- 2 of 41

- 1) Aerobic soil metabolism ( OCSPP guideline # 835.4100). Though there is acceptable aerobic soil metabolism data for one type of soil, t he guideline stipulates that results from at least four relevant soils of different organic carbon content, pH, clay content, and microbial biomass must be submitted in order to characterize the variability in the aerobic biodeg radation of Pryithiobac

- Na in the environment. 2) Aerobic aquatic metabolism (O CSPP guideline # 835.4300). There are no acceptable aerobic aquatic metabolism studies. This study is necessary in order to describe the fate of Pyrithiobac

- Na in surface water bo dies down

- gradient from use sites (e.g., rice paddies). The guideline stipulates that at least two different soil:water systems be submitted that are similar to the potential use sites in the United States. There is currently one supplemental study that la cks information on the aerobicity of the soil:water system. 3) Anaerobic aquatic metabolism ( O CSPP guideline # 835.4400). Submission of an acceptable anaerobic aquatic metabolism study is necessary to understand the degradation of Pyrithiobac

- Na in oxygen

- lim iting environments. 4) Environmental chemistry methods in water being reviewed by EFED. However, definitive conclusions cannot be made until the final report is reviewed which will be done prior to completion of the draft risk assessment. Although these stud ies have been submitted to EPA they will be considered data gaps until the data have been reviewed and found to be acceptable. 5) An independent laboratory validation (ILV) report for Environmental chemistry method in water is needed.

The available effects data are considered incomplete for the purposes of risk assessment. The following data gaps exist:
1) Avian acute oral toxicity ( O CSPP guideline # 850.2100 ) . Avian acute oral toxicity data are not available for passerines, which are required under the new 4 0 CFR Part 158. 2) Seedling emergence ( OCSPP guideline # 850.4 100 ). There is no acceptable tier II data for seedling emergence. The new 40 CFR Part 158 requires the use of typical end use product (TEP), while the submitted study used the technical grade ac tive ingredient (TGAI). Without data on the effects of the TEP on seedling emergence , the data are not sufficient for risk assessment. Herbicidal active ingredients are usually formulated with adjuvants or surfactants that enhance the activity of the pesti cide. Therefore, the sensitivity of terrestrial plants to Pyrithiobac

- Na may be underestimated. 3) Vegetative vigor ( OCSPP guideline # 850.4 1 50). There is no acceptable tier II data for vegetative vigor. The new 40 CFR Pa rt 158 requires the use of typical end use product (TEP), while the submitted study used the technical grade active ingredient (TGAI)

. Without data on the effects of the TEP on vegetative vigor, the data are not sufficient for risk assessment. Herbicidal active ingredients are usually form ulated with adjuvants or surfactants that enhance the activity of the pesticide. Therefore, the sensitivity of terrestrial plants to Pyrithiobac

- Na may be underestimated.
Additional detail on the current data gaps for environmental fate and effect is p rovided in Section 8.0.- 3 of 41

- 

# Problem Formulation for the Environmental Fate and Ecological Risk, Endangered Species, and Drinking

Water Assessments in Support of the Registration Review of Pyrithiobac

- Na

Sodium 2

- chloro

- 6

- [( 4,6

- dimethoxypryrimidin

- 2

- yl0thio]benzoate 

### CAS Registry Number: 123343

- 16

- 8 PC Code: 078905

Prepared by: Elizabeth Riley , Biologist Ibrahim Abdel

- Saheb
, Ph.D., Environmental Scientist U. S. Environmental Protection Agency Office of Pesticide Programs En vironmental Fate and Effects Division Environmental Risk Branch VI 1200 Pennsylvania Ave., NW Mail Code 7507P Washington, DC 20460 Reviewed by: Mark Corbin, Branch Chief William P. Eckel, Ph.D., Senior Science Advisor Mary Frankenberry , Ph.D., Statisticia n Stephanie Syslo, RAPL- 4 of 41

- May 25, 2011

1. Purpose
The purpose of this problem formulation is to provide an understanding of what is known about the environmental fate and ecological effects of the registered uses of Pyrithiobac

- Na (PC Code 078905)

. Py rithiobac

- Na is a selective pre

- and post

- emergent herbicide. This document will provide a plan for analyzing data relevant to Pyrithiobac

- Na and for conducting environmental fate and ecological risk, endangered species, and drinking water assessments for its registered uses. Additionally, this problem formulation is intended to identify data gaps, uncertainties, and potential assumptions used to address those uncertainties relative to characterizing the ecological risk associated with the registered uses of Pyrithiobac

- Na

.

2. Problem Formulation
2.1. Nature of Regulatory Action
Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed or sold in the United States generally must be registered by the Environmenta l Protection Agency (EPA). As part of determining whether a pesticide can be registered in the U.S., the Agency evaluates its safety to non

- target species based on a wide range of environmental and health effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act, and the Agency was mandated to implement a new program for the periodic review of pesticides, i.e ., Registration Review ( http://www.epa.gov/oppsrrd1/registration_re view/ ). The Registration Review program is intended to ensure that, as the ability to assess risk evolves and as policies and practices change, all registered pesticides continue to meet the statutory standard of no unreasonable adverse effects to human health and the environment. Changes in science, public policy, and pesticide use practices occur over time. Through the new Registration Review program, the Agency periodically reevaluates pesticides to make sure that as change occurs, products in the ma rketplace can be used safely.
As part of the implementation of the Registration Review program pursuant to Section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its evaluation of Pyrithiobac

- Na to determin e whether it continues to meet the FIFRA standard for registration. This problem formulation for the environmental fate, ecological risk, endangered species, and drinking water assessment chapter in support of the Registration Review will be posted in the initial docket, which will open the public phase of the review process.

2.2

. Previous Risk Assessments
The Most recent ecological risk assessment was conducted in 1995 in support of Pyrithiobac

Na’s initial registration (New Chemical Review of Environme ntal Fate and Transport Data for the Herbicide Pyrithiobac

- Na (DPX

- PE350, STAPLE ® ) on Cotton, 1995 , DP Barcodes 215858,- 5 of 41

- 215730, 208476, and 208481 and New Chemical Review of Environmental Effects Data for the Herbicide Pyrithiobac

- Na (DPX

- PE350, STAPLE ® ) o n Cotton, 1995 , DP Barcode 208477 and 208482 )

.
Review of the environmental fate data determined that there were some concerns regarding the use of Pyrithiobac

- Na on cotton because the submitted field and laboratory studies suggest it is mobile and slightl y to moderately persistent. Downward transport of Pyrithiobac

- Na may occur in certain environments where it could potentially leach to ground water (i.e., coarse textured soils, shallow depth to ground water) with surplus rainfall or irrigation.
The Agenc y recommended the proposed label to include the following language:

“ This chemical demonstrates the properties and characteristics associated with chemicals detected in groundwater. The use of this chemical in areas with coarse textured soils where the wa ter table is shallow may result in groundwater contamination ”

“ Application should not be made to field areas which are less than 100 feet from permanent natural bodies of surface water or reservoirs”
Based on the submitted field and laboratory studies th at were suggesting mobility and persistence of P y rithiobac

- Na in the environment, in 1995 EFED asked for a prospective groundwater monitoring study to be conducted as a registration requirement

.
Results from the small

- scale prospective groundwater monitor ing study conducted in North Carolina indicated that Pyrithibac

- Na may not be stable enough to leach to ground water at most sites, even in sandy soils. This study appears to have been conducted at a site with groundwater highly vulnerable to contamination . However, it is not clear that the amounts and timing of water input were such that the leaching would be significantly more likely than in an average year at the test site.

Review of the environmental effects data determined that there were no risks to terrestrial and aquatic animals and invertebrates. However, data on the effects of Pyrithiobac

- Na on avian reproduction were not available, so this data was requested to address the uncertainties

. An acceptable avian reproduction study was submitted to the Agency in response to this Data Call In (DCI).

This review also determined that use of Pyrithiobac

- Na does pose a significant risk to terrestrial and aquatic vascular plants, which is expected from an herbicide. The reviewer suggested that mitigation me asures be put in place for use of Pyrithiobac

- Na, including: geographic restrictions on location and soil type, application rate reduction, reduction in the number of annual applications, minimizing drift, and establishment of buffer zones.

In addition t o mitigation measures to reduce impact of Pyrithiobac

- Na on non

- target plant species, the following labeling language was suggested:- 6 of 41

- End use product: “Do not apply directly to water, or areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwater or rinsate”
Manufacturing use: “Do not discharge affluent containing this product into lakes, streams, ponds, estuaries, oceans, or other waters unless in accordance wit h requirements of a National Pollutant Discharge Elimination System (NPDES) permit and the permitting authority has been notified in writing prior to discharge. Do no discharge effluent containing this product to sewer systems without previously notifying the sewage treatment plant authority. For guidance, contact your local State Water Board or Regional Office of the EPA.”

3. Stressor Source and Distribution

3.1. Mechanism of Action
The mode of action for Pyrithiobac

- Na is inhibition of a specific plant enzyme, acetolactate synthase ( acetohydoxyacid synthase AHAS) , resulting in interference with normal branched chain amino acid biosynthesis, cell division, and plant growth. There is some evidence 1

3.2. Overview of Pesticide Use and Usage to suggest plant reproduction may be affected by ALS inhib itors, such as sulfonylurea herbicides, at levels below effects on vegetative growth or visual injury (Fletcher et al ., 1993). Pyrithiobac

- Na can terminate both monocotyledonous and dicotyledonous plant species following application at relatively low rates (35

- 140 g/ha) and has demonstrated a high selectivity for cotton plants (Shimizu et al. 1994).

Pyrithiobac

- Na is a selective pre

- and postemergent herbici de used to control a variety of broadleaf weeds in cotton field s

. Pyrithiobac

- Na is also registered for use on kenaf in three states under a section 24c special local needs registration. The registered end

- use formulation s of Pyrithiobac

- Na include a water soluble powder and soluble

- concentrate

. P yrithiobac

- Na is app lied by aerial or ground spray, broadcast, band, and spot treatment. Use practice limitations prohibit applying or allowing Pyrithiobac

- Na to drift to areas where endangered or desired plant species exis t and discharging into bodies of water

.
There are c urrently six Section 3 registered products as well as three SLN registrations for Pyrithiobac

- Na ( Table 3.1 ).
TABLE 3.1. Summary of Registered Products Containing Pyrithiobac

- Na in the U.S. Registration # Name Company Name Percent Pyrithiobac

352

- 575 DUPONT KIH

- 2031 (DPX

- PE350) TECHNICAL E. I. DU PONT DE NEMOURS AND CO., INC 96.4

1 Snipes et al. 1992, Bansal et al. 1999; Fletcher et al. 1993, 1995,1996; Bhatti et al. 1995; Al

- Khatib et al. 1992; Boutin et al. 2000; Asghari and Evans 1992- 7 of 41

- Registration # Name Company Name Percent Pyrithiobac

352

- 576 DUPONT STAPLE HERBICIDE E. I. DU PONT DE NEMOURS AND CO., INC 85

352

- 613 DUPONT STAPLE LX HERBICIDE E. I. DU PONT DE NEMOURS AND CO., INC 33.6

66222

- 175 PYRIMAX 3.2 L HERBICIDE MAKHTESHIM

- AGAN OF NORTH AMERICA INC 32.88

83558

- 11 PYRITHIOBAC

SODIUM TECHNICAL CELSIUS PROPERTY B.V., AMSTERDAM (NL) 96.5

85588

- 11 PYSONEX HERBICIDE AGSURF CORPORATION 33.6

NC030002 DUPONT STAPLE HERBICIDE E. I. DU PONT DE NEMOURS AND CO. , INC 85

OK970001 DUPONT STAPLE HERBICIDE E. I. DU PONT DE NEMOURS AND CO., INC 85

TN050005 DUPONT STAPLE HERBICIDE E. I. DU PONT DE NEMOURS AND CO., INC 85

A summary of currently registered Pyrithiobac

- Na uses, along with their respective methods a nd rates of application is presented in Table 3.2

. For two registered uses listed below (registration numbers 352

- 613 and 66222

- 175), there is a discrepancy recorded on the label between the number of applications that can be made in one year and the appl ication interval. Based on the label’s seasonal single application rate and application interval, the number of applications should be equal to 2.4 and not 1/yr as indicated on label.

