tinted States Office Gf thft Administrator 1PA-SAB-EETFC-89-020
Environmental Protection Science Advisory ioard May 1989
Agency Washhgton, D.C, 20460
<>EPA Report of the Environmental
Effects, Transport and Fate
Committee
Evaluation of the Proposed
Guidelines for
Exposure-Related
Measurements
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A
7 | UNITED STATES
WASHINGTON. O.C. 204fO
| UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE
TWE AOMINlS
May If, 1989
The Honorable William Reilly
Administrator
O.S. Environmental Protection Agency
401 M. Street, S.W.
Washington, D.C. 20460
Dear Mr. Reillys
The Environmental Effects, Transport and Fate Committee of
the science Advisory Board lias completed its review of the Risk
Assessment Forum's proposed Guidelines for Exposure-Related
Measurements» The review was conducted at the request of EPA'a
Risk Assessment Forum, and was conducted on December 2, 1988, in
Washington, D.C.
The subcommittee recognizes these proposed guidelines as 'a
logical complement to the previously issued Guidelines for
Estimating Exposures. The-prior guidelines, published and
reviewed by the SAB in 1986, provide a framework for exposure
assessment that may be integrated with the current guidelines
resulting in a useful tool for exposure assessors. The
Committee recommends that such integration take place with
careful attention to the necessary linkages between measurements
and modeling.
In addition to integration of the two sets of guidelines,
the Committee recommends some modifications. Since the
guidelines address exposure assessment for human health effects,
this bias should be acknowledged. Alternatively, the guidelines,
which have generic elements that can be brought to bear, on
effects to ecosystems, should be expanded to encompass exposure
assessments in an ecological context. The focus and intended
audience of thi guidelines also need to be defined, and revisions
made accordingly. The Committee discussed quality assurance and
control stringency, the importance of exposure duration
considerations, and needs concerning development and analysis of
data. In addition, a recommendations was made to incorporate
demographics, population dynamics, and population activity
patterns into the process for assessing exposures. Finally, the
Committee requests that the guidelines be amended to include
references to other bodies of work that contain useful
information on exposure assessment.
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Independent comments were received from two members of the
Indoor Air Quality and Total Human Exposure Committee. These
members reviewed the Exposure Measurement Guidelines and provided
a response. These independent comments are attached to the
report to provide further feedback and critiques of the
Guidelines.
The Subcommittee appreciates the opportunity to conduct this
scientific review. We request that the Agency formally respond
to the scientific advice transmitted in the attached report.
Sincerely
Dr. Raymond Loehr, Chairman
Executive Committee
Science Advisory Board
man*
Environmental Effects,
.Transport and Fate
Committee
ENC
cc;
Dorothy Patton
Michael callahan
Sill Wood
Peter Preuss
Donald Barnes
* Dr. Hartung served as Chairman until December 31, 1988. Dr.
Ken Dickson currently serves as Chairman of the Environmental
Effects, Transport and Fate committee. Since this review was
initiated during Dr. Hartung's tenure, his efforts have seen it
to completion.
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U.S. ENVIRONMENTAL PROTECTION AGENCY
NOTICE
This report has been written as a part of the activities of
the Science Advisory Board, a public advisory group providing
extramural scientific information and advice to the Administrator
and other officials of the Environmental Protection Agency. The
Board is structured to provide a balanced expert assessment of
scientific matters related to problems facing the Agency. This
report has not been reviewed for approval by the Agency? and,
hence, the contents of this report do not necessarily represent
the views and policies of the Environmental Protection Agency or
other agencies in Federal government. Mention of trade names or
commercial products does not constitute a recommendation for use.
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
ENVIRONMENTAL EFFECTS, TRANSPORT AND PATE COMMITTEE
ROSTER
CHAIRMAN
Dr. Rolf Hartung
Professor of Environmental Toxicology
School of Public Health
University of Michigan
Ann Arbor, Michigan 48109
MEMBERS
Dr. Martin Alexander
Professor, Department of Agronomy
Cornell University
Ithaca, New York 14853
Dr. Stanley Auerbach
Environmental Sciences Division
oak Ridge National Laboratory
Oak Ridge, Tennessee 37831
Dr. Yoram Cohen
Engineering Department
UCLA Rm. S531
Boelter Hall
Los Angeles, California 90024
Dr. Kenneth Dickson
Institute of Applied Sciences
North Texas State University
P.O. Box 13078
Denton, Texas 76202
Dr. Robert Huggett
Professor of Marine Science
Virginia Institute of Marine Science
College of William and Mary
Gloucester Point, Virginia 23062
Dr. Kenneth Jenkins
Director, Molecular Ecology Institute
California State University
Long Beach, California 90840
Dr. Richard Kimerle
Monsanto Corporation
800 N. Lindbergh Boulevard
St. Louis, Missouri 63167-5842
ii
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* Dr. Brian p. Leaderer,
Yale University School of Medicine
Department of Epidemiology and Public Health
2iO Congress Avenue
New Haven, Connecticut 06519
* Or, Mort Lippmann
Professor, Institute of Environmental Medicine
New York University Medical Center
Tuxedo, Hew York 10987
Dr. John Neuhold
Department of Wildlife Sciences
College of Natural Resources
Utah State University
Logan, Utah 84322
Dr. Donald J. O'Connor
Environmental Engineering Science Program
Manhattan College
Manhattan College Parkway
Bronx, Mew York 10471
Dr. Leonard H. Weinstein
Boyce Thompson Institute for Plant Research at Cornell
Tower Road
Ithaca, New York 14853
Dr. G. Bruce Wiersma
Director, Center for Environmental Monitoring and Assessment
Idaho National Engineering Laboratory (ILF333)
EG6G Idaho, Inc.
P.O. Box 1625
Idaho Falls, Idaho 83415
SCIENCE ADVISORY BOARD STAFF
Ms. Janis C. Kurtz
Environmental Scientist and Executive Secretary
U.S. Environmental Protection Agency
science Advisory Board
401 M Street, S.W. - A101F
Washington, D.C. 20460
Mrs. Lutithia V. Barbee
Secretary to'the Executive Secretary
* Drs. Leaderer and Lippmmitn joined the Environmental, Effects
Transport and Fate Committee for this review, contributing
expertise in epidemiology and exposure assessment.
iii
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TABLE OF CONTENTS
1.0 Executive Summary ..*,..,..» i
2.0 introduction ................ 2
2.1 Revest for Science Advisory Board Review ... 2
2.2 Subcommittee Review Procedures* * . 2
3.0 General Comments ..... .. 3
3.1 Integration of Exposure Guidelines 3
3.2 Scope 4
3.3 Technical issues ............... 5
3.3.1 Quality Assurance and Quality Control, , S
3.3.2 Tine.Course of Exposures and Measurements 6
3.3.3 Development and Analysis of Data . . . . 6
3.3.4 Applicability of Demographics, Population'
Dynamics and Population Activity
Patterns to Exposure Assessments. . . 7
3.3.5 Predictive Exposure Assessments. «... 7
3,4 Referencing Other Sources of Information ... s
3.S Glossary ................... 8
4.0 Specific Comments . 9
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EVALUATION OF TIE PROPOSED GUIDELINES FOE
EXPOSURE-RELATED MEASUREMENTS
l.O EXECUTIVE SUMMARY
The Comaittee considered the draft guidelines for exposure-
related measurements to provide a useful introduction to the
concepts that form the basis for techniques designed to measure
and estimate human exposure. The guidelines represent a logical
complement to the Guidelines for Estimating Exposures that were
published and reviewed toy the Board in 1986* It is recommended
that these guidelines be integrated into a single guideline
document. The integration will require careful attention to the
linkages between measurements and modeling.
The document requires a number of revisions, including a
clarification of the intended audience, and an extension to
explore the role of measurements for assessing exposures that
detect ecosystem effects. In addition, the Committee pointed
out the need for technical corrections regarding industrial
hygiene measurements, and made comments on sampling design and
data interpretation. The Committee also pointed out the need for
increased attention to the study of variability in the context of
defining uncertainty in exposure assessments.
