January 11, 2011 EMPM Agenda and Abstracts

PRESENTER Time TOPIC Duration

Shelby/Garber 9:00 am Welcome and Introduction 10 minutes

Russell Jones, ECPA 

Kinetics Group

9:10 am Estimating Confidence Intervals for Metabolite 

Degradation Rates

35 minutes

Cody Howard, USDA/ARS 9:45 am Determining the Fate and Transport of Pesticide 

Emissions in the Chesapeake Bay Region

35 minutes

10:20 am Break 10 minutes

Ed Odenkirchen, 

USEPA/EFED

10:30 am Developments in Terrestrial Exposure Modeling 45 minutes

Tom Purucker, NERL/EPA 11:15 am Dermal Contact, Movement, and Amphibian 

Pesticide Exposure

35 minutes

William Stiteler, PhD, 

ARCADIS US Inc.

11:50 am Habitat Classification for Ecological Risk 

Assessment Using Aerial Photography and GIS Data 

in a Two-stage Expert System

35 minutes

Shelby/Garber 12:25 pm Wrap-up, Next Meeting 5 minutes

Shelby/Garber 12:30 pm Adjournment
Estimating Confidence Intervals for Metabolite Degradation Rates

R. L. Jones, C. Beigel, B. Erzgraeber, Z. Gao, J. W. Green, B. Harvey, S. Hayes, N. Mackay, K. 

Paul, W. Schmitt, and D. Yon, ECPA Kinetics Group

Regulatory agencies around the world are switch to formation decline kinetics for estimating 

degradation rates of metabolites. Estimating confidence intervals of metabolite degradation rates 

obtained 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 Chain

Monte Carlo) provide more appropriate estimates of confidence intervals since these two 

techniques do not assume that the error variance is the same for parent and metabolites.

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, but relatively little research has been conducted to examine the environmental 

fate of pesticide inactive ingredients, sometimes termed formulants 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 pesticide products. A critical analysis of several available 

methods for estimating VOC emissions and ozone formation potential (OFP) of pesticide 

products was evaluated. The methods examined were 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, 

agriculturally-related emerging contaminants, 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 Pesticide 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.

Developments in Terrestrial Exposure Modeling

Ed Odenkirchen, USEPA/EFED

The Environmental Fate and Effects Division, Office of Pesticide Programs, United States 

Environmental Protection Agency (EFED) has been working to enhance it's 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 will discuss past assumptions, present problem formulation screening tools for 

prioritizing data collection and risk assessment efforts, and development efforts for first tier 

screening risk assessment tools.

Dermal Contact, Movement, and Amphibian Pesticide Exposure

Tom Purucker, National Exposure Research Lab, ORD Athens, GA

Tanja Crk, Ed Odenkirchen, USEPA, EFED

The more terrestrial an amphibian’s life cycle is, the more likely it is to use the skin to regulate 

its 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 molecules have separate pathways for dermal exposure, 

with neutral, lipophilic molecules traditionally getting 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. Therefore, although amphibian 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 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.

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 allow for use to several different habitat 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 particular 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 reference data from field visits showed an overall accuracy of 

approximately 80% for qualitatively different classes and 60% for the full classification scheme 

containing quantitative class divisions, such as those between closed, intermediate, and open 

canopy cover classes.