Document ID: EPA-HQ-OPP-2011-0488-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2012-12-10T05:00Z

\s \* MERGEFORMATUNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            WASHINGTON, D.C.  20460

                                                  OFFICE OF CHEMICAL SAFETY AND
                                             POLLUTION PREVENTION              

MEMORANDUM

DATE: 	February 29, 2012

SUBJECT:	Tolclofos-methyl: Non-food Use For Seed Treatment on Various Crops

PC Code:  128905
DP Barcodes: D395999 and D397276
Decision No.: 443921
Registration No.: NA
Petition No.: NA
Regulatory Action: NA
Risk Assessment Type: Single chemical
Case No.: NA
TXR No.: NA
CAS No.: 57018-04-9
MRID No.: 48341956, 48627101 and 48341957
40 CFR: NA

REVIEWER:	Sheila Piper, Chemist
            Risk Assessment Branch VI
		Health Effects Division (HED, 7509P)

THROUGH:	Felecia Fort, Chief
            Risk Assessment Branch VI
		Health Effects Division (HED, 7509P)

TO:		Lisa Jones/Mary Waller, Risk Management Team 21
            Fungicide Branch
            Registration Division
            Risk Management Division

Executive Summary

Tolclofos-methyl is a seed treatment agent to control a number of soil-borne fungi including Rhizoctonia solani in cotton and other crops. In this study, the radiolabeled test substance, [phenyl-[14]C]tolclofos-methyl, was applied to soybean, corn, lettuce, cucumber, radish, and cotton seeds.  The study was conducted to determine if the seed treatment use of tolclofos-methyl could be designated for non-food.

The registrant, Valent U.S.A. Corporation met with EPA on October 2, 2008 to discuss tolclofos-methyl radiotracer studies which were conducted to support the non-food classification and the required toxicology data requirements which were based on Valent's review of existing data and their interpretation of the 40 CFR Part 158 requirements for nonfood uses.  Subsequently, HED's Chemistry Science Advisory Council (ChemSAC) met on December 3, 2008 to discuss Valent's proposal for non-food use classification of the seed treatment uses of tolclofos-methyl on various crops and crop groups.  ChemSAC concluded if all TRR results are less than 5 ppb (based on memorandum of Chemistry SAC-HED -7509C titled "Classification of Seed Treatments as Food or Nonfood Uses" dated Oct 28, 1999), then the proposed seed treatment uses of tolclofos-methyl on various crops can be classified as non-food.

To determine the total radioactive residue (TRR), aliquots of samples were combusted in a biological oxidizer followed by liquid scintillation counting (LSC) of the aliquot vials. HPLC was used to determine the radiochemical purity of the test substance before and after seed treatment.  The limit of quantification (LOQ) is 0.003 ppm.  The method was adequate for data collection based on acceptable concurrent method recoveries.

Freezer storage stability data for soybean, corn, cotton, cucumber, lettuce and radish are adequate.  The dates that the samples were planted, collected and analyzed were less than 30 days; therefore, a freezer storage stability study is not needed.  The freezer storage period before the extraction analysis of treated radish tops was 13.7 months.  

The submitted TRR data on various crops are adequate to satisfy data requirements and supports the seed treatment uses being classified as non-food uses. The results showed that the soybean, corn, lettuce, cucumber, radish and cotton plants grown for seed treated with [phenyl-[14]C]tolclofos-methyl at 10 or 50 g.ai/100kg did not take up radiolabeled test substance residue ( < 5 ppb). The radish tops showed residue levels above 5 ppb at the rate of 50 g/100 kg.  Only the radish top samples grown from seeds showed TRR residues above 0.005 ppm.  The radish tops grown from seeds contained residues at 0.02  -  0.03 ppm.  Since the radish tops grown for seeds showed residues above 0.005 ppm, additional characterization of the residues was provided.  Two treated and one control crop samples were extracted and analyzed.  The treated samples were radish tops (TRR = 0.029 ppm and TRR = 0.020 ppm) from replicate plots TR1 and TR2, respectively.  The control radish tops grown from untreated seeds were spiked with radiolabeled tolclofos-methyl and analyzed to determine the efficiency of the extraction method. The radish tops grown for seeds were extracted and analyzed by HPLC. Both acetonitrile and aqueous extracts showed some polar radioactive residues, but did not contain any detectable amount of tolclofos-methyl.

There are currently no established or proposed tolerances for tolclofos-methyl in the United States as the proposed seed treatment uses have been deemed non-food uses.  There are currently no established MRLs in Canada; however, there are Codex MRLs for lettuce, potato, and radish.  Since there are no U.S. tolerances for tolclofos-methyl, there are no issues of compatibility with respect to the Codex MRLs.

Regulatory Recommendations and Residue Chemistry Deficiencies

HED has examined the residue chemistry database for tolclofos-methyl.  There are no residue chemistry issues that would preclude granting the tolclofos-methyl seed treatment as non-food uses (40 CFR Part 158) and no food or feed tolerances are required.  Table 1 shows the proposed seed treatment use of tolclofos-methyl as a non-food use on corn, soybean, cucumber, lettuce and radish can be translated to the following crop groups. The chemical structure, nomenclature and pohysicochemical properties of tolclofos-methyl are presented in Table 2.  

Table 1: Translation of Tolclofos-methyl Seed Treatment as a Nonfood Uses

       Translation of Tolclofos-methyl Seed Treatment as a Nonfood Uses
Crop
Crop Group Number
Crop Group Name
Corn*
15
Cereal grains

16
Forage, fodder and straw 
Soybean*
6
Legume vegetable

7
Foliage 

20
Oilseeds
Cucumber*
8
Fruiting vegetable (except cucurbits)

9
Cucurbit
Lettuce*
4
Leafy vegetable (except Brassica vegetables)

5
Brassica cole leafy vegetables
Radish**
1
Root and tuber vegetables (except potatoes)

2
Leaves of root and tuber vegetables (human food and animal feed)

3
Bulb vegetables
Cotton**

*application rate: 10 g ai/100 kg seed
**application rate: 50 g ai/100 kg seed

Table 2: Nomenclature and Physicochemical Properties of Radiolabeled Tolclofos-methyl

Parameter
Structure/Name/Value
Compound Structure

Common Name
[Phenyl-[14]C]tolclofos-methyl (Radiolabeled)
Code Names
V-10178
IUPAC Name
O-2,6-dichloro-p-tolyl O,O-dimethyl phosphorothioate
CAS Name
O-(2,6-dichloro-4-methylphenyl) O,O-dimethyl phosphorothioate
CAS Registry No.
57018-04-9
Molecular Formula
C9H11Cl2O3PS
Molecular Weight
305.0 (Radiolabeled, Inv No. 398)
Lot No.
CFQ15407 (Valent Radiochemical Inv. No. 398) 