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2.0
2.1 Roouest for R«vi«v
At the request of EPA's Risk Assessment Forum, the Science
Advisory Board agreed to conduct a scientific review of the
Proposed Guidelines for Exposure-Related Measurements. The SAB's
Environmental Effects, Transport and Fate Committee performed
this review with the assistance of other SAB members recognized
as experts in exposure assessment.
The Committee was requested to review the adequacy of the
scientific basis of the Guidelines for Exposure-Related
Measurements including these specific issues: adequacy of
guidance for interpreting contaminated blanks, interpretation of
data at or near the limit of detection, approaches to assessing
uncertainty, and the definition of specific scientific terms. In
.addition, the guidelines were examined in relation to previously
identified Strategies for Improved Exposure Assessment*1.
2.1 Subcommittee R«vi«v procedures
The Environmental Effects, Transport and Fate Committee met
on December 1 and 2, 1988, in Washington, D.C. On the second ,
meeting day, Drs. Lippmann and Leaderer joined the committee to
complete the review of the exposure guidelines. Briefings were
provided on the guideline formulation process, and on past SAB
involvement and recommendations. An overview of the exposure
guidelines was given by Michael Callahan, Director of the
Exposure Assessment Group of the Office of Health and
Environmental Assessment within EPA's Office of Research and
Development.
Prior to receiving this briefing, the Committee was provided
with a document, entitled "Draft Guidelines for Exposure-Related
Measurements11 and dated 10-31-88. The introduction to this
document is attached as Appendix A. In addition, the guidelines
have been published in the Federal Register, Volume 53, Issue 232
pages 48830-48853.
Following the receipt of the draft document and the
described briefings, the Committee discussed the guidelines in
detail. Suggestions, 'conclusions, and recommendations were
developed at the meeting. In addition, both general and specific
written comnents on the guidelines were submitted for assembly by
the Chair. These comments were assembled into a draft. report,
which was circulated for comment and consensus, prior to issuance
of this final report.
USEPA, Science Advisory Board. 1988. Future Bisks Research
Appendix iJ Strategies for Exposure
._
Assessment Research, pp 20
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3,0 GENERAL COMMENTS
The draft Guidelines provide a good exposition of the
concepts that form the basis of exposure measurement techniques.
They provide a"logical and internally consistent quantification
framework by which human exposure may be measured and evaluated,.
They represent a logical complement to the 1986 Guidelines for
Estimating Exposures, and are an essential component of an
overall program to insure scientific quality and technical
consistency in risk assessment*
3*1 Integration of Eaqpoaurg Guidelines
The Committee was asked to address the integration of the
proposed Guidelines with a document promulgated previously by the
Agency. This document, entitled "Guidelines for Estimating
Exposures," was published in the Federal Register (51 FR 34042)
in 198€. The Science Advisory Board conducted a review of this
document as part of its 1985 review of EPA's Risk Assessment
Guidelines for Carcinogenicity, Mutagenicity, Chemical Mixtures,
Developmental Effects, and Exposure Assessment.
A conclusion of the prior review was that the 1986
Guidelines for Estimating Exposures provide the framework for
exposure assessment in a useful, diagrammatic way that aids
overall understanding. This framework is missing from the
present draft document.
The current draft Guidelines are logical correlates
to the Guidelines for Exposure Assessment of September 24, 1986,
which emphasized general concepts. The concepts expressed in
both documents are so closely related that integration of the two
is a logical step. This integration should provide a clear
framework for exposure assessment.
In the process of Integrating the two documents,, it is
important to consider previous comments made by the SAB on uses
and abuses of mathematical models. These comments are detailed
in a Report of the Environmental Engineering Committee entitled
"Resolution on Use of Mathematical Models by EPA for Regulatory
Assessment and Decision-Making" (Em-SAB-EEC-89-012, January,
1989), The development of an integrated set of guidelines for
exposure assessment will require careful attention to the
linkages between measurement and modeling. Competent exposure
assessments require an integrated approach that encompasses both
measurements and modeling.
Recommendationi
THE GUIDELINES FOR ESTIMATING EXPOSURES (SEPT., 1986) AND
THE DRJUPT GUIDELINES FOR EXPOSURE-RELATED MEASUREMENTS SHOULD BE
COMBINED INTO AN INTEGRATED DOCUMENT.
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3.1
Contaminants entering the environment through the air,
water, and soil come into contact with living organisms and
materials as these contaminants move through the environment.
Contact of the contaminant with the target, or exposure, can
result in a variety of adverse effects. The Draft Guidelines
provide a good" general review of the concepts behind exposure
measurement techniques, providing a useful introductory overview.
The guidelines emphasize assessment of exposure to humans.
Human exposure assessment techniques play a central role in
environmental epidemiology, risk assessment and risk management.
In environmental epidemiology, appropriate exposure assessment
methods are critical to minimizing errors, such as those caused by
confounding factors and misclassification, and to improving the
probability of uncovering exposure-response relationships. In
risk assessment, exposure assessment provides essential
information on the concentration-frequency.curve (population
exposed at various concentrations) for contaminant(s) in
different media (water, air, soil, food), and identifies the
intensity of exposure and its likely distribution. In risk
management, exposure assessment helps in formulating cost
effective mitigation efforts to reduce or minimize the risk
associated with exposure and to then monitor progress toward the
reduction of risk. Exposure assessment plays yet another role in
generating questions 'for hypothesis testing and research. The
Guidelines presented to the Committee clearly focus on exposure
assessment techniques as they apply to risk assessment* This
should be stated in the Guidelines to target users to appropriate
applications. Some discussion of the role of exposure assessment
and the modifications necessary for other applications could also
be provided.
In spite of an emphasis on exposure assessments for
humans, the document exhibits a general lack of understanding of
the principles and practice of industrial hygiene in exposure
assessment for industrial workers. Advances in this field have
generated many of the approaches that are used in exposure
assessments for humans; therefore, the guidance document should
reflect the state of the art of this discipline. _ -
The draft Guidelines focus on exposure assessments
as part of risk assessments for human health effects. Yet, due
to the general nature of the principles presented, much of the
information is applicable to exposure assessment for ecological
effects. The guidelines should either clearly acknowledge this
bias to human effects, or they should be revised to include a
more extensive framework for the assessment of exposures in an
ecosystem context.
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Reconua«ndat ion:
THE GUIDELINES SHOULD ACKNOWLEDGE THE BIAS TOWARDS EXPOSURE
ASSESSMENT FOR DETERMIKING HUMMt HEALTH EFFECTS, OR PREFERABLY, THE
GUIDELINES SHOOLD BE EXPANDED TO INCLUDE EXPOSURE ASSESSMENTS FOR
THE PROTECTION Of ECOSYSTEMS.
The Guidelines were developed with a focus on exposures to
non-biological agents, such as hazardous chemicals. Therefore,
the document does not aPply to exposures involving agents that
are biological, such as microbiological or viral agents. The
exposure assessment described is not appropriate for assessing
^ioconcentration, species interaction or food chain interactions
i.iat may ultimately affect exposure. This focus should be
explained early in the document.
In addition, the potential audience for the document is not
well defined. The coverage is insufficient for a person new to
the area, Are the guidelines intended to be a primer for
"exposure assessors", or are they intended'to provide an overview
of exposure assessment for a much wider audience?
Recommendation:
THE AGENCY SHOULD CLEARLY DEFINE THE FOCUS AMD INTENDED
AUDIENCES FOR THE GUIDELINES AND REVISE THEM ACCORDINGLY.
3*3 Technical issues
3,3.1 Quality Assurance and Quality Control
The sections which discuss sample 'plans, uncertainty,
quality assurance and control, and analytical methods are
reasonably well constructed and complete, caution is advised on
some of the consequences of being overly stringent on acceptance
and rejection criteria. Some mention of these along with some
guidance to the reader should- be provided in the document. At
present, the guidance is too "Black and White" with no in-
between.
