  


EPA REGISTRATION DIVISION COMPANY NOTICE OF FILING FOR PESTICIDE PETITIONS PUBLISHED IN THE FEDERAL REGISTER  

EPA Registration Division contact: Kathryn Montague, 703-305-1243

Syngenta Crop Protection, LLC 

PP# [3F8225]

   EPA has received a pesticide petition PP# [3F8225] from Syngenta Crop Protection, LLC, P.O. Box 18300, Greensboro, NC 27419-8300 requesting, pursuant to section 408(d) of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR part 180

   1. by establishing a tolerance for residues of

   Bicyclopyrone:  4-hydroxy-3-{2-[(2-methoxyethoxy) methyl}-6-(trifluoromethyl)-3-pyridylcarbonyl} bicyclo [3.2.1]oct-3-en-2-one, in or on the raw agricultural commodities: field corn, forage at 0.4 parts per million (ppm); field corn, grain, at  0.02  ppm; field corn, stover at 0.5 ppm; popcorn, grain, at  0.02 ppm, popcorn, stover at 0.5 ppm; sweet corn, forage at 0.40 ppm; sweet corn, ears at 0.04 ppm; sweet corn, stover at 0.50 ppm; and cattle liver at 0.06 ppm. EPA has determined that the petition contains data or information regarding the elements set forth in section 408 (d) (2) of  FDDCA; however, EPA has not fully evaluated the sufficiency of the submitted data at this time or whether the data supports granting of the petition. Additional data may be needed before EPA rules on the petition.


A. Residue Chemistry

   1. Plant metabolism. Syngenta believes the studies supporting this bicyclopyrone petition well characterize metabolism in plants.  The metabolism and distribution of NOA449280 has been investigated in corn. The uptake, distribution and degradation of NOA449280 were investigated in corn by a pre-emergence treatment at 200 g ai/ha for one treatment group and by a pre-emergence treatment at 200 g ai/ha followed by a post emergence treatment at 200 g ai/ha at the 8  -  9 leaf stage for a second treatment group.  Samples were taken from each treatment group at early foliage (28 days after the post emergence application; foliage only), forage (BBCH 75-79; foliage immature cobs and immature grain) and mature crop (BBCH 89; stover, cobs and grain).  
   The total radioactive residues (TRR) of the harvested commodities and the   percentages of the TRR (%TRR) are summarized below: 


                       [14]C-Labeled Ring Test Substance
   


   Relative Maturity


 Sample/ Commodity

     Pre-emergence Application
     Pre- and post- Emergence Application



  TRR, mg/kg
  % TRR
 extracted
  TRR, mg/kg
  % TRR
 extracted





 Bicyclooctenone
 Early foliage
   Foliage
  0.033
   77.7
  0.354
   83.2



   Forage
   Forage
  0.023
   78.3
  0.459
   84.0


   Immature Cobs
  <0.010
                                        NE
  0.029
   89.1


   Immature Grain
  <0.010
                                        NE
  0.037
   91.9



   Maturity
   Stover
  0.032
   79.1
  0.455
   80.8


   Cobs
  <0.010
                                        NE
  0.036
   73.2


   Grain
  <0.010
                                        NE
  0.058
   76.6





    Pyridine
 Early foliage
   Foliage
  0.042
   83.5
  0.440
   93.1



   Forage
   Forage
  0.083
   88.1
  0.925
   90.6


   Immature Cobs
  <0.010
                                        NE
  0.033
   69.7


   Immature Grain
  <0.010
                                        NE
  0.020
   88.8



   Maturity
   Stover
  0.077
   80.7
  0.762
   83.9


   Cobs
  <0.010
                                        NE
  0.018
   77.4


   Grain
  <0.010
                                        NE
  0.025
   78.8
 NE  -  Not extracted as TRR of commodity <0.010 mg/kg 
      	Analysis of the harvested fractions show that NOA449280 was extensively metabolized to a highly complex mixture of components with the principle biotransformations as follows:
      * hydroxylation of the bicyclooctenone ring in at least two positions to produce isomers of monohydroxylated and dihydroxylated NOA449280
      * O-demethylation, and successive oxidation of the methoxyethoxymethyl side chain of NOA449280 to produce desmethyl, carboxyl and alcohol metabolites
      * cleavage between the bicyclooctenone and pyridine ring systems of NOA449280
      * conjugation of some of the above metabolites to form their O-glycosides
      The most significant metabolites contained both the bicyclooctenone and pyridine rings of NOA449280 and had undergone functional group biotransformation of mono- or dihydroxylation of the bicyclooctenone ring and/or O-demethylation of the methoxyethoxymethyl substituent side chain of the pyridine ring.  



                                       
                              Bicyclooctenone-14C
                                 Pyridine -14C
                                 Corn Sample/
                                   Commodity
                                  Metabolite
                                   % of  TRR
                                    Residue
                                    (mg/kg)
                                     % of
                                      TRR
                                    Residue
                                    (mg/kg)
                                    Forage
   NOA449280
                                      1.6
                                     0.007
                                      ND
                                      ND
                                       
CSAA806573 glycoside
                                      NA
                                      NA
                                      4.6
                                     0.042
                                       
CSCD686480 glycoside
                                      NA
                                      NA
                                      1.8
                                     0.017
                                       
CSCD686481
                                      NA
                                      NA
                                      3.0
                                     0.027
                                       
CSAA589691
                                      4.3
                                     0.020
                                      NA
                                      NA
                                       
Total desmethyl dihydroxy NOA449280 isomers1
                                     15.4
                                     0.070
                                     35.7
                                     0.331

Total desmethyl monohydroxy NOA449280 isomers1 
                                     15.3
                                     0.071
                                     21.7
                                     0.200

Total monohydroxy NO449280 isomers1 
                                      4.1
                                     0.019
                                      2.4
                                     0.022

   CSCD677694
                                       ND
                                       ND
  1.8
                                     0.017

CSCD642512
                                       2.0
                                      0.009
  ND
                                      ND
                                    Stover
Total CSAA806573 (includes conjugates)
                                        NA
                                      NA
                                      6.1
                                     0.046

 CSCD686480 glycoside
                                       NA
                                        NA
  3.1
                                     0.024

CSCD686481
                                       NA
                                        NA
  0.8
                                     0.006

CSAA589691
                                       3.8
                                      0.017
  NA
                                      NA

Total desmethyl dihydroxy NOA449280 isomers1
                                     11.3
                                     0.051
                                     21.4
                                     0.163

Total desmethyl monohydroxy NOA449280 isomers1
                                     11.0
                                     0.050
                                     11.7
                                     0.089
                                       
