Document ID: EPA-HQ-OPP-2007-0388-0031
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-08-13T04:00Z

AGENDA

FIFRA SCIENTIFIC ADVISORY PANEL (SAP)

OPEN MEETING

August 14-15, 2007

FIFRA SAP WEB SITE http://www.epa.gov/scipoly/sap/

OPP Docket Telephone: (703) 305-5805

Docket Number: EPA-HQ-OPP-2007-0388

U.S. Environmental Protection Agency

Conference Center - Lobby Level

One Potomac Yard (South Bldg.)

2777 S. Crystal Drive, Arlington,VA 22202

Review of EPA/ORD/NERL’s SHEDS-Multimedia Model, Aggregate version 3

Tuesday, August 14, 2007

  8:30 A.M.	Introduction and Identification of Panel Members – 

		Steven G. Heeringa, Ph.D. (FIFRA SAP Chair)

  

  8:40 A.M.	Administrative Procedures by Designated Federal Official –

		Steven Knott, Office of Science Coordination and Policy, EPA

  8:45 A.M.	Welcome and Opening Remarks – Tina Levine, Ph.D.,
Director, Health Effects Division, Office of Pesticide Programs, EPA

  8:50 A.M.	Introduction – Dana Vogel, Health Effects Division, Office
of Pesticide Programs, EPA

  9:00 A.M.	Overview of SHEDS-Multimedia Aggregate Residential Model
(v.3) and Future Plans   – Valerie Zartarian, Ph.D., National Exposure
Research Laboratory, Office of Research and Development, EPA 

  9:15 A.M.	Public Comments

10:15 A.M.	Break

10:30 A.M.	SHEDS-Multimedia version 3, (aggregate) Residential Model
Structure and Approach – Valerie Zartarian, Ph.D., and Jianping Xue,
M.D., National Exposure Research Laboratory, Office of Research and
Development, EPA 

12:00 P.M.	Lunch

  1:15 P.M.	Charge to Panel – Issue 1: Documentation, completeness,
and clarity of the technical aspects and usability of the
SHEDS-Multimedia version 3 (aggregate residential) model

Question 1-1: 

The SHEDS-Multimedia version 3 User’s Manual provided to the SAP
presents installation and operational instructions for the software.

a) Were Panel members able to load the software on to their computers?
What, if any, difficulties were encountered in loading or running the
software?

b) The SHEDS-Multimedia version 3 graphical user interface (GUI) was
designed to be user-friendly to exposure modelers and risk assessors.
Please comment on the

organization and usability of the GUI, any difficulties you encountered,
which features and output capabilities were most useful, and whether any
additional options would be helpful. Please also comment or offer
suggestions for improving the GUI/model interface.

c) Please comment on the organization, clarity, completeness, and
usefulness of the User Guide document and provide any suggestions for
improvement.

Question 1-2: 

The SHEDS-Multimedia version 3 Technical Manual provided to the SAP
provides an overview of the SHEDS-Multimedia aggregate residential
model; presents detailed descriptions of key model components; and
describes the model construct and algorithms, required inputs, and
analysis/output capabilities.

a) Please comment on whether the descriptions of specific model
components are scientifically sound and whether the algorithms described
in the Technical Manual represent the state of the science for
performing exposure assessments. Please also comment or offer
suggestions for improving or modifying these algorithms or other aspects
of the model construct.

b) Please comment on the organization, clarity, completeness and
usefulness of the Technical Manual and provide any suggestions for
improvement.

Question 1-3: 

The Source Code Directory on the CD provided to the SAP includes
annotated code for the exposure algorithms used in the SHEDS-Multimedia
aggregate residential model.

a) Please comment on whether the annotated code is sufficiently clear
such that the algorithms can be followed and understood.

b) Please also comment on whether these algorithms are technically
correct and consistent with the descriptions provided in the technical
manual.

