UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D. C., 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES DP Barcode: D330621 PC Code: 118601 Date: September 10, 2004 MEMORANDUM SUBJECT: Ecological Risk Assessment in Support of the Reregistration Eligibility Decision for Chlorsulfuron TO: Susan Jennings, Chemical Review Manager Michael Goodis, Product Manager Special Review and Reregistration Division FROM: Dirk Y. Young, Ph. D., Environmental Engineer Dan Balluff, Wildlife Biologist Environmental Risk Branch 4 THROUGH: Elizabeth Behl, Chief Environmental Risk Branch 4 Environmental Fate and Effects Division The Environmental Fate and Effects Division ( EFED) has revised its ecological risk assessment of chlorsulfuron in response to the 30 day error correction comments ( DP Barcode D295494) received from the technical registrant. Based on available data, exposure to terrestrial or aquatic animals is not expected to exceed either acute or chronic levels of concern ( LOC's). However, the chlorsulfuron uses modeled in the assessment exceed acute risk levels of concern for non target plants by over three orders of magnitude while LOC's for threatened/ endangered plants are exceeded by over four orders of magnitude. Additionally, estimated peak concentrations in surface and groundwater derived drinking water are 1.9

g/ L and 1.6

g/ L, respectively. If you have any questions regarding this document, please do not hesitate to contract the risk assessors. Page i of 90 REGISTRATION ELIGIBILITY DECISION September 10, 2004 ( revised)

ENVIRONMENTAL FATE AND ECOLOGICAL EFFECTS RISK ASSESSMENT for CHLORSULFURON Environmental Fate and Effects Division, Environmental Risk Branch IV:

Dan Balluff Dirk Young Peer Reviewers:

Leo LaSota Norman Birchfield Branch Chief:

Elizabeth Behl DP Barcode: D330621 PC Code: 118601 Page ii of 90 Table of Contents EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Chlorsulfuron Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Chlorsulfuron Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Toxicity and Risk to Non target and Endangered Plants . . . . . . . . . . . . . . . . . . . . . . . . iv Field Studies and Greenhouse Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Non target Plant Incident Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Endangered Plant Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Drinking Water Assessment for Human Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v PROBLEM FORMULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Conceptual Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Identification and Mechanism of Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Use Characterization and Formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Rate and Method of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Current Label Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Assessment Endpoints and Analysis Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ENVIRONMENTAL FATE CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Chlorsulfuron Fate Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Hydrolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Photodegradation in Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Soil Photodegradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Aerobic Soil Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Anaerobic Aquatic Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Bioaccumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Field Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Sorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Water Resource Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Ambient Surface Water ( Farm Pond) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Drinking Water Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Surface Water Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Ground Water Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Drinking Water Estimated Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ECOLOGICAL EFFECTS CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Toxicological Profile for Terrestrial and Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . 13 Risk Quotients for Terrestrial and Aquatic Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Birds and Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Freshwater and Marine/ estuarine Fish and Invertebrates . . . . . . . . . . . . . . . . . . 15 Page iii of 90 Risk Characterization for Terrestrial and Aquatic Wildlife . . . . . . . . . . . . . . . . . . . . . . 16 Plant Effects Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Toxicological Profile for Terrestrial and Aquatic Plants . . . . . . . . . . . . . . . . . . 16 Risk Quotients for Aquatic and Terrestrial Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Aquatic Plant Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Terrestrial Plant Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Terrestrial Plant Assessment for Contaminated Irrigation Water . . . . . . . . . . . . 25 Toxicity Studies ( from Public Literature) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Fletcher et al. 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Coyner et al. 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Field Studies, Greenhouse Studies, and Incident Reports . . . . . . . . . . . . . . . . . . . . . . . 26 Field Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Fletcher et al. 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Bhatti et al. 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Greenhouse Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Non target Plant Incident Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Risk Characterization for Terrestrial and Aquatic Plants . . . . . . . . . . . . . . . . . . . . . . . . 30 Plants Exposed to Chlorsulfuron Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Plants in Semi Aquatic Areas ( Wetlands) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Terrestrial Plants ( Seedling Emergence) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Terrestrial Plants ( Vegetative Vigor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Plants Exposed to Irrigation Water Containing Chlorsulfuron . . . . . . . . . . . . . . 35 Aquatic Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Refined Assessment of Spray drift on non target Terrestrial Plants . . . . . . . . . . 36 ENDANGERED/ THREATENED SPECIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 APPENDIX 1. PRZM and EXAMS input files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 APPENDIX 2. SUMMARY OF CHLORSULFURON TOXICITY TESTS FOR TERRESTRIAL AND AQUATIC ANIMALS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 APPENDIX 3. ESTIMATED ENVIRONMENTAL CONCENTRATIONS ON AVIAN AND MAMMALIAN FOOD ITEMS ( ppm) FOLLOWING A SINGLE APPLICATION AT 1 LB a. i./ A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 APPENDIX 4. NON TARGET TERRESTRIAL PLANT SEEDLING EMERGENCE TOXICITY ( TIER II) FOR 98.2% CHLORSULFURON WITH BUFFER AND VALENT X 77 SURFACTANT IN SOME SOLUTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Page iv of 90 APPENDIX 5. NON TARGET TERRESTRIAL PLANT VEGETATIVE VIGOR TOXICITY ( TIER II) FOR 98.2% CHLORSULFURON WITH BUFFER AND VALENT X 77 SURFACTANT IN SOME SOLUTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 APPENDIX 6. RQ CALCULATIONS FOR SURFACE AND GROUNDWATER IRRIGATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 APPENDIX 7. FIRST ORDER DEGRADATION FOR CHLORSULFURON . . . . . . . . . . . . 71 APPENDIX 8. TIER 1 DRINKING WATER ASSESSMENT MEMORANDUM . . . . . . . . . 72 APPENDIX 9a SURVEY OF AERIAL APPLICATORS TO DETERMINE TYPICAL AIRCRAFT SETUPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 APPENDIX 9b PHYTOTOXICITY RESULTING FROM SPRAY DRIFT DURING A MEDIUM APPLICATION RATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 APPENDIX 9c PHYTOTOXICITY RESULTING FROM SPRAY DRIFT DURING A MEDIUM APPLICATION RATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Page v of 90 EXECUTIVE SUMMARY Chlorsulfuron Usage Chlorsulfuron is a broad spectrum, pre emergent and post emergent sulfonylurea herbicide used on small grains such as wheat, barley and oats. It is also registered for use on pastures, rangeland and fallow. Non crop sites include: unimproved turf, industrial turf, industrial sites, ornamentals, and noncrop restoration. Chlorsulfuron is applied to agricultural crops as a spray by aircraft or ground equipment at single application rates ranging from 0.0078 to 0.0625 lbs ai/ acre; application rates to non crop sites are the highest, ranging from 0.0078 to 0.25 lbs ai/ acre( Table 1). Chlorsulfuron may be tank mixed with other sulfonylurea herbicides.

Chlorsulfuron Risk The results of this screening level ecological risk assessment indicate that chlorsulfuron exceeds EFED's Levels of Concern ( LOC) for non target plants by over three orders of magnitude. LOCs for endangered plants are exceeded by over four orders of magnitude. Risk quotients ( RQs) were calculated using seedling emergence, vegetative vigor and aquatic plant laboratory toxicity tests. Based on available data, exposure to mammals, birds, and aquatic organisms are not expected to exceed either acute or chronic risk levels of concern ( Table 8). Exposure scenarios were based on exposure via spray drift, surface runoff, and irrigation.

Toxicity and Risk to Non target and Endangered Plants Chlorsulfuron is toxic to non target plants with EC 25 equivalent to an application rate 4 x10  6 lbs a. i./ acre and an EC 05 EC 05 equivalent to an application rate 4.6 x 10  8 lbs a. i. / acre based on vegetative vigor studies of the herbicide. A single aerial application of chlorsulfuron, assuming 5% of the applied drifts into non target areas, results in screening level RQs ranging from 267 to 1042 for non target plants and from 17,532 to 68,488 for endangered plants ( Tables 11 and 13). Additionally, for fields irrigated with ground or surface water contaminated with chlorsulfuron, non endangered plant RQs range from 91 to 341 ( Table 14). In regions where chlorsulfuron has been used historically, modeling results indicate that groundwater and surface water irrigation may result in damage to agricultural crops that are sensitive to chlorsulfuron.

The risk to nontarget plants from direct application of chlorsulfuron has not been estimated quantitatively in this risk assessment, but are expected to be higher than those estimated for indirect exposure through runoff and drift. In addition, risk from use on golf courses, sod farms, and nurseries were not assessed quantitatively ( as usage is low) but estimated risk would be higher as application rates for those uses are higher.

A refined assessment was conduced on effects of chlorsulfuron spray drift on non target plants. Refinements are intended to accurately reflect the most important application conditions actually used in applying chlorsulfuron. To estimate a range of spray drift levels, application parameters employed by aerial applicators in Washington and Oregon were used; ground boom configurations were Page vi of 90 assumed to include the range of values available in the AgDRIFT model. Risks to non target plants resulting from spray drift from ground and aerial applications of chlorsulfuron are dependent upon a number of factors. This analysis suggests that most plant species are likely to be affected at low levels ( 10% reductions in shoot weight) more than 1000 feet downwind of applications conducted in winds speeds of 10 mph. Under certain conditions, 80% effect levels may occur to more sensitive species at 1000 feet or more downwind. Higher effect levels are triggered more frequently by aerial applications than with ground boom applications and more frequently with finer sprays.

Field Studies and Greenhouse Studies A number of field studies have been conducted with chlorsulfuron ( see Section 3.7). Several researchers have concluded that small quantities of the chemical, such as might be found in airborne particles traveling long distances, may affect plant reproduction without altering vegetative growth. If the effect of chlorsulfuron on cherry trees is characteristic of other plant species, drift may severely reduce both the crop yields and fruit development on native plants, an important component of the habitat and food web for wildlife. Reproductive effects from chlorsulfuron exposure are difficult to recognize in the field and virtually impossible to associate with chlorsulfuron because the amounts of material required to induce yield reduction are below the detection level of conventional chemical analysis.

Non target Plant Incident Reports There are three non target plant incidents attributed to offsite drift of chlorsulfuron ( Glean ® ) in the EPA's EIIS incident database. One incident occurred in the spring of 1990, near Benton City Washington, orchard growers alleged that herbicides applied to wheat fields in Horse Heaven Hills drifted onto orchards in Badger Canyon and damaged cherry, apple, plum, and apricot crops. Growers contended that sulfonylurea herbicides were most likely responsible because damage of this magnitude never occurred prior to the use of sulfonylurea herbicides on Horse Heaven Hills ( see Section 3.7.3).

Endangered Plant Species Screening level ( Tier 1) deterministic risk quotients ( RQs) for direct effects to endangered plants exceed the endangered species level of concern ( LOC) by several orders of magnitude. For aquatic plants RQs for endangered species range from 18 to 31. For endangered plants in wetlands RQs range from 1200 to 5056. RQs for endangered terrestrial plants range from 3507 for ground applications to wheat to 68,488 from spray drift resulting from aerial applications to rangeland and pastures.

In order to determine the potential risk of chlorsulfuron uses to endangered/ threatened plants, further refinements are needed in the risk assessment. Possible areas of refinement could include: investigating the extent of overlap between species habitat relative to chlorsulfuron use areas and refining site specific exposure scenarios for runoff and spray drift. Drinking Water Assessment for Human Health Page vii of 90 Concentrations of parent chlorsulfuron in drinking water sources were estimated using PRZM/ EXAMS for surface sources. Four standard EFED agricultural scenarios ( PA turf, FL turf, ND wheat, TX wheat) were selected to simulate a broad range of chlorsulfuron uses. The estimated concentrations include a reduction by the percent crop area ( PCA) factor. The Florida turf scenario gave the highest concentrations. Ground water concentrations were estimated with the SciGrow model. Using standard operating guidance for SciGrow inputs, the estimated the groundwater concentration was 1.6 ppb. The 1 in 10 year concentrations are provided below.

Drinking Water Estimated Environmental Concentrations for Chlorsulfuron Acute Concentration ( upper 1 in 10 year peak concentration) Chronic Concentration ( upper 1 in 10 year annual mean concentration)

Surface Water 1.9 µ g/ L 0.96 µ g/ L Groundwater 1.6 µ g/ L 1.6 µ g/ L Page 1 of 90 1. PROBLEM FORMULATION 1.1 Conceptual Model In agricultural ecosystems there is a patchwork of row crops intermixed with pasture and natural plant communities. Chlorsulfuron poses a potential threat to vegetation growing on adjacent land if the herbicide is applied to crop land and inadvertently drifts and/ or runs off into non target areas. Adverse consequences of such an event will vary depending on the extent of exposure ( aerial vs ground application), plant species involved, habitat ( aquatic vs terrestrial), plant size, and stage of development of the plant. The response may range from plant death to no apparent alteration of plant growth and development, depending on different combinations of these variables.

It is often difficult to distinguish between herbicide damage and plant damage caused by insects, pathogens, frost, and nutrient deficiency. Positive proof of drift or runoff damage on many occasions requires chemical identification of the suspected herbicide on the plants and/ or the soil at the nontarget site. Complaints have arisen in numerous parts of the country that herbicides such as the sulfonylureas which are used at 1/ 20th the application rate of older herbicides cause plant damage at chemical concentrations below the level of analytical detection ( Fletcher 1991).

1.2 Identification and Mechanism of Action Chlorsulfuron is a broad spectrum herbicide, structurally classified as a sulfonylurea. Its mode of action is the inhibition of amino acid synthesis in plants through inhibition of acetolactate synthase ( ALS). Chlorsulfuron's herbicidal effect results from its inhibition of an enzyme involved in amino acid biosynthesis. It may be absorbed either through the roots or the foliage and is mobile within the plant and binds to the acetolactate synthase enzyme. Inhibiting this process adversely affects plant growth and reproduction. This enzyme pathway does not exist in animals making the herbicide far less toxic to animals than plants.