The accuracy and precision of exposure-related measurements,
or any Measurement, are a function of toe accuracy and precision
of all of the individual estimations that make up the
measurement. Likewise, the accuracy and precision of risk
assessments 'depend on the accuracy and precision of both hazard
and exposure estimates* While one should strive to produce tfce
best estimates possible, there may be cases where the Hazard
estimation is so uncertain that precise exposure estimates may
not be warranted.
It is important to provide a strong statement on the need
for quality assurance/quality control. Following this statement,
the Guidelines need only refer to other EPA documents
specifically designed to provide the detail needed.
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3.3.2 Tim* Course of Exposures and M«a*tir*in*nts
Exposures can occur in a number of settings in which the
contaminant levels vary. The duration of human contact with the
contaminant also varies considerably, as does the biological
response time. It is therefore important to gather exposure data
on a time scale which is consistent with these factors. The
identification of the health or comfort effects of concern and
the environmental contaminant(s) potentially associated with that
effect are vital to the selection of the exposure assessment
method and sampling strategy to be used.
The draft guidelines caution that care should be exercised
in applying long-term monitoring data to specific exposure
assessments. The draft guidelines acknowledge the importance of
population activity patterns in the case of personal monitoring.
However, in general the guidelines fail to address the question
of averaging times for exposure measurements. Although it is
recognized that population activity patterns are important, the
guidelines do not stress that chemical concentrations in the
different media must be measured over time scales that are
consistent with the activity of the exposed individual or sub-
population that is being monitored and the biological averaging
time.
3.3.3 D*v«lopn«nt and Aaalyai* of Data
Regarding the development of data, in particular the
recommended soil and sediment measurements, many other properties
are important in addition to pH and organic carbon content. In
fact, porosity, cation-exchange capacity, or clay type nay be
more important than the factors mentioned. The Committee
suggests omitting "pH" and "organic carbon content11, or including
all factors important to these processes.
The document is quite specific on the requirements for
blanks, effective methodologies, the need for the measurement
system to be in statistical control, limits of detection, and
other tools for analysis. Such rigid specifications are
essential if the analyst or the exposure assessor is not- familiar
with the science behind the measurement methodologies. There
are, however, certain pitfalls which arise when the criteria for
accepting or rejecting data are very narrow. For example, if the
concentration of a pesticide is well above the limit of detection
of the methodology, one may accept the measured value as long as
the blank concentration is no greater than 20% of the «easi*red
value. This may be inappropriate if the concentrations in both
the blank and sample are high but still within the 20% criteria,
since the high blank value may be indicative of severe analytical
problems and may cast doubt on all the data.'
Along the same lines, one may be willing to accept a lesser
degree of precision, a lesser percentage of spike recovery, etc.,
as concentrations decrease. Replicate measurements that are
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within a factor of two may be acceptable at the ngKg"1 level but
unacceptable at the mgKg level.
The requirement for the measurement system to be in
"statistical control" may also be inappropriate in certain
circumstances. For instance, if concentrations of a chemical of
interest are near the limit of Detection, one may not be able to
determine if the individual observations are randomly distributed
around the mean. This is because one tail of the data set will
be truncated due to the inability of the measurement system to
detect values below a set level. Another example of the
potential inappropriateness of the "statistical control"
requirement is when the hazard of a chemical is extreme at very
low concentrations, or when the sample size must be small (i.e.,
blood). In such cases, the measurement system should be
optimized with less consideration being given to stability.
3.3.4 Applicability of Demographics, Population Dynamics, and
Population Activity Patterns to Exposure Assessments
The Committee agrees that direct measurements of exposure
reflect many sources of variability. This variability is in part
due to the continual changes in activity patterns of the
individuals that make up the population, and in part due to
source factors and environmental factors. The discussions on
pages 44-46 seem to imply that such measurements lack
applicability, even though they are representative of the "real
world." Instead, the draft guidelines continue to seek to
justify the "maximum exposed individual" (HEX) on pages S3 and
54. The MEI concept cannot be scientifically justified as a
component of exposure measurements and assessments* Whether the
NEI concept has a place in risk management or policy is outside
the charter of the committee.
The Exposure Assessment Subcommittee of the Research
Strategies committee (SAB-EC-88-040B) recommended undertaking a
series of steps that would improve the exposure assessments from
multiple sources, and would also help to define the uncertainties
in the process.
Recommendation!
THE GUIDELINES KUST INCORPORATE DEMOGRAPHICS, POPULATION
DYNAMICS, AJTO POPULATION ACTIVITY PATTERNS INTO THE EXPOSURE
ASSESSMENT PROCESS.
3*3*1 Predictive Ixpoiure Aaaevament*
This section (pages 41-60) is more closely related to
modeling and estimating exposures in the context of the
1986 guidelines, than with exposure measurements. This
section'relies heavily on simplistic linear nodels to derive the
LADE and LADD exposure equations. These are essentially
extensions of Haber's Rule in toxicology without any linkage to
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toxicokinetie considerations. The applicability of these models
needs to be demonstrated before they can be adopted.
3.4 Reforancing other Sources of Information
The Committee agrees with the Agency's approach in avoiding
the development of guidelines that are "cookbooks11 for specific
exposure measurement technologies. However, it is important that
guidance be provided to assessors that are new to the field. The
Committee recommends that there be at least an acknowledgment in
the Guidelines that there are some general reference texts and
handbooks which can assist the new "exposure assessor" in
approaching useful measurement options, similarly, reference
should be made to appropriate documents published by the
Environmental Protection Agency, the Occupational Safety and
Health Administration, the National Institute for Occupational
Safety and Health, and the Food and Drug Administration, which
contain well developed sampling and analytical protocols. The
guidelines could be streamlined significantly by providing
extensive references to detailed information, as long as there is
assurance that this reference material is readily available to
the public.
The draft guidelines contain many similarities and analogies
to the concepts and guidelines developed for exposure to and dose
assessment of ionizing radiation. Therefore, reference should be
made to this body of work, over 60 years ago the concept that
exposure to ionizing radiation or radioactivity could have
detrimental as well as beneficial effects led the international
scientific community to develop an organization that would have
the responsibility for developing recommendations for radiation
protection, the International Commission of Radiological
Protection (IC1P). shortly thereafter, the American Roentgen Ray
Society, the Radiological Society of North America, and the
Radium Society joined together to establish a permanent standing
committee that periodically reviews the status of developments in
the field of radiation protection. This body, presently known as
the National Council on Radiation Protection and Measurements
(NCRP), issues reports.and documents updating the development of
concepts and doctrine in the areas of exposure and dose
determination. Reference to these two organizations would lead
the user to this important source of guidance adopted by the SPA
and by all Federal Agencies.
Recommendation)
THE GUIDELINES SHOULD REFER TH* READER TO OTHER 0BHBBM.
SOURCES Or INFORMATION ZM TIB OPEN SCIENTIFIC LITERATURE AND IN
GOVERNMENT DOCUMENTS THAT ADDRESS EXPOSURE ASSESSMENT, AS WELL AS
TO THE DOCTRINE AND CONCEPTS PREVIOUSLY DEVELOPED FOR ASSESSING
EXPOSURE TO IONISING RADIATION.
8
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3*5 Qloaaar;
The Glossary is useful, presenting many technical terms and
defining "then in an appropriate manner. In some cases, extensive
detail in the text might be eliminated by reference to the
Glossary. There are a number of terms that are presented, but
not defined. Expansion is recommended to include all terms used
in the Guidelines. According to two of the definitions, fate
includes transport. The Committee considers this to be
scientifically inconsistent. In addition, the difference between
"ambient medium" and "environmental medium11 is unclear.
4.§ SPECIFIC COMMENTS
Page 3? lines 14-16! The statements on practical significance
vary because of the premises that have been adopted. They should
not be "matters of opinion."
