[Federal Register Volume 75, Number 101 (Wednesday, May 26, 2010)]
[Rules and Regulations]
[Pages 29435-29441]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-12648]



40 CFR Part 180

[EPA-HQ-OPP-2009-0920; FRL-8827-7]

Diquat Dibromide; Pesticide Tolerances

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.


SUMMARY: This regulation establishes tolerances for residues of diquat, 
derived from applications of diquat dibromide, in or on canola meal and 
canola seed. Syngenta Crop Protection, Inc. requested these tolerances 
under the Federal Food, Drug, and Cosmetic Act (FFDCA). This regulation 
also corrects minor errors in the regulations for diquat at 40 CFR 

DATES: This regulation is effective May 26, 2010. Objections and 
requests for hearings must be received on or before July 26, 2010, and 
must be filed in accordance with the instructions provided in 40 CFR 
part 178 (see also Unit I.C. of the SUPPLEMENTARY INFORMATION).

ADDRESSES: EPA has established a docket for this action under docket 
identification (ID) number EPA-HQ-OPP-2009-0920. All documents in the 
docket are listed in the docket index available at http://www.regulations.gov. Although listed in the index, some information is 
not publicly available, e.g., Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. Certain 
other material, such as copyrighted material, is not placed on the 
Internet and will be publicly available only in hard copy form. 
Publicly available docket materials are available in the electronic 
docket at http://www.regulations.gov, or, if only available in hard 
copy, at the OPP Regulatory Public Docket in Rm. S-4400, One Potomac 
Yard (South Bldg.), 2777 S. Crystal Dr., Arlington, VA. The Docket 
Facility is open from 8:30 a.m. to 4 p.m., Monday through Friday, 
excluding legal holidays. The Docket Facility telephone number is (703) 

FOR FURTHER INFORMATION CONTACT: Susan Stanton, Registration Division 
(7505P), Office of Pesticide Programs, Environmental Protection Agency, 
1200 Pennsylvania Ave., NW., Washington, DC 20460-0001; telephone 
number: (703) 305-5218; e-mail address: stanton.susan@epa.gov.


I. General Information

A. Does this Action Apply to Me?

    You may be potentially affected by this action if you are an 
agricultural producer, food manufacturer, or pesticide manufacturer. 
Potentially affected entities may include, but are not limited to those 
engaged in the following activities:
     Crop production (NAICS code 111).
     Animal production (NAICS code 112).
     Food manufacturing (NAICS code 311).
     Pesticide manufacturing (NAICS code 32532).
    This listing is not intended to be exhaustive, but rather to 
provide a guide for readers regarding entities likely to be affected by 
this action. Other types of entities not listed in this unit could also 
be affected. The North American Industrial Classification System 
(NAICS) codes have been provided to assist you and others in 
determining whether this action might apply to certain entities. If you 
have any questions regarding the applicability of this action to a 
particular entity, consult the person listed under FOR FURTHER 

B. How Can I Get Electronic Access to Other Related Information?

    You may access a frequently updated electronic version of EPA's 
tolerance regulations at 40 CFR part 180 through the Government 
Printing Office's e-CFR site at http://www.gpoaccess.gov/ecfr. To 
access the harmonized test guidelines referenced in this document 
electronically, please go to http://www.epa.gov/oppts and select ``Test 
Methods and Guidelines.''

C. How Can I File an Objection or Hearing Request?

    Under FFDCA section 408(g), 21 U.S.C. 346a, any person may file an 
objection to any aspect of this regulation and may also request a 
hearing on those objections. You must file your objection or request a 
hearing on this regulation in accordance with the instructions provided 
in 40 CFR part 178. To ensure proper receipt by EPA, you must identify 
docket ID number EPA-HQ-OPP-2009-0920 in the subject line on the first 
page of your submission. All objections and requests for a hearing must 
be in writing, and must be received by the Hearing Clerk on or

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before July 26, 2010. Addresses for mail and hand delivery of 
objections and hearing requests are provided in 40 CFR 178.25(b).
    In addition to filing an objection or hearing request with the 
Hearing Clerk as described in 40 CFR part 178, please submit a copy of 
the filing that does not contain any CBI for inclusion in the public 
docket. Information not marked confidential pursuant to 40 CFR part 2 
may be disclosed publicly by EPA without prior notice. Submit a copy of 
your non-CBI objection or hearing request, identified by docket ID 
number EPA-HQ-OPP-2009-0920, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the on-line instructions for submitting comments.
     Mail: Office of Pesticide Programs (OPP) Regulatory Public 
Docket (7502P), Environmental Protection Agency, 1200 Pennsylvania 
Ave., NW., Washington, DC 20460-0001.
     Delivery: OPP Regulatory Public Docket (7502P), 
Environmental Protection Agency, Rm. S-4400, One Potomac Yard (South 
Bldg.), 2777 S. Crystal Dr., Arlington, VA. Deliveries are only 
accepted during the Docket Facility's normal hours of operation (8:30 
a.m. to 4 p.m., Monday through Friday, excluding legal holidays). 
Special arrangements should be made for deliveries of boxed 
information. The Docket Facility telephone number is (703) 305-5805.

