### 1 **UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

**WASHINGTON, D.C. 20460** 

**OFFICE OF PREVENTION, PESTICIDES A** **ND TOXIC SUBSTA** **NCES** 

### PC Code: 035506 **DP Barcode: 4058**  **2 9**  **MEMORANDUM** 

### DATE: Ju

ne 1 9 , 2013 

### SUBJECT: Revised Linuron Drinking Water Assessment for an IR
-4 New Use on Coriander, Dill,

Celeriac , Horseradish, Parsley, Dry Peas and Rhubarb 

### TO: Laura No l len, Risk Manager

Barbara Madden, Risk Manager Reviewer Registration Division (7505P) Christine Olinger, Branch Chief Risk A ssessment B ranch III , H ealth E ffects D ivision (7509P) 

### FROM: He Zhong, Ph.D., Biologist

Environmental Risk Branch I Environmental Fate and Effects Division (7507P) 

### THROUGH: Sujatha Sankula, Ph.D., Acting Branch Chief

Environmental Risk Branch I Environmental Fate and Effects Division (EFED) (7507P) This revised linuron D rinking water assessment includes PRZM
- GW model results. 

### The document provides estimated drinking water concentrations (EDWC s ) for linuron (3
- (3,4
- dichlorophenyl)
- 1
-methoxy- 1
-methylurea; (CAS 330
- 55
- 2 ) in support of human health risk assessment for a new use on Coriander, Dill, Celeriac , Horseradish, Parsley, Dry Peas and Rhubarb. The EDWCs for H orseradish, Parsley

and Dry Peas were previou s ly assessed based on the percentage crop area (PCA) value of 0.87 (USEPA 2010)
. These are updated to PCA = 1 based on EFED guidance (USEPA 2012) for non - agricultural weed control ( Proposed Label, page 1 3 ) in this document
. According to the proposed supplemental label, Lorox® 50% DF Herbicide can be applied annually in a single application as pre - emergence or up to two applications as post - emergence b y ground spray, fertilizer spray mixture, and chemigation to control certain broadleaf weeds and grasses . The application directions also specified to not apply b y air, to the sand or loamy sand soil or use on soils with less that 1% organic m atter. **Table 1** is a summary of the proposed supplemental label.

### 2

The chemical and environmental fate properties of linuron are listed in **Appendix I**
. Same as the previous DWA (USEPA2010), a total toxic residue approach is applied in this assessment to include the parent linuron and three degradates, desmethoxy linuron, desmethoxy monolinuron, and norlinuron observed in environmental fate studies. This assessment did not include the common urea herbicide degradate 3,4
- DCA, which was concluded as not a residue of concern for human health for linuron (USEPA 1993). The calculated EDWCs from Tier
- II PRZM/EXAM s (see input values in **Appendix II** ) for surface water are listed in **Table 2**
. The maximum surface water EDWCs in this assessment ( see **Appendix I II**  ) supersede the previous upper bound EDWC values of 77.4 μg/L , 42.4 μg/Land 26.8 μg/L (PCA = 0.87) for peak (acute), annual average (non
- cancer chronic), and 30
- ye ar annual average (cancer chronic) respectively (USEPA 2010, DP371421, 371396, 371471, 371472, 371473). Therefore, EFED recommends the new maximum EDWC values of **8 9**  **.0 5**  **μg/L, 4 8**  **. 69**  **μg/L** and **30 .**  **81 μg/L**  (PCA=1) for surface water peak (acute), annual average (non
- cancer chronic), and 30
- year annual average (cancer chronic) respectivel y. Ground water EDWC from SCI
- GROW model is 0. 23 μg/L (see input and output values in **Appendix I V** ) , which does not supersede the previous recommended value of 0.61 ppb
. Ground water EDWC is also calculated by PRZM
- GW model ( **Table 3 and Appendix V**  PRZM
- GW Modeling Input and Output). The highest daily value is **54.5 μg/L**  and post breakthrough average is 48.8 μg/L with average simulation breakthrough time over 20,101 days for Wisconsin corn scenario
. Ground water EDWC from PRZM
- GW model supersede s the previous postmitigation monitoring concentration of 0.61 ppb and therefore, EFED recommend s the PRZM
GW highest acute value of **54.5 μg/L**  and chronic value of **48.69** for groundwater. **Table 1**  **. Summary of Application Inform ation Used in PRZ** **M/EXAMS for**  **Surface Water EECs Crop**  **PRZ M/EXAMS** 

