Imidacloprid - Amendment to Pesticide Petition 1/97
CHEMICAL PROFILES/INSECTICIDE MITICIDE/imidacloprid
[FR Doc. 97-1491 Filed 1-21-97; 8:45 am]
[Federal Register: January 22, 1997 (Volume 62, Number 14)] [Notices]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
ENVIRONMENTAL PROTECTION AGENCY
Interregional Research Project No. 4; Pesticide Tolerance Petition Filing
AGENCY: Environmental Protection Agency (EPA).
SUMMARY: This notice announces the filing of an amendment to pesticide
petition (PP) 5E4598 proposing to extend the effective date for the time-
limited tolerance established for indirect or inadvertent combined residues of
the insecticide imidacloprid and its metabolites resulting from crop
rotational practices in or on the raw agricultural commodities of the cucurbit
vegetables crop group. This notice includes a summary of the amended petition
that was prepared by Bayer Corporation (Bayer), the registrant, and submitted
by the Interregional Research Project No. 4, the petitioner.
DATES: Comments, identified by the docket number [PF-690], must be received on
or before February 21, 1997.
ADDRESSES: By mail, submit written comments to: Public Response and Program
Resources Branch, Field Operations Division (7506C), Office of Pesticide
Programs, Environmental Protection Agency, 401 M St., SW., Washington, DC
20460. In person, bring comments to: Rm. 1132, CM #2, 1921 Jefferson Davis
Highway, Arlington, VA 22202.
Comments and data may also be submitted electronically by sending electronic
mail (e-mail) to: email@example.com or by submitting disks.
Electronic comments must be submitted either in ASCII format (avoiding the use
of special characters and any form of encryption) or in WordPerfect in 5.1
file format. All comments and data in electronic form must be identified by
the docket number [PF-690]. Electronic comments on this notice may be filed
online at many Federal Depository Libraries.
Information submitted as comments concerning this document may be claimed
confidential by marking any part or all of that information as "Confidential
Business Information" (CBI). Information so marked will not be disclosed
except in accordance with procedures set forth in 40 CFR part 2. No CBI should
be submitted through e-mail. 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.
FOR FURTHER INFORMATION CONTACT: By mail: Hoyt L. Jamerson, Registration
Division (7505W), Office of Pesticide Programs, Environmental Protection
Agency, 401 M St., SW., Washington, DC 20460. Office location and telephone
number: Sixth Floor, Crystal Station #1, 2800 Jefferson Davis Highway,
Arlington, VA 22202, (703) 308-8783, e-mail:
SUPPLEMENTARY INFORMATION: EPA has received an amendment to PP 5E4598 from the
Interregional Research Project No. 4 (IR-4), New Jersey Agricultural
Experiment Station, P.O. Box 231, Rutgers University, New Brunswick, NJ 08903.
The amended petition proposes, pursuant to section 408 of the Federal Food,
Drug and Cosmetic Act (FFDCA), 21 U.S.C. 346a, to amend 40 CFR 180.472 by
extending the effective date to expire on December 31, 1997, for the time-
limited tolerance established for the indirect or inadvertent combined
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, resulting from crop rotational practices in or on
the raw agricultural commodities in the cucurbit vegetables crop group at 0.2
parts per million (ppm). This tolerance will not support registration for
imidacloprid on cucurbit vegetables. EPA will not consider applications for
section 3 or section 24(c) registration for use of imidacloprid on cucurbit
vegetables based on this time-limited tolerance. The tolerance will allow
growers to produce cucurbit vegetables in rotation with crops that are treated
in accordance with registered uses of imidacloprid. Imidacloprid registrations
prohibit growers from planting crops that lack an imidacloprid tolerance on
ground treated with the insecticide within a 12-month period. Crop rotational
studies indicate that plant back crops grown in fields treated with
imidacloprid may contain measurable amounts of the pesticide residue, if the
rotational crop is planted within 12 months of application of the pesticide.