Soil moisture increases the phytotoxicity of chlorsulfuron by increasing availability and absorption by the roots. Although chlorsulfuron is herbicidal when absorbed by roots, herbicide which contacts foliage is also phytotoxic. Foliar absorption may increase when chlorsulfuron is tank mixed with an oil or surfactant. Chlorsulfuron may be applied either pre or post emergence. Phytotoxicity data shows that chlorsulfuron affects plants in both seedling emergence and the vegetative vigor tests at low levels. Chlorsulfuron tolerant plants, such as grains, resist herbicidal effects by metabolizing the herbicide before it causes toxicity ( Weed Science Society 1989). Chlorsulfuron exposure may cause visible symptoms in days or weeks or delayed effects on reproduction ( fruit and seed production) may occur weeks or months after exposure.

Plants that have absorbed sufficient chlorsulfuron on their foliage, in the short term, may show initial symptoms of spotting, and leaf puckering or twisting ( Felsot et al 1996). Exposed plants also may show chlorosis and discolored veins. Chlorsulfuron symptoms may become more pronounced and lead to plant death or the plant may outgrow the symptoms in 1 to 2 months depending on the sensitivity of the plant and the magnitude of the exposure. Developmental/ reproductive effects of Page 2 of 90 chlorsulfuron exposure may not be apparent for three or more months after exposure. Reduced seed and fruit development resulting from chlorsulfuron exposure has been documented in canola, smartweed, soybean, and sunflower ( Fletcher et al 1996). Because reproductive effects may occur in the absence of other more immediate symptoms of herbicide exposure, it is expected to be difficult to recognize delayed chlorsulfuron toxicity in the field.

1.3 Use Characterization and Formulations Chlorsulfuron containing products were first registered in the United States in the early 1980s. There are six products currently registered for use in the U. S. including: TELAR DF ® , GLEAN FC ® , FINESSE ® , Chlorulfuron Technical ® , LANDMARK MP ® , LANDMARK II MP ® , and CORSAIR ® . Over 80% of chlorsulfuron use is on cereal grains ( wheat, oats and barley) to control a wide variety of weed pests. Over 5 million acres are treated annually. Most of the acreage is treated with 0.01 lbs ai/ acre or less. The vast majority of chlorsulfuron is applied to winter wheat. The remaining use is primarily spring wheat, and oats. Registered use sites with little or no usage include lawn and ornamental turf. Most chlorsulfuron usage is in Oklahoma, Texas, Washington, Kansas, Montana, and California.

For cereal grains, the greatest chlorsulfuron usage is in Kansas, followed by Oklahoma, Montana, Washington, Texas, Nebraska, North Dakota, and California. For the non crop market, the greatest usage is in Iowa, followed by Washington, Oregon, Colorado, Idaho, Minnesota, Mississippi, and Nebraska. Chlorsulfuron is also registered for use on pasture and rangeland. The non crop land and industrial turf sites includes use on roadsides, railroads, industrial sites, rights of way, airports, fence rows, and lumberyards for control of noxious weeds.

1.4 Rate and Method of Application Chlorsulfuron is used predominately on grain crops such as barley, wheat, and oats. According to the USGS and USDA, this use accounts for more than 98% of agricultural chlorsulfuron usage ( http:// ca. water. usgs. gov/ pnsp/ use92/ chlrsulf. html). Chlorsulfuron may be broadcast applied by air or ground equipment to small grains at application rates that range from 0.0078 to 0.023 lbs ai/ acre. Acreage may be treated once per crop cycle to once every 36 months.

Chlorsulfuron may be broadcast applied by air or ground equipment to fallow, pasture, and rangeland at rates that range from 0.0078 to 0.0625 lbs ai/ acre. Other non crop uses ( unimproved turf, noncrop sod farms, ornamentals) may only be applied by ground equipment. Application rates range from 0.012 to 0.25 lbs ai/ acre. Acreage may be treated twice per year for some uses; for other uses labels do not specify a maximum number of applications per year. Table 1 summarizes application methods and maximum rates for chlorsulfuron. Page 3 of 90 Table 1. Chlorsulfuron Use Information Crop Application Method Application Rate ( lbs ai/ acre) Maximum number of applications per season Maximum seasonal/ yearly application rate Barley Post emergent Broadcast aerial or ground 0.0078  0.016 Ranges from once per crop season to once every 36 months ( Finesse label does not specify) 0.016 lbs ai/ acre ( Finesse label does not specify)

Oats pre emergent Broadcast aerial or ground Up to 0.023 Range of once per crop season to every 36 months 0.023 lbs ai/ acre Oats Post emergent Broadcast aerial or ground 0.0078  0.016 Range of once per crop season to once every 36 months 0.016 lbs ai/ acre Wheat Pre emergent Broadcast aerial or ground 0.0195  0.023 Range of once per crop season to once every 36 months ( Finesse label does not specify) 0.023 lbs ai/ acre ( Finesse label does not specify)

Wheat Post emergent Broadcast aerial or ground 0.0078  0.016 Range of once per crop season to once every 36 months ( Finesse label does not specify) 0.016 lbs ai/ acre ( Finesse label does not specify)

Pastures and rangeland Broadcast aerial or ground 0.012  0.0625 Label does not specify 0.0625 lbs ai per acre per 12 month period Fallow Broadcast aerial or ground 0.0078  0.016 Label does not specify Label does not specify Unimproved turf Broadcast ground only 0.012 Label does not specify 0.023 lbs ai/ acre/ year Unimproved industrial turf Broadcast ground only 0.012  0.0234 2 per year ( Telar DF label does not specify) 0.0234 lbs ai per acre per 12 month period Non crop sites Broadcast ground only 0.021  0.047 Label does not specify 0.12 lbs ai/ acre/ year Non crop ( industrial) sites Broadcast ground only 0.021  0.14 Label does not specify 0.125 lbs ai/ acre ( Telar DF label does not specify)

Non cropland restoration Broadcast ground only 0.021  0.031 Label does not specify 0.125 lbs ai/ acre/ year Sod farms and golf courses Handheld or boom sprayer 0.047  0.25 2 per year ( 60 day interval) 0.50 lbs ai/ acre/ year Ornamentals/ fine turf Broadcast ground only 0.13  0.25 2 per year 0.25  0.50 lbs ai/ acre per year 1.5 Current Label Restrictions Current chlorsulfuron labels contain a number of restrictions that may tend to mitigate to some degree the potential impacts of chlorsulfuron on non target and endangered plant species. For example, statements on the label for Finesse ® ( EPA Reg. No. 352 445) indicate that " Finesse herbicide is recommended for use on land primarily dedicated to the long term production of wheat and barley". This recommendation may serve to decrease the likelihood that irrigation water contaminated with chlorsulfuron will be inadvertently applied to agricultural crops that are sensitive to chlorsulfuron. Finesse labels provide the following precaution: " Do not apply to irrigated land where tailwater will Page 4 of 90 be used to irrigate other cropland." The extent to which this statement serves to decrease chlorsulfuron contamination of surface water used for irrigation is uncertain.

An indication of the persistence of chlorsulfuron under actual field conditions is provided in the label for Finesse ® , in the table on rotation intervals. The table indicates that the rotation interval for noncereal crops in non irrigated land ranges from 11 months for field corn to 48 months for sorghum. These intervals indicate that chlorsulfuron may persist in the soil at levels that are toxic to plants for extended periods of time. Additionally, labels for Finesse ® provide the following precaution: " To reduce the potential for movement of treated soil due to wind erosion, do not apply to powdery, dry, or light sandy soil until they have been stabilized by rainfall, trashy mulch, reduced tillage or other cultural practices. Injury to adjacent crops may result when treated soil is blown onto land used to produce crops other than cereal grains." The extent to which this statement serves to decrease the movement of chlorsulfuron contaminated soils into nearby fields in which non cereal crops are grown is uncertain.

Several labels have restrictions based on soil pH. Primarily these restrictions are to protect replanted crops after chlorsulfuron application. Several labels ( e. g., Dupont Glean ® and Finesse ® ) prohibit the use of chlorsulfuron on soils with pH greater than 7.9 because chlorsulfuron is quite persistent at high pH and re planting may suffer the effects of residual chlorsulfuron. In certain states these labels require a field bioassay if pH is above 6.5 to determine whether planting is feasible. Crop rotation intervals are pH dependent in some states. Supplemental labels may imply that the maximum pH limitation is less for certain state/ crop conditions. Some labels ( e. g., Dupont Telar ® and Landmark MP ® ) appear not to restrict the use chlorsulfuron based on soil pH, but instead only restrict the replanting interval. Other labels ( e. g., Lesco TFC ® and Riverdale Corsair ® ) specify reduced application rates on soils with pH above 7, but do not prohibit use at any specific soil pH.

Some label precautions suggest that synergistic effects may occur if chlorsulfuron is applied to fields to which certain other insecticides have been applied. The label for Finesse ® states that " Finesse should not be used within 60 days of crop emergence if an organophosphate insecticide ( such as " Di Syston ® " ) was used as an in furrow treatment, or crop injury may result." Presumably, neither of these two pesticides if used alone will cause crop injury to wheat or barley. However, the Finesse label indicates that they apparently do cause crop injury when used together. This suggests that there may be synergistic effects to plants when chlorsulfuron is applied to fields along with organophosphate insecticides. The label for Finesse ® also indicates that " Tank mix applications of Finesse ® plus Assert ® may cause temporary crop discoloration/ stunting or injury when heavy rainfall occurs shortly after application." Additionally, the label restricts the use of Finesse ® plus Malathion ® and the use of Finesse ® plus Lorsban ® in the Northwest, as crop injury may result. The Finesse ® label includes the following statement " Do not apply Finesse during the boot stage or early heading stage, as crop injury may result." This statement suggests that chlorsulfuron may adversely effect plant reproduction.

Several statements have been placed on chlorsulfuron labels to reduce the likelihood of spray drift. The label for Finesse ® provides the following statement: " When applying Finesse by air in areas near sensitive crops, use solid stream nozzles oriented straight back. Adjust swath to avoid spray drift Page 5 of 90 damage to downwind sensitive crops and/ or use ground equipment to treat border edges of fields." A refined analysis of effects of spray drift is provided in this assessment, however, the extent to which these statements reduce risk to plants from spray drift cannot be determined based on the level of detail provided.

1.6 Assessment Endpoints and Analysis Plan Laboratory toxicity tests indicate that chlorsulfuron is practically nontoxic to terrestrial and aquatic animals. However, results of toxicity tests for non target terrestrial and aquatic plants indicate that chlorsulfuron is acutely toxic. Very little data exist on levels that cause chronic toxicity to plants. Therefore, the screening level assessment focuses on endpoints related to acute effects to plants. For terrestrial plants, endpoints include vegetative vigor and seedling emergence. Effects on growth is the endpoint used for aquatic plant risk. Chronic ( reproductive) endpoints for plants were not used in the assessment because current plant test guidelines include only acute endpoints. However, results of field studies indicate that chlorsulfuron may adversely affect plant reproduction at low concentrations ( Section 3.7).

In this screening level assessment, exposure was estimated based on maximum label rates. Acute risk quotients for terrestrial and endangered plant species were calculated for three different habitat types adjacent to application sites: aquatic habitats, wetlands, and terrestrial areas. PRZM/ EXAMS modeling was utilized to evaluate potential exposure to aquatic plants ( Section 2.2). For non target and endangered terrestrial plant spray drift exposure values, 1 or 5% of the application rate was assumed, depending on whether the application method was aerial or with ground equipment. When runoff was included in the RQ calculations for semi aquatic/ wetland exposures, the exposure was assumed to be 5% of the application, based on chlorsulfuron's solubility. Runoff exposure was then added to spray drift exposure. For the pasture/ rangeland use, a direct application scenario was not assessed; however, exposure would be expected to be higher than that estimated to result from spray drift.

This ecological risk assessment focuses on the small grain, turf, rangeland, and pasture use sites because they represent the use sites with the largest amount of current or potential chlorsulfuron use. However, some of the non crop uses have higher application rates than the crop uses. If risk quotients were to be calculated for the chlorsulfuron non crop uses with the higher application rates, they would likely result in higher risk estimates than were calculated for the crop uses. Several of the chlorsulfuron labels do not specify application frequency. This risk assessment assumes a single application where the label is not specific; actual exposure may be substantially higher. Page 6 of 90 Figure 1. Chemical structure of chlorsulfuron. 2.0 ENVIRONMENTAL FATE CHARACTERIZATION Chlorsulfuron ( 2 chloro N[[( 4 methoxy 6 methyl 1,3,5 triazin 2 yl) amino] carbonyl] benzenesulfonamide, see Figure 1) is persistent and highly mobile in the environment. It may be transported by runoff or spray drift. Degradation by hydrolysis appears to be the most significant mechanism for degradation of chlorsulfuron, but is only significant in acidic environments ( 23 day half life at pH = 5); it is stable to hydrolysis at neutral to high pH. Degradation half lives in soil environments were quite variable and ranged from 14 to 320 days. Page 7 of 90 2.1 Chlorsulfuron Fate Studies 2.1.1 Hydrolysis Chlorsulfuron degraded with a half life of 23 days in the pH 5 solution, but was stable in the pH 7 and 9 solutions. Hydrolysis tests ( MRID 421567 01) were performed in buffered solutions at pH values of 5, 7, and 9 at 25o C. Buffered solutions were made from Milli Q water and acetate, phosphate, and borate buffers, respectively. Initial chlorsulfuron concentrations were 5 mg/ L. Chlorsulfuron concentrations were measured at 3, 7, 14, 21, and 31 days. Major degradates were from the pH 5 test were chlorosulfonamide ( 33% of applied), ring opened chlorsulfuron ( 16% of applied), o desmethylchlosulfuron ( 10% of applied), and lesser amounts of triazine and dihydroxy triazine.