Table 3.2. Registered Use Patterns for Pyrithiobac

- Na

.

Use Pattern

(Reg. No) Single App. Rate (lbs ai/A) Number of App. Seasonal App. Rate (lbs ai/A) App. Interval

(days) Application Method Comments

Cotton (352

- 576) 0.095625 Not specified 0.1275 7 Aerial , ground and band

spray Pre

- and post

emergence

Cotton (352

- 613) 0.05292 1/year 0.12852 7 Ground spray Pre

- emergence

Cotton (352

- 613) 0.09576 Not specified 0.12852 7 Aerial, ground and band

spray Post

- emergence

Cotton (66222

- 175) 0.05259516 1/year 0.12773109

-- Ground Pre

- emergence

Cotton (66222

- 175) 0.09517219 Not specified 0.12773109 Not specified Aerial, ground and band

spray Pre

- and post

emergence- 8 of 41

- 3.3. Environmental Fate and Transport
As stated previously, Pyrithio bac

- Na is an herbicide used for weed control on cotton. At this time, 

### t he following data requirements for Pyrithiobac

- Na have been satisfied:
835.2120

- Hydrolysis 835.2240

- Photodegradation in Water 835.2410

- Photodegradation on Soil 835.4200

- Anaer obic Soil Metabolism ' 835.1230/1240

- Mobility (Leaching/Sorption) 835.6100

- Terrestrial Field Dissipation

For details, see Table 8. 1

.

Pyrithiobac

- Na
Empirical Formula: C 13 H 11 CIN 2 NaO 4 S CAS Registry No.: 123342

- 93

- 8 PC Code: 078905
Pyrithiobac

- Na is a pale yellow powder with a faint ester

- like odor and a melting point of 233

- 234oC. Pyrithiobac

- Na solubility varies with pH and ranges from 117

- 728 mg/L water

.
Table 3.4 summarizes the submitted environmental fate data for Pyrithiobac

- Na

. Additiona l characterization of the submitted environmental fate data is located in Appendix A

. Kenaf (NC030002) (TN050005) 0.06375 Not specified 0.1275 Not specified Foliar Post

- emergence- 9 of 41

- Parameter Value Reference (MRID #) Physical/Chemical Parameters Molecular mass (g/mol) 348.74 Footprint Pesticide Properties Database available @ http://sitem.herts.ac.uk/aeru/foo tprint/en/ accessed on April 12, 2011. Vapor pressure (mmHg @ 25°C) 4.80 X 10 - 06 Henry’s Law Constant (25oC) 9.44 X 10 - 16

Water solubility ( g/L @ 20°C) Varies with pH fro m 117 to 690 mg/L MRID# 42856907 Octanol

- water partition coefficient (K OW ) 4.02 (pH 5) 0.15 (pH 7) 0.06 (pH 9) MRID# 42856907

Dissociation constant (pKa) (2 0 oC) 2.34 ±0.21 MRID# 42856907

Mobility Organic carbon partitioning coefficient (K OC, L·kg - 1 ) 16 (sand y loam ) 13.9 (silt loam) 12 ( silt loam ) 27.1 ( silty clay loam) 42909211

Small

- scale Prospective Groundwater Monitoring Study Final results are under review 43530102

Persistence in Water Hydrolysis half

- life (25°C, pH 5, 7, & 9) Stable 428569 45 Aqueous photolysis half

- life (25°C) 9

- 15 days 42856946 Aerobic aquatic metabolism half

- life (20oC) No data available Based on the Terrestrial Non

Food use pattern, this data requirement is a pplicable

. Aerobic aquatic metabolism data are not available, which are required under the new 40 CFR Part 158. Therefore, this is identified as a data gap. Anaerobic aquatic metabolism half

- life (20oC) No data available Based on the Terrestrial Non

Food use pattern, this data requirement is applicable. Anaerobic aquatic metabolism data are not available, which are required under the new 40 CFR Part 158. Therefore, this is identified as a data gap. Persistence in Soil Soil photolysis half

- life (25°C) 30.7

- 55.0 days (silt loam) 42856947 Aerobic soil metabolism h alf

- life (2 5 °C) † 60 days 42856948
Anaerobic soil metabolism half

- life (2 5 oC) 128 days 43455601- 10 of 41

- Parameter Value Reference (MRID #) Field Dissipation Terrestrial field dissipation half

- life; maximum leaching depth (cm) 46 (CA) ; 60

- 75 cm 11 (TX) ; 15 cm 43455603 43317212 Aquatic Bioconcen tration Bioconcentration Factor (BCF) in fish Assumed negligible based on l ow Kow ( ≤ 4.0 ) Dietrich, R. F. 1993. Waiver Request: Fish accumulation potential for JSIH

203 1 (DPX

- PE350). Du Pont Document No. AMR 2728

- 93. Submitted by E.I. du Pont de Nemours and Company, Wilmington, DE Waiver request accepted

3.3.5. Bioaccumulation

Th ere are no data on the bioconcentration potential of Pyrithiobac

- Na in fish. The octanol

- water partition coefficient is sufficiently low, a value of ≤ 4 at 2 0 o C, that bioaccumulation in aquatic organisms is not expected.

4. Receptors

Consistent with the process described in the Overview Document (USEPA 2004), the risk assessment for Pyrithiobac

- Na r elies on a surrogate species approach. T oxicological data generated from surrogate test species, which are intended to be represent ative of broad taxonomic groups, are used to extrapolate the potential effects on a variety of species (receptors) included under these taxonomic groupings.

A cute and chronic toxicity data from studies submitted by pesticide registrant, along with the

a vailable open literature, will be used to evaluate the potential direct and indirect effects of Pyrithiobac

- Na to aquatic and terrestrial receptors. This includes toxicity on the technical grade active ingredient, degradates, and when available, formulate d products ( e.g. , “Six

- Pack” studies). Open literature studies were identified through EPA’s publicly available ECOTOXicology (ECOTOX) database ( April 2011 ) , which employs a literature search engine for locating chemical toxicity data for aquatic and terr estrial plants and wildlife. The evaluation of both sources of data may also provide insight into the direct and indirect effects of Pyrithiobac

- Na usage on biotic communities from loss of species that are sensitive to the chemical and from changes in str ucture and functional characteristics of the affected communities.
A brief summary of the aquatic and terrestrial toxicity data available for the species most sensitive to Pyrithiobac

- Na is provided in Sections 4.1 and 4.2, respectively. A more compl ete summary of the available data is presented in Appendix B . In addition, a summary of ecological incidents associated with Pyrithiobac

- Na and a description of ecosystems potentially at risk are provided in Sections 4.3 and 4.4, respectively.- 11 of 41

- Toxicity to fish and aquatic invertebrates is categorized using the system shown in Table 4.1 (US EPA, 2004). Toxicity to terrestrial fauna (birds and mammals) is categorized using the system shown in Table 4.2 . Toxicity categories for plants have not been defin ed.
Table 4.1. Categories of Acute Toxicity for Aquatic Animals LC 50 (ppm) Toxicity Category < 0.1 Very highly toxic > 0.1

- 1 Highly toxic > 1

- 10 Moderately toxic > 10

- 100 Slightly toxic

> 100 Practically nontoxic
Table 4.2. Categories of Ac ute Toxicity for Terrestrial Animals LD 50 (mg/kg) LC 50 (ppm) Toxicity Category <10 <50 Very highly toxic 10

- 50 50

- 500 Highly toxic 51

- 500 501

- 1000 Moderately toxic 501

- 2000 1001

- 5000 Slightly toxic

>2000 >5000 Practically nontoxic

4.1. Effects to Aquatic Organisms
The aquatic toxicity data from registrant

- submitted studies are provided in Table 4.3 . There are several studies available in ECOTOX which will be reviewed for the risk assessment. Based on the available information, Pyrithiobac

- Na is classified as practically nontoxic to fish and aquatic invertebrates on both an acute and chronic exposure basis. Both vascular and nonvascular aquatic plants are affected by Pyrithiobac

- Na.- 12 of 41

- Table 4.3. Aquatic Toxicity Profile for Pyrithiobac

- Na

Taxon omic Group Species (Common Name) Endpoint (mg ai /L) Acute Classification / Chronic Effect Reference (MRID)

Freshwater Fish Lepomis macrochirus (Bluegill Sunfish) LC 50 >930 Practically nontoxic 42856914
Oncorynchus mykiss (Rainbow Trout) LC 50 >1,000 Prac tically nontoxic 42856915
Ictalurus punctatus (Channel Catfish) LC 50 > 970 Practically nontoxic 43317204 Pimephales promelas (Fathead Minnow) LOEC>100 NOEC=100 MATC>100 None 43317207

Freshwater Invertebrates Procambarus clarkia (Crayfish) EC 50 >910 Prac tically nontoxic 43317206
Daphnia magna (Waterflea ) EC 50 >100 Practically nontoxic 42856916

Waterflea LOEC=500 NOEC=260 MATC=360 Survival 43317208

Estuarine/marine Fish Cyprinodon variegatus (Sheepshead Minnow) LC 50 >145 Practically nontoxic 42856917

Estuarine/marine Invertebrates Crassostrea virginica (Eastern Oyster) LC 50 >130 Practically nontoxic 42856919
Mysidopsis bahia (Mysid Shrimp) LC 50 >140 Practically nontoxic 42856918
Mysid Shrimp LOEC>240 NOEC=240 none 43530101

Vascular plants Lemna gib ba (duckweed) EC 50 = 0.92 μ g ai/L NOAEC=0.27 μ g ai/L -- b 42611701

Nonvascular plants Navicula pelliculosa EC 50 =10.3 NOAEC=6.3 -- 42560301

Selenastrum capricornutum EC 50 =95 μ g ai/L NOAEC=22 μ g ai/L -- 42909204

Skeletonema costatum EC 50 =63 NOAEC=32 -- 43 577501

Anabaena flos

aquae EC 50 =1178 μ g ai/L NOAEC=71 μ g ai/L -- 42909205

a No data available b Toxicity categories for plants have not been defined.- 13 of 41

- 4.2. Effects to Terrestrial Organisms

Table 4. 3 summarizes the terrestrial toxicity endpoints for Pyrithiobac

- Na , based on an evaluation of the submitted data. Open literature studies have been identified through ECOTOX and will be reviewed for the risk assessment. Pyrithiobac

- Na is classified as slightly toxic to birds on an acute oral exposure basi s. Avian rep roduction data shows that Pyrithiobac

- Na has an effect on both the number of viable embryos (30% decrease) and hatchling weight (5% decrease) . Pyrithiobac

- Na is classified as practically nontoxic to small mammals on an acute oral exposure basis . Pyrithiobac