**Scenarios 1**  **Application**

**Rate (lb a.i./A** **) 2**  **Application**

**Rate (kg a.i./ha)**  **2 Maximum** 

**Number of Applications**  3 **Application**

**Date (Day** **** **Month) 4**  Coriander Dill (East of Rocky Mtns) FL Peppers 1.0 1.12 2 24
- 4 FLCarrot 1.0 1.12 2 9
- 10 PA Vegetable 1.0 1.12 2 15
- 5 Coriander Dill (West of Rocky Mtns) CARowCrop 0.75 0.84 2 10
- 1 2

CALettuce 0.75 0.84 2 9
- 2 ORmint 0.75 0.84 2 8
- 4 Celeri ac Rhubarb Horseradish Parsley FL Peppers 1.5 1.68 1 24
- 4 FLCarrot 1.5 1.68 1 9
- 10 PA Vegetable 1.5 1.68 1 15
- 5 CARowCrop 1.5 1.68 1 10
- 1 2 CALettuce 1.5 1.68 1 9
- 2 ORmint 1.5 1.68 1 8
- 4 Dry Peas IL Beans NMC 1.0 1.12 1 9
- 6

MI BeansSTD 1.0 1.12 1 25
- 5 Abbreviations: A=acre ; ha=hectare; a.i.=active ingredient 1 There are no crop scenarios in PRZM/EXAMS for the crops listed in this table
. Alternative surrogate scenarios based on similarities in plant structure and growth characteristics were used in the modeling. 2 Calculated by

the equation : kg a.i./A = (lbs a.i./A) x (1 kg/2.205 lbs) x (2.47 A/hectare)
. 3 A 15
- days application intervals for all two applications 4Application date is estimated for the region one week before crop emergence date per proposed label
.

### 3

**Table 2. S**  **urface W ater EECs**  **for Linuron by**  **PRZ M/EXAMS for**  **IR -**  **4 New U se on Coriander, Dill, Celer** **i ac**  **Horseradish, Parsley, Dry Peas and Rhubarb**  **Crop PRZ** **M/EXAMS**

**Scenarios 1**  **Application**

**Rate (kg a.i./ha)**  **2 Maximum** 

**Number of Applications**  **Peak**

**(ppb) Annual** 

**Me an**  **(ppb) Long**  **- term** 

**Me an**  **(ppb)** Coriander Dill (East of Rocky Mtns) FL Peppers 1.12 2 81.79 17.76 12.97 FLCarrot 1.12 2 88.91 14.81 12.08 PA Vegetable 1.12 2 49.07 25.03 19.57 Coriander Dill (West of Rocky Mtns) CARowCrop 0.84 2 40.35 26.19 16.81

CALettuce 0.84 2 66.74 36.03 27.00 ORmint 0.84 2 11.58 6.91 5.73 Celeriac Rhubarb Horseradish Parsley FL Peppers 1.68 1 72.21 12.11 9.45 FLCarrot 1.68 1 84.91 15.34 8.65 PA Vegetable 1.68 1 37.81 19.08 15.25 CARowCrop 1.68 1 45.16 27.01 17.62 CALettuce 1.68 1 **89.05 48.69**  **30.81** ORmint 1.68 1 13.20 7.09 5.74 Dry Peas IL Beans NMC 1.12 1 30.74 14.22 10.93

MI BeansSTD 1.12 1 23.76 11.99 9.36 **Table 3. Ground Water EECs for Linuron by PRZ M**  **- GW**  **in Six Vulnerable Sites for IR** **- 4 New Use on**  **Coriander, Dill, Celeriac Horseradish, Parsley, Dry Peas and Rhubarb Crop/Scenario**  **Highest Daily Value μg/L**  **Post Breakthrough Average**  **μg/L Average Sim** **ulation**

**Breakthrough Time Days**  DELMARVA sweet corn
- Evesboro loamy sand Met File (13781 .dvf) 16.9 15.1 10 , 082.8 Florida Citrus
- FL Central Ridge, Polk County Astatula sand, hrgb A Met File (12842.dvf) 37.6 37.5 10,009.13 Florida
- potato Jacksonville Met File (13889.dvf) 0.0 246 0.0203 25,376.8 GA
- Southern Coastal Plain, Tifton loamy sand

