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Development and Application of a
Modeling Approach for Predicting
Pyrethroid Residues in Residential Water
Bodies for Use in Environmental Risk
Assessments
Michael Winchell, Stone Environmental
Lauren Padilla, Stone Environmental
Scott Jackson, BASF
On Behalf of the Pyrethroid Working Group
CLA-RISE Spring Conference
April 11th, 2014
4/11/2014
Slide 1
© 2014 by Pyrethroid Working Group. All rights reserved.
Background
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Use of pyrethroid insecticides in urban environments and
detections of these pyrethroids in some urban drainage
systems has led to the evaluation of urban exposure
potential as part of a national risk assessment.
Supported by existing monitoring datasets, simulation
modeling may be used to estimate pesticide concentrations
in urban drainage systems.
The use of modeling in a national risk assessment requires:
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A validated modeling approach
Regionally specific model inputs or a validated worst-case
scenario
Apr 2014 Slide 2
© 2013 by Pyrethroid Working Group. All rights reserved
Challenges
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Pesticide use in urban residential environments is complex!
Multiple potential use sites each with different
characteristics.
Apr 2014 Slide 3
© 2013 by Pyrethroid Working Group. All rights reserved
Objectives
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Develop a residential pyrethroid exposure scenario that:
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Calibrate and validate the model exposure scenario using a
robust monitoring dataset.
Develop regional model parameterizations representing:
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Captures the heterogeneity in use sites found in a residential
environment.
Accounts for the hydrologic processes in residential watersheds.
Allows the flexibility of modifying pyrethroid use assumptions to
regional variations in climate and use practices.
Regionally specific pyrethroid use patterns
Local climate conditions
Apply the residential exposure model scenario for use in a
pyrethroid environmental risk assessment to predict
regionally specific residential aquatic EECs.
Apr 2014 Slide 4
© 2014 by Pyrethroid Working Group. All rights reserved
Discussion Topics
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Residential pyrethroid use data
Model selection
Residential scenario development
Residential scenario calibration
Regional residential parameterizations
Model application for residential aquatic
exposure assessment
Apr 2014 Slide 5
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Pyrethroid Use Data:
Background on Pyrethroid Use Surveys
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The PWG has commissioned two residential use surveys in the
past 5 years:
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The primary survey objectives were:
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California survey (PWG, 2010)
US regional survey (Northwest, North Central, Northeast, Mid Atlantic,
South Central, Southeast) (Winchell and Cyr, 2013; Winchell 2013)
To understand any regional differentiation in pyrethroid use
characteristics for parameterization of residential exposure models
To understand relative significance of different pyrethroids to support
product specific assessments in these regions
Data collected by the surveys included:
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The
The
The
The
Apr 2014 Slide 6
fraction of households receiving treatments
types of sites/surfaces receiving treatments
relative significance of different pyrethroid products for each use site
seasonal frequency of applications on different types of surfaces
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Pyrethroid Use Data:
Specific Use Sites for Exposure Model
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Focus on quantifying
application practices for:
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Building foundation
perimeters
Patios and walkways (away
from garage door/wall)
Driveways (away from
garage door/wall)
Lawns/landscape areas
Apr 2014 Slide 7
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Pyrethroid Use Data: Use
Quantification for Exposure Model
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Fraction of neighborhood households receiving outdoor insecticide
treatments
Fraction of use sites treated with each active ingredient
Seasonal frequency of applications made to each use site
Percentage of a use site’s surface area that is treated
Apr 2014 Slide 8
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Pyrethroid Use Data:
Primary Findings
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Residential pyrethroid use is greater in California than in other
regions of the United States.
Outside of California, pyrethroid use is generally higher in the
southern regions than the northern regions.
Pyrethroid use is most prevalent for the building foundation
perimeter and lawn/landscape area use sites.
The variability in use prevalence (as selection of product)
among the different pyrethroid active ingredients is low, with
the exception of bifenthrin, which has estimated use of 2 to 10
times as frequent use as the other pyrethroids.
The surface area treated for patios/walkways, driveways away
from the building perimeter is low, most commonly <= 10%.
Apr 2014 Slide 9
© 2014 by Pyrethroid Working Group. All rights reserved
Model Selection:
SWMM and AGRO Models
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Storm Water Management Model (SWMM): US EPA
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Watershed scale, urban/residential water quantity and quality
model
Strength in handling of sub-hourly runoff and flow routing
Able to model multiple surface types (lawn, driveway, etc.)
AGRO: Canadian Center for Environmental Modeling (CEMC)
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Water Quality Model: Quantitative Water, Air, Sediment
Interaction (QWASI) Fugacity model (Mackay, 2001).