II. Summary of Petitioned-For Tolerance

    In the Federal Register of February 4, 2010 (75 FR 5793) (FRL-8807-
5), EPA issued a notice pursuant to section 408(d)(3) of FFDCA, 21 
U.S.C. 346a(d)(3), announcing the filing of a pesticide petition (PP 
9F7639) by Syngenta Crop Protection, Inc., P.O Box 18300, Greensboro, 
NC 27419. The petition requested that 40 CFR 180.226 be amended by 
establishing tolerances for residues of the herbicide diquat, 6,7-
dihydrodipyrido(1,2-a:2'1'-c)pyrazinediium, derived from application of 
the dibromide salt and calculated as the cation, in or on canola, meal 
at 3.0 parts per million (ppm); and canola, seed at 1.0 ppm. That 
notice referenced a summary of the petition prepared by Sygenta Crop 
Protection, Inc., the registrant, which is available in the docket, 
http://www.regulations.gov. There were no comments received in response 
to the notice of filing.
    Based upon review of the data supporting the petition, EPA has 
increased the tolerance levels for canola, meal and canola, seed to 6.0 
ppm and 2.0 ppm, respectively. The reason for these changes is 
explained in Unit IV.C.

III. Aggregate Risk Assessment and Determination of Safety

    Section 408(b)(2)(A)(i) of FFDCA allows EPA to establish a 
tolerance (the legal limit for a pesticide chemical residue in or on a 
food) only if EPA determines that the tolerance is ``safe.'' Section 
408(b)(2)(A)(ii) of FFDCA defines ``safe'' to mean that ``there is a 
reasonable certainty that no harm will result from aggregate exposure 
to the pesticide chemical residue, including all anticipated dietary 
exposures and all other exposures for which there is reliable 
information.'' This includes exposure through drinking water and in 
residential settings, but does not include occupational exposure. 
Section 408(b)(2)(C) of FFDCA requires EPA to give special 
consideration to exposure of infants and children to the pesticide 
chemical residue in establishing a tolerance and to ``ensure that there 
is a reasonable certainty that no harm will result to infants and 
children from aggregate exposure to the pesticide chemical residue. . . 
    Consistent with section 408(b)(2)(D) of FFDCA, and the factors 
specified in section 408(b)(2)(D) of FFDCA, EPA has reviewed the 
available scientific data and other relevant information in support of 
this action. EPA has sufficient data to assess the hazards of and to 
make a determination on aggregate exposure for diquat dibromide 
including exposure resulting from the tolerances established by this 
action. EPA's assessment of exposures and risks associated with diquat 
dibromide follows.

A. Toxicological Profile

    EPA has evaluated the available toxicity data and considered its 
validity, completeness, and reliability as well as the relationship of 
the results of the studies to human risk. EPA has also considered 
available information concerning the variability of the sensitivities 
of major identifiable subgroups of consumers, including infants and 
    Diquat dibromide exhibits low acute toxicity via the oral and 
inhalation routes of exposure but is moderately to severely toxic via 
the dermal route of exposure. Diquat dibromide is not a skin irritant 
nor a dermal sensitizer, but it is considered a moderate to severe eye 
    Subchronic 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 
systemic toxicity, including high mortality and clinical signs. 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, mice, and rabbits indicate that target sites include the 
eyes and kidneys in both males and females and the adrenals and 
epididymides in males. There was no evidence of neurotoxicity in acute 
and subchronic studies in rats and no evidence of endocrine disruption 
or immunotoxicity in the toxicology studies available for diquat 
dibromide. In accordance with the 1986 Guidelines for Carcinogen Risk 
Assessment, diquat dibromide was classified in Group E (evidence of 
non-carcinogenicity to humans), based on a lack of evidence of 
carcinogenicity in acceptable studies in rats and mice and a lack of 
concern for mutagenicity.
    There was no evidence of increased quantitative or qualitative 
susceptibility of in utero animals or of offspring in developmental 
toxicity studies in mice, rabbits, and rats or in the 2-generation 
reproduction study in rats. Effects in the offspring were observed only 
at or above dose levels which resulted in parental toxicity.
    Specific information on the studies received and the nature of the 
adverse effects caused by diquat dibromide as well as the no-observed-
adverse-effect-level (NOAEL) and the lowest-observed-adverse-effect-
level (LOAEL) from the toxicity studies can be found at http://www.regulations.gov in the document ``Diquat Dibromide: HED Risk 
Assessment for Tolerance Reassessment Eligibility Document (TRED.),'' 
p. 10 in docket ID number EPA-HQ-OPP-2010-0920.

