Docket Number: EPA-HQ-OPP-2008-0190 www.regulations.gov



# Glufosinate Summary Document Registration Review: Initial Docket March 2008

Case # 7224Page 3 of 71 

### TABLE OF CONTENTS

Page #

I. Preliminary Work Plan................................................................................................ 4

II. Fact Sheet................................................................................................................ ..... 9

III. Ecological Risk Assessment Problem Formulation.............................................. 14

IV. Human Health Effects Scoping Document............................................................ 58

V. Glossary of Terms and Abbreviations .................................................................... 70Page 4 of 71 I. PRELIMINARY WORK PLAN

Introduction:

The Food Quality Protection Act of 1996 manda ted a new program: registration review. All pesticides distributed or sold in the United Stat es generally must be registered by EPA, based on scientific data showing that they will not cause unreasonable risk s to human health, workers, or the environment when used as directed on pr oduct labeling. The new registration review program is intended to make sure that, as the ab ility to assess risk evolves and as policies and practices change, all registered pesticides co ntinue to meet the st atutory standard of no unreasonable adverse effects. Changes in science, public policy, and pesticide use practices will occur over time. Through the new registrati on review program, the Agency periodically reevaluates pesticides to make sure that as change occurs, pr oducts in the marketplace can be used safely. Information on this program is provided at: http://www.epa.gov/oppsrr d1/registration_review/

. The Agency has begun to implement the new registration review program, and will review each registered pesticide every 15 years to determine wh ether it continues to m eet the FIFRA standard for registration. The public phase of registration review begins wh en the initial docket is opened for each case. The docket is the Agency’s opportun ity to state what it knows about the pesticide and what additional risk analyses and data or information it believes are needed to make a registration review decision. Afte r reviewing and responding to co mments and data received in the docket during this in itial comment period, the Agency will develop and commit to a final work plan and schedule for the registration revi ew of glufosinate-ammonium, which is the only active ingredient in the case.

Glufosinate-ammonium (C 15 H 15 N 2 O 4 P) is a non-selective foliar he rbicide that is used for preplant and post-emergent control of broadleaf weeds. Glufosin ate-ammonium acts by inhibiting glutamine synthetase, which leads to poisoning in plants via the overproduction of ammonia. Glufosinate-ammonium was first registered fo r use in 2000. It is registered for use on the following crops: apples, berries, canola, corn, co tton, currants, grapes, grass grown for seed, potatoes, rice, soybeans, sugar be ets, and tree nuts. Registratio ns for non-crop areas include golf course turf, residential lawns, ornamentals, and a variety of industrial, residential, and public

areas.

Anticipated Risk Assessment and Data Needs:

The Agency anticipates conducting comprehe nsive human health and ecological risk assessments, including an endangered species asse ssment for all uses of glufosinate-ammonium.Page 5 of 71 Ecological Risk

• Based upon the information gathered to date , the risks of concer n are mainly to nontarget plants as well as chr onic risk to mammals, with potential indirect effects on terrestrial animals possible due to alterati ons in aquatic plant communities. Acute and chronic risk quotients for birds slightly ex ceeded the LOCs. However, the LOCs were based on the highest dose tested in the subacute dietary study and the two avian reproduction studies. There is also concer n for effects on species listed under the Endangered Species Act, incl uding mammals and birds.

• Preliminary review of the available plant toxicity studies indicates that there are insufficient data on terrestrial plant toxici ty to complete the ecological assessment. Because sufficient data were not report ed, EPA cannot determine the no observed adverse effect concentration (NOAEC) for s eedling emergence, making determination of an action area for an endangered species as sessment difficult. Furthermore, EPA cannot verify the assessment endpoints, creating uncer tainties with regard to the effect of glufosinate-ammonium on non-ta rget terrestrial plants.

• The Agency anticipates requiring terrestria l seedling emergence and vegetative vigor studies using typical end-use product (TEP). Only technical grade active ingredient (TGAI) was tested in the terrestrial plant stud ies. There are concerns that the herbicide formulations are enhanced with the addition of surfactant to impr ove their efficacy, and, therefore, toxicity to non-target plants might have been underestimated in the studies because the TGAI, rather than the TEP was tested.

• The Agency does not anticipate that additional fate data will be needed. However, the analytical methods for residues in water a nd soil that were submitted have not been validated in an independent laboratory. Independent laboratory validation will be required to provide confidence in the quantification level of the submitted analytical method.

• The planned ecological risk assessment will allow the Agency to determine whether glufosinate-ammonium use has “no effect” or “may affect” federally listed threatened or endangered species (listed species) or their desi gnated critical habitat. If the assessment indicates that glufosinate-ammonium “may affect” a listed species or its designated critical habitat, the assessment will be refined. The refined assessment will allow the Agency to determine whether the use of gluf osinate-ammonium is “likely to adversely affect” the species or critical habitat or “not likely to a dversely affect” the species or critical habitat. When an assessment concludes that a pesticide’s use “may affect” a listed species or its designated critical habita t, the Agency will consult with the U.S. Fish and Wildlife Service and National Marine Fisheries Service (the Services), as appropriate.

• The Ecological Fate and Effects Division has indicated that the nonva scular aquatic plant data may possess uncertainties, given that only one of the five nonvascular aquatic plantPage 6 of 71 species were tested. However, given the low risk quotients, the Agency does not anticipate asking for additional nonvascular aquatic plant data.

Human Health Risk:

• In a previous glufosinate-amonium risk a ssessment (August 2003), EPA determined that the toxicology database lacked both a de velopmental neurotoxicity (DNT) study and a 28-day inhalation study in rats that measure glutamine synthetase activity levels in organs. The submitted DNT and inhalation stud ies did not measure glutamine synthetase activity levels. The registrant has submitted a proposal requesting that the Agency accept the DNT and inhalation studies without th e glutamine synthetase activity level measurements due to technical constraints on their ability to conduct such measurements. If this proposal is accepted, it is likely that the toxicity doses, endpoints, and uncertainty factors previously selected for glufosinat e-ammonium would require revisions. This would necessitate revisions to the dietary, re sidential, occupational, and aggregate risk assessments. If the proposal is not accepted, the toxicol ogy database for glufosinateammonium could be considered incomplete and additional data may be required. EPA’s decision on the glutamine synthetase proposal w ill be explained in the Final Work Plan.

Timeline:EPA has created the following estimated timeline for the completion of the glufosinateammonium registration review.

Registration Review of Glufosinate – Pr ojected Registration Review Timeline

Activities Estimated Year/Month Phase 1: Opening the docket Open Public Comment Period for Glufosinate-Ammonium 2008 – March Close Public Comment Period 2008 – June Phase 2: Case Development Final Work Plan (FWP) 2008 – July-Sept. Issue DCI 2009 – Apr.-June Data Submission 2011 – Apr.-June Preliminary Risk Assessment a nd Public Comment 2012 – Oct.-Dec.
Close Public Comment Period 2013 – Jan.-March Phase 3: Registration Review Decision Proposed Registration Review Decision 2013 – Apr.-June Public Comment Period 2013 – July-Sept. Final Registration Review Decision and Begin Post-Decision Follow-up 2013

Total (years) 5Page 7 of 71 Guidance for Commenters: The public is invited to comme nt on EPA’s preliminary regist ration review work plan and rationale. The Agency will carefully consid er all comments as well as any additional information or data provided in a timely manne r prior to issuing a fi nal work plan for the glufosinate-ammonium case.

Through the registration review process, the Ag ency intends to solicit information on trade irritants and, to the extent feas ible, take steps toward facilitating irritant resolution. Growers and other stakeholders are asked to comment on any tr ade irritant issues resulting from lack of Maximum Residue Levels (MRLs) or disparitie s between U.S. tolerances and MRLs in key export markets, providing as much specificity as possible regarding the nature of the concern. Please see page 8, Table 1, Human Health Eff ects Scoping Document, for a listing of the differences among the U.S., Canada, Codex, and Me xico tolerances for glufosinate-ammonium.

Glufosinate-ammonium is not iden tified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, based on information provided at http://oaspub.epa.gov/tmdl/waters_ list.impairments?p_impid=3 . The Agency invites submission of water quality data for this pesticide. To the extent possible, data should conform to the quality standards in Appendix A of the “OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in O PP’s Registration Review Risk Assessment and Management Process” (see: http://www.epa.gov/oppfead1/cb/ ppdc/2006/november06/session1- sop.pdf ), in order to ensure they can be used qua ntitatively or qualitatively in pesticide risk
assessments.

EPA seeks to achieve environmenta l justice, the fair tr eatment and meaningful involvement of all people, regardless of race, color, national origi n, or income, in the deve lopment, implementation, and enforcement of environmental laws, regulati ons, and policies. To help address potential environmental justice issues, the Agency seeks information on any groups or segments of the population who, as a result of thei r location, cultural practices, or other factors, may have atypical, unusually high exposure to glufosinat e-ammonium, compared to the general population. Please comment if you are aware of any sub-populations that may have atypical or unusually high exposure compared to the general population.

Stakeholders are also specifically asked to prov ide information and data that will assist the Agency in refining the human health and ecolo gical risk assessments, including any speciesspecific effects determinations. The Agency is interested in the following information:

1. Confirmation on the following label information.

a. Sites of application b. Formulations

c. Application methods and equipment d. Maximum application rates in units relate d to mass per unit area of treatment zone

e. Frequency of application, applicatio n intervals, and maximum number of applications per season, andPage 8 of 71 f. Geographic limitations on use. 2. Use or potential use distribution ( e.g. , acreage and geographical di stribution of relevant uses). 3. Use history. 4. Median and 90 th percentile reported use rates (lbs . a.i./acre) from usage data—national, state, and county. 5. Application timing (date of fi rst application and applicati on intervals) by use—national, state, and county. 6. Sub-county crop location data. 7. Usage/use information for non-agricultural uses ( e.g. , golf courses, athletic fields, ornamentals). 8. Directly acquired county-level usage data (not derived from state level data).

a. Maximum reported use rate (lbs. a.i. /acre) from usage data – county b. Percent crop treated—county

c. Median and 90 th percentile number of applications – county d. Total pounds per year—county

e. The year the pesticide was last us ed in the county/sub-county area f. The years in which the pesticide was applied in the county/sub-county area. 9. Typical application interval (days). 10. State or local use restrictions. 11. Ecological incidents (non-target plant damage and avian, fish, rept ilian, amphibian and mammalian mortalities) not al ready reported to the Agency. 12. Monitoring data.

Next Steps: After the comment period closes, the Agency w ill review the comments received, and then issue a Final Work Plan for glufosinate-ammonium.Page 9 of 71 II. FACT SHEET

Background Information :

• Glufosinate-ammonium Registra tion Review Case Number: 7224

• Glufosinate-ammonium PC Code: 128850; CAS#: 7182-82-2

• Technical Registrant: Bayer CropScience LP.

• First product registered in 2000, theref ore not subject to reregistration.

• Special Review and Reregist ration Division (SRRD), Chemi cal Review Manager: Karen Santora; santora.karen@epa.gov.

• Registration Division (RD), Product Manager: Joanne Miller; miller.joanne@epa.gov.

Use & Usage Information:

• Glufosinate-ammonium is a non-selective foliar herbicide that is us ed for pre-plant and post-emergent control of broadleaf weeds.

• It acts by inhibiting glutamine synthetase, which leads to poisoning in plants via the overproduction of ammonia.

• It is registered for use on the following cr ops: apples, berries, canola, corn, cotton, currants, grapes, grass grown for seed, potatoes, rice, soybeans, sugar beets, and tree nuts. Registrations for non-crop areas include golf cour se turf, residential lawns, ornamentals, and a variety of industrial, residential, and public areas.

• Both aerial and ground spray are allowed for mo st uses, although some applications are limited to methods using hand wands and backpack sprayers.

• Application rates vary considerab ly by use pattern, with the highest rate (1 .5 lb ai/A) for use patterns including orchar d nuts and fruits, grapes, gras ses grown for seed, and golf course turf. Multiple applications are allowed by most labels, with an annual maximum application rate of 4.5 lbs ai/A for orchards and vineyards.

• The majority of agricultural uses occur in corn (900,000 lb ai/A), followed by cotton (300,000 lb ai/A), canola (60,000 lb ai/A), al monds (30,000 lb ai/A), and grapes (20,000 lb ai/A).

Recent Actions:

• The most recent and comprehensive human h ealth risk assessment was conducted in 2003, when acute, short-term, and chronic aggr egate risk assessments were conducted for glufosinate-ammonium as a part of Secti on 3 registrations for transgenic cotton and cotton, transgenic rice, and bushberry.

• In 2002, EPA conducted an occupational and updated residential exposure risk assessment for the use of glufosinate- ammonium on rice, cotton, and bushberry.

• In 2002, 2006, and 2007, environmental fate a nd effects studies were submitted to support FIFRA Section 3 New Use registrations for cotton, rice, blueberry, corn, soybeans, and canola.

• In 2002 an environmental fate and effects study was also submitted to support a FIFRA Section 18 emergency exemption fo r blueberries in Mississippi.Page 10 of 71 • In 2007, new uses for non-transgenic canol a, corn, and soybean were approved.

• There are no pending new registrations for this chemical.

Ecological Risk Assessment Status : Please refer to Section III of this document, Ecological Risk Assessment Problem Formulation, for a detailed discussion of the anticipated ecological risk assessment needs. The following ecological outcomes and anticipated data n eeds are based on the limited data and risk assessments currently available:

• The Agency anticipates conducting comprehe nsive human health and ecological risk assessments, including an endangered species assessment for all uses of glufosinateammonium.

• Based upon the information gathered to date , the risks of concer n are mainly to nontarget plants as well as chronic risk to mammal s, with potential indirect effects terrestrial animals possible due to alterations in aquati c plant communities. Acute and chronic risk quotients for birds slightly exceeded the LOCs. However, the LOCs were based on the highest dose tested in the subacute dietar y study and the two avian reproduction studies. There is also concern for effects on speci es listed under the Enda ngered Species Act, including mammals and birds.

• Preliminary review of the plan t toxicity studies indicates that there are insufficient data on terrestrial plant toxicity to complete the ecological assessment. Because sufficient data were not reported, EPA cannot determine a NOAEC for seedling emergence, making determination of an action area for an endangered species assessment difficult. Furthermore, EPA cannot verify the assessm ent endpoints, creati ng uncertainties with regard to the effect of glufosinate-amm onium on non-target te rrestrial plants.

• The Agency anticipates requiring additional terrestrial plant seedling emergence and vegetative vigor studies using typical end-use product (TEP). Only technical grade active ingredient (TGAI) was tested in the terrestrial plant studies. There are concerns that the herbicide formulations are enhanced with the addition of surfactant to improve their efficacy, and, therefore, toxicity to non-target plants might have been underestimated in the studies because the TGAI, rather than the TEP was tested.

• The environmental fate and transport data set submitted for glufosinate-ammonium is adequate. However, the analytical methods for residues in water and soil that were submitted have not been validated in an independent laboratory. Independent laboratory validation will be required to provide confidence in the quantification levels of the submitted analytical methods.

Human Health Risk Assessment Status: Please refer to Section IV of this document, Human Health Effects Scoping Document, for a detailed discussion of the anticip ated risk assessment needs for human health. The following is a summary of those anticipated needs:

Dietary (Food and Water):

• The dietary exposure database for gl ufosinate-ammonium is complete.Page 11 of 71 • The Agency recently issued a document updating its estimated drinking water concentrations (EDWCs) for glufosinate-ammo nium in groundwater sources. This update does not change the water values that were used in the most recent risk assessment for glufosinate-ammoni um (August 2003).

• The Agency anticipates that the acute and/or chronic dietary exposur e analysis will be reassessed and include estimates of glufosin ate-ammonium levels in drinking water as well as changes based on the Agency’s decision on the proposal regarding the glutamine synthetase.

Residential:

• A previous risk assessment (August 2003) id entified potential residential exposures relating to residential handler and residential post applicati on exposures to glufosinateammonium as a result of broa dcast application to residen tial lawns (i.e., lawn renovation use). To mitigate the risk, the technical registrant, Bayer Environmental Science, voluntarily canceled the lawn renovation use. All labels for Bayer Environmental Science currently bear directions only for spot treatment of lawns, not the lawn renovation use. However, some end-use registrants still have the broadcast lawn renovation use on their labels. The Agency sent a letter to these registrants, which informed them of Bayer Environmental Science’s voluntar y cancellation of all lawn renovation uses and requested that they submit draft labels deleting the lawn renovation use. Once the lawn renovation use is cancelled, the Agency does not anticipate that a residential risk assessment will be needed for glufosinate-ammonium.

Occupational :

• The Agency believes the current occupational risk assessments and the resulting exposure levels are adequate, but if the registrant’s proposal on gl utamine synthetase (discussed earlier) is accepted, it is likely th e MOEs will need to be revised.

Aggregate :

• The Agency anticipates that the aggregate risk assessments for glufosinate-ammonium may need to be revised to include the followi ng: (1) the addition of water levels directly into the dietary analysis, thus obviating the need for Drinking Water Level of Comparison (DWLOC) analysis, and (2) recons ideration of the uncertainty factors and dose/endpoint selection based on a complete toxicity database for glufosinate.

Incidents:

• The Agency has received 48 ecological incident reports that have been linked to the use of glufosinate-ammonium. The majority of the incidents ( 45) involved damage to corn. Another of these incidents involved a ‘massive ’ fish kill in a farm pond in Maryland after application of glufosinat e-ammonium to plants surrounding the farm pond.

