U. S. ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, DC 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES PC Code No. 080801 DP Barcode:

MEMORANDUM Date: February 17, 2005 SUBJECT: EFED Reregistration Eligibility Document and Risk Assessment for the use of Ametryn on corn, pineapple and sugarcane.

TO: Mark T. Howard, Chemical Review Manager Special Review and Reregistration Division ( 7508C) Reregistration Branch III FROM: Kevin Costello, RAPL John E. Ravenscroft, Jr., Biologist Environmental Risk Branch IV, EFED ( 7507C)

THRU: Elizabeth Behl, Branch Chief Environmental Risk Branch IV, EFED ( 7507C)

Attached please find the Environmental Fate and Effects Division's environmental risk assessment for ametryn as a selective systemic herbicide to control most annual grasses ( pre and postemergent and broadleaf weeds in corn, pineapple and sugarcane. Ametryn is a moderately persistent and mobile compound.

Ametryn is expected to pose a risk to non target terrestrial and aquatic plants. For terrestrial plants, the level of exposure via spray drift estimated with the AgDrift model would exceed levels of concern for all ametryn uses to distances of hundreds of feet from the treated field. In fact, the predicted exposure from aerial applications in sugarcane results in risk quotients which exceed the levels of concern at distances greater than the 999 foot limit of the model spray drift model AgDrift. Since no effect levels were not determined for the most sensitive species used in the plant toxicity tests ( i. e., the no effect level was below the lowest concentration tested), EFED can conclude that the level of concern for endangered plants would be exceeded at some unspecified distance even beyond those calculated for non endangered plants. For aquatic plants, levels of concern were exceeded in both corn and sugarcane.

Ametryn is slightly to moderately toxic to freshwater animals on an acute basis, but under the proposed uses only the acute endangered risk levels of concern are exceeded for freshwater fish and invertebrates in Florida and Louisiana sugarcane. Additionally, chronic exposure of ametryn to freshwater fish resulted in an exceedance of the level of concern in Louisiana sugarcane ( RQ = 1.15). Laboratory tests have shown chronic exposure results in a significant reduction in fry growth, . Levels of concern were also exceeded for chronic exposure of ametryn to freshwater invertebrates in Florida and Louisiana sugarcane ( RQ range: 1.08   3.38). Significantly reduced reproduction rates have been shown in chronic exposure laboratory tests.

Ametryn is classified as moderately toxic to estuarine/ marine animals on an acute basis; however, only acute endangered species levels of concern for estuarine/ marine fish and invertebrates were exceeded in the Florida and Louisiana sugarcane ( RQ range: 0.05   0.37).

Acute endangered species LOC's for estuarine/ marine invertebrates were exceeded in the Florida and Louisiana sugarcane, and for estuarine/ marine fish in Louisiana ( Table 28). No data have been supplied by the registrant demonstrating chronic toxicity for estuarine/ marine fish and invertebrates. Additionally, estuarine/ marine fish and invertebrates appeared to be similarly sensitive to ametryn when compared with their freshwater counterparts. As with the freshwater animals, both sugarcane uses exceeded the acute endangered species LOC for both acute estuarine/ marine fish and invertebrates. Acute RQ values ranged from 0.01   0.15 for estuarine/ marine fish and from 0.03  0.37 for estuarine/ marine invertebrates.

There were no chronic toxicity studies available to assess the chronic toxicity of ametryn to estuarine/ marine fish or invertebrates. Estimated NOEC values were derived for estuarine/ marine fish and invertebrates based on the assumption that the acute to chronic NOAEC ratio for estuarine/ marine fish and invertebrates is the same as that for freshwater fish and invertebrates. There is uncertainty associated with extrapolation from freshwater to estuarine/ marine chronic NOAEC values, because quantifiable taxonomic sensitivity factors between the two broad categories of a2quatic organisms do not exist.

Chronic risk quotients calculated with these extrapolated toxicity endpoints suggest the potential for chronic risk to estuarine/ marine fish and invertebrates. The chronic risk quotient for estuarine/ marine fish in the Florida sugarcane scenario equal to the LOC of 1.0, and the RQ of 3.2 for Louisiana sugarcane exceeds this LOC. Chronic risk quotients for estuarine/ marine invertebrates exceed the chronic LOC for all four corn and sugarcane scenarios, with an RQ range of 3.9 to 40.6.

Ametryn is classified as practically non toxic to birds on an acute basis and no mortality was observed in laboratory tests. The LD 50 and LC 50 were above the highest concentration tested. There may be the potential for chronic risk to birds on at least one of the terrestrial food items in all three use crops ( RQ range: 0.10   6.92). Chronic exposure to ametryn to birds in laboratory tests resulted in effects on adult body weight and egg production.

Based on a screening level assessment of estimated residues on terrestrial food items, the acute levels of concern for mammals were exceeded in pineapple and sugarcane on short grass, and were exceeded for endangered species in all crops. Chronic mammalian levels of concern were exceeded ( RQ range: 2.3 to 160) in all categories for all crops modeled. Chronic exposure may result in decreased pup weights and weight gain in the offspring. Recommended Label Language Based on ametryn's persistence and accumulation potential, the following label language is recommended:

Surface Water Advisory Ametryn can contaminate surface water through spray drift, runoff, and erosion. Under some conditions, spiroxamine may also have a high potential for runoff into surface water, for several months post application. These include poorly draining or wet soils with readily visible slopes toward adjacent surface waters, frequently flooded areas, areas over laying extremely shallow ground water, areas with in field canals or ditches that drain to surface water, areas not separated from adjacent surface waters with vegetated filter strips, and areas overlaying tile drainage systems that drain to surface water.

Specific Label Language Based on the anticipated accumulation of spiroxamine in the environment and the calculated risk quotients, spiroxamine exceeds acute endangered species levels of concern for aquatic organisms. The following label language is proposed:

1. This pesticide is toxic to fish, plants and wildlife.

2. Drift and runoff may be hazardous to terrestrial and aquatic plants and aquatic organisms in neighboring areas. Do not apply directly to water, or to areas where surface water is present or to intertidal areas below mean high water mark. Do not contaminate water when disposing of equipment washwater or rinsate.

3. This product must not be used in areas where impact on threatened or endangered species is likely.

Outstanding Data Requirements Tables A1 and A2 summarize the status of the fate and toxicity studies for ametryn. In general, the studies provided enough information to perform an adequate fate and ecological assessment; however, to reduce the uncertainties within this assessment, EFED recommends that additional studies be submitted as described below.

No chronic toxicity data for estuarine and marine fish and invertebrates were available for review.

EFED requests that the aquatic vascular plant toxicity be conducted. The study used for evaluating vascular aquatic plants came from the open literature, located using ECOTOX, and did not report a NOEC. Table A1. Status of environmental fate data adequacy/ needs for Ametryn.

Guideline # Data Requirement Are Data Adequate for Risk Assessment? MRID #' s Study Classification 161 1 835.2120 Hydrolysis Yes 40885812 acceptable 161 2 835.2240 Photodegradation in Water Yes 41169601 acceptable 161 3 835.2410 Photodegradation on Soil Yes 41169602 41169603 acceptable acceptable 161 4 835.2370 Photodegradation in Air not applicable none not applicable 162 1 835.4100 Aerobic Soil Metabolism Yes 41752401 acceptable 162 2 835.4200 Anaerobic Soil Metabolism Yes 41752401 acceptable 162 3 835.4400 Anerobic Aquatic Metabolism Data are necessary for the RA. none not applicable 162 4 835.4300 Aerobic Aquatic Metabolism Data are necessary for the RA. none not applicable 163 1 835.1240 835.1230 Leaching Adsorption/ Desorption Yes 40995813 41169604 acceptable acceptable 163 2 835.1410 Laboratory Volatility ( requirement waived) not applicable not applicable 163 3 835.8100 Field Volatility ( requirement waived) not applicable not applicable 164 1 835.6100 Terrestrial Field Dissipation yes 41752402 41872302 41872301 supplemental supplemental supplemental 164 2 835.6200 Aquatic Field Dissipation

164 3 835.6300 Forestry Dissipation

164 4 835.6400 Combination Products and Tank Mixes Dissipation

165 4 850.1730 Accumulation in Fish Data are necessary for the RA. none not applicable 165 5 850.1950 Accumulation   Aquatic Non target Organisms no data no data

166 1 835.7100 Groundwater   Small Prospective

201 1 840.1100 Droplet Size Spectrum yes 41336801 acceptable 202 1 840.1200 Spray Drift Field Evaluation no 41268001 41336802 not acceptable not acceptable Table A2. Status of ecological effect data adequacy/ needs for Ametryn.

Guideline Data Requirement MRIDa Study Classification Are the data adequate for risk assessment?

71 1 Avian acute oral LD 50 Bobwhite quail 409958 01 core yes 71 2 Avian subacute dietary LC 50 Bobwhite quail Mallard duck 409958 03 409958 02 core core yes yes 71 4 Avian reproduction Bobwhite quail Mallard duck 415476 01 415476 02 core core yes yes 72 1 Freshwater fish acute LC 50 Rainbow trout Bluegill sunfish Fathead Minnow 428616 02 ( 98.0%) 409958 05 ( 96.7%)

409958 04 ( 96.7%)

428616 01 ( 98.0%) core supplemental supplemental core yes 72 2 Freshwater invertebrate acute LC 50 ( Daphnia magna) 409958 06 core yes 72 3a Estuarine/ marine fish acute LC 50 ( Sheepshead minnow) 411149 02 core yes 72 3b Estuarine/ marine acute invertebrate LC 50 ( Mysid shrimp) 411149 01 core yes 72 3c Estuarine/ marine acute invertebrate LC 50 ( mollusc) Quahog clam 411149 03 423252 01 core yes 72 4a Freshwater fish early life stage ( Fathead minnow) 411897 03 423252 03 core yes 72 4b Freshwater invertebrate life cycle ( Daphnia magna) 411897 02 423252 02 supplemental yes 72 4d Estuarine/ marine life cycle ( mysid) NSb

72 5 Freshwater fish full life cycle ( Fathead minnow) NS

81 1 Acute mammalian oral LD 50 ( rat) 409958 14 core yes 83 1 Mammalian Chronic ( rat) 403499 05 acceptable yes 123 1 Terrestrial plant toxicity Tier II 409958 09 409958 08 409958 07 core core core yes 123 2 Aquatic plant toxicity 409958 10 core yes 141 1 Acute honeybee contact 409958 11 core yes a MRID numbers followed by a percentage in parentheses indicates the amount of active ingredient used in the study. b NS = not submitted N N N S NH HN Environmental Fate and Ecological Risk Assessment for the Re registration of Ametryn CAS Registry Number 834 12 8 PC Code 080801 Prepared by:

John E. Ravenscroft, Biologist Kevin Costello, Risk Assessment Process Leader U. S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division Environmental Risk Branch IV 1200 Pennsylvania Ave., NW Mail Code 7507C Washington, DC 20460 Reviewed by: Elizabeth Behl, Branch Chief 2 Acknowledgment The Environmental Fate and Effects Division would like to thank Syracuse Research Corporation ( Mario Citra, Molly Ramsey, and Philip Goodrum) and Syracuse Environmental Research Associates, Inc., for their assistance in developing the environmental fate assessment for ametryn. 3 TABLE of CONTENTS TABLE of CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Predicted Environmental Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Potential Risk to Non target Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 PROBLEM FORMULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Nature and Use of the Chemical Stressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Mode of Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Use and Use Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Application Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Identification of Assessment Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Key Uncertainties and Data Gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 ENVIRONMENTAL FATE AND TRANSPORT CHARACTERIZATION . . . . . . . . 18 WATER RESOURCES ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Drinking Water EDWCs ( Surface Water) . . . . . . . . . . . . . . . . . . . . . . . 22 Ground Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Monitoring Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Florida Sugarcane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Louisiana Sugarcane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Hawaii Pineapples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 AQUATIC EXPOSURE ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 EECs for Ecological Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Spray Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 TERRESTRIAL EXPOSURE ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Foliar Applications and Residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Exposure to Terrestrial Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Spray Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 ECOLOGICAL EFFECTS CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . 40 ECOTOX database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 RISK CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 RISK ESTIMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Exposure and Risk to Nontarget Terrestrial Animals . . . . . . . . . . . . . . . . . . . . . 45 Nontarget Terrestrial Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Risk to Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Risk to Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Nontarget Terrestrial Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Nontarget Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Nontarget Aquatic Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 RISK DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Risk to Terrestrial Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4 Risk To Terrestrial Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Risk to Birds and Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Acute risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Chronic Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Endocrine Disruption Potential . . . . . . . . . . . . . . . . . . . . . . . . . 61 Risk to Aquatic Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Risk to Aquatic Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Risk to Estuarine/ Marine Species . . . . . . . . . . . . . . . . . . . . . . . . 63 ENDANGERED SPECIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 INDIRECT EFFECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 CRITICAL HABITAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 APPENDICIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 APPENDIX A   USE CLOSURE MEMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 APPENDIX B   ENVIRONMENTAL FATE SUMMARY . . . . . . . . . . . . . . . . . . . . . 84 Abiotic Degradation . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Aqueous Photolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Soil Photolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Metabolism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Aerobic Soil Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Anaerobic Soil Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Mobility and Persistence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Adsorption/ Desorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Laboratory Volatility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Field Volatility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Terrestrial Field Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Bioaccumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 APPENDIX C   PRZM   EXAMS OUTPUTS BY CROP . . . . . . . . . . . . . . . . . . . . . . 89 Corn   NC ( east) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 ECO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Corn   NC ( west) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 ECO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Sugarcane   FL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 ECO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Sugarcane   LA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Drinking water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 ECO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 APPENDIX D   SCI GROW OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5 Corn   NC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Pineapple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Sugarcane   FL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Sugarcane   HI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Sugarcane   LA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Sugarcane   PR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Sugarcane   TX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 APPENDIX E   TERRESTRIAL EECs : ELL FATE and TERRPLANT SPREADSHEETS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Max residues using FATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Corn, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Corn, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Pineapple, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Pineapple, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Sugarcane, FL, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Sugarcane, FL, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Sugarcane, HI, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 Sugarcane, HI, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 Sugarcane, LA, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Sugarcane, LA, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Sugarcane, PR, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Sugarcane, PR, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Sugarcane, TX, max residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Sugarcane, TX, mean residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 TERRPLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 APPENDIX F   ECOLOGICAL EFFECTS ASSESSMENT . . . . . . . . . . . . . . . . . . . 133 Toxicity to Terrestrial Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Acute and Subacute Toxicity to Birds . . . . . . . . . . . . . . . . . . . . . . . . . 133 Chronic Toxicity to Birds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Acute and Chronic Toxicity to Mammals . . . . . . . . . . . . . . . . . . . . . . 135 Toxicity to Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Toxicity to Terrestrial Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Toxicity to Freshwater Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Freshwater Fish, Acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Freshwater Fish, Chronic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Freshwater Invertebrates, Acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Freshwater Invertebrate, Chronic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Toxicity to Estuarine and Marine Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Estuarine/ Marine Fish, Acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Estuarine and Marine Fish, Chronic . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Estuarine and Marine Invertebrates, Acute . . . . . . . . . . . . . . . . . . . . . 142 Estuarine and Marine Invertebrate, Chronic . . . . . . . . . . . . . . . . . . . . . 143 Toxicity to Aquatic Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 6 APPENDIX G   ECOLOGICAL RISK ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . 143 Exposure and Risk to Nontarget Terrestrial Animals . . . . . . . . . . . . . . . . . . . . 145 APPENDIX H   ENDANGERED SPECIES LISTS . . . . . . . . . . . . . . . . . . . . . . . . . 147 Corn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Pineapple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 Sugarcane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 7 EXECUTIVE SUMMARY This report focused on assessing and characterizing potential risks resulting from the proposed agricultural uses of ametryn on corn, pineapples, and sugarcane. Ametryn is a selective systemic herbicide, absorbed by the leaves and roots, with translocation through the xylem. It is used to control most annual grasses ( pre and post emergent) and broadleaf weeds through inhibition of the photosynthesis II pathway.