B. Toxicological Points of Departure/Levels of Concern

    Once a pesticide's toxicological profile is determined, EPA 
identifies toxicological points of departure (POD) and levels of 
concern to use in evaluating the risk posed by human exposure to the 
pesticide. For hazards that have a threshold below which there is no 
appreciable risk, the toxicological POD is used as the basis for 
derivation of reference values for risk assessment. PODs are developed 
based on a careful analysis of the doses in each toxicological study to 
determine the dose at which no adverse effects are observed (the NOAEL) 
and the lowest dose at which adverse effects of concern are identified 
(the LOAEL). Uncertainty/safety factors are used in conjunction with 
the POD to calculate a safe exposure level generally referred to as a 
population-adjusted dose (PAD) or a

[[Page 29437]]

reference dose (RfD) and a safe margin of exposure (MOE). For non-
threshold risks, the Agency assumes that any amount of exposure will 
lead to some degree of risk. Thus, the Agency estimates risk in terms 
of the probability of an occurrence of the adverse effect expected in a 
lifetime. For more information on the general principles EPA uses in 
risk characterization and a complete description of the risk assessment 
process, see http://www.epa.gov/pesticides/factsheets/riskassess.htm.
    A summary of the toxicological endpoints for diquat dibromide used 
for human risk assessment can be found at http://www.regulations.gov in 
the document ``Diquat Dibromide: Human Health Risk Assessment for the 
Section 18 Use on Canola in Oklahoma and Kentucky,'' p. 3 in docket ID 
number EPA-HQ-OPP-2010-0920.

C. Exposure Assessment

    1. Dietary exposure from food and feed uses. In evaluating dietary 
exposure to diquat dibromide, EPA considered exposure under the 
petitioned-for tolerances as well as all existing diquat dibromide 
tolerances in 40 CFR 180.226. EPA assessed dietary exposures from 
diquat dibromide in food as follows:
    i. Acute exposure. Quantitative acute dietary exposure and risk 
assessments are performed for a food-use pesticide, if a toxicological 
study has indicated the possibility of an effect of concern occurring 
as a result of a 1-day or single exposure.
    Such effects were identified for diquat dibromide. In the acute 
neurotoxicity study in rats, clinical signs of systemic toxicity (e.g., 
piloerection, diarrhea, urinary incontinence, upward curvature of the 
spine, subdued behavior) and decreased body-weight gains were observed 
after a single dose. In estimating acute dietary exposure, EPA used 
food consumption information from the United States Department of 
Agriculture (USDA) 1994-1996 and 1998 Nationwide Continuing Surveys of 
Food Intake by Individuals (CSFII). As to residue levels in food, EPA 
assumed tolerance-level residues and 100 percent crop treated (PCT) for 
all existing uses of diquat dibromide and the proposed new use on 
    ii. Chronic exposure. In conducting the chronic dietary exposure 
assessment EPA used the food consumption data from the USDA 1994-1996 
and 1998 CSFII. As to residue levels in food, EPA assumed tolerance-
level residues and 100 PCT for crops with direct diquat uses. For crops 
with tolerances to cover irrigation with diquat-treated water, 
anticipated residue levels from irrigation trials were used in 
conjunction with estimates of percent of crops irrigated. For fish, 
average residues were assumed. Default processing factors from Dietary 
Exposure Evaluation Model v.7.81 were used in the analysis for all 
processed commodities, except potato chips and dried potato flakes, 
which have their own tolerances based on submitted processing data.
    iii. Cancer. Based on the results of carcinogenicity studies in 
rats and mice, EPA classified diquat dibromide in Group E (evidence of 
non-carcinogenicity to humans). Therefore, an exposure assessment to 
evaluate cancer risk is unnecessary for this chemical.
    iv. Anticipated residue and PCT information. Section 408(b)(2)(E) 
of FFDCA authorizes EPA to use available data and information on the 
anticipated residue levels of pesticide residues in food and the actual 
levels of pesticide residues that have been measured in food. If EPA 
relies on such information, EPA must require pursuant to section 
408(f)(1) of FFDCA that data be provided 5 years after the tolerance is 
established, modified, or left in effect, demonstrating that the levels 
in food are not above the levels anticipated. For the present action, 
EPA will issue such Data Call-Ins as are required by section 
408(b)(2)(E) of FFDCA and authorized under section 408(f)(1) of FFDCA. 
Data will be required to be submitted no later than 5 years from the 
date of issuance of these tolerances.
    Section 408(b)(2)(F) of FFDCA states that the Agency may use data 
on the actual percent of food treated for assessing chronic dietary 
risk only if:
     Condition a: The data used are reliable and provide a 
valid basis to show what percentage of the food derived from such crop 
is likely to contain the pesticide residue.
     Condition b: The exposure estimate does not underestimate 
exposure for any significant subpopulation group.
     Condition c: Data are available on pesticide use and food 
consumption in a particular area, the exposure estimate does not 
understate exposure for the population in such area.
In addition, the Agency must provide for periodic evaluation of any 
estimates used. To provide for the periodic evaluation of the estimate 
of PCT as required by section 408(b)(2)(F) of FFDCA, EPA may require 
registrants to submit data on PCT.
    The Agency estimated the PCT for existing uses as follows:
    EPA estimated PCT for several commodities that have tolerances to 
cover inadvertent residues of diquat from irrigation with diquat 
dibromide-treated water: Barley 36%; corn 19%; legume vegetables 
(subgroup 6C) 32%; oats 7%; sorghum 15%; soybean 9%; sugarcane 54%; and 
wheat 14%. One hundred PCT was assumed for all other irrigated crops 
and crops with direct diquat dibromide uses.
    EPA estimated PCT for these commodities by estimating the percent 
crop irrigated, which serves as an upperbound for crops that may be 
exposed to diquat in irrigation water. The percent crop irrigated is an 
estimate of the share of total production that is irrigated, and is 
based on 2009 data from USDA's National Agricultural Statistics 
Service. Use of these estimates in the exposure assessment is 
conservative, because it is the equivalent of assuming 100% of 
irrigated crops are irrigated with water from diquat-treated canals. In 
fact, even in areas with surface water delivery systems, all irrigation 
canals may not be treated with diquat. Additionally, some crops, even 
in the heavily irrigated areas of the West, are not irrigated, such as 
dryland grain production.
    The Agency believes that the three conditions discussed in Unit 
III.C.1.iv. have been met. With respect to Condition a, PCT estimates 
are derived from Federal market survey data, which are reliable and 
have a valid basis. The Agency is reasonably certain that the 
percentage of the food treated is not likely to be an underestimation. 
As to Conditions b and c, regional consumption information and 
consumption information for significant subpopulations is taken into 
account through EPA's computer-based model for evaluating the exposure 
of significant subpopulations including several regional groups. Use of 
this consumption information in EPA's risk assessment process ensures 
that EPA's exposure estimate does not understate exposure for any 
significant subpopulation group and allows the Agency to be reasonably 
certain that no regional population is exposed to residue levels higher 
than those estimated by the Agency. Other than the data available 
through national food consumption surveys, EPA does not have available 
reliable information on the regional consumption of food to which 
diquat dibromide may be applied in a particular area.
    2. Dietary exposure from drinking water. Diquat dibromide is 
registered for both terrestrial and aquatic uses. The Agency used 
screening level water exposure models to estimate residues of diquat in 
drinking water from the terrestrial uses. These simulation