In some areas, however, it is a common practice for growers to plant back
cucurbit vegetables (melons, squash and cucumbers) in fields that have been
used to produce tomatoes and peppers. Imidacloprid is registered and
tolerances are established for the fruiting vegetables crop group (including
tomatoes and peppers).
IR-4 has submitted PP 6E4766, which proposes a permanent tolerance for
residues of imidacloprid and its metabolites in or on the cucurbit vegetables
crop group at 0.5 ppm. Although PP 6E4766 proposes a tolerance in support of
registration for use of imidacloprid on cucurbit vegetables, the proposed
tolerance, if established, will be adequate to cover indirect or inadvertent
residues on cucurbits resulting from registered uses of imidacloprid. EPA's
evaluation of PP 6E4766 will not be completed in time to establish a permanent
tolerance, prior to the December 31, 1996, expiration date for the time-
limited tolerance. Therefore, IR-4 proposes that the time-limited tolerance
for imidacloprid be extended to December 31, 1997, to allow EPA additional
time to review IR-4's petition for permanent tolerance for residues of
imidacloprid on cucurbit vegetables.
As required by section 408(d) of the FFDCA, as recently amended by the Food
Quality and Protection Act IR-4 included in the amendment a summary of the
petition provided by Bayer and authorization for the summary to be published
in the Federal Register in a notice of receipt of the petition. The summary
represents the views of Bayer; EPA, as mentioned above, is in the process of
evaluating the petition. As required by section 408(d)(3) EPA is including the
summary as a part of this notice of filing. EPA may have made minor edits to
the summary for the purpose of clarity.
I. Petition Summary
A. Plant Metabolism and Analytical Method
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
imidacloprid. 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 GC-MS selective
ion monitoring. There is an additional confirmatory method available.
Imidacloprid and its metabolites have been shown to be stable for at least 24
months in frozen storage.
B. Toxicological Profile of Imidacloprid
1. Acute toxicity. The acute oral LD50 values for imidacloprid technical
ranged from 424 to 475 milligrams (mg)/kilogram (kg) body weight (bwt) in the
rat. The acute dermal LD50 was greater than 5,000 mg/kg in rats. The 4-hour
rat inhalation LC50 was >69 mg/ cubic meter (m3) air (aerosol). Imidacloprid
was not irritating to rabbit skin or eyes. Imidacloprid did not cause skin
sensitization in guinea pigs.
2. Genotoxicity. 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 two-generation rat reproduction
study gave a no-observed-effect level (NOEL) 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, respectively.
4. Subchronic toxicity. Ninety-day feeding studies were conducted in rats and
dogs. The NOEL's for these tests were 14 mg/kg bwt/day (150 ppm) and 5 mg/kg
bwt/day (200 ppm) for the rat and dog studies, respectively.
5. Chronic toxicity/oncogenicity. A 2-year rat feeding/ carcinogenicity study
was negative for carcinogenic effects under the conditions of the study and
had a NOEL 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 NOEL 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 that had a NOEL of 1,000 ppm (208
Imidacloprid has been classified under "Group E" (no evidence of
carcinogenicity) by EPA's OPP/HED's Reference Dose (RfD) Committee. There is
no cancer risk associated with exposure to this chemical.
6. Endocrine effects. The toxicology database for imidacloprid is 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.
7. Mode of action. Imidacloprid exhibits a mode of action different from
traditional organophosphate, carbamate, or pyrethroid insecticides.
Imidacloprid acts by binding to the nicotinergic receptor sites at the
postsynaptic membrane of the insect nerve. Due to this novel mode of action,
imidacloprid has not shown any cross resistance to registered alternative
C. Aggregate Exposure
Imidacloprid is a broad-spectrum insecticide with 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 below:
1. Dietary. The EPA has determined that the reference dose (RfD) based on the
2-year rat feeding/carcinogenic study with a NOEL 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 Register 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 theoretical maximum residue contribution (TMRC) from
published uses is 0.008358 mg/kg/bwt/day utilizing 14.7 percent 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. This is equal to 27.1 percent of the RfD.