2.1.2 Photodegradation in Water Chlorsulfuron does not readily photodegrade in water. Tests were conducted at pH 5, 7 and 9 at temperature of 25oC over 31 days ( MRID 421567 02).

2.1.3 Soil Photodegradation Soil photolysis tests ( MRID 421567 03) showed that chlorsulfuron degraded with a half life of 65 days. The test soil was a Nora silty clay ( 20% sand, 52% silt, 29% clay, 2% organic matter, CEC 19.6 meq/ 100 g, pH 8). Minor degradates were observed at less than 10% of the applied and included: dihydroxy triazine, triazine amine, triazine urea, and o desmethyl chlorsulfuron.

2.1.4 Aerobic Soil Metabolism Soil metabolism tests ( MRID 422142 01) conducted at 25oC showed a wide range in variability of the aerobic soil half life of chlorsulfuron. In a silt loam soil ( 21% sand, 63% silt, 17% clay, 2.75% organic matter and a of pH 6.4), chlorsulfuron had a half life of 14 days. In another soil ( 24% sand, 68% silt, 8% clay, 2.6% loam, pH 9, CEC 15.03 meq/ 100g), chlorsulfuron had a half life of 11 months. In older submitted studies ( MRID 0113 0013 and 0113 0024), chlorsulfuron half lives were 1 to 2 months. In more recent publications, Andersen et al. ( 2001) reported chlorsulfuron half lives of 50 days for soil taken from 30 to 35 cm below surface, 160 days for soil taken 40 to 45 cm below surface and 230 days for soil taken at 70 75 cm below surface. One reason for the decrease in degradation rates is possibly due to a decrease in microbial activity with depth. Andersen et al. ( 2001) did not report near surface soil data due to interference problems. Major degradates were 2 chlorobenzenesulfonamide ( 30 35%), 2 amino 4 methoxy 6 methyl 1,3,5 triazine, and 2 chloro N [[( 4 hydroxy 6 methyl 1,3,5 triazin 2 yl)  amino] carbonyl] benzenesulfonamide ( 15%). In all of the studies, it is not clear how much degradation occurred by microbial metabolism or by hydrolysis. Page 8 of 90 2.1.5 Anaerobic Aquatic Metabolism Chlorsulfuron is relatively stable under conditions of anaerobic metabolism. Controls degraded faster than test systems. Hydrolysis was likely the dominant mechanism in the system ( MRID 421467 04). In recent literature, Berger and Wolfe ( 1996) found an anaerobic sediment half life of 89 days and 301 days for unsterile and sterile sediment respectively; however, for another sediment system it was 182 days and only 101 days for the sterile system. These counterintuitive results were attributed to increased hydrolysis due to lowing of pH during heat sterilization.

2.1.6 Bioaccumulation Preliminary fish bioaccumulation studies ( MRID 422142 04) showed channel catfish accumulation factors of 1.5X in edible tissue, 12X in viscera, and 7X in liver. Residues declined by 90 95% during the depuration phase. In preliminary bluegill sunfish studies the bioaccumulation was 4X in the viscera and 6X in the liver with a residue decline of 70 90 % in the depuration phase. Chlorsulfuron has a relatively low K ow of 2.13 at pH 5, 0.10 at pH 7, and 0.04 at pH 9 at 25oC. This information is sufficient to indicate that chlorsulfuron has a low potential to bioaccumulate.

2.1.7 Field Dissipation Although guideline field studies were not submitted, older lysimeter studies were available and provide sufficient information to evaluate chlorsulfuron field dissipation for this assessment. In the field lysimeter studies ( MRID 422142 02), estimated half life ranged from 20 days to several months. MRID 422142 02 is a compilation of several studies identified by the registrant assigned report numbers in parenthesis that follow. Lysimeter studies in Delaware, North Dakota, and Nebraska ( Report No. 63 82) were conducted on both an alkaline and an acidic soil. For the acidic soils the dissipation half life ranged from 1 to 2 months, and for the alkaline soils, dissipation half lives were reported to be 2  4 months. Another study ( Report No. AMR 307 84) was carried out in the Fall in Ohio, Idaho, North Dakota, and in the Spring in Alberta, Manitoba and Saskatchewan, Canada. Dissipation half lives were reported to be 1 to 3 months for the Spring studies and 5 to 11 months for the Fall studies. Leaching of chlorsulfuron was apparent. The time for detectable levels of chlorsulfuron to reach 22  35 cm ranged from 1 to 40 months. In another lysimeter study ( Report No. AMR 1417 89) leaching was also apparent down to the 18 24 inch range. The reported dissipation half life was 20 days. In all the studies, only minor amounts (< 10%) of two degradates ( 2 chlorobenzenesulfonamide and 2 amino 4 methoxy 6 methyl 1,2,3,5 triazine) were observed.

2.1.8 Sorption A summary of batch sorption tests is given in Table 2. Batch studies ( MRID 421567 05) were conducted on four soils with an equilibration time of 24 hours at 25o C. From the sorption parameters chlorsulfuron can be considered mobile ( Table 2). It is expected ( as with many chemicals that become increasingly anionic with increasing pH) that the mobility of chlorsulfuron will increase with increasing pH. Page 9 of 90 Table 2. Summary of Submitted Sorption Studies Registrant's Name for Soil texture % sand % silt % clay % om CEC meq/ 100g soil pH K f mg/ l/( mg/ kg) 1/ n 1/ n Koc a ( ml/ g)

Madera loam 48 35 17 0.8 19.6 8 0.28 0.9 60 Woodstone sandy loam 60 33 7 1.1 5.3 6.6 0.09 0.85 14 Keyport silt loam 20 39 21 1.9 6.4 5.7 0.38 0.88 34 Flanagan silt loam 2 81 17 4.3 21.1 5.4 0.91 0.91 36 a K oc is based on the sorption coefficient at 1 mg/ L.

2.2 Water Resource Assessment Due to its mobility and persistence, chlorsulfuron may contaminate surface and groundwater. Fate studies show that chlorsulfuron is mobile, and that mobility should increase as the environmental pH increases ( chlorsulfuron becomes more anionic as pH increases, see for example the variation in Kow with pH in the bioaccumulation section). Chlorsulfuron is also persistent, and its persistence should also increase with increasing pH.

Few monitoring data are available on chlorsulfuron. Due to its very low application rate and expected low concentrations in the environment it is not often included as a analyte in monitoring programs. To obtain information about the occurrence of sulfonylurea ( SU), sulfonamide ( SA), and imidazolinone ( IMI) herbicides in the Midwestern United States, the USGS collected 212 water samples from 75 surface water sites ( 177 samples taken) and 25 ground water sites ( 29 samples taken) in 1998 ( Battaglin et al., 2000). Samples were collected from streams, large rivers, reservoir outflows, and wells. All reconnaissance samples were analyzed for 16 different herbicides. The 75 surface water sites were located in the Upper Mississippi, Missouri, and Ohio River basins. Twenty ground water samples were collected from a network of municipal wells in Iowa. The depths of the wells ranged from 6 to 83 m. with most wells less than 30 m. Samples were also collected from five observation wells in Lower Illinois; these wells were less than 8 m deep.

Of the 130 samples taken from Midwestern rivers and streams, only one sample contained chlorsulfuron ( 0.013

g/ L) above the method reporting limit of 0.01

g/ L. The USGS scientists reported no detections of chlorsulfuron in the 25 ground water samples. It is unclear to what extent the location of sampling sites overlapped with areas of chlorsulfuron usage. Because of limitations in the monitoring data, estimated environmental concentrations in this assessment were calculated using the models PRZM/ EXAMS and SciGrow.

2.2.1 Ambient Surface Water ( Farm Pond)

Surface water concentrations resulting from chlorsulfuron application to wheat and turf were estimated with PRZM ( version 3.12 beta) coupled to EXAMS ( version 2.98.04). Four scenarios were simulated   one for North Dakota wheat, one for Texas wheat, one for Pennsylvania turf, and Page 10 of 90 one for Florida turf. Application timing was estimated from the product labels, and a range of application dates were used. A summary of chemical properties used as PRZM/ EXAMS inputs is given in Table 3, and copies of input files are in Appendix 1. Because of its low degradation rate, chlorsulfuron concentrations continually increased over the simulation period and chronic and peak concentrations are nearly the same for all scenarios tested. Table 4 presents the peak and average concentrations for the simulated farm pond. Note that the standard EFED pond is confined such that flushing by external flows does not occur, and therefore, concentrations may accumulate over time to a higher degree than would a pond with flow into and out of the system. The date chosen for the application had a small ( absolute) effect on the output, as EEC values are within about 1 ppb ( the relative difference however is substantial   up to about 30%). For a conservative assessment, the highest of these values is used.

Table 3. Salient Chemical Properties of Chlorsulfuron Used for PRZM/ EXAMS Modeling Parameter Value Notes Molecular Weight 357.8 Solubility 31800 mg/ l Vapor Pressure 4.6 e 6 torr K oc 36 ml/ g MRID 421567 05 ( mean of values in Table 2)

Aerobic Soil half life 320 days 90 % ci of submitted studies ( half life data : 14, 330, 60 days) MRID 422142 01 Aerobic aquatic half life stable MRID 421467 04 Photodegradation stable MRID 421567 052; MRID 421567 03 Anaerobic metabolism stable assumption Hydrolysis stable MRID 421567 01 ( scenarios are performed at pH = 7) Page 11 of 90 Table 4. Summary of Ecological Concentrations Modeled with PRZM/ EXAMS. Chlorsulfuron applied once per season at maximum labeled rate. All values in ppb.

scenario formulation and application Date Applied peak 96 hr 21 day 60 day 90 day year ND wheat Glean 0.023 lb/ acre aerial application 1 Apr 4.2 4.2 4.2 4.2 4.2 4.2 1 May 4.1 4.1 4.1 4.1 4.1 4.1 TX wheat Glean 0.023 lb/ acre aerial application 1 Aug 5.5 5.5 5.5 5.5 5.5 5.5 1 Sep 5.8 5.8 5.8 5.8 5.8 5.7 15 Sep 6.0 6.0 6.0 6.0 6.0 5.9 1 Oct 6.3 6.3 6.3 6.3 6.3 6.3 PA turf Telar 0.0625 lb/ acre aerial application 15 Mar 4.0 4.0 4.0 4.0 4.0 4.0 1 Apr 5.0 5.0 5.0 5.0 5.0 5.0 15 Apr 4.5 4.5 4.5 4.5 4.5 4.5 1 May 5.9 5.9 5.9 5.9 5.9 5.8 15 May 5.2 5.2 5.2 5.2 5.2 5.0 FL turf Telar 0.0625 lb/ acre aerial application 1 Mar 6.8 6.8 6.8 6.8 6.8 6.8 1 Apr 9.5 9.5 9.5 9.5 9.5 9.5 1 May 7.5 7.5 7.5 7.5 7.5 7.4 2.3 Drinking Water Assessment 2.3.1 Surface Water Source This drinking water assessment estimates exposure to parent chlorsulfuron only. If metabolites of concern are identified a revised assessment will be prepared. EFED previously conducted a Tier 1 human drinking water assessment which can be found in Appendix 8. The tier 1 drinking water estimates for ground and surface water source drinking water used higher application rates, which bracket all label rates in Table 1. Although HED did not indicate problems with the concentrations from the Tier 1 assessment, EFED performed a Tier 2 human drinking water assessment in order to be consistent with the Tier 2 ecological water assessment described above. Concentrations of chlorsulfuron in drinking water sources for the Tier 2 assessment were estimated with PRZM/ EXAMS for surface sources. Four standard scenarios were investigated.. Because the scenarios are the same as those used for the ecological assessments, the application date chosen was the date that gave the highest exposure values, as determined from the ecological assessment PRZM/ EXAMS runs. The final drinking water estimated concentrations reported in Table 5 are reduced by the percent crop area ( PCA) factors reported in the table. Page 12 of 90 Table 5. Summary of estimated screening level surface water drinking water concentrations. Based on one application scenario formulation PCA application date peak ( upper 1 in 10 year peak concentration) [ ppb] chronic ( upper 1 in 10 year annual mean concentration) [ ppb]

ND wheat Glean 0.023 lb/ acre 0.56 May 1 0.32 0.23 TX wheat Glean 0.023 lb/ acre 0.56 Sep 15 0.95 0.25 PA turf Telar 0.0625 lb/ acre 1.0 April 1 1.5 1.1 FL turf Telar 0.0625 lb/ acre 1.0 April 1 2.2 1.1 2.3.2 Ground Water Source Groundwater concentrations were estimated with SciGrow, which is EFED's standard model for estimating groundwater concentrations of pesticides. For further information on this model see the EFED water model website at http:// www. epa. gov/ oppefed1/ models/ water/. The following model inputs were used: application rate = 0.0625 lb/ acre, one application per year, half life = 320 days, and K oc = 36. With these inputs, SciGrow estimates the groundwater concentration to be 1.6 ppb.

2.3.3 Drinking Water Estimated Concentrations The surface water EECs in Table 6 were based on a PRZM/ EXAMS simulation using EFED's standard Index Reservoir. The Pennsylvania turf scenario was found to provide the highest EECs among the scenarios tested. For groundwater, the SciGrow derived model estimated concentration of 1.6 µ g/ L was derived from the turf scenario ( see previous section). Appendix 8 provides additional details on the Tier 1 drinking water assessment for chlorsulfuron.

Table 6. Drinking Water Estimated Environmental Concentrations for Chlorsulfuron.

Acute Concentration Chronic Concentration Surface Water 2.2 µ g/ L 1.1 µ g/ L Groundwater 1.6 µ g/ L 1.6 µ g/ L Page 13 of 90 3. ECOLOGICAL EFFECTS CHARACTERIZATION This screening level ecological risk assessment was performed to evaluate the potential impact to nontarget mammals, birds, fish, and aquatic invertebrates resulting from the registered uses of chlorsulfuron. Based on available toxicity and environmental fate data, risks to mammals, birds, and aquatic organisms are not expected to exceed EFED's Levels of Concern. Thus risks to birds and aquatic animals resulting from chlorsulfuron use are expected to be low.

