December 18, 2007
EPA-HSRB-07-03
George Gray, Ph.D.
Science Advisor
Office of the Science Advisor
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subject: June 27-29, 2007 EPA Human Studies Review Board Meeting Report
Dear Dr. Gray:
The United States Environmental Protection Agency (EPA or Agency) requested
the Human Studies Review Board (HSRB) to review scientific and ethical issues addressing: (1)
Carroll-Loye Picaridin Mosquito Repellency Protocol LNX-001; (2) ICRPicaridin Mosquito
Repellency Protocol ICR 1 A 044; (3) Acrolein; (4) 4-Amino Pyridine and; (5) Antimicrobial
Exposure Assessment Task Force (AEATF) and Agricultural Handler Exposure Task Force
(AHETF) Research Programs. The enclosed HSRB report addresses the Board's response to
EPA charge questions at its June 27-29, 2007 meeting. A summary of the Board's conclusions is
provided below.
Carroll-Loye Picaridin Mosquito Repellency Protocol LNX-001
• The protocol LNX-001 to study the efficacy of a cream formulation and a pump spray
formulation of picaridin for repelling mosquitoes is sufficiently sound, from a scientific
perspective, to be used to assess the repellent efficacy of these formulations against
mosquitoes.
• The Board concurred with the assessment of the Agency that the protocol LNX-001
submitted for review by the Board, if revised as suggested in EPA's review, would meet
the applicable requirements of 40 CFR 26, subparts K and L. In addition, with the
submission of the amended protocol, the Board believed that the protocol meets the
applicable requirements of 40 CFR 26, subparts K and L.
ICR Picaridin Mosquito Repellency Protocol ICR 1A 044
• If amended and consistent with the Board's concerns and recommendations, the protocol
ICR 1A 044 studying the efficacy of two aerosols formulations of picaridin for repelling
mosquitoes would be sufficiently sound, from a scientific perspective, to be used to
assess the repellent efficacy of these formulations against mosquitoes.
• The Board concurred with the assessment of the Agency that the protocol ICR 1A 044
submitted for review by the Board, if revised as suggested in both EPA's review and by
the Board, would meet the applicable requirements of 40 CFR 26, subparts K and L.
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Acrolein
• The Board concluded that the Weber-Tschopp et al. study contains information sufficient
for assessing human risk resulting from potential acute inhalation exposure. In addition,
the study was sufficiently sound, from a scientific perspective, to be used to estimate a
safe level of acute inhalation exposure to acrolein for the population tested but may not
be generalizable to younger or older groups.
• There was not clear and convincing evidence that the conduct of the Weber-Tschopp et
a!. study was fundamentally unethical. In addition, despite the lack of adequate
information to assess the affirmative, most of the HSRB agreed that there was not clear
and convincing evidence that the conduct of the study was significantly deficient relative
to the ethical standards prevailing at the time the research was conducted.
4-Amino Pyridine
• The Board concluded that the three clinical studies, Grijalva et a!. 2003, Segal et a!. 1999,
and Van Diemen et al. 1993, were sufficiently sound, from a scientific perspective, to be
used to derive a point of departure for estimating risk to humans from exposure to 4-AP.
Thus considering the three studies, an estimate of the LOAEL of 0.07 mg/kg/day was
determined. The Board was reluctant to endorse the use of a 5 mg/day (0.07 mg/kg-day)
LOAEL, given the multiplicity of side effects seen among patients receiving this dose,
and the steep dose-response curve of 4-AP. Thus, the Board cautioned that this
conclusion comes with a degree of uncertainty and advised the Agency to take such
uncertainty into account when using the published information to arrive at a point of
departure for 4-AP.
• The Board concurred with the initial assessment of the Agency that for each of these
three clinical studies (Sega! et al., 1999; Grijalva et a!., 2003; and Van Diemen et al.,
1993), there was no clear and convincing evidence that the conduct of the study was
fundamentally unethical, or that the conduct of the study was significantly deficient
relative to the ethical standards prevailing at the time the research was conducted.
AEATF and AHETF Research Programs
• Risks and Benefits of Handler Research
The AHETF and AEATF governing documents have provided the HSRB with a detailed
and thoughtful analysis of expected benefits and risks associated with the conduct of human
exposure monitoring. The Board recommended that the particular arrangements for providing
the test substance be outlined in the individual protocols. Finally, the Board concurred with the
AHETF and AEATF that the database developed from these studies will improve the quality of
risk assessments, and that they should be considered a valuable societal benefit, provided that the
data collected are accurate, or at the least do not underestimate real-world exposures.
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The Board recommended that AHETF pay more careful attention to the issue of safety
when asking participants to operate equipment with which they do not normally work. In
particular, AHETF should be more explicit about the level of competency expected of workers
when operating such equipment. The Board commended the AHETF for developing clear
guidelines for stopping work based on a heat index. However, the Board concluded that the
approach described in the governing documents was not fully protective of workers, and
recommended that additional attention be given to this matter, including consideration of a lower
heat index threshold for stopping work.
Addressing Potential Sources of Underestimation Bias
The Board recommended that the validity of dose estimates based on passive dosimetry
be reassessed given the variability of previous laboratory data. Given some uncertainty as to
exposure to hands, face and neck for various scenarios, the Board concurred with the Agency’s
intention to evaluate data provided by the task forces for each scenario to determine the relative
contribution from skin residues versus whole body dosimeters. The Board recommended that the
Task Forces either generate data supporting the efficiency of removing their surrogate pesticides
from skin by washing and by wiping, or accept the automatic adjustments being proposed by the
Agency; in fact, the adjustment for wipes could even be increased beyond that being proposed
for washing. This recommendation is consistent with the advice provided in the 1997 OECD
guidance document: “The best that can be achieved for a hand wash or hand rinse method is a
laboratory validation of the efficiency of recovery of material from the hands of human
volunteers.” In addition, the Board suggested a validation study for recovery efficiency of wash or
wipe samples could be tested in vitro and not require human exposure testing.
The HSRB was comfortable with not including concurrent biomonitoring in the protocols. In
fact, the Board recommended that the use of additional monitoring units was more appropriate
than the inclusion of biomonitoring in these programs.
• QA/QC Controls
Overall, the Standard Operating Procedures (SOPs) outlining the overall administration,
report generation and quality assurance (QA) oversight seems reasonably complete. The Board
noted two major areas that should be expanded and/or revised for additional clarity, namely the
SOPs that focused on data quality and sample integrity and compliance.
• Design of Scenario-Level Sampling
The Board acknowledged the great complexity of study design development, given the
many variables associated with exposure and the practical constraints that arise in the conduct of
human exposure studies. The Board commended the Agency and the task forces for their efforts
in developing a detailed discussion of sampling strategies. The Board remained concerned that
the number of variables is large, and that the relative importance of these variables has not yet
been defined adequately. For both the AHETF and AEATF studies, the Board recommended
that prior to data collection, the Agency ensure that the critical variables associated with
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exposure are ranked, accompanied by an appropriate rationale and justification for this ranking.
This ranking would then inform the study design in terms of how sampling sites and individual
participants are selected.
The Board recommended that the following information was necessary for it to provide its
scientific advice on scenario-specific information:
• - Scenario specific information detailing variables that might influence exposure and its
effect;
• A feasible sampling strategy including specifics of population to be tested (including its
size), a list of relevant variables and how they would be collected and analyzed;
• Information on relationship between scenario-specific exposure assessment and the
representative exposure in such scenarios in the target population;
• Essential environmental variables including site description, temperature, humidity, wind
levels as well as subjects’ external clothing, work history and type of pesticide
application;
• Relevant data on inter-subject variability;
• Data analysis plan.
The major limitation of non-random sampling is that it provides no means for estimating the
error associated with any estimate based on the sample. The exposure distributions based on this
type of sample might or might not be anywhere close to the true exposure distributions and there
is no way to tell if the results are representative or not. If the estimated exposure distributions
will be used for regulatory purposes it is particularly important to base those estimates on
samples that at least approximate a random sample and that permit obtaining data-driven
estimates of uncertainty around quantities of interest. Error estimates and other estimates
relevant to determination of quantities in the AEATF and AHETF reports are based on strong
and un-testable assumptions.
• Statistical Justification of Number of Cluster
Purposive sampling method is used as a surrogate for probability sampling, no additional
information seems to be needed for the HSRB to assess the adequacy of the justification for the
number of clusters and the number of monitoring units in specific AHETF and AEATF II study
proposals (however, as noted previously, the Board raised serious concerns about the purposive
sampling strategy).
As the sample size justification for the AEATF II program is based on the ICC estimate
from the AHETF program, it is recommended that the AEAFF II program update the proposed
sample size based on an analysis of whether the ICC estimates agree with that from the AI-IETF
program.
• Within-Worker Variability
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The lack of choosing a within-person design is limiting if the Agency wishes to obtain
data on usual exposures. However, if the Agency wishes to collect data on one-day exposures,
their approach is not limiting, but the Board recommends that as many handler as possible be
observed as costs would allow.
Subject Recruitment and Enrollment Issues
The Board agreed that the Governing Documents and associated Standard Operating
Procedures do include comprehensive and appropriate protections for human subjects.
The Board agreed that the handling of language differences is an area requiring further
refinement and is appropriate to protections for human subjects. Related issues include
mechanisms to ensure understanding and voluntariness in the consent process.
Sincerely,
Celia B. Fisher, Ph.D. Chair
EPA Human Studies Review Board
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NOTICE
This report has been written as part of the activities of the EPA Human Studies Review
Board, a Federal advisory committee providing advice, information and recommendations on
issues related to scientific and ethical aspects of human subjects research. This report has not
been reviewed for approval by the Agency and, hence, the contents of this report do not
necessarily represent the view and policies of the Environmental Protection Agency, nor of other
agencies in the Executive Branch of the Federal government, nor does the mention of trade
names or commercial products constitute a recommendation for use. Further information about
the EPA Human Studies Review Board can be obtained from its website at
http://www.epa.gov/osalhsrb/. Interested persons are invited to contact Paul Lewis, Designated
Federal Officer, via e-mail at lewis.pau1 epa.gov.
In preparing this document, the Board carefully considered all information provided and
presented by the Agency presenters, as well as information presented by public commenters.
This document addresses the information provided and presented within the structure of the
charge by the Agency.
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United States Environmental Protection Agency Human Studies Review Board Members
Chair
Celia B. Fisher, Ph.D., Marie Ward Doty Professor of Psychology, Director, Center for Ethics
Education, Fordham University, Department of Psychology, Bronx, NY *
Vice Chair
William S. Brimijoin, Ph.D., Chair and Professor, Molecular Pharmacology and Experimental
Therapeutics, Mayo Foundation, Rochester, MN
Members
Alicia Carriquiry, Ph.D., Professor, Department of Statistics, Iowa State University
Snedecor Hall, Ames, IA
Gary L. Chadwick, PharmD, MPH, CIP, Associate Provost, Director, Office for Human Subjects
Protection, University of Rochester, Rochester, NY
Janice Chambers, Ph.D., D.A.B.T., William L. Giles Distinguished Professor, Director, Center
for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State
University, Mississippi State, MS
Richard Fenske, Ph.D., MPH, Professor, Department of Environmental and Occupational Health
Sciences, University of Washington, Seattle WA
Susan S. Fish, PharmD, MPH, Professor, Biostatistics & Epidemiology, Boston University
School of Public Health, Co-Director, MA in Clinical Investigation, Boston University School of
Medicine, Boston, MA
Suzanne C. Fitzpatrick, Ph.D., DABT, Senior Science Policy Analyst, Office of the
Commissioner, Office of Science and Health Coordination, U.S. Food and Drug Administration,
Rockville, MD
Dallas E.- Johnson, Ph.D., Professor Emeritus, Department of Statistics, Kansas State University,
1812 Denhoim Drive, Manhattan, KS * *
Kannan Krishnan, Ph.D., Professor, Département de sante environnementale et sante au travail,
Faculté de medicine, Université de Montréal, Montréal, Canada *
KyungMann Kim, Ph.D., CCRP, Professor & Associate Chair, Department of Biostatistics &
Medical Infomiatics, School of Medicine and Public Health, University of Wisconsin-Madison,
Madison, WI
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Michael D. Lebowitz, Ph.D., FCCP, Professor of Public Health & Medicine. University of
Arizona, Tucson, AZ
Lois D. Lehman-Mckeeman, Ph.D., Distinguished Research Fellow, Discovery Toxicology,
Bristol-Myers Squibb Company, Princeton, NJ
Jerry A. Menikoff, M.D., Office of the Director, National Institutes of Health, Bethesda, MD
Sean Philpott, PhD., MS Bioethics, Policy and Ethics Director, Global Campaign for
Microbicides, Program for Appropriate Technology in Health, Washington D.C.
Richard Sharp, PhD., Director of Bioethics Research, Department of Bioethics, Cleveland Clinic,
Cleveland, OH
Human Studies Review Board Staff
Paul I. Lewis, Ph.D., Designated Federal Officer, United States Environmental Protection
Agency, Washington, DC
* Not in attendance at June 27-29, 2007 Public Meeting
* * Become HSRB member August 31, 2007
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TABLE OF CONTENTS
United States Environmental Protection Agency Human Studies Review Board Members. 7
INTRODUCTION 10
REVIEW PROCESS 15
CHARGE TO THE BOARD AND BOARD RESPONSE 16
Proposed Carroll-Loye Picaridin Insect Repellent Efficacy Study LNX-OO1 16
Proposed ICR Picaridin Insect Repellent Efficacy Study 22
Completed Inhalation Study with Acrolein 30
Completed Studies on the Therapeutic and non-Therapeutic Effects of Administration of
4-aminopyridine 38
Design of Research on the Levels of Exposure Received by Pesticide Handlers 43
1 .F F’ERE?JCES 66
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INTRODUCTION
From June 27-29, 2007, the United States Environmental Protection Agency’s (EPA or
Agency) Human Studies Review Board (HSRB) met to address scientific and ethical issues
concerning:
A. Proposed Carroll-Love Picaridin Insect Repellent Efficacy Study LNX-OOl
EPA requires data from efficacy studies using appropriate insect species to support
claims of greater efficacy than have previously been approved.
EPA’s regulation, 40 CFR §26.1125, requires the sponsor or investigator to submit to
EPA, before conducting a study involving intentional exposure of human subjects, materials
describing the proposed human research in order to allow EPA to conduct scientific and ethics
reviews. In addition, EPA’s regulation, 40 CFR §26.160 1, requires EPA to seek HSRB review
of the research proposal.
In previous meetings the HSRB has reviewed and commented favorably on several
proposed insect repellent efficacy protocols to be conducted by Carroll-Loye Biological
Research, submitted by Dr. Scott Carroll. Dr. Carroll has submitted a proposal for new research
to evaluate the efficacy of two conditionally registered repellent products containing the active
ingredient picaridin. The research protocol, identified as LNX-00 1, describes a field study of the
efficacy of the test formulations against mosquitoes. The proposal bears many similarities to the
protocols EMD-004, SCI-001, and WPC-00l that the HSRB has previously reviewed.
EPA has reviewed Dr. Carroll’s protocol and has concluded that, with some required
refinements, it appears likely to generate scientifically sound, useful information and to meet the
applicable provisions of the EPA regulations in 40 CFR part 26, subparts K and L. The sponsor
wishes to submit the data to EPA later this year to satisfy the requirement to provide efficacy
data imposed when it received a conditional registration for picaridin. In the interest of
providing a thorough and timely response to the proposal, and because EPA finds the protocol
generally meets applicable scientific and ethical standards, EPA is presented this protocol for
review at the Board’s June 2007 meeting.
B. Proposed ICR Picaridin Insect Repellent Efficacy Study
EPA requires data from efficacy studies with human subjects to support claims of
efficacy of a new pesticide product intended to repel insects that transmit human diseases.
EPA’s regulation, 40 CFR §26.1125, requires the sponsor or investigator to submit to
EPA, before conducting a study involving intentional exposure of human subjects, materials
describing the proposed human research in order to allow EPA to conduct scientific and ethics
reviews. In addition, EPA’s regulation, 40 CFR §26.1601, requires EPA to seek HSRB review
of the research proposal.
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Dr. Niketas Spero has submitted a proposal for new research to evaluate the efficacy of
two new formulations of a skin-applied repellent product containing picaridin, to be conducted
by Insect Control & Research, Inc. (ICR). The research protocol, identified by Protocol ID
G0590307001A044, describes a field study of the efficacy of the test formulations against
mosquitoes.
EPA has reviewed ICR’s protocol and has concluded that, with a number of required
revisions, it appears likely to generate scientifically sound, useful information and to meet the
applicable provisions of the EPA regulations in 40 CFR part 26, subparts K and L. The sponsor
wishes to submit the data to EPA later this year in support of an application to register one or
more new picaridin products. In the interest of providing a thorough and timely response to the
proposal, and because EPA finds the protocol can meet applicable scientific and ethical
standards, EPA is presented this protocol for review at the Board’s June 2007 meeting.
C. Completed Inhalation Study with Acrolein
In its reregistration program EPA reexamines the safety of previously registered
pesticides. The Agency is currently reviewing pesticides containing the active ingredient
acrolein. Acrolein is registered for use as a biocide in agricultural and industrial water supply
systems. It is also formed as a byproduct in various industrial processes and is a component of
cigarette smoke.
In a review of the published scientific literature, EPA identified a study published in
German in 1977 in which human subjects were exposed to acrolein for various durations and at
varying concentrations in an inhalation chamber. Researchers collected data on subjective
irritation sensations and on eye-blink and respiratory rates. The Agency intends to use the results
of this study in its hazard assessment to derive a “point of departure” (POD) for assessing acute
toxicity resulting from acute exposure to this chemical.
The Agency’s regulation, 40 CFR §26.1602, requires EPA to seek HSRB review of an
EPA decision to rely on the results of any study if the research was “initiated before April 7,
2006, and the research was conducted for the purpose of identifying or measuring a toxic effect.”
EPA has reviewed the study, applying the standards in 40 CFR § 26. 1703 and 26.1704. Those
provisions state:
§26.1703 Prohibition of reliance on research involving intentional exposure of
human subjects who are pregnant women (and therefore their fetuses), nursing
women, or children.
Except as provided in §26.1706, in actions within the scope of §26.1701 EPA shall not
rely on data from any research involving intentional exposure of any human subject
who is a pregnant woman (and therefore her fetus), a nursing woman, or a child.
§26.1704 Prohibition on reliance on unethical research with non-pregnant, non-
nursing adults conducted before April 7, 2006
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Except as provided in §26.1706, in actions within the scope of §26.1701, EPA shall not
rely on data from any research initiated before April 7, 2006, if there is clear and
convincing evidence that the conduct of the research was fundamentally unethical (e.g.,
the research was intended to seriously harm participants or failed to obtain informed
consent), or was significantly deficient relative to the ethical standards prevailing at the
time the research was conducted. This prohibition is in addition to the prohibition in
§26.1703.
