### Page 1 of 21 UNITED STATES ENVIRONMENTAL PROTECTI ON AGENCY WASHINGTON, D.C. 20460 OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES 

### MEMORANDUM Date: 3 December 2009 Subject: Diquat Dibromide : Human Health Risk Assessment for the Section 18 Use on

Canola in Oklahoma and Kentucky. PC Code: 032201 DP Barcode: D355407 Decision No.: 398579 Registration No. : 100
- 1061 Petition No.: 08OK02 Regulatory Action: Section 18 Risk Assessment Type: NA Case No.: NA T XR No.: NA CAS No.: 85
- 00
- 07 M RID No.: None 40 CFR: 180.226 

### From: Michael A. Dohert y, Ph.D., Chemist Shih
- Chi Wang, Ph.D., Biologist Risk Assessment Branch II Health Effects Division 7509P Through: William T. Drew , Chemist

Zaida Figueroa, Industrial Hygenist Edward Sco llon, Ph.D., Toxicologist Christina Swartz, Branch Chief Risk Assessment Branch II Health Effects Division 7509P Susan V. Hummel, Senior Scientist Risk Assessment Branch IV Health Effects Division 7509P To: Libb y Pemberton/Dan Rosenblatt (Te am 05) Risk Integration Minor Use and Emergency Response Branch Registration Division 7505P

### Page 2 of 21

Introduction The Oklahoma and Kentucky Departments of Agriculture have declared crisis exemptions for the use of diquat (as Reglone Desiccant , EPA Reg. No. 1 00
- 1061) on canola as a harvest aid. Rainfall patterns in canola
- growing areas of these states have resulted in secondary blooming of the canola crop. Without the use of a desiccant , the secondary blooming can result in significant yi eld loss. Pesticide use in Oklahoma was authorized to begin 9 June 2008 and discontinue after 23 June 2008. Agency Memoranda Used to Support this Section 18 Exemption Risk Assessment D 369480, 26 October 2009 , M. Dohert y, Diquat: Acute and Chronic Aggregate Dietary (Food an d Drinking Water) Exposure and Risk Assessments for the Section 18 Registration Action for Use on Canola in Oklahoma and Kentucky
. D369862, 21 October 2009, B. Phillips and D. Berwald, Estimates of Crop Irrigation for Endothall Registration. Assessment su mmary Diquat dibromide {6,7
- dihydrodip yrido[1,2
- a :2 ′,1′
- c ]py razinediium dibromide} is a quaternary ammonium herbicide . It is registered for use on a number of crops, primarily non - bearing crops or crops grown for seed, with tolerances [40 CFR 180. 226] r anging from 0.02 ppm to 20 ppm. Many of the tolerances are to cover irrigation of crops with diquat
- treated water. The residue of concern for tolerance
- enforcement and risk
- assessment purposes is the diquat cation. For the purposes of this Section 18, the toxicology data base is adequate to characterize the toxicity of diquat dibromide
. Diquat dibromide exhibits low acute toxicity via the oral (Toxicity Category II for technical, III for formulation) and inhalation (Toxicity Category I II) routes of exp osure but is moderately to severel y toxic via the dermal route of exposure (Toxicity Categories I for technical and II for formulation). Diquat dibromide is not an acute skin irritant (Toxicity Category IV) or a dermal sensitizer, but it is considered a m oderate
- to - severe eye irritant (Toxicity

Category I I). Subchr onic and chronic studies in several species indicate multiple target sites for diquat dibromide toxicity . In subchronic dermal exposure studies in rats, diquat dibromide showed evidence of seve re s ys temic toxicity , i.e. high mortality and clinical signs. In a subchronic inhalation study in rats, the lung was determined to be the primary target site for toxicity . Chronic feeding studies in dogs, rats, mice, and rabbits indicate that target site s include the eyes and kidney s in both males and females and the adrenals and epididy mides in males. Developmental toxicity was observed in rat, rabbit, and mouse studies, and reproductive toxicity was observed in the rat in both generations. Rat and rab bit studies provided evidence of maternal toxicity . Acute and subchronic studies in mice and rats provided no evidence of neurotoxicity . Available data provide no evidence of endocrine disruption following exposure to diquat dibromide. Carcinogenicity s tudies in rats and mice provided no evidence of an increased tumor incidence and diquat dibromide is classified as a Category E (evidence of non
carcinogenicity

to humans), and the weight of the evidence is predominantly negative for mutagenicity . The dat a show no indication of increased sensitivity of rats, mice, or rabbits from in utero and/or earl y postnatal exposure to diquat dibromide. The Health Effects Division

### Page 3 of 21

( HED ) has determined that the FQPA safet y factor should be reduced to 1X. The toxicolog ical doses and associated endpoints for human health risk assessment are summarized in Table s 1 a and 1b
. The same study, with the same doses and effects, was selected to assess exposure from dermal and oral routes . Therefore, it is appropriate to combine these routes when assessing aggregate exposure. The effects associated with inhalation exposure are different from those being used to assess the dermal and oral routes; therefore, inhalation exposures should not be aggregated. Table 1 a . Summary of Tox icological Doses and Endpoints for Diquat for Use in Dietary and Non
- Occupational Human Health Risk Assessment s. Exposure Scenario Dose Endpoint Study Ac ute Dietary general population incl infants and children NOAEL= 75 mg/kg

UF = 100 LOAEL of 1 50 mg/kg based on clinical signs

and decreased body
- weight gain. Ac ute neurotoxicity rat FQPA = 1x Acute RfD = 0.75 mg/kg Acute PAD = 0.75 mg/kg Chronic Dietary NOAEL = 0.5 mg/kg/day UF = 100 LOAEL of 2.5 mg/kg/day based on cataracts in

f emales and decreased adrenal and epididymides weights in males. chronic toxicity dog FQPA = 1x Chronic RfD = 0.005 mg/kg/day Chronic PAD = 0.005 mg/kg/day Short
- Term

Oral (1day
- 1 month) NOAEL = 1 mg/kg/day MOE = 100 LOAEL of 3 mg/kg/day based on body
- weight

loss and decreased food consumption. Developmental toxicity
- rabbit Short
- Term

Dermal a (1 day
- 1 month) NOAEL = 1 mg/kg/day MOE = 100 LOAEL of 3 mg/kg/ day based on body
- weight

loss and decreased food consumption. Develo pmental toxicity
- rabbit Short
- Term Inhalation (1 day
- 1 month) NOAEL = 0.1 μ g/ L

(0.024 mg/k g/d male, 0.026 mg/kg/d female) MOE = 100 LOAEL of 0.49 μ g/L (0.117 mg/kg/day male,

0.128 female) due to increased mean lung weight in males, mottling and red dening of lungs in females, and lung lesions. 21
- day inhalation toxicity rat

a Since an oral value was selected, route
- to - route extrapolation should be follow ed. A dermal absorption factor is required for this risk assessment. Table 1b. Summary of Toxicological Doses and Endpoints for Diquat for Use in Occupational Human Health Risk Assessments Exposure Scenario Dose Endpoint Study Short
- Term

Dermal a (1 day
- 1 month) NOAEL = 1 mg/kg/day MOE = 100 LOAEL of 3 mg/kg/ day based on body
- w eight

loss and decreased food consumption. Developmental toxicity
- rabbit Short
- Term Inhalation (1 day
- 1 month) NOAEL = 0.1 μ g/ L

(0.024 mg/k g/d male, 0.026 mg/kg/d female) MOE = 100 LOAEL of 0.49 μ g/L (0.117 mg/kg/day male,

0.128 female) due to inc reased mean lung weight in males, mottling and reddening of lungs in females, and lung lesions. 21
- day inhalation toxicity rat

a Since an oral value was selected, route
- to - route extrapolation should be follow ed. A dermal absorption factor is required for this risk assessment. 

