UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D. C. 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES MEMORANDUM 05/ 20/ 2002 SUBJECT: Hexazinone Residue Chemistry Chapter for the Tolerance Reassessment Eligibility Decision (TRED); PC Code 107201; DP Barcode D279899; Rereg. Case 0266.

FROM: John S. Punzi, Ph. D., Chemist Reregistration Branch II Health Effects Division (7509C)

THROUGH: Alan Nielsen, Branch Senior Scientist Reregistration Branch II Health Effects Division (7509C)

and Chemistry Science Advisory Council (Chem SAC) 05/ 15/ 2002 Health Effects Division (7509C)

TO: Carol Christensen, Risk Assessor Reregistration Branch II Special Review and Reregistration Division (7509C)

and Dirk Helder, Chemical Review Manager Reregistration Branch II Special Review and Reregistration Division (7508W)

cc: JSPunzi (RRB2), Hexazinone Reg. Std. File, Hexazinone SF, RF, LAN. RD/ I: RRB2 Chem Review Team (05/ 12/ 2002), Alan Nielsen (05/ 25/ 2002). 7509C: RRB2: John S. Punzi: CM2: Rm 712M: 703 305 7727: 05/ 08/ 2002. INTRODUCTION Hexazinone [3 cyclohexyl 6( dimethylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione is a triazine dione herbicide registered for use on alfalfa, blueberries, pasture and range grasses, pineapple, and sugarcane. It is also registered for use on ornamental plants, forest trees, and noncrop areas. Hexazinone is a proprietary chemical of E. I. du Pont de Nemours and Company, Inc. which is the sole producer and primary registrant of this broad spectrum herbicide. The dry flowable (DF), emulsifiable concentrate (EC), and soluble concentrate (SC) are the formulation classes registered to du Pont with food/ feed uses. These formulations, sold under the trade name Velpar®, may be applied for preemergence, postemergence, layby, directed spray, or basal soil treatments using ground or aerial equipment.

EXECUTIVE SUMMARY OF RESIDUE CHEMISTRY DATA REQUIREMENTS The 10/ 8/ 93 Residue Chemistry Chapter required label amendments for: (1) alfalfa to specify a 30 day preharvest interval (PHI) for the feeding of forage and cutting of hay; (2) blueberries to specify PHIs of 90 and 450 days for highbush and lowbush varieties, respectively. These label revisions remain outstanding. Details of the required label amendments are presented in the respective endnote for GLN 860.1500 (Crop Field Trials) in Table B. Data depicting magnitude of the residues of hexazinone and metabolites A, B, C, D, and E in/ on grass forage and hay harvested 0 day following a single broadcast application of representative formulations at 1.125 lb ai/ A are required.

GLN 860.1300: Nature of the Residue  Plants The qualitative nature of the residue in plants is adequately understood. Studies indicate that root uptake is the principal mechanism for the absorption of hexazinone by plants from soils. Hexazinone is translocated through the xylem to the foliage where it blocks the photosynthetic process. The HED Metabolism Assessment Review Committee (MARC) concluded that the hexazinone tolerance expression for plants and rotational crops should include hexazinone and metabolites A, B, C, D, and E (see Figure 1 for structures and proper nomenclature). Toxicity data for the metabolites is not available; but, based on the structural similarity of the metabolites, it is assumed they will exhibit similar toxicity to the parent hexazinone. The current tolerance expression for hexazinone in 40 CFR §180.396 is for "combined residues of the herbicide hexazinone (3 cyclohexyl 6( dimethylamino) 1 methyl 1,3,5 triazine2,4 1H, 3H) dione) and its metabolites, calculated as hexazinone." The tolerance expression should be modified to include specific metabolites A, B, C, D, and E, identified by the appropriate name.

GLN 860.1300: Nature of the Residue  Livestock The qualitative nature of the residue in livestock is adequately understood based on acceptable ruminant and poultry metabolism studies. The HED MARC concluded that the hexazinone tolerance expression for ruminants should include hexazinone plus metabolites B, C, C 2, and F for milk. The Committee concluded that the hexazinone tolerance expression for ruminant tissue should include hexazinone plus metabolites B and F. The Committee concluded that residues of hexazinone and metabolites B, C, C1 C 2, and F should be taken into account when risk assessments are done.

GLN 860.1340: Residue Analytical Methods Plant Commodities Adequate methods are available for purposes of data collection and enforcement of tolerances for residues of hexazinone and metabolites A, B, C, D, and E in/ on plant commodities.

Livestock Commodities The registrant has proposed an LC/ MS method (designated as du Pont AMR 3783 96) as an enforcement method for livestock commodities. The method has been subjected to a successful ILV and a radiovalidation study and will be forwarded to the Analytical Chemistry Branch for a tolerance method validation by Agency chemists. If the results of method validation by Agency chemists are successful, then Method AMR 3783 96 will be proposed for inclusion in PAM Volume II, and no additional data concerning this GLN topic will be required for reregistration.

GLN 860.1360: Multiresidue Methods The reregistration requirements for multiresidue methods data are fulfilled.

GLN 860.1380: Storage Stability Plant Commodities No additional storage stability data for plant and processed commodities are required for reregistration.

Livestock Commodities Adequate storage stability data are available to support the existing ruminant feeding study.

GLN 860.1500: Crop Field Trials Berries Group Blueberry The 10/ 8/ 93 Residue Chemistry Chapter concluded that no additional data are required for blueberries provided all pertinent product labels are amended to specify PHIs of 90 and 450 days for application to highbush and lowbush blueberries, respectively. Based on the combined LOQs (0.55 ppm) of the enforcement method for parent plus metabolites, HED recommends that the RAC tolerance be increased from 0.2 ppm to 0.60 ppm.

Grass Forage, Fodder, and Hay Group Grass (pasture and rangeland) forage An examination of registered uses of hexazinone on pasture and rangeland grasses (see Table A2) reveal that there two distinct use patterns, a basal soil application and a broadcast application. It is noted that the 10 ppm tolerance for grass forage (listed as "grasses, pasture" and "grasses, range" under 40 CFR §180.396) was established based on residue data reflecting basal soil application only. In the absence of residue data reflecting broadcast application, HED is requiring the following additional data for grass forage before the RAC tolerance can be reassessed: Data depicting magnitude of the residues of hexazinone and metabolites A, B, C, D, and E in/ on grass forage harvested 0 day following a single broadcast application of representative formulations at 1.125 lb ai/ A. It is HED policy to require 0 day crop field residue data for grass forage unless it is not feasible (e. g., preplant/ preemergence pesticide uses). The formulations to be tested may be applied in side by side plots. The location and number of trials should be in compliance with the current OPPTS GLN for adequate geographic representation of data.

Grass (pasture and rangeland) hay The reregistration requirements for residue data on grass hay have not been fulfilled. The registrant has submitted a petition (PP# 1F3967), for the establishment of a tolerance for residues of hexazinone and its metabolites in/ on grass hay. The petition is currently in reject status because grass hay data, from field trials with adequate geographical representation, remain outstanding. Since 1991 HED has reviewed two proposals to amend the original petition requesting that the Agency establish tolerances for grass hay based on theoretical grass drying factors. HED recommended against the establishment of grass hay tolerances each time. In addition, HED reviewed two registrant responses to the petition amendment reviews and concluded in each case that the recommendation to require actual field trial data for grass hay is appropriate.

Non Grass Animal Feeds (Forage, Fodder, Straw, and Hay) Group Alfalfa forage and hay The Updated Table A for Residue Chemistry RED Chapter dated 9/ 8/ 94 concluded that adequate residue data are available for alfalfa forage and hay. However, label amendments were required on all product labels for alfalfa, including supplemental labels, to establish a 30 day PHI for the feeding of forage and the cutting of hay.

The available residue data indicate that the combined residues of hexazinone and its metabolites A, B, C, D, and E in/ on treated samples were <1.87 ppm and <3.33 ppm for alfalfa forage and hay, respectively. Based on these data, the established tolerance for alfalfa forage is reassessed at its existing level of 2.0 ppm; however, the tolerance for alfalfa hay should be lowered from 8.0 ppm to 4.0 ppm. Table A2 shows that product labels for the 90% SC (EPA Reg. No. 352 378) and 75% DF (EPA Reg. No. 352 58) formulations have been revised in compliance with previously requested label amendment. However, the product label for the 2 lb/ gal EC (EPA Reg. No. 352 392) formulation does not specify any PHI; this label must be amended to establish a 30 day PHI (or pregrazing interval) for the feeding of forage and the cutting of hay.

Alfalfa seed The available residue data indicate that the combined residues of hexazinone and its regulated metabolites ranged from <1.30 ppm to <1.46 ppm in/ on alfalfa seed following a single broadcast dormant application of the 2 lb/ gal EC or 90% SC formulation at 0.75 lb ai/ A (1.5x the maximum registered rate on alfalfa grown for seed); no data were submitted reflecting 1.0x. HED is requesting the registrant to propose a tolerance for hexazinone residues of concern in/ on alfalfa seed of 2.0 ppm.

Miscellaneous Pineapple The available data indicate that the combined residues of hexazinone and its regulated metabolites were <0.35 ppm in/ on pineapple fruits harvested at a minimum PHI of 181 days following five ground applications of a representative hexazinone formulation at 0.45 0.9 lb ai/ A for a total rate of 3.6 lb ai/ A. Based on the combined LOQs (0.55 ppm) of the enforcement method, HED is now recommending that the RAC tolerance be increased from 0.5 ppm to 0.60 ppm.

Sugarcane The available data indicate that the combined residues of hexazinone and its regulated metabolites were <0.35 ppm in/ on samples of sugarcane treated with the 90% SC formulation of hexazinone from the following test locations: (i) in Puerto Rico where sugarcane was harvested 288 days following a single postemergence application at 0.45 lb ai/ A (0.5x the maximum registered seasonal rate for this area); (ii) in TX where sugarcane was harvested 234 days following one preemergence application followed by one postemergence application at 0.675 lb ai/ A/ application (0.75x the maximum seasonal rate in TX); and (iii) in HI where sugarcane was harvested 179 181 days following a total of four applications (one preemergence application at 1.35 or 1.47 lb ai/ A, a postemergence application at 0.45 lb ai/ A/ application, followed by two postemergence applications at 1.8 lb ai/ A/ application) for a total rate of 5.4 5.5 lb ai/ A/ season (1.5x the maximum seasonal rate in HI). Based on the combined LOQs (0.55 ppm) of the enforcement method, HED is now recommending that the RAC tolerance be increased from 0.20 ppm to 0.60 ppm. GLN 860.1520: Processed Food/ Feed Pineapple process residue and juice Residues of hexazinone and its regulated metabolites did not concentrate in pineapple process residue and juice except for Metabolite B in process residue. The registrant calculated a concentration factor of 3.0x for Metabolite B in pineapple process residue based on quantified residues of 0.06 ppm in pineapple process residue and 0.02 ppm in/ on pineapple RAC after treatment with hexazinone at a 1.0x rate. When this concentration factor of 3.0x is multiplied by the highest average field trial (HAFT) residue of <0.05 ppm, the maximum expected residues of metabolite B in pineapple process residue is 0.15 ppm which is less than the reassessed RAC tolerance of 0.60 ppm. Therefore, no tolerance for pineapple process residues is warranted.

Sugarcane molasses and refined sugar An acceptable sugarcane processing study is available. Following processing of the RAC according to simulated commercial practices, residues of hexazinone and/ or metabolites A through E concentrated in "A molasses" (4.0x). However, residues declined in raw sugar (reduction factor of 0.2x) and processed sugar (reduction factor of 0.2x). Adjusting for the degree of exaggeration (2.0x) used in the processing study, the residue for blackstrap molasses is 3.83 ppm. The available data suggest that the established tolerance for sugarcane molasses should be decreased from 5.0 ppm to 4.0 ppm.

GLN 860.1480: Meat, Milk, Poultry, and Eggs The results of ruminant metabolism study suggest significant transfer of hexazinone residues of concern to meat and milk. The registrant has submitted a dairy cattle feeding study (MRID 43703501) which was deemed acceptable. HED is recommending that; in order to reassess the established hexazinone tolerances for milk and the fat, meat, and meat byproducts of livestock and to compute a maximum theoretical dietary burden (MTDB) of hexazinone to livestock, uses on pasture and rangeland grasses be cancelled. A MTDB could not be calculated including grass and grass hay since additional residue data are required for use patterns for which significant residues are expected in/ on the RACs. HED recognizes that the estimated 100,000 acres of pasture and rangeland treated with hexazinone is relatively low. However, since grass and grass hay are considered major dietary components of ruminants (up to 60% of the diet per current OPPTS GLN), a MTDB for livestock could not be developed when grasses are included. HED has determined that a MTDB could be constructed from potential feed items for livestock and subsequently tolerances for meats and milk can be reassessed. HED has previously determined that tolerances in poultry commodities and a poultry feeding study are not required for reregistration based on results of reviewed poultry metabolism data.

A brief summary of the reviewed dairy cattle feeding study (MRID 43703501) is presented below. Three groups of dairy cows (3 animals/ dose group) were dosed with hexazinone at 29, 87, and 290 ppm in the diet for 28 consecutive days; three additional cows served as control animals. These dose levels are equivalent to 6.25x, 18.75x, and 62.5x, respectively, the MTDB for beef and dairy cattle. These dose levels are equivalent to 64x, 190x, and 640x the MTDB for hogs.

The maximum total hexazinone residues in milk were 0.78 ppm at the 6.25x feeding level (29 ppm in the diet) and 11.09 ppm at the 62.5x level. On day 14, after total residues had reached plateaus, milk was separated into skim milk and cream. Total residues in skim milk were comparable to those in whole milk; total residues in cream were approximately half those in skim milk. In tissues, the maximum total hexazinone residues at the 62.5x feeding level were 3.85 ppm in liver, 2.19 ppm in kidney, 0.32 ppm in muscle, and nondetectable ( # 0.10 ppm) in fat. The maximum total residues at the 6.25x feeding level were 0.24 ppm in liver, 0.47 ppm in kidney, and nondetectable ( # 0.15 ppm) in muscle. Because total residues were nondetectable in all fat samples from the 18.75x and 62.5x levels, fat samples were not analyzed at lower feeding levels.

A tolerance of 0.5 ppm is presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in milk. Based on the MTDB for beef and dairy cattle without grass or grass hay as a potential feed item, it is possible to reassess the animal commodity tolerances. The HED Metabolism Assessment Review Committee has concluded that the hexazinone tolerance expression for ruminants should include hexazinone plus metabolites B, C, C 2, and F for milk. Residue levels of hexazinone and metabolites in whole milk from the feeding study corrected for exaggeration levels ranged from 0.110 ppm to 0.164 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B, C, C 2, and F is 0.20 ppm ; therefore it is appropriate that the tolerance for milk be reduced from 0.5 to 0.20 ppm.

Tolerances of 0.1 ppm are presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in meat. Residue levels of hexazinone and metabolites in muscle from the feeding study corrected for exaggeration levels ranged from 0.003 ppm to 0.039 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B and F is 0.10 ppm therefore it is appropriate that the tolerance for meat byproducts of cattle, goats, horses, and sheep be reassessed at 0.10 ppm. Residue levels of hexazinone and metabolites in muscle from the feeding study corrected for exaggeration levels ranged from 0.0004 ppm to 0.002 ppm therefore tolerances for hog meat are not required.

