UNITED STATES ENVIRONMEN TAL PROTECTION AGENCY WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM

Date: 9 July 2010

SUBJECT: Imazosulfuron . Dissipation of Dislodgeable Fo liar Residues on Tomato Leaves.

PC Code: 118602 DP Barcode: D380799

Decision No.: NA Registration No.: NA

Petition No.: NA Regulatory Action: NA Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 122548-33-8

MRID No.: 47679129 40 CFR: NA

FROM: Nancy J. Tsaur, Chemist Risk Assessment Branch 3 (RAB3) Health Effects Division (7509P)

THROUGH: Barry O’Keefe, Biologist, ORE Team Leader Risk Assessment Branch 3 (RAB3) Health Effects Division (7509P)

TO: Sheila Healy, Toxicologist, Risk Assessor Risk Assessment Branch 3 (RAB3) Health Effects Division (7509P)

Attached is a review of the study “Dissipation of Dislodgeable Fo liar Residues of Imazosulfuron

on Tomato Leaves” submitted by Valent U.S.A. Corporation (Valent). The primary review was conducted by Versar and the secondary review was conducted by the Health Effects Division (HED). This document was reviewed by the HED Exposure Science Advisory Council (ExpoSAC) on 07/08/2010.

Page 1 of 22Dislodgeable Foliar Residue (2008)/Page 2 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Executive Summary

This study was designed to determine the dissipati on of dislodgeable foliar residues (DFRs) of imazosulfuron applied to tomato plants at a test site located in Madera, CA. One application of V-10142 75 WDG, a water dispersible granular formulation containing 75% imazosulfuron as the active ingredient, was made at a target application rate of 0.5 lb ai/A. Applications were made as a foliar broadcast spray at a spray volume of approximately 29.9 gallons per acre (GPA). Samples were collected before the app lication, within 1.5 hours of application and 1, 2, 3, 4, 5, 7, 10, 14, 21, 28, and 35 days after treatment (DAT). At each sampling interval, single samples were collected from the control plot and triplicate samples were collected from the treated plot. Field-fortified sa mples prepared using leaf sample s from the control plot were prepared on days 1, 7, and 14 after the application to evaluate the stability of the field samples during shipment and storage and to determine extr action efficiency in the analytical laboratory.

The Registrant provided dislodge able foliar residues in μg/cm 2 . The overall average low and high level field fortification reco veries were >90%, therefore, HE D did not correct the data for

field fortification recoveries. For calculation purposes, DFR values reported as between the limit of quantitation (LOQ) and the limit of detecti on (LOD) were assigned a value of 1⁄2 LOQ and DFR values less than the LOD were assigned a value of 1⁄2 LOD.

The highest average DFR value occurred immediately after the application (0.761 μ g/cm 2 ). The residues declined rapidly to an average of 0.163 μ g/cm 2 by Day 1, and then declined gradually to less than the LOD by Day 35.

HED assumed first-order dissipat ion kinetics to generate a di ssipation curve for imazosulfuron.

HED used individual residue data collected imme diately after the application through the first day where all of the residue values were below the LOQ (0.00625 μ g/cm 2 ). Based on linear regression of the natural log tr ansformed data, HED’s calculated half-life for imazosulfuron was 4.11 days (R 2 = 0.838). The actual DFR residue level on Day 0 (0.761 μ g/cm 2 ) is significantly greater than the pr edicted DFR (0.178 μ g/cm 2 ), based on linear regression analysis of logtransformed data. Additionally, the analytical method was validated using samples fortified at levels less than the highest initial measurement of 0.808 μg/cm 2 . Since the concurrent laboratory recovery for the highest fortified sample was onl y 85.8%, it is more appropr iate and protective to use the actual residue data for Day 0 while al so correcting for an 85.8% laboratory recovery when assessing risks to postapplication worker s (resulting in a residue value of 0.887 μg/cm 2 ). The field recoveries were much higher than the lab recoveries, and theref ore indicate a greater range of viability.

The Registrant attempted to more clearly char acterize the biphasic dissi pation pattern of the regression by calculating two half life estimates . A half-life of 10 hours was determined for the samples collected in the time peri od immediately after the applicati on to Day 1 and a half-life of 5.2 days was determined for the samples collec ted from Day 2 to Day 28 after application.

This study met the majority of the Series 875.2100 Guidelines. The following issues of concern

are noted:Dislodgeable Foliar Residue (2008)/Page 3 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

• The production of metabolites, breakdown produc ts, or the presence of contaminants of concern were not discussed in the Study Re port. However, the imazosulfuron parent compound has been selected as an adequate marker for tolerance enforcement.

