Minutes of the January 11, 2011 Exposure Modeling Public Meeting

Office of Pesticide Programs (OPP) 4 th Floor Conference Center

2777 South Crystal Drive

– Potomac Yard Two, North

Arlington, VA 22202

Attendees:

Name Amanda Solliday EPA Andrew Jacques RegNet

Andrew Newcombe ARCADIS Avery Fellow Daily Environment Report Bayazid Sarkar EPA

Catherine Aubee EPA Clifford Habig Exponent Cody Howard USDA/ARS Dana Spatz EPA

David Lieu EPA Greg Orrick EPA Jay Overmyer Syngenta

Jeff Evans EPA Jenny Tao EPA Jim Breithaupt EPA

Katherine Carr Monsanto

Katrina White EPA

Khin Oo EPA

Kristian Paul DuPont

Marrietta Echeverria EPA Mary Clock Rust EPA Melissa Panger EPA

Michael Barrett EPA Michael Xiao Huang DuPont Mike Leggett CLA

Mike Re x rode EPA

Mohammed Ruhman EPA Natalia Peranginangin Syngenta

Nathan Mottl EPANick Mastrota EPA

Patrick Havens Dow Paul Hendley Syngenta Pete Coody Bayer Cropscience Phillip Villanueva EPA Qingli Ma Exponent

R. David Jones EPA

Rick Reiss Exponent

Robert Miller EPA Rochelle Bohaty EPA

Rueben Baris EPA

Russell Jones ECPA Kinetics Group

Sarah Winfield EPA

Scott Jackson BASF

Steve Wente EPA

Stuart Cohen Environmental & Turf
Services Subijoy Dutta EPA

Tammara Estes Stone Environmental Inc Tanja Crk EPA Tiffany Mason EPA

William Stiteler ARCADIS US Inc.

Welcome and Introductions

The USEPA/OPP/EFED hosts biannual Exposure Modeling Public M eetin g s (EMPMs)

, which provide a forum for exchang ing information between OPP/ EFED and stakeholders with similar technical expertise o n current issues related to pesticide exposure modeling in support of risk assessment. The overarching theme of this EMPM was “ Spatial Context to Terrestrial Exposure Modeling

. ” Rochelle Bohaty, Tanja Crk, Kris Garber and Andrew Shelby chaired the meeting in the capacity of co

- chairs of the Terrestrial Exposure and the Water Quality Technical

Teams. Former Water Quality Technical Team co

- chair, Chuck Peck, also assisted in the coordination of the meeting.

The minutes and presentation slides for the January 11, 2011 EMPM are posted in the docket (EPA

- HQ

- OPP

- 20 09

- 0879 ), which can be accessed at http://www.regulations.gov/

. The docket ID # is reported on the EMPM w ebpage: http://www.epa.gov/oppefed1/models/water/empm_top.htm

Brief Updates :

None

Presentations :Presentation 1:

“Estimating Confidence Intervals for Metabolite Degradation Rates”

Russell Jones, ECPA Kinetics Group and Bayer CropScience

Regulatory agencies around the world are moving to wards using formation decline kinetics for estimating degradation rates of metabolites. Estimating confidence intervals of metabolite degradation rates using such kinetic analysis has become an important element of the registration process, especially in Europe. When confidence intervals are estimated using ordinary least squares regression techniques, the resulting confidence intervals are overly broad. Other standard techniques such as IRLS (Iteratively Reweighted Least Squares) and MCMC (Markov ChainMonte Carlo) provide more appropriate estimates of confidence intervals since these two techniques do not assume that the error variance is the sam e for parent and
metabolites.

Presentation notes:

Because c onfidence intervals , which are estimated using ordinary least squares (OLS) regression techniques

, may be overly broad

, there is a need to look at other methods for determining these intervals. In his presentation, Russell Jones d escribed his project for exploring other standard techniques for determining confidence intervals

, namely Iteratively Reweighted Least Squares (IRLS) and Markov Chain Monte Carlo (MCMC). Using empirical data, Jones com pared upper and lower confidence limits using OLS, IRLS

, and MCMC. Based
on the data from this comparison

, both IRLS and MCMC techniques are better than OLS because they account for the error variance between the parent and the metabolite or degradate. Both IRLS and MCMC, though, are comparable.

