1

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 080801

DP Barcode: 407650

Date: May 14, 2013

MEMORANDUM

SUBJECT: Registration Review: Preliminary Problem Formulation for Environmental Fate, 

Ecological Risk, Endangered Species, and Human Health Drinking Water 

Exposure Assessments for Ametryn

TO: Molly Clayton, Chemical Review Manager

Patricia Parrot, Branch Chief

Risk Management and Implementation Branch III 

Pesticide Re-evaluation Division

FROM: Andrew Sayer, Ph.D., Biologist

Cheryl Sutton, Ph.D., Environmental Scientist

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED

BY: Jim Carleton, Ph.D., Senior Fate Scientist

Thomas Steeger, Ph.D., Senior Advisor

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

APPROVED 

BY: Marietta Echeverria, Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed the preliminary problem 

formulation for the environmental fate, ecological risk, endangered species, and drinking water 

exposure assessments to be conducted as part of the Registration Review of ametryn, CAS No. 

834-12-8; PC Code 080801. Ametryn is a selective systemic herbicide registered for use on 

corn, pineapple, and sugarcane. Functioning as the first stage of the risk assessment process for 

Registration Review, this problem formulation provides an overview of what is currently known 

about the environmental fate and ecological effects associated with ametryn and its degradation 
2

products. It also describes the preliminary ecological risk hypothesis and analysis plan for 

evaluating and characterizing risk to non-target species in support of the Registration Review of 

ametryn. This document also recommends studies that should be considered for inclusion in a 

generic data call-in (DCI) to address uncertainties surrounding the environmental fate and 

potential ecological effects of ametryn.
3

Problem Formulation for the Environmental Fate, 

Ecological Risk, Endangered Species, and Human 

Health Drinking Water Exposure Assessments in 

Support of the Registration Review of Ametryn

Ametryn: N2-ethyl-N4-isopropyl-6-methylthio-1,3,5-triazine-2,4-diamine

CAS: 834-12-8

PC Code: 080801

Prepared by:

Andrew Sayer, Ph.D., Biologist

Cheryl Sutton, Ph.D., Environmental Scientist

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by: 

Jim Carleton, Ph.D., Senior Scientist

Thomas Steeger, Ph.D., Senior Advisor

Approved by:

Marietta Echeverria, Branch Chief

Date: March 7, 2013
4

Contents

1. Introduction......................................................................................................................... 5

2. Conclusions from Previous Risk Assessments................................................................... 5

2.1. Ecological Risk Assessments........................................................................................ 5

2.2. Drinking Water Exposure Assessments........................................................................ 6

2.3. Clean Water Act Programs........................................................................................... 6

3. Environmental Fate and Transport...................................................................................... 7

3.1. Transformation Products............................................................................................. 11

4. Ecological Effects Summary............................................................................................. 17

4.1 Toxicity of Ametryn Transformation Products................................................................. 20

4.1.1 ECOSAR-Predicted vs. Observed Toxicity Endpoints Relative to Parent Ametryn..... 21

GS-11354 and GS-11355........................................................................................................ 21

NOA 423271........................................................................................................................... 21

NOA 428383........................................................................................................................... 22

NOA 438707........................................................................................................................... 22

G 34048 (2-hydroxy atrazine)................................................................................................. 22

GS-17794 (des-ethyl hydroxy atrazine).................................................................................. 22

4.2. Ecological Incidents.................................................................................................... 24

5. Exposure Pathways of Concern ........................................................................................ 24

6. Analysis Plan .................................................................................................................... 25

6.1. Stressors of Concern ................................................................................................... 25

6.2. Measures of Exposure................................................................................................. 26

6.3. Measures of Effect ...................................................................................................... 27

6.4. Endangered Species Assessments............................................................................... 28

6.5. Endocrine Disruptor Screening Program (EDSP)....................................................... 28

7. Preliminary Identification of Data Gaps........................................................................... 29

7.1. Environmental Fate..................................................................................................... 29

7.2. Ecological Effects....................................................................................................... 32

8. References......................................................................................................................... 35

9. Appendices........................................................................................................................ 37

Appendix A. Submitted Environmental Fate and Effects Studies.......................................... 37

Appendix B. Biological and Economic Analysis Division (BEAD) Report .......................... 50

Appendix C. Output from OPP Aggregate Incident Database for Ametryn........................... 52

Appendix D. SIP Results for Evaluate Potential Risk to Birds and Mammals from Drinking 

Water Exposure................................................................................................................. 53

Appendix E. STIR Results to Evaluate the Potential for Inhalation Risk to Birds and 

Mammals........................................................................................................................... 54

Appendix F. Environmental Fate and Transport Characterization ......................................... 55
5

1. Introduction

The purpose of this problem formulation is to provide an understanding of the environmental fate 

and ecological effects of the registered uses of ametryn in support of Registration Review. 

Ametryn belongs to the triazine class of herbicides; the mode of action is through inhibition of 

the photosynthesis II pathway. Ametryn is a selective systemic herbicide, absorbed by the leaves 

and roots, with translocation through the xylem of vascular plants. The compound is used for 

selective control of broadleaf and grassy weeds (pre- and post-emergent).

According to the Reregistration Eligibility Decision (RED) document completed in 2005 

(USEPA 2005)1ametryn was first registered for use to control broadleaf weeds and annual 

grasses in sugarcane fields in 1964. In 1969, use for general weed control in corn fields, 

currently the largest use of ametryn, was added. Other crop uses added to the registration 

include bananas, grapefruit, oranges, pineapple, plantains, and potatoes for broadleaf weed, 

annual grass, and general weed control and as a desiccant. Ametryn has also been used as a 

general herbicide in uncultivated areas, rights of way, and industrial areas and aquatic weeds. 

Over time, the uses of ametryn have been cancelled so that only four use sites remain: field corn, 

popcorn, pineapple, and sugarcane.

Ametryn is formulated as water dispersible granules and can be applied by conventional ground 

sprayers for use on sugarcane, corn (pop and field), and pineapples (Hawaii only). Aerial 

application is allowed only for use on sugarcane in Florida. The Screening Level Usage 

estimates (USEPA 2012) of agricultural uses of ametryn are corn at 100,000 lbs a.i. and 

sugarcane at 80,000 lbs a.i. which average <1 and 30 percent of the crop total, respectively (data 

not available for pineapple). There were no uncultivated areas indicated in the Screening Level 

Usage estimates. More complete details are available in Appendix B.

Between 2000 and 2005, the crops with the most use in terms of pounds of active ingredient

applied were field corn (65%) and sugarcane (35%). During the 2006-2010 timeframe the same 

two crops accounted for the majority of use (field corn 51%, and sugarcane 49%), even though 

total pounds active ingredient applied decreased from the amount applied during the 2000-2005 

timeframe. Maximum single application rates for corn (field and pop), pineapple, and sugarcane 

are: 1.6, 1.6, and 2.4 lbs a.i./A, respectively. There are no residential, public health, or other 

non-food registered uses of ametryn. Further details on ametryn usage profile and history are 

provided in the Biological and Economic Analysis Division (BEAD) Chemical Profile (USEPA 

2012, Appendix B).

2. Conclusions from Previous Risk Assessments

2.1. Ecological Risk Assessments

 1 USEPA. 2005. Reregistration Eligibility Decision (RED) for Ametryn. Office of Chemical Safety and Pollution 

Prevention formerly Prevention, Pesticides and Toxic Substances. EPA 738-R-05-006. September 2005. 

http://www.epa.gov/oppsrrd1/REDs/ametryn_red.pdf
6

The environmental fate and ecological risk assessment for the re-registration of ametryn was 

issued in June 2005 (USEPA 2005b). The assessment indicated exceedance of the risk level of 

concern (LOC) (RQ≥1) for listed non-target terrestrial and aquatic plants. Although ametryn is 

practically non-toxic to birds and is only slightly toxic to mammals on an acute exposure basis, 

the chemical’s high application rates resulted in risk quotients (RQs) that exceeded the acute risk 

to listed species level of concern (LOC; RQ≥0.1) for mammals, and the chronic risk LOC 

(RQ≥1) for birds. For aquatic animals, the assessment indicated exceedance of the chronic risk 

LOC (RQ≥1) for estuarine/marine fish and invertebrates. 

2.2. Drinking Water Exposure Assessments

The Environmental Fate and Effects Division (EFED) conducted a revised drinking water 

assessment (DWA) for ametryn in 2005 (USEPA 2005a) following proposed reductions in the 

maximum application rate by the registrant in response to the Draft RED. The residues of 

concern considered in that DWA were parent ametryn and two of its transformation products

(see Table 3) GS-11354 and GS-11355. In the Human Health Drinking Water Assessment 

included in the final Environmental Fate and Ecological Risk Assessment for the Re-registration 

of Ametryn (USEPA 2005b), in addition to parent, GS-11354 and GS-11355, the transformation 

products NOA423271 and NOA428383 were included as residues of concern. These compounds, 

which are primarily formed through aerobic soil metabolism of ametryn, were identified in 

coordination with the Health Effects Division as being of possible toxicological concern based 

on their structural similarity to parent ametryn and, in the case of NOA423271 and NOA428383, 

on the fact that they are oxidized forms of ametryn and able to be reduced back to parent under

environmental conditions where redox potential is below -148 mV. As recommended by HED, 

the transformation products G-34048, GS-17794, and NOA 438707 were not considered in the 

DWA, based on a separate risk assessment for atrazine metabolites which concluded that these 

hydroxy transformation products did not raise toxicity concerns and were only expected to be 

present at low levels in drinking water.

The uses assessed in 2005 were corn, pineapple and sugarcane, although a surface water 

estimated drinking water concentration (EDWC) for pineapple was not determined due to a lack 

of an appropriate modeling standard scenario. The maximum EDWC was associated with 

Louisiana (LA) sugarcane use adjusted using the national percentage crop area (PCA) default 

factor of 0.87. The 1-in-10 year acute EDWC was 91 μg/L, and the 1-in-10 year chronic EDWC 

was 19.9 μg/L; the 30-year daily average EDWC was 14.4 μg/L. The maximum groundwater 

EDWC, associated with sugarcane use in HI, was 9.2 μg/L.

2.3. Clean Water Act Programs

Ametryn is not identified as a cause of impairment for any water bodies listed as impaired under 

section 303(d) of the Clean Water Act

2

. In addition, no Total Maximum Daily Loads (TMDL) 

 2 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885
7

have been developed for ametryn3. The Impaired Waters and Total Maximum Daily Loads 

website can be consulted for more information4. EPA aquatic benchmarks, based on the 1996 

RED document, have been established for ametryn5

. 

The Agency invites submission of water quality data for this pesticide. To the extent possible, 

data should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process6, in order to ensure they can be 

used quantitatively or qualitatively in pesticide risk assessments.

3. Environmental Fate and Transport

Although, based on limited data, ametryn is classified as nonpersistent to slightly persistent 

(scale of Goring et al., 1975) in aerobic soils; however, the chemical is sufficiently mobile that it 

may migrate into anaerobic compartments, where available data suggest that it will be 

substantially more persistent. Due to a lack of adequate data, the persistence of the compound in 

aerobic aquatic environments is uncertain; however, data are sufficient to demonstrate that 

ametryn is stable to abiotic hydrolysis at environmental pHs. Due to a lack of adequate data, it is 

uncertain whether the compound photodegrades in water or soil. 

Ametryn is classified as mobile to moderately mobile in soils, under the Food and Agriculture 

Organization (FAO) mobility classification scheme. In leaching studies, ametryn leached 

through sandy loam, loam and sand soil columns, and was detected in the leachate. In a clay soil 

column, ametryn was less mobile, but was still detected at a depth of 8 inches and at low levels 

in the leachate. Although there are no batch equilibrium data for the transformation products of 

ametryn, in aged soil column studies, all of the transformation products monitored (GS-34048; 

GS-11354; GS-11355; GS-26831; GS-32083; GS-28304; and GS-17794; see Tables 2 and/or 5

for identifications) leached through sandy loam soil, and all except GS-17794 were detected in 

the leachate. All of the transformation products studied were more mobile than the parent, and 

have the potential to leach to groundwater. There are no mobility data on major transformation 

products NOA 423271 and NOA 428383.

Ametryn is not expected to volatilize from dry or wet soils or from water, based on its low 

volatility (vapor pressure of 2.74 x10-6 torr) and Henry’s Law constant (2.43 x 10-9

 atm· m 

3

·mole -1). Ametryn is fairly soluble in water (200 ppm at 25°C), and based on its octanol-water 

partition coefficient (log Kow= 2.63) and fish bioconcentration factor (BCF) of 83X, is not

expected to bioconcentrate in fish. 

Ametryn may potentially reach surface water via spray drift, runoff, and/or subsurface lateral 

transport. In the environment, the major known route of degradation of ametryn is aerobic 

 3

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES

4 http://www.epa.gov/owow/tmdl/ 5 http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm. 6 http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf
8

metabolism in soils (t1⁄2= 9.6 to 38 days). In anaerobic soil and aquatic environments, ametryn is 

persistent. Given its mobility, transport to groundwater of ametryn as well as some of its 

transformation products is also likely, as a consequence of normal agricultural use. 

Submitted terrestrial field dissipation studies did not provide much useful information on the fate 

of ametryn, due to issues such as inadequate sampling (depth and times), lack of monitoring for 

all major transformation products, variable data, and applications at less than the maximum rate.

The studies did however indicate that both ametryn and its transformation product G-34048 (2-

hydroxy atrazine) are susceptible to leaching in the field, with G-34048 being detected at depths 

up to 48 inches.

There are multiple transformation products formed in fate studies; these are presented in detail in 

Section 3.1. Table 1 provides a summary of physical/chemical properties and environmental fate 

parameters of ametryn. Additional details of individual studies are discussed in Appendix F.

Table 1. Physical/Chemical Properties and Environmental Fate Parameters of Ametryn.

Parameter Value Description/

Comments

Reference,

Study 

classification

Chemical Classification Triazine --

MRID 40885812 

and USEPA 2005 

Molecular Formula C9H17N5S --

PC Code 080801 --

Chemical Name 

(IUPAC)

N2-ethyl-N4-isopropyl-6-methylthio1,3,5-triazine-2,4-diamine --

Chemical Name (CAS) N-ethyl-N '-(1-methylethyl)-6-

(methylthio)-1,3,5-triazine-2,4-diamine --

CAS Number 834-12-8 --

Pesticide Classification Herbicide (systemic) --

Molecular Weight 227.3 --

Physical State White powder --

Water Solubility (ppm) 185 at 20o

C

200 at 25oC (pH 7) --

Vapor pressure (25oC) 2.74 x10-6 torr --

Henry's Law Constant 

(25oC) 2.43 x 10-9

 atm· m 3·mole -1 Calculated

Octanol/Water 

Partition, Kow

4.27 X 102 (log Kow = 2.63)

PPDB

http://sitem.herts.

ac.uk/aeru/iupac/2

7.htm

Persistence

Hydrolysis Stable at pH 5, 7, 9 -- MRID 40995812, 

Acceptable
9

Parameter Value Description/

Comments

Reference,

Study 

classification

Direct photolysis in 

water at pH 7 No acceptable data.

Data insufficient to 

determine 

photodegradation.

Data are needed.

MRID 41169601, 

Not Acceptable 

(reclassified)

Photolysis on soil No acceptable data.

Data insufficient to

determine 

photodegradation.

MRIDs 

41169602, 

41169603

Not Acceptable 

(reclassified) 

Aerobic soil 

metabolism

No acceptable data. Inadequate analytical 

method.

Accession No. 

146399

Not Acceptable 

No acceptable data. Inadequate analytical 

method.

Accession No. 

255735

Not Acceptable

t1⁄2 = 38.9 days for ametryn (parent only) 

in sandy loam soil at 25°C

t1⁄2 = 51.0 days for total toxic residues 

used in DWA (ametryn plus GS11354 

and GS-11355; transformation products

NOA423271 and NOA428383 were not 

monitored)

Slightly persistent* 

Single soil. Data from 

additional soils (3) are 

needed.