Tolerances of 0.1 ppm are presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in meat byproducts of cattle, goats, hogs, horses, and sheep. Residue levels of hexazinone and metabolites in kidney from the feeding study corrected for exaggeration levels ranged from 0.046 ppm to 0.090 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B and F is 0.10 ppm; therefore, it is appropriate that the tolerance for meat byproducts of cattle, goats, horses, and sheep be reassessed at 0.10 ppm. Residue levels of hexazinone and metabolites in kidney from the feeding study corrected for exaggeration levels ranged from 0.003 ppm to 0.007 ppm therefore tolerances for hog meat byproducts are not required and should be revoked.

Tolerances of 0.1 ppm are presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in fat. Residue levels of hexazinone and metabolites in fat from the feeding study were nondetectable <0.1 ppm at the 62.5x exaggerated rate. HED has determined that tolerances for hexazinone residues in fat of cattle, goats, hogs, horses, and sheep are not required. Tolerances for fat of cattle, goats, hogs, horses, and sheep are not required and should be revoked.

GLN 860.1850: Confined Accumulation in Rotational Crops The data requirements for confined rotational crops are satisfied.

GLN 860.1900: Field Accumulation in Rotational Crops The data requirements for field accumulation in rotational crops are only partially satisfied. This conclusion is based on a recent review of a limited field crop rotation study wherein the 75% DF formulation of hexazinone was applied as a single postemergence broadcast application to mowed alfalfa at 1.5 lb ai/ A (1x the maximum seasonal rate for alfalfa). Approximately one year following application, the remaining alfalfa crop residue was plowed up and returned to the soil, and head lettuce, field corn, and wheat were planted.

Residues were below the respective method LOQs for hexazinone and metabolites A, B, C, D, E, F, G, H, G3170, G3170 NG, A 1, and C 1 in/ on head lettuce, wheat forage and grain, and field corn forage and grain. In wheat straw, residues of metabolite B were <0.02 0.021 ppm; residues of hexazinone and the remaining metabolites were below the LOQ. In field corn stover, residues of hexazinone were 0.02 0.081 ppm, residues of metabolite B were 0.038 0.053 ppm, and residues of the remaining metabolites were below the LOQ.

These data indicate that extended field rotational crop studies and rotational crop tolerances will not be required for residues of hexazinone residues of concern in/ on leafy vegetables provided that labels are amended to specify a rotational crop restriction of at least 12 months. A previous review of a confined rotational crop study concluded that rotational crop tolerances were not needed for root crops provided that a 12 month plantback interval was established; an examination of the basic registrant's labels shows that the 12 month plantback interval for root crops has been established.

Because the data from the limited field trials indicate that quantifiable residues occur in field corn stover and wheat straw, extended field rotational crop trials for corn stover, sorghum stover, and wheat straw to support a 12 month rotational interval and a tolerance for inadvertent hexazinone residues are required. HEXAZINONE TRED: RESIDUE CHEMISTRY CONSIDERATIONS PC Code 107201; Case 0266 (DP Barcode 279899)

TABLE OF CONTENTS page INTRODUCTION ......................................................... 1 REGULATORY BACKGROUND ............................................ 1 SUMMARY OF SCIENCE FINDINGS........................................ 2 GLN 860.1200: Directions for Use ...................................... 2 Product List .................................................... 2 Food/ Feed Use Pattern Table ....................................... 3 Rotational Crop Restrictions ....................................... 4 GLN 860.1300: Nature of the Residue  Plants ............................ 12 GLN 860.1300: Nature of the Residue  Livestock ......................... 16 GLN 860.1340: Residue Analytical Methods ............................. 18 Plant Commodities .............................................. 18 Animal Commodities ............................................ 19 GLN 860.1360: Multiresidue Methods .................................. 20 GLN 860.1380: Storage Stability Data .................................. 20 Plant Commodities .............................................. 20 Animal Commodities ............................................ 21 GLN 860.1500: Crop Field Trials ...................................... 21 Berries Group.................................................. 21 Blueberry ................................................ 21 Grass Forage, Fodder, and Hay Group .............................. 22 Grass (pasture and rangeland) forage........................... 22 Grass (pasture and rangeland) hay............................. 22 Non Grass Animal Feeds (Forage, Fodder, Straw, and Hay) Group ........ 23 Alfalfa forage and hay ...................................... 23 Alfalfa seed .............................................. 23 Miscellaneous Commodities ...................................... 24 Pineapple ................................................ 24 Sugarcane ................................................ 24 GLN 860.1520: Processed Food/ Feed ................................... 25 Pineapple process residue and juice............................ 25 Sugarcane molasses and refined sugar.......................... 25 GLN 860.1480: Meat, Milk, Poultry, and Eggs ............................ 26 Maximum theoretical dietary burden (tentative) .................. 26 Table of Contents (continued) page ix Dairy cattle feeding study ................................... 27 GLN 860.1400: Water, Fish, and Irrigated Crops .......................... 28 GLN 860.1460: Food Handling ........................................ 28 GLN 860.1850: Confined Accumulation in Rotational Crops ................. 28 GLN 860.1900: Field Accumulation in Rotational Crops .................... 28 TOLERANCE REASSESSMENT SUMMARY ................................ 35 Tolerances Listed Under 40 CFR §180.396 (a) ............................. 36 Tolerances Needed Under 40 CFR §180.396 (a) ........................... 36 Tolerances Listed Under 40 CFR §180.396 (c) ............................. 36 CODEX HARMONIZATION .............................................. 38 AGENCY MEMORANDA CITATIONS ..................................... 39 STUDY CITATIONS ..................................................... 45 N N N O O CH 3 N CH 3 CH 3 HEXAZINONE TRED  REPORT ON FQPA TOLERANCE REASSESSMENT PROGRESS AND INTERIM RISK MANAGEMENT DECISION:

RESIDUE CHEMISTRY CONSIDERATIONS PC Code 107201; Case 0266 INTRODUCTION Hexazinone [3 cyclohexyl 6( dimethylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H)dione is a triazine dione herbicide registered for use on alfalfa, blueberries, pasture and range grasses, pineapple, and sugarcane. It is also registered for use on ornamental plants, forest trees, and noncrop areas. Hexazinone is a proprietary chemical of E. I. du Pont de Nemours and Company, Inc. (Dupont) which is the sole producer and primary registrant of this broad spectrum herbicide. The dry flowable (DF), emulsifiable concentrate (EC), and soluble concentrate (SC) are the formulation classes registered to du Pont with food/ feed uses. These formulations, sold under the trade name Velpar®, may be applied as preemergence, postemergence, layby, directed spray, or basal soil treatments using ground or aerial equipment.

REGULATORY BACKGROUND Hexazinone was first registered by the Agency in November 1975 for general weed control in non cropland areas. Uses on Christmas trees and forest trees were added in 1977. Use patterns for the culture of sugarcane and alfalfa were conditionally registered in 1980 and 1981, respectively.

The Agency has issued several regulatory documents summarizing the reregistration status of hexazinone. In February 1982, the Agency issued a Pesticide Registration Standard for hexazinone which identified data gaps according to guidelines then in place. After issuance of the 1982 Standard, new uses for hexazinone were established on blueberries, rangeland and pasture grasses, and pineapple. A second Registration 2 Standard was issued in September, 1988 (NTIS# PB89 126080). The 1988 Standard summarized available data supporting the registration of products containing hexazinone as the active ingredients and required additional residue chemistry data among other requirements. Hexazinone was also the subject of a Final Registration Standard and Tolerance Reassessment (FRSTR) Residue Chemistry Chapter dated 5/ 25/ 88, a Reregistration Standard Update to the Residue Chemistry Chapter dated 9/ 5/ 91, and Product and Residue Chemistry Chapters for Hexazinone Reregistration Eligibility Decision (RED) document in 10/ 8/ 93. An Updated Table A for Hexazinone Residue Chemistry Chapter RED was issued in 9/ 8/ 94 in order to reflect the conclusions of reviews completed since the RED Chapter was completed.

The 10/ 8/ 93 Residue Chemistry Chapter to the Hexazinone RED required label revisions for alfalfa, blueberry, pineapple, and sugarcane in order to reflect use pattern parameters for which residue data are available. In addition, the 10/ 8/ 93 Residue Chapter required additional residue chemistry data pertaining to: animal metabolism (additional data were required to upgrade an existing ruminant study); residue analytical methods (an enforcement method is required for determination of hexazinone residues of concern in milk, meat, and meat byproducts of ruminants); storage stability (alfalfa and certain metabolites for grass); magnitude of the residue in/ on grass hay, sugarcane, and in the processed commodities of pineapple and sugarcane; and rotational crops. The basic registrant, DuPont, has submitted most of the requested residue chemistry data which have been evaluated by HED.

This document is a comprehensive update to the 10/ 8/ 93 Residue Chapter, and the information contained herein incorporates HED's conclusions of recently reviewed residue chemistry studies as well as a reassessment of hexazinone tolerances, as mandated by the Food Quality Protection Act (FQPA) of 1996.

Hexazinone tolerances are established under 40 CFR §180.396 (a) and (b). The tolerance expression, for plant and animal commodities, is in terms of the combined residues of hexazinone and its metabolites (calculated as hexazinone). An adequate enforcement method is available for determination of regulated hexazinone residues in/ on plants. The registrant has proposed an LC/ MS method (designated as du Pont method AMR 3783 96) as an enforcement method for livestock commodities. The method has been subjected to a successful ILV and a radiovalidation study and will be forwarded to the Analytical Chemistry Branch for a tolerance method validation by Agency chemists. If the results of method validation by Agency chemists are successful, then Method AMR 3783 96 will be proposed for inclusion in PAM Volume II, and no additional data concerning this GLN topic will be required for reregistration.

SUMMARY OF SCIENCE FINDINGS 3 GLN 860.1200: Directions for Use Product List A search of the Agency's Reference Files System (REFS) database, conducted on 7/ 26/ 01, identified three active hexazinone end use products (EPs) registered to the basic registrant (DuPont) under FIFRA Section 3 for use on food and feed crops. There are also eight products registered under Section 24 (c). These products are listed below in Table A1.

Table A1. Hexazinone EPs with Uses on Feed/ Food Crops Registered to E. I. du Pont de Nemours and Company. EPA Reg No. Label Acceptance Date Formulation Class Product Name 352 378 1 3/ 27/ 98 90% SC DuPont Velpar ® Herbicide 352 392 2 5/ 22/ 01 2 lb/ gal EC DuPont Velpar ® L Herbicide 352 581 3 5/ 22/ 01 75% DF DuPont Velpar ® DF Herbicide 1 Including SLN TX940008. 2 Including SLN ME980002, MT940001, NC830012, and WY920001. 3 Including SLN ME980003, ND970002, and SD970001.

Food/ Feed Use Pattern Table A summary of hexazinone food/ feed use patterns, based on the product labels registered to E. I. duPont de Nemours and Company, is presented in Table A2. The application rates listed in Table A2 depend on soil texture (coarse, medium, and fine) and percent organic matter (OM) in the soil; a higher rate is recommended for soil with organic matter greater than 5%. Use on gravelly or rocky soils, exposed subsoils, hardpan, sand, poorly drained soil, or alkali soils is prohibited. Unless otherwise specified, applications may be made in a minimum of 5 gal/ A by air or in a minimum of 20 gal/ A using ground equipment.

A tabular summary of the residue chemistry science assessments for reregistration of hexazinone is presented in Table B. The status of reregistration requirements for each guideline topic listed in Table B is based on the use patterns registered to the basic registrant. When end use product DCIs are developed (e. g., at issuance of the RED), RD should require that all end use product labels (e. g., MAI labels, SLNs, and products subject to the generic data exemption) be amended such that they are consistent with the label of the basic registrant.

The 10/ 8/ 93 Residue Chapter required label amendments for: (1) alfalfa to specify a 30 day preharvest interval (PHI) for the feeding of forage and cutting of hay; (2) blueberries to specify PHIs of 90 and 450 days for highbush and lowbush varieties, respectively; (3) pineapple to specify a maximum application rate of 3.6 lb 4 ai/ A/ cropping cycle and a minimum PHI of 181 days; (4) pineapple forage to include a pineapple forage feeding restriction; and (5) sugarcane to specify use rates if hexazinone were to be registered in the state of FL.

The registrant has complied with some of the previously requested label amendments; however, label revisions remain outstanding for alfalfa and blueberries; details of the required label amendments are presented in the respective endnote for GLN 860.1500 (Crop Field Trials) in Table B.

Rotational Crop Restrictions The following rotational crop restrictions have been established for the 90% SC (EPA Reg. No. 352 378), 2 lb/ gal EC (EPA Reg. No. 352 378), and 75% DF (EPA Reg. No. 352 581) following use of hexazinone on alfalfa: (i) do not replant treated areas to any crop except corn, root crops or sugarcane within two years after treatment, as crop injury may result; (ii) corn may be planted 12 months after the last treatment, provided the use rate did not exceed 0.75 lb per acre, except in areas of low rainfall (20" or less); (iii) root crops such as potatoes, sugar beets, radish and carrots may be planted 12 months after the last treatment, provided the use rate did not exceed 0.5 lb/ A. Sites with use rates higher than 0.5 lb/ A should not be replanted to any crop within 2 years of application, or unacceptable crop injury may result; (iv) sugarcane may be planted any time following treatment; (v) in CA, do not replant seed alfalfa areas to any crop within two years after treatment, as crop injury may result.

Based on the results of a recently reviewed field accumulation study (MRID 45084101) in rotational crops, the registrant is required to amend product labels to establish a 12 month plantback interval for leafy vegetables. HED previously recommended the establishment of a 12 month plantback interval for root crops based on the results of a confined rotational crop study (MRID 42824001).

Except for the recommendation to establish a plantback interval of 12 months for leafy vegetables, the existing rotational crop restrictions appear adequate. HED notes that the current labels bear certain plantback intervals of two years for some crops which apparently is largely or wholly based on phytotoxicity considerations. HED further notes that the established plantback intervals are dependent on application rates which are about 0.5x or less the maximum seasonal rate for alfalfa.

Because the data from the limited field trials indicate that quantifiable residues occur in field corn stover and wheat straw, extended field rotational crop trials for corn stover, sorghum stover, and wheat straw to support a 12 month rotational interval and a tolerance for inadvertent hexazinone residues are required. 5 (continued; footnotes follow)

Table A2. Food/ Feed Use Patterns Subject To Reregistration for Hexazinone (PC Code 107201).

Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 Alfalfa (grown for hay)

Broadcast application Dormant, non dormant, and semi dormant Ground or aerial 90% SC [352 378] 1.35 0.675 (for alfalfa less than one year old) 1 1. 35/ year 30 Use prohibited in ND and SD.