3.1 Toxicological Profile for Terrestrial and Aquatic Animals Table 7 provides eco toxicity values for terrestrial and aquatic animals that were used to calculate acute and chronic risk quotients for non target terrestrial and aquatic animals. Based on results of toxicity testing, chlorsulfuron appears to be practically nontoxic to most of the terrestrial and aquatic animals tested.

Adverse reproductive effects were observed in both the avian ( northern bobwhite) and mammalian reproduction studies, although at test concentrations well above the estimated environmental concentrations ( EEC). The NOAEC for northern bobwhite was determined to be 174 mg ai/ kg bw diet based on significant reductions in female body weight, 14 day old survivors/ normal hatchlings, viable embryos/ eggs set, and 14 day hatchling survival/ eggs set at the highest treatment level when compared to the control. Page 14 of 90 Table 7. Chlorsulfuron Toxicity Tests Used to Calculate RQs For Terrestrial and Aquatic Animals .

Study Type (% Active Ingredient) Species Toxicity Value ( ai) Toxicity Category MRID/ Acc.# Author ( Year) Study Classification Dietary LC 50 ( 91%) Mallard duck ( Anus platyrhynchos) LC 50> 5,000 ppm Practically nontoxic 099462 ( 1979) Core Avian Reproduction ( 97.5%) Northern bobwhite ( Colinus virginianus) NOAE = 174 ppm LOEAL= 961 ppm Not applicable 42634001 Beavers, J. B. et al. ( 1992) Core Rat two generation reproduction Laboratory rat NOAEL = 35 mg/ kg/ day Not applicable 40089316 Not Applicable Rat acute oral Laboratory rat LD 50 = 5.5 g/ kg Not applicable 00031406 Not Applicable Acute LC 50 ( 91%) Rainbow trout LC 50 > 250 ppm Practically nontoxic 099462 Core Acute LC 50 ( Technical) Daphnia magna LC 50 > 370 ppm Practically nontoxic 099462 Core Early life stage ( 97.6%) Rainbow trout NOAEC = 32 mg/ l Not applicable 419764 05 Pierson, K. B. ( 1991) Core Life cycle ( 95.4%) Daphnia magna NOAEC = 20 mg/ l Not applicable 419764 08 Hutton, D. G. ( 1989) Supplemental 1 Acute LC 50 ( 98.2%) Mysid ( Mysidopsis bahia) LC 50 = 89 mg/ l slightly toxic 419764 02 Ward, T. J. and R. L. Boeri ( 1991) Core Acute LC 50 ( 98.2%) Sheepshead minnow ( Cyprinodon LC 50 > 980 mg/ l practically nontoxic 419764 01 Ward, T. J. and R. L. Core 1/ This study is scientifically sound. However, it does not fulfill test guideline requirements. It is repairable if additional information on the solvent control and dilution water is submitted.

A summary of guideline ecological toxicity studies is provided in Appendix 2. Page 15 of 90 3.2 Risk Quotients for Terrestrial and Aquatic Animals Table 8 provides risk quotient values for terrestrial and aquatic animals.

Table 8. Chlorsulfuron Risk Quotients for Terrestrial and Aquatic Animals.

Species Toxicity EEC range Risk Quotients acute / chronic Birds Acute LC 50 > 5,000 ppm Chronic NOAEL = 174 mg/ kg/ day 1.9  15 ppm < 0.01 / < 0.01 Mammals Acute LD 50 = 5,500 ppm Chronic NOAEC = 35 mg/ kg/ day 1.9  15 ppm < 0.01 / < 0.01 Freshwater fish Acute LC 50 = > 50 ppm Chronic NOAEC = 32 ppm 0.003  0.0096 ppm < 0.01 / < 0.01 Freshwater invertebrate Acute LC 50 = > 370 ppm Chronic NOAEC = 20 ppm 0.003  0.0096 ppm < 0.01 / < 0.01 Marine fish Acute LC 50 = > 950 ppm Chronic NOAEC = N/ A 0.003  0.0096 ppm < 0.01 / N/ A Marine invertebrate Acute LC 50 = 89 ppm Chronic NOAEC = N/ A 0.003  0.0096 ppm < 0.01 / N/ A Honey bee Acute LD 50 > 25

g/ bee N/ A N/ A 3.2.1 Birds and Mammals Acute and chronic risk quotients do not exceed Levels of Concern ( LOC) for birds and mammals. With acute toxicity values ( LC 50) greater than 5,000 ppm and relatively low EECs, based on 240 ppm per lb ai applied ( Appendix 3) chlorsulfuron is not expected to pose an acute risk to avian species. The NOAEC for avian reproduction ( 174 mg/ kg/ day) is more than an order of magnitude above the highest EEC ( 15 ppm). Because of low acute and chronic toxicity to laboratory rats, risk quotients do not exceed the LOCs for mammals. Therefore, chronic risks to birds and mammals are not expected to exceed the Levels of Concern.

3.2.2 Freshwater and Marine/ estuarine Fish and Invertebrates Acute and chronic risk quotients do not exceed the LOC for freshwater or marine/ estuarine fish and invertebrates. With acute toxicity values ( LC 50) greater than 50 ppm and EECs less than 0.010 ppm, chlorsulfuron is not expected to pose an acute risk to aquatic animal species. Chronic toxicity tests provide NOAECs that are greater than or equal to 20 ppm. Therefore, chlorsulfuron is expected to present low acute or chronic risks to freshwater and marine/ estuarine fish and invertebrates. Page 16 of 90 3.3 Risk Characterization for Terrestrial and Aquatic Wildlife Toxicity tests and estimated environmental concentrations indicate those chlorsulfuron risks resulting from direct exposure to terrestrial and aquatic animals are expected to be low. However, the potential exists for indirect impacts because animals ultimately depend on plants and plant communities for survival.

3.4 Plant Effects Assessment A screening level risk assessment for terrestrial and aquatic plants is provided below. Laboratory toxicity values for plants are compared with estimated environmental concentrations to give deterministic risk quotients.

3.4.1 Toxicological Profile for Terrestrial and Aquatic Plants The standard toxicity level EFED uses for calculating risk quotients for non endangered terrestrial plants is the EC 25. For endangered plants, the EC 05 or the no observable adverse effect level ( NOAEL) is used. The EC x effect level represents an X% effect to a group of plants. The dose required to cause a 25% reduction in the average shoot height of a group of plants is an example of an EC 25 toxicity level. Reduction in the dry weight of the plant can also be used in calculating the EC x. Visual effects, such as spotting or chlorosis, are not generally assessed because of difficulty in quantifying the magnitude of the effect.

Table 9 provides laboratory toxicity values for terrestrial and aquatic plants. Chlorsulfuron is toxic to nontarget terrestrial plants with EC 25 values as low as 4 x 10  6 lbs a. i./ acre and an EC 05 value of 4.6 x 10  8 lbs a. i. / acre ( vegetative vigor). Based on available data, the slope of the dose response curve for chlorsulfuron has a low value; toxicity does not decrease rapidly with decreasing concentration. As a result, terrestrial plant treatment concentrations were not low enough in the seedling emergence and vegetative vigor studies to determine the NOAEC for several plant species. More detailed summaries are provided in Appendices 4 and 5. Aquatic plant toxicity ranged from practically nontoxic to very highly toxic. The most sensitive aquatic plant was Lemna gibba ( duckweed), with an EC 50 of 0.00035 mg ai/ L and a NOAEC of 0.00024 mg ai/ L.

The plants used in phytotoxicity tests are chosen primarily for due to the availability of validated protocols and seed sources. Registrants routinely screen potential products using a wide variety of economically important plants to determine if phytotoxicity concerns exist. The Pesticide Assessment Guideline Subdivision J ( EPA 540/ 9 82 020) states that flexibility is allowed in choosing species in order to maximize use of "... tests that are normally performed by the developer/ registrant during screening and initial field testing...." The registrant must test corn and soybeans primarily because of their economic importance in US agricultural. A dicot root crop must also be tested along with an approximately even ratio of dicots and monocots.

Laboratory toxicity data used in this analysis were limited to effects occurring in a relatively short amount of time after a single exposure. A number of published reports suggest that chlorsulfuron, Page 17 of 90 and other herbicides with the same mode of action, may result in delayed effects on crop yield and plant reproduction at levels lower than those noted to cause short term visible effects ( for a review see Ferenc 2001).

Table 9. Summary of Chlorsulfuron Toxicity Tests for Terrestrial and Aquatic Plants.

Study Type (% Active Ingredient) Species Toxicity Value ( reported application rate) MRID/ Acc.# Author ( Year) Study Classification Seedling emergence and Vegetative vigor ( 98.2% chlorsulfuron purity) All chlorsulfuron stock and test solutions were prepared in pH 7 buffer or HPLC grade acetone. Valent 0.25% X 77 surfactant was used in some test solutions. Seedling emergence: ( onion, sugarbeet, soybean, sorghum, pea, rape, cucumber, corn, and tomato)

Vegetative vigor: ( Wheat, onion, sugarbeet, soybean, sorghum, pea, rape, cucumber, corn, and tomato) Seedling emerge: ( sugarbeet, shoot height) EC 25 = 3.06 x 10 5 lbs ai/ A NOAEC = 6.8 x 10 6 lbs ai/ A Vegetative Vigor: ( onion, shoot weight) EC 25 = 4.0 x 10 6 lbs ai/ A EC 25 = 4.56 x 10  8 lbs ai/ acre 425872 01 and 422010 01 McKelvey, R. A., and H. Kuratle ( 1992) Supplemental 1 Aquatic plant growth ( 98.2%) Selenastrum capricornutum EC 50 = 0.05 mg ai/ L NOAEC = 0.0094 mg ai/ L 421868 01 Blasburg, J. et al. ( 1991) Supplemental 2 Aquatic plant growth ( 97.8%) Skeletonema costatum NOAEC = 126 mg ai/ L EC 50 > 126 mg ai/ L 45832902 R. L. Boeri et al. ( 2001) Core Aquatic plant growth ( 97.8%) Navicula pelliculosa NOAEC = 126 mg ai/ L EC 50 > 126 mg ai/ L 45832904 R. L. Boeri et al. ( 2001) Core Aquatic plant growth ( 97.8%) Anabaena flos aquae NOAEC = 0.236 mg ai/ L EC 50 = 0.609 mg ai/ L 45832903 R. L. Boeri et al. ( 2001) Core Aquatic plant growth ( 97.8 %) Lemna gibba NOAEC = 0.00024 mg ai/ L EC 50 = 0.00035 mg ai/ L 45832901 R. L. Boeri et al. ( 2001) Supplemental 3 1/ This study is scientifically sound but does not fulfill the guideline requirements for seedling emergence and vegetative vigor studies 2/ This study could be upgraded to core if raw data are submitted.

3/ This study was conducted under static conditions.

Because of deficiencies in the plant studies, several are classified as supplemental and do not fulfill data requirements for plant toxicity testing. However, these studies were determined to be scientifically sound and are suitable for use in the screening level risk assessment for non target and endangered plants. Page 18 of 90 3.5 Risk Quotients for Aquatic and Terrestrial Plants 3.5.1 Aquatic Plant Assessment Table 10 provides screening level risk quotients for non target and endangered/ threatened aquatic plants. PRZM/ EXAMS was used to estimate environmental concentrations ( EECs). The assumptions used in this modeling are provided in Section 2.2. For this assessment the peak EEC was used. However, as Table 4 indicates, the EECs after a year are essentially the same as the peak EECs. The duration of exposure in the aquatic plant toxicity testing typically ranges from 5 to 14 days. Therefore, if the long term EECs were used instead of peak, risk quotients would remain the same.

The Level of Concern ( LOC) for non target plants is 1.0. For use on wheat, non target aquatic plant RQs range from 12 to 18 and from 18 to 26 for endangered aquatic plant species. For use on turf ( pasture/ rangeland and fallow), RQs range from 17 to 27 for non target aquatic plants and from 26 to 40 for endangered aquatic plants.

Table 10. Chlorsulfuron Risk Quotients ( RQs) for Non target and Endangered/ Threatened Aquatic Plants Using a E50 of 0.35

g/ L and a NOAEC of 0.24

g/ L for Lemna gibba. ( Single Application).

Crop ( state) Application rate ( lbs ai/ acre) Peak EEC ( ppb) ( PRZM/ EXAMS) RQs for non target aquatic plants 1 RQs for endangered aquatic plants 2 Wheat ( ND) 0.023 4.2 12 18 Wheat ( TX) 0.023 6.3 18 26 Turf ( PA) 0.0625 5.9 17 26 Turf ( FL) 0.0625 9.5 27 40 1/ EEC/ E 50 2/ EEC/ NOAEC Exposure from the sod/ golf course and nursery uses were not estimated due to low overall usage; however, because the maximum application rates for those uses are higher than for the uses modeled, the LOCs would be exceeded for these uses as well.

3.5.2 Terrestrial Plant Assessment The screening level terrestrial assessment consists of the following four scenarios:

1) Off target drift and runoff of chlorsulfuron from a ten acre application site to an adjacent one acre semi aquatic area ( wetland) using seedling emergence toxicity data to calculate risk quotients ( Table 11), based on a single application of chlorsulfuron. Page 19 of 90 2) Off target drift and runoff of chlorsulfuron from a one acre application site to an adjacent one acre terrestrial area using seedling emergence toxicity data to calculate risk quotients ( Table 12), based on a single application of chlorsulfuron.

3) Off target drift and no runoff of chlorsulfuron from a one acre application site to an adjacent one acre terrestrial area using vegetative vigor toxicity data to calculate risk quotients ( Table 13), based on a single application of chlorsulfuron.