MRID 417524011

Acceptable 

t1⁄2 = 9.6 days (parent only) in loam soil 

from Switzerland at 20°C 

t1⁄2= 29.2 days for total toxic residues used 

in DWA (ametryn plus GS-11354 and 

GS-11355)

Unextracted residues were 20% by 14 

days, 41% by 56 days, and 64% by 171 

days. 

Nonpersistent*

Half-life may be 

underestimated due to 

unexplained high levels 

of unextracted residues.

MRID 465338012

Supplemental

Anaerobic soil 

metabolism

Ametryn was stable to anaerobic 

degradation in a sandy loam soil at 25°C. 

Parent ametryn increased during the 

flooded phase due to reduction of a 

degradate(s) back to the parent. A halflife was not determined. 

Persistent under 

anaerobic (flooded) 

conditions. The 

potential 

transformation products

NOA 432271 

(sulfoxide of ametryn) 

and NOA 428383, were 

not monitored. 

MRID 41752401

Acceptable 

Ametryn was stable to anaerobic 

degradation in a loam soil from 

Switzerland at 20°C. Parent ametryn 

increased during the flooded phase. A 

half-life was not determined.

Unextracted residues were 20% at 

flooding, and 31-35% at 28 -150 days.

Persistent under 

anaerobic (flooded) 

conditions. It is 

possible that NOA 

423271 underwent 

reduction and reformed 

parent ametryn under 

flooded conditions. 

MRID 46533801

Supplemental
10

Parameter Value Description/

Comments

Reference,

Study 

classification

Aerobic aquatic 

metabolism No data Data are needed

Data Waiver was 

granted in 

D342463 

(9/15/07). 

Data are now 

considered 

necessary. 

Anaerobic aquatic 

metabolism

t1⁄2 = 1386 days in pond water/loam 

sediment (pH 7.2) at 20°C

Unextracted residues were <6.8% 

throughout the study.

Persistent MRID 46533801

Supplemental

Stable in clay loam sediment (pH 6.5) at 

25°C

Unextracted residues were 14-17% at 360 

days.

Persistent MRID 42861603, 

Acceptable

Field Dissipation

Terrestrial field 

dissipation

No half-life available.

Validity of data was 

questionable due to high 

variability, and 

inadequate sampling.

MRID 255735

Not Acceptable

Biphasic dissipation which slowed after 

60 days on a bareground plot of sand soil 

in IL (at 2.0 lb a.i./A). Ametryn was 

detected to 12 inches. G-34048 was 

detected at all depths to 48 inches. 

Inadequate sampling 

(depth and times), all 

major transformation 

products not monitored, 

variable data, maximum 

application rate not used. 

MRID 41872301

Supplemental

Biphasic dissipation (slowed after 30 

days) observed in a sand soil in IL (at 4.0 

lb a.i./A) planted to corn. Ametryn was 

detected to 12 inches. G-34048 was 

detected at all depths to 48 inches. 

Inadequate sampling 

(depth and times), all 

major transformation 

products not monitored, 

variable data, maximum 

application rate not used. 

MRID 41872302

Supplemental

Biphasic dissipation which slowed after 

60 days in a silty loam sugarcane field in 

LA (at 2.5 lb a.i./A x 2 applications). 

Ametryn, GS-13354 and GS-17794 were 

not detected below 6 inches. G-34048 

was detected below 6 inches twice 

(0.014-0.015 ppm at 20 and 60 days).

All major transformation 

products not monitored, 

variable data, maximum 

application rate not used. 

MRID 41752402

Supplemental

Mobility
11

Parameter Value Description/

Comments

Reference,

Study 

classification

Adsorption/Desorption

Adsorption

Koc = 927, 205, 96, 257 mL/goc

Kd = 26.2, 1.1, 1.1, 1.2 mL/g 

Desorption

Koc = 983, 570, 307, 990 mL/goc

Kd = 27.8, 3.0, 3.4, 4.66 mL/g 

1/n = 0.76-0.93 (ads)

1/n = 0.80-1.0 (des)

Soils studied (pH, % 

o.m.)/Mobility class3: 

MD Clay (5.9, 

4.8%)/mod. mobile;

MD Sand (6.5, 

0.9%)/mod. mobile;

MD Sandy loam (7.5, 

1.9%)/mobile;

CA Loam (6.7, 

0.8%)/mod. mobile

MRID 40995813 

Acceptable

Unaged ametryn was detected at all 

depths and in leachate from sandy loam 

(1.9% om), loam (0.8% om), and sand 

(0.9% om) soil columns. In a clay (4.8% 

om) soil column, 91% of the applied 

remained in the top 1-inch, although 

some residues leached to 8 inches and up 

to 0.14% of the applied was detected in 

leachate.

Parent Ametryn has the 

potential to leach in 

multiple soil types.

MRID 41169604

Acceptable

Aged ametryn and its transformation 

products (GS-34048; GS-11354; GS11355; GS-26831; GS-32083; GS-28304; 

and GS-17794) were mobile in sandy 

loam soil (1.9% om). All except GS17794 were detected in the leachate. All 

transformation products were more 

mobile than the parent. 

Residues were not 

characterized postaging. Study concluded 

that both ametryn and 

its transformation 

products should be 

considered potential 

groundwater

contaminants.

MRID 41169605

Supplemental

Fish Bioconcentration

Bioconcentration in 

fish (BCF)

61X in edible tissues

110X in non-edible tissues

83X in whole fish

Approximately 60-80% of the 

accumulated residues were eliminated 

from fish after 28 days of depuration.

Based on study results 

and a Kow of 4.3 X 102

(log Kow = 2.6), ametryn 

residues are not likely to 

bioconcentrate in fish 

tissues.

MRID 42061901

Acceptable

1

MRID 41752401 contained studies for both aerobic and anaerobic soil metabolism. 2MRID 46533801 contained 

studies for aerobic and anaerobic soil metabolism and anaerobic aquatic metabolism. 3Mobility class based on Food 

and Agriculture Organization soil mobility classification scheme (FAO, 2000).

*Goring et al. 1975 scale was used to describe persistence. Nonpersistent: t1⁄2 < 15 days; slightly persistent t1⁄2 15-45 

days; moderately persistent t1⁄2 45-180 days; persistent t1⁄2 >180 days.

3.1. Transformation Products

Table 2 summarizes the major and/or toxicologically significant transformation products and 

their maximum amounts formed in the fate studies, and identifies which compounds will be 

assessed in the ecological risk assessment to be conducted for ametryn as part of the Registration 
12

Review process. The toxicity of specific transformation products is discussed in detail in 

Section 4.3.

The transformation products of ametryn in the submitted environmental fate studies include 2,4-

diamino-6-methylthio-s-triazine (GS-26831), 2-amino-4-isopropylamino-6-methylthio-s-triazine 

(GS-11354), 2-ethylamino-4-amino-6-methylthio-s-triazine (GS-11355), 2-hydroxy4-ethylamino-6-isopropylamino-s-triazine (G-34048), 2-ethylamino-4-isopropylamino-s-triazine 

(GS-32083), 2-amino-4-isopropylamino-s-triazine (GS-28304), 2-amino-4-isopropylamino-6-

hydroxy-s-triazine (GS-17794), N-ethyl-N-isopropyl-6-methanesulfinyl-[1,3,5]triazine-2,4-

diamine (NOA 423271), 4-Ethylamino-6-isopropylamino-[1,3,5]triazine-2-sulfinic acid sodium 

salt (NOA 428383), 4-Hydroxy-6-isopropylamino-[1,3,5]triazin-2-ylamino-acetic acid (NOA 

438707), and carbon dioxide.
13

Table 2. Ametryn and Its Major and/or Toxicologically Significant Environmental Transformation Products from 

Laboratory Studies

Code Name/ Synonym Chemical Name(s) Chemical Structure Study Type Ref.

(MRID)

Maximum(s) 

%AR1 (day)

Final %AR 

(last detection

day or study 

length)

PARENT

Ametryn2

CAS No.: 834-12-8

CAS Name(s): N-ethyl-N-

(1-methylethyl)-6-

(methylthio)-1,3,5-triazine2,4-diamine OR

2-(ethylamino)-4-

(isopropylamino)-6-

(methylamino)-S-triazine

SMILES String:

CCNc1nc(nc(n1)SC)NC(C)

C (ISIS v2.3/Universal 

SMILES).

CCNc1nc(NC(C)C)nc(SC)

n1 (EPI Suite, v3.12)

MAJOR TRANSFORMATION PRODUCTS

N

N

N

NH

S NH
14

Code Name/ Synonym Chemical Name(s) Chemical Structure Study Type Ref.

(MRID)

Maximum(s) 

%AR1 (day)

Final %AR 

(last detection

day or study 

length)

GS-11354

CAS Name(s): 2-amino-4-

isopropylamino-6-

methylthio-s-triazine (Also:

de-isopropyl prometryn)

. 

Aerobic soil 

metabolism 41752401 11.9% (14) 2.3% (365)

Aerobic soil 

metabolism 46533801 1.9% (14) 0.1% (56)

Anaerobic soil 

metabolism 41752401 9.5% (62) 9.5% (62)

Anaerobic soil 

metabolism 46533801 2.4% (14) 2.2% (150)

Anaerobic 

aquatic

metabolism

46533801 1.6% (56) 1.3% (120)

GS-11355

CAS Name(s):

2-ethylamino-4-amino-6-

methylthio-s-triazine

Aerobic soil 

metabolism 41752401 1.9% (365) 1.9% (365)

Aerobic soil 

metabolism 46533801 1.2% (14) 0.5% (171)

Anaerobic soil 

metabolism 46533801

GS-11355 plus 

an unknown:

1.8% (through 

150 d)

2.3% (150)

Anaerobic 

aquatic

metabolism

46533801 0.5% (91-121) 0.5% (120)
15

Code Name/ Synonym Chemical Name(s) Chemical Structure Study Type Ref.

(MRID)

Maximum(s) 

%AR1 (day)

Final %AR 

(last detection

day or study 

length)

NOA 4232712

CAS Name(s): n-ethyl-nisopropyl-6-methaneslfinyl-

[1,3,5]triazine-2,4-diamine

(sulfoxide of ametryn)

Aerobic soil 

metabolism 46533801 24.7% (7) 0.2% (171)

Anaerobic soil 

metabolism 46533801 20.6% (0 d postflood) 0.1% (56)

NOA 4283832

CAS Name(s): 4-

ethylamino-6-

isopropylamino-

[1,3,5]triazine-2-sulfinic 

acid sodium salt 

Aerobic soil 

metabolism 46533801 14.8% (28) 1.6% (171)

Anaerobic soil 

metabolism 46533801 13.5% (7 d postflood) 8.6% (150)

NOA 438707

CAS Name(s): 4-Hydroxy6-isopropylamino-

[1,3,5]triazin-2-ylaminoacetic acid

Aerobic soil 

metabolism 46533801 10.3-10.6% (56-91) 7.5% (171)

Anaerobic soil 

metabolism 46533801 3.1% (28) 2.0% (150)

G 34048

CAS Name(s): 2-

(ethylamino)-4-hydroxy-6-

(isopropylamino)-s-triazine

(synonym: 2-hydroxy 

atrazine)

Aerobic soil 

metabolism 41752401

2.6% (total for 

G 34048 plus G17794) (92)

1.2% (365)

Aerobic soil 

metabolism 46533801 18.1% (28) 0.2% (171)

Anaerobic soil 

metabolism 46533801 15.4% (150) 15.4% (150)

Anaerobic 

aquatic

metabolism

46533801 0.7% (56) 0.5 (120)

N

N

N

OH

NH NH
16

Code Name/ Synonym Chemical Name(s) Chemical Structure Study Type Ref.

(MRID)

Maximum(s) 

%AR1 (day)

Final %AR 

(last detection

day or study 

length)

CO2

CAS No: 124-38-9

SMILES String: C(=O)=O

Aerobic soil 

metabolism 46533801 27.4-28.9%(120-171) 27.4% (171)

Anaerobic soil 

metabolism 46533801 1.2% (150) 1.2% (150)

1 AR = Percentage of Applied Radioactivity; 2 = To be included in the ERA.
17

4. Ecological Effects Summary

Table 3 and Table 4 provide summaries of the toxicity endpoints for aquatic and 

terrestrial organisms, respectively. These values represent the most sensitive species

tested within each taxon to characterize potential acute and chronic effects of ametryn. In 

addition, the tables provide a preliminary overview of the potential acute toxicity of 

ametryn, by providing the acute toxicity classifications.

Based on the most sensitive toxicity endpoints, ametryn is classified as moderately toxic 

to freshwater fish (and aquatic-phase amphibians for which fish serve as surrogates) and 

slightly toxic to freshwater invertebrates on an acute exposure basis. Chronic toxicity 

studies with freshwater fish indicated reduced growth as the most sensitive measurement 

endpoint. Chronic exposure to freshwater invertebrates resulted in reduced reproduction.

Ametryn is classified as moderately toxic to estuarine/marine fish and invertebrates on an 

acute exposure basis. Chronic toxicity data are not available for ametryn for 

estuarine/marine fish, and previous estimates of chronic toxicity were based on acute-tochronic ratios derived using toxicity data for freshwater species. Chronic toxicity data for 

estuarine/marine invertebrates indicated reduced growth and reproduction. Compared to 

freshwater invertebrates, estuarine/marine invertebrates exhibited toxicity values an order

of magnitude less (more toxic).

Toxicity testing with aquatic plants indicated over a 500-fold difference in the sensitivity

of vascular plants compared (NOAEC=0.002 mg/L) to non-vascular algae (NOAEC=1.14 

mg/L). 

Ametryn is classified as practically non-toxic to birds (and to terrestrial-phase 

amphibians and reptiles for which birds serve as surrogates) on both an acute oral and 

subacute dietary exposure basis; the compound is slightly toxic to mammals on an acute 

exposure basis. Chronic exposure to ametryn resulted in reduced growth and 

reproduction in birds and reduced growth in mammals.

Ametryn is classified as practically non-toxic to honeybees (Apis mellifera) on an acute 

contact exposure basis.

Terrestrial plant seedling emergence showed oat and cucumber as the most sensitive 

monocot and dicot, respectively. Vegetative vigor showed onion and cucumber as the 

most sensitive monocot and dicot, respectively. 
18

Table 3. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 

Ametryn

Taxonomic 

Group

Study 

Type Surrogate Species

Toxicity Value

(all units in terms 

of measured 

active ingredient)

Acute 

Toxicity 

Classification

Source Classification

Freshwater 

fish1

Acute

Rainbow Trout

(Oncorhynchus 

mykiss)

LC50 = 3.6 mg/L Moderately 

toxic

MRID 

42861602 Acceptable

Chronic 

(Early 

LifeStage)

Fathead Minnow 

(Pimephales 

promelas)

NOAEC = 0.7 

mg/L

LOAEC = 1.4 

mg/L

Effects: reduced 

growth

--

MRIDs 

41189703, 

42325203

Acceptable

Freshwater 

invertebrates

Acute Water Flea

(Daphnia magna) LC50 = 28 mg/L Slightly toxic MRID 

40995806 Acceptable

Chronic Water Flea

(Daphnia magna)

NOAEC = 0.24 

mg/L

LOAEC = 0.32 

mg/L

Effects: 

reproduction, 

female body 

length, male dry 

body weight, 

female dry body

weight

--

MRID 

41189702, 

42325202

Supplemental2

Estuarine/

marine fish Acute

Sheepshead 

Minnow 

(Cyprinodon 

variegatus)

LC50 = 5.8 mg/L Moderately 

toxic

MRID 

41114902 Acceptable

Estuarine/

marine 

invertebrates

Acute

Mysid 

(Americamysis 

bahia)

LC50 = 2.3 mg/L Moderately 

toxic

MRID 

41114901 Acceptable

Chronic

Mysid 

(Americamysis 

bahia)

NOAEC = 50 μg/L

LOAEC = 97 μg/L

Effects: male and 

female body 

weight, female 

body length, 

number of female 

offspring, number 

of offspring per 

reproductive day

-- MRID

47399001 Acceptable

Aquatic 

plants and 

algae

Vascular Duckweed

(Lemna gibba)

NOAEC = 0.002 

mg/L

EC50 = 0.013 mg/L

-- MRID 

47399002 Acceptable

Nonvascular

Green Algae 

(Pseudokirchneriell

a subcapitata

formerly 

Selenastrum 

capricornutum)

NOAEC = 1.14

μg/L

EC50 = 3.67 μg/L

-- MRID 

40995810 Supplemental3

1 Freshwater fish represent surrogates for aquatic-phase amphibians. 2 The study was classified as supplemental due to no statistically significance difference in length between the solvent 

control and any of the treatments.
19

3 MRID 40995810 is an acceptable study. However, in addition to this study, additional studies are required to fulfill 

guideline 850.4500.

