UNITED STATES ENVIRONMENTAL PROTECT I ON AGENCY WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

MEMORANDUM

July 24

, 2013

SUBJECT: Pyroxasulfone Human Health Risk Assess m ent for Use of New Active Ingr edient Pyroxasulfone on Wheat and Cot ton.

PC Code: 090099 Decision No.: 464491 & 465295 Petition No.: 2F8026 & 2F8042 Risk Assessment Type: Single Chem i ca l Aggregate TXRNo.: NA MRIDNo.: NA DP Barcode: 410008 & 4100 l 0 Registration No.: 63588-91

, -92, -93 Regulatory Action: Section 3 Registration Case No.: NA CAS N o.: 447399-55-5

FROM: Thurston G. Morton
, Chemist

_ , 40CFR:

# 80**59 ~r);.** **/_ j1-&** **l** James S. Miller , E nvironmental**S~ientist** Abdallah Kha sawin ah

, PhD., Toxicologis

, // Risk Assess ment Branch 4 (RAB IV) 1/ Health Effects Division (7509P)

THROUGH: Donna Davis, Acting Branch Chief Susan V. Hummel, Branch Senior Scientist Ri sk Assessment Branch 4

, HED (7509P)

TO: Michael Walsh H e rb icide Bran ch Re gistrat ion Division (7505P)

This document provides the r evised Health Effects Di v i s ion ' s ( HED ' s) ri sk assessment of the Section 3 use of pyroxasulfone on wheat an d cotton.

Page 1 of821.0 EXECUTIVE SUMMA

_ RY

.. .. ...... . ... . .. .. ........... .. .. . ... .. .. .. .. ... ..... .. ...... . ... ... .. .. .. .. .. .. ... .. .. .. ....... 5


### 2 .0 HED RECOMMENDATIONS .•...

. ....... • ..••..••....•

. .••.••...............•..........•.......

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

Data Deficiencies/Conditions of Registration

. ... . .... . .. .. ... . .. .. ... . .. .. ... . •..

. ... . ... . ... .. ... . ... .. ... . 7 2.1


### 2.2

2.2.1 Tolerance Considerations

. .. . . . . . ... . ... . ... . ... . ... . ... . ... . ... . ... . ....... . . . . . ... . . . ...•..........

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

2.2

. 2
2.2.3
2.2

. 4 Enforcement Analytical Method

. ... . ... . ... . ... . ... . ... .. ... . ... . ... . ... . ... . .•.

. ......... .. ....... ••

.. .•. .• 7
International Harmonization

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

Recommended Tolerances

.. . . .. . ... . ... . ... . ... . ... . ... .. ... . ... . ... . .................•.......•..

. .•... ••

... ..... 8
Revisions to Petitioned-For Tolerances

.. ..................................................... ..... .. ... . 9
2.3 Label Re

- commendations

......... •.

. ... .. .. . ... . ..........................................•.....................

.. •..

.. •. 9 

### 3.0

3.1
3.2


### 3.3 INGREDIENT 

### PROFILE

.. . ... . .. .. .. .. .. .. .. .. .. .. ....... . .. .. ..... . .. ... . ..... . ... . .. .. . . . . ... . ... .. .. .. ... . ... .. ... . . Chemical Identity

. . .. ... . . ..• • ...•................

. . .. . ... . ... . ... . . . . . . . . . . .. . ... . ... . . . . . . .. .. .. . . ....... . ...... •......•. 10
10 Physical/Chemical Characteristics

. ...•..••...... •

................. . . .. . . •..

. ... . ... . ... . ... .. ... . ... . .... . ...... 12
Pesticide Use Pattern ...•.....

. . .. .. ............•.•.............

. . . . . . . . . . ... . . . . . .. . . ...... .. ... . ... . . .. .. .. . . . •. .•• •.

. .• Registered Products

.. . •••.

..... •

.. ••

.. .. .. .. ........ . ..... .. .. ... . ..... . . . ... . ......... •.

... . ... . .... . ... . ... . ... •. 12

12 Proposed New Uses •. • ..•.

. •••.•... •

. . ... . . . . . . . . . ... . ... . . .. . ... .. .. . .. . . . •. ...••.... ..•.....•..................•.. 12 

### 3.3 .1

3.3.2
3.4 Anticipated Exposure Pathways

..... . .. . ..... •.

.. •

... •.

.. ....................... . .........•.•........

.. .. .. .. . . ... 

### 13
3

. 5 Considerations of Environmental Justice

..................... ...... .. .... . ....... .. ... . ... . ... .. ... . ........ 

### 13
4.0

4.1
4.2
4.3 HAZARD CHARACTERIZATION/ASSESSMENT

.................... .. ................... .. ........ 

### 13 Toxicology Studies Available for Ana l ysis

.. .. .. .. .. .. ........................ .. .... .. .......... .. .......... 13 Absorption, Distribution, Metabolism and Excretion

.. ...... .. .............................. .. ...... 14 Toxicological Effects

..... •............................

.. .. .. .. ... . .. .. .... . . . .. . .. .. .. .. ... . ... . ..... .. .. .. .. ... .. .. . ... .. 14
4.4 Safety Factor for Infants and Children (FQPA Safety Factor)

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

4

. 4.1 Completeness of the Toxicology Database

.. . .. .. .. .. ... . .. .. .... .. ... . ... . ... . ......... .. . . .......... 16
4.4.2

4.4.3
4.4.4 Evidence of Neurotoxicity

. .. . •.••...•.....

. . . .. ... . ... . ... . ... . . .. . •••..••...•...

. .. .. ... ... . .. . •..

.. •. ...•.... 16
Evidence of Sensitivity/Susceptibility in the Develop i ng or Young Animal

...... 16
Residual U ncertainty in the Exposure Database

............ .. .. ................................ .. 17

Tox

_ icity Endpoint and Point of Departure

.. . .. ... .. . . . ... . ..... . . . ... . ... . . . ........ . ..•..•. ..•.......•.... 17 4

. 5

4 .5.1

4

. 5

. 2
4.5.3 Dose-Response Assessment

. ...... ... . .. ... . . . ... . ....... . ... . .. ..... . ... . ..... .. .. . .. .. .. .. ... .. .. .. . .... . .... . 17
Recommendations for Combining Exposure Routes

.. ........ .. ................ ...... .. .. .. ... 19

Classification of Carcinogenic Potential

. ... . . . . . . .. .. ... ... .. .. ... . .. .. .. ... . .... ..... .. ... . .......... 19
4.5.4 Summary of Points of Departure Used in Risk Assessment

.. ..... ............ .. .. ........ 19
5.0 DIETARY AND DRINKING WATER EXPOSURE AND RISK ASSESSMENT

.. .. 21

Page 2 of82

### Page 3 of 82

5.1 Metabolite/Degradate Residue Profile

................................ ................................ ......... 21
5.1.1 Summary of Plant and Livestock Metabolism Studies

................................ ........ 21
5.1.2 Comparison of Metabolic Pathways

................................ ................................ ...... 22
5.1.3 Environmental Fate and Transport

................................ ................................ ...... 22
5.1.4 Residues of Concern Summary and Rationale

................................ ..................... 23
5.2 Food Residue Profile

................................ ................................ ................................ ..... 23
5.2.1 Re sidues in Crops

................................ ................................ ................................ .... 24
5.3 Water Residue Profile

................................ ................................ ................................ ... 24
5.3.1 Estimated Drinking Water Concentrations

................................ .......................... 25
5.4.1 Acute Dietary and Drinking Water Analysis

................................ ....................... 25
5.4.2 Chronic Dietary and Drinking Water Analysis

................................ ................... 26
6.0 RESIDENTIAL EXPOSURE AND RISK ASSESSMENT

................................ .......... 26
6.1 Residential Bystander Post

- application Inhalation Exposure

................................ ... 27
6.2 Spray Drift

................................ ................................ ................................ ...................... 27
7.0 AGGREGATE EXPOSURE AND RISK ASSESSMENT

................................ ............ 27
7.1 Acute & Chronic Aggregate Risk

................................ ................................ ................. 28
8.0 CUMULATIVE RISK

................................ ................................ ................................ ...... 28
9.0 OCCUPATIONAL EXPOSURE/RISK CHARACTERIZATION

.............................. 28
9.1 Exposure Scenarios

................................ ................................ ................................ ....... 28
9.2 Hand ler Exposure

................................ ................................ ................................ .......... 29
9.2.1 Handler Exposure Scenarios

................................ ................................ .................. 29
9.2.2 Handler Exposure Data

................................ ................................ .......................... 30
9.2.3 Handler Exposure Assumptions

................................ ................................ ............ 30
9.2.4 Handler Exposure and Risk Estimates

................................ ................................ . 30
9.3 Post Application Exposure

................................ ................................ ............................ 31
9.3.1 Post Application Exposure Scenarios

................................ ................................ ... 32
9.3.2 Post Application Exposure Assumptions

................................ .............................. 32
9.3.3 Post

- Application Exposure and Risk Estimates

................................ ................... 33
9.3.4 Restricted Entry Interval

................................ ................................ ....................... 33
9.3.5 Inhalation Post

- application Risk

................................ ................................ .................. 33
10. REFERENCES

................................ ................................ ................................ .................. 34
A TOXICOLOGY DATA SUMMARY

................................ ................................ .............. 35
A.1 Guideline Data Requirements

................................ ................................ ................ 35

### Page 4 of 82

A.3 Toxicological Endpoints

................................ ................................ ............................. 51
APPENDIX B. Chemical Names And Structures Of Metabolites

................................ ......... 79 APPENDIX C. Physical/Chemical Properties

................................ ................................ .......... 82
APPENDIX D. Studies Reviewed for Ethical Conduct

................................ .......................... 82

### Page 5 of 82

1.0 EXECUTIVE SUMMARY

This assessment provides information to support a Section 3 registration for the use of the active ingredient, pyroxasulfone on wheat and cotton

. This document addresses the exposures and estimated risk associated with the proposed new uses of pyroxasulfone. It provides an assessment of proposed tolerances (pesticide residue limits in food) to ensure that they meet the safety standard established by the Food Quality Protection Act (FQPA) of 1996.

Use Profile

Pyroxasulfone (3

- [5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)pyrazol

- 4

- yl methylsulfonyl]

- 4,5

- dihydro

- 5,5

- dimethyl

- 1,2

- oxazole) is a new herbicide belonging to a class of selective herbicides identified as pyrazole herbicides. It is use d to control a broad spectrum of broadleaf weeds and grasses, including glyphosate

- resistant varieties. Pyroxasulfone is thought
to act as an inhibitor of very

- long

- chain fatty acid biosynthesis. Applications may be made using ground or aerial equipment. There are no pyroxasulfone products registered for homeowner use and there are no products registered for application to residential areas. Proposed tolerances are for combined residues of pyroxasulfone and its major metabolites in/on wheat and cotton

.

K

- I Chemical, U.S.A. Inc. is requesting a Section 3 registration of two pyroxasulfone products; Pyroxasulfone 85 WG Herbicide, an 85% water

- dispersible granule (WG) formulation (EPA Reg. No. 63588

- 92 )

, and V

- 10233 Herbicide, a 42.5% WG formulation (EPA Reg. No. 63588

- 93 ) for use on wheat and cotton . A pplications to wheat and cotton are to be made preplant, preemergence, or early postemergence at an application rate of 0.08

- 0.21 lb ai/A (depending on soil texture) with a maximum seasonal rate of 0.267 lb ai/A. Pre

- harvest intervals (PHIs) and/or
pre

- grazing intervals (PGIs) of 7 days have been proposed for wheat forage

.

Hazard Identification

T he toxicology database for pyroxasulfone is adequate for evaluating and characterizing toxicity and selecting endpoints for purposes of this risk assessment. Pyroxasulfone acute toxicity to mammals is low by all routes of exposure. Subchronic and chronic oral studies in mice, rats and dogs produced a variety of effects including cardiac toxicity (increased card iomyopathy), liver toxicity (centrilobular hepatocellular hypertrophy, histopathological and/or clinical pathological indicators), kidney toxicity (nephropathy), neurotoxicity (impaired hind limb function, ataxia, tremors, sciatic nerve lesions, axonal/mye lin degeneration in the sciatic nerve and spinal cord sections), skeletal muscle myopathy, urinary bladder mucosal hyperplasia, and urinary bladder transitional cell papillomas. Mi nimal to mild cardiac myofiber degeneration and local inflammation were als o seen in a rat dermal toxicity study. Neurotoxicity was also seen in a developmental neurotoxicity study in rats (decreased brain weight, decreased thickness of the hippocampus, corpus callosum and cerebellum in offspring). Dogs appear to be the most

se nsitive species to the neurotoxic effects of pyroxasulfone. Immunotoxicity studies in rats and mice show no evidence of immunotoxic effects from pyroxasulfone. There is evidence of fetal and offspring susceptibility in the developmental neurotoxicity st udy in rats as effects occurred

### Page 6 of 82

in the absence of maternal toxicity. There is no concern for reproductive toxicity as offspring effects occurred only at maternally toxic doses in the reproduction study. The FQPA safety factor was reduced to 1X because all the points of departure (POD) selected for risk assessment are protective of offspring effects seen in the developmental neurotoxicity study

, the fetal/offspring effects occurred at high doses of administration, and a clear dose

- response has been wel l defined with NOAELs and LOAELs for all effects of concern. Thus, there are no residual uncertainties with regard to pre

- and/or postnatal toxicity. P yroxasulfone is classified as

“ Not Likely to be Carcinogenic to Humans ” at doses that do not cause crysta ls with subsequent calculi formation resulting in cellular damage of the urinary tract. The Agency has determined that the quantification of risk using a non

- linear approach (i.e., RfD) will adequately account for all chronic toxicity, including carcinoge nicity, that could result from exposure to pyroxasulfone.

Dose Response Assessment

Toxicological points of departure (PODs) were selected for dietary/drinking water and occupational exposure scenarios for this assessment. Acute and chronic reference d oses (RfDs) were selected for assessment of food and drinking water exposures. The population adjusted dose (PAD) is equivalent to the reference dose (RfD) divided by the additional FQPA Safety Factor, if applied. An acute RfD/PAD for all populations was selected from a developmental neurotoxicity study in rats based on neurotoxicity characterized by decreased brain weights and morphometric brain changes in offspring in the DNT study. A chronic RfD/PAD for all populations was selected from a chronic feed ing study in dogs based on neurotoxic effects. A POD for short

- and intermediate

- term inhalation exposure was selected from subchronic and chronic oral toxicity studies in dogs based on neurotoxic effects. The POD for short

- and intermediate

- term dermal e xposure was chosen from a 28 day dermal toxicity study in rats based on mild cardiac myofiber degeneration and local inflammation. The POD for short

- and intermediate

- term inhalation exposure was chosen from a 90

- day oral dog study based on axonal/myelin degeneration in the sciatic nerve and minimal to mild subacute inflammation of skeletal muscle in males and females and impaired limb function

. An uncertainty factor of 100x was applied to endpoints selected for all exposure routes (10x for interspecies extrapolation, 10x for intraspecies variation).

Exposure/Risk Assessment and Risk Characterization

A dietary (food and water) exposure and risk assessment was conducted for wheat and cotton

. HED assessed occu pational exposure and risk from uses of pyr oxasulfone on soybean recently. The occupational exposure from the use of pyroxasulfone on wheat and cotton will be covered from that assessment . Worker exposures were assessed for handler and post

- application activities. Screening level acute and chronic dietary and drinking water risk assessments for pyroxasulfone show that dietary and drinking water exposure estimates for the assessed wheat

a nd corn use are below HED’s level of concern for the general population and all population subgroups. Occupational exposure and risk estimates indicate that worker handler and post

application exposures are not of concern at the maximum allowable applicat ion rates for the majority of scenarios. Exposure and risk estimates indicate that for most exposure scenarios

non

- cancer risks are not of concern for occupational handler activities for the proposed new use

### Page 7 of 82

(MOEs > 100) . However, risks of concern exist ( MOE<100) for “Inhalation” exposure during mixing and loading activities for aerial applications. Risk s of concern exist for the “mixing and loading” of a water dispersible granular for aerial applications (MOE = 71) with label specific PPE ( long

- sleeved s hirt and long pants, chemical resistant gloves and shoes and socks). However, with a PF5 respirator, risks are not of concern (MOE = 350).

Use of Human Studies

This risk assessment relies in part on data from studies in which adult human subjects were intentionally exposed to a pesticide or other chemical. These studies, listed in Appendix D, have been determined to require a review of their ethical conduct. Some of these studies are also subject to review by the Human Studies Review Board. All of t he studies used have received the appropriate review.

2.0 HED RECOMMENDATIONS

2.1 Data Deficiencies/Conditions of Registration

HED recommends for the establishment of tolerances to support the proposed use of pyroxasulfone on wheat and cotton commoditi es provided requirements in Section 2.1 are met. Deficiencies are stated below. The specific tolerance recommendations are discussed in Section 2.2, and label modifications are discussed in Section 2.3.

Note to PM:

Revised Section B & F required.

Analytical standards for metabolite M

- 28 are not currently available in the EPA National Pesticide Standards Repository. Analytical reference standards of pyroxasulfone and metabolites M

- 1, M

- 3, M

- 25, and M

- 28 must be supplied and supplies replenished as requested by the Repository.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

The petitioner has proposed high performance liquid chromatography/triple quadrupole mass spectrometry (LC/MS/MS) methods for the enforcement of tolerances for pyroxasulfone residues in/on crop commodities. The methods are adequate to determine residues of pyroxasulfone and metabolites M

- 1, M

- 3, and M

- 25 in wheat and cotton commodities. The validated limit of
qua ntitation (LOQ) is 0.0 1 ppm for parent, M

- 1, M

- 3 and M

- 25 in most wheat and cotton commodities. Enforcement methods for milk commodities have an LOQ of 0.001 ppm for parent, M

- 1, and M

- 3.

### Page 8 of 82

2.2.2 International Harmonization

There are no Codex MRLs established for residues of pyroxasulfone in any wheat or cotton commodities. International harmonization is not an issue at this time.

2.2.3 Recommended Tolerances

HED has examined the residue chemistry database for pyroxasulfone. Pending submission of a revised Section B (see requirements under D irections for Use), a revised Section F (see requirements under Proposed Tolerances) and analytical reference standards (see requirements under Submittal of Analytical Reference Standards), there are no residue chemistry issues that would preclude granting conditional Section 3 registration for the requested uses of pyroxasulfone, or establishment of tolerances for residues of pyroxasulfone as follow:

Tolerances are established for residues of the herbicide pyroxasulfone, including its metabolites and degr adates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only the sum of pyroxasulfone [3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methyl]sulfonyl ]

- 4,5

- dihydro

- 5,5

- dimethylisoxazole] and its metabolites [5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methanesulfonic acid (M

- 1), 5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- carboxylic acid (M

- 3), and [5

- (difluoromet hoxy)

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methanesulfonic acid (M

- 25), calculated as the stoichiometric equivalent of pyroxasulfone, in or on the commodity.

Wheat, forage

................................ ................................ ................... 6.0 ppm Wheat, hay

................................ ................................ ....................... 1 .0 ppm Wheat, straw

................................ ................................ .................. 0.60 ppm Cotton, gin byproducts

................................ ................................ ... 0.20 ppm 

### Tolerances are established for residues of the herbicide pyroxasulfone, including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only the s um of pyroxasulfone [3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methyl]sulfonyl]

- 4,5

- dihydro

- 5,5

- dimethylisoxazole] and its metabolite [5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- carboxylic acid (M

- 3) calculat ed as the stoichiometric equivalent of pyroxasulfone, in or on the commodity.

Wheat

, grain

................................ ................................ ................... 0.03 ppm Cotton, undelinted seed

................................ ................................ .. 0.04 ppm 

### Tolerances are established for residues of the herbicide pyroxasulfone, including its metabolites and degradates, in or o n the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only the sum of pyroxasulfone [3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

-

### Page 9 of 82

yl]methyl]sulfonyl]

- 4,5

- dihydro

- 5 ,5

- dimethylisoxazole] and its metabolites [5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methanesulfonic acid (M

- 1) and 5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- carboxylic acid (M

- 3), calculated as the stoichiometri c equivalent of pyroxasulfone, in or on the commodity.

Milk

................................ ................................ .............................. 0.003 ppm



### 2.2.4 Revisions to Petitioned

- For Tolerances

K

- I Chemical proposed that tolerances for pyroxasulfone residues of concern in crop commodities be expressed in terms of combined residue s of pyroxasulfone and its major metabolites M

- 1, M

- 3, and M

- 25, calculated as pyroxasulfone. K

- I Chemical proposed tolerances for pyroxasulfone on wheat and cotton commodities. HED’s recommended revisions to the tolerances submitted by K

- I Chemical fo r wheat and cotton are listed in Table 2.2.4

.

Table 2.2.4 . Tolerance Summary for Pyroxasulfone for Wheat and Cotton

. Commodity Proposed Tolerance (ppm) HED

Recommended Tolerance (ppm)* Comments; Correct Commodity

Definition

Wheat Forage 6.0 6 .0 Wheat

, forage
Wheat Hay 1 .0 1 .0 Wheat , hay
Wheat Grain 0. 01 0.0 3 Wheat, grain
Wheat Straw 0.6 0.60 Wheat, straw
Cotton Undelinted Seed 0.01 0.04 Cotton, undelinted seed Cotton Gin Byproducts 0.20 0.20 Cotton, gin byproducts
Milk none 0.003 Milk *Changes are due to the use of the Organization for Economic Cooperation and Development tolerance calculation procedures , inclusion of different metabolites of concern, significant figures, and use of all residue field trials , unless otherwise stated.



### 2.3 Label Recommendations

The following label revisions must be provided prior to a wheat and cotton tolerance being established for registration.

Because applications to wheat are based on defined growth stages, and crop commodities were harvested at appropriate crop growth stages in the field trials submitted with this petition, no PHIs or PGIs need to be specified for any wheat commodity. Therefo re, the product label for the 85% WG formulation should be amended to remove the following: the 7

- day PGI for wheat forage and hay.

There is a discrepancy in the master label for the 42.5% WG formulation. The directions on page 15 lists 3 oz/A as a ma ximum seasonal application for wheat. However, Table 2

### Page 10 of 82

lists a maximum single application for Fall and Spring Burndown for wheat as 4.5 oz/A. The text before this table only lists corn and soybean while the header on the table includes wheat. The must amend the label to state the maximum single application rate for the fall burndown application and the maximum seasonal application for wheat.

The field rotational crop study submitted (D402247, T. Morton, 1/10/13) is adequate and supports a plantback int erval (PBI) of 120 days.

Risks of concern exist for the “mixing and loading” of a water dispersible granular for aerial applications, therefore, the PPE for this scenario must require a PF5 respirator.

3 .0 INGREDIENT PROFILE

3.1 Chemical Identity

Structure and nomenclature are reported in Table 3.1

.

### Page 11 of 82

T able 3.1 . Pyroxasulfone Nomenclature.

Chemical structure

Common name Pyroxasulfone Company experimental name KIH

- 485; AE 2196191

IUPAC name 3

- [5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)pyrazol

- 4

- ylmethylsulfonyl]

- 4,5

- dihydro

- 5,5

- dimethyl

- 1,2

- oxazole
CAS name 3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl]methyl]sulfonyl]

- 4,5

- dihydro

- 5,5

- dimethylisoxazole
CAS registry number 447399

- 55

- 5
End

- use product (EP) Pyroxasulfone 85 WG Herbicide (85% WG; EPA File Symbol 63588

- OE) V

- 10233 Herbicide (42.5% WG; EPA File Symbol 63588

- OG) Chemical structure of M

- 1 metabolite

[5

- (difluoromethoxy)

- l

- methyl

- 3

- (trifluoromethyl)

- lH

- pyrazol

- 4

- yl)]methanesulfonic acid

Chemical structure of M

- 3 metabolite

5

- (difluoromethoxy)

- l

- methyl

- 3

- (trifluoromethyl)

- lH

- pyrazole

- 4

- carboxylic acid

Chemical structure of M

- 25 metabolite

[5

- (difluoromethoxy)

- 3

- (trifluoromethyl)

- 1H

- pyrazol

- 4

- yl)]methanesulfonic acid

### Page 12 of 82

3.2 Physical/Chemical Characteristics

A detailed description of the physicochemical properties of pyroxasulfone is provided in Appendix C. Pyroxasulfone exhibits relatively low solubility in water and higher solubility in organic solvents. It has a very low vapor pressure. Pyroxasulfone is mobile and persistent in terrestrial and aqu atic environments. Pyroxasulfone does not present significant concerns for bioaccumulation based on the lipophilicity of the compound.

