REREGISTRATION ELIGIBILITY: (Picloram)

 

Based on all available data EFGWB believes that picloram should not be reregistered because its use would pose unreasonable adverse effects to the environment. Because of picloram's mobility in all soil types and its persistence under normal ambient conditions, no practical use restriction can prevent it from contaminating the environment surrounding the target site.

Picloram is among the most mobile of all currently registered pesticides. To date, picloram has been detected in ground water in 11 states including Iowa, Kansas, Maine, Minnesota, Montana, North Dakota, South Dakota, Texas, Virginia, Wisconsin, and Wyoming (Hoheisel et al, 1992; Williams et al., 1988). Concentrations in ground water range up to 49 ppb, which approaches 10 percent of the 500 ppb MCL. In addition, hexachlorobenzene is a contaminant of picloram production and is present in technical picloram at a maximum of 200 ppm and is a class B2 carcinogen with a MCL of 1 ppb.

The use pattern of picloram is highly specialized, but it is almost certain to eventually reach ground water in areas where it persists in the overlying soil. In submitted terrestrial field and forestry studies, picloram exhibited calculated half-lives of up to 278 days and was detected up to the limits of sampling depth (up to 1.8m). Even under the most constrained soil conditions in the submitted field studies (e.g., 1/2 the maximum application rate, high soil organic matter, minimum rainfall) the compound moves through the soil profile to the deepest sampling depth. In addition, in soils of low permeability, picloram residues may be transported by dissolved run-off during rainfall events and potentially reach non-target vegetation. Picloram has a high degree of phytotoxicity (refer to EEB's Science Chapter and incident reports). Thus, off-site movement of picloram from leaching to ground water, run-off/drift to surface waters would have a profound impact on non-target plants when water contaminated with picloram is used for irrigation.

 

Based on the available data the chemical is problematic with respects to its mobility and persistency. Moreover, the applicant has not conducted requested experiments to address specific EFGWB concerns.

165-3. Irrigated Crops; NO DATA REQUIRED ALL AQUATIC USES HAVE BEEN DROPPED.

165-4. Laboratory Accumulation in Fish; Picloram (acid) did not accumulate in bluegill sunfish. BCF factors were <0.54 and < 0.17 in whole fish. The IOE did not accm. BCF of 70, 8, and 74 for whole fish, muscle and remainder tissue (Registration Standard July 1988).

NOT SATISFIED:

With regards to the unsatisfied spray drift data requirements: DowElanco is a member of the Spray Drift Task force and may submit the required data according to the appropriate PR notice.

201-1. Droplet size spectrum; All data are required. (Registration Standard July 1988)

202-1. Drift field evaluation; All data are required. (Registration Standard July 1988)

166-1. Small Scale Prospective Ground Water Monitoring; All data are required.

RESERVED:

164-5. Long Term Terrestrial Field Dissipation (Registration Standard July 1988).

165-2. Rotational crop (field) (Registration Standard July 1988).

165-5. Accumulation in non target organisms (Registration Standard July 1988).

166-2. Small Scale Retrospective Monitoring. (Registration Standard July 1988).

WAIVED:

161-2. Photolysis in Water; Potassium salt. The EFGWB agreed that there is no chemical/environmental difference between the picloram salt and acid (a 5/29/90 letter from Edwin F. Tinsworth, SRRD to Douglas Roby, Dow Chemical).

161-3. Photolysis in Soil; Potassium salt. The EFGWB agreed that there is no chemical/environmental difference between the picloram salt and acid (a 5/29/90 letter from Edwin F. Tinsworth, SRRD to Douglas Roby, Dow Chemical).

161-4. Photolysis in air; Registration Standard July 1988, No data are required because of the relatively low vapor pressure of the picloram salt form. No data are required for the isooctyl ester because there are no terrestrial food uses.

162-3. Waiver granted for the isooctyl ester 6/19/89.

163-1. Leaching/Adsorption/Desorption; Potassium salt. The EFGWB agreed that there is no chemical/environmental difference between the picloram salt and acid (a 5/29/90 Letter from Edwin F. Tinsworth, SRRD to Douglas Roby, Dow Chemical).

163-2. Volatility (lab); Registration Standard July 1988, see above.

163-3. Volatility (field); Registration Standard July 1988, see above.

8. DISCUSSION OF NEW DATA ADDRESSED IN THIS REVIEW:

Aqueous Photolysis of Picloram (acid):

1. The EFGWB has reevaluated the July 1, 1988 review on study MRID #164943, "The Photolysis of Picloram (acid) in Dilute Aqueous Solution" and the registrants response to the above review, MRID #41092501 and has determined study MRID #164943 is acceptable and completely satisfies the photodegradation in water 161-2 data requirement for picloram acid.

2. Study MRID #164943 was previously reviewed (see attached) and was determined to be unacceptable due to a poor material balance and an inadequate light source. After a reevaluation of the DER, the data within study MRID #164943 and the public literature supplied by the registrant, the EFGWB has found the study to be acceptable for the following reasons:

a) The material balances fell below acceptable levels after a significant number of sampling intervals past the established photolysis half-life of the compound.

b) The EFGWB does not generally accept aqueous photolysis studies using phosphor-coated mercury lamps. However, the artificial light source used in study MRID #164943 was substantially similar to sunlight in intensity at the critical spectral irradiance wavelength range for picloram.

c) Results of study MRID #164943 were confirmed in the public literature.

3. According to the reported results picloram (acid) in sterile buffered water as well as natural water degraded with a first order half-life of 2.6 days at 25^oC. The two major photoproducts arising from picloram decomposition are oxamic acid and 3-oxo-Beta-alanine

indicating dechlorination then subsequent cleavage of the pyridine ring to low molecular weight compounds. Oxamic acid reached a maximum of 32.90% at 96 hours and 45.47% at 120 hours in sterile buffered water and natural water respectively.

Aqueous Photolysis: (picloram isooctyl ester) DER 1

1. Study MRID #42811901 completely satisfies the aqueous photolysis 161-2 data requirement for picloram isooctyl ester.

2. Picloram-IOE degraded with a half-life (first order calculated) of 70.6 minutes in sterile aqueous buffered solutions (pH 5) irradiated with a Xenon light source at 25.1 to 26.0^oC. The major photoproducts were an isomer of dichlorohydroxypicloram-IOE and isomers of dichloropicloram-IOE reaching a maximum of 24.6% and 15.0% at 120 minutes. Ion exclusion chromatography separated a polar mixture accounting for 32.3% of applied at 180 minutes into 3 components; one component accounting for 7.8% of applied was a mixture of carboxylic acids including oxamic acid.

Terrestrial Field Dissipation: DER 2

1. Study MRID #42579002 is acceptable and satisfies the terrestrial field dissipation 164-1 data requirement for picloram.

2. Picloram (Tordon 101) applied at 1.6 lb ai/A (80% of maximum label rate) dissipated from a Watsonville loam (4.01% OM) bare soil plot (TBS) and a Watsonville loam (5.61% OM) plot covered with short grass (TSG) near Davenport California with half-lives (assuming first order kinetics) of 278 and 135 days respectively. By using a zero-order kinetics model the DT50 and DT90 for picloram was in the TBS plot was 288 and 518 days respectively. Estimated DT50 and DT90 for picloram in the TGS plot using a zero order equation was 213 and 383 days respectively.

