Page 1 of 71 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON

, D.C. 20460

December 12, 2011 PC Code: 061601 MEMORANDUM DP Barcode: 392076

SUBJECT: EFED Registration Review: Prelimin ary Problem Formulation for Paraquat Dichloride

FROM: Kristina Garber, Senior Biologist James Lin, Environmental Engineer Environmental Risk Branch II Environmental Fate and Effects Division (7507P)

REVIEWED BY: Jean Holmes, DVM, MPH, Risk Assessment Process Leader R. David Jones, Ph.D., Senior Agronomist

THROUGH: Brian Anderson, Chief Environmental Risk Branch II Environmental Fate a nd Effects Division (7507P)

TO: Molly Clayton, Chemical Review Manager Michael Goodis, Chief Risk Management and Implementation Branch III Pesticide Re-Evalua tion Division (7508P)Page 2 of 71 The Environmental Fate and Effects Division (E FED) has completed the preliminary problem formulation (attached) for the ecological risk, environmental fate, endangered species, and drinking water assessments to be co nducted as part of the registra tion review of the herbicide, paraquat dichloride. The problem formulation draws on information from both open literature and studies submitted by the technical registrant in response to data requirements. This document is intended to provide an overview of what is currently known regarding the environmental fate and ecological effects asso ciated with paraquat dichloride and outlines uncertainties, including data gaps. This pr oblem formulation describes the preliminary ecological risk hypothesis and the processes that will be used dur ing the completion of drinking water and ecological risk assessments in support of registration review for paraquat dichloride. This document also identifies information gaps and recommends studies that the Pesticide ReEvaluation Division (PRD) should include in a data call-in (DCI) to address uncertainties surrounding the environmental fate and potential ecological effects of paraquat dichloride.Page 3 of 71 

# Preliminary Problem Formulation for the Environmental Fate and Ecological Risk, Endangered Species, and Drinking Water Assessments in Support of the Registration Review of Paraquat Dichloride

Chemical name: 1,1'-dimethyl-4,4'-bipyridinium dichloride PC: 061601

P repared by: Kristina Garber, Senior Biologist James Lin, Environmental Engineer U. S. Environmental Protection Agency Office of Pesticide Programs E

nvironmental Fate and Effects Division E

nvironmental Risk Branch I I 1200 Pennsylvania Ave., NW Mail Code 7507P Washington, DC 20460 R eviewed by: Jean Holmes, DVM, MPH, Risk Assessment Process Leader R. David Jones, Ph.D., Senior Agronomist Brian Anderson, Branch Chief N

N + + 2Cl-Page 4 of 71 Table of Contents 1. Purpose ................................................................................................................... .................... 5 2. Nature of Regulatory Action ............................................................................................... ....... 5 3. Conclusions from Previous Risk Assessments .......................................................................... 5 4. Stressor Source and Distribution ........................................................................................... ..... 6 4.1. Mechanism of Action ..................................................................................................... ..... 6 4.2. Overview of Pesticide Usage ............................................................................................. . 6 4.3. Environmental Fate and Transport .................................................................................... 13 Mobility .......................................................................................................................... 14 Degradation ................................................................................................................... 15 Field Dissipation ............................................................................................................ 15 4.4. Monitoring Data ......................................................................................................... ....... 16 4.5. Nature of Stressor ...................................................................................................... ....... 16 5. Receptors.................................................................................................................. ................ 17 5.1. Effects to Aquatic Organisms ........................................................................................... 17 5.3. Ecological Incidents .................................................................................................... ...... 19 6. Ecosystems Potentially at Risk .......................................................................................... 22 7. Assessment Endpoints ...................................................................................................... ....... 22 8. Conceptual Model ........................................................................................................... .......... 22 8.1. Risk Hypothesis ......................................................................................................... ....... 23 8.2. Conceptual Diagram ...................................................................................................... ... 23 9. Analysis Plan .............................................................................................................. .............. 25 9.1. Measures of Exposure .................................................................................................... ... 26 9.2. Measures of Effect ...................................................................................................... ...... 28 9.3. Integration of Exposure and Effects ................................................................................. 29 9.4. Endangered Species Assessments ..................................................................................... 30 9.5. Drinking Water Assessment ............................................................................................. 3 1 10. Endocrine Disruptor Screening Program ....................................................................... 31 11. Preliminary Identifica tion of Data Gaps ............................................................................ 32 11.1. Fate .................................................................................................................... 32 11.2. Effects ................................................................................................................ 34 12. References ............................................................................................................... ............... 41 Appendix A. Ecological E ffects Characterization .................................................................... 61Page 5 of 71 

## 1. Purpose

The purpose of problem formulation is to provide the foundation for risk assessment. It sets the assessment objectives, evaluates the nature of th e problem, and provides a plan for analyzing the data and characterizing the risk. This problem formulation provides a plan for analyzing data relevant to paraquat dichloride and for conduc ting environmental fate and ecological risk, endangered species, and drinking water assessments as part of the regist ration review of its registered uses. Additionally, this problem form ulation identifies data gaps, uncertainties, and potential assumptions used to address those uncertainties, relative to characterizing the ecological risk associated with the registered uses of paraquat dichloride.

The active ingredient, paraquat dichloride, is ge nerally applied as a flowable solution. As a result, paraquat dichloride readily dissociates into its cation, paraquat. Therefore, the following discussions involving paraquat dichloride will fo cus on the paraquat catio n as the stressor of

concern.



## 2. Nature of Regulatory Action

The Food Quality Protection Act of 1996 mandate d the Environmental Protection Agency (EPA) to implement a new program for a ssessing the risks of pesticides, i.e ., registration review ( http://www.epa.gov/oppsrr d1/registration_review/ ). All pesticides distributed or sold in the United States generally must be registered by EPA. The decision to register a pesticide is based on the consideration of scientific data and other factors showing th at it will not cause unreasonable risks to human health, workers, or the environment when used as directed on product labeling. The registration re view program is intended to en sure that, as the ability to assess risk evolves and as policie s and practices change, all regist ered pesticides continue to meet the statutory standard of no unreasonabl e adverse effects to human health and the environment. Changes in science, public policy, and pesticide use practices will occur over time. Through the new registration review program, the Ag ency periodically reeval uates pesticides to ensure that as change occurs, products in the marketplace can be used safely.

As part of the implementation of the new registration review progr am pursuant to Section 3(g) of the Federal Insecticide, Fungicide and Rodentic ide Act (FIFRA), the Agency is beginning its evaluation to determine whether paraquat dichlori de continues to meet the FIFRA standard for registration. This problem formulation for the en vironmental fate and ecological risk assessment chapter in support of the registra tion review is intended for the in itial docket, opening the public phase of the review process.



## 3. Conclusions from Previous Risk Assessments

Paraquat has a long regulatory hist ory. A re-registration eligibility decision (RED) was made in 1997. In the 1997 RED, the Agency requested additio nal data in order to establish tolerances onPage 6 of 71 taro foliage, corn and soybean aspirated grain fractions, wheat and hay, cotton and gin byproducts, and processed grapes, as well as data to confirm that the exis ting tolerance for field corn was adequate to cover the specialized use of paraquat as a harvest aid. The ecological risk assessment for the RED concluded that uses of pa raquat dichloride pose risks to birds, mammals and plants. The maximum single application rate of paraquat was 1.6 lb cation/A. This rate was reduced to 1.0 lb cation/A in th e RED in order to reduce risks.

In June 2009, an endangered sp ecies risk assessment was completed by EFED to determine the Risks of Paraquat Use to Federally Thr eatened California Red-legged Frog (CRLF; Rana aurora draytonii ). This assessment considered all registered uses of paraquat that are relevant to the state of California. The assessment concluded that paraquat may affect, and is likely to adversely affect the CRLF based on the direct effects to the terrestrial-phase CRLF, and indirect effects to the aquatic- and terrestrial-phase CRLF. Indirect effects are specifically related to declines in prey (algae, amphibians, mammals) and habitat of the frog.

In July, 2011, EFED completed an ecological risk assessment for the use of paraquat dichloride on tropical and subtropical trees (DP 382001). Ri sk conclusions were similar to previous conclusions and included LOC exceedances for plan ts, aquatic invertebrates, mammals, birds, terrestrial-phase amphibians and reptiles. A decision on that action is pending.


## 4. Stressor Source and Distribution

4.1. Mechanism of Action

Paraquat dichloride is a quaternary ammonium compound widely used for broadleaf weed control. It is a fast-a cting contact herbic ide used to suppress or erad icate a wide spectrum of post-emergent weeds. It also functions as a defoliant and desiccant and is most effective on growing plants with abundant gree n tissue. It is highly toxic (E PA toxicity class I) but readily immobilized. Paraquat is quick ly absorbed by living (especia lly healthy) plant tissue and produces superoxides during photosynthesis, which de stroy plant cells. It is less effective on dry, drought-stressed, woody, or fully mature plants.



### 4.2. Overview of Pesticide Usage

Two formulated products are commercial availabl e: an emulsifiable concentrate (EC) and a liquid (L, only for cotton use). The applica tion equipment include aircraft, ground, and low pressure ground sprayer. The application met hod types include banded and broadcast, or spottreatment sprays and a tree wound treatment.

The uses considered for this Re gistration Review are listed in Table 1 . Many of the current labels do not contain sufficient information to limit maximum annua l numbers of applications or maximum annual application rates. Note that th ese applications rates are based on lb paraquat dichloride/A. A rate of 1.417 lb/A is equivalent to 1 lb cation/A.Page 7 of 71 Table 1. Currently Registered Uses to be Cons idered for Registration Re view (provided by BEAD) 1

Use Site Max App Rate / App Max # Apps / Year or Crop Cycle Use Group: Forest arborvitae (forest/shelterbelt), ash (forest/shelterbelt), elm (forest/shelterbelt), fir (forest/shelterbelt), forest trees (softwoods, conifers), oak (forest/shelterbelt), pine (forest/shelterbelt) 1.417 lb/ac 5

forest trees (hardwoods, broadleaf trees) 1.385 lb/ac 5
use group: terrestrial feed

alfalfa 1.400 lb/ac 2
clover 1.388 lb/ac 2 corn (silage) 0.689 lb/ac 3 crown vetch, legume vegetables , lespedeza, lupine, sainfoin, trefoil, vetch 1.102 lb/ac 1 tyfon 1.417 lb/ac 3 use group: terrestrial food acerola (west indies cherry), appl e, avocado, banana, beech nut, blackberry, blueberry, boysenberry, brazil nut, butternut, calamondin, cashew, chestnut, chinquapin, citron (citrus), cocoa, coffee, currant, elderberry, fig, filbert (hazelnut), gooseberry, grapef ruit, grapes, hickory nut, huckleberry, kumquat, lemon, lime, loganberry, macadamia nut (bushnut), orange, papaya, pear, pecan, pistachio, prune, pummelo (shaddock), raspberry (black, red), walnut (english/black), 1.417 lb/ac 5
apricot, artichoke, asparagus, beans, succulent (lima), broccoli, cabbage, cabbage (chinese), carrot (including tops), cauliflower, chayote, cherry, collards, cucumber, eggplant, gherkin, gourds, gourd (wax), chinese, groundcherry (strawberry tomato/tomatillo), kiwi fruit, lettuce, melons, bitter (balsam pear), melons, cantaloupe, melons, citron, melons, musk, melons, water, nectarine, peach, peas (unspecified), pepino (melon pear), pepper, pineapple, plum, pumpkin, safflower (unspecified), soybeans (unspecified), squash (all or unspecifi ed), sugar beet, sunflower, tomatillo, tomato, turnip (greens), 1.417 lb/ac 3

beans, succulent (snap), corn (sweet), 1.417 lb/ac NS brussels sprouts, vegetables (unspecified), 1.385 lb/ac 3 catjang (jerusalem/marble pea), lentils, yam, 0.692 lb/ac 2 crabapple 1.385 lb/ac NS endive (escarole) 1.400 lb/ac 3 garlic, onion, 1.417 lb/ac 1 ginger 1.385 lb/ac 6 guar, hops, manioc (cassava), strawberry, 0.692 lb/ac 3 guava 1.379 lb/ac 4 kale, kohlrabi 1.385 lb/ac 3 loquat, mayhaw (hawthorn), plantain, quince, tangelo, 1.385 lb/ac 5 melons 0.367 lb/ac 2 mint/peppermint/spearmint 1.049 lb/ac 2 okra 1.385 lb/ac 1 olive 1.417 lb/ac 4 passion fruit (granadilla) 1.379 lb/ac 5Page 8 of 71 Table 1. Currently Registered Uses to be Cons idered for Registration Re view (provided by BEAD) 1

peas, pigeon 0.692 lb/ac 1 pepper (chili type) 0.689 lb/ac NS persimmon 1.311 lb/ac 5 rhubarb 1.417 lb/ac 2 sage, clary, sugarcane, 1.038 lb/ac 2 taro 1.102 lb/ac 2 yautia 0.692 lb/ac 3 use group: terrestrial food + feed agricultural fallow/idleland / conservation reserve 1.417 lb/ac 2 almond, barley, corn (unspecified), corn, field, corn, pop, corn, sweet, cotton (unspecified), rice, small grains (unspecified), sorghum, wheat 1.417 lb/ac NS
beans, asparagus, beans, broad, beans, dried-type, beans, moth, beans, mung, beans, rice, beans, succulent (lima), beans, succulent (snap), beans, tepary, beans, urd, cowpea/blackeyed pea, garbanzos (including chick peas), guar, lupine, grain, peas, dried-type, peas, southern, potato, white/irish 0.692 lb/ac NS

peanuts 0.346 lb/ac NS peanuts (unspecified) 0.354 lb/ac NS vegetables (unspecified) 1.038 lb/ac NS use group: terrestrial non food agricultural fallow/idleland / conservation reserve, 1.417 lb/ac 3 airports/landing fields, commercial/institutional/industrial premises/equipment (outdoor), deciduous fruit trees (unspecified), grasses grown for seed, nonagricultural rights-of-way/fencerows/hedgerows, nonagricultural uncultivated areas/soils, orchards (unspecified), ornamental and/or shade trees, ornamental herbaceous plants, ornamental woody shrubs and vines, 1.417 lb/ac NS

alfalfa, guayule (rubber) 1.385 lb/ac NS corn (unspecified), nonagricultural areas (public health use), 1.400 lb/ac NS pastures 0.692 lb/ac NS
1 Any registrations or uses registered prior to co nduct of the Registration Review risk assessment will also be considered. Form Code: NS = Not Specified on label, CC = Crop Cycle

A national map showing the estim ated poundage of paraquat used in 2002 by county is presented in Figure 1. The map is an illustrated estimat e of the extent of paraquat use. The map was downloaded from the U.S. Geological Survey (USGS), National Water Quality Assessment Program (NAWQA) website. 1 The map represents typical agri cultural use patterns over a five year period from 1999 through 2004. It does not refl ect any new registrations, label changes, changing use patterns, or mitigation measures that may have occurred between that time and the time of this problem formulation.

1 http://water.usgs.gov/nawqa/pnsp/usage/ maps/show_map.php?year=02&map=m1616Page 9 of 71 Figure 1. Paraquat Dichloride Use in Pou nds Per Square Mile in U.S. Counties

BEAD’s Screening Level Usage Analysis (SLUA) es timates of the agricultural uses of paraquat dichloride (in total pounds active intergradient a pplied) are listed in Table 2 . An estimated of over three million pounds of paraqua t dichloride are applied per ye ar in the U.S. The top five uses are corn (700,000 lb), cotton (700,000 lb), soybeans (300,000 lb), almonds (200,000 lb), and grapes (200,000 lb).

Table 2. Screening Level Usage An alysis for paraquat dichloride Percent Crop Ttd. Crop Lbs. A.I. Avg. Max. Alfalfa 100,000 <1 <2.5 Almonds 200,000 25 35 Apples 100,000 20 30 Apricots 1,000 10 20 Artichokes 2,000 25 40 Asparagus 4,000 10 15 Avocados 1,000 <2.5 5 Barley 2,000 <1 <2.5
Beans, Green 1,000 <1 <2.5 Blueberries 3,000 10 20

Broccoli <500 <1 <2.5 Brussels Sprouts <500 N.C. N.C. Cabbage 1,000 <2.5 10Page 10 of 71 Caneberries 6,000 45 70 Cantaloupes 2,000 5 10
Carrots 1,000 <2.5 <2.5 Celery <500 <1 <2.5 Cherries 30,000 20 30 Chicory <500 N.C N.C.
Corn 700,000 <2.5 <2.5 Cotton 700,000 15 25 Cucumbers 3,000 5 30 Dry Beans/Peas 10,000 <2.5 5 Fallow, Summer 40,000 <1 <2.5 Figs 1,000 N.C N.C.

Garlic <500 <1 <2.5 Grapefruit 3,000 <2.5 5 Grapes 200,000 20 30 Kiwifruit 2,000 30 30
Lemons 2,000 <2.5 5 Lettuce 1,000 <1 <2.5 Nectarines 4,000 10 25 Olives 1,000 5 10 Onions 3,000 5 10 Oranges 60,000 5 10 Pasture 50,000 <1 <2.5 Pastureland 40,000 <1 <2.5 Peaches 50,000 30 40
Peanuts 60,000 20 35 Pears 9,000 10 20 Peas, Green <500 <1 <2.5 Pecans 40,000 5 20 Peppers 6,000 10 20 Pistachios 50,000 25 40 Plums 6,000 15 20
Potatoes 20,000 5 10 Prunes 20,000 10 25 Pumpkins 2,000 5 10 Rice 5,000 <1 <2.5 Sorghum 20,000 <1 <2.5 Soybeans 300,000 <1 <2.5 Spinach 1,000 5 10Page 11 of 71 Squash 2,000 5 15 Strawberries 4,000 10 25 Sugar Beets 2,000 <1 <2.5 Sugarcane 20,000 5 10 Sunflowers 4,000 <1 <2.5 Sweet Corn 3,000 <2.5 5 Tangelos <500 10 15 Tangerines 1,000 10 15

Tobacco <500 <1 <2.5
Tomatoes 20,000 5 15 Walnuts 50,000 15 20 Watermelons 2,000 5 5 Wheat 50,000 <1 <2.5 All numbers rounded. <500 Less than 500 pounds of active ingredient <2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated
Publicly available data from the California Depa rtment of Pesticide Re gulation (Cal. DPR) was used to produce Table 3 , which outlines the pounds of paraquat dichloride used in California over the three most recent years available (2007 - 2009).