Accounts for chemical mass exchange between water column
(dissolved and sorbed compartments), benthic layer (dissolved
and sorbed compartments), and air.
Simulation of sediment dynamics, including handling of incoming
sediment; important for high Koc pyrethroids.
AGRO-2014 (Padilla and Winchell, 2013) includes improvement in
parameterization based on comparison with micro-cosm study
data.
Apr 2014 Slide 10
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Development:
Study Location
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Aliso Viejo, Orange
County, CA
Part of CA DPR / UC
Riverside monitoring
program
Drainage area: 67.2 acres
307 homes
Dwelling unit density: 4.6
units/acre.
Watershed boundary
delineated during multiyear monitoring study.
(Haver, 2012a)
Apr 2014 Slide 11
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Development:
Conceptual Model
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Aliso Viejo neighborhood was
spatially delineated.
Particular attention to
impervious use sites.
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Lower driveway
Upper driveway (within 5 ft)
Garage door
Impervious within 5-ft
foundation perimeter
Patios/walkways away from
building
Impervious areas near lawns
(1.5 ft) receive irrigation.
A fraction of impervious
surfaces (other than
driveway) flow into adjacent
lawns.
Apr 2014 Slide 12
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Development:
Conceptual Model, Continued
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Each landscape element in the
model can be sub-divided into
portions receiving pyrethroid
applications and portions not
receiving applications.
Further splitting can be made
to allow multiple application
frequencies (every 6 weeks,
and every 12 weeks).
The watershed is divided into
“sub-watersheds”:
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Allows for more accurate routing
Allows model to build in variability
in pyrethroid application timing
Apr 2014 Slide 13
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Development:
Pyrethroid Use Assumptions
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A best estimate of the extent and frequency of actual
pyrethroid use in California was required for the scenario.
Bifenthrin was chosen based on its relatively extensive use
and frequency of detections in monitoring data.
Key assumptions include:
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75.9% of households use outdoor insecticides (Winchell, 2013)
Some households are treated every 6 weeks, and some every 12 weeks
Fraction of use sites treated with bifenthrin (of households using
insecticides) at these intervals was estimated from survey data and
were set as follows:
Use Site
Foundation Perimeter
Estimated
Total Percent
Treated (%)
Estimated
Estimated Percent
Percent
Treated Every 12
Treated Every
Weeks (%)
6 Weeks (%)
25.7
13.1
12.6
Patios/Walkways
24.9
12.7
12.2
Driveways
24.1
10.6
13.5
Lawns
24.4
5.4
18.9
Apr 2014 Slide 14
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Calibration:
Calibration Approach
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The monitoring study led by Oki and Haver (2011) provided
the following datasets for calibration of the Aliso Viejo
scenario:
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Flow calibrated through adjustment of:
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Daily and hourly flow from the stormwater outfall (Haver, 2012b)
30 bifenthrin concentration analyses from both wet and dry periods
Estimated weekly and annual pyrethroid mass load
Irrigation practices
Hydrologic connectivity of impervious surfaces
Subsurface flow contributions
Routing parameterization
Bifenthrin mass and concentrations calibrated by adjusting:
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Irrigation practices
Hydrologic connectivity of impervious surfaces
Washoff parameters
Apr 2014 Slide 15
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Calibration:
Hydrology Calibration
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Mean daily flows and hourly flows are well simulated:
Flow Bias:
-2%
Daily NSE
(Nash Sutcliffe
Efficiency):
0.83 (Nash and
Sutcliffe, 1970)
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Hourly NSE:
0.57
Surface runoff
rarely occurs
from lawns.
Apr 2014 Slide 16
© 2014 by Pyrethroid Working Group. All rights reserved
Residential Scenario Calibration:
Bifenthrin Calibration, Cumulative Mass
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The simulated cumulative bifenthrin mass load over 1 year was
compared to the observed mass load.
Over the 1
year period,
the model
predicted 10%
more mass load
than observed.
Given high bias
in simulated
mass,
calibration is
conservative.
Apr 2014 Slide 17
© 2014 by Pyrethroid Working Group. All rights reserved
SWMM/AGRO-2014 Application:
California, Historical vs. Current Practices
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Current pyrethroid labels (as of ~2010) limit applications on
hard surfaces to crack and crevice applications.
Bifenthrin EEC distributions show a reduction in annual
maximum EECs of
~10x after
incorporating new
label restrictions
into the residential
scenario.
Results in this
comparison
assumed that the
bifenthrin use
extent was equal
to that of all
pyrethroids
combined.