3.3 Pesticide Use Pattern

3.3.1 Registered Products

Pyroxasulfone is an herbicide belonging to a new class of selective herbicides identified as pyrazole herbicides. Currently, Pyroxasulfone 85 WG Herbicide, an 85% water

- dispersible granule (WG) formulation

, and V

- 10233 Herbicide, a 42.5% WG formulation are registered for

use on soybean, field corn, sweet corn, and pop corn Applications to wheat are to be made preplant, preemergence, or early postemergence at an application rate of 0.0 4

- 0. 133 lb ai/A (depending on soil texture) with a maximum seasonal rate of 0. 133 lb ai/A ; pre

- harvest intervals (PHIs) and/or pre

- grazing intervals (PGIs) of 7 days have been proposed. Applications to cotton are to be made preplant, pre e mergence, early postemergence , or postemergence directed (lay

- by)
at an application rate of 0.0 4

- 0. 112 lb ai/A (depending on soil texture) with a maximum seasonal rate of 0. 112 lb ai/A

. Product registrations and p roposed use patterns and formulations are provided in Table 3.

3.3.2 Proposed New Uses

Table 3 .3.2 . Proposed Use Patterns And Formulations Pyroxasulfone Formulation Use Sites Method of Application Max Single

A R Max Seasonal

AR Timing of Application

85% a.i. WG Reg # 63588

- 92 Wheat broadcast ground 0. 133 0. 133 preplant, preemergence, or early postemergence

42.5% WG * Reg # 63588

- 93 Wheat broadcast aerial, broadcast/band ground 0.11 0. 08 preplant, preemergence

85% a.i. WG Reg # 63588

- 92 Cotton broadcast ground 0.112 0. 223 preplant, preemergence, or early postemergence 42.5% WG Reg # 63588

- 93 Cotton broadcast, ground 0. 08 0.1 6 preplant, preemergence

, post emergence *discrepancy in label

### Page 13 of 82

3.4 Anticipated Exposure Pathways

Dietary (food and water) and occupational exposures via dermal and inhalation pathways are expected based on proposed use of pyroxasulfone on wheat and cotton . A dietary (food and water) exposure and risk assessment was conducted for the requested wheat and cotton uses

. HED previously assessed occupational exposure and risk from the use of pyroxasulfone on soybean commodities which will cover the exposu res from the use of pyroxasulfone on wheat and cotton . Worker exposures were assessed for handler and post

- application activities. There are no residential uses for pyroxasulfone so residential exposure to children via incidental oral activities is not a nticipated.

3.5 Considerations of Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered in this human health risk assessment, in accordance with U.S. Executive Order 12898, “Federal Actions to Address Environmental Justice in Minority Populations and Lo w

- Income Populations,” http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf

. As a part of every pesticide risk assessment, OPP considers a large variety of consumer subgroups accordi ng to well

- established procedures. In line with OPP policy, HED estimates risks to population subgroups from pesticide exposures that are based on patterns of that subgroup’s food and water consumption, and activities in and around the home that involve
p esticide use in a residential setting. Extensive data on food consumption patterns are compiled by the USDA under the Continuing Survey of Food Intake by Individuals (CSFII) and are used in pesticide risk assessments for all registered food uses of a pest icide. These data are analyzed and categorized by subgroups based on age, season of the year, ethnic group, and region of the country. Additionally, OPP is able to assess dietary exposure to smaller, specialized subgroups and exposure assessments are per formed when conditions or circumstances warrant. Whenever appropriate, nondietary exposures based on home use of pesticide products and associated risks for adult applicators and for toddlers, youths, and adults entering or playing on treated areas post

- a pplication are evaluated. Further considerations are currently in development as OPP has committed resources and expertise to the development of specialized software and models that consider exposure to bystanders and farm workers as well as lifestyle and traditional dietary patterns among specific subgroups.

4.0 HAZARD CHARACTERIZATION/ASSESSMENT

4.1 Toxicology Studies Available for Analysis

The studies available for consideration of pyroxasulfone toxicity provide a comprehensive and complete database. All toxicity studies required in accordance with the new 40 CFR Part 158 data requirements have been submitted.

### Page 14 of 82

4.2 Absorption, Distribut ion, Metabolism and Excretion

Pyroxasulfone was shown to be quickly absorbed and excreted after oral administration to rats with the half

- life ranging from 15

– 173 hours; the longer half life corresponded to a high orally administered dose (700 mg/kg). At lower administered oral doses (10 mg/kg) absorption was fast (t max 

### of 1.1

- 7 hours with 77

- 88 % absorption) while at a higher dose (700 mg/kg) absorption was slower (t max 

### 7.0

- 17.3 hours, with 22

- 26% absorption). The main excretory routes were the urine and feces. Biliary excretion was demonstrated. Following absorption pyroxasulfone was widely distributed, with high concentrations observed in the bladder, prostate, adrenals, kidney, liver, abdominal fat, uterus, and blood.

There was no signi ficant sex difference in the metabolism of pyroxasulfone. There appeared to be saturation or induction of metabolism at the high dose, which resulted in an altered metabolic profile. The absorbed pyroxasulfone was extensively metabolized to a number of c ompounds. The major metabolite in the urine of rats dosed with [Py

14 

### C]

- pyroxasulfone was M

- 13, accounting for up to 26% of the dose at the low dose and up to 4% at the high dose. M

- 7 and M

3 were the next most abundant metabolites. Most of the metaboli tes in urine were produced by the cleavage between the pyrazole and isoxazoline ring structure. There were three major metabolites in urine in rats dosed with [Ix

14 

### C]

- pyroxasulfone; M

- 13 accounting for up to 20% of the dose, M

- 16 accounting for up to 1 9% of the dose and M

- 26 accounting for up to 6.4% of the dose. A major portion of the radioactivity was highly polar and multi

- component, containing 5

- methyl

- 5

- isoxazoline carboxylic acid and M

- 30, and accounted for up to 34% of the dose.

A dermal absorpt ion study with pyroxasulfone is not available. A dermal absorption factor can be derived by comparing the toxicity endpoints from a dermal toxicity study and an oral toxicity study of comparative durations. In one 28

- day oral toxicity study in rats (MRID 47889320), the LOAEL was 1000 ppm (75.4/84.4 mg/kg/day for M/F) based on myocardial degeneration/necrosis and the NOAEL is 100 ppm (7.3/8.3 mg/kg/day for M/F). In the 28

- day dermal toxicity study, the LOAEL was 1000 mg/kg/day based on minimal to mild card iac myofiber degeneration with inflammation in males and females and the NOAEL was 100 mg/kg/day. By comparing the LOAELs from both studies a dermal absorption factor of 7.5% is derived.

4.3 Toxicological Effects

T he toxicology database for pyroxasulfon e is adequate for evaluating and characterizing pyroxasulfone toxicity and selecting endpoints for purposes of this risk assessment. Subchronic and chronic toxicity testing of pyroxasulfone technical in mice, rats and dogs produced a variety of adverse ef

fects in several target organs, but the most sensitive eff ect is neurotoxicity in dogs. Effects seen in animal studies ranged from cardiac toxicity (increased cardiomyopathy in mice and rats), liver toxicity (centrilobular hepatocellular hypertrophy, hi stopathological and/or clinical pathological indicators), neurotoxicity characterized by axonal/myelin degeneration in the sciatic nerve (dog, mouse and rat) and spinal cord sections (dog), skeletal muscle myopathy, kidney toxicity (increased incidence of chronic progressive nephropathy in dogs and retrograde nephropathy in mice), urinary bladder mucosal hyperplasia, inflammation, and urinary bladder

### Page 15 of 82

transitional cell papillomas (rats). Decreased body weight, enzyme changes were noted in some studies. Tox ic adverse effects (impaired hind limb function, ataxia, hind limb twitching and tremors; increased creatine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections) in dogs occurred at ≥10 mg/kg/day dos es while in the mouse toxic adverse effects (degeneration of sciatic and trigeminal nerve axons and their associated myelin sheaths and chronic progressive nephropathy, renal tubular adenomas) occurred at higher doses (131 mg/kg/day and above).

Comparing effects by route of administration, pyroxasulfone was moderately toxic to rats following a 4

- week dermal exposure producing local inflammation and systemic effects of minimal to mild cardiac myofiber degeneration at the limit dose of 1000 mg/kg/day with a NOAEL of 100 mg/kg/day. No adverse effects were noted in an inhalation study following exposure for 28 days at 200 mg/m 3 

### /day (equivalent to 52.2 mg/kg/day oral dose), the highest dose tested of an aerosol dust.

In cancer studies in mice and rats, rena l tubular adenomas were observed in male mice at a dietary dose of 0.6 and 255 mg/kg/day (but not at an intermediate dose of 18 mg/kg/day) and urinary bladder transitional cell papillomas were observed in male rats at 42 and 84 mg/kg/day. The CARC met in May, 2011 to consider studies submitted by the registrant to support a mode of action for bladder tumors and a re

- evaluation of the kidney tumors conducted by an external Pathology Working Group (PWG). Based on the evidence provided by the PWG, the CARC concluded that that the kidney adenomas in male mice were not treatment

- related. The CARC considered the transitional cell bladder tumors in male rats to be treatment

- related based on statistically signi ficant trends for urinary bladder transitional cell papillomas and combined papilomas and carcinomas, the occurrence of preneoplastic lesions at 42 and 84 mg/kg/day and the rare occurrence of bladder transitional cell tumors. The CARC concluded that the m ode of action for bladder tumors has been adequately established based on submitted data that support both a dose

- response and temporal concordance of the key events and bladder tumors. The Agency has determined that the quantification of risk using a non

- linear approach (i.e., RfD) will adequately account for all chronic toxicity, including carcinogenicity, that could result from exposure to pyroxasulfone.

Pyroxasulfone did not exhibit developmental toxicity in the rat guideline study at the limit dose of 1000 mg/kg/day and it exhibited slight developmental toxicity in rabbits (reduced fetal weight and resorptions) at the limit dose of 1000 mg/kg/day. However, developmental effects were noted in PND 21 offspring at 300 mg/kg/day in the rat developmental neurotoxicity (DNT) study characterized as decreased brain weight and morphometric changes. In a reproductive toxicity in rats reduced pup weight and body weight gains during lactation) occurred at similar or higher doses causing pronounced maternal toxi city ( reduced body weight, body weight gain and food consumption and increased kidney weight, cardiomyopathy and urinary bladder mucosal hyperplasia with inflammation)

. Pyroxasulfone did not produce immunotoxic effects in mice following dietary feeding for 28 days up to 4000 ppm (633/791 mg/kg/day, M/F) or in rats at dietary concentrations of 7500 ppm (529/570 mg/kg/day in M/F).

### Page 16 of 82

Acute toxicity studies show that pyroxasulfone exhibits low acute toxicity by all exposure routes (EPA Toxicity Category III or IV) and is not a dermal sensitizer.

The complete toxicity profile for pyroxasulfone is provided in Appendix A.

4.4 Safety Factor for Infants and Children (FQPA Safety Factor)

4.4.1 Completeness of the Toxicology Database

The toxicity database for pyroxasulfone is sufficient for a full hazard evaluation and is considered adequate to evaluate risks to infants and children. Acceptable developmental toxicity studies in the rat and rabbit and acceptable multi

- and single generation reproduction studies in the rat have been submitted. Acceptable acute, subchronic and developmental neurotoxicity studies in the rat are available. Acceptable immunotoxicity studies in mice and rats are available.

4.4. 2 Evidence of Neurotoxicity

Pyroxasulfone produced neurotoxic effects in dogs, mice and rats. Dogs appear to be the most sensitive species as minimal to mild axonal/myelin degeneration in the sciatic nerve occurred at ≥ 10 mg/kg/day for 90 days. The nerve effects in dogs were also accompanied by impaired limb function, body and limb hypotonia at a subchronic dose of 15 mg/kg/day. Chronic administration of pyroxasulfone at 10 mg/kg/day to dogs resulted in similar findings of impaired hind limb function, ataxia, hind limb twitching an d tremors and axonal/myelin degeneration of the sciatic nerve and spinal cord sections.

In rats, sciatic nerve lesions (m inimal to mild axon/myelin degeneration within the sciatic nerve sections) were observed in a reproduction study in parental females fed pyroxasulfone at 5000 ppm (383 mg/kg/day) but not at lower doses. These lesions were also seen in female rats administ ered doses of 1000 ppm (54 mg/kg/day) and above after chronic feeding for two years, but not after one year of feeding. However, specific acute and subchronic neurotoxicity tests in rats did not reveal neurotoxic effects following an acute oral dose of 20 00 mg/kg or subchronic dietary administration of 2500 ppm (equivalent to 161/200 mg/kg/day (M/F), the HDT. In the rat DNT studies, pyroxasulfone did not produce behavioral or maternal toxicity at the highest dose tested of 900 mg/kg/day. However, it was associated with offspring toxicity at 300 mg/kg/day resulting in decreased brain weight in male and female offspring accompanied with a decrease in the thickness of the hippocampus, corpus callosum and cerebellum in PND 21 female offspring with a NOAEL of 100 mg/kg/day. Although the offspring are more sensitive, the dose

response is well characterized for neurotoxicity and a NOAEL is identified.

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal

Evidence of increased suscep tibility of fetuses and offspring was seen in a DNT study in rats and a developmental study in rabbits following in utero or post natal exposure to pyroxasulfone.

### Page 17 of 82

However, no susceptibility was seen in the rat developmental or reproduction studies. In ra bbits, developmental toxicity was only seen at the limit dose of 1000 mg/kg/day as reduced fetal weight and increased fetal resorptions with a NOAEL of 500 mg/kg/day for these effects, compared to no maternal toxicity at these doses. In a DNT study in rat s, offspring toxicity was seen at 300 mg/kg/day compared to no maternal toxicity at 900 mg/kg/day. This increased susceptibility is occurring at high doses

. NOAELs and LOAELs have been identified for all effects of concern and thus, a clear dose response has been well defined. Therefore, residual uncertainties or concerns for pre

- and/or post

- natal toxicity are minimal, and HED recommends the FQPA safety factor be reduced to 1x.

4.4.4 Residual Uncertainty in the Exposure Database

S ince the dietary and non

- dietary exposure estimates were based on several conservative assumptions, HED does not believe that the exposure estimates are underestimated. The acute and chronic dietary assessments conducted with DEEM

- FCID were screening level analyses. The assessments utilized tolerance values, default processing factors, and 100% crop treated was assumed for all commodities. The DEEM analysis also assumed that all drinking water will contain pyroxasulfone at th e highest EDWC levels modeled by EFED for ground water or surface water. For these reasons it can be concluded that the DEEM

- FCID analysis does not underestimate risk from acute or chronic exposure to pyroxasulfone. Similarly, HED does not believe that t he non

- dietary occupational exposures are underestimated because they are also based on conservative assumptions, including maximum application rates, labeled PPE, and standard values for unit exposures, acreage treated/amount handled.

4.4.5 FQPA Factor for Infants and Children
HED recommends the FQPA SF be reduced to 1x based on the following:

- The toxicological data base is complete for FQPA assessment.

- There are no r esidual uncertainties or concerns for pre

- and/or post

- natal toxicity

.

- Although an apparent increased quantitative susceptibility was observed in fetuses and offspring based on toxicity at high doses of administration, a clear dose

- response has been well defined with NOAELs and LOAELS for all effects of concern and all points of depar ture (PODs) are protective of the fetal/offspring effects.

4.5 Toxicity Endpoint and Point of Departure

4.5.1 Dose

- Response Assessment

Toxicity endpoints and PODs for dietary (food and water) and occupational exposure scenarios are summarized below. A detailed description of the studies used as a basis for the selected endpoints are presented in Appendix A. PODs for incidental oral, der mal and inhalation for non

occupational (i.e., residential) exposure are not required to assess risk for the proposed uses because there are no pyroxasulfone products registered for homeowner use and there are no products registered for application to resi dential areas.

### Page 18 of 82

An acute POD of 100 mg/kg/day (NOAEL) was selected from a developmental neurotoxicity study in rats based on decreased brain weight in both sexes and decreased thickness of the hippocampus, corpus callosum and cerebellum in PND 21 female offspring occurring at 300 mg/kg/day. An uncertainty factor (UF) of 100x (10x to account for interspecies extrapolation and 10x for intraspecies variation) was applied to the NOAEL to obtain an acute reference dose (aRfD) of 1.0 mg/kg/day. Since the FQPA factor has been reduced to 1X, the acute population adjusted dose (aPAD) is equivalent to the aRfD. The HED DNT committee considers morphometric changes in the hippocampus, corpus callosum and cerebellum during the first 21 days to result from a single a cute exposure. This endpoint is considered to be protective of all populations including women of child

- bearing age and nursing infants.

A chronic POD of 2.0 mg/kg/day (NOAEL) was selected from the one year dog study based on impaired hind limb funct ion, ataxia, hind limb twitching and tremors; clinical pathology: increased creatine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections at 10 mg/kg/day. An UF 100x (10x to account for interspecies extrapolation and 10x for intraspecies variation) was applied to the dose to obtain a chronic reference dose (cRfD) of 0.02 mg/kg/day. Since the FQPA factor has been reduced to 1X, the chronic population adjusted dose (cPAD) is equivalent to the cRfD. The dog was the most sensitive species for the neurotoxic effects of pyroxasulfone . Also the dose ranges used in the dog testing were the narrowest allowing for more accurate determination of a NOAEL. The 2 mg/kg/day NOAEL from this dog study is also pro tective from other adverse effects seen at higher doses in rats and mice such as cardiac and skeletal myopathy, liver, kidney and urinary bladder toxicity.

A POD of 100 mg/kg/day (NOAEL) for short

- and intermediate

- term dermal exposure was selected from the 28

- day dermal toxicity in the rat based on cardiac myofiber degeneration with inflammation at 1000 mg/kg/day. The target margin of exposure (MOE) for dermal toxicity is 100. The 28

- day dermal toxicity study is route specific and is considered approp riate for this exposure scenario. This endpoint is considered protective of developmental effects seen in the DNT study at 300 mg/kg/day and in the rabbit developmental study at 1000 mg/kg/day. While the effects aren’t seen until the limit dose of 1000 mg /kg/day, there is a 10

- fold difference between the dermal NOAEL and LOAEL. Therefore, the true NOAEL is probably higher (between 100 and 1000 mg/kg/day). This POD is also protective of the neurotoxic effects seen in the dog following chronic oral exposur e to 10 mg/kg/day. Dermal absorption is estimated to be 7.5%, so the relative dermally absorbed dose for the dermal NOAEL of 100 mg/kg/day is approximately 7.5 mg/kg/day which is less than the oral LOAEL of 10 mg/kg/day identified in the dog study. In ad dition, rats in general are a more sensitive species for the dermal exposure route because of higher skin permeability.

A POD of 2.0 mg/kg/day for short

- and intermediate

- term inhalation exposure was selected from the oral 90 day dog study (MRIDs 47701696

- 97) based on a LOAEL of 10 mg/kg/day for axonal/myelin degeneration in the sciatic nerve, minimal to mild subacute infl ammation of skeletal muscle in males and females and impaired limb function, body and limb hypotonia, increase in serum creatine kinase activity. The target MOE for inhalation toxicity is 100. This

### Page 19 of 82

endpoint is more protective than the findings in the 28 day rat inhalation study (MRID 47701699) where no effects were seen at the highest dose tested for an aerosol dust of 200 mg/m 3 

### (equivalent to 52.2 mg/kg/day) (NOAEL)

. Since mixer/loader exposures would be to both dust and aerosols (with aerosol exposures typically being more sensitive than dust
exposures ), HED believes the inhalation study was not protective of the neurotoxicity findings in the dog study.

4.5.2 Recommendations for Combining Exposure Routes

Under FQPA, when there are potential residen tial exposures to a pesticide, HED must aggregate exposures from three major sources: oral, dermal and inhalation exposures. These combined residential exposures must then be aggregated with exposure from food and water to determine aggregate risk. Sinc e there are no residential incidental oral exposures to pyroxasulfone, aggregate exposure from food and non

- food oral exposures is not required. Although the dermal and inhalation scenarios are based on muscle effects, the cardiac muscle is histologically very different from skeletal muscle particularly as it relates to its electrophysiology. Therefore, s hort

term dermal and inhalation exposures to workers should be not aggregated with dietary (food and water) exposures because endpoints are not based on common toxicity effects.

4.5.3 Classification of Carcinogenic Potential

In accordance with EPA’s Final Guidelines for Carcinogen Risk Assessment (March 2005) , the CARC classified Pyroxasulfone as “Not Likely to be Carcinogenic to Humans” at doses that do not cause crystals with subsequent calculi formation resulting in cellular damage of the urinary
tract (HED TXR 0055883). This classification was based on ur inary bladder tumors seen in male rats . Crystal formation in the absence of calculi is not associated with hyperplasia or urinary bladder tumors; therefore, the formation of urinary bladder calculi is the prerequisite for subsequent hyperplasia and neoplas ia. The requirement for calculi formation also supports a high

- dose threshold phenomenon for the development of urinary bladder tumors, i.e., tumors do not develop at doses too low to produce calculi. There is no concern for mutagenicity. As noted previo usly, the CARC concluded that the kidney adenomas in male mice were not treatment

related. The Agency has determined that the quantification of risk using a non

- linear approach (i.e., RfD) will adequately account for all chronic toxicity, including carcin ogenicity, that could result from exposure to pyroxasulfone. There is a clear threshold of 1000 ppm (42.55 mg/kg/day) for tumorigenesis. A point of departure (POD) of 50 ppm (2.0 mg/kg/day) is not expected to result in urinary bladder calculi formation w hich is a prerequisite for subsequent hyperplasia and neoplasia.

4.5.4 Summary of Points of Departure Used in Risk Assessment

Toxicological doses/endpoints selected for the pyroxasulfone risk assessment are provided in Tables 4 .5.4 .1 and 4.5.4.2

.

### Page 20 of 82

Table 4 .5.4

. 1. Toxicological Doses and Endpoints for Pyroxasulfone for Use in Dietary Human Health Risk Assessments Exposure/ Scenario Point of

Departure Uncertainty/

FQPA Safety Factors RfD & PAD Study and Toxicological Effects

Acute Dietary (General Population, including Infants and Children) NOAEL= 100

mg/kg UF A = 10 x

UF H =10 x FQPA SF=1x Acute RfD =

1.0 mg/kg

aPAD = 1.0 mg/kg Developmental neurotoxicity study (DNT) in

rats, MRID 47701724. The LOAEL of 300 mg/kg/day is based on decreased brain weight in both sexes, reduced thickness of the hippocampus, corpus callosum and cerebellum in PND 21 female offspring. Chronic Dietary (All Populations) NOAEL= 2

mg/kg/day UF A = 10 x

UF H =10 x FQPA SF=1x Chronic RfD

= 0.02 mg/kg/day

cPAD = 0.02 mg/kg/day One

- year chronic dog study, MRID 47701707

The LOAEL of 10 mg/kg/day is based on impaired hind limb function, ataxia, hind limb twitching and tremors; clinical pathology: increased creatine kinase, aspartate aminotransferase; axonal/ myelin degeneration of the sciatic nerve and spinal cord sections. Cancer (all routes) “Not Likely to be Carcinogenic to Humans” at doses that do not cause crystals with subsequent calculi

formation resulting in cellular damage of the urinary tract. Risk is quantified using a non

- linear (i.e., RfD) approach. Point of Departure (POD) = A data point or an estimated point that is derived from observed dose

- response data and used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures. NOAEL = no observed adverse effect level. LOAEL = lowest observed adverse effect level. UF = uncertainty factor. UF A = extrapolation from animal to human (interspecies). UF H = potential variation in sensitivity among members of the human population (intraspecies). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = reference dose. MOE = margin of exposure. LOC = level of concern. N/A = not applicable.