Table 3. Paraquat dichloride (0616 01) California DPR Usage Data

Commodity 2007 Pounds Applied 2008 Pounds Applied 2009 Pounds Applied alfalfa (forage - fodder) (alfalfa hay) 133988 163439 193301
almond 282732 230243 218579 apple 1962 2747 923 apricot 762 783 1271 artichoke (globe) (all or unspec) 10479 4921 8042 asparagus (spears, ferns, etc.) 772 1087 467 avocado (all or unspec) 57 99 0 barley, general 21 135 171 beans (all or unspec) 30 beans, dried-type 195 54 439 beans, succulent (other than lima) 864 648 343 bermudagrass (forage - fodder) 31 324 blackberry 4 40 14 blueberry 3687 1957 2528 bok choy (wong bok) 9 boysenberry (boysens) 4
broccoli 278 234 684 buildings and structures (non-ag outdoor) 2 cabbage 24 45 cantaloupe 103 301 115Page 12 of 71 cardoon (cardoni) 9 carrots, general 21 95
cauliflower 22 86 10 cherry 15751 10363 13721
chestnut 111 30 2 chinese cabbage (nappa, won bok, celery cabbage) 77 30 37 christmas tree plantations 3 citrus fruits (all or unspec) 37 26 104 clover (all or unspec) (forage - fodder) 54 24 43 commercial, institutional or industrial areas 23 34 commodity fumigation 7 corn (forage - fodder) 6860 5818 4298 corn, field, dent (grain crop) 120 90 corn, human consumption 251 96 707 cotton, general 163085 118074 85617 cucumber (pickling, chinese, etc.) 366 259 235
date 21 eggplant (oriental eggplant) 154 2 17 endive (escarole) 2 23 fig 1553 686 696 forage - fodder grasses (all or unspec) (hay) 42 8 garbanzos (including chick peas) 35 garlic 169 234 112 grapefruit 40 37 95

grapes 143968 72349 81990 grapes, wine 74881 50557 85512
kiwi fruit 1172 1180 1194 landscape maintenance 96 129 61
lemon 1032 680 246 lettuce, head (all or unspec) 1232 835 986 lettuce, leaf (all or unspec) 168 384 176
melons 34 155 1 mint (all or unspec) 1220 881 1370
mushrooms 6
nectarine 6431 8897 7872 n-outdr container/fld grwn plants 407 400 368 n-outdr grwn cut flwrs or greens 235 417 179 n-outdr grwn trnsplnt/prpgtv mtrl 107 274 264 oats, general 82 olive (all or unspec) 1793 1748 1943 onion (dry, spanish, white, yellow, red, etc.) 422 416 482 onions (green) 30 orange (all or unspec) 9089 5171 5227 pastures (all or unspec) 24 5 399 peach 8477 7957 10747

pear 502 402 1986 peas, general 1 8Page 13 of 71 pecan 115 75 88 peppers (chili type) (flavoring and spice crop) 325 442 506 peppers (fruiting vegetable), (bell,chili, etc.) 3681 1411 1640 persimmon 86 66 33 pimento (pimiento type pepper) 14 pistachio (pistache nut) 41606 40423 35381 plum (includes wild plums for human consumption) 7997 8565 9458 pluot 3 potato (white, irish, red, russet) 146 19

prune 12366 8923 9049 pumpkin 60 34 17
radicchio 16 raspberry (all or unspec) 107 17 research commodity 47 189 182 rice (all or unspec) 83 7 62 rights of way 3296 2529 1655 safflower, general 214 2470 5644 soil application, preplant-outdoor (seedbeds,etc.) 499 170 750 sorghum (forage - fodder) (sorgo, etc.) 768 80 38 sorghum/milo general 530 14 squash (all or unspec) 39 19 392 squash (summer) 25 14 1 strawberry (all or unspec) 738 537 370 structural pest control 45 54 10 sugarbeet, general 69 189 sunflower, general 2900 2069 2528 tangelo 51 88 tangerine (mandarin, sa tsuma, murcott, etc.) 2400 1961 2503
tomatillo 4

tomato 1452 672 265 tomatoes, for processing/canning 5436 6287 8886 uncultivated agricultural areas (all or unspec) 28875 25255 30618 uncultivated non-ag areas (all or unspec) 190 458 522 walnut (english wal nut, persian walnut) 34865 28115 27936
watermelons 921 856 192 wheat (forage - fodder) 125 937 1139 wheat, general 883 2555 955
Grand Total 1026158 831646 875207 Date Prepared: 02/10/11, Cal DPR Data: http://www.cdpr.ca.gov/ docs/pur/purmain.htm

, Empty cells indicate no available usage.



### 4.3. Environmental Fate and Transport

The primary route of environmental dissipation of paraquat is adsorption to soil clay particles. Paraquat does not hydrolyze and is photodegraded very slowly in aqueous solutions. It isPage 14 of 71 resistant to microbial degrad ation under aerobic and anaerob ic conditions. Essentially no microbial degradation of paraquat was observed after 180 days of aerobic incubation or after 60 days of anaerobic incubation following a 30 da y aerobic incubation. Environmental fate and transport properties of paraquat are summarized in Table 4

.

Table 4. Physical/Chemical Properties and Environmental Fate Parameters of Paraquat. Parameter Value Reference Physical/Chemical Parameters
Molecular mass 257.2 g/mol (C 12 H 14 N 2 Cl 2 ) Calculated Vapor pressure (25°C) 1.73 x 10 -15 torr MRID 46098802 Henry’s Law constant (25°C) 1.26 x 10 -20 atm – m 3 /mole Calculated Water solubility (20°C) 464,000 mg/L MRID 46098802 Log octanol-water partition coefficient ( log K O W ) 2.44 R. F. Platford, 1983 (Chemosphere, vol. 12, pages 1107 - 1110)

Persistence in Water Hydrolysis half-life no evidence of degradation at pH 5, 7, 9 Upton, Hendley and Skidmore, 1985, no MRID. Aqueous photolysis half-life Very slow and unquantified. N o degradates reported , CO 2 (0.15%) 4-carboxyl-1-methylp yridinium (QINA) (6%) after 85 weeks MRID 40562301

Reviewed by Jordan, 2/14/1986

Aerobic aquatic metabolism half-life No degradates reported. <2 weeks (only represents water phase. Did not measure amount of paraquat sorbed to the soil) MRID 00055093

Persistence in Soil Soil photolysis half-life no evidence of degrad ation No degradates reported. MRID 146807

Aerobic soil metabolism halflife no evidence of degradation. Did not degrade. No degr adates reported. MRID 41319301

Anaerobic soil metabolism halflife Stable. No degradates reported MRID 41319302

Mobility Adsorption/Desorption Study K d-ads (mL/g), 68 – 50,000 (no measureable correlation with % OC). No desorption was observed during the desorption step.

K oc- ads / K oc-des (mL/g), 15,473 to 1,000,000 MRID 40762701

http://www.ermanz.govt.nz/consult ations/ceir/t.pdf
Field DissipationTerrestrial field dissipation halflife No degradates reported. Half-life not calculated; however, cited reference indicates a half-life of > 10 years, no leaching potential MRID 41293202, 42802101, 42738701, 42738702,
42802102

Mobility

In laboratory studies with radiolabeled paraquat, no radioactivity volatilized from the soil surfacePage 15 of 71 to adsorb to glass or to collect in volatile tr aps. With low vapor pressure and extremely high adsorption coefficients, paraquat would not be e xpected to volatilize onc e applied to the soil. Low volatilization would be expected for an ionic compound.

Paraquat dichloride was immobile in silty clay loam, loamy sand, and sand soils. It was not possible to determine Freundlich K ads values because no paraquat wa s detected in the adsorption solution at normal application rates. At a pplication rates 50-1000 times the approved field application rates, K ads values ranged from 68-50,000. There wa s no desorption of paraquat from any of these soils (MRID 40762701).

Degradation
Paraquat dichloride exhibited little or no discernable degradation under any laboratory conditions. Paraquat dichloride at 91 ppm did not hydrolyze at pH 5, 7, or 9 when incubated at 25° or 40° C (Upton et al ., 1985). Paraquat dichloride at 28 pp m in sterile pH 7 aqueous solution did not photodegrade when continuously irradiated with a xenon arc lamp for 32 days at 25° C. Paraquat accounted for 90.2-98.0% of the applie d radioactivity throughout the study in the irradiated and dark control samp les; no degradates were reporte d. Volatiles were trapped and 0.15% of the applied radioact ivity was recovered as CO 2 (MRID 40562301). Paraquat did not photodegrade when mixed with a sterile soil solution and expose d to natural sunlight for 85 weeks (Pack, 1982).

Paraquat (4.32 ppm) did not degrade in sandy lo am soil incubated under aerobic conditions at 20° C for 180 days. Paraquat comprised 93% of a pplied radioactivity at 180 days post-treatment. There was no volatile radioactivit y. No degradates were reported from TLC or HPLC analysis (MRID 41319301). In a 1985 study, paraquat was removed from a water column with a “resident half-life” of <2 weeks. Soil was not sampled, but presum ably contained most or all of the paraquat residues (MRID 00055093).

Paraquat at 4.32 ppm did not de grade in sandy loam soil incuba ted under anaerobic conditions for 60 days following a 30-day aerobic incubatio n. Paraquat comprised 88.8% of the applied radioactivity at 90 days post-treatment. Only 0.29% was recovered in the water phase at 61 days post-treatment. No volatile radioactivity was detected. No degradat es were reported (MRID 41319302).

Field Dissipation

Paraquat dichloride dissipated very slowly in Delaware on a loamy sand soil planted in soybean. Residues decreased from an av erage of 1.1 mg/kg soil immediat ely post-treatment to 0.76 mg/kg at 86 days, and remained at 0.42-0.51 mg/kg from 296 to 657 days post-treatment. Paraquat did not leach below the 0-3.5 inch soil depth.

Four long-term field dissipati on studies were reported with data from: Champaign, IL (MRID 42802101); Visalia, CA (MRID 42738701); Leland, MS (MRID 42738702); and Pikeville, NC (MRID 42802102). Paraquat was applied in three or four single annual applic ations to plots of bare ground, corn, peach trees, soybeans, and co tton. Paraquat did not appreciably degrade at any of the four sites. Half-lives were not calcu lated, but authors cited references for field studiesPage 16 of 71 that indicated a paraquat half-life of >10 years.

Transformation Products

QINA (4-carboxyl-1-methylpyridinium) is a minor degradate formed in the photodegradation in water study. The quantity of QINA present was only 6% of the radioactivit y of paraquat after 85 weeks of natural sunlight irradiation. Due to paraquat degrading very slowly, the minor degradate, QINA, does not pose an important envi ronmental concern and will not be evaluated in this assessment. The structure is shown below:



### 4.4. Monitoring Data

Any available monitoring data from the registra nts and public organizations such as US EPA, USGS, Department of Pesticide Regulation (CDPR), a nd others will be considered in this review
process.



### 4.5. Nature of Stressor

Paraquat dichloride is generally applied as a flowab le solution. As a result, paraquat dichloride is already dissociated into its cation, paraquat. Th erefore, assessments involving paraquat dichloride will focus on the paraquat cation as the stressor of concern. All EECs and toxicity values will be reported in terms of the paraquat cation.

As discussed in the environmental fate and trans port characterization above, no major degradates of paraquat dichloride were reported in the available environmental fate studies. In general, paraquat is stable in the environment. QINA (4-carboxyl-1-methylpyridinium) is a minor degradate (6% of radioactivity) formed by paraquat in an aqueous photolysis study. Because QINA was only observed in one environmental fate study at minor concentrations, this degradate is not considered a stressor of

concern.Page 17 of 71 

## 5. Receptors

Consistent with the process described in th e Overview Document (USEPA 2004), the risk assessment for paraquat dichloride will rely on a surrogate species approach. Toxicological data generated from surrogate test species, which are intended to be representative of broad taxonomic groups, are used to extrapolate to poten tial effects on a variety of species (receptors) included under these ta xonomic groupings.

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the available open literature are used to evaluate th e potential direct and indirect effects of paraquat dichloride on aquatic and terrestrial receptors. Th ese include toxicity data on the technical grade active ingredient, degradates, and when available, formulated products ( e.g . “Six-Pack” studies). The open literature studies are identified using EPA’s ECOTOX database (USEPA 2007 d ), which employs a literature search engine for lo cating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The evaluation of both sources of data can also provide insight into the direct and indirect eff ects of paraquat on biotic communities from loss of species that are sensitive to the chemical and from changes in structure and functional characteristics of the affected communities.



### 5.1. Effects to Aquatic Organisms

On an acute exposure basis, paraquat is slightly toxic to aquatic-phase amphibians and fish and moderately toxic to freshwater invertebrates. No chronic toxicity studies have been identified for fish or aquatic invertebrates exposed to paraqu at. Compared to aquatic animals, paraquat is orders of magnitude more toxic to aquatic plants. Table 5 includes the most sensitive endpoints that may be used for risk assessment purposes ( i.e., to derive RQs) to represent the acute effects of paraquat on aquatic animals as well as eff ects of paraquat on aquatic plants. Additional toxicity data on paraquat ar e provided in Appendix A.

Table 5. Endpoints used to represent acute effects of paraquat on aquatic animals and plants.

Taxa Species (scientific name) Measure of Effect Endpoint Duration (hours) Mean conc. (mg cation/L) Study Classification Ref. (MRID)

Fish and aquatic-phase

amphibians Fowler’s toad ( Bufo woodhousei fowleri ) mortality LC 50 96 15 Supplemental 40098001

Aquatic invertebrates Water Flea ( Daphnia magna ) immobility EC 50 48 1.3 Supplemental 0014473

Non-vascular plants freshwater diatom ( Navicula pelliculosa ) growth EC 50 96 0.00040 Acceptable 42601006 NOAEC 0.00016

Vascular

plants Duckweed ( Lemna gibba ) growth EC 50 14 d 0.071 Acceptable 42601003 NOAEC 0.011Page 18 of 71 The endpoint from a study where fowler’s toad ta dpoles were exposed to technical paraquat may be used to represent fish and aquatic-phase amphi bians. Available toxicity data with freshwater fish exposed to paraquat dich loride in formulated products (see Table A2 of Appendix A) suggests that fish may be more sensitive to paraquat than the fowler’s toad.


### 5.2. Effects to Terrestrial Organisms

Paraquat is moderately toxic to birds and mammals on an acute exposure basis. For honey bees, paraquat is practically non-toxic. In repr oduction studies, paraquat did not impact the reproduction in rats tested up to 108 mg cation/kg-d iet. Paraquat did impa ct the reproduction of mallard ducks at 100 mg cation/kg-diet, resul ting in a NOAEC of 30 mg cation/kg-diet for reproductive effects (decrease in number of eggs laid, number of normal hatchlings, number of 14-d old survivors, and % viable embryos/set). In addition, in a study where pheasant eggs were sprayed with paraquat dichloride, effects to the number of eggs hatched and number of 28-d old survivors were observed at 1.0 lb cation/A, resulting in a NOAEC of 0.5 lb cation/A. Table 6 includes the most sensitive endpoints that may be used for risk assessment purposes (for deriving RQs) to represent the acute and chronic effects of paraquat on terrestrial animals. Additional information on the toxicity of paraquat to te rrestrial animals is pr ovided in Appendix A.

Table 6. Endpoints used to rep resent acute and chronic effects of paraquat on terrestrial animals.

Taxa Species (common

name) Measure of effect Endpoint Mean Concentration Units Study Classification Reference (MRID)

Birds,terrestrialphase amphibians and reptiles Colinus virginianus

(northern bobwhite ) Mortality LD 50 124 mgcation/kgbw acceptable 00029001

Coturnix coturnix (Japanese quail) Mortality LC 50 698 mgcation/kgdiet supplemental 00022923

Anas platyrhynchos (mallard Duck) number of eggs laid, number of normal hatchlings, number of 14-d old

survivors, and % viable embryos/set NOAEC 30 mgcation/kgdiet Acceptable 00110455

Phasianus colchicus (pheasant) Number of eggs hatched, number of 28-d old survivors NOAEC 0.5 lb cation/A Supplemental 43942605

Mammals Rattus norvegicus (laboratory rat) Mortality LD 50 (oral
dose) 91 mgcation/kgbw Acceptable 00054573

Mortality LC 50 (inhalati

on) 0.001 mg/L acceptable 00046105

Reproduction NOAEL 7.5 Mgcation/kgbw Acceptable 00126783, 00149748, & 00149749 NOAEC 108 Mgcation/kgbwPage 19 of 71 Taxa Species (common

name) Measure of effect Endpoint Mean Concentration Units Study Classification Reference (MRID)

Terrestrial invertebrates Apis mellifera (honey bee) Mortality LD 50 52 μ g cation/bee Acceptable 43942603

Plants are sensitive to this herbicide. When co mparing effects of paraquat on seedling emergence and vegetative vigor of plants, vegetative vigor is more sensitive. Table 7 includes the most sensitive seedling emergence and vegetative vigo r endpoints for terrestrial plants exposed to paraquat. These values may be used to generate RQs. Additional information on the toxicity of paraquat to terrestrial plants is provided in Appendix A.

Table 7. Endpoints used to represent ef fects of paraquat on terrestrial plants.

Species NOAEC (lb cation/A) EC 25 (lb cation/A) Most sensitive parameter Test type MRID

Zea mays corn

(monocot) 0.67 >0.67 none Seedling emergence 42639601

Xanthium sp Cocklebur (dicot) 0.37 0.67 Emergence Seedling emergence 42639601
Corn (monocot) 0.064 0.16 Dry weight Vegetative vigor 42601001 Cocklebur (dicot) 0.0065 (EC 05 ) 0.014 Dry weight Vegetative vigor 42601001



### 5.3. Ecological Incidents

A review of the Ecological Incident Informa tion System (EIIS, version 2.1), the ‘Aggregate Incident Reports’ (v. 1.0) data base, and the Avian Incident Monitoring System (AIMS) for ecological incidents involving paraquat di chloride (PC code 061601), paraquat (PC code 061603), and paraquat bis (methyl sulfate) (PC code 061602) was completed on 8/31/2011. Although paraquat and paraquat bis (methyl sulfate) are no longer registered for use in the United States, like paraquat dichloride, the activ e ingredient of both of these chemicals is paraquat. Therefore, it was assumed that incide nts associated with para quat and paraquat bis (methyl sulfate) would be representative of inci dents that may occur when paraquat dichloride is applied. The incidents reported in each database are summarized below. These incidents will be described in more detail in the ecological risk assessment of paraquat dichloride.Page 20 of 71 EIIS

A review of the EIIS database for ecologica l incidents involving paraquat and paraquat dichloride, which are used in terchangeably in the database , was completed on August 31, 2011. Reported incidents occurred betw een 1981 and 2005. The results of th is review for terrestrial, plant, and aquatic incidents are discussed below. A total of 4 incidents involving paraquat were reported, and a total of 26 incidents involving para quat dichloride were reported. There were no incidents reported for para quat bis (methyl sulfate).

There were three reported incide nts involving terrestrial animals after applicati ons of paraquat dichloride. Two incidents were considered to be likely related to paraquat. These are briefly described below:

 The first incident occurred in Virginia in J une 1998. In this report, a formulation with a registered use on corn resulted in the mortalit y of 5 Canadian geese. Paraquat dichloride was the probable cause of the incident (I008168-001).

 The second incident occurred in Illinois in J une 1998. This report included the death of individuals of 4 unknown species of birds after drift/spray exposure. Paraquat was identified as the probable cause of the incident (I007334-001).