Table 4: Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 

Ametryn

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value

(all units in 

terms of 

measured active 

ingredient)

Acute 

Toxicity 

Classification

Source Classification

Birds1

Acute

Bobwhite 

Quail 

(Colinus 

virginianus)

LD50 = >2250 

mg/kg-bw

Practically 

Non-toxic

MRID

40995801 Acceptable

Subacute 

dietary

Mallard Duck

(Anas 

platyrhynchos)

LD50 = >5620 

mg/L

NOAEC= <562 

mg/L

Practically 

Non-toxic

MRID

40995802 Acceptable

Subacute 

dietary

Bobwhite 

Quail 

(Colinus 

virginianus)

LD50 = >5620 

mg/L

NOAEC = 1780 

mg/L

Practically

Non-toxic

MRID

40995803 Acceptable

Chronic

Mallard Duck

(Anas 

platyrhynchos)

NOAEC = 300 

mg/kg-diet

LOAEC = 900 

mg/kg-diet

Effects: Adult 

body weight, eggs 

laid, cracked eggs, 

offspring 

survivors

-- MRID 

41547602 Acceptable

Chronic

Northern 

bobwhite 

quail

(Colinus 

virginianus)

NOAEC = 300 

mg/kg-diet

LOAEC = 900 

mg/kg-diet

Effects: Adult 

body weight, egg 

production

-- MRID 

41547601 Acceptable

Mammals

Acute 

oral

Laboratory 

rat 

(Rattus 

norvegicus)

LD50 = 1356 

mg/kg-bw (males)

LD50 = 1009 

mg/kg-bw

(females)

Slightly Toxic MRID

40995814 Acceptable

Chronic

Laboratory 

rat 

(Rattus 

norvegicus)

NOAEL = 14 

mg/kg/day (males)

14-26 mg/kg/day 

(females)

LOAEL = 131 

mg/kg/day (males)

134-138 mg/kg/day 

(females)

-- MRID

40349905 Acceptable

Insects Acute 

contact

Honey bee 

(Apis 

mellifera L.)

LD50 = >100 

μg/bee

Practically 

non-toxic

MRID

40995811 Acceptable
20

Taxonomic 

Group

Study 

Type

Surrogate 

Species

Toxicity Value

(all units in 

terms of 

measured active 

ingredient)

Acute 

Toxicity 

Classification

Source Classification

Terrestrial 

Plant 

Toxicity

Tier II:

Seedling 

emergence

Monocot: oat

21-day EC25 = 

0.083 lb/A

21-day NOEC = 

0.05 lb/A

(based on dry 

weight)

-- MRID

40995808 Acceptable

Dicot: 

cucumber7

21-day EC05 = 

0.0002 lb/A

21-day EC25 = 

0.0027 lb/A

21-day NOEC = 

<0.002 lb/A

(based on % of 

seedlings 

emerged)

Terrestrial 

Plant 

Toxicity

Tier II

Vegetative 

vigor

Monocot: 

onion

21-day EC25 = 

0.105 lb/A

21-day NOEC = 

0.05 lb/A

(based on dry 

weight)

-- MRID

40995809 Acceptable

Dicot: 

lettuce8

28-day EC05 = 

0.001 lb/A

28-day EC25 = 

0.006 lb/A

28-day NOEC = 

< 0.006 lb/A

(based on dry 

weight) 1 Birds represent surrogates for terrestrial-phase amphibians and reptiles.

Since the NOEC was greater than the EC25, a EC05 was calculated

In 2007, EPA granted a waiver request for an estuarine/marine fish early life stage 

toxicity test (guideline 850.1400)9. EFED determined that although there was

uncertainty regarding the use of the acute-to-chronic ratio (ACR), the use of the ACR did 

not result in an RQ that was above the LOC.

4.1 Toxicity of Ametryn Transformation Products

In addition to parent ametryn, available environmental fate data indicate that the 

transformation products GS-11354, GS-11355, NOA 423271, NOA 428383, NOA 

 7 The IC05 value was calculated because the NOEC was non-definitive and approximately the value of the 

EC25. The EC05 is required for endangered species assessments. 8 The IC05 value was calculated because the NOEC was non-definitive and approximately the value of the 

EC25. The EC05 is required for endangered species assessments. 9 EFED Response to Waiver Request for Estuarine/Marine Fish Early Life Stage Study and Aerobic 

Aquatic Metabolism Study. Date: 09/15/2007. DP Barcode: D342463.
21

438707, G 34048, GS-17794 may be present in the environment following use of 

ametryn. In the absence of toxicity data, predicted acute and chronic toxicity values for 

the major transformation products of ametryn were estimated using EPA’s ECOSAR 

tool (v 1.1)10 which is based on quantitative structure activity relationships (QSAR) for 

effects on fish, daphnids, and green algae. Predicted toxicity values were also generated 

for parent ametryn and compared to observed endpoints from registrant-submitted studies 

to assess confidence in ECOSAR predictions of the toxicity of ametryn’s transformation 

products. ECOSAR-predicted and observed toxicity values for ametryn and its major 

transformation products are provided in Table 5. If available, observed toxicity 

endpoints for transformation products of other triazines that are closely related (i.e., have 

similar structures) to ametryn transformation products were also examined.

4.1.1 ECOSAR-Predicted vs. Observed Toxicity Endpoints Relative to 

Parent Ametryn

ECOSAR-predicted toxicity values for parent ametryn were roughly an order of 

magnitude less (more toxic) than measured toxicity endpoints for daphnids and mysids. 

In contrast, ECOSAR predicted toxicity values for parent ametryn were approximately an 

order of magnitude greater (less toxic) than the observed toxicity endpoint for freshwater 

and estuarine/marine fish and green algae. Other triazine compounds exhibited similar 

ECOSAR-predicted toxicity values. Toxicity values for parent prometon were 1-2 orders 

of magnitude lower than observed prometon toxicity endpoints for fish, daphnids, and 

mysids, and were roughly 3 times less than the observed toxicity endpoint for green 

algae. 

GS-11354 and GS-11355

While the basic structure is similar to ametryn, de-ethylation from the 2-amino group of

the parent produces GS-11354. GS-11354 is also a transformation product of other 

triazine herbicides including prometryn. GS-11355, de-isopropyl ametryn, also has a

structure similar to ametryn with the isopropyl group absent from the 4-amino moiety. 

The ECOSAR-estimated toxicity values indicate that both GS-11354 and GS-11355 are

less toxic than parent ametryn to all aquatic taxa except for green algae. Neither of these 

transformation products will be considered stressors of concern in the Registration 

Review ecological risk assessment.

NOA 423271

Oxidation of the methylthio group of ametryn (-SCH3) to a sulfoxide (-SOCH3) results in 

the minor degradation product NOA 423271 (ametryn sulfoxide). The ECOSARestimated toxicity values indicate that the observed toxicity values are lower (indicating 

higher toxicity) than observed ametryn values for marine fish and invertebrates, and 

freshwater invertebrates. ECOSAR values were greater (less toxic) than parent ametryn 

for freshwater fish and green algae. This compound is formed through aerobic soil 

metabolism, but may be reduced back to the parent form under certain environmental 

 10 http://www.epa.gov/oppt/newchems/tools/21ecosar.htm
22

conditions. Therefore, EPA will consider it a stressor of concern for ecological risk, and 

will assume that the toxicity of this degradation product is equal to that of the parent. 

NOA 428383

In this degradate the methyl group in the 6-methylthio moiety of ametryn has been 

replaced by three oxygen atoms with a net negative charge. ECOSAR-estimated toxicity

endpoints for this degradate predict it to be less toxic than the parent ametryn. This 

degradate is formed by aerobic soil metabolism, but may be reduced back to the parent 

under certain environmental conditions. Therefore, EPA will consider NOA 428383 as a 

stressor of concern for ecological risk. The toxicity of this degradation product will be 

assumed equal to that of the parent. 

NOA 438707

Degradate NOA 438707 is formed from a hydroxyl group substitution of the ametryn 4-

methylthio group, and modification of the 2-ethyamino group to a carboxylic acid (acetic 

acid). The ECOSAR-estimated toxicity values for this degradate indicate it is less toxic

than the parent ametryn. EPA will not consider NOA 438707 as a stressor of concern for 

risk assessment.

G 34048 (2-hydroxy atrazine)

The substitution of the 2-methylthio group to a hydroxyl group results in the formation of 

the major transformation product G 34048, known as 2-hydroxy atrazine. ECOSARestimated toxicity values indicate that G 34048 is less toxic than parent ametryn to all 

aquatic taxa excluding green algae. EPA will not consider G 34048 as a stressor of 

concern for risk assessment.

GS-17794 (des-ethyl hydroxy atrazine)

Removal of an ethylamino group from parent ametryn, and replacement of the thiomethyl 

group with a hydroxyl group forms GS-17794, which was only present as a minor 

transformation product (≤1.7%) in two soil metabolism studies. GS-17794 is also a 

degradate of atrazine (i.e., deethylhydroxyatrazine; OIAT/ DHEA), propazine, prometon, 

and prometryn. The ECOSAR-estimated toxicity values indicate that GS-17794 is less

toxic than parent ametryn to all taxa evaluated. Therefore, GS-17794 will not be 

considered a stressor of concern in the Registration Review ecological risk assessment.
23

Table 5: ECOSAR-predicted and Observed Toxicity Values for Ametryn and Major 

Degradates

Taxon Exposure 

duration

Toxicity Value (mg/L)

Observed ECOSAR-Predicted (Using ECOSAR Class Triazines)

Ametryn GS-11354 GS-11355 NOA 423271

FW fish 96-hr LC50

Chronic value

3.6

0.7

8.55

0.24

58.5

1.53

124

3.18

4.63

0.13

SW fish 96-hr LC50

Chronic value

5.8

No data

9.26

0.91

43.0

0.67

78.2

3.92

5.7

0.65

Daphnid 48-hr EC/LC50

Chronic Value

28

0.24

9.37

0.37

34.3

1.44

56.5

2.45

6.25

0.24

Mysid 

shrimp

96-hr LC50

Chronic value

2.3

0.05

1.33

0.18

2.61

2.96

11.7

9.02

0.81

0.07

Green 

algae

96-hr EC50

Chronic value

0.001

No data

0.05

0.04

0.12

0.07

0.18

0.09

0.04

0.03

Taxon Exposure 

duration

Toxicity Value (mg/L)

ECOSAR-Predicted (Using ECOSAR Class Triazines)

NOA 428383 NOA 438707 G 34048 GS-17794

FW fish 96-hr LC50

Chronic value

4.88e005

10858

11129

271

83.6*

2.16

660

13.8

SW fish 96-hr LC50

Chronic value

1.06e005

1439

4810

152

57.3*

3.2

261

9.02

Daphnid 48-hr EC/LC50

Chronic Value

39782

2056

2758

127

43.7*

1.87

156

7.11

Mysid 

shrimp

96-hr LC50

Chronic value

17100

4.17e005

738

1929

8.5*

4.96

39.7

81.7

Green 

algae

96-hr EC50

Chronic value

46.8

9.78

6.18

2.23

0.15

0.08

0.38

0.14

FW = freshwater; SW = saltwater

* Asterisk designates that chemical may not be soluble enough to measure this predicted effect. If the 

effect level exceeds the water solubility by 10x, typically no effects at saturation (NES) are reported.
24

4.2. Ecological Incidents

The ecological incident information system (EIIS) is an OPP database that houses 

ecological incidents that have been reported to the Agency. When available, EIIS 

includes date and location of an incident, type and magnitude of effects observed in 

various species, use(s) of pesticides known or suspected of contributing to the incident, 

and results of any chemical residue analysis or other analyses conducted during incident 

investigation. EIIS incidents are categorized according to the certainty that the incident 

resulted from pesticide exposure. The Avian Monitoring System (AIMS)11 is a database 

administered by the American Bird Conservancy that contains publicly available data on 

reported avian incidents involving pesticides. Many of the incidents listed in this 

database are also in the EIIS. EIIS returned no major incidents. AIMS was also 

searched on December 5, 2012 and revealed no incidents to birds associated with 

ametryn. 

In the Aggregate Incident Reports there were no incidents attributed to ametryn

(Appendix C). Because of uncertainties regarding the extent to which incidents are 

reported to EPA, the absence of incident reports cannot be construed as the absence of 

incidents. During the risk assessment associated with Registration Review of ametryn, 

these databases will be checked again and any new incidents will be evaluated to 

determine if they represent current use patterns of ametryn. 

5. Exposure Pathways of Concern

For a pesticide to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. An exposure pathway is the means by which a 

pesticide moves in the environment from a source to an ecological receptor. For an 

ecological pathway to be complete, it must include a source, a release mechanism, an 

environmental transport medium, a point of exposure for ecological receptors, and a 

feasible route of exposure.

The environmental fate properties of ametryn indicate the following transport 

mechanisms for potential exposure to aquatic and terrestrial organisms:

• Direct contact

• Spray drift

• Runoff

• Consumption of contaminated food (sprayed food or treated seeds)

• Consumption of contaminated water

• Root uptake (plants)

 11 http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/login.cfm
25

For terrestrial invertebrates, the major routes of exposure to ametryn are considered to be 

direct contact as a result of direct application and spray drift and dietary ingestion of 

plants, animals, and/or soil that have ametryn residues as a result of direct application, 

spray drift, and runoff. 

For aquatic animal species, the major route of exposure to ametryn is considered to be 

uptake via the respiratory surface (gills) or the integument from surface water/sediment 

that has ametryn residues as a result of spray drift and runoff.

For terrestrial (upland and semi-aquatic) non-target plants, the major routes of exposure 

to ametryn are considered to be direct contact as a result of direct application and spray 

drift and root uptake via soil contaminated via spray drift and runoff.

For aquatic plants, the major routes of exposure to ametryn are considered to be uptake 

from surface water/sediment containing ametryn residues as a result of spray drift, runoff, 

and leaching to groundwater from soil.

Drinking water and inhalation exposure pathways were screened using the SIP 

(Screening Imbibition Program) and STIR (Screening Tool for Inhalational Risk) 

programs. SIP results showed chronic exposure to the ametryn through drinking water

represents a potential concern for mammals and birds (LOC exceedances expected) 

(Appendix D). STIR found ametryn inhalation exposures to not likely be significant to

avian species and mammals (no LOC exceedances are expected via this potential route of 

exposure) (Appendix E). SIP and STIR are described in detail at: 

http://www.epa.gov/oppefed1/models/terrestrial/index.htm.

6. Analysis Plan

In order to address the risk hypothesis, the potential for adverse effects on the 

environment is estimated. The use, environmental fate, and ecological effects of ametryn

are characterized and integrated to assess the risks. This is accomplished using a risk 

quotient (ratio of exposure concentration to effects concentration) approach. Although 

risk is often defined as the likelihood and magnitude of adverse ecological effects, the 

risk quotient-based approach does not provide a quantitative estimate of likelihood and/or 

magnitude of an adverse effect. However, as outlined in the Overview Document 

(USEPA 2004), the likelihood of effects to individual organisms from particular uses of 

ametryn is estimated using the probit dose-response slope and either the level of concern 

(discussed below) or actual calculated risk quotient value.

