
                                       
                    UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                               WASHINGTON, D.C.  20460
                                       
	OFFICE OF
		CHEMICAL SAFETY AND
		POLLUTION PREVENTION


MEMORANDUM

Date:  		31-JUL-2013

SUBJECT:	Prometryn in/on Snap Beans and Dill.  Summary of Analytical Chemistry and Residue Data.

PC Code:  080805
DP Barcode:  D408525
Decision No.:  467531
Registration No.:  100-620
Petition No.:  2E8052
Regulatory Action:  Amended Section 3
Risk Assessment Type:  NA
Case No.:  0467
TXR No.:  NA
CAS No.:  7287-19-6
MRID Nos.:  48834201, 48834202
40 CFR:  §180.222

From:		Sarah J. Levy, Chemist
		Risk Assessment Branch 1 (RAB1)
		Health Effects Division (HED, 7509P)

Through:		George F. Kramer, Ph.D., Senior Chemist
         	RAB1/HED (7509P)

         To:		Barbara Madden, RM 05
         	Registration Division (RD; 7505P)

Executive Summary

Prometryn [2,4-bis(isopropylamino)-6-methylthio-s-triazine] is a substituted thiomethyl triazine herbicide (Group 5) registered in the U.S. for the control of weeds in a number of commodities [40 CFR §180.222(a)].  There is also a tolerance with regional registration in/on dill as well as tolerances for indirect or inadvertent residues in/on barley, oat, rye, triticale, and wheat commodities.  The Prometryn Reregistration Eligibility Decision (RED) document was issued FEB-1996.  The Product and Residue Chemistry Chapters for the Prometryn RED were issued 08-DEC-1994.

The Interregional Research Project No. 4 (IR-4), on behalf of the Agricultural Experiment Stations of ID, MI, NC, NJ, NY, OK, OR, TX, and WA has submitted a tolerance petition for new uses of prometryn on snap beans and dill.  A Section 3 label amendment for an end-use product is not being submitted with this action due to indemnification concerns and the intent of the company is to allow this use via a 24(c) in the future.  The end-use product relevant to this registration request is Indemnified Caparol[(R)] 4L (EPA Reg. No. 100-620).  This product is formulated as a flowable-concentrate (FlC) and contains 44.0-44.4% prometryn (equivalent to 4.0 pound active ingredient per gallon (lb ai/gal)).  It is proposed for preemergence (post planting) or postemergence broadcast application using ground equipment with maximum seasonal rates of 1.5 lb ai per acre (A) for dill and 1.5 lb ai/A for snap beans.  The pre-harvest intervals (PHIs) are 30 days for dill and 52 days for snap beans.  In conjunction with these uses, IR-4 proposes the establishment of permanent tolerances for residues of prometryn per se in/on the following:

Bean, snap, succulent ..........
0.05 ppm
Bean, forage ..................
0.09 ppm
Dill, leaves ...................
0.3 ppm
Dill, dried leaves ..............
1.1 ppm
Dill, oil ........................
1.3 ppm

It should be noted that prometryn is already registered for use on dill; however, the current registration is limited to regional registration.  The Registrant has submitted additional data to expand the regional registration to a national registration.  The proposed national use pattern is identical to the currently registered regional use pattern.  

HED previously determined that the residue of concern in plants consists of the parent, prometryn per se, which is the currently regulated residue.  HED concluded that if other major uses were registered in the future, additional metabolism studies would be required.  The petitioner recently submitted a metabolism study in rice which was reviewed as part of the following memorandum:  S. Levy, 13-MAR-2013; D398563.  Although the rice metabolism study was deemed adequate, it presents a qualitatively different metabolic profile than the celery and cotton profiles (Memo, C. Swartz, 05-DEC-1994; D208880 and 09-DEC-1995; D207139, respectively).  In the celery and cotton metabolism studies, parent was the major residue and in the rice metabolism study metabolite GS-17794 was the major residue.  Therefore, HED is still requesting a root crop metabolism study.  This deficiency remains outstanding.  Depending results of the root crop metabolism study, additional field trial data could be required.

The nature of the residue in livestock is adequately understood based on acceptable poultry and ruminant metabolism studies.  The residue of concern (and that which should be regulated) in livestock is the parent, prometryn per se.  As in plants, the metabolism of prometryn in livestock involves N-dealkylation along with hydrolysis and/or amino acid conjugation.

Adequate enforcement methodology is available to enforce the proposed tolerances.  Prometryn is completely recovered (>80% recovery) using the Food and Drug Administration's (FDA's) Multiresidue Section 302.  In addition, an acceptable gas chromatography (GC) method with flame-photometric detection in the sulfur mode (FPD/S), Ciba-Geigy Method AG-559, is available for use as a single-analyte confirmatory method.  

Samples of snap beans and dill commodities were analyzed for residues of prometryn and the triazine impurities GS-11354 and GS-26831 using methods derived from Method AG-559.  Samples of snap beans were analyzed using a GC/FPD/S version of the method, and samples of dill commodities were analyzed using a version with high-performance liquid chromatography and tandem mass spectrometry detection (HPLC/MS/MS).  For both methods, the lowest limit of method validation (LLMV) was 0.05 ppm for each analyte in all matrices.  The methods were adequate for data collection based on method verification and concurrent method validation recoveries.
The 1994 Residue Chemistry Chapter concluded that residues of prometryn per se in meat and milk can be classified under Category 3 of 40 CFR §180.6(a).  That is, there is no reasonable expectation of finite residues in meat and milk.  No tolerances were required in the Residue Chapter; therefore, livestock feeding studies were not required.  Pending submission of an additional plant metabolism study, HED tentatively concludes that the Category 3 situation remains valid for this registration request.  

The submitted snap bean and dill crop field trial and dill processing data are supported by adequate storage stability data.  These data show that corrections for storage degradation of residues are not required for the submitted studies.