The Agency’s reviews concluded that the data were scientifically sound and that there
was no clear and convincing evidence that the conduct of the research was fundamentally
unethical or significantly deficient relative to the ethical standards prevailing at the time the
research was conducted. Nor was there evidence to show that the subjects included nursing or
pregnant women or children.
D. Completed Studies on the Therapeutic and non-Therapeutic Effects of Administration of 4-
aminopyridine
In its reregistration program EPA reexamines the safety of previously registered
pesticides. The Agency is currently reviewing pesticides containing the active ingredient 4-
aminopyridine (4-AP). 4-AP is registered by EPA as a bird repellent under the name Avitrol. It
has also been investigated as a drug to treat various neurological diseases, and was recently
approved for the treatment of chronic functional motor and sensory deficits resulting from
Guillain-Barré syndrome.
In a review of the published scientific literature EPA identified three studies in which
human subjects were exposed to 4-AP to evaluate whether it alleviated neurological symptom in
patients with either spinal cord injury or multiple sclerosis. These clinical trials also report on
the non-therapeutic effects of 4-AP. The Agency intends to use the results of these studies to
derive a point of departure for assessing the risks to humans resulting from all potential durations
of exposure—acute, short term, intermediate or subchronic, and chronic exposure.
The Agency’s regulation, 40 CFR §26.1602, requires EPA to seek HSRB review of an
EPA decision to rely on the results of any study if the research was “initiated before April 7,
2006, and the research was conducted for the purpose of identifying or measuring a toxic effect.”
EPA has concluded that the three studies with 4-AP are subject to HSRB review under 40 CFR
§26.1602. The Agency reviewed the studies, applying the standards in 40 CFR § 26.1703 and
26.1704. Those provisions state:
§26.1703 Prohibition of reliance on research involving intentional exposure of
human subjects who are pregnant women (and therefore their fetuses), nursing
women, or children.
Except as provided in §26.1706, in actions within the scope of §26.1701 EPA shall not
rely on data from any research involving intentional exposure of any human subject
who is a pregnant woman (and therefore her fetus), a nursing woman, or a child.
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§26.1704 Prohibition on reliance on unethical research with non-pregnant, non-
nursing adults conducted before April 7, 2006
Except as provided in §26.1706, in actions within the scope of §26.1701, EPA shall not
rely on data from any research initiated before April 7, 2006, if there is clear and
convincing evidence that the conduct of the research was fundamentally unethical (e.g.,
the research was intended to seriously harm participants or failed to obtain informed
consent), or was significantly deficient relative to the ethical standards prevailing at the
time the research was conducted. This prohibition is in addition to the prohibition in
§26.1703.
The Agency’s reviews concluded that the data were scientifically sound and that there
was no clear and convincing evidence that the conduct of any of the research was fundamentally
unethical or was significantly deficient relative to the ethical standards prevailing at the time the
research was conducted. None of the studies included as subjects nursing or pregnant women or
children.
E. Background Materials Relating to the Design of Research on the Levels of Exposure
Received by Pesticide Handlers
Under FIFRA, EPA requires that all pesticide products must be “registered” before they
may be sold or distributed in commerce. The applicant for registration has the burden of
demonstrating that its pesticide will not cause “unreasonable adverse effects on the
environment.” Among other potential risks, EPA requires applicants to provide information that
allows EPA to assess the potential for adverse effects on people who mix, load, or apply a
pesticide (referred to as pesticide “handlers.”) Accurately characterizing handlers’ potential
exposure is essential to EPA’s risk assessment and regulatory decision-making.
EPA currently relies on a collection of exposure studies mostly contained in the Pesticide
Handlers Exposure Database (PHED) to develop estimates of handlers’ potential exposure.
When dealing with pesticide that have low volatility, EPA assumes that, if field data are
corrected for chemical-specific losses under field conditions, the amount of exposure a handler
receives is independent of the chemical composition of the pesticide he is using, and that his
exposure depends on the amount of active ingredient handled, as well as the particular activity,
the particular type of pesticide formulation and the particular type of equipment used. The
Agency uses the PHED data to develop estimates of “unit exposures” — expressed as an amount
of exposure per amount of active ingredient handled — for specific scenarios. (A scenario is
defined by the activity, formulation, and equipment, e.g. applying a liquid formulation by using
airblast equipment in an open cab.) Using this information, EPA estimates handlers’ potential
exposures for each use of a pesticide and compares those levels with toxicity data. If the
comparisons show potential exposure is acceptably low, EPA concludes there is no risk to
handlers. If, however, the comparisons show that in some scenarios a handler may receive
unacceptably high exposure, EPA takes actions to mitigate the risk. The range of possible
actions to reduce handlers’ exposure includes requiring the use of personal protective equipment,
reduced application rates, changes in formulation, use of specific types of application equipment
or engineering controls, or prohibition of the use pattern.
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The data currently used to estimate handlers’ potential exposure has a number of
limitations. The Agency believes that data from new handler exposure studies would provide a
much sounder basis for estimating potential exposure. In particular, new data should provide a
basis for characterizing the distribution of unit exposures across the population of handlers
performing activities in each scenario. Two industry groups have arisen to undertake the
research necessary to develop new databases — the Agricultural Handlers Exposure Task Force
(AHETF) and the Antimicrobials Exposure Assessment Task Force II (AEATF). The AHETF is
focusing on studies that relate to the use of pesticides in agriculture, and the AEATF will
characterize exposures received by people while handling antimicrobial pesticides, e.g.,
disinfectants, materials preservatives, etc.
Both Task Forces would like to initiate research soon — the AEATF during the winter of
2007—2008, and the AHETF during the pesticide use season in 2008. At least some Task Force
studies would involve intentional exposure of a human subject. EPA’s regulation, 40 CFR
§26.1125, requires the sponsor or investigator to submit to EPA, before conducting research
involving intentional exposure of a human subject, materials describing the proposed human
study in order to allow EPA to conduct scientific and ethics reviews. In addition, EPA’s
regulation, 40 CFR §26.1601, requires EPA to seek HSRB review of the research proposal.
The HSRB has considered the prospect of new handler research at two previous
meetings. In June 2006 the Board reviewed five proposed protocols developed by the AHETF.
The Board raised questions and made numerous comments on both scientific and ethical aspects
of the proposals.
Over the past year EPA and the Task Forces have worked hard to address the issues
identified by the HSRB. In response to scientific concerns raised by the HSRB, EPA analyzed
the existing handler exposure database and relevant scientific literature, and presented its
analysis to the FIFRA Scientific Advisory Panel (SAP) in January 2007. The Agency asked the
SAP to comment on, among other topics, the “limitations [ of existing data] and on EPA’s
conclusion that additional data could improve significantly EPA’s ability to estimate worker
exposure.” The SAP report was released April 2, 2007, and is available at:
http://www.eDa.gov/scipolv/sap/meetings/2007/january/january2007finalmeetingminutes.pdf .
At its April meeting the HSRB received a copy of the SAP report and a presentation by two
members of the Panel that prepared the report.
In addition, for the April 2007 HSRB meeting EPA prepared a draft document identifying
the major elements of the recruitment and enrollment processes that should be considered by
investigators as they prepare protocols for handler exposure research. The document discussed
broad principles which should be considered in the course of research design. In the future,
through a participatory process involving investigators, workers, and other stakeholders EPA
intends to add to the document specific best practices, and to identify publicly available
resources that contain additional discussion, information, and guidance relevant to the
implementation of general ethical principles in occupational exposure research. The draft
document is available at: http://www.eDa.gov/osa/hsrb/files/meeting-materials/apr- 18-20-2007-
public-meetingfDraftFrameworkForDevelopingBest-Practices03 15007 . pdf
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Both the AHETF and AEATF have prepared extensive materials explaining and
justifying their proposed research, and have revised these materials in response to EPA
comments. These materials provided to the HSRB for discussion at its June 2007 meeting,
generally explain the scope of the proposed research programs and describe the general
framework for conducting the research. In addition, each Task Force has provided Standard
Operating Procedures which will guide the conduct of the studies. These materials provide
essential background information to support the Board’s evaluations of Task Force protocols and
related materials at subsequent meetings. Because EPA regards the proposed studies as
“research involving intentional exposure of human subjects,” EPA regulations require the
Agency and the Board to review these proposals before the investigators initiate the studies.
This report transmits the HSRB’s comments and recommendations from its June 27-29,
2007 meeting.
REVIEW PROCESS
From June 27-29, 2007, the Board had a public face-to-face meeting in Arlington,
Virginia. Advance notice of the meeting was published in the Federal Register “Human Studies
Review Board: Notice of Public Meeting (72 Federal Register 108, 31323). At the public
meeting, following welcoming remarks from Agency officials the Board then heard presentations
from the Agency on the following topics:
• A research proposal from Carroll-Loye Biological Research to evaluate the efficacy of
two conditionally registered products containing picaridin in repelling mosquitoes in the
field.
• A research proposal from Insect Control & Research, Inc. to evaluate the efficacy of two
unregistered products containing picaridin in repelling mosquitoes in the field.
• A completed study measuring the effects on human subjects of acute inhalation exposure
to acrolein.
• Three completed studies of the efficacy and side effects of 4-aminopyridine used as a
therapeutic agent.
• Extensive background materials concerning research to quantify the level of exposure
received by people who mix, load, and apply pesticides. These materials were prepared
by the Agricultural Handlers Exposure Task Force and by the Antimicrobial Exposure
Assessment Task Force. -
The following oral comments were presented at the meeting:
(1) Scott Carroll, Ph.D. representing Carroll-Loye Biological Research and Ghona Sangha,
Ph.D. representing LANXESS Corporation addressing the proposed Carroll-Loye
picaridin insect repellent efficacy study LNX-001;
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(2) Mr. Niketas Spero and Robin Todd, Ph.D. representing ICR, Inc. addressing the ICR
picaridin mosquito repellency protocol;
(3) Richard Collier, Ph.D. of Landis International representing the Agricultural Handlers
Task Force, John Ross, Ph.D. of infoscientific.com, representing the Agricultural
Handlers Task Force, Ray McAllister of CropLife America, Inc., and Larry Holden,
Ph.D. of Sielken and Associates Consulting, Inc. addressing the design of research on the
levels of exposure received by pesticide handlers.
For their deliberations, the Board considered the materials presented at the meeting,
written public comments and Agency background documents (e.g. pesticide human study,
Agency data evaluation record (DER) of the pesticide human study, weight of evidence review,
ethics review, pesticide human study protocols and Agency evaluation of the protocol).
CHARGE TO THE BOARD AND BOARD RESPONSE
Proposed Carroll-Loye Picaridin Insect Repellent Efficacy Study LNX-OO1
Charge to the Board
If the proposed research described in Protocol LNX-OOl from Carroll-Loye Biological
Research is revised as suggested in EPA’s review, does the research appear likely to generate
scientifically reliable data, useful for assessing the efficacy of the test substances for repelling
mosquitoes?
Board Response
The active ingredient picaridin in two formulations will be tested in the field by the
Carroll-Loye company for picaridin’s ability to repel mosquitoes. Picaridin is also known as
Icaridin and KBR 3023. Picaridin has a history of use as an insect repellent principally outside
the US. The active ingredient will be formulated into a 20% pump spray and into a 20% cream.
All experiments will be conducted using Good Laboratory Practices. A dosimetry experiment
with 10 individuals will be performed to determine the amount of product that would be utilized
by people using the product as directed.
The experiment will be a field study. Two locations in California could be used, either in
the Central Valley or in southern California. A mixture of Culex and Aedes species will be
present at these sites.
Legs and/or arms will be tested. There will be two experienced persons serving as
negative controls (i.e., without any repellent product) to confirm mosquito biting pressure.
Experimental subjects, in pairs, will monitor landings with intent to bite (LIBe’s) during a one
minute interval each 15 minutes, until the First Confirmed LIBe (FCLIBe) can be detèimined.
Stopping rules will be employed. The Complete Protection Time (CPT) will be determined,
expressed as mean and standard deviation plus 95% confidence interval, if data are normally
distributed, and methods are described to assess normality.
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With respect to the science criteria established earlier by the HSRB, the following
assessments are made:
General HSRB Scientific Criteria
• The scientific question was stated (i.e., to test the efficacy of picaridin formulated as
either a pump spray or a cream in repelling mosquitoes).
• Existing data were not adequate to answer the question of efficacy of these new
formulations.
• Because existing data were not adequate to answer the question of efficacy, new studies
involving human subjects are necessary.
• The potential benefits of the study are clear, i.e., that an effective repellent would be
available that would have either greater efficacy and/or fewer drawbacks than what was
currently approved.
• It is likely that the benefits would be realized because repellent efficacy will be
determined in carefully designed field experiments.
• The risks are minimal because the active ingredient is of very low toxicity, the other
formulation ingredients are of very low toxicity, the mosquitoes will be aspirated before
they have an opportunity to bite, and the regions selected will not have evidence of West
Nile Virus.
• The most likely relevant risk would be irritation from mosquito bites, but participants will
be instructed to remove mosquitoes before they are bitten, or the possibility of infection
with West Nile Virus, but the regions selected will have no evidence of the virus.
Serology tests will be performed on captured mosquitoes.
Study Design Criteria
• The purpose of the study is clearly defined (i.e., efficacy testing).
. There are specific objectives (i.e., to determine the Complete Protection Time that
picaridin in two formulations displays as a mosquito repellent).
• There was a formally stated hypothesis; however, it is broad and untestable. This does
not detract from the value of the study because a hypothesis is not really necessary for an
efficacy study such as this.
• The sample size will be 10 individuals per product along with 2 experienced individuals
to confirm mosquito biting pressure. A dosimetry experiment prior to the field
experiment will quantify the amount of repellent being used.
• There is a plan allocating individuals to treatments.
• It is anticipated that the findings from this study can be generalized beyond the study
sample.
Participation Criteria
• There is justification for the selection of the target population (i.e., selection primarily or
completely from the existing Volunteer Data Base, comprised of individuals previously
participating in similar studies or interested in doing so, who routinely are active
outdoors, and are routinely exposed to mosquitoes).
• The participants will be representative of some of the population of concern. However,
there are others in the population unlike these participants who are likely to use these
products, but it would either be unethical to test them or would be less appropriate to test
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them. The participating population, while not completely representative, is considered
appropriate and reasonable.
• The inclusion/exclusion criteria are appropriate.
• The sample will not be a vulnerable group.
Measurement Criteria
• The measurements will be accurate and reliable as defined. The endpoint will be the First
Confirmed Landing with Intent to Bite (FCLIBe). While this was viewed as an
appropriate endpoint by many of the Board members, there was some concern that the
confirming LIBe criterion was not a sufficiently protective/conservative, and that the first
unconfirmed LIBE should be the endpoint.
• The measurements will be appropriate to the question being asked.
• Quality assurance will be a part of the experimental plan.
Statistical Analysis Criteria
• The data were designed to be analyzed to calculate Complete Protection Time with a
range of variability. There was concern that specific criteria from the standpoint of
statistics for the selection of 10 subjects were not provided or available. There was also
concern about the handling of censored data.
• Measures of uncertainty were addressed.
Laboratory and Field Conditions
• Laboratory experiments are not proposed, except for the dosimetry
• Field experiments will be appropriate.
• The study will include a stop rule plan, medical management plan, and a safety monitor.
EPA’s science analysis identified a deficiency in the lack of a stated hypothesis, and one was
subsequently added. However, the objective of this study, i.e, length of time of efficacy in
repelling mosquitoes in the field, is clear and the lack of a formally stated hypothesis, or a vague
and broad hypothesis, does not detract from the scientific value of the study. EPA also identified
a deficiency in a lack of an explanation for the negative control in the dosimetry experiment;
however, it is a necessary control to determine whether any factors besides the formulated
product (e.g., sweat) might alter the weight of the dosimeters. EPA also noted that the method of
measuring the treatment area was not described. The Board concurred with this deficiency and
urged that it be addressed. There were also two statistical deficiencies identified, and the Board
urged greater consideration of statistical issues with respect to determination of sample size and
analysis of the data.
HSRB Consensus and Rationale
The protocol LNX-00 1 to study the efficacy of a cream formulation and a pump spray
formulation of picaridin for repelling mosquitoes is sufficiently sound, from a scientific
perspective, to be used to assess the repellent efficacy of these formulations against mosquitoes.
Charge to the Board
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b. If the proposed research described in Protocol LNX-001 from Carroll-Loye Biological
Research is revised as suggested in EPA’s review, does the research appear to meet the
applicable requirements of 40 CFR part 26, subparts K and L?
Board Response
Background on Study
The proposed study would evaluate the efficacy of two different skin-applied formulations of
an already registered and marketed insect repellent, Icaridin (registered by the Agency as
Picaridin). Icaridin is also known under the registered trade name BayrepeF and marketed
under the brand name Autan.
The research is to be conducted by Carroll-Loye Biological Research, a private laboratory in
Davis, CA. The sponsor of this study is LANXESS, Inc. of Pittsburg, PA. The submitted
documents assert that the study will be conducted in accordance with the ethical and regulatoiy
standards of 40 CFR 26, Subparts K and L, as well as the requirements of FIFRA §12(a)(2)(P),
the U.S. EPA’s Good Laboratory Practice (GLP) Standards described at 40 CFR 160, and the
California State EPA Department of Pesticide Regulation study monitoring (California Code of
Regulations Title 3, Section 6710). Finally, the protocol was reviewed and approved by an
independent human subjects review committee, Independent Investigational Review Board
(IIRB), Inc., of Plantation, FL prior to submission to the Agency.
The revised research protocol submitted consists of two interdependent studies: 1) a
dosimetry study, performed under controlled laboratory conditions, designed to determine the
amount of an insect-repelling compound, known as KBR 3023 (picaridin; Icaridin), that normal
subjects would typically apply when provided with one of two compound formulations (lotion or
pump-spray); and 2) an efficacy study, performed at field sites in Central California and/or
Southern California, designed to measure the effectiveness of 20% KBR 3023 (Picaridin;
Icaridin), as a mosquito repellent. Dosimetry will be determined either by passive dosimetry
using self-adhesive roll-gauze (spray and aerosol formulations) or by direct measurement of
compound application (lotion formulation). The efficacy of 20% KBR 3023 (picaridin; Icaridin)
as a mosquito repellent will be determined by measuring the ability of the two formulations to
prevent mosquito landings (defined as “Lite with Intent to Bite”; LIBe) under field conditions.
Mosquitoes will be aspirated mechanically after landing but prior to biting; prior to initiation of
the efficacy study, all volunteers will be trained, using laboratory-raised, pathogen-free
mosquitoes in a controlled laboratory setting, both to recognize a mosquito landing with the
intent to bite (LIBe) and to remove such mosquitoes with an aspirator. The strengths and
weaknesses of each study design are described above.
The dosimetry study will enroll 10 healthy volunteers, each of whom will apply both
formulations. These same subjects may or may not participate in the efficacy study. The efficacy
study will be conducted at two field sites located in Central and/or Southern California,
depending on the season. A total of twenty study participants will take place in the two field
trials; ten volunteers will test the lotion formation and ten will test the pump spray formulation.