• A summary report listing the human health-related incident s reported for glufosinateammonium is pending and will be provided for the docket. The reported incidents will be provided during the development of the Final Work Plan.Page 12 of 71 Data Call-In Status:

• No Data Call-In has been issu ed for glufosinate-ammonium.

Tolerances: For a list of the current U.S. tolerances a nd Mexican, Canadian, and Codex maximum residue limits (MRLs) for glufosinate-ammonium, please refer to Table 1 of Section IV of this document, Human Health Effects Scoping Document.

• U.S. tolerances for glufosinate-amm onium are listed under 40 CFR 180.467.

• Except for tree nuts, almond hulls, banana, a nd soybean, the U.S. tolerances and Codex MRLs are not in harmony with respect to numerical levels.

• The U.S. tolerances and the Canadian MRLs are harmonized for field grain and soybeans but no other crops.

• All Mexican MRLs are harmonized with U.S. tolerances.

Labels : A list of registration numbers is included below a nd the labels can be obtained from the Pesticide Product Label System (PPLS) website: http://oaspub.epa.gov/pestlabl/ppls.home

. Glufosinate-Ammonium Registration Numbers:

Registration # Product name Company Name Active Ingredient % Active Ingredient

264-645 Ignite ManufacturingUse Product Bayer CropScience LP Glufosinate-ammonium 50.00

264-646 Ignite Technical Bayer CropScience LP Glufosinate-ammonium 95.00

264-652 Rely Herbicide Bayer CropScience LP Glufosinate-ammonium 11.33

264-660 Liberty Herbicide Bayer CropScience LP Glufosinate-ammonium 18.19

264-663 Remove Herbicide Bayer CropScience LP Glufosinate-ammonium 18.19

264-668 Liberty ATZ Herbicide Bayer CropScience LP Glufosinate-ammonium 10.00

264-829 Liberty 280 SL Herbicide Bayer CropScience LP Glufosinate-ammonium 24.5

270-317 AEH Concentrate Weed, Grass and Brush Killer Farnum Companies, Inc. Glufosinate-ammonium 5.78Page 13 of 71 270-318 AEH Ready-To-Use Weed and Grass Killer Farnum Companies, Inc. Glufosinate-ammonium 1.00

270-319 AEH Super Concentrate Weed, Grass and Brush Killer Farnum Companies, Inc. Glufosinate-ammonium 11.33

432-875 AEH 315 Manufacturing Concentrate Bayer Environmental Science Glufosinate-ammonium 18.19

432-954 FINALE Super Concentrate Weed, Grass and Brush Killer Bayer Environmental Science Glufosinate-ammonium 11.33

432-955 Finale Ready-To-Use Weed and Grass Killer Bayer Environmental Science Glufosinate-ammonium 1.00

432-956 Finale Concentrate Weed, Grass and Brush Killer Bayer Environmental Science Glufosinate-ammonium 5.78

432-960 Derringer F Herbicide Bayer Environmental Science Glufosinate-ammonium 11.33

432-1228 Derringer Herbicide Bayer Environmental Science Glufosinate-ammonium 11.33

432-1229 Finale Herbicide Bayer Environmental Science Glufosinate-ammonium 11.33Page 14 of 71 III. ECOLOGICAL RISK ASSESS MENT PROBLEM FORMULATIONPage 16 of 71 

## REGISTRATION REVIEW

ECOLOGICAL RISK ASSESSMENT PROBLEM FORMULATION FOR:

Glufosinate-ammonium

ammonium-(2 RS )-2-amino-4-(methylphosphinato)butyric acid

CAS Registry Number: 71182-82-2

PC Code: 128850



## O P O

OH O NH 2



## NH 4 +

Prepared by:

Brian Kiernan, Biologist Greg Orrick, Environmental Scientist

Reviewed by:

Melissa Panger, Ph.D., Biologist Marietta Echeverria, Environmental Scientist Elizabeth Behl, Branch Chief U. S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division Environmental Risk Branch IV 1200 Pennsylvania Ave., NW Mail Code 7507P Washington, DC 20460Page 17 of 71 I. Problem Formulation

The purpose of this problem formulation is to provide the foundation for an ecological risk assessment to be conducted fo r glufosinate-ammonium (glufosina te). As such, it articulates the purpose and objectives of the risk assessment, evaluates the nature of the problem, and provides a plan for analyzing the data a nd characterizing the risk (EPA, 1998).

A. Nature of Regulatory Action

The risk assessment will be conducted as part of the Agency’s regi stration review process established under the Food Quality Protection Act (F QPA; 1995). Previous risk assessments that serve as the basis for this problem formula tion include the following (for details, see Appendix A ):

• 1 Section 3 New Chemical (S3NC) Risk Assess ment of proposed uses on corn, soybeans, nut trees, vine crops, and non-agricultura l areas (DP Barcode 203178+; Dec. 7, 1988)

• 5 Section 3 New Use (S3NU) Risk Assessments of proposed uses on corn, soybeans, and non-agricultural areas (DP Barcode 260482+; D ec. 20, 1990); canola, potatoes, and sugar beets (DP Barcode 240586; Apr. 26, 2000); co tton, rice, and blueberries (DP Barcode 280453; Jul. 18, 2002); cotton (DP Barcode 318746+; Feb. 28, 2006); and corn, soybeans, and canola (DP Barcode 344652; Oct. 2, 2007)

• 8 Drinking Water Assessments from 1998 through 2007

• 4 Section 18 Risk Assessments for uses on ca nola, sweet corn, and blueberries from 1998 to 2002

• 1 Response to Comments (DP barcode 287073; Jan. 6, 2003) that was received from the Sierra Club

These previous assessments identify potential adverse effect to non-target plants. Previous assessments noted that the listed sp ecies LOC was exceeded for birds, mammals and aquatic invertebrates.

B. Stressor Source and Distribution

1. Nature of the Chemical Stressor

Glufosinate-ammonium [HOE 039866; ammonium-(2 RS )-2-amino-4- (methylphosphinato)butyric acid] is a non-selec tive foliar herbicide that acts by inhibiting glutamine synthetase, which leads to poisoning in plants via the overproduction of ammonia. Glufosinate-ammonium salt dissolves to produc e ammonia and glufosinate acid, a racemic mixture of ionic isomers; only the L -isomer (or ( S )-enantiomer) mimics the enzyme glutamine synthetase and is, therefore, herbicidally activ e. The product labels and most submitted studies refer to the salt racemate as the active ingredient . In this problem formulation, all glufosinateammonium residues are loosely refe rred to as “glufosinate” unless clarification is warranted.Page 18 of 71 The chemical profile of glufos inate-ammonium is provided in Table 1 . Chemical names and structures of the isomeric mixtures of glufos inate-ammonium and its degradates, as they are formulated in standards used in submitted environmental fate studies, are listed in Appendix B

.

Table 1. Chemical Profile of Glufosinate-ammonium.

Common name Glufosinate-ammonium IUPAC name ammonium-(2 RS )-2-amino-4-(methylphosphinato)butyric acid CAS name ( RS )-2-amino-4-(hydroxymethyl phosphinyl)butanoic acid monoammonium salt Structure

O P O

OH O NH 2

NH 4 +

Pesticide type, such as herbicide or insecticide, Herbicide

Chemical class Glutamin e synthetase inhibitor CAS number 77182-82-2 Empirical formula C 5 H 15 N 2 O 4 P Molecular mass 198.2 g/mol

Glufosinate inhibits the glut amate synthetase enzyme needed for the ammonification of glutamate to glutamine. This disruption in the production of key amino aci ds leads to disruption of the cell membrane, excess ammonium and death of the cell. Although this metabolic pathway exists in animals, the lack of acute toxicity is thought to be due the capacity for animals to supplement glutamine needs from their diet. A lthough neurotoxic effects (s eizures) in mammals have been reported in Health E ffects Divison (HED) studies, gluf osinate is not thought to be a cholinesterase inhibitor.

2. Overview of Pesticide Uses and Usage

Glufosinate-ammonium is an active ingredient in several formulated products registered for preplant and postemergent control of broa dleaf weeds in a variety of crops and non-crop areas. Products include Liberty ® , Ignite ® , Rely ® , Remove TM , AEH ® , Derringer ® and Finale ®

. Crops for which glufosinate is registered include apples, berries, canola, corn, cotton, currants, grapes, grass grown for seed, potatoes, rice, soyb eans, sugar beets, and tree nuts. Registrations for non-crop areas include golf c ourse turf, residential lawns, ornamentals, and a variety of industrial, residential, and public areas. Both aerial and gr ound spray is allowed for most uses, although some applications are limited to methods using hand wands and backpack sprayers. Application rates vary co nsiderably by use pattern. The highe st rate for broadcast spray (ground)Page 19 of 71 is 1.5 lbs ai/A for use patterns in cluding orchard nuts and fruits ( e.g. almonds, apples, hickory), grapes, grasses grown for seed and golf course tu rf. The maximum rate for cotton applications is 0.79 lbs ai/A (also labeled at 0.52 lbs ai/A), for rice is 0.73 lbs ai/A, and for sugar beets is 0.55 lbs ai/A. Corn and soybean broadcast applicatio ns are a maximum of 0.44 lbs ai/A. There are numerous other applications, in cluding turf and patio applications, labele d for 0.03 lbs ai/A. Multiple applications are allowed by most labels , although the interval is not generally specified, with an annual maximum rate of up to 4.5 lbs ai/A for orchards and vineyards. This problem formulation will focus on the highest applicati on rates and broadcast (aerial and ground) spray, because they are expected to result in the highest off-target exposure.

According to the Screening Level Usage Analysis (SLUA) provi ded by the Biological and Economic Analysis Division (BEAD), the majo rity of glufosinate is used on corn (900,000 lbs ai/yr), followed by cotton (300,000), canola (60,000), almonds (30,000) and grapes (20,000). Potatoes, rice and soybeans account for 10,000 lbs a i/yr per crop. No other use pattern exceeded 4000 lbs ai/A. The SLUA reports a maximum of 25% of canola crops treated and 15% of the almond crop, 10% of the potato crop; 5% or less of all other crops are tr eated; however, these data do not included non-agricultural uses.

C. Receptors

1. Aquatic and Terrestrial Effects

The receptor is the biological entity that is exposed to the stresso r (EPA, 1998). Aquatic and terrestrial receptors that live or forage on or adjacent to application sites may be exposed to glufosinate, such as birds, mammals, terr estrial plants, freshwater fish, etc.

Consistent with the process described in the Overview Document (EPA, 2004), the risk assessment will use a surrogate species approach in its evaluation of glufosinate. Toxicological data generated from surrogate test species, wh ich are intended to be representative of broad taxonomic groups, are used to extrapolate to poten tial effects on a variety of species (receptors) included under these ta xonomic groupings.

Acute and chronic toxicity da ta from studies submitted by pesticide registrants along with the available open literature are us ed to evaluate the potential dire ct effects of glufosinate to the aquatic and terrestrial receptors identified in this section. This includes toxicity data on the technical grade active ingredient, degradates, and when available, formulated products (e.g. “SixPack” studies). The open literature studies are identified through EP A’s ECOTOX database (http://cfpub.epa.gov/ecotox/ ), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The eval uation of both sources of data can also provide insight in to the direct and indirect e ffects of glufosinate on biotic communities from loss of species that are sensitive to the chemical and from changes in structure and functional characteristics of the affected communities.

Table 2 provides a summary of the taxonomic groups and the surrogate species tested to help understand potential acute eco logical effects of pe sticides to these non-target taxonomicPage 20 of 71 groups. In addition, the table provides a prelimin ary overview of the poten tial acute toxicity of glufosinate by providing the acu te toxicity classifications.

Table 2. Test Species Evaluated for Assessing Pote ntial Ecological Effects of Glufosinateammonium and the Associated Acute Toxicity Classification. Taxonomic Group Example(s) of Surrogate Species Acute Toxicity Classification

Birds 1 Mallard ( Anas platyrhynchos ) Bobwhite ( Colinus virginianus ) Practically non-toxic
Mammals Laboratory rat ( Rattus norvegicus ) Practically non-toxic Insects Honey bee ( Apis mellifera L. ) Practically non-toxic Freshwater fish 2 Bluegill sunfish ( Lepomis macrochirus ) Slightly non-toxic Freshwater invertebrates Water flea ( Daphnia magna ) Moderately toxic

Estuarine/marine fish Sheepshead minnow (Cyprinodon variegatues) Slightly toxic

Estuarine/marine invertebrates Mysid shrimp (Americamysis bahia) Moderately toxic

Terrestrial plants 3 Monocots – corn ( Zea mays ) Dicots – soybean ( Glycine max ) Not classified

Aquatic plants and algae Duckweed ( Lemna gibba ) Green algae ( Selenastrum capricornutum ) Not classified

1 Birds represent surrogates for terrest rial-phase amphibians and reptiles.
2 Freshwater fish may be surroga tes for aquatic-phase amphibians.
3 Four species of two families of monocots, of which one is corn ; six species of at least four dicot families, of which one is soybeans.

Ecological effect endpoints are derived from registrant-submitted guideline studies as required for registration under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA; 40 CFR Part 158), as well as a review of da ta available through acceptable open literature (ECOTOX; www.epa.gov/ecotox), when available. The most sensitive endpoints (described below) from testing of surrogate species are us ed to estimate risk to the taxonomic group(s) represented by the surrogate teste d. Toxicity testing reported in this document is intended to represent all terrestrial and aquatic organisms. However, only a few surrogate species are used to represent all freshwater fi sh (2000+), bird (680+) and pl ant (19,000+) species in the United States. In addition, neither reptil es nor amphibians are routinely te sted. Bird data are used as surrogates for reptiles and terres trial-phase amphibians; fish da ta are used as surrogates for aquatic-phase amphibians. The Norway rat is typically the surrogate for all mammals.

Neither reptiles nor amphibians ar e tested. The risk assessment a ssumes that avian and reptilian and terrestrial-phase amphibian sensitivities to the chemical are similar. The same assumption is made for fish and aquatic-phase amphibians. Terrestrial plant data are derived from the vegetative vigor and seedling emergence tests, typically on 10 ag ricultural crop species, and do not account for potential chronic or reproductive effects. Typicall y, five aquatic plant species are used to represent potential toxicity to all aquatic plant species.

Most of the studies with non- target organisms were conducted with glufosinate technical. The typical end-use product (TEP), EF-1343, was the test material in the terrestrial plant seedling emergence and vegetative vigor studies. These studies provide the e ffects basis for riskPage 21 of 71 estimation. A summary of the endpoint s that will be used in the ri sk assessment are presented in Table 3

. Further characterization will be possible becau se the TEP was used in several toxicity studies, including freshwater and es tuarine/marine fish and invertebrates and mammals. In many of these studies, the formulated product is considerably more toxi c than glufosinate technical, an important point which will be explored in the risk assessment.

Table 3. The Endpoints Used in Glufosinate Risk Estimation. Environ ment Taxa Species Type of Risk Type of Endpoint Endpoint Units MRID
Aquatic Freshwater Fish Rainbow
trout Acute LC 50 >320 mg ai/L 001424-54 001424-55 Chronic NOAEC No data -- Freshwater Invertebrates Daphnid Acute EC 50 668 mg ai/L 001424-56

Daphnid Chronic NOAEC 32 mg ai/L 405010-10 Estuarine /marine Fish Sheepshead minnow Acute LC 50 >1000 mg ai/L 413961-04

Chronic NOAEC No data -- Estuarine /marine Invertebrates Mysid Acute EC 50 7.5 mg ai/L 413961-07

Chronic NOAEC No data -- Plants Duckweed Acute EC 50 1.47 mg ai/L 422624-04 Duckweed Listed NOAEC 0.80 mg ai/L 422624-04 Terrestrial Avian Mallard Acute LD 50 >2000 mg ai/kg-bw 001424-50 Mallard Chronic NOAEC 400 mg ai/kg-diet 403456-49 Mammalian Rat Acute LD 50 3030 mg ai/kg-bw 001424-30 Rat Chronic NOAEC 6.0 mg ai/kg-diet 403456-12 Plants Carrot Acute EC 25 0.063 lb ai/A 413961-13 Carrot Listed NOAEC 0.05 lb ai/A 413961-13

Many pesticides have potentia l impacts to the growth, re production and survival of receptors via chronic exposure. For chronic asse ssments, the Agency typically evaluates longer duration studies on species similar to those used in acute studies; however, the assessment endpoints derived from these studies is not a median lethal dose, but a no adverse effect concentration/level (NOAEC/L). At this time, the Agency does not evaluate chronic risk to plants. Chronic exposure to avian species di d not result in any e ffects at the highest concentration tested. Chronic effects were obser ved at the highest concentration in the chronic mammal study.

For glufosinate, the only evalua tion of chronic exposure in aqua tic organisms is in a lifecycle study with freshw ater invertebrates ( i.e. , daphnids), in which effect s were seen only at thePage 22 of 71 highest concentrations in the study. Potential chronic effects to fish and estuarine/marine invertebrates are uncertain due to lack of data. Consistent with the Agency’s agreement with the Services, an acute-to-chroni c ratio will be used in the absence of other data to estimate potential risk to these taxa and to help defi ne an action area for listed entities.