Broadcast application Dormant, non dormant, and semi dormant Ground or aerial 2 lb/ gal EC [352 392] 75% DF [352 581] 1.5 For the EC formulation only: 0.75 (for alfalfa <1 year old) 1 1. 5/ year 30 (75% DF only)

Alfalfa (grown for seed)

Broadcast application Dormant, non dormant, and semi dormant Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 0.5 1 0.5 Not specified (NS) Use limited to CA. A maximum rate of 0.5 lb ai/ A is specified for fields with sandy loam or loamy sand soils having 1 2% OM and on seed alfalfa that has been established for only one growing season. Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 6 (continued; footnotes follow)

Alfalfa (grown for forage)

Broadcast application Dormant Ground 2 lb/ gal EC [MT940001] [WY920001] 75% DF [ND970002] [SD970001] 1.0 1 1.0 30 (75% DF) Use limited to MT, ND, SD, and WY for established stands of forage alfalfa.

Application to soils with <1.5% OM is prohibited for the EC formulation.

Blueberry 2 Broadcast application Spring of fruiting year (prior to budbreak) Ground 2 lb/ gal EC [ME980002] 75% DF [ME980003] 2.0 NS 2. 0 450 Use limited to ME for established lowbush blueberries. Do not exceed 2.0 or 1.8 lb ai/ A if soil has been respectively treated with the EC or DF formulations of hexazinone within the past 8 years.

Broadcast application Dormant (prior to budbreak)

Ground 2 lb/ gal EC [NC830012] 2.0 NS NS 50 Use limited to NC. Application may be made in sufficient water to provide thorough and uniform coverage, usually 20 gal/ A. Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 7 (continued; footnotes follow)

Pineapple Broadcast or directed spray application Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 1.8 NS 3. 6/ crop cycle 181 Broadcast applications may be made between successive pineapple crops,

preplant after rows have been mulched, and postplant prior to active growth. Three to ten months after planting, directed spray applications may be made to the soil between crop rows. Broadcast applications may be made in 100 400 gallons of water/ A using ground equipment, or in at least 10 gal/ A using aerial equipment. Directed sprays may be applied at 50 200 gal/ A using ground equipment. Directed spot treatments are also permitted at 0.9 1.8 lb ai/ 100 gal prior to floral induction. Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 8 (continued; footnotes follow)

Pasture Broadcast application Ground 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 1.125 1 1. 125 (implied) 60 Use limited to Bermuda grass/ Bahia grass pastures. Applications may be made in a minimum of 25 gal/ A using ground equipment.

Basal soil application (undiluted) Ground 2 lb/ gal EC [352 392] 2 4 mL of product for each inch of stem diameter NS 0.67/ year NS Use limited to brush control in pastures and rangelands. No restrictions on grazing by domestic animals nor on cutting surrounding vegetation for forage and hay when product is applied as a basal soil treatment.

Basal soil application Ground 75% DF [352 581] 2 lb/ 1 gal [2 4 mL of suspension for each inch of stem diameter] NS 0.67/ year NS Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 9 (continued; footnotes follow)

Rangeland Basal soil application (undiluted) Ground 2 lb/ gal EC [352 392] 2 4 mL of product for each inch of stem diameter NS 0.67/ year NS Use limited to brush control in pastures and rangelands. No restrictions on grazing by domestic animals nor on cutting surrounding vegetation for forage and hay when product is applied as a basal soil treatment.

Basal soil application Ground 75% DF [352 581] 2 lb/ 1 gal [2 4 mL of suspension for each inch of stem diameter] NS 0.67/ year NS Sugarcane Broadcast application Preemergence and postemergence Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 3.6 1 3.6/ crop cycle (18 24 months) 180 Use limited to HI. Application may be made with a nonionic surfactant at 0.25%

v/ v. Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 10 (continued; footnotes follow)

Sugarcane (continued) Broadcast application Preemergence (in fall) and postemergence (in spring before active cane tillering begins) Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 0.9 NS 0. 45/ year for the 90% SC 1.5/ year for the 2 lb/ gal EC and 75% DF 234 Use limited to LA.

Broadcast application Preemergence and postemergence Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 0.45 0.5 NS 0. 9/ crop cycle 288 Use limited to PR.

Preemergence, early postemergence, and/ or directed layby Ground or aerial 90% SC [352 378]

2 lb/ gal EC [352 392] 75% DF [352 581] 0.9 NS 1. 8/ crop cycle 234 Use limited to TX. Two treatments are allowed (one early treatment plus one directed treatment at layby), provided 60 days have elapsed and at least 3" of rainfall have occurred. Table A2. (continued). Site Application Type Application Timing Application Equipment Formulation [EPA Reg. No.] Max. Single Application Rate (lb ai/ A) Max. #

Apps./ Season Maximum Seasonal Rate (lb ai/ A) Preharvest or Pregrazing Interval (Days) Use Directions and Limitations 1 11 Sugarcane (continued) Preemergence, early postemergence, or directed layby Ground or aerial 90% SC [TX940008] 0.45 1 0. 45 NS Tank mix use with diuron (Karmex DF Herbicide) limited to TX. Application may be made in a minimum of 5 gal/ A by air or in a minimum of 25 gal/ A using ground equipment. The feeding of sugarcane forage to livestock is prohibited. Use on gravelly or rocky soils, thinly covered subsoils, coarse textured soils with <2%

OM, or on any soil with <1% OM is prohibited. The planting of any crop other than sugarcane within 18 months of the last application is prohibited.

1 The restricted entry interval (REI) for the 90% SC (EPA Reg. No. 352 378), 2 lb/ gal EC (EPA Reg. No. 352 378), and 75% DF (EPA Reg. No.

352 581) formulations is 24 hours.

2 A REFS search, conducted 7/ 26/ 01, listed blueberries as a use site for the Federal labels of the 2 lb/ gal EC (EPA Reg. No. 352 392) and the 90%

SC (EPA Reg. No. 352 378). However, upon label examination of these products, it was determined that there are no Section 3 registrations of hexazinone on blueberries; only Section 24( c) registrations exist. 12 GLN 860.1300: Nature of the Residue  Plants The qualitative nature of the residue in plants is adequately understood. The 10/ 8/ 93 Residue Chemistry Chapter reported that acceptable metabolism studies had been conducted on alfalfa, pineapple, and sugarcane. These studies indicate that root uptake is the principal mechanism for the absorption of hexazinone by plants from soils. Hexazinone is translocated through the xylem to the foliage where it blocks the photosynthetic process. Hexazinone is metabolized by hydroxylation to metabolite A which is then metabolized to metabolite C by demethylation and to metabolite E after oxidation.

The available plant metabolism data for hexazinone were presented to the HED Metabolism Assessment Review Committee (MARC) in a meeting held January 29, 2002 for a determination of hexazinone residues to be regulated (DP Barcode D279897, 02/ 05/ 2002, S. Kinard). The Committee concluded that the hexazinone tolerance expression for plants and rotational crops should include hexazinone and metabolites A, B, C, D, and E. Toxicity data for the metabolites are not available but based on the structural similarity of the metabolites it is assumed they will exhibit similar toxicity to the parent hexazinone. The current tolerance expression for hexazinone in 40 CFR §180.396 is for "combined residues of the herbicide hexazinone (3 cyclohexyl 6 (dimethylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione) and its metabolites, calculated as hexazinone." Hexazinone metabolites which are currently regulated (because they are measured by the enforcement analytical method) include the parent and metabolites A, B, C, D, and E. The hexazinone enforcement method involves extraction and several cleanup steps, followed by analysis by GLC with nitrogen phosphorus detection. Hexazinone and each of the five metabolites are quantitated as individual peaks. The chemical names and structures of the hexazinone residues of concern in plants and livestock are presented in Figure 1.

Brief summaries of the available plant metabolism data, initially reported in the Hexazinone Registration Standard dated 2/ 82 and then in the Hexazinone FRSTR Residue Chemistry Chapter dated 5/ 25/ 88, are presented below.

Alfalfa (MRID 00104846)

In a study conducted at the University of Kentucky Research Farm, a 12 ft 2 area of alfalfa was isolated and fenced for this study. In mid March, the test plot was sprayed using a hand held sprayer, with 125 mg of [ 14 C] hexazinone dissolved in water; the application rate was equivalent to 1.0 lb ai/ 100 gal/ A. Alfalfa samples were collected at two, three, and six months after treatment. Total radioactive residues (TRR), calculated as hexazinone, declined at each sampling interval, and respectively were 0.6, 0.5, and 0.1 ppm. The extractable percentages of TRR were 95, 84, and 80% for the two, three and six month harvests, respectively. Analysis of the two month alfalfa cutting identified hexazinone (2.7% TRR), free metabolite A (7.1% TRR), free metabolite B 13 N N N O O CH 3 N CH 3 CH 3 (0.7% TRR), and conjugated metabolites A, B, and C (4.5% TRR). The remaining radioactive residues were found in water soluble, polar materials which were subsequently found to be comprised of amino acids, sugars, polybasic acids, and smaller amounts of natural products.

Pineapple (MRID 00126127)

A pineapple metabolism study was submitted by the basic registrant in conjunction with PP# 3F2846. The Hexazinone FRSTR Residue Chemistry Chapter dated 5/ 25/ 88 reported the salient features of this study with respect to residue characterization/ identification only. The fruit (pulp and rind) were extracted with methanol, and 94 99% of TRR was extractable. The following components were identified in the pulp: hexazinone (0.8 1.8% TRR), metabolite A (23 28% TRR), metabolite C (13 15% TRR), metabolite D (16 21% TRR), and metabolite F (1 2% TRR).

Sugarcane (MRID 00078047)

Greenhouse grown dwarf sugarcane were grown in large tubs (2 canes/ tub) and when the canes reached 5.5 to 6.0 feet in height, they were treated with a soil drench application of [ 14 C] hexazinone at rates of 0.54 and 1.0 kg/ ha (0.48 and 0.89 lb ai/ A); a third tub was maintained as a control. About six months after treatment, sugarcane samples were collected. The TRRs, calculated as hexazinone, were 0.07 0.08 and 0.05 ppm in sugarcane treated at 0.89 and 0.48 lb ai/ A, respectively. Following organic solvent extraction, 76% of TRR was recovered. The following components were identified by GC/ MS in sugarcane: metabolite E (30% TRR), metabolite C (23% TRR), metabolite A (14% TRR), metabolite B (1% TRR), metabolite D (3% TRR), and hexazinone (< 1% TRR).

Figure 1. Chemical Structures of Hexazinone and its Regulated Metabolites (Metabolites A through F).

Common Name/ Code Chemical name Structure Hexazinone 3 cyclohexyl 6( dimethylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione Figure A (continued).

Common Name/ Code Chemical name Structure 14 (continued next page) N N N O O CH 3 N CH 3 CH 3 HO N N N O O CH 3 N H CH 3 N N N O O CH 3 N H CH 3 HO N N NH O O CH 3 O Metabolite A 3( 4 hydroxycyclohexyl) 6 (dimethylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione Metabolite A 1 is hydroxylated at the 2 position of the cyclohexyl ring; Metabolite A 2 is hydroxylated at the 3 position of the cyclohexyl ring.

Metabolite B 3 cyclohexyl 6( methylamino) 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione Metabolite C 3( 4 hydroxycyclohexyl) 6 methylamino 1 methyl 1,3,5 triazine 2,4( 1H, 3H dione Metabolite C 1 is hydroxylated at the 2 position of the cyclohexyl ring; Metabolite C 2 is hydroxylated at the 3 position of the cyclohexyl ring.

Metabolite D 3 cyclohexyl 1 methyl 1,3,5 2,4,6 1H, 3H, 5H) trione Figure A (continued).

Common Name/ Code Chemical name Structure 15 N N NH O O CH 3 O HO N N N O O CH 3 NH 2 Metabolite E 3( 4 hydroxycyclohexyl) 1 methyl 1,3,5 triazine 2,4,6( 1H, 3H, 5H) trione Metabolite F 3 cyclohexyl 6 amino 1 methyl 1,3,5 triazine 2,4( 1H, 3H) dione 16 GLN 860.1300: Nature of the Residue  Livestock The qualitative nature of the residue in livestock is adequately understood based on acceptable ruminant and poultry metabolism studies. The requirement to confirm the identities of metabolites in goat tissues and milk by a second method, specified in the 10/ 8/ 93 Residue Chemistry Chapter, has been fulfilled. The requirement to radiovalidate the proposed enforcement method using samples collected from the ruminant metabolism study has also been fulfilled. No additional livestock metabolism data are required for reregistration.

The available livestock metabolism data were presented to the HED MARC in a meeting held January 29, 2002 for a determination of hexazinone residues to be regulated (D279897, 02/ 05/ 2002, S. Kinard). The Committee concluded that the hexazinone tolerance expression for ruminants should include hexazinone plus metabolites B, C, C 2, and F for milk. The Committee concluded that the hexazinone tolerance expression for ruminant tissue should include hexazinone plus metabolites B and F. The Committee concluded that residues of hexazinone and metabolites B, C, C1 C 2, and F should be taken into account when risk assessments are done. The above determination was partially based on the assumption that the current enforcement method listed in the PAM, Volume II for plant commodities could be used for livestock commodities provided additional method validation data are submitted; there is presently no enforcement method listed in PAM Volume II for livestock commodities.

HED has determined that tolerances for hexazinone residues in eggs and poultry tissues are not required (Category 3, 40 CFR §180.6a) based on the results of the reviewed poultry metabolism study. In the poultry study, the liver contained the highest TRR, 0.19 ppm. Considering that the feeding level was about 38x the maximum theoretical dietary burden, the maximum residue in poultry tissue would be 0.005 ppm, an order of magnitude below the limit of detection for hexazinone metabolites.

Brief summaries of available goat and hen metabolism studies are presented below.

Goat (MRIDs 42187901, 43074201, and 43488901)

A lactating goat was dosed orally with [ 14 C] hexazinone radiolabeled in the triazine ring at a dose rate of 136.4 mg/ day, equivalent to 2.2 mg/ kg body weight for five consecutive days. This dose represents a level of approximately 90 ppm in the feed, which is 19.4x the maximum theoretical dietary burden for ruminants. TRRs, expressed as hexazinone equivalents, were 6.74 ppm in milk, 3.03 ppm in liver, 2.54 ppm in kidney, 0.27 ppm in muscle, and 0.03 ppm in fat. Residues were adequately extracted with organic solvents. A list of characterized/ identified residues in goat matrices is presented below. 17 Table 1. Characterization/ identification of residues from goat milk and tissues dosed with 90 ppm of [ 14 C] hexazinone for 5 consecutive days. (Reproduced from DP Barcode D198348, 5/ 25/ 94, S. Hummel).

