<pubnumber>645D81007</pubnumber>
<title>Handbook For Performing Exposure Assessment Draft</title>
<pages>166</pages>
<pubyear>1981</pubyear>
<provider>NEPIS</provider>
<access>online</access>
<origin>hardcopy</origin>
<author></author>
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<abstract></abstract>
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United States	DRAFT
Environmental Protection	OfIFA-' -011
Agen€V	DECEM m 1981
&ER& Research and
Development
HANDBOOK FOR PERFORMING EXPOSURE ASSESSMENTS
Prepared for
PROGRAM OFFICES OF HE U.S. ENVIRONMENTAL
PROTECTION AGENCY
Prepared by
Office of Health and
Environmental Assessment
Washington DC 20460
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e?>f oyj-y
DRAFT
DO NOT QUOTE OR CITE
i r
HANDBOOK FOR
-. i
/
PERFORMING
EXPOSURE ASSESSMENTS
Compiled by
Exposure Assessment Group
Office of Health and Environmental Assessment
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Washington, H.C. 20460
NOTICE
This document is a preliminary draft. It has not been formally released by
EPA and should not at tnis stage be construed to represent Agency policy. It
is being circulated for comment on its technical accuracy and policy
imp!i cati ons.
December 1981
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CONTENTS
FOREWARD	1v
ABSTRACT 	v
ACKNOWLEDGEMENT	vi
I. INTRODUCTION	1-1
II. ORGANIZATION OF EXPOSURE ASSESSMENTS	II-l
A.	Outline of Typical Exposure Assessment Procedures	II-l
from Various EPA Program Offices
Office of Pesticide Programs	II-l
Office of Air Ouality Planning and Standards 		II-1D
Pollutant Assessment Branch	11-10
Ambient Standards Branch	11-11
Office of Radiation Programs	11-16
Office of Toxic Substances 		11-20
Office of Water Regulation and Standards	11-24
B.	Exposure Assessment Activities of Other Federal 		11-28
Regulatory Agencies
III. MODELS EMPLOYED	I II-l
IV. MONITORING EMPLOYED 		IV-1
A.	Monitoring Methods 		IV-1
B.	Data Bases			IV-2
C.	Ongoing Monitoring Activity	IV-5
V. TREATMENT OF UNCERTAINTY	V-l
VI. GLOSSARY OF TERMS USEO	VI-1
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VII. STANDARD FACTORS	VI I-1
A.	Biological Parameters	VII-1
B.	Economic Parameters	V11-3
C.	Chemical Parameters	VI1-8
D.	Physical Parameters 		VI1-9
Appendix A - Guidance for the Preparation of Exposure Assessments
Appendix B - Examples of Exposure Assessments From the Program Offices
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DISCLAIMER
This report is an internal draft for review purposes only and does not
constitute Agency policy. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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FOREWARD
The Exposure Assessment Group is a newly formed office in EPA whose
function is to provide expert scientific oversight of the assessments made by
the various Agency programs of the exposure of humans to toxic substances.
These assessments are critical to the evaluation of the public health risks
that are presented by these toxic substances, to the development of
regulations to protect against the hazards they present, and for the
establishment of research priorities.
In order to define the qualitative and quantitative aspects of an exposure
assessment, Guidelines have been formulated by which the Agency will conduct
assessments in the future. Because these Guidelines fulfill the various needs
of all the Program Offices, they contain general policy/procedure statements.
The following Handbook has been constructed by the Exposure Assessment Group
to provide more specific details of how exposure assessments are to be
performed. Thus, the Handbook can be viewed as directly related to the
Guidelines with both documents helpful for understanding the Agency approach
in conducting exposure assessments.
James W. Falco, Director
Exposure Assessment Group
i v
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ABSTRACT
This Exposure Assessment Handbook was constructed to provide specific
details of how the Agency conducts exposure assessments. The Office of
Pesticide Programs, Office of Air Quality Planning and Standards, Office of
Radiation Programs, Office of Toxic Substances, and the Office of Water
Regulation and Standards have all described their exposure assessment
procedures plus have provided recent examples of their exposure work.
The Handbook also contains a glossary of terms routinely employed,
standard factors used in calculations, examples of modeling and monitoring
studies, and a discussion of how to calculate the uncertainties or errors.
Since the Handbook was designed to expand upon the concepts of the Exposure
Assessment Guidelines, the Guidelines are also included in an appendix to the
Handbook for reference.
v
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ACKNOWLEDGMENTS
The original ideas for the Handbook were suggested by the Director of the
Office of Health and Environmental Assessment, Dr. Elizabeth Anderson.
Ms. Jennifer Craig, a summer intern student, compiled available exposure
information into a rough draft. Or. Alan Senzel constructed the Glossary,
plus did technical editing. Mr. Frank Letkiewicz headed an effort by JRB,
Inc., to complete the first draft, working extensively on the Models and
Uncertainty Sections.
Special thanks to Ms. Judy Theisen and Mrs. Beverly Farmarco for their
patience and support throughout this project.
vi
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I. INTRODUCTION
Under the authorities provided by such statutes as the Toxic Substances
Control Act; the Clean Air Act; the Federal Water Pollution Control Act; the
Safe Drinking Water Act; the Federal Insecticide, Fungicide, and Rodenticide
Act; and the Atomic Energy Act, the U.S. Environmental Protection Agency (EPA)
is responsible for identifying, evaluating, and regulating a variety of chemical
and radiological hazards to human health and the environment. Exposure
assessments are an essential component of the regulatory decision-making process
for understanding and quantifying the nature and magnitude of the hazards
presented by environmental agents and for discerning the most suitable control
options both from a technological and regulatory standpoint.
Although there is a substantial history of exposure assessments conducted by
the various EPA program offices to support both programmatic and regulatory
decisions, there is, at the present time, no clear consensus on how exposure
assessments should be conducted. The recognition of the importance of exposure
assessments to the Agency's mission and the need for a more coordinated and
consistent approach to conducting them by the various program offices led to the
formation of the Exposure Assessment Group within the Office of Research and
Development's Office of Health and Environmental Assessment. The role of the
Exposure Assessment Group is to provide overall guidance and procedures to the
Agency for conducting exposure assessments, to ensure the quality of the
exposure assessments conducted by EPA, and, when needed, to provide independent
assessments of exposure to specific agents. An Agency-wide Exposure Assessment
Work Group was also formed to provide for the full input of the various EPA
program offices to the development of the Exposure Assessment Group.
The initial product of the Exposure Assessment Group and the Exposure
1-1
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Assessment Work Group is a document entitled "Guidance for the Preparation of
Exposure Assessments" (see Appendix A). This guidance document provides an
overview of the kinds of data that should, in most cases, be considered in an
exposure assessment. The guidance document also suggests a format for
organizing and presenting those data. It is intended that the guidance document
will promote consistency in EPA's exposure assessments by providing a uniform
approach.
The present document -- "The Exposure Assessment Handbook" -- was created to
accompany the guidance document. Whereas the guidance document addresses the
requirements of exposure assessments in general terms, this Handbook provides
more practical guidance for the preparation of exposure assessments through the
presentation of specific examples and detailed discussion of some key aspects of
exposure assessments. It must be recognized that exposure assessment is a
rapidly evolving area that will certainly undergo significant changes over the
ensuing months and years. This Handbook and the guidance document that
accompanies it will necessarily be revised to reflect the changes and
developments that occur.
This Handbook begins with a discussion of exposure assessment needs and
procedures of the key EPA program offices: Toxic Substances, Pesticides
Programs, Water Regulation and Standards, Air Quality Planning and Standards,
and Radiation Programs. Examples of current exposure assessments from these
offices are provided in Appendix B, with brief discussions of their content.
There is also a brief discussion on exposure assessment activities of the other
regulatory agencies that comprise the Interagency Regulatory Liaison Group.
The next section provides summary level information on models that may be of
interest in planning exposure assessments. Included is information that could
apply to modeling needs of the user of the Handbook. For example, mathematical
1-2
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descriptions of commonly used elements (e.g., Gaussian dispersion, Sriggs plume
behavior, liquid to vapor phase mass transfer, laminar and turbulent flow, etc.)
could be readily appended to this section of the Handbook.
The Handbook also contains a listing and description of some data bases that
contain useful data on the monitoring and measurement of substances in the
environment. The ensuing section elaborates on uncertainty in exposure
assessment, and the different types of deficiencies apparent in the input data
or the assumed values. A discussion of the utility of sensitivity analysis in
bracketing estimates is also included.
In an attempt to standardize definitions of terms used in exposure
assessments, a glossary has been constructed. Similarly, an attempt has been
made to establish a set of standard (numerical and other) factors for use in
present and future exposure assessments. The use of a basic set of factors
would facilitate assimilation of the quantitative components of an exposure
assessment and the cross-comparison and cross-utilization of the results.
1-3
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II. ORGANIZATION OF EXPOSURE ASSESSMENTS
A. OUTLINE OF TYPICAL EXPOSURE ASSESSMENT PROCEDURES FROM VARIOUS PROGRAM
OFFICES
Each Program Office contributed to the development of the Exposure
Assessment Guidelines (Appendix A) which suggest methods for conducting exposure
assessments for ideal situations. For those readers who are not familiar with
these Guidelines, it is suggested that they be read first.
In this section, the Program Offices were asked to describe their typical
exposure assessment procedures. It is evident that each Program Office has its
own goal with the particular end use and the availability of data dictating the
scope of the assessment.
A thorough review of how each Program Office performs hazard, exposure, and
risk assessments was recently conducted by a contractor (Clement Associates,
Inc.) for OPTS. This report is still in draft form under the title "Review and
Analysis of Hazard, Exposure, and Risk Assessment as practiced by EPA and other
Federal Regulatory Agencies." When finalized, the report will present a
critical analysis of the exposure assessment activities of the Agency.
Office of Pesticide Programs
Purpose--
The following discussion gives the purpose of and procedures used for
preparing exposure assessments for pesticides as part of regulatory activity
under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). These
assessments are prepared by the Environmental Fate Branch of the Hazard
Evaluation Division, Office of Pesticides and Toxic Substances.
The overall goal of a pesticide exposure assessment is to provide the input
necessary for risk assessment. The requirement for exposure assessments is
II-l
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stated in the FIFRA regulations describing the Rebuttable Presumption Against
Registration (RPAR) process, at 40 CFR 162.11. The "Interim Guidelines for
Cancer Risk Assessment," published in May 1976, also specify exposure
information needed for risk assessment. The exposure assessments are used to
prepare risk assessments for chronic human health effects such as cancer, and
also for potentially single-dose toxic effects such as teratogenicity,
reproductive effects, and neurotoxicity.
Exposure assessments prepared under the mandate of FIFRA are limited to the
use of chemicals as pesticides. Exposure from other types of uses, or from
manufacture, formulation, transportation, and disposal, are not generally
considered. In practice, the assessments have been concerned with several
categories of exposed persons:
o the general population exposed through pesticide residues in the food
supply, as well as exposure through air and drinking water contamination
o agricultural applicators, mixer/loaders, and flaggers exposed as a result
of their direct contact with the pesticide
o fieldworkers, harvesters, and others exposed upon re-entering treated
areas
o bystanders or nearby populations exposed as a result of pesticide drift
from the target area
o industrial and institutional users of pesticides
o home users of pesticides and residents of homes in which pesticides have
been used
Procedure—
The information required for a pesticide exposure assessment is of two
general types: information about the use pattern of the pesticide and actual
data on dose of chemical received. The first of these is outlined in Table
11-1. This information is generally received from the Benefits and Field
Studies Division of OPP.
11-2
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Actual field data on pesticide exposure is obtained from several sources:
the published literature; specific studies submitted by pesticide registrants;
field studies conducted by EPA; monitoring studies for food, water, air, human
blood, urine, or adipose tissue; etc. The Environmental Fate Branch (EFB)
maintains an extensive file of pesticide exposure data, and continuously scans
the current literature for new information on exposure methodology and results.
Worldwide literature searches are also conducted for each pesticide exposure
assessment. In some cases, the Hazard Evaluation Division (HED) will fund
specific field studies designed to answer more general questions relating to
pesticide exposure. The EFB staff may advise registrants regarding the types of
exposure information needed and on methods and field procedures for measuring
exposure.
The basic residue data used for a human dietary exposure analysis of a
pesticidal chemical compound are the pesticide tolerance; Food and Drug
Administration and U.S. Department of Agriculture compliance, market basket, and
surveillance data; data from controlled field studies submitted with petitions
for tolerances under the Federal Food, Drug, and Cosmetic Act; company conducted
market basket survey data; EPA monitoring survey data; and the open literature.
The data base of pesticide exposure information is currently expanding very
rapidly. In the near future the entire data base will be abstracted into a
storage and retrieval system which will accommodate it in a more accessible
format.
11-3
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TABLE II-l. USE/USAGE INFORMATION REQUIRED FOR PESTICIDE EXPOSURE ASSESSMENT
Assessment of exposure of pesticide applicators, fieldworkers, ana nearby
populations to pesticides requires information on use practices and extent of
use. T'ne following is a general list of the kinds of information that
contribute to this assessment.
For each use to be analyzed for exposure:
1.	Pesticide label
2.	Types of pesticide formulations used (emulsifiable concentrates, dusts,
granules, etc.)
3.	Packaging information (for example, 5 lb sack of 25% dust, 55 gal drum of 4%
emulsifiable concentrate, etc.)
4.	Methods of mixing and loading (such as open or closed system transfer to
application equipment, pouring dust into hopper, etc.)
5.	Application rates and dilutions (for example, 1 lb per acre active
ingredient in 500 gal water)
6.	Application schedules (when applied during growing season; how often)
7.	Application techniques
description of apparatus used (such as air blast sprayer, hi-boy rig,
backpack sprayer, indoor aerosol spray,
etc.)
common practices during application (spray pressure, speed of spray rig,
soil incorporation practices, type of spray
coverage, etc.)
8.	Number of personnel involved in application and their identity (farmers,
commercial applicators, homeowners, etc.)
9.	Extent of use (total acres treated per year, total pounds used, etc.)
10.	Description of associated personnel used in application (mixer/1oaders,
fl aggers, etc.)
11.	Estimates of duration of exposure including any patterns of exposure
(for example, 10 hours per day for 15 days in March or April; acres per hour
that can be treated)
12.	Information on protective clothing in common use
11-4
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TABLE IT-1 Continued
13.	Percent of crop treated, consumed on farm, exported, etc.
14.	Brief description of important activities at the site following application
(cultivation, application of other agricultural chemicals, harvest
schedules, etc.)
15.	History of past incidents which indicate propensity for non-adherence to
label directions and frequency of accidental exposure.
11-5
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A number of methods have been developed to measure actual exposure to
pesticides under field conditions. The EF3 maintains a separate file of
descriptions of these methods as well as examples of field study designs for
specific exposure monitoring situations. Although there is no single best
method for all exposure situations, the best current practice appears to be as
fol 1 ows:
dermal : Pads made from alpha-cellulose (for dermal exposure to sprays) or
layers of gauze (for exposure to dusts or particulates) are attached to the
forearms, chest, back, thighs, and perhaps the forehead or a combination
pad made by placing gauze over alpha-cellulose (for exposure to dry
formulation while being mixed into a liquid solution) are attached to the
forearms, chest, back, thighs, and perhaps the forehead. The efficiency of
protective clothing might be determined by placing pads under as well as
over any protective equipment. These are collected for pesticide residue
analysis after the period of exposure. The results can be converted to a
mill igram-per-square-centimeter dermal dose; when multiplied by standard
body surface areas, the rate of dermal contact may be estimated. For the
hands, which generally receive the highest dermal exposure during actual
operations with pesticides, both measurement of residues on cotton or nylon
gloves and hand washing with 95% ethanol have been used.
inhalation: Both respirators and personal air sampling devices have been
used to sample air in the breathing zones of exposed persons. The former
give a direct measure of the amount of pesticide that would have been
inhaled, while the latter result in an air concentration that must be
multiplied by an assumed breathing rate in order to obtain a value of the
inhalation exposure. A number of studies are available which evaluate
absorbents available for use in air sampling devices. In situations where
it is important to measure air concentrations of pesticides that may be
present at very low levels, high-volume air samplers should be employed
to ensure the collection of an adequate sample volume. For both dermal and
inhalation exposure measurements, the Office of Research and Development has
prepared detailed reviews of the methods used by their laboratories.
oral: The goal of the oral (dietary) exposure assessment is to predict the
pesticide residues in or on food as consumed. Projections of pesticide
residues in food as consumed can be made if it is known where the pesticide
was applied; the amount applied; what residue losses in commerce,
processing, cooking, etc., are expected; and the time interval from
application until consumption. Tables of food consumption and data on the
extent to which crops are currently treated with the pesticide of interest
are used to calculate the contribution of residues to the diet for each crop
treated. The results of such calculations are summed over all the foods
bearing residues of the pesticide to yield, for a national average, a rate
of ingestion (mg/person/day).
urine: The above routes of exposure are all direct; that is, they result in
measurment of the actual amount of pesticide residue with which a person may
11-6
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come into contact. The appearance of pesticide residues and/or metabolites
in human urine, however, is prima facie evidence of exposure; when data on
the metabolism and the efficiency of excretion is available, the exposure
may be calculated from the amountexcreted. This indirect method of exposure
measurement can be more precisethan the above direct methods; however, it
cannot identify the route ofexposure.
other body tissues: Pesticide residues in blood, adipose tissue, or other
body tissues are often available as evidence of exposure. Adipose tissue
residues are generally limited to 1ipid-soluble and stable pesticides such
as the chlorinated hydrocarbons, which tend to accumulate in these tissues.
Since these residues may be stored over a long period of time, they indicate
continuous exposure rather than the more instantaneous type of exposure that
is measured by the direct methods discussed above. Blood levels of
pesticides are sometimes available; these indicate an immediate type of
exposure since blood is rapidly circulated and cleared by the kidneys.
The exposure estimates for the three routes of exposure are combined to
produce the total exposure assessment. Alternatively, urinary excretion data
might be used to back-calculate the total exposure by all routes, if adequate
information on the pharmacodynamics of the pesticide in humans or animals is
available. For dermal exposure, an estimate of skin absorption is necessary to
arrive at the actual dose by this route; very little data on human skin
penetration rates are available. The units of the dermal and inhalation
exposure are usually expressed in milligrams per hour of exposure-related
activity; when multiplied by the estimated duration of the activity (obtained
from the use data in Table 11-1) and divided by a standard body weight, the
units become milligrams per kilogram per day or per year, depending on whether
the risk assessment addresses single-dose or chronic effects.
Considerable judgment is necessary in order to complete a pesticide exposure
assessment. The evaluation of limited field monitoring data, the influence of
varying meteorological conditions, the use and efficiency of protective
clothing, the use and efficiency of closed mixing/loading/transfer systems, the
largely unknown absorption rates of chemicals through the skin, varying particle
size which affects respiratory exposure, the sporadic but potentially enormous
11-7
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exposure resulting from pesticide leaks and spills, and varying human activity
patterns are all natters of judgment that influence the numerical outcome of the
assessment. A primary requirement of the assessment is to state clearly all
assumptions used to derive the calculated exposure, and, if possible, to give an
estimate of the numerical variability.
Numerical assessments of exposure will often be requested in situations for
which actual field monitoring data are not available. In such cases, a search
of the EFB's exposure data base may reveal data for other similar pesticides
applied under similar circumstances. If the use practices associated with these
measurements are sufficiently similar to those for the pesticide in question,
then a reasonable estimate of exposure may possibly be made, based on the
"surrogate" data.
Procedures for estimating environmental mobility of the pesticide when
experimental data are lacking are available. Computer models for calculating
estimated environmental concentrations (EEC's) from known physical chemical
parameters, along with hydrologic, and metorological data provide information on
the potential movement of pesticides from the site of application via spray
drift, leaching, surface runoff, and unscheduled field flushings. The EEC's are
relevant to human exposure in that potential concentrations of pesticides in
groundwater and surface potable water supplies can be estimated.
Alternatively, exposure may perhaps be calculated from basic physical
properties, such as vapor pressure, by assuming reasonable values of volatility
rates, air circulation patterns, or other information necessary to make a
calculation. These types of procedures clearly call for additional levels of
judgment; such assessment procedures might or might not be attempted, depending
on the nature of the regulatory question.
The general format of pesticide exposure assessments is given in Table 11-2.
11-8
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TABLE 11-2. FORMAT OF THE EXPOSURE ASSESSMENT
1.	Include the common name, important trade names, the structure, relevant
physical properties (generally volatility, solubility, and perhaps partition
coefficient), and other pertinent information such as important metabolites
or degradation products, common impurities, significant inert ingredients in
formulations, etc.
A brief review of the environmental fate and transport of the pesticide
(typically the more important conclusions from the environmental fate
profi1e).
A brief overview of common formulations and use patterns.
Established tolerances.
2.	Exposure through use: For each use, this section contains estimated values
of dermal and inhalation exposure, either from actual field monitoring
studies or derived from data obtained for other pesticides under the same
use conditions. These estimated values are then combined to produce a unit
exposure, as discussed above under Procedure. In general, some estimate of
the possible range of the values should be included. In some cases, no
useful data whatsoever may be available; in such cases, the exposure
assessment should so indicate, and, if possible, suggest how data might be
obtained. No exposure estimate would be prepared in these cases.
The total exposure is then computed by multiplying the unit exposure by the
duration of exposure and then adding in the dietary contribution.
Information on the number of people exposed, and, if appropriate, some
indication of the sporadic or chronic nature of the exposure should also be
included. Thus, the exposure assessment ideally includes the levels at
which people are exposed, the number of people so exposed, and the duration
of the exposure.
3.	Summary table: Lists the use patterns, the unit exposures, the number of
people, and the total daily and annual exposure. The specific dietary
burden for each crop is listed, as well as the total residue contribution.
4.	Bibliography
11-9
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Office of..Air Quality Planning and Standards
Pollutant Assessment Sranch--
Purpose--In the Office of Air Quality Planning and Standards (OAQPS), the
Pollutant Assessment Branch of the Strategies and Air Standards Division is
responsible for performing exposure assessments for hazardous pollutants under
the authority of Section 112 of the Clean Air Act. Hazardous pollutant
standards are health-based, using "ample margin of safety to protect the public
health" as the criterion. Procedures in the proposed Airborne Carcinogen Policy
(44 FR 58642) further define and elucidate exposure assessment needs for
hazardous pollutants.
In regulating hazardous pollutants, exposure assessments are necessary to
show public health impact. Anbient air is the medium of concern, so the general
population is the group surveyed. Sources of air pollution fall into three
categories: point sources, area sources which are generally small but numerous
and of a specified location, and sources which are numerous but of unspecified
location (generally called prototypical sources).
Procedures--Exposure assessments are performed by gathering available data
on source locations and emissions, applying diffusion modeling techniques to
these, and then calculating population exposure to the emissions. Source
location and emission data are gathered through literature search,
trade/technical journals, state/local agencies, and industry contact. Local
meteorology is used where possible, and most recent census data are used to
determine population profiles.
Monitoring is undertaken as an integral part of the exposure assessment only
on a selected basis because of the time and expense involved, and the vagaries
of meteorology. Furthermore, when monitoring is performed, it generally is to
provide confirmatory information supporting regulation rather than to serve as
11-10
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the basis for regulation.
The exposure- assessments done by the Pollutant Assessment	Branch are most
commonly level I types. Their purpose is to estimate the number of persons
exposed to various concentration levels of a pollutant. This	information, along
with input from the Carcinogen Assessment Group, is presented	as evidence for
the Administrator's decision whether to list the substance as	a hazardous
pollutant or not.
Ambient Standards Branch--
Purpose--Section 109 of the Clean Air Act pertains to the establishment of
National Ambient Air Quality Standards (NAAQS). In setting primary ambient air
quality standards, it should be the judgment of the EPA that the attainment and
maintenance of such standards, "allowing an adequate margin of safety, are
requisite to protect the public health." The most meaningful indicator of
margin of safety is a risk assessment of alternative ambient air quality
standards. This risk assessment explicitly accounts for uncertainty of
scientific information concerning adverse health effects and population
exposures. An exposure assessment is an inherent component of a risk
assessment.
The exposure assessments relevant to Section 109 of the Clean Air Act are
conducted by the Ambient Standards Branch of the Strategies and Air Standards
Division of OAQPS. These exposure assessments serve two major purposes: 1) to
support ongoing NAAQS reviews (e.g., for substances such as SO2, CO,
NO?), and 2) to develop an exposure assessment capability to be a part of a
risk assessment methodology currently under development. (The models employed
become more refined with increasing experience in exposure assessment; thus, the
overall quality of exposure assessments improves with time.)
In general, the exposure assessment is intended to estimate the distribution
11-11
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of expected number of human exposures in a given geographical area to any
desired time-averaged ambient pollutant concentration (up to a one-year time
period) at any specified air quality level. The exposure model can be used to
estimate exposures at base year ambient concentrations or future year levels
when an area is in compliance with a given alternative national ambient air
quality standard.
In practice, exposure to a particular pollutant (such as CO) is estimated
for several selected U.S. cities. A typical study area consists of a city and
several suburbs. The findings are then extrapolated to the entire U.S. urban
population of roughly 140 million people. Exposures to rural populations are
not analyzed, as insufficient data from rural areas are available.
Procedure—
Sources of in formation--Some important sources of information for exposure
assessments are listed below.
Census Bureau	Population data, including
age and occupation data
Storage and Retrival of. . . Monitoring data
Aeromatric Data (SAROAD)
Stanford Research Institute,
International (SRI). . . . Time budget studies
Project Engineering Development
Company (PEDCO)	 Analysis of pollutant concentration data
Three major data bases contribute to the exposure assessment. These are
identified below:
1. Pollutant Concentration Data Base
A year is selected for which adequate data are available relevant
to the study area of concern. The SAROAD network (administered by the states)
11-12
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is the source of hourly pollutant concentration data for a one-year period. A
monitoring network exists throughout the study area in order to measure legal
compliance to existing standards. (It is recognized that the monitoring network
does not measure air quality in between monitor locations. Various mathematical
interpolation techniques are used to fill in data gaps.)
Human dosimetry is not employed, as this technique is not yet adequately
developed. The monitoring data is convenient to obtain, as the networks are in
place and are collecting data on an ongoing basis.
2. Human Activity Data Base
Time budget studies (provided by SRI) are conducted to learn how
people spend their time. Currently, people in the study area are considered to
be distributed among five microenvironments:
indoor work
other indoors
inside transportation vehicles
other transportation along roads
other outdoors
The concept of microenvironments is being further refined, and in the near
future AS8 expects to be working with approximately 20 microenvironments for the
populations of interest.
The age and occupation data from the Census Bureau is used to generate 12
age and occupation categories. Using the time budget information and urban
transportation planning data, the fraction of people in each of the 12
categories is determined for the five microenvironments for each hour of the
day.
Furthermore, an estimate is made of the fractions of people at each of three
levels of activity: low (e.g., sitting, lying down), medium (walking), and high
11-13
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(jogging, tennis, etc.)- Thus, a person is considered to be in i of 15 possible
situations at any given time (5 microenvironments x 3 levels of activity). Some
of these situations are null categories (e.g., being inside a transportation
vehicle at a high level of activity).
For longer averaging periods (such as 8 hours), it is not sufficient to
estimate fractions of people in various microenvironments and activity levels;
rather it becomes necessary to follow various types of people through their
activities during the period of interest.
In organizing the data, there are separate sets of data for the three
climatologic regions of the U.S. and for weekdays versus weekends.
3. Population Data Base
This information consists of the number of people living in the
study area, the number in each sector, and the numbers in the 12 age and
occupation categories.
The monitoring network provides base values for pollutant concentrations.
These base values are transformed for each microenvironment depending upon its
relationship to the nearest monitoring station(s). For example, if the
pollutant is carbon monoxide and the microenvironment is the interior of an
automobile, the base value is multiplied by a factor greater than one. Such a
transformation follows from the fact that the monitoring stations are located at
fixed points outdoors and that the carbon monoxide levels are higher within
vehicles and along roads. Alternatively, a pollutant concentration value may be
obtained by interpolation between values taken from two monitoring stations.
Another important consideration is transportation patterns. People will not
only pass between microenvironments in a given sector, but will also move from
one sector into another where different base values will be obtained. For
instance, many people will commute from the suburbs or countryside into the
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heart of the city during the course of a day. In addition, they are likely to
be in a number of microe.nvi ronments within each geographical sector.
Using the model described above, it is the task of the Ambient Standards
3ranch to determine the present exposure of urban populations to air pollutants
and to determine how exposure changes under various alternative control
standards that may be implemented.
In addition, the data for a one-year period are used to project ambient air
concentrations for future years. This area contains considerable uncertainty as
the air concentrations of pollutants are highly dependent upon meteorological
conditions. The data base over the one-year period is used to develop a
probability distribution for future concentrations of air pollutants.
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Office of Radiation Programs
Purpose—
The overall goals of radioactive exposure assessments conducted by the
Office of Radiation Programs are to determine the health effects that result
from radioactive emissions, and to determine whether it is cost effective to
introduce control measures to reduce those emissions in the interest of
protecting the public health.
Although the problems of reactor safety are handled by the Nuclear
Regulatory Commission (NRC), authority over radioactivity in the environment is
within the jurisdiction of the EPA under the National Environmental Policy Act
(NEPA) of 1969. In addition, the Clean Air Act amendments enacted in August
1977, gave the EPA authority to establish standards to control emissions of
radioactive pollutants into the atmosphere and to regulate radioactive
pol1utants.
The scope of the environmental exposure assessments performed by the Office
of Radiation Programs is 1) to determine the isotopic composition of the
radioactive source term, the physical states in which those radionuclides are
emitted, the rates at which they are emitted, the models by which they diffuse
and are absorbed in the environment, the pathways of exposure, individual and
population exposures; 2) to make risk and health effects analyses; and 3) to
perform assessments of the requirement for controls in the interest of public
health.
Procedure—
Sources of information—Although the overall scope of environme.ntal
assessments is essentially the same for all source terms, the details of
developing the data for these broad areas often differ widely. For example,
solid, liquid, and gaseous radioactive effluents containing many radionuclides
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are emitted from nuclear reactors and expose populations through the pathways of
inhalation, ingestion, and direct radiation. On the other hand, the mining,
storage, and combustion of natural gas are concerned with radon and its daughter
products, which expose the population to radioactivity essentially through the
inhalation pathway. In the development of an environmental assessment, data are
drawn from the following sources:
Nuclear Regulatory Commission	reactor emission data
Bureau of Mines	mineral and energy production data
Mine Safety & Health Administration, .radon concentration & ventilation data
Oak Ridge National Laboratory	dose conversion factors
National Academy of Sciences	health risk data
Department of Energy	energy and environmental data
Corps of Engineers, Dept. of Army . . waterways impoundment data
Weather Bureau	meteorological data
Nuclear Reactor Facilities	environmental, dose, and source data
State Health Departments	environmental data
In addition, the following data are obtained from field and laboratory
measurements (see reference 1 for analysis methods):
o stack gas velocity and volume flow rate by EPA method 2
o integrated gas sampling for radon emission from sources by EPA method 3
o particulate emission rate by EPA method 5
o particle size analysis of particulate emissions by Sierra Cascade Impactor
o sample process emissions, including after the last control device - EPA
method 5
o stack height for diffusion estimates
o stack temperature and pressure
o area and volume of tailings piles
o radionuclide concentrations at various points of emissions, e.g.,
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nuclear reactor fission products
thori um
polonium
uranium
radi um
1 ead
234
226
210
228
210
230
235
232
238
o radionuclide concentrations in air, water, and food
Development of the environmental assessment—The computer code described in
Airdos (2) represents a method for estimating radionuclide concentrations in
air, ground surface, water, and in such foods as meat, milk, and fresh produce.
Doses to 11 human organs from these pathways are computed from the rates of
inhalation, ingestion, and dose conversion factors. Individual doses (rem/y)
are converted to population doses (person-rem/y) which, in turn, are converted
to health effects from risk factors (health effects/person-rem/y) (3-5).
The assumptions used in this assessment are as follows:
1.	Health effects calculations are based upon the linear non-threshold
hypothesis that the number of cancers that may occur per unit dose
at low doses and dose rates is the same as observed at higher doses
and dose rates and also that all radiation is harmful.
2.	A modified Gaussian plume equation is used to estimate both
horizontal and vertical dispersion (6-7).
3.	In the calculation of an airborne external immersion dose at ground
level, a semi-infinite cloud was assumed.
4.	Ingestion doses are based upon the assumption of uniform daily
consumption rates for each type of food.
5.	Other assumptions peculiar to the particular source exposure
assessment, e.g., the size of the tailings pile for radon emission
assessment or the size of a nuclear reactor for assessing the
exposure from fission products.
As indicated previously, the broad scope of an exposure assessment is
essentially the same for all sources, the end result being an estimate of the
number of health effects resulting from a radioactive source and a determination
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of which emission control devices are cost effective. However, different source
terns make it necessary to alter the structure of the format in the interest of
making an orderly presentation. A good example of the format, style, and
composition of an exposure assessment is the report "Assessment of Potential
Radiological Health Effects from Radon in Natural Gas" by Raymond H. Johnson et
al., EPA—520/1-73-004.
References--
(1)	EPA test methods and procedures. 40 CFR 60 Section 60.144.
(2)	Moore, R.E., et al. Airdos - EPA: A computerized methodology for
estimating environmental concentrations and dose to man from airborne
releases of radionuclides. EPA 520/1-79-009, U.S. Environmental Protection
Agency, Wash., DC. 1979. 257 pp.
(3)	The effects on populations of exposure to low levels of ionizing radiation.
The .National Academy of Sciences, Washington, DC, 1972. 217 pp.
(4)	Killough, G.G-., P.S. Rohwer, and W.D. Turner. Inrem: A Fortran Code
Which Implements Icrp 2 Models of Internal Dose to Man. 0RNL-5003, Oak
Ridge National Lab., Tenn., 1975. 141 pp.
(5)	Trubey, D.K., and S.V. Kaye. EXREM III Computer Code for Estimating
External Radiation Doses to Populations from Environmental Releases.
0RNL-TM-4322, Oak Ridge National Lab., Tenn., 1973. 445 pp.
(6)	Slade, D.H. Meterology and Atomic Energy. TID-24190, National Technical
Information Service, Springfield, VA, 1968. 445 pp.
(7)	Turner, D.B. Workbook of atmospheric dispersion estimates. Publication
No. AP-26, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina, 1971.
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Office of Toxic Substances
Purpose--
The Toxic Substances Control Act (TSCA) directs the EPA to identify and
appropriately regulate chemical substances and mixtures that present an
unreasonable risk of injury to health or the environment. Sections 4, 5, and 6
of TSCA specifically apply to the work of exposure assessment for toxic
substances.
Section 4 of TSCA gives the EPA the authority to require that testing be
conducted on a chemical substance or mixture for which insufficient data is
available with respect to health and environmental effects or exposures.
Section 4(f) requires the EPA to act within 180 days of receipt of test data
or other information that indicates a chemical may present a significant risk to
health or the environment. Under this subsection the EPA must "initiate
appropriate action ... to prevent or reduce to a sufficient extent such risk or
publish in the Federal Register a finding that such risk is not unreasonable."
Section 5 of TSCA requires the EPA to consider human and environmental
exposure and potential risk to new chemical substances or mixtures for which a
premanufacturing notice has been filed.
Section 6 of TSCA concerns the regulation of existing chemical substances
and mixtures. An exposure assessment is specifically required for substances
falling under this section.
Within the Office of Pesticides and Toxic Substances (OPTS), the Office of
Toxic Substances (OTS) is responsible for preparing risk assessments to support
regulatory decision making. The Exposure Evaluation Division (EED) is
responsible for most of the exposure assessments pursuant to sections 4, 5, and
6. The Economics and Technology Division is responsible for a part of some of
the assessments.
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The Assessment Division combines the exposure assessment with the assessment
of adverse effects of the chemical substance in order to generate a risk
assessment. The Chemical Control Division then utilizes the risk assessment in
the process of generating a Control Options Document.
The exposure assessments performed for OTS will meet different goals
depending upon the applicable section of TSCA. For instance, under Section 6,
the exposure assessment will have a rather broad scope with regard to
consideration of pathways of exposure and populations exposed. In contrast, for
a substance falling under Section 4(f), the exposure assessment may be limited
to the particular exposure pathway and/or exposed population indicated by the
test data or other information received by the Agency.
Procedure--
Sources of information—In conducting an exposure assessment, information
gathering is directed toward the five major areas described in the Guidelines
document: (1) Sources (Materials Balance), (2) Exposure Pathways, (3) Population
or Target Studies, (4) Monitoring or Concentration Levels, and (5) Integrated
Exposure Analysis.
Information and data are obtained through worldwide literature searches,
from industry, through EPA monitoring studies, and from other U.S. Government
Agencies. Exposure information is often obtained from sources such as the
Occupational Safety and Health Administration (OSHA) and the Consumer Product
Safety Commission (CPSC). Population data are often obtained from the Bureau of
the Census and the Worker Population Studies produced by National Institute for
Occupational Safety and Health (NIOSH).
Sources (materials balance)--For exposure assessments on existing chemicals,
the materials balance studies are performed. The information needed to perform
a materials balance study may be found in the Guidelines document in the
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"Suggested Outline for an Exposure Assessment." Usually the entire United
States during a particular calendar year is chosen as a boundary for the system
being balanced, but other geographical or time boundaries can be used for
specific purposes. The environmental releases are reported as amounts and rates
of release to the various media, listed by geographical location and
physical-chemical form of the substance at the point of release.
Exposure pathways and environmental fate--The principal pathways of exposure
are identified and environmental distribution is predicted using models. When
available, monitoring data is compared to the predicted environmental
concentrations.
Population studies—Normally, population characteristies studies will be
done only for those locations where potential exposure exists based upon
information provided by chemical release, environmental fate, or monitoring
studies. For abiotic receptors, population characteristies are replaced by
studies of the receptor (e.g., ozone layer).
Monitoring—Monitoring data are generally obtained from the published
literature or from reports provided by industry. OTS may also perform
monitoring studies for some substances under TSCA.
Integrated exposure analysis--Exposure scenarios and profiles are provided
by subpopulation, and provide information on frequency, duration, and intensity
of exposure.
Exposure projections for new chemicals—Making an exposure projection for a
new chemical (under Section 5 of TSCA) involves developing much of the same kind
of information as for existing chemicals, i.e., materials balance information,
environmental fate information, and population characteristies. In most cases,
however, since the chemical is not yet being produced, monitoring as a
verification tool is limited to follow-up studies. The information developed
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for exposure assessment for new chemicals depends to a large degree upon
estimates, data on chemicals similar to the one being studied, and the data
provided by the potential manufacturer.
Format--The format for exposure assessments for toxic substances closely
resembles that suggested in the Guidelines document. The basic outline is
presented below.
I.
Introduction and Executive Summary
II.
General Information
III.
Sources (Materials Balance)
IV.
Exposure Pathways and Environmental Fate
V.
Population Studies
VI.
Integrated Exposure Analysis
VII.
Bibliography
VIII.
Appendi ces
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Office of Water Regulation and Standards
Purpose--
Tne Clean Water Act (as amended, 1977) set forth a national objective "to
restore and maintain the chemical, physical, and biological integrity of the
Nation's waters." To accomplish this end, several general goals were
established, which include the following:
1.	That the discharge of pollutants into navigable waters be
eliminated by 1985.
2.	That an interim goal of water quality which provides for the
protection and propagation of fish, shellfish, and wildlife and
provides for recreation in and on the water be achieved by
July 1, 1983.
3.	That the discharge of toxic pollutants in toxic amounts be
prohibited.
The requirement for risk assessment for toxic pollutants (and thereby
exposure assessment) is indicated in sections 307(a) (1) and (2) of the Clean
Water Act, Section 307(a) (1) establishes that a list of toxic pollutants
(priority pollutants) be published, to which the EPA may add or delete any
pollutant. In revising the list of priority pollutants, the EPA is required to
take into account the following factors: "the toxicity of the pollutant, its
persistence and degradability, the usual or potential presence of the affected
organisms in any waters, the importance of the affected organisms, and the
nature and extent of the effect of the toxic pollutant on such organisms."
Section 307(a) (2) states that each priority pollutant shall be subject to
effluent limitations, and that the EPA may publish effluent standards fcr
pollutants, after considering the factors listed above as well as "the extent to
which effective control is being or may be achieved under other regulatory
authority."
In accordance with the 1977 amendments to the Clean Water Act, the EPA
listed 129 priority pollutants which it agreed to evaluate. Within the Office
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of Water Regulation and Standards (OWRS), the Monitoring and Data Support
Division (MDSD) is responsible for evaluating the exposure and risks to human
and nonhuman species resulting from the occurrence of the 129 priority
pollutants in the water environment.
In general , the exposure assessments carried out under the mandate of the
Clean Water Act are specifically focused in terms of exposure media and
populations exposed. Exposures via water media are analyzed, and attention is
directed to both human and nonhuman-exposed populations.
Although the exposure assessments conducted by MDSD are limited to exposure
via water media, an attempt is made to put all routes of exposure into
perspective. Where water media are the predominant routes of exposure, MDSD
makes recommendations of ways to reduce water exposure after performing a risk
assessment. When it becomes apparent that other media are important routes of
exposure to a toxic pollutant, the information is directed to the appropriate
program office(s) within EPA for follow-up study.
An important goal of exposure assessments for OWRS is to aid in the
decisions to add to or delete from the list of priority pollutants required by
Section 307(1) (a) of the Clean Water Act.
Another function of exposure assessments is to assist ether program offices
in risk assessment of imminent hazards presented by toxic wastes (e.g., spills
and other emergencies). In these situations, the MDSD provides into the risk
assessment input regarding possible alternatives for clean-up or other
corrective measures.
Procedure--
In the MDSD, the entire staff is responsible for all aspects of each
exposure assessment with which they are involved. Specific division of labor in
a particular exposure assessment may exist between contractors hired for the
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project.
The initial stage in preparing an exposure assessment consists of a cursory
review of the available information on a toxic pollutant. This activity is
valuable in giving direction for in-ciepth analysis of exposure by identifying
target populations, pathways of exposure, and other important parameters. It is
at this stage that an exposure assessment may be referred to another program
office if it becomes apparent that water media are not sigificant routes of
exposure.
Information and data are obtained from worldwide searches of the published
literature, from unpublished reports, from industry, and from other Federal or
State agencies and organizations. The Food and Drug Administration is a helpful
source of information on levels of toxic pollutants in foods. Much information
is gathered through the assistance of contractors.
Monitoring is conducted by the MDSD and by states, EPA Regions,
universities, and contractors. Currently all monitoring data obtained by the
MDSD are stored in a computerized data base, STQRET (Storage - Retrieval system
for water quality data). All states, contractors, universities, and other
organizations receiving Federal funds are required to enter their monitoring
data into STORET; many independent researchers have entered data into STORET on
a voluntary basis. This computerized data base allows rapid access to the
existing monitoring data on a given toxic pollutant under consideration. More
information concerning the monitoring data storage and retrieval system may be
obtained from the STORET User Assistance Branch of the MDSD.
A detailed exposure assessment will include a materials balance, i.e., a
study of sources, production, uses, destruction/disposal, and environmental
release of a substance. The materials balance analysis includes the entire
United States for a particular calendar year as the boundaries of the system
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being analyzed. Often the materials balance will be studied for several
calendar years with special attention directed to any changes from one year to
the next. Projections may be made for future years from observed trends.
Studies of population characteristics are made with particular attention to
the identification of subpopulations which may be at highest risk. Human
populations may be subdivided on the basis of age, geographic location, and
other parameters. Less is known about the characteristics of aquatic
populations, but subdivisions may be made within aquatic systems if the exposure
data permits such differentiation.
Finally, exposure scenarios are devised for a typical individual in each
subpopulation identified above. Commonly used assumptions are employed
concerning daily intake of drinking water, diet, and other parameters in order
to facilitate comparisons between exposure calculations for different
substances. A value for exposure to each subpopulation is estimated,
particularly for groups at highest risk. One then estimates the number of
individuals within the high-risk subpopulation.
The exposure assessment for a toxic pollutant is then incorporated into the
risk assessment with the outline of such a document dictated by the nature of
the pollutant. A general outline is presented below:
I.	Executive Summary
II.	Materials Balance
III.	Environmental Pathways/Fate
IV.	Routes of Exposure
V.	Integrated Exposure Assessment
VI.	Toxicological Data
VII.	Risk Assessment
VIII.	Conclusions
IX.	Bibliography
X.	Appendices
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B. EXPOSURE ASSESSMENT ACTIVITIES OF OTHER FEDERAL REGULATORY AGENCIES
Consumer Product Safety Commission (CPSC)
The Commission's mandate includes assessment of chemical as well as
mechanical injury. The Commission has thus taken steps to develop the means to
conduct comprehensive exposure assessments and has begun to develop assessments
utilizing these evolving techniques.
In the past year, CPSC has supported the development of assessments of
consumer exposure to formaldehyde, indoor air pollutants, and bisazobiphenyl
(i.e., benzidine and some of its congeners) dyes. It has also supported the
development of a comprehensive report on exposure assessment status and
principles. Many procedures, approaches, and problems are discussed in this
report on status and principles. Included are human ecology, dose-time
functions, uncertainty, entropy, non-equilibrium systems, susceptible
populations, and the use of decision logic tables in exposure assessment.
Exposure assessment modeling on benzidine-based dyes follows the sequence of
first establishing exposure scenarios and then estimating corresponding exposure
estimates using composition data, stoichiometric considerations, and mass
balance methods. This approach permits ranking of exposure scenario estimates
in order of perceived severity. Severity depends on chemical nature (e.g.,
reduced or oxidized form), route of entry, quantity or concentration, duration,
outdoor or indoor use, size and sensivity of the population, and other factors
peculiar to individual scenarios. The emphasis in the approach is on using
professional judgment to determine exposure scenarios and the best data sources
and models to use to estimate exposure. Limitations are described and
suggestions for improving the data base or the models are suggested at
appropriate points throughout the report.
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Reports on exposure to formaldehyde and indoor air pollutants begin
similarly with identification of sources and scenarios. Source strength data is
used in an air pollution model based on environmental parameters.
In indoor exposure modeling there are as many scenarios as there are exposed
populations, pollutants, sources, and environmental conditions. For example,
source strength data for formaldehyde emission from plywood, particleboard,
textiles, gas combustion, cigarette smoke, aerosol products, outdoor air
pollution, and insulation must be evaluated in relation to probable values of
many environmental parameters. These parameters include temperature, humidity,
area and/or volume of generation, specific rate of decomposition, smoking rate,
forced filtration and decay affects, and air mixing factors. Probable single
and multiple source scenarios can be obtained as character!stic exposure
(concentration X time) data points by integrating the concentration vs. time
graphs obtained by using a simple programmable calculator.
Health effects are summarily discussed in the formaldehyde and indoor air
pollutants reports, but damage or risk assessment is not attempted.
Food and Drug Administration (FDA)
The broad scope of FDA's responsibilities leads to a spectrum of exposure
assessment needs. Exposure assessments range from the relatively well-defined
problem of evaluating the probable use of specific prescription drugs to complex
exposure assessments, such as exposures resulting from environmental
contaminants (e.g., polychlorinated biphenyls and aflatoxins); food animal
additives/drugs (e.g., diethylstil bestrol); or migrants from food packaging
(e.g., dioctyl adipate and vinyl chloride migration from certain
polyvinylchloride food wraps).
The FDA, often in collaboration with other Federal agencies, has in the past
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been involved in various types of exposure assessments on chemicals of
significant concern, i.e., sacciiarin, nitrites and nitrates, selenium, PCB's,
chiorofluorocarbons, and lead acetate, and is currently involved in exposure
assessments on formaldehyde and the phthalates.
The FDA assesses exposure on at least two different levels. The first level
relates directly to FDA's mandate to ensure that foods, feeds, drugs, cosmetics,
biologies, medical and radiological devices are safe and/or effective for humans
or specific target animals. These exposure assessments often involve mass
balance, dose-type calculations.
Estimates prepared on the safety/efficacy level are generally developed in
terms of the intake of a substance, usually presumed to be a bioactive agent,
e.g., a chemical substance, form of radiation, microorganism, etc., associated
with the use or consumption of foods, drugs, or other carrier vehicles. Intake
normally occurs via ingestion and absorption within the gastrointestinal tract,
passage through the skin, or by inhalation.
On a second level, related to the National Environmental Policy Act (NEPA),
FDA is developing and applying exposure assessment methodology for assistance in
the preparation of environmental assessments and environmental impact
statements. These environmental documents often include exposure assessments
containing both materials balance analysis and estimation of multimedia and
multispecies exposures through prediction of the introduction and fate of
FDA-regulated substances in the environment.
The requirement for assessment of environmental impact relates directly to
the influence of manufacture, use, and disposal of foods, feeds, drugs,
cosmetics, biologies, and medical and radiological devices on environmental
quality. Such efforts by the FDA are being coordinated with other government
agencies, primarily through the Interagency Regulatory Liaison Group.
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Department of Agriculture (USDA)
The USDA is responsible for assuring the safety of meat products. Estimates
of the amounts of toxic substances in foods that are included under USDA's
mandate are prepared by standard mass balance methods.
The Department's recent exposure/risk assessment on nitrosamines in bacon
illustrates a direct approach for determining human exposure to nitrosamines
that can, in turn, be used to estimate cancer risk.
Using knowledge of the average national consumption of bacon per day and
data on the types and amounts of nitrosamines in bacon, it was possible to
estimate average daily exposure (as a dose) to nitrosamines in bacon.
Sensitive, state-of-the art analytical chemistry methods were used to secure
quantitative composition data.
Carcinogenicity response data were reviewed and evaluated in conjunction
with the exposure data with the objective of estimating the increase in human
cancers associated with this national average type of exposure scenario. Other
possible minimum (best case) and maximum (worst case) exposure scenarios were
not considered. These could have been used to bracket the national exposure
average, thus constituting one aspect of a sensitivity analysis related to
exposure and risk.
Occupational Safety and Health Administration (OSHA) and National Institute for
Occupational Safety and Health (NIOSH)
At OSHA, exposure assessments are used to support rule-making activities and
thus, are not in themselves generally anticipatory. These assessments are based
on comprehensive evaluation and assimilation of very large quantities of onsite
monitoring data. Exposure data are compared to standards already in place,
i.e., 8-hour, time-weighted average concentrations. Since concentration data
are available, there is no need to develop or assume concentration-time data
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prior to preparing an exposure assessment of this type.
The anticipatory (research) side of occupational exposure assessment is
performed by the National Institute for Occupational Safety and Health (NIOSH).
Assessment of the health and safety effects of exposure to workplace chemicals
is a component of many NIOSH documents. For example, a recent document on the
benzidine-based dyes illustrates the role of NIOSH in exposure assessment. The
NIOSH report to OSHA assesses the impact of workplace exposure to these dyes and
suggests that exposure be further decreased.
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III. MODELS EMPLOYED IN EXPOSURE ASSESSMENTS
Some general exposure assessment principles of use in this Handbook have
been presented in a review of the state-of-the-art in exposure assessment (1).
An ideal model is described as providing for multiple emission sources;
conversion of emission rates to contaminant concentrations in all media (air,
water, soil, food); exposure to humans, plants, and animals (we would add
materials); multiple routes of exposure to humans (inhalation, ingestion, dermal
absorption); and allowing for interactive effects (synergistic or antagonistic)
of multiple pollutants. Although the ideal model is not available, components
can be assembled into useful models tailored to specific problems. Adequate
characterization and central filing of existing model components, in conjunction
with a decision logic approach, could facilitate the assembly of case-specific
models (2). In the meantime, such synthesis must be left to the reader with a
need to assess exposure.
In this Handbook, the intent is to provide the reader with a general
overview of some of the existing models, with an emphasis on both physical and
biological aspects of exposure assessment. Basic information on a variety of
models is provided in Table III-l, including a model acronym, carrier vehicles,
exposure routes, suitability for estimating the integral of the product of
concentration and the derivative of time (Cdt), basis and summary features, and
contacts and references for further details. No attempt has been made to
critically evaluate the models, provide comparisons between them, or to include
only those models that have been validated.
EPA1s catalog of environmental models (3) is an extensive compilation of
modeling information. Water quality, water runoff, air quality, economic, and
some other specialized models are described in a consistent summary format. For
III-l
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each model, concise statements of overview, capabilities, assumptions, input
data requirements, output calculations, resource requirements, applications,
contacts for further information, and key references are provided.
Along with other documents, the catalog of environmental models was reviewed
with the objective of selecting models that are useful , either in whole or in
part, for estimating exposure. The objective of this Handbook is to provide the
reader with a broad view of existing concepts with which to plan and structure
his or her own action plan. The exercise of prudent professional judgement is
the most important ingredient in exposure assessment at the present state of
development of this field. The information in this Handbook is a basic
framework for displaying possibilities that can be structured and connected by
the reader to meet case-specific requirements.
Table 111-1 displays information that can be scanned to reveal key features
of existing models with components that may be useful in the conduct of exposure
assessments. The reader can select items of interest and proceed through the
columns of information to the summarized descriptive material. Follow-up
activities include contacting key individuals and reviewing the literature.
Although individual requirements may sometimes be met by a single model, a
particular case may necessitate identification and use of a component feature of
a complete model, or sequential application of discrete parts of two or more
models. For example, the equation for time dependence of pollutant
concentration at the coordinates of a home some distance from the source can be
coupled with an indoor air pollution model to provide a hybrid model that may
better meet the needs of a particular user of the Handbook than any single
model. Similarly, an evaporation model can be used as the generation term or
function in a conservative type, air pollution model incorporating various
physical and chemical decay rates.
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For the reader who wishes to relate dose to exposure, a very useful chapter
on exposure and resultant toxic effect models can be found in a comprehensive
report on mathematical models for atmospheric pollutants (4). Compared to the
state of development and application of air pollution source and pathway models,
the state of development of exposure and toxic effect models is lagging. Source
and pathway models can be used to relate emission or generation of pollutants
and ambient concentrations. Exposure models also incorporate attempts to link
concentrations and durations with affected persons, other animals, plants, and
objects in the environment.
Source models provide an estimate of the temporal and spatial variation of
emission increases and decreases. Pathway process models consider physical and
chemical decay of the concentration through the action of physical and chemical
processes along the path between the source and the potentially affected
subject. There is at present no substitute for specific knowledge and decision
logic in assessing exposure and toxic effect.
Multimedia considerations apply to comprehensive exposure assessments
consisting of diverse, yet interrelated, exposure scenarios. For example,
airborne pollutants can be diluted and dispersed by the wind, undergo
coagulation or chemical reactions, settle to the ground, be absorbed in cloud
elements or precipitation, be absorbed on the ground, enter groundwater, or be
washed out in precipitation. Humans, animals, plants, and materials can be
exposed directly and indirectly. Entry can occur through surface contact,
ingestion, or inhalation according to the spectrum of exposure scenarios
applicable to a given system.
Strenge, Watson, and Droppo (5) surveyed radiation exposure models and
classified them according to atmosphere, surface water, ground water, and
terrestrial pathways. Included in information on the 22 models that were
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selected were internal and external doses, susceptible organs, and type of
computer program. Key features of some of these exposure models are summarized
i n Table 111-2.
EPA has prepared the Guideline on Air Quality Models (10) which recommends
air quality modeling techniques that may be applied to air pollution control
evaluations. The Guideline makes specific recommendations concerning air
quality models, data bases, and general requirements for concentration
estimates. The appendix of the Guideline contains summaries of the recommended
models, several of which are listed here in Table III-l.
III-a
 image: 








