Triclopyr - Pesticide Petition Filing 2/98
[Federal Register: February 20, 1998 (Volume 63, Number 34)]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
ENVIRONMENTAL PROTECTION AGENCY
Notice of Filing of Pesticide Petitions
AGENCY: Environmental Protection Agency (EPA).
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 agricultural commodities.
DATES: Comments, identified by the docket control number PF-791, must
be received on or before March 23, 1998.
ADDRESSES: By mail submit written comments to: Information and Records
Integrity Branch, Public Information and Services Divison (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 by following
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: By mail: James A. Tompkins, Product
Manager (PM) 25, Registration Division, (7505C), Office of Pesticide
Programs, Environmental Protection Agency, 401 M St., SW., Washington,
DC 20460. Office location and telephone number: Rm. 239, 1921 Jefferson
Davis Hwy., Arlington, VA., (703) 305-5697; e-mail:
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 raw
agricultural 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
supports grantinig of the petition. Additional data may be needed
before EPA rules on the petition.
The official record for this notice, as well as the public version,
has been established for this notice of filing under docket control
number PF-791 (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. Comment and data
will also be accepted on disks in Wordperfect 5.1/6.1 file format or
ASCII file format. All comments and data in electronic form must be
identified by the docket control number (insert docket number) and
appropriate petition number. Electronic comments on this notice may be
filed online at many Federal Depository Libraries.
Authority: 21 U.S.C. 346a.
List of Subjects
Environmental protection, Agricultural commodities, Food additives,
Feed additives, Pesticides and
pests, Reporting and recordkeeping requirements.
Dated: February 12, 1998.
Donald R. Stubbs,
Acting Director, Registration Division, Office of Pesticide Programs.
Summaries of Petitions
Below summaries of the pesticide petitions are printed. The
summaries of the petitions were prepared by the petitioners. The
petition summary announces the availability of a description of the
analytical methods available to EPA for the detection and measurement
of the pesticide chemical residues or an explanation of why no such
method is needed.
EPA has received a pesticide petition (PP 1F3935) from DowElanco,
9330 Zionsville Road, Indianapolis, IN 46268-1054 proposing pursuant to
section 408(d) of the Federal Food, Drug and Cosmetic Act, 21 U.S.C.
346a(d), to amend 40 CFR part 180 by establishing a tolerance for
residues of triclopyr, (3,5,6-trichloro-2-pyridinyl)oxyacetic acid and
its metabolites 3,5,6-trichloro-2-pyridinol (TCP) and 2-methoxy-3,5,6-
trichloropyridine (TMP) in or on the raw agricultural commodity fish at
3.0 parts per million (ppm), and shellfish at 5.0 ppm. EPA has
determined that the petition contains 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 supports granting of the petition. Additional data
may be needed before EPA rules on the petition.
A. Residue Chemistry
1. Analytical method. Adequate methodology is available for the
enforcement of tolerances for triclopyr residues of concern. Gas
chromatography methods are available for the determination of triclopyr
residues of concern. Residues of triclopyr, 3,5,6-trichloro-2-
pyridinol, and 2-methoxy-3,5,6-trichloropyridine can be separately
determined. The limits of quantitation are 0.01 - 0.05 ppm in fish and
shellfish, depending on the compound being analyzed. The water method
has a limit of quantitation of 0.1 parts per billion (ppb).
2. Magnitude of residues. In field studies, triclopyr and its
metabolites in water have half-lives of 0.5 - 15 days. Triclopyr
residues in lake water treated at the maximum label rate were below 0.5
ppm within 3 - 14 days. In pond water where whole ponds were treated at
the maximum label rate, residues were below 0.5 ppm by 28 days after
treatment. After 42 days in both lakes and ponds, residues were non-
detectable (<0.010 ppm) to 0.013 ppm.
Residues of triclopyr and its metabolites 3,5,6-trichloro-2-
pyridinol and 2-methoxy-3,5,6-trichloropyridine reach a maximum
concentration in fish at 3-14 days after treatment of water, and total
residues of triclopyr and its metabolites were detectable in the edible
flesh at a maximum level of 3.0 ppm in fish and 5.0 ppm in shellfish.
Residues in fish and shellfish decline as residues in water dissipate.
B. Toxicological Profile
1. Acute toxicity. The developmental no-effect level (NOEL) of 30
milligrams/kilograms/day (mg/kg/day) from a rabbit developmental study
was recommended for the acute dietary risk assessment. At the lowest
effect level (LEL) of 100 mg/kg/day, there were embryotoxic and
fetotoxic effects associated with significant maternal toxicity,
including death. Acute exposure assessment will evaluate risk to
pregnant females age 13 and older.