The test substance received from Sumitomo Chemical Co. was purified and isotopically diluted with tolclofos-methyl T.G. to prepare Inventory No. 398A for seed treatment
Specific Activity
4.51 GBq/mmol or 887,200 dpm/ug (Inv. No. 398)
1.23 MBq/mg or 73,500 dpm/ug (Inv. No. 398A)
Radiochemical Purity
98.6% (390A)
Position of Radiolabel
Phenyl ring
n-Octanol/Water Partition Coefficient, log POW
4.56 at 25°C
Water Solubility
1.1 ppm
Vapor Pressure
57 mPa at 20°C
      

Residue Analytical Method

Purification of Radiolabeled Test Substance
  
To determine the total radioactive residue (TRR), aliquots of samples were combusted in a biological oxidizer followed by liquid scintillation counting (LSC) of the aliquot vials. The radiolabeled test substance received from Sumitomo Chemical Co. in solid form, was dissolved with acetonitrile for LSC and HPLC analysis. The test substance was purified as described in the following procedure.

Field Corn, Cotton and Soybean

Batches of field corn, cotton and soybean seeds (one batch for each of the 3 dose levels and one batch for the untreated control per crop) were coated with treated with the appropriate amount of test substance, [phenyl-[14]C]tolclofos-methyl.  The target treatment rates were 2.5, 5.0, and 10.0g/ 100kg of seeds for the field corn and soybean, and 10, 25, 50g/100 kg of seeds for cotton. The actual mean treatment rates were 2.37+0.24, 5.01+0.06, and 10.19+0.15 g of the test substance per 100kg of field corn seeds, 10.32+0.21, 22.39+0.63, and 51.20+1.14g/100 kg of cotton seeds, and 2.82+0.09, 5.76+0.30, 10.33+0.04g/100kg of soybean seeds (See summary Table 3a).

The radiochemical stock solution was rotary evaporated to complete dryness (water bath temp at ~ 30°C).  The flask was kept under vacuum for an additional 30 min to allow traces of toluene to evaporate from the sample.  The test substance was dissolved in 0.5 mL of acetonitrile, and then 0.2 mL of water was added to the solution to lower the acetonitrile concentration to 71%.  The solution was divided equally into 3 portions and each portion was loaded onto a strata-X 1g/12 mL Giga Tube column prepared earlier by passing 1 bed-volume each of methanol and acetonitrile, followed by 4 bed-volumes of water.  The flask containing the test substance was subsequently rinsed with 0.4 mL of 50% acetonitrile and 0.5 mL of 40% acetonitrile and the rinses were loaded onto the columns.  The columns were eluted subsequently with step gradients of 20  -  71% acetonitrile in water.  The collected column fractions were analyzed by LSC and HPLC to locate the test substance band.  

Radish, Lettuce and Cucumber
Batches of radish, lettuce and cucumber seeds were treated with appropriate amounts of the test substance, [phenyl-[14]C]tolclofos-methyl, at the target rate of 50 and 200 g/100kg of seeds for radish, and 10 g/100 kg of seeds for lettuce and cucumber.  The actual mean treatment rates were 51.6+ 0.3 and 194+ 7.6 g of the test substance per 100 kg of radish seeds, and 9.91+ 0.39 and 10.23+ - 1.08 g/100 kg of lettuce and cucumber seeds, respectively.  The actual rates were 97.0-103.2% of the target rates (see summary Table 3b)

The radiochemical stock solution was concentrated to 1.0 mL under a flow of nitrogen at room temperature.  The solution was loaded onto a strata-X 33 um 1g/12 mL column prepared earlier by passing 2 column-volumes of acetonitrile, followed by 4 column-volumes of water.  After the test solution entered the column, two rinses of the test substance vial with 0.5 mL of acetonitrile was loaded onto the column. The columns were eluted with step gradients of 0  -  73% acetonitrile in water.  The collected column fractions were analyzed by LSC and HPLC to locate the test substance band.  

Table 3a:   Total [Phenyl-[14]C]Tolclofos-Methyl Applied to Seeds and the Treatment Rates
                                     Crop
                                     Type
                                     Dose
                                     Level
                                    Target
                                     Rate
                                   g/100 kg
                                     Total
                                    Applied
                                      dpm
                                     Final
                                   Treatment
                                      dpm
                                    Actual
                                   Treatment
                                     Rate
                                   g/100 kg
                                     CV %
                                     % of
                                    Target
                                     Rate
                                  Field Corn
                                      Low
                                      2.5
                                   3,179,562
                                   3,130,422
                                     2.37
                                     10.2
                                     95.0
                                       
                                    Medium
                                      5.0
                                   6,950,225
                                   6,603,275
                                     5.01
                                      1.2
                                     100.2
                                       
                                     High
                                     10.0
                                  14,204,616
                                  13,514,016
                                     10.19
                                      1.5
                                     101.9
                                    Cotton
                                      Low
                                     10.0
                                   4,723,724
                                   4,707,495
                                     10.32
                                      2.1
                                     103.2
                                       
                                    Medium
                                     25.0
                                  11,255,999
                                  10,246,959
                                     22.39
                                      2.8
                                     89.5
                                       
                                     High
                                     50.0
                                  24,121,406
                                  23,153,086
                                     51.20
                                      2.2
                                     102.4
                                    Soybean
                                      Low
                                      2.5
                                   1,644,133
                                   1,627,878
                                     2.82
                                      3.2
                                     112.8
                                       
                                    Medium
                                      5.0
                                   3,305,600
                                   3,284,245
                                     5.76
                                      5.3
                                     115.3
                                       
                                     High
                                     10.0
                                   6,139,779
                                   5,919,522
                                     10.33
                                      0.4
                                     103.3

Table 3b: Total [Phenyl-[14]C]Tolclofos-Methyl Applied to Seeds and the Treatment Rates 
                                     Crop
                                     Type
                                    Target
                                     Rate
                                   g/100 kg
                                   Analyzed
                                   Subsample
                                      No.
                                    Applied
                                dpm/g of seeds
                                     Mean
                                    Applied
                                dpm/g of seeds
                                    Applied
                                   Treatment
                                     Rate
                                   g/100 kg
                                     CV %
                                     % of
                                    Target
                                     Rate
                                    Radish
                                      50
                                       1
                                  38,176,246
                                  37,926,566
                                     51.6
                                      0.7
                                     103.2
                                       
                                       
                                       2
                                  37,668,537
                                       
                                       
                                       
                                       
                                       
                                       
                                       3
                                  37,934,915
                                       
                                       
                                       
