EPA 600/R-99/077
October 1999
PROCEEDINGS OF THE
NHEXAS DATA ANALYSIS WORKSHOP
JULY 26-28, 1999
Sponsored by
National Exposure Research Laboratory
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
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Disclaimer: This Proceedings has been cleared for publication by the National Exposure Research
Laboratory, U.S. Environmental Protection Agency. Mention of trade names does not
imply recommendation for use. This Proceedings does not represent Agency policy. This
Proceedings has not been peer-reviewed because it is a report of a workshop, rather than
an assessment or study report.
Additional copies may be obtained at www.epa.gov/nerl/nhexas.htm.
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NHEXAS ANALYSIS WORKSHOP
ORGANIZING COMMITTEE
Maurice Berry, Ph.D., ORD/NERL*
Judith A. Graham, Ph.D., ORD/NERL
Karen Hammerstrom, ORD/NCEA**
Stephen Hern, ORD/NERL
Kelly Leovic, ORD/NERL
Haluk Ozkaynak, Ph.D., ORD/NERL
Dale Pahl, ORD/NERL
James Quackenboss, ORD/NERL
Gary Robertson, ORD/NERL
Linda Sheldon, Ph.D., ORD/NERL
William Steen, Ph.D., ORD/NERL
*ORD = Office of Research and Development, EPA
NERL = National Exposure Research Laboratory
**NCEA = National Center for Environmental Assessment
The Organizing Committee expresses its gratitude to:
all the participants for contributing their thoughts and recommendations;
Gerald Akland, Research Triangle Institute; Tim Buckley, Ph.D., Johns Hopkins University; Steven
Colome, Ph.D., UCLA and JES; and Steven Knott, ORD/NCEA, for serving as rapporteurs of the
workgroups;
Susan Bass, Brenda Thompson, and Kim Inglett, of ORD/NERL, for their administrative and logistic
contributions;
Emily Lee and Lester D. Grant, Ph.D., both of ORD/NCEA, for assisting in implementing the
workshop;
Personal Communication Service, Inc., for providing workshop support under contract; and
Yvonne Harrison, Bettye Kirkland, and Carolyn Perry, OAO Corporation, for providing word
processing and John Barton, OAO Corporation, for editing the proceedings.
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IV
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TABLE OF CONTENTS
1. INTRODUCTION 1
2. OVERVIEW OF NHEXAS 2
2.1 BACKGROUND ON EXPOSURE TO CHEMICAL POLLUTANTS 2
2.2 THE PURPOSE OF NHEXAS 3
2.3 HISTORY AND PARTICIPATING ORGANIZATIONS 4
2.4 MAJOR DESIGN ELEMENTS 5
2.5 SOURCES OF MORE INFORMATION 7
3. OVERVIEW OF THE WORKSHOP 7
4. PROJECT DESCRIPTIONS 10
4.1 INTRODUCTION 10
4.2 ASSESSMENT GROUP 11
4.2.1 SAB Comments 11
4.2.2 Questions To Address 12
4.2.3 Discussion Considerations 13
4.2.4 Brainstorming List of Projects 14
4.2.5 Project Descriptions 15
4.3 EXPOSURE ANALYSIS GROUP 32
4.3.1 SAB Comments 32
4.3.2 Questions To Address 32
4.3.3 Discussion Considerations 33
4.3.4 Brainstorming List of Projects 35
4.3.5 Project Descriptions 36
4.4 LESSONS LEARNED GROUP 50
4.4.1 SAB Comments 50
4.4.2 Questions To Address 50
4.4.3 Discussion Considerations 51
4.4.4 Brainstorming List of Projects 52
4.4.5 Project Descriptions 55
4.5 MODELING GROUP 70
4.5.1 SAB Comments 70
4.5.2 Questions To Address 71
4.5.3 Discussion Considerations 72
4.5.4 Project Descriptions 73
APPENDIXES
1. LIST OF NHEXAS PAPERS IN PRESS OR IN PREPARATION 99
2. WORKSHOP AGENDA 101
3. LIST OF WORKSHOP PARTICIPANTS 102
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4. LIST OF WORKGROUP PARTICIPANTS 110
5. HANDOUTS Ill
6. COPIES OF OVERHEADS 134
1. INTRODUCTION
The National Human Exposure Assessment Survey (NHEXAS) was developed by the Office of
Research and Development (ORD) of the U.S. Environmental Protection Agency (EPA) early in the
1990s to provide critical information about multipathway, multimedia population exposure distribution
to chemical classes. The first phase consisted of three pilot studies with the objectives of (1) evaluating
the feasibility of NHEXAS concepts, methods, and approaches for the conduct of future population-
based exposure studies; (2) evaluating the utility of NHEXAS data for improved risk assessment and
management decisions; (3) testing the hypothesis that the distributions of exposure given by modeling
and extant data do not differ from the measurement-based distributions of exposure; (4) defining the
distribution of multipathway human exposures for a relatively large geographic area; and (5) stimulating
exposure research and forging strong working relationships between government and nongovernment
scientists. NHEXAS began before the enactment of the Government Performance and Results Act
(GPRA), which was written to ensure accountability in the use of resources. Thus, we add a "new"
objective in the form of a hypothesis: NHEXAS approaches can be used to develop a "GPRA Report
Card" on the efficacy of EPA's regulations to reduce exposure.
As described in the overview (Section 2), NHEXAS is a unique and complex study of
approximately 550 people in three areas of the United States. The data collection phase of NHEXAS
was completed recently, the initial data analyses will be published shortly (see October issue of the
Journal of Exposure Analysis and Environmental Epidemiology (JEAEE), Appendix 1), and the
principal investigators have additional analyses under way (Appendix 1). During a September 1998
review, the Integrated Human Exposure Committee (IHEC) of EPA's Science Advisory Board (SAB)
(U.S. EPA, 1999) praised the NHEXAS pilots and recommended several actions to ensure that as
much benefit as possible is derived from this very rich database. One such action was to develop a
strategy for completing the analysis of the NHEXAS pilot data. To those ends, a workshop was
convened with the goal of obtaining a wide range of expert opinion on which research projects best
would ensure the utility of the NHEXAS data. Section 3 provides an overview of the workshop, and
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as described therein, the workshop projects will be used as information in developing the ORD strategy
for analysis of the NHEXAS pilot data.
The workshop was successful in developing and suggesting a relative priority for research
projects that covered the range of potential data analyses, including those that will support future
exposure assessments, advance the science of exposure analysis, demonstrate lessons learned, and
become part of the development of multimedia, multipathway exposure models. The project
descriptions, categorized within the four research areas, are provided in Section 4.
Supplementary information is provided in the appendixes.
2. OVERVIEW OF NHEXAS
2.1 BACKGROUND ON EXPOSURE TO CHEMICAL POLLUTANTS
To assess the risks posed by chemical pollutants in the environment, EPA must be able to
estimate the number of people exposed to these chemicals and the intensity of exposure. In the past,
most studies have focused on exposure to one chemical at a time by one route of exposure. For
instance, a study might look at how much of a particular chemical is found in outdoor air. In many
cases, these studies have relied on very indirect measures to estimate exposure to the chemicals. An
example would be to sample emissions from a smokestack and then apply air transport models to
predict exposure to residents in the surrounding area.
Although such studies are important, looking at chemicals and sources in isolation does not reflect
actual patterns (distributions) of human exposure to chemicals in the environment. In reality, people can
be exposed to chemicals from a variety of sources that contaminate water, food, air, dust, and other
media. Exposure to a single chemical may occur from contact with several environmental media (e.g.,
air, water), via several pathways (e.g., hand-to-mouth transfers, food), and through several routes (i.e.,
inhalation, oral, dermal). Additional complexities arise when considering an individual's exposure to
multiple chemicals at any point in time or over extended periods. The fact that different people also
spend varying amounts of time indoors and outdoors or otherwise engage in activities that can have
important impacts on chemical exposure adds to this complexity. More accurate assessments of risks,
therefore, must take into account exposure to multiple chemicals from various routes and media.
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By understanding total or aggregate exposure, it also will be possible to identify those pathways and
routes responsible for the greatest exposure, thereby providing direction for decisions on the most
effective strategies to reduce risks.
2.2 THE PURPOSE OF NHEXAS
NHEXAS in its fullest sense is a conceptual design, which, on implementation, will have long-
term implications to exposure research and assessment. The ultimate goal is to document status and
trends of national distributions of human exposure to potentially high-risk chemicals to improve the
accuracy of exposure (and risk) assessments and to evaluate whether exposure (risk) is deteriorating or
improving over time with the application of risk management steps. However, such an extensive
program requires much preparation, including making improvements in the state of exposure science.
The Phase I pilot projects, which are the topic of the workshop, are the beginning. Based on the
scientific advances from this first phase of NHEXAS, two follow-up phases are envisioned. One
encompasses special studies to test particular hypotheses related to issues, such as characterization of a
pathway of concern for a specific subpopulation or a chemical of concern at specific geographic scales
(community and regional) or an uncertainty related to the effect of temporal variability in an exposure
assessment model. The second is the design and implementation of a much broader national survey of
population-based exposures building on the foundation laid by the pilot-phase investigations.
Phase I of NHEXAS (hereafter referred to as just NHEXAS or pilot NHEXAS studies) is
perhaps the most ambitious study ever undertaken to evaluate total human exposure to multiple
chemicals on both community and regional scales. It focuses on the exposure of people during their
daily lives to environmental pollutants. To accomplish this, hundreds of volunteer participants were
selected randomly from several areas of the country to obtain a population-based probability sample.
NHEXAS scientists measured the levels of a suite of chemicals to which participants were exposed in
the air they breathe, in the foods and beverages they consume, in the water they drink, and in the soil
and dust around their homes. Measurements also were made of chemicals or their metabolites in
biological samples (including blood and urine) provided by the participants. Finally, participants
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completed questionnaires to help identify possible sources of exposure to chemicals and to characterize
major activity patterns and conditions of the home environment.
In addition to improving estimates of total exposure to chemicals, NHEXAS has the following
aims.
Identify subgroups of the general population that are likely to be highly exposed (at least the 75th
percentile) to chemicals in their environment.
Provide a baseline of the normal range of exposure to chemicals in the general population that can be
used to compare to the results of other investigations conducted at particular sites of concern or
addressing specific routes.
Compare the results of a one-week "snapshot" of exposure to the results obtained from multiple
sampling cycles over a year.
Evaluate and improve the accuracy of models developed to predict or diagnose exposure of people
to chemicals.
Test and evaluate different techniques and design approaches for performing multimedia,
multipathway human exposure studies.
2.3 HISTORY AND PARTICIPATING ORGANIZATIONS
Currently, NHEXAS consists of three interrelated projects, all of which were funded as
cooperative agreements and coordinated by EPA's Office of Research and Development:
(1) a study of several hundred Arizona residents by the University of Arizona, Battelle Memorial
Institute, and the Illinois Institute of Technology;
(2) a study of several hundred residents from the states of Illinois, Indiana, Michigan, Minnesota, Ohio,
and Wisconsin by the Research Triangle Institute and the Environmental Occupational Health
Sciences Institute, and, also, a smaller scale study focused on children's exposures to pesticides,
conducted with the participation of the Minnesota Department of Health; and
(3) a study of about 60 Maryland residents by Harvard University, Emory University, Johns Hopkins
University, Southwest Research Institute, and Westat.
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Two other federal agencies, the Food and Drug Administration and the Centers for Disease
Control and Prevention (CDC), assisted EPA (under interagency agreements) with sample analysis.
The National Institute for Standards and Technology (NIST) under an interagency agreement, provided
quality assurance (QA) support.
Within EPA's ORD, scientists from the National Exposure Research Laboratory (NERL),
National Center for Environmental Assessment (NCEA), and the National Health and Environmental
Effects Research Laboratory (NHEERL) participated. The first two organizations are engaged actively
in the conduct of the program by serving as project officers and principal collaborators in the research.
Sample collection began in mid-1995 and was completed for all of the projects in late 1997, and
the planned analysis of the samples was completed in early 1998. Publications are beginning. Actual
databases are expected to become available to the public in 2001.
2.4 MAJOR DESIGN ELEMENTS
Table 1 summarizes the major design elements of NHEXAS. There were common features
across the three consortia. All three consortia used the same basic set of questionnaires. Within
chemical classes selected by the consortia, each consortium analyzed for a basic set of chemicals
(primary analytes). However, by utilizing three consortia, alternative and innovative variations on the
theme of multimedia measurements to estimate total human exposure were possible. For example, each
consortium was able to target some specific concerns or opportunities. Two of the consortia focused
on measuring potential exposures of each participant once; one consortia studied fewer people but
repeated the measurements several times over the year to enable estimates of temporal variability for
the exposures and activities of interest.
The participants were selected through a probability sample to permit statistical inferences about
the larger population later. The only exception was a special panel on children exposed to pesticides.
(This was based on oversampling households reporting more frequent applications of insecticides and
on a commercial listing of households with listed telephone numbers that were predicted to have age-
eligible children.)
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Chemicals to be analyzed by NHEXAS were chosen because they are known (or strongly
suspected) to present major environmental health risks, had been found in two or more environmental
media (air, water, soil, or food), and had been identified as being of importance to several EPA
program or regional offices or to other federal agencies. Chemicals were selected only if it was feasible
to collect and analyze them. The chemicals fall into three categories:
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TABLE 1. SUMMARY OF NHEXAS STUDIES
Consortium
University of Arizona/Battelle Memorial
Institute/Illinois Institute of Technology
Research Triangle Institute/Environmental and
Occupational Health Sciences Institute
Harvard/Emory/Johns Hopkins/
Southwest Research
Institute/Westat
Type of Study Exposure field study
Geographic
Region
Design
Approximate
Number of People
Analytes
Samples
Arizona
Representative sample of general population
179 (plus others in sampled households)
Pb, As, Cd, Cr, Ni, Ba, Mn, Se, V, Cu, Zn;
benzene, chloroform, perchloroethylene,
trichloroethylene, methylchloroform, styrene,
toluene, xylene, />-dichlorobenzene,
formaldehyde, 1,3,-butadiene, methylene
chloride, carbon tetrachloride, plus 11 additional
volatile organic compounds (VOCs);
chlorpyrifos, diazinon, malathion, carbaryl
Air, water, food, and beverages; soil/dust and
surfaces; urine and blood
Questionnaire NHEXAS
Exposure field study
Data analysis and hypothesis testing (CAG-PIs
and ORD-PCsa); database integration (NERL and
NCEA)
Region V (Illinois, Ohio, Indiana, Michigan,
Minnesota, and Wisconsin)
Representative sample of general population
249 (plus 52 for pesticides) (no others in sampled
households)
Pb, As, Cd, Cr; benzene, chloroform,
perchloroethylene, trichloroethylene,
methylchloroform, styrene, toluene, xylene,
/>-dichlorobenzene; chlorpyrifos, diazinon,
malathion, atrazine, chlordane, dieldrin,
heptachlor, 4,4'-DDE, -ODD, and -DDT;
B(a)P, anthracene, phenanthrene, pyrene,
B(a)A, acenaphthylene, fluoranthene,
B(g,h,i)perylene, indeno(l,2,3-c,d)pyrene
Children's Study (pesticides andPAHs)
Air, water, food, and beverages; soil/dust and
surfaces; urine and blood
NHEXAS
Special study: relation of short-
term data to longer term exposures
Baltimore and surrounding
counties
Representative sample includes
suburban, urban, and rural groups
53 people sampled six times over
1 year
Pb, As, Cd, Cr; chlorpyrifos,
diazinon, malathion, atrazine (water
only), chlordane, dieldrin,
heptachlor, 4,4'-DDE, -ODD, and
-DDT; B(a)P, anthracene,
phenanthracene, chrysene
Air, water, food, and beverages;
soil/dust and surfaces; dermal;
urine and blood
NHEXAS
"CAG-PIs = principal investigators of cooperative agreements; ORD-PCS = principal collaborators from ORD.
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(1) volatile organic compounds (VOCs), such as trichloroethylene, benzene, and perchloroethylene; (2)
metals, such as lead, arsenic, and cadmium.; and (3) pesticides, such as the herbicide atrazine and the
insecticides chlorpyrifos, diazinon, and malathion. In some media, measurements of selected polycyclic
aromatic hydrocarbons (PAHs) were made.
2.5 SOURCES OF MORE INFORMATION
A special issue of JEAEE (vol. 5, no. 3, July-Sept., 1995) describes all major aspects of
NHEXAS in detail. At present, several manuscripts have been submitted to JEAEE and will be
published in October 1999. Appendix 1 lists the papers in preparation and in press.
3. OVERVIEW OF THE WORKSHOP
On September 28 and 29,1998, EPA's SAB fflEC reviewed the NHEXAS pilot studies and
provided an advisory to EPA. Their major findings are shown below.
NHEXAS pilots are scientifically "outstanding in both design and implementation...."
The NHEXAS design "can help to identify serious human health risks, to decide what interventions
would be helpful in reducing these risks, and to document the effectiveness of interventions in actually
reducing exposures."
The "NHEXAS pilot study is highly relevant to the Government Performance and Results Act
(GPRA) and SAB's "integrated Environmental Decision-Making Framework," which emphasize
performance evaluation as a key to effective environmental health protection."
ORD should develop a feasibility study for a national-scale human exposure survey.
ORD should publicize the significance of NHEXAS framework and continue to build partnerships.
ORD should provide additional resources to strengthen analysis of NHEXAS pilot data or the
"expenditures incurred during the last five years would be of limited utility."
"The EPA should conduct a cost-benefit analysis of the various components of the study."
A database of the NHEXAS information (with appropriate QA) should be developed and made
widely available.
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ORD should develop a strategy for the analyses of the NHEXAS data, and the SAB should review it.
ORD is in the process of following-up on all these recommendations. It was decided that a
workshop format would be used to begin the development of an analysis strategy. Appendix 2 shows
the workshop agenda. Input was sought from individuals with a wide range of expertise so that
perspectives from practitioners of the science as well as users of the science would be represented;
from NHEXAS investigators and their peers; from measurement and modeling experts; and from
federal and non-federal experts (Appendix 4). The goal was to define potential analysis projects (with
priority rankings) as the centerpiece of a proceedings. Then this proceedings would become input into
ORD's development of a draft analysis strategy, with priorities. This draft will be made public at the
time of submission to the SAB (approximately November 1999, assuming that the SAB review will be
in December 1999; however, the date has not been set). After SAB review, ORD will revise the
strategy and use it as a guide to research planning. Research will be implemented, consistent with
resources available, by in-house tasks, contracts, or assistance agreements (cooperative agreements
and grants), as appropriate according to procurement regulations and laws.
Workshop participants were divided into four breakout groups (see Appendix 3) to enable
extensive interchange of ideas. Each group had a mixture of expertise to raise provocative ideas. For
example, participants were from academia, independent research institutes, EPA program offices, all
ORD laboratories and centers, the National Institute of Environmental Health Sciences (NIEHS),
Centers for Disease Control and Prevention, the American Petroleum Institute, and the departments of
health of Minnesota and New York. The groups focused on the areas described below.
Assessment. This covers analyses that would result in descriptive statistics for questionnaire and
measurement data, comparisons among the NHEXAS and other studies, total exposure estimates,
cumulative exposure assessments, identification of relative contributions of pathways to exposure, etc.
Exposure Analysis. This covers analyses that would study design hypotheses (plus those proposed
at this workshop), characterize temporal variability, identify factors that contribute to a high-end
exposure, characterize urban-rural differences, and describe relationships among various components
in the human exposure process (including sources, concentrations, exposures, human activities, and
dose).
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Lessons Learned. This covers analyses that inform everyone about study elements that will be
generally useful in the future or that will require modification or deletion in follow-up research. This
includes descriptions of the achievement of data quality objectives and of response rates and survey
design effects; evaluation of the ability of questionnaire environmental and biological data to predict
exposure and dose; a comparison of sampling and analytical methods; the efficacy of communication
with states, local public health departments, communities; etc.
Exposure Modeling. This covers the application of NHEXAS data to the development or
refinement of multimedia, multipathway exposure models and the evaluation of the reliability of existing
models. This includes applications to other agency models such as the Total Risk Integrated
Methodology (TRIM), Cumulative Exposure Model (CEM), etc., and use in predicting exposures
from biomarker concentration and in predicting biomarker concentrations from exposure and
environmental concentration levels and in characterizing pathways; etc.
The workgroups were charged with identifying, writing, and prioritizing potential analysis projects.
Before the workshop they received some background material (Appendix 6), as well as a list of the
SAB recommendations for analyses and key analyses questions to drive the discussion (see Sections
4.2.1 through 4.2.3, 4.3.1 through 4.3.3, 4.4.1 through 4.4.3, and 4.5.1 through 4.5.3). Within each
group, the participants discussed these and other related issues, developing a preliminary list of a large
number of projects. This list was then prioritized, with the goal of selecting 10 to 15 high-priority
projects to be expanded according to a preestablished format. Project description formats were
developed that would be informative enough for strategic planning, without being so detailed as to
contain intellectual property or to provoke the need for recusals in later resource competitions.
Members of the workgroup were assigned to draft the project descriptions, which then were discussed
by the whole group. The group then created the prioritized list, typically by applying multivoting
techniques. The preliminary lists and the ranked project descriptions are provided in Section 4.
The workgroups reported in plenary session on the last morning. Limited discussion followed to
ensure the project descriptions covered all the NHEXAS objectives and major points.
The workgroup chairs and rapporteurs and others on the organizing committee continued to work
to improve the clarity of the project descriptions, without changing their substance and to create the
proceedings, which are provided in Section 4. The handouts provided either at or prior to the
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workshop, as well as the overheads from the overview presentations on the first day, are provided in
Appendixes 5 and 6, respectively.
4. PROJECT DESCRIPTIONS
4.1 INTRODUCTION
Edited versions of the project descriptions developed at the workshop are presented according
to their workgroup. They all have the same format. The project name is preceded by a code that
consists of an abbreviation of the group name (e.g., LL for lessons learned) and the priority assigned by
the workgroup. Pertinent information is provided (i.e., description, goal, significance, approach). The
entry on data or input needs is valuable to identify pacing items; for example, a data or input need may
be a high-quality database or summary statistics, indicating what work would need to be done first.
Also, the section on feasibility can be quite important. For example, some analyses will require a
certain level of data completeness. Most of these types of details were not available at the workshop,
making it necessary to identify them on the descriptions. The participants also identified research
outputs and timelines, as well as an approximate level of effort. This is important because the level of
effort and timeline are mutually dependent and can be interpreted as broad resource needs.
Each subsection to follow begins with a list of the SAB recommendations, questions to the
participants, and discussion considerations that provided guidance to the workgroups. As mentioned,
all the groups began with brainstorming and then sorted out the highest priorities for development of
project descriptions. The modeling group had similar projects before and after this procedure. The
early brainstorming lists for the other three groups are provided below. The last portion of each
subsection contains the project descriptions, in priority order. It must be emphasized that there are
minimal differences in priorities within groups. Basically, the priorities represent minor variations on a
class of high-priority projects with the exceptions noted in the Assessment Group. The criterion for
priority was very broad (value to science), and the participants (each with one vote) represented a wide
array of interests and perceptions. Therefore, the primary value of the prioritization is that it ensured
that only the highest priorities would emerge, rather than to compare the value of a project of rank 3
versus rank 6.
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As mentioned, each workgroup has a subsection. There was no time available (nor an attempt)
to prioritize among the groups because of the desire to focus effort on identifying analysis needs rather
than polishing suggestions. The reader will notice some actual and apparent overlaps across the
groups. Useful merging will be accomplished in the ensuing ORD strategy. The reader also will see
that there are inputs (e.g., databases, questionnaire results) common to many projects.
4.2 ASSESSMENT GROUP
The assessment breakout group will focus on analyses that will result in descriptive statistics for
questionnaire and measurement data, comparisons among the NHEXAS and other studies, aggregate
exposure estimates, cumulative risk estimates, and identification of relative contributions of pathways to
exposure.
4.2.1 SAB Comments
In their review of the NHEXAS pilot projects, the SAB made several comments regarding the
use of NHEXAS data in exposure assessment; these are presented below.
(1) Key elements of the strategic plan for data analysis should include...critical evaluation of the
potential value of meta-analysis across the three subcomponents of NHEXAS, development of a
plan for any meta-analysis, and, finally, the identification of findings of considerable importance to
help EPA in some current risk management efforts (the early analysis of the NHEXAS data
suggest that there may be findings of this nature) [3.2.2.a, items 6 and 7]1
(2) Once descriptive and summary statistics have been completed, concentration data should be
transformed into exposure data.... Further work needs to be done to integrate total exposures
from all media and to estimate long-term exposures from short-term measurements. [3.2.2.d]
(3) In the near term, prototypical analyses of exposure and assessments of intervention strategies
should be made for a variety of chemicals measured in the NHEXAS pilot program. [3.3.1.a]
'Numbers in brackets are cross-references to section in the SAB report.
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(4) The IHEC recommends the following to improve the quality and utility of the databases from the
three pilot studies [3.3.1.b]:
the databases from Arizona and Region V should be integrated in some fashion;
the NHEXAS researchers should assess the implications of the Maryland study for the Arizona
and Region V studies;
the NHEXAS results should be integrated with information on criteria pollutants from fixed site
monitoring stations; and
the databases from NHEXAS and the National Health and Nutrition Examination Survey
(NHANES) should be cross-referenced in a fashion that fully takes advantage of the
complementarity of the data.
(5) The EPA should use the NHEXAS data to assess source-to-dose trends for chemicals such as
lead, benzene, and PAHs. [3.5.1 .e]
4.2.2 Questions To Address
As a starting point to identify, describe, and prioritize potential projects, the breakout group
should consider the following questions and determine what additional critical questions should be
added.
(1) What exposure assessments should be done using combined data from two or more NHEXAS
studies or combining data from NHEXAS with data from other studies? What comparisons of
results should be made between the NHEXAS studies and other studies, such as the Total
Exposure Assessment Methodology (TEAM) Study and NHANES?
(2) What chemical-specific exposure assessments, identified by target chemicals and routes and
pathways of exposure, should be done? What multipathway assessments should be done?
(3) What exposure assessments should be done for subpopulations represented in the NHEXAS
study?
(4) What multichemical cumulative risk assessments within chemical classes should be done?
(5) What risk assessments should be done comparing risks across chemicals or chemical classes?
(6) What exposure and cumulative risk assessments should be done to examine trends in exposure
concentrations, estimated doses, body burden, and source contributions to dose?
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(7) What analysis of NHEXAS data should be done to provide distributions of exposure factors for
use in assessments?
(8) What, if any, exposure assessments of intervention strategies should be done comparing NHEXAS
data with existing preintervention data.
(9) What exposure and risk assessments should be done to help prioritize EPA program activities?
4.2.3 Discussion Considerations
(1) What are the appropriate methods for combining NHEXAS data for different exposure pathways
and exposure routes? Consider methods such as exposure models, probabilistic assessment, and
physiologically based pharmacokinetic models.
(2) How should the high end of distributions such as an exposure concentration or an intake (above
about the 90th percentile) be treated, given that, at best, the samples are large enough to estimate
the 90th percentile? Can this limitation be overcome by combining data sets?
(3) Are the data for a particular chemical sufficient to support a given exposure or risk assessment? If
the data are not sufficient, what other data are available to fill data gaps?
(4) How should NHEXAS data across the consortia be treated in an exposure assessment of a
common target chemical, such as lead? Should data sets be combined or treated separately?
(5) How does one conduct a multichemical assessment? How are the outcomes of the assessment put
on a common basis so that they can be combined and compared?
(6) How are biological data used in exposure and risk assessments?
(7) How should temporal variability be treated in exposure and risk assessment? What is the
appropriate exposure duration over which exposure can be assessed? How can NHEXAS data
be used to assess acute, subchronic, and chronic exposures, and what are its limitations?
(8) How can uncertainty and variability in exposure and risk assessments be characterized using
NHEXAS data?
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4.2.4 Brainstorming List of Projects
The following is an unranked list of 29 assessment projects proposed by the Assessment Break-
Out Group on July 27, 1999. On July 28, the group combined this list into 13 projects for
development; no areas were eliminated from consideration. The numbers in parenthesis following the
titles are cross-references to the projects in Section 4.2.5.
1. Investigate the use of food frequency data to complement such surveys as the U.S. Department of
Agriculture (USDA) food consumption surveys. (A10)
2. Compare exposure assessments from the duplicate diet study with assessments based on the
traditional diary/recall data and residue databases. (A10)
3. Develop population distributions from NHEXAS data. Include distributions to the total population
and for selected subgroups. (A2)
4. Compare NHEXAS biomarker information to similar information from other studies (e.g.,
NHANES). (A2)
5. Look at correlation between blood levels and air levels of contaminants from Arizona and Region
V studies. (A5)
6. Use NHEXAS to assess risks, compare risks, and set priorities. Determine the contribution of
specific sources, pathways, and routes to risks (e.g., lead versus organophosphates). (A6a)
7. Comparison of questionnaire data to biological data. Use for factor analysis to determine the most
important determinants of exposure. (A5)
8. Use of questionnaire data to screen for highly exposed subgroups. (Al 1)
9. Use diary and time/activity data to assess the association between exposure and repeated versus
infrequent activities. (A6b)
10. Where complete data for an individual exists, correlate activities with exposure (look at space and
time). (A6b)
11. Does integrated personal inhalation exposure correlate with area compliance monitoring? (A9)
12. Determine the relationship between indoor and outdoor exposure. Develop a distribution of ratios
of indoor to outdoor. Compare ratios to other studies. (A9)
13. Determine if there is a good tracer chemical for tracking ambient to indoor exposure. (Al 1)
14. Determine highly exposed groups for specific and multiple chemicals. (A5)
15
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15. Can exposure factors from NHEXAS questionnaires be generalized (e.g., incorporated into the
Exposure Factors Handbook)? Look at distributions and point estimates. (A2)
16. Identify behaviors associated with high exposures. (A5)
17. Correlation analysis between activity/climate and water intake. (A6b)
18. Compare Minnesota children to adults in Arizona and Maryland. Are children more highly
exposed to metals and VOCs in Minnesota? (A8)
19. Correlation of mercury in hair and fish consumption, air levels, etc. (A3)
20. Correlation between biomarkers and environmental samplesidentify important media, pathways,
etc. (A3)
21. Preemptive list of caveats, limitations, etc. Uncertainties. (A2)
22. Can NHEXAS data be used to develop behavior scripts (scenarios)? (A6b)
23. Comparison of methods among the three components of NHEXAS. (Al 1)
24. Compare a cumulative exposure (as measured by biological samples) to co-occurrence in media.
(Al, A3, A6a)
25. Temporal comparisons, geographic comparison, relationship to sources (indoor and outdoor).
(A4, A12)
26. Appropriate averaging timeextrapolations using Maryland study to build a temporal model and
extrapolation model. (A4)
27. Temporal variability in total exposure. (A4)
28. Temporal comparisons with attention to interventions implemented before NHEXAS. (A13)
29. Comparison of questionnaire results to past studies such as TEAM to see if there are trends in
activity (e.g., what is causing increases in asthma?). (A13)
4.2.5 Project Descriptions
[Note: Projects identified with "a" or "b" are tied for ranking (e.g., A6a and A6b), and the top five
projects are clearly of higher priority than the last three projects.]
