UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION

MEMORANDUM PC Code: 109001
DP Barcode: D420615
Date: December 5, 2014

SUBJECT : EFED Registration Review Problem Formu lation for Oxadiazon

FROM:

TO: 

# 1: . .**1~/o~jJy** Hannah Yingling, Biologist**~** 

## 1S. o.--- 

### !r'Mohammed Ruhman, Ph.D.

, enior

# Agroil,~ "'' 

# 11]..,.

'\ Environmental Risk Bran ch 5 t'f.;foC
Environmental Fate and Effects Division (7507P)

Katherine St. Clair, Risk Manager Reviewer

To m Myers

, Team Leader
Risk Management and Impl ementation Branch 2
Pesticide Re-Evaluation Division (7508P)

REVIEWED Ju sti n Housenger, Biologist
BY: Jo se Melendez, Chem i st Environmental Risk Branch 5
Environmental Fate and Effects Division (7507P)

111 /)

d 

### /,.1. 

# v 

# t)V-1-**THROUG~ah** Shamim

, Branch Chief

# ~ "Jo</•r.{

Environmental Risk Branch 5 1

Environmental Fate and Effects Division (7507P)

The Environmental F ate and Effects Division (EFED) has completed the pre liminary problem
formulation (attached) for the ecological risk

, environmental fate, endangered species, and drinking water assessments to be conducted as part of the registration review of oxadiazon.

### 2 OFF ICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION 

### UNITED STATES ENVIRONMENTAL PROTECTION

AGENCY



## EFED Registration Review Problem Formulation for Oxadiazon

Oxadiazon: 3

- [2, 4

- Dichloro

- 5

- (1

- methylethoxy) phenyl]

- 5

- (1, 1

- dimethyl

- ethyl)

- 1, 3, 4

- oxadiazol

- 2( 3H)

- one CAS No. : 19666

- 30

- 9 and PC code : 109001

Hannah Yingling, Biologist Mohammed Ruhman, Ph.D., Senior Agronomist
Environmental Risk Branch 5 Environmental Fate and Effects Division (7507P) December 4, 2014



## Table of Contents

1. Executive summary

................................ ................................ ................................ ................. 4
2. Introduction

................................ ................................ ................................ ............................. 5
3. Use Characterization

................................ ................................ ................................ ............... 5
4. Conclusions from Previous Risk Assessments

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

a. Ecological Risk Assessment

................................ ................................ ................................ .. 6
b. Drinking Wa ter Exposure Assessments

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

### 3

c. Clean Water Act Programs

................................ ................................ ................................ .... 8
5. Environmental Fate and Transport

................................ ................................ .......................... 9
6. Receptors

................................ ................................ ................................ ............................... 12

a. Effects to Aquatic Organisms

................................ ................................ .............................. 12
b. Effects to Terrestrial Organisms

................................ ................................ .......................... 13

c. Ecological Incidents

................................ ................................ ................................ ............. 14
7. Exposure Pathways of Concern

................................ ................................ ............................ 15
8. Analysis Plan

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

a. Stressors of Concern

................................ ................................ ................................ ............ 16
b. Measures of Exposure

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

c. Measure s of Effect

................................ ................................ ................................ ............... 17
9. Endangered Species Assessments

................................ ................................ ......................... 17 10. Endocrine Disruptor Screening Program

................................ ................................ ............... 17 11. Preliminary Identification of Data Gaps

................................ ................................ ................ 18

a. Environmental Fate

................................ ................................ ................................ .............. 18
b. Effects

................................ ................................ ................................ ................................ .. 18
12. References

................................ ................................ ................................ ............................. 23 Appendix A . SIP O utput

................................ ................................ ................................ ............ 32 Appendix B . STIR Output

................................ ................................ ................................ ......... 33

### 4



## 1. Executive summary

This problem formulation describes the methods planned to be used during the completion of drinking water and ecological risk assessments in support of registration review and provides an
overview of the environmental fate, ecological effects, and potential risks associated with the use of oxadiazon as well as uncertainties unique to the risk assessment of this chemical. This
document also identifies additional studies that would be beneficial to the condu ct before executing the future re

- registration ecological risk assessment.

The fate database for oxadiazon is partially complete with the exception of the following studies

, which are requested:

(1) One aerobic soil study (OCSPP 835.4100) for one soil ob tai ned from areas where the pesticide is used; (2) One terrestrial field dissipation study (OCSPP 835.6100) on turf; and (3) ECM s and associated ILVs (OCSPP 850.6100) for soil/sediment and water as explained in the Preliminary I dentification of Data Gaps section, be low.

Additionally, the registrant is requested to:

(1) Address the un

- extracted residues issue in previously submitted aerobic aquatic metabolism study. For this, the registrant is referred to the data evaluation sheet for this newly subm itted study as well as to EFED u n

- extracted residue guidance; and (2) Provide Names, toxicity, structures and CAS n o.’s for degradates listed in S ection 5 , below.

In case data and clarifications are not responded to, EFED will use conservative assumptions such as multiplying hal f

- life with a factor of 3 and include the un

- extracted residues in calculating half

lives.

The ecological database for oxadiazon is largely complete with a few outstanding data gaps
from those listed in the 2001 RED that are shown below . Justification s for these data needs as well as assumptions that will be made in the absence of these data are provided in Table
10 and 11

.

(1) 850.1400

— Early life stage

- Freshwater Fish (Submission of the raw data for the rainbow trout study MRID 41811601) (2) 850.4225

— Acu te toxicity to Terrestrial Vascular Plants: Seedling Emergence (3) 850.4150

— Acute toxicity to Terrestrial Vascular Plants: Vegetative Vigor (4) 850.4550

— Cyanobacteria Toxicity

There are additionally a number of studies that are being requested in support of registration
review:

(1) OECD 213

— Acute oral toxicity to adult honey bees (2) OECD 237

— Acute oral toxicity to lar val honey bees (3) Non

- Guideline

— Chronic oral toxicity to adult honey bees

### 5

(4) Non

- Guideline

— Chronic toxicity to larval honey bees (5) Non

- Guideline

— Pollinator feeding/semi

- field/pollen and nectar residue studies

– The need for these studies is contingent upon the res ults of lower tier bee studies. (6) 850.3040

— Field testing for pollinators

– The need for field testing is contingent upon the
results of lower tier bee studies. (7) 850.2100

— Avian Acute Oral Toxicity Test with Passerine species

Additionally there are a number of studies that have been submitted and are currently under
EFED review:

(1) 850.1735 ( MRID 46473303 )

— Whole Sediment Acute Toxicity Freshwater Invertebrates: Toxicity to Freshwater Amphipods ( Hyalella azteca ) during a 10

- day Sediment Exposure (2) 850. 1735 ( MRID 46 487301 )

— Whole Sediment Acute Toxicity Freshwater Invertebrates: Toxicity to Midge ( Chironomus riparius) during a 10

- day Sediment Exposure (3) 850.1035 ( MRID 46473304 )

— Mysid Chronic Toxicity Test

— Life

- cycle toxicity with Mysids (Americamysis bahia) (4) 850.1400 ( MRID 48759101 )

— Oxadiazon Early Life

- Stage Toxicity Test (Pimpheales promelas) Under High Light Conditions



## 2. Introduction

Oxadiazon is a light

- dependent peroxidizing herbicide (LDPH) in the oxadiazolone chemical class. It is used for pre

- and post

- emergence control of grassy an d broadleaf weeds in turf and
ornamentals. LDPH c h emicals target a specific enzyme, protoporphyrinogen oxidase, in the heme and chlorophyll biosynthetic pathway. Inhibiting protoporphyrin o gen oxidase in plants leads to an accumulation of phototoxic heme and chlorophyll precursors that, in the presence of light, produce activated oxygen species which rapidly disrupt cell membrane integrity.

EFED evaluated the most recent ecological risk assessments for oxadiazon in association with updated toxicity, expos ure, and usage information to determine if sufficient data are available and if further updates are needed to support Registration Review. Recent ecological risk assessments
for oxadiazon include the 200 1 EFED R isk Assessment for the Reregistration Eligib ility Decision of Oxadiazon (200 1 , DP 277968 ). In addition, EFED considered the latest Agency science policies and risk assessment methodologies

.


## 3. Use Characterization

There are 5 9 registered end

- use products for oxadiazon with many formulations includi ng granular (density 0.513 to 1.281 g/cm 3 

### , most commonly used in turf and mostly formulated with fertilizer), soluble concentrate (Liquid/solid), emulsifiable concentrate, flowable concentrate and wettable powder (water soluble packaging). The chemical i s applied by ground equipment as granules (broadcast) or as liquid (foliar spray or weed directed spray depending on the tolerance of plant). Application frequency/rate varies by use. Oxadiazon is a weed pre

- emergent or early post

- emergent herbicide used t o control grassy weeds ( e.g. , goosegrass and crabgrass) and broadleaf weeds. Oxadiazon is not to be applied on residential turf (by either home owners or

### 6

commercial applicators) but could be applied to residential ornamental ground cover and shrub
beds on ly by professional applicators. It could also be applied by professional applicators to turf in apartment/condominium complexes, parks, athletic fields, playground, and cemeteries) and on golf courses (predominant use). In addition, oxadiazon is used on s od farms and on conifer plantations/nurseries, nurseries (containerized or non

- containerized nursery plants. It can also be applied to non

- agricultural areas, right

- of

- way, and landscape ares (i.e., industrial sites, ornamental, roadside plantings, woody, ornamental shrubs, vines and trees and herbaceous ornamentals). Oxadiazon use sites are classified as non

- food sites ( i.e. , primarily golf course fairways), outdoor use, roadsides and nurseries).

Table 1 lists the labeled use patterns categorized by the scenario that will be used in modeling exposure EECs. In this table, use sites, maximum single/yearly application rate, minimum intervals between applications are included. These parameters represent data obtained at least
from one of the use sites within the specified scenario category. This means that rates may be lower and intervals longer for other uses included in the same scenario category.