Page 6; line 30: Easier detection is only one factor, and
probably not the most important one. others include fewer
confounding exposures, easier access for sample collection, more
methods development and validation.
page 7,* line 19; Biological monitoring is not "usually" done
for the purpose of making inferences about absorbed dose;, rather,
it is a technique for providing indications of either effects or
exposure. The guideline values used' in industry are used
primarily to indicate excessive exposure.
Page 8; lines 27-32 (also see page 40, Table 3-1 and page 67i
lines 9-12): Breathing zone measurements are improperly defined
here and on many subsequent pages. Breathing zone measurements
can only be made with fixed monitors when the worker never moves.
Instead, they are generally made using personal samplers or by
having a hygienist or technician hold a sampler inlet within 1 to
2 feet of a worker's nose as the worker moves about. Fixed
location sampling in industry is known as General AirSampling.
Page 12: The guidelines appropriately stress the importance of
clearly defining the overall objectives of the study and the
nature of the decisions that will be made from the data as the
first step in t-he design of a study. However, the authors have
not been consistent in the treatment of this issue, so that the
definition of"objectives has apparently a lower urgency on page
21 and 22.
page 13; lines 12-14 (also page 17;' lines 10-19): It is also
important to indicate that sample averaging times are important.
Page 16; lines 3-5: It is not true that occupational exposure
studies have focused more on transient exposure levels. Most are
focused on chronic exposure evaluations.
Pages 18-20: Condense, with emphasis on media that account for
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direct exposures, such as air, drinking water, food and soil
coming into direct contact with people, especially children.
Page 19; line 10 j Many factors in addition to pH and organic
carbon content influence the bioavailability and other
characteristics of chemicals in soils or sediments. In fact,
porosity, cation-exchange capacity, or clay type may be more
important in some instances than the factors mentioned. The
Committee suggests omitting "pH" and "organic Carbon content11, or
including all factors important to these processes.
Page 21; line 9s Delete the sentence: "Frequently .... to
Page 24; par. 5s Delete the definition of "Kriging", it is too
much detail for a document of this type* References to the
literature dealing with data reduction and interpretation would
be more useful here. The appropriate use of references here and
on page 25 should lead to a condensation of the text and improve
its utility.
Page 27; lines 6-8: The sampling plan should be reviewed by a
good statistician. The design should be directed by a good
scientist who is familiar with the problems likely to be
encountered.
par, 2s sampling duration must take the averaging tine for
the effect into consideration.
par* 3; line 4: The use of spiked samples should be
discussed here, including the treatment of spike recovery data*
par. 6; lines 1-3: Clarify the sentence.
Page 28; lines 3-4; Delete this sentence.
Page 31? Section 2.7.: Condense with reference to other EPA
documents on QA/QC.
Page 35; line 1: Natural background cannot be called
contamination.
Page 41; Table 3-1. Under S.I - Examples col.; adds "Breathing
Zone Sampling in Industry."
Under B, add a new subheading 2; "Passive Vapor sampling.11?
shift existing subheadings to 3 and 4, respectively.
Under C.2 •- Usually Attempts .... Columni change
parenthetical entry to "may be indicative of either relatively
recent exposures or long term body burden."
Pages 48-52; Condense and present concepts in narrative format.
Page 531 line 10: 20 ug/^ chloroform is a more realistic
concentration«
Page 58? lines 7-9j While loach's approach is very good for
occupational hygiene, it is not at all clear that it is generally
applicable to community exposures.
10
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page 64; lines 20-22; It is not EF&'s responsibility to create
work for statisticians. A more appropriate statement is found on
page 65, lines 7-9.
Page 68? lines 2S-27: This is a definition of "Exposure-Response
Assessment,1* it is inconsistent with earlier definitions of
"Dose."
Page 69; line 221 Delete "outdoor natural.*1
Page 70; line 8: Expand the definition to indicate that
exposure rates for air are generally characterized by
concentration,
11
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APPENDIX A
SAB REVIEW DRAFT 10-3\-
DRAFT GUIDELINES FOR EXPOSURE-RELATED MEASUREMENTS
U.S. ENVIRONMENTAL ERQTECTION AGENCY
NQVUfBE! 1988
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O3DHHS
i. :nnsDDi3en:QN ........................ . i
1*1. Purpose of the Guidelines ..... ........... i
1.1.1. Intended Audience ... ...... ........ 2
1.1.2. Organization of the Guidelines ...... ..... 3
1.1.3. Role of ^technical Support Documents ..... ... 3
1.2. Exposure Assessment. ....... ....... .... 3
1.3. Sources of Measurement Data ..... , ...... ... 5
1*3.1. Direct Measurement of Exposure.. .......... 5
1.3.2. Biological Monitoring for Reconstructive Exposure
Assessment. .................... 6
1.3.3. Measurements for Predictive Exposure Assessment . . 7
1.4. Quality Assurance and Quality Control Requirements ... 9
1.5. Other Requirianents ................... iq
2. GU H IKITNES FOR MAKING MEASUREMENTS FOR EXPOSURE ASSESSMENTS. . 11
2.1. Responsibilities of the Exposure Assessor. ....... 12
2.2. Defining Objectives ...... . ............ 12
2.3. Developing a Sampling Strategy .......... ...13
2.3.1. Direct Exposure Measurements ............ 14
2.3.2. Reconstructive Exposure Measurements ...... . . 15
2.3.3. Predictive Exposure Measurements .......... 16
2.4. Setting Data Quality Objectives ...... ....... 20
2.5. Sampling Flan .......... ............ 23
«*
2.5.1* Sampling Design ....... . .......... 24
2.5.2. Sampling location and frequency ....... . , . 26
2.5.3. Sampling Duration ... ..... .. - ....... 27
2.5.4. Sample Preparation. .... ..... * ...... 27
2.6. Evaluating Cheertaiflty
2.6.1. Sampling Errors . ................. 28
2.6.2. laboratory Analysis Errors ...... . ...... 29
2.6.3. Data Manipulation Errors. ......**,.... 30
2.6.4. Reporting Data Near the Detection Idadt ...... 30
2.7. Quality Assurance, Control, and Assessment ....... 31
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2.8. Selection and validation of Analytical Methods 34
2-t. Sadkgrounti Level 34
3. GdEELBiES FOR UBBfS MEASUEEMENIS Bf EXFOSOKE ASSESSMENTS. . . 36
3.1. • Use of Measunanent Data In Ifeking Infereross for
Exposure Assessments ,...,.,,.... 36
3.2. Relevance of Measurarent Data for the Intended Exposure
Assessment ...... .............. ...38
3.2.1. Direct Measurement of Exposure 44
3.2.2. Iteoonstructive Exposure Assessaent 46
3.2.3. Predictive Exposure Assessment. .......... 47
3.2.4. Measuraaents and Modeling . . v 57
3.2.5. Use of Surrogate Data in Etesticide Zs^osure
3.2.6. Oonfcining Measuranent Data Sets frcm
Various Studies ........... 59.
3.3. Adequacy of Measurement Data for the Intended Exposure
3.3.1. Quality Assojaixae and Quality Control for Previously
Generated Data. ..................60
3.3,2. ttw itele of Limit of Detection (1DD) Ttelues in
Measuroaents Used to Estimate Exposure. ...... 61
3.4. Evaluation and Description of uncertainty in the
Use of Measuranenbs. 63
3.4,1. Assigmrent of Limits of Uncertainty to Data .... 64
3.4.2. 'statistical MalysiB of Data 64
3.4.3. Decision Analytic J^po»c4i for Bqaert Opinion ... 65
GLOSSARY OF TEWS. ......66
75
rrr
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sas RETCH? rg&fr
1.
1,1. Bxtpose of tbe *?Tffjpl
In 1984, EPA organized a near program to ensure scientific quality
and technical consistency in the Agency's risk assessments,
in the prograat's goals was the developnent of Agenc^wide guidelines for
risk assessment. Hie first gcoup of five guidelines was issued in 1986
and included Ihe Guidelines for Estimating Ensures (U.S. EPA, 1986a) ,
Tfte Proposed Guidelines for Expoair^-Related Measurements is a
ecopanion and supplement to the Guidelines for Estinating Exposures.