Predicted Environmental Exposure Ametryn is a persistent herbicide. A single aerobic soil metabolism study suggests that this is an important route of dissipation in the environment, with an observed half life of 84 days. Ametryn is stable to hydrolysis, and degrades slowly by aquatic photolysis ( 368 days).

Since ametryn is persistent, degradates were not observed at high concentrations in laboratory tests. Only one degradate was observed at greater than 10% of applied parent ( GS 11355 in the aerobic soil metabolism study). Nonetheless, since degradates 2 amino 4 isopropylamino 6 methylthio s triazine ( GS 11354) and 2 ethylamino 4 amino 6 methylthio s triazine ( GS 11355) are significantly similar in structure to parent ametryn, they were included in the drinking water exposure assessment as possible degradates of concern.

Ametryn was observed to be highly mobile in 3 of 4 soils in laboratory tests ( Kd = 1.07 to 1.21 in loam, sandy loam and sand soils, 26.2 in a clay soil). Given its persistence and mobility, transport of ametryn to ground water and surface water is expected from normal agricultural use. Monitoring of ametryn concentrations in ground water and surface water is limited, however. Ametryn was not included among analytes in the NAWQA program, for instance. Monitoring in Hawaii of ground water in pineapple use areas in the mid 1990' s resulted in a maximum concentration similar in magnitude to that predicted with the ground water screening model SCIGROW ( Screening Concentration in Ground Water). Quarterly surface water monitoring on the borders of the Everglades Agricultural Area ( EAA) has resulted in surface water concentrations well below those estimated for maximum application rates by the PRZM/ EXAMS models, but the frequency of the sampling is not sufficient for the estimation of potential acute exposure, nor extensive enough to allow a conservative estimate of potential chronic exposure.

Potential Risk to Non target Organisms Potential risk to non target organisms is summarized in Table 1a. Consistent with its use as an herbicide, ametryn is expected to pose a risk to non target terrestrial and aquatic plants. Ametryn was very highly toxic to most terrestrial plants tested in laboratory studies, with complete mortality of test plants for some species in the seedling emergence study at application rates well 8 below those indicated on ametryn product labels. The level of exposure via spray drift estimated with the AgDrift model would exceed levels of concern ( LOCs) for all ametryn uses to distances Table 1a. Summary of LOC exceedancesa by taxa and use for Ametryn.

Useb Terrestrial Freshwater Estuarine/ marine Aquatic Plants Birds Mammals Insects Plants Amphibians/ Reptiles Fish Inverts Fish Inverts Corn ( 2/ 1/ NA) C C, E A, E C A, E Pineapple ( 7.2/ 1/ NA) C A, C, E A, E C A, E Sugarcane FL ( 1.2/ 3/ 30) C A, C, E A, E E E C, E C, E C, E A, E Sugarcane HI ( 7.2/ 2.4/ 2.4) C A, C, E A, E A, E Sugarcane LA ( 2, 2.4x4/ 5 / 30) C A, C, E A, E E C, E C, E C, E C, E A, E Sugarcane PR ( 8, 4x2/ 3/ 30) C A, C, E A, E A, E Sugarcane TX ( 2/ 3/ 30) C A, C, E A, E A, E a letter in table corresponds to type of LOC exceedance: A = acute; C = chronic; E = endangered; ND = no data b for each use, the numbers in parentheses indicate: application rate/ number of applications/ interval of hundreds of feet from the treated field. For aerial application to sugarcane, the predicted exposure would be above the LOC at a distance greater than the 999 foot limit of the AgDrift model.

No effect levels were not determined for the most sensitive species in the seedling emergence and vegetative vigor laboratory tests, because effects were observed at the lowest doses tested. Noeffect levels are used to compute risk quotients for endangered plants. Therefore, exposure from spray drift which would lead to exceedence of the endangered species LOC is expected to occur some unspecified distance even beyond those calculated for non endangered plants.

Risk to aquatic plants was evaluated using a single submitted toxicity study performed on green algae, and additional information derived from the ECOTOX database. Risk quotients calculated using Tier II aquatic models exceed the acute LOC for aquatic plants by a large margin for both corn and sugarcane. In addition, the calculated exposure of aquatic habitats by spray drift alone is enough to exceed the LOCs in the screening assessment.

The screening assessment indicates an exceedence of the chronic freshwater fish and invertebrate LOC in Louisiana and chronic freshwater invertebrate LOC in Florida. The endangered species 9 acute risk LOCs for freshwater and estuarine/ marine fish and invertebrates from use on sugarcane in Louisiana and Florida are also exceeded.

Ametryn is practically non toxic to birds, and slightly toxic to mammals. However, due to high application rates, acute risk quotients for mammals were above the acute risk LOC for pineapple and sugarcane, and above the endangered species LOC for all crops. As detailed in Appendix A, the label specifies different application rates and intervals for sugarcane for each state in which it is grown. The screening level risk assessment also indicates a potential for chronic risk to birds for all three uses.

Both acute and chronic risk quotients for birds and mammals are based on maximum application rates, minimum application intervals and the default foliar dissipation half life of 35 days. Chronic risk quotients for birds slightly exceeds the level of concern for corn and for sugarcane in Florida, which represent the two major uses of ametryn. If risk quotients for these two scenarios are calculated using median predicted residues ( for the maximum application rates) on food items instead of peak residues, then the exposure estimates result in risk quotient values below the level of concern.

Chronic mammalian RQs exceed chronic LOCs for all feed items for all uses of ametryn ( RQ range = 2.3 to 160), based on the results of a 2 generation rat study. A rat carcinogenicity study resulted in decreased body weights and gain effects and also histological changes in the testes, kidney and pituitary in males and in the liver and pancreas in females. Risk quotients calculated with the NOAEC from this study would also exceed chronic LOCs for all feed items for all uses of ametryn.

The level of certainty in the prediction of chronic risk to birds and acute risk to mammals could be improved with additional data on potential exposure. If foliar dissipation data specific to ametryn indicate that the herbicide dissipates at a rate faster than the default value of 35 days used in the screening assessment, then estimated exposure and the resulting risk quotients for sugarcane, to which multiple applications can be made, would be reduced. Chemical specific data reporting total foliar residues of ametryn on wildlife feed items would allow a refinement of predicted exposure for all crops using a chemical specific foliar degradation rate.

PROBLEM FORMULATION The purpose of this assessment is to estimate ecological risks from currently registered uses of ametryn. The Agency is required by Federal Insecticide, Fungicide, and Rodenticide Act ( FIFRA) to review and, as warranted, reregister all existing pesticide products that contain active ingredients initially registered before November 1, 1984. The goal of the reregistration program is to update labeling and use requirements and to mitigate ( when possible) potential unreasonable risks associated with older pesticide active ingredients. 10 The analysis plan and rationale for completing this assessment ( i. e., the problem formulation) has been to determine whether current label uses of ametryn provide a means of exposure that could potentially represent an unreasonable likelihood of adverse effects ( risk) to nontarget species, including threatened and endangered species, which could potentially impact the reregistration eligibility decision under FIFRA, the Food Quality Protection Act ( FQPA) and the Endangered Species Act ( ESA).

The Agency routinely incorporates measures of exposure and effects for the pesticide active ingredients in the risk assessment process for all regulatory decisions. Available formulated product information, environmental fate data, and toxicological data are examined to determine the need to expand beyond the focus on the active ingredient and may result in consideration of pesticide formulations, inert ingredients, or degradates of the active ingredient in a particular risk assessment to support ( re) registration of a particular product. This data may come from a number of sources, including section 6( a)( 2) data, open literature data retrieved through ECOTOX ( discussed in the ecological effects characterization section of this document), and direct submission of data in support of ( re) registration.

Maximum application rates on vulnerable soils for representative crops are selected for modeling environmental concentrations for this screening level deterministic ( risk quotient based) assessment. This assessment is not intended to represent a site or time specific analysis, i. e. assessments are intended to represent a national level exposure based on vulnerable soils as opposed to being a regionally specific exposure assessment. Likewise, the most sensitive toxicity endpoints are used from surrogate test species to estimate treatment related direct effects on acute mortality and chronic reproductive, growth and survival assessment endpoints. Toxicity tests are intended to determine pesticidal effects on birds, mammals, fish, terrestrial and aquatic invertebrates and plants. These tests include short term acute, subacute and reproduction studies and are typically arranged in a hierarchical or tiered system which progresses from basic laboratory tests to applied field studies. The studies are used to evaluate the potential of a pesticide to cause adverse effects, to determine whether further testing is required, and to determine the need for precautionary label statements to minimize the potential adverse effects to nontarget animals and plants ( CFR 40 § 158.202, 2002).

Ametryn is not co formulated with other active ingredients, but may be tank mixed with other pesticides. OPP screening level risk assessments do not routinely include an evaluation of mixtures of multiple active ingredients product formulations or those prepared by the applicator ( i. e, commonly referred to as tank mixtures).

Nature and Use of the Chemical Stressor In accordance with risk assessment guidance, the Agency documents the scope of the chemical stressor( s) considered in the risk assessment, the rationale for their consideration, the methods used to evaluate the potential risks, and their contribution to the overall conclusions of the risk assessment. The characterization of pesticide use allows the risk assessors and risk managers to 11 focus the risk assessment on specific use patterns that are considered representative of all uses of a particular pesticide. Concentrating on specific use patterns allows the risk assessor to chose scenarios that reasonably representive of the exposure and those that may have the most potential for ecological impact among all uses of a particular pesticide.

Ametryn is an S triazine herbicide used on terrestrial food and feed crops. Table 1b lists the current commercially available formulations of ametryn. Use and application information contained in this document has been taken from the use closure memorandum found in Appendix A. The EFED ametryn risk assessment has been prepared in support of the re registration eligibility decision ( RED).

Table 1b. Currently available formulations of ametryn.

Registration # Company Name Product Name % Active Ingredient Formulation 100 579 Syngenta Crop Protection Ametryn Technical 90 Technical 100 786 Syngenta Crop Protection EVIK 80 WDG 80* Water dispersible granule 48273 3 Marman USA Inc AMETRYNE 80W 80* Wettable powder 51036 105 Micro Flo Company LLC AMETRYNE 4FL 44 Flowable concentrate * These products are 76.0% Ametryn and 4.0% related compounds, equaling 80.0% active ingredients.

Mode of Action Ametryn is a selective systemic herbicide, absorbed by the leaves and roots, with translocation through the xylem. It is used to control most annual grasses ( pre and post emergent) and broadleaf weeds. It inhibits photosynthesis.

Use and Use Sites The technical registrant is supporting the continued use of ametryn in three terrestrial food crops: sugarcane, corn ( pop, field, and sweet), and pineapples. The technical registrant has agreed to voluntarily cancel all other registered uses including: bananas, plantains, and all general herbicidal uses ( industrial sites, rights of way, airports and landing fields, and uncultivated non agricultural areas). The registrant has also indicated, they do not plan to support established regional residual tolerances for taniers, yams, and cassava roots. Previous to 1996, ametryn had been registered for use on oranges, grapefruit, and potatoes.

Ametryn is applied to corn mostly in southeastern states, particularly North Carolina and South Carolina, with some use in Georgia and Texas. Small amounts are also used in mid western states ( WI, OH, IL). Sugarcane use occurs mostly in Florida, with some use also in Hawaii, Texas and Louisiana. Ametryn is applied to pineapple in Hawaii and in Puerto Rico. Table 2 lists the estimated uses of ametryn in 2003. Figure 1 shows the estimated annual agricultural use of ametryn for the contiguous 48 states in the year 1997 based on data collected by the USGS Pesticide National Synthesis Project. 12 Application Methods Ametryn products are not co formulated with any other pesticide active ingredient ( ai); however, ametryn may be used in tank mixes ( with other pesticides.). Ametryn can be applied by aerial equipment ( sugar cane only) and by ground boom sprayers. For corn ( pop, field, & sweet), ametryn is used as a directed spray for soil treatment post emergence. Ametryn is used as a banded treatment on rattooned sugar cane, or as a broadcast spray ( pre emergence, rattoon, and post emergence). For pineapple, ametryn is applied as a ground spray.

