### 1 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



### DP Barcode: 374620 PC Code: 035301, 035302, 129820 December 16, 2010 MEMORANDUM SUBJECT: Drinking water assessment for ground and aerial application of bromoxy nil on grass grown for seed and ground application of sorghum. TO: Bethany Benbow

Herbicide Branch Registration Division Cassi Walls, Risk Assessment Branch 3 Health Effects Division FROM: Tiffany Mason, Environmental Engineer

Environmental Risk Branch II Environmental Fate and Effects Division THRU: Brian Anderson, Chief

Environmental Risk Branch II Environmental Fate and Effects Division Jean Holmes, DVM, MPH , Risk Assessment Process Leader Environmental Risk Branch II Environmental Fate and Effects Division R. David Jones, Ph.D., Senior Agronomist Environmental Risk Branch II Environmental Fate and Effects Division

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CONCLUSIONS This drinking water assessment is for a mixture of bromox yn il octonoate (PC Code 0 35302), bromox yn il heptanoate (PC Code 128920), and py rasulfotole (PC Code 000692) for two new uses on grasses grown for seed and sorghum. The risk assessment considers the use of bromox yn il octanoate and bromoxy nil heptanoate as proposed on the supplemental label for Huskie Herbicide (EPA Registration Number 264 - 1023). Since bromox yn il heptanoate is chemicall y and ph ys ically similar to bromoxy

nil octanoate (one carbon difference in the ester side chain) and both esters rapidly degrade to bromoxy

nil pheno l (aka bromoxy

nil, PC Code 035301), all calculations have been performed in terms of bromoxy nil. Py rasulfotole, another registered product on the proposed label, is evaluated in a separate assessment and will not be evaluated in this assessment. This ass essment replaces the revised drinking water assessment for the use of bromox ynil on cotton completed August 11, 1997. Although those numbers were higher, the model versions used for that assessment have been superseded and the guidance has been updated. Bromox ynil is a selective herbicide used for pre - and post - emergent weed control for certain broadleaf weeds in wheat, barley , conservation reserve program acres (CRP), grass grown for seed, oats, rye, sorghum (grain and forage), and triticale. This assess ment is for two use patterns: grass grown for seed and sorghum. These use patterns have been previously registered for bromox yn il, however, this new product contains bromoxy nil and py rasulfotole (PC Code 000692) and requires reassessment of the use pattern s for drinking water exposure. The proposed new use for grasses grown for seed has a maximum label - specified use rate per ye ar of 2 applications (30 ounces per acre per ye ar formulation or approximately 0.57 lb a.i. [bromoxy

nil] per acre per ye ar), 30 days apart, at the rate of 0.15 oz of formulated product/acre (approximately 0.286 lb. a.i. [bromox yn il phenol]/acre). The proposed new use for sorghum has a maximum label - specified use rate per year of 2 applications (32 ounces per acre per year formulation o r approximately

0.61 lb a.i. [bromoxy

nil phenol] per acre per year), 11 day s apart, at the rate of 0.16 oz of formulated product/acre (approximately 0.305 lb. a.i. /acre). B ased on the proposed application rate and the environmental fate properties of bromoxy nil, surface and ground water contamination may occur. The estimated environmental concentrations (EECs) generated b y the FIRST model are listed below. For drinking water derived from surface water, the acute and chronic concentrations to be used are 11.5 μg/l and 0.19 μg/l for the ground use on sorghum ( Table 1). For drinking water derived from ground water, the SCI - GROW model estimates bromoxy nil concentrations of 1.33 ng/l for the ground use on sorghum (Table 1). Ground water numbers were not generated in the previous drinking water assessment performed August 11, 1997. The SCI - GROW value that should be used for acute, chronic, and the cancer risk assessment is 3.26 ppb for the revised cotton assessment.

