**FILE NAME: DFB**  **- A357**  **citrus 201 2**  **NOF**



### ATTENTION: **All commodity**  **terms must**  **comply wi** **th the**  **Food and**  **Feed Commodity Vocabulary database (http://w** **ww. epa.gov/pesticides/foodfeed** /**).**

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**2F8015** Summary of Petitions EPA has received a pesticide petition (**2F8015**) from **[ Chemtura**  **Corporation ]**  , **[ 199**  **Benson Road,**  **Middlebury, CT**  **06749 ]**  proposing, 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. **Options (1)** 1. by establishing a tolerance for residues of
**[N -**  **[[(4 -** **chlorophen yl)amino]**  **- carbonyl]**  **- 2,6** **- difluorobenzamide**  **(DFB)** and its metabolites 4

- chlorophenylurea (CPU) and 4

- chloroaniline (PCA) in or on the raw agricultural commodities **[ orange** **, grapefruit,**  **and lemon**  **( citrus**  **fruits crop**  **group 10** **) ,**  **at 1.3**  **ppm, and**  **citrus oil**  **proces sed**  **commodity at**  **39 pp**  **m.]** EPA has determined that the petition contains data or information regarding the elements set forth in section 408(d)(2) of the FFDCA; however, EPA has not fully

evaluated the sufficiency o f the submitted data at this time or whether the data supports granting of the petition. Additional data may b e needed before EPA rules on the petition.2

A. Residue Chemistry 1. Plant metabolism . **The nature**  **of the**  **residue in**  **plants is**  **adequately understo**  **od. In plants, the m** **etabolism of diflubenzuron was investigated in soybeans,**  **citrus, mushroom, and rice.**  **T he main component of residues in rice was**  **CPU; levels**  **of PCA**  **were negligible**  **to non** **- detectable.**  **T he**  **main component**  **of the**  **residues in**  **soybeans and**  **oranges was**  **the parent**  **diflubenzuron. A**  **considerable portion**  **of the**  **residues were**  **bound. Diflubenzuron**  **showed very**  **limited absorption**  **and translocation**  **in plants**  **with most**  **of the**  **residues remaining**  **on the**  **surface. The**  **Agency has**  **concluded that**  **the residues**  **of concern**  **are diflubenzuron and its metabolites CPU and PCA.**  2. Analytical method. **A practical**  **analytical method**  **for detecting**  **and quantifying**  **levels of**  **diflubenzuron in**  **or on**  **food with**  **a limit**  **of detection**  **that allows**  **monitoring of**  **the residue**  **at or**  **above the**  **level set**  **in the**  **tolerance was**  **used to**  **determine residues**  **in citrus**  **RAC and processed commodities.**  **Residues of**  **the individual**  **analytes are**  **detectable and**  **quantifiable using**  **three separate**  **analytical methods.**  **Residues of**  **diflubenzuron (DFB)**  **wer e**  **quantitated by**  **LC -** **MS/MS, and residues of the metabolites 4 -** **chlorophenylurea (CPU) and 4 -** **chloroaniline (PCA) were derivatized with HFBA and quantitated by GC/MS.**  **Residues of diflubenzuron were repeatedly extracted with methylene chloride in the presenc** **e of anhydrous sodium sulfate and the extracts combined. The volume was adjusted to measurable volume and a 50% aliquot was removed for further clean** **- up. The extract**  **was roto -** **evaporated to dryness and reconstituted in acetonitrile. The resultant solvent mi** **xture was partitioned with hexane by shaking for ~1 minute and the acetonitrile layer was collected in a concentration flask. After concentration, the residue was dissolved with 2**  **mL acetonitrile and 8 mL water. Using a preconditioned C18 -**  **SPE cartridge, th e**  **reconstituted acetonitrile extract was passed through the cartridge for clean -** **up followed by additional clean** **- up using a Si SPE cartridge. The solvent was evaporated and the residue**  **was reconstituted in acetonitrile and water. An appropriate volume was t ransferred to**  **a gas chromatography (GC) vial for analysis. The DFB method for citrus juice was slightly**  **different in that no second filtration was required. The DFB method for orange oil involved repeated partition of the oil with acetonitrile and hexane.**  **The combined acetonitrile extracts were analyzed without further cleanup. The samples were analyzed by LC**  **- MS/MS.**  **The limit of quantitation was 0.05 ppm in citrus matrices, except for**  **orange oil with an LOQ of 1.0 ppm.**  **CPU was repeatedly extracted with eth yl acetate in the presence of anhydrous**  **sodium sulfate and the extracts combined. The volume was adjusted to measurable volume and a 50% aliquot was removed for further clean** **- up. The extract was roto** **- evaporated to**  **dryness and reconstituted in acetone and p etroleum ether. Using a preconditio**  **ned Si SPE**3