2. Ecosystems Potentially at Risk

The ecosystems at risk are often extensive in sc ope, and as a result it may not be possible to identify specific ecosystems during the developmen t of a baseline risk assessment. However, in general terms, terrestrial ecosystems potentiall y at risk could include the treated field and areas immediately adjacent to the treated field that may receive drift or runoff. Areas adjacent to the treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats and other un cultivated areas.

Aquatic ecosystems potentially at risk include water bodies adjacent to, or down stream from, the treated field and might include impounde d 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 estuarie s. Within water bodi es, the wate r column, sediments, and pore water are all compartments of concern. Organisms of concern include birds, mammals, reptiles, fish, amphibians, terrestrial and aquatic invertebrate s, and plants. The assessment endpoints are intended to reflect pop ulation sustainability and community structure within ecosystems and hence relate back to ecosystems at risk. If risks are expected for given species/taxa based on the screening- level assessment, then risks might be expected to translate to higher levels of biological organization.

For glufosinate these areas would include ag ricultural areas growing apples, berries, canola, corn, cotton, currants, grap es, grass grown for seed, potatoes, rice, soybeans, sugar beets, or tree nuts, as well as fallow crop land, public and private non-agricu ltural areas including farmsteads, industrial areas, Christmas tree farms, ornamental areas, forests, golf courses, lawns, parks, paths, paved areas, recreational areas, residential areas, rights- of-way, and schools, and water bodies directly adj acent to use sites that may receive ch emical residues via drift, runoff, and/or discharged ground water.

D. Assessment Endpoints

Assessment endpoints represent the actual enviro nmental value that is to be protected, defined by an ecological entity a nd its attributes or characteristic s (EPA, 1998). For glufosinate, the ecological entities may include the followi ng: birds, mammals, freshwater fish and invertebrates, estuarine/marine fish and inverteb rates, terrestrial plants , insects, and aquatic plants and algae. The attributes for each of th ese entities may include growth, reproduction, and survival. The ecological entity can be a speci es, a functional group of species, a community, an ecosystem, or another entity of importance or concer n. An attribute is the characteristic of the entity that is important to prot ect and is potentia lly at risk.Page 23 of 71 Defining an assessment endpoint involves two step s: 1) identifying the valued attributes of the environment that are considered to be at risk, and 2) operationally defining the assessment endpoint in terms of an ecological entity ( e.g. , a community of fish a nd aquatic invertebrates) and its attributes ( i.e. , growth, survival and reproduction). Therefore, selection of the assessment endpoints is based on valued entities ( i.e. , ecological receptors), the ecosystems potentially at risk and the routes by which ecol ogical receptors are exposed to th e pesticide. The selection of clearly defined assessment endpoints is important because they provide direction and boundaries in the risk assessment for addressing risk management issues of concern.

Typical assessment endpoints fo r screening-level pesticide ecological risk assessments include reduced survival and/or reproductive impairment for both aquatic and terrestrial animal species from direct acute or direct chronic expos ures. Aquatic animal groups that are typically characterized in the risk assessment include: freshwater and estuarine/marine fish and invertebrates. Terrestrial animal groups includ e birds, mammals, and, qua litatively, beneficial insects. All assessment endpoints are characterize d at the individual leve l in order to protect threatened and endangered species. Howeve r, risks to higher biological levels ( i.e. , populations and communities) can be inferred from this approach ( e.g. , pesticide effects on individual survival and fecundity may impact population stabil ity, growth, and/or habita t carrying capacity). If warranted, a species-specific assessment contai ning characterization of th e potential for direct and indirect effects to listed species and the potential for advers e effects to designated critical habitat is the next step following completion of the screening-level risk assessment.

For terrestrial and semi-aquatic plants, the ba seline assessment endpoint is the perpetuation of populations of non-target species (crops and non-crop plant spec ies). Existing test requirements only evaluate the seedling emergen ce and vegetative vigor of annuals. Although it is recognized that the endpoint s of seedling emergence and vegetative vigor may not address all terrestrial and semi-aquatic plan t life cycle components, it is assumed that impacts on plant emergence and/or on active growth have the potential to impact individual competitive ability and reproductive success, from whic h population effects can be inferred.

For aquatic plants, the assessment endpoint is the maintenance and growth of standing crop or biomass. Measurement endpoints fo r this assessment focus on nonvascular, e.g. , algae, and vascular plants, e.g. , duckweed ( Lemna gibba ), growth rates and biomass measurements.

E. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically significant c oncentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an eco logical receptor. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptor s, and a feasible route of exposure.

A conceptual model provides a written desc ription and visual re presentation of the predicted relationships between glufosinate, pot ential routes of exposure, and the predictedPage 24 of 71 effects for the assessment endpoint. A conceptual model consists of two major components: risk hypothesis and a conceptual diagram (EPA, 1998).

1. Risk Hypothesis

For glufosinate, the following ecological risk hypothesis will be employed for the ecological risk assessment:

Based on the mode of action, use of glufosin ate according to labe l directions is not expected to result in direct acut e adverse effects to non-listed ani mal species; however, its use as directed may cause acute effects to listed entit ies and chronic effects ar e possible. Adverse effects to nontarget plant sp ecies are expected. Indirect effects on aquatic and terrestrial animals may occur due to alterations in plant communities.

2. Conceptual Diagram

The conceptual model used to depict the poten tial ecological risk associated with the use of glufosinate (the stressor) assumes that as a pesticide, glufosinat e can adversely affect terrestrial and aquatic organisms (the receptors ) if environmental concentrations exceed toxic thresholds as a result of applicati on according to the label directions ( Figure 1 ). Ecological receptors that may potentially be exposed to gl ufosinate include terrestrial and semi-aquatic wildlife ( e.g. , mammals, birds, amphibians and reptiles ), terrestrial and semi-aquatic plants, terrestrial invertebrates ( e.g. , honey bees), and terrestri al soil and aquatic sedi ment invertebrates. Additionally, given the mobility of glufosinate, aquatic organisms ( i.e. , freshwater and estuarine/marine fish and invertebrates, amphibian s, and aquatic plants) ar e potential receptors in adjacent water bodies through off-site transport of glufosinate from the application site through runoff, erosion and/or spray drift.

Routes of exposure to terrestrial and aquati c organisms can occur from direct application, spray drift and/or runoff. Exposure may be th rough ingestion of contaminated food or water sources, dermal contact or abso rption, and/or inhalation.

This assessment does not take into account po tential atmospheric tr ansport in estimating environmental concentrations or potential exposure via groundwater, nor does it account for ingestion of glufosinate residues by animals in contaminated grit, ingestion through preening activities, or uptake thro ugh inhalation or dermal absorption by terrestrial animals. Exposure to terrestrial animals is based primarily on dietary consumption of foliar (and insect) residues. Aquatic assessments assume that all potential routes of direct exposure are accounted for.Page 25 of 71 Figure 1. Conceptual Model for a Screening Level Assessment of Glufosinate. Dashed lines indicate exposure routes not evaluated; bold lines indicate routes of exposure hypothesized to be of greatest importance. Stressor Stressor Glufosinate Applied as Aerial or Ground Spray to Target Crops

Source/ Transport Pathways Volatilization / Wind Suspension Direct Deposition Spray Drift Runoff / Erosion Leaching (infiltration / Percolation)

Source/ Exposure Media Terrestrial Food (foliage, fruits, insects) Receiving Water Body/

Sediment Ground water

Irrigation water
on crops

Exposure Route Ingestion Uptake / Absorption Gill / Integument

Uptake

Receptors Terrestrial Vertebrates Birds, Mammals, Reptiles, Terrestrial Phase Amphibians Aquatic Plants Aquatic Animals Non-target Crop

Attribute Changes Individual Animals Reduced survival Reduced growth Reduced reproduction Plant Population Reduced survival, growth Individual Vertebrates and Invertebrates Reduced survival Reduced growth Reduced reproduction Reduced survival Reduced growth Foliage/Roots/Seeds

Terrestrial Pl a n ts

Bold lines indicate pathways of primary concern in this risk assessmen tPage 26 of 71 F. Analysis Plan and Preliminary Analysis

The proposed label maximum application rates fo r the use of glufosinate will be selected for modeling environmental concentrations for this screening level, deterministic (risk-quotient based) assessment. The most sensitive toxicity endpoints from surrogate test species will be used to estimate treatment-related effects on growth, reproduction and survival assessment endpoints. Estimated environmental concentrati ons (EECs) used in terrestrial and aquatic ecological risk assessments will be based on glufos inate parent residues, as the toxicity of the degradates to ecological entities is not known.

A risk quotient-based approach will be used in the assessment, comparing the ratio of exposure concentrations to effect s endpoints with predetermined le vels of concern (LOCs). The use, laboratory environmental fate and laborator y ecological effects data , all of which provide the basis for these risk quotients, are characte rized in the assessment. Although risk is often defined as the likelihood and magnitude of advers e ecological effects, the risk quotient-based approach does not provide a quantitative estimate of likelihood and/or magnitude of an adverse effect.

Additionally, consideration of potential risk from formulat ed product to the taxa for which data are available will be considered. Available data suggest that formulations of glufosinate exhibit greater toxi city than the parent alone. Exposure to formulations of glufosinate may result in great risk to nontarget taxa. This will be explored in detail in the risk
assessment.

1. Conclusions from Previous Risk Assessments

Previous risk assessments have identified pot ential acute risk to listed terrestrial and aquatic invertebrate species and ch ronic avian risk. Potential risk to nontarget plants was also identified.

2. Preliminary Identification of Data Gaps

Only one ( Selanastrum capricornutum ) of the five guideline nonvascular aquatic plant species studies is available to evaluate potential effects to nonvascular aquatic plants. The submission of the remaining guideline studies w ould allow a better characterization of potential indirect effects, especially within aquatic ecosy stems. Since these non-va scular plant species are representative of important links in the aquati c food chain, a better understanding of the effect of glufosinate on these taxa could be important.

Uncertainty regarding potential chronic risk to freshwater fish and estuarine/marine organisms could be reduced with the submissi on of additional data. Consistent with the Agency’s agreement with the Services, an acute-t o-chronic ratio will be us ed in the absence of other data to estimate potential risk to these taxa and to help define an action area for listed entities.Page 27 of 71 Because sufficient data were not report ed, a determination of a NOAEC for seedling emergence is not possible. Therefore, determ ining an action area for an endangered species assessment will be difficult and subject to conserva tive assumptions. Data are insufficient in all studies to allow verification of the assessment endpoints, leading to heightened uncertainty regarding the effect of glufosin ate on nontarget terrestri al plants. If thes e endpoints cannot be verified, they may not be sufficient for a risk assessment. Additionally, only the TGAI was tested in the terres trial plant studies. Guide line studies conduct testing with the TEP. Since most herbicide formulations are enhanced with the add ition of surfactants, toxic ity to plants may have been greatly underestimated in the studies in-house . Given that glufosinate is an herbicide, these issues are critical to the comp letion of a risk assessment.

Given the greater toxicity of formulated glufos inate to some taxa, avian toxicity data on the formulated product would allow for better char acterization of potential risk to these taxa.

Environmental fate submissions for each guide line requirement and any additional data needs are listed in Table C.1 in Appendix C . The submitted environmental fate data are sufficient to fulfill most data requirements for glufosinate-ammonium. However, the submitted analytical method for residues in water and soil has not been validated in an independent laboratory. Submission of an inde pendent laboratory validation is necessary for confidence in the quantification level of th e submitted analytical method.

3. Measures of Exposure and Effect

The screening level environmental fate and ecological risk assessments use the risk quotient (RQ) deterministic method of evaluating poten tial risk. The RQ, an integration of effect and exposure estimation ( Table 4 ) is calculated by dividing the estimated environmental concentration (EEC) by the measure of effects ( e.g. LD 50 ). The resulting quotient is then compared to a predetermined level of concern (LOC; Table 5 )

Table 4. Measures of Ecological Effects and Exposure for Glufosinate.

Assessment Endpoint Surrogate Species and Measures of Ecological Effect 1 Measures of Exposure

Survival Bobwhite acute oral LD 50 Bobwhite and mallard subacute dietary LC 50 Birds 2

Reproduction and growth Bobwhite and mallard chronic reproduction NOAEC and LOAEC

Mammals
Survival Laboratory rat acute oral LD 50 Maximum residues on food items (foliar)Page 28 of 71 Assessment Endpoint Surrogate Species and Measures of Ecological Effect 1 Measures of Exposure

Reproduction and growth Laboratory rat oral reproduction chronic NOAEC and LOAEC

Survival Rainbow trout and bluegill sunfish acute LC 50 Peak EEC 4 Freshwater fish 3

Reproduction and growth No Data 60-day average EEC 4

Survival Water flea (or other freshwater invertebrates) acute EC 50 Peak EEC 4 Freshwater invertebrates

Reproduction and growth Water flea chronic (life cycle) NOAEC 21-day average EEC 4

Survival Sheepshead minnow acute LC 50 ) Peak EEC 4 Estuarine/marine fish

Reproduction and growth No Data 60-day average EEC 4

Survival Eastern oyster acute EC 50 and mysid acute LC 50 Peak EEC 4 Estuarine/marine invertebrates

Reproduction and growth No Data 21-day average EEC 4

Terrestrial plants 5

Survival and growth Monocot and dicot seedling emergence and vegetative vigor EC 25 and NOAEC values Estimates of runoff and spray drift to non-target areas

Insects Survival (not Honeybee acute contact LD 50 Maximum application ratePage 29 of 71 Assessment Endpoint Surrogate Species and Measures of Ecological Effect 1 Measures of Exposure

quantitatively assessed)

Aquatic plants and algae Survival and growth Algal and vascular plant (i.e., duckweed) EC 50 and NOAEC values for growth rate and biomass
measurements Peak EEC 4

1 If species listed in this table represent most commonly encoun tered species from registrant-submitted studies, risk assessment guidance indicates most sensitive species tested within taxonomic group are to be used for baseline risk assessments.
2 Birds represent surrogates for amphibian s (terrestrial phase) and reptiles.
3 Freshwater fish may be surrogate s for amphibians (aquatic phase).
4 One in 10-year return frequency.
5 Four species of two families of monocots - one is corn, six species of at least four dicot families, of which one is soybeans. LD 50 = Lethal dose to 50% of the test population; NOAEC = No observed adverse effect concentration; LOAEC = Lowest observed adverse effect concentration; LC 50 = Lethal concentration to 50% of the test population; EC 50 /EC 25 = Effect concentration to 50%/25% of the test population.

Table 5. Levels of concern (LOCs) for various taxa.
Risk Presumption RQ LOC

Birds and Mammals

Acute Risk EEC/LC 50 or LD 50 /sqft or LD 50 /day 0.5

Acute Restricted Use EEC/LC 50 or LD 50 /sqft or LD 50 /day (or LD 50 < 50 mg/kg) 0.2

Acute Endangered Species EEC/LC 50 or LD 50 /sqft or LD 50 /day 0.1

Chronic Risk EEC/NOAEC 1
Aquatic Animals

Acute Risk EEC/LC 50 or EC 50 0.5

Acute Restricted Use EEC/LC 50 or EC 50 0.1

Acute Endangered Species EEC/LC 50 or EC 50 0.05

Chronic Risk EEC/NOAEC 1

Terrestrial Plants

Acute Risk EEC/EC 25 1

Acute Endangered Species EEC/NOAEC or EC 05 1
Aquatic Plants

Acute Risk EEC/EC 50 1Page 30 of 71 Risk Presumption RQ LOC

Acute Endangered Species EEC/NOAEC or EC 05 1

4. Measures of Exposure

a. Environmental Fate Characteristics

The environmental fate and transport data set submitted for glufosinate-ammonium is adequate. These data indicate that residue s of glufosinate-ammonium are hydrophilic and mobile in soil. The residues are not likely to persist in aerobic, surface soils; however, they do not hydrolyze and can readily move to surface water via spray drift and runoff. Chemical properties and environmental fate parame ters of glufosinate are listed in Table 6

.

Table 6. General Chemical Properties and Environm ental Fate Parameters of Glufosinateammonium.

Parameter Value Reference Selected Physical/Chemical Parameters Molecular mass 198.2 g/mol Accsn # 263025 Vapor pressure (25°C) <7.5 x 10 -9 torr MRID 44032901 Water solubility (22°C) 1.37 x 10 6 mg/L Accsn # 263025 Octanol-water partition coefficient (K OW ) <0.1 Accsn # 263025 Fish Bioconcentration Factor (28 d) None MRID 41323130
Persistence Hydrolysis half-life pH 5 (25°C) pH 7 pH 9 No significant degradation No significant degradation No significant degradation MRID 40345656

Aqueous photolysis half-life No significant degradation MRID 41323115 Soil photolysis half-life 17 d MRID 41920102 Aerobic soil metabolism half-life range 8.54-8.83 d (1.62 ppm applied) 20.6-23.0 d (7.23 ppm applied) MRID 41323119 MRID 40345659A
Anaerobic soil metabolism half-life 36.9 d MRID 40501014 Anaerobic aqueous metabolism half-life No significant degradation MRID 46258601 Aerobic aqueous metabolism half-lives 38.5, 51.8 d MRID 40345660 Mobility Freundlich organic carbon distribution coefficient (K FOC ) 9.41 L/kg OC (sand) 156 L/kg OC (silt loam) 352 L/kg OC (silt loam) 1230 L/kg OC (volcanic ash clay) MRID 40345662

Field Dissipation Terrestrial field dissipation half-life range 8-23 d MRID 43110402, MRID 43766915, MRID 43766916Page 31 of 71 i. Transport and mobility

Glufosinate residues are readily miscible in water (Accsn # 263025) and will not volatilize significantly due to a lo w vapor pressure of <7.5 x 10 -9 torr (25°C; MRID 44032901). Glufosinate is hydrophilic, with an octanol-water partition co efficient of <0.1 (Accsn # 263025) and does not bioconcentrate in fish (MRID 41323130).