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Tabl e 1. Tier I EEC's for Bromox ynil for the aerial use and ground use on grasses grown for seed and ground use on sorghum using FIRST and SCI - GROW models. Surface Water Ground Water Use Pattern Peak EEC (ug/L ) Annual Mean EEC (ug/L) Peak and Mean EEC

----------------------- ug/L --------------------------- ng/L Grasses for Seed 10.2 0.17 1.24 Sorghum 11.5 0.19 1.33 Revised Cotton Numbers Cotton 4.34 0.07 3.26 Environmental Fate Summary Surface and ground water contamination may occur from the common degradate (bromoxy nil phenol aka bromox ynil) of the two ester bromox ynil formations (bromox ynil octanoate and bromox yn il heptanoate), as opposed to the esters themselves . Since bromoxy nil heptanoate is chemicall y and ph ys ically similar to bromoxy

ni l octanoate (one carbon difference in the ester side chain) and bromox ynil octanoate rapidl y degrades to bromox ynil (t 1/2 

### ≈ 2.1 day s), it is believed that bromox ynil heptanoate would behave similarly. Therefore, all calculations have been performed in ter

ms of bromox yn il instead of the esters. There is no evidence that bromox yn il degrades by abiotic hydrol ys is at any measured pH (MRID 41892901) or b y photolysis (MRID 42234301, 41920401). Residues of bromoxy nil appear to be moderatel y mobile to highly mob ile in with three out of four soil - water partitioning coefficients (Kd 

### ) less than three (MRID 110429) and appear to have no significant correlation with the soil organic carbon content. The field dissipation studies show that bromox yn il residues dissipated with half - lives of 1 to 14 day s and were not detected below 15 cm soil depth (MRID 41653701, 43071001) indicating that leaching is not an anticipated route of dissipation, likely due to the rapid degradation rate. Surface and ground water contamination may occur from the common degradate (bromoxy nil phenol , aka bromox ynil) of the two ester bromox ynil formations (bromox ynil octanoate and bromox yn il heptanoate), as opposed to the esters themselves . Since bromoxy nil heptanoate is chemicall y and ph ys ically similar to bromoxy

nil octanoate (one carbon difference in the ester side chain) and bromox ynil octanoate rapidl y degrades to bromox ynil (t 1/2 

### ≈ 2.1 day s), it is believed that bromox ynil heptanoate would behave similarly. Therefore, all calculations to determine acute toxicity

has been performed in terms bromoxy nil octanoate, and chronic toxicity has been performed in terms of bromoxy nil instead of the esters. Abiotic Hydrolysis Hydroly sis of bromoxy

nil octanoate is base - catalyzed with half - lives of 34.1 day s at pH 5, 11.5day s at pH 7, and 1.7 day s for pH 9. The hydroly sis products were 3,5 - dibromo - 4 -

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hydrox yb enzonitrile(referred to as bromox ynil (phenol)), and 3,5 - dibromo - dihydrox ycyclohexadienylnitrile. Bromoxy nil(phenol), which is stable to hydro ly sis, increased throughout the study , reaching maximumconcentrations at 30 day s of 35%, 77%, and 76% at pH 5, 7, and 9, respectivel y. The degradate 3,5 - Dibromo - dihydroxy- cyclohexadienylnitrile concentrations reached maximum concentrations of 10.4%,10.7%, and 7.9% at pH 5, 7 and 9, respectivel y, but declined from those values by the end of the study,indicating that it was not stable to hydrol ys is. (MRID41892901). In another study bromoxynil octanoate hydrol yz ed with calculated half - lives of 43 day s at pH 5,28 day s at pH 7, and 1.5 day s for pH 9. Hydroly sis of bromoxy nil buty rate (an ester of bromox yn ilwhich is currently not being registered) is base - catal yz ed with calculated half - lives of 44 day s at pH 5,52 day s at pH 7, and 1.1 day s for pH 9. Bromoxy ni l (phenol) was the hydrol ys is product for both theoctanoate and the butyr ate. It was stable to hydrol ys is at pH 5, 7, and 9. The study was consideredacceptable. (MRID 00130424). Aqueous Photolysis Bromox ynil octanoate degraded with a calculated photol ytic half - life of 4.6 day s at pH 5. Eachphotoperiod consisted of 12 hours of light (artificial - xenon arc lamp) and 12 hours of darkness.Bromox ynil octanoate was stable in the dark controls with a 110.7 - day half - life. In the irradiatedsamples there were 3 major degradates: 4 - cyano - 2 - bromophenyl octanoate (maximum meanconcentration of 13.9% at day 3), bromoxy