This analysis plan will be revisited and may be revised depending upon the information 

submitted by the public in response to the opening of the Registration Review docket for 

ametryn.

6.1. Stressors of Concern
26

Ecological Risk Assessment

Comparative toxicity modeling conducted in Section 4 indicates that the ametryn 

degradate NOA 423271 (ametryn sulfoxide) is potentially as toxic as parent ametryn to 

aquatic organisms. Additionally, both NOA 423271 and NOA 428383 are formed by 

aerobic soil metabolism, but may be reduced back to the parent form under certain 

environmental conditions. In the absence of data on the toxicity of NOA 423271 and 

NOA 428383, the conservative method of considering the stressors of concern in total, 

i.e., the total toxic residue (TTR) approach will be used. Therefore, these two degradates 

will be included as residues of concern for modeling aquatic exposure estimates for 

ecological risk assessment. For terrestrial assessments, exposure will be based on the 

parent compound alone since there is not a defined process for including specific 

degradates in terrestrial exposure estimates using the current model (TREX).

The stressors of concern are as follows:

• Terrestrial environment: parent ametryn

• Aquatic environment: parent ametryn, degradate NOA 423271, and degradate 

NOA 428383

The decision whether to include unextracted residues in TTR estimates will be 

determined once the additional requested aerobic soil metabolism data have been 

reviewed as part of the Registration Review process. 

Drinking Water 

HED has determined that an updated drinking water assessment (DWA) is not needed to 

support future human health dietary risk assessments for ametryn. 

6.2. Measures of Exposure

EFED will use standard available models (identified in Table 6) to evaluate potential 

exposures to aquatic and terrestrial organisms as described at 

http://www.epa.gov/pesticides/science/models_db.htm. 

Aquatic exposure estimates will be based on estimated environmental concentrations 

(EECs) in a waterbody that is considered vulnerable and representative of static ponds 

and low-order streams. Terrestrial exposure will be estimated using a model (TREX; 

version 1.5) that assumes direct application to a variety of avian, mammalian and 

reptilian food items. Exposure to terrestrial plants will be estimated using a model 

(TerrPlant version 1.2) that assumes ametryn drifts or moves with runoff to adjacent 

habitats. For more information on the various models that will be used in the risk 

assessment see the links as outlined in Table 6.
27

Two spray drift models, AgDISP and AgDRIFT, are used to assess exposures of aquatic 

and terrestrial organisms to ametryn deposited in terrestrial and aquatic habitats by spray 

drift. AgDRIFT (version 2.1.1; dated 03/07/2012) is the model most commonly used to 

simulate spray drift into terrestrial and aquatic environments. AgDISP (version 8.26; 

dated 03/07/2012) is used when a parameter needs to be modeled that is not available in 

AgDRIFT. Spray drift analysis will be an important part of the analysis in defining the 

potential area of effects for endangered species.

A “downstream dilution” model (under development) may be used to identify waters 

downstream from a use area that may have EECs high enough to result in a risk concern. 

Such an analysis would be used to define potential areas of effects for listed species. 

 

Table 6. List of the various models and the related taxa for which the models will be 

used.

Environment Taxa of 

Concern Model(s) Link

Aquatic

Fish/ 

Invertebrates

/Plants

PRZM/EXAMS http://www.epa.gov/oppefed1/models/

water/

Terrestrial

Vertebrate 

TREX (dietary 

item)

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

errestrial/trex/trex_v1_5_webversion.xl

sm

AGDISP (Spray 

drift)

http://www.continuumdynamics.com/pr-agdisp.html

Plant

TerrPlant (Run-off) http://www.epa.gov/oppefed1/models/t

errestrial/index.htm#terrplant

AgDRIFT (Spray 

drift)

http://www.agdrift.com/AgDRIFt2/Do

wnloadAgDrift2_0.htm

AGDISP (Spray 

drift)

http://www.continuumdynamics.com/pr-agdisp.html

6.3. Measures of Effect

Toxicity data presented in Section 4 of this problem formulation will be used to calculate 

risk quotients. Any additional information submitted by the registrant or found in the 

open literature prior to conduct of the risk assessment will also be considered. The open 

literature studies are identified using EPA’s ECOTOXicology database (ECOTOX) 

(USEPA 2007), which employs a literature search engine for locating chemical toxicity 

data for aquatic life, terrestrial plants, and wildlife. The evaluation of both sources of 

data can also provide insight into the direct and indirect effects of pesticides on biotic 

communities from loss of species that are sensitive to the chemicals and from changes in 

structure and functional characteristics of the affected communities.
28

6.4. Endangered Species Assessments

Consistent with its responsibility under the Endangered Species Act (ESA), the Agency 

will evaluate risks to listed species from registered uses of ametryn. These assessments 

will be conducted in accordance with standard EPA procedures and best professional

judgment. The process for evaluating potential risks to listed species is further described

in the Overview Document (USEPA 2004) athttp://www.epa.gov/oppfead1/endanger/litstatus/riskasses.htm. 

The assessment of effects associated with registrations of ametryn is based on an action 

area. The action area is considered to be the area directly or indirectly affected by the 

federal action, as indicated by the exceedance of Agency LOCs used to evaluate direct or 

indirect effects. The Agency’s approach to defining the action area under the provisions 

of the Overview Document (USEPA 2004) considers the results of the risk assessment 

process to establish boundaries for that action area with the understanding that exposures 

below the Agency’s defined LOCs constitute a no-effect threshold. For the purposes of 

this assessment, attention will be focused on the footprint of the action (i.e., the area 

where ametryn application occurs), plus all areas where offsite transport (i.e., spray drift, 

runoff, etc.) may result in potential exposure that exceeds the Agency’s LOCs. Specific 

measures of ecological effect that define the action area for listed species include any 

direct and indirect effects and/or potential modification of its critical habitat, including 

reduction in survival, growth, and reproduction as well as the full suite of sublethal 

effects available in the effects literature. Therefore, the action area extends to a point 

where environmental exposures are below any measured lethal or sublethal effect 

threshold for any biological entity at the whole organism, organ, tissue, and cellular level 

of organization. In situations where it is not possible to determine the threshold for an 

observed effect, the action area is not spatially limited and is assumed to be the entire 

United States. 

6.5. Endocrine Disruptor Screening Program (EDSP)

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential 

adverse outcomes from exposure to chemicals. Collectively, these studies include acute, 

subchronic and chronic toxicity, including assessments of carcinogenicity, neurotoxicity, 

developmental, reproductive, and general or systemic toxicity. These studies include 

endpoints which may be susceptible to endocrine influence, including effects on 

endocrine target organ histopathology, organ weights, estrus cyclicity, sexual maturation, 

fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For ecological 

hazard assessments, EPA evaluates acute tests and chronic studies that assess growth, 

developmental and reproductive effects in different taxonomic groups. As part of its 

reregistration decision, EPA reviewed these data and selected the most sensitive 

endpoints for relevant risk assessment scenarios from the existing hazard database. 

However, as required by FFDCA section 408(p), ametryn is subject to the endocrine 

screening part of the Endocrine Disruptor Screening Program (EDSP). 
29

EPA has developed the EDSP to determine whether certain substances (including 

pesticide active and other ingredients) may have an effect in humans or wildlife similar to 

an effect produced by a “naturally occurring estrogen, or other such endocrine effects as 

the Administrator may designate.” The EDSP employs a two-tiered approach to making 

the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays 

to identify the potential of a chemical substance to interact with the estrogen, androgen, 

or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening 

and are found to have the potential to interact with E, A, or T hormonal systems will 

proceed to the next stage of the EDSP where EPA will determine which, if any, of the 

Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to 

identify any adverse endocrine-related effects caused by the substance, and establish a 

dose-response relationship between the dose and the E, A, or T effect. 

Under Federal Food Drug and Cosmetic Act (FFDCA) section 408(p), the Agency must 

screen all pesticide chemicals for potential endocrine disruptor activity. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group 

of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. 

Ametryn is not among the group of 58 pesticide active ingredients on the initial list to be 

screened under the EDSP. Accordingly, as part of Registration Review, EPA will issue 

future EDSP orders/data call-ins, requiring the submission of EDSP screening assays for

ametryn. For further information on the status of the EDSP, the policies and procedures, 

the list of 67 chemicals, future lists, the test guidelines and the Tier 1 screening battery, 

please visit our website: http://www.epa.gov/endo/.

7. Preliminary Identification of Data Gaps

Several environmental effects and ecological effects studies on ametryn are needed to 

better assess the potential risk of exposure to non-target organisms. Tables 1, 3, and 4

summarized data that have been submitted for the parent compound. The following 

studies are recommended to reduce uncertainty in risk estimation and characterization of 

ametryn. 

7.1. Environmental Fate

Table 7 identifies environmental fate studies by Master Record Identification (MRID) 

number that provide data for each guideline requirement, as well as study classifications 

and whether or not further data are needed in order to support risk assessment. For the 

parent compound, data are needed for:

• aqueous photolysis (OCSPP Guideline 835.2240), 

• aerobic soil metabolism (OCSPP Guideline 835.4100), and 

• aerobic aquatic metabolism (OCSPP Guideline 835.4300). 
30

The submitted aqueous photolysis study (MRID 41169601; reclassified as not acceptable) 

failed to adequately show whether photodegradation was occurring, the rate of 

degradation, and which photodegradates might be formed. While the soil 

photodegradation study had similar deficiencies, the data for that study did indicate that 

photodegradation on soil would not be a significant fate pathway, thus new data are not 

likely to provide additional useful information for risk assessment. Additional aerobic 

soil metabolism data on three soils representative of the intended use areas are necessary 

to meet current data requirements. Analysis for the transformation products NOA 

423271, NOA 428383, and NOA 438707, which were not tested for in previously 

submitted studies, should be included. Aerobic aquatic metabolism data for two 

sediment/water systems are required. In the past, a default of two times the aerobic soil 

metabolism half-life was used for modeling. However, this is an inadequate estimate of 

metabolism rates in an aquatic environment where the parent may reform from NOA

423271 and NOA 428383, which are oxidized forms of ametryn that may be reduced 

back to parent in environmental conditions where the redox potential is below -148 mV.

The level at which these degradates may form is uncertain, as they were not monitored in 

all of the submitted metabolism studies.

Table 7. Submitted Environmental Fate Data for Ametryn

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Justification and Assumptions EPA 

will Make in Absence of Data 

835.2120 Hydrolysis 40995812 Acceptable No Not applicable

835.2240 Aqueous 

photolysis 41169601 Not acceptable 

(reclassified) Yes

Data are needed for modeling input and 

to clarify which transformation products

may form/transform in water.

835.2410 Soil photolysis 41169602 & 

41169603

Not acceptable 

(reclassified) No

Because the half-lives in the irradiated 

soils were near or greater than 100 days, 

the stability of ametryn to 

photodegradation on soil will be 

assumed for the fate characterization. 

Soil photolysis is expected to be less of 

a significant fate pathway for ametryn 

than aerobic soil metabolism. 

Photodegradation 

in air Waived -- No Not applicable

835.4100 Aerobic soil 

metabolism

41752401 Acceptable

Yes

Data are required for 3 additional soils 

representative of intended use areas. 

The transformation products NOA 

423271, NOA 428383, and NOA 

438707 should be included in the 

monitoring along with other potential 

transformation products.

46533801 Supplemental

255735 Not acceptable 

835.4200 Anaerobic soil 

metabolism

41752401 Acceptable

46533801 Supplemental No Not applicable

255735 Not acceptable
31

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Justification and Assumptions EPA 

will Make in Absence of Data 

835.4300 Aerobic aquatic 

metabolism No data -- Yes

EPA will assume stability in the absence 

of data. The use of 2X the aerobic soil 

metabolism half-life as a default input 

value in lieu of data will likely 

overestimate any potential degradation 

in an aquatic environment where the 

parent may reform from NOA 423271 

and NOA 428383, which are oxidized 

forms of ametryn that may be reduced 

back to parent in environmental 

conditions where the redox potential is 

below -148 mV. 

835.4400

Anaerobic 

aquatic 

metabolism

46533801 Supplemental

No Not applicable

42861603 Acceptable

835.1230

835.1240

Adsorption/ 

desorption and 

leaching

41169604 Acceptable 

41169605 Supplemental No _

40995813 Acceptable

835.1410 Volatility 

laboratory Waived -- No Not applicable

Field volatility Waived -- No Not applicable

835.6100 Terrestrial field 

dissipation

41872301

41872302

41752402

Supplemental No

TFD data requirement was waived in 

1991 in favor of a small-scale 

prospective groundwater study.

Groundwater

Monitoring

45629801

45870401 Not Classified Not at this 

time. _

Droplet Size 

Spectrum 41336801 Acceptable No Not Applicable

Drift field 

evaluation

41336802 

41268001 Not Acceptable No Spray Drift Task Force data are used for 

this data requirement.

835.6100

Environmental 

chemistry 

method in soil 

and sediment and 

water and 

associated ILV

No MRID 

(Report No. 

ECM0063SlS4)

Acceptable No Not Applicable

850.6100

Environmental 

chemistry 

method in water 

and associated 

ILV

No data -- Yes --
32

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct risk 

assessment?

Justification and Assumptions EPA 

will Make in Absence of Data 

850.1730 Fish 

bioconcentration 42061901 Acceptable No

Based on study results and a Kow of 4.3 

X 102 (log Kow = 2.6), ametryn residues 

are not expected to bioconcentrate in 

fish to a significant extent.

7.2. Ecological Effects

One ecological effects study on ametryn is needed to better assess the potential risk of 

exposure to non-target organisms. Tables 3 and 4 summarized data that have been 

submitted for the parent compound. The following studies are recommended to reduce 

uncertainty in risk estimation and characterization of ametryn:

• Algal and Cyanobacteria (Anabaena flos-aqua) Toxicity – (guidelines 

850.4500 and 850.4550) [3 Studies]

Data for aquatic non-vascular plant species are required under 40 CFR Part 158. No 

studies have been submitted for a freshwater diatom (e.g., Navicula pelliculosa), a marine 

diatom (e.g., Skeletonema costatum), or a cyanobacterium (e.g., Anabaena flos-aqua). 

Given that the 2005 RED (DP 316704) identified a risk concern for aquatic non-vascular 

plants, fulfilling this data requirement has a high potential to add value to the Registration 

Review risk assessment. 

Table 8 and 9 identify ecological effects studies by MRID that provide data for each 

guideline requirement, as well as study classifications and whether or not additional data 

are needed in order to support risk assessment. 

Table 8. Submitted Aquatic Ecological Effects Data for Ametryn

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct 

risk 

assessment?

Justification and 

Assumptions EPA will 

Make in Absence of 

Data 

850.1010

Freshwater 

invertebrate

acute toxicity

40995806 Acceptable No --

850.1025

850.1035

Saltwater 

invertebrate

acute toxicity

41114901 Acceptable

No -- 41114903, 

42325201 Acceptable

850.1075

Freshwater 

fish acute 

toxicity

42861601 Acceptable

No --

42861602 Acceptable

40995804 Supplemental

40995805 Supplemental

00116257 Acceptable
33

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct 

risk 

assessment?

Justification and 

Assumptions EPA will 

Make in Absence of 

Data 

00033309 Supplemental

00033706 Acceptable

850.1075 Saltwater fish 

acute toxicity 41114902 Acceptable No --

850.1300

Freshwater 

invertebrate

life cycle

41189702, 

42325202 Supplemental No

The study was classified 

as supplemental due to no 

statistically significance 

difference in length 

between the solvent 

control and any of the 

treatments. However, 

data can still be used for 

risk assessment.