2. Short- and Intermediate-Term Toxicity. Based on the available
data, short- and intermediate-term dermal and inhalation risk
assessments are not required. A systemic NOEL of 1,000 mg/kg/day, the
highest dose tested (HDT), was determined in a 21-day dermal toxicity
study in rabbits. The LC50 from the acute inhalation study
in rats was determined to be > 2.6 mg/L (Toxicity Category III).
3. Chronic toxicity. The Reference Dose (RfD) for triclopyr is 0.05
mg/kg/day. This RfD is based on a 2-generation reproductive toxicity
study in rats with a NOEL of 5.0 mg/kg/day using an uncertainty factor
of 100. At the next higher dose level of 25 mg/kg/day, an increased
incidence of slight degeneration of the proximal tubules of the kidneys
was observed in some P1 and P2 parents of both sexes. Chronic exposure
assessment will evaluate risk using this RfD.
4. Carcinogenicity. Environmental Protection Agency's Cancer Peer
Review Committee (CPRC) concluded that triclopyr should be classified
as a "Group D chemical" - not classifiable as to human
carcinogenicity. A cancer risk assessment is not required.
5. Animal metabolism. Disposition and metabolism of 14C-
triclopyr in rats demonstrated that triclopyr was well absorbed after
oral administration. Excretion was relatively rapid with a majority of
radioactivity eliminated in the urine by 24 hours. At the high dose of
60 mg/kg, urinary elimination of 14C-triclopyr was decreased
due to apparent saturation of renal elimination mechanisms. Fecal
elimination of 14C-triclopyr was a minor route of excretion,
as was elimination via exhaled air. Unmetabolized parent chemical
represented >90% of urinary radioactivity, with the remainder accounted
for by the metabolite 3,5,6-trichloro-2-pyridinol (3,5,6-TCP), and
possible glucuranide and/or sulfate conjugates of 3,5,6-TCP. Plasma
elimination following intravenous administration of 14C-
triclopyr was consistent with a one-compartment model with an
elimination half-life of 3.6 hr and zero-order kinetics from 0-12 hours
at the 60 mg/kg dose.
6. Bioequivalency. Toxicology studies conducted with triclopyr have
been performed using both the free acid or the triethylamine salt from
of triclopyr. Bioequivalency of the two chemical forms of triclopyr has
been addressed through the conduct of special studies with the
triethylamine from of triclopyr. These studies, which included data on
comparative disposition, plasma half-life, tissue distribution,
hydrolytic cleavage under physiological and environmental conditions
for triclopyr triethylamine salt were found to adequately address the
issue of Bioequivalency. In addition, subchronic toxicity studies
supported the pharmacokinetics data in demonstrating bioequivalence.
Therefore, studies conducted with any one from of triclopyr can be used
to support the toxicology database as a whole.
7. Endocrine effects. An evaluation of the potential effects on the
endocrine systems of mammals has not been determined; However, no
evidence of such effects were reported in the chronic or reproductive
toxicology studies described above. There was no observed pathology of
the endocrine organs in these studies. There is no evidence at this
time that triclopyr causes endocrine effects.
C. Aggregate Exposure
1. Dietary exposure. The RfD for triclopyr is based upon the 2-
generation reproduction toxicity study in rats with a NOEL of 5.0 mg/
kg/day, the lowest dose tested. An uncertainty factor of 10 for
interspecies differences in response and an uncertainty factor of 10
for intraspecies differences in response was applied. Thus, the RfD for
triclopyr was established at 0.05 mg/kg/day by the RfD Peer Review
Committee on September 4, 1996.
A chronic dietary exposure analysis was performed using tolerance
residues and 100 percent crop treated information to estimate the
Theoretical Maximum Residue Contribution (TMRC) for the general
population and 22 subgroups. Existing tolerances, including the
proposed tolerances for fish and shellfish, result in a TMRC that
represents 1.25% of the RfD for the U.S. general population. The
highest subgroup, Non-Nursing Infants (<1 year old) occupies 2.65% of
the RfD. The chronic analysis for triclopyr is a worse case estimate of
dietary exposure with all residues at tolerance level and 100 percent
of the commodities assumed to be treated with triclopyr. Based on the
risk estimates calculated in this analysis, the chronic dietary risk
from the uses currently registered is not of concern.
Since the toxicological endpoint to which exposure is being
compared in the acute dietary risk analysis is a developmental NOEL (30
mg/kg/day), females (13+ years) are the sub population of particular
interest. The Margin of Exposure (MOE) is a measure of how close the
high end exposure comes to the NOEL (the highest dose at which no
effects were observed in the laboratory test), and is calculated as the
ratio of the NOEL to the exposure (NOEL/exposure = MOE.) Generally,
acute dietary margins of exposure greater than 100 tend to cause no
dietary concern. The high end MOE value of 1,639 is above the
acceptable level and demonstrates no acute dietary concern.