– PEANUTS Met File (w93805 Extended .dvf) 7.13 6.51 20,395.9

NC Eastern Coastal Plain
- Norfolk loamy sand

– Cotton Met File (13722 .dvf) 19.4 18.2 10,755.64 Wisconsin Corn
- WI Central Sands Met File (14920 Extended .dvf) **54.5 48.8**  **20,101.2**

### 4

References USEPA. 1993. Linuron Plant and Animal Metabolism: Results of the HED Metabolism Committee Meetings held October 21, and October 29, 1993. MARC’s Memo. Pp3 USEPA. 2010. Drinking Water Assessment for the Section 3 Registration of Linuron for New Use on Parsley, Dry

Pea and Horseradish. DP Barcodes: 371421, 371396, 371471, 371472, 371473. pp10 USEPA. 2012. Guidance on Deve lopment and Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update. pp50

### 5 **Appendix I**  **Chemical and Environmental Fate P roperties of**  **L inuron**  **Chemical/Fate Param eter**  **Value(s) Source (MRID)**  Common Name Linuron Product Chemistry Em pirical formula C 9H 10 C l2N2 O 2 EPI V4.10 SMILES O=C(N(OC)C)Nc(ccc(c1Cl)Cl)c1 EPI V4.10 Chemical Name (CAS) N '
- (3,4
- dichlorophenyl)
-N

methoxy
-N

- methylurea http://sitem.herts.ac.

uk/aeru/iupac/419.ht m (Accessed 3/20/2013) IUPAC 3
- (3,4
- dichlorophenyl)
- 1
- methoxy
- 1
- methylurea http://sitem.herts.ac. uk/aeru/iupac/419.ht m (Accessed 3/20/2013) CAS No 330
- 55
- 2 Product Chemistry

Structural formula

Molecular weight (MW) (g/mol) 249.1 Product Chemistry Vapor pressure (VP) (torr; at 24  C) 1.5 × 10 - 5 Product Chemistry Water solubility (mg/L; at 20  C) 81 Product Chemistry Henry’s Law Constant (atm
- m 3 /mol; at 25  C) 6.1 x 10 - 8 Calculated 1 Hydrolysis half

- lives (25  C) (days) , pH 5 , 7 and 9 Stable 40916201 Water photolysis half

- life 49 days 40103601 Soil photolysis half

- life >15 days (assumed stable) 40171711 (supplemental) Aerobic soil metabolism half
- life (days) 49 days 2 , 71 days 3 and 113 days 3 41625401 (valid) 4 Organic carbon normalized partition coefficients (KOC) (L/kg OC) 1200 (Sandy loam) 2200 (Sandy loam) 830 (Silt loam) 550 (Clay loam) 43995301 (supplemental) Octanol
- water partition coefficient (KOW) 1010 Product Chemistry Fish bioconcentration 34x (muscle) 39× (carcass) 240× (viscera) 49× (whole fish) 00142933

1 Calculated according to USEPA 2002 by: (VP*MW) ÷ (760*solubility). 2 Calculation from original data evaluation revie w. 3 Calculated using total toxic residue method. 4 This study was found to be valid under old review standards.

### 6 **Appendix I I**  **PRZ M/EXAMS**  **1 mo**  **deling i** **nput values for linuron use on**  **Coriander, Dill, Celer i**  **ac Horseradish, Parsley, Dry Peas**  **and Rhubarb Model Input Param** **eter Input Value and Unit**  **Source/Comments** Molecular Weight. 249.1 Product Chemistry Henry’s Law Constant ( atmm3 /mole) 6.1 x 10 - 8 Calculated according to Input Parameter Guidance: (VP*MW) / (760*solubility) Vapor pressure (torr @ 24°C) 1.5 x 10 - 5 Product Chemistry Solubility ( mg/L @ 20 o C) 81 Koc (ml/g) 1195 MRID 43995301; average of 4 values per Input Parameter Guidance (1200, 2200, 830 and 550) Kd 6.3 MRID 43995301; average of 4 values per Input Parameter Guidance (5.5,17,12 and 13) Ty pe of Application CAM 1 The proposed label recommends pre
- emergent crop application. Incorporation Depth 0 Proposed label Application Efficiency 0.99 (ground spray) Input parameter guidance Spray Drift Fraction 0.064 (ground) Input parameter guidance IPSCND 1 (surface applied) Input parameter guidance Hydrolysis half

- lives (25°C) (days)
. pH5 , pH7 and pH9 Stable MRID 40916201 Aqueous Photolysis Half
- life (days) 49 MRID 40916201 Aerobic Aquatic Metabolism Half
- life (days) 426 Calculated: 71 (aerobic soil metabolism) x3 x2 per input parameter guidance. Anaerobic Aquatic Metabolism Half

- life (days) Stable In the absence of an acceptable study this metabolic half

- life is considered to be stable Aerobic Soil Metabolism Half
- life (days) 213 MRID 41625401; calculated using total toxic residue method. 71 x 3 per input guidance when only one valid study is available.

