### Page 2 of 133 

# Preliminary Ecological Risk Assessment in Support of the R egistration Review of Hexazinone

Hexazinone (CAS 51235

- 04

- 2 )

Prepared by: Hannah Yingling , Biologist

José M e l é ndez

, Chemist U. S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division

Environmental Risk Branch V 1200 Pennsylvania Av e., NW
Mail Code 7507P Washington, DC 20460 Reviewed by: Geoffrey Sinclair, Ph.D., Biologist Mohammed Ruhman, Ph.D., Senior Agronomist Mah Shamim, Ph.D. , Branch Chief 

## Office of Ch emical Safety

and Pollution Prevention

### Page 3 of 133 

### Table of Contents

Executive Summary

................................ ................................ ................................ ........................ 4

1.0 Problem Formulation

................................ ................................ ................................ ......... 6

1.1 Nature of Regulatory Action

................................ ................................ ............................. 6

1.2. Mechanism of Action

................................ ................................ ................................ ........ 6

1.3 Use Characterization

................................ ................................ ................................ ......... 7

1.4 Stressors of Concern

................................ ................................ ................................ .......... 7

1.5 Risk Hypothesis

................................ ................................ ................................ ................. 8

1.6 Analysis

................................ ................................ ................................ ............................. 9

2.0 Exposure Characterization

................................ ................................ ................................ 9

2.1 Use Information

................................ ................................ ................................ ................. 9

2.2 Environmental Fate and Transport

................................ ................................ .................. 16

2.3 Aquatic Modeling Approach

................................ ................................ ........................... 30

2.4 Terrestrial Exposure Modeling

................................ ................................ ........................ 37

3.0 Ecological Toxicity

................................ ................................ ................................ ......... 44

3.1 Aquatic Organ isms

................................ ................................ ................................ .......... 45

3.2 Terrestrial Organisms

................................ ................................ ................................ ...... 48

3.3 Incident data

................................ ................................ ................................ .................... 50

4.0 Risk Characterization

................................ ................................ ................................ ...... 51

4.1 Risk Estimation for Aquatic Organisms for Spray and Granular Uses

........................... 54

4.2 Risk Estimation for Terrestrial O rganisms Non

- Granular Uses

................................ ..... 60

4.3 Risk Estimation to Terrestrial Organisms for Granular and Pelleted Uses

..................... 70

4.4 Risk Description

................................ ................................ ................................ .............. 72

4.5 Endangered species

................................ ................................ ................................ ......... 79

4.6 Uncertainties and Limitations

................................ ................................ ......................... 81

References

................................ ................................ ................................ ....................... 87 Appendix A. Environmental Fate / Chemistry Bibliography

................................ ........................ 89 Appendix B. Ecological Effects Bibliography

................................ ................................ .............. 96 Appendix C. Hexazinone and its transformation products

................................ ......................... 101 Appendix D. Sample SWCC Output File

................................ ................................ ................... 109 Appendix E. T

- REX non

- granular example output

................................ ................................ .... 111 Appendix F. LD 50 

### per ft 2 

### T

- REX example output

................................ ................................ ....... 115 Appendix G. Granular Characterization T

- REX example output

................................ ............... 117 Appendix H. Terrplant example output

................................ ................................ ...................... 119 Appendix I. Classifications of Env ironmental Fate Studies

................................ ....................... 120 Appendix J. Hexazinone Refresh Acceptable Bibliographies November 2014

......................... 125 Appendix L. STIR Output

................................ ................................ ................................ ........... 132

### Page 4 of 133 

# Executive Summary

Hexazinone is a systemic herbicide for weed control in certain crops like pineapples, sugarcane

and blueberries , Christmas trees, forestry site preparation and release areas, industrial areas,

reforestati on areas, rangeland, pastures and noncrop areas. The herbicide belongs to the triazinone chemical family. Hexazinone is usually applied once per year, in the winter or early spring.

Based on the available information, hexazinone residues (sum of hexazin one and Metabolites A1 (or A

- 1) , B, D, G, 1, 2

, and minor Metabolite A) a re persistent and mobile in soil and aquatic

environments and considered as the stressors in this ecological risk assessment. The mobility of hexazinone was demonstrated in batch equ ilibrium as well as terrestrial field, forestry dissipation, and a prospective groundwater monitoring studies. Hexazinone is stable to hydrolysis and photolysis and degrades at relatively slow rates under aerobic soil metabolism conditions. Aerobic

and a naerobic aquatic metabolism and anaerobic soil metabolism studies show slow degradation for hexazinone. Consistent with this persistence and mobility, field dissipation half

- lives were 123 to 154 days for the parent compound in bare ground silt loam, silt y clay loam and sandy loam soils. Laboratory adsorption data show low water/soil partitioning for hexazinone (K OC 

### = 38

- 77 mL/g OC 

### , mobile according to FAO 2000). Given this mobility and persistence, h exazinone has a strong potential to leach to ground wat er systems, especially in soil systems such as loamy and sandy soils that are poor in organic matter. H exazinone is not expected to bioconcentrate substantially

in fish tissue

, with its low K OW 

### value of 15 ( i.e. , log K OW 

### = 1.1).

Table 1 provides a summar y of the environmental risk conclusions for hexazinone, for aquatic and terrestrial organisms, based on primarily on risk quotient (RQ) values and whether they exceed levels of concern (LOCs) for Federally

- listed threatened and endangered species (hereafte r refers to as listed species) and non

- listed species.

Table 1. Summary of Ecological Risk Conclusions for Hexazinone Uses

Taxonomic Group Summarized Risk Characterization and Major Uncertainties

Fish and Aquatic

Invertebrates (freshwater and

estuarine /marine) The potential for acute or chronic risk to freshwater fish, freshwater

invertebrates and estuarine/marine invertebrates is considered low for flowable and granular uses , as acute and chronic RQ values do not

exceed the risk to listed or nonlisted species LOC. Aquatic and

Terrestrial Plants The re is a potential for risk to aquatic and nontarget terrestrial plants, aquatic vascular plants, and aquatic nonvascular plants for all uses.

This risk is consistent with the mode of action of the chemical.

Birds There is a potential for acute and chronic risk to birds for flowable and granular uses; only one flowable use resulted in a chronic LOC

exceedance. RQ values that exceed the risk to listed species at the

LOC were observed with higher application rates, smaller bird sizes, and birds consuming short grass, tall grass and broadleaf plants.

LD 50 

### per ft 2 

### analysis for granular and pelleted uses showed concern

for small and medium birds. Pelleted uses were further characterized

based on the size of th e pellet; despite toxic risk to all bird sizes, only the largest birds are expected to consume the pellets (640 mg). There

### Page 5 of 133 

### is some uncertainty due to the lack of avai lable data for smaller birds (passerine species)

. Mammals There is the potential for a cute and chronic risk to mammals for flowable and granular uses

. A cute dose based RQs and dietary based RQ values that exceed the risk to listed species LOC trend toward to higher application rates, smaller mammal size, and mammals consuming short grass, t all grass and broadleaf plants. Chronic dose

based RQ values exceeded the LOC across the top 6 application rates

for small and medium mammals across all feeding strategies. LD 50 

### per ft 2 

### analysis for granular and pelleted uses showed concern for

small and medium mammals. Pelleted uses were further characterized based on the size of the pellet; despite toxic risk to all mammal sizes, only the largest mammals are expected to consume the pellets (640 mg).

Bees The potential for risk to terrestrial invertebra tes is considered low

because the LC 50 

### >100 μg/bee. However, there is uncertainty concerning the lack of toxicity data from chronic exposure to adults and acute and chronic exposure for larva

. The chemical is persistent but is applied in winter or early spring.

### Page 6 of 133 

# 1. 0 Problem Formulation

The pu rpose of problem formulation is to provide the foundation for the environmental fate and ecological risk assessment being conducted for hexazinone . The problem formulation sets the objectives for the risk assessment and provides a plan for analyzing the d ata and characterizing the risk ( USEPA 1998 ). As part of the Registration Review process, a detailed Problem Formulation (DP Barcode D3 69269 ) for this risk assessment was published to the docket [Docket ID: EPA

HQ

- OPP

- 2009

- 0 755 ] in March 31, 2010 . The fo llowing section s summarize the key points of that document and discusses any differences between the analysis outlined previously and the analysis

conducted in this risk assessment.



## 1.1 **Nature of Regulatory Action**

This risk assessment is conducted as par t of the Agency’s Registration Review process for pesticide active ingredients. The Registration Review process was established under the Food Quality Protection Act (FQPA 1996).



## 1 **.2. Mechanism of Action** 

Hexazinone ( Figure 1 ) , CAS Name: 3

- cyclohexyl

- 6

- ( dimethylamino)

- 1

- methyl

- 1,3,5

- triazine

2,4(1 H ,3 H )

- dione, and IUPAC Name: 3

- cyclohexyl

- 6

- dimethylamino

- 1

- methyl

- 1,3,5

- triazine

2,4(1 H ,3 H )

- dione, has a CAS Number of 51235

- 04

- 2 and a PC Code of 107201. It is a triazinone

herbicide. According to the sample label for Velpar L, hexazinone is an “herbicide...applied as a spray for weed control in certain crops, Christmas trees, forestry site preparation and release areas, and industrial areas. It may also be applied undiluted as a basal soil treatment for brush c ontrol in reforestation areas, rangeland, pastures and noncrop areas, or by stem injection for brush control.” Hexazinone “is an effective general herbicide providing both contact and residual control of many annual, biennial and perennial weeds and woody plants.” It appears that hexazinone is systemic since it “can absorb...through roots extending into treated areas.” According to the Herbicide Resistance Action Committee (HRAC 1 

### ), hexazinone belongs to the HRAC Group C1 with a site

of action inhibition of photosynthesis at photosystem II. The herbicide belongs to the triazinone chemical family (o ther members of the trizinone family include ametridione, amibuzin, ethiozin, isomethiozin, metamitron, metribuzin and trifludimoxazin ; however, only a few of the se chemicals are currently approved for use in the U.S. )

.

1 http://www.hracglobal.com/Education/ClassificationofHerbicideSiteofAction.aspx (accessed 12/04/2014).

### Page 7 of 133 O

N C H 3

N

C H 3 C H 3

O N

N



### Figure 1. Structure of Hexazinone



## 1.3 **Use Characterization**

Nationally, hexazinone is an herbicide used to control a broad spectrum of weeds including undesirable woody plants in alfalfa, rangeland and pasture, woodland, pineapples, sugarcane and blueberries. It is also used on ornamental plants, forest trees and other non

- crop areas (right

- of

way) . Hexazinone is registered for pre

- emergent, post

- emerg ence, layby, directed spray and basal soil applications. It is used as a non

- selective herbicide in non

- cropland areas and as a selective herbicide in reforestation practices. Hexazinone products are formulated as pellets/tablets,

emulsifiable concentrate s, soluble concentrates/solids and a technical grade active ingredient. Products are applied using aerial or ground equipment, by hand, or using a hand

- held, boom, knapsack or power sprayer. There are no indoor uses. Refer to Section 2.1 for further det ail about

the use information.



## 1.4 **Stressors of Concern**

According to the available environmental fate data for hexazinone, it undergoes a number of transformations, which result in transformation products with essentially the same backbone

structure of t he parent compound (with the exception of G) , with slight differences in substituent moieties. Hexazinone degradates include Metabolites A

- 1, B, D, G (or G3170) , 1, 2 and minor

metabolite A. Structures of these degradates are presented in Table 8 . Infor mation about maximum formation in the individual studies is presented in the Appendix C . Inspection of Table

8 shows that all the metabolites except for metabolite G have two rings from the parent structure. Metabolite G contains only the triazine ring. Based on the available information, hexazinone residues (hexazinone plus a ll its metabolites) appear to be persistent and mobile in soil and aquatic

environments and they are all considered as the stressors of concern. Exposures in aquatic habitats

will be quantified considering hexazinone plus all these metabolites , considered of concern (total toxic residues or TTRs)

. More information about the degradates is available in Section 3.1.1 and

the table in the Appendix K

.

Since there were high levels of un extracted residues (UERs) in the aerobic soil metabolism studies and it appeared that the extraction methods may not have been exhaustive , additionally

, aquatic exposure will be quantified using estimated exposure concentrations ( EECs ) for TTR s (hexazinone

### Page 8 of 133 

### plus its metabolites) and the UERs for selected representative scenarios . It should be noted that in the aerobic and anaerobic aquatic metabolism studies the levels of UERs were very low . As will be discussed later, including the UERs in the expression of the TTRs did not change the overa ll risk picture, since the hexazinone plus its ’ degradates (TTRs excluding the UERs) and the TTRs plus the UERs are very persistent in the environment

. [ The soil was only extracted three times by shaking for 30 minutes with methanol:water (80:20, v:v). ]

Exposures in terrestrial habitats will be calculated using hexazinone parent only.



## 1.5 **Risk Hypothesis**

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 have a source, a release mechanism, an e nvironmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure.

The risk hypothesis for hexazinone provides a written description of the predicted relati onships

between hexazinone , potential routes of exposur e, and the predicted effects for the assessment endpoint. The previous assessments highlighted in the preliminary problem formulation and more recent data serve as a basis for the risk hypothesis and conceptual model developed for current registered uses o f hexazinone

.

A r isk hypothes i s descri bes the predicted relationship among the stressor, exposure, and assessment endpoint response along with the rationale for their selection. For hexazinone , th e following ecological risk hypothesis is being employed for this national

- level ecological risk

assessment:

Hexazinone , when used in accordance with current label s , can result in off

site movement of the compound and its transformation products via runoff,

spray

- drift, and atmospheric transport leading to exp osure of nontarget plants

and animals. M onitoring data indicate frequent detections of hexazinone and

its residues in surface waters. Applications of hexazinone may result in

exposure to non

- target aquatic and terrestrial organisms at concentrations high enough to result in adverse effects upon the su rvival, growth, and reproduction. These nontarget organisms include Federally

- listed threatened and endangered species.

### Page 9 of 133 

### The ecosystems potentially at risk are often extensive in scope; therefore, it may no t be possible to identify specific ecosystems during the development of a nationwide ecological risk assessment. However, in general terms, terrestrial ecosystems potentially at risk could include the treated field and immediately adjacent areas that may receive drift or runoff. Areas adjacent to the treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats, and other uncultivated areas.

Aquatic ecosystems potentially at r isk include water bodies adjacent to, or downstream from, the treated field and might include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes ma rine ecosystems, including estuaries.



## 1.6 **Analysis**

The analysis plan will follow the approach described in the Preliminary Problem Formulation ( DP

barcode D3 6926 9)

. Modifications or updates to the approach described in the preliminary problem

formulation are described below.



# 2.0 Exposure Characterization

**2.1 Use Information** 

Nationally, hexazinone is an herbicide used to control a broad spectrum of weeds including undesirable woody plants in alfalfa, rangeland and pasture, w oodland, pineapples, sugarcane and

blueberries , among others . It is also used on ornamental plants, forest trees and other non

- crop

areas ( e.g. , rights

- of

- way) . Hexazinone is registered for pre

- emergent, post

- emergence, layby, directed spray and basal so il applications. It is used as a non

- selective herbicide in non

- cropland areas and as a selective herbicide in reforestation practices. Hexazinone products are formulated as pellets/tablets, emulsifiable concentrates, soluble concentrates/solids and a tec hnical grade active ingredient. Products are applied using aerial or ground equipment, by hand, or using a hand

held, boom, knapsack or power sprayer. There are no indoor uses.

Currently there is only one technical registration and there are 14 Section 3 registrations and 2 Special Local Needs (SLNs) . Of the Section 3 registrations, seven are multi

- active ingredient ( co

formulations ) that include hexazinone with either sulfometuron (EPA Reg. Nos. 352

- 603, 352

- 626) or diuron (EPA Reg. Nos. 352

- 618, 352

- 6 34, 352

- 663, 352

- 665, 352

- 666) . The active SLNs

are in the state of Louisiana. National (Section 3) uses for hexazinone are presented in Table 2 with label maximum application rates. For some uses the maximum number of applications per year at the maxim um rate is one ( i.e. , 1 application/year), while for some uses assumptions were made based on additional information found on the label or what is known about the crop and the

chemical

. For this assessment, 1 (one) application/year for those other uses wa s assumed . For example, blueberry uses may be modeled at a maximum of one application per year due to no application 450 days before harvest (note that it would mean fewer than one application per year)

. Pineapple may be modeled as one application per y ear due to the growing season, which is nearly

### Page 10 of 133 

### a year long. Non

- crop uses and forest site preparation and rangeland, are modeled as one application per year since rain fall is required to activate hexazinone and because maximum effects

are achieved after 1 2

- 24 months (thus, it is unlikely that repeated applications are made, considering that a waiting period is required to observe the effects) . Hexazinone is usually applied in the spring after ground thaws, or in the fall before snowfall (see Timing of App lication in Table

2 ). Note that the table also presents available Surface Water Concentration Calculator (SWCC) PRZM crop scenarios, which will be discussed later in this document ( Section 2.3.1 )

.

There are two granular products and one pelleted product containing hexazinone as the sole active ingredient as follows : DuPontTM Velpar ® 

### ULW (352

- 450) and Alligare Hexazinone 75 ULW (81927

- 31) herbicides are formulated as soluble granules, while Pronone ® 

### Power Pellet (33560

- 41) is formulated as pellets. All thr ee products contain 75% hexazinone and 25% other ingredients. For Velpar ® 

### , according to the label, “ Rainfall dissolves the VELPAR ® 

### ULW granules, releasing the active ingredient (hexazinone) into the root zone, where it is absorbed during periods of vigoro us plant growth.” For Alligare, the instructions say that, “Alligare Hexazinone 75 ULW granules are activated by rainfall. The active ingredient in Alligare Hexazinone 75 ULW, hexazinone, dissolves in the water and is moved into the soil.” Finally, for the pelleted product, Pronone, according to the label, “Moisture is required to activate PRONONE POWER PELLETS in the soil. Best results are obtained when the soil is moist at time of application and 1⁄4 to 1⁄2 inch of rainfall occurs within 2 weeks after app lication. ”

Table 2 . Summary of Hexazinone Uses and Application Information

Available

SWCC Scenario Crop Methods of Application Max Application

Rate (lb a.i./A) Timing of Application



### Non

- granular applications

NC alfalfa Alfalfa (grown for hay or seed p roduction),

Alfalfa (MT, ND, SD, WY)

Seed alfalfa (CA, ID, MT, NV, OR, UT, WA),

Seed alfalfa (Walla Walla, WA) Ground, aerial, chemigation, or impregnated on dry bulk fertilizer

(except CA & AZ) 1.5 (PHI = 30 d),

1,

1.5,

1.5 Most western

states wint er;

eastern states spring

LA sugarcane, (using a HI meteorological file

to represent sugarcane in HI) Sugarcane (except in FL) Ground; or aerial (for pre

emergence only) HI 3.6 (PHI= 180 d);

LA 0.9 and 1.5/yr (PHI=

234 d);

PR 0.5 and 1/yr (PHI=

288 d);

TX 1.75 and 1.75/yr (PHI= 234 d) Pre and post

emergence; Spring and fall;

Pre

- and post

emergence;

Pre

- emergence &

layby (60

- day

interval)

### Page 11 of 133 

### Table 2 . Summary of Hexazinone Uses and Application Information

Available

SWCC Scenario Crop Methods of Application Max Application

Rate (lb a.i./A) Timing of Application

No available scenario, not

modeled , but note that sugarcane in HI represents the same application

rate than pineapp le. Pineapple

Field edges and roadsides Ground;

or aerial 1.75/A/app, 3.6/A/year (PHI=181 d);

3.6 Intercrop period,

post

- mulch pre

plant, post

- plant,

post

- emergence (3

- 10 months after planting)

CA wine grape Blueberry (low bush);

Blueberry (hig h bush) Ground (avoid

contact with leaves), or impregnated on dry bulk fertilizer 3 (PHI 450 d);

2 (PHI 90 d) Spring

CA rights

- of

- way Non

- crop sites (weed and brush control): Uncultivated nonagricultural areas (such as, airports, highway, railroad and ut ility right

- of way, sewage disposal areas); Uncultivated agricultural areas (non

- crop producing, which includes: farmyards, fuel storage areas, fence rows, barrier strips); industrial sites (outdoor, such as, lumberyards, pipeline and tank farms);

Non

- cro p brush control.

Basal (soil) single stem treatment Ground or aerial (helicopter only);

Handgun applicator 8 ground and

6 for aerial

apps;

2

- 4 mL 3 per ea. stem in diameter, do

not exceed 8 lb a.i./A/yr Pre

- emergence or post

- emergence when weeds are actively growing

Late winter through summer

CA forestry (using

a MI meteoro

logical station or file to represent

eastern and lakes states) Forestry site preparation Eastern and Lakes states;

Western US

Grid application (applied directly to the soil surface)

Basal (soil) single stem treatment

Injection Ground or aerial (helicopter only)

Handgun applicator

Handgun applicator

Tree injector 5;

4;

5;

2

- 4 mL 3 per ea. stem in diameter;

1 mL 3 through

the bark of

undesirable

trees Early spring to early summer;

Rain belt late winter or spring and snow belt fall;

From hardwood bud break to early

summer;

NS;

Summer

### Page 12 of 133 

### Table 2 . Summary of Hexazinone Uses and Application Information

Available

SWCC Scenario Crop Methods of Application Max Application

Rate (lb a.i./A) Timing of Application

CA forestry (using

a MI meteoro

logical station or

file to represent
eastern and lakes

states ) Conifer releas e Eastern and Lakes states;

Western US

Grid application (applied directly to the soil surface)

Basal (soil) single stem treatment

Injection Ground, aerial (helicopter only), or impregnated on dry bulk fertilizer

Handgun applicator

Handgun applica tor

Tree injector 4;

3;

4;

2

- 4 mL 3 per ea. stem in diameter;

1 mL 3 through

the bark of

undesirable

trees Early spring to early summer;

Rain belt late winter or spring and snow belt fall;

From hardwood bud break to early

summer;

NS;

Summer

OR Chr istmas

trees Christmas tree plantations (except in the following 22 states

listed in label : Alabama, Louisiana, New Jersey, Texas, Arkansas, Maine, New York, Vermont, Connecticut, Maryland, North Carolina, Virginia, Delaware, Massachusetts, Pennsylvania, W est Virginia, Georgia, Mississippi, Rhode Island, Florida, New Hampshire, and South Carolina) Ground or aerial First year plantings 1.5;

Established

trees 2 lb

a.i./A East spring;

West >20 in rainfall spring;

West <20 in

rainfall fall

Not modeled

, but

may be represented by OR Christmas

trees or CA forestry, which are

modeled separately. Yellow poplar plantations Ground or aerial 2 Spring

CA rangeland hay (using a NY meteorological file

to represent eastern
and lakes states ) Pastures/Rangeland

Brush contro l: Eastern and lakes states,

Western US;

Basal (soil) single stem treatment Ground or aerial (helicopter only);

Handgun applicator 4,

3;

2

- 4 mL 3 per ea. stem in diameter,

do not exceed 0.8 lb a.i./yr Late winter through summer

PA turf Bermudagrass /Bahiagrass;

Industrial turf grass Ground 1.125 When weeds are actively growing



### Granular and pelleted applications

CA rangeland hay Rangeland (pellets) By hand or in a grid pattern for

area control 600 pellets/A=

0.63 lb a.i./A 2 Late Winter to early Summ er

CA forestry Conifer release (granular)

Conifer release (pellets) NS (assumed ground) By hand or in a grid pattern for

area control 3;

3800 pellets/A=

4.0 lb a.i./A 2 Late Winter to early Summer

### Page 13 of 133 

### Table 2 . Summary of Hexazinone Uses and Application Information

Available

SWCC Scenario Crop Methods of Application Max Application

Rate (lb a.i./A) Timing of Application

CA forestry Forestry site preparation (granular)

Fores try site preparation (pellets) NS (assumed ground)

By hand or in a grid pattern for

area control 4.7 (Eastern), 4 (Western);

5800 pellets/A

~ 6.1 lb a.i./A 2 Spring Spring or Fall

CA rights

- of

- way Non

- crop sites (granular) Uncultivated, nonfood producing agricultural areas: farmyards, fuel storage areas, fence rows, rights

- of

- way, fallow land, barrier strips; Uncultivated, outdoor nonagricultural areas: airports, highway rights

- of

- way, railroad rights

- of

- way, utility rights

of

- way (pipelines), sewage dispo sal areas; Industrial sites (lumberyards, tank farms), etc.

Non

- crop sites (p ellets) Noncropland areas such as utility, highway, pipeline and railroad rights

- of

- way, petroleum tank farms, lumberyards, storage areas, industrial plant sites, the berm of dra inage ditches (do not apply to the inside of ditch banks or to the inside of banks along waterways) and other similar areas. Ground, except for military

installations (aerial allowed)

By hand or in a grid pattern for

area control 8

7000 pell ets/A= 7.4

lb a.i./A 2 Late Winter to

Summer

NS

1 Uses assessed based on LUIS report Table 1, EFED label data report, and inspection of labels.

2 Based on the n umber of pellets in a 5.5 lb container ~3900, and 75% A.I. in formulation (source of nu mber of pellets is Pro

- Serve Inc.’s website (registrant’s website), at http://www.pro

- serveinc.com/powerpellet.html

, accessed 06/05/2015 ). 3 Application rates in mL /stem are representative of Vel par L labels. The rate in mL /stem vary for other products with different percent hexazinone , but the rate in lb a.i. is the same.



### Inspection of the labels for hexazinone indicates that the application rate range for the chemical may vary according to soi l texture and organic matter content and/or pest to be treated. For example, in the sample label for Velpar L, on rights

- of

- way the range in application rates is wide (range is 2

– 8 lb a.i./A). For rights

- of

- way, the recommended range is 2

– 5 lb a.i./A for certain pests, and 6

– 8 lb a.i./A for others. Further, the maximum rate is higher for the ground (8 lb a.i./A) than aerial (6 lb a.i./A) applications. The label instructs the applicator to...“Use lower rate on coarse textured soils (sand to sandy loam). U se the higher rate on fine textured soils (clay loam to clay) and on soils high in organic matter.” Similar instructions regarding the soil types are expressed in the majority of the labels and uses.



## Environmental Hazard Statements : The following statemen ts appear in the example label for Velpar L Herbicide . Similar statements appear in other labels. It should be noted that a groundwater advisory is stated :

“Do not apply directly to water, or to areas where surface water is present or to intertidal

area s below the mean high water mark. Do not contaminate water when disposing of equipment wash waters.

### Page 14 of 133 

### The active ingredient, hexazinone, in this product is known to leach through soil into ground water under certain conditions as a result of agricultural u se. Use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in groundwater contamination.”



## 2.2.1 Usage Information

A summary from the Screening Level Usage Analysis (SLUA, provided by BEAD) for h exazinone is provided in Table 3 . According to the SLUA, the major use for hexazinone by far is alfalfa, followed by sugarcane and pastureland. For all crops, ≤10% of the crop is treated. It should be pointed out that the SLUA does not provide informati on about non

- agricultural use patterns of

hexazinone . H exazinone has uses such as non

- cropland (represented by rights

- of

- way) and forestry , which are not represented in the SLUA

. SLUA data sources include: USDA

- NASS (United States Department of Agricultu re’s National Agricultural Statistics Service); 2001

- 2007; Private Pesticide Market Research, 2001

- 2007; NPUD 2002 (National Pesticide Use Database) of the CropLife America Foundation and California DPR data. These results reflect amalgamated data develop ed by the Agency and are releasable to the public.

Table 3. Summary of Screening

- Level Estimates of Agricultural Uses of Hexazinone (SLUA, dated 06/16/2009)

Crop (alphabetical) lb a.i. Percent (%) Crop Treated

Average Maximum

Alfalfa 300,000 <2.5 5

Cotton + 1,000 <1 <2.5
Fallow, Summer <500 <1 <2.5 Hay, Other (NPUD ’02) 4,000 N/C <1

Pasture 20,000 <1 <2.5

Pastureland 8,000 <1 <2.5 Sugarcane 20,000 5 10

All numbers rounded. N/C = Not Calculated. ‘<500’ indicates less than 500 pounds of activ e ingredient. ‘<2.5’ indicates less than 2.5 percent of crop is treated. ‘<1’ indicates less than 1 percent of crop is treated. + These crops were not known to be listed on active end use product or emergency exemption (Section 18) registrations w hen this report was run.



### The U.S. Geological Survey (USGS) pesticide use map ( Figure 2 ) shows regional scale patterns in use intensity within the United States. In comparison to the SLUA, the major use of hexazinone

in 200 8

- 12 is alfalfa (> 90% of the use), followed by pastures and hay ( < 10%). It is noted that the

USGS website 2 

### provides additional usage maps for other years . It is apparent from the map, that hexazinone was more intensively used in the western half of the continental U.S. in 20 12

. Add itionally, it was used intensively in FL, areas of the MS Delta, and sections of the Midwest

.

2 At http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2012&map=HEXAZINONE&hilo=L (accessed 06/29/2015).

### Page 15 of 133 

### Figure 2. Hexazinone Estimated Agricultural Use (20 12 ) and Use by Year and Crop

### Page 16 of 133 

## 2.2 **Environmental Fate and Transport**

The chemical profile of hexazinone is p rovided in Table 4 . Environmental fate characteristics of the parent compound hexazinone are listed in Tables 5 a, 5b

, and 6 and are discussed in greater detail in the following sections.

Hexazinone has a moderately high molecular weight of 252.3 g/mol , w i th a very high solubility (29

, 800 ppm)

, and a low octanol/water partition coefficient (K OW 

### = 15). Based on these properties, it appears that hexazinone has a very low potential to bioaccumulate/bioconcentrate. With a very high solubility, a relatively l ow vapor pressure (1.9 x 10

- 7 

### mmHg), and a very low Henry’s Law Constant (2 x 10

- 12 

### atm

- m 3 

### /mol), hexazinone is not expected to volatilize substantially from

wet/moist surfaces.

Table 4. Chemical Profile of Hexazinone

Property Value Reference

and Comme nts

Chemical Structure O

N C H 3

N

C H 3 C H 3

O N

N Product Chemistry

Pesticide type Herbicide

Product Chemistry Chemical class Triazinone

Molecular Formula C 12 H 20 N 4 O 2 Molecular Weight 252.3 g/mol

CAS No. 51235

- 04

- 2

CAS name 3

- Cyclohex yl

- 6

- (dimethylamino)

- 1

- methyl

- 1,3,5

- triazine

2,4(1 H ,3 H )

- dione

IUPAC name 3

- Cyclohexyl

- 6

- dimethylamino

- 1

- methyl

- 1,3,5

- triazine

2,4(1 H ,3 H )

- dione Water solubility 29800 ppm at 25°C

MRID 41203201 ( reported

in DP Barcode D279324) Vapor pressure 1.9 x 10

- 7 torr at 25°C [‘ Non

- volatile under field conditions’ from dry non

adsorbing surfaces (1) ] Henry’s Law Constant 2 x 10

- 12 atm

- m 3 /mol; at 25°C Calculated from WS and VP

Octanol/Water Partition 15 at pH 7.0 (temperature unspecified) MRID 41203201 ( reported

i n DP Barcode D279324)
(1) For classification scheme, see “ Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations,” available at http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_work group/esa_reporting_fate.htm#guidance (acces sed 12/04/2014).

### Page 17 of 133 

### Synopsis of Environmental Fate Based on the available information, hexazinone residues ( sum of hexazinone and Metabolites A1, B, D, G, 1, 2 and minor Metabolite A ) appear to be persistent and mobile in soil and aquatic

environments and c onsidered as the stressors in this assessment . T he half

- lives for parent

hexazinone are summarized in Table 5 , while the representative half

- lives for the total toxic residues or TTRs of hexazinone are presented in the Table 6 ( t otal toxic residues (TTRs) include hexazinone and its transformation products, which were found to be of concern : Metabolites A

- 1, B, D, G, 1, 2 and minor Metabolite A ) . The mobility of hexazinone was demonstrated in batch equilibrium as well as terrestrial field, forestry dissipa tion, and a prospective groundwater monitoring studies ( Table 7 ). Hexazinone is stable to hydrolysis and photolysis and degrades at relatively slow rates under aerobic soil metabolism conditions. Aerobic and anaerobic aquatic

metabolism and anaerobic soi l metabolism studies show slow degradation for hexazinone. Consistent with this persistence and mobility , field dissipation half

- lives were 123 to 154 days for the parent compound in bare ground silt loam, silty clay loam and sandy loam soils. Laboratory adsorption data show low water/soil partitioning for hexazinone (K OC 

### = 38

- 77 mL/g OC 

### , mobile according to FAO 2000 mobility classification). These data indicate that hexazinone is mobile, thus, combined with its persistence, having strong potential to lea ch to ground water systems, especially in soil systems such as loamy and sandy soils that are poor in organic matter. Based on laboratory bio concentration in rainbow trout, hexazinone is not expected to bio concentrate substantially in fish tissue, which i s consistent with the low K OW 

### value of 15 (i.e., log K OW 

### = 1.1).

Table 5. Summary of Degradation and Metabolism Fate Properties of Parent Hexazinone

Study System Name/ Characteristics Value for Parent Hexazinone 1 (Kinetic Model if Applicable) Referenc e, Study

Classification* DT 50 (days) DT 90 (days)

Abiotic Hydrolysis pH 5, 25 0 C Stable Stable
41587301 (A) pH 7, 25 0 C Stable Stable
pH 9, 25 0 C Stable Stable Atmospheric Degradation Hydroxyl radical 2 0.119 (estimated) EPI Suite v.4.11

Aqueous Photolysis pH 7, 25 0 C Stable Stable 41300801 (A)

Soil Photolysis Sandy loam from CA, pH 6.5,
0.6% OM, 20 0 C 82 (light exposed); stable (dark

control) 41300802 (A)

Aerobic Soil

Metabolism Sandy loam (CA), pH 6.5, 0.6%
OM, 25 0 C 216 41807401/ 42635001 (A) Audrain clay loam soil (MO), pH
6.6, 4.1% OM, 20 ° C 45.2 (IORE) 180 (IORE)

48898 001 (S) Sassafras sandy loam (MD), pH
5.4, 2.0% OM, 20 ° C DFOP slow

t 1/2 = 143 days Porterville loam (CA), pH 7.7,
1.11% OM, 20 ° C 115 (SFO) 381 (SFO)

Anaerobic Soil

Metabolism Raymondville sandy clay loam (TX), pH 8.0, 0.83% OM, 20oC 389 (SFO) 1,292 (SFO)
48898002 (S) Mexico clay loam (MO), pH 6.6,
4.1% OM, 20 ° C 997 (SFO) 3,311 (SFO)

### Page 18 of 133 

### Table 5. Summary of Degradation and Metabolism Fate Properties of Parent Hexazinone

Study System Name/ Characteristics Value for Parent Hexazinone 1 (Kinetic Model if Applicable) Referenc e, Study

Classification* DT 50 (days) DT 90 (days) Sassafras sandy loam (MD), pH
5.4, 2.0% OM, 20 ° C 309 (SFO) 1,026 (SFO)

Porterville loam (CA), pH 7.7,
1.11% OM, 20 ° C 1,165 (SFO) 3,872 (SFO)

Aerobic Aquatic Wa ter:sandy loam sediment (CA), water pH 7.9

- 8.0 3

, sediment pH not reported, 0.7% OM, 25 ° C >2 months 41811801 (A)

Wabasha Water:sandy loam sediment (MN), water pH 7.2, sediment pH 6.0, 7.1% OM, 20 ° C 528 (SFO) 1755 (SFO) 49109901 (S)

Tift Water:sandy loa m sediment GA, water pH 7.7, sediment pH
7.5, 1.2% OM, 20 ° C 719 (SFO) 2,389 (SFO)

Anaerobic Aquatic Water:loam sediment (CA), water pH 7.83, sediment pH 8.5, 1.24%
OC, 25 ° C 230 41807402 (A)

Wabasha Water: sandy loam sediment (MN), water pH 7.2,

sedime nt pH 6.0, 7.1% OM 20 ° C 482 (SFO) 1602 (SFO)

49109902 (S) Tift Water:sandy loam sediment (GA), water pH 7.7, sediment pH
7.5, 1.2% OM, 20 ° C 961 (SFO) 3192 (SFO)

* (A) = Acceptable; (S) = Supplemental

1 DT 50 and DT 90 values were calculated using nonlinea r regression and single first

- order (SFO), double first

- order in

parallel (DFOP), or indeterminate

- order equation (IORE). For DFOP, the overall DT 50 and DT 90 are reported when available. Otherwise, a first and second DT 50 are reported. The equations ca n be found in the document, Standard Operating Procedure for Using the NAFTA Guidance to Calculate Representative Half

- life Values and Characterize Pesticide Degradation, U.S. Environmental Protection Agency dated November 30, 2012 and approved December

17 , 2012.

2 Estimated value. In order to make this estimate, there are certain assumptions made by the module of EPISUITE,

which represent a typical hydroxyl reaction in the atmosphere (refer to AOPWIN module at http://www.epa.gov/opptintr/exposure/pubs/episuite.htm accessed 12/09/14 ). There is no ozone reaction calculation

available in EPI Suite v.4.1 for this chemical.

