PMEP Home Page --> Pesticide Active Ingredient Information --> Insecticides and Miticides --> Insecticides, F to M --> Imidacloprid --> Imidacloprid - Pesticide Petition Filing 4/99

Imidacloprid - Pesticide Petition Filing 4/99

[Federal Register: April 8, 1999 (Volume 64, Number 67)]
[Page 17171-17179]
From the Federal Register Online via GPO Access []
[PF-869; FRL-6071-2]
Notice of Filing of Pesticide Petitions
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice.

SUMMARY: This notice announces the initial filing of pesticide
petitions proposing the establishment of regulations for residues of
certain pesticide chemicals in or on various food commodities.

DATES: Comments, identified by the docket control number PF-869, must
be received on or before May 10, 1999.

ADDRESSES: By mail submit written comments to: Public Information and
Records Integrity Branch, Information Resources and Services Division
(7502C), Office of Pesticides Programs, Environmental Protection
Agency, 401 M St., SW., Washington, DC 20460. In person bring comments
to: Rm. 119, CM #2, 1921 Jefferson Davis Highway, Arlington, VA.
    Comments and data may also be submitted electronically to: opp- Follow the instructions under "SUPPLEMENTARY
INFORMATION." No confidential business information should be submitted
through e-mail.
    Information submitted as a comment concerning this document may be
claimed confidential by marking any part or all of that information as
"Confidential Business Information" (CBI). CBI should not be
submitted through e-mail. Information marked as CBI will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2. A copy of the comment that does not contain CBI must be submitted
for inclusion in the public record. Information not marked confidential
may be disclosed publicly by EPA without prior notice. All written
comments will be available for public inspection in Rm. 119 at the
address given above, from 8:30 a.m. to 4 p.m., Monday through Friday,
excluding legal holidays.

FOR FURTHER INFORMATION CONTACT: The product manager listed in the
table below:

                                   Office location/
        Product Manager            telephone number          Address
Sidney Jackson................  Rm. 272, CM #2, 703-    1921 Jefferson
                                 305-7610, e-            Davis Hwy,
                                 mail:jackson.sidney@e   Arlington, VA
Lisa D. Jones.................  Rm. 259, CM #2, 703-    Do.
                                 308-9424, e-

SUPPLEMENTARY INFORMATION: EPA has received pesticide petitions as
follows proposing the establishment and/or amendment of regulations for
residues of certain pesticide chemicals in or on various food
commodities under section 408 of the Federal Food, Drug, and Comestic
Act (FFDCA), 21 U.S.C. 346a. EPA has determined that these petitions
contain data or information regarding the elements set forth in section
408(d)(2); however, EPA has not fully evaluated the sufficiency of the
submitted data at this time or whether the data support granting of the
petition. Additional data may be needed before EPA rules on the
    The official record for this notice of filing, as well as the
public version, has been established for this notice of filing under
docket control number [PF-869] (including comments and data submitted
electronically as described below). A public version of this record,
including printed, paper versions of electronic comments, which does
not include any information claimed as CBI, is available for inspection
from 8:30 a.m. to 4 p.m., Monday through Friday, excluding legal
holidays. The official record is located at the address in
"ADDRESSES" at the beginning of this document.
    Electronic comments can be sent directly to EPA at:

    Electronic comments must be submitted as an ASCII file avoiding the
use of special characters and any form of encryption. Comments and data
will also be accepted on disks in Wordperfect 5.1 file format or ASCII
file format. All comments and data in electronic form must be
identified by the docket number (insert docket number) and appropriate
petition number. Electronic comments on notice may be filed online at
many Federal Depository Libraries.

List of Subjects

    Environmental protection, Agricultural commodities, Food additives,
Feed additives, Pesticides and pests, Reporting and recordkeeping

    Dated: April 2, 1999.

onald R. Stubbs, Acting

Director, Registration Division, Office of Pesticide Programs.