Picloram in the TBS plot dissipated slowly during the dry summer months and was generally restricted to the 0- to 6- inch (0.6 to 0.8 ppm) soil depth. By 252 DAT picloram was detected in the 6- to 12- inch depth at 0.01 ppm, then increased to 0.045 ppm at that depth by 434 days after treatment (DAT) and then after the rainy winter season picloram was detected in the subsequent 12- to 18- inch depth at 0.022 ppm by 371 DAT and then decreased in concentration at that depth to 0.015 ppm by 434 DAT. The maximum depth of detectable residue was 18 inches at 53 and 62 WAT. During the study (4/12/91-8/1/92), rainfall plus irrigation totaled 34.6 inches corresponding to 110% of the normal rainfall for the same period.

Picloram concentrations in the soil from the TSG plot were initially variable because of lack of analysis of the biomass from the plots and rainfall washing residues off of the grass to the soil. Half-life calculations were taken from the point were maximum concentration were reached in the 0- to 6- inch soil layer which was 656 ppb at 57 DAT. In the 0- to 6- inch soil depth picloram ranged from an average 0.656 ppm 8 weeks after treatment (WAT) to 0.046 ppm (52-WAT). In the 6- to 12- inch soil depth picloram was detected at 0.008 ppm (2-WAT), reached a maximum of 0.026 ppm at 36-WAT, then fell to 0.020 at 65-WAT (last sampling interval). In the 12- to 18- inch soil depth picloram was detected at 0.010 ppm at 29-WAT, then increased to 0.015 ppm at 65-WAT. The maximum depth of detectable residue was 24 inches at 461 DAT (<0.005 ppm).

The total amount of precipitation (rainfall plus supplemental irrigation) for the study period April 1991 through August 1, 1992 was 37.9 inches corresponding to 121% of the normal rainfall for the same period.

Terrestrial Field Dissipation: DER 3

1. Study MRID #42579001 is acceptable and satisfies the terrestrial field dissipation 164-1 data requirement for picloram.

2. Picloram (Tordon 101) applied at 2.0 lbs ai/A dissipated from a Colfax sandy loam bare soil (TBS) and short grass plot (TSG) in Alamance county, North Carolina with pseudo first order half-lives of 108 and 104 days respectively.

Picloram residues in the 0 to 15 cm soil core layer, bare soil plot (TBS), was a maximum average of 0.7467 ppm at day 0. Residue concentrations in that layer then decreased to below the detection limit by week 52. Residues were found in the 15 to 30 cm layer by day 3 at an average of 0.0510 ppm and decreased to not detectable by week 44. Between the week 4 and week 8 sampling interval significant rainfall occurred causing the residues to move to the 30-45, 45-60, 60-75, and 75-90 cm soil increments. Residues were detected at the lower 3 soil segments 45-60, 60-75, 75-90 cm throughout the sampling intervals to week 52.

Picloram residues in the 0 to 15 cm soil core layer, short grass plot (TSG), reached a maximum average of 0.6237 ppm on day 3. Picloram residues at 0.0412 ppm reached the 15 to 30 cm depth by week 4. By week 8 and after a number of rainfall events picloram residues were found throughout the entire soil profile to 90 cm. Picloram residues ranged from 0.01 to 0.03 ppm in the 75 to 90 cm soil core throughout all sampling intervals and the study's duration.

Forestry Dissipation: DER 4

1. Study MRID #42579003 is acceptable and completely satisfies the forestry dissipation (164-3) data requirement for picloram.

Terrestrial Field Dissipation: DER 5

1. Studies MRID #42535302 and MRID #42558302 are acceptable for field dissipation only and satisfies the terrestrial field dissipation data requirement for picloram.

2. The average of 4 first order dissipation values yielded a calculated half-life of 256 days with a deviation of 37 days. The theoretical concentration from day zero was used in the calculations because of picloram residues in the soil increased during the first 2 weeks of the study due to wash/off deposition from the vegetation. In the 0 to 6 inch depth picloram reached a maximum (average of 4 treated plots) of approx. 0.4857 ppm on 27 DAT (days after treatment), that value decreased slowly to approx. 1.63% of applied (approx. 0.0082) ppm by 1357 days after treatment. Picloram residues reached a maximum of approx. 19.69% of applied (approx. 0.0985 ppm) by 354 DAT in the 6 to 12 inch soil layer, then decreased to 0.82% of applied (approx. 0.0041 ppm) by 1357 DAT. Picloram residues in the 12 to 18 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied at 481 DAT, then decreased to a minimum of 0.20% (approx. 0.001 ppm) of applied by 1357 DAT. Picloram residues in the 18 to 24 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied by 110 DAT, then decreased to a minimum of 0.20% (approx. 0.0010 ppm) of applied by 1357 DAT. Picloram residues in the 24 to 36 inch depth reached a maximum of 2.24% (approx. 0.0112 ppm) of applied by 846 DAT, then decreased to ND (not detectable) by 1357 DAT. Picloram residues in the 36 to 48 inch depth reached a maximum of 0.71% (approx. 0.0036 ppm) of applied at 715 DAT, then decreased to ND at 1357 DAT. Picloram was detected at the 48 to 60 inch soil layer at 1.07% (0.0054 ppm) of applied at 790 DAT.

9. BACKGROUND :

The data requirements that are still pending for the purpose of reregistration of picloram are the spray drift (202-1), droplet size spectrum (201-1) and the ground water monitoring (166-1). Registrants are required to submit (201-1) and (202-1) data for herbicides that are aerially applied and have a high degree of phytotoxicity (refer to the EEB science chapter) as is the case for picloram. DowElanco is a participant of the spray drift task force and may submit this data in accordance with the appropriate PR notice.

In response to EPA's request from the 1985 Picloram Registration Standard for a small scale prospective monitoring study, DowElanco submitted a terrestrial field dissipation study conducted in Bremond, Texas; MRID #41646901, EFGWB #91-0634, 8/27/91, this study was not an acceptable substitute for a ground water study and the validity of the study is questionable since the data was generated by Craven laboratory. DowElanco later submitted two small prospective (166-1) monitoring protocols for a South Carolina and Montana site which were not accepted by the Groundwater Technology Section (1/6/92; EFGWB# 92-0114). The studies were initiated without protocol approval and therefore the two studies (MRID #42535302, #42558302 and MRID #41395301) that were conducted under the unacceptable protocols were determined to be unacceptable as Ground Water studies (1/6/92; EFGWB# 92-0114, D184754).

The aqueous photolysis (the acid and the isooctyl ester) (161-2), terrestrial field (164-1), and forestry dissipation (164-3) data requirements were satisfied by studies addressed in this review. Studies MRID #164943 and MRID #41092501 completely satisfy the aqueous photolysis (161-2) data requirement for the acid. Study MRID #42811901 completely satisfy the aqueous photolysis (161-2) data requirement for the isooctyl ester. Studies MRID #42579002, MRID #42579001, MRID #42535302 and MRID #42558302 satisfy the terrestrial field dissipation (164-1) data requirement. Study MRID #42579003 completely satisfies the forestry dissipation (164-3) data requirement for the K⁺ salt of picloram.

Picloram (acid, TGAI) has no currently registered uses, it is used in formulations only;

Picloram isooctyl ester (picloram isooctyl ester) is registered for basal bark treatments only in forestry, and terrestrial non-food industrial areas nonagricultural rights of ways, fencerows, hedgerows, and nonagricultural uncultivated areas/soils. The application is low volume ground.