- Na is classified as practically nontoxic to young adult honey bees ( Apis mellifera ) on an acute contact exposure basis.
As expected with an herbicide, Pyrithiobac

- Na has adverse effects on plants. The studies were conducted with technica l Pyrithiobac

- Na rather than typical end use product (TEP) as required under 40 CFR Part 158. Herbicidal active ingredients are usually formulated with adjuvants or surfactants that enhance the activity of the pesticide. Therefore, the sensitivity of ter restrial plants to formulated Pyrithiobac

- Na may be underestimated.
Table 4.3 Terrestrial Toxicity Profile for Pyrithiobac

- Na
Taxonomic

Group Surrogate Species (Common Name) Endpoint Acute Classification/ Chronic effect Reference (MRID)

Birds Colinu s virginianus (Northern Bobwhite) LD 50 =1599 mg ai /kg bw Slightly toxic 42856911

Northern Bobwhite NOEC=60 mg ai/kg LOEC=300 mg ai/kg Number of viable embryos 43811101

Anas platyrhynchos (Mallard Duck) LC 50 >5620 mg ai /kg diet Practically nontoxic 428 56913

Mallard Duck NOEC=300 mg ai/kg LOEC=1500 mg ai/kg Reduced hatchling weight 43811102

Mammals Rattus norvegicus (Laboratory Rat) LD 50 =3200 mg ai /kg bw Practically non toxic 42856920

Terrestrial Invertebrates Apis mellifera (Honey bee) LD 50 > 25 μ g/bee NOAEC=25 μg/bee Practically nontoxic 42856944

Seedling emergence Sorghum bicolor (Sorghum EC 25 =2.63 x 10 - 4 lb ai/A EC 05 a =7.5 x 10 - 6 lb ai/A -- b 42856943- 14 of 41

- Taxonomic

Group Surrogate Species (Common Name) Endpoint Acute Classification/ Chronic effect Reference (MRID)

Brassica napus (Rape) EC 25 =2.63 x 10 - 4 lb ai/A NOAEC=2.44 x 10 - 4 lb ai/A -- 42856943

Vegetat ive vigor Sorghum bicolor (Sorghum) EC 25 =4.34 x 10 - 5 lb ai/A EC 05 a =1.25 x 10 - 5 lb ai/A -- 42856943

Brassica napus (Rape) EC 25 =8.75 x 10 - 5 lb ai/A EC 05 a =2.5 x 10 - 5 lb ai/A -- 42856943

a EC 05 used in lieu of a reported NOAEC
b Toxicity categories for plant s have not been defined

. Although avian subacute and mammalian acute endpoints are nondefinitive values, preliminary calculation of RQs (not shown) indicate that the highest dose tested ( e.g. 5000 mg ae ai /kg

- bw) are sufficiently higher than the EECs that f urther data are not needed at this time.

4.3. Incident Database Review
A review of the Ecological Incident Information System (EIIS) database for incidents involving Pyrithiobac

- Na was conducted on May 13, 2011

. One plant incident is reported in the da tabase. Similarly, a search of the Avian Incident Monitoring System (AIMS; http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm ), a database administered by the American Bird Conservancy which contains publicly available data on report ed avian incidents involving pesticides did not report any incidents for Pyrithiobac

- Na as of April 6, 2011

. Pesticide registrants report certain types of incidents to the Agency as aggregate counts of incidents occurring per product per quarter. One agg regate plant incident has been reported to the Agency associated with Pyrithiobac

- Na in an aggregated incident report from June, 2006. Although only one incident associated with the use of Pyrithiobac

- Na has been reported to the EPA, the lack of incident r eports cannot be construed as the absence of incidents as there can be many reasons why the Agency is not notified of adverse effects resulting from the use of a pesticide. Unless additional information on this 2006 aggregated incident report becomes avai lable, it will be assumed to be due to a registered use of Pyrithiobac

- Na in the risk assessment.- 15 of 41

- 4.4. Ecosystems Potentially at Risk
The ecosystems at risk are often extensive in scope; therefore, it may not be possible to identify specific ecosystems during the development of a nation

- wide ecological risk assessment. However, in general terms, terrestrial ecosystems potentially at risk could include the treated field and immediately adjacent areas that may receive drift or runoff. Areas adjacent to t he treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats and other uncultivated areas.
Aquatic ecosystems potentially at risk include water bodies adjacent to, or downs tream from, the treated field and could include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuaries.
Pyrit hiobac

- Na is mainly used on cotton. According to the USDA National Agricultural Statistics Service (NASS 2009

- 2010), cotton was grown in the following states: AL, AZ, AR, CA, FL, GA, KS, LA, MO, MS, NC, NM, OK, SC, TN, TX, and VA
See Figure 1. Pyrithioba c

- Na is also used on kenaf in the following states only: NC, OK, and TN.- 16 of 41

- Figure 1. The 2002 estimated annual agricultural use of pyrithiobac

- Na according to the USGS

NAWQA data

. (http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m2020 )

5. Assessment Endpoints
Assessment endpoints are defined as “explicit expressions of the actual environmental value that is to be protected.” 2 Selection of the assessment endpoints is based on valued entities ( e.g., fish, birds), the ecosystems poten tially at risk ( e.g., waterbodies, riparian vegetation, and upland habitats), the migration pathways of Pyrithiobac

- Na ( e.g., runoff, drift, etc .), and the routes by which ecological receptors are exposed to Pyrithiobac

- Na ( e.g., direct contact, etc. )

.
As sessment endpoints for Pyrithiobac

- Na include direct toxic effects on the survival, reproduction, and growth of the receptors, as well as indirect effects, such as reduction of the prey base or modification of habitat. Each assessment endpoint requires on e or more “measures of ecological effect,” defined as changes in the attributes of an assessment endpoint or changes in a surrogate entity or attribute in response to exposure to a pesticide. Specific measures of ecological effect are generally evaluated based on acute and chronic toxicity information from registrant

- submitted guideline tests that are performed on a limited number of organisms. Additional ecological effects data from the open literature will also be considered.

6. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological receptor. For an ecologica l pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure.
The conceptual model for Pyrithiobac

- Na provides a written description (risk hypothesis) and visual representation (conceptual diagram) of the predicted relationships between Pyrithiobac

Na , potential routes of exposure, and the predicted effects for the assessment endpoint. A conceptual model consists of two major component s: risk hypothesis and a conceptual diagram (USEPA 1998b).
Based on the available data, Pyrithiobac

- Na is highly to very highly soluble, stable in water without light, and unstable in water and on soil under light

. . Pyrithiobac

- Na is considered persisten t in soil under aerobic conditions, and very stable in soil and sediment under anaerobic conditions. Pyrithiobac

- Na is very mobile in soil, Pyrithiobac

- Na is not volatile, and will not likely accumulate in aquatic food webs. With these properties, it appea rs that Pyrithiobac

- Na is highly mobile and has a strong potential to leach into ground water or m ove offsite into surface water . However, and based on the small

- scale prospective groundwater monitoring study

2 From U.S. EPA (1992). Framework for Ecological Risk Assessment. EPA/630/R

- 92/001.- 17 of 41

- conducted in North Carolina is being reviewed b y EFED. Preliminary result s indicated that Pyrithibac

- Na may not be stable enough to leach to ground water at most sites, even in sandy soils. However, definitive conclusions cannot be made until the final report is reviewed which will be done prior to com pletion of the draft risk assessment.
Given its relatively low K ow , Pyrithiobac is not expected to bioaccumulate in aquatic food chains.

6.1. Risk Hypothesis
A risk hypothesis describes the predicted relationship among the stressor, exposure, and

asses sment endpoint response along with the rationale for their selection. For Pyrithiobac

- Na , the following eco logical risk hypothesis will be employed for the national

- level ecological risk assessment:
Given the uses of Pyrithiobac

- Na and its environmental fate properties, there is a likelihood of exposure to non

- target terrestrial and aquatic organisms. When used in accordance with the label, Pyrithiobac

- Na may result in potential adverse effects upon the survival, growth, and reproduction of non

- target te rrestrial and aquatic organisms.

6.2. Conceptual Diagram
The conceptual model used to depict the potential ecological risk associated with the use of Pyrithiobac

- Na (the stressor) assumes that as a pesticide, Pyrithiobac

- Na can adversely affect terre strial and aquatic organisms (the receptors) if environmental concentrations exceed toxic thresholds as a result of application according to the label directions ( Figure 1 ). Ecological receptors that may potentially be exposed to Pyrithiobac

- Na include te rrestrial and semi

- aquatic wildlife ( e.g. , mammals, birds, terrestrial

- phase amphibians and reptiles), terrestrial and semi

aquatic plants, and terrestrial invertebrates ( e.g. , honey bees) ( Figure 2) . Additionally, given the mobility of Pyrithiobac

- Na , aq uatic organisms ( i.e. , freshwater and estuarine/marine fish and invertebrates, aquatic

- phase amphibians, and aquatic plants) are potential receptors in adjacent water bodies through off

- site transport of Pyrithiobac

- Na from the application site through

run off, erosion, and spray drift.- 18 of 41

- Figure 1

. Conceptual model for Pyrithiobac

- Na exposure to aquatic organisms. Dashed lines indicate route of exposure considered of lower importance for Pyrithiobac

- Na

.- 19 of 41

- Figure 2

. Conceptual model for Pyrithiobac

- Na exposure to terrestrial organisms. Dashed lines indicate route of exposure considered of lower importance for Pyrithiobac

- Na

.- 20 of 41

- 7. Analysis Plan
In order to address the risk hypothesis, the poten tial for adverse effects on the environment will be estimated. The use, environmental fate, and ecological effects of Pyrithiobac

- Na will be characterized and integrated to assess the risks. This will be accomplished using a risk quotient (ratio of expos ure concentration to effects concentration) approach. Although risk is often defined as the likelihood and magnitude of adverse ecological effects, the risk quotient

- based approach does not provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined in the Overview Document (USEPA 2004), the likelihood of effects to individual organisms from particular uses of Pyrithiobac

- Na may be estimated using the probit dose

- response slope and either the level of concern (discussed below) or the actual calculated risk quotient value.
This analysis plan will be revisited and may be revised depending upon the information submitted by the public in response to the opening of the Registration Review docket for Pyrithiobac

- N a.
7.1. Stressors of Concern

The stressor of concern in the assessment will be Pyrithiobac

- Na

. There are no known applications of specific mixtures of Pyrithiobac

- Na with other chemicals. In its ecological risk assessments, the Agency does not routine ly include an evaluation of mixtures of active ingredients, either those mixtures of multiple active ingredients in product formulations or those in the applicator’s tank. In the case of the product formulations of active ingredients (that is, a registere d product containing more than one active ingredient), each active ingredient is subject to an individual risk assessment for regulatory decision regarding the active ingredient on a particular use site. If effects data are available for a formulated prod uct containing more than one active ingredient, the data may be used qualitatively or quantitatively in accordance with the Agency’s Overview Document and the Services’ Evaluation Memorandum (USEPA, 2004; Williams and Hogarth, 2004)

.