Therefore, Bayer believes that dietary exposure from the existing uses
(including this time-limited tolerance) will not exceed the reference dose for
any subpopulation (including infants and children).
2. Water. Although the various imidacloprid labels contain a statement that
this chemical demonstrates the properties associated with chemicals detected
in groundwater, Bayer is not aware of imidacloprid being detected in any
wells, ponds, lakes, streams, etc. from its use in the United States. In
studies conducted in 1995, imidacloprid was not detected in 17 wells on potato
farms in Quebec, Canada. In addition, groundwater monitoring studies are
currently underway in California and Michigan. Therefore, Bayer believes that
contributions to the dietary burden from residues of imidacloprid in water
would be inconsequential.
3. Non-occupational-- a. 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 to
41,546 for 10-year-old children and 6,859 to 45,249 for 5-year-old children
were estimated by comparing dermal exposure doses to the imidacloprid no-
observable effect level 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 to 38.2 micrograms
(μg)/square centimeter (cm2) and for 5-year-old children from 5.1 to
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 dried.
b. 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 EPA's Occupational and Residential Exposure
Branch and Bayer. Data indicate that the Margins of Safety 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.
c. 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 percent 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 NOEL of 5.5 mg/m3, it is apparent that exposure to imidacloprid
from smoking (direct and/or indirect exposure) would not be significant.
d. Pet treatment. Human exposure from the use of imidacloprid to treat dogs
and cats for fleas has been addressed by EPA's Occupational and Residential
Exposure Branch who have concluded that due to the fact that 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
4. Cumulative effects. No other chemicals having the same mechanism of
toxicity are currently registered, therefore, Bayer believes that there is no
risk from cumulative effects from other substances with a common mechanism of
D. Safety Determinations
1. 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 percent of the RfD for the U.S. population. EPA generally has no concerns
for exposures below 100 percent 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, Bayer concludes that there is a
reasonable certainty that no harm will result from aggregate exposure to
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 two- 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 two generations, as well as
any observed systemic toxicity.
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 NOEL 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 NOELs 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 children.
Using the conservative exposure assumptions described above, EPA has concluded
that the TMRC from use of imidacloprid from published uses is 0.008358
mg/kg/bwt/day utilizing 14.7 percent 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.
This is equal to 27.1 percent of the RfD. Therefore, Bayer concludes that
dietary exposure from the existing uses including the currently proposed
tolerances will not exceed the reference dose for any subpopulation (including
infants and children).
E. Other Considerations
There is no reasonable expectation that secondary residues will occur in milk
and eggs, or meat, fat, and meat byproducts of livestock or poultry; there are
no livestock feed items associated with the cucurbit vegetables.
F. International Tolerances
No CODEX Maximum Residue Levels (MRL's) have been established for residues of
Imidacloprid on any crops at this time.
II. Public Record
EPA invites interested persons to submit comments on this notice of filing.
Comments must bear a notification indicating the docment number [PF-690].
A record has been established for this notice of filing under docket number
[PF-690] (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 4:00 p.m., Monday through Friday,
excluding legal holidays. The public record is located in Room 1132 of the
Public Response and Program Resources Branch, Field Operations Division
(7506C), Office of Pesticide Programs, Environmental Protection Agency,
Crystal Mall #2, 1921 Jefferson Davis Highway, Arlington, VA.
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.
The official record for this notice of filing, as well as the public version,
as described above will be kept in paper form. Accordingly, EPA will transfer
all comments received electronically into printed, paper form as they are
received and will place the paper copies in the official record which will
also include all comments submitted directly in writing. The official record
is the paper record maintained at the address in "ADDRESSES" at the
beginning of this document.
List of Subjects
Environmental protection, Administrative practice and procedure, Agricultural
commodities, Pesticides and pests, Reporting and recordkeeping requirements.
Dated: January 10, 1997.
Peter Caulkins, Acting Director
Office of Pesticide Programs