TABLE III-l. FEATURES OF MODELS WITH EXPOSURE COMPONENTS
Model	Carrier Exposure Ease of Inte-	Basis and Summary Features	References
Acronym1 Vehicles Routes	grating Cdt
EPA/
GEOMFT
Ai r
Inhalation Direct
Mass balance, conservative type,
deterministic equation. Applicable
to indoor/outdoor air. Generation
term and two types of decay. Suit-
able for hand calculator.
CPSC/
JRB
Ai r
Inhalation Direct
Mass balance, conservative type,
deterministic equation. Generation
term and three types of decay for
indoor use with outdoor air infil-
tration. Suitable for developing
tailored exposure profiles by user
interaction with a programmable
calculator.
7,8
CPSC/
JRB
I
en
Consumer
Products
CPSC/
ABERDEEN
Ai r
Inhalation,
Skin absorp-
tion, GI
tract
Inhalation
Direct (but
requi res
knowledge of
use duration
and frequency)
Indirect (re-
qui res coup-
ling with time-
dependent model)
Mass balance, conservative type
analyses of discrete scenarios
with case-by-case analysis. Suitable
for hand calculator.
Mass balance. Models evaporation
from a liquid surface. Provides
generation output that can be used
with conservative indoor/outdoor
models to obtain concentration-
time exposure profiles.
ISee key to Acronyms at end of table,
(continued on following page)
 image: 








TABLE III-l. (continued)
Model
Acronym
Carrier
Vehicles
Exposure
Routes
SEM
Water All determin-
able from
knowledge of
concentration
Ease of Inte-
grating Cdt
Basis and Summary Features
Integration
possible
Refe rences
Handles only point source inputs to
streams, rivers, and shallow non-
stratified lakes. 1st order decay.
Simulates dilution, advection, and
temperature effects. 1-dimensional.
Considers uncoupled chemical re-
actions. Suitable for hand calculator.