Table 1. Labeled Use Patterns for Oxadiazon

Scenario Category Labeled Use Pattern Maximum Single Rate (lbs a.i/

A)* Maximum No. of

Applications* Maximum Yearly

Rate (lbs a.i/A)* Minimum

Intervals (Months)

Turf Golf course 4.0 2 8.0 NS

Sod farm and all other turf, except home lawns 4.0

- NDC 2 & NS 8.0 & NS 4 & NS

Residential Shade trees and Ornamentals including: ground

cover, grasses, lawns and turf, herbaceous plants, nonflowering plants, woody shrubs and vines and unspecified 4.0

- NDC 2 & NS 8.0 & NS 3 & NS

2.0 4 & NS 8.0 & NS 2

1.4 2 2.8 4 Right

- of

- Way Right

- of

- way and non

- agricultural areas 4.0 2 8.0 ? NS

X

- Mass Tree Conifer plantations 4.0 2 & NS 8.0 + & NS 4 & NS

1.4 2 2.8 4 Nursery Established & containerized plants 4.0

- NDC NS ? NS 3 & NS

* For some labels the maximum number of applications/year is calculated from the specified single application rate and the maximum application per year. For example, if the yearly rate= 8 and the single rate is equal 4, then the maximum number of applicati ons/year= 8 divided by 4= 2. However, if the single and yearly rate is specified in the label then the maximu m number of applications per year is calculated; in this example 8 divided by 4= 2 applications. It is also noted that the crop cycle rates stated in some labels are taken to mean yearly rates and the registrants are requested to correct the labels accordi ngly.

+ For some labels this value is nearly 8.1 lbs a.i/A requested to be corrected as well as other errors specified by the BEAD re port.



### The registrant is requested to review the information presented above for labeled uses of this
chemical and inform EFED of any discrepancy. It is noted, that values entered in bold in Table 1 will be considered the maximum exposure scenarios and entries marked “?” n eed to be given, by the registrant, or high conservative values will be used. Registrants are request ed to review Table
1 , above and BEAD chemical profile in the docket for accuracy.



## 4. Conclusions from Previous Risk Assessments

a. Ecological Risk Assessment

EFED has conducted ecological risk assessments on oxadiazon that serve as the basis for this

### 7

problem formulation, including the 200 1 EFED chapter for the RED Document, as cited above.
Risk conclusions are listed below and summarized in Table 2 :

 Chronic exposure to freshwater fish and aquatic invertebrate s; Chronic LOC was exceeded by 132

- fold for freshwa ter fish and 37

- fold for aquatic invertebrates. No
chronic data for estuarine/marine fish was available at time of assessment.

 Chronic exposure to mammals may result in significant reproductive effects . Effects seen in maternal toxicity and developmental toxicity included slightly decreased body weight change in maternal females, inactive mammary tissue resulting in possible starvation of pups, increased fetal reabsorption/post implantation loss, decreased fetal weight, and increased incidence of incomplet e ossification.

 Chronic exposure to avian species; maximum three application scenarios resulted in
LOC exceedances.

 Acute exposure to mammals and avian species does not present significant short term
toxic risk

 Acute and chronic exposure to aquatic and t errestrial systems may result in a potential risk to endangered species that may include mammals, birds, fish and aquatic
invertebrates.

 Potential for impact to non

- target terrestrial and aquatic plants based on herbicidal properties of the compound; lim ited plant data was available at time of the assessment.

Table 2 . Summary of Conclusions from 2001 RED

Birds Mammals Terr
Plants Terr

Inverts Fish BCF Aquatic
Inverts Aquatic

Plants Groundwater

Contamination Persistence Degradates
of Concern

Yes 1 Yes 2 Yes 3 No Yes 4 Refer to 5 Yes 6 Yes No Yes No 7

1 Potential for chronic risk to birds ; no acute risk

2 Potential for chronic risk to mammals ; no acute risk

3 No data was available for risk conclusion; risk was assumed

4 Potential for chronic risk to fish med iated by reproductive effects compounded by potential for photo

- toxicity

5 Although the chemical has a high K ow , a study on bioconcentration in fish indicated a moderate bio

- concentration potential due to rapid depuration.

6 Potential for chronic risk to aquatic invertebrates mediated by reproductive effects compounded by potential for compound to bind to sediment and accumulate as well as potential for photo

- toxicity

7 Based on current fate data and may change upon review of requested studies and inform ation



### The RED recommended that all oxadiazon labels contain the following language:

 For Manufacturing Use Product:

“This pesticide is toxic to fish and aquatic invertebrates. Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans, or other water unless in accordance with the requirements of a National Pollutant Discharge Elimination System (NPDES) permit and the permitting authority has been notified in writing prior to discharge. For guidance, contact your State Water Board or Regional Office of EPA.

 For End

- use Product:

“This pesticide is toxic to fish and aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. D o not contaminate water when disposing

### 8 of equipment washwaters or rinsate. Do not apply when weather conditions favor drift from treated areas. Runoff and drift from treated areas may be hazardous to aquatic organisms in neighboring areas. Do not allow this product to drift.”

In addition, the RED proposed risk mitigation measures to reduce risk to non

- target plants and aquatic organisms. The mitigation measures included the addition of a well maintained buffer zone (to decrease the amount of spray drif t reaching bodies of water) and making a compulsory statement that the turf should be moved prior to application and irrigated after application (to assure that most of the chemical reaches the soil surface where it is less prone to run

- off).



### b. Drinking Wate r Exposure Assessments

The latest drinking water exposure assessment for oxadiazon was conducted in the year 2002 and was based on tier II PRZM/ EXAMS modeling 1 

### . The stressor of concern

was considered to be parent oxadiazon and modeling was done with FL t urf scenario with a maximum of three applicat ions at a rate of 8.0 lbs a.i/A /year . This was based on the assumption that this use would give the maximum surface water exposure. In modeling, the first application of 2.0 lbs a.i/A was assumed to be applied m id

- March followed by a second application of 2.0 lbs a.i/A and a third application of 4.0 lbs/A at 3 0 and 135

- day intervals , respectively.

This problem formulation requests new studies in order to address identified
deficiencies in the oxadiazon suite of data. In addition, more information/confirmation on the labeled use patterns are also requested. Future estimation of the drinking water exposure will take in to consideration the data obtained from requested studies, a possible change in what is conside red to be the stressor of concern , and will use official models at that time. In this respect, it is noted that current surface water exposure models include tier II surface water concentration calculator (SWCC model) for surface water exposure and PRZM gr ound water (PRZM

- GW model) for ground water. Finally, a report 2 

### on the possible effects on oxadiazon in the treatment process for drinking water will be considered.



### c. Clean Water Act Programs

Oxa diazon is not identified as a cause of impairment for any wat er bodies listed as impaired under section 303(d) of the Clean Water Act at: http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d ?p_cause_group_id=88
5

.

1 Tier I1 Estimated Drinking Water Concentrations (EDWCs) for Human Health Risk for oxadiazon on Florida Golf Course (DP Barcode: 281176 Dated April 15, 2002

2 Rahman. M. M., Kim T

- H, Kwon G

- S, Yang J.E, Park M, and Kim J

- E. 2009. Removal Efficiency of the Herbicide Oxadiazon in Treatment Processes for Drinking Water . J. Korean Soc. Appl. Biol. Chem.; 52(3); 252

- 257

### 9

Furthermore, no Total Maximum Daily Load (TMDL) criteria or Office of Water aquatic life criteria have been developed for this chemical. OPP aquatic life benchmarks (fresh water) have
been established for oxidiazon and can be fou nd at: http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm

.



## 5. Environmental Fate and Transport

Based on submitted fate studies, Oxadiazon [3

- [2, 4

- Dichlor o

- 5

- (1

- methylethoxy) phenyl]

- 5

- (1,
1

- dimethyl

- ethyl)

- 1, 3, 4

- oxadiazol

- 2(3H)

- one; CAS No. 19666

- 30

- 9; PC code 109001] is expected to be mainly affected by abiotic degradation: photolysis in water and hydrolysis in alkaline conditions. Therefore, significa nt degradation of the chemical is expected in alkaline conditions and in shallow clear water bodies. In contrast, the chemical appears to be highly persistent in most other important environmental compartments/conditions. It is hydrolytically
stable in aci d and neutral condition, degrades very slowly by photolysis on soil and by biodegradation in soils and water/ sediment systems under aerobic/anaerobic conditions.

Volatilization of oxadiazon into the air from dry/wet soils and water is expected to be lim ited due
to its relatively low vapor pressure and Henry’s low constant. Possible bio

- accumulation in fish and aquatic organisms is suggested by the relatively high Kow of 63,096, however, results of the bioaccumulation test in bluegill sunfish indicated lo wer bioconcentration factors and rapid depuration.

Oxadiazon is characterized by slight mobility and high persistence in the soil system therefore there is potential for the chemical to leach to ground water when applied to coarse

- textured soils
low in or ganic matter. Oxadiazon physical, chemical, fate and transport data are summarized in
Table 3

.

