United Ststw Office of Pwieidei and Toxic Sutetanen
Environmental Protection Office of Pesticide Prograiro (TS-766C)
Agency Washington, DC 20460
Pesticide
Fact Sheet
Name of Chemical:
Reason for Issuance:
Date Issued: ^^ 31f 1985
Fact Sheet Number:
50
1. Description of the chemical;
Generic name: N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitro-
benzenamine
Empirical formula: ^3^9^04
Common name: Pendimethalin
Trade name: Prowl®, Herbadox®, Stomp®, and AC 92553
Chemical Abstracts Service (CAS) Registry number: 40487-42-1
Office of Pesticides Program's EPA Chemical Code Number:
108501
Year of initial registration: 1974
Pesticide type: Herbicide
Chemical family: Dinitroaniline
U.S. producer: American Cyanamid Company
2. Use patterns and formulations;
Application sites: Pendimethalin is registered for control of
broad leaf weeds and grassy weed species on the following
sites: soybeans, cotton, field corn, beans, peanuts, pota-
toes, rice, sorghum, sunflower, tobacco, ornamentals, non-
bearing fruit and nut crops, and vineyards.
One site, jojoba, is registered under Section 24(c) in
Arizona.
Types of formulations: Pendimethalin is available in qranular,
dispersable granular, and emulsifiable concentrate
formulations.
Types and methods of applications: Pendimethalin is mainly
applied as a preplant incorporation (except in corn, rice
and sorghum), preemergence spray, early postemergence
(rice), and late postemergence "culti-spray" (field corn
and sorghum) applications.
Application rates: 0.5 to 2.0 Ibs a.i./A on crop sites.
Usual carriers: Attapulqite clay and water.
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3. Science Findings :
Summary science statements:
Pendimethalin is not acutely toxic by the oral, dermal, in-
halation and occular routes of exposure. The available
data is insufficient to show that any of the risk criteria
listed in § 162.11(a) of Title 40 of the U.S.Code of Federal
Regulations have been met or exceeded for the uses of
pendimethalin at the oresent time. There are no valid
mutaaenicity and chronic rat studies for pendimethalin and
insufficient oncogenicity data. There are also extensive
residue chemistry and environmental fate data gaDs.
Pendimethalin is highly toxic to coldwater fish, highly to
moderately toxic to warmwater fish and highly to moderately
toxic to freshwater jnvertehrates. A detailed ecological
hazard assessment cannot be made until certain environmental
chemistry data requirements, and a monitoring study of
aquatic sites next to treated rice fields are fulfilled.
Chemical characteristics:
Pendimethalin is crystalline at room temperature and has a
fruit like odor. Its molecular weight is 281.30. The boil-
ing point is 330°C. Pendimethalin is soluble in water ( at
20°C) to <0.50 ppm and soluble in aromatic and chlorinated
hydrocarbon solvents.
‘roxicoloqical characteristics:
Acute toxicoloqy effects on pendimethalin are as follows:
Acute Oral Toxicity in rats: >1,250 mq/kq body weight,
‘ roxicity Category III
Acute Dermal Toxicity in rabbits: >5,000 mg/kg body
weight, Toxicity Cateqory III
Acute Inhalation Toxicity in rats: >320 mq/l (4 hour
exposure) Toxicity Category IV
Skin irritation in rabbits: slight irritant, Toxicity
Category III
Eye irritation in rabbits: corneal irritation clearing
in less than seven days, Toxicity Category III.
Subchronic toxicology data except for the 90-day rat feeding
study have met the current toxicity requirements.
Chronic toxicology effects on pendimethalin have not been
completely evaluated because there are no valid mutageni—
city and chronic rat studies for pendimethalin, and
insufficient oncogenicity data.
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A 2—year doc feedinq study indicated that pendirnethalin
tested at 12.5 mg/kg, 50.0 ma/kq and 200.0 mq/kq producer
increases in alkaline phos hatase level and liver weight.
The NOEL is 12.5 mq/kg/ day.
A teratology test in rats has shown that pendimethalin
tested at 300.0 mq/kg, highest dose tested (HIYr), failed
to induce teratogenic, or fetotoxic effects. A teratoloav
test in rabbits has shown that pendimethalin tested at
60.0 mg/kg (HDT), failed to induce teratogenic or feto-
toxic effects.
A reproduction study (3—generation rat) indicated that
pendimethalin tested at 500 ppm to 5,000 ppm induced
slightly fewer offsprinq, with no corresponding increase
in deaths and decreased weiqht gain from weaning to
maturity. The NOEL is 500 ppm.
Major routes of human exposure:
Non—dietary exposure to pendiinethalin by a farmer as an
applicator during mixing, loading , spraying and flagging
is probable.
Physiological and biochemical behavioral characteristics:
Absorption characteristics: Pendimethalin is absorbed in
limited amounts by monocotvledonous niants and in moderate
amounts by small dicotyledonous plants.