Metabolite Liver TRR = 3.03 ppm Kidney TRR = 2.54 ppm Muscle TRR = 0.27 ppm Milk TRR = 6.74 ppm %TRR PPM %TRR PPM %TRR PPM %TRR PPM Hexazinone 0.1 0. 04  <0.01  <0.01 1. 2 0.08 B 56.7 1. 70 28.3 0. 72 40.7 0. 11 48.1 3. 24 A 2  <0.01 0.4 0. 01  <0.01 0.4 0. 03 A, A 1 0. 1 0.04 2.0 0. 05  <0.01 3.9 0. 26 C  <0.01 3.1 0. 08  <0.01 3.4 0. 23 C 1, C 2 11.9 0. 36 18.5 0. 47 7. 4 0.02 16.6 1. 12 E  <0.01 1.2 0. 03  <0.01  <0.01 F 11.6 0. 35 37.4 0. 95 25.9 0. 07 17.1 1. 15 Others* 5. 8 0.19 5.1 0. 13 14.8 0. 04 4. 0 0.27 Total Identified 86.2 2. 68 96.0 2. 44 88.9 0. 24 94.7 6. 38 Unknown  <0.01  <0.01  <0.01 5.2 0. 35 Unextracted 11.9 0. 36 4. 7 0.12 11.1 0.03 0.1 0. 01 Total 98.1 3. 03 101 2.56 100 0.27 100 6.74 *Others identified at <0.01 ppm each Poultry (MRIDs 41524801, 42690601, 43074201)

Five ISA Brown laying hens were dosed orally at 6.9 mg/ day with carbonyl labeled [ 14 C] hexazinone for six consecutive days. The daily dose rate was equivalent to 57 ppm in the feed, which is 38x the maximum theoretical dietary burden. Mean TRR levels, expressed as hexazinone equivalents, were 0.189 ppm in liver, 0.02 ppm in fat, 0.078 and 0.106 ppm in thigh and breast muscle, respectively, and 0.059 ppm in skin. TRR level in eggs (day 6) was 0.12 ppm. Residues were adequately extracted with organic solvents. No single metabolite in edible poultry tissue was greater than 0.04 ppm, and unidentified metabolites represented less than 0.05 ppm in all edible tissues. A list of characterized and identified residues in poultry muscle and eggs is presented below. 18 Table 2. Characterization/ identification of residues from hen eggs and muscle tissues dosed with 57 ppm of [ 14 C] hexazinone for six consecutive days. (DP Barcode D198348, 5/ 25/ 94, S. Hummel).

Metabolite Muscle TRR = 0.12 ppm Eggs TRR = 0.13 ppm %TRR PPM %TRR PPM Hexazinone – <0.01  <0.01 A, A 1, A 2 16.7 0. 02 23.1 0. 03 C 16.7 0.02 23.1 0. 03 A OH, C OH 16.7 0. 02 7. 7 0.01 E  <0.01  <0.01 Others* 33.3 0. 04 15.4 0. 02 Total Identified 83.5 0. 10 69.3 0. 09 Unknown 16.7 0. 02 23.1 0. 03 Unextracted 8.4 0.01 7.7 0. 01 Total 109 0.13 100 0.13 *Others identified at <0.01 ppm.

GLN 860.1340: Residue Analytical Methods Plant Commodities The 10/ 8/ 93 Residue Chapter concluded that adequate methods are available for purposes of data collection and enforcement of tolerances for residues of hexazinone and metabolites A, B, C, D, and E in/ on plant commodities. No additional data on residue analytical methods for plant commodities are required for reregistration.

For tolerance enforcement, the PAM, Volume II lists Method I as available for the determination of hexazinone residues of concern in/ on plant commodities. Using this method, residues of hexazinone and metabolites A, B, D, and E are extracted with chloroform and cleaned up by liquid liquid partitioning. Residues of Metabolite C, a highly polar metabolite, are extracted from samples with methanol in a separate isolation scheme. Both schemes use derivatization of residues with trifluoroacetic anhydride and determination of the derivatives by nitrogen selective GLC. Some samples (e. g., alfalfa and grasses) require additional cleanup on a gel permeation column, before derivatization, or on a deactivated Florisil column, either before or after derivatization. The combined limit of quantitation (LOQ) for hexazinone residues by Method I in PAM, Volume II, is 0.55 ppm.

For data collection, the registrant utilized Method Nos. 92013 V2 and 92013 V3 during analyses of samples collected from field trials on alfalfa. These methods are similar to the PAM, Volume II method but were modified to include additional clean up steps. They have been deemed adequate for data collection based on acceptable method 19 validation and concurrent recovery data.

Livestock Commodities The 10/ 8/ 93 Residue Chapter required data collection and tolerance enforcement methodology for determination of hexazinone residues of concern in livestock commodities. In an attempt to fulfill this requirement, the registrant requested a meeting with HED to report progress of their work in developing a new method prior to submitting it for an independent laboratory validation (ILV). In a meeting held 8/ 31/ 94, the registrant advised that the current method in PAM, Volume II for plant commodities did not appear appropriate for livestock commodities because of complications with matrix effects and the inability to detect metabolite F, among other problems.

The registrant instead proposed an LC/ MS method (designated as du Pont AMR 3783 96) as an enforcement method. The proposed method would determine residues of parent hexazinone, metabolite B, metabolite C and its isomer (C 2), and metabolite F in milk. In livestock tissues, Method AMR 3783 96 would determine residues of parent hexazinone, metabolite B, and metabolite F. Briefly, residues in milk and animal tissues are extracted three times with acetone: aqueous 0.1 M potassium phosphate/ 0.5 M sodium chloride solution (1: 1, v: v). The extract is concentrated to remove the acetone, and purified using solid phase extraction (SPE) cartridges. A combination of reverse (C8) and normal (silica) phase SPE sorbents is used to remove most substances that may interfere with the instrument analysis. Residues of hexazinone and metabolites B and F are quantitated in tissue samples and residues of hexazinone and metabolites B, C, C 2, and F are quantitated in milk using LC/ MS with an electrospray interface and selected ion monitoring (SIM). The reported LOQs were 0.02 ppm for hexazinone and metabolite B and 0.05 ppm for metabolites C, C 2, and F.

The proposal to develop DuPont Method AMR 3783 96 as an enforcement method was based on a cattle feeding study which had been reviewed by HED and deemed acceptable. Data from the cattle feeding study indicate that in milk, the metabolites determined by the proposed method represent nearly 95% of total hexazinone residues. In tissues, parent and metabolite B represent at least 85% of total residues in liver and 63% of total residues in kidney; metabolite B is the only residue detected in muscle, even at the 10x feeding level; and all residues are nondetectable in fat at the 10x level.

DuPont Method AMR 3783 96 has been subjected to a successful ILV and a radiovalidation study. The ILV data did support the reliability of and reproducibility of the method for the determination of residues of hexazinone, metabolite B, metabolite C and its isomer (C 2), and metabolite F in milk; the ILV data also showed that Method AMR 3783 96 can adequately recover residues of hexazinone, metabolite B, and metabolite F in livestock tissues. Method AMR 3783 96 will be forwarded to the Analytical Chemistry Branch (ACL; Beltsville, MD) for a tolerance method validation 20 by Agency chemists. If the results of method validation by Agency chemists are successful, then Method AMR 3783 96 will be proposed for inclusion in PAM, Volume II, and no additional data concerning this GLN topic will be required for reregistration.

GLN 860.1360: Multiresidue Methods The reregistration requirements for multiresidue methods data are fulfilled. The 10/ 99 FDA PESTDATA database (PAM, Volume I, Appendix I) indicates that hexazinone is only partially recovered (50 80%) using Multiresidue Method Sections 302 (Luke Method; Protocol D) and is not recovered using Sections 303 (Mills, Onley, Gaither; Protocol E  nonfatty foods) and 304 (Mills; Protocol E  fatty foods).

There is a small recovery (< 50%) of metabolite A (IN T3937) and metabolite C INT3935 using Multiresidue Method Section 302 (Luke Method; Protocol D). There is also a small recovery (< 50%) of metabolite B (IN T3928) and metabolite E (IN T3936) using Multiresidue Method Section 302 (Luke Method; Protocol D) but the metabolites are not recovered using Sections 303 (Mills, Onley, Gaither; Protocol E  nonfatty foods) and 304 (Mills; Protocol E  fatty foods). Metabolite D (IN B2838) is partially recovered (50 80%) using Multiresidue Method Sections 302 (Luke Method; Protocol D) and is not recovered using Sections 303 (Mills, Onley, Gaither; Protocol E  nonfatty foods) and 304 (Mills; Protocol E  fatty foods).

GLN 860.1380: Storage Stability Data Plant Commodities The Updated Table A for Residue Chemistry RED Chapter dated 9/ 8/ 94 required additional storage stability data for: (1) hexazinone and metabolites in alfalfa, and (2) metabolite C in grass. The registrant has submitted the requested data which were deemed adequate to support the storage conditions and intervals of samples used for tolerance reassessment. No additional storage stability data for plant and processed commodities are required for reregistration. A summary of the available storage stability data is presented below.

Residues of hexazinone and its metabolites A, B, C, D, and E are relatively stable under frozen ( 20 to 10 °C) storage conditions in/ on blueberries for up to 13 months, in/ on pineapple for up to 8 months, in pineapple juice for up to 6 months, in/ on sugarcane for up to 12 months, and in sugarcane processed commodities for up to 6 months. Hexazinone and metabolites A, B, D, and E are also stable in grass samples during frozen ( 20 °C) storage for up to 24 months, and metabolite C is stable in grass samples during frozen ( 20 ± 10 °C) storage for up to 36 months.

Livestock Commodities 21 Adequate storage stability data are available to support the existing ruminant feeding study. Samples of milk, liver, kidney, muscle, and fat samples were stored under freezer storage conditions for maximums of 8, 10, 14, 2, and 2 months, respectively, prior to residue analysis. In a fortification study, hexazinone residues of concern were found to be stable during maximum storage times for samples collected and analyzed from the feeding study.

GLN 860.1500: Crop Field Trials Pending label revisions for certain crops, the reregistration requirements for data depicting magnitude of the residue in/ on the following raw agricultural commodities (RACs) are satisfied: alfalfa forage, alfalfa hay, alfalfa seed, blueberries, pineapple, and sugarcane. An adequate number of field trials have been conducted for these RACs, and the trials were conducted using registered hexazinone formulation( s) at the maximum registered rate.

Brief summaries of available hexazinone residue data, deemed useful for tolerance reassessment, are presented below. It is noted that product labels of registrants other than du Pont were not examined in the preparation of this document.

Berries Group Blueberry The 10/ 8/ 93 Residue Chapter concluded that no additional data are required for blueberries provided all pertinent product labels are amended to specify PHIs of 90 and 450 days for application to highbush and lowbush blueberries, respectively.

Data (MRIDs 41964101 and 41964102) reviewed in the Hexazinone Update indicate that the combined residues of hexazinone and its regulated metabolites, as measured by the data collection method, were <0.3 ppm (nondetectable; <0.05 ppm for each compound) in/ on: (1) 12 samples of lowbush blueberries harvested 433 446 days following a single application of the 2 lb/ gal EC or 90% SC formulation at 3 or 6 lb ai/ A (1.5 or 3.0x the maximum registered rate) using ground or aerial equipment; and (2) 12 samples of highbush blueberries harvested 68 97 days following a single application of the 2 lb/ gal EC or 90% SC formulation at 2 or 4 lb ai/ A (0.8 or 1.3x the maximum registered rate). Based on the combined LOQs (0.55 ppm) of the enforcement method, HED is now recommending that the RAC tolerance be reassessed from 0.2 ppm to 0.60 ppm.

Although uses of hexazinone on blueberries (see Table A2) are limited to Section 24( c) registration, label revisions remain a requirement. The product labels for ME980002 22 and ME980003, which are limited for use on lowbush blueberries, should be amended to specify a PHI of 450 days. The product label for NC830012 should also be amended to specify PHIs of 90 and 450 days for application to highbush and lowbush blueberries, respectively.

Grass Forage, Fodder, and Hay Group Grass (pasture and rangeland) forage An examination of registered uses of hexazinone on pasture and rangeland grasses (see Table A2) reveal that there two distinct use patterns, a basal soil application and a broadcast application. It is noted that the 10 ppm tolerance for grass forage (listed as "grasses, pasture" and "grasses, range" under 40 CFR §180.396) was established based on residue data reflecting basal soil application only.

Data reflecting basal soil application were submitted under PP# 1F2513 and summarized in the Hexazinone FRSTR Residue Chemistry Chapter dated 5/ 25/ 88. Samples of range and pasture grasses were harvested at various intervals following application of the 2 lb/ gal EC formulation at 3 or 6 mL per one inch of diameter at breast height (0.75 or 1.5x the maximum registered rate for directed spray basal soil application). Samples were taken 2", 12", and 24" in radius from the treatment point on days 0 56 after application. The FRSTR Residue Chemistry Chapter did not report specific residues; however, it was concluded that the combined residues of hexazinone and its metabolites (calculated as hexazinone) did not exceed the established tolerances of 10 ppm in/ on treated samples of pasture and range grass forage.

In the absence of residue data reflecting broadcast application, HED is requiring the following additional data for grass forage before the RAC tolerance can be reassessed: "Data depicting magnitude of the residues of hexazinone and metabolites A, B, C, D, and E in/ on grass forage harvested 0 day following a single broadcast application of representative formulations at 1.125 lb ai/ A. It is the Agency policy to require 0 day crop field residue data for grass forage unless it is not feasible (e. g., preplant/ preemergence pesticide uses). The formulations to be tested may be applied in side by side plots. The location and number of trial should be in compliance with the current OPPTS GLN for adequate geographic representation of data.

Grass (pasture and rangeland) hay The reregistration requirements for residue data on grass hay have not been fulfilled. The registrant has submitted a petition (PP# 1F3967) for the establishment of a tolerance for residues of hexazinone and its metabolites in/ on grass hay. The petition is currently in reject status because additional grass hay data, from field trials with adequate 23 geographical representation, remain outstanding. Since 1991 HED has reviewed two proposals to amend the original petition requesting that the Agency establish tolerances for grass hay based on theoretical grass drying factors. HED recommended against the establishment of grass hay tolerances each time. In addition, HED reviewed two registrant responses to the petition amendment reviews and concluded in each case that the recommendation to require actual field trial data for grass hay is appropriate (D162863, D181318, D172408, D201738).

Non Grass Animal Feeds (Forage, Fodder, Straw, and Hay) Group Alfalfa forage and hay The Updated Table A for Residue Chemistry RED Chapter dated 9/ 8/ 94 concluded that adequate residue data are available for alfalfa forage and hay. However, label amendments were required on all product labels for alfalfa, including supplemental labels, to establish a 30 day PHI for the feeding of forage and the cutting of hay.

The available residue data (MRIDs 43074401 and 43074402) indicate that the combined residues of hexazinone and its metabolites A, B, C, D, and E did not exceed the established tolerances of 2.0 ppm in/ on alfalfa forage and 8.0 ppm in/ on alfalfa hay harvested 29 31 days following a single broadcast dormant or non dormant application of the 2 lb/ gal EC or 90% SC formulation at 1.5 lb ai/ A (~ 1x). The maximum combined residues in/ on treated samples were <1.87 ppm and <3.33 ppm for alfalfa forage and hay, respectively. Based on these data, the established tolerance for alfalfa forage is reassessed at its existing level of 2.0 ppm; however, the tolerance for alfalfa hay should be lowered from 8.0 ppm to 4.0 ppm.

Table A2 shows that product labels for the 90% SC (EPA Reg. No. 352 378) and 75% DF (EPA Reg. No. 352 58) formulations have been revised in compliance with the requested label amendment. However, the product label for the 2 lb/ gal EC (EPA Reg. No. 352 392) formulation does not specify any PHI; this label must be amended to establish a 30 day PHI (or pregrazing interval) for the feeding of forage and the cutting of hay.

Alfalfa seed The Updated Table A for the Residue Chemistry RED Chapter dated 9/ 8/ 94 concluded that adequate residue data have been submitted for alfalfa seed; the Chapter, however, required the registrant to propose a tolerance for this commodity in order to support registered uses of hexazinone on alfalfa grown for seed.