Apr 2014 Slide 18
© 2014 by Pyrethroid Working Group. All rights reserved
SWMM/AGRO-2014 Application:
Regional Model Parameterization
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Regional parameterizations of weather and treatment
characteristics were developed for the Southeast (Orlando),
South Central (Houston), Northwest (Seattle), North Central
(Chicago), Northeast (Boston), and Mid-Atlantic (Philadelphia)
Weather:
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Irrigation:
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30-year time series of hourly precipitation
30-year time series of daily average temperature
Monthly average evaporation
Irrigation schedules for the California scenario were calibrated based on
observed flow data.
Irrigation schedules for other regions were modified to achieve a similar
amount of irrigation relative to plant evapotranspiration demands of the
regional climate.
Pyrethroid Applications: Derived from survey data
The parameterization of the California residential scenario was
modified to represent these regionally specific characteristics.
Apr 2014 Slide 19
© 2014 by Pyrethroid Working Group. All rights reserved
SWMM/AGRO-2014 Application:
Regional Pyrethroid Use Frequency
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The frequency of pyrethroid applications (number of times a
household use site is treated annually) varied by region and
use site.
Foundation
perimeters are
treated most
frequently.
The highest
number of
applications is
in California.
The lowest
number of
applications is
in the
Northeast.
Apr 2014 Slide 20
© 2014 by Pyrethroid Working Group. All rights reserved
SWMM/AGRO-2014 Application:
Comparison of Regional Parameterizations
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Annual maximum 24-hour EEC distributions were simulated
using SWMM/AGRO-2014 for 7 regional parameterizations and
7 pyrethroids.
The overall EEC
distribution for
California was
higher than the
other 6 regions.
The Northeast
and Mid-Atlantic
had the lowest
EECs.
All pyrethroids
showed similar
patterns across
regions.
Apr 2014 Slide 21
© 2014 by Pyrethroid Working Group. All rights reserved
Summary and Conclusions
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A SWMM/AGRO-2014 residential pyrethroid exposure modeling
scenario was developed, calibrated, and parameterized for 7
different geographic regions.
The scenario’s conceptual model, based on a high density
California neighborhood, accounts for pyrethroid application
practices for a diverse set of residential use sites.
In California, EECs based on historical pyrethroid labels (pre2010) were over 10x higher than EECs based on current labels.
As part of an environmental risk assessment, EECs in California
were found to be higher than in any of the other 7 regions.
The urban residential modeling approach developed can be
used for exposure assessments of other pesticide classes.
Apr 2014 Slide 22
© 2014 by Pyrethroid Working Group. All rights reserved
For Further Information on the Urban
Exposure Modeling Approach …
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“Development and Application of a Higher Tier Urban Modeling
Approach for Estimating Pyrethroid Concentrations in Static
Water Bodies Using SWMM and AGRO-2014”, Winchell, Padilla,
and Jackson (2014), PWG-ERA-11
Apr 2014 Slide 23
© 2014 by Pyrethroid Working Group. All rights reserved
References
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Haver, D. 2012a. Watershed Boundary for Aliso Viejo Subdivision. Personal
Communication, Darren Haver, South Coast Research & Extension Center.
Haver, D. 2012b. Hourly Flow Data for Aliso Viejo Subdivision. Personal
Communication, Darren Haver, South Coast Research & Extension Center.
Mackay, D. 2001. Multimedia Environmental Models: The Fugacity Approach - Second
Edition. Lewis Publishers, Boca Raton, pp.1-261.
Oki, L, and D. Haver. 2011. Evaluating Best Management Practices (BMPs)
Effectiveness to Reduce Volumes of Runoff and Improve the Quality of Runoff from
Urban Environments.
Nash, J. E. and Sutcliffe, J. V.. 1970. River flow forecasting through conceptual
models, Part I - A discussion of principles. J. Hydrol. 10: 282–290.
Padilla, L. E., & Winchell, M. F. 2013. Development And Testing Of An Improved Agro
Model (AGRO-2014) For Use In Predicting Aquatic And Benthic Pesticide
Concentrations In Ponds. PWG Report - PWG-ERA-03b. Stone Environmental Inc.
PWG (Pyrethroid Working Group). 2010. California 2009 Urban Pesticide Use Pattern
Study. US EPA MRID Number 48762913.
Winchell, M.F., M.J. Cyr. 2013. Residential Pyrethroid Use Characteristics in
Geographically Diverse Regions of the United States. PWG-ERA-02a.
Winchell, M.F. 2013. Pyrethroid Use Characteristics in Geographically Diverse Regions
of the United States: Parameterization of Estimated Pyrethroid Treatment Extent and
Frequency for Urban Exposure Modeling. PWG-ERA-02b. Stone Environmental Inc.
Apr 2014 Slide 24
© 2014 by Pyrethroid Working Group. All rights reserved