16
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Project Name:
A-l. Analysis of the Joint Distributions (Co-occurrence) of
Chemical Exposures
Short Project
Description:
Using data on individual chemical species in personal air, dust, dietary, and biological
samples (each analyzed separately), use multivariate statistical methods to determine whether
concentrations co-vary across subjects for different chemicals or not. If not, identify groups
of chemicals that vary together across the population and/or that cluster together in upper
percentiles of exposures (e.g., upper 10th, upper 25th, depending on availability of data), and
analyze the ability of questionnaire-based variables to predict whether a person falls in the
upper tail of the joint distribution.
Goal/Objective:
(1) Where feasible, combine data on individual chemical species across the three NHEXAS
sites for personal air, dust, dietary, and biological samples.
(2) Test whether the distributions of individual chemical exposures correlate with one
another across the pooled population.
(3) Using factor analysis and discrete multivariate methods (for measurements and strata,
respectively), identify groups of chemicals that vary jointly.
(4) Analyze whether there are questionnaire-based variables that can predict high-end, joint
multichemical exposures.
Significance of
Project:
A key question in assessing risks of environmental exposures is whether distributions across
people in exposures to chemicals A, B, C, ... are independent of one another, or whether,
instead, the distributions are correlated? That is, are there individuals who fall in the upper
tails of more than one chemical exposure distribution, or, put another way, are there groups of
chemicals that tend to rise and fall together across the population? If so, this would have
important implications for risk assessments addressing cumulative exposures.
Suggested
Approach:
(1) Using pooled data (if possible) across NHEXAS studies, construct bivariate correlation
matrices for all chemicals analyzed. Construct separate tables for personal air, dust, diet,
blood, and urine data.
(2) Carry out factor analyses to identify groups of chemicals that vary together across the
population.
(3) Dichotomize exposure distributions into 90th percentile or not. Analyze whether
assignments are correlated across chemicals.
(4) Characterize the chemical groupings, if any, and use regression analysis to identify
predictors of high joint exposures.
Data or Input
Needs:
Chemical-specific concentrations measured in personal air, dust, diet, blood, and urine
samples from the three NHEXAS pilots.
Feasibility
(of analyses with
current
NHEXAS
databases):
High feasibility. This analysis exploits the rich data on multiple chemical exposures provided
in the NHEXAS database. Each consortium will be developing summary statistics for its data,
which will be used in this project.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
Month
0-6
9
18
24
Research Outputs
(1) Initiate project: Assemble, combine, check data from three sites
(2) Initial descriptive analyses including bivariate correlations
(3) Complete multivariate analyses
(4) Final outputs: Report and publish
17
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Approximate
Level of Effort:
% Time
10-20
100
Month
s
24
24
Type of Expertise Needed
Principal investigator (exposure assessment/biostatistics)
Post-doc or doctoral student trained in exposure assessment and
biostatistics
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: Many scientific issues must be dealt with (e.g., things may be correlated, but is there a causal
relationship?), and issues related to different sampling protocols may arise.
Project Name:
Short Project
Description:
A-2. Univariate Statistics for Use in Exposure and Risk Assessment
Develop univariate descriptive statistics (distributional information) forNHEXAS data that
can be used broadly in exposure and risk assessment.
Goal/Objective:
To provide risk assessors and other users with information for use in exposure and risk
assessment and in the design of human health effects studies and to compare NHEXAS
results to other existing relevant study results.
Significance of
Project:
Exposure and risk assessors use estimates of various exposure concentrations and "exposure
factors" in their calculations of exposure and risk. These are quite often point estimates or
distributions from very limited data sets. The data collected by NHEXAS can be used to
better define distributions of these concentrations and exposure factors (e.g., activities, time
spent in specific locations, dietary intake, product use). This will reduce the uncertainty
associated with these assessments. Major users of this information will be risk assessors in
EPA, other federal agencies, industry, academia, and state and local governments, as well as
epidemiologists and other health effects researchers who need to classify members of a
cohort based on exposure.
Suggested
Approach:
Work with EPA/NCEA to identify factors and point estimates that commonly are used in risk
assessment and for which data were collected in one or more of the NHEXAS pilots. Develop
summary statistics (including distributional information) for these data. These analyses
should include distributions for the total population and for selected subgroups where the
data will allow. These should be suitable for inclusion in EPA guidance, such as the
Exposure Factors Handbook. These analyses should identify the appropriate caveats,
limitations, and uncertainties associated with the data and resulting statistics. The results
should also compare the statistics with similar information from other studies (e.g., NHANES,
TEAM).
Data or Input
Needs:
The activity and concentration data collected by all NHEXAS pilot studies.
Summary descriptive statistics.
Meta-data to understand caveats.
Other data sets (e.g., NHANES, TEAM, Exposure Factors Handbook).
Feasibility
(of analyses with
current
NHEXAS
databases):
This is highly feasible with NHEXAS data. Each consortium will be developing summary
statistics for its data. It should be feasible to identify factors for inclusion in EPA guidance.
Approximate Project Time Table and Level of Effort
18
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Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
% Time
5
10
100
100
0
6
12
24
Month
s
24
24
24
24
Research Outputs
(1) Initiate project
(2) Scoping description and project plan
(3) Provide statistics to EPA, including descriptions of the data and its
limitations for use in risk assessment
(4) Revision of Exposure Factors Handbook
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Senior statistician
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: Significant ORD involvement will be needed on this project.
Project Name:
Short Project
Description:
A-3. Aggregate Assessment
This project will estimate aggregated exposures from all media and all pathways for a sinj
chemical using environmental concentrations and biological testing results.
lie
Goal/Objective:
(1) Identify the important media, pathway, and routes that contribute the most to total
exposure;
(2) Identify or develop methodologies (or models) to analyze the relationships between
biological testing results (i.e., blood and urine samples), environmental and personal
concentrations, and exposure/dose.
(3) Investigate correlation between exposure (dose) via single pathways and total exposure
(dose).
Significance of
Project:
(1) Address the important regulatory issues associated with single- and multimedia exposures
(e.g., air, water, and contaminated soil or food).
(2) Advance the exposure assessment methodology (multimedia and multipathways).
(3) Help EPA to prioritize resources to address the most important media or pathways and to
design intervention strategies to protect public health.
Suggested
Approach:
(1) Look at correlation between biomarkers (blood and urine concentrations) and
environmental concentrations (e.g., correlation between blood levels and air levels of
contaminants from Arizona and Region V studiesindoor, outdoor, personal (e.g.,
correlation of blood lead and concentrations in house dust and soil).
(2) Identify or develop an aggregate model structure to assess the exposure for an individual
(multimedia, multipathways). The Department of Energy has developed several multimedia
exposure models for its dose reconstruction projects. It is suggested that those models be
reviewed for this project's use.
(3) Identify exposure factors from questionnaires (e.g., intake rates).
(4) Calibrate models using NHEXAS data; therefore, the models can be used in the future.
(5) Evaluate uncertainties and limitations associated with methodologies, data, and models.
19
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Data or Input
Needs:
(1) Environmental concentration data in all media.
(2) Total biological testing data.
(3) Exposure pathways and routes associated with each media.
(4) Coefficients (e.g., uptake rates, absorption rates).
Feasibility
(of analyses with
current NHEXAS
databases):
(1) Adequate environmental concentration data.
(2) Biological testing results.
(3) Knowledge about correlation between media concentrations and biological results.
Therefore, this project can only be done for the chemical that has the above information.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
%
Time
60
80
100
0
18
12
Month
s
30
30(2)
30(2)
Research Outputs
(1) Initiate project: Identify NHEXAS target chemical to be studied,
conduct literature search, assemble data, and design study
(2) Develop and calibrate probabilistic aggregate exposure model; develop
regression models to assess correlations between biological and
environmental measurements
(3) Final outputs: Exposure assessment, including uncertainty analysis
and contributions of various pathways to total exposure
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
A-4. Temporal Variability in Exposure Concentrations and Aggregate
Exposure Using NHEXAS Data
Short Project
Description:
Analysis of NHEXAS databases to determine the temporal components of variability in
various measures of exposure. The analysis will include both single-medium, single-pollutant
class analyses, as well as total or aggregate exposure estimates over all media.
Goal/Objective:
To determine optimum strategies and designs for future NHEXAS national investigations.
Questions to be addressed include when is it possible to estimate exposure from a single set
of cross-sectional measurements, and what is the optimum number of such measurements that
must be made for each pollutant medium class and for total exposure? Of interest is an
understanding of the temporal span of the toxicological effect (i.e., what is the exposure
duration of interest and does variability occur over such time spans?).
20
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Significance of
Project:
A future national investigation of exposures must be designed to assess exposures to
members of the population that are accurate and reflect patterns and variability present in true
exposures. Improved understanding of temporal variability across days, weeks, and seasons
is necessary to ensure good estimates. This project has important implications for risk
assessment because it will help account for uncertainty because of statistical "compression"
of chronic exposure distributions compared to single-measure exposure distributions because
of intraindividual correlations of exposure over time. It also has implications for epidemiology
because it will help reduce uncertainty because of misclassification resulting from bias
introduced by failing to account for temporal variability in exposure indicators.
Suggested
Approach:
(1) Descriptive analysis of exposure concentration distributions by time period.
(2) Use statistical techniques to assess population variability and test whether the
population means vary over the duration of the studies.
(3) Assess intraindividual temporal variability.
(4) Evaluate aggregate exposure by summing potential or absorbed doses, as appropriate
(with appropriate weighting for time, etc.), over individual pathways.
(5) Evaluate temporal variability in total exposure.
(6) Assessment of intraindividual variability versus temporal variability in total exposure.
(7) Assess statistical strategies for determining optimum sample number for temporal
variability.
(8) Implement chosen strategy to determine optimum number of exposure measures to
determine exposures of fixed length.
Data or Input
Needs:
Repeated measurement exposure data for all studies, particularly the NHEXAS-Maryland
investigation, identified with specific individual identifiers and temporal spacing. Certain
questionnaire data to identify changes in exposure patterns attributable to other-than-usual
exposure variability (e.g., a change in job status or introduction of anew source into the
home).
Feasibility
(of analyses with
current
NHEXAS
databases):
Data exist in the NHEXAS-Maryland study and, to a limited degree, in the other studies, that
would allow this to be completed. Repeated measurement data are available for most media in
the Region V study. Sample sizes of 2 to 6 repeated measurements are available.
21
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Project Name:
A-4 (cont'd). Temporal Variability in Exposure Concentrations and
Aggregate Exposure Using NHEXAS Data
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
Month
% Time
10
100
100
0
3
12
15
18
18
21
24
Month
s
24
24
24
Research Outputs
(1) Initiate project
(2) Prepare databases for analysis of temporal variability
(3) Perform univariate temporal analyses of selected pollutant-class/-
medium combinations
(4) Construct aggregate exposure estimates
(5) Evaluate temporal variability in exposure estimates for tar§
chemicals
5et
(6) Construct optimum sampling strategy for target chemicals
Final outputs:
Intermediate manuscripts on univariate temporal variability
Manuscripts on aggregate exposure variability and optimum sampling
strategy
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: Information on seasonal trends in environmental concentrations (indoor, outdoor) might help to explain
temporal variability.
22
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Project Name:
A-5. Identifying Predictors of Exposure
Short Project
Description:
To identify primary predictors of exposure, using questionnaires and biological or
environmental measures for use in epidemiology studies and other studies where individuals'
exposure levels are sorted into categories such as high, medium, and low.
Goal/Objective:
Classification of individuals (and populations) into exposure categories for use in
epidemiologic studies and risk assessment. Two products: (l)identify primary predictors of
exposure for epidemiologic exposure assessment and (2) identify potentially highly exposed
populations for future health effect studies or risk management.
Significance of
Project:
Epidemiologists, risk assessors, and risk managers need the ability to classify people into
exposure categories. EPA, ATSDR, CDC, NIEHS, and the National Institutes of Health all
could use this information.
Suggested
Approach:
Using the available NHEXAS data, including questionnaire, biological marker, and
environmental data, prioritize chemicals based on the population prevalence or toxicological
importance. For the chemicals (or chemical class), construct regression models to identify the
predictors of exposure. These analyses should identify which questions predict measured
exposure, both biological and environmental. Factor analysis or principal components
analysis should be used to identify the most important questions that predict chemical
exposure. NHEXAS data should be analyzed to determine how well the environmental data
predict exposure and how well questionnaire and environmental measures predict exposure.
Predictive models should be developed that can be used in subsequent studies. Key issues
would be accurate separation of the population into low, medium, and high categories and
development of models to identify highly exposed individuals. Ultimately, efforts should be
made to attempt, on an overall basis, to identify which questions identify individuals who are
highly exposed to many chemicals and those that are specific for one chemical or one
chemical class. Risk managers and study designers will be able to use the results of this
analysis to identify sample collection strategies by incorporating predictive ability of the data
from each source (questionnaire, biological, and environmental) and the cost to collect and
analyze data collected via these methods.
Data or Input
Needs:
NHEXAS data from all study sites (or each individually): questionnaires, biological samples,
and environmental and personal exposure samples. No additional data needed unless
external validation of questionnaire responses is done.
Feasibility
(of analyses with
current NHEXAS
databases):
All data are currently available. Much of the questionnaire data is nominal or ordinal and
may not be well suited for the usual regression approaches.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration"
Month
Month
Month
% Time
20
50
0
24
36
Month
s
36
36
Research Outputs
(1) Initiate project: Assemble data and priorities
(2) Preliminary analyses by chemical/chemical category
(3) Final outputs: Identification of potentially highly exposed
individuals and tools to identify them
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
23
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100
36
Junior-level staff ("assistant", technician), students (2 to 4)
(programmers, epidemiologists, environmental scientists, statisticians)
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
24
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Project Name:
A-6a. Comparisons of Pollutants and Pathways Driving Cumulative Risks
Short Project
Description:
Assess cumulative risks of various health effects associated with aggregate exposures
measured in NHEXAS projects to compare the relative significance of various pollutants and
pathways.
Goal/Objective:
To prioritize pollutants and pathways as to their contribution to cumulative risk of various
health effects to focus pollution control and other public health activities on higher risk
contributors.
Significance of
Project:
The results of this project will assist public health agencies (national, state, and local) in
effectively and efficiently targeting resources to control pollutants and pathways of higher
risk. This project, in conjunction with Al and A3, will begin laying the foundation for EPA
efforts in cumulative (multistressor) risk assessment.
Suggested
Approach:
(1) Perform cumulative risk assessment of chemical exposures for individual study
participants measured in NHEXAS projects (Use existing EPA guidance and scientific
understanding for assessment of mixtures of stressors).
(2) Characterize relative contributions to cumulative risk of individual pathways and
pollutants per participant and describe distributions across study populations. Report
relative contribution of individual pathways and pollutants for representative low-end,
average, and high-end NHEXAS subjects.
(3) Develop relative ranking of pathways and pollutants in terms of contribution to
cumulative risk; identify key driving pathways and pollutants.
(4) Compare across studies.
Data or Input
Needs:
Exposure measurements from NHEXAS studies.
Population descriptions (e.g., body weights, ages, food intakes, etc.) from NHEXAS studies.
Toxicity data.
Feasibility
(of analyses with
current NHEXAS
databases):
Limitations include number of pollutants for which quantitative dose-response values are
available. Initially, the project probably would consider those chemicals with common health
endpoints or modes of action. Also assumptions on nondetects will have to be made (e.g.,
evaluate using nondetects set to zero versus set to one-half the detection limit (DL) versus
omitting large nondetect chemicals from analysis). Cumulative risks would be assessed for
variety of health endpoints.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
% Time
10
0
24
Month
s
24
Research Outputs
(1) Initiate project
(2) Final outputs:
Multipathway, multichemical assessments with estimates
total risk
of
Comparison of multichemical risk via single pathways, with total
risk for selected NHEXAS compounds
Comparison of risk via single chemical with total risk from
selected NHEXAS compounds
Type of Expertise Needed
Principal investigator
25
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25
100
24
24
Senior-level staff ("associate")
Junior-level staff ("assistant", technician),
students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name: | A-6b. Use of NHEXAS Data To Test Assumptions about Activity Pattern
Factors and Other Exposure Factors in EPA Risk Assessments
Short Project This project encompasses a series of individual projects that will examine the use of activity
Description: pattern factors and other exposure factors in EPA risk assessments as they are done in the
Air, Water, Hazardous Waste, Pesticides, and Toxics Programs. Examples of tasks under this
project area were raised at the workshop and include the following: (1) examine NHEXAS
time/activity diaries and follow-up questionnaire data to determine the repetitiveness
(frequency) of behavior over a 6- or 7-day period and compare to existing time/activity
databases used to evaluate factors in EPA assessments, (2) examine the relationship between
climate, season, level of exertion, and drinking water intake, (3) prepare exposure scenarios,
evaluate scenarios with NHEXAS data, and compare those results to results obtained using
current exposure assessment methods, scenarios, and assumptions as they are used in EPA
programs, and (4) use NHEXAS data to design scripted sampling protocols for subsequent
model testing or trend monitoring.
Goal/Objective: Current regulatory exposure models in the Air, Water, Hazardous Waste, Pesticides and
Toxics Programs often use default values that are based on limited and perhaps
unrepresentative data. Often, assumptions are used to fill data gaps. NHEXAS data will be
used to test assumptions and scenarios used in current assessment procedures, to improve
the current EPA methodologies, and to identify factors where further study is needed.
Significance of
Project:
Suggested
Approach:
Data or Input
Needs:
Feasibility
(of analyses with
current
NHEXAS
databases):
The results of this project area will be useful to any program office that does assessments
that rely on factors on which data were collected in the NHEXAS study. These include all
EPA programs Air, Water, Hazardous Waste, Pesticides, and Toxics.
These are examples provided by members of the Assessment Breakout Group: compare 6-day
sequences of individual time/activity patterns to 6-day sequences of daily patterns
stochastically chosen from multiple individuals to determine impacts and frequency of
repeated activities. Assess relationships of individual time/activity patterns to food and
water ingestion across subject classes (e.g., age, gender, race) and local climate conditions.
Compile individual time/activity and exposure data for subjects with complete data sets as
input for exposure model testing and validation. Compile behavioral scenarios characteristic
of more highly exposed subjects for use in developing scripted sampling protocols in
subsequent exposure model testing and analysis.
Individual time/activity data and exposure measurements from NHEXAS and other
appropriate comparative databases (e.g., time/activity, local meteorological data.)
Feasible. NHEXAS data set contains data on activity patterns, exposure factors, varying
climates, and the like that can be used to test and refine current EPA assessment methods.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Research Outputs
26
-------
Approximate
Level of Effort:
Year
Year
Years
% Time
25
25
50
2001
2003
18 mo
Month
s
18
12
18
(1) Initiate project: Identify issue to be studied, conduct literature
search, assemble data, and design study
(2) Conduct analysis
(3) Final outputs: Journal article comparing frequency and duration of
various activities over 1-day and 7-day periods in NHEXAS with
data collected in other activity pattern surveys
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
A-8. Comparison of Children's and Adults' Exposures to Pesticides and
Other Chemicals in the Region V, Arizona, and Maryland Studies
Short Project
Description:
Compare children's and adults' exposures to pesticides, VOCs, metals, and PAHs, using
biomarker and environmental data collected in the Minnesota Children's Pesticide Exposure
Study, Region 5 study, and Arizona and Maryland studies. Data from the children's studies
in Arizona and Washington also may be compared as they become available.
Goal/Objective:
To determine if children's exposures differ or do not differ from adults for pesticides and
other NHEXAS chemicals.
Significance of
Project:
Children have been identified as a potentially vulnerable subpopulation for exposure to
pesticides and other chemicals (e.g., lead). NHEXAS data may be used to better understand
differences between adults and children's exposures and, ultimately, to determine if federal
and state regulatory policies adequately protect children.
Suggested
Approach:
(1) Determine what data may be compared (see limitations below).
(2) Develop a set of consistent procedures for analyzing the data across studies to take into
account between-study differences (e.g., methods for handling values below the
detection limit, methods for handling nonnormal distributions, methods for data sets with
a large number of values below the detection limit).
(3) Compare children's and adults' exposures (where appropriate). Focus on biomarker data
(urine and blood) and then expand to diet, personal air, and other measurements.
(4) Assess health risks for children and adults using appropriate toxicity values (e.g., RfDs,
RfCs, cancer potency slopes). Compare health risks for adults and children.
Data or Input
Needs:
Data may be used from the Minnesota Children's Pesticide Study, the Region V study, and
the Arizona and Maryland studies. Data from the children's studies that are being
conducted in Arizona and Washington also may be included (as the data become available).
27
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Feasibility
(of analyses with
current NHEXAS
databases):
Data between these studies may not be comparable because of differences in types of
measurements (chemicals and media), detection limits, methods or strategies of collection,
methods of analysis, and spatial and temporal factors. Consistent procedures for data
analysis must be developed for comparisons to be valid. Data are available on children for
metals and VOCs as well as pesticides. Also need to consider the effects of regional
differences on differences between children and adults in different regions. Child subjects in
the Region V and Arizona studies possibly might be used to address this, but there may be a
limitation based on the number of children in those two studies (about 15%).
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
%
Time
25
50
100
0
24
Months
24
24
24
Research Outputs
(1) Initiate project
(2) Final outputs: Assessment comparing total exposure (dose)
children in the Minnesota study to total exposure (dose) for
in Region V or other appropriate studies
for
adults
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
28
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Project Name:
A-9. Indoor, Outdoor, and Personal Air Relationships
Short Project
Description:
This project will evaluate the relationships between indoor and outdoor air concentrations
and personal air exposure measurements. Results of these evaluations will provide
information to be used in modeling human inhalation exposures to indoor and outdoor
sources for use in air pollutant risk assessments (single- or multipollutant). These
assessment results will inform public health agencies in evaluating the need to reduce
emissions, as well as in prioritizing air pollutants, with regard to relative risks posed by
various air pollutants and indoor/outdoor exposures, for the various agencies and offices
involved in communicating potential risks and protecting public health.
Goal/Objective:
(1) Evaluate indoor/outdoor air concentration relationships (categorized as appropriate
[e.g., urban versus nonurban, seasonal, regional, climatic]) for use in inhalation
exposure modeling.
(2) Characterize relationship between outdoor air concentrations and indoor air
concentrations and personal inhalation exposures and identify key variables affecting
these relationships.
Significance of
Project:
Assessments of human health risk from indoor and outdoor air pollutants rely heavily on
inhalation exposure modeling. Information on the outdoor contributions to indoor air
levels are sorely lacking; consequently, assumptions are made (e.g., extrapolation from
fixed monitors and air quality models to indoor air concentrations). Additionally,
characterization of indoor air pollutant exposures are needed for comprehensive inhalation
route risk assessments. This information also is needed to evaluate the uncertainty in
exposures in epidemiology studies implicating PM as a cause of adverse effects.
Information on the relationship between indoor, outdoor, and personal air concentrations
will be used to test assumptions about exposure levels based on fixed monitors.
Suggested
Approach:
(1) Perform pollutant-by-pollutant and multichemical pairwise analysis of outdoor and
indoor concentrations, outdoor concentrations and personal exposures, and indoor
concentrations and personal exposures.
(a) subdivide analyses via spatial/source considerations (e.g., urban/rural,
smoker/nonsmoker) that are key drivers of pairwise relationships.
(2) Develop pollutant-by-pollutant distributions of indoor/outdoor concentration ratios,
(a) subdivide distributions based on spatial/source considerations (e.g., urban/rural,
smoker/nonsmoker).
(3) Identify fixed monitors in study sites and evaluate correlations of study measurements
(outdoor, indoor air, and personal exposure) to fixed monitor measurements in each
study area.
(a) identify variables that may play a role in variation in these relationships (e.g.,
urban/rural, etc.).
Data or Input
Needs:
NHEXAS: Indoor air measurements
Outdoor air measurements
Personal exposure measurements
Some activity data to help understand personal exposure data (e.g., time
outdoors, time indoors, time near particular sources)
Sample dates, geographic locations, sampling protocols
Other: Fixed air monitor sites and data in study site
Feasibility
(of analyses with
current NHEXAS
databases):
Good, assuming the availability of sets of measurements with sufficient percentage of
samples above the detection limit where the same particle size fraction was collected.
29
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Project Name:
A-9 (cont'd). Indoor, Outdoor, and Personal Air Relationships
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
Month
Month
% Time
10
10
200
0
Months
18
18
18
Research Outputs
(1) Initiate project
(2) Relationships (e.g., pairwise analyses)
(3) Identification of fixed monitors, categorization of data via
important variables (e.g., smoker/nonsmoker, urban/rural, etc.)
(4) Final outputs: Pollutant-by-pollutant indoor: outdoor ratios
(5) Final comprehensive report/papers
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
30
-------
Project Name:
A-10. Comparison of Traditional Indirect Method of Estimating Dietary
Exposures to NHEXAS Duplicate Diet Data
Short Project
Description:
Comparison of exposure data from NHEXAS duplicate diet measurements with exposure
estimates indirectly derived based on combining food intake rates and data on
concentrations of NHEXAS chemicals in food from studies such as the Total Diet Study
(IDS). Also compare food intake rates from NHEXAS questionnaire surveys with those
from USDA and NHANES food intake surveys of comparable years, geographical regions,
and population subgroups
Goal/Objective:
Compare dietary exposure estimates from the dietary exposure model (i.e., concentration in
food x reported food consumption rates) with direct measures of dietary exposure obtained
from NHEXAS duplicate diet sampling.
Significance of
Project:
Dietary exposure based on the indirect method of combining food intake with residue data
has been the cornerstone of many pesticide regulations. In addition, estimates of human
exposure to metals and other chemicals through food consumption have been based on
this indirect approach. Although this model approach to dietary exposure assessment is
widely used, validation of such estimates with real monitoring data have not been done.
NHEXAS data provided an opportunity for such validation to enhance the scientific bases
for decision making. Such validation would help to direct future efforts in dietary exposure
assessment.
Suggested
Approach:
(1) Code food intake data from NHEXAS food diary or food checklist into formats that are
consistent with USDA food codes.
(2) Compare NHEXAS food intake rates with those from USDA and NHANES for
comparable time frames, regions, and population subgroups, including evaluation of
weighting for nonresponse, single-day intakes versus averaging intake over several
days (where data allow such evaluation).
(3) Estimate exposure based on consumption data and residue data from FDA IDS, USDA
Pesticide Data Program (PDF) data, NHEXAS Maryland minimarket basket survey, and
other existing residue data.
(4) Estimate exposure using NHEXAS food diary or checklist data and existing
concentration data from other sources and compare results with results obtained with
indirect method across population subgroups.
(5) Estimate exposure using NHEXAS duplicate diet measurements and compare these
results with results obtained from indirect method across population subgroups.
Data or Input
Needs:
NHEXAS food diary and checklist data and duplicate diet data from each study. USDA
and NHANES food intake data and codes. USDA and Food and Drug Administration
(FDA) food contaminant data. The food diaries have not been coded and it may not be
possible to code to all the USDA codes. The food checklist is limited to 100 to 200 food
items. The big discrepancy between number of items that could make cross-coding
difficult.
Feasibility
(of analyses with
current NHEXAS
databases):
The duplicate diet studies and diet questionnaires were administered to a sufficiently large
number of individuals in the Region V and Arizona studies to support these analysis. In
addition, the Maryland data obtained food intake longitudinally to allow an in-depth
comparison of short- and long-term average intake.
-------
Project Name:
A-10 (cont'd). Comparison of Traditional Indirect Method of Estimating
Dietary Exposures to NHEXAS Duplicate Diet Data
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
Month
Month
Month
% Time
15
35
50
0
6
9
12
18
24
Months
24
24
24
Research Outputs
(1) Initiate project
(2) Harmonizing food codes between NHEXAS, USDA, and
NHANES
(3) Compare food intake rates between the various surveys
(4) Estimate exposure based on intake rates and residue data
(5) Compare exposure from NHEXAS duplicate diet studies with
those obtained from indirect method
(6) Final outputs:
Report consistency or inconsistency between the two
approaches and identify approaches (if any) to improve the
indirect method of estimating dietary exposure
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
32
-------
Project Name:
A-ll. Improved Methods for Collecting Data for Exposure Assessments
Short Project
Description:
Compare or link methodologies and results between and within the NHEXAS studies to
determine potential improvements in techniques or procedures currently used in human
exposure studies.
Topics include (but are not limited to):
(1) establish potential for NHEXAS chemicals to be used as tracers to indicate the
contribution of ambient air to indoor air concentrations,
(2) evaluate questionnaire implementation procedures,
(3) evaluate environmental and biological sampling, and
(4) evaluate food frequency survey methodology and compare to national food consumption
methodology.
Goal/Objective:
Significance of
Project:
To improve current techniques or procedures used to measure human exposure and the
factors that contribute to exposure.
Critical to designing future studies using more cost effective methods.
Suggested
Approach:
(1) For chemicals with only outdoor sources, determine (model) how indoor concentrations
relate to outdoor sources. Establish potential for these chemicals to be used as tracers to
determine the contribution of ambient air to indoor air concentrations.