Total monohydroxy NO449280 isomers1
                                       2.1
  0.010
  4.5
    0.034

 CSCD677694
                                       1.6
                                     0.007
                                       ND
                                      ND

 CSCD642512
                                       2.2
                                     0.010
                                       2.6
    0.020
                                 Mature Grain
 CSAA589691
                                      41.7
                                      0.024
                                       NA
                                        NA

Total desmethyl monohydroxy NOA449280 isomers
                                      ND
                                      ND
                                     27.9
                                     0.007

Total monohydroxy NO449280
                                      ND
                                      ND
                                     19.3
                                     0.004

 CSCD642512
  ND
                                        ND
  5.9
                                     0.001
ND = not detected		NA = not applicable
1Total of all isomers with these structural characteristics including specific metabolites, metabolites of undefined substitution specificity, and conjugates 	
Comparison of the qualitative profile of metabolites present in samples from the pre- emergence only application with those from the combined pre- and post-emergence applications demonstrated a high degree of similarity. Metabolism studies conducted in corn and sugarcane have provided a detailed understanding of the biotransformation of NOA449280 in these crops.  The metabolic pathways in these crops are similar.  NOA449280 was found only in corn forage and was absent in all other samples examined.  The majority of the metabolites were formed by hydroxylation on one or more sites on the bicyclic ring or demethylation of the methoxyethoxymethyl side chain followed by hydroxylation.  Some conjugation to glycosides was observed with the hydroxyl derivatives and some cleavage between the two ring systems was also observed. 
      

Analytical method. For data submitted with this petition, the following analytical methods were utilized:

Substrate
                                  Analyte(s)
                                    Method
                  Limit of Quantification
(mg/kg) as reported
                               Method/ Reference
                                   (MRID#) 
Crops
CSCD6864801, SYN5037802, 
CSAA806573
LC-
MS/MS
0.01
0.01
0.01
GRM030.05A
 47841946
Crops
CSAA5896913
LC-MS/MS
0.01
GRM030.09A
47841972
Milk, eggs, tissues
NOA449280, SYN5037802, CSCD6864801
LC-MS/MS
0.01
0.010.01
GRM030.08A
47842046
[1]Residues are determined as CSCD686480 but reported as CSAA915194 equivalents (LOQ 0.01 mg/kg)
[2] Residues are determined as SYN503780 but reported as NOA449280 equivalents (LOQ 0.01 mg/kg)
[3] Only corn grain samples were analysed with method GRM030.09A. 

The LOQ for the various crop and animal matrix methods is 0.01 mg/kg as either NOA449280 or CSAA915194 equivalents. Control samples were analyzed in duplicate and fortified samples were analyzed in quintuplet at the limit of quantification (LOQ, 0.01 ug/L) for each analyte and in quintuplet at ten times the LOQ (0.1 mg/kg).  Acceptable mean recoveries of between 70% and 120% with a relative standard deviation of <20% were found for all matrices. Analytical methods GRM030.03A, GRM030.05A and GRM030.08A have also undergone independent laboratory validation (ILV) to demonstrate the suitability of the methods for the monitoring of residues of NOA449280 in crops and animal tissues. All study methods and validation reports will be submitted with this data package.
3. Magnitude of residues.  A comprehensive program of residue field trials has been conducted to support the use of bicyclopyrone as a selective herbicide for the control of broad leaf weeds and annual grasses in corn. Bicyclopyrone is to be applied from pre-emergence through to early post-emergence using standard spraying equipment.  Bicyclopyrone is generally to be applied once annually at a rate of 50 g bicyclopyrone/ha in corn.  Additionally, a split application pre-emergent and early post emergent maybe used equating to the maximum recommended application/year.  Twenty-nine corn crop-field trials (7 field corn/simulated sweet corn, 7 sweet corn, 12 field corn, and 3 popcorn) were successfully conducted in the United States to support the registration of a soluble concentrate (SL) formulation containing the active ingredient bicyclopyrone.  When the corn was 30 inches tall or at the 8-leaf stage (V8), whichever occurred first, one over-the-top foliar broadcast spray application was made at a nominal rate of 0.045 lb ai/A (50 g ai/ha).  The sample information is summarized in the following table.  

                              SAMPLE INFORMATION
FIELD CORN / SIMULATED SWEET CORN
                                  Sample Type
                                 Sample Event
                                  DAA1 Range
                          Simulated Sweet Corn Forage
                                  Milk Stage
                                     37-54
                           Simulated Sweet Corn Ears
                                  (K+CWHR)[2]
                                  Milk Stage
                                     37-54
                               Field Corn Forage
                                 45 +- 3 DALA 
                        or Late Dough/Early Dent Stage 
                             whichever comes first
                                     41-47
                                       
                                     Grain
                                   Maturity
                                    79-113
                                    Stover 
                                   Maturity
                                    80-113
SWEET CORN 
                                    Forage
                                  Milk Stage
                                     25-51
                                Ears  (K+CWHR)2
                                  Milk Stage
                                     25-51
                                    Stover 
                                  97-99 BBCH
                                     48-96
POPCORN
                                     Grain
                                  At Maturity
                                    98-100
                                    Stover 
                                  At Maturity
                                    98-100
[1] DAA = Days After Application
[2] K+CWHR = Kernels plus cob with husks removed.


The analytical phase was conducted at ABC Laboratories, Columbia, MO.  The analytical methods used to determine bicyclopyrone-related residues in these samples are listed in the following table. 

                             Analytical Method[1]
                                   Matrices
                               Analyte Measured
                              Analyte Equivalent 
NOA449280  -  Analytical Method (GRM030.05A) for the Determination of Residues of NOA449280 and Structurally Related Metabolites as the Moieties SYN503780 and CSCD686480 and for the Determination of CSAA806573 in Crop Matrices. Final Determination by LC-MS/MS  (MRID: 47841946)
                                      All
                                   SYN503780
                                   NOA449280

                                       
                                  CSCD686480
                                  CSAA915194
NOA449280  -  Analytical Method GRM030.09A for the Determination of NOA412101 (CSAA589691) in Field Corn Grain (MRID: 47841972)
                                  Grain Only
                                   NOA412101
                                 (CSAA589691)
                                Not Applicable
[1] See Analytical Phase Report (Appendix 2) for method modifications.

The definition of residue (DoR) for tolerance enforcement in crop and animal commodities is parent NOA449280 and its structurally related metabolites determined as SYN503870 and CSCD686480 by a common moiety method.