3 Measured in the first test interval.



### Table 6 . Summary of Info rmation Used to Derive Input Parameters for the Total Toxic Residues

of Hexazinone *

Study System Name/

Characteristics Description Half

- life Value

Used to Derive

Model Input

Parameters TTRs 1,2 Reference, Study

Classification* *

Abiotic Hydrolysis pH 7, 25 0 C Stable (0) 41587301 (A)

Aqueous Photolysis pH 7, 25 0 C Stable (0) 41300801 (A)

Aerobic Soil

Metabolism Sandy loam (CA), pH
6.5, 0.6% OM, 25 0 C 604 days (SFO) 41807401/ 42635001 (A)

### Page 19 of 133 

### Table 6 . Summary of Info rmation Used to Derive Input Parameters for the Total Toxic Residues

of Hexazinone *

Study System Name/

Characteristics Description Half

- life Value

Used to Derive

Model Input

Parameters TTRs 1,2 Reference, Study

Classification* *

Audrain clay loam soil (MO), pH 6.6, 4.1% OM,

20 ° C 208 days (S FO)

48898001 (S) Sassafras sandy loam (MD), pH 5.4, 2.0% OM,

20 ° C 416 days (SFO)

Porterville loam (CA), pH
7.7, 1.11% OM, 20 ° C 534 days (SFO)

Input value for modeling
with the SWCC, at 25 0 C.

from the four above mentioned systems (for the TTRs) 90 % percent upper confidence

limits on the mean half

- life

value: four values are available: 208, 416 and 534 (at 20°C), and 604 (at 25°C) days;

the corrected half

- lives at 25°C, are 147, 294, 378, and 604 days; mean = 355.75 days; std. dev. = 191.06 days, n = 4,

t 90,n

- 1 = 1.638. n s t t t 1

- n 90,

1/2 input + =



### = 512.2 days

Aerobic Aquatic Water:sandy loam sediment (CA), water pH

7.9

- 8.0 3

, sediment pH not reported, 0.7% OM, 25 ° C 1,046 days (SFO) 41811801 (A)

Wabasha Water:sandy loam sediment (MN), water pH 7.2, s ediment pH 6.0, 7.1% OM, 20 ° C 1,274 days (SFO)

49109901 (S) Tift Water:sandy loam sediment GA, water pH 7.7, sediment pH 7.5,
1.2% OM, 20 ° C 1,900 days (SFO)

Input value for modeling
with the SWCC, at 25 0 C.

from the three above mentioned systems (for the TTRs) 90% percent upper confidence

limits on the mean half

- life

value: three values are available: 1274 and 1900 days (at 20°C), and 1046 days (25°C); the corrected half

- lives at 25°C, are 901, 1344, and 1046 days; mean = 1097 days;

std. dev. = 225.86 days, n = 3,

t 90,n

- 1 = 1.886. n s t t t 1

- n 90,

1/2 input + =



### = 1,343 days

Anaerobic Aquatic Water:loam sediment (CA), water pH 7.83, sediment pH 8.5, 1.24%
OC, 25 ° C 1,837 days (SFO) 41807402 (A)

Wabasha Water: sandy loam sediment (MN), water pH 7.2, sediment pH 6.0, 7.1% OM 20 ° C 1,395 days (SFO) 49109902 (S)

### Page 20 of 133 

### Table 6 . Summary of Info rmation Used to Derive Input Parameters for the Total Toxic Residues

of Hexazinone *

Study System Name/

Characteristics Description Half

- life Value

Used to Derive

Model Input

Parameters TTRs 1,2 Reference, Study

Classification* *

Tift Water:sandy loam sediment (GA), water pH 7.7, sediment pH 7.5,
1.2% OM, 20 ° C 1,343 days (SFO)

Input value for modeling with the SWCC, at 25 0 C.

from the three above mentioned systems (for

the T TRs) 90% percent upper confidence

limits on the mean half

- life

value: three values are available: 1395 and 1383 days (at 20°C), and 1837 days (25°C); the corrected half

- lives at 25°C, are 986, 978, and 1837 days; mean = 1267 days; std. dev. = 493.65 days, n = 3, t 90,n

- 1 = 1.886. n s t t t 1

- n 90,

1/2 input + =



### = 1805 days

* Total toxic residues (TTRs) include hexazinone and its transformation products, which were found to be of concern ( Metabolites A

- 1, B, D, G, 1, 2 and minor Metabolite A ).

** (A) = Acceptable; ( S) = Supplemental

Bolded values represent input values in the aquatic modeling in SWCC ( and/or PRZM

- GW )

. A discussion of the SWCC and additional details about the modeling approach are provided below.

1 DT 50 and DT 90 values were calculated using nonlinear regression and single first

- order (SFO), double first

- order in

parallel (DFOP), or indeterminate

- order equation (IORE). The equations can be found in the document, Standard Operating Procedure for Using the NAFTA Guidance to Calculate Representative Hal f

- life Values and Characterize Pesticide Degradation, U.S. Environmental Protection Agency dated November 30, 2012 and approved December 17, 2012.

2 The value used to estimate a model input value is the calculated SFO DT 50 , t R IORE , or the 2 nd DT 50 from th e DFOP

equation. The model chosen is consistent with that recommended using the, Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media , Health Canada, U.S. Environmental Protection Agency, December 21, 2012.

3 Measured in the first test interval.



### Degradation and Metabolism Hexazinone was stable to hydrolysis in buffered solutions at pH 5, 7 and 9 at 25oC. The chemical comprised from 99

- 100% of the total radioactivity in all samples. When exposed to an artificial light sour ce, hexazinone did not appear to degrade significantly in pH 7 buffered solutions. Similar hexazinone recoveries were observed for the light irradiated and dark control samples. No major degradates were identified in these samples. In a soil photodegrad ation study, using a sandy loam soil from Modesto, CA (pH 6.5), hexazinone’s half

- life was 82 days, equivalent to an

environmental half

- life of 228 days at latitude 30 to 50oN, assuming a 12

- hour photoperiod. The major transformation product was Met abolit e B, which was 9.5

- 10.1% of the applied at 30 days (last test interval).

Hexazinone’s half

- lives were 216 and 1

, 440 days, when applied to viable and sterile (autoclaved) sandy loam soil (pH 6.5) from Modesto, CA, and maintained under aerobic conditions in the dark at 25oC. The viable and sterile soil data indicate that degradation was mainly a result of microbial activity. Carbon dioxide accounted for 2.2 and 0.03% of the applied after 365 days for the viable

### Page 21 of 133 

### and sterile soils, respectively. The aerobic transformation of hexazinone was also studied in three U.S. soils in a separate study: a sandy loam from MD (Sassafras, pH 5.4), a clay loam soil from Missouri (Audrain, pH 6.6), and a loam soil from CA (Porterville, pH 7.7) for up to 150 days at

20°C. I ORE t R IORE 

### half

- life was 54.3 days in the clay loam soil; slow t 1/2 

### DFOP was 143 days in the sandy loam soil; the SFO half

- life was 115 days in the loam soil . Evolved 14 

### CO 2 

### totalled a

maximum of 2.8

- 9.7% of the applied at study termination. Unextracted radioactivity was significant and increased to a maximum of 25.6% of the applied at 150 days (for the Audrain clay loam soil)

. A transformation pathway was provided by the study author ( Figure 3 ). In general, EFED agrees with the proposed pathway, except that the possible presence of metabolites of

concern in the “non

- extractable residues” in the figure is uncertain. EFED regards those residues as unextracted radioactivity instead. 3 

### ( The soil s were extracted three times by shaking for 30

minutes with me thanol:water (80:20, v:v). )

Figure 3 . Transformation Pathway Proposed by the Registrant (source: MRID 48898001)

The anaerobic soil metabolism of hexazinone was studied in four U.S. soils: a sandy clay loam

3 It should be noted that in the aerobic and anaerobic aquatic metabolism studies the levels of unextracted radioactivity were very low, and not considered.

### Page 22 of 133 

### soil from TX (Raymondville, pH 8.0), a clay lo am soil from MO (Mexico, referred to as Audrain; pH 6.6), a sandy loam soil from MD (Sassafras, pH 5.4), and a loam soil from CA (Porterville, pH 7.7) for 31 days under aerobic conditions, followed by 149 days under anaerobic conditions in

darkness at 20 ° C

. Half

- lives were 389 days in the Raymondville sandy clay loam soil, 997 days in the Audrain clay loam soil, 309 days in the Sassafras sandy loam soil, and 1,165 days in the Porterville loam soil (SFO in all instances)

. Unextracted radioactivity increase d to a maximum of 28.2% of the applied at 31 days posttreatment (0 day post

- flood), and was 12.6% at 180 days (149 days post

- flood) in the clay loam soil. Total evolved 14 

### CO 2 

### was ≤1.3% of the applied in all four

soils.

The half

- life for hexazinone in an aerobic aquatic metabolism study, consisting of a sandy loam sediment (pH 7.8, %OM = 0.7) and water (pH 8.2) from Madera, CA was >60 days, both in viable and sterile (autoclave) systems. Hexazinone accounted for ~80

- 84% and ~86

- 87% of the applied

radioact ivity at the end of the study (56 days) in the viable and sterile samples, respectively. The majority of the applied radioactivity was related to the water (as opposed to the sediment). At the beginning and end of the study, 88.3% and 76.4% of the applie d radioactivity were related to the water, respectively. T he aerobic aquatic metabolism of hexazinone was also studied in a MN water:sandy loam sediment system (Wabasha; water pH 7.2, sediment pH 6.0 and OC 4.1%) and a GA water:sandy loam sediment system (Tift; water pH 7.7, sediment pH 7.5, and OC 0.70%) in closed systems at 20 ° C. Hexazinone dissipated with half

- lives of 528 days in the Wabasha water:sandy loam sediment system and 719 days in the Tift water:sandy loam system. Unextracted radioactivity w as ≤4.9%. 14 

### CO 2 

### was a maximum of 0.1% of the applied at 100 days posttreatment.

In an anaerobic aquatic metabolism study, that consisted of a loam (pH 8.5, OC = 1.24%) and pond water (pH 7.83), the half

- lives were 230 and >1,500 days for the viable and st erile (autoclaved) systems. Hexazinone was an average of 95.6% of the applied radioactivity (AR) and decreased to

29.0% AR , at times 0 and 365 days, respectively. In another study, t he anaerobic aquatic

transformation of hexazinone was studied in a MN wa ter:sandy loam sediment system (Wabasha; water pH 7.2, sediment pH 6.0 and OC 4.1%) and a GA water:sandy loam sediment system (Tift; water pH 7.7, sediment pH 7.5, and OC 0.70%) in closed systems at 20 ° C. Hexazinone dissipated

with half

- lives of 482 days in the Wabasha water:sandy loam sediment system and 961 days in the Tift water:sandy loam system. Unextracted radioactivity was ≤4.8% AR and 14 

### CO 2 

### was not detected during the study.

Table 7 . Summary of Mobility, Field Dissipation, and Fish BCF Fate Pro perties of Hexazinone *

Study System Name/

Characteristics Value (units if applicable) Reference, Study Classification* *

and Comments

Mobility for

Hexazinone Soil \ Property K F (mL/g) K FOC (mL/g OC ) MRID 43621501 (A);

K OC model describes the mobility better than the K d model. For K OC the

coefficient of variation is Sassafras sandy loam 0.21 40 Trevino sandy loam 0.59 77

Chino loam 0.84 75

Tama silt loam 0.53 38

Mean Value 57.5 Mobile 1

### Page 23 of 133 

### Table 7 . Summary of Mobility, Field Dissipation, and Fish BCF Fate Pro perties of Hexazinone *

Study System Name/

Characteristics Value (units if applicable) Reference, Study Classification* *

and Comments

Additional notes 1/n ran ge 0.86

- 0.93 for the adsorption isotherms. Desorption step done at a single concentration. smaller than for K d

.

Terrestrial

Field Dissipation Bareground silt loam in Newark, DE 123 days; >95% confined to the upper 30 cm of

soil 42377901 (A); Met abolite s A, A

- 1, B, C, and 1 were identified in one or more sites at max. of 0.04, 0.21, 0.31, 1.23, and 0.71 ppm,

respect ively

. Bareground silty clay loam in Greenville,

MS 154 days; hexazinone did move to a depth of 60

- 75 cm

Bareground sandy loam soil in Madera,

CA 140 days; h exazinone leached to the 90 cm depth

level of soil. 4237920 1 (S); Met abolite s A, A

- 1, B, C, and 1 were

identified in soils at max. of 0.05, 0.04, 0.29, 0.62, and 0.20 ppm, respect ively

.

Forestry

Field Dissipation Forest

- land watersheds (loams)

in Coosa co unty, AL ; hexazinone was applied at 6.72 lb

a.i./A Hexazinone dissipated with half

- lives of 26 to 59 days and 19 to 36 days in plants, for the Velpar

ULW site and the Velpar L site, respectively.

Half

- lives of 55 to 77 days were reported for

litter and so il. For litter covered soil, a half

- life of 265 days was reported. Hexazinone was observed in soil at depths >30 cm (0.01 to 0.04

ppm ). Hexazinone was detected in runoff water up to 6 months post

- application (80 to 140 ppb).

Hexazinone was detected in stream samples at
both sites. 42336401 (A); Met abolites A, B, C, D, E, G, and B were discernible in various matrices (soil, water, litter and/or vegetation) samples.

Hexazinone and metabolites were consistently discernible in soil samples taken to a depth of 15 to 30 cm from

both sites.

Prospective groundwater monitoring Velpar L was applied

at 0.75 lb a.i./A in Merced County, CA sand planted with

alfalfa The leaching potential of hexazinone and

Met abolite s A, B, C, A

- 1, 1 , and G3170 (or G)

was studied in a vulnerable site for up to 35 months. Soil, groundwater, and soil pore

- water samples were analyzed for hexazinone and

metabolites. Hexazinone dissipated from the upper 2 feet of soil with a calculated half

- life of 25 days. Results indicated that hexaz inone and its degradates are very mobile and persistent. They leached through the soil profile and into the groundwater. Hexazinone concentrations above background (~0.05 ppb) were first detected in pore water at the 3

- foot depth at 60 days

posttreatment and in the 6

- and 9

- foot depths at 95 days. The breakthrough of hexazinone and

Metabolite B into the shallow groundwater occurred at 152 days posttreatment. 45132801 (S); Hexazinone and all metabolites except

Met abolite G moved at the same rate through t he

unsaturated zone and into groundwater as the bromide tracer, while Met abolite G

movement was somewhat

retarded. Met abolite G was the predominant degradate in the soil, soil pore water, and groundwater; its breakthrough into the shallow groundwater

occu rred at 336 days.

Fish BCF Rainbow trout The studies showed that hexazinone did not have the tendency to bio concentrate in fish. Further,

b ased on its low octanol/water partition coefficient (15 at pH 7.0, temperature unspecified ), hexazinone is not be e xpected to substantially accumulate in fish. 00064265 (00078032); 41203201 ( reported in DP Barcode D279324) (W)

### Page 24 of 133 

### Table 7 . Summary of Mobility, Field Dissipation, and Fish BCF Fate Pro perties of Hexazinone *

Study System Name/

Characteristics Value (units if applicable) Reference, Study Classification* *

and Comments

* Monitored and detected metabolites in the field.

* * (A) = Acceptable; (S) = Supplemental; (W) = Waived

Bolded values represent input values in the aquatic modeling in SWCC and/or PRZM

- GW.

1. Mobility classification per FAO 2000.



## 2.2.1 Mobility

In a Madera loam, Hanford sandy loam, Cecil sandy loam and Flanagan silty loam, the adsorption

K d 

### values were 10.8, 0.24, 0.45 and 1.03 mL/g, respectively . Meanwhile, in a Tama silty loam,

Chino loam , Trevino sandy loam and Sassafras sandy loam, the Freundlich K F 

### values were 0.53, 0.84, 0.59 and 0.21, respectively. For the latter soils, the Freundlich K FOC 

### values were 38, 75, 77 and 40, respectively. The 1/N values were relatively close to unity (0.93, 0.91, 0.91 and 0.86, respectively). Additional supplemental data provided by the second study, indicate that the metabolites A, B, D, H, 1, 2 and A

- 1 have similar mobility than the parent compound ( Table 8 ).

Table 8 . Mobility of Hexazinone Metabolites

Adsorption (Mobility) Studies K d K OC Source (MRID)

Metabolite 1 0.20 122

43621501 (supplemental portion of the study) Metabolite 2 0.15 45

Metabolite A 0.69 176

Metabolite A

- 1 0.03 27

Metabolite B 0.44 90

Metabolite D 0.34 59

Metabolite H 0.31 51



## 2.2.2 Terrestrial F ield Dissipation Studies

One terrestrial field dissipation study was conducted on a silt loam in Newark, DE and another on a silty clay loam in Greenville, MS. The respective half

- lives were 123 and 134 days in bare ground plots. The maximum hexazinone residue level in the 0

- 15 cm segments were 3.93 and 3.74 ppm, at 0 and 7 days posttreatment, respectively for the DE and MS sites

. The metabolites A, A

1, B, C and 1 were identified in soils at maximum concentrations of 0.04, 0.21, 0.31, 1.23 and 0.71

ppm in the soil , respectively. The reported data indicate that hexazinone, at 12 lb a.i./A, did not move substantially beyond the top 30 cm of soil (>95% confined to the upper 30 cm of soil) at the Newark site. However, hexazinone did move to a depth of 60

- 75 cm at the Greenville site. In addition, the hexazinone metabolites (particularly C in Newark) leached to a depth of 75 cm of soil during the testing period.

In another study, h e xazinone at 12 lb a.i./A, had a dissipation half

- life of 140 days in a bareground sandy loam in Madera, CA. The maximum hexazinone residue level in the 0

- 15 cm segment was 3.08 ppm, at 60 days posttreatment. Metabolites A, A

- 1, B, C and 1 were identified at maximum concentrations of 0.05, 0.04, 0.29, 0.62 and 0.20 ppm in the soil , respectively. The reported data indicate that hexazinone leached through the 90 cm soil depth. The hexazinone metabolites were

### Page 25 of 133 

### not reported below a depth of 30 cm of soil duri ng the testing period. The study was considered supplemental because the concentrations at time zero were too low, compared to the theoretical (or expected) value; however, the day 7 thru 60 post

- treatment samples had concentrations of 40

- 51% of the theor etical maximum rate.



## 2.2.3 Forestry Field Study

In a forestry study, h exazinone dissipated with reported half

- lives of 26 to 59 days and 19 to 36 days in plants for the Velpar ULW site and the Velpar L site, respectively [note that the sites are

identified by the end

- use products containing hexazinone used: Velpar ULW and Velpar L]

. Hexazinone was aerially (helicopter) applied to typical piedmont pine forestland; an application rate of 6.72 lb a.i./A was used on separate forestland watersheds in Coosa Coun ty, AL. Similar

half

- lives of 55 to 77 days were reported for litter and soil for the two sites (except litter covered soil). For litter

- covered soil, a half

- life of 265 days was reported. By day 365 post

- treatment, hexazinone was discernible only in se diment samples. Hexazinone moved off

- site through leaching and runoff. Hexazinone (0.01 to 0.04 ppm) was observed in soil at depths >30 cm. In addition, it was detected (80 to 140 ppb) in runoff water up to 6 months post

- application. In the study, hexaz inone was detected from stream samples from both sites (maximum concentration 473 ppb at 1150 hours post

- treatment at the Velpar L site).

M etabolites A, B, C, D, E, G, and H were discernible in various matrices (soil, water, litter and/or vegetation) samp les. Metabolite G was not confirmed by MS. Metabolites A, B and H were detectable in drainages sampled and located in the periphery of the site (1

- 3 ppb, <25 of 293 samples). Metabolites A, B, C, D and E were discernible in fern, dogwood, grass and blu eberry plant tissues (both sites). B and D were the most frequently detected metabolites (Velpar L site). In the soil samples, hexazinone and its metabolites were consistently observed thru 30 cm depth,

with detections thru 75

- 90 cm soil depth. The meta bolites A

- 1 and 1 were not analyzed for in the study. A prescripted burn of all three watersheds (Velpar ULW, Velpar L and control plots) took place 6 months post

- treatment.



## 2.2.4 Small Scale Prospective Groundwater Monitoring Study

Hexazinone [ end

- use p roduct Velpar L, 2 lb a.i/gallon water

- dispersible liquid] was broadcast applied once at 0.75 lb a.i./A in January 1996 onto a field of alfalfa underlain with sandy soil in Merced County, CA. The site is located within the recharge area for a shallow unco nfined aquifer. The treated area consisted of five 100 x 300 foot strips separated by irrigation berms, and the control area was 100 feet distant and upgradient from the treated area. The organic matter content

of the soil was ≤ 0.7%, the pH was 7.5

- 8.9 i n the upper 1.5 feet, and there were no continuous impeding layers.

The first rainfall was received at 7 days and the first irrigation event was at 75 days. T he site ran a slight water deficit through January 29, 1996 (18 days posttreatment). The cumula tive water budget was ca. 1.5 inches by 1 month and 2 inches by 2 and 3 months posttreatment. During the length of the study, the total rainfall received was 41.62 inches and the total irrigation received was 133.7 inches for a combined water input of ca. 175 inches, which was reported as 111% of the normal water input. The cumulative water budget through the study was positive, as the sum of precipitation plus irrigation remained greater than evapotranspiration. However, the cumulative

### Page 26 of 133 

### water budget decr eased in the summer when evapotranspiration was high, despite the irrigation, while the water budget increased in the winter when evapotranspiration was low. No substantial runoff events were reported.

Bromide concentrations in soil pore

- water and ground water showed that the total water input was sufficient to facilitate leaching to groundwater during the study period. The depth of the water table ranged from 8 to 15 feet below ground surface (bgs) during the study. Potassium bromide

was used as a trace r; breakthrough into the shallow groundwater occurred at about 152 days post

treatment. Soil (measured to 2 feet), soil pore water (lysimeters at 3, 6, 9, and 12 feet), and groundwater (wells screened at ~14

- 19 and ~20

- 25 feet bgs) samples were collected at up to 1063 days (~35 months) post

- treatment and analyzed using HPLC for hexazinone and six metabolites:

G3170 (or G) , A, B, C, A1, and 1.

Hexazinone dissipated from the upper 2 feet of soil with a calculated half

- life of 25 days.

Hexazinone and its de gradates exhibited a pattern of leaching through the soil profile and into the groundwater. Hexazinone concentrations above background (~0.05 ppb) were first detected in pore water at the 3

- foot depth at 60 days post

- treatment and in the 6

- and 9

- foot dep ths at 95 days. The breakthrough of hexazinone and degradate B into the shallow groundwater occurred at 152 days post

- treatment. G3170 (or Met. G) was the predominant degradate in the soil, soil pore water, and groundwater; G3170 breakthrough into the sh allow groundwater occurred at 336 days.

Hexazinone and Metabolites G3170, B, and A

- 1 were the major analytes detected when the residues reached groundwater at 336 days posttreatment. Following 824 days and at the end of the study period, Met. G3170 was t he dominant analyte.

A verage background hexazinone concentrations in shallow monitoring wells were 0.05

- 0.18 ppb from pre

- application to 214 days, increasing to 0.43 ppb at 271 days, 0.71 ppb at 336 days, and 2.02 ppb at 363 days. The first detections in groundwater were observed between 125 and 152 days in Clusters 1 and 4, with higher detections observed beginning at 271 days. Met abolite G3170 first increased above background levels to an average of 1.27 ppb at 363 days, and was a maximum

average con centration of 2.95 ppb in shallow wells at 424 days. Met abolite B first increased above background levels at 363 days, and was an average maximum concentration of 1.31 ppb at 424 days. Met abolite A

- 1 first increased above background levels at 363 days, a nd was an average maximum concentration of 0.71 ppb at 424 days. Met abolite 1 first increased above background levels at 363 days, and was an average maximum concentration of 0.42 ppb at 424 days.

Met abolite C was first observed consistently above backgr ound levels at 641 days, and was an average maximum concentration of 0.54 ppb at 851 days. Met abolite A was not observed above background levels.

H exazinone was first detected in deep monitoring wells above background levels in Cluster 1 at 214 days (0. 258 ppb), in Cluster 4 at 487 days (0.113 ppb), in Cluster 6 at 522 days (0.212 ppb), in Cluster 2 at 578 days (0.408 ppb), in Cluster 3 at 673 days (0.142 ppb), in Cluster 7 at 673 days (0.115 ppb), and was not observed in deep wells at Clusters 5 and 8, which were located in the eastern portion of the test plot (refer to next paragraph).

There was a distinct difference in the movement of hexazinone through soil in the western and eastern portions of the site. Hexazinone residues were detected infrequent ly and at later intervals

### Page 27 of 133 

### in groundwater in the eastern portion of the site, where soils were less sandy with thicker soil lens ( thicker regions of heavier soils) . Results indicated that hexazinone and its degradates are very mobile and persistent. The M et abolites D and 2 were not monitored in the small

- scale prospective groundwater monitoring study.



## 2.2.5 Bioconcentration in Fish

Based on laboratory bioaccumulation in rainbow trout, hexazinone is not expected to

bio concentrate in fish substantially, whi ch is consistent with the low octanol/water partition coefficient, K OW 

### value of 15 (log K OW 

### = 1.12).



## 2.2.6 Transformation Products

Transformation products of hexazinone are generally formed slowly and are also mobile and persistent ( Table 9 ). The major ph otodegradation product on soil, was Met. B (10.1% of applied). Under aerobic soil and aquatic conditions, major metabolites included G, 1, and A

- 1, with various other minor metabolites observed. In anaerobic soil and aquatic conditions, Mets. G, 1, D, an d 2 were among the major degradates. Mets. A, A

- 1, B, C and 1 were identified in soils in terrestrial

field. M et s

. A, B, C, D, E, G, and H were discernible in various matrices (soil, water, litter and/or vegetation) samples in forestry field samples. Me ts. D and 2 were major degradates found in anaerobic conditions; however, the field dissipation and the small

- scale prospective groundwater monitoring studies did not monitor these two metabolites. The fate of Mets. D and 2 could not be

assessed under nat ural environment; the registrant believed that both field studies were mostly aerobic and the metabolites were unlikely to be observed. The field dissipation studies did not monitor the fate of Met. G3170; however, it was found to be at the highest concen trations in the

small

- scale prospective groundwater monitoring study. This metabolite was found to increase

with time in three aerobic soils in a 150

- day long aerobic soil metabolism study

. 

### Further information about the degradates of hexazinone , includin g maximum formation and levels at study termination, can be found in Appendix C

.

Table 9 . Transformation Products of Hexazinone

Common Name Chemical Name Structure

IN

- G3170; Met. G

or G3170 IUPAC: 1

- Methyl

- 6

- (methylamino)

- 1,3,5

- triazine

2,4

- dione

Fo rmula: C 5 H 8 N 4 O 2 MW: 156.14 g/mol

SMILES: [H]n1c(=O)nc(n(c1=O)C)N([H])C H

N

O N

C H 3 N C H 3

H N O

### Page 28 of 133 

### Table 9 . Transformation Products of Hexazinone

Common Name Chemical Name Structure

IN

- JS472; Met. 1 IUPAC: 6

- (Dimethylamino)

- 1

- methyl

- 3

- (4

- oxocyclohexyl)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 18 N 4 O 3 MW: 266.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCC(=O)CC2)N(C)C O

N N

N

C H 3 C H

N

C H 3 O O

IN

- B2838; Met. D IUPAC: 1

- Cyclohexyl

- 3

- methyl

- 1,3,5

- triazinane

2,4,6

- trione

Formula: C 10 H 15 N 3 O 3 MW: 225.2 g/mol

SMILES: Cn1c(=O)[nH]c(=O)n(c1=O)C2CCCCC2 N

O N

C H 3 O N O

IN

- G3453; Met. A

- 1 IUPAC: 6

- (Dimethylamino)

- 3

- (2

- hydroxycyclohexyl)

- 1

- methyl

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 20 N 4 O 3 MW: 268.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCCCC2O)N(C)C

O H

O N

N

C H 3 N C H 3

C H 3 N O

IN

- A3928; Met. B IUPAC: 3

- Cyclohexyl

- 1

- methyl

- 6

- (methylamino)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 11 H 18 N 4 O 2 MW: 238.28 g/mol

SMILES: [H]N(C)c1nc(=O)n(c(=O)n1C)C2CCCCC2 N

O N

C H 3 N H

C H 3 N O

### Page 29 of 133 

### Table 9 . Transformation Products of Hexazinone

Common Name Chemical Name Structure

IN

- JT677; Met. 2 IUPAC: 6

- (Dimethylamino)

- 1

- methyl

- 3

- (2

-

oxo cyclohexyl)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 18 N 4 O 3 MW: 266.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCCCC2=O)N(C)C

O N

O N

C H 3 N

C H 3 C H 3 N O

IN

- T3937; Met. A IUPAC: 6

- (Dimethylamino)

- 3

- (4

- hydroxycyclohexyl)

- 1

- methyl

- 1,3,5

- triazine

- 2,4

- di one

Formula: C 12 H 20 N 4 O 3 MW: 268.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCC(CC2)O)N(C)C O

N N

N

C H 3 C H 3

N

C H 3 O O H

Carbon dioxide IUPAC: Carbon dioxide

Formula: CO 2 MW: 44 g/mol

SMILES: C(=O)=O C O O



## 2.2.7 Unextracted Residues

It was observed that in the aerobic soil and anaerobic soil metabolism studies high levels of unextracted radioactivity were formed, by using only simple extraction techniques. The soil s were only extracted three times by shaking for 30 minutes w ith methanol:water (80:20, v:v) , with no attempt to use other extraction solvents of different polarit y

. It was not clear whether the unextracted residues (UERs) contained in fact any degradate of ecological concern. In this assessment, to clear the unce rtainty relative to the UERs, E E Cs were calculated using both the

total toxic residues (TTRs), and the TTRs plus the UERs, to provide an upperbound level for the

E E Cs. In the aquatic metabolism studies, the levels of unextracted residues were low. As wil l be shown later, the aquatic EECs obtained from the TTRs plus the UERs were similar to the EECs

obtained with the TTRs alone.



## 2.2.8 Uncertainties

Even though the database for hexazinone is substantially complete, one major limitation of the

aerobic soil metabolism studies is that they showed high levels of unextracted radioactivity (UERs). However, for the aquatic metabolism studies, the levels of unextracted radioactivity were

### Page 30 of 133 

### very low. As per EFED UER Guidance ( USEPA 2014 ), u pper bound estimates of t he EECs were calculated using the half

- lives derived for the total toxic residues (TTRs) and the UERs for a

selected number of SWCC runs

. This was done due to the lack of evidence that a reasonable effort was executed to extract/identify these significant residues in the aerobic soil systems. As will be shown later, the aquatic EECs obtained from the TTRs plus the UERs were similar to the EECs

obtained with the TTRs alone.

Furthermore, for some of the studies, the duration was too short compared to the de rived representative half

- lives ( i.e. , estimated half

- lives were beyond the study duration) . Uncertainty

arises in these half

- life estimates.



## 2.3 **Aquatic Modeling Approach**

A brief description of the aquatic models used in this risk assessment follows. A dditional information about these models is provided in the Agency’s website at http://www.epa.gov/pesticides/science/models_pg.htm#aquatic . For agricultural and certain non

agricultural uses, exposure concentrations for surface waters assessments are estimated based on EFED’s Tier II aquatic model PRZM/VVWM. A graphical user interface Surface Water Concentration Calculator (SWCC v.1.106, May 6, 2014), developed by the EPA, w as used to facilitate inputting chemical and use specific parameters into the appropriate input files and chemical files, replacing the older PE5 shell (November 2006), which used PRZM3 and EXAMS. The SWCC estimates pesticide concentrations in water bodie s that result from pesticide applications to land. The calculator was designed for regulatory applications as applied in the Office of Pesticide Programs, USEPA, as well as PMRA, Health Canada. The calculator uses the Pesticide Root Zone Model (PRZM v5. 0+, May 6, 2014) and the Varying Volume Water Body Model (VVWM, May 6, 2014, a replacement for the older EXAMS model). The PRZM field or orchard crop scenario is the basic file which describes the local or regional climatological information, soil hydrolo gy, soil characteristics, crop characteristics, and the pesticide properties necessary to determine pesticide loadings to surface water. This basic file constitutes the first part of the “exposure scenario.” It simulates the processes in the agricultural field, such as runoff and erosion, on a daily time step. The runoff and erosion flux output data from PRZM are used as chemical loadings to the VVWM, which simulates surface water, in order to predict the EECs. The VVWM is conceptually similar to the cu rrent EXAMS

- based model in that both are 2

- compartment models driven by first

- order processes. It simulates the USEPA standard water bodies (i.e., farm pond and/or index reservoir) but with greater efficiency and flexibility for incorporation into a user interface. The VVWM also allows for variations in water body volume on a daily basis due to runoff, precipitation, and evaporation. Temperature, wind speeds, and pesticide dissipation processes are also allowed to vary daily. EECs were determined using the standard pond scenario which describes a vulnerable surface waters scenario for the VVWM component of the modeling exercise.



## 2.3.1 Scenario Selection

Three representative agricultural crops were modeled: alfalfa, sugarcane and blueberries. For

alfalf a, the NC alfalfa scenario was selected (note that there are other alfalfa scenarios; however, to the extent possible, crops from diverse regions from across the U.S. were selected ; Table 10 )

.

### Page 31 of 133 

### For sugarcane, it was noted that the highest application rate applies only to sugarcane in Hawaii. Since there is no available scenario for HI sugarcane, the LA sugarcane was used as a surrogate, with a HI weather scenario. For blueberries, the CA wine grape scenario was used as a surrogate for the crop.

For the n on

- agricultural crops, the CA rights

- of

- way scenario was used to model both aerial and ground applications (the rights

- of

- way has the maximum allowed application rate among all uses and the application rate for ground applications is higher than for aerial applications). Additionally, other crops were run as shown in Table 10

.



## 2.3.2 Model Inputs

Tables 10 and 1 1 show the input values used in SWCC. It should be noted that three non

agricultural uses may be applied aerially, but only by means of helicopter . At this time, EFED does not recommend to use the forestry module of AgDRIFT; thus the agricultural module of AgDRIFT was used as a surrogate, to estimate forestry spray drift , using the Wasp Helicopter as

the aircraft

. For aerial applications, the foll owing assumptions were made: Tier II Aerial application using ASABE Fine to Fine to Medium DSD, 5 gallons diluted product per acre, wind speed 10 mph, aircraft Wasp Helicopter, boom height 10 feet.

Two representative runs were performed, one for granular and the other for pelleted applications, where the value of spray drift was assumed to be 0 (zero) and the application efficiency 1.00, using other similar assumptions, compared to spray applications. It was found that the EECs for the forestry applicatio ns decreased substantially while for the rights

- of

- way the EECs were around two thirds those for the ground spray applications at the same active ingredient application rate.

Table 10 . Hexazinone Uses, Scenarios, and Application Information Used for Aqu atic Exposure Inputs in Ecological Exposure Assessment (all applications are into the surface)

Run Number, Scenario (bold font)/ Uses Represented (meteorological file if not the default one) App. Equipment Drift/ App Efficiency Single App

Rate kg a.i./A
( lb a.i./A) Max

No. of Apps

at Max

Rate Min.

Interval

Between

Apps (days) Day of App (day

month) App. Method

Agricultural Use Patterns

NC alfalfa /Alfalfa Aerial 0.125/0.95 1.68 (1.5) 1 N/A 01

- 04 Foliar

LA sugarcane (HI meteoro

logical file 22521)/Sugarca ne in HI Aerial 0.125/0.95 4.03 (3.6) 1 N/A 10

- 01 Foliar

CA wine grape /Blueberries Ground 0.062/0.99 2.24 (2) 1 N/A 01

- 04 Ground

Non

- Agricultural Use Patterns CA rights

- of

- way / Non

- crop sites (weed and brush control) Aerial helicopter 0.113/0.95 6.72 (6 ) 1 N/A 01

- 04 Foliar

CA rights

- of

- way / Non

- crop sites (weed and brush control) Ground 0.062/0.99 8.97 (8) 1 N/A 01

- 04 Foliar

### Page 32 of 133 

### Table 10 . Hexazinone Uses, Scenarios, and Application Information Used for Aqu atic Exposure Inputs in Ecological Exposure Assessment (all applications are into the surface)

Run Number, Scenario (bold font)/ Uses Represented (meteorological file if not the default one) App. Equipment Drift/ App Efficiency Single App

Rate kg a.i./A
( lb a.i./A) Max

No. of Apps

at Max

Rate Min.

Interval

Between

Apps (days) Day of App (day

month) App. Method

CA forestry (MI meteorological file 14850)/

Conifer release in Eastern and

Lakes states Aerial helicopter 0.113/0.95 4.48 (4) 1 N /A 01

- 05 Foliar

OR Christmas trees / Christmas trees plantations (except in 22 states listed in label) Aerial 0.125/0.95 2.24 (2) 1 N/A 01

- 04 Foliar

CA rangeland hay (NY meteorological file 14860)/ Pastures/Rangeland in Eastern

U.S. Aerial helicopter 0.11 3/0.95 4.48 (4) 1 N/A 01

- 03 Foliar

PA turf / Bermudagrass/ Bahiagrass; Industrial turfgrass Ground 0.062/0.99 1.26 (1.125) 1 N/A 01

- 03 Foliar

Pellet and Granule Applications CA forestry (MI meteorological file 14850)/Conifer release Ground (Pellets) 0.00 /1.00 4.48 (4) 1 N/A 01

- 05 Ground

CA rights

- of

- way / Non

- crop sites (weed and brush control) Ground (Granules) 0.00/1.00 8.97 (8) 1 N/A 01

- 04 Ground



### The chemical input parameters are summarized in Table 1 1 . Note that two aerobic soil metabolism input h alf

- lives are included in the table (see bold and underlined font). One is for the total toxic residues (TTRs), which are hexazinone plus its metabolites of concern. The other one includes the TTRs (as defined above), plus the unextracted residues (UERs) . For the aerobic and anaerobic aquatic metabolism studies, only one half

- life for the TTRs is reported since the levels of unextracted radioactivity were very low in these studies and the UERs were not considered.