2:45 P.M.	Break

3:00 P.M.	Plans for Extending SHEDS-Multimedia version 3 to version 4
– Valerie Zartarian, Ph.D., National Exposure Research Laboratory,
Office of Research and Development, EPA 

4:00 P.M.	Charge to Panel – Issue 2 Technical Aspects of Planned
Methodologies to Extend SHEDS-Multimedia version 3 (aggregate) to
version 4 (cumulative)

Question 2-1: 

SHEDS-Multimedia version 3 simulates exposures of individuals to one
chemical at a time. As discussed in the Planned Methodologies document
provided to the SAP, SHEDS-Multimedia version 4 will also allow tracking
exposures of individuals to multiple chemicals at the same time. Unlike
version 3, which has a single chemical focus, version 4 will have a
“product formulation” orientation since a single product may contain
multiple chemicals. A product-related co-occurrence priority system like
the version 3 co-occurrence approach will be used to minimize the number
of product combinations. In version 3, the running exposures of the
chemical are tracked in three carriers (air, surface residues, and
dust/soil), but the masses of the carriers themselves are not tracked.
In version 4, the mass of each chemical and each carrier (soil, dust,
residue, air, food, water) will be tracked. The basic operation of
SHEDS-Multimedia will be unaffected by these changes, but the list of
variables (vectors rather than single numbers for chemical-specific
inputs, exposures, and doses) and model run time will be longer, and the
GUI will need to be modified accordingly.

Please comment on the technical aspects and usefulness of the planned
methodology for extending SHEDS-Multimedia version 3 to address multiple
chemicals in version 4.

Question 2-2: 

SHEDS-Multimedia version 3 combines media concentration or residue data
with simulated individuals’ contact rates (e.g., m3/hr for inhalation,
cm2/hr for dermal, or appropriate contact factors for ingestion via hand
to mouth activity) to estimate exposure. The media (air, dust/soil,
surfaces) concentrations or residue levels can be derived with a simple
decay/dispersion model, from user-specified series of concentrations
from either measurement studies or an external model, or from
user-specified post-application distributions (as described in the
Technical Manual). ORD intends to include a fugacity-based model as an
added (fourth) option to SHEDS-Multimedia v 4. Fugacity can be
considered the “escaping tendency” of a chemical from a given phase
or compartment, and the fugacity-based model uses the thermodynamic,
equilibrium, and physical-chemical properties of substances to model
chemical transfers/movements of chemicals across these compartments. The
proposed SHEDS v 4 fugacity model is more sophisticated and detailed
than the other options currently available in SHED v 3 and will require
more extensive inputs on the part of the user. It divides a dwelling
into treated and untreated areas, each having four compartments or
phases (vinyl or untextured surface, carpet or textured surface, air,
and wall), and the output concentration time series for the different
compartments will be used as contacted concentrations for simulated
individuals in SHEDS v 4.

Please comment on the technical aspects and usefulness of the planned
methodology for incorporating a fugacity-based source-to-concentration
module into SHEDS-Multimedia version 4. Does the Panel recommend
additional efforts with the fugacity module (e.g., modeling more
realistic multi-room dwellings) given available information?

5:00 P.M. 	Adjournment

AGENDA

FIFRA SCIENTIFIC ADVISORY PANEL (SAP)

OPEN MEETING

August 14-15, 2007

FIFRA SAP WEB SITE http://www.epa.gov/scipoly/sap/

OPP Docket Telephone: (703) 305-5805

Docket Number: EPA-HQ-OPP-2007-0388

U.S. Environmental Protection Agency

Conference Center - Lobby Level

One Potomac Yard (South Bldg.)

2777 S. Crystal Drive, Arlington,VA 22202

Review of EPA/ORD/NERL’s SHEDS-Multimedia Model, Aggregate version 3

Wednesday, August 15, 2007

8:30 A.M.	Introduction and Identification of Panel Members - 

		Steven G. Heeringa, Ph.D. (FIFRA SAP Chair)  

8:40 A.M.	Administrative Procedures by Designated Federal Official - 

		Steven Knott, Office of Science Coordination and Policy, EPA

8:45 A.M.	Follow-up from Previous Day’s Discussion

8:50 A.M.	Charge to Panel - Issue 2 Continued

Question 2-3:  

SHEDS-Multimedia version 3 requires the construction of human activity
diaries that cover the entire simulation period of a model run (e.g.,
several months, a year, or longer). The human activity diaries are drawn
from EPA’s Consolidated Human Activity Database (CHAD) and typically
include just one day (24 hours) of activities from each person.
SHEDS-Multimedia version 3 uses eight one-day diaries (one weekend and
one weekday from each of four seasons) to assemble a longer-term
activity profile for each simulated individual. A distinct and
recognized disadvantage of this method is that any activity that happens
at all will happen many times, since each diary is re-used many times
and there is an absence of activities that happen only once or just a
few times over the year.

