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Exposure 		Modeling Public Meeting (EMPM) Information and Products

Minutes of the October 4, 2004 Exposure Modeling Public Meeting

Minutes of the October 4, 2004 Exposure Modeling Public Meeting

OPP Conference Room

Crystal Mall Building 2

Room 1126

On this Page

Attendees

Status of Action Items

Introduction

Brief Updates

Ongoing Actions

Attendees

Name	Association

Dirk Young	OPP/EFED

Betsy Behl	OPP/EFED

Ron Parker	OPP/EFED

Mark Corbin	OPP/EFED

Jim Lin	EPA/EFED

Nelson Thurman	EPA/EFED

R. David Jones	EPA/EFED

James Hetrick	OPP/EFED

Lucy Shanaman	OPP/EFED

Norm Birchfield	OPP/EFED

Michael Barrett	OPP/EFED

Marietta Echeverria	OPP/EFED

Faruque Khan	OPP/EFED

Alex Clem	OPP/EFED

Mohammed A. Ruhman	OPP/EFED

Piyush Singh	DuPont

Mark Russell	DuPont

Kathy Carr	Monsanto

Mary Nett	WQC

Mark Shocken	Crompton

Pat Havens	Dow

Russell Jones	Bayer

T. S. Ramanarayanan	Bayer

Paul Hendley	Syngenta

Wenlin Chen	Syngenta

Cecil Dharmasri	Syngenta

Scott Jackson	BASF

Alan Rose	Valent

Greg Leyes	ISK BC

Mark Cheplick	Waterborne Environmental

Amy Ritter	Waterbcrne Environmental

Les Carver	Waterborne Environmental

Cathleen Hapeman	USDA/ARS

Tamara Estes	Stone Environmental

Susan Alexander	Stone Environmental

Tom Gilding	CLA

Kevin Armbrust	MS State Chemists Office

Beth Julien	ILSI

Andrew Hewitt	Univ Queensland

Dean Scott	BNA

Lizanne Avon	PMRA (Canada)

Jim Cooper	EarthSat

Francois Smith	EarthSat

Yong-Hwa Kim	Korean Institute of Toxicity

Stuart Cohen	ETS

Qingli Ma	ETS

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Status of Action Items

Industry will hold its review of EXPRESS until EFED releases the user's manual and the report on final ORD revisions.

ORD and EFED will decide whether the volatilization feature should be turned on in PRZM and EFED will make an internal decision on whether to use a constant soil temperature. Decision to be communicated over list server or via reporting at the next EMWG. Action: David Jones will follow-up.

Jim Lin distributed copies of a CD containing the presentations from the drinking water treatment workshop.

Paul Hendley will feed back the collection of presentations from the ACS Terrestrial Field Dissipation Study Symposium to Mark Corbin for inclusion on the web site; CD's are now available from Al Barefoot (Dupont).

Russell Jones will mention EPA's availability to attend Landscape and Mitigation 2 group which starts 2005 at upcoming EEASG meeting in Europe to formally obtain an invitation.  Action:  Betsy Behl will follow-up with Russell Jones.

All will try to download the revised PRZM model and try it out with their own datasets.

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Introduction

Jim Lin introduced the meeting and reviewed actions as shown above. Ron Parker and Marietta Echeverria will take over chairmanship of the Water Quality Tech team and will thus become responsible for the Agendas, Federal Register announcements and chairmanship of FIFRA EMWG.

As a reminder the FIFRA EMWG web site can be found at
http://www.epa.gov/oppefed1/models/water/emwg_top.htm

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Brief Updates

PRZM-EXAMS model/ EXPRESS (R. David Jones)

David Jones reported on current work which is based around QA/QC of PRZM version 3.12.2   Work is going on to re-examine the volatilization and irrigation routines . Irrigation handling is being improved but the volatilization is still under evaluation especially with regard to the availability of the necessary soil albedo data for parameterizing the soil temperature routines - ACTION: This is still to be completed.