• DFR data should be collected from at least th ree geographically distin ct locations but only one geographical location wa s used in this study.

• Although few samples exceeded the field fortific ation levels used in the study (0.0500 and 0.250 μg/cm 2 ), HED does not believe this to be of significant concern given the relative performance.

• Field fortifications were performed on only three of the study days -- days 1, 7, and 14.

• Information verifying that the applicati on equipment was properly calibrated was not included in the Study Report.

• It is uncertain if this site is representative of reasonable worst-case climatic conditions expected in intended use areas. Meteorol ogical conditions including temperature, wind speed, daily rainfall, and humi dity were not provided for the duration of the study. Only precipitation/irriga tion data were provided for the duration of the study.

• Results from a separate storage stability study were not provided with the study. Field fortification samples were intended to assess the stability of imazosulfuron during storage. The longest storage interval for a field sample was 55 days, and the longest storage interval for a set of field fortification samples was 55 days (demonstrating an overall recovery >90%).

• The Registrant validated the analytical method using samples fortified at 0.0063 and 0.031 μg/cm 2 . One concurrent laboratory fortified sa mple was analyzed with a concentration approximating the highest concentration found in the field samples (0.808 μg/cm 2 ). The concurrent recovery for this laboratory for tified sample was corrected based on the percent recovery (85.8%).

• According to the product label, the maximum app lication rate is 0.3 lb ai/A. In this study, the target application rate was 0.5 lb ai/A.Dislodgeable Foliar Residue (2008)/Page 4 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

EPA Reviewer: Nancy J. Tsaur Date: 25 June 2010 Risk Assessment Branch 3 (RAB3) Health Effects Division (7509P) Template version 02/06

DATA EVALUATION RECORD

STUDY TYPE : Determination of Dislodgeable Foliar Imazosulfuron Residues from

Tomato Leaves Treated w ith V-10142 75 WDG: OPPTS 875.2100

PC CODE : 118602

TEST MATERIAL V-10142 75 WDG is formulated as a water dispersible granular formulation containing 75% activ e ingredient, imazosulfuron.

SYNONYMS : Imazosulfuron; CAS No. 122548-33-8.

CITATION : Authors: C.A. Green Title: Dissipation of Dislodg eable Foliar Residues of Imazosulfuron on Tomato Leaves (122 pages). Report Date: June 5, 2008 Analytical Laboratory: Va lent U.S.A. Corporation

Valent Technical Center 6560 Trinity Court Dublin, CA 94568 Identifying Codes: Valent Project No. 30582; MRID 47679129; Unpublished

SPONSOR : Valent U.S.A. Corporation

P.O. Box 8025 Walnut Creek, CA 94596-8025

COMPLIANCE :

Signed and dated GLP, Quality Assurance, and Da ta Confidentiality statements were provided. The study sponsor waived claims of confidentia lity within the scope of FIFRA Section 10 (d)1(A), (B), or (C). The Study Report indi cated that the study wa s conducted under EPA Good Laboratory Practice Standards ( 40 CFR Part 160), with the follo wing exceptions: Weather data, pesticide history, cultural practic es, application of maintenance chemicals, irrigation data, crop history and the pH measurement of the carrier water were not documented in compliance with GLP Standards. In addition, the dilution of a fo rtification standard (w hich had degraded) was not documented in compliance with GLP Standards.

CONCURRENT EXPOSURE STUDY: NoDislodgeable Foliar Residue (2008)/Page 5 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

GUIDELINE OR PROTOCOL FOLLOWED : Series 875, Part B: Dislodgeable Foliar Residue Dissipation: Agri cultural, Guideline 875.2100.

I. MATERIALS AND METHODS

A. MATERIALS :

1. Test Material :

Formulation: V-10142 75 WDG is formulated as a water dispersible granular formulation containing 75% activ e ingredient, imazosulfuron.

Batch/Lot #: V06C-102DG-3 (formulated product) AS 2146a (reference standard)

Formulation Guarantee: The Study Report stat ed that the test product contained 76.1% imazosulfuron (assayed on March 8, 2006). Expiration date: March 8, 2007.

Purity: The imazosulfuron reference standard was analyzed and found to have a purity of 99.7% (assayed on January 12, 2004). Expiration date: January 5, 2007.

CAS #: 122548-33-8

Other Relevant Information: EPA Registration Number 59639-RLL.

2. Relevance of Test Material to Proposed Formulation(s) :

The test product used in this study was V-10142 75 WDG, containing 75% imazosulfuron. A label for V-10142 AG Herbicide (EPA Reg. N o. 59639-RLL) was provided with the Study Report. This label appears to be the sa me or similar to the test product.

