United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-97-007
June 1997
R.E.D. FACTS
Pendimethalin
Pesticide
Reregistration
Use Profile
Regulatory
History
All pesticides sold or distributed in the United States must be
registered by EPA, based on scientific studies showing that they can be
used without posing unreasonable risks to people or the environment.
Because of advances in scientific knowledge, the law requires that
pesticides which were first registered before November 1, 1984, be
reregistered to ensure that they meet today's more stringent standards.
In evaluating pesticides for reregi strati on, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human
health and environmental effects of each pesticide. To implement
provisions of the Food Quality Protection Act of 1996, EPA considers the
special sensitivity of infants and children to pesticides, as well as aggregate
exposure of the public to pesticide residues from all sources, and the
cumulative effects of pesticides and other compounds with common
mechanisms of toxicity. The Agency develops any mitigation measures or
regulatory controls needed to effectively reduce each pesticide's risks. EPA
then reregisters pesticides that meet the safety standard of the FQPA, and
can be used without posing unreasonable risks to human health or the
environment.
When a pesticide is eligible for reregi strati on, EPA explains the basis
for its decision in a Reregistration Eligibility Decision (RED) document.
This fact sheet summarizes the information in the RED document for
reregi strati on case 0187, pendimethalin.
Pendimethalin is a selective herbicide used to control broadleaf weeds
and grassy weed species in a number of crop and noncrop areas and on
residential lawns and ornamentals. Formulations include liquid, solid,
granular, emsulsifiable concentrate, and dry flowables. Pendimethalin is
applied by broadcast, chemigation, conservation tillage, containerized plant
treatment, soil incorporation, and directed spray.
Pendimethalin was first registered as a pesticide in the U.S. in 1972.
EPA issued a Registration Standard for pendimethalin in March 1985
(PB86-172814). A October 1990 Data Call-In (DCI) required additional
product and residue chemistry, toxicology, ecological effects and
environmental fate data. Currently, 58 pendimethalin products are
registered.
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Human Health Toxicity
AsS6SSm6nt In studies using laboratory animals, pendimethalin generally has been
shown to be of low acute toxicity. It is slightly toxic by the oral and eye
route and has been placed in Toxicity Category III (the second lowest of
four categories) for these effects. It is practically non-toxic by the dermal
and inhalation routes and has been placed in Toxicity Category IV (the
lowest of four categories).
Dietary Exposure
People may be exposed to residues of pendimethalin through the diet.
Tolerances or maximum residue limits have been established for
pendimethalin (please see 40 CFR 180.361). EPA has reassessed the
pendimethalin tolerances and found that data for cotton gin by-products and
tobacco are required. The need for additional tolerances will be determined
upon receipt and evaluation of these data.
EPA has assessed the dietary risk posed by pendimethalin. For the
overall U.S. population, exposure from all current pendimethalin tolerances
represents less than 1% of the Reference Dose (RfD), or amount believed
not to cause adverse effects if consumed daily over a 70-year lifetime. The
exposure level of the most highly exposed subgroup, non-nursing infants,
represents less than 2% of the RfD. Actual risks using anticipated residue
information would be considerably less than 1% of the RfD for all
population subgroups. Therefore, it appears that chronic dietary risk is
minimal.
Occupational and Residential Exposure
Based on current use patterns, handlers (mixers, loaders, and
applicators) may be exposed to pendimethalin during and after normal use
of pendimethalin formulations.
Human Risk Assessment
Pendimethalin generally is of low acute toxicity, but causes thyroid
follicular cell adenomas in male and female rats and has been classified as a
Group C, possible human carcinogen. Many food and feed crops are
registered; however, dietary exposure to pendimethalin residues in foods is
extremely low, as is the cancer risk posed to the general population.
Of greater concern is the risk posed to occupational handlers involved
in food, feed, fiber, ornamental, turf, rights-of-way and other noncrop
treatments; and homeowner handlers making applications to residential turf.