Table 4 .5.4

. 2

. Toxicological Doses and Endpoints for Pyroxasulfone for Use in Occupational Human Health Risk Assessments Exposure/ Scenario Point of

Departure Uncertainty/

FQPA Safety Factors Level of

Concern Study and Toxicological Effects

Incidental Oral Not required. Incidental exposure not anticipated. There are no registered residential uses

### Page 21 of 82

Table 4 .5.4

. 2

. Toxicological Doses and Endpoints for Pyroxasulfone for Use in Occupational Human Health Risk Assessments Exposure/ Scenario Point of

Departure Uncertainty/

FQPA Safety Factors Level of

Concern Study and Toxicological Effects

Dermal Short

- (1

- 30 days) & Intermediate

- Term (1

- 6 months) NOAEL = 100

mg/kg/day UF A = 10 x

UF H =10 x Occupational

MOE = 100 28

- day dermal toxicity study in rats MRID 47701698

The LOAEL of 1000 mg/kg/day was based on minimal to mild cardiac myofiber degeneration with in inflammation in males and females

Inhalation Short

- (1

- 30 days) & NOAEL = 2

mg/kg/day 100% absorption UF A = 10 x

UF H =10 x Occupational

MOE = 100 90

- day toxicity study in dogs MRIDs 47701696 and

4770169 7 LOAEL of 10 mg/kg/day: axonal/myelin degeneration in the sciatic nerve. Minimal to mild subacute inflammation of skeletal muscle in males and females. Impaired limb function, body and limb hypotonia, increase in serum creatine kinase activity.

Inhalation Intermediate

- Term (1

- 6 months) NOAEL = 2

mg/kg/day 100% absorption UF A = 10 x

UF H =10 x Occupational

MOE = 100 One

- year chronic dog study, MRID 47701707

The LOAEL of 10 mg/kg/day is based on impaired hind limb function, ataxia, hind limb twitching and tremors; clinical pathology: increased creatine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections. Cancer (all routes) “Not Likely to be Carcinogenic to Humans” at doses that do not cause crystal s with subsequent calculi

formation resulting in cellular damage of the urinary tract. Risk is quantified using a non

- linear (i.e., RfD) approach. Point of Departure (POD) = A data point or an estimated point that is derived from observed dose

- response data and used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human exposures. NOAEL = no observed adverse effect level. LOAEL = lowest observed adverse effect level. UF = uncertainty factor. UF A = extrapolation from animal to human (interspecies). UF H = potential variation in sensitivity among members of the human population (intraspecies). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = reference dose. MOE = margin of exposure. LOC = level of concern. N/A = not applicable.



### 5.0 DIETARY AND DRINKING WATER EXPOSURE AND RISK ASSESSMENT

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Livestock Metabolism Studies

The metabolism studies submitted for pyroxasulfone are adequate to satisfy data requirements on the nature of the residue in plants . The nature of the residue in plants is adequately understood based on the submitted studies. The metabolic pathway of pyr oxasulfone involves cleavage of the methyl sulfone bridge of the parent compound, oxidation and/or demethylation of the pyrazole cleavage product to yield metabolites M

- 1 and M

- 25, and reaction of the isoxazoline cleavage product with cysteine and/or gluta thione; further demethylation, deamination, and/or conjugation of these metabolites occurs, yield additional metabolites including M3 (chemical structures are provided in Appendix B).

The submitted livestock metabolism studies with goats and hens are ad equate to satisfy data requirements for the nature of the residue in livestock. The nature of the residue in livestock is

### Page 22 of 82

adequately understood based on submitted metabolism studies. Metabolism of pyroxasulfone in livestock occurs primarily via cleavage between the rings, to form metabolites M

- 1, M

- 8, M

- 10, and/or M

- 15, followed by oxidation, to yield metabolite M

- 3, and/or demethylation, to yield metabolites M

- 12 and M

- 9. The parent compound may also undergo demethylation, hydroxylation followed by oxid ation, or oxidation followed by ring cleavage.

5.1.2 Comparison of Metabolic Pathways

The proposed metabolic pathway for pyroxasulfone in plants is provided in Appendix B. The major pyroxasulfone metabolites in plants are M

- 1, M

- 3, M

- 25, M

- 28. All o f the plant metabolites exhibit low acute toxicity (Toxicity Category IV). The M

- 1 and M

- 3 metabolites, which are also found in rat, were not toxic in rats after 14 days of oral dosing at 1000 mg/kg/day. Structure

- activity relationship (SAR) analysis (DE REK) did not reveal any alerts for any of the major metabolites. All of the tested metabolites were negative in the Ames test. M1, M25, and M

- 28 are potentially less toxic than the parent as they are lower molecular weight acids (i.e., more easily excret ed). However, there are no data to demonstrate that they do not retain the toxic properties of the parent compound. Based on the limited testing data available, pyroxasulfone metabolites appear to be equal or less toxic than the parent material.

The metabolic pathway of pyroxasulfone in plants mainly involves cleavage of the methyl sulfone bridge of the parent compound followed by oxidation and/or demethylation of the pyrazole cleavage product to yield metabolites M

- 1 and M

- 25, and reaction of the isoxazoline cleavage product with cysteine and/or glutathione; further demethylation, deamination, and/or conjugation of these metabolites occurs, yield additional metabolites including M

- 3.

The metabolism of pyroxasulfone in rats appears to proceed by two main routes. One route, similar to the metabolic pathway seen in plants, involves cleavage of the sulfonyl group and subsequent sequential oxidations of this group on the pyrazole moiety or glutathione conjugation and subsequent hydrolysis of the isox azoline moiety. The second route involves sequential oxidations of the parent compound.

5.1.3 Environmental Fate and Transport

Pyroxasulfone is mobile (average K oc 

### = 94.75) and persistent (t 1/2 

### = 142 to 533 days) in terrestrial and aquatic environments There are two major degradation products (>10% of applied radioactivity) and 6 minor degradation products (<10 % of applied radioactivity) detected in laboratory metabolism studies. Additionally, there is a high percentage of applied radioactivity (8

- 25% of applied radioactivity) identified as “bound” soil/sediment residues. Because the extraction of pyroxasulfone residues was conducted using only acetonitrile/water without the use of sequentially harsher soil extractants, there is uncertainty regarding the identity and availability of the “bound” soil residues.

The Environmental Fate and Effects Division ( 

### EFED) conducted a drinking water assessment for the proposed uses of pyroxasulfone o n cotton

. Previously they have conducted drinking water

### Page 23 of 82

assessments of the use of pyroxasulfone on corn, wheat, and soybean. EF ED provide d modeling

- based drinking water exposure estimates using the Tier II PRZM GW drinking water assessment from surface w at er sources for the proposed use of pyroxasulfone. Residues of concern for drinking water for risk assessment purposes were parent, M1, and M3. E stimated drinking water residues for peak concentration of 0.210 mg/L (ppm) were used in the acute

assessmen t . Estimated 30 yr annual average drinking water concentrations of 0.174 mg/L (ppm) were used the chronic assessment

.
5.1.4 Residues of Concern Summary and Rationale

Previously

, in order to harmonize with Canada and Australia, HED has concluded the residues of concern for Corn, field, grain and Corn, sweet, kernel plus cob with husks removed consist of pyroxasulfone and its metabolite M

- 3. Residues of concern for drinking water for risk assessment purposes were parent, M

- 1, and M

- 3. The modelin g was conducted for pyroxasulfone and total pyroxasulfone residues (parent+M

- 1+M

- 3, and total pyroxasulfone residues (parent+M

- 1+M

- 3+M

- 5+M

- 6+M

- 8+M

- 9+M

- 10+M

- 11+unidentified bound soil residues). Another acidic metabolite, M3, was proposed as a residue of c oncern by the petitioner. Although not a major component of the total radioactive residue (TRR), ROCKS recommends that M3 be included in the residues of concern since it is analyzed concurrently with the parent compound in the proposed analytical enforcem ent method.

Table 5.1.4 . Compounds to be Included in the Risk Assessment and Tolerance Expression.

Matrix Residues included in Risk Assessment Residues included in Tolerance Expression for Compliance Monitoring

Plants Cereal Grains Pyroxasulfone, M1, M3, M25 Pyroxasulfone, M1, M3, M25 ***

Soybeans Pyroxasulfone, M1, M3, M25, M28 ** Pyroxasulfone, M1, M3, M25 , M28*
Livestock Pyroxasulfone, M1, M3, M25, M28 Pyroxasulfone, M1, M3 Drinking Water Pyroxasulfone, M1, M3 Not Applicable Pyroxasulfone = 3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

- (trifluoromethyl)

- 1 H

- pyrazol

- 4

- yl]methyl]sulfonyl]

- 4,5

- dihydro

- 5,5

- dimethylisoxazole. M1 = [5

- (difluoromethoxy)

- l

- methyl

- 3

- (trifluoromethyl)

- l H

- pyrazol

- 4

- yl)]methanesulfonic acid. M3 = 5

- (difluoromethoxy)

- l

- methyl

- 3

- (tri fluoromethyl)

- l H

- pyrazole

- 4

- carboxylic acid. M25 = [5

- (difluoromethoxy)

- 3

- (trifluoromethyl)

- 1 H

- pyrazol

- 4

- yl)]methanesulfonic acid. M28 = 3

- [1

- carboxy

- 2

- (5,5

- dimethyl

- 4,5

- dihydroisoxazol

- 3

- ylthio)ethylamino]

- 3

- oxopropanoic acid. Metabolite C = 3

- [1

- carboxy

- 2

- (5,5

- dimethyl

- 4,5

- dihydroisoxazol

- 3

- ylthio)ethenylamino]

- 3

- oxopropanoic acid. * reanalysis of the seed samples showed residues of M28 and therefore M28 needs to be included in both the tolerance expression and risk assessment as a residue of concern in soybean seed

. M

- 1 is included for soybean forage and hay.

** residues of concern for soybean seed is p yroxasulfone and metabolite M

- 1, M

- 3, M

- 25, & M

- 28 for risk assessment and does not include M

- 1 for tolerance enforcement purposes

. ***residues of concern for wheat grain, cotton seed, corn, field, grain and corn, sweet, kernel p lus cob with husks removed is pyroxasulfone and metabolite M

- 3.



### 5.2 Food Residue Profile

### Page 24 of 82

5.2.1 Residues in Crops

K

- I Chemical submitted new field trial data from wheat and cotton field trials conducted in the U.S. The purpose of this study was to obtain Raw Agricultural Commodity (RAC) residue data for pyroxasulfone (KIH

- 485) and its metabolites M

- 1, M

- 3, M

- 25, and M

- 28 (in wheat grain only) o n wheat and cotton following a single application of pyroxasulfone for wheat and two applications for cotton

. The results from these field trials along are discussed below and summarized in Table s 5.2.1.1 and 5.2.1.2

.
For all studies, HED converted res idues of metabolites to parent equivalents for calculation of total residues; molecular weight conversion factors of 1.262 for M

- 1, 1.504 for M

- 3, 1.321 for M

- 25, and 1. 286 for M

- 28 were used. The full LOQ value was used for residues <LOQ for calculating total residues.

Table 5.2.1.1

. Summary of Residue Data from Wheat Crop Field Trials with Pyroxasulfone 85 WG. Crop matrix Target Applic. Rate (lb ai/A) [g ai/ha] PHI

(days) Total Residues of Pyroxasulfone and Metabolites M

- 1, M

- 3, and M

- 25, M

- 28 (ppm) 1

n Min. Max. HAFT 2 Median Mean Std. Dev. Wheat (proposed use = 0.134 lb ai/A total application rate) Wheat forage 0.134

[150] 3 22

- 72 14 <0.145 <3.428 <3.205 <0.949 <1.321 1.1 Wheat hay 53

- 118 14 <0.057 <0.74 <0.594 0.165 <0.246 0.17
Wheat Straw 63

- 129 14 <0.051 <0.478 <0.455 <0.135 <0.156 0.115
Wheat Grain 60

- 129 14 <0.064 <0.064 <0.064 <0.064 <0.064 0.000

1 For the purposes of calculating total residues, HAFT, median, mean, and standard deviation, the LOQ was used for residues reported as < LOQ. Metabolite residues were converted to parent equivalents. M

- 28 was only analyzed in wheat grain samples.
2 HAFT = Highest average field trial result.

Table 5.2.1.2

. Summary of Residue Data from Cotton Crop Field Trials with Pyroxasulfone 85 WG. Crop matrix Total Applic. Rate (lb ai/A) PHI

(days) Total Residues of Pyroxasulfone and Metabolites M

- 1, M

- 3, and M

- 25 1

n Min. Max. HAFT 2 Median Mean Std. Dev. 3

Cotton (proposed use = 0. 223 lb ai/A total seasonal application rate,
Cotton seed 0. 231

- 0. 245 30

- 69 12 <0.0 51 < 0. 056 < 0. 054 < 0. 051 < 0.0 51 0.0 01 Cotton gin byproducts 30

- 69 3 < 0.0 51 < 0. 109 < 0. 109 < 0. 076 < 0. 078 0.0 29

1 For the purposes of calculating total residues, HAFT, median, mean, and standard deviation, the LOQ was used for residues reported as <LOQ. Metabolite residues were converted to parent equivalents. 2 HAFT = Highest average field trial result.



### 5.3 Water Residue Profile

### Page 25 of 82

5.3. 1 Estimated Drinking Water Concentrations

Pyroxasulfone is mobile (average K oc 

### = 94.75) and persistent (t 1/2 

### = 142 to 533 days) in terrestrial and aquatic environments There are two major degradation products (> 10% of applied radioactivity) and 6 minor degradation products (<10 % of applied radioactivity) detected in laboratory metabolism studies. Additionally, there is a high percentage of applied radioactivity (8

- 25% of applied radioactivity) identified as “bo und” soil/sediment residues. Because the extraction of pyroxasulfone residues was conducted using only acetonitrile/water without the use of sequentially harsher soil extractants, there is uncertainty regarding the identity and availability of the “bound” soil residues.

The Environmental Fate and Effects Division ( 

### EFED ) conducted a drinking water assessment for the proposed uses of pyroxasulfone on cotton and wheat (D402603, J. Hetrick, 01/31/13 )

. These estimated drinking water concentrations (ED WCs) have identical to the EDWCs provided for the initial registration of pyroxasulfone. EFED provide d modeling

- based drinking water exposure estimates using the Tier II PRZM GW drinking water assessment from surface wat er sources for the proposed uses of pyroxasulfone. Residues of concern for drinking water for risk assessment purposes were parent, M1, and M3. E stimated drinking water residues for peak concentration of 0.210 mg/L (ppm) were used in the acute assessment . Estimated average drinking water concentrations of 0.174 mg/L (ppm) were used the chronic assessment

.

5

. 4 Dietary and Drinking Water Exposure and Risk

HED conducted screening

- level acute and chronic dietary and drinking water exposure and risk assessments using the Dietary Exposure Evaluation Model with the Food Commodity Intake Database (DEEM

- FCIDTM). Dietary risk assessment incorporates both exposure and toxicity of a given pesticide. For acute and chronic dietary assessments, the risk is expressed as a percentage of a ma ximum acceptable dose (i.e., the dose which HED has concluded will result in no unreasonable adverse health effects). This dose is referred to as the population adjusted dose (PAD). The PAD is equivalent to the reference dose (RfD) divided by the additio nal FQPA Safety Factor, if applied. For acute and non

- cancer chronic exposures, HED is concerned when estimated dietary risk exceeds 100% of the PAD.

P roposed use on wheat and cotton w as assessed for dietary and drinking water exposure. DEEM ® 

### residue i nputs for wheat and cotto n commodities used tolerance level residue s adjusted for metabolites which are not in the tolerance expression from specific use patterns for the acute and chronic dietary exposure analyses. Percent crop treated was set at 100 %.

5

. 4 .1 Acute Dietary and Drinking Water Analysis

A new dietary assessment was conducted for the proposed use. The proposed use results dietary risk estimates below HED’s level of concern; see Table 5.4.1

. The highest is All Infants <1 year resulting

### Page 26 of 82

in 3.6 % of the aPAD.

Table 5.4.1 . Results of Acute Dietary Exposure Analysis for Food and Drinking Water

Population Subgroup aPAD (mg/kg/day) 95th Percentile Exposure (mg/kg/day) % aPAD General U.S. Population

1.0 0.011743 1.2 All Infants (< 1 year old) 0.036358 3.6
Children 1

- 2 years old 0.018433 1.8
Children 3

- 5 years old 0.014987 1.5
Children 6

- 12 years old 0.011420 1.1
Youth 13

- 19 years old 0.009830 1.0
Adults 20

- 49 years old 0.011468 1.2
Adults 50

- 99 years old 0.010223 1.0
Females 13

- 49 years old 0.011618 1.2



### 5

. 4 .2 Chronic Dietary and Drinking Water Analysis

A new dietary assessment was conducted for the proposed use s of pyroxasulfone and results in dietary risk estimates below HED’s level of concern; see Table 5.4.2

.

Table 5.4.2 . Results of Chronic Dietary Exposure Analysis for Food and Drinking Water

Population Subgroup cPAD (mg/kg/day) Exposure (mg/kg/day) % cPAD General U.S. Population

0. 02 0.003812 19 All Infants (< 1 year old) 0.0 09660 48 Children 1

- 2 years old 0.00 5808 29 Children 3

- 5 years old 0.00 4876 24 Children 6

- 12 years old 0.003492 18 Youth 13

- 19 years old 0.002831 14 Adults 20

- 49 years old 0.003765 19 Adults 50+ years old 0.003695 19 Females 13

- 49 years old 0.003749 19



### 6 .0 RESIDENTIAL EXPOSURE AND RISK ASSESSMENT

A residential assessment is not required because there are no pyroxasulfone products registered for homeowner use and there are no products registered for application to residential areas.

### Page 27 of 82

6.1 Residential Bystander Post

- application Inhalation Exposure

Based on the Agency's current practices, a quantitative residential bystander post

- application inhalation exposure assessment was not performed for pyroxasulfone at this time. However, volatilization of pesticides may be a potential source of po st

- application inhalation exposure to individuals nearby to pesticide applications. The Agency sought expert advice and input on issues related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisor y Panel (SAP) in December 2009. The Agency received the SAP’s final report on March 2, 2010( http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html ). The Agency is in the process of evaluating the SAP report and may, as appropriate, develop polic ies and procedures, to identify the need for and, subsequently, the way to incorporate post

- application inhalation exposure into the Agency's risk assessments. If new policies or procedures are put into place, the Agency may revisit the need for a quantit ative postapplication inhalation exposure assessment for pyroxasulfone

.

6.2 Spray Drift

Spray drift is always a potential source of exposure to residents nearby to spraying operations. This is particularly the case with aerial application, but, to a les ser extent, could also be a potential source of exposure from the ground application method employed for pyroxasulfone

. The Agency has been working with the Spray Drift Task Force, EPA Regional Offices and State Lead Agencies for pesticide regulation and other parties to develop the best spray drift management practices (see the Agency’s Spray Drift website for more information at http://www.epa.gov/opp00001/factsheets/spraydrift.htm). On a chemical by chemical basis, the Agency is now requiring interim m itigation measures for aerial applications that must be placed on product labels/labeling. The Agency has completed its evaluation of the new database submitted by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is developing a policy on how to appropriately apply the data and the AgDRIFT computer model to its risk assessments for pesticides applied by air, orchard airblast and ground hydraulic methods. After the policy is in place, the Agency may impose further refinements in spray drift management practices to reduce off

- target drift with specific products with significant risks associated with drift.

7 .0 AGGREGATE EXPOSURE AND RISK ASSESSMENT

In accordance with the FQPA, when there are potential residential exposures to a pesticide, aggregate risk assessment must consider exposures from three major routes: oral, dermal, and inhalation. There are three sources for these types of exposures: food , drinking water, and residential uses. In an aggregate assessment, exposures from relevant sources are added together

### Page 28 of 82

and compared to quantitative estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can be aggregated. When aggregating ex posures and risks from various sources, HED considers both the route and duration of exposure. The proposed/registered pyroxasulfone uses are not expected to result in residential exposure. Therefore, the acute and chronic exposure estimates provided in the Dietary Exposure Section represent aggregate exposure.

7.1 Acute & Chronic Aggregate Risk

Acute and chronic aggregate exposures include food plus drinking water exposures. As demonstrated under Section 5

. 4, acute and chronic aggregate risks are not of concern.

8.0 CUMULATIVE RISK

Section 408(b)(2)(D)(v) of FFDCA requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider “available information” concerning the cumulative effects of a particular pesticide's residues and “other substances that have a common mechanism of toxicity.”

EPA does not have, at this time, available data to determine whether pyroxasulfone has a common mechanism of toxicity with other subs tances. Unlike other pesticides for which EPA has followed a cumulative risk approach based on a common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as to pyroxasulfone and any other substances and, pyroxasulfone does not appear to produce a toxic metabolite produced by other substances which have tolerances in the U. S. For the purposes of this tolerance reassessment action, therefore, EPA has not assumed that pyroxasulfone has a common mechanism of toxicity with other s ubstances. For information regarding EPA’s efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the policy statements released by EPA’s OPP concerning common mechanism deter minations and procedures for cumulating effects from substances found to have a common mechanism on EPA’s website at http://www.epa.gov/fedrgstr/EPA_PEST/2002/January/Day_16/

.

9 .0 OCCUPATIONAL EXPOSURE / RISK CHARACTERIZATION

9.1 Exposure Scenarios

Occupational handler and post

- application exposure scenarios were assessed for the registered use on soybean s . The proposed use s of pyroxasulfone on cotton and wheat have application rates ≤ the rate assessed in the soybean assessment. Therefore, the exposure to occupational

### Page 29 of 82

handler and post

- application exposure will not increase from the proposed uses. Based on the product labels and information provided by the registrant, short

- and intermediate

- term exposure is assessed for occupational handlers and post

- application activities. Dermal and inhalation exposures to workers are not aggregated for pyroxasulfone because the toxicity endpoints for these exposure routes are not based on common toxicological effects. Labels for both pyroxasulfone formulations require that applicators and other handlers wear long

- sleeved shirt and long pants, chemical resistant gloves and shoes and socks.

9

. 2 Handler Exposure

The term “handler” applies to individuals who mix, load, and apply the pesticide product. There is a potential for exposure to pyroxasulfone during mixing, loading, and application activities through the dermal and inhalation routes. Pyroxasulfone is app lied in the spring at preplant and preemergence growth stages and in the fall to minimum or no tillage fields to be planted the following spring. Pyroxasulfone products are applied using aerial, right of way and or handgun sprayers, as well as groundboom equipment. The following handler exposure scenarios evaluated for this assessment are based on information provided in the proposed labels.

9.2.1 Handler Exposure Scenarios

The term “handler” applies to individuals who mix, load, and apply the pesticide product. There is a potential for exposure to pyroxasulfone during mixing, loading, and application activities through the dermal and inhalation routes. Pyroxasulfone is app lied in the spring at preplant and preemergence growth stages and in the fall to minimum or no tillage fields to be planted the following spring. Pyroxasulfone products are applied using aerial, right of way and or handgun sprayers, as well as groundboom equipment. The following handler exposure scenarios evaluated for this assessment are based on information provided in the proposed labels.

9.2.1.1 Mixing and Loading Scenarios

• Mixing and Loading a water

- dispersible granule formulation for groundboom application. • Mixing and Loading a water

- dispersible granule formulation for aerial application.

9.2.1.2 Application Scenarios

• Applying a water

- dispersible granule formulation with groundboom equipment.

• Applying a water

- dispersible granule formulation with aerial equipment.

• Flagging for aerial application scenarios.

### Page 30 of 82

9.2.2 Handler Exposure Data

No chemical

- specific handler exposure data were submitted in support of this registration. It is HED’s polic y to use data from the USEPA OPP Occupational Pesticide Handler Unit Exposure Surrogate Reference Table (5/4/11). http://www.epa.gov/pesticides/science/handler

- exposure

data.htm l ).

9.2. 3 Handler Exposure Assumptions

• Average body weight of an adult handler is 8 0 kg.

• Exposure duration short

- term (1

- 30 days), intermediate

- term (1

- 6 months)

• Maximum label application rates:

- 0.21 lb ai/A for soybean

• Area treated:

- 1200 acres per day for aerial application

- 200 acres per day for groundboom application.

- 350 acres for flagging during aerial application scenarios.

- 9.2. 4 Handler Exposure and Risk Estimates

A t arget LOC or MOE of 100 is considered adequate for dermal and inhalation exposure . All worker exposures are assessed as short

- term based on label prescribed uses and expected exposure durations. Exposure and risk estimates indicate that for most exposure scenarios non

cancer risks are not of concern for occupational handler activities for the proposed new use (MOEs > 100) . H owever , risks of concern exist (MOE<100) for “Inhalation” exposure during mixing and loading activities for aerial applications A summary of occupational handler exposure and risk ca lculations, assumptions, and results is provided in Table 9.2.4

.