B. STUDY DESIGN :

The study protocol was provided in the Study Re port. There was one amendment to the study protocol: the lot number for the test substance was changed and the VC# listed was changed to the correct number. The Study Report did not provide any information detailing protocol

deviations.Dislodgeable Foliar Residue (2008)/Page 6 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

1. Site Description :

Test Locations: The DFR portion of the study was conduc ted at a test site in Madera,

CA. The test site was said to be representative of climate and crop growing conditions expected in the in tended-use areas. One control plot and one treated plot were established at the test site. According to the study protocol, the control plot was to be located upwind and upslope from the treated plot at a minimum distance of 50 feet.

Areas Sprayed and Sampled: The treated plot measured 120 ft by 21.6 ft (2,592 ft 2 or 0.0595 acre). The untreated plot measured 50 ft by 20 ft (1,000 ft 2 or 0.0230 acre).

Meteorological Data: Precipitation data were reported for the months of the trial along with comparative 10-year historical data . Total monthly rainfall for the

months of the trial was within the hi storical 10-year average. No rainfall occurred during the sampling period; furrow irrigation was applied four hours after the first postapp lication sampling interval.

Air temperature and wind speed and direction recordings were provided for the day of application. Air temp erature was recorded as 81°F during the application; wind speed was repor ted as ranging from 0 to 1 mph (NW direction) during the applicati on. No other meteorological data were provided; however, the protocol required daily air temperature and relative humidity to be recorded, whic h could be in the form of reports from the nearest NOAA or other governmental recording station.

2. Crop Characteristics :

Crop, Variety: Tomato, Sun Br ight; planted April 29, 2006.

Row Width, Plant Spacing: 8 rows spaced 5 ft apart.

Stage of Growth: Green and ripe tomato fruit.

Other Products Used on Crop: No maintena nce or fertilizer compounds were applied immediately before the application or during the study.

3. Application Rates and Regimes :

Application Rate(s): The target application rate was 0.5 lb ai/A; the actual application rate was 0.4996 lb ai/A (99.8% of target ra te). According to the label for V-10142 AG Herbicide (EPA Reg. No. 59639-RLL), the maximum recommended application rate fo r tomatoes is 0.3 lb ai/A.

Application Regime: One application was made at the test site on July 24, 2006.Application Equipment: A 60-gal power sprayer was used fo r the test substance application. The power sprayer was equipped with Tee Jet 8002 VS flat fan

nozzles.

Spray Volume: The product label for V-10142 AG Herbicide (EPA Reg. No. 59639- RLL) indicates that the product shou ld be applied in 20 to 40 gallons of water carrier per acre (GPA). The actual spray volume used was 29.9 GPA. No additives or adjuvants were used.

Equipment Calibration

Procedures: The Study Report did not menti on calibrating th e application equipment.

4. Dislodgeable Foliar Residue Sampling Procedures :

Method and Equipment: DFR samples replicates consiste d of 40 leaf discs which were

collected with a leaf puncher (1-inch diameter). The punch samples were collected directly into pre- labelled glass jars on July 24, 2006.

Sampling Procedure: At each sampling interval, three samples were collected from the treated plot; a single sample was coll ected from the control plot. Leaf

discs were collected when the folia ge was dry. The untreated plot was sampled prior to the treated plot. A specific randomization procedure was used for sampling throughout the plot.

Total Surface Area per Replicate: The double sided surface area per leaf punch was approximately 10

cm 2 and 40 leaf discs were collected for each replicate (400 cm 2 ).

Replicates per Activity:

- Replicates per sampling time: At each sampling interval, triplicate DFR samples were collected from the treated plot and one sample was collected from the control plot. - Number of sampling times: Ther e were a total of 13 sampling

events, including one pre-application sampling event.

Times of Sampling: Samples were collected before th e application, with in 1.5 hours of application and 1, 2, 3, 4, 5, 7, 10, 14, 21, 28, and 35 days after the application.

Part(s) of Foliage Sampled: The Study Report stated that all ar eas of the plants were sampled.

5. Sample Handling :

Samples were transported in coolers with substi tute ice to the field laboratory for dislodging. According to the Study Report, dislodging was perf ormed within 2 hours of sample collection. The dislodged samples were maintained frozen at the testing facility until they were shipped. Sample bottles were shipped in dry ice overnight to Valent Technical Center. Samples were

Page 7 of 22Dislodgeable Foliar Residue (2008)/Page 8 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

received at the analytical f acility from July 27, 2006 through A ugust 31, 2006 and stored at about

-20oC until extraction and analysis. The analytical portion of the study was carried out from September 6, 2006 through September 25, 2006. The maximum length of frozen storage was 55 days for the field samples and field fortification samples.