The triisopropanolamine salt of picloram is registered for use on

terrestrial feed, terrestrial non-food and forest sites. The application rate is a maximum of 2.0 lb ai/A. The triisopropanolamine salt is applied using aerial or ground (broadcast, spot, frill, or stump treatment) equipment.

The potassium salt of picloram is registered for use on terrestrial food/feed crop (small grains, pasture and rangeland grasses), terrestrial feed crop, terrestrial nonfood (noncrop agricultural areas, right-of-ways, industrial sites), and forest sites. Application rates of the single active ingredient is a maximum of 2.0 lb ai/A. The potassium salt of picloram is not formulated with other pesticides or fertilizers. Single active ingredient formulation consist of the 34.7% (30% ai), 5.8% (5% ai), and 11.6% (10% ai) P/T; and the 2 lb ai/gal SC/L. The potassium salt is applied using aerial or ground (broadcast or spot soil treatment) equipment.

All compounds are restricted use.

DATA EVALUATION RECORD

DER 1

SHAUGHNESSY No. 005101 COMMON NAME: Picloram

CHEMICAL NAME: 4-amino-3,5,6-trichloropicolinic acid, K⁺ salt

FORMULATION: Isooctyl ester

DATA REQUIREMENT: 161-2

MRID No: 42811901

F.R. Batzer, R.N. Lubinski. June 10, 1993. Aqueous Photolysis of Picloram-IOE. Performed by DowElanco North American Chemistry Laboratory 9410 Zionsville Road Indianapolis, IN 46268-1053 Study Id ENV93003

REVIEWED BY: Kevin L. Poff Signature:

Chemist EFGWB/EFED

Date:

APPROVED BY: Akiva Abramovitch, Ph.D. Signature:

Chemist EFGWB/EFED

Date:

CONCLUSIONS:

1. Study MRID #42811901 completely satisfies the aqueous photolysis 161-2 data requirement for picloram isooctyl ester.

2. Picloram-IOE degraded with a half-life (first order calculated) of 70.6 minutes in sterile aqueous buffered solutions (pH 5) irradiated with a Xenon light source at 25.1 to 26.0^oC. The major photoproducts were an isomer of dichlorohydroxypicloram-IOE and isomers of dichloropicloram-IOE reaching a maximum of 24.6 and 15.0% at 120 minutes. Ion exclusion chromatography separated a polar mixture accounting for 32.3% of applied at 180 minutes into 3 components; one component accounting for 7.8% was a mixture of carboxylic acids including oxamic acid.

MATERIALS AND METHODS:

Radiolabeled ¹⁴C(2,6-ring)-picloram-IOE, the ethylhexyl ester (radiochemical purity 96.6%, specific activity 28.4mCi/mmole, DowElanco) was added to acetonitrile to achieve 0.1 ppm (26.1 uCi), the solubility level is 0.23 ppm at 25C. The solution was added to a pH phosphate 5 buffer and placed in sterile quartz photolysis vessels. The dark controls were kept under the same conditions. The samples were irradiated by a Xenon lamp with a wavelength band of 290-800 nm and an intensity range of 400W/m² to 765W/m². The samples were irradiated under the lower intensity. Duplicate samples were taken at 0, 20, 40, 60, 90, 120, 180, minutes. The actinometer for the samples was a solution of pyridine and p-nitroanisole (PNA). Samples were counted by LSC, then analyzed by HPLC with 2 different gradients. The fractions were analyzed by LSC then radiochromatograms were constructed by HPLC45.BAS Version 2.2 (DowElanco).

RESULTS:

1. The degradation half-life of picloram-IOE at pH 5 25.1 to 26.0C using a first order kinetics model was 70.6 minutes.

2. An isomer of dichlorohydroxypicloram-IOE and isomers of dichloropicloram-IOE reaching a maximum of 24.6 and 15.0% at 120 minutes were the major photoproducts.

3. An unresolved polar photoproduct mixture was separated into several components accounting for a maximum of 7.8, 8.0 and 16.5% of applied at 180 minutes. One component (7.8%) contained various carboxylic acids including oxamic acid.

4. After 20 hours the primary photoproducts had degraded to a myriad of secondary photoproducts accounting for < 10% of applied.

5. Material balance for the duration of the experiment was 93.5 to 99.9%. The extended exposure samples gave 92.5% for the 20 hour sample, 87.6 and 84.4% for the 72 hour sample.

6. Hydrolysis was not a factor in that the dark control samples showed no degradation over 3 hours.

DISCUSSION:

1. The test system was not adequately described, ie. it was not clear whether volatiles were trapped.

DATA EVALUATION RECORD

DER 2

SHAUGHNESSY No. 005101 COMMON NAME: Picloram

CHEMICAL NAME: 4-amino-3,5,6-trichloropicolinic acid

FORMULATION: triisopropanolamine salt

DATA REQUIREMENT: 164-1

MRID No: 42579002

Buttler et al. November 25, 1992. Non-Crop Right of Way Terrestrial Dissipation of Picloram in California. Performed by DowElanco North American Environmental Chemistry Laboratory Indianapolis, Indiana, DowElanco Residue Research Laboratory Greenfield, Indiana. Study ID ENV91020.

REVIEWED BY: Kevin L. Poff Signature:

Chemist EFGWB/EFED

Date:

APPROVED BY: Akiva Abramovitch, Ph.D. Signature:

Chemist EFGWB/EFED

Date:

CONCLUSIONS:

1. Study MRID #42579002 is acceptable and satisfies the terrestrial field dissipation 164-1 data requirement for picloram.

2. Picloram (Tordon 101) applied at 1.6 lb ai/A (80% of maximum label rate) dissipated from a Watsonville loam (4.01% OM) bare soil plot (TBS) and a Watsonville loam (5.61% OM) plot covered with short grass (TSG) near Davenport California with half-lives (assuming first order kinetics) of 278 and 135 days respectively. By using a zero-order kinetics model the DT50 and DT90 for picloram was in the TBS plot was 288 and 518 days respectively. Estimated DT50 and DT90 for picloram in the TGS plot using a zero order equation was 213 and 383 days respectively.

Picloram in the TBS plot dissipated slowly during the dry summer months and was generally restricted to the 0- to 6- inch (0.6 to 0.8 ppm) soil depth. By 252 DAT picloram was detected in the 6- to 12- inch depth at 0.01 ppm, then increased to 0.045 ppm at that depth by 434 days after treatment (DAT) and then after the rainy winter season picloram was detected in the subsequent 12- to 18- inch depth at 0.022 ppm by 371 DAT and then decreased in concentration at that depth to 0.015 ppm by 434 DAT. The maximum depth of detectable residue was 18 inches at 53 and 62 WAT. During the study (4/12/91-8/1/92), rainfall plus irrigation totaled 34.6 inches corresponding to 110% of the normal rainfall for the same period.