Residues of SYN503780 and CSCD686480 were determined in or on all of the samples (via method GRM030.05A).  The mean recoveries from concurrently fortified samples ranging from 0.01 to 0.5 ppm as NOA449280 and CSAA915194 equivalents were within 70-128%.  The relative standard deviation (RSD) was <20%.  These data demonstrate acceptable performance of the analytical method during the conduct of this study.  

Residues of NOA412101 (CSAA589691) were determined in grain samples only (via method GRM030.09A).  The mean recoveries from concurrently fortified samples (from 0.01 to 0.5 ppm) were within 70-120%. The relative standard deviation (RSD) was <20%.  These data demonstrate acceptable performance of the analytical method during the conduct of this study.  

Residues of NOA449280 and CSAA915194 (detected as SYN503780 and CSCD686480 respectively) were not found in any non-treated control samples at levels above 0.01 ppm.  A summary of the residues (sum of the two common moiety analytes) found in corn matrices treated at a nominal application rate of 0.045 lb ai/A (50 g ai/ha) is presented in the following table.

                                    Matrix 
                                     n[1]
         Sum of NOA449280 Related Residues via GRM 030.05A (ppm)[2,3]
                                       
                                       
                                      Min
                                      Max
                                    HAFT[4]
                                    Median
                                     Mean
                                   Std. Dev.
                               Sweet Corn Forage
                                      28
                                      ND
                                     0.280
                                     0.229
                                     0.113
                                     0.117
                                    0.0694
                                Sweet Corn Ears
                                  (K+CWHR)[5]
                                      28
                                      ND
                                    0.0355
                                    0.0346
                                    <LOQ
                                    0.0162
                                    0.0056
                               Sweet Corn Stover
                                      14
                                    <LOQ
                                     0.373
                                     0.291
                                    0.0889
                                     0.143
                                     0.119
                               Field Corn Forage
                                      38
                                      ND
                                     0.229
                                     0.178
                                    0.0974
                                     0.100
                                     0.047
                        Field Corn & Popcorn Grain
                                      44
                                      ND
                                    <LOQ
                                    <LOQ
                                    <LOQ
                                    <LOQ
                                    0.0019
                        Field Corn & Popcorn Stover
                                      44
                                      ND
                                     0.277
                                     0.270
                                    0.0495
                                    0.0731
                                    0.0665
[1] n = number of treated samples
2 The sum of SYN503780 and CSCD686480 expressed as NOA449280 and CSAA915194 equivalents respectively.
[3] LOQ = 0.01 ppm for each analyte (0.02 ppm total). For statistical purposes an individual sample residue value of 0.005 ppm (1/2 LOQ) was used for non-detectable (ND) residues and 0.01 ppm (LOQ) was used for sample residues <LOQ. 
4 HAFT = Highest Average Field Trial
[5] K+CWHR = Kernels plus cob with husks removed.

	Residues of NOA412101 (CSAA589691) were quantified in five of the non-treated control samples ranging from 0.011 to 0.017 ppm. At the time of study initiation the definition of residue had not yet been proposed.  Therefore, analysis of NOA412101 (CSAA589691) was included in this study.  Since that time the Definition of the Residue (DoR) for tolerance enforcement and risk assessment was proposed to be parent NOA449280 and its structurally related metabolites, which are determined as SYN503780 and CSCD686480 by a common moiety method. NOA412101 was not part of the proposed Definition of Residue (DoR).   It appears that NOA412101 (CSAA589691) residues are not unique to bicyclopyrone. A summary of NOA412101 (CSAA589691) residues found in corn grain treated with bicyclopyrone at a nominal application rate of 0.045 lb ai/A (50 g ai/ha) is presented in the following table:



                                    Matrix 
                                     n[1]
                                    Analyte
                       NOA412101 (CSAA589691) Residues 
                           via GRM 030.09A (ppm)[2]
                                       
                                       
                                       
                                      Min
                                      Max
                                    HAFT[3]
                                    Median
                                     Mean
                                      SD
                        Field Corn & Popcorn Grain
                                      44
                                   NOA412101
                                 (CSAA589691)
                                    <LOQ
                                    0.0258
                                    0.0258
                                     0.010
                                    0.0123
                                    0.0038
[1] n = number of treated samples
2 LOQ = 0.01 ppm; for statistical purposes a value of 0.01 was used for <LOQ.
3 HAFT = Highest Average Field Trial

Results from this study support the registration of bicyclopyrone applied to corn at 0.045 lb ai/A (50 g ai/ha).

Cattle Liver

The corn residue data from the 50 g/ha rate residue study (MRID# 49227101) being submitted has an impact on the calculated cattle dietary burdens, the residues that could be found in animal commodities consuming these corn products, and the tolerances proposed for the animal commodities.   Using the 100% Crop Treated (Acute Exposure model) and the Highest Average Field Trial (HAFT) residues from the 50 g/ha rate corn study, the dietary burdens for cattle were calculated to be 0.082 ppm (beef cattle) and 0.34 ppm (dairy cattle).  Applying the residue transfer factors from the dairy cattle feeding study (MRID# 47842154) to these dietary burdens the calculated residues that could be found in the various animal commodities showed that only cattle liver would exceed 0.01 ppm (0.057 ppm in dairy cow liver and 0.014 in beef cattle liver). The tolerance is proposed at 0.06 ppm to cover the higher residue in dairy cow liver.


B. Toxicological Profile

      1.      Acute toxicity.  NOA449280 is of low acute toxicity by the oral, dermal of low acute toxicity by the oral, dermal and inhalation routes of exposure and is not irritating to the eyes or skin.  Under conditions of a local lymph node assay in the mouse NOA449280 is not considered to have a sensitising potential following contact with the skin.  NOA449280 SL (A16003E) is of low acute toxicity by the oral, dermal and inhalation routes. It is not irritating to the skin and only slightly irritating to the eye. It is a sensitizer in the Buehler test in the guinea pig. NOA449280 ZC (A19707A) is of low acute toxicity by the oral, dermal and inhalation routes. It is moderately irritating to the skin and to the eye. It is a sensitizer in the Buehler test in the guinea pig. NOA449280 is of low acute toxicity by the oral, dermal and inhalation routes of exposure and is not irritating to the eyes or skin.  Under conditions of a local lymph node assay in the mouse, NOA449280 is not considered to have a sensitising potential following contact with the skin.  NOA449280 SL (A16003E) is of low acute toxicity by the oral, dermal and inhalation routes. It is not irritating to the skin and only slightly irritating to the eye. It is a sensitizer in the Buehler test in the guinea pig. NOA449280 ZC (A19707A) is of low acute toxicity by the oral, dermal and inhalation routes. It is moderately irritating to the skin and to the eye. It is a sensitizer in the Buehler test in the guinea pig.  A summary of the acute toxicity studies are cited below: 