Table 11 . Environmental fate data used for aquatic exposure inputs in Hexazinone aquatic risk assessment in the SWCC 1

Parameter (units) Value(s) Sources Comments

Chemical Name Hexazinone Labels Label Application Rate ( Kg a.i./ha) Refer to Table 10 Labels Highest single application rates

acc ording to the labels.

Number of Applications Allowed Refer to Table 10 Labels Maximum allowed by the label, at the

maximum rate.

Interval between Applications (days) Refer to Table 10 Labels Minimum allowed by the label.

Crop Names and Days of Applicati on (day

- month) Refer to Table 10 Labels

---

### Page 33 of 133 

### Table 11 . Environmental fate data used for aquatic exposure inputs in Hexazinone aquatic risk assessment in the SWCC 1

Parameter (units) Value(s) Sources Comments

K OC (ml/g OC ) 57.5 43621501 Sorption is better correlated with organic carbon content. Represents the

mean of four values

. Aerobic Soil Metabolism (days)

25°C = 512.2 for the TTRs 41807401/ 42635001;

488980 01 90% percent upper confidence limits on the mean for the following corrected

half

- life value s at 25°C: 147, 294, 378, and 604 days

.

= 1

, 093 for the TTRs +

UERs 41807401/ 42635001;

48898001 90% percent upper confidence limits on the mean for the follo wing corrected

half

- life values at 25°C: 432, 762, 1134, and 1023 days

. Solubility in Water (ppm) (25°C) 29,800 41203201 DP Barcode D279324.

Aerobic Aquatic Metabolism (days)

25°C = 1343 for the TTRs 2 41811801;

49109901 90% percent upper confidence lim its on the mean for the following corrected

half

- life values at 25°C: 901, 1344, and 1046 days; mean = 1097 days

. Anaerobic Aquatic Metabolism (days)

25°C = 1805 for the TTRs 2 41807402;

49109902 90% percent upper confidence limits on the mean for the fo llowing corrected

half

- life values at 25°C: 986, 978, and 1837 days; mean = 1267 days

. Hydrolysis at pH 7 0 41587301 Stable at pH 5

- 9. Aqueous Photolysis (days) 0 41300801 Stable under the testing conditions. For the modeling, assume 40° latitude.

Mole cular Weight (g/mol) 252.32 EPI Suite

v.4.11 ---

Vapor Pressure (25°C) (torr) 1.9 x 10

- 7 41203201 DP Barcode D279324.

Henry’s Law

Constant

Dimensionless (25°C) 8.65 x 10

- 11 VP/WS This value is calculated by the SWCC.

PRZM Scenario and

Metfile As suggest ed by the shell SWCC, with exceptions noted

in Table 10

. SWCC shell Exceptions include LA sugarcane (run with a HI met file), and CA forestry (run with a MI met file). See Table 10

for selected met file.

Foliar Half

- life 0 Default

value Assume no degrada tion.

Post

- harvest Foliage Surface applied Default

value ---

FEXTRC, Foliar

extraction 0.5 Default

value ---

PLVKRT,

Volatilization rate from foliage 0 Default

value ---

UPTKF, Uptake

factor 0 Default

value ---

1 Data were selected according to EFED G uidance on Input Parameters v.2.1, dated 10/22/2009 and approved t t t s

n input n

= + −
1 2 90 1

/ , ( )

t t t s

n input n

= + −
1 2 90 1

/ , ( )

t t t s

n input n

= + −
1 2 90 1

/ , ( )

t t t s

n input n

= + −
1 2 90 1

/ , ( )

### Page 34 of 133 11/10/2009 (USEPA 2009). 2 In the aerobic and anaerobic aquatic metabolism studies the levels of UERs were very low at all test intervals. Thus,

the UERs were not considered.



### Table 12 . T ier II Estimated Environmental Concentrations (EECs) for surface water based on application of hexazinone products modeled in the SWCC, including the TTRs (but excluding the UERs)

Scenario App.

Method App.

Rate (lb a.i./A) Date of

First Application

(dd

- mm ) No. of Apps App.

Interval (days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

NC alfalfa /Alfalfa Aerial 1.5 01

- 04 1 N/A 139 138 137 LA sugarcane (HI met file)/Sugarcane

in HI Aerial 3.6 10

- 01 1 N/A 600 596 593 CA wine grape /

Blueberries Ground 2 01

- 04 1 N/A 78.8 78.6 78.1 CA rights

- of

- way/

Non

- crop sites (weed and brush control) Aerial helicopter 6 01

- 04 1 N/A 645 644 640 CA rights

- of

- way/

Non

- crop sites (weed and brush control) Ground 8 01

- 04 1 N/A 653 651 648 CA forestry (MI met file)/Conifer release

in Eastern and La kes

states Aerial helicopter 4 01

- 05 1 N/A 369 368 366

OR Christmas

trees /Christmas trees Aerial 2 01

- 04 1 N/A 161 160 160 CA rangeland hay (NY met file)/ Pastures/Rangeland

in Eastern US Aerial helicopter 4 01

- 03 1 N/A 493 492 490

PA turf / Bermudagrass / Bahiagrass; Industrial turfgrass Ground 1.125 01

- 03 1 N/A 41.7 41.6 41.4 CA forestry (MI meteorological file 14850)/Conifer

release Ground (Pellets) 4 01

- 05 1 N/A 24.1 24.0 23.8 CA rights

- of

- way /

Non

- crop sites (weed and brush control) Ground (Granules ) 8 01

- 04 1 N/A 408 407 405



### EECs were calculated using the half

- lives for the TTRs + UERs for the agricultural and non

agricultural crops that yielded the highest EECs (from Table 1 2 ). The EECs for the TTRs plus the UERs provide an upper bound estimate of the TTRs should the UER contain any residue of ecological concern. It was noted that the EECs with and without the UERs for the selected scenarios were very similar; therefore, the overall risk picture for hexazinone is not expected to vary substantia lly.

### Page 35 of 133 

### Table 13 . Tier II Estimated Environmental Concentrations (EECs) for surface water based on application of hexazinone products modeled in the SWCC, including the TTRs

and UERs

Scenario App.

Method App.

Rate (lb a.i./A) Date of

First Application

(dd

- mm) No. of Apps App.

Interval (days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L) LA sugarcane (HI met file)/Sugarcane

in HI Aerial 3.6 10

- 01 1 N/A 601 597 594 CA rights

- of

- way/

Non

- crop sites (weed

and brush co ntrol) Ground 8 01

- 04 1 N/A 656 654 651



## 2.3.3 Monitoring

There is available monitoring data for this chemical. Hexazinone in groundwater was previously

considered and evaluated by the California Department of Pesticide Regulation (CDPR), as shown

in th e following site http://www.cdpr.ca.gov/docs/emon/grndwtr/hexazinone.htm (accessed 01/12/2015). Their findings were summarized as follows: “The Director concurs with the

subcommittee that based on the detected concentrations of hexazinone (ranging from 0.05 to 0.27 μg/L) and the health

- protective drinking water level of 170 μg/L established by the Office of Environmental Health Hazard Assessment (OEHHA), hexazinone cannot be found to h ave polluted ground water.” (It should be noted that the safety of hexazinone to humans is not within the scope of this ecological risk assessment or the Environmental Fate and Effects Division , and the citation is provided only to state the range of dete cted concentrations in the California groundwater database.)

Hexazinone and a number of its degradates were found to be monitored in the USGS National Water Quality Assessment Data Warehouse (NAWQA), when verified by constituent finder (at http://cida.usgs.gov/nawqa_public/apex/f?p=136:1:0 , accessed 01/12/2015). Table 1 4 summarizes the findings for hexazinone. Across the U.S. (excluding territories), a total of 6,185 samples were analyzed for hexazinone, of which 1

, 2 86 (21 %) were positive detections. Of the detections, 1,134 (18%) were positive surface water detections and 15 2 (2.5 %) were po sitive groundwater detections. The maximum surface water concentration was 0.545 μg/L (detected in Riverside, CA), and the maximum groundwater detection was 0.265 μg/L (detected in Mitchell, GA).

Table 14 . Summary of Hexazinone Monitoring Data from the NAWQA Database

State Total No. Samples Total No.

Detects (%) No. SW

Detects Max. Conc. in

SW (μg/L) No. GW

Detects Max. Conc. in

GW (μg/L )

Alabama 189 39 39 0.0948 0 N/A

Alaska 2 0 0 N/A 0 N/A

Arizona 103 13 12 0.0937 1 0.0058

Arkansas 19 4 4 0.0102 0 N/A

California >5 00 4 16 396 0.545 20 0.0635

Colorado 240 32 27 0.0228 5 0.0237

### Page 36 of 133 

### Table 14 . Summary of Hexazinone Monitoring Data from the NAWQA Database

State Total No. Samples Total No.

Detects (%) No. SW

Detects Max. Conc. in

SW (μg/L) No. GW

Detects Max. Conc. in

GW (μg/L )

Connecticut 123 39 39 0.0368 0 N/A

Delaware 33 0 0 N/A 0 N/A

District of

Columbia 0 0 0 N/A 0 N/A

Florida 337 99 50 0.0303 49 0.0867 Georgia 268 80 59 0.132 21 0.265

Hawaii 15 4 0 N/A 4 0.0869

Idaho 148 9 5 0.0281 4 0.0173

Illinois 188 3 3 0.0315 0 N/A

Indiana 13 1 4 4 0.0258 0 N/A

Iowa 218 7 7 0.0195 0 N/A

Kansas 31 0 0 N/A 0 N/A Kentucky 4 1 1 0.0521 0 N/A

Louisiana 274 61 61 0.0669 0 N/A

Maine 37 0 0 N/A 0 N/A Maryland 128 3 3 0.0101 0 N/A

Massachusetts 86 2 0 N/A 2 0.0079 Michigan 113 0 0 N/A 0 N/A

Minnes ota 172 4 1 0.0097 3 0.156 Mississippi 97 28 28 0.0213 0 N/A

Missouri 43 1 1 0.0022 0 N/A

Montana 43 0 0 N/A 0 N/A

Nebraska 105 2 2 0.0096 0 N/A

Nevada 55 2 2 0.0168 0 N/A

New Hampshire 35 0 0 N/A 0 N/A

New Jersey 264 36 36 0.264 0 N/A

New Mexico 1 57 3 0 N/A 3 0.0411

New York 131 7 3 0.0143 4 0.0565

North

Carolina 126 25 25 0.0738 0 N/A

North Dakota 0 0 0 N/A 0 N/A

Ohio 78 8 8 0.0602 0 N/A

Oklahoma 12 0 0 N/A 0 N/A Oregon 252 181 181 0.339 0 N/A Pennsylvania 40 0 0 N/A 0 N/A

Rhode Island 5 1 0 N/A 1 0.0097

South

Carolina 211 42 39 0.0214 3 0.0343

South Dakota 1 0 0 N/A 0 N/A

Tennessee 113 6 0 N/A 6 0.153

Texas 414 43 30 0.0495 13 0.126

Utah 124 4 1 0.0084 3 0.0109

Vermont 3 0 0 N/A 0 N/A Virginia 110 36 36 0.167 0 N/A Washington 275 4 1 31 0.0483 10 0.177 West Virginia 5 0 0 N/A 0 N/A

Wisconsin 121 0 0 N/A 0 N/A Wyoming 6 0 0 N/A 0 N/A

Total s 6,185 1,2 86 1,134 0.545 15 2 0.265

### Page 37 of 133 

### It is noted that sampling and testing for hexazinone in the NAWQA database does not represent necessarily vulnerable bodies of surface waters or vulnerable aquifers . Despite the relatively high level of detections, EFED believes that modeling reflects concentrations in surface waters, which are realistically conservative for each site represented. The NAWQA monitoring program analyzed for this assessment does not specifically target hexazinone. Consequently, detections cannot be directly associated with a particular use pattern or site, nor are the detections expected to represent the potential peak hexazino ne exposure. This result is attributed to the fact that water monitoring sampling programs do not specifically target hexazinone use areas, may not represent high hexazinone use areas, and may not correspond with applications of hexazinone; therefore,

pea k concentrations of hexazinone may not be detected. Therefore, currently available monitoring

data may underestimate hexazinone concentrations, and monitoring results are not an appropriate prediction of the potential exposure resulting from hexazinone us e. For these reasons, EFED does

not recommend that hexazinone water monitoring data be used by EFED in ecological effects risk

assessment quantitatively and only a qualitative discussion was provided.

Seven metabolites of hexazinone were monitored on a f ew occasions only in the state of Texas; however, no detections were reported. Sampling occurred once or twice per metabolite. The following metabolites were included: D, G, E, 4

- hydroxyhexazinone (A), didemethyl hexazinone (F), demethyl hexazinone (B), and C.



## 2.4 **Terrestrial Exposure Modeling**

2.4.1 Exposure to Birds and Mammals

For spray applications, the T

- REX model (Terrestrial Residue EX posure model; v. 1.5.2; June 6, 2013) is used to predict dietary exposure to hexazinone residues on foliar surfac es and insects using the Kenaga nomogram as modified by Fletcher (Hoerger and Kenaga 1972, Fletcher et al. 1994). Estimated exposures of terrestrial insects to hexazinone are evaluated in terms of the insects’ potential relevance as dietary items for terre strial vertebrates and for use in risk

characterization for listed terrestrial invertebrates.

T

- REX (v. 1.5.2) is used to calculate dietary and dose

- based EECs of hexazinone residues on food items for mammals and birds generated by spray applications for the labeled uses. Input values for the use scenarios used to derive EECs using T

- REX and TerrPlant are located in Table 1 5 for foliar spray uses that represent a range of single as well as seasonal application rates and in Table

16 for pelleted and granul ar applications . Upper

- bound Kenaga nomogram values are used to derive EECs for hexazinone exposures to terrestrial mammals and birds based on a 1

- year time period. Consideration is given to different types of feeding strategies for mammals, including

herb ivores, insectivores and granivores. Dose

- based exposures are estimated for three weight classes of birds (20 g, 100 g, and 1000 g) and three weight classes of mammals (15 g, 35 g, and 1000 g). Terrestrial EECs for foliar spray uses and seed treatment uses of hexazinone are provided

in Tables 17

, 18

, and 19

.

### Page 38 of 133 

### Table 15 . Input Parameters for Deriving Terrestrial EECs for Labeled Spray Uses of Hexazinone Related to Terrestrial Plants and Animals. A foliar dissipation half

- life of 35 days was used.

Use Maxim um Single App Rate (lb. a.i./A) N umber of Apps. at Max

Rate M aximum Seasonal App.

Rate (lb. a.i./A) M inimum

Interval Between

Apps. (days) 1 A pplication

Method Used in Modeling Pre

Harvest

Inter val Agricultural Uses

Alfalfa 1.5 1 1.5 NA Aerial NA Sugarcan e HI 3.6 1 3.6 NA Aerial NA

Blueberries 2.0 1 2.0 NA Ground NA

Non

- Agricultural Uses

Non

- crop sites 6.0 1 6.0 NA Aerial NA

Non

- crop sites 8.0 1 8.0 NA Ground NA

Christmas Tree

Plantation 2.0 1 2.0 NA Aerial NA

Rangeland 4.0 1 4.0 NA Aerial NA

Indust rial Turfgrass 1.125 1 1.125 NA Ground NA

N/A=does not apply; G=ground; A=aerial, S=spray (low or high volume), AB=airblast



### Differences in exposures between ground and aerial applications cannot be assessed with the

current T

- REX model; exposure and ri sk estimates from the T

- REX model are considered relevant to both application scenarios. A further uncertainty with the model is the inability to model systemic chemicals like hexazinone as T

- REX only simulates residues directly on food items.

T

- REX (v. 1.5.2) and Terr Plant are also used to calculate dietary and dose

- based EECs of hexazinone residues on food items for mammals and birds generated by granular and pelleted applications for the labeled uses. Input values for the use scenarios used to derive EECs using T

REX and TerrPlant are located in Ta ble 16

. The LD 50 

### /ft 2 

### tab is used estimate risk for granular and pelleted formulations. It is designed to estimate the amount of pesticide estimated to kill 50% of exposed animals in each square foot of appl ied area. Although a square foot does not have defined ecological relevance, risk presumable increases as the LD 50 

### /ft 2 

### increases. The LD 50 

### /ft 2 

### is calculated using a toxicity value (adjusted LD 50 

### ) and the EEC and is directly compares with the Agency’s LOC

.

Table 1 6. Input Parameters for Deriving Terrestrial EECs for Labeled Granular and

Pelleted Uses of Hexazinone Related to Terrestrial Plants and Animals.

Use Maximum Single App Rate (lb. a.i./A) Number of Apps. at Max

Rate Maximum Seasonal App.

Rate (lb. a.i./A) Minimum

Interval Between Apps. (days) 1 Application

Method Used in Modeling Pre

- Harvest

Interval

Rangeland 0.63 1 0.63 NA Ground/ Granular NA

Conifer Release 3 1 3 NA Ground/ Granular NA

Conifer Release 4 1 4 NA Ground/ Pellet NA Forestry Site Prep:

Eastern 4.7 1 4.7 NA Ground/ Granular NA

Forestry Site Prep:

Western 4 1 4 NA Ground/ Granular NA

Forestry Site Prep 6.1 1 6.1 NA Ground/ Pellet NA

Non Crop Sites 8 1 8 NA Ground/ Granular NA Non Crop Sites 7.4 1 7.4 NA Ground/ Pelleted NA N/A=does not apply; G=ground; A=aerial, S=spray (low or high volume), AB=airblast

### Page 39 of 133 

### Terrestrial wildlife exposure estimates are typically calculated for birds and mammals by emphasizing the dietary exposure route of uptake of pesticide active ingredients . These exposures are considered to be surrogates for exposures to terrestrial

- phase amphibians and reptiles. For exposures to terrestrial organisms, such as birds and mammals, pesticide residues on food items

are estimated based on the assumption that the pesticide residues on the organism’s food are dependent on the use pattern of the pesticide

.

### Page 40 of 133 Table 1 7 . Dose

- based EECs (mg/kg bw) as Food Residues for Birds, Reptiles, and Terrestrial

- phase Amphibians from Labeled Non

- Granular Uses of Hexazinone (T

- R ex v. 1.5.2). Toxicity to birds is based on data for hexazinone.

Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size*  Small Med Large Small Med Large Small Med Large

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 1 

Non

- Agricultural Uses

Alfalf a 410 187 230 25.6 233 107 131 14.6 104 47.9 58.8 6.54 160 91.5 41 5.69 3.25 1.45

Sugarcane in HI 984 451 553 61.5 561 257 315 35.0 251 115 141 15.7 385 219 98.4 13.6 7.79 3.49

Blueberries 546 250 307 34.1 311 142 175 19.4 139 63.9 78.5 8.72 214 122 54.6 7.59 4.33 1.94

Agricultural Uses

Non

- Crop sites (Aerial) 1640 751 922 102 935 428 526 58.4 418 191 235 26.1 642 366 163 22.7 12.9 5.82

Non

- Crop sites (Ground) 2180 1002 1230 136 1240 571 701 77.9 558 255 314 34.9 856 4888 218 30.3 17.3 7.75

Christmas Tree

Plantations 546 250 307 34.1 311 142 175 19.4 139 63.9 78.5 8.72 214 122 54.6 7.59 4.33 1.94

Rangeland 1093 501 615 68.3 623 285 350 38.9 279 127 157 17.4 428 244 109 15.1 8.66 3.88

Industrial Turfgrass 307 140 172 19.2 175 80.3 98.6 10.9 78.5 35.9 44.1 4.91 19.22 68.8 30.75 4.27 2.44 1.09

Avian adjusted LD 50 (mg/kg bw): 1626 (20g bird); 2070 (100g bird); 2925 (1000g bird)

### Page 41 of 133 

### 0

Table 1 8 . Dose

- based EECs (mg/kg bw) as Food Residues for Mammals from Labeled Non

- Granular Uses of Hexazinone (T

- Rex v. 1.5. 2).

P rimary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size*  Small Med Large Small Med Large Small Med Large

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 1 

Non

- Agricultural Uses

Alfalfa 343 157 193 21.4 237 108 133 14.8 55 25.2 30.9 3.44 134 92.9 21.5 4.76 3.29 0.763

Sugarcane in HI 823 377 463 51.4 569 260.9 320 35.5 132 60.5 74.2 8.25 322 222 51.7 11.4 7.90 1.83

Blueberries 457 209 257 28.6 316 144 177 19.7 73.3 33.6 41.2 4.58 179 123 28.7 6.35 4.39 1.01

Agricultural Uses

Non

- Crop sites (Aer ial) 1372 629 772 85.8 948 434 533 59.3 220 100 123 13.7 537 371 86.1 19.0 13.1 3.05

Non

- Crop sites (Ground) 1830 839 1029 114 1265 579 711 79.0 293 134 165 18.3 716 495 114 25.4 17.5 4.07

Christmas Tree Plantations 457 209 257 28.6 316 144 177 19.7 73.3 33.6 41.2 4.58 179 123 28.7 6.35 4.39 1.01

Rangeland 915 419 514 57.2 632 289 355 39.5 146 67.2 82.5 9.17 358 247 57.4 12.7 8.78 2.03

ndustrial Turf grass 257 117 144 16.0 177 81.5 100 11.1 41.2 18.9 23.2 2.58 100 69.6 16.1 3.57 2.47 0.572

*Mammalian a djusted LD 50 (mg/kg bw): 1164 (15g mammal); 942 (35g mammal); 407 (1000g mammal)



### 1

### Page 42 of 133 

### Table 1 9 . Dietary

- based EECs (mg/kg bw) as Food Residues for Mammals, Birds, Reptiles, and Terrestrial

- phase Amphibians from Labeled Non

- Granular Uses of Hexazinone (T

- Re x v. 1.5.2).
Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Arthropods

Use(s) 

Non

- Agricultural Uses

Alfalfa 360 165 202 22.5 141

Sugarcane in HI 864 396 486 54.0 338

Blueberries 480 220 270 30 188

Agricultural Uses

Non

- Crop sites (Aerial) 1440 660 810 90.0 564

Non

- Crop sites (Ground) 1920 880 1080 120 752

Christmas Tree Plantations 480 220 270 30 188

Rangeland 960 440 540 60.0 376

Industrial Turfgrass 270 123 151 16.8 105



### Another route of exposure to pesticides for mammalians and avian wildlife is through inhalation.

STIR (Screening Tool for Inhalation Risk v. 1.0) is a screening to used to assess the potential for

risk to brid and mammals from inhalation exposure; STIR is intended to be run at the Problem Formulation stage, however the model was not finalized at the time of publication for Hexazinone. STIR uses the avian oral toxicity data with the mammalian oral and inha lation toxicity data to derive an estimate of avian inhalation toxicity. STIR relied on the application rate, application method, defined droplet spectra, molecular weight, and vapor pressure to obtain an estimate of the droplet and vapor concentration i n the air. These concentrations are compared with an estimated

inhalation LD 50 

### of a specific chemical as a ratio that is then compared with a threshold of 0..1 If the ration of the exposure to the toxicity exceed 0.1, then the screening tool indicates tha t the results should be refined. For this assessment, an application of 8.0 lb ai/A (association with non

crop sites) was used for modeling. Based on this application rate, and an LD 50 

### >2258 mg/kg/day exposure is not likely significant for vapor dose or inhalation dose for avian species. For mammals,

an LD 50 

### = 530 mg/kg/day, and an inhalation LC 50 

### = 3.94 mg/L determined that exposure was not likely significant for vapor dose or inhalation dose. An example output table can be found in Appendix L

.



## 2.4.2 Exposure to Terrestrial and Semi

- Aquatic Plants

The TerrPlant Model (v. 1.2.2; December 26, 2006) is used to derive EECs relevant to terrestrial and wetland plants for hexazinone. The model employs the assumption that default fractions of the intended app lication are transported to an adjacent field through runoff and spray drift. Measures of exposure to terrestrial plants are expressed as a fraction of the mass of hexazinone

### Page 43 of 133 

### applied to the treated field. Total for Dry areas is representative of the sum of spray drift and runoff to dry areas; total for semi

- aquatic areas is representative of the sum of spray drift and

runoff to semi

- aquatic areas.

Loading via spray drift to dry, nontarget, adjacent areas is assumed to occur from one acre of

treated land to one acre of an adjacent non

- target area. Runoff is also expected to be a source of pesticide loading to non

- target areas. TerrPlant calculated EECs as a function of application rate, solubility, and default assumptions regarding spray drift. The defa ult spray drift assumptions are 1% of the application rate for ground spray applications and 5% for aerial applications (USEPA 2006b). The EECs for terrestrial and semi

- aquatic plants for a single application of hexazinone at

the maximum labeled rates for representative uses are presented in Table 20

. See example output

in Appendix H

.

Table 20 . Screening

- level based EECs (ppm) for Terrestrial Plants from Labeled Uses of Hexazinone (TerrPlant v. 1.2.2)

Use (s) App. Method App

Rate

(lb ai/A) Runoff

to Dry

Areas Runoff

to
Semi

Aquatic

Areas Spray

Drift Total for Dry

Areas Total

for

Semi

Aquatic

Areas

Agricultural Sites

Alfalfa Flowable/ Aerial 1.5 0.075 0.75 0.075 0.15 0.825

Sugarcane in HI Flowable/ Aerial 3.6 0.18 1.8 0.18 0.36 1.98

Blueberries Flo wable/ Ground 2.0 0.1 1.0 0.02 0.12 1.02

Non

- Agricultural Sites

Non

- crop sites (weed

and brush control) Flowable/ Aerial helicopter 6.0 0.3 3.0 0.3 0.6 3.3

Non

- crop sites (weed

and brush control) Flowable/ Ground 8.0 0.4 4.0 0.08 0.48 4.08

Conifer release in

Eastern and Lakes states Flowable/ Aerial helicopter 4.0 0.2 2.0 0.2 0.4 2.2

Christmas trees Flowable/ Aerial 2.0 0.1 1.0 0.1 0.2 1.1

Rangeland in Eastern US Flowable/ Aerial helicopter 4.0 0.2 2.0 0.2 0.4 2.2

Industrial turfgrass Flowable/ Ground 1.125 0.56 0.56 0.011 0.0675 0.573

Rangeland Pellets/Ground 0.63 0.0315 0.315 0 0.0315 0.315

Conifer Release Granular/Ground 3.0 0.15 1.5 0 0.15 1.5

Conifer Release Pellet/Ground 4.0 0.2 2.0 0 0.2 2.0

Forestry Site Prep

Eastern US Granular/Ground 4.7 0.235 2.35 0 0.235 2.35

Forestry Site Prep

Western US Granular/Ground 4.0 0.2 2.0 0 0.2 2.0

Forestry Site Prep Pellet/Ground 6.1 0.305 3.05 0 0.305 3.05

Non

- Crop sites Pellet/Ground 7.4 0.37 3.7 0 0.37 3.7

### Page 44 of 133 

### Table 20 . Screening

- level based EECs (ppm) for Terrestrial Plants from Labeled Uses of Hexazinone (TerrPlant v. 1.2.2)

Use (s) App. Method App

Rate

(lb ai/A) Runoff

to Dry

Areas Runoff

to
Semi

Aquatic

Areas Spray

Drift Total for Dry

Areas Total

for

Semi

Aquatic

Areas

Non

- crop sites Granular/Ground 8.0 0.4 4.0 0 0.4 4.0



# 3

. 0 Ecological Toxicity

Ecological effect data are used as measures of direct and indirect effects to biological receptors. Data were obtained from registrant

- submitted studies or from literature studies identified by ECOTOX. The ECOTOXicology database (ECOTOX) was searched in order to provide more ecological effects data to bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data and potential chemical mixture toxicity data for aquatic life, terrestrial plants, and wild life. ECOTOX was created and is maintained by the USEPA, Office of Research and Development, and the National Health and Environmental Effects Research Laboratory's Mid

Continent Ecology Division (USEPA 2007 b ). A search of the ECOTOXicology database in 2015, yielded additional data from suitable studies to complement those data submitted by the registrant. Those studies that have been considered as acceptable have been tabulate in Appendix J

. There were no studies that were considered acceptable for qu antitative use that yielded endpoints more sensitive than the registrant submitted studies.

Information on the potential effects of hexazinone on non

- target animals is also collected from the Ecological Incident Information System (EIIS; USEPA 2007 c ). The EIIS is a database containing adverse effect (typically mortality) reports on non

- target organisms where such effects have been associated with the use of pesticides. Other Ecological Incident databases used are IDS, Aggregated Incident Database and Avi an Information System, AIMS.

Where available, sublethal effects observed in both registrant

- submitted and open literature studies will be evaluated qualitatively. Such effects h ave included behavioral changes . Quantitative assessments of risks, though , are limited to those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired survival, growth and reproduction.

The assessment of risk for direct effects to non

- target organisms makes the assumption t hat toxicity

of hexazinone to birds is similar to terrestrial

- phase amphibians and reptiles. The same assumption is made for fish and aquatic

- phase amphibians.

The acute measures of effect used for animals in this assessment are the LD 50 

### , LC 50 

### and EC 50



### . LD stands for "Lethal Dose", and LD 50 

### is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” and LC 50 

### is the concentration of a chemical that is estimated t o kill 50% of the test organisms. EC stands

### Page 45 of 133 

### for “Effective Concentration” and the EC 50 

### is the concentration of a chemical that is estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic measures of exposure

for listed a nd non

- listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for “No

Observed

- Adverse

- Effect

- Level” and refers to the highest tested dose of a substance that has been reported to have no harmful (adverse) effects on test organisms. The NOAEC ( i.e. , “ No

- Observed

Adverse

- Effect

- Concentration”) is the highest test concentration at which none of the observed effects were statistically different from the control. The NOEC is the No

- Observed

- Effects

Concentration. For non

- listed plants, only acute exposur es are assessed ( i.e. , EC 25 

### for terrestrial plants and EC 50 

### for aquatic plants); for listed plants, either the NOAEC or EC 05 

### is used.

The following section presents a summary of the data that have been submitted since the preliminary problem formulation , their classification, and their impact upon the risk assessment ( i.e. , whether they represent more sensitive endpoints that could alter the risk conclusion). Table

21 and 2 2 provide a summary of the taxonomic groups and the surrogate species tested to f urther characterize the potential acute and chronic ecological effects of hexazinone following the preliminary problem formulation.



## 3.1 **Aquatic Organisms**

Technical grade hexazinone is classified as practical ly nontoxic to freshwater fish and freshwater invertebrates on an acute exposure basis. Hexazinone is classified as slight l y toxic to

estuarine/marine inverte brates. T he most sensitive endpoints used quantitatively in this

assessment have been summarized in Table 21

.

There are four fish acute ex posure mortality studies available for hexazinone. For technical grade hexazinone, the reported 96 hour LC 50 

### values were >320 mg/L for rainbow trout (MRID

001 04980), and 274 mg/L for Fathead minnow (MRID 00104980). Two studies were available for bluegill sunfish, 96 hour LC 50 

### > 370mg/L and 96 hour LC 50 

### = 505 mg/L (MRID 00104980 and 00076959). The results of these tests indicate that hexazinone is practically nontoxic to fish. The

fathead minnow LC 50 

### of 274 mg/L will be used to assess the acute effects to freshwater fish for hexazinone. There are no studies available for estuarine/marine fish; the data was waived in previous assessments due to the low toxicity to freshwater fish.

In MRID 00104980, for rainbow trout, there was no morality in the controls o f in the three lowest dosage levels. At 24 hours, mortality was 100% in the highest treatment level (490 ppm). Within 96 hours, mortality was 100% at the second highest treatment level (420 ppm). Sublethal effects were reported in the 320 ppm dosage gro up; the fish began to darken, the number of fish exhibiting these effects were not reported. In MRID 00104980, for the fathead minnow, there was no mortality seen in the controls. At 24 hours, there was 100% mortality in the highest treatment level (560 ppm). The second highest level showed 100% mortality at 48 hours, and the third and fourth levels showed 60% mortality by 96 hours. In MRID 00104980 for bluegill sunfish, there was 100% mortality shown at 24 hours in the highest treatment group (490 pp m), and showed one partial mortality in the second highest concentration; there were no other mortalities seen in the

lower three doses.

### Page 46 of 133 

### A fish full life cycle test with a fathead minnow was submitted for hexazinone (MRID 41406001).

No abnormal behavio r f or juvenile fish was noted at any test concentration. A chronic NOAEC = 17 mg/L was reported for juvenile surviv al (day 39), length and weight; the MATC was reported to be 24 mg/L. The NOAEC will be used in the assessment.

There are four invertebrate acute exposure studies available for hexazinone. For freshwater invertebrates, there is one study available using the preferred test species, Dap h nia magna . The study found a 48 hour EC 50 

### = 151.6 mg/L (MRID 00116269), indicating that hexazinone is practi cally nontoxic to aquatic invertebrates. This value will be used in the risk assessment to represent freshwater invertebrates. There is data available for three estuarine/marine species to determine the effects of hexazinone (MRID 00047164). A 48

- h EC 50 

### > 320 mg/L for the Eastern Oyster ( Crassostrea virginica) was estimated, as well as the grass shrimp ( Palaemonetes pugio)

with a 96 hour LC 50 

### = 78 mg/L and the fiddler crab (Uca pugila) with a 96 hour LC 50 

### > 1,000 mg/L. These studies demonstrate that h exazinone ranges from slightly to practically nontoxic to mollusks and slightly toxic to practically nontoxic to crustaceans. The value for the grass shrimp

will be used in this assessment.

Chronic toxicity values are available for the Daphnia magna. T wo supplemental studies for daphnia resulted in NOAECs of 20 mg/L for survival and reproduction (MRID 00078041) and 29 mg/L for daphnid survival (MRID 41406002). MRID 00078041 was classified as supplemental because the dilution water, volume of water and source of water were not provided; these are deficiencies do not affect the endpoints from the study. MRID 41406002 was classified as supplemental because the dry weight for the first g eneration of daphnids wasn n ot taken. The reproductive NOAEC will be u sed in this assessment as the most sensitive endpoint.

Due to the lack of estuarine/marine toxicity data, an acute to chronic ratio was calculated using t he acute and chronic values for the daphnid, LC 50 

### = 151.6 and NOAEC = 20 mg/L, and the acute

value fo r the grass shrimp, LC 50 

### = 78 m g /L. The resulting NOAEC for grass shrimp was 10.3 mg/L. This value will be used in the assessment.

Aquatic plant toxicity studies are used to estimate the potential non

- target effects to plants. An acceptable study is av ailable for vascular aquatic plants using Lemna gibba with frond count as an endpoint. The EC 50 

### = 0.0374 mg/L (MRID 43225101) will be used in the assessment to estimate risk to nonlisted species and the NOAEC = 0.026 mg/L will be used in the assessment to estimate risk to listed species.

Four studies for nonvascular aquatic plants were available. The acceptable nonvascular aquatic plant study with Anabaena flos

- aquae resulted in an EC 50 

### = 0.210 mg/L and NOAEC of 0.15 mg/L based on growth inhibition (MR ID 43302701). The acceptable study with freshwater diatom Navicula pelliculosa resulted in an EC 50 

### = 0.012 mg/L with a NOAEC = 0.035 mg/L based on growth inhibition (MRID 43302701). The acceptable study with the estuarine/marine diatom

Skeletonema costat um resulted in an EC 50 

### = 0.012 mg/L and a NOAEC of 0.041 mg/L based on growth inhibition (MRID 43225102). An acceptable study is available for Selenastrum capricornutum. The EC 50 

### = 0.007 mg/L with a NOAEC = 0.004 mg/L based on cell density (MRID 4128700 1) were based on nominal concentrations. The most sensitive value for Selenastrum capricornutum will be used to calculate RQs.

### Page 47 of 133 

## 3.1.1. Estimating Aquatic Toxicity to Metabolites using ECOSAR

ECOSAR v. 1.11 was u sed to determine the potential toxicity of Hexazinone and its metabolites to aquatic organisms. ECOSAR is able to estimate based on the structure of the chemical, input into the database as a SMILES code. ECOSAR will return toxicity estimates for the par ents, degradates for one or more of the QSAR classes; the neutral organic model is always included. Several other QSAR chemical classes are usually included, each with a somewhat different estimate of toxicity. A table of comparisons between the degradat e, parents and different chemical classes is compiled

for each tax on ; t hese results have been tabulated in Appendix K. The QSAR estimates are compared to available laboratory data to judge the ability of the program to estimate the toxicity for that parti cular structure; for hexazinone, there was significant variability between the known parent val ues and predicted parent values. I t was determined that ECOSAR would not be a reliable resource to predict the toxicity of the individual metabolites for any sp ecific chemical class

.

