# U

. S. ENVIRONMENTAL PROTECTION AGENCY

Wash i ngton, D.C. 20460

OFF I CE OF

C H EMICAL SAFETY AN D

POLL U T I ON PREVE NT I ON



# Date: 

# September 1 1, 2014

PC Code: 

# 103901

DP Barcode: 

# DP 422778

MEMORANDUM

SUBJECT:

TO:

FROM:

THRU: 

# Drinking Water Assessment in support of the Registration Review Preliminary

Ri sk Assessment and C l arification on the Degrada t es of Concern for t h e Sodium

Salt ofBentazon

Caro l y n Sc h roeder, Chemica l R eview Manager

Kathr y n Montague, Risk Manager

Risk Management and Implementation Branch IV

Pesti ci de Re-evaluation Division (7508P)



# Steph e n P. Wente

, Ph.D.

, Bio l ogist

E nvironmental Risk Branch I

# __sr~

Environm e nta l Fa t e and Effects D ivisio n**(7;~4P)** 

# }q.**~**



# Suja tha Sankula, Ph

. D., Branch Chief

# .~-L~._,___ =:<""'



# Environmental Risk Branch I

Enviro nm e n ta l Fate and Effects Divisio n (7504P)

This memo addresse s two subjects: the sodium salt of bentazon (hereafter referred to as

bentazon) dr inki ng wate r assessme n t (DWA) and t h e clarificatio n on the degradates of concern

for benta zo n.

Drinking Water Assessment for Bentazon



# The environmental Fate and Effects Division (EF E D) has developed a conservative (tier 1 )

DWA for bentazon uses in support of the Bentazon Registrat i on Review

. Typically EFED would

prepare a more refin ed (h i gher tier) D WA for bentazon b ecause p r evious Agency assessments

have ident i fied ground a n d surface water as an important source of bentazon exposure t o humans

( USEPA 1994). However, there are two reasons that suggest a l ower tier assessm e nt is

appropriate. First, th e Health E ffects Division has recently revised the chron i c drinking water



# en d point to a higher (l ess t oxic) va lu e, which w i ll red u ce t he nee d for a hig he r tier DWA :

. Second

, many of the b entazon labe l s are missing important application information (number of



# 1

# 2 applications on an annual basis, annual applica tion rate, and re-applicatio n intervals) necessary

for the higher tier DWA (the Agency is currentl y working with registrants to remedy these label

omissions). Rather than delay the time-line for the registrati on review of bentazon, EFED is

providing a conservative assessment which HED belie ves will not result in ch ronic risk concerns

(George Kramer email, 8/28/2014) based on the revised chronic endpoint. If this conservative

assessment does for unforeseen reasons result in risk issues, a more refined (higher tier) DWA

for surface water and groundwater sources will be produced once the label i ssues are rectified.

Bentazon has a rice use for which label informati on is sufficient. EFED has a Tier 1 Rice Model 1



# which produces highly conservative estimates be cause it does not consider degradation in the

rice paddy. Additionally, the rice model EDWCs will not be adjusted by the percent crop

adjustment (PCA) factors. EFED believes th ese estimated drinking water concentrations

(EDWCs) would be much higher than any of the other bentazon uses 2 

# . Based on two applications

of 1.1 lbs ai/acre for a total application of 2.2 lbs ai/acre/ year and a Kd of 0.898 (MRID

40470501), the tier 1 Rice Model produces a surfa ce water EDWC of 2112 μg/L for both

acute and chronic risk concerns . Therefore EFED believes all of the other uses of bentazon

would produce EDWCs lower than this conserva tive value for both surf ace and groundwater.

USGS NAWQA monitoring data has maximum bent azon concentrations in surface water of 8.6

μg/L and 11.46 in groundwater. This monitoring is not targeted to bentazon applications in

neither time nor location. This contrasts with a registrant-submitted aquatic field dissipation

study (MRID 43431901) of applications to rice paddies , which measured a p eak concentration of

3157 μg/L. However, this application was to onl y a 1.38 in. depth of paddy water (the Tier 1

Rice Model assumes a 3.94 in. depth). (Note that unlike the Tier 1 Rice Model, the measured

concentration in rice paddy water dropped to 912 μg/L after 1 day a nd to 500 μg/L after 7 days.)