(2) Compare across and within the NHEXAS studies, the study design, incentives,
procedures used to implement the questionnaire, and the like. Evaluate differences and
similarities in response rate and reliability of responses in relation to procedural
differences. Evaluations should consider regional, socio-economic, education and other
demographic issues as appropriate.
(3) For contaminants or biological factors tested in more than one study, compare any
differences in methodology or implementation techniques and evaluate how these
differences may have positively or negatively impacted results.
(4) Investigate the use of the food frequency data from the NHEXAS study as a bridge with
the USDA food intake data and data from future surveys to improve the information
available for estimations of food intake.
(5) In the Maryland study, evaluate whether participants improved in filling out
questionnaires through repetition or deteriorated as a result of fatigue.
Data or Input
Needs:
(1) Basic distribution statistics of NHEXAS data.
(2) Full procedural descriptions of each study.
(3) Meta data for NHEXAS (sampling and analytical protocols, study designs, etc.).
Feasibility
(of analyses with
current
NHEXAS
databases):
High
Approximate Project Time Table and Level of Effort
Time Table:
Duration"
Month
Month
Month
0
6
12
Research Outputs
(1) Initiate project: Identify issue to be studied, conduct literature
search, assemble data, and design study
(2) Conduct analysis
(3) Final outputs: Journal article (e.g., an article discussing the utility of
various NHEXAS analysis to serve as tracers to quantify the
infiltration of outdoor air to the indoor environment)
33
-------
Approximate
Level of Effort:
% Time
25
100
Month
s
12
12
Type of Expertise Needed
Principal investigator
Senior-level staff (
Junior-level staff (
'associate")
'assistant", technician), students
Other (describe):
Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
A-12. Spatial Variability
Short Project
Description:
NHEXAS data will be used to investigate spatial variability in concentrations, doses, and
activity patterns. Possible areas of investigation include different states and counties, rural
versus urban areas, locations near sources, and different climates and elevations.
Goal/Objective:
The goals of this research are to identify spatial and geographic factors contributing to high
exposures for consideration in exposure assessment, to determine representativeness of
local/regional data for use in assessments of other regions, and to identify geographically
defined point and area sources.
Significance of
Project:
These analyses will help assessors understand the geographic variability of pollutant
concentrations and exposures and the impacts of such things as population density, climate,
elevation, and local cultural factors. It also will examine the impact of identifiable,
geographically located sources on exposure levels. Information on spatial variability also will
contribute to more efficient design of future studies.
Suggested
Approach:
(1) The following is an approach for comparing different geographical areas: select variables
for comparison (e.g., a particular chemical/media combination), consider differences in
sampling methodology that could account for differences between NHEXAS studies,
account for confounding factors, and make statistical comparisons of distribution
parameters.
(2) The following is an approach for analysis of sources: identify potential sources of
NHEXAS chemicals based on other data, such as data in the literature and the EPA Toxic
Release Inventory Data; and perform analysis of correlation of exposure concentrations
and locations of sources using geostatistical methods.
Data or Input
Needs:
(1) Sufficient number of people in each geographic group to make meaningful comparison.
Data set needs to have sufficient percentage of detectable levels of NHEXAS target
chemicals. Sampling protocols and equipment for each location need to be similar
enough so that differences are not attributable to the methods used.
(2) Independent database to provide latitude and longitude and perhaps some estimate of
emissions for target sources. Latitude-longitude and concentration/exposure data for
NHEXAS participants.
Feasibility
(of analyses with
current
NHEXAS
databases):
(1) This study could be done for a few categories (e.g., state-by-state) in Region V. There
may be a problem comparing environmental samples between studies because of different
sampling methodologies. Parameters selected for comparison need to have similar
sampling protocols (e.g., blood, urine, drinking water, etc.).
(2) Data on latitude and longitude of sources is critical as is data on latitude and longitude of
participants (may be available only for Arizona). There also would need to be some
method to protect the confidentially of respondents that could be compromised by
revealing the latitude-longitude of their residences.
Approximate Project Time Table and Level of Effort
34
-------
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
%
Time
10
25
50
0
24
Month
s
24
24
24
Research Outputs
(1) Initiate project: Identify issue to be studied, conduct literature
search, assemble data, and design study.
(2) Conduct analysis
(3) Final outputs: Comparison of measurements, activity pattern
duration/frequency, or total exposures in different geographical areas.
Description of similarities and differences between sampling and
analytical methods of NHEXAS consortia and potential impact on
comparisons of results.
Type of Expertise Needed
Principal Investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
A-13. Analysis of NHEXAS Questionnaire and Activity Diary Data to
Identify Temporal Trends in Behavior and Exposure Patterns
Short Project
Description:
Comparison of NHEXAS activity pattern data to past studies such as TEAM, NHANES,
and the National Human Activity Pattern Survey (NHAPS) to identify any temporal trends
in activity patterns that may be important predictors of changes in exposure patterns over
time.
Goal/Objective:
To identify changes in behavior over time that can explain changes in exposure patterns.
Significance of
Project:
Identifying temporal trends in behaviors that have an impact on exposure can lend insight
into the success of intervention strategies (such as increasing public awareness of
environmental hazards). The SAB/IHEC recommended such evaluations. In addition,
studying temporal trends in behavior and exposure can inform the selection of future
intervention strategies and help to evaluate their performance and ultimate results.
Suggested
Approach:
(1) Use questionnaire and diary data from all studies to develop activity specific
distributions.
(2) Compare activity distributions from the NHEXAS study to past studies, noting any
shifts in important parameters.
(3) Identify factors (qualitative) that could explain the shift in behavior (e.g., a home use
pesticide product was removed from the market between the NHAPS and NHEXAS
studies).
Data or Input
Needs:
Questionnaire and diary data from each of the studies involved in the comparison.
Identification of the codes used for questions that are the same (or similar) in each study.
Feasibility
(of analyses with
current NHEXAS
databases):
Feasibility depends on the availability of similar questionnaire data in the historical studies.
Availability of such data judged to be unlikely. There may be a problem with the timing of
data collection.
35
-------
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
Month
Month
% Time
10
25
50-100
0
6
12
18
24
Month
s
24
24
24
Research Outputs
(1) Initiate project
(2) Build questionnaire databases and develop activity specific
distributions
(3) Make comparisons between distributions and prepare analyses.
(4) Identify factors contributing to shifts in behavior
(5) Final outputs: Produce report documenting temporal trends in
activity patterns that are important for changes in exposure
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), Students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
36
-------
4.3 EXPOSURE ANALYSIS GROUP
This group focused on research that advances the state-of-the-science of exposure analysis. It
covers such issues as descriptive/demographic analyses, associations/models of internal dose,
associations/models of exposure, and methods.
4.3.1 SAB Comments
The SAB identified several issues relating to analyses of exposures and the development of a
strategic plan for data analysis [3.2.2.a]2 that are described below.
(1) Complete quality assurance and quality control (QC) of the study data. [3.2.2.a]
(2) Conduct descriptive analyses.
(3) Test study hypotheses that can be addressed with the collected data. [3.2.2.e]
(4) Evaluate questionnaires and activity diaries and the relationships between these data and
environmental, exposure, and biomarker measurements. [3.2.2(b,c)]
(5) Critically evaluate the potential value of meta-analysis across the three consortia, given limitations
because of differences in study designs and methods. [3.2]
(6) Integrate total exposures across all media, and assess the relative contribution of different sources,
pathways, routes to exposure, and body burden. [3.2.2(c,d,g)]
(7) Estimate long-term exposures from short-term measurements. [3.2.2(d,g)]
(8) Identify factors related to high-end exposures and correlate exposure to various chemicals/classes.
[3.2.2.g]
4.3.2 Questions To Address
As a starting point to identify, describe, and prioritize potential projects, the breakout group
should consider the following question and formulate a list of specific analyses for further discussion.
What analyses need to be done? These might be identified by the types of analyses (or intended
use of the results).
2Numbers in brackets are cross-references to sections in the SAB report.
37
-------
(1) Descriptive (in addition to those conducted by/for each study)
Summary statistics
Distributional analyses (or fitting)
Weighted and unweighted analyses
(2) Comparative
Hypothesis testing (including study design hypotheses)
Exploratory analyses (hypothesis generating)
Results of analyses conducted by each study (combine data sets or results)
Structural (model-based) analyses of exposure (or dose)
Temporal analysis
Within- and between-season (visit, cycle)
(3) Grouping or classification analyses
For future human exposure surveys and epidemiological studies
Identification of factors related to the "high-end" of exposures
(4) Questionnaire analyses
Item analysis (association between responses, reliability)
Internal and external consistency (validity)
Cross-study comparisons
(5) Survey design results
Estimates of variance components (e.g., geographic clustering, correlation between
chemicals/classes and measurements)
Use of variance estimates and design effects to determine sample sizes for estimating median
populations and population subgroup exposures
(6) QA/QC data analyses
Calculation of data quality parameters (e.g., precision, bias, quantifiable limit, or method
detection limit)
Identification of QA goals and performance measures
38
-------
4.3.3 Discussion Considerations
In discussing and developing proposals for the analyses (or projects) identified above, consider
the following questions.
(1) What statistical approaches or techniques could (or should) be used to understand or explore
relationships among the following types of measurements or information?
Environmental/individual characteristics (questionnaires)
Environmental concentrations
Human activity patterns
Human exposures measurements (or estimates) for multiple routes and pathways
Estimates of intake or uptake (dose) that are derived from concentration or exposure
measurements and activity data or exposure factors
Biological markers of exposure (and total absorbed dose)
(2) Which of these are feasible and appropriate, given the understanding of the study and survey
designs?
Types of samples and questionnaire data that were collected in the current NHEXAS projects
Quantity and quality of these results (e.g., based on response and completion rates, and
proportion detectable/measurable)
Limitations for combining data sets (or results) to permit meaningful joint (or meta-) analyses
(3) What are the top priority/most important analyses? These might depend on the intended
application.
For exposure or risk assessments
To advance our understanding of multi-pathway human exposure (and dose)
For designing future human exposure studies
39
-------
4.3.4 Brainstorming List of Projects
Descriptive/Demographic Analyses
Meta-analysis of exposure parameters and biomarkers of dose for children, adults, and elders
Comparing distributions of "total exposure" by population subgroups
Epidemiology of biomarkers, pathways, and media (compare distributions in different subgroups)
Identification of susceptible populations (for high exposure) and comparison with other studies
Spatial and temporal variability in multichemical exposure and risk
Evaluation of upper percentiles in three exposure studies with chemical exposure levels associated with health
effects
Meta-analysis of heavy metal exposures from NHEXAS and other surveys
Comparison of NHEXAS exposure levels with other studies (creation of baseline or benchmark exposures and
reference ranges)
Consistency of demographic data with other representative population surveys
Principle component analysis for grouping biomarker, environmental concentrations, and questionnaire
information
Clustering of exposures from different media (concentrations and questionnaire information)
Associations/Models of Internal Dose
Multivariate analysis of risk factors for internal exposure-demographics, questionnaire data, and measures of
external exposure
Health indicators for differences in exposure
Contribution of environmental media to body burden and clearance of chemical pollutants
Relation of biomarkers of dose to reported illnesses
Associations/Models of Exposure
Association between exposure measurements and housing or activity factors (sources and removal)
Characterization of indoor dust and soil measurements (relationship to exposure)
Multivariate (logit) analysis and comparison of exposure to activity patterns and environmental concentrations
Questionnaire elements that predict high-end exposures
Long-term exposure related to short-term measurements
Multichemical exposures to chemicals with similar mechanism of action and health endpoints
Aggregate exposure to pesticides-ranking of pathways
Population modeling analysis of high-end exposures in Arizona and Region V NHEXAS (for risk assessment)
Methods
Differences and similarities in dietary exposures estimated by the Maryland checklist, compared with the diet
diary and duplicate diet approach
Comparison of duplicate diet measurements with model estimates based on extant food contaminant data
combined with individual consumption
Relation between intra- and interindividual variability in exposure metrics and different time scales; implications
for risk assessment and environmental epidemiology
40
-------
Methods (cont'd)
Comparison of the approaches used to collect longitudinal data, Region V, Maryland)-selection of future
methods
Modeling/estimation of THMs in NHEXAS from the chloroform measurements, based on data from other national
studies
Analysis of the impact of different measurement sensitivity DL or quantitation limit and censored data on
estimates of total exposure
Comparison of modeled to measured estimates of exposure
Critical pathway analysis (risk from exposure) for three studies-how to combine results, findings
Potential use of NHEXAS pilot study data to estimate national exposure distributions
Cost-benefit analysis of the value of alternative exposure measurements relative their costs in reducing
uncertainty in exposure models
Estimation of dermal exposure from NHEXAS data
4.3.5 Project Descriptions
41
-------
Project Name:
EA-01. Analysis and Comparison of NHEXAS Exposure Data to
Residential Pollutant Sources and Activity Patterns
Short Project
Description:
Analysis of questionnaire, time/activity, environmental, and exposure data collected in the
three NHEXAS studies to determine the associations between measured exposures and
pollutant sources, housing characteristics, and human activities (e.g., the relationship
between the use of cleaning supplies and VOC exposures; the characterization of residential
dust and soil measurements; and the relationship to personal exposure monitoring).
Goal/Objective:
To evaluate and identify hypotheses about those residential pollutant sources, housing
characteristics, and activity patterns that contribute to human exposures, especially high-end
exposures.
Significance of
Project:
To provide policymakers with information to develop guidance for reducing exposures by
both modifying pollutant sources and housing characteristics and educating the public about
how their activities contribute to exposure. In addition, the project will help researchers
refine the questions to be asked and pollutant measurements to be made in subsequent
similar studies. Identification of associations with questionnaire information also is useful for
classification of exposures in epidemiological studies.
Suggested
Approach:
(1) For each of the NHEXAS pilots, explore associations between residential pollutant
sources, concentrations, and exposures; housing characteristics, concentrations, and
exposures; concentration measurements in different media; and human activities,
concentrations, and exposures.
(2) Compare these results among the three studies.
(3) Conduct multivariate analysis to determine the combined impact of residential pollutant
sources, housing characteristics, and activity patterns on exposures.
Data or Input
Needs:
For all three studies, measured concentrations in all media, exposure activity information
(diaries and questionnaires), housing characteristics, and occupational data.
Feasibility
(of analyses
with current
NHEXAS
databases):
Need to review availability of samples for some media, proportion of analyses above
detection limits, and substitution of measurements obtained from nearby households during
the same periods of time (e.g., for outdoor air and soil measurements in Region V study).
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
% Time
25
25
100
0
3
12
15
24
Months
24
24
36
Research Outputs
(1) Initiate project
(2) Develop analysis plan
(3) Complete multivariate analysis of individual NHEXAS pilots
(4) Compare analysis among studies to help combined study analysis
(5) Final outputs: Complete combined study multi-variate analysis and
final report
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
42
-------
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Association/Models of Exposure.
43
-------
Project Name:
Short Project
Description:
Goal/Objective:
Significance of
Project:
EA-02. An Analysis of Media Concentrations, Exposure, and Biomarkers
by Population Demographics
Descriptive analysis of media concentrations, exposure, and biomarker measurements for
population subgroups (age, gender, ethnicity, socio-economic status [SES], urban/rural, or
other important groupings) for each NHEXAS study.
To provide a descriptive analysis of media concentrations and biomarker measurements by
population characteristics in order to identify susceptibility factors and differences among
groups and to compare distributions with other studies.
(l)Will serve as basis for planning and interpretation of NHEXAS data and to identify
subpopulations for further study.
(2)Provides baseline information for comparison to other locations such as Superfund sites
and to assess trends.
(3)Useful to EPA and others doing analysis of NHEXAS data and for planning further
studies
Suggested
Approach:
Statistical comparison of weighted distributions (frequency, means, etc.) by population
subgroups (from questionnaire data) for media concentrations, biomarkers, and exposure to
assess differences and similarities between or among subgroups.
Data or Input
Needs:
Questionnaires and time/activity data from each of the studies.
Biomarker and environmental measurements data from each study.
Detection limits for environmental chemicals from each study.
Population weights and stratification variables.
Feasibility
(of analyses with
current NHEXAS
databases):
Data currently exists, questionnaires are the same across groups, comparability of analytic
results will be assessed using information about detection levels. There is concern over the
level of stratification (limited cell sizes) that can be achieved because of measurements below
detection and incomplete sampling of some media (e.g., subsampling of homes for outdoor
air measurements).
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration"
Month
Month
Month
% Time
15
50
50
0
12
24
Months
24
24
24
Research Outputs
(1) Initiate project
(2) Identify those chemicals for which there is adequate data for
analysis; determine strata to be used in analysis
(3) Final outputs: Manuscript, tables, and graphs of distributions by
strata, and completed statistical analysis and interpretation
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Second student
' Duration = approximate time (in months) needed, from start of project, to complete each step.
44
-------
NOTES:
Classification: Descriptive/Demographic Analysis.
45
-------
Project Name:
Short Project
Description:
Goal/Objective:
EA-03. Risk Factors for Biomarkers of Internal Dose: Demographics,
Questionnaire Data, Concentrations, and Exposures
Analyses to determine the association of biomarkers of internal dose with (1) demographic
characteristics; (2) questionnaire information on behaviors, activity patterns, health indices,
etc.; and (3) measures of personal exposures and media concentrations.
To develop simple methods of estimating internal dose that can be used in studies of health
outcomes.
Significance of
Project:
Analytic or epidemiologic studies of health endpoints need effective methods for estimating
internal dose, but direct measurement is often impractical. For example, studies of chronic
health effects may require estimates of long-term average or historical exposures. NHEXAS
provides a rich source of information that allows inferences about internal dose based on data
collected from questionnaires, measures of chemicals in external media, and other sources.
Suggested
Approach:
For appropriate chemicals and classes of chemicals:
(1) Bivariate analyses of the association of biomarkers of internal dose and risk factors,
including demographics, housing characteristics, questionnaire data, and measures of
exposure.
(2) Examine correlations among risk factors.
(3) Multivariate modeling of the association of biomarkers with risk factors.
Data or Input
Needs:
Biomarker concentrations, demographics, questionnaire data, and environmental media
concentrations and exposure measurements.
Feasibility
(of analyses with
current NHEXAS
databases):
These analyses will be feasible only for chemicals where biomarkers of internal dose exist at
detectable levels for a sufficiently large sample. For a given risk factor, there also must be
sufficient variability. Also requires knowledge of biomarker characteristics (e.g., half-life) to
relate measurements to time of exposures.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Research Outputs
Approximate
Level of Effort:
Month
Month
Month
Month
% Time
5
50
200
0
6
12
24
Months
24
24
24
(1) Initiate project
(2) Conduct bivariate analyses
(3) Examine interrelationships of covariates
(4) Final outputs: Results of multivariate modeling
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Associations/Models of Internal Dose.
46
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Project Name:
EA-04. Estimation of Dietary Exposure and Comparison of Methodologies
Utilized in NHEXAS
Short Project
Description:
Direct estimates of dietary intakes by duplicate diet for various contaminants will be analyzed
to describe, compare, and evaluate the validity, reproducibility, and cost effectiveness of the
collection methods relative to indirect estimates based on the combination of consumption
(reported in the diary or checklist) and extant data from other sources (e.g., TDS, NHANES,
etc.).
Goal/Objective:
To estimate the reliability and validity of the dietary intakes for several of the contaminants
included in NHEXAS and to evaluate the value added over estimates derived from extant
data. To evaluate alternative and less costly methods for measuring dietary exposure relative
to the duplicate diet approach.
Significance of
Project:
Addresses several issues related to analyses of exposures including testing of hypotheses
(adequacy of extant data and models to predict exposure), evaluation of survey instruments,
and prediction of dietary exposure as a component of total exposure. Comparison of dietary
measurement and estimation approaches may help to identify less costly alternatives for
dietary exposure monitoring, and to provide estimates of long-term exposures from short-term
estimates.
Suggested
Approach:
(1) Calculate dietary exposures using consumption data (diary or checklist) and extant food
contaminant data.
(2) Comparisons of calculated exposures with measured duplicate diets.
(3) Comparative analysis of dietary data from checklist, duplicate diet collection, and mini-
market basket approach in terms of validity, reliability, and cost effectiveness.
(4) Analyses of calculated dietary exposures in relation to various demographic variables.
Data or Input
Needs:
Individual dietary consumption records, coding of food consumption to USDA or
EPA/Dietary Exposure Potential Model (DEPM) codes, duplicate diet measurements from
each consortia, existing food contaminant data for those target chemicals measured in diet
samples (from DEPM).
Feasibility
(of analyses with
current NHEXAS
databases):
High, as soon as the verified databases are available on each of the above parameters. May
be limited to quality/resolution of dietary consumption and duplicate diet measurement data.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
% Time
25
100
0
3-6
6-12
18
Month
s
18
18
Research Outputs
(1) Initiate project
(2) Determine the compatibility of the data sets
(3) Formulate and test methods of statistical analyses
(4) Final outputs: Reports/manuscripts of estimated dietary exposures
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
47
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50
12
Junior-level staff (
'assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Methods.
Project Name:
EA-05. Spatial and Temporal Variability in Multichemical Exposure
Short Project
Description:
Project will better characterize the magnitude and variability in exposure to multiple chemicals
measured in all environmental media by the three NHEXAS studies for different locations of
the country. Both within- and between-study variability will be examined, and analyses will be
conducted to determine whether exposure to one chemical in a given class is predictive of
exposures to other compounds in that class or other classes.
Goal/Objective:
The goal of this project is to provide information that will improve the efficiency (e.g., cost-
effectiveness) of future exposure, risk assessment, and epidemiologic investigations of health
risks of cumulative chemical exposure. This study will provide some of the first information
on multichemical and multipathway exposures required for cumulative risk assessments.
Significance of
Project:
The need to assess risks of cumulative chemical exposures is well recognized within the
scientific and regulatory communities. Little information is available for such assessments.
Analysis of the temporal and spatial aspects of the NHEXAS data is important to reduce
uncertainty in the exposure estimates for these assessments.
Suggested
Approach:
The suggested approach is to examine multiple chemical exposure, first for each route of entry
and second for aggregate exposure. This approach should be limited to two or three chemical
classes, but utilize all of the NHEXAS data even if a compound was not collected in all media
(e.g., VOCs). Analyses will be performed on measurements of environmental concentrations,
exposure, and biomarkers (related to internal dose). Investigators should determine the
appropriate chemical classes for study.
Data or Input
Needs:
Concentration, exposure, and biomarker measurements from each NHEXAS study.
Feasibility
(of analyses with
current NHEXAS
databases):
The feasibility of the proposed project is high for analyses of data within the Maryland study.
Some limitations are anticipated in the types of samples available from the Region V study.
(Longitudinal samples were not collected for Arizona.)
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
0
12
24
Research Outputs
(1) Initiate project: Identification of common variables across studies
(2) Initiate investigations within each medium and combine data
across media where feasible for each study
(3) Complete single-route and aggregate analyses of cumulative
exposure
48
-------
Approximate
Level of Effort:
Month
% Time
10
25
50
36
Months
36
36
36
(4) Final outputs:
Compare findings between studies
Report findings, write reports and manuscripts on cumulative
chemical exposure.
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Descriptive/Demographic Analyses.
Project Name:
EA-06. Comparison of Cross-Sectional and Longitudinal Variability in
Exposure Metrics: Implications for Study Design
Short Project
Description:
This project will provide for the analysis of the variability in media concentrations, exposures,
and doses over space and time among and within the NHEXAS studies. It will examine the
variability of exposure distributions based on short-term measurements compared to those
based on long-term measurements or averages and determine the reliability of a short-term
measure of exposure for assessment of long-term exposure for populations and individuals.
Goal/Objective:
The goal of this project is to provide information that will improve the efficiency (e.g., cost-
effectiveness) of future exposure, risk assessment, and epidemiologic investigations. Such
information will allow for improved selection of sample size (number of subjects), sample type
(concentration, exposure, or dose), and number of repeated measurements per subject in
cross-sectional and longitudinal studies.
Significance of
Project:
Little information is available to aid in the design of studies intended to assess risk of acute
and chronic exposure to environmental pollutants. Analysis of the temporal and spatial
aspects of the NHEXAS data is anticipated to provide information suitable for this purpose.
Suggested
Approach:
Analyses will be performed on measurements of environmental concentrations, exposure, and
internal dose. This approach should be limited to two or three chemicals for which there are
measures of all three metrics (e.g., arsenic, chlorpyrifos, benzene). Between- and within-
person variability of exposure will be assessed and compared within and across NHEXAS
studies.
Data or Input
Needs:
Concentration, exposure, and dose measures from each NHEXAS investigation.
Feasibility
(of analyses with
current NHEXAS
databases):
The feasibility of the proposed study is high for analyses of data within a NHEXAS study.
Some limitations are anticipated for analysis of data across the different NHEXAS
investigations.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Research Outputs
49
-------
Approximate
Level of Effort:
Month
Month
Month
Month
% Time
10
25
50
0
12
24
36
Months
36
36
36
(1) Initiate project
(2) Initiate investigations within a study and combine data across
studies where feasible
(3) Complete within-study analyses and continue analysis of data
combined across studies
(4) Final outputs: Report findings, write reports and manuscripts on
the implication of temporal and spatial variability for improved
study design
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Methods.
50
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Project Name:
EA-07. Impact of Censoring and Method Sensitivity and Precision on
Multimedia Exposure Distributions and Associations
Short Project
Description:
This study will examine how method sensitivity and precision, and the censoring of data
below detection limits, affect the estimation of distributions and means for exposure, media
concentration, and biomarker measurements; and the evaluation of associations among such
measurements. To the extent possible, intakes will be used in order to make the assessment
on a total exposure basis.
Goal/Objective:
To investigate the degree to which the NHEXAS goal of measuring total exposure may be
limited by the method precision, sensitivity, and censoring of data below DLs.
Significance of
Project:
A major goal of NHEXAS was to estimate exposure through multiple routes, especially for
those most highly exposed. This goal may be limited by the proportion of measurements that
are below DLs for some target analytes and media and because method sensitivities differed
across both media and studies. This project will be valuable in determining methods and
approaches for conducting future NHEXAS or other multimedia human exposure studies.
Suggested
Approach:
(1) Determine the percent of measurements above DLs, and the availability of health
thresholds and QC data in order to focus the study on the most relevant media and
chemicals.
(2) Use uncensored results where available and impose censoring on them (i.e., set values
-------
35
8
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Methods.
Project Name:
EA-08. Providing Improved Exposure Models Using Cost-Effective
Approaches
Short Project
Description:
Comparison of uncertainty in exposure estimates obtained using different types of
measurements or other data (e.g., screening measurements or questionnaires) with those
based on the more intensive direct exposure measurements conducted in NHEXAS.
In addition, comparisons of costs and uncertainty will be made between direct exposure
measurements and indirect estimates based on existing data and models.
Goal/Objective:
To assess the cost and uncertainty differences between exposure models using screening
level measurements, questionnaire information, nonprobability samples (i.e., purposive
samples), and existing exposure-related data relative to the NHEXAS measurements and
study designs.
Significance of
Project:
Clearly, multimedia, multipathway studies are needed. This study will help to identify the
incremental differences in model performance associated with more detailed (sensitive and
accurate) methods, and with representative population samples-relative to more focused
stratified or specialized substudies. Stratification can be based on SES characteristics,
inexpensive screening techniques or any other means deemed appropriate. Resources are
limited, and great care must be taken to wisely allocate them. This study will provide
information to help determine
(1) how to minimize exposure measurement costs for a national study,
(2) how to prioritize resource allocation, and
(3) approaches with the necessary utility and accuracy for specific exposure assessment
studies.
Suggested
Approach:
Build multiple models and compare them.
(1) Comparison of exposure models derived from existing measurement data (or
questionnaire data) contrasted with models using new subject-specific chemical
measurements, characteristics, and activities (i.e., NHEXAS).
(2) Comparison of exposure models derived from data with different sensitivities (e.g.,
questionnaires and screening measures with differences in analytical performance).
Data or Input
Needs:
Example for Approach 1: Use existing Aerometric Information Retrieval System data to
model residential concentrations and exposures, and compare with measured Region V
indoor/outdoor and personal air data; existing TDS concentrations used to model dietary
intake, and compare with duplicate diet measurements.
Examples for Approach 2: Comparison of Arizona XRF data compared with (ICP/mass
spectrophotometry) data (Arizona study); comparison of questionnaire-based models with
measurement-based contaminant models.
Exposure and intake models from each study.
52
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Feasibility
(of analyses with
current NHEXAS
databases):
Limitations include equivalency in terms of temporal and geographic variability,
SES/demographic/population variability/representativeness, collection and analytical
methods.
53
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Project Name:
EA-08 (cont'd). Providing Improved Exposure Models Using Cost-Effective
Approaches
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration"
Month
Month
Month
Month
Month
Month
% Time
20
50
100
0
6
12
12
24
30
Months
30
30
18
Research Outputs
(1) Initiate project
(2) Identifying relevant data sets and obtaining data sets
(3) Generating comparison-compatible data sets
(4) Obtaining models from each NHEXAS study for comparison
(4) Analysis and summary of results
(6) Final outputs: Three or more published papers
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Methods.
54
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Project Name:
EA-09. Analysis of Variable Groupings in the NHEXAS Data Sets for
Evaluating the Usefulness of Questionnaires for Exploring Relationships
Between Exposure, Dose, and Risk Factors
Short Project
Description:
Suggested
Approach:
The NHEXAS databases include a wide spectrum of measurements: questionnaire
responses, exposure measurements, and dose/biomarker measurements. These data will be
analyzed without a priori decisions about relationships among the variables to generate
new hypotheses regarding environmental exposures.
Goal/Objective:
Significance of
Project:
Identifying and evaluating associations among the NHEXAS variables. This goal is related
to the multivariate analyses called for in proposals EA-1 and EA-3 and understanding
differences and similarities among subpopulations (EA-2).
Classification of NHEXAS data into variable groups will help focus future exposure
assessments in national surveys, epidemiological studies, and risk assessments. (It also
provides a comparison between the questions and the rationale for their use.)
The strengths and limitations of the data will be evaluated initially using univariate
analyses of individual variables. Next, a multivariate classification technique will be
selected and run (e.g., principal components, classification and regression trees [CART], or
factor analysis) to identify groupings of variables.
