Document ID: EPA-HQ-OPP-2007-0388-0010
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-07-30T04:00Z

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 –
Mr. Steven Knott, Office of Science Coordination and Policy, EPA

8:45 A.M.	Welcome and Opening Remarks – Debbie Edwards, Ph.D.,
Director, Office of Pesticide Programs, EPA

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

9:00 A.M.	Overview of SHEDS-Multimedia Residential and Dietary Models,
and Future Plans   – Valerie Zartarian, Ph.D., 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, Residential Model Structure and
Approach – Valerie Zartarian, Ph.D., Office of Research and
Development, and Jianping Xue, Ph.D., 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

Charge Question 1:  The SHEDS-Multimedia version 3 User’s Manual
provided to the SAP presents installation and operational instructions
for the software. 

1(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? 

1(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.

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

Charge Question 2: The SHEDS-Multimedia version 3 Technical Manual
provided to the SAP provides an overview of the SHEDS-Multimedia version
3; presents detailed descriptions of key model components; and describes
the model construct and algorithms, required inputs, and analysis/output
capabilities.

2(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.

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

Charge Question 3: The Source Code Directory on the CD provided to the
SAP includes annotated code for the exposure algorithms used in the
SHEDS-Multimedia version 3.

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

3(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.	Planned Methodologies to Extend version 3 to version 4 –
Valerie Zartarian, Ph.D., Office of Research and Development, EPA;
Jianping Xue, Ph.D., Office of Research and Development, EPA; and Graham
Glen, Ph.D., Alion Science and Technology  

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)

Charge Question 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.

Charge Question 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 v3 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 - 

		Mr. 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

Charge Question 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.

ance 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

Charge Question 4: SHEDS-Multimedia is sophisticated physically-based
probabilistic model with numerous inputs. One of the unique advantages
of SHEDS-Multimedia are 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 model: all random determinations must be re-expressed as
independent input variables; and random number seeds in SHEDS must be
careful 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.

Charge Question 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.

Question 5(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.

Question 5(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.	SHEDS-Multimedia, Dietary Model Structure and Approach –
Steve Nako, Ph.D., Office of Pesticide Programs, and Jianping Xue,
Ph.D., 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

		Charge Question 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 multple eating
occasions.

		Charge Question 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).

		Charge Question 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

		Charge Question 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.

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

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

		Charge Question 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.

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5:00 P.M.	Adjournment

Please be advised that agenda times are approximate; when the discussion
for one topic is completed, discussions for the next topic will begin. 
For further information, please contact the Designated Federal Official
for this meeting, Mr. Steven Knott, via telephone:  (202) 564-0103; fax:
 (202) 564-8382; or email: knott.steven@epa.gov

DRAFT 07-30-07