The examples presented were based on single, first

- order modeling; however, Jones
stated that other models can be used. He has performed similar analysis for 20

- 30 other individual studies (3

- 4 individual studies per chemical)

, and the results were similar (MCMC and IRLS provide similar results which are better than OLS). In response to questions related to the statistical analysis

, J ones referred attendees to the following articles

, which will be publi shed in
the near future :

Görlitz, Linus; Gao, Zhenglei; Schmitt, Walter. Statistical Analysis of Chemical Transformation Kinetics using Markov

- Chain Monte

- Carlo Methods. Submitted to Environmental Science & Technology and accepted for publication.

Ga o, Zhenglei; Green, John; Vanderborght, Jan; Schmitt, Walter. Improving Uncertainty Analysis in Kinetic Evaluations Using Iteratively Reweighted Least Squares. Submitted to Environmental Toxicology and Chemistry.

Jones RL, Beigel C, Erzgraeber B, Gao Z , Green JW, Harvey B, Hayes S, Mackay N, Paul KW, Schmitt W, Yon D Estimating Confidence Intervals for Metabolite Degradation Rates. A ccepted for presentation and inclusion in the proceedings at theXIV Symposium in Pesticide Chemistry, 30th August

- 1st September 2011, Piacenza,

Italy.

Presentation 2 :

“Determining the Fate and Transport of Pesticide Emissions in the Chesapeake Bay Region”

Cody Howard, USDA/ARS

Environmental scientists have primarily focused on the fate, transport, and toxicity of pesticide active ingredients, while relatively little research has been conducted on the environmental fate of pesticide inactive ingredients, sometimes termed formula nts or inerts. Many formulants are volatile organic compounds that may contribute to ground

- level ozone pollution. In California, a system of formulation testing using thermogravimetric analysis (TGA) is used to estimate VOC emission potential for pestic ide products. In this study, several available methods for estimating VOC emissions and ozone formation potential (OFP) of pesticide products w ere evaluated. The methods examined included TGA alone; TGA with
calculated OFP from confidential formulation information; TGA

- FTIR of evolved gases and calculation of OFP; and gas

- chromatography

- mass spectrometry and calculation of OFP.

Further research studies are focused on measuring the concentration of selected pesticides, agricultur al

- related emerging con taminants, and VOCs in surface agricultural soils collected from representative sites across the agriculture

- urban interface of the Chesapeake Bay. The collected data will be used to develop emissions inventories for selected gaseous compounds using the P esticide Emissions Model. Input files for initial model calibration will be populated with soil concentration, soil property, soil moisture, and meteorological data from a multi

- year study of pesticide fate carried out at the USDA.

Presentation notes:

Dr. Howard explained the motivation behind this work

, citing the Presidential Executive
Order 13508

, which mandates that the governments at the local, state, and federal levels restore Chesapeake Bay to an acceptable level . This project is currently being di rected by a mul ti

agency government task force. In addition, there is interest in quantif ying agricultural sources of
SVOC ozone

- precursors since acceptable ozone standards are proposed to be more restrictive in
the future.

Throughout the U

. S

. , urban and agricultural communities have become more spatially
intertwined

, resulting in blurred land use boundaries. Emissions from urban areas such as NOx, particulate matter, and VOCs can contribute to ground

- level ozone pollution, causing damage to crops. A gricultural operations also emit pollutants to the atmosphere