nil (phenol) (maximum mean concentration of 53.4% at day30), and phenyl carbamate (maximum mean concentration of 26.6% at day 2). (MRID 42234301 an d 41920401). Soil Photolysis Bromox ynil octanoate degraded with a calculated photoly tic half - life of 2.6 day s in the irradiatedsamples (artificial - xenon arc lamp) and 3.6 day s in the dark control. The 3.6 day half - life in the darkcontrols suggests oth er degradation processes such as hydroly sis or microbial metabolism, wereoccurring. (MRID 41920402). Aerobic Soil Metabolism [Cyano labeled 14C] - bromoxy nil octanoate degraded in a sandy loam soil with a calculated halflifeof 2 day s. The major degradate was CO2 which accounted for 64.28% of the applied radioactivity

at 90 day s. (MRID 42234302 and MRID 41897701). Bromoxy nil (phenol) exhibited half

- lives of 51 hr in sandy

loam and 31 hr in loam soils (MRID 00142958). (MRID 42234302, 41897701 and 00142958 ). Anaerobic Aquatic Metabolism Bromox ynil octanoate degraded in a sandy loam sediment with a calculated half - life of 3.7 day sbased on the results obtained over the first 14 day s of the experiment. The degradate 4 - hydrox yb enzonitrile reached a maximum co ncentration of 45.52% b y Day 14 before decreasing to 0.14% at 26 weeks. Bromox ynil (phenol) was also formed, reaching a maximum concentration of48.5% by day 7, then decreasing to 3.5% at 8 weeks. (MRID 42234303 and 41892902).

### 5

Aerobic Aquatic Metabolis m Bromox ynil octanoate degraded with a half - life of <12 hours when treated sandy loam soil wasflooded with pond water which was aerobically incubated in the dark at approximately 25 C.Bromox ynil octanoate was 87.64% of the applied at time 0 and declined t o undetectable levels by 48hours posttreatment. The major nonvolatile degradates were bromoxy nil (phenol), p hydrox yb enzonitrile, 3 - bromo - 4 - hydrox ybenzonitrile, and 3,5 - dibromo - 4 - hydroxy benzoic acid. Thedegradate bromox yni l (phenol) was 6.59% of the appl ied immediatel y posttreatment, 66.47% at 12hours, 78.77% at 48 hours posttreatment, 39.68% at 168 hours, and 2.39 - 4.56% at 336 through 720 hours. (MRID 42364901). Unaged Soil Column Leaching [14C]Bromox yn il OctanoateBromoxy nil octanoate was mobile in co lumns of sand, sandy loam, and loam soils that weretreated at 228.9 g/column with phenyl ring - labeled [14C] bromoxy nil octanoate and leached with 50.8cm of a 0.005 M calcium chloride solution. Residues were distributed throughout the length of eachsoil co lumn and ranged from 2.7 - 18.2% of the applied in the leachates from the sandy loam - 1, sandyl oam - 2, and loam soil columns; and from 52.4 - 58.9% in the leachates from the sand soil columns. Inthe 0 - 7 cm segment of the columns for sandy loam - 1, sandy loam - 2 and sand soil, the recoveries wereapproximately 31 - 43%, 31 - 35%, and 13%, respectivel y. (MRID 42271101). Aged Bromoxynil Octanoate Residues Aged bromox ynil octanoate (2,6 - dibromo - 4 - cyanophenyl octanoate) residues were not mobilein columns of four soils and an aquatic sediment that were treated with bromoxy nil octanoate that hadbeen aerobically

aged (aerobic half

- lives of 28 - 100 hours) and then leached with 50.8 cm of a 0.01 Mcalcium chloride solution. Residues in the sandy loam, loam, clay

loam, and aqu atic sediment columnswere concentrated in the segment composed of the aged soil and the segment immediately