4) Application of contaminated irrigation water ( groundwater or surface water inadvertently containing chlorsulfuron) using the vegetative vigor toxicity data to calculate risk quotients ( Table 14), based on a single irrigation event.

Table 11 provides screening level RQs for semi aquatic areas ( wetlands) resulting from off target drift ( concentrations estimated at the edge of the treated field) and runoff of chlorsulfuron from the application site ( ten acres to one acre). The toxicity endpoint used in the RQ calculations is seedling emergence. A ten acre application area running off into a one acre wetland is simulated to determine the estimated environmental concentrations from runoff into wetlands.

RQs for ground application of chlorsulfuron to small grains ( wheat, barley, and oats), pasture and rangeland range from 267 to 1,042 for non target plants and from 1200 to 4,688 for endangered/ threatened plants. RQs for aerial application to small grains, pasture and rangeland range from 288 to 1123 for non target plants and from 1,294 to 5,056 for endangered/ threatened plants. Therefore, for this scenario, ( which assumes 10 acres treated to one acre runoff), risk quotients for aerial applications are approximately 8% higher than the risk quotients from ground applications. Since the LOC ( 1.0) is exceeded by over three orders of magnitude, the application of chlorsulfuron to small grains, rangeland and pasture greatly exceeds levels of concern for non target and endangered/ threatened plants found in semi aquatic areas ( wetlands). The highest calculated RQs are from non crop uses: industrial sites and pasture/ rangeland Exposure from the sod/ golf course and nursery uses were not estimated due to low overall usage; however, because the maximum application rates for those uses are higher than for the uses modeled, the LOCs would be exceeded for these uses as well. Direct exposure scenarios were also not calculated, but RQs for plants and endangered plants would be higher than those estimated from exposure via spray drift or runoff. Page 20 of 90 Table 11. Chlorsulfuron Risk Quotients ( RQs) for Non Target Semi Aquatic Areas ( Wetlands) Using a EC25 of 3.06 x 10  5 lbs ai/ acre for Non Target Plants and a NOAEC of 6.8 x 10  6 lbs ai/ acre for Endangered Plants ( Using Sugarbeets, Seedling Emergence, Shoot Height) with Ten Acres to One Acre Runoff.

Crop Appl. rate ( lbs ai/ A)

Single application EEC for ground appl. 1 ( lbs ai/ A) EEC for aerial appl. 2 ( lbs ai/ A) RQs for ground application RQs for aerial application Non target plants 3 Endangered plants 4 Non target plants 5 Endangered plants 6 Barley ( post emergent) 0.016 0.00816 0.0088 267 1200 288 1294 Oats ( preemergent 0.023 0.01173 0.01265 383 1725 413 1860 Oats ( postemergent 0.016 0.00816 0.0088 267 1200 288 1294 Wheat ( preemergent 0.023 0.01173 0.01265 383 1725 413 1860 Wheat ( postemergent 0.016 0.00816 0.0088 267 1200 288 1294 Pastures and rangeland 0.0625 0.03188 0.03438 1042 4688 1123 5056 Fallow 0.016 0.00816 0.0088 267 1200 288 1294 Unimproved turf 0.012 0.00612 N/ A 200 900 N/ A N/ A Unimproved industrial turf 0.023 0.01173 N/ A 383 1725 N/ A N/ A Non crop sites 0.047 0.024 N/ A 783 3530 N/ A N/ A Non crop ( industrial sites) 0.14 0.0714 N/ A 2333 10500 N/ A N/ A Non crop land restoration 0.031 0.01625 N/ A 531 2390 N/ A N/ A 1/ EEC for ground applications = drift + runoff = total load Drift = application rate ( lbs ai/ acre) x 0.01 ( drift) Runoff = application rate ( lbs ai/ acre) x 0.05 ( based on solubility) x 10 ( 10 acres to one) 2/ EEC for aerial applications = drift + runoff = total load Drift = application rate ( lbs ai/ acre) x 0.05 ( drift) Runoff = application rate ( lbs ai/ acre) x 0.05 ( based on solubility) x 10 ( 10 acres to one) 3/ RQ = EEC for ground application / EC25 4/ RQ = EEC for ground application / NOAEC 5/ RQ = EEC for aerial application / EC25 6/ RQ = EEC for aerial application / NOAEC Table 12 provides risk quotients for non target and endangered terrestrial plants. This scenario uses toxicity endpoints from the seedling emergence study and assumes one acre to one acre runoff. Page 21 of 90 RQs for ground application of chlorsulfuron to small grains, pasture and rangeland range from 31 to 123 for non target plants and from 141 to 551 for endangered/ threatened plants. RQs for aerial application to small grains, pasture and rangeland range from 52 to 204 for non target plants and from 235 to 919 for endangered/ threatened plants. Therefore, for this scenario, ( which assumes one acre to one acre runoff), risk quotients for aerial applications are approximately 67% higher than the risk quotients for ground applications.

RQs for non target plants range from 31 to 204 for small grains, rangeland and pasture. For endangered plants they range from 141 to 919. The highest RQs are for non crop industrial sites ( 275 to 1,235). The LOC for non target and endangered terrestrial plants is 1.0. Therefore, the application of chlorsulfuron to small grains, rangeland, pasture and non crop sites greatly exceeds LOCs for non target and endangered/ threatened terrestrial plants. Exposure from the sod/ golf course and nursery uses were not estimated due to low overall usage; however, because the maximum application rates for those uses are higher than for the uses modeled, the LOCs would be exceeded for these uses as well. Direct exposure scenarios were also not calculated, but RQs for plants and endangered plants would be higher than those estimated from exposure via spray drift or runoff. Page 22 of 90 Table 12. Chlorsulfuron Risk Quotients ( RQs) for Non Target and Endangered Terrestrial Plants Using an EC25 of 3.06 x 10  5 lbs ai/ acre for Non Target Plants and a NOAEC of 6.8 x 10  6 lbs ai/ acre for Endangered Plants ( Using Sugarbeets, Seedling Emergence, Shoot Height) with One Acre to One Acre Runoff.

Crop Appl. rate ( lbs ai/ A)

Single application EEC for ground appl. 1 ( lbs ai/ A) EEC for aerial appl. 2 ( lbs ai/ A) RQs for ground application RQs for aerial application Non target plants 3 Endangered plants 4 Non target plants 5 Endangered plants 6 Barley ( post emergent) 0.016 0.00096 0.0016 31 141 52 235 Oats ( preemergent 0.023 0.00138 0.0023 45 203 75 338 Oats ( postemergent 0.016 0.00096 0.0016 31 141 52 235 Wheat ( preemergent 0.023 0.00138 0.0023 45 203 75 338 Wheat ( postemergent 0.016 0.00096 0.0016 31 141 52 235 Pastures and rangeland 0.0625 0.00375 0.00625 123 551 204 919 Fallow 0.016 0.00096 0.0016 31 141 52 338 Unimproved turf 0.012 0.00072 N/ A 24 106 N/ A N/ A Unimproved industrial turf 0.023 0.00138 N/ A 45 203 N/ A N/ A Non crop sites 0.047 0.0028 N/ A 92 412 N/ A N/ A Non crop ( industrial sites) 0.14 0.0084 N/ A 275 1235 N/ A N/ A Non crop land restoration 0.031 0.00186 N/ A 61 274 N/ A N/ A 1/ EEC for ground applications = drift + runoff = total load Drift = application rate ( lbs ai/ acre) x 0.01 ( drift) Runoff = application rate ( lbs ai/ acre) x 0.05 ( based on solubility) 2/ EEC for aerial applications = drift + runoff = total load Drift = application rate ( lbs ai/ acre) x 0.05 ( drift) Runoff = application rate ( lbs ai/ acre) x 0.05 ( based on solubility) 3/ RQ = EEC for ground application / EC25 4/ RQ = EEC for ground application / NOAEC 5/ RQ = EEC for aerial application / EC25 6/ RQ = EEC for aerial application / NOAEC Table 13 provides RQs for non target and endangered terrestrial plants resulting from spray drift alone ( no runoff). RQs resulting from aerial application of chlorsulfuron were five times greater than for ground application. RQs for non target plants range from 40 to 156 for ground applications to small grains, rangeland and pasture. For endangered plants they range from 3,507 to 13,698. For Page 23 of 90 aerial applications RQs for non target plants range from 200 to 800 for small grains, rangeland and pasture. For endangered plants they range from 17,533 to 68,488. The toxicity endpoint used in these RQ calculations was the shoot weight from the vegetative vigor study. If root weight was used instead, the risk quotients would be much higher ( Appendix 5). Therefore, the application of chlorsulfuron to small grains, rangeland and pasture exceeds LOCs for non target and endangered/ threatened terrestrial plants by several orders of magnitude. For this scenario ( which assumes no runoff), the risk quotients for aerial applications are approximately 5 times higher than for ground applications. Exposure from the sod/ golf course and nursery uses were not estimated due to low overall usage; however, because the maximum application rates for those uses are higher than for the uses modeled, the LOCs would be exceeded for these uses as well. Direct exposure scenarios were also not calculated, but RQs for plants and endangered plants would be higher than those estimated from exposure via spray drift or runoff. Page 24 of 90 Table 13. Chlorsulfuron Risk Quotients ( RQs) for Non Target and Endangered Terrestrial Plants Resulting From Drift Exposure Alone ( No Runoff) Using a EC25 of 4.0 x 10 6 lbs ai/ acre for Non Target Plants and a EC05 of 4.5625 x 10  8 lbs ai/ acre for Endangered Plants ( Using Vegetative Vigor, Onion Shoot Weight).

Crop Appl. rate ( lbs ai/ A)

Single application EEC for ground appl. 1 ( lbs ai/ A) EEC for aerial appl. 2 ( lbs ai/ A) RQs for ground application RQs for aerial application Non target plants 3 Endangered plants 4 Non target plants 5 Endangered plants 6 Barley ( post emergent) 0.016 1.6 x 10  4 8.0 x 10  4 40 3507 200 17533 Oats ( preemergent 0.023 2.3 x 10  4 1.15 x10 3 58 5040 290 25202 Oats ( postemergent 0.016 1.6 x 10  4 8.0 x 10  4 40 3507 200 17533 Wheat ( preemergent 0.023 2.3 x 10  4 1.15 x 10 3 58 5040 290 25202 Wheat ( postemergent 0.016 1.6 x 10  4 8.0 x 10  4 40 3507 200 17533 Pastures and rangeland 0.0625 6.25 x 10  4 3.13 x 10 3 156 13698 800 68488 Fallow 0.016 1.6 x 10  4 8.0 x 10  4 40 3507 200 17533 Unimproved turf 0.012 1.2 x 10  4 N/ A 30 2630 N/ A N/ A Unimproved industrial turf 0.023 2.3 x 10  4 N/ A 58 5040 N/ A N/ A Non crop sites 0.047 4.7 x 10  4 N/ A 118 10300 N/ A N/ A Non crop ( industrial sites) 0.14 1.4 x 10  3 N/ A 350 30683 N/ A N/ A Non crop land restoration 0.031 3.1 x 10  4 N/ A 78 6794 N/ A N/ A 1/ EEC for ground applications = drift = total load Drift = application rate ( lbs ai/ acre) x 0.01 ( drift) 2/ EEC for aerial applications = drift = total load Drift = application rate ( lbs ai/ acre) x 0.05 ( drift) 3/ RQ = EEC for ground application / EC25 4/ RQ = EEC for ground application / EC05 5/ RQ = EEC for aerial application / EC25 6/ RQ = EEC for aerial application / EC05 Page 25 of 90 3.5.3 Terrestrial Plant Assessment for Contaminated Irrigation Water Risk quotients were also calculated to evaluate whether there is a potential for adverse impacts to plants if exposed to irrigation water inadvertently containing chlorsulfuron. Modeled estimates suggest that irrigation water from groundwater and surface water sources may contain high enough levels of chlorsulfuron to damage non target plants and sensitive crops within irrigated fields.

Table 14 provides risk quotients for non target plants resulting from exposure to irrigation water containing 1.6 ppb of chlorsulfuron in groundwater, derived from SCIGROW ( Table 6) or 6.0 ppb of chlorsulfuron in surface water, generated using PRZM/ EXAMS. The 6.0 ppb estimate roughly covers North Dakota, Texas, and Pennsylvania scenarios, although Florida could be as high as 9.5 ppb ( Table 4).

Toxicity endpoints from the vegetative vigor study were used in the RQ calculations because it was assumed that non target plants are exposed to chlorsulfuron directly from irrigation water. This screening level assessment indicates that irrigation water may inadvertently contain high enough levels of chlorsulfuron to adversely impact sensitive agricultural crops such as soybeans, sugarbeets, onions, etc. if they are grown in fields that are irrigated with water containing chlorsulfuron. Risk quotients for sensitive crops within irrigated fields range from 91 for irrigation using groundwater to 341 for using surface water to irrigate fields. Since the LOC for plants is 1.0, the risk quotients exceed the LOC by over two orders of magnitude. Therefore, in regions where chlorsulfuron has been used historically, agricultural crops grown in fields irrigated with groundwater or surface water containing chlorsulfuron may be adversely effected. For this assessment it was assumed that there are no endangered plants that occur within irrigated fields.

Table 14. Risk Quotients for Non target Plants Resulting From Exposure to Irrigation Water Containing 1.6 ppb Chlorsulfuron in Groundwater or 6.0 ppb in Surface Water ( using the vegetative vigor EC25 of 4.0 x 10  6 for non endangered plants).

Location EEC: chlorsulfuron in irrigation groundwater and surface water ( lbs ai/ acre) 1 Risk Quotients for groundwater ( GW) and surface water ( SW) irrigation Non Endangered plants2 ( EEC/ EC 25)

Within the irrigated field1 Groundwater: 3.634 x 10 4 Surface water: 1.363 x 10 3 GW: 91 SW: 341 1/ Estimated Environmental Concentration assuming 1 inch of irrigation water is applied to the target field. 2/ It is assumed that there are no endangered plants within agricultural fields that are irrigated.