The nature of the residue in rotational crop is adequately understood.  The metabolism of prometryn in rotational crops is similar to that in celery and cotton.  HED previously determined that the minimum plantback restrictions for crops not listed on prometryn labels should be as follows (with these PBIs and the proposed application rates, that currently established rotational crop tolerances are adequate):  (1) following maximum application to any primary crop at up to 3.2 lb ai/A:  a 5-month plantback interval (PBI) for leafy vegetables, an 8-month PBI for root crops, and a 9-month PBI for small grains and all other crops.  (2) Following application at rates higher than 3.2 lb ai/A and up to 6.0 lb ai/A:  an 8-month PBI for root crops; rotation to all other crops is prohibited.  The PBI restrictions listed on the EPA-registered Caparol[(R)] 4L Label remain appropriate for the proposed crops.

There are currently no established Codex MRLs for prometryn; therefore, harmonization is not an issue. 

Analytical standards for prometryn are currently available in the EPA National Pesticide Standards Repository.

Regulatory Recommendations and Residue Chemistry Deficiencies

Pending submission of a revised Section F, there are no residue chemistry issues that would preclude granting registration for the requested uses or establishment of tolerances for residues of prometryn.  Furthermore, in accordance with the most recent guidance concerning tolerance expressions, HED recommends that the tolerance expression for 40 CFR §180.222 be changed as indicated below.
 
"(a) General.  Tolerances are established for residues of the herbicide prometryn, including its metabolites and degradates, in or on the commodities in the table below.  Compliance with the tolerance levels specified below is to be determined by measuring only prometryn [2,4-bis(isopropylamino)-6-methylthio-s-triazine] in or on the following raw agricultural commodities:"

            Snap, bean, succulent	0.05 ppm
            Dillweed, fresh leaves	0.30 ppm
            Dill, dried leaves	1.1 ppm

and

(d) Indirect or inadvertent residues.  Tolerances are established for indirect or inadvertent residues of the herbicide prometryn, including its metabolites and degradates, in or on the commodities in the table below.  Compliance with the tolerance levels specified below is to be determined by measuring only prometryn ([2,4-bis(isopropylamino)-6-methylthio-s-triazine] in or on the following raw agricultural commodities:"

The following data gap has been identified:   

*  Nature of the Residue Study in a Root crop; OCSPP 860.1300 (depending on results of the root crop metabolism study, additional field trial data could be required).
      
Note to PM:  Concurrent with the establishment of the HED-recommended tolerances for residues in/on dillweed, fresh leaves and dill, dried leaves, the established tolerance of 0.3 ppm in/on dill with regional restriction should be removed in 40 CFR §180.222(c).

A human-health risk assessment is forthcoming (DP# 403975).

Background

The chemical structure and nomenclature of prometryn and the triazine impurities GS-11354 and GS-26831 are presented in Table 1.  The physicochemical properties of the technical grade of prometryn are presented in Table 2.

Table 1.  Prometryn Nomenclature.
Chemical structure
                                       
Common name
Prometryn
Company experimental name
G-34161
IUPAC name
N,N'-diisopropyl-6-(methylthio)-1,3,5-triazine-2,4-diamine
CAS name
N,N'-bis(1-methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine 
CAS registry number
7287-19-6
End-use product (EP)
Caparol[(R)] 4L (4 lb/gal FlC; EPA Reg. No. 100-620)
Prometryn 4L Herbicide (4 lb/gal FlC; EPA Reg. No. 66222-15)
Triazine Impurity
GS-11354
                                       
               2-amino-4-iospropylamino-6-methylthio-s-triazine
Triazine impurity
GS-26831
                                       
                     2,4-bis-amino-6-methylthio-s-triazine

Table 2.  Physicochemical Properties of Prometryn.
Parameter
Value
Reference
Melting range
118-120C
Memo, C. Swartz, 08-DEC-1994; D207139
pH
6.7 at 20ºC (saturated solution)

Density
1.16 g/mL at 20ºC

Water solubility
33 ppm at 20ºC

Solvent solubility
10-30 g/100 mL in acetone,
dichloromethane, methanol, 
octanol, and toluene at 20ºC

Vapor pressure
8.54 x 10-7 mm Hg at 25ºC

Dissociation constant, pKa
4.09 at 20ºC

Octanol/water partition coefficient
KOW = 2140 at 25ºC

UV/visible absorption spectrum
Not available.


860.1200 Directions for Use

The end-use product relevant to this registration action is Caparol[(R)] 4L (EPA Reg. No. 100-620) registered to Syngenta.  This product is formulated as a FlC and contains 44.0-44.4% prometryn (equivalent to 4.0 lb ai/gal).  A summary of the proposed use directions for prometryn on the requested crops is presented in Table 3.  The petitioner submitted a Section B and draft labeling.  On the labeling, it says to follow all applicable directions, restrictions, requirements, and precautions on the EPA-registered Caparol[(R)] 4L label.

Table 3.  Summary of Directions for Use of Prometryn.
                       Applic. Timing, Type, and Equip.
                          Formulation [EPA Reg. No.]
                          Max. Applic. Rate (lb ai/A)
                          Max. No. Applic. per Season
                     Max. Seasonal Applic. Rate (lb ai/A)
                                  PHI (days)
                        Use Directions and Limitations
                                   Snap Bean
                                  Groundboom
                                  Chemigation
Caparol[(R)] 4L,  44% prometryn (ai), 4 lb ai/gal liquid formulation
[100-620]
                                      1.5
                                       1
                          1.5 lb ai/A per crop cycle
                                    52 days
Can be applied preemergence (post planting).  Do not use on sand or loamy sand soil.
                                     Dill
                                  Groundboom
                                  Chemigation
Caparol[(R)] 4L,  44% prometryn (ai), 4 lb ai/gal liquid formulation
[100-620]
                                      1.6
                                       1
                          1.6 lb ai/A per crop cycle
                                    30 days
Can be applied either pre-emergence (post planting) or post-emergence.  Do not use on sand or loamy sand soil.