850.1350

Saltwater 

invertebrate

life cycle

47399001 Acceptable No

850.1400

Freshwater 

fish

early-life 

stage

41189703,

42325203 Acceptable No --

850.1400

Saltwater fish 

early-life 

stage

Waiver request 

granted -- No --

850.1500 Fish life 

cycle No Data -- No

Although fish full lifecycle testing is currently 

required under 40 CFR

Part 158, chronic toxicity 

data are available for 

ametryn through a fish 

early life stage study that 

has been classified as 

acceptable. Therefore 

data for this study is not 

required at this time.

850.4400

Aquatic plant 

growth:

Tier II 

vascular 

plants

47399002 Acceptable No --

850.4500 Aquatic Plant 

Growth:

40995810

(Green Algae) Acceptable No --
34

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed to 

conduct 

risk 

assessment?

Justification and 

Assumptions EPA will 

Make in Absence of 

Data 

Tier II algae

No data for 

freshwater 

diatom

-- Yes

Data for aquatic nonvascular plant species 

including a freshwater 

diatom are required under 

40 CFR Part 158.

No data for 

marine diatiom -- Yes

Data for aquatic nonvascular plant species 

including a marine diatom 

are required under 40 

CFR Part 158.

850.4550

Aquatic Plant 

Growth 

(aquatic nonvascular 

plant: 

cyanobacteria 

toxicity)

No data -- Yes

Data for aquatic nonvascular plant species 

including a

cyanobacterium are 

required under 40 CFR 

Part 158.

Table 9. Submitted Terrestrial Ecological Effects Data for Ametryn

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Justification and 

Assumptions EPA will Make 

in Absence of Data 

850.2100

Avian oral 

toxicity

(upland game 

bird)

40995801 Acceptable No --

Avian oral 

toxicity 

(passerine)

No data -- No

While passerine testing is now 

required under 40 CFR Part 

158, available data indicate that 

ametryn is practically nontoxic 

to birds on an acute oral and 

subacute dietary exposure basis 

and there are no incident data to 

indicate that passerine testing 

should be required at this time.

850.2200 Avian dietary 

toxicity

40995802 Acceptable

No -- 40995803 Acceptable

00080617 Acceptable

00115791 Acceptable

850.2300 Avian 

reproduction

41547602 Acceptable

No -- 41547601 Acceptable
35

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are data 

needed for 

risk 

assessment?

Justification and 

Assumptions EPA will Make 

in Absence of Data 

850.3020

Honey bee 

acute contact 

toxicity

40995811 Acceptable No --

850.4100

Seedling 

emergence

and seedling 

growth

40995808 Acceptable No --

850.4150 Vegetative 

vigor 40995809 Acceptable No --

8. References

Davis, A., S. Lewis, Z. Bainbridge, J. Brodie and E. Shannon. 2008. Pesticide Residues 

in Waterways of The Lower Burdekin Region: Challenges in Ecotoxicological 

Interpretation of Monitoring Data. Australasian Journal of Ecotoxicology Vol. 

14, Pp. 89-108, 2008.

Food and Agriculture Organization of the United Nations. 2000. FAO PESTICIDE 

DISPOSAL SERIES 8. Assessing Soil Contamination: A Reference Manual. 

Appendix 2. Parameters of pesticides that influence processes in the soil. 

Editorial Group, FAO Information Division. Rome.

Goring, C.A.I., D.A. Laskowki, J.H. Hamaker, and R.W. Meikle. 1975. Principles of 

pesticide degradation in soil. Pages 135-172 in (R. Haque and V.H. Freed, eds.) 

Environmental dynamics of pesticides. Plenum Press, New York.

SFWMD, 2009. Pesticide Surface Water and Sediment Quality Report March 2008 

Sampling Event. South Florida Water Management District. August 2009.

SFWMD, 2012. Pesticide Surface Water Quality Report March 2011 Sampling Event. 

South Florida Water Management District. 2012.

Sposito, G. 1989. The Chemistry of Soils. 277 pp. New York, Oxford: Oxford University 

Press.

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of 

Pesticide Programs. United States Environmental Protection Agency (USEPA). 

Environmental Fate and Effects Division. Office of Pesticide Programs. 

Available at http://www.epa.gov/espp/consultation/ecorisk-overview.pdf

(Accessed January 7, 2013).
36

USEPA. 2005a. Drinking Water Exposure Assessment for Proposed Reregistration of

Ametryn Use on Corn, Pineapple and Sugarcane (Revised). DP Barcode 307097. 

United States Environmental Protection Agency (USEPA). Environmental Fate 

and Effects Division. Office of Pesticide Programs. May 2005.

USEPA. 2005b. Environmental Fate and Ecological Risk Assessment for the Reregistration of Ametryn. DP Barcode 316704. United States Environmental 

Protection Agency (USEPA). Environmental Fate and Effects Division. Office of 

Pesticide Programs. June 2005.

USEPA. 2005c. PRZM 3.12.2: Users Manual. Online at:

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

USEPA. 2005d. EXAMS 2.98.04.06: Users Manual. Online at:

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

USEPA. 2006. Water models PE Version 5: User Manual. Online at:

http://www.epa.gov/oppefed1/models/water/pe5_user_manual.htm 

USEPA. 2007. 40 CFR Part 158. Pesticides; Data Requirements for Conventional 

Chemicals: Final Rule. 72 FR 60934. October 26, 2007.

USEPA. 2012. BEAD Chemical Profile for Registration Review: Ametryn (080801). 

Memorandum From S. Ratnayake, S. Haddad, and A. Lee to Molly Clayton. 

Biological and Economic Analysis Division to Pesticide Reevaluation Division. 

March 21, 2012.

USFWS/NMFS. 1998. Endangered Species Consultation Handbook: Procedures for 

Conducting Consultation and Conference Activities Under Section 7 of the 

Endangered Species Act. Final Draft. United States Fish and Wildlife Service 

(USFWS) and National Marine Fisheries Service (NMFS). Available at:

http://www.fws.gov/endangered/consultations/s7hndbk/s7hndbk.htm
37

9. Appendices

Appendix A. Submitted Environmental Fate and Effects Studies

SUBMITTED FATE STUDIES (as of 2/6/13)

Hydrolysis

23963 Burkhard, N. (1976) Project Report 17/76: Hydrolysis of 2-Chloro- and 2-Methylthio-4,6-

bis-(alkylamino)-s-triazines under Laboratory Conditions. (Unpublished study received

Apr 27, 1977 under 100-588; prepared by Ciba-Geigy, Ltd., submitted by Ciba-Geigy

Corp., Greensboro, N.C.; CDL:229641-A)

24013 Pape, B.E.; Zabik, M.J. (1970) Photochemistry of bioactive compounds: Photochemistry of selected 

2-Chloro- and 2-Methylthio- 4,6-di-(alkylamino)-s-triazine herbicides. Journal of

Agricultural and Food Chemistry 18(2):202-207. (Also in unpublished submission received

Aug 28, 1975 under 100-437; submitted by Ciba-Geigy Corp., Greensboro, N.C.;

CDL:221042-N)

24328 Burkhard, N.; Guth, J.A. (1976) Photodegradation of Atrazine, Atraton and Ametryne in

aqueous solution with Acetone as a photosensitiser. Pesticide Science 7(1):65-71. (Also in

unpublished submission received Jul 19, 1978 under 201-403; submitted by Shell Chemical

Co., Washington, D.C.; CDL:234469-C)

24329 Ruzo, L.O.; Zabik, M.J.; Schuetz, R.D. (1973) Photochemistry of bioactive compounds.

Kinetics of selected s-Triazine in solution. Journal of Agricultural and Food Chemistry 21

(6):1047- 1049. (Also in unpublished submission received Jul 19, 1978 under 201-403;

submitted by Shell Chemical Co., Washington, D.C.; CDL:234469-D)

27855 Burkhard, N. (1976) Hydrolysis of 2-Chloro- and 2-Methylthio-4,6- bis-(alkylamino-striazines under 

Laboratory conditions: Project Report 17/76. (Unpublished study received

Jul 17, 1978 un- der 100-541; prepared by Ciba-Geigy, Ltd., submitted by Ciba- Geigy

Corp., Greensboro, N.C.; CDL:234454-A)

63054 Burkhard, N. (1976) Hydrolysis of 2-Chloro- and 2-Methylthio-4,6- bis-(alkylamino)-striazines 

under Laboratory Conditions: Proj- ect Report 17/76. (Unpublished study received

Nov 18, 1980 un- der 40810-2; prepared by Ciba-Geigy, Ltd., Switzerland, submit- ted by

Ciba-Geigy Corp., Ardsley, N.Y.; CDL:243792-D)

147564 Balu, K. (1984) Summary of Environmental Fate Studies Ametryn: Report No: EIR-84028. 

Unpublished study prepared by Ciba-Geigy Corp. 13 p.

40995812 Spare, W. (1988) Hydrolysis of carbon 14|-Ametryn: Final Report: Project No. 12135. 

Unpublished study prepared by Agrisearch Inc. 94 p.

92002035 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995812. AmetrynHydrolysis Study: Project 12135. Prepared by AGRISEARCH, INC. 11 p.

Bibliography Page 29 of 66 

161-2 Photodegradation in water

146397 Halama, P.; Balu, K.; Hofberg, A. (1972) Photolysis of Ametryne in Aqueous Solution

under Natural and Artificial Sunlight Condi- tions: Report No: GAAC-72117. Unpublished
38

study prepared by Ciba-Geigy Corp. 14 p.

147564 Balu, K. (1984) Summary of Environmental Fate Studies Ametryn: Report No: EIR-84028. 

Unpublished study prepared by Ciba-Geigy Corp. 13 p.

41169601 Spare, W. (1989) Aqueous Photolysis of ?carbon 14|-Ametryn: Final Report: Study No. 12136. 

Unpublished study prepared by Agri- search Inc. 125 p.

92002036 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169601. AmetrynAqueous Photolysis Study: Project 12136. Prepared by AGRISEARCH, INC. 16 p.

161-3 Photodegradation on soil

146398 Burkhard, N. (1979) Photolysis of Ametryn (Gesapax) on Soil Sur- faces under Artificial

Sunlight Conditions: Project Report 07/ 79. Unpublished study prepared by Ciba-Geigy

Ltd. 10 p.

147564 Balu, K. (1984) Summary of Environmental Fate Studies Ametryn: Report No: EIR-84028. 

Unpublished study prepared by Ciba-Geigy Corp. 13 p.

41169602 Spare, W. (1989) Soil Photolysis of Ametryn by Natural Sunlight at Vero Beach, Florida:Final 

Report: Study No. 12137. Unpublished study prepared by Arisearch Inc. 85 p.

41169603 Spare, W. (1989) Soil Photolysis of Ametryn by Natural Sunlight and Artificial Light:

Final Report: Study No. 12137. Unpublished study prepared by Agrisearch Inc. 141 p.

92002037 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169603 and Related 

MRIDs 41169602. Ametryn-Soil Photolysis Study: Project 12137. Prepared by

AGRISEARCH, INC. 14 p.

162-1 Aerobic soil metabolism

146397 Halama, P.; Balu, K.; Hofberg, A. (1972) Photolysis of Ametryne in Aqueous Solution

under Natural and Artificial Sunlight Condi- tions: Report No: GAAC-72117. Unpublished

study prepared by Ciba-Geigy Corp. 14 p.

147564 Balu, K. (1984) Summary of Environmental Fate Studies Ametryn: Report No: EIR-84028. 

Unpublished study prepared by Ciba-Geigy Corp. 13 p.

41169601 Spare, W. (1989) Aqueous Photolysis of ?carbon 14|-Ametryn: Final Report: Study No. 12136. 

Unpublished study prepared by Agri- search Inc. 125 p.

92002036 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169601. AmetrynAqueous Photolysis Study: Project 12136. Prepared by AGRISEARCH, INC. 16 p.

146398 Burkhard, N. (1979) Photolysis of Ametryn (Gesapax) on Soil Sur- faces under Artificial

Sunlight Conditions: Project Report 07/ 79. Unpublished study prepared by Ciba-Geigy

Ltd. 10 p.

147564 Balu, K. (1984) Summary of Environmental Fate Studies Ametryn: Report No: EIR-84028. 

Unpublished study prepared by Ciba-Geigy Corp. 13 p.

41169602 Spare, W. (1989) Soil Photolysis of Ametryn by Natural Sunlight at Vero Beach, Florida: Final 

Report: Study No. 12137. Unpublished study prepared by Arisearch Inc. 85 p.

41169603 Spare, W. (1989) Soil Photolysis of Ametryn by Natural Sunlight and Artificial Light:

Final Report: Study No. 12137. Unpublished study prepared by Agrisearch Inc. 141 p.
39

92002037 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169603 and Related 

MRIDs 41169602. Ametryn-Soil Photolysis Study: Project 12137. Prepared by

AGRISEARCH, INC. 14 p.

146399 Ercegovich, C.; Bogus, E. (1975) The Fate of 2-Ethylamino-4-isopropylamino-6-

methylthio-s-triazine (Ametryn) in Hagerstown Silt Loam Soil Maintained under Aerobic

and Anaerobic Conditions: Report E-6/5-75CG. Unpublished study prepared by

Pennsylvania State University. 41 p.

41752401 Spare, W. (1990) Ametryn: Aerobic and Anaerobic Soil Metabolism of ?Carbon 14|-

Ametryn: Lab Project Number: 12138. Unpublished study prepared by Agrisearch Inc. 166

p.

43407105 Burnett, G. (1994) Response To The United States Environmental Protection Agency

Bibliography Page 30 of 66 

162-2 Anaerobic soil metabolism

146399 Ercegovich, C.; Bogus, E. (1975) The Fate of 2-Ethylamino-4-isopropylamino-6-

methylthio-s-triazine (Ametryn) in Hagerstown Silt Loam Soil Maintained under Aerobic

and Anaerobic Conditions: Report E-6/5-75CG. Unpublished study prepared by

Pennsylvania State University. 41 p.

41752401 Spare, W. (1990) Ametryn: Aerobic and Anaerobic Soil Metabolism of ?Carbon 14|-

Ametryn: Lab Project Number: 12138. Unpublished study prepared by Agrisearch Inc. 166

p. 

162-3 Anaerobic aquatic metabolism

42861603 Skinner, W. (1993) Anaerobic Aquatic Metabolism of (Carbon 14) Ametryn: Lab Project 

Number: 354W: 171-91. Unpublished study prepared by PTRL-West, Inc. 167 p.

163-1 Leaching/adsorption/desorption

.

23700 Suzuki, H.K. (1979) Dissipation of Banvel or Banvel in Combination with Other

Herbicides: Two Soil Types: Report No. 197. (Unpub- lished study received Mar 5, 1979

under 876-25; prepared in co- operation with Craven Laboratories, Inc., submitted by

Velsicol Chemical Corp., Chicago, Ill.; CDL:241224-B)

24365 Jordan, L.S.; Day, B.E.; Clerx, W.A. (1964) Photodecomposition of Triazines. Weeds 12

(? ):5-6. (Also~In~unpublished submission received Jul 19, 1978 under 201-403; submitted

by Shell Chemical Co., Washington, D.C.; CDL:234470-G)

27128 Rodgers, E.G. (1968) Leaching of seven s-Triazines. Weed Science 16(? ):117-120. (Also

in unpublished submission received Jul 19, 1978 under 201-403; submitted by Shell

Chemical Co., Washington, D.C.; CDL:234472-B)

38374 Guth, J.A. (1972) Adsorption and Leaching Characteristics of Pesticides in Soil. A

translation of: Adsorptions- und Einwaschverhalten von Pflanzenschutzmitteln in Boeden.