Occupational/Short and Intermediate Term:
Agency calculations indicate that Margins of Exposure (MOEs) for
handlers wearing baseline attire (long-sleeve shirt, long pants, shoes and
socks) are acceptable (over 100) for all but three scenarios: (1)
mixing/loading liquid for aerial applications and irrigation systems, (2)
mixing/loading liquid for rights-of-way spraying, and (3) mixing/loading
liquid for groundboom applications. These MOEs range from 1.5 to 59.
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The risks to handlers in these scenarios are reduced to an adequate level
(MOEs range from 110 to 33,333) when chemical-resistant gloves are
added to the baseline attire.
Occupational/Post Application:
The Agency has determined that there are risks following
applications to commercial or research food, feed, fiber, turf, and
ornamental crops. Restricted Entry Intervals ( REIs) can allow sufficient
time to pass for residues to dissipate to levels that result in adequate MOEs.
Pending the development of pendimethalin specific data, the Agency is
requiring that the 12-hour interim REI be increased to 24 hours for all
pendimethalin uses within the scope of the Worker Protection Standard
(WPS).
However, REIs are generally not feasible as a mitigation measure for
occupational exposures in noncrop areas (such as rights-of-way).
Therefore, as a risk mitigation measure, the Agency is requiring a reduction
in the maximum use rate from 3 Ibs active ingredient(ai)/acre to 2 Ibs.
ai/acre. The registrant agreed to this reduction in the maximum application
rate.
Residential/Post Application:
Again, REIs are not practical or feasible for residential or recreational
turf; consequently, the Agency is requiring a reduction in the maximum use
rate to 2 Ibs. ai/acre.
FQPA Considerations
EPA has determined that the established tolerances with amendments
and changes as specified in this document, meet the FQPA safety standard
for the general population. In reaching this determination, EPA has
considered the available information on aggregate exposures (both acute
and chronic) from non-occupational sources, food and drinking water.
Pendimethalin has both food and non-occupational uses; therefore,
the considerations for aggregate exposure are those from food, drinking
water, and residential non-occupational sources.
Chronic dietary risks utilizing tolerance level residues and 100% crop
treated (TMRC) are <1% of the RfD for the general population.
Based on limited ground water monitoring data (data from 8 states
with 2 states with detectable residues), the maximum level found was 0.9
ppb. The maximum level of pendimethalin found in surface water is 17.6
ppb. Based on this information, the estimated risks from water are <2%
RfD for all population subgroups, including those most highly exposed to
pendimethalin residues.
In evaluating the potential for cumulative effects, EPA does not have,
at this time, available data to determine whether pendimethalin has a
common mechanism of toxicity with other substances or how to include this
pesticide in a cumulative risk assessment. Unlike other pesticides for which
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Environmental
Assessment
EPA has followed a cumulative risk approach based on common
mechanism of toxicity, pendimethalin does not appear to produce a toxic
metabolite produced by other substances. For the purposes of this tolerance
action, therefore, EPA has not assumed that pendimethalin has a common
mechanism of toxicity with other pesticides.
Environmental Risk Characterization
Pendimethalin dissipates in the environment by binding to soil,
microbially-mediated metabolism and volatilization. It is essentially
immobile in soil.
Based on laboratory studies and limited field study information,
pendimethalin is slightly to moderately persistent in aerobic soil
environments. Persistence decreases with increased temperature, increased
moisture and decreased soil organic carbon.
Additional terrestrial field dissipation studies for major pendimethalin
uses (cotton and soybeans) are requested to fully characterize the fate of
pendimethalin.
Pendimethalin may contaminate surface water from spray drift
associated with aerial and ground spray application, or in runoff from
rainfall events and through irrigation waters (chemigation). However, its
high affinity to bind to soil and sediment particles should limit
concentrations of pendimethalin in surface waters.
Although pendimethalin has been detected in ground water (at very
low levels), the potential for ground water contamination from
pendimethalin residues is low.
Pendimethalin would not represent a high acute risk to birds or a high
acute or chronic risk to mammals. The chronic risk to birds could not be
determined because avian reproduction studies have not been submitted.
