### 1 OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION 

### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

May 15 , 2014

PC Code: 122804 MEMORANDUM DP Barcode: 41 2861

SUBJECT : Abamectin : Drinking Water Exposure Assessment for Proposed New Uses on Soybeans, Sweet Corn, Caneberries (Crop Group 13

- 07A) , and Golf Course Tee s , Greens, and Fairways

FROM : Greg ory Orrick, Environmental Scientist
ERB2 /EFED (7507P)

THROUGH: James Lin

, Environmental Engineer
Brian Anderson

, Branch Chief
ERB2 /EFED (7507P)

TO : Nancy Dodd, Risk Assessor Christine Olinger , Branch Chief
RAB 3 /HED (7509 P)

Sydney Jackson, Risk Manager Barbara Madden, Team Leader, RM Team 5
RIMUERB/RD (7505P)

Thomas Harris, Risk Manager Meredith Laws, Branch Chief IRB/RD (7507P)

This Environmental Fate and Effects Division (EFED) memorandum is a drinkin g water exposure assessment for proposed FIFRA §3 new uses of abamectin (list ed in Table 2 )

. This

assess ment provides screening

- level estimated drinking water concentrations (EDWC) of the residues of concern (ROC), which include abamectin and the structurally similar degradates

, NOA 448111, NOA 448112, NOA 426289, NOA 445495, NOA 457464, and NOA 457465. The
maximum screening

- level acute and chronic EDWC s ( 0.76 and 0.30 μg/L, respectively) are
based on the proposed use o f abamectin on soybeans at 0.037 lbs a.i./acre per year and the current use on beans at 0.056 lbs a.i./acre per year . The EDWCs are estim ated with SWCC

, which is a Tier I I surface water exposure model

.

### 2 Table 1 . Screening

- Level ROC EDWCs for Proposed Uses of Abamectin A



### Source (Tier: Model) Use Site (Max. Annual App. Rate) Acute EDWC (μg/L) Chronic EDWC (μg/L)

Surface water (Tier II: SWCC) Soybeans (0.0 3 7 lbs a.i./A) / Beans (0.056 lbs a.i./A) 0 .76 (soybeans) 0.30 (beans) Ground water (Tier I: PRZM

- GW) Golf courses (0. 27 lbs a.i./A) 0.074 N/A Ground water (Tier I: SCI

- GROW) Golf courses (0. 27 lbs a.i./A) ≤ 0.0031

A Maximum values in bold.



### A maximum screening exposure estimate in fish that may be consumed by humans was also calculated with KABAM and SWCC, at 588 mg/kg

- bw (ww).

The main uncertainties with abamectin r esidue of concern ( ROC ) exposure estimates are the toxicity and soil mobility of the degradates of concern and the use of screening exposure
models

. If the degradates of concern we re shown to be much less toxic than abamectin , then exposure estimates would be 29

- 65% lower

. If the degradates of concern were shown to be more mobile in soil than abamectin, then exposure estimates would be higher.

1. Use Characterization

Abamectin is registered for use on numerous fruit, vegetable , and other agricultural crops, including seed treatments, cattle ear

- tag uses, and numero us non

- agricultural uses

. The proposed FIFRA §3 new uses on soybeans, caneberries (Crop Group 13

- 07A) , sweet corn, and golf course tees, greens, and fairways are listed in Table 2 with the associated use patterns of maximum exposure.

Ta ble 2. Maximum Use Patterns for Proposed Uses of Abamectin

Use Max. Single App

. Rate (lbs a.i./A) Max. Annual App. Rate (lbs a.i./A) App.
Interval (d) App. Type Additional Application Directions

Soybeans, sweet corn 0.018 0.037 A 7 Aerial or ground (ground only in NY) Must be mixed with a spray adjuvant. Do not apply abamectin products

more than twice in sequence.

Caneberries (Crop Group 13

- 07A) 0.019 0.056 A 7 Do not apply abamectin products more than twice in sequence.

Golf course tees,

greens, and fairways 0.067 0.267 21 Ground Do not apply to golf course roughs, residential turf, sports fields, or
commercial turf.

A Proposed label directions provide a seasonal application rate limit that approximate s an annual limit

.


### Figure 1 depicts a national

- level summary o f the estimated agricultural usage of
abamectin in 2011 ( USGS, 2014 ). Less than 100,000 lbs a.i. were applied on agricultural crops in 2011. But usage was generally increasing over the years. Most usage was on cotton, orchards, a nd vineyards.

### 3 Figure 1. Agricultural Usage of Abamectin in 2011 (USGS, 2014)

### 4 2. Environmental Fate Characterization

Abamectin is a mixture of avermectins containing at least 80% avermectin B 1a 

### and up to 20% avermectin B 1b



### . This compound mixture is stable to hydrolysis, moderately photodegradable and biodegradable in aerobic conditions

, and persistent in anaerobic conditions. Abamectin is non

- volatile in dry (vapor pressure of 1.5 × 10

- 9 

### torr at 25°C ) and wet (K AW 

### of 7.0

× 10

- 9 

### ) field conditions

. The compound mixture is also hydrophobic, with a solubility limit in

water of 0.010 mg/L (at 21°C) and with octanol

- water partition coefficients (K OW 

### ) of 100,000

- 300,000. This flags abamectin as a potential bioaccumulat or

. However, the molecular weights of the avermectins (859

- 873 g/mol) and hydroxyl structural groups likely limit bioaccumulation

, which is confirmed by a whole fish b ioconcentration factor of 69x

.

Sorption coefficients i n soil indicate that abamectin displa ys a wide range of low mobility (K F 

### range of 56 to 313 L/kg), with strong correlation between absorption to soils and their organic carbon content (FAO soil mobility classification of slightly mobile ; FAO, 2014 )

. T he high sorption coefficients indicate th at the compound mixture is not likely to be a ground water

concern. However, leaching of abamectin to the 3

- inch to 12

- inch depth was observed within days of application in three field dissipation studies , indicating that abamectin residues may have
incre ased mobility in some soils (MRIDs 49071013,

- 14,

- 15 ).

Important means of transport off of agricultural fields following application will include spray drift

, runoff of residu es (mostly sorbed to suspended solids), and, in some cases, leaching

. Abamectin dissipated i n the field following four applications with half

- lives of 2

- 12 days on bare
soil and 14

- 81 days on turf. Table 3 summarizes the chemical properties and environmental fate parameters of abamectin . Many of the environmental fate stud ies (which were conducted on
avermectin B 1a 