Summaries of Petitions

    Petitioner summaries of the pesticide petitions are printed below
as required by section 408(d)(3) of the FFDCA. The summaries of the
petitions were prepared by the petitioners and represent the views of
the petitioners. EPA is publishing the petition summaries verbatim
without editing them in any way. The petition summary announces the
availability of a description of the analytical methods

[[Page 17172]]

available to EPA for the detection and measurement of the pesticide
chemical residues or an explanation of why no such method is needed.

1. Interregional Research Project No. 4 (IR-4)

PP 6E4766, 7E4898, 7E4899

    EPA has received pesticide petitions [6E4766, 7E4898, 7E4899] from
the Interregional Research Project Number 4 (IR-4) New Jersey
Agricultural Experiment Station, P.O. Box 231, Rutgers University, New
Brunswick, NJ 08903 proposing, pursuant to section 408(d) of the
Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a(d), to
amend 40 CFR part 180 by establishing tolerances for residues of the
insecticide imidacloprid [1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-
imidazolidinimine and its metabolites containing the 6-chloropyridinyl
moiety, all expressed as 1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-
imidazolidinimine, in or on the raw agricultural commodities (RAC):
    1. PP 6E4766 proposes the establishment of a tolerance for
cucurbits vegetables (Crop Group 9) at 0.5 parts per million (ppm).
    2. PP 7E4898 proposes the establishment of a tolerance for tuberous
and corm vegetables at 0.3 ppm and dasheen (taro) at 3.5 ppm.
    3. PP 7E4899 proposes the establishment of a tolerance for
watercress, upland at 3.5 ppm.
    EPA has determined that the petitions contain data or information
regarding the elements set forth in section 408(d)(2) of the FFDCA;
however, EPA has not fully evaluated the sufficiency of the submitted
data at this time or whether the data support granting of these
petitions. Additional data may be needed before EPA rules on these
petitions. Imidacloprid is produced by the Bayer Corporation (Bayer),
the registrant.

A. Residue Chemistry

    1. Plant and animal metabolism. The nature of the imidacloprid
residue in plants and livestock is adequately understood. The residues
of concern are combined residues of imidacloprid and it metabolites
containing the 6-chloropyridinyl moiety, all calculated as
    2. Analytical method. The analytical method is a common moiety
method for imidacloprid and its metabolites containing the 6-
chloropyridinyl moiety using a permanganate oxidation, silyl
derivatization, and capillary gas chromatography mass spectrometry (GC/
MS) selective monitoring. This method has successfully passed a
petition method validation in EPA labs. There is a confirmatory method
specifically for imidacloprid and several metabolites utilizing GC/MS
and high performance liquid chromotography using ultra-violet detection
(HPLC-UV) which has been validated by the EPA as well. Imidacloprid and
its metabolites are stable for at least 24 months in the commodities
when frozen.
    3. Magnitude of residues. For cucurbits, IR-4 performed 6 trials on
cucumber, 6 trials on summer squash, and 6 trials on cantaloupe spread
over two growing seasons (1992 and 1993). Trials conducted during the
1992 growing season used the following use pattern: i) a plant drench
plus foliar applications, ii) a plant drench, iii) an in-furrow, and
iv) a sidedress application. In 1993, IR-4 performed work on only the
plant drench plus foliar treatment use pattern with a zero day pre-
harvest interval (PHI).
    The use pattern with the highest residue levels was the plant
drench plus foliar application with a zero day. The maximum residues
observed were 0.39 ppm for melon, 0.34 ppm for cucumber, and 0.28 ppm
for summer squash. These maximum levels are all very similar and
support the crop group concept and proposed 0.5 ppm proposed tolerance
for imidacloprid on cucurbit vegetables.
    Bayer believes that the data used to support the establishment of
the imidacloprid 3.5 ppm leafy greens tolerance can be used to extend
the tolerance to cover upland watercress. This is based on the
similarities of upland watercress to upland cress and garden cress
(members of crop subgroup 4A). The use patterns and restrictions for
use on upland watercress would be the same as currently registered for
garden cress and upland cress.
    Even at exaggerated rates, imidacloprid residues in the potato
tubers were only 0.25 ppm. Therefore, IR-4 contends that a crop
subgroup tolerance for tuberous and corm vegetables to include dasheen
(taro) is justified and appropriate, and no additional crop-specific
data are required.
    Although Dasheen (taro) leaves are seldom consumed, they are
occasionally harvested from dasheen (taro) plantings grown primarily
for the corms. In support of the proposed tolerance on dasheen (taro)
leaves, IR-4 has noted that a tolerance of 3.5 ppm has been established
on lettuce under pesticide petition (PP) 3F4231. IR-4 is requesting
that the EPA use the data presented in PP 3F4231 to establish a
tolerance for dasheen (taro) leaves. The proposed use pattern on taro
does not include any foliar applications of imidacloprid. Therefore, it
is unlikely that imidacloprid residues in or on taro leaves would
exceed the proposed 3.5 ppm tolerance.