Conclusions:  The proposed use directions are adequate to allow evaluation of the residue data relative to the proposed uses.  

860.1300 Nature of the Residue - Plants

Residue Chemistry Chapter of the Prometryn RED, C. Swartz 08-DEC-1994; D207139
Memo, W. Wassell, 22-DEC-2010; D382622  

Acceptable cotton and celery metabolism studies were previously reviewed.  The 1994 Residue Chemistry Chapter concluded that the qualitative nature of the residue in plants was adequately understood for the registered/proposed uses at that time (including registered uses on celery, cotton, and pigeon peas, and proposed uses on parsley, dill, and sesame).  The results of the metabolism studies showed metabolic pathways involving N-dealkylation and hydrolysis of prometryn.  HED determined that the residue of concern in plants consists of the parent, prometryn per se, which is the currently regulated residue.  HED concluded that if other major uses were registered in the future, additional metabolism studies would be required.

The petitioner recently submitted a metabolism study in rice which was reviewed as part of the following memorandum:  S. Levy, 13-MAR-2013; D398563.  Although the rice metabolism study was deemed adequate, it presents a qualitatively different metabolic profile than the celery and cotton profiles (Memo, C. Swartz, 05-DEC-1994; D208880 and 09-DEC-1995; D207139, respectively).  In the celery and cotton metabolism studies, parent was the major residue and in the rice metabolism study metabolite GS-17794 was the major residue.  

Conclusions:  The available cotton, celery, and rice metabolism data are adequate to support the proposed uses; however, no data are available reflecting metabolism in a root crop to support the proposed uses on carrot and celeriac.  OCSPP 860.1300 specifies that a metabolism study should be submitted for each type of plant for which use is proposed or metabolism studies on three dissimilar crops must be provided which indicate a similar metabolic route.  Note that IR-4 and Syngenta submitted a letter stating that they were working together to plan and conduct a nature of the residue study of prometryn on carrots or another root crop and asked for additional time to conduct this study (with a deadline of January 5, 2012).  HED responded that this request was reasonable, considering the length of the study.  HED has not received this root crop metabolism study and therefore this deficiency remains outstanding.  Depending on results of the root crop metabolism study, additional field trial data could be required.

860.1300 Nature of the Residue - Livestock

Residue Chemistry Chapter of the Prometryn RED, C. Swartz 08-DEC-1994; D207139

The nature of the residue in livestock is adequately understood based on acceptable poultry and ruminant metabolism studies.  The residue of concern (and that which should be regulated) in livestock is the parent, prometryn per se.  As in plants, the metabolism of prometryn in livestock involves N-dealkylation along with hydrolysis and/or amino acid conjugation.
860.1340 Residue Analytical Methods

Residue Chemistry Chapter of the Prometryn RED, C. Swartz 08-DEC-1994; D207139
DER References:   48834201.der.doc, 48834202.de2.doc, and 48834202.de2.doc

Enforcement methods:   Adequate enforcement methodology is available to enforce the proposed tolerances.  The FDA PESTDATA database (dated JUN-2005) indicates that prometryn is completely recovered (>80% recovery) using the multiresidue method (MRM) in the Pesticide Analytical Manual, Volume I (PAM, Vol. I) Section 302 and partially recovered (22-87% recovery) using Sections 303 and 304, with the recovery varying depending upon the choice of Florisil system used.

In addition, an acceptable GC/FPD/S method, Ciba-Geigy Method AG-559, is available for use as a single analyte confirmatory method.  Method AG-559 has undergone a successful independent laboratory validation (ILV) and was radiovalidated using samples from the celery metabolism study; however, these samples contained no detectable residues of prometryn.  HED previously concluded that Method AG-559 is acceptable for enforcement purposes, pending completion of a successful Agency method validation trial.  The Residue Chemistry Chapter of the Prometryn RED also required radiovalidation of the method using samples from the cotton metabolism study.

In response to the radiovalidation data requirements, Syngenta submitted a method description and validation data for a GC/NPD method, Method No. AG-673, for the determination of prometryn residues in/on cotton matrices.  The method determines residues of prometryn and its metabolites GS-11354 and GS-26831 in cotton seed and gin byproducts.  

Briefly, samples of homogenized cotton seed and gin byproducts are extracted with methanol/water at reflux, and the extract is concentrated and acidified prior to cleanup by C-18 solid-phase extraction (SPE) and then strong-cation exchange SPE.  The extract is then basified, partitioned into dichloromethane/ethyl acetate, and dissolved in toluene/methanol for analysis by GC/NPD.  The validated limit of quantitation (LOQ) is 0.05 ppm for each analyte in each commodity.  

The method was adequately validated using samples of cotton seed and gin byproducts fortified with a mixed standard of prometryn and metabolites at 0.05, 0.1, and 1.0 ppm.  Recoveries were in the respectable range.  Method AG-673 specifies that analyte residues may be confirmed by equipping the GC system with a flame photometric detector (FPD), as described for Method AG-559.  The extraction procedures of Method AG-673 are similar to those of AG-559.

Adequate radiovalidation data were submitted demonstrating that Method AG-673 adequately extracts aged residues of prometryn and GS-11364 from samples of cotton gin byproducts.  Although no residues of prometryn, GS-11364, or GS-26831 were detected in the cotton seed samples, and no residues of GS-26831 were detected in the cotton gin byproducts samples used for radiovalidation, no residues of these compounds were found in cotton seed samples in the cotton metabolism study, and the levels of GS-26831 found in cotton stalk samples in the cotton metabolism study were below the LOQ of Method AG-673.  