### ) were not available for previous drinking water exposure assessments.

Table 3. Chemical Properties and Environmental Fate Parameters of Abamectin

Parameter Value Reference Physical/Chemical Parameters

Molecular mass avermectin B 1a 

### : 873.1 g/mol avermectin B 1b 

### : 859.1 g/mol Calculated

Vapor pressure (25°C) 1.5 x 10

- 9 

### torr MRID 47436204 Henry’s Law constant (25°C) 1.7 x 10

- 7 

### atm·m 3 

### /mol Calculated Water solubility (21°C) 0.010 mg/L MRID 47436204

Octanol

- water partition coefficient (K OW 

### ); (log K OW 

### ) (25°C) avermectin B 1a 

### : 300,000; (5.5)
avermectin B 1b 

### : 100,000; (5.0) MRID 46877502

Dissociation constant (pKa) 7.22 MRID 46877502

Persistence in Water Hydrolysis half

- life (pH 5, 7, and 9) Relatively stable MRID 131083 Aqueous photolysis half

- li fe (25°C) 2.5 d MRID 49071005 Aerobic aquatic metabolism half

- life (20°C) 87 d (SFO 1 

### ) 91 d (SFO 1 

### ) MRID 49071004

Anaerobic aquatic metabolism half

- life (20°C) 233 d (SFO 1 

### ) 314 d (SFO 1 

### ) MRID 49071004

### 5 Parameter Value Reference

Persistence in Soil Soil photolysis half

- li fe (25°C) 24 d (SFO 1 

### ) MRID 49071001

Aerobic soil metabolism half

- life (20°C) 27 d (IORE 1 

### ) (Gartenacker silt loam) MRID 49071006
26 d (IORE 1 

### ) (Gartenacker loam) MRID 49071007
23 d (SFO 1 

### ) (Pappelacker loamy sand) MRID 49178901
16 d (IORE 1 

### ) (18 acres sandy clay loam)
49 d (SFO 1 

### ) (Marsillargues silty clay loam)

Anaerobic soil metabolism half

- life (20°C) 1,660 d (DFOP 1 

### ) (Gartenacker loam) MRID 49071007

Mobility Freundlich organic carbon normalized

s oil

- water partitioning coefficient (K FOC 

### ) 4500, 4590, 5710, 6260, 6380 L/kg OC 

### M RID 49071002

Field Dissipation Field dissipation half

- life 2 

### (leaching depth of concentrations >0.5 μg/kg and sampling interval) Celery plot: CA: 31±6 d (12

- 18” depth at day 28) MRID 41191501/
42627601

Bare soil plot: NY: 8.1

- 25 d (3

- 6” depth at day 0)
GA: 2.5

- 15 d (3

- 6” depth at day 0)
CA: 1.8

- 3.3 d (12+” depth at day 2) MRID 49071013; 49071014; 49071015 Turf plot: NY: 8.3

- 81 d (6

- 12” depth at day 13) GA: 4.9

- 26 d (3

- 6” depth at day 0)
CA: 3.1

- 23 d (6

- 12” depth at day 2) Fish bioconcentration factors (depuration rate) 69x (whole); 110 (inedible); 30 (edible) (95% depuration in 2 wks) MRID 159163

1 Kinetics models used to calculate half

- lives include Single First

- Order (SFO), Double First

- Order in Parallel (DFOP), and Indeterminate Order Rate Equation (IORE) in accordance with NAFTA guidance (USEPA, 2012).

2 Field dissipation half

- life ranges includ e values following each of four applications to the field. Half

- lives following the fourth application were 2

- 12 days on bare soil and 14

- 81 days on turf.



### Table 4 lists the transformation products of abamectin and the amounts formed in the
submitted envi ronmental fate studies. All of the chemical structures share the sec

- butyl side
chain because all of studies were conducted with avermectin B 1a 

### . The degradates are expected to
maintain the B 1a 

### :B 1b 

### structural ratio of the parent compound mixture. Abamectin is hydroxylated or carbonylated under the tested aerobic and anaerobic, terrestrial and aquatic conditions to form up to six major organic degradates. Further transformation products are numerous, polar, and minor in concentration, eventually resulting i n carbon dioxide formation or strongly sorbing to soil or sediment.

There is uncertainty in the availability of the unextracted residues because nonpolar extraction solvents were not used in the submitted studies. However, the unextracted residue formation patterns indicate that they do not contain the parent compound mixture (MRID 49071001) . And they do not extract well with a range of p olar solvents (MRID 49178901)

. Therefore, they are assumed to either be strongly sorbed or a weakly sorbed nonpolar product(s). Due to the nearly adequate extraction procedure in MRID 49178901, the unextracted residues are assumed, amid some remaining un certainty, to be well enough sorbed to the solid matrix to not be of exposure concern

.

### 6 Table 4

. Abamectin (Avermectins B 1a 

### and B 1b 

### ) and Its Environmental Transformation Products. A



### Code Name/ Synonym Chemical Name Chemical Structure

PARENT

Avermectin B 1a 

### NOA 422601

CGA 140327

MK 936 IUPAC: (10 E ,14 E ,16 E )

- (1 R ,4 S ,5′ S ,6 S ,6′ R ,8 R ,12 S ,13 S ,20 R ,21 R ,24 S )

- 6′

- [( S )

- sec

- butyl]

- 21,24

- dihydroxy

- 5′,11,13,22

- tetramethyl

- 2

- oxo

- (3,7,19

- trioxatetracyclo[15.6.1.1 4,8 .0 20,24 ]pentacosa

10,14,16,22

- tetraene)

- 6

- spiro

- 2′

- (5′,6′

- dih ydro

- 2′ H

- pyran)

- 12

- yl 2,6

- dideoxy

- 4

- O

- (2,6

- dideoxy

- 3

- O

methyl

- α

- L

- arabino

- hexopyranosyl)

- 3

- O

- methyl

- α

- L

- arabino

- hexopyranoside

CAS: 5

- O

- demethyl

- a vermectin A 1a

CAS No.: 65195

- 55

- 3

Formula: C 48 H 72 O 14 MW: 873. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C@@]2(O1)C[C@@H]3C[C@H](O2)C/C=C(/[C@H]([C@ H](/C=C/C=C/4 \ CO[C@H]5[C@@]4([C@@H](C=C([C@H]5O)C)C(=O)O3)O)C)O[C@H]6C[C@ @H]([C@H]([C@@H](O6)C)O[C@H]7C[C@@H]([C@H]([C@@H](O7)C)O)OC)OC) \ C)C 

### Avermectin B 1 b 

### NOA 421704 IUPAC: (10 E ,14 E ,16 E )

- (1 R ,4 S ,5′ S ,6 S ,6′ R ,8 R ,12 S ,13 S ,20 R ,21 R ,24 S )

- 21,24

- dihydroxy

- 6′

- isopropyl

- 5′,11,13,22

- tetramethyl

- 2

- oxo

- (3,7,19

- trioxatetracyclo[15.6.1.1 4,8 .0 20,24 ]pentacosa

10,14,16,22

- tetraene)

- 6

- spiro

- 2′

- (5′,6′

- dihydro

- 2′ H

- pyran)

- 12

- yl 2,6

- dideoxy

- 4

- O

- (2,6

- dideoxy

- 3

- O

methyl

- α

- L

- arabino

- hexopyranosyl)

- 3

- O

- methyl

- α

- L

- arabino

- hexopyranoside

CAS: 5

- O

- demethyl

- 25

- de(1

- methylpropyl)

- 25

- (1

- methylethyl)