### Data depicting residues of diquat in/on canola seed have been submitted as part of the Section 18 request. Based on those data, the NAFTA MRL
- Tolerance Harmonization Spreadsheet recommends a tolerance of 4.0 ppm. There are cur rentl y diquat residue limits in/on canola seed (rapeseed) of 2 ppm for Codex and 1 ppm for Canada. For harmonization purposes and since the

### Page 4 of 21

submitted data show most of the residue levels to be below 1 ppm, HED is recommending 1 ppm as the appropriate tole rance level for this Section 18. The acute dietary exposure assessment is based on tolerance
- level residues and assum es 100% crop treated . The analy sis indicate s that acute risks associated with diquat are approximately 1% of the acute population
- adjuste d dose (aPAD), which is well below HED’s level of concern ( i.e. , less than 100% of the aPAD)
. T he chronic assessment is based on tolerance
- level residues and 100% crop treated for crops with direct diquat uses. For crops with tolerances to cover irrigati on with diquat
- treated water, anticipated residue levels from irrigation trials are used in conjunction with estimates of % of crops irrigated. For fish, average residues are assumed. The resulting chronic dietary risk estimates are below HED’s level of concern , ranging from 13 to 34% of the chronic population
adjusted dose (cPAD). Diquat dibromide can be applied to turf, to recreational ponds & lakes, for general weed control in and around home & garden sites, and for landscape uses b y residential handl ers. These uses can result in oral, dermal, and inhalation exposures to diquat. MOEs for these exposures range from 140 to 11,000,000 . None of these residential/recreational MOEs exc eed HED’s level of concern (diquat MOEs of < 100 are considered to be o f concern to HED)
. Aggregate exposures from the agricultural, aquatic, and residential uses of diquat result in MOEs of 104 to 66 0 , depending on the age group. The se MOE s represent risk estimates that are below HED’s level of concern for all population s ubgroups. For purposes of this Section 18, HED has assumed that diquat does not share a common mechanism of toxicity

with another pesticide and, therefore, has not undertaken a cumulative risk assessment for this compound. HED has assessed the risks asso ciated with occupational exposure to diquat. Mixer, loader, applicator, flagger, and post
- application scenarios have been assessed. Provided proper personal protective equipment (PPE) is used, there are no occupational MOEs that HED considers to be risks of concern. For purposes of this Section 18, HED is recommending that the e mergency exemption be granted and that time
- limited tolerance s be established for residues of diquat cat ion in/on canola seed at 1.0 ppm and in/on canola meal at 3.0 ppm
. Toxicol ogical Considerations HED completed an FQPA human health risk assessment as part of the RED process for diquat (Diquat Tolerance Reassessment Eligibility D ocument, D281890, B. Daiss, 22 March 2002). At that time, it was determined that the toxicological database for diquat was adequate for risk assessment purposes. Due to changes in pesticide registration data requirements [40 CFR Part 158], an immunotoxicity

study (OPPTS 870.7800) is now required
. HED is not requiring th is study as part of this Section 18 assessment. Should the registrant wish to pursue a Section 3 registration for this use or an y other new use of diquat, then the study will be required. The following is from the 2002 TRED and does not reflect the need for newly required data :

### Page 5 of 21

Subchr onic and chronic studies in several species indicate multiple target sites for diquat dibromide toxicity . In subchronic dermal exposure studies in rats, diquat dibromide showed evidence of severe s ys temic toxicity , i.e. high mortality and clinical signs. While a dermal study was available, the dermal endpoint is based on a rabbit developmental gavage stud y because the dermal study was determined to be inappropriate for endpoint selection. Route specific endpoints are available for all other exposure pathway s. In a subchronic inhalation study in rats, the lung was determined to be the primary target site for inhalation toxicity . Chronic feeding studies in dogs, rats, and mice indicate that target sites include the eyes and kidney s in both males and females an d the adrenals and epididy mides in males. Developmental toxicity was observed in rat, rabbit, and mouse studies, and reproductive toxicity was observed in the rat in both generations. Rat and rabbit studies provided evidence of maternal toxicity . The acute and subchr onic neurotoxicity

studies in rats provided no evidence of neurotoxicity . Available data provide no evidence of endocrine disruption following exposure to diquat dibromide. Carcinogenicit y studies in rats and mice provided no evidence of increas e tumor incidence and diquat dibromide was classified as a Category E (evidence of non
carcinogenicity

to humans) by

the HED Reference Dose (RfD)/Peer Review Committee based on the 1999 EPA Draft Proposed Guidelines for Carcinogen Risk Assessment. The weight of the evidence was predominantl y negative for mutagenicity . The data provided no indication of increased sensitivity of rats, mice, or rabbits to in utero and/or earl y postnatal exposure to diquat dibromide. The terminal residue of concern is the parent compound, diquat cation. There is no indication that metabolites are present in significant quantities. FQPA Considerations
- HED’s FQPA committee determined that the FQPA safet y factor could be removed (1 X ) in assessing the risk posed by this chemical because the toxicological database is complete for FQPA assessment, there is no indication of quantitative or qualitative increased susceptibility of rats or rabbits to in utero and/or postnatal exposure, a developmental neurotoxicity study is not required , and the dietary (food and drinking water) and residential exposure assessments will not underestimate the potential exposures for infants and children. The HIARC and FQPA Committee determined that a developmental neurotoxicity study was not required for diquat dibromide based on the fact that (1) there is no indication of abnormalities in the development of the fetal nervous sy stem in prenatal developmental toxicity studies in rats, mice, and rabbits at oral dose levels that were maternall y toxic, (2) the re was no evidence of neuropathology in either the acute or subchronic neurotoxicity studies, (3) the clinical and functional observational battery observations in the acute neurotoxicity study , which could not be unequivocall y correlated to an effect on the nervous sy stem, were not observed in the subchronic neurotoxicity study , and (4) no neurotoxic effects were observed in the brain weights or histopathology of the nervous s ys tem in the chronic toxicity studies with diquat in several species. No new inf

ormation has been submitted to the Agency that would change the toxicological conclusions described in the 2002 TRED. Based on the available data , which do not show any indications of immunotoxicity , and for purposes of this Section 18 only , HED does not believe