Due to its hydrophilicity, glufosinat e is mobile to highly mobile (K FOC of 9.41 to 352 in soils representative of use si tes; MRID 40345662). Mobility of glufosinate residues may be explained by affinity to organic matter, as the coefficient of vari ation (CV) across four soils for the Freundlich organic carbon partition coeffici ent (99.7%) is less than that for the Freundlich soil-water partition coefficient (116%).

Regarding degradates of gl ufosinate, HOE 061517 (3-methyl phosphinico-propionic acid) is mobile to highly mobile, si milar to glufosinate parent (K FOC range = <10 to 158 in soils representative of use sites; MRID 4 0345662). However, HOE 064619 (2-methylphosphinicoacetic acid) appears to be less m obile than the parent compound (K OC = 3260; MRID 41323121).

ii. Degradation

Glufosinate does not significantly degrade unde r the abiotic processe s of hydrolysis and photolysis (MRID 40345656, 41323115). The compound is moderately biodegr aded in aerobic soils, with an apparent sensitivity to concentr ation. Applied at 7.23 μg/g soil, glufosinate was biodegraded with a half-life range of 20.6- 23.0 days (MRID 40345659A). Applied at 1.62 μg/g soil, glufosinate biodegrade d with shorter half-lives of 8.54-8.83 days (MRID 41323119). Biodegradation occurs less readily in anaerobic soils (t 1/2 = 36.9 days; MRID 40501014) and aerobic water bodies (t 1/2 range = 38.5-51.8 days; MRID 40345660) and is insignificant in anaerobic water bodies (MRID 46258601).

iii. Field studies

Several terrestrial field dissipation studies of glufosinate have been submitted. In these studies, glufosinate dissipates from the upper 6 inches of soil with half-lives of 1-4 weeks. This range of dissipation rates is gene rally consistent with those expect ed from the submitted fate and transport studies. Rates of aerobic soil metabolism, which is the sole major route of degradation, are similar. Glufosinate is expected to be m obile, but did not appear to leach further than 6 inches in loam or clay soils or further than 24 inches in a sand soil. Leaching may have been attenuated by the presence of 2-3% soil organic matter. Analytes in the submitted studies include degradates HOE 061517 and HOE 064619. HOE 061517 exhibits a faster rate of formation and decline and gr eater mobility than HOE 064619. HOE 061517 also exhibits greater mobility than glufos inate parent (MRID 43110402, 43766915, 43766916).Page 32 of 71 iv. Degradates

Major degradates of glufosinate incl ude HOE 061517 (MPP, 3-methylphosphinicopropionic acid), HOE 064619 (MPA, 2-methyl phosphinico-acetic aci d), HOE 085355 (NAG, 2- acetamido-4-methylphosphinico-butanoic acid), and carbon dioxide (chemical names and structures are tabulated in Appendix B ). Two minor degradates have been identified, HOE 086486 [3-methylphosphinico-3-oxo-propionic aci d] and HOE 065594 [4-methylphosphinico-2- oxo-butanoic acid].

Submitted studies have not reported toxic e ffects resulting from exposure to the major degradates. Therefore, exposure is assessed in terms of residues of the parent compound only for ecological assessments of glufosinate.

b. Aquatic Exposure

The Tier I screening model (GEN)eric (E)s timated (E)nvironmental (C)oncentration (Version 2.0, Aug. 1, 2001) was used to generate preliminary upper-bound EECs for glufosinate that may occur in surface waters adjacent to use sites. GENEEC simulates a vulnerable scenario run by the Tier II coupled exposure models PRZM and EXAMS, which simulate pesticide movement and transformation from crop applica tion through soil residue processes and loading into an adjacent pond via runoff and spray drift. These models assume a standard pond scenario in which a 10-hectare field drains into an adjace nt 1-hectare pond of 2-meter depth (EPA 2006).

The exposure estimates listed in Table 7 reflect upper-bound concentrations of glufosinate residues in surface water based on the highest use patterns, e.g. tree nuts, apples, grapes (3 applications at 1.5 lb s ai/A each, unspecified interval). GENEEC is not sensitive to application timing; therefore, the screening-level estimated exposure concentrations (EEC) below represent all application timings at th e modeled application ra tes. These EECs are considered conservative values relative to ma ny of the registered glufosinate use patterns. Further crop- and area-specific refinements may be conducted using Tier II modeling. The model input parameters used to gene rate these EECs are presented in Table 8

.

Table 7. Tier I surface water upper-bound exposure estima tes of glufosinate from the highest label use patterns.

Crop Annual App. Rate (lbs ai/A) Peak EEC (ppb) 4-Day Avg EEC (ppb) 21-Day Avg EEC (ppb) 60-Day Avg EEC (ppb)

Tree nuts, apples, grapes 4.5 158 156 148 131Page 33 of 71 Table 8. Tier I input parameter values for aquatic ecological exposure modeling of glufosinate using GENEEC. Input Parameter Value Justification Source Application Rate in lbs a.i./A 1.5 Maximum single applica tion rate Current labels

Applications per Year 3 Label directions for maxi mum rate Current labels Application Interval (days) 5 Assumption in absence of stated interval Current labels Organic Carbon Partition Coefficient (K OC ) 156 Represents the lowest non-sand K OC . MRID 40345662

Aerobic Soil Metabolism Half-life (days) 19.5 Represents the 90 th percentile confidence bound on the mean half-life. MRID 41323119 MRID 40345659A Wetted In? No Label directions Current labels Application Method Ground Label directions Current labels Nozzle Height (inches) 20 to 50 La bel directions Current labels Droplet size distribution Me dium to coarse Label di rections Current labels Width of No-Spray Zone (ft) 0 Label directions Current labels

Depth of incorporation (inches) 0 Value for broadcast spray Current labels

Solubility in Water (mg/L) 1.37 x 10 6 Study value Accsn # 263025 Aerobic Aquatic Metabolism Half-life (days) 65.6 Represents the 90 th percentile confidence bound on the mean half-life. MRID 40345660

Aqueous Photolysis Half-life (days) Stable Study value MRID 41323115

i. Aquatic Exposure Monitoring

A cursory review of currently available ground water and surface water monitoring data on glufosinate was conducted. No analyses of glufosinate were located. The compound is an upcoming analyte in the USGS NAWQA program, but no analyses have been reported through September 30, 2006 (USGS 2007). Glufosinate was not analyzed in monitoring conducted for the USGS NASQAN program (USGS 2006) or th e California Department of Pesticide Regulation (DPR) Surface Water Database (CDPR 2006) . Glufosinate is not an analyte listed in STORET (EPA 2007), in the EPA Pesticides in Ground Water Database (EPA 1992), or on the Safe Water Drinking Act (SWDA) Contaminant Ca ndidate Lists. The co mpound is not listed in the EPA Safe Drinking Water Information Syst em (SDWIS/FED) database (EPA 2007a), and not found in the EPA Unregulated Contamin ants Monitoring Rules (UCMR) chemical monitoring database (EPA 2006a).

ii. Drinking Water Exposure

Separate from this ecological risk assessm ent, drinking water exposure assessment will be conducted as part of the Agency’s registration review process in support of the Health Effects Division’s human health risk assessment. For dr inking water, the residues of concern include glufosinate, HOE 061517, HOE 064619, a nd HOE 099730 (a.k.a. 085355) (EPA 2002). Exposure estimates of previous drin king water assessments are listed in Table A.2 of Appendix A . 1-in-10-year peak and annual av erage estimates in surface water ( e.g. 823 ppb) and groundPage 34 of 71 water ( e.g. 30.7 ppb) from the maximum use patterns lis ted in the latest drinking water exposure assessment (EPA 2007b) are expected to be us ed in support of assessment under registration review.

b. Terrestrial Exposure

i. Animals Terrestrial wildlife exposure estimates are typically calculated for birds and mammals emphasizing a dietary uptake of pe sticide through residue s on vegetative and insect forage items. Avian terrestrial EECs are considered representa tive of potential exposure for terrestrial-phase amphibians and reptiles as well, unless more appropriate data are available through ECOTOX. For exposure to terrestrial organisms, pestic ide residues on food items are estimated, based on the assumption that organisms are exposed to a single pesticide residue in a given exposure scenario. Exposure was evaluated using EECs ge nerated from a spreadsheet-based screening model (TREX v.1.3.1) that calculates the dissipati on of a chemical applied to foliar surfaces for single or multiple applications. The terrestria l animal exposure assessment is based on the methods of Hoerger and Kenaga (1 972) as modified by Fletcher et al. (1994). When data are absent, as in this case, EFED assumes a 35-da y foliar dissipation half-life. The predicted maximum residues of glufosinate that may be e xpected to occur on selected avian or mammalian food items immediately following application at the maximum rate for a single growing season are presented in Table 10

.

Table 9. Unadjusted dietary-based estimated envir onmental concentrations (EECs) on terrestrial animal forage items following application of glufosinate based on TREX (version 1.3.2).

Application Rate Food Items Upper-bound EEC (ppm) a Mean EEC (ppm) a

Short grass 981 348
Tall grass 450 147
Broadleaf plants/small insects 552 184 1.5 lbs ai/A 3 applications

5d interval

Fruits, pods, seeds, and large insects 61 29

a Predicted residues based on Hoerger and Kenaga (1972) as modified by Fletcher et al. (1994).

ii. Plants Exposure to upland and wetland plants is estim ated using the TerrPlant (v1.2.2) screening model. TerrPlant estimates potential exposure from a singl e application using default assumptions for runoff and spray drift ( Table 11 ). For runoff plus drift, TerrPlant incorporates two similar conceptual models for depicting dry and semi-aquatic areas of terrestrial habitats. For both models, a non-target area is adjacent to th e treated field. Pesticide exposures to plants adjacent to the treated field are estimated to incl ude runoff and drift from the treated field. For a dry area adjacent to the treated fi eld, runoff exposure is estimated as sheet runoff. In the model, sheet runoff is defined as the amount of pesticide in water that runs off of the soil surface of a treated field which is equal in size to the non-targ et area (1:1 ratio of areas). For semi-aquaticPage 35 of 71 areas, runoff exposure is estimated as channelized runoff. In the model, channelized runoff is the amount of pesticide that runs off of a treated field 10 times the si ze of the area adjacent to the treated field (10:1 ratio of areas). The drift component is calcula ted as 1% of applied mass (for ground spray) or 5% of applied ma ss (for aerial spray). Estimate d exposures through runoff plus drift and drift alone are then comp ared to measures of plant surv ival and growth (e.g. effects to seedling emergence and vegetative vigor) to develop RQ values.

Table 10. Estimated environmental concentrations (EECs) on plants following label-specified applications of glufosinat e determined using the TerrPlant model (lbs ai/A).
Rate Application Method Adjacent Upland Loading a Adjacent Wetland Loading Drift Only

Aerial 0.15 0.825 0.075 1.5 lbs ai/A Ground 0.09 0.765 0.015

a Loading is runoff plus drift (lbs ai/A)

5. Measures of Effect

Most of the studies with non- target organisms were conducted with glufosinate technical. The typical end-use product (TEP), EF-1343, was the test material in the terrestrial plant seedling emergence and vegetative vigor studies. These studies provide the e ffects basis for risk estimation. Further characteriz ation is possible due the subm ission of non-guideline toxicity studies, as the TEP was tested in several aquati c studies. A summary of the endpoints used in this risk assessment were presented in Table 2

. a. Aquatic Effects

i. Freshwater Fish

In two 96-hour acute static t oxicity studies, rainbow trout ( Oncorhynchus mykiss ; MRID001424-54) and pumpkinseed sunfish ( Lepomis gibbosus ; MRID 001424-55) were exposed to glufosinate TGAI at nominal concentr ations of 0 (control), 100, 180 and 320 mg ai/L. No mortality or other adverse e ffects were observed. The 96-h LC 50 and NOAEC values for the technical glufosinate were >320 and 320 mg a i/L, respectively. Glufosinate technical is classified as practically non-toxic to th e rainbow trout on an acute exposure basis.

In a 96-hr study, bluegill sunfish ( Lepomis macrochirus ; MRID 001443-38) were exposed to formulated glufosinate (19% ai) at nominal concentrations of 0 (control), 1.8, 2.4, 3.2, 4.2, 5.6, 7.5, 10, 13.5, 18, 24, 32, 42, 56 and 75 mg ai/L. There was 100% mortality at the highest concentration within 24 hrs, and th ere was 30 % mortality in the second highest concentration at 48 hrs. No other clinical signs of toxicity were noted. The NOEC and LC 50 values for this study were 42 and 60 mg ai/L.

A second acute toxicity study of formulated glufosinate with the bluegill (MRID 001599- 14) was conducted at nominal concentra tions of 0 (control), 10, 13.5, 18, 24, 32, 42, 56, 75, 100Page 36 of 71 mg ai/L. There was 100% mortality in the two hi ghest concentrations after 24 hrs. No other clinical signs were reported. The study resulted in a NOEC and LC50 of 56 and 65 mg ai/L

A study with formulated glufosinate ( 16.22%) was conducted with rainbow trout (formerly Salmo gairdneri ; MRID 001599-13). Rainbow trou t were exposed at nominal concentrations of 0 (control), 5.6, 10, 18, 56 and 100 mg ai/L. After 24 hrs, there was 100% in the two highest concentrations after 48 hrs. There was 10% mortality at the 32 mg ai/L concentration after 48 hrs, and by 72 hrs, there wa s 80% mortality. Signs of toxicity at the 32 mg ai/L concentration included surface and head -down swimming and slow reaction to stimuli. The NOEC and LC 50 for formulated glufosinate was 18 and 26.7 mg ai/L, respectively. Based on these studies, formulated glufosinate is cla ssified as slightly toxic to freshwater fish.

The chronic toxicity of glufosin ate to freshwater fish cannot be estimated due to lack of data.

ii. Freshwater Invertebrates

An acute 48-hour static t oxicity study was conducted to determine the effect of glufosinate technical on fi rst instar water fleas ( Daphnia magna ; MRID 001424-56). The nominal test concentrations were 0 (control), 100, 135, 180, 240, 320, 420, 560, 750 and 1000 mg ai/L. At 48 hours, there was 100% mortality at the highest concentration, 80% at 750 mg ai/L, and 10% at 560 mg ai/L. No effects were ob served at test concentrations of 420 mg ai/L and lower. Therefore, the 48-h EC 50 value was 668 mg ai/L and the 48-h NOAEC was 420 mg ai/L. Glufosinate is classified as practically non-toxic to daph nids on an acute exposure basis.

Three studies evaluating the to xicity to daphnids of the formulated glufosinate are available, two at 19% ai and one 16.3% ai. The LC 50 s for these studies ranged from 15 to 79.5 mg ai/L, with 20% mortality noted as low as 1.0 mg /L. Formulated glufosinate is classified as slightly toxic to daphnids on an acute exposure basis.

A chronic 21-day (life-cycle) static renewal toxicity study (MRID 405010-10) was conducted to determine the effects of glufosin ate technical on daphnids. The nominal test concentrations were 0 (control), 10, 18, 32, 56, 64.8 a nd 100 mg ai/L, to which first instars were exposed. Seven beakers of one daphnid each were used to evaluate effects on reproduction and growth, and three replicates of five daphnids each were used to evaluate effects on mortality. The 21-day NOAEC was 32 mg ai/L based on reproductive rate.

iii. Estuarine/Marine Fish

In a 96-hour acute static toxi city study, sheepshead minnow ( Cyprinodon variegatus ; 413961-04) were exposed to glufosin ate technical at nominal concentrations of 0 (control), 100, 180, 320, 560 and 1000 mg ai/L, prepared with reconst ituted sea water. No mortality or other adverse reactions were reported. The 96-hour LC 50 and NOAEC values were >1000 and 1000Page 37 of 71 mg ai/L, respectively, and glufosinate is classifi ed as practically non-toxi c to estuarine/marine fish on an acute exposure basis.

In a 96-hour acute static toxi city study, sheepshead minnow ( Cyprinodon variegatus ; 413961-08) were exposed to formulated glufosinate at nominal concentrations of 0 (control), 7.0, 11.7, 19.4, 32.4 and 54.0 mg ai/L. Mortality was 100% at the two highest concentration after 24 hours and 100% at the 19.4 mg ai/L at 48 hours. Mortality was 30% at 11.7 mg ai /L after 24 hours, but no further mortality was recorded. Th ere was no mortality in the control or at the lowest concentration tested. The 96-hour LC 50 and NOAEC values were 13.5 and 7 mg ai/L, respectively, and glufosinate is cl assified as slightly toxic to es tuarine/marine fish on an acute exposure basis

iv. Estuarine/Marine Invertebrates

A 96-hour acute toxicity study was conducted un der static conditions to determine the effect of glufosinate tech nical on the mysid shrimp ( Mysidopsis bahia ; MRID 413961-07). The shrimp were exposed to nominal concentr ations of 0 (control), 1.0, 1.8, 3.2, 5.6, 10.0, 18.0 and 32.0 mg ai/L. Mortality ranged from 0 at th e 1.0 mg ai/L to 100% at the 32.0 mg ai/L concentration. There was 10% mortality in the control after 24 hours. The 96-hour LC 50 and NOAEC were 7.5 and 1.0 mg ai/L, respectively. Glufos inate is classified as moderately toxic to mysid shrimp on an acute exposure basis.