Table 3

. Physical / Chemical and fate transport properties of Oxadiazon

Paramete r Value Reference MRID(Classification)

And Notes 1

M o l ecula r M ass 345.20 g mol e - 1 EFED, 2003 2

M o l ecular Formula C 15 H 18 Cl 2 N 2 O 3 EFED, 2003 2

Aqueous Solubility (mg/L
@ 20 °C ) 1.0 EFED, 2003 2 ; Hardly S o l u b l e 3

Va por P res s u re ( 2 0

°C ) 1.0 x 1 0

- 6 to r r EFED, 2003 2 ; Limited volatility
f r om dry s u rfaces

H e n ry's Law Const a n t ( 20°C; Calculat ed ) 4.5 x 10

- 7 atm.m 3 mole

- 1 EFED, 2003 2 ; Limited volatility
f r om water or wet s u r faces

O ctanol/Water Partition Coefficient (Kow) and ( l og K o w) 63,096 (4.8) EFED, 2003 2 ; Indicates possible bioaccumulation in aquatic organisms such as fish

Hydrolysis t 1⁄2 ( 25°C ) Stable in pH 5 & 7 ; 38 days in pH 9 418636

- 03 (A) ; Data indicate the
chemical is m oderately affected by hydrolysis only in alkaline
conditions

### 10 Paramete r Value Reference MRID(Classification)

And Notes 1
Aque o u s P h otoly s i s t 1⁄2 ( 25°C ) 3 days 418972

- 01 (A) ; Rapid photolysis in
clea r / s h allow wat e r s

Soil Ph oto lysis t 1⁄2 (2 5 ° C ) 165 days 418982

- 01 (A) ; Data indicate that the degrad a t i on pathway is not important

Aerobic Soil Metab o l i s m t
1⁄2 (2 4 ° C ) 841 days 427738

- 01 (A) ; Only one soil indicating that the degrad a t i on pathway is not important

Anaerobic Aquatic

Me tabolism t 1⁄2 ( 25°C ) 365 days 427738

- 02 (S) ; Only one system indicating that the degrad a t i on pathway is not important

Aero b i c Aqua t i c Metaboli s m t 1⁄2 ( 25°C ) 133 & 139 days (un

- certain values) 465947

- 01 (S) ; Two systems and half

lives were calculated consi dering the
unidentified un

- extracted residues as a sink; Need to identify the significant un

- extracted residues

Soil Water Partition Coefficient (Koc) 2,357 L Kg

- 1 418982

- 02 (A) ; Average of 4 soils; Slightly mobile 4

Terrestrial Field Dissipation t 1⁄2 and Observed Field Mobility 65 days in CA Sandy loam soil planted with junipers and
40 days in NC Loamy sand soil planted with azaleas
No dissipation observed during

winter 417674

- 01 (A) ; Relatively slow

dissipation; Mobility: Residues were detected only in t he top 30 cm of the soils, with occasional small detections
in the 15

- 30

- cm layers

F i s h Bio

- concentrat i on Factors (BCFs) and Depuration BCFs: 368 ( edible), 2,239 ( non
- edible) and 1,111 ( w h o l e )
and depuration t1⁄2 ~ 3 days 422267

- 01 (A) ; Moderate b i o

concent ration potential

1 Refer to text below for information about observed degradation products in various fate studies; Classification: A= Acceptable; S= Supplemental

2 EFED 2003: EFED Revised Risk Assessment for the Reregistration Eligibility Decision of Oxa diazon (PC Code 109001)

3 When considering that the expected concentration in the top 6” of the soil upon a single application of 4 lb a.i/A gives an estimated concentration of nearly 2 ppm.

4 FAO Mobility Classification



### With the exception of hydrolysis at pH 9 and aqueous photolysis, the degradation profile for oxadiazon shows the presence of many transformation product s with minor ( i.e <10%) rates of
formation ( Table 4 ). In all studies, only seven to eight transformation products were identified
and man y were not. For example, in aqueous photolysis 20 degradates were isolated at <8%; in hydrolysis other metabolites (number not specified) were present at <10%; in the aerobic soil three areas of radioactivity were isolated, but not identified at 1%; and in the anaerobic aquatic study, six transformation products were isolated at <2% and one at <6%. Very limited
mineralization to CO 2 

### was observed in the aerobic soil (3%) and much lower in the aerobic/anaerobic aquatic metabolism (1

- 2% and 0.02%, respectively ). Un

- extracted [ 14 

### C] residues comprised a maximum of 5% in the aerobic soil and 3% in the anaerobic aquatic study (both conducted in 1993). In contrast, un

- extracted residues reached 31 to 36% of the applied radioactivity in the newly submitted aerobic aq uatic study (conducted in 2014).

### 11

Table 4. Oxadiazon transformation profile: Maximum formed (@T= at termination; D= declined after reaching stated maximum, ND= No decline)

Study

TP 1 RP26123 RP 25496
AE 0608021 RP 1 7272

AE 0618784 RP 26471 RP 26449 RP 36939 RP 37084 RP 36227 Alkaline Hydrolysis 45% @T None None None None None None None
Aqueous Photolysis None None None None None 5% @T 12% @T None Soil Photolysis None small small None None None None None
Aerobic Soil <1% ND <1% ND <2% ND <1% ND <1% ND None None None Aerobic Aquatic None <0.5% D None None None None None None Anaerobic Aquatic <2% <2% None < 2% None None None ≤ 4%
TFD 2 None None <1% D None ~ 6% ND None None None

1 TP= Registrant designations for the transformation products:
RP26123: 1

- trimethylacetyl

- 2

- (2,4

- dichloro

- 5

- isopropoxyphenyl)hydrazine
RP25496: 2

- tertiobutyl

- 4

- (2,4

- dichloro

- 5

- hydroxyphenyl)

- 5

- oxo

- 1, 3,4

- oxadiazolin RP17272 (AE 0618784): 3

- (2,4

- dichloro

- 5

- methoxyphenyl)

- 5

- tertiobutyl

- 1,3,4

- _4

- oxadiazolin

- 2

- one RP26471: 2

- (carboxy

- 2

- propyl)

- 4

- (2,4

- dichloro

- 5

- hydroxyphenyl)

- 5

- oxo

- 1,3,4

- oxadiazolin
RP26449: 2

- (2

- carboxy

- 2

- propyl)

- 4

- (2,4

- dichloro

- 5

- isoprop oxyphenyl)

- 5

- oxo

- 1,3,4

- oxadiazolin
RP36939 and RP37084: No names reported
RP36227: 2,4

- dichloroisopropoxybenzene

2 TFD= Terrestrial Field Dissipation



### Not all of the structures for the transformation products were reported by the registrant. However

exa mination of the three available metabolite structures indicates the transformation occurring in specific moieties as shown in Table 5

.

Table 5 . Changes in the chemical structure of oxadiazon that produce four of its transformation products.

Chemical First Moiety Second Moi e ty

Parent (CH 3 ) 2 - C

- O C

- (CH3) 3 RP 17272 (methoxy) CH 3 - O No change

RP 25496 (phenolic) OH No change

RP 26449 (carboxylic acid) No change C

- (CH3) 2 COOH



### Review of the available fate data reveals the following inadequacies:

(1) Only one aerobic soil metabolism data is available, a minimum of three is required; However, due to the expected persistence of the chemical a study with one soil will be acceptable at this time. (2) Extraction of oxadiazon residues appears not to be complete in t he newly submitted aerobic aquatic study. Un

- extracted residues reached over 30% of the applied radioactivity with no apparent decline. These residues were not identified and apparently no attempt was executed to extract these residues. In this respect, it is noted that apparent good extraction procedures were employed. In addition, the experiment was terminated much earlier than the expected

### 12

half

- life of the chemical; (3) No structures were reported for most of the metabolites; and (4) No terrestrial field dissipa tion study was submitted for turf use which is the most important

u s age for this chemical in terms of pounds of active ingredient used annually.



## 6. Receptors

Table 6 and T able 7 provide a summary of the aquatic and terrestrial taxonomic groups and most
sensi tive surrogate species tested to characterize the acute and chronic ecological effects of
oxadiazon. As an LDPH compound, there is the potential for oxadiazon to exhibit enhanced toxicity through exposure to high levels of solar radiation and increase tox ic effects to aquatic organisms that inhabit small water bodies. There is currently one study in review conducted under enhanced UV lighting. The extent to which UV light enhances the toxicity of oxadiazon to other taxa or other life stages is unknown. Anemia and other hematologic consequences have been observed in developmental studies with mammals (USEPA, 2002). In wild mammal populations, hematologic effects have the potential to magnify since the lack of natural sunlight in the laboratory reduces th e likelihood of activating the phototoxic effects of oxadiazon. A summary of all ecological studies can be found in the 2001 RED document.



### a. Effects to Aquatic Organisms

Oxadiazon is considered to be moderately toxic on an acute basis to freshwater fish

, estuarine/marine fish, and freshwater invertebrates. On a chronic basis, egg hatchability was the most sensitive endpoint upon which the NOAEC was based. The freshwater invertebrate toxicity test showed effects in survival, adult mean length, and mean time to brood, and young/adult reproduction day. Oxadiazon is considered highly toxic to estuarine/marine invertebrates. There
is no data available on chronic toxicit y of oxadiazon to estuarine/marine fish and estuarine/marine
invertebrates.



### Table 6

. Most Sensitive Endpoints for Aquatic Species for Oxadiazon

Taxonomic Group Study Type Surrogate Species Toxicity Value Acute Toxicity
Classification Source

Freshwater
fish Acute Rainbow Trout Oncorhynchus mykiss LC 50 =1.2 mg ai/L Moderately
toxic 42330401

Acceptable

Chronic Fathead Minnow

Pimephales promelas NOAEC=33 μg

ai/L
LOAEC=84 μg ai/L (based on egg hatchability) - 41811601 Acceptable 1

Freshwater
Invertebrates Acute Water flea Daphnia magna EC 50 =2.18 mg ai/L Moderately
toxic McCann

Study 1977 Supplemental 2

### 13

Taxonomic Group Study Type Surrogate Species Toxicity Value Acute Toxicity
Classification Source

Chronic Water flea

Daphnia magna NOAEC=33 μg

ai/L
LOAE C=55 μg ai/L (based on survival; adult mean length;
mean time to brood and young/adult reproduction day) - 41784301 Acceptable

Estuarine/
marine fish Acute Sheepshead
Minnow Cyprinodon variegatus LC 50 =1.5 mg ai/L Moderately
toxic 42615801

Core

Chronic No data available

Estuarine/
marine
invertebrates Acute Mysid shrimp Americamysis
bahia EC 50 =0.27 mg ai/L Highly toxic 42615802
Core

Chronic No data available

Aquatic plants and algae Vascular Duckweed Lemna gibba EC 50 =41 μg ai/L

NOAEC=8 μg ai/L - 4161 0107 Supplemental 3

Nonvascular Freshwater green

algae
Selenastrum capricornutum EC 50 =8 μg ai/L

NOAEC=5.6 μg ai/L - 41610108
Core

Marine Diatom
Skeletonema

costatum EC 50 =5.2 μg ai/L

NOAEC=1.4 μg ai/L - 41610105
Core

Freshwater
Diatom
Navicula pellic ulosa EC 50
- 126 μg ai/L

NOAEC=27 μg ai/L - 41610106
Core

1 A study conducted using Rainbow Trout was two orders of magnitude more sensitive than the Fathead minnow endpoint with NOAEC = 0.88 ppb and a LOAEC of 1.7 ppb; the study was classified as supplement al because individual growth data were not included in the repo r t and thus the statistics could not be verified. This data has been requested.