Method AG-673 was previously proposed for enforcement purposes for cotton seed and gin byproducts.  No independent laboratory validation (ILV) data were submitted for Method AG-673; however, adequate ILV data have been submitted previously for Method AG-559 (Memo, E. Zager, 24-MAY-1991; DP# 160100).  HED will not require ILV data for Method AG-673.  Methods AG-673 and Method AG-559 are both considered adequate for enforcement purposes.

Data-collection methods:  Samples of snap beans and dill from the magnitude of the residue and processing studies were analyzed for residues of prometryn and the triazine impurities GS-11354 and GS-26831 using methods derived from Method AG-559.  Modifications to Method AG-559 were implemented to improve method performance.  

Snap Beans:  Briefly, homogenized samples were extracted with methanol:water (90:10, v:v) at reflux for one hour, and filtered.  Half of the extract was acidified with 1 N hydrochloric acid, and it was concentrated by rotary evaporation.  The aqueous phase was made basic (pH 9.5-10 using 50% sodium hydroxide) and partitioned with ethyl acetate.  The ethyl acetate phase was concentrated to near dryness and brought to volume with ethyl acetate for analysis by GC/FPD/S.  Extracts were stored refrigerated (1-11°C) if not analyzed immediately after extraction. 

Dill:  Briefly, samples of homogenized fresh or dried dill leaves/stems, and seed were extracted with methanol:water (90:10, v:v) at reflux for one hour, and filtered.  An aliquot of the extract was concentrated, acidified with 1 N hydrochloric acid, and partitioned twice with hexane.  The aqueous phase was made basic (pH >9 using 50% sodium hydroxide), diluted with pH 9 water, and cleaned up by Strata-X (weak cation exchange) solid-phase extraction; residues were eluted with methanol.  The eluate was then diluted with methanol and 10 mM ammonium acetate for analysis by LC/MS/MS.

The methods were validated prior to and in conjunction with the analysis of field trial samples.  The LLMV was 0.05 ppm for each analyte in each matrix.  Individual LOQs and limits of detection (LODs) were calculated statistically for each analyte in each matrix using the validation data at the LLMV.

The methods were adequately validated prior to and concurrently with the analysis of treated samples.  The fortification levels were adequate to bracket residues found in treated samples.  Method verification and concurrent method recoveries were generally within the acceptable range of 70-120% for snap beans, snap bean plants, dill fresh, dill dried, and dill seed fortified with each analyte at 0.05-0.5 ppm.  

Conclusions:  The submitted residue analytical methods data are adequate to satisfy data requirements for the subject action.  Acceptable enforcement methodology is available for tolerance enforcement purposes for the proposed uses, and adequate data-collection methods were used in the submitted field trial and processing studies.

860.1360 Multiresidue Methods

The FDA PESTDATA database (dated JUN-2005) indicates that prometryn is completely recovered (>80% recovery) using the multiresidue method (MRM) in the Pesticide Analytical Manual, Volume I (PAM, Vol. I) Section 302 and partially recovered (22-87% recovery) using Sections 303 and 304, with the recovery varying depending upon the choice of Florisil system used.

860.1380 Storage Stability

Residue Chemistry Chapter of the Prometryn RED, C. Swartz 08-DEC-1994; D207139
DER References:   48834201.der.doc, 48834202.de2.doc, and 48834202.de2.doc

Storage stability data are available for fortified samples of celery, cotton seed, fresh and dried parsley, pigeon peas, and sesame seed.  Residues of prometryn and the impurities/metabolites GS-11354 and GS-26831 were found to be stable in/on cotton seed and celery samples stored frozen at -20°C for up to 37 months, in/on fresh and dried parsley samples stored frozen for up to 21.7 months, and in/on sesame seed stored frozen for up to 14 months.  Residues of prometryn per se were found to be stable in pigeon peas stored at -12°C for up to 42 days.

Concurrent storage stability data were generated with snap beans, snap bean plants, fresh and dried dill and seed matrices, as well as dill oil.  For all matrices, untreated samples were fortified with prometryn, GS-11354, and GS-26831 at 0.5 ppm for each analyte and stored frozen under conditions similar to those of the field samples.  The data demonstrate that residues of prometryn, GS-11354, and GS-26831 were stable in/on snap beans and snap bean plants stored frozen for up to 401-402 days (13.2 months), up to 841 days (27.6 months) in/on fresh dill leaves/stems, up to 842 days (27.7 months) in/on dried dill leaves/stems, up to 836 days (27.5 months) in/on dill seed and up to 843 days (27.7 months) in/on dill, oil. 

The storage durations and conditions of samples from the crop field trials submitted to support this petition are presented in Table 4.

Table 4.  Summary of Storage Conditions and Durations of Samples from Crop Field Trial Studies.
Matrix 
                           Storage Temperature (°C)
                          Actual Storage Duration[1]
                  Interval of Demonstrated Storage Stability
Snap beans
                                     <=2
                                 269-338 days
                               (8.8-11.1 months)
                           402 days (13.2 months); 
                      concurrent storage stability data.
Snap bean plants
                                     <=2
                                 267-337 days
                               (8.8-11.1 months)
                            401 days (13.2 months);
                      concurrent storage stability data.
Dill, fresh leaves/stems
                                      20
                                538- 933 days 
                              (17.7-30.7 months)
                           841 days (27.6 months); 
                      concurrent storage stability data.
Dill, dried leaves/stems
                                      20
                                   932 days 
                                 (30.6 months)
                           842 days (27.7 months); 
                      concurrent storage stability data.
Dill, seed
                                      20
                                 501-900 days
                              (16.5-29.6 months)
                           836 days (27.5 months); 
                      concurrent storage stability data.
Dill, oil
                                      20
                                   918 days 
                                 (30.2 months)
                           843 days (27.7 months); 
                      concurrent storage stability data.
[1]  From harvest to extraction for analysis.  Snap bean matrices:  samples were analyzed within 1-9 days of extraction; Dill matrices:  samples were analyzed within 0-1 days of extraction.