A 48-hour acute toxicity study was conducted under static conditions to determine the effect of glufosinate technical on the larvae of the Eastern oyster ( Crassostrea virginica ; MRID 413961-05). The larvae were exposed to nominal concentrations of 0 (control), 4.9, 8.1, 13.5, 22.8, 37.4, 62.3 and 104.0 mg ai/L. Hormesis was reporte d at the lowest test concentration, with 20% more normal larvae compared to the control. Mortality ranged from 66% at the 8.1 mg ai/L to 100% at the 104.0 mg ai/L concentration. Th ere was 10% mortality in the control after 24 hours. The 48-hour calculated LC 50 and NOAEC were 8.0 and 4.9 mg ai/L, respectively. Glufosinate is classified as moderately toxi c to Eastern oyster on anacute exposure basis.

A 48-hour acute toxicity study was conducted un der static conditions to determine the effect of glufosinate technical on the larvae of the quahog clam ( Mercenaria mercenaria ; 413961-06). The larvae were exposed to nominal concentrations of 0 (control), 16, 27, 45, 75 and 125 mg ai/L. Mortality ranged from 0% at the 16 mg ai/L to 31% at the 125 mg ai/L concentration. The 48-hour calculated LC 50 and NOAEC were >125 and 75 mg ai/L, respectively. Glufosinate is classified as s lightly toxic to quahog clam on an acute exposure basis.

A second study with the quahog clam was conducted with formulated product (MRID 422624-02), at mean-measured concentrati ons of 0.52, 0.90, 1.54, 2.62, 4.22 and 7.12 mg ai/L. Reduction in normal larvae ranged from 100% at the three highest test concentrations to 24% at the lowest test concentration. The 48-hr EC 50 was 0.69 mg ai/L with a NOAEC <0.52 mg ai/L.Page 38 of 71 A 96-hour acute toxicity study (MRID 413961-10) was conducted under static conditions to determine the effect of formulated glufosinat e on the mysid shrimp. The shrimp were exposed to nominal concentrations of 0 (control) , 1.4, 2.7, 5.4, 10.8, 21.6 and 43.2 mg /L (whole product). No mortality was reported in the 1.4, 2.7 or 5.4 mg ai/L concentrations, but there was 15%, 5% and 50% mortality in the 10.8, 21.6 and 43.2 mg ai/L concentrations. Partial loss of equilibrium was reported in some shrimp at all but the lowest concentration. The 96-hour LC 50 and NOAEC were 43.2 and 1.4 mg ai/L, respectively. Formulated gl ufosinate is classified as slightly toxic to mysid shrimp on an acute exposure basis.

Two studies examining the effect of formul ated glufosinate on th e Eastern oyster have been submitted. In one study (MRID 413961-09), larvae were exposed to nominal concentrations of 0 (control), 0.21, 0. 35, 0.58, 0.97, 1.62 and 2.7 mg/L (whole product). Hormesis (9%-33%) was reported at all but the hi ghest test concentratio ns, with 52% reduction in normal larvae at the highest dose compared to the control. Th e 48-hour calculated LC 50 and NOAEC were >1.62 and 1.62 mg/L, respectively. Fo rmulated glufosinate is classified as moderately toxic to eastern oyste r on an acute exposure basis.

The second study evaluated the effect of fo rmulated glufosinate on shell deposition (MRID 422624-03). Eastern oysters were exposed to nominal concentrations of 0 (control), 0.29, 0.50, 0.76, 1.32, 2.26 and 3.98 mg ai/L. Shell deposi tion was inhibited at the two highest test concentrations (45 and 55% resp ectively). The 48-hour calculated LC 50 and NOAEC were 2.9 and 1.32 mg ai/L, respectively. Formulated glufos inate is classified as moderately toxic to eastern oyster on an acute exposure basis.

a. Aquatic Plants

In a static laboratory toxicity test, the freshwater unicellular green alga, Selenastrum capricornutum (MRID 403456-53), was exposed to glufosin ate ammonium technical at nominal concentrations of 0 (control), 2.5, 5.0, 10.0, 20.0, 40.0 and 80.0 mg ai/L. Significant reduction in cell counts, compared to those of the control, ra nged from 10% at 5 mg ai/L to 71% at 80 mg ai/L. The 5-day NOEC and EC 50 values, based on cell count, were 2.5 and 7.8 mg ai/L, respectively.

In a 14-day static toxi city test, duckweed ( Lemna gibba ; MRID 422624-04) was exposed to glufosinate ammonium tec hnical at nominal concentratio ns of 0 (control), 0.78, 1.3, 2.2, 3.6, 6.0 and 10 mg ai/L. After 14 days, inhibition of growth ranged from 11% at 0.78 mg ai/L (not statistically significant) to 100% at the two highest doses, relative to the control. The NOEC and EC 50 values, based on frond number, were 0.80 and 1.5 mg ai/L, respectively.Page 39 of 71 b. Terrestrial Effects

i. Avian Acute Oral, Dietary and Chronic

The acute oral toxicity of glufosinate to bobwhite quail ( Colinus virginianus ; MRID 001424-51) and mallard duck ( Anas platyrhynchos ; MRID 001424-50) was assessed in separate studies. Glufosinate was administered to the bird s in gelatin capsules as a single oral dose at nominal concentrations of 0 (cont rol), and 2000 mg ai/kg-bw. No mortalities were observed in the studies. Sublethal effects, including passivity and diarrhea were reported in the bobwhite quail study; no sublethal eff ects were reported in the mallard duck study. The LD 50 was >2000 mg ai/kg-bw in both studies. Based on these resu lts, glufosinate is classi fied as practically nontoxic to birds on an acu te oral exposure basis.

The subacute dietary toxicity of glufos inate to bobwhite quail and mallard duck was assessed over 8 days (MRIDs 001509-88; 001424-50). Glufosinate was administered to the birds in the diet at nominal levels of 0 (control ), 1250, 2500 and 5000 mg ai/kg- diet for the bobwhite quail and at nominal levels of 0 (control ), 312.5, 625, 1250, 2500 and 5000 mg ai/kg-diet for the mallard ducks. Bobwhite mortalities were 0, 10, 20 and 40 percent, respectively. There were no compound-related toxic effects to the mallards. The LC 50 in both studies is >5000 mg ai/kg diet. Based on these studies, glufosinat e is classified as practically non-toxic to bobwhite quail and mallard duck on a subacute dietary exposure basis.

The chronic toxicity of glufosinate to 5-month-old bobwhite quail and 23-week-old mallard duck was assessed (MRIDs 403456-49, 403456-50) . The birds were fed diets containing glufosinate at nominal concentrations of 0 (c ontrol), 25, 100 and 400 mg a i/kg diet. At the end of the studies, there were no com pound-related toxic effects at any of the concentrations tested. The NOAEC for chronic toxicity to birds is 400 mg ai/kg diet.

ii. Mammalian Acute and Chronic

Glufosinate is classified as practically nontoxic to rats ( Rattus norvegicus ) with acute oral LD 50 value of 3030 mg ai/kg-bw in a study re viewed by HED (MRID 00142430). HED reports an LD 50 for formulated product (24. 3% ai) of 1000 mg/kg-bw.

After reviewing a 2-generation rat re production study (MRID 40345612) HED reported a NOAEL of 6.0 mg ai/kg-bw/d for o ffspring and reproductive effect s (decreased number of viable pups). Glufosinate-ammonium (HOE 039866 Techni cal, 95.3% ai) was ad ministered to groups of 30 male and 30 female Wistar/Han rats in the diet at concentrations of 0 (control), 40, 120 or 360 ppm (approximately 2.0, 6.0, 18.0 mg/ kg) for two generations.

At 360 ppm there wa s a significant (p< 0.05) reduction in the mean number of viable pups/litter in all generati ons (-21% to -37%) with the exception of the F 2a generation where the reduction (-11%) was not statistically significant. Surviving pups and the weight of survivorsPage 40 of 71 were unaffected by treatment. No other reproduc tive or developmental effects were reported. There were no dose- or treatment-re lated clinical signs of toxicity in the offspring of either generation. On June 4, 2002, the HIARC considered that the increased kidney weights seen in both sexes and generations as an adaptive respon se and not an adverse effect. The LOAEL for reproductive/developmental toxicity is 360 ppm ( 18 mg/kg/day) based on decreased number of viable pups in all generations. Th e NOAEL is 120 ppm (6.0 mg/kg/day).

iii. Non-target Invertebrates

In an acute oral and an acute contact toxicity study, honey bees ( Apis mellifera ) were exposed to glufosinate at the rate of 345.5 μ g ai/bee. No mortalities or sublethal symptoms were observed in either study. The LC 50 was >100 μ g ai/bee; therefore, glufosinate technical is classified as practically non-toxic to h oneybees on an acute oral exposure basis.

In an acute oral and an acute contact toxicity study, honey bees ( Apis mellifera ) were exposed to formulated glufosin ate (Basta) at a rate of 100 μ g ai/bee. No mortalities or sublethal symptoms were observed in either study. The LC 50 was >100 μ g ai/bee; therefore, this glufosinate formulation is classified as practic ally non-toxic to honeybees on an acute exposure basis.

iv. Terrestrial Plants

In a seedling emergence laboratory toxici ty test (MRID 41396-11), a total of four monocotyledonous species [corn ( Zea mays ), oat ( Avena sativa ), onion ( Allium cepa ) and ryegrass ( Lolium spp.)] and six dicotyledonous species [carrot ( Daucus carota ), cucumber ( Cucumis sativus ), cabbage ( Brassica oleracea ), soybean ( Glycine max ), lettuce ( Lactuca sativa ) and tomato ( Lycopersicon esculentum )] were exposed to nominal c oncentrations of 0 (control), 0.09, 0.38, 0.75 and 1.5 lbs ai/A. Percent emergence was not affected for any of the test species except for onion, which demonstrated an EC 25 of 0.85 lbs ai/A and a NOEC of 0.38. Seedling dry weight was affected at all test concentrations. The affect on dry weight was greatest in lettuce and cabbage, with EC 25 s of 0.15 and 0.16 lbs ai/A, respec tively, and least affected in soybean with an EC 25 of 1.24 lbs ai/A. Plant height was aff ected the most in onion and least in soybean with EC 25 s of 0.23 and 1.4 lbs ai/A, respectively. The dicotyledonous endpoints used for risk estimation are the dry weight EC 25 (0.15 lbs ai/A) and NOEC (< 0.15 lbs ai/A) for lettuce. The most sensitive monocot endpoints are the onion height EC 25 (0.23 lbs ai/A) and NOEC (<0.23 lbs ai/A.). The data reported in th e study are not sufficient to calculate an EC 05
. In a vegetative vigor study (MRID413961-12) , four monocotyledonous species [corn ( Zea mays ), oat ( Avena sativa ), onion ( Allium cepa ) and ryegrass ( Lolium spp.)] and six dicotyledonous species [carrot ( Daucus carota ), cucumber ( Cucumis sativus ), cabbage ( Brassica oleracea ), soybean ( Glycine max ), lettuce ( Lactuca sativa ) and tomato ( Lycopersicon esculentum )] were exposed to nominal concentra tions of 0 (control), 0.025, 0.05, 0.1, 0.2 and 0.4 lbs ai/A. A continuation study was conducted on ryegrass at rates of 0.005, 0.01, 0.02 and 0.04Page 41 of 71 lbs ai/A. Oat, corn and onion were unaffected at the highest test conc entration, but ryegrass dry weight was significantly reduced, with an EC 25 of 0.61 lbs ai/A and a NOEC of 0.04 lbs ai/A. The most sensitive dicot endpoint, based on an EC 25 of 0.137 lbs ai/A, was lettuce, which had a NOEC of 0.05 lbs ai/A.

A second vegetative vigor study (M RID 413961-13) was conducted on corn ( Zea mays ), oat ( Avena sativa ), onion ( Allium cepa ), carrot ( Daucus carota ), cucumber ( Cucumis sativus ), cabbage ( Brassica oleracea ), soybean ( Glycine max ) and tomato ( Lycopersicon esculentum ). In that study, carrot was the most sensitive dicot with a dry weight EC 25 of 0.063 lbs ai/A and a NOEC of 0.05 lbs ai/A, while onion was the most sensitive monocot with a dry weight EC 25 of 0.11 and a NOEC of 0.10. All test species were aff ected at the highest con centration except oat, which demonstrated a NOEC of 0.8, the highest dose tested.

Based on the results of the two vegetative vi gor studies, the risk estimation endpoints are carrot (EC 25 = 0.063 lbs ai/A; NOEC = 0.05 lbs ai/A) and onion (EC 25 = 0.11; NOEC = 0.10).

c. ECOTOX

The Agency’s publicly-available ECOTOX database ( www.epa.gov/ecotox ) was reviewed for toxicological endpoi nts. There were no additional data on glufosinate in the database when accessed 10/15/2007. Some of the terrestrial plant endpoints reported in the database are more sensitive than those used in this assessment, however, those endpoints were either from seedling germination studies, which are not considered reliable for pesticides, or were from phytotoxic scoring. Phytotoxicity sc ores are highly subjective and are not used quantitatively in the risk assessment.

d. INCIDENT REPORTS

The Agency has received 48 reports of advers e field effects to plants that have been linked to the use of glufosinate. Most of thes e incidents (45) involved damage to corn. The Agency considered the cause to be ‘possible’ or ‘likely’ in all but one incident, which was considered ‘unlikely’. A ‘massive’ fish k ill was reported in a farm pond in Maryland after application of glufosinate to plants surrounding a farm pond; this incident was classified as ‘probable’.

A lack of reported incidents does not necessa rily mean that such incidents have not occurred. In addition, incident reports for non-target plants and animals typically provide information on mortality events on ly. Reports for other adverse e ffects, such as reduced growth or impaired reproduction, are rarely received.Page 42 of 71 5. Preliminary Risk Estimation

Based on the most sensitive endpoint for each of the taxa evaluated and the highest rate (1.5 lbs ai/A, 3 applications, 5 da y interval) the acute RQ values for may be exceeded for some birds and for non-target terrestrial plants exceed the LOC for the use of glufosinate. The listed species LOC may be exceeded for some mammal s and the chronic LOC is exceeded for both birds and mammals. There are no exceedances for aquatic plants or animals, although chronic risk to fish is uncertain due to lack of data.. Consideration of various use patterns and potential risk will be explored in the risk assessment.

Additionally, consideration of potential risk from formulat ed product to the taxa for which data are available will be considered in th e risk assessment. Available data suggest that formulations of glufosinate exhibit greater toxi city to fish, aquatic i nvertebrates and mammals than the parent alone. Exposure to formulations of glufosinate may resu lt in great risk to nontarget taxa, including avian species.

a. Aquatic Species

i. Freshwater Fish

Glufosinate is classified as practically nontoxic on an acute exposure basis to freshwater fish, i.e. the LC 50 is greater than 100 mg ai/L, and the potentia l for acute risk to freshwater fish is presumed to be low. An RQ calculated using 320 mg/L (the highest dose tested) is several orders of magnitude below (calcu lated RQ <0.0005) even the acute risk to listed species LOC of 0.05. The RQ for chronic exposure to freshwat er fish is unknown due to lack of data.

ii. Freshwater Invertebrates

Glufosinate is classified as practically nontoxic on an acute exposure basis to freshwater invertebrates (LC 50 =668 mg ai/L), and the potential for acute risk to freshwater invertebrates is presumed to be low. The RQ is several orde rs of magnitude below (RQ=0.0002) even the acute risk to listed species LOC of 0.05. The RQ for chr onic effects to freshwater invertebrates is also orders of magnitude below (calculate d RQ=0.007) the chronic risk LOC of 1.0.

iii. Estuarine/Marine Fish

Glufosinate is classified as practically nontoxic on an acute exposure basis to estuarine/marine fish, i.e. the LC 50 is greater than 100 mg ai/L, a nd the potential for acute risk to freshwater fish is presumed to be low. An RQ calculated using 1000 mg/L (the highest dose tested) is several orders of magnitude below (cal culated RQ <0.0002) even th e acute risk to listed species LOC of 0.05. The RQ for chronic exposure to freshwater fish is unknown due to lack of data.Page 43 of 71 iv. Estuarine/Marine Invertebrates

Glufosinate is classified as moderately toxic on an acute exposure basis to estuarine/marine invertebrates (most sensitive LC 50 =7.5 mg ai/L); however, the acute risk and listed species LOCs are not exceeded by the RQ of 0.02. The RQ for chronic exposure to estuarine/marine invertebrates is unknown due to lack of data.

v. Aquatic Plants

Neither the acute risk nor the listed species RQ for aquatic plants exceed the LOC. The RQ for listed vascular aquatic plants is 0.2 and is well below the acute risk to listed species LOC of 1.0. The RQ for nonlisted vascular aquatic plan ts is 0.11 and is again below the acute risk LOC of 1.0.

b. Terrestrial

i. Avian Acute and Chronic

When both dose-based and dietar y-based toxicity estimates are available for birds, acute risk quotients are calculated using both a dos e-based and dietary-based approach. The dosebased RQs are calculated using a body weight-a djusted and consumption-weighted equivalent dose. The adjustments account for the fact that smaller-sized animals have to consume more food in terms of their body weight than larger animals and that differential amounts of food have to be consumed depending on the water content and nutritive value of the food. By expressing the Kenaga nomogram (Fletcher et al. 1994) estimated residues in te rms of daily equivalent dose, estimated environmental concentrations can then be compared to the dose-based LD 50
. Glufosinate is classified as pr actically nontoxic to birds on both an acute and subacute dietary exposure basis; therefore, the potential for risk is presumed low. Although the avian acute oral studies tested up to the Agency’s limit doses ( e.g. 2000 mg ai/kg-bw), definitive endpoints were not derived. Using the highest dos es tested, three applications of 1.5 lbs ai/A potentially results in acute risk exceedances for small birds fora ging on small grass (‘RQ’<1.08) and broadleaf plants/small insects (‘RQ’<0.61). The listed sp ecies LOC would be potentially exceeded for small birds foraging on tall grass (‘RQ’<0.49), medi um sized birds foraging on short grass, tall grass and broadleaf plants/small insects (‘ RQ’<0.48, 0.22 and 0.27) and large birds foraging on short grass (‘RQ’ <0.15). Using the highest dose tested in the subacute dietary study (LC 50 >5000 mg ai/kg-diet) would result in possible exceedances for birds foraging on short grass and broadleaf plants/small insects (‘RQ< 0.20 and 0.11).