**cartridge, the reconstituted organic extract was passed through the cartridge for clean** **- up**  **with gradient elution. The solvent was evaporated and the residue was reconstituted in hexane. The CPU residue method f**  **or oil involved a partition of the oil between hexane and acetonitrile:water. The combined acetonitrile:water phases were concentrated and were**  **cleaned up by means of a C18 -**  **SPE cartridge followed by a Si -**  **SPE cartridge. The CPU was derivatized with HFBA and**  **submitted for analysis by GC/MS. The limit of quantitation was 0.01 ppm in citrus.**  **The determination of PCA residues in citrus matrices utilizes an internal standard method. Samples of matrix to be analyzed are fortified with an internal standard.**  **Resid ues of PCA and the internal standard are subjected to acid and base hydrolysis.**  **The extraction was repeated two more times and the extracts were combined. The pH of the**  **combined extracts was adjusted to pH>12 and the sample was repeatedly partitioned with hexane. The combined organic phases were partitioned with a small volume of aqueous**  **acid. The aqueous acid phase was basified to pH >12 and was repeatedly partitioned with**  **a small volume of hexan**  **e. The resultant extract was passed through a Florisil SPE cl** **eanup prior to derivatization with HFBA. All citrus matrices were conducted by the same method,**  **with the exception that filtration was not required for orange juice or oil. The PCA present was determined by GC/MS analysis. The limit of quantitation was 0.0**  **05 ppm (5.0 ppb) in citrus.**  **The methods were successfully**  **validated on**  **orange fruit,**  **orange juice,**  **orange dried**  **pulp, and orange citrus oil prior to or concurrently with sample analysis.** 3. Magnitude of residues **A complete crop residue program has been completed for**  **diflubenzuron and its metabolites**  **in the major citrus**  **growing areas of the US .**  **Raw agricultural commodities, treated according to the proposed label, were sampled.**  **T he**  **analytical data demonstrated that residues in crops are not expected to exceed the proposed**  **tolerance levels. A total of 23 citrus fruit trials (12 orange, 6 grapefruit, and 5 lemon) were**  **conducted in EPA Regions 3, 6, and 10 during the 2008 and 2009 growing seasons. Twelve orange trials were conducted in U.S. EPA Regions**  **3 (FL, 8 trials), 6 (TX, 1 trial), and 10 (CA, 3 trials).**  **S ix grapefruit trials were conducted in U.S. EPA Regions 3 (FL, 3**  **trials), 6 (TX, 1 trial), and 10 (CA, 2 trials). F** **ive lemon trials were conducted in Regions 3 (FL, 1 trial) and 10 (CA, 4 trials** **). O**  **ne decline orange trial was conducted in EPA Region 3, one decline lemon trial and one decline grapefruit trial were conducted in EPA Region**  **10. A** **further 5 trials (3 orange and 2 grapefruit) were also conducted using ultra low volume (ULV) equipment** **. A** **dditionally, data on orange processed commodities were provided from one site in EPA Region 10.**  **T he number and geographic locations of field**  **trials are adequate to support a revised U.S. tolerance for residues of diflubenzuron (DFB) and its 4**  **- chloroph**  **enylurea (CPU) and 4 -** **chloroaniline (PCA) metabolites in the citrus fruits crop group, based on the proposed field use conditions.** 4

**Chemtura Corporation**  **is proposing a citrus**  **crop group**  **tolerance of**  **1.3 ppm** **, and**  **a tolerance of 39 ppm on citrus oil process**  **ed commodity.** B. Toxicological Profile 1. Acute toxicity

. **Studies for diflubenzuron technical indicate the acute oral toxicity in**  **rats and**  **mice is**  **>4,640 mg/kg,**  **and the**  **acute dermal**  **toxicity in**  **rats is**  **>10,000 mg/kg.**  **The acute**  **inhalation LC**  **50 in**  **rats i** **s >35**  **mg/l (6**  **hours). Diflubenzuron**  **technical is**  **not an**  **eye or skin irritant to rabbits, and is not a dermal sensitizer in guinea pigs.** 2. Genotoxicity

. **Diflubenzuron did**  **not show**  **any mutagenic**  **activity in**  **point mutation**  **assays employing**  **S. typhimurium,**  **S. cerevisiae,**  **or L5178Y**  **Mouse Lymphoma**  **cells. D**  **iflubenzuron did**  **not induce**  **chromosomal aberrations**  **in Chinese**  **Hamster Ovary**  **cells and**  **did not**  **induce unscheduled**  **DNA synthesis**  **in human**  **WI -** **38 cells.**  **Diflubenzuron was**  **also negative**  **in Mouse**  **Micronucleus a** **nd Mouse**  **Dominant Lethal**  **assays and it did not induce cell transformation in Balb/3T3 cells.** 3. Reproductive and developmental toxicity