(Unpublished study including German text, received Jul 19, 1978 under 201- 403; prepared

by Ciba-Geigy, AG, submitted by Shell Chemical Co., Washington, D.C.; CDL:234472-S)

143342 Hazleton Laboratories America, Inc. (1985) The Absorption-desorp- tion of Radiolabelled Ametryn 

on Representative Agricultural Soils: Study No. 6015-158. Unpublished study. 45 Bibliography Page 31 of 

66
40

158732 Liu, L.; Cibes-Viade, H.; Koo, F. (1970) Adsorption of ametryne and diuron by soils.

Weed Science 18(4):470-474.

5016652 Helling, C.S. (1971) Pesticide mobility in soils: II_ Applications of soil thin-layer

chromatography. Proceedings of the Soil Science Society of America 35(5):737-743.

40079901 Warren, J. (1986) Leaching Characteristics of Parent [Carbon 14]- Ametryn: Final Report: 

Laboratory Study No. 34998. Unpublished study prepared by Analytical Bio-Chemistry

Laboratories, Inc. 144 p.

40995813 Spare, W. (1988) Adsorption/Desorption of ?carbon 14|-Ametryn: Final Report: Project No. 

12141. Unpublished study prepared by Agrisearch, Inc. 100 p.

41169604 Spare, W. (1989) Leaching Characteristics of ?carbon 14|-Ametryn: Final Report: Study No. 

12139. Unpublished study prepared by Agrisearch Inc. 81 p.

41169605 Spare, W. (1989) Leaching Characteristics of Aged Ametryn: Final Report: Study No.

12140. Unpublished study prepared by Agri- search Inc. 71 p.

41189704 Spare, W. (1988) Adsorption/Desorption of ?carbon|-Ametryn: Final Report: Study No. 

Agrisearch Project No. 12141. Unpublished study prepared by Agrisearch Inc. 100 p.

43407105 Burnett, G. (1994) Response To The United States Environmental Protection Agency

Review Of The Prometryn Environmental Fate Data: Lab Project Number: ABR-94079.

Unpublished study prepared by Ciba Crop Protection. 54 p.

92002038 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995813. Ametryn -

Adsorption/Desorption: Project 12141. Prepared by Agrisearch Inc. 11 p.

92002045 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169605. Ametryn- Aged 

Leaching Characteristics: Project No. 12140. Prepared by AGRISEARCH, INC. 14 p.

92002046 Hochman, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41169604. Ametryn -

Leaching Characteristics: Project 12139. Prepared by AGRISEARCH, INC. 12 p.

164-1 Terrestrial field dissipation

15644 Suzuki, H.K.; Takado, D.Y.; Whitacre, D.M. (1979) Laboratory Report: Dissipation of

Banvel or Banvel in Combination with Other Herbicides: Two Soil Types: Report No. 197.

(Unpublished study received Mar 5, 1979 under 876-25; prepared in cooperation with

Craven Laboratories, Inc., submitted by Velsicol Chemical Corp., Chicago, Ill.;

CDL:237957-I)

17711 Liu, L.C.; Cibes-Viade, H.R.; Gonzalez-Ibanez, J. (19??) Persistence of several herbicides

in a soil cropped to sugarcane. Journal of Agriculture of University of Puerto Rico ?

(? ):147- 152. (Also In unpublished submission received Aug 20, 1976 under 39445-1;

submitted by American Carbonyl, Inc., Tenafly, N.J.; CDL:228229-Y)

38292 Maier-Bode, H. (1972) Behavior of Herbicides in Water, Muck, and Fish after Application in Fish 

Ponds. A translation of: Verhalten von Herbiziden in Wasser, Schlamm und

Fischen nach Applikation in Fischteichen. (Unpublished study including German text,

received Jul 19, 1978 under 201-403; submitted by Shell Chemical Co., Washington, D.C.;

CDL:234470-K)
41

115781 Geigy Chemical Corp. (1972) Petition for a Negligible Residue Tolerance of 0.25 PPM in 

Grapefruit and Oranges for the Herbicide... Ametryne|. (Compilation; unpublished study

received May 30, 1973 under 3F1299; CDL:092199-A)

140127 Cassidy, J. (1971) Metabolism of ?delta|-14C-ametryne in Soil and Mature Corn Silage and Grain: 

Report No.: GAAC-71032. (Unpublished study received 1971 under 3F1299;

submitted by Ciba- Geigy Corp., Greensboro, NC; CDL:098818-B)

158995 Horowitz, M. (1969) Evaluation of herbicide persistence in soil. Weed Res. 9:314-321.

41701601 Judy, D.; Jacobson, B. (1990) Ametryn: Terrestrial Field Dissipation for Evik 80W--

Bareground Application, Louisiana Site: Final Report: Lab Project Number: 37895.

Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 219 p.

41752402 Judy, D.; Jacobson, B.; Gresham M. (1991) Ametryn: Terrestrial Field Dissipation for Evik 

80W-Crop Application, Louisiana Site: Final Report: Lab Project Number: 37894.

Unpublished study pre- pared by Analytical Bio-Chemistry Laboratories in assoc. with Pest

Management Enterprises, Inc. 267 p.

41872301 Jacobson, B.; Gresham, M. (1991) Terrestrial Field Dissipation for Evik 80W-Bareground 

Application, Illinois Site: Ametryn: Final Report: Lab Project Number: 38184.

Unpublished study prepared by ABC Laboratories, Inc., & Agri-Research Associates, Inc.

247 p.

41872302 Rice, F.; Jacobson, B.; Gresham, M. (1991) Terrestrial Field Dissipation for Evik 80WCrop 

Application, Illinois Site: Ametryn: Final Report: Lab Project Number: 38183.

Unpublished study prepared by ABC Laboratories, Inc., & Agri-Research Asso- ciation,

Inc. 256 p.

42325204 Jacobson, B. ; Graham, M. (1991) Terrestrial Field Dissipation for Evik 80W—Bareground 

Application, Hawaii Site (Ametryn, Final Report): Lab Project Number: FR 37896.

Unpublished study prepared by ABC Labs, Inc. 205 p.

165-4 Bioaccumulation in Fish

42061901 Dionne, E. (1991) Bioconcentration and Elimination of (Carbon 14) Residues by (Lepomis 

macrochirus) Exposed to Ametryn: Lab Project Number: 1781. 1090. 6264. 140: 91-5-

3760: 155-90. Unpublished study prepared by Springborn Labs, Inc. and Ciba- Geigy Corp.

156 p. 

166-1 Small GW prospective

45629801 Yokley, R. (2002) FIFRA Section 6(a)(2) Annual Ground Water Report for 2001. Unpublished 

study prepared by HAES Resources Department, Syngenta Crop

Protection, Inc. 33 p.

45870401 Yokley, R. (2003) FIFRA Section 6(a)2 Annual Ground Water Report for 2002:Final Report: 

Lab Project Number: 2240-02. Unpublished study prepared by

Syngenta Crop Protection, Inc. 34 p.

Dawson, Jeffrey et al. "Evik 80W Droplet Size Spectrum Study'. Conducted by Agrisearch

lncorporated for Ciba-Geigy Corporation. Study completed on December 11, 1989 and received

by EPA on December 26, 1989. MRlD #: 41336801.

Merricks, D. Larry. "Evik 80W Aerial Spray Drift Study- Louisiana Siten. Conducted by Agrisearch

lncorporated for Ciba-Geigy Corporation. Study completed on April 10, 1989 and received by EPA
42

on October 16, 1989. MRlD #: 41268001.

Merricks, D. Larry. "Evik 80W Aerial Spray Drift Study- Hawaii Site". Conducted by Agrisearch

Incorporated for Ciba-Geigy Corporation. Study completed on October 11, 1989 and received by

EPA on December 26, 1989. MRlD #: 41336802.

SUBMITTED EFFECT STUDIES (as of 1/25/13)

71-1 Avian Single Dose Oral Toxicity

MRID Citation Reference

56908 Ciba-Geigy Corporation (1967) Toxicology: (Evik(R)). (Reports by various sources; unpublished 

study including IBT nos. B4715, C4716 and P4709, received Apr 14, 1971 under 1G1142; CDL: 

090929-B) 

116260 Fink, R.; Beavers, J.; Brown, R. (1977) Acute Oral LD 50--Mallard Duck: Ametryn: Project No. 

108-130. Final rept. (Unpublished study received Dec 29, 1977 under 100-579; prepared by 

Wildlife International, Ltd. and Washington College, submitted by Ciba- Geigy Corp., Greensboro, 

NC; CDL:232548-I) 

40995801 Grimes, J.; Jaber, M. (1988) Ametryn: An Acute Oral Toxicity Study with the Bobwhite: Final 

Report: Project No. 108-291. Unpu- blished study prepared by Wildlife International Ltd. 20 p. 

92002004 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995801. Acute Oral Toxicity of 

Ametryn Technical to Bobwhite Quail: Report No. 108-291. Prepared by Wildlife International 

LTD. 17 p. 

71-2 Avian Dietary Toxicity

MRID Citation Reference

33704 or 

80617

Beliles, R.P.; Woodard, G. (1964) Ametryne: Subacute Toxicity of Ametryne in Bobwhite Quail. 

(Unpublished study received on un- known date under 100-473; prepared by Woodard Research 

Corp., submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:000475-B) 

48236 Woodard Research Corporation (1949?) Ametryne: Subacute Toxicity in Mallard Ducks. 

(Unpublished study received Jul 23, 1965 un- der unknown admin. no.; submitted by Ciba-Geigy 

Corp., Greens- boro, N.C.; CDL:222959-B) 

48238 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1964?) Ametryne: Sum- mary of Safety Evaluation on 

Fish and Wildlife. Summary of studies 222959-A through 222959-C. (Unpublished study received 

Jul 23, 1965 under unknown admin. no.; prepared by Woodard Re- search Corp., submitted by 

Ciba-Geigy Corp., Greensboro, N.C.; CDL:222959-D) 

80617 Beliles, R.P.; Woodard, G. (1964) Ametryne: Subacute Toxicity of Ametryne in Bobwhite Quail. 

(Unpublished study received Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., 

submitted by Geigy Chemical Corp., New York, N.Y.; CDL:091109-K) 

80619 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1949) Ametryne: Sub- acute Toxicity in Mallard Ducks. 

(Unpublished study received Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., 

submitted by Geigy Chemical Corp., New York, N.Y.; CDL:091109-M) 

80621 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1964) Ametryne: Sum- mary of Safety Evaluation on 
43

Fish and Wildlife. Summary of studies 091109-I through 091109-N. (Unpublished study received 

Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., submitted by Geigy Chemical 

Corp., New York, N.Y.; CDL:091109-O) 

115791 Beliles, R.; Scott, W.; Knott, W. (1964) Ametryne Safety Evaluation in Fish and Wildlife (Final 

Report) (Rainbow Trout, Mallard Duck, Oysters). (Unpublished study received Aug 30, 1965 

under unknown admin. no.; prepared by Woodard Research Corp., submitted by Ciba-Geigy Corp., 

Greensboro, NC; CDL:129363-A) 

116261 Gough, B.; Shellenberger, T. (1972) Letter sent to J. Forsythe dated Jan 28, 1972: Acute and 

subacute toxicity feeding studies of ametryne with young adult bobwhite quail: GSRI No. NC-459. 

(Unpublished study received Dec 29, 1977 under 100-579; prepared by Gulf South Research 

Institute, submitted by Ciba-Geigy Corp., Greensboro, NC; CDL:232548-J) 

40995802 Grimes, J.; Jaber, M. (1988) Ametryn: A Dietary LC50 Study with the Mallard: Project No. 108-

290A. Unpublished study prepared by Wildlife International Ltd. 19 p. 

40995803 Grimes, J.; Jaber, M. (1988) Ametryn: A Dietary LC50 Study with the Bobwhite: Project No. 108-

289. Unpublished study prepared by Wildlife International Ltd. 18 p. 

92002005 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995803. Acute Dietary Toxicity 

of Ametryn Technical to Bobwhite Quail: Report No. 108-289. Prepared by Wildlife International 

LTD. 16 p. 

92002006 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995802. Acute Dietary Toxicity 

of Ametryn Technical in Mallard Duck: Report No. 108-290A. Prepared by WILDLIFE 

INTERNATIONAL LTD. 16 p. 

71-4 Avian Reproduction

MRID Citation Reference

41547601 Beavers, J. (1990) Ametryn Technical: A One-Generation Reproduction Study with the Northern 

Bobwhite (Colinus virginianus): Lab Pro- ject Number: 108-303. Unpublished study prepared by 

Wildlife International Ltd. 116 p. 

41547602 Beavers, J. (1990) Ametryn Technical: A One-Generation Reproduction Study with the Mallard 

(Anas platryhyncos): Lab Project Number: 108-304. Unpublished study prepared by Wildlife 

International Ltd. 119 p. 

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

31150 or 

33309 or 

43665

Sleight, B.H., III (1971) Acute Toxicity of Some Ciba-Geigy Experimental Chemicals to Fathead 

Minnows (Pimephales promelas). (Unpublished study received Jan 16, 1974 under 1F1154; 

prepared by Bionomics, Inc., submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:092100-

W) 

33308 Gast, A. (1963) Toxicity Experiments on Trout for Breeding. (Unpublished study including pp. 1-

2 of appended German translation entitled: Toxizitaetsversuche an Brutforellen, received May 16, 

1973 under 1769-234; submitted by NCH Corp., National Chemsearch Div., Irving, Tex.; 

CDL:221976-E) 

33309 or 

43665

Sleight, B.H., III (1971) Bioassay Report: Acute Toxicity of Some Ciba-Geigy Experimental 

Chemicals to Fathead Minnows (Pimephales promelas). (Unpublished study received May 16, 

1973 under 1769-234; prepared by Bionomics, Inc., submitted by NCH Corp., National 

Chemsearch Div., Irving, Tex.; CDL:221976-N) 
44

43665 Macek, K.J.; Sleight, B.H., III (1971) Bioassay Report: Acute Toxicity of Some Ciba-Geigy 

Experimental Chemicals to Fathead Minnows (Pimephales promelas). (Unpublished study 

received Apr 27, 1977 under 100-541; prepared by Bionomics, Inc., submitted by Ciba-Geigy 

Corp., Greensboro, N.C.; CDL:229607-S) 

80616 or 

33705

Beliles, R.P.; Woodard, G. (1964) Ametryne: Acute Toxicity in Gold- fish. (Unpublished study 

received Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., submitted by Geigy 

Chemical Corp., New York, N.Y.; CDL:091109-J) 

80618 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1964) Acute Toxicity in Rainbow Trout. (Unpublished 

study received Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., submitted by 

Geigy Chemical Corp., New York, N.Y.; CDL:091109-L) 

80621 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1964) Ametryne: Sum- mary of Safety Evaluation on 

Fish and Wildlife. Summary of studies 091109-I through 091109-N. (Unpublished study received 

Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., submitted by Geigy 

Chemical Corp., New York, N.Y.; CDL:091109-O) 

80622 Lowe, J.I. (1964) Letter sent to H.E. Fairchild dated Jul 28, 1964 (Acute aquatic toxicity tests: 

ametryn and other chemicals). (U.S. Fish and Wildlife Service, Bureau of Commercial Fisheries, 

Biological Laboratory; unpublished study, including Geigy Chemical Corp. CDL:091109-P) 

92511 Hughes, J.S. (1970) Letter sent to Aithel McMahon dated Feb 10, 1970 ?Toxicity of Princep 80W 

and Ametryne to bluegill and channel catfish|: 71201. (Louisiana, Wild Life and Fisheries 

Commission; unpublished study, including letter dated Feb 16, 1970 from J. Becton to Stan Pruss; 

CDL:006629-K) 

94180 Hughes, J.S. (1970) Letter sent to Athel McMahon dated Feb 10, 1970 ?Toxicity of Princep 80 W 

and Ametryne|: 71201. (Lou- isiana, Wild Life and Fisheries Commission; unpublished study, 

including letter dated Feb 16, 1970 from J. Becton to Stan Pruss; CDL:220070-A) 

106510 Macek, K.; Sleight, B. (1971) Acute Toxicity of Some Ciba-Geigy Experimental Chemicals to 

Fathead Minnows (Pimephales promelas). (Unpublished study received on unknown date under 

3G1394; pre- pared by Bionomics, Inc., submitted by Ciba-Geigy Corp., Ardsley, NY; 

CDL:093722-L) 

115791 Beliles, R.; Scott, W.; Knott, W. (1964) Ametryne Safety Evaluation in Fish and Wildlife (Final 

Report) (Rainbow Trout, Mallard Duck, Oysters). (Unpublished study received Aug 30, 1965 

under unknown admin. no.; prepared by Woodard Research Corp., submitted by Ciba-Geigy 

Corp., Greensboro, NC; CDL:129363-A) 

115792 McCann, J. (1970) ?Ametryne 80W: Rainbow Trout (Salmo gairdneri)|: Test No. 254. (U.S. 

Agricultural Research Service, Pesticides Regulation Div., Animal Biology Laboratory; 

unpublished study; CDL:129704-A) 

116257 or 

33706

Beliles, R.; Woodard, G. (1964) Ametryne: Acute Toxicity in Sun- fish. (Unpublished study 

received Dec 29, 1977 under 100-579; prepared by Woodard Research Corp., submitted by CibaGeigy Corp., Greensboro, NC; CDL:232548-C) 

165368 Woodard Research Corp. (1965?) Ametryne...Acute Toxicity in Rainbow Trout. Unpublished 

study. 3 p. 