The available residue data (MRIDs 43074401 and 43074402) indicate that the combined residues of hexazinone and its regulated metabolites ranged from <1.30 ppm 24 (sum of the LOQs) to <1.46 ppm in/ on alfalfa seed following a single broadcast dormant application of the 2 lb/ gal EC or 90% SC formulation at 0.75 lb ai/ A (1.5x the maximum registered rate on alfalfa grown for seed); no data were submitted reflecting 1.0x. HED is requesting the registrant to propose a tolerance for hexazinone residues of concern in/ on alfalfa seed; the available data suggest that a tolerance level of 2.0 ppm is appropriate.

Residue data and a tolerance proposal for alfalfa seed screenings, previously requested in the Updated Table A for the Residue Chemistry RED Chapter dated 9/ 8/ 94, are no longer required because this item has been deleted from Table 1 of OPPTS 860.1000 as a significant livestock feed item.

Miscellaneous Commodities Pineapple The 10/ 8/ 93 Residue Chapter concluded that no additional residue data are required for pineapple provided all pertinent product labels are amended to specify a maximum application rate of 3.6 lb ai/ A/ cropping cycle and a minimum PHI of 181 days. The basic registrant has complied with this requirement as shown in Table A2.

The available data (MRID 42535601) indicate that the combined residues of hexazinone and its regulated metabolites, as measured by the data collection method, were <0.35 ppm (or <0.05 ppm for each compound) in/ on pineapple fruits harvested at a minimum PHI of 181 days following five ground applications of a representative hexazinone formulation at 0.45 0.9 lb ai/ A for a total rate of 3.6 lb ai/ A. Based on the combined LOQs (0.55 ppm) of the enforcement method, HED is now recommending that the RAC tolerance be reassessed from 0.5 ppm to 0.60 ppm.

HED's request to impose a feeding restriction on pineapple forage, previously specified in the Updated Table A for the Residue Chemistry RED Chapter dated 9/ 8/ 94, is no longer required because this item has been deleted from Table 1 of OPPTS 860.1000 as a significant livestock feed item.

Sugarcane The Updated Table A for Residue Chemistry RED Chapter dated 9/ 8/ 94 concluded that no additional residue data are required for sugarcane provided all pertinent product labels are amended to prohibit use of hexazinone on sugarcane grown in FL. The basic registrant has complied with the requested label amendment (see Table A2). Presently, registered uses of hexazinone on sugarcane are limited to those grown in the states of HI, LA, TX, and in Puerto Rico. 25 The available data (MRID 42322701) indicate that the combined residues of hexazinone and its regulated metabolites, as measured by the data collection method, were <0.35 (or <0.05 ppm for each compound) in/ on samples of sugarcane treated with the 90% SC formulation of hexazinone from the following test locations: (i) in Puerto Rico where sugarcane was harvested 288 days following a single postemergence application at 0.45 lb ai/ A (0.5x the maximum registered seasonal rate for this area); (ii) in TX where sugarcane was harvested 234 days following one preemergence application followed by one postemergence application at 0.675 lb ai/ A/ application (0.75x the maximum seasonal rate in TX); and (iii) in HI where sugarcane was harvested 179 181 days following a total of four applications (one preemergence application at 1.35 or 1.47 lb ai/ A, a postemergence application at 0.45 lb ai/ A/ application, followed by two postemergence applications at 1.8 lb ai/ A/ application) for a total rate of 5.4 5.5 lb ai/ A/ season (1.5x the maximum seasonal rate in HI). Based on the combined LOQs (0.55 ppm) of the enforcement method, HED is now recommending that the RAC tolerance be reassessed from 0.20 ppm to 0.60 ppm.

GLN 860.1520: Processed Food/ Feed Pineapple process residue and juice The registrant has submitted a pineapple processing study (MRIDs 42492101 and 43401901) which was first deemed inadequate but later upgraded as acceptable. Residues of hexazinone and its regulated metabolites did not concentrate in pineapple process residue and juice except for Metabolite B in process residue. The registrant calculated a concentration factor of 3.0x for Metabolite B in pineapple process residue based on quantified residues of 0.06 ppm in pineapple process residue and 0.02 ppm in/ on pineapple RAC after treatment with hexazinone at a 1.0x rate. When this concentration factor of 3.0 x is multiplied by the highest average field trial (HAFT) residue of <0.05 ppm, the maximum expected residues of metabolite B in pineapple process residue is 0.15 ppm which is less than the reassessed RAC tolerance of 0.60 ppm. Therefore, no tolerance for pineapple process residues is warranted.

Sugarcane molasses and refined sugar An acceptable sugarcane processing study (MRIDs 42276001 and 42417901) is available. The reviewed study indicate that residues of the parent hexazinone were 0.23 ppm in/ on the RAC (sugarcane) following application of the 90% SC formulation at a total rate of 7.2 lb ai/ A (2.0x the maximum seasonal application rate for sugarcane grown in HI). Residues of metabolites A, B, C, D, and E were each nondetectable (< 0.05 ppm) in/ on treated RAC samples. Following processing of the RAC according to simulated commercial practices, residues of hexazinone and/ or metabolites A through E concentrated in bagasse (1.6x) and "A molasses" (4.0x). However, residues 26 declined in raw sugar (reduction factor of 0.2x) and processed sugar (reduction factor of 0.2x). The presently regulated processed commodities of sugarcane are molasses and refined sugar; bagasse has been removed from Table 1 of OPPTS 860.1000.

Samples of treated "A molasses" from the above study were re analyzed to confirm results. The average total residues of hexazinone and its regulated metabolites, from duplicate analysis, were 1.915 ppm for "A molasses". Based on this re analysis, residues of hexazinone and metabolites concentrated about 8.0x in "A molasses". The registrant reported that a 4.0x concentration factor should be considered when "A molasses" is further processed to final (blackstrap) molasses, the form of molasses typically fed to livestock.

To reassess the adequacy of the established 0.5 ppm tolerance for sugarcane molasses, HED will consider the HAFT residue reported from the field study as well as the concentration factors observed from the processing study. Data from the sugarcane field trials indicate that residues of hexazinone and its regulated metabolites, as measured by the data collection method, were <0.35 ppm (or <0.05 ppm for each compound) in/ on samples of sugarcane treated according to the maximum registered use pattern. According to OPPTS GDLN 860.1520, if no quantifiable residues are found in the RAC from the maximum registered rate, but the exaggerated rate does produce quantifiable residues, the latter samples should be adjusted for the degree of exaggeration. These adjusted residues should then be compared to the LOQ for the RAC. If the adjusted residues are greater than or equal to twice the LOQ, then a tolerance is needed.

The maximum average combined residue of hexazinone and its regulated metabolites was 1.915 ppm for "A molasses". To correct concentrations in "A molasses" to blackstrap molasses, residues in "A molasses" are multiplied by a concentration factor of 4.0x, resulting in 7.66 ppm. Adjusting for the degree of exaggeration (2.0x) used in the processing study, the residue for blackstrap molasses is 3.83 ppm. Because this result is greater than twice the LOQ for the RAC (sugarcane), the available data suggest that the established tolerance for sugarcane molasses should be decreased from 5.0 ppm to 4.0 ppm.

GLN 860.1480: Meat, Milk, Poultry, and Eggs The Agency changed the data requirement status for this GLN topic from "Reserved" to "Required" because the results of ruminant metabolism study suggested a very significant transfer of hexazinone residues of concern to meat and milk (Memo, 2/ 4/ 93, R. Perfetti). The registrant has since submitted an acceptable dairy cattle feeding study (MRID 43703501) which was deemed acceptable. HED is recommending that in order to reassess the established hexazinone tolerances for milk and the fat, meat, and meat byproducts of livestock and to compute a maximum theoretical dietary burden (MTDB) 27 of hexazinone to livestock, uses on pasture and rangeland grasses must be revoked. A MTDB could not be calculated including grass and grass hay since additional residue data are required for use patterns in which significant residues are expected in/ on the RACs. HED recognizes that the estimated 100,000 acres of pasture and rangeland treated with hexazinone is relatively low. Since grass and grass hay are considered major dietary components of ruminants (up to 60% of the diet per current OPPTS GLN) a MTDB for livestock could not be developed when grasses are included in the registered uses. HED has determined that a MTDB could be constructed from other potential feed items for livestock and subsequently tolerances for meats and milk can be reassessed. HED has previously determined that tolerances in poultry commodities and a poultry feeding study are not required for reregistration based on results of reviewed poultry metabolism data.

Maximum theoretical dietary burden (tentative, pending revocation of uses on pasture and rangeland grasses and hay)

There are no registered direct livestock treatments for hexazinone on cattle, goats, hogs, horses, or sheep. However, hexazinone residues of concern may transfer to milk and edible tissues of livestock as a result of ingestion of feed items such as: alfalfa forage, hay, meal, and silage; grass forage, hay, and silage; pineapple process residue; and sugarcane molasses. The maximum theoretical dietary burdens of hexazinone to beef and dairy cattle are tentatively calculated to be 4.64 ppm (see Table 3 below). The dietary burden calculations are tentative because it assumes use on pasture and rangland grasses will be canceled and tolerances revoked Table 3. Tentative calculation of maximum ruminant dietary burden for hexazinone.

Feed Commodity Reassessed Tolerance (ppm) % Dry Matter 1 Beef Cattle Dairy Cattle % of Diet 1 Burden (ppm) 2 % of Diet 1 Burden (ppm) 2 Alfalfa, forage 2 35 60 3. 43 60 3. 43 Alfalfa, hay (as meal) 4 89 15 0.68 15 0.68 Sugarcane molasses 4 75 10 0.53 10 0.53 TOTAL 85 3 4.64 85 3 4.64 1 Table 1 (OPPTS Guideline 860.1000). 2 Contribution = [tolerance / % DM (if cattle)] X % diet). 3 All beef and dairy cattle in the U. S. should have in their diet 15% cottonseed meal, peanut meal, soybean meal, canola meal, or flax seed meal. Hexazinone is not registered for use on any of these commodities. Therefore, to account for these commodities in the diet of beef and dairy cattle, the percentage has been reduced by 15% to 85%.

Dairy cattle feeding study 28 A brief summary of the reviewed dairy cattle feeding study (MRID 43703501) is presented below. Three groups of dairy cows (3 animals/ dose group) were dosed with hexazinone at 29, 87, and 290 ppm in the diet for 28 consecutive days; three additional cows served as control animals. The registrant indicated that these dose levels represent feeding level of 1.0x, 3.0x, and 10.0x based on a diet of grass forage. These dose levels are equivalent to 6.25x, 18.75x, and 62.5x, respectively, the maximum theoretical dietary burden for beef and dairy cattle when grass or grass hay is not included. An additional treatment group, fed at 17.4 ppm (3.88x), was added later, and one animal was held over from the control group for this phase of the study. These dose levels are equivalent to 64x, 190x, and 640x the MTDB for hogs. Hexazinone was placed into gelatin capsules and administered by balling gun, twice daily after each milking. Milk was collected twice daily. The cattle were sacrificed 13 21 hours after administration of the final dose, and samples of liver, kidney, muscle, and fat were collected.

The collected milk and tissue samples were analyzed for residues of hexazinone and its metabolites using two analytical methods. One method was used for milk, muscle, and fat, and another method for liver and kidney. Although cumbersome and complicated, the method was deemed adequate for data collection. Based on the data collection method used in this study, the registrant is now proposing an LC/ MS method (designated as du Pont AMR 3783 96) as an enforcement method for milk and animal tissues. Refer to "GLN 860.1340: Residue Analytical Methods  Animal Commodities" for a discussion of this method and a list of specific hexazinone residues that the method can determine. Assuming Method AMR 3783 96 passes a successful tolerance method validation, the tolerance expression for milk and tissues will be changed.

The maximum total hexazinone residues in milk were 0.78 ppm at the 6.25x feeding level (29 ppm in the diet) and 11.09 ppm at the 62.5x level. On day 14, after total residues had reached plateaus, milk was separated into skim milk and cream. Total residues in skim milk were comparable to those in whole milk; total residues in cream were approximately half those in skim milk. In tissues, the maximum total hexazinone residues at the 62.5x feeding level were 3.85 ppm in liver, 2.19 ppm in kidney, 0.32 ppm in muscle, and nondetectable ( # 0.10 ppm) in fat. The maximum total residues at the 6.25x feeding level were 0.24 ppm in liver, 0.47 ppm in kidney, and nondetectable ( # 0.15 ppm) in muscle. Because total residues were nondetectable in all fat samples from the 18.75x and 62.5x levels, fat samples were not analyzed at lower feeding levels.

A tolerances of 0.5 ppm is presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in milk. Based on the MTDB for beef and dairy cattle without grass or grass hay as a potential feed item, it is possible to re assess the animal commodity tolerances. The HED MARC has concluded that the hexazinone tolerance expression for ruminants should include 29 hexazinone plus metabolites B, C, C 2, and F for milk. Residue levels of hexazinone and metabolites in whole milk from the feeding study corrected for exaggeration levels ranged from 0.110 ppm to 0.164 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B, C, C 2, and F is 0.20 ppm; therefore, it is appropriate that the tolerance for milk be reduced from 0.5 to 0.20 ppm.

Tolerances of 0.1 ppm are presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in fat, meat, and meat byproducts of cattle, goats, hogs, horses, and sheep. The Committee concluded that the hexazinone tolerance expression for ruminant tissue should include hexazinone plus metabolites B and F. Residue levels of hexazinone and metabolites in kidney from the feeding study corrected for exaggeration levels ranged from 0.046 ppm to 0.090 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B and F is 0.10 ppm therefore it is appropriate that the tolerance for meat byproducts of cattle, goats, horses, and sheep be reassessed at 0.10 ppm. Residue levels of hexazinone and metabolites from the feeding study corrected for exaggeration levels ranged from 0.003 ppm to 0.007 ppm therefore tolerances for hog meat are not required.

Residue levels of hexazinone and metabolites in muscle from the feeding study corrected for exaggeration levels ranged from 0.003 ppm to 0.039 ppm. Based on the enforcement method, the sum of the LOQ's for hexazinone and metabolites B and F is 0.10 ppm; therefore, it is appropriate that the tolerance for meat byproducts of cattle, goats, horses, and sheep be reassessed at 0.10 ppm. Residue levels of hexazinone and metabolites in muscle from the feeding study corrected for exaggeration levels ranged from 0.0004 ppm to 0.002 ppm therefore tolerances for hog meat are not required.

Tolerances of 0.1 ppm are presently established for the combined residues of hexazinone and its metabolites (calculated as hexazinone) in fat. Residue levels of hexazinone and metabolites in fat from the feeding study were nondetectable (< 0.1 ppm) at the 62.5x exaggerated rate. The Agency has determined that tolerances for hexazinone residues in fat of cattle, goats, hogs, horses, and sheep are not required (Category 3, 40 CFR §180.6a). Tolerances for fat of cattle, goats, hogs, horses, and sheep are not required and should be revoked.

GLN 860.1400: Water, Fish, and Irrigated Crops Hexazinone is presently not registered for direct use on water and aquatic food and feed crops; therefore, no residue chemistry data are required under these guideline topics.

GLN 860.1460: Food Handling 30 Hexazinone is presently not registered for use in food handling establishments; therefore, no residue chemistry data are required under this guideline topic.