The groups will be evaluated in order to generate hypotheses, to guide in the design of
other studies, and to identify important questions and/or measurements for future
exposure assessments and risk assessments.
Analyses are to be conducted by pertinent subpopulations because the variables may
group differently by subpopulation.
Data or Input
Needs:
Database of complete measurement data including all chemical measurements and
questionnaire responses.
Feasibility
(of analyses with
current NHEXAS
databases):
Feasibility of the project will be limited by the number of observations within strata.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
% Time
10
50
25
0
6
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Univariate analyses
(3) Final outputs: Final report and journal article
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
55
-------
Classification: Descriptive/Demographic Analyses.
56
-------
Project Name:
EA-10. Determinants of Dose Measurements (Biomarkers) from the
NHEXAS Studies
Short Project
Description:
Absorbed dose may be estimated by questionnaire and measurement data including air,
water, diet, and contaminated surfaces. Predictive associations between measurements of
exposure and dose will be evaluated. Questionnaire response data will be considered as a
modifier of the exposure/dose association. This association will be evaluated further by
taking into account existing pharmacokinetic models and parameters. Methods and
approaches for assessing the dermal exposure contribution relative to the biomarker
measurements are of particular importance because dermal exposure methods are not well
developed. Measured biomarkers will be related to potential exposure using algorithms
used to estimate aggregate human exposure.
Goal/Objective:
To identify and evaluate environmental and questionnaire determinants of dose and to
better understand the time course associations between exposure and dose. The dermal
contribution to exposure will be analyzed.
Rationale for
Project:
Study results will aid in the interpretation of exposure biomarker measurements and will help
in the efficient design of future exposure and epidemiologic studies. Further understanding
in the interpretation of biomarker levels is valuable because they are believed to provide a
better predictor of health outcome than environmental concentration measurements that do
not account for contact, uptake/intake, and absorption processes.
Suggested
Approach:
Biomarker measurements represent the absorption and clearance of chemical contaminants
measured in the NHEXAS program. The predictive relationship between these
measurements will be evaluated with questionnaire responses, and with exposure and
environmental media concentrations using multivariate analysis methods. Pharmacokinetic
models will be applied in order to explain the relationship between exposure and dose
(biomarker) measurements. Contributions of contaminated media can be estimated using
exposure algorithms routinely used in exposure assessment.
Data or Input
Needs:
Chemical measurements in biological, exposure, and environmental media, questionnaire
data, exposure factors, and pharmacokinetic parameters.
Feasibility
(of analyses with
current NHEXAS
databases):
Sufficient detectable results are needed in media of exposure relevance for biomarker
analytes. Need to consider timing of biomarker collection relative to exposure and
environmental measurements (e.g., Maryland study samples collected at beginning of
sampling), and the availability and suitability of available pharmacokinetic parameters for
the subpopulations (e.g., children).
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Research Outputs
Approximate
Level of Effort:
Month
Month
Month
% Time
25
0
12
24
Months
24
(1) Initiate project
(2) Multivariate statistical analyses; evaluation of short-term
clearance models
(3) Final outputs: Journal article identifying predictors of dose
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
57
-------
100
24
Junior-level staff
("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Associations/Models of Internal Dose.
Project Name:
EA-11. Critical Exposure Pathway Analysis and Comparison of Findings
Among NHEXAS Studies
Short Project
Description:
This study will compare the results of analyses (or models) developed by each of the
NHEXAS studies that apportion the relative contributions of environmental media and
routes of exposure to "total exposure" or dose.
Goal/Objective:
To compare the approaches, data, and estimates used to apportion pathway-specific
exposures used in the NHEXAS studiesidentify similarities and differences and compare
or pool results where possible.
Significance of
Project:
Determine how the results (parameter estimates) from the individual NHEXAS studies can
be systematically compared to each other, or pooled to provide combined estimates of
associations between pathway-specific measurements/estimates and "total" exposure or
dose.
Suggested
Approach:
For each study, examine the sampling and analytical methods to determine if the resulting
measurements are similar or different. Construct exposure distributions for each media.
Compile estimates for associations of media concentrations and route-specific exposures
(or surrogates) with "total" exposure or absorbed dose estimates from each study.
Compare results (parameters and error terms) among individual studies. Pool data where
measurements are similar to make generalized statements about exposure if reasonable.
Data or Input
Needs:
Summary information about sampling and analytical methods. Individual study results for
analyses of pathway-specific contribution to total exposure or dose.
Feasibility
(of analyses with
current NHEXAS
databases):
Information (publications) and data should be readily available. Analyses may be limited
by nondetectable or missing measurements.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
0
12
18
Month
s
Research Outputs
(1) Initiate project
(2) Individual distributions of exposure data, pooled data sets,
comparative analyses
and
(3) Final outputs: Report on the similarities and differences of
NHEXAS data and an assessment of linkages of activities to
pathways
Type of Expertise Needed
58
-------
25
25
50
18
18
18
Principal investigator
Senior-level staff ("associate") statistician
Junior-level staff ("assistant", technician),
students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Methods.
59
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Project Name:
EA-12. Cumulative Exposures to NHEXAS Chemicals Having Similar
Health Endpoints and Possible Additive or Synergistic Effects
Short Project
Description:
This project will calculate a toxic-equivalency weighted index of population "cumulative"
exposures for suites of chemicals that are associated with common health endpoints and the
exposure measurements from the NHEXAS studies. The NHEXAS target chemicals will be
reviewed, using existing toxicological or epidemiological literature, to identify suites of
chemicals having similar health endpoints (risks) and possible additive or synergistic effects.
Possible health endpoints include neurological, reproductive/developmental, cancer, and
immunological effects. Chemical classes include metals, VOCs, pesticides, and PAHs.
Goal/Objective:
To assess cumulative exposure to multiple chemicals of similar action/toxicity.
Significance of
Project:
The Food Quality Protection Act calls for assessment of cumulative risk to pesticides (and
toxic substances) having common endpoints and mechanisms of effect. This project will
allow calculation of cumulative exposure indexes and their distributions, based on exposures
to more than one chemical.
Suggested
Approach:
(1) Using common health effects and additive or synergistic endpoints, and toxic
equivalency or potency factors.
(2) Examine the target chemicals and data from NHEXAS to identify chemicals that could be
combined to provide a common exposure metric.
(3) Calculate a weighted index of "cumulative" exposure using the absorbed dose estimated
from the NHEXAS study data.
Data or Input
Needs:
Data on selected chemical exposures and biomarkers from the three NHEXAS studies.
Toxicological information on chemicals with common health endpoints and mechanisms and
potency estimates (or toxic equivalency factors). Epidemiological information on possible
additive or synergistic effects.
Feasibility
(of analyses
with current
NHEXAS
databases):
Toxicological data on potency should be readily available; information on "cumulative" risks
(common endpoint and mechanism of action) may be limited to certain classes of chemicals
(e.g., pesticides). The NHEXAS data may be limited in providing measurements in all
exposure media for contaminants and classes.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
% Time
20
50
50
0
6
9
12
18
24
Month
s
24
6
24
Research Outputs
(1) Initiate project
(2) Collect toxicology data on NHEXAS chemicals
(3) Obtain NHEXAS measurement data for selected chemicals
(4) Calculated exposure index for NHEXAS pesticides
(5) Calculated exposure index for metals
(6) Calculated exposure index for VOCs
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
60
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I I Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES:
Classification: Associations/Models of Exposure.
4.4 LESSONS LEARNED GROUP
The lessons learned breakout group will focus on analyses that identify study elements that will be
generally useful in the future or that will require modification or deletion in follow-up research. This
includes, for example, a description of the achievement of data quality objectives; a description of
response rates and survey design effects; the ability of the questionnaire and environmental and
biological data to predict exposure and dose; a comparison of sampling and analytical methods; and the
efficacy of communication with states and communities and local and public health departments.
4.4.1 SAB Comments
(1) "The EPA should use the experience, lessons learned, and wisdom gained from the pilot studies to
guide the Agency and external investigators on how to optimize the measurement and analytical
approaches." [3.4.2, 4]3
(2) "Another important issue to address is the amount and nature of the new knowledge derived from
the pilot studies as it relates to the methodologies implemented." [3.4.1]
(3) "The Committee recommends that the EPA use the data from the NHEXAS pilot studies to build
the premises for a national exposure survey. Planning for Phase 2, a national surveillance plan,
should require a plan that uses the experience of the pilot study so that the most appropriate
multimedia measurements (including questionnaires) are used in Phase 2." [3.5.2.e]
4.4.2 Questions To Address
3Numbers in brackets are cross-references to sections in the SAB report.
61
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As a starting point to identify, describe, and prioritize potential projects, the breakout group
should consider the following questions and determine what additional critical questions should be
added.
(1) What are the critical "lessons-learned" questions associated with
(a) Aspects of overall program management including planning and conducting the study, and
documenting and reporting the results?
(b) Representativeness of survey designs and effects related to probability sampling, sample size
and weighting, stratification and oversampling, and demographics?
(c) Recruiting participants and the possible impact of different procedures and incentives on
response rates?
(d) Effectiveness and limitations of study designs for estimating multimedia, multipathway
exposures for the general population, for susceptible subpopulations, and for the highest
exposed?
(e) Use of field monitoring procedures (e.g., questionnaires, sampling methods, sample
handling and tracking), their burden on participant, practicality of application, and costs
versus benefits?
(f) Effectiveness of questionnaires/diaries in collecting information to estimate or describe
exposures (e.g., burden, cooperation, compliance utility)?
(g) Limitations associated with sample analysisin selecting analytes; attaining appropriate
detection limits and QC; and holding, shipping, and storing samples?
(h) Creating and archiving databases!
(i) Communicating data to participants, state and local health agencies, and the scientific
community?
(2) What are the most critical QA/QC analyses that must be conducted?
(3) How are relative costs of each component of the study evaluated? How are the costs of one
approach evaluated relative to another?
(4) What analysis approaches can be used to predict exposure and dose from questionnaires and
environmental and biological data? How are these approaches evaluated?
62
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4.4.3 Discussion Considerations
(1) What statistical analysis can be conducted with the information obtained in the demonstration
studies to answer each of these questions? Which are feasible?
(2) Are there other approaches to answering each of these questions?
(3) What analyses can be conducted to evaluate the limitations of the studies?
(4) What analyses can be conducted to develop an efficient design for future studiesto measure
central tendencies, to measure high upper percentiles of the exposure distribution, to identify
distributions for susceptible subpopulations?
4.4.4 Brainstorming List of Projects
The following is an unranked listing of the lessons learned project titles proposed by the Lessons
Learned Breakout Group as a result of the brainstorming sessions held on July 27 and 28, 1999. The
projects are listed below each of the questions they address, in accordance with the organization and
format of the brainstorming sessions. Question 10 incorporates additional questions and projects
considered by the group. Following the brainstorming session, the group combined this list into 14
project areas, of which 13 were further developed into the project descriptions in Section 4.4.5 (the
14th was passed to the Exposure Assessment Group for consideration). None of the project areas
was eliminated from consideration. The numbers in parentheses following the projects are cross-
referenced to the project descriptions in Section 4.4.5.
1. Aspects of program management, including planning and conducting the study and
documenting and reporting the results?
(1) Document what has been learned to build for the future. (LL-3)
(2) Survey start-up costs associated with NHEXAS, with the goal of minimizing costs by and
across consortia:
infrastructure costs,
identify cost efficiencies in conducting NHEXAS projects. (LL-11)
(3) EPA should analyze coordination and communication within and across agencies, and across
consortia. (LL-11)
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(4) What is impact of nonuniformity of methods and procedures across the consortia? (LL-10,
LL-11)
(5) Identify and evaluate appropriate QA/QC across laboratories and data reporting formats;
include NIST evaluation and optimize for future studies. (LL-10)
2. Representativeness of survey designs and effects related to probability sampling, sample size
and weighting, stratification, over sampling, and demographics?
(1) Analyze the data for variance components, including spatial, time, population and
subpopulation, activities by different pathways, and different pollutants for impact on future
NHEXAS survey designs. (LL-2)
(2) Analyze the NHEXAS-generated data to address the quality of assumptions about the design
effects and variables as presented in the paper by Callahan et al., 1995. (LL-1)
3. Recruiting participants and the possible impact of different procedures and incentives on
response rates?
(1) Analyze data to compare strategies and recommendations for recruitment, impact on response
rates, and incentives (utilize NHEXAS and data from other studies)a retrospective look at
successes and failures. (LL-5)
(2) Identify key factors associated with recruitment and response rates. (LL-5)
(3) Analyze nonresponse bias for the population and various subgroups across consortia. (LL-5)
4. Effectiveness and limitations of study designs for estimating multimedia, multipathway
exposures for the general population, for susceptible subpopulations, and for the most
exposed?
(1) Similar to analyses proposed to address question 2 and also to include analysis of participant
and field team burden. (LL-7)
(2) Summarize experiences related to use of screening tools for future study by chemical and
media. (LL-6)
(3) Analyze data to address strategies for designing NHEXAS studies related to time intervals of
concern and limits of detection and method sensitivity. (LL-6)
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(4) Compile data and experiences across consortia to optimize future studies across media,
pathways, pollutants, and pollutant classes. (LL-3)
5. Use of field monitoring procedures (e.g., questionnaires, sampling methods, sample handling
and tracking), their burden on participant, practicality of application, and costs versus
benefits?
(1) Document field monitoring logistics, including procedures (and recommendations for
improvement), shipping, sample preservation, etc. (LL-7)
(2) Document successes and failures. (LL-7)
(3) Evaluate monitoring procedures across consortia, against various criteria, such as burden,
costs, accuracy and precision, sensitivity, relevancy to study objectives, etc. (LL-7)
6. Effectiveness of questionnaires and diaries in collecting information to estimate or describe
exposures (e.g., burden, cooperation, compliance utility)?
(1) Compliance issues. (LL-12)
(2) Consistencies of response. (LL-12)
(3) Reliability and validity. (LL-12)
(4) Indicators of exposure (referred to the Exposure Assessment Group).
(5) Relate the questionnaire rationale used in the Office of Management and Budget (OMB)
approval with actual responses. (LL-12)
(6) Evaluate the effectiveness of dietary check-off list with food diary. (LL-12)
(7) Time/activity pattern and video analysis with comparisons to exposure (referred to the
Exposure Assessment Group).
7. Limitations associated with sample analysis, selecting analytes, attaining appropriate
detection limits and QC, and holding, shipping, and storing samples?
(1) Provide an interpretive report of the comparability experiment across consortia, including an
analysis of data quality. (LL-10)
(2) Evaluate methods across media (equivalency, etc.). (LL-7)
8. Creating and archiving databases ?
(1) Document limitations of NHEXAS data. (LL-13)
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(2) Standardize ways to document data across consortia. (LL-13)
(3) Creation and standardization of an information shell that includes field collection observations
and issues. (LL-13)
(4) Assessment of the processes used by each consortium. (LL-13)
(5) QC data and coordination with EPA data quality indicator project. (LL-13)
9. Communicating data to participants, state and local health agencies, and the scientific
community?
(1) Develop a uniform strategy for future studies that is consistent with human subjects
Institutional Review Board review requirements and participant confidentiality issues. (LL-7)
(2) Participant interpretation issuesdevelop a plan for the future through interviews with
NHEXAS researchers. (LL-7)
10. Other questions and projects proposed by the group:
(1) Time integration issues: acute verses long-term exposures. (LL-2)
(2) Analysis of variance (population versus individual). (LL-2)
(3) Value of information and cost benefit of
questionnaires,
biomarkers,
environmental concentration, and
personal exposures. (LL-8)
(4) Identify clusters, factors, and principal components associated with population distributions
resulting from NHEXAS. (LL-2)
(5) What have we learned and what do we still need to know? (LL-4)
(6) How can pilot information be analyzed to design the optimum national NHEXAS survey?
(LL-4)
(7) Define methods to optimize exposure management and reduction and the effectiveness of
regulations. (LL-4)
(8) Identify differences between NHEXAS and NHANES. (LL-4)
(9) Evaluate hypotheses; what was testable, why or why not? (LL-1)
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4.4.5 Project Descriptions
67
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Project Name:
LL-1. Survey and Statistical Aspects of the Design of an Exposure Field
Study: Lessons Learned from the NHEXAS Pilot Studies
Short Project
Description:
This project is a review, revision, and updating of the discussions, analyses, and conclusions
in the Callahan et al. paper (JEAEE, 1995) in light of the NHEXAS experience. The hypothetical
calculations in Callahan would be replaced with calculations based on actual NHEXAS data.
In addition, the analytical and statistical hypotheses that were generated in the design of the
NHEXAS pilots will be reviewed to determine which hypotheses were testable and which were
not.
Goal/Objective:
The objective of the project is to provide directly relevant and specific guidance for the sample
and survey design aspects of a national NHEXAS or other large multichemical, multimedia
exposure field study.
Significance of
Project:
The Callahan paper influenced the design of the NHEXAS pilots. Its revision will provide
scientifically relevant, specific, and current guidance for the design of a full national NHEXAS,
and also for other regional or national human exposure field studies, especially multichemical,
multimedia studies.
Suggested
Approach:
Callahan et al. (JEAEE, 1995) discussed the statistical and survey design issues involved in
designing a population-based environmental exposure study. It made a number of design
recommendations - about the optimal selection of Primary and Secondary Sampling Units
(PSUs and SSUs) and households, about screening strategies, about the selection of target
household member, etc. Many of these recommendations were based on calculations of
hypothetical intraclass correlations, design effects, and variances. There is now a wealth of
data available from the three NHEXAS pilot studies that is germane to these survey design
issues. This project would involve a review of the discussions, analyses, and conclusions in
Callahan in light of the NHEXAS experience. The hypothetical calculations of design effects
and intraclass correlations would be replaced with calculations based on actual data, and the
conclusions and recommendations revisited. These analyses would be repeated for different
pollutants and classes of pollutants to determine if different conclusions would be reached for
different pollutants. In addition, the analytical and statistical hypotheses that were generated
in the design of the NHEXAS pilots will be reviewed to determine which hypotheses were
testable and which were not. Testability would be measured through the calculation of the
statistical powers of the tests. Tests with high powers would be deemed testable, whereas
tests with low power would be deemed not testable. Through a review of the data, the reasons
for the ultimately testability will be determined. These calculations will lead to conclusions
regarding the testability of the hypotheses, and the optimal design of future environmental
exposure studies.
Data or Input
Needs:
For each household in each of the three NHEXAS pilots, the following data are needed: the
PSU and SSU containing the household; the design stratum containing the household; and
the data on each pollutant/medium sampled.
Feasibility
(of analyses with
current NHEXAS
databases):
The current NHEXAS data files have the necessary data to perform the calculations. At worst,
there are potentially small or empty cells in the survey designs that might force combining cells
or qualifying the conclusions.
Approximate Project Time Table and Level of Effort
Time Table:
Duration"
Month
Month
Month
Month
Month
0
1-3
4-8
9
9-12
Research Outputs
(1) Initiate project
(2) Gather data sets; plan, review, and approve the
statistical analyses
(3) Perform the statistical analyses
(4) Draft the report
(5) Review, revise, and finalize the report
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Approximate
Level of Effort:
Month
% Time
25
50
100
12
Months
12
9
6
(6) Final output: Report with recomendations for the optimal design of
a national-scale human exposure study
Type of Expertise Needed
Senior and mid-level survey statisticians, systems analysts,
programmers
Principal investigator
Senior-level staff ("associate"), senior survey statistician, database
manager/programmer, data analyst
Junior-level staff ("assistant", technician) students, mid-level survey
statistician, programmers
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
LL-2. Characterization of the Variance Components of NHEXAS Data to
Optimize Future Designs
Short Project
Description:
Characterize the variance components of NHEXAS data, including the inter- and
intrapersonal, temporal (e.g., integration time, seasonal, weekly), activity-related, and spatial
variabilities by sample size for each of the pollutants by pathway/medium and by integrated
total exposure. Results will be used to optimize future NHEXAS design.
Goal/Objective:
The primary goal of the proposed project is to use the NHEXAS data to determine the
appropriate sampling strategies for the different pollutants and pathways. To achieve this
goal, the proposed project will characterize the variance components of the NHEXAS
exposure data to
estimate the optimum sample size and number of repeated measures (SAB comments
II.A.2and4);
determine how exposure distributions vary across time and space and identify factors that
influence this variation (II.A.2);
assess whether the variance components differ by subpopulation, including susceptible
and highly exposed subpopulations (II.A.4); and
investigate how the exposure characteristics of the various subpopulations are influenced
by activity patterns, geographic area, and SES (II.A.4).
Significance of
Project:
The proposed project directly addresses SAB concerns and, as a result, will improve
substantially the ability to optimize the design of future NHEXAS and other exposure
studies. It will incorporate findings from each of the three NHEXAS consortia and will allow
the sampling plan of each consortium to be examined in a systematic and quantitative
manner.
Suggested
Approach:
Exposure data from each of the three NHEXAS studies will be analyzed to determine the inter-
and intrapersonal, temporal, and spatial variabilities in exposure distributions. Analysis will
be performed by pollutant, both pathway-specific and as integrated total exposure, as well as
by subpopulation. Variabilities will be assessed using standard statistical approaches,
including the coefficient of variation and one-way analysis of variance (ANOVA) and mixed
model approaches. Graphical techniques will be used to evaluate and determine appropriate
pollutant- and media-specific sampling strategies. As possible, pollutants will be grouped
based on identified appropriate sampling strategies.
Data or Input
Needs:
From each pilot study (and primarily the Maryland NHEXAS study for temporal data), the
following data will be needed:
environmental concentration and exposure data,
questionnaire data, and
time/activity data.
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Feasibility
(of analyses with
current NHEXAS
databases):
High, all the necessary data exists.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
10
100
100
0
3-18
15-24
Month
s
24
24
24
Research Outputs
(1) Initiate project: Compilation of the data from the consortia
(2) Analyses of the data
(3) Final outputs:
Reporting of the optimized sampling strategies by pollutant and
pathway
Publishing in peer reviewed journals
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
LL-3. Using Lessons Learned To Move to a National NHEXAS or Other
Major Field Study
Short Project
Description:
This project will capture and integrate the knowledge gleaned from the analysis,
interpretation, and evaluation of the experiences in undertaking the NHEXAS pilot studies
for assisting in designing and planning the next generation of NHEXAS or other major field
studies. Included would be an evaluation of the ability of each consortium to achieve the
objectives or hypotheses originally proposed for each type of investigation.
Goal/Objective:
(1) To compile the results and conclusions from the analyses conducted by the NHEXAS
studies.
(2) To evaluate the successes and failures of the individual pilot studies in achieving the
original hypotheses proposed by each consortium.
(3) To document the successes and shortcomings of the NHEXAS pilot studies based on
the outcomes of implementing the entire strategic analysis plan.
(4) To synthesize a strategy to begin the process of designing the next generation of
NHEXAS based on the successes and shortcomings from the evaluation of the
NHEXAS pilot studies.
Significance of
Project:
The products and outcome of this effort are needed to provide justification and a defensible
scientific basis to begin designing a national-scale NHEXAS.
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Suggested
Approach:
(1) Obtain completed significant analyses on the databases and information content
obtained by each consortium, and from the implementation of the Strategic Analysis
Plan.
(2) Develop a plan to utilize a multidisciplinary team to undertake and complete
Goals/Objectives 1 through 3 for this project.
(3) On completion of Goals/Objectives 1 through 3, Goal/Objective 4 will be implemented by
EPA.
Data or Input
Needs:
The analyses conducted to achieve each study's hypotheses and objectives and the results
from the implementation of the SAB-approved Strategic Analysis Plan. The project
initiation is contingent on having sufficiently completed products from other projects in the
Strategic Analysis Plan.
Feasibility
(of analyses with
current NHEXAS
databases):
High, if the Strategic Analysis Plan is implemented, including the lessons learned projects.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
% Time
50
300
0
100
1
2-4
5-7
12
Month
s
6
36
0
12
Research Outputs
(1) Initiate project:
(2) Collect and compile from other project
(3) Evaluate information and summarize findings
(4) Final outputs: Final report
Type of Expertise Needed
Principal Investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Secretarial support
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
LL- 4. Optimizing NHEXAS Pilot Information and Methods To Achieve
Exposure Management, Exposure Reduction, and Improved Effectiveness
of Regulatory Strategies
Short Project
Description:
A thorough evaluation will be performed of single- and multimedia pollutant issues and
regulatory initiatives for the purpose of designing the national scale NHEXAS. The
information obtained in the pilot studies and other source and effects information will be
utilized to prioritize the selection of pollutants and pathways leading to exposure.
Goal/Objective:
(1) To build a knowledge base on the current and emerging scientific and regulatory issues
associated with pollutants and their occurrence in multimedia.
(2) To build a knowledge base on the prevalence of xenobiotics measured in biological
samples from human populations.
(3) To develop strategies for optimizing exposure information that permit effective
management and reduction programs.
(4) To link the accomplishments of objectives 1 through 3 to support moving forward, as part
of the input to the design of the national-scale NHEXAS.
Significance of
Project:
This project provides scientific and policy buy-in for justifying the implementation of a
national-scale NHEXAS.
Suggested
Approach:
The implementation of this project is an EPA initiative. It requires NERL to identify a team of
scientists to work with the program offices, other government agencies, states, and other
stakeholders to acquire the knowledge base for selecting and prioritizing pollutants and
pathways and for identifying innovative exposure reduction strategies. Evaluate the success
and completeness of the above in workshops composed of EPA and extramural scientists,
other professionals, and stakeholders. Incorporate the output from the workshops to refine
and augment the knowledge base to be used for designing the national-scale NHEXAS. The
knowledge building should begin as soon as practical and be completed in a timely fashion to
be ready to support moving to the future NHEXAS.
Data or Input
Needs:
Information is obtained from the NHEXAS Strategic Analysis Plan results, program office
activities and initiatives, NHANES, other exposure and health-related studies (e.g., EPA/ORD
STAR Grant Program, NIEHS, National Cancer Institute, Health Effects Institute, National
Institute for Occupational Safety and Health, ATSDR), and state exposure data and pollution
reduction initiatives.
Feasibility
(of analyses with
current NHEXAS
databases):
High, if initiated in a timely manner.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
% Time
100
0
1-4
5-7
8-9
Months
9
Research Outputs
(1) Initiate project
(2) Building a knowledge base
(3) Identifying strategies and conducting a workshop
(4) Final outputs: Synthesis of information and transferring output
to support moving to the future NHEXAS
Type of Expertise Needed
Principal investigator
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200
50
100
18
4.5
9
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Secretarial and other support staff
Cost of workshop
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
LL-5. Influence of Incentives, Response Rates, and Nonresponse Bias on
Survey Design
Short Project
Description:
Analysis of NHEXAS recruitment procedures and incentives and their effects on response
rates for various subpopulations.
Analysis of potential bias resulting from NHEXAS nonresponse based on information
obtained from the Descriptive Questionnaire, and information/observations recorded by
interviewers on noncontacts or nonrespondents for each study and for various
subpopulations.
Goal/Objective:
Determine the recruitment procedures and incentives that should be recommended for a
national NHEXAS or other large field study.
Determine the extent of nonresponse bias that can be expected at each stage of these
studies.
Significance of
Project:
Projected participant incentives and response rates will be a major consideration for OMB
approval of a national NHEXAS. It will be necessary to project reasonably high response
rates and to justify the incentives and procedures proposed to achieve those response rates.
Suggested
Approach:
Contrast recruitment strategies, information provided to potential respondents, incentives,
and response rates across (and within, where feasible) the three NHEXAS pilot studies
for subpopulations of interest.
Compare NHEXAS recruitment procedures, incentives, and response rates with those from
other studies collecting comparable data (e.g., TEAM and NHANES).
Use the NHEXAS Descriptive Questionnaire data to compare characteristics or respondents
and nonrespondents
for each NHEXAS pilot study,
for each stage of participation, and
for subpopulations of interest (e.g., race/ethnicity; gender; urbanicity).
Data or Input
Needs:
Indicators from each NHEXAS pilot study of participation for each stage of the study:
Households contacted (no answer/refusals/number of contacts)
Descriptive Questionnaire
Baseline Questionnaire
Core monitoring
Sampling for each matrix and pollutant
Documentation of the recruitment procedures (including information provided, informed
consent, approaches used for questionnaires and sampling, communications and
contacts with press/community, etc.) and incentives used by each NHEXAS pilot study
NHEXAS Descriptive Questionnaire data
Incentives, recruitment procedures, and response rates for other studies collecting
comparable data (e.g., TEAM and NHANES)
Quality Systems Implementation Plans, protocols for survey sampling and training manuals
for survey teams
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Feasibility
(of analyses with
current NHEXAS
databases):
Must complete QC on Descriptive Questionnaire data for each NHEXAS consortium.
Must complete NHEXAS chemical analyses, set respondent flags, and QC those flags.
Must document all NHEXAS respondent selection procedures for each stage of each study.
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Project Name:
LL-5 (cont'd). Influence of Incentives, Response Rates, and Nonresponse
Bias on Survey Design
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
10
50
50
0
6
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Secure necessary data; QA data
(3) Final outputs: Impact of response rates on survey design
Type of Expertise Needed
Principal Investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
75
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Project Name:
LL-6. Application of Screening Tools for Large-Scale
Exposure Field Studies
Short Project
Description:
Analyze data from NHEXAS pilot studies to assess the reproducibility, accuracy (i.e., false
positive/false negative), limits of detection (LODs), ranges, interferences, and costs of
screening methods relative to data obtained. From the analysis, identify methods that were
unsuccessful and other methods (i.e., questionnaires) that could serve as screening tools in
large-scale exposure studies to identify more highly exposed individuals and reduce costs.
Goal/Objective:
To evaluate the utility of low-cost screening methods
(1) for identifying households or subjects requiring more intensive monitoring and
(2) for providing data useful for exposure assessment (e.g., distributions).
Significance of
Project:
Multimedia, multipathway studies are expensive to implement. For some pollutants and
media, a large proportion of the samples may have no detectable analytes. A study design
may require identifying highly exposed individuals for intensive study. Screening methods
are needed to provide a low-cost approach that can identify highly exposed individuals and
which samples or media should be analyzed. In addition, screening methods with sufficient
quantitative power may provide data adequate for exposure analysis. Assessment of
screening methods and concentration data obtained from the pilot studies will provide
valuable information to guide future NHEXAS studies.
