Richard Brain, JiSu Bang, Jeff Perine

Proposals for Refining Screening Level Risk 

Assessments for Endangered Species; an 

Herbicide Example

April 22, 2014
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• 1,853 co-occurrence counties 

between soybean growing counties 

and EPA/FWS species counties 

were identified.

• 52,948,707 soybean acres (~83% 

of total soybean acres in US) were 

reported in the 1,853 counties. 

Example of Potential Soybean Acreages – using currently 

planned step 1 approach by EPA / Services 
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Example Refinements

● Incorporation of more realistic exposure assumptions in 

models

● Collation of field crop identity, field dimensions, field 

coordinates, and locations of listed species and habitat for 

use in geospatial analyses

● Biological considerations including life-history 

characteristics, dietary and habitat requirements, foraging 

behavior, reproduction and migration timing, obligate 

relationships and other species-specific biological data

● Use of community-level effects endpoints such as species 

sensitivity distributions (SSDs) to estimate impacts on prey 

availability and habitat of listed species

● Incorporation of probabilistic techniques
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Estimation of Spray Drift Deposition Using REGDISP (v1.0)

● REGDISP adds 49 unique AAFC* datasets from 2000-2011

- 9 nozzles (air induction/chamber)

- 2 boom heights (60 cm, 90 cm)

- Wind speeds 5.9 – 20.0 mph

● Built on AGDISP v8.26 platform

- Mechanistic code unchanged

- Empirical equations for datasets processed by AGDISP calculators

- Linear regression (y = mx + b) based on log-transformed deposition curves

*Agriculture and Agri Food Canada
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REGDISP Datasets Used and Model Outputs (Distances in Feet)

(AAFC Datasets, Boom Height = 60 cm, Wind Speed ≤10 mph)

ASABE S-572.a

Spray Quality Year Nozzle DV50(μm)

Wind 

Speed 

(mph)

Lettuce EC251 Lettuce NOEC2

Coarse 

Spray

Medium 

Spray

Coarse 

Spray

Medium 

Spray

Coarse

2000 AI110025 580 7.95

9.88

10

39

39

203

2011 AIXR110-025 526 7.88

9.72

16

30

62

82

Medium

2000 XR8003 257 7.71 23 105

2011 XR80-03 217

5.91

6.18

6.39

16

26

36

82

108

121

2004 XR8003 217 9.57 66 276

STATISTICS

 Median 23 26 72 108

 Mean 24 33 97 138

 90th Percentile 36 54 167 214

1 Lettuce EC25 = 0.0005371 lb ai/A (lowest among 10 plant species)

2 Lettuce NOEC = 0.0000857 lb ai/A (lowest among 10 plant species)
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No LOC Exceedances for Aquatic Animals

0.00001 0.003 0.0002 <0.0001 <0.0001 0.00003 0.00001 0.0004
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No LOC Exceedances for Aquatic Plants

0.003 0.0002 0.00008 0.0006

0.61
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No LOC Exceedances for Terrestrial Animals

0.05 0.04

0.01

0.53

0.01

0.27

0.03
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Terrestrial Plants

TERRPlant NTP RQ Values for Ground Applications Incorporating PRZM Edge of Field Runoff Flux1

Ground Drift2 Dry Areas3 Semi-Aquatic3

Plant EC25 NOEC EC25 NOEC EC25 NOEC

Allium cepa (onion) 0.1 0.3 0.1 0.2 0.3 0.5

Zea mays (corn) 0.01 0.01 0.008 0.008 0.03 0.03

Avena sativa (oat) 0.01 0.01 0.04 0.1 0.1 0.4

Lolium perenne (ryegrass) 0.01 0.03 0.05 0.08 0.1 0.3

Glycine max (soybean) 0.3 0.9 0.008 0.008 0.03 0.03

Brassica rapa (turnip) 1.9 7.8 0.08 0.1 0.2 0.4

Lactuca sativa (lettuce) 3.7 23 0.8 2.2 2.6 7.0

Cucumis sativa (cucumber) 1.5 2.6 0.05 0.1 0.1 0.4

Lycopersicon esculentum (tomato) 2.3 2.6 0.1 0.2 0.4 0.5

Brassica oleracea (cabbage) 0.8 2.6 0.2 0.2 0.7 0.7

1EC25 and NOEC values were used to evaluate model indicators of potential indirect and direct effects, 

respectively; vegetative vigor endpoints were used for the drift scenario and seedling emergence endpoints were 

used for dry areas and semi-aquatic scenarios

2Vegetative vigor endpoints were sourced from MRID 46562904

3Seedling emergence endpoints were sourced from MRID 44505119 
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Probabilistic Drift Example

Histogram of RegDisp deposition estimates at a defined 

distance with MLE estimated lognormal distribution (x = lb 

a.i./A; output from PROC UNIVARIATE in SAS Version 9.3)
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Probabilistic Drift Example

SSD models fit to log transformed dry weight ER25s 

from the vegetative vigor study (e.g. OCSPP 850.4150) 
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Probabilistic Drift Example
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Geospatial Analysis (Species Data) 

● FESTF Aggregated Species Database 

- 2013 IMS Database 

• Aggregated county-level species location database from various 

sources 

- 2013 MJD Spatial Data

• Element Occurrence (EO) data (sub-county level location data)

US FWS 

NMFS

Nature Serve

US EPA
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Geospatial Analysis (Species Data) 

● Critical Habitat Data 

- U.S. FWS data were downloaded from the Critical Habitat (CH) Portal 

- For species for which the spatial data for their Critical Habitats are not available 

in the Portal, spatial data was digitized based on the Federal Register (FR) 
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Geospatial Analysis (Land cover data)

