 66
7.2.1 Spills of Formaldehyde from Railroad Tank Cars 70
7.2.2 Spills of Formaldehyde from Trucks 72
7.2.3 Summary 73
8. SUMMARY AND CONCLUSIONS 75
9. REFERENCES 76
106
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA 560/5-85-001
3. Recipient's Accession No.
4. Title and Subtitle
Methods for Assessing Exposure to Chemical Substances
Volume 1 : Introduction
5. Report Date
7/P.Fi
7. Author Michael A. Callahan, Gina H. Dixon, Stephen H. Nacht,
Douglas A. Dixon, John .1. Don'a
8. Performing Organization Rept. No.
9. Performing Organization Name and Address
Versar, Inc.
6850 Versar Center
Springfield, Virginia 22151
10. Project/Task/Work Unit No.
Task 9
11. Contract(C) or Grant(G) No.
(o EPA 68-02-3968
(G)
12. Sponsoring Organization Name and Address
13. Type of Report & Period Covered
U.S. Environmental Protection Agency
Office of Toxic Substances
Exposure Evaluation Division
Washinnt.nn. D.r. 70460
Final Report
14.
15. Supplementary Notes
EPA Project Officer for this report was Michael A. Callahan
16. Abstract (Limit: 200 words)
This document is the first in a series of volumes developed for the U.S.
Environmental Protection Agency, Office of Toxic Substances to assist in the
assessment of exposure to chemical substances. This introductory volume discusses
issues of general interest in all exposure assessments, including a discussion on
planning an assessment,and summarizes the contents of the next eight volumes.
Planning an exposure assessment is a function of the purpose, scope, depth, and
approach of the assessment. The report presents a list of questions that, when answered,
aid the assessor in determining the resources and tools needed to do the assessment.
The organization of an exposure assessment is discussed, and a basic outline that can
be used is provided. The content of major sections in an exposure assessment are
discussed: General Information, Sources, Exposure Pathways and Environmental Fate,
Monitoring or Estimated Concentrations, Exposed Populations, and the Integrated
Exposure Analysis. An overview of exposure assessments in different settings is
presented. Different types of assessments (screening level, intermediate level,
detailed, and special assessments) are described.
17. Document Analysis a. Descriptors
b. Identifiers/Open-Ended Terms
Exposure Assessment
Toxic Substances
Exposure Assessment Methods
c. COSATI Field/Group 44C
18. Availability Statement
Distribution Unlimited
19. Security Class (This Report)
Unclassified
20. Security Class (This Page)
21. No. of Pages
106
22. Price
(SeeANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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US EPA Region 5
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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