There were a total of 4 plant incidents lis ted for paraquat and 17 incidents for paraquat dichloride. These are br iefly described below:

 For the paraquat incidents, plant damage wa s sustained to three non-target species, including: radishes, apples, and ornamentals (I014409-001, I013884-038, and I013884- 014). Mortality of alfalfa was also reporte d (I014409-024). All 4 in cidents were from Washington, one from a registered use on p eas where ornamentals were affected, and paraquat was the probable cause of plant da mage; one from a misuse (alfalfa) where paraquat was a possible cause of mortality ; and, for the other two, the use was of undetermined legality, and paraquat was a possi ble cause of plant damage. All exposures occurred from drift, with apples also being exposed from direct spray.

 Two accidental misuse incidents occurred in an agricultural area in Wisconsin resulting in plant damage to alfalfa, ash, and ornamentals (I005660-005), and ash, oats and discoloration to alfalfa (I005880-005) from drift exposure. Paraquat was the probable cause of these incidents.

 Three accidental misuse incide nts on corn resulted in plant damage to grass (I007371- 033, I007371-034, and I007371-035) on June 17, 1997, and paraquat was the probable cause of these incidents.

 120 acres of a corn field was damaged after a broadcast application of undetermined legality occurred May 9, 2000. Paraquat was a possible cause of this incident (I012366- 023).

 Plant damage to 181 acres of peppermint o ccurred after registered use May 1, 1996, and paraquat was a possible cause of this incident (I013636-029).

 A paraquat dichloride application of undeterm ined legality use was the possible cause of 150 (75% of 200) acres of corn damage d on May 11, 1999 in Alabama (I009573-009).Page 21 of 71  After a legally-applied app lication of paraquat dichlori de,10 acres of peanuts were damaged on June 19, 2001 in North Carolina. Paraquat was a possible cause of this incident (I011838-055).

 Carryover from the broadcast application of paraquat dichloride was the probable cause of damage to 1040 acres of corn May 24, 2002 in Illinois (I013554-040).

 The label-use application of pa raquat dichloride was a possible cause of the damage to 60 acres of pasture grass April 23, 2003 in Georgia (I014034-009).

 The label-use of paraquat dich loride on peanuts was a possibl e cause of plant damage to 5 acres of peanuts in Virgin ia May 23, 2001 (I012684-010).

 An application of paraquat dichloride on p eanuts of undetermined legality use was a possible cause of plant damage to 80 acres of peanuts in Oklahoma (I011838-091) and all 25 acres in Georgi a (I011838-038).

 A label-use broadcast applica tion of paraquat dichloride to soybeans was a possible cause of plant damage to an unknown tree as a result of drift June 27, 1994 in Arkansas (I001131-001).

 It is highly probable that the accidental misuse of paraquat dichloride on soybeans resulted in plant damage to unknown amounts of soybeans as the result of drift May 20, 1997 in Pennsylvania (I007371-008).

 Intentional misuse of paraquat dichloride by spray application on wheat was the probable cause of plant damage to 120 of 184 acres from drift January 26, 2005 in California (I016940-005).

 In June 1998, plant damage was reported on 18 of 103 acres of corn in Illinois from drift/spray exposure (I007334-001) ; paraquat was of probable cau se for the incident.

There were six reported aquati c incidents listed for paraquat dichloride. Incidents where paraquat was suspected of being the prim ary cause are briefly described below:

 A use of paraquat dichloride of undetermin ed legality on an ag ricultural area was a possible cause of the mortality of 54 fish (1 largemouth bass, and 53 sunfish) due to runoff on June 4, 1981 in Virginia (B0000-502-18).

 The application of paraquat dichloride on a field was a possible cause of the mortality of fish (bass, bluegill, and crappie) in Indiana on June 2, 1997 (I009314-005).

 An application of paraquat dichloride of unde termined legality was a possible cause of the mortality of an unknown amount of bass, bl uegill, and crappie to die in Indiana on January 1, 1997 (I005805-001).

 Paraquat dichloride was a possible cause of the 200 bass and bluegills that were found dead after an application of paraquat dichloride of undete rmined legality on June 3, 1999 (I008768-007).

Aggregate Incident Database

For paraquat dichloride, the aggregate incident database included 82 mi nor plant incidents, 4 minor fish and wild life incidents and 3 other non- target incidents that were reported between 1995 and 2010. For paraquat, there was one minor in cident involving other non-target organisms that was reported in 2004. There were no incidents reported for pa raquat bis (methyl sulfate).

AIMSPage 22 of 71 Two indicents are reported in the AIMS database . One incident, involving Canadian geese, was also reported in EIIS (Incident I008168-001).

The other incident involved mortalities of se veral passerines (robins, sparrows, starlings and grackles). This incident also involved exposures of birds to carbofuran. Th e report indi cated that it was certain that carbofuran was responsible fo r the mortalities and probable that paraquat was responsible. This incident was also cap tured by EIIS (I005750-001, I004169-026 and I000097- 015). 

## 6. Ecosystems Potentially at Risk

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible to identify specific ecosystems during the deve lopment of a nation-wide ecological risk assessment. However, in general terms, terrest rial ecosystems potentially at risk could include the treated field and immediately adjacent areas that may receive drift or runoff. Areas adjacent to the treated field could incl ude cultivated fields, fencerow s and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats, and other un cultivated areas.

Aquatic ecosystems potentially at risk include wa ter bodies adjacent to, or downstream from, the treated field and might include impounded bodies such as ponds, lake s and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuaries.



## 7. Assessment Endpoints

Assessment endpoints represent the ac tual environmental value that is to be protected, defined by an ecological entity (species, community, or othe r entity) and its attri bute or characteristics (USEPA 1998). For paraquat, the ecological enti ties include the following: birds, reptiles, terrestrial-phase amphibians, mammals, freshwat er fish, freshwater aquatic-phase amphibians and invertebrates, estuarine/mari ne fish and invertebrates, terre strial plants, insects, aquatic plants, and algae. The attributes for each of these entities include growth, reproduction, and survival.



## 8. Conceptual Model

For a pesticide to pose an ecological risk, it mu st reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological recepto r. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, an d a feasible route of exposure.Page 23 of 71 The conceptual model for paraquat provides a wri tten description and visual representation of the predicted relationships between paraquat, potential routes of exposure, and the predicted effects for the assessment endpoint. A conceptual mode l consists of two major components: risk hypothesis and a conceptual diagram (USEPA 1998).



### 8.1. Risk Hypothesis

A risk hypothesis describes the predicted re lationship among the stre ssor, exposure, and assessment endpoint response along with the ra tionale for their sele ction. For paraquat dichloride, the following ecologi cal risk hypothesis is being em ployed for this national-level ecological risk assessment:

Based on use patterns of paraquat dichloride , its fate and transport potential, and the sensitivity of non-target aquatic and terrestri al species, paraquat has the potential to reduce survival, reproduction, and/or grow th in non-target te rrestrial and aquatic organisms when used in accordance with labels. These non-target organisms include Federally-listed threatened and endangered species as well as non-listed species



### 8.2. Conceptual Diagram

The environmental fate properties of paraquat i ndicate that runoff and spray drift represent potential transport mechanisms of paraquat to a quatic habitats where non-target organisms may be exposed. It is expected that non-target te rrestrial organisms can be exposed to paraquat through consumption of contaminated food items. These transport mechanisms ( i.e ., sources) are depicted in the conceptual models below ( Figures 1 and 2 ) along with the receptors of concern and the potential attribute changes in the receptors due to exposures of paraquat. Dotted lines represent transport pathways that are assumed to have a low likelihood of occurring and/or of contributing to ecological risk.Page 24 of 71 Figure 1. Conceptual model for paraqu at effects on terrestrial organisms. Stresso r

Source

Receptors

Attribute Change Paraquat dichloride applied to use site

Direct deposition Spra y drift

Birds/terrestrialphase amphibians/ reptiles/mammals

Terrestrial

insects

Individual organisms Reduced survival Reduced growth Reduced reproduction Food chain Reduction in prey Effects to PCEs related to prey availability Habitat integrity Reduction in primary productivity Reduced cover Community change Effects to PCEs related to habitat Terrestrial/riparian plants grasses/forbs, fruit, seeds (trees, shrubs) Runoff

Mammals

/ Birds Exposure Media Soil

Ingestion Ingestion

Ingestion Ingestion Dermal Long range atmospheric

transport

Root Wet/dry deposition

Terrestrialphase

am p hibians IngestionPage 25 of 71 Figure 2. Conceptual model for paraquat effects on aquatic organisms.



## 9. Analysis Plan

In order to address the risk hypot hesis, the potential for adverse effects on the environment is estimated. The use, environmental fate, and ecol ogical effects of paraqua t are characterized and integrated to assess the risks. This is accomp lished using a risk quotient (ratio of exposure concentration to effects concentr ation) approach. Although risk is often defined as the likelihood and magnitude of adverse ecological effects, the risk quotient-based approach does not provide a quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined in the Overview Document (USEPA 2004), the likelihood of effects to individual organisms from particular uses of paraquat dichloride is estimated using the prob it dose-response slope and either the level of concern (d iscussed below) or actual calcu lated risk quotient value.

This analysis plan will be revisited and may be revise d depending upon the information submitted by the public in response to the opening of the registration revi ew docket for paraquat dichloride. Stresso r

Source

Receptors

Attribute Change Paraquat dichloride applied to use site

Spra y drift

Fish/aquaticphase amphibians

Individual organisms Reduced survival Reduced growth Reduced reproduction Food chain Reduction in algae Reduction in prey Effects to PCEs related to prey availability Habitat integrity Reduction in primary productivity Reduced cover Community change Effects to PCEs related to habitat Surface water/

Sediment Runoff

Aquatic Animals Invertebrates Vertebrates Exposure Media

Uptake/gills or integument

Ingestion Ingestion Long range atmospheric

transport

Wet/dry deposition Soil Groundwate r

Uptake/gills or integument

A quatic Plants Non-vascular Vascular Uptake/cell, roots, leaves Riparian plant terrestrial exposure pathways see Figure 1Page 26 of 71 

### 9.1. Measures of Exposure

In order to estimate risks of paraquat exposures in aquatic and terres trial environments, all exposure modeling and resulting risk conclusion s will be based on maximum application rates and methods cited in Section 4.2 and will be estimated for each use of paraquat dichloride. Measures of exposure are based on aquatic and terrestrial models that predict estimated environmental concentrations (EECs) of paraquat. The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled w ith the Exposure Analysis Modeling System (PRZM/EXAMS). The model used to predict te rrestrial EECs on food items is the Terrestrial Residue Exposure (T-REX). The model used to derive EECs relevant to terrestrial and wetland plants is TerrPlant. These models are parameteri zed using relevant reviewed environmental fate data from registrant submissions and the literature; model input values will be consistent with the most recent version of the input parameter guidance. 2

PRZM (currently version 3.12.2; 5/15/05) a nd EXAMS (currently version 2.98.04.06; 4/25/05) are simulation models coupled with the linkage program shell: PE (P RZM E XAMS Model Shell; v5 .0; 11/15/06), which incorporates the standard scenarios developed by EFED. The models generate daily exposures and calculated 1-in-10 year EECs of paraquat re sidues of concern that may occur in surface water bodies adjacent to applic ation sites. PRZM simulates pesticide fate and transport as a result of l eaching, direct spray drift, runoff and erosion from an agricultural field, and EXAMS estimates environmental fate a nd transport of pesticides in a surface water body for a 30-year period. The combined model is designed to estimate pesticide concentrations found in water (standard pond) at the edge of the treated field. As such, it provides high-end values of the pesticide concentrations that might be found in ecologically sensitive environments following pesticide application. The location of the field is specif ic to the crop being simulated using site-specific information on the soils, weather, cropping, and management factors associated with the scenario. The crop/locati on scenario is intended to represent a high-end exposure site on which the crop is normally grow n. Based on historical rainfall patterns, the receiving water body receives multiple runoff even ts during the years simulated. Weather and agricultural practices are simulated for 30 years so that the 10-year exceedance probability at the site can be estimated. The simulation is ge nerated using 30 years of meteorological data, encompassing the years from 1961 to 1990. Additional information on these models can be found at: http://www.epa.gov/oppefed1/models/water/index.htm

. The standard scenarios used for ecological pest icide assessments assume application to a 10- hectare agricultural field that drains into an ad jacent 1-hectare water body that is 2 meters deep (20,000 m 3 volume) with no outlet. PRZM/EXAMS is used to estimate screening-level exposure of aquatic organisms to paraquat. The measure of exposure for aquatic species is the 1-in-10 year return peak or ro lling mean concentration. The 1-in- 10 year peak is used for estimating acute exposures of direct effects to aquatic organisms. The 1-in-10-year 60-day mean is used for assessing chronic exposure to fish and aquatic-ph ase amphibians. The 1-in-10-year 21-day mean is used for assessing chronic expos ure to aquatic invertebrates.

2 Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides, Version 2.1. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division. 2009.Page 27 of 71 Exposure estimates for terrestrial an imals assumed to be in the target area or in an area exposed to spray drift are derived using the T-REX model (version 1.4.1, 10/09/2008). This model incorporates the Kenega nomogr aph, as modified by Fletcher et al. (1994), which is based on a large set of field residue data . The upper limit values from the nomograph represent the upper bound of residue values from actual field meas urements (Hoerger and Kenega 1972). The Fletcher et al. (1994) modifications to the Kenega nomograph are based on measured field residues from 249 published research papers, incl uding information on 118 species of plants, 121 pesticides, and 17 chemical classes.

The S creening I mbibition P rogram (SIP v.1.0, Released June 15, 2010) was used to calculate an upper bound estimate of exposure us ing paraquat’s solubility ( 464,000 mg/L ), the most sensitive acute and chronic avian toxicity endpoints (see Ta ble 6) and the most sensitive acute and chronic mammalian toxicity endpoints (see Table 6). Dr inking water exposure alone was not determined to be a potential pathway of concern for avian or mammalian species on an acute or chronic basis (See Appendix B). Although drinking water exposur e alone does not appear to be of concern, this does not take into account that when aggreg ated with other exposure pathways (dietary food sources, dermal, inhalation) drinking water may cont ribute to a total exposure that has a potential for effects on non-target animals and should be expl ored further. Because there is a high degree of conservatism in the SIP 1.0 exposure estimate, there is lim ited expectation that use scenarios not triggering a SIP 1.0 concern w ould contribute significantly to a ggregate risks from water plus diet when a refined water exposure model is in corporated in the actual quantitative risk assessment. Detailed information about SIP v.1.0, as well as the tool, can be found on the EPA’s website at http://www.epa.gov/pesticides/s cience/models_pg.htm#terrestrial

.

The S creening T ool for I nhalation R isk (STIR v.1.0, November 19, 2010) was used to calculate an upper bound estimate of exposure using paraquat’ s vapor pressure and molecular weight for vapor phase exposure as well as the maximum a pplication rate and method of application for spray drift. STIR incorporates results from several toxicity studies including acute oral and inhalation rat toxicity endpoints obt ained from the “six-pack” of core studies, which are a series of six guideline studies that are submitted to the Registration Division of the Office of Pesticide Programs for technical and formulat ed products of a pesticide (Tab le 6) as well as the most sensitive acute oral avia n toxicity endpoint (Table 6). Based on the results of the STIR model, inhalation exposure alone was determined to be a potential pathway of concern for avian and mammalian species on an acute basis. The inha lation pathway via spray drift is of potential significance. This pathway will be explored furt her by requesting additional toxicity or exposure data (non-guideline acute avian inhalation to xicity) that may reduce uncertainty and the incorporation of this data into the inhalation risk assessment for birds and mammals. For a sample of the output generated by STIR v.1.0, please see Appendix C. Detailed information about the STIR v.1.0 tool can be found on the EPA’s website at: http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial

. EECs for terrestrial plants inha biting dry and wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006). This model uses estimates of pe sticides in runoff and in spray drift to calculate EECs. EECs are based upon solubilit y, application rate and minimum incorporation depth.Page 28 of 71 Available monitoring data will be used to qual itatively characterize exposure and compare with modeling results. The Agency is aware of mon itoring conducted by Federal and state agencies and this route of exposure will be considered in the assessment to the extent that data on paraquat are available.

Two spray drift models, AGDISP and AgDRIFT are used to assess exposures of terrestrial plants to paraquat deposited in terr estrial habitats by spray drift. AGDISP (version 8.13; dated 12/14/2004) (Teske and Curbishley 2003) is used to simulate aerial applications. AgDrift (version 2.01; dated 5/24/2001) is used to simu late ground spray and orchard blast applications.



### 9.2. Measures of Effect

Ecological effect data are used as measures of di rect and indirect effect s to biological receptors. Data were obtained from registrant-submitted st udies or from literature studies identified by ECOTOX. The ECOTOXicology data base (ECOTOX) was searched in order to provide more ecological effects data to bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data and potential chemical mi xture toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX wa s created and is maintained by the USEPA, Office of Research and Development, and the National Health and Environmental Effects Research Laboratory's Mid-Continent Ecology Division (USEPA 2007).

Information on the potential effects of paraquat on non-target animals is al so collected from the Ecological Incident Information System (EIIS ; USEPA 2007b). The EIIS is a database containing adverse effect (typic ally mortality) reports on non -target organisms where such effects have been associated w ith the use of pesticides.

Where available, sublethal effects observed in both registrant-submitted and open literature studies will be evaluated qualitatively. Such effects have included behavioral changes ( e.g. , lethargy, changes in coloration and olfaction eff ects). Quantitative asse ssments of risks, though, are limited to those endpoints that can be direc tly linked to the Agency’s assessment endpoints of impaired survival, growth and reproduction.

The assessment of risk for direct effects to non-target organisms makes the assumption that toxicity of paraquat to birds is similar to terr estrial-phase amphibians and reptiles. The same assumption is made for fish a nd aquatic-phase amphibians.

The acute measures of effect used for animals in this screening-level assessment are the LD 50 , LC 50 and EC 50 . LD stands for "Lethal Dose", and LD 50 is the amount of a material, given all at once, that is estimated to cause the death of 50% of the test orga nisms. LC stands for “Lethal Concentration” and LC 50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC 50 is the concentration of a chemical that is estimated to produce a specific e ffect in 50% of the test organisms. Endpoints for chronic measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and NOEC. NOAEL stands for “No Observed-Adverse-E ffect-Level” and refers to the highest tested dose of a substance that has been reported to have no harmful (adverse) effects on test organisms. The NOAEC ( i.e. , “No-Observed-Adverse-Effect-Concen tration”) is the highest testPage 29 of 71 concentration at which none of the observed effects were statistically different from the control. The NOEC is the No-Observed-Effects-Concen tration. For non-liste d plants, only acute exposures are assessed ( i.e. , EC 25 for terrestrial plants and EC 50 for aquatic plants); for listed plants, either the NOAEC or EC 05 is used.


### 9.3. Integration of Exposure and Effects

Risk characterization is the integration of e xposure and ecological effects characterization to determine the potential ecological risk from the use of paraquat on crops listed in Section 4.2 and the likelihood of direct and i ndirect effects to non-target orga nisms in aquatic and terrestrial habitats. The exposure and toxicity effects data ar e integrated in order to evaluate the risks of adverse ecological effects on non-targ et species. For the assessmen t of paraquat risks, the risk quotient (RQ) method is used to compare exposur e and measured toxicity values. EECs are divided by acute and chronic toxicity values. The resulting RQs are then compared to the Agency’s LOCs (USEPA 2004; Table 8 ). These criteria are used to indicate when paraquat’s uses, as directed on the label, have the potential to cause adverse di rect or indirect effects to nontarget organisms. As noted previously, where da ta are lacking on the toxicity of paraquat, risk will be presumed.