1 Model input values for ‘Application rate and data’, and ‘Number of applications’, are presented in Table 1.

### 7 **Appendix I II**  **Examples of PRZ M/EXAMS Modeling Output**  stored as CALettuce
- 1app.out Chemical: Linuron PRZM environment: CAlettuceSTD.txt mo dified Tuesday, 21 February 2006 at 15:38:22 EXAMS environment: ir298.exv mo dified Tuesday, 26 August 2008 at 06:14:07 Metfile: w23273.dvf mo dified Tuesday, 26 August 2008 at 06:15:39 Water segment concentrations (ppb) Year Peak 96 hr 21 Day 60 Day 90 Day Yearly 1961 14.52 14.14 12.86 8.053 5.709 2.497 1962 118 116 112 93.68 83.77 49.8 1963 78.12 76.7 72.42 69.24 67.12 49.06 1964 39.95 39.64 38.66 37.21 37.1 32.51 1965 38.96 38.45 36.64 33.48 31.75 27.17 1966 28.99 28.55 26.97 25.27 24.89 20.91 1967 31.48 31.05 29.45 28.54 27.89 22.2 1968 23.99 23.69 22.64 21.09 20.53 17.13 1969 54.57 53.36 50.21 43.92 40.58 27.69 1970 57.76 56.57 52.95 46.22 42.55 30.09 1971 29.56 29.3 28.32 27.67 27.1 22.93 1972 28.46 27.95 26.18 22.67 19.65 17.26 1973 89.66 87.97 81.14 71.29 65.38 43.22 1974 63.77 62.77 60.01 55.23 51.92 39.32 1975 45.52 44.98 43.06 40.41 39.25 31.6 1976 51.52 50.58 47.28 42.98 4 0.43 31.48 1977 38.26 37.89 36.23 33.27 32.76 27.67 1978 121 119 110 104 95.66 62.88 1979 58.42 57.92 56 53.79 52.2 42.19 1980 83.6 82.57 78.58 69.59 64.53 45.4 1981 70.44 69.2 65.76 59.45 55.6 41.01 1982 44.59 44.08 42.57 40.48 39.4 32.24 1983 56.38 55.4 52.23 47.42 44.87 32.78 1984 26.8 26.6 25.87 24.64 24.35 20.34 1985 23.31 23.05 22.09 20.79 20.63 16.95 1986 76.93 75.02 68.13 65.3 61.14 39.88 1987 58.73 57.85 54.18 48.16 44.95 34.02 1988 45.15 44.46 41.89 38.68 37.85 29.85 1989 27.56 27.33 26.44 25.35 2 5.01 19.85 1990 21.59 21.33 20.45 19.07 18.21 14.39 Sorted results Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly 0.032258064516129 121 119 112 104 95.66 62.88 0.0645161290322581 118 116 110 93.68 83.77 49.8 0.0967741935483871 89.66 87.97 81.14 71.29 67.12 49.06 0.129032258064516 83.6 82.57 78.58 69.59 65.38 45.4 0.161290322580645 78.12 76.7 72.42 69.24 64.53 43.22 0.193548387096774 76.93 75.02 68.13 65.3 61.14 42.19 0.225806451612903 70.44 69.2 65.76 59.45 55.6 41.01 0.258064516129032 63.77 62.77 60.01 55.2 3 52.2 39.88 0.290322580645161 58.73 57.92 56 53.79 51.92 39.32 0.32258064516129 58.42 57.85 54.18 48.16 44.95 34.02 0.354838709677419 57.76 56.57 52.95 47.42 44.87 32.78 0.387096774193548 56.38 55.4 52.23 46.22 42.55 32.51