For each field trial, two additional untreated control subjects (experienced field-workers or
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frequent participants of Carroll-Loye-conducted repellency studies) will be enrolled to determine
ambient LIBe pressure under field conditions; such measurements are necessary to determine
20% KBR 3023 (picaridin; Icaridin) efficacy as a mosquito repellent. Each control subject may
or may not participate in both field trials, thus a total of two to four control subjects may be
enrolled. The test compounds would be administered to a standardized skin surface area, with a
comparison to the two control participants. Each untreated subject will be attended by two
assistants who will aspirate mosquitoes prior to biting, thus minimizing risk of exposure to
vector-borne illnesses. In addition, three alternate subjects will be enrolled to: 1) replace any
subject who withdraws from participating; and 2) protect the confidentiality of any subject
excluded from the study as a result of pregnancy or other potentially stigmatizing condition, as
described below. The number of participants enrolled in this study thus will total a minimum of
25 volunteers and a maximum of 37 volunteers, a number that appears to be adequately justified
(Carroll 2007a; Carroll 2007b).
Ethics and Regulatory Compliance Review
The Board concurred with the factual observations of the strengths and weaknesses of the
study, as detailed in the EPA’s initial Science and Ethics Review, dated May 24, 2007 (Carley
and Sweeney 2007a). With the provision of an amended protocol on June 14, 2007 (Carroll
2007b), the proposed research described in Protocol LNX-001 comports with the applicable
ethical and regulatory requirements of 40 CFR 26, subparts K and L.
Subpart K of the Agency’s fmal human studies rule requires that the investigator submit
to the EPA all information that pertains to the IRB review of proposed research (40 CFR
26.111 5a) as well as additional information specified in 40 CFR 26.1125, if not already included
in the IRB documentation. The information requested under 40 CFR 26.1125 includes a
discussion of the potential risks to human subjects, the measures proposed to minimize these
risks, expected benefits if any and to whom, alternative means to obtain comparable information,
and the balance of risk and benefits of the research. In addition, subject information sheets and
approved written informed consent agreements should be provided, along with any information
about recruitment and the presentation of this subject information. Finally, the investigator
should provide copies of all correspondence with the IRB, including official notification of IRB
review and approval. As submitted to the Agency, the amended protocol (Carroll 2007a; Carroll
2007b) meets the regulatory requirements of 40 CFR § 26.11159 . For example, the original and
amended protocols were reviewed and approved by IIRB. Documentation previously provided to
the EPA by IIRB indicates that it reviewed this study pursuant to the standards of the Common
Rule (45 CFR 46, Subpart A) and determined it to be in compliance with that Rule.
With respect to study design, the risks to participants are minimal and justified by the
likely societal benefits, including data on the efficacy of 20% KBR 3023 (picaridin; Icaridin) as a
mosquito repellent. The nature and likelihood of any side effects or adverse events are described
clearly in the informed consent documents (with separate documents outlining the risks for
treated volunteers and experienced, untreated controls). The risks to study participants are three-
fold: 1) allergic reaction to test materials themselves; 2) exposure to biting arthropods; and 3)
possible exposure to arthropod-bome diseases.
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Reasonable attempts have been taken to minimize any potential harm, and plans for the
medical management of any side effects or adverse events have been developed. Although 20%
KBR 3023 (picaridin; Icaridin) is not currently used as an insect repellent in the United States,
for example, repellent formulations containing 20% KBR 3023 are commercially available in
Europe and Australia, and have been used for years with little evidence of toxic effects.
Laboratory analyses, as summarized by Dr. Ghoma Sangha of LANXESS at the public meeting
of the HSRB, also suggest that participants enrolled in this study are unlikely to be at increased
risk of experiencing adverse side effects upon exposure to the test materials.
Reactions to mosquito bites are usually mild and easily treated with over-the-counter
steroidal creams. Excluding subjects who have a history of such severe skin reactions will
minimize the risk of a subject experiencing a severe physical reaction to a mosquito bite. In
addition, the study protocol is designed specifically to minimize the likelihood that a mosquito
will bite, through the use of clear stopping rules, limited exposure periods, pre-bite aspiration
and joint observation.
To minimize the risk that study subjects will be exposed to illnesses such as West Nile
Virus, field tests of repellent efficacy will be conducted only in areas where known vector-borne
diseases have not been detected by county and state health or vector/mosquito control agencies
for at least one month. Finally, mosquitoes collected while attempting to bite control and treated
subjects during the field tests will be subjected to multiplex RT-PCR assays for several known
arthropod-borne diseases—including West Nile Virus, Western Equine Encephalitis Virus, and
St. Louis Encephalitis Virus—with clear plans to contact study participants and alert them if a
transmissible pathogen is detected.
In accordance with the provisions in the EPA’s final human studies rule (40 CFR §
26.1701-1704), minors and pregnant women are explicitly excluded from participation, the latter
being confirmed by requiring all female volunteers to undergo a self-administered over-the-
counter pregnancy test on the day of the study. The use of so-called “alternate” subjects ensures
that the results of over-the-counter pregnancy tests would be kept private; that study participants
may be designated as alternate subjects and automatically excluded from participation allows for
potentially pregnant volunteers to withdraw without compromising their confidentiality.
Finally, the study protocol also included several mechanisms designed to minimize
coercive subject recruitment and enrollment. For instance, although the study is to be conducted
by Carroll-Loye Biological Research, a private research laboratory in Davis, California, the
Principal Investigator of the study and Co-Owner of the research laboratory, Dr. Scott P. Carroll,
also is an adjunct faculty member of the Department of Entomology at the University of
California, Davis. The majority of research participants will be recruited from the University’s
student population, including from Dr. Carroll’s own department, but the protocol specifically
excludes any student or employee of the Study Director and includes a substantial waiting period
between recruitment and study enrollment and an interview by Dr. Carroll designed to minimize
coercive subject recruitment and enrollment. In addition, compensation for study participation is
not so high as to unduly influence enrollment. It is important to note, however, that the planned
use of a convenience sample of study participants may limit the broad applicability of the study
results to the general population; this fact is noted by the study investigators in the protocol.
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HSRB Consensus and Rationale
The Board concurred with the assessment of the Agency that the protocol LNX-00 1
submitted for review by the Board, if revised as suggested in EPA’s review, meets the applicable
requirements of 40 CFR 26, subparts K and L. In addition, with the submission of the amended
protocol, the Board believed that the protocol meets the applicable requirements of 40 CFR 26,
subparts K and L.
Proposed ICR Picaridin Insect Repellent Efficacy Study
Charge to the Board
If the proposed research described in ICR’s proposed picaridin protocol is revised as
suggested in EPA’s review, does the research appear likely to generate scientifically reliable
data, useful for assessing the efficacy of the test substances for repelling mosquitoes?
Board Response
This protocol was submitted with Confidential Business Information (CBI) redacted. The
name of the sponsor was withheld as was the concentration of the active ingredient, picaridin. A
workgroup of the HSRB had decided prior to the HSRB review that the information being
withheld was not critical to the scientific review of the protocol.
The protocol was clearly written and described a field study to be conducted on two picaridin
aerosol formulations at two locations. The locations, selected to achieve different species
composition of mosquitoes, would be: Site 1: Savannah-Ogeechee Canal Museum and Nature
Center, Savannah, GA, and Site 2: Pine Island, Lee County Mosquito Abatement District, FL.
The testing would last up to 14 hours on any particular test day.
There is an adequate pool of test subjects from individuals previously tested for repellent
efficacy from which the specific subject pool will be selected. Fourteen individuals will be
selected for the conduct of the protocol at each site, 10 test subjects, 2 alternates, and 2 untreated
controls. The treated subjects will have one test formulation on one arm and the other on the
other arm. A standard amount, as indicated in EPA test guidelines, will be applied to the
subjects’ arms; no dosimetry study will be conducted to determine likely consumer use rate. The
treated skin will be exposed to potential mosquito bites for 5 minutes out of each 30 minutes.
During the remaining 25 minutes of each 30 minute interval, the subjects will be in a screened
area that is impervious to mosquitoes. The treated area of skin will not be covered during these
25 minute intervals to avoid any rubbing off of the product. The endpoint will be time to First
Confirmed Bite (FCB), monitoring bites from only those mosquitoes which have all 6 legs on the
skin. Two negative controls will be selected randomly; these individuals are not anticipated to
receive bites. No positive control will be conducted. The ICR staff will record the data.
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There was concern raised by the Board because of the lack of a dosimetry study. The Board
understands that a standardized amount of the repellent is the guideline. However, the Board
considered a dosimetry experiment as a valuable addition to the protocol and recommended that
it be included so that the most likely amount of product applied by the consumer will be tested.
The Board recommended that a sample of mosquitoes be taken from those biting the
participants so that subsequent serology for pathogenic viruses can be performed; this
information can be provided to the participants to assist them in medical management if there is
any evidence of diseases present in the mosquitoes.
The Board also had concerns about the use of the First Confirmed Bite as the endpoint. The
Board understands that the FCB is at present the guideline endpoint, and appreciates that it may
be the more rigorous criterion for efficacy. However, the Board has been impressed with the
added safety to participants of the Landing with Intent to Bite (LIBe) endpoint on some of the
previously reviewed protocols, even though this endpoint is not that stated in the current
guidelines. There is insufficient information to judge how reflective the LIBe is of the bite. The
Board is also cognizant of the possibility of a lack of consistency in the labels if new criteria are
introduced, and the resultant confusion and/or unfairness to consumers who wish to compare
products. However, balancing these issues (consistency of endpoints, safety to test subjects, and
accuracy of the results) needs to be a priority item for EPA; thus the Board strongly urged EPA
to confirm or update its guidelines with the best possible balance of safety, consistency with past
studies, and accuracy of the results (including statistical validity).
With respect to the science criteria established earlier by the HSRB, the following
assessments are made:
General HSRB Scientific Criteria
• The scientific question was stated (i.e., to test the efficacy of picaridin formulated as one
of two aerosols in repelling mosquitoes).
• Existing data were not adequate to answer the question of efficacy of these new
formulations.
• Because existing data were not adequate to answer the question of efficacy, new studies
involving human subjects are necessary.
• The potential benefits of the study are clear, i.e., that an effective repellent would be
available that would have either greater efficacy and/or fewer drawbacks than what was
currently approved.
• It is likely that the benefits would be realized because repellent efficacy will be
determined in carefully designed field experiments.
• The risks are low because the active ingredient is of very low toxicity, and the regions
selected will not have evidence of West Nile Virus during the previous week, although
this one week interval may not be sufficient protection. Because the protocol specifies
that the test subjects must be bitten, there is the possibility of infection from virus-bearing
mosquitoes in the repellent-treated subjects.
• The most likely relevant risk would be irritation from mosquito bites, or the possibility of
infection with West Nile Virus or other mosquito-borne diseases, but the regions selected
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will have no evidence of the West Nile Virus during the week prior to the test. A more
intensive medical management plan should be described.
Study Design Criteria
• The purpose of the study is clearly defined (i.e., efficacy testing).
• There are specific objectives (i.e., to determine the protection time that picaridin in two
formulations displays as a mosquito repellent).
• There was no formally stated hypothesis; however, this does not detract from the value of
the study.
• The sample size will be 10 individuals (plus selection of 2 alternates) along with 2
experienced individuals to confirm mosquito biting pressure. A dosimetry experiment
prior to the field experiment will not be performed, but the standardized amount in the
guidelines will be used. The Board recommended that a dosimetry test be performed to
quantify the amount of repellent a consumer would apply, and that this be used in the
field tests.
• There is a plan allocating individuals to treatments.
• It is anticipated that the findings from this study can be generalized beyond the study
sample.
Participation Criteria :
• There is justification for the selection of the target population (i.e., selection primarily or
completely from the existing Volunteer Data Base, comprised of individuals previously
participating in similar studies).
• The participants will be representative of some of the population of concern; however,
there are others in the population unlike these participants who are likely to use these
products, but it would either be unethical to test them or would be less appropriate to test
them. Even though the participant group is not totally representative, the participating
population is considered appropriate and reasonable.
• The inclusion/exclusion criteria are appropriate, except that individuals over the age of 55
should not be participants.
• The sample will not be a vulnerable group.
Measurement Criteria
• The measurements will be accurate and reliable as defined. The endpoint will be the First
Confirmed Bite (FCB), which is the endpoint in the testing guidelines. While this would
be consistent with the tests that have been conducted in the past, there was some concern
that the bite would place the participants at greater risk than necessary because of the
possibility of contracting a mosquito-borne disease.
• The measurements will be appropriate to the question being asked, with the possible
exception of the exclusion of bites from mosquitoes which do not have all 6 legs on the
skin.
Statistical Analysis Criteria
• The data were designed to be analyzed to calculate mean time to FCB, plus standard
deviation and 95% confidence interval. There was concern that specific criteria from the
standpoint of statistics for the selection of 10 subjects were not provided or available.
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• Information on determining the normality of data was not included.
• The originally-suggested exclusion of “outliers” should be abandoned and the data from
all participants should be included.
• Measures of uncertainty were addressed, but need to be considered in relationship to
whether the data are normally distributed or not.
Laboratory and Field Conditions
• Laboratory experiments are not being proposed.
• Field experiments will be appropriate.
EPA’s science analysis identified a deficiency in the lack of a stated hypothesis, and there
was a promise to add a hypothesis about a test of a specified length of repellent efficacy;
however, the objective of this study, i.e., determination of the length of efficacy in repelling
mosquitoes in the field, is clear and the lack of a formally stated hypothesis does not detract from
the scientific value of the study. In reality, for this type of study, it does not matter whether there
is a hypothesis of a specific time or not because the study’s data will indicate what the length of
efficacy is for that particular product, which is what the EPA needs for its regulatory purposes.
EPA also identified a deficiency in a lack of information about determination of the normality of
the acquired data, and the handling on non-normally distributed data (should this be the case),
and the Board concurred that such information is needed. The Board concurred with EPA
regarding the necessity for addressing the identified deficiencies in statistical approaches and
Good Laboratory Practices.
HSRB Consensus and Rationale
If amended and consistent with the Board’s concerns and recommendations, the protocol
ICR IA 044 studying the efficacy of two aerosols formulations of picaridin for repelling
mosquitoes would be sufficiently sound, from a scientific perspective, to be used to assess the
repellent efficacy of these formulations against mosquitoes.
Charge to the Board
If the proposed research described in ICR’s proposed picaridin protocol is revised as suggested
in EPA’s review, does the research appear to meet the applicable requirements of 40 CFR part
26, subparts K and L?
Board Response
Background on the Study
The proposed study (Spero 2007) would evaluate the efficacy of two different skin-
applied formulations of picaridin-based insect repellents. Picaridin is already registered and
marketed as an insect repellent in the United States, under the registered trade name Bayrepel
and marketed under the brand name Autan. The goal of this study is to evaluate the efficacy of
two formulations under field conditions.
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The research is to be conducted by ICR, Inc., a commercial organization based in
Catonsville, Maryland; ICR provides testing and regulatory consulting services for companies
developing and marketing pesticides and insecticides in the United States and Canada. The study
is managed by toXcel, LLC of Gainesville, Virginia. The sponsor of this study is unknown;
because of claims of CBI, the documents for this study were provided to the HSRB in redacted-
form, with neither the sponsor’s identity nor the exact composition of the two test formulations
provided. The submitted documents assert that the study will be conducted in accordance with
the ethical and regulatory standards of 40 CFR 26, Subparts K and L, as well as the requirements
of FIFRA §12(a)(2)(P), and the U.S. EPA’s Good Laboratory Practice (GLP) Standards
described at 40 CFR 160. Finally, the protocol was reviewed and approved by an independent
human subjects review committee, Essex Investigational Review Board (EIRB), Inc., of
Lebanon, NJ prior to submission to the Agency.
Efficacy of the two picaridin-based formulations will be evaluated under field conditions
by using healthy volunteers. The study will be performed at two field sites in Georgia
(Savannah-Ogeechee Canal Museum and Nature Center) and Florida (Pine Island, Lee County).
The effectiveness of the two compounds as mosquito repellents will be determined by measuring
the ability of each formulation to prevent mosquito bites under field conditions. The strengths
and weaknesses of the study design are described above.
The efficacy study will enroll a total of up to 28 subjects. 14 subjects will participate in
field tests in Georgia and 14 in Florida. Of the 14 participants at each site, twelve will be treated
and test the effectiveness of the two Picaridin-based repellent formulations. The study protocol
justifies the enrollment of twelve treated participants at each field site, with ten volunteers
needed to obtain statistical validity and an additional two participants enrolled as alternates
(Spero 2007). The compounds will be applied to 250 cm 2 patches of skin on the forearms of each
study participant; one compound will be applied to the right forearm and one to the left forearm,
with the effectiveness of each formulation simultaneously evaluated. Treated skin will be
exposed for five minutes at half-hour intervals, with repellency of each formulation ascertained
by measuring the time from application to “breakdown” of repellency. “Breakdown” is defined in
the protocol as either two bites in a single five-minute exposure period, or one bite in each of two
consecutive exposure periods. Treated study participants will work in pairs, observing mosquito
landings and alerting attendant ICR staff of potential bites; ICR staff will determine whether to
count an event as a bite. Probes (i.e., “bites” where the mosquito punctures the skin but does not
collect blood) and bites from mosquitoes that do not fully alight (i.e., all six legs on the surface
of the exposed skin) will not be counted as bites. Once breakdown has occurred for a particular
repellent formulation, no further exposure of the subject’s treated skin will occur.
Two participants at each site, chosen by lottery, will remain untreated and will be
monitored to determine ambient mosquito biting pressure under field conditions. A 250 cm 2
patch of untreated skin will be exposed for five minutes at half-hour intervals, with the ambient
biting pressure determined by counting the mosquitoes landing on the skin. A minimum rate of 1
and a maximum rate of 10 landings per minute is necessary for the field trial to be conducted.
Landing mosquitoes will be brushed away by attendant ICR staff, and a small number will be
collected for later laboratory identification.
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Ethics and Regulatory Compliance Review
The Board concurred with the factual observations of the strengths and weaknesses of the
study, as detailed in the EPA’s Science and Ethics Review, dated May 24, 2007 (Carley and
Sweeney 2007b). If the recommended changes included therein are incorporated, the proposed
research described in Protocol ICR 1A 044 is likely to meet the ethical and regulatory
requirements of 40 CFR 26, subparts K and L. As submitted to the Agency, however, the current
protocol (Spero 2007) fails to meet the applicable requirements of 40 CFR 26, subparts K and L.
Subpart K of the Agency’s Final Human Studies Rule requires that the investigator
submit to the EPA all information that pertains to the IRB review of proposed research (40 CFR
26.111 5a) as well as additional information specified in 40 CFR 26.1125, if not already included
in the IRB documentation. The information requested under 40 CFR 26.1125 includes a
discussion of the potential risks to human subjects, the measures proposed to minimize these
risks, expected benefits if any and to whom, alternative means to obtain comparable information,
and the balance of risk and benefits of the research. In addition, subject information sheets and
approved written informed consent documents should be provided, along with any information
about recruitment and the presentation of this subject information. Finally, the investigator
should provide copies of all correspondence with the IRB, including official notification of IRB
review and approval.