[[Page 29438]]

models take into account data on the physical, chemical, and fate/
transport characteristics of diquat dibromide. Further information 
regarding EPA drinking water models used in pesticide exposure 
assessment can be found at http://www.epa.gov/oppefed1/models/water/index.htm.
    Based on the First Index Reservoir Screening Tool (FIRST) and 
Screening Concentration in Ground Water (SCI-GROW) models, the 
estimated drinking water concentrations (EDWCs) of diquat dibromide 
from terrestrial uses for acute exposures are estimated to be 13.2 
parts per billion (ppb) for surface water and 0.006 ppb for ground 
water. The EDWCs for chronic exposures are estimated to be 0.4 ppb for 
surface water and 0.006 ppb for ground water.
    Diquat dibromide 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 EPA Office of 
Water is 20 ppb. EPA does not expect residues from direct applications 
of diquat dibromide to water to exceed the MCL because of the tendency 
of diquat to sorb nearly irreversably to soil and sediment.
    Since direct aquatic applications are estimated to result in higher 
concentrations of diquat in drinking water than terrestrial uses, EPA 
used the MCL of 20 ppb to assess the contribution to drinking water in 
both the acute and chronic dietary risk assessments.
    3. From non-dietary exposure. The term ``residential exposure'' is 
used in this document to refer to non-occupational, non-dietary 
exposure (e.g., for lawn and garden pest control, indoor pest control, 
termiticides, and flea and tick control on pets).
    Diquat dibromide is currently registered for the following uses 
that could result in residential exposures: Applications to turf, 
recreational ponds and lakes; general weed control in and around home 
and garden sites; and landscape uses by residential handlers. EPA 
assessed residential exposure using the following assumptions: 
Residential handlers may receive short-term dermal and inhalation 
exposure when applying diquat dibromide products. EPA assessed short-
term dermal and inhalation residential handler exposures for four 
scenarios: Mixing, loading, and applying products with a low-pressure 
handwand or backpack sprayer; and applying diquat dibromide products in 
an aerosol can or using a trigger pump sprayer. Adults and children may 
also be exposed to diquat dibromide residues on a short-term basis 
through dermal contact with treated turf and from swimming activities 
in treated recreational ponds and lakes. In addition, toddlers may 
receive short-term oral exposure from incidental ingestion during post-
application activities on treated turf. EPA assessed the following 
post-application exposure scenarios:
    i. Adult and toddler post-application dermal exposure,
    ii. Recreational exposure from playing golf on treated turf,
    iii. Toddlers' incidental ingestion of pesticide residues on lawns 
from hand-to-mouth transfer,
    iv. Toddlers' object-to-mouth transfer from mouthing of pesticide-
treated turfgrass,
    v. Toddlers' incidental ingestion of soil from pesticide-treated 
residential areas, and
    vi. Recreational exposure of adults and children from swimming in 
treated ponds and lakes.
    Further information regarding EPA standard assumptions and generic 
inputs for residential exposures may be found at http://www.epa.gov/pesticides/trac/science/trac6a05.pdf.
    4. Cumulative effects from substances with a common mechanism of 
toxicity. Section 408(b)(2)(D)(v) of FFDCA requires that, when 
considering whether to establish, modify, or revoke a tolerance, the 
Agency consider ``available information'' concerning the cumulative 
effects of a particular pesticide's residues and ``other substances 
that have a common mechanism of toxicity.''
    EPA has not found diquat dibromide to share a common mechanism of 
toxicity with any other substances, and diquat dibromide does not 
appear to produce a toxic metabolite produced by other substances. For 
the purposes of this tolerance action, therefore, EPA has assumed that 
diquat dibromide does 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 EPA's website at http://www.epa.gov/pesticides/cumulative.