Table 9.2.4 . Short and Intermediate

- Term Occupational Handler Exposure and Risk for Pyroxasulfone

Exposure Scenario 1 Crop or

Target App

Rate (lb ai/A) 2 Acres

Treated Daily 3 Unit Exposure 3 Dose (mg/kg/Day) 4,5 Risk Estimation

Dermal (mg/lb ai) Inhalation

(μg/lb ai) Dermal Inhal MOEs 6,7

Dermal Inhal

### Page 31 of 82 BL Resp. PF5 Mixer/Loader ( water

- dispersible granule )

Groundboom Baseline

S oybean 0.21 200 0.227 8.96 0.1 19 0.004 7 84 0 4 30

Groundboom Gloves 0.052 8.96 0.0 271 0.004 7 3 ,7 00 43 0

Aerial Baseline 1200 0.227 8.96 0. 715 0.0 2 8 3 1 4 0 7 1 350

Aerial Gloves 0.052 8.96 0.1 63 0.0 2 8 3 6 10 71 350
Applicator ( water

- dispersible granule )

Groundboom Baseline S oybean 0. 21 200 0.0786 0.34 0.04 13 0.0002 2 ,4 00 110,0 00

Groundboom Gloves 0.0161 0.34 0.00 845 0.0002 1 20,0 00 110,000

Aerial Protected by Groundboom A pplication Flagging

Aerial S oybean 0. 2 1 350 0.0 11 0.35 0.010 1 0.000 3 9 ,9 00 6,2 00

1. Baseline and PPE unit exposure values are reported USEPA OPP Occupational Pesticide Handler Unit Exposure Surrogate Reference Table
2 Application rates based on proposed label rate.
3. Amount treated based on information provided ExpoSAC Policy 9
4. Dermal dose (mg/kg/event) = [unit dermal exposure (mg/lb ai) * application rate (lb ai/A) * Amount treated / body weight ( 8 0 kg)].
5 Inhalation dose (mg/kg/event) = [unit exposure (kg/lb ai) * (1mg/1000 kg) conversion * appl. rate (lb ai/lbs seed) * Amount treated / body weight ( 8 0 kg)].
6. Dermal MOE = short

- term endpoint for dermal (NOAEL 100 mg/kg/day)/Dermal Dose
7. Inhalation MOE = short

- term endpoint for dermal (NOAEL 2 mg/kg/day)/Inhalation Dose



### Note; Risk s of concern exist for the “mixing and loading” of a water dispersible granular for aerial applications (MOE = 71) with label specific PPE ( long

- sleeved shirt and long pants, chemical resistant gloves and shoes and socks). However, with a PF5 respirator, risks are not of concern (MOE = 350).

9.3 Post Application Exposure

HED uses the term “post

- application” to describe those individuals who can be exposed to pesticides after entering areas previously treated with pesticides and performing certain tasks or activities (also often referred to as reentry exposure). Post

- application exposures are expected to occur primarily via the dermal route. Based on current Agency's p ractices, a quantitative post

-

### Page 32 of 82

application inhalation exposure assessment was not performed. However, the Agency is in the process of evaluating available data and information on post

- application inhalation exposure. If new policies or procedures are put into place based on that evaluation, the Agency may revisit the need for a quantitative occupational post

- application inhalation exposure assessment for pyroxasulfone

. Minimal exposure during harvesting or other late season activities is expected for pre

- emergent applications of pyroxasulfone for the following reasons. Preemergence herbicides are applied to the surface soil directly or are incorporated into the soil well before the crops mature. Pyroxasulfone is proposed for use on the high acreage fiel d crop soybean. This c rop is mechanically planted early in the season which minimizes the potential for dermal contact. Based on these considerations, HED does not require a post

- application occupational exposure assessment for pre

- emergent herbicides u sed on crops that are mechanically planted (HED Exposure Science Advisory Council Policy No. 008). However, there is potential exposure to persons entering treated sites after application of pyroxasulfone as an early post

- emergence herbicide to soybean (a pplication up to third trifoliate leaf stage). Consequently, post

- application exposure from early post

- emergence uses is assumed to occur during minimum foliage development for soybean (ExpoSAC Policy No. 003.1).

9.3.1 Post Application Exposure Scenarios

The following post

- application exposure scenarios were assessed for proposed post

emergence uses of pyroxasulfone.

• Hand weeding soybean at low crop height and minimum foliage development

Note: B ased on label specific directions, the application method and timing for soybeans is preplant and pre

- emergence only . Therefore the TC of 70 for “hand weeding” was appropriate because the crop height is low with minimal foliage. However, since pyroxasulfone is used to control a broad spectrum of broadleaf weeds and grasses, therfore scouting will be the activity associated with this TC.

In accordance with the Worker Protection Standard (WPS), a 12

- hr restricted entry interval (REI) is required for chemicals classified under Toxicity Categ ory III/IV.

9.3.2 Post Application Exposure Assumptions

No chemical

- specific handler exposure data were submitted in support of this registration. Therefore, agricultural transfer coefficients used for this assessment are taken from HED’s Science Advisory Council for Exposure Policy on Agricultural Transfer Co efficients (SOP # 003.1, 8/7/00).

### Page 33 of 82

• Average body weight of an adult handler is 8 0 kg.

• Exposure duration is short

- term (1

- 30 days)

• Maximum label application rates:

- 0.21 lb ai/A for soybean

• T ransfer Coefficients:

- 70 cm 2 

### /hour for scouting immatu re soybean crop

• Initial fraction of ai retained on foliage is 2 5 %

• Exposure is assumed to occur on the day of application (day 0)

9.3.3 Post

- Application Exposure and Risk Estimates

A target LOC or MOE of 100 is considered adequate for dermal exposure. Exposure and risk estimates indicate post

- application risks are not of concern (MOEs > 100) as shown on Table 9.3.3

.

Table 9.3.3

. Estimated Pyroxasulfone Exposure & MOEs for Occupational Post

- Application Exposure
Exposure Scenario App Rate

(lb ai/A) 1 DFR

( μ g/cm 2 ) 2 TC

(cm 2 /hr) 3 Exposure Duration

(hrs/day) Dermal dose

(mg/kg/day) 4 MOE 5

Soybean

- Scouting immature plants 0.21 0. 589 70 8 0.00412 24,000

1 Application rates are based on maximum values based on proposed label.
2 DFR (mg/cm 2 ) = Dislodgeable Foliar Residues corresponding to day 0. Application Rate (lb ai/A) x CF (4.54E+5 mg/lb) x CF (2.47E

- 8 A/ cm 2 ) x 2 5 % (initial fraction of ai retained on fo liage) 3 TC cm 2 /hr = Transfer coefficients and associated activities (ExpoSAC Policy Memo #003.1)
4 Dermal Dose (mg/kg/day) = DFR (mg/cm 2 ) x TC (cm 2 /hr) x 8 (hrs/day) / Body weight ( 8 0 kg).
5 Dermal MOE = short

- term endpoint for dermal (NOAEL 100 mg/kg/day )/Dermal Dose



### 9.3. 4 Restricted Entry Interval

P yroxasu l fone has been classified in Toxicity Category III for acute dermal and Category IV for eye irritation and primary skin irritation. Per the Worker Protection Standard (WPS), a 12

- hr restricted entry interval (REI) is required for chemicals classified under Toxicity Category III/IV.

9.3.5 Inhalation Post

- application Risk

Based on the Agency's current practices, a quantitative occupational postapplication inhalation exposure assessment was not performed for pyroxasulfone at this time. However, there are multiple potential sources of post

- application inhalation exposure to individuals performing post

application activities in previously treated fields. These potential sources include volatilization

### Page 34 of 82

of pesticides and resuspension of dusts and/or particulates that contain pesticides. The Agency sought expert advice and input on issues related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (SAP) in December 2009. The Agency received the SAP’s final report on March 2, 2010 ( http://www.epa.gov/scipoly/SAP/m eetings/2009/120109meeting.html ). The Agency is in the process of evaluating the SAP report as well as available post

- application inhalation exposure data generated by the Agricultural Reentry Task Force and may, as appropriate, develop policies and proce dures, to identify the need for and, subsequently, the way to incorporate occupational post

- application inhalation exposure into the Agency's risk assessments. If new policies or procedures are put into place, the Agency may revisit the need for a quantit ative occupational post

- application inhalation exposure assessment for pyroxasulfone

.

10. REFERENCES

Pyroxasulfone. Application for Section 3 Registration for Use on Wheat and Cotton

– T. Morton, D 40 2249

, 7 / 24 / 1 3

Pyroxasulfone. Acute and Chronic Aggregate Dietary Exposure and Risk Assessments for the Section 3 Registration Request for Use of Pyroxasulfone on Wheat and Cotton

. – T. Morton, D 4 10009

, 7/24/13

Pyroxasulfone, Herbicide End

- Use Product: V

- 10233 , Fierce TM Herbicide and Pyroxasulfone 85 WG Herbicide, Herbicide Drinking Water Assessment of Pyroxasulfone Proposed Use on Cotton.

– J. Hetrick, D 402603

, 1 / 3 1/201 3

Pyroxasulfone: Occupational and Residential Exposure Assessment for Proposed Uses on Cotton and Wheat.

– J. S

. Miller , D 413467

, 7 /24/13

### Page 35 of 82

APPENDICES

A TOXICOLOGY DATA SUMMARY

A .1 Guideline Data Requirements The requirements (40 CFR 158.340) for food use for pyroxasulfone are in Table 1.

Guideline No. Study Type Technical MRID No. Required Submitted

870.3100

870.3150

870.3200 870.3250 870.3465 Subchronic (Oral) Toxicity

- Rodent

................................ ...............................

Subchronic (Oral) Toxicity

- Non

- Rodent

................................ ......................

21/28

- Day Dermal Toxicity

................................ ................................ ............ 90

- Day Dermal Toxicity 90

- Day Inhalation Toxicity

................................ ................................ ............. Y

Y

N N N Y

Y

Y N Y 47701692

47701693 47701694 47701695 47701696 47701697 47701698

--- 47701699

870.3700a

870.3700b

870.3800 Prenatal Developmental Toxicity

- Rodent

................................ .....................

Prenatal Developmental Toxicity

- Non

- Rodent

................................ ............. Reproduction and Fertility Effects

................................ ................................ .. Y

Y

Y Y

Y

Y 47701701

47701702 47701703 47701704 47746840 47701705 47701706

870.4100a 870.4100b 870.4200a 870.4200b 870.4300 Chronic (Oral) Toxicity

- Rodent

................................ ................................ ....

Chronic (Oral) Toxicity

- Non

- Rodent (Dog)

................................ ................. Carcinogenicity

- Rat Carcinogenicity

- Mouse Combined Chronic Toxicity /Carcinogenicity

................................ ................ Y N N Y Y Y

Y N Y Y 47701708

47701707

--- 47701710 47701709

870.6100a 870.6100b 870.6200a 870.6200b 870.6300

870.7800 Neurotoxicity

- Acute Delayed Neurotox.

- Hen

................................ ..............

Neurotoxicity

- Subchronic

- Hen

................................ ................................ .. Neurotoxicity Screening Battery

- Acute

- Rat

................................ ............... Neurotoxicity Screening Battery

- Subchronic

- Rat

................................ ........ Developmental Neurotoxicity..................

Immunotoxicity.............................

................................ ......................... N N Y Y N

Y N

N Y Y Y

Y ---

--- 47701721 47701722 47701723 47701724 47701731 47701732

### Page 36 of 82

A.2 TOXICITY PROFILES

A.2.1 Acute Toxicity

Table A.2.1.1 Acute Toxicity Profile

– Pyroxasulfone Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral

– rat (females) 47701677 LD 50 = >2000 mg/kg III 870.1200 Acute dermal

– rat 47701684 LD 50 >2000 mg/kg M & F III

870.1300 Acute inhalation

– rat 47701685 LC 50 >6.56 mg/L M & F IV 870.2400 Acute eye irritation

– rabbit 47701686 Minimally irritating IV 870.2500 Acute dermal irritation

– rabbit 47701687 Non

- irritating IV 870.2600 Skin sensitization

– local lymph

node

- mice 47701688 No sensitization

-

TableA.2.1.2 Acute Toxicity Profile

– Pyroxasulfone Metabolites Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral

– rat (females) M

- 1 47701678 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) M

- 3 47701679 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) M

- 25 47701680 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) M

- 28 47701755 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) I

- 3 47701681 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) I

- 4 47701682 LD 50 = >2000 mg/kg III 870.1100 Acute oral

– rat (females) I

- 5 47701683 LD 50 = >2000 mg/kg III

### Page 37 of 82

A.2.2 Subchronic, Chronic, Other Toxicity

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.3050 28

- Day Dietary

toxicity

– Han Wistar Rat
5 rat/sex/dose 47701689 (2003), Covance

Labs 0, 500, 5000, 20,000 ppm M: 64.3, 649.6, 2677.5 mg/kg/day F: 62.2, 673.9, 2584.7 mg/kg/day Acceptable/guideline NOAEL = 500 ppm (64.3/62.2 mg/kg/day in males/females) LOAEL = 5000 ppm ( 650/674 mg /kg/day in males/females) based on hepatocyte and myocardial vacuolation; myocardial degeneration.

Non

- Guideline Special Study 28

- Day Dietary

toxicity

– Rat Myocardial toxicity and enzyme markers
5 rat/sex/dose 47889320 (2004)

Covance Labs 0, 100, 1000, 5000, 20000
ppm M: 7.3, 75.4, 367.2, and 1364.0 mg/kg/day F: 8.3, 84.4, 388.0, and 1676.1 mg/kg/day

Acceptable/Non

- Guideline Aspartate aminotransferase was increased by 138% in the 20,000 ppm females on Day 22. On Day 29, increases in aspartate aminotransferase were noted in the 5000 (incr 150%) and 20,000 (incr 93%) ppm females. On Day 29, increases in lactate dehydrogenase were observed in the 5000 ppm group (incr 119

- 167%) and 20,000 ppm group (incr 57

- 87%). Decreases (p≤0.05) in alanine ami notransferase and creatinine phosphokinase were observed, but were not considered toxicologically relevant. hepatic lesions were noted at 1000 ppm and above and 20,000 ppm females myocardial degeneration/necrosis in the 1000 ppm and above males and fem ales, vacuolation in 5000 and 20,000 ppm males and fibrosis in 20,000 ppm males and females. CPK enzymes were not predictive markers of myocardial toxicity.

870.3100 90

- Day oral toxicity

-

Han Wistar Rat 10 rats/sex/dose,
5 rats/sex/dose for
recovery 47701692(2005); Covance

Labs 0, 100, 500, 2500, 5000 ppm; M: 0, 8.9, 43.9, 221.4, 451.2 mg/kg/day; F: 0, 10.2, 48.9, 255.8, 514.2 mg/kg/day Acceptable/guideline NOAEL 500 ppm (44/49 mg/kg/day in M/F) LOAEL = 2500 ppm (221/256 mg/kg/day in M/F) based on either altered organ weights, histopathological indicators or clinical pathological indicators in liver, skeletal and cardiac muscle and the pancreas (liver centrilobular hepatocyte hypertrophy and eosinophilia in m ales, a dose related increased incidence of myocardial degeneration or necrosis in the heart of males and skeletal muscle myopathy in females). Full or partial recovery was evident in all the above effects apart from kidney weights in females.

### Page 38 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.3100 90

- Day oral toxicity

-

Crl:CD®(SD)IGS BR
rats
10 rats/sex/dose 47701693 (2005) Haskell

Labs 0, 25, 250, 2500 ppm M: 0, 1.7, 16.4, 171.2 mg/kg/day F: 0, 2.20, 20.6, 205.4 mg/kg/day Acceptable/guideline NOAEL = 250 ppm (16/21 mg/kg/day in males/females) LOAEL = 2500 PPM (171/205 mg/kg/day in males and females, based on increased liver weight, centrilobular hepatocellular hypertrpophy, focal/multifocal myofiber degeneration and inflammation, urinary bladder diffuse mucosal hyperplasia.

870.3100 90

- Day oral toxicity

B6C3F1 mouse
12 mice/sex/dose 47701694 (2005); Covance

Labs 0, 500, 1000, 5000, 10000/7500 ppm; M: 0, 103, 206, 1424, 2494 mg/kg/day; F: 0, 96, 202, 1228, 1941mg/kg/day Acceptable/guideline NOAEL = 1000 ppm (equivalent to 206/202 mg/kg/day, M/F) LOAEL = 5000 ppm (1424/1228 mg/kg/day in males/females) based decreased body weight, changes in clinical chemistry parameters, changes in organ weights (including increased kidney and liver weights), and microscopic effects in the kidney (cortical tub ular nephropathy) and heart (myocardial degeneration/fibrosis). Target organs at 5000 ppm and above are heart, liver, kidney.

870.3100 90

- Day oral toxicity

B6C3F1 mouse
10 mice/sex/dose 47701695 (2005); Haskell

Labs 0, 25, 250, 2500 ppm M: 4.0, 39.8, 394 mkd F: 5.4, 51.2, 531.3 mkd Acceptable/guideline NOAEL = 250/2500 ppm in females /males (51.2/394 mg/kg/day in females /males). LOAEL = 2500 ppm in females (equivalent to 531 mg/kg/day) based on an increased incidence of chronic
progress ive nephropathy (minimal to mild), multifocal tubules lined by basophilic epithelium indicative of tubular regeneration in females. LOAEL in males is >2500 ppm (394 mg/kg/day).

870.3150 90

- day oral toxicity

–

Dog 4 dogs/sex/dose 47701696 (2004); Biosafety

Research Center, Japan 0, 0.2, 2.0, 10.0 mg/kg/day in gelatin caps Acceptable/guideline NOAEL = 2 mg/kg/day LOAEL =10 mg/kg/day. Slight muscle fiber degeneration of the diaphragm and hyperplasia of satellite cells; nerve fiber degeneration, in a ddition to the similar adverse effects occurring at 15 mg/kg/day dose in a subsequent 90

- day dog study (MRID 47701697).

870.3150 90

- day oral toxicity

–

Dog 4 dogs/sex/dose 47701697 (2006); Haskell

0, 15 mg/kg/day in gelatin
caps Acceptable/guideline LOAEL = 15 mg/kg/day: Decreased BW gain (↓40%) in males; Minimal to mild axonal/myelin degeneration in the sciatic nerve of all males and 3⁄4 females. Minimal to mild subacute inflammation of skeletal muscle in males and females. Impaired limb function, bod y and limb hypotonia, increase in serum creatine kinase activity.
870.4100 1

- yr oral toxicity

–

Dog 4/dog/sex/dose 47701707 (2008) MPI

Research (Mattawan Michigan) 0, 0.2, 2.0, 10.0 mg/kg/day in gelatin caps Acceptable/guideline NOAEL = 2 mg/kg/day
LOAEL = 10 mg/kg/day based on impaired hind limb function, ataxia, hind limb twitching and tremors; clinical pathology: increased creatine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections

### Page 39 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.3465 4

- week inhalation

–

Rat
10/sex/dose 47701699 (2008)

– Dupont

0, 10 40, 200 mg/m 3 /day aerosol dust/nose only Acceptable/guideline NOAEL = 200 mg/ m 3 /day based on lack of adverse toxic effects at this HDT.

870.3200 28

- Day dermal

– Rat

10/sex/dose 47701698 (2005)

Dupont 0, 20, 100, 1000 mg/kg/day Acceptable/guideline NOAEL = 100 mg/kg/day LOAEL = 1000 mg/kg/day based on minimal to mild cardiac myofiber degeneration with inflammation in males and females

870.3700a Prenatal

developmental in (rat) Crj:CD (SD)IGS[SPF] Range finding
7/dose 47701701 (2004) Biosafety

Res. Ctr. Japan 0, 125, 250, 1000 mg/kg GD 5

- 19 Acceptable/non

- guideline NOAEL for maternal and developmental toxicity = 1000 mg/kg/day (HDT) unossified hyoids at 1000 mg/kg/day and this finding was not considered to be an unequivocally treatment

- related effect

870.3700a Prenatal

developmental in Crl:CD(SD) (rat)
22 rats/dose 47701702 (2007) Haskell

0, 100, 50, 1000 mg/kg/day on GD 6

- 20 Acceptable/guideline NOAEL for maternal and developmental toxicity = 1000 mg/kg/day (HDT)

870.3700b Prenatal

developmental in (rabbit) ) Range finding
7/dose 47701703 (2004) Covance

0, 250, 500, 1000 mg/kg/day on GD 7

- 28 Acceptable/non

- guideline NOAEL for maternal and developmental toxicity = 1000 mg/kg/day (HDT)

870.3700b Prenatal

developmental in (rabbit) 22/dose 47701704 (2007) Haskell

0, 250, 500, 1000 mg/kg/day on GD 7

- 28 Acceptable/guideline Maternal toxicity NOAEL = 1000 mg/kg/day (HDT) Developmental toxicity NOAEL = 500 mg/kg/day LOAEL = 1000 mg/kg/day reduced fetal weight and increased fetal resorptions

### Page 40 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.3800 Reproduction and

fertility effects (rat) Crl:CD®(SD)IGS BR
One

- Gen Study 12/sex/dose Range

- finding 47701705 (2006)

Dupont Haskell 0, 25, 250, 5000 ppm
P M premating 1.69,16, 339 mg/kg/day P F premating 1.98, 19.6, 383 mg/kg/day P F gestation 1.78, 18, 332 mg/kg/day P F lactation 3.82, 37.9, 728 mg/kg/day F1 M postweanling 2.73, 27.9, 564 mg/kg/day F1 F postweanling 2.99, 30.4, 643 mg/kg/day Acceptable/nonguideline Parental toxicity NOAEL = 250 ppm (16/20 mg/kg/day M/F) LOAEL = 5000 ppm, (339/383 mg/kg/day) reduced body weight and gain and food consumption, cardiac myofiber and sciatic nerve lesions, microscopic effects in the heart, liver, muscle, and sciatic nerve of males and females Reproductive toxicity NOAEL = 5000 ppm (339 mg/kg/day) (HDT) Offspring toxicity NOAEL = 250 ppm (16/20 mg/kg/day) LOAEL = 5000 ppm (339 mg/kg/day) reduced pup weigh t during lactation (27%

- 30% lower than control mean) and delayed sexual maturation in both sexes.

870.3800 Reproduction and

fertility effects (rat) Crl:CD®(SD)IGS BR
2

- gen study 30/sex/dose 47701706 (2008)

Dupont Haskell 0, 5, 100, 2000 ppm
Mean substance intake 0.4/0.4, 7.2/8.4, 144/165 mg/kg/day for Males/Females Acceptable/guideline Parental toxicity NOAEL = 100 ppm (7.2/8.4mg/kg/day) LOAEL = 2000 ppm (144/165mg/kg/day) reduced body weight, body weight gain and food consumption and increased kidney weight, cardiomyopathy and urinary bladder mucosal hyperplasia with inflammation. Reproductive toxicity NOAEL = 2000 ppm (135 mg/kg/day) (HD T) Offspring toxicity NOAEL = 100 ppm (11 mg/kg/day) LOAEL = 2000 ppm (144/165 mg/kg/day) reduced pup weights and body weight gains during lactation

### Page 41 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.4200b Carcinogenicity

(mouse) Crl:CD1(ICR) mice 50+10/sex/dose 47701710 (2009)

Dupont Haskell 0, 5, 150, 2000 ppm After 14 months 2000 ppm reduced to 1000 ppm for M and 500 ppm for F. M: 0, 0.63/0.61, 18.33/18.56, 255.13/131.34 mg/kg/day F: 0, 0.88/0.71, 26.33/22.44, 371.64/76.49 mg/kg/day
Overall mean 0, 0.62/0.84, 18.4/25.5, 228/306, M/F Acceptable/guideline NOAEL = 150 ppm ( 18.4/25.5 mg/kg/day) (M/F)
LOAEL = 228/306 mg/kg/day M/F, based on degeneration of sciatic and trigeminal nerve axons and their associated myelin sheaths and an increase in the incidence of chronic progressive nephropathy (females). R enal tubular adenomas at this dose in 3 of 50 main study males, in the presence of a 17% reduction of body weight gain compared to control males.
The test substance was considered initially oncogenic in male mice. Revaluation of the renal tubular adenomas of the male mice was conducted by an independent kidney expert pathologist (MRID 48354403) and reviewed by a Pathology Working Group (MRID 48354405). The renal tubular adenomas observed in male mice were considered by the PWG t o be incidental and unrelated to the administration of pyroxasulfone. A dose

- related increase in retrograde nephropathy in males was also identified.
870.4100 One year chronic

(Rat)
20 rats/sex/dose 47701708 (2008)

Dupont Haskell 0, 5, 50, 1000, 2000 ppm M: 0, 0.22, 2.22, 46.2, 91.91 mg/kg/day F: 0, 0.3, 3.12, 60.80, 121.33 mg/kg/day Acceptable/guideline NOAEL = 50 ppm mg/kg/day. LOAEL = 1000 ppm or 46.2/60.8 mg/kg/day (M/F) based on reduced body weight parameters in males (↓ 5

- 10%) and microscopic findings in the liver (centrilobular hepatocellular hypertrophy (males)), heart (increased cardiomyopathy (females)) and urinary bladder (mucosal hyperplasia (males and females)). At 2000 ppm, these effects were accompanied by increased clinical observati ons of red discharge from the penis and associated red

- stained cage boards as well as increased liver and kidney weights.
870.4200a Carcinogenicity

(rat) 70/sex/dose 47701709 (2009)

Dupont Haskell 0, 5, 50, 1000, 2000 ppm M: 0, 0.21, 2.05, 42.55, 84.55 mg/kg/day F: 0, 0.28, 2.69, 54.28, 106.74 mg/kg/day Acceptable/guideline NOAEL = 50 ppm or 2.05/2.69 (M/F) mg/kg/day LOAEL = 1000 ppm or 42.55/54.28 (M/F) mg/kg/day based on reduced body weight parameters (males and females), reduced food consumption (females), and increased red

- stained urine on cageboards (males) at 2000 ppm and reduced body weight and food consumption parameters (females) and increased red

- stained urine on cageboards (males) at 1000 ppm. Increased cardiomyopathy (males and females); urinary bladder mucosal hyperplasia, inflammation, and transitional cell papillomas (males); and sciatic nerve degeneratio n (females) at 1000 ppm and above. Based on a low incidence in urinary bladder transitional cell papillomas in the 1000 ppm and 2000 ppm males , the test substance was considered oncogenic in male rats at exposures of 1000 ppm and above.