                                Hazard Indicator
                                (Guideline No.)
                                        
                            Bicyclopyrone Technical
                                  (NOA449280)
                                   SYNA16003
                                      (SL)
                                 SYNA19707 (ZC)
                          Tox Category (respectively)
 Acute Oral LD50, Rat
 (870.1100)
                              LD50 >5000 mg/kg
                              LD50 >5000mg/kg
                                       
                                LD50= 1750mg/kg
                                        
                                 IV , IV,  III
 Acute Dermal LD50, Rat
 (870.1200)
                                     LD50
                                >5000 mg/kg
                                     LD50
                                 >5000mg/kg
                                        
                                        
                                     LD50 
                                 >5000 mg/kg
                                   IV, IV, IV
  Acute Inhalation LC50, Rat
  (870.1300)
                                       
                              LC50 >5.21 mg/L
                              LC50 >5.08 mg/l
                                       
                                       
                                       
                              LC50 >2.59 mg/l
                                        
                                   IV,IV, IV
 Eye Irritation, Rabbit
 (870.2400)
                                 Not irritant
                               Slightly irritant
                                       
                             Moderately irritating
                                        
                                  IV, IV, III
 Skin Irritation, Rabbit
 (870.2500)
                                 Not irritant
                                 Not irritant
                                       
                             Moderately irritating
                                        
                                  IV, IV, III
 Skin Sensitization
 (LLNA)
 (870.2600)
                                   Negative
                                  Sensitizer
                                       
                                       
                                  Sensitizer
                                        
                                 Not Applicable

      
            2. Genotoxicity. Bicyclopyrone has been examined in a range of in vitro and in vivo genotoxicity assays, including end points of gene mutation, chromosomal damage and DNA repair.  NOA449280 is not mutagenic to bacterial or mammalian cells in vitro and is not clastogenic in human lymphocytes in vitro. It is not clastogenic and does not induce DNA repair in vivo.  NOA449280 shows no genotoxic potential either in vitro or in vivo.
      3. Reproductive and developmental toxicity. 


      Reproductive

            The potential reproductive toxicity of NOA449280 has been studied in a multigeneration study in the rat.  Dose levels of 0, 25, 500 or 5000ppm, selected on the basis of a preliminary range finding study, were administered in the diet to groups of 25 male and 25 female F0 generation  rats. Treated diet was administered continuously throughout pre-mating and mating in both sexes and to females throughout gestation and lactation until pups were weaned at day 21. Selected pups were then maintained on diet, forming the F1 generation, were mated at weeks old and females were maintained until the F2 litters were weaned. NOA449280 had no toxicologically significant effect on reproductive parameters in either generation. In adults, lower bodyweight and bodyweight gain were noted in F0 and F1 animals at 5000ppm and in F1 animals at 500ppm. Systemic toxicity was evident in adults at 500 ppm and above including corneal opacity, histopathological and weight changes in the thyroid reflecting minor perturbations in thyroid homeostasis and increased kidney weight accompanied by histopathological changes in the kidney, pelvic dilatation, in F1 animals only. At 25 ppm ocular opacity was noted in F0 males and in F1 males and females. The NOAEL for systemic toxicity in adults was considered to be < 25 ppm based on ocular effects. The relevance of such effects in rats on human risk assessment is recognized as being low. In pups, body weights gain was reduced in F1 and F2 pups at 5000ppm and in F1 pups at 500ppm. Treatment related ocular effects and kidney weight increase were also evident at these dose levels. The NOAEL for systemic toxicity and sexual development in the offspring was considered to be 25ppm. 
      
Developmental
      
            A range of developmental toxicity studies have been conducted with NOA449280 comprised of a dose range-finding study and guideline compliant study in the Wistar rat, and dose range-finding and guideline compliant studies in two strains of rabbit: New Zealand White and Himalayan.
            Groups of 24 bred female Wistar rats were administered NOA449280 by oral gavage at dose levels of 0, 100, 500 or 1000 mg/kg/day on gestation days 6-20, and cesarean section performed on gestation day 21.  Effects on maternal body weight and weight gain were observed at all doses tested, and food consumption was depressed at the two highest doses tested (500 and 1000 mg/kg/day).  There was no evidence of a teratogenic response.  Pelvic girdle mal-positioning (alternatively diagnosed as the presence of 27 pre-sacral vertebrae in other laboratories) along with extra rib(s) was observed in all dose group.  Slight changes in the pattern of ossification were also observed in the foetuses. Effects seen in foetal rats were categorized as variations or slight delays in ossification that would not be expected to have any long-term effects on survival and development.
            In the New Zealand White rabbit, dose levels of 0, 10, 50 or 200 mg/kg/day were selected based on preliminary studies.  Groups of 25 bred females were administered NOA449280 by gavage on gestation days 7-28, and cesarean section performed on gestation day 29.  Significant maternal toxicity was noted at 200 mg/kg/day, with decreases in body weight gain and food consumption leading to the loss of approximately 28% of the animals at this dose level due to euthanasia, abortion and/or early deaths.  There were no treatment-related malformations noted at external or visceral examination. Despite having exceeded the MTD, minimal evidence of an increase in a single grouping of skeletal changes, that was considered a malformation in this strain, was noted. These changes, classified as costal cartilage anomalies, though seen at a low incidence, were outside the historical control range. At 50 mg/kg/day, a low incidence of costal cartilage anomalies was within the historical control, though an association with treatment could not be excluded.  The only statistically significant treatment-related changes observed in the New Zealand White rabbit foetuses were increased incidences of an extra vertebra (27 pre-sacral vertebrae) and an extra (13[th]) pair of ribs in all dose groups.  Maternal tyrosine was elevated at all dose levels and skeletal effects of this nature have been shown to be associated with plasma tyrosine elevations, consistent with HPPD inhibition, the known mode of action of NOA449280.  These effects are considered to be of no toxicological significance.
            Two separate studies were conducted with the Himalayan rabbit over a range of dose levels from 1- 250 mg/kg/day.  The data generated in this strain presented a different picture than that seen in the New Zealand White. Maternal toxicity demonstrated in this strain was substantially less evident; a low incidence of maternal mortality and lower body weight gain was observed at 250 mg/kg/day in one of the two studies.  
            Foetal examination produced profiles of two separate responses to treatment. At 10 mg/kg/day and above, minor skeletal changes consisting of an increase in the foetal incidence (but not the litter incidence) of supernumerary ribs was observed. At 50 mg/kg/day and above, increases in the litter incidence of caudal displacement of the pelvic girdle (27 pre-sacral vertebrae) and supernumerary ribs were seen. These variations, which are commonly observed in rabbits, have been shown to be associated with elevated plasma tyrosine and were likely a reflection of the increase in tyrosine seen in the maternal plasma The flat dose-response in these changes parallels the plasma tyrosine levels measured in these rabbits, which rapidly reached an apparent plateau.   Similar skeletal changes were also observed in the New Zealand White rabbit and were correlated with elevated tyrosine. The biological significance of these changes is questionable, and they are generally regarded as of little or no toxicological significance.
            Superimposed on this background of tyrosine-related minor skeletal changes was an increase in the overall malformation rate at the high dose level (250 mg/kg/day) in both Himalayan rabbit studies.  The malformations affected different organs/structures and were observed at visceral and skeletal examination.  At 50 mg/kg/day, there was a slight (non-significant) increase in the incidence of skeletal malformations. These changes were considered to be effects of NOA449280.  
            Overall, the NOAEL for maternal animals was considered to be 50 mg/kg/day in both strains of rabbit. At a dose level of 10 mg/kg/day, the only treatment-related foetal effects noted were minor changes which are considered non-adverse, or transient in nature; this dose represents a no-observed-adverse effect level (NOAEL) in both strains of rabbit.  A dose of 1 mg/kg/day has been clearly identified as a no-observed-effect level (NOEL).

