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[Federal Register Volume 77, Number 187 (Wednesday, September 26, 2012)]
[Rules and Regulations]
[Pages 59106-59113]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-23738]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 180

[EPA-HQ-OPP-2009-0813; FRL-9363-6]

Glufosinate Ammonium; Pesticide Tolerances

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This regulation establishes tolerances for residues of 
glufosinate ammonium in or on multiple commodities which are identified 
and discussed later in this document. Interregional Research Project 
Number 4 (IR-4) and Bayer CropScience requested these tolerances under 
the Federal Food, Drug, and Cosmetic Act (FFDCA).

DATES: This regulation is effective September 26, 2012 except for the 
addition of the tolerance for Fruit, stone, group 12-12 to the table in 
Sec.  180.473 (a), which is effective October 22, 2012. Objections and 
requests for hearings must be received on or before November 26, 2012, 
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: The docket for this action, identified by docket 
identification (ID) number EPA-HQ-OPP-2009-0813, is available at http://www.regulations.gov or at the Office of Pesticide Programs Regulatory 
Public Docket (OPP Docket) in the Environmental Protection Agency 
Docket Center (EPA/DC), EPA West Bldg., Rm. 3334, 1301 Constitution 
Ave. NW., Washington, DC 20460-0001. The Public Reading Room is open 
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744, and the telephone number for the OPP Docket is (703) 305-
5805. Please review the visitor instructions and additional information 
about the docket available at http://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Sidney Jackson, Registration Division 
(7505P), Office of Pesticide Programs, Environmental Protection Agency, 
1200 Pennsylvania Ave., NW., Washington, DC 20460-0001; telephone 
number: (703) 305-7610; email address: jackson.sidney@epa.gov.

SUPPLEMENTARY INFORMATION:

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. 
The following list of North American Industrial Classification System 
(NAICS) codes is not intended to be exhaustive, but rather provides a 
guide to help readers determine whether this document applies to them. 
Potentially affected entities may include:
     Crop production (NAICS code 111).
     Animal production (NAICS code 112).
     Food manufacturing (NAICS code 311).
     Pesticide manufacturing (NAICS code 32532).

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://ecfr.gpoaccess.gov/cgi/t/text/text-idx?&c=ecfr&tpl=/ecfrbrowse/Title40/40tab_02.tpl.

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-2009-0813 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 before 
November 26, 2012. 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 (excluding any CBI) for inclusion in the public docket. 
Information not marked confidential pursuant to 40 CFR part 2

[[Page 59107]]

may be disclosed publicly by EPA without prior notice. Submit the non-
CBI copy of your objection or hearing request, identified by docket ID 
number EPA-HQ-OPP-2009-0813, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the online instructions for submitting comments. Do not submit 
electronically any information you consider to be Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute.
     Mail: OPP Docket, Environmental Protection Agency Docket 
Center (EPA/DC), (28221T), 1200 Pennsylvania Ave. NW., Washington, DC 
20460-0001.
     Hand Delivery: To make special arrangements for hand 
delivery or delivery of boxed information, please follow the 
instructions at http://www.epa.gov/dockets/contacts.htm.
    Additional instructions on commenting or visiting the docket, along 
with more information about dockets generally, is available at http://www.epa.gov/dockets.

