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: 412861

SUBJECT: Abamectin: Drinking Water Exposure Assessment for Proposed New Uses on 

Soybeans, Sweet Corn, Caneberries (Crop Group 13-07A), and Golf Course Tees, 

Greens, and Fairways

FROM: Gregory 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

RAB3/HED (7509P)

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 drinking water 

exposure assessment for proposed FIFRA §3 new uses of abamectin (listed in Table 2). This 

assessment 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 EDWCs (0.76 and 0.30 μg/L, respectively) are 

based on the proposed use of 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 estimated with SWCC, 

which is a Tier II 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 (0.037 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 residue 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 were 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 numerous 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.

Table 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 approximates an annual limit.

Figure 1 depicts a national-level summary of 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, and 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 B1a and up to 

20% avermectin B1b. 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 (KAW 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 (KOW) of 100,000-

300,000. This flags abamectin as a potential bioaccumulator. 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 bioconcentration factor of 69x.

Sorption coefficients in soil indicate that abamectin displays a wide range of low mobility 

(KF 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). The 

high sorption coefficients indicate that 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 

increased mobility in some soils (MRIDs 49071013, -14, -15).

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

spray drift, runoff of residues (mostly sorbed to suspended solids), and, in some cases, leaching. 

Abamectin dissipated in 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 studies (which were conducted on 

avermectin B1a) 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 B1a: 873.1 g/mol

avermectin B1b: 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·m3/mol Calculated

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

Octanol-water partition coefficient (KOW); 

(log KOW) (25°C)

avermectin B1a: 300,000; (5.5)

avermectin B1b: 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-life (25°C) 2.5 d MRID 49071005

Aerobic aquatic metabolism half-life 

(20°C)

87 d (SFO1)

91 d (SFO1)

MRID 49071004

Anaerobic aquatic metabolism half-life 

(20°C)

233 d (SFO1)

314 d (SFO1)

MRID 49071004
5

Parameter Value Reference

Persistence in Soil

Soil photolysis half-life (25°C) 24 d (SFO1) MRID 49071001

Aerobic soil metabolism half-life (20°C) 27 d (IORE1) (Gartenacker silt loam) MRID 49071006

26 d (IORE1) (Gartenacker loam) MRID 49071007

23 d (SFO1) (Pappelacker loamy sand) MRID 49178901

16 d (IORE1) (18 acres sandy clay loam)

49 d (SFO1) (Marsillargues silty clay loam)

Anaerobic soil metabolism half-life 

(20°C)

1,660 d (DFOP1) (Gartenacker loam) MRID 49071007

Mobility

Freundlich organic carbon normalized 

soil-water partitioning coefficient (KFOC)

4500, 4590, 5710, 6260, 6380 L/kgOC MRID 49071002

Field Dissipation

Field dissipation half-life2

(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 include 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 environmental fate studies. All of the chemical structures share the sec-butyl side 

chain because all of studies were conducted with avermectin B1a. The degradates are expected to 

maintain the B1a:B1b 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 in 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 polar 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 uncertainty, to be well enough sorbed to the solid matrix to not 

be of exposure concern.
6

Table 4. Abamectin (Avermectins B1a and B1b) and Its Environmental Transformation Products. A

Code Name/ 

Synonym Chemical Name Chemical Structure

PARENT

Avermectin B1a

NOA 422601

CGA 140327

MK 936

IUPAC: (10E,14E,16E)-(1R,4S,5′S,6S,6′R,8R,12S,13S,20R,21R,24S)-6′-[(S)-sec-butyl]-21,24-

dihydroxy-5′,11,13,22-tetramethyl-2-oxo-(3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa10,14,16,22-tetraene)-6-spiro-2′-(5′,6′-dihydro-2′H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-Omethyl-α-L-arabino-hexopyranosyl)-3-O-methyl-α-L-arabino-hexopyranoside

CAS: 5-O-demethyl-avermectin A1a

CAS No.: 65195-55-3

Formula: C48H72O14

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 B1b

NOA 421704

IUPAC: (10E,14E,16E)-(1R,4S,5′S,6S,6′R,8R,12S,13S,20R,21R,24S)-21,24-dihydroxy-6′-

isopropyl-5′,11,13,22-tetramethyl-2-oxo-(3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa10,14,16,22-tetraene)-6-spiro-2′-(5′,6′-dihydro-2′H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-Omethyl-α-L-arabino-hexopyranosyl)-3-O-methyl-α-L-arabino-hexopyranoside

CAS: 5-O-demethyl-25-de(1-methylpropyl)-25-(1-methylethyl)-avermectin A1a 

CAS No.: 65195-56-4

Formula: C47H70O14

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-oxoavermectin 

B1a

CAS: 5-O-demethyl-8a-oxo-Avermectin 

A1a

Formula: C48H70O15

MW: 887.1 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

H C3

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

H C3

O

O

H C3

H O

H C O 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% (90 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-Hydroxyavermectin 

B1a

CAS: 5-O-demethyl-8a-hydroxyAvermectin A1a

Formula: C48H72O15

MW: 889.1 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

H C3

H

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

H C3

O

O

H C3

H O

H C O 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) 13.7% (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”-Oxoavermectin 

B1a

Formula: C48H70O14

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

H C3

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

H C3

O

O

H C3

H C O 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”-Demethylavermectin 

B1a

Formula: C47H70O14

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

H C3

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

H C3

O

O

H C3

H O

H O

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: C48H73O16

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

H C3

H

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

H C3

O

O

H C3

H O

H C O 3

835.4100

49178901

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: C48H71O16

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

H C3

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

H C3

O

O

H C3

H O

H C O 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: CO2

MW: 44 g/mol

SMILES: C(=O)=O

O C 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) 13.5% (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 