Conclusions:  The storage conditions and durations of samples from the magnitude of the residue and processing studies on snap beans and dill are supported by adequate storage stability data.  These data show that corrections for storage degradation of residues are not required for the submitted studies.  Although the storage intervals tested in the concurrent storage stability study are less than the maximum storage intervals of dill field trial samples, each interval is 90% as long as the longest storage duration.  These data are adequate to support the storage conditions and durations of samples from the submitted dill field trials.

Zero-day data were not provided with the concurrent storage stability studies for the snap bean or dill matrices; IR-4 is reminded that storage stability studies should always include a 0-day sampling interval to establish the residue levels present at the time samples are placed into storage [see OCSPP 860.1380(d)(6)(i)].

860.1480 Meat, Milk, Poultry, and Eggs

Residue Chemistry Chapter of the Prometryn RED, C. Swartz 08-DEC-1994; D207139

The 1994 Residue Chemistry Chapter concluded that residues of prometryn per se in meat and milk can be classified under Category 3 of 40 CFR §180.6(a).  "That it is not possible to establish with certainty whether finite residues will be incurred, but there is no reasonable expectation of finite residues."  No tolerances were required, and therefore, livestock feeding studies were not needed.  In the current petition, there are no significant livestock feed items; therefore, a newly constructed dietary burden was not warranted for this petition.  Pending submission of an additional plant metabolism study, HED tentatively concludes that the Category 3 situation remains valid for this registration request.  

860.1500 Crop Field Trials

Dill

DER Reference:   48834202.de1.doc

Two dill field trials were conducted in the United States during the 2008 and 2009 growing season in North American Free Trade Agreement (NAFTA) Growing Zones 5 (OH) and 11 (WA).  Each trial site consisted of one untreated plot and one treated plot.  The treated plots received a single foliar broadcast application of a 4 lb ai/gal suspension-concentrate (SC) formulation of prometryn (Caparol[(R)] 4L) at 1.62 or 1.70 lb ai/A (~1X) when plants were at the vegetative growth stage.  Applications were made using ground equipment in 34 or 38 gal/A spray volumes; no adjuvants were added to the spray mixture.  Fresh dill leaves with stems were harvested at commercial maturity (pre-bloom) at PHIs of 27 (untreated only) or 29 days, and dill seed was harvested at seed maturity at PHIs of 62 or 68 days.  At one trial, additional fresh dill leaves with stems were harvested and dried to generate dried dill leaves with stems.  Residue decline was not evaluated.

Following a single foliar broadcast application of the 4 lb ai/gal SC formulation of prometryn to dill at 1.6-1.7 lb ai/A, prometryn residues (and per-trial averages) were <0.05-0.10 (<0.05-0.077) ppm in/on fresh dill leaves/stems.  For dried dill, a single foliar broadcast application of the 4 lb ai/gal SC formulation of prometryn was applied to one dill trial at 1.6 lb ai/A; prometryn residues (and per-trial average) were 0.26-0.29 (0.28) ppm in/on dried dill leaves/stems.  Prometryn residues were below the LLMV (<0.05 ppm) in/on dill seed (2 trials) harvested 62 or 68 days after treatment (DAT).  Residues of the triazine metabolites (GS-11354 and GS-26831) were each less than the LLMV (<0.05 ppm) in/on all samples of dill fresh leaves/stems, dried leaves/stem, and seeds.  There was no residue-decline study.

Table 5.  Summary of Residue Data from Dill Field Trials with Prometryn.
Commodity
                              Total Applic. Rate
                                   (lb ai/A)
                                      PHI
                                    (days)
                             Residue Levels1 (ppm)



                                       n
                                  Sample Min.
                                  Sample Max.
                                    LAFT[2]
                                    HAFT[2]
                                    Median
                                     Mean
                                   Std. Dev.
Prometryn
Dill, fresh leaves/stems 
                                  1.62, 1.70
                                      29
                                       2
                                   <0.05
                                     0.10
                                   <0.05
                                     0.077
                                   <0.063
                                   <0.063
                                      N/A
Dill, dried leaves/stems
                                     1.62
                                      29
                                       1
                                     0.26
                                     0.29
                                     0.28
                                     0.28
                                     0.28
                                     0.28
                                      N/A
Dill, seed
                                  1.62, 1.70
                                    62, 68
                                       2
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      N/A
[1]  Only the residue of concern (prometryn) is summarized.  Except for sample min/max, values reflect per-trial averages; n = no. of field trials.  NA = not applicable.  For calculation of median, mean, and standard deviation, the LLMV (0.05 ppm) was used for any results reported as <LLMV.  
[2]  LAFT = lowest-average field trial; HAFT = highest-average field trial.

Conclusions:  Adequate documentation was provided for the field and laboratory portions of the submitted field trials for dill.  An acceptable method was used for residue quantitation, and the study is supported by adequate storage stability data.  The number and locations of the crop field trials are in accordance with OPPTS Guideline 860.1500 (Table 6).  The available data will support the proposed use pattern. 

Table 6.  Trial Numbers and Geographical Locations.
NAFTA Growing Zones
                                     Dill

                                   Submitted
                                   Requested

                                       
                                    Canada
                                    U.S.[1]
5
                                       1
                                      --
                                      --
11
                                       1
                                      --
                                      --
Total
                                       2
                                      --
                                       2
[1]  As per OCSPP 860.1500, Table 1 for dill.

Currently there is a prometryn tolerance established in/on dill, leaves at 0.3 ppm with regional restriction.  This tolerance level is adequate and HED agrees with the petitioner to remove the regional restriction for this crop.  However, the tolerance definition should be changed to Dillweed, fresh leaves.  A revised Section F should be submitted.  The data show that residues concentrate by a factor of 3.6 in/on dill dried leaves; therefore, HED agrees with the petitioner's requested tolerance of 1.1 ppm in/on dill, dried leaves.