                                       
                                       
                                      200
                                       1
                                  142,696,560
                                  142,616,028
                                     194.0
                                      3.9
                                     97.0
                                       
                                       
                                       2
                                  136,965,195
                                       
                                       
                                       
                                       
                                       
                                       
                                       3
                                  148,186,329
                                       
                                       
                                       
                                       
                                    Lettuce
                                      10
                                       1
                                   7,054,295
                                   7,280,646
                                     9.91
                                      4.0
                                     99.1
                                       
                                       
                                       2
                                   7,180,130
                                       
                                       
                                       
                                       
                                       
                                       
                                       3
                                   7,607,512
                                       
                                       
                                       
                                       
                                   Cucumber
                                      10
                                       1
                                   8,010,039
                                   7,516,276
                                     10.23
                                     10.6
                                     102.3
                                       
                                       
                                       2
                                   7,939,973
                                       
                                       
                                       
                                       
                                       
                                       
                                       3
                                   6,598,815
                                       
                                       
                                       
                                       
[cv=coefficient of variation; dpm=disintegrations per minute]

HED Conclusions

An adequate data collection method is available for tolclofos-methyl residues in/on crops, liquid scintillation counting (LSC) and HPLC.  Batches of seeds were treated with appropriate amounts of the test substance, [phenyl-[14]C]tolclofos-methyl. The target treatment rates were 2.5, 5.0 and 10.0 g/100 kg of seeds for the field corn, cotton and soybean, and 10, 50 and 200 g/100 kg of seeds for radish, lettuce, and cucumber.  The percentage of target rate ranged from 89.5- 115.3.

Storage Stability

Crop samples were collected at their proper growth stage.  The treated batches of seeds were placed in labeled 30 or 50 mL glass vials fitted with caps and shipped at ambient temperature to Research for Hire via commercial carriers on a next-day delivery schedule.  All RAC samples were shipped frozen on Dry Ice from Research for Hire by commercial carriers on overnight delivery schedules to Valent Technical Center in Dublin CA.  The samples were analyzed within 30 days with the exception of soybean forage (stored for 41 days) (Table 4).  Additionally, samples of radish tops were stored for up to 13.7 months before extraction (Table 5).

Table 4: Harvest and TRR Analysis Dates of Radish, Cucumber and Lettuce Samples

                              Sample Description
                                Date Harvested
                                 Date Shipped
                                Date Processed
                             Date of TRR analysis
                   Storage period (days) before TRR analysis
Radish 
                                   07/10/09
                                   07/13/09
                                   07/20/09
                                   07/28/09
                                      18
Cucumber
                                   08/10/09
                                   08/12/09
                                    8/18/09
                                   08/31/09
                                      21
Lettuce
                                   07/22/09
                                   08/04/09
                                    8/12/09
                                   08/19/09
                                      28
Soybean forage
                                   07/30/07
                                   07/31/07
                                   09/04/07
                                   09/10/07
                                      41
Soybean seed and hay
                                   09/21/07
                                   09/25/07
                                   10/04/07
                                   10/11/07
                                      16
Field corn forage
                                   08/17/07
                                   08/21/07
                                   08/28/07
                                   09/07/07
                                      17
Field corn grain and stover
                                   09/14/07
                                   09/17/07
                                   09/21/07
                                  09/25-26/07
                                      8-9
Cotton seed
                                   10/18/07
                                   10/23/07
                                   11/01/07
                                   11/12/07
                                      20
Cotton gin trash
                                   10/18/07
                                   10/23/07
                                   11/06/07
                                   11/14/07
                                      22

Table 5: Harvest and TRR Analysis Dates of Radish Top Samples

                              Sample Description
                      Date Harvested and Storage Started
                          Date Extracted for Analysis
               Storage period (days) before extraction analysis
                             Treated Radish Tops 
                                   07/10/09
                                   08/24/10
                               410 (13.5 months)
                          Spiked Control Radish Tops
                                   07/10/09
                                   08/30/10
                               416 (13.7 months)

To determine the stability of radish tops under frozen storage, the registrant also submitted a freezer storage stability study for tolclofos-methyl in/on lettuce (MRID 201000183, 3/14/02).  The study examined the stability of tolclofos-methyl fortified at 0.1 mg/kg in lettuce stored frozen at <-18[o]C for 0, 3, 6, 12 and 18 months.  The overall percent recovery of the method for lettuce freshly fortified with 0.1 mg/kg of tolclofos-methyl ranged from 83-102%.  Lettuce were extracted with acetone: water (2:1 v:v).  For liquid-liquid partition ethyl acetate/ cyclohexane and sodium chloride was added and after repeatedly mixing excess water was separated.  The residue containing fraction is concentrated and analyzed for residues of tolclofos-methyl by gas chromatography using a flame photometric detector (FPD, phosphorus mode). The LOQ was 0.01 ppm.

HED Conclusions

The available storage stability data for soybean, corn, cotton, cucumber, lettuce, and radish is adequate.  The dates that the samples were planted, collected and analyzed were less than 30 days except for soybean forage which was stored for 41 days.  The freezer storage period before the extraction analysis of treated radish tops was 13.7 months.  The petitioner submitted the results of storage stability for lettuce that showed tolclofos-methyl was stable for up to 18 months.

Radiolabeled Field Trials

Field corn, cotton and soybean seeds were planted in outdoor field plots (Greenville, MS) following normal agricultural practices. Each plot was approximately 30 x 30 inches and had one row of plants grown from treated seeds of one dose level at 3 inches apart from each other.  The boundary of each plot was surrounded by a plastic edge liner buried in soil with a minimum of about 6 inches below ground.  Five seeds from each dose level were planted per plot, and 3 plants of normal crop density were selected for sampling to provide triplicate samples for each RAC.  

Radish, lettuce and cucumber seeds were also planted in outdoor field plots (Stockton, CA) following the normal agricultural practices. Each plot was approximately 2 ft x 2 ft, in which seeds were planted at appropriate crop density for the respective plant.  The boundary of each plot was surrounded by a plastic-lined wooden frame, which was buried in soil about 6 inches below ground.  Duplicate plots were planted with treated seeds from each dose level and approximately 30 seeds were planted per plot for radish, 20 seeds per plot for lettuce and 10 seeds per plot for cucumber. A total of 5 plots (1 for untreated control, 2 for low dose rate and 2 for high dose rate) were used for the radish crop, and 3 plots (1 control and 2 treated) were planted with each of the lettuce and cucumber crops.  

Treatment of Field Corn Seed

Field corn forage, stover and grain were harvested from the untreated control plot and three treatment plots which were planted with seeds treated with [14]C-tolclofos methyl at the nominal dose rates of 2.5, 5.0, and 10.0 g/100 kg of seeds.  