            4. Subchronic toxicity. The short-term toxicity of bicyclopyrone has been evaluated by the oral route of administration in rats, dogs and mice.  In addition, dermal toxicity was evaluated in rats in a 28-day study. 
      
      Rat
      
            NOA449280 was administered in the diet to rats for 90-days in two studies, one a preliminary study in the AlpkAPfSD rat (Rattray 2003) at dose levels 500, 2000 or 5000ppm and one OECD guideline study in the Han Wistar rat (Shearer 2009) at dose levels 2.5, 10, 2500 or 5000ppm. In neither study was there a clear treatment related effect on clinical observations, functional observational battery (FOB), haematology or blood clinical chemistry parameters. In common with other inhibitors of 4-hydroxyphenyl pyruvate dioxygenase (HPPD), the rat is the most sensitive species and toxicity noted in both studies in this case is attributable to significantly elevated plasma tyrosine concentrations. Dose levels of 2500ppm bicyclopyrone and above resulted in reduced body weight and weight gain in both sexes. The characteristic sign of tyrosine toxicity, corneal opacity/keratitis, was noted in both sexes at dose levels 500ppm and above. Increased kidney weights were noted in males at dose levels of 500ppm and above but despite a tenfold increase in dose level there was no clear dose relationship and no accompanying histopathological change in the kidney. Similarly an increase in liver weight was noted at dose levels of 500ppm and above in males and 2000ppm and above in females. As with the kidney there was no clear dose response and the change was not accompanied by any significant changes in clinical chemistry or histopathology of the liver. The NOAEL in the 90 day rat studies was 10ppm (equivalent to 0.72 /0.88g/kg bwt/day for males and females, respectively).
      
            In a 28-day dermal toxicity study,  histopathological effects in the cornea, keratitis and minimal degeneration of the corneal epithelium, were noted in a small number of animals of sexes at 1000 and 250 mg/kg/day. Minor increases in liver weights (< 120% of control) in dosed males were within the historical control range and in the absence of any associated differences in histopathology or clinical chemistry were concluded to be of no toxicological significance. Similarly minor increased in kidney weights in males were without histopathological correlates and were considered to be of no toxicological significance. The 28-day dermal NOAEL was concluded to be 50 mg/kg/day. 
      
      Mouse
      
            NOA449280 was administered in the diet to mice for 90 days at dose levels 100, 3500 or 7000ppm to establish suitable dose levels for an 80 week carcinogenicity study. Administration of 7000ppm (equivalent to > 1000mg/kg bwt/day), the limit dose for this study type, to CD-1 mice did not adversely affect bodyweight or haematology parameters. Dose levels of 7000 and 3500ppm resulted in increased liver weight accompanied by minimal hepatocyte hypertrophy. At 100ppm minimal increase in liver weight in females only was not accompanied by any change in liver histopathology and was therefore considered not to be of toxicological significance. A dose level of 100ppm (equivalent to 15.4/20.8 mg/kg bwt/day in males and females respectively) was concluded to be the NOAEL for this study.
      
      Dog
      
            In a 28 day study at dose levels 10, 100 or 250 mg/kg the male dog dosed with 250 mg/kg bwt/day NOA449280 was killed for humane reasons after 7 days of dosing; the top dose group was therefore terminated. Treatment related clinical observations included hypoactivity, unsteady gait, nystagmus, opisthotonus, rapid heart rate and vomiting. No adverse pathology was noted in central or peripheral nervous system. There were no adverse effects of treatment following 28 days dosing at the lower dose levels of 100 and 10 mg/kg/day. Plasma tyrosine levels and increased levels of tyrosine metabolites in the urine were noted at all dose levels and considered to reflect exposure toNOA449280.  A dose level of 125 mg/kg/day was selected as the top dose level for the 90 day study Following 90 days dosing at a maximum of 125 mg/kg no adverse effects were noted on bodyweight, clinical observations, haematology or histopathology of organs examined. A decrease in cholesterol was noted in both sexes at 125 mg/kg. An increase in liver weight was noted in females only at 125 mg/kg but in the absence of any histopathological changes or any similar change noted in the subsequent 1 year study this finding was considered adaptive and of no toxicological significance. A dose of 125 mg/kg bwt/day NOA449280 was concluded to be the NOAEL for the 90 day study in dogs. In the 1 year study at dose levels of 2.5, 25 or 125 mg/kg one male from the top dose group was found dead after 336 days; there had been no prior clinical signs. Signs of toxicity in all animals included corneal opacity and keratitis in some males and females at 125 and 25 mg/kg and histopathological changes in the nervous system, chromatolysis and swelling of selected neurones in the dorsal root ganglion and minimal fibre degeneration in the sciatic nerve in some dogs from all dosed groups. A dose level of 2.5 mg/kg/wt NOA449280 was reported to be the LOEL for the 1 year dog study.  Syngenta concludes the No Observed Adverse Effect level (NOAEL) for the 52-week toxicity study in dogs is 2.5 mg/kg based on an increase in corneal opacity in dogs treated with 25 mg/kg and above.

