1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES PC Code: 058001 DP Barcode: D307567 12 July 2005 MEMORANDUM SUBJECT: Azinphos Methyl Insecticide: Ecological Risk Assessment for the Use of Azinphos Methyl on Caneberries, Cranberries, Peaches, Potatoes, and Southern Pine Seeds ( Group 2 Uses) IUPAC Name: O, O dimethyl S[ 4 oxo 1,2,3 benzotriazin 3( 4H) yl) methyl] phosphoro dithioate CAS Registry Number: 86 50 0 FROM: Colleen Flaherty, Biologist ( ERB 3) R. David Jones, Senior Agronomist ( ERB 4) Environmental Fate and Effects Division ( 7507C)

THRU: Elizabeth Behl, Branch Chief ( ERB 4) Daniel Rieder, Branch Chief ( ERB 3) Environmental Fate and Effects Division ( 7507C)

TO: Diane Isbell, Risk Manager ( RRB 2) Special Review and Reregistration Division ( 7505C)

In 1999, the Environmental Fate and Effects Division ( EFED) assessed the potential ecological risks associated with the use of azinphos methyl, an organophosphate insecticide, on a variety of agricultural uses. EFED concluded that azinphos methyl posed high acute and chronic risks to all endangered and non endangered aquatic and terrestrial organisms for all uses. Mitigation efforts following the 2001 IRED resulted in the cancellation ( with a phase out period) of several uses, including caneberries, cranberries, peaches, potatoes, and southern pine seeds. EFED has reassessed the ecological risks associated with the use of azinphos methyl on these uses, taking into account the current label application rates and other mitigation efforts, such as buffers. EFED has concluded that these uses of azinphos methyl pose acute and chronic risks to endangered and non endangered aquatic and terrestrial animals. Environmental exposures are likely to exceed known toxicity thresholds ( i. e. LC 50, NOAEC) for aquatic and terrestrial animals. Table of Contents 2 I. Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 II. Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 A. Stressor Source and Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Source and Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Physical/ Chemical/ Fate and Transport Properties . . . . . . . . . . . . . . . . . . 6 3. Pesticide Type, Class, and Mode of Action . . . . . . . . . . . . . . . . . . . . . . . 7 4. Overview of Pesticide Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 a. Caneberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 b. Cranberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 c. Peaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 d. Potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 e. Southern Pine Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 B. Assessment Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. Ecosystems Potentially at Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2. Ecological Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 C. Analysis Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Measures of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 a. Aquatic Exposures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 b. Terrestrial Exposures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. Measures of Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3. Measures of Ecosystem and Receptor Characteristics . . . . . . . . . . . . . . 12 III. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 A. Use Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 B. Exposure Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1. Environmental Fate and Transport Characterization . . . . . . . . . . . . . . . 13 a. Abiotic Hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 b. Photolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 c. Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 d. Foliar Degradation and Washoff . . . . . . . . . . . . . . . . . . . . . . . . 17 e. Batch Equilibrium/ Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 f. Bioaccumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 g. Field Dissipation Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 h. Field Runoff Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 i. Chemistry Input Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2. Measures of Aquatic Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 a. Aquatic Exposure Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 b. Southern Pine Seed Environmental Impact Statement . . . . . . . . 31 3. Measures of Terrestrial Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 a. Terrestrial Exposure Modeling . . . . . . . . . . . . . . . . . . . . . . . . . 33 3 b. Southern Pine Seed Environmental Impact Statement . . . . . . . . 34 C. Ecological Effects Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 1. Aquatic Effects Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 a. Acute Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 b. Chronic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 c. Sublethal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 d. Field Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2. Terrestrial Effects Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 a. Acute Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 b. Chronic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 c. Sublethal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 d. Field Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 IV. Risk Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 A. Risk Estimation  Integration of Exposure and Effects Data . . . . . . . . . . . . . . . 50 1. Non target Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 a. Peaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 b. Potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 2. Non target Terrestrial Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3. Non target Terrestrial Insects and Other Invertebrates . . . . . . . . . . . . . . 54 B. Risk Description  Interpretation of Direct Effects . . . . . . . . . . . . . . . . . . . . . . 54 1. Risks to Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 a. Caneberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 b. Cranberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 c. Peaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 d. Potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 e. Southern Pine Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 2. Risks to Terrestrial Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 a. Caneberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 b. Cranberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 c. Peaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 d. Potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 e. Southern Pine Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 C. Assumptions, Limitations, Uncertainties, and Data Gaps . . . . . . . . . . . . . . . . . 70 1. General Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 a. Maximum Use Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 b. Additive and/ or Synergistic Effects . . . . . . . . . . . . . . . . . . . . . . 70 2. Terrestrial Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 a. Location of Wildlife Species . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 b. Routes of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 c. Incidental Releases Associated With Use . . . . . . . . . . . . . . . . . . 71 d. Residue Levels Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 e. Dietary Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4 3. Effects Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 a. Sublethal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 b. Age Class and Sensitivity of Effects Thresholds . . . . . . . . . . . . . 73 Appendix A   Terrestrial Exposure ( T REX) Information Appendix B   Definitions of Levels of Concern for Risk Assessment Appendix C   Detailed Terrestrial Risk Quotients Appendix D   Adverse Ecological Incidents Associated With Azinphos Methyl Use in the U. S Appendix E   Endangered Species Lists Appendix F   Literature Cited 5 I. Executive Summary This ecological risk assessment specifically focuses on the potential ecological risks associated with the use of azinphos methyl on caneberries in Oregon, cranberries in Wisconsin, peaches nationally except California, potatoes, and southern pine seeds. Current label application rates and other mitigation efforts, such as buffers, were taken into account in this assessment.

To assess risk of azinphos methyl to non target aquatic animals for peaches and potatoes, surface water EECs for azinphos methyl were modeled using the Tier II model PRZM/ EXAMS based on the label recommended usage scenarios. Aquatic risks for caneberries, cranberries, and southern pine seeds were evaluated qualitatively. A terrestrial exposure model, T REX, was used to estimate exposures and risks in conservative scenarios to avian species for four forage food types and to mammalian species for five forage food types for application rates of azinphos methyl to all five of the assessed uses ( caneberries, cranberries, peaches, potatoes, southern pine seeds).

Based on reduced maximum application rates and mandatory buffer zones the results of this ecological risk assessment suggest that direct adverse effects to non target fish and invertebrates may occur as a result of azinphos methyl use on caneberries, cranberries, peaches, potatoes, and southern pine seeds. Acute and chronic risk quotients for fish and invertebrates, which were calculated for peaches and potatoes, exceed the Agency's LOCs. Although acute risks to aquatic phase amphibians may not be likely, chronic risks cannot be precluded at this time. Azinphos methyl exposures are likely to exceed known fish and aquatic invertebrate toxicity thresholds, resulting in individual mortality or sublethal effects ( i. e. reduced fecundity and/ or growth). Aquatic animals that survive initial ( peak) exposures may be vulnerable to sublethal effects on normal life processes, such as growth and reproduction. Widespread mortality and/ or reproductive impairment in a given population could have profound ecological consequences. These risk conclusions are supported by over 130 adverse aquatic incidents that have resulted in the deaths of hundreds of thousands of aquatic animals. There is a potential for direct effects to federally listed fish and invertebrates that inhabit areas where these crops are grown.

Birds ( surrogate for terrestrial phase amphibians and reptiles) and mammals ( up to 1000 g) are likely to be exposed to dietary residues that exceed known mortality and sublethal ( i. e. reproduction, growth) effects thresholds. Based on maximum and mean predicted terrestrial exposures, acute and chronic RQs exceed the Agency's LOCs for herbivorous and insectivorous birds and mammals for all five of the assessed Group 2 uses. Although risks to terrestrial invertebrates were not quantitatively assessed, it is expected that azinphos methyl, an insecticide, poses risks to non target ( beneficial) insects. Depending on the magnitude of the effects on individual fitness, higher level ecological impacts are possible. Terrestrial field/ pen studies and several terrestrial incidents support these risk conclusions. Further risk mitigation measures ( i. e. application rate reduction) are unlikely to significantly alter these acute and chronic terrestrial risk conclusions. There is a potential for direct effects to federally listed birds, mammals, reptiles, terrestrial phase amphibians, and terrestrial invertebrates that inhabit areas where these crops are grown. 6 II. Problem Formulation A. Stressor Source and Distribution 1. Source and Intensity In 1999, the EFED assessed the potential ecological risks associated with the use of azinphos methyl, an organophosphate insecticide, on a variety of agricultural uses. Mitigation efforts following the 2001 IRED resulted in the cancellation ( with a phase out period) of several uses, including caneberries, cranberries, peaches, potatoes, and southern pine seeds. This ecological risk assessment specifically focuses on the potential ecological risks associated with the use of azinphos methyl on caneberries in Oregon, cranberries in Wisconsin, peaches nationally except California, potatoes, and southern pine seeds ( hereafter referred to collectively as the " Group 2" uses). These particular locations are being considered in this assessment because growers in these locations have requested that the use of azinphos methyl on these crops be extended beyond the phase out, which is to occur in 2005. Current label application rates and other mitigation efforts, such as buffers, will be taken into account in this assessment.

2. Physical/ Chemical/ Fate and Transport Properties Common Name: azinphos methyl Chemical Name: O, O dimethyl S[ 4 oxo 1,2,3 benzotriazin 3( 4H) yl) methyl] phosphoro dithioate CAS Number: 86 50 0 PC Code: 058001 Molecular Formula: C 10 H 12 N 3 O 3 PS 2 Class: organophosphate Physical/ Chemical Properties Molecular Mass: 317.32 g

mol 1 Physical State: white to beige granular material Melting Point: 67 70  C K ow: 543 Vapor Pressure: 2.20 x 10 7 torr Solubility in Water: 25.10 mg

L 1 at 25  C Henry's Law Constant: 3.66 x 10 9 m3

mol 1 ( calculated)

Azinphos methyl ( Figure 1) is mobile ( K f = 12 27) and can reach surface water dissolved in runoff but not likely to leach to ground water in most situations. It is moderately persistent with aerobic soil metabolism DT 50 of 27 d. It degrades rapidly by direct aqueous photolysis ( T 1/ 2 = 77 h), but rather slowly by soil photolysis ( T 1/ 2 = 180 d). Hydrolysis is alkaline catalyzed and is fairly rapid at high pH, on the order of several days. It is moderately persistent at acid and neutral pH. There is some uncertainty in the assessment of the hydrolysis data because data were not collected below 30  C. There are data on the degradates formed through aerobic aquatic 7 Figure 1. Molecular structure of azinphos methyl. metabolism, but no usable rate data are available.

Degradates include anthranilic acid, methyl anthranilate, azinphos methyl oxygen analog, mercaptomethyl benzazimide, hydroxymethyl benzazimide, benzazamide, and bis methyl benzazamide sulfide, and methyl benzazimide sulfonic acid. Because of the limited concentrations of the identified degradates and their properties, this risk assessment has been based solely on the parent compound. This is not a major limitation of the assessment since all levels of concern are exceeded by the parent compound alone, and the fraction of additional toxicity that could be due to degradates will be small to that due to the parent. Ecological incident data support the risk presumptions.

A second source of uncertainty in the fate assessment is due to the field dissipation studies. The two guideline studies are both from California and are of limited quality due to very poor recoveries at initiation of the study. ( Two new field dissipation studies have been submitted in support of the Group 3 uses but were not reviewed in time to support this assessment.) In addition, these studies were run on fairly alkaline soils ( pH = 6.9  8.7), so they represent locations where azinphos methyl would be expected to be least persistent. Two non guideline studies from Georgia and Mississippi suggest that DT 50' s in Southeast may be relatively short, at 3 and 8 days respectively. However, these studies only sampled the top inch of soil.

In general, the laboratory fate data for parent azinphos methyl provide a reasonable level of confidence for the risk assessment. In contrast to most other pesticides, there is a fair amount ( 7 values) of foliar dissipation data. Additional metabolism data would increase our confidence in the chronic exposure assessment and may result in lower terrestrial estimated environmental concentrations ( EECs).

3. Pesticide Type, Class, and Mode of Action Azinphos methyl is an organophosphate insecticide that has both contact and stomach action. It is an inhibitor of cholinesterase activity and interferes with nervous system functioning. Cholinesterase inhibition can have impacts on survivorship, reproduction, growth, and behavior of 8 affected animals.

4. Overview of Pesticide Usage Azinphos methyl is geographically restricted to several high use locations, including the Mississippi Delta, the Blue Ridge Mountains, the Texas Panhandle, central Washington, Central Valley of California, and Michigan. This ecological risk assessment specifically focuses on the potential ecological risks associated with the use of azinphos methyl on caneberries in Oregon, cranberries in Wisconsin, peaches across the nation ( except California), potatoes, and southern pine seeds.

a. Caneberries Caneberries ( black raspberries, red raspberries, marion blackberries, evergreen blackberries, boysenberries, loganberries) are grown throughout the United States ( USDA NASS, 2004); however, this assessment is focuses specifically on the use of azinphos methyl to control the raspberry crown borer in Oregon caneberries. Oregon produces about one third of the nation's caneberries. Usage information is summarized in Table 2.1.

Table 2.1 Azinphos methyl Use on Caneberries in Oregon ( Source: USDA/ NASS Database Agricultural Chemical Statistics; crop acreage based on 2002 data, azinphos methyl usage based on data from 1990 to 2001.

Crop Acreage % Crop Treated Average Usage ( lbs a. i./ yr) Average No. Applications Average Single Application ( lbs a. i./ A)

Raspberries 3600 13 500 1.0 0.76 Blackberries 5980 15 360 1.1 0.39 b. Cranberries Approximately 38% of the nation's cranberry crop is treated with azinphos methyl, which adds up to about 9,000 pounds of azinphos methyl being applied annually to cranberries. This assessment focuses on the use of azinphos methyl to control the cranberry fruitworm in Wisconsin. Wisconsin cranberry production areas are located mainly in the central and northern parts of the state ( Figure 2). Wisconsin leads the nation in cranberry production ( USDA NASS, 2004) and is the largest user of azinphos methyl on cranberries, with approximately 61% of the crop treated. 9 Figure 2. Distribution of Cranberry Growing Areas in Wisconsin ( Source: Wisconsin State Cranberry Growers Association; http:// www. wiscran. org/ facts. htm)

c. Peaches Peach growing areas in the United States are widespread and include a wide range of soils, climates, altitude, hydrology, and weather patterns that can support different and distinct ecosystems. This assessment focuses on peaches grown everywhere in the U. S. except California. Because peaches are grown practically within all latitudes of the country, the timings of planting and insect emergence, lengths of the growing season, and harvest times can vary considerably from region to region.