Approximately 0.2 mg, 0.3 mg and 0.6 mg of Rizolex 50FL Formulation were transferred to 3 separate 25 mL flasks marked for low, medium and high dose, respectively.  After adding 43 uL of water to each flask, the formulation blank and water were mixed by sonication.  The batches of 15 field corn seeds were then transferred to the respective flask and swirled gently and briefly to coat them evenly with the formulation blank.  The seeds were then transferred onto labeled weighing-trays and allowed to dry at room temperature.  Each of the 15 seeds of the low dose batch was individually spiked with 1.0 uL of the test substance stock solution 390A and 1.0 uL of the dilution solution 390AD1.  Each of the 15 seeds of the medium dose batch was individually spiked with 3.0 uL of 390A only.  Finally, each of the 15 seeds of the high dose batch was individually spiked with 6.0 uL of 390A and 1.0 uL of the dilution solution 390AD3.  Identical triplicate aliquots of the stock and dilution solution used in each batch as the dose were transferred to empty vials, diluted to 5.0 mL with acetonitrile, and subaliquots of these dilution solutions were counted by LSC for dose verification.  Three treated seeds from each batch were rinsed individually with 5.0 mL of acetonitrile. The radioactivity applied to each seed was verified by LSC analysis of the rinse and combustion analysis of the rinsed seed.  The remaining 12 treated seeds were allowed to dry at room temperature, then placed individually in labeled glass vials and shipped to Research for Hire for planting. 

All of the corn forage, stover, and grain samples showed TRR levels below the LOQ (0.0003 ppm), and the majority of the corn samples had radioactivity level below the limit of detection (0.0001 ppm). The total radioactive residues in field corn are presented in Table 6.  
      
Treatment of Cotton Seeds
Cotton seed and gin trash were harvested from the untreated control plot and three treatment plots which were planted with seeds treated with [14]C-tolclofos methyl at the nominal dose rates of 10, 25, and 50 g/100 kg of seeds.  

Approximately 0.2 mg, 0.5 mg and 1.1 mg of Rizolex 50FL formulation blank were transferred to 3 separate 25 mL capacity flasks marked for low, medium and high dose, respectively.  After adding 28 uL of water to each flask, the formulation blank and water were mixed by sonication.  The batches of 15 cotton seeds were then transferred to the respective flask and swirled gently and briefly to coat them evenly with the formulation blank.  The seeds were then transferred onto labeled weighing-trays and allowed to dry at room temperature.  Each of the 15 seeds of the low dose batch was individually spiked with 2.0 uL of the test substance stock solution 390A and 1.0 uL of the dilution solution 390AD2.  Each of the 15 seeds of the medium dose batch was individually spiked with 5.0 uL of 390A and 1.0 uL of 390AD3.  Finally, each of the 15 seeds of the high dose batch was individually spiked with 10.0 uL of 390A and 1.0 uL of 390AD4.  Identical triplicate aliquots of the stock and dilution solution used in each batch as the dose were transferred to empty vials, diluted to 5.0 mL with acetonitrile, and subaliquots of these dilution solutions were counted by LSC for dose verification.  Three treated seeds from each batch were rinsed individually with 5.0 mL of acetonitrile. The radioactivity applied to each seed was verified by LSC analysis of the rinse and combustion analysis of the rinsed seed. The remaining 12 treated seeds were allowed to dry at room temperature, then placed individually in labeled glass vials and shipped to Research for Hire for planting. 

All of the cotton seed meal, seed hull and gin trash samples (except one replicate of high dose gin trash sample) showed TRR levels below the LOQ (0.00035 ppm), and the majority of the cotton samples had radioactivity level below the limit of detection (0.0001 ppm). The total radioactive residues in cotton are presented in Table 7.  

Treatment of Soybean Seeds

Soybean forage, hay and seed were harvested from the untreated control plot and three treatment plots planted with seeds treated with [14]C-tolclofos methyl at the nominal dose rates 2.5, 5.0, and 10 g/100 kg of seeds.

Approximately 0.1 mg and 0.3 mg of Rizolex 50FL formulation blank were transferred to 3 separate 25 mL capacity flasks marked for low, medium and high dose, respectively.  After adding 10 uL of water to each flask, the formulation blank and water were mixed by sonication.  The batches of 15 soybean seeds were then transferred to the respective flask and swirled gently and briefly to coat them evenly with the formulation blank.  The seeds were then transferred onto labeled weighing-trays and allowed to dry at room temperature. Each of the 15 seeds of the low dose batch was individually spiked with 2.0 uL of the dilution solution 390AD5.  Each of the 15 seeds of the medium dose batch was individually spiked with 1.0 uL of the test substance stock solution 390A and 1.0 uL of 390AD5.  Finally, each of the 15 seeds of the high dose batch was individually spiked with 2.0 uL of 390A and 2.0 uL of 390AD5.  Identical triplicate aliquots of the stock and dilution solution used in each batch as the dose were transferred to empty vials, diluted to 5.0 mL with acetonitrile, and subaliquots of these dilution solutions were counted by LSC for dose verification.  Three treated seeds from each batch were rinsed individually with 5.0 mL of acetonitrile. The radioactivity applied to each seed was verified by LSC analysis of the rinse and combustion analysis of the rinsed seed. The remaining 12 treated seeds were allowed to dry at room temperature, then placed individually in labeled glass vials and shipped to Research for Hire for planting.
      
Three additional batches of soybean seeds (10 in each batch) were treated for replanting after some soybean seeds from the first treatment failed to germinate (the germination rate of soybean seeds was generally low in all dosing levels including the untreated control). The repeat treatment procedure was similar to the one described above, except that the treated seeds were not analyzed in addition to the analysis of the dosing aliquots.

All of the soybean forage and seed samples showed TRR level below the LOQ (0.00034 ppm), and the majority of them had radioactivity level below the limit of detection (0.0001 ppm).  The low and high dose soybean hay samples showed mean TRR levels of 0.00049ppm and 0.00067, respectively.  The total radioactive residues in soybean are presented in Table 8.  