B1a

NOA 427011

CAS: 5-O-demethyl-, (8Z)-(9Cl)-

avermectin A1a

Formula: C48H72O14

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

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

Monosaccharide of 

avermectin 

B1a

Desoleandrosyl

-avermectin 

B1a

Formula: C41H60O11

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

H C3

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

H C3

O

H O

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 toxicity 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 ROCs are substantially 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 ROCs 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) Stable (abamectin is relatively stable) MRID 131083

Aqueous photolysis half-life (25°C) 2.9 d MRID 49071005

Anaerobic aquatic metabolism 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 (20°C) 23 (IORE), 87 (SFO), 114 (IORE), 161 

(DFOP), 288 d (IORE) A

MRID 49071006, 

49071007, 49178901

Mobility

Freundlich organic carbon normalized 

soil-water partitioning coefficient (KFOC)

4500, 4590, 5710, 6260, 6380 L/kgOC

(values for abamectin are sole available)

MRID 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 represent the residues of concern because the 

residues are structurally similar and degradate-specific data are not available. EPISuite (v4.0) 

estimated KOC 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 expected to inaccurately estimate their KOC values as 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 II exposure 

model SWCC (v1.102; May 1, 2014). Chemical input 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

coefficient (KOC) (L/kgOC) 5,500 Represents the mean KFOC value (n=5) for abamectin MRID 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 half-life at pH 7 

(days) 0 Represents the value for the residues of concern

MRID 131083

Aerobic soil metabolism halflife (days) [temp. (°C)]203

[20]

Represents the upper 90% confidence 

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 mass (g/mol) 873.1 Molecular mass of abamectin B1a (Calculated)

Vapor pressure (torr) 1.5 × 10-9 Study value for abamectin B1a MRID 47436204

Solubility in water (mg/L) 0.010 Study value for abamectin B1a 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 bounds 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 include 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 within 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 Parameters 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 0.95/0.135

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. 13 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 Abamectin 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, 

2012c). Because abamectin is labeled and proposed for use on both agricultural and nonagricultural sites, PCA values cannot be used to modify exposure estimates, with the exception 

that 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 Appendix 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 

(EDWC). 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) for 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 aquatic metabolism halflife of 95 days, an anaerobic aquatic metabolism half-life of 398 days, and an aqueous 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 SCIGROW (v2.3, Jul. 29, 2003) and PRZM-GW (v1.01, Dec. 26, 2012) (USEPA, 2012d). 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 organic carbon partition coefficient for abamectin (KFOC = 5,700 L/kgOC) 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 Parameters 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 (KOC) (L/kgOC) 5,700 Represents the median KFOC value for abamectin MRID 49071002

Aerobic Soil Metabolism 

Half-life (days) 114

Represents the median of five halflives 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 0.0031 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 0.075 kg a.i./hectare, 

21 days apart. The initial date of application (April 1) is within the application season and 

selected to result in high-end concentrations in ground water due to vulnerability to precipitation.

Chemical inputs for the residues of concern follow the PRZM-GW Input Parameter 

Guidance (USEPA, 2012b). The parent compound mixture does not hydrolyze. The surface soil 

half-life model input (203 days) is the upper 90th percentile confidence bound on the mean of 

five residue-of-concern half-lives from studies conducted at 25°C. The organic carbon partition 

coefficient (5,500 L/kgOC) is the mean of five values for abamectin, which represents the 

residues of concern in 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

MRID 131083

Surface Soil Half-life (days) 203

Represents the upper 90% confidence 

bound on the mean of five half-lives for 

the residues of concern

MRID 49071006, 

49071007, 

49178901

Sorption Coefficient (KOC)

(ml/g) 5,500 Represents the mean KFOC value (n=5) for abamectin MRID 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 11.
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 

moves slower than surface water). For example, the maximum daily concentration for the 

Florida citrus scenario was 1% less for applications beginning on June 1st rather than April 1st.

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

4. Modeling Results Summary

Table 12 summarizes the screening-level exposure model results for abamectin ROCs.

Table 12. Screening-Level ROC EDWCs for Abamectin Uses A

Source (Tier: Model) Use Site

(Max. Annual App. Rate)

Acute 

EDWC 

(μg/L)

Chronic 

EDWC 

(μg/L)

Surface water (Tier II: SWCC) Soybeans (0.037 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 avermectins 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 screening estimate of abamectin residues of concern in potentially human-consumed 

fish was generated using the KOW (based) Aquatic BioAccumulation Model (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 relies on a pesticide's octanolwater partition coefficient (KOW) 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 for different trophic levels of a food web 

through diet and respiration. The KABAM model and user’s manual are available from the EPA 

Water Models web-page (USEPA, 2014a). 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 KOW of 5.5, a 

KOC of 5,500 L/kgOC, a metabolism rate constant (kM) for small to large fish of 0.155 d-1

, a studyderived water temperature of 22°C, and surface water and pore water 1-in-10-year concentrations

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 (k2 + kE +kG of 0.064 d-1) from the study-derived depuration rate constant 

(kT 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 represents 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 are 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 pesticides 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 (USEPA). 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. 2012a. Identification and Evaluation of Existing Models for Estimating Environmental 

Pesticide Transport to Groundwater. Final Report (Draft). U.S. Environmental Protection 

Agency; Health Canada. Jan. 27, 2012.

USEPA. 2012b. 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. 2012c. Guidance on Development 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 and Pollution Prevention. Mar. 16, 2012.

USEPA. 2012d. 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 Pollution 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. 2014a. Water Models. U.S. Environmental 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 (USGS). 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) Hydrolysis of Avermectin 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 compilation. 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 & Dohme 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: Flammability: 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: Water 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 (Avermectin 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 Degradation 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 study 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 (Degrees 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 Turf 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.; Perez, 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. 104p.
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