beneath it: 14 

### C in the leachates was 0.27% of the applied. Residues in the sand soil columns moved slightly

morethan in the other soils, but remain ed concentrated in the upper two segments of the columns (top 10cm); any 14C - residues in the leachates were [14C] - carbonates and were 3.50 - 3.58% of the applied. (MRID 42271101 and 43775001). Adsorption/Desorption Batch Equilibrium Bromox ynil octanoate wa s found to be mobile in sandy loam soil with pH 7.2 and 1.1% organicmatter. The Kd was 7.0 (Koc=1,003). The study was considered supplemental and did not satisfy

datarequirements because the study authors failed to show that the aerobic soil metabolism h alf

- life of thesandy

loam soil was much greater than the equilibration time of 24 hours in the batch equilibrium study (MRID #00116557 and 00114338). However, this data requirement is fulfilled using the agedand unaged column leaching studies (GLN 163 - 1; MRID 42271101 and 43775001). Laboratory Volatility and Field Volatility This data requirement was waived based on the low vapor pressure (1.39 x 10 - 6 mm Hg) and

### 6

estimated Henry ’s Law Constant (9.76 x 10 - 8 atm - m3 /mol). (EFGWB # 91 - 0200 - 0199, 1/17/91). Fish Accumulation [14C]Bromox yn il octanoate residues accumulated in bluegill sunfish continuously exposed to [14C]bromox yn il octanoate at 1.3 - 4.7 g/L. The maximum bioconcentration factors were 63x for edible tissue, 400x for inedible tissue, and 230x f or whole fish. Depuration occurred with 85 - 97% of theaccumulated residues eliminated b y Day 14. (MRID42277301 - a and 42277301 - b). Terrestrial Field Dissipation Bromox ynil, spray applied at 0.56 kg ai/ha to plots planted in wheat, dissipated with observe d half - lives (DT 50 

### ) of approximately 14 day s from a Sorrento silt loam soil in California and 1 day from a Norfolk sandy loam soil in North Carolina. At both sites, bromox yn il octanoate residues were not detected below the 0 - 15 cm soil depth indicating le aching was not an important route of dissipation. In San Juan Bautista, California, air temperatures ranged from 39 o 

### to 96 o 

### F and the soil temperatures(10 - cm depth) ranged from 55 o 

### to 77 o 

### F . The field plots in California were irrigated with 30.5 mm of water to supplement the limited rainfall before day 20. In Clay ton, North Carolina, air temperatures ranged from 19 o 

### to 35 o 

### C and soil temperatures (10 - cm depth) ranged from 23 o 

### to 30 o 

### C. Total rainfall during the study was 245 mm; therefore, irrigation was not applied to field plots. Results of a freezer storage stability study indicate there was no significant degradation of either bromox ynil octanoate orbromox ynil (phenol) in the Califo rnia or North Carolina soils used in the field studies. (MRID 41653701 and 43071001). Nitrification Inhibition Bromox ynil has been shown to inhibit nitrification in soils (Frear, 1976). Nitrification is defined as the oxidation of reduced nitrogen (e.g. , ammonium) by bacteria (Nitrosomonas, Nitrobacter species) to nitrate through the intermediate product, nitrite (Brady and Weil, 1996). Various environmental factors such as soil reaction (acidity and alkalinity), aeration, moisture, carbon sources, temp erature and nutrient availability influence the nitrification process. For certain environmental conditions, commerciall y- available nitrification inhibitors (Dwell®, N - Serve®) are used in production agricultureto temporarily slow conversion of ammonium fertilizers to nitrate because nitrate can be lost through leaching or denitrification. In the environment, adaptation to nitrification inhibitors, such as bromoxyn il, is demonstrated by the increasing bromox yn il concentrations that are needed to cause 50% inhibition(Frear, 1976). In addition, these adaptation studies support the observation that microbial - mediatedmetabolism (aerobic soil metabolism half