GLN 860.1850: Confined Accumulation in Rotational Crops The data requirements for confined rotational crops are satisfied. The basic registrant has submitted acceptable studies (MRIDs 41008401, 42824001, 43892401) which indicate that [ 14 C] hexazinone residues accumulate at 0.01 ppm in/ on tested rotational crop commodities at certain plantback intervals. Based on these data, the registrant was required to conduct a limited field rotational crop study in order to assess the adequacy of existing rotational crop restrictions on the registrant's end use product labels and to determine whether rotational crop tolerances are needed.

The major residue components that were identified from the confined rotational crop study were either the glucose conjugate of G3170 or hexazinone or both. The remaining ten identified metabolites all contain the triazinone ring structure, and four of these compounds (metabolites A, B, C, and F) have been determined to be residues of concern in/ on primary crops.

GLN 860.1900: Field Accumulation in Rotational Crops The data requirements for field accumulation in rotational crops are only partially satisfied. This conclusion is based on a recent review of a limited field crop rotation study (MRID 45084101) wherein the 75% DF formulation of hexazinone was applied as a single postemergence broadcast application to mowed alfalfa at test sites in MN and CA at 1.5 lb ai/ A (1x the maximum seasonal rate for alfalfa). Approximately one year following application, the remaining alfalfa crop residue was plowed up and returned to the soil, and head lettuce, field corn, and wheat were planted (350 days after treatment, DAT, for the MN test site and 358 DAT for the CA test site).

Residues were below the respective method LOQs for hexazinone and metabolites A, B, C, D, E, F, G, H, G3170, G3170 NG, A 1, and C 1 in/ on head lettuce, wheat forage and grain, and field corn forage and grain. In wheat straw, residues of metabolite B were <0.02 0.021 ppm; residues of hexazinone and the remaining metabolites were below the LOQ. In field corn stover, residues of hexazinone were 0.02 0.081 ppm, residues of metabolite B were 0.038 0.053 ppm, and residues of the remaining metabolites were below the LOQ.

These data indicate that extended field rotational crop studies and rotational crop tolerances will not be required for residues of hexazinone residues of concern in/ on leafy vegetables provided that labels are amended to specify a rotational crop restriction of at least 12 months. A previous review of a confined rotational crop study concluded 31 that rotational crop tolerances were not needed for root crops provided that a 12 month plantback interval was established; an examination of the basic registrant's labels shows that the 12 month plantback interval for root crops has been established.

Because the data from the limited field trials indicate that quantifiable residues occur in field corn stover and wheat straw, extended field rotational crop trials for corn stover, sorghum stover, and wheat straw to support a 12 month rotational interval and a tolerance for inadvertent hexazinone residues are required.

The data for the application rate used in this study are sufficient to support rotation from alfalfa and pasture and rangeland grass only. The registrant has stated previously that they intend to modify product labels to restrict rotation from sugarcane to sugarcane only (HED memorandum, 10/ 31/ 96, J. Abbotts). 32 Table B. Residue Chemistry Science Assessments for Reregistration of Hexazinone.

GLN: Data Requirements Tolerances [40 CFR] (ppm) Must Additional Data Be Submitted? References 1 860.1200: Directions for Use N/ A = Not Applicable Yes 2 See Table A 860.1300: Plant Metabolism N/ A No 00078047, 00104846, 00126127 860.1300: Animal Metabolism N/ A No 00104843, 41524801, 42187901 3 , 42219301 4 , 42248901 5 , 42690601 6 , 43488901 7 860.1340: Residue Analytical Methods  Plant commodities N/ A No 00038868, 00101574, 00126127, 41964101, 41964102, 42987201 8 , 430025401 9  Animal commodities N/ A Reserved 10 00038868, 43074201 11 , 44259101 12 , 44259102 12 860.1360: Multiresidue Methods N/ A No 41572101, 41572102, 41572103, 41572104, 41572105, 41572106 860.1380: Storage Stability Data  Plant commodities N/ A No 42276001 13 , 42322701 14 , 42418001 15 , 42423001 16 , 42492101 17 , 42535601 18 , 42867501 19 , 43524301 20 , 43936501 21 , 44133501 22  Animal commodities N/ A No 43703501 23 860.1500: Crop Field Trials Berries Group  Blueberries 0.2 [§ 180.396( a)] No 24 00101574, 41964101, 41964102 Grass Forage, Fodder, Hay Group GLN: Data Requirements Tolerances [40 CFR] (ppm) Must Additional Data Be Submitted? References 1 33  Grasses (pastures and rangeland), forage and hay 10, grasses, pasture and rangeland [§ 180.396( a)] Yes 25, 26 00138226, 41898301 27 , 42419101 15 , 42867501 19 Table B (continued).

GLN: Data Requirements Tolerances [40 CFR] (ppm) Must Additional Data Be Submitted? References 1 34 Non grass Animal Feeds (forage, fodder, straw, and hay) Group  Alfalfa, forage, hay, and seed 2.0, forage 8.0, hay [§ 180.396( a)] No 28 , 29 00118050, 43074401 30 , 43074402 30 Miscellaneous Commodities  Pineapple 0. 5, whole fruit [§ 180.396( a)] No 00126127, 42535601 18  Sugarcane 0. 2 [§ 180.396( c)] No 00028733, 00114039, 42322701 14 860.1520: Processed Food/ Feed  Pineapple None No 42492101 17 , 43401901 31  Sugarcane 5. 0, molasses [§ 180.396( c)] No 42276001 13 , 42417901 32 , PP# 8F2119/ FAP# 4H5683 33 860.1480: Meat, Milk, Poultry, Eggs  Milk, Fat, Meat, and Meat Byproducts of Cattle, Goats, Hogs, Horses, and Sheep 0.1, milk, fat, meat, and meat byproducts [§ 180.396( a)] No 34 00028866, 00140161, 43703501 23  Eggs and the Fat, Meat, and Meat Byproducts of Poultry None No 35 00104845 860.1400: Water, Fish, and Irrigated Crops NA No 860.1460: Food Handling NA No 860.1850: Confined Rotational Crops NA No 41008401 36 , 42824001 37 , 43892401 38 860.1900: Field Rotational Crops None Yes 39 45084101 40 Table B (continued).

35 1. Bolded references were reviewed in the Reregistration Update of 9/ 5/ 91. Unbolded references were reviewed in the Residue Chemistry Science Chapter of the Final Registration Standard and Tolerance Reassessment (FRSTR) dated 5/ 25/ 88. All other references were reviewed as noted.

2. Label amendments are required for alfalfa and blueberries, and details of the required label amendments are presented in the respective endnote for GLN 860.1500 (Crop Field Trials) of this table. Label amendments are also required to establish a 12 month plantback interval for leafy vegetables.

3. DP Barcode D174764, CBRS No. 9418, 5/ 22/ 92, J. Abbotts.

4. DP Barcode D175243, CBRS No. 9510, 7/ 14/ 92, J. Abbotts.

5. DP Barcode D176715, CBRS No. 9697, 9/ 15/ 92, J. Abbotts.

6. DP Barcode D189285, CBRS No. 11656, 6/ 25/ 93, J. Abbotts.

7. DP Barcode D210574, CBRS No. 14889, 1/ 19/ 95, J. Abbotts.

8. DP Barcode D196446, CBRS No. 12815, 1/ 6/ 94, J. Abbotts.

9. DP Barcode D197342, CBRS No. 12932, 1/ 6/ 94, J. Abbotts.

10. The registrant has proposed an LC/ MS method (designated as du Pont AMR 3783 96) as an enforcement method for animal commodities. Method AMR 3783 96 has been subjected to a successful ILV and a radiovalidation study. Method AMR 3783 96 will be forwarded to the Analytical Chemistry Branch (ACL; Beltsville, MD) for a tolerance method validation by Agency chemists. If the results of method validation are successful, then Method AMR 3783 96 will be proposed for inclusion in PAM Volume II, and no additional enforcement methodology for animal commodities will be required for reregistration.

11. DP Barcode D198348, CBRS No. 13076, 5/ 25/ 94, S. Hummel.

12. DP Barcode D282683, 05/ 15/ 02, J. S. Punzi.

13. DP Barcode D177572, CBRS No. 9808, 6/ 18/ 92, S. Funk.

14. DP Barcode D178771, CBRS No. 9985, 9/ 22/ 92, J. Abbotts.

15. DP Barcode D181318, CBTS No. 10354, 1/ 28/ 93, R. Lascola.

16. DP Barcode D181480, CBRS No. 10365, 11/ 9/ 92, J. Abbotts.

17. DP Barcode D183296, CBRS No. 10702, 2/ 23/ 93, J. Abbotts.

18. DP Barcode D184852, CBRS No. 10924, 2/ 25/ 93, J. Abbotts.

19. DP Barcode D195426, CBRS No. 12617, 10/ 25/ 93, J. Abbotts.

20. DP Barcode D211642, CBRS No. 15101, 3/ 14/ 95, J. Abbotts.

21. DP Barcode D282685, 05/ 15/ 02, J. S. Punzi. Table B (continued).

36 22. DP Barcode D282682, 05/ 15/ 02, J. Punzi.

23. DP Barcode D217257, CBRS No. 15881, 9/ 25/ 95, J. Abbotts.

24. No additional data are required for blueberries. However, label revisions remain a requirement. The product labels for ME980002 and ME980003, which are limited for use on lowbush blueberries, should be amended to specify a PHI of 450 days. The product label for NC830012 should also be amended to specify PHIs of 90 and 450 days for application to highbush and lowbush blueberries, respectively.

25. Uses on grass should be cancelled and tolerances revoked. The following grass forage would be required for grass: "Data depicting magnitude of the residues of hexazinone and metabolites A, B, C, D, and E in/ on grass forage harvested 0 day following a single broadcast application of representative formulations at 1.125 lb ai/ A. It is the Agency policy to require 0 day crop field residue data for grass forage unless it is not feasible (e. g., preplant/ preemergence pesticide uses). The formulations to be tested may be applied in side by side plots. The location and number of trials should be in compliance with the current OPPTS GLN for adequate geographic representation of data.

26. Uses on grass should be cancelled and tolerances revoked. Additional grass hay data would be required. The registrant has submitted a petition (PP# 1F3967) for the establishment of a tolerance for residues of hexazinone and its metabolites in/ on grass hay. The petition is currently in reject status because additional grass hay data, from field trials with adequate geographical representation, remain outstanding.

27. DP Barcodes D165324, D165303, and D165277, CBRS Nos. 8147, 8148, 8149, 8134, 8152, and 8153, 11/ 14/ 91, J. Smith.

28. No additional data are required for alfalfa forage and hay. However, the product label for the 2 lb/ gal EC (EPA Reg. No. 352 392) formulation must be amended to establish a 30 day PHI (or pregrazing interval) for the feeding of forage and the cutting of hay.

29. No additional data are required for alfalfa seed. However, the registrant is required to propose a tolerance for hexazinone residues of concern in/ on alfalfa seed; the available data suggest that a tolerance level of 2.0 ppm is appropriate.

30. DP Barcode D198336, CBRS No. 13075, 6/ 22/ 94, S. Hummel.

31. DP Barcode D208605, CBRS No. 14591, 1/ 20/ 95, C. Eiden and DP Barcode D215057, 11/ 28/ 95, C. Eiden.

32. DP Barcode D181308, CBRS No. 10333, 10/ 26/ 92, B. Cropp Kohlligian.

33. DP Barcode D196510, CB No. 12796, 9/ 1/ 94, S. Hummel.

34. An acceptable dairy cattle feeding study is available. HED is able, at this time, to reassess the established hexazinone tolerances for milk and the fat, meat, and meat byproducts of livestock using maximum theoretical dietary burdens of hexazinone to livestock, calculated without grass or grass hay. Since additional residue data are required for grass forage and hay, for which significant residues are expected in/ on the RACs and are considered major dietary components of ruminants, HED recommends that the uses be canceled and tolerances revoked.

35. HED has determined that tolerances for hexazinone residues in eggs and poultry tissues are not required (Category 3, 40 CFR §180.6) based on the results of the reviewed poultry metabolism study.

36. DP Barcode D188349, CBRS No. 11458, 5/ 14/ 93, L. Cheng. Table B (continued).

37 37. DP Barcode D192877, CBRS No. 12222, 3/ 3/ 94, F. Fort.

38. DP Barcode D222455, CBRS No. 16791, 7/ 1/ 96, L. Cheng.

39. Because the data from the limited field trials indicate that quantifiable residues occur in field corn stover and wheat straw, extended field rotational crop trials for corn stover, sorghum stover, and wheat straw to support a 12 month rotational interval and a tolerance for inadvertent hexazinone residues are required.

40. DP Barcode D282684, 05/ 15/ 02, J. S. Punzi. 38 TOLERANCE REASSESSMENT SUMMARY Tolerances for residues of hexazinone in/ on plant, livestock, and processed commodities are currently expressed in terms of the combined residues of hexazinone and its metabolites (calculated as hexazinone). Permanent tolerances are established for several raw agricultural commodities and livestock commodities under 40 CFR §180.396( a). Tolerances with regional registrations which exclude use of hexazinone on sugarcane in Florida are established under 40 CFR §180.396( c).

The qualitative nature of the residue in plants and livestock is adequately understood. The HED MARC concluded that the hexazinone tolerance expression for plants and rotational crops should include hexazinone and metabolites A, B, C, D, and E. The qualitative nature of the residue in livestock is adequately understood based on acceptable ruminant and poultry metabolism studies. The HED MARC concluded that the hexazinone tolerance expression for ruminants should include hexazinone plus metabolites B, C, C 2, and F for milk. The Committee concluded that the hexazinone tolerance expression for ruminant tissue should include hexazinone plus metabolites B and F. The Committee concluded that residues of hexazinone and metabolites B, C, C1 C 2, and F should be taken into account when risk assessments are done. HED has determined that tolerances for hexazinone residues in eggs and poultry tissues, hog meat and meat by products, and fat of livestock are not required (Category 3, 40 CFR §180.6) based on the results of the respective metabolism and feeding studies.

An adequate enforcement method is available for plant commodities. Method I of PAM, Volume II is a nitrogen selective GLC method capable of determining residues of hexazinone and metabolites A, B, C, D, and E. The combined limit of quantitation (LOQ) for hexazinone residues by Method I is 0.55 ppm. An enforcement method, Method AMR 3783 96, has been proposed for milk and livestock tissues. Method AMR 3783 96 has been subjected to a successful ILV and a radiovalidation study. It will be forwarded to the Analytical Chemistry Branch for a tolerance method validation by Agency chemists.

HED is recommending that the hexazinone tolerances listed under 40 CFR §180.396 (a) and (c) be reorganized, as listed below, to indicate the specific residues of concern that can be quantitated by the existing plant enforcement method and the proposed livestock enforcement method. This proposal to reorganize hexazinone tolerances is contingent upon successful validation of Method AMR 3783 96. Note that for simplicity the tolerence expression is shown as "Hexazinone and its metabolites A, B, C, D, and E (calculated as hexazinone)" however the metabolites must be identified by the appropriate chemical name.