Translocation: Pendimethalin is taken up from the soil by
plants in very limited amounts.
Mechanism of pesticidal action: Pendimethalin inhibits plant
cell division and cell elongation.
Metabolism in plants: Pendimethalin is principally degra-
dated in plants by oxidation of the 4—methyl qroup(benzene
ring) and the N—1-ethylpropyl group in the amine moiety.
Environmental characteristics:
Adsorption and leachina in basic soil types: Pendimethalin
is strongly adsorbed by soil organic matter and clay and
does not readily leach through the soil.
Microbial breakdown: Soil microorganisms do not appear to
play a significant role in degradation of pendimethalin.
Loss from photodecomposition and/or volatilization: Slight
losses.
Average persistence at recommended rates: When used at re-
commended rates under normal environmental conditions,
little if any pendimethalin occurs in the subsequent
crop.
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Ecological characteristics:
Avian acute oral toxicity: 1,421 mg/kg.
Avian eight—day dietary toxicity (Bobwhite Quail): > 3,149
ppm.
Avian eight—day dietary toxicity (Mallard Duck): > 4,640
ppm.
96—hour fish toxicity: 0.199 ppm for blueqill sunfish
(highly toxic) and 0.138 ppm for rainbow trout (highly
toxic).
48-hour aquatic invertebrate toxicity: 0.28 ppm (highly
toxic for Daphnia magna .
Potential problem for endangered species:
The Slackwater darter and certain freshwater mussels are
endariqered species at risk from the use oF pendimethalin
on cotton. The Aqency is addressing appropriate means of
labelinq pesticides that may threaten the continued exis-
tence of endangered species. The labeling should he com-
pleted by the 1986 growina season. If it is not, this
standard may be amended to impose interim labeling to
protect endangered soecies.
The Agency believes that the conventional labeling ap-
proach may be inadequate to properly inform the users on
how to protect the endangered species. The Agency anti-
cipates that appropriate labeling will be developed in
time for the 1986 growing season for cotton.
Tolerance assessments:
The Agency is unable to complete a full tolerance reassess-
ment of pendimethalin because of certain residue chemistry
and toxicology data gaps. The additional data may cause
specific tolerances to be revised in the future.
The Acceptable Daily Intake (ADI) for oendimethalin was original)y
based upon a 2—year feedinq study on rats, which was subsequently
declared invalid. Subsequently, the Provisional Acceptable Daily
Intake (PADI) for pendimethalin was calculated, using the 90 day
portion of the same study. The subchronic portion of this study
was used instead of a 2—year dog study because the (P)ADI value
calculated for the rat is the more conservative value on a mg/kg
basis than for the dog:
NOEL Safety (P)ADI (P)MPI
(mq/kg) Factor mu/kg/day mg/day (60 kg
Rat 25.0 2,0fl0 0.0125 0.7500
Dog 12.0 100 0.1250 7.5000
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The No—Observable-Effect—Level (NOEL) for the rat study is 25.0
mg/kg. A 2,000—fold safety factor was used and the PADI was
calculated as 0.0125 mg/kg/day with a Maximum Permissible Intake
(MPI) of 0.7500 mg/day for a 60 kg person. The Theoretical Maxi-
mum Residue Contribution (TMRC) for pendimethalin—based permanent
tolerances is 0.0166 mq/day for a 1.5 ka diet. Currently, the
permanent tolerances utilize 2.22 % of the PADI.
In the United States, tolerances are currently established in 40
CFR § 180.361 for the combined residues of the herbicide, pendi—
methalin: N—(1—ethyl propyl)—3,4—dimethyl—2,6—dinitrobenzenamine
and its metabolite: 4-El—ethyl propvl)aminoj—2—methyl-3,5—dinitro-
benzvl alcohol, in or on the raw agricultural commodities listed
below:
Commodities Parts per million
** Beans (lima, dry, snap) 0.1
** Beans, forage 0.1
** Beans, hay 0.1
Corn, fodder 0.1
Corn, forage 0.1
** Corn, fresh(including sweet, K+CWHR) 0.1
Corn, grain 0.1
Cottonseed 0.1
Peanuts 0.1
Peanut hay 0.1
Peanut forage 0.1
Rice grain 0.05
Soybeans 0.1
Soybeans, forage 0.1
Soybeans, hay 0.1
Sunflower seeds 0.1
** The tolerances for these commodities were established after the
science reviews for the pendimethalin reaistration standard
were completed.
International Tolerances
Presently, there are no tolerances for residues of pendimethalin
in Canada, Mexico, or in the Codex Alimentarius .