The quantitative assessment of risk will primarily depend on the deterministic point-estimate based approach described in the risk assessment. An effort will be made to further qualitatively describe risk using probabilistic tools that the Agency has developed. These tools have been reviewed by FIFRA Scientific Advisory Panels and have been deemed as appropriate means of refining assessments where deterministic approaches have identified risks.

Table 8. Agency risk quotient (R Q) metrics and levels of concern (L OC) for Federally-listed (listed) threatened/endangered and non- listed species per risk class.

Risk Class Risk Description RQ LOC
Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from acute exposures Peak EEC/LC 50 1 0.5

Acute Restricted Use Potential for effects to animals from acute exposures. Risks may be mitigated through restricted use classification. Peak EEC/LC 50 1 0.1

Acute Listed Species Listed species may be potentially affected by acute exposures Peak EEC/LC 50 1 0.05

Chronic Potential for effects to non-listed and listed animals from chronic exposures 60-day EEC/NOEC (fish)

1 21-day EEC/NOEC (invertebrates)

Terrestrial Animals (mammals and birds)

Acute Potential for effects to non-listed animals from acute exposures EEC 2 /LC 50 (Dietary) 0.5 EEC/LD 50 (Dose)Page 30 of 71 Risk Class Risk Description RQ LOC

Acute Restricted Use Potential for effects to animals from acute exposures. Risks may be mitigated through restricted use classification EEC 2 /LC 50 (Dietary) 0.2 EEC/LD 50 (Dose)

Acute Listed Species Listed species may be potentially affected by acute exposures EEC 2 /LC 50 (Dietary) 0.1 EEC/LD 50 (Dose)

Chronic Potential for effects to non-listed and listed animals from chronic exposures EEC 2 /NOAEC 1

Plants

Non-Listed Potential for effects to non-target, non-listed plants from exposures EEC/ EC 25 1

Listed Plant Potential for effects to non-target, listed plants from exposures EEC/ NOEC 1 EEC/ EC 05

1 LC 50 or EC 50 . 2 Based on upper bound Kenaga values.



### 9.4. Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to Federally-listed th reatened and/or endangere d (listed) species from registered uses of paraquat dichloride. This assessment will be conducted in accordance with the Overview Document (USEPA 2004), provisi ons of the ESA, and the Services’ Endangered Species Consultation Handbook (USFWS/NMFS 1998).

The assessment of effects associat ed with the registration of para quat dichloride is based on an action area. The action area is considered to be the area directly or indi rectly affected by the federal action, as indicated by the exceedance of Agency LOCs used to evaluate direct or indirect effects. The Agency’s approach to defining the action area under the provisions of the Overview Document (USEPA 2004) consider s the results of the risk assessment process to establish boundaries for that action area with the understa nding that exposures below the Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this assessment, attention will be focused on the footprint of the action ( i.e ., the area where paraquat dichloride application occurs), plus all areas where offsite transport ma y result in potential exposure that exceeds the Agency’s LOCs. Specific measures of ecologica l effect that define the action area for listed species include any direct and indirect effects and/ or potential modification of its critical habitat, including reduction in survival, growth, and reproduction as well as the full suite of sub-lethal effects available in the effects literature. Ther efore, the action area extends to a point where environmental exposures are below any measured lethal or sub-le thal effect threshold for any biological entity at the whole organism, organ, tissu e, and/or cellular level of organization. In situations where it is not possible to determin e the threshold for an observed effect, the action area is not spatially limited and is assumed to be the entire United States.Page 31 of 71 

### 9.5. Drinking Water Assessment

In order to bring the drinking wa ter assessment up to date with current data, simulation models and guidance, a new drinking water exposure a ssessment will be conducted to support future human health dietary risk assessments of paraquat. The drinking water assessment will incorporate model estimates of pa raquat in surface water and gr ound water. Concentrations of paraquat in surface waters will be estimated us ing PRZM/EXAMS (see description above) with Index Reservoir as the receiving water body. With paraquat’s high adsorptive properties, the regular water treatment process is expected to rem ove almost all paraqat in the water. EFED is requesting the treatability study form the registrant to confir m this property.

An Estimated Drinking Water Concentration (E DWC) of paraquat in groundwater will be estimated using the Tier I aquatic model SCIG ROW (Screening Concentration in Ground Water, version 2.3; 8/8/2003). SC IGROW is a regression model used as a screening tool to estimate pesticide concentrations found in ground water used as drinking water. The output of SCIGROW represents the concentrations that might be expected in shallow unconfined aquifers under sandy soils, which is repres entative of the ground water most vulnerable to pesticide contamination likely to serve as a drinking water source.

The drinking water assessment will also include available surface and ground water monitoring data with consideration of change s in use patterns that may have occurred. States are encouraged to submit monitoring data for review.


### 10. Endocrine Disruptor Screening Program

As required under FFDCA section 408(p), EP A has developed the Endocrine Disruptor Screening Program (EDSP) to determine whether certain substances (inc luding pesticide active and other ingredients) may have an effect in humans or wildlife si milar to an effect produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator may designate.” The EDSP employs a two-tiered ap proach to making the statutorily required determinations. Tier 1 consists of a battery of 11 scr eening assays to identify the potential of a chemical substance to interact with the estroge n, androgen, and or thyroid (E, A, or T) hormonal systems. Chemicals that go th rough Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed to the next stag e of the EDSP where EPA will determine which, if any, of th e Tier 2 tests are necessary base d on the available data. Tier 2 testing is designed to identify a ny adverse endocrine related eff ects caused by the substance, and establish a dose-response relationship between the dose and the E, A, or T effect.

Between October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals, which contains 58 pesticid e active ingredients and 9 inert ingredients. This list of chemicals was selected based on th e potential for human exposure through pathways such as food and water, residen tial activity, and certain post-applic ation agricultural scenarios. This list should not be construed as a lis t of known or likely e ndocrine disruptors.

Paraquat is not among the group of 58 pesticide ac tive ingredients receiving EDSP test orders. For information on the status of the orders i ssued under the EDSP for each chemical, please visitPage 32 of 71 our website at http://www.epa.gov/ endo/ and click on the "Status of EDSP Orders/DCIs" in the Highlights Box. Additional inform ation on the EDSP, including the policies and procedures, the list of 67 chemicals, the te st guidelines and the Ti er 1 screening battery, ca n also be found at this website.


### 11. Preliminary Identification of Data Gaps

11.1. Fate

Table 9. Available environ mental fate data for paraquat and remaining data gaps.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Classification Data Gap? Comments

835.2120 Hydrolysis No MRID Acceptable No -- 835.2240 Aqueous photolysis 40562301 Acceptable No -- 835.2410 Soil photolysis 0 0146807 Acceptable No --

835.4100 Aerobic soil metabolis m 41319301 Acceptable No --

835.4200 Anaerobic soil metabolis m 41319302 Acceptable No --
835.4300 Aerobic aquatic metabo lism 00055093 Accep table No --
835.4400 Anaerobic aquatic metabolism No data No Yes --

835.1230 835.1240 Adsorption/ desorption and leaching 40762701 Acceptable No --

835.6100 Terrestrial field dissipation 41293202

Acceptable No -- 42802101

42738701

42738702

42802102
835.6200 Aquatic field dissipation No data Waived No No aquatic uses

850.1730 Fish bioaccumulation No data Waived No Log Kow is below 3, indicating that bioaccumulation of paraquat is not expected.

840.1100 Spray Drift - Droplet size spectrum No data No Yes --

840.1200 Spray Drift – Drift field evaluation No data No Yes --

Anaerobic Aquatic Metabolism (Guideline 835.4400)

Acceptable data have not been provided to quantif y the metabolism of paraqua t under anaerobic aquatic conditions. According to Code of Federal Regulations 40 (CFR40 2007) Part 158 Subpart D (data requirements for pesticides) anaerobic aquatic metabolis m are required for pesticides with terrestrial orPage 33 of 71 aquatic uses. Since paraquat uses are classified as terrestrial, anaerobic aquatic metabolism data for paraquat should be submitted to fulfill OPPTS Guideline 835.4400.

Currently there are no acceptable anaerobic aquatic metabolism studies that track the formation and decline of paraquat and its degradates. The submitted data will be used to characterize and quantify the environmental fate of paraquat and its degradates in aquatic environments . For quantitative exposure estimation, these data will be used to confirm the co nceptual model of paraquat fate and transport in aquatic environments.

Without these required data, the fate of paraquat cannot be fully characterized and exposure to potentially toxic degradates cannot be quantified. The persistenc e of paraquat and its degradates to which terrestrial and aquatic organisms will be exposed to is uncertain. In the absence of acceptable data, conservative assumptions will be made regarding the potential for formation of paraquat degradates. Therefore, potential for risk to aquatic organisms may be overes timated and the use of paraquat might need to be restricted in areas where endangered species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in co ming into compliance with the Endangered Species Act and could result in use restrictions for paraquat which are unnecessarily severe.

Drinking Water Treatability (non-guideline study)

EFED notes that submission of a drinking water treatability study (i.e., Ja r Test) would be of high value to drinking water assessments. The study is a laboratory bench scale test to mimic the processes of chemical addition, co agulation, and sedimentation in a typical water treatment plant. This study provides the simplest a nd most direct method to show that paraquat is removed during drinking water treatment.

Guideline Number: N/A - Special study Study Title: Drinking Water Treatability Study Rationale for Requiring the Data Use of paraquat can result in th e presence of this chemical in the drinking water reservoirs and rivers by off-target spray drift and r unoff. For drinking water exposure assessment, EFED will be using the PRZM/EXAMS model’s Index Reservoir scenario to estimate exposures in the receiving water body to derive the estimated drinking water concentrations. With paraqua dichloride’s high adsorptive proper ties, the Agency believes that the regular water treatment process may rem ove most of the paraquat from the water. However, EFED has no data to confirm this. Since EFED doe s not have any water treatment studies for paraquat quantifying the removal mechanism, the Agency would have to assume in the registration review risk assessment that no removal occurs in water treatment.

A bench scale drinking water treatability study (similar to the Jar Test) is necessary to determine how much paraquat dichloride is removed from water during the regular water treatment process. These data will be used to refine the expected drinking water exposure values. Practical Utility of the Data
How will the data be used? The data will be used to assess the removal efficiency of paraquat dichloride in typical drinking water treatment facili ties through the processes of ch emical addition, coagulationPage 34 of 71 and sedimentation. The removal efficiency derive d from the bench scale water treatment test will be used to refine the expected drinking water exposure assessment.

How could the data impact the Ag ency’s future decision-making? The Agency will use these data to refine th e drinking water exposure risk from paraquat dichloride. Without these data, the Agency woul d have to assume that paraquat dichloride is not removed in drinking water treatment faci lities. This assumption would lead to high drinking water exposure values. These values, if used in a dietary risk assessment, would yield risk estimates above the Agency’s le vel of concern, which would necessitate the implementation of mitigation measures such as reduced application rates and cancellation of some uses. The lack of these data will limit th e flexibility the Agency and registrants have in coming into compliance with the Federal Food Drug and Cosmetic Act and the Federal Insecticide, Fungicide and Rodenticide Act and could result in use restrictions for this chemical that may be unnecessary.



### 11.2. Effects

Although many submissions have been made to provide data on the effects of paraquat to aquatic and terrestrial organisms, data gaps still exist. The available ecological effects data submitted for paraquat dichloride and the remaini ng data gaps are summarized in Tables 10, 11 and 13 . The data gaps are also described below, along with EFED’s rationales for recommending PRD required certain studies to fulfill the guideline requirements.Page 35 of 71 Table 10. Available ecological eff ects data for terrestrial an imals exposed to paraquat and remaining data
gaps.
Guideline # Description MRID Classification Data Gap? Comments

850.2100 Acute avian oral toxicity 29001 acceptable Yes No toxicity data are available for a passerine species. 160000 invalid

none Acute avian inhalation toxicity none Not applicable Yes STIR indicates that inhalation exposure may be a concern for birds; therefore, acute inhalation toxicity ddata for birds should be submitted.

850.2200 Avian dietary toxicity 22923 acceptable

No MRID 22923 included 4 test species, including the bobwhite

quail and the mallard duck.

MRID 90975 is the same submission as MRID 55103. 55103* invalid

850.2300 Avian reproduction 110453 supplemental

No MRIDs 110454 and 110455 are currently being re-reviewed by EFED; however, available data are adequate for risk assessment. 110454 Under review

110455 Under review

43942604 supplemental

43942605 supplemental

850.3020 Honeybee acute contact toxicity 36935 acceptable

No None 5001991 acceptable

111488* supplemental

43942603 acceptable

850.3030 Honey bee toxicity or residues on foliage none Not applicable No Study is not required because acute contact LD 50 is >11 μg a.i./bee.

850.3040 Field testing for pollinators none Not applicable No Study is not required.
*Formulated product exposure.

Avian Acute Oral Toxicity with a passerine species (Guideline 850.2100)

The Part 158 data requirements specify that acute avian oral toxicity data be submitted for either a mallard duck or bobwhite quail AND a passerine sp ecies. These studies are required for TGAI. Acceptable data have been submitted for th e bobwhite quail exposed to TGAI (MRID 29001); however, no acute oral data have been submitted for a passerine species. Therefore, EFED recommends that PRD require an avian oral toxicity test (OPPT S Guideline 850.2100) for a passerine species exposed to TGAI paraquat dich loride. The registrant will need to submit a passerine study protocol for review by the Agency prior to initiation of the passerine study.

Avian Acute Inhalation toxicityPage 36 of 71 Guideline Number: Non-guideline Study Title: Avian inhalation toxicity Rationale for Requiring the Data Acceptable avian acute toxicity data were submitted for oral exposures of birds to paraquat; however, data are not available for inhalation toxi city to birds. An eval uation of inhalation as a route of exposure using the Screening Tool fo r Inhalation Risk (STIR, v. 1.0) suggests that inhalation exposure is a pathway of concern for avian wildlife due to drift of the pesticide. In addition, paraquat is moderately toxic to av ian species on an acute exposure basis, and paraquat is highly toxic to mammals on an acu te inhalation basis. Therefore, EFED recommends that PRD require an acute avian i nhalation toxicity test using the most sensitive avian species as shown by avian acute oral st udies. The study being re quested will aid in evaluating this pathway of concern for avian taxa. An avian inhalation study protocol must be submitted for review and approval by the Agency prior to initiation of this study. Practical Utility of the Data
How will the data be used? Acute avian inhalation toxicity data will be us ed to identify potential risks to birds form acute exposure to paraquat. The data will reduc e uncertainties associated with the current risk assessment for birds and will improve the Agency’s understanding of the potential effects of paraquat on terrestrial species. If inhalation acute toxicity data are not submitted for birds, then risk to birds from acute inha lation exposure to paraquat will be presumed. If acute inhalation toxicity data are not submitte d for birds, the method used by STIR will be used to estimate an acute inhalation endpoi nt for birds from the available mammalian toxicity data.

How could the data impact the Ag ency’s future decision-making? If future endangered species risk assessments are performed without th ese data, the Agency would have to assume that paraquat “may a ffect” listed bird species directly (and listed species from other taxa indirec tly), and the use of paraquat dichloride and its formulated may need to be restricted in areas where listed sp ecies could be exposed. The lack of these data will limit the flexibility of the Agency a nd the registrants for compliance with the Endangered Species Act and could result in use re strictions for paraquat dichloride that are unnecessarily severe.

Table 11. Available ecological effect s data for aquatic animals exposed to paraquat and remaining data gaps.Page 37 of 71 Guideline Description MRID Classification Data Gap? Comments

850.1075 Freshwater fish – Acute toxicity 162736 supplemental

Yes A TGAI study is needed. No acceptable studies are available for this guideline; formulated product endpoints are more sensitive than the most sensitive TGAI endpoint. 162737 supplemental

162738 supplemental

40098001 supplemental

850.1075 Saltwater fish – Acute toxicity 40228401* Supplemental Yes TGAI study needed

850.1010 Freshwater invertebrates – Acute toxicity 114473 Supplemental

No Although no acceptable studies are available for this guideline, the results of several scientifically valid studies are all consistent. Therefore acute toxicity of paraquat to aquatic invertebrates is not considered a data gap. 162752 Supplemental

40098001 supplemental

850.1025 850.1035 Saltwater invertebrates – Acute toxicity 40228401* Supplemental Yes TGAI studies needed

850.1300 Freshwater invertebrate – life cycle test none Not applicable Yes none

850.1350 Saltwater invertebrates – life cycle test none Not applicable Yes none

850.1400 Freshwater fish – early life stage test none Not applicable Yes none

850.1400 Saltwater fish – early life stage test none Not applicable Yes none

850.1735 Freshwater invertebrate – acute

sediment toxicity none Not applicable Yes none

Nonguideline Freshwater invertebrate – chronic sediment toxicity none Not applicable Yes Protocol must be submitted prior to study initiation.

*Formulated product exposure.

Acute toxicity data for freshwater (warm and co ld water species) and estuarine/marine fish

In order to satisfy guideline 850.1075, toxicity data should be submitted for 3 species of fish: one warm freshwater species, one cold, freshwater fish and one saltwater fish exposed to TGAI; however, acceptable toxicity data involving fres hwater fish exposed to technical paraquat dichloride are not available.

Acute toxicity data are available for warm and cold species of freshwater fish ( i.e., bluegillPage 38 of 71 sunfish and rainbow trout, resp ectively) and saltwater fish ( i.e., longnose killifish) exposed to a formulated product containing para quat (Table 12). Available formulated product data suggest that paraquat is moderately to slightly toxic to freshwater fish. Data are also available from a study involving exposures of fowler’s toad tadpol es to TGAI paraquat dichloride. These data suggest that paraquat is slightly toxicity to aquatic-phase amphibians.

Table 12. 96-h LC50 values for fi sh and aquatic-phase amphibians exposed to paraquat. All values are expressed as paraquat cation.

Test species (scientific name) Water type TGAI (T) or formula (F) LC 50 (mg cation/L) MRID Study classification
Longnose killifish ( Fundulus similis ) SW F >0.72 40228401 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 6.1 162736 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 8.1 162738 supplemental
Bluegill sunfish (Lepomis macrochirus) FW F 12 40098001 supplemental

Fowler’s toad (Bufo woodhousei fowleri) FW T 15 40098001 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 16 40098001 supplemental
Bluegill sunfish (Lepomis macrochirus) FW F 32.7 162737 supplemental

Channel catfish (Ictalurus punctatus) FW T >100 40098001 supplemental

In order to fulfill guideline 850.1075, the registra nt should submit toxicity data with TGAI paraquat dichloride for a two freshwater fish (cold and warm water) and one saltwater fish species. These data are necessary because 1) EFED uses endpoints from TGAI studies with aquatic organisms to derive RQs that consider both runoff and spray drift transport (the formulated product endpoints should be used for spray drift EECs only); 2) available formulated product data for fish are more sensitive than TGAI studies that involve ot her test species; 3) the relative toxicity of TGAI para quat dichloride to formulated products containing paraquat dichloride is unknown; 4) incide nt reports have been identified through EIIS where paraquat was related to mortalities of fish, sugge sting a concern for acute exposures.