The Guidelines for Estimating Exposures were developed to help
avoid inadvertent mistakes of omission. They present thft risk
assessor with a set of questions to be considered in carrying out an
exposure assessment and provide a procedural framework for estimating,
the degree of human contact with a chemical of concern* The Guidelines
for Estimating Exposures 'set forth internal Agency procedures that
facilitate consistency by developing timun approaches to exposure
assessnents and by promoting the quality and accuracy of science
underlying EPA exposure assessments.
As stated in the Guidelines for Estimating Exposures, "ideally,,
exposure ineasurements are baaed on measured data. EEA recognizes that
gaps in data will be comnon, ' but the Guidelines will nevertheless serve
to assist in organizing the data that are available, including new data
developed as part of the exposure assessment. Hi the absence of
sufficient reliable data and the time to obtain appropriate
way be baaff^ Otl
mathematical models. Whenever possible, exposure assessjnents based on
Should be ccnpl€anented by reliable ineasurtaiifents** Qomnfts
received on the Guidelines for Estinatirg Exposures, including conments
fron EPA's Science Mvisory Board (SAB) , suggested a supplement dealing
in mare Aafcuji with how to nake and use measurenents in expos ire
ssraent. In accord with these suggestions, the Agency p&epaxed the
Proposed Guidelines for Exposure-Related MeasureDents.
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document focuses primarily en conical measurements in
physical and biological media. She guidelines are intended to
help closure assessors make informed choices regarding collection and
interpretation of these types of data. Otter types of e^qposure-related
measuronents (e.g. , activity profiles) are tat considered in detail
here.
•ffie Proposed Guidelines for Exposure-Belated Jfeasurements (herein-
after Guidelines) are not intended to serve as a step-*iy-step
instructional guide, but to convey general principles. Rather, they
represent a collection of information already ref ired by consensus
approval. As the Agency perform more exposure assessments and
incorporates various novel approaches, these Guidelines vill be
revised.
1.1.1. Xntenfel
Hicse Guidelines are intended to assist those who must recem&end,
conduct, or evaluate an exposure assessment. Exposure assessment is a
luLtidisciplinary process that should reflect the combined input of
analytical and environmental chemists, biologists, engineers,
statisticians, and others as appropriate. Tto ensure a credible
exposure assessment, the assessor must be familiar with the site or
program-specific needs and the factors that affect how well these
needs will be fulfilled.
Important aspects to be considered when generating new data
(i.e., making measurements) include sampling plans, field activities,
and analytical methodologies. Exposure assessors will enhance thHr
expert judgment with' sample designs that provide objective
raits. H» purpose of sampling an environmental medium, or of
sampling exposures directly for an individual, or of sampling tlreaire
or body fluids, is to make an inference about the nature or quality of
the whole mdium, population, or absorbed dose. Statistics, while a
useful tool, cannot alone provide the rationale for the link betssen
the sample and the whole. It is the exposure assessor, as builder of
the assessment, who mjst provide the explanation and justification for
this link, usually through carefully laid out logic as to tf& the
sample is accurate and representative. Statistics, and the help of a
-------
statistician, however, are often essential parts of establish!*^ the
link between the ample and the population of inference.
ttaen evaluating data (i.e., using ej^csure— related measurarents)
exposure assessors should carefully examine the relationship between
the population on iMch the, »easuranents were made and the population
about which inferences are desired. Another natter to be ccrssidered
and understood is the possible difference between statistical
significance and practical significance. The former **"""! relates to
whether observed differences could be the result of the variability of
the data used in a decision process. Hie latter relates to whether the
difference, if real, would be of practical iicportarwe* Star a given set
of circumstances,, measures of statistical significance should not vary
one assessor to another because they arc
established procedures, while statements on practical significance are
very likely to vary from, assessor to assessor since they are matters of
opinion.
1*1.2. organizaticxi of the Qiictelines
These Guidelines consist of three parts, Ihe iirtroducticri
describes seme general aspects of exposure assessment and some major
sources of measurement data used in exposure assessments, The second
chapter HigftMaaea the making (i.e., generation) of measurements for
exposure assessments including the role of the exposure assessor,
sanpling plans, uncertainty analysis, quality assurance, quality
control, and method selection. Tfce third efiipter describes the use of
mesasureoents in exposure assessments including evaluation of
uncertainty to the use of measwtiaetits, the role of limit-of-^aetection
values, and th» use of surrogate data.
1.1.3, Bate of Technical Support Documents
It i» iBFraettobie to create fuMelines that give specific step-
by-step imtructions for every situation. Ite assessor should consult
technical sutyjil obcunEnts, such as those referred to in these
Guidelines, for more specific information,
1*2. Expo
The National Iteseardi Gameil (NEC) fa 1983 described risk
assessment as ctrtainlncf some or all of the following fair steps;
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hazard ident^g^cation (the determination of iitether a particular
chemical is or is not causally linked to particular healtii effects) ,
dflse»-ireBDonee ?«eypartenfc (the detejmnaticn of the relation between
magnitude of exposure and the probability of occurrence of the health
effects in question) , exposure assessment (the determination of the
extent of human ejqposure before or after s^pliration of regulatory
centrals) , and risk characterization (the description of the nature and
often the magnitude of human risk, including attendant uncertainty) .
Once a 6jose-respcr*se relationship is established, ant often this
is done in a ccntrolled situation such as a laboratory, one can make
statements such, as, "If the dose is % * then the response should be
*y. >n A major problem ccrifronting risk assessors when trying to apply
the dose-response relationship to an actual "real-world** problem is the
question of what dose to use as representative of the actual situation.
Use prinary purpose of an exposure assessment is usually to estimate
the real-*rerlfi6« terns tend to be confusing and should not be used to
If avoidable. Exposure a««g*j*AjiiiMitog often present not
only the cotposures, but also the absorbed doses, which can be
calculated from exposure if the absorption fraction is tae*m (see the
Glossary of Tenre) .
Over the last decade, exposure assessors have generally
approached the evaluation of real-world e
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measuremEnt approach™) f by trying to reconstruct an absorbed
dose from evidence within an organism after the exposure and absorpticm
have taken place ("the reconstructive approach") , or by trying to
estimates of the distribution of the chemical ar*4 the organism
separately, then linking them ("the predictive aj^dctach11) . Jttl of
these approaches involve measurements of «a™» kind,, and the
measur^nents used in these approaches to determine or estimate
exposure are generally f^T"***. "exposure-related raeasureaents."
twin applies to measuranents taken for use in an exposure assessment,
%Siether or not they measure actual exposures directly, or directly
provide inf onration upon which exposure will ultimately be estimated,
1.3. Sources of Jfeasureinent Data
This section describes some of the methods currently used to
provide reliable measurements for closure assessment needs* "Sm
methodologies djgra»aaari below focus on direct •n>aa»a i * wmmnh of
measurement of biological markers, and measurements for
c±jyaracterization of' mpdia for predictive assessments. These GuMelines
will not <3i<5a,iSiS the collection of data on population activity
patterns, although it is recognized that these data play an important
JL'Qjjt? 1 1*|.. ^"MlTM'jH^Ol1'"^ ^fffifffi^ill'tf^l"f iTi w
The reader should keep in mini that the measurements dififniswd in
sections i.3.1 througjEi 1.3.3 share a similarity in that for most of
them, a substance or nedimn is being analyzed for chemical content.
However, the use of the resulting Deasument data is fundamentally
different for the three different approadses to exposure assessment,
and therefore considerations in F^;||gy these measurements vary also.
1.3.1. DlmufcL MMMMreoient of
Direct ibasureraent of exposure measures the contact of a chemical
with an CB^anism (himan or ncsrihuinan) xhile it occurs, by measuring the
chemical conoentrmtions at human physical exchange boundaries (skin,
lungs, etc.) as a function of time (e«g., tbrougiMt a day) to obtain
an erasure profile. A rajdber of individual profiles can be
statistically aggregated to make statements about the exposure profiles
for nunan or nonhuman pxjpulations, provided the individuals sampled
have a known relationship to the entire population.