7.2. Measures of Exposure

In order to estimate ri sks of Pyrithiobac

- Na exposures in aquatic and terrestrial environments, exposure modeling will be based on maximum application rates and methods cited in Table 3.2. Measures of exposure are based on aquatic and terrestrial models that predict estimated

en vironmental concentrations (EECs) of Pyrithiobac

- Na . The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure Analysis Modeling System (PRZM/EXAMS). The model used to predict terrestrial EECs on food items is the Terrestrial Residue Exposure model (T

- REX). The model used to derive EECs relevant to terrestrial and wetland plants is TerrPlant. The AgDrift model will be used to estimate the distance off

- field that effects may occur. These models are parameterized usi ng relevant reviewed environmental fate data from registrant submissions and the literature. Model input values will be consistent with the most recent version of the input parameter guidance (Version 2.1; USEPA 2009).- 21 of 41

- PRZM (v 3.12.2; 5/15/05 ) and EXAMS ( v 2.98.04.06; 4/25/05 ) are simulation models coupled with the linkage program shell: PE5 ( P RZM E XAMS Model Shell; v 5 .0; 11/15/06), which incorporates the standard scenarios developed by EFED. The models generate daily exposures and calculated 1

- in

- 10 year E ECs of pyrithiobac

- Na and possibly (depending on the outcome of environmental fate studies) toxicologically significant degradatation products (e.g., sulfanilamide). PRZM simulates pesticide fate and transport as a result of leaching, direct spray drift, r unoff and erosion from an agricultural field, and EXAMS estimates environmental fate and transport of pesticides in a surface water body for a 30

- year period. The combined model is designed to estimate pesticide concentrations found in water (standard pon d) at the edge of the treated field. As such, it provides high

- end values of the pesticide concentrations that might be found in ecologically sensitive environments following pesticide application. The location of the field is specific to the crop being si mulated using site

- specific information on the soils, weather, cropping, and management factors associated with the scenario. The crop/location scenario is intended to represent a high

- end exposure site on which the crop is normally grown. Based on histori cal rainfall patterns, the receiving water body receives multiple runoff events during the years simulated. Weather and agricultural practices are simulated for 30 years so that the 10

- year exceedance probability at the site can be estimated. The simulatio n is generated using 30 years of meteorological data, encompassing the years from 1961 to 1990. Additional information on these models can be found at: http://www.epa.gov/oppefed1/models/water /index.htm

. The standard scenarios used for ecological pesticide assessments assume application to a 10

- hectare agricultural field that drains into an adjacent 1

- hectare water body that is 2 meters deep (20,000 m 3 volume) with no outlet. PRZM/EXAMS is used to estimate screening

- level exposure of aquatic organisms to Pyrithiobac

- Na . The measure of exposure for aquatic species is the 1

- in

10 year return peak or rolling mean concentration. The 1

- in

- 10 year peak is used for estimating acute exposures of d irect effects to aquatic organisms. The 1

- in

- 10

- year 60

- day mean is used for assessing chronic exposure to fish and aquatic

- phase amphibians. The 1

- in

- 10

- year 21

- day mean is used for assessing chronic exposure to aquatic invertebrates.
Exposure estimates for terrestrial organisms assumed to be in the target area or in an area exposed to off

- site deposition are derived using the T

- REX model (version 1.4.1, 10/09/2008). This model incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), whi ch is based on a large set of field residue data. The upper limit values from the nomograph represent the upper bound of residue values from actual field measurements (Hoerger and Kenaga 1972). The Fletcher et al. (1994) modifications to the Kenaga nomog raph are based on measured field residues from 249 published research papers, including information on 118 species of plants, 121 pesticides, and 17 chemical classes. Based on these data, T

- REX assumes a 35

- day foliar dissipation half

- life in the absence of other data.
In order to determine if Pyrithiobac

- Na residues in drinking water is a potential pathway of concern for avian and mammalian species, t he S creening I mbibition P rogram (SIP v.1.0, Released June 15, 2010) was used to calculate an upper bound estimate of exposure using Pyrithiobac

- Na’s solubility ( 728 ppm), the most sensitive acute and chronicavian toxicity endpoints (LD 50 = 1599 mg ai/kg

- bw; NOAEL = 60 mg ai/kg

- bw ) and the most sensitive acute and chronic mammalian toxicity endpoints (LD 50 = 3200 mg ai/kg

- bw; NOAEL not available ). Drinking water exposure alone was determined to be a potential pathway of concern for avian- 22 of 41

- species on an acute and chronic basis . Drinking water exposure alone was determined to not be a potential pathway of concern for mammalian species on an acute basis but cannot be precluded on a chronic basis due to insufficient data. This pathway will be explored further with the development of SIP v.2.0 in the risk assessment for Pyrithiobac

- Na . Detailed information about the SIP v.1.0, as well as the tool, can be found on the EPA’s website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial

. EECs for terrestrial plants will be deriv ed using TerrPlant (version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in spray drift to calculate EECs. EECs are based upon solubility, application rate and minimum incorporation depth.
The AgDRIFT (v2.01; May 2001) or AgDisp (version 8.15) spray drift model may be used to assess exposures of organisms to Pyrithiobac

- Na deposited on terrestrial habitats by spray drift.

7.3. Measures of Effect
Ecological effects data are used as measures of direct and indirect effects to biological receptors. Effects data are obtained from registrant

- submitted studies or from literature studies identified by the ECOTOX database.

The acute measures of effect used for animals in this assessment are the LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” and LC 50 is the concentration of a chemical that is estimated to kill 50% o f the test organisms. EC stands for “Effective Concentration” and the EC 50 is the concentration of a chemical that is estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic measures of exposure for listed and non

- liste d animals are the NOAEL/NOAEC and NOEC. NOAEL stands for “No Observed

- Adverse

- Effect

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

- Observed

- Adverse

- Effect

- Concentration”) is the highest test concentration at which none of the observed effects were statistically different from the control. For non

- listed plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 for aquatic plants); for listed plants either the NOAEC or EC 05 is used.
Where available, sublethal effects observed in both registrant

- submitted and open literature studies will be evaluated qualitatively. Such effects may include behavioral changes ( e.g. , lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired survival, growth and reproduction.

In the absence of taxon

- speci fic data, t he assessment of risk for direct effects to non

- target organisms makes the assumption that toxicity of Pyrithiobac

- Na to birds is similar to terrestrial

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

- phase amphibians. In the absence of data for either acute or chronic effects, the conservative assumption will be to presume that Pyrithiobac

- Na is toxic.- 23 of 41

- 7.4. Integration of Exposure and Effects
Risk characterization is the integration of exposure and ecological effects characterization to determine the potential ecological risk from the registered uses of Pyrithiobac

- Na and the likelihood of direct and indirect effects to non

- target organisms in aquatic and terrestrial habitats. The expo sure and toxicity effects data are integrated in order to evaluate the risks of adverse ecological effects on non

- target species. For the assessment of Pyrithiobac

- Na risks, the risk quotient (RQ) method is used to compare exposure and measured toxicity v alues. EECs are divided by acute and chronic toxicity values. The resulting RQs are then compared to the Agency’s Levels of Concern (LOCs) (USEPA 2004). These criteria are used to indicate when Pyrithiobac

- Na use, as directed on the labels, has the pote ntial to cause adverse direct or indirect effects to non

- target organisms. In addition, incident data from the EIIS will be considered as part of the risk characterization.

7.5. Deterministic and Probabilistic Assessment Methods
The quantitative a ssessment of risk will primarily depend on the deterministic point

- estimate (RQ) based approach described in the risk assessment. An effort will be made to further qualitatively describe risk using probabilistic tools that the Agency has developed. These tools have been reviewed by FIFRA Scientific Advisory Panels ( http://www.epa.gov/scipoly/sap/index.htm ) and have been deemed as appropriate means of refining assessments where deterministic approaches have identified risks. Newer tools may be available to assess the routes of exposure ( e.g. TIM and SWAMP models) and will be applied as appropriate in Registration Review.

7.6. Endocrine Disruptor Screening Program
As required under FFDCA section 408( p), EPA has developed the Endocrine Disruptor Screening Program (EDSP) to determine whether certain substances (including pesticide active and other ingredients) may have an effect in humans or wildlife similar to an effect produced by a “naturally occurri ng estrogen, or other such endocrine effects as the Administrator may designate.” The EDSP employs a two

- tiered approach to making the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed to the next stag e of the EDSP where EPA will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to identify any adverse endocrine related effects caused by the substance, and establish a dose

- response relatio nship between the dose and the E, A, or T effect.
Between October 2009 and February 2010, EPA issued test orders/data call

- ins for the first group of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. This list of chemi cals was selected based on the potential for human exposure through pathways such as food and water, residential activity, and certain post

- application agricultural scenarios. This list should not be construed as a list of known or likely endocrine disrup tors.- 24 of 41

- Pyrithiobac

- Na is not among the group of 58 pesticide active ingredients on the initial list to be screened under the EDSP. Under FFDCA sec. 408(p) the Agency must screen all pesticide chemicals. Accordingly, EPA anticipates issuing future EDSP te st orders/data call

- ins for all pesticide active ingredients

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

.

7.7. Endangered Species Assessment
Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to Federally

- listed threatened and/or enda ngered (listed) species from registered uses of Pyrithiobac

- Na . This assessment will be conducted i n accordance with the Overview Document (USEPA 2004), provisions of the ESA, and the Services’ Endangered Species Consultation Handbook (USFWS/NMFS, 1998).
The assessment of effects associated with the registration of Pyrithiobac

- Na is based on an action area. The action area is considered to be the area directly or indirectly affected by the federal action, as indicated by the exceedance of Agency Levels o f Concern (LOCs) used to evaluate direct or indirect effects. The Agency’s approach to defining the action area under the provisions of the Overview Document (USEPA 2004) considers the results of the risk assessment process to establish boundaries for tha t action area with the understanding that exposures below the Agency’s defined LOCs constitute a no

- effect threshold. For the purposes of this assessment, attention will be focused on the footprint of the action ( i.e ., the area where Pyrithiobac

- Na applic ation occurs), plus all areas where offsite transport ( i.e ., spray drift, runoff, etc .) may result in potential exposure that exceeds the Agency’s LOCs. Specific measure s of ecological effect that define the action area for listed species include any dire ct and indirect effects and/or potential modification of its critical habitat, including reduction in survival, growth, and reproduction as well as the full suite of sublethal effects available in the effects literature. Therefore, the action area extends to a point where environmental exposures are below any measured lethal or sublethal effect threshold for any biological entity at the whole organism, organ, tissue, and cellular level of organization. In situations where it is not possible to determine t he threshold for an observed effect, the action area will initially be assumed to include all counties where Pyrithiobac

- Na is used in the United States.

7.8. Drinking Water Assessment
In order to bring the drinking water exposure assessment up to date with current data, models and simulation model guidance, a new drinking water assessment will be conducted to support future human health dietary risk assessments of Pyrithiobac

- Na . The drinking water exposure assessment will be conducted for the maximum labeled use in support of the human health dietary risk assessment. The drinking water assessment will incorporate model estimates of Pyrithiobac

- Na alone in surface water and ground water including any residues that are- 25 of 41

- determined to be of toxicological concern. Concentrations of Pyrithiobac

- Na in surface waters will be estimated using PRZM/EXAMS (see description above) but using the Index Reservoir scenario rather than the standard pond used with aquatic exposure assessment.
An Estimated Drinking Wate r Concentration (EDWC) of Pyrithiobac

- Na in ground water will be estimated using EFED’s Tier I aquatic model SCIGROW (Screening Concentration in Ground Water, version 2.3; 8/8/2003). SCIGROW is a regression model used as a screening tool to estimate pesti cide concentrations found in ground water used as drinking water. The output of SCIGROW represents the concentrations that might be expected in shallow unconfined aquifers under sandy soils, which is representative of the ground water most vulnerable to p esticide contamination likely to serve as a drinking water source. If significant amounts of Pyrithiobac

Na are found to deposit in the environment due to releases from the use on cotton , a drinking water assessment will be performed for this use using PR ZM/EXAMS and SCIGROW. In this case, the deposited residues will be treated as if they were a soil application of a pesticide in PRZM.
The drinking water assessment will also include available surface and groundwater monitoring data with consideration of changes in use patterns that may have occurred. States are encouraged to submit monitoring data for review.