In 2003, about 39,000 pounds of azinphos methyl were applied to peaches across the nation. On average, approximately 16% of the nation's peaches are treated annually with azinphos methyl. South Carolina was the largest user of azinphos methyl on peaches, with about 17,000 pounds applied to 48% of 15,000 acres. New Jersey had the highest percentage of acres treated with 57% of 8000 acres ( about 11,000 pounds of azinphos methyl total).

d. Potatoes Although potatoes are grown throughout the country, this assessment mainly focuses on the use of azinphos methyl to control the tuber moth on potatoes in the Columbia River basin ( Washington, Oregon). The National Potato Growers has requested an extension of the use to mid Atlantic and Colorado. In 2003, about 4,000 pounds of azinphos methyl were applied to potatoes across the nation, with about 2 3% of the crop treated. In Washington and Oregon, only about 1% of the potato crop was treated with azinphos methyl.

e. Southern Pine Seeds 10 Southern pine seed orchards are located throughout the southeastern United States and span from Texas to as far north as Delaware. In 2004, approximately 11% the southern pine seed orchards were treated with azinphos methyl. Azinphos methyl is used to control coneworms and seed bugs in southern pine seed orchards.

B. Assessment Endpoints 1. Ecosystems Potentially at Risk The terrestrial ecosystems potentially at risk include the treated area and areas immediately adjacent to the treated area that might receive drift or runoff, and might include other cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats and other uncultivated areas. For Tier I assessment purposes, risk will be assessed to terrestrial animals assumed to exclusively occur in the treated area. Risks to terrestrial plants will not be assessed and are presumed to be minimal.

Aquatic ecosystems potentially at risk include water bodies adjacent to, or downstream from the treated field and might include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuaries. For Tier I assessment purposes, risk will be assessed to aquatic animals assumed to occur in small, static ponds receiving runoff and drift from treated areas. These ponds are used as surrogates for a number of small vulnerable waterbodies that occur near the tops of watersheds including swamps, bogs, prairie potholes, vernal pools, playa lakes, and first order streams. Risks to aquatic plants will not be assessed and are presumed to be minimal.

2. Ecological Effects For azinphos methyl, ecological measures of effect are based on multiple lines of evidence, including a suite of registrant submitted toxicity studies as well as field studies and adverse ecological incidents. Acute and chronic endpoints are selected from available test data, as the data sets allow. A complete discussion of all toxicity data available for this risk assessment and the resulting measures of ecological effect selected for each taxonomic group are included in the Section III. C of this document. A summary of the assessment endpoints and measures of ecological effect selected to characterize potential ecological risks associated with exposure to azinphos methyl is provided in Table 2.2. Terrestrial and aquatic plants were not assessed.

Table 2.2 Summary of Ecological Risk Assessment Endpoints for Azinphos Methyl Assessment Endpoint Measurement Endpoint 1. Survival, reproduction and growth of individuals and populations of birds 1a. Oral LD50 ( mallard duck, bobwhite quail, ring necked pheasant, chukar) 1b. Dietary LC50 ( mallard duck; bobwhite, Japanese quail; ring necked pheasant) 1c. Reproductive NOAEC, LOAEC ( bobwhite quail, mallard duck) 11 2. Survival, reproduction and growth of individuals and populations of mammals 2a. Oral LD50 ( lab rat; lab, house, deer mouse; gray tailed vole) 2b. Dietary LC50 ( lab, deer mouse; gray tailed vole) 2c. Reproductive NOAEC, LOAEC ( lab rat)

3. Survival and reproduction of individuals and populations of freshwater fish and invertebrates 3a. LC50 ( coho, Atlantic salmon; rainbow, brown, brook trout; goldfish; carp; fathead minnow; black bullhead; channel catfish; green, bluegill sunfish; largemouth bass; black crappie; yellow perch; gold orfe; northern pike) 3b. Reproductive NOAEC, LOAEC ( rainbow trout) 3c. LC50 ( Daphnia magna, Asellus brevicaudus, Procambarus sp., Gammarus fasciatus, Palaemonetes kadiakemsis, Pteronarcys californica) 3d. Reproductive NOAEC, LOAEC ( Daphnia magna)

4. Survival and reproduction of individuals and populations of estuarine/ marine fish and invertebrates 4a. LC50 ( sheepshead minnow, spot, striped mullet) 4b. LC50 ( Eastern oyster, brown shrimp, blue crab, mysid shrimp)

5. Survival and reproduction of individuals and populations of amphibians 5a. LC50 ( Fowler's toad, Western chorus frog)

6. Survival of beneficial insect populations 6a. Contact LD50 honeybee acute 6b. Foliar residue toxicity to honeybees LC 50 = Lethal concentration to 50% of the test population. LD 50 = Lethal dose to 50% of the test population. NOAEC = No observed adverse effect level. LOAEC = Lowest observed adverse effect level.

C. Analysis Plan 1. Measures of Exposure a. Aquatic Exposures Aquatic estimated environmental concentrations ( EECs) for the use of azinphos methyl on peaches and potatoes will be modeled using the Tier II linked Pesticide Root Zone Model ( version 3.1.2 beta; Carsel et al., 1997) and Exposure Analysis Modeling System ( version 2.98.04; Burns, 1997); referred to as PRZM/ EXAMS. The linked PRZM/ EXAMS model is typically used by EFED to estimate pesticide concentrations in aquatic systems. PRZM is employed to evaluate run off loading from a ten hectare agricultural field to a receiving surface water body ( one hectare by two meter deep " standard" pond).

Aquatic exposures for the other three uses ( caneberries, cranberries, southern pine seeds) will be estimated in a qualitative manner. PRZM/ EXAMS modeling will not be used for these uses because there are no appropriate exposure scenarios. As part of the aquatic assessment of azinphos methyl use on southern pine seeds, an environmental impact statement from the United States Department of Agriculture Forest Service ( USDA, 1994) will also be reviewed ( see " Measures of Aquatic Exposure" Section B for more details). 12 b. Terrestrial Exposures Terrestrial exposures will be modeled for all five of the assessed Group 2 uses. Residues in potential dietary items for mammals and birds ( e. g., vegetation, insects, seeds) will be estimated using the conceptual approach given in the model T REX ( Version 1.12, 2004). In addition, an environmental impact statement for southern pine seed orchards ( USDA, 1994) will be reviewed ( see " Measures of Terrestrial Exposure" Section B for more details).

2. Measures of Effect Measures of effect are based on changes in the attribute of an entity in response to a stressor and are generally based on the results of a toxicity study, although monitoring data may also be used to provide supporting lines of evidence for the risk characterization. Examples of measures of acute effects ( e. g., lethality) include an oral LD 50 for birds and mammals and an LC 50 for fish and invertebrates. Examples of measures of chronic effects include the reproductive or developmental NOAEL for birds and mammals. Table 4.1 summarizes the toxicity endpoints that will be used to assess ecological risks associated with the use of azinphos methyl on peaches and potatoes. This risk assessment only addresses potential risks to non target aquatic and terrestrial animals; given the low phytotoxicity of azinphos methyl, risks to aquatic and terrestrial plants are presumed to be minimal.

3. Measures of Ecosystem and Receptor Characteristics The model that will be used to predict aquatic exposures for peaches and potatoes is the Tier II PRZM/ EXAMS model. Aquatic exposure and risks will be estimated qualitatively for caneberries, cranberries, and southern pine seeds. The Tier I T REX model will be used to estimate dietary exposure for terrestrial animals for all of the assessed Group 2 uses. Selected ecosystems used in exposure modeling are intended to be generally representative of any aquatic or terrestrial ecosystem associated with areas where azinphos methyl is used. For aquatic assessments, fish and aquatic invertebrates in both freshwater and estuarine/ marine environments are represented. For terrestrial assessments, three different size classes of small mammals are represented, along with five potential foraging categories ( short grass, tall grass, broadleaf plants/ small insects, fruits/ pods/ seeds/ large insects, and seeds). For birds, four potential foraging categories are considered ( short grass, tall grass, broadleaf plants/ small insects, and fruits/ pods/ seeds/ large insects).

III. Analysis A. Use Characterization Application rate information for assessed uses of azinphos methyl on Oregon caneberries, Wisconsin cranberries, peaches across the nation ( except California), potatoes in the Columbia River basin ( WA, OR), and southern pine seeds are summarized below ( Table 3.1). 13 Table 3.1 Azinphos methyl application rates and management practices for the " Group 2 Uses".

Crop Application Rate ( lbs a. i./ A) Maximum No. Applications Minimum Application Interval ( Days) Buffer Width ( feet) Method Caneberries 0.5 2 10 25 Ground Cranberries 1.0 2 14 50 Aerial Peaches 0.75 3 14 60, 100 Air blast Potatoes 0.75 2 7 150 Aerial Southern Pine Seeds 1.5 2 30 50 Aerial B. Exposure Characterization 1. Environmental Fate and Transport Characterization Azinphos methyl is mobile ( K f = 12 27) and can reach surface water dissolved in runoff, but it is not likely to leach to ground water in most situations. It is moderately persistent with aerobic soil metabolism DT 50 of 27 d. Azinphos methyl degrades rapidly by direct aqueous photolysis ( T 1/ 2 = 77 h), but rather slowly by soil photolysis ( T 1/ 2 = 180 d). Hydrolysis is alkaline catalyzed and is fairly rapid at high pH, on the order of several days. It is moderately persistent at acid and neutral pH. There is some uncertainty in the assessment of the hydrolysis data because data were not collected below 30  C. There are data on the degradates formed through aerobic aquatic metabolism, but no usable rate data are available.

Degradates include anthranilic acid, methyl anthranilate, azinphos methyl oxygen analog, mercaptomethyl benzazimide, hydroxymethyl benzazimide, benzazamide, and bis methyl benzazamide sulfide, and methyl benzazimide sulfonic acid. The processes which produced each degradate are listed in Table 3 c. Because of the limited concentrations of the identified degradates and their properties, this risk assessment has been based solely on the parent. To the extent that toxic degradates were present but not considered, the risk is commensurately increased. However, we do not believe this to be a major limitation of this assessment, since all levels of concern are already exceeded, and adverse ecological incident provide addition support of the risk conclusions. Furthermore, none of the degradates that are produced by metabolic pathways, which are the primary routes of degradation for azinphos methyl, are present at any time at concentrations greater than 10% of the nominal starting concentration of the parent, so they would not be expected to contribute substantially to the total toxicity of azinphos methyl in the environment.

A second source of uncertainty in the fate assessment is due to the field dissipation studies. The two guideline studies are both from California and are of limited quality due to very poor recoveries at initiation of the study. In addition, these studies were run on fairly alkaline soils ( pH = 6.9  8.7), so they represent locations where azinphos methyl is somewhat less persistent. Two non guideline studies from Georgia and Mississippi suggest that DT 50' s in the Southeast may be relatively short, at 3 and 8 days, respectively. However, these studies only 14 sampled the top inch of soil.

In general, the laboratory fate data for parent azinphos methyl provides a reasonable level of confidence for the risk assessment. In contrast to most other pesticides, there is a fair amount ( 7 values) of foliar dissipation data. Additional metabolism data would increase our confidence in the chronic exposure assessment and may result in reduced EEC values.

a. Abiotic Hydrolysis An hydrolysis study ( MRID 40297001) was conducted at three pH's ( 4, 7, and 9) and two temperatures ( 30  C and 40  C). This study was acceptable for regulatory purposes. Note that the standard guideline hydrolysis study is conducted at pH's 5, 7, and 9 and at a single temperature of 25  C. Starting concentrations of 1 mg L 1 and 10 mg L 1 were tested for each set of conditions for a total of 12 test systems. Rate constants were the same regardless of the starting concentration as would be expected if a first order degradation model holds true. The rate constants were estimated using linear regression of log transformed data. The corresponding half lives as a function of pH and temperature are listed in Table 3.2. The Arrhenius equation was used to correct for the temperature and estimate half lives at for pH 5, 7, and 9 by extrapolation from the higher temperature data. These 25  C half lives are 38 d, 37 d, and 6.9 d respectively.

Table 3.2 Half life ( in days) of azinphos methyl as function of pH and temperature.

Temperature ph 4 pH 7 pH 9 30 C 49 26 3.7 40 C 23 13 1.8 Several degradates were found at concentrations greater than 10% of the parent ( Table 3.3). In general, starting concentration and temperature did not appear to affect the amount of each degradate that was found after 30 days. Mercaptomethyl benzazimide was found at 4.9% to 10.4% after 30 days in pH 7, hydroxymethyl benzazimide and benzazimide, which were measured as single analyte, were found after 30 days at 8.1% to 12.2% at pH 4, 6.0 to 14.2% at pH 7, and 32.4 to 38.9% at pH 9. as a single anthranilic acid, was identified a concentration above 10% of the applied parent. Anthranilic acid was found at between 18.1 and 22.8% of the parent a 30 days in the pH 9 test systems. An unidentified degradate which was possibly an ester of was found in the pH 9 test systems at 7.4% to 14.5%. Bis methyl benzazamide sulfide was also found at concentration less than 10% of the applied radioactivity.

b. Photolysis Azinphos methyl degrades by photolysis on both soil and in water. In the aqueous photolysis experiment ( MRID 40297001) conducted at pH 4.35 and 30  C, a direct photolysis 15 half life of 76.7 hours was estimated from the first order rate constant calculated using linear regression on log transformed data. Note that while the standard guidance is for the study to be conducted at 25  C the data was found to acceptable for regulatory use as photolysis is usually relatively insensitive to temperature. The experiment was run in January in Kansas City with natural sunlight over 87 hours. Two major degradates were identified, benzazimide and anthranilic acid. In this experiment, each ` degradate' actually is a complex of two degradates that could not be separately identified by the analytical procedure used in the study. The benzazimide complex consisted of benzazimide and ( 1N) methoxybenzazimide while the anthranilic acid complex consisted of anthranilic acid and methyl anthranilate ester. Benzazimide complex represented 39.1% of the radiolabeled residues at the end of the experiment, the anthranilic acid complex reached 7.2% of the radiolabeled residues at the end of experiment.