The supporting documentation provided by EIRB and submitted to the Agency appears to
meet the regulatory requirements of 40 CFR 26.11 iSa and 40 CFR 26.1125. A description of
EIRB procedures was provided to the EPA with a claim of confidentiality, so was not available
for review by the HSRB. Agency staff, however, reviewed the documentation provided by EIRB
and determined these procedures and policies to be in compliance with the applicable standards
of the Common Rule (45 CFR 46, Subpart A). The minutes from the meetings at which Protocol
ICR 1A 044 was discussed, however, provide minimal information and are inadequate in that
there is no substantial discussion of the ethical issues such a study design would be expected to
raise. The minutes are little more than a list of editorial changes to the protocol and consent
form while noting that there were “no controverted issues” raised by any EIRB member present
(Spero 2007). Nevertheless, the protocol as submitted to the Agency is substantially compliant
with the regulatory requirements of review and documentation in 40 CFR § 26.1125, minor
deficiencies notwithstanding.
With respect to study design, the risks to participants (if properly minimized) are justified
by the likely societal benefits, including data on the efficacy of these new picaridin-based
formulations of mosquito repellents. The risks to study participants are three-fold: 1) allergic
reaction to test materials themselves; 2) exposure to biting arthropods; and 3) possible exposure
to arthropod-borne diseases. Although plans for the medical management of any side effects or
adverse events have been developed, it is not unreasonable to expect greater efforts to be taken to
minimize any potential harm. Allergic reactions to the test materials themselves are unlikely.
Picaridin is commercially available and has been used at higher doses as a repellent with little
evidence of toxic effects, so the subjects enrolled in this study are unlikely to be at increased risk
of experiencing adverse side effects upon exposure to the test materials. The inert ingredients are
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also widely used in cosmetic and personal care products, and have previously been reviewed and
approved for use in other pesticide products registered by the Agency under FIFRA. It is
disturbing to note, however, that picaridin is listed in the informed consent documents as a
seemingly innocuous Toxicity Category IV compound. This may mislead participants into
believing that picaridin is less toxic than it actually is, given that the EPA lists picaridin as a
Toxicity Category III compound for acute oral, dermal and eye exposure. In toXcel’s response to
the Agency’s science and ethics review of the protocol, however, Dr. Micah Reynolds indicates
that this misleading information has been corrected in the informed consent documents
(Reynolds 2007).
The endpoints of the study protocol require two mosquito bites—the second confirming
the first within 30 minutes—to document breakdown of repellent efficacy. Reactions to mosquito
bites are usually mild and easily treated with over-the-counter steroidal creams; such a cream, in
addition to calamine lotion and rubbing alcohol, will be provided to study participants to
alleviate minor symptoms associated with mosquito bites. Excluding subjects who have a history
of such severe skin reactions will minimize the risk of a subject experiencing a severe physical
reaction to a mosquito bite. Given the risk of contracting arthropod-borne disease in field
conditions, it is unclear, however, if confirmed mosquito bites are necessary to measure repellent
efficacy; previous repellent protocols reviewed by the HSRB have used an alternative endpoint,
“Landing with Intent to Bite” (LIBe). Use of confirmed bites rather than alternative endpoints
should be justified, as well as the exclusion of probes and bites from mosquitoes that do not fully
alight as evidence of repellency breakdown. This justification was given in subsequent
documents submitted to the Agency as well as in public testimony provided to the Board, and
these justifications seem adequate. In written comments provided to the Agency (Reynolds
2007), for example, ICR and toXcel justify reliance on time to first confirmed bite (TFCB) rather
than LIBe as the primary study endpoint by citing current and proposed Agency guidelines for
efficacy testing; OPPTS 810.3300 and 810.3700 specify use of first bite or first confirmed bite
for determining protection time. The Board is aware that landings with intent to bite as an
endpoint is not part of the Agency’s guidelines. However, many Board members argued—from
both a scientific and an ethical perspective—that the Agency should give considerable weight to
revising these guidelines to specify use of LIBe for determining protection time in future studies
submitted to the EPA for registration.
The protocol states that to minimize the risk that study subjects will be exposed to
arthropod-borne illnesses such as West Nile Virus, field tests of repellent efficacy will be
conducted only when “cases” of known vector-borne diseases have not been detected by local
vector/mosquito control agencies for at least one week prior to initiation of the field trials.
However, disease prevalence and incidence can change rapidly. Conducting field trials in areas
that have been certified as “disease-free” only for a single week may be inadequate to minimize
the potential risk of vector-borne disease for study participants, and the Board recommended that
the protocol be amended such that trials only be conducted in areas in which known arthropod-
borne viruses have not been detected in weekly testing for at least one month prior to initiation of
the field studies. As researchers also will be collecting mosquitoes for species identification, to
further minimize the risk of arthropod-borne disease these mosquitoes should be subjected to
serologic or DNA-based assays for known arboviruses, with clear and workable plans to contact
study participants and alert them if a transmissible pathogen is detected. Given that many of
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these diseases can have long incubation periods in infected individuals (e.g., 2-14 days for West
Nile Virus), and that many of the symptoms of arthropod-borne illnesses can be diffuse or
subacute, simply following up with study participants via phone two weeks after the completion
of the field studies is insufficient.
Study investigators also should clarify in both the protocol and the informed consent
document whether or not “cases” refers to actual reports of human disease, or the detection of
pathogens in the local mosquito population by using sentinel flocks or other laboratory based
methods. In the site-specific informed consent documents, the term “case” is used to describe
both actual cases of human disease and detection of known arboviruses in mosquito pools in
adjoining paragraphs detailing the risk to study participants of vector-borne disease. This may be
confusing to study participants, and interfere with their accurate assessment of the risks. The
Board recommended that reference to rates of West Nile Virus and other arthropod-borne
diseases-(human “cases”) be deleted from the informed consent documents, as should the
suggestion that the species known to transmit these viruses most frequently are uncommon at the
sites where the field trials will be conducted. These statements may lead study participants to
underestimate the risk of exposure to these agents. Although these illnesses were rare in Georgia
and Florida in 2006, for example, rates of vector-borne diseases like West Nile Virus were
substantially higher in previous years and it is difficult for even the most seasoned arbovirologist
to predict what the likely incidence will be in the field test areas in 2007 and 2008.
Finally, as effects of arthropod-borne diseases are particularly severe in the elderly or
those with compromised immune systems, it may be prudent to: I) exclude participants greater
than 55 years of age (rather than the current protocol’s current 65 years and older), and 2)
explicitly describe the risk for those with immune disorders—many with asymptomatic HIV-
disease, for example, may consider themselves healthy enough for study participation yet may be
at increased risk of illness. In written comments provided to the Agency (Reynolds 2007), ICR
and toXcel apparently agree with the recommended change to the protocol’s age-based inclusion
and exclusion criteria.
In accordance with the newly promulgated provisions in the EPA’s final human studies
rule (40 CFR § 26.1701-1704), minors and pregnant women are explicitly excluded from
participation, the latter being confirmed by requiring all female volunteers to undergo a self-
administered over-the-counter pregnancy test on the day of the field study. In order to protect the
confidentiality of these results, however, it may be prudent to have study participants conduct the
pregnancy tests just prior to travel to the sites in Georgia and Florida, with an investigator-
confirmed test performed before exposure at the field site, so that pregnant participants can self-
exclude themselves from study participation prior to travel; exclusion of female participants once
they have arrived at the field sites may otherwise be difficult to explain while ensuring that the
results of over-the-counter pregnancy tests are kept private. Additional procedures to ensure
confidentiality are also recommended. As noted in the Agency’s science and ethics review
(Carley and Sweeney 2007b), identification of study participants by first name and last initial
was inappropriate and it is rather surprising that the EIRB did not request the use of unique
identifiers to further protect participant identity. In written comments provided to the Agency
(Reynolds 2007), however, ICR and toXcel apparently agree with this assessment and have
modified to protocol accordingly to require the use of unique numerical identifiers.
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A number of additional concerns should also be raised. First, a more detailed explanation
of study recruitment is needed, particularly a description of plans to minimize coercive subject
recruitment and enrollment. Although compensation for study participation is not so high as to
unduly influence enrollment, it may be appropriate to exclude all employees and contractors of
ICR, toXcel and the sponsor (as well as family members), not just full-time employees of ICR, in
order to minimize coercion; in written comments provided to the Agency (Reynolds 2007), ICR
and toXcel apparently agree with this assessment and have modified the protocol. Enrollment
and informed consent procedures should also be described in greater detail; informed consent is a
process, not just a discrete moment in time. Although the informed consent document will be
described and discussed with potential subjects—in person or via telephone—prior to initiation
of the field studies, discussion of the risks and benefits of study participation should be ongoing.
It is insufficient to simply state that, on the evening prior to the field trials, “ [ investigators] will
review with [ study participants] the specifics of the study as described in the lCD” (e.g., Spero
2007, 53). A detailed explanation of study procedures for risk and benefit is required.
Furthermore, the additional risks to untreated control subjects (chosen by lottery rather than via
separate enrollment of more experienced study participants) should be clearly listed in both the
protocol and the informed consent document. However, it should be noted that mosquitoes are
supposed to be aspirated from untreated controls prior to biting
Finally, there was considerable debate about whether or not the recruitment of research
subjects from distant sites, with transport to field sites in Georgia and Florida, might be coercive
with respect to enabling study withdrawal; volunteers may be less willing to withdraw from
study participation if withdrawal involves considerable inconvenience and delay in returning
home or if they believe that they have some reciprocal obligation to the researchers for the travel
and lodging. In addition, given the amount of time involved and the additional risks associated
with study-related travel and out-of-state housing (though not directly related to the study
intervention), researchers and study sponsors should more clearly justify the recruitment and
transport of experienced study participants from across the United States rather than recruiting
and enrolling volunteers from the local populations in Savannah, Georgia and Lee County,
Florida. At least one member of the Board, for example, believed that a more ethically-
appropriate study design would involve recruitment of local research participants and specialized
training sessions for those volunteers.
HSRB Consensus and Rationale
The Board concurred with the assessment of the Agency that the protocol ICR 1A 044
submitted for review by the Board, if revised as suggested in both EPA’s review and by the
Board, would meet the applicable requirements of 40 CFR 26, subparts K and L.
Completed Inhalation Study with Acrolein
Charge to the Board
The Agency has concluded that the Weber-Tschopp et. a! (1977) study contains information
sufficient for assessing human risk resulting from potential acute inhalation exposure. Please
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comment on whether the study is sufficiently sound, from a scientific perspective, to be used to
estimate a safe level of acute inhalation exposure to acrolein.
Board Response
The Board began by highlighting the toxicological evaluation of acrolein as prepared by the
Agency for Toxic Substances and Disease Registry (ATSDR, 2005) and the EPA Integrated Risk
Information System (IRIS 2003). The information below is reproduced from these reviews.
Acrolein is toxic by inhalation, oral, and dermal exposures (toxicity category I for all routes). It
is a potent irritant to the mucous membranes. As such, its toxicity is exerted at the point of
contact with tissues. Signs and symptoms resulting from inhalation exposure to airborne acrolein
may include irritation of the nose, throat and lungs, pulmonary edema, lung hemorrhage, and
death. The nasal tissues appear to be the most sensitive target of inhalation exposure, with onset
of noticeable irritation occurring in seconds (0.3 ppm). Higher airborne concentrations of
acrolein (2— 5 ppm) result in increasingly severe manifestations of irritation over the entire
respiratory tract. Oral acrolein exposure may result in gastrointestinal discomfort, vomiting, and
stomach ulceration and/or hemorrhage. The stomach epithelium appears to be the most sensitive
target for oral exposure (0.75 mg/kg). Higher concentrations of ingested acrolein have primarily
resulted in increasingly severe irritation effects in the stomach (2 mg/kg and higher). Exposure to
acrolein vapors or liquids may cause stinging of the eyes, lacrimation, and reddening, ulceration,
or necrosis of the skin (10% acrolein solution). The eye appears to be the most sensitive target
for exposure (0.3 ppm). Histological changes in respiratory and gastrointestinal epithelium have
been observed from both inhalation and oral exposures, respectively. Changes in body and organ
weights, hematology, and serum biochemistry, as well as developmental effects have been
observed. Some of these effects are believed to be secondary effects of gastrointestinal and/or
respiratory tract irritation (i.e., loss of appetite and weight loss due to gastrointestinal irritation).
Inhaled acrolein is retained primarily in the upper respiratory tract (Egle, 1972) because of its
high solubility and reactivity. Draminski et al. (1983) identified a low level of acrolein derived
conjugates in the urine of rats following oral dosing. Orally administered acrolein is excreted (as
metabolites) in the urine, feces and as carbon dioxide. The main pathway of metabolism for
acrolein is the addition of GSH to the activated double bond followed by conversion to
mercapturic acid. A second pathway is that of epoxidation of the double bond followed by attack
on the epoxide by glutathione. A third pathway is addition of water to acrolein to form 3-
hydroxypropionaldehyde, which can be further metabolized and ultimately incorporated into
normal metabolic pathways (Parent et al., 1998). Exposure of the general population occurs
primarily through atmospheric contact (HSDB, 2003).
3
EPA reported mean ambient acrolein concentrations of 14.3 pg/rn (6.2 ppb), ranging
from 8.2 to 24.6 pg/rn (3.6 to 10.7 ppb), for two urban locations based upon data from 1961 to
1980 (U.S. EPA, 1993). Acrolein has been detected in exhaust gases from both gasoline engines
(0.05-27.7 mg/rn ) and diesel engines (0.12-0.21 mg/rn ) (IARC, 1995). Concentrations in
indoor air may exceed outdoor levels 2- to 20-fold times (Environment Canada, 2000). Levels
between 2.3 and 275 pg/rn have been reported in smoky indoor environments such as bars and
restaurants (IARC, 1995). In residences where wood stoves were used, concentrations from 0.7-
6.0 pg /m have been reported (IARC, 1995). IARC (1995) noted that the acrolein concentrations
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in the smoke from various cigarettes ranged from 3-220 pg/cigarette. Levels as high as 463-684
pg/cigarette were reported (Kuwata Ct al., 1979). Jones et al. (1999) reported concentrations of
acrolein in mainstream smoke ranging from 10— 140 pg per cigarette, and estimated
concentrations in side stream smoke in the range of 100— 1700 pg per cigarette (IRIS 2003)”
It is fairly well known that the annoyance effect of environmental tobacco smoke (ETS) is likely
due to acrolein, as indicated in the EPA document on ETS (1992, reprinted by NIH in 1992-93);
Weber (ibid.) indicated it was more pronounced for nasal irritation than eye irritation, though
probably not the primary cause of irritation from ETS.
While the Weber-Tschopp et al. study is the focus of the review, the EPA IRIS review
(2003) reports another human exposure study by Sim & Pattle (1957) in which 12 volunteers
were exposed in a chamber to 0.8 and 0.12 ppm acrolein for 10 and 5 minutes, respectively; the
volunteers reported it was extremely irritating to all exposed mucosal surfaces. No chronic
studies of human exposure to acrolein have been reported. NIOSH has recommended that the
concentration in workroom air be limited to 0.1 ppm averaged over an 8-hour shift. The ATSDR
toxicology profile stated that “acrolein exposure levels were very comparable for the appearance
of cellular changes in nasal epithelium of animals and onset of nasal irritation in humans”
(Weber-Tschopp Ct al., infra vide), implying that acute nasal effects are similar.
The Weber-Tschopp et al. study provides the most comprehensive description of acute
effects in humans. For this research, healthy male and female college student volunteers were
exposed to acrolein in a 30 m chamber at an 0.1 hourly air exchange rate in 3 trials:
(1) A continuous exposure at constantly increasing acrolein concentrations,
(2) Discontinuous short exposures to successively increasing concentrations, and
(3) Constant concentration for one hour.
Acrolein was injected with a micro liter syringe, vaporized and blown into the test
chamber via a carrier gas stream. Acrolein concentration in the test chamber was quantitatively
determined and results were reproducible [ sd = 0.023 ppm = 3.8%].
In the fir t experiment, 31 male and 22 female students in groups of three participated.
One trial with acrolein and one control trial under identical conditions but without acrolein were
performed with each subject. Students were exposed to increasing acrolein concentration from 0
to 0.6 ppm in the first 35 minutes and to a constant 0.6 ppm concentration in the last 5 minutes.
The subjects had to fill out a questionnaire every 5 minutes. The questions were: Is air quality
good? Acceptable or bad? And do you have a desire to leave the chamber? After that, two
subjects in each group were immediately compared for eye blinking frequency. With the third
subject the breathing frequency during the entire exposure was measured. Eye irritation was
significantly higher (p<0.01) than controls at 0.09 ppm and above. Nasal irritation was
significantly higher (p<0.01) than controls beginning at 0.26 ppm. Throat irritation was
experienced at 0.43 ppm and above. Eye blinking rate was experienced at 0.26 ppm and above
(p<0.01). Respiration rate decreased by 25% (p<0.Ol) at 0.6 ppm concentration.
In the discontinuous short exposure experiment there were 42 students (17 males and 25
females). The subjects in groups of 4 were each exposed 5 times for 1 ‘/2 minutes to variously
high acrolejn concentrations (0, 0.15, 0.3, 0.45, and 0.6 ppm). After a minute of exposure, they
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were given the questionnaire form to fill. Between each exposure they were allowed to
recuperate in a clean room for 8 minutes. The same controls from the first experiment were used.
Eye and nasal irritation was significantly higher (p<0.05) than controls beginning at 0.3 ppm and
0.06 ppm, respectively. Throat irritation was not evident.
In the constant one hour exposure duration, 46 students in groups of threes (21 males and
25 females) were exposed to 0.3 ppm acrolein concentration for 60 minutes. Measurements of
eye blinking frequency, breathing frequency and subjective symptoms of irritation were taken at
the beginning of exposure and during exposure. Measurement of control values were obtained in
the subjects at the beginning of exposure. Eye, nose and throat irritation increased significantly
(p <0.01), reached a plateau after 20-30 minutes of exposure, while eye blinking frequency
plateaued after 10 minutes. Respiratory rate decreased 20% after 40 minutes exposure (p
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0.26 ppm; Breathing frequency 0.30 ppm; Throat irritation 0.30 ppm. The investigators
concluded also that the threshold value for irritation is at least at the lower end of the spectrum,
i.e., around 0.1 ppm.