### Page 42 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.5100 Bacterial reverse

mutation test 47701712 (2003), Covance

TA98, TA1535 and TA1537

- S typhimurium & WR2 uvrA of E coli Acceptable/guideline Test article has no reverse mutagenic potential under these experimental conditions either in the presence or absenc e of metabolic activities. Precipitation of the test article was observed on all E coli test plates treated at 1581 μg/plate, and on all S typhimurium test plates treated at 632.4 μg/plate and above.

870.5380 In vivo studies in

germ cells

- Mammalian spermatogonial chromosomal aberration test NA Because all other genotoxicity studies are negative, no studies for this data point were performed with regulatory agency concurrence per 28 February 2009 OECD meeting.

870.5550 In vivo genotoxicity

testing

– Unscheduled DNA synthesis NA Because all other genotoxicity studies are negative, no studies for this data point were performed with regulatory agency concurrence per 28 February 2009 OECD meeting.

870.5300 In vitro mammalian

cell gene mutation test: Mouse Lymphoma L5178Y Cells 47889311 (2009)

Huntingdon Acceptable/guideline Pyroxasulfone TGAI was tested up to the limit of solubility and up to cytotoxic effects and was not mutagenic in the presence or absence of S9

- activation.

870.5375 In vitro mammalian

cell chromosome aberration test, CHO cells 47701719 (2003) , Covance

Acceptable/guideline Test article did not induce chromosome aberrations in cultured (CHO) cells when tested up to its limit of solubility in both the absence and presence of metabolic activation (S

- 9).

870.5395 Mammalian

erythrocyte micronucleus test 47701720 (2007), Dupont

500, 1000, 2000 mg/kg orally to male and female mice Acceptable/guideline Under the conditions of this study, KIH

- 485TGAI did not induce biologically relevant increases in micronucleated polychromatic erythrocytes in animal bone mar row. The test substance was concluded to be negative in this in vivo study.

870.6200a Acute neurotoxicity

screening battery Crl:CD(SD) rat
10/sex/dose 47701721 (2007), Dupont

0, 20, 200, 2000 mg/kg Acceptable/guideline NOAEL = 2000 mg/kg/day in males and females (HDT).

870.6200b Subchronic

neurotoxicity screening battery Crl:CD(SD) rat
12/sex/dose 47701722 (2007), Dupont

0, 25, 250, 2500 ppm M: 0, 1.56, 15.85, and 161.48 mg/kg/day F: 0, 1.92, 19.60, and 199.59 mg/kg/day Acceptable/guideline Systemic NOAEL = 2500 ppm or 161/200 mg/kg/day (M/F), the HDT Neurotoxicity NOAEL = 2500 ppm or 161/200 mg/kg/day (M/F), the HDT

### Page 43 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.6300 DNT Study

Crl:CD(SD) rat Preliminary Range Finding
8 mated females/dose 47701723 (2007),

Huntingdon 0, 100, 300, 600, 1000 mg/kg/day GD6

- LD7; Offspring Day 7

- 20 of age Acceptable/nonguideline There was no effect of maternal treatment, or direct treatment of the offspring with KIH

- 485, on the clinical condition, survival, or macropathology findings of the dams or the offspring. Treatment of adult females at 1000 mg/kg/day was associated with up to 16% lower mean numbers of implantations and litter sizes at birth and on Day 4. The use of a dose above 1000 mg/kg/day may be associated with a more marked reduction in the implantation rate and litter size sufficient to preclude a meaningful evaluation of developmental neurotoxicity in the offspring. Treatment at 600 mg/kg/day was associated with up to 8% lower mean numbers of implantations and l itter size at birth.

870.6300 DNT Study

Crl:CD(SD) rat
24 mated females/dose 47701724 (2008),

Huntingdon 0, 100, 300, 900 mg/kg/day GD6

- LD7; Offspring Day 7

- 20 of age (EPA reviewed protocol) Acceptable/guideline Maternal NOAEL = 900 mg/kg bw /day (HDT), the LOAEL was >900 mg/kg/day. Functional development NOAEL = 900 mg/kg/day. Offspring NOAEL = 100 mg/kg/day based on decrease in brain weight in male and female offspring accompanied with a decrease in the thickness of the hippocampus,
corpus c allosum and cerebellum in PND 21 female offspring at 300 mg/kg/day

870.7800 Immunotoxicity

Feeding Study in mice
10/mice/sex/dose 47701732 (2008)

Dupont 0, 40, 400, 4000 ppm for 28 days M: 0, 6, 61, 633 mg/kg/d F: 0, 8, 77, 791 mg/kg/d Acceptable/guideline Systemic toxicity NOAEL = 61/77 (M/F) mg/kg/day LOAEL = 633/791 (M/F) mg/kg/day based on reduction in body weight (

- 5 to

- 9%) and body weight gain (

- 32%) Immunotoxicity: NOAEL = 633/791 (M/F) mg/kg/day (HDT) based on absence of immun otoxic effects.

870.7800 Immunotoxicity

Feeding Study in rats
10/rats/sex/dose 47701731 (2006)

Dupont 0, 25, 250, or 7500 ppm for 28 days (0/0, 2/2, 18/19, and 529/570 mg/kg/day in males/females). Acceptable/guideline Systemic toxicity NOAEL = 250 ppm (18/19 mg/kg/day M/F) LOAEL = 7500 ppm (529/570 (M/F) mg/kg/day based on reduction in body weight gain (

- 30% to

- 56%) and food consumption (

- 19% to

– 52%) Immunotoxicity: NOAEL = 529/570 (M/F) mg/kg/day (HDT) based on absence of immunotoxic effects.

870.7600 Dermal penetration NA Not required for US or Australia and waived for Canada per 28 February 2009 OECD meeting.

### Page 44 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.7485 Metabolism and

pharmacokinetics (beagle dog) 47701726 (2005),

Covance One female dog: single oral dose of 10 mg of pyrazole

14 C /kg bw, urine and feces were collected over 120 h. Sequential blood samples were and the dog was killed at 120 h after dosing. The level of radioactive residues was determined in the blood, plasma, and selected tissues (heart, kidney and liver) at

necr opsy. The excreta were analyzed to determine the number and nature of any metabolites present using HPLC and HPLC/MS. Acceptable/nonguideline Overall recovery of radioactivity was 98%. Oral absorption of radioactivity was at least 51%. The majority of the radioactivity (76.9%) was eliminated in the first 24 h. The radioactivity was equally excreted in urine and feces. C max was of 3.954 and 2.116 μg equivalents/g at 8 h in blood and plasma respectively and were still quantifiable at 120 h. The terminal h alf

- life was of 89.58 and 40.80 h in blood and plasma respectively. The levels of radioactivity in the tissues were highest in the liver and blood (0.334 and 0.327 μg equivalents/g, respectively). The kidney, plasma and heart contained the next highest

co ncentrations. The feces contained only unchanged KIH

- 485. Urine contained no parent compound. HPLC chromatography showed that there were several metabolites, some of which were changed following treatment with ß

- D

- glucuronidase. Metabolites M

- 3, M

- 7

a nd M

- 8 were identified in the dog, though M

- 3 was only a minor metabolite. Structures were proposed for three other metabolites.

870.7485 Metabolism and

pharmacokinetics (Mouse) 47701730 (2007)

Huntingdon single oral dose of 10 mg pyrazole

14 C pyroxasulfone/kg bw, Autoradiography: 4 ♀ Excretion/balance:3 ♀ Tissue distribution: 12 ♀ Acceptable/nonguideline KIH

- 485 was rapidly absorbed, metabolized and eliminated. ~ 78% excreted in the urine after 120 hours (about 73% was excreted within the fi rst 24 hours). The remainder in the feces. Only about 0.2% of the dose was retained in the tissues. Fifteen metabolites were resolved by the chromatographic and three products resulting from oxidative phase I processes (KIH

- 485

- MI, KIH

- 485

- M3 and KIH

- 485

- 13) were identified by co

- chromatography. One minor metabolite was identified as a glucuronide or sulfate conjugate. KIH

- 485 itself was not present in urine. Concentrations of total radioactivity in the liver and heart were highest at the earliest sacrifice time of 2 hours: 3.186 μg KIH

- 485 equivalents/g in the liver and 0.603 μg KIH

485 equivalents/g in the heart. After 48 hours these levels had declined to 0.430 and 0.031 μg KIH485 equivalents/g, respectively.
Whole

- body autoradiography showed. At 2 hours after dosing, radioactivity had been absorbed from the GI tract and was distributed into the vast majority of tissues. High concentrations in the liver and gallbladder were consistent with an appreciable first

- pass elimination of 14 C

- KIH

- 485 and/o r its metabolites by the liver, followed by biliary excretion. Low radioactivity concentrations were associated with the bone surfaces, brain, spinal cord and the lens of the eye. By 24 hours after dosing, radioactivity concentrations in the majority of ti ssues (including the central nervous system) were close to

, or indistinguishable from, background levels.

### Page 45 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.7485 Metabolism and

pharmacokinetics (rat) 4/sex/group 47701728 (2008)

Covance Single oral dose 10, 700 mg/kg of either the pyrazole

14 C or the isoxzzoline

14 C radiolabel Acceptable/guideline 91

- 104% recovery. Absorption at the low dose based on bile and urine >76% AD. Cmax 2 hrs at low dose, 11 hrs at the high dose. T 1/2 longer for the IX label. Saturation of absorption with increasi ng dose; a 70

- fold dose level increase produced a 10

- fold increase in C max and a 20 to 50

- fold increase in AUC (0

- t) with [Py

14 C]

- KIH

- 485, and a 20

- fold increase in C max and a 10

- fold increase in AUC (0

- t) with [Ix

14 C]

- KIH

- 485. Excretion rapid and complet e within 48

- 72 hrs. Low dose animals’ excretion mostly in urine. High dose animals mostly in feces. Residual in carcass <7% in low dose and <0.5% in high dose. No significant sex differences in elimination or metabolism. No significant 14 CO2 elimination . Liver and kidney highest residues. Extensive metabolism ~30 chromatographic regions in urine, 19 in feces, 31 in bile. Major metabolite of [Py

14 C] urine was M

- 13 (up to 26% of the low dose level and up to 4% at the high dose level) followed by M

- 7 an d M

- 3. Cleavage between the pyrazole and isoxazoline ring structure. Major metabolites of [Ix

14 C]

- compound in the urine were M

- 13 (20% of the dose), M

- 16 (19% of the dose) and M

- 26 (6.4% of the dose). The major fecal radioactivity was unabsorbed KIH

- 485 (10% of the dose at the low dose level and up to 78% at the high dose level). The next most abundant metabolite was M

- 13 (up to 3% of the dose). In bile of the [Py

14 C] rats a sulphate conjugate of hydroxy KIH

- 485 and M

- 13 glucuronide accounted for up
to 3.1% of the dose each plus free M

- 13 metabolite (~ 1.6% of the AD). [Ix

14 C]

- KIH

- 485 bile, M

- 26 (10% of the AD) tentatively identified and was produced by the cleavage of the pyrazole ring and subsequent loss of the fluorine moieties. A sulphate conjugate of hydroxy KIH

- 485 (7%) and the other M

- 13 glucuronide (3%). A glutamyl cysteine conjugate of the isoxazoline ring (4%) was tentatively identified.

### Page 46 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.7485 Metabolism and

pharmacokinetics (rat) 47701729 (2008)

Covance Steady State: 10mg/kg/day to 4 females of the pyrazole

14 C for 14 days Pharmacokinetics: 10 mg/kg/day to 4 females for 7days followed by 10 mg/kg of either radiolabel Excretion Balance: 10 mg/kg/day to 4 females for 7days followed by 10 mg/kg of either radiolabel Tissue Distribution: 10 mg/kg/day to 10 females for 7days followed by 10 mg/kg of either radiolabel Acceptable/guideline Steady state reached after 7 doses. Recoveries ranged from between 92.4 to 99.6% of administered radioactivity. Absorption, based on urinary excretion, was >69% of the dose. Absorbed radioactivity was rapidly excreted, primarily in the urine. KIH

- 485 or its radiolabeled metabolites were associated with the cellular fraction of blood. For the Py

14 C, Cmax 1 hr. There were no apparent d ifferences in the t max in plasma and blood but the t 1⁄2 was ca 7

- fold greater in blood; the t 1⁄2 was 16.8 hours in plasma and 112 hours in blood. For the Ix

14 C, Cmax ca 1.5 hours in plasma and at ca 7.5 hours in blood. The t max in blood was approximately double the levels in plasma and the t 1⁄2 was ca 5

- fold greater in blood; the t 1⁄2 was 60.9 hours in plasma and 302 hours in blood. Absorbed radioactivity was rapidly distributed throughout tissues and rapidly cleared without accumul ation of radioactivity in the tissues. KIH

- 485 underwent extensive metabolism with the major metabolite being M

- 13. Excretion was rapid with 85

- 95% of radioactivity being excreted within 24 hours. There was minimal difference in the routes and rates of e xcretion between the two radiolabeled forms. Elimination half life in plasma was extended following [Ix

14 C]

- KIH

- 485 administration.

Compared with single dose animals, there was saturation or induction of metabolism which resulted in an altered metabolic profile, particularly for the [Py

14 C] label, and this may also have resulted in small shift (6%) from urinary to fecal excretion in repeat dose animals. Otherwise, repeat dosing did not discernibly affect the overall pharmacokinetics of KIH

- 485. There was no discernible difference in the tissue distribution between single dose and repeat dosing.

------------- Metabolism and

pharmacokinetics Transfer to milk (rat) 47701727 (2006)

Covance single oral dose of 250 mg [ 14 C]

- KIH

- 485/kg to 18 female lactating rats Milk collected from 3 rats each interval at 0.5, 2, 8, 24, 48, 96 hours, then sacrificed for blood collection acceptable/non

- guideline The concentrations of radioactivity in the milk and plasma reached maximal concentrations of 23.48 and 47.89 μg equivalents/g respectively at 2 h post

- dose before decreasing to 0.667 and 0.184 μg equivalents/g respectively at 96 h post

- dose.
The elimination half

- lives of the test substance from the milk and plasma were similar at 21.4 h and 22.5 h, respectively. T he milk: plasma ratio of levels of radioactivity increased throughout the study, from 0.189 at 30 min after dosing, reaching near parity at 24 h, to 3.625 at 96 h after dosing.

### Page 47 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.7485 Metabolism and

pharmacokinetics Transfer to offspring (rat) 4770125(2006)

Huntingdon 3 female rats dose at 10 mg/kg/day of pyrazole

- 5

- 14 C]

- KIH

- 485 from GD 6 until Day 9 after parturition. Ten mated undosed rats provided naïve pups. Three naïve pups at each interval of 3, 5, 7, 9, 10, 11, 13 days post parturition r eplaced the pups of the dosed mothers and allowed to suckle for 1 hour, then sacrificed and stomach contents analyzed. acceptable/non

- guideline During the dosing period at Days 3

- 9 after parturition, concentrations in maternal plasma (1.31

– 1.76 μg equivalents/g ) were ~ double those in pup stomach contents (0.672

– 1.013 μg equivalents/g). After cessation of dosing (1

- 4 days after last dose) concentrations dropped rapidly for both matrices (13 days after parturition, pup stomach contents: <0.028 μ g equivalents/g; maternal plasma: <0.060 μg equivalents/g). Changes in concentrations of radioactivity in both matrices mimicked each other. The ratio of the mean concentrations of pup stomach contents to maternal plasma remained relatively constant with an overall mean value, both during and after dosing, of 0.49.

Toxicity of Metabolites
870.3050 14

- Day oral gavage

toxicity

– Han Wistar Rat 3 females/dose 47701690 (2005) Safepharm Labs 0, 1000 mg/kg/day of KIH

- 485 M

- 1 acceptable/non

- guideline NOAEL = 1000 mg/kg/day no observed adverse effects.

870.3050 14

- Day oral gavage

toxicity

– Han Wistar Rat 3 females/dose 47701691 (2008) Safepharm Labs 0, 100, 1000 mg/kg/day of KIH

- 485 M

- 3 acceptable/non

- guideline NOAEL = 1000 mg/kg/day no observed adverse effects.

870.5100 Bacterial reverse

mutation test 47701713 (2005), Safepharm Labs TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 50

- 5000 μg/plate KIH

- 485 M

- 1 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

870.5100 Bacterial reverse

mutation test 47701714 (2004), Safepharm Labs TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 50

- 5000 μg/plate KIH

- 485 M

- 3 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

### Page 48 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

870.5100 Bacterial reverse

mutation test 47701715 (2008), RCC Ltd., Germany TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 33

- 5000 μg/plate KIH

- 485 M

- 25 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

870.5100 Bacterial reverse

mutation test 47701756 (2009), Huntingdon TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 50

- 5000 μg/plate KIH

- 485 M

- 28 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

870.5100 Bacterial reverse

mutation test 47701716 (2007), Safepharm Labs TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 15

- 5000 μg/plate KIH

- 485 I

- 3 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions e ither in the presence or absence of metabolic activities.

870.5100 Bacterial reverse

mutation test 47701717 (2007), Safepharm Labs TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 50

- 5000 μg/plate KIH

- 485 I

- 4 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

870.5100 Bacterial reverse

mutation test 47701718 (2007), Safepharm Labs TA98, TA1535, TA100 and TA1537

- S typhimurium & WP2 uvrA of E coli 50

- 5000 μg/plate KIH

- 485 I

- 5 acceptable/guideline Test article has no reverse mutagenic potential under the experimental conditions either in the presence or absence of metabolic activities.

### Page 49 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

NA DEREK Evaluation 47701757 (2009) LSR Associates Metabolites: M

- 1, M

- 3, M

- 9, M

- 25, M

- 29 and parent Pyroxasulfone All available toxicity endpoints were searched (carcinogenicity, chromosome damage, genotoxicity, hepatotoxicity, HERG channel inhibition, irritation, mutagenic ity, reproductive toxicity, respiratory sensitization, thyroid toxicity and other miscellaneous endpoints). Toxicity to humans, mammals and bacteria was assessed. Neither pyroxasulfone nor the five metabolites evaluated fired any structural alerts for
to xicity.

NA (Special Study: A Toxicological Mechanism Study ) Effects on motor

systems in mice after 14

- day dietary exposure using a glutathione depletion animal model. 48046901 (2009) Female CD1 mice (3/group) were administered 0, 4500
ppm p yroxasulfone + 20 mM BSO, 20 000 ppm pyroxasulfone + 20 mM BSO and 20 mM BSO alone for 14 days

. acceptable/non

- guideline G ross pathological observation showed waste d body muscle volumes in the 20 000 ppm p yroxasulfone + BSO group animals. H istopathological examination showed degeneration/necrosis, calcification, cellular infiltration and the features of regenerating muscular tissue, namely proliferation of satellite cells in skeletal muscle in all BSO treated animals. Pyroxasulfone appeared to augment the depletion of the intracellular GSH in muscular tissues.

NA (Special Study: A Toxicological Mechanism Study ) Heart histopathology for

a toxicological mechanism study of Pyroxasulfone (KIH

485): effects on motor systems in mice after 14

- days dietary exposure using a glutathione depletion animal model 48046902 (2010) mice (3 females/group) were treated with pyroxasulfone at 0, 4500

+ 20 mM BSO , and 20000

+ 20 mM BSO or 20 mM BSO alone mg/kg/day for 14 days. acceptable/non

- guideline Hearts (2 slices/animal) of all animals in control and treated groups were routinely fixed, processed, embedded in paraffin wax, sectioned at 4 μm, stained and examined microscopically. Pyroxasulfone induced very mild myocardial toxicity in mice at the dietary level of 20000
ppm under the GSH depleted conditions of the study

NA (Special Study: A Toxicological Mechanism Study ) Investigation for Cell

Proliferation Activity and Oxidative Stress in Rat Urinary Bladder After Dietary Exposure for 14 Days 48046903 (2009) Male rats at 0, 2000, and 20000 ppm Pyroxasulfone ( 160 and 1632 mg/kg/day ) acceptable/non

- guideline B oth the 2000 and 20000 ppm groups showed an increase in Ki

- 67 labeling index associated with hyperplasia in the urinary bladder epithelium.

NA (Special Study: A Toxicological Mechanism Study ) Investigation for Cell

Proliferation Activity and Oxidative Stress in Mouse Kidneys After Dietary Exposure for 14 Days 48046904 (2009) Male Crlj:CD1 (ICR) mice (8 / group) at 2000 or 15000 ppm pyroxasulfone (292 and 2199 mg/kg/day) acceptable/non

- guideline The Ki

- 67 labeling indices, an indicator of cell proliferation activity, in all regions of both treatment groups were almost equal to those in the control groups. Malondialdehyde contents in the kidneys of both KIH

485

- treated groups from confirmation of the oxidative stress were comparable to that in the control group. I t is unlikely that KIH

- 485 treatment is involved in cell proliferation activity and oxidative stress in the mouse kidney under the conditions of the pre sent study.

### Page 50 of 82 Table A.2.2 Subchronic, Chronic and Other Toxicity Profile of Pyroxasulfone

Guideline No. Study Type MRID No. (year)/ Classification /Doses Results

NA (Special Study: A Toxicological Mechanism Study ) Electron Microscopic

Examination of Rat Urinary Bladder Treated with Pyroxasulfone (KIH

- 485) for 14 Days 48354402 (2011) Male Crl:CD(SD) rats (5 / group) at 0, 500, 2000 or 20000 ppm pyroxasulfone ( 44, 177 and 1765 mg/kg/day ) D oses of 2

, 000 and 20

, 000 ppm of KIH

- 485 (pyroxasulfone) induced morphological changes (suggesting hyperplastic and toxic effects) in the surface of the bladder epithelium.

NA (Special Study) Rat In Vivo Comet Test

. 48046906 (2010) Male rats at 0, 500, 1000 and 2000 mg/kg pyroxasulfone : one dose at 0 time, 2 nd dose after 21 hrs. P ositive control group received ethyl methanesulphonate at 200 mg/kg. acceptable/non

- guideline A statistically significant increase in the tail intensity was observed in the liver of rats treated with Pyroxasulfone at 2000 mg/kg/day (

p <0.001), compared to vehicle control values, Statistically significant increases in the tail intensity were observed in the bladder of rats trea ted with Pyroxasulfone at 1000 and 2000 mg/kg/day ( p <0.001),

NA (Special Study) Mouse In Vivo Comet

Test

. 48046907 (2010) Male mice at 0, 500, 1000 and 2000 mg/kg pyroxasulfone : one dose at 0 time, 2 nd dose after 21 hrs. P ositive control
group received ethyl methanesulphonate at 200 mg/kg. acceptable/non

- guideline A statistically significant increase in the tail intensity was observed in the liver of CD1 mice treated at 500, 1000 and 2000 mg/kg/day (

p <0.01), compared to vehicle control values. G roup mean values are within historical control range, considered not biologically significant. Statistically significant increases in the tail intensity were observed in the kidney at 1000 ( p <0.05) and 2000 mg/kg/day (

p <0.001)

.