No effects on any adult, offspring or reproduc tive parameter were observed at the highest dose tested in the two submitted avian repr oduction studies (NOAEC = 400 mg/kg-diet). However, based on the highest dose tested, chr onic RQ values would be 2.45 for birds foraging on short grass, 1.12 for birds foraging on tall grass and 1.38 for birds foraging on broadleaf plants/small insects.Page 44 of 71 ii. Mammalian Acute and Chronic

The RQ based on the LC 50 from the rat acute oral toxici ty study is 3030 mg ai/kg-bw, and glufosinate is classified as pr actically nontoxic to mammals on an acute oral exposure basis; therefore, risk is presumed to be low. Howeve r, given the potential exposure, the RQs for smalland medium-sized mammals foraging on short grass (RQ=0.14 and 0.12) exceed the listed species LOC.

Reduced litter size was observed in rats foll owing chronic exposure to glufosinate. Using the NOAEL (120 mg ai/kg-diet), all dose-based chronic mammalian RQ s (except large and medium-sized granivores) exceed the LOC of 1.0. Dose-based RQs exceedances range from 1, for small-sized granivores, to 71 for small-si zed mammals foraging on sh ort grass. Dietary based chronic RQs range from 8.2 for mammal s foraging on short grass to 0.5 for mammals foraging on fruits/pods/large insects.

iii. Nontarget Plants

RQs for nontarget plants exceed the LOC fo r plants inhabiting wetlands adjacent to glufosinate use sites (RQs 3.3-5.1). Because NOE Cs could not be calculated for the seedling emergence study, it is not possible to determine listed plant species RQ s. RQs for nonlisted upland plants exposed via run-off and plants exposed to spraydrif t alone do not exceed the LOC. Because the RQ for nonlisted plants in wetlands is exceeded, there will be potential concerns for indirect effects to some terrestrial species. Howe ver, because the TGAI was used in the studies, toxicity of glufosinat e to plants may be gr eatly underestimated.

G. Other Information Needs

There is specific information that will assist the Agency in refini ng the ecological risk assessment, including any species-specific effects determinations. The Agency is interested in obtaining the following information:

1. confirmation on the following label information a. sites of application b. formulations c. maximum application rates d. frequency of application, applicati on intervals, and maximum number of applications per season e. geographic limitations on use 2. use or potential use distribution ( e.g ., acreage and geographical distribution of relevant uses) 3. use historyPage 45 of 71 4. median and 90 th percentile reported use rates (lbs. ai/acre) from usage data – national, state, and county 5. application timing (date of first application and application intervals) by use – national, state, and county 6. sub-county crop location data 7. usage/use information for non-agricultural uses ( e.g ., golf courses, athletic fields, ornamentals) 8. directly acquired county-level usage da ta (not derived from state level data) a. maximum reported use rate (lbs. ai/acre) from usage data – county b. percent crop treated – county c. median and 90 th percentile number of applications – county d. total pounds per year – county

The analysis plan will be re visited and may be revised de pending upon the data available in the open literature and the information submitted by the public in respon se to the opening of the Registration Review docket.Page 46 of 71 II. Bibliography

CDPR. 2006. Surface Water Database. California De partment of Pesticide Regulation, Surface Water Protection Program. Last updated: May 12, 2006. Online at: http://www.cdpr.ca.gov/docs/sw/surfdata.htm

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger . 1994. Literature review and evaluation of the EPA food-chain (Kenaga) nomogram, an instru ment for estimating pesticide residues on plants. Environ. Toxicol. Chem. 13: 1383-1391.

Hoerger, F. and E.E. Kenaga. 1972. Pesticide re sidues on plants: correlati on of representative data as a basis for estimation of their magnitude in the environment. Environmental Quality and Safety. 1: 9-28.

Urban D.J. and N.J. Cook. 1986. Hazard Evalua tion Division Standard Evaluation Procedure Ecological Risk Assessment. EPA 540/9-85-001. U.S. Envir onmental Protection Agency, Office of Pesticide Programs, Washington, DC.

USEPA. 1992. Pesticides in Ground Water Data base: A Compilation of Monitoring Studies: 1971-1991: National Summary. U. S. Environmental Protection Agency, Washington, DC.

USEPA. 1998. Guidance for Ecological Risk As sessment. Risk Assessment Forum. EPA/630/R95/002F, April 1998.

USEPA. 2002. Guidance for Selecting Input Parame ters in Modeling the E nvironmental Fate and Transport of Pesticides. U.S. Environmen tal Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division. Feb. 28, 2002. Online at: http://www.epa.gov/oppefed1/mode ls/water/input_guidance2_28_02.htm/

USEPA. 2004. Overview of the Ecological Risk Assessment Process in th e Office of Pesticide Programs, U.S. Environmental Protection Ag ency. Endangered and Threatened Species Effects Determinations. Office of Prevention, Pe sticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. January 23, 2004. Online at: http://www.epa.gov/oppfead1/endanger /consultation/ecorisk-overview.pdf

USEPA. 2006. Water Models. U.S. Environmenta l Protection Agency, Pesticides: Science and Policy. Last updated May 2, 2006. Online at: http://www.epa.gov/oppefed1/models/water/

USEPA. 2006a. Unregulated Contaminant Monitoring Rules (UCMR). U.S. Environmental Protection Agency, Unregulated Contaminan t Monitoring Program. Last updated: Nov. 24, 2006. Online at: http://www.epa.gov/safewater/data/ucmrgetdata.htmlPage 47 of 71 USEPA. 2007. STORET Data Warehouse. U.S. E nvironmental Protection Agency. Last Updated Jun. 20, 2007. Online at: http://www.epa.gov/storet/dw_home.html

USEPA. 2007a. Safe Drinking Water Information System/Federal Version (SDWIS/FED). U.S. Environmental Protection Agency. Last updated: May 7, 2007. Online at: http://www.epa.gov/safewater/data/getdata.html

USEPA. 2007b. Glufosinate-ammonium New Uses (P re-plant Application for Corn, Canola, and Soybeans): Drinking Water Exposure Assessment. DP Barcode 335331, 335333. U.S. Environmental Protection Agency, Office of Pe sticide Programs, Environmental Fate and Effects Division, Memorandum to RD. Sep. 7, 2007.

USGS. 2006. Kelly, V., R. Hooper, B. Aulenbac h, and M. Janet. Concentrations and Annual Fluxes for Selected Water-Quality Constituents from the USGS National Stream Quality Accounting Network (NASQ AN), 1996-2000. U.S. Geological Survey. Last updated: Nov. 13, 2006. Online at: http://pubs.usgs .gov/wri/wri014255/resu lts/detect.htm

USGS. 2007. National Water-Quality Assessment (N AWQA) Program. U.S. Geological Service. Last updated: Dec. 12, 2007. Online at: http://infotrek.er.usgs.gov /traverse/f?p=136:1:1779537078393353::NO :::

Willis, Guye H., and Leslie.L. McDowell. 1987. Pesticide Persistence on Foliage. in Reviews of Environmental Contamination and Toxicology . 100:23-73

A. Submitted Environmental Fate Studies

Accsn # 263025. Willms, Klockner, Rochling, Albrecht, K. Re xer, G. Gorlitz, W. Bartsch, E. Dorn, Heinrich. 1985. Petition for Multi-Use Experimental Use Permit and Te mporary Tolerance. Unpublished product chemistry studies perfomed by Pflanzenschutzforschung-Chemie, Pflanzenschutzforschung-Formulierung, and Analytisches Laboratorium; submitted by Ho echst. Jul. 15, 1981 to Oct. 9, 1985.

MRID 40345656. Goerlitz, G.; Kloeckner, C.; Eyrich, U. 1986. Abiotic Hydrolysis as a Function of pH and Amendment and Separation of Potential Hydrolysis Pr oducts of HOE 039866 from the Active Ingredient by HPLC: Project Nos. (B)277/85 and (B)110/86. Unpublished study prepared by Hoechst AG. 48 p.

MRID 40345659. Gildemeister, H.; Jordan, H.; Stumpf, K. ; et al. 1987. Aerobic Soil Metabolism Studies with HOE 039866-[carbon 14] and Amendment and Degradation in Soil Study with HOE 061517-[carbon 14]: Project Nos. CB066/85, CB060/86 and CB065/86. Unpublished study prepared by Hoechst AG. 152 p.

MRID 40345660. Gildemeister, H.; Jordan, H.; Schink, C. 1987. HOE 039866-[carbon 14]: Aerobic Aquatic Metabolism Study: Project No. CB064/86. Unpublished study prepared by Hoechst AG. 56 p.

MRID 40345662. Goerlitz, G. 1985. Adsorption/Desorption in the System--Soil/Water for HOE 039866 and HOE 061517: Project Nos. CP055/85 and CP062/ 85. Unpublished study prepared by Hoechst AG. 81 p.

MRID 40345666. Specht, W.; Kunzler, K.; Idstein, H. 1986. Method Verification of the Analytical Method for the Analysis of HOE 039866 and HOE 061517 in Crops and Soil and Validation of the Analytical Method ALPage 48 of 71 38/85 for the Residue Analysis of HOE 039866 in Plan t Mate- rials, Water and Soil: Project Nos. 31-A and (B)104/86. Unpub- lished study prepared by Institut fur Ruckstandsanalytik. 300 p.

MRID 40501014. Gildemeister, H. 1987. Hoe-039866-?Carbon 14|--Anaerobic Soil Me- tabolism Study: Study No. CB008/86. Unpublished study prepared by Hoechst Ag. 31 p.

MRID 41323115. Stumpf, K. 1989. HOE 039866-?Carbon 14|: Photodegradation in Water at pH 5, 7, and 9: Lab Project Number: A40989: CB/89/88. Unpublished study prepared by Hoechst AG. 73 p.

MRID 41323119. Stumpf, K. 1989. HOE 039866-3,4-?Carbon 14|: Degradation and Meta- bolism in Different Soils Under Aerobic and Anaerobic Conditions at an App lication Rate of 1.6 mg/kg: Lab Project Number: CB019- 88: A41299. Unpublished study prepared by Hoechst AG. 92 p.

MRID 41323130. Schwalbe-F ehl, M.; Fischer, R. 1988. HOE 039866: Bioaccumulation in Fish: Lab Project Number: A39698. Unpublished study prepared by Hoechst AG. 14 p.

MRID 41920102. Stumpf, K. 1990. Photolysis of HOE 039866-14C (Glufosinate-Ammoni- um) on Soil: Lab Project Number: CB90/097: A44730. Unpublished study prepared by Hoechst Aktiengesellschaft. 76 p.

MRID 43110402. Mayasich, J.; Czarnecki, J. 1994. Terrestrial Field Dissipation of Ignite Herbicide Applied to a Citrus Grove in Florida: Lab Project Number: 89-0093: 90-0008: 90-0081 HOE. Unpublished study prepared by Hoechst Celenese Corp. 346 p.

MRID 43766915. Novak, R. 1995. Terrestrial Field Dissipa tion of Ignite Herbicide Applied to Transgenic Corn: Lab Project Number: HRAV 93-0014: F93-1929: H93-04R. Unpublished study prepared by Heartland Technologies; En-Cas Analytical Labs and NPC, Inc. 962 p.

MRID 43766916. Novak, R. 1995. Terrestrial Field Dissipati on of Ignite Herbicide Applied to Transgenic Soybean: Lab Project Number: HRAV 93-0015: F93-1930: A54506. Unpublished study prepared by Stewart Agricultural Research Services, Inc.; En-Cas Analytical Labs; and NPC, Inc. 956 p.

MRID 44032901. Miklautz, H. 1995. The Vapor Pressure of Glufosinate-Ammonium (Hoe 039866) at 25 (degrees) C: Lab Project Number: 0910: A55227: APC 126/95. Unpublished study prepared by Schering AG, Institute of Physical Chemistry. 16 p.

MRID 46258601. Stupp, H. 2003. Degradation and Metabolism of Glufosinate Ammonium in Soil Under Anaerobic Conditions. Project Number: M1261285/5, MEF/367/03, C038925. Unpublished study prepared by Bayer Ag, Institute of Product Info. 62 p.Page 49 of 71 APPENDIX A. Past Ecological Risk and Drinking Water Exposure Assessments for Glufosinate-ammonium.

TABLE A.1. Past Ecological Risk Assessments for Glufosinate-ammonium.

DATE TYPE OF ACTION USE(S) ASSESSED POTENTIAL RISK IDENTIFIED SUMMARIZED ECOLOGICAL CONCLUSIONS

12/12/1984 EUP Soybeans,tree/vine, nonag, homeowner No Risk assessment was not conducted due to a lack of data.

11/20/1986 EUP Soybeans,tree/vine, nonag Yes No acute risk to birds. Chronic exposure to birds not expected. Hazard to aquatic organisms not assessed due to lack of data. Should not result in hazard to listed birds. Sites should be kept away from habitats of listed aquatic animals and listed plants. 12/7/1988 S3NC Corn, soybean, nut/vine, non-ag Yes Minimal acute risk to terrestrial and aquatic animals. EUP 12X more toxic than tech product to rainbow trout; 44X more toxic to Daphnia magna . Lack of chronic toxicity data. No listed species risk exceedances, but conclusions pend submission of data. 12/20/1990 S3NU Corn, soybean,
non-ag Yes Little acute risk to terrestrial or aquatic animals or algae. Risk to terrestrial plants, including all listed plant species. 12/3/1998 §18 Canola-MN Yes Little acute risk to terrestrial and aquatic animals. No chronic risk to birds. No chronic toxicity data for aquatic animals. No toxicity data on aquatic plants. Risk to terrestrial plants. Risk to listed plant, Western Prairie Orchid. 12/3/1998 §18 Canola-ND Yes Little acute risk to terrestrial and aquatic animals. No chronic risk to birds. No chronic toxicity data for aquatic animals. No toxicity data on aquatic plants. Risk to terrestrial plants. No risk to listed species. 4/26/2000 S3NU Canola, potato, sugar beet Yes Little acute risk to terrestrial and aquatic animals. No chronic risk to terrestrial animal s. No chronic toxicity data for aquatic animals. Risk to terrestrial plants. Risk to listed plants, but not to other listed species. 1/18/2002 §18 Blueberry-MS Yes Little acute risk to birds or mammals; no acute risk to aquatic animals. Lack of chronic toxicity data for animals. Risk to plants. Listed LOCs slightly exceeded for birds and mammals, but species not affected. 7/18/2002 S3NU Cotton, rice, blueberry Yes Little acute risk to birds or mammals; no acute risk to aquatic animals. Lack of chronic toxicity data for animals. Risk to plants. Listed LOCs slightly exceeded for birds and mammals and exceeded for aquatic invertebrates. 1/6/2003 RTC Not applicable Yes Likely to impact terrestrial insect species.

2/28/2006 S3NU Cotton Yes Acute risk to terrest rial plants. Chronic risk to terrestrial and aquatic animals in absence of data.Page 50 of 71 TABLE A.2. Past Drinking Water Exposure Assessments for Glufosinate-ammonium.

DATE TYPE OF ACTION USE(S) ASSESSED Surface Water 1-in10-year Peak EDWCs (ppb) Surface Water 1-in10-year Annual Avg. EDWCs (ppb) Ground Water 1- in-10-year EDWCs (ppb)

10/23/1998 S3NU Canola 69.5 52.3 0.34

12/1/1998 S3NU Potatoes 209 158 1.16 12/1/1998 S3NU Canola, sugar beets 237 178 1.16

12/3/1998 §18 Canola-MN 69.5 52.3 0.34 12/3/1998 §18 Canola-ND 69.5 52.3 0.342/22/1999 §18 Sweet cornWI 209 158 1.16

6/30/1999 S3NU Apples, sugar beets 34.1 0.79 1.16

1/18/2002 §18 Blueberry-MS 234 40.5 0.406 7/18/2002 S3NU Cotton, rice, blueberry 1168 (rice) 356 (other uses) 1168 (rice) 56 (other uses) 0.855

4/22/2003 S3NU Not reported 823 (rice) 94 (other uses) 823 (rice) 43 (other uses) 9.0

2/28/2006 S3NU Cotton 823 (rice) 94 (other uses) 823 (rice) 43 (other uses) 30.7

9/7/2007 DWA Corn, canola, soybean 823 (rice) 94 (other uses) 823 (rice) 43 (other uses) 30.7Page 51 of 71 APPENDIX B. Chemical Names, Structu res, and Maximum Reported Amounts of Glufosinate-ammonium and its Degradates.