Based on the nose and throat irritation and a decrease in respiratory rate in humans
exposed to acrolein, ATSDR derived an acute-duration inhalation MIRL of 0.003 ppm calculated
from the LOAEL of 0.3 ppm from the Weber-Tschopp et al. 1977 study. They also derived an
intermediate duration inhalation MRL of 0.04 ppb from their extrapolation based on animal nasal
epithelial metaplasia. EPA also has an RIC for acrolein. EPA concluded in its WOE that “the
study demonstrated that subjective eye irritation was the most sensitive indicator for the acute
acrolein exposure in humans with a threshold effect of 0.09 ppm (0.2 mg/rn ). Protection of the
eyes from the irritating effects of acrolein will protect against other respiratory effects of nasal
and throat irritation and breathing effects which occurred at slightly higher thresholds.”
Critique of Weber-TschoDp Ct al. Study
Strengths
This was a very well designed and conducted study in a lab with known scientific ability,
QA capabilities, and institutional ethical review. Acrolein monitoring, chemical analysis, and
low variability in chamber concentrations are indicative of the study’s strength. A large number
of healthy subjects were used (though the total number of subjects involved is unknown),
including controls (though the controls may not have been very “blind”). The measurements of
the subjects were performed well with appropriate methods, the most important being the
objective measurements. The three studies looked at intermittent and continuous exposures over
a sufficient range of concentrations and of times for the acute effects to be manifested. LOAELs
could be determined from these data. The study appears to meet the HSRB scientific criteria.
Weaknesses
No positive controls were used, and negative controls may have been biased by not being
completely “blind”. There is no justification for the sample size, so there may have been a false
negative rate in some comparisons where statistically significant differences were not found. The
periods between studies are unknown. The results may not be generalizable to younger or older
groups.
HSRB Consensus and Rationale
The Board concluded that the Weber-Tschopp et al. study contains information sufficient
for assessing human risk resulting from potential acute inhalation exposure to acrolein. In
addition, the study was sufficiently sound, from a scientific perspective, to be used to estimate a
safe level of acute inhalation exposure to acrolein for the population tested but may not be
generalizable to younger or older groups.
Charge to the Board
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Please comment on the following:
1) Is there clear and convincing evidence that the conduct of the study was fundamentally
unethical?
2) Is there clear and convincing evidence that the conduct of the study was significantly deficient
relative to the ethical standards prevailing at the time the research was conducted?
Board Response
Introduction
This is a report of third party research involving human subjects that was conducted prior
to April 6, 2006 and was not conducted with the intention of submission to EPA under the
pesticide laws. Rather, this study was conducted in order determine the relative contribution of
acrolein to the irritating effects of cigarette smoke. The study was conducted at the Institute for
Hygiene and Occupational Physiology, Swiss Federal Engineering College, in Zurich
Switzerland. Financial support for the study was provided by the Association Suisse des
Fabricants de Cigarettes, located in Fribourg, Switzerland.
Because the document was not submitted to EPA, 40 CFR §26.1303, which requires
documentation of ethical conduct of studies submitted after April 6, 2006, does not apply. In
addition, because the study was conducted prior to that date, it is not subject to those
documentation requirements. 40 CFR §26.1602(b)(2) requires HSRB review, 40 CFR §26.1703
forbids EPA reliance on research involving intentional exposure of pregnant or nursing women
or children, and 40 CFR §26.1704 forbids EPA reliance on pre-rule research if there is “clear and
convincing evidence” that its conduct was fundamentally unethical or significantly deficient
relative to standards prevailing when it was conducted. When evidence concerning subject age
and reproductive status is both absent and unobtainable, EPA’s policy is that §26.1703 does not
prohibit reliance on a study.
This report describes three sub-studies:
A) Continuous exposure to acrolein concentrations increasing over 40 minutes from zero
to 0.60 parts per million (ppm)
B) 90-second exposures separated by 8-minute recovery periods to concentrations
increasing from 0.15 to 0.60 ppm
C) Continuous exposure over 60 minutes to constant concentration of 0.30 ppm.
All sub-studies were conducted in a 30-cubic meter (m 3 ) chamber using healthy research
subjects. Subjective measures of annoyance were obtained from the responses of the research
volunteers to questions about air quality (“good”, “acceptable”, or “poor”), a wish to leave the
room (“no”, “don’t know”, or “yes”), and perceived eye, nose, and throat irritation (l=not at all;
2=a little; 3medium; 4=strong). Objective measures of response were recorded only for tests A
and C and included measurement of eye blink rate for two out of three subjects and respiratory
rate and depth for the remaining one out of three subjects.
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There were 53, 42, 46 subjects in sub-studies A, B and C respectively. It is not known
whether this represents a maximum of 141 individual subjects, a minimum of 56 individual
subjects ( [ based on 25 women, which is the largest number of women in any of the three sub-
studies, and 31 men, which is the largest number of men in any of the three sub-studies], or some
number in between. This range of somewhere between 56 and 141 individual research subjects in
the three sub-studies assumes that no subject participated more than once in a given substudy.
The only information provided about the subjects is the gender distribution, and that they were
“healthy college students.”
There is no indication in the results or discussion sections of the publication that any
subjects withdrew from participation in any of the three sub-studies.
The presentation by EPA described the compound acrolein as “highly toxic,” although
clarification from HSRB members familiar with acrolein indicated that at the exposure levels of
this study, acrolein was not considered “highly toxic.” Airborne concentrations higher than those
used in this study (between 2 and 5 ppm) result in increasing irritation over the entire respiratory
tract. Relative to this, the doses used in this study were not considered highly toxic. Acrolein is
highly irritating, has an odor threshold, and manifests toxicity at the point of contact, rather than
leading to systemic toxicity.
Critique of Study
The prevailing standard is assumed to be the 1975 version of Declaration of Helsinki
(DoH), because the study was published in 1977. However, the previous version of the DoH
(1964) may have been in effect if the study was conducted prior to 1975. In addition, because
this study was not performed by medical doctors, the DoH may not have applied, regardless of
when the study was conducted.
Because this study was published in 1977, the report is missing much information on
which to base a thorough assessment of the ethical conduct of the study. The number of
individual subjects used could range from 56 to 141 and how many may have participated in
more than one test is unknown. There also is little information about the subjects themselves:
whether any were students or employees of the investigators; how they were recruited; and what
they were told about risks, their freedom to withdraw, or the informed consent process. The
description of expressing a “wish” to leave the chamber is problematic because it does not
necessarily indicate that a subject would leave if given the opportunity; a subject may have
“wished” to leave but might not actually leave. The Agency provided a more direct translation
of the original German language publication. This offered the Board a more exact understanding
of the actual question being asked of the research volunteers, which was whether they would
have preferred to leave the room, rather than did they want/need to leave the room. There is no
information concerning compensation, possible undue influence, or the applicable version of the
DoH, or whether, in fact, the DoH would have been applicable to research. There was no
justification for the sample size, which raised questions as to whether more subjects than
necessary were placed at risk. Another issue concerns whether the study should have been
stopped when indications of a wish to leave (e.g., 72 % of subjects expressed a wish to leave the
chamber at 20 minutes but did not withdraw from the study) became evident. The subjects were
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tested in groups of three and it is unclear whether the investigators analyzed the data as it was
obtained to determine irritation levels or if the analysis was not performed until all subjects had
been tested. Thus, it is unknown whether the study should have been stopped sooner, as
accumulating evidence suggested irritation was occurring.
40 CFR §26.1703 forbids EPA from using research involving intentional exposure of
pregnant or nursing women or children; the research subjects were described as college students,
and thus were likely to have been at least 18 years old. Approximately half the subjects were
female, but the report does not indicate their reproductive or nursing status.
The Board was in agreement that there was a great deal of information lacking in the
published report of this study. In addition, several members of the HSRB expressed discomfort
in having to assess the ethics of the research in this situation. Many members agreed with the
recommendation to EPA that as they decide whether or not to use this information, they should
carefully consider whether use of this information would lead to more protective standards and
consider whether the information from the animal studies would suffice for its risk assessment
work.
Although a majority of members found no clear and convincing evidence that the
research was significantly ethically deficient or was so deficient as to place subjects at risk or
seriously impair the informed consent process, members felt that they were limited by the
standard of “clear and convincing evidence”, and were uncomfortable with assessing the conduct
of this study in the absence of information necessary to make that assessment.
One Board member disagreed with the majority opinion, with the Board member stating
that the study was significantly deficient relative to ethical standards prevailing at the time it was
conducted. This position was based on an analysis of the potential benefits of the study (to the
extent that these benefits could be predicted at the time the study was initiated) and the potential
risks to individual research volunteers. Prevailing ethical standards at the time, as described for
example in the Declaration of Helsinki (Tokyo revision, 1975), included a commitment to the
idea that, to be ethically acceptable, research with human subjects must have a favorable risk-to-
benefit ratio and “cannot be legitimately carried out unless the importance of the objective is in
proportion to the inherent risk to the subject” (Declaration of Helsinki, 1975, section 1.4). In the
judgment of this HSRB member, the potential benefits of the study did not justify the risks to
research subjects. In EPA’s presentation, acrolein was characterized as “highly toxic” and there
was no intent of the research to provide therapeutic benefit or diagnostic results, and no benefit
at all to the subjects. Intentional exposure to this highly toxic substance thus constituted an
inappropriate risk-to-benefit ratio. However, subsequent to the publication, information from
this study was applicable and considered during development of the Clean Air Act. Data from
this and similar research was instrumental in developing tobacco smoke exposure regulations and
laws that banned tobacco smoke in many places. The societal benefits of these activities, in the
forms of occupational and societal regulations and worker protection standards, have been
substantial by reducing tobacco smoke exposure to many people. This and other studies were
considered scientifically sufficient given the standards of the time to justify placing regulations
on tobacco smoke. However post hoc benefit is not relevant to the prospective risk-benefit
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balance and the potential societal benefit at the time of study conduct was not felt by one Board
member to be reasonable in relation to the risks to subjects.
HSRB Consensus and Rationale
There was not clear and convincing evidence that the conduct of the Weber-Tschopp et
al. study was fundamentally unethical. In addition, despite the lack of adequate information to
assess the affirmative, most of the HSRB agreed that there was not clear and convincing
evidence that the conduct of the study was significantly deficient relative to the ethical standards
prevailing at the time the research was conducted.
Completed Studies on the Therapeutic and non-Therapeutic Effects of Administration of 4-
aminopyridine
Charge to the Board
The Agency’s weight-of-evidence (WOE) document for 4-aminopyridine describes the study
design and results of three clinical trials (Grijalva et al. 2003, Segal et a!. 1999, and Van Diemen
et al. 1993). The WOE document also discusses the Agency’s conclusion that these studies
provide sufficient information to establish a point of departure for the assessment of the risk to
humans resulting from all potential durations of exposure to 4-AP. Please comment on whether
the studies are sufficiently sound, from a scientific perspective, to be used to derive a point of
departure for estimating risk to humans from exposure to 4-AP.
Board Response
To inform this question, EPA provided HSRB with a number of background documents,
including an extensive review of the health and environmental effects of 4-AP conducted by the
Agency in January 1989, as well as the WOE document and electronic copies of the 3 published
studies on which the proposed estimates of risk are to be based.
Salient background information includes the following. 4-AP exerts its major biological
actions by blocking fast acting potassium channels. This effect enhances or prolongs action
potentials in muscle and nerve, and also increases transmitter release at neuronal synapses in the
periphery and brain. 4-AP is acutely toxic in animals and humans. Toxicity at low doses is
primarily mild, including tremors, sweating, and salivation. The dose-effect curve is very steep.
Higher doses cause muscular incoordination, seizures, and death. There is little evidence of
metabolism, most of the drug appears unchanged in urine. There is little selectivity between
humans and other mammals, or birds. The compound is tightly bound to soil particles and
persists in the environment for a year or longer under many circumstances.
4-AP has been used or considered for therapy of botulism, overdose of non-depolarizing
muscle relaxant drugs in surgical anesthesia, for spinal cord injury, and for certain demyelinating
disorders such as multiple sclerosis and Guillain-Barré syndrome (FDA approval for the latter
use was granted by FDA under the orphan drug program in December 2006).
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Present EPA concern is focused on the use of 4-AP as a “bird repellant” (eg., Avitrol). This
terminology appears somewhat misleading as the chemical does not drive birds away by adverse
sensory stimuli such as odor but by poisoning, which elicits distress calls that warn the flock to
avoid a baited area. The database on animal studies is quite extensive. In fact the 1989 EPA
document presents tabular information on LD5O values for a wide variety of vertebrates and
invertebrates and numerous species of birds. The WOE document, however, states that “there
are no reliable animal toxicity studies to derive an appropriate point for departure for assessing
human health risk”. The limitation appears to be that the animal studies have chiefly focused on
LD5O values—ideal for comparing potency across species and genera but insufficient to
establish a point of departure such as NOAEL, LOAEL, or BMDIO. Hence the perceived need
to rely on human toxicity studies. It should be noted, however, that the 1972 study by Mistov
and Uzunov (summarized by EPA, 1989) did reveal dose-related histopathology in white rats
treated for 1 or 6 months with 1 to 5 mg/kg 4-AP. Thus, the LOAEL in rats appears to lie at 5
mg/kg or lower. It should also be noted that tabular data in EPA 1989 show rats to be one of the
less sensitive species with regard to 4-AP toxicity.
EPA’s WOE document concluded that 4-AP has short residency time in the body, and
therefore “one can conclude that a single PoD value is sufficient for risk assessments of 4-AP for
different potential exposure scenarios (short-, intermediate- or long-term exposures).” The EPA
analysis also noted that the minimal daily oral dose of 4-AP producing side effects ranged from 5
to 30 mg/day. EPA reviewers also concluded that 4-AP has a very steep dose-response
relationship. In conclusion, the Agency proposed a 5 mg/day (0.08 mg/kg-day) as a LOAEL, and
a point of departure for risk assessments.
The WOE document considers three published human clinical studies, 1. MRID 47093602
(Segal et al., 1999); 2) MRID 47093601 (Grijalva et al., 2003); and 3) MRID 47093603 (Van
Diemen et al., 1993
While the studies were conducted primarily to evaluate efficacy, they all included a
discussion of safety. The investigators frequently indicated that subjects were able to “tolerate”
doses, which is quite understandable, given the severity of the disease/injury in these patients. In
many cases it was no clear which subjects (at which doses) suffered side effects. The lowest oral
dose tested in these studies was 5 mg/day. The Agency translated this dose to 0.08 mg/kg-day.
A critique of the three studies is provided below. As clinical studies, the three reference
studies have major weaknesses of design or outcome.
Segal et al .
Segal Ct al. (1999) created an active control group of 5 spinal cord injury patients, each of
whom received doses of 6 mg/day, as well as 16 patients in a high dose group. It was not clear
from the article whether any of the active control patients experienced side effects. The article
simply states, “Nervousness, giddiness or dizziness, and gastrointestinal upset manifesting as
mild abdominal cramping or nausea were the most frequent side effects.” The frequency of these
side effects was not provided. The article also states, “All side effects were transient, self-
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limited, or disappeared with changes in dosage or the timing of drug ingestion to coincide with
meals or snacks.” In summary, it was not clear from this study the extent to which patients who
received a 6 mg/day, the lowest dose in the study, experienced side effects.
Grijalva et. at .
Grijalva et at. (2003) completed a study with 21 spinal cord injury patients. The lowest
dose in the study was 5 mg/day. The authors reported that 56 probable adverse reactions were
registered over the 26-week study. Adverse effects (dry mouth, dizziness, and gastritis) began
with 4-AP at 5 or 10 mg/day. Fourteen patients receiving 4-AP treatment had 26 probable
adverse reactions. The authors report the frequency of these side effects, but did not specify
which side effects occurred at which dose level.
Van Diemen et at .
Van Diemen et at. (1993) conducted a randomized, double-blind, placebo-controlled
cross-over trial with 70 multiple sclerosis patients. In the intravenous phase of the study,
parathesias occurred at a minimal dose of 1 mg. In the oral phase of the study (69 patients), 54 of
69 (78%) patients experienced at least one side effect. Table 2 in the article indicated that 75 side
effects were observed in those patients who received the minimal daily dose of 5 mg, so
presumably some of the patients reported multiple side effects. At 5 mg/day, these side effects
included paresthesias/dysesthesias (15), dizziness/light-headedness (36), gait instability (11),
nausea/vomiting (9), and restlessness/anxiety (4).
Conclusion of Studies
Overall the therapeutic effects as noted from each of the three studies were of minor degree
or of marginal statistical significance, particularly as concerns improved function after spinal
cord injury. Powerful placebo effects were noted, further weakening confidence in treatment-
related improvements. These weaknesses do not in themselves impair the potential usefulness of
these studies in defining toxic endpoints. Unfortunately, clinical studies are typically not
designed in a manner that allows one to estimate toxic endpoints with confidence, but rather to
establish efficacy at doses that are not “overly toxic” in relation to a therapeutic benefit.
As for toxic signs and symptoms, the results of the Grijalva study are difficult to interpret
because adverse reactions were reported by 56% of the treated patients and, apparently, by a still
higher proportion of the placebo controls. The Segal study (1999) is weakened, by the absence
of a placebo control. For this reason it is uncertain which if any adverse effect is truly treatment-
related. Actually, Segal et at did not specifically report adverse effects but merely stated that
“nervousness, giddiness or dizziness, and GI upset like mild abdominal cramping or nausea were
the most frequent side effects. It therefore seems reasonable to state that neither the Grijalva
study nor the Segal study by itself is sufficiently sound for the purpose of deriving a point of
departure for estimating risk to humans from exposure to 4-AP. On the other hand, the Van
Diemen study (1993) was comparatively rigorous and provided a wealth of detail on the
occurrence and intensity of treatment-related side effects. Unfortunately, this study did not
employ doses low enough to establish a NOAEL but it does seems to indicate that a total daily
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oral dosage of 5 mg was associated with definite but mild discomfort unaccompanied by changes
in blood chemistry or EEG.
HSRB Conclusion and Rationale
The Board concluded that the studies that the three clinical studies, Grijalva et a!. 2003,
Sega! et al. 1999, and Van Diemen et a!. 1993, were sufficiently sound, from a scientific
perspective, to be used to derive a point of departure for estimating risk to humans from
exposure to 4-AP. Thus considering the three studies, an estimate of the LOAEL of 0.07
mg/kg/day was determined. The Board was reluctant to endorse the use of a 5 mg/day (0.07
mg/kg/day) LOAEL, given the multiplicity of side effects seen among patients receiving this
dose, and the steep dose-response curve of 4-AP. Thus, the Board cautioned that this conclusion
comes with a degree of uncertainty and advised the Agency to take such uncertainty into account
when using the published information to arrive at a point of departure for 4-AP.
Charge to the Board
Please comment on the following:
1) Is there clear and convincing evidence that the conduct of any of the three clinical studies
(Sega! et al., 1999; Grijalva et al., 2003; Van Diemen et a!., 1993) any of the clinical studies was
fundamentally unethical?
2) Is there clear and convincing evidence that the conduct of any of the clinical studies was
significantly deficient relative to the ethical standards prevailing at the time the research was
conducted?