- a verm ectin A 1a

CAS No.: 65195

- 56

- 4

Formula: C 47 H 70 O 14 MW: 859.1 g/mol SMILES: C[C@@H] \ 1[C@@H](/C(=C/C[C@H]2O[C@]3(O[C@@H]([C@H](C=C3)C)[C@@H](C)C)C[C @H](C2)OC(=O)[C@H]4[C@@]5(/C(=C/C=C1)/CO[C@@H]5[C@@H](C(=C4)C)O)O)/C)O[C@ @H]6O[C@H]([C@@H]([C@H](C6)OC)O[C@@H]7O[C@H]([C@@H]([C@H](C7)OC)O)C)C O O HO

O

O O

O

O O O

O

OH O

OH O O HO

O

O O

O

O O O

O

OH O

OH

### 7 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length) MAJOR (>10%) TRANSFORMATION PRODUCTS
NOA 448111 Oxo 8a

- oxo avermectin
B 1a CAS: 5

- O

- demethyl

- 8a

- oxo

- Avermectin
A 1a

Formula: C 48 H 70 O 15 MW: 8 87

. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ C(= O)O[C@H]5[C@@]4([C@@H](C=C([ C@H]5O)C)C(=O)O3)O)C)O[C@H]6C[ C@@H]([C@H]([C@@H](O6)C)O[C@ H]7C[C@@H]([C@H]([C@@H](O7)C) O)OC)OC) \ C)C H

C H 3 O

H

C H 3

C H 3

H

O

O O H

H H

O H H O O H C H 3 H

C H 3
C
H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O H O C H 3 835.2240 49071005 pH 7 6.1% ( 18 d ) 3.0 % ( 37.5 d)

835.2410 49071001 Loam 6.2% ( 21 d ) 5.2% ( 28 d)

835.4100 49178901 Loamy sand 9.4% ( 28 d ) 1.6 % ( 196 d) Sandy clay
loam 3.8 % ( 14 d ) 1.0 % ( 196 d)

Silty clay loam 6.2 % ( 126 d ) 3.9 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 16.3 % ( 28 d ) 4.7 % ( 120 d)

Silt loam

(20 ° C) 10.6 % ( 14 d ) 8.1 % ( 120 d)

Silt loam

(10 ° C) 11.5 % ( 9 0 d ) 11.3% ( 120 d)

Silt loam

(30 ° C, 25%WHC) 9.3% ( 56

- 90 d ) 7.7 % ( 120 d)

49071007 Loam 12.4 % ( 28 d ) 1.0 % ( 365 d)

835.4200 Loam 12.6 % ( 14 d ) 5.3% ( 120 d)

835.4300 49071003 River water:
loam 7.9% (100 d) 7.9% (100 d)

Stream water: sand 6.8% (30 d) 4.8% (100 d)

49071004 River water: sandy loam 2.2% (100 d) 2.2% (100 d)

Pond water: silty clay loam 2.9% (100 d) 2.9% (100 d)

### 8 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length)
NOA 448112 8

- OH 8a

- Hydroxy

avermectin
B 1a CAS : 5

- O

- demethyl

- 8a

- hydroxy

Avermectin A 1a

Formula: C 48 H 72 O 15 MW: 8 89

. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ C(O[ C@H]5[C@@]4([C@@H](C=C([C@H] 5O)C)C(=O)O3)O)O)C)O[C@H]6C[C@ @H]([C@H]([C@@H](O6)C)O[C@H]7 C[C@@H]([C@H]([C@@H](O7)C)O) OC)OC) \ C)C H

C H 3 O

H

C H 3

C H 3

H

O H

O O H

H H

O H H O O H C H 3 H

C H 3
C H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O H O C H 3 835.2410 49071001 Loam 4.4% (21 d) 3.7 % ( 28 d)

835.4100 49178901 Loamy sand 13.5% ( 28 d ) 1.2 % ( 196 d) Sandy clay
loam 1.2 % ( 57 d ) 0.5 % ( 196 d)

Silty clay loam 8.8 % ( 91 d ) 4.1 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 13.0 % ( 28 d ) 4.4 % ( 120 d)

Silt loam

(20 ° C) 14.5 % ( 28 d ) 6.3 % ( 120 d)

Silt loam

(10 ° C) 15.5 % ( 90 d ) 1 3 .7% ( 120 d)

Silt loam

(30 ° C, 25%WHC) 13.3 % ( 28 d ) 7.7 % ( 120 d)

49071007 Loam 16.1 % ( 28 d ) 0.9 % ( 365 d)

835.4200 Loam 15.9 % ( 0 d ) 8.0 % ( 120 d)

835.4300 49071003 River water:
loam 6.0% (100 d) 6.0% (100 d)

Stream water: sand 19.3% (30 d) 13.8% (100 d)

49071004 River water: sandy loam 2.1% (35

- 70 d) 1.7% (100 d)

Pond water: silty clay loam 1.8% (35 d) 1.5% (100 d)

835.4400 49071004 River water: sandy loam 0.7% (70 d) 0.3% (100 d)

Pond water: silty clay loam 0.7% (70 d) 0.5% (100 d)

### 9 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length)
NOA 426289
4”

- Oxo

avermectin
B 1a Formula: C 48 H 70 O 14 MW: 871.1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ CO[ C@H]5[C@@]4([C@@H](C=C([C@H] 5O)C)C(=O)O3)O)C)O[C@H]6C[C@@ H]([C@H]([C@@H](O6)C)O[C@H]7C[ C@@H](C(=O)[C@@H](O7)C)OC)OC ) \ C)C O H

C H 3 O

H

C H 3

C H 3

H

O O H

H H

O H H O O H C H 3 H

C H 3
C H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O C H 3

835.4300 49071004 River water: sandy loam 8.2% (100 d) 8.2% (100 d)

Pond water: silty clay loam 10.1% (100 d) 10.1% (100 d)

835.4400 49071004 River water: sandy loam 0.7% (100 d) 0.7% (100 d)

Pond water: silty clay loam 0.9% (70 d) 0.7% (100 d)



### NOA 445495 3”

- Demethyl

avermectin
B 1a Formula: C 47 H 70 O 14 MW: 859.1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ CO[ C@H]5[C@@]4([C@@H](C=C([C@H] 5O)C)C(=O)O3)O)C)O[C@H]6C[C@@ H]([C@H]([C@@H](O6)C)O[C@H]7C[ C@@H]([C@H ]([C@@H](O7)C)O)O) OC) \ C)C H

C H 3 O

H

C H 3

C H 3

H

O O H

H H

O H H O O H C H 3 H

C H 3
C H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O H O

H 835.4300
Aerobic aquatic
metabolism 49071004 River water: sandy loam 2.8% (100 d) 2.8% (100 d)

Pond water: silty clay loam 1.9% (70 d) 1.5% (100 d)

835.4400
Anaerobic

aquatic
metabolism 49071004 River water: sandy loam 12.8% (100 d) 12.8% (100 d)

Pond water: silty clay loam 8.3% (100 d) 8.3% (100 d)

### 10 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length)
NOA 457464 Formula: C 48 H 73 O 16 MW: 906

. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ C(O[ C@H]5[C@@]4([C@@H](=CC(C5O)( C)O)C(=O)O3)O)O)C)O[C@H]6C[C@ @H]([C@H]([C@@H](O6)C)O[C@H]7 C[C@@H]([C@H]([C@@H](O7)C)O) OC)OC) \ C)C