6. Analytical Methodology :

Dislodging Solution: Imazosulfuron residues we re dislodged with 0.01% Aerosol® OT solution to dislodge surface residue.

Dislodging Procedure: Samples were dislodged within the sampling jars twice. Each dislodging used 100 mL of the 0.01% Aerosol OT solution. Dislodging was conducted by shaking the sample on a mechanical

shaker for 10 minutes. The resultin g solutions were combined and the foliage was discarded.

Time Interval (Sample Collection to Dislodging): All samples were dislodged within 2 hours of collection.

Extraction Method: The DFR solution samples were extracted with methylene chloride. After rotary evaporation to remove the methylene chloride, residues were re-dissolved in acetonitrile, partitioned with hexane and rotary evaporated to remove the acetonitrile. Residues were then dissolved in ammonium acetate solution (in methanol/water) and analyzed by high-pressure liquid chromatogra phy with mass selective detection (LC/MS-MS).

Detection Methods: All samples were analyzed using high-pressure liquid chromatography with mass select ive detection (LC/MS-MS). A summary of the conditions are shown in Table 1.

Table 1. Summary of Typical LC/MS-MS Conditions

HPLC Conditions

Column: Luna (C18), 3 μm, 50 mm x 3.0 mm

Mobile Phases: A = Methanol, 0.05% formic acid and B = Water, 0.05% formic acid

Flow Rate: 300 μL/minute

Injection Volume: 10 μL

Gradient Program: Time (min) %A %B

0 50 50

0.5 50 50

7.0 90 10

10.5 90 10

12 50 50

14 50 50

Retention Time: 14 minutesDislodgeable Foliar Residue (2008)/Page 9 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Table 1. Summary of Typical LC/MS-MS Conditions

LC/MS Interface Conditions

Interface: Electrospray Ionization

Source CID Collision Energy: 16

Polarity: Positive

Q2 Collision Gas Pressure: 0.9 mTorr

Scan Type: SRM

Parent Ion Mass: m/z 413

Quantitation Ion Mass: m/z 156.1

Collision Energy: 34

Method

Validation: Samples of dislodging solution were an alyzed for residues of imazosulfuron using analytical method RM-42D-1. The method was validated prior to analysis of the field samples collected fo r this study. Recoveries from samples fortified with 2.5 μg (0.00625 μg/cm 2 ) ranged from 81.9 to 90.4%, and recoveries from samples fortified with 12.5 μg (0.03125 μg/cm 2 ) ranged from 94.5 to 102%. The validated limit of quantitation (LOQ) was 0.00625 μg/cm 2

. The limit of detection (LOD) was 0.0031 μg/cm 2

.

Instrument

Performance: The linearity of the LC system was ve rified within each analytical sequence with five linearity standards. The calibration was performed using a linear fit with a non-zero intercept. The slope and the intercept were calculated using a linear regression weighed by 1/concentr ation. The r-squared value was also calculated from this data set, and this value was required to be greater than 0.99 for the instrument response to be considered linear for the range of standard concentrations. In addition, th e concentration calculated from the peak area of each of the standards, using the slope and intercept form the linear fit, was required to be within 15% of the actual concen tration. All of the sample sets met this requirement.

The reproducibility of the LC system was verified by comparison of the detector responses obtained from the repe ated analysis of a reference standard analyzed with the study samples. The coefficient of variation of these responses was required to be 10% or le ss for an analytical sequence to be acceptable. All of the samples sets met this requirement.

Quantification: The analyte concentration in the sample extracts was determined using the slope and intercept of the linear fit equation, the peak area of the sample, and the dilution factor, if any. The resulting concentration in μg/mL was converted to μg/ cm 2 using the total volume of the deterg ent solution used to dislodge the

residues and the surface ar ea of the leaf punches.Dislodgeable Foliar Residue (2008)/Page 10 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

7. Quality Control :

Lab Recovery: Concurrent laboratory fortif ied samples were analyzed with each set of field samples. Control 0.01% AOT samples were fortified with imazosulfuron at concentrations ranging from 0.00625 μg/cm 2 to 0.750 μg/cm 2 . Individual concurrent laboratory recoveries ranged from 84.5% to 97.5% with an overall mean recovery of 89.9% ± 4.4% (n= 14).

Field Blanks: One control sample was collected at each sampling interval from the untreated plot. There were no imazosulfuron residue s detected above the LOQ in any of the untreated control samples.