Table B.1. Maximum Reported Amounts of Glufosinat e Degradation Products (Major Amounts in Bold). Degradate Maximum % of Applied Study Type MRID HOE 085355, NAG 19.6 (8 d) Soil photolysis MRID 41920102
HOE 061517, MPP 70.8 (30 d) 55.4 (64 d) 47.7 (7 d) 69.1 (33 d) 42.2 (60 d) 55.1 (64 d) 50 (10 d) 47 (42 d) 52 (14 d) Soil photolysis Aerobic soil metabolism Aerobic soil metabolism Anaerobic soil metabolism Anaerobic soil metabolism Aerobic aquatic metabolism Terrestrial field dissipation Terrestrial field dissipation Terrestrial field dissipation MRID 41920102 MRID 40345659A MRID 41323119 MRID 41323119 MRID 40501014 MRID 40345660 MRID 43110402 MRID 43766915 MRID 43766916 HOE 064619, MPA 11.4 (30 d) 18.5 (95 d) 28.2 (14 d) 24.4 (18 d) 5.8 (60 d) 17.8 (94 d) 39 (183 d) 24 (296 d) 34 (45-65 d) Soil photolysis Aerobic soil metabolism Aerobic soil metabolism Anaerobic soil metabolism Anaerobic soil metabolism Aerobic aquatic metabolism Terrestrial field dissipation Terrestrial field dissipation Terrestrial field dissipation MRID 41920102 MRID 40345659A MRID 41323119 MRID 41323119 MRID 40501014 MRID 40345660 MRID 43110402 MRID 43766915 MRID 43766916

HOE 086486 5.9 (32 d) 5.7 (60 d) 5.0 (94 d) Aerobic soil metabolism Anaerobic soil metabolism Aerobic aquatic metabolism MRID 40345659A MRID 40501014 MRID 40345660

HOE 065594 5.7 (8 d) Aerobic soil metabolism MRID 40345659A

CO 2 5.0 (30 d) 60.6 (120 d) 7.5 (78 d) Soil photolysis Aerobic soil metabolism Anaerobic soil metabolism MRID 41920102 MRID 41323119 MRID 41323119

Unextracted residues 13.9 (16 d) 19.9 (4 d) 45.2 (60 d) 13.7 (7 d) Soil photolysis Aerobic soil metabolism Aerobic soil metabolism Anaerobic soil metabolism MRID 41920102 MRID 40345659A MRID 41323119 MRID 41323119Page 52 of 71 Table B.2. Chemical Names and Structures of Gl ufosinate-ammonium and its Degradates (MRID 45204401, 45204403).

Chem. Group Chemical Name Description Structure

HOE 039866, AE F039866, Glufosinate-ammonium

IUPAC: ammonium-(2 RS )-2-amino-4- (methylphosphinato)butyric acid

ammonium-DL-homoalanin-4- yl(methyl)phosphinate

CAS: ( RS )-2-amino-4- (hydroxymethylphosphinyl)butanoic acid monoammonium salt

CAS Re g . No. 77182-82-2 Racemic salt

O P O

OH O NH 2

NH 4 +

HOE 035956, AE F035956, Glufosinate

IUPAC: ( RS )-2-amino-4- [hydroxy(methyl)phosphinoyl]butyric acid

DL-homoalanin-4- yl(methyl)phosphinate

CAS: ( RS )-2-amino-4- (hydroxymethylphosphinyl)butanoic acid

CAS Re g . No. 51276-47-2 Racemic free acid

P OH

O O

OH NH 2 1

HOE 058192, AE F058192

IUPAC: ( S )-2-amino-4- [hydroxy(methyl)phosphinoyl]butyric acid

L-homoalanin-4- yl(methyl)phosphinate L-isomeric free acid

P OH

O O

OH NH 2Page 53 of 71 Chem. Group Chemical Name Description Structure

HOE 099730, AE F099730

IUPAC: disodium-( S )-2-acetamido-4- methylphosphinico-butanoic acid L-isomeric salt

O P O

O O NH O Na + 2

HOE 099729, AE F099729, N-acetyl glufosinate, NAG

IUPAC: ( S )-2-acetamido-4- methylphosphinico-butanoic acid L-isomeric free acid

O P

OH O NH O

O H 2

HOE 085355, AE F085355, N-acetyl glufosinate, NAG

IUPAC: 2-acetamido-4- methylphosphinico-butanoic acid Racemic free acid

O P

OH O NH O

O H

3 HOE 061517, AE F061517, MPP, MPPA

IUPAC: 3-methylphosphinicopropionic acid

CAS: 3- (hydroxymethylphosphinyl)propanoic acid

CAS Reg. No. 15090-23-0 Free acid

O P O H OH

OPage 54 of 71 Chem. Group Chemical Name Description Structure

4 HOE 064619, AE F064619, MPA, MPAA

IUPAC: 2-methylphosphinico-acetic acid

CAS: (hydroxymethylphosphinyl)acetic acid

CAS Reg. No. 72651-25-3 Free acid

O P O H O

OH

5 HOE 086486, AE F086486

IUPAC: 3-methylphosphinico-3-oxopropionic acid Free acid

O P OH O H O O

6 HOE 065594, AE F065594

IUPAC: 4-methylphosphinico-2-oxobutanoic acid Free acid

O P O O

O H

OH

HOE 042231, AE F042231

IUPAC: disodium-2-hydroxy-4- methylphosphinico-butanoic acid Racemic salt

O P O

O O OH

Na + 2 7

HOE 053705, AE F053705

IUPAC: 2-hydroxy-4- methylphosphinico-butanoic acid Racemic free acid

O P O OH

O H

OH

8 HOE 039046, AE F039046

IUPAC: 4-methylphosphinicobutanoic acid Free acid

O P O O H

OHPage 55 of 71 Chem. Group Chemical Name Description Structure

HOE 084658, AE F084658

IUPAC: disodium-methylphosphinicoformic acid Salt

O P O
O O

Na + 2 9

HOE 130947, AE F130947

IUPAC: methylphosphinico-formic acid Free acid

O P O

O H
OH

10 HOE 130948, AE F130948

IUPAC: methylphosphonic acid Free acid

O P OH O H

11 HOE 078091, AE F078091

IUPAC: methylphosphinic acid Free acid

O O H

P HPage 56 of 71 APPENDIX C. Submitted Data for Glufosinate-ammonium.

Table C.1 identifies studies by MRID or Accessi on Number that offer data for each guideline requirement. Also listed are study cl assifications, whether or not the studies are collectively sufficient for the data requirement, a nd whether or not the cu rrent action necessitates data submission in support of guideline requ irement completion. Table C.2 lists the same information for ecological effects.

TABLE C.1. Environmental fate data submitted for glufosinate-ammonium.
Subdivision N

Guideline # Data Requirement Sufficient for EFED? Submitted Studies (MRID/Acc. #) Classification Cu rrent Additional Data Need 161-1 Hydrolysis Yes 40345656 Acceptable None 161-2 Aqueous photolysis Yes 40345657 41323115 Supplemental Acceptable None

161-3 Soil photolysis Yes 40345658 41323116 41323117 41920102 Supplemental Unacceptable Unacceptable Acceptable None

162-1 Aerobic soil metabolism Yes 40345659A,C,D 40345659B 40501018 41323118 41323119 41920103 Supplemental Supplemental Unacceptable Supplemental Supplemental Supplemental None

162-2 Anaerobic soil metabolism Yes 40501014 41323119 41323120 41920103 Supplemental Supplemental Supplemental Supplemental None

162-3 Anaerobic aquatic metabolism Yes 45215401 46258601 (Under review) Supplemental None

162-4 Aerobic aquatic metabolism Yes 40345660 45204401 45204402 Acceptable (Under review) (Under review) None

163-1 Aged leaching/ adsorption/ desorption Yes 40345661 40345662 41323121 Unacceptable Acceptable Supplemental None

163-2 Volatility - lab Yes 41323122 41920104 Unacceptable Supplemental None

164-1 Terrestrial field dissipation Yes 40345663 40345664 40345665 41323123 41323124 41920106 43110402 43766915 43766916 Supplemental Supplemental Supplemental Unacceptable Supplemental Unacceptable Acceptable Acceptable Acceptable None

164-2 Aquatic field dissipation Yes 45204403 (Under review) NonePage 57 of 71 Subdivision N

Guideline # Data Requirement Sufficient for EFED? Submitted Studies (MRID/Acc. #) Classification Cu rrent Additional Data Need
165-4 Fish bioaccumulation Yes 40501017 41323130 Supplemental Acceptable None

(OPPTS 850.7100) Data Reporting for Environmental Chemistry Methods No 40345666 Not classified Independent laboratory validation of submitted analytical method for residues in soil and water

TABLE C.2. Ecological effects data submitted for glufosinate-ammonium.
Subdivision J

Guideline # Data Requirement Sufficient for EFED? Submitted Studies (MRID/Acc. #) Classification Cu rrent Additional Data Need
71-1 Avian Oral Yes 00142450 00142451 Acceptable Acceptable None

71-2 Avian Dietary Yes 00150988 00150989 Acceptable l Acceptable None

71-4 Avian Reproduction Yes 40345650 40345650 Acceptable Acceptable None

72-1 Acute FW Fish Yes 00142454 00142455 Acceptable Acceptable None

72-2 Acute FW Invertebrates Yes 00142456 Acceptable None

72-3 Acute E/M Organisms Yes 00128850 41396107 Acceptable Acceptable None

72-4 Fish ELS/Invertebrate Life Cycle Yes 00128850 Acceptable None

123-1a,b Seedling Emergence/Veget ative Vigor No 41396111 41396112 41396113 Supplemental Supplemental Supplemental Seedling emergence NOEC

123-2 Aquatic Plants No 40345653 42262404 Acceptable Acceptable Four nonvascular plantsPage 58 of 71 IV. HUMAN HEALTH EFFECTS SCOPING DOCUMENTPage 60 of 71 Introduction. The HED Glufosinate Ammonium Registra tion Review Team has evaluated the status of the human health risk assessments for the herbicide gl ufosinate ammonium to determine whether sufficient data are available and whether new human health risk assessments are needed to support Registration Review. The primary sources for the status update were the most recent human health risk assessment (August 2003), Agency memoranda, and an OPPIN bibliography of submitted studies (MRIDs). Memoranda regarding proposed label amendments were also considered (February 2005, September 2007). Incident databases were also reviewed.

Technical glufosinate ammonium is a racemic mixture of the D and L enantiomers; only the L enantiomer is herbicidally active. The compound is a non-selective herbicide and acts as an inhibitor of glutamine synthetase which leads to poisoning of the plant by ammonia. Glufosinate ammonium is currently registered for use on both transgenic and nontra nsgenic crops. The transgenic plants currently registered (canola, sugar beet, corn, soybean, rice, and cotton) have been genetically engineered to express phosphi othrion-acetyltransferase (PAT) which enables the plant to metabolize glufosinate a mmonium into N-acetylglufosinate.

Although the current glufosinate ammonium to lerance listing in 40 CFR 180.473 distinguishes between nontransgenic (40 CF R 180.473(a)(1)) and transgenic crops (40 CFR 180.473(a)(2)), HED concurs with a recent recommendation th at this distinction be removed (D335330, T. Bloem, 12-SEP-2007). This recommendation was based on a determination by the Metabolism Assessment Review Committee (MARC) that a single tolerance expr ession (glufosinate ammonium, N-acetyl-glufosinate, and 3-methyl phosphinico-propionic acid) applies to both transgenic and nontra nsgenic crops.

Hazard Characterization and Toxicology . Contingent on conclu sions of the HED HASPOC regarding a waiver request for determination of glutamine synthetase levels, the toxicity database for glufosinate ammonium is substan tially complete for the purpose of assessing human health risks.

No acute reference dose was selected for the ge neral population because an endpoint attributable to a single exposure was not available from the t oxicity studies. However, an acute reference dose applicable to females 13-50 years old was se lected from a rabbit developmental toxicity study based on reduced fetal body weight s and increased fetal deaths.

Chronic toxicity testing has revealed a variety of effects including increased mortality, inhibition of brain glutamine synthetase and increas ed liver and kidney weights. In dogs, electrocardiogram (EKG) alterati ons were also observed. The da tabase for carcinogenicity is considered complete. Glufosinate ammonium has been classified as not likely to be a human carcinogen (Group E). The mutagenicity/genetic t oxicity database is considered complete and indicates no mutagenicity concern.Page 61 of 71 Previous assessments have concluded that the sp ecial FQPA safety factor should be reduced to 1x for the following reason: There was no quantita tive or qualitative evidence of increased susceptibility following in utero exposure in the prenatal devel opmental study in rats. There is qualitative evidence of increased susceptibility in the prenatal developmental study in rabbits and quantitative evidence of increased suscepti bility in the 2-genera tion reproduction study in rats. In this study, a decrease in the number of viable pups was observed in the absence of parental toxicity at any dose. Since there is qual itative evidence of increased susceptibility of the young following exposure to glufosinate ammonium, the HED H azard Identification Assessment Review Committee (HIARC) performe d a degree of concern analysis to: (1) determine the level of concern for the effects obs erved when considered in the context of all available toxicity data; and (2) identify any residual uncertainties after establishing toxicity endpoints and traditional un certainty factors to be used in th e risk assessment of this chemical. Based on the data gaps listed above, the HIARC did not identify any other residual uncertainties. The established endpoints are protec tive of pre-pre/postnatal toxicity following acute and chronic exposures.

In an April 2003 report of the HIARC, it was conc luded that a 10X database uncertainty factor (UF DB ) should be applied to all exposure scenario s to account for the lack of a DNT study with comparative glutamine synthetase activity measurements in organs.

The previous glufosinate ammonium risk as sessment (August 2003) identified two primary toxicology data gaps: a developmental neur otoxicity (DNT) study in rats, and a 28-day inhalation study in rats with glut amine synthetase activity measurements in brain, kidney, liver and lung for both studies. HED subsequently received the following two toxicological submissions:

1) MRID 46455701. Developmental Neur otoxicity Study in Rats.

This study was reviewed recently (TXR# 0053106, R.J. Mitkus, 8/24/2005) and found adequate to satisfy the registration requi rement of a developmental neurotoxicity study. However, the review noted that the study did not measure gl utamine synthetase levels in organs.

2) MRID 47058101. 28-Day Inhalation Toxicity Study in Rats.

This study was reviewed recently (TXR# 0053314, L. Austin, 9/6/2007) and was classified as Acceptable/Non-guideline. However, the review noted that the study did not measure glutamine synthetase levels in organs. While this study did not determine a NOAEL, the LOAEL was established at 0.056 mg a.i./L based on lung/ bronchial congestion in female rats.

Dietary Exposure. With respect to the a ssessment of dietary risk s, the dietary exposure database is complete. There are adequate re sidue data reflecting the use of all existing formulations on representative commodities. Ac ute and chronic dietary exposure analyses have been conducted using DEEM-FCID (version 1.30) (D292560, T. Bloem, 07-AUG-2003). HEDPage 62 of 71 identified a reference dose for chronic exposur e (cRfD) of 0.006 mg/kg/ day from a “weight-ofevidence” approach from three studies base d upon glutamine synthe tase inhibition and alterations in the electrocardiog ram found in the studies. The NOAE L from the three studies was 6.0 mg/kg/day and the cRfD was derived by applyi ng a 1000X uncertainty factor (10x database UF, 100X inter-/intra-species UF). Because the FQPA SF was determined to be 1X, the cRfD and the cPAD are numerically equivalent. Chroni c dietary exposure estimates greater than 100% of the cPAD would exceed HED’s level of concer n. Chronic dietary (foo d only) risk estimates were less than 30% of the cPAD for all populations using a partia lly refined exposure assessment (tolerance or average field trial residue levels, percent crop treated information for several crops, and processing factors when available). Any upda te of the chronic dietary exposure analysis should include recommendations of the HASPOC regarding the glutamine synthetase waiver request and estimates of glufosinate a mmonium levels in drinking water.

HED identified a reference dose for acute e xposure (aRfD) of 0.0063 mg/kg for females 13-49 years old only. The NOAEL of 6.3 mg/kg wa s based on reduced fetal body weights and increased fetal deaths seen at the LOAEL of 20 mg/kg. A 1000x un certainty factor (10x database UF, 100X inter-/intra-species UF) was in corporated in the aRfD. Because the FQPA SF was determined to be 1X, the aRfD and the aPAD are numerically equivalent. Acute dietary exposure estimates greater than 100% of the aPAD would exceed HED’s level of concern. Acute dietary (food only) risk esti mates were less than 50% of the aPAD for females 13-49 years old using a partially refined exposure assessment (t olerance, highest or aver age field trial residue levels depending on the level of blending of a given commodity, 100% crop treated information for all crops, and processing factors when availabl e). Any update of the acute dietary exposure analysis should follow recommendations of th e HASPOC regarding the glutamine synthetase waiver request and should include estimates of gl ufosinate ammonium levels in drinking water.