Table 21 . Most sensitive aquatic species evaluated for assessing potential ecological

effects of Hexazinone

Study Type Test ed Species Toxicity Endpoint Study MRID and Toxicity

Classification

850.1075 Acute Freshwater Fish Fathead minnow (Pimephales promelas) LC 50 1 = 274 mg/L 00104980 Practically non

toxic

850.1400 Chronic Freshwater

Fish Fathead minnow (Pimephales promelas) NOAEC = 17 mg/L 41406001

NA

850.1010 Acute Freshwater

Invertebrate Daphnid (Daphnia magna) EC 50 = 151.6 mg/L 00116269 Practically non

toxic

850.1300 Chronic Freshwater

Invertebrate Daphnid (Daphnia magna) NOAEC = 20 mg/L 00078041

NA

850.1075 Acute Estua rine/marine

Fish Waived on the basis of low Freshwater Fish Toxicity

850.1400 Chronic

Estuarine/marine fish

850.1350 Acute Estuarine/marine

Invertebrate Grass Shrimp LC 50 = 78 mg/L 00047164 Slightly toxic

NA Chronic

Estuarine/marine

Invertebrate Grass Shrimp NOAEC 2 = 10.3 mg/L NA

850.4400 Vascular Plant Duckweed ( Lemna gibba ) EC 50 = 0.0374 mg/L

NOAEC = 0.026 mg/L 43225101

NA

850.4550 Nonvascular Plant Cyanobacteria 

### Skeletonema

costatum EC 50 = 0.007 mg/L NOAEC = 0.004 mg/L 41287001

NA

1 Freshwater fis h are considered surrogates for aquatic

- phase amphibians.

2 NOAEC based on ACR ratio calculated using acute and chronic daphnid data, and acute grass shrimp data from

table

### Page 48 of 133 

## 3.2 **Terrestrial Organisms**

Technical grade hexazinone is practically nontoxic to avian species, mammals and terrestrial invertebrates on an acute exposure basis. The available toxicity studies have been summarized below; the most sensitive endpoints used in this assessment have been tabulated in Table 22

.

There is one avian acute oral toxicity study available for hexazinone. The study was conducted using a bobwhite (Colinus virginianus) and resulted in an LD 50 

### = 2,258 mg/kg

- bw (M RID 00073988). These results indicate that hexazinone is practically nontoxic to birds. This value will be used for risk assessment purposes. There is not acute oral data available for a passerine species.

There are t wo dietary acute toxicity studies a vailable using the bobwhite (MRID 0010787, MRID 0010498) and mallard ( Anas platyrhynchos) (MRID 0010498) both resulting in LC 50 

### > 5,000 mg/kg

- diet. For the bobwhite study, there were no treatment related mortalities. There was no

abnormal behavior observed ; gross pathological examination did not reveal any tissue alterations. Food consumption and body weight increased over the course of the study. For the mallard study, there was no mortality in the control or test groups. Food consumption and body weigh t both

increased. These values indicate that hexazinone is practically nontoxic to birds.

Chronic reproductive toxicity data is available for the bobwhite resulting in a reproductive

NOAEC = 1,000 mg/kg

- bw. This was the highest concentration tested. There was no overt signs of toxicity observed at any concentration; clinical signs such as lethargy, wing droop, depression, reduced reaction to external stimuli, ruffled appearance, and lower limb weakness were observed but were not reported as treatment related. There were no significantly significant differences in adult body weights between the groups. There was no apparent treatment related effects upon food consumption among birds at test concentrations of 100 and 300 ppm. There was a slight but

s tatistically significant reduction in food consumption at 100 ppm during week 3. There was also a slight reduction in food consumption during weeks 6 and 12 at all test concentrations. In all cases, these reductions were not considered to be treatment re lated

. At 1,000 ppm there was a treatment related increase in feed consumption from week 14 through termination that was statistically confirmed. There were no apparent treatment related effects upon reproductive parameters or eggshell thickness at any o f the concentrations tested; there were no apparent treatment related effects upon hatchling body weight of 14

- day old survivor body weight at any tested concentration. The NOAEC for reproductive parameters was 1,000 ppm; based upon the effects upon feed c onsumption at 1,000 ppm, the NOAEC was 300 ppm. The reproductive NOAEC will be used in the assessment as increased food consumption is not considered an adverse effect. Another additional avian chronic study is available conducted using the mallard, resu lting in a NOAEC = 1,000 ppm (MRID 41764902).

A registrant submitted rat acute oral study, LD 50 

### = 1,200 mg/kg, indicated that hexazinone is practically nontoxic to mammals (MRID 41235004).

An acceptable two

- generation rat study (MRID 42066501) is avail able. The systemic toxicity LOAEC is 2000 ppm (117

- 154 mg/kg/day for males and 143

- 180 mg/kg/day for females) based on reduced body weight and body weight gains by F 1 

### males and F 0 

### and F 1 

### females. Decreased mean weight gains of 11 to 18% were observed in the 5000 ppm in F 1 

### males. In P1 and F 1 

### female

### Page 49 of 133 

### rats, there were significant decreases in body weight and weight gain at 5000 ppm and at 2000 ppm for P1 females. The systemic toxicity NOAEC is 200 ppm (11.8

- 153 mg/kg/day for males

and 14.3

- 17.7 mg/kg/day f or females). No reproductive effects were seen in the study aside from the weight effects on the offspring. The offspring LOAEC is also 2000 ppm (117

- 154 mg/kg/day

for males and 143

- 180 mg/kg/day for females) based on reduced female pup body weights at bi rth and during lactation. The reproductive NOAEC was 200 ppm (11.8

- 15.3 mg/kg/day for males and

14.3

- 17.7 mg/kg/day for females). The systemic toxicity NOAEC and reproductive toxicity NOAEC = 200 ppm will be used in this assessment.

Terrestrial invert ebrate toxicity data are used to assess the potential direct and indirect effects of

hexazinone to non

- target species, as well as to endangered species. An acceptabl e honeybee acute contact study resulted in LD 50 

### >100 μg/bee (MRID 41216502)

. At test termin ation the negative control and solvent control mortalities were 2% and 0%. Morality at the 13, 22, 36, 60 and 100 μg ai/bee doses were 4%, 8%, 2%, 4% and 8% respectively. No sublethal effects were reported.

Based on the LC 50 

### <100 μg/bee, the study indicat es that hexazinone is practically nontoxic to terrestrial invertebrates; t his value will be used qualitatively in the risk description.

Plant toxicity data was available for seedling emergence and vegetative vigor registrant submitted studies (MRID 43162 501). Sublethal endpoints such as plant growth, dry weight and biomass are

evaluated for both monocots and dicots in the seedling emergence and vegetative life stages. The

results of the studies are used to evaluate the effects on non

- target plants and a re used to evaluate direct and indirect effects for endangered species

.

For the vegetative vigor study, the cucumber data is considered to be invalid because the seeds were treated with a different pesticide

. The percent germination was not reported; in addition, a description of the phytotoxicity rating system was not included in the report. The weight parameter was mostly affected. The most sensitive monocot species were wheat and corn. The most sensitive dicot species was oilseed rape. In this st udy, cucumber was treated with thiram and hexazinone

— this is unacceptable since it is difficult to evaluate the effects of hexazinone on cucumber. A baseline for the cucumber is needed with and without the treatment. It is important to understand

if there are antagonistic or synergistic interactions between or among the three pesticides used. This part of the study was classified as invalid and a new study is thus required. The study results suggest that cucumber has the potential to be th e most sensitiv e species tested, however this cannot

be determined with the available data.

For the seedling emergence data, the cucumber data is also considered to be invalid because the seeds were treated with a different pesticides. The onion and pea data is also co nsidered to be invalid due to damage to the plants observed. Sorghum, soybean, pea and tomato showed growth retardation. The other species did not show growth retardation. The percent germination of oilseed rape was low for controls (54%); the study rep ort suggests that a better stock of seed should have been used. The seeds of cucumber were treated with multiple pesticides; a control for the two pesticides should have been included in the study design. This would have been helpful in evaluating the ef fects of hexazinone on the cucumber seeds. This part of the study in invalid.

### Page 50 of 133 

## 3.3 **Incident data**

The Ecological Incident Information System (EIIS, v. 2.1.1), which is maintained by the Agency’s Office of Pesticide Programs, was searched to determine if ecological incidents have been reported for hexazinone. Based on a search of EIIS conducted in May 2015, there were 13 reported incidents with the use of hexazinone, all of which involved terrestrial plants only. There were no

in cident s reported involv ing terrestrial or aquatic animals.

A summary of the incidents found in EIIS can be found in Table 23

. Each incident is accompanied by whether the incident occurred due to a misuse, registered use, or whether it is undetermined. Of the 13 incidents, 2 were considered a misuse, 4 were undetermined, and 7 of them were due to a registered use. 6 of the incidents occurred in the last 10 years. Each incident is additionally classified with a certainty to indicate whether hexazinone w as responsible for the incident; these classifications are as follows: “highly probable,” “probable,” “possible,” and “unlikely.” Of the 7 incidents that occurred due to a registered use, 1 of them was listed as “highly probable,” 2 were listed as “probab le ,” 3 were listed as “possible,” and 1 was listed as unlikely.

Table 2 2 . Most sensitive terrestrial species evaluated for assessing potential ecological

effects of Hexazinone.

Study Type Tested Species Toxicity Endpoint Study MRID

and Toxicity

Classification

850.2100 Avian Acute Oral Northern Bobwhite Quail (Colinus virginianu) LD 50 = 2,258 mg/kg 00073988 Practically

nontoxic

850.2200 Avian Dietary Northern Bobwhite Quail (Colinus virginianus) LC 50 > 5,000 mg/kg diet 00107878

Practic ally

nontoxic

850.2300 Avian Reproduction Northern Bobwhite Quail (Colinus virginianus) NOAEC = 300 mg/kg diet 41764901

NA

- Mammalian Acute

Oral Norway Rat (Rattus novegicus) LD 50 = 530 mg/kg bw Kennedy, 1984 Practically

nontoxic

- Mammalian Reproducti on Norway Rat (Rattus novegicus) NOAEL = 200 mg/kg diet 42066501

NA

850.3020 Honeybee Acute Contact Toxicity Honeybee (Apis mellifera) LD 50 > 100 μg/bee 41216502 Practically

nontoxic

850. 4100 Seedling Emergence Wheat EC 25 = 0.0259 lb a.i./A

NOAEC = 0

. 0781 lb

a.i./A 4316250

NA

Tomato EC 25 = 0.0063 lb a.i./A

NOAEC =0.00695 lb

a.i./A

850.4150 Vegetative Vigor Wheat EC 25 = 0.020 lb a.i ./A

NOAEC = 0.010 lb a.i./A 43162501

NA Oilseed Rape EC 25 = 0.011lb a.i./A

NOAEC = 0.0071 lb

a.i./A

### Page 51 of 133 

### Table 23 . Summary of Incidents from EIIS v. 2.1.1

Incident ID Use Site State Appl.

Method Air/Gnd Year Magnitude Legality Certainty

I000548

- 001 Forest FL Broadcast Air NR NR Registered Use Highly

Probable

I000611

- 001 N/R GA Broadcast Air 1993 NR Undetermined Possible

I005822

- 001 Residential LA NR NR 1997 NR Misuse (intentional) Highly

Probable

I007984

- 008 Tree TX Spray Gnd NR NR Misuse (intentional) Probable

I012233

- 001 Home/Lawn KS Spray Gnd NR NR Registered Use Unlikely

I014407

- 036 Alfalfa WA NR NR 1994 NR Registered use Possible

I015265

- 001 Seedling TX Unknown Gnd 2004 NR Registered use Possible

I016312

- 001 Forest OR Spray Both 2005 300 acres Undetermined Possible

I016680

- 001 R ight

- of

way OR Spray Gnd 2005 13 acres Undetermined Possible

I020000

- 001 Ornamental MO Broadcast Gnd 2008 NA Registered Use Probable

I020592

- 001 Agricultural

area WI Broadcast Gnd 2008 80 acres Registered Use Possible

I020744

- 001 Pasture FL NR Gnd 2008 135 acres Registered Use Probable

I025246

- 001 Potato ME Broadcast Gnd 2013 30 acres Undetermined Unlikely

“NR” indicates that the information was Not Reported in the Incident report.



### The American Bird Conservancy (ABC) Avian Incident Monitoring System (AIMS) was searched in May 2015 and returned zero records of incidents associated with hexazinone

.

A search in May 2015 of the Incident Database System (IDS) maintained by OPP’s Information Technology and Resource Management Division (ITRMD) yielded 23 a ggregate ecological incidents (18 involving plants and 5 involving wildlife). It is not possible to discern from the available information if the aggregated wildlife incidents involve fish, birds, and/or mammals. Because only limited data are currently a vailable for the aggregate incidents, they are assumed to be from registered uses of hexazinone.



# 4.0 Risk Characterization

As discussed in the problem formulation, risk characterization integrates EECs and toxicity

estimates and evaluated the likelihood of adverse ecological effects to non

- target species. For

### Page 52 of 133 

### hexazinone , a deterministic approach is used to evaluate the likelihood of adverse ecological

effects to non

- target species. In this approach, RQs are calculated by dividing EECs by acute and

chro nic ecotoxicity values for non

- target species.

Risk Quotient (RQ) = Exposure Estimate/Toxicity Estimate

RQs are then compared to LOCs. These LOCs are criteria used to indicate potential risk to non

target organisms and the need to consider regulatory action. LOC exceedance is interpreted to mean that the labeled use (or proposed use) of the pesticide has the potential to cause adverse

effects on non

- target organisms. LOCs currently address the following risk presumption categories:

Animals:

• Acute ri sk

— potential for acute risk to non

- target organisms which may warrant regulatory action in addition to restricted classification

• Acute risk, restricted use

— potential for acute risk to non

- target organisms, but may be mitigated through restricted use classi fication

• Acute risk, listed species

— listed species may be potentially affected by use

• Chronic risk

— potential for chronic risk may warrant regulatory action, listed species may potentially be affected through chronic exposure

Plants:

• Non

- listed plant risk

— potential for effects in non

- target (non

- endangered) plants

• Listed plant risk

— potential for effects in endangered plants

### Page 53 of 133 

### Table 24 . Agency Risk Quotient (RQ) Metrics and Levels of Concern (LOC) Per Risk

Class.

Risk Class Risk Description RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non

- listed animals from acute

exposures Peak EEC/LC 50 1 0.5

Acute

Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use classifica tion Peak EEC/LC 50 1 0.1

Acute Listed Species Listed species may be potentially affected by acute

exposures Peak EEC/LC 50 1 0.05

Chronic Potential for effects to non

- listed and listed animals from chronic exposures 60

- day EEC/NOAEC (fish) 1 21

- day EEC/N OAEC (invertebrates)

Aquatic Plants

Non

- Listed Potential for effects to non

- listed plants from exposures Peak EEC/LC 50 1 1

Listed Potential for effects to listed plants from exposures Peak EEC/NOAEC 1

Terrestrial Animals (mammals and birds) 2

Acute Pot ential for effects to non

- listed animals from acute

exposures EEC/LC 50 (Dietary) 0.5 EEC/LD 50 (Dose)

Acute

Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use classification EEC/LC 50 (Diet ary) 0.2 EEC/LD 50 (Dose)

Acute Listed Species Listed species may be potentially affected by acute

exposures EEC/LC 50 (Dietary) 0.1 EEC/LD 50 (Dose)

Chronic Potential for effects to non

- listed and listed animals from chronic exposures EEC/NOAEC 1

Terrestrial and Semi

- Aquatic Plants

Non

- Listed Potential for effects to non

- target, non

- listed plants from

exposures EEC/ EC25 1

Listed Plant Potential for effects to non

- target, listed plants from

exposures EEC/ NOAEC 1 EEC/ EC05



### The resulting u nitless RQ values are compared to the Agency’s LOCs, as shown in Tables 2 2

. The LOCs are used by the Agency to indicate when the use of a pesticide, as directed through the label, has the potential to cause adverse effects to non

- target organisms. In thi s assessment, RQs

that exceed the non

- listed species LOC also exceed the listed species LOC.

Tables 23

- 36 prove the resulting, screening level RQ values, for taxa with sufficient data. Note that with plants, unlike with animals, RQ values are not presen ted for acute versus chronic risk; instead, RQ values are presented for listed and nonlisted species based on a comparison of a given

EEC to NOAEL and EC 25 

### /EC 50 

### values respectively. A discussion of the RQ values for hexazinone

and of other information tha t provides context for the interpretation of potential risk to various taxa is presented in the Risk Description.

### Page 54 of 133 

## 4.1 Risk Estimation for **Aquatic Organisms for Spray and Granular** 

**Uses**

4.1.1 Freshwater and Estuarine/Marine Fish

For hexazinone there is only acute and chronic data available for freshwater fish ; RQ calculations

can be found in Table 2 5 . Maximum acute RQ values are an order of magnitude below the acute risk to listed species LOC, thus there were no LOC exceedances for listed or nonlisted specie s

. The RQs for freshwater fish range d were <0.01 across all scenarios . Additionally, there were no LOC exceedances for freshwater fish on a chronic basis; the chronic RQs ranges from <0.01 to
0.03

.

Table 25 . Acute and Chronic RQs for Direct Effects to Freshwater Fish from Hexazinone

TGAI. 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Acute RQ

calculated

using

Freshwater

EC 50 = 274 mg/L 60

- day

EECs

(μg ai/L) Chronic RQ calculated using

Freshwater

NOAEC = 0.43 mg/L

Alfalfa NC alfalfa Aerial 139 <0. 01 137 <0.01

Sugarcane in HI LA sugarcane (HI meteorological file 22521) Aerial 600 <0.01 593 0.03

Blueberries CA wine grape Ground 78.8 <0.01 78.1 <0.01

Non

- crop sites (weed and brush control) CA rights

- of

- way Aerial helicopter 645 <0.01 640 0.0 3

Non

- crop sites (weed and brush control) CA rights

- of

- way Ground 653 <0.01 648 0.03

Conifer release in

Eastern and Lakes

states CA forestry (MI meteorological file 14850) Aerial helicopter 369 <0.01 366 0.02

Christmas trees plantations (except

in 22 st ates listed in label) OR Christmas trees Aerial 161 <0.01 160 <0.01

Pastures/Rangeland

in Eastern U.S. CA rangeland hay (NY meteorological file 14860) Aerial helicopter 493 <0.01 490 0.02

Bermudagrass/

Bahiagrass; Industrial turfgrass PA tur f Ground 41. 7 <0.01 41.4 <0.01

Conifer release CA forestry (MI meterological file 14850) Ground

Pellets 24.1 <0.01 23.8 <0.01

Non

- crop sites CA rights

- of

- way Ground 408 <0.01 405 0.02

### Page 55 of 133 

### Table 25 . Acute and Chronic RQs for Direct Effects to Freshwater Fish from Hexazinone

TGAI. 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Acute RQ

calculated

using

Freshwater

EC 50 = 274 mg/L 60

- day

EECs

(μg ai/L) Chronic RQ calculated using

Freshwater

NOAEC = 0.43 mg/L

(weed and brush control) Granules

App. = Application

Bolded and shaded values ind icate an exceedance of an LOC

1 Acute listed species LOC = 0.05; acute restricted use LOC = 0.1, acute high risk LOC = 0.5; chronic risk LOC = 1.0



### RQs were additional ly calculated using the EECs generated from inclusion of TTRs and UERs for

two of the s cenarios and the data for freshwater fish. The scenarios selected to run the TTRs and UERs were the ones that yielded the highest EECs among the conventional agricultural and non

agricultural crops, following the current Unextracted Residue G uidance. The resulting RQ

calculations can be found in Table 26

. There were no LOC exceedances on an acute or chronic basis. Acute RQs were 0.002 and were similar to those calculated for parent plus degradates only. Chronic RQs ranged from 0.034 and 0.038 and were also similar to those calculated for the parent only.

Table 26 . Acute and Chronic RQs for Direct Effects to Freshwater Fish with Hexazinone, including

TTRs and UERs

Use(s) Scenario App. Method Peak

EECs

(μg ai/L) Acute RQ calculated using

Freshwater

EC 50 = 274 mg/L 60

- day

EECs

(μg ai/L) Chronic RQ

calculated

using

Freshwater

NOAEC = 0.43 mg/L

Sugarcane in HI LA sugarcane (HI meteorological file 22521) Aerial 601 <0.01 594 0.03

Non

- crop sites (weed and brush control) CA rights

- of

- way Ground 656 <0. 01 651 0.03

App. = Application

Bolded and shaded values indicate an exceedance of an LOC

1 Acute listed species LOC = 0.05; acute restricted use LOC = 0.1, acute high risk LOC = 0.5; chronic risk LOC = 1.0



## 4.1.2 Freshwater and Estuarine/Marine Invertebr ates

For aquatic invertebrates there is data available for freshwater and estuarine/marine species on an

acute and chronic basis ; the data has been tabulated in Table 27 . Maximum acute RQ values are

### Page 56 of 133 

### an order of magnitude below the acute risk to listed spe cies LOC, there were no LOC exceedances

for listed or non

- listed species. The acute RQs for freshwater inverteb rates were all <0.01 ; acute RQs for estuarine/marine invertebrates were all<0.01 . Maximum chronic RQ values are also an order or magnitude belo w the chronic risk LOC. For freshwater invertebrates the chronic RQs ranged from <0.01 to 0.03 ; for estuarine/marine invertebrates the chronic RQs ranged from <0.01

to 0.06

.

Maximum acute RQ values are two orders of magnitude below the acute risk to lis ted species LOC,

thus there were no LOC exceeda nces. The RQs for freshwater invertebrates were all <0.01

. Additionally, there were no LOC exceedances for freshwater invertebrates on a chronic basis; the chronic RQs ranges from <0.01 to 0.03

.

Table 27

. Acute and Chronic RQs for Direct Effects to Freshwater and Estuarine/Marine

Invertebrates from Hexazinone TGAI. 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 50 = 151.6 mg/L Estuarine/

Marine

EC 50 = 78

mg/L 21

- day

EECs (μg ai/L) Fres hwater

NOAEC = 20.0 mg/L Estuarine/

marine

NOAEC =

10.3 mg/L

Acute RQ Chronic RQ

Alfalfa NC alfalfa Aerial 139 <0.01 <0.01 138 <0.01 0.013

Sugarcane in HI LA sugarcane (HI meteorological

file 22521) Aerial 600 <0.01 <0.01 596 0.02 0.05

Blueberri es CA wine

grape Ground 78.8 <0.01 <0.01 78.6 <0.01 <0.01

Non

- crop sites (weed and brush control) CA rights

- of

way Aerial helicopter 645 <0.01 <0.01 644 0.03 0.06

Non

- crop sites (weed and brush control) CA rights

- of

way Ground 653 <0.01 <0.01 651 0.03 0. 06

Conifer release in

Eastern and Lakes

states CA forestry (MI meteoro

logical file

14850) Aerial helicopter 369 <0.01 <0.01 368 0.01 0.03

Christmas trees plantations (except

in 22 states listed in label) OR Christmas

trees Aerial 161 <0.01 <0.01 160 <0. 01 0.01

Pastures/Rangeland

in Eastern U.S. CA rangeland hay (NY meteorological

file 14860) Aerial helicopter 493 <0.01 <0.01 492 0.02 0.04

Bermudagrass/

Bahiagrass; PA turf Ground 41.7 <0.01 <0.01 41.6 <0.01 <0.01

### Page 57 of 133 

### Table 27

. Acute and Chronic RQs for Direct Effects to Freshwater and Estuarine/Marine

Invertebrates from Hexazinone TGAI. 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 50 = 151.6 mg/L Estuarine/

Marine

EC 50 = 78

mg/L 21

- day

EECs (μg ai/L) Fres hwater

NOAEC = 20.0 mg/L Estuarine/

marine

NOAEC =

10.3 mg/L

Acute RQ Chronic RQ

Industrial turfgrass

Conifer release C A forestry (MI metero

logical file

14850) Ground

Pellets 24.1 <0.01 <0.01 24 <0.01 <0.01

Non

- crop sites (weed and brush control) CA rights

- of

way Ground

Granules 408 <0.01 <0.01 407 0.02 0.04

App. = Application

Bolded and shaded values indicate an exceed ance of an LOC

1 Acute listed species LOC = 0.05; acute restricted use LOC = 0.1, acute high risk LOC = 0.5; chronic risk LOC = 1



### RQs were additionally calculated using the EECs generated from inclusion of TTRs and UERs for

two of the scenarios and the d ata for freshwater and estuarine/marine invertebrates. The resulting RQ calculations can be found in Table 2 8

. There were no LOC exceedances on an acute or chronic basis. Acute RQs for freshwater invertebrates were <0.01 ; acute RQs for estuarine/marine

invert ebrates were <0.01

. Chronic RQs for fre shwater invertebrates were 0.02 and 0.03 ; chronic RQs for estuarine /marine invertebrates were 0.05 and 0.06 . Both acute and chronic RQs for

freshwater and estuarine/marine invertebrates were similar to those ca lculated for the parent plus degradates only.

Table 2 8 . Acute and Chronic RQs for Direct Effects to Freshwater and Estuarine/Marine Invertebrates with Hexazinone, including TTRs and UERs

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 5 0 = 151.6 mg/L Estuarine/

Marine

EC 50 = 78

mg/L 21

- day

EECs (μg ai/L) Freshwater

NOAEC = 20.0 mg/L Estuarine/

marine

NOAEC = 10.3 mg/L

Acute RQ Chronic RQ

Sugarcane in HI LA sugarcane (HI meteoro

logical file

22521) Aerial 601 <0.01 <0.01 597 0.0 2 0.05

Non

- crop sites (weed and brush control) CA rights

- of

way Ground 656 <0.01 <0.01 654 0.03 0.06

### Page 58 of 133 

### Table 2 8 . Acute and Chronic RQs for Direct Effects to Freshwater and Estuarine/Marine Invertebrates with Hexazinone, including TTRs and UERs

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 5 0 = 151.6 mg/L Estuarine/

Marine

EC 50 = 78

mg/L 21

- day

EECs (μg ai/L) Freshwater

NOAEC = 20.0 mg/L Estuarine/

marine

NOAEC = 10.3 mg/L

Acute RQ Chronic RQ

App. = Application

Bolded and shaded values indicate an exceedance of an LOC

1 Acute listed species LOC = 0.05; acute restricted use LOC = 0.1, acute high risk LOC = 0.5; chronic risk LOC = 1



## 4.1.3 Aquatic Plants

All scenarios for aquatic vascular plants and aquatic nonvascular plants result in LOC exceedances for listed and nonlisted RQs; the results have been tabulated in Table 2 9 . For aquatic vascular plants, the RQs range from 1.60 to 25.1 for listed species and from 1.11 to 17.4 for nonlisted species. Aquatic nonvascular plants, the RQs range from 10.4 to 163 for listed species and 5.95 to 93.2 for nonlisted species. The maximum RQs were associated with the CA rights

- of

- way scenario (ground application, at 8 lb a.i./A) across both taxa.

Table 29 . RQ Values for Direct Effects to Aquatic Vascular and Nonvascular Plants from

Hexazinone TGAI. 1,2

Use(s) Scenario Applicat

ion

Method Peak

EECs (μg ai /L) Aquatic Vascular Plants

EC 50 = 0.0374 mg/L

NOAEL = 0.026 mg/L Aquatic Nonvascular

Plants

EC 50 0.007 mg/L

NOAEL = 0.004 mg/L

Listed RQs 3 Nonlisted RQs 4 Listed RQs 3 Nonlisted RQs 4

Alfalfa NC alfalfa Aerial 139 5.34 3.71 34.7 19.8

Sugarcane in HI L A sugarcane (HI meteoro

logical file 22521) Aerial 600 23.0 16.0 150 85.7

Blueberries CA wine grape Ground 78.8 3.03 2.10 19.7 11.2

Non

- crop sites (weed and brush control) CA rights

- of

- way Aerial helicopter 645 24.8 17.2 161 92.1

Non

- crop sites (weed an d brush control) CA rights

- of

- way Ground 653 25.1 17.4 163 93.2

Conifer release

in Eastern and

Lakes states CA forestry (MI

meteoro

- logical

file 14850) Aerial helicopter 369 14.1 9.86 92.2 52.7

Christmas trees

plantations (except in 22

states listed in

l abel) OR Christmas

trees Aerial 161 6.19 4.30 40.2 23.0

### Page 59 of 133 

### Table 29 . RQ Values for Direct Effects to Aquatic Vascular and Nonvascular Plants from

Hexazinone TGAI. 1,2

Use(s) Scenario Applicat

ion

Method Peak

EECs (μg ai /L) Aquatic Vascular Plants

EC 50 = 0.0374 mg/L

NOAEL = 0.026 mg/L Aquatic Nonvascular

Plants

EC 50 0.007 mg/L

NOAEL = 0.004 mg/L

Listed RQs 3 Nonlisted RQs 4 Listed RQs 3 Nonlisted RQs 4

Pastures/Rangela

nd in Eastern

U.S. CA rangeland hay (NY meteorological

file 14860) Aerial helicopter 493 18.9 13.7 123 70.4

Bermudagrass/

Bahiagrass;

Industrial turfgrass PA turf Ground 41.7 1.60 1 .11 10.4 5.95

Conifer release CA forestry (MI meterological file 14850) Ground

Pellets 24.1 0.92 0.64 6.02 3.44

Non

- crop sites (weed and brush control) CA rights

- of

- way Ground

Granules 408 15.6 10.9 102 58.2

1 Bolded and shaded values indicate an exceeda nce of an LOC.

2 Listed aquatic plant LOC = 1; Non

- listed aquatic plant LOC = 1

3 Estimated by dividing the peak EEC by the most sensitive NOAEC

4 Estimated by dividing the peak EEC by the most sensitive EC50



### RQs were additionally calculated using the EECs generated from inclusion of TTRs and UERs for two of the scenarios and the data for aquatic vascular and nonvascular plants. The resulting RQ

calculations can be found in Table 30

. There were LOC exceedances for both listed and nonlisted species for both species. RQs for aquatic vascular plants were 23.1 and 25.2 for listed species and 16.0 and 17.5 for nonlisted species. RQs for aquatic nonvascular plants were 150 for 164 for listed species and 85.8 and 93.7 for nonlisted species.

Table 30 . Listed and Non

- listed RQs for Direct Effects to Vascular and Nonvascular Aquatic Plants with Hexazinone, including TTRs and UERs

Use(s) Scenario Applica

tion

Method Peak

EECs (μg ai/L) Aquatic Vascular Plants

EC 50 = 0.0374 mg/L NOAEL = 0.026 mg/L Aquatic Nonvasc ular

Plants

EC 50 0.007 mg/L NOAEL = 0.004 mg/L

Listed RQs 3 Nonlisted RQs 4 Listed RQs 3 Nonlisted RQs 4

Sugarcane in HI LA sugarcane (HI meteoro

logical file 22521) Aerial 601 25.2 17.5 164 93.7

Non

- crop sites (weed and brush control) CA rights

- of

- way Ground 656 23.1 16.0 150 85.8

1 Bolded values indicate an exceedance of an LOC.

2 Listed aquatic plant LOC = 1; Non

- listed aquatic plant LOC = 1

3 Estimated by dividing the peak EEC by the most sensitive NOAEC

### Page 60 of 133 

### Table 30 . Listed and Non

- listed RQs for Direct Effects to Vascular and Nonvascular Aquatic Plants with Hexazinone, including TTRs and UERs

Use(s) Scenario Applica

tion

Method Peak

EECs (μg ai/L) Aquatic Vascular Plants

EC 50 = 0.0374 mg/L NOAEL = 0.026 mg/L Aquatic Nonvasc ular

Plants

EC 50 0.007 mg/L NOAEL = 0.004 mg/L

Listed RQs 3 Nonlisted RQs 4 Listed RQs 3 Nonlisted RQs 4

4 Estimated by dividing the peak EEC by the most sensitive EC50



## 4.2 **Risk Estimation for Terrestrial Organisms**  **Non**

**- Granular Uses** 

4.2.1 Acute Dose

- based Risk to Birds

Acute dose based RQs for birds exceed the LOCs for listed and non

- listed species for some uses

. Exceedances trend toward smaller bird siz es and use s associated with higher application rates.

Results have been summarized in Table 31

.

For a small bird, there were a number of scenarios resulting in RQs exceeding the listed and nonlisted species LOCs. For a small bird consuming short grass, the RQs ranged from 0.19 to 1.34

with four of the use s exceeding the nonlisted species LOC and four of the use s exceeding the listed species LOC. For a small bird consuming tall grass, RQs ranged from 0.09 to 0.62 with only one

of the use s exceeding the n onlisted species LOC, six of the use s exceeding the listed species LOC

and one of the use s that does not exceed any LOC. For a small bird consuming broad

- leaf plants RQs ranged from 0.11 to 0.76 with two of the use s exceeding the nonlisted species LOC and 6 of

the use s resulting in RQs which exceed the listed species RQ. For small birds consuming arthropods RQs ranged from 0.07 to 0.53 with only one use exceeding the nonlisted species LOC,

five use s exceeding the listed species LOC and one use with an RQ below both LOC levels.

For a medium bird, there were fewer use s resulting in RQs exceeding the listed and nonlisted species LOCs as compared to a small bird; only one of the use s across all feeding strategies resulting in an RQ above the nonlisted specie s LOC. For a medium bird consuming short grass, the RQs ranged from 0.08 to 0.60 with only one of the use s above the LOC for nonlisted species,

six of the use s above the LOC for listed species. For medium birds consuming tall grass, broadleaf plants, and arthropods, four of the use s resulted in RQs above the LOC for listed species, and four

of the use s did not exceed any LOCs. The RQs for tall grass ranged from 0.04 to 0.28, 0.05 to 0.3 for broadleaf plants and 0.03 to 0.24 for birds consuming arthropods

.

For a large bird, there were even fewer use s resulting in RQs exceeding the listed species LOCS

and no use s resulting in RQs above the nonlisted species LOC. For a large bird consuming short grass, there were three uses resulting in RQs above the LOC f or listed species. The RQs ranged from 0.03 to 0.19. For a large bird consuming broadleaf plants, only one of the use s resulting in an RQ above the LOC with the remaining seven use s below the LOC; the RQs ranged from 0.02 to 0.11. For large birds consum ing tall grass and arthropods, there were no use s resulting in RQs above the LOC for listed species. RQs ranged from 0.01 to 0.09 for large birds consuming tal grass and 0.01 to 0.07 for large birds consuming arthropods.

### Page 61 of 133 

### For small, medium and large birds consuming fruits, pods, seeds etc. and seeds, grains etc. there

were no use s that resulted in RQs above the LOC for listed species or nonlisted species. For birds consuming fruits, pods, seeds etc. RQs ranged from <0.01 to 0.08. For granivores consuming seeds, grains etc. RQs ranged from <0.01 to 0.02 across all birds sizes.

### Page 62 of 133 Table 31 

### . Acute Dose

- based RQ values for Birds Exposed to Hexazinone (T

- REX v. 1.5.2) 1,2 

### for Non

- Granular Uses
Primary Feeding Strategy  Herbivores and Omnivores Insectivores G ranivores

Animal Size
 Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

. Use(s) 

Agricultural Uses

Alfalfa 0.25* 0.12* 0.14* 0.02 0.11* 0.05 0.06 0.01 0.04 0.02 0.02 <0.01 0.10* 0.04 0.01 <0.01 <0.01 <0.01

Sugarcane in HI 0.60 0.28* 0.34* 0.04 0.27* 0.12* 0.15* 0. 02 0.09 0.04 0.05 0.01 0.24* 0.11* 0.03 0.01 <0.01 <0.01

Blueberries 0.34* 0.15* 0.19* 0.02 0.15* 0.07 0.08 0.01 0.05 0.02 0.03 <0.01 0.13* 0.06 0.02 <0.01 <0.01 <0.01

Non

- Agricultural Uses

Non

- Crop sites (Aerial) 1.01 0.46* 0.57 0.06 0.45* 0.21* 0.25* 0.03 0.14* 0.07 0.08 0.01 0.39* 0.18* 0.06 0.01 0.01 <0.01

Non

- Crop sites (Ground) 1.34 0.62 0.76 0.08 0.60 0.28* 0.34* 0.04 0.19* 0.09 0.11* 0.01 0.53 0.24* 0.07 0.02 0.01 <0.01

Christmas Tree

Plantations 0.34* 0.15* 0.19* 0.02 0.15* 0.07 0.08 0.01 0.05 0.02 0.03 <0.01 0.13* 0.06 0.02 <0.01 <0.01 <0.01

Rangeland 0.67 0.31* 0.38* 0.04 0.30* 0.14* 0.17* 0.02 0.10* 0.04 0.05 0.01 0.26* 0.12 0.04 0.01 <0.01 <0.01

Industrial Turfgrass 0.19* 0.09 0.11* 0.01 0.08 0.04 0.05 0.01 0.03 0.01 0.02 <0.01 0.07 0.03 0.01 <0.01 <0.01 <0.01

1 RQ values in bold exceed the non

- listed species LOC of 0.5. Values in red indicate that the RQ exceeds the LOC for acute risk to listed birds.

2 Acute endangered species LOC = 0.1; acute restricted use LOC = 0.2; acute high risk LOC = 0.5

### Page 63 of 133 

## 4.2.2 Acute Dietary

- based Risk to Birds

RQs for acute dietary based risk to birds cannot be calculated based on the non

- definitive endpoints found in the studies (both reported LC 50 

### >5000 ppm). When making a conservative assumption

c omparing the highest test concentration, 5,000 ppm, to the EECs reported in T able 19

, there are no LOC exceedances for nonlisted species, but some uses associated with the highest application rates exceed the LOC for listed species consuming short grass, tall grass and broadleaf plants.



## 4.2.3 Chronic Dose

- based Risk to Birds

Chronic dietary based RQs for birds have been tabulated in Table 32

. These RQs are based on a

NOAEC from a non

- adverse effect at the highest dos e. For birds consuming short grass, two use s resulted in RQ s which exceeded the chronic LOC; short gra ss RQs ranged from 0.27 to 1.92

. There were no RQs above the LOC for birds consuming tall grass ; the RQs ranged from 0.12 to 0.88

. Birds consuming broadleaf plants showed one use that resulted in an RQ that narrowly exceeded

the LOC ; the RQs ranged from 0. 15 to 1.08 . For birds consuming fruits, pods, seeds etc. the RQs ranged from 0.0 2 to 0. 12 and had no use s that resulted in LOC exceedances. For birds consuming arthropods there were no RQs that exceeded the LOC; the RQs ranged from 0.11 to 0.75

.

