Transcript Overview of a National Aquatic Risk Assessment of

A tiered aquatic risk
assessment of pyrethroid
insecticides for agricultural and
residential use
Jeffrey Giddings Compliance Services International
Paul Hendley Phasera Ltd.
Scott Jackson BASF
Michael Dobbs Bayer CropScience
Al Barefoot DuPont Crop Protection
Gary Mitchell FMC
Kevin Henry Syngenta Crop Protection
Richard Allen Valent USA
On behalf of the Pyrethroid Working Group
The Pyrethroid Working Group (PWG) is a US task force whose members include eight primary pyrethroid
registrants (AMVAC Chemical Corporation, BASF Corporation, Bayer CropScience LP, Cheminova A/S, DuPont
Crop Protection, FMC Corporation, Syngenta Crop Protection, LLC, Valent U.S.A. Corporation).
11/13/2014
© Pyrethroid Working Group 2014
Slide 1
Conceptual model guides refinement of pyrethroid
risk assessment




Dissolved
Organic
Carbon
DOC
Water
Column
Biota
Py
r-
Er
os
io
n
f

Extremely hydrophobic, fate dominated by
sediment
processes
Potential for
Volatile loss
under still conditions
Dissipate quickly from water column, partition to
Pyrethroid – Spray Drift Entry
sediment
Emergent
Real World
Monolayers/
Plants
surface film
Receiving Waters
Only freely dissolved pyrethroid
is bioavailable
Chemical
Submerged
Rate of
World
Plants
Desorption/
and contributes
to toxicity
Exchange
Readily degraded by microorganisms
Adsorption
Rate of
Magnitude
Biofilms
Degradation
Koc
Plants and biofilms
play
a
role
in
dissipation
on
Plants
Rapidly metabolized by animals,Model
not Water
highly
Column
World
Pyrethroid
Sloping
Biofilms on
Resuspension
bioaccumulative,
food
webDeposition
transport Concentrations
not a
Sides/
Sediment
Variable
concern
Depths
Sediment
Pore Water
Py
r-R
un
of

Diffusion
/Mixing
Suspended
Sediment
Suspended
Sediment
Perfect
mixing
Epibenthic
Biota
Sediment
Burial
11/13/2014
Sed
Biota
Sed
OC
© Pyrethroid Working Group 2014
Pyrethroid
Concentrations
Sed
OC
Pyrethroid
Concentrations
Slide 2
Screening level RQs indicate potential pyrethroid
risk to some taxonomic groups for all uses…
Example: Screening-level RQs for deltamethrin
Plants
Mollusks
Scenario
Fish
Arthropods (Insects and Crustaceans)
Acute
Chronic
Acute
Chronic
Pore Water
CA Onion
<0.01
<0.01
0.08
0.15
69
4.0
1.5
IN Corn
<0.01
<0.01
0.08
0.13
74
5.5
2.2
CA Almond
<0.01
<0.01
0.09
0.20
84
6.3
3.0
FL Pepper
<0.01
<0.01
0.15
0.26
129
8.6
3.7
GA Pecan
<0.01
<0.01
0.27
0.44
239
13
6.7
IL Corn
<0.01
<0.01
0.28
0.44
244
13
7.5
OR Sweet Corn
<0.01
<0.01
0.28
0.50
244
18
7.5
MS Soybean
<0.01
<0.01
0.36
0.92
319
32
16
MS Cotton
<0.01
<0.01
0.96
1.1
844
35
16
TX Cotton
<0.01
<0.01
1.1
1.1
1006
39
16
Residential
<0.01
<0.01
1.3
1.4
1172
48
15
KEY
RQ < LOC
RQ < 2x LOC
RQ > 2x LOC
11/13/2014
Note: EPA does not distinguish mollusks from
other invertebrates. PWG considers mollusks
separately from arthropods (insects and
crustaceans).
© Pyrethroid Working Group 2014
Slide 3
…but screening-level exposure predictions greatly
exceed measured concentrations
Example: Cyfluthrin concentrations (bulk water column)
estimated by Tier II modeling, and concentrations in surface
waters (whole water samples) from extensive monitoring
database.
Modeling (ng/L)
Agriculturala
90th
%ile
22-444
95th
%ile
45-607
45-694
Max
Monitoring (ng/L)
Agricultural
(n=1504)
Residential
(n=534)
232
90th
%ile
<RLb
3.9
293
95th
%ile
<RL
11
298
99th
%ile
4.0
85
Residential
aRange
bLess
11/13/2014
of EECs for 18 crop scenarios
than reporting limit
© Pyrethroid Working Group 2014
Slide 4
Refining the exposure analysis (1)

Tier II+

Replace EXAMS with AGRO-2014, a validated, calibrated
model that simulates critical sediment processes





Suspended solids remove pyrethroid from water column
Deposition, resuspension, burial
Incorporate mitigations (no-spray buffers, vegetative
filter strips) specified on all pyrethroid labels
Other aspects of Tier II retained
Tier II+AR (Agronomic Realism)



11/13/2014
Simulate application timing and method (aerial, ground)
to match actual agronomic practice
Maximum rates, number of applications retained
Other aspects of Tier II/II+ retained
© Pyrethroid Working Group 2014
Slide 5
Refining the exposure analysis (2)