3.6 Toxicity Studies ( from Public Literature)

A number of published reports suggest that chlorsulfuron, and other herbicides with the same mode of action, may result in delayed effects on crop yield and plant reproduction at levels lower than those noted to cause short term visible effects ( for a review see Ferenc 2001). Page 26 of 90 3.6.1 Fletcher et al. 1995 The influence of chlorsulfuron on the reproduction of green pea ( Pisum sativum) was examined by exposing plants at three different stages of development to three different exposure levels ( 46, 92, and 180 mg ha 1), corresponding to 2 x10 3, 4 x 10 3, and 8 x 10 3 of the recommended field application rates for small grain crops. The most susceptible stage of development was when plants possessed six expanded leaves and one visible flower bud. At that stage an application rate of 180 mg ha 1 ( 0.8% of the recommended field rate) reduced yield of treated plants by 99% of that of control plants without severely altering height or appearance of mature plants.

When corresponding low application rates of atrazine, glyphosate, and 2,4 D were administered at this same development stage there were no effects on either growth or reproduction. Thus chlorsulfuron had an influence on plant reproduction that was not produced by other herbicides at low levels. The researchers concluded that small amounts of drifting sulfonylureas are potentially more damaging to the yield of non target plants than that of other commonly used herbicides.

3.6.2 Coyner et al. 2000 The effect of chlorsulfuron on the non target freshwater macrophyte, Potamogeton pectinatus ( sago pondweed) was evaluated using environmental growth chambers. This ecologically important submerged plant is a food source for many species of wildlife such as ducks, geese and swans, as well as marsh and shorebirds ( Hurly, 1994). P. pectinatus also provides habitat and nursery area for many fish and other aquatic life. It grows in regions where chlorsulfuron is used.

In this study P. pectinatius was exposed to chlorsulfuron at 0.25, 0.50. 1.0 or 2.0 ppb for 4 weeks. Plants exposed to 0.25 ppb chlorsulfuron showed a 76% reduction in length and a 50% reduction of stems and leaves compared to control plants. Increased mortality was observed at 1.0 ppb or greater. Correll and Wu ( 1982) found that P. pectinatus exposed to 650 ppb atrazine for 4 week period did not have a mortality rate higher than the control plants.

Comparing the test results from this study to those from the guideline aquatic plant studies ( Table 9) suggest that vascular plants such as duckweed ( Lemna gibba), may be more susceptible to chlorsulfuron than non vascular plants such as the freshwater diatom Navicula pelliculosa. Results of risk quotient calculations using the results from Coyner et al. ( 2000) are presented in Section 2.6.1.

3.7 Field Studies, Greenhouse Studies, and Incident Reports Results from a number of field studies, greenhouse studies, laboratory studies and incident reports support the conclusion that chlorsulfuron applied at labeled rates may result in high risk to non target plants grown in the vicinity of application sites. Several of the fields studies below were conducted by researchers from the EPA laboratory in Corvalis, Oregon and one of the non target plant incidents ( at Horse Heaven Hills) was investigated by a researcher from the same EPA laboratory. Page 27 of 90 Several researchers have concluded that these studies indicate that small quantities of the chemical, such as might be found in airborne particles traveling long distances, may change plant reproduction without altering vegetative growth. If the effect of chlorsulfuron on cherry trees is characteristic of other plant species, drifting sulfonylureas may severely reduce both the crop yields and fruit development on native plants, an important component of the habitat and food web for wildlife.

Plant reproductive processes may be more sensitive to chlorsulfuron than growth effects. Low levels of chlorsulfuron appear to adversely influence plant reproduction, which is not characteristic of many common herbicides. If such events are occurring in agriculture, not only will it be difficult to recognize them but it will be virtually impossible to prove that chlorsulfuron was responsible for the episode, because the amounts of chlorsulfuron inducing yield reduction are often below the detection level of conventional chemical analysis.

3.7.1 Field Studies Fletcher et al. 1993 Researchers at the Oregon State University Lewis Brown Horticulture Farm near Corvallis, Oregon investigated the influence of chlorsulfuron on cherry trees during the fall of 1991 and the spring of 1992, by comparing the weight of fruit collected from treated and control branches. Single applications of chlorsulfuron were administered until wetness with a dual nozzle spray wand at five concentrations representing 0, 1/ 1000th, 1/ 500th, 1/ 100th, and 1/ 10th of the recommended tank mixture rate of chlorsulfuron for use on small grain crops in Washington, Oregon, and California. Three multiple applications experiments were also conducted at 1 week intervals.

Results indicate that exposure of the developing buds to low levels of chlorsulfuron in September caused the next spring's yield to be reduced to 15% of the controls. Spring treatment resulted in yields of treated branches of 40% that of controls. Study authors determined that the low dose herbicides are approximately 100 times more toxic than herbicides used prior to 1982. Significant adverse effects on yields ( up to 85% yield loss) was measured following treatment at, during, or shortly after bloom. These effects on the full grown, woody perennial cherry tree occurred from the use of 1/ 500th the maximum label rate for chlorsulfuron herbicide ( 1/ 500th of 1/ 3 oz. ai/ acre).

The researches concluded that " the results from this series of experiments showed that at low levels of chlorsulfuron ( 4.6 x 10 7 M), reproduction of cherry trees was reduced without visible disruption of vegetative organs. The high sensitivity cherry trees displayed toward chlorsulfuron indicates that small quantities of the chemical, such as might be found in airborne particles traveling long distances, may change plant reproduction without altering vegetative growth. If the effect of chlorsulfuron on cherry trees is characteristic of other plants species, drifting sulfonylureas may severely reduce both the crop yields and fruit development on native plants, an important component of the habitat and food web for wildlife".

Bhatti et al. 1995 Page 28 of 90 Field experiments were conducted at the Irrigated Agricultural Research and Extension Center, Prosser, Washington in 1992 and 1993 to study the effects of simulated chlorsulfuron drift by treating branches of three cherry ( Prunus avium) cultivars at different growth stages. In single exposure experiments, the yield and quality of fruit decreased significantly with the increase of chlorsulfuron concentrations. The concentrations correspond to 1/ 900th, 1/ 300th, 1/ 100th and 1/ 10th the field application rates ( 23.34 g/ ha) recommended for wheat. In multiple exposure experiments, fruit yield, fruit size, and color was significantly reduced with increasing chlorsulfuron concentrations and numbers of exposures. The data suggest that multiple exposures of a susceptible cherry cultivar to low levels of chlorsulfuron at full bloom and post bloom stages can reduce yield and delay maturity of cherries while increasing firmness.

The researchers concluded that these results concur with the observations by Fletcher et al. ( 1993), in that the toxicity of chlorsulfuron to cherries was correlated with concentration and reproductive growth stage at the time of exposure. However, if visible symptoms were not present, there were no yield reductions. Reproduction in cherry trees can be adversely affected by exposure to concentrations of chlorsulfuron substantially lower than field application rates.

3.7.2 Greenhouse Studies The influence of low application rates of chlorsulfuron on the growth and reproduction of four taxonomically diverse plant species ( canola, smart weed, soybean, and sunflower) were examined ( Fletcher et al. 1996). Exposure ranged from 1 x10 3 to 8 x 10 3 of the recommended field rates for cereal crops. Each species received a single application at one of the three different stages of reproduction development. The comparative effects of four different herbicides ( atrazine, chlorsulfuron, glyphosate, and 2,4 D) were determined in the same manner.

Chlorsulfuron reduced the yields of all plants tested, with the amount of reduction depending on the time and rate of application. For canola and soybean, applications of 9.2 x 10 5 and 1.8 x 10 4 kg/ ha, respectively, reduced seed yields by 92 and 99% as compared to controls without causing significant changes in vegetative growth. These low application rates are within the range of reported herbicide drift levels and suggest that chlorsulfuron may cause severe reductions in the yields of some nontarget crops if they are subject to exposure at critical stages of development. Application of other herbicides at comparable rates and stages of plant development had no influence on either canola or soybean.

Researchers concluded that chlorsulfuron and perhaps other sulfonylurea herbicides appear to have influences on plant reproduction which are not characteristic of many common herbicides. Low application rates of chlorsulfuron influenced the reproduction of four taxonomically diverse species in a manner similar to that shown previously for cherries and green pea ( see above). In this study, canola and soybean were the most sensitive species to chlorsulfuron. Smart weed, a food source for waterfowl, was moderately sensitive and sunflower was insensitive except at the highest application rate and only one stage in development. Page 29 of 90 Analysis of spray drift data collected under field conditions have been reported by Bird ( 1992) to range, depending on meteorological conditions, from 0.02 to 2% of application at a distance as great as ¼ mile from the application zone. Since the application rates of chlorsulfuron used in this investigation fall withing this range, it follows that there may be occasions where chlorsulfuron may drift onto non target vegetation and severely curtail yield without causing noticeable effects on the vegetative growth or foliar appearance of the non target plants. If such events are occurring in agriculture, not only will it be difficult to recognize them but it will be virtually impossible to prove that chlorsulfuron was responsible for the episode, because the amounts of chlorsulfuron inducing yield reduction of soybean in this study are below the detection level of conventional chemical analysis ( Zahnow, 1982). The yield reduction that chlorsulfuron may cause in crops such as canola and soybean would not be expected for the other herbicides examined in this investigation.

Chlorsulfuron and other sulfonylurea herbicides are 100 times more toxic to the vegetative growth of plants than older, commonly used herbicides such as atrazine and 2,4 D ( Beyer, et al. 1988). Results of this greenhouse study suggest that sulfonylurea herbicides are even more toxic to plant reproduction. If certain crops such as soybean are exposed to chlorsulfuron concentrations of 1.8 x 10 4 kg/ ha or higher at critical stages during reproductive development, chlorsulfuron may be as much as 10,000 times more toxic to yield than other conventional herbicides such as atrazine and 2,4 D.

3.7.3 Non target Plant Incident Reports There are three non target plant incidents attributed to off site drift of chlorsulfuron ( Glean ® ) in the EPA's EIIS incident database. One incident occurred in the spring of 1990, near Benton City Washington ( Fletcher, 1991). Orchard growers alleged that herbicides applied to wheat fields in Horse Heaven drifted onto orchards in Badger Canyon and damaged cherry, apple, plum, and apricot crops. On numerous occasions between May 2 and June 5, 1990 investigators employed by the state of Washington investigated allegations of herbicide drift damage in Badger Canyon.

A report from the Washington State Dept. of Agriculture ( Fletcher, 1991) indicated that sulfonylureas, Express ® and Glean ® ( chlorsulfuron) were applied within a 5 to 15 mile arc south and west of Badger Canyon on dates ranging from March 26 to April 14, a time span which coincides with flowering and fruit set for cherry trees in Badger Canyon. The report also indicated that the wind direction and velocity favored drift of Glean herbicide from Horse Heaven Hills toward Badger canyon. Growers contended that sulfonylurea herbicides were most likely to be responsible for the damage because damage of this magnitude never occurred prior to the use of sulfonylurea herbicides on Horse Heaven Hills.

Examinations of two cherry and one apricot orchard clearly showed that the crop was exceptionally light in 1990 with some trees having virtually no fruit. There appeared to be less fruit on the west side of the orchards, the side facing Horse Heaven Hills. One orchard had numerous young apple trees with leader stems showed growth abnormalities typical of herbicide damage. Fletcher concluded that some of the damage observed in the orchards, such as viral infected leaves, was not due to herbicide drift. Fruit loss may have been due to herbicide drift. However, there is no conclusive evidence, such Page 30 of 90 as analytical data showing the presence of a sulfonylurea compound at the site of reported plant damage, in Badger Canyon.

According to another incident report (# I000230 001) in Benton WA, there was off target drift of aerially applied chlorsulfuron from a plateau devoted to wheat farming. The off target movement approximated a front equivalent to one land section. The drift allegedly resulted in extensive crop damage to an orchard. Peach trees were severely damaged, cherries and prunes suffered some damage. Young and old plantings were damaged alike. Peaches were not affected.

Consulting agrologists were called in to identify the source of the damage. They were able to duplicate the incident with the original resulting damage to peaches, cherries and prunes without damage to pears. This was achieved through the use of various herbicides and simulated drift. They were able to narrow the herbicide to one, to pinpoint the location of the treated wheat crop, and duplicate the drift pattern. The date of this event was not recorded. The certainty index in the EIIS report indicates that it is highly probable that this incident was caused by chlorsulfuron.

A third incident that was attributed to chlorsulfuron ( Telar ® ) and/ or 2,4 D occurred in Kentucky during April May, 1994 (# I001473 001). The report indicates that the state highway department applied two herbicides to a roadway. Subsequently, a farmer alleged injury to tobacco seedlings in a nearby greenhouse. The injury was described as turning yellow and stopping growth; a condition referred to as lance shaped leaves. The EIIS report indicates that 0.016 ppm of chlorsulfuron was found in samples taken during the incident. The certainty index indicates that this incident was possibly caused by chlorsulfuron and/ or 2,4 D.

It is often difficult to determine the cause of plant damage because many symptoms of toxicity in plants appear similar to disease and nutrient deficiencies. Furthermore, chlorsulfuron adversely effects plant growth and reproduction at such low levels that detecting residues in plant tissues or in soil samples may be extremely difficult or impossible using conventional analytical methods.

3.8 Risk Characterization for Terrestrial and Aquatic Plants Chlorsulfuron Estimated Environmental Concentrations ( EECs) resulting from labeled use rates and application methods greatly exceed LOCs for non target and endangered plants. Chlorsulfuron is very highly toxic to non target plants, as measured by an EC 25 of 4.0 x 10 6 lbs a. i./ acre and an EC 05 of 4.6 x10  8 lbs a. i. per acre ( vegetative vigor). Based on available data, it appears that the dose response curve for chlorsulfuron is shallow. Therefore, test concentrations were not low enough in the seedling emergence and vegetative vigor studies to determine the NOAEC for several plant species. More detailed summaries are provided in Appendices 4 and 5.