Table 4. 39 40 CFR Reserved for Tolerance Expression §180.396 (a) (1) Permanent tolerances for plant and processed commodities Hexazinone and its metabolites A, B, C, D, and E (calculated as hexazinone)

§180.396 (a) (2) Milk Hexazinone and its metabolite B, metabolite C and its isomer (C 2), and metabolite F (calculated as hexazinone)

§180.396 (a) (3) Ruminant tissues Hexazinone and its metabolite B and metabolite F (calculated as hexazinone)

§180.396 (c) Tolerances for plant and processed commodities with regional registration Hexazinone and its metabolites A, B, C, D, and E (calculated as hexazinone)

NOTE: See Figure 1 for full chemical names of regulated hexazinone metabolites.

A summary of hexazinone tolerance reassessments is presented in Table C. Discussions of residue data used for tolerance reassessment are presented in the "Summary of Science Findings" section for GLNs 860.1500 (Crop Field Trials) and 860.1480 (Meat, Milk, Poultry, and Eggs). Certain commodity definitions need to be corrected.

Tolerances Listed Under 40 CFR §180.396 (a):

Sufficient data are available to ascertain the adequacy of tolerances listed in 40 CFR §180.96 (a) for alfalfa forage, alfalfa hay, blueberries, and pineapple. Tolerances for pasture and rangeland grasses should be revoked and uses cancelled.

An acceptable ruminant feeding study is available; HED is able to reassess the established hexazinone tolerances for milk and the fat, meat, and meat byproducts of livestock using a maximum theoretical dietary burden of hexazinone to livestock assuming revocation of tolerances for grasses and hay.

The established tolerances for blueberries and pineapple should be increased to 0.60 ppm to reflect the combined LOQs of the enforcement method. The available field trial data indicate that residues of hexazinone and its regulated metabolites, as measured by the data collection method, were nondetectable in/ on these RACs following treatment at 1.0x.

Tolerances Needed Under 40 CFR §180.396 (a):

The registrant is required to propose a tolerance for hexazinone residues of concern in/ on alfalfa seed; the available data suggest that a tolerance level of 2.0 ppm is appropriate.

Tolerances Listed Under 40 CFR §180.396 (c): 40 Adequate data are available for sugarcane and sugarcane molasses. The tolerance for sugarcane molasses should be reduced from 5.0 ppm to 4.0 ppm based on re calculation of expected residues. 41 (continued; endnotes follow) Table C. Tolerance Reassessment Summary for Hexazinone.

Commodity Current Tolerance (ppm) a Range of residues (ppm) b Tolerance Reassessment (ppm) Comment/ Correct Commodity Definition Tolerances listed under 40 CFR §180.396( a):

Alfalfa green forage 2 <1.87 2.0 Alfalfa, forage Alfalfa hay 8 <3.33 4. 0 Alfalfa, hay Blueberries 0.2 <0.3 ppm (nondetectable; <0.05 ppm for each compound) 0.60 Tolerance should be increased based on the combined LOQ (0.55 ppm) of the enforcement method. Blueberry Cattle, fat 0. 1 Revoke c Cattle, mbyp 0.1 0. 10 Cattle, meat 0.1 0. 10 Goat, fat 0. 1 Revoke c Goat, mbyp 0.1 0. 10 Goats, meat 0.1 0. 10 Grasses, pasture 10 Revoke d Grass, forage Grass, hay Grasses, rangeland 10 Revoke d Hog, fat 0.1 Revoke c Hog, mbyp 0.1 Revoke c Hog, meat 0.1 Revoke c Horses, fat 0. 1 Revoke c Horses, mbyp 0.1 0. 10 Horses, meat 0.1 0. 10 Milk 0.5 0. 20 Pineapple 0. 5 <0.35 (or <0.05 ppm for each compound) 0.60 Tolerance should be increased based on the combined LOQ (0.55 ppm) of the enforcement method.

Sheep, fat 0. 1 Revoke c Sheep, mbyp 0.1 0. 10 Sheep, meat 0.1 0. 10 Tolerances needed under 40 CFR §180.396( a):

Alfalfa, seed  <1.30< 1.46 2. 0 Table C (continued).

Commodity Current Tolerance (ppm) a Range of residues (ppm) b Tolerance Reassessment (ppm) Comment/ Correct Commodity Definition 42 Tolerances listed under 40 CFR §180.396( c):

Sugarcane 0. 2 <0.05 ppm (nondetectable) each for hexazinone and its metabolites 0.60 Tolerance should be increased based on the combined LOQ (0.55 ppm) of the enforcement method.

Sugarcane molasses 5 (1.915 x 4x) ÷ 2x = 3.83 4.0 a Expressed in terms of the combined residues of hexazinone and its metabolites (calculated as hexazinone). b Refer to section on Magnitude of Residues in Crop Plant for detailed discussion of residues in crops. c Tolerances for fat are not required (Category 3, 40 CFR §180.6). d HED is recommending revocation of these tolerances and cancellation of uses, since grasses are a major feed item and required data are not available for reassessment.

CODEX HARMONIZATION No maximum residue limits (MRLs) for hexazinone and its metabolites have been established or proposed by Codex for any agricultural commodity. Therefore, no compatibility questions exist with respect to U. S. tolerances.. 43 AGENCY MEMORANDA CITATIONS Agency Memoranda Citations Relevant to Hexazinone Reregistration.

Date DP Barcode CB No. From To MRID Nos. Subject 7/ 18/ 91 D162863 7835 R. Lascola J. Miller/ D. Wilson None PP# 1F3967. Hexazinone (Velpar L) in/ on Pasture and Rangeland Hay.

11/ 14/ 91 D165277, D165303, D165324 8134, 8147, 8148, 8149, 8152, 8153 J. Smith J. Miller 41898301 Hexazinone. Amendment of label reflecting a new pregrazing interval for forestry use, new replanting instructions following alfalfa, reduced use on sugarcane, and overall clarifications.

3/ 11/ 92 D174869 9463 D. McNeilly A. Ertman None Hexazinone reregistration; question concerning pineapple forage feeding restriction from DuPont Agricultural Products.

5/ 22/ 92 D174764 9418 J. Abbotts L. Rossi 42187901 Hexazinone. Du Pont Company Response to the Reregistration Standard: Animal Metabolism Data for Goat.

6/ 18/ 92 D177572 9808 S. Funk A. Ertman 42276001 Reregistration of Hexazinone (Velpar). 171 4( l):

Sugarcane Processing Study. 171 4( K): Sugarcane Field Trial Time Extension Request.

6/ 24/ 92 D172408 9127 R. Lascola E. Wilson/

J. Miller None PP# 1F3967. Hexazinone (Velpar L) in/ on Pasture and Rangeland Hay. Amended Response to Registration Standard Data Gap.

7/ 14/ 92 D175243 9510 J. Abbotts L. Rossi 42219301 Hexazinone. Du Pont Company Response to the Reregistration Standard: Storage Stability Data for Animal Metabolism in Poultry.

8/ 21/ 92 D178781 9961 J. Abbotts A. Ertman None Hexazinone. Du Pont Company Response to the Reregistration Update to the Residue Chemistry Chapter. Agency Memo Citations for Hexazinone (continued).

Date DP Barcode CB No. From To MRID Nos. Subject 44 8/ 25/ 92 D174070 9366 M. Bradley J. Miller None Hexazinone. Label Amendment to Add Pregrazing Intervals for Forestry and Non Crop Land Use.

9/ 15/ 92 D176715 9697 J. Abbotts L. Rossi 42248901 Hexazinone. Du Pont Company Response to the Reregistration Standard: Storage Stability Data for Animal Metabolism in Goat.

9/ 22/ 92 D178771 9985 J. Abbotts L. Rossi 42322701 Hexazinone. Du Pont Company Response to the Reregistration Standard: Residue Data for Sugarcane.

10/ 26/ 92 D181308 10333 B. Cropp Kohlligian L. Rossi 42417901 Hexazinone: Supplemental Data Submitted to Address Sugarcane Processing Study Deficiencies.

11/ 9/ 92 D181480 10365 J. Abbotts L. Rossi 42423001 Hexazinone. Du Pont Company Response to the Reregistration Standard: Storage Stability Data for Blueberry.

1/ 28/ 93 D181318 10354 R. Lascola E. Wilson/

J. Miller 42418001 and 42419101 PP 1F3967. Hexazinone (Velpar L) in/ on Pasture and Rangeland Hay.

2/ 4/ 93 None None R. Perfetti L. Rossi and E. Saito None Animal Feeding Studies: Requirement Status Modification.

2/ 23/ 93 D183296 10702 J. Abbotts L. Rossi 42492101 Hexazinone. Du Pont Company Response to the Reregistration Standard: Processing Data for Pineapple.

2/ 25/ 93 D184852 10924 J. Abbotts L. Rossi 42535601 Hexazinone. Du Pont Company Response to the Reregistration Standard: Residue Data for Pineapple.

5/ 14/ 93 D188349 11458 L. Cheng A. Ertman/ W. Waldrop 41008401 Hexazinone. Rotational Crop Data Requirement.

6/ 25/ 93 D189285 11656 J. Abbotts A. Ertman 42690601 Hexazinone, Reregistration. Supplemental Data on Poultry Metabolism. Agency Memo Citations for Hexazinone (continued).

Date DP Barcode CB No. From To MRID Nos. Subject 45 7/ 22/ 93 None None R. Perfetti L. Rossi and A. Rathman None Animal Feeding Studies. Requirement Status Modification: Reconsideration.

9/ 9/ 93 None None M. Metzger L. Rossi None Animal Feeding Studies (171 4( j)); Requirement Status Modification.

10/ 5/ 93 D194489 12425 J. Abbotts A. Ertman None Hexazinone, Reregistration. Animal Feeding Study Protocol.

10/ 5/ 93 D194395 12427 J. Abbotts A. Ertman None Hexazinone, Reregistration. Pineapple Residue Data.

10/ 8/ 93 None None J. Abbotts L. Rossi and F. Chow/ C. Frick None Hexazinone. Reregistration Eligibility Document Chapters for Product Chemistry and Residue Chemistry, Current Status.

10/ 8/ 93 None None J. Abbotts Hexazinone Reregistration File None Hexazinone. Anticipated Residues for Reregistration Eligibility Document.

10/ 25/ 93 D195426 12617 J. Abbotts A. Ertman 42867501 Hexazinone, Reregistration. Storage Stability Data in Grass.

1/ 6/ 94 D196446 12815 J. Abbotts A. Ertman 42987201 Hexazinone, Reregistration. Analytical Method for Sugarcane Commodities.

1/ 6/ 94 D197342 12932 J. Abbotts A. Ertman 43025401 Hexazinone, Reregistration. Independent Laboratory Validation of an Analytical Method for Sugar Commodities.

3/ 3/ 94 D192877 12222 F. Fort L. Rossi/ W. Waldrop 42824001 Hexazinone. Supplemental Information Pertaining to Rotational Crop Requirements. List A Case No. 0266.

Chemical I. D. No. 107201.

3/ 16/ 94 D199887 13301 S. Hummel A. Ertman None Hexazinone (107201), Reregistration Case No. 0266.

Storage Intervals and Conditions in Grass Time Extension Request for Livestock Feeding Study. Agency Memo Citations for Hexazinone (continued).

Date DP Barcode CB No. From To MRID Nos. Subject 46 4/ 20/ 94 D201203 13492 F. Suhre A. Ertman None Hexazinone (ID 107201). Magnitude of the Residue,

Cattle Feeding Study [171 4( j)]; Protocol Amendment.

4/ 29/ 94 D201738 13527 G. Kramer E. Wilson/

J. Miller None PP# 1F3967. Hexazinone (Velpar L) in/ on Pasture and Rangeland Hay. Amendment of 3/ 28/ 94.

5/ 16/ 94 None None S. Hummel Metabolism Committee None Hexazinone (107201), Reregistration Case No. 0266.

Issues to be Presented to the Metabolism Committee.

5/ 25/ 94 D198348 13076 S. Hummel A. Ertman 43074201 Hexazinone (107201), Reregistration Case No. 266.

Livestock Metabolism  Confirmatory Analyses Hexazinone Tolerance Expression.

5/ 25/ 94 D203472 None S. Hummel HED Metabolism Committee None Hexazinone (107201) Plant and Animal Metabolism:

Results of HED Metabolism Committee Meeting Held May 19, 1994.

6/ 1/ 94 D202919 13649 F. Suhre W. Waldrop None Hexazinone (107201). Pineapple Processing Study 171 4( l).

6/ 22/ 94 D198336 13075 S. Hummel A. Ertman 43074401 and 43074402 Hexazinone (107201) Residue Data on Alfalfa.

9/ 1/ 94 D196510 12796 S. Hummel E. Wilson/

J. Miller/ A. Ertman None PP# 8F2119/ FAP# 4H5683 Hexazinone (107201)

Residue Data on Sugarcane Reregistration Case No.

0266.

9/ 8/ 94 D207225 14319 S. Hummel A. Ertman None Hexazinone (107201)  Reregistration Case No. 0266.

Updated Table A for Residue Chemistry RED Chapter.

9/ 22/ 94 D207493 14363 S. Hummel E. Wilson/

J. Miller/ A. Ertman None PP# 8F2119/ FAP# 4H5683 Hexazinone (107201) on Sugarcane Reregistration Case No. 0266. Clarification of CB 12796, DP Barcode D196510. Agency Memo Citations for Hexazinone (continued).

Date DP Barcode CB No. From To MRID Nos. Subject 47 10/ 12/ 94 D207995 14455 S. Hummel E. Wilson/

J. Miller/ A. Ertman None PP# 8F2119/ FAP# 4H5683 Hexazinone (107201) on Sugarcane Amendment of 9/ 21/ 94 EPA Reg. No. 352

378 DuPont Velpar Herbicide Reregistration Case No.

0266 Amended Registration, Deletion of Use in FL.

11/ 30/ 94 D209648 14740 S. Hummel E. Wilson/ A. Ertman None PP# 8F2119/ FAP# 4H5683 Hexazinone (107201) on Sugarcane Amendment of 11/ 2/ 94, Draft FR Notice EPA Reg. No. 352 378 DuPont Velpar Herbicide Reregistration Case No. 0266 Justification for Disallowing Use in FL.

1/ 19/ 95 D210574 14899 J. Abbotts A. Ertman 43488901 Hexazinone (107201), Reregistration Case 0266.

Ruminant Metabolism, Supplemental Data.

1/ 20/ 95 D208605 14591 C. Eiden W. Waldrop 43401901 Hexazinone. Pineapple Processing Study.

3/ 14/ 95 D211642 15101 J. Abbotts A. Ertman 43524301 Hexazinone (107201), Reregistration Case 0266.

Storage Stability of Metabolite C in Grass, Interim Report.

9/ 25/ 95 D217257 15881 J. Abbotts A. Ertman 43703501 Hexazinone (107201), Reregistration Case 0266.

Cattle Feeding Study.

11/ 28/ 95 D215057 15974 C. Eiden W. Waldrop/

A. Ertman None Hexazinone. Pineapple Processing Study Follow Up:

Response from Registrant.

4/ 15/ 96 None None J. Abbotts A. Ertman None Hexazinone (107201), Reregistration Case 0266.

Meeting with Registrant DuPont, 4/ 9/ 96, on Progress Toward Analytical Method, Animal Commodities.

7/ 1/ 96 D222455 16791 L. Cheng P. Deschamp 43892401 Hexazinone. Case 0266. Confined Rotational Crop Studies (GLN 165 1).