II. Summary of Petitioned-for Tolerance

    In the Federal Registers of January 6, 2010 (75 FR 864) (FRL-8801-
5) and March 19, 2010 (75 FR 13277) (FRL-8813-2), EPA issued notices 
pursuant to FFDCA section 408(d)(3), 21 U.S.C. 346a(d)(3), announcing 
the filing of pesticide petitions; (PP 9E7604) by Interregional 
Research Project Number 4 (IR-4), IR-4 Project Headquarters, 500 
College Road East, Suite 201 W, Princeton, NJ 08540 and (PP 9F7655) by 
Bayer CropScience LP, 2 T. W. Alexander Drive, Research Triangle Park, 
NC 27709, respectively. The petitions requested that 40 CFR 180.473 be 
amended by establishing tolerances for residues of the herbicide 
glufosinate ammonium, butanoic acid, 2-amino-4-
(hydroxymethylphosphinyl)- monoammonium salt, and its metabolites, 2-
acetylamino-4-methylphosphinico-butanoic acid and 3-methylphosphinico-
propionic acid, calculated as the stoichiometric equivalent of 2-amino-
4-(hydroxymethylphosphinyl), in or on corn, sweet, forage at 4.0 parts 
per million (ppm); corn, sweet, kernel plus cob with husks removed at 
0.2 ppm; corn, sweet, stover at 6.0 ppm (PP 9E7604); citrus, fruit 
(crop group 10) at 0.05 ppm; olives at 0.05 ppm; pome, fruit (crop 
group 11) at 0.10 ppm; and stone fruit (crop group 12) at 0.10 ppm (PP 
9F7655). These notices referenced a summary of the petition prepared by 
Bayer CropScience LP, 2 T. W. Alexander Drive, Research Triangle Park, 
NC 27709, the registrant, which is available in the docket, http://www.regulations.gov. There were no comments received in response to the 
notices of filing.
    Based upon review of the data supporting the petition, EPA is: (1) 
Correcting certain crop definitions to comply with current Agency 
policies; (2) establishing tolerance levels for certain commodities 
other than the proposed levels; (3) removing the proposed tolerance for 
plum, prune, dried; (4) modifying the crop group tolerances requested 
to the revised and expanded citrus fruit group 10-10, pome fruit group 
11-10 and stone fruit group 12-12; and 5) revising the tolerance 
expression for all established commodities to be consistent with 
current Agency policy. The reasons for these changes are 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 FFDCA section 408(b)(2)(D), and the factors 
specified in FFDCA section 408(b)(2)(D), 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 glufosinate ammonium including 
exposure resulting from the tolerances established by this action. 
EPA's assessment of exposures and risks associated with glufosinate 
ammonium follows.

A. Toxicological Profile

    EPA has evaluated the available toxicity data and considered their 
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 
children.
    Technical grade glufosinate ammonium has low toxicity in the oral, 
dermal, inhalation studies and is not an eye or dermal irritant or a 
dermal sensitizer.
    Subchronic toxicity studies in rats showed inhibition of glutamate 
synthetase and lead the Agency to conclude that the changes in brain 
glutamine synthetase activity are of significant concern for possible 
neurotoxicity and/or expression of clinical signs. Observed alterations 
in liver and kidney glutamate synthetase are considered an adaptive 
response. The primary effects in the mouse subchronic study were 
increased liver and kidney weights with increases in serum aspartate 
amino transferase and alkaline phosphatase.
    Additional toxicity testing was conducted with the L-isomer of 
glufosinate ammonium, and degradates glufosinate propanoic acid (MPP), 
and 2-acetamido-4-methylphosphinico-butanoic acid (NAG). These 
compounds, tested in subchronic rat, mouse, and dog studies, and in 
developmental toxicity studies in rat and rabbit, are generally less 
toxic than the parent compound. However, L-isomer of glufosinate 
ammonium was found to be slightly more toxic than the racemic parent 
compound. This finding is not concern since this isomer is included in 
the toxicity testing of the parent compound at the levels in the 
technical material.
    In chronic studies in the rat, inhibition of brain glutamine 
synthetase, increased mortality, and increased occurrence of retinal 
atrophy were noted, as were increased liver and kidney weights. In the 
mouse, increased mortality was noted, as were changes in glucose levels 
consistent with changes in glutathione levels. Increased mortality and 
electrocardiogram alterations were observed in dogs. The developmental 
toxicity study in the rat produced dilated renal pelvis and/or 
hydroureter in the fetuses at levels that produced significant 
increases in hyperactivity and vaginal bleeding in dams. In the rabbit, 
decreased fetal body weight and increased mortality were observed at 20 
milligrams/kilogram/day (mg/kg/day), while in rabbit dams, decreased 
food consumption, body weight, and body weight gain were observed at 20 
mg/kg/day. Since increased fetal mortality was observed in the presence 
of less severe maternal