### Page 6 of 21

that the newl y required data will result in lower doses for assessing risk and, therefore, is not adding a database uncertainty factor at this time. Occupational Exposure Considerations This Section 18 emergency exemption is being requested for the end
- use product containing diquat di bromide as the active ingredient. The proposed action is to use Reglone Desiccant (EPA Reg. No. 100
- 1061, liquid, 2 lbs. diquat cation per gallon) as a harvest aid on canola grown in Oklahoma and Kentucky . The prod uct will be applied at a rate of 24 to 30 fl. oz per acre (30 fl. oz/acre = 0.468 lb. ai/acre) b y ground or aerial equipment when the crop is at the 60
- 75% seed turn (green to brown) stage. Handlers Equations/Calculations The following equations are used to estimate handler exposure and risk: Derm al Dose (mg/kg/day) = Rate (lb ai/A) x UE (mg/lb ai) x DA (0
. 003) x Acre Treated (A/day) BW (kg) Inhalation Dose (mg/kg/day) = Rate (lb ai/A) x UE (mg/lb ai) x Acre Treated (A/day) BW (kg) Where: Rate (Application Rate) = Maximum application rate on product label (lb ai/A) UE (Unit Exposure) = Exposure value derived from August 1998 PHED Surrogate Exposure Table (mg/lb ai handled) DA = Dermal absorption factor (0.3% , from 2002 RED ) Acre Treated = Maximum area treated per day (A/day) BW = Body w eight (kg) Derm al MOE = Dermal NOAEL (1 mg/kg/day) Dermal Daily Dose (mg/kg/day) Inhalation MOE = Inhalation NOAEL (0.024 mg/kg/day) Inhalation Daily Dose (mg/kg/day) 

### Exposure Scenarios There are 5 handler scenarios that are expected to result in the highest exposure for the proposed uses:
 Mixing/loading liquid for ground application (Scenario 1)  Mixing/loading liquid for aerial application (Scenario 2)  Applying spray s using ground equipment (Scenario 3)  Applying spray s using fix ed
- wing aerial equipment (Scenario 4)  Flagging during aerial application (Scenario 5)

### Page 7 of 21

Application Rate The maximum application rate provided b y the Oklahoma Department of Agriculture, Food, and Forestry is 0.468 lb ai per acre. The Amount of Pesticide Handled per Day Based on HED’s Exposure Science Advisory Council Policy

Number 9.1, (1) 80 acres/day for application using ground
- boom and (2) 350 acres/day for application using fix ed
- wing aircraft are assumed. Bod y Weight The average bod y weight for general population (70 kg) is used for this assessment. Exposure Frequency No data on the number of exposure day s per ye ar was provided
. For this risk assessment, it is assumed that handlers would be exposed for less than 30 d ay s per ye ar (short
- term exposure). Intermediate
- and long
- term exposures are not expected. Unit Exposures The unit exposures are based on the Pesticide Handler’s Exposure Database ( PHED ) Version 1.1 as presented in the August 1998 PHED Surrogate Exp osure Guide. PHED was designed b y a task force of representatives from the U.S. EPA, Health Canada, the California Department of Pesticide Regulation, and member companies of the American Crop Protection Association. PHED is a software sy stem consisting of two parts

– a database of measured exposure values for workers involved in the handling of pesticides under actual field conditions and a set of computer algorithms used to subset and statistically summarize the selected data. Currentl y, the database contains values for over 1,700 monitored individuals (i.e., replicates). Users select criteria to subset the PHED database to reflect the exposure scenario being evaluated. The subsetting algorithms in PHED are based on the central assumption that the magni tude of handler exposures to pesticides is primarily a function of activity

(e.g., mixing/loading, applying), formulation ty pe (e.g., wettable powders, granulars), application method (e.g., aerial, ground
- boom), and clothing scenarios (e.g., gloves, double layer clothing). The Surrogate Exposure Guide, which contains the most commonly used subsets of PHED, was used to develop exposure estimates. Once the data for a given exposure scenario have been selected, the data are normalized for the amount of pesti cide handled , resulting in standard unit exposures (milligrams of exposure per pound of active ingredient handled). Following normalization, the data are statistically summarized. The distribution of exposure values for each body part (e.g., chest, upper arm) is categorized as normal, lognormal, or “other” (i.e., neither normal nor lognormal). A central tendency value is then selected from the distribution of the exposure values for each body part.

### Page 8 of 21

These values are the arithmetic mean for normal distrib utions, the geometric mean for lognormal distributions, and the median for all “other” distributions. Once selected, the central tendency values for each body part are composited into a “best fit” exposure value representing the entire body
. There are three basic risk mitigation approaches considered appropriate for controlling occupational exposures. These include administrative controls, the use of PPE, and the use of engineering controls. Occupational handler exposure assessments are often completed by HED using baseline, PPE, and engineering controls. [Note: Administrative controls available generall y involve altering application rates for handler exposure scenarios. These are ty pically not utilized for completing handler exposure assessments.] The baseline clothing level scenario for occupational exposure scenarios is generall y an individual wearing long pants, a long
- sleeved shirt, no chemical resistant gloves, and no respirator. The first level of mitigation generall y applied is PPE. As reflecte d in the calculations included herein, PPE may involve the use of an additional layer of clothing, chemical
- resistant gloves, and a respirator. The next level of mitigation considered in the risk assessment process is the use of appropriate engineering co ntrols which, b y design, attempt to eliminate the possibility of human exposure. Examples of commonly

used engineering controls include enclosed tractor cabs and cockpits, closed m ixing/loading/transfer systems, and water
- soluble packets. Handlers’ Expos ure and Risk HED’s level of concern (LOC) for occupational exposure to diquat is 100 (i.e., MOE>100 not of concern). All dermal handler scenarios result in MOEs greater than 100 if chemical resistant gloves are worn in addition to the baseline attire. A ll inhalation scenarios, except one, result in MOEs greater than 100 if dust
- mist respirators are worn. A close d sy stem i s needed for the mixer/loader of aerial application sy stem s to result in MOEs greater than 100 . HED recommends that RD ensures proper PPE & engineering controls are on the final label. A summary

of the exposures/risks for handlers is presented in Table 2
. The handler exposure estimates in this assessment are based on a central tendency estimate of unit exposure and an upper
- percentile assumption for the application rate, and are assumed to be representative of high
- end exposures. The uncertainties associated with this assessment stem from the use of surrogate exposure data (e.g., differences in use scenario and data confidence), and a ssumptions regarding th e amount of chemical handled. The estimated exposures are believed to be reasonable high
- end estimates based on observations from field studies and professional judgment. Post - application Based on th e requested use, there is pote ntial post
- application exposure to workers performing hand harvest ing of canola. T he transfer coefficient (TC) for hand harvesting of canola assigned in the HED’s Science Advisory Council for Exposure Policy Number 3.1 is 2,500 cm 2 

### /hr . Based on this TC, the post
- application dermal MOE for hand harvesting canola on D ay 0 is 1,100 which indicates the risk is not of concer n . T he calculations are shown in Table 3.