Table 32 . Chronic D ose

- Based RQs for Birds, Reptiles, and Terrestrial

- phase Amphibians of Different Feeding Classes (T

- REX v. 1.5.2) * 

### for Non

- Granular Uses
Primary Feeding Strategy  Herbivores, Omniv ores, and Granivores Insectivores

Dietary Items 

Short

Grass Tall

Grass Broad

leaf

Plants Fruits, pods, seeds,

etc

. Arthropods

Use(s) 

Agricultural Uses

Alfalfa 0.36 0.17 0.20 0.02 0.14

Sugarcane in HI 0.86 0.40 0.49 0.05 0.34

Blueberries 0.48 0.22 0.27 0.03 0.19

Non

- A gricultural Uses

Non

- Crop sites (Aerial) 1.44 0.66 0.81 0.09 0.56

Non

- Crop sites (Ground) 1.92 0.88 1.08 0.12 0.75

Christmas Tree Plantations 0.96 0.44 0.54 0.06 0.38

Rangeland 0.48 0.22 0.27 0.03 0.19

Industrial Turfgrass 0 .27 0.12 0.15 0.02 0.11

*RQ values in bold exceed the chronic LOC of 1 for both listed and non

- listed species.

### Page 64 of 133 

## 4.2.4 Acute Dose

- based Risk to Mammals

Acute dose based RQs for mammals exceed the LOCs for listed and nonlisted species for some

use s. Exce edances trend toward smaller mammal sizes and use s associated with higher application

rates. Results have been summarized in Table 33

.

For a small mammal, there were five uses resulting in RQs exceeding the non

- listed species LOCs.

For a small mammal co nsuming short grass, the RQs ranged from 0.10 to 0.79 with three of the uses exceeding the nonlisted species LOC and five of the uses exceeding the listed species LOC. For a small mammal consuming tall grass, RQs ranged from 0.04 to 0.36 with four of the uses exceeding the listed species LOC; none of the uses exceeded the non

- listed species LOC. For a small mammal consuming broadleaf plants, RQs ranged from 0.05 to 0.44 with six of the uses exceeding the listed species LOC; none of the uses exceeded the n onlisted species LOC. For a small mammal consuming arthropods, RQs ranged from 0.04 to 0.31 with four of the uses exceeding the listed species LOC; none of the uses exceeded the nonlisted species LOC. For small mammals consuming fruits, pods, seeds etc. or seeds, grains etc., RQs ranged from 0.01 to 0.05 and <0.01 to 0.01 respectively; there were no LOC exceedances for listed or nonlisted species.

For medium sized mammals, there were fewer uses resulting in R Qs exceeding the listed and non

listed species LOCs as compared to small mammals. For a medium mammals consuming short

grass , the RQs ranged from0.08 to 0.67, with two of the uses resulting in RQs above the nonlisted species LOC and five of the uses exceeding the listed species LOC. For a medium mam mals consuming tall grass, RQs ranged from 0.04 to 0.31 with four of the uses exceeding the listed species LOC; there were no exceedances for non

- listed species. For a medium mammals consuming broadleaf plants, RQs ranged from 0.05 to 0.38 with four of the uses exceeding the listed species LOC and none of the uses exceeding the nonlisted species LOC. For a medium mammals consuming arthropods, there were four uses which exceeded the listed species LOC and RQs ranged from 0.03 to 0.26 . For medium mammals co nsuming fruits, pods, seeds etc. or seeds, grains etc. RQs ranged from 0.01 to 0.04 and <0.01 to 0.01 respectively; there were no LOC exceedances for listed or nonlisted species.

For large mammals, there were no LOC exceedances for any nonlisted species. For large mammals consuming short grass there were five uses resulting in RQs above the listed species LOC; RQs ranged from 0.04 to 0.36. For large mammals consuming tall grass there were three uses resulting in RQs above the listed species LOC with RQs ranging from 0.02 to 0.16. For large mammals consuming broadleaf plants there were three uses with RQs exceeding the listed species LOC; RQs ranged from 0.03 to 0.20. For large mammals consuming arthropods there were two uses with RQs exceeding the list ed species LOC, ranging from 0.02 to 0.14. For large mammals consuming fruits, pods, seeds etc. and seeds, grains etc. there were no exceedances for listed species; RQs ranged from <0.01 to 0.02 and <0.01 to 0.01 respectively.

### Page 65 of 133 Table 33 

### . Acute Dose

- base d RQ values for Mammals Exposed to Hexazinone (T

- REX v. 1.5.2) 1,2 

### for Non

- Granular Uses
Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size  Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

. Use(s) 

Agricultural Uses

Alfalfa 0. 13 * 0.06 0.07 0.01 0.11 * 0.05 0.06 0.01 0.06 0.03 0.03 <0.01 0.05 0.04 0.02 <0.01 <0.01 <0.01

Sugarcane in HI 0.31 * 0.14 * 0.17 * 0.02 0.27 * 0.12 * 0.15 * 0.02 0.14 * 0.07 0.08 0.01 0.12 * 0.10 * 0.06 <0.01 <0.01 <0.01

Blueberries 0.17 * 0.08 0.10 * 0.01 0.15 * 0. 07 0.08 0

. 01 0.08 0.04 0.04 <0.01 0.07 0.06 0.03 <0.01 <0.01 <0.01

Non

- Agricultural Uses

Non

- Crop sites (Aerial) 0.52 0.24 * 0.29 * 0.03 0.44 * 0.20 * 0.25 * 0.03 0.24 * 0.11 * 0.13 * 0.01 0.20 * 0.17 * 0.09 0.01 0.01 <0.01

Non

- Crop sites (Ground) 0.69 0.32 * 0.39 * 0.04 0.59 0.27 * 0.33 * 0.04 0.32 * 0.15 * 0.18 * 0.02 0.27 * 0.23 * 0.12 * 0.01 0.01 <0.01

Christmas Tree Plantations 0.17 * 0.08 0.10 * 0.01 0.15 * 0.07 0.08 0

. 01 0.08 0.04 0.04 <0.01 0.07 0.06 0.03 <0.01 <0.01 <0.01

Rangeland 0.79 0.36 * 0.44 * 0.05 0.67 0.31 * 0 .38 * 0.04 0.36 * 0.16 * 0.20 * 0.02 0.31 * 0.26 * 0.14 0.01 0.01 <0.01

Industrial Turfgrass 0.10 * 0.04 0.05 0.01 0.08 0.04 0.05 0.01 0.04 0.02 0.03 <0.01 0.04 0.03 0.02 <0.01 <0.01 <0.01

1 RQ values in bold exceed the non

- listed species LOC of 0.5. Starred va lues indicate that the RQ exceeds the LOC for acute risk to listed mammals.

### Page 66 of 133 

## 4 .2.5 C hronic Dose and Dietary

- based Risk to Mammals

Chronic dose based RQ values for mammals exposed to hexazinone resulted in a significant

number of LOC exceedances across all use s, mammal sizes and feeding strategies; results have

been tabulated in Table 34

.

For small mammals, chronic RQs exceeded the LOC for all use for mammals consuming short grass, tall grass, broadleaf plants and arthropods. The RQs ranged as follows: 11.7 to 83.2 for short grass, 5.37 to 38.1 for tall grass, 6.59 to 46.8 for broadleaf plants, and 4.59 to 32.6 for arthropods. For small mammals consuming fruits, pods, seeds etc. there were two use s that did not exceed the chronic LOC; RQs ranged from 0 .73 to 5.21. For small mammals consuming seeds, grains etc. there were six use s that resulted in RQs below the chronic LOC.

For medium mammals, chronic RQs exceeded the LOC for all use s for mammals consuming short grass, tall grass, broadleaf plants and arthropods. The RQs ranged as follows: 10.0 to 71.1 for short grass, 4.59 to 32.6 for tall grass, 5.63 to 40.0 for broadleaf plants, and 3.92 to 27.8 for arthropods. For medium mammals consuming fruits, pods, seeds etc. there were two use s that did

not e xceed the chronic LOC; RQs ranged from 0.63 to 4.45. For medium mammals consuming seeds, grains etc. there were no use s that resulted in RQs exceeding the chronic LOC.

For large mammals, chronic RQs exceeded the LOC for all use s for mammals consuming sho rt grass, tall grass, broadleaf plants and arthropods. The RQs ranged as follows: 5.36 to 38.1 for short grass, 2.46 to 17.4 for tall grass, 3.02 to 21.4 for broadleaf plants and 2.10 to 14.9 for arthropods. For medium mammals consuming fruits, pods, see ds etc. there were four use s that did not exceed the chronic LOC with RQs ranging from 0.34 to 2.38. For large mammals consuming seeds, grains etc. there were no use s that resulted in RQs exceeding the chronic LOC.

### Page 67 of 133 

### Table 34 . Chronic Dose

- based RQ Value s for Mammals Exposed to Hexazinone (T

- REX v.1.5.2) 1,2 

### for Non

- Granular Uses

Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size  Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

. Use(s) 

Agricultural Uses

Alfalfa 15.9 7.16 8. 78 0.98 13.3 6.11 7.50 0.83 7.15 3.28 4.02 0.45 6.12 5.22 2.80 4.77 0.19 0.10

Sugarcane in HI 37.4 17.1 21.0 2.34 32.0 14.6 18.0 2.00 17.1 7.87 9.65 1.07 14.6 12.4 6.72 0.52 0.44 0.24

Blueberries 20.8 9.84 11.7 1.30 17.7 8.15 10.0 1.11 9.53 4.37 5.36 0.6 0 8.16 6.97 3.73 0.29 0.25 0.13

Non

- Agricultural Uses

Non

- Crop sites (Aerial) 62.4 28.6 35.1 3.90 53.3 24.4 30.0 3.33 28.6 13.1 16.0 1.79 24.4 20.9 11.2 0.87 0.74 0.40

Non

- Crop sites (Ground) 83.2 38.1 46.8 5.21 71.1 32.6 40.0 4.45 38.1 17.4 21.4 2.38 3 2.6 27.8 14.9 1.16 0.99 0.53

Christmas Tree Plantations 20.8 9.54 11.7 1.30 17.7 8.15 10.0 1.11 9.53 4.37 5.36 0.60 8.16 6.97 3.73 0.29 0.25 0.13

Rangeland 41.6 19.0 23.4 2.60 35.5 16.3 20.0 2.22 19.0 8.74 10.7 1.19 16.3 13.9 7.47 0.58 0.49 0.26

Industr ial Turfgrass 11.7 5.37 6.59 0.73 10.0 4.59 5.63 0.63 5.36 2.46 3.02 0.34 4.59 3.92 2.10 0.16 0.14 0.07

1 RQ values in bold exceed the chronic LOC of 1 for both listed and non

- listed species. 2 Using adjusted NOAEL values of 21.98

, 17.78 , and 7.69 for small, medium, and large mammals, respectively.

2 Chronic risk LOC = 1.

### Page 68 of 133 

### Chronic dietary based RQs for mammals exceed the LOC for some use s across mammals consuming short grass, tall grass and broadleaf plants; the results have been tabulated in Table 35

. For mammals consuming short grass, the chronic LOC is exceeded for all use s and the RQs ranged from 1.35 to 9.60. For mammals consuming tall grass, the chronic LOC is exceeded for six of the eight use s with RQs ranging from 0.62 to 4.40. For mammals consumi ng broadl eaf plants, the

chronic LOC is exceeded for seven of the eight use s with RQs ranging from 0.76 to 5.40. For mammals consuming arthropods, the chronic LOC is exceeded for 4 use s, with four of the use s resulting in RQs below the LOC; the RQs range from 0.53 to 3.76. Lastly, for mammals consuming fruits, pods, seeds etc. there are no use s that result in RQs exceeding the chronic LOC.

Table 35 . Chronic Dietary

- Based RQs for Mammals of Expose d to Hexazinone (T

- REX v.1.5.2) 1,2 

### for Non

- Granular Use s Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items 

Short

Grass Tall

Grass Broad

leaf

Plants Fruits, pods, seeds,

etc

. Arthropods

Use(s) 

Agricultural Uses

Alfalfa 1.80 0.83 1.01 0.11 0.71

Sugarcane i n HI 4.32 1.98 2.43 0.27 1.69

Blueberries 2.40 1.10 1.35 0.15 0.94

Non

- Agricultural Uses

Non

- Crop sites (Aerial) 7.20 3.30 4.05 0.45 2.82

Non

- Crop sites (Ground) 9.60 4.40 5.40 0.60 3.76

Christmas Tree Plantations 2.40 1.10 1.35 0.15 0.94

Rangeland 4 .80 2.20 2.70 0.30 1.88

Industrial Turfgrass 1.35 0.62 0.76 0.08 0.53

1 Chronic risk LOC = 1.



## 4.2.6 Risk to Terrestrial Plants

The LOC for non

- target monocots adjacent to hexazinone use areas for non

- granular uses was exceeded across use s for spray dr ift only, runoff and spray drift in dry areas and runoff and spray drift in semi aquatic areas with a single exception. For nonlisted species considering spray drift only, the lowest use rate resulted in an RQ below the LOC for nontarget monocots. The RQ s ranged from 0.56 to 15.0. The highest RQs can be found for nontarget monocots in semi

- aquatic areas, with RQs ranging from 22.1 to 157 for nonlisted monocots, and 73.4 to 522 for listed species.

The results have been summarized in Table 36

.

### Page 69 of 133 

### Table 36

. RQs for Nontarget Monocots Adjacent to Hexazinone Use Areas 1 

### for Non

Granular Uses

Crop Single Max. Application

Rate (lbs ai/A) Monocot RQ Values

Spray Drift Only Runoff and Spray Drift (Dry Areas) Runoff and Spray Drift (Semi

- Aquatic Areas)

N onlisted

Species Listed Species Nonlisted Species Listed Species Nonlisted Species Listed Species

Alfalfa Aerial: 1.5 3.75 7.50 5.79 19.2 31.8 105
Sugarcane in HI Aerial: 3.6 9.00 18.0 13.9 46.0 76.4 253

Blueberries Ground: 2.0 1.00 2.00 4.63 15.3 39.3 130

Noncrop sites Aerial: 6.0 15.0 30.0 23.1 76.8 127 422

Ground: 8.0 4.0 8.0 18.5 61.4 157 522

Forestry Aerial: 4.0 10.0 20.0 15.4 51.2 84.9 281

Christmas trees Aerial 2.0 5.0 10.0 7.72 25.6 42.4 140
Eastern Rangeland Aerial 4.0 10.0 20.0 15.4 51.2 84.9 281
Industrial turfgrass Ground: 1.125 0.56 1.13 2.61 8.64 22.1 73.4

1 LOCfor listed and non

- listed species = 1 ; values in bold exceed the LOC



### The LOC for non

- target dic ots adjacent to hexazinone use areas for non

- granular uses was exceeded across uses for spray drift only, runoff and spray drift in dry areas and runoff and spray drift in semi aquatic areas. The lowest RQs can be found for nontarget dicots when considering spray drift only with RQs ranging from 1.79 to 47.6 for nonlisted species a nd 1.62 to 43.1 for listed species. The highest RQs can be found for nontarget dicots in semi

- aquatic areas, with RQs ranging from 91.0 to 647 for nonlisted species , and 82.5 to 5 87 for listed species. The results have

been summarized in Table 37

.

Tabl e 37 . RQs for Nontarget Dicots Adjacent to Hexazinone Use Areas 1 

### for Non

Granular Uses

Crop Single Max. Application

Rate (lbs ai/A) Monocot RQ Values

Spray Drift Only Runoff and Spray Drift (Dry Areas) Runoff and Spray Drift (Semi

- Aquatic Areas)

Nonlisted

Species Listed Species Nonlisted Species Listed Species Nonlisted Specie s Listed Species

Alfalfa Aerial: 1.5 11.9 10.7 23.8 21.5 130 118
Sugarcane in HI Aerial: 3.6 28.5 25.9 57.1 51.8 314 284

Blueberries Ground: 2.0 3.17 2.88 19.0 17.2 161 146

Noncrop sites Aerial: 6.0 47.6 43.1 95.2 86.3 523 474

Ground: 8.0 12.7 11.5 76.1 69.0 647 587

Forestry Aerial: 4.0 31.7 28.7 63.4 57.5 349 316

Christmas trees Aerial 2.0 15.8 14.3 31.7 28.7 174 158
Eastern Rangeland Aerial 4.0 31.7 28.7 63.4 57.5 349 316
Industrial turfgrass Ground: 1.125 1.79 1.62 10.7 9.71 91.0 82.5

1 LOCfor listed and non

- listed species = 1; values in bold exceed the LOC

### Page 70 of 133 

## 4.3 **Risk Estimation to Terrestrial Organisms for Granular and** 
**Pelleted Uses** 

4.3.1 Risk to Birds and Ma mmals

Granular and pelleted applications have been summarized in Table 2. S ummary of Hexazinone Uses and Application Information under the Granular Applications tab. There are four crops that have a pelleted and/or granular application.

For the granula r and pelleted applications the LD 50 

### per ft 2 

### tab within T

- REX (v.1.5.2) have been used to quantify the risk to terrestrial organisms. Although a bird’s or mammal’s habitat is not limited to a square foot, there is presumably a direct correlation between t he concentrations of a pesticide in the environment (mg/ft 2 

### ) and the chance than an animal will be exposed to a concentration that could adversely affect its survival. Typically for granular applications

, terrestrial EECs are calculated based on an estima ted loading of pesticides per unit area. This approach compares the available mass of pesticide per square foot to the acute oral dose for toxicity (LD 50 

### ) ; the resulting value can be compared directly the Agency’s LOC . Results have been

tabulated in Table 38 for birds and Table 39 for mammals. A sample output can be found in Appendix F

. Because the mass of the pellets is known, the pelleted formulations will later be characterized using T

- REX; there will be no further characterization of the granular for mulations.

A comparison of the LC 50 / 

### ft 2 

### show that consumption of the granules and pellets affect the smallest weight class more than the largest weight class. The highest values are associated with the smallest bird and highest application rates.

T able 38

. Analysis LD 50 

### per ft 2 

### for Birds for Granular and Pelleted Uses

Application Weight Class

Use Application

Rate mg a.i./ft 2 20 g 100 g 1000 g

Rangeland

(pellets) 0.63 lb ai/A 4.92 0.15 0.02 0.00

Conifer Release (granular) 3 lb ai/A 23.43 0.72 0. 11 0.01

Conifer Release (pellets) 4.0 lb ai/A 31.24 0.96 0.15 0.01

Forestry Site Preparation

Eastern (granular) 4.7 lb ai/A 36.71 1.13 0.18 0.01

Forestry Site Preparation

Western (granular) 4.0 lb ai/A 31.24 0.96 0.15 0.01

Forestry Site Preparation 6.1 lb ai/A 47.64 1.46 0.23 0.02

### Page 71 of 133 (pe llets)

Non

- Crop Site (pellets) 8.0 lb ai/A 62.48 1.92 0.30 0.02

Non

- Crop Site

(granular) 7.4 lb ai/A 57.79 1.78 0.28 0.02



### Table 39

. Analysis LD 50 

### per ft 2 

### for Mammals for Granular and P elleted Uses

Application Weight Class

Use Application

Rate mg a.i./ft 2 

### 15 g 35 g 1000 g

Rangeland

(pellets) 0.63 lb ai/A 4.92 0. 12 0. 07 0.01

Conifer Release (granular) 3 lb ai/A 23.43 0.59 0.31 0. 0 3

Conifer Release (pellets) 4.0 lb ai/A 31.24 0.79 0. 42 0. 0 3

Forestry Site Preparatio n

Eastern (granular) 4.7 lb ai/A 36.71 0.93 0.49 0.0 4

Forestry Site Preparation

Western (granular) 4.0 lb ai/A 31.24 1.58 0.84 0.07

Forestry Site Preparation

(pellets) 6.1 lb ai/A 47.64 1.20 0.64 0.05

Non

- Crop Site (pellets) 8.0 lb ai/A 62.48 1.58 0.84 0.07

Non

- Crop Site

(granular) 7.4 lb ai/A 57.79 1.46 0.77 0.06



## 4.3.2 Risk to Terrestrial Plants

The LOC for non

- target monocots adjacent to hexazinone use areas for granular and pelleted uses was exceeded across all uses for dry areas and semi

- aquatic areas. Because it is a granular or pelleted formulation, there is negligible spray drift. For non

- listed species, the lowest application rate resulted in an RQ minimally above the LOC for nontarget monocots. For dry areas, the RQs ranged from 1.22 to 15 .4 for non

- listed species and 4.03 to 51.2 for listed species. For semi

- aquatic areas, the RQs ranged from 12.1to 154 for nonlisted species and 40.3 to 5 12 for listed species.

Results have been tabulated in Table 4 0

.

### Page 72 of 133 

### Table 4 0 . RQs for Nontarget Monoc ots Adjacent to Hexazinone Use Areas 1 

### for Granular

and Pelleted Uses

Crop Single Max. Application

Rate (lbs ai/A) Monocot RQ Values

Spray Drift Only Runoff and Spray Drift (Dry Areas) Runoff and Spray Drift (Semi

- Aquatic Areas)

Nonlisted

Species Listed Species Nonlisted Species Listed Species Nonlisted Species Listed Species
Rangeland Ground: 0.63 <0.1 <0.1 1.22 4.03 12.1 40.3

Conifer Release Ground: 3.0 <0.1 <0.1 5.79 19.2 57.9 192.

Ground: 4.0 <0.1 <0.1 7.72 25.6 77.2 256

Forestry Site Pre p Ground: 4.7 <0.1 <0.1 9.07 30.0 90.7 300

Ground: 4.0 <0.1 <0.1 7.72 25.6 77.2 256

Ground: 6.1 <0.1 <0.1 11.7 39.0 117 390

Non

- Crop sites Ground: 7.4 <0.1 <0.1 14.2 47.3 142 473

Ground: 8.0 <0.1 <0.1 15.4 51.2 154 512

1 LOCfor listed and non

- listed species = 1; values in bold exceed the LOC



### The LOC for non

- target dicots adjacent to hexazinone use areas for granular and pelleted uses was exceeded across all uses for dry areas and semi

- aquatic areas. The lowest RQs are found in dry areas. For nonl isted species in dry areas, the RQs range from 5.00 to 63.4 and 4.53 to 57.5 for listed species. For nonlisted species in semi

- aquatic areas, RQs range from 50.0 to 634 and 45.3 to 575 for listed species.

Table 4 1 . RQs for Nontarget Dicots Adjacent to Hexazinone Use Areas 1 

### for Granular

and Pelleted Uses

Crop Single Max. Application

Rate (lbs ai/A) Monocot RQ Values

Spray Drift Only Runoff and Spray Drift (Dry Areas) Runoff and Spray Drift (Semi

- Aquatic Areas)

Nonlisted

Species Listed Species Nonlisted Species Listed Species Nonlisted Species Listed Species
Rangeland Ground: 0.63 <0.1 <0.1 5.00 4.53 50.0 45.3

Conifer Release Ground: 3.0 <0.1 <0.1 23.8 21.5 238 215

Ground: 4.0 <0.1 <0.1 31.7 28.7 317 287

Forestry Site Prep Ground: 4.7 <0.1 <0.1 37.3 33.8 373 338

Ground: 4.0 <0.1 <0.1 31.7 28.7 317 287

Ground: 6.1 <0.1 <0.1 48.4 43.8 484 438

Non

- Crop sites Ground: 7.4 <0.1 <0.1 58.7 53.2 587 532

Ground: 8.0 <0.1 <0.1 63.4 57.5 634 575

1 LOCfor listed and non

- listed species = 1; values in bold exceed the LOC



## 4.4 **Risk Description**

### Page 73 of 133 

### In risk description, the results from the risk estimation are interpreted and synthesized into overall risk conclusions. This description considers other lines of evidence ( e.g ., monitoring data, field data, refined exposure and effects modeling) for characterizing ecological risk. In addition, the risk description also contains a discussion of relevant sources of uncertainty in the risk assessment and sensitivity of the risk assessment findings to important methodological assumptions. The risk description also addresses other concerns including risks to threatened and endangered species, a discussion of uncertainty, and the sensitivity of risk conclusions to assumptions made in the

assessment.



## 4. 4.1 Risk t o Aquatic Organisms

A summary of the maximum hexazinone acute and chronic RQ values derived for aquatic animals

is shown i n Table 4 2

. The RQ values for freshwater fish, freshwater invertebrates and

estuarine/marine invertebrates do not exceed the acute or chronic LOC for listed or nonlisted species for flowable or granular uses . Specifically, the chronic values are multiple orders of magnitude below the chronic LOC of 1.0. There is no data available for estuarine/marine fish, however based on the toxicity of hexazinone to freshwater fish, there is no risk expected to

estuarine/marine fish.

Table 4 2 . Summary of aquatic animal risk profile for Hexazinone

Exposure FW Fish RQ FW Invert. RQ SW Invert. RQ

Acute 0.002 0.004 0.032

Chronic 0.038 0.008 0.06 3 RQ values based on the maximum aquatic EECs derived from the 05_ CA rights of way scenario; see

Risk Estimation Section 5.1 for derivation of these RQ values



## Characterization of UER and TTR data

RQs for freshwater fish, freshwater invertebrates and e stuarine/marine invertebrates were calculated using the EECs for Hexazinone including the TTRs and UERs. A comparison of the TTR and UER EECs to the parent and degradates EECs show that the TTR and UER EECs are vary no more than 5 μg/L from parent only E ECs . Thus the resulting RQs of the TTS and UER are not significantly different from the parent and degradates and do not change the risk picture for any aquatic organisms. The reason for the similarity between the EECs for the parent plus degradates (TTR s) and parent plus degradates plus UERs is that the levels of UERs were high only in the aerobic soil metabolism study. In both the aerobic and anaerobic aquatic metabolism studies the levels of UERs were very low.



## Risk Characterization Fish :
Based on t he results of risk estimation, EFED does not perceive the potential for risk to freshwater fish. None of the RQ values for freshwater fish exceed the applicable acute or chronic risk LOC. Additionally there were no incident s reported in EIIS; there is so me uncertainty concerning IDS, as it is unknown if fish were involved in the reported wildlife incidents, however considering the

### Page 74 of 133 

### toxicity profile for fish, this is unlikely.

There is some uncertainty regarding the lack of toxicity data for estuarine/mar ine fish. However, based on the lack of toxicity as is illustrated in freshwater fish, it can be assumed that estuarine/marine fish will exhibit a similar response. Additionally, based on the mode of action of the chemical, risk to aquatic animals is ass umed to be low.



## Risk Characterization Aquatic Invertebrates : Based on the results of risk estimation, EFED does not perceive the potential for risk to freshwater and estuarine/marine invertebrates. None of the acute or chronic RQ values resulted in

exceed ances for the listed or nonlisted species. Additionally, there were no incidents reported in EIIS, AIMS, or IDS

.



## Risk Characterization Aquatic Plants : A summary of the maximum hexazinone RQ values derived for aquatic plants is shown in Table

4 3

. The RQ values for aquatic vascular and nonvascular plants for both listed species and nonlisted species exceed the LOC. These toxicity values are consistent with the mode of action of the

chemical in that it is an herbici de acting through photosynthesis inhibition

. The primary exposure is through run off leaching rather than spray drift. There were no incidents reported for aquatic plants in EIIS or IDs.

Table 4 3 . Summary of Aquatic Plant Risk Profile for Hexazinone

Exposure Aquatic Vascular Aquatic Nonvascular

Listed 25.1 163

Nonlisted 17.4 93.2
RQ values based on the terrestrial EECs derived from 05 CA Rights of way ; see Risk Estimation for derivation of these RQ values

Bolded values exceed LOC risk



## 4. 4.2 Ris k to Terrestrial Organisms

A summary of the maximum hexazinone acute and chronic RQ values derived for terrestrial

animals is shown in Table 4 4

. The dose based and dietary based RQ values for both birds and

mamma ls exceed and acute and chronic LOC. Avian acute dose based risk exceeds Nonlisted species LOC. The avian dietary RQ is the only value that exceeds the LOC for listed species but not for nonlisted species; all other RQs for avian dose based, and mammalia n dose and dietary based exceed the LOC for listed and nonlisted species.

Table 4 4 . Summary of the Avian and Mammalian Risk Profile for

Hexazinone for Non Granular Uses

Exposure Avian Dose RQ Avian Dietary RQ Mammalian Dose RQ Mammalian Dietary RQ

### Page 75 of 133 Acut e 1.34 0.38 1.57 NA

Chronic NA 1.92 83.2 9.60
RQ values based on the terrestrial EECs derived from 05 CA Rights of way; see Risk Estimation for derivation of these RQ values

Bolded values exceed LOC risk



## Risk Characterization Birds for Non

- Granular Us es : Based on the results of risk estimation, there is a potential risk to avian sp ecies. The maximum dose based RQ was 1.34 and exceeds the LOC for listed and nonlisted species. An examination

of the entire Acute dose

- based RQ values for birds exposed to hexazinone, T able 31

, shows that the LOC exceedances for nonlisted species are concentrated in small birds consuming s hort grass. Of the eight use s resulting in LOC exce edances for birds, four of them occurred for nonlisted species. For other bird sizes, the LOC exceedances for listed species tended to concentrate around

the short grass feed items, followed by tall grass and then broadleaf plants. The dietary and chronic based RQs exhibited a similar pattern of RQs increased with the food items as previo usly listed.

There is uncertainty in the acute toxicity data for birds due to the absence of passerine data. A passerine study was requested as part of the DCI released with the 2010 Problem Formulation for Hexazinone (D369269). The submitted study ( MRI D 48718401) was deemed invalid and did not fill the guideline requirement for 850.2100; the submitted document consisted of a simulation of existing data and was not an actual passerine study that was conducted in a lab.

Due to the lack of available pass erine data, the avian RQs were based on t oxicity values for a

mallard. In the absence of passerine data, there is significant uncertainty as to whether or not the RQs predict a sensitivity representative of smaller birds on the field which tend to exhibit higher sensitivities than larger birds.



## Risk Characterization Mammals for Non

- Granular Uses : Based on the results of risk estimation, there is a potential risk to small mammalian species. The

maximum dos e based RQ was 0.79 and exceeds the LOC for liste d and nonlisted species. An

examination of the entire Acute Dose

- Based RQ values for Mammals Exposed to Hexazinone,

Ta ble 3 3 , shows that the LOC exceedances for nonlisted species are concentrated in small mammals consuming short grass, however there are s till LOC exceedances for nonlisted species

for medium mammals.

Chronic dietary based RQs show a maximum of 9.60; exceedances are found across all use s and dietary items, with the exception of fruits, pods, seeds etc. For tall grass and broadleaf plants

, there was no LOC exceedance for the lowest application rate, industrial turfgrass and for arthropods there were only four use s resulting in LOC exceedances. Chronic dose

- based RQs,

found in Table 3 4 , show a maximum of 83.2 and are found across all use s, mammalian sizes, and feeding strate gies with the exception of granivores. For the alfalfa and turfgrass, the two lowest application rates, there is no LOC exceedance for small medium or large mammals consuming

### Page 76 of 133 

### fruits, pods, seeds etc.



## Risk Characte rization for Birds and Mammals for Granular Uses:

There are eight uses of hexazinone that are granular or pelleted and are not assessed via T

- REX spray drift calculations. The LD 50 

### per ft 2 

### analysis can be found in the risk estimation for all eight

uses. Because there was no data available on the mass of the granule, no further characterization can be made to the granular uses. Information available stated that the granular formulations were “Ultra Low Weight” and were intended to have smaller granules th an the pelleted

formulations. The model assumes that 100% of the granules are available for consumption; some of the labels instruct the granular formulated products to be watered into the soil, this there is some uncertainty as to what percent of the gra nules would be available for the organisms to

consume. The size of the granules used in the formulations are needed to properly characterize the risk to small birds and mammals; until this information is submitted risk to birds and mammals due to granular uses will be considered an uncertainty. There is additional uncertainty as to the likelihood that the birds and mammals would purposefully consume the granules.



## Risk Characterization for Birds and Mammals for Pelleted Uses:

This characterization will seek to refine the pelleted formulations of hexazinone. There are eight

use s of hexazinone that are granular or pelleted and are not assessed via T

- REX spray drift

calculations. The LD 50 

### per ft 2 

### analysis can be found in the risk estimation for all eight uses. This characterization will seek to refine the pelleted formulations; because there was no data available on the mass of the granule, no further characterization can be made to the granular use s. The characterization was run for the highest applicat ion rate, Non

- Crop Site. The pellets for hexazinone formulated product are 640 mg 4



### — due to the size of the pellet, it is assumed that it will only be potentially consumed by the largest weight class of birds and mammals. The output from T

- REX

can be found in Appendix G

.

Table 4 5

. shows the estimated of the nu mber of granules, and area foraged needed for a 1000 g bird to achieve the EEC equivalent dose that would trigger an exceedance of the acute risk (0.1) and acute endangered species (0.5) LOC for the Non

- Crop Site pelleted formulation used at an application rate of 8.0 lb ai/A; this use scenario is representative of the highest application rate. This analysis shows that a 1,000 gram bird would have to consume less than one pellet to exceed

the LOC fo r listed species and would consume a little over three pellets to exceed the LOC for nonlisted species.

Table 4 5 . Estimates of the number of granules, area foraged, and process time needed for a 1000 g bird to achieve the EEC equivalent dose that would trigger an exceedance of the acute risk (0.1), and acute endangered species (0.5) level of concern for the Non

- Crop Site

Pelleted formulated at 8 lb ai/A

4 Based on the n umber of pellets in a 5.5 lb container ~3900, and 75% A.I. in formulation (source of number of pellets is Pro

- Serve Inc.’s website (registrant’s website), at http://www.pro

- serveinc.com/powerpellet.html , accessed 06/05/2015).

### Page 77 of 133 

### EPA Level of Concern

0.1 0.5 EEC Equivalent Dose requires to reach the specified LOC (mg ai/kg

- bw ) 292 1,460

Number of Consumer Granules required to reach the specified

LOC 0.61 3.05

Area of field to be foraged (ft 2 

### ) Assuming 100% feeding efficiency 4.68 ft 2 

### 23.3 ft 2


### Assuming 50% feeding efficiency 9.36 ft 2 

### 46.7 ft 2


### Assuming 10% feeding efficie ncy 46.8 ft 2 

### 233 ft 2



### Table 4 6

. shows the estimated of the number of granules, area foraged needed for a 1000 g mammal to achieve the EEC equivalent dose that would trigger an exceedance of the acute risk (0.1) and acute endangered species (0.5) LOC for the Non

- Crop Site pelleted formulation used at an application rate of 8.0 lb ai/A; this use scenario is representative of the highest application rate. This analysis shows that the acute LOC would be exceeded for both listed and non listed species

should they consume one granule or more.

Table 4 6 . Estimates of the number of granules, area foraged, and process time needed for a 1000 g mammal to achieve the EEC equivalent dose that would trigger an exceedance of the acute risk (0.1), and acute endangered sp ecies (0.5) level of concern for the Non

- Crop

Site Pelleted formulated at 8 lb ai/A

EPA Level of Concern

0.1 0.5 EEC Equivalent Dose requires to reach the specified LOC (mg ai/kg

- bw) 92.3 462

Number of Consumer Granules required to reach the specifie d

LOC 0 .19 0. 95

Area of field to be foraged (ft 2 

### ) Assuming 100% feeding efficiency 1.48 ft 2 

### 7.40 ft 2


### Assuming 50% feeding efficiency 2.95 ft 2 

### 14.8 ft 2


### Assuming 10% feeding efficiency 14.8 ft 2 

### 74.0 ft 2



## Risk Characterization Pollinators:

A 48

- hour ac ute contact study was conducted with the honeybee ( Apis mellifera) , MRID 41216502. The study concluded that hexazinone was relatively nontoxic to bees based on an LD 50 

### > 100 μg/bee with a NOAEC of 100 μg/L. The toxicity of hexazinone to larval bees on an acute and chronic basis, and the chronic toxicity of hexazinone to adult bees is unknown and will be considered an uncertainty at this time.

To characterize risk to p ollinators, a back calculation was used to understand the EEC required to exceed the Agency’s acute risk LOC of 0.4. With an endpoint of >100 μg/bee, the EEC which

c ould result in an LOC exceedance is 400μg.

### Page 78 of 133 

## Risk Characterization Terrestrial Plants :

Bas ed on the results of risk estimation there is potential risk to nontarget terrestrial plants. A summary of the maximum hexazinone RQ values derived for terrestrial plants is shown in Table

4 7

. The RQ values for m onocots and dicots for both listed and nonlisted species exceed the LOC. These toxicity values are consistent with the mode of that action in that it is an herbicide acting through photosynthesis inhibitions. There were a number of incidents reported for terrestrial plants

in EIIS and IDS. These incidents have been summarized in Table 2 3

.

Table 4 7 . Summary of Terrestrial Plant Risk Profile for Hexazinone

Exposure Monocot Dicot

Listed 522 587

Nonlisted 157 647
RQ values based on the terrestrial EECs derived from 05 CA Rights of way; see Risk Estimation for derivation of these RQ values

Bolded values exceed LOC risk



## Spray Drift Analysis A spray drift analysis was conducted for the ground and aerial applications of hexazinone. In order

to conduct th is analysis, the most sensitive species (terrestrial plants) was selected. The tomato seedling emergence endpoint was found to be the most sensitive of all terrestrial plant species (EC 25 

### = 0.00695 lb a.i./A). In short, a buffer zone needed to approach t he LOC was calculated (LOC for terrestrial plants is 1.0). The example label used for this analysis was Velpar L. For this product, there are no special spray drift restrictions, other than the spray volume, which is specified in specific instances.