. **In a**  **rat developmental**  **toxicity study,**  **diflubenzuron was**  **administered by**  **oral gavage**  **to pregnant**  **female rats**  **at dosag** **e levels**  **of 0,**  **1, 2**  **and 4**  **mg/kg/day. No**  **treatment related**  **effects were**  **seen. A**  **subsequent study**  **was conducted**  **in pregnant**  **Sprague Dawley**  **rats at**  **a dose**  **of 0** **a nd**  **1,000 mg/kg/day.**  **No maternal**  **toxicity was**  **observed. The**  **incidence of**  **fetuses with**  **skeletal abn**  **ormalities was**  **slightly increased**  **in the**  **treated group,**  **but was**  **within historical**  **background range.**  **The NOEL for maternal and developmental toxicity in rats was greater than 1,000 mg/kg/day.**  **Diflubenzuron was**  **also administered**  **by oral**  **gavage to**  **pregnant New**  **Zealand White**  **rabbits at dosage levels of 0, 1, 2 and**  **4 mg/kg/day.**  **No treatment**  **related effects**  **were seen.**  **A subsequent**  **study was**  **conducted in**  **pregnant rabbits**  **at a**  **dose of**  **0 and**  **1,000 mg/kg/day.**  **No maternal**  **or developmental**  **toxicity was**  **seen. The**  **NOEL for**  **maternal and**  **developmental toxicity in rabbits was greater than 1,000 mg/kg/day. In**  **a rat**  **reproduction study,**  **diflubenzuron was**  **fed to**  **two generations**  **of male**  **and female**  **rats at**  **dietary concentrations**  **of 0,**  **10, 20,**  **40, and**  **160 ppm.**  **No effects**  **were se** **en on**  **parental body**  **weight gain**  **and there**  **were no**  **reproductive effects.**  **In a**  **subsequent study,**  **diflubenzuron was fed to two generations of male and female rats at dietary concentrations of**  **500, 5,000**  **and 50,000**  **ppm. S** **ystemic adult**  **toxicity was**  **seen at**  **all dosage**  **levels. N** **o effects**  **were seen**  **on reproductive**  **p arameters,**  **however, litter**  **and mean**  **pup weights**  **of F1**  **offspring were**  **reduced at**  **50,000. T**  **he NOEL**  **for reproductive**  **toxicity in**  **rats was**  **50,000 ppm**  **(2.5 g/kg/day),**  **and for**  **pre -** **weaning development**  **it wa** **s 5,000**  **ppm (250**  **mg/kg/day).** 4. Subchronic toxicity. **[To assess**  **subchronic toxicity,**  **a four** **- week**  **inhalation study** 5

**and a three -** **week dermal study were conducted. I** **n the inhalation study rats were exposed nose**  **only to**  **10, 30**  **or 100**  **mg/m 3**  **for 6**  **hours per**  **da y,**  **5 days**  **per week**  **for 4**  **weeks. Treatment**  **related findings**  **w ere**  **a slight**  **reduction in**  **erythrocytes, hemoglobin**  **and hematocrit in male and female rats at a concentration of 100 mg/m** **3 and an increase in total**  **bilirubin in**  **high dose**  **female rats.**  **T here**  **was no**  **effect on**  **methemoglobin concentration**  **at any dose level. T**  **he NOEL for subchronic inhalation toxicity was 30 mg/m 3** 

