i

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# [2E8098]

EPA has received a pesticide petition PP# ([2E8098]) 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 an import 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: sugarcane, stalks at 0.01 parts per million (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 profile supports the use of an 

analytical enforcement method that accounts for parent bicyclopyrone. The 

metabolism and distribution of NOA449280 has been investigated in corn and 

sugarcane. For this study, NOA449280 radiolabelled with 14C in either the 

pyridine or the bicyclooctenone ring was used. The uptake, distribution and 

degradation of NOA449280 were investigated in sugarcane by a single treatment 

at a nominal rate of 300 g ai/ha post emergence to the cane at the 7-8 leaf stage 

(BBCH 17-18). Foliage samples were taken 42 days after treatment (BBCH 23-

24) to facilitate determination of the biotransformation pathway. Foliage (all 

leaves) and cane were collected at maturity, 301 days after treatment (BBCH 39). 

The total radioactive residues (TRR) of the harvested commodities and the 

percentages of the TRR (%TRR) are summarized below.
2

Radiolabelled 

experiment Relative Maturity Sample/Commodity

TRR

mg/kg

% TRR

Extracted1

Bicycloocetenone

42 DAT Foliage 0.778 85.4

Maturity (301 DAT) Foliage 0.004 Not extracted2

Sugarcane 0.002 Not extracted2

Pyridine

42 DAT Foliage 0.888 88.5

Maturity (301 DAT) Foliage 0.003 Not extracted2

Sugarcane 0.004 Not extracted2

1Extractable radioactivity prior to aqueous extraction and hydrolysis

2The maturity samples were not extracted or analyzed since the TRR was < 0.01 mg/kg

Due to the low residues of the mature samples, the 42 DAT samples for both radiolabels 

were used to elucidate the biotransformation of NOA449280 in sugarcane. Analysis of 

these samples shows an absence of parent NOA449280 and that extensive metabolism 

has occurred with the principle biotransformations as follows:

 hydroxylation of the bicyclooctenone ring in at least two positions to produce

isomers of monohydroxylated and dihydroxylated NOA449280

 cleavage between the bicyclooctenone and pyridine ring systems of NOA449280

 O-demethylation, and successive oxidation of the methoxyethoxymethylside chain

of NOA449280 to produce desmethyl, carboxyl and alcohol metabolites

 conjugation of some of the above metabolites to form their O-glycosides

The largest percentage of the residue contained metabolites where the bicyclooctenone

ring of NOA449280 had undergone mono-hydroxylation or mono-hydroxylation and Odemethylation of the methoxyethoxymethyl side chain. These combined metabolites 

accounted for 50-55% of the TRR. Di-hydroxylation of the bicyclooctenone ring coupled 

with demeththylation of the side chain was present to a lesser extent. Cleavage between 

the rings also made a significant contribution to the residue by the presence of 

CSCD686480 which is the pyridine specific metabolite formed by cleavage of 

NOA449280. The results are summarized below:

Bicyclooctenone14C

Pyridine -

14C

Sugarcane 

Sample Component % of TRR

Residue 

(mg/kg)

% of 

TRR

Residue 

(mg/kg)

42 DAT 

Foliage

CSCD6864801 ND ND 19.7 0.175

CSCD686481 ND ND 6.4 0.057

CSCD677692 5.5 0.043 6.5 0.058

Total desmethyl monohydroxy 

NOA449280 isomers1 37.1 0.289 33.9 0.301

Total monohydroxy NOA449280 

isomers1 25.8 0.201 20.7 0.184

ND = not detected, 

1Total of all isomers with these structural characteristics including specific metabolites, metabolites 

of undefined substitution specificity, and conjugates
3

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. 

2. Analytical method. For data submitted with this petition, the following analytical 

methods were utilized:

Method Identification Analyte

Limit of Quantification (ppm)

In Sugarcane Stalks

POPIT MET.116

(based on GRM030.03A)

NOA449280 (Parent) 0.01

SYN503780 0.01

POPT MET.117

(based on GRM030.05A1)

Common Moiety SYN503780 0.01

Common Moiety CSCD686480 0.01

CSAA806573 0.01

POPIT MET.114 Ametryn 0.01

1Analysis covers parent and all other structures similar to parent. 