Suggested
Approach:
(1) Identify screening methods, or methods that could be used for screening, from the
NHEXAS pilot studies.
(2) Assess the ranges, reproducibility, accuracy (i.e., false positives/false negatives) and
LODS for identified screening methods with more rigorous and expensive methods.
(3) Evaluate questionnaire data as a screening tool.
(4) Determine which methods were successful (or could be successful) and those that were
not.
(5) Assess the cost and burden (participant and field staff) of methods that show promise
for use in future studies.
Data or Input
Needs:
(1) A listing of field and analysis methods used by each NHEXAS pilot study consortium
with the applicable analytes, LODS, range, and associated QC data.
(2) Results for paired low-cost/high-cost methods at homes where two adults were
employed.
(3) Information about the time and effort needed to implement each field collection or
measurement method and any associated laboratory and analysis costs.
Feasibility
(of analyses with
current NHEXAS
databases):
There are sufficient data groups to allow the proposed analysis. Some examples include, for
VOCs, photoionization detector and passive diffusion badges versus actively pumped
sorbent tubes; for pesticides, immunoassay methods and analyses by gas chromatography
with various detectors; for metals, XRF versus inductively coupled plasma (ICP) with
various detectors, atomic emission spectrophotometry and ICP/MS; for PAHs in air,
real-time PAH monitor.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
0
4
12
Research Outputs
(1) Initiate project
(2) Compile listings of methodology and associated data (QC, range,
LOD) from databases
(3) Statistical comparisons of paired sample results, assessment of
success and cost of potential screening methods
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Approximate
Level of Effort:
Month
% Time
10%
25%
50%
18
Months
18
18
6
(4) Final outputs: Final report or manuscript describing screening
method assessment results
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
LL-7. Lessons Learned from Field Sampling and Laboratory Experience in
the NHEXAS Pilot Studies
Short Project
Description:
Actual experiences of NHEXAS pilot study personnel will document important lessons
learned from conducting field monitoring and laboratory analyses.
Goal/Objective:
Document field and laboratory procedures used in the NHEXAS pilot studies, identify
procedures that worked well, and provide recommendations for improvement. Pilot study
sampling and analysis outcomes will be compared with expected outcomes to assess their
applicability and utility for future NHEXAS studies.
Significance of
Project:
A great deal of the actual experience gained from the NHEXAS pilot studies has not been
documented formally and would be invaluable in the design and implementation of a large-
scale exposure study.
Suggested
Approach:
(1) Develop interview questions/issues.
(2) Interviews and/or a workshop for pilot study field and laboratory personnel.
(3) Document procedures and practices not captured in standard operating procudures
(SOPs) that are critical for efficient implementation of large-scale multimedia and
multipathway studies.
(4) Compare actual QC (accuracy, precision, and LODS) and data range results with expected
results to assess the applicability of the procedures to large-scale exposure studies.
(5) Evaluate process of administering questionnaires, sampling methods, sample handling
and tracking, laboratory procedures, participant training and burden (time and level of
understanding), field staff burden (time and training), etc.
Data or Input
Needs:
(1) Interviews with NHEXAS pilot study personnel (consortium, federal agencies, and federal
contract labs). Information collected from interviews will address procedures and
practices, including the effectiveness of administering questionnaires, sampling methods,
sample handling and tracking, laboratory procedures, participant training and burden
(time and level of understanding), field staff burden (time and training), etc.
(2) Quality control data and sample result ranges for each of the sampling/analysis methods
used in the NHEXAS pilot study.
Feasibility
(of analyses with
current
NHEXAS
databases):
This project is currently feasible if initiated in a timely manner because most personnel
associated with the NHEXAS pilot studies are available and able to recall anecdotal
information. It will be important to implement the interviewing portion of this project as soon
as possible to capture this information. The other data needed for this evaluation is available
now, or will be available as the NHEXAS pilot study databases are completed.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
Month
Month
Month
0
3
6
6
9
12
Research Outputs
(1) Initiate project
(2) Develop interview questions
(3) Implement interviews with NHEXAS personnel
(4) Assemble QC and sample result ranges
(5) Compare actual results with expected results
(6) Final outputs: Report documenting field monitoring and
laboratory analysis experience and lessons learned. Report or
manuscript comparing actual to expected QC and data range
results
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Approximate
Level of Effort:
% Time
5
20
100
Months
12
12
9
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Visits to NHEXAS centers; travel needed
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
LL-8. Value of Information and Cost-Benefit Analysis of Exposure
Measures
Short Project
Description:
The proposed project will evaluate the cost-effectiveness of the various exposure measures
for each of the pollutants and pathways using decision analysis, value of information, and
cost-benefit analysis techniques. Specifically, the proposed project will compare the relative
cost effectiveness of questionnaires, environmental sampling, personal sampling, and
biomarkers to assess exposures to each of the pollutants. The proposed analyses will
include exposure assessment methods used in the NHEXAS pilot studies, as well as
assessment methods developed more recently.
Goal/Objective:
The primary objective of the proposed project is to compare the costs and benefits of
methods used to characterize multimedia exposures for each pollutant and examine their
implications on sample size needs, sampling costs and burdens to the study subjects.
Significance of
Project:
The proposed project directly addresses SAB concerns (Comments A, B, and C) and, as a
result, will improve substantially the ability to optimize the design of future NHEXAS and
other exposure studies. Findings from each of the NHEXAS pilot studies will be used to
design the most cost-efficient exposure data sampling strategy for the future NHEXAS.
Suggested
Approach:
For each pollutant and pathway, the proposed study will:
identify the exposure assessment tools and methods (e.g., questionnaires, micro-
environmental and personal sampling, biomarkers) used in each of the three studies and
from other post-NHEXAS efforts;
estimate the associated costs, data quality, and sample size requirements for each method;
use value of information and cost-benefit analysis tools to determine the cost-effectiveness
of each method; and
develop methods selection criteria.
Data or Input
Needs:
From each NHEXAS study, the following will be needed:
concentration, biomarker, questionnaire, and time/activity data;
methods performance data;
the method-specific direct costs and other resource requirements; and
relevant data from recent method development studies.
Feasibility
(of analyses with
current NHEXAS
databases):
High, all needed data exist.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Research Outputs
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Approximate
Level of Effort:
Month
Month
Month
% Time
10
100
100
0
3-12
12-18
Months
9
18
18
(1) Initiate project: Data collection and compilation
(2) Data analyses
(3) Final outputs: Comparative analysis of different exposure
assessment methodologies, methods selection criteria, and peer-
reviewed publications
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
LL-9. Assessments and Recommendations for Effective Communications
Short Project
Description:
The purpose of this project is to review the communications procedures put in place by each
of the three NHEXAS pilot studies, as they shared individual results with respondents and
composite data or other data with local, state, and federal officials and organizations.
Goal/Objective:
The goal of this project is to compare and contrast the participant communication strategies
implemented by the three consortia and to determine which strategies or components worked
well and which components need improvement.
Significance of
Project:
Participant communication is a component of human exposure assessment that often is
overlooked or given low priority by both project planners and sponsors, yet it is an
important component of the overall package of benefits that are provided to the respondents
and which serves as a significant component of the package of incentives used to promote
participation. In addition, timely reporting of values that exceed nominal thresholds is a
mandatory component of all human exposure research.
Suggested
Approach:
The processes used in the three pilot studies to share individual results with the
respondents will be reviewed and compared. The respondent may be recontacted for a
brief interview to determine how well the respondent understood the information that was
provided and to determine what questions were not answered for the respondent. As part
of the interview, or in a focus group setting, the same data information using each of the
processes used in the three studies will be shared. This will allow direct comparison of
varying approaches and should determine the best means of sharing data in this setting.
' Next, interviews with the local and state agencies that received notification from any of the
three studies for measured values exceeding state or local reporting thresholds will be held.
The process by which the data were shared, what each agency did after receiving the data,
and the range of thresholds reported by the states will be reviewed. Threshold values used
at the local, state, and federal level will be compiled.
' Then, the reporting mechanisms in place for the three studies will be reviewed for common
approaches. A sample of the recipients of the reports will be selected and interviews or
focus groups will be conducted to assess the utility of the reports and will seek to
determine the information missing from the reports or the information that was provided in
a manner that minimized its utility. Attempts will be made to determine what means of data
reporting are of value to different levels of users, and to develop a basic format to be used
in reporting composite data to subjects.
Finally, meetings will be held with state and local government agencies to review their role
in release of data and dissemination of results. The ultimate product of these efforts would
be a communication evaluation manual.
Data or Input
Needs:
Copies of material used by each of the consortia to provide results to the respondents.
Copies of reports providing composite data to local, state, and federal agencies that
provided support or assistance during the survey design phase or during data collection
Feasibility
(of analyses with
current NHEXAS
databases):
No database access is required. This effort will require access only to copies of material
used by the consortia to share information with respondents and to the reports used to
provide composite data. Therefore, this project is feasible without access to current or
future databases. Recontacting participants and state and local representatives may be
problematic.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
0
6
9
Research Outputs
(1) Initiate project
(2) Compare NHEXAS processes
(3) Complete local/state interviews
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Approximate
Level of Effort:
Month
% Time
25
40
50
25
12
Months
12
12
12
12
(4) Final outputs: Document: Evaluation of approaches for
effective communication
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Secretary
* Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
LL-10. Evaluation of NHEXAS Results To Derive an Optimal Set of
QA/QC Activities for Human Exposure Field Studies
Short Project
Description:
This project will identify and evaluate the QA/QC across laboratories and consortia. This will
include an analysis of the NIST and comparability study data. The project will develop an
annotated inventory of recommended QA/QC activities needed to successfully conduct
large-scale human exposure measurement studies. This will include all phases of the study
from planning to final database development.
Goal/Objective:
The goal of this project is to provide an optimum set of QA/QC activities for future human
exposure studies. This is needed to assure that the studies produce data of the required
quality while keeping costs to a minimum.
Significance of
Project:
Effective QA/QC is essential to produce high-quality data from the funds invested in any
field exposure study. Because of the high cost of these types of studies, it is also important
not to include unnecessary QA/QC that might increase costs. By examining the QA/QC used
in the NHEXAS studies, guidance can be developed for this critical study component.
Suggested
Approach:
(1) Identify the QA/QC activities performed by each consortium and laboratory, including
the NIST standards and performance evaluations studies, the interlaboratory
comparability study, QA documentation, reviews, audit reports, reviews of field
performance, and QA samples.
(2) Evaluate the success of each activity and the benefits it provided to the study.
(3) Identify areas where data quality could have been improved with additional QA/QC
activities or areas where excess QA/QC activities might have been employed.
(4) Develop an annotated inventory of the recommended QA/QC activities needed to
conduct a large-scale human exposure study.
Data or Input
Needs:
Access is needed to the complete sets of data and documentation, including all QA/QC
information of each consortium and laboratory and the NIST and comparability study results
and reports.
Feasibility
(of analyses with
current
NHEXAS
databases):
The study is feasible given access to the data from all studies. A mixture of laboratory, field
and QA expertise is needed to evaluate information.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
0
12
Research Outputs
(1) Initiate project
(2) Review consortia documents
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Approximate
Level of Effort:
Month
% Time
20
100
200
18
Months
18
18
18
(3) Final outputs:
Consolidate information from documents and develop annotated
inventory
Guidance document on optimal QA/QC for human exposure field
studies
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
LL-11. Effectiveness of Questionnaires/Diaries, in Collecting Information
To Estimate or Describe Exposures for Determinants of Exposure
Short Project
Description:
The NHEXAS pilot studies utilized questionnaires for various determinants of exposure.
This project will analyze the questionnaire data obtained from the three NHEXAS pilot
studies for understanding the following aspects of exposure: compliance issues,
consistencies of response, reliability and validity of questions, effectiveness of dietary
questionnaires/check lists, and relationship of questionnaire rationale with response. This
analysis will provide information needed to design better questionnaires/diaries for the
national-scale NHEXAS.
Goal/Objective:
Determine the value of questionnaires for understanding various aspects of exposure and
the reliability and validity of the instrument for ascertaining these factors. This analysis will
influence the design and expected participant burden costs associated with future NHEXAS
or similar exposure studies.
Significance of
Project:
The relative value of questionnaires and diaries for understanding public health and
exposure, as well as the item-by-item value of asking each question, will be determined with
the overall goal of minimizing participant burden and costs.
Suggested
Approach:
Each study utilized the same OMB-cleared questionnaire and activity diary instruments.
The proposed analysis will evaluate the information content obtained from the
questionnaires, the lessons learned from the administration and compliance issues, and
other attributes to estimate their relative value. This will involve some comparison with
exposure and environmental measurements to determine the value of the questionnaire item.
Data or Input
Needs:
Databases, questionnaire information, and field observational data from each pilot study.
Monitor sensor data to evaluate activity pattern diaries (NHEXAS Region V study only).
Feasibility
(of analyses with
current NHEXAS
databases):
This analysis should be straightforward.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration"
Month
Month
Month
% Time
20
50
50
0
3
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Obtain needed data
(3) Final outputs: Guidance document on formulating effective
questions for future exposure studies
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
Short Project
Description:
Goal/Objective:
Significance of
Project:
Suggested
Approach:
Data or Input
Needs:
Feasibility
(of analyses with
current NHEXAS
databases):
LL-12. Scaling Up: Evaluation of the NHEXAS Pilot Fixed-Costs,
Coordination and Degree of Standardization
This project will evaluate the NHEXAS pilot start-up expenditures and cost implications for
various scales of coverage. The evaluation also will address the effectiveness of
coordination/communication approaches that were used and their application to a full scale
survey. A key component of the analysis will be the evaluation of approaches that were
standardized explicitly and a determination of whether or not the degree of standardization
was adequate.
To transfer the experience of the pilot to develop the most cost-effective full survey
possible.
A full-scale survey will provide the data necessary to evaluate status and trends of human
exposures on a national scale. Using empirical data from the pilot ensures that the most
cost-effective approaches are used.
(1) Interviews will be conducted addressing coordination, communication, and degree of
standardization of management and staff from the involved agencies and consortia.
(2) Collect cost information.
(3) Review pilot documentation to determine where standardization occurred.
(4) Review NHEXAS database.
(5) Formulate recommendations for an optimum scale-up strategy.
Cost data; available documentation; NHEXAS database.
Highly feasible; all information ultimately available.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration"
Month
Month
Month
% Time
20
33
100
0
6
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Collect needed data
(3) Final outputs: Report recommending optimum scale-up strategy
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
LL-13. Cross-Studies Evaluation and Recommendations for
Standardization of Data Management Procedures in a National NHEXAS
or Other Large-Exposure Field Study
Short Project
Description:
This project will analyze the data collection and automated survey management procedures
developed for each NHEXAS pilot study from sampling, through sample analysis and to
inclusion in the final database. The data QA/QC procedures will be evaluated, and the
resulting database structures will be examined. The strengths and weaknesses of the three
approaches will be noted with respect to ongoing EPA data management initiatives.
NHEXAS pilot QC data will be analyzed, and recommendations for current and future studies
will be developed. These recommendations will include areas that would benefit from
standardization; for example, data transfer from analytical laboratories, database elements,
QA/QC codes, information shells, etc.
Goal/Objective:
To have appropriate conventions and procedures for recording data and data quality and to
increase the efficiency of future data collection efforts.
Significance of
Project:
Management of large EPA databases as a valued resource is currently a high priority within
EPA. Procedures and conventions used to manage the integrity of data are evolving but are
essential to both primary and secondary data users. The NHEXAS studies are an excellent
opportunity to analyze the procedures used by three different organizations to develop and
populate study databases. Results of this project will be used for improving/optimizing data
collection and storage for future human exposure studies and other EPA primary data
collection efforts.
Suggested
Approach:
(1) Assess the data management processes and conventions used in each NHEXAS pilot
study.
(2) Review the status of EPA efforts with respect to Reinventing Environmental Information
(REI), specifically current status of data standards (Chemical ID, Location ID, etc.), the
Environmental Data Registry (EDR), the Environmental Information Management System
(EIMS) and any other relevant efforts to insure the quality and accessability of EPA
databases.
(3) With stakeholder input (EPA program offices, involved Federal agencies, etc.),
recommend application of EPA conventions and procedures for a future national-scale
NHEXAS or other large exposure field database. Recommend conventions in areas where
none exist. Conventions that document the limitations of the data are particularly
important.
(4) Analyze available quality control information (i.e., batch level laboratory QC information)
and develop Data Quality Indicators that can be stored with the data for the benefit of
secondary data users.
Data or Input
Needs:
Needed information includes the following for each consortium: data management
plan/procedures; field data collection procedures; procedures for transferring the field,
analytical, questionnaire/diary and related data into the final databases; data QA/QC
procedures; and final database design. Each consortium also will need to provide an analysis
of how well their procedures worked and problems encountered.
Feasibility
(of analyses with
current
NHEXAS
databases):
Data collection and processing SOPs are available from each consortium. The analysis of
how well the procedures worked in each consortium will need to be done in the relatively near
future, while the staff involved are still available. EPA-level initiatives in this area are active
and ongoing.
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Project Name:
LL-13 (cont'd). Cross-Studies Evaluation and Recommendations for
Standardization of Data Management Procedures in a National NHEXAS
or Other Large-Exposure Field Study
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
20
50
50
0
6
12
Month
s
12
12
12
Research Outputs
(1) Initiate project
(2) Collect and review NHEXAS SOPs and QA documentation
(3) Final outputs:
exposure field
A data management strategic plan
studies
for future
Type of Expertise Needed
Principal investigator
Senior-level staff (
"associate")
Junior-level staff ("assistant", technician), Students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
4.5 MODELING GROUP
The charge to the modeling breakout group is to consider a number of multimedia and
multipathway exposure and dose modeling approaches that can be implemented with the NHEXAS
data collected. Specifically, the group is asked to recommend a number of robust modeling strategies
for estimating pathway-specific and aggregate exposures and dose from a variety of NHEXAS
pollutants. The participants also will suggest investigations designed to calibrate, test, and evaluate
multimedia and multipathway models using the NHEXAS concentration exposure and biomarker data.
4.5.1 SAB Comments
In its review of the NHEXAS pilot study, the SAB recommended conducting modeling studies
with the NHEXAS data. Specific comments include the following.
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(1) Develop physical models that integrate exposures from different media in order to estimate long-
term exposures from short-term measurements [3.2, 3.2.2.d, 3.2.2.g].4
(2) Develop models for identifying factors related to high-end exposures [3.2.2.g].
(3) Address model validation and refinement [3.2.2.a, 3.2.2.g].
(4) Apply NHEXAS data to ongoing modeling projects such as TRIM and CEM [3.2.2.g].
4.5.2 Questions To Address
As a starting point to identify, describe, and prioritize potential projects, the breakout group
should consider the following questions and determine what additional critical questions should be
added.
(1) In modeling population exposures, which sets of NHEXAS study measurements are expected to
provide representative population exposure distributions in each of the study areas?
(2) For which pollutants/media, are the NHEXAS data sufficient to develop, calibrate, and evaluate
multimedia, multipathway exposure models?
(3) What types of route and pathway-specific microenvironmental exposure models can be
developed or tested with the available NHEXAS demographics, concentration, questionnaire,
time/activity, and dietary data?
(4) What approaches or optimal methodologies/models can be used to estimate pathway-specific
exposures and dose?
(5) What are some suggested strategies for integrating media and pathway-specific exposures and
dose estimates?
(6) What models best describe the relationship between the short-term NHEXAS measurements and
long-term exposures?
(7) What is the comparison of modeled dose estimates and biomarkers?
(8) What models should be developed and applied in order to identify factors related to high-end
exposures?
4Numbers in brackets are cross-references to sections in the SAB report.
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(9) What are the model input uncertainties using the NHEXAS data, and what are the resulting
uncertainties in the exposure and dose model predictions?
(10) What model analyses should be used to determine how much uncertainty in exposure
measurements can be reduced by collecting more detailed measurements on exposures, pollutant
concentrations, and different exposure factors?
(11) What is the influence of the spatial and temporal scales in concentration and exposure
measurements based on NHEXAS data and model predictions?
(12) What is the comparison of the exposure and media-specific concentration distributions from the
initial (pre-NHEXAS) exposure assessments to the NHEXAS pilot results?
(13) How can the initial pre-NHEXAS study multimedia, multipathway models developed for lead,
benzene, and chlorpyrifos using the NHEXAS study measurements be verified or extended?
(14) How can the multipathway exposure and dose models using the NHEXAS data and other data
sets be best calibrated and evaluated?
(15) What NHEXAS analyses will benefit ongoing modeling projects such as TRIM and CEM?
4.5.3 Discussion Considerations
In discussing and developing proposals for the analyses (or projects) identified above, consider
the following questions.
(1) What statistical or analytical techniques should be used to address the analysis or modeling issues
raised by the questions?
(2) What approaches are best suited for estimating averages and upper percentiles of the exposure
and dose distributions for the different population subgroups (e.g., children, adults, elderly)?
(3) How should NHEXAS data across the consortia be treated in modeling exposures and dose?
Should the data sets be combined or treated separately?
(4) How can we model exposures to multiple pollutants?
(5) What analyses or modeling studies should be conducted in order to design future field studies that
will improve the current and new multimedia, multipathway modeling projects?
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4.5.4 Project Descriptions
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Project Name: M-l. Review Format and Content of NHEXAS Databases for Modeling
Utility
Short Project This project will examine the NHEXAS database and establish optimal format required for
Description: exposure modeling projects. Other users should be included in this process to maximize
utility of the combined database.
Goal/Objective: NHEXAS data must be available in a format that is readily accessible to potential users.
Data should be accessible for input to existing models to allow for model testing and
investigation of NHEXAS relationships (i.e., correlations among various dependent and
independent variables). Models that are being developed or expected to be developed in
the future are also likely to require standard database formatting, which should allow for
convenient access and inquiry.
Significance of
Project:
Suggested
Approach:
Data or Input
Needs:
Feasibility
(of analyses with
current NHEXAS
databases):
An essential first step prior to pursuing any other NHEXAS modeling project.
Review existing exposure models to assess model input needs and to compare with
available NHEXAS data. Confer with NHEXAS study data developers, exposure model
developers, and other potential NHEXAS data users to establish the optimal format for
NHEXAS database. Establish a task force (or committee) and/or hold a workshop to set a
standard for the present and future NHEXAS databases.
Data from all three NHEXAS studies including data code books, final databases, and
QA/QC data.
This project is of the utmost importance since the availability and format of the NHEXAS
database will affect directly the success of interpreting the results of NHEXAS. Because
the preparation of the NHEXAS database is already underway, it is feasible and necessary
to give this proposed project high priority. In particular, this project could benefit from the
ongoing database projects at the three NHEXAS consortia.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
% Time
30
50
50
0
3
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Convene workshop
(3) Final outputs: Report summarizing workshop findings and
conclusions
Type of Expertise Needed
Principal investigator/EPA Coordinator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Task force of EPA and approximately 10 external
experts who will participate in at least one workshop
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
M-2. Evaluation of Existing Multimedia Models Using the NHEXAS
Data Set
Short Project
Description:
High-quality and reliable multimedia monitoring data are virtually nonexistent in the
literature, and, as such, the opportunity to test existing models, even on a qualitative scale,
is rarely available. Several multimedia models have been developed, or are under
development, that predict media concentrations in residential environments based on inputs
such as source characterization and fate and transport, etc. Information available from the
NHEXAS questionnaires, particularly those related to local source characterization, fate and
transport, receptor characterization and activity patterns (supplemented by default values)
should be analyzed and used in these models to predict media concentrations and personal
exposures of the NHEXAS respondents. These predictions should be compared with the
individual's exposures and microenvironmental concentrations monitored in NHEXAS.
Examples of models that can be evaluated include, but are not limited to, TRIM, MEPAS,
CARES, LIFELINE, and CONSEXPO, as well as other linked and nested compartmental
models.
Goal/Objective:
To improve the understanding of the strengths and limitations of existing multimedia
models and identify opportunities for improving current and future models.
Identify the usefulness of the data set and determine how future NHEXAS studies could
better meet the need for testing models.
Significance of
Project:
Multimedia models provide the basis for regulatory decision for pesticides, hazardous waste
sites, and the evaluation of releases to air and water. Currently, there are very limited
opportunities to evaluate these models. NHEXAS provides a unique opportunity for such
evaluations.
Suggested
Approach:
This project would be performed in phases.
(1) Determine how the data set could be used (selection of pollutants, interim findings,
activity/dietary patterns, etc.).
(2) Identification of the models, modeling strategies (e.g., linked and nested multimedia
models) and the development of the strategy for developing model inputs and relating
outputs to the dose measurements in the NHEXAS data set.
(3) Model teams (preferably the developers of each multimedia model) perform the
evaluations.
(4) Analyze the model's prediction and NHEXAS findings to determine how and why the
models did or did not match with the survey.
(5) Develop recommendations on how future NHEXAS projects could be better designed to
meet the evaluation needs of multimedia modelers.
(6) Publish a final report/peer review publication.
Tasks 1 and 2 could be performed by a panel of exposure assessment experts, through one
or more workshops. Where possible, model owners should be involved in these
workshops. A clear methodology should be established for the evaluation procedures. The
selected models should be divided into modules, if possible, for estimating intermediate and
final exposure results. Modules should include source characterization, fate and transport,
receptor characteristics, activity patterns, and exposure assessment (Task 3). A consistent
strategy for dealing with data gaps should be established. The model's predictions of
interim findings (air and surface levels, hand wipe, dietary levels, activity patterns, etc.) also
should be compared to the NHEXAS data set.
Data or Input
Needs:
The complete data set (including the data from the questionnaires) should be available prior
to the development of the specific model test sets. Models should be well characterized and
model developers should participate in the project.
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Feasibility
(of analyses with
current NHEXAS
databases):
The project should be feasible. Only existing models will be evaluated. Where appropriate,
model developers will be included in the project team. Models of many source terms cannot
be included in this exercise because they were not included in NHEXAS.
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Project Name:
M-2 (cont'd). Evaluation of Existing Multimedia Models Using the
NHEXAS Data Set
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration"
Month
Month
Month
Month
% Time
40
100
80
0
6
12
18
Months
18
18
18
Research Outputs
(1) Initiate project
(2) Selection of models for evaluation, development of a modeling
strategy that addresses differences in the type of models and
how data gaps will be addressed
(3) Development of a charge to the individual running the
models
(4) Final outputs: Report/peer review publication
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Two to three workshops are anticipated
' Duration = approximate time (in months) needed, from start of project, to complete each step.
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Project Name:
M-3. Develop Model Parameters from Qualitative and Quantitative
NHEXAS Monitoring Data, Questionnaires, Time/Activity, and
Survey Data
Short Project
Description:
Develop exposure model parameter (e.g., ingestion rates, emission rates, etc.) values,
ranges, and distributions making use of both quantitative and qualitative data generated in
NHEXAS. Exposure parameters should be developed in accordance with the current state
of the art in exposure assessment and corresponding model input requirements. Specific
emphasis should be placed on key exposure parameters common in multimedia exposure
assessment and those that are likely to contribute to high-end exposures.
Goal/Objective:
Generate deterministic values and stochastic distributions for exposure model parameters,
using available NHEXAS database. Exposure parameters that are selected should be
relevant to exposure assessments that are based either on mechanistic, statistical, or
empirical models.
Significance of
Project:
Improve exposure parameter values and the utility of questionnaires for quantitative
exposure analysis.
Suggested
Approach:
Develop methods to interface available selected exposure models with qualitative and
quantitative questionnaire data (e.g., time/activity patterns, identified sources and exposure
pathways) for the purpose of deriving magnitude, ranges, and distributions of exposure
parameters. The combination of artificial intelligence and statistical methods is one
possible approach for the automated analysis of large data sets.
Data or Input
Needs:
NHEXAS chemical monitoring data for all media (where available) and
qualitative/quantitative data generated from questionnaires and other sources (e.g., local
survey of potential sources).
Feasibility
(of analyses with
current NHEXAS
databases):
The use of mathematical and computer methods to combine qualitative and quantitative
data for the purpose of generating quantitative exposure parameters represent a new and
challenging approach. The proposed approach is feasible given the rich NHEXAS
database and existing state-of-the-art mathematical methods of quantifying descriptive data
in the context of model development. Analysis may be limited by censored (e.g.,
nondetects) data for chemical measurements in some media.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
% Time
50%
100%
50%
0
12
24
Months
24
24
24
Research Outputs
(1) Initiate project
(2) Development of methodology and demonstration of general
test cases (Phase I)
(3) Final outputs: Final report and peer reviewed papers
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
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96
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Project Name:
M-4. Quantify Uncertainties in NHEXAS Data and Assess Contribution
to Model Errors
Short Project
Description:
Provide uncertainty estimates within the NHEXAS database that are available to
researchers and the public, so that uncertainty is addressed consistently and does not lead
to redundant effort by modelers. Identify how the data uncertainties may impact modeling
uncertainties and illustrate with case studies.
Goal/Objective:
Provide consistent, understandable uncertainty estimates of the NHEXAS data within the
NHEXAS database
Provide guidance/advice on applicability and use of various types of data in models to
minimize inappropriate model construction.
Significance of
Project:
The NHEXAS database will be used by many researchers and the public. Inclusion of
uncertainty estimates/descriptions will avoid duplication of effort in calculating these
values, will mean that the data uncertainties are treated consistently, and will alert the
public and regulatory community of possible limitations in the use of the data.
Suggested
Approach:
Analytical Measurements
(1) Ensure that NHEXAS data are QA'd and flagged appropriately.
(2) Ensure that NHEXAS data include Limit of Detection information.
(3) Calculate standard errors for each analytical methodology (including sampling and
analysis).
(4) Tag uncertainty data to all NHEXAS data entries and provide a methodology for error
estimation with the public database.
Survey and Time/Activity Information
(1) Provide qualitative assessments of data and their applicability for modeling by
including meta data from field staff on reliability of individual household;
include expert panel judgment of uncertainties of the methodology in general, including
effects of sample size, inaccuracies of recall diaries, observer effects, time resolution
effects, etc.; and
compare survey results from NHEXAS with other data sources.