Treatment of Radish Seed

Two batches (5.0 g each) of radish seeds were weighed into separate containers. Into a 30 mL capacity glass vial, 216 uL of the test substance solution in acetonitrile, 398A, was transferred.  The solution was evaporated to dryness under nitrogen at room temperature, and the residue was redissolved in 50 uL of acetonitrile.  An aliquot of 3.59 uL of the formulation blank and 77 uL of water were added to the radiolabeled solution in the vial. The first 5.0 g batch of the radish seeds was transferred to the vial.  The seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  The seeds were poured out of the vial and discarded.  New slurry was prepared in the emptied vial as described above, using 216 uL of 398A (concentrated to 50 uL), 3.59 uL of formulation blank, and 77 uL of water. The slurry was mixed well using the vortex mixer, and spread around the inner wall of the vial. The second 5.0 g batch of the radish seeds was transferred to the vial.  The seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  Three subsamples (0.25 g each) of these treated seeds were withdrawn from the vial for analysis.  Seeds in each subsample were rinsed with 2 lots of acetonitrile (5 mL each), and the pooled seed rinse (total volume, 10 mL) was analyzed by LSC.  The rinsed seeds were air-dried at room temperature before combustion analysis. A dose rate of 200 g/100kg of radish was also analyzed.

Only the radish root samples grown from seeds treated at the rate of 51.6 g/100 kg showed TRR level below the LOQ. All other radish samples showed residues above 0.005 ppm. The radish tops grown from seeds treated at the rates of 51.6 g/100 kg and 194.0 g/100 kg contained 0.02 - 0.03 ppm and 0.04 - 0.06 ppm, respectively. The radish root from the higher dose rateshowed residue levels of ~0.03 ppm.  The total radioactive residues in radish are presented in Table 9.  

Treatment of Lettuce Seeds
Two batches (5.0 g each) of lettuce seeds were weighed into separate containers. Into a 30 mL capacity glass vial, 0.72 uL of the formulation blank, 43 uL of the test substance solution in acetonitrile, 398A, and 87 uL of water were transferred.  The slurry was mixed well using a vortex mixer, and spread around the inner wall of the vial. The first 5.0 g batch of the lettuce seeds was transferred to the vial and the seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  The seeds were poured out of the vial and discarded.  New slurry was prepared in the emptied vial as described above, using 0.72 uL of formulation blank, 43 uL of 398A, and 87 uL of water. The slurry was mixed well using the vortex mixer, and spread around the inner wall of the vial. The second 5.0 g batch of the lettuce seeds was transferred into the vial and the seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  Three subsamples (ca 0.25 g each) of these treated seeds (designated as LT) were withdrawn from the vial for analysis.  Seeds in each subsample were rinsed with 2 lots of acetonitrile (5 mL each), and the pooled seed rinse (total volume, 10 mL) was analyzed by LSC.  The rinsed seeds were air-dried at room temperature before combustion analysis.

The lettuce samples grown from seeds treated at the rate of 9.91 g/100 kg showed TRR level below the minimum quantification limit. The control lettuce samples also showed no radioactivity above background. The total radioactive residues in lettuce are presented in Table 9.  

Treatment of Cucumber Seeds
Two batches (10 g each) of cucumber seeds were weighed into separate containers. Into a 50 mL capacity glass vial, 1.43 uL of the formulation blank, 86 uL of the test substance solution in acetonitrile, 398A, and 173 uL of water were transferred.  The slurry was mixed well using a vortex mixer, and spread around the inner wall of the vial. The first 10 g batch of the cucumber seeds was transferred to the vial and the seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  The seeds were poured out of the vial and discarded.  New slurry was prepared in the emptied vial as described above, using 1.43 uL of formulation blank, 86 uL of 398A, and 173 uL of water. The slurry was mixed well using the vortex mixer, and spread around the inner wall of the vial. The second 10 g batch of the cucumber seeds was transferred into the vial and the seeds were mixed with the slurry by gentle shaking until no liquid was visible in the vial.  Three subsamples (ca 0.25 g each) of these treated seeds (designated as CT) were withdrawn from the vial for analysis.  Seeds in each subsample were rinsed with 2 lots of acetonitrile (5 mL each), and the pooled seed rinse (total volume, 10 mL) was analyzed by LSC.  The rinsed seeds were air-dried at room temperature before combustion analysis. The total radioactive residues in field corn are presented in Table 6.

The cucumber samples grown from seeds treated at the rate of 10.23 g/100 kg showed TRR level below the minimum quantification limit. The control cucumber samples also showed no radioactivity above background. The total radioactive residues in lettuce are presented in Table 9.  

Table 6: Total Radioactive Residue in Field Corn RAC Samples
                                          
                                    Sample
                                  Description
                                        
                                  Dose level
                                  [g/100 kg]
                                    Sample
                                      No.
                                     Rep.
                                      No.
                              Mean Aliquot wt., g
                                     Mean
                                    Aliquot
                                      dpm
                                      TRR
                                       
                                       
                                       
                                       
                                       
                                       
                                     Mean
                                     dpm/g
                                      ppm
                                     ug/g
                               Field Corn Forage
                                    Control
                                     [0.0]
                                      62
                                       1
                                     0.266
                                      11
                                    <126
                                  <0.00030
                                       
                                       
                                      63
                                       2
                                     0.262
                                       5
                                    <35
                                  <0.00008
                                       
                                       
                                      64
                                       3
                                     0.274
                                       4
                                    <34
                                  <0.00008
                                       
                                      Low
                                     [2.5]
                                      65
                                       1
                                     0.278
                                      10
                                    <121
                                  <0.00028
                                       
                                       
                                      66
                                       2
                                     0.264
                                       4
                                    <35
                                  <0.00008
                                       
                                       
                                      67
                                       3
                                     0.258
                                       4
                                    <36
                                  <0.00008
                                       
                                    Medium
                                     [5.0]
                                      68
                                       1
                                     0.261
                                      17
                                    <129
                                  <0.00030
                                       
                                       
                                      69
                                       2
                                     0.262
                                       3
                                    <35
                                  <0.00008
                                       
                                       
                                      70
                                       3
                                     0.270
                                       8
                                    <34
                                  <0.00008
                                       
                                     High
                                    [10.0]
                                      71
                                       1
                                     0.260
                                      12
                                    <129
                                  <0.00030
                                       
                                       
                                      72
                                       2
                                     0.266
                                       3
                                    <35
                                  <0.00008
                                       
                                       
                                      73
                                       3
                                     0.265
                                       5
                                    <35
                                  <0.00008
                               Field Corn Stover
                                    Control
                                     [0.0]
                                      74
                                       1
                                     0.283
                                      10
                                    <116
                                  <0.00027
                                       
                                       
                                      75
                                       2
                                     0.259
                                       4
                                    <35
                                  <0.00008
                                       
                                       
                                      76
                                       3
                                     0.251
                                       1
                                    <36
                                  <0.00008
                                       
                                      Low
                                     [2.5]
                                      77
                                       1
                                     0.256
                                      11
                                    <129
                                  <0.00030
                                       
                                       
                                      78
                                       2
                                     0.247
                                       3
                                    <37
                                  <0.00008
                                       