Field Recovery: Field fortification samples were prepared at two concentrations using control dislodging solution fortified with imazo sulfuron. The samples were prepared on days 1, 7, and 14 after application. The fortification levels were 0.05 and 0.250 μg/cm 2 . The field fortified samples we re shipped and stored in the freezer for up to 55 days under the same conditions as the field samples.

Field Blanks: One control sample was collected at each sampling interval from the untreated plot. There were no imazosulfuron residue s detected above the LOQ in any of the untreated control samples.

The field fortification recoveries were reported as corrected for the concurrent recovery of the high level la b fortification sample from the analytical set that the fortified samples were analyzed wit h. Because the residue levels were not corrected for concurrent laboratory r ecovery, HED found it more appropriate to present field fortification values which were also not corrected for concurrent laboratory recovery. Ta ble 2 provides a summary of the

uncorrected field for tification recoveries. The overall mean field fortification recovery was 93.1% ± 5.97%.

The fortification levels did not bracket the residue levels found in the field samples. The first sampling interval fi eld samples had residues greater than the high field fortificat ion level of 0.250 μg/cm 2

.

Table 2. Summary of Fiel d Fortification Recoveries

Sampling

Event Fortification

Level (μg/cm 2 ) Imazosulfuron

Residue (μg/ cm 2 ) Percent Recovery (%) Average

Percent Recovery

p er Level (%) Overall

Low Level

Percent Recovery (%) Overall High Level

Percent Recovery (%) Overall

Percent Recovery (%) Std. Dev.

0.0500 0.0473 94.7

0.0500 0.0461 92.2

0.0500 0.0459 91.7 92.9

0.250 0.240 95.8

0.250 0.245 98.2 1 DAT

0.250 0.235 93.8 95.9 94.1 92.0 93.1 5.97Dislodgeable Foliar Residue (2008)/Page 11 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Table 2. Summary of Fiel d Fortification Recoveries

Sampling

Event Fortification

Level (μg/cm 2 ) Imazosulfuron

Residue (μg/ cm 2 ) Percent Recovery (%) Average

Percent Recovery

p er Level (%) Overall

Low Level

Percent Recovery (%) Overall High Level

Percent Recovery (%) Overall

Percent Recovery (%) Std. Dev.

0.0500 0.0481 96.2

0.0500 0.0478 95.7

0.0500 0.0471 94.2 95.3

0.250 0.176 70.2

0.250 0.232 92.8 7 DAT

0.250 0.243 97.2 86.7

0.0500 0.0466 93.2

0.0500 0.0476 95.2

0.0500 0.0470 94.0 94.1

0.250 0.233 93.1

0.250 0.238 95.0 14 DAT

0.250 0.230 91.9 93.3

Formulation: V-10142 75 WDG is formulated as a wate r dispersible granular formulation containing 75% active ingredient, imazosulfuron.

Tank Mix: Tank mix samples were not collected for this study.

Travel Recovery: Travel recovery sa mples were not used in this study.

Storage Stability: A separate storage stability study wa s not conducted. However, the fieldfortified samples were stored and sh ipped under the same conditions as the field samples and were used to provide storage stability data for the treated samples. The resulting field fortification recovery data indicate that imazosulfuron was stable under the freezer storage and shipping conditions used in the study for up to 55 days. The field samples were stored in the freezer for up to 55 days.

II. RESULTS AND CALCULATIONS

The Registrant provided dislodge able foliar residues in μg/cm 2 . The overall average low and high level field fortification reco veries were >90%, therefore, HE D did not correct the data for

field fortification recoveries. For calculation purposes, DFR values reported as between the limit of quantitation (LOQ) and the limit of detecti on (LOD) were assigned a value of 1⁄2 LOQ and DFR values less than the LOD were assigned a value of 1⁄2 LOD.

A summary of the DFR values calculated by HED is provided in Table 3. Additionally, a graphical presentation of the DFR values is sh own in Figure 1. The highest average DFR value occurred immediately afte r the application (0.761 μ g/cm 2 ). The residues declined rapidly to an average of 0.163 μ g/cm 2 by Day 1, and then declined gradually to less than the LOD by Day 35.Dislodgeable Foliar Residue (2008)/Page 12 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Additionally, the analytical method was validated us ing samples fortified at levels less than the highest initial measurement of 0.808 μg/cm 2 . Since the concurrent laboratory recovery for the highest fortified sample was only 85.8%, it is more appropriate and protec tive to use the actual residue data for Day 0 while also correcting fo r an 85.8% laboratory recovery when assessing risks to postapplication workers (resu lting in a residue value of 0.887 μg/cm 2 ).