### Page 9 of 21

The State of Oklahoma indicated that the emergency exemption will specify a pre - harvest inter val (PHI) of 7 day s. Given the properties of diquat, the inhalation exposure on the 8 th 

### day after application is considered to be very limited. Review of Human Research This risk assessment relies in part on data from studies in which adult human subje cts were intentionally

exposed to a pesticide or other chemical. These studies, which comprise the PHED, have been determined to require a review of their ethical conduct, and have received that review. The studies in PHED were considered appropriate (or ethicall y conducted) for use in risk assessments. Table 2. Non - cancer Risk s Estimates for Diquate Dibromide Handlers. Exposure Scenario (Scenario #) Mitigation Level a Dermal

Unit Exposure b (m g/lb ai) Inhalation

Unit Exposure c (μg/lb ai) Applic .

Rate ( lb ai/A) Am ount

Treated d (A/day) Daily

Dermal Dose e (m g/k g/day) Daily Inhalation Dose f (m g/k g/day) Dermal

MOE g Inhalation

MOE h Mixer/Loader Li quid for Ground application (1) Baseline 2.9 1.2 0.468 80 0.0047 0.00064 210 38

Dust
- Mist Respirator 1.2 x 2 0% 0.468 80
--- 0.000128
--- 190 Li quid for Aerial application (2) Baseline 2.9 1.2 0.468 350 0.020 0.0028 50 9

Baseline +Gloves 0.023 0.468 350 0.00016
--- 6,300
--- Org. Vapour Respirator 1.2 x 10% 0.468 350
--- 0.00028
--- 90 Close d Syst em, single layer +gloves 0.0086 0.083 0.468 350 0.00006 0.000194 17,000 120 A pplicator Sprays with Gr oundboom (3) Baseline 0.014 0.74 0.468 80 0.000022 0.00040 45,000 60

Dust
- Mist Respirator 0.74 x 2 0% 0.468 80
--- 0.000082
--- 300 Sprays with Fix
Wing aircraft (4) Eng. Cont 0.0050 0.068 0.468 350 0.000035 0.00016 29,000 150 Flagger Flagging during aerial applications (5) Baseline 0.012 0.35 0.468 350 0.000084 0.00082 12,000 29

Dust
- Mist Respirator 0.35 x 2 0% 0.468 350
--- 0.000164
--- 150 a Baseline consists of long
- sleeve shirt, long pants, shoes, and socks and no respirator. Eng. Cont. consists of enclosed cockpit. b Baseline Dermal Unit Exposure represents long pants, long sleeved shirt, no gloves, open mixing/loading, and open cab tractors, as appropriate. Eng. Cont. Dermal Unit Exposure represents enclosed cockpit. c Baseline I

nhalation Unit Exposure represents no respiratory protection , open mixing/loading, and open cab tractors, as appropriate. Eng. Cont. I nh alation Unit Exposure represents enclosed cockpit. d Daily acres treated values are from EPA estimates of acreage that could be treated in a single day for each exposure scenario of concern. Exposure SAC Policy 9, 7/5/2000. e Daily dermal dose (mg/kg/d ) = [unit dermal exposure (mg/lb ai) x dermal absorption (0.003) x application rate (lb ai/acre) x daily acres treated / body weight (70kg). f Daily inhalation dose (mg/kg/d) = (unit exposure (μg/lb ai) x (1mg/1000 μg) conversion x appl. rate (lb ai/acre ) x daily acres treated / body weight (70kg). g Dermal MOE = Dermal NOAEL (1 mg/kg/d) / Dermal daily dose. UF = 100. h Inhalation MOE = I

nhalation NOAEL (0.024 mg/kg/d) / I nhalation daily dose. UF = 100.

### Page 10 of 21

Table 3. Post - Application Exposure and Risk Est im ates for Hand Harvesting Diquat - treated canola. Crop Application Rate

(lb ai/A) Work

Activity Transfer

Coefficients a (cm2 /hr) Post application Day b DFRc

(μg/cm2 ) Daily Dose d

(m g/k g/day) MOE e Field/row Crop, low/medium, Canola 0.468 Hand Harvesting 2 ,500 0 1.050 0.00090 1,100
a Transfer coefficient from Science Advisory Council for Exposure: 01/31/08. b Day after treatment represents approximately 12 hours following application when sprays have dried. c DFR = Application Rate (lb ai/acre) x Fractio n of active ingredient that remains on the foliage when sprays have dried x 4.54E8 μg/lb x 24.7E
9 acre/cm 2

. d Daily dose = DFR (μg/cm2 ) x TC (cm2 /hr) x conversion factor (1 mg/1,000 μg) x dermal absorption (0.003) x exposure time (8 hrs/day) / body weight (70 kg). e MOE = NOAEL (1 mg/kg/day) / daily dose (mg/kg/day) . 

### Residue Chemistry Considerations The reregistration requirements for plant metabolism are fulfilled. The qualitative nature of the residue in plants is adequately understood and the termina l residue of concern in plants is the diquat cation. Similarly , the qualitative nature of the residue in livestock is adequatel y understood based on acceptable poultry , ruminant, and fish metabolism studies, and the residue of concern is the diquat cation The Pesticide Anal yt ical Manual (PAM) Vol. II. lists a spectrophotometric method, designated as Method A, as available for the enforcement of tolerances for residues of diquat in/on plant and in livestock commodities. The limit of detection is 0.01 ppm. FDA’s multiresidue methods are unlikely to be successful for the analy sis of diquat. Data depicting residues of diquat in/on canola seed, cake, and oil were submitted with the Section 18 materials. Data are from Canadian and European trials, conducted at application rates ranging from 0.2 to 3.8 kg/ha (0.18 to 3.4 lb/A) with PHI s ranging from 0 to 32 day s. The use pattern associated with the Section 18 is 0.52 kg/ha (0.47 lb/A) per season with a PHIof 7 day s. Using the subset of the submitted data whi ch most closely matches the use pattern results in residues ranging from <0.05 ppm to 1.3 ppm. The average residue for this subset is 0.5 ppm. Using the NAFTA Tolerance/MRL Calculator, assuming that <0.05 ppm equals 0.05 ppm, gives a recommended toleranc e of 4 ppm (Attachment 1). Maximum Residue L imits (MRL s) are listed for Codex and Canada at 2 ppm and 1 ppm, respectivel y (Attachment 2 ). For purposes of harmonization, HED is recommending a time
limited tolerance of 1.0 ppm in canola seed. The data sub mitted for the canola press cake shows that diquat concentrates in the cake relative to levels in the seed. Due to limitations in the data presentation, it is difficult to determine the exact processing factor for an y given data set; nevertheless, the max imum factor appears to be on the order of 3X. Therefore, HED is recommending a time
- limited tolerance for residues of diquat in/on canola meal at 3.0 ppm. The data show no detectable residues of diquat in canola oil, as would be expected for an ionic compound. A tolerance in canola oil is not needed.