8. Preliminary Identification of Data Gaps

8.1. Environmental Fate
The studies submitted to fulfill environmental fate data requirements for P yrithiobac

- Na are not complete to conduct an exposure assessment

. The current 40 CFR (2010) requires the following fate studies for terrestrial uses of pesticides:
1) Aerobic soil metabolism (OCSSP guideline # 835.4100). Though there is acceptable aerobic so il metabolism data for one type of soil, t he guideline stipulates that results from at least four relevant soils of different organic carbon content, pH, clay content, and microbial biomass must be submitted in order to characterize the variability in the aerobic biodegradation of Pryithiobac

- Na in the environment. 2) Aerobic aquatic metabolism (OCSSP guideline # 835.4300). There are no acceptable aerobic aquatic metabolism studies. This study is necessary in order to describe the fate of Pyrithiobac

- Na in sur face water bodies down

- gradient from use sites (e.g., rice paddies). The guideline stipulates that at least two different soil:water systems be submitted that are similar to the potential use sites in the United States. There is currently one supplemental study that lacks information on the aerobicity of the soil:water system. 3) Anaerobic aquatic metabolism (OCSSP guideline # 835.4400). Submission of an acceptable anaerobic aquatic metabolism study is necessary to understand the degradation of Pyrithiobac

- Na in oxygen

- limiting environments. 4) Environmental chemistry methods in water being reviewed by EFED. However, definitive conclusions cannot be made until the final report is reviewed which will be done prior to completion of the draft risk assessment. Althou gh these studies have been- 26 of 41

- submitted to EPA they will be considered data gaps until the data have been reviewed and found to be acceptable. 5) An independent laboratory validation (ILV) report for Environmental chemistry method in water is needed.

Table 8.1. Summary of available environmental fate data.

Guideline Study Title MRID Classification Data Gap? Comments

835.2120 Hydrolysis 42856945 Acceptable No No significant issues affecting the acceptability of the study were noted.

835.2240 Photodegradation in Water 42856946 Acceptable No No significant issues affecting the acceptability of the study were noted.

835.2410 Photodegradation on Soil 42856947 Acceptable No No significant issues affecting the acceptability of the study were noted.

835.4100 Aerobi c Soil Metabolism 42856948 Acceptable Y es Per 40 CFR part 158, promulgated July 1, 2009, requires aerobic soil metabolism data for pesticide food and nonfood terrestrial uses. Currently the Agency has received one acceptable study on one soil types.

Per OCSPP guideline 835.4100, at least three additional soils should be used to determine transformation rate.

835.4200 Anaerobic Soil Metabolism 43455601 Acceptable No No significant issues affecting the acceptability of the study were noted.

835.4300 Aero bic Aquatic Metabolism N/A N/A Yes Based on the Terrestrial Non

- Food use pattern, this data requirement is applicable. Aerobic aquatic metabolism data are not available, which are required under the new 40 CFR Part 158. Therefore, this is identified as a data gap.

835.4400 Anaerobic Aquatic Metabolism N/A N/A Yes Based on the Terrestrial Non

- Food use pattern, this data requirement is applicable. Anaerobic aquatic metabolism data are not available, which are required under the new 40 CFR Part 158. Theref ore, this is identified as a data gap.

835.1240 Mobility

- Adsorption / Desorption 42909209 Acceptable

No No significant issues affecting the acceptability of the study were noted. 42909210 Acceptable No significant issues affecting the acceptabili ty of the study were noted.

835.1230 4290921 1 Acceptable No significant issues affecting the acceptability of the study were noted.- 27 of 41

- Guideline Study Title MRID Classification Data Gap? Comments

835.6100 Terrestrial Field Dissipation 43455603 Acceptable

N o No significant issues affecting the acceptability of the study were noted.

43317212 Acceptable No significant issues affecting the acceptability of the study were noted.

43455602 Supplementa l Limited rainfall confounds mobility interpretation 43647401 Supplementa l

850.1730 Fish Accumulation N/A A waiver request from the registrant, was accepted No This study is not required because the K OW is below 4.

835.7100 Prospective Groundwater Monitoring 43530102 Pyrithibac

- Na may not be stable enough to leach to ground water even in sandy soils. No This study appears to have been conducted at a site with groundwater highly vulnerable to contamination. However, it is not clear that the amounts and timing of water input were such that the leaching would be significantly more likely than in an average year at the test site.

8.2. Effects
The available ecological effects data for Pyrithiobac

- Na consists of acute and chronic effects studies on animals and effects to plants. There are no chronic data on estuarine/marine fish. Additionally, an avian a cute oral study with a passerine is now required under the current 40 CFR Part 158 and is not yet been submitted for Pyrithiobac

- Na . Available data on the toxicity of Pyrithiobac

- Na to terrestrial plants are based on technical Pyrithiobac

- Na rather than t he required TEP. Therefore effects to non

- target plants may be appreciably underestimated by the available studies. The available effects studies for Pyrithiobac

- Na are presented in Tables 8.2

- 8.4 . The following data gaps have been identified:

850.2100

- Avian Oral Toxicity , Passerine 850.4 100

- Terrestrial Plants: Seedling Emergence , Tier II 850.4 150

- Terrestrial Plants: Vegetative Vigor , Tier II- 28 of 41

- TABLE 8.2. Available ecological effects data for terrestrial animals exposed to Pyrithiobac

- Na.

Guidelin e Description MRID/ Accession Classification Data Gap? Comments

850.2100 Avian oral toxicity (for bobwhite quail) 42856911 Acceptable Yes* *Avian acute oral toxicity data are not available for passerines, which are required under the new 40 CFR Part 158. Therefore, this is identified as a data gap. 850.2200 Avian dietary toxicity (for bobwhite quail and mallard) 42856912 42856913 Acceptable No

850.2300 Avian reproduction (for bobwhite quail and mallard) 43811101 43811102 Acceptable No

850.3020 Honeybee acute contact toxicity 42856944 Acceptable No

TABLE 8.3. Available ecological effects data for aquatic animals exposed to Pyrithiobac

- Na

. Guideline Description MRID/ Accession Classification Data Gap? Comments

850.1075 Freshwater fish

– Acu te toxicity 42856914 Acceptable
No 42856915 Acceptable
43317204 Acceptable

850.1075 Saltwater fish

– Acute toxicity 42856917 Acceptable No

850.1010 Freshwater invertebrates

– Acute toxicity 42856916 Acceptable No 43317206 Supplemental

850.1025 850.1035 Saltwater invertebrates

– Acute toxicity 42856918 Acceptable No 42856919 Acceptable

850.1300 Freshwater invertebrate

– life cycle test 43317208 Acceptable No

850.1350 Saltwater invertebrates

– life cycle test 43530101 Acce ptable No

850.1400 Freshwater fish

– early life stage test 43317207 Acceptable No

850.1400 Saltwater fish

– early life stage test None No Per 40 CFR Part 158, this test is conditionally required; conditions for requiring this test are not met.- 29 of 41

- TA BLE 8.4. Available ecological effects data for plants exposed to Pyrithiobac

- Na

.

Guideline Description MRID Classification Data Gap? comments

850.4100 Terrestrial Plant toxicity: Tier I seedling emergence none No Per 40 CFR Part 158, not required for kn own phytotoxicants.

850.4225 Terrestrial Plant toxicity: Tier II seedling emergence 42856943 Supplemental Yes Study used technical grade product while 40 CFR Part 158 requires the formulated product . Herbicidal active ingredients are usually formulated wi th adjuvants or surfactants that enhance the activity of the pesticide. Therefore, the sensitivity of terrestrial plants to Pyrithiobac

- Na may be underestimated.

850.4150 Terrestrial Plant toxicity: Tier I vegetative vigor none No Per 40 CFR Part 158, not required for known phytotoxicants.

850.4250 Terrestrial Plant toxicity: Tier II vegetative vigor 42856943 Supplemental Yes Study used technical grade product while 40 CFR Part 158 requires the formulated product. Herbicidal active ingredients are usu ally formulated with adjuvants or surfactants that enhance the activity of the pesticide. Therefore, the sensitivity of terrestrial plants to Pyrithiobac

- Na may be underestimated.

850.5 400 Aquatic Plant Growth: algae 42909204 Acceptable

No 42909205 Acceptable 42909206 Acceptable 42909207 Invalid
43577501 Acceptable

850.4400 Aquatic Plant Growth: vascular plants 42909208 Supplemental No 43577502 Acceptable

9 . References

Open Literature Citations- 30 of 41

- Fletcher, J.S., J.E. Nell essen, and T.G. Pfleeger. 1994. Literature review and evaluation of the EPA food

- chain (Kenaga) nomogram, an instrument for estimating pesticide residues on plants. Environ. Tox. Chem. 13:1383

- 1391.
Hoerger, F., and E.E. Kenaga. 1972. Pesticide resid ues on plants: Correlation of representative data as a basis for estimation of their magnitude in the environment. In F. Coulston and F. Korte, eds ., Environmental Quality and Safety: Chemistry, Toxicology, and Technology, Georg Thieme Publ, Stuttgart, We st Germany, pp. 9

- 28.
Shimizu, T., I. Nakayama, T. Nakao, Y. Nezu, and H. Abe. 1994. Inhibition of Plant Acetolactate Synthase by Herbicides, Pyrimidinylsalicylic Acids. Journal of Pesticide Science. 19: 56

- 97.
U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. Endangered Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. March 1998.

U SDA. 2010. Acreage. Na tional Agricultural Statistics Service (NASS), Agricultural Statistics Board, U.S. Department of Agriculture . May 2011. http://usda.mannlib.cornell.edu/usda/current/Acre/Acre

- 06

- 30

- 2010.pdf
USEPA. 2004. Overview of the Ecological Risk Assessment Proces s in the Office of Pesticide Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004.
USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of Research and Development, Washington, D.C. EPA/630/R

- 95/002F. April 1998. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759

Williams S and W Hogarth. 2004. Letter to Susan B Hazen regarding the USFWS and NMFS (Services) evaluation of US EPA’s Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, Environmental Protection Agency (January 2004).
Willis, G.H. a nd L.L. McDowell. 1987. Pesticide Persistence on Foliage in Reviews of Environmental Contamination and Toxicology. 100:23

- 73

. 