ES001
Water
OEM
Water
I
cr>
TTM
Water
HMO 3
Water
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
A1 I determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
Integration
possible
Di rect:
Dynamic
Di rect:
Dynamic
Indi rect:
Steady
State
Mass balance. Can be used for sequential 3(p.l2)
reactions of two substances having 1st
order kinetics. Tidal 1y averaged, steady-
state model. Suitable for complex water
networks (100 junctions, 50-100 sections).
Requires computer.
Real-time, link node model simulating	3(p.15)
unsteady tidal flow and dispersion in an
estuary. Two-dimensional flow. Hydraulic
and quality (pollutant concentration)
model components. Mass balance checks at
each junction. Predicts time varying
concentrations. Requires computer.
Derivative model of DEM. Handles up to 4 3(p.20)
constituents with coupled or noncoupled
reactions with 1st order decay. Used for
networks (300 junctions, 300 channels).
Requires computer.
Mass balance. Multidimensional, steady-	3(p.23)
state model for two reacting substances.
Handles 1st order kinetics. Incorporates
convective-diffusive mass transport with
source and decay terms. Requires computer.
(continued on following page)
 image: 








TABLE 111 -1. (continued)
Model
Acronym
Carrier
Vehicles
Exposure
Routes
Ease of Inte-
grating Cdt
Basis and Summary Features
References
FEDBAK03 Water
PLUME
Water
QIJAL-11 Water
I
Ell
REDEQL
Water
Water
RECEIV-II Water
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
Indi rect:
Steady
State
Indi rect:
Steady
State
Di rect :
Dynamic
[)i rect:
Dynamic
Indi rect:
Kinetics not
considered
Di rect:
Dynaini c
"Mass balance. Handles consecutive reactions 3(p.27)
and 1st order kinetics. Assumes that steady
state conditions apply. Requires computer.
Considers only mixing and dilution with no 3(p.32)
water flow in a steady state stratified
environment. 3-dimensional output. Provides
concentration data along plume centerline.
Requires computer.
Simulates dynamic behavior of constituents 3(p.36)
subject to dispersion, flow, nutrient
cycles, and algal growth. 1-diinensional for
networks. Considers 1st order decay. Only
point discharges and constant inflows are
considered. Instantaneous mixing is assumed.
Requires computer.
Simulates near shore currents and exchange 3(p.48)
precesses. Sophisticated treatment of dis-
persion, advection, and dynamic plumes.
Requires computer.
Computes equilibria for up to 20 metals and 3(p.52)
30 anions in a system. Includes complexa-
ation, precipitation, redox, and pll depen-
dent reactions. Requires computer.
Two-dimensional model representing advec- 3(p.62)
tion, dispersion and dilution. Used on
networks. Can simulate coupled and non-
coupled chemical reactions. 1st order decay
considered. Assumes instantaneous mixing.
Requires computer.		
(continued on fol 1 owfrig page]"
 image: 








TAULE 111 -1. (continued)
Model
Acronym
Carrier
Vehicles
Exposure
Routes
Ease of Inte-
grating Cdt
EXPLORE-1 Water
MS
CLEANER
DIURNAL
Water
Water
AGRUN
Runoff
Water
ARM-11
Runoff
Water
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentration
All determin-
able from
knowledge of
concentrati on
All determin-
able from
knowledge of
concentrati on
All determin-
able from
knowledge of
concentration
Direct:
Dynamic
Direct:
Dynami c
Indi rect
Steady
State
Di rect:
Dynamic
Di rect:
Dynamic
Basis and Summary Features
References
Handles 1-dimensional flow in streams and
rivers, 2-dimensional flow in shallow lakes
and estuaries. Capable of handling constant
or time-varying point or diffuse sources
of substances. Requires computer.
Sophisticated model with
bioacciiinul ation of toxic
quires computer.
Used to predict diurnal fluctuations during
periodic steady-state conditions. Useful
when algal oxygen production is related to
concentration of affective agent. Requires
computer.
Simulates hydrology and channel pollutant
loads for agricultural watersheds. Uses
the universal soil loss equation and
Morton's equation to compute infiltration
rates. Requires specification of soil
parameters. Requires computer.
Mass balance. Assumes all runoff water
from locations in the watershed. Pollutant
transformations are approximated by a
series of 1st rate expressions. Arrhenius
equation used to adjust rates to different
temperatures. Partitioning between phases
assumed to be instantaneous. Requires
computer.
~3(p766)
use in determining
substances. Re-
3 (p. 7 0)
3(P-77)
3(p.80)
3 (p. 8 3)
(continued on following page)
 image: 








TABLE
Model
Acronym
Carri er
Vehicles
Exposure
Routes
Ease of
grati ng
Inte-
Cdt
GWMTM1 Ground All determin-	I)irect:
Water able from	Unsteady
knowledge of	State
concentration
GWMTM2 Ground All determin-	Direct:
Water able from	Unsteady
knowledge of	State
concentration
~ EPAURA Runoff
V	Water
All determin- Indirect
able from
knowledge of
concentration
EPARRB Runoff A1I determin-
Water able from
knowledge of
concentration
NPS	Runoff All determin-	Direct:
Water able from	Various
knowledge of	time
concentration
11-1. (continued)
Basis and Summary Features	References
"Based on convective-dispersive mass trans- 3 (p.97)
port equation modified for 1st order decay.
1-dimensional treatment. Surface concentra-
tion can be constant or exponentially
varying. Vertical seepage constant.
Soil saturated or unsaturated. Requires
computer.
Describes concentration distribution in 2 3(p.99)
underground dimensions. Advection and
dispersion in 2 dimensions with 1st order
decay and an exponentially decaying
Gaussian boundary condition. Useful for
sanitary landfills, wastewater lagoons,
and chemical dumps. Requires computer.
Assumes accumulated pollutants are all	3(p.l01)
carried off in rainfall on an area of
impervious surface. Requires computer.
Assumes all rural areas have slope per-	3(p.l03)
centages allowing erosion to take place.
Calculates delivered sediment to a water
body based on the universal soil loss
equation. Pollutant loads are outputed.
Requires computer.
Used to estimate nonpoint source pollutant 3(p.112)
loads in urban and rural settings. Requires
computer.
(continued on following page)
 image: 








TABLE 111-1. (continued)
Model	Carrier Exposure Ease of Inte-	Basis and Summary Features	References
Acronym Vehicles Routes	grating Cdt
IIIVJAY 2 Air Inhalation
APRAC 1-A Air Inhalation
Di rect:
Hourly
values
outputed
Di rect:
Only for
CO
Applies to uniform wind conditions and level 3(p.l20)
terrain. Based on Gaussian plume. No physical
removal or consideration of chemical reac-
tions. Requires small computer.
Computes hourly averages of CO concentra-
tions at any urban location. Plume rise
not treated. Requires small computer.
Could input carboxyhemoglobin model for
determination of effective dose.
3(p.K>2)
APRAC 2 Air Inhalation
Di rect:
Only for
CO, HC,
and NOv
Makes use of historical CO concentration
records. Useful for hydrocarbons, CO,
oxides of nitrogen. Requires computer.
3(p-127)
PSM* S
Ai r
Inhalation
o
Indi rect:
Only for
maximum,
short-term
levels
Based on Briggs plume rise methods and
Pasquil1-Gifford dispersion methods.
Assumes Gaussian spreading both horizon-
tally and vertically. Requires computer.
3(p.133)
TEM
Ai r
Inhalation
TCM
Air Inhalation
Di rect :
Depends
on updating
Di rect:
Depends
on updating
Based on an emissions data inventory and 3(p.138)
a set of meteorological parameters over
over a grid. Gaussian plume, Briggs plume
rise. Available as a computer program.
Similar to CDM, but requires less computer 3(p.l40)
time. Gaussian plume, Briggs plume rise.
Requires computer.
(continued on foil owing page)
 image: 








TABLE IIl-l. (continued)
Model	Carrier Exposure Ease of Inte-	Basis and Summary Features	References
Acronym Vehicles Routes	grating Cdt
ISC
Air Inhalation
PAL
Air Inhalation
i— CRSTER Air Inhalation
I
AQ DM
Air Inhalation
Di rect:
Dynamic
Di rect:
One-hour
concentration
increments
Di rect:
Dynami c
Indi rect:
Steady
State
Similar to CRSTER except multiple source
separation, polar or cartesian coordinates.
Gravitational settling and dry deposition
of particulates. Simulates line area and
volume sources. Evaluates building wake
effects. Exponential decay of pollutants.
Concentration estimates for 1-hour to
annual average. Requires computer.
For small-scale point, line, and area sources 3(p.147)
of pollutants. Flat terrain assumed. Briggs
pluine behavior, Gaussian plume dispersion.
No provision for chemical reactions.
Requires small computer.
Provides concentrations for each hour of a 3(p.l51)
one year period. Handles up to 19 colocated
elevated stack emissions. Employs modified
form of Gaussian plume equation. Average
emission rates assumed. Horizontal and
vertical dispersion considered. Requires
small computer.
Used to evaluate area sources in urban	3(p.l56)
areas. Treats physical processes of
transport and diffusion. Limited to SO2
and suspended particulates. Assumes
Gaussian diffusion and homogeneous
diffusion. CDM/CDMQC is perferred model.
Requires computer.
(conti nueiT on foYlowiny page)
 image: 








TABLE III-l. (continued)
"MmfiFl	Carrier Exposure
Acronym Vehicles Routes
Ease of Inte-
grating Celt
Basis and Summary Features
References
RAM
Air
Inhalation
VALLEY Air Inhalation
I
l\3
NRRM
S AI
Ai r
Ai r
Inhalation
Inhalation
Di rect:
Concentrations
detenni ned
hourly
Di rect:
Concentrations
determi ned
daily or
yearly
Di rect
Di rect:
Dynamic
Employs hourly meteorological data. Based	3(p.l59)
on Briygs plume rise and the Pasquill-
Gifford dispersion equations with parameters
valid for urban areas. Constant emission
rates assumed for each point and area
source. Chemical decay half-life can be
inputed. Requires computer.
Model is a steady-state, univariate Gaussian 3(p.l66)
plume algorithm. Provides ground level con-
centrations at 112 receptor sites in a
radial grid. Incorporates plume rise and
limited mixing. Chemical reactivity and
physical decay can be introduced (both ex-
ponential). Requires computer.
Model only for ozone/oxidants and single
precursor hydrocarbons. Requires concentra-
tion data. Does not require computer.
3(p.172)
Three-dimensional model for area sources in 3(p.l74)
urban areas. Simulates transport, diffusion,
and photochemical oxidation reactions. Out-
puts hourly concentrations of photochemical
oxidants and ozone. Requires computer.
(continued orTTolTowing page")"
 image: 








TABLE 111-1. (continued)
Model
Acronym
Carrier
Vehicles
Exposure
Routes
Ease of Inte-
grating Cdt
Basis and Summary Features
Re ferences
CDM/CDMQC Ai r
REPS
SEAS
C0PM0D1
Ai r
Poten-
tial ly
Ai r,
Water,
Soli ds
Inhalation
Inhalation
Ai r,
Water,
Sol i ds
All reducible
to concen-
trations
Direct (but
provides long-
term concentra-
tion values
only)
Indi rect:
(This is a
projection
model)
Indi rect:
(This is a
projecti on
model)
Used to determine seasonal or annual	3(p.177)
quasistable concentrations at ground level
receptors. Treats one or two pollutants
simultaneously. Briggs formula for plume
behavior. Gaussian plume for vertical dis-
persion. Permits exponential decay for
chemical half-life considerations. CDMQC out-
put allows source contribution table. Requires
computer.
Used to determine the impact of changes in 3(p.182)
national characteristics and parameters on
future air quality. Covers five of the
criteria pollutants for the 243 Air Quality
Control Regions in the U.S. Requires
computer.
Used to determine environmental, economic, 3(p.l85)
and energy effects of differing growth
patterns and policies. Forecast from 1 to
50 years into future. Would require study
to determine applications in exposure
assessment. Requires computer.
Used to estimate the impact on copper	3(p.l92)
producer's costs from pollution abate-
ment expenditure. The model requires
study to determine applications in
exposure assessment. Requires computer.
(continued on following page[
 image: 








TABLE 111 -1. (continued)
Ttadel
Acronym
CONMOL)
PTM
CARMOD
I
h-4
ABTRES
"Carrier
Vehicles
Exposure
Routes
Ease of Inte-
Grating Cdt
Basis and Summary Features
References
Poten-
tial ly
Water
Poten-
tial ly
Ai r,
Water,
Sol ids
Ai r,
Water
Ai r,
Water
Inhalation,
Others depend-
dent on con-
centration
Indi rect:
(This is a
projection
model)
Econometric model. Used for estimating the 3(p.l95)
economic impact resulting from EPA's sewer
and sewer treatment plant expenditure
program. Requires computer.
Provides economic outputs (income statement, 3(p.198)
flow of funds summary, balance sheet) from
production arid pollution control cost inputs.
Model would require study to determine appli-
cations in exposure assessment. Requires
computer.
Econometric model for estimating long run 3(p.204)
levels of automobile demand. Connection with
automobile induced pollution is not apparent.
Would require study to determine suitability
for inputing exposure assessments. Requires
computer.
Forecasts costs associated with pollution
control systems. May be useful in exposure
assessment work because specific types of
pollutants can be studied. Residual levels
of pollutants provided as output data. Useful
for "what if" questions relating cleanup
extent with associated costs. Requires
computer.
3(p.211)
(continued on following page")"
 image: 








TABLE 111-1. (continued)
Model
Acronym
Basis and Summary Features
Carrier
Vehicles
Exposure
Routes
Ease of
Grati ng
Inte-
Cdt
References
WRAP
MMMSPT-
EPM
NRM
Sol ids
Ai r
Inhalation
Elec-
tro-
magnetic
Radi a-
tion
Body/Organ
Direct for
C02: (This
is a dose
model by proxy)
Di rect:
(Converts
dose)
to
Used to determine the most efficient	3(p.214)
regional system design for resource
recovery system. Requires study to deter-
mine if useful for exposure assessment
inputs. Requires computer.
Based on the effects of pollutants on the 3(p.219)
rate of CO2 excretion from the lungs,
which is a measure of efficiency of respiratory
function. Often reduces observation period
for an effect of a pollutant to minutes
instead of hours. Effects of pollutants are
based on the difference of integral
CcQpVco?^ between control animals
ana exposed animals. Calculator can be used.
Used for predicting thermal load to animal
organ when animal is exposed to radiation
converted to heat within the organ. Applies
to microwave radiation. Requires small
computer.
3(p.2Z2)
 image: 








KEY TO ACRONYMS
Model Acronym	Name of Model
Water Quali ty Models
SEM	Simplified Estuary Model
ESOOl	Estuarine Water Quality Model
DEM	Dynamic Estuary Model
TTM	Tidal Temperature Model
HAR03	Water Quality Model
FEDBAK03	Water Quality Feedback Model
PLUME	Outfall Plume Model
QUAL-11	Stream Quality Model
REDEQL.EPA	Computer Program for Chemical
Equilibria in Aqueous Systems
RECEIV-II	Receiving Water Model
EXPLORE-1	Water Quality Model
MS.CLEANER	Multi-Segment Comprehensive Lake
Ecosystem Analyzer for Environmental
Resources
DIURNAL	Receiving Water Model
Water Runoff Models
AGRUN	Agricultural Watershed Runoff Model
ARM II	Agricultural Runoff Model (Version II)
GWMTM1	One Dimensional Groundwater Mass
Transport Model
GWMTM2	Two Dimensional Groundwater Mass
Transport Model
EPAURA	Non-Point Runoff Model for a Single Storm
Even in an Urban/Suburban Setting
EPARRB	Non-Point Runoff Model for a Rural Setting
NPS	Non-Point Source Pollutant Loading Model
Ai r Quality Models
HIWAY 2	EPA HIWAY Model
APRAC-1A	Air Pollution Research Advisory Committee
Model 1A
APRAC-2	Air Pollution Research Advisory Committee
Model 2
PSM'S	Point Source Models
TEM	Texas Episodic Model
TCM	Texas CIimatoloaical Model
LIRAQ	Livermore Regional Air Quality Model
PAL	Point, Area, Line Source Algorithm
111-16
 image: 








Model Acronym
Name of Model
Air Quality Models (Cont.)
CRSTER	Single Source Model
AQDM	Air Quality Display Model
RAM	Gaussian Plume Multiple Source
Ai r Quali ty A1gorithm
VALLEY	Gaussian Plume Dispersion Algorithm
- - -	Nonlinear Rol1 back/Roll forward Model
SAI	Systems Applications, Inc., Model
CDM/COMQC	CIimatological Display Model
REPS	Regional Emissions Projection System
ISC	Industrial Source Complex Model
Economic Models
SEAS	Strategic Environmental Assessment Syst
C0PM0D1	U.S. Copper Industry Model
CONMOD	Construction Model
PTM	Steel Industry Model
CARMOD	Automobile Demand Model
ABTRES	Abatement and Residual Forecasting
Model
Other Models
WRAP	Waste Resources Allocation Program
MMMSPT-	Mathematical Model for Fast Screening
EPM	Procedure for Testing the Effects of
Pollutants in Mammals
NRM	Nonionizing Radiation Models
111-17
 image: 








TABLE 11 1-2. EXPOSURE-EFFECTIVE DOSE MODELS
Fluid Flow	Compartments	Compatibility with	Reference
Regions	Modeling of Stable
Gases and Particles
Air: Nose,
Throat, Lungs	Lung	Compatible
T.G. Hatch and P. Gross. Pulmonary Deposi-
tion and Retention of Inhaled Aerosols.
New York: Academic Press, 1964.
Blood	Blood	Compatible
Robert T. Jones. "Blood Flow." Annual
Review of Fluid Mechanics, 1. Palo Alto,
CA: Annual Reviews, Inc., 1969. pp. 223-244.
Air, Surface
and Ground
Water
Atmosphere,
Water, Humans,
Aquatic Plants
Compatible
00
Dale D. Huff and Paul Kurger. "Simulation
of the Hydrologlc Transport of Radioactive
Aerosols." Radionuclides in the Environ-
ment. Washington, D.C.: Adv. in Chem. Ser.
American Chemical Society, 93, 1970.
pp. 487-505.
Air, Water
Ai r, Soi 1, Plants,
Animals, Humans
Coinpatibl e
(also includes transfer
coefficients for
inhalation, direct
radiation, and ingestion
of food)
A. Cardinale, V. Gervasio, A. Marxocchi ,
and E. Nardelli. "A Proposed Approach
on Modeling Techniques for Ecological
Purposes Using Dynamic Criteria. "In
Proceedings of the Second Meeting of the
Expert Panel on Air Pollution Modeling.
Paris, France: NATO Committee on the
Challenges of Modern Society, July 26-27
1971. Chapter II, pp. 11-1 to 11-20.
(continuedTbn following page)"
 image: 











TABLE I I 1-2. (con
tinued)

Fluid Flow
Regions
Compartments
Compatibility with
Modeling of Stable
Gases and Particles
Reference

Air: Nose,
Throat, Lungs
Air, Pulmonary
Region, Blood,
Lymph Nodes,
Bone, GI Tract
Compatible
U.S. Nuclear Regulatory Commission. Reactor
Safety Study, An Assessment of Accident
Risk in U.S. Commercial Nuclear Power
Plants. 1975. NUREG-75/014, WASH 1400.

Air, Surfaces,
Liquid and Solid
Foods
Target population
growing at an
exponential rate,
Susceptible organs
Compatible
(and most comprehensive
radiation model)
J.L. Rider and S.K. Beal. A Model to
Estimate Radiation Dose Commitments to the
World Population from the Atmospheric
Release of Radionuclides. West Mifflin, PA:
Bettis Atomic Power Laboratory, February
1978. WAPD-TM-1274.
»—I
t-H
»—«
1
n£>
Ai r
Human as a single
compartment
Compatible (but assumes
even distribution
over whole body)
Robert llandy and Anton Schindler. Estima-
tion of Permissible Concentrations of
Pollutants for Continuous Exposure.
Research Triangle Park, N.C.
Research Triangle Institute for U.S.
Environmental Protection Agency, EPA-
600/2-76-155, June, 1976.

Air, Water
Plants: Many
compartments and
envi ronmental
variables
Coinpatibl e
W.W. Heck and C.S. Brandy. "Effects on
Vegetation: Native, Crops, Forests." Air
Pollution. Third Edition, II. New York:
Academic Press, 1977. Editor A.C. Stern,
pp. 157-229.
S.B. McLaughlin and D.S. Shriner. "Plant
Pollutant Interactions and the Oak Ridge
Approach to Air Pollutant Impact Analysis."
Oak Ridge, TN: Oak Ridge National
Laboratory 1976.
(continued on following page)
 image: 








TABLE 111-2. (continued)
Fluid Flow	Compartments	Coinpatibil ity with	Reference
Regions	Modeling of Stable
Gases and Particles
Air, Water	Plants:	Compatible	J.H. Bennett and A.C. Hill. "Interactions
Atmosphere,	of Air Pollutants with Canopies of Vegeta-
vegetative canopy,	tion." Response of Plants to Air Pollution,
soil, root system,	New York: Academic Press, 1975. pp. 273-306.
leaf, stomatal zone,
plant tissues and
eel 1s.
 image: 