            5. Chronic toxicity. The long-term toxicity and carcinogenic potential of NOA449280 has been evaluated in a 104 week study in the rat which included a 52 week long-term toxicity phase and in an 80 week carcinogenicity study in the mouse.

		Rat

            NOA449280 was administered in the diet to Han Wistar rats for 104 week in an OECD 453 guideline study (Robertson and Perry 2012) at dose levels of 0, 5, 500, 2500 and 500ppm. In common with other inhibitors of 4-hydroxyphenyl-pyruvate dioxygenase (HPPD) corneal opacity accompanied by keratitis and regenerative hyperplasia of the cornea was evident from week 4 of dosing until the end of the treatment period in animals given diets containing 500ppm NOA449280 and above. The findings were noted to be more severe in male rats and towards the end of the 104 week period a low incidence of squamous cell carcinomas and papillomas were noted in male rats at 50ppm and above. Similar tumours have been noted with other HPPD inhibitors in 104 week studies in the rat and are considered to be attributable to the continued damage to, and consequent regenerative hyperplasia of, the corneal epithelium in this most sensitive species. A clear No Observed Adverse Effect Level (NOAEL) for toxicity to the cornea was identified as 5ppm.  Other toxicities identified in the NOA449280 chronic/carcinogenicity study in the rat and identified as resulting from chronic systemic exposure to significantly elevated tyrosine are an increased incidence of thyroid hypertrophy and hyperplasia, indicative of a perturbation in thyroid function  and an increased incidence of chronic glomerulonephropathy, accompanied by elevated covariant kidney weights and changes in urinary proteins, in males rats. The NOAEL for these findings was concluded to be 5ppm NOA449280.  Other treatment related findings including an increased incidence of acinar atrophy of the pancreas in male rats and a decrease covariant heart weight, accompanied in male rats by a decreased incidence of cardiomyopathy, had clear NOAEL at 500ppm.


		
		

		Mouse

            NOA449280 was administered in the diet to CD-1 mice for 80 weeks in an OECD 451 guideline study (Robertson and Perry 2012). In contrast to the toxicities noted in the rat but consistent with findings noted for other HPPD inhibitors (Lewis and Botham 2012) long-term dosing of up to the limit dose of NOA449280 resulted in few adverse effects in the mouse. At the top dose of 7000ppm a slight reduction in bodyweight and bodyweight gain was noted in both sexes and an increased liver weight was accompanied in males only by an increased incidence of mild centrilobular hepatocyte hypertrophy. There was a numerically higher incidence of bronchio-alveolar adenomas in male mice receiving 7000 ppm NOA449280. However, no similar finding was noted in females and there were no other histopathological changes in the lung. Although higher than the study control, the incidence at 7000ppm was within the control range of studies running concurrently in the conducting laboratory. This numerically higher incidence of bronchio-alveolar adenomas in male mice at 7000ppm was concluded not to be related to treatment with NOA449280.  A clear NOAEL for the 80 week study in the mouse was 1700ppm equivalent to 233 and 242 mg/kg bwt/day in male and female mice respectively.  Dietary dosing of NOA449280 for 104 weeks to rats has been shown to result in squamous cell tumors of the cornea which are associated with constant damage and repair of the corneal epithelium and can be attributed to the significantly elevated tyrosine levels resulting from HPPD inhibition in this most sensitive species. Although it is known that inhibition of HPPD in humans can result in elevated tyrosine a detailed analysis of the mode of action and its relevance to humans against accepted scientific criteria has shown that humans are unlikely to exhibit the toxicities seen in the rat (Lewis and Botham 2012). In addition, the US EPA have recognized that data available for HPPD inhibitors support the view that the high levels of plasma tyrosine seen in male rats and the consequent corneal damage is unlikely to be seen in humans (Hazard Science Policy Council Memo D 341612 dated 07/02/2007). Therefore, the tumors noted in male rats are considered to be rat specific and not relevant for human risk assessment.

            No treatment-related tumors were identified in the mouse following dietary dosing a limit dose (approximately 1000mg/kg bwt/day) for 80 weeks. It is concluded that NOA449280 does not present a carcinogenic hazard to humans.
            
            6. Animal metabolism. The metabolism and distribution of bicyclopyrone has been investigated in livestock, using laying hens and lactating goats as representative species for poultry and ruminates, respectively.  In each study bicyclopyrone radiolabelled with 14C in either pyridinyl or bicyclooctenone ring was used.  
		Poultry 
            The absorption, distribution, metabolism and excretion of [pyridinyl-14C] NOA449280 and [bicyclooctenone-14C] NOA449280 were investigated following repeated oral administration to the laying hen.  Excretion balance and tissue distribution investigations were performed following repeated oral administrations for 10 consecutive days at a nominal dose level of 20 mg NOA449280/kg of dry diet.  The total radioactive recovery was 81% and 79% for the pyridinyl and bicyclooctenone labels respectively.  The majority of the administered radioactivity was recovered in the excreta (pyridinyl label: 76%, bicyclooctenone label: 76%).
            The highest residues were found in liver (1.752 mg/kg and 1.776 mg/kg for pyridinyl and bicyclooctenone labels respectively) and accounted for only ca 0.3% of the administered dose.  Residue levels in other commodities such as egg yolk, egg white, muscle, peritoneal fat and skin and subcutaneous fat were low and in total accounted for <0.25% of the administered dose for both radiolabels.  Radioactive residues in eggs (mean for a 24 hour period) reached a plateau of 0.10 mg/kg in both labels at approximately 6 to 8 days.
            Each of the samples along with excreta was analyzed for characterization and identification of metabolites and to elucidate the biotransformation of NOA449280 in laying hens.  Results from analysis of samples from both radiolabels provided the following observations:
         * Radioactive residues in edible tissues consisted predominantly of NOA449280
         * There was no appreciable difference in excretion profiles between the radiolabels
         * Eggs contributed a minor route of excretion of the radioactivity
            