Board Response
Three studies are being evaluated. The EPA is seeking to use these studies to derive a point
of departure for estimating risks to humans from exposure to 4-aminopyridine (4-AP). Each of
them is a completed and published study, and the information about the studies is derived solely
from the published articles.
The earliest of the three studies, by Van Diemen and colleagues, was conducted at the Free
University Hospital in Amsterdam in the early I 990s, for the primary purpose of determining the
efficacy and safety of 4-AP in treating persons with multiple sclerosis. This was a cross-over
study, in which subjects were randomized between 4-AP and placebo. The initial portion of the
study involved the use of intravenous 4-AP, while a second phase used oral 4-AP. It is stated in
the article that the study was approved by the “ethical committee” of the hospital where it was
conducted, and that the informed consent of all subjects was obtained. No specific ethical
standard is mentioned in the article, although presumably this study would have been governed
by the 1989 version of the Declaration of Helsinki.
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The second of the three studies, by Segal and colleagues, was conducted at the VA Medical
Center in Long Beach California in the late 1990s, for the primary purpose of determining the
efficacy and safety of 4-AP in treating persons with chronic traumatic spinal cord injury. One
group of subjects was randomized between low and high doses of oral 4-AP, while another group
of subjects (which had previously been exposed to this compound) received only the high dose.
It is stated in the article that the study was “institution-approved”, and that the written informed
consent of all subjects was obtained. No specific ethical standard is mentioned in the article,
although because this study was conducted in a VA hospital which also holds a Federal-Wide
Assurance from the federal Office for Human Research Protections, presumably this study was
governed by the Common Rule (45 CFR 46 Subpart A).
The third of the studies, by Grijalva and colleagues, was conducted at the Specialties
Hospital, Centro Medico Nacional Siglo XXI, in Mexico City, in 1999 and 2000, for the primary
purpose of determining the efficacy and safety of 4-AP in subjects with long-term spinal cord
injury. This was a cross-over study in which subjects were randomized between oral 4-AP and
placebo. It is stated in the article that the study was approved by the local research committee of
the hospital where it was conducted, and by the National Research Council of the Instituto
Mexicano del Seguro Social, and that all subjects were fully informed about the study and signed
an “informed consent letter.” No specific ethical standard is mentioned in the article, but the
Institute Mexicano del Seguro Social has an IRB listed with OHRP, and holds a Federal-Wide
Assurance, and thus presumably this study was governed by the Common Rule (45 CFR 46
Subpart A).
Critique of Studies
Because each of these three studies was completed prior to the effective date of the
EPA’s final rule, “Protections for Subjects in Human Research” (April 7, 2006), the Board is
required to evaluate these studies under a rule that allows their results to be used by the EPA
unless there is clear and convincing evidence that either a study was fundamentally unethical, or
that it was significantly deficient relative to the ethical standards at the time the research was
conducted. The consequence of that review standard is that in the absence of information about
particular aspects of a study, all uncertainties must be resolved in favor of the study having been
properly conducted. Given that circumstance, the Board believed it would be appropriate, in the
future where such studies that pre-date the effective date of the final rule are being reviewed, for
the EPA (as it has reported to the Board with other similar studies previously) to attempt to
collect additional information about the studies, such as the records of IRB review including any
consent forms.
Given that such additional information was not available to the Board with regard to
these three studies, the Board can only rely on the information presented in the published reports
regarding these studies. Those reports indicate that in each case the study was reviewed by an
IRB or an equivalent type of body. In addition, in each instance, it was stated that informed
consent of the subjects was obtained. With regard to that aspect of the studies, there is no
evidence before the Board suggesting that the consent obtained was not appropriate under the
then-applicable standards.
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With regard to the relationship between benefits and risks, each of the studies involved an
examination of 4-AP as a treatment for a very serious medical condition, either multiple sclerosis
or spinal cord injury. Given the information that was known about the possible risks of using 4-
AP in each instance, there was no evidence before the Board suggesting that there was not an
appropriate relationship between risks and benefits under the then-applicable ethical standards.
In none of the published reports for these three studies is there any evidence suggesting
that any subjects under age 18 were enrolled, or that any pregnant or nursing women were
enrolled. Given that circumstance, it appears that the provisions of 40 CFR § 26.1703 have been
complied with.
HSRB Consensus and Rationale
The Board concurred with the initial assessment of the Agency that for each of these
three clinical studies (Segal Ct al., 1999; Grijalva Ct al., 2003; and Van Diemen et al., 1993).,
there is was no clear and convincing evidence that the conduct of the study was fundamentally
unethical, or that the conduct of the study was significantly deficient relative to the ethical
standards prevailing at the time the research was conducted.
Design of Research on the Levels of Exposure Received by Pesticide Handlers
Risks and Benefits of Handler Research
Charge to the Board
Will the Task Forces’ Governing Documents considered in conjunction with the additional
study- and scenario-specific information specified above provide an adequate basis for assessing
whether the risks of conducting a particular study are justified by the expected benefits of the
proposed research? If not, what additional information should be provided for an IRB, EPA, and
the HSRB?
Board Response
The Agency has provided the HSRB with a document entitled, “A}IETF Human
Research Monitoring Program”. This report serves as the “governing document” for the pesticide
handler studies sponsored by the Agricultural Handlers Exposure Task Force. Section 4 of the
report discusses study benefits, section 5 discusses risks to subjects, and section 6 provides a
benefit-risk comparison.
The Board also received a document entitled, “Governing Document for a Multi-Year
Antimicrobial Chemical Exposure Monitoring Program”. Section 9 of this report discusses study
benefits, sections 10 through 12 discuss risks to subjects, and section 13 provides a benefit-risk
comparison.
Both documents indicated that no direct benefits will accrue to study participants, and
that the risks to participants must be justified by societal benefits. The primary societal benefit
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cited by the authors was the ability for EPA and other regulatory agencies to use new handler
exposure to data to improve the quality of worker risk assessments. The AHETF authors pointed
out that growers or landowners who participate in these studies would benefit through use of the
test substance at no cost. However, the Board questioned whether the free pesticide would
indeed be considered a benefit, as opposed to a means to encourage growers to participate in the
research. In addition the Board questioned whether such a benefit would also be appropriate to
study participants (e.g. commercial applicators).
The documents also indicated that the database would be a benefit to the sponsors of the
studies. However, a benefit to pesticide manufacturers is not considered in the benefit-risk
analyses mandated by FIFRA.
The document indicated that risks to subjects in these studies were greater than minimal.
The AHETF authors identified six types of risks: heat-related illness, exposure to surrogate
chemicals, scripting of field activities, psychological, exposure to detergents used in sampling,
and injuries. Each of these risks was discussed in detail, and plans to minimize risks were
included in the report. Risk categories described by the AEATF included chemical risks related
to use of a surrogate antimicrobial chemical and exposure to alcohol/water face and hand rinse
solutions. Physical risks might arise from heat stress or exaggeration of normal activities.
The authors concluded that the risks to study participants are outweighed by the benefit to
society in the form of high quality exposure data for use in evaluating pesticide safety.
Critique
The Board’s discussion focused primarily on the Agricultural Handler Exposure Task
Force (AHETF) document. Most of these comments are applicable to the AEATF document as
well. The document states that there will be no direct benefits to participants. However, it is
arguable that there could be a direct benefit of feedback on work and safety performance. Study
participants will be provided with their own results. Knowledge of one’s ranking among workers
could have educational or motivational value for a worker. There is also the potential for direct
feedback related to safe and unsafe practices. For example, an individual using a ground boom
sprayer with a blocked nozzle might remove the nozzle and attempt to dislodge the blockage by
blowing through it. This is clearly poor practice, but it does happen. If the study supervisor
observed such behavior then it would be sensible for him/her to provide advice to that individual
on safe work practices. A second example would be the identification of more widespread poor
working practices. In the United Kingdom, studies in seed treatment facilities documented that,
contrary to good practice, some operators were using compressed air to clean residues of seed
treatment products from application equipment. This obviously created an airborne hazard. The
fact that this practice was commonplace indicated a need to communicate the hazard to the
whole industry sector. In this particular case, the industry task force involved with the studies
produced a poster illustrating the findings that was distributed to seed treatment facilities. The
dissemination of this type of feedback as part of stewardship could be seen as a benefit to
pesticide handlers in general. How such information will be communicated to participants and
the pesticide handler community in general should be described in the protocol.
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The discussion of benefits to growers, landowners, or commercial applicators focused on the
provision of free pesticide product for use in the study. The Board agreed with the AHIETF’s
conclusion that the magnitude of this benefit is not likely to result in coercion of employees to
volunteer to participate in a study. However, the timing and conditions of how this free offer is
made should be explained explicitly as a part of each protocol’s discussion of recruitment. This
would permit the HSRB to evaluate the specifics of the arrangement, and would permit the
AHETF to assure some uniformity in how such offers are being made in different studies
(clusters) or/and scenarios. However, the Board questioned whether the free pesticide would
indeed be considered a benefit, as opposed to a means to encourage growers to participate in the
research. In addition the Board questioned whether such a benefit would also be appropriate to
study participants (e.g. commercial applicators).
The nature of risks is discussed thoroughly in the governing documents, but the Board
concluded that several issues warranted further clarity. The first issue is related to the scripted
nature of the AHETF studies, and the possibility that workers may be asked to use equipment
that they would not normally use. Lack of familiarity with equipment could increase the risk of
injury; for example, a mechanical injury through collapsing hydraulic systems or an
electrocution through folded or folding booms coming into close proximity or contact with
overhead power cables. The AHETF document indicates that workers need to be “familiar” with
the type of equipment to be used. The Board was concerned that familiarity with equipment was
not sufficiently described and might be inadequate. In the United Kingdom, for example, the
requirement would be that the workers should be “competent”. The Board recommended that
future AI-IETF protocols identify equipment use requirements for workers and the steps that will
be taken to ensure that workers can operate the equipment unsupervised in a safe manner. This
concern was not applicable to the AEATF studies.
The second issue is related to potential heat stress. The AHETF document outlines a
strategy that includes encouraging participants to drink water or sports drinks throughout the
monitoring period. It is considered bad practice in occupational hygiene to combine working
with hazardous substances and drinking (or eating and smoking). The document provides no
advice to minimize potential inadvertent exposure during drinking. In fact the document states
that hand washes are not necessary. The document’s only guidance is for researchers to remind
workers just prior to participation about general ways to minimize exposure to chemicals, such
as washing their hands before eating and before removing clothing. The Board recommended
that the AHETF develop a consistent policy regarding drinking water or sports drinks and
personal hygiene. These same recommendations could be applied to AEATF studies, but the risk
from heat stress was judged to be much lower for these studies.
The Board commended the AHETF for developing clear stopping rules to minimize the
risk of heat-related health concerns based on the National Oceanic and Atmospheric
Administration’s (NOAA) National Weather Service heat index. In particular, the AFIETF has
proposed hourly measurement of heat and humidity when the ambient air temperature exceeds
70°F, with increasing vigilance for signs of heat exhaustion and sunstroke on the part of study
investigators as the heat index increases. A study would be halted when the heat index exceeds
130°F, as severe heat-related illness is likely with prolonged physical exertion under such
conditions. AHETF researchers also recognize that direct exposure to the sun can contribute to
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heat-related illness, and have proposed adjusting the heat index accordingly for agricultural
handlers working in the direct sun. The Board was very supportive of these efforts, but
concluded that further protection of study participants was warranted.
As calculated, the National Weather Service heat index assumes that the person in
question is 5’ 7” tall, 147 pounds, Caucasian, clothed in long trousers and a short-sleeved shirt,
walking at a speed of 3.1 mph in the shade in a breeze of 6 mph, and not dripping with sweat. It
is unclear whether or not these characteristics and conditions apply to the agricultural handlers
likely to be enrolled in the proposed studies. The whole body dosimeter used for the proposed
research, for example, is described in study documents as “long underwear”. The Board
recommended that the heat index threshold be adjusted to account for the increased amount of
clothing that volunteers will wear during study participation. The Board further recommended
that AHETF document the expected levels of physical exertion in its protocols, and consider
whether a further adjustment to the heat index threshold would be appropriate.
Finally, the Board was concerned with the use of the 130°F heat index value as a
threshold. According to the NOAA website, “heatstroke/sunstroke [ is] highly likely with
continued exposure” under such conditions (http://www.crh.noaa.gov/arx/heatindex.php). It is
important to note, however, that the website also states “sunstroke, heat cramps or heat
exhaustion [ are] likely, and heat stroke [ is] possible with prolonged exposure and/or physical
activity” with a heat index of 105-129°F. The Board recommended that the AHETF revisit the
issue of heat stress, and develop a stopping point that will minimize risk for the study
participants.
HSRB Consensus and Rationale
The AHETF and AEATF documents have provided the HSRB with a detailed and
thoughtful analysis of expected benefits and risks associated with the conduct of human exposure
monitoring. The Board recommended that the particular arrangements for providing the test
substance be outlined in the individual protocols. Finally, the Board concurred with the AHETF
and AEATF that the database developed from these studies will improve the quality of risk
assessments, and that they should be considered a valuable societal benefit, provided that the
data collected are accurate, or at the least do not underestimate real-world exposures.
The Board recommended that AHETF pay more careful attention to the issue of safety
when asking participants to operate equipment with which they do not normally work. In
particular, AHETF should be more explicit about the level of competency expected of workers
when operating such equipment. The Board commended AHETF for developing clear guidelines
for stopping work based on a heat index. However, the Board concluded that the approach
described in the governing documents was not fully protective of workers, and recommended
that additional attention be given to this matter, including consideration of a lower heat index
threshold for stopping work.
Addressing Potential Sources of Underestimation Bias
Charge to the Board
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1) Has EPA appropriately characterized the limitations on the scientific usefulness of a handler
database that does not include data characterizing the efficiency of residue removal procedures?
If not, what limitations have been overlooked?
Board Response
Introduction
The Agency presented its concerns regarding potential underestimation of dermal
exposure. It relied on the work of the January 2007 EPA Scientific Advisory Panel (SAP) report,
as well as a review of the scientific literature. The SAP observed that whole body passive
dosimetry and biological monitoring comparisons did not seem to indicate a systematic bias. The
SAP concluded that bias may exist, but the extent of potential bias between dermal exposure and
biological monitoring could not be detected because of the statistical uncertainty inherent in the
exposure and biomonitoring data. The SAP also noted that passive dosimetry can generate data
that can be used to develop predictive estimates of exposure for a number of different scenarios
and activities. The SAP suggested that biological monitoring could be a useful check on passive
dosimetry, but declined to suggest that require biological monitoring be included in a protocol.
EPA agreed with the overall SAP conclusions and described some disadvantages to biological
monitoring including additional cost, logistical considerations (e.g., number of days required for
metabolites to clear), and a lack of acceptable biomonitoring methods for many of the surrogate
compounds proposed for the AHETF and AEATF studies.
The SAP gave particular attention to potential underestimation bias resulting from the use
of hand wash and skin rinse techniques. The scientific literature indicates that hand wash/rinse
performance can be influenced by the chemical properties of the pesticide, such as solubility,
octanol/water partition coefficient, or formulation type; residence time on the skin before hand
rinsing is performed; type of solvent used to rinse the hands (e.g., alcohol, soap and water);
concentration of the chemical on the skin (microgramlcm 2 ); duration of the exposure monitoring
period; and nature of the residue (whether exposed to pesticide concentrates, dilute sprays, or
field residues). Hand rinse removal efficiency values from several studies involving human
subjects ranged from approximately 70 to 90 percent; however, in the case of chlorpyrifos the
efficiency was approximately 20 to 40 percent). An unpublished AEATF hand rinse efficiency
study reported up to 90 percent efficiency for didecyl dimethyl ammonium, but further details
were not provided.
Face/neck wipes were not specifically discussed at the SAP meeting. This method was
not among those recommended by the Agency in its 1987 Subdivision U Agency guidelines for
pesticide handler exposure studies but this does not mean the EPA would not accept its use. It
was also not included in the later (1997) Agency 875 guidelines for occupational and residential
exposure assessment. The Agency has concluded that exposure to the head/face and neck is
expected to be very low for the majority of exposure scenarios planned by the AFIETF. The
Agency pointed to an exception in the case of the open-cab airbiast application AHETF studies.
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The SAP was equivocal about the need to correct the results from hand washing for its
efficiency at recovering pesticides from skin. The SAP would accept a rinse validation study if it
could decrease the uncertainty in exposure estimates at a reasonable cost, and be done within
approved human studies guidelines.
The AHETF argued that no correction was needed for any potential method bias because
of reasonable congruence in exposure estimates between studies based on biological monitoring
and those using passive dosimetry. AEATF argued that no correction was needed in studies
where individuals will not be wearing gloves and that the hand correction factor was reasonable.
The EPA concluded that substantial underestimation by whole body garments was
unlikely, and that the most relevant methods to be corrected for potential underestimations were
the handwash and the face/neck wipe. For the proposed AI-IETF studies, the Agency stated that
the contribution of hand exposure was expected to be minimal because all subjects will be
wearing chemical resistant gloves (CRG) during all operations. The AEATF intends to collect
data based on individuals not wearing gloves (consumer products), but for most scenarios the
Agency again expects exposure to head, face, and neck to be low. The Agency proposed two
options to the task forces: biological monitoring could be included as a check for potential
breakthrough or other losses when using surrogate chemicals that have well-established methods;
cotton gloves beneath the CRG and hat patches when measuring head, face, and neck exposures
could be used in scenarios for which exposures to these body regions might be relatively high.
The Agency concluded that conditions should be established for correcting hand rinse
and face/neck wipe exposure values. The EPA proposed a set of conditions for consideration by
both task forces; namely, if measured exposures from hands, face, and neck contribute less than
20 percent of total exposure, no action is required; if measured exposure contribution represents
between 20 and 60 percent of total exposure, an automatic 50 percent adjustment can be made or
a validation study can be submitted; if measured exposure contribution is greater than 60 percent,
a validation study is required. Because validation studies involve intentional exposure of human
subjects, review of such studies by the HSRB would be required.
Critique
Dermal exposure assessment methods are considered to be of three types: interception,
removal and visual. Interception methods use a collection device on the skin to capture
chemicals; removal methods use washing or wiping to remove residues from the skin; visual
methods use dyes or fluorescent compounds to visualize chemical deposition patterns on skin
and clothing. Interception techniques can overestimate exposures because they capture more
material than the skin would normally collect. They can also underestimate exposure if
breakthrough occurs. Removal techniques typically underestimate exposure, since they can only
remove chemicals that have not been adsorbed irreversibly onto or absorbed into the skin. Visual
techniques have been most useful in qualitative evaluations of exposure and worker education.
The use of the term “passive dosimetry” to describe the dermal sampling methods
proposed by A1-IETF and AEATF can lead to some confusion. First, the approach relies on both
interception (whole body garments) and removal (handwash, face/neck wipe) techniques. It is
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difficult to reconcile the very active procedures required to remove chemicals from the skin with
the notion of a “passive” measurement method. Second, the term “dosimetry” is a misnomer, as
it is exposure rather than dose that is being measured.