, including ammonia, odorous VOCs, and particulate matter which can create nuisance problems in residential communities. Agricultural emissions can also interact with urban pollutants that contr ibute to poor air quality. In addition to air pollutants, p esticides and other organic pollutants used in both urban and agricultural communities can have negative effects on ecosystems. In order to mitigate th e risk from these chemicals , the project t eam will seek to discern the chemical nature, fate, and transport of critical agricultural pollutants emitted to the atmosphere and consider the potential risks posed by reactivity and/or deposition of these chemicals to sensitive ecosystems.Dr. Howard is currently working to develop a pesticide emission inventory using l and use

data and sales data in tandem with the Pesticide Emission Model (PEM). The emissions inventory will be processed in the SMOKE (Sparse Matrix Operator Kernel Emission Model)

pre

- processor program in order to utilize the CMAQ (Community Multi

- scale Air Quality) model to ultimately determine the loading in the B ay from deposition processes associated with pesticide concentrations in the air. The PEM model for soil emissi ons will be calibrated with a
robust USDA 10

- year field volatility study on a trazine and m etolachlor. Additional field volatility studies will be needed for crop canopy and orchard type of applications in order to
calibrate PEM.

Presentation 3:

“ Developm ents in Terrestrial Exposure Modeling ”

Ed Odenkirchen, USEPA/ OPP/ EFED

The Environmental Fate and Effects Division, Office of Pesticide Programs, United States Environmental Protection Agency (EFED) has been working to enhance its methods for problem formulation and exposure assessment phases of the ecological risk assessment process for terrestrial wildlife to be more mindful of the potential for toxicologically significant exposures from a variety of pathways beyond the traditionally assessed dietary route. These enhanced methods are intended to provide transparent, reasonable, concise

, and consistent evaluations of the potential pesticide risks posed by the drinking water, inhalation, and dermal exposure routes. This presentation discuss es past ass umptions, present problem formulation screening tools for prioritizing data collection and risk assessment efforts, and development efforts for first tier screening risk assessment tools.

Presentation notes:

Historically, EPA ’s ecological risk assessments for pesticides have focused solely on dietary routes of exposure to birds and mammals. Although the LD 50 /ft 2 tool in the T

- REX model addresses potential exposure to non

- target organisms from all possible routes, this analysis d oes not distinguish which pathways (diet, drinking water, inhalation and/or dermal) are significant sources of chemical exposure. Current modeling efforts within the Office of Pesticide Programs are addressing this need to examine other potential exposure pathways. New risk assessment tools include the drinking water Screening Imbibition Program (SIP), the Screening Tool for Inhalation Risk (STIR) and a soon

- to

- be

- developed Dermal Uptake Screening Tool (DUST). The purpose of these tools is to utilize both c hemical fate and toxicity information to identify when a route of exposure can be considered negligible during the problem formulation stage of Registration Review. If an exposure pathway is determined to be a potential source of risk based
on the conserva tive estimates provided by these screening tools, then a clear rationale exists to request additional data to address these concerns. T

- REX, SIP

, and STIR can be found online at http://www.epa .gov/oppefed1/models/terrestrial/

Question and Answer Session :

Q: Is your ultimate goal to include these pathways in T

- REX?A: Yes

Q: For the dermal model, why do you assume that 100% of the pesticide is absorbed by the skin
of birds and mammals?

A: If the potential for risk is identified with this conservative assumption, then this highlights the need for additional information. If sufficient additional data is submitted, then the percentage of pesticide absorbed could be adjusted.

Q: Do you anticipa te a peer review, such as a Scien tific Advisory Panel (SAP) before employing
these tools?

A: No, a Scien tific Advisory Panel is not necessary as the underlying basis for these tools has previously been reviewed by former SAPs.

Q: Can STIR handle inhalation of granulars?

A: The tool can evaluate a chemical if the vapor pressure is known.