REFERENCES
1.	Miller, C. Exposure Assessment Modeling: A State-of-the-Art Review.
EPA-600/3-78-065, U.S. Environmental Protection Agency, Athens, Georgia,
1978. 66 pp.
2.	Hadermann, A.F., and J.M. Kelley. Exposure to Benzidine-Based Dyes. Draft
final report. Consumer Product Safety Commission, Wash., D.C., 1980.
3.	System Architects, Inc. Environmental Modeling Catalog. Prepared for
Management Information and Data Systems Division, U.S. Environmental
Protection Agency, Wash., D.C. 1979.
4.	Drake, R.L. Mathematical Models for Atmospheric Pollutants. Prepared for
Electric Power Research Institute under contract EA-1131, Research Project
805, 1979.
5.	Strenge, D.L., C.E. Watson, and J.G. Droppo. Review of Calculational
Models and Computer Codes for Environmental Dose Assessment of Radioactive
Releases. Unpublished report prepared by Battelle Pacific N.W.
Laboratories, 1976.
6.	Moschandreas, D.J. and J.W.C. Stark. The GEOMET Indoor-Outdoor Air
Pollution Model. EPA-600/7-78-106, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, 1978. 75 pp.
7.	Pendergrass, Jr., J.A., and A.F. Hadermann. Relative Contributions of
Various Sources to Home Formaldehyde Levels. Draft final report. Consumer
Product Safety Commission, Wash., D.C., 1980.
8.	Pendergrass, Jr., J.A., A.F. Hadermann, and R.J. Douglas. Contributions of
Other Indoor Air Pollutants to Formaldehyde Symptoms. Draft final report.
Consumer Product Safety Commission, Wash., D.C., 1980.
9.	Rife, R.R. Calculation of Evaporation Rates for Chemical Spills. Interim
report. The U.S. Army Toxic and Hazardous Materials Agency, Aberdeen, MD,
1980.
10.	Monitoring and Data Analysis Division, Office of Air Quality Planning and
Standards, EPA. Guideline on Air Quality Models. EPA-450/2-78-027, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina,
1978. 84 pp.
11.	Bowers, J.F., J.R. Bjorklund, and C.S. Cheney. Industrial Source Complex
(ISC) Dispersion Model Users' Guide. EPA-450/4-79-030, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1979. 360 pp.
111-21
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IV. MONITORING EMPLOYED IN EXPOSURE ASSESSMENTS
This chapter consists of three sections: monitoring methods, data bases,
and monitoring activity.
Part A gives some examples of the available methodologies for monitoring
chemical, biological, and physical parameters. It is designed as a compendium,
referring the reader to referenced texts and reports.
Part B, which is a listing of some of the available computer files, should
serve as a reference to the reader who desires access to past or current data
generated from monitoring studies. By examination of the various data bases one
may decide which would be likely to contain the desired information. No attempt
has been made to report whether or not the data contained in these data bases
has been validated.
Part C is a listing of past or ongoing monitoring activity. The purpose of
this presentation is to make the reader aware of other monitoring studies. This
may be helpful in providing more references on certain methodologies as well as
examples for examination and possible application to future studies.
A. MONITORING METHODS
This section includes the monitoring of chemical, biological, and physical
data. For details of the procedures and instruments used, refer to the
referenced reports.
Chemical Data Monitors
Concentrations of substances in the following media may be monitored with
available methodology.
Ai r--
Aliphatic Aldehydes 1
Ammonia 1
Carbon Dioxide 1
Carbon Monoxide
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Elements of Atomic No. 16 - 35 and 82 1
Lead 1
Metals 2
Methane 1
Nitrogen Oxides ->3
Organic Vapors 1
Ozone and Oxi dants 1>d
Polynuclear Aromatic Hydrocarbons 2
Respirable Particles 1»3
Sulfur Oxides 1
Total Hydrocarbons 1
Total Suspended Particles 1
Water, Blood, Urine^—
Halogenated Hydrocarbons and Benzene
Metals
Pesticides and PCB's
Polynuclear Aromatic Hydrocarbons
Ha i r- -
Arsenic, Cadmium, and Lead
Polychlorinated Biphenyls
°olynuclear Aromatic Hydrocarbons
Biological Data Monitors
Personal Cardiopulmonary Electrode Monitors 4
Physical Data Monitors
The following parameters may be monitored using available methodology.
Ai r- -
Wind Speed 1
Wind Direction 1
Temperature 1
Relative Humidity *
Water--
Sedimentation--
B. DATA BASES
Listed below are the available data bases generated from monitoring studies.
(Source: Enviro-Control , Rockville, MD)
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SAROAD (Storage and Retrieval of Aeromatic Data System)
EPA data base with ambient air quality data from over 4D00 active air
monitoring sites across the country.
HATREMS (Hazardous and Trace Emissions System)
EPA emissions data base for pollutants not regulated by the Primary
Ambient Air Standards.
NEDS (National Emissions Data System)
EPA data base on emissions of pollutants for which there are Primary
Ambient Air Standards. Collection is from about 75,000 point sources
and 3,200 area sources.
EHIS (Emissions History Information System)
EPA data base containing reports of U.S. pollutant emissions estimates
for previous years.
AEROS (Aerometric and Emissions Reporting Systems)
EPA data base of pollution data.
STORET (Storage and Retrieval for Water Quality Data)
EPA data base on water quality.
NPDES (National Pollutant Discharge Elimination System)
EPA data base with information on the quantity and quality of discharges
which have been permitted under the National Discharge Permit Program for
all point source discharges into U.S. water.
NAWDEX (National Mater Data Exchange)
U.S. Geographical Survey data base of water monitoring data from
federal, state, and local programs.
WATERDROP (Distribution Register of Organic Pollutants in Water)
EPA data base of organics in water.
EDAS (Environmental Data Analysis System)
EPA data bases on fine particle emissions, liquid effluents, solid
wastes, and gaseous emissions.
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Environmental Contaminant Monitoring Program
Department of Interior data base with pesticide monitoring data for
fish, ducks, and starlings. Twenty pesticides, organics, and heavy
metals are included.
Pesticides Soils Monitoring Program
Results of EPA monitoring programs to measure levels of pesticides in
soi 1.
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C. ONGOING MONITORING ACTIVITY
Beaumont - Lake Charles Environmental Study
This is a multimedia study of air, food, and drinking water in the Texas-
Louisiana Gulf Coast. Body burden measurements will be studied by taking blood
samples. The target pollutants that will be investigated are halocarbons,
benzene, vinyl chloride, cadmium, and mercury. This study will be performed by
the Office of Research and Development, Region VI, and the National Enforcement
and Investigative Center.
The first phase of this investigation has now been completed. A number of
monitoring methods were tested in the field, including personal air quality
monitors to measure direct human exposure to 15 volatile organic compounds
(VOC), a method of collecting and analyzing human breath samples for VOC levels,
an analytical protocol for determining VOC levels in blood, and a collection
method and fractionation scheme for bioassay of particulate organics. Eight
sampling trips between August 1978 and March 1980 resulted in determining levels
of 10 to 20 toxic substances in about 40 air samples, 20 water samples, 12 food
composites, and 22 blood and urine samples taken from local non-occupationally
exposed individuals. Major conclusions to date are as follows:
1.	Use of personal monitors coupled with breath analysis appears to be a
promising technique for field monitoring studies.
2.	Individual exposures at Lamar University in Beaumont and ambient
concentrations at Lake Charles, LA are high for many organic species.
3.	Investigations of sources identified several industrial or waste
disposal sites of concern.
Southern Ohio Integrated Exposure Assessment Study
This study is an effort to establish outdoor gradients in concentrations of
several pollutants: benzo(a)pyrene, arsenic, cadmium, and benzene. There are
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plans to extend the monitoring to indoor and personal exposures. This study is
being performed by the EPA Environmental Monitoring and Support Laboratory in
Las Vegas, Nevada.
Carbon Monoxide Studies
In this study 1 ,000 vehicles in Denver and Boston including school buses,
police vehicles, and taxicabs, are being tested for carbon monoxide (CO) levels
inside passenger compartments. Stain tubes and personal monitors in conjunction
with CO analyzers are being used. Commuting pathways and other activity
patterns are also to be studied. This study is being performed at EPA's
Environmental Monitoring and Support Laboratory, Researach Triangle Park.
World Health Organization (WHO) Air Quality Monitoring Project
There are two goals of this project. The first is to establish and develop
air monitoring systems, and the second is to exchange information on the levels
and trends of air pollution. There are currently about fifty counties
participating in this project, and a supporting monograph, "Analyzing and
Interpreting Air Monitoring Data" (WHO 1980), has been published.
Total Exposure Assessment Methodology (TEAM) Study
The goal of this research program is to provide field tested methods for
estimating total human exposure to selected toxic or hazardous substances. All
major pathways contributing to human exposure for a geographical area are to be
investigated simultaneously for each individual in the study. A comparative
analysis is to be made on the air each person breathes, the water he/she drinks,
and the food he/she eats. Concurrently, the same chemicals or their metabolites
will be measured in each person's biological fluids. The program will attempt
to establish, for each chemical, the relative importances of certain routes of
exposure as well as to determine whether a predictable correlation exists
between exposure and body burden.
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This initial study, with a duration of about 6 months, will be conducted on
nine individuals selected from the communities of Elizabeth and Bayonne, New
Jersey. The specific aims of this pilot study are as follows:
1.	To develop, test, and apply portable or personal air quality monitors
capable of determining ambient air concentrations of selected toxic chemicals in
the microenvironment of an individual.
2.	To develop and/or field test sampling and analytical protocols and
questionnaires for measuring the toxic chemicals of interest in air, food,
drinking water, and human body fluids.
Subobjectives include the following:
1.	To determine which substances are important in terms of exposure.
2.	To determine biological variability within and between individuals.
REFERENCES
1.	Moschandreas, D.J. Indoor Air Pollution in the Residential Environment.
EPA-600/7-78-229b, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, 1978. 240 pp.
2.	Pellizzari, E.D., et al. Preliminary Study on Toxic Chemicals in
Environmental and Human Samples. Research Triangle Institute (Draft Report,
1980).
3.	Selected Methods of Measuring Air Pollutants. WHO offset publication No.
24, World Health Organization, Geneva, Switzerland, 1976. 112 pp.
4.	Mage, D.T. , and L. Wallace. Proceedings of the Symposium on the Development
and Usage of Personal Monitors for Exposure and Health Effects Studies.
EPA-600/9-79-032, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, 1979. 525 pp.
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V. TREATMENT OF UNCERTAINTY IN EXPOSURE ASSESSMENTS
Uncertainty in exposure assessments arises because frequently such
assessments are derived from limited monitoring data, simulation models, and
assumptions about parameters for approximating actual exposure conditions. Both
data based on estimated parameters and assumptions about parameters are likely
to contain uncertainties which affect measurements introduced in exposure
assessments. It is true that good and ample monitoring data and realistic
assumptions will reduce, to a large extent, the magnitude of uncertainty
associated with exposure assessments. However, quality data for various
elements of exposure assessments are rare, and this is one area where future
efforts need to be directed to improve exposure assessment analysis.
In general, two approaches are available for dealing with uncertainties in
exposure assessments. The first, a parametric approach, is usually based on a
mathematical model which links the output and input variables. The model itself
can range from simple to complex. Using the most probable input values as
estimates, the estimate of output is derived through the specified model.
Uncertainties in the input variables or parameters are expressed as likely
ranges for the variables and estimates of the variables. The variation in
output variable due to perturbations in input values or parameters can be
evaluated by partial derivatives or by a simple method of calculation,
substituting new values of the variables or parameters.
The above treatment of uncertainty, conducted through sensitivity analysis
of exposure assessments due to parametric variations, is based on a mathematical
model and ranges of input values, and uses partial derivatives as the principal
tools. In the second approach, which can be termed a statistical approach,
parameters are estimated statistically from the data. The uncertainties of the
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parameters in this case can be expressed by statistical confidence intervals,
which are ranges in which the true values of the parameters are expected to lie
with a certain level of confidence. Furthermore, uncertainties associated with
individual parameters can be progressively combined by the method of error
propagation of certainty to obtain the confidence interval or uncertainty of the
output variable. The model in this case can be considered as statistical rather
than mathematical. Further explanation of the above two approaches follows.
A. PARAMETRIC APPROACH
Johnson (1) has given a good example of one approach for thoroughly
investigating uncertainties in exposure assessments. The approach is a
parametric analysis of the numerical effects of possible variations in input
terms on the estimated dose of radiation from radon in natural gas. This is
just one example of how to deal with uncertainty and is far from a complete
treatment of how to quantitate uncertainty in all types of exposure assessments.
A schematic diagram of the overall assessment of the exposure from radon
contamination is depicted in Figure 1. This sort of graphical representation is
very helpful, as it presents an organized approach to the assessment and shows
all its major components, including a listing of the important parameters
involved. Following this schematic diagram, a table showing the most probable
input values or parameters used for analysis and their possible variations
(ranges) seems useful and needs to be given. The input term values are first
selected and defended or justified as being representative of a probable,
well-defined scenario. In the analysis given by Johnson, these information bits
include the radon concentration in the gas at the point of use, the type of
appliance, and parameters related to gas use, such as degree days, house size,
air exchange rate, mode of exposure, critical organ, and other factors.
V-2
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222
Rn concentration
V/ell location,
depth and pressure
seasonal
variations
production rate
Hatural
gas
wel 1 s
Gas use, heating, cooking,
etc.
Use rate, venting, dilution,
volume
222
Rn concentration
Daughter product equilibria,
free Ion fraction, ventilation
rate, aerosol properties,
dispersion and removal processes

Transport
time
Home use
of
natural gas
Radon dosimetry
Critical mode of
exposure
Critical organ
Population statistics
Geographical gas uso
Dose
equivalent
person-rem
Mot ty
I In i I <il i ty
llt.-al th
ri sk
Gas processing
and distribution,
mixing from
different well fields
Radon concentration
to dose conversion
factors
Dose equivalent to
heal Hi u li octs
conversion factors
SOURCE
TERM
EXPOSURE
CONDITIONS
POPULATION
EXPOSURE
HEAL Til
LI FECTS
Figure 1. Model for estimating potential health effects from radon In natural gas.
SOURCE: Johnson, R.H., Jr., D.E. Bernhardt, N.S.' Nelson, and II.N. Calley, Jr. November 197.'). Assessments
potential radiological health effects from radon in natural gas. EPA !>?0/l-73-004.
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Possible variations in each of the above parameters are then listed, e.g.,
although the radon concentration used in the assessment was 20 pCi/liter, the
possible variation is 10 to 100 pCi/litar. A table (Table V-l) is used to
provide representative values of the parameters and their possible variations.
A second table (Table V-2) is then used to provide simple, one-at-a-time
factors for use in estimating the effects on the assessment of output value for
variations in the input terms. To facilitate such "what if" analyses by the
reader, correction multipliers are provided for each value. For example, since
the exposure decreases exponentially with increasing air exchange rate, and 1.0
air exchanges per hour is the reference level, multipliers at 0.25 and 2.0 air
exchanges per hour are given. The correction at 0.25 air exchanges per hour is
6.01, i.e., the exposure is 6.01 times as great at 0.25 than at 1 air exchange
per hour. The correction multiplier at 2.0 air exchanges per hour is 0.339,
which is 0.339 of the dose at 1 air exchange per hour. Also, the dose at 2 air
exchanges per hour is i/18th of the dose at 0.25 air exchanges per hour, thus
showing the pronounced influence of air exchange rate on radon-related dose to
the bronchial epithelium.
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TABLE V-1. EXPOSURE CONDITIONS AND POSSIBLE	VARIATION IN PARAMETERS FOR
ANALYZING DOSE FROM RADON IN	NATURAL GAS
Parameter	Condition for this	Possible variations^
analysi sa
Radon concentration in
gas at point of use
Gas appliances
Gas use:
Ranges
Heaters
Degree-days
Appliance venting
House size
Ai r change rate
20 pCi/1
Cooking ranges
Space heaters
0.765 m3/day
0.354 m^/degree-day
Average for each state
Unvented
226.6 m3
One per hour
10-100 pCi/1
Could include
refrigerators, clothes
dryers, etc.
Up to 1.19 m3/day
0.28-0.42 m3/degree-
day
+_ 25% within states
Ranges could be partly
vented
142-425 rn3
0.25-5 per hour
aThese are intended to be typical average conditions, although some of the
less well understood parameters were chosen to give a higher or more
conservative dose estimate.
^These are reasonable variations which could be encountered for a large
fraction of the exposure conditions or population at risk.
cSee original document for average annual degree-days and for variation
with degree-days/day.
^Ratio of Rn, RaA, RaB, RaC (RaC1).
eThis factor includes assumptions for daughter equilibria, critical mode
of exposure, lung model, and other dosimetry factors.
(continued on following page)
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TABLE V-l. (continued)
Parameter	Condition for tnis	Possible variations^5
analysi sa
Radon concentration in home
from ranges
from heaters0
Radon daughters:
in gas
in home
Percent free RaA
Critical mode of exposure
Critical organ
Dose conversion factore
Quality factor	
0.0028 pCi/1
0.01 pCi/1
No daughters
1, 0.8, 0.6, 0.4Q
8.5 percent
Inhalation of radon
daughters
Bronchial epithelium
100 rads/year for
continuous exposure
at 1 WL (100 pCi/1)
10
0.001-0.05 pCi/1
0.005-0.3 pCi/1
1, 1, 1, ld
1, 1, 1, 1 tod
1.0, 0.5, 0.25, 0.1
5-25 percent
Radon alone gives
< 1% of dose
Some exposure also to
nasopharynx, lung,
and whole body
50-125 rads/year
3-10
aThese are intended to be typical average conditions, although some of the
less well understood parameters were chosen to give a higher or more
conservative dose estimate.
^These are reasonable variations which could be encountered for a large
fraction of the exposure conditions or population at risk.
cSee original document for average annual degree-days and for variation
with degree-days/day.
^Ratio of Rn, RaA, RaB, RaC (RaC1).
eThis factor includes assumptions for daughter equilibria, critical mode
of exposure, lung model, and other dosimetry factors.
V- 6
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TABLE V-2. CORRECTIONS TO ADJUST ESTIMATED HEALTH EFFECTS FOR DIFFERENT
EXPOSURE CONDITIONS
Parameter
Correction multiplier
Ai r changes per hour
0.25
1.0
2.0
Radon activity
Quantity of gas used
House size
Daughter equilibria
Ratio 1, 1, 1, 1
1, 0.9, 0.8, 0.7
1, 0.8, 0.6, 0.4
1, 0.75, 0.5, 0.3
1, 0.5, 0.25, 0.1
Percent unattached RaA
3
8.5
10
25
Dose conversion factor
Quality conversion factor
Health effects conversion factor
6.01
1.0
0.339
Li near3
Li near
Li near
1.9
1.3
1.0
0.84
0.39
0.75
1.0
1.3
2
Linear
Linear
Linear
aA linear correction means the correction is proportional to the variation
in the parameter.
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Finally, no exposure assessment should be considered complete without a
review of uncertainties. This review should include a qualitative evaluation of
the significance of pertinent assumptions in light of reasonable variations
which could be encountered for actual exposure conditions. If possible, special
emphasis should be placed on evaluating extremes in each assumption. For
example, have parameters been chosen to evaluate extreme or average exposure
conditions? Is the final assessment likely to be an overestimate or
underestimate? In addition, the review of uncertainties could also include a
comparison of exposure estimates with actual monitoring data (if any exists),
and a mathematical/statistical propagation of errors for each of the assessment
parameters.
The approach outlined above is a simple one based on calculating results
after substituting the new values of the parameters. To summarize, this simple
approach has four basic components:
1.	A schematic diagram of the overall assessment.
2.	A table listing the main assumptions and possible quantitative variation
of each parameter.
3.	A sensitivity analysis of the effects of the output variable(s) with
variations of the input variables or parameters.
4.	A/review of uncertainties.
This approach provides answers to "what if" questions identical to those
that can be generated by partial derivatives. An elegant exposition of the
partial derivative approach was given in the GEOMET Indoor-Outdoor Air Pollution
Model (2). The model estimates indoor air pollutant concentrations as a
function of outdoor pollutant levels, indoor pollutant generation source rates,
pollutant chemical decay rates, and air exchange rates. Sensitivity studies on
the model parameters were conducted with partial derivatives indicating change
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in outdoor pollutant levels for variations in input variables or parameters. The
main advantage of the partial derivative approach is that formulas for
evaluating partial derivatives can be provided. Simple graphs of output vs.
input parameter variations, taken one at a time, can be used to show the forms
and strengths of the various dependencies.
Mathematically, for a given general model y = f(X,P), model sensitivity is
defined as:
9^U*o.P„)
where
f = the function defining the mathematical model,
X = (Xi, X2> •••» *n) = the vector of independent variables,
p = (Pl» P2> •••> Pn) = the vector of parameters,
X0 = (Xio, X20. ..•» *no) = fixed value of X, and
po = (P10» P20» •••> Pno) = fixed value of P.
The term a f(X,P) = (X0, P0) is the partial derivative of
3 Pi
the function f with respect to the parameter pi at fixed values of the input
and parameter vectors X0 and P0. The partial derivatives can be considered
as sensitivity coefficients. The change in the function f due to perturbations
of several parameters is given by the following equation:
k
df = 1 9 f dp,	(1)
i = l 3 Pi
Equation (1) indicates that the approximate uncertainty (df) of f is a linear
combination of the uncertainties in the individual parameters (dpi, i=l, ...,
k), where the coefficient of each dp^ is the sensitivity coefficient. The
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approach can be used for error or sensitivity analysis when Af, the actual
change in the function, can be approximated by df.
B. STATISTICAL APPROACH
In the parametric approach, the effects of the variations of the input
values on the output value is either determined numerically through the
substitution of the new values of the input variables or through evaluation of
the partial derivatives. Statistical methods are not used directly for analysis
of uncertainty but the ranges of the input variables can be determined
indirectly through statistical analysis.
In the statistical approach, uncertainty is analyzed through more rigorous
use of statistical methods. Essentially, in this approach uncertainty of an
unknown parameter is given by a confidence interval where the true value of the
parameter will lie. The level of confidence can be set accordingly as desired
by the analyst. Furthermore, uncertainties associated with individual
parameters can be propagated, and the manner in which they are propagated will
depend on the functional relationships between variables and upon the type of
uncertainty (random or systematic) involved.
The uncertainty or error in the estimate of a parameter can be broken down
into two components known as random error and systematic error. Random error
results from imprecision of measurements, which is indicated by the scatter of
the independent measurements on a parameter. Systematic error, on the other
hand, results from the inherent bias in the measurement process and cannot be
eliminated even if the sample size is greatly increased. Failure to measure
something that is intended results in bias. If bias is zero, then uncertainty
will consist solely of random error.
R.W. Serth et al. (3) have provided practical and useful formulas for
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evaluation of uncertainty or errors when random or systematic errors are
present. Tables V-3 and V-<i give error propagation formulas for various
operations of variables for random and systematic errors. In the case of random
errors, uncertainty is expressed by confidence intervals determined from
samples. For example, consider two independent variables X]_ and whose
measurements are subject to random errors. The true means and X2 are
unknown and are estimated from samples n^ and n£. The errors of measurement
for Xj and X2 are assumed to be normally distributed with zero means and
variances crj2 an(j c^. The sample means A and B are the estimates of
true means. With these assumptions, (1-ct) x 100% confidence intervals for
X} and X2 are given by A _+ a and B _+ b. The terms a and b are evaluated by
a 1	a 2
7	x	7
~ a and a ^ where Zais the (l-a/2) percentage point of the
normal distribution and can be obtained from the table of normal distribution.
The propagation of error for addition of Xj and X2 can be obtained by
considering y = X^ +_ X2. The confidence interval of "x^ + "X2 is given by
A + B _+ vV + b^ (see Table V-3). Confidence intervals for other functions
of X]_ and X2 are given in Table V-3. In practice, the population variances
2 and a22 are not known, and they have to be estimated by sample
variances. Where the variances <^2 ancj ^2 are not known and are
replaced by sample estimates, the terms a and b are given by t„,sl and
/Ml
t„, j2 where ta is the (l-ct/2) percentage point of 't' distribution and
•/n2
S}2 and S22 are sample estimates of c^2 and ~22. when the
sample size is large, confidence intervals can be approximated well by using
normal distribution.
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The determination of confidence intervals and propagation of errors provides
another possible approach to determine uncertainty associated with exposure
assessments. The output variable related to exposure assessments usually
depends on various input parameters whose estimates are needed to make sound
exposure assessments. If sample data are available for estimating parameters,
the uncertainty or confidence interval for each parameter can be constructed by
the method discussed above. Furthermore, propagation of error formulas can be
used for determination of uncertainty of any function of the parameters.
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TABLE V-3. ERROR PROPAGATION FORMULAS FOR RANDOM ERRORS
Operation
Error Propagation Formula
Addi ti on
Xi + x2
A + B + /a2 + b2
Subtraction Xi - X?
A - B + "'a2 + b2
Multiplication X i X2
AB + ,/B2a2 r A2b2
Divi sion
Xi/X2
General case f(XjX2)
f(A,B) sf(A,B)Zjg + cf(A,B)~[2 b2
3 Xi i 3*2 |
Note:
A ^ a and B +_ b are confidence intervals for Xj and X?, where Xi and
"XJ are the true average values and A and B are the samp] e"~means based on
samples n^ and n?. It is assumed that the variables Xj and X2 are
statistically independent. The errors are assumed to be normally distributed
with zero means and variances a^2 an(j c^2. The error propagation
formulas give (l-ci ) x 100 percentage confidence intervals for various
operations of X and y, where a = ol and b = Z_, a2 , and
a /rr a 'W
za is the (1-a/2) percentage point of the normal distribution. The formulas
for multiplication, division, and the general case are only approximations, as
they are based only on the first two terms in the Taylor Series expansion.
V -13
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TABLE V-4. ERROR PROPAGATION FORMULAS FOR SYSTEMATIC ERRORS
Operati on
Lower Bound
Upper Bound
Addi tion
(A + 3) - (a + b)
(A +3) + (a + b)
Subtraction
(A - B) - (a + b)
(A - B) + (a + b)
Multip!i cation
AB + sgn(AB)ab - (a|B|+b|A|)
AB + sgn(A3)ab + (ajBj+b|AI)
Di vi sion
A - a t B ] +b | A |
A + a|B|+b|A|

S 8^ + sgn(AB)b)B|
B B^ - sgn(AB)b|3j
Mote:
A + a and 3 _+ b are error bounds for Xj and Xi, where A and 3 are
estimates. The formulas give lower and upper bounds of four basic mathematical
operations of X]_ and X?. The formulas are valid only when Xj and X£ are
functionally independent variables. Sgn (AB) denotes the algebraic sign of the
product AB.
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As an axampis of the application of error propagation of uncertainty,
consider that a certain pollutant is released to the air and that solid wastes
are disposed of from a plant. It is required to estimate the mean emission
factors of air and solid waste separately, as well as the total mean emission
factor, which is the sum of the two individual emission factors. Consider that
the following sample data are available for estimation.
TABLE V-5. HYPOTHETICAL DATA

Ai r
Solid Waste
Number of observations, n
10
15
Sample mean emission factor, g/kg
0.403
0.760
Sample standard deviation, s, g/kg
0.318
0.540
tO.975, n-1 (0.975 point of 1t'
distribution)
2.262
2.145
Following the notation of Table V-3, the estimates of mean emission factors
for the pollutant to air and solid waste are as follows:
Estimate of mean air emission factor = A = 0.403 g/kg
Estimate of mean solid waste emission factor = B = 0.760 g/kg
The 95* confidence intervals for mean emission factors to air and solid waste
are given as:
95% confidence interval of mean air emission factor = 0.403 +
0.228 g/kg, a = 0.228 g/kg
95% confidence interval of mean solid waste emission factor = 0.760 +
0.298 g/kg, b = 0.298 g/kg
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The total emission factor is the sum of the air and solid waste emission
factors. T'ne confidence interval of the mean of the total emission factor is
calculated by the error propagation formula for addition (see Table 3) as
fol1ows:
Confidence interval of total emission factor = A + B +y/a2 +• b2
= 1.163 + 0.375 g/kg
Though rigorous statistical analysis of uncertainty in exposure assessments
is desirable, it might be difficult to adopt. The sampling data for estimation
of various parameters are often unavailable or scanty, making them unsuitable
for reliable statistical analysis. In these situations, a simpler parametric
analysis or a combination of parametric and practical statistical analyses can
prove to be useful.
REFERENCES
1. Johnson, R.H. Jr., D.E.	Bernhardt, N.S. Nelson, and H.W. Calley, Jr.
Assessment of Potential	Radiological Health Effects from Radon in Natural
Gas. EPA 520/1-73-004,	U.S. Environmental Protection Agency, Wash., D.C.,
1973.
2.	Moschandreas, D.-J., and J.W.C. Stark. The GEOMET Indoor-Outdoor Air
Pollution Model. EPA-600/7-78-106, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, 1978. 65 pp.
3.	Serth, R.W., T.W. Hughes, R.E. Opferkuch, and C. Eimutis. Source
Assessment: Analysis of Uncertainty Principles and Applications.
EPA-600/2-78-004u, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, 1978. 180 pp.
V—16
 image: 








VI. GLOSSARY OF TERMS USED IN EXPOSURE ASSESSMENTS
This chapter of the Handbook contains many terms commonly used in the
exposure assessments of the various program offices. It is important that these
terms be defined since they are not universally understood as having only one
meaning. It is hoped that the definitions presented here will be used by all
program offices in future assessment reports.
abiotic: referring to nonliving elements of the environment.
absorption, chemical: the uptake of a pollutant by its penetration into living
or nonliving material through a physical or biological process.
absorption, radiation: the process by which radiation imparts some or all of
its energy to any material through which it passes.
acute: referring to exposure of short duration. Traditionally a general term
used for serious adverse effects following brief exposure, such as "acute
studies" referring to LD50 estimates.
adsorption: the adhesion of pollutants to the surfaces of materials.
ambient: environmental or surrounding conditions.
area source: a pollutant source that releases emissions over a relatively large
geographical area.
background, chemical: normal environmental concentrations of a pollutant
resulting from non-specified sources.
background, radiation: radiation arising from radioactive material other than
the one directly under investigation.
bioaccumulation: the ingestion and concentration of a substance (pollutant) by
an organism.
bioassay: the determination of the biological effect of a substance on a test
organi sm.
bioconcentration: the increase in concentration in tissues of aquatic organisms
over that in water due to the water only, and not due to ingestion (see
bioaccumulation).
biodegradation: the decomposition of a pollutant by organisms into more
elementary compounds.
VI-1
 image: 








biomagnification: the total accumulation of a pollutant by a series of
organisms in the food chain normally showing increasing concentrations of
the pollutant in each succeeding trophic level.
biotransformation: the changing of a substance into other compounds; includes
bi odegradati on.
burden: the quantity of a substance contained in a given constituent at a given
time.
carcinogenicity: the capacity of a substance (pollutant) to cause or induce
cancer.
CAS registration number: a number assigned by the Chemical Abstracts Service to
identify a chemical substance unambiguously.
chronic: referring to adverse effects resulting from long term and/or
frequently occurring exposure to a pollutant.
critical pathways: those pathways by which a significant amount of pollutant
moves from the source to the receptors.
critical receptor: a designated segment of the human population or of the
environment which is most adversely affected by exposure to a pollutant.
critical source(s): the pollutant source(s) that contributes significantly to
the exposure of the critical receptor.
cumulative exposure: the summation of exposures of a receptor to a pollutant,
over a period of time.
Curie: the unit used in measuring radioactivity amounting to a decay rate of
3.7 x lOlO disintegrations per second.
damage/response: the mathematical relationship between exposure and likelihood
or extent of injury to the receptor.
decomposition: the reduction of net energy level and cnange in chemical
composition of organic matter because of actions by microorganisms.
degradation: the chemical or biological transformation of a complex compound
into simpler compounds.
dermal exposure: exposure of an organism's external membrane (generally the
skin) to a pollutant.
diffusion: the movement of a pollutant in an environmental medium resulting in
its dilution.
direct exposure: exposure resulting from occupational or consumer contact with
a chemical.
VI - 2
 image: 








dose, chemical: the quantity of a pollutant absorbed across the exchange
boundaries of the receptor and available for interaction with metabo1ic
processes.
dose, radiation: the quantity of radiation absorbed, expressed in units of
rads.
dose commitment, radiation: the sum of doses to all individuals over the period
a radioactive substance (pollutant) persists in the environment in a state
available for interaction with humans; measured in person-rems.
dose equivalent, radiation: ' biologically effective radiation, expressed as the
product of absorbed dose, a quality factor, and a distribution factor;
measured in units of rems.
dose rate: the quantity of material (pollutant) absorbed across the exchange
boundaries per unit of time.
dose response: the function relating dose to the likelihood of adverse
effects to an organism.
dosimetry: (1) instrumentation to measure dose; (2) process of measuring dose.
ecological (or environmental) exposure: exposure of a nonhuman receptor to an
environmental pollutant.
ecology: the interrelationships of living things to one another and to their
environment or the study of such interrelationships.
ecosystem: the interacting system of a biological community and its nonliving
envi ronment.
effective stack height: the sum of the stack height and the plume rise.
effluent: gaseous or liquid outflow (including aerosols and particulates) of a
pollutant from a source to the environment.
emission factor: a term relating the amount of a pollutant released to the
environment by a source to the level of activity of the source.
emission rate: the amount of a pollutant released to the environment by a
source per unit of time.
environmental fate: the destiny of a pollutant after release to the
environment; it involves temporal and spatial considerations of pollutant
transport, transfer, and transformation.
epidemiology: the science that deals with the incidence, distribution, and
as the final outcome, control of disease.
V1-3
 image: 








exposure, chemical: a measure of the amount of a pollutant available at the
exchange boundaries, i.e., lungs, gut, and skin of the receptor during
speci fied times.
exposure, radiation: a measure of the ionization produced in air by X or gamma
radiation; expressed in units of roentgens.
exposure assessment: an estimation of the magnitude of exposure to an
environmental pollutant; it generally requires that an estimation be made of
all of the pollutant's major features including sources, releases, fate, and
contact.
foliar uptake: the uptake of a pollutant by plant leaves.
fugitive emissions: emissions which are not directly out of the stacks.
Fugitive emissions are leaks which aren't captured in the exhaust system.
fume: an airborne dispersion of minute solid particles commonly formed by the
condensation of a volatilized solid, often molten metal, and frequently
accompanied by oxidation.
gradient: the rate of change of a quantity with distance.
half-life: the length of time required for the mass, concentration, or activity
of a pollutant to be reduced by one-half.
histogram: a bar chart depicting the frequency of occurrence of each of various
outcomes of an experiment or series of events.
hydrolysis: The process by which a compound is degraded by reaction with water.
indirect exposure: exposure not resulting from either occupational or consumer
contact with a chemical.
intake: that amount of pollutant inhaled, ingested, or absorbed dermally during
a specified period of time.
integrated exposure assessment: a summation over time, in all media, of the
magnitude of exposure to an environmental pollutant.
intermedia: concerning the transfer of a pollutant from one environmental
medium to another.
leaching: the movement or removal of a pollutant by the action of a percolating
liquid (generally water).
materials balance: an accounting of sources, production, uses,
destruction/disposal, and environmental release of a substance.
metabolite: any product of metabolism, especially a transformed pollutant.
mobile source: a moving pollutant source such as an automobile.
VI-4
 image: 