- lives of 31 - 51 hours; field dissipation half - life of 1 - 14 days) is an important process for degradation of bromoxy nil in soils; therefore, nitrification inhibition would generall y occur onl y on a temporary basis. Thus, nitrification inhibition by bromoxy nil does not appear to be a concern. Table 3. Summary of Bromoxynil Environmental Fate Properties

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Study Value and unit Major Degradate Minor Degradates MRID # or Citation Study

Classification, Comment Abiotic Hydrolysis Half - life 1 = pH 5 = 34.1 - 43 days pH 7 = 11.5 - 28days pH 9 = 1.1 - 1.7 days 3,5 - dibromo - 4 - hydroxybenzonitrile, 3,5 - dibromo - dihydroxy cyclohexadienylnitrile(10.7%), Bromoxynil Phenol (76%) MRID 41892901 00130424 Acceptable

Direct Aqueous Photolysis Half - life 1 = 4.6 days (pH 5, 12 hrs of darkness) 4 - cyano - 2 - bromophenyl octanoate (max mean concentration 13.9%), Bromoxynil phenol (max mean 53.4%), Phenyl carbamate (max mean 26.6%) MRID 42234301 41920401 Acceptable Soil Photolysis Half - life 1 = 2.6 days (irradiated sample, 3.6 days in dark control) Bromoxynil phenol (99%) MRID 41920402 Acceptable Aerobic Soil Metabolism Half - life 1 = 2 days, sandy loam Bromoxynil phenol: Half - life 1 = 31 - 51 days, loam soils CO 2 (64.28%)

Bromoxynil phenol (44.59%) 3 - bromo - 4 - hydroxybenzamide (0.42%) 3,5 - dibromo - 4 - hydroxybenzamide (5.41%) 3,5 - dibromo - 4 - hydroxybenzoic acid (0.37 %) MRID 42234302 41897701 00142958 Acceptable

Anaerobic Soil Metabolism Half - life 1 = 3.7 days 4 - hydroxybenzonitrile

(45.52%), Bromoxynil phenol (48.5%) MRID 42234303 41892902 Acceptable Aerobic Aquatic Metabolism Half - life 1 = < 12 hrs Bromoxynil phenol (78.77%),

p - hydroxybenzonitrile (25.6%), 3 - bromo - 4 - hydroxybenzonitrile (12.10%), 3,5 - dibromo - 4 - hydroxybenzoic acid (12.0%) MRID 42364901 Acceptable Anaerobic Aquatic Metabolism Half - life 1 = 3.7 days Bromoxynil phenol (48.48%),

4 - hydroxybenzonitrile (46.32%), 3 - bromo - 4 - hydroxybenzonitrile (nominal) MRID 42234303 41892902 Acceptable Solid - water distribution coefficient (Kd) Kd = 7.0 L/kg (sandy loam, pH 7.2, 1.1% organic matter) Not reported MRID 00116557 00114338 42271101 43775001 Supplemental Organic - carbon normalized KOC = 1,003 L/kg (sandy loam, Not reported MRID 00116557 Supplemental

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Study Value and unit Major Degradate Minor Degradates MRID # or Citation Study

Classification, Comment distribution coefficient (KOC ) pH 7.2, 1.1% organic matter) 00114338 42271101 43775001 Soil Column Leaching Residues very mobile in sand, sandy loam, and loam soils, 2.7

– 18.2% radioactivity remained in soil column and 52.4

– 58.9% recovered in leachate. CO 2 (12.1%), Bromoxynil phenol (found in sandy loam soil and lechate - % not reported), 3 - bromo - 4 - hydroxybenzonitrile (found in lechate only - % not reported) MRID 42271101 43775001 Acceptable Volatility from Soil (Laboratory) No Study No Study No Study Waived Terrestrial Field Dissipation Bromoxynil octanoate: No study Bromoxynil phenol: Dissipation Half