B. Toxicological Profile

    1. Acute toxicity. The acute oral lethal dose (LD)50
values for imidacloprid technical ranged from 424-475 milligram/
kilogram body weight (mg/kg bwt) in the rat. The acute dermal
LD50 was greater than 5,000 mg/kg in rats. The 4-hour rat
inhalation lethal concentration (LC)50 was > 69 mg/cubic
meters (m 3) air (aerosol). Imidacloprid was not irritating to rabbit
skin or eyes. Imidacloprid did not cause skin sensitization in guinea
    2. Genotoxicty. Extensive mutagenicity studies conducted to
investigate point and gene mutations, DNA damage and chromosomal
aberration, both using in vitro and in vivo test systems show
imidacloprid to be non-genotoxic.
    3. Reproductive and developmental toxicity. A 2-generation rat
reproduction study gave a no-observed adverse effect level (NOAEL) of
100 ppm (8 mg/kg bwt). Rat and rabbit developmental toxicity studies
were negative at doses up to 30 mg/kg bwt and 24 mg/kg bwt,
    4. Subchronic toxicity. 90-day feeding studies were conducted in
rats and dogs. The NOAEL's for these tests were 14 mg/kg bwt/day (150
parts per million (ppm)) and 5 mg/kg bwt/day (200 ppm) for the rat and
dog studies, respectively.
    5. Chronic toxicity/carcinogenicity. A 2-year rat feeding/
carcinogenicity study was negative for carcinogenic effects under the
conditions of the study and had a NOAEL of 100 ppm (5.7 mg/kg/ bwt in
male and 7.6 mg/kg bwt female) for noncarcinogenic effects that
included decreased body weight gain in females at 300 ppm and increased
thyroid lesions in males at 300 ppm and females at 900 ppm. A 1-year
dog feeding study indicated a NOAEL of 1,250 ppm (41 mg/kg bwt). A 2-
year mouse carcinogenicity study that was negative for carcinogenic
effects under conditions of the study and had a NOAEL of 1,000 ppm (208
    Imidacloprid has been classified under "Group E" (no evidence of
carcinogenicity) by EPA's reference dose (RfD) committee. There is no
cancer risk associated with exposure to this chemical. The RfD based on
the 2-year rat feeding/carcinogenic study with a NOAEL of 5.7 mg/kg bwt
and 100-fold uncertainty factor, is calculated to be 0.057 mg/kg bwt.
    6. Endocrine disruption. The toxicology database for imidacloprid is

[[Page 17173]]

current and complete. Studies in this database include evaluation of
the potential effects on reproduction and development, and an
evaluation of the pathology of the endocrine organs following short- or
long-term exposure. These studies revealed no primary endocrine effects
due to imidacloprid.