[[Page 59108]]

toxicity in the rabbit developmental study, there is evidence of 
qualitative increased susceptibility in fetuses.
    The reproductive toxicity study in rats indicated postnatal 
developmental toxicity at the highest dose tested in the form of 
decrease in viable pups. No parental toxicity was seen at the highest 
dose tested. Since pup mortality was observed in the absence of 
parental toxicity, there is evidence of quantitative increased 
susceptibility in offspring.
    There were indications of neurotoxicity in several studies. Of 
particular concern is that the developmental neurotoxicity study 
demonstrated alterations in brain morphometrics in the adult offspring 
exposed in utero or during lactation at dose levels not associated with 
maternal toxicity. Retinal atrophy was observed in a rat oral study. In 
the 90-day dietary neurotoxicity study, increases in the incidence of 
decreased exploratory activity, decreased alertness, and decreased 
startle response, increased incidence of fearfulness, increased pain 
response and meiosis were reported. The subchronic dermal toxicity 
study indicated aggressive behavior, a high startle response and 
piloerection. The 28-day subchronic inhalation study demonstrated tono-
clonic convulsions at the high dose in at least some males. However, in 
a 37-day dietary neurotoxicity study, there was no evidence of 
neurotoxicity at doses up to 143.3 mg/kg/day. There was no evidence of 
neurotoxicity in two acute neurotoxicity studies at doses up to 500 mg/
kg/day. Also, there was no evidence of neurotoxicity in White Leghorn 
hens following an acute dose of up to 10,000 mg/kg. Changes in 
glutamine synthetase levels were observed in liver, kidney, and brain 
in rats. The altered electrocardiograms seen in the dog studies imply a 
possible neuromuscular effect.
    There is no concern for immunotoxicity based on an adequate 
database.
    There is no concern for mutagenic activity in several available 
studies including: Salmonella E. Coli, in vitro mammalian cell gene 
mutation assays, mammalian cell chromosome aberration assays, in vivo 
mouse bone marrow micronucleus assays, and unscheduled DNA synthesis 
assays.
    Glufosinate ammonium was classified as ``not likely to be a human 
carcinogen.'' There was no evidence of a treatment-related increase in 
tumors in either rats or mice.
    Specific information on the studies received and the nature of the 
adverse effects caused by glufosinate ammonium 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 document ``Glufosinate Ammonium. Updated Human 
Health Risk Assessment for the Proposed New Use of Glufosinate Ammonium 
in/on Citrus Fruit (Crop Group 10), Pome Fruit (Crop Group 11), Stone 
Fruit (Crop Group 12), Olives and Sweet Corn'', dated July 25, 2012 at 
page number 34 in docket ID number EPA-HQ-OPP-2009-0813.

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 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 glufosinate ammonium 
used for human risk assessment is shown in the following Table.

    Table--Summary of Toxicological Doses and Endpoints for Glufosinate Ammonium for use in Human Health Risk
                                                   Assessment
----------------------------------------------------------------------------------------------------------------
                                    Point of departure
        Exposure/Scenario            and uncertainty/     RfD, PAD, LOC for     Study and toxicological effects
                                      safety factors       risk assessment
----------------------------------------------------------------------------------------------------------------
Acute Dietary (General              No endpoint attributable to a single exposure was identified for the general
 Population, including Infants                       population, including infants and children.
 and Children).
----------------------------------------------------------------------------------------------------------------
Acute dietary (Females 13-50       NOAEL = 6.3 mg/kg/    aRfD = 0.063 mg/kg/  Developmental Toxicity Study in
 years of age).                     day.                  day.                 Rabbits.
                                   UFA = 10x...........  aPAD = 0.063 mg/kg/  LOAEL = 20 mg/kg/day based on
                                   UFH = 10x...........   day.                 increased fetal deaths.
                                   FQPA SF = 1x........
----------------------------------------------------------------------------------------------------------------
Chronic dietary (All populations)  NOAEL = 6 mg/kg/day.  cRfD = cPAD = 0.006  ``Weight of evidence'' approach
                                   UFA = 10x...........   mg/kg/day.           from four studies. Rat subchronic
                                   UFH = 10x...........                        and chronic studies with the
                                   FQPA SF = UFL = 10x.                        LOAEL based on inhibition of
                                                                               brain glutamate synthetase. A dog
                                                                               chronic study with the LOAEL
                                                                               based on altered
                                                                               electrocardiogram and mortality.
                                                                               The rat developmental
                                                                               neurotoxicity study with a LOAEL
                                                                               (without a NOAEL, basis for UFL)
                                                                               based on altered morphometrics in
                                                                               the offspring as adults.
----------------------------------------------------------------------------------------------------------------