Water Considerations. The Environmental Fate and Effects Division (EFED) recently issued a memo updating its estimated drinking water conc entrations (EDWCs) for glufosinate ammonium in ground water sources (D335331, J. Stone, 07-SE P-2007). However, this update does not change the water values used in HED’s 2003 risk assessment since the surface water EDWCs exceed the ground water EDWCs, and the surface wa ter values were made use of in the HED risk assessment.

Residential Exposure. Residential Handlers According to a previous human health risk asse ssment (August 2003), pote ntial residential (nonoccupational) exposures were anti cipated as a result of applicati ons of glufosinate ammonium to residential lawns. Risks were estimated for both residential handler exposures (adults) and residential postapplication exposur es (adults and toddlers). Reside ntial exposure was of concern for adults and toddlers for several exposure scen arios as a result of br oadcast application of glufosinate ammonium to residential lawns acco rding to the lawn renovation section of the Finale Super Concentrate label (EPA Reg. No. 45639-191). However, according to OPPIN Query, EPA Reg. No. 45639-191 was transferred fr om Agrevo USA to Bayer EnvironmentalPage 63 of 71 Science as EPA Reg. No. 432-954. The last accepte d label in PPLS for this registration, Finale Super Concentrate Weed, Grass and Brush Killer, only bears directions for spot treatment in lawns (personal communication, James Stone, 10-DEC-2007).

The available residential exposure and risk as sessment for homeowner handlers/applicators combined the short-term inhala tion and short-term dermal expos ure estimates since the same toxicological endpoint was selected for both routes of exposure. An ARI approach was used to estimate risk to account for the different targ et MOEs for residen tial dermal (>1000) and inhalation (>3000) exposures. Th ese calculations showed spot tr eatments to result in exposure levels below HED’s level of concern (ie ARIs >1 ) and only to exceed HED’s level of concern for the lawn renovation use, which is no longer supported. Once the glutamine synthetase issue is resolved by the HASPOC, the residential handler risk assessment will likely need revisions to reflect any updates to the NOAE Ls and UFs, but the exposure levels should not change.

Residential Post Application The 2003 risk assessment mentions lawn renova tion uses of glufosin ate ammonium which exceeded HED’s level of concern and that the registrant will voluntarily cancel the lawn renovation use. Indeed, a residential assessment of the lawn renovation use from Finale Super Concentrate label (EPA Reg. No. 45639-191) showed risks of con cern for incidental oral and dermal exposures for children, and for dermal exposures for adults (D284811, J.T. Swackhammer, 09-AUG-2002). However, accor ding to OPPIN Query, EPA Reg. No. 45639- 191 was transferred from Agrevo USA to Bayer Environmental Science EPA Reg. No. 432-954. The last accepted label in PPLS for this regist ration, Finale Super Concentrate Weed, Grass and Brush Killer, only bears directions for spot tr eatment in lawns (personal communication, James Stone, 10-DEC-2007). In accordance with the HED Exposure Science Advisory Committee (ExpoSAC) guidance, the registered spot treatment use is not expect ed to result in significant post application exposure and thus no residential post application risk assessment is necessary.

Aggregate Risk Assessment. Acute, short-term, and chronic a ggregate risk assessments were conducted for glufosinate ammonium in the 200 3 assessment. Drinking water risks were included in the aggregate assessments using th e Drinking Water Level of Comparison (DWLOC) approach. In the 2003 risk assessment, the acute surface water EEC (94 ppb; provided by the Ecological Fate and Effects Division/EFED 2003) was nearly equal to the acute DWLOCs for females 13-49 years old (98 ppb). The chronic surface water EEC of 43 ppb was considerably less than the short-term DWLOCs of 156-187 ppb for the population subgroups included in the short-term aggregate analysis, i ndicating risk levels below HED’ s level of concern. However, the chronic surface water EEC of 43 ppb was nearly equal to the DWLOC values determined for the infant and children populati on subgroups (44-51 ppb for all infa nts < 1 year old, children 1-2 years old, children 3-5 years old and children 6-12 years old).

Revisions to the aggregate ri sk assessments for glufosinat e ammonium should include the following: 1) the addition of wa ter levels directly into the di etary analysis, thus obviating the need for DWLOC analysis, and 2) reconsideration of UFs and dose/ endpoint selection to includePage 64 of 71 recommendations of the HASPOC based on the co mplete toxicity database for glufosinate ammonium.

Occupational Exposure . The 2003 glufosinate ammonium assessment presented an occupational risk assessment based on the highe st supported use rates for cotton, bushberry, and rice. Subsequent to the 2003 risk assessment, Bayer CropSciences requested an amendment to the registered product Liberty Herbicide for an in crease in the rate of a single application to cotton from 0.52 to 0.786 lb ai/A. Consequently, the occupational handler risk assessment for the cotton scenario was updated to reflect the higher use rate (D318745, M.I. Dow, 07-FEB2006). While the exposure levels from these asse ssments are adequate, the MOEs are likely to need revision, contingent on the decision of the HASPOC with regards to the glutamine synthetase waiver request. Once this determina tion is made, and the relevant toxicity endpoints and doses are updated, the occupational risk assessment may be revised accordingly.

Public Health and Pesticide Epidemiology Data. A summary report listi ng reported incidents for glufosinate ammonium will be provided for the docket. The reported incidents will be screened in more detail duri ng the development of the Preliminary Work Plan (PWP) for glufosinate ammonium.

Cumulative Risk Assessments. The Agency has not determined whether glufosinate ammonium shares a common mech anism of toxicity with other chemical substances, and whether a cumulative assessment is warranted. The following reference contains information regarding determination of common mechanisms of toxicity: “Guidance for Identifying Pesticide Chemicals and Other Substances that have a Common Mechanism of Toxicity” (January 29, 1999). To date, the Agency has assessed the pote ntial for a common mechanism of toxicity for four groups of chemicals: organophosphates, N-methyl carbamates, S-triazines, and chloroacetanilides. If glufosinate ammonium is determined to share a common mechanism of toxicity with other s ubstances, then methods for aggreg ating exposures and risks will be developed. Until glufosinate ammonium is sche duled for a common mechanism determination and a decision is made, the Agency would not a priori assume a common mechanism of toxicity exists for glufosinate ammonium and other substances.

Environmental Justice. Potential areas of environmental justice concerns, to the extent possible, were considered in the human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions to A ddress Environmental Justice in Minority Populations and Low-Income Populations," http://www.eh.doe.gov/nepa/tools/guidan ce/Volume1/2-6-EO_12898envjustice.pdf ). The Office of Pesticide Programs (OPP) typi cally considers the highest poten tial exposures from the legal use of a pesticide when conducting human health risk assessments, including, but not limited to, people who obtain drinking water fro m sources near agricultural ar eas, the variability of diets within the U.S. (including different ages), and people who may be exposed when harvesting crops. Should these highest exposures indicate po tential risks of concern, OPP further refines the risk assessments to ensure that the risk estimat es are based on the best available information.Page 65 of 71 Registration Review Conclusions: HED has determined that t oxicity and exposure databases for glufosinate ammonium are substantially comp lete. However, due to recent submissions of DNT and inhalation studies, it is likely that the toxicity doses and endpoints previously selected for glufosinate ammonium may require revisions, as well as the uncertainty factors. This would necessitate revisions to the diet ary, residential, occupational, a nd aggregate risk assessments. However, prior to making these revisions, the issue of glutamine synthetase measurements should be resolved. The HED HASPOC w ill be consulted on this issue.

Harmonization Issues . The Codex Alimentarius Commissi on has established several maximum residue limits (MRLs) for residues of glufosinat e ammonium and its meta bolites in/on various raw agricultural and processed commodities. The Codex MRLs are expressed in terms of glufosinate ammonium and its me tabolites and are presented in Table 1 below. Except for tree nuts, almond hulls, banana, and soybean, the U. S. tolerances and Codex MRLs are not in harmony with respect to numerical levels. The U.S. tolerances and the Canadian MRLs are harmonized for field corn grain and soybeans but not other crops. All Mexican MRLs are harmonized with U.S. tolerances.Page 66 of 71 Table 1. Comparison of U.S., Canadian, and Me xican tolerances to Codex MRLs for glufosinate ammonium. 

### US Canada Mexico Codex
Residue Definition:
40CFR 180.473 butanoic acid, 2-amino-4- (hydroxymethylphosphinyl)- monoammonium salt and its metabolites, 2-acetamido-4- methylphosphinico-butanoic acid and 3-methylphosphinico-propionic acid, expressed as 2-amino-4- (hydroxymethylphosphinyl)butanoic acid equivalents

As an inadvertent residue: butanoic acid, 2-amino-4- (hydroxymethylphosphinyl)-, monoammonium salt and its metabolite, 3- methylphosphinicopropionic acid ammonium(±)-2-amino4- (hydroxymethylphosphinyl) butanoate, including the metabolite propanoic acid, 3- (hydroxymethylphosphinyl) Glufosinate ammonium Sum of glufosinate-ammonium, 3- [hydroxy(methyl)phosphinoyl]propionic acid, and N-acetyl-glufosinate, calculated as glufosinate (free acid)

.

Commodity Tolerance (ppm) /M aximum Residue Limit (mg/kg) Commodity US Canada Mexico Codex Almond, hulls 0.50 0.5 Apple 0.05 Asparagus - 0.05 (*) Banana 0.30 0.3 0.2 Banana, pulp 0.20 Beans, dry white - 0.5 Beet, sugar, molasses 5.0 Beet, sugar, roots 0.9 0.05 (*) Beet, sugar, tops (leaves) 1.5
Bushberry subgroup 13B 0.15 0.1 (Berries and other small fruits) Broad bean (dry) 2 Canola, meal 1.1
Canola, seed 0.40 3 (rape seed) 5 (rape seed) Canola oil (rape seed oil), crude - 0.05 (*)

Carrot - 0.05 (*) Cattle, fat 0.40 0.1Page 67 of 71 

### US Canada Mexico Codex

Cattle, meat 0.15 0.1 0.05 (*) meat (from mammals other than marine)
Cattle, meat byproducts 6.0 0.1; 1 (liver, kidney) 0.1 (*) (edible offal, mammalian) Citrus fruits - 0.1 Common bean (dry) - 2 Common bean (pods and/or immature seeds) - 0.05 (*)

Corn, field forage 4.0 5
Corn, field, grain 0.20 0.2 0.2 (maize) 0.1 (maize)

Corn, field, stover 6.0 10 (maize, fodder (dry)) Corn salad - 0.05 (*) Cotton, gin byproducts 15 Cotton, undelinted seed 4.0 Cottonseed oil - 3.5 Currants, black and red - 0.5 Egg 0.15 0.1 0.05 (*) Goat, fat 0.40 0.1 Goat, meat 0.15 0.1 Goat, meat byproducts 6.0 0.1; 1 (liver, kidney) Grain aspirated fractions 25 Grape 0.05 0.05 Hog, fat 0.40 0.1 Hog, meat 0.15 0.1 Hog, meat byproducts 6.0 0.1; 1 (liver, kidney) Horse, fat 0.40 Horse, meat 0.15 Horse, meat byproducts 6.0 Lentils - 6 Juneberry 0.10 Lingonberry 0.10 Milk 0.15 0.04 0.02 (*) Nut, tree, group 14 0.10 0.1 Onion, bulb - 0.05 Peas, dry - 3 3 Pistachio 0.10 Pome fruits - 0.05 (*) Potato 0.80 0.4 0.5 Potato, chips 1.6Page 68 of 71 

### US Canada Mexico Codex Potato granules/flakes 2.0 Poultry, fat 0.15 0.1 Poultry, meat 0.15 0.1 0.05 (*)
Poultry, meat byproducts 0.60 0.1; 1 (liver, kidney) 0.1 (*) (edible offal) Rice, grain 1.0 1 Rice, hull 2.0 Rice, straw 2.0 Salal 0.10 Sheep, fat 0.40 0.1 Sheep, meat 0.15 0.1 Sheep, meat byproducts 6.0 0.1; 1 (liver, kidney) Soybean 2.0 2 2 2 Soybean, hulls 5.0 Stone fruits - 0.05 (*) Sunflower seed - 5 Sunflower seed oil, crude - 0.05 (*)Tropical fruit and subtropical fruits, assorted – inedible peel- 0.05 (*)

Wheat - 0.2

Inadvertent Residues Barley, hay 0.40 Barley, straw 0.40 Buckwheat, fodder 0.40 Buckwheat, forage 0.40 Oat, forage 0.40 Oat, hay 0.40 Oat, straw 0.40 Rye, forage 0.40 Rye, straw 0.40 Teosinte 0.40 Triticale 0.40 Wheat, forage 0.40 Wheat, hay 0.40 Wheat, straw 0.40Page 69 of 71 Referenced Memoranda

Glufosinate Ammonium (PC Code 128850). Section 3 Registrations for Transgenic Cotton and Cotton (ID# 0F06140), Trasgenic Rice (ID#0F 06210), and Bushberry (ID# 2E06404). Human Health Risk Assessment . DP# 290086, T. Bloem, PV Shah, and M. Dow, August 7, 2003.

Glufosinate Ammonium. Label Amendment to Incr ease the Registered Cotton Application Rate and Reduce the Plant-Back Intervals Following Application to Cotton. DP#s 318744 & 319568, T. Bloem, February 22, 2005.

Glufosinate Ammonium (PC Code 128850). Label Amendment fo r Pre-Plant Application of Glufosinate Ammonium to the Transgenic and No n-Transgenic Varieties of Field Corn, Canola, and Soybean. Residue Chemistry Summary . DP#s 335330, 335332, and 339226, T. Bloem, September 12, 2007.

Glufosinate Ammonium – Review of Developm ental Neurotoxicity Study in Rats (MRID 46455701). DP# 312684, R.J. Mitkus, August 24, 2005.

Glufosinate Ammonium – Revi ew of 28-Day Inhalation To xicity Study (MRID 47058101). DP# 337298, L Austin, September 6, 2007.

Glufosinate Ammonium – 3 rd Report of the Hazard Identifica tion Assessment Review Committee. TXR# 0051833, B. Tarplee, April 17, 2003.

Glufosinate-Ammonium – Exposur e/Risk Assessment for the Us e of Glufosinate-ammonium on Cotton at Higher Rates . DP# 318745, M.I. Dow, February 7, 2006.

Occupational and Updated Residential Exposure Ri sk Assessment for the use of Glufosinate Ammonium on Rice, Cotton, and Bushberry . DP# 284811, J.T. Swackhammer, 09-AUG-2002.Page 70 of 71 V. GLOSSARY OF TERMS AND ABBREVIATIONS

A Acre ai Active Ingredient aPAD Acute Population Adjusted Dose aRfD Acute Reference Dose BEAD Biological and Ec onomic Analysis Division CDPR California Department of Pesticide Regulation CFR Code of Federal Regulations cPAD Chronic Population Adjusted Dose DCI Data Call-In DEEM-FCID Dietary Exposure Evaluati on Model software with Food Commodity Intake Database DNT Developmental Neurotoxicity DWLOC Drinking Water Level of Comparison. EDWC Estimated Drinking Water Concentration EEC Estimated Environmental Concentration EFED Ecological Fate and Effects Division EPA Environmental Protection Agency FIFRA Federal Insecticide, Fungicide, and Rodenticide Act FQPA Food Quality Protection Act FWP Final Work Plan GENEEC Tier I Surface Water Computer Model HED Health Effects Division HIARC Hazard Identification Assessment Review Committee LC 50 Median Lethal Concentration. A st atistically derived concentration of a substance that can be expected to cause death in 50% of test animals. It is usually expressed as the weight of substance per weight or volume of water, air or feed, e.g., mg/l, mg/kg or ppm. LD 50 Median Lethal Dose. A statisti cally derived single dose that can be expected to cause death in 50% of th e test animals when administered by the route indicated (oral, dermal, inhalati on). It is expresse d as a weight of substance per unit weight of animal, e.g., mg/kg. LOC Level of Concern LOAEL Lowest Observed Adverse Effect Level mg/kg/day Milligram Per Kilogram Per Day mg/L Milligrams Per Liter MOE Margin of Exposure MRID Master Record Identification ( number). EPA's system of recording and tracking studies submitted. MRL Maximum Residue Level NAWQA USDA’s National Water-Quality Assessment Program NOAEC No Observed Adverse Effect ConcentrationPage 71 of 71 NOAEL No Observed Adverse Effect Level NOEC No Observed Effect Concentration OPP EPA Office of Pesticide Programs OPPIN Office of Pesticide Programs Information Network OPPTS EPA Office of Prevention, Pe sticides and Toxic Substances PAD Population Adjusted Dose ppb Parts Per Billion PPLS Pesticide Product Label System PRZM/EXAMS Tier II Surface Water Computer Model RD Registration Division RfD Reference Dose SDWIS/FED Safe Drinking Wate r Information System/Federal SLUA Screening Level Usage Analysis SRRD Special Review and Reregistration Division TEP Technical End-Use Product TGAI Technical Grade Active Ingredient TREX Terrestrial Residue EXposure model USGS United States Geological Survey UF Uncertainty Factor