Both HED and the Registrant assumed first order d ecline of the residues in determining the halflife of dislodgeable imazosulfu ron residues for tomato leaves and performed a linear regression analysis. The Registrant stat ed that the decline in dislodge able residues was biphasic and therefore, estimated half-life values for the time period betw een Day 0 and Day 1 after the application and the time period from Day 2 to Day 28 after the application. The Registrant’s half-life for the time period betw een Day 0 and Day 1 was 10 hours (R 2 = 0.9582) and the halflife for the time period from Day 2 to Day 28 was 5.2 days (R 2 = 0.8934).

HED assumed first-order dissipat ion kinetics to generate a di ssipation curve for imazosulfuron.

HED used individual residue data collected imme diately after the application through the first day where all of the residue values were below the LOQ (0.00625 μ g/cm 2 ). HED used a value of 1⁄2 the LOD for residue values which dropped below the LOD and 1⁄2 the LOQ when values dropped below the LOQ but were greater than th e LOD. As shown in Appendix B, HED's

estimated half-life value was 4.11 days (R 2 = 0.838).

III DISCUSSION:

A. LIMITATIONS OF THE STUDY:

This study met the majority of the Series 875.2100 Guidelines. The following issues of concern

are noted:

• The production of metabolites, breakdown produc ts, or the presence of contaminants of concern were not discussed in the Study Re port. However, the imazosulfuron parent compound has been selected as an adequate marker for tolerance enforcement.

• DFR data should be collected from at least th ree geographically distin ct locations but only one geographical location wa s used in this study.

• The field fortification levels us ed in the study (0.0500 and 0.250 μg/cm 2 ).

• Field fortifications were performed on only three of the study days -- days 1, 7, and 14.

• Information verifying that the applicati on equipment was properly calibrated was not included in the Study Report.

• It is uncertain if this site is representative of reasonable worst-case climatic conditions expected in intended use areas. Meteorol ogical conditions including temperature, wind speed, daily rainfall, and humi dity were not provided for the duration of the study. Only precipitation/irriga tion data were provided for the duration of the study.Dislodgeable Foliar Residue (2008)/Page 13 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

• Results from a separate storage stability study were not provided with the study. Field fortification samples were intended to assess the stability of imazosulfuron during storage. The longest storage interval for a field sample was 55 days, and the longest storage interval for a set of field fortification samples was 55 da ys (demonstrating an overall recovery >90%).

• The Registrant validated the analytical method using samples fortified at 0.0063 and 0.031 μg/cm 2 . One concurrent laboratory fortified sa mple was analyzed with a concentration approximating the highest concentration found in the field samples (0.808 μg/cm 2 ). The concurrent recovery for this laboratory for tified sample was corrected based on the percent recovery (85.8%).

• According to the product label, the maximum app lication rate is 0.3 lb ai/A. In this study, the target application rate was 0.5 lb ai/A.

B. CONCLUSIONS :

Immediately following application of imazosulfur on, 15.8% of the original application rate was dislodged from the tomato leaves. Average DFR values dissipated rapidly from 0.761 μg/cm 2
collected at approximately 1 hr after the application to 0.163 μg/cm 2 by Day 1; average DFR residues then declined gradually to less than the LOD by Day 35.Dislodgeable Foliar Residue (2008)/Page 14 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Table 3. Imazosulfuron DFR Residues from Tomato Leaves Treated with V-10142 75 WDG

Sample Interval Measured

Residue ( μ g/cm 2 ) Arithmetic

Mean ( μ g/cm 2 ) Standard

Deviation ( μ g/cm 2 ) Coefficient of

Variance (%) Natural Log of

Mean ( μ g/cm 2 ) Percent of Application

Rate Dislodgeable

0.942

0.902 0.042DAT a

0.818 0.887 0.063 7.11 -0.121 15.8

0.218

0.140 1 DAT

0.130 0.163 0.048 29.6 -1.816

--

0.135

0.118 2 DAT

0.0770 0.110 0.030 27.11 -2.207

--

0.0980

0.0923 3 DAT

0.0929 0.094 0.003 3.3 -2.360

--

0.0800

0.0636 4 DAT

0.0602 0.068 0.011 15.6 -2.689

--

0.0423

0.0492 5 DAT

0.0713 0.054 0.015 27.9 -2.914

--

0.0505

0.0417 7 DAT

0.0455 0.046 0.004 9.6 -3.081

--

0.0321

0.0254 10 DAT

0.0216 0.026 0.005 20.2 -3.636

--

0.0101

0.0116 14 DAT

<LOQ 0.008 0.005 54.65 -4.795

0.0063

0.0080 21 DAT

0.0109 0.008 0.002 27.7 -4.780

--

<LOQ

<LOD 28 DAT

<LOQ 0.003 0.001 35.0 -5.952

--

<LOD

<LOD 35 DAT

<LOD 0.002 0.000 0.0 -6.470

--

a Measured residues for Day 0 were corr ected based on concurrent laboratory recovery of highest fortified sample (85.8%). Actual measurements were: 0.808, 0.774, and 0.702 μg/cm 2