Table 2. Screening level estimates of agricultural uses of ametryn as of April, 2003 Crop Pounds of Active Ingredient Percent of Crop Treated Corn 200,000 < 2.5 Hay, Other < 500 Sugarcane 90,000 30 Sweet Corn 3,000 < 2.5 13 Figure 1. 1997 estimate of annual agricultural use of ametryn based on data collected by the USGS Pesticide National Synthesis Project.

Identification of Assessment Endpoints Assessment endpoints are defined, per Agency guidelines, as " explicit expressions of the actual environmental value that is to be protected" which are " operationally defined by an ecological entity and its attributes" ( USEPA, 2004). The ecological entity can be a species, a functional group of species, a community, an ecosystem, or another entity of importance or concern. An attribute is the characteristic of the entity that is important to protect and is potentially at risk.

Defining an assessment endpoint involves two steps: 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 ( i. e., a community of fish and aquatic invertebrates) and its attributes ( i. e., survival and reproduction). Therefore, selection of the assessment endpoints is based on valued entities ( i. e., ecological receptors), the ecosystems potentially at risk, the migration pathways of pesticides, and the routes by which ecological receptors are exposed to pesticide related contamination. 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 for 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 exposures. Aquatic animal groups that are typically characterized in the risk assessment include: freshwater fish and invertebrates, estuarine/ marine fish and invertebrates, and amphibians. Terrestrial animal groups include: birds, mammals, beneficial insects, and earthworms. All assessment endpoints are characterized at the individual level in order to protect threatened and endangered species. However, 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 both population stability and growth and habitat carrying capacity). Indirect effects to listed species and critical habitat are also examined and, when required, are characterized in a species specific assessment conducted after the screening level risk assessment is completed.

For terrestrial and semi aquatic plants, the screening assessment endpoint is the perpetuation of populations of non target species ( crops and non crop plant species). Existing testing requirements have the capacity to evaluate emergence of seedlings and vegetative vigor. Although it is recognized that the endpoints of seedling emergence and vegetative vigor may not address all terrestrial and semi aquatic plant life cycle components, it is assumed that impacts at emergence and in active growth have the potential to impact individual competitive ability and reproductive success. 14 For aquatic plants, the assessment endpoint is the maintenance and growth of standing crop or biomass. Measurement endpoints for this assessment endpoint focus on algal and vascular plant ( i. e., duckweed) growth rates and biomass measurements.

The ecological relevance of selecting the above mentioned assessment endpoints is as follows: 1) complete exposure pathways exist for these receptors; 2) the receptors may be potentially sensitive to pesticides in affected media and in residues on plants, seeds, and insects; and 3) the receptors could potentially inhabit areas where pesticides are applied, or areas where runoff and/ or spray drift may impact the sites because suitable habitat is available.

Ecological measurement endpoints for this screening level risk assessment are based on a suite of registrant submitted toxicity studies performed on a limited number of organisms, supplemented by the open literature where applicable, in the following broad groupings:

4. Birds ( mallard duck and bobwhite quail) used as surrogate species for terrestrialphase amphibians and reptiles, 5. Mammals ( laboratory rat), 6. Freshwater Fish ( rainbow trout and fathead minnow) used as a surrogate for aquatic phase amphibians, 7. Freshwater invertebrates ( Daphnia magna), 8. Estuarine/ marine fish ( sheepshead minnow), 9. Estuarine/ marine invertebrates ( Americamysis bahia), 10. Terrestrial plants ( corn, onion, ryegrass, wheat, buckwheat, cucumber, soybean, sunflower, tomato, and turnip), and 11. Algae and aquatic plants ( Pseudokirchneriella subcapitatum).

Within each of these very broad taxonomic groups, an acute and chronic endpoint is selected from the available test data. The selection is made from the most sensitive species tested within a particular surrogate group. If additional toxicity data is available from other sources, the selection of an endpoint may not be limited to the surrogate species listed above, but may be expanded to include those data for other groups or species which has been deemed of sufficient quality by EFED scientists for use in the risk assessment.

A summary of the assessment and measurement endpoints selected to characterize potential ecological risks associated with exposure to ametryn and its degradates is provided in Table 3.

Conceptual Model In order for a chemical to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations. Exposure pathways are defined as the means by which a contaminant moves in the environment from a source to an ecological receptor. For an ecological exposure pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure. 15 Potential mechanisms of transformation of the parent are another area of consideration. Which degradates are formed in the environment, their potential concentrations, and their physiochemical and toxicological characteristics are examined.

Ecological receptors that may potentially be exposed to ametryn include terrestrial and semiaquatic wildlife ( i. e., mammals, birds, and reptiles), terrestrial and semi aquatic plants, and terrestrial soil and aquatic sediment invertebrates. Additionally, aquatic organisms ( i. e., freshwater and estuarine/ marine fish and invertebrates, amphibians, and aquatic plants) are potential receptors via exposure through the potential migration of ametryn from the application site through runoff and spray drift. The routes of exposure are considered and presented in the conceptual model ( Figure 2).

Table 3. Summary of Assessment and Measurement Endpoints for Ametryn.

Assessment Endpoint Measurement Endpoint Abundance ( i. e., survival, reproduction, and growth) of individuals and populations of birds a. Bobwhite quail acute oral LD50 b. Bobwhite quail and mallard duck subacute dietary LD50 c. Bobwhite quail and mallard duck chronic reproduction NOAEC and LOAEC Abundance ( i. e., survival, reproduction, and growth) of individuals and populations of mammals a. Laboratory rat acute oral LD50 b. Laboratory rat chronic NOAEC and LOAEC Survival and reproduction of individuals and communities of freshwater fish and invertebrates a. Rainbow trout and fathead minnow acute LC50 b. Fathead minnow chronic ( early life) NOAEC and LOAEC c. Water flea acute EC50 d. Water flea chronic ( life cycle) NOAEC and LOAEC Survival and reproduction of individuals and communities of estuarine/ marine fish and invertebrates a. Sheepshead minnow acute LC50 b. Estimated chronic NOAEC and LOAEC values based on the acute to chronic ratio for freshwater fish c. Mysid shrimp and Quahog clam acute LC50 Perpetuation of individuals and populations of nontarget terrestrial and semi aquatic species ( crops and non crop plant species) Monocot and dicot seedling emergence, seed germination, and vegetative vigor EC25 values Survival of beneficial insect populations Honeybee acute contact LD50 Maintenance and growth of individuals and populations of aquatic plants from standing crop or biomass Algal EC50 values for growth rate and biomass measurements LD 50 = Lethal dose to 50% of the test population. NOAEC = No observed adverse effect level. LOAEC = Lowest observed adverse effect level. LC 50 = Lethal concentration to 50% of the test population. 16 Ametryn Application to Foliage Ametryn Biolysis Chemolysis Spray Drift Runoff / Erosion Aquatic Environments Leaching / Subsurface Transport Dermal Uptake Gill Uptake Ingestion Aquatic Vertebrates / Invertebrates Terrestrial Environments Dermal Uptake Ingestion Birds / Mammals Direct Contact / Root Uptake Aquatic Plants Direct Contact / Root Uptake Terrestrial Plants EC 50/ EC 25 = Effect concentration to 50%/ 25% of the test population.

Figure 2. Conceptual model depicting ecological risk based on the proposed ametryn application to foliage.

The sources and mechanisms of release of ametryn are aerial and ground applications via foliar applications to crop and soil pre emergence applications. As ametryn exhibits moderate to high mobility in soils, surface water runoff and ground water percolation is expected from application sites. Spray drift from aerial applications to sugar cane may potentially transport ametryn to nontarget areas. Volatilization is not considered to be a viable release mechanism for ametryn.

Key Uncertainties and Data Gaps 17 The following uncertainties and information gaps were identified as part of the problem formulation. Except where indicated below, it is not clear whether additional data meant to clarify this points would lead to lesser or greater predictions of risk:

12. Chronic data for estuarine/ marine fish and invertebrates were not submitted by the registrant; therefore, measurement endpoints were estimated based on the acuteto chronic NOAEC ratio for freshwater fish or invertebrates, respectively. 13. Chronic data for estuarine/ marine invertebrates were not submitted by the registrant. 14. Risks to semiaquatic wildlife via consumption of pesticide contaminated fish were not evaluated. However, given that bioaccumulation of ametryn is low, ingestion of fish by piscivorus wildlife is not likely to be of concern 15. Surrogates were used to predict potential risks for species with no data ( i. e., reptiles and amphibians). It was assumed that use of surrogate effects data is sufficiently conservative to apply the broad range of species within taxonomic groups. If other species are more or less sensitive to ametryn and its degradates than the surrogates, risks may be under or overestimate, respectively. 16. Additional environmental fate data would allow refinement of the exposure assessment through the replacement of default assumptions with this data. For instance, the aerobic aquatic metabolism half life used in the assessment was estimated, in the absence of data, as twice the 90th percentile on the mean of the aerobic soil metabolism study data. Actual data could provide a half life well below that value of 504 days. Since the default half lives in the the exposure models leads to a simulated year to year accumulation in the standard pond scenario, lower half lives could lead to significantly lower risk quotients, perhaps changing the conclusion of the aquatic risk assessment. 17. For terrestrial exposure, foliar dissipation data would replace the conservative default assumption of 35 days. This could lead to a significant reduction in predicted risk to birds and mammals through ingestion of treated feed. 18. Ecological effects data are not available for ametryn degradates, and they are not included in the ecological risk assessment. Due to the persistence of ametryn in laboratory studies, the only degradation product observed at > 10% of total residues was 2 ethylamino 4 amino 6 methylthio s triazine ( GS 11355), observed at 12.2% 14 days post application in an aerobic soil metabolism study ( MRID 41752401). The Health Effects Division suggested that this thiomethyl metabolite be included in the drinking water exposure assessment, both in light of the amount formed, and because its structural similarity to parent ametryn suggests it is of possible toxicological concern to humans. Because another minor thiomethyl metabolite, 2 amino 4 isopropylamino 6 methylthio s triazine ( GS 11354), is also formed through aerobic soil metabolism of ametryn, it is included in the drinking water exposure assessment along with GS 11355. 19. PRZM/ EXAMS modeling simulates estimated ecological concentrations ( EECs) in a standard pond resulting from runoff from agricultural fields and spray drift. The 18 applicability of these runoff models to the highly managed hydrology of the Everglades Agricultural Area is uncertain, leading to uncertainty in the EECs for Florida sugarcane. In addition, PRZM EXAMS scenarios for Hawaii and Puerto Rico have not been developed; the potential screening EECs in these areas are assumed to be similar to those predicted for Florida and Louisiana.

ENVIRONMENTAL FATE AND TRANSPORT CHARACTERIZATION Based on the submitted environmental fate data, its physio chemical properties, the proposed use patterns, and information found in the published literature, ametryn is, in general, expected to be a persistent compound that exhibits moderate to high mobility in most soils except for clay where its mobility is low. Table 4 summarizes the physio chemical properties of ametryn. More complete information on the environmental fate studies can be located in APPENDIX B.

Ametryn is persistent in the environment. Photolysis half lives on soil surfaces and in water were 85 123 days ( MRIDs 41169602, 41169603) and 368 days ( MRID 41169601), respectively. Ametryn did not hydrolyze in sterile buffer solutions at 25 oC at pH 5, 7, and 9 ( MRID 40995812), suggesting that it is stable to hydrolysis under environmental conditions. The main route of degradation appears to be aerobic degradation with an observed half life of 84 days in a sandy loam held at a constant temperature of 25 oC during a laboratory controlled study ( MRID 41752401).

Based on packed soil columns leaching studies, ametryn is likely to be mobile in sandy loams and loam soil, but relatively immobile in clays with high organic matter content ( MRID 41169604). Approximately 40% of the applied radioactivity was found in either the leachate, or the soil column at depths greater than 3 inches for the sand, loam, and sandy loam; while over 90% of the applied radioactivity was detected in the upper 1 inch of the clay packed column. The mobility did not appear to be dependent upon the percentage of organic matter, clay content, or cation exchange capacity ( CEC) of the soils. In a second study, Freundlich adsorption coefficients of 26.16, 1.09, 1.07, and 1.21 were measured for a clay, sandy soil, sandy loam, and loam soil, respectively ( MRID 40995813). Using the linear portion of the adsorption isotherm and accounting for the percentage of organic carbon, organic carbon partition coefficient ( K oc) values were 927, 205, 96, and 257 for the clay, sandy soil, sandy loam, and loam soil, respectively. These K oc values suggest that ametryn has high to moderate mobility in all the soils except for the clay where its mobility is low. These data also suggest that adsorption to suspended solids and sediment in the water column will be limited. Ametryn has a low vapor pressure ( 2.74x10 6 mm Hg) at room temperature and is unlikely to volatilize significantly from soil surfaces. 19 The only degradation product observed at > 10% of total residues was 2 ethylamino 4 amino 6 methylthio s triazine ( GS11355), observed at 12.2% 14 days post application in an aerobic soil metabolism study ( MRID 41752401). Similar to the parent, ametryn's degradation products are persistent and relatively mobile in many soils and should be considered possible groundwater contaminants. Degradation products of other triazine herbicides, such as atrazine, have been identified as among the most frequent ground water contaminants of any pesticide residue.