- life 1,2 = 14 days (silt loam soil in CA), 1 day (sandy loam soil in NC) CO 2 (33.6%), 3,5 - dibromo - 4 - hydroxybenzamide (21.6%), 3,5 - dibromo - 4 - hydroxybenzoic acid (34.8%) MRID 41653701 43071001 Acceptable Aquatic Field Dissipation No Study N o Study No Study No Study Bioconcentration Factor (BCF) Bluegill sunfish (63 x for edible tissue, 400x for indedible tissue, 230x for whole fish) Bromoxynil phenol (79%, in fish tissue) MRID 42277301 - a 42277301 - b Acceptable Abbreviations: wt=weight 1 Half - lives were calculated using the single - first order equation and nonlinear regression, unless otherwise specified. 2 The value may reflect both dissipation and degradation processes. *D egradates less than 10% are considered minor degradates unless deemed of toxicological concern. All minor and major degradates above were not included in modeling calculations because they do not appear to be of toxicological conern. The esters and the phenol are much more toxic with the esters being an order of magnitude (in some cases) more toxic than the phenol. 

### Water Resources Summary A. Monitoring Below (Table 2) is a summary of monitoring data found on bromoxy nil from the USGS NAWQA surface and ground water database (http://infotrek.er.usgs.gov/apex/f?p=136:1:0::NO :::) and California Department of Pesticide Regulation ( CDPR) surface water database (http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm).

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The NAWQA database had taken 7,218 samples for bromox yn il across the United States. It is believed that these samples represent bromox ynil phenol, but cannot be verified since USGS did not differentiate between bromoxy nil phenol, bromoxy

nil octanoate, bromoxy

nil heptanoate, or bromox yn il buty

rate. Out of 7, 218 samples, there were 54 confirmed detections ranging in concentration from 0.001 μg/L to 6.1 μg/L . Of those 54 detections, 40 were s amples taken from streams, 8 from ground water sources, 4 from waste water treatment effluent, and 1 from a water distribution system. The rest of the samples were below the detection limit. The California Department of Pesticide Regulation ( CDPR) datab ase looked for both bromox ynil and bromox ynil octanoate. Out of 531 samples and approximately 29 sites, taken from February 8, 1993 to January

6, 2005, 192 were for bromoxynil octanoate, and 339 were for bromoxy nil. There were two detections, one for brom oxy nil and one for bromoxy

nil octanoate. Both occurred on May

9, 1997 in Yolo County , CA with a concentration of 0.06 μg/L . It is possible these two detections at the same location, date, and concentration could be the same bromoxy nil compound.

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Table 2 . Surface and Groundwater detections of Bromoxy nil from CDPR and USGS NAWQA databases. USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Allegheny and Monongahela Basins ST PA - ALLEGHENY 3049646 Deer Creek Near Dorseyville, Pa 0.07 Williamette Basin ST OR - CLACKAMAS 14202000 Pudding River At Aurora, Or 0.03 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0032 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0043 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0059 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.006 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0074 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0086 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0096

### 11 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0344 Williamette Basin ST OR - MARION 14201300 Zollner Creek Near Mt Angel, Or 0.0409 Williamette Basin ST OR - MULTNOMAH 14211720 Willamette River At Portland, Or 0.0043 White, Great and Little Miami River Basins ST IN - HAMILTON 395743086030501 White R, W Bank, 1 Rmi Us 116th St At Fishers In 0.0041 Upper Mississippi River Basin ST MN - CARVER 5330000 Minnesota River Near Jordan, Mn 0.02 Upper Illinois River Basin ST IL - LA SALLE 5553500 Illinois River At Ottawa, Il 0.02 South Platte River Basin ST CO - WELD 6753990 Lonetree Creek Near Greeley, Co. 6.1 San Joaquin - Tulare Basins ST CA - MERCED 11273500 Merced R A River Road Bridge Nr Newman Ca 0.0132 San Joaquin - Tulare Basins ST CA - STANISLAUS 11274538 Orestimba Cr At River Rd Nr Crow s Landing Ca 0.0132