NA (Special Study) One week oral

cytotoxicity study in male rats 48354404 (2010) Male rats 918/group) at 0, 50, 1000 or 2000 ppm pyroxasulfone. 6 rats/group sacrificed at 1, 3 or 7 days, SEM of urinary bladders acceptable/non

- guideline This study provides evidence to the cytotoxicity of pyroxasulfone the urinary bladder epithelium of male rats.

### Page 51 of 82

A.3 Toxicological Endpoints

A.3.1 Acute Reference Dose (aRfD)

– General Population

Study Selected: Developmental Neurotoxicity Study

- Rats MRID No: 47701724 Dose and Endpoint for Risk Assessment : 100 mg/kg/day based on decreased brain weight in both sexes and decreased thickness of the hippocampus, corpus callosum and cerebellum in PND 21 f emale offspring occurring at 300 mg/kg/day. Uncertainty Factor: 100x (10x interspecies extrapolation, 10x intraspecies variability. 1X FQPA safety factor)

Comments: The HED DNT committee considers morphometric changes in the hippocampus, corpus callosum and cerebellum during the first 21 days to result from a single acute exposure.

A.3.2 Chronic Reference Dose (cRfD )

Study Selected: 1

- year oral toxicity study

- Dog MRID No: 47701707 Dose and Endpoint for Risk Assessment : 2 mg/kg/day based on impaired hind limb function, ataxia, hind limb twitching and tremors; clinical path ology: increased creatine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections at 10 mg/kg/day. Uncertainty Factor: 100x (10x interspecies extrapolation, 10x intraspecies variability, 1X FQPA safety factor)

Comments about Study/Endpoint/Uncertainty Factors: In the various species tested, the dog exhibited adverse toxic effects at lower doses of exposure to pyroxasulfone. Also the dose ranges used in the dog testing were the narrowest allowing for more accurate determination of a

### Page 52 of 82

NOAEL. The 2 mg/kg/day NOAEL from this dog study is also protective from other adverse effects seen at higher doses in rats and mice such as cardiac and skeletal myopathy, liver, kidney and urinary bladder toxicity and developmental effects in the DNT and rabbit developmental studies . This endpoint is considered to be protective of all populations including women of child

- bearing age and nursing infants.

A.3.3 Incidental Oral Exposure

Pyroxasulfone has not been proposed for residential uses; therefore, selection of a toxicity endpoint is not necessary for this exposure scenario at this time.

A.3.4 Dermal Absorption

A dermal absorption study with pyroxasulfone is not availabl e.
A.3.5 Dermal Exposure (Short

- & Intermediate

- Term)

Critical Study Selected: 28

- day Dermal

-- Rat MRID No: 47701698 Dose and Endpoint for Risk Assessment: Dermal NOAEL= 100 mg/kg/day based on cardiac myofiber degeneration/inflammation cutaneous myofiber degeneration/inflammation at 1000 mg/kg/day.

Uncertainty Factor: 100x (10x interspecies extrapolation, 10x intraspecies variability)

Comments about Study/Endpoint/Uncertainty Factors: A 28

- day dermal toxicity study was selected as for the do se and endpoint for short and intermediate term dermal exposure. This study is route specific and is appropriate for this exposure scenario. The LOAEL of 1000 mg/kg/day is based on minimal to mild cardiac myofiber degeneration with inflammation in males a nd females

. This endpoint is also considered protective of developmental effects in DNT at 300 mg/kg/day and rabbit developmental study at 1000 mg/kg/day. This POD is also protective of the neurotoxic effects seen in the dog following chronic oral exposu re to 10 mg/kg/day. Dermal absorption is estimated to be 7.5%, so the relative dermally absorbed dose for the dermal NOAEL of 100 mg/kg/day is approximately 7.5 mg/kg/day which is less than the oral LOAEL of 10 mg/kg/day identified in the dog study. In a ddition, rats in general are a more sensitive species for the dermal exposure route because of higher skin permeability.

A.3.6 Inhalation Exposure (Short

- Term , 1

- 30 days )

Critical Study Selected: 90 day oral toxicity study in dogs. MRID No: 47701696 and 47701697 Dose and Endpoint for Risk Assessment: 2 mg/kg/day based on a LOAEL of 10 mg/kg/day for axonal/myelin degeneration in the sciatic nerve, minimal to mild subacute inflammation of skeletal muscle in males and females and impaired lim b function, body and limb hypotonia,

### Page 53 of 82

increase in serum creatine kinase activity.

. 

### The assumed inhalation absorption factor is 100%.

Uncertainty Factor: 100x (10x interspecies extrapolation, 10x intraspecies variability)

Comments about Study/Endpoint/Uncertainty Factors: A 28 day inhalation toxicity study in rats (MRID 47701699) was considered for selecting an endpoint of toxicity for assessing this route specific exposure. However the endpoint based on the 90

- day dog study is more pr otective than the findings in the 28 day inhalation toxicity study in rats where the NOAEL was 200 mg/m 3 

### (equivalent to 52.2 mg/kg/day oral dose), the highest dose tested using an aerosol dust of pyroxasulfone, not an aerosol. Since no effects were seen a t the highest dose tested in the inhalation study and since mixer/loader exposures would be to both dust and aerosols (with aerosol exposures typically being more sensitive than dust exposures), HED believes that a dust exposure study was not as protectiv e. Since no effects were seen at the highest dose tested in the inhalation study, use of the oral dog would compensate for this uncertainty, and is protective of neurotoxicity. The inhalation NOAEL of 200 mg/m 3 

### /day is equivalent to 52.2 mg/kg/day oral dose using the following formula:

mg/kg/day = mg/L x A x CF x D x AF

where

A is absorption factor using 1 as a default value CF is a conversion factor in L/hr/kg to account for respiratory volume and body weight for a given species and strain. For the rat strain used in this study it is 43.5 D is duration of daily exposure in hours. A 6 hour daily exposure was used. AF is activity factor. The animal default factor of 1 was used.

MOE: 100

A.3. 7 Inhalation Exposure (Intermediate

- Term 1

- 6 months )

Critical Study Selected: 1

- year toxicity study in dogs. MRID No: 47701707 Dose and Endpoint for Risk Assessment: 2 mg /kg/day based on impaired hind limb function, ataxia, hind limb twitching and tremors; clinical pathology: increased crea tine kinase, aspartate aminotransferase; axonal/myelin degeneration of the sciatic nerve and spinal cord sections at 10 mg/kg/day. The assumed inhalation absorption factor is 100%.

Comments about Study/Endpoint/Uncertainty Factors: Among the various species tested, the dog exhibited adverse toxic effects at lower doses of exposure to pyroxasulfone. Also the dose ranges used in the dog testing were the narrowest allowing for more accurate determination of a NOAEL. The 2 mg/kg/day NOAEL fr om this dog study is also protective from other adverse effect seen at higher doses in rats and mice such as cardiac and skeletal myopathy, liver, kidney and urinary bladder toxicity

.

MOE : 100

### Page 54 of 82

A.4 EXECUTIVE SUMMARIES

A.4.1 Subchronic Toxicity

870.31 00 90

- Day Oral Toxicity

– Rat

In a subchornic oral toxicity study (MRID 47701692), Pyroxasulfone (KIH

- 485; 99.1% a.i.; Lot/Batch No. RCT301) was administered in the diet to Crl:WI(Glx/BRL/Han)BR rats (10/sex/dose) for up to 13 weeks at doses of 0, 100, 50 0, 2500, or 5000 ppm (equivalent to 0/0, 8.9/10.2, 43.9/48.9, 221.4/255.9, and 451.2/514.2 mg/kg bw/day in males/females). In the control and 5000 ppm group, an additional 5 rats/sex/group were fed the test diets for 13 weeks followed by a 4

- week recovery period.

Assessment of toxicity was based on mortality, clinical observations, and clinical and anatomic pathology evaluations. There were no effects on food consumption, ophthalmoscopy, or functional observational battery parameters.

The target organs were liver, skeletal muscle, cardiac muscle, and the pancreas based on altered organ weights, histopathological indicators, and/or clinical pathological indicators. Reduced body weight gain was observed in the 5000 ppm group.

At 2500 an d 5000 ppm, slight decreases in overall body weight gain were noted in both sexes (decr 12

- 15%). Additionally, the following adverse findings were observed that each may indicate an adverse effect on muscle tissue: (i) decreased ambulation and total moveme nt in males (decr 24

- 38%); (ii) decreased creatinine in males (decr 11

- 12%); (iii) increased minimal to slight myocardial degeneration in both sexes (8

- 10/10 treated vs 0

- 1/10 controls); (iv) increased minimal quadriceps myopathy in males (6/10 each treate d vs 3/10 controls); and (vi) increased minimal to slight myopathy in skeletal muscles other than quadriceps in both sexes (4

- 9/10 treated vs 1/10 controls). In the females, increased aspartate aminotransferase (AST; incr 122%, each dose) and increased liv er weights (decr 10

- 23%) were also noted.

Additionally at 5000 ppm, the following adverse findings were observed: (i) pale teeth in both sexes; (ii) decreased body weight and body weight gain in both sexes; (iii) increased AST in males; (iv) increased ur ine volume in both sexes; (v) increased liver weights in males; (vi) gross changes in the liver (large, mottled, and/or pale) in both sexes; (vii) dark pancreas in females; (viii) microscopic changes in the liver (agonal congestion/hemorrhage, centrilobula r hypertrophy/eosinophilia, and/or hepatocyte vacuolation) in both sexes; and (ix) degranulation in the pancreas of females.

After the recovery period, increased incidences in agonal congestion/hemorrhage in the liver was observed at 5000 ppm in males (3/ 5 treated vs 0/5 controls), and pale teeth was noted in 1/5 rats

### Page 55 of 82

in each sex (vs 0 controls). Decreased body weights were noted in the 5000 ppm males (decr 7

- 19%) with body weights remaining decreased during the recovery period (decr 10

- 12%), although a sl ight increase in body weight gain was noted during the recovery period. However, all other microscopic findings in the liver, heart, muscle and pancreas in the 5000 ppm animals were comparable to control rats.

The LOAEL is 2500 ppm (equivalent to 221/256 mg/kg/day in males/females), based on the findings detailed above. The NOAEL is 500 ppm (equivalent to 44/49 mg/kg/day in males/females).

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.3100; OECD 408) for a subchronic oral toxicity study in the rat.

870.3150 90

- Day Oral Toxicity

– Dog

The purpose of this study was to evaluate the potential toxicity of KIH

- 485 TGAI when administered via oral capsule dose administration (MRID 47701696 ) . Four dogs per sex per dose level were administered the test substance via gelatin capsules at concentrations of 0.2, 2.0, and 10.0 mg/kg/day for the 90 day (13 week) in

- life test period. An additional group of four dogs per sex served as the control and received the empty gelatin capsules. The dogs were observed twice daily for signs of toxicity. Body weights and food consumption were measured weekly and a battery of urinalysis, hematological and clinical pathology examinations was conducted at initiation and at six and thirteen weeks. Ophthalmological examinations were done at initiation and at 13 weeks. The post

- life phase of the study included organ weight measurements, gross and pathologic assessments.

No deaths occurred during the study period. Ther e were no treatment related changes in body weight, food consumption, hematology, blood chemistry, coagulation, ophthalmological or urinalysis parameters. Pathological examination (organ weight measurement and gross observation), found no effects attribut able to the administration of the test substance.

Slight muscle fiber degeneration of the musculature portion of the diaphragm, slight hyperplasia of satellite cell of the muscle, and slight nerve fiber degeneration of the sciatic nerve were observed in one 10 mg/kg/day male dog. In a subsequent 90

- day dog toxicity study (MRID 47701697), dogs administered pyroxasulfone at 15 mg/kg/day developed minimal to mild axonal/myelin degeneration in the sciatic nerve of all males (4/4) and 3⁄4 females in addition to minimal to mild subacute inflammation of skeletal muscle in males and females. Considering these two studies together, the LOAEL for these adverse effects in dogs is 10 mg/kg/day and the NOAEL is 2 mg/kg/day.

### Page 56 of 82

When reviewed in conjunction with MRID 47701 697 (concurrently reviewed), this study is classified acceptable/guideline and satisfies the guideline requirements (OPPTS 870.3150; OECD 409) for a subchronic oral toxicity study in dogs.

870.3200 21/28

- Day Dermal Toxicity

– Rat

In a 29

- day dermal toxicity study (MRID 47701698 ), Pyroxasulfone (97.2% a.i.; Lot No. L001) in deionized water was applied to the shaved, intact skin of male and female Crl: CD ® 

### (SD) IGS BR rats (10 sex/dose) at dose levels of 0, 20, 100, or 1000 mg/kg bw/ day for 6 hours/day for 29 consecutive days.

No adverse, treatment

- related effects was observed on mortality, clinical signs, body weight, body weight gain, food consumption, food efficiency, hematology, clinical chemistry, organ weights, or gross patholo gy.

An increased incidence of minimal to mild focal/multifocal cardiac myofiber degeneration with inflammation was observed in the hearts of the 1000 mg/kg/day males (90% treated vs 0% controls) and females (40% treated vs 10% controls). An increased inci dence of minimal focal/multifocal cutaneous myofiber degeneration with inflammation was observed in the treated skin of 1000 mg/kg/day male rats (60% treated vs 0% controls).

The LOAEL is 1000 mg/kg/day (the limit dose), based on cardiac myofiber degenera tion/inflammation in both sexes and cutaneous myofiber degeneration/inflammation in males . The NOAEL is 100 mg/kg/day.

This 29

- day dermal toxicity study is classified as acceptable/guideline and satisfies the guideline requirement for a 28

- day dermal toxi city study (OPPTS 870.3200; OECD 410) in rats.

870.3465 28

- / 90

- Day Inhalation

– Rat

In a 28

- day inhalation study (MRID 47701699), f our groups of 10 male and 10 female rats each were exposed to aerosols of KIH

- 485TGAI dust at targeted concentrations of 10, 40, or 200 mg/m 3 (mean, gravimetrically determined concentrations were 9.4, 40, and 200 mg/m 3 ). The mass median aerodynamic equivalent diameter of the aerosols ranged from 2.9 to 3.3 μm.

Rats were exposed nose

- only for 6 hours per day for a total of 20 exposures for each sex over a 4

- week period. A similar control group of 10 males and 10 female rats were simultaneously exposed to air only. On the day following the last exposure, blood samples were collected for clinical analyses from each rat, and all rats were sacrificed for anatomic pathology examination.

### Page 57 of 82

There were no test substance

- related adverse effects on mortality, body weights, clinical signs, or food consumption
as a result of KIH

- 485TGAI exposure. Clinical pathology evaluations show ed no test substance

- related effects in hematology, coagulation, serum chemistry, or urine parameters as a result of exposure to KIH

- 485TGAI dust.

There were no test substance

- related organ

- weight effects observed in the tested animals in this study. His tologic evaluation showed no effects in the respiratory tract or in any other organ systems. The fact that there were no test particles observed in the lung in the pathologic exam, despite the very high dust concentrations, was attributed to the absorptio n or metabolism of the test substance in the respiratory tract.

The NOAEL for repeated inhalation exposure to KIH

- 485TGAI dust was considered to be 200 mg/m 3 , the highest concentration tested. The LOAEL was not observed.

At the request of the Agency, thi s study was conducted for 4 weeks, instead of the 13 weeks required by Guideline OPPTS 870.3465. Aside from the different study duration, this study was conducted in accordance with Guideline
OPPTS 870.3465.

This 4

- week study is classified as acceptable/g uideline and satisfies the guideline requirement (OPPTS 870.3465; OECD 413) for a subchronic inhalation study in the rat.



### A.4.2 Prenatal Developmental Toxicity

870.3700a Prenatal Developmental Toxicity Study

– Rat

The purpose of this study (MRID 47701702) was to determine the potential maternal and developmental toxicity of KIH

- 485 (Pyroxasulfone; 99.1%; Lot #05TG005) in rats, when administered orally, by gavage. Time

- mated female Crl:CD(SD) rats were assigned to fo ur groups (22 animals/group). Each group received dose preparations containing the control article or 100, 500 or 1000 mg of test article/kg of body weight/day (mg/kg/day) at a dose volume of 10 ml/kg of body weight from Days 6 to 20 of gestation. All dams were observed for general conditions. Body weights and food consumption were recorded during the gestation period. On GD 21, caesarean section and necropsy were conducted on the dams, and the fetuses were examined for external, visceral, and skeletal malf ormations and variations.

There were no maternal deaths and no dose related clinical signs or necropsy findings. There was no adverse effect of treatment on group mean body weights or food intake.

The maternal LOAEL was not observed. The maternal NOAEL is 1000 mg/kg/day (limit dose).

### Page 58 of 82

There were no abortions, premature deliveries, dead fetuses, late resorptions, or complete litter resorptions and no effects of treatment on the numbers of litters, live fetuses, or early resorptions. Additionally, sex ratio and mean litter weight in the treated groups were comparable to controls. There were no external, visceral, or skeletal defects attributable to treatment.

The developmental LOAEL was not observed. The developmental NOAEL is 1000 mg/kg/day (limit dose).

This study is classified accep table/guideline and satisfies the guideline requirement (OPPTS 870.3700a; OECD 414) for a developmental toxicity study in rats.

Rat Developmental Study

In a rat developmental toxicity study (MRID 47701702), 22 female rats/dose group were administered 0 , 100, 500 or 1000 mg of pyroxasulfone from gestation day (GD) 6

- 20. There were no maternal deaths and no dose related clinical signs or necropsy findings. There was no adverse effect of treatment on group mean body weights or food intake. The maternal LOAEL was not observed. The maternal NOAEL is 1000 mg/kg/day (limit dose). There were no abortions, premature deliveries, dead fetuses, late resorptions, or complete litter resorptions and no effects of treatment on the numbers of litters, live fetuses, or early resorptions. Sex ratio and mean litter weight in the treated groups were comparable to controls. There were no external, visceral, or skeletal defects attributable to treatment. The developmental LOAEL was not observed. The developmental NOAEL is 1000 mg/kg/day (limit dose).

870.3700b Prenatal Developmental Toxicity Study

– Rabbit

In a developmental study (MRID 47701704), time mated female Hra :(NZW)SP rabbits (22 animals/group) were administered by oral gavage 0, 250, 500 or 1000 mg of KIH

- 485 TGAI (Pyroxasulfone; Lot/Batch #05TG005; 99.1%)/kg of body weight/day at a dose volume of 5 ml/kg of body weight from Gestation Day (GD) 7 to 28. All d ams were observed for general conditions. Body weights and food consumption were recorded during the gestation period. On GD 29, caesarean section and necropsy were conducted. Fetuses were examined for external, visceral, and skeletal abnormalities.

Seven females died or were euthanized prior to scheduled necropsy, 3 due to premature abortion and 4 because of intubation injury. One abortion occurred at 250 mg/kg/day and 2 occurred at 1000 mg/kg/day.

There were no test substance

- related deaths, clinical si gns of toxicity, or gross post

- mortem findings in dams at any dosage. There were no test

- substance related reductions in body weight

### Page 59 of 82

or food consumption parameters at any level tested. The LOAEL for maternal toxicity was not observed. The NOAEL for materna l toxicity is 1000 mg/kg/day (limit dose).

There were test substance

- related effects on fetal weights and the number of resorptions (total and early) at 1000 mg/kg/day; these effects were relatively slight, but statistically significant. The mean number o f corpora lutea, implantation sites, live fetuses, and sex ratio were comparable across all groups. Totals of 164, 164, 170 and 125 fetuses were examined for abnormalities and variations at 0, 250, 500 and 1000 mg/kg/day, respectively. There were no test

s ubstance

- related fetal external, visceral, or skeletal malformations or variations observed at any dosage.

The LOAEL for developmental toxicity is 1000 mg/kg/day (limit dose) based on reduced fetal weight and increased fetal resorptions. The NOAEL for dev elopmental toxicity is 500 mg/kg/day.

This study is classified acceptable/guideline and satisfies the guideline requirement (OPPTS 870.3700a; OECD 414) for a developmental toxicity study in rats.

A.4.3 Reproductive Toxicity

870.3800 Reproduction and Fertility Effects

– Rat

The purpose of this study (MRID #47701705) was to determine the reproductive toxicity of the test article, KIH

- 485TGAI (Pyroxasulfone; 97.2%; Lot/Batch #L001), following oral (dietary) administration to the rat. This study was con ducted as a pilot study for a multigenerational reproduction study. Crl:CD®(SD) IGS BR rats (12/sex/concentration) were fed diets containing 0, 25, 250, or 5000 ppm KIH

- 485TGAI for at least 28 days prior to mating to produce the F1 litters. Dams were allow ed to deliver and rear their offspring until weaning (postpartum day 21). At weaning, 12 F1 rats/sex/group were randomly selected to continue on study until post

- natal day (PND) 60 and were fed the same dietary concentration level as their parents.

There was a significant (p<0.05) trend for stained perineum in the P dams during lactation, with 3/12 animals affected at 5000 ppm compared to 0/11 controls.

In P males test substance

- related reductions in weight gain were observed at 250 and 5000 ppm. At 5000 ppm, weekly mean body weight gains were decreased throughout most of the study, most notably on Days 0

- 7 and 21

- 28 and resulted in reductions in overall weight gain for the pre

mating period and the entire exposure period. At 250 ppm, weekly mean body weig ht gains were also decreased throughout the study, and, except for Days 0

- 7, the reductions were of similar magnitude as those in the 5000 ppm group, despite the 20

- fold difference in dietary

### Page 60 of 82

concentration. Overall weight gains for the pre

- mating period an d the entire exposure period were decreased in this group. In P females , there were test substance

- related reductions in body weights at 5000 ppm and weight gain at 250 and 5000 ppm. At 5000 ppm, weekly body weight gains were decreased during pre

- mating a nd during the first and last week of gestation. As a result of these decreases in weekly weight gain, overall weight gain for the pre

- mating and gestation periods were 36

- 38% lower than the control group mean. In addition, weekly mean body weights were dec reased at the end of the pre

- mating period and throughout gestation and lactation. At 250 ppm, body weight gain was decreased during the last week of gestation, which resulted in a decrease in overall weight gain during gestation.

In F 1 

### adult males and fe males

, test substance

- related reductions in body weights and weight gain were observed at 5000 ppm. Overall mean body weight gain for the post

- weaning period for this group was 20% lower than the controls in males and 18% lower in females as a result of de creased weekly body weight gains throughout the post

- weaning period. These reductions in weekly weight gains were reflected in weekly mean body weights that were lower than controls throughout the post

- weaning period. In the 5000 ppm F 1 

### adult males and fe males , weekly decreases in food consumption throughout most of the post

- weaning period resulted in decreases of 16

- 18% in overall food consumption for the post

- weaning period (Days 0

- 39).

In P males

, food efficiency was decreased during pre

- mating at 5000 ppm and reflected lower food efficiency throughout the pre

- mating period, most notably on Days 0

- 7 and 21

- 28. In P females , there were test

- substance related effects on food efficiency at 250 and 5000 ppm. At 5000 ppm, weekly food efficiency was decrease d throughout pre

- mating and gestation. At 250 ppm, weekly food efficiency was decreased during the last week of gestation; as a result of this decrease, overall food efficiency during gestation in this group was 14% lower than control.

Dietary exposure to 5000 ppm of the test substance resulted in increased mean relative liver weights (%body wt.) in both P and F 1 

### adult males and females. The increased liver weights correlated with microscopic hepatocellular hypertrophy (in P adults) and were interpreted to be the result of non

- adverse induction of hepatocellular enzymes by a xenobiotic. All other organ weight differences were interpreted to be the result of general body weight loss and not indicative of organ

- specific effects.

In the 5000 ppm P adult rats, there were test substance

- related microscopic findings in the liver, quadriceps muscle, heart, and sciatic nerve. Minimal centrilobular hepatocellular hypertrophy was observed in the livers of five (5/12) male and three (3/12) female rats exposed to 5000 ppm in the P generation. Locally extensive, minimal to mild atrophy of the quadriceps muscle was observed in all of the 5000 ppm females in the P animals and in none of the other rats examined. The atrophy consisted of a minimal (10/12 rats) to mild (2/12 rats) decrease in the cross

- sectional area of the muscle fibers, as compared to the control tissue. Minimal to mild focal and multifocal degeneration of heart myofibers (i.e., myocardium) was present in five (5/12) 5000 ppm P

### Page 61 of 82

females and was considered a h eart

- specific adverse effect. Minimal to mild axon/myelin degeneration within the sciatic nerve sections was observed in all (12/12) of the 5000 ppm female rats. The occurrence of myocardial and peripheral nerve fiber degeneration exclusively in females tr eated at 5000 ppm may be related to substantially increased food consumption, and test substance dose, during lactation.