**. In**  **the dermal**  **toxicity study,**  **diflubenzuron was**  **applied to**  **the backs**  **of male**  **and female**  **CD rats**  **for three**  **weeks at**  **dose levels**  **of 20,**  **5 00**  **and 1,000**  **mg/kg/day. Hematology**  **evaluation showed**  **reductions in**  **red blood**  **cell (RBC),**  **hemoglobin (Hgb)**  **and hematocrit**  **values at**  **500 and**  **1,000 mg/kg/day.**  **A n**  **increased incidence**  **of polychromasia,**  **hypochromasia and**  **anisocytosis was**  **seen at**  **500 and**  **1,000 m** **g/kg/day. A** **n increase**  **in methemoglobin**  **and sulfhemoglobin**  **values was**  **seen at**  **1,000 mg/kg/day.**  **T he**  **NOEL for**  **systemic toxicity**  **was 20**  **mg/kg/day. Also,**  **a dermal**  **absorption factor**  **of 0.5%**  **for systemic**  **absorption, was**  **derived from**  **a study**  **where rats**  **were dose** **d with**  **either 0.005**  **or 0.05**  **mg/cm 2**  **of [**  **14 C]**  **diflubenzuron technical.**  **This value**  **can be**  **used for**  **converting dermal**  **exposure to oral equivalents. 5. Chronic toxicity.**  **D iflubenzuron was given by capsule to male and female Beagle**  **dogs for**  **one year**  **at dose**  **le vels**  **of 0,**  **2, 10,**  **50 and**  **250 mg/kg/day.**  **B ody**  **weight gain**  **was slightly**  **reduced in**  **females at**  **250 mg/kg/day.**  **A bsolute**  **liver and**  **spleen weights**  **were increased**  **in males**  **given 50**  **and 250**  **mg/kg/day. A** **r eduction**  **in hemoglobin**  **and mean**  **corpuscular hemoglobin**  **co ncentration,**  **with an**  **elevation in**  **reticulocyte count,**  **was seen**  **at 50**  **and 250**  **mg/kg/day. M** **ethemoglobin and**  **sulfhemoglobin values**  **were increased**  **at doses**  **of 10**  **mg/kg/day and**  **greater. H** **istopathological findings**  **were limited**  **to pigmented**  **macrophages and**  **Kupf fer**  **cells in**  **the liver**  **at doses**  **of 50**  **and 250**  **mg/kg/day. The**  **NOEL for chronic toxicity in dogs was 2 mg/kg/day.**  **Diflubenzuron was**  **fed to**  **male and**  **female Sprague**  **Dawley rats**  **for two**  **years at**  **dose levels**  **of 0**  **, 156,**  **625, 2,500**  **and 10,000**  **ppm. Methemoglobin**  **values were**  **elevated in**  **female rats**  **at all**  **dose levels**  **and in**  **male rats**  **at the**  **two highest**  **dose levels.**  **Sulfhemoglobin was**  **elevated in**  **females, only,**  **at dose**  **levels of**  **2,500 and**  **10,000 ppm.**  **Mean corpuscular**  **volume (MCV)**  **and reticulocyte**  **counts were**  **incre ased**  **in high**  **dose females.**  **Spleen and**  **liver weights**  **were elevated**  **at the**  **two highest**  **doses. Histopathological**  **examination demonstrated**  **an increase**  **in hemosiderosis**  **of the**  **liver and**  **spleen, bone marrow and erythroid hyperplasia and areas of cellular altera tion in the liver.**  **In another**  **study diflubenzuron**  **was administered**  **to male**  **and female**  **CD rats**  **for two**  **years at**  **dose levels**  **of 0,**  **10, 20,**  **40 and**  **160 ppm.**  **Elevated methemoglobin**  **levels were**  **seen in**  **high dose**  **males and**  **females. N** **o additional**  **effects, includ** **ing carcinogenic**  **findings, were observed.**  **T he NOEL for chronic toxicity in rats was 40 ppm (2 mg/kg/day).**  **A ninety** **- one**  **week oncogenicity**  **study in**  **CFLP mice**  **was conducted**  **at doses**  **of 0,**  **16, 80,**  **400, 2,000**  **and 10,000**  **ppm. T**  **here was**  **no increase**  **in tu**  **mor incidence**  **as a**  **result of** 6

**diflubenzuron administration.**  **T arget**  **organ effects**  **included: increased**  **methemoglobin and**  **sulfhemoglobin values,**  **Heinz bodies,**  **increased liver**  **and spleen**  **weight, hepatocyte**  **enlargement and**  **vacuolation, extramedullary**  **hemopoiesi s**  **in the**  **liver and**  **spleen, siderocytosis**  **in the**  **spleen and**  **pigmented Kupffer**  **cells. A** **N OEL**  **for these**  **effects was**  **16 ppm (2 mg/kg/day).**  **Diflubenzuron was**  **fed to**  **male and**  **female Sprague**  **Dawley rats**  **for two**  **years at**  **dose levels**  **of 0,**  **156, 625,**  **2,500 and**  **1 0,000**  **ppm. M** **ethemoglobin values**  **were elevated**  **in female**  **rats at**  **all dose**  **levels and**  **in male**  **rats at**  **the two**  **highest dose**  **levels. B** **lood sulfhemoglobin**  **was elevated**  **in females,**  **only, at**  **dose levels**  **of 2,500**  **and 10,000**  **ppm. MCV and reticulocyte counts were**  **increased in high dose females. Spleen and liver weights were**  **elevated at**  **the two**  **highest doses.**  **H istopathological**  **examination demonstrated**  **an increase**  **in hemosiderosis**  **of the**  **liver and**  **spleen, bone**  **marrow and**  **erythroid hyperplasia**  **and areas of cellular alteration**  **in the liver. There**  **was no**  **increase in**  **tumor formation.**  **I n**  **another study diflubenzuron was administered to male and female CD rats for two years at dose**  **levels of**  **0, 10,**  **20, 40**  **and 160**  **ppm. Elevated**  **methemoglobin levels**  **were seen**  **in high**  **dose m** **ales and**  **females. N** **o additional**  **effects, including**  **carcinogenic findings,**  **were observed.**  **Immunotoxicity. Diflubenzuron**  **was fed**  **to mice**  **at concentrations**  **of 0,**  **80, 400,**  **2,000 and**  **10,000 ppm**  **for 28**  **days. There**  **was no**  **observed effect**  **of diflubenzuron,**  **at any**  **dose tested,**  **on the**  **anti -**  **SRBC IgM**  **response. T**  **he immunotoxicity**  **NOAEL for**  **this study**  **was the highest dose tested dose concentration of 10,000 ppm.** 6. Animal metabolism