40995804 Surprenant, D. (1989) Ametryn: Acute Toxicity of Ametryn Technical to Bluegill (Lepomis 

macrochirus) Under Static Conditions: Study No. 89-1-2917. Unpublished study prepared by 

Springborn Life Sciences, Inc. 43 p. 

40995805 Surprenant, D. (1989) Ametryn: Acute Toxicity of Ametryn Technical to Rainbow Trout (Salmo 

gairdneri) Under Static Conditions: Stu- dy No. 89-1-2919. Unpublished study prepared by 

Springborn Life Sciences, Inc. 42 p. 
45

42861601 Ward, T.; Kowalski, P. (1993) Acute Toxicity of Ametryn Technical to the Fathead Minnow, 

Pimephales promelas: Lab Project Number: 219-CG. Unpublished study prepared by T.R. 

Wilbury Labs, Inc. 31 p. 

42861602 Ward, T.; Kowalski, P. (1993) Acute Toxicity of Ametryn Technical to the Rainbow Trout, 

Oncorhynchus mykiss: Lab Project Number: 220-CG. Unpublished study prepared by T.R. 

Wilbury Labs, Inc. 31 p. 

45202909 Grande, M.; Andersen, S.; Berge, D. (1994) Effects of pesticides on fish: experimental and field 

studies. Norwegian Journal of Agricultural Sciences Suppl. 13: 195-209. 

92002043 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995804. Acute Toxicity of 

Ametryn Technical to Bluegill (Lepomis macrochirus) under Static Conditions: Report No. 89-1-

2917. Prepared by SPRINGBORN LIFE SCIENCES, INC. 16 p. 

92002044 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995805. Acute Toxicity of 

Ametryn Technical to Rainbow Trout (Salmo gairdneri) under Static Conditions: Report No. 89-

1-2919. Prepared by Springborn Life Sciences Inc. 15 p. 

116258 Hutchinson, C. (1971) Continuous Exposure of Bluegill ... to Ametryne in Water. (Unpublished 

study received Dec 29, 1977 under 100-579; prepared by Bionomics, Inc., submitted by CibaGeigy Corp., Greensboro, NC; CDL:232548-G) 

40098001 Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Inter- pretation and Data Base for 

410 Chemicals and 66 Species of Freshwater Animals. US Fish & Wildlife Service, Resource 

Pub- lication 160. 579 p.

72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

158301 Vilkas, A. (1977) Acute Toxicity of Ametryn FL-761356 to the Water Flea: Daphnia magna 

Straus: Project No. 11506-04-01. Unpublish- ed study prepared by Union Carbide Environmental 

Services. 10 p. 

40995806 Surprenant, D. (1989) Ametryn: Acute Toxicity of Ametryn Technical to Daphnids (Daphnia 

magna) under Static Conditions: Study No. 89-1-2912. Unpublished study prepared by 

Springborn Life Sciences, Inc. 44 p. 

92002007 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995806. Acute Toxicity of 

Ametryn Technical to Daphnia Magna Under Static Conditions: Report No. 89-1-2912. Prepared 

by SPRINGBORN LIFE SCIENCES INC. 15 p. 

72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

27094 Lowe, J.I. (1964) Gulf Shellfish: Effects of Pesticides. (Unpub- lished study including letter dated 

Jul 28, 1964 from J.I. Lowe to H.E. Fairchild, received Jul 28, 1964 under unknown admin. no.; 

prepared by U.S. Fish and Wildlife Service, Bureau of Com- mercial Fisheries, submitted by 

Ciba-Geigy, Greensboro, N.C.; CDL:131211-A) 

80620 Beliles, R.P.; Scott, W.; Knott, W.; et al. (1961) Ametryne: Effect on Shell Growth of Oysters. 

(Unpublished study received Mar 27, 1967 under 8F0638; prepared by Woodard Research Corp., 

submitted by Geigy Chemical Corp., New York, N.Y.; CDL:091109-N) 

41114901 Surprenant, D. (1989) Acute Toxicity of Ametryn Technical To Mysid Shrimp (Mysidopsis 

bahia) under static Conditions: Study No. 89- 3-2960. Unpublished study prepared by Springborn 
46

Life Sciences, Inc. 47 p. 

41114902 Surprenant, D. (1989) Acute Toxicity of Ametryn Technical To Sheep- shead Minnow 

(Cyprinodon variegatus) under Static Conditions: Study No. 89-4-2967. Unpublished study 

prepared by Springborn Life Sciences, Inc. 43 p. 

41114903 Surprenant, D. (1989) Acute Toxicity of Ametryn Technical to Quahog Clam (Mercenaria 

mercenaria) Embryos-Larvae under Static Condi- tions: Study No. 89-4-2971. Unpublished study 

prepared by Springborn Life Sciences, Inc. 47 p. 

42325201 Surprenant, D. (1989) Supplement to Acute Toxicity of Ametryn Technical to Quahog Clam 

(Mercenaria mercenaria) Embryos-Larvae under Static Conditions. Unpublished study prepared 

by Ciba-Geigy Corp. 6 p. 

92002008 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41114902. Acute Toxicity of 

Ametryn Technical to Sheepshead Minnow (Cyprinodon Varieqatus) Under Static Conditions: 

Report No. 89-4-2967. Prepared by SPRINGBORN LIFE SCIENCES, INC. 18 p. 

92002009 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41114903. Acute Toxicity of 

Ametryn Technical to Quahog Clam (Mercenaria mercenaria) Embryos-Larvae Under Static 

Conditions: Report No. 89-4-2971. Prepared by SPRINGBORN LIFE SCIENCES, INC. 16 p.

92002010 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41114901. Acute Toxicity of 

Ametryn Technical to Mysid Shrimp (Mysidopsis bahia) under Static Conditions: Report No. 89-

3-2960. Prepared by SPRINGBORN LIFE SCIENCES, INC. 18 p. 

33707 Lowe, J.I. (1964) Annual Report: July 1, 1963-June 30, 1964: Pro- grams: Gulf Shellfish: Effects 

of Pesticides. (Unpublished study including letter dated Jul 28, 1964 from J.I. Lowe to H.E. 

Fairchild, received on unknown date under 100-473; prepared by U.S. Fish and Wildlife Service, 

Bureau of Commercial Fisheries, Biological Laboratory, submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:000475-E) 

48237 Woodard Research Corporation (1961?) Ametryne: Effect on Shell Growth of Oysters. 

(Unpublished study received Jul 23, 1965 under unknown admin. no.; submitted by Ciba-Geigy 

Corp., Greens- boro, N.C.; CDL:222959-C) 

40228401 Mayer, F. (1986) Acute Toxicity Handbook of Chemicals to Estuarine Organisms: 

EPA/600/X/86/231. Prepared by US EPA Environmental Research Laboratory, Gulf Breeze, Fl. 

275 p.

Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study and 850.1350 Mysid Chronic toxicity

MRID Citation Reference

32791 Lowe, J.I. (1964) Effects of Pesticides--Laboratory Studies. (Un- published study received Apr 

12, 1965 under 100-471; prepared by U.S. Fish and Wildlife Service, Bureau of Commercial 

Fisheries, submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:000460-A) 

33310 Loyal, S.W. (1969) An Investigation into the Effects of Simazine 80 WP, Ametryne 25 E, and 

GS14260 80 WP at 5, 1, .5, and .1 PPM on Bluegill (?~Lepomis_macrochirus~?) in Small Field 

Ponds. (Unpublished study including letter dated Nov 13, 1970 from J.A. Norton to J.E. Dorr, 

received May 16, 1973 under 1769-234; pre- pared by California State Polytechnic College, 

submitted by NCH Corp., National Chemsearch Div., Irving, Tex.; CDL:221976-O) 

41189702 McNamara, P. (1989) Ametryn: The Chronic Toxicity of Ametryn Tech- nical to Daphnia Magna 

Under Flow-through Conditions: Study No. 89-6-3002. Unpublished study prepared by 

Springborn Laborato- ries, Inc. 50 p. 

41189703 Surprenant, D. (1989) Ametryn: The Toxicity of Ametryn Technical to Fathead Minnow 
47

(Pimephales Promelas) Embryo and Larvae: Study No. 89-7-3022. Unpublished study prepared 

by Springborn Labora- tories, Inc. 48 p. 

42325202 McNamara, P. (1989) Supplement to the Chronic Toxicity of Ametryn Technical to Daphnia 

magna under Flow-through Conditions. Unpublished study prepared by Ciba-Geigy Corp. 55 p. 

42325203 Surprenant, D. (1989) Supplement to the Toxicity of Ametryn Technical to Fathead Minnow 

(Pimephales promelas) Embryos and Larvae. Unpublished study prepared by Ciba-Geigy, Inc. 36 

p. 

92002011 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41189703. Toxicity of Ametryn 

Technical to Fathead Minnow (Pimephales Promelas) Embryos and Larvae: Report No. 89-7-

3022. Prepared by SPRINGBORN LAB, INC. 18 p. 

92002012 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 41189702. Chronic Toxicity of 

Ametryn Technical to Duphnia Magna Under Flow- through Conditions: Report No. 89-6-3002. 

Prepared by SPRINGBORN LABS, INC. 19 p. 

47399001 Lee, M. (2008) Ametryn: Life-Cycle Toxicity Test with Mysids (Americamysis bahia): Final 

Report. Project Number: 1781/6689, T013322/05. Unpublished study prepared by Springborn 

Smithers Laboratories. 124 p.

72-7 Simulated or Actual Field Testing

MRID Citation Reference

43665 Macek, K.J.; Sleight, B.H., III (1971) Bioassay Report: Acute Toxicity of Some Ciba-Geigy 

Experimental Chemicals to Fathead Minnows (Pimephales promelas). (Unpublished study 

received Apr 27, 1977 under 100-541; prepared by Bionomics, Inc., submitted by Ciba-Geigy 

Corp., Greensboro, N.C.; CDL:229607-S) 

123-1 Seed germination/seedling emergence and vegetative vigor

MRID Citation Reference

40995807 Canez, V. (1988) Ametryn: Nontarget Phytotoxicity Test: Seed Germi- nation Tier 2: Study No. 

LR88-55B. Unpublished study prepared by Pan-Agricultural Labs, Inc. 72 p. 

40995808 Canez, V. (1988) Ametryn: Nontarget Phytotoxicity Test: Seedling Emergence Tier 2: Study No. 

LR88-55C. Unpublished study pre- pared by Pan-Agricultural Labs, Inc. 281 p. 

40995809 Canez, V. (1989) Ametryn: Nontarget Phytotoxicity Test: Vegetative Vogor Tier 2: Study No. 

LR 88-55A. Unpublished study prepared by Pan-Agricultural Labs, Inc. 281 p. 

92002030 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995807. Nontarget 

Phytotoxicity: Tier 2 Seed Germination Test with Ametryn Technical: Report No. LR88-55B. 

Prepared by PAN-AGRICULTURAL LABS, INC. 18 p. 

92002031 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995808. Nontarget 

Phytotoxicity; Tier 2 Seedling Emergence Test with Ametryn Technical: Report No. LR88-55C. 

Prepared by PAN-AGRICULTURAL LABS. 23 p. 

92002032 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995809. Nontarget 

Phytotoxicity: Tier 2 Vegetative Vigor Test with Ametryn Technical: Report No. LR88-55A. 

Prepared by PAN-AGRICULTURAL LABS, INC. 22 p. 

21912 Coupland, R.T.; Skoglund, N.A. (1962) Response of native grasses to various herbicides, 1962. 

Pages 124-125,~In~Research Report for the National Weed Committee, Western Section: 
48

Volume 9. Edmon- ton, Alberta: Natl. Weed Comm.; Pages 84-85,~In~19th Annual Research 

Report for the North Central Weed Control Conference; Dec 3-5, 1962, St. Paul, Minn. N.P. 

(Univ. of Saskatchewan, Dept. of Plant Ecology, Contribution # 340; also~In~unpublished 

submission received Sep 10, 1968 under 876-29; submitted by Velsicol Chemical Corp., 

Chicago, Ill.; CDL:005055-A) 

123-2 Aquatic plant growth 850.4400 Lemna spp Toxicity test

MRID Citation Reference

40995810 Hughes, J. (1989) Ametryn: The Toxicity of Ametryn Technical to Selenastrum capricornutum: 

Study No. 0267-42-1100-1. Unpublish- ed study prepared by Malcolm Pirnie, Inc. 38 p. 

92002033 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995810. The Toxicity of 

Ametryn Technical to Selenastrum Capricornutum: Report No. 0267-42-1100-1. Prepared by 

MALCOLM PIRNIE, INC. 17 p. 

47399002 Softcheck, K. (2007) Ametryn: 7-Day Toxicity Test with Duckweed (Lemna gibba): Amended 

Final Report. Project Number: 1781/6688, T013324/05. Unpublished study prepared by 

Springborn Smithers Laboratories. 62 p.

47954502 Ma, J.; Liang, W.; Xu, L.; et al. (2000) Acute Toxicity of 33 Herbicides to the Green Alga 

Chlorella pyrenoidosa. Bulletin of Environmental Contamination and Toxicology 66:536-541.

47954503 Ma, J. (2001) Differential Sensitivity to 30 Herbicides Among Populations of Two Green Algae 

Scenedesmus obliquus and Chlorella pyrenoidosa. Bulletin of Environmental Contamination and 

Toxicology 68:275-281.

40228401 Mayer, F. (1986) Acute Toxicity Handbook of Chemicals to Estuarine Organisms: 

EPA/600/X/86/231. Prepared by US EPA Environmental Research Laboratory, Gulf Breeze, Fl. 

275 p.

141-1 Honey bee acute contact

MRID Citation Reference

40995811 Hoxter, K.; Jaber, M. (1988) Ametryn: An Acute Contact Toxicity Study with the Honey Bee: 

Project No. 108-288. Unpublished stu- dy prepared by Wildlife International Ltd. 15 p. 

92002034 Plautz, J. (1990) Ciba-Geigy Corp. Phase 3 Summary of MRID 40995811. Acute Contact 

Toxicity of Ametryn Technical to the Honey Bee: Report No. 108-288. Prepared by WILDLIFE 

INTERNATIONAL LTD. 13 p. 

Non Target Insect Toxicity Testing

7897 Leigh, T.F. (1966) LDI50^ Values and~b~Values for 34 Insecticides When Applied Topically to 

Adult Male and Female~Lygus hesperus~ Knight: Shafter, California: 1960-1966: Table 1. 