(2) Include qualitative assessments in database.
Assessment of Model Uncertainties
Convene workshop of modelers to evaluate impacts of uncertainties for variety of analytes,
with differing critical routes of exposure. Provide qualitative descriptions of uncertainties
and caveats for inclusion in the database. Provide case studies to illustrate how errors
impact modeling uncertainties.
Data or Input
Needs:
Paced by the availability of the database, the NHEXAS data need to be quality assured to
flag/remove inappropriate data. Duplicate sample data, split sample data, blanks, and other
QA/QC information on the analytical measurements need to be included in the database.
A description of the sampling and analytical methods also must be included.
Feasibility
(of analyses with
current NHEXAS
databases):
The first part of the effort is quite doable, and should build on normal QA/QC procedures.
This work is to insure that the synopsized uncertainty data also are made readily available
for researchers and the public. The impact on modeling errors is much more likely to be
case dependent, varying with each analyte and model used.
97
-------
Project Name:
M-4 (cont'd). Quantify Uncertainties in NHEXAS Data and Assess
Contribution to Model Errors
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
Month
Month
Month
Month
% Time
n/a*
n/a*
n/a*
n/a*
0
2
3
6
6
6
12
Months
11
6
6
5
Research Outputs
(1) Initiate project
(2) Review NHEXAS databases now under development for
data to be included and make sure that QA/QC data and
metadata on QC are in database for both analytical and
survey data
(3) NHEXAS database becomes available
(4) Calculate synopsis information from data sets now
scheduled to be delivered in FY01
(5) Convene workshop or expert panel to provide qualitative
description of uncertainties associated with survey
information
(6) Convene workshop or expert panel to evaluate impact of
uncertainties of modeling-prepare case studies for
specific analytes/major routes of exposure
(7) Final outputs: Incorporate uncertainty estimates and case
studies into public database
Type of Expertise Needed
Principal investigator (PI)
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Clerical
* Duration = approximate time (in months) needed, from start of project, to complete each step.
* NOTES: Level of Effort [FTE equivalent] estimates:
Review NHEXAS database:
0.5 mo PI level * 6 PI (3 external experts +1 from each of 3 consortia) [3 mo]; 0.5 mo senior level at each of 3
consortia [1.5 mo]; 0.5 mo junior level staff at each of 3 consortia [1.5 mo]; 0.5 mo clerical staff at each of 3
consortia + 0.5 mo general support [2 mo].
Calculate synopsis uncertainty data from database:
1 mo. senior level [1], 1 mo junior level [1].
Workshop on Survey uncertainties:
0.5 mo for 6 PI level experts [3.0]; 0.5 mo clerical support [0.5].
Workshop on modeling errors:
0.5 mo for 6 PI level experts [3.0]; 0.5 mo clerical support [0.5].
Develop case studies:
0.5 mo for 3 PI level experts [1.5], 1 mo for 3 senior level [3], 1 mo for 3 junior level staff [3].
98
-------
Incorporation into database:
0.5 mo PI level, 0.5 mo senior level, 0.5 mo junior level, 2 mo clerical support.
99
-------
Project Name: M-5. Incorporation of Modeling Considerations in the Design of Future
NHEXAS Studies
Short Project
Description:
Goal/Objective:
Significance of
Project:
Suggested
Approach:
Data or Input
Needs:
Feasibility
(of analyses with
current NHEXAS
databases):
In conducting field studies, usually a study is designed, monitoring data and other related
data are gathered and then statistical analyses performed to interpret the data. However,
from a model development, model application, or model evaluation perspective, the data
gathered may be insufficient (particularly for inferential purposes). Future NHEXAS studies
should accommodate the needs of existing or modified multimedia models. To achieve this,
the model parameters should be understood and incorporated in the study design. Sample
parameters include those related to time/activity patterns, contact rates, dermal exposure
(e.g., surface coverings in residences, time spent on these surfaces).
To establish a procedure wherein modeling considerations are accommodated in the early
stages of the design of future NHEXAS studies.
The power of any future NHEXAS study lies in interpreting the measurement results within
the risk assessment/risk management paradigm used by EPA to select actions designed to
protect the public. This interpretation can be done effectively only through modeling the
exposures and the changes resulting from the risk management actions. It is critical that
future NHEXAS field studies incorporate modeling considerations in their design from the
very inception to ensure their usefulness for protecting human health and the environment.
The results of the NHEXAS pilot studies can be used to identify a multimedia exposure
assessment methodology, either currently implemented in a model or that can be later
modified. This methodology can be used to establish the parameters to be monitored in
future studies.
All available data from NHEXAS pilot studies.
This project is immediately feasible and should be undertaken before any future NHEXAS
studies.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
50
50
0
3
6
Months
9
9
Research Outputs
(1) Initiate project
(2) Determine model parameters to be monitored
(3) Final outputs: Demonstrate use of poststudy data
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
: Duration = approximate time (in months) needed, from start of project, to complete each step.
100
-------
Project Name:
M-6. Identification of Factors Contributing to High-End Exposures in the
NHEXAS Study
Short Project
Description:
Determine factors ( activities, sources, and housing or personal characteristics) that
contribute to the upper region of the exposure distribution, as well as to exposures received
by sensitive members of the population (e.g., children and the elderly). Ideally, factors will be
revealed for pollutants each representing a chemical type (VOCs, metals, and pesticides). A
variety of statistical methods may be appropriate for investigating the complete range of the
NHEXAS data, including analytical, questionnaire, and time/activity data.
Goal/Objective:
Identify the major contributions, routes, and sources, to high-end exposures for different
classes of pollutants.
Significance of
Project:
Identification of the factors that influence or contribute to exposure is necessary for
interpretation of the NHEXAS data, applying the results to risk assessments and
identification of remedial actions. Analysis of the data could indicate which questionnaire
items or activities may be suitable for predicting high exposures or where additional targeted
questions may be necessary.
Suggested
Approach:
There are a variety of methods that may be applicable to this project. Suitable methods
should be able to handle a variety of data types (binary, integer, categorical, ordinal, and
continuous), possibly after suitable transformations of the data. Potential methods may be
based on regression trees, neural networks, or factor analysis. Methods of order statistics
(i.e., statistics of extreme events), not previously used in exposure assessments, also may
reveal important relationships.
Data or Input
Needs:
Investigators will need to construct a distribution of exposure using environmental
concentrations and exposure factors, or biomarkers. The criteria for identifying individuals at
the high end then will need to be determined.
Feasibility
(of analyses with
current
NHEXAS
databases):
The proposed types of analyses will be applicable for only chemicals where a comprehensive
set of measurements for an adequate number of subjects exists. Some methods also may
require a substantial number of properly classified subjects to "train" a model. Potential
chemicals for which comprehensive data appear to exist are metals, chlorpyrifos, and benzene.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
% Time
20
0
3
9
12
18
24
Months
24
Research Outputs
(1) Initiate project: On availability of NHEXAS data; timeline
based on the analysis of three pollutants (metal, VOC, and
pesticide)
(2) Obtain and merge databases
(3) Develop estimate of exposure and fit a possible distribution
(4) Identification of highly exposed individuals
(5) Development or training of models
(6) Final outputs: Draft manuscript detailing potential important
factors and sources of uncertainty in the identification
Type of Expertise Needed
Principal Investigator
101
-------
50
50
24
24
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
: Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
M-7. Implementation of Existing Multimedia/Pathway Exposure Models
To Aid in the Interpretation of NHEXAS Data
Short Project
Description:
Multimedia fate and exposure models have been constructed to represent the current state of
the science regarding chemical, environmental, and populations dynamics. These models are
powerful tools for investigating NHEXAS data. These investigations should help to identify
critical exposure pathways and factors that contribute to high-end exposures. In short, these
models can aid to better understand and explain results from the NHEXAS project and to
design future studies.
Goal/Objective:
Utilize existing multimedia/pathway exposure models to aid the interpretation of NHEXAS
data and to help identify critical exposure pathways, processes, and factors that contribute
to high-end exposures.
Significance of
Project:
This project is significant in that it will utilize existing tools that assimilate or represent the
current level of understanding of fate and exposure processes to extract relevant and useful
information from the NHEXAS results.
Suggested
Approach:
(1) Ideally this project should include at least one pesticide, a semi-volatile compound (with
differing source characteristics than the pesticide, such as a PAH), and a metal.
(2) For each chemical class, identify specific case studies within NHEXAS that warrant
investigation (elevated concentrations in multiple media, elevated exposure, sensitive
populations [children]).
(3) Summarize and utilize available and appropriate data.
(4) Augment missing input data using a combination of alternative data sources, parameter
space analysis techniques, and expert judgment.
(5) Utilize various methods in forward model application and inverse modeling to identify
critical pathways, processes, and assumptions in the models.
(6) Develop plausible explanations for survey results.
(7) Prepare a report and/or peer review publication.
Data or Input
Needs:
NHEXAS data to include monitoring results, time/activity data, food/water intake data, and
source data, when available and appropriate. The analysis will benefit from including
information from other data sources.
Other data sources may include the Toxics Release Inventory (TRI), population density,
local and regional pesticide use records and other information that might be useful in
approximating/constructing source term information.
Feasibility (of
analyses with
current NHEXAS
databases):
Several models are already available that can be used to aid in the interpretation of NHEXAS
data, and many of the methods that utilize these existing models are established. Effort will
need to be directed at identifying appropriate case studies within the survey results.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
0
6
Research Outputs
(1) Initiate project
(2) Identify important case studies with input from EPA
102
-------
Approximate
Level of Effort:
Month
Month
Month
% Time
30
100
50
12
18
24
Months
24
24
24
(3) Complete paramaterization of selected case studies anc
models
(4) Complete initial evaluations and produce concept draft
select
report
(5) Final outputs: Submit final report or draft manuscript for peer
review
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
M-8. Investigate Stability of Individuals in Population Exposure Ranks
Over Time
Short Project
Description:
Temporal variability in measurements of individuals may have a significant effect on
estimates of exposure factors and distributions. This project will investigate the effect of
using cross-sectional studies on estimates of exposure factor distributions. Cross-
sectional studies are cost efficient because they collect minimal observations per
individual, but provide no indication of temporal variability. Measures of intraindividual
temporal variability do not necessarily tell the complete story, as individuals may vary in
concert, because of factors such as seasonal changes. It is also useful to examine the
stability of individual's position or rank in the population exposure distribution to
determine how this stability influences predictive ability of various exposure distribution
parameters.
Goal/Objective:
To examine the importance of temporal variability and evaluate sources of variability in
exposure factor measurements of an individual over time. To examine this variability on
stability of an individual's rank or position in exposure factor population distributions.
Significance of
Project:
It is important to understand the temporal variability in individual's measurements to
assessment of potential bias of cross-sectional studies as estimates of exposure factor
population distributions. A clear understanding of temporal variability will be useful in
deciding when and where cross-sectional studies are appropriate for estimation of
population exposure distributions and what modifications may improve these studies in a
cost-efficient manner. This work also would provide highly relevant information on
estimating the upper tails of the distribution.
Suggested
Approach:
(1) Identify feasible and relevant variables from NHEXAS for study.
(2) Develop/assess methods for examining temporal variability and stability of individuals.
(3) Use mixed models to develop repeated measure/temporal correlation estimates and
consider automation of methodology for examination of large numbers of variables.
Data or Input
Needs:
The entire NHEXAS data set, especially the Maryland NHEXAS longitudinal data.
Feasibility
(of analyses with
current NHEXAS
databases):
Feasible for variables where longitudinal data are collected for at least some individuals.
Focus is likely to be on the Maryland study, with confirmation/validation use of Region V
and Arizona NHEXAS studies.
103
-------
104
-------
Project Name:
M-8 (cont'd). Investigate Stability of Individuals in Population Exposure
Ranks Over Time
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
% Time
15-20
50
50
50
0
12
18
24
Months
24
24
24
24
Research Outputs
(1) Initiate project
(2) Develop methods for examining temporal variability and stability
of individuals
(3) Apply mixed models to develop repeated measure/temporal
correlation estimates
(4) Final outputs
Determination of factors influencing temporal variability in
individuals exposed to environmental pollutants
Identification of limitations of cross-sectional population
exposure surveys and recommendation of optimal spatio-
temporal survey designs for future NHEXAS-type studies
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
105
-------
Project Name:
M-9. Reconstruct Exposure and Dose Profiles from Biomarker Data
Utilizing Questionnaire and Environmental Measurements
Short Project
Description:
The relationships among environmental measurements, time/activity data, and biomarker
levels will be investigated with the goal of classifying exposure scenarios into steady-state
cases (e.g., from long-term average exposures) and intermittent events. There are several
assumptions regarding the route and timing of dose that need to be addressed in making
these estimates, and the questionnaires and time/activity data will be used to make these
determinations. There is the potential to focus on the exposures of children, in addition to
the general population.
Goal/Objective:
To develop and evaluate a methodology that provides realistic estimates of the dose and
exposure associated with a biomarker measurement as a function of the types of exposure
that occurred.
Significance of
Project:
Biomarkers can provide an indicator of total absorbed dose. However, making quantitative
estimates of this dose requires several assumptions about the timing and route of the
exposures, as well as the suitability of the model being used. The estimates of total
absorbed dose may help to evaluate current exposure assessment models and assumptions
(e.g., Office of Pesticide Programs' [OPP's] Residential SOPs) and to develop and test
models describing residential exposure.
Suggested
Approach:
The total absorbed dose from a steady-state exposure will be modeled by a mass-balance,
and the absorbed dose from discrete events will be estimated by an inverted
pharmacokinetic model (in the case of compact classical compartmental models) or
maximum likelihood optimization procedure (in the case of comprehensive physiologically
based models).
1 These dose estimates will be linked to a range of possible exposures and environmental
concentrations and then compared with those measured in the NHEXAS study.
Differences will reveal areas of improvement for modeling methods and indicate additional
information that will be useful to collect in future studies.
Data or Input
Needs:
1 Pollutant concentrations in solid-food, personal air, dermal rinse, surface press and wipe,
urine (pesticide metabolite), and measurements.
1 Pesticide use from household screening, baseline, and follow-up questionnaires.
1 Time/activity and food consumption diaries.
1 Information on urine volume, creatinine concentration, time of last void, and body weight.
Feasibility
(of analysis with
current NHEXAS
databases):
This project can be implemented in a 2-year time period assuming the availability of the
NHEXAS database. Likely candidate chemicals are chlorpyrifos, lead, arsenic, and
benzene.
The food diaries may not be coded to link with ranges of pesticide residues (by food
type), which may limit the temporal resolution of the dietary data estimates.
There are concerns about applying model parameters (e.g., absorption and elimination
rates) determined in a small number of individuals to the general population because of
differences in personal characteristics such as age, gender, race, and health status.
106
-------
Project Name:
M-9 (cont'd). Reconstruct Exposure and Dose Profiles from Biomarker
Data Utilizing Questionnaire and Environmental Measurements
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration*
Month
Month
Month
Month
Month
Month
Month
Month
% Time
10
50
25
10
0
3
6
9
12
18
21
24
Months
24
24
03
2
Research Outputs
(1) Initiate project: On availability of NHEXAS data; timeline
based on the analysis of a single pollutant
(2) Obtain and merge databases
(3) Analysis of questionnaire/activity data to group by types
exposure
of
(4) Review metabolite data by individual to identify intermittent
and steady -state patterns
(5) Solving and programming the models
(6) Incorporation of the model in an estimation methodology
(7) Uncertainty analysis
(8) Final outputs: Draft manuscript on approaches to estimate
chlorpyrifos dose from a biomarker and exposure information
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe): Consultant (statistical)
' Duration = approximate time (in months) needed, from start of project, to complete each step.
107
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Project Name:
M-10. Use NHEXAS Dietary and Activity Pattern Data to Develop
Predictive Relationships Between Single Day Observations and Long-Term
Patterns of Behaviors
Short Project
Description:
To use statistical techniques to determine the relationships between measurements of
exposure-related behaviors (e.g., dietary and activity patterns) on a single day and subsequent
longitudinal measurements. Use the short-term relationships to develop predictive models of
longer term behaviors. The NHEXAS data set provides a unique source of information for this
study.
Goal/Objective:
To develop models of the relationship between short- and long-term measurements of
exposure-related behaviors that can be used in models of long-term exposures.
Significance of
Project:
Collection of longitudinal data on exposure-related activities are resource intensive and
subject to a number of technical difficulties. However, such data are critical to the accurate
estimation of dose rates over periods longer than a single day.
Suggested
Approach:
Longitudinal data on exposure-related behaviors will be extracted from the data set. Statistical
techniques such as, but not limited to, random walk, Markov chains, correlation, and pattern
recognition will be investigated as potential tools to identify relationships between short- and
long-term patterns of behaviors. It is anticipated that the relationships will vary greatly across
behaviors. No one method is likely to predict the relationship between short- and long-term
behavior. Attention should be given to developing methods of estimating the upper bound of
long-term behaviors as a function of short-term data. Patterns in time/activity data from the
Maryland NHEXAS study should be compared/contrasted with data collected in the Region V
and Arizona NHEXAS studies. Certain endpoints such as dietary records should be
compared to the results of other longitudinal dietary studies to determine consistency across
different populations.
Data or Input
Needs:
The NHEXAS data set and other studies of long-term dietary patterns.
Feasibility
(of analyses with
current NHEXAS
databases):
The data for this task are available. No limitations are anticipated.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
% Time
10
30
20
0
4
4
4
12
18
Months
18
18
12
Research Outputs
(1) Initiate project
(2) Extract data for data set
(3) Obtain other dietary surveys
(4) Reconcile differences in dietary survey methods
(5) Perform Statistical analyses
(6) Final outputs: Develop final report
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
108
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I I Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: Dietary studies may be performed using different recording methodologies.
Project Name:
M-ll. Identify and Investigate Exploratory Data Analysis Methods That
Are Appropriate for Providing Additional Insights into NHEXAS Output
Short Project
Description:
Several different methods are now available for analyzing complex data sets to identify
patterns, relationships, sociodemographic variables, important factors, and combinations of
factors that influence or affect exposure distributions.
Goal/Objective:
Identify useful and appropriate tools for investigating large and complex data sets such as
NHEXAS. Specifically, there is a need to identify the factors that contribute to high
exposures and establish relationships among these factors and exposure
magnitudes/distributions.
Significance of
Project:
It is essential that one understand the data prior to using it for model evaluation or
identification of significant exposure pathways/processes. Several data analysis methods
are available that are based on neural networks, principal component analysis, multiple
regression, CART, and other techniques. These various methods or approaches that are
designed to investigate complex data sets should be compared and contrasted in order to
determine the most appropriate approach for identifying important contributing factors in
the NHEXAS data.
Suggested
Approach:
(1) Develop general case studies using NHEXAS data, as well as that of other national
data-rich surveys (NHANES, NHAPS, CSFII), and investigate the ability of various data
analysis tools to identify characteristics of the data.
(2) Identify strengths and limitations for each method in relation to the NHEXAS data.
(3) Recommend appropriate methods for analyzing NHEXAS data with special attention
paid to the upper tails of the distributions.
Data or Input
Needs:
The fully compiled database containing results from each of the NHEXAS surveys,
including exposure, chemical, activity, dietary and socio-demographic variables.
Feasibility
(of analyses with
current NHEXAS
databases):
The large number of qualitative and quantitative data types included in the NHEXAS data
sets (ordinal, continuous and binary) require special consideration when identifying
appropriate methods or approaches used to analysis data. Attention should be given to
the upper tails of the exposure distributions.
109
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Project Name:
M-ll (cont'd). Identify and Investigate Exploratory Data Analysis
Methods That Are Appropriate for Providing Additional Insights into
NHEXAS Output
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
% Time
30
100
50
0
3
10
10
12
Months
12
12
12
Research Outputs
(1) Initiate project
(2) Finalize list of models/methods to include in study
(3) Complete baseline analysis/comparison
(4) Submit concept draft for review
(5) Final outputs: Final report or manuscript for submission to
peer review journal
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: Clearly the time and effort required for this project will depend on the models/methods that are included
in the comparison and analysis. The number of appropriate methods can be reduced by the constraint introduced
by the wide range of data types in the survey data. This may need to be addressed in a preliminary 3- to 6-month
investigation designed to identify candidate models or methods for inclusion in the study.
110
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Project Name:
Short Project
Description:
Goal/Objective:
Significance of
Project:
Suggested
Approach:
Data or Input
Needs:
Feasibility
(of analyses with
current NHEXAS
databases):
M-12. Investigate National Representativeness of NHEXAS Sampling
Results by Comparing Measurement and Exposure Results Across the
Three Regions
Very few national studies are available for use in development of national exposure
distributions; therefore, local or regional studies are used instead. The question then is
raised about the effect of using this restricted information on national exposure estimates.
The three NHEXAS studies provide a method for comparing very similar studies to
determine the magnitude of regional differences for various exposure factors.
To determine bias in estimates of national exposure factors and distributions by use of local
or regional sampling represented by NHEXAS pilot studies.
The information provided by this project also will advance knowledge of uncertainty in
model parameters used in a variety of exposure models. The information also will help to
ascertain the geographic scale at which variables may be collected in future studies.
Examination of sample population distributions for various measurements collected in all
three studies. Examination should be based on current methodologies as much as possible
to facilitate quick turnaround. Appropriate analysis methods used to determine
"similarity" between studies and quantification of uncertainty should be based on methods
that provide simple, robust measures as feasible.
NHEXAS data from all three studies.
Study should be feasible. Possible difficulties may arise for some variables where
collection methods differ among studies.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
% Time
10
25
0
2
8
9
10
12
Month
s
12
12
Research Outputs
(1) Initiate project
(2) Collect and gain familiarity with study data
(3) Develop/assess framework for comparing study measurements
(4) Implement automation of comparisons
(5) Run analyses for selected variables
(6) Final outputs: Report on regional differences between studies,
suggested values for use in national exposure models and values of
uncertainty.
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
111
-------
50
50
12
12
Junior-level staff (
'assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
112
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Project Name:
M-13. Evaluate Implications of NHEXAS Results for Existing Chronic
Exposure Assessments Methodologies
Short Project
Description:
Screening models (sets of algorithms) are used widely to make preliminary decisions for
Superfund sites, pesticide regulations, and the evaluation of emissions to air and water.
However, high quality and reliable multimedia monitoring data to validate these models are
virtually nonexistent in the literature, and, as such, the opportunity to test screening models,
even on a qualitative scale, is rarely available. This project will take the dose estimates from
personal monitoring or biomarkers and compare the estimates to those produced from EPA
screening methodologies (also referred to as Tier 1 or initial Tier assessments). Examples of
these methods include recommended exposure models under the Superfund program and the
residential SOPs.
Goal/Objective:
To improve the understanding of the strengths and limitations of existing screening models
and identify opportunities for improving future models.
Significance of
Project:
Screening models provide the basis for preliminary regulatory decisions for pesticides,
hazardous waste sites, and the evaluation of releases to air and water. NHEXAS databases
provide a unique opportunity to evaluate these models.
Suggested
Approach:
This project would be performed in phases,
(1) Determine how the NHEXAS data set would be used (selection of pollutants, interim
findings, activity/dietary patterns, etc.).
(2) Development of the strategy for developing model inputs and relating outputs to the
data set.
(3) Perform the evaluations.
(4) Analyze the results to determine why the models did or did not match with the survey.
(5) Publish a final report.
A clear methodology should be established for the evaluation procedure that will be reviewed
scientifically. A consistent strategy for dealing with data gaps should be established.
Data or Input
Needs:
The complete data set (including the data from the questionnaires) should be available prior
to the development of the specific model test sets. Participation from the relevant EPA
program offices is desirable to confirm detail on how screening exposure models actually are
used.
Feasibility
(of analyses with
current NHEXAS
databases):
The project is feasible with the indicated data resources.
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
10
0
6
12
Month
s
12
Research Outputs
(1) Initiate project
(2) Development of a modeling strategy that addresses differences in
the type of models and how data gaps will be addressed
(3) Final outputs: Report/peer review publication
Type of Expertise Needed
Principal investigator
113
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30
20
12
9
Senior-level staff ("associate")
Junior-level staff ("assistant", technician),
students
Other (describe): Two meetings
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: This project could be run in conjunction with Project M.
Project Name:
M-14. Development and Evaluation of Models for Interpreting and
Quantifying Inter- and Intraindividual Variability in Pesticides
Exposure/Dose Using NHEXAS Data
Short Project
Description:
Analyze cross-sectional and longitudinal biomarker and exposure data for pesticides
considered in NHEXAS (such as chlorpyrifos and atrazine) to develop and test population-
based pharmacokinetic (i.e., pharmacostatistical) models that explicitly discern and quantify
intra- and interindividual variability in human doses.
Goal/Objective:
To develop, test/evaluate, and make available to EPA and the scientific community at large, a
mechanism-based computational tool for characterizing and quantifying inter- and
intraindividual variability (i.e., cross-sectional and longitudinal variability) in pesticides
exposure/dose of human populations.
Significance of
Project:
Quantitative characterization of inter- and intraindividual dose (and corresponding exposure)
to common pesticides will reduce the uncertainty in, and thus improving, relevant
dose/response studies and corresponding risk assessments. The mechanistic approach to be
developed and evaluated should be applicable to a wide range of exposure situations and
U.S. population segments.
Suggested
Approach:
(1) Develop general formulations for population-based (pharmacostatistical) models of
selected pesticides considered in NHEXAS (primary candidates are chlorpyrifos and
atrazine) that explicitly incorporate/describe inter- and intraindividual variability of
biological uptake/distribution/fate. This step primarily should consider existing
"individual-based" "classical" (compartmental) models, as well as the possibility of
formulating simplified population physiologically based models.
(2) Perform analyses of appropriate NHEXAS data components to develop parameterizations
for the above formulations (the Maryland study database being the primary candidate
because it contains extensive longitudinal data); assess and interpret magnitudes of
different types of variability.
(3) Test the population pharmacostatistical model, with parameterizations derived as in the
step above, with relevant independent data from other NHEXAS components to evaluate
its ability to reproduce variability observed in these studies.
(4) Review the available literature for other relevant data sets that may exist on dose
variability for the pesticides of concern and extend the model evaluation to include these
data sets.
(5) Finally, evaluate the new model/method for its applicability to children's exposure to
pesticides (using the NHEXAS Minnesota study data) and derive recommendations for
appropriate model refinements/modifications and possibly additional data collection that
would help to extend the model to children's exposure.
Data or Input
Needs:
Pesticide exposure- and dose-related data from all three NHEXAS studies; other
exposure/dose-related data from these studies (from both monitoring and questionnaires),
such as activity patterns and additional literature data
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Feasibility
(of analyses with
current
NHEXAS
databases):
At a minimum, it should be feasible with the collected data to at least evaluate the
applicability of a population-based pharmacokinetic model for pesticide dose estimation to
multiple regions and population segments of the United States. In some cases, biological
half-life considerations may influence the modeling choices. In the best case, a widely
applicable tool will be available; in the worst case, data needs for characterizing nationwide
variability to dose will be identified.
115
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Project Name:
M-14. Development and Evaluation of Models for Interpreting and
Quantifying Inter- and Intraindividual Variability in Pesticides
Exposure/Dose Using NHEXAS Data
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
% Time
10
75
100
0
12
24
Month
s
24
24
24
Research Outputs
(1) Initiate project
(2) Data analysis/evaluation
Comparison and evaluation of existing approaches for individual-
based pharmacokinetic modeling of the selected pesticides
(3) Final outputs:
Tested operational population-based model with explicit
descriptions of inter- and intraindividual variability
Peer-reviewed manuscript
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
' Duration = approximate time (in months) needed, from start of project, to complete each step.
116
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Project Name:
M-15. Comparison of NHEXAS Findings with Cumulative Exposure
Project Estimates for Ambient Air Levels and Exposures for Selected
VOCs and Metals
Short Project
Description:
Compare patterns and trends in monitored neighborhood ambient air levels of VOCs and
metals to the annual average estimates of the same compounds derived through the
Cumulative Exposure Project (CEP); evaluate the relevance of CEP predictions to the types
of exposure situations characterized in NHEXAS.
Goal/Objective:
To evaluate the relevance of CEP predictions to the types of exposure situations
characterized in NHEXAS; to identify gaps and potential improvements in both screening
modeling methods for ambient air quality characterization and in data collection for
exposure characterization.
Significance of
Project:
The CEP study has attracted remarkable attention, including the media's and the general
public's, as well as some criticism regarding its relevance to exposures actually experienced
by individuals and populations. This project will help in understanding and characterizing
both the relevance and the limitations of CEP (and potentially of similar approaches), as
well as in identifying specific steps in improving exposure estimates to airborne
contaminants through screening modeling approaches.
Suggested
Approach:
(1) Extract ambient air concentration estimates from the 1990 CEP database (or from the
follow-up database utilizing more recent TRI emission data, depending on its
availability at the time of project implementation) for a set of selected airborne VOCs
and metals monitored in the NHEXAS studies and for the approximate locations of the
monitors.
(2) Incorporate both the CEP estimates and the corresponding NHEXAS observations in a
Geographic Information System linked with appropriate statistical/geostatistical
software routines to ensure maximum usability, visualization, and analysis options for
these data and estimates.
(3) Perform qualitative and statistical comparisons of relevant ambient air concentration
estimates/data from CEP and NHEXAS, with focus on identifying general patterns and
trends.
(4) Perform screening calculations of exposure for selected subsets of the NHEXAS
components, using the CEP estimates as the starting point and utilizing partial
information from the NHEXAS databases (such as activity patterns and other
questionnaire-based information). Compare these results to personal exposure
measurements and estimates that utilize additional NHEXAS data.
(5) Consider, evaluate conceptually, and, if possible, investigate through limited case-
specific studies, potential improvements in CEP-type methodologies for screening
ambient and exposure characterization.
Data or Input
Needs:
For phase I (steps 1 to 3 of the approach), NHEXAS monitored selected VOCs and metals
with corresponding geographical location information. CEP data are publicly available but
certain additional information may need to be provided by EPA. For phase II (steps 4 and
5), access to more extensive information from the NHEXAS databases (e.g., activity
patterns and household attributes).