The EXPRESS model

QA/QC still requires completion of the final user's manual.  EPA have sent revisions to the contractor and a final draft will be issued soon. Realistically, the EXPRESS review is unlikely to be completed until early 2005. ACTION: EPA will make sure the revised version of EXPRESS along with the new manual are made available (via OPP CEAM website or EFED website as appropriate) as soon as possible after they are completed so that Industry can conducts its formal review.

Standard Scenarios (Ron Parker)

Ron reported that he hopes to see responses/comments available to the public commnnts within a month. Good progress is being made.  Corrections will be included in the scenarios in the PE4 shell.

Terrestrial Field Dissipation - new technical document (Mark Corbin)

Draft now going through a French translation for PMRA and then there will be a public comment period (60 day).; few surprises are expected. CD's of the ACS proceedings can be obtained from Al Barefoot at Dupont.

Direct application of herbicides to water bodies (Mark Corbin)

EPA is looking at developing a tiered system that will allow for the introduction of various levels of complexity ranging from application to the total water body to the inclusion of partial applications, flow, dissipation rates, uptake etc.

Spray Drift Task Force Ground Spray Drift Data (T. S. Ramanarayanan)

Rama presented information on plans to develop the new ground spray model developed by EPA and Forest Service.  He suggested that FIFRA EMWG would be a valid forum to discuss developments Norm Birchfield made a strong point that EPA is  planning on developing the tool for regulatory evaluations within an AgDISP based computational platform. Norm pointed out that a key aspect of a mechanistic tool is that probabilistic approaches are possible.

Cumulative Drinking Water Assessment - Method Review (Nelson Thurman)

More data can be found at http://www.epa.gov/pesticides/cumulative/rra-op. The presentation at this meeting is relevant to the carbamates and it should be noted that this class has some strategic differences from the organo-phosphate (OP) assessments. The common endpoint  is based on an acute effect, ground water and drinking water exposure contributions for residential use both have to be considered more carefully than was necessary for the OP's.

EPA will use similar regions to those used for the OP's (which were based on USDA farm regions). They have examined the relative vulnerability of drinking water sources to runoff and to ground water using USGS approaches for leaching vulnerabilities (see presentation later).  They then zoom in further to pull together co-occurrence assessments of the likely significance of drinking water within the cumulative assessment.

They are using Doane's and NASS data for average application rates across several years and identifying use per acre. Looking at application date estimated via USDA crop profiles, Doane's data and other information that can best assess the likelihood of temporal co-occurrence. EPA will be running sensitivity analyses to understand impact of different application windows.

They will be looking at NAWQA and state water monitoring data in order to make comparisons to measured data. Ideally looking for monitoring data associated with regions for which the EPA have performed modeling estimates. Similar approaches will be used for groundwater (looking at FEMVTF and USGS evaluations). The approach for GW will be discussed at a Science Advisory Panel (SAP) meeting in mid February. Therefore, public documents will be released around mid January.  After SAP, a preliminary carbamate cumulative assessment will be released for error correction and this will be followed by the corrected version.  One more SAP may take place before August 2006.

Cumulative and Aggregate Risk Evaluation System (CARES) Model Update

Beth Julian of the International Life Sciences Institute (ILSI) provided a summary of the administrative issues associated with the transfer of CARES from Crop Life America (CLA) to the ILSI organization. CARES is now a publicly available model and training and education initiatives are under development. CARES is one of several models regarded by a recent Science Advisory Panel (SAP) meeting as tools for assign human exposure. Key data on the CARES model and its accessibility are available from
http://cares.ilsi.org/

Scott Jackson (BASF): Technical review of CARES with a focus on the drinking  water component.