### 12 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Lo wer Illinois River Basin ST IL - PIATT 5572000 Sangamon River At Monticello, Il 0.002 Lo wer Illinois River Basin ST IL - SCOTT 5586100 Illinois River At Valley City, Il 0.0095 Eastern Iowa Basins ST IA - JOHNSON 5454500 Iowa River At Iowa City, Ia 0.0008 Eastern Iowa Basins ST IA - JOHNSON 05465500 Iowa River At Wapello, Ia 0.02 Eastern Iowa Basins ST IA - TAMA 5464220 Wolf Creek Near Dy sart, Ia 0.22 Central Nebraska Basins ST NE - DOUGLAS 6800500 Elkhorn River At Waterloo, Nebr. 0.0432 Central Columbia Plateau - Yakima River Basin ST WA - BENTON 461032119194900 Drain At Badger Road, Mile 8.8 0.0069 Central Columbia Plateau - Yakima River Basin ST WA - BENTON 12510500 Yakima River At Kiona, Wa 0.0081 Central Columbia Plateau - Yakima River Basin ST WA - FRANKLIN 12473740 El 68 D Wasteway Near Othello, Wa 0.02

### 13 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Central Columbia Plateau - Yakima River Basin ST WA - KITTITAS 465640120265700 Johnson Drain At South Ferguson Road 0.0171

Central Columbia Plateau - Yakima River Basin ST WA - WHITMAN 13351000 Palouse River At Hooper, Wa 0.013 Central Columbia Plateau - Yakima River Basin ST WA - WHITMAN 13351000 Palouse River At Hooper, Wa 0.007 Central Columbia Plateau - Yakima River Basin ST WA - WHITMAN 13351000 Palouse River At Hooper, Wa 0.006 Central Columbia Plateau - Yakima River Basin ST WA - WHITMAN 13351000 Palouse River At Hooper, Wa 0.0041 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 12505450 Granger Drain At Granger, Wa 0.0076 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 12505450 Granger Drain At Granger, Wa 0.0096 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 12505450 Granger Drain At Granger, Wa 0.0122

### 14 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 12505450 Granger Drain At Granger, Wa 0.023 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 12505450 Granger Drain At Granger, Wa 0.0233 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 462018120075200 Jd 32.0 Upstream Of Dr 2 0.0367 Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 462023120075200 Dr 2 At Yakima Valley Highway Near Granger, Wa 0.006

Central Columbia Plateau - Yakima River Basin ST WA - YAKIMA 462046120065600 Dr 2 At Vanbelle Road 0.0473 Upper Snake River Basin GW ID - BONNEVILLE 433021112001001 02n 38e 16bcc1 0.0088 Upper Snake River Basin GW ID - MINIDOKA 424617113421901 07s 23e 36daa1 0.0054 Upper Snake River Basin GW ID - TWIN FALLS 423115114290401 10s 17e 29dcd1 0.0447 Tennessee River Basin GW TN - BEDFORD 353211086271201 Bd:L - 41 0.0162 Santa Ana River Basin GW CA - RIVERSIDE 340033117204001 002s004w07l001s 0.0061

### 15 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L Puget Sound Basin GW WA - UNSPECIFIED 490040122240501 092g.008.2.2.2 - 91 - 12 0.0005 Lake Erie - Lake Saint Clair Drainage GW MI - HILLSDALE 414520084374800 Ag059 - 9 0.02 Apalachicola - Chattahoochee - Flint River Basin GW FL - JACKSON 305137085060301 Nwfwmd 80'Tot/65'Cased Well 0.0005 Ozark Plateaus FA - WTP AR - STONE 355453092061301 Finished Water Near Allison 0.0016 Northern Rockies Intermontane Basins FA - WTP WA - SPOKANE 12424000 Hangman Creek At Spokane Wa 0.2837 Northern Rockies Intermontane Basins FA - WTP WA - SPOKANE 12424000 Hangman Creek At Spokane Wa 0.0275 Mississippi Embayment FA - WTP LA - TENSAS 315913091154900 Lake Bruin [Finish] Nr St Joseph, La 0.0115 Lake Erie - Lake Saint Clair Drainage FA - WDS OH - DEFIANCE 411645084230502 Maumee River At Holgate Avenue F 0.0033

CDPR Surface Water Database - all samples taken in State of CA Date of Sample Site Type Code County in CA Chemical Found Place Name Concentration μg/L