2 EFED considered the McCann study as scientifically sound and useful for risk assessment purposes

3 Study was cla ssified as supplemental because the exposure concentrations used in the test were too high to establish
a NOAEC



### b. Effects to Terrestrial Organisms

Oxadiazon may be categorized as practically nontoxic to birds on an acute oral and dietary basis.
The a vian r eproduction test showed no effect on any reproductive parameter or viability of the offspring. However, mor t ality among females at the highest level was 33% and considered to be

### 14

treatment. Oxadiazon is characterized as practically nontoxic to mammals on an acute oral basis

. Chronic toxicity was based on the developmental toxicity test where increased fetal reabsorption/post implantation loss, decreased fetal weight and increased incidence of incomplete
ossification were observed . Oxadiazon is considered practically non

- toxic to bees on an acute contact basis . Submitted terrestrial plant data were deemed inadequate for determining
EC 25 

### /NOAEC values of the most sensitive species (D166982; 1995 memo to SRRD requesting repeat of all ten species due to numer ous deficiencies and guideline deviations). Table 7 summarizes the most sensitive endpoints for terrestrial points. No data is available on the acute oral toxicity of oxadiazon to passerines.

Table 7

. Summary of Most Sensitive Endpoints for Terrestrial Organisms to Oxadiazon

Taxonomic Group Study Type Surrogate Species Toxicity Value Acute Toxicity
Classification Source

Birds Acute Northern
Bobwhite
Colinus virginianus LD 50 >2150 mg/kg

(no mortality) Practically
nontoxic 41610101 1

Acceptable

Sub

- acute Northern

Bobwhite
Colinus virginianus LC 50 >5000 ppm

(no mortality) Practically
nontoxic 41610102

Acceptable

Chronic Northern

Bobwhite
Colinus virginianus NOAEC=500 ppm

LOAEC=1000 (based on mortality among adult females) - 41993202 Acceptable

Mammals Acu te Laboratory rat

Rattus norvegicus LD 50 >5000 mg/kg Practically
nontoxic 41866501

Acceptable

Chronic Sprague

Dawley rat NOAEC=12 mg/kg/day

LOAEC=40 mg/kg/day (maternal and developmental toxicity) - 40470202

Insects Acute

Contact Honeybee

Apis mellifer

a LD 50 >25 μg/bee Practically
nontoxic 42468301

Acceptable

Terrestrial
Plants Seedling

Emergence No data available

Vegetative Vigor No data available

1 Additional study conducted on the Mallard in 1971 found a more sensitive endpoint of LD 50 =1040 mg/kg; the

s tudy was deemed satisfactory for registration of oxadiazon in the 1970’s but EFED requested a study in 1991 to replace the older study (classified under MRID 111806)



### c. Ecological Incidents

The Ecological Incident Information System (EIIS) is an OPP database that houses ecological incidents that have been reported to the Agency. When available, EIIS includes date and location of an incident, type and magnitude of effects observed in various species, uses of pesticides

### 15

known or suspected of contributing to th e incident and results of any chemical residue analysis or other analyses conducted during incident investigation. EIIS incidents are categorized a c or d ing to the certainty that the incident results from pesticide exposure. The Avian Monitoring System (AI MS) is a database maintained by the American Bird Conservancy that contains publicly available data on reported avian incidents involving pesticides. Many of the incidents listed here
are also listed in EIIS.

A preliminary review on September 2, 2014 of EIIS returned two incidents attributed to
oxadiazon use.

 Incident I003822

- 001 occurred in June 1996 at a country club in Orlando, Florida. There had been three applications of a product containing oxadiazon , glyphosate, fonofos and fenamiphos at the beg inning of the month, after which irrigation had been applied in the evening. Six days after the first application, a rain event caused the small retention ponds and canals to overrun the banks and cover the fairways for several hours before receding. The fish kill was found in the shallowest water bodies; most individuals were tilapia and shiners.
O xadiazon was classified as “unlikely” the cause of the incident whereas fonofos and fenamiphos were listed as the “probable” causes of the incident.

 Incident I012094

- 001 occurred in August 2001 in Tarrant, Texas. There was a complaint
issued from a gol f course, that Ronstar , containing pendimethalin and oxadiazon, had damaged 30 acres of Tifsport Bermuda Fairways. Oxadiazon and pendimethalin were
classified as the “possible” cause of the incident.

The Aggregate Incident Report for EFED reported 1 minor fish and wildlife incident from 1998 to 2000, and 8 minor plant incidents occurring from 2000 to 2006. There were no avian incidents reported from AIMS.



## 7. Exp osure Pathways of Concern

The environmental fate and transport properties and use patterns of oxadiazon indicate that runoff with eroded soil and spray drift represent the important transport mechanisms of the chemical to aquatic and terrestrial organisms . Drinking water and inhalation exposure pathways were investigated using the Screening Imbibition Program ( SIP) and Screening Tool for Inhalation
Ri sk ( STIR) screening methods and were found to be exposure pathways of low concern

. SIP and
STIR are descr ibed in detail at: http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial

SIP is used to provide an upper bound estimate of exposure of birds and mammals t o pesticides through drinking water alone. It is used to determine whether or not drinking water exposure alone is a potential pathway of concern; it does not aggregate drinking water exposure with other exposure routes. The results of SIP conclude that drinking water exposure alone is not a potential
concern for mammals on an acute basis or chronic basis. For avian species , it concludes that exposure through drinking water alone is not a potential concern on an acute or chronic basis.
STIR indicated th at exposure via the inhalation pathway was not likely significant for mammals or avian species. Output from models can be found in Appendix A an d Appendix B

.

### 16



## 8. Analysis Plan

a. Stressors of Concern

The stressor of concern for drinking water and aquatic an d terrestrial organisms is parent Oxadiazon. This decision might change because it is based on currently available data which indicate that the chemical is highly persistent. Degradates forming in most important environmental compartments, are therefore e xpected to be at low concentrations. Upon receiving requested studies, the degradation profile for the chemical will be established along with expected intensity of surface water exposure resulting from the chemical residues of concern. In this future

exer cise, the residues of concern will be revisited based on expected concentrations of varied degradates, structural similarity to parent and their toxicity.



### b. Measures of Exposure

EFED will use standard available mod els (identified in Table 8 ) to evaluate potential exposures to aquatic and terrestrial organisms as described at http://www.epa.gov/pesticides/science/models_db.htm

.

Aquatic exposure esti mates will be based on estimated environmental concentrations (EECs) generated using the Surface Water Concentration Calculator (SWCC) model to simulate a waterbody that is considered representative of vulnerable aquatic environmental ( e.g. , ponds and

str eams in headwater watersheds). Terrestrial exposure will be estimated using a model (T

- REX
version 1.5 .2 ; March 22, 2012

. As indicated by the usage data, granular formulations of oxadiazon had the highest historical usage. Therefore, the granular charac terization module of T

REX will be used in terrestrial exposure. Inputs request to run this module include amount of a.i. per granule for mesh sizes of the granular formulations. Conservative default values will be used
in the assessment unless data are provided by the registrants. Exposure to terrestrial plants will be estimated using a model (TerrPlant; version 1.2.2 ; December 26, 2006 ) that assumes oxadiazon drifts or moves with runoff to adjacent habitats. For more information on the various models that
will be used in the risk assessment see the links as outlined in Table 8

.

Two spray drift models, A G DISP and/or AgDRIFT, will be used to assess exposures of aquatic

a nd terrestrial organisms to Oxadiazon deposited in terrestrial and aquatic habitat s by spray drift. AgDRIFT (version 2.1.1; dated 03/07/2012) is the model most commonly used by EFED to simulate spray drift into terrestrial and aquatic environments. A G DISP (version 8.26; dated 03/07/2012) is used when a parameter needs to be modeled th at is not available in AgDRIFT. Spray drift analysis will be an important part of the analysis in defining the potential area of effects for listed species.

### 17

Table 8

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

Environm ent Taxa of Concern Model(s)

Aquatic Fish/Invertebrates/Plants SWCC

Terrestrial Vertebrate T

- REX (dietary item)
A G DISP (Spray drift)

Plants TerrPlant (run

- off) AgDRIFT
A G DISP (spray drift)

The Agency is aware of monitoring conducted by the r egistrant (MRID 471993

- 01 and 465637

- 01), federal and state agencies and the literature. This route of exposure will be considered in the
future risk assessment to the extent that data on oxadiazon are available.



### c. Measures of Effect

Toxi city data presented in Table 6 and Table 7 of this problem formulation will be used to calculate risk quotients in future risk assessments . Any additional information submitted by the registrant or found in the open literature prior to conduct of the risk assessment will also be
considered. The open literature studies are identified using EPA’s EC OTOXicology database (ECOTOX), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial pla nts, and wildlife. The evaluation of both sources of data can also provide insight into the direct and indirect effects of pesticides on biotic communities from loss of species that are sensitive to the chemicals and from changes in structure and function al
characteristics of the affected communities.