In column studies using a sandy loam, the degradation product, 2 ethylamino 4 isopropylamino 6 hydroxy s triazine ( GS 34048) was identified throughout the column, as were degradation products 2 amino 4 isopropylamino 6 methylthio s triazine ( GS 11354), 2 ethylamino 4 amino 6 methylthio s triazine ( GS11355), 2,4 diamino 6 methylthio s triazine ( GS 26831), 2 ethylamino 4 isopropylamino s triazine ( GS 32083), and 2 amino 4 isopropylamino s triazine ( GS 28304). Two minor degradation products were also identified: 2,4 Diamino 6 hydroxy s triazine ( GS 17791) and 2 Amino 4 isopropylamino 6 hydroxy s triazine ( GS 17794). Very little CO 2 evolution ( 2%) was observed from ametryn treated soil 84 days post application. Neither ametryn nor its degradation products are considered volatile.

Three terrestrial field dissipation studies have been submitted to the Agency, all of which were characterized as " supplemental". The half lives for ametryn in these studies ranged from 35 to 62 days. Degradates GS 34048, GS 17794, and GS 11354 were included among the analytes in these studies. Parent ametryn was not detected in these studies at depths below 12 inches. Degradate GS 34048 was detected at low concentrations at all depths sampled ( to 48 inches) in two of three studies.

Table 4. General fate and physical chemical properties of ametryn based on information submitted by the registrant.

PARAMETER VALUE SOURCE Chemical Name Ametryn

Chemical Name ( CAS) N ethyl N '( 1 methylethyl) 6 ( methylthio) 1,3,5 triazine 2,4 diamine CAS Registry No.: 834 12 8 Molecular Formula C 9 H 17 N 5 S Molecular Weight 227.3

Water Solubility ( 25 oC) 185 mg/ L MRID 40995812 Vapor Pressure ( 25 oC) 2.74 x 10 6 mmHg MRID 40995812 Hydrolysis Half life ( pH 5, 7, 9; 25 oC) stable MRID 40885812 Aqueous Photolysis Half life ( pH 7) t1/ 2 = 368 days MRID 41169601 Soil Photolysis Half life t1/ 2 = 85 123 days MRIDs 41169602, 41169603 Aerobic Soil Metabolism Half life t1/ 2 = 84 days MRID 41752401 Anaerobic Soil Metabolism Half life stable MRID 41752401 PARAMETER VALUE SOURCE Chemical Name Ametryn

Chemical Name ( CAS) N ethyl N '( 1 methylethyl) 6 ( methylthio) 1,3,5 triazine 2,4 diamine CAS Registry No.: 834 12 8 Molecular Formula C 9 H 17 N 5 S Molecular Weight 227.3

Water Solubility ( 25 oC) 185 mg/ L MRID 40995812 Vapor Pressure ( 25 oC) 2.74 x 10 6 mmHg MRID 40995812 Hydrolysis Half life ( pH 5, 7, 9; 25 oC) stable MRID 40885812 Aqueous Photolysis Half life ( pH 7) t1/ 2 = 368 days MRID 41169601 Soil Photolysis Half life t1/ 2 = 85 123 days MRIDs 41169602, 41169603 Aerobic Soil Metabolism Half life t1/ 2 = 84 days MRID 41752401 20 Organic Carbon Partition Coefficient ( Koc) 927, 205, 96, 257 MRID 40995813 Soil Partition Coefficient ( Kd, mL/ g) 26.16, 1.09, 1.07, 1.21 MRID 40995813 Bioconcentration Factor ( BCF) in fish No Data

WATER RESOURCES ASSESSMENT This section identifies the data used as the source of the input parameter values, as well as the actual input parameter values, used in modeling to determine the Estimated Drinking Water Concentrations ( EDWC) for the drinking water assessment and the Estimated Environmental Concentrations ( EEC) for the ecological risk assessment; and specifies which values are to be used as EDWCs or EECs for the two risk assessments.

In determining surface water EDWCs for the drinking water assessment and the EECs for the ecological risk assessments, OPP utilized the Tier II screening models PRZM/ EXAMS; groundwater EDWCs for the drinking water assessment were generated using the screening model SCI GROW. Reported values are chosen to represent the maximum estimated contamination levels resulting from the labeled uses. The general fate and physical chemical property data used as the source of the input parameter values for modeling were obtained from the guideline studies and other submissions from the registrant.

Surface Water 21 The EDWCs/ EECs for surface water bodies were determined using the Tier II screening level simulation models PRZM ( v. 3.12; input generated by PE4VO1. pl, dated 8/ 8/ 03) and EXAMS ( 2.98.04). Table 5 presents parameter values utilized for PRZM/ EXAMS modeling for the four use scenarios for which surface water modeling was conducted. Input parameters representing the chemical properties of ametryn were chosen consistent with the EFED guidance document " Guidance for Chemistry and Management Practice Input Parameters For Use in Modeling the Environmental Fate and Transport of Pesticides." Model results are also sensitive to simulation of agronomic practices, such as application method and application dates. Such input parameters were chosen by consulting the product label, USDA crop profiles for each state, or in the case of Florida sugarcane, consulting the Palm Beach County Extension ( Curtis Rainholt, Regional Extension Agent, University of Florida Institute of Food and Agricultural Sciences, personal communication).

Potential contaminants of concern considered in the drinking water exposure assessment are parent ametryn and the degradates 2 amino 4 isopropylamino 6 methylthio s triazine ( GS 11354) and 2 ethylamino 4 amino 6 methylthio s triazine ( GS 11355). These metabolites, which are primarily formed through aerobic soil metabolism of ametryn, were identified by the Health Effects Division as being of possible toxicological concern based on their structural similarity to parent ametryn; no data are available to assess the toxicity of these degradates, though.

The EECs calculated for the ecological risk assessment are based on data for parent ametryn alone. No toxicity data is available for the degradates. Given the persistence of ametryn, however, the aerobic soil metabolism half life for total toxic residues in a single study was not much longer than for ametryn alone ( 91 vs 84 days). Additional information on the models PRZM and EXAMS can be located at: http:// www. epa. gov/ oppefed1/ models/ water/.

Modeling scenarios were chosen for this assessment based on nationwide distribution of ametryn use. These scenarios are intended to represent ametryn use on the crop in locations simulated, and to serve as surrogates for other areas in which those crops are grown:

Ametryn is applied to corn mostly in southeastern states, particularly North Carolina and South Carolina, with some use in Georgia and Texas. Small amounts are also used in midwestern states ( WI, OH, IL). Therefore, corn scenarios for eastern and western North Carolina were chosen to reflect the predominant use of ametryn on corn in the southeastern United States.

Sugarcane use occurs mostly in Florida, with some use also in Hawaii, Texas and Louisiana. Standard scenarios are available for Florida and Louisiana sugarcane, and the simulations with these scenarios modeled ametryn applications according to the labels for those states. As described below, drinking water in Hawaii is predominantly derived from ground water, and the DWEC calculated with the screening model SCI GROW is recommended for Hawaii sugarcane. Surface water is the main source of drinking water in the Texas sugarcane region; the DWECs from the Florida and Louisiana scenarios are recommended as surrogates for sugarcane in Texas.

Ametryn is applied to pineapple in Hawaii and in Puerto Rico. The ground water DWEC from SCI GROW is recommended for Hawaii pineapple. No PRZM scenario is currently available for 22 Puerto Rico. The DWECs from the Florida and Louisiana sugarcane scenarios are recommended as screening surrogates for pineapple in Puerto Rico, since the higher concentrations from these scenarios make them more conservative surrogates than the corn scenarios, and because the weather data for Louisiana and Florida should be better surrogates for Puerto Rico than data from North Carolina.

Table 5. PRZM/ EXAMS input parameter values for ametryn.

Parameter Value Source Application Rate ( lb a. i./ A/ application) NC corn ( east): 2 NC corn ( west): 2 FL sugarcane: 1.2 LA sugarcane: 2.4 Maximum label rates, Product label for ` Evik DF' ( Syngenta)

Number of Applications NC corn ( east): 1 NC corn ( west): 1 FL sugarcane: 3 LA sugarcane: 5 Maximum label rates, Product label for ` Evik DF' ( Syngenta)

Interval Between Applications ( days) NC corn ( east):  NC corn ( west):  FL sugarcane: 30 LA sugarcane: : 30 Product label for ` Evik DF' ( Syngenta)

Application Type and Depth of Incorporation ( cm) ground spray: 0 aerial: 0 Input parameter guidance Date of First Application NC corn ( east): April 18th NC corn ( west): April 18th FL sugarcane: February 15th LA sugarcane: August 23rd Organic Carbon Partition Coefficient ( K oc; mL/ g) 371 ( average of K oc) MRID 40995812 Aerobic Soil Metabolism Half life ( days) 252 ( ametryn parent) 273 ( total toxic residues for DW assessment) MRID 41752401 input value is three times the aerobic soil metabolism half life ( 90th percentile on mean for a single value)

Spray Drift Fraction ( aerial spray) ground: 0.01 ( eco) 0.064 ( dw) aerial: 0.05 ( eco) 0.16 ( dw) Input parameter guidance Application Efficiency ground: 0.99 aerial: 0.95 Input parameter guidance Molecular Weight ( g/ mole) 227.. 3 MRID 40995812 Vapor Pressure ( Torr) 2.74 x 10 4 MRID 40995812 Solubility in Water at 25oC ( ppm) 1850 input value based on 10 times the water solubility value reported in MRID 40995812 as per input parameter guidance ( Table 2.5)

Aerobic Aquatic Metabolism Half life ( days) 504 ( ametryn) 546 ( total toxic residues) input value is 2 times the aerobic soil metabolism halflife input value ( as per input parameter guidance, Table 2.5).

Hydrolysis Half life @ pH 7 ( days) stable MRID 40885812 Aquatic Photolysis Half life @ pH7 ( days) 368 MRID 41169601 23 Drinking Water EDWCs ( Surface Water)

The EDWCs recommended by OPP for use in the human health risk assessment for ametryn are presented in Table 6. PRZM/ EXAMS modeling was performed for corn scenarios in North Carolina, and sugarcane scenarios in Florida and Louisiana. Scenarios have not been developed for pineapple in Hawaii or Puerto Rico. However, since most drinking water in Hawaii use areas is derived from ground water supplies, recommended EDWCs for pineapple and sugarcane uses in Hawaii are those calculated using the ground water screening model SCI GROW2 ( which does not require specific use scenarios).

When estimating surface water DWEC's, model output concentrations are adjusted with percent cropped area factors ( PCAs). The PCAs used represent the maximum areal fraction that any HUC 8 watershed in the United States is planted to the crop of interested. The PCA for corn is 0.46, which is consistent with a HUC 8 watershed in Illinois. For crops which do not currently have a crop specific PCA, the national default of 0.87 is used, which represents the HUC 8 watershed with the greatest areal fraction planted to any crop nationally.

Because the use areas for the three crops treated with ametryn are distinct from one another, they are unlikely to be co located. Therefore, the DWECs for each crop can be considered separately for the human dietary risk assessment. The DWECs below for the scenarios modeled reflect values from PRZM/ EXAMS which have been adjusted with regional percent cropped area factors. The regional PCAs used represent the maximum areal fraction that any HUC 8 watershed in the particular major basin ( HUC 2 watershed) of the United States is planted to the crop of interest.

As described above, the sugarcane simulations for Louisiana and Florida are recommended as surrogates for sugarcane in Texas and Puerto Rico, and the corn simulations in North Carolina are recommended as surrogates for the less common corn use elsewhere in the country. The regional PCA factors for Florida, Louisiana and North Carolina do not apply to those outside areas. Therefore, the DWECs adjusted with the default national PCAs should be used for dietary exposure assessments for these other areas.

Table 6. Surface water DWECs based on ametryn use on sugarcane and corn, adjusted for regional PCAs.

Scenario Region Regiona l PCA 1 in 10 year acute ( ppb) 1 in 10 year chronic ( ppb) 30 year daily average ( ppb)

Florida sugarcane South Atlantic Gulf 38% 96 19 12 Louisiana sugarcane Lower Mississippi 85% 362 92 73 24 Eastern North Carolina corn South Atlantic Gulf 38% 23 7.3 4.7 Western North Carolina corn Tennessee 38% 22 7.6 5.4 The DWEC's below are adusted with national scale PCA's, and are recommended for ametryn uses for which the modeled scenarios serve as surrogates ( such as Texas sugarcane, midwest corn, and Puerto Rico sugarcane and pineapple). The PCAs used represent the maximum areal fraction that any HUC 8 watershed in the United States is planted to the crop of interested. The PCA for corn is 0.46, which is consistent with a HUC 8 watershed in Illinois. Since a cropspecific PCA has not been derived for sugarcane, the national default of 0.87 is used, which represents the HUC 8 watershed with the greatest areal fraction planted to any crop.

Table 7. Surface water EEC's for drinking water exposure assessment based on ametryn use on sugarcane and corn, adjusted with national PCA's Scenario Surrogate for: 1 in 10 year acute ( ppb) 1 in 10 year chronic ( ppb) 30 year daily average ( ppb)

Florida sugarcane Puerto Rico crops 219 44 27 Louisiana sugarcane Puerto Rico crops 371 94 75 Eastern North Carolina corn Midwestern corn 28 8.8 5.7 Western North Carolina corn Midwestern corn 26 9.2 6.6 Ground Water Estimates for groundwater concentrations were made using the Tier I screening model SCIGROW2 ( Screening Concentrations in Ground Water). SCI GROW2 is based on a regression approach which relates ground water concentrations measured in prospective ground water monitoring studies to the aerobic soil metabolism rate and soil water partitioning properties of the chemical. The model provides a groundwater exposure value to be used in determining the potential risk to human health from drinking water contaminated with the pesticide. SCI GROW2 estimates likely groundwater concentrations if the pesticide is used at the maximum allowable rate in areas where groundwater is vulnerable to contamination. Characteristics of such vulnerable areas include high rainfall, rapidly permeable soil, and a shallow aquifer. In most cases, a large majority of the use area will have groundwater that is less vulnerable to contamination than the areas used to derive the SCI GROW2 estimate. Input parameter values utilized for SCI GROW2 are presented in Table 8. The aerobic soil metabolism half life shown accounts for the degradation of parent ametryn plus degradates of concern GS 11354 and GS 11355. The result of the SCI GROW modeling for the seven use scenarios are presented in Table 9.