The analytical methods are available for enforcement purposes with limits of detection 

that allows monitoring of food with residues at or above the levels set in these tolerances. 

Residues of NOA449280 and SYN503780 were by two different methods, direct analysis 

and common moiety method. Additionally, residues of CSAA915194, CSCD686480 and 

CSAA806573 were also determined. CSAA806573 and ametryn were analysed via a 

direct method. CSAA915194 was analysed by a common moiety method. 

A method validation was conducted in the laboratory via recoveries of samples fortified 

with the compounds being quantified in the study. The overall confidence intervals of 

recovery means at a 95% confidence level for NOA449280 and its metabolites were as 

follows: NOA449280 (POPIT MET 116) was 108±1, SYN503780 (POPIT MET 116) 

was 107±1, NOA449280 (POPIT MET 117) was 75+3 to 82 ±3, CSAA915194 (POPIT 

MET 117) was 93±5, CSAA806573 (POPIT MET 117) was 87±5 to 95+5 and ametryn 

(POPIT MET 114) was 84±7. These data indicate acceptable performance of the 

methods used to support this study. The LOQ for all analytes in all sample matrices, 

including processed fractions, was 0.01 ppm. 

The mean recoveries were all between 70 and 120% for all analytes using both methods. 

The percent relative standard deviations (%RSD) were all ≤ 20%. These data indicate 

acceptable performance by the two methods used to support this study. Analytical 

methods GRM030.03A and GRM030.05A 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 residue study was conducted to support the 
4

registration of NOA449280 on sugarcane in Australia and an import tolerance in 

the US. Studies were also conducted in Brazil and are included herein as 

additional support for import tolerances for the United States.

The maximum label rate per year will be 300 g ai/ha. The number of allowed 

applications will be up to 2 applications/year but not exceeding 300 g ai/ha.

The product will be applied pre-emergent to cane and weeds and/or early post 

emergent to cane and weeds (as a directed spray) up to the out-of-hand stage of 

sugarcane. Shortest interval between applications would be 4 weeks. The 

proposed PHI or harvest withholding period is “not required when used as 

directed” since the interval between the last possible application (out-of-hand 

stage or prior to row closure as indicated in the residue report) and harvest is very

long (at least 112 days).

AUSTRALIA

Eight crop residue trials were conducted with NOA449280 in 2009 and 2010 in 

Australia. 

Site Number Location Treatment

1 Tweed Valley, New South Wales Split Application (Ratoon crop – no trash)

2 Proserpine, Queensland Split Application

3 El Arish, Queensland Split Application

4 Mareeba, Queensland Split Application

5 Gunalda, Queensland Single Application

6 Garget, Queensland Single Application

7 McDesme, Queensland Single Application (Ratoon crop – no trash)

8 Gordonvale, Queensland Single Application

Formulation A16003E, a soluble concentrate (SL), containing 200 g/kg 

NOA449280 was applied to the sugarcane. Application scenarios are presented 

below. A non-ionic surfactant (NIS) was included in each of the spray

applications. 

Sites Treatment

Nominal Application 

Rate (g ai/ha) Nominal Application Timings

1, 2, 3, and 4

(Split Application)

1 (Control) -- Not Applicable

2 App 1: 150

App 2: 150

App 1: 4 weeks prior to Timing 2 (approx. 60-80 

cm)

App 2: Just before row closer (out of hand stage)

3 App 1: 300

App 2: 300

App 1: 4 weeks prior to Timing 2 (approx. 60-80 

cm)

App 2: Just before row closer (out of hand stage)

5, 6, 7, and 8

(Single 

Application)

1 (Control) -- Not Applicable

2 300 Just before row closer (out of hand stage)

3 600 Just before row closer (out of hand stage)
5

In the split application trials, sugarcane billets and tops were collected 

immediately before the last application, immediately after the last application and 

at nominal timings of 7, 16, 28, 56 and 112 days after last application (DALA). 

For the single application trials, samples were collected at 0, 7, 14, 18, 56 and 112 

DALA.