● Sub-county level analyses conducted using three land cover data 

development approaches 

1. NLCD 2006 class 82 (cultivated cropland)

2. 5-year (2008-2012) soybean composite constructed from the NASS CDL

- CDL Classes 5 (Soybeans), 239 (Dbl Crop Soybeans/Cotton), 240 (Dbl Crop 

Soybeans/Oats), and 254 (Dbl. Crop Barley/Soybeans) were included to 

develop soybean footprint data

3. Probabilistic land cover approach

- Refined land cover data developed by varying degrees of certainty or 

uncertainty of crop occurrence in a given location using multi-data 

layers weighted based on frequency, data quality and resolution 

(under the methodology development)
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Probabilistic Geospatial Analysis (Land cover)
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Geospatial Analysis 

● Consideration of registration area: Continental U.S. only

● Co-occurrence/proximity analyses 

1. County-level co-occurrence analysis performed with species county 

database and soybean growing counties from Ag Census 

2. Subcounty-level proximity analysis (where EO data is available)

 Historical EOs were not included in the analysis: observed in Pre-1980 or recorded as 

“Extirpated” or “Historical” (21 % of total number of EOs in MJD database are historic 

records)

 Distances between EO and soybean footprint data were used to identify known species 

locations (EOs) found within potential use areas including off-target use areas. 

3. County-level analysis (if a habitat location is reported in the database 

from EPA/FWS/NMFS/ NS MJD; but where spatial data for EOs are not 

available)

 Biological considerations (taxonomic comparison)
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Taxonomic Comparison 

(An Example of Biological Considerations) 

● Prairie Bush Clover (Lespedeza leptostachya)

- According to FESTF aggregated species 

database, this species has potential habitats and 

known occurrences found in the major soybean 

growing counties of IA, IL, WI and MN (~14% of 

total soybean acres in US).

- Prairie Bush Clover is a member of the pea family 

and the taxonomic comparison was considered. 
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Taxonomic Considerations?

● Case Study: Prairie bush-clover (Dicot taxonomic comparison)

Species Common 

Name Subclass Order Family Genus Species

Soybean Rosidae Fabales Fabaceae 

Pea family Glycine Willd. Glycine max (L.) Merr. 

Prairie Bush 

Clover Rosidae Fabales Fabaceae 

Pea family Lespedeza Michx. Lespedeza leptostachya 

Engelm. 

Garden lettuce Asteridae Asterales Asteraceae 

Aster family Lactuca L. Lactuca sativa L. 

TERRPlant NTP RQ Values for Ground Applications Incorporating PRZM Edge of Field Runoff Flux

Ground Drift Dry Areas Semi-Aquatic

Plant EC25 NOEC EC25 NOEC EC25 NOEC

Glycine max (soybean) 0.3 0.9 0.008 0.008 0.03 0.03

Lactuca sativa (lettuce) 3.7 23 0.8 2.2 2.6 7.0

● Among tested species, prairie bush-clover is most taxonomically related 

to soybean down to the Family level; lettuce is only related down to class

● Thus soybean is a more appropriate surrogate species than lettuce

● Given the NLAA conclusion for, and taxonomic relatedness to soybeans, 

prairie bush clover can be excluded
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● Preliminary sub-county analysis was conducted for the species county, 

where EO data (dicot, conifer, ferns, and lichens) were available.

 

● Preliminary results showed that 1,120 EOs of 70 species were 

identified with the potential to be within 225 ft distance of potential 

soybean growing areas using the soybean composite data based on 

5-year NASS CDLs. 

Preliminary Results from Geospatial Analysis 

(Subcounty-level proximity analysis where the EO data available) 

Distance (ft) 

NLCD 2006, Class 82 

(Number of Terrestrial 

Non-Monocot Plant Species)

2008-2012 CDL

(Number of Terrestrial 

Non-Monocot Plant Species)

0 144 63

<= 225* 165 70

* From the REGDISP modeling based on Lettuce NOEC described in Slide 5

Number of species overlapped with land cover data
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Preliminary Results from Geospatial Analysis 

(An example of Probabilistic Approach) 

Data Source:

Hypothetical EO shown 

for mapping purpose only 

due to data confidentiality

• Probabilistic analysis showed that > 20% of 1,120 EOs represented <0.1% 

probability of soybean occurrence within the EO area.
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Preliminary Results from Geospatial Analysis 

(County-level analysis for a county is reported as the species habitat; but EO 

data are not available)

● Spatial analyses showed that a total of 86 terrestrial non-monocot plant 

species co-occurred with soybean growing areas; EO data were 

available for 70 species, but 30 of the 70 species were double-counted 

from both EO and non-EO analyses.

● Considerations for refinements 

- Biological considerations (i.e. taxonomic 

 comparison). 

- Additional species data sources 

• State Natural Heritage Programs

- No EO data for the listed terrestrial plants in NJ 

- However, Natural Heritage Program data 

(http://www.nj.gov/dep/gis/stateshp.html) 

 could be considered for a refined analysis. 
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Example of Potential Soybean Acreages

For a species that was reported in EPA/FWS database; but no EO 

data was available

• 304 co-occurrence counties between 

soybean growing counties and 

EPA/FWS species counties were 

identified.

• 3,944,970 soybean acres (~6% of 

total soybean acres in US) were 

reported in the 304 counties. 
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Example of Potential Soybean Acreages - where best available 

science and data used – EO data available

• 1,120 current EOs were 

identified within 225 ft 

distance area of soybean 

growing areas.

• 46,081 soybean acres 

(~0.07% of total soybean 

acres in US) were identified 

within 225ft distance areas of 

EOs. 
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Questions?