Clarification on the Degradat es of Concern for Bentazon

In preparation for the registration review of bentazon, a meeting was held on August 14, 2014

between the Health Effects and Environmental Fate and Effect s Divisions to better identify

bentazon degradates of concern to be include d in the registration review drinking water

assessment. The meeting was organized by Ed Sc ollon of EFED. Other EFED attendees included

Sujatha Sankula, Meghan Radtke, and Steve We nte. HED attendees included Charles Smith,

Anwar Dunbar, George Kramer, and Ray Kent. The meeting identified O-amino-N-isopropyl

benzamide (AIBA), O-nitro-N-isopropyl ben zamide, O-nitroso-N-isopropylbenzamide,

photoproduct 10 from MRID 00040785, and 8-Cl-benta zon as degradates of concern (see

Appendix A for structures).

1 

# http://www.epa.gov/oppefed1/models/water/index.htm#rice

2 

# Other applications include foliar applications: alfalfa, clover grown for seed, beans, beans, dried-type, beans,

succulent, beans, succulent (lima), peas, dried-type, and peas, succulent, corn (silage), corn (unspecified), corn,

field, corn, pop, and corn, sweet, flax, nonagricultural rights-of-way/fencerows/hedgerows, and nonagricultural

uncultivated areas/soils, nursery stock, ornamental and/or shade trees, ornamental herbaceous plants, ornamental

lawns and turf, ornamental nonflowering plants, and ornamental woody shrubs and vines, ornamentals (unspecified),

paved areas (private roads/sidewalks), peanuts (unspecified), peppermint and spearmint, residential lawns, sorghum

and sorghum (silage), soybeans (unspecified), and soybeans, edible (edamame); as well as at planting/pre-plant

applications: almond, apple, apricot, avocado, blackberry, blueberry, cherry, crabapple, date, fig, grapefruit, grapes,

lemon, lime, macadamia nut (bushnut), nectarine, olive, orange, peach, pear, pecan, pistachio, plum, pomegranate,

prune, raspberry (black, red), tangelo, tangerines, and walnut (English/black)

# 3 Note that the bentazon degradates of concer n do not affect the Tier 1 Rice Model EDWCs

because of the conservative assumption in this ti er 1 model that the pesticide parent does not

degrade. If for unseen reasons these Tier 1 Rice Model EDWCs ne ed to be further refined, the

degradates of concern will be consid ered in any higher tier modeling.

References

USEPA. 1994. Reregistration Eligibility Decisi on (RED): Bentazon (EPA 738-R-94-029). U.S.

Environmental Protection Agency, Office of Pr evention, Pesticides and Toxic Substances.

September 1994. 198 pp.

USEPA. 2007. Tier I Rice Model v1.0 for Estimati ng Pesticide Concentrations in Rice Paddies.

Environmental Fate and Eff ects Division, Office of Pesticide Programs, United States