## 9. Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally listed threatened and/or endangered (listed) sp ecies from registered uses of pesticides in registration review

. The process for evaluating potential risks to listed species is further described at http://www.epa.gov/oppfead1/en danger/litstatus/riskasses.htm



## 10. E ndocrine Disruptor Screening Program

Under Federal Food Drug and Cosmetic Act (FFDCA section 408(p), the Agency must screen all pesticide chemicals for potential endocrine disruptor activity. Between October 2009 and February 2010, EPA issues test orders/data call

- ins for the first group of 67 chemicals, which compromises 58 pesticide active ingredients and 9 inert ingredients. The herbicide Oxadiazon is not among the group of 58 pesticide active ingredients on t he initial list to be screened under the

### 18

EDSP . For further information on the status of the EDSP, policies and procedures, the list of 67 chemicals, future lists, the test guidelines and the Tier 1 screening batter, please visit our website http://www.epa.gov/endo/



## 11. Preliminary Identification of Data Gaps

a. Environmental Fate

Table 9 identify environmental fate studies by MRID that offer data for each guideline requirement, a s well as study classifications. Re quested data needed to support the future risk assessment are listed earlier in the executive summary

.

Table 9. Submitted environmental fate and transport data for oxadiazon

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications

835.2120 Hydrolysis 418636

- 03 Acceptable

835.2240 Aqueous photolysis 418972

- 01 Acceptable

835.2410 Soil photolysis 418982

- 01 Acceptable

835.4100 Aerobic soil metabolism 427738

- 01 Acceptable: One soil

835.4300 Aerobic aquatic metabolism 465947

- 01 Supple mental: Un

- identified/Un

extracted Residue

835.4400 Anaerobic aquatic metabolism 427738

- 02 Acceptable: One system and no need for another system because the chemical is practically stable

835.1230
835.1240 Adsorption/ desorption & leaching 418982

- 02 Acce ptable

835.6100 Terrestrial field dissipation 417674

- 01 Acceptable: None on Turf the major use pattern

850

- 1730 Bio

- concentration in Fish 422267

- 01 Acceptable

850.6100
ECM & ILV* for
soil/sediment and water An environmental chemistry method with self

- v alidation was included as part of the TFD study (MRID 417674

- 01 ) to determine oxadiazon and three of its metabolites the methoxy (RP17272) , the phenolic (RP25496), and the carboxylic ( RP26449) in soil only. The method sensitivity is approximately 0.01 p pm (10 ppb). This submittal does not satisfy current requirements for ECMs and associated ILVs for soil and water. These studies are requested as per OCSPP Guideline number 850.6100. Requested procedures should be more sensitive, state

- of

- the

- art.

* ECMs= Environmental Chemistry Methods & Associated ILVs= Independent Laboratory Validations (ILVs)



### b. Ecological Effects

Table 10 and Table 11 identify ecological effects studies by MRI D that offer data for each guideline requirement, as well as study classific ations and whether or not further data are needed in order to support risk assessment. Rationale for the additional data requested is presented below
the tables.

### 19

Table 10

. Submitted Aquatic Ecological Effects Data for Oxadiazon

OCSPP
Guideline Data

Req uirement Submitted

Studies (MRID) Study

Classifications Are data needed

to conduct risk
assessment? Justification and Assumptions EPA

will Make in Absence of Data

850.1010 Freshwater

invertebrate acute toxicity McCann

1 9 7 7 Supplemental No

--

42331801 Acceptable

850.1025
850.1035
850.1045
850.1055 Saltwater

invertebrate acute toxicity 42570301 Supplemental No

--

42615802 Acceptable

850.1075 Freshwater fish

acute toxicity McCann

1977 Supplemental No

--

42350601 Acceptable

McCann
1977 Supplemental

42330401 Acceptable

850.1075 Saltwater fish

acute toxicity 42615801 Acceptable No

--

850.1300 Freshwater

invertebrate life cycle 41784301 Acceptable No

--

850.1350 Saltwater

invertebrates life cycle None NA Yes
In review --

850.1735 Whole

Sediment Acute toxicity 10

- day 46487301 NA Yes
In review --

46473303

850.1400 Freshwater fish

early

- life stage 41811601 Supplemental Yes
In review
, pending
submission of
raw data for
rainbow t rout (MRID 41811601) The Rainbow Trout (MRID 41811601)

was found to be more sensitive than the fathead minnow in the ELS testing. The study results of the Rainbow Trout
could not be verified because individual growth data were not included in the report.

This information was requested (D165510) in 1997 and has not yet been
submitted thus Guideline 850.1400 is
unfulfilled. 42921601 Acceptable

### 20

OCSPP
Guideline Data

Req uirement Submitted

Studies (MRID) Study

Classifications Are data needed

to conduct risk
assessment? Justification and Assumptions EPA

will Make in Absence of Data

850.1400 Saltwater fish

early

- life stage None NA No

--

850.1500 Fish life cycle None NA No

--
850.440 0 Aquatic plant

Toxicity Test using Lemna

spp. 41610107 Supplemental No

--

850.4500 Algal toxicity 41610108 Acceptable Yes
G reen algae ( Anabaena flos

aquae)

— In
review --
41610105 Acceptable

41610106 Acceptable

Table 11

. Terrestrial Ecolog ical Effects Data for Oxadiazon

OCSPP
Guideline Data

Requirement Submitted

Studies (MRID) Study

Classifications Are data

needed for
risk
assessment? Justification and Assumptions EPA will Make
in Absence of Data

850.2100 Avian oral

toxicity 111807

(112622) Supplemental Yes Acute oral to xicity data for a passerine species are required under 40 CFR Part 158. A study has not been submitted for this data requirement.

A guideline

- compliant passerine acute oral toxicity test is needed. Acute oral toxicity data are only available for one a vian species ( i.e.

, bobwhite quail). Passerine birds may utilize metabolic pathways that are different from larger
birds and therefore be more sensitive to

ox adiazon . Furthermore, passerines exhibit behavioral responses to pesticide dosing that are poten tial indicators of reduced fitness in the field ( e.g. , regurgitation of contaminated diet) even when direct biochemically

- mediated lethal toxicity is not apparent.

Though acute toxicity was not detected for the mallard or bobwhite, significant effects a nd 33% mortality seen in the avian rep roduction study raise concern for passerine species.

In the absence of these data, passerine toxicity data for surrogate pesticides may be used to characterize the acute toxicity of ox adiazon to passerine species. 111806 Supplemental

41610101 Acceptable

850.2200 41610102 Acceptable No

--

### 21

OCSPP
Guideline Data

Requirement Submitted

Studies (MRID) Study

Classifications Are data

needed for
risk
assessment? Justification and Assumptions EPA will Make
in Absence of Data

Avian dietary toxicity 41610103 Acceptable

850.2300 Avian

reproduction 41993201 Supplemental No

--

41993202 Acceptable

850.3020 Honey bee

acute contact

tox icity 42468301 Acceptable No

--

OECD 213 Acute oral

toxicity to adult honey
bees None NA Yes As part of the Guidance for assessing pesticide risks to bees (USEPA, 2014) , the following Tier
I studies are recommended :

 Acute oral toxicity to adult honey be es

 Acute oral toxicity to larval honey bees

 Chronic oral toxicity to adult honey bees

 Chronic oral toxicity to larval honey
bees

In the absence of these data, honey bee oral toxicity data for surrogate pesticides

– starting with data for closely related p esticides ( e.g. , diphenyl ethers) and proceeding to data for less related pesticides

– may be used to characterize the oral toxicity of o xadiazon to larval and adult honey bees.

Tier II (feeding/semi

- field/polle n and nectar residue) and Tier III (full fi eld) studies may be needed, contingen t upon the results of lower tier
studies. OECD 237 Acute oral

toxicity to
larval honeybees None NA Yes

Non
Guideline Chronic oral

toxicity to adult honey
bees None NA Yes

Non
Guideline Chronic oral

toxicity t o larval honey
bees None NA Yes

Non
Guideline Pollinator

feeding/semi

field/pollen
and nectar
residue
studies

– None NA Need for
data

c ontingent

upon results of
Tier I bee
studies

850.3040 Field testing

for pollinators None NA Need for
data

c onting ent

upon results of
Tier I bee
studies

850.4100 S eedling

E mergence and Seedling
Growth None NA Yes Since Oxadiazon is an herbicide, toxic effects to plants are anticipated . Lack of adequate data represents uncertainty with regards to risk. A new study was requested in 1995 (D166982) after
a definitive NOAEC and EC 25 were not established.

### 22

OCSPP
Guideline Data

Requirement Submitted

Studies (MRID) Study

Classifications Are data

needed for
risk
assessment? Justification and Assumptions EPA will Make
in Absence of Data

850.4150 Vegetative

Vigor None NA Yes Since Oxadiazon is an herbicide, there is potential for risk to nontarget plants. Lack of adequate data represents uncertainty with regards to risk. Study repeat was requested in 1995 (D166982)
after NOAEC and EC 25 were not established.

### 23



## 12. R eferences

a. Fate and Transport Studies

MRID Citation Reference

41863603 Corgier, M.; Robin, J. (1991) [ 14 

### C]

- Oxadiazon Hydrolysis at 25

Degrees Centigrade: Lab Project Number: 91

- 02. Unpublished study prepared by Rhone

- Poulenc, Secteur Agro. 56 p.

41897201 Corgier, M.; Plewa, A. (1991) [ 14 

### C]

- Oxa diazon Photodegradation in

Aqueous Solution: Lab Project Number: 90

- 29: AG/CR LD/AN/ 9115609. Unpublished study prepared by Rhone

- Poulenc Secteur Agro. 8 p.

41898201 Das, Y. (1989) Photodegradation of Phenyl(U) [ 14 

### C]

- Oxadiazon on

Soil Under Artificial Sunlight: Lab Project Number: 89110. Unpublished study prepared by Innovative Sci entific Services, Inc. 119 p.

42773801 Waring, A. (1993) Aerobic Soil Metabolism: [ 14 

### C]

- Oxadiazon:

Final Report: Lab Project Number: 68/111: 7218. Unpublished study prepared by Hazleton UK. 79 p.

42773802 Waring, A. (1993) Aerobic Aquatic Metabolism: (carbon 14)

-

Oxadiazon: Final Report: Lab Project Number: 68/112: 7214. Unpublished study prepared by Hazleton UK. 95 p.