In a soil photolysis experiment ( MRID 40297002) done with natural sunlight in January through April in Kansas City, Missouri, the photolysis half life corrected for the dark control was 180 d. The data from this study is acceptable for regulatory use. The soil was an unidentified sandy loam from Stanley, Kansas with a pH of 5.1. The half life was estimated from rate constants calculated by linear regression on log transformed data. Eighty nine per cent of the initial radioactivity remained after 31 d in the dark control where as 79% was present in the irradiated test system. The soil used was an unidentified sandy loam. No specific degradates were identified and none exceeded 4% of the applied radioactivity at any point during the experiment.

c. Metabolism There is one submitted aerobic soil metabolism study for azinphos methyl ( MRID 29900). The study was conducted on an unidentified sandy loam soil. Ten measurements were made over the course of 1 year. The DT 50 was 27 d and the DT 90 was 146 d as estimated by exponential interpolation. The reaction does not appear to follow first order kinetics, hence a half life estimate is inappropriate. However, since the current environmental fate models require first order rate constant, an estimate was generated using non linear regression on the untransformed data. This method often provides estimates that better describe the data when there is significant lack of fit of the first order model, as is the case here. The half life estimate generated using this method was 32 d. No single identified metabolite was found at greater than 10% of the applied radioactivity; the oxygen analog of azinphos methyl ( azinphos methyl oxon) peaked at 5.3% of the applied radioactivity 186 d after application. Four benzazamide metabolites, namely mercaptomethyl benzazimide, hydroxymethyl benzazimide, benzazamide, and bis methyl benzazamide sulfide, were reported as a single analyte, with a maximum of 12% of the applied occurring at 120 d. Only 4.1 % of residues were trapped as volatiles in a NaOH trap; this is likely to have been CO 2. Seventy two per cent of the radioactivity was in unidentified soil bound residues at the end of the experiment.

A single anaerobic soil metabolism was submitted ( MRID 29900). This study was found to be acceptable for regulatory use. In this study, the soil was incubated aerobically for 30 d, prior 16 to flooding and purging with nitrogen. Three samples were collected and analyzed over the subsequent 60 d duration of the study. Forty four percent of the applied radioactivity was present at the initiation of anaerobic conditions and 24% was present as azinphos methyl at the completion of the study 60 d later. No DT 50 was estimated as the less than 50% of the parent that was present at the initiation of anaerobic conditions was degraded during the course of the study. The data was fit to a first order degradation model using linear regression of log transformed data, resulting in a half life estimate of 66 d. The confidence in this estimate is low since it is based on only three measurements. No single metabolite was present at greater than 10% of the application rate. At the conclusion of the study, 50% of the radioactivity was present as unidentified soil bound residues.

A single aerobic aquatic metabolism study was submitted ( MRID 44411801). This study was found to provide supplemental data on the degradates, but not to be fully acceptable. The study is not upgradeable. Eight or nine degradates of azinphos methyl were found in the two systems: des methyl azinphos methyl, des methyl azinphos methyl S methyl isomer, methyl benzazimide, methylsulfinyl methyl benzazimide, methylsulfonyl methyl benzazimide, methyl benzazimide sulfonic acid, methylthiomethyl benzazimide, and either/ or hydroxy methyl benzazimide/ benzazimide. The last two degradates were not resolved by the chromatography. Only methyl benzazimide sulfonic acid occurred at greater than 10% ( 11.4%) of the nominal concentration. The study could not be used to establish the rate of azinphos methyl degradation under aerobic aquatic conditions.

Table 3.3 Degradates found in azinphos methyl studies.

Degradate Soil Photolysis Aqueous Photolysis Hydrolysis Aerobic Soil Metabolism Aerobic Aquatic Metabolism Anaerobic Soil Metabolism des methyl azinphos methyl X des methyl azinphos methyl S methyl isomer X anthranilic acid X X methyl anthranilate X benzazimide X X X X azinphos methyl oxygen analog X X hydroxymethyl benzazimide X X X X mercaptomethyl benzazimide X X bis methyl benzazamide sulfide X X methyl benzazimide X methylsulfinyl methyl benzazimide X 17 methylsulfonyl methyl benzazimide X methyl benzazimide sulfonic acid X methylthiomethyl benzazimide X d. Foliar Degradation and Washoff A major route of dissipation for azinphos methyl is foliar degradation and washoff. There are seven measurements available for foliar degradation of azinphos methyl ( Table 3.4), six from the open literature and one from a study submitted by the registrant. Note that there are currently no requirements nor guidance for the conduct for foliar degradation and washoff studies. The study by the registrant was conducted concurrently with a runoff study at Benoit, Mississippi ( Coody 1992). The mean dissipation half life over these studies was 7.2 d. The background variability among studies is fairly high,   = 4.9 d. Note that most of these studies are field studies, so they may include washoff. Note also that there is some evidence ( see Jones, D190581. McDowell, 1984) that foliar dissipation is not a first order process, so the half lives used in this calculation may not accurately reflect the true degradation process on foliar surfaces for azinphos methyl. There were no degradate data in these studies.

One washoff estimate was available for azinphos methyl ( Gunther et al, 1977). This study showed that 60% of the azinphos methyl of leaf surfaces washed of with 0.33 cm of simulated rainfall. This would correspond to a first order washoff rate constant of 0.937 cm 1. A description of the method of estimating the washoff rate constant is in Jones, 1998.

Table 3.4 Foliar dissipation half lives for azinphos methyl.

Half life ( days) Source 1.6 Hoskins, 1961 7.9 Hoskins, 1961 5.2 Hoskins, 1961 7.4 Pree et al., 1976 9.8 Pree et al., 1976 16.0 Winterlin et al., 1974 2.56 MRID 425167 02 e. Batch Equilibrium/ Mobility Soil water partition coefficients were estimated from batch equilibrium studies for three unidentified soils ( MRID 42959702). K f values for adsorption varied from 7 to 17 and varied from 12 to 28 for desorption ( Table 3.5). In all cases 1/ n values were less than 1, indicating that the adsorption/ desorption isotherms are not linear. Binding of azinphos methyl to soil was not 18 significantly correlated to soil organic carbon content ( R2 = 51%). These values suggest that azinphos methyl should not be particularly mobile by leaching but should be relatively mobile to surface waters in the dissolved form in runoff. An aged soil column leaching study ( MRID 00029887) confirmed the low mobility by leaching of azinphos methyl and its degradates: 90% of the radioactivity was in the top 5 cm of the column after leaching with 35.5 cm of water over 45 d. The soil material was aged for 28 d and then dried before being packed into the column. A total of 4.4% of the radioactivity leached from the bottom of the 30.5 cm column.

Table 3.5 Fruendlich Adsorption and Desorption constants for azinphos methyl on four soils.

Soil Texture % Organic Carbon Kf for adsorption 1/ n for adsorption Kf for desorption 1/ n for adsorption sandy loam 1.6 7.6 0.83 12.3 0.86 silt loam 2.9 16.8 0.82 27.5 0.94 silty clay 0.3 9.8 0.93 12.3 0.95 f. Bioaccumulation A bioaccumulation study is not required as the K ow is less than 1000. The K ow of azinphos methyl is 543.

g. Field Dissipation Studies Four terrestrial field dissipation studies are available for azinphos methyl. Two additional field dissipation studies have been submitted are currently in review. The first two were submitted to satisfy the terrestrial field dissipation guideline. The second two were submitted in conjunction with runoff studies. They provide supporting information on the dissipation of azinphos methyl under some conditions but do not satisfy the guideline requirement. The first two ( MRID 42647901) were conducted in California on alfalfa fields. There were no uncropped plots at either site. One of the studies was conducted at Watsonville, California on a Salinas silt loam where azinphos methyl was applied in July. The pH of the soil at this site ranged from 6.9 to 8.0. We would expect azinphos methyl to degrade more rapidly under these pH conditions when compared to most agricultural fields where the pH is acid to neutral. The duration of the experiment was 60 days. There were two plots, one receiving one application of 3 lb acre 1, and the other receiving two applications 7 days apart at the same rate. Parent azinphos methyl degraded with a DT 50 of 9 days ( estimated by exponential interpolation) from the upper 6 inches of soil in the single application plot. The DT 50 was bracketed by 7 and 14 days after the second application in the two application plot. Azinphos methyl was only detected in one sample below 6 inches after 28 days in the single application plot. Only one degradate, azinphos methyl oxygen analog, was analyzed, but was not detected. The quantitation limit for both parent and degradate was 0.01 mg

kg 1. A total of 12.9 inches of rain plus irrigation was applied to the plots during the course of the study. However, no evapotranspiration data was supplied so it is not possible to 19 assess leaching with the data provided. The value of this study is limited, because the recovery at time 0 was only 55% and there was no uncropped plot.

The same experimental setup was used at the Fresno site. Applications were made in May. The soil here was a Hesperia fine sandy loam. The pH of the soil at this site ranged from 7.6 to 8.7. As with the previous study, we would expect azinphos methyl to degrade more rapidly under pH conditions such as this as compared to most other agricultural fields where the pH is acid to neutral. The experiment was conducted for 60 days. The DT 50, estimated by exponential interpolation was two days in the single application plot, and bracketed by 7 and 14 days in the 2 application plot. No azinphos methyl was detected below the top 6 inches. Azinphos methyl oxygen analog was detected once in the top layer at the quantitation limit of 0.01 mg

kg 1. A total of 16.2 inches of rainfall and irrigation were applied to the plots during the study, but as in the previous study, no evapotranspiration data was collected so leaching at the site cannot be assessed. The recovery of azinphos methyl at time zero was 60% and there was no uncropped plot, limiting the utility of this study.

The two other field dissipation studies were conducted in conjunction with runoff studies in cotton fields in Colquitt County, Georgia ( MRID 425167 02) and Benoit, Mississippi ( MRID 425167 01). They provide marginal data, as no samples were collected at zero time, no samples were collected below the top inch, and degradates were not analyzed. The soils at the Colquitt County site were an Alapaha sandy loam, a Carnegie sandy loam, a Tifton loamy sand, and a Tifton sandy loam. The soils at the Benoit site were dominantly a Bosket very fine sandy loam with smaller amounts of Dubbs very sandy loam. A single application of 0.25 lb

acre 1 was made to the Colquitt County site on August 7 and to the Benoit site on August 22. The DT 50 at the Colquitt County site was 3 d, and 8.2 d at the Benoit site. It is possible that these dissipation rates include a substantial amount of leaching as the sampling depth was so shallow.

h. Field Runoff Studies Two runoff studies were conducted to measure pesticide runoff under field conditions. These studies provide supplemental information on runoff potential of azinphos methyl. These studies were voluntarily submitted by the registrant. There is currently no requirement nor guidance for conducting field runoff studies. The studies were conducted in Colquitt County, Georgia ( MRID 425167 02) and Benoit, Mississippi ( MRID 425167 01) in cotton fields.

At the Mississippi site, a total of 14.9 g of azinphos methyl ran off the 5.2 acre plot in a storm of 3.08 inches on August 9, 1989. Approximately 31.5% of the precipitation ran off the plot during the rainfall event. Although the study was otherwise well conducted, the method used to confirm the application rate ( collection of the spray on cards placed in the field during application) was only able to collect ~ 20% of nominal application rate. It is difficult, if not impossible, to make accurate assessments of the fate of the pesticide when the amount and distribution of the pesticide immediately following application cannot be determined. We can therefore only say that the percent of azinphos methyl that ran off the field was between 0.9% 20 ( based on spray tank calibration of the nominal application rate) and 3.5% ( based on the spray card recovery). It is more likely to be the former of these values as the pesticide mass on the spray cards are not reflective of the application rate due to interception from adjacent foliage.

The rainfall event represented a storm with a one in seven year return frequency during the summer in this part of Mississippi. The return frequency of the runoff event is somewhat less than that for the precipitation event, as the soil was fairly dry due to lack of precipitation in the week prior to the runoff event. Furthermore, because this study was conducted later in the season than when most azinphos methyl is applied, the canopy was more closed than would usually be the case. The site represents what appears to be a fairly typical site for cotton culture. However, data was not provided that would allow a more precise estimate of how likely the site was to produce adverse aquatic exposures, as compared to other cotton agricultural sites.

To summarize the results from Mississippi, the runoff event in the study represents a less than one in seven year event on a typical site. It generated between 0.9% and 3.5% of the applied azinphos methyl in the runoff, with the value more likely to be close to the 0.9% value.

At the Colquitt County, Georgia site, the field occupied 49 acres of a 50 acre watershed and drained into a 3.5 acre pond. Nine acres of the field was separated from the rest of the field with a berm. This isolated area was used to quantify the runoff and the azinphos methyl in it. Eight applications of azinphos methyl were made at three day intervals starting on August 1.