No residues of NOA449280 (parent), SYN503780, the common moiety

SYN503780, the common moiety CSCD686480 or CSAA589691 were found in 

any untreated control samples of any sugarcane billets or tops in this study (all 

<LOQ). In the treated samples, the residues decrease quickly with increasing 

time between spray and harvest, i.e. 1 day after application to 28 days after 

application. No residues at or above the LOQ were found at harvest (112 DAA).

BRAZIL

Five crop residue trials were performed across Brazil in Itápolis (SP), Rio das Pedras 

(SP), Bandeirantes (PR), Jaboticabal (SP) and in Uberlândia (MG). Formulation 

A16003E, a soluble concentrate (SL), containing 200 g/kg NOA449280 was applied to 

the sugarcane. A non-ionic surfactant (NIS) was included in the post-emergent 

application. 

Treatment Nominal Application Rate Nominal Application Timings

1 (Control) -- Not Applicable

2

300 g ai/ha 

(1.5 L product /ha)

Pre-emergence, soon after the crop was cut and cultivated

BBCH 00

3

300 g ai/ha 

(1.5 L product /ha)

Post-emergence, when the sugarcane plants already had 5 leaves

BBCH 15-16

Sugarcane stalks were sampled at normal harvest. No residues of NOA449280 or 

any of its other metabolites were found in any of the mature sugarcane stalks 

samples after the treatment of plots with 300 g as NOA449280 /ha (1.5 L 

product/ha) either pre-emergent (BBCH 00) or post-emergent (BBCH 15-16).

Four crop residue trials were performed across Brazil in the cities of Rio das 

Pedras (SP), Bandeirantes (PR), Jaboticabal (SP) and Tupaciguara (MG).

Formulation A16361B, a soluble concentrate (SL) containing 57 g/L NOA449280 

and 434 g/L of ametryn, was applied to the sugarcane. A non-ionic surfactant 

(NIS) was included in the post-emergent application. 

Treatment Application Rate Nominal Application Timings

1 (Control) -- Not Applicable

2

286 g NOA449280/ha + 2143 g 

ametryn/ha 

(5.0 L product /ha)

Pre-emergence, soon after the crop was cut and 

cultivated

BBCH 00

3

171 g NOA449280/ha + 1286 g 

ametryn/ha 

(3.0 L product /ha)

Post-emergence, when sugarcane plants already had 5 

leaves

BBCH 15-16
6

Sugarcane stalks were sampled at normal harvest. When A16361 was applied at 

the maximum intended use rates for both pre-emergence and post-emergence, 

there was no quantifiable residues of the analysed compounds in samples of 

sugarcane collected at normal harvest time.

In Brazil, two crop residue trials were performed at exaggerated rates in Carpina 

(PE) and Ares (RN) to generate samples for processing into sugar, molasses and 

bagasse.

Formulation A16003E, a soluble concentrate (SL), containing 200 g/kg 

NOA449280 was applied to the sugarcane. Treatment scenarios included preemergent application soon after the crop was cut at 900 h ai/ha (3X label rate) and 

at 1500 g ai/ha (5X label rate). 

Treatment Nominal Application Rate Nominal Application Timings

1 (Control) -- Not Applicable

2

900 g ai/ha 

(4.5 L product /ha)

Pre-emergence, soon after the crop was cut and cultivated

BBCH 00

3

1500 g ai/ha 

(7.5 L product /ha)

Pre-emergence, soon after the crop was cut and cultivated

BBCH 00

Sugarcane stalks were sampled at normal harvest. No residues of NOA449280 or 

any of its other metabolites were found in any of the mature sugarcane stalks 

samples after the pre-emergent (BBCH 00) treatment of plots with exaggerated 

rate applications of 900 g ai NOA449280 /ha (4.5 L product/ha) or 1500 g ai/ha 

NOA449280 (7.5 L product/ha). 

CONCLUSIONS

NOA449280 is intended for use as an herbicide on sugarcane in Australia and 

proposed for an import tolerance for the US. Supporting field residue data from 

Australia and Brazil are being submitted with this data package. The data 

indicate that when NOA449280 is applied at a rate of 300 g ai/ha) either preemergent (BBCH 00) or post-emergent (BBCH 14-16), no quantifiable residues 

will result in raw agricultural sugarcane commodities (billets, tops, stalks).