For ground applications, the following assumptions were made: high boom height, ASABE Very Fine to Fine drop size distribution (DSD), 90 th 

### percentile data percentile (USEPA 2013). For aerial applications, the following assumptions were made: Tier II Aerial a pplication using ASABE Fine to Fine to Medium DSD, 5 gallons diluted product per acre, wind speed 10 mph, aircraft Wasp Helicopter, boom height 10 feet.

The Terrestrial Point module calculates the buffer zone required. It was found that for the ground

ap plications, the buffer needed ranged from 384 feet for turfgrass to >1000 feet (out of range) for

non

- crop sites. For all the aerial applications, the buffer zone was >1000 feet (out of range).

Table 38 . Needed Buffer Distances to Approach or Exceed the Non

- Listed LOC for Terrestrial Plant Exposure for Hexazinone , Using EFED’s Default Assumptions

Scenario App. Rate (lb a.i./A) App. Method Need Buffer Distance (ft) App. Method Need Buffer Distance (ft)

Alfalfa 1.5 Ground 476 Aerial >1000 Sugarcane in H I 3.6 Ground 869 Aerial >1000 Blueberries (low bush) 3 Ground 771

### Page 79 of 133 

### Table 38 . Needed Buffer Distances to Approach or Exceed the Non

- Listed LOC for Terrestrial Plant Exposure for Hexazinone , Using EFED’s Default Assumptions

Scenario App. Rate (lb a.i./A) App. Method Need Buffer Distance (ft) App. Method Need Buffer Distance (ft)

Non

- crop sites (weed and brush control) 6 for aerial; 8 for ground Ground >1000 Aerial (helicopter) >1000

Conifer release in Eastern and

Lakes states 4 Ground 932 Aerial (helicopter) >1 000

Christmas trees 2 Ground 584 Aerial >1000 Pastures/Rangeland in Eastern US 4 Ground 932 Bermudagrass/Bahiagrass; Industrial turfgrass 1.125 Ground 384 Out of range is >1000 feet for aerial and ground applications.



### For additional characterizat ion, runs were performed using different less conservative assumptions. For ground applications, the following assumptions were made: low boom height,

ASABE Fine to Medium/Coarse drop size distribution (DSD), 90 th 

### percentile data percentile. For

aerial a pplications, the following assumptions were made: Tier II Aerial application using ASABE

Medium to Coarse DSD, 5 gallons diluted product per acre, wind speed 10 mph, aircraft Wasp Helicopter, boom height 10 feet.

As expected, the buffer distances were low er with the less conservative assumptions. It was found that for the ground applications, the buffer needed ranged from 66 feet for turfgrass to 709 feet for

non

- crop sites. For all the aerial applications, the buffer zone was 932 feet for alfalfa and >1 000 feet (out of range) for all the other crops

.

Table 4 9 . Needed Buffer Distances to Approach or Exceed the Non

- Listed LOC for Terrestrial Plant Exposure for Hexazinone , Using Less Conservative Assumptions

Scenario App. Rate (lb a.i./A) App. Method Nee d Buffer Distance (ft) App. Method Need Buffer Distance (ft)

Alfalfa 1.5 Ground 95 Aerial 932 Sugarcane in HI 3.6 Ground 292 Aerial >1000 Blueberries (low bush) 3 Ground 236

Non

- crop sites (weed and brush control) 6 for aerial; 8 for ground Ground 70 9 Aerial (helicopter) >1000

Conifer release in Eastern and

Lakes states 4 Ground 331 Aerial (helicopter) >1000

Christmas trees 2 Ground 141 Aerial >1000 Pastures/Rangeland in Eastern US 4 Ground 331 Bermudagrass/Bahiagrass; Industrial turfgrass 1.125 Ground 66 Out of range is >1000 feet for aerial applications.



## 4.5 **Endangered species**

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) (collectively, the Services) , and the U .S. Department of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to

### Page 80 of 133 

### listed species from pesticides. The Interim Approaches were developed jointly by the agencies in response to the National Academy of Sciences’ (NAS) recommendations and reflect a common approach to risk assessment shared by the agencies as a way of addressing scientific differences

between the EPA and the Services. The NAS report ou tlines recommendations on specific scientific and technical issues related to the development of pesticide risk assessments that EPA and the Services must conduct in connection with their obligations under the Endangered Species Act (ESA) and FIFRA.

The joint Interim Approaches were released prior to a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 Pesticide Program Dialogue Committee (PPDC) and State

- FIFRA Issues Research and Evaluation Group ( SFIREG) meetings, and held a stakeholder workshop in April 2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, iterative process for developing the Interim Approaches, t he agencies will also consider public comments on the Interim Approaches in connection with the development of upcoming Registration Review decisions. The details of the joint Interim Approaches are contained in the white paper “Interim Approaches for National

- Level Pesticide Endangered Species Act Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report,” dated November 1, 2013.

Given that the agencies are co ntinuing to develop and work toward implementation of the Interim Approaches to assess the potential risks of pesticides to listed species and their designated critical habitat, this preliminary risk assessment for hexazinone does not contain a complete ES A analysis that includes effects determinations for specific listed species or designated critical habitat. Although EPA has not yet completed effects determinations for specific species or habitats, for this preliminary assessment EPA conducted a n assessm ent for all taxa of non

- target wildlife and plants that assumes for the sake of the assessment that listed species and designated critical habitats may be present in the vicinity of the application of hexazinone . This screening level assessment

will allo w EPA to focus its future evaluations on the types of species where the potential for effects exists once the scientific methods being developed by the agencies have been fully vetted. This

risk assessment for hexazinone indicates potential risks of direct effects to listed aquatic plants, terrestrial plants, birds and mammals on some of its registered use sites. Listed species of birds,

mammals and terrestrial invertebrate taxa may also be affected through indirect effects because of the potential for dir ect effects on listed and non

- listed species upon which such species may rely.

Potential direct effects on listed birds, mammals and terrestrial invertebrates from the use of

hexazinone may be associated with modification of Primary Constituent Elements ( PCEs) of designated critical habitats, where such designations have been made. Once the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for endangered and threatened (listed) species and their de signated critical habitats, these methods will be applied to subsequent analyses for hexazinone as part of completing this registration

review.

### Page 81 of 133 

## 4.6 **Uncertainties and**  **Limitations**

4.6 .1 Input Parameters

It appears that the main route of dissipation of hex azinone is aerobic soil metabolism (even though

it occurs at moderately slow rates ). There are four half

- lives available (refer to Tables 5 for the

half

- lives of the parent only ) . Three of them were obtained at 20 0 C; temperature adjustment was required f or the SWCC, resulting in shorter half

- lives at 25 0 C (refer to Table 6 for the half

- lives for the TTRs)

.

As indicated earlier, the environmental fate database for hexazinone is essentially complete. It was noted that for the aquatic metabolism studies, the study duration was short compared to the

half

- lives obtained. For example, t he aerobic soil metabolism study (MRID 48898001) was conducted for a period of only 150 days (in a study where three soils were tested), with half

- lives

of 54

- 143 days (note t hat these half

- lives do not include the total residues or the unextracted residues, they include only the parent compound). The aerobic aquatic metabolism study (MRID 49109901) was conducted for a period of only 100 days, compared to half

- lives of 528

- 719 days (for the parent only). Meanwhile, the anaerobic aquatic metabolism study (MRID 49109902) was conducted for 101 days, compared to a half

- life of 482

- 961 days (for the parent only). In this assessment two aerobic and two anaerobic aquatic systems wer e available. Further four aerobic soils were available. There is also an anaerobic soil metabolism study (four soils, MRID 48898002), but the results of this study were not used in modeling in the SWCC, since the

anaerobic soil metabolism is not used as an input value in the model when anaerobic aquatic

metabolism studies are available . The fact that multiple soils and sediments were available tends to reduce the uncertainty; however, the short duration of the studies increases the uncertainty in

the hal f

- life estimates.



## 4.6 .2 Application Rates

In this assessment , a number of uses were assessed; rights

- of

- ways ( non

- agricultural crop ) and sugarcane ( conventional agricultural crop ) were found to yield the highest E EC s. The range of application rates on r ights

- of

- ways is ~2 to 8 lb a.i./A (depending on the weeds controlled and the soil texture), and on HI sugarcane it is ~0.45 to 3.6 lb a.i./A (depending on the soil texture). In both cases the maximum application rate was assumed to be applied in a single application per year. It is uncertain the degree to which this is true under actual use conditions.



## 4.6 .3 Environmental Fate Database

Regarding the input values used in this risk assessment, the environmental fate database for

hexazinone was considered to be complete and no estimated values, or uncertainty factors were

used . See also Input Parameters above.



## 4.6 .4 Application Information

Meteorological data and crop profiles, as well as best professional judgment , and label

information , were used to est ablish an application date for modeling; however, the selected date

### Page 82 of 13 3 

### may not represent the intended or actual application dates. The application date used for model runs can significantly alter the EECs; thus, EECs reported could over or under predict the p otential

exposure. The dates of application used in this risk assessment were generally selected based on the crop cycle and label information . It is unclear how much the application dates differ from the typical timing of application, which is based on pest pressure , and in some instances, the weather

forecast

.



## 4.6 .5 Number of Seasons per Year

Although the maximum number of applications from the label for some of the uses is one, for certain uses the maximum number of applications per year is not specif ied. For this assessment, one application per year for those other uses was assumed, based on additional information from the label. For example, blueberry uses may be modeled at a maximum of one application per year due to no application within 450 days of harvest (therefore, on average, fewer than one application per year would be used) . Pineapple may be modeled as one application per year due to the growing season, which is nearly a year long (note that pineapple was not modeled in this assessment). Non

crop uses and forest site preparation and rangeland, are modeled as one application per year due to the requirement for rain to activate hexazinone and because maximum effects are achieved after

12

- 24 months ; therefore, it is likely that a waiting per iod would occur prior to the next application

. Hexazinone is usually applied in the spring after ground thaws, or in the fall before snowfall (see Timing of Application in Table 3 ).



## 4.6 .6 Use of Maximum Labeled Rates

According to the labels, hexazinone i s a n herbicide to which plants can develop resistance if applied repeatedly in the same field in consecutive years. “N aturally

- occurring resistant biotypes may survive a correctly applied herbicide treatment, propagate, and become dominant in that

field.” For that reason, it is recommended to avoid its consecutive use and to base its use on a comprehensive Integrated Pest Management ( IPM ) program “ that can include biological, cultural, and genetic practices aimed at preventing economic pest damage

. ” Thus , even though the initial

E E Cs were based on maximum application rates and annual applications , it appears unlikely that users will apply this chemical under these circumstances on a yearly basis for 30 consecutive years, like the modeling performed in thi s ecological risk assessment

. The frequency at which actual uses approach this maximum use application may be dependent on pest resistance, timing of applications, cultural practices, and market forces.



## 4.6 .7 Unextracted Radioactivity

Regarding the aerob ic soil metabolism studies , there were observed high levels of unextracted radioactivity. ( The soil s were extracted three times by shaking for 30 minutes with methanol:water (80:20, v:v). ) In this assessment, besides the EECs calculated using the half

- li ves for the total toxic residues (TTRs, these are hexazinone and its degradates of concern , corrected half

- life values at 25°C: 147, 294, 378, and 604 days, 90% upper confidence limit 512.2 days ), EECs were also calculated using half

- lives for the TTRs plu s the unextracted residues (UERs, corrected half

- life values at 25°C: 432, 762, 1134, and 1023 days, 90% upper confidence limit 1,093 days) . These EECs provide upperbound estimates of what could be the EECs should the unextracted

### Page 83 of 133 

### radioactivity be residues of ecotoxicological concern. Nonetheless, it was observed that the EECs derived for the TTRs and for the TTRs plus the UERs were similar and that the UERs were not

the risk drivers.



## 4.6 .8 SWCC

In general, the linked SWCC model produces EDWCs that are e xpected to be exceeded once within

a ten

- year period. The Pesticide Root Zone Model is a process or “simulation” model that calculates what happens to a pesticide in an agricultural field on a day

- to

- day basis. It considers factors such as rainfall and p lant transpiration of water, as well as how and when the pesticide is applied. It has two major components: hydrology and chemical transport. Water movement is simulated by the use of generalized soil parameters, including field capacity, wilting point, and saturation water content. The chemical transport component can simulate pesticide application on the soil or on the plant foliage. Dissolved, adsorbed, and vapor

- phase concentrations in the soil are estimated by simultaneously considering the proces ses of pesticide uptake by plants, surface runoff, erosion, decay, volatilization, foliar wash

- off, advection, dispersion, and retardation. Note

that t he latter three processes are not actually simulated by PRZM when calculating runoff (they only come int o play in simulating infiltration).

Uncertainties associated with each of these individual components add to the overall uncertainty of the modeled concentrations. Additionally, model inputs from the environmental fate degradation studies ( i.e. , half

- li fe inputs) are chosen to represent the upper confidence bound on the mean values that are not expected to be exceeded in the environment approximately 90 percent of the time. Mobility input values are chosen to be representative of conditions in the envir onment (an average value is used) . The natural variation in soils adds to the uncertainty of modeled values. Factors such as application date, crop emergence date, and canopy cover can also affect estimated concentrations, adding to the uncertainty of mo deled values. Factors within the ambient environment such as soil temperatures, sunlight intensity, antecedent soil moisture, and surface water temperatures can cause actual aquatic concentrations to differ for the modeled values.



## 4.6 .9 Aquatic Modeling with the SWCC

The standard ecological water body scenario (VVWM standard pond) used to calculate potential aquatic exposure to pesticides such as hexazinone is intended to represent conservative estimates, and to avoid underestimating the actual exposure. The standard scenario consists of application to

a 10

- hectare field bordering a 1

- hectare, 2

- meter deep (20,000 m 3 

### ) pond with no outlet. Exposure estimates generated using the VVWM pond is intended to represent a wide variety of vulnerable

water bodies t hat occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal pools, man

- made and natural ponds, and intermittent and lower order streams. As a group,

there are factors that make these water bodies more or less vulnerable t han the VVWM pond. Static water bodies that have larger ratios of pesticide

- treated drainage area to water body volume would be expected to have higher peak EECs than the VVWM pond. These water bodies will be either smaller in size or have larger drainag e areas. Smaller water bodies have limited storage capacity and thus may overflow and carry pesticide in the discharge, whereas the VVWM pond has no discharge. As watershed size increases beyond 10

- hectares, it becomes increasingly unlikely that the enti re watershed is planted with a single crop that is all treated simultaneously

### Page 84 of 133 

### with the pesticide. Headwater streams can also have peak concentrations higher than the VVWM pond, but they likely persist for only short periods of time and are then carried an d dissipated

downstream.

The Agency acknowledges that there are some unique aquatic habitats that are not accurately captured by this modeling scenario and modeling results may, therefore, under

- or over

- estimate exposure, depending on a number of variabl es. For example, some organisms may inhabit water bodies of different size and depth and/or are located adjacent to larger or smaller drainage areas than the VVWM pond. However, the existing VVWM pond represents the best currently available approach for estimating aquatic exposure to pesticides.

In general, the linked PRZM/VVWM model (through the SWCC GUI) produces EECs that are expected to be exceeded once within a ten

- year period. The Pesticide Root Zone Model is a process or “simulation” model that c alculates what happens to a pesticide in an agricultural field on a day

- to

- day basis. It considers factors such as rainfall and plant transpiration of water, as well as how and when the pesticide is applied. It has two major components: hydrology and ch emical transport. Water movement is simulated by the use of generalized soil parameters, including field capacity, wilting point, and saturation water content. The chemical transport component can simulate pesticide application on the soil or on the plan t foliage. Dissolved, adsorbed, and vapor

phase concentrations in the soil are estimated by simultaneously considering the processes of pesticide uptake by plants, surface runoff, erosion, decay, volatilization, foliar wash

- off, advection, dispersion, and retardation.

Uncertainties associated with each of these individual components add to the overall uncertainty of the modeled concentrations. Additionally, model inputs from the environmental fate degradation studies are chosen to represent conservative estimates of the mean half

- life, given the observed variability in the limited sample size of data . Mobility input values are chosen to be representative of conditions in the environment (an average value) . The natural variation in soils

adds to the unce rtainty of modeled values. Factors such as application date, crop emergence date, and canopy cover can also affect estimated concentrations, adding to the uncertainty of modeled values. Factors within the ambient environment such as soil temperatures, su nlight intensity, antecedent soil moisture, and surface water temperatures can cause actual aquatic concentrations

to differ for the modeled values.



## 4.6 .10 Uncertainties Regarding Dilution and Chemical Transformations in

Estuaries

SWCC modeled EECs are in tended to represent exposure of aquatic organisms in relatively small ponds and low

- order streams. Therefore it is likely that EECs generated from the SWCC model

will over

- estimate potential concentrations in larger receiving water bodies such as estuarie s, embayments, and coastal marine areas because chemicals in runoff water (or spray drift, etc. ) should be diluted by a much larger volume of water than would be found in the ‘typical’ VVWM pond. However, as chemical constituents in water draining from fr eshwater streams encounter

brackish or other near

- marine

- associated conditions, there is potential for important chemical transformations to occur. Many chemical compounds can undergo changes in mobility, toxicity, or persistence when changes in pH, E h 

### (r edox potential), salinity, dissolved oxygen (DO) content,

### Page 85 of 133 

### or temperature are encountered. For example, desorption and re

- mobilization of some chemicals from sediments can occur with changes in salinity (Jordan et al. , 2008; Means, 1995; Swarzenski

et al.

, 2003) , changes in pH ( e.g ., Wood and Baptista 1993), E h 

### changes (Velde and Church, 1999; Wood and Baptista, 1993) , and other factors. Thus, although chemicals in discharging rivers may be diluted by large volumes of water within receiving estuaries and e mbayments, the hydrochemistry of the marine

- influenced water may negate some of the attenuating impact of the greater water volume; for example, the effect of dilution may be confounded by changes in chemical mobility (and/or bioavailability) in brackish w ater. In addition, freshwater contributions from discharging streams and rivers do not instantaneously mix with more saline water bodies. In these settings, water will commonly remain highly stratified, with fresh water lying atop denser,

heavier saline water

– meaning that exposure to concentrations found in discharging stream water may propagate some distance beyond the outflow point of the stream (especially near the water surface). Therefore, it is not assumed that discharging water will be rapidly d iluted by the entire water volume within an estuary, embayment, or other coastal aquatic environment. SWCC model results should be considered consistent with concentrations that might be found near the head of an estuary unless there is specific informati on

– such as monitoring data

– to indicate otherwise. Conditions nearer to the mouth of a bay or estuary, however, may be closer to a marine

- type system, and thus more subject to the notable buffering, mixing, and diluting capacities of an open

marine env ironment. Conversely, tidal effects (pressure waves) can propagate much further upstream than the actual estuarine water, so discharging river water may become temporarily partially impounded near the mouth (discharge point) of a channel, and resistant to mixing until

tidal forces are reversed.

The Agency does not currently have sufficient information regarding the hydrology and hydrochemistry of estuarine aquatic habitats to develop alternate scenarios for assessed species that inhabit these types of eco systems. The Agency acknowledges that there are unique brackish and estuarine habitats that may not be accurately captured by SWCC modeling results, and may, therefore, under

- or over

- estimate exposure, depending on the aforementioned variables.



## 4.6 .11 Terrestrial Exposure Modeling

There is some uncertainty regarding the extent to which the chronic dose based RQs exceed the LOC. For the model inputs, the default value of 35 days was used for the foliar dissipation half

life. Due to the magnitude of th e half

- life, there is uncertainty surrounding the T

- REX generated

chro nic RQs; these EECs compared to those exhibited on the field may be different because T

REX is unable to model the dissipation of the pesticide in the environment. These RQs may be

refi ned in the future with the submittal of a foliar dissipation half

- life study. There is additional uncertainty in that T

- REX assumes that organisms diet consists 100% of one feed item; thus when the LOC is triggered for a bird consuming short grass, there is a chance that bird does not derive 100% of their diet via a single feeding strategy.

Another terrestrial model

, TERRPlant

, was used to derive the EECs and RQs for terrestrial plants.

There are a number of uncertai nties concerning this model and its ability to predict the EECs on the field. Modeled pesticide concentrations in runoff are dependent solely upon the solubility of the pesticide; the amount of pesticide in the runoff does not consider other relevant transport properties of the pesticide.

### Page 86 of 133 

## 4.6.12 Formulation T oxicity

There are seven multi

- active ingredient co

- formulations that include hexazinone with sulfometuron or diuron. There are no toxicity studies available with multi a.i. products, thus there is uncertainty as to whether the formula tion products exhibit additive or synergistic toxicity to organisms on the field.



## 4.6.13 Size of Granules

There is uncertainty in characterizing risk to birds and mammals because the size of the granules in the granular formulations is unknown. This i nformation would enable further characterization and an understanding of the number of granules the organism could consume without exceed ing the LOC. Without this information, this characterization is incomplete and considered an uncertainty. There is ad ditional uncertainty in the attractiveness of the pellets and granules to the organisms and whether they would be attractive enough for an organism to consume to the extent that it would trigger risk.



## 4.7 **Identification of Data Gaps**

4.7 .1 Environmental Fa te

Even though the environmental fate data base for hexazinone is essentially complete, there are two environmental chemistry methods (soil and water; MRIDs 45132802 and 45132803), that were classified as unacceptable, but upgradable. Portions of the stud ies appeared to meet guideline criteria and may be upgrad ed with the submission of additional information. For further details,

refer to the Appendix I

.



## 4.7 .2 Environmental Effects

The toxicological database for hexazinone is essentially complete with th e exception of 850.2100 passerine study, and a tier II vegetative vigor and seedling emergence study. Portions of the vegetative vigor and seedling emergence study may be upgradeable with the submission of

additional information. There is additional plan t uncertainty with regards to effects on non

- target woody plants. There is no data available for toxicity of hexazinone to woody plants , as they are not part of the standard suite of species submitted in the registrant studies; based on the mode of

action , risk would be expected. Without toxicity studies, risk to woody plants remains an uncertainty. In accordance with the pollinator guidance, there are a number of data gaps concerning pollinators; these include larval acute toxicity, larval chronic toxi city, residue on foliage, adult chronic toxicity and semi

- field test. There is currently one acute contact honeybee study available; the study found an LD 50 

### >100 μg/bee. However, there is uncertainty concerning the systemic toxicity of hexazinone and the potential affects this may have on pollinators.

### Page 87 of 133 

## References

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL SERIES

8. As sessing Soil Contamination: A Reference Manual. Appendix 2. Parameters of pesticides that influence processes in the soil. Editorial Group, FAO Information Division:
Rome, 2000. http://ww w.fao.org/DOCREP/003/X2570E/X2570E00.htm (accessed January 29, 2015 ). Jordan, T. E., Cornwell, J. C., Walter, R. B., & Anderson, J. T. 2008. Changes in phosphorus biogeochemistry along an estuarine salinity gradient. Limnology and Oceanography 53 (1),

172

- 184. Means, J. C. 1995. Influence of salinity upon sediment

- water partitioning of aromatic hydrocarbons. Marine Chemistry, 51 (1), 3

- 16. Swarzenski, P. W., Porcelli, D., Andersson, P. S., & Smoak, J. M. 2003. The behavior of U

- and

Th

- series nuclides in the estuarine environment. Reviews in Mineralogy and Geochemistry REviews in Mineralogy and Geochemistry, 52 (1), 577

- 606. USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R

- 95/002F. Published in 63 FR 26846; May 14, 1998. U.S. Environmental Protection Agency, Washington, DC. April, 1998.

USEPA

. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. Endangered and Threatened Species

Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. Available online at http://www.epa.gov/oppfead1/endanger/consultation/ecor isk

- overview.pdf (accessed January 27, 2015 )

. USEPA. 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides, Version 2.1. Office of Chemical Safety and Pollution Prevention, Office of Pesticide Progra ms, Environmental Fate and Effects Division, dated October 22, 2009 and issued November 10, 2009. Available online at: http://www.epa.gov/oppefed1/models/water/input_para meter_guidance.htm (accessed January 27, 2015 ).

USEPA. 2010 a

. Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations for Registration Review, Registration Review Risk Assessments, Listed Species Litigation Assessments, New Chemical Risk Assessments, and Other Relevant Risk Assessments. Memorandum from Donald Brady dated January 25, 2010

. Office of Pesticide Programs. Environmental Fate and Effects Division. ( http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_ species_reregistration_workgroup/esa_reporting_fate.htm , accessed January 27, 2015)

. USEPA. 2010 b . Guidance for Making Temperature Adjustments to Metabolism Inputs to EXAMS

and PE5 and WQTT Advisory Note Number 9: Temperature Adjustments for Aquatic Metabolism Inputs to EXAMS and PE5. OCSPP/OPP/Environmental F ate and Effects Division. Dated 09/21/2010 and approved 10/18/2010.

USEPA. 2010c. EFED Registration Review Problem Formulation for Hexazinone. Office of Pesticide Programs, Environmental Fate and Effects Division, DP Barcode D369269, dated January 12, 201 0 , document ID EPA

- HQ

- OPP

- 2009

- 0755

- 0007

. USEPA. 2013. Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water Assessments, dated December 19, 2013

. Memorandum from Donald Brady dated and approved December 2 0, 2013. Office of Pesticide Programs.

### Page 88 of 133 

### Environmental Fate and Effects Division.

USEPA. 2014. Guidance for Addressing Unextracted Residues in Laboratory Studies. Memorandum from Donald Brady dated and approved September 12, 2014. Office of

Pesticide Pro grams. Environmental Fate and Effects Division. URL: http://www.epa.gov/pesticides/science/efed/po licy_guidance/team_authors/environmental _fate_tech_team/Unextracted_Residues_in_Lab_Studies.htm (accessed June 3, 2015). Velde, B., & Church, T. 1999. Rapid clay transformations in Delaware salt marshes. Applied Geochemistry, 14 (5), 559

- 568. Wood, T. M., & Baptista, A. M. 1993. A model for diagnostic analysis of estuarine geochemistry.

Water Resources Research 29 (1), 51

- 71.

### Page 89 of 133 

## Appendix A. Environmental Fate / Chemistry Bibliography

161

- 1 Hydrolysis

MRID Citation Reference

64260 Rhodes, R.C. (1974) Studies with Velpar Weed Killer in Water. (Unpublished study received May 7, 1975 under 352

- 378; submit

- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 110699

- E)

104982 Rhodes, R. (1973) Biodegradation Studies on 14C

- DPX

- 3674. Interim pro gress rept., Oct 15, 1973. (Unpublished study received Dec 5, 1973 under 352

- EX

- 85; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:223386

- O)

41587301 Chrzanowski, R. (1990) Hydrolysis of ?carbon 14| Hexazinone in pH 5, 7 and 9 Buffe r Solutions: Lab Project Number: AMR 1643

- 90. Unpublished study prepared by E. I. Du Pont de Nemours and Co., Ag Products Dept. 51 p.



## 161

- 2 Photodegradation

- water

MRID Citation Reference

64260 Rhodes, R.C. (1974) Studies with Velpar We ed Killer in Water. (Unpublished study received May 7, 1975 under 352

- 378; submit

- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 110699

- E)

104982 Rhodes, R. (1973) Biodegradation Studies on 14C

- DPX

- 3674. Interim progress rept., Oct 15, 1973. (Unpublished study received Dec 5, 1973 under 352

- EX

- 85; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:223386

- O)

41587301 Chrzanowski, R. (1990) Hydrolysis of ?carbon 14| Hexazinone in pH 5, 7 and 9 Buffer
Solutions: Lab Pro ject Number: AMR 1643

- 90. Unpublished study prepared by E. I. Du Pont de Nemours and Co., Ag Products Dept. 51 p.



## 161

- 3 Photodegradation

- soil

MRID Citation Reference

64261 Rhodes, R.C. (1974?) Decomposition of Velpar Weed Killer in So il. (Unpublished study received May 7, 1975 under 352

- 378; submit

- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 110699

- F)

### Page 90 of 133 41300802 Hawkins, D.; Elsom, L.; Gray, S. (1989) The Photodegradation of ?Carbon

- 14|

- hexazinone on Soil: HRC Report No. HRC/DPT 197/ 891455; Du Pont Document No.

AMR

- 1413

- 89. Unpublished study prepared by Huntingdon Research Centre Ltd., Dept. of Chemical Metabolism and Radiosynthesis. 63 p.



## 162

- 1 Aerobic soil metabolism

MRID Citation Reference

64261 Rhod es, R.C. (1974?) Decomposition of Velpar Weed Killer in Soil. (Unpublished study received May 7, 1975 under 352

- 378; submit

- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 110699

- F)

104982 Rhodes, R. (1973) Biodegradation Studies on 14C

- DPX

- 3674. Interim progress rept., Oct 15, 1973. (Unpublished study received Dec 5, 1973 under 352

- EX

- 85; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:223386

- O)

41807401 Hawkins, D.; Elsom, L.; Kane, T.; et al. (1990) The Metabolism of ?carbon 14|

- Hexazinone in a California Type Soil Under Aerobic Conditions: Lab Project Number:
HRC/DPT 194/901364: AMR

- 1329

- 88. Unpublished study prepared by Huntingdon Research Centre Ltd. 68 p.

42635001 Hawkins, D.; Elsom, L.; Kane, T.; et al. (1993 ) The Metabolism of (carbon 14)

- Hexazinone in a California Type Soil under Aerobic Conditions: Supplement 1: Lab Project Number: HRC/DPT 194/901364. Unpublished study prepared by Huntingdon Research Centre Ltd. 17 p.

48898001 Clark, B. 2012. Aerobic Soil Metabolism of 14 C

- Hexazinone. Unpublished study performed by ABC Laboratories, Inc., Columbia, Missouri; sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmington, Delaware. DuPont Study No.: 32436; ABC Study No.: 66928. Experimental work conducted between June 15, 2011, and February 22, 2012 (p. 6). Final report issued July 25, 2012.



## 162

- 2 Anaerobic soil metabolism

MRID Citation Reference

48898002 Clark, B. 2012. Anaerobic Soil Metabolism of 14 C

- Hexazinone. Unpublished study performed by ABC Laboratories, Inc., Columbia, Missouri; sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmington, Delaware. DuPont Study No.: 32400; ABC Study No.: 66929. Experimental work conducted between June 22, 2011 and February 22, 2012 (p. 6). Final report issued July 25, 2012.



## 162

- 4 Aerobic aquatic metabolism

MRID Citation Reference

### Page 91 of 133 41811801 Chrzanowski, R. (1991) Aerobic Aquatic Metabolism of ?Carbonyl

- ?carbon 14|| Hexazinone in Madera, California Field Water and Se diment: Lab Project Number:

AMR 1690

- 90. Unpublished study prepared by E.I. du Pont de Nemours and Co. 64 p.

44196301 Chrzanowski, R. (1996) The Degradation of (Carbonyl

- (carbon 14))Hexazinone in Aerobic Aquatic Sediment Systems Under Natural Sunlight: L ab Project Number:

AMR 2102

- 91. Unpublished study prepared by DuPont Agricultural Products. 157 p.

49109901 Clark, B. 2013. Aerobic Aquatic Metabolism of [ 14 C]DPX

- A3674 (Hexazinone) in Two

Water

- Sediment Systems. Unpublished study performed by ABC Labora tories, Inc., Columbia, Missouri; sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmington, Delaware. DuPont Study No.: 32435; ABC Study No.: 66974. Experimental work conducted between April 17, 2012 and October 25, 2012 (p. 6). Final rep ort issued January 11, 2013.



## 162

- 3 Anaerobic aquatic metabolism

MRID Citation Reference

41807402 Hawkins, D.; Elson, L.; Kane, T.; et al. (1990) The Anaerobic Aqua

- tic Metabolism of ?carbon 14|

- Hexazinone: Lab Project Number: AMR

- 1328

- 88: HRC /DPT 193/901475. Unpublished study prepared by Huntingdon Research Centre Ltd. 80 p.

42657301 Hawkins, D.; Elsom, L.; Kane, T.; et al. (1993) The Anaerobic Aquatic Metabolism of (carbon 14)

- Hexazinone: Supplement 1: Analysis of 2 Additional Non

- Sterile

A naerobic Water

- Sediment Systems after 365 Days Incubation and Structural Assignment of Metabolite 2: Lab Project Number: HRC/DPT 193/901475: AMR

- 1328

- 88. Unpublished study prepared by Huntingdon Research Centre Ltd. 20 p.

49109902 Clark, B. 2013. Anaerob ic Aquatic Metabolism of [ 14 C]DPX

- A3674 (Hexazinone) in

Two Water

- Sediment Systems. Unpublished study performed by ABC Laboratories, Inc., Columbia, Missouri; sponsored and submitted by E.I. du Pont de Nemours and Company, Wilmington, Delaware. DuPont Stud y No.: 32437; ABC Study No.: 66975. Experimental work conducted between April 17, 2012 and October 29, 2012 (p. 6). Final report issued January 11, 2013.



## 163

- 1 Leach/adsorption/desorption

MRID Citation Reference

64262 Rhodes, R.C. (1974?) Mobi lity and Adsorption Studies with Velpar Weed Killer on Soils. (Unpublished study received May 7, 1975 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:110699

- G)

104982 Rhodes, R. (1973) Biodegradation Studies on 14C

- DPX

- 36 74. Interim progress rept ., Oct 15, 1973. (Unpublished study received Dec 5, 1973 under 352

- EX

- 85; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:223386

- O)

41528101 Priester, T.; Sheftic, G. (1990) Batch Equilibrium (Adsorption/Des

- orption)of ?Carbon 14|Hexazinone and Soil Thin

- Layer Chromato

- graphy Studies of ?Carbon 14|Hexazinone and Its Major Soil De

- grades: Lab Project Number: AMR

- 1421

- 89. Unpublished study pre

- pared by E. I. du Pont de Nemours and Co. 85 p.

### Page 92 of 133 43621501 Sheft ic, G. (1995) Batch Equilibrium (Adsorption/Desorption) of (Carbonyl

- (carbon 14)) Hexazinone and its Major Soil Degradates: Lab Project Number: AMR 3019

- 94. Unpublished study prepared by Dupont Agricultural Products and Harris Labs, Inc. 90

p.



## 164

- 1 Terrestrial field dissipation

MRID Citation Reference

64267 Holt, R.F. (19??) Residues Resulting from Application of DPX

- 3674 to Soil. (Unpublished study received May 7, 1975 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:110699

- L)

42377901 Bollin, E. (1992) Field Soil Dissipation of Hexazinone Herbicide: Lab Project Number:

AMR 1474

- 89: 9045258: 9140414. Unpublished study prepared by E. I. du Pont de Nemours and Comp., Harris Environmental Tech., Inc. and Envi ro Test Laboratories. 419 p.

42379201 Bollin, E. (1992) Dissipation of Hexazinone in California Soil Following Application of Velpar L Herbicide: Lab Project Number: AMR 1923

- 91: 9100226: 91

- P1368. Unpublished study prepared by E. I. du Pont de Nemours a nd Comp., Harris Environmental Technologies, Inc., Enviro

- Test Laboratories. 272 p.



## 164

- 3 Forest field dissipation

MRID Citation Reference

72664 Neary, D.G.; Douglass, J.E.; Bush, P.B.; et al. (1980) Movement of Hexazinone in

Forest Watershed s after a Hand Application of Velpar^(R)I Gridball^(TM)I Pellets for Site Preparation. Progress rept., Nov 1980. By U.S. Forest Service, Southeastern Experiment Station, Coweeta Hydrologic Laboratory and Univ. of Georgia, Extension Poultry Science Dept. an d Institute of Ecology. ?: USFS, SE. (FS

- SE

- 1651

- 26(1); available from: U.S. Government Printing Office; published study; CDL:244106

- B)

42336401 Michael, J. (1992) Fate of Hexazinone After Application for Pine Planting Site Preparation: Lab Project Numbe r: 1786

- 90. Unpublished study prepared by Auburn University. 700 p.



## 165

- 1 Confined rotational crop

MRID Citation Reference

41008401 Rapisarda, C. (1980) Rotational Crop Studies with ?Carbon 14|

- Lab

- eled

hexazinone: Proj. ID AMR

- 26

- 80. Unpubl ished study prepared by E.I. du Pont de Nemours and Co., Inc. 25 p.

42824001 Rapisarda, C. (1993) Rotational Crop Studies with (carbon 14)

- Labeled Hexazinone: Supplement No. 1: Lab Project Number: AMR 26

- 80. Unpublished study prepared by
E. I. du Pont de Nemours and Co. 11 p.

### Page 93 of 133 43892401 Djanegara, T.; Reardon

- Green, L. (1996) Confined Accumulation Study of (4

- Carbonyl

- (carbon 14))

- Hexazinone (DPX

- A3674) in Rotational Crops: Lab Project

Number: AMR 2800

- 93. Unpublished study prepared by DuPont Agricultural Products. 115 p. Relates to letter L0000071.



## 165

- 2 Field rotational crop

MRID Citation Reference

45084101 Brill, F. (2000) Magnitude of Residues of Hexazinone in Rotational Crops Following Application of Velpar Herbicide at Maximum Label Rat es to Alfalfa: Lab Project

Number: AMR 4336

- 97. Unpublished study prepared by E.I. du Pont de Nemours and Co. 253 p. {OPPTS 860.1900}



## 166

- 1 Ground water

- small prospective

MRID Citation Reference

44060101 DeAndrea, P.; Kelley, J.; Murrow, D.; et al. (1996) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Interim Report #2: Site Instrumentation: Lab Project Number: AMR 3202

- 94: 94210. Unpublished study prepared by Stone Environmental, Inc.; ABC Labs, Inc.; and DuPont Agricu ltural Products. 142 p.