                                       
                                      79
                                       3
                                     0.258
                                       5
                                    <35
                                  <0.00008
                                       
                                    Medium
                                     [5.0]
                                      80
                                       1
                                     0.260
                                      12
                                    <127
                                  <0.00030
                                       
                                       
                                      81
                                       2
                                     0.262
                                       4
                                    <34
                                  <0.00008
                                       
                                       
                                      82
                                       3
                                     0.249
                                       5
                                    <36
                                  <0.00009
                                       
                                     High
                                    [10.0]
                                      83
                                       1
                                     0.253
                                      11
                                    <130
                                  <0.00030
                                       
                                       
                                      84
                                       2
                                     0.259
                                       6
                                    <35
                                  <0.00008
                                       
                                       
                                      85
                                       3
                                     0.267
                                       7
                                    <34
                                  <0.00008
                               Field Corn Grain
                                    Control
                                     [0.0]
                                      86
                                       1
                                     0.286
                                      10
                                    <119
                                  <0.00008
                                       
                                       
                                      87
                                       2
                                     0.295
                                       5
                                    <32
                                  <0.00027
                                       
                                       
                                      88
                                       3
                                     0.284
                                       2
                                    <33
                                  <0.00007
                                       
                                      Low
                                     [2.5]
                                      89
                                       1
                                     0.283
                                      13
                                    <120
                                  <0.00028
                                       
                                       
                                      90
                                       2
                                     0.276
                                       6
                                    <34
                                  <0.00007
                                       
                                       
                                      91
                                       3
                                     0.289
                                       6
                                    <32
                                  <0.00008
                                       
                                    Medium
                                     [5.0]
                                      92
                                       1
                                     0.293
                                      21
                                    <116
                                  <0.00027
                                       
                                       
                                      93
                                       2
                                     0.279
                                      25
                                    <122
                                  <0.00028
                                       
                                       
                                      94
                                       3
                                     0.280
                                      21
                                    <121
                                  <0.00028
                                       
                                     High
                                    [10.0]
                                      95
                                       1
                                     0.292
                                       5
                                    <32
                                  <0.00007
                                       
                                       
                                      96
                                       2
                                     0.284
                                       3
                                    <33
                                  <0.00008
                                       
                                       
                                      97
                                       3
                                     0.300
                                       3
                                    <31
                                  <0.00007

 
 Table 7: Total Radioactive Residue in Cotton RAC Samples
                                          
                                    Sample
                                  Description
                                        
                                  Dose level
                                  [g/100 kg]
                                    Sample
                                      No.
                                     Rep.
                                      No.
                              Mean Aliquot wt., g
                                     Mean
                                    Aliquot
                                      dpm
                                      TRR
                                       
                                       
                                       
                                       
                                       
                                       
                                     Mean
                                     dpm/g
                                      ppm
                                     ug/g
                                    Cotton
                                   Seed Meal
                                    Control
                                     [0.0]
                                      38P
                                       1
                                     0.248
                                       2
                                    <41
                                  <0.00009
                                       
                                       
                                      39P
                                       2
                                     0.255
                                       5
                                    <39
                                  <0.00009
                                       
                                       
                                      40P
                                       3
                                     0.247
                                       3
                                    <41
                                  <0.00009
                                       
                                      Low
                                    [10.0]
                                      41P
                                       1
                                     0.254
                                       1
                                    <40
                                  <0.00009
                                       
                                       
                                      42P
                                       2
                                     0.264
                                       3
                                    <38
                                  <0.00009
                                       
                                       
                                      43P
                                       3
                                     0.246
                                       0
                                    <41
                                  <0.00010
                                       
                                    Medium
                                    [25.0]
                                      44P
                                       1
                                     0.254
                                       8
                                    <40
                                  <0.00009
                                       
                                       
                                      45P
                                       2
                                     0.248
                                       2
                                    <48
                                  <0.00009
                                       
                                       
                                      46P
                                       3
                                     0.264
                                       1
                                    <38
                                  <0.00009
                                       
                                     High
                                    [50.0]
                                      47P
                                       1
                                     0.259
                                       7
                                    <39
                                  <0.00009
                                       
                                       
                                      48P
                                       2
                                     0.251
                                       4
                                    <40
                                  <0.00009
                                       
                                       
                                      49P
                                       3
                                     0.260
                                       5
                                    <39
                                  <0.00009
                                    Cotton
                                   Seed Hull
                                    Control
                                     [0.0]
                                      38H
                                       1
                                     0.257
                                       2
                                    <36
                                  <0.00008
                                       
                                       
                                      39H
                                       2
                                     0.247
                                       2
                                    <38
                                  <0.00009
                                       
                                       
                                      40H
                                       3
                                     0.243
                                      19
                                    <139
                                  <0.00033
                                       
                                      Low
                                    [10.0]
                                      41H
                                       1
                                     0.257
                                       4
                                    <36
                                  <0.00008
                                       
                                       
                                      42H
                                       2
                                     0.248
                                       3
                                    <38
                                  <0.00009
                                       
                                       
                                      43H
                                       3
                                     0.249
                                       2
                                    <37
                                  <0.00009
                                       
                                    Medium
                                    [25.0]
                                      44H
                                       1
                                     0.235
                                       7
                                    <40
                                  <0.00009
                                       
                                       
                                      45H
                                       2
                                     0.248
                                       4
                                    <38
                                  <0.00009
                                       
                                       
                                      46H
                                       3
                                     0.244
                                       3
                                    <38
                                  <0.00009
                                       
                                     High
                                    [50.0]
                                      47H
                                       1
                                     0.255
                                       7
                                    <37
                                  <0.00009
                                       
                                       
                                      48H
                                       2
                                     0.257
                                       6
                                    <36
                                  <0.00008
                                       
                                       
                                      49H
                                       3
                                     0.253
                                       5
                                    <37
                                  <0.00009
                                    Cotton
                                   Gin Trash
                                    Control
                                     [0.0]
                                      50
                                       1
                                     0.246
                                       1
                                    <40
                                  <0.00009
                                       
                                       
                                      51
                                       2
                                     0.244
                                       0
                                    <41
                                  <0.00010
                                       
                                       
                                      52
                                       3
                                     0.255
                                       1
                                    <39
                                  <0.00009
                                       
                                      Low
                                    [10.0]
                                      53
                                       1
                                     0.263
                                       8
                                    <38
                                  <0.00009
                                       
                                       
                                      54
                                       2
                                     0.263
                                       2
                                    <38
                                  <0.00009
                                       
                                       
                                      55
                                       3
                                     0.255
                                       4
                                    <39
                                  <0.00009
                                       