Table 8. SCI GROW2 input parameter values for ametryn. 25 Parameter Value Source Maximum Application Rate ( lb a. i./ A/ application) corn: 2 pineapple: 7.2 sugarcane: varies by state Maximum label rates, Product label for ` Evik DF' ( Syngenta)

Maximum Number of Applications per Year corn: 1 pineapple: 1 sugarcane: varies by state Maximum label rates, Product label for ` Evik DF' ( Syngenta)

Aerobic Soil Metabolism Half life ( days) 91 ( total toxic residues) MRID 41752401 Organic Carbon Partition Coefficient ( K oc) 96 Input value is lowest value of four reported values in MRID 40995813 as per input parameter guidance Table 9. Ground water EDWCs based on ametryn use on sugarcane, pineapple and corn.

Scenario Ground water concentration ( ppb)

Florida sugarcane 4.7 Louisiana sugarcane 15.1 Texas sugarcane 7.8 Puerto Rico sugarcane 21 Hawaii sugarcane 15.6 Hawaii pineapple 9.4 Corn 2.6 Monitoring Data Since ametryn was not included among the analytes in the National Water Quality Assessment NAWQA program, surface water monitoring data are limited. Some monitoring data are available, but the frequency of the sampling is not sufficient for the estimation of potential acute exposure, nor extensive enough to allow a conservative estimate of potential chronic exposure. The monitoring data and hydrology information described below is important, however, to help put the modeling results described above in perspective.

Florida Sugarcane Sugarcane in Florida is grown in the Everglades Agricultural Area, which is located to the south and east of Lake Okeechobee, and north of the Florida Everglades ( Figure 3). The South Florida Water Management District ( SFWMD), the State of Florida, and the United States Army Corps of Engineers ( USACE) have worked to maintain the viability of the EAA as cropland and to control and reduce transport of agricultural chemicals ( particularly phosphorus) into Lake Okeechobee and the Everglades. This is being accomplished through the adoption of Best Management Practices ( BMPs) in agriculture, and through the extensive engineering involved in the Comprehensive Everglades Restoration Plan ( CERP). 26 Figure 3: The Everglades Agricultural Area 27 While the Best Management Practices are intended mainly for sediment control and phosphorus reduction, they may also serve to reduce pesticide transport. For instance, farmers in south Florida pump water from their fields during a normal rainy season ( June to November) into drainage canals to prevent damage to their crops ( Ken Todd, Water Resource Manager Palm Beach County, personal communication, 2002). One BMP recommends waiting for the first inch of rainfall to occur before pumping, to reduce particulates and ( to some extent) phosphorus discharge. BMPs which extend holding time, or settle organic matter from agricultural water, can allow time for pesticide degradation or reduce transport of entrained pesticides.

Water management to achieve these goals is accomplished through pumping of water into and out of drainage canals. In order to maintain the viability of sugarcane in the EAA, the water table must be maintained at a depth of at least 6 to 12 inches below ground surface. Ground water pumped from the EAA is directed through a series of private canals to four main public drainage canals which bring water out of the EAA: the Miami Canal, the North New River Canal, the Hillsboro Canal, and the West Palm Beach Canal.

The water from each of the public drainage canals is directed through constructed wetlands known as Stormwater Treatment Areas ( STAs). Each STA is a collection of constructed wetlands built to meet phosphorous loading goals established by the CERP. The retarded flow of water through the STAs, although designed to reduce phosphorous levels, should also reduce the load of pesticides leaving the EAA as well by providing more time for the pesticides to degrade. Since ametryn degrades slowly relative to water movements in the canals, and it does not bind too strongly to sediments, this may be a less efficient removal mechanism for ametryn than for phosphorous.

The SFWMD includes pesticides among the analytes it monitors in surface water samples taken at the inflow and outflow points of the public canals. Monitoring results from quarterly sampling between 1998 and 2003 indicate that, despite traveling through the canals of the EAA, or constructed wetlands, ametryn is still detectable in the water of the drainage canals.

The concentrations reported in these monitoring studies are significantly less than those resulting from PRZM EXAMS simulation modeling. This can be accounted for, in part, by the dissimilarity of the PRZM/ EXAMS reservoir modeling scenario to the hydrology of the EAA. Some reduction in concentrations would be expected from flow to and through the STAs. Also, the monitoring of ametryn by the SFWMD is for parent only, and does not include the metabolites of potential toxicological concern.

In addition, while the modeling results appear to be a conservative estimate, the lesser concentrations in the monitoring may also be due to the frequency of sampling in the monitoring program. Quarterly sampling is not sufficient to establish potential acute drinking water concentrations of ametryn. By possibly missing peak concentrations of ametryn in surface water, chronic concentrations that could be calculated with the monitoring data should also be considered a rough estimate. 28 The highest concentrations detected in the quarterly sampling ( up to 0.7 ppb) occurred during the winter and early spring. Ametryn is applied as a post emergent pesticide to sugarcane, and would most likely be applied during that period. Florida sugarcane is planted from September to February, although emergence of the ratoon crops could lead to treatment at other times. The use closure memo for ametryn indicated that treatment of sugarcane in Florida occurs 3 times per year, with a minimum 30 day interval.

Another uncertainty in the drinking water assessment for ametryn use on Florida sugarcane stems from the location of drinking water sources in relation to the EAA. Drainage canals from sugarcane fields are not used directly for drinking water, but water from drainage canals eventually feeds water bodies used in southern Florida for drinking water supply.

The Everglades Restoration Plan includes Water Preserve Areas in the current Water Conservation Areas, which will be used in part to redirect water away from the coast, restoring flow through the Everglades. The city of West Palm Beach derives part of its water supply from the drainage canal L 8, which passes through the Water Conservation Area. Water from this canal is diverted to M Canal, which travels through 25 square miles of water catchment and wetlands and into Clear Lake, where the CWS for West Palm Beach is located. The distance from L 8 to Clear Lake is about 22 miles.

Three community water systems ( CWS) draw from the southern end of Lake Okeechobee. Water flows from Lake Okeechobee predominantly through the Caloosahatchee River to the west, the St. Lucie River to the east, and south through the EAA toward the Everglades ( South Florida Water Management District, http:// www. sfwmd. gov/ org/ wrp/ wrp_ okee/ 2_ wrp_ okee_ info/ maps/ homepagemap. html). The South Florida Water Management District ( SFWMD) tightly manages water in this area to direct water where it is needed or for flood control. However, water may also be flushed back from the EAA into Lake Okeechobee, perhaps once every two years ( US Army Corps of Engineers, personal communication, 2002).

Louisiana Sugarcane According to the 1997 USDA Census of Agriculture, and information provided by registrant Syngenta, there is little use of ametryn on sugarcane in Louisiana. Monitoring studies support the supposition that concentrations of herbicides in surface water would decrease with decreasing use ( Scribner, et al, 2000). The results of the PRZM/ EXAMS modeling are an indication of the concentrations that could occur if the chemical is used according to the label, and may be conservative on a regional scale if few growers use ametryn on sugarcane in Louisiana.

A study of herbicide runoff from treated fields in Louisiana indicated that the soils and weather in the area are conducive to offsite transport ( Bengston and Selim, 2001). The study investigated the runoff from three types of applications of metribuzin and triazine herbicide atrazine between 1994 to 1999. The application types were a high rate broadcast ( 1.8 lb for atrazine, 2.0 for metribuzin), a " standard" application of half those rates in a 36 inch band over the row, and a low rate of 0.6 lb and 0.7 lb, respectively, in a 24 inch band. Atrazine was applied to the test field in January and 29 December, 1994. The average rate of atrazine loss in runoff for these treatments was 7.8, 5.7 and 5.0 percent of applied active ingredient for the high, standard and low application rates, respectively. Metribuzin was applied in the spring of 1994, 1995 and 1997, and had average loss in runoff of 3.5, 2.9 and 1.2 percent of applied active ingredient for the high, standard and low application rates, respectively.

In June, 1997, atrazine and metribuzin were applied 2 hours before the onset of a 75 year storm. Metribuzin was detected at maximum if 431 ppb the day of the storm, with 99% of the total loss ( 51% of applied) occurring that day. Total atrazine loss after the storm was only 4.5% of active ingredient applied, 88% of which occurred the first day. However, the maximum concentration of atrazine ( 85 ppb) was not observed until day 21; the day 0 concentration of atrazine was 30 ppb. The total loss of atrazine during this rare event was much less than that of metribuzin, and was not significantly different than that which can occur under normal, high precipitation conditions of Louisiana.

It is not clear that ametryn loss would be equivalent to that of atrazine, although both chemicals are triazine herbicides. The recent interim RED for atrazine describes it similarly persistent to ametryn ( aerobic soil metabolism half life of " 3 to 4 months" compared to 84 days for ametryn), and slightly more mobile ( K d values < 1.0 for sand, sandy loam and loam soils, 2.49 on clay).

There are a number of community water supplies which draw from the Mississippi and Atchafalaya Rivers in the sugarcane production area of southern Louisiana ( Figure 4). Transport of pesticides in surface water is complicated by leveeing of the Mississippi River in Louisiana and the system of drainage canals in southern Louisiana. While agricultural areas around tributaries can potentially contribute to contamination of drinking water supplies, drainage from fields along leveed portions of the Mississippi River may follow the longer path through managed drainage canals to a potential drinking water supply.

Residents of the western portion of the Louisiana sugarcane area draw drinking water from the ground water of the Chicot aquifer of southwest Louisiana. This aquifer is a " sole source" aquifer that is susceptible to contamination ( Figure 5).

In order to comply with TMDL requirements, the Louisiana Department of Agriculture and Forestry ( LDAF) conducted surface water monitoring in 2002 and 2003 in the Barataria Basin, a major sugarcane production area. However, ametryn was not included among the analytes. Atrazine, another triazine herbicide, is " the most commonly used herbicide in sugarcane culture," and was detected at all 10 sites sampled. The highest concentrations found in monthly sampling were those most directly correlated with the times of use on sugarcane 30 Figure 4: Sugarcane production in Louisiana vs. ground water as drinking water supply 31 Figure 5: Sole source aquifers of EPA Region 6 32 Hawaii Pineapples Pineapple is produced primarily on the islands of Oahu and Maui. Public water supplies in Oahu are provided entirely by ground water. The deep volcanic rock aquifer in central Oahu and Honolulu supplies more than 90 percent of the island's public water supply and is designated as a Sole Source Drinking Water Aquifer by the USEPA. The aquifer is highly permeable and unconfined except near the coast ( see map, p. 20), making it vulnerable to contamination despite depths to water of hundreds of feet in most places. ( NAWQA Circular 1239).

Most public drinking water on Maui is also derived from ground water. The USGS reports that " in 1998, about 76 percent of the ground water supplied by the County of Maui Department of Water Supply ( DWS) to the island was from the Iao aquifer". A portion of the land which overlies the Iao aquifer, which lies on the flank of the West Maui Volcano, consists of sloping alluvial and colluvial plains extending east from the mountains. In the past, sugarcane was grown on these plains, " but presently the land is used for macadamia nuts, pineapple, papaya, or left fallow" ( Meyer and Presley, 2001).

Ametryn was included among the analytes in a ground water monitoring study in pineapple growing areas. Samples were collected by the Ciba Geigy Corporation from 1992 to 1994, and analyzed for residues of atrazine and ametryn. Ametryn degradates GS 11354, GS 26831 and rarely GS 11355 were also included as analytes. Ametryn was rarely detected in ground water samples, although the maximum concentration detected was 7.6 ppb. Degradates of ametryn were not detected in any sample. The total toxic residue concentration calculated by SCI GROW for this annual application rate is 9.8 ppb.

Ground water in Hawaii is particularly vulnerable to contamination from agricultural chemicals. The USGS NAWQA program reports that, " although overlying rock is weathered to depths of 50   200 feet ( Hunt, 1996), this soil and clay rich overburden does not prevent downward migration of chemicals applied or spilled at land surface." A recent ground water monitoring program on Oahu confirmed the correlation of land use with the types of organic chemicals detected. However, radioisotope dating indicated that most ground waters in the 30 public supply wells sampled were last in contact with air ( at or above the water table) sometime between 1950 and 1980 ( Hunt, 2004). Therefore, detections of herbicides in present and former agricultural areas reflect pesticide applications of several decades past. Three herbicides introduced to the island since 1990 were only detected in samples from 15 monitoring wells sampled to study contamination of more recently recharged ground water.

Ametryn was not included among the analytes in this study. Atrazine, however, was detected in 57 percent of the public supply wells, and 93 percent of the monitoring wells. Atrazine degradates were also detected in as many as 23% of the supply wells, and 47% of the monitoring wells. Most other pesticides detected followed the pattern of a higher detection rate in the shallower monitoring wells. The results of this study suggest that use of herbicides such as ametryn may lead to long term, low concentration contamination of public supply wells on Oahu. 33 AQUATIC EXPOSURE ASSESSMENT EECs for Ecological Risk Assessment Table 10 displays peak, 21 day maximum and 60 day maximum surface water concentrations predicted using PRZM/ EXAMS. There is some uncertainty in the results of the modeling shown below since there are not sufficient data available describing the persistence of ametryn. As shown in Table 5, the aerobic soil metabolism half life used in the modeling was derived by multiplying the single available half life by a factor of three ( approximating the 90th percentile on the mean). Since aerobic aquatic metabolism data are not available for ametryn, the default model input was derived by multiplying the aerobic soil metabolism input by a factor of two. The resulting half lives used in the EEC modeling were 252 and 504 days, respectively.