[[Page 59109]]

 
Dermal short-term (1 to 30 days).  LOAEL= 14 mg/kg/day   LOC for MOE = 1,000  Developmental Neurotoxicity Study
                                    (LDT).                                     in Rats
                                   UFA=10x.............                       LOAEL = 14 mg/kg/day based on
                                   UFH=10x.............                        brain morphometric changes at PND
                                   FQPA SF= UFL= 10x...                        72. No NOAEL identified.
----------------------------------------------------------------------------------------------------------------
Cancer (Oral, dermal, inhalation)     Classification: ``Not likely to be Carcinogenic to Humans'' based on the
                                            absence of significant tumor increases in two adequate rodent
                                                              carcinogenicity studies.
----------------------------------------------------------------------------------------------------------------
FQPA SF = Food Quality Protection Act Safety Factor. LOAEL = lowest-observed-adverse-effect-level. LOC = level
  of concern. mg/kg/day = milligram/kilogram/day. MOE = margin of exposure. NOAEL = no-observed-adverse-effect-
  level. PAD = population adjusted dose (a = acute, c = chronic). RfD = reference dose UF = uncertainty factor.
  UFA = extrapolation from animal to human (interspecies). UFH = potential variation in sensitivity among
  members of the human population (intraspecies). UFL = use of a LOAEL to extrapolate a NOAEL.

C. Exposure Assessment

    1. Dietary exposure from food and feed uses. In evaluating dietary 
exposure to glufosinate ammonium, EPA considered exposure under the 
petitioned-for tolerances as well as all existing glufosinate ammonium 
tolerances in 40 CFR 180.473. EPA assessed dietary exposures from 
glufosinate ammonium 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 glufosinate ammonium for females 
13 through 50 years old. In estimating acute dietary exposure 
assessment of glufosinate ammonium, EPA used the Dietary Exposure 
Evaluation Model software with the Food Commodity Intake Database DEEM-
FCIDTM, Version 3.10, which incorporates consumption data 
from USDA's National Health and Nutrition Examination Survey/``What We 
Eat in America'' (NHANES/WWEIA) dietary survey conducted in 2003-2008. 
The 2003-2008 data are based on the reported consumption of individuals 
over two non-consecutive survey days.
    As to residue levels in food, EPA assumed tolerance level residues 
for all established and recommended tolerances along with default 
processing factors, and 100 percent crop treated (PCT) assumptions.
    ii. Chronic exposure. In conducting the chronic dietary exposure 
assessment, EPA also used the Dietary Exposure Evaluation Model 
software with the Food Commodity Intake Database DEEM-
FCIDTM, Version 3.10.
    As to residue levels in food, EPA used anticipated residues based 
on average residue levels from field trial studies. The DEEM default 
processing factors were used for all commodities except apple juice, 
pear juice, grape juice, and raisins, for which factors derived from 
the processing studies were used in the assessment. One hundred percent 
crop treated values were used for all proposed new uses and some 
registered uses. Average PCT estimates were used in the chronic dietary 
analysis for crops that are currently registered for glufosinate 
ammonium if available.
    iii. Cancer. Based on the data summarized in Unit III.A., EPA has 
concluded that glufosinate ammonium does not pose a cancer risk to 
humans. Therefore, a dietary exposure assessment for the purpose of 
assessing cancer risk is unnecessary.
    iv. Anticipated residue and percent crop treated (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 FFDCA section 408(f)(1) 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 FFDCA section 408(b)(2)(E) and authorized under 
FFDCA section 408(f)(1). 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 FFDCA section 408(b)(2)(F), EPA may require 
registrants to submit data on PCT.
    The Agency estimated the average PCT for existing uses as follows: 
Almond: 15%; blueberry: 5%; field corn, 5%; grape, 15%; pecan, 1%; 
potato, 10%; soybean, 1%; walnut, 10%; canola, 25%; cotton, 5%; 
filbert, 10%; pistachio, 20%; and rice, 1%.
    In most cases, EPA uses available data from United States 
Department of Agriculture/National Agricultural Statistics Service 
(USDA/NASS), proprietary market surveys, and the National Pesticide Use 
Database for the chemical/crop combination for the most recent 6-7 
years. EPA uses an average PCT for chronic dietary risk analysis. The 
average PCT figure for each existing use is derived by combining 
available public and private market survey data for that use, averaging 
across all observations, and rounding to the nearest 5%, except for 
those situations in which the average PCT is less than one. In those 
cases, 1% is used as the average PCT and 2.5% is used as the maximum 
PCT. EPA uses a maximum PCT for acute dietary risk analysis. The 
maximum PCT figure is the highest observed maximum value reported 
within the recent 6 years of available public and private market survey 
data