Ideally, self-reported longitudinal diaries that cover the same person
over a long period of time would exist for estimating longer-term
exposures of days, weeks, or months; however, these studies are
relatively rare and the data require substantial and sustained effort to
collect, verify, and analyze. As a result, EPA is developing a new
approach for longitudinal diary assembly for SHEDS version 4 which
allows for more control over the characteristics and longitudinal
properties of the assembled diaries. The new diary assembly method
requires the modeler to identify a diary property most relevant to
exposure for the current application; to apportion the total variance
for this selected property into within- (σw2) and between- variances
(σw2); and to specify the relevant 1-day lag autocorrelation. The Panel
has been provided with background material and a journal preprint
entitled “A New Method of Longitudinal Diary Assembly for Human
Exposure Modeling”.

Please comment on the technical aspects, potential utility, and added
value of the planned methodology for longitudinal diary assembly in
SHEDS-Multimedia version 4. Does the Panel believe that this new method
will create an assemblage of diaries that better simulates reality and
provides more accurate estimates of exposures related to
within-individual time-activity patterns? Please suggest procedures
and/or longitudinal data which could be used to select factors (the
“D” factor intra-class correlation coefficient, and the 1-day lag
autocorrelation) or refine/evaluate this method in SHEDS.

10:00 A.M.	Break

10:15 A.M.	Charge to Panel – Issue 2 continued

Question 2-4: 

SHEDS-Multimedia is a sophisticated physically-based probabilistic model
with numerous inputs. One of the unique advantages of SHEDS-Multimedia
is sensitivity analysis methods that can be used to determine model
inputs most influential on model output values. SHEDS-Multimedia version
3 utilizes “one-at-a-time” and “multivariate” sensitivity
analysis methods, as described in the Technical Manual provided to the
SAP. The Sobol multivariate method, described in the journal article
provided in SAP background materials, provides significantly more
information than current alternatives, but requires some reorganization
of SHEDS code and redefining some inputs. The advantages of including
the Sobol method as another option for SHEDS sensitivity analyses are:
(1) it is capable of determining both direct and interaction influences
for each input; (2) handles categorical, other non-numeric inputs;
accounts for non-linear response; (3) can examine aspects (e.g., diary
assembly) not easily handled by other methods; and (4) has not been used
with a probabilistic model before SHEDS. Implementation of Sobol’s
method in SHEDS requires two main alterations to the model: all random
determinations must be re-expressed as independent input variables; and
random number seeds in SHEDS must be carefully tracked. It requires that
SHEDS be run a total of (2N+2) times.

Please comment on the technical aspects and usefulness of the planned
methodology for utilizing Sobol’s method for sensitivity analysis in
SHEDS-Multimedia version 4, and whether Sobol’s method would be a
useful supplement to the existing sensitivity analysis methods used for
the SHEDS-Multimedia version 3 model.

Question 2-5: 

Section 5 of the Background document entitled “Planned Methodologies
for Extending SHEDS-Multimedia Version 3 (aggregate) to SHEDS Multimedia
Version 4 (cumulative or aggregate)” describes some of the upcoming
modifications and enhancements that are planned for SHEDS-Multimedia
Version 4. The residential module of SHEDS-Multimedia Version 3 does not
currently address cumulative exposures to multiple chemicals, does not
utilize the MOE approach for aggregating exposures across routes, does
not permit the user to repeat runs using the same random number seed,
does not accept empirical input distributions, and does not allow
outputs to be linked with PBPK models (e.g. ERDEM). These -- along with
development and integration of the SHEDS dietary module -- are
considered to be high priorities for SHEDS-Multimedia Version 4.

a) Please comment on (and prioritize, as appropriate) the technical
aspects and usefulness of planned changes to the SAS code and GUI for
SHEDS-Multimedia version 4 that are listed items in Section 5 of the
above-referenced background document.

b) Please comment on any additional modules, features, or capabilities
that the Panel feels should also be high priorities for the next version
of SHEDS including issues associated with the code, user interface/user
friendliness, input, and output/output display. Are there modules,
features, or capabilities of other human exposure models that should be
considered for inclusion in SHEDS-Multimedia version 4 (e.g., simulation
of individuals; longitudinal diary assembly)?

12:15 P.M.	Lunch

  1:15 P.M.	An Update on the Development of the SHEDS-Dietary Model – 

		Steven Nako, Ph.D., Health Effects Division, Office of Pesticide
Programs, and Jianping Xue, M.D., National Exposure Research Laboratory,
Office of Research and Development, EPA

2:00 P.M.	Charge to Panel - Issue 3: An Update on the Development of the
SHEDS-Dietary Model

Question 3-1: 

Eating Occasion Analyses.