46594701 Roohl, A. 2003. [ 14 

### C]

- Oxadiazon: Degradation and retention in

two water/sediment systems. Unpublished study performed by

B attelle AgriFood Ltd., Ongar, Essex, United Kingdom, sponsored by Bayer CropScience SA, Lyon, France, and submitted by Bayer CropScience, Stilwell, Kansas. Battelle Study No. CX/02/075. PSI Activity Code: MEOAX007. Experiment started August 21, 2002,

an d completed March 16, 2003 (p. 7). Final report issued May 19,

2003.

41898202 Dykes, J. (1990) Soil Adsorption/Desorption with carbon 14|

-

Oxadiazon: Final Report: Lab Project Number: 37723. Unpublished study prepared by Analytical Bio

- chemistry Laborato ries, Inc. 57 p.

42226701 Norris, F. (1991) A Terrestrial Field Soil Dissipation Study with

Oxadiazon: Lab Project Number: 900102: 40642: EC/P

- 89

- 0014.
Un

- published study prepared by Rhone

- Poulenc Ag Co., in cooperation with A & L Eastern Agric., Labs. Inc. and others. 221

p.

### 24

42226701 Armstrong, K.; Cameron, B.; Chapleo, S.; (1991) Oxadiazon:

Bioaccumulation Test in Bluegill Sunfish: Lab Project Number: 8385: 381195. Unpublished study prepared by Inveresk Research International. 94 p.

47199301 Nendih alli, U.B. and D.L. Woodard. 2007. Surface Water

Monitoring for Residues of Oxadiazon in High Use Areas in the United States. An unpublished study performed by Bayer CropScience (Residue Analyses), Stillwell, KS, and sponsored by Bayer CropScience, Resea rch Triangle Park, NC. Study Number
04RAOAY001.

46563701 Nendihalli, U.B. and D.L. Woodard. 2005. Interim Report 1.

Surface Water Monitoring for Residues of Oxadiazon in High Use Areas in the United States. An unpublished study performed by Bayer Cro pScience (Residue Analyses), Stillwell, KS, and sponsored by Bayer CropScience, Research Triangle Park, NC. Study No 04RAOAY001, Doc. No B004944, Lynx/PSI Code
RAOAY001.



### b. Ecological Effects Studies

71

- 1 Avian Single Dose Oral Toxicity

MRID Citat ion Reference

111806 Posner, S.; McGee, G.; Freeman, L. (1971) Acute Toxicity (LD50) in

Mallard Ducks: ?RP

- 17623 Technical Assay 99.1|: Experimental
Reference No. A

- 408. (Unpublished study received Aug 23, 1972 under
359

- 658; prepared by Biometric Testing, Inc., submitted by Rhone

Poulenc, Inc., Monmouth Junction, NJ; CDL:003179

- B)

111807 Posner, S.; McGee, G.; Freeman, L. (1971) Acute Toxicity (LD50) in

Bobwhite Quail: ?RP

- 17623 Technical Assay 99.1|: Experimental
Reference No. A

- 408. (Unpublish ed study received Aug 23, 1972 under
359

- 658; prepared by Biometric Testing, Inc., submitted by Rhone

Poulenc, Inc., Monmouth Junction, NJ; CDL:003179

- C)

112622 Posner, S.; McGee, G.; Freeman, L. (1971) Acute Toxicity (LD50) in

Bobwhite Quail: Experimen tal Reference No. A

- 408. (Unpublished study received Oct 14, 1972 under 2F1269; prepared by Biometric Testing, Inc., submitted by Rhodia, Inc., New Brunswick, NJ; CDL:091824

- D)

41610101 Pedersen, C. (1990) Oxadiazon Technical: 21

- Day Acute Oral LD50 Stu dy

in Bobwhite Quail: Lab Project Number: BLAL/NO/89 QD 139. Unpublished study prepared by Bio

- Life Associates, Ltd. 35 p.

### 25

71

- 2 Avian Dietary Toxicity

MRID Citation Reference

41610102 Pedersen, C. (1990) Oxadiazon Technical: 8

- Day Acute Dietary LC50

Study in Bobwhite Quail: Lab Project Number: BLAL/NO/89 QC 141. Unpublished study prepared by Bio

- Life Associates, Ltd. 82 p.

41610103 Pedersen, C. (1990) Oxadiazon Technical: 8

- Day Acute Dietary LC50

Study in Mallard Ducklings: Lab Project Number: BLAL/NO/89 DC 137. Unpublished study prepared by Bio

- Life Associates, Ltd. 80 p.

ACC 091824 1974. 8

- Day Acute Dietary LC50 Study in Bobwhite Quail: Biometric

testing

- supplemental

71

- 4 Avian Reproduction

MRID Citation Reference

41993201 Fletcher, D.; Pedersen, C. (1991) Oxadiazon Technical: Toxicity and

Reproduction Study in Mallard Ducks: Lab Project Number: 89 DR 35. Unpublished study prepared by Bio

- Life Associates, Ltd. 138 p.

41993202 Fletcher, D.; Pedersen, C. (1991) O xadiazon Technical: Toxicity and

Reproduction Study in Bobwhite Quail: Lab Project Number: 89 QR 39. Unpublished study prepared by Bio

- Life Associates, Ltd. 145 p.

72

- 1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

68524 Rob erts, S. (1977) Report: Static 96

- hour Toxicity Study of Rhodia

Oxadiazon in Bluegill Sunfish and Rainbow Trout: Laboratory No. 7E

5605. (Unpublished study received Mar 31, 1977 under 359

- 679; prepared by Cannon Laboratories, Inc., submitted by Rhone

- Poule nc Chemical Co., Monmouth Junction, N.J.; CDL: 229201

- A)

68525 Roberts, S. (1977) Report: Static 96

- hour Toxicity Study of Rhodia

Ronstar EC in Bluegill Sunfish and Rainbow Trout: Laboratory No. 7E

5604. (Unpublished study received Mar 31, 1977 under 35 9

- 679; prepared by Cannon Laboratories, Inc., submitted by Rhone

- Poulenc Chemical Co., Monmouth Junction, N.J.; CDL: 229201

- B)

111808 Posner, S.; Jolly, E.; Grim, J. (1971) Acute LC50 96

- hour (Static) of RP

17623 to Rainbow Trout (Salmo Gairdneri); Cray fish (Oronectes) and Brown Bullheads (Ameiurus Nebulous): Experi

- mental Reference No.

### 26 49

- 269A. (Unpublished study received Aug 23, 1972 under 359

- 658; prepared by Biometric Testing, Inc., submitted by Rhone

- Poulenc, Inc., Monmouth Junction, NJ; CDL: 00317 9

- D)

112623 Posner, S.; Jolly, E.; Grim, J. (1971) Acute LC50 96

- hour (Static) of RP

17623 to Rainbow Trout (Salmo gairdneri); Crayfish (Oro

- nectes) and Brown Bullheads (Ameiurus nebulosus): Experimental Reference No. 49

- 269A. (Unpublished study receiv ed Oct 14, 1972 under 2F1269; prepared by Biometric Testing, Inc., submitted by Rhodia, Inc., New Brunswick, NJ; CDL:091824

- E)

42330401 Sword, M.; Northup, R. (1992) Acute Flow

- Through Toxicity of

Oxadiazon to Rainbow Trout (Oncorhynchus mykiss): Lab Pr oject Number: 39729. Unpublished study prepared by ABC Laboratories, Inc. 211 p.

42350601 Sword, M.; Northup, R. (1992) Acute Flow

- through Toxicity of

Oxadiazon to Bluegill (Lepomis macrochirus): Final Report: Lab Project Number: 39728. Unpublished stud y prepared by ABC Labs., Inc. 194 p.

TN 1075 McCann, J.A. 1977. Beltsville Animal Biology Lab Acute Rainbow trout

test with 2% formulation

TN 1077 McCann, J.A. 1977. Beltsville Animal Biology Lab Acute Rainbow trout

test with technical

TN 1082 McC ann, J.A. 1977. Beltsville Animal Biology Lab Acute Rainbow trout

test with 25%EC Formulation

TN 1086 McCann, J.A. 1977. Beltsville Animal Biology Lab Acute Bluegill test

with technical

92135003 Gregg, B. (1990) Rhone

- Poulenc Ag Company Phase 3 Summ ary of

MRID 00068524 and Related MRIDs 00068525. Oxadiazon

- Static 96

- hr Toxicity Study of Rhodia Oxadiazon (Technical) in Bluegill Sunfish and Rainbow Trout: Project 7E

- 5605 and Project 7E

- 5604. Prepared by Cannon Laboratories, Inc. 26 p.

72

- 2 A cute Toxicity to Freshwater Invertebrates

MRID Citation Reference

61810 Rhone

- Poulenc Chemical Company (19??) Herbicides

--

Toxicity of Oxa

- diazon to Daphnia (~Daphnia pulex~): Addendum to Report R.P./ R.D./C.N.G. No. 18939. (Unpublished study rec eived Apr 27, 1977 under 359

- 679;
CDL:229610

- A)

### 27

66074 Roberts, S.; Parke, G.S.E.; Charles, S.J., III (1977) Report:

Static 96

- hour Toxicity Study of Oxadiazon Technical 97.2% in Daphnids: Laboratory No. 7E

- 6485. (Unpublished study received Jul 18, 1977 under 359

- 679; prepared by Cannon Laboratories, Inc., submitted by Rhone

- Poulenc Chemical Co., Monmouth Junction, N.J.; CDL:230862

- A)

111808 or
112623 Posner, S.; Jolly, E.; Grim, J. (1971) Acute LC50 96

- hour

(Static) of RP 17623 to Rainbow Trout (Salmo Gairdneri); Crayfish (Oronectes) and Brown Bullheads (Ameiurus Nebulous): Experi

- mental Reference No. 49

- 269A. (Unpublished study received Aug 23, 1972 under 359

- 658; prepared by Biometric Testing, Inc., submitted by Rhone

Poulenc, Inc., Monmouth Junctio n, NJ; CDL: 003179

- D)
CDL:091824

- E)

111809 Jolly, E.; Grim, J. (1971) RP17623 (Ronstar): Subacute

Toxicity and Residues in Crayfish (Oronectes): Biological Phase (Static): Experimental Reference No. F

- 269. (Unpublished study received Aug 23, 1972 under 3 59

- 658; prepared by Biometric Testing, Inc., submitted by Rhone

Poulenc, Inc., Monmouth Junction, NJ; CDL: 003179

- E)

111842 Roberts, S.; Parke, G. (1977) Static 48

- hour LC50 of Ronstar in

Daphnids: Laboratory No. 7E

- 7354. (Unpublished study received Apr 24, 1978 under 359

- 675; prepared by Cannon Laboratories, Inc., submitted by Rhodia, Inc., Monmouth Junction, NJ; CDL: 097047

- B)

42331801 Blasberg, J.; Bowman, J. (1992) Acute Toxicity of Oxadiazon

to Daphnia magna under Flow

- through Conditions: Amended Final Report: Lab Project Number: 39730. Unpublished study prepared by ABC Labs, Inc. 254 p.