44082801 Farajalla, N.; Kelley, J.; Klein, T.; et al. (1996) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Interim Report #3: Application and First Quarterly Report: Lab Project Number: AMR 3202

- 94: 94210. Unpublished study prepared by Stone Environmental, Inc. and ABC Labs., Inc. 116 p.

44106601 Kelley, J.; Klein, T.; McElwain, D.; et al. (1996) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Interim Report #4: Second Quarterly Rep ort, April

- June, 1996: Lab Project Number: AMR 3202

- 94: 94210. Unpublished study prepared by DuPont Agricultural Products; Stone Environmental, Inc.; and ABC Labs, Inc. 82 p.

44194001 Kelley, J.; Klein, T.; McElwain, D.; et al. (1996) A Small

- Scale Prosp ective Groundwater Monitoring Study for Hexazinone: Interim Report #5, Third Quarterly Report: Lab Project Number: 94210: AMR 3202

- 94. Unpublished study prepared by E.I. du Pont de Nemours and Co., Stone Environmental, Inc.; and ABC Laboratories, Inc. 97 p

.

44310901 Kelley, J.; Klein, T.; Stone, C.; et al. (1997) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Interim Report #6: Fourth Quarterly Report October

December, 1996: Lab Project Number: AMR 3202

- 94: 94210. Unpublished study prepared by Stone Environmental, Inc.; ABC Laboratories, Inc.; and Morse Lab., Inc. 113 p.

44389001 Kelley, J.; Klein, T.; Stone, C. et al. (1997) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Interim Report #7: Fifth Quarterly Report: January

March, 1997: Lab Project Number: AMR 3202

- 94: 94210:. Unpublished study prepared by Stone Environmental, Inc., ABC Labs., Inc. and Morse Labs., Inc. 96 p.

### Page 94 of 133 44442801 Kelley, J.; Klein, T.; Stone, C. et al. (1997) A Small

- Scale Prospective G roundwater Monitoring Study for Hexazinone: Interim Report #8: Sixth and Seventh Quarter Report April

- September, 1997: Lab Project Number: 94210: AMR 3202

- 94. Unpublished study prepared by Stone Environmental, Inc., ABC Labs., Inc. and Morse Labs., Inc. 80 p.

45132801 Hanson, C.; Collins, M.; Warren, R. et al. (2000) A Small

- Scale Prospective Groundwater Monitoring Study for Hexazinone: Lab Project Number: AMR 3202

- 94: 94210. Unpublished study prepared by E.I. du Pont de Nemours and Company. 499

p.



## 201

- 1 Droplet size spectrum

MRID Citation Reference

41322701 Dawson, J. (1989) Velpar L Droplet Size Spectrum Study of Nozzle Systems Used in Aerial Application: Lab Project Number: 1707: AMR/1475/89. Unpublished study prepared by Agrisearch Inc. 4 3 p.



## 202

- 1 Drift field evaluation

MRID Citation Reference

41309003 Merricks, L. (1989) Velpar L Aerial Application Spray Drift Study: Lab Project Number: 1706 : AMR/1478/9. Unpublished study prepared by Agrisearch, Inc. 87 p.

41309004 Collu m, W. (1989) Spray Drift Evaluation of Velpar ULW Herbicide: Lab Project Number: AMR/1538/89. Unpublished study prepared by du Pont de Nemours and Co. 46 p.

94681 Akesson, N.B.; Yates, W.E. (1980) Report on Field Application and Drift Loss Tests with Dup ont Herbicides. (Unpublished study received Feb 4, 1982 under 352

- 378; prepared by Univ. of Cali

- fornia

-- Davis, submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.; CDL:246737

- A)



## 850.6100 Environmental Chemistry Method/Independent Labora tory
Validation

45132802 Zheng, S. (1999) Independent Laboratory Validation of a Proposed Environmental Chemistry Analytical Method for the Determination of Hexazinone and Metabolites in Soil By GC/NPD Analysis and Confirmation by LC/MS/MS: Lab Project Num ber: 008

- 036: DUPONT

- 2547. Unpublished study prepared by E.I. du Pont de Nemours and Company. 145 p.

45132803 Zheng, S. (1999) Independent Laboratory Validation of a Proposed Environmental Chemistry Analytical Method for the Determination of Hexazinone a nd Metabolites in Water By GC/NPD Analysis and Confirmation by LC/MS/MS: Lab Project Number: 008

- 035: DUPONT

- 2548. Unpublished study prepared by E.I. du Pont de Nemours and Company. 193 p.

### Page 95 of 133 

## N on
- Guideline Selections

41713 Mattson, A.M.; Kahrs, R.A.; Murph y, R.T. (1970) Quantitative deter

- mination of Triazine herbicides in soils by chemical analysis. Pages 371

- 390, ~In~ Residue
Reviews: Volume 32. Edited by Fran

- cis A. Gunther. New York, N.Y.: Springer

Verlac. (GAC 903811; also~In~unpublished submission r eceived Jul 30, 1971 under 2F1284; CDL:092076

- F)

64263 Krause, R.L. (19??) Evaluation of Possible Effects of DPX

- 3674 on Soil Microorganism Populations. (Unpublished study received May 7, 1975 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wi lmington, Del.; CDL:110699

- H)

64264 Williams, M.H. (19??) Evaluation of Possible Effects of Velpar Weed Killer on Nitrifying Bacteria in Two Different Soils. (Unpublished study received May 7, 1975 under 352

- 378; submit

- ted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 110699

- I)

46575001 Mulderig, L. (1996) Magnitude of Residues of Hexazinone in Forest Grasses Following Application of Velpar Herbicides at Maximum Label Rates. Project Number: AMR/2896/94, ML94/0483/DUP, 008/04. Unpublished st udy prepared by E.I. du Pont de Nemours and Co., Inc., Morse Laboratories, Inc. and Centre Analytical Laboratories, Inc. 444 p.

### Page 96 of 133 

## Appendix B. Ecological Effects Bibliography

71

- 1 Avian Single Dose Oral Toxicity

MRID Citation Reference

73988 F ink, R.; Beavers, J.B.; Brown, R. (1978) Final Report: Acute Oral LD50

-- Bobwhite Quail: Project No. 112

- 121. (Unpublished study received May 23, 1978 under 352

- 387; prepared by Wildlife Inter

- national, Ltd., and Washington College, submitted by

E.I. du Po nt de Nemours & Co., Wilmington, Del.; CDL:233989

- A)

44112701 Palmer, S.; Grimes, J.; Beavers, J. (1996) DPX

- KG333

- 5: An Acute Oral Toxicity Study with the Northern Bobwhite: (Final Report): Lab Project Number: 112

- 433: AMR

3907

- 96: 3907

- 96. Unpublished study prepared by Wildlife International Ltd. 45 p

. Possibly a Mixture



## 71

- 2 Avian Dietary Toxicity

MRID Citation Reference

72663 Dudeck, S.H.; Bristol, K.L. (1980) Avian Dietary Toxicity (LC50) Study in Bobwhite Quail: Project No. 201

- 547. Fin al rept. (Un

- published study received Jan 23, 1981

under 352

- 387; prepared by Hazleton Laboratories America, Inc., submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:244106

- A)

104970 E.I. du Pont de Nemours & Co., Inc. (1973 ) Toxicity Sum mary : DPX

- 3674. Summary of studies 223386

- C through 223386

- N. (Unpub

- lished study received Dec 5, 1973 under 352

- EX

- 85; CDL:223386

- B)

104981 Fletcher, D. (1973) Report to...: 8

- day Dietary LC50 Study with H

- 7759; MR

- 581 in Mallard Ducklings: IBT No. 65 1

- 03194. (Unpub

- lished study received Dec 5, 1973

under 352

- EX

- 85; prepared by Industrial Bio

- Test Laboratories, Inc., submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:223386

- N)

107878 Fletcher, D. (1973) Report to E.I. du Pont de N emours & Company: 8

- day Dietary LC50 Study with H

- 7759; MR

- 581 in Bobwhite Quail: IBT No. 651

- 03199. (Unpublished study received Dec 5, 1973 under 352

- EX

- 85; prepared by Industrial
Bio

- Test Laboratories, Inc., submitted by E.I. du Pont de Nemours & Co., I nc., Wilming

- ton, DE; CDL:223386

- M)



## 71

- 4 Avian Reproduction

MRID Citation Reference

41764901 Beavers, J.; Campbell, S.; Smith, G. (1991) H 17,705: A One Generation Reproduction Study With the Northern Bobwhite (Colinus virginianus): Lab Proj ect
Number: 112

- 225: 772

- 90. Unpublished study prepared by Wildlife International Ltd. 168 p.

### Page 97 of 133 41764902 Beavers, J.; Campbell, S.; Smith, G. (1991) H 17,705: A One Generation Reproduction Study With the Mallard (Anus platyrhynchos) Lab Project Number: 112

- 226: 773

- 90. Unpublished study prepared by Wildlife International Ltd. 167 p.

41938001 Beavers, J.; Campbell, S.; Smith, G.; et al. (1991) Supplement to H 17,705: A One

Generation Reproduction Study with the Mallard (Anas platyrhynchos): Lab Project

Num ber: 112

- 226: HLO

- 773

- 90. Unpublished study prepared by Wildlife International Ltd. 9 p.



## 72

- 1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

76959 Schneider, P.W., Jr. (1976) 96

- hour LC50 to Bluegill Sunfish: Haskell Laboratory No.

408

- 76. (Unpublished study received May 20, 1981 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:245117

- D)

76960 Okolimna (1980) Fish Toxicity: ?~Leuciscus idus melanotus~|. (Translation; unpublished study received May 2 0, 1981 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:245117

- E)

76961 Okolimna (1980) Fish Toxicity: ?~Salmo gairdneri~|. (Transla

- tion; unpublished study received May 20, 1981 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:245117

- F)

104970 E.I. du Pont de Nemours & Co., Inc. (1973) Toxicity Summary: DPX

- 3674. Summary
of studies 223386

- C through 223386

- N. (Unpub

- lished study received Dec 5, 1973

under 352

- EX

- 85; CDL:223386

- B)

104 980 Sleight, B. (1973) Acute Toxicity of H

- 7759, MR

- 581 to Bluegill (Lepomis macrochirus), Rainbow Trout (Salmo gairdneri) and Fathead Minnow (Pimephales promelas). (Unpublished study re

- ceived Dec 5, 1973 under 352

- EX

- 85; prepared by Bionomics, Inc., sub mitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE;
CDL:223386

- L)

41235001 Hutton, D. (1989) Static Acute 96

- Hour LC50 of IN A3674

- 208 to Bluegill Sunfish (Lepomis macrochirus): Project ID 462

- 89. Un

- published study prepared by E. I. du
Pont de Nemours and Co., Inc. 17 p.

41235002 Hutton, D. (1989) Static Acute 96

- Hour LC50 of IN A3674

- 208 to Rainbow Trout (Salmo gairdneri): Project ID 463

- 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 18 p.

47178 E.I. du Pont de Nemour s & Company (1976) 96

- Hour LC50 to Bluegill Sunfish: Haskell Laboratory Report No. 409

- 76. (Unpublished study received Aug 29, 1978

under 352

- 378; CDL:099674

- E)

40098001 Mayer and Ellersieck 1986 USFWS

- multiple species tested



## 72

- 2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

### Page 98 of 133 116269 Schneider, P. (1976) 48

- hour LC50 to Daphnia magna: Haskell Labo

- ratory Report

No. 262

- 76. (Unpublished study received Dec 30, 1977; under 352

- 387; submitted by
E.I. du Pont de Nemours & Co. , Inc., Wilmington, DE; CDL:232556

- A; 235401)

41235003 Hutton, D. (1989) Static Acute 48

- Hour EC50 of IN A3674

- 208 to Daphnia magna: Project ID 452

- 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 17 p.



## 72

- 3 Acute Toxicity to Estuari ne Organisms

47164 or

78018 Heitmuller, T. (1976) Acute Toxicity of H

- 9877 to Embryos of East

- ern Oysters (~Crassostrea virginica~), to Grass Shrimp (~Palaemonetes pugio~), and to Fiddler Crabs (~Uca pugila~

- ~tor~). (Unpublished study received Jul 25, 1 979 under 352

- 378; prepared by EG&G Bionomics, submitted by E.I. du Pont de Nemours & Co., Wilmington, Del.; CDL:099674

- B)



## 72

- 4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

41406001 Pierson, K. (1990) Eff ects of IN A3674

- 207 on the Embryos and Lar

- vae of Fathead Minnows (Pimephales promelas): Lab Project Number HLR 656

- 89: MR

- 8705

- 001. Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 221 p.

41406002 Pierson, K. (1990) Chronic Toxicit y of IN A3674

- 207 to Daphnia mag

- na: Lab Project

Number: HLR 68

- 90: MR

- 8705

- 001. Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 198 p.

114038 Schneider, P. (1977) Chronic Toxicity of ... (INA

- 3674) to Daphnia magna: Haskell

Laborat ory Report No. 544

- 77. (Unpublished study received Aug 29, 1978 under 352

- 378; submitted by E.I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL:097321

- D)



## 122

- 1 Seed Germination/Seedline Emergence and Vegetable Vigor

MRID Citation Reference

41216501 Leavitt, J. (1988) Hazard Evaluation of Hexazione on Non

- Target Plants Grown under
Greenhouse and field Conditions

- Tiers I, II, III: Project ID JRCL 89

- 1. Unpublished study prepared by E. I. Du Pont de Nemours and C0., Inc. 51 p.

43162501 M cKelvey, R.; Heldreth, K. (1994) Influence of Hexazinone on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab Project

Number: AMR 2678

- 93: AMR 2736

- 93. Unpublished study prepared by DuPont Agricultural Products. 351 p.

43605001 McKelvey, R. (1995) Influence of Hexazinone on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Supplement No. 1: Lab Project Number: AMR 2678

- 93. Unpublished study prepared by DuPont Agricultural Products. 112 p.

### Page 99 of 133 

## 122

- 2 Aquatic plant growth

MRID Citation Reference

41287001 Forbis, A. (1989) Acute Toxicity of Hexazinone to Selenastrum capricornutum Printz: Lab Project Number 38069; AMR

- 1446

- 89. Unpublished study prepared by Analytical

B io

- Chemistry Laboratories, Inc. 31 p.

41287002 Schuster, L. (1989) Method Validation for the Analysis of Hexazinone in Algae Test Media: Dupont Study No. AMR

- 1503

- 89; ABC Final Report No. 38068. Unpublished study prepared by Analytical Bio

- Chemistry Labo ratories, Inc. 20 p.



## 123

- 1 Seed germina tion/seedling emergence and vege tative vigor

MRID Citation Reference

41216501 Leavitt, J. (1988) Hazard Evaluation of Hexazione on Non

- Target Plants Grown under
Greenhouse and field Conditions

- Tiers I, II, III: Project ID JRCL 89

- 1. Unpublished study prepared by E. I. Du Pont de Nemours and C0., Inc. 51 p.

43162501 McKelvey, R.; Heldreth, K. (1994) Influence of Hexazinone on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrest rial Plants: Lab Project
Number: AMR 2678

- 93: AMR 2736

- 93. Unpublished study prepared by DuPont Agricultural Products. 351 p.

43183901 Vaught, R. (1994) Letter Sent to Office of Pesticide Programs Dated Mar. 29, 1994 (Hexazinone: influence on seed germin ation seedling emergence and vegetative vigor of several terrestrial plants). Prepared by DuPont Agric. Products. 2 p.

43605001 McKelvey, R. (1995) Influence of Hexazinone on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestri al Plants: Supplement No. 1 : Lab Project Number: AMR 2678

- 93. Unpublished study prepared by DuPont Agricultural Products. 112 p.



## 123

- 2 Aquatic plant growth

MRID Citation Reference

41287001 Forbis, A. (1989) Acute Toxicity of Hexazinone to Sel enastrum capricornutum Printz: Lab Project Number 38069; AMR

- 1446

- 89. Unpublished study prepared by Analytical

Bio

- Chemistry Laboratories, Inc. 31 p.

43225101 Kannuck, R.; Sloman, T. (1994) Hexazinone (DPX

- A3674): Influence on Growth and Reproduction of Lemna gibba G3: Lab Project Number: AMR 2874

- 93: MR 9785

- 001. Unpublished study prepared by Stine

- Haskell Research Center, DuPont Agricultural Products. 41 p.

43225102 Baer, K. (1994) Hexazinone (DPX

- A3674): Influence on Growth and Reproduction of
Skelet onema costatum : Lab Project Number: 241

- 94: AMR 2884

- 93: MR 8785. Unpublished study prepared by Stine

- Haskell Research Center, DuPont Agricultural

### Page 100 of 133 Products. 38 p.

43241101 Vaught, R. (1994) Letter Sent to Office of Pesticide Programs dated May 18, 1994: Report of studies with hexazinone: Plant protection studies. Prepared by Du Pont Ag. Products. 2 p.

43302701 Thompson, S. (1994) Hexazinone (DPX

- A3674): Influence on Growth and Reproduction of Two Select Algal Species: Lab Project Number: AMR 3011

- 94: 33 5

- 94: 9785. Unpublished study prepared by Wildlife International Ltd. and E.I. du Pont de Nemours & Co. 75 p.

43340001 Vaught, R. (1994) Letter Sent to Office of Pesticide Programs dated August 10, 1994 concerning a plant protection study with hexazinone . Prepared by DuPont Ag Products. 1 p.

43400401 Baer, K. (1994) Hexazinone (DPX

- A3674): Influence on Growth and Reproduction of
Skeletonema costatum: Revision No. 2: Lab Project Number: AMR 2884

- 93: MR

9785 : HLR 241

- 94. Unpublished study prepared by DuPo nt Haskell Lab for Toxicology and Industrial Medicine. 40 p.



## 141

- 1 Honey bee acute contact

MRID Citation Reference

41216502 Hoxter, K.; Thompson, M.; Jaber, M. (1989) An Acute Contact Toxici

- ty with the Honey Bee: Project ID 112

- 217. Unpubli shed study prepared by Wildlife International Ltd. 15 p.



## N on
- Guideline Selections

43149701 Vaught, R. (1994) Letter Sent to Office of Pesticide Programs dated March 1, 1994 containing follow

- up report of leaf spotting and hexazinone detection on vegeta tion adjacent to a site treated with DuPont Velpar ULW Herbicide . Prepared by DuPont Agricultural Products. 2 p.

43329501 Crosswhite, F.; Feldman, W.; Minch, E. (1993) Impact of Pesticides on Cacti: Lab Project Number: E

- 009572

- 01

- 0. Unpublished study pr epared by University of Arizona and Arizona Dept. of Agriculture. 33 p.

47164601 Moore, D.; Breton, R.; Rodney, S.; et al. (2007) Generic Problem Formulation for
California Red

- Legged Frog. Project Number: 89320, 05232007. Unpublished study prepared by C antox Environmental Inc. 87 p.

47164602 Holmes, C.; Vamshi, R. (2007) Data and Methodology Used for Spatial Analysis of California Red Legged Frog Observations and Proximate Land Cover Characteristics. Project Number: 3152007, WEI/252/03. Unpublished stud y prepared by Waterborne Environmental, Inc. (WEI). 19 p.

### Page 101 of 133 

# Appendix C

. Hexazinone and its transformation products

Hexazinone and Its Environmental Transformation Products. A

### Page 102 of 133 

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

PARENT

Hexaxinone (DPX

- A3674) IUPAC: 3

- Cyclohexyl

- 6

- dimethylamino

- 1

- methyl

- 1,3,5

- triazine

- 2,4(1 H ,3 H )

- dione

CAS: 3

- Cyclohexyl

- 6

- (dimethylamino)

- 1

- methyl

- 1,3,5

- triazine

- 2,4(1 H ,3 H )

- dione

CAS No.: 51235

- 04

- 2

Formula: C 12 H 20 N 4 O 2 MW: 252.3 g/mol

SMILES: O=C(N=C(N(C1=O)C)N(C)C)N1C (CCCC2)C2 O

N C H 3

N

C H 3 C H 3

O N

N Hydrolysis 41587301 pH 5 99.5 (0 d) 99.6 (30 d)
Hydrolysis 41587301 pH 7 99.3 (0 d) 99.4 (30 d)
Hydrolysis 41587301 pH 9 99.6 (0 d) 99.5 (30 d)
Aq Photol 41300801 Irradiated 92.8 (0 d) 86.6 (30 d) B

Aq Photol 41300801 Dark (pH 7) 94.3 (0 d) 93.6 (30 d)

Soil Photol 41300802 Sandy loam 88.1 (0 d) 67.5 (30 d) C

Soil Photol 41300802 SL dark ctrl 88.9 (0 d) 86.7 (30 d)

835.4100

Ae robic

soil

metabolism 41807401 /

42635001 Non

- sterile sandy loam 92.6 (0 d) 34.3 (365 d)

Sterile 91.5 (0 d) 82.3 (365 d)

48898001 Clay loam 101.2% (0 d) 15.5% (150 d)
Sandy loam 103.1% (0 d) 52.8% (150 d)

Loam 100.0% (0 d) 38.6% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 100.7% (0 d) 60.7% (180 d)

Clay loam 101.2% (0 d) 36.1% (180 d)
Sandy loam 100.7% (0 d) 61.4% (180 d)

Loam 100.4% (0 d) 69.6% (180 d)

835.4300

Aerobic aquatic

metaboli sm 41811801 Non

- sterile sandy loam 99.7 (3) 80.3 (56)

Sterile 99.9 (7) 86.8 (56)

49109901 Wabasha water:sandy

loam 101.3% (0 d) 87.4% (100 d)

Tift water:sandy

loam 100.5% (0 d) 91.6% (100 d)

835.4400

Anaerobic

aquatic

metabolism 418074 02 Non

- sterile

loam 96.7 (7 d) 39.7 (365 d)

Sterile 96.0 (0 d) 81.3 (365 d)

49109902 Wabasha water:sandy

loam 101.6% (0 d) 86.5% (101 d)

Tift water:sandy 100.5% (0 d) 92.1% (101 d)

### Page 103 of 133 

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

loam

MAJOR (>10%) TRANSFORMATION PRODUCTS

IN

- G3170; Me t. G IUPAC: 1

- Methyl

- 6

- (methylamino)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 5 H 8 N 4 O 2 MW: 156.14 g/mol

SMILES: [H]n1c(=O)nc(n(c1=O)C)N([H])C

H

N

O N

C H 3 N C H 3

H N O 835.4100

Aerobic

soil

metabolism 48898001 Clay loam 42.2% (150 d) 42.2% (150 d)
Sandy loam 16.4% (150 d) 16.4% (150 d)

Loam 26.8% (150 d) 26.8% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 4.8% (46 d) 4.7% (180 d)

Clay loam 25.7% (122 d) 20.4% (180 d)
Sandy loam 8.9% (180 d) 8.9% (1 80 d)

Loam 11.1% (122 d) 10.4% (180 d)

835.4300

Aerobic aquatic

metabolism 49109901 Wabasha water:sandy

loam 0.2% (15 d) ND (100 d)

Tift water:sandy

loam 0.2% (15 d) ND (100 d)

835.4400

Anaerobic

aquatic

metabolism 49109902 Wabasha

wat er:sandy

loam 1.3% (70 d) ND (101 d)

IN

- JS472; Met. 1 IUPAC: 6

- (Dimethylamino)

- 1

- methyl

- 3

- (4

- oxocyclohexyl)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 18 N 4 O 3 MW: 266.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCC(=O)C C2)N(C)C O

N N

N

C H 3 C H 3

N

C H 3 O O 835.4100

Aerobic

soil

metabolism 41807401 /

42635001 Non

- sterile sandy loam 13.9 (180 d) 10.8 (365 d)

Sterile 4.0 (120 d) ND (365 d)

48898001 Clay loam 9.4% (10 d) 4.7% (150 d)
Sandy loam 8.3% (60 d) 7.5% (150 d)

Loam 13.3% (150 d) 13 .3% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 6.6% (31 d) 5.5% (180 d)

Clay loam Aerobic 14.8% (14 d) ND (180 d)

Anaerobi c 14.7% (33 d)
Sandy loam 8.5% (33 d) 5.0% (180 d)

Loam 8.1% (33 d) 6.7% (180 d)

835.4300 41811801 Non

- sterile 6.5 (28 d) 3.7 (56 d)

### Page 104 of 133 

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

Aerobic aquatic

metabolism sandy loam

Sterile 2.0 (56 d) 2.0 (56 d)

49109901 Wabasha water:sandy

loam 5.8% (100 d) 5.8% (100 d)

Tift water:sandy

loam 4.4% (100 d) 4.4% (100 d)

835.4200

Anaerobic

soil

metabolism 49109902 Wabasha water:sandy

loam 6.5% (101 d) 6.5% (101 d)

IN

- B2838; Met. D IUPAC: 1

- Cyclohexyl

- 3

- methyl

1,3,5

- triazinane

- 2,4,6

- trione

Formula: C 10 H 15 N 3 O 3 MW: 225.2 g/mol

SMILES: Cn1c(=O)[nH]c(=O)n(c1=O)C2CC

CCC2

N

O N

C H 3 O N O 835.4100

Aerobic

soil

metabolism 41807401 /

42635001 Non

- sterile sandy loam 5.1 (365 d) 5.1 (365 d)

Sterile 4.1 (365 d) 4.1 (365 d)

48898001 Clay loam 1.1% (150 d) 1.1% (150 d)
Sandy loam 4.2% (150 d) 4.2% (150 d)

Loam 1.3% (150 d) 1.3% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 32.0% (180 d) 32.0% (180 d)

Clay loam 2.2% (180 d) 2.2% (180 d)
Sandy loam 2.9% (180 d) 2.9% (180 d)

Loam 2.9% (150 d) 2.8% (180 d)

835.4300

Aerobic aquatic

metabolism 41811801 Non

- sterile sandy loam 1.3 (56 d) 1.3 (56 d)

Sterile 0.1 (56 d) 0.1 (56 d)

49109901 Wabasha water:sandy

loam 0.8% (15, 70 d) 0.4% (100 d)

Tift water:sandy

loam 1.8% (100 d) 1.8% (100 d)

835.4400

Anaerobic

aquatic

metabolism 41807402 Non

- sterile

loam 24.2 (365 d) 24.2 (365 d)

Sterile 12.5 (90 d) 1.9 (365 d)

49109902 Wabasha 0.4% (70 d) 0.3% (101 d)

### Page 105 of 133 

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

water:sandy

loam

Tift water:sandy

loam 1.6% (70, 101 d) 1.6% (101 d)

IN

- G3453; Met. A

- 1 IUPAC: 6

- (Dimethylamino)

- 3

- (2

- hydroxycyclohexyl)

- 1

- methyl

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 20 N 4 O 3 MW: 268.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCCCC2O )N(C)C O H

O N

N

C H 3 N C H 3

C H 3 N O 835.4100

Aerobic

soil

metabolis m 41807401 /

42635001 Non

- sterile sandy loam 19.5 (365 d) 19.5 (365 d)

Sterile 2.0 (120 d) ND (365 d)

835.4200

Anaerobic

soil

metabolism 48898002 Clay loam 9.5% (180 d) 9.5% (180 d)
Sandy loam 4.0% (150 d) 2.6% (180 d)

Loam 0.7% (122 d ) 0.6% (180 d)

835.4300

Aerobic aquatic

metabolism 41811801 Non

- sterile sandy loam 5.1 (14 d) 5.0 (56 d)

Sterile 6.8 (56 d) 6.8 (56 d)

IN

- A3928; Met. B IUPAC: 3

- Cyclohexyl

- 1

- methyl

- 6

- (methylamino)

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 11 H 18 N 4 O 2 MW : 238.28 g/mol

SMILES: [H]N(C)c1nc(=O)n(c(=O)n1C)C2C

CCCC2

N

O N

C H 3 N H

C H 3 N O Soil Photol 41300802 Sandy loam 10.1 (30 d) C 10.1 (30 d) C

SL dark ctrl 1.4 (30 d) 1.4 (30 d)

835.4100

Aerobic

soil

metabolism 41807401 /

42635001 N on

- sterile sandy loam 2.4 (60 d) 2.3 (365 d)

Sterile 2.3 (120 d) 1.8 (365 d)

48898001 Clay loam 3.7% (122 d) 3.2% (150 d)
Sandy loam 5.3% (150 d) 5.3% (150 d)

Loam 3.5% (150 d) 3.5% (150 d)

835.4200

Anaerobic

soil

metabolism 4889 8002 Sandy clay

loam 1.1% (33, 180 d) 1.1% (180 d)

Clay loam 2.6% (180 d) 2.6% (180 d)
Sandy loam 6.2% (180 d) 6.2% (180 d)

Loam 3.2% (46 d) 2.8% (180 d)

835.4300

Aerobic aquatic

metabolism 41811801 Non

- sterile sandy loam 5.3 (28 d) 0 .7 (56 d)

Sterile 6.3 (56 d) 6.3 (56 d)

49109901 Wabasha water:sandy

loam 2.2% (100 d) 2.2% (100 d)

### Page 106 of 133 

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

Tift water:sandy

loam 0.2% (70 d) ND (100 d)

835.4400

Anaerobic

aquatic

metabolism 41807402 Non

- sterile

loam 3.5 (365 d) 3.5 (365 d )

Sterile 7.1 (270 d) 5.3 (365 d)

49109902 Wabasha water:sandy

loam 1.6% (70 d) ND (101 d)

Tift water:sandy

loam 0.2% (70 d) ND (101 d)

IN

- JT677; Met. 2 IUPAC: 6

- (Dimethylamino)

- 1

- methyl

- 3

- (2

- oxocyclohexyl)

- 1,3,5

- triazine

- 2,4

- dione

F ormula: C 12 H 18 N 4 O 3 MW: 266.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCCCC2= O)N(C)C

O N

O N

C H 3 N

C H 3 C H 3 N O 835.4100

Aerobic

soil

metabolism 48898001 Clay loam 1.4% (122 d) ND (150 d)
Sandy loam 0.8% (122 d) ND (150 d)

Loam 1.1% (122 d) ND (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Clay loam 1.9% (150 d) 1.8% (180 d)
Sandy loam 1.2% (150 d) ND (180 d)

Loam 1.0% (180 d) 1.0% (180 d)

835.4300

Aerobic aquatic

metabolism 49109901 Wabasha water:sandy

loam 1.3% (15 d) ND (100 d)

835.4400

Anaerobic

aquatic

metabolism 41807402 Non

- sterile

loam 27.5 (365 d) 27.5 (365 d)

Sterile 2.7 (90 d) ND (365 d)

49109902 Wabasha water:sandy

loam 1.3% (70 d) ND (101 d)

Carbon dioxide IUPAC: Carbon dioxide

Formul a: CO 2 MW: 44 g/mol

SMILES: C(=O)=O C O O Soil Photol 41300802 Sandy loam 0.23 (30 d) C 0.23 (30 d) C

SL dark ctrl 0.02 (30 d) 0.02 (30 d)

835.4100

Aerobic

soil

metabolism 41807401 /

42635001 Non

- sterile sandy loam 2.0 (365 d) 2 .0 (365 d)

Sterile <0.1 (365 d) <0.1 (365 d)

48898001 Clay loam 9.7% (150 d) 9.7% (150 d)
Sandy loam 2.8% (150 d) 2.8% (150 d)

### Page 107 of 133 

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

Loam 2.8% (150 d) 2.8% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 0.5% (180 d ) 0.5% (180 d)

Clay loam 1.3% (90

- 180 d) 1.3% (180 d)
Sandy loam 0.4% (180 d) 0.4% (180 d)

Loam 0.7% (180 d) 0.7% (180 d)

835.4300

Aerobic aquatic

metabolism 41811801 Non

- sterile sandy loam 0.5 (56 d) 0.5 (56 d)

Sterile 0.1 (56 d) 0.1 (56 d)

49109901 Wabasha water:sandy

loam 0.1% (100 d) 0.1% (100 d)

Tift water:sandy

loam 0.1% (100 d) 0.1% (100 d)

Unextractable residues

NA NA 835.4100

Aerobic

soil

metabolism 48898001 Clay loam 25.6% (150 d) 25.6% (150 d)
Sandy loam 14.3% (150 d) 14.3% (150 d)

Loam 14.3% (150 d) 14.3% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 11.0% (33 d) 5.1% (180 d)

Clay loam 28.2% (31 d) 12.6% (180 d)
Sandy loam 10.6% (180 d) 10.6% (180 d)

MINOR (<10%) TRANSFORMATION PRODUCTS

IN

- T3937; Met. A IUPAC: 6

- (Dimethylamino)

- 3

- (4

- hydroxycyclohexyl)

- 1

- methyl

- 1,3,5

- triazine

- 2,4

- dione

Formula: C 12 H 20 N 4 O 3 MW: 268.3 g/mol

SMILES: Cn1c(nc(=O)n(c1=O)C2CCC(CC2) O)N(C)C O

N N

N

C H 3 C H 3

N

C H 3 O O H 835.4100

Aerobic

soil

metabolism 48898001 Clay loam 0.5% (150 d) 0.5% (150 d)
Sandy loam 0.5% (150 d) 0.5% (150 d)

Loam 2.6% (150 d) 2.6% (150 d)

835.4200

Anaerobic

soil

metabolism 48898002 Sandy clay

loam 1.0% (60 d) ND (180 d)

Clay loam 5.8% (180 d) 5.8% (180 d)
Sandy loam 3.4% (180 d) 3.4% (180 d)

Loam 2.5% (90 d) 1.3% (180 d)

### Page 108 of 133 A AR means “applied radioactivity”. MW means “molecular weight”. ND means “not detected”. NA means “not applicable”. B Equivalent to 69 .0 days of natural sunlight. C Equivalent to 84.0 days of natural sunlight.

### Page 109 of 133 

# Appendix D

. Sample SWCC O utput File

Summary of Water Modeling of Hexazinone and the USEPA

Standard Pond

Estimated Environmental Concentrations for Hexazinone are presented in Table 1 for the USEPA standard pond with the LAsugarcaneSTD field scenario. A graphical presentation of the

year

- to

- year peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Crit ical input values for the model are

summarized in Tables 2 and 3.

This model estimates that about 4.4% of Hexazinone applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by runoff (71. 2% of the total transport), followed by spray drift (28.3%) and erosion (0.43%). In the water body, pesticide dissipates with an effective water column half

- life of 1363.8 days. (This value does not include dissipation by transport to the benthic region; i t includes only processes that result in removal of pesticide from the complete system.) The main source of dissipation in the water column is metabolism (effective average half

- life = 1363.8 days) followed by volatilization (7.926746E+07 days).

In the be nthic region, pesticide dissipation is negligible (1833.0 days). The main source of dissipation in the benthic region is metabolism (effective average half

- life = 1833 days). Most of the pesticide in the benthic region (86%) is sorbed to sediment rather th an in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for Hexazinone.

Peak (1

- in

- 10 yr) 600.

4

- day Avg (1

- in

- 10 yr) 599.

21

- day Avg (1

- in

- 10 yr) 596.

60

- day Avg (1

- in

- 10 yr) 593.

365

- day Avg (1

- in

- 10 yr) 546.

Entire Simulation M ean 391.

Table 2. Summary of Model Inputs for Hexazinone.

Scenario LAsugarcaneSTD

Cropped Area Fraction 1

Koc (ml/g) 57.5

Water Half

- Life (days) @ 25 °C 1343

Benthic Half

- Life (days) @ 25 °C 1805

### Page 110 of 133 

### Photolysis Half

- Life (days) @ 40

°Lat 0

Hydrolysis H alf

- Life (days) 0

Soil Half

- Life (days) @ 25 °C 512.2

Foliar Half

- Life (days) 0

Molecular Wt 252.32

Vapor Pressure (torr) 1.9E

- 7

Solubility (mg/l) 29800

Table 3. Application Schedule for Hexazinone.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

01/ 10 Foliar 4.03 0.95 0.125

Figure 1. Yearly Peak Concentrations

### Page 111 of 133 

# Appendix E

. T

- REX non
- granular example output

### Page 112 of 133 

### Summary of Risk Quotient Calculations Based on Upper Bound Kenaga EECs

Table X. Upper Bound Kenaga, Acute Avian Dose

- Base d Risk Quotients

Size

Class (grams) Adjusted

LD50 EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

20 1626.73 2186.69 1.34 1002.23 0.62 1230.01 0.76 136.67 0.08 8 56.45 0.53 30.37 0.02

100 2070.91 1246.94 0.60 571.52 0.28 701.40 0.34 77.93 0.04 488.39 0.24 17.32 0.01

1000 2925.24 558.27 0.19 255.87 0.09 314.03 0.11 34.89 0.01 218.66 0.07 7.75 0.00

Table X. Upper Bound Kenaga, Subacute Avian Dietar y Based Risk Quotients

LC50 EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

5000 1920.00 0.38 880.00 0.18 1080.00 0.22 120.00 0.02 752.00 0.15

Size class not used fo r dietary risk quotients

### Page 113 of 133 Table X. Upper Bound Kenaga, Chronic Avian Dietary Based Risk Quotients

NOAEC (ppm) EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

300 1920.00 6.40 880.00 2.93 1080.00 3.60 120.00 0.40 752.00 2.51

Size class not used for dietary risk quotients

Table X. Upper Bound Kenaga, Acute Mammalian Dose

- Based Risk Quotients

Size

Class (grams) Adjusted

LD50 EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 1164.85 1830.57 1.57 839.01 0.72 1029.70 0.88 114.41 0.10 716.9744 0.6155 25.425 0.0218

35 942.49 1265.17 1.34 579.87 0.62 711.66 0.76 79.07 0.08 495.5252 0.5258 17.572 0.0186

1000 407.66 293.33 0.72 134.44 0.33 165.00 0.40 18.33 0.04 114.8893 0.2818 4.0741 0.01

Table X. Upper Bound Kenaga, Acute Mammalian Dietary Based Risk Quotie nts

LC50 (ppm) EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

0 1920.00 #DIV/0! 880.00 #DIV/0! 1080.00 #DIV/0! 120.00 #DIV/0! 752.00 #DIV/0!