. **The qualitative**  **nature of**  **the residues**  **in livestock**  **is adequately**  **understood bas**  **ed on**  **data from**  **ruminant and**  **poultry metabolism**  **studies. The**  **Agency has**  **concluded that**  **the residues**  **of concern**  **are diflubenzuron**  **and its**  **metabolites CPU**  **and PCA.**  **DFB in rats at a single dose of 100 mg/kg and 5 mg/kg single and multiple oral doses depicted**  **limited absorption**  **from the**  **gastrointestinal tract.**  **N o**  **major difference**  **was observed**  **between the**  **single and**  **multiple doses.**  **I n**  **single dose**  **t reatments,**  **after 7**  **days, 20%**  **and 3%**  **of the**  **applied dose**  **5 and**  **100 mg/kg,**  **respectively were**  **excreted in**  **urine, w** **hile 79%**  **and 98%**  **of the**  **applied dose**  **5 and**  **100 mg/kg,**  **respectively, were**  **eliminated in**  **the feces.**  **V ery**  **little bioaccumulation**  **in the**  **tissues was**  **observed. I** **n the**  **feces, only**  **unchanged parent**  **compound was**  **detected. S**  **everal metabolites**  **were observed**  **in th**  **e urine which are, among others, 2**  **- 6** **- difluorobenzoic acid (DFBA), 2,6** **- diflurophippuric acid,**  **2 -** **6 -** **difluorobenzamide (DFBAM),**  **and 2**  **- hydroxydiflubenzuron**  **(2 -** **HDFB). A** **n unresolved**  **peak that**  **was characterized**  **as p**  **- chloroaniline**  **(PCA) and/or**  **p -** **chlorophenylurea (CPU)**  **was f**  **ound. T**  **his latter**  **peak accounted**  **for about**  **2% of**  **the administered**  **dose (5**  **mg/kg). T**  **o resolve**  **if PCA**  **and CPU**  **are indeed**  **metabolites of**  **DFB, rats**  **were administered**  **a single**  **oral dose,**  **100 mg/kg**  **of 14C**  **DFB. T**  **he major**  **metabolites identified**  **in r** **at urine**  **were 4**  **- chloroaniline** **- 2**  **- sulfate,**  **accounting f**  **or almost**  **50% of**  **the**7

**total radioactive**  **residue (TRR)**  **in the**  **urine and**  **N -**  **(4 -** **chlorophenyl)oxamic acid**  **which accounted**  **f**

**or about**  **15% of**  **the (TRR).**  **N either**  **CPU, PCA**  **nor their**  **N -** **hydroxylderivatives w** **ere f**  **ound in**  **rat urine**  **at a**  **limit of**  **detection of**  **23 parts**  **per billion (ppb).**  **A s in the previous study, DFB was the only residue found in the feces.**  **7. Metabolite**  **toxicology. NCI/NTP**  **conducted chronic**  **feeding and**  **gavage studies**  **with p**  **- chloroaniline**  **(PCA), a**  **m inor**  **potential metabolite**  **of diflubenzuron,**  **in Fischer**  **344 rats and**  **B 6C3F1 mice.**  **PCA was**  **administered in**  **the diet**  **to Fischer**  **344/N rats**  **at dietary**  **concentrations of**  **250 and**  **500 ppm**  **for 78**  **weeks, followed**  **by a**  **24 week**  **observation period.**  **A s** **light body**  **we ight**  **depression was**  **seen in**  **high dose**  **females rats,**  **compared to**  **controls. S**  **urvival was**  **reduced in**  **high dose**  **males compared**  **to controls.**  **I n**  **male rats**  **there was**  **a slight**  **increase in**  **uncommon fibromas**  **or fibrosarcomas**  **of the**  **spleen, which**  **was not**  **statistica lly**  **significant. N** **on -** **neoplastic proliferative**  **and chronic**  **inflammatory lesions**  **were found**  **in spleens of treated rats.**  **I t**  **was concluded that, under the conditions of**  **the assay,**  **sufficient evidence was not found to establish the carcinogenicity of PCA for**  **Fischer 344/N rats. PCA was administered 5 days/week by oral gavage, as a hydrochloride salt in water,**  **to male**  **and female F344/N rats at doses of 0, 2, 6**  **or 18**  **mg/kg/day. M** **ean body**  **weights of**  **dosed rats were generally within 5% of those of controls throu ghout**  **the study.**  **H igh**  **dose animals**  **generally showed**  **mild hemolytic**  **anemia and**  **dose -** **related methemoglobinemia.**  **Non -** **neoplastic lesions**  **seen were**  **bone marrow**  **hyperplasia, hepatic**  **hemosiderosis and**  **splenic fibrosis, suggesting treatment related effects on th e hematopoietic system.**  **A drenal**  **medullary hyperplasia**  **was observed**  **in high**  **dose female**  **rats. T**  **he incidence**  **of uncommon**  **sarcomas of**  **the spleen**  **was significantly**  **increased in**  **high dose**  **male rats.**  **A marginal**  **increase in**  **pheochromocytomas of**  **the adrenal**  **gla nd**  **was seen**  **in high**  **dose male**  **and female**  **rats. I** **t was**  **concluded that,**  **under the**  **conditions of**  **this 2**  **year gavage**  **study, there**  **was clear**  **evidence of**  **carcinogenic activity**  **of PCA**  **hydrochloride for**  **male Fischer**  **344/N rats and equivocal evidence of carcinogen ic activity of PCA hydrochloride for female**  **Fischer 344/N rats. PCA was administered in the diet to B6C3F6 mice at dietary concentrations of 2500**  **and 5000 ppm for 78 weeks followed by a 13 -** **week observation period. A** **body weight depression was seen in tre**  **ated mice of both sexes, compared to controls. A** **n increased incidence of hemangiomas and hemangiosarcomas in spleen, kidney, liver**  **a nd other sites**  **was seen in treated mice of both sexes; however this increase was not statistically significant compared to**  **controls. N** **on -** **neoplastic proliferative and chronic inflammatory lesions were found in spleens of treated mice.**  **T he evidence was considered insufficient to**  **conclusively relate the hemangiomatous tumors in mice to compound administration. I** **t was conclude**  **d that, under the conditions of the assay, sufficient evidence was not found to establish the carcinogenicity of PCA for B6C3F1 mice.** 8