92135004 Gregg, B. (1990) Rhone

- Poulenc Ag Company Phase 3

Summary of MRID 00066074. Oxadiazon

-- Static 96

- hr Toxicity Study

-- Daphnids: Project 7E

- 6485. Prepare d by Cannon Laboratories, Inc. 25 p.

36620 or
113944 Rhodia, Incorporated (1971) Report of the Analysis of the

Crayfish and Water for RP 17623 Samples Obtained in the Study Titled: RP 17623 (Ronstar) Subacute Toxicity and Residues in Crayfish (Oronecte s) Biological Phase (Static). (Unpublished study re

- ceived Oct 14, 1972 under 2F1269;
CDL:092170

- I) CDL:091824

- G)

113943 Jolly, E.; Grim, J. (1971) RP17623 (Ronstar): Subacute

Toxicity and Residues in Crayfish (Oronectes) Biological Phase (Static): Expe rimental Reference No. F

- 269. (Unpublished study received Oct 14, 1972 under 2F1269; prepared by

### 28 Biometric Testing, Inc., submitted by Rhodia, Inc., New Brunswick, NJ; CDL:091824

- F)

48561 Ambrosi, D.; Desmoras, J.; Savary, ? (1976) Herbicides:

Toxicity of Oxadiazon to Daphnia (~Daphnia pulex~): R.P./R.D./ C.N.G. No. 18 939. (Translation; unpublished study received Jan 28, 1977 under 359

- 659; prepared by Rhone

Poulenc Industries, France, submitted by Rhone

- Poulenc Chemical Co., Monmouth Junc

- tion, N.J.; CDL:227657

- C)

TN 1087 McCann, J.A. 1977. Beltsville Animal Biology Lab Acute

daphnia test with technical

72

- 3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

42570301 Dionne, E. (1992) Oxadiazon Technical

-- Acute T oxicity to Eastern

Oyster (Crassostrea virginica) under Flow

- through Conditions: Final Report: Lab Project Number: 92

- 7

- 4329: 10566. 0392.6238.504. Unpublished study prepared by Springborn Labs, Inc. 63 p.

42615801 Machado, M. (1992) Oxadiazon Technical

-- Acute Toxicity to Sheepshead

Minnow (Cyprinodon variegatus) under Flow

- through Conditions: Final Report: Lab Project Number: 92

- 8

- 4383 10566.0392.6237.505. Unpublished study prepared by Springborn Labs, Inc. 66 p.

42615802 Machado, M. (1992) Oxadiazon Technical

-- Acute Toxicity to Mysid

Shrimp (Mysidopsis bahia) under Flow

- through Conditions: Final Report: Lab Project Number: 92

- 7

- 4348: 10566.0392.6236.515. Unpublished study prepared by Springborn Labs, Inc. 65 p.

72

- 4 Fish Early Life Stage/Aqu atic Invertebrate Life Cycle Study

MRID Citation Reference

41784301 Blakemore, G.; Burgess, D. (1991) Chronic Toxicity of Oxadiazon

Technical to Daphnia magna under Flow

- thru Conditions: Final Report: Lab Project Number: 38369. Unpublished study prepared by Analytical
Bio

- Chemistry Labs., Inc. 349 p.

41811601 Rhodes, J.; McAllister, W.; Leak, T. (1991) Early Life

- sta ge Toxi

- city of

?carbon 14|

- Oxa diazon Technical to the Rainbow Trout (Oncorhynchus mykiss) Under Flow

- through Conditions: Final R eport: Lab Project Number: 38370. Unpublished study prepared by ABC Laboratories, Inc. 129 p.

### 29

42921601 Rhodes, J. (1993) Early Life

- Stage Toxicity of Oxadiazon Technical to

the Fathead Minnow (Pimephales promelas) Under Flow

- Through Conditions: Lab Proj ect Number: 40024. Unpublished study prepared by ABC Labs. Inc., Environmental Toxicology. 432 p.

46473304 Lima, W. (2004) Oxadiazon Technical

- Life

- Cycle Toxicity Test with

Mysids (Americamysis bahia). Project Number: EBOAX014, 13798/6146, 040103/FIFR A/MYSID/LC. Unpublished study prepared by Springborn Smithers Laboratories. 86 p.

46473301 Chalmers, A. (2005) Rationale for Waiver Requests for Three Aquatic

Studies with Oxadiazon: 850.1400 Fish Early Life

- Stage Toxicity Test, Aquatic Phototoxicity S tudy, Aquatic Sediment Testing (Chronic). Unpublished study prepared by Bayer CropScience LP. 8 p.

122

- 1 Seed Germination/Seedline Emergence and Vegetable Vigor

MRID Citation Reference

46676501 Christ, M.; Lam, C. (2005) Tier I Seedling Em ergence and Vegetative

Vigor Nontarget Toxicity Study. Project Number: 2011154, Y0455001, Y0455002. Unpublished study prepared by Bayer Environmental Science. 47 p.

122

- 2 Aquatic plant growth

MRID Citation Reference

42659001 Mihaich, E. ( 1993) Response to EPA Review of Oxadiazon Anabaena

flos

- aquae Study (MRID 41610104) and Selenastrum caprocornutum (sic) Study (MRID 41610108): Lab Project No. NS/EMM

- 93

- 03. Unpublished study prepared by Rhone

- Poulenc Ag Co. and Springborn Labs., Inc. 10

p.

123

- 1 Seed germination/seedling emergence and vegetative vigor

MRID Citation Reference

41898001 Hoberg, J. (1991) Oxadiazon Technical

-- Determination of Effects on

Seed Germination, Seedling Emergence and Vegetative Vigor of Ten Plant Sp ecies: Final Report: Lab Project Number: 90

- 11

- 3547: 10566

- 0790

- 6165

- 610. Unpublished study prepared by Springborn Laboratories, Inc. 164 p.

### 30

46676502 Christ, M.; Lam, C. (2005) Tier II Seedling Emergence: Nontarget

Phytotoxicity Study Using Ronstar WP50 . Project Number: 201246, EBOAX011. Unpublished study prepared by Bayer CropScience LP. 57

p.

46676503 Christ, M.; Nuessle, C. (2005) Tier II Vegetative Vigor: Nontarget

Phytotoxicity Study Using Ronstar WP50. Project Number: 201247, EBOAX013. Unpublishe d study prepared by Bayer CropScience LP. 69

p.

123

- 2 Aquatic plant growth

MRID Citation Reference

41610105 Giddings, J. (1990) Oxadiazon Technical

- Toxicity to the Marine Dia

- tom

Skeletonema costatum: Lab Project Number: 90

- 7

- 3384: 1 0566

- 1089

- 6137

- 450. Unpublished study prepared by Springborn Labora

- tories, Inc. 55 p.

41610106 Giddings, J. (1990) Oxadiazinon Technical

- Toxicity to the Fresh

- water

Diatom Navicula pelliculosa: Lab Project Number: 90

- 8

- 3423; 10566

- 1089

- 6137

- 440. Unp ublished study prepared by Springborn Laboratories, Inc. 52 p.

41610107 Giddings, J. (1990) Oxadiazon Technical

- Toxicity to the Duckweed

Lemma gibba G3: Final Report: Lab Project Number: 90

- 7

- 3389; 10566.1089.6137.410. Unpublished study prepared by Spri ngborn Laboratories, Inc. 48 p.

41610108 Giddings, J. (1990) Oxadiazon Technical

- Toxicity to the Freshwater Green

Alga Selenastrum capricornutum: Amended Report: Lab Pro

- ject Number:
90

- 8

- 3422; 10566.1089.6137.437. Unpublished study prepared by Springb orn Laboratories, Inc. 52 p.

141

- 1 Honey bee acute contact

MRID Citation Reference

42468301 Beevers, M. (1992) Acute Contact Toxicity of Oxadiazon Technical to

Honey Bees (Apis mellifera L.): Lab Project Number: CAR 160

- 92. Unpublished s tudy prepared by California Agricultural Research, Inc. 14 p.

850.1735 Whole sediment: acute freshwater invertebrates

### 31

MRID Citation Reference

46473303 Putt, A. (2004) Oxadiazon

- Toxicity to Freshwater Amphipods (Hyalella

azteca) During a 10

- Day Sediment Exposure. Project Number: EBOAY002, 13798/6152, 102803/10/DAY/HYALELLA. Unpublished study prepared by Springborn Smithers Laboratories. 64 p.

46487301 Putt, A. (2004) Oxadiazon

- Toxicity to Midge (Chironomus tentans)

During a 10

- Day Se diment Exposure. Project Number: EBOAY/003, 13798/6151. Unpublished study prepared by Springborn Smithers Laboratories. 69 p.