### Submitted Fate Studies

MRID Citation Reference

42856945 Bramble, F.; Shalaby, L. (1993) Hydrolysis of (carbon 14)

- KIH

- 2 031 (DPX

PE350) in Buffer Solutions of pH 5, 7, and 9: Lab Project Number: AMR 2093

-- 31 of 41

- 91. Unpublished study prepared by Du Pont Agricultural Products. 25 p.
42856946 Shalaby, L.; Bramble, F. (1993) Photodegradation of (carbon 14)

- KIH

- 2031 (DPX

- PE350) in Bu ffer Solutions of pH 5, 7, and 9: Lab Project Number: AMR 2094

- 91. Unpublished study prepared by Du Pont Agricultural Products. 63 p.
42856947 Dietrich, R.; Taylor, T. (1993) Photodegradation of Radiolabeled KIH

- 2031 (DPX

- PE350) on Soil Conducted in Simu lated Sunlight: Lab Project Number: AMR 2310

- 92. Unpublished study prepared by Du Pont Agricultural Products. 53 p.
42856948 McFetridge, R.; Houben, K. (1993) Aerobic Soil Metabolism of (carbon 14)

- KIH

- 2031 (DPX

- PE350): Lab Project Number: AMR 2076

- 91. U npublished study prepared by Du Pont Agricultural Products. 59 p.
43455601 McFetridge, R.; Houben, K. (1993) Anaerobic Soil Metabolism of (carbon 14) KIH

- 2031 (DPX

- PE350): Lab Project Number: AMR/2077/ 91. Unpublished study prepared by E.I. du Pont de Ne mours and Co. 54 p.
42909209 Hawkins, D.; Kirkpatrick, D.; Aikens, P.; et al. (1993) Soil Column Leaching of (Carbon 14)

- KIH

- 2031 (DPX

- PE350): Lab Project Number: AMR 2359

- 92: HRC/DPT 277/921239. Unpublished study prepared by Huntingdon Research Centre, Ltd. 87 p.
42909210 Hawkins, D.; Kirkpatrick, D.; Dean, G.; et al. (1993) Soil Mobility of (Carbon 14)

- KIH

- 2031 (DPX

- PE350) and (Carbon 14)

- IN

- JW212 By Soil Thin

- Layer Chromatography: Lab Project Number: AMR 2462

- 92: HRC/DPT 285/921353. Unpublished study prepared by Huntingdon Research Centre, Ltd. 45 p.
42909211 Hoffman, D. (1993) Batch Equilibrium (Adsorption/Desorption) Studies of Radiolabeled KIH

- 2031 (DPX

- PE350): Lab Project Number: AMR 2123

- 91. Unpublished study prepared by E. I. du Pont De Nemour s and Co. 49 p.
43317212 McFetridge, R. (1994) Field Soil Dissipation of DPX

- PE350 Experimental Herbicide: Lab Project Number: AMR 2289

- 92: 92

- P1289.REP. Unpublished study prepared by DuPont Agricultural Products, Global Technology Division and Enviro

- Te st Labs. 273 p.
43317213 Houben, K. (1994) Freezer Storage Stability of KIH

- 2031 (DPX

- PE350) and IN

- JW212 in Soil: Lab Project Number: AMR 2392

- 92. Unpublished study prepared by DuPont Agricultural Products, Global Technology Division. 41 p.
43455602 M cFetridge, R.; Dietrich, R. (1994 ) Supplement No. 1 to: Field Soil Dissipation of DPX

- PE350 Experimental Herbicide: DPX

- PE350: Lab Project Number: AMR/2289/92. Unpublished study prepared by E.I. du Pont de Nemours and Co. 10 p.
43455603 McFetridge, R.; H ouben, K. (1994) Terrestrial Field Soil Dissipation of (carbon 14) KIH

- 2031 (DPX

- PE350) in Madera, California: Lab Project Number: 92121: 2333/92. Unpublished study prepared by E.I. du Pont de Nemours and Co.; Pan

- Agricultural Lab., Inc.; and Agvise Lab. 182 p.
43577503 Houben, K. (1995) Freezer Storage Stability of KIH

- 2031 (DPX

- PE350) and IN

- JW212 in Soil: Revision No. 1: Lab Project Number: AMR 2392

- 92, REVISION NO. 1. Unpublished study prepared by E. I. du Pont de Nemours and Co. 51 p.
43647401 McF etridge, R.; Houben, K. (1995) Field Soil Dissipation of (carbon 14) KIH

2031 (DPX

- PE350) Experimental Herbicide in Greenville, Mississippi: Lab- 32 of 41

- Project Number: AMR 2290

- 92. Unpublished study prepared by DuPont Agricultural Products and Harris Environmenta l Technologies, Inc. 214 p.
42856950 Gaddamidi, V.; Hashinger, B.; Bookhart, S. (1993) Confined Accumulation Study of (carbon 14)KIH

- 2031 (DPX

- PE350) in the Rotational Crops: Lab Project Number: AMR 2020

- 91. Unpublished study prepared by Du Pont Agricult ural Products. 119 p.
43404602 Gaddamidi, V.; Hashinger, B. (1994) Supplement No. 1 To: Confined Accumulation Study of (carbon 14)KIH

- 2031 (DPX

- PE350) in the Rotational Crops: Lab Project Number: AMR 2020

- 91. Unpublished study prepared by E. I. du Pont d e Nemours and Co. 8 p.
43812701 Hiscock, A. (1995) A Small

- Scale Prospective Ground

- Water Monitoring Study for Pyrithiobac Sodium (Stable, DPX

- PE350, KIH

- 2031: Progress Report Number 3: Lab Project Number: AMR 2870

- 93: 423.06 2870

- 93. Unpublished study p repared by Blasland, Bouck & Lee, Inc.; Midwest Labs, Inc.; and DuPont Agricultural Products. 71 p.
43963401 Hiscock, A. (1996) A Small

- Scale Prospective Ground

- Water Monitoring Study for Pyrithiobac Sodium (Staple, DPX

- PE350, KIH

- 2031): Progress Report No. 4: Lab Project Number: AMR 2870

- 93

- PR4: AMR 2870

- 93: 95220. Unpublished study prepared by Stone Environmental, Inc.; DuPont Agricultural Products and Blasland, Bouck & Lee, Inc. 100 p.
44373804 Hiscock, A. (1997) A Small

- Scale Prospective Ground

- Wate r Monitoring Study for Pyrithiobac Sodium (Staple, DPX

- PE350, KIH

- 2031): Final Report: Lab Project Number: AMR 2870

- 93

- REPFI: 95220: AMR 2870

- 93. Unpublished study prepared by Stone Environmental, Inc. and Blasland, Bouck & Lee, Inc. 562 p.
43588101 Hisc ock, A. (1995) A Small

- Scale Prospective Ground

- Water Monitoring Study for Pyrithiobac

- Sodium (Staple, DPX

- PE350, KIH

- 2031): Site Selection, Characterization, and Instrument Report: Lab Project Number: AMR 2870

- 93: 423.06. Unpublished study prepared by Bla sland, Bouck & Lee, Inc.; Lancaster Labs; and DuPont Agricultural Products. 260 p.
43588102 Hiscock, A. (1995) A Small

- Scale Prospective Ground

- Water Monitoring Study for Pyrithiobac

- Sodium (Staple, DPX

- PE350, KIH

- 2031): Progress Report Number 1: Lab Pro ject Number: AMR 2870

- 93

- PR1: 423.06: AMR 2870

- 93. Unpublished study prepared by Blasland, Bouck & Lee, Inc.; Lancaster Labs; and DuPont Agricultural Products. 82 p.
43647601 Goetz, M.; Tillotson, P.; Hiscock, A. (1995) A Small

- Scale Prospective Ground

- W ater Monitoring Study for Pyrithiobac

- Sodium (STAPLE, DPX

PE350, KIH

- 2031): Progress Report No. 2: Lab Project Number: AMR/2870/93: 423/06: AMR/2870/93/PR2. Unpublished study prepared by Blasland, Bouck & Lee, Inc.; Midwest Labs, Inc. and Dupont Agricultur al Products. 74 p.
43530102 Mulderig, L.; Ledeker, K. (1995) Analytical Method for the Determination of Pyrithiobac Sodium in Water Using Liquid Chromatography with UV Absorption and Confirmation by Mass Spectrometric Detection: Lab Project Number: AMR 3 050

- 94. Unpublished study prepared by DuPont Agricultural Products. 64 p.
43317214 ECM Evaluation in Water
44373805 Sumpter, S.; Peterson, B.; Muldering, L. et al. (1997) Analytical Method for the- 33 of 41

- Determination of Pyrithiobac Sodium in Soil Using Subcri tical Water Extraction, Graphitized Carbon Clean

- Up, and Column

- Switching LC/UV Analysis with Confirmation by LC/MS: Revision No. 1: Lab Project Number: AMR 2745

- 93. Unpublished study prepared by Dupont Agricultural Products. 84 p.



### Submitted Ef fects Studies

MRID Citation Reference

42856911 Campbell, S.; Smith, G. (1993) KIH

- 2031 (DPX

- PE350): An Acute Oral Toxicity Study with the Northern Bobwhite: Lab Project Number: 112

- 288A: 42

- 93. Unpublished study prepared by Wildlife International Lt d. 22 p.
42856912 Campbell, S.; Lynn, S. (1992) KIH

- 2031 (DPX

- PE350): A Dietary LC50 Study with the Northern Bobwhite: Lab Project Number: 112

- 286: 141

- 92. Unpublished study prepared by Wildlife International Ltd. 27 p.
42856913 Campbell, S.; Lynn, S. (1992) KIH

- 2031 (DPX

- PE350): A Dietary LC50 Study with the Mallard: Lab Project Number: 112

- 287: 140

- 92. Unpublished study prepared by Wildlife International Ltd. 27 p.
43811101 Beavers, J.; Sipler, O.; Marselas, G.; et al. (1994) H

- 19,187 (KIH

- 2031, DPX

PE350

- 10): A One

- Generation Reproduction Study with the Northern Bobwhite (Colinus virginianus): Lab Project Number: 112

- 297: HLO 88

- 94. Unpublished study prepared by Wildlife International Ltd. 240 p.
43811102 Beavers, J.; Sipler, O.; Marselas, G.; et al. (1994) H

- 19,187 (KIH

- 2031, DPX

PE350

- 10): A One

- Generation Reproduction Study with the Mallard (Anas platyrhynchos): Lab Project Number: 112

- 298: HLO 89

- 94. Unpublished study prepared by Wildlife International Ltd. 249 p.
42856914 Baer, K. (1992) Sta tic, Acute, 96

- Hour LC50 of KIH

- 2031 (DPX

- PE350

- 10) to Bluegill Sunfish, Lepomis macrochirus: Lab Project Number: 188

- 92. Unpublished study prepared by Du Pont's Haskell Laboratory for Toxicology and Industrial Medicine. 21 p.
42856915 Baer, K. (1992) St atic, Acute, 96

- Hour LC50 of KIH

- 2031 (DPX

- PE350

- 10) to Rainbow Trout, Oncorhynchus mykiss: Lab Project Number: 184

- 92: 4581

- 946. Unpublished study prepared by Du Pont's Haskell Laboratory for Toxicology and Industrial Medicine. 21 p.- 34 of 41

- 43317204 Kreamer, G . (1994) Static, Acute, 96

- Hour LC50 of KIH

- 2031 (DPX

- PE350

- 9) to Channel Catfish, Ictalurus punctatus: Lab Project Number: 450

- 93: HLR 450

- 93: 9602

- 001. Unpublished study prepared by DuPont Haskell Lab for Toxicology and Industrial Medicine. 32 p.
42856 916 Baer, K. (1992) Static, Acute, 48

- Hour EC50 of KIH

- 2031 (DPX

- PE350

- 10) to Daphnia magna: Lab Project Number: 172

- 92: 4581

- 946. Unpublished study prepared by Du Pont's Haskell Laboratory for Toxicology and Industrial Medicine. 22 p.
43317205 Baer, K. (1994) Supplement No. 1 to Static, Acute, 48