### 16 USGS NAWQA Database** River Basin Site Type Code* State and County USGS Staion ID Place Nam e Concentration μg/L

May 9, 1997 SW YOLO bromoxynil Colusa Basin Drain above Knights Landing 0.06

May 9, 1997 SW YOLO bromoxynil octanoate Colusa Basin Drain

above Knights Landing 0.06 * SW : Surface Water, ST: Stream, GW: Ground Water, FA - WTP: Water - supply treatment plant, FA - WDS: Water - distribution system **USGS NAWQA database only stated bromoxynil. What form of bromoxynil was present is undetermined. The database did not provide a date of when the samples were taken either.

### 17

B. Surface Water The Tier I screening models FIRST Version 1.1.1 (FQPA Index Reservoir S creening T ool) with Percent Crop Area adjustment factor was used to determine drinking water concentrations of Bromox ynil derived from surface water sources. Bromox ynil may

move from the treated field to surface water or ground water through run - off shortly after application. Residues of bromoxy nil are highl y to moderately mobile in soil. Tier 1 drinking water concentrations derived from surface water for bromox ynil was estimated using Version 1.1.1 of FIRST model. Input values for the FIRST model are reported in Table 3. Table 3 . FIRST Input Parameters for Bromox ynil aerial and ground use on grasses grown for seed and ground use on sorghum. Parameter Input value Data Source/Rationale* Application Rate (lbs ai/A) 0.286 (grasses) 0.305 (sorghum) Label

Maximum No. of Applications/season 2 Label Application Interval (days) 30 (grasses) 11 (sorghum) Label

Percent Cropped Area (as decimal) 0.87 Default Incorporation depth (inch) 0 Label Kd 4.61 Average Kd from 4 soils (MRID 110429), range of 1.4 to 12.54 Aerobic Soil Metabolism Half - life (days) 3.00 Upper 90 th percentile confidence bound on two values Is the pesticide wetted - in? No Grasses: Aerial and Ground

### 18

Parameter Input value Data Source/Rationale* Method of application Sorghum: Ground Solubility (ppm) 130 Product Chemistry Aerobic aquatic t 1/2 (days) 6.0 2 x (aerobic soil value) Photolysis Half

- life (days) 0 Stable (MRID 42234301, 41920401) 

### * Parameters were selected in accordance with the Proposed Interim Guidance for Input Values document, dated September 22, 2009. It is important to note, that s ince bromox ynil heptanoate is chemically and phy sicall y similar to bromox yn il octanoate (one carbon difference in the ester side chain) and both esters rapidl y degrade to brom oxy

nil phenol (aka bromoxy

nil), all calculations have been performed in terms of bromox yn il. C. Ground Water SCI - GROW model ( Screening Concentration in Ground Water Program (SCI - GROW) VERSI ON 2.3.0 was used to predict the maximum chronic and acute co ncentration of Bromox ynil derived from shallow ground water. Bromox ynil is mobile, but has a short metabolic half - life in soil under aerobic conditions. Therefore, bromox ynil should not be a ground water concern in most environments. In the event that bromox yn il did reach ground water it is expected to degrade slo wl y due to microbial activity (faster under aerobic conditions than anaerobic conditions) but is rather persistent otherwise. Table 4 below summarizes the results of the screening level groundwater model, SCI GROW 2.3.0, for bromox ynil. Table 4 . SCIGROW i nput parameters used to estimate Bromox ynil aerial and ground use on grasses grown for seed and ground use on sorghum. Parameter Input value Data Source/Rationale* Koc 

### 192.1 Average Koc 

### from 4 soils (MRID 110429), Clay- loam: 228.6 Loam y- sand: 107.7 Loam: 193.3 Sandy- loam: 238.9

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Parameter Input value Data Source/Rationale* Application Rate (lbs ai/A) 0.286 (grasses) 0.305 (sorghum) Label Maximum No. of Applications/season 2 Label Aerobic Soil Metabolism Half - life (day s) 1.71 Mean value as per input parameter guidance. Half - lives 2.13 and 1.29. (MRID 142958).