                 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460
                                       

										
                                                      OFFICE OF PREVENTION, 
                                                      PESTICIDES AND TOXIC 
                                                      SUBSTANCES	
                                                                PC Code: 035506
                                                             DP Barcode: 405829
                                                                               
MEMORANDUM						     			

DATE:	June 19, 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 Nollen, Risk Manager
		Barbara Madden, Risk Manager Reviewer
      Registration Division (7505P)
      
		Christine Olinger, Branch Chief
		Risk Assessment Branch III, 
      Health Effects Division (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 Drinking water assessment includes PRZM-GW model results.  The document provides estimated drinking water concentrations (EDWCs) 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 Horseradish, Parsley and Dry Peas were previously 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 13) in this document.  According to the proposed supplemental label, Lorox(R) 50% DF Herbicide can be applied annually in a single application as pre-emergence or up to two applications as post-emergence by ground spray, fertilizer spray mixture, and chemigation to control certain broadleaf weeds and grasses.  The application directions also specified to not apply by air, to the sand or loamy sand soil or use on soils with less that 1% organic matter.  Table 1 is a summary of the proposed supplemental label.  
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/EXAMs (see input values in Appendix II) for surface water are listed in Table 2.  The maximum surface water EDWCs in this assessment (see Appendix III) supersede the previous upper bound EDWC values of 77.4 μg/L, 42.4 μg/L and 26.8 μg/L (PCA = 0.87) for peak (acute), annual average (non-cancer chronic), and 30-year annual average (cancer chronic) respectively (USEPA 2010, DP371421, 371396, 371471, 371472, 371473).  Therefore, EFED recommends the new maximum EDWC values of 89.05 μg/L, 48.69 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) respectively.  

Ground water EDWC from SCI-GROW model is 0. 23 μg/L (see input and output values in Appendix IV), 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 supersedes the previous post-mitigation monitoring concentration of 0.61 ppb and therefore, EFED recommends the PRZM-GW highest acute value of 54.5 μg/L and chronic value of 48.69 for groundwater.

Table 1.  Summary of Application Information Used in PRZM/EXAMS for Surface Water EECs
                                     Crop
                            PRZM/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
                                     10-12

                                   CALettuce
                                     0.75
                                     0.84
                                       2
                                      9-2

                                    ORmint
                                     0.75
                                     0.84
                                       2
                                      8-4
Celeriac
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
                                     10-12

                                   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
[4]Application date is estimated for the region one week before crop emergence date per proposed label.

Table 2.  Surface Water EECs for Linuron by PRZM/EXAMS for IR-4 New Use on Coriander, Dill, Celeriac Horseradish, Parsley, Dry Peas and Rhubarb 
Crop
                            PRZM/EXAMS Scenarios[1]
                               Application Rate 
                                (kg a.i./ha)[2]
                        Maximum Number of Applications
                                  Peak (ppb)
                               Annual Mean (ppb)
                             Long-term Mean (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 PRZM-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 
                                     ug/L
                          Post Breakthrough Average 
                                     ug/L
                     Average Simulation 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) 
                                       
                                    0.0246
                                       
                                    0.0203
                                       
                                   25,376.8
          GA - Southern Coastal Plain, Tifton loamy sand  -  PEANUTS
                         Met File (w93805Extended.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 (14920Extended.dvf)
                                     54.5
                                     48.8
                                   20,101.2
                                       

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 Development and Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update.  pp50

                                  Appendix I
                                        
             Chemical and Environmental Fate Properties of Linuron
                            Chemical/Fate Parameter
                                   Value(s)
                                 Source (MRID)
Common Name
Linuron
Product Chemistry
Empirical formula
C9H10Cl2N2O2
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.htm (Accessed 3/20/2013)
IUPAC
3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea
http://sitem.herts.ac.uk/aeru/iupac/419.htm (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 24C)
1.5 x 10[-5]
Product Chemistry
Water solubility (mg/L; at 20C)
81
Product Chemistry
Henry's Law Constant (atm-m[3]/mol; at 25C)
6.1 x 10[-8]
Calculated[1]
Hydrolysis half-lives (25C) (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 days3 
41625401 (valid)[4]
Organic carbon normalized partition coefficients (KOC) (L/kgOC)
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)
39x (carcass)
240x (viscera)
49x (whole fish)
00142933 
[1] Calculated according to USEPA 2002 by: (VP*MW) / (760*solubility).
[2] Calculation from original data evaluation review.
[3] Calculated using total toxic residue method.
[4] This study was found to be valid under old review standards.  

                                  Appendix II

               PRZM/EXAMS modeling input values for linuron use 
    on Coriander, Dill, Celeriac Horseradish, Parsley, Dry Peas and Rhubarb
Model Input Parameter
Input Value and Unit
Source/Comments
Molecular Weight.
 249.1
Product Chemistry
Henry's Law Constant (atm-m[3]/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)
Type 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.


                                 Appendix III
                                       
                    Examples of PRZM/EXAMS Modeling Output
stored as CALettuce-1app.out
Chemical: Linuron
PRZM environment: CAlettuceSTD.txt	modified Tuesday, 21 February 2006 at 15:38:22
EXAMS environment: ir298.exv	modified Tuesday, 26 August 2008 at 06:14:07
Metfile: w23273.dvf	modified 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	40.43	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	25.01	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	55.23	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
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
0.741935483870968	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:	30.8105666666667

Inputs generated by pe5.pl - November 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
Molecular 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	Reservoir
Flag for runoff calc.	RUNOFF	total	none, monthly or total(average of entire run)

                                  Appendix IV

SCI-GROW2 Input:

Input values used for modeling groundwater concentrations of linuron using SCI-GROW2
Model Input Parameter
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 
 ************************************************************************

                 Appendix V  PRZM-GW Modeling Input and Output
                                       
                                       
                            PRZM-GW Modeling Input
                                       
                                       
                                       

                                       
                            PRZM-GW Modeling Output