C. Aggregate Exposure

    Imidacloprid is a broad-spectrum insecticide with excellent
systemic and contact toxicity characteristics with both food and non-
food uses. Imidacloprid is currently registered for use on various food
crops, tobacco, turf, ornamentals, buildings for termite control, and
cats and dogs for flea control. Those potential exposures are addressed
    1. Dietary exposure. For purposes of assessing the potential acute
and chronic dietary exposure, the registrant, Bayer, has estimated
exposure based on the Theoretical Maximum Residue Contribution (TMRC).
The TMRC is obtained by using a model which multiplies the tolerance
level residue for each commodity by consumption data. The consumption
data, based on the National Food Consumption Survey (NFCS) 1989-92 data
base, estimates the amount of each commodity and products derived from
the commodities that are eaten by the U.S. population and various
population subgroups.
    i. Acute. For acute dietary exposure the model calculates a margin
of exposure (MOE) by dividing the estimated human exposure into the
NOAEL from the appropriate animal study. Commonly, EPA finds MOEs lower
than 100 to be unacceptable. The EPA has determined that a NOAEL of 24
mg/kg/day from a developmental toxicity study in rabbits should be used
to assess acute toxicity and the risk assessment should evaluate acute
exposure to females 13 years.
    The MOE for imidacloprid derived from previously established
tolerances, including time limited tolerances, plus the use on dasheen
(taro) proposed by IR-4 would be 628 for the U.S. population (48
States), 258 for nursing infants, and 929 for females 13+ years at the
99 percentile. These MOEs do not exceed the EPA's level of concern for
acute dietary exposure.
    ii. Chronic. The EPA has determined that the RfD based on the 2-
year rat feeding/carcinogenic study with a NOAEL of 5.7 mg/kg bwt and
100-fold uncertainty factor, is calculated to be 0.057 mg/kg bwt. As
published in the Federal Registers of December 13, 1995 (60 FR 64006),
and June 12, 1996 (61 FR 2674) (petition to establish tolerances on
leafy green vegetables (PP 5F4522/R2237)), the TMRC from published uses
is 0.008358 mg/kg bwt/day which utilizes 14.7% of the RfD for the
general population. For the most highly exposed subgroup in the
population, non-nursing infants (< 1 year old), the TMRC for the
published tolerances is 0.01547 mg/kg/day, which utilizes 27.1% of the
RfD. Using these conservative assumptions, Bayer has determined that
the TMRC from published and proposed uses is 0.008498 mg/kg bwt/day
(15% of the RfD) for the general population and 0.015684 mg/kg/day
(27.5% of the RfD) for the most highly exposed subgroup in the
population, non-nursing infants (< 1 year old). Therefore, Bayer
concludes that dietary exposure from the existing uses and proposed
uses on cucurbits will not exceed the reference dose for any
subpopulation (including infants and children).
    iii. Drinking water. The EPA has determined that imidacloprid is
persistent and could potentially leach into groundwater. However, there
is no established Maximum Contamination Level (MCL) or health advisory
levels established for imidacloprid in drinking water. EPA's
"Pesticides in Groundwater Database" has no entry for imidacloprid.
In addition, Bayer is not aware of imidacloprid being detected in any
wells, ponds, lakes, streams, etc. from its use in the U.S. In studies
conducted in 1995, imidacloprid was not detected in 17 wells on potato
farms in Quebec, Canada. Therefore, Bayer concludes that contributions
to the dietary burden from residues of imidacloprid in water would be
    2. Non-dietary exposure--i. Residential Turf. Bayer has conducted
an exposure study to address the potential exposures of adults and
children from contact with imidacloprid treated turf. The population
considered to have the greatest potential exposure from contact with
pesticide treated turf soon after pesticides are applied are young
children. Margins of safety (MOS) of 7,587 - 41,546 for 10-year old
children and 6,859 - 45,249 for 5-year old children were estimated by
comparing dermal exposure doses to the imidacloprid NOAEL of 1,000 mg/
kg/day established in a 15-day dermal toxicity study in rabbits. The
estimated safe residue levels of imidacloprid on treated turf for 10-
year old children ranged from 5.6 - 38.2 μg/cm2 and
for 5-year old children from 5.1 - 33.5 μg/cm2. This
compares with the average imidacloprid transferable residue level of
0.080 μg/cm2 present immediately after the sprays
have dried. These data indicate that children can safely contact
imidacloprid-treated turf as soon after application as the spray has
    ii. Termiticide-- Imidacloprid is registered as a termiticide. Due
to the nature of the treatment for termites, exposure would be limited
to that from inhalation and was evaluated by Bayer. Data indicate that
the MOS for the worst case exposures for adults and infants occupying a
treated building who are exposed continuously (24 hours/day) are 8.0 x
107 and 2.4 x 108, respectively - and exposure
can thus be considered negligible.
    iii. Tobacco smoke. Studies have been conducted to determine
residues in tobacco and the resulting smoke following treatment.
Residues of imidacloprid in cured tobacco following treatment were a
maximum of 31 ppm (7 ppm in fresh leaves). When this tobacco was burned
in a pyrolysis study only 2% of the initial residue was recovered in
the resulting smoke (main stream plus side stream). This would result
in an inhalation exposure to imidacloprid from smoking of approximately
0.0005 mg per cigarette. Using the measured subacute rat inhalation
NOAEL of 5.5 mg/m3, Bayer believes that exposure to
imidacloprid from smoking (direct and/or indirect exposure) would not
be significant.
    iv. Pet treatment. Bayer concludes that human exposure from the use
of imidacloprid to treat dogs and cats for fleas does not pose
unacceptable risks to human health since imidacloprid is not an
inhalation or dermal toxicant and that while dermal absorption data are
not available, imidacloprid is not considered to present a hazard via
the dermal route.