Picloram concentrations in the soil from the TSG plot were initially variable because of lack of analysis of the biomass from the plots and rainfall washing residues off of the grass to the soil. Half-life calculations were taken from the point were maximum concentration were reached in the 0- to 6- inch soil layer which was 656 ppb at 57 DAT. In the 0- to 6- inch soil depth picloram ranged from an average 0.656 ppm 8 weeks after treatment (WAT) to 0.046 ppm (52-WAT). In the 6- to 12- inch soil depth picloram was detected at 0.008 ppm (2-WAT), reached a maximum of 0.026 ppm at 36-WAT, then fell to 0.020 at 65-WAT (last sampling interval). In the 12- to 18- inch soil depth picloram was detected at 0.010 ppm at 29-WAT, then increased to 0.015 ppm at 65-WAT. The maximum depth of detectable residue was 24 inches at 461 DAT (<0.005 ppm).

The total amount of precipitation (rainfall plus supplemental irrigation) for the study period April 1991 through August 1, 1992 was 37.9 inches corresponding to 121% of the normal rainfall for the same period.

MATERIALS AND METHODS:

Picloram (Tordon 101, formulation No. XRM-3779, Lot No. MM 900210-59) as the triisopropanolamine salt was broadcast applied at 1.6 lb picloram ai/A to a bare soil plot (Watsonville loam, 39.2% sand, 35.0% silt, 25.8% clay, pH = 5.5, 4.01% OM, CEC 12.40) and a plot covered with short grass (Watsonville loam, 41.2% sand, 35.0% silt, 23.8% clay, pH = 5.3, 5.61% OM, CEC 14.87) near Davenport California on April 12, 1991. Soil samples were taken from the treated plots on 2 days prior to application, on the day of application, 3 and 7 days after application and 2, 4, 8, 12, 16, 20, 29, 36, 53, and 62 weeks after application. Samples from the control plot were taken prior to application. Samples were composited to yield five replicate samples with 3 cores in each sample. Incremental soil cores were taken with successively smaller diameter soil probes. Five samples were taken from the control plot and composited into one sample per depth increment. Samples were placed in an on site freezer within 2 hours after sampling. Field spiking on soil samples collected on 0 DAT (days after treatment), 36 WAT (weeks after treatment), and 52 WAT events and were used to determine potential losses during shipping.

Soil samples were extracted using 90% acetone/10% 1.0N HCL solution. The acetone was evaporated and the sample was diluted with 0.1N HCL and purified by running through a C18 and alumina solid-phase extractions (SPE). The eluent was evaporated to dryness and derivatized with acidic methanol. The MeOH was then evaporated from the derivatizing solution and the picloram methyl ester was partitioned from an aqueous sodium chloride solution into toluene containing picloram butyl ester as an internal standard. A toluene sample was then analyzed by capillary gas chromatography with an electron capture detector.

RESULTS:

Picloram dissipated from the bare ground soil plot with a half-life of 278 days (R² = 0.80) (assuming first order kinetics) in California during the 62 weeks following a broadcast application of picloram triisopropanolamine salt at 1.6 lb ai/A to a loam on April 12, 1991. By using a zero-order kinetics model the DT50 and DT90 for picloram was 288 and 518 days respectively. In the 0- to 6- inch soil depth picloram ranged from an average of 1.020 (2-WAT) to 0.108 ppm (62-WAT). In the 6- to 12- inch soil depth picloram was detected at 0.010 ppm (36-WAT) increased to 0.110 (53-WAT), then decreased to 0.045 ppm (62-WAT). In the 12- to 18- inch soil depth picloram was detected at 0.022 ppm (53-WAT) and then decreased slightly to 0.015 ppm (62-WAT). The maximum depth of detectable residue was 18 inches at 53 and 62 WAT.

The total amount of precipitation (rainfall plus supplemental irrigation) for the study period April 1991 through August 1, 1992 was 34.6 inches corresponding to 110% of the normal rainfall for the same period.

Due to the interception of compound by the biomass present in the short grass study and the lack of analysis of the biomass picloram reached a maximum concentration in the soil during the 8-WAT sampling (69% of theoretical). Using a first order equation fitting data beyond 8-WAT the half-life was 135 days (R² = 0.953). Estimated DT50 and DT90 for picloram in the short grass plot using a zero order equation was 213 and 383 days respectively. In the 0- to 6- inch soil depth picloram ranged from an average 0.656 ppm (8-WAT) to 0.046 (53-WAT). In the 6- to 12- inch soil depth picloram was detected at 0.008 ppm (2-WAT), reached a maximum of 0.026 ppm at 36-WAT, then fell to 0.020 at 62-WAT. In the 12- to 18- inch soil depth picloram was detected at 0.010 ppm at 29-WAT, then increased to 0.015 ppm at 62-WAT. The maximum depth of detectable residue at 461 DAT was 24 inches.

The total amount of precipitation (rainfall plus supplemental irrigation) for the study period April 1991 through August 1, 1992 was 37.9 inches corresponding to 121% of the normal rainfall for the same period.

The air temp (both sites, monthly average) ranged from 51.7 to 60.8 F, and soil temperatures (monthly average at 1 inch depth) 49.7 to 76.4 F. The test plots had a slope of <2.0% and depth to the water table was 150 ft.

Recovery efficiencies from soil samples fortified with picloram at 0.0050, 0.0100, 0.0500, and 2.0000 ppm ranged from 61 to 106% (Appendix G). Results were expressed on a dry weight basis for soil; results were not corrected for recovery efficiency.

DISCUSSION:

1. The maximum label application rate for picloram is 2.0 lbs/ai/A but only 1.6 lb picloram lbs ai/A (approximately 80% of maximum label rate) were actually applied to the test plots.

2. The registrant failed to confirm the application rate in the short grass plot. The registrant reported that the target application rate of 1.6 lb/ai/A would be expected to result in an initial concentration of 949 ppb per composite soil sample as based on wet gross residues (see Results and Discussion /Degradation and movement of Picloram, Bare Soil Plot, of study text); however, in the soil at day 0 posttreatment, concentrations of picloram were 504 ppb comprising only 53% of the theoretical 949 ppb applied. (Table V). Further into the study (57 DAT) and after a number of rainfall events picloram reached a maximum of 656 ppb in the soil which represented 69% of applied. From this data it could not be determined if any method was used to determine the amount of spray solution that intercepted the soil at the time of application.

3. Because the biomass from the short grass study was not analyzed for picloram and because there was insufficient movement of picloram from the turf to the soil at the time of application a large portion (>30% of the 80% of maximum label rate) of the applied mass cannot be accounted for in the short grass study.

4. The soil was analyzed for parent only; The registrant maintains that there is some photodegradation (2.6 days, major degradate oxamic acid) and aerobic soil metabolism (167-513 days, major degradate CO₂) that takes place in the field, however the pattern of formation and decline of degradates was not addressed.

5. Freezer storage stability data were not provided to confirm that picloram did not degrade in the soil samples during frozen storage for 564 days. However, picloram appears to be stable chemically and would not decompose very readily under frozen storage conditions.

6. The soil samples that were field spiked and analyzed for picloram in the 0 DAT, 36 DAT, and 52 DAT samples showed losses of 15.7%, 5.3% and 6.5% respectively. The analytical results were not corrected for field spike recoveries.

7. Picloram was found to a depth of 24 inches in the short grass plot study even through the unusually intolerant leaching conditions of 5.61% OM and a total precipitation (rainfall plus supplemental irrigation) for the study period April 1991 through August 1, 1992 being 37.9 inches.