                                    Medium
                                    [25.0]
                                      56
                                       1
                                     0.259
                                      13
                                    <138
                                  <0.00032
                                       
                                       
                                      57
                                       2
                                     0.267
                                       8
                                    <37
                                  <0.00009
                                       
                                       
                                      58
                                       3
                                     0.251
                                       2
                                    <40
                                  <0.00009
                                       
                                     High
                                    [50.0]
                                      59
                                       1
                                     0.239
                                      25
                                    <150
                                  <0.00035
                                       
                                       
                                      60
                                       2
                                     0.251
                                      21
                                    <142
                                  <0.00033
                                       
                                       
                                      61
                                       3
                                     0.248
                                      37
                                      151
                                    0.00035

                                          
Table 8: Total Radioactive Residue in Soybean RAC Samples
                                          
                                    Sample
                                  Description
                                        
                                  Dose level
                                  [g/100 kg]
                                    Sample
                                      No.
                                     Rep.
                                      No.
                              Mean Aliquot wt., g
                                     Mean
                                    Aliquot
                                      dpm
                                      TRR
                                       
                                       
                                       
                                       
                                       
                                       
                                     Mean
                                     dpm/g
                                      ppm
                                     ug/g
                                Soybean Forage
                                    Control
                                     [0.0]
                                       2
                                       1
                                     0.266
                                      13
                                    <129
                                  <0.00030
                                       
                                       
                                       3
                                       2
                                     0.254
                                       1
                                    <37
                                  <0.00009
                                       
                                       
                                       4
                                       3
                                     0.277
                                       1
                                    <34
                                  <0.00008
                                       
                                      Low
                                     [2.5]
                                       5
                                       1
                                     0.268
                                      12
                                    <127
                                  <0.00030
                                       
                                       
                                       6
                                       2
                                     0.268
                                       5
                                    <35
                                  <0.00008
                                       
                                       
                                       7
                                       3
                                     0.263
                                       2
                                    <36
                                  <0.00008
                                       
                                    Medium
                                     [5.0]
                                       8
                                       1
                                     0.268
                                      14
                                    <127
                                  <0.00030
                                       
                                       
                                       9
                                       2
                                     0.269
                                       7
                                    <35
                                  <0.00008
                                       
                                       
                                      10
                                       3
                                     0.266
                                       4
                                    <35
                                  <0.00008
                                       
                                     High
                                    [10.0]
                                      11
                                       1
                                     0.249
                                      15
                                    <137
                                  <0.00032
                                       
                                       
                                      12
                                       2
                                     0.249
                                       5
                                    <38
                                  <0.00009
                                       
                                       
                                      13
                                       3
                                     0.265
                                       7
                                    <36
                                  <0.00008
                                    Soybean
                                      Hay
                                    Control
                                     [0.0]
                                      14
                                       1
                                     0.222
                                      15
                                    <151
                                  <0.00035
                                       
                                       
                                      15
                                       2
                                     0.209
                                      12
                                    <161
                                  <0.00038
                                       
                                       
                                      16
                                       3
                                     0.195
                                      13
                                    <172
                                  <0.00040
                                       
                                      Low
                                     [2.5]
                                      17
                                       1
                                     0.221
                                      43
                                      194
                                    0.00045
                                       
                                       
                                      18
                                       2
                                     0.206
                                      50
                                      200
                                    0.00047
                                       
                                       
                                      19
                                       3
                                     0.212
                                      42
                                      162
                                  <0.00038
                                       
                                    Medium
                                     [5.0]
                                      20
                                       1
                                     0.209
                                      32
                                    <160
                                  <0.00038
                                       
                                       
                                      21
                                       2
                                     0.200
                                      27
                                    <168
                                  <0.00039
                                       
                                       
                                      22
                                       3
                                     0.209
                                      23
                                    <160
                                  <0.00038
                                       
                                     High
                                    [10.0]
                                      23
                                       1
                                     0.209
                                      40
                                      188
                                    0.00044
                                       
                                       
                                      24
                                       2
                                     0.198
                                      35
                                      176
                                    0.00041
                                       
                                       
                                      25
                                       3
                                     0.194
                                      97
                                      497
                                    0.00116
                                    Soybean
                                     Seed
                                    Control
                                     [0.0]
                                      26
                                       1
                                     0.255
                                       5
                                    <39
                                  <0.00009
                                       
                                       
                                      27
                                       2
                                     0.263
                                       0
                                    <38
                                  <0.00009
                                       
                                       
                                      28
                                       3
                                     0.261
                                       0
                                    <38
                                  <0.00009
                                       
                                      Low
                                     [2.5]
                                      29
                                       1
                                     0.260
                                       7
                                    <38
                                  <0.00009
                                       
                                       
                                      30
                                       2
                                     0.247
                                       2
                                    <40
                                  <0.00009
                                       
                                       
                                      31
                                       3
                                     0.254
                                       2
                                    <39
                                  <0.00009
                                       
                                    Medium
                                     [5.0]
                                      32
                                       1
                                     0.244
                                       7
                                    <41
                                  <0.00010
                                       
                                       
                                      33
                                       2
                                     0.252
                                       3
                                    <39
                                  <0.00009
                                       
                                       
                                      34
                                       3
                                     0.249
                                       3
                                    <40
                                  <0.00009
                                       
                                     High
                                    [10.0]
                                      35
                                       1
                                     0.258
                                      11
                                    <138
                                  <0.00032
                                       
                                       
                                      36
                                       2
                                     0.258
                                      10
                                    <139
                                  <0.00032
                                       
                                       
                                      37
                                       3
                                     0.249
                                      13
                                    <143
                                  <0.00034

Table 9: Total Radioactive Residue Levels in Radish, Lettuce and Cucumber Samples Grown from Seeds Treated with [Phenyl-[14]C]Tolclofos-Methyl 

                                    Sample
                                  Description
                                        
                                   Dose Rate
                                   g/100 kg
                                     Plot
                                      ID
                              Mean Aliquot wt., g
                                     Mean
                                    Aliquot
                                      dpm
                                      CV%
                                      TRR
                                       
                                       
                                       
                                       
                                       
                                       
                                     Mean
                                     dpm/g
                                      ppm
                                     ug/g
                                  Radish Tops
                                      0.0
                                      CR1
                                    0.2387
                                       1
                                      nm
                                    <245
                                   <0.003
                                       
                                     51.6
                                      TR1
                                    0.2384
                                      508
                                    34.7[a]
                                     2,133
                                     0.029
                                       
                                       
                                      TR2
                                    0.2415
                                      344
                                    36.6[b]
                                     1,435
                                     0.020
                                       