### Page 11 of 21

Drinking Water Considerations Diquat is registered for aquatic weed control and, as such, may be applied directly

to bodies of water. The maximum contaminant level (MCL) for diquat established by the Offi ce of Water is 20 ppb (0.02 ppm). As per the 2002 Tier 1 drinking water assessment 1 

### , the MCLof 20 ppb (0.02 ppm) was assumed for both the acute and chronic assessments, based on results of diquat monitoring data. As a point of characterization, the FQPA Index Reservoir Screening Tool (FIRST) model was used to estimate environmental concentrations in drinking water from surface water contaminated by terrestrial use s of diquat. The following scenarios were modeled: trees/vines/small fruits/vegetables (maximum use rate of 1 lb a.i./A, single application, 87 PCA); potatoes (0.5 lb a.i./A, 2 applications, 14 day application interval, 87 PCA); and alfalfa/clover/non
- crop (0.5 lb a.i./A, 1 application, single application, 87 PCA) . The surface water estimated environmental concentrations (EECs) generated b y F IR ST ranged from 6.3
- 13.2 ppb (ug/L) for peak exposure and 0.2
- 0.4 ppb for annual average exposure. The model and its description are available at the EPA internet site: http://www.epa.gov/oppefed1/models/water/
. Dietary Exposure Analysis Acute and chronic aggregate dietary (food and drinking water) exposure and risk assessments were conducted using the Dietary Exposure Evaluation Model DEEM
- FCID TM, Version 2.03 which use s food consumption data from the U.S. Department of Agriculture’s Continuing Survey s of Food Intakes by Individuals (CSFII) from 1994
- 1996 and 1998. The anal ys es were performed to support a Section 18 use of diquat on canola. Def ault processing factors from DEEM v.7.81 were used in the anal ys is. Acute Dietary

(Food and Drinking Water) Exposure Results and Characterization The acute dietary

assessment assumes 100% crop treated and tolerance
- level residues of diquat for all foods with registered uses. For drinking water, the acute assessment uses the Office of Water’s MCL ( 0.02 ppm), which is considered to be a worst
- case estimate. Acute dietary risk estimates are below HED’s LOC ( i.e. , < 100% of the aPAD) for all population subgroups (Table 4 )
. Chronic Dietary

(Food and Drinking Water) Exposure Results and Characterization T he chronic assessment is based on tolerance
- level residues and 100% crop treated for crops with direct diquat uses. For crops with tolerances to cover irri gation with diquat
- treated water, anticipated residue levels from irrigation trials are used in conjunction with estimates of % of crops irrigated. For fish, average residues are assumed. Default processing factors from DEEM v.7.81 were used in the analy sis. For drinking water, the chronic assessment uses the Office of Water’s MCL ( 0.02 ppm), which is considered to be a worst
- case estimate. Chronic dietary risk estimates are below HED’s LOC ( i.e. , < 100% of the c PAD) for all population subgroups (Table 4).

1 Tier I Drinking Water and Aquatic Ecological Exposure Assessments f or Diquat Dibromide. J Breithaupt ( 5 March 20 02, D281199)
.

### Page 12 of 21

Diquat has been classified as not carcinogenic to humans; therefore, cancer risk is not a concern for this compound. Table 4 . Summary of Dietary (Food + Drinking Water) Exposure and Risk for Diquat Population Subgroup Ac ute Dietary ( 95 th Percentile ) Chronic Dietary Dietary Exposure (mg/kg/day) % aPAD Dietary Exposure (mg/kg/day) % cPAD General U.S. Population 0.007339 1 0.000848 17 All Infants (< 1 year old) 0.006505 1 0.001752 35 Children 1 - 2 years old 0.010082 1 0.001688 34 Children 3
- 5 y ear s old 0.009391 1 0.001444 29 Children 6
- 12 y ears old 0.006599 1 0.000975 20 Youth 13
- 19 y ears old 0.005566 1 0.000670 13 Adults 20
- 49 y ears old 0.007337 1 0.000761 15 Adults 50+ years old 0.007101 1 0.000756 15 Females 13
- 49 y ears old 0.005907 1 0.000 709 14 

### Non - Dietary, Non - Occupational Exposure Diquat dibromide can be applied to turf, to recreational ponds & lakes, for general weed control in and around home & garden sites, and for landscape uses by residential handlers. Application rates for diqu at dibromide range from 0.25 to 4.0 pounds active ingredient per acre. Diquat dibromide is formulated for residential uses as a read y - to - use liquid and as a soluble concentrate/ liquid that can be mixed with water and then applied with a low
- pressure handwand, bac kpack spray er or with a trigger
- pump sprayer. This residential exposure and risk assessment is based on the previous assessment (Tom Brennan, D279507, 14 December 2001) with the following changes to reflect: (1) the use o f a new dermal absorption rate of 0.3%, (2) the use of PHED unit exposures for some handler’s exposure calculations, and (3) the corrections of miscalculations found in exposure estimation s. Handlers There are four residential handler scenarios that are expected from the resid ential uses: ● Mixing, loading, and applying with a low
- pressure handwand; ● Mixing, loading, applying with a backpack sprayer; ● Applying with a ready
- to - use product in an aerosol can; and ● Applying with a trigger pump spray er. The following e xposure assumptions are made in the exposure calculations: ● Average bod y weight of an adult handler is 70 kg/day. ● The highest application rate of 0.018 lb ai/gallon of spray solution is used. ● Backpack sprayers and low pressure handwands are a pplied at a rate of 5 gallons per day
. ● Aerosol cans and triggers spray ers are applied at a rate of 0.125 gallons per day
. ● No protective clothing is worn for these residential handl er exposure/risk scenarios. ● Exposure frequency
- a short
- term exposure duration (less than 30 day s).

### Page 13 of 21

Low - Pressure Handwand This scenario estimates exposure and risk to a handler who performs mixing, loading, and applying diquat dibromide with a low
- p ressure handwand to control weeds in and around lawns, gardens, around buildings, driveway s, fence lines and other such edge areas. The dermal and inhalation unit exposures for this scenario are based on the PHED Version 1.1 (8/98) . The dermal MOE is 2,6 00 and the inhalation MOE is 620 (Table 5 ) . These MOEs indicate that risks are not of concern
. Backpack sprayer This scenario estimates exposure and risk to a handler who performs mixing, loading, and applying diquat dibromide with a backpack sprayer to control weeds in and around lawns, gardens, around buildings, driveway s, fence lines and other such edge areas. The dermal and inhalation unit exposures for this scenario are based on the PHED Version 1.1 (8/98) . The dermal MOE is 100,000 and the inhalation MOE is 620 (Table 5 ) . These MOEs indicate that risks are not of concern
. Aerosol Can This residential scenario estimates exposure and risk to a handler who appl ies diquat dibromide with an aerosol spray

can to control weeds in and around lawns, gardens, around buildings, driveway s, fence lines and other such edge areas. The dermal and inhalation unit exposures for this scenario are based on the PHED Version 1.1 (8/98) . The dermal MOE is 55,000 and the inhalation MOE is 570 (Table 6) . These MOEs in dicate that risks are not of concern
. Trigger - Pu mp Sprayer This residential scenario estimates exposure and risk to a handler who appl ie s diquat dibromide with a trigger
- pump sprayer to control weeds in and around lawns, gardens, around buildings, driv eway s, fence lines and other such edge areas. The dermal and inhalation unit exposures for this scenario are based on a carbaryl study (ORETF study