C H 3 H

C H 3 O

H

O H

C H 3

H

O H

O O H

H O H

H H O O H C H 3 H

C H 3
C H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O H O C H 3

835.4100 4917890 1 Loamy sand 8.1 % ( 126 d ) 6.6 % ( 196 d)
Sandy clay
loam 0.9 % ( 126 d ) <LOD ( 196 d)

Silty clay loam 5.5 % ( 161 d ) 3.3 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 6.3% ( 56 d ) 3.2 % ( 120 d)

Silt loam

(20 ° C) 10.1 % ( 90 d ) 9.4 % ( 120 d)

Silt loam

(10 ° C) 7.2% ( 120 d ) 7.2 % ( 120 d)

Silt loam

(30 ° C, 25%WHC) 9 .2% ( 120 d ) 9.2 % ( 120 d)

49071007 Loam 10.0 % ( 56 d ) 3.9 % ( 365 d)

835.4200 Loam 5.2% ( 0 d ) 3.5 % ( 120 d) 

### NOA 457465 Formula: C 48 H 71 O 16 MW: 904

. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ C(= O)O[C@H]5[C@@]4([C@@H](=CC(C 5O)(C)O)C(=O)O3)O)C)O[C@H]6C[C @@H]([C@H]([C@@H](O6)C)O[C@ H]7C[C@@H]([C@H]([C@@H](O7)C) O)OC)OC) \ C)C H

C H 3 O

H

C H 3

O H C H 3

H

O

O O H

H O H

H H O O H C H 3 H

C H 3
C H 2

H

C H 3 H O O H C H 3

H

O O C H 3 O

O

C H 3 O H O C H 3

835.4100 49178901 Loamy sand 10.8% ( 126 d ) 9.9% ( 196 d) Sandy clay
loam 4.4 % ( 7 d ) 0.2 % ( 196 d)

Silty clay loam 5.2 % ( 161 d ) 2.8 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 6.3 % ( 56 d ) 3.2 % ( 120 d)

Silt loam

(20 ° C) 9.3 % ( 90 d ) 7.9 % ( 120 d)

Silt loam

(10 ° C) 4.4 % ( 120 d ) 4.4 % ( 120 d)

Silt loam

(30 ° C, 25%WHC) 9.2 % ( 120 d ) 9.2 % ( 120 d)

49071007 Loam 9.0% ( 168 d ) 7.0 % ( 365 d)

835.4200 Loam 3.3% ( 91 d ) 2.8 % ( 120 d)

### 11 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length)
Carbon dioxide IUPAC: Carbon dioxide

Formula: CO 2 MW: 44 g/mol SMILES: C(=O)=O

C O O 835.2240 49071005 pH 7 3.0% (37.5 d) 3.0% (37.5 d)

835.2410 49071001 Loam 7.6% (28 d) 7.6% (28 d)

835.4100 49178901 Loamy sand 18.8% ( 196 d) 18.8% (196 d) Sandy clay
loam 12.9 % ( 161 d ) 12.5 % ( 196 d)

Silty clay loam 13.5 % ( 196 d ) 1 3.5 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 17.1% ( 120 d ) 17.1% ( 120 d)

Silt loam

(20 ° C) 8.1% ( 120 d ) 8.1% ( 120 d)

Silt loam

(10 ° C) 1.4% ( 90

- 120 d ) 1.4% ( 120 d)

Silt loam

(30 ° C, 25%WHC) 8. 2 % ( 120 d ) 8. 2 % ( 120 d)

49071007 Loam 27.7 % ( 365 d ) 27.7% ( 365 d)

835.4200 Loam 3.1% ( 120 d ) 3.1 % ( 120 d)

835.4300 49071003 River water:
loam 3.03% (100 d) 3.03% (100 d)

Stream water: sand 10.8% (100 d) 10.8% (100 d)

49071004 River water: sandy loam 4.1% (100 d) 4.1% (100 d)

Pond water: silty clay loam 3.6% (100 d) 3.6% (100 d)

835.4400 49071004 River water: sandy loam 0.2% (100 d) 0.2% (100 d)

Pond water: silty clay loam 0.1% (100 d) 0.1% (100 d)

### 12 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length)

Unextractable residues

NA NA 835.2410 49071001 Loam 26.2% (28 d) 26.2% (28 d)

835.4100 49178901 Loamy sand 33.4 % ( 196 d ) 33.4 % ( 196 d) Sandy clay
loam 44.3 % ( 196 d ) 44.3 % ( 196 d)

Silty clay loam 30.7 % ( 196 d ) 30.7 % ( 196 d)

49071006 Silt loam (30 ° C, 40%WHC) 35.8 % ( 120 d ) 35.8 % ( 120 d)

Silt loam

(20 ° C) 27.2 % ( 120 d ) 27.2 % ( 120 d)

Silt loam

(10 ° C) 14.4 % ( 120 d ) 14.4 % ( 120 d)

Silt loam

(30 ° C, 25%WHC) 27.0 % ( 120 d ) 27.0 % ( 120 d)

49071007 Loam 34.5 % ( 365 d ) 34.5 % ( 365 d)

835.4200 Loam 31.4 % ( 120 d ) 31.4% ( 120 d)

835.4300 49071003 River water:
loam 17.3% (100 d) 17.3% (100 d)

Stream water: sand 18.4% (100 d) 18.4% (100 d)

49071004 River water: sandy loam 21.8% (100 d) 21.8% (100 d)

Pond water: silty clay loam 24.7% (100 d) 24.7% (100 d)

### 13 Code Name/ Synonym Chemical Name Chemical Structure Study Guideline MRID System Maximum %AR (day) Final %AR (study length) MINOR (< 10%) TRANSFORMATION PRODUCTS 8,9

- Z

Avermectin
B 1a 

### NOA 427011 CAS: 5

- O

- demethyl

- , (8Z)

- (9Cl)

-

a vermectin A1a

Formula: C 48 H 72 O 14 MW: 8 73

. 1 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H ]3C[C@H](O2)C/ C=C(/[C@H]([C@H]( \ C=C/C=C/4 \ CO[ C@H]5[C@@]4([C@@H](C=C([C@H] 5O)C)C(=O)O3)O)C)O[C@H]6C[C@@ H]([C@H]([C@@H](O6)C)O[C@H]7C[ C@@H]([C@H]([C@@H](O7)C)O)OC )OC) \ C)C 835.2240 49071005 pH 7 8.3 % ( 0.54 d ) NP ( 37.5 d)

835.6100 49071013 New York (bare) 1.0% ( 1.5 d) 0.0 % ( 401 d)

New York

(turf) 0.8 % ( 3 d) 0.0 % ( 401 d)

49071014 Georgia (bare) 0.6% ( 0 d) 0.0 % ( 406 d) Georgia (turf) 0.8 % ( 2 d) 0.0 % ( 406 d)

49071015 California (bare) 0.6% ( 1.5 d) 0.0 % ( 402 d)

California

(turf) 1.0% ( 0.5 d) 0.0 % ( 402 d)