**PCA hydrochloride was administered 5 days/week by oral gavage to male and female B6C3F1 mice at doses of 0, 3, 10, or 30**  **mg/kg/day. M** **ean body weights of high dose male and female mice were generally within 5% of those of controls throughout the**  **study. T**  **he incidence of hepatocellular adenomas or carcinomas (combined) was increased in a non** **- dose** **- dependent manner in treated m** **ale mice. Metastasis of carcinoma to the lung was seen in the high dose group.**  **A n increased incidence of hemangiosarcomas**  **of the liver or spleen was seen in high dose male mice. It was concluded that, under the conditions of this 2**  **- year gavage study, ther** **e was some evidence of carcinogenic activity of PCA hydrochloride for male B6C3F1 mice and no evidence of carcinogenic activity of PCA**  **hydrochloride for female B6C3F1 mice.**
**In addition to PCA, 4 -** **chlorophenylurea (CPU) is also a potential minor metaboli te of**  **diflubenzuron. B** **y association with Monuron, the EPA had assumed that CPU has** **oncogenic potential with the same carcinogenic potency (q1*) as Monuron.**9

9

. **Endocrine disruption.**  **T he**  **standard battery**  **of required**  **studies has**  **been completed**  **and evalu**  **ated to**  **determine potential estrogenic or endocrine effects**  **of diflubenzuron.**  **These studies**  **include an**  **evaluation of**  **the potential**  **effects on**  **reproduction and**  **development, and**  **an evaluation**  **of the**  **pathology of**  **the endocrine**  **organs following**  **repeated or**  **lon g** **- term**  **exposure. These**  **studies are**  **generally considered**  **to be**  **sufficient to**  **detect any**  **endocrine effects.**  **No such**  **effects were**  **noted in**  **any of the studies with diflubenzuron.**  **C. Aggre gate Exposure** 10