[[Page 59110]]

for the existing use and rounded up to the nearest multiple of 5%.
    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 and private 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 glufosinate ammonium may be applied in a particular area.
    2. Dietary exposure from drinking water. The Agency used refined 
drinking water exposure models in the dietary exposure analysis and 
risk assessment for glufosinate ammonium. These simulation models take 
into account data on the physical, chemical, and fate/transport 
characteristics of glufosinate ammonium. 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.
    Environmental fate studies indicate glufosinate ammonium is 
relatively stable and is very mobile. The main degradation pathway in 
water and soil is via microbial action, metabolizing primarily to 
CO2, glufosinate propanoic acid (MPP), 2-methylphosphinico 
acetic acid (MPA), and 2-acetamido-4-methylphosphinico-butanoic acid 
(NAG). EPA recently reconsidered the appropriate residues of concern 
for drinking water to be used in risk assessment and determined that 
only the parent, glufosinate ammonium is the residue of concern for 
drinking water. Though MPA is a major degradate in some studies, a 90-
day rat feeding study showed no effects at the highest dose tested 
which is about 100-fold higher than the NOAEL of the parent. Based on 
the rabbit developmental studies NAG is considered slightly less toxic 
than the parent. However, it was only observed as a major degradate 
during photolysis in soil; therefore, its exposure is significantly 
lower to that of the parent in drinking water. The parent glufosinate 
ammonium and MPP show different toxicities and therefore should not be 
aggregated. Moreover, the Agency has determined that the acute 
concentrations of MPP are not likely to be significantly greater than 
that of glufosinate in drinking water. However, given the minimal fate 
data available for MPP that indicates MPP does not degrade in aerobic 
aquatic environments, it is unclear if this will be true for chronic 
concentrations of MPP and glufosinate. Since MPP is considered less 
toxic than the parent compound and should not be aggregated with the 
parent, EPA concluded that if estimated drinking water concentrations 
(EDWCs) of MPP are not significantly greater than those for 
glufosinate, the risk assessment for the parent will be protective of 
any toxicity associated with exposure to MPP in drinking water.
    Previous analyses for glufosinate ammonium demonstrated that the 
maximum acute and chronic EDWCs result from surface water estimates 
arising from the rice use; the surface water values for rice are nearly 
an order of magnitude higher than any surface or ground water values 
for any other use of glufosinate ammonium. Therefore, a comprehensive 
refinement of the drinking water assessment for the rice use of 
glufosinate ammonium, should be protective of other uses.
    The Agency estimated acute EDWCs for glufosinate ammonium and MPP 
using the Tier I Rice Model and Pesticide Flooded Application Model 
(PFAM) [version 0.70] without the index reservoir. To estimate chronic 
EDWCs, the acute concentrations from PFAM without the index reservoir 
were assumed to degrade over a 365-day period, using aerobic aquatic 
degradation half-lives; thus allowing calculation of average 
concentrations over a one-year period. This method results in chronic 
values approximately 76% and 3% lower than the acute values for 
glufosinate-ammonium and MPP, respectively.
    The EDWCs for surface water are expected to be 390 parts per 
billion (ppb) for glufosinate and 183 ppb for MPP for acute exposures. 
The EDWCs for surface water are expected to be 95 ppb for glufosinate 
and 177 ppb for MPP for chronic exposures. The maximum chronic EDWC for 
rice for MPP is approximately 2X higher than the corresponding value 
for glufosinate: 177 and 95 ppb, respectively. Since MPP is considered 
less toxic than the parent compound and should not be aggregated with 
the parent, EPA concluded that if the EDWCs for MPP are not 
significantly greater than those for glufosinate, the risk assessment 
for the parent will be protective of any toxicity associated with 
exposure to MPP in drinking water. Given the estimated EDWCs for MPP 
concentrations are not likely to be more than twice the corresponding 
levels of glufosinate in drinking water, EPA concluded a quantitative 
risk assessment for MPP in drinking water is not needed. Accordingly, 
for purposes of acute and chronic dietary analyses, the recommended 
glufosinate EDWCs are 390 and 95 ppb, respectively.
    Modeled estimates of drinking water concentrations were directly 
entered into the dietary exposure model. For acute dietary risk 
assessment, the water concentration value of 390 ppb was used to assess 
the contribution to drinking water. For chronic dietary risk 
assessment, the water concentration of value 95 ppb was used to assess 
the contribution to drinking water.
    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). Glufosinate ammonium 
is currently registered for the following uses that could result in 
residential exposures: spot treatments of lawns and turf. EPA assessed 
residential exposure using the following assumptions:
    Residential handler exposure is expected to be short-term. 
Intermediate-term exposures are not likely because of the intermittent 
nature of applications by homeowners. Dermal and inhalation exposures 
are possible for applications from mixing/loading/applying liquids with 
a hose-end sprayer, a backpack sprayer, and a sprinkler can and 
applications for manually pressurized handgun. However, only the dermal 
route of exposure was included in the aggregate analysis since 
potential dermal risks are higher than potential inhalation risks and 
the EPA determined it is not appropriate to aggregate the dermal and 
inhalation exposures since the toxicity endpoints are different.
    The Agency did not quantify post-application exposures. Post-
application exposure is expected to be minimal. Any exposure to 
children via incidental non-dietary ingestion (i.e., hand-to-mouth, 
object-to-mouth (turfgrass), and soil ingestion) after application to 
treated turf is expected to be low since