### NOA 419150

Mono

Mono

saccharide of avermectin
B 1a 

### Desoleandrosyl

- avermectin
B 1a Formula: C 41 H 60 O 11 MW: 728.9 g/mol SMILES: CC[C@H](C)[C@@H]1[C@H](C=C[C @@]2(O1)C[C@@H]3C[C@H](O2)C/ C=C(/[C@H]([C@H](/C=C/C=C/4 \ CO[ C@H]5[C@@]4([C@@H](C=C([C@H] 5O)C)C(=O)O3)O)C)O[C@H]6C[C@@ H]([C@H]([C@@H](O6)C)O)OC) \ C)C C H 3 O

H

H C H 3

H O H H H H H

C H 3

H O

C H 3 H C H 3
C
H 2 O C H 3

O O

O H H C H 3 O O

H C H 3

O O H

835.4300 49071003 River water:
loam 2. 9% (100 d) 2.9% (100 d)

Stream water:
sand 3.4% (100 d) 3.4% (100 d)

A AR means “applied radioactivity”. MW means “molecular weight”. LOD means “limit of detection”. NA means “not applicable”. O O HO

O

O O

O

O O O

O

OH O

OH

### 14 3. Exposure Modeling

The available physical/chemical and environmental fate properties of abamectin and its degradates of concern were used to calculate exposure model input parameters to estimate potential drinking water concentrations (EDWC).

3.1. Residues of Concern

The abamectin residues of concern include the parent compound mixture and the six major structurally similar degradates : NOA 448111

, NOA 448112, NOA 426289, NOA 445495, NOA 457464, and NOA 457465 ( USEPA, 2014 ). The degradates of concern are assumed in the
absence of t oxicity data to have toxicity profiles similar to that of abamectin on the basis of the
structural similarities.

Table 5 provides the environmental fate parameters for the abamectin residues of concern (ROC). The soil biodegradation half

- lives for the ROC s are substantia lly more variable and generally longer (23

- 288 days) than for the parent compound mixture (16

- 49 days) due to some degradates of concern persisting in some soils. The aquatic biodegradation half

- lives for
the ROC s are also longer to a lesser degree, while photolysis half

- lives for the ROCs are similar to those of the parent compound mixture

.

Table 5

. Environmental Fate Parameters of Abamectin Residues of Concern

Parameter Value Source

Persistence in Water
Hydrolysis half

- life ( pH 5, 7, and 9) S table (abamectin is relatively stable) MRID 131083
Aqueous photolysis half

- life (25 ° C) 2. 9 d MRID 49071005
Anaerobic aquatic met abolism half

- life (20°C ) 498, 586 d MRID 49071004

Aerobic aquatic metabolism half

- life (20°C) 122, 139 d MRID 49071004

Persistence in Soil

Soil photolysis half

- life (25 °C) 28 d MRID 49071001

Aerobic soil metabolism half

- life (2 0 °C) 23 (IORE), 87 (SFO), 114 (IORE), 161 (DFOP), 288 d (IORE) A 

### MRID 4 9071006

, 49071007, 4 9178901
Mobility
Freundlich organic carbon normalized

s oil

- water partitioning coefficient (K FOC 

### ) 4500, 4590, 5710, 6260, 6380 L/kg OC 

### (values for abamectin are sole available) M RID 49071002

A 

### IORE, DFOP, and SFO are kinetics models used to generate the reported half

- lives . The models were selected following the NAFTA kinetics guidance (USEPA, 2012).



### The soil mobility of abamectin is used to re present the residues of concern because the residues are structurally similar and degradat e

- specific data are not available. EPISuite (v4.0)
estimated K OC 

### values for abamectin (76 and 876,700 L/kg) did not correlate with measured values (4,500

- 6,380 L/kg). Because the degradates of concern are structurally similar to

### 15 abamectin, EPISuite is ex pected to inaccurately estimate their K OC 

### values a s well and was not
used to do so.

3.2. Surface Water

The Total Residues of Concern (TRC) modeling approach was used to estimate aquatic exposure with the ROC half

- lives (from Table 5 ) and the soil mobility and chemical properties of abamectin (from Table 3 )

. The TRC approach is appropriate because there are multiple degradates of concern, for none of which a full environmental fate data profile is available.

Surface water sourced drinking water exposure was estimated using the Tier I I exposure model SWCC ( v1.102 ; May 1 , 20 14 ). Chemical i nput parameters for SWCC follow in Table 6

.

Table 6

. SWCC Chemical Input Parameters for Abamectin ROCs A


### Input Parameter Value Justification Source
Organic carbon partition

c oefficient (K OC 

### ) (L/kg OC 

### ) 5,500 Represents the mean K FO C 

### value (n=5 )
for abamectin M RID 49071002

Aerobic aquatic metabolism
half

- life (days) [temp. (°C)] 157 [20] Represents the upper 90% confidence
bound on the mean of two half

- lives for
the residues of concern MRID 49071004

Anaerobic aquatic metabolism
half

- life (days) [temp. (°C)] 677 [20] Represents the upper 90% confidence
bound on the mean of two half

- lives for
the residues of concern MRID 49071004

Aqueous photolysis half

- life (days) [latitude (°N)] 2.9 [40] Represents the single value for the
residues of concern MRID 49071005

Hydrolysis h alf

- life at pH 7 (days) 0 Represents the value for the residues of

concern MRID 131083

Aerobic soil metabolism half

life (days) [temp. (°C)] 203 [20] Represents the upper 90% confi dence
bound on the mean of five half

- lives for
the residues of concern MRID 49071006, 49071007, 49178901

Foliar half

- life (days) 0 Default value in the absence of data USEPA, 2009

Molecular m ass (g/mol) 873.1 Molecular mass of abamectin B 1a 

### (Calculated)

V apor p ressure ( torr ) 1

. 5 × 10

- 9 

### Study value for abamectin B 1a 

### MRID 47436204
Solubility in w ater (mg/L) 0.010 Study value for abamectin B 1a 

### MRID 47436204

A Source data are in Tables 3 and 5

.


### Chemical property and environmental fate input values were chosen in accordance with current input parameter guidance (USEPA, 2009). Based on analysis of the residues of concern, the 90% confidence bound s on the mean half

- lives for aerobic soil metabolism, aerobic aquatic
metabolism , and anaerobic aquatic metabolism were selected.

SWCC use pattern inputs are listed in Table 7 . Modeled SWCC scenarios were those applicable to the proposed and current use sites that resulted in the highest exposure . Modeled
use sites includ e the proposed use sites and the use site of highest exposure in past assessments,
beans. Modeled application rates and numbers of applications per year include the maximum

### 16 allowed on the (proposed) label. Dates of initial application were selected withi n the scenario

crop season and characterized by vulnerability to runoff. Runoff vulnerability was explored by modeling a range of initial application dates within the crop season with a 15

- day step and selecting the date for which exposure estimates were highest. This was expected to produce high

- end exposure estimates that are conservative but that may not represent the highest possible

exposure.