Acute toxicity data for est uarine/marine invertebrates

Acute toxicity data are available for brown shri mp and eastern oyster exposed to a formulated product containing paraquat (MRID 40228401). In order to fulfill guidelines 850.1025 and 850.1035 for estuarine/marine invertebrates, da ta should be submitted for TGAI paraquat dichloride.

Chronic toxicity data for fish and aquatic in vertebrates (both fres hwater and saltwater)

At this time, no chronic toxicity data have been submitted for aquatic animals exposed to paraquat. According to 40 CFR Part 158, chroni c toxicity data with freshwater fish and invertebrates (guidelines 850.1300 a nd 850.1400) are required for all pesticides with terrestrial uses. Chronic toxicity data for saltwater fish and invertebrate s (guidelines 850.1400 and 850.1350) are required when “studies of other orga nisms indicate the reproductive physiology ofPage 39 of 71 fish and/or invertebrates may be affected.” Available chronic toxicity data for birds indicate that paraquat may have reproductive effects on animals; therefore, EFED recommends that PRD require chronic toxicity data for estuar ine/marine fish and invertebrates.

Acute and chronic toxicity data for sediment dwelling invertebrates

No data are currently available to characterize the acute or chronic t oxicity of paraquat to sediment dwelling invertebrates. The updated Pa rt 158 data requirements, published in October 2007, specify that acute and chroni c toxicity data for sediment invertebrates are conditionally required if the half-life of th e pesticide in sediment >10 da ys in aerobic soil or aquatic metabolism studies and if any of the following conditions exist: a) the K d is ≥ 50; b) the log K ow is ≥ 3 or c) the K oc is ≥ 1000. Since the half-live of paraquat in soil under aerobic conditions is >10 days (41319301) and the K d is >50 (MRID 40862701), EFED r ecommends that PRD require acute and chronic toxicity data for one species of sediment-dwe lling invertebrate for paraquat. Paraquat dichloride registrants must submit a study protocol for review by the Agency prior to initiation of the ch ronic toxicity study with sediment dwelling invertebrates.

Although there is no guideline fo r the chronic sediment toxic ity study, the following methods by the USEPA’s Office of Research and Development may be consulted:

 ORD study method EPA 600/R-099-064: chronic freshwater sediment testing flowthrough (Hyalella azteca)

 ORD study method EPA 600/R-099-064: chronic freshwater sediment testing flowthrough (Chironomus dilutus or C. tentans)

 ORD study method EPA 6001R-0l/020: chronic estuarine/marine sediment testing flowthrough (Leptocheirus plumulosus)Page 40 of 71 Table 13. Available ecological ef fects data for plants exposed to paraquat and remaining data gaps.
Guideline Description MRID Classification Data Gap? Comments

850.4100 Terrestrial Plant toxicity: Tier 2 seedling emergence 42639601 Supplemental Yes Tier II data are required for 4 monocot and 6 dicot species. Tier I data involving exposures at 1 lb cation/A may be submitted to fulfill this guideline if <25% effects to a test species are observed.

850.4150 Terrestrial Plant toxicity: Tier 2 vegetative vigor 42601001 Supplemental Yes Data are required for 6 dicot species and 4 monocot species as specified in the guideline.

850.5400 Aquatic Plant Growth: algae 40228401 Supplemental No none
42601002 Acceptable

42601004 Acceptable

42601005 Acceptable

42601006 Acceptable

850.4400 Aquatic Plant Growth: vascular plants 42601003 Acceptable No none

Terrestrial plant toxic ity – seedling emergence

According to the 850.4100 guideline, seedling emergen ce data are required for a total of 10 plant species, including 4 monocot and 6 dicot species. Th e 4 monocot species must be from at least 2 families. One species of monocots must be corn. The 6 dicot species must be from 4 different families, and must include soybean and a root crop.

Acceptable seedling emergence data are available for 2 monocot species, including: corn and purple nutsedge (MRID 42639601). These data are fr om species from two different families ( i.e.
, Poaceae and Cyperaceae). In these studies, no eff ects were observed at the highest test concentration (i.e., 0.67 lb cation/A); however, th is application rate is below the highest application rate permitted for paraquat (i.e., 1 lb cation/A). Therefore, 850.4100 is not fulfilled for monocots.

Acceptable seedling emergence data are available for 6 species of di cots (family in parentheses), including soybean (Fabaceae), beet (Chenopodia ceae), oilseed rape (Brassicaceae), morning glory (Convolvulaceae), velvetleaf (Malvaceae) and cocklebur (A steraceae; MRID 42639601). Effects were observed in cocklebur; however, the EC 25 was equivalent to the highest application rate of the study. This leaves uncertainty in the endpoint for cocklebur, since the EC 25 is not bound by higher test concentrations. As with the monocots, no effects were observed for soybean, beet, oilseed rape, morni ng glory and velvet leaf at the highest test concentration (i.e., 0.67 lb cation/A); however, this application rate is below the highest application rate permitted for paraquat (i.e., 1 lb cation/A). Ther efore, 850.4100 is not fulfilled for dicots.

In order for the 850.4100 guideline requirement to be fulfilled, EFED recommends that PRDPage 41 of 71 require a test involving 4 monocots and 6 dicots exposed up to the highest single application rate. Since no effects were observed in the major ity of the test species in MRID 42639601 when exposed to 0.67 lb cation/A, it may be possible to fulfill this guideline using a Tier I seedling emergence study involving exposures to 1 lb cation/A. If ≥ 25% effects are observed for any species exposed to 1 lb cation/A, a Tier II s eedling emergence study must be submitted for that species.

Terrestrial plant toxic ity – vegetative vigor

According to the 850.4150 guideline, vegetative vigor data are requi red for a total of 10 plant species, including 4 monocot and 6 dicot species. Th e 4 monocot species must be from at least 2 families. One species of monocots must be corn. The 6 dicot species must be from 4 different families, and must include soybean and a root crop.

Supplemental vegetative vigor data are availa ble for 1 monocot and 6 dicot species (MRID 42601001). Although these data are sc ientifically valid, they ar e uncertain due to guideline deviations. Therefore, EFED reco mmends that PRD require Tier II vegetative vigor data for 6 dicot and 4 monocot species as i ndicated in the paragraph above.



## 12. References

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

Hoerger, F. and E. E. Kenaga. 1972. Pe sticide Residues on Plants: Correlation of Representative Data as a Basis for Estimation of their Magnitude in the Environment. In F. Coulston and F. Korte, eds., Environmental Quality and Safety : Chemistry, Toxicology, and Technology, Georg Thieme Publ., Stuttg art, West Germany, pp. 9-28.

USEPA. 1998. Guidelines for Ecological Risk A ssessment. Risk Assessment Forum, Office of Research and Development, Washi ngton, D.C. EPA/630/R-95/002F. April 1998. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. U.S. Environmental Protection Agen cy, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Prog rams, Washington DC. January 23, 2004.

USEPA. 2007. ECOTOXicology Database. Of fice of Research and Development National Health and Environmental Effects Research La boratory’s (NHEERL’s) Mid-Continent Ecology Division (MED). http://cfpub.epa.gov/ecotox/

.

USEPA. 2007 b . Ecological Incident Information System. http://www.epa.gov/espp/consultation/ecorisk-overview.pdfPage 42 of 71 U.S. Fish and Wildlife Service (USFWS) and Na tional Marine Fisheries Service (NMFS). 1998. Endangered Species Consultation Handbook: Pr ocedures for Conducting Consultation and Conference Activities Under Section 7 of the E ndangered Species Act. Final Draft. March 1998.

Environmental Fate Studies:

161-1 Hydrolysis

MRID Citation Reference

67161 Funderburk, H.H., Jr.; Negi, N.S.; La wrence, J.M. (1966) Photo- chemical decomposition of diquat and paraquat. Weeds 14:240- 243. (Also~In~unpublished submission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical C o., Richmond, Calif.; CDL:231432-L)
85678 Harned, W.H.; Lengen, M.R. (1981) The Photolysis of Harvade in Aqueous and Soil Environments: Project No. 8031. (Unpublished study received Aug 19, 1981 under 1F2560; submitted by Uniroyal Chemical, Bethany, Conn.; CDL:070240-E)
114412 Slade, P. (1965) Photochemical degradation of paraquat. Nature 207 (4996):515-516. (Also In unpublished s ubmission received on unknown date under 5G0440; submitted by Californi a Chemical Co., Richmond, CA; CDL:092728-A)

161-2 Photodegradation-water

MRID Citation Reference

40562301 Parker, S.; Leahey, J. (1988) Paraquat Aqueous Photolysis at pH 7: Laboratory Project ID R0633B. Unpublished stu dy prepared by ICI Plant Protection Division. 51 p.

161-3 Photodegradation-soil

MRID Citation Reference

17934 Hance, R.J. (1967) Decomposition of herb icides in the soil by non- biological chemical processes. J. Sci. Fd Agric. 18(?/Nov):544- 547.Page 43 of 71 (Also~In~unpublished submission received Aug 20, 1976 under 39445-1; submitted by American Carbonyl, In c., Tenafly, N.J.; CDL:228229-AX)
67161 Funderburk, H.H., Jr.; Negi, N.S.; La wrence, J.M. (1966) Photo- chemical decomposition of diquat and paraquat. Weeds 14:240- 243. (Also~In~unpublished submission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical C o., Richmond, Calif.; CDL:231432-L)
85678 Harned, W.H.; Lengen, M.R. (1981) The Photolysis of Harvade in Aqueous and Soil Environments: Project No. 8031. (Unpublished study received Aug 19, 1981 under 1F2560; submitted by Uniroyal Chemical, Bethany, Conn.; CDL:070240-E)
108334 Corbin, F. (1967) Influence of pH on the Detoxication of Herbicides in Soil. Abstracted from: Weeds 15(4):370-3 77. (Unpublished study received Nov 4, 1971 under 1F1042; prepared by North Ca rolina State Univ., Dept. of Crop Science, submitted by Stauffer Chemi cal Co., Richmond, CA ; CDL:091932-L)
140344 Tucker, B.V.; Pack, D.E. (1965) Para quat Metabolic Fate-- Status Re- port. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Rich mond, Calif.; CDL:180001-C)
140345 Baldwin, B.C.; Slade, P. (1968) The Fa te of Carbon-14 Labelled Par- aquat in Soil under Field Conditions: AR 2220 B. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-D)
140346 Chevron Chemical Company (1970) The Fate of Carbon 14 Labelled Paraquat in Soil under Field Conditions. (Unpublis hed study received Apr 7, 1971 under unknown admin. no.; CD:180001-E)
140350 Tucker, B.V.; Pack, D.E. ( 1966) The Metabolism 4-Carboxy-1- methylpyridinium Ion in Soil. (Unpub lished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-M)
146806 Day, S.; Hemingway, R. (1981) [Car bon-14] Paraquat: Degradation on a Sandy Soil Surface in Sunlight: Report Seri es RJ 0168B. Unpublished study prepared by ICI Plant Protection Division. 40 p.
146807 Pack, D. (1982) Long Term Exposure of [Carbon 14] Paraquat on a Sandy Soil to California Sunlight. Unpublished study prepared by Chevron Chemical Company. 16 p.

162-1 Aerobic soil metabolism

MRID Citation ReferencePage 44 of 71 55092 Burns, R.G.; Audus, L.J. (1970) Distri bution and breakdown of Paraquat in soil. Weed Research 10:49-58. (Also~In~ unpublished submission received Apr 7, 1971 under unknown admin. no.; sub- mitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-H)
91369 Chevron Chemical Company (19??) The Fate of Paraquat in Soils. (Unpublished study received Mar 2, 1966 under 6F0483; CDL: 090543-F)
114414 Chevron Chemical Co. (1967) Name, Chem ical Identity and Composition of the Pesticide Chemical: (Para quat). (Compilation; unpub- lished study received Apr 3, 1967 under 7F0592; CDL:092880-A)
140345 Baldwin, B.C.; Slade, P. (1968) The Fa te of Carbon-14 Labelled Par- aquat in Soil under Field Conditions: AR 2220 B. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-D)
140346 Chevron Chemical Company (1970) The Fate of Carbon 14 Labelled Paraquat in Soil under Field Conditions. (Unpublis hed study received Apr 7, 1971 under unknown admin. no.; CD:180001-E)
140350 Tucker, B.V.; Pack, D.E. ( 1966) The Metabolism 4-Carboxy-1- methylpyridinium Ion in Soil. (Unpub lished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-M)
140355 Anderson, J.R.; Drew, E.A.; Tomlin son, T.E. (1971) Distribution of ?~Lipomyces starkey~in Some Soils and Its Ability To Degrade Paraquat in Soil or Clay Associations: Report No. AR 2236 A. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Imperial Chemical Industries, Ltd., submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-R)
140356 Anderson, J.R.; Drew, E.A.; Tomlinson, T.E. (1971) Growth Charac- teristics of, and Paraquat Degradation by, a Speci es of~Lipo~?- ?~myces: Report No. AR 2238 A. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Imperial Chem- ical Industries, Ltd., submitted by Chevron Chemical Co., Rich- mond, Calif.; CDL:18001-S)
41319301 Vickers, J.; Hurt, A.; Bewick, D. (1989) Paraquat: Degradation in Aerobic Soil: Lab Project Number: 88JH386. Unp ublished study prepared by ICI Agrochemicals. 33 p.

162-2 Anaerobic soil metabolism

MRID Citation Reference

41319302 Vickers, J.; Hurt, A.; Bewick, D. ( 1989) Paraquat: Degradation in Anaerobic Soil: Lab Project Number: 88JH386. Unpublished study prepared by ICIPage 45 of 71 Agrochemicals. 34 p.