The representativeness of plants used in phytotoxicity testing of non target naturally occurring plants is uncertain. The range of plants used in testing is limited to annuals despite the fact that woody plants and other perennials are commonly found in agricultural areas. Moreover, homogenous crop test plant seed lots lack the variation that occurs in natural populations, so the test plants are likely to have less variation in response than would be expected from wild populations. Page 31 of 90 In some instances, specific test species may be indicative of an effect to another naturally occurring non target species. Native plants sharing species, genus or family affinity with the tested crop plant may show similar levels of sensitivity to a pesticide. For instance wild onions may show similar sensitivity to commercially grown onions to a particular herbicide. However, given the intensive breeding and selection that is used to develop commercial strains of a species, it is possible that natural and commercial plants of the same species may show very different responses.

A single aerial application of chlorsulfuron, assuming 5% of the applied drifts into non target areas, results in EECs as high as 0.003 lbs ai/ acre. Therefore, RQs for cereal, pasture/ rangeland, and fallow use sites based on maximum application rates range up to 1,042 for non target plants and up to 68,488 for endangered plants. The toxicity endpoint used in these RQ calculations was the shoot weight from the vegetative vigor study. If root weight was used instead, the risk quotients would be much higher ( Appendix 5).

Several of the non agricultural uses have multiple applications and several chlorsulfuron product labels do not specify important information on maximum application rates, numbers of applications, and methods of application. The risk quotients in Tables 10  14 were calculated assuming only one application of chlorsulfuron. If multiple applications are assumed, the risk quotients would be higher.

Most of the plant risk quotients are based on toxicity values derived from the seedling emergence and vegetative vigor study ( MRID 4258720 01). However, the test concentrations in this study were not low enough to determine the NOAEC for some endpoints and the EC 25 was calculated to be lower than the lowest test concentration. Therefore, the EC 05 was used in risk quotients for endangered species and the accuracy of this measurement is uncertain.

The amount of time that the LOC is exceeded was estimated using first order degradation. The results indicate that based on maximum application rates and a soil dissipation half life for chlorsulfuron of 60 days and using the seedling emergence endpoint, the LOC for non target plants is exceeded for approximately 300 days following a single application of 0.016 lbs ai/ acre to small grains and for well over a year for plants living in wetlands ( Appendix 7).

While EFED guideline laboratory plant toxicity tests required by the EPA do not include reproduction endpoints, results of field studies and green house studies conducted by researchers from the EPA laboratory in Corvalis, Oregon ( Fletcher et al. 1993 and Fletcher et al. 1996) indicate that chlorsulfuron adversely effects plant reproduction at concentrations likely to be found in the environment.

Additionally, the Dupont Vegetation Management Report of 2002 indicates that Telar DF ® ( chlorsulfuron) herbicide inhibits seed formation and the production of viable seed. This aspect is characteristic of Telar DF ® herbicide when applied at the rosette bloom stages of growth. The viability of weed seed is greatly reduced or eliminated following the application of Telar DF ® herbicides when applied prior to maturation of the seed embryo. The report also indicates that while grasses are very tolerant to Telar DF ® at early or late stages of growth, it should not be used on grasses grown for seed. Field research and practical use experience have demonstrated that numerous Page 32 of 90 desirable tree and shrub species ( established plantings) have a high degree of tolerance to Telar DF ® from incidental soil residual contact when used according to the label. However, tolerances to this product varies from species to species and site considerations.

Another source of uncertainty is the fact that current product labels recommend that chlorsulfuron be tank mixed with other common herbicides to ensure that resistant weeds are killed, which may result in synergistic effects to non target plants. Toxicity data on combinations of herbicides are lacking. However, current label precautions appear to suggest that synergistic effects may occur if chlorsulfuron is applied to fields to which certain other insecticides have been applied. For example, the label for Finesse ® states that " Finesse should not be used within 60 days of crop emergence if an organophosphate insecticide ( such as " Di Syston ® " ) was used as an in furrow treatment, or crop injury may result." Presumably, neither of these two pesticides if used alone will cause crop injury to wheat or barley. However, the label for Finesse ® indicates that they apparently do cause crop injury when used together. The label restricts the use of Finesse ® plus Malathion ® and the use of Finesse ® plus Lorsban ® in the Northwest, as crop injury may result. This suggests that there may be synergistic effects to plants when chlorsulfuron is applied to fields along with organophosphate insecticides. The Finesse Label also indicates that " Tank mix applications of Finesse plus Assert may cause temporary crop discoloration/ stunting or injury when heavy rainfall occurs shortly after application".

Furthermore, the extent to which indirect effects of chlorsulfuron occur in relation to endangered terrestrial and aquatic animals is uncertain. Several field studies have documented adverse effects of chlorsulfuron to cherry trees and other non target plant species. If these impacts are characteristic of native plant species, drifting chlorsulfuron may severely reduce growth and reproductive development of native plants, an important component of the habitat and food web for endangered wildlife.

3.8.1 Plants Exposed to Chlorsulfuron Drift Non target plants in areas where chlorsulfuron is applied may be exposed to short range drift ( 1 m to 1 km) and/ or longer range drift ( greater than 1 km). Drift may result from fine droplets which blow off target before settling ( spray drift) or potentially from treated soil blowing off target ( secondary drift). Although plants growing in proximity to application sites are expected to be at greatest risk of experiencing relatively high exposures to chlorsulfuron, longer range drift has been alleged to occur and cause visible effects to terrestrial plants ( Felsot et al. 1996). Symptoms of chlorsulfuron exposure to non target plants in areas away from application sites were documented during the same time period as spray applications, suggesting that drift in these instances was mostly due to the movement of spray droplets.

However, chlorsulfuron labels ( e. g. Finesse) include the following precaution: " To reduce the potential for movement of treated soil due to wind erosion, do not apply to powdery, dry, or light sandy soil until they have been stabilized by rainfall, trashy mulch, reduced tillage or other cultural practices. Injury to adjacent crops may result when treated soil is blown onto land used to produce crops other than cereal grains." Chlorsulfuron is persistent on soil at most pH's and the majority of Page 33 of 90 it is applied to winter wheat ( pre or post plant), which is commonly grown in dry regions. Therefore, the potential for treated soil to be blown off target and result in exposure to non target plants, should not be discounted.

While for some pesticides, application of fine sprays is important for control of target pests, chlorsulfuron's solubility, persistence, relatively low soil binding, and mobility within plants ( Weed Science Society 1989) suggests that covering weeds evenly with fine droplets is not necessary to control them. Because chlorsulfuron can move with soil water and be taken up by plant roots or absorbed through plant foliage and be transported systemically throughout the weed, relatively large droplets of chlorsulfuron contacting weeds or surrounding soil are expected to be effective in killing weeds. Coarse sprays minimize drift and are not expected to reduce efficacy. Chlorsulfuron product labels ( e. g. Finesse ® ) provide the following statement: " The most effective way to reduce drift potential is to apply large droplets (> 150  200 microns). The best drift management strategy is to apply the largest droplets that provide sufficient coverage and control." The language which is standard on most DuPont pesticide product labels provides suggestions of particular droplets sizes that reduce drift but do no require the applicator to use a specific droplet size spectrum. Although a range of droplet diameters is mentioned, chlorsulfuron labels do not describe a droplet size distribution ( such as the American Society of Agricultural Engineers standard definitions for droplet size) which is more appropriate for describing spray quality in regard to spray drift. When the product is applied according to the label directions, many fine, driftable droplets may be produced that do not result in improved weed control and result in off target movement and potentially in nontarget plant damage.

The distance that fine spray droplets may travel is largely dependent on their size, release height, and meteorological conditions like wind speed. Larger droplets tend to deposit in the application area or nearby while smaller droplets may be blown farther downwind. Droplet settling velocity, the speed at which droplets settle in air without turbulence, can be useful for conveying the importance of droplet size on off target movement. While a droplet with a diameter of 1000 µ m ( 1 mm) takes 1.3 seconds to fall 10 feet and would travel 13.7 feet downwind, in a 10 mph wind, a 100 µ m droplet takes 14 seconds to reach the ground and will travel 185 feet, and a 10 µ m droplet will take 18 minutes to reach the ground and travel 2.7 miles downwind. These calculations are simplified in that they don't take into account vertical mixing in the atmosphere, the range of droplet sizes produced by a nozzle, or, for aerial applications, the wake of aerial application equipment. It is possible to use spray drift models better account for these aspects of off target drift.

3.8.2 Plants in Semi Aquatic Areas ( Wetlands)

The EC 25 for non target plants is 3.1 x 10 5 lbs ai/ acre and the NOAEC for endangered species is 6.8 x 10  6 lbs ai/ acre based on the sugarbeet seedling emergence tests ( Table 11). For a single ground application of chlorsulfuron the EECs ranged from 0.0082 lbs ai/ acre for small grains ( wheat, barley and oats) to 0.032 lbs ai/ acre for pastures and rangeland. These EECs are calculated assuming 1.0 % off site drift and 5.0% runoff ( ten acres to one acre). Page 34 of 90 The RQs for non target plants range from 267 to 383 for small grains up to 1,042 for pasture and rangeland and for endangered plants RQs range from 1,200 to 1,725 for small grains up to 4,688 for pasture and rangeland. Therefore, ground application of chlorsulfuron to small grains, pastures and rangeland greatly exceed LOCs for non target and endangered plants inhabiting wetlands located near application sites. Based on PRZM/ EXAMS modeling, estimated environmental concentrations remain constant; therefore, the LOC is exceeded for well over a year ( Appendix 7). To calculate the EEC for aerial applications, 5.0% drift and 5.0% runoff ( 10 acres to one acre) are assumed. This results in RQs for aerial applications that are approximately 9% higher than for ground applications.

In the RQ calculations it is assumed that 1.0 % of the ground applied chlorsulfuron drifts to offsite areas and for aerial applications 5.0 % drifts offsite. However, field studies submitted by the Spray Drift Task Force ( Hewitt et al. 2002) and others reviewed by EPA ( Bird et al. 1996) suggest that downwind deposition from spray drift can be higher or lower than these values depending largely on droplet size applied, release height, and wind speed. RQs would be higher if it was assumed that a larger percent of applied chlorsulfuron drifts offsite. Spray drift data and models show droplets can travel more than a thousand feet downwind ( Teske et al. 2002). Given the high toxicity of chlorsulfuron to plants, and the distances that spray drift can travel, the potentially affected area around a treated field may be very large.

3.8.3 Terrestrial Plants ( Seedling Emergence)

To calculate the RQs for terrestrial plants the EC 25 for non target plants ( 3.1 x 10  5 lbs ai/ acre) and the NOAEC for endangered species ( 6.8 x 10  6 lbs ai/ acre) were used ( Table 12). For a single ground application of chlorsulfuron the EECs ranged from 9.6 x 10  4 lbs ai/ acre for small grains ( wheat, barley and oats) to 0.0038 lbs ai/ acre for pastures and rangeland. These EECs are calculated assuming 1.0 % off site drift and 5.0% runoff ( one acre to one acre). The RQs for non target plants range from 31 to 45 for small grains up to 123 for pasture and rangeland. For endangered plants RQs range from 141 to 203 for small grains up to 551 for pasture and rangeland. Therefore, ground application of chlorsulfuron to small grains, pastures, and rangeland greatly exceed risk LOCs for non target and endangered plants inhabiting areas near application sites.

The RQs for a single aerial application ( Table 12) are approximately 60% higher than for a ground application. To calculate EECs for an aerial application of chlorsulfuron, 5.0% drift and 5.0% runoff ( one acre to one acre) are assumed. The RQs for non target plants range from 52 to 75 for small grains up to 204 for pasture and rangeland. For endangered plants RQs range from 235 to 338 for small grains up to 919 for pasture and rangeland. Therefore, aerial application of chlorsulfuron to small grains, pastures and rangeland greatly exceeds risk LOCs for non target and endangered plants inhabiting areas near application sites. The LOC is exceeded for well over a year following chlorsulfuron application.

3.8.4 Terrestrial Plants ( Vegetative Vigor)

The vegetative vigor EC 25 for non target plants ( 4.0 x 10  6 lbs ai/ acre) and the EC 05 for endangered species ( 4.6 x 10  8 lbs ai/ acre) were used to calculate the RQs for terrestrial plants ( Table 13). For Page 35 of 90 a single ground application of chlorsulfuron the EECs ranged from 1.6 x 10  4 lbs ai/ acre for small grains ( wheat, barley and oats) to 6.3 x 10  4 lbs ai/ acre for pastures and rangeland. These EECs are calculated assuming 1.0 % off site drift and no runoff. The risk quotients for non target plants range from 40 to 58 for small grains up to 156 for pasture and rangeland. For endangered plants RQs range from 3,507 to 5,040 for a small grains up to 13,698 for pasture and rangeland. Therefore, ground application of chlorsulfuron to small grains, pastures and rangeland exceeds LOCs for nontarget and endangered plants inhabiting areas near application sites.

The RQs for a single aerial application ( Table 13) are five times higher than for a ground application. To calculate the EEC for an aerial application, 5.0% drift and no runoff was assumed. The risk quotients for non target plants range from 200 to 290 for small grains up to 800 for pasture and rangeland. For endangered plants RQs range from 17,533 to 25,202 for a small grains up to 68,488 for pasture and rangeland. Therefore, aerial application of chlorsulfuron to small grains, pastures and rangeland greatly exceeds LOCs for non target and endangered plants inhabiting areas near application sites.

Field studies conducted by researchers from the EPA laboratory in Corvalis Oregon have determined that chlorsulfuron adversely effects plant reproduction at concentrations likely to be found in the environment ( Fletcher et al. 1993 and Bahatti et al. 1995). However, laboratory plant toxicity tests required by the EPA do not include reproduction endpoints and available data evaluating this effect are very limited.