DATA EVALUATION RECORD

DER 3

SHAUGHNESSY No. 005101 COMMON NAME: Picloram

CHEMICAL NAME: 4-amino-3,5,6-trichloropicolinic acid

FORMULATION: triisopropanolamine salt

DATA REQUIREMENT: 164-1

MRID No: 42579001

D.G. Petty, D.D. Fontaine, B.J. Harnick. November 24, 1992. Non-Crop and Right of Way Terrestrial Dissipation Study of Picloram in North Carolina. Performed by DowElanco North American Environmental Chemistry Laboratory Midland, MI 486411706. Study ID 90094.

REVIEWED BY: Kevin L. Poff Signature:

Chemist EFGWB/EFED

Date:

APPROVED BY: Akiva Abramovitch, Ph.D. Signature:

Chemist EFGWB/EFED

Date:

CONCLUSIONS:

1. Study MRID #42579001 is acceptable and satisfies the terrestrial field dissipation 164-1 data requirement for picloram.

2. Picloram (Tordon 101) applied at 2.0 lbs ai/A dissipated from a Colfax sandy loam bare soil (TBS) and short grass plot (TSG) in Alamance county, North Carolina with pseudo first order half-lives of 108 and 104 days respectively.

Picloram residues in the 0 to 15 cm soil core layer, bare soil plot (TBS), was a maximum average of 0.7467 ppm at day 0. Residue concentrations in that layer then decreased to below the detection limit by week 52. Residues were found in the 15 to 30 cm layer by day 3 at an average of 0.0510 ppm and decreased to not detectable by week 44. Between the week 4 and week 8 sampling interval significant rainfall occurred causing the residues to move to the 30-45, 45-60, 60-75, and 75-90 cm soil increments. Residues were detected at the lower 3 soil segments 45-60, 60-75, 75-90 cm throughout the sampling intervals to week 52.

Picloram residues in the 0 to 15 cm soil core layer, short grass plot (TSG), reached a maximum average of 0.6237 ppm on day 3. Picloram residues at 0.0412 ppm reached the 15 to 30 cm depth by week 4. By week 8 and after a number of rainfall events picloram residues were found throughout the entire soil profile to 90 cm. Picloram residues ranged from 0.01 to 0.03 ppm in the 75 to 90 cm soil core throughout all sampling intervals and the study's duration.

MATERIALS AND METHODS:

Picloram (Tordon 101M, Lot No. MM 900210-59) as the triisopropanolamine salt was broadcast applied at 2.0 lbs picloram ai/A to a bare soil plot (Colfax sandy loam, 70% sand, 22% silt, 8% clay, pH = 5.5, 4.01% OM, CEC 12.40) and a plot covered with short grass (same soil characteristics) in Patterson Township, Alamance County, North Carolina on August 29, 1990. Soil samples were taken from the treated plots at 1 day prior to application, on the day of application, 3 and 7 days after application and 2, 4, 8, 12, 16, 20, 28, 36, 44, and 52 weeks after application. Soil cores were taken from the control plots at four separate intervals. Five soil cores per sampling time for both the treated and control plots were composited by 15 cm depth increments. This resulted in 3 composite samples per depth increment per sampling event. Acetate lined soil cores were capped, labeled, and placed into coolers for transport to DowElanco in Midland, Michigan. Field spikes on the soil from the day of application were prepared using analytical standard picloram at a concentration of 1.4 mg in 2 ml of acetone.

Soil samples were extracted using 90% acetone/10% 1.0N HCL solution. The acetone was evaporated and the sample was diluted with 0.1N HCL and purified by running through a C18 and alumina solid-phase extractions (SPE). The eluent was evaporated to dryness and derivatized with acidic methanol. The MeOH was then evaporated from the derivatizing solution and the picloram methyl ester was partitioned from an aqueous sodium chloride solution into toluene containing picloram butyl ester as an internal standard. A toluene sample was then analyzed by capillary gas chromatography with an electron capture detector. The limit of quantitation was 0.005 ppm.

RESULTS:

Picloram dissipated from a bare ground soil plot with a pseudo first order half-life of 108 days in North Carolina during the 52 weeks following a broadcast application of picloram triisopropanolamine salt at 2.2 lb ai/A to a Colfax sandy loam on August 29, 1990. On day 0 in the 0 to 15 cm depth picloram residues (picloram residues were corrected for recovery and percent soil moisture) averaged 0.7467 ppm. There were also detections below the limit of quantification throughout the soil profile on day 0. On day 3 in the 0 to 15 cm depth picloram residues averaged 0.7227 ppm. In the 15 to 30 cm soil core picloram residues averaged 0.0510 ppm. There were also sporadic detections below the limit of quantification throughout the soil profile. On day 7 after 1 inch of irrigation picloram residues averaged 0.7467 ppm in the 0 to 15 cm depth and were below the limit of quantification at the 15 to 30 cm depth. The two week sample showed picloram decreasing in the 0 to 15 cm depth at an average residue concentration of 0.5233 ppm and sightly increasing in the 15 to 30 cm depth at an average of approx. 0.0210 ppm. At the four week sample picloram residues increased to an average of 0.9063 ppm in the 0 to 15 cm soil core, increased to 0.0415 ppm in the 15 to 30 cm depth and was not detected throughout the profile to 90 cm. From week 8 to week 52 picloram residues decreased in concentration the top soil profiles (from an average of 0.0277 ppm to being less than the limit of quantification) and increased in concentration in the subsequent soil profiles to 90 cm (see appendix A, Table of Picloram Residues). The maximum depth of detectable residue was 90 cm beginning at week 8 and continuing through the duration of the study to week 52. Total on site rainfall plus irrigation was 55.88 inches which is 124% of the NOAA 30 yr. normal.

Picloram dissipated from a short grass soil plot with a pseudo first order half-life of 104 days in North Carolina during the 52 weeks following a broadcast application of picloram triisopropanolamine salt at 2.2 lb ai/A to a Colfax sandy loam on August 29, 1990. On day 0 in the 0 to 15 cm depth picloram residues (picloram residues were corrected for recovery and percent soil moisture) averaged 0.5700 ppm and were at an average of approx. 0.0513 ppm in the 15 to 30 cm depth and were not detected throughout the rest of the soil profile. On day 3 the average picloram residues increased to 0.6237 ppm in the 0 to 15 cm core and was detected at around the limit of quantification in the 15 to 30 cm and the 75 to 90 cm depth core. On day 7 average residues in the 0 to 15 cm depth were an average of 0.5323 ppm and were variable around the limit of quantification in the 15 to 30 cm depth. There were no detections throughout the rest of the soil profile. On week 2 residues decreased to an average of 0.3333 ppm and increased to an average of 0.1263 ppm in the 15 to 30 cm core. There were no detections in the various other soil cores. At week 4 average residues were 0.1777 ppm in the 0 to 15 cm core and were an average of 0.0494 ppm in the 15 to 30 cm core. Between the 4 and 8 week sampling a significant amount of rainfall occurred and picloram residues were found throughout the soil profile; all concentrations are an average of at least 3 samples: 0.0533 ppm in the 0 to 15 cm core, 0.0925 ppm in the 15 to 30 cm core, 0.1210 ppm in the 30 to 45 cm core, 0.0543 ppm in the 45 to 60 cm core, 0.0177 ppm in the 60 to 75 cm core, and 0.0163 ppm in the 75 to 90 cm core. Picloram reached a averaged maximum of 0.0283 ppm at week 28 in the 75 to 90 cm soil core and was detected at this depth throughout the studies progress. The maximum depth of detectable residue was 90 cm beginning at week 8 and continuing through the duration of the study to week 52. Total on site rainfall plus irrigation was 55.88 inches which is 124% of the NOAA 30 yr. normal.