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Problems known to have occurred with use
The Pesticide Incident Monitorina System (PTMS) indicates
four incidents involving aqricultural. uses of oendimethalin
alone from 1966 throuqh 1Q80. Of the Four incidents, three
required medical attention, two involved dermal exposure
durina ground aoolication, one involved mixer! loader ex o—
sure and one involved a truck/ container s i1l. No fatalities
were reported.
PIMS does not include any details or conseauences of these
exposures, nor does it attempt to validate these voluntarily
submitted reports. The PIMS data do not provide infformation
on chronic health effects from exposure to pendimethaliri,
but do support the need for precautions relating to careful
handling of pendimethalin products.
4. Summary of regulatory position and rationale :
Based on the review and evaluation of all available data and
other relevant information on pendimethalin the Agency has
made the following determinations:
The available data do not indicate that any of the risk cri-
teria listed in 162.11(a) of Title 40 of the tJ.S.Code of
Federal Regulations have been met or exceeded for the uses
of pendimethalin at the present time.
Pendimethalin is not acutely toxic by the oral, dermal, in-
halation and occular routes of exposure.
The chronic doq study, rat and rabbit teratology studies,
and a 3—generation reproduction study did not indicate
adverse chronic effects.
There are no valid mutagenicity and chronic rat studies for
pendimethalin, and insufficient oncoqenicity data. There
are also extensive residue chemistry and environmental
fate data gaps.
The Agency is requiring monitoring data for potential resi-
dues in aquatic sites next to treated rice fields. Once
the Agency has evaluated these additional data, it will
determine if EPA should impose more stringent measures to
minimize exposure of aauatic organisms to pendimethalin.
Ecological effect studies indicate that pendimethalin is
highly toxic to certain coldwater and warrnwater fish;
moderately to highly toxic to marine and estuarine
organisms.
The Agency is requiring that levels of N-nitroso—pendi—
methalin contaminant not exceed 6Oppm in the technical
Product arid that the technical be analysed for other
impurities.
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Specific label warning statement:
Hazard Information
The human hazard statements must appear on all EP labels
as presribed in 40 CFR 162.10.
Environmental Hazard Statements
All manufacturinq—use products (MPs) intended for formu-
lation into end-use products (EPs) must bear the follow—
inq statements:
“This pesticide is toxic to fish. Do not discharge
effluent containing this product directly into lakes,
streams, ponds, estuaries, oceans or public waters un-
less this product is specifically identified and ad-
dressed in a National Pollutant Discharqe Elimination
System (NPDES) permit. Do not discharge effluent con—
tainina this product into sewer systems without pre-
viously notifying the sewage treatment plant authority.
For guidance, contact your State Water Board or Regional
Office of the Environmental Protection Aqency”.
End—Use Product Statements
a. Non Aquatic Uses (C,ranular oroducts)
The following environmental hazard statement must appear
on all EPs:
“This pesticide is toxic to fish. Do not apply directly
to water. Runoff from treated areas may be hazardous
to aquatic organisms in neicihborina areas. Do not
contaminate water by cleaning of equipment or disposal
of wastes. In case of spills, either collect for use
or dispose of properly”.
b. Non Aquatic Uses (Nongranular products)
The following environmental hazard statement must appear
on all EPS:
“This pesticide is toxic to fish. Do not apply directly
to water. Drift and runoff from treated areas may be
hazardous to fish in neighboring areas. Do not conta-
minate water by cleaninq of equipment or disposal of
wastes”.
c. Aquatic Uses (Rice)
The following environmental hazard statement must appear
on all EPs:
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“This pesticide is toxic to fish and aquatic orqanjsms.
Fish may be killed at application rates recommended on
the label. Do not contaminate water by cleanina of
equipment or disposal of wastes”.
“Do not apply to rice fields if fields are used for
catfish or crayfish farming”.
Restrictions on Rotational Crops
“Pending the submission of rotational crop data, do not
apply pendimethalin on rice fields in which crayfish or
catfish farminq are included in the cultural practices,
and do not plant crops in pendimethalin—treated fields
unless pendimethalin is reqistered for use on those
crops”.
Restrictions on Irrigated CroDs
“Pending the submission of irriQated crop data, do not
use water containinq pendimethalin residues from rice
cultivation to irrigate food or feed crops which are not
reqistered for use with peridimethalin”.
5. Summary of major data qaos :
The followinq toxicological studies are reauired:
A dermal sensitization study in guinea ig is required
by October 30, 1985,
A 90—day feeding study in the rat is required by January
30, 1986,
A chronic toxicity study in rat is required by April 30,
1989,
An oncogenicity study in rat and in mouse is required by
April 30, 1989.
The following mutagenicity data are required by October
30, 1985:
a. Gene mutation in bacteria,
b. Gene mutation in mammalian cells in culture,
c. Chrornosomal aberration analysis in mammalian cells
in culture, and
d. DNA damage in mammalian cells in culture.