B. Toxicological Profile

1. Acute toxicity. 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. 
7

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

LD 50 

>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 on a preliminary range finding study, were 

administered in the diet to groups of 25 male and 25 female F0 generation 
8

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 on human risk assessment is recognised 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 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 
9

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 (13th) 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 presacral 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. 
10

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 noobserved-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 
11

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 
12

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 also 

discussed further in 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 contract to the 
13

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 tumours 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 recognised 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 tumours noted in male rats are considered to be rat specific and not 

relevant for human risk assessment.

No treatment-related tumours 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 [pyridinyl14C] 
14

NOA449280 and [bicyclooctenone14C] 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 [pyridinyl14C] 

NOA449280 and [bicyclooctenone14C] 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. 
15

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:

o The principal components present in tissues and milk were 

unchanged parent and the desmethyl metabolite CSAA915194. 

Other minor metabolites were found in liver

o O-demethylation produced the metabolite CSAA915194

o Hydroxylation of the bicyclooctenane ring occurred in 2 or more 

positions.

o Trace levels of a pyridine specific metabolite were observed 

indicating that cleavage of the rings was a very minor pathway

o Very little conjugation was observed

o There was no appreciable difference in excretion profiles between 

the radiolabels and distribution of residues was essentially the 

same for both labels

o 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
16

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 II acute and chronic dietary exposure evaluation 

was completed for bicyclopyrone (NOA449280) using the Dietary

Exposure Evaluation Model (DEEM-FCIDTM), version 2.16 from 

Exponent. 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

(separate Tolerance Petition and Notice of Filing submitted with this data 

package). 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 
17

assessment using the higher of the estimated drinking water concentrations 

(EDWCs) for surface and ground water. All consumption data for these 

assessments was taken from the USDA’s Continuing Survey of Food 

Intake by individuals (CSFII) with the 1994-96 consumption database and 

the Supplemental CSFII children’s survey (1998) consumption database.

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 

178,571 (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 subpopulation within the infants and children population subgroups was all 

infants (<1 year old) with a MOE of 295,710 (<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 31,871 (0.3% 

of the chronic RfD of 0.0028 mg/kg-bw/day). The most sensitive subpopulation was children (3-5 years old) with a MOE of 13,284 (0.8% 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 
18

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. Tier II acute and chronic dietary exposure evaluation 

was completed for bicyclopyrone (NOA449280) using the Dietary

Exposure Evaluation Model (DEEM-FCIDTM), version 2.16 from 

Exponent. 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. All consumption data for these 

assessments was taken from the USDA’s Continuing Survey of Food 

Intake by individuals (CSFII) with the 1994-96 consumption database and 

the Supplemental CSFII children’s survey (1998) consumption database.

Acute Exposure from Drinking Water. The acute surface water EDWC of 

2.365 ppb was input directly into the DEEM-FCIDTM software as “water, 

direct and indirect, all sources” to model the acute drinking water 

exposures. Exposure contributions at the 99.9th%-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 127,551 (0.1% of the acute RfD of 0.5 mg/kgbw/day). The most exposed sub-population was females (13-49 years old) 

with a MOE of 36,496 (0.3% of the aRfD of 0.1 mg/kg/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 drinking water exposure 

to residues arising from the proposed uses for bicyclopyrone.
19

Chronic Exposure from Drinking Water. The chronic surface water 

EDWC of 0.689 ppb was input directly into the DEEM-FCIDTM 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 19,281 (0.5% of the chronic RfD of 0.0028 mg/kgbw/day). Chronic drinking water exposure to the most exposed subpopulation (infants, <1 year old) resulted in a MOE of 5,881 (1.7% of the 

chronic RfD of 0.0028 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 drinking exposure to residues arising from the 

proposed uses for bicyclopyrone.

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 104,119 (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 30,303 or 0.3% of the aRfD (Benchmark MOE = 100; aRfD = 0.1 
20

mg/kg/day). The chronic dietary exposure analysis (food plus water) 

showed that exposure from proposed bicyclopyrone crop uses result in a 

MOE of 11,667 (0.9% 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 nonoccupational 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 41,995 (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 4,748 (2.1% 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.