-------
As the name implies/ the direct measurement method relies
essentially en measured data. Hie test-krown example of the direct
weasxaxsaegA. of exposure is the radiation dosimeter, a fflal.l badge-likE
device worn in areas where exposure to radiation is possible. Hie
dosimeter ©f f ectively measures exposures to radiation while it is
taxing place, then indicates when a preset level has been exceeded,
Another example of direct measurement of pollutant exposure is provided
by the Total Exposure Assessment Methodology (1£%M) studies (U.S. EPA,
1987a) conducted by EPA. In the ISM studies, a sagm puap with a
collector and absorbent is attached to a person's clothing and measures
the exposures to airborne solvents or other pollutants while the
exposure takes place. The absorbent cartridges are then analyzed for a
variety of chemicals. A third direct measurement example is given by
the carbon nonoxide (CO) studies dene by EEA in Che 1980s, where a
small CO measuring device was carried by a number of people over
several days (U.S. Em, 1984a) . The device had a recording capability
which allowed the a33r?"ior to analyze the exposure to CD over that time
period. In all three of these examples, the key to direct measurement
techniques is that the measurements must be taken at the interface
between the person and the environment and measure the exposure while
it is taking place.
1.3.2. Biological Jfcnitnring for RDOoneUuctivc Exposure Assessment
Another method, yielding useful nBasurenent data for
exposure assessments/ involves biological monitoring.
Biological tiggw or fluid neasureiKnts that reveal the presence of a
chemical may indicate directly that an exposure has occurred, provided
the chemical is not a metabolite of other chemicals. There has been
BEX** lntar^t in relating biological sample levels to exposure,
particularly for occupational gxptfeUCT where chemical ccnoentrations
are hi^ wcu^i to permit easier detection.
Fbur types of fflBasurcDents using biological monitoring can be
to evaluate the amount of a chemical in the body:
1. IteasuraaBnt of the oonoentration of the chaaical itself in
various biological »jpa«« or fluids (blood, urine, faraatb,
hair, ^viip^ea tissue, etc,) (body burden) .
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2* MsasureaeiTt of the concentration of QJJ^ or nore of
biotransfanmtian products (metabolites} of the chemical.
3. Measurerent of a biological effect that occurs as a result of
human ejqposure to the chemical (e.g. , altylated heroglobin)
Ctypes of biowarfcers) .
4. Measurement of the amount of a chemical bouna to target
molecules (e.g. , IKA adducts or <±axxsc3sas^ aberrations (types
of biomarkers) .
Bie results of bianonitoring can be used to estimate the anoint of
chemical uptake during a specific interval If the relationship between
uptake and the markers selected is known (i.e. , phannacoldjr^tics are
known) and if background levels before the exposure interval are known*
exposure assessDent relies heavily on measured
data. However, the data on body burden or bionarker values cannot be
used directly for exposure assessment unless a relationship can be
established between these levels and absorbed dose, and interfering
reactions (e.g. , from metabolism of nonrelated chemicals) can be
accounted for or ruled cut. Biological monitoring for exposure
assessment usually involves sampling tissues or fluids for the purpose
of making inferences about absorbed dose.
nents for Predictive Exposure
In predictive exposure assessment, the assessor attempts to
match, or link, individuals or collections of individuals with the
concentrations of chemicals or agents they are contacting. Usually,
the assessor addresses the characterization of the individuals or
population separately from the characterization of the chemical or
agent. Emulation characterization involves identifying those
irdividuals tfco an exposed and the activities (habits) that brijng
than Into contact nitto the chemical or agent, mis nay involve
dCTogr^fctca, survey statistics, behavior observation, activity
diari*», or other wans of obtaining this information. Although
population characterization may involve raeasureoients, these
neasurenents are fundaaentally different fron the chemical/media
characterization d*e«*MM>d in these Guidelines, ani therefore will not
be specifically discussed further here.
-------
Jfeasureneots employed in characterising the cheaical or agent in
predictive cKpaswre assessaents are quite varied, bat they all share a
niinni purpose: to use sampling to mate inferences about the
distribution of chemical/agent ooncentraticrts in the media being
saspled. Measurooents are often used as inputs to models* Once the
concentration distribution has been estimated or measured, this
information can be combii>ed with the population characterization to
estimate exposure.
•fte following are a few examples of the types of measurements used
in predictive exposure assessment to characterize the ccrcentrations of
chemicals or agents in various ****!* t Fixed location tcnitogijp has
been used by the Agency and other groups to provide a record of
pollutant concentration at one spot over *""» length of time,
Nationwide air and water monitoring programs have been established to
provide continuous monitoring of pollutant concentration so that
"baseline" values In these environmental ***ti* can be documented.
fnreSy^y^^^BBnflS jJHt JSpy'l ^^^nn^mf -^ r BJP^y^lilt CHIilt ^ ^O r^^ QORC JlZlt fOff^Sftoi: ^^^i^^ff
which look for specific chemicals or agents in specific places and
tunes. Indoor air* measurements smjjly refer to the geographic zone
mcnitored. Itiere are valid reasons for differentiating indoor
measurements froro outdoor ones, since when performing an exposure
assessment, the considerable tine spent indoors for most persons needs
to be linked with the concentrations they are exposed to indoors.
here, office, autoaobile, or otter defined areas are often called
miegoenvitoiiii^ntff and are used In predictive exposure asfiftwu-'tit to
better link chemical concentrations with individuals or populations.
^"^^iftinif MTU Httflgynt:gg(:int-s' usually assq^lafr^ with industrial
studies of tarter exposure, refer to measurements taken by a fixed
location device situated at approximately head height at or near where
the vorkBr spends a substantial amount of time. Note that this differs
fron direct measurement, since the wnitor is fixed rather than moving
with the worker/* if^od and drijflQpo uafcpr ft^^yBBffents are often up"0
to characterize these potential exposure pathways. General
characterization of these media, such as market basket studies, shelf
studies (where foodstuffs are taken from store shelves and analysed),
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ATIACHMEMI?
Letter from Dr. Jerome J. Wesolowski to Or. Mort Lippmann
Letter from Dr. James w. Woods to Mr* A. Robert Flaak
12
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(415) 540-2476
April 14, 1989
Dr, Mort Lippmann
Institute of Environmental Medicine
New York University Medical Center
A. J, Lanza. Laboratories
Longmeadow Road
Tuxedo, NY 10987
Dear More*.
This responds to the request made at the March sfteeting of the IAQ/THE that
committee members review EFA's expo sure -related measurement guidelines
dated October 31, 1988, and the EET & FC draft review of these guidelines
dated April 1989.
Ic was my understanding that since the EET & FC already reviewed the
guidelines and since time was of the essence, a. detailed review vas not
required, 1 shall therefore make some general comments followed by
specific ones which I believe will give credence to che criticisms
contained in the general comments,
Comments
The report Is poorly written. It's style is cumbersome,
bureaucratic, redundant: and in many parts vague. It is not cleat
for whom the authors intended the report. Those already
knowledgeable about exposure measurements would find it tedious and
minimally informative. Those new to the field would find it
confusing.
The report: is replete with technical inaccuracies, and with
misinformation on basic exposure concepts. Most important, the
definition of exposure, which is the foundation on which the report
rests, is inconsistent with that currently acceptable to most
exposure experts in the scientific community, as well as with other
recent EPA reports, some of which have already received SAB review
and approval. This will be discussed in more detail under specific
comments .