Table 7 . PRZM Scenarios and Input P arameters Describing Maximum Patterns of Abamectin Use on Representative Use Sites A

Use Site (Current/ Proposed) PRZM Scenario Date of Initial App. App. Rate in lbs a.i./A (kg a.i./ha) App.

per Year App.
Interval

(days) CAM Input PCA (%) B Application Efficiency/ Spray Drift
Beans (current) MI bean Aug. 1 0 .019 (0.021 ) 3 6, 12 C 2 100 0.95/0.13 5
Golf course tees, greens, fairways (proposed) PA turf Jun . 1 0 .067 (0.075 ) 4 21 2 34 0.99/0.066

Caneberries (proposed) OR berry Jul . 1 0.019 (0.021) 3 7 , 14 C 2 100 0.95/0.135

Sweet corn (proposed) KS corn Jun. 14 0.018 (0.020) 2 7 2 100 0.95/0.135
Soybeans (proposed) MS soybean Sep. 1 3 0.018 (0.020) 2 7 2 100 0.95/0.135

A Source data are in Table 2

. B Percent cropped areas (PCA) were 100% because abamectin is labeled for and proposed for use on both agricultural and non

- agricultural use sites

. A golf course adjustment factor of 34% applies to the proposed use on golf course tees, greens, and fairways.

C A bamectin cannot be applied more than twice in sequence to agricultural use sites. So, for these use patterns, the
initial interval is followed by a second interval twice as long to allow for an interim application of a pesticide with a
different mode of action

.


### Standard percent cropped areas (PCA) are used as conservative default estimates of the
extent of watershed on which agricultural crops of unknown specific PCA are grown (USEPA,
2012 c ). Because abamectin is labeled and proposed for use on both agricultural and non

agricultural sites, PCA values cannot be used to modify exposur e estimates, with the exception
th at a golf course adjustment factor of 34% applied to the proposed use on golf course tees, greens, and fairways.

Surface water exposure estimates for abamectin residues of concern are listed in Table 8

. Model input and output files are attached in Append ix A . The proposed use patterns and the current use on beans resulted in similar exposure estimates. The maximum use pattern on soybeans results in the highest 1

- in

- 10

- year peak estimated drinking water concentrations (E DW C). The maximum use pattern on beans results in the highest annual mean EDWC. The use pattern on caneberries results in the highest 30

- year mean EDWC.

### 17 Table 8

. SWCC Output (PCA

- adjusted) f or Abamectin ROCs A

Use Site (Current/ Proposed) PRZM Scenario 

### 1

- in

- 10

- year Peak (μg/L) Annual Mean (μg/L) 30

- year Mean (μg/L)

Beans (current) MI bean 

### 0.64 0.30 0.20
Golf course tees, greens, fairways (proposed) PA turf 

### 0.61 0.27 0.16
Caneberries (proposed) OR berry 

### 0.46 0.28 0.22
Sweet corn (proposed) KS corn 

### 0.75 0.21 0.17
Soybeans (proposed) MS soybean 

### 0.76 0.21 0.14

A Maximum values are in bold.



### For characterization, surface water exposure was also estimated for abamectin , without the degradates of concern. Model inputs for abamectin alone were the same as for the total
residues of concern model run for use on soybeans , with the following abamectin

- specific
differences: an aerobic soil metabolism half

- life of 37 days, an aerobic aq uatic metabolism half

life of 9 5 days, an anaerobic aq uatic metabol ism half

- life of 398 days , and an aqu eous photolysis
half

- life of 2.5 days. The resulting abamectin

- only EDWCs were 0.54 μg/L (1

- in

- 10

- year peak; 29% less), 0.074 μg/L (annual mean ; 65% less ), and 0.054 μg/L (30

- year mean ; 61% less ).

3.3. Ground Water

3.3.1. SCI

- GROW

Current modeling methodology is to estimate exposure in ground water using both SCI

GROW (v2.3, Jul. 29, 2003) and PRZM

- GW (v1.01, Dec. 26, 2012) (USEPA, 2012 d )

. Input parameters for SCI

- GROW appear in Table 9

. Four applications of 0.067 lbs a.i./acre were modeled to produce the maximum annual application rate of 0. 27 lbs a.i./acre. The median Freundlich organ ic carbon partition coefficient for abamectin (K FOC 

### = 5,700 L/kg OC 

### ) was selected. The median residue

- of

- concern half

- life (114 d) from five aerobic soils was selected to approximate the biodegradation kinetics of the residues of concern in aerobic soil environments.

Table 9

. SCI

- GROW Input P arameters for Abamectin ROC A



### Input Parameter Value Comments Source Application Rate (lbs a.i./A) 0.067 Maximum labeled single application
rate for golf courses Proposed label Applications per Year 4 Maximum number of applications per year at the maximum application rate Organic Carbon Partition Coefficient (K OC 

### ) (L/kg OC 

### ) 5,700 Represents the median K FO C 

### value for
abamectin M RID 49071002

Aerobic Soil Metabolism
Half

- life (days) 114 Represents the median of five half

lives for the residues of concern that range from 23 to 288 days MRID 49071006, 49071007, 49178901

A Source data are in Tables 2 and 5

.



### The SCI

- GROW output represents the highest 90

- day running mean concentration following one year of application. The output value is 0. 0 0 31 μg/L.

### 18 3.3.2. PRZM

- GW

PRZM

- GW model inputs are listed in Table 10 . Application inputs represent the use pattern of maximum exposure, which is four applications per year , each at 0.0 75 kg a.i./ hectare,
21 days apart

. The i nitial date of application (April 1) is within the application season and
selected to result in high

- end concentrations in ground water du e to vulnerability to precipitation.

Chemical inputs for the residues of concern follow the PRZM

- GW Input Parameter Guidance (USEPA, 2012 b ). The parent compound mixture does not hydrolyze. The surface soil
h alf

- life model input ( 2 03 days) is the upper 90 th 

### percentile con fidence bound on the mean of
five residue

- of

- concern half

- lives from studies conducted at 25 °C. The organic c arbon partition coefficient (5,500 L/kg OC 

### ) is the mean of five values for abamectin, which represents the
residues of concern i n the absence degradate

- specific data

.

Table 10 . PRZM

- GW Input Parameters for Abamectin ROC A



### Input Parameter Value Justification Source
Application Rate (kg a.i./ha) 0.075 Maximum labeled single application rate
for golf courses
Proposed label Applications per Year 4 ; every
year Maximum number of applications per year at the maximum application rate
Reapplication interval (days) 21 Minimum labeled interval

Initial application date Apr. 1 Selected within application season and for high

- end vulnerability due to precipitation (calculated)

Hydrolysis Half

- life (days) 0 Represents the value for the residues of

concern M RID 131083

Surface Soil Half

- life (days) 203 Represents the upper 90% confi dence
bound on the mean of five half

- lives for
the residues of concern MRID 49071006, 49071007,
49178901
Sorption Coefficient (K OC 

### ) (ml/g) 5,500 Represents the mean K FO C 

### value (n=5 ) for
abamectin M RID 49071002

A Source data are in Tables 2, 3, and 5

.


### All six available scenarios were modeled as surrogates for golf course use sites with the maximum annual application rate of 0.27 lbs a.i./acre

. EDWCs increased over 100 simulated years without reaching a maximum value in all six scenarios. The Florida citrus scenario produced the highest daily EDWC (which is used for acute exposure assessment) , due to the shallow aquifer depth (3 meters) and high water inputs

. While the maximum values were arbitrary concentrations occurring after 100 years of simulated use, post

- breakthrough mean
values (which are used for chronic exposure assessment) could not be calculated due to incomplete breakthrough

. PRZM

- GW outputs are listed in Table 1 1

.