Size class not used for dietary risk quotients

### Page 114 of 133 Table X. Upper Bound Kenaga, Chronic Mammalian Dietary Based Risk Quotients

NOAEC (ppm) EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds/ Large Insects Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

200 1920.00 9.60 880.00 4.40 1080.00 5.40 120.00 0.60 752.00 3.76
Size class not used for dietary risk quotients

Table X. Upper Bound Kenaga, Chronic Mammalian Dose

- Based Risk Quotients

Size

Class (grams) Adjusted

NOAEL EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 21.98 1830.57 83.29 839.01 38.17 1029.70 46.85 114.41 5.21 716.97 32.62 25.42 1.16

35 17.78 1265.17 71.15 579.87 32.61 711.66 40.02 79.07 4.45 495.53 27.87 17.57 0.99

1000 7.69 293.33 38.14 134.44 17.48 165.00 21.45 18.33 2.38 114.89 14.94 4.07 0.53

### Page 115 of 133 

# Appendix F. LD 50 

# per ft 2 

# T

- REX example output

Chemical: Hexazin one

LD50 ft

- 2

INPUTS Do not overwrite these numbers. 

### Changes to the inputs must be

Application Rate: 8 lbs /

acre 

### made in the "INPUTS" worksheet.

% A.I.: 75.00% Avian LD50 (20g): 1626.73 mg/kg bw (100g) 2070.91 (1000g) 2925.24 Mammalian LD50 (15g): 1164.85 mg/kg bw (35g) 942.49 (1000g) 407.66 Row Spacing: 0 inches

Band width: 0 inches
Unincorporation: 100%



### Row/Band/In

- furrow applications

Granular N/A

Intermediate Calculations Intermediate Calculations

# rows acre

- 1: N/A mg a.i./ 1000 ft row: N/A row length (ft): N/A bandwidth: N/A

lb ai/1000 ft row: N/A mg a.i./ft2: N/A

bandwidth (ft): N/A exposed mg a.i./ft2: N/A mg ai/ft2: N/A exposed mg ai/ft2: N/A



### LD50 ft

- 2 N/A
wgt class

(grams) wgt class (grams)

Avian 20 N/A Avian 20 N/A

100 N/A 100 N/A

1000 N/A 1000 N/A

Mammal 15 N/A Mammal 15 N/A

35 N/A 35 N/A

1000 N/A 1000 N/A



### Broadcast applications

Granular

### Page 116 of 133 Intermediate Calculations

mg ai/ft2: 62.48



### LD50 ft

- 2
wgt class (grams)

Avian 20 1.92

100 0.30

1000 0.02

Mammal 15 3.58

35 1.89

1000 0.15

Formulas used in the calculations are in the User's Guide

### Page 117 of 133 

# Appendix G. Granular Characterization T

- REX example output

Estimation of the number of granules needed to achieve toxicity thresholds
Step 1. Estimate m ass of a.i. consumed for the assessed species weight to achieve the desired toxicity threshold

Parameter Value

Comment Bird Mammal

Weight of assessed animal (kg) 1.00 1.000 INPUT (0.02 kg and 0.015 kg are typically used for general assessments for

bi rds and mammals, respectively).

LD50, mg/kg

- bw 2925.24 407.66 Calculated from the body weight entered in B13 and C13 and the LD50 entered in the "Inputs" sheet.

Mg a.i. needed to achieve the LD50 for animal of assessed weight 2925.24 407.66

mg a.i./kg

- bw * kg

- bw = mg a.i. Mg a.i. needed to achieve the LOC of 0.5 (1/2 LD50) for animal of assessed weight 1462.62 203.83

Mg a.i. needed to achieve the LOC of 0.1 (1/10th LD50) for animal of assessed weight 292.52 40.77

Step 2. Determine the mass of a.i. p er granule
Percent of a.i. in formulated product 75.00% 75.00% Must enter percent a.i. specified on the label

Weight of 1 granule (mg, obtained from registrant) 640.00 640.00 INPUT (Note: Be sure to enter units in mg!)

mg a.i./granule 480.0000 480.0000 weight of granule (mg) x fraction of a.i. = mg a.i./granule Step 3. Calculate number of granules with mass of a.i. equivalent to adjusted LD50 for bird of assessed weight

The analysis below calculates the number of granules needed to be consumed by a bird and mammal to achieve a dose that would exceed the LD50 and trigger the LOC of 0.1 and 0.5. In addition, the minimum foraging area with sufficient number of granules to achieve a dose that exceeds the LD50, 1/2 the LD50, or 1/10th the LD50 is estimated by assuming that a bird consumes 100%, 50%, and 10% of the available granules. This analysis ma y be used to characterize the LD50/squ are foot calculation presented in the "LD50 ft

- 2" worksheet.

### Page 118 of 133 No. of granules needed to achieve LD50 6.09 0.85 mg a.i. needed to achieve adjus ted LD50 (B/C14) / mg a.i. per granule (B/C20)

No. of granules needed to achieve the LOC of 0.5 (1/2 LD50) 3.05 0.42 mg a.i. needed to achieve 1/2 adjusted LD50 (B/C15) / mg a.i. per granule (B/C20)

No. of granules needed to achieve the LOC of 0.1 (1/10 LD50) 0.61 0.08 mg a.i. needed to achieve 1/10 adjusted LD50 (B/C16) / mg a.i. per granule (B/C20)

Minimum Foraging Area Needed to Allow for Ingestion of Sufficient Mass of a.i. to Achieve LOC Exceedance EEC (mg a.i./square foot) 62. 48 62.48 From LD50 ft

- 2 page

Foraging area (square feet) needed to
achieve LOC of 0.1 exceedance assuming 100% feeding efficiency 4.68 0.65 mg a.i. needed to achieve LD50 in 20

- gram bird (B/C16) / mg a.i.per sq. ft (B/C27)

Foraging area (square feet) nee ded to
achieve LOC of 0.1 exceedance assuming 50% feeding efficiency 9.36 1.30 Foraging area needed to achieve LOC Exceedance assuming 100% feeding efficiency (B/C28) * 2 (i.e., twice the foraging area is needed for 50% feeding efficiency)

Foraging area (square feet) needed to
achieve LOC of 0.1 exceedance assuming 10% feeding efficiency 46.82 6.52 Foraging area needed to achieve LOC Exceedance assuming 100% feeding efficiency (B/C28) * 10 (i.e., 10 times the foraging area is needed for 10% feeding effici ency)

### Page 119 of 133 

# Appendix H . Terrplant example output

TerrPlant v. 1.2.2 Green values signify user inputs (Tables 1, 2 and 4). Input and output guidance is in popups indicated by red arrows.

Chemical Name

PC code

Use Application Method

Application Form Solubility in Water (ppm)

Input Parameter Symbol Value Units

Application Rate A 4.5 lb. a.i/A

Incorporation I 1 none
Runoff Fraction R 0.05 none

Drift Fraction D 0.05 none

Equation EEC

(A/I)*R 0.225 (A/I)*R*10 2.25

A*D 0.225 ((A/I)*R)+(A*D) 0.45 ((A/I)*R*10)+(A*D) 2.475

Plant type EC 25 NOAEC EC 25 NOAEC

Monocot 1.48 0.745 1.46 0.48

Dicot 0.84 0.23 1.51 0.5

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 0.30 1.67 0.15

Monocot listed 0.60 3.32 0.47

Dicot non-listed 0.54 2.95 0.27

Dicot listed 1.96 10.76 0.98 Total for semi-aquatic areas Table 1. Chemical Identity.

Dimethoate

Douglas fir (seed orchards) (only in OR and WA)

Table 2. Input parameters used to derive EECs. Aerial

Airblast

39800 128975

Table 3. EECs for Dimethoate . Units in lb. a.i/A.

Runoff to dry areas Runoff to semi-aquatic areas Spray drift Total for dry areas Description

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group. Vegetative Vigor Seedling Emergence

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Dimethoate through runoff and/or spray drift.* Table 4. Plant survival and growth data used for RQ derivation. Units are in lb. a.i/A.

### Page 120 of 133 

# Appendix I

. Classifications of Environmental Fate Studies

Table I

- 1 . Classification of Environmental Fate Studies Conducted on Hexazinone

Guideline

No. Data Requirement Study ID Study

Classification Classifi cation Justifications or Comments (for Supplemental and Unacceptable Studies)

835.2120 Hydrolysis 41587301 Acceptable

---

835.2240 Photolysis in

Water 41300801 Acceptable

---

835.2410 Photodegradation

on Soil 41300802 Acceptable

---

835.2370 Photodegr adation

in Air Not

available Not applicable

---

835.4100 Aerobic Soil

Metabolism 41807401/

42635001 Acceptable (Partial) ---

48898001 Supplemental (Partial) The soil extraction procedures may not have been adequate to extract all identifiable [ 14 C]res idues in the soils; unextracted residues totaled

maximums of 14.3

- 25.6% of the applied for the three test soils. In the absence of details about the suitability of the extractions, the total toxic residue approach will be taken ( i.e. , hexazinone residues + unextracted residues). Insufficient data were provided regarding the soils used in this study, including collection and storage procedures, and whether they were free of pesticide residues prior to use.

835.4200 Anaerobic Soil

Metabolism 48898002 Suppl emental Measured rather than standard redox potentials were provided by the study author, so it was uncertain whether study conditions were oxic or suboxic. The viability of the test soils at the initiation and finalization of the study was not reported. The soil extraction procedures may not have been adequate to extract all identifiable [ 14 C]residues in the soils; in the clay loam soil, unextracted [ 14 C]residues totaled a maximum of 28.2% of the applied. Soil collection and storage procedures prior to use were not described. It was not confirmed that the soils were free of pesticide residues prior to use. Tests were conducted for a period of only 149 days of anaerobic incubation; all observed DT 50 s were reported as >149 days. The pattern of decline o f the degradate IN G3170 could not be established in the Audrain soil. Also, the degradate IN B2838 was a maximum at 149 days of anaerobic incubation in the Raymondville soil.

835.4300 Aerobic Aquatic

Metabolism 41811801 Acceptable (Partial) ---

49109 901 Supplemental (Partial) Measured rather than standard redox potentials were provided by the study author, so it was uncertain whether study conditions were oxic or suboxic. Insufficient data were provided regarding the soils and water used in this

stud y, including source of the water, collection and storage procedures, and whether they were free of pesticide residues prior to use. The study lasted only 100 days, at which time 87.4

- 91.6% AR was still undegraded hexazinone, and the calculated half

- lives were considerably beyond the study duration. Data on certain individual replicate concentrations was not provided. The LOQ for the HPLC analysis of the aqueous phase appeared to be extraordinarily high (30.5% AR) and is not in line with all the other LOQ s.

835.4400 41807402 Acceptable (Partial) ---

### Page 121 of 133 Guideline

No. Data Requirement Study ID Study

Classification Classifi cation Justifications or Comments (for Supplemental and Unacceptable Studies)

Anaerobic Aquatic

Metabolism 49109902 Supplemental (Partial) Measured rather than standard redox potentials were provided by the study author, so it was uncertain whether study conditions were oxic or subox ic. Given the presence of dissolved oxygen in the waters of both test systems, they may not have been anaerobic. Storage stability data for the water samples and soil extracts were not provided. Insufficient data were provided regarding the soils and wa ter used in this study, including source of the water, collection and storage procedures, and whether the soils were free of pesticide residues prior to use. HPLC data for the replicate samples were not reported. The study lasted only 101 days, at which time

86.5

- 92.1% AR was still undegraded hexazinone, and the calculated half

lives were considerably beyond the study duration. Data on certain individual replicate concentrations was not provided. For HPLC of the aqueous phase, the LOQ was 29.40%. This value appeared to be extraordinarily high, compared to all the other LOQs.

835.1230 Leaching

Adsorption/ Desorption 43621501 Acceptable

---

835.1410 Laboratory Volatility No data

submitted Not applicable

---

835.6100 Terrestrial Field Dissipation 423779 01 Acceptable

---

42379201 Supplemental The application rate was not confirmed by the Day 0 posttreatment sample. The Day 0 posttreatment sample was <30% of the theoretical application rate. However, the Day 7 thru Day 60 posttreatment samples

had a h igher concentration (40 to 51% of the theoretical application rate) of hexazinone than the Day 0 posttreatment.

835.6100 Long

- term Soil Dissipation No data

submitted Not applicable

---

835.6200 Aquatic Dissipation No data

submitted Not applicable

---

83 5.6300 Forestry 42336401 Acceptable

---

835.6400 Combination and

Tank Mixes No data

submitted Not applicable

---

860.1400 Accumulation in Irrigated Crops No data

submitted Not applicable

---

850.1730 Accumulation in

Fish 00064265, 00078032;

41203201 Wai ved R eported in DP Barcode D279324.

850.1950 Aquatic Non

target Organism No data

submitted Not applicable

---

835.7100 Ground Water Monitoring 45132801 Supplemental Storage stability of the analytes could not be adequately determined in soil

or water sam ples. No rainfall or irrigation was received within the first week of the test application.

835.8100 Field Volatility No data

submitted Not applicable

---

### Page 122 of 133 Guideline

No. Data Requirement Study ID Study

Classification Classifi cation Justifications or Comments (for Supplemental and Unacceptable Studies)

850.6100 ECM/ILV in Soil 45132802 Unacceptable (Upgradable) This analytical method is considered unacceptable, for the following

reasons.

• No originating ECM performance data were reported for either

method. For both methods, complete, finalized ECM reports with implemented ILV major modifications were not provided. Two sets of performance data shoul d be submitted, one for the initial or other internal validation (ECM), and one for the ILV. Furthermore, these reports should be provided separate from

each other.

• For ILV analysis of IN

- T3935 by GC

- NPD, no performance data at 10xLOQ were provided.

• For t he LC/MS/MS method, ILV performance data for 2.0 μg/kg (LOQ) fortified IN

- JS472 and 20 μg/kg (10x LOQ)

fortified IN

- G3170 in soil did not meet OCSPP Guideline

850.6100 criteria.

• The determination of LOQ and LOD were not based on scientifically acceptable p rocedures (for guidance, refer to the references section of this DER).

• Linearity (r 2 ) of the calibration standards was not always
≥0.995. Portions of the study appeared to meet guideline criteria and may be upgradable with the submission of additional information.

ECM/ILV in

Water 45132803 Unacceptable (Upgradable) This analytical metho d is considered unacceptable, for the following

reasons.

• For both methods, complete, finalized ECM reports with implemented ILV major modifications were not provided. No originating ECM performance data were reported for either method. Two sets of perfor mance data should be submitted, one for the initial or other internal validation (ECM), and one for the ILV. These reports should be provided separate from

each other.

• For ILV analysis of all analytes in lysimeter water, insufficient performance data were provided to validate either method at the LOQ or 10x LOQ (minimum of 5 samples required).

• For ILV ground water analysis of IN

- T3935 and IN

- G3170 by

GC

- NPD and all analytes by LC/MS/MS, no performance data at 10x LOQ were provided.

• ILV performance data for 2.0 μg/L (LOQ) fortified hexazinone in ground water using GC

- NPD did not meet OCSPP Guideline

850.6100 criteria.

• The determination of LOQ and LOD were not based on scientifically acceptable procedures (see reference at the end of this DER for guidance).

• I LV reported recoveries were corrected if residues were present in the matrix controls.

• Water matrices used in the ILV were not characterized.

• Linearity (r 2 ) of the calibration standards was not always
≥0.995. Portions of the study appeared to meet guidelin e criteria and may be upgradable with the submission of additional information.
ECM=Environmental Chemistry Method; ILV=Independent Laboratory Validation

### Page 123 of 133 

### Table I

- 2 . Classification of Environmental Effects Studies Conducted on Hexazinone

Guideline

No. Da ta Requirement Study ID Study

Classification Classification Justifications or Comments (for Supplemental and Unacceptable Studies)

8 50.2100 Avian Acute Oral 00073988 Acceptable

---

850.2100 Avian Acute Oral (passerine) 48718401 Invalid A passerine study was requested as part of the DCI released with the 2010 Problem Formulation for Hexazinone (D369269). The submitted study (MRID 48718401) was deemed invalid and did not fill the guideline requirement for 850.2100; the submitted document consisted of a

sim ulation of existing data and was not an actual passerine study that was

conducted in a lab.

850.2200 Avian Dietary 00107878

00072663

00010498 Acceptable

---

850.2300 Avian Reproduction 41764901

41764902 Acceptable

---

850. 2400 Wild Mammal Toxicity No da ta
submitted Not applicable

---

850.2500 Terrestrial Field Testing No data

submitted Not applicable

---

850.1075 Acute Freshwater

Fish 00076959

00104980 Acceptable

---

850.1075 Acute Freshwater Fish (TEP) No data

submitted Not applicable

---

850.1010 A cute Freshwater

Invertebrate 00116269 Acceptable

---

850.1010 Acute Freshwater

Invertebrate (TEP) 41235003 Acceptable

---

850.1075 Acute

Estuarine/marine

Fish Waived Not applicable

---

850.1075 Acute

Estuarine/marine Fish (TEP) No data

submitted Not app licable

---

850.1350 Acute

Estuarine/Marine

Invertebrate 00047164 Acceptable

---

850.1350 Acute

Estuarine/marine

Invertebrate (TEP) No data

submitted Not applicable

---

850.1400 Early Life Stage

Fish 41406001 Acceptable

---

850. 1300 Life Cycle Aquatic

Invertebrate 00078041

41406002

45822101 Acceptable

---

850. 1500 Life Cycle Fish No data

submitted Not applicable

---

850 .1950 Aquatic Field Study No data

submitted Not applicable

---

### Page 124 of 133 Guideline

No. Da ta Requirement Study ID Study

Classification Classification Justifications or Comments (for Supplemental and Unacceptable Studies)

850.4100 Seedling Emergence 43162501 Partial There were a number of de viations that resulted in the invalidation of some of the species included in the seedling emergence study:

• Cucumber seeds were treated with Thiram resulting in invalidation of cucumber results; a control for the two pesticides should have been included in the design in order to

isolate the effects of hexazinone

• Onion and Pea data were invalidated based on significant damage to the plants

• Sorghum, soybean, pea and tomato showed growth retardation

• Percent germination of oilseed rape was low in the controls ( 54%)

850.4150 Vegetative Vigor 43162501 Partial There were a number of deviations that resulted in the invalidation of some of the species included in the vegetative vigor:

• Cucumber seeds were treated with Thiram resulting in

invalidation of cucumber resu lts; a control for the two pesticides should have been included in the design in order to

isolate the effects of hexazinone

• The percent germination was not reported and the phytoxicity rating was not included

850.4400 Aquatic Vascular

Plant Growth 4322510 1 Acceptable

---

850.4550 Aquatic

Nonvascular Plant

Growth 41287001

43302701

43225102 Acceptable

---

850.3020 Honeybee Acute

Contact No data

submitted Not applicable

Pollinator data will be requested as part of the newly implemented plan to

assess risk t o Pollinators. 850.3030 Honeybee toxicity

on residues on foliage No data

submitted Not applicable

850.3040 Field Testing for

Pollinators No data

submitted Not applicable

NG Honeybee Acute

Adult Oral No data

submitted Not applicable

NG Honeybee larva e Acute Oral No data

submitted Not applicable

NG Honeybee Adult

Chronic Oral Toxicity No data

submitted Not applicable

NG Honeybee Larvae

Chronic Oral No data

submitted Not applicable

NG Semi

- field testing for pollinators (tunnel or colony feeding

s tudies) No data

submitted Not applicable

NG Field trial of

residues in pollen and

nectar No data

submitted Not applicable

### Page 125 of 133 

# Appendix J. Hexazinone Refresh Acceptable Bibliographies

November 2014

1. Cai, Z.; Brauen, S. E.; Gealy, D. R.; Johnston, W. J., and Lumpkin, T. A. Tolerance of Chinese Milkvetch (Astragalus sinicus) to Herbicides. GRO,MOR,PHYSOIL,ENV; 1992; 6, (1): 104

- 107.

Rec #: 10 Call Number: LITE EVAL CODED (ACF,BT,HXZ,PZM), OK (ACR,CPP,DCPA,DU,EPTC,LCF,MTL,PMT,QZFE,SXD,TFN)

Notes: EcoRe ference No.: 161547

Chemical of Concern: 24DB,ACF,ACR,BMN,BT,CPP,DCPA,DFPM,DU,EPTC,FZFB,HXZ,IMQ,IZT,LCF,MBZ,MCPA, MTL,PMT,PZM,QZFE,SXD,TFN,TRB,TRL

2. Cain, M. D. Japanese Honeysuckle and Associated Ground Cover Inhibit Establishment and Growth of Pine

See dlings in All

- Aged Stands. GRO,MOR,POPSOIL,ENV; 1985; 54, 300

- 304.

Rec #: 20 Call Number: LITE EVAL CODED (HXZ)

Notes: EcoReference No.: 161024

Chemical of Concern: HXZ

3. Chenault, E. W. and Wiese, A. F. Annual Grass Control in Irrigated Alfalfa.

PH Y,POPSOIL,ENV,MIXTURE; 1977; 30, 147

- 151.

Rec #: 30 Call Number: LITE EVAL CODED (HXZ,SZ), OK (CPP,DU,PDM,PRM,PZM,TFN)

Notes: EcoReference No.: 163875 Chemical of Concern: CPP,DU,HXZ,MBZ,PDM,PRM,PZM,SZ,TFN,TRB

4. Diaz, G.; Carrillo, C., and Honrubia, M . Differential Responses of Ectomycorrhizal Fungi to Pesticides in Pure Culture. POPENV; 2003; 24, (3): 199

- 211.

Rec #: 180 Call Number: LITE EVAL CODED (HXZ,HYX), OK (GYP,SZ), TARGET2012 (BMY,Captan,IPD,THM)

Notes: EcoReference No.: 167816

Chemical of C oncern: BMY,Captan,GYP,HXZ,HYX,IPD,SZ,THM

5. Elskus, A. A. Pilot Study of Sublethal Effects on Fish of Pesticides Currently Used and Proposed for Use on Maine Blueberries. BEH,GRO,MOR,PHYAQUA,MIXTURE; 2007: 14 p. (NTIS #PB2008

- 108606).

Rec #: 130

Call Number: LITE EVAL CODED (HXZ,PSM)

Notes: EcoReference No.: 104953 Chemical of Concern: HXZ,PSM,SS

6. Figueroa, P. F. First

- Year Results of a Herbicide Screening Trial in a Newly Established Red Alder Plantation

with 1 + 0 Bare

- Root and Plug Seedling Stoc k. GRO,MOR,POPSOIL,ENV,MIXTURE; 1988; 41,

108

- 124.

Rec #: 40 Call Number: LITE EVAL CODED (HXZ), NO MIXTURE (24D,24DXY,ATZ,OYZ,SXD,SZ,TPR), OK (GYP,IZP,MTSM,PZM,SMU)

Notes: EcoReference No.: 161862

Chemical of Concern: 24D,24DXY,ATZ,CPR,GYP,HXZ,IZP,MTSM ,NPP,OYZ,PZM,SMU,SXD,SZ,TPR

### Page 12 6 of 133 7. Flores, F.; Collier, C. J.; Mercurio, P., and Negri, A. P. Phytotoxicity of Four Photosystem II Herbicides to Tropical Seagrasses. PHY. a.negri@aims.gov.au//: AQUA; 2013; 8, (9): 12 p. (e75798).

Rec #: 200

Call Number: LI TE EVAL CODED (ATZ,DU,HXZ,TET)

Notes: EcoReference No.: 167314 Chemical of Concern: ATZ,DU,HXZ,TET

8. Frans, R. E.; Richardson, J. T., and Gordon, E. C. Herbicide Field Evaluation Trials on Field Crops, 1976. GRO,PHY,POPSOIL,ENV,MIXTURE; 1977; 249, 33 p. Rec #: 120 Call Number: LITE EVAL CODED (ATZ,HXZ), NO MIXTURE (BT), OK (ACR,DU,FDE,LNR,MFD,MTL,PDM,PMT,PRM,TFN)

Notes: EcoReference No.: 78899

Chemical of Concern: ACR,ATZ,BFL,BT,BTL,CZE,DEE,DFPM,DU,EFL,FDE,FMU,HXZ,LNR,MBZ,MFD,MSMA,MT
L,MTZ,PDM,PMT,PRM, TFN,VNT

9. Haywood, J. D. Effects of Herbaceous and Woody Plant Control on Longleaf Pine Growth and Understory Plant Cover. GRO,POPSOIL,ENV,MIXTURE; 2013; 37, 108

- 112.

Rec #: 210 Call Number: LITE EVAL CODED (HXZ), NO MIXTURE (SXD), OK (TPR)

Notes: Ec oReference No.: 167326 Chemical of Concern: HXZ,SXD,TPR

10. Holt, H. A.; Wickham, S. H., and Wichman, J. R. Forest Nursery Weed Control Results. GRO,POP. Dep. For. Nat. Resour., Purdue Univ., West Lafayette, IN//: SOIL,ENV; 1975; 30, 175

- 177.

Rec #: 1 10 Call Number: LITE EVAL CODED (HXZ,SZ), OK (DCPA)

Notes: EcoReference No.: 71304 Chemical of Concern: DCPA,HXZ,NPP,ODZ,SZ

11. James, T. K. and Atkinson, G. C. Control of Browntop in Lucerne on Pumice Soils. POPSOIL,ENV,MIXTURE; 1979; 32, 58

- 61.

Rec #: 50 Call Number: LITE EVAL CODED (GYP,HXZ,PZM), NO MIXTURE (SZ), OK (PAQT)

Notes: EcoReference No.: 161678 Chemical of Concern: CZE,GYP,HXZ,PAQT,PZM,SZ,TRB

12. Kalmbacher, R. S.; Colvin, D. L.; Martin, F. G., and Kretschmer, A. E. Jr. Reaction of Suert e Paspalum atratum to Herbicides. MOR,PHY,POPSOIL,ENV; 1996; 55, 110

- 115.

Rec #: 60 Call Number: LITE EVAL CODED (HXZ), OK (CMZ,DMB,DMDP,DU,GYPI,MTSM,NFZ,SMM,TFN,TPR)

Notes: EcoReference No.: 162657

Chemical of Concern: CMZ,DMB,DMDP,DU,FMU,FZFB,GYPI,HXZ ,IZT,MBZ,MTSM,NFZ,NSF,SMM,TFN,TPR

13. Liu, M. Y.; Hulting, A. G., and Mallory

- Smith, C. A. Characterization of Multiple

- Herbicide

- Resistant Italian Ryegrass (Lolium perenne spp. multiflorum). CEL,GRO,PHYSOIL,ENV,MIXTURE; 2014; 70,

1145

- 1150.

Rec #: 22 0 Call Number: LITE EVAL CODED (HXZ), OK (ATZ,CLT,DU,GFSNH,GYPMK,IZPI,SMM,SXD)

Notes: EcoReference No.: 167327 Chemical of Concern: ATZ,CLT,DU,FFC,FZFB,GFSNH,GYPMK,HXZ,IZPI,PXSF,SMM,SXD

14. Meyers, S. L.; Jennings, K. M.; Monks, D. W.; Ballington, J. R., and Jordan, D. L. POST Control of Carolina

### Page 127 of 133 Redroot (Lachnanthes caroliniana). POPSOIL,ENV; 2013; 27, 534

- 537.

Rec #: 230 Call Number: LITE EVAL CODED (HXZ), OK (DU,FMX,FSF,GFSNH,GYPMK,PQT,SXD)

Notes: EcoReference No.: 167324 Chemical of Concern: CPR,DU ,FMX,FSF,GFSNH,GYPMK,HXZ,PQT,SXD

15. Meyers, S. L.; Jennings, K. M.; Monks, D. W.; Jordan, D. L., and Ballington, J. R. Effect of PRE and POST Herbicides on Carolina Redroot (Lachnanthes caroliniana) Growth. POPSOIL,ENV; 2013; 27, 747

- 751.

Rec #: 240 Call Number: LITE EVAL CODED (HXZ), OK (FMX,GFSNH,GYPMK,MTC,PQT)

Notes: EcoReference No.: 167323 Chemical of Concern: FMX,GFSNH,GYPMK,HXZ,MTC,PQT,TRB

16. Miller, J. H. and Andrews, G. W. Banded Herbicides can be as Effective as Windrowing. GRO,POPSOIL,E NV; 1985; 38, 216

- 225.

Rec #: 160 Call Number: LITE EVAL CODED (HXZ,TET), OK (DMB)

Notes: EcoReference No.: 162948 Chemical of Concern: DMB,HXZ,PCLK,TET

17. Moyer, J. R.; Hironaka, R.; Kozub, G. C., and Bergen, P. Effect of Herbicide Treatments on Dandelion, Alfalfa and Sainfoin Yields and Quality. POPSOIL,ENV; 1990; 70, (4): 1105

- 1113.

Rec #: 90 Call Number: LITE EVAL CODED (HXZ,SZ), NO EFFECT (EPTC,TFN)

Notes: EcoReference No.: 7 0404 Chemical of Concern: CSF,EPTC,HXZ,MBZ,SZ,TFN,TRB

18. Peng, S. Y. Isouron and Velpar in a New Criterion for Field Evaluation of Herbicides. GRO,POPSOIL,ENV,MIXTURE; 1980; 27, (3): 94

- 99.

Rec #: 70 Call Number: LITE EVAL CODED (HXZ), NO MIXTURE (ATZ ,NaDPA), OK (DU)

Notes: EcoReference No.: 163466 Chemical of Concern: ASM,ATZ,CZE,DU,HXZ,NaDPA

19. Peters, E. J.; McKelvey, R. A., and Mattas, R. Controlling Weeds in Dormant and Nondormant Alfalfa (Medicago sativa). POPSOIL,ENV; 1984; 32, (2): 154

- 157.

Rec #: 80 Call Number: LITE EVAL CODED (HXZ,SZ), OK (BT,DU,PAQT,PZM)

Notes: EcoReference No.: 161968 Chemical of Concern: BT,DU,HXZ,MBZ,PAQT,PZM,SZ,TRB

20. Samples, T. J.; Cargill, L. M., and Brede, A. D. Silver Beardgrass (Andropogon saccharoides) Con trol on Highway Rights

- of

- Way. POPSOIL,ENV,MIXTURE; 1987; 35, (1): 123

- 126.

Rec #: 140 Call Number: LITE EVAL CODED (ATZ,HXZ,SZ), NO MIXTURE (MTL), OK (DU,GYP,PZM,SMU)

Notes: EcoReference No.: 31143 Chemical of Concern: ATZ,DU,GYP,HXZ,MTL,PZM,SMU,SZ

21. Schoenholts, S. H. and Barber, B. L. The Impact of Hericides on Loblolly Pine Plantation Establishment in East Texas. GRO,MOR,PHY,POPSOIL,ENV,MIXTURE; 1989; 74, 341

- 348.

Rec #: 150 Call Number: LITE EVAL CODED (HXZ), NO MIXTURE (24D,24DXY,GYPI,SMM), O K (DMB,TPRT)

Notes: EcoReference No.: 44193

### Page 128 of 133 Chemical of Concern: 24D,24DXY,DMB,GYPI,HXZ,PCL,SMM,TPRT

22. Sellers, B. A.; Ferrell, J. A., and MacDonald, G. E. Influence of Hexazinone on Pensacola Bahiagrass Growth and Crude Protein Content. BCM,POPSOIL,E NV; 2008; 100, (3): 808

- 812.

Rec #: 170 Call Number: LITE EVAL CODED (HXZ)

Notes: EcoReference No.: 163441

Chemical of Concern: HXZ

23. Shipman, R. D. and Prunty, T. J. Effects of Herbicide Residues on Germination and Early Survival of Red

Oak Acorns. GRO,REP. Pennsylvania State Univ., University Park, PA, 16802//: SOIL,ENV,MIXTURE; 1988; 42, 86

- 91.

Rec #: 100 Call Number: LITE EVAL CODED (HXZ,SZ), OK (24D,24DXY,DMB,GYP,SMM,TPR)

Notes: EcoReference No.: 71308 Chemical of Concern: 24D,24DXY,DMB,GYP,HXZ ,PCL,SMM,SZ,TPR

24. Sutton, R. F. and Weldon, T. P. White Spruce Establishment in Boreal Ontario Mixedwood: 5

- Year Results. GRO,MORSOIL,ENV; 1995; 71, (5): 633

- 638.

Rec #: 190 Call Number: LITE EVAL CODED (HXZ), OK (GYPI)

Notes: EcoReference No.: 16344 0 Chemical of Concern: GYPI,HXZ

25. Velisek, J.; Kouba, A., and Stara, A. Acute Toxicity of Triazine Pesticides to Juvenile Signal Crayfish (Pacifastacus leniusculus). MORAQUA; 2013; 34, (2): 31

- 36.

Rec #: 250 Call Number: LITE EVAL CODED (ATZ,HXZ,PMT, SZ)

Notes: EcoReference No.: 167249 Chemical of Concern: ATZ,HXZ,MBZ,PMT,SZ

### Page 129 of 133 

# Appendix K

. Summary Hexazinone ECOSAR Runs

96

- hr Fish LC 50 

### (ppm)

Chemical Aliphatic Amines Imides

Substituted Ureas Triazines Amides

Neutral Organics

Hexazinone

Mea sured Fathead Minnow LC 50 

### = 274 ppm

Hexazinone

Estimated 38.465 6.138 49.424 45.150 54.251 151.119

IN

- G3170; Met. G 1293.132 130.602 na 3752.027 8680.794 24467.182*

IN

- JS472; Met. 1 850.211* 95.771 1930.158* 1987.807* 3933.477* 11055.558*

IN

- B2838; Met . D Na 0.207 0.547 0.432 0.283 0.780

IN

- G3453; Met. A

- 1 401.056 49.278 789.944 789.565 1379.543 3868.724

IN

- A3928; Met. B 49.699 7.65 67.716 62.629 79.222 220.881

IN

- JT677; Met. 2 274.584 35.204 504.537 496.969 817.016 2288.694

IN

- T3937; Met. A 401.056 49.278 789.944 789.565 1379.543 3868.724

Values marked w/ yellow are lower than the measured fathead minnow endpoint.

### Page 130 of 133 48

- hr Daphnid LC 50 

### (ppm)

Chemical Aliphatic Amines Imides

Substituted Ureas Triazines Amides

Neutral Organics

Hexazinone

Measured Daphnia magna acute EC 50 

### = 151.6 ppm

Hexazinone

Estimated 4.667 2.669 8.963 30.009 47.912 82.302

IN

- G3170; Met. G 123.980 4.495 Na 593.454 1184.400 7995.650

IN

- JS472; Met. 1 86.227 6.037 2654.802* 442.845 837.993 4081.089*

IN

- B2838; Met. D Na 0.943 0.008 1.085 1.409 0.682

IN

- G3453; Met. A

- 1 42.536 5.029 655.377 231.050 419.068 1573.630

IN

- A3928; Met. B 5.920 2.727 15.131 37.192 60.430 115.570

IN

- JT677; Met. 2 29.767 4.548 326.871 166.186 295.233 976.200

IN

- T3937; Met. A 42.536 5.029 655.377 231.050 419.068 1573.630

Values marked w/ yellow are lower than the measured Daphnia magna endpoint.

### Page 131 of 133 

# 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 Hexazinone

Enter Chemical Use Pastures Is the Application a Spra y? (enter y or n) y If Spray What Type (enter ground or air) ground Enter Chemical Molecular Weight (g/mole) 252.3 Enter Chemical Vapor Pressure (mmHg) 1.90E

- 07 Enter Application Rate (lb a.i./acre) 8

Toxicity Properties

**Bird**

Enter Lowest Bird Oral LD 50 (mg/kg bw) 2258 Enter Mineau Scaling Factor 1.15 Enter Tested Bird Weight (kg) 0.178

**Mammal**

Enter Lowest Rat Oral LD 50 (mg/kg bw) 530

Enter Lowest Rat Inhalation LC 50 (mg/L) 3.94

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/m 3 ) 2.58E

- 03

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 3.24E

- 04

Adjusted Inhalation LD 50 9.36E+ 01

Ratio of Vapor Dose to Adjusted Inhalation LD 50 3.46E

- 06 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 8.45E

- 01 Ratio of Droplet Inhalation Dose to Adjusted Inhalation

LD 50 9.03E

- 03 Exposure not Likely Sign ificant



### Results Mammalian (0.015 kg )
Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.58E

- 03

### Page 132 of 133 

# ppendix L. STIR Output Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 4.08E

- 04

Adjusted Inhalation LD 50 2.35E+02

Ratio of Vapor Dose to Adjusted Inhalati on LD 50 1.74E

- 06 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 1.06E+00 Ratio of Droplet Inhalation Dose to Adjusted Inhalation

LD 50 4.53E

- 03 Exposure not Likely Significant

### Page 133 of 133