The following environmental fate data are required:
A photodeqradation study in water is required by October
30, 19R5,
A photodearadation study on soil is required by October
30, 1985,
. metabolism test in aerobic soil is required by April
30, 1987,
A metabolism test under anaerobic aquatic conditions is
required by April 30, 1987,
A metabolism test under aerobic aquatic conditions is re-
quired by April 30, 1987,
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A mobility study involving leachinq and adsorption/de—
sorption is required by October 30, 1985,
A mobility study involving volatility in the lab is re-
quired by October 30, 1985,
A mobility study involving volatility in the field is
required by October 30, 1985,
A soil dissipation study in the field is required by
April 30, 1987,
A dissipation study in aquatic (sediment) is required
by April 30, 1987,
An accumulation study in rotational crops (confined) is
required by October 30, 1987,
An accumulation study in rotational crops (field) is re-
quired by April 30, 1Q87,
An accumulation study in irrigated crops (field) is re-
quired by October 30, 1987,
An accumulation study in fish is required by October 30,
1985.
The following ecological effects data are reauired:
An acute freshwater invertebrate toxicity study using a
typical EP is required by October l9sc.
An aquatic field study to monitor residues next to rice
fields using a typical EP is required by April 1987.
The following product chemistry data are required by
October 30, 1985:
The name and address of the manufacturer or producer of
each starting material used in the 90% technical
product,
A discussion of each impurity believed to he present at
>0.1% based on the beginning materials, all chemical
reactions and any contamination is required by April
30, 1986,
Five or more samples must be analyzed for the active
ingredient (A.I.) and each impurity present for which
a certified limit is required by April in, 1q86,
A current Confidential Statement of Pormula,
Ouantitative methods to determine the remaining imourities
in the technical oroduct by April 30, 1986.
Data are required for ppm solubility in various solvents
at 20 C,
Dissociation Constant data,
Octanol/water partition coefficient data,
Data on the p 1, and
The following data are required for chemical stability:
discussion of sensitivity of the A.I. to metal and
metal ions, stability of the A.I. at normal and elevated
temperatures, and the sensitivity of the Pi.I. to
sunlight.
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The following residue chemistry data are required:
Additional plant metabolism data are required with radio—
labeled pendimethalin by April 30, 1987.
Levels of metabolites remaininq unextractable in plant
tissues and in polar fractions must be determined for
possible toxicological residue concerns by April 30,
1987.
Metabolism studies utilizing ruminants dosed with 4 C rina
labeled pendimethalin required by April 30, 1986.
Distribution and characterization of residues must be
determined in milk, muscle, kidney, and liver. If the
ruminant metabolism differs significantly from the rat
data, then swine metabolism data will also be required.
If the additional metabolism data show the presence of
new metabolites, then additional methodoloqy data may
be required.
Additional data are required by April 30, 1986 to show the
stability of pendimethalin and its 3,5—dinitrobenzl
alcohol metabolite in or on representative plant and
animal samples stored at freezing temperatures.
Residue data are required by July 30, 1986 for carrot,
radish, sugar beet.
Residue data are required by July 30, 1986 beans and peas.
Additional data are required by July 30, 1986 to support
the established tolerance for soybean hay.
Data are required by July 30, 1986 for pendimethalin and
its metabolite in or on soybean hay and straw.
If new metabolites are found, then additional field residue
data for field corn may be required. When necessary,
data will be extrapolated from the soybean processing
study to corn.
If new residue metabolites are found, additional metabo-
lism and field residue data may be reauired for sorghum.
Additional processing data may be required for cottonseed.
When necessary, data will be extrapolated from the
requested soybean processing study.
Additional metabolism and processinq data on peanuts may
be required. When necessary, data will be extrapolated
from the soybean processinq study.
Additional processinq data may be required for sunflower
seeds. When necessary, data will be extrapolated from
the requested soybean processing study.
Residues of pendimethalin and its metabolite in catfish
and crayfish are required by July 30, 1986.
Lactating ruminants must be dosed with pendimethalin to
determine residues levels in milk.
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A study on metabolites of oendimethalin in poultry will
be reguired if additional metabolites of concern areS
found in the plant metabolism studies. The need for a
poultry feeding study will depend upon the results of a
poultry metabolism study.
The followinq data are required by July 30, 1986 for
tobacco: Residue data involving the metabolism of pendi—
methalin in tobacco. If residues exceed 0.1 ppm, addi-
tional data on pyrolysis products must be submitted.
6. Contact Person at EPA :
Robert J.Taylor (703) 557—1800
Office of Pesticide Programs, EPA,
Registration Division (TS—767C)
Fungicide-Herbicide Branch
401 M Street., S.W.
Washington, DC 20460.
DISCLAIMER: The information presented in this Chemical Information
Fact Sheet is for informational purposes only and may not be used
to fulfill data requirements for pesticide registration and
reregistration.
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