[[Page 59111]]

treatments to lawns and turf are limited to spot treatments.
    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 glufosinate ammonium to share a common mechanism 
of toxicity with any other substances, and glufosinate ammonium does 
not appear to produce a toxic metabolite produced by other substances. 
For the purposes of this tolerance action, therefore, EPA has assumed 
that glufosinate ammonium 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 Web site 
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 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 reproductive toxicity 
study in rats indicated postnatal developmental toxicity at the highest 
dose tested in the form of decrease in viable pups. No parental 
toxicity was seen at the highest dose tested. Since pup mortality was 
observed in the absence of parental toxicity, there is evidence of 
quantitative increased susceptibility in offspring. Although in the rat 
developmental toxicity study dilated renal pelvis and hydroureter were 
observed in fetuses at 250 mg/kg/day, significant toxicity in the dams 
occurred at lower doses (vaginal bleeding and hyperactivity in the dams 
at 50 mg/kg/day), doses at which no developmental effects were 
observed. Therefore, no increased sensitivity was seen in this study.
    Since increased fetal mortality was observed in the presence of 
less significant maternal toxicity in the rabbit developmental study, 
there is evidence of qualitative increased susceptibility in fetuses. 
Finally, the developmental neurotoxicity study demonstrated alterations 
in brain morphometrics in the adult offspring exposed in utero or 
during lactation at dose levels not associated with maternal toxicity. 
This shows quantitative sensitivity in the young.
    3. Conclusion. EPA has determined that reliable data show the 
safety of infants and children would be adequately protected if the 
FQPA safety factor were reduced to 1X for acute dietary exposure. For 
all other exposure scenarios where the developmental neurotoxicity 
study or the 28-day inhalation study is used as an endpoint for risk 
assessment, EPA is retaining a 10X FQPA safety factor. That decision is 
based on the following findings:
    i. Although all required studies for glufosinate ammonium have been 
submitted, the glufosinate ammonium database has a completeness issue 
in that the developmental neurotoxicity and the 28-day inhalation 
studies used for risk assessment did not demonstrate NOAELs, and LOAELs 
were used as endpoints. Therefore, the 10X FQPA safety factor was 
retained for use of a LOAEL to extrapolate a NOAEL. EPA has reduced the 
10X safety factor when relying on a LOAEL in circumstances that suggest 
that the LOAEL is approaching a NOAEL (e.g., very minimal effects seen 
at the LOAEL). EPA, however has no reliable data supporting selection 
of a different safety factor value other than the default value of 10X 
for glufosinate ammonium.
    ii. Although there were indications of neurotoxicity in several 
studies, the PODs and safety factors chosen for risk assessment are 
protective for these effects. The developmental neurotoxicity study 
showed altered brain morphometrics at the LOAEL, and this study is used 
in the weight-of-the evidence decision-making process for selection of 
an endpoint. Applying the 10X FQPA Safety Factor for the LOAEL to NOAEL 
extrapolation, as well as the 10X inter- and intra-species uncertainty 
factors, to this LOAEL will be protective against possible 
neurotoxicity as indicated in the laboratory animal studies.
    iii. Although there is evidence that glufosinate ammonium results 
in increased qualitative or quantitative susceptibility in the 
developmental neurotoxicity study (rats), a prenatal developmental 
study (rabbits), and in the 2-generation reproduction study (rats), the 
PODs selected for risk assessment are protective for these effects 
because they are either based on clear NOAELs for the effects in young 
animals or they are based on a LOAEL adjusted by a 10X safety factor to 
account for the lack of a NOAEL in that study.
    iv. There are no residual uncertainties identified in the exposure 
databases. The acute dietary food exposure assessment was performed 
based on 100 PCT and tolerance-level residues. The chronic dietary 
exposure analysis was performed using anticipated residues from field 
trial data, processing factors, and PCT information. With limited 
monitoring data available, upper-bound assumptions were used to 
determine exposure through drinking water sources. EPA made 
conservative (protective) assumptions in the ground and surface water 
modeling used to assess exposure to glufosinate ammonium in drinking 
water. These assessments will not underestimate the exposure and risks 
posed by glufosinate ammonium.