The Board expressed some reservation regarding the SAP and Agency conclusion that
passive dosimetry does not underestimate dermal exposure. The conclusion was based primarily
on a recent article by Ross et al. (2007). In that article it is stated, in regard to the methods
proposed by the AHETF and AEATF, that “the passive dosimetry methods used have never been
validated.” The article then analyzed 14 concurrent or consecutive passive dosimetry-
biomonitoring studies, and reported that this analysis produced “generally similar” estimates of
absorbed dose from these two methods. However, when these datasets were examined in detail,
this conclusion was not well-supported. For some chemicals the passive dosimetry estimates
under-predicted the biomonitoring estimates, while in others the opposite was true (see Table 3
of the article, with reference to chlorpyrifos and atrazine, respectively). Dose estimates based on
passive dosimetry measurements were dependent on laboratory studies of dermal absorption.
Dose estimates from biomonitoring studies were based on laboratory studies of urinary
metabolite excretion. In each case, the laboratory data are characterized by very high variability
and uncertainty. Given the variability of these data, the Board was not persuaded that this
analysis provided a validation of passive dosimetry measurements.
Many studies of pesticide handlers have demonstrated that hand exposure can be a major
contributor to total dermal exposure. The heretofore cited OECD guidance document states,
“Monitoring of hand exposure may be the most important measurement in a dermal exposure
study. The contribution of the hands to total exposure has been well documented by many
investigators, using a variety of methods.” The Board supported the Agency’s plans to evaluate
the relative importance of hand, neck and face exposures for each study submitted by the Task
Forces.
The Board concurred with the Agency’s concerns regarding potential under-estimation of
exposure by the handwash and face/neck wipe methods. No justification has been given to
support the validity of AHETF’s proposal to use “AOT” (or of the AEATF’s proposal to use
either propanol or “AOT”) in the hand wash or/and face/neck wipe sampling methods to assess
dermal exposure. A great deal of information is available suggesting that wash data can
significantly underestimate exposure and wipe data can be worse than wash data. The Board
recommended that the task forces either generate data supporting the efficiency of removing
their surrogate pesticides from skin by washing and by wiping, or accept the automatic
adjustments being proposed by the Agency; in fact, the adjustment for wipes could even be
increased beyond that being proposed for washing. This recommendation is consistent with the
advice provided in the 1997 OECD guidance document: “The best that can be achieved for a hand
wash or hand rinse method is a laboratory validation of the efficiency of recovery of material from
the hands of human volunteers.”
Existing data clearly indicate that adsorption (more than absorption) of certain pesticides
can occur within a matter of minutes after the exposure has occurred. For example, data
presented in Fenske and Lu (1994) show that several handwashings recovered less than 50% of
chlorpyrifos from the skin immediately after exposure, and recovered only about 20% from the
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hands one hour after exposure. The handwashing efficiency data summarized in Table I of a
review by Brouwer et a!. (2000) range from 23 to 96%, an even wider range than the values
summarized in the Agency’s presentation. These data indicate that the results from washing can
range from negligibly biased to a four-fold underestimation of the true exposure, although the
frequent washings indicated within the preliminary protocols may limit the bias to about two-
fold.
In contrast to hand washing, much of the hand wipe data presented (such as the 10% mean
recovery with a CV of 33% for azinphos-methyl from Fenske eta!. (1999) and the many
chemicals with circa 50% mean recovery with a similar CV in Table 2 of the review by Brouwer
et a!. (2000)) indicate that head/neck wipes may be both more biased and more variable than
hand washes. The above data support the Agency’s proposal that, lacking a validation study of
the wash method, a 50% adjustment (multiply the results by 2x) should be applied. The above
data support an even larger adjustment (of circa 3x) for unvalidated wipe data. In both cases, a
validation study for recovery efficiency f wash or wipe samples could be tested in vitro and
would not require human exposure testing. Some Board members also recommended that the
Agency explore the use of modeling to adjust hand exposure, and offered as an example an
algorithm based on some of the literature cited by the Agency in the SAP documentation.
HSRB Consensus and Rationale
The Board recommended that the validity of dose estimates based on passive dosimetry
be reassessed given the variability of previous laboratory data. Given some uncertainty as to
exposure to hands, face and neck for various scenarios, the Board concurred with the Agency’s
intention to evaluate data provided by the task forces for each scenario to determine the relative
contribution from skin residues versus whole body dosimeters. The Board recommended that the
Task Forces either generate data supporting the efficiency of removing their surrogate pesticides
from skin by washing and by wiping, or accept the automatic adjustments being proposed by the
Agency; in fact, the adjustment for wipes could even be increased beyond that being proposed
for washing. This recommendation is consistent with the advice provided in the 1997 OECD
guidance document: “The best that can be achieved for a hand wash or hand rinse method is a
laboratory validation of the efficiency of recovery of material from the hands of human
volunteers.” in addition, the Board suggested a validation study for recovery efficiency of wash or
wipe samples could be tested in vitro and not require human exposure testing.
Charge to the Board
2) Has EPA identified the relevant scientific and practical considerations affecting the choice to
include biomonitoring, and has EPA appropriately characterized the limitations on the scientific
usefulness of the resulting data if no biomonitoring is conducted? If not, what other
considerations should bear on a decision to conduct biomonitoring in addition to WBD?
Board Response
The HSRB discussed the perspective that, although inclusion of biomonitoring data in the
conduct of the AEATF and AHETF research programs was intellectually satisfying, this was not
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an easy task. Furthermore, the difficulties in assessing the utility of biomonitoring in the conduct
of the Task Force’s programs were evidenced by the response previously provided by the EPA’s
Scientific Advisory Panel. After lengthy discussion, the HSRB recommended that
biomonitoring did not need to be included in the AEATF and A1-IETF programs. The Board felt
that the EPA had not filly characterized the scientific and practical issues and considerations
relative to the use of biomonitoring. If anything, the I-ISRB added to the reasons to not use
biomonitoring, with the following points emphasized:
1. The goal of the Task Force programs is to describe exposure from a particular use scenario.
Biomonitoring provides data that is chemical-specific rather than scenario-specific. Hence,
whole body dosimetry is the most appropriate measure by which to provide an estimate of
exposure under a specific use condition.
2. Given the list of surrogate chemicals provided by the Task Forces, it is not clear whether
biomonitoring is technically feasible and would provide reliable data. Technical feasibility
requires that there are well-established analytical methods in place along with knowledge of
the metabolism and kinetics of a given compound in order to accurately assess internal
dosimetry. Such studies would also increase the complexity of the design and execution, as
they would require pre- and post-exposure sample collection, with the post-exposure time
period determined by the kinetic properties of the compound.
3. Biomonitoring is important to understanding, determining and estimating risk. The Task
Force programs are focused on establishing exposure so as to assess risk, and any risk
assessment would be performed in a chemical-specific manner.
Additional points raised during Board discussion included observations that requiring
concurrent biomonitoring would impose additional burdens on participants and would severely
restrict study participants to those with no recent prior or immediately subsequent exposure to
the chemical, a restriction that has the potential to seriously bias the results. Inclusion of
biomonitoring would also restrict the range of surrogate chemicals that have sufficiently
sensitive metabolites to be useful at the low levels expected in these studies. Furthermore, the
variability implicit in back-calculating any detectable biomonitoring data to dermal dose
(necessary for use in the data base) is likely to add as much uncertainty as clarity to the
conclusions.
HSRB Consensus and Rationale
The HSRB was comfortable with not including concurrent biomonitoring in the protocols. In
fact, the Board recommended that the use of additional monitoring units was more appropriate
than the inclusion of biomonitoring in these programs.
OA and OC Controls
Charge to the Board
Do the Task Forces’ Standard Operating Procedures appear adequate to ensure that the
data resulting from the proposed research will be of high quality? If not, what other Quality
Assurance or Quality Control procedures need to be addressed?
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Board Response
The HSRB noted that the volume of Standard Operating Procedures (SOPs) provided by the
Task Forces represents a significant effort to develop the infrastructure required to develop the
procedures that govern this work. To this point, it was noted that several of the governing
documents provided to the Board contained information that was relevant to the SOPs, and
should be added as appropriate. Overall, the SOPs outlining the overall administration, report
generation and quality assurance (QA) oversight seem reasonably complete. The HSRB
reviewers noted two major areas that should be expanded and/or revised for additional clarity,
namely the SOPs that focused on data quality and sample integrity and compliance. Specific
recommendations were as follows:
1. The SOPs need to define what represents a “good sample.” What general guidance will be
provided to define sample quality? How long after completion of work is a sample
collected? What tolerances are allowed in targeted airflow or environmental conditions?
What conditions determine whether a sample is to be “weathered” and how will
“weathering” be performed?
2. On-site spiking of samples is intended to be used for analytical standardization and
reliability. No details were provided on how such samples were generated, and how they
were handled to simulate actual exposure conditions.
3. The roles of the study director and the principal investigator are unclear and should be
expanded.
4. There was a recognized need for training in the execution of these studies along with
information detailing how compliance to the protocol would be established.
5. The SOPs should provide for the means by which incidents relating to lack of compliance or
possible negligent conduct can be reported.
HSRB Consensus and Rationale
Overall, the Standard Operating Procedures (SOPs) outlining the overall administration,
report generation and quality assurance (QA) oversight seems reasonably complete. The Board
noted two major areas that should be expanded and/or revised for additional clarity, namely the
SOPs that focused on data quality and sample integrity and compliance.
Design of scenario-level sampling strategies
Charge to the Board
With regard to the AHETF and AEATF plans to conduct their proposed handler research
using purposive diversity sampling strategies:
1) Has EPA identified the relevant scientific and practical considerations affecting the
choice of a strategy for sample selection? If not, what other considerations should bear on the
choice?
Board Response to the Charge
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The Task Forces have proposed study designs focused on scenario-level sampling. The
target population was considered to be the set of all possible handler-days in which scenario-
specific tasks would be performed. It was estimated by the AHETF that this would include
approximately 1.1 million handlers and approximately 2 million handler-days. The Agency
considered two approaches for gathering a probability sample: a simple random sample and a
complex probability sample. For example, the National Health and Nutrition Examination
Survey (NHANES) has used complex probability sampling to sample a representative U.S.
population. Considerations associated with complex probability sampling for the Task Force
exposure monitoring programs include likely high cost, the absence of a sampling frame, and the
likelihood of significant selection bias.
In light of these issues, the Agency and the task forces have considered two alternative
sampling strategies: purposive representative sampling and purposive diversity sampling (PDS).
Purposive representative sampling captures a small sample of handler-days that is a “miniature”
of the target population, with respect to important factors concerning the range and extent of
exposure, while PDS captures a small sample of handler-days that are diverse with respect to
factors related to the range and extent of exposure. The task forces have proposed PDS as the
strategy more likely to reflect a broad range of heterogeneous conditions. PDS can be diversified
on the amount of active ingredient handled, the individual (MU), location and time, and other
factors (such as equipment type, crops, rates, and micro-location). Site selection will emphasize
more common conditions and the task forces will be required to provide a rationale and/or
justification for selection of sites or site conditions based on diversity criteria.
The Task Forces’ statistical consultants have argued that PDS permits a non-random
sample to perform at least as well as a small, same-sized probability sample. It provides greater
assurance of obtaining a sample that reflects a broad range of conditions, and makes it less likely
that high end or low end exposure conditions would be missed. Augmenting scenario data with
new clusters in the future would be straightforward, and conditions of interest would be easier to
target. Nonetheless, it was acknowledged that PDS is not a probability-based sample and can
only be used to establish a surrogate distribution of exposures. A surrogate distribution cannot be
equated to the actual distribution in a target population using pure statistical sampling theory;
however, PDS can capture major aspects of an actual distribution. The Task Forces assert that
the results using this type of sample are not expected to be substantially different from those
derived using a small, same-sized cluster random sample. Therefore the Task Forces argue PDS
should also be considered adequate for practical regulatory purposes.
The EPA’s Scientific Advisory Panel (SAP) has expressed concern with the proposed
purposive nature of sample selection because PDS assumes underlying random selection can be
used to estimate sample sizes. In Appendix C of its January 2007 report, the SAP provided a
discussion of potential for bias and an alternative stratified approach. The SAP expressed
concern that use of a non-probability sample would essentially preclude consideration of
appropriate weighting to estimate distributional parameters including means, standard deviations,
upper percentiles, etc. Thus, the SAP recommended an informal approach for identifying top
factors and for assigning probability weights to approximate frequencies. In response to the SAP
concerns, the task forces have outlined the constraints regarding available data and resources.
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The Agency plans to evaluate the data and documentation that will be submitted by the task
forces to support their approach. However, given the unique aspects of this monitoring program
and its relatively small size, the Agency continues to believe that PDS is adequately
representative of the target population and can be used to develop exposure assessments of
occupational handler populations.
Critique
The Board commended the Agency and the task forces for the work they have conducted
over the past year to develop a viable sampling strategy for pesticide handler and consumer
exposures. However, the Board had a number of questions regarding the sampling strategy, and
in particular the selection of purposive diversity sampling as the foundation for these studies.
The more practical aspects of the sampling strategy are addressed in this section of the Board’s
report, while certain scientific aspects are addressed below in response to specific charge
questions put forth by the Agency.
Acentral consideration in the sampling strategy design is the choice of key variables that
will define the scenarios and the particular tasks carried out by workers within these scenarios.
The Board was not clear as to the criteria by which these variables would be selected. One
variable that appeared central to the proposed study design was the amount of active ingredient
handled. The Agency currently normalizes exposure based on this variable. The task forces
would like to collect data sufficient to test whether or not this is a sound scientific practice. Thus,
the study design calls for collecting data over a-wide range of values for this variable. It was not
clear to the Board whether this particular scientific question should be an important driver of the
study design. There may be other factors equally worthy of study. For example in the AHETF
study crop, type of equipment, or mixing and loading procedures. One variable — farm size --
was of particular concern to the Board based on practical experience. Farm size tends to be
correlated with many other factors that can influence exposure, such as different sizes of
equipment used, different training procedures, behaviors, and application details. Larger farms
tend to have larger and more modem equipment with more technical/engineering controls, make
more timely applications, and use more innovative application practices. The Board also
indicated that the level of training of study participants was an important variable to consider in
the study design. In the United States, pesticide handlers do not need to be certified to mix, load
and apply pesticides in many situations; instead they work under the supervision of a certified
applicator. There are important differences in training by a supervisor versus certification
training. Specific to the AHETF protocols, the Board coricluded that any attempt at diversity
sampling should include an appropriate number of non-certified applicators.
For both the AHETF and AEATF studies the Board recommended that prior to data
collection the Agency ensure that the critical variables associated with exposure are ranked,
accompanied by an appropriate rationale and justification for the ranking. This ranking would
then inform the study design in terms of how sampling sites and individual participants are
selected.
HSRB Consensus and Rationale
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The Board acknowledged the great complexity of study design development, given the
many variables associated with exposure and the practical constraints that arise in the conduct of
human exposure studies. The Board commended the Agency and the task forces for their efforts
in developing a detailed discussion of sampling strategies. The Board remained concerned that
the number of variables is large, and that the relative importance of these variables has not yet
been defined adequately.
For both the AFIETF and AEATF studies, the Board recommended that prior to data
collection, the Agency ensure that the critical variables associated with exposure are ranked,
accompanied by an appropriate rationale and justification for this ranking. This ranking would
then inform the study design in terms of how sampling sites and individual participants are
selected.
Charge to the Board
2) Does the HSRB agree with EPA that the Task Forces should provide scenario-specific
information about the availability of data to identify significant variables (other than AaiH)
potentially influencing exposure and about the feasibility of developing a sampling strategy to
address those variables quantitatively? If not, what additional information is needed?
Board Response to the Charge
To be scientifically assessed, and for the Board to provide its scientific advice, scenario-
specific information needs to be provided. This information would necessarily include significant
variables that would potentially influence exposure and its effect, in addition to AaiH, and a
feasible sampling strategy, that would be essential to meet the scientific criteria to provide
reliable and useful data. Such would reaffirm the EPA Scientific Advisory Panel’s
recommendation that all major factors of importance be included in each scenario-specific study
to be conducted. The information could be provided briefly for the Board to consider, not
necessarily to the extent provided by the AEATF example. It could be presented as one would a
study design for the scenario-specific study to be evaluated (with appropriate references) and
would contain in such design not only the specifics of the population (including its size) to be
studied but also the list of variables and how they were to be collected and analyzed. It could
also briefly respond to the scientific criteria proposed previously by the Board.
Critical to the Board’s evaluation and to the representativeness and usefulness of the
exposure data collected and provided, would be the information as to the relationship between
the scenario-specific exposure assessment and the representative exposure in such scenarios in
the target population.
In terms of the relevant variables, one could group them into those that are essential or
less so, and whether they would significantly affect the exposure (or exposure scenario and data
collection) or might be important to have. Description of the target population and the subjects
selected are essential, including inclusion and exclusion criteria. Description of the primary
measuring instruments and how they are to be used is essential. Because environmental
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conditions are significant determinants of exposure, essential environmental variables (e.g., site
description, temperature and humidity) would have to be measured, and others (e.g., wind speed,
microclimatic conditions [ including, presence of significant factors that affect airflow]) might or
might not be necessary. The subjects’ type of external clothing could be considered essential, and
the subjects’ work history with the type of application and pesticide would be important, whereas
minor differences between the subjects would not; gender and age would be necessary. It might
be important to record, if possible, the subjects’ health status and any physical deformities that
might influence how they handle the pesticide and perform the application required. It would be
worth noting by observation and recording significant features of the handling and application.
Of course, prior experience and documented studies of this nature will illustrate what was and
should have been critically measured.
Known variability in similar data previously collected, including inter- and inter-subject
variability in exposures, would even help design the study and determine the type and size of the
population to be studied. Finally, and repetitiously, how one would analyze these variables is
important to know.
HSRB Conclusion and Rationale
The Board recommended that the following information was necessary for it to provide its
scientific advice on scenario-specific information:
• Scenario specific information detailing variables that might influence exposure and its
effect;
• A feasible sampling strategy including specifics of population to be tested (including its
size), a list of relevant variables and bow they would be collected and analyzed;
• Information on relationship between scenario-specific exposure assessment and the
representative exposure in such scenarios in the target population;
• Essential environmental variables including site description, temperature, humidity, wind
levels as well as subjects’ external clothing, work history and type of pesticide
application;
• Relevant data on inter-subject variability;
• Data analysis plan.
Charge to the Board
3) Has EPA appropriately characterized the limitations on the scientific usefulness of the
resulting data attributable to the choice of the sampling strategy? If not, what has EPA
overlooked?
Board Response
The AHETF and AEATF reports make a persuasive argument in favor of purposive
sampling. The reports are very well written and the issue of sampling has clearly received much
attention. The task forces should be commended for a thorough and rather sophisticated analysis.
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Many of their points are well taken. The limitations of the proposed sampling strategy have not
been fully discussed.