Snap Beans

DER Reference:   48834201.der.doc

Seven snap bean field trials were conducted in the United States during the 2007 growing season in NAFTA Growing Zones 1 (NY), 2 (MD), 3 (FL), 5 (MI, OH, and WI; 1 trial each), and 11 (WA).  Each trial site consisted of one untreated plot and two treated plots.  The treated plots received a single preemergence (1-2 days after planting) broadcast application of a 4 lb ai/gal SC formulation of prometryn (Caparol[(R)] 4L) to the soil at 0.74-0.76 lb (0.5X) ai/A or 1.46-1.56 lb ai/A (~1X).  Applications were made using ground equipment in 25-34 gal/A spray volumes; no adjuvants were added to the spray mixture.  Snap beans (pods with seed) and snap bean plants (foliage with pods and seed) were harvested at commercial maturity at PHIs of 52-68 days.  Residue decline was not evaluated. 

Following a single preemergence broadcast application of the 4 lb ai/gal SC formulation of prometryn to the soil at 0.74-0.76 lb ai/A (0.5X), prometryn residues were below the LLMV (<0.05 ppm) in/on all samples of snap beans harvested 52-68 days after treatment.  Residues of prometryn (and per-trial averages) were <0.05-0.077 (<0.05-<0.064) ppm in/on snap bean plants; quantifiable residues of prometryn were observed in/on only one snap bean plant sample.  Residues of the triazine metabolites (GS-11354 and GS-26831) were each less than the LLMV (<0.05 ppm) in/on all samples of snap beans and snap bean plants.  

Following a single preemergence broadcast application of the 4 lb ai/gal SC formulation of prometryn to the soil at 1.46-1.56 lb ai/A (~1X), prometryn residues were below the LLMV (<0.05 ppm) in/on all samples of snap beans harvested 52-68 days after treatment.  Residues of prometryn (and per-trial averages) were <0.05-0.061 (<0.05-<0.055) ppm in/on snap bean plants; quantifiable residues of prometryn were observed in/on only one snap bean plant sample.  Residues of the triazine metabolites (GS-11354 and GS-26831) were each less than the LLMV (<0.05 ppm) in/on all samples of snap beans and snap bean plants.  There was no residue-decline study.

Table 6.  Summary of Residue Data from Snap Bean Field Trials with Prometryn.
Commodity
                              Total Applic. Rate
                                   (lb ai/A)
                                      PHI
                                    (days)
                            Residue Levels[1] (ppm)



                                       n
                                  Sample Min.
                                  Sample Max.
                                    LAFT[2]
                                    HAFT[2]
                                    Median
                                     Mean
                                   Std. Dev.
                                   Prometryn
Snap beans
                                   0.74-0.76
                                     52-68
                                       7
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      N/A
Snap bean plants 
                                       
                                       
                                       7
                                   <0.05
                                     0.077
                                   <0.05
                                   <0.064
                                   <0.05
                                   <0.052
                                     0.005
Snap beans
                                   1.46-1.56
                                     52-68
                                       7
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                   <0.05
                                      N/A
Snap bean plants 
                                       
                                       
                                       7
                                   <0.05
                                     0.061
                                   <0.05
                                   <0.055
                                   <0.05
                                   <0.051
                                     0.002
[1]  Only the residue of concern (prometryn) is summarized.  Except for sample min/max, values reflect per-trial averages; n = no. of field trials.  NA = not applicable.  For calculation of median, mean, and standard deviation, the LLMV (0.05 ppm) was used for any results reported as <LLMV.  
[2]  LAFT = lowest-average field trial; HAFT = highest-average field trial.

Conclusions:  Adequate documentation was provided for the field and laboratory portions of the submitted field trials for snap beans.  An acceptable method was used for residue quantitation, and the study is supported by adequate storage stability data.  The number and locations of the crop field trials are in accordance with OPPTS Guideline 860.1500 (Table 7).  The available data will support the proposed use pattern.

Table 7.  Trial Numbers and Geographical Locations.
NAFTA Growing Regions
                                   Snap Bean

                                   Submitted
                                 Requested[1]

                                       
                                    Canada
                                     U.S.
1
                                       1
                                      --
                                      1/1
2
                                       1
                                       
                                      1/1
3
                                       1
                                       
                                      1/1
5
                                       3
                                       
                                      3/2
10
                                      --
                                       
                                      1/0
11
                                       1
                                       
                                      1/1
Total
                                       7
                                      --
                                      8/6
[1]  As per OCSPP 860.1500, Table 5 for snap bean.  The second number reflects a 25% reduction in the number of trials allowed for the crop as a representative commodity in support of a crop group/subgroup tolerance or when application results in no quantifiable residues.  

The submitted prometryn data for snap beans are adequate and will support a tolerance of 0.05 ppm for bean, snap, succulent.  The Organization for Economic Co-operation and Development (OECD) tolerance-calculation procedures were not used to determine an appropriate tolerance level for bean, snap, succulent because all of residues values were below the LOQ.  The petitioner proposed a tolerance for residues of prometryn in/on bean, forage; however, a tolerance is not necessary for this commodity as it is an insignificant livestock feed item.  A revised Section F should be submitted.

860.1520 Processed Food and Feed

DER Reference:   48834202.de2.doc

Note:  Dried leaves/stems, which were previously considered a processed commodity of herbs, are now considered to be a raw agricultural commodity [based on the minutes of the Chemistry Science Advisory Council (ChemSAC) meeting of 14-JAN-2009]; refer to the 860.1500 DER for MRID 48834202 (48834202.der1) for the fresh and dried dill residue data.
 