Landscape Refinement 1



Replace assumption of 100 percent cropped area (PCA)
with distributions of actual PCA in catchments where
each crop is grown (national or regional)
Other aspects of Tier II+AR retained
Landscape Refinement 2


Replace soil and weather parameters for standard EPA
crop scenarios with distributions of actual runoff/erosion
potential in catchments where each crop is grown
Other aspects of Landscape Refinement 1 retained
Probabilistic exposure analysis addresses spatial
variability in key model parameters, replaces
worst-case assumptions with actual distributions.
11/13/2014
© Pyrethroid Working Group 2014
Slide 6
Landscape probabilistic data significantly impact
EEC distributions
24-h water column EECs – deltamethrin use on cotton
Tier II+AR
LR1: PCA
distribution
LR2: PCA plus
runoff/erosion (R/E)
potential
LR2 + PTA
11/13/2014
© Pyrethroid Working Group 2014
Slide 7
Other factors that potentially influence exposure
were also considered and quantified if possible

Examples of factors considered











11/13/2014
Percent of crop area treated with any pyrethroid (PTA)
Variation in wind speed and direction on multiple
application dates
Interception of spray drift by vegetation
Sediment delivery ratio
Drainage area to pond volume
Receiving water dimensions and hydrology
Variability of degradation rates
Application rates and number of applications
Use of drift reduction technology
Tillage practices
etc.
© Pyrethroid Working Group 2014
Slide 8
Urban exposure refinements

Replaced PRZM with SWMM (Storm Water
Management Model)




Configured for high-density residential neighborhood in
California
Calibrated for pyrethroids measured in storm water
runoff
Replaced EXAMS with AGRO-2014
Incorporated results of surveys of residential
pest control professionals in California and 6
other regions of the US


11/13/2014
Pyrethroids applied, frequency of application, areas
treated (driveway, perimeter, lawn, etc.)
Retain assumption that applications are made at
maximum rate
© Pyrethroid Working Group 2014
Slide 9
Assumptions and uncertainties affecting exposure
estimates were analyzed



Directional influence of assumptions and
uncertainties were evaluated.
Magnitude of influence was quantified using
sensitivity analysis and professional judgment.
The cumulative effect of the assumptions and
uncertainties was found to be 1 to 2 orders of
magnitude in the direction of overestimation of
exposure and risk.
11/13/2014
© Pyrethroid Working Group 2014
Slide 10
Effects refinement: use data for all species, not
only the most sensitive
Fraction of
arthropod
species
potentially
affected
Species Sensitivity
Distributions for
arthropods are
similar across
pyrethroid class:
• shape of curve
• position of
species
11/13/2014
© Pyrethroid Working Group 2014
Slide 11
Combined pyrethroid SSD for arthropods takes
advantage of similarity of toxicity profiles
Toxicity data
were normalized
to Hyalella
equivalents and
SSD fitted to
combined data
for all
pyrethroids.
Taxon
Species
Crustaceans
47
Insects
58
Acarids
2
All
arthropods
11/13/2014
Daphnia magna
Americamysis bahia
HC5 = 5.3 Hyalella equivalents
107
© Pyrethroid Working Group 2014
12
Risk characterization: RQs indicate less risk at
successive tiers of the assessment
Example: Risk Quotients for deltamethrin for soybeans and
CA residential use
Plants
Mollusks
Tier
Fish
Arthropods (Insects and Crustaceans)
Acute
Chronic
Acute
Chronic
Pore Water
Tier II
<0.01
<0.01
0.35
0.50
319
18
7.5
Tier II+
<0.01
<0.01
0.08
0.13
13
7.6
1.2
Tier II+AR
<0.01
<0.01
0.07
0.14
10
5.5
1.3
LR1
<0.01
<0.01
0.02
<0.01
3.4
1.8
0.33
LR2
<0.01
<0.01
0.01
<0.01
3.1
1.7
0.13
LR2+PTA
<0.01
<0.01
<0.01
<0.01
0.12
0.049
<0.01
Tier II
<0.01
0.02
1.3
1.4
1170
48
15
SWMM-AGRO
<0.01
<0.01
0.01
0.03
1.7
0.99
0.17
Residential (CA)
KEY
RQ < LOC
RQ < 2x LOC
RQ > 2x LOC
11/13/2014
© Pyrethroid Working Group 2014
Slide 13
Key aspects of tiered risk assessment for
pyrethroids

The refinements in exposure and effects analysis made
full use of available data to replace conservative
assumptions.



Examples: PCA, SSDs
However, many conservative aspects of the screeninglevel assessment were retained throughout the higher
tiers, and the outcome was still protective.
The higher-tier assessment indicated that pyrethroid
exposure from residential and agricultural uses
according to current labels is unlikely to cause
ecologically significant effects in aquatic systems.

11/13/2014
This conclusion is supported by monitoring data, mesocosm
studies, and bioassessments.
© Pyrethroid Working Group 2014
Slide 14
THANK YOU!
[email protected]
11/13/2014
© Pyrethroid Working Group 2014
Slide 15