Since outflow is not simulated from the standard pond as it is for the index reservoir for estimated drinking water concentrations, these long half lives result in an accumulation of ametryn in the standard pond over the 30 year simulation. Additional data on the aerobic soil metabolism and aerobic aquatic metabolism of ametryn would allow modeling of possible concentrations without the use of default input parameters for ametryn persistence. If the submitted half lives are shorter than the calculated default values, the predicted aquatic EECs could be significantly lower.

Table 10. Surface water 1 in 10 year 21 day and 1 in 10 year 60 day concentrationsa ( in ppb) of ametryn for ecological risk assessments Crop Application Rate ( lb ai/ acre) Peak ( ppb) 1 in 10 Year 21 day ( ppb) 1 in 10 Year 60 day ( ppb)

NC corn ( east) Surface water 2 84 82 80 NC corn ( west) Surface water 2 78 77 75 FL sugarcane Surface water 1.2 ( 3x, 30 day interval) 309 302 295 LA sugarcane Surface water 2/ 2.4 ( x4) ( 30 day interval) 792 759 755 a concentrations predicted using PRZM/ EXAMS model.

Spray Drift Since aquatic plants are very sensitive to ametryn, spray drift exposure estimates were refined using the spray drift model AgDrift ( v. 2.01). Default drift assumptions used in PRZM/ EXAMS simulate 5% and 1% at 100 feet from the edge of a treated field for aerial and ground applications, respectively. AgDrift allows the user to estimate the concentration of a chemical that could occur in an adjacent pond or wetland from instantaneous incorporation of spray drift at points as far as 999 feet from the treated field. 34 Tables 11 and 12 show the estimated concentration in a pond or wetland at varying distances from the aerial application of ametryn to sugarcane, using a Tier 1 AgDrift simulation. Sugarcane is the only crop for which aerial application is allowed. Tables 13 and 14 show the rate of deposition at varying distances from ground application of ametryn to sugarcane, corn and pineapple. The estimates for each crop are based on the maximum single application that can be made according to ametryn product labels. For crops that have multiple applications per season, the maximum exposure could be greater, if plants treated with the first application survive and are exposed to additional applications. Since wind direction and velocity will not necessarily be the same each time a chemical is applied, it is not certain that plants exposed during the first application would be exposed to the second application.

Table 11. Estimated concentration of ametryn in a nearby pond through spray drift from a single application at varying distance from the edge of field ( aerial spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Pond 0 feet 50 feet 100 feet Sugarcane ( FL) 1.2 8.5 5.0 3.4 Sugarcane ( HI) 7.2 51 30.0 20.6 Sugarcane ( LA) 2.4 17.0 10.0 6.9 Sugarcane ( PR) 8 56.7 33.3 22.9 Sugarcane ( TX) 2 14.2 8.3 5.7 Table 12. Estimated concentration of ametryn in a nearby wetland through spray drift from a single application at varying distance from the edge of field ( aerial spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Wetland 0 feet 50 feet 100 feet Sugarcane ( FL) 1.2 113 67 46 Sugarcane ( HI) 7.2 681 400 275 Sugarcane ( LA) 2.4 227 133 92 Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Wetland 0 feet 50 feet 100 feet 35 Sugarcane ( PR) 8 756 444 305 Sugarcane ( TX) 2 189 111 76 Table 13. Estimated concentration of ametryn in a nearby pond through spray drift from a single application at varying distance from the edge of field ( ground spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Pond 0 feet 50 feet 100 feet Sugarcane ( FL) 1.2 1.8 0.5 0.4 Sugarcane ( HI) 7.2 10.8 3.1 2.2 Sugarcane ( LA) 2.4 3.6 1.0 0.7 Sugarcane ( PR) 8 12.0 3.4 2.4 Sugarcane ( TX) 2 3.0 0.9 0.6 Corn 2 3.0 0.9 0.6 Pineapple 7.2 10.8 3.1 2.2 Table 14. Estimated concentration of ametryn in a nearby wetland through spray drift from a single application at varying distance from the edge of field ( ground spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Wetland 0 feet 50 feet 100 feet Sugarcane ( FL) 1.2 24 6 4 Sugarcane ( HI) 7.2 144 40 29 Sugarcane ( LA) 2.4 48 13 9 Crop ( State) Max. Single Application Rate lbs. a. i./ A Concentration of Ametryn ( ppb) at Specified Distance From Edge of Field In a Nearby Wetland 0 feet 50 feet 100 feet 36 Sugarcane ( PR) 8 160 45 32 Sugarcane ( TX) 2 40 11 8 Corn 2 40 11 8 Pineapple 7.2 144 40 29 The Tier 1 scenario assumes a 10 mph wind during application, a 10 foot release height for aerial applications, and a default spray droplet size ( fine to medium for aerial application, very fine to fine for ground application). Specific label language which proscribes certain spray practices would allow a refinement of the exposure assessment.

TERRESTRIAL EXPOSURE ASSESSMENT Foliar Applications and Residues Exposure to feed items for terrestrial animals was evaluated using estimated environmental concentrations generated from a spreadsheet based model ( Ell FATE) that calculates the decay of a chemical applied to foliar surfaces for single or multiple applications. The model uses the same principle as the batch code models FATE and TERREEC for calculation of terrestrial estimated exposure concentrations ( TEEC) on plant surfaces following application. Further explanation of the model is presented in APPENDIX E.

The terrestrial exposure assessment is based on the methods of Hoerger and Kenaga ( 1972) as modified by Fletcher et al. ( 1994). Terrestrial estimated environmental concentrations ( EECs) for nongranular formulations were derived for ametryn use crops ( corn, pineapple, and sugarcane) using maximum application rates and minimum intervals between applications. The predicted maximum and mean residues of ametryn that may be expected to occur on selected avian or mammalian food items immediately following application for corn, pineapple, and sugarcane are presented in Table 15. Uncertainties in the terrestrial EECs are primarily associated with a lack of data on interception and subsequent dissipation from foliar surfaces. When data are absent, as in this case, EFED assumes a 35 day foliar dissipation half life, based on the work of Willis and McDowell ( 1987).

Table 15. Estimated environmental concentrations on avian and mammalian food items ( ppm) following label specified applications of Ametryn to corn, pineapple, and sugarcane. 37 Crop Application Rate lbs. a. i./ A (# app / interval, days) Food Items Predicted Maximum Residue EEC ( ppm) 1 Predicted Mean Residue EEC ( ppm) 2 Corn 2 ( 1 / NA) Short grass 480 170 Tall grass 220 72 Broadleaf plants/ small insects 270 90 Fruits, pods, seeds, and large insects 30 14 Pineapple max 7.2 ( 1 / NA) Short grass 1728 612 Tall grass 792 259 Broadleaf plants/ small insects 972 324 Fruits, pods, seeds, and large insects 108 50 Sugarcane FL 1.2 ( 3 / 30) Short grass 535 189 Tall grass 245 80 Broadleaf plants/ small insects 301 100 Fruits, pods, seeds, and large insects 33 16 Sugarcane HI 7.2 / 2.4 / 2.4 ( 3 / 30) Short grass 1728 612 Tall grass 792 259 Broadleaf plants/ small insects 972 324 Fruits, pods, seeds, and large insects 108 50 LA 2 / 2.4 ( x 4)

( 5 / 30) Short grass 1211 429 Tall grass 555 182 Broadleaf plants/ small insects 681 227 Fruits, pods, seeds, and large insects 76 35 PR 8 / 4 ( x2)

( 3 / 30) Short grass 2075 735 Tall grass 951 311 Broadleaf plants/ small insects 1167 389 Fruits, pods, seeds, and large insects 130 61 TX 2 ( 3 / 30) Short grass 891 316 Tall grass 408 134 Broadleaf plants/ small insects 501 167 Fruits, pods, seeds, and large insects 56 26 1 Predicted maximum and mean residues are based on Hoerger and Kenaga ( 1972) as modified by Fletcher et al. ( 1994). 2 Predicted mean residues from Fletcher et al.: Short grass = 85; Tall grass = 36; Broadleaf plants / insects = 45; and Seeds / fruits = 7 Exposure to Terrestrial Plants Terrestrial plants inhabiting dry and semi aquatic ( wetland) areas may be exposed to pesticides from runoff and/ or spray drift. The EEC values for potential nontarget terrestrial plant exposure from a non granular pesticide application were calculated using EFED's TerrPlant Excel worksheet ( Table 16). The exposure characterization to this group employs runoff and spray drift scenarios to estimate the amount of pesticide that could potentially move offsite. Exposure 38 calculations are based on a pesticide's water solubility and the amount of pesticide present on the soil surface within the first inch of soil depth. For dry areas, the loading of pesticide active ingredient from runoff to an adjacent nontarget area is assumed to occur from one acre of treatment to one acre of nontarget area. For semi aquatic areas, runoff is considered to occur from a larger source area with active ingredient loading originating from 10 acres of treated area to a single acre of nontarget wetland. Default spray drift assumptions are 1% for ground applications and 5% for aerial, airblast, forced air and chemigation applications. Ametryn is formulated as a flowable, wettable product and is meant to be sprayed. Ametryn's aerial application to sugarcane has the potential for high nontarget impact via spray drift, while its moderately high mobility and persistence can potentially cause non target impacts through runoff. Applied ametryn is assumed not to be incorporated, based on application method.

Table 16. Estimated Environmental Concentrations ( EECs) for applications of ametryn to terrestrial plants ( lbs a. i./ A).

Crop Application Rate lbs a. i./ A # app / interval, days Application Method Total loading to adjacent areas1 Total loading to semi aquatic areas2 Drift EEC3 Corn 2 ( 1 / NA) Ground spray 0.12 1.02 0.02 Pineapple 7.2 ( 1 / NA) Ground spray 0.43 3.67 0.072 Sugarcane FL 1.2 ( 3 / 30) Ground spray 0.07 0.61 0.01 Aerial spray 0.096 0.42 0.06 HI 7.2 / 2.4 / 2.4 ( 3 / 30) Ground spray 0.43 3.67 0.07 Aerial spray 0.58 2.52 0.36 LA 2 / 2.4 ( x4)

( 5 / 30) Ground spray 0.12 1.02 0.02 Aerial spray 0. 16 0.70 0.10 PR 8 / 4 ( x2)

( 3 / 30) Ground spray 0.48 4.08 0.08 Aerial spray 0.64 2.80 0.40 TX 2 ( 3 / 30) Ground spray 0.12 1.02 0.02 Aerial spray 0.16 0.70 0.10 1 EEC = Sheet Runoff + Drift 2 EEC = Channelized Runoff + Drift 3 for ground: application rate x 0.01; for aerial: application rate x 0.05 39 Spray Drift Since terrestrial plants are sensitive to ametryn, spray drift exposure estimates were refined using the spray drift model AgDrift ( v. 2.01). Default drift assumptions used in the TERR PLANT model simulate 5% and 1% at 100 feet from the edge of a treated field for aerial and ground applications, respectively. AgDrift allows the user to estimate the effective application rate in pounds of active ingredient per acre ( lb ai/ acre) of a chemical by spray drift at points as far as 999 feet from the treated field.

Table 17 shows the rate of deposition at varying distances from the aerial application of ametryn to sugarcane. Sugarcane is the only crop for which aerial application is allowed. Table 17 shows the rate of deposition at varying distances from ground application of ametryn to sugarcane, corn Table 17. Off target terrestrial exposure to ametryn through spray drift at varying distance from the edge of field ( aerial spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Rate of Ametryn Deposition ( lb ai/ acre) at Specified Distance From Edge of Field ( feet)

0 100 200 400 600 800 900 Sugarcane ( FL) 1.2 0.6 0.12 0.056 0.03 0.02 0.015 0.015 Sugarcane ( HI) 7.2 3.6 0.7 0.34 0.17 0.12 0.10 0.089 Sugarcane ( LA) 2.4 1.2 0.23 0.11 0.056 0.04 0.032 0.030 Sugarcane ( PR) 8 4 0.78 0.38 0.19 0.13 0.11 0.099 Sugarcane ( TX) 2 1 0.20 0.094 0.047 0.033 0.027 0.025 Table 18. Off target terrestrial exposure to ametryn through spray drift at varying distance from the edge of field ( ground spray)

Crop ( State) Max. Single Application Rate lbs. a. i./ A Rate of Ametryn Deposition ( lb ai/ acre) at Specified Distance From Edge of Field ( feet)

50 100 200 400 600 800 900 Sugarcane ( FL) 1.2 0.02 0.01 0.006 0.003 0.002 0.002 0.001 Sugarcane ( HI) 7.2 0.13 0.07 0.04 0.02 0.01 0.009 0.008 Sugarcane ( LA) 2.4 0.04 0.02 0.01 0.006 0.004 0.003 0.003 Crop ( State) Max. Single Application Rate lbs. a. i./ A Rate of Ametryn Deposition ( lb ai/ acre) at Specified Distance From Edge of Field ( feet)

50 100 200 400 600 800 900 40 Sugarcane ( PR) 8 0.14 0.08 0.04 0.02 0.01 0.01 0.009 Sugarcane ( TX) 2 0.04 0.02 0.01 0.005 0.003 0.003 0.002 Corn 2 0.04 0.02 0.01 0.005 0.003 0.003 0.002 Pineapple 7.2 0.13 0.07 0.04 0.02 0.01 0.009 0.008 and pineapple. The estimates for each crop are based on the maximum single application that can be made according to ametryn product labels. For crops that have multiple applications per season, the maximum exposure could be greater, if plants treated with the first application survive and are exposed to additional applications.