mobilization: the physical, chemical or biological disturbance of chemicals
that may be relatively harmless if left undisturbed in bones, adipose
tissue, ore deposits, landfills, or bottom sediments of water bodies so that
these chemicals can move into the general environment where exposures can
occur.
modeling: the development of mathematical procedures to simulate real events
and processes.
monitoring: measuring concentrations or behavior of pollutants in environmental
media or in human or other biological tissue.
morbidity: (1) relating to diseases caused by exposure to environmental
pollutants; (2) the rate of illness in a population caused by exposure to
pol1utants.
mortality: (1) relating to fatalities caused by exposure to environmental
pollutants; (2) the rate of deaths in a population caused by exposure to a
pol1utant.
mutagenicity: (1) the ability of a substance (pollutant) to cause a permanent,
hereditary change in an organism such that the affected characteristic will
be transmitted to future generations of descendants; (2) the ability of a
substance (pollutant) to cause a change in the genetic material of a cell.
particulates: finely divided solid or liquid particles in the air or in an
emission. Particulates include dust, smoke, fumes, mist, spray, and fog.
pathogenic: causing or capable of causing disease.
pathways: the sequence of environmental interactions of a pollutant extending
from its source to the receptor.
percolation: downward flow or infiltration of water through the pores or spaces
of a rock or soi1.
permissible dose: the dose of radiation or hazardous substance that may be
received by an individual within a specified period with the expectation of
no significantly harmful result.
person rem: the product of the average individual dose in a population and the
number of individuals in the population.
pharmacokinetics: the dynamic behavior of chemicals inside biological
(especially animal) systems; it includes the processes of uptake,
distribution, metabolism, potentiation or detoxification, and excretion.
photochemical smog: air pollution associated with oxidants rather than with
sulfur oxides, particulates, etc., and arising from the interaction of light
with organic matter.
V1-5
 image: 








photolysis: the decomposition or dissociation of a molecule as the result of
the absorption of light.
point source: a geographically small, stationary amission source.
population at risk: the population subgroup that is susceptible to the toxic
effects of the pollutant in question at the exposed concentration levels.
prototype source: a source that is used as a typical example to represent other
similar sources (of a certain size category) in lieu of individual modeling.
rad: the acronym for radiation absorbed dose. A dose of one rad equals the
absorption of 100 ergs of radiation energy per gram of absorbing material.
radiation: the transmission of electric or magnetic energy through any medium,
with or without matter. The term has been extended to include streams of
particles, e.g., alpha particles, beta particles, and cosmic radiation.
Examples of radiation are heat rays, sunlight, radio waves, X or gamma
rays, and lightning discharges. (Alpha particles are helium nuclei and beta
particles are electrons.)
receptor: a living or nonliving object that receives, may receive, or has
received environmental exposure to a pollutant.
rem: acronym for roentgen equivalent man. The unit of dose of any ionizing
radiation which produces the same biological effect as a unit of absorbed
dose of ordinary X-rays.
reservoir: a place in the environment where a pollutant collects for possible
later release.
risk: the potential for realization of unwanted negative consequences of an
event.
risk assessment: a quantification of the environmental and/or health risk
resulting from exposure to a pollutant; it combines exposure assessment
results with dose/response and/or damage/response information to estimate
ri sk.
root uptake: the absorption of a pollutant by a plant through its roots.
route of exposure: the nature of exposure to an organism; this includes
inhalation, ingestion, dermal contact, and less frequently, injection and
imp!antation.
runoff: the portion of rainfall, melted snow, or irrigation water that flows
across ground surfaces and into streams, lakes, ponds, discharge basins,
sewage treatment plants, etc.
sedimentation: the settling of solids under the action of gravity.
y 1-6
 image: 








sink: a place in the environment where a pollutant collects more or less
permanently.
sorption: the process of taking up and holding either by adsorption or
absorption.
source: the origin of the emissions of a pollutant to the environment.
species, chemical: a specific kind of chemical molecule or radical ion, as
opposed to a class, mixture, or unspecified substance; the helium atom, the
benzene molecule, and the OH radical are chemical species.
stratification: (1) the division of a population into subpopulations for
sampling purposes; (2) the separation of environmental media into layers as
in lakes.
synergism: cooperative action of two or more agents such that the total effect
is greater than the sum of the individual effects taken independently.
teratogenicity: the capacity of a substance (pollutant), to cause nonhereditary
changes, e.g., birth defects, in a first-generation descendant.
threshold: the lowest dose at which a specified measureable effect is observed
and below which it is not.
threshold limit value (TLV): the largest exposure at which no measurable
adverse effects are expected to be produced; a list of values is published
periodically by the American Conference of Governmental Industrial
Hygienists for various chemical compounds.
time-weighted average: an average of a sample of observations weighted to
represent time history, usually applied to environmental concentrations.
toxicant: a substance that kills or injures an organism through its chemical or
physical action or by altering its environment.
toxicity: the quality or degree of being poisonous or harmful to plant or
animal life.
transfer: the movement of a pollutant from one environmental medium to another.
transformation: the change in chemical state or structure of a pollutant.
transport: the movement of a pollutant from one environmental medium to
another.
uncertainty: a range of values (probability estimates) or the statistical
confidence limits associated with an estimated value.
uptake: See dose, chemical.
V1-7
 image: 








VII. STANDARD FACTORS USED IN EXPOSURE ASSESSMENTS
This section of the Handbook contains some of the parameters used in the
exposure assessments of the Program Offices. We have classified these
parameters as biological, economic, chemical, and physical. The Program Offices
reserve the right to exercise judgement in the use of these standard factors as
mitigating circumstances (such as current data) may warrant the substitution of
more appropriate numbers.
A. BIOLOGICAL PARAMETERS
Mass of Standard Humans^
male adult: 70 kg
female adult: 60 kg
Skin Surface Area?
1.85 m^ _ totally exposed (man 180 cm high)
0.294 m? - assuming short-sleeved, open-necked shirts, pants,
shoes, with no gloves or hats
0.091 m? - assuming long sleeved shirts, gloves, pants, shoes.
Effective Pore Size of Skin and Other External Membranes3
4 Angstroms (0.4 nm)
Amount of Food Consumption^
1500 gm/day (excluding beverages)
Drinking Water Consumption^
2.0 1 iters per day
Respiratory Rate^
Adult male
resting	0.5 m^/hr
1 iaht work	1.2 m3/hr
medium or heavy work	1.8 m^/hr
Adult female
0.27 m3/hr
1.0 m3/hr
1.5 m3/hr
VII-1
 image: 








Size of Respirable Particulates (aerodynamic diameterp
< 1/jm : 100" reach the alveoli; 0% retention in nasal passage
?. jum : 30% reach the alveoli; 20% retention in nasal passage
5 Aim : 50% reach the alveoli; 50% retention in nasal passage
>10/jm : almost complete retention in nasal passage
- mouth breathers can inhale particles up to 15/jm aerodynamic diameter
VI1-2
 image: 








3. ECONOMIC PARAMETERS
1977 U.S. Population by Agg and State (in thousands)?
*. No, Oral..
lo*a	
Mo		
N. Dak.
S. Da*....
Nflir
Kurtt.
S. All	
IX	
	 U.MT
MI..
iMonU.
lihilio.
w yo-
fat"
N.
Anx.___
uua	
Ht	__
«ali	
Cm<	....
3. 4.V5
rs:.'
i.M
\.Z?9
:ca
uVj
3.330
3i
571
z.is^
:u
401
2!.Tor
l. 757
3.3*3
1,144
1M
31*

»

2.511
309
3W7
i*,A30
l.cw
;,m
10.831
17*
1.3 IT
Tf.l
iV
112
W7
n
133
4C*
as
u I
:,si9
w
ZsQ
;.:v)
ia".
LVL&

»i
343
i.r*
132
710
C3
4&
9C
a.rc
1333
4.1*1
3.va
;w
:jjs

ifj*
333
zx,**
1.372
3,:<m
4f»7
~o
72

7i
U4




\S


J *-,*3
T!~*4

\ .• \f t
>r-»M

> ?nr;
•-TVJ

'lUi
',1111




<SVPT
uvcr

i2.:r.o
::.Di5
43.777
2Z.131
t32.f.*^
5-11

4.SII
3.573
1.421
3 7"
J:
w

2V2
130
;•/,

4M
•>''

¦m
"M

31

M
M

««~
SM
l.'U
:.r-j
,«lv:
4. !'•¦*»
TO
M
:v,

i i*
573
^3
173
l.IKi
AMI
340
2.23d
:.rm
2.012
u.r<


zt.ai'

¦,»:x
J


::.^7'i

3->*»
2.-7*;
i.r^


Vi
rj.'i
3.724
2.r»»3
1.432

:.~3
Z.i 74
u.rs:
A. IM
4.::o
^ 57S
M7
M7


l.m
7. ^ \
4?:
:.-j
1.774
7"o^ i

3.^«»

6-VJ
3 :;i

1. !f»*

73*
•V.7
3.0M
1. "4


3w
2Ni
1.31G
w*i
^4
3.244
1.^60
*.«2
5.4*1
3.3«
2. mT
n.??:

:w
;.:.u
T34
I-4
Z. 7-V»
rnr.
lhA
iw.
'«(

:! ^
571
3?4
I.Vj*

i *_>
3.417
37
4:

!'«i
77
*Vl
:o
43
?«
i;n
\.N
47S
t23
V5
3111
,TIM>
\\m)
I.W5
173
143
7*
4T/.
753
l.f*4
:.iw
2.010
n.:n


:i. X-.
4f,
>
.Ml
n.^
?-3
4*r?
asn
1*3
1. 4*»V
.".IT
1^9
;, ?rj;
4fi
4<J
2/4
134
71

4<j0
333

1,010
<'4
:.rji
i 37

.'•M
417
2t9
1.3:3

337

i.wr
vtn
3. >*4
rr.»
t*3
'J*!)

2t?
1.1*«3
393
3/T
i. ma
'TiS

3. 4M
334
443
2,1a
I.W7
1.444
i.:;o
l.SW
MT
4.310
2.412
1.310
1.3 H
-71
7.H
l.«40
or*
ZM
2.4*r:
3^
2H
1.4 V,
Ml*
4 ro,
i i
733
21*
1.7M
7w
.1'^
z.'ii
25e
143
NO
4*J4
2CA
1,373
I.7I?
1.3*1
7. ro
4.105
N
* •
I!
U.JK1
\r»r
\l&
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4V4
2M
1.4m
114
2U
1.7*7
717
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2.«>^
•:u
1&3
919
ifO
3i?
1.9W
1.U06
773
4.344
2. *rj
i.ia
S.773
123
a
3.3U
I.571

t*7Xt
CO
43
2V4
1^

r.*3
71
U
274
1U
¦ 4
A74
33
23
134
M
33
2T3J
2157
ir:
9«
477
Zls
I.
HIT
77

21.'4

>3
1*4
111
740
4J7


102
Mi*
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J4
7*J?
41
37
2Jt
{34
31
439
«
l.ru
:o.:u
5. *77
2.31)
a.rsi
£\4

11 »77
. 7110

;. .*"*•
1»M»
103
Ml.'
4V\
274
1/rtL'.
i.u:
t.2«
7,fA7
4, 4>* 7
2.1V.
13, sr
26
2i
if. w
i*
V
r^>
73
(U
3JI
i 72
Q
*U
VI1-3
 image: 








1977 U.S. Population by Age and Sex (in thousands)?

Ma 1 e
Fsmale
Total
Total , al 1 years
105,2-0
111,092
216,332
under 5 years
7,790
7,446
15,236
5-13 years
15,4 38
15,789
32,227
14-17 years
2,553
8,228
16,731
18-21 years
3,436
8,361
16,798
22-24 years
5,740
5,311
11,551
25-34 years
16,312
16,677
32,990
35_44 years
11,433
12,047
23,480
45-54 years
11,319
12,062
23,332
55-64 years
11,319
12,062
23,382
65 years and over
9,599
13,925
23,491
16 years and over
76,756
83,763
160,521
13 years and over
72,460
89,629
152,089
21 years and over
66,060
73,270
139,320
median age (yrs.)
28.2
30.6
29
Number of People Exposed to the Chemical (exclusive of a workplace
envi ronment)d
Number of People
> 20 x 106
2 - 20 x 106
0.2 - 2 x 106
< 2 x
10s
Examples
-	widely used househola products
-	general air, food, and water
contami nants
-	automotive products
-	products used widely in
commercial environments
-	less widely used household
products
-	regional air and water
pollutants, farm chemicals
(exclusive of pesticides)
-	specialty hobbies, specialty
products
-	neighborhood air and water
pol1utants from 1 oca!
industries
-	chemical intermediates rarely
found outside the workplace
V11-4
 image: 








Frequency of Exposure to the Chemical (exclusive of a workplace environment^
Frequency	Examples
Daily or more often	- general air, food, and water
contami nants
-	household products in regular use
-	material used inside
automobi1es
-	clothing
Weekly
Monthly
Yearly or less frequently
-	hobby crafts
-	household products used
intermittently
-	bleaches
-	gardening products
-	dry clearn"ng
-	certain solvents
-	house maintenance
-	automobile maintenance
-	application of household
paints
-	specialty products
Intensity of Exposure to the Chemical (exclusive of a workplace environment)^
Intensity
High (10~- or more grams
per exposure)
Medium (10~1 to 10"2 grams
per exposure)
Low (10-3 t0 i0"
per exposure)
grams
Very low (less than 10-5
gram per exposure)
Examples
plastics, fabrics, surface
coatings, volatile solvents used
in closed spaces, liquids
contacting skin, high
concentration gases
fabric additives, solvents in
open spaces or outdoor, dusts,
solutes, transitory exposures to
vapors or aerosols
low level indoor exposure,
volatile substances from home
furnishings and building
materials (e.g. piasticizers, flame
proofers), low volatility solvents,
pigments
environmental contaminants (Tow
level air, food, and water
contaminants), monomers in polymers
VI1-5
 image: 








Time SDent in Various Activities^
activity budget for 3 hr workday:
6
hr
1 i ght

2
hr
heavy
activity budget for 2- hr workday:
12
hr
rest

10
hr
1 i ght

2
hr
heavy
Birth Rate?
1976: 14.8 per 1,000 population
Death Rate?
1976: 8.9 per 1,000 population
Average Life Expectancy?
Maie - 69.0 years
Fema1e - 76.7 years
VI1-6
 image: 








Employment by Industry (1977)7
Agriculture, forestry, fisheries
Mi ni ng
Constructi on
Manufacturing
Transportation, communications, and
other public uti1ities
Wholesale and retail trade
Wholesale trade
Retail trade
Finance, insurance, and real estate
Banking and other finances
Insurance and real estate
Servi cesa
Business services
Automobile services
Personal services3
Private households
Hotels and lodging places
Entertainment and recreation
Professional and related services
Hospi tals
Health services except hospitals
Elementary, secondary schools
Colleges and Universities
Welfare and religious agencies
Public administrationb
aIncludes industries not shown
^Includes workers involved in
judicial and legislative
Total
Percent Ff
(x 10-)

3,383
18.5
814
8.5
5,504
6.4
20,637
29.8
5,833
22.3
18,706
44.3
3,597
23.6
15,109
49.2
5,038
54.1
2,061
63.2
2,977
47.0
25,658
60.5
1,924
43.0
794
11.0
3,826
73.6
1,406
86.1
1,068
58.2
968
36.4
17,644
64.5
3,6*5
76.0
2,683
72.9
5,106
70.6
2,016
47.9
1,429
57.5
4,972
32.9
separately
niquely governmental activities, e.g.,
VI1-7
 image: 








Farms'7
number of farms in the U.S. - 1.1 ;< 10°
total farm acreage in the U.S. - 1 x 1Q9 acres
average farm size in the U.S. - 397 acres
Total Land in U.S.?
2.264 x 109 acres
Home Gardens^
average size - 750 ft 2
annual value of home grown produce - $14 billion
percentage of U.S. household with gardens - 44"
total amount of land used as gardens - 5 million acres
House Si2el1
142 - 425 m3
Building Size for Typical Endosed Production Facility^
7,000 - 25,000 m3 (250,000 - 925,000 ft3)
C. CHEMICAL PARAMETERS
Chemical Composition of Dry Airl?
Substances found in greater non-variable concentrations—
Substances found in lesser non-variable concentrations--
Nitrogen 78.084 _+ 0.004%	(percent by volumes)
Oxygen	20.946 _+ 0.002% (percent by volumes)
Argon	0.934 _+ 0.001% (percent by volumes)
Neon
Heli um
Krypton
Nitrous Oxide
Hydrogen
Xenon
18.13 0.04 ppm
5.24 _+ 0.004 ppm
1.14 _+ 0.01 ppm
0.5 + 0.1 ppm
0.5 ppm
0.087 - 0.001 ppm
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Substances found in variable concentrations; may depart significantly from
normal, from time to tine and place to place-
Carbon Dioxide 330 10 ppm
Methane	2.0 ppm
Sulfur Dioxide	0-1 ppm
gZOne	0 " 0.07 PPm (summer)
0 - 0.02 ppm (wi nter)
Nitrogen Dioxide	0 - 0.02 ppm
Iodine	0 - 0.01 ppm
.Ammonia	trace
Carbon Monoxide	0 - trace
Chemical Composition Sea Water, Surface Water, and Ground Waterl3
See the CRC Handbook of Environmental Control, Volume III, Water
Supply and Water Treatment.
pH Ranges for Various Water Quality Categories^
Category	Range
Recreation and Aesthetics	5.0 - 9.0
Public Water Supplies	6.0 - 8.5
Fish, Aquatic, and Wildlife	6.0 - 9.0
Marine and estaurine organisms	6.7 - 8.5
Wildlife	7.0 - 9.2
Fresh water organisms	6.0 - 9.0
Agricultural Use	5.5 - 9.0
Irrigation Water Supplies	4.5 - 9.0
D. PHYSICAL PARAMETERS
Air Change Rate (Home Dwelling)!'l
0.25 - 5 per hour
VI1-9
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Characterization of Production Emissions^
Emission Route
Process Vents
Fugitive Emissions
Storage and Transportation
Sol id and Li qui d Waste
Stream Emissions
% of Total Emissions of Air
66 -
- 70%
15 -
• 20%
8 -
¦ 10%
o .
Lm *
• 5%
Average Wind Speed^
5.5 m/sec
711-10
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REFERENCES
1.	Abraham, S. Weight and Height of Adults 18-74 Years of Age, Uni-ed
States, 1971-1974. OHEW Publication No. (PHS) 79-1659, U.S. department of
Health, Education, and Welfare, Hyattsville, MD, 1979. 4g pp.
2.	Sendroy J., Jr., and L.P. Cecchini. Determination of Human Body Surface
Area From Height and Weight. Journal of Applied Physiology, 7(1) :1-12,
1954.
3.	Becker, D., E. Fochtman, A. Gray, and T. Jacobius. Methodology for
Estimating Direct Exposure to New Chemical Substances. EPA-560/13-79-008,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina, 1979. 132 pp.
4.	Lehman, A.J. Appraisal of the Safety of Chemicals in Foods, Drugs, and
Cosmetics. The Association of Food and Drug Officials of the United
States, 1975. p. 1.
5.	Kimm, V.J. National Interim Primary Drinking Water Regulations.
EPA-570/9-76-003, U.S. Environmental Protection Agency, Wash., D.C., 1976.
159 pp.
6.	Hayes, W.J., Jr. Toxicology of Pesticides. (Some modification by Office
of Pesticide Programs.) William and Wilkins Co., Baltimore, MD, 1975.
Chap 5, pp. 250.
7.	Lemer, W. Statistical Abstract of the U.S. National Data Book and Guide
to Sources. U.S. Department of Commerce, Bureau of the Census, 1979.
1057 pp.
8.	Hushon, J. Enviro Control, Rockvilie, MD, 1980. Unpublished data.
9.	Roddin, M.F., H.T. Ellis, and M.W. Siddiqee. Background Data for Human
Activity Patterns. Draft final report, prepared by SRI International for
the U.S. Environmental Protection Agency (Contract No. 68-02-2835),
Research Triangle Park, NC, 1979.
10.	Yost, K.J., and L.J. Miles. Dietary Consumption Distributions of Selected
Food Groups for the U.S. Population. Prepared for the U.S. Environmental
Protection Agency (Contract No. 68-01-4709), Office of Testing and
Evaluation, Wash. D.C., 1980. 63 pp.
11.	Johnson, R.H., Jr., D.E. Bernhardt, N.S. Nelson, and H.W. Calley, Jr.
Assessment of Potential Radiological Health Effects from Radon in Natural
Gas. EPA-520/1-73-004, U.S. Environmental Protection Agency, Wash., D.C.,
1973.
V11 -11
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12.	Altman, P.L., and O.S. Dittmer. Biology Data Book, Second Edition (Volume
II). Federation of American Societies for Experimental Biology, 3ethesda,
MD , 1973. 1432 pp.
13.	3ond, R.G., and C.P. Straub. CRC Handbook of Environmental Control.
Volume III: Water Supply and Treatment. CRC Press, Cleveland, OH, 1973.
14.	Liptak, B.G. Environmental Engineers' Handbook, Volume 1: Water
Pollution. Chilton Book Co., Radnor, Pennsylvania, 1974. p. 1321.
V11 -12
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APPENDIX A
GUIDANCE FOR THE PREPARATION OF
EXPOSURE ASSESSMENTS
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I. PURPOSE
The guidelines presented in this document provide the Agency with a
general aoproach and framework for carrying out human or nonhuman exposure
assessments for specified pollutants. The guidelines have been developed with
the intention that they will assist in future assessment activities and
encourage improvement in those EPA programs which require, or could benefit
from, the use of exposure assessments. The guidelines are procedural and are
not intended to usurp the substantive basis for regulatory standards or the
data requirements for regulatory action under any statute. They should be
followed to the extent possible in instances where exoosure assessment is a
required element in the regulatory process or where exposure assessments are
carried out on a discretionary basis by EPA management to support regulatory
or programmatic decisions. In some cases, the guidelines will be useful only
as a rough template to help ensure that significant oversights do not occur.
In other cases, the guidelines will serve more closely as a model.
The purpose of the guidelines is threefold. First, the document, by
laying out a set of questions to be considered in carrying out an exposure
assessment, should help avoid inadvertent mistakes of omission. EPA
recognizes that gaps in data will be common, but the guidelines will
nevertheless serve to assist in organizing the data that are available,
including any new data developed as part of the exoosure assessment. It is
understood that exposure assessments may be performed at many different levels
of detail depending on the scope of the assessment.
The second major purpose of the guidelines is to promote consistency, to
tne extent feasible, among the various exposure assessment activities that are
carried out by the Agency. Consistency with respect to common physical ,
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chemical, and biologist par-meters, with respect to assumptions about typical
exposure situations, and with respect to the presentation of the possible
ranges of estimates, will enhance the comparability of results ana enaale trie
Agency to improve the state-of-the-art of exposure assessment over time
through the sharing of common data and experiences.
Finally, the guidelines provide a format for organizing the contents of an
exposure assessment document. This common approach to format will simplify
the process of reading and evaluating the assessments and, thereby, increase
the utility of exposure assessment documents.
As the Agency performs more exposure assessments, the guidelines will
be revised to reflect the benefit of experience.
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II. GENERAL GUIDELINES AND PRINCIPLES
exposure a;;d jjose
Exposure is me contact between a subject of concern ana a chemical ,
biological, or physical entity, hereafter designated as an agent. The
magnitude of the exposure is determined by measuring or estimating the amount
of an agent available at the exchange boundaries, i.e., lungs, gut, skin,
during some specified time. Exposure assessment is the determination or
estimation 'qualitative or quantitative) of the magnitude, frequency,
duration, and route of exposure. Exposure assessments may consider past,
present, and future exposures with varying techniques for each phase, i.e.,
modeling of future exposures, measurements for existing exposure, and
biological accumulation for past exposures. Exposure assessments are often
combined with environmental and healtn effects data in performing risk
assessments.
In considering the exposure of a subject to a hazardous agent, there are
several related or subsequent processes. The contact between the subject of
concern and the agent may lead to the intake of some of the agent. If
absorption occurs, this constitutes an uptake (or an absorbed dose) which then
may lead to health effects.
R. DECISION PATH TO DETERMINE SCOPE OF THE ASSESSMENT
The first step in preparing an exposure assessment should be the
circumscribing of the problem at hand to minimize resource utilization by use
of a narrowing process. This process could take tne form of a decision logic
path as shown in Figure 11-1. The two phases of such a logic path would be
the preliminary assessment phase and the in-cepth assessment phase.
The preliminary assessment phase should commence by considering what risk
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5 linear study ami what law might; regulate the exposure to the agent. Within
us framework, a pre! im"inary data base should be compiled from readily
available scientific data and exposure info mat ion based on manufacturer,
processor, and user practices. Next, the most likely areas of exposure
(manu factur i ng, processing, consumer, distribution, disposal, amoient, water
anc fooa, etc.) should be defined. Many of these areas will have already bee
eliminated from consideration because of the risk under study and the
regulatory law. Since a complete data search has not been conducted, well
identified assumptions and "ball park" estimates are used to further narrow
the exposure areas of concern.
Hata from this preliminary exposure assessment can then be coupled with
toxicity information to perform a preliminary risk analysis. As a result of
this analysis, a decision will be made that either an in-depth exposure
assessment is necessary or that there is no need for further exposure
information. The organization and contents of an in-aepth exposure assessmen
are given in Section III.
In assembling the information base for either a preliminary assessment or
nore detailed assessment, its adequacy should be ascertained by addressing th
following considerations:
-	availability of information in every area needed for an adequate
assessment;
-	quantitative and qualitative nature of the data;
-	reliability of information;
-	limitations on the ability to assess exposure.
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FIGURE II-1
EXZ'!PLARY DECISION ?A::i rOR EXPOSURE AS3ES3MENl
REGULATORY CONCERN
IrIC DATS;
POPULATION
exposure
-ROOUCT Lirl CYC'.
:RELi::iNARV EXPOSURE
iccrc^.rpv-
GENERAL INFORMATION
GATHERING

MOST 2R03A8LE AREAS
of ^pos'jre:




PRELIMINARY exposure assessment!
HAHAPO IDENTIFICATION:

TOXICITY

ENV.
CONC., ETC.


\
•
preliminary ris<: analysis!