### 19 Table 11 . PRZM

- GW Output for Abamectin ROCs A



### Use Site Modeled Scenario Max. Daily Conc. (μg/L) Mean Breakthrough Time (yrs) Post

- breakthrough
Mean (μg/L)

Golf courses DMV corn 0.00013

Incomplete breakthrough Not calculable FL citrus 0.074
FL potato 1.4 × 10

- 10


### GA peanut 1.9 × 10

- 7



### NC cotton 0.00025

WI corn 0.00026

A Maximum values are in bold.



### Figure 2 displays ground water concentrations over time for the Florida citrus scenario. Note that breakthrough was incomplete over 100 simulated years. EDWCs were not sensitive to application dates (which is expected for residues in ground water since the medium typically

m oves slower than surface water)

. For example, the maximum daily concentration for the
Florida citrus scenario was 1 % less for applications beginning on June 1 st 

### rather than April 1 st



### .

F igure 2 . Ground Water EDWCs (μg/L ) per Time (years) for the Florida Citrus Scenario

4. Modeling Results Summary

T able 1 2 summarizes the screening

- level exp osure model results for abamectin ROCs.

Table 1 2 . Screening

- Level ROC EDWCs for Abamectin Uses A



### Sour ce (Tier: Model) Use Site (Max. Annual App. Rate) Acute EDWC (μg/L) Chronic EDWC (μg/L)

Surface water (Tier II: SWCC ) Soybeans ( 0.0 3 7 lbs a.i./A) / Beans (0.056 lbs a.i./A) 0 .76 (soybeans) 0.30 (beans) Ground water (Tier I: PRZM

- GW) Golf courses (0. 27 lbs a.i./A) 0.074 N/A Ground water (Tier I: SCI

- GROW) Golf courses (0. 27 lbs a.i./A) ≤ 0.0031

A Maximum values in bold. “N/A” means “not available.”

### 20 5. Monitoring Data

Abamectin and avermectin s are not analytes in the following water monitoring programs:
the California Department of Pesticide Regulation ( CDPR) surface water database ( http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm , the USGS NAWQA surface and ground water database ( http://cida.usgs.gov/nawqa_queries_public/ ), the USEPA STORET Data Warehouse ( http://www.epa.gov/storet/ ), and the USDA Pesticide Data Program drinking water monitoring analyses ( http://www.ams.usda. gov/AMSv1.0/ams.fetchTemplateData.do?template=TemplateG&navID= &rightNav1=&topNav=&leftNav=ScienceandLaboratories&page=PDPDownloadData/Reports& resultType=&acct=pestcddataprg )

.

6. Fish Exposure

A sc ree ning estimate of abamectin residues of concern in potentia lly human

- consumed fish was generated using the K OW 

### (based) A quatic B io A ccumulation M odel (KABAM v.1.0) and
the SWCC. The bioaccumulation portion of KABAM is based on an aquatic food web bioaccumulation model published by Arnot and Gobas (2004) that relie s on a pesticide's octanol

water partition coefficient (K OW 

### ) to estimate uptake and elimination constants through respiration and diet of aquatic organisms in different trophic levels. Pesticide tissue concentrations in aquatic organisms are calculated fo r different trophic levels of a food w eb through diet and respiration . The KABAM model and user’s manual are available from the EPA
Water Models web

- page ( USEPA, 2014 a ). Calculations are in Appendix A

.

SWCC inputs were as listed in Tables 6 and 7 for drinking water exposure modeling. KABAM was run in default mode (see user’s guide for full description), with a log K OW 

### of 5.5 , a K OC 

### of 5

, 5 00 L/kg OC 

### , a metabolism rat e constant (k M 

### ) for small to large fish of 0. 155 d

- 1 

### , a study

derived water tempera ture of 22°C, and surface water and pore water 1

- in

- 10

- year concentration s of 0.288 (90

- day mean) and 0 .267 μg/L (21

- day mean)

, respectively, which were the reported
values with durations closest to the KABAM

- calculated time to steady state (88 days). The metabolism rate constant was calculated by subtracting the sum of elimination rate constants estimated by KABAM (k 2 

### + k E 

### +k G 

### of 0.064 d

- 1 

### ) from the study

- derived depuration rate constant (k T 

### of 0.219 d

- 1 

### ). This was done because KABAM does not account for metabolism by default. The resulting abamectin residues concentration in large fish was 588 mg/kg

- bw (ww).

This screening estimate represent s a high

- end concentration in fish that may occur in a stagnant fish

- bearing farm pond . Dissipation processes such as dilution, flow downstream, and partitioning to water body sediment were neglected. If these screening concentrations in fish result in risk concerns, then exposure assessment refinements ar e needed (the concentrations do not necessarily reflect actual exposure that may occur or may have occurred).

7. References

Food and Agriculture Organization of the United Nations ( FAO ) . 2014. Assessing soil contamination A reference manual; Parameters of p esticides that influence processes in the soil. Agriculture and Consumer Protection Department. http://www.fao.org/docrep/003/x2570e/x2570e06.htm

### 21 U.S. Environmental Protection Agency ( USEP A ) . 2005. Golf Course Adjustment Factors for Simulated Aquatic Exposure Concentrations . Environmental Fate and Effects Division. Internal memorandum. Dec. 7, 2005.

USEPA. 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides. Version 2.1. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division, Oct. 22, 2009. http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

USEPA. 2012. NAFTA Guidance for Evaluating and Calculating Degradation Kinetics in
Environmental Media. Office of Chemical Safety and Pollution Prevention, Environmental Fate and Effects Division. Internal guidance memorandum. Dec. 17,
2012.

USEPA. 2012 a . Identification and Evaluation of Existing Models for Estimating Environmental
Pesticide Transport to Gr oundwater . Final Report (Draft). U.S. Environmental Protection Agency ; Health Canada. Jan. 27 , 2012.

USEPA. 2012 b . Guidance for Selecting Input Parameters for Modeling Pesticide Concentrations in Groundwater Using the Pesticide Root Zone Model

. Version 1. 0. U.S. Environmental Protection Agency , Office of Pesticide Programs, Environmental Fate and Effects Division; Health Canada, Pesticide Management Regulatory Agency, Environmental
Assessment Directorate

. Oct. 15 , 2012.

USEPA. 2012 c . Guidance on Developme nt and Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update.
Internal Environmental Fate and Effects Division memorandum. U.S. Environmental Protection Agency, Office of Chemical Safety an d Pollution Prevention. Mar. 16, 2012.

USEPA. 2012 d . Approval of PRZM

- GW for Use in Drinking Water Exposure Assessments.
Internal Environmental Fate and Effects Division memorandum. U.S. Environmental Protection Agency, Office of Chemical Safety and Pollu tion Prevention. Dec. 11, 2012. http://www.epa.gov/oppefed1/models/water/przm_gw/wqtt_przm_gw_guidance.htm

USEPA. 2014. Dodd, N. and W. Phang. Abamectin: Recommendation for the Residue of Concern in Drinking Water. DP barcode 420073 . Memorandum from the Health Effects
Division to the Environmental Fate and Effects Division. Apr. 25 , 2014.