Environmental Protection Agency.4Appendix A: Bentazon Sodium Salt and Its Environmental Transformation ProductsAppendix Table A-1. Bentazon Sodium Salt and Its Environmental Transformation Products.AChemical Name, Solubility, and KOCChemical StructureStudy TypeMRIDLabel,Maximum%AR (day)Final %AR(study length)PARENTBentazon(BAS 351H)IUPAC:3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one2,2-dioxideCAS:3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxideCAS No.:25057-89-0Formula:C10H12N2O3SMW:240.3 g/molSMILES:O=C1N(C(C)C)S(=O)(=O)Nc2ccccc12MobilityWater solubility:500 mg/L (measured); 268.13 mg/L (EPISuite estimate)Kd:0.176 L/kg (measured); Koc: 10 L/kg (MCI method)Aqueous Photolysis 00040785NA19 (1)Soil Photolysis 00040785 56.1 (5)Aqueous Photolysis 00161294pH 5: 22.4 (10.7)pH 7: 44.1 (4.8)pH 9: 41.2 (1.3)Aqueous Photolysis 4364201 28.4 (5.9)Aerobic Soil Metab. 404705022.6 (367)0.9 (367)0.4 (367)Aerobic Soil Metab. 00040209 9.7 (266)MAJOR (>10%) TRANSFORMATION PRODUCTSO-amino-N-isopropyl benzamide (AIBA) – drinkingwater degradate of concernCAS:2-amino-N-isopropylbenzamideCAS No.:30391-89-0Formula:C10H14N2OMW:178.24 g/molSMILES:O=C(NC(C)C)c1ccccc1NMobilityWater solubility:33,247 mg/L (EPI Suite estimate)Koc:27.83 L/kg (MCI method)Aqueous Photolysis 0004078527(1)27(1)O-nitro-N-isopropyl benzamide (7) ) – drinking waterAqueous Photolysis 0004078527(1)27(1)NNHSO2OCH3CH3NHNH2OCH3CH35Chemical Name, Solubility, and KOCChemical StructureStudy TypeMRIDLabel,Maximum%AR (day)Final %AR(study length)degradate of concernFormula:C10H12N2O3MW:208.22 g/molSMILES:O=C(NC(C)C)c1ccccc1[N+](=O)[O-]MobilityWater solubility:1327 mg/L (EPI Suite estimate)Koc:89.72 L/kg (MCI method)Aerobic Soil Metab. 00040209 0.63 (140) 0.23 (266)O-nitroso-N-isopropylbenzamide (8) ) – drinking waterdegradate of concernFormula:C10H12N2O2MW:192.22 g/molSMILES:O=C(NC(C)C)c1ccccc1N=OMobilityWater solubility:660.3 mg/L (EPI Suite estimate)Koc:53.09 L/kg (MCI method)Soil Photolysis 0004078522(1) 5.7 (5)Photoproduct 10 (MRID 00040785) ) – drinking waterdegradate of concernFormula:C17H20N4O2MW:312.37 g/molKoc:66.37 L/kg (MCI method)Upper StructureSMILES:C(=O)(NN(C(=O)(c1ccccc1N))C(C)C)c1ccccc1NMobilityWater solubility9790mg/L (EPI Suite estimate)Or:Lower StructureSMILES:C(N)(=O)c1c(NN(C(=O)c2c(N)cccc2)C(C)C)cccc1MobilityWater solubility6617.4mg/L (EPI Suite estimate)Structure is Approximate:Or:Soil Photolysis 0004078513(5)13(5)Aqueous Photolysis 0004078514(1)14(1)NHNO2OCH3CH3NHNOOCH3CH3CONHN CCH3H3CONH2H2NNHN CCH3H3COH2NOH2N6Chemical Name, Solubility, and KOCChemical StructureStudy TypeMRIDLabel,Maximum%AR (day)Final %AR(study length)Photoproduct 12 (MRID 00040785)Formula:C21H23N3O6S2MW:477.55 g/molSMILES:C1(=O)c2c(c(N3c4c(C(=O)N(C(C)C)S3(=O)=O)cccc4)ccc2)NS(=O)(=O)C1C(C)CMobilityWater