The spray drift estimates above were derived using Tier 1 terrestrial exposure assumptions in AgDrift. These include assumptions such as a spray release height of 10 feet for aerial application, applying spray with a fine to medium droplet size. Ground applications for Tier 1 assume a very fine to fine spray as a default, and both scenarios simulate application in a 10 mile per hour wind.

Language included on the ametryn product labels suggests best management practices to reduce spray drift from aerial application to sugarcane. These suggestions include an 800 foot buffer from " sensitive plants" when using a formulation of ametryn alone, or 500 feet for ametryn formulated with diuron. The label language also suggests use of " low drift nozzles," but a target droplet size is not specified.

ECOLOGICAL EFFECTS CHARACTERIZATION APPENDIX F discusses the 17 ecological toxicology studies submitted by the registrant for consideration: 82% were classified as core and having provided useful information toward fulfilling the required guidelines. The remaining ( 18%) studies were classified as supplemental.

Toxicity testing reported in this section does not represent all species of terrestrial or aquatic organisms. Only a few surrogate species for both freshwater fish and birds are used to represent all freshwater fish ( 2000+) and bird ( 680+) species in the United States. For mammals, acute studies are usually limited to Norway rat or the house mouse. Estuarine/ marine testing is usually limited to a crustacean, a mollusk, and a fish. Also, neither reptiles nor amphibians are tested. The assessment of risk or hazard makes the assumption that avian and reptilian toxicities are similar. The same assumption is used for fish and amphibians.

Ametryn is slightly toxic to mammals on an acute oral exposure basis ( LD 50 = 1162 mg/ kg bodyweight); following chronic exposure, reduced growth ( NOEC = 13 mg/ kg) was observed. 41 Ametryn is practically nontoxic to bees based on an acute contact study. No mortality was observed in subacute dietary toxicity studies with mallard ducks and bobwhite quail ( LC 50 > 5620 ppm). Both surrogate species responded similarly ( NOEC = 300 mg/ kg diet) with reduced growth and reproduction following chronic exposure ( Table 19).

Table 19. Summary of acute and chronic toxicity data for terrestrial organisms exposed to ametryn.

Species Acute Toxicity Chronic Toxicity LD 50 ( mg/ kg bw) Acute Oral Toxicity ( MRID) 5 day LC 50 ( ppm) Subacute Dietary Toxicity ( MRID) NOEC/ LOEC ( ppm) ( MRID) Affected Endpoints Northern bobwhite quail Colinus virginianus > 2250 practically nontoxic ( 409958 01) > 5620 practically non toxic ( 409958 03) 300 / 900 ( 415476 01) growth and reproduction Mallard duck Anas platyrhynchos   > 5620 practically non toxic ( 409958 02) 300 / 900 ( 415476 02) growth and reproduction Honey bee Apis meliferus > 0.1 ( mg/ bee contact) practically nontoxic ( 409958 11)

Laboratory rat Rattus norvegicus 1162 slightly toxic ( 409958 14)   21 / 145 mg/ kg/ d ( 406499 06, 411842 01, 403820 01)

13 / 130 mg/ kg/ d ( 403499 05) growth; testes, kidney, liver, pancreas effects pup weights and reduced weight gain Consistent with its chemical use as an herbicide, ametryn is toxic to terrestrial plants; dicots are more sensitive to ametryn than monocots, with lettuce ( EC 25 = 0.006 lb ai/ acre) and cucumbers ( EC 25 = 0.002 lb ai/ acre) being the most sensitive indicators in the vegetative vigor and seedling emergence tests, respectively. Table 20 summarizes the most sensitive toxicity endpoints calculated or observed in terrestrial plant toxicity studies.

Table 20. Summary of nontarget terrestrial phytotoxicity using both monocotyledon and dicotyledon plant species exposed to ametryn. a Study Type Species EC25 ( lb ai/ A) EC50 ( lb ai/ A) NOEC ( lb ai/ A) MRID Author, Year Vegetative Vigor Monocot  onion 0.105 dw 0.209 ph 0.05 dw 409958 09 Canez, 1998 Dicot  lettuce 0.006 dw 0.015 dw < 0.006 dw 409958 09 Canez, 1998 Study Type Species EC25 ( lb ai/ A) EC50 ( lb ai/ A) NOEC ( lb ai/ A) MRID Author, Year 42 Seedling Emergence Monocot  oat 0.083 dw 0.335 dw 0.05 dw 409958 08 Canez, 1998 Dicot  cucumber 0.002 pe 0.016 pe < 0.002 pe 409958 08 Canez, 1998 Dicot  lettuce 0.027 dw 0.093 dw 0.013 ph, dw 409958 08 Canez, 1998 Seed Germination Monocot  onion 25.9 pg 644 pg 2.0 pg 409958 07 Canez, 1998 Dicot  cabbage ND pg ND pg

8.0 all 409958 07 Canez, 1998 a For each toxicity endpoint, the parameter in which these concentrations were observed are listed. dw = dry weight, ph = plant height, pr = phytotoxicity rating, pe = percentage of seedlings emerged, rl = radicle length measurements, pg = percentage of seed germinated, all = all parameters measured; ND = not determined Table 21 summarizes the most sensitive endpoints used in the hazard assessment of aquatic animals. Ametryn is slightly to moderately toxic to freshwater fish and invertebrates, and moderately toxic to estuarine/ marine fish and invertebrates on an acute exposure basis. Following chronic exposure, freshwater fish exhibited reduced growth ( NOEC = 0.7 mg/ L) while freshwater invertebrates exhibited reduced reproduction ( Daphnia NOEC = 0.24 mg/ L).

Table 21. Summary of acute and chronic aquatic toxicity estimates using Ametryn.

Species Acute Toxicity Chronic Toxicity 96 hr LC 50 ( mg/ L) 48 hr EC 50 ( mg/ L) Acute Toxicity ( MRID) NOEC / LOEC ( mg/ L) Affected Endpoints ( MRID)

Rainbow trout Oncorhynchus mykiss ( TGAI) 3.6  moderately toxic ( 428616 02)

Fathead minnow Pimephales promelas 16  slightly toxic ( 428616 01) 0.7 / 1.4 Growth ( 411897 03, 423252 03)

Water flea Daphnia magna  28 slightly toxic ( 409958 06) 0.24 / 0.32 Reduced reproduction ( 411897 02, 423252 02)

Sheepshead minnow Cyprinodon variegatus 5.8  moderately toxic ( 411149 02) 0.25*

Mysid shrimp Mysidopsis bahia 2.3  moderately toxic ( 411149 01) 0.02**   * based on fathead minnow ACR of 22.9 ** based on daphnid ACR of 116.7 No chronic toxicity data were available for estuarine/ marine fish. A chronic toxicity value for sheepshead minnow is estimated from the results of the acute toxicity study, assuming that the acute/ chronic toxicity ratio ( ACR) is the same as that seen in the freshwater fathead minnow study ( 16 mgL 1/ 0.7 mg L 1 = 22.9). Based on this ACR, the estimated chronic toxicity to sheepshead minnow is 0.25 mg/ L). Similarly, the ACR from the freshwater invertebrate study is used to 43 estimate a chronic toxicity for estuarine/ marine invertebrates. Using the ACR from the Daphnia studies ( 28 mg L 1/ 0.24 mg L 1 = 116.7), a chronic toxicity value of 0.02 mg/ L is estimated for mysid shrimp.

Table 22 contains the aquatic plant registrant submitted data that were available for use in this assessment. Only one submitted study was available to evaluate the toxicity of ametryn to nonvascular aquatic plants.

Table 22. Summary of the toxicity of ametryn to aquatic plants.

Species EC50 ( µ g/ L) Acute toxicity ( MRID)

Green algae Pseudokirchneriella subcapitatum 3.67 ( NOEC = 1.14) very highly toxic ( 409958 10)

ECOTOX database OPP utilized the ECOTOX ( Ecotoxicology Database System) on line database to supplement the registrant submitted data for the parent compound as well as its degradates. ECOTOX is a comprehensive computer based system that provides single chemical toxic effect data for aquatic life, terrestrial plants and terrestrial wildlife derived predominately from peer reviewed literature. For a more in depth discussion of the ECOTOX on line database, see http:// www. epa. gov/ ecotox/.

ECOTOX contained 120 records covering acute toxicity studies examining ametryn effects on aquatic plants and animals. Of the 44 records for fish species, there were 19 records that specified tests similar to OPP's acute freshwater fish 96 hr LC 50 toxicity test ( Guideline 72 1). The LC 50 values reported in these records ranged from 0.3 mg/ L ( Poecilia reticulata, guppy) to 27 mg/ L ( Carassius carassius, Crucian carp). One amphibian, the Japanese toad ( Bufo japonicus), was listed in the database output and exhibited an LC 50 of 3.8 to 5.6 mg/ L. These data suggest that amphibians exhibit sensitivity roughly similar to freshwater fish. Additionally, there were four freshwater and marine snail studies with reported endpoints ranging from 6.0 to 6.8 mg/ L. These snails were less sensitive than the other invertebrate species for which data were submitted to the Agency.

Forty five records contained toxicity information on aquatic plants, both vascular and non vascular species. Two of those records reported 7 day EC 50 ( similar test to the registrant submitted nonvascular plant study) endpoints of 10 and 52 µ g/ l for the vascular species of duckweed Lemna perpusilla and Spirodela polyrhiza, respectively. While neither species is as sensitive to the guideline green algal study, these data are useful in this assessment as there was no vascular aquatic plant study submitted in support of the registration of ametryn.

Also, 26 aquatic plant records report short term photosynthesis inhibition toxicity tests on various species of algae and diatoms with an EC 50 range of 10 to 135 µ g/ l. While these data are useful in characterizing potential non target effects of ametryn, none of the reported endpoints were as sensitive as the guideline study with the green algae, Pseudokirchneriella subcapitatum. 44 The terrestrial database output contained 117 records covering acute toxicity studies to plants and animals. Twenty seven records listed were registrant submitted studies in support of the reregistration of ametryn. The balance of the output consisted of plant efficacy studies reporting a percent effect and not a discrete endpoint. The guideline plant studies, seedling emergence and vegetative vigor, were submitted to OPP and classified as core, so EFED did not need to rely on open literature for terrestrial plant data.

RISK CHARACTERIZATION RISK ESTIMATION To evaluate the potential risk to nontarget organisms from the use of ametryn, risk quotients ( RQs) are calculated from the ratio of estimated environmental concentrations ( EECs) to ecotoxicity values. RQs are then compared to levels of concern ( LOC's) used by OPP to indicate potential risk to nontarget organisms and the need to consider regulatory action. Risk presumptions, along with the corresponding RQs and LOCs are summarized in Tables 23 through 25 ( see APPENDIX G for more discussion). The exposure estimates in this screening assessment are derived using maximum label rates and minimum application intervals for each use. Since the sugarcane label has state specific application rates and intervals, the estimated environmental concentrations are different for each state in which sugarcane is grown. When available, field studies and incident data are compared to risk estimates for ametryn.

Table 23. Risk presumptions for terrestrial animals ( birds and wild mammals)

Risk Presumption RQ LOC Acute High Risk EEC1/ LC 50 or LD 50/ ft2 or LD 50/ day3 0.5 Acute Restricted Use EEC/ LC 50 or LD 50/ ft2 or LD 50/ day ( or LD 50 < 50 mg/ kg) 0.2 Acute Endangered Species EEC/ LC 50 or LD 50/ ft2 or LD 50/ day 0.1 Chronic Risk EEC/ NOEC 1 1 abbreviation for Estimated Environmental Concentration ( ppm) on avian/ mammalian food items 2 mg/ ft2 3 mg of toxicant consumed/ day LD 50 * wt. of bird LD 50 * wt. of bird Table 24. Risk presumptions for aquatic animals Risk Presumption RQ LOC Acute High Risk EEC1/ 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/ NOEC 1 1 EEC = ( ppm or ppb) in water Table 25. Risk presumptions for plants Risk Presumption RQ LOC 45 Terrestrial and Semi Aquatic Plants Acute High Risk EEC1/ EC 25 1 Acute Endangered Species EEC/ EC 05 or NOEC 1 Aquatic Plants Acute High Risk EEC2/ EC 50 1 Acute Endangered Species EEC/ EC 05 or NOEC 1 1 EEC = lbs ai/ A 2 EEC = ( ppb/ ppm) in water Exposure and Risk to Nontarget Terrestrial Animals For pesticides applied as a nongranular product ( e. g., liquid, dust), the estimated environmental concentrations ( EECs) on food items following product application are compared to LC 50 values to assess risk. The predicted peak and mean residues of a pesticide that may be expected to occur on selected avian or mammalian food items immediately following a direct single application at 1 lb ai/ A is presented in Table 26.

Table 26. Estimated environmental concentrations on avian and mammalian food items ( ppm) following a single applications at 1 lb ai/ A.

Application Rate Food Items EEC ( ppm) Predicted Maximum Residue1 EEC ( ppm) Mean1 1 lb a. i./ A Short grass 240 27 Tall grass 110 10 Broadleaf/ forage plants and small insects 135 11 Fruits, pods, seeds, and large insects 15 1 1 Predicted maximum and mean residues are for a 1 lb ai/ a application rate and are based on Hoerger and Kenaga ( 1972) as modified by Fletcher et al. ( 1994).

Nontarget Terrestrial Animals The estimated environmental concentrations ( EECs) used for terrestrial exposure on potential food items are derived from the Kenaga nomograph, as modified by Fletcher et al. ( 1994), based on a large set of actual field residue data. The upper limit values from the nomograph represent the 95th percentile of residue values from actual field measurements ( Hoerger and Kenega, 1972). The Fletcher et al. ( 1994) modifications to the Kenaga nomograph are based on measured field residues from 249 published research papers, including information on 118 species of plants, 121 pesticides, and 17 chemical classes. These modifications represent the 95th percentile of the expanded data set. Risk quotients are based on the most sensitive acute LC 50 and chronic NOAEC for birds ( in this instance, bobwhite quail) and acute LD 50 and chronic NOAEC for mammals ( based on lab rat studies).