The LOAEL for parental toxicity is 5000 ppm (equivalent to 339/383 mg/kg/day in males/females, respectively) based and microscopic eff ects in the heart, liver, muscle, and sciatic nerve of males and females , decreased body weight gains in the P males and females and decreased food efficiency in the P dams. The NOAEL for parental toxicity is 250 ppm (equivalent to 16/20 mg/kg/day in males /females, respectively). The decreased body weigh gains at the 250 ppm dose were transient and mostly not statistically significant, and the bodyweights were not affected. The effects at 250 ppm are therefore equivocal.

There were no treatment

- related effects on litter size, sex ratio, or pup survival. At 5000 ppm, mean pup weights were decreased by 27

- 30% compared to controls throughout the post

- natal period. There were test substance

- related effects on developmental landmarks at 5000 ppm. The mean d ay of achievement of preputial separation was increased by 3 days in this group compared to the control group, and the mean age of achievement of vaginal patency was increased by 1.8 and 2.7 days in the 250 and 5000 ppm groups, respectively; changes that w ere considered due to reductions in body weight and weight gain in these groups.

The LOAEL for offspring toxicity is 5000 ppm (equivalent to 339/383 mg/kg/day in males/females, respectively) based on decreased pup weight and delayed sexual maturation in b oth sexes. The NOAEL for offspring toxicity is 250 ppm (equivalent to 16.0/19.6 mg/kg/day in males/females, respectively).

There were no test substance

- related effects on mating, fertility, gestation duration, number of implantation sites, or implantatio n efficiency in P adult females at any concentration.

The LOAEL for reproductive toxicity was not observed. The NOAEL for reproductive toxicity is 5000 ppm (equivalent to 339/383 mg/kg/day in males/females, respectively), the highest concentration tested.

This study is classified acceptable/non

- guideline provides data for use in dose selection for the definitive 2

- generation reproductive toxicity study in rats.

A.4.4 Chronic Toxicity

870.4100a (870.4300) Chronic Toxicity

– Rat

### Page 62 of 82

In a chronic feeding toxicity study (MRID 47701708), KIH485 TGAI (pyroxasulfone), was administered to male and female rats Crl:CD(SD) from Charles River Lab. Twenty rats per sex per level were administered test material by daily feeding at concentrations o f 0, 5, 50, 1000 and 2,000 ppm for the one year. Data for body weights and food consumption clinical observations and ophthalmological examinations were collected. A full battery of hematological and clinical pathology examinations was conducted at three, six and twelve months. The post

- life phase of the study included organ weight measurements and gross and microscopic pathologic
assessments.

The mean daily intake of KIH

- 485 TGAI in males was 0, 0.22, 2.22, 46.20 and 91.91 mg/kg/day at 0, 5, 50, 1000 an d 2000 ppm, respectively. In females, the mean daily intake of the test substance was 0, 0.30, 3.12, 60.80 and 121.33 mg/kg/day at the same respective dietary levels.

Test substance

- related effects occurred at 1000 ppm and above that included reduced body weight parameters and microscopic findings. These findings were observed in the liver (centrilobular hepatocellular hypertrophy (males)), heart (increased cardiomyopathy (females)) and urinary bladder (mucosal hyperplasia (males and females)). At 2000 pp m, these effects were accompanied by increased clinical observations of red discharge from the penis and associated red

- stained cageboards as well as increased liver and kidney weights. A slight increase in liver and kidney weights was observed in the 2000 ppm male and female dietary exposure groups.

The lowest

- observed

- adverse

- effect level (LOAEL) of KlH

- 485 TGAI, given as a dietary mixture, was 1000 ppm (46.20 and 60.80 mg/kg/day for males and females, respectively). The

no

- observed

- adverse

- effect level (NOAEL) was 50 ppm (2.22 and 3.12 mg/kg/day for males and females, respectively).

This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.4100a; OECD 452) for a chronic study in rats.

870.4100b Chronic Toxicity

– Dog

In a 1

- year dog study (MRID: 47701707), KIH

- 485, (99.1%) was administered daily to 4 beagle dogs/ sex/dose in capsules at dose levels of 0.0, 0.2, 2.0, and 10.0 mg/kg bw/day) for 364 consecutive days.

No effects of treatment were observed o n mortality, body weights, body weight gains, food consumption, food efficiency, ophthalmoscopic examinations, electrocardiograpic examinations, urinalysis, organ weights, or gross pathology.

### Page 63 of 82

Toxicity was observed at 10 mg/kg/day. Impaired hind limb funct ion and tremors was noted in two males, and impaired hind limb function was noted in one female. One of the males was also observed with hind limb twitching and ataxia. Dogs in this group (3 males and one female) also had abnormal, test article

- related neu robehavioral observations including mild, moderate, and/or severe limb weakness, primarily in the hind limbs. Limb tone was sometimes noted as hypotonic. Abnormal gait, mobility, and limb position were noted. Clonic (quivering) or tonic (rigid limbs)

movem ents were noted infrequently. Increases were observed in aspartate aminotransferase (not statistically significant) and creatine kinase (p < 0.05) starting during Week 13 and continuing throughout the treatment period. Females approached control values by Week 52. All males (4 of 4) and females (4 of 4) had minimal to mild axonal/myelin degeneration of the sciatic nerve. Minimal axonal/myelin degeneration was observed in the spinal cord as follows: (i) in the cervical cord of two (2 of 4) males and two (2 o f 4) females; (ii) in the lumbar cord of all (4 of 4) males and one (1 of 4) female; and (iii) in the thoracic cord of two (2 of 4) males and three (3 of 4) females.

Additionally at 10 mg/kg/day, minimal myofiber degeneration/necrosis was observed in the following skeletal muscles: (i) in the biceps femoris of two (2 of 4) males; (ii) in the diaphragm of one (1 of 4) male; and (iii) in the quadriceps of one (1 of 4) males. Skeletal muscles of the 10 mg/kg/day females were unremarkable. Although elevations of aspartate aminotransferase and creatine kinase in both sexes indicated a possible effect on skeletal muscle, the microscopic findings were minimal in severity, and the clinical chemistry findings appeared to be returning to normal levels by Week 52. The se observations suggested that any test article

- related effects on muscle were transient and/or reversible.

Beginning at Week 13 in females only, there was a mild, dose

- dependent trend towards decreased erythrocyte mass as illustrated by sequential decrea ses in erythrocytes (↓8

- 16%) , hemoglobin (↓8

- 14%), and hematocrit (↓7

- 12%) relative to controls at 2.0 and 10.0 mg/kg/day. However, group means were within expected ranges, and statistical significance was rarely and sporadically attained. Therefore, thes e findings were considered equivocal.

The LOAEL is 10.0 mg/kg/day, based on clinical and neuromuscular observations of the hind limbs as described above, increased serum aspartate aminotransferase and serum creatine kinase, minimal to mild axonal/myelin degeneration of the sciatic nerve, and minimal axonal/myelin degeneration in all three levels of the spinal cord in males and females . The NOAEL is 2.0 mg/kg/day.

This study is classified acceptable/guideline and satisfies the guideline requirements (OPPT S 870.4100; OECD 452) for a chronic oral toxicity study in dogs.

A.4.5 Carcinogenicity

### Page 64 of 82

870.4200a Carcinogenicity/Chronic Study

– Rat In this oncogenicity study (MRID # 47701709), Crl:CD®(SD)IGS BR rats (70/sex/group) were administered diets that contain ed 0, 5, 50, 1000 or 2000 ppm of pyroxasulfone (M: 0, 0.21, 2.05, 42.55, 84.55 mg/kg/day; F: 0, 0.28, 2.69, 54.28, 106.74 mg/kg/day) for two years. Males were exposed for at least 99 weeks and females were exposed for at least 97 and surviving males and f emales were euthanized and examined for gross and microscopic pathologic alterations. The decision to terminate these groups prior to the intended termination at 104 weeks was necessitated by the expected survival of the rats. Unscheduled deaths were app roaching the minimum deemed adequate for ensuring robust data sets and regulatory compliance. All surviving rats were sacrificed and subjected to gross and microscopic pathological examination. Assessment of toxicity was based on mortality, clinical obser vations, and clinical and anatomic pathology evaluations.

Test substance

- related effects occurred at 1000 and 2000 ppm. At 2000 ppm, effects included reduced body weight parameters (males and females), reduced food consumption (females), and increased red

- stained urine on cageboards (males). At 1000 ppm, effects included reduced body weight and food consumption parameters (females) and increased red

- stained urine on cageboards (males). Dietary exposure of male and female rats to 1000 ppm or more of the test substance, for approximately two years, resulted in incre ased cardiomyopathy (males and females); urinary bladder mucosal hyperplasia, inflammation, and transitional cell papillomas (males); and sciatic nerve degeneration (females); and liver peribiliary fibrosis/inflammation (females).

An increase in urinary bladder transitional cell papillomas was observed in males at 1000 ppm and above in association with a marked increase in mucosal hyperplasia. A slight increase in mucosal inflammation also appeared to be associated with the mucosal hyperplasia. There were no test substance

- related urinary bladder effects in females. Therefore, the test substance was interpreted to be oncogenic in male but not female rats.

An increase in the background incidence and severity of cardiomyopathy occurred in both sexes at 10 00 ppm and above. The lesion included myocardial degeneration, inflammation, and fibrosis and resembled naturally occurring cardiomyopathy of control rats of this age and strain.

An increase in the background incidence of sciatic nerve degeneration was o bserved in female rats at 1000 ppm and above. The lesion was graded minimal in most cases. Test substance

related sciatic nerve degeneration was not observed in males.

An increase in liver peribiliary fibrosis/inflammation was observed in females at 1000 ppm and above. An increase in bile duct hyperplasia was observed in females at 2000 ppm.

There were no test substance related effects on causes of death, organ weights or gross

### Page 65 of 82

observations made at necropsy. There were no treatment

- related changes in wh ite blood cell relative differential counts at any dietary concentration tested.

Under the conditions of the current study, test substance

- related effects that were considered adverse were observed at 1000 and 2000 ppm. There were no test substance

- related or adverse effects at either 5 or 50 ppm. Therefore, the no

- observed

- adverse

- eff ect level (NOAEL) was 50 ppm. Based on an increase in urinary bladder transitional cell papillomas in the 1000 ppm and 2000 ppm males, the test substance was considered oncogenic in males at exposures of 1000 ppm and above.

This study is classified as acc eptable/guideline and satisfies the guideline requirements (OPPTS 870.4200a; OECD 451) for a carcinogenicity study in rats.

870.4200b Carcinogenicity (feeding)

– Mouse

The purpose of this study (MRID: 47701710) was to determine oncogenic potential of KIH

- 485 in mice, following oral (dietary) administration to the mouse for 18 months. Four groups of young adult male and female Crl:CD1(ICR) mice (60/sex/group) were administered diets that contained 0, 5, 150, or 2000 ppm or 4000 ppm (males )/4000 ppm (females) substance (equivalent to 0, 0.62/0.84, 18.4/25.5, 228/306, and 465/668 mg/kg/day in males/females) of the test substance for up to 18 months. Treatment at 4500/4000 ppm exceeded the maximum tolerated dose, and this group was terminat ed prior to the scheduled sacrifice. After approximately 14 months on study, dietary concentrations for the 2000 ppm groups were reduced to 1000 and 500 ppm for males and females, respectively, in order to insure a satisfactory survival rate at the schedul ed sacrifice. To provide interim data at one year, 10 mice per sex per group were sacrificed and given gross and microscopic pathological examinations. After approximately 18 months of dietary exposure, all surviving mice were sacrificed and given a
gross and microscopic pathological examination. Assessment of toxicity was based on mortality, clinical observations, and clinical and anatomic pathology evaluations.

In the 4500/4000 ppm group, marked body weight losses occurred during the first 2 months of th e study, which warranted the reduction of the dietary concentration to 3000 ppm. This reduction appeared to stabilize the body weights. However, after about 10 (females) or 12 (males) months on the study, clinical observations (principally, affects on the hindlimbs) began to be noted with a frequency and severity that was dose

- related. These effects included abnormal hindlimb gait, low carriage, curled toes, extended hindlimbs, and splayed limbs. The progression of effect on the hindlimbs began to interfere with the mice access to food and water. Therefore, this group was terminated before the scheduled sacrifice.

Test substance

- related adverse effects were observed in males and females at 2000/1000 and

### Page 66 of 82

2000/500 ppm, respectively. No adverse effects were observed in males or females at 150 ppm or lower. In males and females at 2000/1000 and 2000/500 ppm, respectively, test substance

related effects during the in

- life period included reductions in body weight parameters and increases in adverse clinical sig ns. The clinical signs consisted of hindlimb gait/stance abnormalities and included abnormal hindlimb gait, low carriage, curled toes, extended hindlimbs, and splayed limbs. These clinical observations were not overtly obvious until about 10 months on stud y and correlate with the histopathologic lesions of the nervous system described below.

At 2000 ppm, the one

- year interim sacrifice data indicated that daily dietary exposure of male and female mice had adverse effects on the kidneys and nerve fibers in both sexes. Minimal to mild tubular nephrosis in the pars recta, and an associated decrease in kidney weight parameters, was observed in both sexes. Minimal to mild degeneration of nerve fiber axons and myelin was observed in the sciatic nerve of some mice . Minimal trigeminal nerve degeneration was observed in one male and one female mouse. There were no test substance

- related effects on gross pathology.

At 2000 ppm, the 18 month terminal sacrifice data indicated test substance

- related changes in the kidn eys, sciatic nerve, and trigeminal nerve (detailed below). Test substance

- related causes of death were limited to five 2000 ppm female mice that were euthanized due to clinical signs secondary to test substance

- related sciatic nerve degeneration.

At one year, minimal to mild tubular nephrosis in the pars recta, and an associated decrease in kidney weight parameters, was observed in both sexes at 2000 ppm. Minimal to mild degeneration of nerve fiber axons and myelin was observed in the sciatic nerve of som e mice, observed in one male and one female mouse, also at 2000 ppm.

Minimal to mild hepatocellular hypertrophy in the 2000 ppm females was associated with a small increase in mean liver weight parameters. Both liver effects were consistent with pharmaco logical enzyme induction and were interpreted to be not adverse.

Organ weight effects at 2000 ppm included lower mean kidney (both sexes), as compared to controls. Lower mean kidney weights in both sexes correlated with adverse microscopic changes. At ne cropsy, there was a small increase in gross kidney deformity in males. Microscopic kidney effects in males included the presence of an intratubular precipitate as well as increased tubular epithelial nephrosis (degeneration/necrosis), hyperplasia, and aden oma. An increase in the incidence (females) and severity (males) of chronic progressive nephropathy (CPN) was also observed.

At 2000 ppm, microscopic nervous tissue effects in both sexes included degeneration of sciatic and trigeminal nerve axons and the ir associated myelin sheaths. Degeneration of axons in the

### Page 67 of 82

dorsal funiculi of the spinal cord and the trigeminal tract in the pons of the brain (females only) were interpreted to be an extension of the sciatic and trigeminal nerve lesions, respectively.

The LOAEL is 2000 ppm (equivalent to 228/306 mg/kg/day in males/females, based on decreased body weight and body weight gain, nervous system toxicity, and renal toxicity in both sexes. The NOAEL was 150 ppm (equivalent to 18/25 mg/kg/day in males/females).

Three (3/50) benign tubular adenomas in the 2000/1000 ppm male kidneys were observed and may have been related to the test substance

- related degenerative and hyperplastic changes observed in the 2000 ppm males. Based on this finding, the test substance was initially considered oncogenic in male mice. Revaluation of the renal tubular adenomas of the male mice was conducted by an independent kidney expert pathologist (MRID 48354403) and reviewed by a Pathology Working Group (MRID 48354405). The renal tu bular adenomas observed in male mice were considered by the PWG to be incidental and unrelated to the administration of pyroxasulfone. HED CARC considered the evidence presented by the PWG and concluded that the renal tubular adenomas observed in this mou se study were not treatment related.

Dosing was considered adequate based on decreased body weight and body weight gain, nervous system toxicity, and renal toxicity in both sexes.

This study is classified as acceptable/guideline and satisfies the guideli ne requirements (OPPTS 870.4200b; OECD 451) for a carcinogenicity study in mice.

A.4.6 Mutagenicity

### Page 68 of 82

Gene Mutation Guideline # 870.5100 Bacterial assay

Guideline #870.5300, In vitro mammalian cell gene mutation test MRID 47889311 Acceptable Guideline Not mutagenic

Not mutagenic in the presence or absence of S9

- activation up to the limit of solubility and cytotoxic effects.

C ytogenetics

Guideline # 870.5375, Clastogenicity in mammalian cells MRID 47701719 Acceptable Guideline

Guideline #870.5395 Micronucleus test in bone marrow MRID 47701720 Acceptable Guideline No evidience of clastogenicity up to its limit of solubility

No evidence of genotoxicity



### A.4.7 Neurotoxicity

870.6100 Delayed Neurotoxicity Study

– Hen

- NA

870.6200 Acute Neurotoxicity Screening Battery

- Rat

In an acute neurotoxicity study ( MRID # 47701721) , 10 Sprague

- Dawley rats/sex/dose were administered a single oral (gavage, 10 mL/kg) dose of KIH

- 485 TGAI (99.1% purity) suspended in 0.5% me thylcellulose and Tween 80 at doses of 0, 20, 200, or 2000 mg/kg (limit dose) and were observed for 2 weeks. A functional observational battery (FOB) and motor activity testing were performed during the pretest period (baseline), and on Days 1 (approximat ely 2 hours post

dosing, time of peak effect), 8, and 15. At termination, 6 rats/sex/dose underwent whole

- body in situ perfusion, and tissues from the control and 2000 mg/kg groups were processed for neuropathology. References to 5 positive control studies were cited; however, no data were provided. No compound

- related effects on mortality, clinical signs, body weight, body weight gain, food consumption, and gross or neuropathology were observed at any dose in either sex. No evidence of neurotoxicity was observed in the FOB or motor activity assessments.

The LOAEL was not observed. The NOAEL is 2000 mg/kg (limit dose) in rats.

This study is classified as acceptable/guideline and satisfies the guideline requirement (870.6200; OECD 424) for an acute neurotoxicity study in rats.

### Page 69 of 82

870.6200 Subchronic Neurotoxicity Screening Battery

In a subchronic neurotoxicity study ( MRID# 47701722) , 12 Sprague

- Dawley rats/sex/dose were administered KIH

- 485 TGAI (99.1% purity) in the diet at concentrations of 0, 25, 250, or 2500 ppm (equivalent to 0/0, 1.56/1.92, 15.85/19.60, and 161.48/199.59 mg/kg/day [M/F]) for 13 weeks. A functional observational battery (FOB) and motor activity testing were performed during the pretest period (baseline), and during Weeks 4, 8, a nd 13. At termination, 6 rats/sex/dose underwent whole

- body in situ perfusion, and tissues from the control and 2500 ppm groups were processed for neuropathology. References to 5 positive control studies were cited; however, no data were provided.

No com pound

- related effects on mortality, clinical signs, body weight, body weight gain, food consumption, food efficiency, and gross or neuropathology were observed at any dose in either

sex. No evidence of neurotoxicity was observed in the FOB or motor activi ty assessments.

The LOAEL is 2500 ppm (equivalent to 161.48/199.59 mg/kg/day) based on muscular degeneration observed in females. The NOAEL is 250 ppm (equivalent to 15.85/19.60 mg/kg/day).

The study is classified as acceptable/guideline and satisfies the Guideline requirements (870.6200b) for a subchronic neurotoxicity study in the rat.

870.6300 Developmental Neurotoxicity Study

- Rat

In a developmental neurotoxicity study (MRID# 47701724), KIH

- 485 (Pyroxasulfone, 99.1% a.i., Batch# 05TG005) in 0.5% (w/v) sodium carboxymethylcellulose was administered daily by gavage (5 mL/kg) to groups of 24 mated female Sprague

- Dawley rats/dose at dose levels of 0, 100, 300, or 900 mg/kg/day from gestation day (GD) 6 through lactation day (LD) 7, in clusive. Subsequently, the pups were directly dosed via gavage at the same doses as their dams from post

- natal day (PND) 7 to 20 or 21, inclusive.

Dams were allowed to deliver naturally and were killed on LD 21, following weaning of their respective litt ers. On PND 4, at least twenty litters of appropriate size (≥ 8 pups/litter) were available. These litters were standardized to 8 pups/litter; the remaining offspring and dams were sacrificed and discarded without further examinations. Subsequently, 10

- 12 pups/sex/group were allocated to Subsets 1

- 6 for neurobehavioral testing (Subsets 2, 3, 4, and 5), neuropathological examination (Subsets 1 and 2). References for 7 positive control studies that provided data that validated the procedures and observers of the performing lab to assess motor activity, neurotoxicity and behavioral effects were provided; however, data from these studies were not provided.

### Page 70 of 82

Treatment of pregnant and lactating female rats with KIH

- 485 from GD 6 to LD 7 at doses up to 900 mg/kg/d ay was well tolerated. There were no treatment

- related effects on mortality, clinical signs of toxicity, body weight, body weight gain, food consumption, FOB parameters, gestation length, macropathology findings, or brain weights. Additionally, there was n o effect of treatment on the mean number of implantations or litter size.

The maternal LOAEL was not observed. The maternal NOAEL is 900 mg/kg bw/day.

No effects on offspring survival or bodyweight performance of the offspring to PND 7 (commencement of direct treatment of the offspring) were observed at any dose. Additionally, no effects on clinical condition or mean bodyweight gain were observed in the offspring during direct administration of KIH

- 485 from PND 7 to 20/21.

Sexual maturation, assessed by the time of vaginal opening or balano

- preputial separation was unaffected by treatment at all dose levels. There was no clear effect of treatment on the FOB performance including all activity measures, auditory startle response habituation, pre

- pulse inhibition, or on the learning and memory of the offspring at any dose level.

Motor activity assessments on PND 13 and 17 of age indicated several differenc es in the activity of treated offspring of both sexes relative to concurrent controls. However, reported motor activity measurements were very highly variable making conclusions difficult to make. Coefficients of variation exceeded 50% and reached above 20 0%.

There were no treatment

- related macroscopic findings observed at scheduled termination and no histopathological changes in the tissues presented for neuropathological examination on PND 21 or 66.

The mean absolute brain weights of male offspring in the 900 mg/kg/day group and female offspring in the 900 and 300 mg/kg/day groups on PND 21 were significantly lower (p<0.05) than concurrent controls and the laboratory historical control, and this decrease was dose

- related. There was no effect of treatm ent on the mean length and width of the brain of males or females on either PND 21 or 66.

Although the mean brain morphometric changes were stated to be within the limits of accuracy of the measurement, no valid positive control data were available to dem onstrate that the testing laboratory was capable of detecting changes in brain morphometry with known positive control substances (e.g., methimazole). The measurements in the treated groups were less than HC, as were the concurrent control values; however , a consistent pattern in reduced thicknesses was observed. This is better seen when brain morphometric values in PND 21 males and females were compared to the conducting laboratory historical control data from four studies . The hippocampus thickness wa s decreased in males (

- 11%) and females (

- 8%) in the 900 mg/kg/day

### Page 71 of 82

dose groups and in females at the 300 mg/kg/day dose (

- 6%). In female PND21 offspring this was accompanied by reduction in the thickness of the cerebellum (

- 19 to

- 20%) in the 300 and 900 mg/kg/day groups and a reduction in the thickness of the corpus callosum (

- 38%) in the 300 and 900 mg/kg/day dose groups. The decrease in the cerebellum thickness at the 100 mg/kg/day dose in females was not considered to be treatment related since it wa s not accompanied by a decrease in the hippocampus thickness and the lack of effect on PND 66 and the absence of associated neurobehavioral effects.

It is concluded that the LOAEL for offspring toxicity derived from this DNT study is 300 mg/kg/day based on decrease in brain weight in male and female offspring accompanied with a decrease in the thickness of the hippocampus, corpus callosum and cerebellum in PND 21 female offspring. The NOAEL is 100 mg/kg/day.

With the deficiencies reported above, this s tudy is classified acceptable/guideline and satisfies the guideline requirement (OPPTS 870.6300; OECD 426) for a developmental neurotoxicity study in rats.