A total of 13.3 g of azinphos methyl ran off the 9 acre portion of the field in four storms which occurred on August 8 ( 32 mm), August 26 ( 61 mm), August 31 ( 37 mm), and October 1 ( 33 mm). These produced 3.6 g, 8.3 g, 1.3 g and 0.0012 g of azinphos methyl in the runoff, respectively. The method used to confirm the application rate ( collection of the spray on cards placed in the field during application) showed about 75% of nominal application rate was reaching the study site on average. A second method of confirmation, using the tank calibration data, along with measurements of the azinphos methyl in the spray solution gave a separate estimate of the application rate. This method generally gave higher estimates than the spray cards. It is more likely that the tank calibration method is the more accurate of these estimates, as the pesticide mass on the spray cards may not be reflective of the application rate due to interception from adjacent foliage. The percent runoff was calculated both by using the application estimate based on the tank calibration measurements and upon the amount found on the spray cards. The percent azinphos methyl in runoff ranged from 1.7 x 10 4 to 0.17% using the tank calibration data and from 2.2 x10 4 to 0.26% based on the spray cards. The total applied that ran off was 0.18% by the tank calibration method and 0.24% by the spray card method. Measurements of the sediment transported from the 9 acre study area ranged from 22 kg due to the October 31 runoff event to 2,200 kg for the August 26 event. The concentration of azinphos methyl on the sediment was not determined. The mean azinphos methyl concentration in the pond was about 2 and 3 µ g

L 1. However, the variance among the measurements in the pond was very high in the first few days after the runoff event as the pond did not yet appear to be well mixed. so the uncertainty is higher than would normally be the case. 21 Data were not provided on the return frequency of the runoff events. Some anecdotal information ( a tornado occurred nearby) was provided on the return frequency of the August 26 storm, indicating that storms of that intensity ( 61 mm in 30 to 40 min) were relatively rare in that area. However, given the soil was likely to have been fairly dry before the event, it is likely that the runoff event ( as opposed to the storm event) was not particularly severe. Furthermore, because this study was conducted later in the season than when most azinphos methyl is applied, the canopy was more closed than would usually be the case. The site represents what appears to be a fairly typical site for cotton culture in Georgia, but data was not provided that would allow a more precise estimate of how likely the site was to produce adverse aquatic exposures, as compared to other cotton agricultural sites. It should be noted that a fish kill of 500 to 1000 fish occurred in the pond adjacent to the site two days following the August 26 storm.

To summarize the results from Georgia, four runoff events occurred in the study that moved less than 0.3% of the applied pesticide in runoff, but the relative frequency of the events and the relative severity of the site cannot be determined with the data provided.

i. Chemistry Input Parameters Azinphos methyl is an organophosphate insecticide used on a wide variety of food and non food crops. Azinphos methyl environmental fate data used for generating model parameters are listed in Table 3 j. The input parameters for PRZM and EXAMS are in Table 3 k. Descriptions of special considerations used to select environmental fate parameters or to generate modeling input values are described below.

Hydrolysis. As noted above, measurements of the hydrolysis rates were made at 30  C and 40  C rather than the standard 25  C. The Arrhenius Rate Law was used to calculate the degradation rate by hydrolysis at 25  C for use EXAMS.

Soil and Aquatic Metabolism. Only one anaerobic and one aerobic soil metabolism value was available for azinphos methyl. No aquatic metabolism data are currently available. Current policy for generating input parameters for PRZM 3 when only one value is available is to multiply the half life by three resulting in a PRZM input parameter for aerobic soil degradation of 95.3 d. In previous modeling for azinphos methyl, the anaerobic soil metabolism value was used as input to PRZM representing the degradation rate in the sub surface horizons. For this set of simulations, the aerobic soil metabolism half life was used for all depths. This will have no effect on the EECs.

Since no aquatic metabolism data was available, current policy is to use the value of the corresponding half life for aerobic soil metabolism and multiply that value by 2 to represent aerobic aquatic metabolism. This is done as there is usually some correspondence between soil and aquatic metabolism rates and in the absence of aquatic data this is judged to be a reasonable conservative surrogate. The aerobic aquatic metabolism input parameters was multiplies by 2 again to estimate the degradation rate in the pond sediment. The resulting half lives for aerobic and anaerobic aquatic metabolism are 190.8 and 381.6 d respectively. In practice these values are 22 of little importance as the degradation in the water column will be dominated by hydrolysis.

Soil Water Partition Coefficients. In previous modeling, a K oc value based on K f's was used in the simulations. The method for generating soil water partition coefficient input values has changed substantially from this in the new simulations. In selecting a value for the soil water partition coefficient to use in the simulations, four issues needed to be considered. First, adsorption and desorption isotherms are not equal, so it must be decided whether to use the adsorption or desorption isotherm. Current policy is to use the desorption values in PRZM because the dominant process during a runoff event is desorption and to use the adsorption isotherm in EXAMS as that it is the dominant process in the pond. Secondly, the data for each of the three soils ( both adsorption and desorption processes) were fitted to a Fruendlich isotherm and the 1/ n or " curvature" term in the equation was significantly different than 1, indicating that concentration adsorbed to soil was curvilinearly related to concentration in solution. Unfortunately, PRZM and EXAMS only have a linear ( K d) partition model for handling soil water partitioning of pesticides. For the desorption isotherm, this was handled by calculating the partitioning between soil and water at the maximum concentration it would be expected to occur in each media. While this method does not give the most accurate soil water partitioning of the pesticide over the range of the isotherm, it should be most accurate at near application rate, where the greatest portion of the runoff occurs. For the calculated desorption K d's for PRZM 2, the soil concentration of 17.2 µ g  kg soil 1 was used, which corresponds to the concentration resulting from the application rate being mixed into the top 1 cm of soil. The soil water was content was assumed to be 0.35 cm3 H 2 O  cm 3 soil and the bulk density of the soil was assumed to be 1.3 kg  L 1. The partitioning under these conditions was used to calculate a K d appropriate for this soil content. Note that for each soil, four different desorption experiments were done and Fruendlich parameters were given for each separate experiment. The average of the four sets of parameters was used to calculate a single K d for the soil at the application rate rather than four different K d's being calculated and then averaged.

Finally, a Pearson's Correlation Analysis of the of the calculated K d with organic carbon content was used to calculate a K oc. for neither adsorption nor desorption was there a significant correlation between the calculated K d's and organic carbon content, so the K d value for the silty clay soil, 8.414 L  kg 1 for desorption and 7.55 L  kg 1 for adsorption was used. Finally it should be noted that the concentrations in the soil water partitioning study are only about 1 tenth the concentration of pesticide that could be found in the soil at the application rate. Hence, we are extrapolating considerably beyond the range of the experimental data for calculating the EEC and this usually results in substantial error.

Table 3 j. Environmental fate parameters for azinphos methyl.

Fate Parameter Value Source Molecular Mass 317.32 g

mol 1 EFGWB One Liner Aerobic Soil Metabolism Rate Constant 2.17 x 10 2 d 1 MRID 29900 Anaerobic Soil Metabolism Rate Constant 1.04x10 2 d 1 MRID 29900 23 K d 7.6 L

kg soil 1 ( sandy loam) MRID 42959702 Solubility 25.10 mg

L 1 EFGWB One Liner Vapor Pressure 2.2x10 7 torr EFGWB One Liner Acidic Hydrolysis Rate Constant 4.78 L

( mol H+) 1

d 1 EFGWB One Liner Neutral Hydrolysis Constant 7.83x10 4 d 1 Wilkes et al., 1979 Alkaline Hydrolysis Constant 82 L

( mol OH+) 1

d 1 Wilkes et al., 1979 Aqueous Photolysis Constant 3.19 d MRID 40297001 Washoff Fraction 0.937 Gunther et al., 1977 Foliar Degradation Rate Constant 7.2 d see text Foliar Washoff and Degradation. Foliar dissipation is an important process for estimating the EEC of azinphos methyl. Data for foliar washoff of azinphos methyl ( Gunther et al., 1977) is not presented in a manner that is most amenable to direct use in PRZM 2. The value available for foliar washoff is 60% of the amount applied washed off in the first 0.33 cm of rainfall. The PRZM foliar washoff parameter, FEXTRC, is the amount of pesticide washed off in 1 cm of rainfall, expressed as a fraction. There is some indication ( McDowell et al., 1984) that a hyperbolic model ( 1/[ a+ bt]) best predicts the concentration profile with washing volume of methyl parathion, a similar compound, in washoff, but integration of the regression equations failed to provide meaningful estimates of the percent washed off in 1 cm of rainfall ( Values calculated exceeded the initial concentration). To obtain a meaningful, if not particularly accurate or precise estimate of foliar washoff, the following assumptions were made: first, that washoff rate was proportional to the amount on the leaf ( i. e. d[ AM]/ dV =  k[ AM], where [ AM] is the azinphos methyl concentration on the leaf, V is the volume of runoff expressed as cm of precipitation and k is the washoff rate constant). The exponential removal model which was selected for the first assumption was chosen over a linear model as there is some indications that an exponential model better described the structure of the data. Based on the first assumption, the equation describing the washoff fraction as a function of the precipitation amount, V, in 1 cm is:

W

e

kV where W is the fraction remaining on the foliage. The 40% remained after 0.33 cm of precipitation allows to calculate a point estimate of k as 2.78. Using this value for k, the fraction washed off ( 1 W) with 1 cm of rainfall is 0.937.

For foliar degradation, 7 foliar half lives measurements are available ( Lindquist and Krueger, 1975; Hoskins, 1962; Pree et al., 1976; Winterlin et al., 1974, McDowell et al, 1984). Assuming these values are distributed normally, the value which represents the one tail upper 90% confidence limit of the mean is 9.8 d. 24 Table 3 k. Chemistry input parameters for Tier II ( PRZM/ EXAMS) simulation of azinphos methyl for aquatic assessment of the peach and potato uses. Source data is in Table 10.

Input Parameter Value Justification Quality Molecular weight 317.32 g mol 1 calculated excellent Solubility 25.10 mg

L 1 measured very good Hydrolysis 39.4 ( pH 5) adjusted for temperature excellent Photolysis 3.19 d measured Aerobic Soil Metabolism 95.4 d single value x 3 fair Water Column Metabolism 190.8 d aerobic soil x 2 poor Sediment Metabolism 381.6 d water column x 2 poor Foliar Degradation 9.8 d UCB90 on 7 values good Foliar Washoff Coefficient 0.937 cm 1 point estimate from 1 fair Henry's Law Constant 3.66 x 10 6 L atm mol 1 estimated from solubility poor Vapor Pressure 2.2 x 10 7 torr good good Soil Water Partition Coefficient 7.6 L

kg soil 1 lowest non sand Kd good The following changes were made from the assessment in the IRED ( Homes et al, 1999) and the current assessment. These changes reflect changes in model versions, changes in policy and updated scenarios:

The version of PRZM changed from PRZM 2.3 to 3.12beta. While there are substantial differences between the two versions, these changes do not substantially affect the routines used to calculate the EECs for azinphos methyl.

The version of EXAMS changed from 2.94 to 2.98. The changes in EXAMS were dominantly in output reporting and the use of weather data. This results in minor changes in the EECs.

The peach scenario was upgraded for use with PRZM 3.12beta and revised to be consistent with current guidance for scenario input seelction and quality assurance. The soil was changed from a Boswell sandy loam to a Greenville fine sandy loam. The weather location was moved from Augusta, Georgia to Macon, Georgia.

The PE4 shell was used to run PRZM and EXAMS. Degradation rates are entered as halflives rather than as rate constants into PE4 which converts them to rate constants internally. For the previous simulations, EXAMS output was processed withe SZ2 postprocessor Post processing methods in SZ2 and PE4 are essentially identical.

The Henry's Law constant was externally from the solubility and vapor pressure and entered directly into EXAMS rather than have the program calculate it. This was to ensure compatibility with the PE4 shell.

The AgDrift model was used to estimate spray drift values in addition to using the default values currently indicated by the input parameter document. This allows the estimation of 25 the effect of spray buffers on drift reduction.

2. Measures of Aquatic Exposure a. Aquatic Exposure Modeling Two models were used in tandem for the Tier II surface water assessments for peaches and potatoes. PRZM simulates fate and transport on the agricultural field. The version of PRZM ( Carsel et al., 1998) used was PRZM 3.12 beta, dated May 24, 2001. The water body is simulated with EXAMS version 2.98, dated July 18, 2002 ( Burns, 1997). Tier II simulations are run for multiple ( usually 30) years and the reported EECs are the concentrations that are expected once every ten years based on the thirty years of daily values generated by the simulation. PRZM and EXAMS were run using the PE4 shell, dated May 14, 2003, which also summarizes the output. Spray Drift was simulated using the AgDrift model version 2.01 dated May 24, 2001.

Three scenarios were used to represent high exposure sites for azinphos methyl use, two for potatoes and one for peaches. All these sites represent 10 hectare fields draining into a 1 hectare pond, 2 m deep with no outlet. For peaches, this scenario is essentially the same as a meadow at the same site and is appropriate for modeling other meadow like fields, such as vineyards, which is reasonable given the state of the art in computer modeling of agricultural production systems. Metadata for the scenarios is documented in Pesticide Root Zone Model Field and Orchard Crop Scenario Metadata, dated December 24, 2004 ( EFED, 2004).

The field used to represent peach production in Georgia is located in Peach County in Southwest Georgia ( MLRA133) and the weather station representing the orchard is in MLRA 137 and located in Macon, GA. Peaches are grown throughout the state, and Peach County represents the highest producing county in Georgia and the 7th highest producing county in the U. S. Tree row spacing is generally 15 to 20 feet and within row spacing varies with the variety and maintenance size of the tree from as little as 8 feet to 20 feet. Tree heights are maintained from 8 feet to over 20 feet. Tree size and density is carefully maintained to optimize fruit production and pesticide and growth regulator applications. Flower buds begin to swell in late Winter to early Spring in the South as heat accumulates followed closely by bud bloom. At the time of flowering the fruiting stage commences and continues through harvest. For high yields of quality fruit, proper soil and site management, among other factors are necessary. Soil characteristics have a significant influences on tree development, fruit bearing capacity, and tree life. Of these, soil texture and drainage are among the most important for peach tree health. Peach trees do best in moderately to well drained soils of a sandy to silt loam texture. Trees do not tolerate wet soils for prolonged periods of time ( days to weeks) during the growing period. The soil selected to simulate the field is a Greenville fine sandy loam in the Greenville Faceville Orangeburg Association. Greenville fine sandy loam is a fine, kaolinitic, thermic Rhodic Kandiudults. These soils are often used for peach, truck crop and grain production. The Greenville fine sandy loam is a very deep, well drained, medium runoff, moderately permeable soil that formed in clayey marine sediments on the Coastal Plain. These soil are generally found on 26 uplands and have slopes generally less than 8 percent, but may range up to 18 percent. The soil is extensive in the Coastal Plains of the South. Greenville fine sandy loam is a Hydrologic Group B soil. The scenario input file for PE4 is GapeachC. txt, dated March 1, 2002.