Feasibility
(of analyses with
current NHEXAS
databases):
The study is straightforward and feasible, depending only on on-time availability of
NHEXAS data for Phases I and II (as identified in the Data Needs).
117
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Project Name:
M-15 (cont'd). Comparison of NHEXAS Findings with Cumulative
Exposure Project Estimates for Ambient Air Levels and Exposures for
Selected VOCs and Metals
Approximate Project Time Table and Level of Effort
Time Table:
Approximate Level
of Effort:
Duration
Month
Month
Month
% Time
10
50
100
0
12
24
Months
24
24
24
Research Outputs
(1) Initiate project
(2) Report summarizing evaluation of the relevance of the CEP
estimates for exposure assessments
(3) Final outputs:
Evaluation of methodologies for screening exposure
assessments for airborne contaminants
Specific recommendations for improving screening
modeling methodologies and data collection approaches
Peer-reviewed manuscript(s)
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
NOTES: This is a two-phase project (Phase I - Year 1; Phase II - Year 2). Critical results evaluating the relevance of
CEP estimates will become available from Phase I, whereas Phase II will focus on more exploratory aspects of the
problem, leading to recommendations for methodological improvements in screening exposure assessments.
118
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Project Name:
Short Project
Description:
Goal/Objective:
Compare pre-NHEXAS model results for benzene, lead, and chlorpyrifos with NHEXAS
measurements. Update pre-NHEXAS models with information from the measurement data.
Assess validity of pre-NHEXAS models by comparing with measurements. Improve these
models based on data to better predict exposures.
Significance of
Project:
M-16. Compare Pre-NHEXAS Model Results with NHEXAS
Measurements
If models and data compare well, this provides a validated model for use in predicting human
exposures to these pollutants. This then can be applied to populations outside of the
NHEXAS study region. Differences between measured and modeled results can be used to
improve model predictions and provide information on limitations in the use of disparate
studies. Overall, this comparison will provide confidence in using models to estimate
multimedia exposures.
Suggested
Approach:
(1) Compare environmental concentrations as predicted from pre-NHEXAS benzene, lead,
and chlorpyrifos models with corresponding measurements, with special attention to
high-end concentrations.
(2) Extend pre-NHEXAS models to go from exposure to dose and compare NHEXAS
biomarker measurements to this version with special attention to high-end measurements.
(3) Examine different parameters to determine possible reasons for discrepancies between
models and measurements. This should include comparison of measured and modeled
time/activity diaries and concentrations in air, food, water, and other media. In addition,
algorithms for calculation should also be examined.
(4) Determine if model predicts better/worse for a certain population subgroup, based on
location, age, race, sex or other factors.
(5) Improve model estimates based on results of tasks 1 through 4.
Data or Input
Needs:
Questionnaire and time/activity data, environmental concentration data, and analyte
concentrations.
Feasibility
(of analyses
current
NHEXAS
databases):
with
Pre-NHEXAS model code, documentation, and their results should be made available.
Questionnaire data and concentration data that correspond to the pre-NHEXAS models will
be available.
Approximate Project Time Table and Level of Effort
Time Table:
Duration*
Month
Month
Month
Month
Month
Month
0
2
4
10
14
18
Research Outputs
(1) Initiate project
(2) Compare environmental concentrations from measured and modeled
results
(3) Extend exposure model to dose and compare with urine/blood
concentrations
(4) Determine which inputs/algorithms/population subgroups are
responsible for discrepancies between model and measurements
(5) Improve model based on results
(6) Final outputs:
Report on comparison between measured and
Improve model based on results
modeled data
119
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Approximate
Level of Effort:
% Time
15
35
25
Month
s
18
18
10
Type of Expertise Needed
Principal investigator
Senior-level staff (
Junior-level staff (
"associate")
"assistant", technician), students
Other (describe):
* Duration = approximate time (in months) needed, from start of project, to complete each step.
Project Name:
M-17. Construction of an Empirical Multimedia/Multipathway Exposure
Distribution Model Including Temporal Variability Based on
NHEXAS Data
Short Project
Description:
The NHEXAS study collects data that can be used for the development of
multimedia/multipathway exposure models and also can incorporate temporal variability in
exposure factor measurements. Pre-NHEXAS models were based on data from studies that
often were limited in scope to single media/single pathway. Using the NHEXAS data, the pre-
NHEXAS models can be extended to include multimedia/multipathway correlation between
variables, both between and within individuals. This project examines the issues involved in
constructing this type of model based on the data available in the NHEXAS study.
Goal/Objective:
(1) Determine limitations of NHEXAS study design in construction of empirical
multimedia/multipathway exposure distributions that include temporal variability.
(2) Construct empirical multimedia/multipathway exposure distribution model, including
temporal variability, using NHEXAS data to the extent possible.
(3) Examine issues in constructing empirical models involving temporal variability, including
development of methodology for estimating multivariate distributions.
Significance of
Project:
Project would extend empirical exposure distribution models to include temporal variability in
individual exposure measures and development of multivariate joint and conditional
distributions for use in empirical exposure distribution models. It also will highlight the
limitations in the NHEXAS study design for construction of such models and provide
information to improve future multimedia/multipathway exposure studies.
Suggested
Approach:
(1) Use of NHEXAS Mary land data.
(2) Assessment of data for use in development of multivariate exposure factor distributions.
(3) Extension of pre-NHEXAS model framework to include multivariate distributions.
(4) Estimation of parameters for empirical model exposure factor distributions.
Data or Input
Needs:
NHEXAS study data.
Pre-NHEXAS exposure models.
Feasibility
(of analyses with
current
NHEXAS
databases):
No feasibility issues beyond data and input needs.
120
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Project Name:
M-17 (cont'd). Construction of an Empirical Multimedia/Multipathway
Exposure Distribution Model Including Temporal Variability Based on
NHEXAS Data
Approximate Project Time Table and Level of Effort
Time Table:
Approximate
Level of Effort:
Duration*
Month
Month
Month
Month
Month
Month
Month
Month
Month
% Time
15
50
100
100
0
2
9
12
12
15
15
15
20
Month
s
20
20
20
12
Research Outputs
(1) Initiate project
(2) Collection and familiarity with database
(3) Development of methodologies for multivariate distributions
(4) Estimation of distribution parameters from NHEXAS data
(5) Development of framework for empirical distribution model
(6) Running and analysis of model
(7) Multimedia/multipathway exposure distribution model, including
temporal variability
(8) Empirical multivariate distributions and associated uncertainties based
on NHEXAS data that can be used by other modelers
(9) Report assessing results of model analysis
Type of Expertise Needed
Principal investigator
Senior-level staff ("associate")
Junior-level staff ("assistant", technician), students
Other (describe):
'Duration = approximate time (in months) needed, from start of project, to complete each step.
121
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APPENDIX 1: LIST OF NHEXAS PAPERS IN PRESS OR
IN PREPARATION
In Press Journal Articles (Special October 1999 Issue of JEAEE)
NHEXAS Arizona
"The National Human Exposure Assessment Survey (NHEXAS) Study in ArizonaIntroduction and
Preliminary Results"
"Spatial Distributions of Arsenic Exposure and Mining Communities from NHEXAS Arizona"
"Residential Environmental Measurements in the National Human Exposure Assessment Survey
(NHEXAS) Pilot Study in Arizona: Multimedia Results for Pesticides and VOCs"
"Evaluations of Primary Metals from NHEXAS, Arizona: Methods, Distributions, and Preliminary
Exposures"
NHEXAS Baltimore
"A Longitudinal Investigation of Dietary Exposure to Selected Elements"
"A Longitudinal Investigation of Selected Pesticide Metabolites in Urine"
"Long-Term Average Microenvironmental Time Budgets in Maryland"
NHEXAS Region V
"Sampling Design, Response Rates, and Nonresponse Compensation for the National Human
Exposure Assessment Survey (NHEXAS) in EPA Region V"
"National Human Exposure Assessment Survey (NHEXAS): Distributions and Associations of
Lead, Arsenic, and Volatile Organic Compounds in EPA Region V"
"Population-Based Dietary Intakes and Tap Water Concentrations for Selected Elements in the EPA
Region V National Human Exposure Assessment Survey (NHEXAS)"
"Responses to the Region V NHEXAS Time/Activity Diary"
"Analysis of Mercury in Hair of EPA Region V Population"
"Quantification of Children's Hand and Mouthing Activities Through a Videotaping Methodology"
"The EL Sampler: A Press Sampler for the Quantitative Estimation of Dermal Exposure to Pesticides
in House Dust"
List of Manuscripts "In Preparation" Under EPA Contracts or Cooperative Agreements
Arizona
"Occurrence/Distributions of Pollutant Concentrations in Different Media, with Comparisons Across
Media for Each Pollutant" (1999)5
"Exposure Model Formulation and Validation for Pesticides using the Arizona NHEXAS Database"
(1999)
"Total Exposure Assessment Estimates and their Distributions for Pesticides" (2000)
'Estimated year of completion.
122
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"Total Exposure Assessment: The 90th Percentile of Total Exposure to Pesticides and Their Media
Components" (2000)
Baltimore
"Pesticide Residues in Urine: Temporal and Population Variability and Associations with Activities
and Diet" (1999)
"Population and Temporal Variability Analyses of Dietary Checklist Data" (1999)
"Pesticide Residues in Urine: Associations with Questionnaire Data and Environmental
Concentrations" (2000)
"Estimated Chlorpyrifos Exposure in U.S. EPA Region V and Arizona" (2000)
Region V
"Analysis of Dietary and Other Exposure Pathways for Metals, with Comparisons Between Media
Concentrations and Routes of Exposure" (1999)
"Assessment of Data Quality for the EPA Region V NHEXAS Study" (2000)
"Contribution of Activity Patterns to Personal Exposures of NHEXAS Participants"
"Relationship of Residential Sources and Residential Conditions to Household Contaminant Levels"
"Relationship Between Pesticide Levels in and Around the Home and Hand Rinse Measurements
from Children"
"Relationship Between Activity Pattern Data and Hand Rinse Measurements of Pesticides in
Children"
"Estimation of Pesticide Exposure from Biomarker Measurements Using Environmental and Time-
Activity Data To Constrain the Solutions"
123
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APPENDIX 2: WORKSHOP AGENDA
National Human Exposure Assessment Survey (NHEXAS) Workshop
Analysis of Pilot Study Data
North Raleigh Hilton Hotel
3415 Wake Forest Road
Raleigh, N.C. 27609
(919) 872-2323
FAX (919) 876-0890
Tuesday, July 27, 1999
8:30-8:45 a.m.
8:45-9:30 a.m.
Introduction (William Steen, NERL)
NHEXAS overview, workshop goals (Judith Graham, NERL)
Overview of the hypotheses, design, and status of data analyses for each NHEXAS pilot study:
9:30 -10:00 a.m.
10: 00-10:30 a.m.
10:30-1 1:00 am.
11:00-1 1:30 am.
11:30-12:00 am.
12:00 a.m.-l:00 p.m.
1:00-5:00 p.m.
5:15 p.m.
The RTI-EOSHI consortia (Andy Clayton, RTI)
Break
Arizona consortia (Mary Kay O'Rourke, University of Arizona)
Harvard/Emory consortia (Barry Ryan, Emory University)
Discussion of break-out session objectives, assignments, and charge (Judith Graham,
NERL)
Lunch
Break-out sessions
Status meeting with session chairs, rapporteurs, and workshop organizers
Wednesday, July 28, 1999
8:30-12:00 am.
12:00 a.m.-l:00 p.m.
1:00 -5:00 p.m.
5:15 p.m.
Break-out sessions continue meet in designated rooms
Lunch
Break-out sessions continue
Status meeting with chairs, rapporteurs, and workshop organizers
Thursday, July 29, 1999
8:30 -11:30 am.
11:30 am
12:00 am
Project presentations and discussion in plenary session (group chairs and rapporteurs)
Final plenary session: "Next Steps" (Judith Graham, NERL)
Workshop adjourns
124
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1:00 p.m.
Status meeting with chairs, rapporteurs, and workshop organizers
APPENDIX 3: LIST OF WORKSHOP PARTICIPANTS
John Adgate, Ph.D
Assistant Professor
University of Minnesota
Box 807 6MHC
420 Delaware Street, S.E.
Minneapolis, MN 55455
612-624-2681 Phone
612-624-0650 Fax
j adgate@cccs.umn.edu
Gerald Akland
Principal Scientist for Exposure Research
Research Triangle Institute
P.O. Box 12194
3040 Cornwallis Road
Research Triangle Park, NC 27709-2194
919-217-2594 Phone
919-217-2591 Fax
Akland@RTI.org
Maurice Berry, Ph.D
Program Manager, Dietary Exposure
U.S. EPA/NERL
U.S.EPAMS-564
26 W Martin Luther King Blvd.
Cincinnati, OH 45268
513-569-7284 Phone
513-569-7757 Fax
Berry.Maurice@EPA.gov
Robert Buck, Ph.D
Assistant Professor
Western Michigan University
Department of Mathematics and Statistics
Kalamazoo, MI 49008
616-3 87-4569 Phone
robert.buck@wmich.edu
Timothy Buckley, Ph.D
Assistant Professor
Dept. of Environmental Health and Sciences
Johns Hopkins University, Room 6010
615 N.Wolfe Street
Baltimore, MD 21205
410-955-3602 Phone
TBUCKLEY@JHSPH.EDU
Laureen Burton, M.P.H.
Chemist/Toxicologist
U.S. EPA
401 M Street, SW
Mail Code 66045
Washington, DC 20460
202-564-9032 Phone
202-565-2071 Fax
burton. laureen@epa. gov
David Camann
Staff Scientist, Statistics
Southwest Research Institute
P.O. Drawer 28510
San Antonio, TX 78228
210-522-2673 Phone
210-522-3649 Fax
dcamann@swri.org
Andy Clayton
Statistician
Research Triangle Institute
3040 Cornwallis Road
P.O. Box 12194
Research Triangle Park, NC 27709-2194
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919-541-6392 Phone
919-541-5966 Fax
clayton@rti.org
79 Alexander Drive
MD-77
Research Triangle Park, NC 27711
919-541-2454 Phone
919-541-0435 Fax
cupitt.larry@epamail.epa.gov
Robert Clickner, Ph.D.
Associate Director, Environmental Studies
Westat, Inc.
1650 Research Boulevard
RoomRP4012
Rockville, MD 20850
301-294-2815 Phone
301-294-2829 Fax
clicknb 1 @westat.com
Yoram Cohen, Ph.D.
Professor
UCLA
Dept. of Chemical Engineering
553 IBoelter Hall
Los Angeles, CA 90095-1592
310-825-8766 Phone
301-477-3868 Fax
yoram@ucla.edu
Steve Colome, Sc.D.
Adjunct Professor
UCLA
5319 University Drive #430
Irvine, CA 92612
949-786-0206 Phone
949-786-0206 Fax
scolome@pacbell .net
Larry Cupitt, Ph.D.
Director, Human Exposure and Atmospheric
Sciences Div.
U.S. EPA/ORD/NERL
Michael Dellarco, Ph.D.
Environmental Health Scientist
U.S. EPA/NCEA-W
401 M Street, SW
Washington, DC 20460
202-564-3239 Phone
202-565-0079 Fax
delarco.mike@epa.gov
Julie Du, Ph.D.
lexicologist
U.S. EPA
401 M Street, SW
Washington, DC 20460
202-260-7583
du.julie@epamail.epa.gov
Ying Feng, Ph.D.
Chief, Health Assessment Branch
Ohio Department of Health
Bureau of Environmental Health and
Toxicology
246 N. High Street
Columbus, OH 43215-2412
614-644-6447 Phone
614-644-7740 Fax
Kenneth Fisher, Ph.D.
Senior Nutrition Consultant
ODPHP/DHHS
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738-G Humphrey Bldg.
200 Independence Ave., S.W.
Washington, DC 20201
202-690-5526 Phone
202-205-0463 Fax
kfisher@osophs.dhhs.gov
Natalie Freeman, Ph.D.
Adjunct Assistant Professor
EOSHI-RWJMS
170 Frelinghuysen Road
Piscataway, NJ 08854
732-445-0151 Phone
732-445-0116 Fax
nfreeman@eohsi.rutgers.edu
Panos Georgopoulus, Ph.D.
Professor
EOHSI-RWJMS
170 Frelinghuysen Road
Piscataway, NJ 08854
732-445-0159 Phone
732-445-0915 Fax
Melissa Gonzales, Ph.D.
Post Doctorate Research Fellow
U.S. EPA-NHEERL
MD-58A
Research Triangle Park, NC 27711
919-966-7549 Phone
919-966-7584 Fax
gonzales.melissa@epamail.epa.gov
Syd Gordon, Ph.D.
Research Leader
Battelle Columbus Laboratories
505 King Avenue
Columbus, OH 43201-2693
614-424-5278 Phone
614-424-3638 Fax
gordon@battelle.org
Judith Graham, Ph.D.
Associate Director for Health
U.S. EPA-NERL
MD-75
Research Triangle Park, NC 27711
919-541-0349 Phone
919-541-3615 Fax
graham.judith@epa.gov
Zhishi Quo, Ph.D.
Environmental Scientist
U.S. EPA/NRMRL
MD-54
Research Triangle Park, NC 27711
919-541-0185 Phone
919-541-2157 Fax
guo.zhishi@epa.gov
Karen Hammerstrom
U.S. EPA
MC 8601D
401 M Street, SW
Washington, DC 20460
Mike Herman
Physical Scientist
U.S. EPA - ORD/NERL/HEASD/HEAB
ERC Annex, 79 Alexander Dr.
MD-56
Research Triangle Park, NC 27709
19-541-0928 Phone
19-541-0905 Fax
herman.mike@epamail.epa.gov
Jane Hoppin, Sc.D.
StaffFellow
NIEHS
P.O. Box 12233
Research Triangle Park, NC 27709
919.541-7622 Phone
919-541-2511 Fax
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hoppin 1 @niehs.nih.gov
Matti Jantuneu, Ph.D.
Department Director
KTL - Environmental Hygiene
P.O. Box 95
Neulaniemeutie 4
Kupio,
Finland
358 400 587 816 Phone
358 17201 1184 Fax
matti j antuneu@j re .it
Lora Johnson
Director, Quality Assurance
U.S. EPAMD-587
26 W. Martin Luther King Drive
Cincinnati, OH 45268
513-569-7299 Phone
513-569-7424 Fax
j ohnson.lora@epa.gov
Elizabeth Julian, Ph.D.
Exposure Analyst
Novigen Sciences, Inc.
1730 Rhode Island Avenue, N.W.
Washington, DC 20036
202-293-5374 Phone
202-293-5377 Fax
bj ulien@novigensci. com
Freja Kamel, Ph.D., MPH
Staff Scientist
MEHS/Epidemiology
P.O. Box 12233
Research Triangle Park, NC 27709
919-541-1581 Phone
919-541-2511 Fax
kamel@niehs.nih.gov
Wendy Kaye, Ph.D.
Chief, Epidemiology and Surveillance
Branch
Agency for Toxic Substances and Disease
Registry
1600 Clifton Road, NE, Mail Stop E-31
Atlanta, GA 30333
404-639-6203 Phone
404-639-6219 Fax
wekl@cdc.gov
Patrick Kennedy
Chemist
U.S. EPA
401 M Street, SW
Washington, DC 20460
202-260-3916 Phone
202-260-0981 Fax
kennedy.patrick@epa.gov
Pat Kinney, Ph.D.
Columbia University
School of Public Health
600 Haven, B-l
New York, NY 10032
212-305-3663 Phone
Steve Knott
Exposure Science Coordinator
U.S. EPA
401 M Street, SW
Washington, DC 20460
202-564-3359 Phone
202-565-0066 Fax
knott. steven@epa.gov
Ann Kukowski
Minnesota Dept. of Health
121 E. 7th Place
St. Paul, MN 55164
651-215-0854
Jack Leiss
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Analytical Sciences, Inc.
2605 Meridian Parkway
Suite 200
Durham, NC 27712
919-544-8500 Phone
Kelly Leovic
Environmental Engineer
U.S. EPA/NERL/HEAB
MD-56
Research Triangle Park, NC 27711
919-541-7717 Phone
919-541-0905 Fax
leovrc.kelly@epa.gov
Paul Lioy, Ph.D.
Deputy Director
EOHSI - UMDNJ
170 Frelinghuysen Street
Piscataway, NJ 08855
732-445-0155 Phone
732-445-0116 Fax
plioy@eohsi.rutgers.edu
David Macintosh, Sc.D.
Assistant Professor
University of Georgia
206 Environmental Health Building
Athens, GA 30602-2102
706-542-5542 Phone
706-542-7472 Fax
dmac@arches.uga.edu
Randy Maddalena, Ph.D.
Scientist
Lawrence Berkeley National Labs
1 Cyclotron Road
MD-90-3058
Berkeley, CA 94720
209-962-5680 Phone
209-962-5680 Fax
rlmaddalena@lbl .gov
Scott Masten, Ph.D.
Staff Scientist
NIEHS
111 T.W. Alexander Drive
Research Triangle Park, NC 27709
919-541-5710 Phone
919-541-7666 Fax
masten@niehs.nih.gov
Suzanne McMaster
Assistant Director
U.S. EPA/NHEERL
MD-51A
Research Triangle Park, NC 27711
919-541-3 844 Phone
919-541-1440 Fax
mcmaster. suzanne@epa.gov
Lisa Melnyk, Ph.D.
Dietary Exposure Scientist
US.EPA-NERL-C1
26 W. M.L. King Drive
Cincinnati, OH 45268
513-569-7494 Phone
513-569-7757 Fax
Deirdre Murphy, Ph.D.
Environmental Scientist/Toxicologist
U.S. EPA/OAR/OAQPS
MD-13
Research Triangle Park, NC 27711
919-541-0729 Phone
919-541-0237 Fax
murphy.deirdre@epa.gov
Larry Needham, Ph.D.
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Chief, Toxicology Branch
Centers for Disease Control and Prevention
NCEH/EHL (Mail Stop F17)
4770 Buford Hwy., NE
Atlanta, GA 30341-3724
770-488-4598 Phone
770-488-4546 Fax
llnl@cdg.gov
Miles Okino, Ph.D.
Post-Doctoral Researcher
U.S. EPA
P.O. Box 93478
Las Vegas, NV 89193-3478
702-798-2355 Phone
702-798-2261 Fax
okino.miles@epamail.epa.gov
Will Ollison, Ph.D.
Senior Scientist
American Petroleum Institute
1220 L. Street, NW
Washington, DC 20005
202-682-8262 Phone
202-682-8270 Fax
ollisonus@apl.org
520-882-5014 Fax
maryk@hrp. arizona. edu
Haluk Ozkaynak, Ph.D.
U.S. EPA(MD-56)
Research Triangle Park, NC 27711
Ozkaynak.Haluk@epa.gov
Mulihan Pandian
2920 North Green Valley
Suite 524
Henderson, NV 89014
702-433-8843
Edo Pellizzari, Ph.D.
Vice President for Research
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709-2194
919-541-6579 Phone
919-541-7208 Fax
edp@rti.org
Paul Price
129 Oakhurst Road
Cape Elizabeth, ME 04107
207-774-8263
Mary Kay O'Rouke, Ph.D.
Research Assistant Professor
University of Arizona
EOH, Box 210468
1435 N Fremont Avenue
Tucson, AZ 85721
520-626-6835 Phone
James J. Quackenboss
Environmental Scientist
U.S. EPA
P.O. Box 93478
Las Vegas, NV 89193-3478
702-798-2442 Phone
702-798-2261 Fax
quackenboss.j ames@epa.gov
Gary Robertson
Research Chemist
U.S. EPA
130
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P.O. Box 93478
Las Vegas, NV 89193
702-798-2215 Phone
702-798-2261 Fax
robertson.gary@epamail.epa.gov
Seumas Rogan
Field Coordinator and Data Analyst
University of Arizona
EOH, Box 210468
1435 North Fremont Ave.
Tucson, AZ 85719
520-626-6835 Phone
520-882-5014 Fax
seumarsr@hrp. arizona. edu
Barry Ryan, Ph.D.
Dept. of Environmental and Occupational
Health
Rollins School of Public Health
Emory University
1518 Clifton Road, NE
Atlanta, GA 30322
Christopher Saint, Ph.D.
U.S. EPA
401 M Street, SW
Washington, DC 20460
202-564-6909 Phone
saint.chris@epa.gov
Susan Schober, Ph.D.
Epidemiologist
CDC/National Center for Health Statistics
6525 Belcrest Road, Room 1000
Hyattsville, MD 20782
301-436-7072x171 Phone
301-436-5431 Fax
sus2@cdc.gov
Judy Schreiber, Ph.D.
Chief, Special Investigations
New York State Dept. of Health
547 River Street
Flanigan Square, Room 330
Troy, NY 12180-2216
518-402-7810 Phone
518-402-7819 Fax
j ss05@health. state.ny .us
Keith Schwer
UNLV, Center for Business and Economic
Research
4505 Maryland Pkwy.
P.O. Box 456002
Las Vegas, NV 89154-6002
Les Sparks, Ph.D.
Senior Chemical Engineer
U.S. EPA/NRMRL
MD-54
Research Triangle Park, NC 27711
919-541-2458 Phone
919-541-2157 Fax
sparks.les@epa.gov
Chuck Stroebel
Environmental Research Scientist
Minnesota Department of Health
121 East Seventh Place
Suite 220
St. Paul, MN 55164
651-215-0919 Phone
651-215-0975 Fax
chuck. stroebel@health. state.mn.us
Helen Suh, Sc.D
Assistant Professor
Harvard School of Public Health
235 Lincoln St
Newton, MA 02461
617-432-0647 Phone
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617-432-4122 Fax
suh@sparca. harvard. edu
Keven Teichman
U.S. EPA
401 M Street, SW (8104R)
Washington, DC
202-564-6705
202-565-2917
teichman@epamail.epa.gov
Kent Thomas
Physical Scientist
U.S. EPA-NERL
79 T.W. Alexander Drive
MD-56
Research Triangle Park, NC 27711
919.541-7939 Phone
919-541-0905 Fax
thomas.kent@epamail.epa.gov
Nga Tran, Ph.D., Cffl
Assistant Professor
Johns Hopkins University
School of Hygiene and Public Health
624 N. Boardway
Baltimore, MD 21205
410-614-5454 Phone
410-614-2797 Fax
ntran@jhsph.edu
Gene Tucker, Ph.D.
Senior Research Engineer
U.S. EPA/NRMRL
Research Triangle Park, NC 27711
919-541-2746 Phone
919-541-5485 Fax
tucker.gene@epa.gov
Edward Washburn
Environmental Scientist/Multimedia Theme
Planner
US EPA/ORD/OSP
401M Street, SW(8104R)
Washington, DC 20460
202-564-1134 Phone
202-564-2916 Fax
washburn.edward@epa.gov
Roy Whitmore, Ph.D.
Senior Research Statistician
Research Triangle Institute
P.O. 12194
3040 Cornwallis Road, Cox Bldg.
Research Triangle Park, NC 27709-2194
919-541-5809 Phone
919-541-5966 Fax
rww@rti.org
Harvey Zelon
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, 27709
Maria Zufall, PhD.
Environmental Engineer
U.S. EPA/NERL/HEAB
MD-56
Research Triangle Park, NC 27711
919-541-5461 Phone
919-541-0905 Fax
zufall.maria@epa.gov
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Periann Wood, Ph.D.
U.S. EPA/NHEERL
ERC Building, MD-66
Research Triangle Park, NC 27711
919-541-3690
Bob Krieger
Personal Chemical Exposure Program
University of California
Dept. of Entomology
Riverside, CA 92521
Chuck Steen, Ph.D.
U.S. EPA/NERL
MD-75
Research Triangle Park, NC 27711
APPENDIX 4: LIST OF WORKGROUP PARTICIPANTS
Break-Out Groups
Assessment
Karen Hammerstrom6
Steve Knott7
Exposure Analysis
Jim Quackenboss
Tim Buckley
Lessons Learned
Maurice Berry
Gerry Akl and
Modeling
Haluk Ozkaynak
Steve Colome
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Laureen Burton
Julie Du
Ying Feng
Jane Hoppin
Beth Julian
Wendy Kay
Pat Kinney
Deirde Murphy
Will Ollison
Barry Ryan
Chris Saint
Chuck Stroebel
Nga Tran
Periann Wood
John Adgate
Andy Clayton
Mike Dellarco
Kenneth Fisher
Natalie Freeman
Melissa Gonzales
Mike Herman
FrejaKamel
Pat Kennedy
Bob Krieger
Anne Kukowski
Jack Leiss
David Macintosh
Lisa Melnyk
Mary Kay O'Rourke
Susan Schober
Judith Schreiber
Kieth Schwer
Chuck Steen
Kevin Teichman
Gene Tucker
David Camann
Bob Clickner
Syd Gordon
Matti Jantunen
Laura Johnson
Kelly Leovic
Paul Lioy
Larry Needham
Edo Pellizzari
Gary Robertson
Seumas Rogan
Helen Suh
Kent Thomas
Ed Washburn
Roy Whitmore
Harvey Zelon
Robert Buck
Yoram Cohen
Larry Cupitt
Panos Georgopoulus
Zhishi Quo
Alan Huber
Randy Maddalena
Scott Masten
Miles Okino
Muhilan Pandian
Paul Price
Les Sparks
Maria Zufall
6Chair
^Rapporteur
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APPENDIX 5: HANDOUTS8
Overview of NHEXAS Pilot Study
and Summary Tables for the
Data Analysis Planning Workshop
July 27 to 29,1999
Raleigh, NC
8Handouts not already included elsewhere in the proceedings document.
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The ultimate goal of the National Human Exposure Assessment Survey (NHEXAS) is to
document status and trends of national distributions of human exposure to potentially high-risk
chemicals to improve the accuracy of exposure (and risk) assessments and to evaluate whether
exposure (risk) is deteriorating or improving over time with the application of risk management steps.
The Phase I pilot projects, which are being discussed at this Workshop, are the beginning. Based on
the scientific advances from this first phase of NHEXAS, a national exposure survey is envisioned.
Phase I of NHEXAS (hereafter referred to as just NHEXAS) is perhaps the most ambitious
study ever undertaken to evaluate total human exposure to multiple chemicals on a community and
regional scale. It focuses on the exposure of people to environmental pollutants during their daily lives.