D. Safety Factor for Infants and Children

    1. In general. Section 408(b)(2)(C) of FFDCA provides that EPA 
shall apply an additional tenfold (10X) margin of safety for infants 
and children in the case of threshold effects to account for prenatal 
and postnatal toxicity and the completeness of the database on toxicity 
and exposure unless EPA determines based on reliable data that a 
different margin of safety will be safe for infants and children. This 
additional margin of safety is commonly referred to as the Food Quality 
Protection Act (FQPA) Safety Factor (SF). In applying this provision, 
EPA either retains the default value of 10X, or uses a different 
additional safety factor when reliable data available to EPA support 
the choice of a different factor.
    2. Prenatal and postnatal sensitivity. The prenatal and postnatal 
toxicity database for diquat dibromide includes developmental toxicity 
studies in rats, mice, and rabbits and a 2-generation reproduction 
toxicity study in rats. There was no evidence of increased quantitative 
or qualitative susceptibility of fetuses or offspring in any of these 
    In the developmental study in rats, fetal effects (decreased fetal, 
litter, and gravid uterine weights; an increased incidence of fetuses 
with hemorrhagic kidney; and delayed skeletal ossification) occurred at 
a higher dose than the dose causing effects in maternal animals 
(decreased body-weight gains and food consumption during dosing). At 
the LOAEL for fetal effects, maternal effects included one death and 
clinical signs (piloerection and subdued activity). In the 
developmental study in rabbits, fetal effects (decreased fetal body 
weight, an increased incidence of friable/mottled livers, and an 
increased incidence of minor skeletal alterations) also occurred at a 
higher dose than the dose causing maternal toxicity (body-weight loss 
and decreased food consumption). At the LOAEL for fetal effects, 
maternal effects included deaths and clinical signs (diarrhea, subdued 
activity, thin appearance, mucus, blood, little or no feces in tray). 
Results in the mouse developmental toxicity study were similar. Fetal 
effects (decreased fetal body weight and an increased incidence of 
overall skeletal alterations) occurred at a higher dose than the dose 
causing maternal toxicity (mortality, clinical signs (piloerection, 
respiratory sounds), and decreased body weight gain during the dosing 
period). Maternal effects at the LOAEL for fetal effects included 
additional clinical signs (abnormal posture, lethargy, tremors, 
unsteadiness on feet, emaciation, ptosis) and a slight decrease in body 
weight (91% of control) at termination.
    In the 2-generation reproduction study in rats, offspring effects 
included a decreased number of live pups per litter on days 1-22, 
decreased pup body weight gain during lactation, and an increased 
incidence of kidney lesions. Parental effects, including clinical 
signs, ulceration of the tongue, and partial/

[[Page 29439]]