. DAT = Day after Treatment LOQ = 0.00625 μg/cm 2Dislodgeable Foliar Residue (2008)/Page 15 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9aDislodgeable Foliar Residue (2008)/Page 16 of 22

Imazosulfuron/PC Code 118602 OPPTS 875.2100 / DACO 5.9a

APPENDIX A

Compliance Checklist for

“

Dissipation of Dislodgeable Foliar Residu es of Imazosulfuron on Tomato Leaves ”Dislodgeable Foliar Residue (2008)/Page 17 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Compliance Checklist for "Dissipation of Dislodgeable Foliar Resi dues of Imazosulfuron on Tomato Leaves"

Compliance with OPPTS Series 875, Occupational and Residentia l Exposure Test Guidelines, Group B: Postapplication Exposur e Monitoring Test Guidelines, Dislodgeable Foliar Residue Dissipation: Agricultural, 875.2100 is critical. The itemized checklist below describes compliance with the major techni cal aspects of OPPTS 875.2100.

• The test substance must be the typical end use product of the active ingredient. This criterion was

met.

• The production of metabolites, breakdown products , or the presence of contaminants of concern, should be considered in the study design on a case-by-case basis. It is not certain if this criterion was met. Metabolites or breakdown prod ucts for imazosulfuron were not discussed in the Study Report. However, the imazosulfuron parent compound has been selected as an adequate marker for tolerance

enforcement.

• Applications should occur at the time of season that the end-use product is normally applied to achieve intended pest control . This criterion was met.

• Initiating testing immediately before a precipitation event should be avoided. This criterion was met.

• The end use product should be applied by the application method recommended for the crop. Information that verifies that the application e quipment (e.g., sprayer) was properly calibrated

should be included. These criteria were partially met. The Study Report stated that the application equipment at each test site was calibrated before use. However, the procedures used for calibrating the equipment were not provided in the Study Report

• The application rate used in the study should be pr ovided and should be the maximum rate specified on the label. However, monitoring following application at a typical application rate is more appropriate in certain cases. This criterion was mostly met. According to the product label, the maximum application rate is 0.3 lb ai/A. In this st udy, the target applicati on rate was 0.5 lb ai/A.

• If multiple applications are made, the minimum allowable interval between applications should be

used. Not applicable. Only one application was made.

• Dislodgeable foliar residue (DFR) data should be collected from at least three geographically distinct locations for each formulation and cr op type. The sites should be representative of the regions (and crops) where the chemical is used. Technically, this criterion was not met. Only one geographical location was used in this study. Ho wever, persistence of residues in California is expected to be higher due to minimal rainfall, and the DFR data are well representative of the anticipated geographical high use areas of tomatoes and peppers.

• The site(s) treated should be representative of reasonable worst-case climatic conditions expected in

intended use areas. Meteorological conditions including temperature, wind speed, daily rainfall, and humidity should be provided for the duration of the study. These criteria were partially met. Air temperature, wind speed, wind direction, and rainfall were recorded for each application event. Only precipitation/irrigation data were provided for the duration of the study.Dislodgeable Foliar Residue (2008)/Page 18 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

• Sampling should be sufficient to characterize th e dissipation mechanisms of the compound (e.g., three half-lives or 35 days after the final application, unl ess the compound has been found to fully dissipate in less time; for more persistent pesticides, l onger sampling periods may be necessary). Sampling intervals may be relatively short in the beginning and lengthen as the study progresses. Background samples should be collected before application of the test substance occurs. These criteria were met. Samples were collected out to 35 days after the application.

• Triplicate, randomly collected samples shoul d be collected at each sampling interval. This criterion

was met.

• A leaf punch apparatus should be used unless the nature of the crop precludes its use. Samples should represent at least an area of 400 cm 2 . These criteria were met.

• Control plots should be established from which suffic ient control samples can be collected. Control sites should be upwind and a reasonable distance from the treatment site. These criteria were mostly met. However, it is uncertain if the control pl ots were located upwind and at a reasonable distance from the treated plots.

• Residues should be dislodged from leaf surfa ces using an aqueous surfactant solution within a reasonable time period (i.e., EPA recommends that dislodging occur within 4 hours). Dislodging should be repeated at least once and the resultant solutions pooled for analysis. This criterion was

met.