163-1 Leach/adsorp/desorption

MRID Citation Reference

17934 Hance, R.J. (1967) Decomposition of herb icides in the soil by non- biological chemical processes. J. Sci. Fd Agric. 18(?/Nov):544- 547. (Also~In~unpublished submission received Aug 20, 1976 under 39445-1; submitted by American Carbonyl, In c., Tenafly, N.J.; CDL:228229-AX)
22802 Warnock, R.E.; Leary, J.B. (1978) Para quat, Atrazine and Bladex- Dissipation in Soils. (Unpublished study received Jul 30, 1979 under 201-279; prepared by Chevron Chemical Co., submitted by She ll Chemical Co., Washington, D.C.; CDL:238889-G)
25063 Shell Chemical Company (1975) Dissip ation of Bladex^(R)I Herbicide and Paraquat in Soil following Application of Bladex, Paraquat, or a Tank Mix of Bladex and Paraquat: TIR-24-135-74. (Unpub- lished study received Apr 22, 1976 under 201-279; CDL:224461-F)
29088 Mangels, G.D. (1979) CL 222,705: Determination of Mobility by Soil ThinLayer Chromatography: Project No. 0414. (Unpublished study received Apr 22, 1980 under 241-259; submitted by American Cyanamid Co., Princeton, N.J.; CDL:099383-E)
32006 Weissler, M.S.; Prashad, S.; Hill, I.R. (1979) Paraquat: Strong Ad- sorption Capacities, Measured by Wheat Bioa ssay, of Seven Sandy Soils from West Germany: Report Series RJ 0097 B. (Unpublished study received May 2, 1980 under 239-2186; prepared by ICI, sub- mitted by Chevron Chemical Co., Richmond, Calif.; CDL:242382-B)
32045 Reichert, B.L.; Knoll, B.A. (1979) CL 217,300: Determination of Mobility in Soil: Project No. 0420. (Unpublished study received Jun 11, 1980 under 241- 260; submitted by American Cyanamid Co., Princeton, N.J.; CDL:099457-C)
33449 Clinch, R.C.; Middleton, M.R.; Wi nchester, J.N. (1962) Bipyridylium Herbicides: Adsorption of Diquat and Paraquat Salts and Formula- tions by Soils: Experimental Report No. PP/E/ 178. (Unpublished study received Jun 10, 1963 under 239-1994; prepared by Imperial Chemical Industries, Ltd. in cooperation with Plant Protection, Lt d., submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 001407-B)
33837 California Chemical Company (1964) Bi o-assay of Extracts from Para- quatTreated Soils with~Lemna minor~?. (U npublished study re- ceived Oct 14, 1965 under 239-1994; submitted by Chevron Chemi- cal Co., Richmond, Calif.; CDL:001432-C)Page 46 of 71 52390 Gowman, M.A.; Riley, D.; Newby, S. E. (1980) Paraquat and Diquat: LongTerm High-Rate Trial, Frensham, UK. 2. Persistence and Movement in Soil, and Glasshouse Bioassays: Report Series RJ 0014 B. (Unpublished study received Jun 4, 1980 under 239-2186; prepared by ICI, submitted by Chevron Chemical Co., Richmond, Calif.; CDL:242577-B)
55086 Coats, G.E.; Funderburk, H.H., Jr.; Lawrence, J.M.; et al. (1966) Factors affecting persistence and inactivation of Diquat and Paraquat. Weed Research 6(1):58-66. (Also~In~unpublished sub- mission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-B)
55087 Knight, B.A.G.; Denny, P.J. (1970) The interaction of Pa raquat with soil: Adsorption by an expanding lattice clay mineral. Weed Research 10:40-48. (Also~In~unpublished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical C o., Richmond, Calif.; CDL:180000-C)
55088 Knight, B.A.G.; Tomlinson, T.E. (1967) The interaction of Paraquat (1:1'- Dimethyl 4:4'-dipyridylium dichloride) with mineral soils. Journal of Soil Science 18(2):233-243. (Also~In~unpublis hed submission received Apr 7, 1971 under unknown admin. no.; sub- mitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-D)
55089 Tomlinson, T.E.; Knight, B.A.G.; Bastow, A.W.; et al. (1968) Structural factors affecting the adsorption of bipyridylium cations by clay minerals. Pages 317- 333,~In~Physico-Chemical and Biophysical Factors Affecting the Activity of Pesticides. By ? London, England: Soc. of Chem. Ind. (S.C.I. monograph no. 29; also~In~unpublished submission r eceived Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical C o., Richmond, Calif.; CDL:180000-E)
55090 Weber, J.B.; Perry, P.W.; Upchurch, R. P. (1965) The influence of temperature and time on the adsorption of Paraquat, Diquat, 2,4-D and Prometone by clays, charcoal, and an anion-exchange resin. Soil Science Society of America Proceedings 29:678-688. (Also~In~unpublished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-F)
55092 Burns, R.G.; Audus, L.J. (1970) Distri bution and breakdown of Paraquat in soil. Weed Research 10:49-58. (Also~In~ unpublished submission received Apr 7, 1971 under unknown admin. no.; sub- mitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-H)
55093 Coats, G.E.; Funderburk, H.H., Jr.; Lawr ence, J.H.; et al. (1 964) Persistence of Diquat and Paraquat in pools and ponds. Pr oceed- ings, Southern Weed Control Conference 17:308-320. (Also~In~ unpub lished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 180000-I)
55097 Austin, W.G.L.; Calderbank, A. (1964) Diquat and Paraquat: Residues in Water and Toxicity to Fish and Other Aqua tic Fauna: Experi- mental Report No.Page 47 of 71 PP/E/303. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Plant Protection, Ltd., submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-M)
56053 Tucker, B.V. (19??) Lack of Effect of a Polar Hydroxy triazine Com- pound on Paraquat Leaching in Soil. (Unpublis hed study received Jun 19, 1973 under 1F1014; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:091760- C)
64796 Pack, D.E. (1980) Mobility of Naled a nd Dichlorvos in Soil As De- termined by Soil Thin-layer Chromatography: File No. 722.2. (Unpublished study received Oct 20, 1980 under 239-1633; submit- ted by Chevron Chemical Co., Richmond, Calif.; CDL:243547-A)
65606 Baldwin, B.C.; Knight, B.A. G. (1967) The Fate of Di quat in Soils: Survey of Present Knowledge: TMJ 224. (Unpublished study re- ceived Aug 22, 1977 under 239-1663; prepared by Imperial Chem- ical Industries Ltd., England, submitted by Chevron Chemical C o., Richmond, Calif.; CDL:231430-F)
65609 Gamar, Y.; Mustafa, M.A. (1975) Adsorp tion and desorption of di- quat^2tI and paraquat^2tI on arid-zone soils . Soil Science 119(4):290-295. (Also~In~unpublished submission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:231430-I)
65610 Haque, R.; Lilley, S.; Coshow, W.R. ( 1970) Mechanism of adsorption of diquat and paraquat on Montmorillonite surface. Journal of Colloid and Interface Science 33(1):185-188. (Also~In~unpub~ lished submission received Aug 22, 1977 under 239-1663; submit- ted by Chevr on Chemical Co., Richmond, Calif.; CDL:231430-J)
65611 Hayes, M.H.B.; Pick, M.E.; Toms, B.A. (1972) Application of microcalorimetry to the study of interactions between or ganic chem- icals and soil constituents. Science Tools 19:9- 12. (Also~In~ unpublished submission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 231430-K)
65613 Khan, S.U. (1974) Adsorption of bi pyridylium herbicides by humic acid. Journal of Environmental Qualit y 3(3):202-206. (Also ?~In~unpublished submission received Aug 22, 1977 under 239- 1663; submitted by Chevron Chemical Co., Richmon d, Calif.; CDL:231430-M)
65614 Khan, S.U. (1973) Interaction of bipy ridylium herbicides with or- gano-clay complex. Journal of Soil Science 24(2):244-248. (Al- so~In~unpublished submission received Aug 22, 1977 under 239- 1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:231430-N)
65615 Philen, O.D., Jr.; Weed, S.B.; Weber, J. B. (1970) Estimation of surface charge density of mica and vermiculite by competitive adsorption of Diquat^2I^+I vs. Paraquat^2I^+I. Soil Science Society of America Proceedings 34:527-531. (Also~In~unpublished submission received Aug 22, 1977 under 239-1663;Page 48 of 71 submitted by Chevron Chemical C o., Richmond, Calif.; CDL:231430-O)
65618 Tucker, B.V.; Pack, D.E.; Ospenson, J. N. (1967) Adsorption of bipy- ridylium herbicides in soil. Journal of Agricu ltural and Food Chemistry 15(6):1005-1008. (Also~In~unpublished submission re - ceived Aug 22, 1977 under 239-1663; submitted by Chevron Chemi- cal C o., Richmond, Calif.; CDL:231430-S)
65619 Weber, J.B.; Weed, S.B. (1968) Adsorp tion and desorption of diquat, paraquat, and prometone by montomorillanitic and kaolinitic clay minerals. Soil Science Society of America Proceedings 32:485- 487. (Also~In~unpublished submission received Aug 22, 1977 un- der 239-1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:231430-T)
65621 Weber, J.B.; Perry, P.W.; Upchurch, R. P. (1965) The influence of temperature and time on the adsorption of paraquat, diquat, 2,4-D and prometone by clays, charcoal, and an anion-exchange resin. Soil Science Society of America Proceedins 29(6):678- 688. (Also~In~ unpublished submission received Aug 22, 1977 un- der 239-1663; submitted by Chevr on Chemical Co., Richmond, Calif.; CDL:231430-V)
65622 Weed, S.B.; Weber, J.B. (1969) The e ffect of cation exch ange caparity on the retention of Diquat 2I+I a nd Paraquat21+I by three-layer type clay minerals: I. Adsorption and release. Soil Scienc e Society of America Proceedings 33(3):379-382. (Also in unpublished s ubmission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:231430-W)
65623 Weed, S.B.; Weber, J.B. (1968) The effect of adsorbent charge on the competitive adsorption of divalent organic cations by layer- silicate minerals. American Mineralogist 53(Mar -Apr):478-490. (Also~In~unpublished submission received Aug 22, 1977 under 239- 1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 231430-X)
65624 Best, J.A.; Weber, J.B.; Weed, S. B. (1972) Competive adsorption of Diquat^2I^+I, Paraquat^2I^+I, and Ca^2 I^+I on organic matter and exchange resins. Soil Science 114(6)444-450. (Also~In~unpub- lished submission received Aug 22, 1977 under 239-1663; submit- ted by Chevron Chemical Co., Richmond, Calif.; CDL:231430-Y)
68226 Coats, G.E.; Funderburk, H.H., Jr.; Lawr ence, J.M.; et al. (1964) Persistence of diquat and paraquat in pools and ponds. Pro- ceedings of the Southern Weed Control Conference 17:308-320. (Also~ In~unpublished submission received Aug 22, 1977 under 239- 1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 231431-J)
70873 Pack, D.E. (1980) Paraquat, Atrazine a nd Terbutryn--Dissipa tion in Soils Alone and in Combination: File No. 721.7/R-127. (Unpub- lished study received Mar 24, 1981 under 239-2186; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:244725-A)Page 49 of 71 82259 Spinks, C.A.; Hendley, P.; Arnold, D. J. (1976) PP796--Degradation in Soil under Laboratory Conditions: Report Se ries TMJ 1419 B. (Unpublished study received Apr 13, 1977 under PP0796; prepared by Imperial Chemical Industries, Ltd., England, submitted by Chevron Chemical Co., Richmond, Calif.; CDL:098315-G)
90396 California Chemical Company (1964) Pa raquat Residues in Soil. (Compilation; unpublished study received Feb 25, 1965 under 5G0440; CDL:090479-B)
91369 Chevron Chemical Company (19??) The Fate of Paraquat in Soils. (Unpublished study received Mar 2, 1966 under 6F0483; CDL: 090543-F)
91370 Chevron Chemical Company (1965?) Ad sorption of Bipyridylium Herbi- cides in Soil. (Unpublished study receiv ed Mar 2, 1966 under 6F0483; CDL:090543- G)
96972 Pack, D.E. (1977) Soil Mobility of Capt an, Folpet and Captafol As Determined by Soil Thin-layer Chromatography: File No. 722.0. (Unpublished study received May 30, 1978 under 239-2211; sub- mitted by Chevron Chemical Co., Richmond, Calif.; CDL:234046-N)
105942 Leake, C.; Lines, D.; Tiffen, K. (1981) The Leaching of NC 21 314 in Four Soil Types Using Soil TLC: METAB/81/40. (Unpublished study received Jul 1, 1982 under 45639-EX-7; prepared by FBC Ltd., Eng., submitted by BFC Chemicals, Inc., Wilmington, DE; CDL:070966-E)
111528 McCall, H.; Bovey, R.; McCully, M; et al. (1972) Adsorption and desorption of picloram, trifluralin, and paraquat by i onic and nonionic exchange resins. Weed Science 20(3):250-255. (Also In unpublis hed submission received Sep 26, 1974 under 464-323; submitted by Dow Chemical U.S.A., Midland, MI; CDL:120317-U)
113707 Clinch, R.; Middleton, M.; Winchester, J. (1962) Bipyridylium Herbicides: Adsorption of Diquat and Paraquat Salts and Formula- tions by Soils: Report No. PP/E/178. (Unpublished study re- ceived Aug 1, 1962 under unknown admin. no.; submitted by Imperial Ch emical Industries Ltd., London, Eng.; CDL:121729-A)
114299 Leake, C.; Somerville, L.; Lines, D.; et al. (1982) The Leaching of Amitraz in Four Soil Types Using Soil T.L.C. : METAB/82/16. (Un- published study received Sep 8, 1982 under 45639-49; prepared by FBC, Ltd., Eng., submitted by BFC Chemicals, Inc., W ilmington, DE; CDL:248318-B)
116619 Kinne, L.; Reynolds, J.; Froelich, L.; et al. (1982) Soil Mobility of FMC 57020: M-4862. (Unpublished study received Oct 1, 1982 under 279-EX-93; submitted by FMC Corp., Philadelphia, PA; CDL: 248476-C)
121311 Hayes, M.; Pick, M.; Toms, B. (1972) A pplication of microcalor- imetry to the study of interactions between organi c chemicals and soil constituents. LKB Instrument Journal 19:9-12. (Also In unpublished submission received Dec 21,Page 50 of 71 1982 under 239-2247; submitted by Chevron Chemical Co., Richmond, CA; CDL:249102-K)
121313 Philen, O.; Weed, S.; Weber, J. (1970) Estimation of surface charge density of mica and vermiculite by competitive adsorption of di- quat vs. paraquat. Soil Science Society of America Proceedings 34:527-531. (Also In unpublished submission received Dec 21, 1982 under 239-2247; submitted by Chevron Chemical Co., Rich- mond, CA; CDL:249102-O)
121317 Weber, J.; Weed, S. (1968) Adsorption and Desorption of diquat, paraquat, and prometone by montmorillonitic and kao linitic clay minerals. Soil Science Society of America Proceedings 32:485- 487. (Also In unpublished submission received Dec 21, 1982 under 239-2247; submitted by Chevron Chemical Co., Richmond, CA; CDL:249102-T)
121318 Weed, S.; Weber, J. (1968) The effect of adsorbent charge on the competitive adsorption of divalent organic cations by layer-sil- icate minerals. American Mineralogist 53(Mar-Apr):478-490. (Also in unpublished submission received Dec 21, 1982 under 239-2247; submitted by Chevron Chemical Co., Richmond, CA; CDL: 249102-X)
128974 LaFleur, K. (1979) Sorption of pesticid es by model soils and agro- nomic soils: Rates and equilibria. Soil Science 127(2):94-101. (Also In unpublished submission received Jun 16, 1983 under 464-502; submitted by Dow Chemical U.S.A., Midland, MI; CDL: 250517AE)
135717 Chevron Chemical Co. (1970) Diquat: Residue Tolerance Petition: The Results of Tests on the Amount of Residue Rema ining, Including a Description of the Analytical Methods Used: ?Water, Aqua tic Life and Soil|. (Compilation; unpublished study received Dec 12, 1970 under 1F1101; CDL:090861-A)
140075 Chevron Chemical Company (1965) L eaching of Paraquat in Soil. (Unpublished study received Apr 7, 1971 under unknown admin. no.; CDL:180001- AH)
140076 Chevron Chemical Company (1971) Effect of Massive Paraquat Soil Treatment on Soil Leaching. (Unpublished study received Apr 7, 1971 under unknown admin. no.; CDL:180001-AI)
140346 Chevron Chemical Company (1970) The Fate of Carbon 14 Labelled Paraquat in Soil under Field Conditions. (Unpublis hed study received Apr 7, 1971 under unknown admin. no.; CD:180001-E)
140358 Tucker, B.V. (1969) Paraquat Stability in Soil. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-V)
5016652 Helling, C.S. (1971) Pesticide mobility in soils: II_ Applicat ions of soil thinlayer chromatography. Proceedings of the Soil Science Society of America 35(5):737-743.Page 51 of 71 164-1 Terrestrial field dissipation

MRID Citation Reference

23515 Ballantine, L.G.; Herman, M.M.; Coan, R.M.; et al. (1979) Bi- cep^(R)I plus Roundup^(R)I or Paraquat and Dual^( R)I/Prin- cep^(R)I plus Roundup or Paraquat Tank Mix Soil Dissipati on Studies: Report No. ABR-79101. (Unpublished study received Dec 10, 1979 under 100-583; prepared in cooperation with Chevron Chemical C o. and others, submitted by Ciba-Geigy Corp., Greens- boro, N.C.; CDL:241649-A)
27021 Chevron Chemical Company (1976) Resi due Data Sheet: Soil: Test Number T4088 (AG-A 4084 I-IV). (Unpublished study received Dec 10, 1979 under 100- 583; submitted by Ciba-Geigy Corp., Gr eens- boro, N.C.; CDL:241649-F)
27022 Chevron Chemical Company (1976) Resi due Data Sheet: Soil: Test Number T4089 (AG-A 4085 I-IV). (Unpublished study received Dec 10, 1979 under 100- 583; submitted by Ciba-Geigy Corp., Gr eens- boro, N.C.; CDL:241649-G)
27023 Chevron Chemical Company (1978) Resi due Data Sheet: Soil: Test Number T4834 (AG-A 6061). (Unpublished study received Dec 10, 1979 under 100-583; submitted by Ciba-Geigy Corp., Greensboro, N.C.; CDL:241649-H)
33836 Chevron Chemical Company (1957) Pa raquat Residues in Soil. (Unpub- lished study received Oct 14, 1965 under 239-1994; CDL:001432-B)
52390 Gowman, M.A.; Riley, D.; Newby, S. E. (1980) Paraquat and Diquat: LongTerm High-Rate Trial, Frensham, UK. 2. Persistence and Movement in Soil, and Glasshouse Bioassays: Report Series RJ 0014 B. (Unpublished study received Jun 4, 1980 under 239-2186; prepared by ICI, submitted by Chevron Chemical Co., Richmond, Calif.; CDL:242577-B)
52394 Tucker, B.V.; Agbakoba, C.S.O. (1978) ?Paraquat Soil Residue Stud- ies|. (Unpublished study received Jun 4, 1980 under 239-2186; submitted by Chevron Chemical Co., Rich mond, Calif.; CDL: 242577-G)
55091 O'Toole, M.A. (1965) Residual effects of Paraquat on peat soil. Irish Journal of Agricultural Research 4(2):231- 233. (Also~In~ unpublished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-G)
55093 Coats, G.E.; Funderburk, H.H., Jr.; Lawr ence, J.H.; et al. (1 964) Persistence of Diquat and Paraquat in pools and ponds. Pr oceed- ings, Southern Weed Control Conference 17:308-320. (Also~In~ unpub lished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 180000-I)
55109 Geoghegan, M.J.; Newman, J.F.; Wilkinson, W. (1966) Bipyridylium Herbicides--Paraquat, Preliminary Observations on the Effects on SoilPage 52 of 71 Organisms: Central File No. A.126,3 93. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Imperial Chemical Industries, Ltd., submitted by Chevron Chemi- cal Co., Richmond, Calif.; CDL:180000- AB)
65606 Baldwin, B.C.; Knight, B.A. G. (1967) The Fate of Di quat in Soils: Survey of Present Knowledge: TMJ 224. (Unpublished study re- ceived Aug 22, 1977 under 239-1663; prepared by Imperial Chem- ical Industries Ltd., England, submitted by Chevron Chemical C o., Richmond, Calif.; CDL:231430-F)
73770 Frank, P.A.; Comes, R.D. (19??) He rbicidal residues in pond water and hydrosoil. Weeds 15(Jul):210-213. (A lso~In~unpublished submission received Aug 29, 1979 under 2217-624; submitted by PBI-Gordon Corp., Kansas City, Kans.; CDL:240872-P)
90396 California Chemical Company (1964) Pa raquat Residues in Soil. (Compilation; unpublished study received Feb 25, 1965 under 5G0440; CDL:090479-B)
113724 Thompson-Hayward Chemical Co. (1967) Proposed Irrigatio n Study with Water Treated with Dichlobenil. (Compila tion; unpublished study received Jan 12, 1968 under 148-673; CDL:000651-A)
114414 Chevron Chemical Co. (1967) Name, Chem ical Identity and Composition of the Pesticide Chemical: (Para quat). (Compilation; unpub- lished study received Apr 3, 1967 under 7F0592; CDL:092880-A)
114443 Whipp, A.; Thompson, R. (1962) Progre ss Report: Diquat and Paraquat Soil Residue Studies. (Unpublished st udy received Sep 4, 1962 under unknown admin. no.; submitted by Chevron Chem ical Co., Richmond, CA; CDL:120436- A)
118549 Amchem Products, Inc. (1971) Fenac Re sidue Data--Total Water Treat- ment. (Compilation; unpublished study r eceived Jul 7, 1972 under 2F1213; CDL:091039-T)
122696 Newman, J. (1976) Diquat: Biological E ffects and Residues in Soil and Crops in a High Rate Field Trial on a Loam y Sand: TMJ 1225A. (Unpublished study received Dec 21, 1982 under 239-2247; pr e- pared by Plant Protection, Ltd., Eng., submitted by Chevron Chemical Co., Richmond, CA; CDL:249103-E)
122704 Coats, G.; Funderburk, H.; Lawrence, J.; et al. (1963) Persistence of Diquat and Paraquat in Pools and Ponds. (Unpublis hed study received Dec 21, 1982 under 239-2247; prepared by Auburn Univ., Ag ricultural Experiment Station, submitted by Chevron Chemical Co., Richmond, CA; CDL:249104-I)
140345 Baldwin, B.C.; Slade, P. (1968) The Fa te of Carbon-14 Labelled Par- aquat in Soil under Field Conditions: AR 2220 B. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180001-D)
140346 Chevron Chemical Company (1970) The Fate of Carbon 14 Labelled ParaquatPage 53 of 71 in Soil under Field Conditions. (Unpublis hed study received Apr 7, 1971 under unknown admin. no.; CD:180001-E)
140359 Baldwin, B.C.; Slade, P. (1970) Bipyri dylium Herbicides: Residues of Paraquat in Soil following Field Application of Gramoxone: Report No. AR 2219 B. (Unpublished study received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Rich mond, Calif.; CDL:180001-W)
140361 Gratton, R.P. (1970) The Significance of Paraquat Residues from the South African Trial PE/G/20 (b): Report Seri es TMJ 588 B. (Un- published study received Apr 7, 1971 under unknown admin. no.; prepared by Plant Protection, Ltd., submitted by Chevron Chemi- cal Co., Richmond, Calif.; CDL:18001-Y)
5013351 Doughty, C.C. (1978) Terbacil phytotoxi city and quackgrass (?~Agropyron repens?~) control in hig hbush blueberries (?~Vaccinium corymbosum?~). Weed Science 26(5):448-492.
41293201 Earl, M.; Anderson, L.; Muir, G. (19 89) Paraquat: Field Soil Dissipation under In-use Conditions in the USA (Champai gn, Illinois) during 1987-89--Analytical Report: Lab Project Nos. PP148BD0 5; RJ0781B; TMR0089B. Unpublished study prepared by ICI Agrochemicals, Jealott's Hill Research Station in cooperation with ICI Western Research Center. 93 p.
41293202 Anderson, E.; Muir, G. (1989) Paraquat Short Term Field Soil Dissipation under In-use Conditions in the USA (Su ssex County, Delaware) during 1987-89: Analytical Report: Lab Project Numbers PP148BD04; RJ0776B; TMR0068B. Unpublished study prepared by ICI Agrochemicals, Jealott's Hill Research Station in cooperation with ICI Ameri cas Western Research Center. 85 p.
41319303 Anderson, L.; Emburay, G.; Hoag, R.; et al. (1989) Paraquat: Field Soil Dissipation Under In-use Conditions in the USA (Leland, Mississippi) During 1987-1988: Lab Project Number: PP148B D05. Unpublished study prepared by ICI Agrochemicals. 122 p.
41319304 Anderson, L.; Muir, G.; Hoag, R. (1989) Paraquat: Field Dissipation under Inuse Conditions in the USA (Visalia, Ca lifornia) during 1987-89: Lab Project Number: PP148BD05. Unpublished study prepared by ICI Agrochemicals. 129
p. 41352101 Anderson, L.; Embury, G.; Hoag, R.; et al. (1989) Paraquat: Short Term Field Soil Dissipation Under In-use Conditions in the USA (Pullman, Washington) during 1987-1989: Lab Project Number : PP148BD04: Report No. RJ0797B. Unpublished study prepared by ICI Agrochemicals. 102 p.
41352102 Anderson, L.; Embury, G.; Hoag, R. et al. (1989) Paraquat: Short Term Field Soil Dissipation under In-use Conditions in the USA (Clermont, Florida) During 1987-1989: Lab Project Number: PP 148- BD04: Report No. RJ0794B. Unpublished study prepared by ICI Agrochemicals. 91 p.