The air temp (for both sites) monthly average ranged 5.0 to 25.2 C. Analysis of the field spike samples showed an average recovery of 86.4% for the five samples. Mean recoveries of picloram from soil were approximately 89%. The estimated depth to the seasonal high water table was 25 feet.

DISCUSSION:

1. Preliminary data indicate picloram is stable in frozen North Carolina soils for up to 401 days. However, the length of time from sampling to analysis was not reported and a detailed frozen storage stability study was not included. But as was previously state picloram is chemically stable and would not be expected to degrade under frozen storage conditions.

2. The registrant failed to confirm the application rate in the short grass plot as well as the bare ground plot. The registrant stated the calculated application rate for both the bare ground and the short grass plot was 2.2 lbs. picloram a.e. per acre. In the section entitled Analytical Results the registrant reported the nominal application rate of 2 lbs. a.e. per acre to calculate the initial soil concentration of picloram in the bare ground plot which was 69% of the theoretical applied (using 2 lbs ae/A instead of the reported 2.2 lbs ae/A), the short grass plot was not discussed and it is unclear from the presentation of the data what the actual application rate was for both plots.

3. It was unclear from the data in the short grass plot if the biomass was analyzed for picloram residues. The data show a large percentage of the applied mass not being accounted for (<65% of applied using 2.0 lbs/ae/A or <60% applied using 2.2 lbs/ae/A).

4. The soil was not sampled deep enough to determine the leaching of picloram. Picloram was detected in the deepest soil segments sampled (75 to 90 cm) at all sampling intervals beyond 8 weeks. It is possible that pesticide residues could have leached below the deepest sampled soil increment. Additionally, the original study protocol was not included to determine if in fact the sampling procedure was followed.

5. The soil was analyzed for parent only; The registrant maintains that there is some photodegradation (2.6 days, major degradate oxamic acid) and aerobic soil metabolism (167-513 days, major degradate CO₂) that takes place in the field, however the pattern of formation and decline of degradates was not addressed.

DATA EVALUATION RECORD

DER 4

SHAUGHNESSY No. 005101 COMMON NAME: Picloram

CHEMICAL NAME: 4-amino-3,5,6-trichloropicolinic acid, K⁺ salt

FORMULATION: potassium salt

DATA REQUIREMENT: 164-3

MRID No: 42579003

Steven A. Cryer, (DowElanco),Tim A. Cooley and Larissa L. Schuster (Pan-Agricultural Laboratories, Inc.) November 24, 1992. The Dissipation and Movement of Picloram in a Northern USA Forest Ecosystem. Testing Facility; Pan-Agricultural Laboratories, Inc. 32380 Avenue 10 Madera, California 93638. Performing Laboratories; Pan-Agricultural Laboratories, Inc. Collins Agricultural Consultants, Inc. DowElanco. DowElanco No ENV91088. Study No: PM91-2501.

REVIEWED BY: Kevin L. Poff Signature:

Chemist EFGWB/EFED

Date:

APPROVED BY: Akiva Abramovitch, Ph.D. Signature:

Chemist EFGWB/EFED

Date:

CONCLUSIONS:

1. Study MRID #42579003 is acceptable and completely satisfies the forestry dissipation (164-3) data requirement for picloram.

2. Picloram (TORDON K, potassium salt), was applied aerially at 1.08 lb picloram lbs ai/A (54% of maximum label rate) to about 70 acres of clear cut commercial timber land at a forest site near Ostrander, Washington on August 6, 1991. Picloram dissipated with a calculated first order half-life of 123 + 13 days (average of 3 subplots) in the exposed (bareground) soil and 34 + 18 days in the unexposed (soil covered with leaf litter) soil. Dissipation of picloram in pond water and pond sediment yielded a half-life of 9.6 and 49.5 days respectively. Dissipation on the leaf litter and vegetation samples yielded a half-life of 7.9 + 4.6 days and 4.6 + 1.9 days respectively. Picloram residues in the exposed (bareground) soil were detected up to the deepest sampling depth (36 inches) at the 9 MAT (months after treatment) sampling interval. Picloram residues in the unexposed (covered with leaf litter/vegetation) did not detectably leach below the 24 inch soil layer through the duration of the study (13 months).

MATERIALS AND METHODS:

Picloram as the potassium salt (TORDON^*K) was aerially applied at 1.08 acid equivalents per acre to about 70 acres of clear cut commercial timber land at a forest site near Ostrander, Washington on August 6, 1991. Two runoff gullies, an artificial pond (10 inch depth), a stream, four observation wells, exposed (bareground) and unexposed soils were examined for residues. The soil (0-12 inches) was a loam (44% sand, 32% silt, 24% clay, 3.7% OM, 6.7 CEC (meq/100g), 33.04% of 1/3 bar) and 12 to 48 inches was a clay loam (table XXIV). Six soil cores taken to a depth of 36 inches (six inch increments) from each of two grids per subplot on prior to application, 0, 1, 3, 7, 14 DAT; 4 WAT, and 2, 4, 6, 9, and 13 MAT. Stream and pond sediment as well as foliage and leaf litter were collected generally on the same schedule as the soils. Field samples were fortified with picloram to determine stability under field conditions. Field samples were also kept on dry ice then stored in a walk-in freezer (-8 to 31F). See method summaries for analytical methodology. Study sample analysis was initiated August 8, 1991 and completed on November 8, 1992.

RESULTS:

Blotter paper analysis:

Blotter paper was used in conjunction with day 0 soil analysis at the time of application to confirm the application rate. Blotter pad residue indicates that all subplots (except subplot A) had received >70% of target rate application.

Picloram residues in surface water:

The stream was to be avoided by the applicator and was used as a determination for runoff only. Picloram was detected in four samples prior to treatment at levels greater than the minimum quantifiable level (MQL; 0.000100 ppm), ranging from 0.000105 to 0.000195 ppm. On day 0 (post application) picloram levels averaged 0.00579 and 0.000602 ppm for the upstream and downstream samples respectively. On 3 DAT after 0.22 inch of rainfall levels of picloram increased to an average of 0.00736 to 0.00380 ppm for the upstream and downstream samples respectively indicating some runoff. On 7 DAT levels averaged 0.000222 ppm and <MQL respectively for the upstream and downstream samples. Generally upstream samples were at a higher level than downstream. On 14 DAT and 4 weeks after treatment (WAT) the upstream levels were at 0.000234 ppm for both samples while downstream samples were <MQL. No residue was found in the 6 WAT and 2 months samples. On the 4 MAT the upstream samples averaged 0.000115 ppm. The final 5 MAT, 6 MAT, and 8 MAT samples indicated picloram at <MQL.

The estimated picloram mass transported past the automatic collection or continuous sampler located at the weir downstream and upstream was determined from four sampling intervals during runoff events as 1.68 X 10^-4, 1.49 X 10^-3, 6.43 X 10^-4, and 2.12 X 10^-4 pounds of picloram. Runoff under those conditions present was not a major mode of dissipation of picloram.