Files will be made available via the EPA web site. (ACTION:  Beth Julien and Scott Jackson will make copies of their CARES presentations available). Scott showed detailed examples in the area of assessing dietary intake from water sources; templates he demonstrated are available from the ILSI site. Many questions were asked relating to the way the water exposure data are generated and used. ACTION:  Another presentation on details of the water aspects of the CARES model may be useful. Question should be sent to the list server. ILSI can provide additional assistance as needed.

Depth to Ground Water Maps Using Classification and Regression Tree (CART) Approach

Francois Smith provided a detailed presentation on the new technology developed by EarthSat.  The specific goal was to produce a DTW GIS layer within a few feet of accuracy for Nebraska at a 30 by 30 m resolution. Data they used was from Nebraska Department of Natural Resource Conservation and represents observation well measurements.. Twelve "dependent variable" data layers were used - lots of no-data raster points due non-continuous datasets only providing a relatively few "point" occurrences.  Among the 12 datasets used were: areas of thin or absent aquifer, thickness of the aquifer, watershed boundaries, stream discharge, elevation of aquifer, bedrock geology, DTW, ground water management boundaries, ground water regions, GeoCover land cover, STATSGO data layers and DEM (NED).

RuleQuest (CUBIST) software was used to establish rules that were applied to raster data in ERDAS IMAGINE; each rule outcome was based on independent variable datasets and compared with the dependent layer.  The "internal validation" with 361 sites gave a correlation of 0.82. Two "external" validations were conducted; the first attempt had a correlation of 0.83 and the average error in DTW was 19 ft.  The second attempt gave a correlation of 0.80 and average error in DTW of 21 ft.  EarthSat did not look at the error associated with greater than 50 foot DTW which is where pesticide interest lies. The contribution of the errors associated with the greater depths to water is not reported. As yet, EarthSat have not applied the data to other states using the same rules. They have a list of suggestions for how to improve the system and view the CART approach as a potentially efficient approach for inexpensive production of national GIS layers or relevance for exposure modeling. ACTION: Francois Smith (EarthSat) to send relevant paper to Jim Lin for circulation via listserver.

Groundwater model selection and evaluation of GW models (Dirk Young)

Ground water modeling is being driven by the upcoming carbamate cumulative assessment group. Selection is considering USGS report, looking at EU models, LEACH family of modelsX and the PRZM FEMVTF evaluation. From USGS assessment set of models, EFED selected RZWQM, LEACHM and PRZM. EPA views RZWQM as good because it deals with preferential flow, detailed agricultural management, many other bonuses, free model, good documentation, advanced hydrology.

Model factors important in the selection of a Tier 2 regulatory groundwater model: version control, long-term support, documentation, user friendliness, resource requirements for scenario development  (reflects ease, cost), and the processes captured in the model. A question was raised on the importance of the dispersion lengths in PRZM; all agreed that great care is needed in understanding the numerical working of any selected model.

There was also a capacity model versus Richards equation discussion; PRZM, being faster, may work better for Monte Carlo assessments.  In defining scenarios for ground water / drinking water, EFED are hoping to use GIS as a tool across the board for identifying potentially vulnerable areas.  Action Item: FEMVTF to provide ET&C references - See Environ Toxicol Chem 21:1535-1590 and in particular the leaching reference.

Detailed Review of Ground Water Models - Tom Nolan - USGS

NAWQA cycle 2 has topical teams which include an Agricultural Chemicals Sources group and a Transport and Fate (ACT) group, who are studing  five  areas with particular focus on ground water. Model qualities they evaluated included model capability, ease of use, adequate documentation, preferential flow, 2D flow and transport, degradation and transport as well as the ability to model agricultural mitigation practices. They used seven vadose zone models (CALF, GLEAMS, PRZM, ZWQM, LEACHP, HYDRUS-2D and VS2DT) and field data from four sites. They also used un-calibrated model runs for one location per dataset with best estimates of parameters and other approaches. Most models missed the peak at the surface. In the Merced bromide study in a sandy soil with natural vegetation the HYDRUS model gave two peaks. PRZM dispersal length was non-ideal; various approaches were used for VS2DT. At White river, breakthrough curves matched  RZWQM and HYDRUS for both the parent and for daughter products with reasonable prediction. All models under-predicted granddaughter product.