total cataract, were observed at the same dose causing toxicity in the 
    3. Conclusion. EPA has determined that reliable data show the 
safety of infants and children would be adequately protected if the 
FQPA SF were reduced to 1X. That decision is based on the following 
    i. The toxicity database for diquat dibromide is adequate to assess 
its prenatal and postnatal toxicity. In accordance with Part 158 
Toxicology Data requirements, an immunotoxicity study (Harmonized Test 
Guideline 870.7800) is required for diquat dibromide. In the absence of 
specific immunotoxicity studies, EPA has evaluated the available 
toxicity data for evidence of immunotoxicity. There are no indications 
in the available studies that organs associated with immune function, 
such as the thymus and spleen, are affected by diquat dibromide. 
Therefore, EPA does not believe that conducting immunotoxicity testing 
will result in a point of departure lower than those already selected 
for diquat dibromide, and an additional database uncertainty factor is 
not needed to account for the lack of this study.
    ii. There is no indication that diquat dibromide is a neurotoxic 
chemical and there is no need for a developmental neurotoxicity study 
or additional UFs to account for neurotoxicity.
    iii. There is no evidence that diquat dibromide results in 
increased susceptibility in in utero rats, rabbits, or mice in the 
prenatal developmental studies or in young rats in the 2-generation 
reproduction study.
    iv. There are no significant residual uncertainties identified in 
the exposure databases for diquat dibromide. Additional information 
from the canola residue studies on the length of storage of canola 
samples prior to analysis and confirmatory residue data for canola are 
required. However, as explained in this Unit, EPA does not expect these 
data to have a measurable impact on exposure estimates for diquat 
    a. Data from the West German and United Kingdom field trials on the 
length of storage of canola samples prior to analysis were not 
submitted. EPA is requiring these data; however, EPA already has data 
for other crops showing that diquat dibromide is stable in frozen 
storage for 6 to 8 months. In addition, based on its structure, EPA 
expects diquat dibromide to be stable in frozen storage much longer 
than the 6 to 8 months for which data are available. Therefore, EPA 
does not expect the length of time the samples were stored to affect 
its conclusions regarding the field trial studies.
    b. EPA has determined that the residue trials conducted in European 
Union (EU) countries are adequate to support tolerances and conditional 
registration of diquat dibromide as a preharvest desiccant on canola in 
the United States. However, EPA is aware that the Interregional 
Research Project number 4 (IR-4) has conducted field trials in the U.S. 
that would support this same use pattern. Residues of diquat dibromide 
on canola grown in the U.S. are not expected to differ significantly 
from residues reported in the EU studies, since harvest aid/desiccant 
applications are made late in the growing season with little time 
between application and harvest. In addition, since the recommended 
tolerances for canola seed and meal have been increased by a factor of 
2X to harmonize with Codex (See Unit IV.C below), there is little 
chance residues in the U.S. trials will exceed these tolerances. 
Nevertheless, since the IR-4 field work has already been completed and 
the study reports will be available in July, 2011, EPA is requiring 
that these studies be submitted as a condition of registration to 
confirm the tolerance levels. EPA notes that canola is a minor 
contributor to estimated dietary exposure in both the acute and chronic 
dietary exposure assessments, accounting for less than 1% of total 
exposure for the most highly exposed population subgroup (children 1 to 
2 years old) in each case. Therefore, even if the U.S. field trials 
were to indicate higher residues than the EU trials, the impact on 
dietary exposure would be negligible.
    The acute dietary food exposure assessment was performed based on 
100 PCT and tolerance-level residues. The chronic dietary exposure 
assessment was refined using reliable irrigation data from USDA, 
average residues for fish from valid residue studies, and anticipated 
residues for irrigated crops that were derived from valid irrigation 
trials. The established MCL of 20 ppb used in the acute and chronic 
dietary exposure assessments is a conservative value that is considered 
protective of exposures from both terrestrial and direct aquatic 
applications of diquat dibromide. EPA used similarly conservative 
assumptions to assess postapplication exposure of children as well as 
incidental oral exposure of toddlers. These assessments will not 
underestimate the exposure and risks posed by diquat dibromide.

E. Aggregate Risks and Determination of Safety

    EPA determines whether acute and chronic dietary pesticide 
exposures are safe by comparing aggregate exposure estimates to the 
acute aPAD and chronic cPAD. For linear cancer risks, EPA calculates 
the lifetime probability of acquiring cancer given the estimated 
aggregate exposure. Short-, intermediate-, and chronic-term risks are 
evaluated by comparing the estimated aggregate food, water, and 
residential exposure to the appropriate PODs to ensure that an adequate 
MOE exists.
    1. Acute risk. Using the exposure assumptions discussed in this 
unit for acute exposure, the acute dietary exposure from food and water 
to diquat dibromide will occupy 1% of the aPAD for children, 1 to 2 
years old, the population group receiving the greatest exposure.
    2. Chronic risk. Using the exposure assumptions described in this 
unit for chronic exposure, EPA has concluded that chronic exposure to 
diquat dibromide from food and water will utilize 35% of the cPAD for 
children, 1 to 2 years old, the population group receiving the greatest 
exposure. Based on the explanation in Unit III.C.3., regarding 
residential use patterns, chronic residential exposure to residues of 
diquat dibromide is not expected.
    3. Short-term risk. Short-term aggregate exposure takes into 
account short-term residential exposure plus chronic exposure to food 
and water (considered to be a background exposure level). Diquat 
dibromide is currently registered for uses that could result in short-
term residential exposure, and the Agency has determined that it is 
appropriate to aggregate chronic exposure through food and water with 
short-term residential exposures to diquat dibromide.
    Using the exposure assumptions described in this unit for short-
term exposures, EPA has concluded the combined short-term food, water, 
and residential exposures result in aggregate MOEs of 110 for infants 
and toddlers, 150 for children 6 to 12 years old, and 260 for teenagers 
and adults. The aggregate MOEs for infants and toddlers include dietary 
exposures from food and drinking water as well as dermal and incidental 
oral postapplication exposures from activities on treated turf. The 
aggregate MOE for children includes dietary exposures from food and 
drinking water as well as dermal postapplication exposure from 
activities on treated turf and exposures from swimming in ponds and 
lakes treated with diquat dibromide. The aggregate MOEs for teenagers 
and adult population subgroups include dietary exposures, residential 
handler dermal exposures, dermal postapplication