Picloram residues present in stream sediment:

The only sample that had picloram residues higher than the MQL was the 4 WAT upstream sample at 0.0126 ppm. This detection followed the largest runoff event. All other samples were at <MQL or there were no detections.

Picloram residues in pond water:

The pond was sprayed directly by the applicator and was constructed so that no runoff water or sediment could enter the water. Samples were collected from the center and the edge of the pond. On 0 DAT picloram residues levels for pond water averaged (average of 2 samples) 0.423 and 0.429 ppm for the center and edge samples respectively. On 1 DAT residues were at 0.450 ppm and 0.422 ppm respectively and reached a maximum on 3 DAT at an average of 0.538 and 0.485 ppm respectively. By the 2 MAT samples picloram averaged 0.0117 and 0.0131 ppm respectively and decreased to an average level of 0.000194 and 0.000156 ppm by the last sampling interval (8 MAT). The differences in detection values was attributed to diffusion, mixing, evaporation and seeping/leakage of pond water and residues.

Picloram residues in pond sediment:

Sediment was collected at the center and edge of the pond. First order dissipation for picloram in pond sediment was calculated at 49.5 days. On 0 DAT (post application) picloram residues averaged (average of 2 samples) 0.0718 and 0.0845 ppm for the center and edge respectively. On the 1 DAT picloram residues averaged 0.144 and 0.0766 ppm respectively for the center and edge. Then at 3 DAT the residues averaged 0.0870 and 0.114 ppm respectively. By 7 DAT concentrations were at 0.0933 and 0.130 ppm respectively and at 14 DAT residues were at 0.109 and 0.268 ppm respectively. Concentrations continued to decline to the 8 MAT sampling where they were at 0.200 and 0.208 ppm respectively for the center and edge. Concentrations first increased in the indicating time for settling out and sorption of picloram residues then a phase where dissipation had occurred after recharging had ceased.

Picloram residues in foliage/vegetation and leaf litter:

A first order plot for the dissipation of picloram from leaf foliage yielded a calculated half-life of 4.6 + 1.9 days. Residues were not detected on pretreatment and were at a maximum of 39.5 ppm (average of 3 samples) on 0 DAT. Residues steadily declined and were 27.9 ppm (1 DAT), 24.0 ppm (3 DAT), 12.8 ppm (7 DAT), 6.19 ppm (14 DAT), 1.70 ppm (4 WAT), 1.12 ppm (2 MAT), 0.101 ppm (4 MAT), 0.299 ppm (6 MAT), and 0.220 (9 MAT).

A first order plot for the dissipation of picloram from leaf litter yielded a calculated half-life of 7.9 + 4.6 days. The leaf litter sample size was non-uniform (litter depth, and homogeneity) which lead to variability in residue concentration. The average (18 samples from 3 subplots) picloram residues in leaf litter at 0 DAT was 8.65 ppm. At 1 DAT the residues decreased to 6.20 ppm, then to 2.90 ppm (3 DAT), 2.05 ppm (7 DAT), 1.57 (14 DAT), 0.742 (4 WAT), 0.898 ppm (2 MAT), 0.206 ppm (4 MAT), 0.0748 ppm (6 MAT), 0.0531 ppm (9 MAT) and was not detected at 13 MAT which was the last sampling interval.

Picloram residues in soil:

The first order half-life of the dissipation of picloram in the exposed (bareground) soil was calculated at 123 + 13 days (average of 3 subplots). Six composite (0 to 6 inch) soil samples from the exposed plot (bareground) were analyzed for each subplot on 0 DAT. The average values for those samples were 0.717 ppm (subplot A), 0.861 ppm (subplot B), and 1.43 ppm (subplot C). The average values of picloram residues (0 to 6 inch soil core) in subplot A, B, and C at 1 DAT were 0.631, 0.807, and 0.821 ppm respectively. Residues were detected at the 6 to 12 inch layer. At 7 DAT the average values of residues in the three subplots in the 0 to 6 inch layer were an average of 0.713, 0.580, and 0.918 ppm respectively. Residues were not detected in the 6 to 12 inch layer on this sampling which give an indication that the 1 DAT 6 to 12 inch detection was due to contamination. Residues generally remained in the 0 to 6 inch soil layer up to the 4 MAT sampling interval where residues were detected at a maximum of 0.494 ppm in the 6 to 12 inch layer and 0.0320 ppm in the 12 to 18 inch soil layer. Residues were then detected in the 18 to 24 inch depth at a maximum of 0.0142 ppm by 6 MAT; by 9 MAT in the 18 to 24 inch depth at a maximum of 0.0470 ppm, the 24 to 30 inch soil layer at a maximum of 0.0202 ppm, and the 30 to 36 inch depth at a maximum of 0.0250 ppm (approximately 2% of applied chemical). By 13 MAT there was only 1 detection of picloram residues below the 12 inch layer and that was at the 24 to 30 inch layer at 0.0121 ppm. Picloram residues were found up to 36 inches, the deepest sampling depth.

The first order half-life of the dissipation of picloram in the unexposed (soil covered with vegetation) soil was calculated at 34 + 18 days (average of 3 subplots). Six composite (0 to 6 inch) soil samples from the unexposed plot (covered with vegetation) were analyzed for each subplot on 0 DAT. The average values for those samples were 0.215 ppm (subplot A), 0.434 ppm (subplot B), and 0.467 ppm (subplot C). No further sampling was completed on day 0. The 0 to 6 inch average residues at 1 DAT were an average of 0.423, 0.265 and 0.519 ppm respectively, then by 3 DAT (0.22 inch precipitation) residues increased to an average of 0.776, 0.508, and 0.624 ppm respectively. Residues were then detected in the subsequent 6 to 12, 12 to 18 and 18 to 24 inch soil layer by 4 WAT at a maximum of 0.0589, 0.0115, and 0.0362 ppm. At 2 MAT the deepest detectable residue (0.0439 ppm) was at the 12 to 18 inch depth. Picloram residues did not detectably leach below the 24 inch soil layer through the 13 MAT sampling interval.

The increase in picloram residues in the first 1 to 2 week sampling interval was attributed to washoff and or deposition from the foliage/litter.

The air temp (for both sites) monthly average ranged 4.6 to 18.0C. The total rainfall for the study period August 1991 to September 1992 was 36.85 inches, historical average (1980 to 1989) is 46.55 inches. The soil temperature (top 4 inches) ranged from 5.4 to 19.5C.

DISCUSSION:

1. The maximum label application rate for picloram is 2.0 lbs/ai/A but only 1.08 lb picloram ai/A (approximately 54% of maximum label rate) were actually applied to the test plots.

2. It is possible that picloram residues moved beyond the deepest sampling depth by 13 MAT in the exposed (bareground) soil plot.

3. The soil was analyzed for parent only; The registrant maintains that there is some photodegradation (2.6 days, major degradate oxamic acid) and aerobic soil metabolism (167-513 days, major degradate CO₂) that takes place in the field, however the pattern of formation and decline of degradates was not addressed.

4. Freezer storage stability data were not provided to confirm that picloram did not degrade in the soil samples during frozen storage. However, picloram appears to be stable chemically and would not decompose very readily under frozen storage conditions.