• Samples should be stored in a manner that will minimize deterioration and loss of analytes between collection and analysis. Information on storage stability should be provided. These criteria were met. A storage stability study was not performed. However, storage stability of imazosulfuron during the study period was demonstrated by analysis of fo rtified field samples stored and shipped under the same conditions as the field samples.

• Validated analytical methods of sufficient sensitiv ity are needed. Information on method efficiency (residue recovery), and limit of quantitat ion (LOQ) should be provided. These criteria were met. The limit of quantitation (LOQ) was 0.00625 μ g /cm 2 . The method was validated prior to sample analysis using samples fortified at 0.0063 and 0.031 μg/cm 2 . Field samples with high concentration were diluted up to 16 times for quantitation purposes.

• Information on recovery samples must be included in the study report. A complete set of field recoveries should consist of at least one blank cont rol sample and three or more each of a low-level and high-level fortification. These fortifications shoul d be in the range of anticipated residue levels in the field study. This criterion was partially met. The field fortification samples were prepared at two levels: 0.0500 and 0.250 μg/cm 2 . Many of the first field samples collected demonstrated residue levels higher than the highest field fortification value.

• Raw residue data must be corrected if appropr iate recovery values are less than 90 percent. This criterion did not apply. Average low and high level field fortification recoveries were >90%, therefore the raw residue data did not require correction.

• Dislodgeable foliar residues should be reported as mg or μg per m 2 or cm 2 of leaf sampled. Distributional data should be reported, to the extent possible. This criterion was met.Dislodgeable Foliar Residue (2008)/Page 19 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

APPENDIX B

Regression Analysis ResultsDislodgeable Foliar Residue (2008)/Page 20 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

Regression Analysis: Summary Output for Imazosulfuron - CA

Regression Statistics Multiple R 0.908947 R Square 0.826185 Adjusted R 2 0.820578

Standard Error 0.68183

Observations 33

ANOVA df SS MS F Signif. F Regression 1 68.50204 68.50204 147.35053 2.5873E-13

Residual 31 14.41164 0.464892

Total 32 82.91368

Coeff. Std. Error t Stat P-value Lower 95% Upper 95%

Intercept -1.69607 0.168759 -10.0502 2.843E-11 - 2.04025067 - 1.35187967

Slope -0.16854 0.013885 -12.1388 2.587E-13 - 0.19686118 - 0.14022526

Half Life = 4.112578 Days

Predicted DFR Levels

Time (Days) Residue (ug/cm 2 ) Time (Days) Residue (ug/cm 2 )

0 0.183404 21 0.0053243

1 0.154957 22 0.0044985

2 0.130922 23 0.0038007

3 0.110616 24 0.0032112

4 0.093458 25 0.0027131

5 0.078963 26 0.0022923

6 0.066715 27 0.0019368

7 0.056367 28 0.0016364

8 0.047624 29 0.0013826

9 0.040238 30 0.0011681

10 0.033997 31 0.0009869

11 0.028723 32 0.0008339

12 0.024268 33 0.0007045

13 0.020504 34 0.0005952

14 0.017324 35 0.0005029

15 0.014637

16 0.012367

17 0.010448

18 0.008828

19 0.007459

Page 20 of 22Dislodgeable Foliar Residue (2008)/Page 21 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

20 0.006302

Regression Analysis: Means and CVs for Imazosulfuron - CA

Days after Last

Treatment Residues (ug/cm 2 ) Mean (ug/cm 2 ) Standard

Deviation (ug/cm 2 ) Coefficient

of

Variation (%)

0.042 0.941725 0.887 0.0631 7.11

0.902098

0.818182

1 0.218000 0.163 0.0482 29.6

0.140000

0.130000

2 0.135000 0.11 0.0298 27.1

0.118000

0.077000

3 0.098000 0.0944 0.00313 3.32

0.092300

0.092900

4 0.080000 0.0679 0.0106 15.6

0.063600

0.060200

5 0.042300 0.0543 0.0151 27.9

0.049200

0.071300

7 0.050500 0.0459 0.00441 9.62

0.041700

0.045500

10 0.032100 0.0264 0.00532 20.1

0.025400

0.021600

14 0.010100 0.00828 0.00452 54.6

0.011600

0.003125

21 0.006300 0.0084 0.00233 27.7

0.008000

0.010900

28 0.003125 0.0026 0.000909 35

0.001550

0.003125

Page 21 of 22Dislodgeable Foliar Residue (2008)/Page 22 of 22

Imazosulfuron//PC Code 118602 OPPTS 875.2100 / DACO 5.9a

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