A.4.8 Metabolism

870.7485 Metabolism

– Rat

– Single Dose

In a rat metabolism study (MRID 47701728 ), four Sprague Dawley [Crl:CD(SD)] rats/sex/group were gavaged with a single dose of one of two radiolabeled forms of KIH

- 485 in 0.5% aqueous carboxymethylcellulose: [pyrazole

14 

### C]

- KIH

- 485 or [isoxazoline

14 

### C]

- KIH

- 485 at doses of either 10 mg/kg (low dose ) or 700 mg/kg (high dose) in a nominal dose volume of 10 mL/kg. Urine and feces were collected up to 96 hours after dosing, and expired air was collected in one group for up to 48 hours after dosing. For tissue distribution studies, 9 rats/sex/group were treated, and 3 rats/sex/group were sacrificed at 3 (10 mg/kg) or 9 (700 mg/kg), 54 (both doses), and 96 (both doses) hours after treatment. Upon sacrifice, selected tissue/organ samples, as well as the residual carcass, were collected. All these samples we re radioassayed, and selected fecal and urine samples were pooled and analyzed to determine a metabolic profile.

Absorption was at least 77

- 88% of the administered dose (AD) at 10 mg/kg, based on residues isolated in the urine, bile, and carcass. Absorption was at least 22

- 26% AD at 700 mg/kg, based on residues isolated in the urine, carcass, and tissues. Although bile was not collected in the 700 mg/kg animals, the parent was isolated in feces at 61

- 77% AD suggesting that limited absorption

was oc curring. (Absorbed parent compound is extensively metabolized as detailed below.)

Absorption was relatively quick at 10 mg/kg, with a t max 

### of 1.1

- 7.0 h in the blood and plasma of both sexes; at 700 mg/kg, the t max 

### was 7.0

- 17.3 hours. A 70

- fold increase in dose resulted in an increase in radioactivity concentrations in the whole blood and plasma (C max 

### ) of 9

- 12 fold in both

### Page 72 of 82

sexes treated with [pyrazole

14 

### C]

- KIH

- 485 and the [isoxazoline

14 

### C]

- KIH

- 485 treated females

an d 17

- 18 fold in the [isoxazoline

14 

### C]

- KIH

- 485 treated males. One possible explanation for this observation is limited absorption at the high dose, an explanation that was corroborated by the large amount of parent compound isolated in the feces. An apparen t sex

- related difference was noted in the [isoxazoline

14 

### C]

- KIH

- 485 animals. Half

- lives were highly variable and ranged from 15

- 173 hours. Half

- lives were always greater in the blood than in the plasma, suggesting the possibility of protein binding.

Excl uding the gastrointestinal tract (GIT), the highest tissue concentrations (μg equiv/g) were initially found in the bladder (males: 245

- 227; females: 12

- 19 at low dose and 178 at high dose) at both doses and labels. Initially, very high tissue concentration s were also isolated in the prostate (16

- 47) at both doses and labels. High concentrations were also noted in the adrenals, kidney, liver, abdominal fat, uterus, blood, and plasma at both doses, sexes (except uterus), and labels. After 96 hours, the concen tration (μg equiv/g) in blood was 0.08

- 2.49 (4.58 in the [isoxazoline

14 

### C]

- KIH

- 485 treated females) and in kidney was 0.10

- 1.30 in each sex, dose, and label.

Following administration of [Ix

14 

### C]

- KIH

- 485, it was noticeable that concentrations in the
stomac h and stomach contents were much greater than in the [pyrazole

14 

### C]

- KIH

- 485 group

. This suggested the possibility of active secretion of radioactivity into the stomach following administration of [Ix

14 

### C]

- KIH

- 485.

Total recovery was 91

- 105% AD. Most of the dose was excreted in the urine within 24 hours regardless of sex, dose, or radiolabel; although, excretion was slowest in the 700 mg/kg males. Excretion was essentially complete by 48 hours (approximately 90% AD recovered in all the groups).

In the 1 0 and 700 mg/kg [pyrazole

14 

### C]

- KIH

- 485 group; slightly less residues were excreted in the urine and more residues in the feces in males compared to females; however, no sex difference was noted when the other radiolabel was used. In the excretion balance g roups, the excretion profiles were generally similar regardless of radiolabel. At 10 mg/kg, residues were found primarily in the urine (63

- 76% AD) and feces (13

- 29% AD). Less than 5% AD was isolated in the carcass and tissues, and <7% AD and was found in t he cage wash and debris. Only negligible amounts of residues (<0.2% AD) were found in the expired air.

The excretion profile was different at 700 mg/kg compared to 10 mg/kg. At 700 mg/kg, residues were found primarily in the feces (70

- 80% AD) and urine ( 22

- 26% AD). Less than 0.3% AD was isolated in the carcass and tissues, and <5% AD and was found in the cage wash and debris.

In the 10 mg/kg bile

- duct cannulated animals, there was a differing metabolic profile depending on the radiolabel. In the [pyrazol e

14 

### C]

- KIH

- 485 group, residues were found in the urine (62

-

### Page 73 of 82

63% AD), bile (13

- 16% AD), feces (6

- 10% AD), cage wash (6

- 7% AD), and cage debris and carcass (<1.2% AD). In the [isoxazoline

14 

### C]

- KIH

- 485 group, residues were found primarily in the urine (44

- 50% AD), bile (33

- 37% AD), feces (1

- 6% AD), cage wash (7

- 9% AD), and cage debris and carcass (6

- 8% AD).

Techniques used in the isolation and identification of the metabolites included the use of metabolite standards with HPLC, TLC, LC

- MS, and GC

- MS; enzyme de conjugation was used with some samples. KIH

- 485 underwent extensive metabolism following oral administration with up to 30 chromatographic regions of interest seen in the urine, up to 19 in the fecal extracts and up to 31 in bile. There was no significant sex difference in the metabolism of KIH

- 485. Compared with low dose animals, there appeared to be saturation or induction of metabolism at the high dose, which resulted in an altered metabolic profile.

The major metabolite in the urine of rats dosed with [Py

14 

### C]

- KIH

- 485 was M

- 13, accounting for up to 26% of the dose at the low dose level and up to 4% at the high dose level. M

- 7 and M

- 3 were the next most abundant metabolites. Most of the metabolites in urine were produced by the cleavage between the pyra zole and isoxazoline ring structure.

When the rats were dosed with [Ix

14 

### C]

- KIH

- 485, there were three major metabolites in urine, M

- 13 accounting for up to 20% of the dose, M

- 16 accounting for up to 19% of the dose and M

26 accounting for up to 6.4% of the dose. A major portion of the radioactivity was highly polar and multi

- component, containing 5

- methyl

- 5

- isoxazoline carboxylic acid and M

- 30, and accounted for up to 34% of the dose.

The major component of the feces following dosing with both radiolabe ls was unabsorbed KIH

485 accounting for up to 10% of the dose at the low dose level and up to 78% at the high dose level. The next most abundant metabolite was M

- 13, accounting for up to 3% of the dose.

In bile, the major metabolites of rats dosed with [ Py

14 

### C]

- KIH

- 485 were two conjugated compounds one of which co

- eluted with a sulphate conjugate of hydroxy KIH

- 485 and the other

co

- eluted with M

- 13 glucuronide. These two regions each accounted for up to 3.1% of the dose. Another metabolite was M

- 13, accou nting for up to 1.6% of the dose.

When the rats were dosed with [Ix

14 

### C]

- KIH

- 485, the major metabolite in bile was tentatively identified as M

- 26 accounting for up to 10% of the administered dose and was produced by the cleavage of the pyrazole ring and s ubsequent loss of the fluorine moieties. There were also two conjugated compounds one of which co

- eluted with a sulphate conjugate of hydroxy KIH

- 485 and the other co

- eluted with M

- 13 glucuronide. These two regions accounted for up to 7% and 3% of the dose each. There was one further metabolite with a molecular weight of 347 accounting for up to 4% of the dose, which was tentatively identified as a glutamyl cysteine conjugate of the isoxazoline ring.

### Page 74 of 82

This metabolism study in the rat is classified acceptabl e/guideline and satisfies the guideline requirement for a metabolism study [OPPTS 870.7485, OECD 417] in rats when considered in conjunction with the concurrently submitted metabolism study in rats (MRID 47701729).

870.7485 Metabolism

– Rat

– Repeat Dose

In a rat metabolism study (MRID 47701729), non

- radiolabeled KIH

- 485 was orally administered to four female Sprague Dawley (Crl:CD(SD) strain rats per group at a nominal dose level of 10 mg/kg/day for 7 days, followed by a dose radiolabeled with 14 

### C at eit her the pyrazole (Py) or isoxazole (Ix) ring in 0.5% aqueous carboxymethylcellulose and Tween 80 (<0.02% v/v): in a volume of 10 mL/kg. Additionally, one group of 4 rats were administered 10 mg/kg [pyrazole

14 

### C]

- KIH

- 485 in an oral gavage dose for 14 cons ecutive days. Urine and feces were collected up to 96 hours after dosing. For tissue distribution studies, 12 rats/group were treated, and 3 rats/sex/group were sacrificed at 1, 20, 48, and 72 hours after treatment with [pyrazole

14 

### C]

- KIH

485 or 2, 65, 168 , and 288 hours after treatment with [isoxazoline

14 

### C]

- KIH

- 485. Upon sacrifice, selected tissue/organ samples, as well as the residual carcass, were collected. All these samples were radioassayed, and selected fecal and urine samples were pooled and analyz ed to determine a metabolic profile.

This regime was based on an initial experiment in which four females received 14 daily doses of [Py

14 

### C]

- KIH

- 485. Blood and plasma concentrations had essentially achieved steady state conditions after 7 repeated oral administrations of [Py

14 

### C]

- KIH

- 485.

Absorption was at least 69% of the administered dose (AD) in all animals, based on residues isolated in the urine. Absorption was relatively quick at 10 mg/kg, with a t max 

### of 0.9

- 1.5 h in the blood and plasma (or 7.0 h in the blood of the of [isoxazoline

14 

### C]

- KIH

- 485 treated animals). Half

- lives were highly variable (17

- 302 h) and seemed to be higher in blood and higher in the [isoxazoline

14 

### C]

- KIH

- 485 treated animals. As half

- lives were always greater in the blood tha n in the plasma, protein binding may be occurring. The following parameters were higher in the [isoxazoline

14 

### C]

- KIH

- 485 treated animals than the [pyrazole

14 

### C]

- KIH

- 485 treated animals in blood and plasma: t max 

### , t 1/2 

### , and AUC; C max 

### was higher in the blood only.

Excluding the gastrointestinal tract (GIT), the highest tissue concentrations (μg equiv/g) were initially found in the bladder (20.7) and remained higher than plasma at 96 hours after dosing (0.04 in bladder vs 0.03 in plasma). After 96 hours post

- d ose, the highest residues were found in the erythrocytes, regardless of radiolabels. As indicated by pharmacokinetic parameters, the concentration of radioactivity remaining in the tissues at 96 hours after treatment were higher in the [isoxazoline

14 

### C]

- KI H

- 485 treated animals than the [pyrazole

14 

### C]

- KIH

- 485 treated animals.

### Page 75 of 82

Following administration of [Ix

14 

### C]

- KIH

- 485, it was noticeable that concentrations in the stomach and stomach contents were much greater than in the [pyrazole

14 

### C]

- KIH

- 485 group

. This suggested the possibility of active secretion of radioactivity into the stomach following administration of [Ix

14 

### C]

- KIH

- 485.

Total recovery was 92

- 100% AD. Most of the dose was excreted within 24 hours (>80% AD), predominantly in the urine (>60% AD). After 96 hours, 0.5

- 3.9% AD remained in the carcass and tissues (higher in the [isoxazoline

14 

### C]

- KIH

- 485 treated animals). The excretion profiles were generally similar regardless of radiolabel in that urine was the predominant route of excretion, feces wa s a major but secondary route, and relatively little residues were isolated in the other samples.

KIH

- 485 is extensively metabolized, and there were up to 16 regions of interests found during chromatography of the urine. Up to 17 proposed structures are presented in the proposed metabolic pathway of KIH

- 485. The major metabolites (structures presented in this report) include M

- 3, M

- 7, and M

- 16 in urine and M13 in the urine and feces. Thus, metabolism in the repeated dose animals was similar to that of the single dose animals. Differences were noted, but these differences typically involved minor metabolites. Overall, the metabolism of KIH

- 485 appears to proceed by two main routes. One route involved the cleavage of the sulfonyl group and subsequent sequent ial oxidations of this group on the pyrazole moiety or glutathione conjugation and subsequent hydrolysis of the isoxazoline moiety. The second route involved sequential oxidations of the parent compound.

This metabolism study in the rat is classified acc eptable/guideline and satisfies the guideline requirement for a metabolism study [OPPTS 870.7485, OECD 417] in rats when considered in conjunction with the concurrently submitted metabolism study in rats (MRID 47701728).

870.7600 Dermal Absorption

– Rat

- NA

A.4.9 Immunotoxicity

870.7800 Immunotoxicity

– Rat

The purpose of this study was to evaluate the potential of KIH

- 485 TGAI to suppress the primary humoral immune response following exposure via the diet for 28 days. Groups of 10 rats per sex were administered the test substance at dietary levels of 0, 25, 250, or 7500 ppm (equivalent to 0/0, 2/2, 18/19, and 529/570 mg/kg/day in males/females). Body weights, food consumption measurements, and clinical observations were recorded during the in

- life period. Prior to sacrifice, the immune system was stimulate d by injecting sheep red blood cells (SRBC) on test

### Page 76 of 82

day 22 and blood samples were collected from each rat on test day 28. The serum samples were assayed for their concentration of SRBC

- specific IgM antibodies to provide a quantitative assessment of humora l immune response. Serum from animals similarly challenged with a positive control immunosuppressive agent was analyzed concurrently to provide confirmation that the assay performance was acceptable for detection of immunosuppression. At sacrifice, each animal was examined grossly and selected organs were weighed (brain, spleen, and thymus).

There were no test substance

- related effects observed on clinical observations, organ weights, or gross pathology.

Systemic toxicity was observed at 7500 ppm. Body weights and food consumption were decreased in the males throughout the study, resulting in an overall (Days 0

- 28) decrease in body weight gains of 30% and an overall decrease in food consumption of 13%. In the females, body weights were decreased on Days 21 and 28, resulting in an overall decrease in body weight gains of 56%, and food consumption was slightly decreased throughout the study, resulting in an overall decrease of 8%. Overall food efficiency was also decreased by 19% in males and by 52% in fema les.

There was no evidence of test substance

- related toxicity in male or female rats at 250 ppm or lower.

The LOAEL for systemic toxicity is 7500 ppm (equivalent to 529/570 mg/kg/day in males/females), based on reduced body weights, body weight gains, fo od consumption, and food efficiency in both sexes. The NOAEL for systemic toxicity is 250 ppm (equivalent to 18/19 mg/kg/day in males/females).

There was no test substance

- related evidence of immunosuppression in either male or female rats at any dietary concentration tested. The IgM titers were generally comparable across all groups. The serum samples for the positive control groups that received 20 mg/kg/day of cyclophosphamide for 6 consecutive days demonstrated 60 and 68% decreases in the IgM antibody response to SRBC for male and female rats respectively.

The LOAEL for immunotoxicity was not observed. The NOAEL for immunotoxicity was 7500 ppm (equivalent to 529/570 mg/kg/day in males/females).

This study is classified acceptable/guideline and satisfies the guideline requirements (OPPTS 870.7800) for an immunotoxicity study in rats.

870.7800 Immunotoxicity

– Mouse

### Page 77 of 82

The purpose of this study was to evaluate the potential of KIH

- 485 TGAI to suppress the primary humoral immune response follo wing exposure via the diet for 28 days. Groups of 10 mice per sex were administered the test substance at dietary levels of 0, 40, 400, or 4000 ppm (equivalent to 0/0, 6/8, 61/77, and 633/791 mg/kg/day in males/females). Body weights, food consumption

me asurements, and clinical observations were recorded during the in

- life period. Prior to sacrifice, the immune system was stimulated by injecting sheep red blood cells (sRBC) on test day 23 (males) and 24 (females). Blood samples collected from each mouse on test day 28 (males) and 29 (females) were assayed for their concentration of sRBC

- specific IgM antibodies to provide a quantitative assessment of humoral immune response. Serum from the animals similarly challenged with a positive control immunosuppre ssive agent (cyclophosphamide) was analyzed concurrently to provide confirmation that the assay performance was acceptable for detection of immunosuppression. At sacrifice, each animal was examined grossly and selected organs were weighed (brain, spleen, and thymus).

There were no test substance

- related effects observed on clinical observations, food consumption, organ weights, or gross pathology.

At 4000 ppm, body weights were decreased in the males throughout the study by 7

- 9%, resulting in an overall (Days 0

- 28) decrease in body weight gains of 31%. Decreased (p<0.05) food efficiency was noted in the males on Days 0

- 7 (↓42%) and overall (Days 0

- 28; ↓31%); this was considered a reflection of the effects on body weight. In the females, body weights were slightly decreased throughout the study, resulting in an overall decrease in body weight gains of 32%.

There was no evidence of test substance

- related toxicity in male or female mice at 400 ppm or lower.

The LOAEL for systemic toxicity is 4000 ppm (equiv alent to 633/791 mg/kg/day in males/females), based on reduced body weights and body weight gains in both sexes, and decreased food efficiency in males. The NOAEL for systemic toxicity is 400 ppm (equivalent to 61/77 mg/kg/day in males/females).

There was no test substance

- related evidence of immunosuppression in either males or females at any dietary concentration tested. The IgM titers were generally comparable across all groups. In contrast, male and female mice injected for five consecutive days with 5 0 mg/kg/day of the known immunosuppressive agent, cyclophosphamide, demonstrated 100% and 92% inhibition, respectively, of the IgM antibody response to SRBC.

The LOAEL for immunotoxicity was not observed. The NOAEL for immunotoxicity was 4000 ppm (equival ent to 633/791 mg/kg/day in males/females).

### Page 78 of 82

This study is classified acceptable/guideline and satisfies the guideline requirements (OPPTS 870.7800) for an immunotoxicity study in mice.

### Page 79 of 82

APPENDIX B. Chemical Names And Structures Of Metabolites

B.1 Chemical Names and Structures of Pyroxasulfone and Metabolites.
Code IUPAC Name Common Name Chemical Structure

KIH

- 485 3

- [[[5

- (difluoromethoxy)

- 1

- methyl

- 3

-

(trifluoromethyl)

- 1 H

- pyrazol

- 4

- yl]methyl]sulfonyl]

- 4,5

- dihydro

- 5,5

- dimethylisoxazole Pyroxasulfone

M

- 1 [5

- (Difluoromethoxy)

- 1

- methyl

- 3

-

(trifluoromethyl)

- 1 H

- pyrazol

- 4

- yl]methanesulfonic acid N/A

M

- 3 5

- (Difluoromethoxy)

- 1

- methyl

- 3

-

(trifluoromethyl)

- 1 H

- pyrazol

- 4

- carboxylic acid N/A

M

- 5 3

- (5

- Difluoromethoxy

- 3

- trifluoromethyl

- 1 H

pyrazol

4

- ylmethanesulfonyl)

- 4,5

- dihydro

- 5,5

- dimethylisoxazole N/A

M

- 6 3

- (5

- Difluoromethoxy

- 1

- methyl

- 3

-

trifluoromethyl

- 1 H

- pyrazol

- 4

- ylmethanesulfonyl)

- 4,5

- dihydro

- 5,5

- dimethylisoxazol

- 4

- ol N/A

M

- 8 (5

- Difluoromethoxy

- 1

- methyl

- 3

- trifluoromethyl

1 H

- pyrazol

- 4

- yl)methanol N/A

M

- 9 5

- Difluoromethoxy

- 3

- trifluoromethyl

- 1 H

pyrazole

- 4

- carboxylic acid N/A

### Page 80 of 82

B.1 Chemical Names and Structures of Pyroxasulfone and Metabolites.
Code IUPAC Name Common Name Chemical Structure

M

- 9 malonyl glucoside (RT26) 1 None provided NA

N

- glycoside of M

- 9 (Unknown @ 13 mins.) 1 None provided NA

M

- 10 5

- Difluoromethoxy

- 1

- methyl

- 3

- trifluoromethyl

1 H

- pyrazole

- 4

- carbaldehyde N/A

M

- 11 [3

- (5

- Difluoromethoxy

- 1

- methyl

- 3

-

trifluoromethyl

- 1 H

- pyrazol

- 4

- ylmethanesulfonyl)

- 4,5

- dihydro

- 5

- methylisoxazol

- 5

- yl] methanol N/A

M

- 12 (5

- Difluoromethoxy

- 3

- trifluoromethyl

- 1 H

pyrazol

- 4

- yl) methanol N/A

M

- 13 3

- (5

- Difluoromethoxy

- 1

- methyl

- 3

-

trifluoromethyl

- 1 H

- pyrazol

- 4

- ylmethanesulfonyl)

- 4,5

- dihydro

- 5

- methylisoxazole

- 5

- carboxylic acid N/A

M

- 15 2

- Amino

- 5

- [1

- (carboxymethylamino)

- 3

- (5,5

-

dimethyl

- 4,5

- dihydroisoxazol

- 3

- ylthio)

- 1

- oxopropan

- 2

- ylamino]

- 5

- oxopentanoic acid N/A

M

- 16 2

- Acetylamino

- 3

- (5,5

- dimethyl

- 4,5

-

dihydroisoxazol

- 3

- ylthio)propanoic acid N/A

### Page 81 of 82

B.1 Chemical Names and Structures of Pyroxasulfone and Metabolites.
Code IUPAC Name Common Name Chemical Structure

M

- 22 5,5

- Dimethyl

- 4,5

- dihydroisoxazole N/A

M

- 25 [5

- (Difluoromethoxy)

- 3

- (trifluoromethyl)

- 1 H

pyrazol

- 4

- yl]methanesulfonic acid N/A

M

- 28 3

- [1

- Carboxy

- 2

- (5,5

- dimethyl

- 4,5

-

dihydroisoxazol

- 3

- ylthio)ethylamino]

- 3

- oxopropanoic acid N/A

M

- 29 3

- (5,5

- Dimethyl

- 4,5

- dihydroisoxazol

- 3

- ylthio)

- 2

-

hydroxypropanoic acid N/A

M

- 30 2 3

- cyano

- 2

- hydroxy

- 2

- methylpropanoic acid N/A

Metabolite A 1 None provided (cysteine glucose conjugate of

isoxazoline

- ring metabolite) N/A

Metabolite B 1 None provided (dimethylpropyl cysteine

sulfoxide derivative) N/A

Metabolite C 1 None provided (malonyl dehydrogenated cysteine

derivative of isoxazoline group) N/A

Metabolite D 1 None provided (cysteine conjugate of dimethyl

acrylic acid) N/A

P1 1 None provided ( malonyl cysteine conjugate of

isoxazoline

- ring products following reaction of pyroxasulfone or metabolites with glutathione) N/A

### Page 82 of 82

APPENDIX C. Physical/Chemical Properties

Appendix C. Physicochemical Properties of Pyroxasulfone.
Parameter Value Reference 1 Melting point 130.7 oC MRID 47701615 pH 5.03 at 22 oC MRID 47701613 Density 1.60 g/cM

- 3 MRID 47701616 Water solubility 3.49 x 10 - 3 g/L at 20.0 ± 0.5 oC MRID 47701619 Solvent solubility g/L at 20 oC Methanol: 11.4 Acetone: > 250 Ethyl acetate: 97.0

n

- Hexane: 0.0721 Toluene: 11.3 Dichloromethane: 151 MRID 47701620

Vapor pressure 2.4 x 10 - 6 Pa at 25 oC MRID 47701621 Dissociation constant, pK a Not applicable (pyroxasulfone N

containing rings are not expected to be protonated in a practical pH range) MRID 47701617

Octanol/water partition coefficient, Log(P OW ) log P OW = 2.39 at 25 oC, pH 8.7 MRID 47701618

UV/visible absorption spectrum at pH 1.13: λ max = 225.5 nm; ε = 7291 Lmol - 1 cm - 1 at pH 7.23: λ max = 225.0 nm; ε = 7340 Lmol - 1 cm - 1 at pH 10.91: λ max = 225.5 nm; ε = 7334 Lmol - 1 cm - 1 MRID 47701614



### APPENDIX D. Studies Reviewed for Ethical Conduct

The PHED Task Force, 1995. The Pesticide Handlers Exposure Database, Version 1.1. Task Force members Health Canada, U.S. Environmental Protection Agency, and the National Agricultural Chemicals Association, released February, 1995.

Agricultural Re

- entry Task Force (ARTF) data base (SOP #3.1)