DATA EVALUATION RECORD

DER 5

SHAUGHNESSY No. 005101 COMMON NAME: Picloram

CHEMICAL NAME: 4-amino-3,5,6-trichloropicolinic acid, K⁺ salt

FORMULATION: potassium salt

DATA REQUIREMENT: 164-1

MRID No: 42535302

S.A. Cryer, J.R. Peterson, C.A. Lacey, and G. Kennett. November 26, 1992. Picloram Fate in the Northern Rangeland Ecosystem. Performing Laboratory, DowElanco North American Environmental Chemistry Laboratory Midland, MI 48641-1706. A&L Great Lakes Laboratories, Inc. 3505 Conestoga Drive Fort Wayne, IN 46808-4413. A&L Midwest Laboratories, Inc. 13611 inBin St. Omaha, NE 68144. Lab Study ID ENV88088.

MRID No: 42558302

Steven A. Cryer. November 4, 1992. Supplement to Picloram Fate in the Northern Rangeland Ecosystem. Submitting Laboratory DowElanco North American Environmental Chemistry Laboratory Midland, Michigan 48641-1706. Lab Study ID 88088.

REVIEWED BY: Kevin L. Poff Signature:

Chemist EFGWB/EFED

Date:

APPROVED BY: Akiva Abramovitch, Ph.D. Signature:

Chemist EFGWB/EFED

Date:

CONCLUSIONS:

1. Studies MRID #42535302 and MRID #42558302 are acceptable for field dissipation only and satisfies the terrestrial field dissipation data requirement for picloram.

2. At 1.0 bl/ picloram ai/A (50% of maximum label rate) the average of 4 first order dissipation values yielded a calculated half-life of 256 days with a deviation of 37 days. The theoretical concentration from day zero was used in the calculations because of picloram residues in the soil increased during the first 2 weeks of the study due to wash/off deposition from the vegetation. In the 0 to 6 inch depth picloram reached a maximum (average of 4 treated plots) of approx. 0.4857 ppm on 27 DAT (days after treatment), that value decreased slowly to approx. 1.63% of applied (approx. 0.0082) ppm by 1357 days after treatment. Picloram residues reached a maximum of approx. 19.69% of applied (approx. 0.0985 ppm) by 354 DAT in the 6 to 12 inch soil layer, then decreased to 0.82% of applied (approx. 0.0041 ppm) by 1357 DAT. Picloram residues in the 12 to 18 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied at 481 DAT, then decreased to a minimum of 0.20% (approx. 0.001 ppm) of applied by 1357 DAT. Picloram residues in the 18 to 24 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied by 110 DAT, then decreased to a minimum of 0.20% (approx. 0.0010 ppm) of applied by 1357 DAT. Picloram residues in the 24 to 36 inch depth reached a maximum of 2.24% (approx. 0.0112 ppm) of applied by 846 DAT, then decreased to ND (not detectable) by 1357 DAT. Picloram residues in the 36 to 48 inch depth reached a maximum of 0.71% (approx. 0.0036 ppm) of applied at 715 DAT, then decreased to ND at 1357 DAT. Picloram was detected at the 48 to 60 inch soil layer at 1.07% (0.0054 ppm) of applied at 790 DAT.

MATERIALS AND METHODS:

Picloram as the potassium salt (Tordon 22K) was broadcast applied with Clopyralid (Lontrel 3A herbicide) and fluroxypyr at the rate of 1 lb ai per acre to 4 test plots in Missoula County Montana. The test plot had grass and other herbaceous foliage as ground cover and was characterized as an Alberton very fine sandy loam (properties varied per test plot) 56% sand, 26% silt, 18% clay, 9.1 CEC meq/100ml, pH 6.8, 2.2% OM, 16.08 of the 1/3 bar. A calcium bromide tracer was also applied to the study site at a rate of 9.9 lb/A. Soil samples were taken pre application, day of application, then on day 5, 14, 27, 55, 110, 354, 419, 482, 715, 790, 846, and 1357. Soil was sampled up to 7 incremental sampling depths to 72 inches from the surface. Similar depth increments from each subplot were composited in plastic lined cloth bags at the time of sampling.

The lower limit of quantitation of picloram in soils was 5 ppb, the limit of detection was 2.5 ppb. Soils were extracted with 0.5N KOH centrifuged then an aliquot of extract was acidified and extracted with diethyl ether. The ether extracts were passed through a 3% deactivated alumina column then the picloram was eluted with ammonium hydroxide/methanol solution. After concentration and acidification the column eluent was treated with potassium permanganate, sodium bisulfite, extracted with diethyl ether and derivatized with excess diazomethane. The ester was analyzed using GC with an EC detector.

RESULTS:

The average of 4 first order dissipation values yielded a calculated half-life of 256 days with a deviation of 37 days. The theoretical concentration from day zero was used in the calculations because of picloram residues in the soil increased during the first 2 weeks of the study due to wash/off deposition from the vegetation. In the 0 to 6 inch depth picloram reached a maximum (average of 4 treated plots) of approx. 0.4857 ppm on 27 DAT (days after treatment), that value decreased slowly to approx. 1.63% of applied (approx. 0.0082) ppm by 1357 days after treatment. Picloram residues reached a maximum of approx. 19.69% of applied (approx. 0.0985 ppm) by 354 DAT in the 6 to 12 inch soil layer, then decreased to 0.82% of applied (approx. 0.0041 ppm) by 1357 DAT. Picloram residues in the 12 to 18 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied at 481 DAT, then decreased to a minimum of 0.20% (approx. 0.001 ppm) of applied by 1357 DAT. Picloram residues in the 18 to 24 inch depth reached a maximum of 4.23% (approx. 0.0212 ppm) of applied by 110 DAT, then decreased to a minimum of 0.20% (approx. 0.0010 ppm) of applied by 1357 DAT. Picloram residues in the 24 to 36 inch depth reached a maximum of 2.24% (approx. 0.0112 ppm) of applied by 846 DAT, then decreased to ND (not detectable) by 1357 DAT. Picloram residues in the 36 to 48 inch depth reached a maximum of 0.71% (approx. 0.0036 ppm) of applied at 715 DAT, then decreased to ND at 1357 DAT. Picloram was detected at the 48 to 60 inch soil layer at 1.07% (0.0054 ppm) of applied at 790 DAT.

Frozen storage of picloram residues in soil at 0.05 ppm for 739 days yielded recoveries of 71 to 83%; in water at 1 ppm for 769 days 72 to 79%; and grass at 1 and 100 ppm 1092 days ranged from 88 to 105%.

Average precipitation in the region varies between 12 to 15 inches annually. Depth to ground water ranged from 10 to 15 ft. From study initiation to the completion a total of 114% of the long term (30 year) average rainfall had been applied through natural precipitation and irrigation.

DISCUSSION:

1. The maximum label application rate for picloram is 2.0 lbs/ai/A but only 1.0 lb picloram ai/A (50% of maximum label rate) was actually applied to the test plots.

2. An aqueous tank mix of Clopyralid (Lontrel 3A herbicide) and fluroxypyr was coapplied by broadcast with picloram at the time of application.

3. The materials and methods section were not adequately prepared to describe the study; ie. there were no descriptions of the field storage conditions of soil samples. It is also in the registrants best interest to present the results/numerical data in a section that will facilitate fast review.

4. The registrant failed to confirm the application rate. The registrant stated that the application rate was 1.0 lb/ai/A picloram which was calculated from tank mix amounts applied and not direct measurement with a method used to determine the amount of spray solution that intercepted the soil at the time of application.