A Maine potato scenario was selected to represent potatoes on a national basis and specifically to represent potatoes in the Mid Atlantic and Colorado as there is a request to extend the use into these two areas. The current label use pattern for potatoes is restricted to Washington and Oregon. The field used to represent potato production in Maine is located in Aroostook County (# 1 producing county in Maine) in Northeastern Maine ( MLRA143/ 146), although potato production areas include other regions of Maine. Aroostook County produces approximately 90 percent of Maine's potatoes. A wide variety of potatoes are grown in Aroostook County, and are generally classified as early, mid, and late season. According to the 1997 Census of Agriculture, Maine is the 3rd largest producer of potatoes in the U. S. behind Idaho and Pennsylvania. Potatoes are generally grown on a range of soils from sandy to clay loam, though deep, well drained sandy loam is ideal because they tend to dry out and warm up earlier facilitating early planting. Poorly drained soils should be avoided. Potato seed pieces, 3.5 to 5 cm in size, are planted " eyes" facing upward about 10 15 cm deep and between 12 to 14 inches apart. Rows are generally 32 36 inches on center, but may be less or greater depending on equipment. Planting is not recommended until soil temperatures reach 45 50oF. In Maine, potatoes should not be planted more than once in a three year period on the same field to avoid soil borne diseases. Rotations with strawberries, tomatoes or legumes should be avoided because these crops can be infected with the same diseases. Rotation with crops such as hay, alfalfa and small grains is common. Planting begins in May and harvest begins in late September through October. The soil selected to simulate the field is an Conant gravelly silt loam. Conant gravelly silt loam is a fine loamy, isotic, frigid Aquic Haplorthods These soils are extensively used for potatoes, oats and peas. Conant gravelly silt loam is a very deep, moderately well drained and somewhat poor drained, slow runoff, moderately permeable soils located on till plains and lower slopes of till ridges derived mainly from metamorphosed limestone and calcareous sandstone and shale. Slopes are 0 to 15 percent at elevations of 350 to 800 feet above mean sea level. The soil is of moderate extent in the MLRA. Conant gravelly silt loam is a Benchmark soil in Hydrologic Group C. The scenario input file for PE4 is MEpotatoC. txt, dated August 6, 2002.

The standard Idaho potato scenario was selected to represent the use of azinphos methyl for the currently labeled practice. In general, crops grown on the west coast tend to be less vulnerable to runoff than eastern coast crop due to the lesser precipitation during the growing season. The field used to represent potato production in Idaho is located in Bingham County (# 1 producing Idaho county) in Southeast Idaho ( MLRA13), although potato production areas include other regions of Idaho such as the southwest and south central regions. According to the 2002 Census of Agriculture, Idaho is the major producer of potatoes in the U. S. producing 29 percent of the crop. Potatoes are generally grown on a range of soils from sandy to clay loam of volcanic origin along the Snake River Plain of southern Idaho. Potatoes are in rotation with crops such as hay and various grains. Potatoes are generally grown once ever three years on the same field to limit disease pressures ( Willem Schrage, Minnesota Sept. of Agriculture). Potato seed 27 pieces are planted " eyes" facing upward about 10 12 cm deep and between 12 to 14 inches apart. Rows are generally 36 40 inches on center, but may be less or greater depending on equipment. Sprinkler irrigation is used on about 99 percent of the crop and furrow and rill irrigation is used on the remainder. Planting begins April and runs through Mid June depending on region. Harvest also depends on regions, beginning in mid July and running through November 15.

The soil selected to simulate the field is an Malm fine sandy loam. Malm soil is classified as a Coarse loamy, mixed, superactive, frigid Xeric Haplocalcids. These soils are mainly used for irrigated pasture, potatoes, and small grains, but some are used as rangeland. The Malm series consists of moderately deep, well drained soils formed mainly in aeolian deposits. Malm soils are on lava plains and have slopes of 0 to 20 percent at elevations of 4500 to 5200 feet above mean sea level. Potatoes were planted in soils with 0 to 8 percent slopes. The soil is well drained with slow to medium runoff and moderately rapid permeability. The soil is moderately extensive in southeastern Idaho. The Malm soil is a Hydrologic Group C soil. The scenario input file for PE4 is IDpotatoC. txt, dated May 10, 2002.

A standard watershed is used for all assessments consisting of a 10 ha watershed draining into a 1 ha pond 2 m deep with no outlet. Exposure estimates generated using the standard pond are intended to represent a wide variety of vulnerable water bodies that occur at the top of watersheds including prairie pot holes, playa lakes, wetlands, vernal pools, man made and natural ponds, and intermittent and first order streams. As a group there are factors that make these water bodies more or less vulnerable than the standard surrogate pond. Static water bodies that have larger ratios of drainage area to water body volume would be expected to have higher peak EECs than the standard pond. These water bodies will be either shallower or have large drainage areas ( or both). Shallow water bodies tend to have limited additional storage capacity and thus tend to overflow and carry pesticide in the discharge whereas the standard pond has no discharge. As watershed size increases beyond 10 ha, it at some point becomes unlikely that the entire watershed is planted to a single crop, which is all treated with the pesticide. Headwater streams can also have peak concentrations higher than the standard pond, but they tend to persist for only short periods of time and are then carried downstream.

Spray Drift. Current policy ( EFED, 2002) is to model spray drift with a set fraction of the application rate ( 5% for aerial; 1% for ground spray) reaching the pond for each application. In the previous modeling for azinphos methyl, spray drift from spray blast application was simulated using 3% drift. There is currently no guidance regarding spray blast drift so in this simulation spray blast was assumed to be a ground spray. While this is standard drift policy, this approach does not allow the consideration of the mitigation possible with a spray drift buffer.

To assess different buffer widths, the AgDrift model was used. For aerial applications Tier II aerial mode was used. Aerial application was simulated assuming the aircraft was an Air Tractor AT 401. Standard weather and application parameters used for these simulations are in Table 3.6. Other parameters, which can be varied with the management practices defined on the label, are described below, along with management practices for aerial application to potatoes. 1Personal communication, Dan Horton to Diane Isbell, March 2005.

28 Table 3.6 Standard spray drift scenario input parameters for AgDrift.

Parameter Value Aircraft Air Tractor AT 401 Boom length ( fraction of wing length) 76.3%

Swath Width ( fixed) 60 ft.

Flight lines 20 Relative Humidity 50%

Flux Plane 0 ft Air blast buffer strips for peaches were modeled with AgDrift in Tier II Orchard Airblast mode. A sparse orchard was modeled, and the output value for the loading into the standard pond was tripled in order to reflect the upper 95% confidence bound on the drift. The only management practice that was varied was the buffer strip width.

Peaches A request has been made to extend the use of azinphos methyl on peaches to help control the occurrence of lesser peach tree borer in the Eastern United States. The peach use pattern that was simulated was not the current maximum label practice, but a practice proposed by Dan Horton1, a representative of the peach industry on the east coast of the United States. In previous peach Tier II modeling, application was started on March 14, at anthesis for control of plum curculio and use of azinphos methyl for this pest is still allowed on the label. However, because the pest which is generating the request for the use extension is lesser peach tree borer, an additional run with the 60 ft buffer and a date for the first application of July 4 was performed to gauge the change in exposure that might result if azinphos methyl use shifted to control this pest. Control of lesser peach tree borer can continue through the summer into late fall, and may occur at different times in this window in different fields.

Aerial application is generally restricted from use on peaches. However, a Special Local Needs registration exists for aerial application of azinphos methyl to peaches in Idaho. This use was not evaluated as the risk from use on the east coast are generally expected to exceed the risks in Idaho in spite of the difference in application method.

Spray drift was evaluated in five different ways for peaches ( Table 3.7). Two buffer strips were evaluated using AgDrift. A 60 foot buffer strip was suggested by Dr. Horton in order to mitigate spray drift to water. Secondly, a 100 foot buffer was also evaluated at the request of SRRD. The modeled drift from AgDrift for these was 1.9% and 0.9% respectively. For comparison purposes, an AgDrift simulation with no buffer strip was done which resulted in 12.4% spray drift. An application efficiency of 97.7% was used for all three of these management practice simulations, as estimated by AgDrift. Also, for comparison purposes, a simulation was done with no spray drift and 100% application efficiency. In practice, it is not possible to 29 0 2 4 6 8 10 12 14 16 Peak Day 4 Day 21 Day 60 Day 90 Mean AZM Concentration ( ug/ L) 60 ft buffer ( March) 100 ft buffer ( March) No buffer ( March) 60 ft buffer ( July) No drift ( March) completely stop spray drift from spray blast applications, but this provide an idea of the relative potential risk reduction that can be gained from spray drift mitigation. Finally, a simulation using the spray drift percentile of 1% for ground application with a 99% application efficiency was performed in accordance with our current policy.

Table 3.7 Management practices simulated for azinphos methyl use on peaches*.

Crop App Rate ( lbs a. i./ A) Max. No. Apps. App. Interval ( days) Buffer Width ( ft) App. Method (% drift) First App. Date Peaches 0 0.75 3 14 NA no drift ( 0%) March 14 Peaches 1 0.75 3 14 100 air blast ( 9.0%) March 14 Peaches 2 0.75 3 14 60 air blast ( 1.9%) March 14 Peaches 3 0.75 3 14 0 air blast ( 12.4%) March 14 Peaches 4 0.75 3 14 NA air blast ( 1%) March 14 Peaches 5 0.75 3 14 60 air blast ( 9.0%) July 4 * For all simulations, IPSCND, the disposition of foliar pesticide residues on foliage at harvest was set to 1, so that the residues are applied to the soil.

Figure 3 displays the range of aquatic EECs for the use of azinphos methyl on Georgia peaches. The PRZM/ EXAMS model suggests that the addition of a 60 ft buffer could potentially reduce peak azinphos methyl exposures by more than 50% ( from 14 to 6 µ g/ L). Assuming that a 60 or 100 foot buffer zone is present at the application site, the peak 1 in 10 year average aquatic EEC for Georgia peaches is about 6 µ g/ L, and the 90 day average is approximately 2 µ g/ L. There is no appreciable difference between EECs with a 60 foot or a 100 foot buffer. Aquatic exposures could further be reduced if azinphos methyl is applied later in the season.

Figure 3. Aquatic EECs for azinphos methyl use on Georgia peaches. 30 Potatoes The potato use is currently restricted to Columbia River Basin in Washington and Oregon. Potatoes is a group 2 use which is to be phased out in 2005. A request has been made to extend this use because tuber worm has now been found in the Columbia River Basin. However, as noted above, a request has been made by the National Potato Growers to extend the use to mid Atlantic and Colorado. Aerial application is allowed for this use, but a 150 foot buffer is required around ` rivers, natural ponds, lakes, streams, reservoirs, marshes, estuaries, and commercial fish ponds.'

The simulated use pattern ( Table 3.8) reflects the maximum application practice on the current label. The dates of application were set to be as close to harvest as possible as this is the best time to apply for the control of tuber worm. In the Idaho scenario, harvest is on October 10 and azinphos methyl has a 7 day pre harvest interval for potatoes, so the two applications are made 7 and 14 days prior to harvest. By similar reasoning, the first application date for Maine was September 26. Four different management practices were simulated for potatoes. First, the standard 5% drift with 95% application efficiency was simulated, which is current EFED policy. Three different AgDrift runs were simulated.

Table 3.8 Management practices simulated for azinphos methyl use on potatoes*.

Crop App Rate ( lbs a. i./ A) Max. No. Apps. App. Interval ( days) Buffer Width ( ft) App. Method (% drift) First App. Date Potatoes 0 0.75 2 7 NA aerial ( 5%) September 26 Potatoes 1 0.75 2 7 NA no drift ( 0%) September 26 Potatoes 2 0.75 2 7 150 aerial ( 4.6%) September 26 Potatoes 3, 0.75 2 7 150 aerial ( 4.6%) September 26 Potatoes 4 0.75 2 7 0 aerial ( 21.8%) September 26 * For all simulations, IPSCND, the disposition of foliar pesticide residues on foliage at harvest was set to 1, so that the residues are applied to the soil.

As opposed to the orchard air blast simulation, there are a number of input parameters in AgDrift which can be varied to reflect management practices on the label ( Table 3.9). The azinphos methyl labels restrict application height over the canopy to 10 ft, so the ` boom height' parameter was set to this value. Droplet size distribution was set to ` fine to medium' as the label indicates that medium spray should be used. The non volatile, and active rates were set to maximum application rate of azinphos methyl on potatoes of 0.75 lb acre. The spray volume was set to a default value of 2 gal/ acre as no spray volume limitation was indicated on the label. A maximum wind speed of 10 mph is specified so this value was used in the simulation. Finally, the carrier type was set to water to reflect common practice for the pesticide. 31 0 2 4 6 8 10 12 14 16 18 Peak Day 4 Day 21 Day 60 Day 90 Mean Azinphos Methyl Concentration ( ug/ L) ID Potatoes, 150 ft buffer ME Potatoes, 150 ft buffer ID Potatoes, no buffer ID Potatoes, no drift Table 3.9 Label Spray Drift Management practice for aerial Application height above canopy ( boom height) 10 ft.

Swath displacement ( fraction of swath) 0 ft Droplet Size Distribution fine to medium Non volatile rate 0.75 lb/ acre Active Rate 0.75 lb/ acre Spray Volume 2 gal/ acre Carrier Type Water Wind Speed 10 mph Figure 4 displays the range of aquatic EECs associated with the use of azinphos methyl on potatoes. Due to the frequency of rainfall events in the eastern U. S., aquatic EECs for the Maine potato scenario are considerably higher than those for the Pacific Northwest ( i. e. Idaho). With a 150 foot buffer, the Maine scenario yields a peak EEC of 11 µ g/ L while the Idaho scenario is about 5 µ g/ L. The PRZM/ EXAMS model suggests that the addition of a 150 ft buffer in the Pacific Northwest could potentially reduce peak azinphos methyl exposures by about 70% ( from 17 to 5 µ g/ L).