Presentation 4:

“ Dermal Contact, Movement, and Amphibian Pesticide Exposure ”

Tom Purucker, EPA

/ORD/NERL

The more terrestrial an amphibian’s life cycle is, the mo re likely its skin will be used to regulate water content in order to maintain hydration. Therefore, amphibian dermal contact from enhanced skin permeability can be a key exposure pathway compared to non

- amphibian receptors. Hydrophilic and lipophilic m olecules have separate pathways for dermal exposure, with neutral, lipophilic molecules traditionally receiving the most attention in humans and other mammals. However, preferential water uptake by the seat patch in amphibians increases the effective surface area for osmosis and may enhance the potential for low Kow dermal contaminant exposures. A lthough amphibia n epidermis has some capability to limit exposures to contaminants, positive linear relationships between Kow and contaminant flux across amphibian skin are significantly higher in amphibians versus mammals. In addition, sustained direct
contact with soil from daily movement patterns, overnight burrowing, and aestivation/hibernation periods further complicates chronic exposure estimation for amphibians.
We review ed recent data and methods concerning amphibian exposures to identify a set of algorithms and parameters for screening and higher

- tier model selection purposes that accounts for the increased dermal contact exposure potential and movement behavior.

Presentation notes:

The p urpose of this project is to re view recent literature on amphibian dermal exposure , d evelop a model to estimate dermal contact exposure in amphibians

, and c ompare the relative importance of dermal exposure across animal classes . Th is presentation explores factors related to dermal exposure in amphibians although knowledge is la cking on several key factors.Mammals have a strong hydrophobic barrier in the epidermis that limits absorption of all

but non

- ionic, lipophilic molecules. On the other hand, a mphibians lack this hydrophobic layer.

E stimates of dermal exposure doses in children vary greatly, by three orders of magnitude, depending on the methodology used. I n mammals

, decreasing relative dermal absorption is
correlated with increasing dermal loading. This correlation has important implications for extrapolating from la b studies (high loading) to field conditions (low loading). A mphibians
differ from mammals in the following ways: 1) they have l ower metabolic demand than
mammals ; 2) they have g reater surface area relative to body weight (due in part to the seat patch)
than mammals ; 3) they have t hin skin without a h ydrophobic barrier to chemicals

, resulting in greater absorption ; 4) they absorb water through the skin ; and 5) g as exchange is mainly through
the skin. Studies have shown that dermal exposure is an impor tant pathway for amphibians. The seat patch on the ventral side of amphibians ’ skin is an adaptation that is responsible for fluid
intake and osmotic release of chemicals

. With their high moisture levels , irrigation fields are especially attractive to amphibians and are sources of chemical exposure . Amphibians may also receive high exposure to pesticides in agricultural soils when they burrow into soil at night and

over the winter. When amphibians burrow over winter, they eat their shed skin, resulti ng in a dietary route of exposure in addition to dermal exposure

. The more terrestrial an amphibian is, the more likely it will be exposed to pesticides. Chemicals with high K ow ’s are likely to be more
of a concern than those with low K ow ’s

. The dermal exposure model includes coefficients for dermal penetrability (K p ), surface area (SA), skin thickness (H), time of exposure (T), bioavailability (BF), and body weight (BW). Walker et al . (2003) showed that there is a close linear relationship between K p and K ow in humans , while Quaranta et al . (2009) looked at this relationship in frogs and pigs. Both researchers found a similar relationship (i.e., similar slopes), but the log(K

p )was much greater for frogs than for pigs (i.e., the intercept was greater). Unfortunately the results from the human study (Walker et al., 2003) are not comparable to those from the pig and frog study (Quaranta et al., 2009) because of differences in experimental design. T he ratio of frog permeability to pig permeability varied greatly, ranging from about 25x
to about 300x. The dermal exposure model was used to estimate dermal and dietary doses for mammals, birds, reptiles, and amphibians and to compare the relative contribution of the exposure routes in different classes of an imals

. Metabolic rates are lower for cold

- blooded reptiles and amphibians than for warm

- blooded birds and mammals. The relationship between metabolic rate and body weight is more uncertain for reptiles and amphibians than for birds and
mammals

. F or all classes, doses were higher for chemicals with higher K ow values. The order of dermal dose by class is as follows : amphibians > reptiles > birds and mammals. K ow does not affect dietary dose for any class. The order of dietary dose by class is as follo ws : birds and mammals > reptiles and amphibians. The relative contribution of dermal exposure is much greater for amphibians than for other classes. For reptiles, the relative contribution is strongly depend e nt on the K ow , and is high for high