(Unpublished study including letter dated Sep 19, 1967 from T.F. Leigh to Donald L. Burgoyne,

received Apr 16, 1971 under 1G1144; prepared by Univ. of California--Davis, Agricultural 

Experiment Station, Dept. of Entomology, submitted by E.I. du Pont de Nemours & Co., Inc., 

Wilmington, Del.; CDL:090931-B) 

Non Guideline

28430 Ballantine, L.G.; Holt, B.E.; Akesson, N.B.; et al. (1980) Poten- tial Hazard to Nontarget Plants 

Resulting from Aerial Appli- cations of Aatrex^(R)I, Bicep^(R)I, Dual^(R)I, Evik^(R)I, 

Igran^(R)I, Milocep^(R)I, Sancap^(R)I, Aatrex + Karmex^(R)I, Aatrex + Evik, Dual + Aatrex, 

Dual + Lorox^(R)I, Dual + Lex- one^(R)I/Sencor^(R)I, Evik + Karmex, and Igran + Aatrex: 
49

Report No. ABR-80014. (Unpublished study including published data, re- ceived Apr 29, 1980 

under 100-439; prepared in cooperation with Univ. of California--Davis, Agricultural 

Engineering Dept. and others, submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL: 242535-

A) 

50459 E.I. du Pont de Nemours & Company (1971) Environmental and Wildlife Information Relating to 

the Use of Lannate Methomyl Insecticide in Pineapple in Hawaii. (Reports by various sources; 

unpub- lished study including published data, received Jan 6, 1981 un- der 352-EX-106; 

CDL:099858-A) 

116259 Macek, K.; Sleight, B. (1971) Preliminary Investigations of the Accumulation of Ametryne 

Residues by Bluegill Continuously Exposed to Ametryne in Water. (Unpublished study received 

Dec 29, 1977 under 100-579; prepared by Bionomics, Inc., sub- mitted by Ciba-Geigy Corp., 

Greensboro, NC; CDL:232548-H) 
50

Appendix B. Biological and Economic Analysis Division (BEAD) Report

BEAD Chemical 

Profile: Ametryn
51

EFED’s Label Data Report for Ametryn as of 1/31/13

Use Site

Application 

Method 

Type

Application 

Method 

Equipment

Formulation 

Desc

Application 

Method 

Timing

Original 

(Product / 

A. I.) Max 

App Rate

A. I. 

Max 

App 

Rate

Max # 

Apps 

@ Max 

Rate / 

CC

A. I. 

Max 

App 

Rate/

Year

Product 

Seasonal 

Max 

Dose/CC

Minimum 

Retreat

ment 

Interval

Corn, 

Field

Basal spray 

treatment Sprayer

Dry 

Flowable Foliar 2 lb/ 1 a

1.578 

lb / a NS NS NS NS

Corn, 

Field Spray Sprayer

Dry 

Flowable

Postemergence 2 lb/ 1 a1.578 

lb / a NS NS NS NS

Corn, Pop

Basal spray 

treatment Sprayer

Dry 

Flowable Foliar 2 lb/ 1 a

1.578 

lb / a NS NS NS NS

Corn, Pop Spray Sprayer

Dry 

Flowable

Postemergence 2 lb/ 1 a1.578 

lb / a NS NS NS NS

Pineapple Broadcast. Sprayer

Dry 

Flowable Ratoon 2 lb/ 1 a

1.578 

lb / a NS NS 4 lb / a NS

Pineapple Spray Sprayer

Dry 

Flowable Post-plant 2 lb/ 1 a

1.578 

lb / a NS NS 4 lb / a NS

Pineapple Spray Sprayer

Dry 

Flowable Preharvest 2 lb/ 1 a

1.578 

lb / a NS NS 4 lb / a NS

Sugarcane

Band 

treatment Ground

Dry 

Flowable Ratoon 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane

Basal spray 

treatment Sprayer

Dry 

Flowable Ratoon 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Aircraft

Dry 

Flowable Foliar 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Ground

Dry 

Flowable Preemergence 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Ground

Dry 

Flowable Ratoon 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Sprayer

Dry 

Flowable

Postemergence 1.5 lb/ 1 a1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Sprayer

Dry 

Flowable Preemergence 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS

Sugarcane Broadcast Sprayer

Dry 

Flowable Ratoon 1.5 lb/ 1 a

1.1835 

lb / a NS NS 3 lb / a NS
52

Appendix C. Output from OPP Aggregate Incident Database for Ametryn

Aggregate Incident Report for EFED

Ametryn

PC Code:080801

Total Count of Minor Incidents from Aggregated Reports

Minor Fish and Wildlife Incidents (W-B): 0

Minor Plant Incidents (P-B): 0

Minor "Other Nontarget" Incidents (ONT): 0
53

Appendix D. SIP Results for Evaluate Potential Risk to Birds and Mammals from 

Drinking Water Exposure.

Table 1. Inputs

Parameter Value

Chemical name Ametryn

Solubility (in water at 25o

C; mg/L) 185

Mammalian LD50 (mg/kg-bw) 1009

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 14

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2250

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 562

Bobwhite quail NOAEC (mg/kg-diet) 1780

NOAEC (mg/kg-diet) for other bird species 0

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird species 0

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 31.8200 31.8200

Adjusted toxicity value (mg/kg-bw) 776.0830 10.7682

Ratio of exposure to toxicity 0.0410 2.9550

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Exposure through drinking 

water alone is a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 149.8500 149.8500

Adjusted toxicity value (mg/kg-bw) 1620.9664 27.8823

Ratio of exposure to acute toxicity 0.0924 5.3744

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Exposure through drinking 

water alone is a potential 

concern for birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when 

aggregated with other routes (i.e ., diet, inhalation, dermal), pesticide exposure through drinking water may contribute to a 

total exposure that has potential for effects to non-target animals.
54

Appendix E. STIR Results to Evaluate the Potential for Inhalation Risk to Birds 

and Mammals

Welcome to the EFED 

Screening Tool for Inhalation Risk

This tool is designed to provide the risk assessor with a rapid method for determining the potential

significance of the inhalation exposure route to birds and mammals in a risk assessment.

Input

Application and Chemical Information

Enter Chemical Name Ametryn

Enter Chemical Use Herbicide

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 227.3

Enter Chemical Vapor Pressure (mmHg) 2.74E-06

Enter Application Rate (lb a.i./acre) 2.4

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2250

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 1009

Enter Lowest Rat Inhalation LC50 (mg/L) 5.03

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3

) 3.35E-02

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 4.21E-03

Adjusted Inhalation LD50 6.25E+01

Ratio of Vapor Dose to Adjusted Inhalation LD50 6.74E-05 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.54E-01

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 4.06E-03 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3

) 3.35E-02

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 5.30E-03

Adjusted Inhalation LD50 2.99E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.77E-05 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 3.19E-01

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 1.06E-03 Exposure not Likely Significant

**NOTE**: When entering values, press 

order to update linked cells.
55

Appendix F. Environmental Fate and Transport Characterization

Available data indicate that ametryn is stable to hydrolysis at environmental pHs (MRID 

40995812). Aqueous photolysis (MRID 41169601) and photodegradation on soil studies 

(MRIDs 41169602, 41169603) were reclassified as not acceptable due to multiple 

experimental method deficiencies. Although aqueous photolysis data are needed to 

adequately characterize the fate of ametryn in aquatic environments, new data for 

photodegradation on soil are not considered likely to be useful, as that degradation 

pathway is expected to be of limited significance in the environment, where aerobic soil 

degradation and soil mobility will have a greater effect on the fate of the compound. 

Available soil metabolism data demonstrate that ametryn biodegrades in aerobic soil, 

with half-lives of approximately 10 days (MRID 46533801) and 40 days (MRID 

41752401), indicating that it will be nonpersistent to slightly persistent (based on Goring 

et al. 1975) in such soil. However, data are only available for two soils, and the 10-day 

half-life may underestimate the degradation of ametryn given that there were high 

percentages of unextracted residues in the study (20% of the applied by 14 days, 41% by 

56 days, and 64% by 171 days). In that study (MRID 46533801), a transformation 

pathway was proposed by the study author in which ametryn rapidly degraded to the 

sulfoxide, NOA 423271, then further oxidized to the sulfonic acid, NOA 428383. NOA 

423271 was hydroxylated to G 34048 and subsequently oxidized to NOA 438707. In a 

second pathway, ametryn degraded to GS-11355 and GS-11354. GS-11354 was 

hydroxylated to GS-17794. The proposed endpoint of the pathway is the mineralization 

of the metabolites to carbon dioxide and the formation of bound residues. Data for three 

additional soils, representative of intended use areas, are needed to more completely 

characterize the aerobic soil degradation of ametryn.

Available anaerobic soil and anaerobic aquatic metabolism data indicate that ametryn is 

stable to degradation and thus persistent (based on Goring et al. 1975) under 

flooded/anaerobic conditions. In both of the anaerobic soil metabolism studies, the 

concentration of parent increased during the flooding period (relative to pre-flood levels). 

It is possible that the potential transformation products NOA 432271 (sulfoxide of 

ametryn) and NOA-428383, oxidized forms of ametryn which can undergo reduction 

when the redox potential is below -148 mV, were reduced back to the parent compound; 

however, they were not monitored in one of the studies (MRID 41752401). In one 

anaerobic soil metabolism study, unextracted residues were 20% at flooding, and 31-35% 

at 28 -150 days (MRID 46533801). Harsh extraction of the 150-day sample released an 

additional 7.0% of the applied; G 34048 was the predominant compound in these extracts 

at 3.5% of the applied. Fractionation of the nonextracted residues in the 150-day harshextracted soil (26.9% of the applied) determined that 7.1%, 8.5%, and 11.3% of the 

applied was associated with fulvic acids, humic acids, and humin, respectively. In the 

anaerobic aquatic metabolism studies, unextracted residues were <6.8% throughout one 

study (MRID 46533801) and were 14-17% at 360 days (MRID 42861603) in the other 

study. 
56

There are no available aerobic aquatic metabolism data. While a data waiver was 

approved in the past for this guideline requirement, data are now considered necessary in 

order to more fully understand the fate of ametryn and its transformation products in the 

environment. In the past, a default value of two times the aerobic soil metabolism halflive was used for modeling. However, given the persistence of the compound in 

flooded/anaerobic conditions, as well as the potential for the transformation products 

NOA 432271 and NOA 428383, which are oxidized forms of ametryn, to undergo 

reduction back to parent ametryn when the redox potential is below -148 mV, the use of a 

default value derived from aerobic soil metabolism half-lives may greatly overestimate 

the potential for degradation in an aerobic aquatic environment. 

Ametryn is expected to be mobile to moderately mobile in soil based on the FAO 

mobility classification scheme (FAO, 2000) and organic-carbon normalized partition 

coefficients (Koc) that ranged from 96 to 927 in four soils (MRID 40995813). In aged 

(MRID 41169605) and unaged (MRID 41169604) column leaching experiments, ametryn 

leached through sandy loam (aged and unaged), loam (unaged) and sand (unaged) soil 

columns, and was detected in the leachate from the columns. In a clay soil column, 

ametryn was less mobile, but was still detected at a depth of 8 inches and at low levels in 

the leachate. Although there are no batch equilibrium data for the transformation 

products, in the aged soil column studies, all of the compounds monitored (GS-34048; 

GS-11354; GS-11355; GS-26831; GS-32083; GS-28304; and GS-17794; see Section 3.1

for identifications) were mobile (i.e., showed leaching) in sandy loam soil, and all except 

GS-17794 were detected in the leachate. All of the compounds studied were more mobile 

than the parent. Thus, ametryn and many of its transformation products may potentially 

leach to groundwater. There are no mobility data on the major transformation products

NOA 423271 and NOA 428383, which are oxidized forms of ametryn and can be 

reduced back to parent under certain environmental conditions.

Field studies were conducted on bareground and corn plots (sand soils) in IL, and a 

sugarcane plot in LA (silty loam soil). All of the studies were classified as supplemental 

due to both experimental and analytical method deficiencies. In each of the field studies, 

ametryn dissipated more rapidly in an initial phase (30 or 60 days), followed by a period 

of slower degradation. Dissipation half-lives calculated from the complete data sets were 

35 days (IL corn), 48 days (IL bareground), and 62 days (LA sugarcane). In both of the 

IL sand plots, ametryn was detected to a maximum depth of 12 inches and G-34048 was 

detected at all depths to 48 inches. In the LA silty loam plots, ametryn was detected to a 

maximum depth of 6 inches and G-34048 was detected to a maximum depth of 6 inches, 

with the exception of two detections below 6 inches. The transformation products GS11794 and GS-11354 were also detected in all plots to a maximum depth of 6 inches. It 

is unclear whether the aerobic soil metabolism transformation products, NOA 423271 

and NOA 428383, which are of toxic concern, were monitored in any of the studies.

Ametryn that reaches aquatic habitat (through spray drift and/or runoff) is not likely to 

accumulate in tissues of aquatic organisms, as indicated by the results of a 

bioconcentration study conducted on bluegill sunfish (Lepomis macrochirus). 
57

Bioconcentration factors (BCF) were: 61X in edible tissues, 110X in non-edible tissues, 

and 83X in whole fish. During depuration, with 60-80% of accumulated 14C residues 

were eliminated from the fish tissues after 28 days. The transformation products

identified in the edible and nonedible tissues GS-11354, GS-11355, di-amino ametryn 

(GS-26831), GS-11354 sulfoxide, a cysteine conjugate of 2-ethylamino-4-

isopropylamino s-triazine, 2-hydroxy-4-isopropylamino-6-N-acetyl cysteine s-triazine, a 

cystine conjugate of ametryn, and 4-isopropylamino-2,6-diamino triazine.

In a registrant-submitted groundwater monitoring study conducted on multiple triazines, 

ametryn was detected in only 2 of 413 well samples in 2001, at 0.12 and 0.21 ppb (LOQ 

= 0.10 ppb; MRID 45629801). In 2002, ametryn was not detected in any of the 80 well 

samples (LOQ = 0.10 ppb; MRID 45870401).

In a small-scale retrospective groundwater monitoring study at two turf sites in Florida, 

ametryn was detected in six of 13 wells at concentrations of 0.14 – 1.5 ppb in August 

1993. The ametryn transformation product GS-11354 was detected in one well, at 0.13 

ppb (MRID 43141400).

Monitoring in Hawaii of groundwater in pineapple use areas in the 1990's resulted in a 

maximum ametryn concentration similar in magnitude to that predicted (9.8 ppb) for 

TTR with the groundwater screening model SCIGROW (USEPA 2005). Samples were 

collected by the Ciba-Geigy Corporation from 1992 to 1994, and analyzed for residues of 

atrazine and ametryn. Ametryn degradates GS-11354, GS-26831 and rarely GS-11355 

were also included as analytes. Ametryn was rarely detected in groundwater samples, 

although the maximum concentration detected was 7.6 ppb. Degradates of ametryn were 

not detected in any sample. 

Quarterly surface-water monitoring from the South Florida Water Management District’s 

(SFWMD, 2012 inter al.) quarterly ambient monitoring program on the borders of the 

Everglades Agricultural Area (EAA) has resulted in surface water concentrations well 

below those estimated in the past (USEPA 2005) for maximum application rates by the 

PRZM/EXAMS models. However, the frequency of the sampling is not sufficient for 

the estimation of potential acute exposure, nor extensive enough to allow a conservative 

estimate of potential chronic exposure. 

Ametryn was detected in pesticide monitoring conducted from 2004 to 2008 in the 

developed floodplain of the lower Burdekin River and downstream marine environments 

in Australia during high and low flow conditions (Davis et al., 2008). Ametryn and other 

pesticides associated with sugarcane use were among the ones detected at the highest 

concentrations during low flow conditions. Ametryn was detected at 80 of 143 sampling 

locations, at a range of ≤0.1 0.31 ug/L (event flow conditions) and ≤0.1 – 2.10 ug/L 

(ambient flow conditions). The analytical detection limit was 0.1 ug/L.