To accomplish this, hundreds of volunteer participants were randomly selected from several areas of
the country to obtain a population-based probability sample. NHEXAS scientists measured the levels
of a suite of chemicals to which participants were exposed in the air they breathe, in the foods and
beverages they consume, in the water they drink, and in the soil and dust around their homes.
Measurements were also made of chemicals or their metabolites in biological samples (including blood
and urine) provided by the participants. Finally, participants completed questionnaires to help identify
possible sources of exposure to chemicals and to characterize major activity patterns and conditions of
the home environment.
In addition to improving estimates of total exposure to chemicals, NHEXAS aims to:
Identify sub-groups of the general population that are likely to be highly exposed (at least the
75th percentile) to chemicals in their environment.
Provide a baseline of the normal range of exposure to chemicals in the general population that
can be used to compare to the results of other investigations conducted at particular sites of
concern or addressing specific routes.
Compare the results of a one-week ?snapshot" of exposure to the results obtained from
multiple sampling cycles over a year.
Evaluate and improve the accuracy of models developed to predict or diagnose exposure of
people to chemicals.
Test and evaluate different techniques and design approaches for performing multimedia,
multipathway human exposure studies.
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The NHEXAS pilots consist of three interrelated projects, all of which were funded as
co-operative agreements and coordinated by EPA's Office of Research and Development:
1) A study of several hundred Arizona residents by the University of Arizona, Battelle Memorial
Institute, and the Illinois Institute of Technology.
2) A study of several hundred residents from the states of Illinois, Indiana, Michigan, Minnesota,
Ohio, and Wisconsin by the Research Triangle Institute and the Environmental Occupational
Health Sciences Institute. In addition, a smaller-scale study focused on children's exposures
to pesticides, which was conducted with the participation of the Minnesota Department of
Health.
3) A study of about sixty Maryland residents by Harvard University, Emory University, Johns
Hopkins University, and Westat.
Two other federal agencies - the Food and Drug Administration and the Centers for Disease
Control and Prevention - are assisting EPA (under Interagency Agreements) with sample analysis. The
National Institute for Standards and Technology (under an Interagency Agreement) is providing quality
assurance support.
Within EPA's Office of Research and Development, scientists from the National Exposure
Research Laboratory, National Center for Environmental Assessment, and the National Health and
Environmental Effects Laboratory participate. The first two organizations are actively engaged in the
conduct of the program by serving as project officers and principal collaborators in the research.
Sample collection began in mid-1995 and was completed for all of the projects in late 1997.
Analysis of almost all of the samples was completed in early 1998. After statistical analysis and
summary, initial publications will be available beginning in 1999. The Consortia will be providing their
databases for the NHEXAS studies to EPA in late 1999/early 2000. We expect to make the data
available on the Internet by September of 2000. The two additional studies, Minnesota Childrens
Study and the Arizona Border Study will be made available on the Internet as the data becomes
available, possibly late 2001 or early 2002.
The attached nine tables summarize the major design elements of NHEXAS and the target
analytes/methods for metals, PAHs, pesticides, and VOCs. There were common features across the
three consortia. For example, all three consortia used the same basic set of questionnaires. Within
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chemical classes selected by the consortia, each consortium analyzed for a basic set of chemicals.
However, by utilizing three consortia, alternative and innovative variations on the theme of multimedia
measurements to estimate total human exposure were possible. For example, each consortium was
able to target some specific concerns or opportunities. Two of the consortia focused on measuring
potential exposures of each participant once; one consortia studied fewer people but repeated the
measurements several times over the year to enable estimates of temporal variability for the exposures
and activities of interest.
TABLE
1
2
3
4
5
6
7
8
9
CONTENTS
Study Design
Data Analysis
Environmental and Biological Sampling
Objectives and Hypotheses
Questionnaires
Target Analytes/Methods for Metals
Target Analytes/Methods for PAHs
Target Analytes/Methods for Pesticides
Target Analytes/Methods for VOCs
The participants were selected through a probability sample to permit statistical inferences about
the larger population later. The only exception was a special panel on children exposed to pesticides.
(This was based on oversampling households reporting more frequent applications of insecticides and
on a commercial listing of households with listed telephone numbers that were predicted to have age-
eligible children.)
Chemicals to be analyzed by NHEXAS were chosen because they are known (or strongly
suspected) to present major environmental health risks, have been found in two or more environmental
138
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media (air, water, soil, food), and have been identified as being of importance to several EPA program
or regional offices or other federal agencies. Chemicals were selected only if it was feasible to collect
and analyze them. The chemicals fall into three categories: (1) volatile organic compounds (VOCs),
such as formaldehyde, trichloroethylene, benzene, and perchloroethylene; (2) metals, such as lead,
mercury, arsenic, and cadmium.; and (3) pesticides, such as the herbicide atrazine and the insecticides
chlorpyrifos, diazinon, and malathion. In some media, measurements of selected polyaromatic
hydrocarbons (PAHs) were made.
SOURCES OF MORE INFORMATION
Abstracts of NHEXAS results presented at the last two annual meetings of the International
Society for Exposure Analysis, along with a Special Issue of the Journal of Exposure Analysis and
Environmental Epidemiology (vol.5, no.3, July-Sept., 1995) which describes all major aspects of
NHEXAS, will be available for review at the Workshop.
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TABLE 1. SUMMARY OF NHEXAS STUDY DESIGN
Consortium
Arizona/Battelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Overview
Study Design
Population
Selection and
Recruitment
Population-based personal exposure measurementP.opulation-based personal exposure measurementslnvestigate the relationship between shor
of metals, pesticides, & VOCs of metals & VOCs; MN children's pesticide study term (1-7 day) and long-term (annual
included pesticides & PAHs average) exposure measurements for meta'
& pesticides
Probability-based sample selection using multi- Probability-based sample selection using multi-stagErobability-based sample selection using
stage sampling; phased data collection involving sampling; phased data collection involving varyingmulti-stage sampling; participants must
varying levels of participation in each phase levels of participation in each phase agree to participate in all phases of the
study
Representative sample of general AZ
population
Divide AZ into 15 regions each containing a
number of "combined census block groups"
with similar populations
Of these 400-600 primary sampling units
(PSUs), 50 selected and divided into area
segments
5 area segments, containing 20-30 housing
units each, selected as secondary sampling
units (SSUs)
All houses in each SSUs randomly listed &
sequentially selected until 5 participating
households obtained
Seventy seven percent of the households
eligible for intensive sampling agreed to
participate, of these 179 (43 %) were
actually sampled due to resource
constraints. Lower number of samples
anlyzed by Battelle in last 3 counties due to
resource constrains.
Representative sample of EPA Region 5
(IL,IN,MI, MN,OH,WI)
Select 32 PSUs (generally counties) with
probability proportional to size (PPS) based on
1990 Census
- stratified by size and racial makeup
- four loops through Region with random starts
Select -24 households (HHs) per PSU (for
descriptive questionnaire), and one (or zero)
participant per HH, to yield ~9 participants per
PSU (for monitoring)
Longitudinal follow up by mail for participants
in the first 22 sample counties for 2 different
times
Incentive scale, based on burden (e.g., $5
baseline questionnaire, $15 for Core monitoring,
+$40 aerosol monitoring, +$75 duplicate
diet+reimburse for foods); eligible for Raffle
(1 ticket each for food monitoring and aerosol
monitoring)
Response Rates (weighted)
- Descriptive questionnaire ~ 72%
- Baseline questionnaire ~ 74%
- Visit 1 - Core monitoring ~ 80%
- Optional items: 50-70%
- Visit 2 - Core monitoring ~ 57%
- Personal VOCs -41%
- Visit 3 - Core monitoring ~ 48%
-Personal VOCs-38%
Representative sample includes
suburban, urban, & rural groups in
Baltimore and surrounding counties
Study conducted in 5 political areas in
Maryland: Anne Arundel County, Cit;
of Baltimore, Baltimore County
excluding the City, Queen Anne
County, and Talbot County. Stratify
U.S. Census block groups into 5
categories: 1. Urban, predominantly
white, 2. Urban, predominantly
minority; 3. Suburban, predominantly
4. Suburban, predominantly minority,
and 5 rural. 5 block groups. Select 5
Census block groups from each stratu: i.
Select 20 households from each block
group. Holdholds called until 90
households recruited (9-10 per
stratum). Goal to retain 50 household:
through to end of study
Each participant/household received f
sampling and questionnaire protocol t
times evenly spaced over one year.
ill
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TABLE 1 (cont'd). SUMMARY OF NHEXAS STUDY DESIGN
Consortium
Arizona/Battelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Administer Descriptive (n=555 households) and
Baseline (n=326) questionnaires
Monitor 249 participants; only 1 participant
per household
Two longitudinal follow ups by mail
(101 participants in first follow up and
86 participants second follow up)
Number of Collect baseline questionnaire data on
Participants and 900-1250 households
Temporal Environmental sampling and additional
Monitoring questionnaires for 450 households (primary
respondent, plus other interested residents)
In 179 of the 450 households, intensive &
temporal sampling with re-evaluation for the
same pollutants using methods with greater
resolution & reliability
Questionnaire data and intensive sampling
conducted on an additional 85 households along
the Arizona/Mexico border using NHEXAS
protocols.
Baseline questionnaire data collected in an
additional 200 homes and secondary sampling
conducted in approximately 50 households.
Types of Data Human activity (questionnaires & diaries); questionnaires & diaries: Personal and
Collected environmental concentrations (air, water, soil/dustenvironmental characteristics and activities;
surface residues); personal exposure concentratiofisre monitoring: Air-VOCs (indoor/outdoor,
(air, diet); human tissues/fluids (blood, urine) personal), Tap Water (metals, VOCs);
Aerosol Monitoring: Air(Indoor, Personal Air),
House Dust, and Soil (metals);
Duplicate Diet: solid foods and beverages (including
drinking water), diet diary and follow-up
questionnaire;
Biomarkers: blood, urine, hair
62 randomly selected people sampled
remained in the study through 6 samp] i
cycles
Human activity (questionnaires & diaries)
environmental concentrations (air, water,
soil/dust surface residues); personal
exposure concentrations (air, diet, residue
on hands); human tissues/fluids (blood,
urine)
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TABLE 2. SUMMARY OF NHEXAS DATA ANALYSIS
Consortium
Arizona/B attelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Journal Articles "In
Press" (Special Issue
ofJEAEE)
oo
The NHEXAS Study in Arizona-
Introduction and Preliminary Results
Spatial Distributions of Arsenic
Exposure and Mining Communities
from NHEXAS Arizona
Residential Environmental
Measurements in the National Human
Exposure Assessment Survey
(NHEXAS) Pilot Study in Arizona:
Multimedia Results for Pesticides and
VOCs
Evaluations of Primary Metals from
NHEXAS, Arizona: Methods,
Distributions and Preliminary
Exposures
Population Based Exposure
Measurements in AZ: A Phase I Field
Study in Support of the National
Human Exposure Assessment Survey
Sampling Design, Response Rates and
Nonresponse Compensation for the NHEXAS in
EPA Region 5
NHEXAS: Distributions and Associations of
Lead, Arsenic and Volatile Organic Compounds
in EPA Region 5
Population-based Dietary Intakes and Tap Water
Concentrations for Selected Elements in the EPA
Region 5 NHEXAS
Responses to the Region 5 NHEXAS
Time/Activity Diary
Analysis of Mercury in Hair of EPA Region 5
Population
Quantification of Children's Hand and Mouthing
Activities Through a Videotaping Methodology
The EL Sampler: A Press Sampler for the
Quantitative Estimation of Dermal Exposure to
Pesticides in House Dust
A Longitudinal
Investigation of Dietary
Exposure to Selected
Elements
A Longitudinal
Investigation of Selected
Pesticide Metabolites in
Urine
Long-Term Average
Microenvironmental Time
Budgets in Maryland
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TABLE 2 (cont'd). SUMMARY OF NHEXAS DATA ANALYSIS
Consortium
Arizona/B attelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Manuscripts "In
Preparation" Under
EPA Contracts
(estimated year of
publication)
Occurrence/Distributions of Pollutant
Concentrations in Different Media, with
Comparisons Across Media for each
Pollutant (1999)
Exposure Model Formulation and
Validation for Pesticides using the AZ
NHEXAS Database (1999)
Total Exposure Assessment Estimates
and their Distributions for Pesticides
(2000)
Total Exposure Assessment: The 90th
percentile of Total Exposure to
Pesticides and their Media Components
(2000)
Analysis of Dietary and Other Exposure
Pathways for Metals, with Comparisons
Between Media Concentrations and Routes of
Exposure (1999)
Assessment of Data Quality for the EPA Region
V NHEXAS Study (2000)
Pesticide Residues in Urine:
Temporal and Population
Variability and Associations
with Activities and Diet
(1999)
Population and Temporal
Variability Analyses of
Dietary Checklist Data
(1999)
Pesticide Residues in Urine:
Associations with
Questionnaire Data and
Environmental
Concentrations (2000)
Estimated Chlorpyrifos
Exposure in US EPA Region
V and Arizona (2000)
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TABLE 2 (cont'd). SUMMARY OF NHEXAS DATA ANALYSIS
Consortium
Arizona/B attelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Proposed
Manuscripts
to
o
Total Exposure Assessment for Metals
(same as contract papers 2-4 for metals,
including Border data & comp)
Exposure Assessment for VOCs,
(including Border and comparisons)
Exposure Assessment for PM10,
(including Border and comparisons)
Total Exposure Assessment for
Pesticides on the Border (similar to
contract papers 2-4, including
comparisons with the State)
Total Exposure Assessment for
Children (including Border, including
secondary respondents)
Total Exposure Assessment for
Hispanics (including Border, including
secondary respondents)
Complete Questionnaire Analysis: stat
models with exposures & biomarkers
Description of Time Activities in the
population and sub-populations in
relation to exposures and demo, char
Use of Portable
Contribution of Activity Patterns to Personal
Exposures of NHEXAS Participants
Relationship of Residential Sources and
Residential Conditions to Household
Contaminant Levels
Relationship Between Pesticide Levels in and
Around the Home and Hand Rinse
Measurements from Children
Relationship Between Activity Pattern Data and
Hand Rinse Measurements of Pesticides in
Children"
"Estimation of Pesticide Exposure from
Biomarker Measurements Using Environmental
and Time-Activity Data to Constrain the
Solutions"
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Consortium
TABLE 3. SUMMARY OF NHEXAS ENVIRONMENTAL AND BIOLOGICAL SAMPLING
(refer to Tables 6-9 for details)
Arizona/Battelle
RTI/EOHSI
Harvard/Emory/Johns Hopkins
Personal Air 1. Personal VOC passive badge sample (6-day
integrated).
2. Non-occupational personal VOC passive
badge.
3. Active personal pump with Teflon coated
filter (18-24 hour integrated).
Indoor Air 1. Indoor VOC passive badge sample (7-day
integrated).
2. Indoor VOC active pump sample (24-hour
integrated).
3. Indoor active pump sample (Two 3-day
integrated, including weekend).
Outdoor Air 1. Outdoor VOC passive badge sample (7-day
integrated).
2. Outdoor VOC active pump sample (24-hour
integrated).
3. Outdoor active pump sample (7-day
integrated).
Water Drinking water sample.
House Dust 1. Vacuum Sampler (floors).
2. Surface wipes (surfaces).
3. Adhesive tape transfer (surfaces).
Soil 1. Composite sample at foundation.
2. Composite sample from yard area
Dermal Dermal wipe sample.
Food One-day composite of duplicate diet and
beverages.
1. Personal VOC passive badge sample (6-day
integrated).
2. Non-occupational personal VOC passive
badge.
3. Active personal pump (6-day integrated).
Active personal pump sample (24-hour
integrated).
1. Indoor VOC passive badge sample (6-day Indoor active pump sample (7-day
integrated) integrated).
2. Indoor active pump sample (6-day integrated)
1. Outdoor VOC passive badge sample (6-day
integrated).
2. Outdoor active pump sample (6-day
integrated).
1. Drinking water samples (2).
2. Standing tap water sample.
1. Dust wipe samples on surfaces (2).
2. Plate deposition dust sample.
3. Carpet deposition dust sample.
Composite sample from yard area.
Dermal wipe sample.
Composite of four day duplicate diet and
beverage samples.
Outdoor active pump sample (7-day
integrated).
Flushed Tap Water Sample.
Vacuum Sample at Fixed Surface Area.
Composite sample from yard area.
Dermal wipe sample.
1. Composite of four day duplicate diet
and beverage samples.
2. Mini-market Basket.
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to
to
Consortium
Urine
Blood
TABLE 3 (cont'd). SUMMARY
Arizona/Battelle
One first daily void.
Personal Air
OF NHEXAS ENVIRONMENTAL AND
(refer to Tables 6-9 for details)
RTI/EOHSI
Two first daily voids.
50ml venous puncture.
BIOLOGICAL SAMPLING
Harvard/Emory/Johns Hopkins
One first daily void.
50ml venous puncture.
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TABLE 4. NHEXAS OBJECTIVES AND HYPOTHESES
Obj ective/Hypothesis
Analytical Approach
Consortia
to
1. TEST ADEQUACY OF INITIAL EXPOSURE
ASSESSMENTS
1 a. Exposure and/or concentration distributions from the
initial exposure assessment are/are not comparable to
the NHEXAS Phase I results.
Ib. Exposure and/or concentration data from NHEXAS
Phase I field studies can/cannot be used to improve
exposure assessment results.
2. IDENTIFY POSSIBLE SUBPOPULATION FOR WHICH
EXPOSURES ARE DIFFERENT
2a. Biologically sensitive subpopulations have/do not have
total exposures similar to those of the general
population.
2b. Exposures for certain segments of the population are/are
not different from those of the general population.
2c. Biological measurements for certain segments of the
population are/are not different from those of the general
population.
2d. Environmental media concentrations for certain
segments of the population are/are not different from
those of the general population.
3. IDENTIFY POSSIBLE CAUSES FOR DIFFERENCES IN
EXPOSURE
3a. Exposures for segments of the population reporting
contact with certain sources are/are not different from
the general population.
Weighted data analysis is used to furnish population
estimates.
Models used to develop initial exposure assessment will
be rerun using Phase I data.
Questionnaire data will be used to identify
subpopulations and a weighted data analysis will be
used to furnish (sub)population estimates.
Questionnaire data will be used to identify segments
and define the domains and a weighted data analysis
will be used to furnish (sub)population estimates.
Questionnaire data will be used to identify segments
and define the domains and a weighted data analysis
will be used to furnish (sub)population estimates.
Questionnaire data will be used to identify segments
and define the domains and a weighted data analysis
will be used to furnish (sub)population estimates.
Questionnaire data will be used to identify participants
that report contact with potential pollutant sources and
a weighted data analysis will be used to furnish
(sub)population estimates.
RTI/EOHSI UA/Bat/IIT
HSPH/JHU RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
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3b. Environmental media concentrations for segments of the
of the population reporting contact with certain sources
are/are not different from the general population.
Questionnaire data will be used to identify homes with
potential pollutant sources and a weighted data analysis
will be used to furnish (sub)population estimates
RTI/EOHSI UA/Bat/IIT
TABLE 4 (cont'd). NHEXAS OBJECTIVES AND HYPOTHESES
Obj ective/Hypothesis
Analytical Approach
Consortia
3c. Personal exposure measurements do/do not correlate
with measures of source intensity.
3d. Environmental media concentration measurements do/do
not correlate with measures of source intensity.
4. TEST FOR ASSOCIATIONS
4a. Personal exposure measurements do/do not correlate
with biological concentrations.
4b. Personal exposure measurements do/do not correlate
t° with environmental media concentrations.
5. APPORTION EXPOSURES AMONG MEASURED
PATHWAYS
5a. All measured pathways contribute equally/unequally to
dose.
5b. Pathway contributions are/are not independent.
6. PROVIDE DATA TO DEVELOP AND IMPROVE
EXPOSURE MODELS
6a. Individual dietary exposures estimated by combining
consumption data with concentration data from the FDA
Total Diet Study are/are not different from those derived
from Phase I data.
6b. Individual dietary exposures estimated using a food use
diary, coupled with a mini-market basket data collection
procedure are/are not comparable to those derived from
a duplicate diet procedures.
Questionnaire data will be used to define measures of
source intensity.
Questionnaire data will be used to define measures of
source intensity.
Calculate correlations (Spearman and Pearson for
original and log-transformed data).
Calculate correlations (Spearman and Pearson for
original and log-transformed data).
Convert concentrations to average mass/day. Estimate
population means and percentiles of these measures
and compare corresponding estimates across pathways.
Calculate inter-pathway correlations.
Food diary data are used to provide consumption
estimates. Pollutant concentrations for food items are
derived from the FDA Total Diet Study and duplicate
plates.
Food diary data are used to provide consumption
estimates. Pollutant concentrations for food items are
derived from the mini-market basket survey and
duplicate plates.
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
HSPH/JHU
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT HSPH/JHU
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT HSPH/JHU
HSPH/JHU
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TABLE 4 (cont'd). NHEXAS OBJECTIVES AND HYPOTHESES
Obj ective/Hypothesis
Analytical Approach
Consortia
to
6c. Distributions of long-term measurements (exposures,
doses, and environmental media concentrations)
can/cannot be estimated directly from short-duration
measurements
6d. Questionnaire data are/are not sufficient to afford
prediction of exposures experienced by a study
population.
7. IMPROVE DESIGN FOR NHEXAS PHASE II AND III
7a. Response rates are/are not sufficient to use the
NHEXAS Phase I methodology in NHEXAS Phase II.
7b. Respondents are/are not a biased subset of sample
subjects.
7c. Variance- and cost-component estimates from Phase I
are/are not useful for optimizing Phase II designs.
Extrapolate measurements to annual averages. Estimate
autocorrelation functions of exposure measurements by
grouping observations by months. Perform seasonal
adjustments. Other statistical tests such as the multiple
t-test and analysis of variance will be performed.
Develop regression-type prediction models. Correlate
predictions with measured exposures and biological
markers.
Qx data are used to define domains with potentially
different response rates. Response rates are computed
for each stage of participation both overall and by these
domains.
For each level of participation, respondents and
nonrespondents are compared based on characteristics
known for all participants at the previous levels
Cost- and variance-components from NHEXAS Phase I
(e.g, intracluster correlation for environmental and
biological measurements) will be used to determine the
minimum sample allocations for Phase II.
HSPH/JHU
RTI/EOHSI UA/Bat/IIT HSPH/JHU
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
RTI/EOHSI UA/Bat/IIT
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TABLE 5 QUESTIONNAIRES USED FOR NHEXAS
All three NHEXAS Phase I Field Studies used the same set of questionnaires. They were
developed by EPA in cooperation with a number of recognized experts in the collection analysis of
human activity pattern data, human exposure to contaminants in air and non-air media, and
environmental epidemiology. These questionnaires were developed to: 1) provide descriptive
information for the households and individuals included in the NHEXAS population sample compared
with the target population (e.g., Census data), 2) explain variability or predict differences in
exposure/dose measurements, 3) identify the presence (and, possibly, usage patterns) for major
pollutant sources in the microenvironments most frequently visited by individuals in the survey (e.g.,
home and work place); and 4) characterize the distributions of "exposure factors" which are needed to
compare and contrast exposure estimates made in the initial assessment with those derived from the
NHEXAS pilot studies.
To meet these objectives, the questionnaires are designed to elicit information about each of the
following topic areas: a) demographic characteristics of household residents and of selected
respondents), b) basic household characteristics, c) activity and lifestyle factors related to pollutant
exposure for the selected respondents, d) occupational factors, e) general dietary patterns and f)
information health status for use in identifying high risk subpopulations..
The NHEXAS pilot study questionnaires are organized into six modules for simplicity in
administration (to minimize respondent burden and maximize participation rates at each step) and for
collecting information that can be temporally related to the exposure, concentration and/or biological
measurements collected in NHEXAS. The six modules are:
1) Descriptive Questionnaire - to enumerate individuals within a household for sampling
purposes (basis for selection of sample individual), to identify general characteristics of the
living quarters and occupants, and to provide a basis for assessing potential bias due to
refusals in subsequent steps;
2) Baseline Questionnaire - to provide more detailed information on the characteristics of the
sample individual and housing, and on the usual frequency of activities over a longer time
frame (i.e., last month or year) relative to persistence in environmental or biological media;
150
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3) Technician Questionnaire - to identify and inventory the presence of pollutant sources and
document physical characteristics of the building (technician completed to minimize burden on
respondents);
4) Follow-up Questionnaire - to provide information on relatively infrequent (e.g., less than
daily) activities during the sampling period to explain variation in the sample (or differences
between sub-groups) for the monitoring results;
5) Time Diary and Activity Questionnaires - for collecting data on detailed (daily) time and
location information and activity patterns (for relatively frequent activities when recalling
events over several days would be more burden on the respondent); and
6) 24-hour Dietary Diary - for collecting information on actual daily consumption patterns
from the participant for use in estimating dietary exposures. The NHEXAS Phase I Field
Studies will evaluate two types of self-completed food diaries: 1) an open-ended dairy and
2) a checklist of specified food categories. The main aim of the food diaries and food sample
collection is to develop a suitable protocol for NHEXAS Phase n. Another aim is to test the
need for making direct dietary measurements through comparisons with assessments using
existing data and approaches.
151
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TABLE 5. QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline
Follow-up Technician
Activity
to
oo
DEMOGRAPHIC
gender
age (date of birth)
race/
hispanic origin
education
height
weight
income
location (county, city; census tract, block)
nearest major intersection
region, urban/rural
distance to street
HEALTH STATUS
current health
specific diseases, diagnoses, ages
medications
pregnancy or lactation
BASIC HOUSING CHARACTERISTICS
structure
floors
D5c
D5d
D5e, D5f
cover
D6
B2
B3
Bl
B4
B5
B44
cover
B20
B21(a-w)
cover
cover
T5
T6a
T6b
F6(a-e)
F8
T1,T2
rooms
D7
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TABLE 5 (cont'd). QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline
Follow-up Technician
Activity
to
VO
carpeting/rugs
own/rent
farm/ranch
building age
tenure
remodeling, painting
water sources, treatment
enclosed/attached garage
gas-powered engines
air conditioning
evaporative coolers (AZ only)
fans
heating fuels, system
space heaters (kerosene and gas)
wood/coal stove
wood/coal fireplace
air cleaner/filter
humidifier (ultrasonic)
pesticide treatments inside/outside
pesticide treatments lawn/garden
mothballs
T3
D8
B22
B23
B24
B25
B26(a-e)
B27(a-d)
B28
B29(a-c)
B30(a-f)
B31,B32,B33
B34(a-c), B35(a-c)
B36(a-d)
B37(a-d)
B38(a-i), B39(a-g)
B40(a-f)
B41
F2(d,e)
Fl(a-b)
Fl(c)
Fl(d-f)
Fl(h),Fia)
Fl(ij)
Fl(g)
Fl(k)
Fl(m,o)
Fl(n)
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TABLE 5 (cont'd). QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline
Follow-up Technician
Activity
room deodorizers
pets
flea/tick treatments
open doors/windows
dust level/control
exterior siding
paint exterior/interior
materials at entrance and in yard
drip line, roof
roof type/composition
foundation
swimming pool, hot tub, Jacuzzi
EXPOSURE ACTIVITIES
duration of time spent inside and outside by location
category
tobacco smoking
smokeless tobacco
time near someone who was smoking
smoking at home
paint walls, furniture, cars, or other objects
chemical paint strippers
D5h
D5i
B42
B43(a-d)
B43(e-f)
B6(a-c), B7(a-c)
B7d
B8(a-d)
B9(a-c)
B10(a)
B10(b)
A26
T4
T6c
T6(d,e)
T6(f), T6(i)
T6(g)
T6(h)
T6©
T7(a,b), T8(a,b)
home
work/school/other, or
in-transit
A20,A21
-------
other paint removal
B10(c)
F2(f) sander
TABLE 5 (cont'd). QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline
Follow-up Technician
Activity
solder pipes, electronic repairs, stained glass
lead-based oil paint (pictures or jewelry)
paints or solvents
glues and adhesives
kerosene, fuel oil
Bll(a)
F2(a)
F2(b)
F2(c)
mold lead
metal working/welding
pump gas
spill gas on skin
enclosed garage with parked car
contact with soil or dirt
grass or leaves
fireplace or wood stove
grilling, burning
tobacco smoked in home
drinking water
tobacco use
hand washing
travel on roads
shower, bath
Bll(c)
F3(g)
F5(a-c)
F4(a-d)
Al
A2
A3
A4
A5
A6,A7
A8
A9
A14
A15,A16,A17
A18
A19
A10,A11
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to
TABLE 5 (cont'd).
QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline Follow-up Technician Activity
swimming
prepare/apply pesticides
using cleaning supplies
vacuum, sweep, dust
gardening
woodworking
lay /sit on carpet at home
time in enclosed workshop
vigorous and moderate exercise
DIETARY AND NON-DIETARY
non-market foods.
non-market fish
non-market game
cruciferous vegetables
grapefruit
alcoholic beverages
grilled, flame broiled, smoked, or blackened foods
vitamins and mineral supplements
special diet
A22
F2(g,gl) A12.A13
A23
F3(a-c)
F3(e)
F3(f)
A24
A25
A27-A28
B12(a,b)
F9(a-d)
F9(e)
F9(f)
F9(g)
F7 (a-d)
F10,F11
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TABLE 5 (cont'd). QUESTIONNAIRES USED FOR NHEXAS
Descriptive Baseline
Follow-up Technician
Activity
OCCUPATION
work full- or part-time away from home
second job
time at work
working at home
business type
job title
activities/duties
protective clothing
exposures to dusts, fumes, gas, or vapors
exposures to pesticides
attend classes as student
time at school/day care
school/day care outside the home
other time spent outside the home
transportation to work/school
D5j
D6p
D6o
D5k
D6n
B13
B15
B14a,B16a
B14i,B16i
B14b,B16b
B14c,B16c
B14d,B16d
B14(e,f),B16(e,f)
B14(g,h),B16(g,h)
B17a
B17b
B18(a-b)
B19
diary
diary
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APPENDIX 6: COPIES OF OVERHEADS
158
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