164-2 Aquatic field dissipationPage 54 of 71 MRID Citation Reference

31833 Yeo, R.R. (19??) Dissipation of Diqua t and Paraquat and effects on aquatic weeds and fish. Weeds ? (? ):42- 46. (Also~In~unpub- lished submission received Sep 15, 1972 under 1F1101; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:090862-D)
31853 Austin, W.G.L.; Calderbank, A. (1964) Diquat and Paraquat: Residues in Water and Toxicity to Fish and Other A quatic Fauna: Experimental Report No. PP/E/303. (Unpublished study received Sep 15, 1972 under 1F1101; prepared by Imperial Chemical Industries, Ltd., submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 090862-AC)
55093 Coats, G.E.; Funderburk, H.H., Jr.; Lawr ence, J.H.; et al. (1 964) Persistence of Diquat and Paraquat in pools and ponds. Pr oceed- ings, Southern Weed Control Conference 17:308-320. (Also~In~ unpub lished submission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 180000-I)
55097 Austin, W.G.L.; Calderbank, A. (1964) Diquat and Paraquat: Residues in Water and Toxicity to Fish and Other Aqua tic Fauna: Experi- mental Report No. PP/E/303. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Plant Protection, Ltd., submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-M)
55100 Grzenda, A.R.; Nicholson, H.P.; Cox, W.S. (1966) Persistence of four herbicides in pond water. Journal of the American Water Works Association 58(Mar):326-332. (Also~In~unpublished sub- mission received Apr 7, 1971 under unknown admin. no.; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-P)
68226 Coats, G.E.; Funderburk, H.H., Jr.; Lawr ence, J.M.; et al. (1964) Persistence of diquat and paraquat in pools and ponds. Pro- ceedings of the Southern Weed Control Conference 17:308-320. (Also~ In~unpublished submission received Aug 22, 1977 under 239- 1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 231431-J)
68232 Yeo, R.R. (1967) Dissipation of diquat and paraquat and effects on aquatic weeds and fish. Weeds 15:42-46. (Also~In~unpublished submission received Aug 22, 1977 under 239-1663; submitted by Chevron Chemical Co., Richmond, Calif.; CDL:231431-R)
73770 Frank, P.A.; Comes, R.D. (19??) He rbicidal residues in pond water and hydrosoil. Weeds 15(Jul):210-213. (A lso~In~unpublished submission received Aug 29, 1979 under 2217-624; submitted by PBI-Gordon Corp., Kansas City, Kans.; CDL:240872-P)
113724 Thompson-Hayward Chemical Co. (1967) Proposed Irrigatio n Study with WaterPage 55 of 71 Treated with Dichlobenil. (Compila tion; unpublished study received Jan 12, 1968 under 148-673; CDL:000651-A)
113733 Thompson-Hayward Chemical Co. (1967) Disappearance of Dichlobenil and 2,6-Dichlorobenzoic Acid in Water: Re port R-649. (Compila- tion; unpublished study received Feb 23, 1967 under 148-673; CDL:000655-A)
116737 3M Co. (1970) ?Residue Analyses of 3MCAP-D and Other Chemicals in Various Products|. (Compilation; unp ublished study received on unknown date under 10556-EX-1; CDL:127733-A)
118549 Amchem Products, Inc. (1971) Fenac Re sidue Data--Total Water Treat- ment. (Compilation; unpublished study r eceived Jul 7, 1972 under 2F1213; CDL:091039-T)
122704 Coats, G.; Funderburk, H.; Lawrence, J.; et al. (1963) Persiste nce of Diquat and Paraquat in Pools and Ponds. (Unpublis hed study received Dec 21, 1982 under 239-2247; prepared by Auburn Univ., Ag ricultural Experiment Station, submitted by Chevron Chemical Co., Richmond, CA; CDL:249104-I)
135717 Chevron Chemical Co. (1970) Diquat: Residue Tolerance Petition: The Results of Tests on the Amount of Residue Rema ining, Including a Description of the Analytical Methods Used: ?Water, Aqua tic Life and Soil|. (Compilation; unpublished study received Dec 12, 1970 under 1F1101; CDL:090861-A)

164-5 Long term soil dissipation

MRID Citation Reference

146803 Abell, J. (1984) High Rate Paraquat Soil Residue Trial: Mt. Holly New Jersey. Unpublished study prepared by Chevron Chemical Company. 12 p.
146804 Abell, J. (1984) High Rate Paraquat Soil Residue Trial: Fresno California. Unpublished study prepared by Chevron Chemical Company. 13 p.
146805 Riley, D.; Abell, J. (19??) Long Term Fate and Biological Activity of Bound Paraquat Residues in Soil. Unpublished st udy prepared by Jealotts Hill Research Station and Chevron Chemical Co. 16 p.
42738701 Anderson, L.; Hoag, R.; Anders, C. et al . (1992) Paraquat: Fi eld Soil Dissipation under In-Use Conditions in the USA During 1987-91 (Visalia, California): Lab Project Number: PP148BD05: RJ1191B. Unpublished study prepared by ICI Agrochemicals. 132 p.
42738702 Anderson, L.; Hoag, R.; Anders, C. et al . (1992) Paraquat: Fi eld Soil Dissipation under In-Use Conditions in the USA During 1987-89 (Leland, Mississippi): Lab Project Number: PP148BD05: RJ1206B. Unpublished study prepared by ICI Agrochemicals. 98 p.Page 56 of 71 42802101 Anderson, L.; Hoag, R.; Safford, J. et al. (1992) Paraquat: Field Soil Dissipation under In-Use Conditions in the USA During 1987-91 (Champaign, Ill.): Lab Project Number: PP148BD05: RJ1187B. Unpublished study prepared by ICI Agrochemicals, Jealott's Hill. 127 p.
42802102 Anderson, L.; Hoag, R.; Anders, C. et al . (1992) Paraquat: Fi eld Soil Dissipation under In-Use Conditions in the USA During 1987-91 (Golddsboro, NC): Lab Project Number: PP148BD05: RJ1146B. Unpublished study prepared by ICI Agrochemicals, Jealott's Hill. 116 p.

Ecological Effects Studies:

850.2100 Avian Single Dose Oral Toxicity

MRID Citation Reference

29001 Fink, R.; Beavers, J.B.; Grimes, J.; et al. (1979) Acute Or al LDI50^--Bobwhite Quail: Paraquat dichloride Technica l Salt (SX- 1142): Project No. 162-121. Final Rept. (Unpublished study re ceived Feb 21, 1980 under 239-2422; prepared by Wildlife International, Ltd., submitted by Chevron Chemical Co., Rich- mond, Calif.; CDL:241819-A)
0160000 Hudson, R.; Tucker, R.; Haegele, M. ( 1984) Handbook of toxicity of pesticides to wildlife: Second edition. US Fi sh and Wildlife Service: Resource Publication 153. 91 p. Mallard study

850.2200 Avian Dietary Toxicity

MRID Citation Reference

22923 Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. (1975) Lethal Diet ary Toxicities of Environmental Pollutants to Birds: Special Scientific Report--Wildlife No. 191. Mallard, Japanese quail, Ring-necked pheasant, and bobwhite quail
55103 Ives, M. (1965) Report to Imperial Ch emical Industries, Limited: Toxicity Studies on Pheasants and Wild Mall ard Ducks: Paraquat Formulation. (Unpublished study received Apr 7, 1971 under unknown admin. no.; prepared by Industrial Bio-Test Labora- tories, Inc., submitted by Chevron Chemical Co., Richmond, Calif.; CDL:180000-S)

850.2300 Avian ReproductionPage 57 of 71 MRID Citation Reference

110452 Leary, J.; Tucker, B. (1981) Assessment of Diet Homogeneity and Stability of Paraquat Technical (SX-1305) in Game Bird Ration (W ildlife International Ltd. Project 162-136): Chevron File No. 721.11/S-1951. (Unpublished study received Aug 18, 1982 under 239-2186; submitted by Chevron Chemical Co., Richmond, CA; CDL:248133-A)
110453 Fink, R.; Beavers, J.; Joiner, G.; et al . (1981) Subacute F eeding-- Reproduction Screening Bioassay (Bobwhite Quail ): Paraquat Techni cal (SX-1305): Project No. 162-138; S-1994. Final rept. (Un published study received Aug 18, 1982 under 239-2186; pre- pared by Wildlife International Ltd., submitted by Chevron Chemical Co., Richmo nd, CA; CDL:248133-B)
110454 Fink, R.; Beavers, J.; Joiner, G.; et al. (1982) One-gene ration Reproduction-- Bobwhite Quail: Paraquat Technical (SX-1305): Project No. 162-142. Final rept. (Unpublished study received Aug 18, 1982 under 239-2186; prepared by Wildlife International Ltd., submitted by Chevron Chemical Co., Richmond, CA; CDL: 248133-C) LOEC=215 PPM
110455 Fink, R.; Beavers, J.; Joiner, G.; et al. (1982) One-gene ration Reproduction-- Mallard Duck: Paraquat Technical (SX- 1305): Project No. 162-145. Final rept. (Unpublished study received Aug 18, 1982 under 239-2186; prepared by Wildlife International Ltd., submitted by Chevron Chemical Co., Richmond, CA; CDL: 248133-D) LOEC= 100 PPM
43942604 Hakin, B.; Chanter, D. (1988) The Eff ect of Paraquat on the Hatchability of Fertile Mallard Duck Eggs: Lab Project Number: ISN 170/881711: ISN/170. Unpublished study prepared by Hunti ngdon Research Centre, Ltd. 128 p.
43942605 Roberts, N.; Hakin, B.; Chanter, D. (1989) The Effect of Paraquat on the Hatchability of Fertile Pheasant Eggs: Amended Report: Lab Project Number: ISN 171/881712: ISN/171. Unpublished study prepared by Huntingdon Research Centre, Ltd. 134 p.

850.1075 Acute Toxicity to Freshwater Fish

MRID Citation Reference

162736 Palmateer, S. (1980) Biological Report of Analysis: [Toxicity Test of Paraquat on Rainbow Trout]. Unpub lished study prepared by U.S.Page 58 of 71 Environmental Protection Agenc y, Terrestrial & Aquatic Biology Laboratory. 1 p.
162737 Palmateer, S. (1979) Biological Report of Analysis: [Toxicity Test of Paraquat on Bluegills]. Unpublished st udy prepared by U.S. Environmental Protection Agency, Terrestrial & A quatic Biology Laboratory. 1 p.
162738 McCann, J. (1977) Biological Report of Analysis: [Toxicity Test of Ortho Paraquat CL Concentrate on Rainbow tr out]. Unpublished study prepared by U.S. Environmental Protection Agen cy, Animal Biology Laboratory. 1 p.
40098001 Mayer, F.; Ellersieck, M. (1986) Manu al of Acute Toxic ity: Inter- pretation and Data Base for 410 Chemicals and 66 Species of Freshwater Animals. US Fish & Wildlife Service, Res ource Pub- lication 160. 579 p. Rainbow trout, channel cat, bluegill,

850.1010 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

114473 Wheeler, R. (1978) 48 Hour Acute Static Toxicity of Paraquat Dichloride Salt (SX957) to 1st Stage Nymph Water Fleas (Daphnia magna Straus). (Unpublished study received Sep 15, 1978 under 239-2422; submitted by Chevron Chemical Co., Ri chmond, CA; CDL:235419-A)
162752 Tompkins, J. (1979) Biological Report of Analysis: [Toxicity of Ortho Paraquat to Daphnia magna]. Unpub lished study prepared by U.S. Environmental Protection Agency, Te rrestrial & Aquatic Bio- logy Unit Laboratory. 1 p.
40098001 Mayer, F.; Ellersieck, M. (1986) Manu al of Acute Toxic ity: Inter- pretation and Data Base for 410 Chemicals and 66 Species of Freshwater Animals. US Fish & Wildlife Service, Resource Pub- lication 160. 579 p. - Daphnia, stonefly nymph and Gammarus faciatus

850.1075 Acute Exposures to Estuarine/marine fish

MRID Citation Reference

40228401 Mayer, F.L. USEPA Gulfbreeze Estuarine Toxicity tests - marine algaes, brown shrimp, oyster, longnose killifish

850.1025/850.1035 Acute Exposures to Estuarine/marine invertebratesPage 59 of 71 MRID Citation Reference

40228401 Mayer, F.L. USEPA Gulfbreeze Estuarine Toxicity tests - marine algaes, brown shrimp, oyster, longnose killifish

850.4400 Aquatic plant growth – vascular plants

MRID Citation Reference

42601003 Smyth, D.; Sankey, S.; Cornish, S.; et al (1992) Paraquat Dichloride: Toxicity to the Duckweed Lemna Gibba: Lab Project Number: BL4493/B: T168/E (FT10/92). Unpublished study prepared by Imperial Chemical Industries PLC. 24 p.

850.5400 Aquatic plant growth - algae

MRID Citation Reference

40228401 Mayer, F.L. USEPA Gulfbreeze Estuarine Toxicity tests - marine algaes, brown shrimp, oyster, longnose killifish 42601002 Smyth, D.; Sankey, S.; Penwell, A. (1992) Paraquat Dichloride: Toxicity to the Green Alga Selenastrum capricornutum: Lab Project Number: BL4578/B: T168/G (FT11/92). Unpublishe d study prepared by Imperial Chemical Industries PLC. 23 p. 42601004 Smyth, D.; Sankey, S.; Penwell, A. (1992) Paraquat Dichloride: Toxicity to the Marine Alga Skeletonema cost atum: Lab Project Number: BL4580/B: T168/C (FT08/92). Unpublished study prepared by Imperial Chemical Industries PLC. 22 p. 42601005 Smyth, D.; Sankey, S.; Cornish, S. (1992) Paraquat Dichloride: Toxicity to the Blue-green Alga Anabaena flos-a quae: Lab Project Number: BL4579/B: T168/B (FT07/92). Unpublished study prepared by Imperial Chemical Industries PLC. 26 p. 42601006 Smyth, D.; Sankey, S.; Cornish, S. (1992) Paraquat Dichloride: Toxicity to the Freshwater diatom Navicula pelliculosa: Lab Project Number: BL4464/B: T168/D (FT09/92). Unpublishe d study prepared by Imperial Chemical Industries PLC. 22 p.

850.4150 Vegetative VigorPage 60 of 71 42601001 Canning, L. and J.S. White. 1992. Paraquat: A Glasshouse Study to Evaluate the Effects on Vegetati ve Vigour of a 300 g ai litre -1 (2.5 lb ai US gal -1 ) Soluble Concentrate Formulation on Terrestrial Non-target Plants. Laboratory Project ID No. 92JH088. Conducted by ICI Agrochemicals, Jealotts Hill Research Station, Bracknell, Berkshire, UK. Submitted by ICI Americas, Inc., Wilmington, DE. EPA MRID No. 426010-01.

850.4100 Seedling Emergence

42639601 Canning, L. and J.S. White. 1992. Paraquat: A Glasshouse Study to Evaluate the Effects on Seedling Emergence of a 300 g ai litre -1 (2.5 lb ai US gal -1 ) Soluble Concentrate Formulation on Terrestrial Non-target Plants. Laboratory Project ID No. 92JH089. Conducted by ICI Agrochemicals, Jealotts Hill Research Station, Bracknell, Berkshire, UK. Submitted by ICI Americas Inc., Wilmington, DE. EP A MRID No. 426396-01.

850.3020 Honey bee acute contact

MRID Citation Reference

36935 Atkins, E.L.; Greywood, E.A.; Macdonald, R.L. (1975) Toxicity of Pesticides and Other Agricultural Chemicals to H oney Bees: Labo- ratory Studies. By University of California, Dept. of Entomolo- gy. ?: UC, Cooperative Extension. (Leaflet 2287; published study.)
5001991 Stevenson, J.H. (1978) The acute toxicity of unformulated pesticides to worker honey bees (?~Apis mellifera~L_ ). Plant Pathology 27(1):38-40.
111488 Moffett, J.; Morton, H.; MacDonald, R. (1972) Toxicity of some herbicidal sprays to honey bees. Journal of Ec onomic Entomology 65(1):32-36. (Also In unpublished submission received Sep 26, 1974 under 464-323; submitted by Dow Chemical U.S.A., Midland, MI; CDL:120345-H)
43942603 Bull, J.; Wilkinson, W. (1987) Paraquat: Acute 5-Day Contact and Oral Toxicity to Honey Bees (Apis me llifera): Lab Project Number: RJ0578B: PP148CM008. Unpublished study prepared by ICI Plant Protection Division. 27 p.Page 61 of 71 Appendix A. Ecological E ffects Characterization

A1. Aquatic Organisms

On an acute exposure basis, paraquat is sli ghtly toxic to aquatic-phase amphibians and fish and moderately toxic to freshwater inve rtebrates. No chronic toxicity studies have been identified for fish or aquatic invertebra tes exposed to paraquat. Compared to aquatic animals, paraquat is orders of magnitude more toxic to aquatic plants. Table A1 includes the most sensitive endpoints that may be used for risk assessment purposes ( i.e., to derive RQs) to represent the acute effects of paraqua t on aquatic animals as well as effects of paraquat on aquatic plants. Add itional information on the toxi city of paraquat to aquatic organisms is provided below.

Table A1. Endpoints used to represent acute effe cts of paraquat on aquatic animals and plants.