- K ow chemicals. The relative contribution of dermal exposure is small for birds and mammals. D ermal exposure to pesticides can be estimated by using : (1) exposure associated with moving animals

, which is based on K p , or (2) exposure
based on a “finite” sou rce in the vicinity of an aestivating animal. In conclusion, a mphibians and reptiles receive a significant dose of pesticides from dermal exposure, whereas birds and mammals receive very little. Th ese findings have important implication s for the surroga te use of birds to protect amphibians and reptiles from pesticides.Laboratory and field data sets for amphibians need to be examined to better define the

parameters used in dermal exposure models.

Question and Answer Session :

Q : In the plots of K p versus K ow , most of the data were for chemicals with relatively low log(Kow) values of 2 to 3. What would the plot show for chemicals which have much greater K ow values? Would the line level off?

A (Tom Purucker): My guess is that the linear relationsh ip probably would not hold for chemicals with high K ow values. The slope would probably change.

Q : Will you consider the behavior and ecology of amphibian species when you predict their dermal exposure? For example, some amphibians come out only at nigh t, and seek out areas where insect densities are higher.

A (Tom Purucker): You could account for such ecological factors to some degree. For example, you could adjust the time spent in field based on ecological characteristics.

A (Edward Odenkirchen): W ith all of these models, there needs to be a balance between being general and being realistic for specific species. To be effici ent , the EPA needs to keep the model fairly generic for species so that we can apply the results to protect a wide range of no ntarget species.

Presentation 5:

“Habitat Classification for Ecological Risk Assessment Using Aerial Photography and GIS Data

in a Two

- stage Expert System”

William Stiteler, PhD, ARCADIS US Inc.

There are many challenges in performing a land cover classification that can be used for habitat suitability analysis of multiple species in ecological risk assessments. The classification scheme must be detailed enough to accomodate several different h abitat requirements, as well as flexible enough to be applicable to different species. Because habitat suitability often has minimum area requirements, but does not require regular shapes of contiguous cover, high spatial resolution is useful, but imagery of high spatial resolution often lacks the spectral resolution useful for habitat classification. We present the results of a land cover classification designed to allow for the modeling of habitat suitability for a variety of receptors, such as shrews, robins, and deer. A hybrid remote sensing / GIS approach was developed that uses both aerial photography and ancillary GIS data. A two

- stage expert system is used to bring together different data sources. This expert system was designed to work with a p articular set of data sources, but it can be easily adapted to other sources. The result is a land cover classification with fourteen classes, a minimum mapping unit of 1/20 acre, and distinct polygons that can be as
narrow as four feet wide. Ground refe rence data from field visits showed an overall accuracy of approximately 80% for qualitatively different classes and 60% for the full classification schemecontaining quantitative class divisions, such as those between closed, intermediate, and open

canopy cover classes.

Presentation notes:

A method to classify habitat based on aerial photography conditioned on GIS coverages of soils data and tax parcel data was presented. Complications in developing accurate coverages using this method are effects of shadows, compression of digital photograp hs, and e ffects due to time of the year ( i.e.

, you can’t see through a forest canopy except in winter). In some cases, boundary data are defined differently in different jurisdictions

, and this situation require s special handling. In the prepared example, a dam along the boundary of two counties was described differently in the boundary data

, and consequently the software had trouble classifying the river and land around the dam. The analysis was conducted in two stages : first a draft set of polygons from the photos and GIS coverages was developed and secondly the resulting polygons into
habitat classes were aggregated . The resulting coverage had accuracy (~73%) similar to the

NLC D (National Land Cover Database)

.
Question and Answer Session:

Q: Were standard USDA boundaries used for the assessment as it can be difficult to combine local coverages such as that presented in the paper with broader regional or
national assessments ?

A: USDA boundaries were not used for the assessment.

Wrap up :

The next EMPM will be held on September 13, 2011. The meeting theme will be announced through the “empm listserve” forum on the LYRIS list serve at:

https://lists.epa.gov/read/?forum=empmlist