**1. D**  **ietary Exposure.**  **An evaluation**  **of chronic**  **dietary e** **xposure, including**  **drinking water,**  **has been**  **performed for**  **the U.S.**  **population and**  **various population**  **subgroups including**  **infants and**  **children. O**  **ne day**  **single dose**  **oral studies**  **in rats**  **and mice**  **indicated there**  **were no**  **significant acute**  **effects observed.**  **A s**  **only marginal**  **effects were**  **noted, an**  **acute exposure**  **assessment is**  **not needed**  **for diflubenzuron.**  **i. Food**  **T he dietary exposure from diflubenzuron was estimated based on the average residue values**  **from the**  **various currently**  **labeled raw**  **agricultural commo**  **dities (RAC’s),**  **and the**  **proposed citrus**  **crop group**  **uses. P** **ercent of**  **crop treated**  **was also**  **factored into**  **the estimate.**  **R esidues**  **in meat,**  **milk and**  **egg products**  **were obtained**  **from extrapolation**  **of metabolism**  **study data**  **to anticipated**  **l ivestock**  **dietary burd ens.**  **A chronic**  **dietary exposure**  **assessment was**  **conducted on**  **diflubenzuron using**  **DEEM -** **FCID TM**  **Version 2.14,**  **which incorporates**  **consumption data**  **fromUSDS’s CSFII,**  **1994 -**  **1996 and**  **1998. Chemtura**  **predicts that**  **28% of**  **citrus crops**  **will be**  **treated at**  **market matu**  **rity (~5**  **years following**  **introduction of**  **the new**  **use pattern**  **on citrus).**  **P ercent**  **crop treated**  **for mushrooms**  **has declined**  **considerably over the years from 31% (previous EPA’s assessments) to no more than 3.2% for a**  **5 -** **year average.**  **A partially**  **refined asses**  **sment in**  **which the**  **percent crop**  **treated information**  **for citrus**  **and mushroom**  **was incorporated,**  **while the**  **percent crop**  **treated values**  **for all**  **other crops**  **were maintained**  **at 100%.**  **W ith**  **this refinement,**  **the chronic**  **dietary exposure**  **to the**  **US Population**  **(total )**  **was estimated**  **was 12.4%**  **of the**  **cPAD (0.00248**  **mg/kg/day). The**  **most highly**  **exposed subpopulation,**  **children 1**  **- 2**  **years, has**  **an estimated**  **total exposure**  **of 39.9%**  **of the**  **cPAD. The**  **total chronic**  **dietary exposure**  **associated with**  **current and**  **proposed uses**  **of difl** **ubenzuron on**  **citrus has**  **been demonstrated**  **to be less than the cPAD (0.02 mg/kg/day) and are therefore not of concern. Using updated percent crop**  **treated estimates**  **on all**  **crops would**  **further refine**  **the exposure**  **estimate. Use**  **of percent**  **crop treated**  **informat ion for**  **all crops**  **and switching**  **to average**  **residues rather**  **than tolerances**  **would further**  **refine the exposure downward.**  **Incremental cancer risk assessments were conducted for CPU and PCA with the proposed modified uses on citrus. When the 28% crop treate** **d factor is included in the analysis for citrus, the incremental cancer risks are estimated to be**  **0.000042 mg/kg bw/day for CPU and**  **0.000007 mg/kg bw/day**  **for PCA. ii.**  **Drinking water** **. Diflubenzuron**  **degrades in**  **soil relatively**  **quickly with**  **an aerobic**  **half -** **life ranging**  **from 3**  **- 7**  **days. Major**  **degradates include**  **difluorobenzoic acid**  **(DFBA) and**  **CPU. DFBA**  **is further metabolized through decarboxylation and ring cleavage by soil microbes whereas CPU is slowly**  **degraded to soil -** **bound entities.**  **Under anaerobic**  **aquatic conditions,**  **diflubenzuron has**  **a half**  **- life**  **of 34**  **days with**  **the main**  **degradates being**  **DFBA and**  **CPU. In**  **surface water,**  **diflubenzuron is**  **degraded by**  **microbes with a half**

**- life of 5**  **- 10 days.**  **Based on**  **EPA’s SCI** **- GRO**  **and Tier**  **II PRZM** **- EXAM**  **modeling, the**  **average a** **nnual mean** 11 **concentration of**  **diflubenzuron in**  **ground and**  **surface water**  **sources is**  **not expected**  **to exceed**  **the level**  **of concern.**  **The DWLOC**  **for chronic**  **(cancer) exposure**  **to diflubenzuron**  **and CPU**  **in surface/** **drin king**  **water was**  **determined as**  **2.76 ppb**  **for the**  **U.S .**  **population (total).**  **The groundwater**  **estimate from**  **SCIGROW is**  **0.208 ppb.**  **The estimated**  **maximum concentrations**  **of diflubenzuron**  **and CPU**  **in ground**  **and surface**  **water are**  **less than**  **the DWLOC’s**  **as a**  **contribution to**  **chronic aggregate**  **exposure. 2. Non** **- dietary e** **xposure. Diflubenzuron is a restricted use pesticide based on its toxicity to aquatic invertebrates.**  **This restricted**  **use classification**  **makes it**  **unavailable for**  **use by**  **homeowners. Occupational uses of diflubenzuron may expose people in residential location**  **s, parks, or forests treated with**  **diflubenzuron. Based**  **on very**  **low residues**  **detected in**  **forestry dissipation**  **studies, a**  **low dermal**  **absorption rate**  **(0.5%), and**  **extremely low**  **dermal and**  **inhalation toxicity,**  **these uses**  **are expected**  **to result in insignificant**  **risk, and are therefore not included in the aggregate risk assessment. D. Cumu** **lative Effects The**  **registrant has**  **considered the**  **potential for**  **cumulative effects**  **of diflubenzuron**  **and other**  **substances with**  **a common**  **mechanism of**  **toxicity. T**  **he mammalian**  **toxi city**  **of diflubenzuron**  **is well**  **defined. Chemtura**  **is not**  **aware of**  **any other**  **pesticide product**  **registered in**  **the United**  **States that**  **could be metabolized to p -** **chloroaniline. For this reason, consideration of potential cumulative effects of residues**  **from pesti** **cidal substances**  **with a**  **common mechanism**  **of action**  **as diflubenzuron**  **is not**  **appropriate. Thus,**  **only the**  **potential exposures**  **to diflubenzuron**  **were considered**  **in the**  **total exposure**  **assessment. E. Saf**  **ety Determination 1. U.S. population. Based on the availab**  **le toxicology and exposure database for diflubenzuron, the registrant**  **has determined**  **that the**  **total non** **- occupational**  **aggregate exposure**  **from diflubenzuron**  **would occur**  **from food**  **and drinking**  **water routes.**  **B ased**  **on the**  **0.02 mg/kg/day**  **RfD (reference**  **dose) de** **rived from**  **the dog**  **chronic NOEL**  **of 2**  **mg/kg/day and**  **a 100**  **- fold**  **safety factor,**  **chronic dietary**  **exposure to**  **the U.S.**  **population (total)**  **is 12.4**  **% of**  **the RfD.**  **Aggregate exposure**  **does not**  **exceed 100%**  **of the RfD when the potential theoretical residues in drinking water are included.** 