XPOSU
^ r-\ —-
i
!0£::s:0N I
7~\
| BEGIN IN-DE=TH
NO NEED -OR FURTHER
X3OSl">E ASSESSMENT
ENVIRONMENTAL CONC.
NO TONICITY OVERLAo;
|£<PQSURE ASSESSMENT ! EX'OSl">E ASSESSMENT
(ENVIRONMENTAL CONC. SHOW
'"ULTI-OISCI'LINARY
= EER REVIEW
DESIGN iSSESSMEN7 3TUQV ='_i,NI
|com3°e-en;ive data gathering.
I
	v		
iCONDUCT REFINED EXPOSURE MOOElING ¦
iN-OE^Tn EXPOSURE ASSESSMENT
EGULA7CRY
;n;Dnv::
DECISION
SCIENCE DANEL
R;VIE«
HAZARD INPUT
\ J /
FORMAL RISC)
ASSESSMENT |
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C. 'JNCERTAINTY
Exposure assessments are c~~ten based on limited monitoring data,
31u 13~ i on models, and assumptions about parameters for approximating actual
exposure conditions. 3oth data and assumptions contain varying degrees of
uncertainty which influence the accuracy of exposure assessments. An
evaluation of these uncertainties is imcorta.nt and may be helpful to program
offices when the assessments are the basis for regulatory action. A rigorous
statistical analysis of uncertainty is often impossible. However, there are
simpler approaches which would be useful in describing generally the
uncertainty inherent in an exposure assessment.
The elements of a simplified evaluation of uncertainty might include the
fo11owi ng:
1.	a schematic diagram cf the overall assessment
2.	a table listing the main assumptions and possible quantitative
range for each parameter
1. a sensi ti vity analysi s
. a review of uncertainties
The schematic diagram may be helpful in several ways. It presents an
organized approach to the assessment and shows all the major components of the
assessment, including a listing of important parameters to be evaluated. Such
a model enables technical and nontechnical persons to visualize quic'cly the
overall scope of the assessment.
The table that lists all the parameters for the assessment is a place for
specifying all the values or assumptions detailing the conditions of the
e<posure assessment. This table should correspond to the parameters
identified in the schematic diagram. The table should also include a listing
of possible variations m each parameter which would encompass a reasonable
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ranee of actual exposure conditions that mi grit be expected. The text
accompanying this table should give reasons for each assumption.
Since actual exoosure conditions may have parameters with values differsn
from those chosen for the assessment, a table of correction factors could be
helpful. This table would show how the overall exposure assessment can be
varied by adjusting each parameter. With the table, one caul a quickly see th
effect of an increase or decrease of any parameter on the overall assessment.
This selective variation of parameters is called a sensitivity analysis. A
properly utilized sensitivity analysis will provide an estimate of the
possible variations in calculated exposure concentrations when relevant
parameters and process rates are varied within pre-established ranges.
A review of uncertainties should include a qualitative evaluation of the
significance of pertinent assumptions in light of reasonable variations .vhich
could be encountered for actual exposure conditions. If possible, special
emphasis should be placed on evaluating extremes in each assumption. For
example, have parameters been chosen to evaluate extreme or average exposure
conditions? Is the final assessment likely to be an overestimate or
underestimate?
In addition, the review of uncertainties could also include a comparison
of exposure estimates with actual monitoring data (if any exists), and a
mathematical/statistical evaluation based on propagation of errors for each o
the assessment parameters.
Some exposure assessments may be based largely on monitoring data. In
these cases, the uncertainty in the exposure assessments will depend coth on
the sample collection and analysis errors and on the statistical variation
associated with extrapolat:ng the observations maae for the sample to the
assessed population and time frame.
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When jsing model s, several types of ma t iie:r:a c i ca 1 and statistical methods
can be employee to calculate uncertainty in the exposure assessments from the
uncertainties in the input components. Examples of input jncertd i n ti es are
simulation models, emission rates, and evaporation rates. T'ney can be
combined to estimate the uncertainty in the exposure assessments through an
analytical approach. This approach usually requires the expected values and
variances, and sometimes requires -the covariances of the variables, as input;
the output is the variance of an estimated exposure. Simulation techniques
(such as Monte Carlo techniques) may also be used to estimate uncertainty.
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::e. organ:zatiom and contents of an exposure assoS^emt
7'ne structure of a specific -exposure assessment will depend on its
purpose, the sources of concern, and the exposure media evaluated. The actual
order in which tooics aopea- in the document is arbitrary, but the document
should 3tte^c t to include seme discussion o~ all five major topics listed
below and should proceed in a logical order from sources to exposure
estimates. A suggested outline for an exposure assessment document is given
in Exhibit 111 -1.
Since exposure assessments are written at many different levels of detail,
the extent to which any assessment contains the items listed as subheadings in
Exhibit 111 -1 depends on the purpose, scope, and level of detail of the
assessment. The outline is a guide to organizing the data whenever they aro
available, or organizing data developed as part of the exposure assessment.
The five major topics to address within most exposure assessments are as
-pllows: (1) Source(s); (2) Exposure Pathways; (3) Exposed Population(s); (4)
Monitoring or Estimated Concentration Levels;' and (5) Integrated Exposure
Analysis. Addressing a tooic may be as simple as a single statement
concerning a broad assumption tnade, or it may involve description of some or
all of the data outlined in the subheadings of Exnibit 111-1. These five
topics are appropriate for exposure assessments in general, whether the
assessments are of global, national, regional , local, si te-speci fic,
workpl aca-rel ated, or other scope. The topics are appropriate for exposure
assessments on new or existing chemicals and radionuclides. T'ney are also
applicable to both single media and -multimedia assessments.
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Ex hib i t 111 -1
SUGGESTED OUTL:'IE -OR AM EXPOSURE ASSESSMENT
1. EXECUTIVE SUMMARY
II. INTRODUCTION
A. Purpose
3. Scope
II. GENERAL INFORMATION
A.	Identity
1.	Molecular formula and structure, CAS number, TSL number
2.	.description of technical grades, contaminants, additives
3.	Other identifying character!sties
B.	Chemical and Physical Properties
IV. SOURCES
A. Character!zation of Production and Distribution
1.	Production and processing
2.	Distribution in commerce
3. Uses
C.	Disposal
0. Summary of Envi ronmental Releases
•/. EXPOSURE PATHWAYS AMD ENVIRONMENTAL FATE
A.	Transport and Transformation
B.	Identification of Principal Pathways of Exposure
C.	Estimates of Environmental Concentrations (distribution) Using
Models
VI. MONITORING OR ESTIMATED CONCENTRATION LEVELS
A.	Summary of Monitoring Oata
B.	Comparison of Concentration Estimates with Monitoring Data
C.	Estimation of Environmental Concentrations
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v: I. EXPOSED POPULATIONS
A. Hunan Populations 'Size, Location, and Habits)
1.	Popu"> -ation size and characteristics
2.	Population location
3.	Population habi ts
o. Nonhunan Populations (where appropriate)
1.	Dopulation size and character!-sties
2.	Population location
3.	Population habi ts
VIII. INTEGRATED EXPOSURE ANALYSIS
A. Development of Exposure Profiles and Scenarios
1.	Identification and characterization of the exposed populations
and critical elements of the ecosystem
2.	Pathways of exposure
3. Hunan Dosimetry and Monitorina
0. Calculation of Exposures
D. Evaluation of Uncertainty
IX. REFERENCES
X. APPENDICES
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Detailed Explanation of Outline
I.	EXECUTIVE SUMMARY
The "Executive Summary" should be written so that it can stand on its
own as a miniature report. Its main focus should be on a succinct description
of the procedures used, assumptions employed, and on summary tables or charts
of the results. Some discussion of the uncertainties associated with the
results should be included.
II.	INTRODUCTION (Purpose and Scope)
This section should state the intended purpose of the exposure
assessment and identify the agent being investigated, the types of sources and
exposure routes included, and the populations of concern.
III.	GENERAL INFORMATION
A.	Identi tv
1. If appropriate, molecular formula and structure, synonyms, CAS
number, TSL number
Z. If appropriate, description of technical grades, contaminants,
addi ti ves
3. Where appropriate (e.g., for radionuclides), other identifying
characteri sties
B.	Chemical and Physical Properties
This is a summary description of the chemical and physical
properties of the agent. Particular attention should be paid to the features
that would affect its behavior in the environment. Examples of factors to be
included, if available or appropriate, are nolecular weigit, density, boiling
point, melting point, vapor pressure, solubility, pKa, vapor density,
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partition coefficients, and half-lives.
IV. SOURCES
The points at which a hazardous substance is believed to enter the
environment should be described, along with any known rates of entry. [The
environment includes the natural (outdoor) surroundings and indoor or
anthropogenic surroundings.] A detailed exposure assessment will include a
"materials balance," defined here as a study of sources, production, uses,
destruction/disposal, and environmental release of a substance. The materials
balance should include a description of man's activities with respect to the
substance and the environmental releases resulting from those activities. It
should account for the controlled mass flow of the substance from creation to
destruction and provide estimates of environmental releases at each step in
this flow. Seasonal variations in environmental releases should also be
examined. All sources of the substance are balanced (as in accounting) with
the sum of the uses, destruction, and the environmental releases. The
environmental releases can be described in terms of geographic and temporal
distribution and the receiving environmental media, with the form identified
at the various release points.
A. Characterization of Production and Distribution
All sources of the substance's release to the environment,
consistent with the scope of the assessment, should be included, such as
production, extraction, processing, imports, stockpiles, transportation,
accidental/incidental production as a side reaction, and natural sources.
Where appropriate, the sources should be located, and activities involving
exposure to the substance should be identified.
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3. Uses
T'ne substance is traced from its sources through various uses (with
further follow-up on the products made to determine the presence of the
original material as an impurity), exports, stockpile increases, etc.
C.	Pi sposal
;.'here necessary, this section may involve an evaluation of disposal
sites and destruction processes, such as incineration of industrial chemical
waste, incineration of ihe substance as part of an end-use item in nunicipal
waste, landfilling of wastes, biological destruction in a secondary wastewater
treatment plant, or destruction in the process of using the end product. As
necessary, hazardous contaminants of the substance may be included, and
products containing the substance as a contaminant may be followed from
production through destruction/disposal .
D.	Summary of Environmental Releases
Estimates should be made of the quantities of the substance released
to the various environmental media. Sources of release to the environment
iiclude production, use, distribution/transport, natural sources, disposal,
and contanination of other products. Environmental releases should be
presented at a reasonable level of detail. Extremely detailed exposure
estimates would attempt to specify, to the extent feasible, for each
significant emission source: location, amount of the substance being released
as a function of time to each environmental nediun, physical character!sties
of the emission source, and the physical and chemical form of the substance
being released. Some evaluation of the uncertainties associated with the
emission estimates should be given.
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V. EXPOSURE PATHWAYS AND ENVIRONMENTAL FATE
The exposure pathways section should address, wherever possible, 'now a
hazardous agent gets from the source to the exposed population or subject.
For a less detailed assessment, broad generalizations on environmental fate
and pathways may be made. In the absence of data, e.g., for new substances,
fate estimates may have to be predicted by analogy with data from othe'*
substances. Fate estimates may also be made by using models and
1aboratory-derived process rate coefficients. At any level of detail, certain
pathways may be judged insignificant and not pursued further.
For more detailed assessments involving environmental ^ate, the sources
(materials balance) analysis described previously should provide the amount
and rate of emissions to the environment, and possibly the locations and form
of the emissions. The environmental pathways and fate analysis follows the
substance from its point of initial environmental release through the
environment to its ultimate fate. It may result in an estimation of the
geographic and temporal distribution of concentrations of the substance in the
various contaminated environmental media.
A. Transport and Transformation
The substance, once released to the environment, may be transported
(e.g., carried downstream in water or on suspended sediment, carried on air
currents, etc.) or physically transformed (e.g., volatilized, melted,
absorbed/desorbed, etc.); undergo chemical transformation such as photolysis,
hydrolysis, oxidation, reduction; undergo biotransformation such as
oiodegradation; or accumulate in one or more media. These processes may yield
an environmental distribution quite different from that associated with the
initial environmental load. Thus, the environmental behavior of a substance
should be evaluated before exposures can be assessed.
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Factors that nay be addressed include:
o How does the agent behave in air, water, soil, and biological
¦Tiedid? Joes it oioaccumulate or biodegrade? Is it absorbed or
taken up by plants?
o What are the principal mechanisms for change or removal in each
of the environmental media?
o Does the agent react with other compounds in the environment?
o Is there intermedia transfer? What are the mechanisins for
intermedia transfer? What are the rates of the intermedia
transfer or reaction mechanisms?
o How long might the agent remain in each environmental medium?
How does its concentration change with time in each medium?
o What are the products into which the agent might degrade or
change in the environment? Are any of these degradation
products ecologically or biologically harmful? What is the
environmental behavior of the harmful products?
o Is a "steady state" concentration distribution in the
environment, or specific segments of the environment, achieved? If
not, can the non-steady state distribution be described?
o What is the resultant distribution in the environment -
for different media, different types or forms of the agent, for
different geographical areas, at different times or seasons?
3. Identification of Principal Pathways of Exposure
The principal pathway analysis should evaluate the sources,
locations, and types of environmental release together with environmental
behavioral factors to determine the significant routes of human and
environmental exposure to the substance. Thus, by listing the important
charactsristies of the environmental release (entering media, emission rates,
etc.) and the agent's behavior (intermedia transfer, persistence, etc.) after
release to each of the entering media, it should be possible to follow the
flow of the agent from its initial release to its subsequent fate in the
envi ron-nent. *t any point along these environnental flow lines, human or
environmental exposure night occur. Points with sufficient concentration of
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the agent arv ;.sufficient potential for human or environmental contact,
including th<. (5 pathways where no environmental fate is involved, are the
principal exposure pathways.
C. Estimates of Environmental Concentrations (Distribution)
Where appropriate, models can be used to predict environmental
concentrations. Many models are based on monitoring data, and the two are
closely linked, as described in section VI below.
In this section an estimation is made, using appropriate models, of
average or representative concentrations of the agent in different
environmental media, and its time dependence in specific geographical
locations (e.g., river basins, streams, etc.).
VI. f'OMITORIMG OR ESTIMATED CONCENTRATION LEVELS
A. Summary of Monitoring Data
As discussed in the previous sections, monitoring data are used
throughout the materials balance and exposure pathways assessments to allow
quantitative estimates of both sources (releases) and environmental
concentrations. Some examples of monitoring data used in a materials balance
would be: (a) sampling of stacks or discharge pipes for emissions to the
environment; (b) testing of products for chemical or radionuclide content; (c)
testing of products for chemical or radioactive releases; (d) sampling of
appropriate points within a manufacturing plant to determine releases from
industrial processes or practices; and (e) sampling of solid waste for
chemical or radionuclide content. These data should be put into perspective
as to accuracy, precision, and representativeness. If actual environmental
'¦monitoring data are unavailable, concentrations can be estimated by various
means, including the use of fate models (see previous section), or in the case
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of new chemicals, by analogy with existing chemicals.
6. Comparison of Concentration Estimates with Monitoring Data
Examination of monitoring data has often been considered a
substitute for environmental pathways and fate analysis, since monitoring data
directly provide the environmental distributions of pollutants. The analysis
of monitoring data should be considered a complement to environmental pathway
and fate analysis for the following reasons: (a) for most pollutants,
particularly organic and new chemicals, monitoring data are limited ; (b)
analysis of monitoring data does not often yield relationships between
materials balance and environmental concentration distribution in media or
geographic locations that have not been monitored; (c) analysis of monitoring
data does not provide information on how and where biota influence the
environmental distribution of a pollutant; and (d) monitored concentrations
may not be traceable to individual sources that EPA can regulate. Monitoring
data are, however, a direct source of information for exposure analysis and,
furthermore, they can be used to calibrate extrapolate models or
calculations to assess snvironmental distribution.
C. Estimation of Environmental Concentrations
Where consistent with the purpose of the exposure assessment, it is
necessary to estimate the environmental concentrations of the agent resulting
from its release, behavior, and subsequent fate. Concentrations should be
estimated for all e.nvironmental media that the release, behavior, and fate
analysis indicate might contribute to significant exposures. Generally, the
environmental concentrations are estimated from monitoring data, mathematical
models, or a combination of the two.
The concentrations must be estimated and presented in a format
consistent with available dose-response or damage-response information. In
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some cases an estimate of annual average concentrations will be sufficient,
while in other cases the temporal distribution of concentrations -nay be
reauired. Future environmental concentrations resulting from current or past
releases may also be projected. In some cases, both the temporal and
geographic distributions of the concentration may be assessed. Moreover, if
the agent has natural sources, the contribution of these to environmental
concentrations may be relevant. These "background" concentrations may be
particularly important when the results of tests of toxic effects show a
threshold or distinctly nonlinear dose-response.
The uncertainties associated with the estimated concentrations
should be evaluated by an analysis of the uncertainties of the model
parameters and input variables. When the estimates of the enviromnental
concentrations are based on mathematical models, the model results should be
ccompared to available monitoring data, and any significant discrepancies
di scussed.
VII. EXPOSED POPULATIONS
°ODulations selected for study may be done a priori, but many times the
populations will be identified as a result of the sources and fate studies.
From an analysis of the distribution of the agent, populations and
subpopulations (i.e., collections of subjects) at potentially high exposure
can be identified, which will then form the basis for the populations studied.
Subpopulations of high sensitivity, such as pregnant women, youth, chronically
ill, etc., may be studied separately.
In many cases, exposed populations can be described only generally. In
some cases, however, more specific information may be available on matters
such as the following:
A-19
 image: 








A. Human Populations
1.	Population size and character!'sties (e.g., trends, sex/age
di stribution)
2.	Population location
3.	Population habits - transportation habits, eating habits,
recreational habits, workplace habits, product use habits, etc.
3. Nonhuman Populations (if appropriate)
1.	Population size and character!sties (e.g., species, trends)
2.	Population location
3.	Population habits
Census and other survey data may be used to identify and describe
the exposed population for the various contaminated environmental ledia.
Depending on the characteristies of available toxicological data, it may be
appropriate to describe the exposed population by other characteristics such
as species, race-age-sex distribution, and health status.
VIII. INTEGRATED EXPOSURE ANALYSIS
The integrated exposure analysis combines the estimation of
environmental concentrations (sources and fate information) with the
description of the exposed population to yield exposure profiles and exposure
pathway analyses. If available, significant data should be provided on the
size of the exposed populations; duration, frequency, and intensity of
exposure; and route of exposure. To the extent possible, consistent with the
scope of the exposure assessment, exposures should be related to sources.
For more detailed assessments, the estimated environmental
concentrations should be considered in conjunction with the geographic
distribution of the human and environmental populations. To the extent
A-20
 image: 








desirable, the behavioral and biological characters sties of the exposed
populations should be considered and population exposures to various
concentration profiles should be estimated. The results can be presented in
tabular or graphic form, and an approximation of the uncertainty associated
with them should be estimated.
A. Development of Exposure Scenarios and Profiles
Depending on the scope of the exposure assessment, the total
exposure picture may be fractionated into one or more "exposure scenarios" to
facilitate quantification of exposure. As an example, Table III-l lists seven
very broad scenarios: OccuDational , Consumer, Transportation, Disposal, Food,
Drinking Water, and Ambient. For each of the scenarios, the major topics
necessary to quantify exposure, namely sources, pathways, monitoring, and
population characteristies, are involved. Investigation of only one scenario
may be necessary for the scope of some assessments. For example, a pesticide
application exposure assessment may consider the occupational scenario, which
would cover the exposure to applicators and populations in the vicinity of the
site. An exposure assessment around a hazardous waste site >nay focus on the
disposal scenario. The exposure assessment also may consider other scenarios.
The more extensive and comprehensive the scope, the more scenarios are usually
i nvolved.
It will usually be advantageous in performing an exposure assessment
to identify exposure scenarios, quantify the exposure in each scenario, and
then integrate the scenarios for a total exposure picture. In this
"integrated exposure analysis," the adding of independent exposures from
different scenarios (keeping exposure routes separate) will often result in a
breakout of exposure by subpopulations, since the individual scenarios usually
treat exposure by subpopulation. Therefore, the integration'of the scenarios,
A-21
 image: 








TAlllt 111-1 . rxmUKIl ASStSSMLNf MltDS fOU VAItlOIIS tXPOSURC SCLNAKIOS
Exposure Scenario
Sources Me oils
Idle Needs
Copulation Characteristics Heeds
Monitoring Needs
t^>
N>
Occupational
(chemical production
processing, use)
Consumer
(direct use of
chemical or
inadvertent use)
Transportation/
Storuge/SpllIs
Disposal (include
Incineration, land-
fill)
site/plant locations,
iu-plant/on-site
materials balance
consumption rates,
distribution pattern
amounts in products
patterns of distribu-
tion & transportation;
models for spills
materials balance
around disposal method,
efficiency, releases
to environment
chemical properties
models?
chemical properties,
shelf 1Ife, release
rates, models?
chemical properties,
environmental fate
models
fate willtin disposal
process; envlroanen
tal fate of releases;
models
workers, families,
population around sites/
plants
consumers
storage, transportation
workers; general
population in area
workers at site of disposal,
general population around
si to
in-plant/on-site levels,
releases, ambient levels
surrounding site/plants
human monitoring
levels in products,
releases
releases, ambient levels
releases, levels at
various points within
process, ambient levels
Food
food chain, packaging,
addltlves
food cliaIn models,
fate during prepara-
tion or processing of
food
general population,
nonhuman populations
levels in food, feed-
stuff; food chain
saiupl Ing
Drinking Uatei
Ami) ient
groundwater, surface
water, distribution
system
releases to environ-
ment; air, land, water
leach rates from
pipes, chlorination
processes, fate in
water; mudels
environmental fate
models
general population
general population;
nonliuman populations
levels in drinking
water; ground water,
surface water; treat-
ment plants
ambient air, water,
soil, etc.; human
monitoring
 image: 








or integrated exposure analysis, will often result in an exposure profile such
as that shown in Figure II I-1.
For each exposed subpopulation (or group), exposure profiles should
include, -where relevant data are available, the size of the group, the source
of the agent, the exposure pathways, the frequency and the intensity of
exposure by each route (dermal, inhalation, etc.), duration of exposure, and
the form of the agent when exposure occurs. The following discussion, and the
discussion under Section 3 and C below, refers to calculating the exposures
under each scenario.
1. Identification of the Exposed Population and Critical Elements
of the Ecosystem
The estimate of environmental concentrations also should give the
aeographic areas and environmental media contaminated. The stated purpose of
the assessment should have prescribed the human and environmental subjects for
which exoosures are to be calculated. If the subjects are not listed, the ¦
contaminated geographic areas and environmental media can be evaluated to
determine major subjects. The degree of detail to be utilized in the exposed
population distribution depends on the concentration gradient over geographic
areas.
A-23
 image: 








o
T3
o	"3
C-	c
r—	3
<"0	$-
w
1)
c	u
oj	<tj
o	a
c
OJ I—
s- c.
<
o
c c
!L-
to 3
c	o
0)	*3
T3	4-
¦i*»	3
</> w
<y rt3
C£ Z
</>
O
<T3
O
u
o
108
107
10°
105
104
1q3
102
1a1
JXa
10-4 10-2 -iqO iq2
10"
10° 103
EXPOSURE fug/day from all sources)
Figure 111-1. Typical Exposure "Profile" of General Population
A-24
 image: 








2. Pathways of Exposure
where necessary for the regulatory purpose of the exposure
assessment, some or all of the following shoul d be provided:
a.	Qualitative - Identification and description of the routes
by which the substances travel from production site, through
uses, through environmental releases/sources, through
transport and fate processes, if any, to the target
population.
b.	Quantitative - Attaching available numerical values to the
amounts of the chemical following each exposure pathway.
Such estimates allow the various pathways to be put in the
perspective of relative importance.
3. Human Dosimetry and Monitoring
After the exposure estimates are made, they can be checked by
comparison with any available human dosimetry, human tissue monitoring, or
non-invasive human monitoring.
C. Calculation of Exposures
From the geographic and temporal distribution of environnental
concentrations, the exposed population, the behavioral characteristies, and
the critical elements of the ecosystem, exposure distributions can be
estimated. The way the exposure calculations are made should be consistent
with the requirements of the dose-response or damage-response functions that
may later be used in a risk assessment. Examples of requirements are annual
average exposures, peak exposures, exposures that are greater than sone
threshold value, or the frequency and distribution of intermittent exposures.
Many past exposure assessments have been based on the average exposure
occurring over the exposure period. The range of possible exposures is
A-25
 image: 








usually divided into intervals, and the exposures within each interval are
counted. The results can be presented in tabular form or as a histogram (see
rigure 111-1).
The population residing in a specific geographic area may be
environmentally exposed to a substance from several different sources and
through several exposure routes. Exposures for individuals in these
populations ^ay be determined by summing over sources for the same exposure
route, but exposures through different exposure routes should be kept
separate. Combined exposures should be stated only if the metabolic fate
processes are well understood. 3ecause EPA regulates sources of releases, the
contribution to exposures from each type of source with respect to which
regulation is being considered should be displayed, if the information is
available. Estimates should be presented for exposure from all relevant
exposure routes (i.e., those routes consistent with the regulatory purpose),
and the results should be tabulated in such a way that total exposures can be
determined. (For example, see Table 111-2 as one way of presenting the
results.)
0. Evaluation of Uncertainty
See II. GENERAL GUIDELINES AND PRINCIPLES, section C.
A-26
 image: 








TA3LE 111-2. EXAMPLE OF A PRESENTATION FOR MULTIROUTE EXPOSURES
Population Population

Exposure Route

Subgroup Subgroup Size
Inhal ation
(mg/yr)
Ingesti on
(mg/yr)
Dermal
(mg/yr)
Manufacturing facility
workers 200
40
5
0.5
General population
i n area around 54,000
industrial or
manufacturing facility
20
1
0.1
Farmers 3,000'
5
2
0.2
IX.	REFERENCES
The references should contain a listing of all reports, documents,
articles, memoranda, contacts, etc. that have been cited in the report.
X.	APPENDICES
The appendices may contain such items as memoranda and letters that are
not readily accessible by others, tables of monitoring data, detailed lists of
enission sources, detailed tables of exposures, process flow diagrams,
mathematical model formulations, or any other item that may be needed to
describe or document the exposure assessment.
A-27
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APPENDIX B. EXAMPLES OF EXPOSURE ASSESSMENTS
Examples of typical exposure assessment are presented here from five EPA
program offices. Because of space limitations, no attempt is made to discuss
any example in depth. For more details about each of the examples, the reader
should refer to the source documents themselves.
1. "Assessment of Potential Radiological Health Effects from Radon in
Natural Gas." U.S. EPA Office of Radiation Programs, Washington, D.C.
20460. November 1973.
Release Estimates—
This document primarily covers the release of radon (222r0) in dwellings
through use of natural gas in unvented cooking ranges or space heaters. Radon
concentrations in natural gas at production wells and in gas processing,
distribution, and storage systems are also presented and discussed.
Environmental Fate Estimates-
Environmental fate estimates for 222r0 are not addressed directly in this
document. The principal 222r0 exposure pathway considered is to individuals
in private residences.
Exposure Estimates—
The document contains a discussion of indoor human exposure to 222r0 an(j
its important daughter isotopes, 218p0j 214ptJj 214gi, and 214p0. jhe
primary concern for exposure to radon is from inhalation and retention of radon
daughters which release their alpha decay energy to tissues of the respiratory
system, especially the lungs. Various lung models are presented and discussed
in an attempt to determine the relationship of exposure to radon daughters and
the development of precancerous cells. Dose conversion factors for radon and
radon daughters are tabulated for conditions in normal rooms representative of
3-1
 image: 








typical dwellings. Exposure conditions are postulated on the basis of an
average kitchen range use of 0.765 m3 of natural gas per day in a home with a
volume of 225.6 m3 having an air change rate of once per hour (dilution volume
= 226.6 x 24 = 15,438 rc3).
The authors calculated the estimated annual dose to an individual at 0.028
rems/year in the following manner:
226.6 »3 house x 24 air chafes	?m (d11utl0n factor)
0.765 gas used per day (in ranges)
Assumed natural gas
2228n concentration * 20 pCi/1 . 0J]028 pCf/1
dilution factor	7111
0.0028 pCi/1 x 100 rads/year _ „ nnoo ,	
100 pCi/1	 " °-0028 rads/year
0.0028 rads/year x 10	= 0.028 rems/year
quality ractor
Further assumptions and calculations are made to estimate the average
tracheobronchial dose to individuals from unvented kitchen ranges and space
heaters at 15 and 54 mrem/year, respectively, or 2.73 million person-rems per
year for the entire United States population.
Oi scussion—
The tracheobronchial dose effect or risk of concern from radon daughter
exposure is lung carcinoma. The authors calculated an absolute risk of 35
excess deaths/10® persons/year/rem from exposure to radon and its daughter
isotopes. This factor is multiplied by the dose of 2.73 x 10®
B-2
 image: 








person-rems/year to obtain an estimate of 95 excess deaths per year. However,
uncertainties in and corrections for loss of daughter products by plating out or
deposition on surfaces; low ventilation rate; nose breathing instead of mouth
breathing; a lower, more realistic continuous residence time in dwellings; and
other factors lower this estimate to a more.likely estimated excess mortality of
15 deaths/year, which represents only 0.03 to 0.08 percent of normal lung cancer
mortality. Several methods for reducing exposure to 222fjn through additional
controls in production, processing, distribution, use, and storage of the gas
are discussed. It is calculated that controls for reducing radon concentrations
in natural gas by storage methods would cost over $100 million for the
elimination of each potential excess death. The authors concluded that controls
would not be cost effective on a national basis and that the use of natural gas
containing 222Rn for average exposure conditions does not contribute
significantly to lung cancer deaths in the United States. (For more details
from the text of this report see pages V-5 - V-7.)
3-3
 image: 








2. "DDVP/Trich!orofon/Naled Exposure Assessment." U.S. EPA Office of Pesticide
Programs, Washington, D.C. 20460. February 1981.
B-4
 image: 