                                     194.0
                                      TR3
                                    0.2447
                                     1,140
                                      8.9
                                     4,655
                                     0.063
                                       
                                       
                                      TR4
                                    0.2439
                                      682
                                      7.3
                                     2,796
                                     0.038
                                 Radish Roots
                                      0.0
                                      CR1
                                    0.2427
                                       0
                                      nm
                                    <241
                                   <0.003
                                       
                                     51.6
                                      TR1
                                    0.2362
                                      61
                                      nm
                                    <250
                                   <0.003
                                       
                                       
                                      TR2
                                    0.2401
                                      32
                                      nm
                                    <243
                                   <0.003
                                       
                                     194.0
                                      TR3
                                    0.2407
                                      563
                                    17.1[b]
                                     2,343
                                     0.032
                                       
                                       
                                      TR4
                                    0.2401
                                      560
                                    11.5[b]
                                     2,331
                                     0.032
                                    Lettuce
                                      0.0
                                      CL1
                                    0.2375
                                       0
                                      nm
                                    <226
                                   <0.003
                                       
                                      9.9
                                      TL2
                                    0.2406
                                       2
                                      nm
                                    <223
                                   <0.003
                                       
                                       
                                      TL3
                                    0.2442
                                       0
                                      nm
                                    <220
                                   <0.003
                                   Cucumber
                                      0.0
                                      CF1
                                    0.2542
                                       0
                                      nm
                                    <211
                                   <0.003
                                       
                                     10.2
                                      TF1
                                    0.2555
                                       0
                                      nm
                                    <210
                                   <0.003
                                       
                                       
                                      TF2
                                    0.2535
                                       0
                                      nm
                                    <212
                                   <0.003
[a: mean of 15 aliquots; b: mean of 9 aliquots, all others: mean of 3  -  6 aliquots]

Characterization of Radish Seeds

Since the radish tops grown for seeds treated at the rate of 51.6 g/100 kg, showed residues above 0.005 ppm, additional characterization was provided.  Two treated and one control crop samples were extracted and analyzed.  The treated samples were radish tops (TRR = 0.029 ppm and TRR = 0.020 ppm) from replicate plots TR1 and TR2, respectively.  The control radish tops grown from untreated seeds were spiked with radiolabeled tolclofos-methyl and analyzed to determine the efficiency of the extraction method.

To investigate the nature of these low level residues further and to quantify the test substance, tolclofos-methyl was extracted with aqueous acetonitrile, which was separated into acetonitrile and aqueous extracts.  The replicate samples showed similar total radioactive residue (TRR) distribution in the extracts and in the post-extraction solids (PES). Approximately 81 and 80% of TRR (0.023 and 0.016 ppm) was extractable from samples TR1 and TR2, respectively, while about 19 and 20% (0.005 and 0.004 ppm) remained bound to PES. The major portion of the extractable residue (60% TRR, 0.017 ppm in TR1, and 56% of TRR, 0.011 ppm in TR2) was in the aqueous extract.  Approximately 22% of TRR (0.006 ppm) in TR1 and 24% (0.005 ppm) in TR2 remained soluble in the acetonitrile extract. The extraction TRR levels in TR1 and TR2, respectively, were 96 and 102% of the levels determined by combustion analysis in the original study. Extraction of approximately 100 g of untreated control radish tops spiked with [[14]C]tolclofos-methyl under similar conditions showed that the entire spiked radioactivity was extractable (97% TRR in acetonitrile extract, and 3% in aqueous extract).

The acetonitrile extracts were purified using strataX column chromatography, and finally analyzed by HPLC.  Both acetonitrile and aqueous extracts of treated radish tops samples, TR1 and TR2, showed multiple components of polar low level radioactive residues, but did not contain any detectable amount of tolclofos-methyl.  Acetonitrile extract of control radish tops spiked with [[14]C]tolclofos-methyl, which was subjected to identical purification procedure, showed a single peak of [[14]C]tolclofos-methyl in the HPLC analysis.  The extraction and HPLC results are presented in Table 10. 

Table 10: Extraction and HPLC Results for Tolclofos-methyl in Radish Tops 
Extract/Residue Fraction
                              Radish Tops Sample

                                Spiked Control
                                  Treated TR1
                                  Treated TR2

                                     % TRR
                                      ppm
                                     % TRR
                                      ppm
                                     % TRR
                                      ppm
Acetonitrile Extract
Tolclofos-methyl
                                     97.3
                                     0.027
                                      ND
                                      ND
                                      ND
                                      ND
Unknowns (multiple components)
                                      ND
                                      ND
                                     21.7
                                     0.006
                                     23.8
                                     0.005
Aqueous Extract
Unknowns (multiple components)
                                      2.7
                                   <0.001
                                     59.5
                                     0.017
                                     56.2
                                     0.011
Total extractable
                                     100.0
                                     0.027
                                     81.2
                                     0.023
                                     80.0
                                     0.016
Total bound in PES
                                      0.0
                                      0.0
                                     18.8
                                     0.005
                                     20.0
                                     0.004
Total radioactive residue
                                     100.0
                                     0.027
                                     100.0
                                     0.028
                                     100.0
                                     0.020
[ND= not detected]

HED Conclusions

Batches of radish, lettuce, cucumber, corn, soybean, and radish seeds were treated with formulated [phenyl-[14]C]tolclofos-methyl.  The target treatment rates were 50 g/100 kg of seeds for cotton and radish, and 10 g/100 kg of seeds for corn, soybean, lettuce and cucumber. The results showed that the seeds treated with [phenyl-[14]C]tolclofos-methyl did not take up the radiolabeled test substance residue (<5 ppb).  Only the radish top samples grown from seeds treated at the rate of 51.6 g/100 kg showed TRR level residues above 0.005 ppm.  The radish tops grown from seeds contained residues at 0.02  -  0.03 ppm.  Since the radish tops grown for seeds showed residues above 0.005 ppm, additional characterization of the residues was provided.  Two treated and one control crop samples were extracted and analyzed.  The treated samples were radish tops (TRR = 0.029 ppm and TRR = 0.020 ppm) from replicate plots TR1 and TR2, respectively.  The control radish tops grown from untreated seeds were spiked with radiolabeled tolclofos-methyl and analyzed to determine the efficiency of the extraction method. The radish tops grown for seeds were extracted and analyzed by HPLC. Both acetonitrile and aqueous extracts showed some polar radioactive residues, but did not contain any detectable amount of tolclofos-methyl.

REFERENCES

DP#:	362358
Subject:	Tolclofos-methyl: Non-food Use for Seed Treatment
From:	S. Piper
To:		C. Giles-Parker 
Date:	02/28/09
MRIDs:	NA