**For PCA, the total non** **- occupational aggregate exposure would occu**  **r from the dietary route. The**  **risk from**  **diflubenzuron -** **derived PCA**  **can be**  **estimated using**  **a linear**  **extrapolation of**  **the dose** **- response**  **from the**  **rat chronic**  **study c** **onducted by**  **the National**  **Toxicology Program**  **in which**  **rats were**  **dosed via**  **gavage with**  **p -** **chloroaniline [hydrochloride]**  **for 24**  **mo nths.**  **E PA**  **has determined**  **the Q**  ***** **as 0.112**  **based on**  **the combined**  **incidence of**  **liver adenomas**  **and carcinom** **as in**  **male mice.**  **U sing**  **t his**  **Q** ***, the**  **theoretical risk**  **to the**  **U.S. population**  **(total) from**  **dietary exposure**  **to diflubenzuron** **- derived PCA was estimated at**  **7.87 x 10**  **- 7** 

**.**

**For CPU,**  **total aggregate**  **exposure could**  **occur from**  **food and**  **drinking water.**  **The EPA**  **has determined**  **tha t**  **since CPU**  **is structurally**  **relat ed**  **to Monuron**  **the most**  **potent Q**  ***** **of 1.52**  **x 10**  **- 2**  **(based**12

**on male**  **rat liver**  **neoplastic nodule**  **a nd/or**  **carcinoma combined**  **tumor rates)**  **from the**  **NTP carcinogenesis**  **data for**  **Monuron should**  **be used**  **for assessing**  **canc er**  **risk from**  **CP U.**  **U sing**  **this Q**  ***** **the theoretical**  **risk to**  **the U.S.**  **population (total)**  **from dietary**  **exposure to**  **CPU was**  **estimated at**  **6.41 x**  **10 -** **7**

**. The aggregate cancer risk including drinking water does not exceed the level of concern.**  **2. Infants**  **and children.**  **The dietary**  **exposure of**  **diflubenz uron**  **was calculated**  **as 0.000986**  **and 0.002911**  **mg/kg/day respectively**  **for nursing**  **and non** **- nursing**  **infants. These**  **values are**  **4.9% and**  **14.6 %**  **respectively of**  **the RfD**  **for diflubenzuron.**  **T he**  **dietary exposure**  **from diflubenzuron**  **in children**  **1 -** **6 and**  **7 -**  **12 years**  **old was**  **determined as**  **0 .006601**  **mg/kg/day and**  **0.003509 mg/kg/day,**  **respectively. These**  **values are**  **33.0 %**  **and 17.5**  **% of**  **the RfD,**  **respectively. A** **ggregate exposure**  **from food and drinking water does not exceed the level of concern.** 

**A s**  **previously discussed,**  **the NOEL’s**  **for maternal**  **and developmental**  **toxicity in**  **rats and**  **rabbits were**  **greater than**  **1,000 mg/kg/day,**  **and the**  **NOEL for**  **reproductive toxicity**  **was greater**  **than 5,000**  **mg/kg/day. T**  **herefore, based**  **on the**  **completeness and**  **reliability of**  **the toxicity**  **data and**  **the conservative**  **exposure assessment,**  **the registrant**  **concludes that**  **there is**  **reasonable certainty**  **that no**  **harm will**  **result in**  **infants and**  **children from**  **aggregate exposure**  **to residues**  **of diflubenzuron**  **and its**  **conversion products co nta** **ining the p**  **- chloroaniline moiety.**  **F. Inte rnational Tolerances**  **Codex MRL**  **s have**  **been established**  **for diflubenzuron**  **per se**  **on many**  **commodities including**  **: citrus**  **fruit (** **0.5 ppm** **), mushrooms**  **(0.3 ppm),**  **pome fruits**  **(5 ppm),**  **rice (0.01**  **ppm), rice**  **straw and**  **f odder**  **(dry; 0.7**  **ppm), edible**  **offal (mammalian)**  **(0.1 ppm),**  **eggs (0.05**  **ppm), poultry**  **meat (0.05**  **ppm), milk**  **(0.02 ppm).**  **MRLs have**  **been established**  **for diflubenzuron**  **in the**  **EU for**  **citrus (1.0**  **ppm), pome**  **fruit (** **5 ppm), apricot (1 ppm), strawberry (2 ppm), grape** **s (1 ppm), and brassica vegetables (1 ppm)**  **.**