9/ 27/ 96 D228808 17552 J. Abbotts M. Metzger None Hexazinone (107201), Reregistration Case 0266.

Registrant DuPont Agricultural Products. Guideline 860.1900. Field Rotational Crops, Limited. Agency Memo Citations for Hexazinone (continued).

Date DP Barcode CB No. From To MRID Nos. Subject 48 10/ 31/ 96 None None J. Abbotts P. Deschamp None Hexazinone (107201), Reregistration Case 0266.

Meeting with Registrant DuPont, 10/ 30/ 96, on Requirements for Limited Field Rotational Trials.

02/ 05/ 02 D279897 None S. Kinard C. Olinger None Hexazinone. The Outcome of the HED Metabolism Assessment Review Committee.

05/ 15/ 02 D282685 None J. Punzi D. Helder 43936501 Hexazinone (107201), Reregistration Case 0266.

Storage Stability Study for Hexazinone and Metabolites A, B, C, D, and E in Pasture and Range Grasses.

05/ 15/ 02 D282682 None J. Punzi D. Helder 44133501 Hexazinone (107201), Reregistration Case 0266.

Storage Stability Study for Hexazinone and Metabolites A, B, C, D, and E in Alfalfa Forage, Hay,

and Seed.

05/ 15/ 02 D282683 None J. Punzi D. Helder 44259101 Hexazinone (107201), Reregistration Case 0266.

Enforcement Method For the Determination of Hexazinone and its Metabolites in Animal Tissue and Milk Using ESI LC/ MS 05/ 15/ 02 D282683 None J. Punzi D. Helder 44259102 Hexazinone (107201), Reregistration Case 0266.

Independent Laboratory Validation of Proposed Enforcement Method For the Determination of Hexazinone and its Metabolites in Animal Tissue and Milk Using ESI LC/ MS 05/ 15/ 02 D282684 None J. Punzi D. Helder 45084101 Hexazinone (107201), Reregistration Case 0266. Field Accumulation in Rotational Crops 49 STUDY CITATIONS 00028733 E. I. du Pont de Nemours & Company (1976) Determination of Hexazinone Metabolite C. Undated method. (Unpublished study received Jan 21, 1980 under 352 378; CDL: 099225 A)

00028866 Holt, R. F.; Baude, F. J.; More, D. W. (1979) Hexazinone Livestock Feeding Studies: Milk and Meat. (Unpublished study received Mar 14, 1980 under 352 378; submitted by E. I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 099298 F)

00038868 Holt, R. F. (1980) Determination of Hexazinone and Metabolite Residues Using Nitrogen Selective Gas Chromatography. Undated method. (Unpublished study received Jul 1, 1980 under 352 378; submitted by E. I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 099514 E)

00038869 Rapisarda, C. (1978) Metabolism of 14C Labeled Hexazinone in the Goat. (Unpublished study received Jul 1, 1980 under 352 378; submitted by E. I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 099514 F)

00078047 Rhodes, R. C. (1975) Letter sent to 324 File dated Aug 12, 1975: Uptake and metabolism studies with 14 C DPX 3674 on sugarcane in the greenhouse. (Unpublished study received Mar 22, 1976 under 352 EX 91; submitted by E. I. du Pont de Nemours & Co., Wilmington, Del.; CDL: 095980 E)

00101574 Interregional Research Project No. 4 (1982) Residue Studies of Hexazinone on Blueberries and Methomyl on Sugarcane. (Compilation; unpublished study received May 17, 1982 under 2E2687; CDL: 070861 A)

00104843 Study ADP record deleted. Study is a duplicate of MRID 38869 00104845 E. I. du Pont de Nemours & Co., Inc. (1979) Results of Tests on the Amount of Residue Remaining on Treated Crop: Hexazinone plus Metabolites. (Compilation; unpublished study received May 24, 1979 under 9G2214; CDL: 098309 C)

00104846 Rapisarda, C. Metabolism of 14C labeled Hexazinone in Alfalfa: Doc. No. HME 12 79. (Unpublished study received May 24, 1979 under 9G2214; submitted by E. I. du Pont de Nemours & Co., Inc., Wilmington, DE; CDL: 098309 D)

00114039 E. I. du Pont de Nemours & Co., Inc. (1978) Investigations Made with Respect to Residue Chemistry: [Velpar]. (Compilation; unpublished 50 study received Aug 29, 1978 under 352 378; CDL: 097321 E)

00118050 E. I. du Pont de Nemours & Co., Inc. (1982) Data Supporting Amendment of Velpar Weed Killer Use on Alfalfa and Adding Velpar L Weed Killer Use on Alfalfa. (Unpublished study received Nov 15, 1982 under 352 378; CDL: 248831 A)

00126127 E. I. du Pont de Nemours & Co., Inc. (1983) Results of Tests on the Amount of Residue Remaining on Treated Crop: Hexazinone. (Compilation; unpublished study received Feb 28, 1983 under 352 378; CDL: 071438 A)

00138226 E. I. du Pont de Nemours & Co., Inc. (1984) Residue Chemistry Data Supporting the Use of Velpar L Weed Killer for Control of Undesirable Woody Plants in Rangeland. (Compilation; unpublished study received Apr 4, 1984 under 352 392; CDL: 252954 A)

00140161 Magnitude of the Residue in Animals 41008401 Rapisarda, C. (1980) Rotational Crop Studies with 14C LabeledHexazinone Laboratory Project AMR 26 80. Unpublished study prepared by E. I. du Pont de Nemours & Co. 25 p.

41524801 Hawkins, W.; Elsom, L.; Gray, S., et al. (1990) The Metabolism of Carbon 14 Hexazinone in Laying Hens: Lab Project Number: 203/ 90454: AMR 1517 89. Unpublished study prepared by Huntingdon Research Centre, Ltd. 80 p.

41572101 Fomenko, J. (1990) Testing of DPX A3674 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1489 89: DP001 01. Unpublished study prepared by Spectralytix. 67 p.

41572102 Fomenko, J. (1990) Testing of IN T3937 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1490 89: DP001 02. Unpublished study prepared by Sprectalytix Inc. 57 p.

41572103 Fomenko, J. (1990) Testing of IN A3928 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1491 89: DP001 03. Unpublished study prepared by Spectralytix, Inc. 67 p.

41572104 Fomenko, J. (1990) Testing of IN T3935 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1492 89: DP001 04. Unpublished study prepared by Spectralytix Inc. 57 p. 51 41572105 Fomenko, J. (1990) Testing of IN B2838 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1493 89: DP001 05. Unpublished study prepared by Spectralytix Inc. 67 p.

41572106 Fomenko, J. (1990) Testing of IN B3936 through FDA Multi Residue Protocols A E: Lab Project Number: AMR 1494 89: DP001 06. Unpublished study prepared by Spectralytix Inc. 67 p.

41898301 Bollin, E. (1991) Magnitude of Residues of Velpar Herbicide in Pasture and Range Grasses: Lab Project Number: AMR 1429 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 241 p.

41964101 Bollin, E.; Hay, R. (1991) Magnitude of Residues of Velpar and Velpar L Herbicide in Lowbush Blueberries: Lab Project Number: AMR 1431 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 46 p.

41964102 Bollin, E.; Hay, R. (1991) Magnitude of Residues of Velpar and Velpar L Herbicide in Highbush Blueberries: Lab Project Number: AMR 1434 89. Unpublished study prepared by E. I. du Pont de Nemours and Co. 46 p.

42187901 Hawkins, D.; Elsom, L.; Dighton, M.; et al. (1992) The Metabolism of Carbon 14 Hexazinone in the Goat: Lab Project Number: 245/ 91718: AMR 1906 90. Unpublished study prepared by Huntingdon Research Centre Ltd. 105 p.

42219301 Hawkins, D.; Elsom, L.; Dighton, M.; (1992) The Metabolism of Carbon 14 Hexazinone in Laying Hens: The Freezer Storage Stability of Tissues, Eggs and Excreta from Laying Hens Dosed with Carbon 14 Hexazinone: Supplement to: Lab Project Number: HRC/ 203/ 90454; AMR 1517 89. Unpublished study prepared by Huntingdon Research Centre Ltd. 33 p.

42248901 Hawkins, D.; Elsom, L.; Dighton, M. (1992) The Metabolism of Carbon 14 Hexazinone in the Goat, Supplement 1: The Freezer Storage Stability of Carbon 14 Residues in Tissues and Milk from a Lactating Goat Dosed with Carbon 14 Hexazinone: Lab Project Number: HRC/ DPT 245/ 91718: AMR 1906 90. Unpublished study prepared by Huntingdon Research Centre. 36 p.

42276001 Powley, C.; Tomic, D. (1992) Magnitude of the Residue of Velpar Herbicide in Sugarcane and its Processed Fractions: Lab Project Number: AMR 1473 89: 35 5300: 14 5308. Unpublished study prepared by Dupont and Hawaiian Sugar Planters Association. 151 p. 52 42322701 Powley, C.; Tomic, D. (1992) Magnitude of Residues of Velpar Herbicide in Sugarcane: Lab Project Number: AMR 1472 89: 14 5308. Unpublished study prepared by E. I. DuPont de Nemours and Co. and Hawaiian Sugar Planters Assoc. 180 p.

42417901 Mulcahey, L. (1992) Magnitude of the Residues of Velpar Herbicide in Sugarcane and its Processed Fractions (Supplemental): Lab Project Number: AMR 1473 89 (SUPP 1): 35 5300: 14 5308. Unpublished study prepared by E. I. DuPont de Nemours and Co. in coop with the Hawaiian Sugar Planters' Assoc. 40 p.

42418001 Klemens, A.; Tomic, D. (1992) Freezer Storage Stability of Hexazinone and Metabolites in Pasture and Range Grasses. Lab Project Number: AMR 1582 90: A022.005. Unpublished study prepared by E. I. DuPont de Nemours and Co. in coop with Huntingdon Analytical Services. 54 p.

42419101 Mulcahey, L. (1992) Magnitude of Residues of Velpar Herbicide in Pasture and Range Grasses: A Supplement: Lab Project Number: AMR 1429 89: 1022.004: 91012. Unpublished study prepared by E. I. du Pont de Nemours and Co. 89 p.

42423001 Klemens, A.; Devine, P. (1992) Freezer Storage Stability of Velpar Herbicide and Metabolites on Blueberries: Lab Project Number: AMR 1911 90. Unpublished study prepared by E. I. DuPont de Nemours and Co. 47 p.

42492101 Powley, C.; Tomic, D. (1992) Magnitude of Residues of Velpar Herbicide in the Processed Fractions of Pineapples: Lab Project Number: AMR 1471 89: MP 90 03.01: 36 5309. Unpublished study prepared by E. I. du Pont de Nemours & Co. 114 p.

42535601 Powley, C.; Tomic, D. (1992) Magnitude of Residues of Velpar Herbicide in Pineapples: Lab Project Number: AMR 1570 89: 36 5309. Unpublished study prepared by E. I. du Pont de Nemours and Co.; Hawaiian Sugar Planters' Association. 81 p.

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42987201 Powley, C.; Zhou, M.; DeBernard, P. (1993) Method for the Determination of Hexazinone in Sugarcane and Processed Fractions: Lab Project Number: AMR 2654 93. Unpublished study prepared by DuPont Agricultural Products. 30 p.

43025401 Bruns, G. (1993) Independent Laboratory Validation of the Analytical Enforcement Method for the Determination of Hexazinone in Sugarcane, Molasses, and Bagasse by Gas Chromatography: Lab Project Number: DUP69/ REP: AMR/ 2804/ 93. Unpublished study prepared by Enviro Test Labs. 34 p.

43074201 Hawkins, D.; Elsom, L.; Dighton, M.; et al. (1993) A Comparison of (carbon 14) Hexazinone Metabolites in Hen Tissues and Eggs and Goat Tissues and Milk Synthesised Metabolite Standards: Lab Project Number: 294/ 932331: DPT/ 294/ 932331: HRC/ DPT/ 294/ 932331. Unpublished study prepared by Huntingdon Research Centre Ltd. 110 p.

43074401 Djanegara, T.; Devine, P. (1993) Magnitude of Residues of Hexazinone in Alfalfa Forage, Hay, and Seed Grown in the Western United States Following Application of Velpar Herbicide: Lab Project Number: AMR 1924 91: 92013. Unpublished study prepared by E. I. du Pont de Nemours & Co. and Spectralytix, Inc. 330 p.

43074402 Djanegara, T.; Devine, P. (1993) Magnitude of Residues of Hexazinone in Alfalfa Forage and Hay Grown in the Eastern United States Following Application of Velpar Herbicide: Lab Project Number: AMR 2010 91: 92025. Unpublished study prepared by E. I. du Pont de Nemours & Co. and Spectralytix, Inc. 316 p.

43401901 Powley, C.; Devine, P. (1994) Magnitude of Residues of Velpar Herbicide in the Processed Fractions of Pineapples: Supplement No. 1: Lab Project Number: MP/ 90/ 03/ 01: 5309: AMR/ 1471/ 89. Unpublished study prepared by E. I. du Pont de Nemours and Co.; Maui Pineapple Co., Ltd.; and Hawaiian Sugar Planters' Association. 74 p.

43488901 Hawkins, D.; Elsom, L.; Dighton, M. et al. (1994) A Comparison of (carbon 14) Hexazinone Metabolites in Hen Tissues and Eggs and Goat Tissues and Milk With Synthesised Metabolite Standards: Supplement 1: 54 Examples of Calculations and Chromatographic Raw Data: Lab Project Number: DPT 294/ 932331: AMR 2633 93. Unpublished study prepared by Huntingdon Research Centre, Ltd. 94 p.

43524301 Mulcahey, L.; Orescan, D. (1995) Freezer Storage Stability of Hexazinone and Metabolites in Pasture and Range Grasses: Supplement No. 2: Lab Project Number: AMR 1582 90: HAS A022.005: SPX 92020. Unpublished study prepared by DuPont Agricultural Products; Huntingdon Analytical Services; and Spectralytix. 76 p.

43703501 Mulcahey, L.; George, S.; Brisbin, J. et al. (1995) Magnitude of Residues of Hexazinone in Edible Tissues and Milk of Lactating Dairy Cows: Lab Project Number: .

43892401 Djanegara, T.; Reardon Green, L. (1996) Confined Accumulation Study of (4 Carbonyl( carbon 14)) Hexazinone (DPX A3674) in Rotational Crops: Lab Project Number: AMR 2800 93. Unpublished study prepared by DuPont Agricultural Products. 115 p. Relatesto letter L0000071.

43936501 Mulcahey, L. (1996) Freezer Storage Stability of Hexazinone and Metabolites in Pasture and Range Grasses: Supplement No. 3 (Final): Lab Project Number: AMR 1582 90: HAS A022.005: SPX 92020. Unpublished study prepared by DuPont Agricultural Products; Huntingdon Analytical Services and Environmental Analytical Services. 63 p.

44133501 Bollin, E. (1996) Magnitude of the Residue of Hexazinone in Alfalfa Forage, Hay, and Seed Grown in the Western United States Following Application of Velpar Herbicide: Supplement No. 1 to MRID 43074401: Lab Project Number: AMR 1924 91: 92013. Unpublished study prepared by DuPont Agricultural Products and Environmental Analytical Services, Inc. 40 p.