The IR-4 submitted a processing study for prometryn on dill.  In a dill field trial conducted in NAFTA Growing Zone 11 (WA) during the 2008 growing season, a single foliar broadcast application of a 4 lb ai/gal SC formulation of prometryn (Caparol[(R)] 4L) was made at 1.62 lb ai/A (~1X) when plants were at the vegetative growth stage.  Applications were made using ground equipment in a 34 gal/A spray volume; no adjuvants were added to the spray mixture.  Dill leaves with stems were harvested 49 days after application and processed on the day of harvest into oil using simulated commercial procedures.

Residues of prometryn, GS-11354, and GS-26831 were each less than the LLMV (<0.05 ppm) in/on dill fresh leaves/stems harvested 49 days following a foliar broadcast application at 1.6 lb ai/A.  Residues of prometryn in dill oil processed from treated dill were 0.33 ppm, for a processing factor of >6.6x.  Residues of GS-11354 and GS-26831 were each below the LLMV (0.05 ppm) in both dill fresh leaves/stems and processed oil.

The processing factor (>6.6x) for dill oil indicates that residues of prometryn concentrate with processing.  HED does not require residue data for dill oil (OCSPP 860.1000) and therefore, a maximum theoretical concentration factor is not provided under OCSPP 860.1520.  

Table 8.  Residue Data from Dill Seed Processing Study with Prometryn.
Trial:  City, State; Year (Trial ID No.)
                                 Applic. Rate 
                                   (lb ai/A)
                                  PHI (days)
                                     Dill
                                   Commodity
                               Residues (ppm)[1]
                        Prometryn Processing Factor[2]


                                       
                                       
                                   Prometryn
                                   GS-11354
                                   GS-26831
                                       
Moxee, WA; 2008
(A3040.08-WA*25)
                                     1.62
                                      49
                              Fresh leaves/stems
                                   <0.05
                                    <0.05
                                   <0.05
                                      --



                                    Oil[3]
                                  0.33, 0.32
                                    [0.33]
                              <0.05, <0.05
                                  [<0.05]
                              <0.05, <0.05
                                  [<0.05]
                                   >6.6x
[1]  All residues are the mean of duplicate analyses (injections).  The LLMV (0.05 ppm) was used as the reporting limit for each analyte.
[2]  Processing factors were calculated using only the prometryn residues and were calculated by the study reviewer, using the LOQ for residues reported <LOQ.
[3]  The oil sample was extracted and analyzed in duplicate (each replicate was also injected twice).  The average of the duplicate analyses is presented in brackets.

Conclusions:  The submitted dill seed processing study is adequate.  Dill fresh leaves/stems bore non-quantifiable residues of prometryn, GS-11354, and GS-26831 following application of the 4 lb ai/gal SC formulation of prometryn at 1.62 lb ai/A.  Although the guidelines require that processing studies be conducted at an exaggerated rate to obtain quantifiable residues in the unprocessed commodity, quantifiable residues were observed in the processed commodity.  An acceptable method was used for quantitation of prometryn residues and the sample storage conditions and durations are supported by adequate storage stability data.

The processing factor (>6.6x) for prometryn in dill oil indicates that residues of prometryn concentrate with processing.  Residues of GS-11354 and GS-26831 were each below the LLMV (0.05 ppm) in dill oil.  The petitioner recommended a tolerance for residues of prometryn in/on dill, oil; however, a tolerance is not necessary for this commodity.  A revised Section F should be submitted.

860.1650 Submittal of Analytical Reference Standards

Analytical standards for prometryn are currently available [expiration 01-APR-2016] in the EPA National Pesticide Standards Repository (personal communication with Theresa Cole, ACB, 03-APR-2013).  

860.1850 Confined Accumulation in Rotational Crops

Residue Chemistry Chapter of the Prometryn RED, C. Swartz, 08-DEC-1994; D207139

The nature of the residue in rotational crops is adequately understood.  The metabolism of prometryn in rotational crops is similar to that of celery and cotton and involves dealkylation, oxidation, hydroxylation, deamination, and conjugation.

Ring-labeled [[14]C]prometryn was applied to trial sites containing sandy loam soil in MS and CA.  At the MS site, prometryn was applied at 2.8 lb ai/A at the time of planting to a primary crop of cotton.  Further applications were made when the plants were 3-6" tall (0.65 lb ai/A) and 12-18" tall (1.6 lb ai/A) for a total application rate of 5.0 lb ai/A.  At the CA site, a single application of prometryn was made at 3.2 lb ai/A when the primary crop, celery, was immature.  After harvesting the primary crop, the rotational crops were planted:  lettuce was planted 111 and 229 (MS) and 193 (CA) days after the final prometryn treatment (DAT), wheat was planted 111 (MS) and 350 DAT (CA), soybeans were planted 193 (CA) and 328 DAT (MS), and table beets were planted 193 (CA) and 249 DAT (MS).

The total radioactive residues (TRR) in all raw agricultural commodities (RACs) from all PBIs at both sites exceeded 0.01 ppm.  The TRR values ranged 0.030-0.447 ppm.  Prometryn and the following metabolites were identified in the rotational crops:  GS-11957, GS-17794, MCO-III-25, MCO-IV-34, GS-11526 and its side chain alcohol, along with unidentified acetyl and sugar conjugates of triazines.  Although [14]C-residues were not quantified, greater than 50% of the TRR appeared to consist of triazine-containing metabolites.  Based on these data, the registrant conducted limited field rotational crop studies.

860.1900 Field Accumulation in Rotational Crops

Memo, C. Swartz, 05-DEC-1994; D207717
DP#s 315763 & 357098

No new field accumulation data in rotational crops were submitted with this petition.  Previously reviewed studies include a limited rotational crop study (Memo, G. Kramer, 03-SEP-1993; DP#191118) reflecting application to a primary crop or bare soil at 5-12 lb ai/A, with rotational crops planted at PBIs of 3-4 and 7-9 months, and an extensive rotational crop study (Memo, C. Swartz, 05-DEC-1994; D207717) on small grains reflecting application at 5-6 lb ai/A and a 3- to 6-month PBI.  Based on these studies, HED previously recommended a rotational crop restriction of 8 months for root crops, required additional rotational crop data for leafy vegetables, and recommended a 3-month PBI with establishment of rotational crop tolerances for small grain forage, hay, and straw.  The requested tolerances have been established.