solubility:1.37 mg/L (EPI Suite estimate)Koc:59.61 L/kg (MCI method)Soil Photolysis 9.4 (3)7.9 (5)Photoproduct 13 (MRID 00040785)Formula:C21H23N3O6S2MW:477.55 g/molSMILES:C1(=O)c2c(ccc(N3c4c(C(=O)N(C(C)C)S3(=O)=O)cccc4)c2)NS(=O)(=O)C1C(C)CMobilityWater solubility:1.37 mg/L (EPI Suite estimate)Koc:58.42 L/kg (MCI method)Aqueous Photolysis0004078514(1)14(1)Soil Photolysis 8.8 (5)8.8 (5)NNSO2OCH3CH3NHNSO2OCH3CH3NNSO2OCH3CH3NHNSO2OCH3CH37Chemical Name, Solubility, and KOCChemical StructureStudy TypeMRIDLabel,Maximum%AR (day)Final %AR(study length)Photoproduct B (MRID 4364201)IUPAC:3-isopropyl-2,2-dioxo-5-oxo-cyclopentano[d]IH2,1,3-thiadiazln-4(3H)-oneβ-carbonic acidFormula:C10H10N2O6SMW:286.26g/molSMILES:C(=O)(O)C1C(=O)C2C(=O)N(C(C)C)S(=O)(=O)NC=2C=1MobilityWater solubility:286,510 mg/L (EPI Suite estimate)Koc:10 L/kg (MCI method)Aqueous Photolysis 436420121(5.9)21(5.9)Unextracted residues(not applicable)Aerobic Soil Metab. 0001020973.3(140)70(266)Aerobic Soil Metab. 4047050260.3(180)80.4(180)62.2(367)59.5(367)74.8(367)62.2(367)Carbon dioxideFormula:CO2MW:44.1 g/molSMILES:O=C=OAerobic Soil Metab. 4047050224.2(367)12.4(367)23.3(367)24.2(367)12.4(367)23.3(367)MINOR (<10%) TRANSFORMATION PRODUCTSN-methylbentazon ) – drinking water degradate ofconcernFormula:C11H14N2O3SMW:254.31 g/molSMILES:O=C1N(C(C)C)S(=O)(=O)N(C)c2ccccc12MobilityWater solubility:135.43 mg/L (EPI Suite estimate)Koc:10 L/kg (MCI method)Aerobic Soil Metab. 404705023.8 (367)2.3 (367)1.8 (367)3.8 (367)2.3 (367)1.8 (367)NNHSO2OCH3CH3OOHOC OONNSO2OCH3CH3CH38Chemical Name, Solubility, and KOCChemical StructureStudy TypeMRIDLabel,Maximum%AR (day)Final %AR(study length)8-Cl-bentazonFormula:C10H11ClN2O3SMW:274.72 g/molSMILES:O=C1N(C(C)C)S(=O)(=O)Nc2c(Cl)cccc12MobilityWater solubility:62.32 mg/L (EPI Suite estimate)Koc:11.23 L/kg (MCI method)Aerobic Soil Metab. 404705023.8 (367)2.3 (367)1.8 (367)3.8 (367)2.3 (367)1.8 (367)Photoproduct 11 (MRID 00040785)Formula:C21H23N3O4SMW:413.49 g/molSMILES:C1(=O)c2c(ccc(N3c4c(C(=O)N3C(C)C)cccc4)c2)NS(=O)(=O)C1C(C)CMobilityWater solubility:133.99 mg/L (EPI Suite estimate)Koc:260.6 L/kg (MCI method)Soil Photolysis 00040785 5.3 (5) 5.3 (5)Photoproduct C (MRIDs 00161294, 4364201)IUPAC:1-{N-(1-methylethyl)}-2-sulfoamino benzamideFormula:C10H14N2O3SMW:242.29 g/molSMILES:C(=O)(c1c(NS(=O)=O)cccc1)NC(C)CMobilityWater solubility:49452 mg/L (EPI Suite estimate)Koc:10 L/kg (MCI method)Aqueous Photolysis 00161294pH 5: 9.2 (10.7)pH 7: 3.4 (4.8)pH 9: <1 (1.3)pH 5: 9.2 (10.7)pH 7: 3.4 (4.8)pH 9: <1 (1.3)Aqueous Photolysis 4364201 6.5 (5.9) 6.5 (5.9)And means “not detected”. AR means “applied radioactivity”. MW means “molecular weight”. LOQ means “limit of quantitation”.Bolded values are laboratory study values>10%AR.NNHSO2OCH3CH3ClNNHNSO2OCH3CH3NOCH3CH3NHNHOCH3CH3SO3H