Figure 4. Aquatic EECs for azinphos methyl use on potatoes in Idaho and Maine with various buffer widths.

b. Southern Pine Seed Environmental Impact Statement As part of the aquatic assessment of azinphos methyl use on southern pine seeds, an environmental impact statement from the United States Department of Agriculture Forest Service ( USDA, 1994) was reviewed. Although there are notable differences between the ecological risk assessment methodologies employed by USDA and USEPA, the environmental impact statement ( EIS) provides a useful comparative risk analysis for several pesticides used in southern pine seed orchards. The following summary is meant to highlight the EIS conclusions related specifically to 32 azinphos methyl and to identify key differences and similarities between the methodologies that may impact exposure and risk estimations.

The EIS assumed that chemical pesticides have the potential to directly or indirectly affect aquatic species if the chemicals enter water bodies via runoff or leaching. Uncertainties in the aquatic risk assessment, such as differences among species sensitivities, the influence of water quality parameters ( i. e. pH, temperature, etc.), were acknowledged in the EIS. Aquatic EECs were calculated for relevant water bodies.

In the EIS, application patterns listed were different for aerial and spray blast applications, although aerial application is apparently used much more frequently for southern pine seed orchards than spray blast. For aerial application, the typical application pattern was 1.5 lb acre 1 applied 6 times at 28 day intervals, and the maximum application pattern was 3 lb acre 1 applied in the same temporal pattern. For spray blast, the typical application practice was 4 lb acre 1 and the maximum application rate was 8 lb acre 1 with 20 acres treated per day, but no maximum number of treatments for each site listed. The use pattern as modeled for the aquatic exposure assessment was somewhat different. A single application at either the typical rate or the maximum rate was made with a 2 inch storm the day after application for the maximum application practice or two days after application for the typical practice.

The GLEAMS model ( Leonard et al., 1988) was used to estimate runoff. Spray drift was apparently not considered as an exposure route in the aquatic exposure assessment. The model was run to estimate the runoff from a single hectare in a 24 hour period. Pesticide was applied on March 24, and then 2 inches of precipitation was applied either on March 25 or 26 depending upon whether a typical or maximum application was made, as noted above. The authors assert that the 2 inch storm was assumed to be a ` 95%' event, but no documentation of storm exceedance probability distribution was provided. The runoff mass from 1 hectare was divided by the flow estimated to leave the Cypress Creek watershed ( the watershed for the Erambert Seed Orchard) in a day based on the flow that equaled or exceeded 95% of the days ( or the one in 20 day return frequency). It is not clear whether the loading of azinphos methyl in runoff was scaled for the size of the watershed.

The chemical input parameters used in GLEAMS were: a foliar half life of 2 days; a soil half life of 28 days; a K oc of 638 L/ kg ; and a foliar washoff fraction of 0.638 cm 1. EFED's best estimates of the mean value for each of these parameters ( based on data provided to the Agency in support of registration) is 7.2 days; 32 days; 579 L kg 1 ( median) and 0.937 cm 1, respectively. The source of the data for the chemistry input parameters used by USDA was not provided. It would appear, based on comparison with the environmental fate values evaluated by USEPA, that the values used in the EIS will underestimate the exposure and risk.

It is important to point out that the risk assessment in the EIS is about 2 orders of magnitude less protective than that developed by the Office of Pesticide Programs, based on the chosen return frequency. OPP uses a 1 in 10 year return frequency, as opposed to the 1 in 20 day 33 ( or, 1 in 0.05 year) value used in the EIS. The impact of this short return frequency is equivalent to allowing a pesticide concentration to be above the level of concern for 18 days per year. This level of concern could result in substantial adverse impacts on the aquatic life in the water body without exceedence of the risk threshold.

3. Measures of Terrestrial Exposure a. Terrestrial Exposure Modeling The EFED terrestrial exposure model, T REX ( Version 1.1, dated February 24, 2005), is used to estimate exposures and risks to avian and mammalian species. This model was used to assess the dietary residues of azinphos methyl for all 5 of the assessed Group 2 uses. Input values on avian and mammalian toxicity as well as chemical application and foliar dissipation half life data are required to run the model. The model generates estimated exposure concentrations ( EECs) and calculates risk quotients ( RQs). Specifically, the model provides estimates of upper bound and mean concentrations of chemical residues on the surfaces of different food items that may be sources of dietary exposure to avian, mammalian, reptilian, or terrestrial phase amphibian receptors. The surface residue concentration ( ppm) is estimated by multiplying the application rate ( pounds active ingredient per acre) by a value specific to each food item. These values ( termed the Hoerger Kenaga estimates) along with a more detailed discussion of the methodology implemented by T REX, are presented in Appendix A. T REX was run using the inputs provided in Table 3.10.

Table 3.10 T REX ( Terrestrial Exposure) Model Inputs for Azinphos Methyl.

Use Application Rate ( lbs a. i./ A) Minimum Application Interval ( Days) Maximum Number of Applications Per Year Half life ( Days)

Caneberries 0.5 10 2 9.8 Cranberries 1.0 14 2 9.8 Peaches 0.75 14 3 9.8 Potatoes 0.75 7 2 9.8 Southern Pine Seeds 1.5 30 2 9.8 EECs on food items may be compared directly with dietary toxicity data or converted to an oral dose, as is done for small mammals. For mammals, the residue concentration is converted to daily oral dose based on the fraction of body weight consumed daily as estimated through mammalian allometric relationships. The screening level risk assessment for azinphos methyl uses upper bound predicted residues as the measure of exposure. A graphical display of the predicted upper bound residues of azinphos methyl that may be expected to occur on selected avian or mammalian food items immediately following application is presented in Figure 5. 34 0 50 100 150 200 250 300 350 400 450 Caneberries Cranberries Peaches Potatoes Southern Pine Seed Orchards Azinphos Methyl Use Maximum Terrestrial EEC Short Grass Tall Grass Broadleaf Plants, Small Insects Fruits, Pods, Seeds, Large Insects Figure 5. Maximum ( upper bound) terrestrial EECs on various avian and mammalian food items immediately following azinphos methyl application to a variety of agricultural crops.

This terrestrial exposure model assumes that exposure is a direct function of the application rate and that non target, small mammals are not likely to reduce pesticide exposure by moving out of the contaminated area. Wang et al. ( 1999) tested this assumption by placing graytailed voles into enclosures planted with a mixture of pasture grasses and applying 1.5 kg a. i/ ha ( 1.34 lbs a. i./ A) azinphos methyl ( Guthion ® 2S) in three treatments: full spray ( 100% of habitat sprayed), half spray ( 50% habitat sprayed with azinphos methyl; 50% sprayed with water), and control ( 100% habitat sprayed with water). Forty four female and three male voles were tracked before and after azinphos methyl applications using radio telemetry. Following treatment, none of the 47 voles moved out of their established home ranges or from contaminated to uncontaminated areas. Home range size and daily movement patterns were not significantly affected by azinphos methyl treatment. Given access to uncontaminated habitat, gray tailed voles did not move away from contaminated habitat to avoid azinphos methyl exposure. For this ecological risk assessment, it is reasonable to assume that terrestrial wildlife exposure is directly related to the application rate of azinphos methyl.

b. Southern Pine Seed Environmental Impact Statement As part of the evaluation of potential risks associated with the use of azinphos methyl on southern pine seeds, EFED reviewed an environmental impact statement ( USDA, 1994). Terrestrial exposures in the EIS were estimated for wildlife species that may be found in the seed orchard area and that represent different body sizes, diets, and habitat niches. The terrestrial exposure analysis estimated doses from direct and indirect dermal contact; oral doses from diet items, water, and grooming; and inhalation. The methodology used to determine terrestrial exposures is consistent with that used in the EISs prepared by the U. S. Department of Justice, Drug Enforcement Administration on the eradication of cannabis with herbicides ( DEA 1985, 35 1986); and the EISs prepared by the U. S. Department of the Interior, Bureau of Land Management, on the control of noxious weeds with herbicides ( DOI 1987), and on vegetation treatment on BLM lands ( DOI 1989). Average and above average ( upper bound) estimated environmental concentrations ( EECs) were modeled. The EIS risk analysis compared estimated exposures to LD 50 s and LC 50 s for tested species. The EIS risk assessment criteria for terrestrial species are similar to EFED's levels of concern for terrestrial animals. However, the EIS did not consider chronic exposure.

C. Ecological Effects Characterization Aquatic and terrestrial effects characterization for azinphos methyl is based on registrantsubmitted acute and chronic toxicity studies for aquatic and terrestrial animals as well as toxicity information from the open literature, field studies, and adverse ecological incidents. Toxicity testing reported in this section does not represent all species of birds, mammals, or aquatic organisms. Only a few surrogate species for both freshwater fish and birds are used to represent all freshwater fish and bird species in the United States. For mammals, acute studies are usually limited to the Norway rat or the house mouse. Estuarine/ marine testing is usually limited to a crustacean, a mollusk, and a fish. Testing for reptiles and amphibians is not required, but in this case, amphibian toxicity data are available. Terrestrial and aquatic plants were not assessed; azinphos methyl is practically non toxic to plants and poses minimal risks to plants.

In general, categories of acute toxicity ranging from " practically nontoxic" to " very highly toxic" have been established for aquatic organisms ( based on LD 50, LC 50, and EC 50 values), terrestrial mammals ( based on LD 50 values), avian species ( based on LC 50 and LD 50 values), and non target insects ( based on LD 50 values for honey bees) ( U. S. EPA, 2001).

In addition to data submitted in support of registration, several studies from peer reviewed journals ( i. e. the open literature) have been reviewed and incorporated into this assessment. An " official" search of the ECOTOX database ( http:// www. epa. gov/ ecotox) was not performed. Given the vast amount of literature on the ecological effects of azinphos methyl, only the most salient studies were selected for review.

1. Aquatic Effects Characterization Relevant acute data are derived from standardized toxicity tests with lethality as the primary endpoint. These tests are conducted with what is generally accepted as the most sensitive life stage of aquatic animals ( i. e. very young fish from 0.5 5 grams in weight) and with species that are usually among the most sensitive. The intent of acute tests with aquatic animals is to statistically derive a median effect level for lethality ( LC 50). Based on this endpoint, toxicity categories can be assigned ( Table 3.11). 36 Table 3.11 Qualitative descriptors for categories of aquatic animal acute toxicity ( US EPA, 2001)

LC50 Toxicity Category < 0.1 mg/ L Very highly toxic 0.1 1 mg/ L Highly toxic 1  10 mg/ L Moderately toxic 10  100 mg/ L Slightly toxic > 100 mg/ L Practically non toxic Laboratory and field tests have revealed that azinphos methyl is very highly toxic to a variety of freshwater fish and invertebrates. Azinphos methyl has been implicated in over 130 adverse aquatic incidents ( i. e. fish kills). Freshwater organisms appear to be slightly more sensitive than their saltwater counterparts. The most sensitive freshwater fish, the northern pike, has an LC 50 of 0.36 µ g/ L, and the most sensitive estuarine/ marine fish has an LC 50 of 2.7 µ g/ L. For aquatic invertebrates, the most sensitive freshwater invertebrate, the scud ( Gammarus fasciatus), has an LC 50 ( mortality) of 0.16 µ g/ L, and the most sensitive estuarine/ marine invertebrate, the mysid shrimp, has an LC 50 ( mortality) of 0.21 µ g/ L. These endpoints will be used to calculate risk quotients for aquatic organisms exposed to azinphos methyl.

a. Acute Effects Freshwater Fish There is a wealth of acute toxicity data for freshwater fish. These data indicate that technical grade azinphos methyl is very highly toxic to most fishes, including salmonids ( Table 3.12). A static acute toxicity test ( MRID 40098001) revealed that the northern pike appears to be the most sensitive fish species, with an LC 50 of 0.36 ( 0.27 0.48) µ g/ L. Catfish and bullheads appear to be somewhat less sensitive than the other species tested. For some species, multiple tests were conducted at various temperatures and pH, and the toxicity range is provided.

Table 3.12 Acute toxicity of azinphos methyl to freshwater fish.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category MRID Northern pike Esox lucius TGAI 93 0.36a very highly toxic 40098001 Brook trout Salvelinus fontinalis TGAI 93 1.2 very highly toxic 40098001 Atlantic salmon Salmo salar TGAI 93 1.8 18 ( 5 tests) a 2.1 3.6 ( 7 tests) very highly toxic 40098001 Yellow perch Perca flavescens TGAI 93 2.4 40 ( 13 tests) very highly toxic 40098001 Unspecified Degradate 10 33 ( days 0 21) very highly toxic 40098001 Rainbow trout Oncorhynchus mykiss TGAI 93 2.9 7.1 ( 4 tests) very highly toxic 40098001 00158231 Table 3.12 Acute toxicity of azinphos methyl to freshwater fish.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category MRID 37 Guthion 50WP 8.8 ( 4.4 a. i) very highly toxic EPA Reg. No. 3125193 22 Guthion 2S 27.5 ( 6.2 a. i.) very highly toxic 00066046 Black crappie Pomoxis nigromaculatus TGAI 93 3 very highly toxic 40098001 Coho salmon Oncorhynchus kisutch TGAI 93 3.2 6.1 ( 4 tests) very highly toxic 40098001 Brown trout Salmo trutta TGAI 93 3.5 6.6 ( 6 tests) very highly toxic 40098001 Bluegill sunfish Lepomis macrochirus TGAI 93 4.1 34 ( 7 tests) very highly toxic 40098001 22 Guthion 2S 40.4 ( 8.8 a. i.) very highly toxic 00066046 Largemouth bass Micropterus salmoides TGAI 93 4.8 very highly toxic 40098001 Green sunfish Lepomis cyanellus TGAI 93 52 very highly toxic 40098001 Golden orfe Leuciscus idus melanotus TGAI 93 120 highly toxic 00067596 Fathead minnow Pimephales promelas TGAI 93 148 293 ( 2 tests) highly toxic 40098001 Carp Cyprinus carpio TGAI 93 695 highly toxic 40098001 Channel catfish Ictalarus punctatus TGAI 93 3290 moderately toxic 40098001 Black bullhead Ictalurus melas TGAI 93 3500 4810 ( 3 tests) moderately toxic 40098001 a Yolk sac fry Estuarine/ Marine Fish Estuarine/ marine fish appear to be about as sensitive to azinphos methyl as their freshwater counterparts. Acute exposure toxicity data indicate that azinphos methyl is very highly toxic to estuarine/ marine fish ( Table 3.13). The most sensitive estuarine/ marine fish, the sheepshead minnow, has a 96 hour LC 50 for technical grade azinphos methyl of 2.0 ( 1.8 2.2) µ g a. i/ L with a probit slope of 8.8. This flow through toxicity test was procured from the open literature ( Morton et al., 1997). This study assessed the acute toxicity of azinphos methyl to the sheepshead minnow at the following nominal ( measured) treatments: 0 ( control), 0 ( solvent control), 0.38 ( 0.33) 0.75 ( 0.78), 1.5 ( 1.3), 3.0 ( 2.8), and 6.0 ( 5.6) µ g a. i/ L. Recoveries ranged from 78 to 103%. At 96 hours, the NOAEC for mortality was 0.78 µ g a. i/ L.