		Lactating Ruminants
            The absorption, distribution, metabolism and excretion of [pyridinyl-14C] NOA449280 and [bicyclooctenone-14C] NOA449280 were investigated following repeated oral administration to the lactating goat.  Excretion balance and tissue distribution investigations were performed following repeated oral administrations for 7 consecutive days at a nominal dose level of 30 mg NOA449280/kg of dry diet. The total radioactive recovery was 87% and 82% for the pyridinyl and bicyclooctenone labels respectively.  The majority of the administered radioactivity was recovered in the urine (pyridinyl label: 60%, bicyclooctenone label: 62%).
            The highest residues were found in liver (2.726 mg/kg and 2.965 mg/kg for pyridinyl and bicyclooctenone labels respectively) and accounted for only ca 0.7% of the administered dose.  Residue levels in other commodities such as kidney, muscle and fat were low and in total accounted for <0.1% of the administered dose for both radiolabels.  Radioactive residues in milk (mean for a 24 hour period) reached a plateau of about 0.008 mg/kg for both labels at approximately 2 to 3 days.
            Each of these samples along with the urine, faeces and bile were analyzed for characterization and identification of metabolites and to elucidate the biotransformation of NOA449280 in lactating goats.  Results from analysis of samples from both radiolabels provided the following observations:
         * The principal components present in tissues and milk were unchanged parent and the desmethyl metabolite CSAA915194.  Other minor metabolites were found in liver
         * O-demethylation produced the metabolite CSAA915194
         * Hydroxylation of the bicyclooctenane ring occurred in 2 or more positions.
         * Trace levels of a pyridine specific metabolite were observed indicating that cleavage of the rings was a very minor pathway
         * Very little conjugation was observed
         * There was no appreciable difference in excretion profiles between the radiolabels and distribution of residues was essentially the same for both labels
         * Milk contributed a minor route of excretion of the radioactivity
      
            Metabolism studies conducted in laying hens and lactating goats have provided a detailed understanding of the biotransformation of NOA449280 in livestock.  The metabolic pathways in these species are similar. Tissue residues in both animals consisted primarily of parent NOA449280 and CSAA915194 (desmethyl parent) and several very minor metabolites found in the liver for the goat and several samples for the laying hen.  Analysis of the excreta and urine provided a more detailed understanding of the biotransformation of NOA449280 in these animals and allowed for a comparison of the metabolic pathways with that found in the rat.  Both animals, goat and hen, show similar biotransformation pathways for NOA449280. The primary metabolic processes observed include O-demethylation, oxidation on one or more sites of the bicyclooctenone ring, a minor amount of bridge cleavage between the rings, and conjugation to some extent.  Eggs and milk were minor routes of excretion for NOA449280.

            7. Metabolite toxicology. Metabolites that are common to crop and mammalian metabolic pathways have been assessed as part of the in vivo toxicological assessment of Bicyclopyrone. In addition, based on structural analysis, crop degradates are considered to have lower toxicity potential than parent Bicyclopyrone and to be of no toxicological significance.

            8. Endocrine disruption. The bicyclopyrone safety database does not contain any indication of a potential for direct effects of the compound on the mammalian endocrine system.

            9. Immunotoxicity. The purpose of this study is to provide information on suppression of the immune system which might occur as a result of repeated exposure to a test chemical. Based on the results of this study, treatment of female Crl:CD-1(ICR) mice with NOA449280 in the diet for a minimum of 28 consecutive days did not result in suppression of the humoral component of the immune system. The no-observed-effect level (NOEL) for immune suppression was 5000 ppm (equivalent to 1192.3 mg/kg/day). The only effect attributed to NOA449280 was higher liver weights noted for the 50, 500, and 5000 ppm groups; this effect was not considered to be adverse. There were no indications in this study that NOA449280 was immunotoxic. Similarly, data from subchronic, chronic, and reproductive toxicity studies of NOA449280 in the rat, mouse and dog, as appropriate, did not provide any evidence of an effect of NOA449280 on the immune system. Based on data from all relevant studies, Syngenta concludes that there is no evidence of immunotoxicity associated with NOA449280, and therefore, no need to conduct additional immunotoxicity assessments, specifically a natural killer cell (NKC) activity assay. 

C. Aggregate Exposure

            1. Dietary exposure. Tier III acute and chronic dietary exposure evaluation was completed for bicyclopyrone (NOA449280) using the Dietary Exposure Evaluation Model (DEEM-FCID[TM]), version 3.16 from Exponent.  DEEM-FCID software incorporates food consumption data from the National Health and Nutrition Examination Survey)/ "What We Eat in America" (NHANES/WWEIA) dietary survey conducted in 2003-2008. These exposure assessments included the proposed use on corn (including field corn, sweet corn and popcorn).  In addition to the corn use, a sugarcane import tolerance was proposed for bicyclopyrone.  All residues were below the LOQ (0.01 ppm) at the 1X label rate and no residues in sugarcane stalks were found even at exaggerated label rates of 3X and 5X.  As such, dietary exposure contribution from imported sugar considered negligible and imported sugar was not included in the risk assessments.  The assessments utilized residue data from field trials where bicyclopyrone was applied at the maximum intended use rate and samples were harvested at the minimum pre-harvest interval (PHI) to obtain maximum residues.  Percent of crop treated values were estimated based upon economic, pest and competitive pressures.  Secondary residues in animal commodities were estimated based on "maximum reasonably balanced diets" and transfer information from feeding studies.  Drinking water estimates were incorporated directly into the dietary exposure assessment using the higher of the estimated drinking water concentrations (EDWCs) for surface and ground water.  
            
            i. Food. Acute Exposure. The acute dietary (food only) risk assessment for females 13 to 49 years old was performed using an acute reference dose (aRfD) of 0.1 mg/kg-bw/day, based upon a rabbit developmental toxicity study with a no observed adverse effect level (NOAEL) of 10 mg/kg/day and an uncertainty factor (UF) of 100X for intra- and inter-species variations; no additional FQPA safety factor was applied.  Acute (food only) exposure to the females 13 to 49 years old resulted in a MOE of 290,215 (<0.1% of the acute RfD of 0.1 mg/kg-bw/day).  The acute dietary (food only) risk assessment for all general population subgroups was performed using an acute reference dose (aRfD) of 0.5 mg/kg-bw/day, based upon a New Zealand white rabbit maternal toxicity study with a no observed adverse effect level (NOAEL) of 50 mg/kg/day and an uncertainty factor (UF) of 100X for intra- and inter-species variations; no additional FQPA safety factor was applied.  The most sensitive sub-population within the infants and children population subgroups was children 1-2 years old with a MOE of 442,131 (<0.1% of the acute RfD of 0.5 mg/kg-bw/day).  Since the benchmark MOE for this assessment was 100 and since the EPA has no concern for exposures resulting in a MOE above the Benchmark MOE or below 100% of the reference dose, Syngenta believes that there is a reasonable certainty that no harm will result from dietary (food only) exposure to residues arising from the proposed uses for bicyclopyrone.
            