J"
i £t^
i	1	UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. O C. 20460
o»fic< o# rtkiioot* aho to«ic	AhCii
o 3 mar lag)
W
i
un
"ODYP/Trlchlorofon/Naled: Exposure Assessment." US EPA Office of Pesticide
Programs, Washington, 0. C. 20460. February, 1981.
This document develops the human exposure assessment for three related
pesticides: DUVP, trIchlorofon. and naled, for possible Inclusion In position
document I, the OPP preliminary risk assessment for these pesticides. Each
pesticide Is an organopliosphorus Insecticide used to control a number of
different species of Insects. These three Insecticides show 4 similarity
both chemically and metabolleally.
This exposure assessment focuses on the InterconversIon possibilities of
these three pesticides. A review of the literature leads to the conclusion
that the conversion of naled and trlchlurofon to DDVP Is plausible In
mammalian systems. In addition, the metabol Ism of DDVP by hydrolysis and/
or demethylatlon lias been shown to produce other degradates In many species
Including man.
The environmental fate of these three pesticides Is Incompletely under-
stood. However, It appears that long-term persistence under natural
environmental conditions does not appear to bo a factor.
The quantitative non-dietary exposure data for affected populations
represent the best currently available estimates of exposure occurlng
during the most Important registered uses of these pesticides. Die
dietary burden was calculated by detenu tiling the rate of Ingestion of
food commodities bearing the legal tolerance limits.
OUVP/ TRIC'.II.CKOS O!!/ N\l I!)
Expoauca Aaaeamaotic
Product Chemla t cy
Syncheilia Foruu J-i c loa
EavirooauMicji Fjcu
Phya lcoclicul ca I D«yr j4ji lou jo.1 Hcc-iboll i-a
Non-01 cjry 2.tpo«jur«j
DUticy 2.\po«ur<i
Buv i rotimeac a I race SrJitch
Udiurd Cv^luuciou OivlJloo
Office oc PcaclciJe Pru^rama
Prepared by:
\	i r ' '
Rlclurd 7. Murjakl, Ph.D.
Chcial J c
Rcvleu iucclott N>>. 4
Pebruj ry I 2 , I'Jd 1
 image: 








T.\bi— of orrrprrs
Pajje
Hat of ?l4»irca		11
Llac of 			Ill
I. Overview 			 .......	I
II. Produce Chemistry		I
III* S/uchuaU aud Fornuladoo		7
^ IV, Eovlrooa^ncal Fat®		8
i
cr\
V. pliyiIcochcalcal Degradation and Mtftabollait		14
VI. Noa-QltfCary Exposure	*		2?
VII. Dtaiaiy Expoauro			45
LI at oc finite**
L.	Metabolic pathway* oil DDVP After Jo-I^aon aud CjjMi, l'Jo2 . .	16
2.	McCjbullsa oil DOVP afCur Dlcuwaky ar*l Hoccilo, I«i7l		16
3.	ODVP aacabollia 44 Jeteralucd by Uucaou «C ai, 1^71		1/
4.	Degradation of DDVP after Pag* ttc al . , 1972 		I'J
5.	Hucabollam pathways of nalcd, trlctilorofoii, atul dlchlorvou ...	.!6
-I I-
 image: 








Llac of Tabids
Produce Cliemlacry Ufonuclon	
Pormjlacloua ot Halod, Trlchlorofau, and Dlchlarvoa. .......
Half-lives foe ch« Dehydrochlorlnacloa of TC? and for cha
Uytlrolyala of DOVP la lutfici at Var/lug pa *ad iC ]7.}*C	
Ualf-llvea of cha la vlcro Dagradac loa ot TC? aad DDVP ac 37-J'C .
Ia Vlco Dvcdraloacloa of B*lf-Llv«a b( 3 x 10~6 H DDVP la BlooJ. .
Dlacary Zxpaaura fcoM Tolaraocaa: DDVP	
Dlacary Expaaura frow Tolacaocaa: Trlchlorof		
Dlacac7 Expuauro froa Tolaraacca; :UU4	
-111-
SUMtURY -- IIUN-0 IE TAKY CXI'OillHf.
The numerical values generated In tills summary are based on the .nulyiis
of the available literature and represent the best currently jvjiIjI>1c
estimates of exposure.
A.	Haled
I. Aerial Application for Nosqul to Control
Urine concentration of dfmettiylphosiiliate - O.au ppm
B.	Trlchlorofon
I. Warehouse Workers Expose.I as a Result of Storage of TIF
Dally Respiratory Exposure
exposure range: 0.06-1.391 hmj/id^
exposure mean: 0.72 mg/ra^
absorption factor: loot
0.72 mg/oi3 x 1.8 ai^/lir x 8 hr/.luy x person/70 k<j
¦ 0.15 lug/kg/day
II. Turf Applicators
a) Boom Appl Icatlon
Dally Resplratory Exposure
N. D.
Dally Dermal Exposure
Trlchlorofon detected: 2 ug/m^ body surface
Body area exposed:	0.20} in? (hand and forearm)
Absorption factor:	101
2 ug/m^/day x 0.203 in? x person/70 kg x 0.1
• 0.0006 u'j/kg/djy
bl Spray Gun Applicators
Dally Respiratory Exposure
0.002 mg/iuT x 1.8 m'/lir x Q lir/day x persun//0 kg
» 0.0004 mg/kg/diy
-40-
 image: 








pally Dcrosl Exposure
Trlchlorofon dec acted; 0.33 u g/a- body surface
Body area exposed;	0*6 a^
Absorption factor;	10Z
0.83	u&/»*/day x 0.6 x person/70 kg x 0.1
" Q-OQO? ug/kg/day
DDVP
1. Workers la Warehouses
Assumpt Ions i
1.	two Insectlcldal treatments per week
2.	effective level of Insecticide; 2 ag DDVP/ft*
3.	normal work day Is fl hours
Dally Respiratory Exposure
a) Inoectlcido aprlokled oq floor
Tina After DDVP Concent
TreacoeoC	Iq Air	
4 lir	1-7 ng/nj
24 hr	0*9 »g/ia*
48 hr	<0.4 og/m*
Possible weekly exposure;
Exposure during first day after treatment!
1./	ag/o* x 1.8 atyhr x 8 hr/day x peraoo/70 kg
- 0.35 ag/kg/day
Exposure during second day after treatments
0.9 ag/ia^ x 1.8 aVhr x 8 hr/day x parson/70 kg
• 0.15 ag/kg/day
Exposure during third day after treatment;
0.4 ng/«^ x 1.8 atyhr x 8 hr/day x person/70 kg
0-1 ag/kg/day
Total cor week (two treatments pe i ueek): 0./ + ij. ) c ») . ¦>
-	1-2 ag/kg/uk
Approximate average dally e.tpoeure - 0.2 m-j/ V, d-iy
b) Aerosol Treatment
Time After DDVP Content
Treatment	iu_A£r	
4 hr	2.2 ag/iu^
24 hr	0.14 ag/m^
72 hr	0.07 ug/tn^
Possible weekly exposura:
Exposure during first day after treatment;
2.2 ag/ia* x 1.8 uVhr x 8 hr/day x pcr^on/70 k.j
-	0.4 5 ag/kg/day
Exposure during secoitl day after treatment;
0-14 aig/o^ x 1.8 tatyhr x 8 hr/day x person/70 kg
-	0-03 ag/kg/day
Exposure dtulng third day after treatment;
0.07 tag/a-* x 1.8 a^/hr x 8 hr/day x p'jrjou/70 kg
-	0.15 ag/kg/day
Total for week (two treatments po r wuck); 0.9 + 0.0b * 0.03
0.99 mg/kg/wk
Approximate average dally exposure - 0.2	m»j/k^/d.*^
II* Aircraft Personnel -- Disinsection of Airplanes
Respiratory Exposure
DUVP sir concentrat ions. range. 0.15-0.25 mg/u»^
mean;	0.20 mg/a^
Assumption:); 30 mln/treatment, 3 tr«atmenc»/Jjy
0.2 mg/ia^ x 1.8 m^/ltr x 1.5 hi/day x pcr*on//0
0.007 mtf/k>j/da^
 image: 








III. tloiiiclioliicia with Resin Scrips
Aaaiiupc Ion; over the period of 90 days, the dally average duounc
of DOVP In Che air la 0.03 ng/ia^
The oaxlauia potential daily inhalation exposure to homeowner;
Por 2 hours of aoderate work:
0.03 mg/to^ * 1.8 ntyhr x 2 hr - 0.1 ag
For 10 hours of light work;
0.03 og/ia^ x 1.2 a^/hr x 10 hr - 0.4 ng
For 12 hours of reat;
0.03 ag/n^ x 0.3 n^/lir x 12 hr - 0.2 ag
Total dally average exposure; 0.7 og/day x person - 0.01 ag/kg/day
W	707kg
to
It Is recognised that 0DVP concentration* la the sir do not remain
constant over 4 period of 90 days, the effective lifeciae of tho scrip.
Therefore, daily exposures co DDVP are also calculated for four different
Intervals froa the tine of Installation of the strip; one day after
the stflp Is hung and approximately one month, two months, and throe
months after installation. Based on the data of Collins and DeVrles
(1973) and on the same activity schedule used in the previous calculatIon,
the daily exposures are estimated to be as follows;
A.	I day after liistallat ions 0.06 ag DDVP/n^ of air
Tocal dally exposure; 0.02 ag/kg/day
B.	21J days after ins tal la t ion; 0.02 tag DDVP/n* of air
Tocal daily exposure: 0.005 ag/kg/day
0. 56 day* after inatal latlon; 0.01 tag DOVP/n^ of air
Tocal daily exposure; 0.003 ag/kg/day
D. 91 days after 1 ils tal 1 a t Ion: <0.01 ng DOVP/n^ of air
Tocal dally exposure; <0.003 ag/kg/day
-43-
IV. Householder with One Flea Collar on Pec
Concentrjclou of DDVP (o
A.	Boots (casual exposure) range:	0.00013 - 0.00)1 a^/ u * (1-77 d.iyj)
oeeu;	0 0016
B.	Breathing Zone	range:	0.003-0.29 an;/.n^ (l-d1) Jjyi)
seen:	0.15 mg/ia^
If casual exposure to the pet Is for 0 houra/day and iho jvor
breathing rate is 1.2 aVhr ji«1 in the breathing :ano or the pot
the exposure tine li I hour/day, then the potential o^otnr^ la:
A.	Casual exposure;
0.0016 Bg/;a^ x 1.2 io~Vhr x ti hour/day - 0.015 10^/djy
B.	Breathing zone;
0.15	x 1.2 uVhr x 1 hour/day - 0.18 m^/Jay
Total potential dally exposure due to Inhalation frota pet wuarlng
one flea collar Is 0 > 2 u^/ day or 0.003 .a^/V^/day.

 image: 








3. "Human Exposure to Atmospheric Concentrations of Selected Chemicals." U.S.
EPA Office of Air Quality Planning and Standards, Research Triangle Park,
N.C. 27711. May 1980.
Introduction-
Systems Applications, Incorporated, in conjunction with Hydroscience,
Incorporated, and Minimax Research Corporation, estimated the atmospheric
concentrations of, and magnitude of, populations exposed to 35 chemicals. Three
different methodologies were employed to make exposure estimates. The
methodology used depended on the type of source being considered. Sources were
classified into three major categories:
1.	Major, Specific Point Sources - Sources considered as specific point
sources individually accounted for significant emission fractions and had enough
information available to estimate emissions. Most specific point sources were
chemical manufacturing facilities.
2.	General Point Sources - General point sources were sources for which
sufficient information to make emissions estimates was generally not available
or which were too small or too numerous to consider practically as specific
point sources. Estimates of exposure to chenicals released from general point
sources were made by developing estimates for one or more prototypes and by
multiplying those estimates by the number of sources the prototype(s)
represents.
3.	Area Sources - Sources that were even more numerous and widely
distributed than general point sources were more conveniently treated as area
sources. Examples of sources that are generally combined and treated as area
sources are home chimneys and automobiles.
3-10
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Estimates of Exposure to Chemicals Released from Specific Point Sources-
Estimates of emissions from specific point sources were made by multiplying
emission factors (mass emitted/mass produced or used) by production or use data.
Emission factors were developed by several different methodologies. A number of
emission factors were estimated for model plants based on data obtained during
onsite visits to chemical manufacturers "Emission Control Options for the
Synthetic Organic Chemical Manufacturing Industry," (EPA 68-02-2577). Emission
factors were also estimated from process monitoring data taken from state air
emissions inventory questionnaires (EIQ). In addition, emission factors were
obtained from various reports published by EPA. Finally, if no other
information was available, the emission factor for a given process was either
assumed to be equal to the emission factor estimated for another similar process
or was taken as the average of emission factors estimated for several different
processes.
Three types of emissions evolving from the production and intermediate use
of a chemical were considered.
1.	Process emissions - "discrete losses that occur at process vents from
reactors, columns, and other types of plant equipment." Process emissions are
often obtained by direct monitoring of process vents.
2.	Storage emissions - losses from storage tanks as well as from loading
and handling. Storage emissions estimates were generally obtained from AP-42
(Compilation of air pollutant factors," 2nd ed. US EPA, Research Triangle Park,
N.C. 27711. Publication No. AP-42. April 1976) calculations.
3.	Fugitive emissions - "losses that result from plant equipment leaks,
visual openings, evaporation from waste products, and other nondiscrete
sources." Estimates of fugitive emissions are generally obtained by material
3-11
 image: 








balance. For most chemical manufacturing facilities, separate emission factors
for process vent, storage, and fugitive emissions were estimated. However, in
cases of insufficient information, an overall emissions factor was estimated.
For each specific point source, average annual atmospheric concentrations
at ground level were estimated for 10 distances from the source in each of 16
wind directions. The concentrations were estimated by the use of a computer
program which combined unidirectional Gaussian solutions for each combination of
atmospheric stability classes and 6 wind speed categories with meterological
data on the annual frequencies of each of the 16 wind directions, 7 atmospheric
stability categories and 6 wind speed categories for the geographical vicinity
of the specific point source. The meteorological data used were modified STAR
data, which are climatological frequency of occurrence summaries formatted for
use in EPA Gaussian dispersion models and are recorded for numerous
meteorological stations throughout the country. The estimated concentrations
were not only functions of distance, wind direction, emission rates, and
effective stack heights but were also modified to account for the chemicals'
atmospheric reactivities.
Three major types o'f reactions were considered in estimating a chemical's
average atmospheric reactivity: photolysis, reaction with the hydroxy! radical,
and oxidation by ozone. Psuedo-first order rate constants were estimated based
on assumed concentrations of hydroxyl radical and ozone.
Population exposure to various concentrations of a chemical were estimated
by use of U.S. Census Bureau data at the level of finest resolution available:
Enumeration District/Block Groups (ED/BG's). As mentioned above, concentrations
were estimated for 160 points (receptors) around each specific point source (10
distances 1n each of 16 wind directions). At small radii from the point source
(e.g., up to 2.8 km), a single ED/BG contained several neighboring receptors, so
3-12
 image: 








the population within the ED/BG was apportioned among the receptors falling
inside the ED/BG. At larger radii (e.g., >2.8 km), most ED/BGs contained no
receptors, so concentrations that populations within those ED/BGs were exposed
to were estimated from the estimated concentrations at surrounding receptors.
The estimates were based on an approximately linear relationship between the log
of concentration and the log of distance from the source for large distances and
on interpolation between neighboring wind directions.
Estimates of Exposure to Chemicals Released from General Point Sources—
Exposure estimates were made for prototype point sources in each of nine
geographical regions. The methodology employed was similar to that used to
obtain exposure estimates for chemicals released from specific point sources.
However, exposure estimates were generally made only for urban areas. The
population exposed to a given concentration estimated at one of the 160
receptors was assumed to be equal to the area of the radial sector whose center
is the receptor times the average urban density for the geographical region
considered. The data from a STAR meterological station that was representative
of the geographical region being considered was used to estimate atmospheric
concentrations. 'Exposure estimates for a prototype point source within a given
geographical region were multiplied by the number of sources within the same
geographical region represented by the prototype to be overall exposure
estimates.
Estimates of Exposure to Chemicals Released from Area Sources-
Atmospheric concentrations of chemicals emitted from urban area sources were
estimated by use of the Hanna-Gifford equation:
X = CQq/u
3-13
 image: 








where
X = average atmospheric concentration,
C = coefficient dependent on city size,
Q0 = effective emissions rate per unit area, and
u = average wind speed.
Specific values of C have been estimated by Hanna and Gifford (1973) for a large
number of U.S. cities.
The effective emissions rate for a given city Q0 was assumed to be the sum
of emissions from mobile sources (e.g., automobiles), stationary heating sources
(e.g., chimneys), and non-heating sources. The emissions from mobile sources
for a specific city were estimated from the following equation:
where
EM = national total mobile source emissions of the chemical,
A = land area of the city,
a 3 estimated number of autos in the city,
t = estimated number of trucks and buses in the city,
R = ratio of average truclt-bus emissions to auto emissions,
a' = estimated national total of autos, and
t' = estimated national total of buses/trucks.
The emissions from heating sources for a specific city were estimated from the
following equation:
where
EH =» national total heating source emissions of the chemical
A = area of the city,
B-14
 image: 








P = population of the city,
HR = heating requirements (degrees-days/yr),
P' = population of United States, and
4633 = population-weighted nationwide per capita heating requirement
(degree-days/yr).
The emissions from non-heating stationary sources for a specific city was
estimated from the following equation
EN = national total emissions from non-heating stationary area sources, and
A, P, and P' are given above.
The overall psuedo-first order decay constants used in the dispersion
modeling for point sources were also used for area source modeling. The
following equation was used tfo estimate the overall effective emissions rates:
where
Q0 = <Qm + Qh + Qn) * exp(-Kd A/2)
u
exp(-Kn a72T
u
where
Qm> Qh, and Qn are defined above,
= average daytime psuedo-first order decay constant, and
Kn = average negative psuedo-first order decay constant.
3-15
 image: 









CONTENTS
£aae
FIGURES	 <11
TABLES•••••¦««•••*¦•*••••••••••¦•••••••••••••••••••••««¦••••••¦• 1v
}. EXECUTIVE SUMMARY	 1
2.	DATA BASES	 37
Emissions Dataa*.37
Meteorological Data			46
Population Distribution Data Bases		55
Atmospheric Transformations of Toxic Compounds		65
•
3.	EXPOSURE-DOSAGE ESTIHAT10N APPROACH		94
Hajor (Specific) Point Sources		94
Prototype Point Source Exposure and Dosage Estimations...	120
Area Source Modeling Approach		144
4.	UNCERTAINTIES	 203
Uncertainties Involved in Emissions Estimations		 203
Uncertainties in Exposure/Dosage Estimations	 204
REFERENCES226
ATTACHMENTS
A Summary of Human Exposure Estimations for
35 Selected Chemi caIs..A—1
B Supplementary Document for Human Exposure Estimations.. B-l
H
 image: 








FIGURES
NunAar	Page
1	U.S. Geographic Regions		16
2	Specific Chemical-Emitting Point Sources	 25
3	STAR Station Selection Process Hap I		90
4	STAR Station Selection Process Hap II..		91
5	STAR Station Selection Process Hap III		92
6	STAR Station Selection Process Hap IV..*..		93
7	Effects of Chemical Reactivity on Concentration
Distribution of Chloroprene	 98
8	Effect of Building Wake on Concentration Distribution
of Chloroprene				100
9	Impacts of Release Height on Concentration Distribution
of Chlqroprene				101
10	Schematic Illustration of Virtual Point Source Concept		ill
11	Reference Points for An E0/6G Centrold				118
12	U.S. Geographical Regions		122
13	U.S. Urbanized Areas (1970)		146
14	U.S. Standard Metropolitan Statistical Areas (1970)		147
111
TABLES
Humber	Pa'
1	List of Chemicals for Human Exposure/Dosage Estimation		i
2	Rank Order Listing of Chemicals by Total Emissions		2i
3	Rank Order Listing of the Top Twenty Sites by Total
Emissions With Individual Chemical Contribution		2
4	Studied Chemicals Ranked by Estimated Total U.S. Dosage		2i
5	Top Twenty Major Point Sources R&nked by Total Dosage 		2.
6	Location and Recording Period of STAR Stations In the
Reprocessed File				74
7	Location of Six Major Chemical-Emitting Sources		Si
8	Location of Selected STAR Station of Specific
Point Sources		8c
9	Selected STAR Stations for PCB Incinerators		54
10	Selected STAR Stations Representing Various
CIImatologlcal Conditions		56
11	Distribution of ED/BGs With Population Centrolds
Located Outside Their Corresponding Counties		63
12	Oecay Rate Estimation Categories for 25 Chemicals		69
13	Photochemical Reactivities of Selected Chemicals		73
14	Pasqulll-Glfford Stability Classes Used In Point
Sources Analysis		104
15	Sequence of Input Data Cards for Program Gauss			110
16	Chloroprene Concentration Pattern Around the Denka
Plant at Houston		116
I v
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TABLES (Continued)
Number	Page
17	Nationwide Trlchloroethylene Emissions from Solvent
Degreasers	 121
18	1970 Population Density and Number of Trichloroethylene-
Using Degreasers In the Nine Geographic Regions	 124
19	Major Parameters and Concentration-Dosage Results of
Uniform Emissions Approach	*	 12f
20	Emissions Parameters for Generic Point Sources of
Trlchloroethylene	 127
21	Thrlchloroethylene Concentration Pattern Around a Model
Open Top Vapor Oegreaser In New England Region	 128
22	Land Areas for Specified Concentration Centers	 129
^ 23 Population Exposure to Trlchloroethylene Emitted from
i	a Model Oegreaser				132
CO
24	Trlchloroethylene Dosage Resulting from a Model
Oegreaser Emissions....			 13S
25	Nationwide Trlchloroethylene Exposure Resulting from
Emissions from Oegreaslng Operations	.. 140
26	Nationwide Trlchloroethylene Dosage Resulting from
Emissions from Oegreaslng Operations	 141
27	Nationwide Trlchloroethylene Exposures and Dosages
Resulting from Emissions from Different Types of
Oegreaslng Facilities	 142
28	Exposure/Oosage Analysis Oata Base for Type I City
Areas Sources	 180
29	Exposure/Dosage Analysis Data Base for Type II City
Area Sources				 192
30	Exposure/Dosage Analysis Data Base for Type III City
Area Sources			 199
31	Major State Statistics Related to Area Source Emissions
Distribution					 151
J.- Major Parameters for Estimating Exposure/Dosage Result-
ing from Area .Source,Emtsslon; of Beryllium		 <S55
TABLES (Concluded)
Number	£i
33	Beryllium Exposure and Dosage Resulting from Area
Source Emissions In Type l Cities	 1!
34	Beryllium Exposure and Dosage Resulting from Area
Source Emissions in Type II Cities	 li
35	Beryllium Exposure and Dosage Resulting from Area Source
Emissions In Type III Cities	 1
36	Summary of Beryllium Exposure and Dosage Resulting From
Area Source Emissions	 1
37	Definition of Uncertainty Levels In Chemical Source
Locations and Emissions Estimations	 2i
38	Levels of Uncertainty for Assessed Chemicals	 2i
39	Percentage of Change In Dosage from Base Case
Resulting From Location Shift	'	 2
40	Percentage of Change In Exposure from Base Case
Resulting From Location Shift	 2
 image: 








4. "Priority Review Level 1: Formaldehyde." Draft Report. U.S. EPA Office of
Toxic Substances, Washington, O.C. 2Q460. February 1981.
3-19
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PRIORITY REVIEW I.FVEb 1} FOPMAl/PEIIbYE
February 19, I9fll
Office of Toxic Substances
Office of Pesticides am) Toxic Substances
U.S. Environmental Protection Agency
Washington, D.C. 20460
Appendix A
Exairple Categor 1t J" i on of c'or.naldehy !•; Fipn.nr*--;
Docause of the large and illvoca»i number of poioiit i aI) •/ .»\*i -<j^>d
subpopu la 11 oil s and the potential diversity of lufui n.r. ion nooilo
for further assessment of rinhs and reduction of Uiom? riskn, A
has attempted to establish categories and assign pi* i«>r I t i o:» for
further action. Although many different criteria could iu» uued
to establish categories, the attached table presents an a:Mr^lo
of a somewhat subjective cato^orizai. ion based on: 'ii/e of the
potentially exposed subpopul a t ion; conf lilance in data on e::posu
levels; and aignl f icanco of the risk. In this table, first
priority is given to those situations where confidour" In the
exposure flats is fair or good and either the total por.ont i.»I) y
exposed subpopulat ion is	(i.e. the number of poi.ontially
affected persons is large) or the estimated Individual ri-.K is
high*. Second priority is given where a moderate number of
individuals ar* potentially exposed, confidence in tho e<posure
data is fair, and tho estimated individual risk is mo.lerate.
Third priority is given whore the number of potentially exposed
Individuals is either small or unknown, confidence in the
exposure level is poor, and/or the estimated risks may be
considered low. Obviously, these priorities are subject to
change ao additional information becomes available.
^Because tho risk estimator derivod in thia asnesf.mont an? upre
951 confidence liinltr. for lifetime risks, and are likely ovor-
ostimalen in many cqoch, the lowest risk estimated for i o i y.jn
subpopuIation was used to recommend priorities for further
act ion.
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TALll.K OF COHTKilTS
1111 roilu..: t ion	
Gviiai" Jl Info rnvit ion	
Soiirc.':) IJiiCj and 		
Saaina ry	
Direct Production			
Indirect Product ion	
Incciiiplete Cambii a t ion of Hydrocarbons...
Photocher.iicaI Oxidation of Airborne
llyd L'oca 		
Hi ucol laneous Sources an«l Processes	
llaos and Imports	
PaeiKlo Consumptive Uses	_	
Urea-Fotnia1dehyda Resins	
Fiberboard Particleboard, Plywood
and I.aininatea	
Uroa-Fo rmaI doliyde Foams	
Molding Compounds	
Paper, Textiles and Protective
Coa I i (Kj 		
Uraa-For;naldehyde Concentrates	
Iloxame tliylonetetrainina	
Iloii-Coiisuinpt ivo Mac a	
Disinfectant and Pr aso r/a tivo s	
Cosureties and Toiletries	
11 i o I oi i •; il Sr).joiui-:n:;		23
Other Ap>>l Lc 11 ion::		?3
' Deodorant		2 1
Mi soo 1 lane hi j ".ppl icat lou:i		2*1
ConcroLe		M
T et i I is a		2 <1
Paper		2t
Conaui'ipt ivrs Uses		2-1
Mcisiui no-Fonna Ivlelv/'la Rosins		25
Molding Compounds			25
Fiberlioi rd , Pa rt lc leboard , Plyv.ood
I.ainina t ; a	 2 5
Paper and Textiles'		27
Phenol-Fonnaldeliydu Resins		27
Fiberboard, Pa rt lc leboard , Plywood. .	20
Iitsulation		29
Pentaery tlir ito I		20
1, 4-Butandiol		30
Acetyi Rosins		30
Tr imethylol		30
Ml ac el la neou 3 Consumptive Usoa		31
Exports		32
Exposure pathways and Env I roi ana n Lai Fato		32
Fata of Fonnaldoliyde Role isqs to Air		32
Fate Processes		32
Plioto 1 ys 1 3		J J
Ox Ida t Ion		3 1
Sorption		3}
11
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Dioacciimul it ion, lli.ot rans fo r.na t ion
lliodogr j. I a t) on	
		