A study with the formulated product, Guthion 2L ( 22% active ingredient) reported a sheepshead minnow LC 50 of 1.86 ( 1.51 2.3) µ g a. i/ L with a probit slope of 5.0. This flowthrough study ( MRID 41202001) assessed the acute toxicity of Guthion 2L to the sheepshead 38 minnow at mean measured concentrations of 0.235, 0.386, 0.703, 1.36, and 3.14 µ g a. i/ L. The NOAEC for mortality was 0.703 µ g a. i/ L. Fish exposed to the highest treatment concentration exhibited lethargy and loss of equilibrium after 24 hours, and fish in the 1.36 µ g a. i/ L treatment group were showed the same sublethal effects after 48 hours. For both groups, these effects continued until mortality occurred or test termination.

Table 3.13 Acute toxicity of azinphos methyl to estuarine/ marine fish.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category Study Classification MRID Sheepshead minnow Cyprinodon variegatus 98 2.0 very highly toxic Acceptable Morton et al. 1997 88.8 2.7 very highly toxic Acceptable 40380501 Guthion 2L 22.3 1.86 a. i. very highly toxic Acceptable 41202001 Striped mullet Mugil cephalus 96 3.2a very highly toxic Supplemental 40228401 Spot Leiostomus xanthurus 96 28a very highly toxic Supplemental 40228401 a 48 h test Amphibians EFED typically uses fish toxicity data as a surrogate for amphibian species. In this case, azinphos methyl toxicity information is available for two amphibian species. These data suggest that azinphos methyl is highly toxic to amphibians. Based on these studies ( Table 3.14) it appears that amphibians may be less sensitive to azinphos methyl than fish and aquatic invertebrates; nevertheless, azinphos methyl is still categorized as highly toxic to amphibians. The LC 50 for the most sensitive amphibian, the Fowlers toad, is 109 µ g a. i/ L, which is approximately three orders of magnitude higher than that of the most sensitive aquatic invertebrate, the scud ( Gammarus fasciatus). Sensitivity differences between fish and amphibians exposed to azinphos methyl have been previously observed. Ferrari et al. ( 2004) reported that rainbow trout ( Oncorhynchus mykiss) are approximately three orders of magnitude more sensitive than the toad, Bufo arenarum.

Table 3.14 Acute toxicity of azinphos methyl to freshwater amphibians.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category Study Classification Reference Fowlers toad Bufo fowleri 93 109 Highly toxic Supplemental MRID 40098001 Western chorus frog Pseudacris triseriata 93 3200 Moderately toxic Supplemental MRID 40098001 Argentine Toad Bufo arenarum 99 10,440 Slightly toxic Supplemental Ferrari et al. 2004 39 Freshwater Invertebrates Toxicity studies are available for a wide range of freshwater invertebrates. The most sensitive species appears to be a common amphipod, the scud ( Gammarus fasciatus), which has a 96 hour LC 50 of 0.16 ( 0.08 0.32) µ g/ L ( Table 3.15). Crayfish may be relatively less sensitive to azinphos methyl. Azinphos methyl is very highly toxic to freshwater invertebrates.

Table 3.15 Acute toxicity of azinphos methyl to freshwater invertebrates.

Species Purity (% a. i.) 48 h LC50 ( µ g/ L) Toxicity Category Study Classification MRID Scud Gammarus fasciatus TGAI 93 0.16 0.25 ( 2 tests) very highly toxic Acceptable 40098001 Water flea Daphnia magna TGAI 91 1.13 very highly toxic Acceptable 00068678 Guthion 50WP 4.8 ( 2.4 a. i.) very highly toxic Acceptable 40301302 Glass shrimp Palaemonetes kadiakemsis TGAI 93 1.2a very highly toxic Supplemental 40098001 Stonefly Pteronarcys californica TGAI 93 1.9a very highly toxic Acceptable 40098001 Sowbug Asellus brevicaudus TGAI 93 21a very highly toxic Supplemental 40098001 Crayfish Procambarus sp. TGAI 93 56a very highly toxic Supplemental 40098001 a 96 h test Estuarine/ Marine Invertebrates Azinphos methyl is very highly toxic to estuarine/ marine invertebrates. Bivalves, such as the Eastern oyster, may be slightly more tolerant to azinphos methyl than other aquatic invertebrates ( Table 3.16). The mysid shrimp is the most sensitive estuarine/ marine invertebrate, with an LC 50 of 0.21 µ g/ L. This flow through study ( MRID 40380502) evaluated the acute toxicity of azinphos methyl to mysid shrimp at mean measured concentrations of 0.13, 0.26, 0.63, 1.1, and 1.8 µ g/ L. The LC 50 was estimated to be 0.21 ( ± 0.04) µ g/ L with a probit slope of 5.8. The NOAEC was determined to be less than the lowest concentration tested, 0.13 µ g/ L.

Table 3.16 Acute toxicity of azinphos methyl to estuarine/ marine invertebrates.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category Study Classification MRID Mysid shrimp Mysidopsis bahia 88.8 0.21 very highly toxic Acceptable 40380502 22.3 Guthion 2L 0.26 a. i. very highly toxic Acceptable 41202002 98 0.29 very highly toxic Acceptable Morton et al. 1997 Table 3.16 Acute toxicity of azinphos methyl to estuarine/ marine invertebrates.

Species Purity (% a. i.) 96 h LC50 ( µ g/ L) Toxicity Category Study Classification MRID 40 Brown shrimp Penaeus aztecus 96 2.4 very highly toxic Acceptable 40228401 Blue crab Callinectes sapidus 96 320 highly toxic Supplemental 40228401 Eastern oyster Crassostrea virginica 96 1000 highly toxic Acceptable 40228401 88.8 > 3100 not determined Acceptable 40452001 b. Chronic Effects Freshwater Fish Azinphos methyl triggers adverse effects on the normal life processes ( i. e. growth, reproduction) of fish at very low levels ( less than one part per billion). Chronic toxicity information is available for the rainbow trout from a fish early life stage study ( Table 3.17). Rainbow trout were exposed to mean measured azinphos methyl treatments of 0.051, 0.14, 0.23, 0.44, and 0.98 µ g/ L for 60 days.

Table 3.17. Chronic toxicity of azinphos methyl to freshwater fish during an early life stage toxicity test Species Purity (% a. i.) NOAEC ( µ g/ L) LOAEC ( µ g/ L) Endpoints Affected MRID Classification Rainbow trout Oncorhynchus mykiss 88.8 0.44a 0.98 Larval survival, length, and growth at day 60 40579601 Acceptable a NOAEC for behavioral effects ( lethargy) is 0.23 µ g/ L Estuarine/ Marine Fish Available data indicate that chronic exposure to low levels ( less than one part per billion) of azinphos methyl adversely affects survivorship and reproduction of the sheepshead minnow, an estuarine/ marine fish ( Table 3.18). In a 28 day, flow through fish early life stage toxicity test ( Morton et al., 1997), sheepshead minnows were exposed to azinphos methyl at the following nominal ( measured ± standard deviation) treatments: 0 ( control), 0 ( solvent control), 0.12 ( 0.17 ± 0.03), 0.25 ( 0.34 ± 0.07), 0.50 ± ( 0.62 ± 0.04), 1.0 ( 1.2 ± 0.13), and 2.0 ( 2.3 ± 0.29) µ g/ L. Recoveries ranged from 79 to 107%. After 28 days, the mortality rate was 100% for fish exposed to 1.2 and 2.3 µ g/ L. The NOAEC and LOAEC for survival were 0.17 and 0.34 µ g/ L, respectively. There were no statistically significant effects on growth ( weight, length) at concentrations below 0.62 µ g/ L. 41 Table 3.18 Chronic toxicity of azinphos methyl to estuarine/ marine fish Species Test Type Purity (% a. i.) NOAEC ( µ g/ L) LOAEC ( µ g/ L) Endpoints Affected Study Classification MRID Sheepshead minnow Cyprinodon variegatus Early Life Stage 98 0.17 0.34 Survival Acceptable Morton et al. 1997 Life cycle 92.5 0.20 0.41 2nd generation embryo survival; hatchling success Acceptable 42021601 Freshwater Invertebrates Available data indicate that azinphos methyl also adversely affects the normal life processes of a common freshwater zooplankton, Daphnia magna. Sublethal effects in freshwater invertebrates and fish are triggered at approximately the same level of azinphos methyl. Daphnids were exposed to five test concentrations ( 0.070, 0.12, 0.24, 0.42, and 0.97 µ g/ L) in a 21 day flow through chronic toxicity study. Survivorship, length, and fecundity ( mean number of young per adult per reproductive day) were significantly reduced in the 0.40 and 0.99 µ g/ L ( meanmeasured treatments ( Table 3.19).

Table 3.19 Chronic toxicity of azinphos methyl to freshwater invertebrates during a life cycle toxicity test Species Purity (% a. i.) NOAEC ( µ g/ L) LOAEC ( µ g/ L) Endpoints Affected Study Classification MRID Water flea Daphnia magna 99.6 0.25 0.40 Adult length, survival, number of young/ adult/ day Acceptable 00073606 Estuarine/ Marine Invertebrates Chronic toxicity information for estuarine/ marine invertebrates is available in the open literature ( Table 3.20). Morton et al. ( 1997) performed a 26 day, flow through test with mysid shrimp to assess the toxicity of azinphos methyl at the following nominal ( measured ± standard deviation) treatments: 0 ( control), 0 ( solvent control), 0.022 ( 0.020), 0.036 ( 0.030 ± 0.005), 0.06 ( 0.061 ± 0.022), 0.10 ( 0.097 ± 0.026), 0.17 ( 0.18 ± 0.054), and 0.28 ( 0.28 ± 0.072) µ g/ L. Recoveries were95 to 109%. The mean day of first brood release in the pooled control was day 19.2, and initiation of reproduction was not significantly affected by azinphos methyl exposure. Survival was significantly affected at 0.18 and 0.28 µ g/ L; mortality was 100% in the 0.28 µ g/ L treatment group. Thus, the NOAEC for mortality was 0.097 µ g/ L. Fecundity ( number of young/ female) was significantly reduced in the 0.030, 0.061, and 0.097 µ g/ L treatment groups. Mysids in the 0.030 µ g/ L group produced an average of 4.6 offspring, about one third fewer than their control counterparts, which produced an average of 6.9. The NOAEC for sublethal ( reproductive) effects was 0.020 µ g/ L. 42 Table 3.20 Chronic toxicity of azinphos methyl to estuarine/ marine invertebrates.

Species Purity (% a. i.) NOAEC ( µ g/ L) LOAEC ( µ g/ L) Endpoints Affected Study Classification Reference Mysid Shrimp Mysidopsis bahia 98 0.02 0.03 Fecundity ( Number of offspring/ female) Acceptable Morton et al. 1997 c. Sublethal Effects Several studies have shown that very low levels of azinphos methyl and other organophosphates inhibit cholinesterase ( ChE) activity in aquatic animals, such as fish and frogs. Ferrari et al. ( 2004) reported that the azinphos methyl IC 50 ( i. e. concentration that produces 50% cholinesterase inhibition) for rainbow trout, is 0.4 ( ± 0.1) µ g/ L, which is approximately one order of magnitude below the LC 50. The IC 50 for the toad ( Bufo arenarum) is 5610 ( ± 810) µ g/ L, which is about half of the LC 50. Sublethal ChE inhibition of 70 90% has been observed in other fish species as well ( Gruber and Munn, 1998; Varó et al., 2003).

The relationship between sublethal ChE inhibition and the ultimate fitness of a given aquatic species is not well understood ( Fulton and Key, 2001). However, Beauvais et al. ( 2000) reported that two organophosphate insecticides altered the normal behavior of larval rainbow trout through cholinesterase inhibition. As cholinesterase activity declined, fish swimming speed and distance were significantly reduced. These types of behavioral responses have the potential trigger serious ecological consequences by altering predator/ prey relationships, reproductive strategies, migration patterns, etc.

d. Field Studies Sierszen and Lozano ( 1997) studied the effects of a single application of 0.2, 1.0, 4.0, and 20.0 µ g/ L azinphos methyl on natural zooplankton communities using littoral ecosystem enclosures. Mean measured concentrations were 1.33, 4.72, and 20.4 µ g/ L in the 1.0, 4.0, and 20.0 µ g/ L nominal treatments, respectively. ( The 0.2 nominal treatment was below the LOQ µ g/ L). Zooplankton were sampled 10 times   twice pre treatment and 8 times post treatment. Of the three main groups of zooplankton ( cladocerans, copepods, and rotifers), cladocerans were most sensitive to azinphos methyl. Cladoceran taxa accounted for 82% of all significant treatment effects on individual taxa. Most of the effects were observed at the 20 µ g/ L treatment level; however, 8 of the 12 cladoceran taxa were significantly affected at the 4 µ g/ L treatment. Azinphos methyl exposure did not elicit consistent, adverse effects on copepods, rotifers, or ostracods. Taxon richness ( diversity) decreased with increasing azinphos methyl exposure and was significantly different in the 4.0 and 20.0 µ g/ L treatments. Recovery of populations and communities ranged from one month ( at 4.0 µ g/ L) to longer than 78 days ( at 20 µ g/ L) following a single application of azinphos methyl. Peak aquatic EECs generated by PRZM/ EXAMS are in the range of Sierszen and Lozano's test concentrations. Based on their results, azinphos methyl has the potential to elicit population or community level effects on zooplankton. The consequences may trigger cascading effects on organisms that are higher ( i. e. fish) and/ or lower 43 ( i. e. algae) in the food chain.