            Chronic Exposure.  The bicyclopyrone chronic dietary (food only) risk assessment was performed for all population subgroups with a chronic reference dose of 0.0028 mg/kg-bw/day based on a chronic rat chronic study a no observed adverse effect level (NOAEL) of 0.28 mg/kg-bw/day and an uncertainty factor of 100X for intra- and inter-species variations; no additional FQPA safety factor was applied.  For the purpose of the aggregate risk assessment, exposure values were expressed in terms of margin of exposure (MOE), which was calculated by dividing the NOAEL by the exposure for each population subgroup.  In addition, exposure was also expressed as a percent of the reference dose (%RfD).  Chronic (food only) exposure to the U.S. population resulted in a MOE of 48,182 (2.1% of the chronic RfD of 0.0028 mg/kg-bw/day).  The most sensitive sub-population was children (3-5 years old) with a MOE of 20,338 (4.9% of the chronic RfD).  Since the benchmark MOE for this assessment was 100 and since the EPA has no concern for exposures resulting in a MOE above the Benchmark MOE or below 100% of the reference dose, Syngenta believes that there is a reasonable certainty that no harm will result from dietary (food only) exposure to residues arising from the proposed uses for bicyclopyrone.

            Cancer.  Bicyclopyrone is considered "not likely to be a human carcinogen".  Therefore, no cancer dietary risk assessment was performed for bicyclopyrone.

            ii. Drinking water. The Estimated Drinking Water Concentrations (EDWCs) of NOA449280 from proposed use on corn were determined using Tier I FIRST and Tier II PRZM/EXAMS which estimate pesticide concentration in surface water; Tier l SCI-GROW and data from NOA449280 field studies which are appropriate for estimating potential pesticide concentrations in ground water. The surface water EDWCs resulting from PRZM/EXAMS modeling were 2.365 ppb and 0.689 ppb for acute and chronic, respectively. The ground water EDWCs determined from NOA449280 small scale field studies were 0.35 ppb and 0.22 ppb for acute (peak) and chronic (annual average), respectively. Since the surface water EDWCs exceed the ground water EDWCs, the surface water values were used for risk assessment purposes and will be considered protective for any ground water concentration concerns.  

            Acute Exposure from Drinking Water.  The acute surface water EDWC of 2.365 ppb was input directly into the DEEM-FCID(TM) software as "water, direct and indirect, all sources" to model the acute drinking water exposures.  Exposure contributions at the 99%-ile of exposures were determined by taking the difference between the aggregate (food + drinking water) exposures and the food (alone) exposures for each population subgroup.  Acute drinking water exposure U.S. population resulted in a MOE of 139,276 (0.1% of the acute RfD of 0.5 mg/kg-bw/day).  The most exposed sub-population was females 13-49 years old with a MOE of 42,194 (0.2% of the aRfD of 0.1 mg/kg/day).  Since the benchmark MOE for this assessment was 100 and since EPA generally has no concern for exposures below 100% of the acute RfD, Syngenta believes that there is a reasonable certainty that no harm will result from acute drinking water exposure to residues arising from the current uses for NOA449280.

            Chronic Exposure from Drinking Water.  The chronic surface water EDWC of 0.689 ppb was input directly into the DEEM-FCID(TM) software as "water, direct and indirect, all sources" to model the chronic drinking water exposures.  Chronic drinking water exposure to the U.S. population resulted in a MOE of 19,408 (0.5% of the chronic RfD of 0.012 mg/kg-bw/day).  Chronic drinking water exposure to the most exposed sub-population (infants, <1 year old) resulted in a MOE of 7,527 (1.3% of the chronic RfD of 0.0028 mg/kg-bw/day).  Since the Benchmark MOE for this assessment was 100 and since EPA generally has no concern for exposures below 100% of the chronic RfD, Syngenta believes that there is a reasonable certainty that no harm will result from chronic drinking water exposure to residues arising from the current uses for NOA449280.

            2. Non-dietary exposure. There are currently no planned uses for bicyclopyrone that would result in residential handler (mixer/loader/applicator) or post-application exposure.  A nondietary exposure risk assessment is therefore was not performed for bicyclopyrone.
      
D. Cumulative Effects

            Cumulative Exposure to Substances with a Common Mechanism of Toxicity.  Section 408(b)(2)(D)(v) requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider "available information" concerning the cumulative effects of a particular pesticide's residues and "other substances that have a common mechanism of toxicity".  The EPA does not have, at this time, available data to determine whether bicyclopyrone has a common mechanism of toxicity with other substances or how to include this pesticide in a cumulative risk assessment.  For the purposes of this tolerance action, the EPA has not assumed that bicyclopyrone has a common mechanism of toxicity with other substances.

E. Safety Determination

            1. U.S. population. The acute dietary exposure analysis (food plus water) showed that exposure from the proposed bicyclopyrone crop uses resulted in a MOE of 119,073 (0.1% of the acute RfD of 0.5 mg/kg-bw/day) for the general U.S. population.  For the acute aggregate assessments, females 13-49 years old were the most sensitive subgroup with an acute aggregate MOE of 36,917 or 0.3% of the aRfD (Benchmark MOE = 100; aRfD = 0.1 mg/kg/day).  The chronic dietary exposure analysis (food plus water) showed that exposure from proposed bicyclopyrone crop uses result in a MOE of 13,835 (2.6% of the chronic RfD of 0.0028 mg/kg-bw/day) for the general U.S. population.  Based on the completeness and reliability of the toxicity data supporting these petitions, Syngenta believes that there is a reasonable certainty that no harm will result from aggregate exposure to residues arising from all proposed bicyclopyrone uses, including anticipated dietary exposure from food, water, and all other types of non-occupational exposures.  

            2. Infants and children. The acute dietary exposure analysis (food plus water) showed that exposure from all proposed bicyclopyrone uses would result in a MOE of 61,997 (0.2% of the acute RfD of 0.5 mg/kg-bw/day) for infants less than one year old population subgroup.  The chronic dietary exposure analysis (food plus water) showed that exposure from all proposed bicyclopyrone uses would result in a MOE of 5,840 (5.1% of the chronic RfD of 0.0028 mg/kg-bw/day) for infants less than one year old (the most sensitive population subgroup).  Since all aggregate MOEs exceed the benchmark MOE of 100, Syngenta believes that there is a reasonable certainty that no harm will occur to infants and children from aggregate exposure to residues arising from all proposed bicyclopyrone uses, including anticipated dietary exposure from food, water and all other types of non-occupational exposures.


      F. International Tolerances

            There are currently no Maximum Residue Limits (MRLs) set for bicyclopyrone for crops by the Codex Alimentarius Commission and international MRLs for the herbicide bicyclopyrone have not been established.