Fate of Fo rinaldeliyde Re]iv:i:iOU to Watur	
fate 		
Di UCUS3 ion	
Monitoring Data	
Introduct 					
Monitoring and Analysis Metliods	
Formaldehyde In Air	
Chronotropic Acid Technique	
MBTII Method	
Pararos<11111 ine inatliod	
Gas Chroi.Ktegraplilc Method	
D.)
>	Draqer Docioctora	
ho
Formaldehyde In Water	
Co Lorano tr ic Method	
I' 1 »o r o.iia Lr ic Method	
Formaldehyde in Food (Analytic
Techniguus)	
Formaldehyde ill Work place Air	
Formaldehyde Lovula in Residential Air	
Formaldehyde Levels in Ambient Air	
Foniui 1 dshyde Levels in Ambient Water	
For.n.ilduhyde Levels in Drinking Water	
fo nna I do liydo Love la In Food	
Exposed Pomilations	
Occupational Problems	
1 1I
33
3 4
3 1
34
35
36
36
45
45
45
47
47
47
48
48
40
49
49
49
49
50
51
52
52
5 4
55
Direct Producers oi Fo mi a Id is liyie	 61)
Production of IJrea-I'o rma 1 dr;liyd.i,
pheno l-l'o rm.i 1 doliydo Ma 1 ojn l no- Fo iuii'_l «i-; hy. !.•,
and Acetyl Heslns	 to
Producers of Plywood and Pai-ticlulio.ir.l	 GO
n
Producers, Dlstr ibutorj Hoalora and
lnoLjl leia of llr ea-t-'orma Uleliyde
Foam Ina ula t ion	 (, [
Cotton Textile Finishers	 61
Wholesale and Retail Piucu Goods Worker-;. 61
tlanu factur ers of Paper and paper Pro.iin.-tf.	61
Producers of Fertilizer	 6 2
Persons in Bio 1 03 lc.il Sciences	 62
Producers of Rubber and III seal laneous
Plastic Products	 62
Producers of Leather Products		62
Producers of Metal and Metal products		6 3
Consumer Population		63
Persons Living in Mobile lloiues		63
Persons Living Conventional Homes		63
Ge11ur.1l Population		61
Integrated Exposure Analysis		6.1
Assumptions and Data LUniations		71
Residential Ex [>0311103		72
Dlology Laboratory Exiiosiires		73
Autopay Room Exposures		73
Exposures frcin lluslircon Farming		73
Other Occupational Exposures		7.1
Consumer Exposures				7.;
Iv
 image: 








Smo);er-i		74
Amluont l£::po » ur-j a		74
Rocjcnitn^iula t ions for I'uturu Wo it;		74
lit. lltialLh Etfacts As j.s 5 aiuhu t		76
Abborption au,l Mo Lcibol i. Gin		76
Carciiiocjcn Lei cy		02
Elpldeui lo lojy		8B
IV. Risk Aaaed:Jinont		89
V. Rufoi'encca	99
AppouilLx A - Proroaoil ami Omjoing Epidemiology
Sttu	I 20
ho
 image: 








zy.p.cjr r ivr. 3n:iriARV
Fo rni.i 1 iloliy 1 •;	the si::ipli»aL member of the a 1 duhv.-i e
chei.ii.cal r»: c 'j'jory, exists in many different forma. Pure jnono-
moric f o l ititi Id	(1004 f orma Idehyd e) la a color 1 ess, punuent
ga.i that nponi..\n*.»oiialy po 1 ymes* iisey in the temperature range of
-00 c to lO(r_C. Aqueous £ n*ina»dehyd 3 (formalin) is a clear,
coloi'lesj, pungent solution of about 373 by weight of
foriua 1 dehydo gus» J11 wnler, usually with 10-15% methanol acldud to
prevent polymerization. Formaldehyde also exUtu In polymer Jc
forms, the b-sr.t (iiiown of which are paraformaldehyde and trlortane
or trioxymethylane.
Formaldehyde iii manuf actureJ commercially by 15 companies at
52 sites by the catalytic oxidation of (nutlianoi. A second source
of formaldehyde J 3 its Indirect production by naturaL processes
and human activity such as tho photochemical oxidation of air-
borne hyd roca rbonn and the Incomplete conibiiBtion of hydrocarbons
in fouail fuels and refuse. Approximately 1,580,000 kkg of
formaldehyde wore generated in the U.S. In 1979 j 1,070,000 KKa
fL'oiti commt:rclal production and 510,000 kkg from Indirect
product ion.
Almost all of the commercially produced formaldehyde ia
consumed domestically; loos than it was exported in 197B. The
uuefl of forma Idehyde can be broken into three major categories:
non-consutnpL ivo nuus; paeiulo-connumpt I ve uses; and conoumpt i v*
H303. In 1970, non-coiiaiuupt i vo uses, wherein the chemical
identity ia not changed, most likely consumed legs than 57. of the
commercially prcducod formaldehyde. These uses generally employ
forma Idtdiyde as a prosorvativa and disinfectant (a.a., In
couinuLlcs and toiletries), aa a preservative (e.g., Cor
biological npecliv.cns and in eiuba lining), or aa a fungicide (o.n.,
in Lhe nianufucturo of antibotics and d 1 a in feet 1 on of sick rooms).
Appi o::i mat a 1 y 37£ of the comnus rci a I 1 y produced forin.i 1 dehyde was
11 nod in pfi<!iido-con;iu:iipr ive une<i (chemical Identity not
Irreversibly altered), primarily In tho manu fact ur<» of three*
p roduc t <3: urea- forma 1 dehyd o r e:» i ns; u rca-- forma 1 1 ehy I •;
oonooii t r \ 112:1; and he Xante thy 1 one»>i t rani ut:. Tho se product. i
i" cgene L'al^ 301.10 or all of Lh«* orLgiual t onmldehydo i n 1 he oourse
of their intended uae or lncid<-n(;al decomposition. lhe
consumptive 1 mod of formaldehyde, accounting for about S/'\ of the
total production volume, include th«» cyuthe^is of pro duo*. » ijiieh
aa melaming and phenol - forma 1 ilehyrte ru'ilnc, p.fritaery l hr I t.ol , 1,4-
butancdJol, acatal resins, and Lrimcthy1oIpropane.
Although indirect productions 13 believed Lo be t he larger
contributor to environmental ro. l«as«s of formaldehyde,
commercially produced forma id 2hyde appears to be responsible for
the most significant human expoaurec to this substance. Indirect
production accounts for about 9/1 (510,000 kkg) of the annual
formaldehyde emissions to Lhe atmosphere. Since the major
mechanisms for atmoBplieric degradation depend on tnml ic»hl-, the
persistence of nicborne formaluehyde Ih oxpected co be gr<»<iter in
indoor air tlian in outdoor air. For outdoor air, the levels in
urban areas are expected to be higher than the levels in rural
^J-C. because of the larger number of indirect uoiirco:i (e.g.,
vehicular exhausts and incinerators) in urban are?i3. with indoor
environments, however* the absence of the relatively fast,
6tin I Igh t-induced degradation is expected to allow airborne
releases to build U£ in concentration. Physical proces:.*»s such
aa ventilation will"the major factor) affecting the formaldehyde
concentrations in the^ue situations.
Ho waterborne releases of formaidehyde were identified or
quantified in this report; any such releases are expected to be
short lived. Formaldehdye, per se, lo not persistent in water
because it rapidly hydrates to glycols which are biodegrad11»Io.
Very low concontrat Lona of fomaldehyde, thus, are projected for
ambient waters, except in e.xtremo casoii such as spill j of con-
centrated solutions.
Monitoring data indicate that tho highest potential expo-
sures to formal dohydo arti Lhe result of its direct product ion and
tho commercial and consumer uneii of formaldehyde and foi/»«tlde-
vl 1
 image: 








hyde-containing products. Although the available inon i tor I ng data
are limited In their statistical renresentatlveness of the
popular ions a iTcl i ed, it apptfora Lh tt a i tua 11 ona having a
particularly high potential for exposure to forma 1 dehydo include:
workplace uiv/l roninents in industries as diverse as formaldehyde
maiiufaci.urlnj. resln-manufacturing, textile and garment manu-
facturing, plywood and part icleho;. id production and those
involved in the production and application of uraa-formildehyde
foam; residences containing partlcI aboard manufactured with urea-
formaMuhylc resins; residences containing urea-fornalilehyde foam
InsulaLlon; biology laboratories; and autopsy rooms. Two othsr
situations, i.uiahroom fari.ilng and partlcleboard venoorlnq, also
show a high potential for formaIdohydu exposure based on
monitoring data, but these data may not be representatlva of
general levels for these occupations. The entire U.S. population
also Is exposed to formaldehyde in the ambient air at the low
part pur billion level, and potentially through the use of
products containing formaldehyde as a preservative/disinfectant.
133	The potential for exposure to high concentration of
to	forma 1dehyde is of concern because of the preliminary results of
ON
a recent bioast,ay conducted by the Chemical [ndusLry Institute of
Toxicology (CUT). Hie CUT bioassay results provide evlJoncu
that foir.ia ldehydu causes cancer In rats receiving leng-terin
exposures via Inhalation (the major route of human exposure). In
the CUT bioassay, rata (1 20/s ei/d(i3<i) war a exposed via
inhalation to 2, 6, and IS ppm formaldehydij (actual measured
concentrations were 2.1, 5.6, ami 1-1.1) for ft hours per day, 5
days pur wee); for 24 months.* Examination of rats serially
sacrificed at months 6, 12, IB, and 24 showed distinct
hyperplasia and metaplasia of the nasal epithelium. In addition,
95 tumors (92 oaLaolyLic squamous Cull carcinomas of the nasal
'The Sitiue type of bioassay also wan conducted using mice.
Penults from the inousa bioassay wore not lined In thi-i report
because u£ prol>le'ti3 in Interproljng the available data.
vl 11
turbinate:! and 3 respiratory . i > i the I I .i I li:uor,) w.-ru .l.i.. t_. ¦. I in
r<iLs (all tinschc.lii 1 i?d di.iLh:; ...ii.l £.cli-:.-< In 1 I	i i i ¦ , i.hi'Ki.,!! i Iw
2 l-monlh sacrifice) e::porud lo 14-1 pi'." r > > r • 1 ¦ • hy I ''I i r >¦
Illinois also were deLecLed JL 1 inonLhs in iaL-. j	:d i o S . ,'i pnm
f oi ma ldelr/il e .
The Ci IT bioa-j.iuy prolocol was r.iviiiwu'l l.y a p.ui.-l i,;"
e s'i'.i-' c t a convened by l.lm Cons iii.i j r Product Jjfciy O.. ,nr i ¦. s i ¦ >u
(CPSC), under the aegis of Lli.j National Toxicology ¦' i". | l.-; i (: ITI1) ,
and found to be consistent with accept..-! staiiil.u-.lj fir •:> .n>lu<:: 1.1 u-i
inhalation e::posiiru bioasj.:iy.<i. The /.'Tl' panel, u.-, ing 11 i .,ay
data uvailabla through thu lfl-month sacrifice (I..:., Jo sipiairau.-j
cell carcinomas of the nasal turbinates) concluKd th.it
"formaldehyde poses a cancer risk to lu.inana".
Using a linearised multistage carcinogenesis model, in
conjunction with the available results from the CI IT bioassay and
QStimated levels of fori>ia 1 deliyde exposures for vc,; ions
uubpopulatlons In Lhe U.S., the upper 95'4 confidence Initili on
lifetime human carcinogenic risks were cjiouljto I. I1ic
calculated risk estimates suggest that a high level ol risk may
be associated with a number of situations Involving oxpoaiir :j Lo
formaldehyde. For inost of the identified suhpupu I at i ons , the
estimated risks are equal to or greater than ln~^, howuvei , in
ao.ne instances the risks are in the range of 10~l (e.g., 11 -1' foam
producers/distributors exposed Lo 5.4 ppu , pa i ho l .">M i a L s .. <po:,ed
to 7.9 ppm), 10"^ (e.g., workers in II-F foam insulated lm I II l im.i
ex[)Oaed to 3.1 ppm ll-K foain i ns ta 1 I era/dea lo r j exposed lo . I
ppm), and 10"' (o.g., direct producers of foriiiri Idehyde) . ill.;
reader, however, ahonl.i note that these risk e s I. i ma l.:s a re upper
951 confidence limits; i.e., risks generally will noi e>:oio.l
these estJiuatua, but may, in fact, be considerably K-..a.
 image: 








"An Exposure and Risk Assessment for Zinc." U.S. EPA Office of Water
Regulations and Standards, Washington D.C. 20460. August 1980.
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FINAL DRAFT
Auguet 1980
AH EXPOSURE AND RI9K A3SE3SI1EJIT
FOR ZINC
FINAL DRAFT REPORT
by
Joanna Parwak
Muriel Coyer, Laalia Hal ken, 0. Sclilofca, Kate Scow
f	Pamela Walker, and Douglaa Wallace
co	Arthur D. Little, tnc,
CO
and
Charlaa Deloe
U.S. Environmental Protection Agency
CPA Contract 68-01-3857
Monitoring and Data Support Dlvialon (W1I-553)
Office of Water Regulations and Standards
Washington, O.C. 20460
OFFICE OF MATER HEGULATIOHS AND STANDARDS
OFFICE OF UATER AND WASTE MANAGEMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
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TABLE Of CONTENTS
Pa
I.	EXECUTIVE SUMMARY	I-
II.	INTRODUCTION	II
III.	HATERIALS BALANCE	U
A.	Introduction and Methodology	II
B.	Materials Baianco Checklist	II
1.	Primary and Secondary Zinc Production	II
2.	Production In which Zinc la a
Byproduct/Contaminant	11
]. Environmental Releaae of Zinc during
Consumptive Use	II
4.	Other Sources	II
5.	Hunlclpal Disposal	u
C.	8imuaary	H
D.	References	Ii:
IV.	DISTRIBUTION OF ZINC IN TIIE ENVIRONMENT
' A. Monitoring Data	IV-
1.	Zinc In Aquatic Environment a	IV-
2.	Zinc In Aquatic Organisms	iv-
3.	Zinc la Plant Tlaaue	IV-
4.	Zinc In Soil	iv-
5.	Zinc In Air	iv-
B.	Environmental Fate	IV-
1.	Overview	iv-
2.	General Fate Dlacusalon	IV-
1. Phyalcocliemlcal Pathways	IV-
4. Biological Pathways	IV-
C.	References	XV-
V.	Effects of Zinc	v-J
A. Human Toxicity	v-]
1.	Introduction	V-l
2.	Hatabollpo and Bloaccumulatlon	V-'
3.	Animal Studies	V-!
4.	Human Studies	v-l
5.	Overview	v-l
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TABIC Of C0HTEHT8 (Continued)
Page
B.	Effects of Zinc on Aquatic Organisms	V-18
1.	Introduction	V-18
2.	Itttliwitar Organisms	V-lfl
3.	Saltwater Organisms	W-26
4.	factors Affecting the Toxicity of Sine	V-28
5.	8unmary of Aquatic Toxicity	V-33
C.	References	V-35
VI.	EXPOSUHB	VI-1
A. Hunan Exposure	VI-1'
1.	Introduction	VI-l
2.	Ingestion	VI-1
3.	Inhalation	VI-2
~ . Absorption	VI-2
w	B. Exposure of Zinc to Aquatic Animals	VI-2
M	C. Conclusions	VI-9
<o
0. References	VI-10
VII.	Risk Considerations	Vll-1
A. Introduction	Vll-1
8. Huaana	VII-1
C. Aquatic Organleaa	VII-3
APPENDIX Al UUHAN TOXICITY	A-l
LIST OF TABLES	lv.
LIST OF FIGUBGS	v-
iv
FINAL DflAFT
LIST OF TABLES
TABLE
NUMBER	U
III-l	Suaraary of U.S. Zinc Supply and Demand (1977)	1!
XII-2	Suonary of Environmental Releases of Zinc	II
III-3	Zinc Releasee from Hlnlng and Hilling Activities	II
III-4	Zinc Released by Copper Hlnlng Operations	II
III-3	Zinc Releaaea by Other Metallic Ore Hlnlng Operations I]
I1I-6	Zinc Content In Coal Asli by Region	II
III-7	Other Zinc Releases to Environment by Region	II
111-8	Regional Distribution of Zinc Accumulation
Hear Paved Roads	II
III-9	Summary of POTU Zinc Budget	II
III-10	Sources of Zinc to POTH	II
IV-1	Total Zinc In Ambient Waters	l\
IV-2	Zinc In Sedlnent In U.S. River Bsslne	It
IV-3	Northeast, Hajor Baain 1, Total Zinc In Hater
for 1978	IV
IV-4	Distribution of Zinc In Stream Waters	IV
IV-5	Profile of Zinc In Selected Sedlnent Cores	IV
IV-6	Bloaccumulation of Zinc by Aquatic Organlsma	IV
V-l	Hepatomas Resulting from Zinc In the Diet of Mice	V-
V-2	Data Cor Zinc-Related Flail Kllla	V-
V-3	Chronlc/Sublethal Effects on Freshwater Fish	V-
¥-4	Acute Toxicities for Freshwater Flsli	V-
V-5	Sublethal Effects of Zinc on Marine Invertebrates	V-
V-6	Effects of Zinc on Harlne Plants	V-
VI-1	Zinc Concentrations In U.S. Minor River Baslns-1978	VI
VII-1	Adverse Effects of Zinc on Maiumala	VI
VI1-2	Zinc Exposure to lluaana	VI
VII-3	Factors Contributing to Risk to Aquatic Organisms	VI
A-l	Acute Toxicity of Zinc Salts'	A-
A-2	Assessment of Health Risks Due to Environmental
Pollutants - lluman Tissue Concentrations	A-
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FINAL DRAFT
LIST OF FIGURES
FIGURE
HUHBER	PAGE
III-l Environmental Behavior pf Zinc	III-S
III-2	Typical Flowsheet - Lead/Zinc Ore*	III-6
XIl-3 Location of Active and Inactive Mines In the
United States	II1-8
IV-1	Distribution of Total Zinc in Ambient Haters la
Che United States	IV-4
XV-2	Zinc Concentration in U.S. Hinor River Basin*	IV-6
IV-3	Major Environmental Pathways of Zinc Emissions	IV-12
IV-4	Schematic Diagram of Major Pathways of Anthropogenic
Zinc Released to the Environment in the U.S. (1979)	IV-14
IV-5	Speciatlon of Zn (II) In Natural Fresh Waters sa a
O)	Function of pll in presence of 1.55x10"^ tia/L SiO.	IV-17
i
w IV-6	Adsorption of Heavy Hetala in Oxidising Freeh Waters
°	as a Function of Surface Areas of SIO. in ha/L pS--log
(S102) lia/L.	*	IW-19
IV-7	Adsorption of Heavy Hetala on Soil Mineral* and Oxides Itf-20
IV-8	Zinc Content of Soils near Smelters	IV-24
IV-9	Zinc Content of Soils near Smsltets vs. Soil Depth	IV-24
IV-10 Average Zn Content in Soils near Highways at
Different Soil Depths	IV-27
IV-11 The pH in Kerber Creek	IV-31
IV-12 Dissolved Zinc Concentrations In Kerber Creek	IV-Jl
IV-13 Bicarbonate Concentrations In Kerber Creek	IV-32
IV-14 Concentrations of Zinc vs. Sediment Depth of a
Polluted Lake	IV-40
IV-13 Total Zinc In Sewage, Grand Rapids, Hlchlgan	IV-44
IV-16 Partitioning In Biota, Sediments, and Uater	IV-S2
VI-1	Ratio of Observed Zn and Criteria Zn (Acute)	VI-4
VI-2	Ratio of Observed Zn and Criteria Zn (Chronic)	VI-5
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ABSTRACT
This report sssessea the risk of exposure to zinc, as part of ar
ongoing program of the Honltoring and Data Support Division, Office c
Wager Regulations and Standarda, U.S. Environmental Protection Agenc)
The goal of tills program la to identify the sources of and evaluate t
expoaure to tlie 129 priority pollutanta.
A materials balance la developed for zinc that considers major
sources of release from the cultural and natural envlronmenta to the
first point of entry into air, soil, or water. The amount of materia
released from each source is estimated and, to the degree possible, l
locations of releases sre identified.
The distribution of zinc in the environment Is assessed by con-
sideration of available monitoring data and the physical, chemical, i
biological processes that determine the environmental pathways and ul
mate fate of pollutant releases.
For both humans and other biota, the significant routes of expos
are identified and the extent find magnitude of exposure estimated. 1
available data on deleterious effects are reviewed in order to ldenti
the nature of the effects reported pnd potentially harmful levels of
posure.
Information concerning all of the above topics is combined In en
attempt to assess the risks of exposure to line for various aubpopu-
latlons.
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FINAL DRAFT
1. EXECUTIVE SUHHAM
MATERIALS BALAUCB
Approximately 1.19 million metric Cons (MT) of line were consumed in Che
U.S. lu 1977, about half of which was Imported. Zinc la uaed primarily
In metallic fora lu galvanising (41*). alloy* and dla casting (36Z),
breas (121). and rolled aloe (31) In construction, transportation,
eloctrlcal, machinery and other lndustrlea. Ttie remainder (81) la uaed
as sine oxide and other sine compounds, vlilcti are uaed In a wide
variety of products, such as plastics, paper, paints and cosmetics.
teas than 10X of the sine supply la recycled domestically. An unknown
amount Is accumulating within Che econoalc ayatea, and th« remainder la
W released to the environment, primarily aa aolld wastes disposed of to
h land. Refuse comprised of speht product* containing tine, ore alne
tailings, netala working wastea, coaL ash, and municipal and industrial
sludges constitute major aourcea of landfilled sine. In addition, sig-
nificant quantities of sine are agriculturally lahdspread aa fertiliser
adjuvant.
Ths largest input of sine to water results from eroelon of aoll particles
containing natural traces of sine (43,400 HT/yr). Culturally accelerated
erosion accounts for 70S of this soil loasi geologic or natural erosion
constitutes the other 30X. However, aa tills source la dilute and widely
disperaed It la unlikely Co reault In significantly elevated aquatic
coucentrationa. Oil the other hand, urban runoff (S250 HT/yr). inactive
nine drainage (4060 HT/yr), and aunlclpal and industrial effluents
(17,000 HT/yr combined) are smaller but more concentrated sources,
capable of affecting many local areas. Drainage from active mining
areaa la considerably lesa than from Inactive areas due to the disposal
metlinda currently employed.
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POTW represent the largest total point source zinc discharges, receivi
contributions froa water supply and distribution system corrosion, con
blned sewer area runoff, induatrlal wastea, and human excroment.
Industries with large discharges of zinc directly to water iuclude
iron and ateel, sine smelting (primarily from a single mill), and
poaalbly plastics and electroplating.
The total quantity of sine estimated to be emitted to air (.7130 HT/yr)
la a amall portion of the total environmental releaae. defuse Inclner
stlon, coal combustion, and soiae metals working Industries conacltute
the major sourcea. Along with releases of sine through metal corroalo
and tire abrasion, these sources contribute to urban runoff contamlnat
DISTRIBUTION OF ZINC IN THE ENVIRONMENT
Zinc in ambient water la usually found at concentrations of leas than
SO ug/1. However, In many locations concentrations of 100-1000 ug/1
are found. The fact that higher concentrations are more common In
Hew England, the Southeast, the Missouri River Basin, the Mo Grande
River Basin and the Upper Colorado, appears to be correlated with
mining activities In these areas. However, In all river baalns there
are some locations with sine concentrations of 100-1000 ug/1.
Zinc has a tendency to absorb to sedimentary material. Con-
sequently, anthropogenic discharges of sine in excess of levels natural
in equilibrium with aquatic aedlments result In removal from the water
column and enrlclunent of sediments. Severe sine contamination thus
tends to be confined to the region'of the source. Zinc In Che water
column Is primarily In the fora of the free iou.
Zinc la generally found In soils at concentrations between 10 mg/kg and
300 ing/kg, with a mean of about SO mg/kg. Soils near highways and
smelters have been found to contain higher concentrations, due Co
deposition of sine released in tire abrasion and stack emlsalona.
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FINAL DRAFT
The mobility of zinc in soil depends on the eolublllty of the compound
and, to acme extent, on the soil properties. Zinc In a soluble form,
such as xlnc sulfate, Is (airly mobile in oast sails. However, as
relatively little land disposed sine is iu soluble fora, tlie slow rate
of dissolution will Unit nobility. Consequently, movement toward
groundwater Is expected to be slow unless zinc Is applied to soil in
soluble fora (such as in agricultural applications) or scconpsnled by
corrosive substances (such ao in nine tailings). The transport of
soil zinc may also result from surface runoff or entraliuaant of
particle/) lata the atmosphere.
Annual average airborne sine concentrations iu urban areas of the United
States are generally less than 1 ug/n . Although data are sparse,
higher airborne concentrations of sine would be expected In the vicinity
to
^ of iron end steel-producing plants end sine smelters. Atmospheric
M emissions of sine, consisting primarily of sine aorbed to submlcron
particulate Batter and the oxide of zinc,are expected to be short-lived
la the atmosphere, with deposition upon aoll and pavement occurring as
fallout and washout.
EFFECTS OF 2IHC
Zinc li an essential trace element in human and animal nutrition} the
recommended dietary allowance for humans la 3-1$ mg/dsy in hunans.
Zinc deficiency in humans has been sssoclated with Such effectB as
growth impairments, inhibition of sexual maturation, loss of appetite,
Inability to gain weight, skeletal abnormalities, perakerstotic
esophageal snd skin lesions, and halt loss.
Hoderately hlgli levels of zinc appear to have few adverse effects on
humans or animals; the metal has not baen shown to ba either csrcinogenlc
or mutagenic. Ifunsn survfval liss been reported sfter ingestion of up
to 12,000 ng of metallic sine, and most individuals appear capable of
ingesting ISO lag xlnc on a dally basis without adverae effect.
:.ii( and diarrhea, acting to reduce further assimilation, are
FINAL DRAFT
generally the threshold effects. However, It is zinc's disagreeabl
metallic taste which constrains the drinking water criterion to 5 »
well below sny emetic threshold.
Inhalation of zinc oxide at concentrations of IS nig/m5 of zinc or s
produces fever, malaiae, headache, and occaalonal vomiting, thus
necessitating the occupational exposure standards currently in effe
The effects of zinc on aquatic orgsnisms are of more concern. Seve
fish kills in recent years liave been attributed to zinc from runoff
discharges from mining areas and smelters. However, the concentrat
causing mortality were generally not well documented, and in many c
hlgli levels of other metsls were also present.
In the laboratory, avoidance reactions have been observed In rainbo
trout at concentrations as low as S.6 ug/1. Effects on growth,
reproduction and survival are reported in various freshwater fish
species after chronic exposure to concentrations of 106-1130 ug/1.
There are not enough data to permit generalizations concerning lnver
brates as a group. The proposed fresh water critarlon ranges from
approximately IS-80 ug/l depending on hardness.
Acute toxicity studies have been conducted for many species of fres
water fish. LCj^ values range from 90-102,000 ug/1, with aalmonids
and striped baas reported as being the most aensitive. Invertebrat
are, with some exceptions, sensitive to the same range of concentra
The limited information available suggests that marine invertebrate'
are less susceptible than freshwater species. Harine invertebrates
such as oysters and crabs exhibit growth reductions at 50-125 ug/1.
A strong negstlve correlation between water hardness and zinc toxic
has been confirmed for freshwater organisms. The effects of temperi
pll, end other water quality parameters are not as well understood.
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FINAL DRAFT
EXPOSURE AND RISK
Humana arc primarily exposed to tine through Ingestions the dietary
Intake of an average teenage male lias boon estimated to be 18.6 mg
zinc/day. Dietary supplements nay provide up to an additional 75 mg
tine per tablet. The mean Intake of sine In drinking water Is 0.4
ng/doy (maximum of 26 mg/day). Negligible quantities are Inhaled In
ambient air. Since humane are able to tolerate ISO ng/dcy without
adverse effects. Little risk appears to be associated with these
exposures.
Exposure of aquatic organisms to 100-1000 ug/1 total tine Is common
In the United States, especially In Uew'Eugland, the Western Gulf add
the Southeast regions. Since calclua hardneaa appears to Mitigate the
toxicity of tine, risk may be greater In Hew England and parte of the
^ Southeast, which have soft water.
ut
oi
Saloonlds and invertebrates are acutely sensitive to tine concentration
In the range of 100-1000 ug/1. Over 20Z of the water samples taken
nationwide have sine concentrations exceeding 100 ppb. About 25* of
all samples exceed the proposed chronic exposure veter quality criterion.
However, there is some uncertainty In estimating risk from laboratory
toxicity data coupled with ambient monitoring data. Organisms in the
environment may be somewhat leas ausceptlble to toxicity than those in
the laboratory due to dlfferencea in the oake-up of the two systems.
Compared to laboratory watera, where the toxic free ion of tine can be
expected to predominate, a portion of tine in environmental waters may
be adaorbed to sol Ida or, under certain conditions, complexed with
organic or Inorganic material. In addition, acclimation may occur in
environments receiving chronic exposures.
Consequently, estimation of the actual ecological rlak due to zinc
requires closer examination of areas having elevated aquatic zinc levels,
pipl«»ylug both field and laboratory measures of stress. Also needed la
' '.r understanding of the relationship between toxicity and chemical
si'.u:, ¦;;> of zinc .
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