Taxa Species (scientific name) Measure of Effect Endpoint Duration (hours) Mean conc. (mg cation/L) Study Classification Ref. (MRID)

Fish and aquatic-phase

amphibians Fowler’s toad ( Bufo woodhousei fowleri ) Mortality LC 50 96 15 Supplemental 40098001

Aquatic invertebrates Water Flea ( Daphnia magna ) Immobility EC 50 48 1.3 Supplemental 0014473

Non-vascular plants freshwater diatom ( Navicula pelliculosa ) growth EC 50 96 0.00040 Acceptable 42601006 NOAEC 0.00016

Vascular

plants Duckweed ( Lemna gibba ) growth EC 50 14 d 0.071 Acceptable 42601003 NOAEC 0.011

Fish and Aquatic-phase Amphibians

Two acute toxicity studies ar e available where aquatic vertebrates were exposed to technical paraquat dichloride: one for the aqua tic-phase amphibian fowler’s toad and the other for the channel catfish. These two species exhibited orders of magnitude differences in sensitivities to paraquat. The fowler’s toad had a 96-h LC50 of 15 mg cation/L.

In this supplemental study, Daphnia magna exhibited a 48h EC 50 value of 1.3 mg cation/L (MRID 0014473). Several st udies are available where a quatic invertebrates were exposed to paraquat through formulated produc ts (Table A2). Based on these data, paraquat is classified as moderately toxic ( i.e., LC 50 is between 1 and 10 mg/L) to freshwater invertebrates.Page 62 of 71 Table A2. 96-h LC50 values for fish and aquatic-phase amphibians exposed to paraquat. All values are expressed as paraquat cation.

Test species (scientific name) Water type TGAI (T) or formula (F) LC 50 (mg cation/L) MRID Study classification
Longnose killifish ( Fundulus similis ) SW F >0.72 40228401 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 6.1 162736 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 8.1 162738 supplemental
Bluegill sunfish (Lepomis macrochirus) FW F 12 40098001 supplemental

Fowler’s toad (Bufo woodhousei fowleri) FW T 15 40098001 supplemental

Rainbow Trout (Oncorhynchus mykiss) FW F 16 40098001 supplemental
Bluegill sunfish (Lepomis macrochirus) FW F 32.7 162737 supplemental

Channel catfish (Ictalurus punctatus) FW T >100 40098001 supplemental

No chronic toxicity studies have been id entified for fish exposed to paraquat.

Invertebrates

One acute toxicity study is available where aquatic inve rtebrates were exposed to technical paraquat dichloride. In this supplemental study, Daphnia magna exhibited a 48h EC 50 value of 1.3 mg cation/L (MRID 0014473). Several studies are available where aquatic invertebrates were exposed to paraqua t through formulated products (Table A3). Based on these data, paraquat is classified as moderately toxic ( i.e., LC 50 is between 1 and 10 mg/L) to freshwat er invertebrates.

Table A3. EC50 values for aquatic invertebrates ex posed to paraquat. All values are expressed as paraquat cation.

Test species (scientific name) Water type TGAI (T) or formula (F) Duration (days) EC 50 (mg cation/L) MRID Study classification

brown shrimp ( Penaeus aztecus) SW F 4 >0.72 40228401 supplemental
eastern oyster ( Crassostrea virginica ) SW F 4 >0.72 40228401 supplemental
Waterflea ( Daphnia magna ) FW T 2 1.3 114473 supplemental
Waterflea ( Daphnia magna ) FW F 2 1.7 162752 supplemental
Waterflea ( Daphnia pulex ) FW F 2 3.6 40098001 supplemental Waterflea ( Simocephalus serrulatus ) FW F 2 3.8 40098001 supplemental

Stonefly ( Pteronarcys californica ) FW F 4 >10 40098001 supplemental Scud ( Gammarus fasciatus) FW F 4 12 40098001 supplemental

No chronic toxicity studies have been iden tified for aquatic invertebrates exposed to paraquat.Page 63 of 71 Aquatic plants

Data are available from registrant-subm itted and federal laboratory studies involving exposures of aquatic plants to paraquat (Table A4). The freshwater diatom ( Navicula pelliculosa ) was the most sensitive non- vascular plant with a 4d EC 50 of 0.40 μ g/L and a corresponding NOAEC of 0.16 μ g/L (MRID 42601006). In a study with the vascular plant Lemna gibba, the 14d EC 50 was 71 μ g/L, with a corresponding NOAEC of 11.5
μ g/L (MRID 42601003).

Table A4. EC50 values for aquatic plants exposed to paraquat. All values are expressed as paraquat cation.

Test species (common) Duration (days) EC 50 (μg cation/L) NOAEC (μg cation/L) MRID

Navicula pelliculosa (Freshwater diatom) 4 0.40 0.16 42601006
Anabaena flos-aquae (Blue-green algae) 5 11 2.3 42601005
Lemna gibba (duckweed) 14 71 11 42601003 Selenastrum capricornutum (green algae) 4 230 58 42601002

Skeletonema cosatum (Marine diatom ) 4 2045 158 42601004 Isochrysis galbana (hapatophyte algae) 10 3600 NA 40228401 Phaeodactylum tricornutum (marine diatom) 10 7200 NA 40228401

Dunaliella tertiolecta (green algae) 10 14400 NA 40228401 Chlorococcum sp. (green algae) 10 36000 NA 40228401 NA = not available
A2. Terrestrial Organisms

Paraquat is moderately toxic to birds and mammals on an acute dose basis and slightly toxic to birds on a sub-acute dietary basis. For honey bees , paraquat is practically nontoxic. In reproduction studies, paraquat did not impact the re production in rats tested up to 108 mg cation/kg-diet. Paraquat did impact the reproduction of ma llard ducks at 100 mg cation/kg-diet, resulting in a NOAEC of 30 mg cation/kg-diet for reproductive effects. In addition, in a study where ph easant eggs were sprayed with paraquat dichloride, effects to the numb er of eggs hatched and numbe r of 28-d old survivors were observed at 0.72 lb cation/A, resulting in a NOAEC of 0.36 lb cation/A. Table A5 includes the most sensitive endpoints that may be for risk assessment purposes (for deriving RQs) to represent the acute and chronic effects of pa raquat on terrestrial animals. Additional information on the toxicity of paraquat to terrestrial animals is provided below.Page 64 of 71 Table A5. Endpoints used to represent acute and chro nic effects of paraquat on terrestrial animals.

Taxa Species (common

name) Measure of effect Endpoint Mean Concentration Units Study Classification Reference (MRID)

Birds,terrestrialphase amphibians and reptiles Colinus virginianus (Bobwhite

quail) Mortality LD 50 124 mgcation/kgbw acceptable 00029001

Coturnix coturnix (Japanese quail) Mortality LC 50 698 mgcation/kgdiet acceptable 00022923

Anas platyrhynchos (Mallard Duck) number of eggs laid, number of normal hatchlings, number of 14-d old

survivors, and % viable embryos/set NOAEC 30 mgcation/kgdiet Acceptable 00110455

Phasianus colchicus (pheasant) Number of eggs hatched, number of 28-d old survivors NOAEC 0.5 lb cation/A Supplemental 43942605

Mammals Rattus norvegicus (laboratory rat) Mortality LD 50 91 mgcation/kgbw Acceptable 00054573

Reproduction NOAEL 7.5 mg/kg-bw Acceptable 00126783, 00149748, & 00149749 NOAEC 108 mg/kg-bw

Terrestrial invertebrates Apis mellifera (Honey Bee) Mortality LD 50 52 μ g cation/bee Acceptable 43942603

Plants are sensitive to this herbicide. Wh en comparing effects of paraquat on seedling emergence and vegetative vigor of plants, vege tative vigor is more sensitive. Table A6 include the most sensitive seedling emer gence and vegetative vigor endpoints for terrestrial plants exposed to paraquat. Thes e values may be used to generate RQs. Additional information on the toxicity of paraqu at to terrestrial plan ts is provided below.

Table A6. Endpoints used to represent ef fects of paraquat on terrestrial plants.

Species NOAEC (lb cation/A) EC 25 (lb cation/A) Most sensitive parameter Test type MRID

Corn (monocot) 0.67 >0.67 none Seedling emergence 42639601 Cocklebur (dicot) 0.37 0.67 Emergence Seedling emergence 42639601 Corn (monocot) 0.064 0.16 Dry weight Vegetative vigor 42601001 Cocklebur (dicot) 0.0065 (EC 05 ) 0.014 Dry weight Vegetative vigor 42601001Page 65 of 71 Birds

In an avian acute oral study with Northern Bobwhite quail exposed to technical paraquat dichloride, the LD 50 value was 124 (99-148) mg cation/kg-bw. In this test, mortality, effects to body weight and lethargy were obs erved in birds dosed with 115 mg/kg-bw. The slope of the dose-response curve was 6.6 (3.5-9.7) (MRID 00029001).

The most sensitive subacute dietary LC 50 value was 698 ppm for the Japanese quail. Three additional studies with the same formulated product resulted in 5d LC 50 values of 706 ppm for the northern bobwhite quail, 1057 ppm for the ring-necked pheasant and 2915 ppm for the mallard duck. This subacute study involved exposures of birds to 29.1% paraquat dichloride (MRI D 22923; Table A7). Paraquat is considered moderately toxic to birds on an acute oral and sub-acute dietary basis.

Table A7. Five-day, dietary LC50 values for birds exposed to paraquat (MRID 22923). All values are expressed as paraquat cation.

Test species (scientific name) LC 50 (95% Confidence Interval) (mg cation/kg) Slope (sd)* MRID

Japanese quail ( Coturnix cortunix ) 698 (593-821) 6.059 (1.307) 22923 Bobwhite quail ( Colinus virginianus ) 706 (564-873) 5.022 (1.283) 22923 Ring-necked pheasant ( Phasianus colchicus ) 1057 (927-1205) 5.846 (1.973) 22923 Mallard duck ( Anas platyrhynchos ) 2915 (2471-3518) 6.765 (1.281) 22923

Avian reproductive toxicity endpoints we re submitted for two species: the northern bobwhite quail (MRID 00110454) and the mallard duck (MRID 00110455). Reproduction of the northern bobwhite was not affected by paraquat at the highest test concentration ( i.e., 100 mg cation/kg-diet). At that same concentration, several reproductive effects were observed in the malla rd duck study, including: number of eggs laid, number of normal hatchlings, number of 14-d old survivors, and % viable embryos/set. The resulting NOAEC for the ma llard duck is 30 mg cation/kg-diet.

In two non-guideline studies, a formulated pr oduct containing paraqu at dichloride was sprayed onto the eggs of pheasant (MRID 43942605) and mallard ducks (MRID 43942604). In the pheasant study, a decrease in the number of eggs hatched and the number of 28-d old survivors was observed at 1.0 lb cation/A, resulting in a study NOAEC of 0.5 lb cation/A. In the mallard study, an application rate of 2.0 lb cation/A increased the number of embryonic deaths (at days 13 and 19) as well as the number of dead embryos in the shell at day 31. At this concentration, the numbe r of hatchlings and number of chicks surviving to 28 d were also decreased. The resulting NOAEC was 1.0 lb cation/A.

Mammals

Paraquat is classified as mode rately toxic on an acute oral basis to mammals. This is based on an acute oral LD 50 value of 91 mg cation/kg-bw (MRID 00054573).

In an acceptable 3-generation reproduction a nd fertility study, paraquat was administeredPage 66 of 71 to Wistar Derived Rats-Alderle y Park Strain (MRIDs 00126783, 00149748, & 00149749). The study NOAEL was 7.5 mg catio n/kg-bw (NOAEC = 108 ppm), which was the highest test concentration. No LOAEL was established in this study for endpoints related to survival, growth or reproduction of rats. At a lower test concentration (3.75 mg/kg-bw), an increased incidence of alveol ar histiocytes was observed in the parents; however, this value is not used for de riving chronic mammalian RQs because the relationship of this endpoi nt to survival, growth or reproduction is unknown.

Terrestrial Invertebrates

Several toxicity studies are available involving acute expos ures of honey to paraquat, including contact and oral dos es. The most conservative acute contact and oral 48-h LD 50 s are 52 and 22 μ g cation/bee, respectively (Table A8). These data indicate that paraquat is practically non-toxic ( i.e., >11 μ g a.i./bee) to honey bees. Available data suggest that formulated paraquat is more toxic compared to th e TGAI and that paraquat is more toxic as an oral dose compared to a contact dose.

Table A8. Endpoints from acute toxicity studies in volving exposures of honey bees to paraquat or paraquat dichloride. Values are expressed as paraquat cation.

48-h LD 50 ( μ g cation/bee) Exposure TGAI (T) or Formula (F) MRID Study Classification

22 oral F 43942603 Acceptable
>35 contact T 05001991 Acceptable
37 oral T 43942603 Acceptable
52 contact F 43942603 Acceptable
>104 contact T 43942603 Acceptable

Several acute contact studies have been conducted with honey bees being exposed to technical paraquat (or paraquat dichloride). N one of these studies have established 48-h LD 50 values. In a study from the open literatur e, exposure of honey bees to technical paraquat through dusting to 6.04 μ g a.i./bee resulted in 2.74% mortality (MRID 36935). In two other honeybee acute contact studies with technical pa raquat, the 48h LD 50 values were > 35 and >104 μ g/bee (MRID 05001991 and 43942603, respectively).

In an acute toxicity study with Gramoxone, a formulated product containing paraquat dichloride, the 48-h contact LD 50 value was 52 μ g a.i./bee (MRID 43942603). This value suggests that the toxicity of formulated products containi ng paraquat may be higher than TGAI paraquat, where the 48-h acute contact LD 50 from the same study was >104 μ g a.i./bee.

In another literature study, caged bees were exposed to a direct application of 4 lb a.i./A formulated paraquat. After 2 days, approxi mately 55% mortality was observed (MRID 00111488).

In acute oral studies with honey bees, tec hnical and formulated (Gramoxone) paraquat yielded oral 48-h LD 50 values of 37 and 22 μ g a.i./bee (MRID 43942603). WhenPage 67 of 71 compared to acute contact values for TGAI and formulated paraquat from the same study ( i.e., >104 and 52 μ g a.i./bee, respectively), these data suggest that paraquat is more toxic as an oral dose compared to a contact dose.

Terrestrial Plants

Supplemental vegetative vigor data involvi ng paraquat (in a formulated product) are available for 1 monocot (corn; Zea mays ) as well as 6 dicots, the most sensitive of which is cocklebur ( Xanthium strumarium ). For corn, the EC 25 and NOAEC values are 0.16 (95% CI 0.073–0.36) lbs cation/A, and the NOAEC value was 0.064 lbs cation/A. For cocklebur, a NOAEC could not be established; th erefore the EC 05 is used as the endpoint for listed dicots. The EC 25 and EC 05 values for vegetative vigor effects to cocklebur are 0.014 (95% CI 0.01–0.019) 0.0065 EC 05 (95% CI 0.0040–0.01) lbs cation/A, respectively. Other dicot test species included: beet ( Beta vulgaris ), soybean ( Glycine

max ), oilseed rape ( Brassica napus ), velvetleaf ( Abutilon theophrasti ) and morning glory ( Ipomoea hederacea ). Although these test species were less sensitive than cocklebur, their EC 25 values were on the same order of magnitude as cocklebur (MRID 42601001).

Compared to vegetative vigor, seedling emergence is much less sensitive to paraquat. Acceptable seedling emergence data are av ailable for 2 species of monocots [corn and purple nutsedge ( Cyperus rotundus )] and 6 species of dicots (cocklebur, beet, soybean, oilseed rape, velvetleaf and morning glory). Th e only test species that showed effects was cocklebur, with an EC 25 of 0.67 lb cation/A based on decreased emergence and a NOAEC of 0.34 lb cation/A (LOAEC = 0.67 lb catio n/A). For all other test species, no effects to emergence or dry weight were observed, resultin g in NOAEC values of 0.67 lb cation/A for those test species (MRID 42639601)Page 68 of 71 Appendix B. Output from SIP v1.0

Table 1. Inputs Parameter Value Chemical name paraquat Solubility (in water at 25 o C; mg/L) 464000

Mammalian LD 50 (mg/kg-bw) 91 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 7.5 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg-bw) 124 Avian test species mallard duck Body weight (g) of "other" avian species Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 30 Bobwhite quail NOAEC (mg/kg-diet) NOAEC (mg/kg-diet) for other bird species Body weight (g) of other avian species NOAEC (mg/kg-diet) for 2nd other bird species Body weight (g) of 2nd other avian species

Table 2. Mammalian Results Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 79808.0000 79808.0000 Adjusted toxicity value (mg/kg-bw) 69.9936 5.7687 Ratio of exposure to toxicity 1140.2183 13834.6493

Conclusion* Exposure through drinking water alone is a

potential concern for mammals Exposure through drinking water alone is a

potential concern for mammals

Table 3. Avian Results Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 375840.0000 375840.0000 Adjusted toxicity value (mg/kg-bw) 64.3840 1.4884 Ratio of exposure to acute toxicity 5837.4796 252516.6874Page 69 of 71 Conclusion* Exposure through drinking water alone is a

potential concern for birds Exposure through drinking water alone is a

potential concern for birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when aggregated with other routes ( i.e ., diet, inhalation, dermal), pesticide exposure through drinking water may contribute to a total exposure that has potential for effects to non-target animals.Page 70 of 71 Appendix C. Output from STIR v1.0



## Welcome to the EFED Screening Tool for Inhalation Risk This tool is designed to provide the risk assesso r with a rapid method for determining the potentia significance of the inhalation exposure route to birds and mammals in a risk assessment.


## Input

Application and Chem ical Information
Enter Chemical Name paraquat Enter Chemical Use agriculture Is the Application a Spray? (enter y or n) y If Spray What Type (enter ground or air) air Enter Chemical Molecu lar Weight (g/mole) 257.2 Enter Chemical Vapor Pressure (mmHg) 1.73E-15 Enter Application Rate (lb a.i./acre) 1

Toxicity Properties
Bird Enter Lowest Bird Oral LD 50 (mg/kg bw) 124 Enter Mineau Scaling Factor 1.15 Enter Tested Bird Weight (kg) 0.178 Mammal Enter Lowest Rat Oral LD 50 (mg/kg bw) 90 Enter Lowest Rat Inhalation LC 50 (mg/L) 0.001 Duration of Rat Inhalation Study (hrs) 6 Enter Rat Weight (kg) 0.35


## Output Results Avian (0.020 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.39E-11 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.01E-12 Adjusted Inhalation LD 50 1.15E-02 Ratio of Vapor Dose to Adjusted Inhalation LD 50 2.61E-10 Exposure not Likely Significant Maximum Post-treatment Spray Inhalation Dose (mg/kg) 9.61E-02 Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 8.34E+00 Proceed to Refinements

Results Mammalian (0.015 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.39E-11 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.78E-12Page 71 of 71 Adjusted Inhalation LD 50 8.93E-02 Ratio of Vapor Dose to Adjusted Inhalation LD 50 4.24E-11 Exposure not Likely Significant Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.21E-01 Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 1.35E+00 Proceed to Refinements