MRID # 44459801) on ready
- to - use insect sprayer application to home garden vegetables. The dermal MOE is 2 00,000 and the inhalation MOE is 11,000,000 (Table 6) . These MOEs indicate that risks are not of concern. Post - Application Diquat dibromide is used on dormant turf grass for weed control. There are potential short
- term post - application exposures (1 to 30 day s) associated with this ty pe of use because of residents ’ activities on treated lawns in the initial hours and day s following treatment. Post
- application exposure to golfers who play on a treated golf course is also assessed. Additionally , a post ap plication assessment for swimmers is assessed to address diquat use in recreational ponds and lakes for aquatic weed control. Six residential post
- application scenarios are assessed:

### Page 14 of 21

● Dermal exposure to treated turf grass (adults and children); ● Recreational exposure from playing golf (adults); ● Incidental ingestion of treated turf grass via object
- to - mouth activity (toddlers); ● Incidental ingestion of residue via hand
- to - mouth activity (toddlers); ● Incidental ingestion of soil from treated area (toddlers); and ● Recreational exposure from swimming in treated ponds and lakes (adults and children). Dermal Exposure Scenarios Following assumptions are made in the dermal exposure calculations: ● The highest application rate of 0.50 lbs ai/acre is used. ● Turf transferable residue is equal to 5 % of the application rate. ● Turf transfer coefficient is 14,500 cm 2 

### /hr for adult and 5,200 cm 2 

### /hr for children. ● Expos ure duration is 2 hours for residential lawns, and 4 hours for golf course turf. ● Body weight is 70 kg for adults, and 15 kg for toddlers. ● No protective clothing is assumed for these post
- application exposure/risk scenarios. Dermal Exposure in Resi dential Lawns This scenario estimates dermal exposure and risk to adults (females were assessed due to the developmental toxicity

endpoint) and toddlers from dermal contact with turf treated with diquat dibromide when they

enter treated yards for recreati on, yard work, or other homeowner activities. The adult MOE is 32,000 and toddler MOE is 19,000 (Table 6 ) . These MOEs indicate that risks are not of concern. Dermal Exposure at a Golf Course. This scenario estimates dermal exposure and risk to adult go lfers (females were assessed due to the developmental toxicity endpoint) golfers from dermal contact with diquat
- treated turf grass when they

enter the golf course after diquat dibromide spray s have dried and then play four hours of golf. The MOE for gol fers is 480,000 (Table 6 ) and indicates that the risk is not of concern . Incidental Oral Exposure Scenarios Following assumptions are made in the incidental oral exposure calculations: ● The highest application rate of 0.50 lbs ai/acre is used. ● 5 % of the application rate is available for transfer from treated turf to wet hands and objects. ● Surface are a of the portion of the hand put into the mouth is 20 cm 2



### . ● Hand
- to - mouth exposure frequency is 20/times per hour. ● Body weight is 15 kg for toddlers. ● Exposure time is 2 hours. ● Saliva extract factor (for hand
- to - mouth onl y) is 50 percent.

### Page 15 of 21

● No protective clothing is assumed for these post
- application exposure/risk s cenarios. Toddler Ingestion of Treated Turf Grass via Object - to - Mouth Activities This scenario estimates doses to toddlers from incidental ingestion of diquat
- treated turf grass while they

play in the treated areas. The MOE for object
- to - mouth is 6,300 (Table 7 ) and indicates that the risk is not of concern. Toddler Ingestion of Residue via Hand - to - Mouth Activities This scenario estimates doses to toddlers from incidental ingestion of diquat residues as a result of hand
- to - mouth transfer when they play on treated yards. The MOE for hand
- to - mouth is 140 (Table 7 ) and and indicates that the risk is not of concern
. Toddler Ingestion of Soil from Treated Area This scenario estimates doses to toddlers from incidental ingestion of soil containing pesticide residues while they

play in treated areas. The MOE for ingesting treated soil is 800,000 (Table 7 ) and indicates that the risk is not of concern
. Swimming Exposure Scenario The potential exposures to swimmers who enter treated ponds and lakes are based on the Swimmer Exposure Assessment Model (SWIMODEL) which was developed for estimating the human exposure doses to the pesticides and toxic pollutants in swimming pools. This model is a modification of a study

used by J. A. Beech (1980) for estimating exposure to Trihalomethanes (THM s ) in swimming pools. Clearly in many way s swimming in ponds and lakes is different from that in pools; however , the basic exposure to chemicals in the water column is similar enough to warrant using this model for this asses sment. The model is based on exposure routes and age
- specific contact factors, exposure duration and frequency , chemical/physical properties of the pollutant, and pollutant concentration . With these parameters, total exposure doses can be approximated b y the model. For this assessment, non
competitive children swimmers (age 7
- 10), non - competitive adult female swimmers, and a diquat dibromide concentration of 260 ppb (the highest value based on nationwide monitoring data
- reported b y FEAD ) in the lake are modeled
. The MOE for non
- competitive children swimmers age 7
- 10 is 180 (Table 8 ) . The MOE for non
competitive swimming adult females is 770 (Table 9) . These MOEs indicate that risks are not of concern . The calculations for post
- application exposure to swimmers are described in the previous diquat assessment ( D279507 , T. Brennan, 14 December 2001). T he SWIMODEL runs , including detail ed anal ys is for each of the model inputs, assumptions, and results , are provided in the Appendix 1 of D279507
.