USEPA. 2014 a

. Water Models. U.S. Environmenta l Protection Agency, Pesticides, Science and Policy, Models and Databases. Last updated Jul. 9, 2013

. http://www.epa.gov/oppefed1/models/water/

United States Geological Survey (US GS). 2014. National Water

- Quality Assessment (NAWQA) Program

, Pesticide National Synthesis Project

, Pesticide Use Maps

– Abamectin

. http: //water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2011&map=ABAM ECTIN&hilo=L&disp=Abamectin (accessed Apr. 17, 2014)

### 22 7.1. Submitted Environmental Fate and Product Chemistry Studies

MRID Citation Reference

131083 Maynard, M.; Ku, C.; Gruber, V.; et al. (1982) Hydrol ysis of Aver mectin B1a (MK

- 0936). (Unpublished study received Jan 3, 1983 under 618

- EX

- 10; submitted by Merck & Co., Inc., Rahway, NJ; CDL:249152

- F)

159163 MSD Agvet Inc. (1983) Residue and Environmental Data: [MK

- 936]. Unpublished compilatio n. 160

p.

41191501 Wehner, T. (1989) Additional Soil Residue Data in Support of Applications for Registration of Abamectin Soil Leaching and Dissipation Study: Project ID: Merck No. 001

- 87

- 6045R; ADC No. 992. Unpublished study prepared by Merck Sharp & Do hme Research Laboratories and Analytical Development Corp. 18 p.

42627601 Wertz, P. (1993) Soil Residue Data in Support of an Application for Registrations of Abamectin: Soil Leaching and Dissipation Study 001

- 87

- 6045R: A Supplement: Lab Project Number: 618

- 936

- 6045. Unpublished study prepared by Analytical Development Corp. 603 p.

46877502 Friis, M. (2006) Product Chemistry

- Abamectin Technical (CHA 204)

- EPA Reg. No. 4787

- (none yet) Group B

- Physical /Chemical Properties. Project Number: MVF/060500/ABA/204/B/USA, PYC/170, PYC/171. Unpublished study prepared by Cheminova Agro A/S. 399 p.

47436204 Wagner, J. (2008) Abamectin Technical Herbicide: Stability to Normal and Elevated Temperatures, Metals, and Metal Ions: Oxidation/Reduction: Flam mability: Explodability: Storage Stability: Miscibility: Corrosion Characteristics: Dielectric Breakdown Voltage: Viscosity: Boiling Point: Dissociation Constants in Water: Particle Size, Fiber Length, and Diameter Distribution: Partition
Coefficient: Wate r Solubility: Vapor Pressure. Unpublished study prepared by Wagner Regulatory Associates, Inc. 6 p.

49071001 Phaff, R. (2001) NOA422601

- Soil Photolysis of [23

- (Carbon 14]

- Labelled NOA422601 (Avermectin B1a)

- Under Laboratory Conditions: Final Report. Project Number: TK0176242/OCR, 00RP04. Unpublished study prepared by Syngenta Crop Protection, AG. 85p.

49071002 Morgenroth, U. (2001) NOA422601

- Adsorption/Desorption of [23

- (Carbon14)]

- NOA422601 (Avermectin B1a) in Various Soils: Final Report. Project Number: TK0176241/OCR, 99MO05. Unpublished study prepared by Syngenta Crop Protection, AG. 83p.

49071004 Buckel, T. (2002) NOA422601: Metabolism and Rate of Degradation of [23

- (Carbon 14)]

- Labelled NOA422601 (Avermetin B1a) Under Aerobic and Anaerobic Laboratory Conditions in Aquatic Systems: Final Report. Project Number: TK0176250/OCR, 01TB01. Unpublished study prepared by Syngenta Crop Protection, AG. 181p.

49071005 Adam, D. (2001) Aqueous Photolysis of [23

- (Carob 14)]

- Labelled NOA422601 (Avermecti n B1A) Under Laboratory Conditions (Including Amendment No. 1 to Report on Study 01DA01): Final Report. Project Number: TK0176249/OCR, 01DA01. Unpublished study prepared by Syngenta Crop Protection, AG. 104p.

49071006 Adam, D. (2001) NOA422601: Rate of De gradation of [23

- (Carbon 14)]

- Labelled NOA422601 (Avermectin B1A) in One Soil Under Various Laboratory Conditions at 10 (Degrees Celsius), 20 (Degrees Celsius) and 30 (Degrees Celsius): Final Report. Project Number: TK0176246/OCR, 00DA07. Unpublished stu dy prepared by Syngenta Crop Protection, AG. 92p.

49071007 Nicollier, G. (2001) NOA422601: Metabolism and Rate of Degradation of [23

- (Carbon 14)]

- Labelled NOA422601 (Avermetin B1a) Under Aerobic and Anaerobic Laboratory Conditions in One Soil at 20 (Deg rees Celsius): Final Report. Project Number: TK0176252/OCR, 99AG07. Unpublished study prepared by Syngenta Crop Protection, AG. 158p.

### 23 MRID Citation Reference

49071013 Jacobson, B.; Hampton, R.; Perez, R.; et al. (2013) Abamectin

- Dissipation of Abamectin SC (020) Applied to Tur f in New York: Final Report. Project Number: TK0047099/OCR, 796/43, 903/TK0047099. Unpublished study prepared by Waterborne Environmental, Inc. (WEI), Syngenta Crop Protection, LLC and ADPEN Laboratories, Inc. 702p.

49071014 Jacobson, B.; Hampton, R.; Per ez, R.; et al. (2013) Abamectin

- Dissipation of Abamectin SC (020) Applied to Turf in Georgia: Final Report. Project Number: TK0047101/OCR, 796/44, 903/TK0047101. Unpublished study prepared by Waterborne Environmental, Inc. (WEI), ADPEN Laboratories, Inc. and Syngenta Crop Protection, LLC. 704p.

49071015 Jacobson, B.; Hampton, R.; Perez, R.; et al. (2013) Abamectin

- Dissipation of Abamectin SC (020) Applied to Turf in the Central Valley of California: Final Report. Project Number: TK0047103/OCR, 796/42, 903/TK0047103. Unpublished study prepared by Waterborne Environmental, Inc. (WEI), Syngenta Crop Protection, LLC and ADPEN Laboratories, Inc. 710p.

49178901 Zbaeren, A.; Nicollier, G. (2012) Rate of Degradation of [23

- (Carbon 14)]

- Labelled NOA422601 (Avermectin B1a)

- in Various Soils under Aerobic Laboratory Conditions at 20 Degrees Celsius (Including Amendment No. 1 to Final Report 01RP02): Final Report. Project Number: TK0176243 01RP02. Unpublished study prepared by Syngenta Crop Protection, AG. 10 4p.

### 24 Appendix A. Aquatic Model Calculations

Model Input & Output Files

Total Residue of Concern Environmental Fate Calculations

122804_412861_DW

A_TRC-calcs.xls



### KABAM File

KABAM_abamectin_

DWA_5-8-14.xls