An acute dietary exposure analysis was performed using tolerance
level residues and 100 percent crop treated to estimate the high end
exposure for the general population and females (13+, pregnant, non-
nursing). The high end exposure was assumed to be the upper 0.5% of
consumers, that is, the 99.5 percentile. The resulting exposure
estimates and margins of exposure are as follows:
Exposure (mg/kg BW/
Population Subgroup day) MOE
U.S. Population 0.01359 2208
Females 0.01831 1639
These high end MOE values are above the acceptable level and
demonstrate no acute dietary concerns.
2. Drinking water. The use of triclopyr as described on the label
allows only slight additional exposure of triclopyr to humans. The
proposed labeling requires that the product not be applied within one-
quarter mile of a potable water intake and that treated water not be
used for domestic purposes until the residue level is demonstrated to
be at or below 0.5 ppm as determined by laboratory analysis or
immunoassay. The basis for these restrictions is a series of aquatic
dissipation studies conducted in lakes and ponds. In these studies,
triclopyr was applied to lakes and ponds at the maximum concentration
of 2.5 ppm triclopyr in water. Triclopyr residues in the lakes at one-
quarter mile from the treatment areas were well below 0.1 ppm
throughout the study, with a maximum reported value of 0.058 ppm.
Within the treatment area, triclopyr residues of less than 0.5 ppm were
reported at 3 - 14 days after treatment in the Lake Minnetonka and Lake
Seminole studies. In seven test ponds treated with triclopyr at a water
concentration of 2.5 ppm, total residues of triclopyr were less than
0.5 ppm by 28 days after application, with the highest residue value
being 0.193 ppm. At 42 days after treatment, total residues in both
treated lakes and ponds ranged from non-detectable to 0.013 ppm.
If the proposed labeling is followed precisely, that is, potable
water is not collected within one-quarter mile of a treated area, there
will be little contribution from water to the "risk cup" for
triclopyr. If drinking water is collected from the treatment area when
water analysis indicates triclopyr residues are 0.5 ppm or less, the
risk is still acceptable on an acute basis. On a chronic basis, the
value of 0.013 ppm, found to be the highest triclopyr residue at 42
days after treatment in all studies, uses only 0.9% of the RfD for
females (13+, pregnant, not nursing) and 2.6% of the RfD for children
For a worst case estimate of potential drinking water exposure, the
water residue at the proposed allowable water level at 0.5 ppm was
utilized. When this residue level is considered, the following analysis
indicates no level of concern for acute exposure:
For a 60 kg pregnant female consuming 2 liters a day (Acute)
(0.5 mg/L x 2 L/day) / 60 kg = 0.0167 mg/kg/day
MOE = NOEL / Exposure = (30 mg/kg/day) / ( 0.0167 mg/kg/day) =
For a 60 kg pregnant female consuming 2 liters a day (Chronic)
(0.013 mg/kg/day x 2 L/day) / 60 kg = 0.00043 mg/kg/day
% RfD = (0.00043 mg/kg/day x 100) / (0.05 mg/kg/day) = 0.9 %
For a 10 kg child consuming 1 liter a day (Acute)
(0.5 mg/L x 1 L/day) / 10 kg = 0.05 mg/kg/day
MOE = (30 mg/kg/day) / (0.05 mg/kg/day) = 600
For a 10 kg child consuming 1 liter a day (Chronic)
(0.013 mg/L x 1 L/day) / 10 kg = 0.0013 mg/kg/day
% RfD = (0.0013 mg/kg/day x 100) / (0.05 mg/kg/day) = 2.6 %
3. Non-dietary exposure. There are potential exposures to
homeowners during usual use-patterns associated with triclopyr. These
involve application of triclopyr-containing products by means of
aerosol cans, pump spray bottles, squeeze bottles, "weed sticks,"
hose-end sprayers, power sprayers, paint brush, rotary and drop
spreaders. It is unlikely that power sprayers will be used by
homeowners; this is an application method requiring special applicator
equipment more apt to be used by agricultural or commercial applicator.
Homeowner exposure will not be significant for the following
reasons: the percent ai in products for homeowner use is less than that
for agricultural or industrial use; the areas treated are usually
limited in size; all products are intended for outdoor use which is
likely to reduce the concentration in the environment by allowing
dissipation in the outdoor air; the application methods recommended or
commonly used by homeowners are not expected to provide significant
exposure. Additionally, no toxicological endpoints of concern have been
identified by EPA for dermal exposure to triclopyr, therefore, no
exposure assessment is required for this exposure; an inhalation
exposure assessment is also not required and no chronic use pattern is
expected for homeowner use of triclopyr products.