These studies are required.
Chronic risk Levels of Concern (LOCs) for fish were exceeded by a
small margin. But it is presumed that overall, pendimethalin does not
represent a high risk to aquatic animals and plants, including estuarine
organisms.
The use of pendimethalin may adversely effect endangered species of
terrestrial and semi-aquatic plants, aquatic plants and invertebrates
including mollusks, fish, and birds (specifically grazers).
The risk to nontarget terrestrial and semi-aquatic plants is expected to
be moderate.
Risk Mitigation To lessen the risks posed by pendimethalin, EPA is requiring the following
risk mitigation measures:
For occupational handlers/use sites:
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Additional Data
Required
Product Labeling
Changes
Required
° increase restricted entry interval from 12 to 24 hours;
o add chemical resistant gloves;
° engineering controls—all WP formulations must be contained in water-
soluble packaging.
For residential lawns and sod farm use sites:
o reduce maximum application rate from 3 Ibs. ai/acre to 2 Ibs. ai/acre for
residential and sod farm use sites
To reduce risks to nontarget plants:
o Add spray drift best management practices.
EPA is requiring the following additional generic studies for
pendimethalin to confirm its regulatory assessments and conclusions: post
application reentry studies (guidelines 132-la, b), physical/chemical
properties for the 86.8% and 60% FIs (61-1 through 61-3, 62-2, 62-3),
magnitude of residue for tobacco and cotton gin byproducts (171-4k),
processing for rice (171-41), avian chronic (71-4), field dissipation for
cotton and soybeans (164-1), and aquatic dissipation for rice (164-2).
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregi strati on.
All pendimethalin end-use products must comply with EPA's current
pesticide product labeling requirements and with the following. For a
comprehensive list of labeling requirements, please see the pendimethalin
RED document.
The Agency is establishing minimum (baseline) engineering controls
for occupational uses of pendimethalin end-use products formulated as
wettable powders. All wettable powder formulations must be contained in
water-soluble packaging.
Products Intended for Occupational Use- WPS Uses
The minimum (baseline) PPE for occupational uses of pendimethalin end-
use products are:
For emulsifiable concentrate formulations:
Mixers and loaders must wear:
— long-sleeved shirt and long pants,
— chemical-resistant gloves, and
— shoes plus socks
For water-dispersible granule, wettable powder, and
emulsifiable concentrate formulations whose use directions
reasonably permit application using hand-held sprayers:
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Commercial Handlers (mixers, loaders, and applicators) who apply
this product using hand-held equipment or hoses (not including hoses
attached to truck-mounted equipment) must wear:
— long-sleeved shirt and long pants,
— chemical-resistant gloves, and
— shoes plus socks
Restricted-entry interval:
A 24-hour restricted-entry interval (REI) is required for uses on
food, feed, fiber, ornamental, forestry, and turf crops within the scope
of the WPS on all pendimethalin end-use products.
Exception: if the product is soil-injected or soil-incorporated, the
Worker Protection Standard, under certain circumstances, allows
workers to enter the treated area if there will be no contact with
anything that has been treated.
The labels of all pendimethalin end-use products must be
revised to bear the following application rate for the respective uses:
For residential lawn and sod farm uses:
"Maximum application rate of 2.0 Ibs. active ingredient per
acre."
NonWPS uses
For liquid applications:
"Do not enter or allow others to enter the treated area until sprays
have dried."
For dry applications:
"Do not enter or allow others to enter the treated area until dusts have
settled."
Products Intended Primarily for Homeowner Use
Entry restrictions:
The Agency is establishing the following entry restrictions for
all homeowner uses of pendimethalin end-use products (NOTE: This
presumes the registrant reduces the maximum application rate for turf
at residential sites and parks and recreation areas to two pounds active
ingredient per acre.):
For liquid applications:
"Do not allow people or pets to touch treated plants until the sprays
have dried."
For dry applications:
"Do not allow people or pets to enter the treated area until dusts have
settled."