- Hour EC50 of KIH

2031 (DPX

- PE350

- 10) to Daphnia magna: Lab Project Number: HLR 172

- 92: 172

- 92: 4581

- 946. Unpublished study prepared by DuPont Haskell Lab for Toxicology and Industrial Medicine. 6 p.
43317206 B owman, J.; Yang, Y. (1994) Acute Flow

- Through Toxicity of KIH

- 2031 (DPX

- PE350

- 9) to Crayfish (Procambarus clarkii): Lab Project Number: HLO 309

- 94: 40983: 309

- 94. Unpublished study prepared by ABC Labs., Inc. 155 p.
42856917 Ward, T.; Boeri, R. (1992) Ac ute Flow

- Through Toxicity of KIH

- 2031 (DPX

PE350

- 10) to the Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: 202

- 92: 91203

- DU: 4581

- 946. Unpublished study prepared by EnviroSystems Division, Resource Analysts, Inc. 32 p.
42856918 Ward, T.; B oeri, R. (1992) Acute Flow

- Through Toxicity of KIH

- 2031 (DPX

PE350

- 10) to the Mysid, Mysidopsis bahia: Lab Project Number: 165

- 92: 91202

- DU: 4581

- 946. Unpublished study prepared by EnviroSystems Division, Resource Analysts, Inc. 32 p.
42856919 Ward, T.; Boeri, R. (1992) Acute Flow

- Through Mollusc Shell Deposition Test with KIH

- 2031 (DPX

- PE350

- 10): Lab Project Number: 244

- 92: 91201

- DU: 4581

- 946. Unpublished study prepared by EnviroSystems Division, Resource Analysts, Inc. 31 p.
43317207 Baer, K. (1994) E arly Life

- Stage Toxicity Test of KIH

- 2031 (DPX

- PE350

- 9) with Fathead Minnows, Pimephales promelas: Lab Project Number: 9602

- 001: 786

- 93: HLR 786

- 93. Unpublished study prepared by DuPont Haskell Lab for Toxicology and Industrial Medicine. 271 p.
43317208 Kreamer, G. (1994) Chronic Toxicity of KIH

- 2031 (DPX

- PE350

- 9) to Daphnia magna: Lab Project Number: 536

- 93: 9602

- 001: HLR 536

- 93. Unpublished study prepared by DuPont Haskell Lab for Toxicology and Industrial Medicine. 397 p.
43530101 Ward, T.; Kowalski, P.; Boeri, R. (1995) Life

- cycle Toxicity of KIH

- 2031 (DPX

- PE350

- 9) to the Mysid, Mysidopsis bahia: Lab Project Number: 9981

- 001: 519

- DU: HLO 24

- 95. Unpublished study prepared by T. R. Wilbury Labs, Inc. 419 p.
42856943 Carski, T. (1993) Influence of KIH

- 2031 (DPX

- PE350) on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab Project Number: AMR 2303

- 92. Unpublished study prepared by Du Pont's Stine

- Haskell Research Center. 239 p.
43317211 McKelvey, R. (1994) Sup plement No. 1 to: Influence of KIH 2031 (DPX

PE350) on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab Project Number: AMR 2303

- 92. Unpublished study prepared by DuPont Agricultural Products, Stine

- Haskell Rese arch Center. 15 p.- 35 of 41

- 42856943 Carski, T. (1993) Influence of KIH

- 2031 (DPX

- PE350) on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab Project Number: AMR 2303

- 92. Unpublished study prepared by Du Pont's Stine

- Ha skell Research Center. 239 p.
43317211 McKelvey, R. (1994) Supplement No. 1 to: Influence of KIH 2031 (DPX

PE350) on Seed Germination, Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab Project Number: AMR 2303

- 92. Unpublished st udy prepared by DuPont Agricultural Products, Stine

- Haskell Research Center. 15 p.
42909204 Hughes, J.; Alexander, M. (1993) KIH

- 2031 (DPX

- PE350): Toxicity to Selenastrum capricornutum: Lab Project Number: B382

- 158

- 1: AMR 2449

- 92. Unpublished study prepa red by Malcolm Pirnie, Inc. 29 p.
42909205 Hughes, J.; Alexander, M. (1993) KIH

- 2031 (DPX

- PE350): Toxicity to Anabaena flos

- aquae: Lab Project Number: B382

- 158

- 2: AMR 2450

- 92. Unpublished study prepared by Malcolm Pirnie, Inc. 30 p.
42909206 Hughes, J. ; Alexander, M. (1993) KIH

- 2031 (DPX

- PE350): Toxicity to Navicula pelliculosa: Lab Project Number: B382

- 158

- 3: AMR 2451

- 92. Unpublished study prepared by Malcolm Pirnie, Inc. 29 p.
42909207 Hughes, J.; Alexander, M. (1993) KIH

- 2031 (DPX

- PE350): Toxicity to Skeletonema costatum: Lab Project Number: B382

- 158

- 4: AMR 2452

- 92. Unpublished study prepared by Malcolm Pirnie, Inc. 30 p.
42909208 Hughes, J.; Alexander, M. (1993) KIH

- 2031 (DPX

- PE350): Toxicity to Lemna gibba G3: Lab Project Number: B382

- 158

- 5: AMR 2453

- 92. Unpublished study prepared by Malcolm Pirnie, Inc. 29 p.
43577501 Thompson, S. (1995) DPX

- PE350: Influence on Growth and Reproduction of Skeletonema costatum: Lab Project Number: AMR 3234

- 94: 112A

- 135. Unpublished study prepared by Wildlife Int ernational, Ltd. 45 p.
43577502 Kannuck, R.; Sloman, T. (1995) DPX

- PE350: Influence on Growth and Reproduction of Lemna gibba G3: Lab Project Number: AMR 3222

- 94: HA

95

- 006. Unpublished study prepared by DuPont's Stine

- Haskell Research Center. 45 p.
42 856944 Hoxter, K.; Bernard, W.; Smith, G. (1993) KIH

- 2031 (DPX

- PE350): An Acute Contact Toxicity Study with the Honey Bee: Final Report: Lab Project Number: 112

- 289: 101

- 93: 9329

- 001. Unpublished study prepared by Wildlife International Ltd. 17 p.
470079 07 Brown, A. (2006) Metabolism of N

- Acetylglyphosate (IN

- MCX20) in Plants and Animals. Project Number: DUPONT/21333. Unpublished study prepared by E. I. du Pont de Nemours and Co, Inc. 16 p.- 36 of 41

- Appendix A Summary of available fate studies

1

- Persis tence in Water An acceptable hydrolysis study (MRID# 42856945 ) shows that Pyrithiobac

- Na is stable to degradation by abiotic hydrolysis . On the other hand, it degrades by aqueous photolysis with half

- lives range between 9

- 15 days ( MRID# 42856946) . The deg radates i dentified in the irradiated solutions were: ammonium 2

- chloro

- 6

- sul fobenzoate (mono

- and di

- salt of INKD303) ; 4,6

- dimethoxy

- 2

- pyrimidinol ; urea ; and methyl 1

- ureacarboxylate .

2

- Persistence in soil In acceptable study (MRID# 42856948, Pyrithio bac

- Na degrades with half

- life of 60 days in silt loam soil. The degradates identified i n the soil were: carbon dioxide; 2

- chloro

- 6

- [(4

- hydroxy

- 6

- methoxypyrimidin

- 2

- y1 ) thiobenzoic acid (IN

- JW212); and 4,6

- dimethoxy

- 2

- pyrimidinol.

Under anaerobic soil c onditions, Pyrithiobac

- Na degrades with half

- life of 128 days in an anaerobic (nitrogen atmosphere) silt loam soi1:water system (MRID# 43455601)

. The non

volatile degradate identified was (2

- chloro

- 6

- [(4

- hydroxy

- 6

- methoxypyrimidin

- 2

- yl)thi o]benzoic acid) w ith a maximum concentration of = 15 % of the applied radioactivity .

3

- Mobility Based on acceptable batch equi1ibrium experiments (MRID# 42909211), pyrithiobac

- Na was very mobile in sandy loam, si1t loam, and silty clay loam. Freundlich K ads values were 0.0 6 for the silt loam soil (1.1% OM) , 0.08 for the sandy loam soi1 (1.1%OM). 0.32 for the silt loam soi1 (5.1% OM), and 0.61 for the silty clay loam s oil (5.0% OM).
In another acceptable studies (MRID# 42909209, and 42909210), pyrithiobac

- Na

a nd metabolite (2

- chl oro

- 6

- C(4

- hydroxy

- 6

- methoxypyrimidin

- 2

- yl )thio]benzoic acid appear to be mobile in sandy loam, silty clay loam and silt loam soils.

4

- Dissipation : Terrestrial field- 37 of 41

- 

### Results of the four terrestrial field dissipation studies indicate Pyrithiobac

- Na dissipates rapidly in Texas (acceptable; MRID # 43317212 ) and Mississippi field locations (supplemental, MRID# 43455602, 43647401) , and was moderately persistent in a California study using irrigation (acceptable, MRID# 43455603) . Some downward movement of Pyrithiobac

- Na was observed in the i r rigated California study; however, this result would be anticipated because the study was conducted with weekly irrigation in a coarse

- textured soil.

Appendix B Summary of available effects studies

I. Aqua tic Organisms

Freshwater fish
An acceptable 96

- hr acute toxicity study with Bluegill Sunfish ( Lepomis macrochirus ) is available for Pyrithiobac

- Na (MRID 4 2856914 ). The fish were exposed to mean

- measured concentrations of 0 (control)
, 400, 540, 590, 770, and 930 mg ai /L. No effects were reported at any concentration and the LC 50 is reported to be > 930 mg ai / L.
An acceptable study with Rainbow Trout ( Oncorynchus mykiss ; MRID 00098505) is available for Pyrithiobac

- Na

. Trout were exposed to mean

- measured concentrations of 0 ( control ) , 120, 190, 340, 580, 1000 mg ai /L

. No effects were reported at any concentration and the LC 50 is reported to be > 1000 mg ai / L.
An acceptable study with Channel Catfish ( Ictalurus punctatus ; MRID 43317204) is available for Pyr ithiobac

- Na. The fish were exposed to mean

- measured concentrations of 0 (control), 120, 210, 350, 580, 970 mg ai/L. No effects were reported at any concentration and the LC 50 is reported to be > 970 mg ai/L.
As a result of these studies, Pyrithiobac

- Na is classified as practically nontoxic to freshwater fish on an acute exposure basis.

Freshwater invertebrates
An acceptable 48

- hr acute study with the freshwater invertebrate Daphnia magna is available for Pyrithiobac

- Na (MRID 42856916 ). Twenty daphnids p er level were exposed at mean measured concentrations of 0 ( negative control), 430, 540, 670, 840, and 1100 mg ai /L. No effects were reported at any concentration and the EC 50 is reported to be > 1100 mg ai/L.- 38 of 41

- A supplemental 48

- hr acute study with the f reshwater invertebrate Procambrus clarkia ( crayfish; MRID 43317206 ) is also available for Pyrithiobac

- Na. Crayfish were exposed at measured concentrations of 0 (negative controls), 130, 230, 350, 520, and 910 mg ai /L. No effects were reported at any conce ntration and the EC 50 is reported to be > 910 mg ai/L.
An acceptable chronic toxicity study with the freshwater invertebrate Daphnia magna is available for Pyrithiobac

- Na (MRID 43317208). Daphnids were exposed at mean measured concentrations of 0 (negati ve control), 20, 36, 68, 130, 260, 500, 1000 mg ai/L. The most sensitive en dpoint was survival , with a NO A EC of 260 mg ai /L, a LO A EC of 500 mg ai/L , and a MATC of 360 mg ai/L

. Based on these studies, Pyrithiobac

- Na is classified as practically non toxic t o freshwater invertebrates on an acute and chronic exposure basis.