At the second Merced site RZWQM hugely over-predicted for compound "H". PRZM did well for compound O; sensitivity was found to be significant for Kd and half life. PRZM did well for compound "O" degradate while RZWQM over-predicted.

Pro's and con's of each model were also reported. In brief, HYDRUS is not very easy to use and has capability of simulating only one daughter product. LEACHP and CALF are easier. RZWQM has capability of simulating up to three pesticides, has macropore capability but crop evelopment database is  limited, greater input needs; simulations used to be limited to 3 meters but now has capacity of up to thirty meters. VS2DT has a good GUI and flexible boundary conditions, but can handle only a single compound. GLEAMS is limited to only 1.5 meters. PRZM covers complex scenarios; its input format is relatively complex USGS will choose RZWQM for macro-pore flow and ag management practices. HYDRUS is the back-up based on ability to cover porosity.

Assessing the vulnerability of ground water to contamination - recent approaches - Jack Barbash

A national vadose zone assessment on atrazine is being done by Sandy Ebert based community water supply wells. Ground water vulnerability is defined as the probability that a specific surface derived contaminant will be detected at or above a specific concentration in the subsurface at a specific location.

General approaches listed were: scoring and index methods, statistical methods (regression, cluster, PCA, neural networks, overlay methods, hydrogeological and chemical indicators methods and process based simulation modeling) . USGS is no longer in favour of  index based methods. A table was provided of vulnerability studies; all agreed that models should be tested against existing monitoring data. PRZM3 predictions were compared with NAWQA data for 1254 wells. The was limited agreement between PRZM predictions and observations; major concerns related to selection of compartment thickness. ACTION: More complete details will be presented at the January EMWG meeting.

Tom Nolan :  Logistic Regression Using NAWQA Data.

Found that nitrogen load correlated to nitrogen fertilizer applied, NLCD pasture, log population density, percent well drained soils, depth to seasonal high water table, present or absence of unconsolidated aquifers. The model validation approach suggested general agreement.

Reported on a South Eastern nitrate study; factors that involved nitrate reduction accounted for 23% of the variance, calcite dissolution impacted 18% and phosphate dissolution impacted 9%.

Also reported on a New Jersey study looking at spatial variability of recharge using sediment cores at 50 different wells near Glassboro; soil data was fed into a pedo-transfer function. Additional report covered studies on transport of anthropogenic and natural contaminants to supply wells.

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ONGOING ACTIONS

Old Items Carried Through

Industry will hold review of EXPRESS until EFED release the manual and report that key aspects of the final ORD revisions to the code are fixed. Preliminary review undertaken, full review will follow release of revised EXPRESS manual by EPA (ORD or OPP).

ORD and EFED to agree whether the volatilization feature should be turned on in PRZM/EXPRESS and EFED to make an internal decision on whether to use a constant soil temperature.  Decision to be communicated over list server or via reporting at the next EMWG.  Still under review reporting in January.

Russell Jones to mention EPA availability to attend Landscape and Mitigation 2 group (starts 2005) at upcoming EEASG meeting in Europe to formally obtain an invitation. Action:  Betsy Behl to talk further to Russell Jones.

New Items

All presenters to make copies of their presentations available for EPA to put on the website.

EPA to make sure the revised version of EXPRESS along with the new manual are made available (via OPP CEAM website or EFED website as appropriate) as soon as possible after they are completed so that Industry can conducts its formal review.

EPA to circulate information when the revised scenario files are available (and presumably the list of associated changes made to each scenario and relevant dates).

Another presentation on details relating to the water aspects of the CARES model may be useful. All to send questions of interest to the list server. ILSI can provide helpful participation as needed.

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