As described in the SHEDS dietary background document, the timing
information available in CSFII can be used to model food and indirect
water intake throughout the day. With the ability to incorporate the
timing of eating occasions in dietary exposure assessments, it is
possible to assign either the same residue or a different residue to
foods consumed on multiple eating occasions. In certain instances, the
former seems logical (e.g., consumption of leftovers) while in other
instances the latter appears appropriate (e.g., hash browns at home for
breakfast and fried potatoes away from home for dinner).

Please comment on developing simple decision rules -- as described in
the document -- for assigning residues to commodities eaten on multiple
eating occasions.

Question 3-2: 

Longitudinal Dietary Consumption

To estimate exposures associated with longer time periods than 1 day,
SHEDS-Dietary draws from diary pools based on gender, age group, season
and day-type (weekday, weekend). The 8-diary approach of SHEDS described
in the background document limits each individual’s diet to 2 per
season, one of which corresponds to a weekday and the other corresponds
to a weekend day.

Please comment on the 8-record approach in SHEDS-dietary and the
selection of age group, gender, season and day-type from which to create
the “diary pools”. What other approaches does the Panel recommend?
Can the Panel suggest any “bounding approaches” that may - based on
knowledge of actual eating patterns -- provide upper and lower limits
for longitudinal exposure estimates (e.g., yearlong consumption of the
same diary throughout the year vs. random daily selection of CSFII
diaries).

Question 3-3: 

Bayer Drinking Water Consumption Survey Data

The CSFII data does not contain information on the time and amounts of
direct drinking water consumption. Bayer CropScience sponsored a study,
Drinking Water Consumption Survey (DWCS) that was designed to obtain a
distribution of water intake for a 24-hour time period from a
representative sample of the US population. Participants recorded their
water consumption (time of day and amount consumed) over a one-week (7
consecutive day) period. The authors, Barraj et al. (2004) suggested
that it may be possible to “allocate the total daily water consumption
amount reported in the CSFII into various drinking occasions” using
information from the DWCS. In addition to offering a fixed option for
allocating direct drinking water throughout the day, the Agency is
planning to include in SHEDS-Multimedia v 4 the option to allocate
direct drinking water consumption throughout the day through empirical
use of the Bayer DWCS data.

Please comment on the advantages and disadvantages of providing an
option to use the Bayer DWCS data in SHEDS-Multimedia v. 4. Please
include in your comments any statistical concerns or issues associated
with the design and conduct of the DWCS study.

3:15 P.M.	Break

3:30 P.M.	Charge to Panel - Issue 3 Continued

Question 3-4: 

Bootstrap Approach to Uncertainty Analysis

Sensitivity and contribution analyses are a routine part of OPP risk
assessments. These analyses help inform the risk manager how exposures
may change when certain model inputs are modified. These modifications
to the model inputs are typically performed “one at a time” to
permit isolation of the effect. In a typical risk assessment, all the
dietary consumption data (i.e., reported CSFII diaries) are used along
with the best available pesticide residue data. OPP risk assessors
specify a sufficiently large number of Monte-Carlo iterations such that
exposure estimates are stable with respect to the random seed.

The Agency has not conducted formal quantitative uncertainty analyses.
The Agency presented a simple bootstrapping procedure for conducting
uncertainty analyses, utilizing only a subset of the consumption and
residue data inputs. That procedure was designed to provide some insight
into the question “How much better would our exposure estimates be if
we had more data” by conducting the uncertainty analysis in the other
direction.

a)  Please comment on the scientific soundness and utility of the
proposed bootstrap uncertainty approach.

b)  Can the Panel recommend alternative approaches -- and how they might
be interpreted and used -- for conducting uncertainty analyses of
dietary exposure estimates?

Question 3-5: 

NHANES Dietary Consumption Survey

The SHEDS-Dietary paper noted that the NHANES 1999-2006 dietary
consumption data does not contain information on season nor region.

Please suggest statistical or other methods that might be used to
determine the extent to which region- and season- specific dietary
consumption amounts and patterns might be important in developing
dietary exposure estimates. Please consider in your response whether and
how quantitative uncertainty methods could be used in addressing this
issue.

5:00 P.M.	Adjournment

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; fax:  (202) 564-8382; or email: knott.steven@epa.gov