Estuarine/marine fish
An acceptable 96

- hr acute toxicity study with Pyrithiobac

- Na was conducted on the Sheepshead Minnow ( Cyprinodon variegatus ; MRID 42856917) . Fish were exposed at a me an

- measured concentration of 145 mg ai/L. No mortality was reported so the LC 50 is reported to be > 145 mg ai/L.
There are no data assessing the chronic effect s of Pyrithiobac

- Na on estuarine/marine fish

. Based on this study , Pyrithiobac

- N a is classifie d as practically nontoxic to estuarine/marine fish on an acute exposure basis.

Estuarine/marine invertebrates
An acceptable 96

- hr shell deposition study was conducted on the Eastern Oyster ( Crassostrea virginica ; MRID 42856919) is available for Pyrithio bac

- Na. Oysters were exposed to a mean

measured concentration of 130 mg ai/L. No effects were reported so the EC 50 is reported to be > 130 mg ai/L.
An acceptable acute flow

- through study with Pyrithiobac

- Na was conducted on the estuarine/marine mysid s hrimp ( Mysidopsis bahia ; MRID 42856918 ). Shrimp were exposed at a

mean

- measured concentration of 140 mg ai/L. No mortality was reported so the LC 50 is reported to be >140 mg ai/L

. An acceptable life

- cycle study with Pyrithiobac

- Na was also conducted on the mysid shrimp (MRID 43530101). Shrimp were exposed at mean

- measured concentrations of 0 (control), 13, 28, 59, 120 and 240 mg ai/L. No effects were reported so the NOAEC is 240 mg ai/L and the LOAEC is > 240 mg ai/L.
Based on these studies, Pyrithiob ac

- Na is classified as practically nontoxic to estuarine/marine invertebrates on an acute and chronic exposure basis.- 39 of 41

- Plants
Two guideline studies are available assessing the toxicity of Pyrithiobac

- Na to the aquatic vascular plant duckweed ( Lemna gibba )

. In the first study, d uckweed was exposed to nominal concentrations of Pyrithiobac

- Na of 0 (control) 0.063, 0.125, 0.25, 0.5, 1.0, 2.0, and 40 μg ai /L. The 14

- day EC 50 , based on frond number, is 0. 9 μg ai /L , the NOAEC is 0. 5 μg ai /L , and the LOAEC is 1. 0 μg ai/L (MRID 42909207; Supplemental)

. In the second study, duckweed was exposed to mean

- measured concentrations of Pyrithiobac

- Na of 0 (control), 0.077, 0.13, 0.27, 1.2, and 5.5 μg ai/L. The 14

- day EC 50 , based on frond number, is 0.92 μg ai/L and the NOAC is 0.27 μg ai/L (MRID 43577502; Acceptable).
Four guideline studies are available assessing the toxicity of Pyrithiobac

- Na to aquatic nonvascular plants. The green algae Pseudokirchneriella sub capitata (formerly known as Selanastrum capricornutum ) w as exposed to mean

- measured concentrations of Pyrithiobac

- Na of 0 (control), 13.55, 21.87, 56.12, 95.47, 181.74, 369.18, and 756.05 μg ai /L. The five

- day EC 50 , based on cell density, is 95 μg ai /L and the NOAEC is 22 μg ai /L (MRID 42909204 ; Acceptable).
The cyanobacteria Anabaena flos aqua (MRID 4 2909205 ; Acceptable) was exposed to initial

measured concentrations of Pyrithiobac

- Na of 0 (control), 71, 289, 514, 1190, 2320, and 4810 μg ai /L. The five

- day EC 50 , based on cell density, 1178 μg ai /L and the NO AEC is 71 μg ai /L.

The diatom Skeletonema costatum (MRID 43577501 ; Acceptable) was exposed to mean

measured concentrations of Pyrithiobac

- Na of 0 (control)
, 7.8, 16, 32, 64, 130, and 250 mg ai /L. The five

- day EC 50 , based on cell density, is 63 mg ai /L an d the NOAEC is 32 mg ai /L.

The diatom Navicula pellicosa (MRID 42909206 ; Acceptable) was exposed to mean

- measured concentrations of pyrithiobac

- Na of 0 (control ), 0.83, 1.66, 3.23, 6.31, 12.7, 27.5, and 49.5 mg ai /L. The five

- day EC 50 , based on cell dens ity, is 10.3 mg ai /L and the NOAEC is 6.3 mg ai /L.

II. Terrestrial Organisms

Avian
An acceptable acute oral toxicity study of Pyrithiobac

- Na was conducted on the Northern Bobwhite ( Colinus virginianus ; MRID 42856911 )

. The birds were exposed to Pyrith iobac

- Na at doses of 0 (control), 998 , 1175, 1382, 1626, 1913, and 2250 mg ae /kg

- bw

. The LD 50 for the Northern Bowhite , based on reduction in body weight, i s 1599 mg ai /kg

- bw and the NOAEC is 998 mg ai/kg

- bw

. Pyrithiobac

- Na is classified as slightly toxi c to avian species on an acute oral exposure basis. There is no data available for a passerine species; therefore, sensitivity to avian species may be underestimated on an acute oral basis.

The 5

- day subacute dietary toxicity of Pyrithiobac

- Na was studi ed in the northern bobwhite ( MRID 42856912; Acceptable ). Birds were exposed to nominal concentrations of 0 (control), 562, 1000, 1780, 3160, and 5620 mg ai /kg

- bw

. Signs of toxicity, based on reduced body weight,- 40 of 41

- was recorded for birds exposed to 5620 mg ai/kg

- bw for the first portion of the study. Based on these data, the LC 50 is greater than 5620 mg ai/kg

- bw and the NOAEC was 1780 mg ai/kg

- bw.

The 5

- day subacute dietary toxicity of Pyrithiobac

- Na was studied in mallard ducklings ( MRID 42856913; Accepta ble). Birds were exposed to nominal concentrations of 0 (control), 562, 1000, 1780, 3160, and 5620 mg ai /kg

- bw

. There were no mortalities or signs of toxicity reported. Based on these data, the LC 50 is greater than 5620 mg ai/kg

- bw.
An acceptable avian reproduction study was conducted on the Northern Bobwhite (MRID 43811101). Birds were exposed to Pyrithiobac

- Na at nominal concentrations of 0 (control) 60, 300, and 1500 mg ai/kg

- bw. Based on a significant decrease in the number of viable embryos and live 3

- week embryos, the NOAEC is 60 mg ai/kg

- bw and the LOAEC is 300 mg ai/kg

- bw.
An acceptable avian reproduction study was conducted on mallard ducklings (MRID 43811102). Birds were exposed to Pyrithiobac

- Na at nominal concentrations of 0 (control) 60, 30 0, and 1500 mg ai/kg

- bw. Based on a reduction in hatchling weight, the NOAEC is 300 mg ai/kg

- bw and the LOAEC is 1500 mg ai/kg

- bw.

Mammals
Mammal toxicity data are drawn from the Health Effects Division (HED) chapter in support of the RED. The data ar e summarized below.

Acute t oxicity testing with the TGAI ( 85% Pyrithiobac

- Na ) produced an acute oral LD 50 = 3200 mg ae /kg

- bw. Based on these data, Pyrithiobac

- Na is classified as practically nontoxic to mammals on an acute exposure basis (MRID 42856920 ).
Chronic toxicity data is not reported.

Terrestrial Invertebrates

An acceptable 48

- hr acute contact study with young adult honeybees ( Apis mellifera ; MRID 42856944 ) exposed honeybees to concentrations of Pyrithiobac

- Na of 0 (control), 1.6, 3.1, 6.3, 12.5, and 25 μg ai /bee . There were no treatment related effects on honeybees so the LD 50 is greater than 25 μg ai/bee and the NOAEC is 25 μg ai/bee. This data indicates Pyrithiobac

- Na is practically nontoxic to honeybees.

Plants
The toxicity of Pyrith iobac

- Na to terrestrial plant seedling emergence and vegetative vigor was assessed in separate studies reported under MRID 4 2856943 (Supplemental)

. The studies were conducted with technical Pyrithiobac

- Na rather than typical end use product as required un der 40 CFR Part 158. Herbicidal active ingredients are usually formulated with adjuvants or surfactants- 41 of 41

- that enhance the activity of the pesticide. Therefore, the sensitivity of terrestrial plants to Pyrithiobac

- Na may be underestimated.
For seedling emergence, corn ( Zea mays ), cucumber ( Cucumis sativus ) , soybean ( Gly c ine max ) , sorghum ( Sorghum bicolor ), sugar beet ( Beta vulgaris ), pea ( Pisum sativum ), tomato ( Solanum lycopersicum ) , onion ( Allium cepa ), wheat ( Triticum aestivum ), and rape (Brassica nap a) were tested at measured concentrations of 0 (control), 0.00781, 0.0156, 0.0312, 0.0625, 0.125 oz ai/A. Biomass (dry weight), a preferred parameter, was not measured in the seedling emergence test. Of the parameters reported, shoot length was the most s ensitive for all species. Rape was the most sensitive dicot with an EC 25 of 0.0042 oz ai/A (2.63 x 10 - 4 lb ai/A) and a NOAEC of 0.0039 oz ai/A (2.44 x 10 - 4 lb ai/A)

. Sorghum was the most sensitive monocot, with an EC 25 of 0.0067

oz ai/A (2.63 x 10 - 4 lb a i/A) ; since NOAEC was not provided the EC 05 , 0.0012 oz ai/A (7.5 x 10 - 6 lb ai/A) , will be used for the listed species assessment

.
For vegetative vigor corn ( Zea mays ), cucumber ( Cucumis sativus ) , soybean ( Gly c ine max ) , sorghum ( Sorghum bicolor ), sugar be et ( Beta vulgaris ), pea ( Pisum sativum ), tomato ( Solanum lycopersicum ) , onion ( Allium cepa ), wheat ( Triticum aestivum ), and rape (Brassica napa) were tested at measured concentrations of 0 (control), 0.00781, 0.0156, 0.0312, 0.0625, 0.125 oz ai/A. Root weight was the most sensitive parameter reported. Rape was the most sensitive dicot with an EC 25 of 0.0014 oz ai/A (8.75 x 10 - 5 lb ai/A) ; since a NOAEC was not provided the EC 05 , 0.0004 oz ai/A (2.5 x 10 - 5 lb ai/A) , will be used for the listed species assessment. Sorghum was the most sensitive monocot with an EC 25 of 0.0007 oz ai/A (4.34 x 10 - 5 lb ai/A) ; since a NOAEC was not provided the EC 05 , 0.0002 oz ai/A (1.25 x 10 - 5 lb ai/A) , will be used for the listed species assessment.

There is some evidenc e 3 to suggest plant reproduction may be affected by sulfonylurea herbicides at levels below effects on vegetative growth or visual injury (Fletcher et al ., 1993). T o the extent that terrestrial plant reproduction are more sensitive to Pyrithiobac

- Na than g rowth endpoints, risks to terrestrial plants may be underestimated.

3 Snipes et al. 1992, Bansal et al. 1999; Fletcher et al. 1993, 1995,1996; Bhatti et al. 1995; Al

- Khatib et al. 1992; Boutin et al. 2000; Asghari and Evans 1992