### c. Other References

Rahman. M. M., Kim T

- H, Kwon G

- S, Yang J.E, Park M, and Kim J

- E. 2009. Removal Efficiency of the Herbicide Ox adiazon in Treatment Processes for Drinking Water . J. Korean Soc. Appl. Biol. Chem.; 52(3); 252

- 257

USEPA. 2001. EFED Risk Assessment for the Reregistration Eligibility Decision of Oxadiazon.
DP Barcode D277968.

USEPA. 1995. Data Reviews for Oxadi azon. D166982.

### 32



### Appendix X. SIP output

Table 1. Inputs

Parameter Value
Chemical name Oxadiazon Solubility (in water at 25 o C; mg/L) 1

Mammalian LD 50 (mg/kg

- bw) 5000 Mammalian test species laboratory rat Body weight (g) of "oth er" mammalian species

Mammalian NOAEL (mg/kg

- bw) 12 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg

- bw) 2150 Avian test species northern bobwhite quail Body weight (g) of "other" avian species Mineau scaling factor 1.15

Mallard NOAEC (mg/kg

- diet) 1000 Bobwhite quail NOAEC (mg/kg

- diet) 500 NOAEC (mg/kg

- diet) for other bird species 0 Body weight (g) of other avian species NOAEC (mg/kg

- diet) fo r 2nd other bird species 0 Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic Upper bound exposure (mg/kg

- bw) 0.1720 0.1720 Adjusted toxicity value (mg/kg

- bw) 3845.8028 9.2299 Ratio of expos ure to toxicity 0.0000 0.0186

Conclusion* Drinking water exposure alone is NOT a potential concern for mammals Drinking water exposure alone is NOT a potential concern for mammals

Table 3. Avian Results

Parameter Acute Chronic Upper bound ex posure (mg/kg

- bw) 0.8100 0.8100 Adjusted toxicity value (mg/kg

- bw) 1548.9235 49.6126 Ratio of exposure to acute toxicity 0.0005 0.0163

Conclusion* Drinking water exposure alone is NOT a potential concern for birds Drinking water exposure alone is NOT a potential concern for birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when aggregated with other routes ( i.e ., diet, inhalation, dermal), pesticide exposure through drinking water may cont ribute to a total exposure that has potential for effects to non

- target animals.

### 33 

### Appendix X. STIR Output for

Oxadiazon 

# Welcome to the
EFED Screening Tool for Inhalation Risk

This tool is designed to provide the risk assessor with a rapid method for determining the potential significance of the inhalation exposure route to birds and mammals in a risk assessment.



## Input

Application and Chemical Information

Enter Chemical Name Oxadiazon
Enter Chemical Use Turf Is the Applicat ion a Spray? (enter y or n) y If Spray What Type (enter ground or air) ground Enter Chemical Molecular Weight (g/mole) 345.2 Enter Chemical Vapor Pressure (mmHg) 1.00E

- 06 Enter Application Rate (lb a.i./acre) 4

Toxicity Properties

Bird

Enter Lowest Bird Oral LD 50 (mg/kg bw) 2150 Enter Mineau Scaling Factor 1.15 Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD 50 (mg/kg bw) 5000

Enter Lowest Rat Inhalation LC 50 (mg/L) 1.94
Duration of Rat Inhalation Study (hrs) 4 Enter Rat Weight (kg) 0.35



## Output
Results Avian (0.020 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.86E

- 02
Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 2.34E

- 03
Adjusted Inhalation L D 50 4.65E+00
Ratio of Vapor Dose to Adjusted Inhalation LD 50 5.02E

- 04 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 4.23E

- 01 Ratio of Droplet Inhalation Dose to Adjusted Inhalation
LD 50 9.09E

- 02 Exposure not Likely Significant



### Results Mammalian (0.015 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 1.86E

- 02

### 34

Maximum 1

- hour Vapor Inhalation Dose (mg/kg) 2.94E

- 03
Adjusted Inhalation LD 50 1.15E+02
Ratio of Vapor Dose to Adjust ed Inhalation LD 50 2.54E

- 05 Exposure not Likely Significant

Maximum Post

- treatment Spray Inhalation Dose (mg/kg) 5.31E

- 01 Ratio of Droplet Inhalation Dose to Adjusted Inhalation
LD 50 4.60E

- 03 Exposure not Likely Significant

### 35

APPENDIX C. Study Just ification Tables

Oxadiazon is not to be applied on residential turf (by either home owners or commercial applicators) but could be applied to residential ornamental ground cover and shrub beds only by professional applicators. It could also be applied by professional applicators to turf in apartment/condominium complexes, parks, athletic fields, playground, and cemeteries and on golf courses (predominant use). In addition, oxadiazon is used on sod farms and on conifer plantations/nurseries, and other nur series (containerized or non

- containerized nursery plants ) . It can also be applied to non

- agricultural areas, right

- of

- way, and landscape are a s (i.e., industrial sites, ornamental, roadside plantings, woody, ornamental shrubs, vines and trees and herbaceou s ornamentals). Oxadiazon use sites are classified as non

- food sites ( i.e. , primarily golf course fairways , outdoor use, roadsides and nurseries )

.

Guideline Number: Special Study Study Title: Adult Honey Bee Chronic Oral Toxicity
Rationale for Requ iring the Data
This study is needed for the assessment to evaluate risks to honey bees if the registered uses of oxadiazon will result in adverse effects to honey bees or other insect pollinators. Registered use sites of oxadiazon include: ornamental gro und cover, turf in parks, field, playground, cemeteries and golf courses, sod farms, conifer nurseries, and landscapes. Therefore, oxadiazon residues may result in exposure to foraging bees. Residues can in turn be brought back to bee colonies
where in

- hi ve bees including young adult and developing brood ( i.e. , eggs, larvae and pupae) may be exposed. Therefore, exposure at all bee life stages would be expected and may extend for chronic exposures.

EPA now requires this study for all use sites where p otential exposure to pollinators may occur (2014)

. Registrants may request a waiver of the study if use practices significantly restrict exposure of the pesticide to bees.

Although EPA has not developed a guideline for this study and OECD has yet to fina lize test guidance for chronic studies, efforts are currently underway to develop standardized guidelines for assessing effects from chronic (10

- day) exposures to adult bees in the laboratory. At this time, EFED is asking that a protocol for the study be submitted beforehand to increase the likelihood of an acceptable study submission.
Practical Utility of the Data
How will the data be used and how could the data impact the Agency’s future decision

making?

The 10

- day toxicity study with young adult bee s provides no

- observed adverse effect level (NOAEL) and lowest

- observed adverse effect level (LOAEL) for assessing potential chronic effects. Data obtained from this study will be used in estimating chronic risk to individual adult
bees. Risk estimates ba sed on these data will be considered along with other lines of evidence to determine whether higher

- tier studies are needed at the whole colony level.

### 36

Guideline Number: Special Study Study Title: Adult Honey Bee Chronic Oral Toxicity
Rationale for Requ iring the Data These data are needed for the registration review risk assessment and for future endangered species

asse ssments. The data would allow the Agency better characterize the potential for risk to insects (including beneficial pollinators) from the use of oxadiazon . These data will help the Agency determine whether any mitigations are needed. If the registration review and any future endangered species risk assessments are performed without these data, the Agency would have to
assume that oxadiazon "may affect" insects, including bees and beneficial pollinators, directly (and endangered species from other taxa in directly), and uses of oxadiazon might need to be restricted in areas where pollinators could be exposed.

Guideline Number: Non

- Guideline Study Title: Larval Honey Bee Acute and Chronic Oral Toxicity
Rationale for Requiring the Data
This study is ne eded for the assessment to evaluate risks to honey bees if the registered uses of
oxadiazon will result in adverse effects to honey bees or other insect pollinators. Registered use sites of oxadiazon include: ornamental ground cover, turf in parks, field, playground, cemeteries and golf courses, sod farms, conifer nurseries, and landscapes. Therefore, oxadiazon residues may result in exposure to foraging bees. Residues can in turn be brought back to bee colonies
where in

- hive bees including young adult an d developing brood ( i.e. , eggs, larvae and pupae) may be exposed. Therefore, exposure at all bee life stages would be expected and may extend for chronic exposures.

EPA now requires this study for all use sites where potential exposure to pollinators m ay

occur. Registrants may request a waiver of the study if use practices significantly restrict exposure of the pesticide to bees.

Although EPA has not developed a guideline for this study, the 21

- day larval toxicity study currently under development by OECD provides both acute and chronic oral toxicity data on developing bee brood and (when this guidance is finalized) may be used to satisfy the requirement for both acute and chronic oral toxicity to honey bee larvae. Registrant may submit a separate acu te (single dose) larval toxicity study following OECD TG237 as well as the 21

- day repeat dose chronic toxicity study.
Practical Utility of the Data
How will the data be used and how could the data impact the Agency’s future decision

making?

The 21

- da y larval toxicity study under development by OECD provides both acute and chronic toxicity data on developing bee brood and will yield a median lethal dose (LD 50 

### ) for assessing acute toxicity during the early part of the study as well as a 21

- day no

- observ ed adverse effect level (NOAEL) and lowest

- observed adverse effect level (LOAEL) for assessing chronic
effects. Effects on survival and development (adult bee emergence) from repeat exposures to the active ingredient will be used in estimating chronic ris k to individual brood. Risk estimates based

### 37

Guideline Number: Non

- Guideline Study Title: Larval Honey Bee Acute and Chronic Oral Toxicity
Rationale for Requiring the Data on these data will be considered along with other lines of evidence to determine whether higher

tier studies are needed at the whole colony level.

These data are needed for the registration review risk assessme nt and for future endangered species

assessments. The data would allow the Agency better characterize the potential for risk to insects (including beneficial pollinators) from the use of oxadiazon . These data will help the Agency determine whether any mit igations are needed. If the registration review and any future endangered species risk assessments are performed without these data, the Agency would have to
assume that oxadiazon "may affect" insects, including bees and beneficial pollinators, directly ( and endangered species from other taxa indirectly), and uses of oxadiazon might need to be restricted in areas where pollinators could be exposed.