There is a potential for post-application exposure to swimmers
following applications to aquatic sites
that may be used for recreational purposes. There are no triclopyr-
specific exposure data to assess swimmer exposure. However, an
assessment was conducted using information provided in EPA's Dermal
Exposure Assessment: Principles and Applications. The dermal
permeability constant (Kp) was calculated to be 6.5 x 10-8
mg/cm2/hr. The assessment of swimmer exposure was based on a
six-year old boy having a body weight of 21.9 kg and a surface area of
0.88 m2. The swimming period was assumed to be 3 hours on
the day of treatment in water containing 2.5 ppm triclopyr.
Total dermal exposure (mg) = 3 hr/day x 0.88 m2 x
104 cm2/m2 x 6.5 x 10-8 mg/
cm2/hr = 1.716 x 10-3 mg/day
Oral absorption could also account for a portion of the exposure.
It was assumed that 1% of the water in residence in the mouth while
breathing will be swallowed.
Oral exposure = 3 hr/day x 0.05 L/hr x 2.5 mg/L = 0.375 mg/day
Combining the dermal exposure and oral exposure for a 21.9 kg
child, the swimming exposure for one day was estimated to be 0.377 mg/
day/21.9 kg = 0.017 mg/kg/day. Compared to the acute NOEL of
30 mg/kg/day, an MOE of 1,765 was obtained. No dermal or inhalation
endpoint has been established for triclopyr, so this represents a very
conservative estimate of the risk due to swimming in triclopyr-treated
D. Cumulative Effects
The potential for cumulative effects of triclopyr and other
substances that have a common mechanism of toxicity was considered. The
mammalian toxicity of triclopyr is well defined. However, the
biochemical mechanism of toxicity of this compound is not known. No
reliable information exists to indicate that toxic effects produced by
triclopyr would be cumulative with those of other similar compounds.
Therefore, consideration of a common mechanism of toxicity with other
compounds is not appropriate. Thus, only the potential risks of
triclopyr are considered in the aggregate exposure assessment.
E. Safety Determination
1. U.S. population. Because of the toxicological characteristics of
triclopyr (no dermal endpoint of concern), post-application exposure
assessment was not necessary. Residential exposure is considered to be
negligible. Swimming in treated water was shown to be a minimal risk.
Therefore, residential and swimming exposure were not considered in the
aggregate risk calculation.
For the population subgroup of concern, pregnant females age 13 and
older, an MOE of 857 was estimated for the acute aggregate dietary risk
(food + water) from exposures to triclopyr residues.
MOE = (30 mg/kg/day) / (0.0183 + 0.0167) mg/kg/day = 857
Using the TMRC exposure assumptions described above, the percentage
of the RfD that will be utilized by aggregate exposures (food + water)
to residues of triclopyr ranges from 2.1% to 5.3% for the U.S.
population. The major identifiable subgroup with the highest aggregate
exposure is non-nursing infants <1 year old. The water exposure value
used the highest water residue concentration at 42 days after treatment
of lakes and ponds (the longest sampling time interval common to all
studies), 0.013 ppm, in the calculations below:
Total U.S. Population (Dietary + Drinking Water)
(0.00062 + 0.00043) mg/kg/day x 100 / (0.05 mg/kg/day) = 2.1%
Non-nursing Infants (Dietary + Drinking Water)
(0.00133 + 0.0013) mg/kg/day x 100 / (0.05 mg/kg/day) = 5.3%
Determination of Safety for U.S. Population
Based on the current state of knowledge for this chemical, the
RfD approach accurately reflects the exposure of the U.S.
population, infants and children to triclopyr.
2. Infants and children. Studies cited earlier in this document
indicate that triclopyr is not a selective developmental toxicant, and
an additional uncertainty factor for infants and children is
unnecessary. This decision is based on the following data.
Since the developmental and reproductive NOELs were either the same
or greater than the maternal or parental, it is unlikely that there is
additional risk concern for immature or developing organisms which is
not reflected by the risk assessment utilizing the established
reference dose. The effects noted for the RfD NOEL are parental
effects, not developmental.
F. International Tolerances
There are no established or proposed Codex MRLs for triclopyr
residues. Therefore, there are no issues of compatibility with respect
to U.S. tolerances and Codex MRLs.
[FR Doc. 98-4187 Filed 2-19-98; 8:45 am]
BILLING CODE 6560-50-F