[[Page 29440]]

exposures from activities on treated turf, and exposures from swimming 
in ponds and lakes treated with diquat dibromide. EPA did not aggregate 
residential handler inhalation exposures with exposures by other routes 
in the aggregate exposure assessment for teenagers and adults, since 
the effects associated with inhalation exposure (increased mean lung 
weight in males, mottling and reddening of lungs in females, and lung 
lesions) are different from those used to assess the dermal and oral 
routes (body-weight loss and decreased food consumption). Inhalation 
MOEs for residential handlers ranged from 570 (aerosol can application) 
to 11,000,000 (trigger sprayer). Because EPA's level of concern for 
diquat dibromide is a MOE of 100 or below, these MOEs are not of 
    4. Intermediate-term risk. Intermediate-term aggregate exposure 
takes into account intermediate-term residential exposure plus chronic 
exposure to food and water (considered to be a background exposure 
    EPA did not establish a POD for use in assessing intermediate-term 
residential exposures, because diquat dibromide is not registered for 
any use patterns that would result in such exposures. Intermediate-term 
risk is assessed based on intermediate-term residential exposure plus 
chronic dietary exposure. Because there is no intermediate-term 
residential exposure and chronic dietary exposure has already been 
assessed under the appropriately protective cPAD (which is at least as 
protective as the POD used to assess intermediate-term risk), no 
further assessment of intermediate-term risk is necessary, and EPA 
relies on the chronic dietary risk assessment for evaluating 
intermediate-term risk for diquat dibromide.
    5. Aggregate cancer risk for U.S. population. Based on the lack of 
evidence of carcinogenicity in two adequate rodent carcinogenicity 
studies, diquat dibromide is not expected to pose a cancer risk to 
    6. Determination of safety. Based on these risk assessments, EPA 
concludes that there is a reasonable certainty that no harm will result 
to the general population, or to infants and children from aggregate 
exposure to diquat dibromide residues.

IV. Other Considerations

A. Analytical Enforcement Methodology

    Adequate enforcement methodology (High Performance Liquid 
Chromatographic Method (HPLC)) is available to enforce the tolerance 
expression. The method may be requested from: Chief, Analytical 
Chemistry Branch, Environmental Science Center, 701 Mapes Rd., Ft. 
Meade, MD 20755-5350; telephone number: (410) 305-2905; e-mail address: 
residuemethods@epa.gov. Method A (a spectrophotometric method) in the 
Pesticide Analytical Manual (PAM) Vol. II. is also available to enforce 
tolerances for residues of diquat in/on plant and livestock 

B. International Residue Limits

    In making its tolerance decisions, EPA seeks to harmonize U.S. 
tolerances with international standards whenever possible, consistent 
with U.S. food safety standards and agricultural practices. EPA 
considers the international maximum residue limits (MRLs) established 
by the Codex Alimentarius Commission (Codex), as required by section 
408(b)(4) of FFDCA. The Codex Alimentarius is a joint U.N. Food and 
Agriculture Organization/World Health Organization food standards 
program, and it is recognized as an international food safety 
standards-setting organization in trade agreements to which the United 
States is a party. EPA may establish a tolerance that is different from 
a Codex MRL; however, section 408(b)(4) of FFDCA requires that EPA 
explain the reasons for departing from the Codex level.
    The Codex has established an MRL for diquat in or on rapeseed 
(which includes canola seed) at 2.0 ppm. This MRL is the same as the 
tolerance being established for diquat dibromide on canola, seed in the 
United States.

C. Revisions to Petitioned-For Tolerances

    EPA has increased the tolerance level for canola, seed from 1.0 ppm 
to 2.0 ppm to harmonize with the established Codex MRL of 2.0 ppm for 
rapeseed. EPA has also increased the tolerance level for canola meal 
from 3.0 ppm to 6.0 ppm. The tolerance level for meal was derived by 
applying the maximum theoretical concentration factor of 3X for canola 
meal to the canola seed tolerance of 2.0 ppm.
    EPA is also correcting minor errors in the regulations for diquat 
at 40 CFR 180.226, as follows: EPA is correcting typographical errors 
in the chemical name for diquat in paragraphs (a)(2)(i) and (a)(3). EPA 
is also removing paragraph (a)(4), which reads ``There are no U.S. 
registrations as of December 6, 1995.'' This statement was originally 
included as a footnote to import tolerances for banana and coffee, 
established in the Federal Register of March 27, 1996 (61 FR 13474) 
(FRL-5348-1). The statement was inadvertently moved to a separate 
paragraph in subsequent editions of the CFR. EPA is correcting this 
error by removing paragraph (a)(4) and adding an updated statement 
regarding U.S. registrations as a footnote to the banana and coffee 
tolerances. The updated footnote to the table in paragraph (a)(3) reads 
``There are no U.S. registrations as of May 26, 2010.''

V. Conclusion

    Therefore, tolerances are established for residues of diquat, 6,7-
dihydrodipyrido(1,2-a:2'1'-c)pyrazinediium derived from application of 
the dibromide salt and calculated as the cation, in or on canola, meal 
at 6.0 ppm; and canola, seed at 2.0 ppm.