No one knows what factors affect exposure. It appears that not only are there myriad
factors but that their importance is not clear. The only way to protect against potentially
significant biases introduced by unknown or unaccounted for factors is through randomization.
Purposive sampling has a definite role to play in qualitative research and in fact is most
common in applied social sciences applications. The goal in qualitative studies is often to
explore and describe a universe. In quantitative studies, in contrast, the goal is typically to obtain
a point estimate of some quantity and also a measure of the uncertainty around that estimate.
Because purposive sampling includes no random mechanism, the machinery of probability
theory is not available to the researcher and thus an estimate of the uncertainty around point
estimates cannot be computed. As a consequence, results from a purposive sample cannot be
generalized beyond the sample except on faith. An example of faith is the discussion in the
reports that state that the estimated exposure distributions obtained from the purposive samples
will approximate the true exposure distributions at least in the major attributes.
It is true that purposive sampling or its close relative, judgment sampling, is sometimes
justifiable when the sample is very small. However, this is true if in addition, the universe is also
small and its characteristics are known to the investigator. One argument given against the use of
a probability sample in the report is that the sampling frame (the universe) is unknown and
difficult to characterize. Unfortunately, this fact also diminishes considerably the advantages of
purposive sampling even in small samples (see, e.g., Jessen, 1978, Statistical Survey Techniques
one of the standard reference survey sampling books).
A basic question arises: “how small does the sample have to be before non-random selection
is a better option?” The answer is “very small.” It has been argued (again, see Jessen and
others) that with sample sizes as small as about 8 or 10, the advantages of the non-random
sampling mechanism vanish.
The relevant sample size for comparing sampling designs is the effective sample size and not
the number of MUs in a cluster (5) as is presented in the review documents. For a 5 x 5
sampling matric and an assumed ICC of 0.3, the effective sample size is 1 (see Snijders and
Bosker, pg. 23). A sample of 11, while small, is large enough to eliminate or at least decrease
the advantage of purposed sampling over probability sampling (see Jesssen, 1978, Chapter 1).
In most cases ofjudgment or purposive selection, a bias will occur. The bias can be
negligible or very large, depending on the person actually carrying out the selection. Regretfully,
the bias will always be unknown. This is not obvious from the very nice simulations shown in
Appendix B of the AHETF report. From some of those simulation studies, it would appear that
the biases associated with purposive sampling can be small. This is true if we have a large
number of purposive samplers and average over them (central limit theorem). However, a single
sampler (even over repeated sampling exercises) can introduce very large biases that are very
difficult (or impossible) to quantify or anticipate.
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Reliability (defined as the closeness of each observation to its own average over repeated
trials) is typically higher in purposive samples than in random samples of similar size. Accuracy
(also known as validity, a combination of bias and sampling error and a measure of closeness of
an estimator to the targeted value) however is difficult to forecast and can be quite low. Because
non-random samples provide no means for computing accuracy, the value of such samples is
rather questionable.
One major argument against at least a quasi-random selection of MUs appears to be the cost
of selection. However the Board believed the argument is not convincing. Major expenses
would be incurred if MUs were to be randomly selected from the entire universe of MUs for a
given scenario. But if a stratification step is carried out purposively (as proposed here) the
random selection of MIUs within cluster should not significantly add to the cost. Suppose that the
five clusters are selected purposively. Given a cluster and relative to the actual cost of collecting
the dosimetry data, it should be possible for example to first randomly select firms and within
firms, randomly select handler-days. Not everyone will agree to participate and not everyone
might be handling the desired products on the selected dates, but all that will require is a few
additional visits or phone calls to the selected firms.
Random sampling is no more impractical and may be no more costly within the context of
costs of the whole study than PDS. Irrespective of response rate, random sampling provides
more information regarding the representative of participating sites or operations.
To assist the Agency, the Board recommended the following approach:
• Purposively select locations.
• Within location, list operations.
• Roughly stratify producers by crop and by size.
• Randomly select operations and within operations, randomly select operators. Observe them
next time they apply the chemical of interest.
HSRB Consensus and Rationale
The major limitation of non-random sampling is that it provides no means for estimating the
error associated with any estimate based on the sample. The exposure distributions based on this
type of sample might or might not be anywhere close to the true exposure distributions and there
is no way to tell if the results are representative or not. If the estimated exposure distributions
will be used for by EPA, it is important to base those estimates on samples that at least
approximate a random sample and that permit obtaining data-driven estimates of uncertainty
around quantities of interest. Error estimates and other estimates relevant to determination
quantities in the AEATF and AHETF reports are based on strong and un-testable assumptions
(NRC 1994, 1991, and 1983).
Statistical justification for number of clusters and monitoring units
Charge to the Board
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What additional information, if any, would the HSRB need to assess the adequacy of the
justification for the number of clusters and number of MUs in specific AHETF and AEATF
study proposals?
Board Response to the Charge
The primary objective of the AHETF and AEATF II human exposure monitoring
programs is to collect sufficient data for each handler scenario to characterize the distribution of
the exposure level, both dermal and inhalation. In other words, both programs are interested in
knowing the statistical distribution of the exposure level within an acceptable bound (K) for their
relative accuracy. The fold relative accuracy (fR 4) measures how far the sample estimate is from
the true parameter in a relative sense. The sample size estimation for both programs is based on
the same justification of a 3-fold accuracy (K3), i.e.jRA is less than or equal to 3, for the
parameter of interest.
In both programs, the purposive sampling is used to select clusters. However, the sampling
of MUs within clusters will be random. Therefore it requires a set of assumptions for the
“surrogate sampling model”:
1. Observed exposures are viewed as arising (at least approximately) from a random sample
of clusters and then from a random sample of MUs within each cluster.
2. The sampling distribution of normalized exposures within and between clusters is, at
least approximately, lognormal.
The second assumption is reasonable, and even if it is violated, its impact should be minimal.
However, the first assumption is problematic. Depending on how the clusters and the MUs
within clusters are selected, bias can be introduced in a way that cannot be corrected.
Therefore the sample size justification based on Monte Carlo simulations has its limits.
Under these assumptions, the sample size is estimated based on the nested variance
component model for the normalized exposure level. In order to determine the relative accuracy
of the estimates of the parameters associated with the statistical distribution for the exposure
level, one needs as design parameters reasonable estimates for the geometric standard deviation
(GSD) of the exposure level and the “intra-cluster” correlation coefficient, i.e. intraclass
correlation coefficient (ICC) due to cluster sampling.
Nested lognormal variance component assumptions were used in a surrogate-sampling
model to determine the sample sizes necessary to achieve a 3-fold relative accuracy of
distributional parameter estimates. Reasonable values for the GSD and the ICC of exposure
normalized by the amount of ai handled were obtained from an analysis of existing data.
The Board provides specific comments to each task force proposal as noted below
AHETF: The GSD and ICC were estimated respectively as 3.8 and 0.26 for normalized
dermal exposure and 4.2 and 0.37 for inhalation exposure from the AITIETF monitoring data
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based on the nested variance component model. For planning purposes, a GSD of 4.0 and ICC
of 0.3 seems reasonable defaults for both dermal and inhalation exposure. Simulation analyses
indicate that N =5 clusters with Nm5 MUs per cluster will achieve the desired benchmark goal
and is more cost-effective than other feasible configurations. As long as a cluster size of 5 is not
exceeded, the same total number of MUs (N=25) will also achieve this same level of relative
accuracy even if the number of MUs per cluster varies slightly.
AEATF II: A GSD of 2.86 was derived from four dermal exposure monitoring studies
(three by the Chemical Manufacturers Association in wipe, mop and aerosol-hands setting and
one by the Pesticide Handlers Exposure Database in aerosol), a coefficient of variation 1.42 was
derived from the log-scale standard deviation under the assumption of a lognormal distribution,
and an ICC between 0 (independence among observations within a cluster) and 0.3 (a moderate
dependence) was assumed. Simulation analyses indicate that N =3 clusters with Nm= 6 MUs per
cluster will achieve the desired benchmark goal and is more cost-effective than other feasible
configurations.
The recommended sample size of five clusters with five MUs per cluster for the AHETF
program and three clusters with six MUs per cluster for the AEATF II program is considered a
‘default’ or ‘standard’ configuration only. It strictly applies only to scenarios without existing
data and when the default variability is GSD=4 or 2.86 and ICC=0.3, respectively, for the
AHETF and AEATF II program, and benchmark accuracy (K3) is considered reasonable. In
other cases, the simulation techniques can be used to develop optimal sampling plans for each
scenario it addresses.
The AHETF and AEATF II human exposure monitoring programs have done an
outstanding job of considering the effects of both the numbers of clusters and the numbers of
MUs within each cluster.
Given the assumptions made regarding the surrogate sampling, the Governing
Documents from the AHETF and the AEATF II human exposure monitoring programs provide a
very thorough justification for the sample size in terms of the number of clusters and the number
of MUs per cluster in specific AHETF and AEATF II study proposals. The sample size
justification includes determination of feasible values of N and Nm, optimal configuration of N
and Nm based on relative cost of sampling cluster vs MUs, sensitivity of the relative accuracy
bound to the GSD and ICC, and the impact of unequal number of MUs per cluster which may be
expected when MUs drop out. It also recognizes its limitations and suggests scenario-specific
simulation studies to estimate adequate sample size.
AHETF’s initial conclusion that a total of 25 MUs is needed provided that there is no
more than 5 MUs per cluster appears valid and likely to be very useful. However, the choice of
only three clusters by the AEATF seems risky and it should be increased if at all possible. Three
clusters will only give 2 degrees of freedom for estimating the cluster variance component, and
making statistical inferences based on samples of size 3 would be considered less than desirable.
It seems that the major cost associated with the protocols for the AEATF database is with
analyzing the measurement data, and using only three clusters is a matter of convenience. The
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AEATF II program should give consideration to increasing the number of monitoring units to 25
with no more than 5 MUs per cluster, which results in at least five clusters per scenario
HSRB Consensus and Rationale
If the purposive sampling method is selected as a surrogate for a probability sampling, no
additional information seems to be needed for the HSRB to assess the adequacy of the
justification for the number of clusters and the number of MUs in specific AHIETF and AEATF
II study proposals (however, as noted previously, the Board raised serious concerns about the
purposive sampling strategy
As the sample size justification for the AEATF II program is based on the ICC estimate
from the AFIETF program, it is recommended that the AEATF II program update the proposed
sample size based on their study in the future to verify whether the ICC estimates agree with that
from the AHETF program.
Within-Worker variability
Charge to the Board
Has EPA appropriately characterized the limitations on the scientific usefulness of a
database that does not include repeated measures? If not, what limitations has EPA overlooked?
- Board Response
A database that does not include repeated measures will have limited usefulness in the
context of some analysis goals but not in the context of others.
With a dataset that includes one observation per person it is not possible to obtain an
estimate of the within-person variance in exposure. This variance reflects the variability in
exposures of a handler across different days, even if using the same product and the same
application equipment and can be quite large. The impact of ignoring the within-person variance
is directly proportional to the relative sizes of the within to the between person variance in
exposure.
If the objective of the study is to obtain an estimate of the mean exposure of workers in a
given scenario, or to obtain an estimate of the on-day distribution of exposure, then a single
observation per person will suffice. This is true even when the quantity of interest is a median, a
geometric mean or in general, any distributional attribute associated with the center of the
distribution. We refer to this as the distribution of usual exposures under a given scenario.
Ideally, this usual exposure distribution would be estimated from the mean handler exposures
computed from observing each handler during a large number of randomly selected days. This is
clearly an impractical approach. Alternatively, it can also be estimated from a database that
includes at least one replicate observation on at least a randomly selected sub-sample by fitting
the appropriate random effects model (see, e.g., Nusser, Carriquiry, Doddand Fuller, Journal of
the American Statistical Association, 1996; Carriquiry, Public Health Nutrition, 1999;
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Carriquiry, Journal of Nutrition, 2003). This approach has been recommended by both the US
National Academy of Sciences (2002) and by the World Health Organization (2006) for
estimating the distributions of usual exposures to components in food and drinking water.
The estimated distribution that is based on a single measurement,has a variance that
includes the between-person variance and the within-person (or day-to-day) variance. The latter
is problematic and inflates the overall variance of the exposure distribution by an amount that
can be quite significant. As a consequence, upper-tail quantiles of the exposure distribution tend
to be overestimated. We refer to this estimate as the one-day estimate of the distribution.
From a regulatory stand-point, using the one-day distribution in lieu of the usual exposure
distribution tends to be conservative. That is, estimated percentiles such as the 95 th percentile
will typically be larger than what they would be if estimated using the distribution with the
correct variance. In this sense, the one-day distribution is protective. If the sample of MUs in
each scenario were large enough to allow estimation of the one-day distribution, then using the
one-day distribution as a proxy for the usual exposure distribution would be acceptable.
The reports by the AHETF and AEATF argue strongly against collecting within-person
repeated observations. The two main arguments are the following:
1. Cost: given the already rather small sample sizes per scenario, collecting replicate
observations would imply increasing the number of measurements since reducing the number
of MUs is not reasonable.
2. The distribution of mean exposures can be analytically derived given information about the
one-day distribution of exposures.
It is difficult to argue with issues of cost. While any experiment involving replication would
indeed be more costly, it is possible to minimize the additional cost by using an efficient design..
The second argument, however, is not convincing. First, it is not at all a given that the log-
normal is the correct probability model for exposures under all possible scenarios. Even if the
log-normal model was the appropriate model, the report confuses the distribution of within-
person means with the distribution of the mean of a log-normal. Those two distributions are in
general not the same unless we are willing to believe that the within-worker exposure
distribution (i.e., the distribution of exposures in a worker observed during a very large number
of days) is also log-normal. Thus, without imposing the log-normal model at the worker level as
well, the Board was not sure it is possible to analytically derive the distribution of the conditional
expectation of daily exposure given handler (which is the distribution of interest).
The task forces propose “borrowing” an estimate of the intra-class correlation in order the
“correct” the one-day distribution so that it will better approximate the usual exposure
distribution. In principle, using an external estimate of the within-person variance (or of the ICC)
might be reasonable, but the actual estimate needs to be carefully selected and very well
justified. Is it reasonable to expect, for example, that the within-person variance in exposure will
be the same across scenarios?
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The limitations introduced by the lack of replication and the assumed model are compounded
by the very small sample sizes. Without imposing the log-normal model on the data it would not
even be possible to obtain a point estimate of the 95 th percentile (at least a reliable one) let alone
get an estimate of its standard error. In addition to allowing for estimation of the two relevant
variance components, replicate observations would increase the sample size even after
accounting for correlation between observations collected from the same person.
HSRB Conclusion and Rationale
The lack of choosing a within-person design is limiting if the Agency wishes to obtain
data on usual exposures. However, if the Agency wishes to collect data on one-day exposures,
their approach is not limiting, but the Board recommends that as many handler as possible be
observed as costs would allow.
Subject recruitment and enrollment issues
Charge to the Board
1) Does the Board agree that the Governing Documents and associated SOPs of the
AHETF and AEATF research programs include comprehensive and appropriate protections for
human subjects of the research? If not, what has been overlooked?
Board Response
The Board was very impressed with the quality of the work done, and the amount of
effort that has clearly gone into producing these documents. The Board had only a few
suggestions:
The documents might provide greater clarity regarding input from organizations that
represent the subjects (such as farm labor organizations or advocates). For example, at page 94
of 468 of the AHETF materials, it indicated that such organizations “might” be invited to provide
input with regard to a particular study. It could be helpful to provide some guidance regarding
those situations in which the participation of such organizations would be especially important.
In addition, such organizations could also provide useful advice with regard to the Governing
Documents and associated SOPs themselves, and not merely limited to particular protocols.
The sample consent form that was provided would benefit from increased attention to the
reading level. In a variety of places (e.g., in discussing how compounds will be applied to
“vertical” and “horizontal” surfaces), the language could be rewritten at a lower reading level
(e.g., by including examples referring to floors, walls, and blinds), particularly given the likely
educational background of many of the subjects.
With regard to pregnancy testing of subjects, the AEATF and AHETF documents appear
to take different approaches. The former group tests only subjects under age 50, while the latter
group tests all female subjects. It would seem appropriate to use the same standard in both types
of studies, or else to provide a justification for the difference.
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Also on the issue of pregnancy testing, the documents mention that if a pregnancy test is
positive, the records relating to that person would be discarded. It would be better to use a word
such as “shredded,” to make it clearer that the documents will be destroyed, not merely put aside
or thrown out where they could be accessed by others.
Given the language, economic and educational characteristics of many of the prospective
subjects, it would be appropriate for the documents to consider additional specific measures that
might better protect a worker’s right to say no. For example, protocols might be designed so that
substantially less than 100% of an employer’s workers can participate in the study (e.g., only 5
out of 10). By taking this measure, it would decrease the likelihood that an employer could
determine which employees chose not to participate, because the employer could not be sure that
some of them were merely unable to participate due to the limit on participation.
HSRB Consensus and Rationale
The Board agreed that the Governing Documents and associated SOPs do include
comprehensive and appropriate protections for human subjects.
Charge to the Board
2) In singling out the handling of language differences as an area requiring further
refinement, has EPA overlooked other areas in need of revision? If so, what?
Board Response
The Board reaffirmed the importance of making all paper and electronic documents
distributed to study volunteers available in both English and Spanish. The Board also expressed
strong support for the need for both Spanish- and English-speaking study staff to be available at
study sites to answer any questions that research volunteers may have regarding the study or
their participation in the study. Spanish- and English-speaking staff should also be available
during other study interactions with research volunteers, including data-collection encounters
and via telephone lines that are made available to subjects who may have questions about their
participation in the study or rights as a research volunteer. The Board expressed concerns about
reliance on translators of convenience, such as co-workers and others who may lack sufficient
familiarity with the study.
The Board expressed support for the Agency’s proposal to have impartial third-party
witnesses observe the consent process when a research subject is unable to read relevant study
documents. As specific studies are proposed, however, it will be important for investigators to
describe the procedures to be employed in recruiting these witnesses. It would be inappropriate,
for example, to ask translators to serve as witnesses (as suggested in the materials reviewed by
the Board), because one of the main purposes of employing a witness is to ensure that the
communication of study-related materials is adequate (and the translator would be conflicted
with regard to that assessment). If feasible, the Agency may wish to consider using impartial
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“consent monitors” or “research subject advocates” as witnesses, as is increasingly done in
certain clinical studies.
The Board also returned to an issue raised at the last Board meeting. At that earlier
meeting the Board suggested that in many areas of the U.S., agricultural workers often speak
neither English nor Spanish but instead speak another language, such as one of several
indigenous languages of Northern Mexico. The Agency may wish to consider this possibility
(and its implications for sample bias and just distribution of research benefits and risks) in
deciding whether to restrict eligibility to English- and Spanish-speaking subjects.
HSRB Consensus and Rationale
The Board agreed that the handling of language differences is an area requiring further
refinement and is appropriate to protections for human subjects. Related issues include
mechanisms to ensure understanding and voluntariness in the consent process.
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