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 PAD (aPAD) and chronic PAD (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 glufosinate ammonium will occupy 39% of the aPAD for females 13-49 
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 
glufosinate ammonium from food and water will utilize 98% of the cPAD 
for all infants (loader/applicators. Because EPA's level of 
concern for glufosinate ammonium is an MOE of 1,000 or below, these 
MOEs are not of concern.
    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 
level).
    An intermediate-term adverse effect was identified; however, 
glufosinate ammonium is not registered for any use patterns that would 
result in intermediate-term residential exposure. 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 glufosinate ammonium.
    5. Aggregate cancer risk for U.S. population. Based on the lack of 
evidence of carcinogenicity in two adequate rodent carcinogenicity 
studies, glufosinate ammonium is not expected to pose a cancer risk to 
humans.
    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 glufosinate ammonium residues.

IV. Other Considerations

A. Analytical Enforcement Methodology

    Two analytical methods have been validated by EPA for enforcement 
of the currently established tolerances: (1) Method HRAV-5A for the 
determination of glufosinate ammonium and glufosinate propanoic acid 
in/on apple, grape, almond, soybean seed, corn grain, and corn forage, 
and (2) Method BK/01/99 for determination of glufosinate ammonium, N-
acetyl-glufosinate, and glufosinate propanoic acid in/on canola seed 
and sugar beet root.
    Based on the similarity in the two methods and the results from the 
petition method validations (PMVs), EPA concludes that method BK/01/99 
is a suitable method for enforcement of sweet corn, stone fruit, pome 
fruit, citrus fruit, and olive tolerances.
    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; email address: 
residuemethods@epa.gov.

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 FFDCA 
section 408(b)(4). The Codex Alimentarius is a joint United Nations 
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, FFDCA section 408(b)(4) requires that EPA explain 
the reasons for departing from the Codex level.
    The Codex has not established MRLs for glufosinate ammonium in or 
on olives and sweet corn commodities. However, for glufosinate ammonium 
in or on citrus fruit, pome fruit, and stone fruit, Codex has set MRLs 
of 0.1, 0.05, and 0.05 ppm, respectively. EPA is establishing 
tolerances in this action for citrus fruit, pome fruit, and stone 
fruit, at 0.15, 0.25, and 0.25 ppm, respectively. EPA cannot harmonize 
these tolerance values with the Codex MRLs because the lower MRLs could 
be exceeded with the uses petitioned-for in this action.

C. Revisions to Petitioned-for Tolerances

    EPA modified/revised certain IR-4 proposed tolerances for 
glufosinate ammonium residues. Higher tolerance levels were established 
for citrus, pome fruit, stone fruit, and olives because EPA concluded 
that it was appropriate to sum the full level of quantification (LOQ) 
for each of the three residues of concern in situations where pre>
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