VI. Statutory and Executive Order Reviews

    This final rule establishes tolerances under section 408(d) of 
FFDCA in response to a petition submitted to the Agency. The Office of 
Management and Budget (OMB) has exempted these types of actions from 
review under Executive Order 12866, entitled Regulatory Planning and 
Review (58 FR 51735, October 4, 1993). Because this final rule has been 
exempted from review under Executive Order 12866, this final rule is 
not subject to Executive Order 13211, entitled Actions Concerning 
Regulations That Significantly Affect Energy Supply, Distribution, or 
Use (66 FR 28355, May 22, 2001) or Executive Order 13045, entitled 
Protection of Children from Environmental Health Risks and Safety Risks 
(62 FR 19885, April 23, 1997). This final rule does not contain any 
information collections subject to OMB approval under the Paperwork 
Reduction Act (PRA), 44 U.S.C. 3501 et seq., nor does it require any 
special considerations under Executive Order 12898, entitled Federal 
Actions to Address Environmental Justice in Minority Populations and 
Low-Income Populations (59 FR 7629, February 16, 1994).
    Since tolerances and exemptions that are established on the basis 
of a petition under section 408(d) of FFDCA, such as the tolerance in 
this final rule, do not require the issuance of a proposed rule, the 
requirements of the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et 
seq.) do not apply.
    This final rule directly regulates growers, food processors, food 
handlers, and food retailers, not States or tribes, nor does this 
action alter the relationships or distribution of power and 
responsibilities established by Congress in the preemption provisions 
of section 408(n)(4) of FFDCA. As such,

[[Page 29441]]

the Agency has determined that this action will not have a substantial 
direct effect on States or tribal governments, on the relationship 
between the national government and the States or tribal governments, 
or on the distribution of power and responsibilities among the various 
levels of government or between the Federal Government and Indian 
tribes. Thus, the Agency has determined that Executive Order 13132, 
entitled Federalism (64 FR 43255, August 10, 1999) and Executive Order 
13175, entitled Consultation and Coordination with Indian Tribal 
Governments (65 FR 67249, November 9, 2000) do not apply to this final 
rule. In addition, this final rule does not impose any enforceable duty 
or contain any unfunded mandate as described under Title II of the 
Unfunded Mandates Reform Act of 1995 (UMRA) (Public Law 104-4).
    This action does not involve any technical standards that would 
require Agency consideration of voluntary consensus standards pursuant 
to section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272 

VII. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report to each House of the Congress and to 
the Comptroller General of the United States. EPA will submit a report 
containing this rule and other required information to the U.S. Senate, 
the U.S. House of Representatives, and the Comptroller General of the 
United States prior to publication of this final rule in the Federal 
Register. This final rule is not a ``major rule'' as defined by 5 
U.S.C. 804(2).

List of Subjects in 40 CFR Part 180

    Environmental protection, Administrative practice and procedure, 
Agricultural commodities, Pesticides and pests, Reporting and 
recordkeeping requirements.

    Dated: May 18, 2010.
Daniel J. Rosenblatt,
Acting Director, Registration Division, Office of Pesticide Programs.

Therefore, 40 CFR chapter I is amended as follows:


1. The authority citation for part 180 continues to read as follows:

    Authority: 21 U.S.C. 321(q), 346a and 371.

2. Section 180.226 is amended as follows:
    i. Alphabetically add commodities to the table in paragraph (a)(1);
    ii. Revise introductory text in paragraph (a)(2)(i);
    iii. Revise paragraph (a)(3);
    iv. Remove paragraph (a)(4); and
    v. Redesignate paragraph (a)(5) as (a)(4).
    The amendments read as follows:

Sec.  180.226  Diquat; tolerances for residues.

    (a) * * * (1) * * *

                      Commodity                        Parts per million
                                * * * * *
Canola, meal.........................................                6.0
Canola, seed.........................................                2.0
                                * * * * *

    (2)(i) Tolerances are established for residues of the herbicide 
diquat (6,7 dihydrodipyrido(1,2-a:2'1'-c)pyrazinediium) (calculated as 
the cation) derived from the application of the dibromide salt to 
ponds, lakes, reservoirs, marshes, drainage ditches, canals, streams, 
and rivers which are slow-moving or quiescent in programs of the Corp 
of Engineers or other Federal or State public agencies and to ponds, 
lakes and drainage ditches only where there is little or no outflow of 
water and which are totally under the control of the user, in or on the 
following food commodities:
* * * * *
    (3) Tolerances are established for the plant growth regulator 
diquat (6,7 dihydrodipyrido(1,2-a:2'1'-c)pyrazinediium) derived from 
application of the dibromide salt and calculated as the cation in or on 
the following food commodites:

                      Commodity                        Parts per million
Banana\1\............................................               0.05
Coffee, bean, green\1\...............................               0.05
Soybean, hulls.......................................                0.6
1There are no U.S. registrations as of May 26, 2010.

* * * * *

[FR Doc. 2010-12648 Filed 5-25-10; 8:45 am]