Greenhouse studies provide further evidence of potential adverse effects to non target plants. Fletcher et al. ( 1996) demonstrated that chlorsulfuron applications of 9.2 x 10 5 and 1.8 x 10 4 kg/ ha, respectively, reduced seed yields of canola and soybean by 92 and 99%, respectively, as compared to controls without causing significant changes in vegetative growth. These low application rates are within the range of reported herbicide drift levels and suggest that chlorsulfuron may cause severe reductions in the yields of some non target crops if they are subject to exposure at critical stages of development. Application of other herbicides at comparable rates and stages of plant development had no influence on either canola or soybean.

Additionally, as discussed in Section 3.7.3, a non target plant incident report from the Washington State Dept. of Agriculture ( Fletcher, 1991) indicates that growers contended that sulfonylurea herbicides, Express and Glean ( chlorsulfuron) were most likely responsible for damage to cherry trees in Badger Canyon because damage of this magnitude never occurred prior to the use of sulfonylurea herbicides on Horse Heaven Hills.

3.8.5 Plants Exposed to Irrigation Water Containing Chlorsulfuron Results of ground and surface water modeling indicate that in regions where chlorsulfuron is historically used, irrigation water from groundwater or surface water sources may contain levels of chlorsulfuron high enough to adversely effect non target plants. We are aware of only one groundwater monitoring study included chlorsulfuron as an analyte. Chlorsulfuron was only detected in one Page 36 of 90 sample at the limit of detection; however, the extent to which the monitoring occurred in the highest chlorsulfuron use area was not determined.

Risk quotients were also calculated for sensitive crops within irrigated fields. It was assumed that there are no endangered plants within the irrigated field. The RQs for crops range from 91 for irrigation using groundwater to 341 for using surface water to irrigate fields. Therefore, in regions where chlorsulfuron has been used historically, groundwater and surface water irrigation may result in damage to agricultural crops that are sensitive to chlorsulfuron. Irrigation using surface water increases the risk by over a factor of 3.

The above risk quotients were calculated assuming a one time exposure to irrigation water containing chlorsulfuron. If multiple irrigation events are assumed, the risk quotients would be higher. There may be a need for additional plant toxicity tests to determine how toxicity resulting from relatively low concentrations ( i. e 1.6 ppb) of chlorsulfuron in an inch of simulated irrigation water compares to the toxicity levels demonstrated in the vegetative vigor and seedling emergence studies that have already been conducted.

3.8.6 Aquatic Plants Several chlorsulfuron product labels do not specify important information on maximum application rates, numbers of applications, and methods of application. The risk quotients calculated in the assessment were based on a single application of chlorsulfuron to various agricultural crops. If multiple applications are assumed, risk quotients would be higher.

The peak EECs ( PRZM/ EXAMS) based on a single chlorsulfuron application range from 4.2

g/ L for wheat to 9.5

g/ L for turf ( Table 4). The assumptions used in this modeling are provided in section 2.2. The EC 50 for Lemna gibba is 0.35

g/ L the NOAEC is 0.24

g/ L ( Table 9). The RQs for non target aquatic plants range from 12 to 21 and for endangered aquatic plants the RQs range from 18 to 40 ( Table 10). Therefore, RQs for non target and endangered aquatic plants found in water bodies adjacent to application sites exceed the LOCs.

Additionally, results of Coyner et al. ( 2000) indicate that P. pectinatius, exposed to chlorsulfuron at 0.25 ppb for 4 weeks showed a 76% reduction in length and a 50% reduction of stems and leaves compared to control plants. Calculations using these toxicity values and the above EECs result in risk quotients ranging from 17 to 30 for non target aquatic vascular plants.

3.8.7 Refined Assessment of Spray drift on non target Terrestrial Plants The following assessment is focused primarily on chlorsulfuron use on crops and is intended to accurately reflect the most important application conditions actually used in applying chlorsulfuron to assess spray drift risks to non target plants. Application parameters used by aerial applicators in Washington and Oregon were used to estimate a range of spray drift levels in this assessment. Reports of set ups for ground boom applications were not available and thus ground boom configurations were assumed to include the range of values available in the AgDRIFT model. Page 37 of 90 Laboratory toxicity data used in this analysis were limited to effects occurring in a relatively short amount of time after a single exposure. A number of published reports suggest that chlorsulfuron, and other herbicides with the same mode of action, may result in delayed effects on crop yield and plant reproduction at levels lower than those noted to cause short term visible effects ( for a review see Ferenc 2001). If reproductive effects occur at similar or lower levels than laboratory phytotoxicity data used in this analysis, delayed effects may occur at distances substantially greater than 1000 feet from applications.

This assessment focuses on the effects of spray drift on non target terrestrial plants. Exposure from chlorsulfuron runoff can also cause phytotoxicity to non target plants. Chlorsulfuron's mobility and persistence in soil suggests that runoff may be an important route of exposure to non target plants down slope of application areas. Plants in up slope areas are not affected by runoff but may be damaged by spray drift.

Use Pattern Evaluated This refined assessment focused on chlorsulfuron use on grain crops, such as wheat. According to the USGS and USDA, this use accounts for more than 98% of agricultural chlorsulfuron usage. The maximum application rate for wheat on the Glean product label is 0.023 lbs ai/ acre. Product label rates for wheat are 0.0078 to 0.016 lbs ai / acre with application per crop season ( Finesse product label). Up to 0.0625 lbs ai/ acre may be used on pasture/ rangeland and higher application rates are allowed for industrial areas. Use information is summarized in Table 1.

Chlorsulfuron is applied as a liquid spray and, for most uses, may be applied by ground or air. Directions for ground applications to wheat ( Glean label) suggest that spray volume should be at least 3 gallons/ acre for flat fan nozzles or 20 gallons/ acre for Raindrop or flood jet nozzles. The lower volume is presumably allowed for the flat fan nozzle because this commonly used nozzle can produce a fine enough spray to cover the field with the low volume of 3 gallons/ acre. With a volume of 3 gallons/ acre, a relatively coarse spray would result in too few drops per unit area to adequately distribute the herbicide and control weeds in that area. Raindrop and flood jet nozzles are two models of nozzle that can be used to produce coarser sprays. With coarser sprays, higher volumes are generally necessary to result in adequate coverage of treated fields and weeds for control. ( For information on the design of flat fan and flood jet nozzles and their relative drift levels see http:// www. hardi international. com/ Agronomy/ Educat ion_ Material/ pdf/ 04a. pdf or http:// lancaster. unl. edu/ ag/ factsheets/ 289. htm).

DuPont conducted a small survey of aerial applicators as an indication of typical aerial application parameters ( see Appendix 9a). The DuPont survey included 15 aircraft set ups for chlorsulfuron applications in Washington and Oregon. Reported in the survey is the application volume ( gallons per acre), boom length ( relative to wingspan), nozzle type, nozzle angle, aircraft speed, spray pressure, and variables that were assumed in order to calculate spray droplet size. The droplets size spectra estimated from the equipment variables ranged from ASAE medium to ASAE coarse. Page 38 of 90 Toxicity Toxicity tables for the successive plant life stages ( seedling emergence and vegetative vigor) are in Appendix 4 and 5. The most sensitive species tested were sugarbeet ( seedling emergence, EC 25 3.8 x 10 5 lbs ai/ acre) and onion ( vegetative vigor, EC 25 4.4x10 6 lbs/ ai acre). The most sensitive effects measured in these tests were reductions in shoot weight and plant height. The phytotoxicity data was limited in that the confidence in the estimated EC 05 and NOAEL was low.

Non target plants exposed to herbicides may be killed outright or weakened, reducing their fitness. Non lethal effects could cause plants to become more susceptible to plant pathogens, become less effective in competing with sympatric species, or reduce reproductive success. In instances where herbicide exposure effects fertilization or seed production, reproduction of plants in the wild would be expected to be reduced and population level changes could occur.

The representativeness of plants used in phytotoxicity testing of non target naturally occurring plants is uncertain. The range of plants used in testing is limited to annuals despite the fact that woody plants and other perennials are commonly found in agricultural areas. Moreover, homogenous crop test plant seed lots lack the variation that occurs in natural populations, so the test plants are likely to have less variation in response than would be expected from wild populations.

In some instances, specific test species may be indicative of an effect to another naturally occurring non target species. Native plants sharing species, genus or family affinity with the tested crop plant may show similar levels of sensitivity to a pesticide. For instance wild onions may show similar sensitivity to commercially grown onions to a particular herbicide. However, given the intensive breeding and selection that is used to develop commercial strains of a species, it is possible that natural and commercial plants of the same species may show very different responses.

Phytotoxicity Tests and Spray Drift Spray drift exposure to plants away from field edges is expected to result in relatively few concentrated droplets depositing on and around plants. In contrast, laboratory vegetative vigor and seedling emergence phytotoxicity tests, use relatively high volumes of spray to better cover the test plant or the soil surface. In instances where an herbicide's movement in plants or soil is limited, the test conditions of the phytotoxicity studies may result in higher measured toxicity than would result from spray drift away from the field's edge. In the instance of herbicides that are mobile within plants and soil, such as chlorsulfuron which is mobile in soil and can be transported throughout exposed plants, the volume of spray used for the exposure may not alter the magnitude of the toxic effect.

Exposure Current Label Directions relevant to Spray Drift Chlorsulfuron product labels have very few restrictions on how and under what conditions the product may be applied. For instance there are no droplet size, wind speed, or boom height Page 39 of 90 restrictions. The absence of bounds makes it more difficult to determine what conditions should be used for risk assessment. The absence of basic mandatory label language also allows applicators to make unnecessarily high drift applications. Applicator common sense would prevent worst case applications but may not result in optimal applications. For instance it is unlikely that an applicator would make a ground boom application with a high boom and a fine spray because drifting spray would be visible and it would be apparent that the efficiency of the application was low. However, without proper guidance an applicator may use a low boom but a finer spray than necessary to achieve control. Under this scenario drifting spray would be less visible but still unnecessarily high. Specifying basic spray drift control measures provides applicators with the necessary information to perform an effective and low drift application and risk assessors with the necessary information to model drift.

AgDRIFT Background AgDRIFT is a computer model that can be used to estimate downwind deposition of spray drift from aerial, ground boom, and orchard and vineyard airblast applications. The model contains three tiers of increasing complexity. In Tier 1, the user can assess downwind deposition from a single application from all three application methods under default conditions. The current version of AgDRIFT only allows Tier 1 level analyses for ground and airblast application methods. In higher tiers more options are available for aerial applications. The aerial portion of the model is based on a mechanistic US Forest Service model ( AGDISP. Bilanin et al 1989). The ground boom and orchard airblast portions are empirical models based on data collected by the Spray Drift Task Force ( SDTF). The SDTF field data were used to validate the aerial portion of AgDRIFT ( Bird et al 1996a and 1996b). AgDRIFT was developed under a cooperative research and development agreement between EPA, USDA, and the SDTF.

Aerial AgDRIFT: The most important factors affecting drift from aerial applications are spray quality ( droplet size), release height, and wind speed. The aerial part of the model predicts mean values based on the inputs provided. The Tier 1 aerial results are generated using the specified droplet size spectra, 10 foot release height, and a 10 mph wind speed. When wind speed and/ or release height is lower than the modeled values the spray drift levels would be expected to be lower. Conversely, in instances where applications may be made in higher wind speeds or at a higher release height these inputs may not be adequately conservative and higher tier modeling may be necessary.

Ground boom sprayers in AgDRIFT: The most important factors affecting drift from ground boom applications are spray quality, release height, and wind speed. The ground boom part of AgDRIFT is based on field trial data from bare ground applications. The results of the model reflect the quality and conditions of the data on which it is based. The data from the field trials were grouped into categories by spray quality ( droplet size) and release height. Results from field trials conducted with different wind speeds were averaged. The average wind speed over all the trials was approximately 10 mph. AgDRIFT outputs for ground boom applications estimate the 50th and 90th percentile of data collected from field trials. For this analysis the 50th percentile data was used. The field trial data were not corrected for incomplete analytical recoveries, suggesting the true mean deposition values would be approximately 20% higher than the model's deposition results. 1 Toxicity slopes are calculated from dose response relationship of chlorsulfuron on of the test plant species. Species with high ( steep) slopes show large increases in toxicity from small increases in exposure. Species with low ( shallow) slopes show small increases in toxicity from relatively large increases in exposure.

2 A log normal toxicity distribution is assumed. The following equation is used to calculate the various EC x levels: [ EC 25 / 10 0.67/ slope] x 10 a/ slope = EC x where a = 1.28, 0.84, 0.54, 0.25, 0,  0.25,  0.54,  0.84, and  1.28 for EC 10, EC 20, EC 30, EC 40, EC 50, EC 60, EC 70, EC 80, EC 90, respectively.

Page 40 of 90 Phytotoxicity and Downwind Distance Using the AgDRIFT model ( version 2.01) and registrant submitted phytotoxicity data ( MRID 42587201, McKelvey and Kuratle 1992) it is possible to estimate distances downwind from application areas at which a particular toxic effect level would be experienced by a particular tested plant species. To make Figures 2 through 7 below, EC 25 values ( for vegetative vigor shoot weight) of the tested species were used with the toxicity slope1 from each species to calculate EC 10, EC 20, EC 30, to EC 90 effect levels2. These EC x values were entered into an Excel spreadsheet with Tier 1 AgDRIFT ( version 2.01) deposition distance results and the maximum chlorsulfuron application rate for pasture/ rangeland ( 0.0625 lbs ai/ acre). Excel then calculated estimated downwind deposition levels for chlorsulfuron use on pasture/ rangeland and compared the deposition values to the EC x values to identify the downwind distance at which the EC x values would be reached. Excel arranged the distances into three dimensional bar charts showing the downwind distance at which a particular toxicity level for each species is expected to occur under the Tier 1 AgDRIFT conditions with the specified application rate.