### Page 16 of 21

Tabl e 5. Residential Handler’s Short - term Exposure and Risk Estimates Associated with Diquat Dibromide. Exposure Scenario Dermal

Unit Exposure (m g/lb ai) Inhalation

Unit Exposure (m g/lb ai) Crop Application Rate Am ount

Treated Dermal

Daily Dose (m g/k g/day ) c Dermal

MOE d Inhalation

Daily Dose (m g/k g/day) e Inhalation

MOE f Mixer/Loader/Applicator Mixing/Loading/ Applying Liquids for Low
- Pressure Handwand application a 100 0.03 Turf 0.018 lb ai per gallon 5 Gallons

per day 0.000386 2,600 0.0000386 620 Mixing/L oading/ Applying Liquids for Backpack sprayer application a 2.5 0.03 Turf 0.018 lb ai per gallon 5 Gallons

per day 0.0000096 100,000 0.0000386 620 Applicator Aerosol can application a 190 1.3 Turf 0.018 lb ai per gallon 0.125

Gallons per day 0 .000018 55,000 0.000042 570 Trigger Spr ayerb 53 0.000067 Turf 0.018 lb ai gallon 0.125

Gallons per day 0.0000051 200,000 0.000000002 11,000,000

a Unit exposure values from PHED V1.1. b Unit exposure values from ORETF study MRID # 44459801. c Dermal daily dose (mg/kg/ day) = daily unit exposure (mg/ lb ai) x application rate (lb ai/gallon) x amount handled per day (gallons) x dermal absorption factor (0.3%) / body weight (70 kg). d Dermal MOE = Dermal NOAEL (1 mg/kg/day) / Dermal daily dose (mg/ kg/ day). e Inhalation daily dose (mg/ kg/day) = inhalation unit exposure (mg/lb ai) x application rate (lb ai/gallon) x amount handled per day (gallons) / body weight (70 kg). f Inhalation MOE = I nhalation NOAEL (0.024 mg/ kg/day) / Inhalation daily dose (mg/kg/day). Table 6. Post
- Application Dermal Exposure and Risk Estimates for Toddlers and Adults on Day 0. Scenario Application

Rate 1 (lb ai/ acre) Fraction of

Residue Retained Transfer

Coefficie nt (cm 2 /hr) Exposure Duration (hours) Body

Weight (kg) Daily Dermal Dose 2 (mg/kg/ day) Dermal

MOE 3 T oddler 0.5 0.05 5,200 2 15 0.000052 19,000 Adult 0.5 0.05 14,500 2 70 0.000031 32,000 Golfer
- Adult 0.5 0.05 500 4 70 0.0000021 480,000

1 The application rate is based on the highest labeled rates EPA Reg. No. 1 0182
- 404. 2 Daily Dermal Dose on day “t” PDR t (mg/kg/day) = DFRt x CF1 x Tc x ET x DA / BW where: DFR t = dislodgeable foliar residue on day “t” (ug/cm 2 ), CF1 = weight unit onversion factor to convert ug units in the DFR to mg for the daily dose (0.00 1 mg/ug), Tc = transfer coefficient (cm2 /hr), ET = exposure time (hr/day), DA = Dermal Absorption factor (0.3%), BW = body weight (kg); and DFR t = AR x F x (1
- D) t x CF2 x CF3 where: AR = application rate (lbs ai/ft 2 or lb ai/acre), F = fraction of ai retained on foliage (unitless), D = fraction of residue that dissipates daily (unitless), t = post
- application day on which exposure is being assessed, CF2 = weight unit conversion factor to convert the lbs ai in the application rate to ug for the DFR value (4.54E8 ug/lb), CF3 = area unit conversion factor to convert the surface area units (ft 2 ) in the application rate to cm2 for the DFR value (1.08E
- 3 ft 2 /cm 2 or 24.7E
- 9 acre/cm 2 if the application rate is per acre) 3 Post
- application dermal MOE = Dermal NOAEL (1 mg/ kg/day) / Daily Dermal Dose (mg/kg/day)

### Page 17 of 21

Table 7. Post
- Application Incidental Oral Exposure and risk estimates for Toddlers Entering Treated Lawns. Ty pe of Exposure Applic
.

Rate 1 (lb ai/ acre) Fraction

of Residue Available on Foliag e Ingestion

Rate or Other Assumptions Saliva

Extraction Factor ( %ile ) Exposure

Duration (hours) Body

Wgt (kg) Daily

Oral Dose 2 (mg/kg/day) MOE 3 Object
- to - mo uth activities While on Treated Turf Grass 0.5 0.20 25 cm 2 / day ingestion NA 2 15 0.00016 6,300
Hand
- to - Mouth Activity While on Treated Turf Grass 0.5 0.05 20 events/hr; 20 cm 2 exposed area/event 50% 0.0074 140 Ingestion of Soil from Treated Area 0.5 0.05 100 mg/ day ingestion NA 0.00000125 800,000 Com bined 130 1 The application rate is based on the highest labeled rates EPA Reg. No. 10182
- 404. 2 Object - to - mo uth potential dose PDRt (mg/kg/day) = GRt x IgR x CF1 / BW where: GRt = grass (and plant matter) residue on day “t” (ug/cm 2 ), IgR = ingestion rate of grass (cm 2 /day), CF1 = weight unit conversion factor to convert ug units in the DFR to mg for the daily dose (0.001 mg/ug), BW = body weight (kg); and GR t = AR x F x (1
- D) t x CF2 x CF3 where: AR = application rate (lbs ai/ft 2 or lb ai/acre), F = fraction of ai available on the grass (unitless), D = fraction of residue that dissipates daily (unitless), t = post
- application day on which exposure is being assessed, CF2 = weight unit conversion factor to convert the lbs ai in the application rate to ug for the grass residue value (4.54E8 ug/lb), CF3 = area unit conversion factor to convert the surface area units (ft2 ) in the application rate to cm2 for the grass residue value (1.08E
- 3 ft 2/cm2 or 24.7E
- 9 acre/cm 2 if the application rate is per acre). Hand - to - mo uth potential dos e PDRt (mg/kg/day) = DFRt x SA x FQ x SEF x ET x CF1 / BW where: DFRt = dislodgeable foliar residue on day “t” (ug/cm 2 turf), SA = surface area of the hands (cm2/event), SEF = saliva extraction factor (%), FQ = frequency of hand
- to - mouth activi ty (events/hr), ET = exposure time (hr/day), CF1 = weight unit conversion factor to convert ug units in the DFR value to mg for the daily exposure (0.001 mg/ug), BW = body weight (kg); and DFR t = AR x F x (1
- D) t x CF2 x CF3 where: AR = application rate (lbs ai/ft 2 or lb ai/acre), F = fraction of ai retained on foliage (unitless), D = fraction of residue that dissipates daily (unitless) , t = post - application day on which exposure is being assessed, CF2 = weight unit conversion factor to convert th e lbs ai in the application rate to ug for the DFR value (4.54E8 ug/lb), CF3 = area unit conversion factor to convert the surface area units (ft2 ) in the application rate to cm2 for the DFR value (1.08E
- 3 ft2 /cm 2 or 24.7E
- 9 acre/cm 2 if the application rate is per acre). Ingestion of soil p otential dose PDR t (mg/kg/day) = SRt x IgR x CF1 / BW where: SRt = soil residues on day “t” (ug/g), IgR = ingestion rate of soil (mg/day), CF1 = weight unit conversion factor to convert ug units in the residues on the soil to g for the daily dose (1.0E
- 6 g/ug), BW = body weight (kg); and SR t = AR x F x (1
- D) t x CF2 x CF3 x CF4 where: AR = application rate (lbs ai/ft 2 or lb ai/acre), F = fraction of ai available in uppermost cm of the soil (fraction/cm), D = fraction of residue that dissipates daily (unitless), t = post - application day on which exposure is being assessed, CF2 = weight unit conversion factor to convert the lbs ai in the application rate to ug for the soil residue value (4.54E8 ug/lb), CF3 = area unit conversion factor to convert the surface area units (ft 2 ) in the application rate to cm2 for the SR value (1.08E
- 3 ft2 /cm 2 or 24.7E
- 9 acre/cm 2 if the application rate is per acre), CF4 = volume to weight unit conversion factor to convert the volume units (cm 3 ) to weight units for the SR value (0.67 cm 3 /g soil). 3 Post
- application oral MOE = Oral NOAEL(1 mg/kg/day)/Daily Oral Dose(mg/kg/day). Table 8. Swimmers’ Exposure and Risk Estimates from a Treated Lake on Day 0. Exposed Populatio n Concentration

in Lake (ppb) 1 Total Exposure

(mg/event) 2 Body

Weight (kg) 3 Total Dose

(mg/kg/day) 4 MOE 5 Child (age 7
- 10) 260 0.21 37.8 0.0055 180 Adult (female) 260 0.11 84.4 0.0013 770 1 The concentration in the lake was run at 260 ppb (the highest v alue based on nationwide monitoring data