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Dr. Lippmann
Page 2
April 14, 1989
I found the EET & FC review included many useful criticisms,
However, I was surprised Chat the committee appeared to agree with
the fundamental exposure concepts espoused in the EPA guidelines,
including the definitions as given in the report and the glossary
(cf. p.' 14 which states "The glossary is useful, presenting many
technical terms and defining them in an appropriate manner."). I
also note that on p. 5, the committee states "... exposure
assessment provides essential information on the concentration
frequency curve (population at various concentrations)..,". I
maintain exposure assessaent provides information on the population
at various exposures. I do not wish to criticize the coaaittee for
these oversights since I do not know how much time the members had
to review the guidelines and I realize that the committee review is
only a draft.
• I do not recommend that these guidelines be published, I agree with
the EET & FC that only one guideline be published, utilizing
information in this guideline and the 1986 guideline. Further, I
recommend that this be done only after the intended Audience be
defined, the committee's remarks as well as those in this memo be
taken into account, and that an appropriate committee of SAB review
the integrated document.
Speeific Comments
« The glossery contains many definitions at variance with those
commonly accepted by professional exposure assessors. The most
serious descrepaney, since It lays the foundation for other
definitions and for the scientific content of the entire document,
is that of exposure itself (p. 69). This definition states that
"Exposure Is quantified as the amount of the agent available at the
exchange boundaries...*. The authors appear to equate exposure with
dose. For example, on p. 63 "dose-response assessment" If defined
as "The determination of the relationship between the magnitude of
exposure and the probability of occurrence of the health effects in
question", while on p. 69 they equate "administered dose" with
exposure. Although EPA can define terns as suits their specific
needs, I believe they should do so with Internal consistency and
whenever possible in concert with the scientific community outside
EPA, This is not the case. For example, in the February 1988 acid
aerosols issue paper, EPA repeatedly expresses acid particle
exposures, in units of (/ig/n* * h), that is, exposure takes into
account both, concentration and the cine an individual is exposed.
On the other hand, the November 4, 1988 EPA document "Interrelation
of Experimental Exposure and Ambient Air Quality Data for Comparison
of Ozone Exposure Indices and Estimating Agricultural Losses*
repeatedly gives exposure the units of concentration. For example,
on p, 3-6 of that document the authors state "exposure should not
exceed 21 ppa". Thus there is disagreement, even within EPA, on
this very basic definition. Since EPA is considering the total
human exposure concept as a guiding scientific principle in risk
assessment and risk management, I think it critical that the agency
establish one definition for this basic concept.
-------
Dr. Lippaann
-*j w ri
April 14, 19S9
A committee of the National Research Council has recently completed
a. draft report on "Advances in Assessing Human Exposure to Airborne
Follutants". Included are suggested definitions for concepts
related CO exposure assessment. The committee draft report states
that "Human exposure consists of contact at one or more boundary
layers between the human and the environment with a containinant(s)
at a specific concentration s) for a specified period of time. Thus
the units of exposure are concentration multiplied by time.". The
committee goes on to define other concepts such as total exposure,
Integrated exposure, dose, total dose, internal or administered
dose, and biologically effected dose* I recommend thac the EPA
staff who rewrite the guidelines attempt to accept the
recommendations of the NEC (for information as to when a draft
document might be available for review I suggest calling Ray Wassel
of the NRC at (202} 334-2617).
Clearly if E?A should accept this recommendation it will be
necessary to make substantial revisions in the text, since the text
discussion and equations all flow from the definitions in the
glossary.
p. 66 The authors state; "Indoor ambient and outdoor ambient are
sometimes used to deferenciate between indoor and outdoor
surroundings". I have, never seen this deferentiatlon. Rather ch«
most common use of the. word ambient is to refer to outdoor- air,
which I agree is a. misnomer.
p, 67 The authors state; "Breathing zone measurements are
frequently made ... by placing monitors at fixed locations ..."
Breathing zone measurements are usually made using personal samplers
attached to the person,
p, 71 The authors equate the word microenvironments with "a series
of areas" The definition of mlcroenvironment. is a three-dimensional
space having A Yplunjg such that the concentration for the pollutant
of interest can be considered constant during a specified
measurement time interval. Further if properly coupled with
activity pattern data, micreenvironment&l measurements need not be
carried out sequentially.
p, 10 Paragraph one. The statement *.. .dose-response .assessment
(the determination of the relation between the magnitude of exposure
and the probability of occurrence of the health effects in question)
,..* shows the lack of the authors distinction between dose and
exposure,
p. 4 Second paragraph. The primary purpose of an exposure
assessment is not to estimate "the real world dose*, but simply to
estimate exposure. Also, the authors use the Phrase "real world" a
number of times during this report. What other worlds do they have
in mind?
p. 4-5 The nomenclature that the authors use to describe the three
methods for measuring exposure are not as pedagogically useful as
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Page 4
April 14, 1989
Che descriptors used by many scientists and also by che KB.C
committee discussed above. I recommend, that exposure assessment
approaches be divided Into two categories; indirect methods (which
combine microenvironmental measurements with activity diaries
through-models to obtain exposure)t and the direct mechod. The
direct method has two subeategories, personal monitoring and
biological markers.
F. 5, last par. The authors state that direct measurements are made
by "measuring concentrations at human physical exchange boundaries
(skin, lungs, etc.)...". Personal nonitors are not placed in
people's lungs. Of course the authors realize this since on the
next page they give as direct measurement example, the use of a CO
measuring device which is carried by people. This is just one of
many cases of imprecise writing.
p. 7, par. 2 Biological monitoring is not usually done to make
inferences about: adsorbed dose. Biological monitoring is used for a
variety of purposes, for example, toxicolagical purposes, screening
purposes, etc.
p. 7, last par. In the indirect method (what the authors refer Co
as predictive exposure assessment) population characterization
involves much more than just who is exposed and what their
activities are that bring them into contact with the chemical or
agent. One of the most important parameters is the activity time
pattern data. These sections on the different methods for measuring
exposure are vague and Incomplete.
p, 8. Indoor air measurements do not "simply refer to the
geographic zone monitored". If the authors feel a need to define
the term, why not say indoor measurements refer Co measurements made
indoors. Perhaps the intelligent reader would not require an entire
sentence, but could deduce the location from the adjective "indoor".
p.8, par. 2 The home office, etc. are not microenvlronments. They
are environments. See an earlier comment for the correct definition
of microenvironment.
p.8, last par. Breathing zone measurements are not taken by a. fixed
location device unless the worker does not move from his work
location.,
p,9 The authors say that "... measurements of food and drinking
water are taken as split samples sTj^u.ltaneous1y as an individual is
ingesting them*. This indeed must be a painful experience for the
individual under test.
p. 9, par. 1 The authors say that "Source characterization
measurements usually refer co sampling to determine the rate of
release of chemicals ...*. Such measurements are usually referred
to as. source emission measurements.
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?£.;; = 5
-.pril 14, 1989
p, 9, last par. The authors stace chat the proof of reliability of
data is embodied in the form of quality assurance and quality
control. It is quality assurance chat yields che "proof. Put
simply, quality control is the system of procedures that is used
before and during data collection to make it good data, whereas
quality assurance is the system used to assure (i.e. "prove") that
the data that has already been collected is indeed accurate and
precise (the authors use these definitions on p, 31).
p. 11, par. 1. The authors state "... the exposure assessors task
is to obtain or estimate does Information ...". Clearly the authors
do not differentiate between dose and exposure. This kind of
confusion is contained throughout the report.
p 11, par, 1. The sentence "Since dose involves both the organism
and tha chemical, obtaining representative dose Information involves
establishing a link between the organism and the chemical" says
nothing.
p. 11, par, 1, The authors equate measurement data with samples*
Data are not the same as samples.
p. 12. The sentence "It is incumbent on the exposure assessor to be
well informed and to participate in such decisions relating to the
making of measurements so that the sampling process is relevant to
the questions being asked to the assessor.", is another meaningless
sentence.
p. 14, last par. The authors state "... measurements are made of
the actual pollutant concentrations contacting a person's body by
essentially using split samples of the air breathed,...". It is
unclear what the authors are referring to when they speak of
spitting air samples.
p, 17, par. 1. I think It inappropriate to state that
"environmental media are primarily responsible for the wide
dispersion of anthropogenic chemicals that reach the
environment...". Perhaps man's activities have something to do vith
the wide dispersion of chemicals. It is not clear what the authors
are trying to say.
p. 46, The authors state that "... the exposure assessor is advised
to consult A statistician .,.* Statements about bringing
statisticians occur a number of times in .this report. If it is
necessary to bring in this point why not also refer to the need to
consult: with chemists, engineers, meteorologists, toxicologists,
etc.,. etc.,
p. 48-57. Should the EPA accept the NRG definitions for exposure,
dose etc. this entire section would have to b* completely rewritten,
Even now, using the definitions of tha authors, there mr* errors in
the mathematics. For example, the light side of equation (3-5) and
equation (3-6) are identical. Therefore, T - ED. Yet, the authors
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April 14, 1989
imply T is the time of incerest, whereas, ED, Is the duration of
exposure over all events vhere exposure occurs.