Additional data reflecting application to a primary crop or bare soil at 3.2 lb ai/A (~0.5X maximum proposed seasonal rate for carrot) and PBIs of 5 and 9 months were submitted (DP#s 315763 & 357098).  These data show that residues of prometryn are non-quantifiable in leafy vegetables at both PBIs, and in root crops and small grains at the 9-month PBI.

Conclusions:  HED previously determined that the minimum plantback restrictions for crops not listed on prometryn labels should be as follows:  (1) following maximum application to any primary crop at up to 3.2 lb ai/A:  a 5-month PBI for leafy vegetables, an 8-month PBI for root crops, and a 9-month PBI for small grains and all other crops.  (2) Following application at rates higher than 3.2 lb ai/A and up to 6.0 lb ai/A:  an 8-month PBI for root crops; rotation to all other crops is prohibited.  The PBI restrictions listed on the EPA-registered Caparol[(R)] 4L Label remain appropriate for the proposed crops.


860.1550 Proposed Tolerances

HED has determined that the residue of concern for tolerance enforcement in the subject and rotated crops is prometryn per se.  In accordance with the most recent guidance concerning tolerance expressions, HED recommends that the tolerance expression for 40 CFR §180.222 be changed as indicated:  

"(a) General.  Tolerances are established for residues of the herbicide prometryn, including its metabolites and degradates, in or on the commodities in the table below.  Compliance with the tolerance levels specified below is to be determined by measuring only prometryn ([2,4-bis(isopropylamino)-6-methylthio-s-triazine] in or on the following raw agricultural commodities:

            Snap, bean, succulent	0.05 ppm
            Dillweed, fresh leaves	0.30 ppm
            Dill, dried leaves	1.1 ppm
and

(d) Indirect or inadvertent residues.  Tolerances are established for indirect or inadvertent residues of the herbicide prometryn, including its metabolites and degradates, in or on the commodities in the table below.  Compliance with the tolerance levels specified below is to be determined by measuring only prometryn ([2,4-bis(isopropylamino)-6-methylthio-s-triazine] in or on the following raw agricultural commodities:"

The proposed tolerances and the HED's recommendations are presented in Table 9.  The submitted prometryn data for snap beans are adequate and will support a tolerance of 0.05 ppm for bean, snap, succulent.  The OECD tolerance-calculation procedures were not used to determine an appropriate tolerance level for bean, snap, succulent because all of the residues values were below the LOQ.  The petitioner proposed a tolerance for residues of prometryn in/on bean, forage; however, a tolerance is not necessary for this commodity as it is an insignificant livestock feed item. 
 
Currently there is a prometryn tolerance established in/on dill, leaves at 0.3 ppm with regional restriction.  This tolerance level is adequate and HED agrees with the petitioner to remove the regional restriction for this crop.  The data show that residues concentrate by a factor of 3.6 in/on dill dried leaves; therefore HED recommends a tolerance of 1.1 ppm in/on dill, dried leaves.  The petitioner recommended a tolerance for residues of prometryn in/on dill, oil; however, a tolerance is not necessary for this commodity. 

The proposed tolerances should be revised to reflect the HED-recommended tolerance levels and correct commodity definitions as specified in Table 9.  A revised Section F is requested.

There are currently no established Codex MRLs for prometryn. 

Table 9.  Tolerance Summary for Prometryn.
Commodity
                           Proposed Tolerance (ppm)
                        HED-Recommended Tolerance (ppm)
Comments
Correct Commodity Definition
Bean, snap, succulent
                                     0.05
                                     0.05

Bean, forage
                                     0.09
                                      --
A tolerance is not necessary for this commodity.
Dill, leaves
                                      0.3
                                     0.30
Concurrent with granting a national registration, the removal of the regional restrictions on dill should be removed.
Dillweed, fresh leaves
Dill, dried leaves
                                      1.1
                                      1.1

Dill, oil
                                      1.3
                                      --
A tolerance is not necessary for this commodity.

Attachments

Attachment 1:  International Residue Limits Sheet




RDI:  RAB1 (17-APR-2013)
Petition Number:  PP#2E8052
DP Number:  408525
PC Code:  080805
S. Levy:S10953:Potomac Yard 1:703-305-0783:7509P:RAB1

Template Version September 2005
                         International Residue Limits
                                       
                    Prometryn (PC Code 080805; 15-MAR-2013)
Summary of US and International Tolerances and Maximum Residue Limits 
Residue Definition:  prometryn (2,4-bis(isopropylamino-6-methylthio-s-triazine)
US
Canada
Mexico[2]
Codex
40 CFR 180.222
Plants:  prometryn (2,4-bis(isopropylamino-6-methylthio-s-triazine)
None

None
Commodity[1]
Tolerance (ppm) /Maximum Residue Limit (mg/kg)

                                      US
Canada
Mexico[2]
Codex
Bean, snap, succulent
                                     0.05



Dillweed, fresh leaves
                                     0.30



Dill, dried leaves
                                      1.1




                                       




                                       




                                       




                                       




                                       




                                       
                                                                               

                                                                               

                                       
                                                                               

                                                                               

                                       


                                                                               

                                       
                                                                               

                                                                               

                                                                               
                                                                               

                                                                               
Completed:  M. Negussie; 22-MAR-2013
[1] Includes only commodities of interest for this action.  Tolerance values should be the HED recommendations and not those proposed by the applicant.
2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