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Products Intended Primarily for Occupational Use
The Agency is requiring the following labeling statements to be
located on all end-use products containing pendimethalin that are
intended primarily for occupational use.
Application Restrictions
"Do not apply this product in a way that will contact workers or other
persons, either directly or through drift. Only protected handlers may
be in the area during application."
Engineering Controls
"When handlers use closed systems, enclosed cabs, or aircraft in
a manner that meets the requirements listed in the Worker
Protection Standard (WPS) for agricultural pesticides (40 CFR
170.240)(d)(4-6), the handler PPE requirements may be reduced
or modified as specified in the WPS."
Application Restrictions
"Do not apply this product in a way that will contact workers or other
persons, either directly or through drift. Only protected handlers may
be in the area during application."
Engineering Controls
"When handlers use closed systems, enclosed cabs, or aircraft in
a manner that meets the requirements listed in the Worker
Protection Standard (WPS) for agricultural pesticides (40 CFR
170.240)(d)(4-6), the handler PPE requirements may be reduced
or modified as specified in the WPS."
Products Intended Primarily for Home Use
Application Restrictions
"Do not apply this product in a way that will contact any person or
pet, either directly or through drift. Keep people and pets out of the
area during application."
User Safety Recommendations
• "Users should wash hands before eating, drinking, chewing
gum, using tobacco, or using the toilet."
• "Users should remove clothing immediately if pesticide gets
inside. Then wash thoroughly and put on clean clothing."
Environmental Hazards Statement
"Do not apply directly to water, or to areas where surface water
is present or to intertidal areas below the mean high water mark.
Do not contaminate water when disposing of equipment
washwaters."
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Regulatory
Conclusion
For More
Information
Application Rates
The labels of all pendimethalin end-use products must be revised to
bear the following application rate for the respective uses:
For residential lawn and sod farm uses:
"Maximum application rate of 2.0 Ibs. active ingredient per acre."
Spray Drift
A spray drift labeling advisory is required for labels of all products
that can be applied aerially.
The use of currently registered products containing pendimethalin in
accordance with approved labeling will not pose unreasonable risks or
adverse effects to humans or the environment. Therefore, all uses of these
products are eligible for reregi strati on.
Pendimethalin products will be reregistered once the required
product-specific data, revised Confidential Statements of Formula, and
revised labeling are received and accepted by EPA.
EPA is requesting public comments on the Reregi strati on Eligibility
Decision (RED) document for pendimethalin during a 60-day time period,
as announced in a Notice of Availability published in the Federal Register.
To obtain a copy of the RED document or to submit written comments,
please contact the Pesticide Docket, Public Response and Program
Resources Branch, Field Operations Division (7506C), Office of Pesticide
Programs (OPP), US EPA, Washington, DC 20460, telephone 703-305-
5805.
Electronic copies of the RED and this fact sheet can be downloaded
from the Pesticide Special Review and Reregi strati on Information System
at 703-308-7224. They also are available on the Internet using ftp on
FTP.EPA.GOV, or using WWW (World Wide Web) on WWW.EPA.GOV.
Printed copies of the RED and fact sheet can be obtained from EPA's
National Center for Environmental Publications and Information
(EPA/NCEPI), PO Box 42419, Cincinnati, OH 45242-2419, telephone 1-
800-490-9198, fax 513-489-8695.
Following the comment period, the pendimethalin RED document
also will be available from the National Technical Information Service
(NTIS), 5285 Port Royal Road, Springfield, VA 22161, telephone 703-487-
4650.
For more information about EPA's pesticide reregi strati on program,
the pendimethalin RED, or reregi strati on of individual products containing
pendimethalin, please contact the Special Review and Reregi strati on
Division (7508W), OPP, US EPA, Washington, DC 20460, telephone
703-308-8000.
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For information about the health effects of pesticides, or for assistance
in recognizing and managing pesticide poisoning symptoms, please contact
the National Pesticides Telecommunications Network (NPTN). Call toll-
free 1-800-858-7378, between 9:30 am and 7:30 pm Eastern Standard
Time, Monday through Friday.
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