Risk to Birds 46 Since ametryn is practically nontoxic to birds on both an acute oral and subacute dietary basis and no mortality was observed at the highest dose of ametryn tested ( i. e., LC 50> 5620 ppm), no acute risk quotients are calculated.

Chronic LOC's for birds, based on maximum estimated environmental concentrations, were exceeded for some feed items ( RQ range: 0.10   6.92) in all of the crops modeled ( Table 27). The highest chronic LOC exceedances were calculated for sugarcane uses ( RQ range: 0.11   6.92). Only the " fruits/ pods/ seeds/ large insect" category for these crops had RQs below the LOC. Estimated mean residue values are roughly 65% less than maximum estimated concentrations used in calculating chronic RQ's; chronic RQ's based on mean residues would decrease by roughly the same percent. However, even using the estimated mean residue values, there were still chronic risk LOC exceedances for use on sugarcane.

Table 27. Avian chronic risk quotients for selected uses of nongranular products of Ametryn based on a bobwhite quail NOAEC of 300 ppm.

Use Application Rate lbs. a. i./ A (# app / interval, days) Food Items Maximum EEC ( mg/ kg) a Chronic RQ ( EEC/ NOAEC)

Corn 2 ( 1 / NA) Short grass 480 1.60e Tall grass 220 0.73 Broadleaf plants/ small insects 270 0.90 Fruits, pods, seeds, and large insects 30 0.10 Pineapple 7.2 ( 1 / NA) Short grass 1728 5.76e Tall grass 792 2.64e Broadleaf plants/ small insects 972 3.24e Fruits, pods, seeds, and large insects 108 0.36 Sugarcane FL 1.2 ( 3 / 30) Short grass 535 1.78e Tall grass 245 0.82 Broadleaf plants/ small insects 301 1.00e Fruits, pods, seeds, and large insects 33 0.11 HI 7.2 / 2.4 / 2.4 ( 3 / 30) Short grass 1728 5.76e Tall grass 792 2.64e Broadleaf plants/ small insects 972 3.24e Fruits, pods, seeds, and large insects 108 0.36 Use Application Rate lbs. a. i./ A (# app / interval, days) Food Items Maximum EEC ( mg/ kg) a Chronic RQ ( EEC/ NOAEC)

47 LA 2 / 2.4 ( x 4)

( 5 / 30) Short grass 1211 4.04e Tall grass 555 1.85e Broadleaf plants/ small insects 681 2.27e Fruits, pods, seeds, and large insects 76 0.25 PR 8 / 4 ( x2)

( 3 / 30) Short grass 2075 6.92e Tall grass 951 3.17e Broadleaf plants/ small insects 1167 3.89e Fruits, pods, seeds, and large insects 130 0.43 TX 2 ( 3 / 30) Short grass 891 2.97e Tall grass 408 1.36e Broadleaf plants/ small insects 501 1.67e Fruits, pods, seeds, and large insects 56 0.19 a estimated environmental concentrations predicted using 1st order degradation model based on foliar dissipation. e exceeds chronic risk level of concern ( RQ

1.0)

Table 28. Avian chronic risk quotients for uses of ametryn based on a bobwhite quail NOAEC of 300 ppm and using the mean residue EECs.

Use Application Rate lbs. a. i./ A (# app / interval, days) Food Items Mean EEC ( mg/ kg) a Chronic RQ ( EEC/ NOAEC)

Corn 2 ( 1 / NA) Short grass 170 0.57 Tall grass 72 0.24 Broadleaf plants/ small insects 90 0.30 Fruits, pods, seeds, and large insects 14 0.05 Pineapple 7.2 ( 1 / NA) Short grass 612 2.04b Tall grass 259 0.86 Broadleaf plants/ small insects 324 1.08b Fruits, pods, seeds, and large insects 50 0.17 Sugarcane FL 1.2 ( 3 / 30) Short grass 189 0.63 Tall grass 80 0.27 Broadleaf plants/ small insects 100 0.33 Fruits, pods, seeds, and large insects 16 0.05 Use Application Rate lbs. a. i./ A (# app / interval, days) Food Items Mean EEC ( mg/ kg) a Chronic RQ ( EEC/ NOAEC)

48 HI 7.2 / 2.4 / 2.4 ( 3 / 30) Short grass 612 2.04b Tall grass 259 0.86 Broadleaf plants/ small insects 324 1.08b Fruits, pods, seeds, and large insects 50 0.17 LA 2 / 2.4 ( x 4)

( 5 / 30) Short grass 429 1.43b Tall grass 182 0.61 Broadleaf plants/ small insects 227 0.76 Fruits, pods, seeds, and large insects 35 0.12 PR 8 / 4 ( x2)

( 3 / 30) Short grass 735 2.45b Tall grass 311 1.04b Broadleaf plants/ small insects 389 1.30b Fruits, pods, seeds, and large insects 61 0.20 TX 2 ( 3 / 30) Short grass 316 1.05b Tall grass 134 0.45 Broadleaf plants/ small insects 167 0.56 Fruits, pods, seeds, and large insects 26 0.09 a estimated environmental concentrations predicted using 1st order degradation model based on foliar dissipation. b exceeds chronic risk level of concern ( RQ

1.0)

Risk to Mammals Although ametryn is practically nontoxic to mammals on an acute oral exposure basis, estimated environmental concentration are sufficiently high to exceed acute risk, acute restricted use and acute endangered species LOCs for pineapple and sugarcane, except for Florida ( Table 29). Acute restricted use and endangered species LOC's are exceeded for mammals feeding on short grass for all of the uses modeled.

Table 29. Acute RQ values for small ( 15 g), intermediate ( 35 g) and large ( 1,000 g) mammals feeding on short or tall grass, broadleaf plants/ small insects, fruits/ pods/ large insects and seeds exposed to Ametryn following single and multiple applications based on a rat LD50 = 1162 mg/ kg diet. 49 Use Application Rate lbs. a. i./ A (# app / interval, days) Body Weight, g Mammalian Acute Risk Quotients Short Grass Tall Grass Broadleaf Plants/ Small Insects Fruits/ pods/ large insects Seeds Corn 2 ( 1 / NA) 15 0.39b 0.18c 0.22b 0.02 0.01 35 0.27b 0.12c 0.15c 0.02 0.00 1000 0.06 0.03 0.03 0.00 0.00 Pineapple max 7.2 ( 1 / NA) 15 1.41a 0.65a 0.79a 0.09 0.02 35 0.98a 0.45b 0.55a 0.06 0.01 1000 0.22b 0.10c 0.13c 0.01 0.00 Sugarcane FL 1.2 ( 3 / 30) 15 0.44b 0.20b 0.25b 0.03 0.01 35 0.30b 0.14c 0.17c 0.02 0.00 1000 0.07 0.03 0.04 0.00 0.00 HI 7.2 / 2.4 / 2.4 ( 3 / 30) 15 1.41a 0.65a 0.79a 0.09 0.02 35 0.98a 0.45b 0.55a 0.06 0.01 1000 0.22b 0.10 0.13 0.01 0.00 LA 2 / 2.4 ( x4)

( 5 / 30) 15 0.98a 0.45b 0.56a 0.06 0.98a 35 0.22b 0.32b 0.69a 0.04 0.22b 1000 0.16c 0.07 0.09 0.01 0.00 PR 8 / 4 ( x2)

( 3 / 30) 15 1.70a 0.78a 0.95a 0.11c 0.02 35 1.18a 0.54a 0.66a 0.07 0.02 1000 0.27b 0.12c 0.15c 0.02 0.00 TX 2 ( 3 / 30) 15 0.73a 0.33b 0.41b 0.05 0.01 35 0.51a 0.23b 0.28b 0.03 0.01 1000 0.12c 0.05 0.06 0.01 0.00 a exceeds acute risk ( RQ

0.5), restricted use ( RQ

0.2) and endangered species level of concern ( RQ

0.1) b exceeds acute restricted use ( RQ

0.2) and endangered species level of concern ( RQ

0.1) C exceeds acute endangered species level of concern ( RQ

0.1)

A 2 generation rat reproduction study resulted in a NOAEL of 13 mg/ kg/ day, based on reduction in growth in the F2 generation. Resulting RQ's exceed chronic LOC's for all feed items for all uses of ametryn ( RQ range = 2.3 to 160) ( Table 30). Although not an equivalent type of study to the two generation rat chronic study, a rat carcinogenicity study resulted in a NOAEL of 21 mg/ kg/ day, based on decreased body weights and gain effects and also histological changes in the testes, kidney and pituitary in males and in the liver and pancreas in females. The effects in the males indicate a potential for effects on organs involved in endocrine processes. While the NOAEL from this study was not used quantitatively, the qualitative results from the study ( i. e., effects on the endocrine organs) are useful in substantiating the results of the chronic rat data. 50 Table 30. Chronic RQ values for mammals feeding on short grass, tall grass, broadleaf plants/ insects, and seeds exposed to ametryn following single and multiple applications based on NOAEL of 13 mg/ kg/ d.

Crop ( State) Application Rate lbs. a. i./ A (# app / interval, days) Body Weight, g Mammalian Chronic Risk Quotients Short Grass Tall Grass Broadleaf Plants/ Insects Fruits/ pods/ large insects/ seeds Seeds Corn 2 ( 1 / NA) 15 16 7 9 1 0.22 35 14 6 80 0.86 0.19 1000 7 3 4 0.45 0.09 Pineapple ( max) 7.2 ( 1 / NA) 15 57 26 32 4 0.79 35 49 23 28 3 0.70 1000 26 12 15 2 0.32 Sugarcane ( FL) 1.2 ( 3 / 30) 15 18 8 10 1 0.25 35 15 7 9 0.95 0.22 1000 8 4 5 0.50 0.10 Sugarcane ( HI) 7.2 / 2.4 / 2.4 ( 3 / 30) 15 57 26 32 4 0.79 35 49 23 28 3 0.70 1000 26 12 15 2 0.32 Sugarcane ( LA) 2 / 2.4 ( x4) ( 5 / 30) 15 40 18 23 3 0.56 35 35 16 19 2 0.49 1000 18 8 10 1 0.23 Sugarcane ( PR) 8 / 4 ( x2) ( 3 / 30) 15 69 32 39 4 0.96 35 59 27 33 4 0.84 1000 31 14 18 2 0.39 Sugarcane ( TX) 2 ( 3 / 30) 15 30 14 17 2 0.41 35 25 12 14 2 0.36 1000 13 6 8 0.84 0.17 Nontarget Terrestrial Plants Acute non endangered and acute endangered RQs were calculated using TerrPlant following the procedure outlined in APPENDIX F and then were compared to the LOC = 1.0. Acute nonendangered species emergence RQs in adjacent and semi aquatic areas ( Table 31) exceeded the LOC in all crops modeled ( adjacent RQ range: 1.45   15.4 ( monocots), 60   640 ( dicots); semi aquatic RQ range: 8.43   98.3 ( monocots), 350   4080 ( dicots)). Non endangered species drift RQs exceeded the LOC in all crops modeled for dicots ( RQ range: 3.33   133). Non endangered monocot drift RQs were lower ( RQ range: 0.19   7.62), but many uses for both ground unincorporated and aerial application methods still exceeded the LOC, with the exception of corn. 51 Table 31 . Acute non endangered RQ values for plant species from non granular applications of ametryn.

Crop Application Rate lbs a. i./ A # app / interval, days Application method Emergence RQs Adjacent Areas1 Emergence RQs Semi aquatic Areas2 Drift RQs3 Monocot Dicot Monocot Dicot Monocot Dicot Corn 2 ( 1 / NA) Ground spray 1.45 60.0 12.3 510 0.19 3.33 Pineapple max 7.2 ( 1 / NA) Ground spray 5.20 216 44.2 1836 0.69 12.0 Sugarcane FL 1.2 ( 3 / 30) Ground spray 0.87 36 7.4 306 0.11 2.0 Aerial spray 1.2 48 5.1 210 0.6 10 HI 7.2 / 2.4 / 2.4 ( 3 / 30) Ground spray 5.2 216 44 1836 0.7 12.0 Aerial 6.9 288 30.4 1260 3.4 60 LA 2 / 2.4 ( x4) ( 5 / 30) Ground spray 1.5 60 12.3 510 0.2 3.3 Aerial 1.9 80 8.4 350 0.95 16.7 PR 8 / 4 ( x2) ( 3 / 30) Ground spray 5.8 240 49.2 2040 0.8 13.3 Aerial 7.7 320 33.7 1400 3.8 66.7 TX 2 ( 3 / 30) Ground spray 1.5 60 12.3 510 0.19 3.3 Aerial spray 1.9 80 8.4 350 0.95 16.7 1 RQ = EEC/ Seedling Emergence EC25 2 RQ = EEC/ Seedling Emergence EC25 3 RQ = Drift EEC/ Vegetative Vigor EC25 Acute endangered terrestrial nontarget plant RQs in adjacent and semi aquatic areas ( Table 32) exceed the LOC for all crops modeled ( adjacent RQ range: 2.4   25.6 ( monocots), 9.23   98.5 ( dicots); semi aquatic RQ range: 14   163 ( monocots), 53.9   628 ( dicots)). Endangered species dicot drift RQs exceeded the LOC in all uses ( RQ range: > 3.3   > 133). The most sensitive dicot NOAEC was in lettuce (< 0.006 mg/ kg ai, the lowest treatment level tested). As a result, all calculated RQs are greater than the value reported.. Endangered species monocot drift RQs were lower ( RQ range: 0.4   16); however, the LOC was exceeded in sugarcane, except for ground spray in Florida. 52 Table 32. Acute Endangered RQ values for plant species from non granular applications of ametryn.