### 8

0.419354838709677 54.57 53.36 50 .21 43.92 40.58 32.24 0.451612903225806 51.52 50.58 47.28 42.98 40.43 31.6 0.483870967741936 45.52 44.98 43.06 40.48 39.4 31.48 0.516129032258065 45.15 44.46 42.57 40.41 39.25 30.09 0.548387096774194 44.59 44.08 41.89 38.68 37.85 29.85 0.580645161290323 39 .95 39.64 38.66 37.21 37.1 27.69 0.612903225806452 38.96 38.45 36.64 33.48 32.76 27.67 0.645161290322581 38.26 37.89 36.23 33.27 31.75 27.17 0.67741935483871 31.48 31.05 29.45 28.54 27.89 22.93 0.709677419354839 29.56 29.3 28.32 27.67 27.1 22.2 0.741935483 870968 28.99 28.55 26.97 25.35 25.01 20.91 0.774193548387097 28.46 27.95 26.44 25.27 24.89 20.34 0.806451612903226 27.56 27.33 26.18 24.64 24.35 19.85 0.838709677419355 26.8 26.6 25.87 22.67 20.63 17.26 0.870967741935484 23.99 23.69 22.64 21.09 20.53 17.13 0.903225806451613 23.31 23.05 22.09 20.79 19.65 16.95 0.935483870967742 21.59 21.33 20.45 19.07 18.21 14.39 0.967741935483871 14.52 14.14 12.86 8.053 5.709 2.497 0.1 89.054 87.43 80.884 71.12 66.946 48.694 Average of yearly averages: 30.810566666666 7 Inputs generated by pe5.pl
- Novem ber 2006 Data used for this run: Output File: CALettuce
- 1app Metfile: w23273.dvf PRZM scenario: CAlettuceSTD.txt EXAMS environment file: ir298.exv Chemical Name: Linuron Description Variable Name Value Units Comments M olecular weight mwt 249.1 g/mol Henry's Law Const. henry 6.1e
- 8 atm- m^3/mol Vapor Pressure vapr 1.5e
- 5 torr Solubility sol 81 mg/L Kd Kd mg/L Koc Koc 1195 mg/L Photolysis half

- life kdp 49 days Half
- life Aerobic Aquatic Metabolism kbacw 426 days Halfife Anaerobic Aquatic Metabolism kbacs 0 days Halfife Aerobic Soil Metabolism asm 213 days Halfife Hydrolysis: pH 7 0 days Half
- life Method: CAM 1 integer See PRZM manual Incorporation Depth: DEPI 0 cm Application Rate: TAPP 1.68 kg/ha Application Efficiency: APPEFF 0.99 fraction Spray Drift DRFT 0.064 fraction of application rate applied to pond Application Date Date 9
- 2 dd/mm or dd/mmm or dd
- mm or dd
-mmm Record 17: FILTRA IPSCND 1 UPTKF Record 18: PLVKRT PLDKRT FEXTRC 0.5 Flag for Index Res. Run IR Re servoir Flag for runoff calc. RUNOFF total none, monthly or total(average of entire run)

### 9 **Appendix I V**  **SCI -**  **GROW2 Input:**

**Input values used for m odeling groundwater concentrations of linuron using SCI**  **- GROW2**  **Model Input Param eter**  **Input Value and Unit Source/** **Comments** Aerobic Soil Metabolism Half
life (days) 213 days MRID 41625401; calculated using total toxic residue method ; 71 x 3 per input guidance when only one valid study is available Organic
- Carbon Normalized Partition Coefficient Koc 1195 (mL/g) MRID 43995301; average of 4 values per Input Parameter Guidance Application Rate 1. 0 lbs ai/A Proposed label Maximum No. of Applications/Year 2 Proposed label



### SCI **- GROW2 Output:**  SCIGROW VERSION 2.3 ENVIRONMENTAL FATE AND EFFECTS DIVISION

OFFICE OF PESTICIDE PROGRAMS U.S. ENVIRONMENTAL PROTECTION AGENCY

SCREENING MODEL FOR AQUATIC PESTICIDE EXPOSURE SciGrow version 2. 3 chemical:Linuron time is 4/ 4/2013 14:32:47

----------------------------------------------------------------------- ---------------- - Application Number of Total Use Koc Soil Aerobic rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------ ---------------- 1.0 2.0 2.000 1.20E+03 213.0

----------------------------------------------------------------------- ------------- --- - groundwater screening cond (ppb) = 2.30E
- 01 ************************************************************************

### 10 Appendix V **PRZ M**  **- GW Modeling In** **put and Output** 

**PRZ M**  **- GW Modeling I** **n put** 

### 11 **PRZ M**  **- GW**  **Modeling Output**

### 12