D. Cumulative Effects

    No other chemicals having the same mechanism of toxicity are
currently registered, therefore, Bayer concludes that there is no risk
from cumulative effects from other substances with a common mechanism
of toxicity.

E. Safety Determination

    1. U.S. population--U.S. population in general. Using the
conservative exposure assumptions described above and based on the
completeness and reliability of the toxicity data, Bayer concludes that
total aggregate exposure to imidacloprid from all current uses
including those currently proposed will utilize little more than 15% of
the RfD for the U.S. population. EPA generally has no concerns for
exposures below 100% of the RfD, because the RfD represents the level
at or below which daily aggregate exposure over a lifetime will not
pose appreciable risks to human health. Thus, it can be

[[Page 17174]]

concluded that there is a reasonable certainty that no harm will result
from aggregate exposure to imidacloprid residues.
    2. Infants and children. In assessing the potential for additional
sensitivity of infants and children to residues of imidacloprid, the
data from developmental studies in both rat and rabbit and a 2-
generation reproduction study in the rat have been considered. The
developmental toxicity studies evaluate potential adverse effects on
the developing animal resulting from pesticide exposure of the mother
during prenatal development. The reproduction study evaluates effects
from exposure to the pesticide on the reproductive capability of mating
animals through 2-generations, as well as any observed systemic
    FFDCA Section 408 provides that EPA may apply an additional safety
factor for infants and children in the case of threshold effects to
account for pre- and post- natal effects and the completeness of the
toxicity database. Based on current toxicological data requirements,
the toxicology database for imidacloprid relative to pre- and post-
natal effects is complete. Further for imidacloprid, the NOAEL of 5.7
mg/kg bwt from the 2-year rat feeding/carcinogenic study, which was
used to calculate the RfD (discussed above), is already lower than the
NOAELs from the developmental studies in rats and rabbits by a factor
of 4.2 to 17.5 times. Since a 100-fold uncertainty factor is already
used to calculate the RfD, Bayer surmises that an additional
uncertainty factor is not warranted and that the RfD at 0.057 mg/kg
bwt/day is appropriate for assessing aggregate risk to infants and
    Using the conservative exposure assumptions described above under
aggregate exposure, Bayer has determined from a chronic dietary
analysis that the percent of the RfD utilized by aggregate exposure to
residues of imidacloprid ranges from 9.3% for nursing infants up to
32.2% for children (1-6 years). EPA generally has no concern for
exposure below 100% of the RfD. In addition, the MOEs for all infant
and children population groups do not exceed EPA's level of concern for
acute dietary exposure. Therefore, based on the completeness and
reliability of the toxicity data and the conservative exposure
assessment, Bayer concludes that there is a reasonable certainty that
no harm will result to infants and children from aggregate exposure to
the residues of imidacloprid, including all anticipated dietary
exposure and all other non-occupational exposures.

F. International Tolerances

    No CODEX Maximum Residue Levels (MRLs) have been established for
residues of imidacloprid on any crops at this time.

[FR Doc. 99-8775 Filed 4-7-99; 8:45 am]