Schulz and Thiere ( 2002) evaluated the impacts of azinphos methyl on stream macroinvertebrate communities using a combined microcosm and field approach. Stones were collected from the Lourens River ( South Africa) from a control site ( free of pesticide contamination) upstream of a 400 ha orchard and transferred to outdoor microcosms so that each microcosm had 12 core macroinvertebrate species and approximately 350 individuals. Microcosms were treated with azinphos methyl at 0 ( control), 0.2, 1, 5, or 20 µ g/ L ( meanmeasured concentrations were < 0.01 ( LOQ), 0.2, 1.0, 4.9, and 19.2 µ g/ L). Survivorship was assessed 6 days after treatment. Microcosms treated with 4.9 and 19.2 µ g/ L had significantly lower invertebrate densities. Species diversity was significantly lower in the 19.2 µ g/ L treatment group, which had an average of 9.7 species compared to 14 in the control group. Schulz and Thiere conducted a parallel macroinvertebrate survey at the control site and a contaminated site ( downstream of the orchard) on the Lourens River. Species number was similar at both sites, but abundance and diversity were significantly different. Five of the eight species that were affected by azinphos methyl in the microcosm studies occurred at significantly lower densities or were completely absent at the contaminated field site. Of the four species that were unaffected by azinphos methyl in the microcosm studies, all of them occurred at significantly higher densities at the contaminated field site.

To evaluate the potential impacts of pesticide exposure and other abiotic factors on species abundance and diversity in the Lourens River, Thiere and Schulz ( 2004) surveyed stream macroinvertebrates above and below a 400 ha orchard area. The sampling site above the orchard ( LR1) was free of pesticide contamination, and the site 4000 m downstream of the orchard ( LR2) received transient peaks of azinphos methyl, chlorpyrifos, malathion, and endosulfan. The two sampling sites were similar in bottom substrate composition and most abiotic factors, except turbidity and pesticide concentration. The macroinvertebrate communities were similar in terms of number of total individuals, but LR1 had significantly more taxa ( 11.7) compared to LR2 ( 8.9). Seven out of 17 taxa occurred had a significantly reduced population or were completely absent at LR2. Based on a community indices for water quality bioassessment, LR2 had a less sensitive community structure, indicating poorer water quality compared to LR1. The authors concluded that pesticide exposure and increased turbidity were the most important factors impacting community structure.

2. Terrestrial Effects Characterization Relevant acute data are derived from standardized toxicity tests with lethality as the primary endpoint. These tests are conducted with what is generally accepted as the most sensitive life stage and with species that are usually among the most sensitive. Acute toxicity tests with birds and mammals are intended to statistically derive a median effect level for acute oral exposure ( LD 50) and subacute dietary exposure ( LC 50). Based on these endpoints, toxicity categories can be assigned ( Table 3.21). 44 Table 3.21 Qualitative descriptors for avian and mammalian toxicity ( US EPA, 2001)

Toxicity Category Oral LD50 Dietary LC50 Very highly toxic < 10 mg/ kg < 50 ppm Highly toxic 10  50 mg/ kg 50  500 ppm Moderately toxic 51  500 mg/ kg 501  1000 ppm Slightly toxic 501  2000 mg/ kg 1001  5000 ppm Practically non toxic > 2000 mg/ kg > 5000 ppm Available laboratory and field toxicity data indicate that azinphos methyl is highly toxic to terrestrial animals, including birds and mammals. The acute oral LD 50 for the most sensitive bird ( bobwhite quail) is 32 mg/ kg, and for the most sensitive mammal the laboratory rat, the LD 50 is 7.8 mg/ kg. Subacute dietary LC 50 is 488 ppm for the bobwhite quail and 406 ppm for the graytailed vole. The NOAEC for sublethal effects on growth, development, and reproduction occur at 10.5 ppm for the mallard duck and 5 ppm for the laboratory rat. Field studies have confirmed the toxicity of azinphos methyl to non target terrestrial animals, and several adverse terrestrial incidents have provided additional corroboration.

Azinphos methyl exhibits high acute toxicity due to irreversible inhibition of cholinesterase enzymes. As with humans, exposure of wildlife to cholinesterase inhibiting pesticides disrupts normal neuromuscular control. Death can occur rapidly, due primarily to respiratory failure. Organophosphate exposure can also result in chronic effects in animals such as reproduction impairment and delayed neuropathy.

a. Acute Effects Birds Acute oral toxicity data are available for a number of avian species. These studies indicate that azinphos methyl ranges from moderately to highly toxic to birds ( Table 3.22). The most sensitive species, the bobwhite quail, has an LD 50 of 32 ( 25 41) mg/ kg with a probit slope of 8.8. In this study ( MRID 40254801), adult ( 15 week) bobwhite quail were exposed to 5.6, 11.2, 23.0, 45.0, and 90.0 mg a. i./ kg bw. The NOAEL for mortality was 11.2 mg/ kg. Sublethal effects including ataxia, wing drop, wing spasms, hyporeactivity, immobility, labored breathing, salivation, and convulsion were observed in all treatments except the lowest dose; thus, the NOAEL for clinical signs of toxicity was 5.6 mg/ kg.

Table 3.22 Acute oral toxicity of azinphos methyl to birds.

Species Purity (% a. i.) LD50 ( mg a. i./ kg) Toxicity Category Study Classification MRID Bobwhite quail Colinus virginianus TGAI 88.8 32 highly toxic Acceptable 40254801 TGAI Not specified 33 highly toxic Supplemental 40605801 Table 3.22 Acute oral toxicity of azinphos methyl to birds.

Species Purity (% a. i.) LD50 ( mg a. i./ kg) Toxicity Category Study Classification MRID 45 TGAI 90 60 moderately toxic Supplemental 00160000 Mallard duck Anas platyrhynchos TGAI 90 136 moderately toxic Supplemental 00160000 Ring necked pheasant Phasianus colchicus TGAI 90 74.9 moderately toxic Supplemental 00160000 Formulation Not specified 283 moderately toxic Supplemental 00160000 Chukar Alectoris chukar TGAI 90 84.2 moderately toxic Supplemental 00160000 Bobwhite quail is also the most sensitive avian species on a subacute dietary toxicity basis, with an LC 50 of 488 ( 394 601) ppm ( Table 3.23). Based on this endpoint, azinphos methyl is highly toxic to birds on a subacute dietary basis.

Table 3.23 Subacute dietary toxicity of azinphos methyl to birds.

Species Purity (% a. i.) LC50 ( ppm) Toxicity Category Study Classification MRID Northern bobwhite quail Colinus virginianus TGAI 92 488 highly toxic Acceptable 00022923 Japanese Quail Coturnix japonica TGAI 92 639 moderately toxic Supplemental 00022923 Ring necked pheasant Phasianus colchicus TGAI 92 1821 slightly toxic Acceptable 00022923 Mallard duck Anas platyrhynchos TGAI 92 1940 slightly toxic Acceptable 00022923 Acute oral toxicity studies indicate that the most sensitive mammalian species is the laboratory rat, which has an LD 50 of 7.8 mg/ kg ( Table 3.24) for azinphos methyl. Based on this endpoint, azinphos methyl is categorized as very highly toxic to mammals.

Table 3.24 Acute oral toxicity of azinphos methyl to mammals.

Species Purity (% a. i.) LD50 ( mg/ kg) Toxicity Category Study Classification MRID/ Reference Laboratory rat Rattus norvegicus 85 7.8 very highly toxic Acceptable 40280101 House mouse ( wild) Mus musculus 99.1 10 highly toxic Supplemental Meyers and Wolff 1994 Laboratory mouse Mus musculus 99.1 11 highly toxic Supplemental Meyers and Wolff 1994 Gray tailed vole Microtus canicaudus 99.1 32 highly toxic Supplemental Meyers and Wolff 1994 Table 3.24 Acute oral toxicity of azinphos methyl to mammals.

Species Purity (% a. i.) LD50 ( mg/ kg) Toxicity Category Study Classification MRID/ Reference 46 Deer mouse Peromyscus maniculatus 99.1 48 highly toxic Supplemental Meyers and Wolff 1994 Subacute dietary toxicity data are available for three mammalian species ( Table 3.25). These data suggest that azinphos methyl is highly toxic to mammals on a subacute dietary toxicity basis. The gray tailed vole is the most sensitive species, with a 5 day LC 50 of 406 ( 312 858) ppm ( Meyers and Wolff, 1994).

Table 3.25 Subacute dietary toxicity of azinphos methyl to mammals.

Species Purity (% a. i.) LC50 ( ppm) Slope ( SE) Toxicity Category Study Classification MRID/ Reference Gray tailed vole Microtus canicaudus 99.1 406 1.93 ( 0.6) highly toxic supplemental Meyers and Wolff 1994 Laboratory mouse Mus musculus 99.1 543 2.57 ( 0.84) moderately toxic supplemental Meyers and Wolff 1994 Deer mouse Peromyscus maniculatus 99.1 2425 1.45 ( 0.35) slightly toxic supplemental Meyers and Wolff 1994 92 > 5000  practically nontoxic supplemental 40858301 Terrestrial Invertebrates The use of azinphos methyl on agricultural crops such as peaches and potatoes may result in exposure to non target beneficial insects, such as the honey bee. Given that azinphos methyl acts as an insecticide, it is not surprising that this chemical is highly toxic to beneficial insects as well as pest insects. Acute oral and contact studies suggest that azinphos methyl highly toxic to honey bees ( Table 3.26). In addition, a foliar residue study with Guthion 50WP indicates that toxic residues can persist on vegetation for up to 13 days post treatment.

Table 3.26 Acute toxicity of azinphos methyl to honey bees. ( TGAI = Technical Grade Active Ingredient)

Species Purity (% a. i.) Test Type Results Toxicity Category Study Classification MRID Honey bee Apis mellifera TGAI acute contact ( 48 h LD50) LD50 = 0.063  g/ bee highly toxic Acceptable 05004151 TGAI acute oral ( 48 h LD50) LD50 = 0.15  g/ bee highly toxic Acceptable 05004151 TGAI (% NR) acute contact ( 48 h LD50) LD50 = 0.423  g/ bee highly toxic Acceptable 00066220 Guthion 50 WP foliar residue ( 3 lb ai/ A) Residues highly toxic for 4 13 days post treatment not applicable Acceptable 40466301 Additional toxicity data for non target soil and surface insects and mites are available 47 ( Table 3.27). Results indicate that azinphos methyl is highly toxic to non target beneficial insects, including bees, wasps, beetles, and mites.

Table 3.27 Acute toxicity of azinphos methyl to non target beneficial insects ( other than honey bees).

Species Purity (% a. i.) Application Rate Results MRID Parasitic wasp Aphytis melinus Guthion 50 WP 380 ppm ( on lemons) Highly toxic 05004003 Predaceous beetles ( 2 spp.) Parasitic wasps ( 2 spp.) Guthion 25 WP 0.0477% a. i. ( in honey bait) Highly toxic 05005640 Predaceous beetles ( 6 spp.) Predaceous wasps ( 5 spp.) Guthion 25 WP 0.5 lb ai/ 100 gal ( on waxed paper) Highly toxic 05003978 Predaceous mite Amblyseius hibisci Guthion 25 WP 0.5 lb ai/ 100 gal Highly toxic 05004148 b. Chronic Effects Birds Chronic avian toxicity data are available for two species ( Table 3.28). The most sensitive species is the mallard duck, with a reproductive NOAEC of 10.5 ppm. This one generation reproduction study ( MRID 40844201) evaluated the chronic dietary toxicity of azinphos methyl to 18 week old mallard ducks at mean measured treatment concentrations of 10.5, 32.5, and 96.5 ppm. No treatment related mortalities or clinical signs of toxicity were observed in adults throughout the course of the study. Females in the 32.5 and 96.5 ppm groups weighed significantly ( approximately 20%) less than their control counterparts.

Table 3.28 Chronic avian toxicity information for azinphos methyl Species Purity (% a. i.) NOAEC ( ppm) LOAEC ( ppm) Endpoints Affected Study Classification MRID Mallard duck Anas platyrhynchos 88.8 10.5 32.5 Female weight gain Acceptable 40844201 Northern bobwhite quail Colinus virginianus 88.8 36.5 87.4 Eggs laid Eggs set Viable embryos Surviving embryos Surviving hatchlings Acceptable 41056101 Mammals Chronic mammalian data are available for one species, the laboratory rat ( Table 3.29). In a two generation reproduction study in Wistar rats ( MRID 40332601), azinphos methyl ( 87.2%) was administered at dietary concentrations of 0, 5, 15, or 45 ppm ( equivalent to 0.25, 0.75, or 2.25 mg/ kg/ day). The systemic parental NOAEL was 15 ppm ( 0.75 mg/ kg/ day), based upon mortality of dams, decreased body weight for P males and F1 males and females, and clinical signs of toxicity, including poor condition and convulsions, at the systemic LOAEL of 45 ppm ( 2.25 48 mg/ kg/ day). The reproductive ( offspring) NOAEL and LOAEL were 5 and 15 ppm ( 0.25 and 0.75 mg/ kg/ day), respectively. The LOAEL was based on a reduction in pup viability and lactation indices ( death of the offspring between the time periods of postnatal days 0 5 and 5 28) and decreased mean total litter weights at weaning on postnatal Day 28. No cholinesterase measurements were taken for either parental animals or pups.