» p. 56, par, 2. What do the authors mean by ehe statement "the
Carlo Method Immediately uses she fact ..." that is, what is the
purpose of the phrase "immediately uses"?
» p. 60, par. 3, The authors state; "Even In the case of serious
flaws, data should not be discarded entirely unless better data are
available". The authors would have to define the phrase "serious
flaws" very carefully before I could accept this statement. Bad
data is bad data and should be discsarded. Put another way, garbage
in, garbage out,
» I could not find a definition or reference to the important exposure
metric, "integrated exposure".
I believe these specific comments adequately support my general
criticisms. It Is never pleasant to criticize a report, particularly so
thoroughly, I also am aware that should the abova recommendations be
taken, the report will have to be rewritten. However, in light of the
fact that EPA management Is seriously considering adopting the total human
exposure concept as the guiding scientific principle In carrying out ,the
agency's mandate for risk assessment and risk management, it is critical
that the exposure assessment guidelines which form the scientific
foundation of the total human exposure concept be useful, readable and
scientifically accurate, I compliment EPA on its foresight in embracing
the total human exposure concept Att'l in taking these first steps to
develop exposure assessment guidelines. I look forward to the integrated
exposure assessment guidelines. .
Sincerely,
srome/J. Wesolowski, Ph.D., Chief
& Industrial Hygiene Laboratory
JJtfist
cc: R. Flaak
P. Lioy
R.
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JAMES E. WOODS Ph.D., P.E,
1235 Yale Place, #805
Minneapolis MN 55403
22 April 1989
Mr, A. Robert Flaak, Executive Secretary
Science Advisory Board (A-1Q1F)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
Dear Bob,
The enclosed comments are submitted as requested at our lAQtHE Committee of
28-29 March 1989, These comments are based on my review of the "Draft
Guidelines for Exposure-Related Measurements" of November 1988, the "Report of
the Environmental Effects, Transport and Pate Committee" of April 1989, and my
participation in the 28~2f March IAQTHS Committee meeting.
General Comments
1. This draft contains much useful information, and has the potential of being
an important Guide for researchers and investigators. However, as indicated
by the EETFC, major revisions will be required, I concur in this opinion.
2. If this document is to provide credible guidance for exposure measurement,
it must clearly and authoritatively define "exposure" in weasureable
terminology* Only in Chapter 3 is a quantitative definition proposed.
Moreover, the proposed definition is not universally accepted. If the units
of exposure are to be consistently expressed as mass, then the measurements
of intensity, I, and time, dt» must be clearly described. It is recommended
that these terms be clearly defined and discussed in Chapter 1.
3. The three methods of "measuring1* exposure are presented in a
confusing manner. Does the Direct Method provide a "measure" of
concentration or a measure of exposure? If it is to be exposure, is the
measure in terms of mass or the integral of mass and tine? The other two
methods are "indirect" indicators (not measures) of exposure. If
uncertainty principles are to be used, a clear distinction of measures and
indicators is necessary.
4. The fact that this document is limited to discussions of measuring chemical
contaminants should be clearly indicated in its objective and title.
5. I concur that this draft document should be integrated with the previously
issued Guidelines for Estimating Exposures. The integrated document should
then be reviewed and published.
Specific^ Comments
Page 2 - The focus of the document on chemical measurements, without
consideration of physical (e.g., thermal, lighting, acoustic, etc) or
biological (e.g., microbiological) influences of the factors, is a serious
limitation.
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Robert Flaak
James Woods' Comments
Page 2
April 22, 1989
Page 4, par 2 - In the proposed definition of exposure, which boundaries
distinguish measures of exposure from measures of dose?
ga^e 5, top of page - The units of measure of exposure should be defined.
Also, they should be distinguished from the units of measure of dose. When
assessing total exposure, how are units of measure of exposure by various
pathways rationalized?
Page 5, par 1 - How can measurements of population activity or duration of
exposure be neglected in a document purported to be a Measurement
Guideline? These factors must be addressed.
Page 5, par 2 - Other environmental factors (e.g., physical, psychosocial,
etc*} that affect exposure should be identified and measurement methods
should be discussed.
Page 6, par 1 - The description of a dosimeter to measure exposure adds to the
confusion between the concepts of dose and exposure* Clarification is
needed,
Page 6, par 2 - "Biological monitoring" is not technically a "measure" of
exposure, although it may be an "indicator". Pleas* clarify. Ho* biological
monitoring differs from dose measurement must be clarified in terms of
exchange boundaries and target organs.
Pages 6 and 7 - The "indirect" measurement methods of biological monitoring
and predictive assessments should be clearly classified differently than
the "direct'"~measurement nethod. In fact, is it even possible to determine
total exposure by "direct measurement"? Since the "direct" method probably
yields incomplete information, and the "indirect" methods require
prediction to assess exposure, how can exposure be assessed without
modeling and simulation? This Guideline should be rewritten integrally with
the 1986 Guide,
Page 7, par2 - The "geographic zone" of indoor air is a confusing concept.
Does this refer to Che difference of an indoor environment in Los Angeles
and Bostoo, or Co two adjacent rooms in the same building?
Page 12t par 1 - Hhy would an objective be to support a type of assessment?
The "direct" and "indirect" (reconstructive and predictive) methods may be
chosen to meet an objective, but they should not be objectives themselves.
Page _I4, par 2 - How cat! methods of measuring be considered science? What is a
split sample and how is it obtained? Is it real? Mow can & sample of air
and food be split? How can these results be combined with those of a patch
to get a direct measurement of total exposure? This whole concept is
confusing and needs clarification.
Pages 20 - 23 - The discussion on "Setting Data Quality Objective" is very
good.'
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Robert Plaak
James Woods' Comments
Page 3
April 22, 1989
Pages 23 - 31 (Sections 2.5 and 2.6) - The discussions are primarily directed
to the "predictive assessment" method. What plans and uncertainty
evaluations ate needed for the other methods?
Page 36, par 1 j__gage_46, par 1; page 47, par I - Substitute for the tens
"absorbed dose". As indicated in Chapter I of the Guide, the term confounds
the concepts of dose and exposure.
Page 48 - The dimensions of exposure (i.e., mass) in Equation 3.1 are not
consistent with others generally acepepted internationally (e.g.,
concentration x time). However, if it is assumed here that S ™_/"ldt, rather
than E = J"cdt, then previous sections of this Guide should have extensive
discussions on how to accurately and precisely measure I by direct and
indirect methods. Also is E, aa defined its this Section, consistent with
the measures of exposure using "direct" and other "indirect** (i.e.,
biological monitoring) methods?
Page 51 - The Equation for dose (IQ 3*12) is not consistent with generally
accepted definitions (e.g., absorption in target organ). How does the .
proposed definition rationalize with the more common definitions? Also, the
discussion on dose goes beyond the scope of this document (EQs 3.12 to
3.14) and should be deleted.
Best regards,
James E, Woods, Ph.D., P.I.
Member, IAQTHE Committee of SAB
cc: Dr. Morton Lippmann
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