– reported by FEAD) 2 Total Exposure is a combination of exposures via the following routes: oral, dermal, buccal/sublingual, orbital/nasal, aural, and inhalation. 3 Body weights represent the 90% for the population being modeled. 4 Total dose (mg/kg/day) = Total exposure (mg/event) / body weight (kg) 5 MOE = Oral NOAEL 1 mg/kg/day / Total dose (mg/kg/day)

### Page 18 of 21

Aggregate Risk Aggregate risk estimates that combine exposures from agricultural, residential, and recre ational sources of diquat have been calculated for this Section 18 assessment. There are no use patterns that would result in intermediate
- or long
- term residential exposure; therefore, acute and chronic aggregate risks are equivalent to the dietary risk discussed above. Short
- term MOEs are presented in Table 9 . All MOEs are greater than 100 and, therefore, represent risks that are not of concern
. Table 9
. Short
- Term Aggregate Risk Estimates for Diquat Population Subgroup Chronic

Dietary, mg/kg/day S hort
- Term

NOAEL, mg/kg/day MOE

Dietary a Mixer/

Loader/ Applicator b Post
- Application Swimmer b Aggregate c

Dermal b Incidental

Oral b General U.S. Population 0.000848 1 1100 570 32000
-- 770 250 All Infants (< 1 year old) 0.001752 1 5 7 0
-- 19000 130
-- 10 5 Children 1
- 2 years old 0.001688 1 590
-- 19000 130
-- 10 6 Children 3
- 5 years old 0.001444 1 690
-- 19000
-- -- 660 Children 6
- 12 years old 0.000975 1 1000
-- 19000
-- 180 150 Youth 13
- 19 years old 0.000670 1 1 4 00 570 32000
-- 770 260 Adults 20
- 49 years old 0.000761 1 1300 570 32000
-- 770 2 6 0 Adults 50+ years old 0.000756 1 1300 570 32000
-- 770 2 6 0 Females 13
- 49 years old 0.000709 1 1400 570 32000
-- 770 260
a Dietary MOE = Short
- term NOAEL ÷ Chronic Dietary Exposure b From Tables 5
- 8
. c Aggregate MOE = 1 ÷ [(1 ÷ MOE Dietary ) + (1 ÷ MOE MLA) + (1 ÷ MOE Dermal ) + (1 ÷ MOE Incidental Oral ) + (1 ÷ MOE Swimmer)] 

### Cumulative Risk Unlike other pesticides for which EPA has followed a cumulative risk approach based on a common mechanism of toxi city , EPA has not made a common mechanism of toxicity finding for diquat and an y other substances, and diquat does not appear to produce a toxic metabolite produced b y other substances. For the purposes of this action, therefore, EPA assumed that diquat d oes not have a common mechanism of toxicity with other substances. For information regarding EPA’s efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the policy statements released b y EPA’s OPP concerning common mechanism determinations and procedures for cumulating effects from substances found to have a common mechanism on EPA’s website at http://www.epa.gov/pesticides/cumulative/.

### Page 19 of 21

Conclusions HED is recommending in fav or of the emergency exemption for the use of diquat dibromide on canola in Oklahoma and Kentucky, and is recommending that time
- limited tolerances be established for residues of the diquat cation in/on canola commodities as follows: Canola, seed 1.0 ppm Canola, meal 3.0 ppm
.

### Page 20 of 21

Attachment 1 Re gu la to r: EP A Ch em ica l: Di qu at Cro p: Ca no la PH I: Ap pr ox . 7 d ay s Ap p. R at e: Ap pr ox . 0. 5 kg /h a Su bmit te r: n: 25 mi n: 0. 05 ma x: 1. 30 me dia n; 0. 41 aver ag e: 0. 49 95 th P er ce nt il e 99 th Pe rc en ti le 99 .9 th Pe rc en ti le 1. 2 1. 4 1. 7 (1 .4 ) (1 .8 ) (- -) 1. 9 4. 0 9. 0 (4 .0 ) (9 .0 ) (- -) 1. 7 1. 7 UP LM ed ia n9 5t h 2. 5 0. 92 56 p- va lue > 0 .0 5 : D o no t re je ct lo gn or ma li ty as su mp ti on App ro xi ma te Sh api ro -F ra nc ia No rm al ity T es t EU M et ho d II Di st ri bu ti on -F ree Ca li fo rn ia M et hod μ + 3 σ EU Me th od I No rma l EU Me th od I Lo g Nor ma l

Lognormal Probability Plot

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 2.0000

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313 y = 1.044x - 1.1381 R 2 = 0.9256

PercentilesConcentrations EPA Diquat Canola Approx. 7 days Approx. 0.5 kg/ha

### Page 21 of 21

Attachment 2 

# INTERNATIONAL RESIDUE LIMIT STATUS Chemical Name: 

### 6,7
- dihydrodip yrido[1,2
- a :2 ′,1′
- c ]py

razinediium dibromide Common Name: Diquat X Proposed tolerance

 Reevaluated tolerance  Other Date: 12/4/08


# Codex Status (Maximum Residue L imits) 

# U. S. Tolerances  No Codex proposal step 6 or above  No Codex proposal step 6 or abo ve for the crops requested Petition Number: PP#08OK02 DP Barcode: D355407 Other Identifier: Residue definition (step 8/CXL): Diquat cation. Generally available as dibromide. Revie wer/Branch: M. Doherty/RAB2 Residue definition: Diquat cation 

### C rop (s) MRL (mg/kg) Crop(s) Tolerance (ppm) Rape seed 2. Canola 4.0


# Limits for Canada Limits for Mexico  No Limits  No Limits for the crops requested  No Limits  No Limits for the crops requested Residue definition: 9,10
- di hydro
- 8a,10a
diazoniaphenanthrene ion Residue definition: diquat 

### Crop(s) MRL(mg/kg) Crop(s) MRL(mg/kg) Rapeseed 1.0 Notes/Special Instructions: S. Funk, 12/04/2008.