United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-96-019
March 1997
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Mepiquat Chloride
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 reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human
health and environmental effects of each pesticide. As required by the Food
Quality Protection Act (FQPA) of 1996, the review process must consider
the potential for increased susceptibility of infants and children to the toxic
effects of pesticide residue. In establishing or reassessing tolerances
(maximum residue limits in food), FQPA requires the Agency to consider
available information on aggregate exposures to pesticide residues, including
all anticipated dietary exposures and other exposures for which there is
reliable information, as well as the potential for cumulative effects from a
pesticide and other compounds with a common mechanism of toxicity. The
Agency develops any mitigation measures or regulatory controls needed to
effectively reduce each pesticide's risks. EPA then reregisters pesticides
that can be used without posing unreasonable risks to human health or the
environment.
When a pesticide is eligible for reregistration, 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
reregistration case 2375, mepiquat chloride.
Mepiquat chloride is a plant growth regulator used exclusively on
cotton. It is intended to increase yield by inhibiting gibberellic acid
synthesis. Registered product formulations include soluble concentrate/
liquid (SC/L) and dry flowable (DF) forms. It is applied aerially or using
ground boom equipment. Application rates are limited to 0.044
Ib/application/acre and seasonally to 0.132 Ib/acre. Overuse of mepiquat
chloride is likely to overly inhibit plant growth. Other crops must be
planted at least 75 days after the last application.
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Regulatory
History
Human Health
Assessment
Mepiquat chloride was first registered as a pesticide in the U.S. in
1980. There are currently nine products registered to three companies.
The two subsequent registrants entered the market after the original patent
expired. The April 1991 and January 1994 Data Call-Ins (DCIs) required
additional human health, ecotoxicity, and environmental fate data. In
October 1995, a DCI covering agricultural workers was issued covering
about 200 chemicals, including mepiquat chloride.
Toxicity
In studies using laboratory animals, mepiquat chloride generally has
been shown to be of low acute toxicity. Although it is moderately toxic by
the oral route and has been placed in Toxicity Category II (moderately
toxic) for this effect, for all other acute effects it was either slightly toxic or
practically non-toxic. Testing indicated that mepiquat chloride is of low
chronic toxicity and that it is negative for mutagenic effects.
Dietary Exposure
People may be exposed to residues of mepiquat chloride through the
diet. Tolerances have been established for cottonseed, cotton forage, and
for animal commodities including milk and eggs, and the fat, meat and meat
byproducts of cattle, hog, poultry, sheep, goat and horse byproducts (please
see 40 CFR §180.384). EPA has reassessed the mepiquat chloride
tolerances and found that all of those except for milk, eggs, and poultry fat,
meat and meat byproducts are acceptable. The established tolerances for
milk, eggs, and poultry fat, meat and meat byproducts must be revoked
because no significant residues are expected in these commodities. A new
tolerance must be proposed for cotton gin byproducts. The established
tolerance for cottonseed meal (please see 40 CFR §186.2275(a)) is
proposed for revocation. Residues in this commodity will be covered by the
existing cottonseed tolerance.
EPA has assessed the dietary risk posed by mepiquat chloride. The
Theoretical Maximum Residue Contribution (TRMC) for the overall U.S.
population 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. This assessment also applies to non-nursing infants less than one
year old, as well as all other potentially exposed subgroups. This low
fraction of the allowable RfD is considered to be an acceptable dietary
exposure risk.
Occupational and Residential Exposure
Exposure to homeowners is not expected since there are no residential
uses. Based on current use patterns, handlers (mixers, loaders, and
applicators) may be exposed to mepiquat chloride during and after normal
agricultural use. Both ground and aerial application methods were
considered. Since all dermal and inhalation Margins of Exposure (MOEs)
were greater than 10,000, greatly exceeding the action level of 100, the
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Agency did not identify any effects for which there was concern.
Therefore, the personal protective equipment (PPE) required for early entry
is the minimum PPE required under the Worker Protection Standard
(WPS): coveralls, chemical resistant gloves, socks and shoes.
Human Risk Assessment
Mepiquat chloride generally is of low acute toxicity and has been
classified in Group E (no evidence of carcinogenicity for humans).
Although mepiquat chloride is registered for feed uses, dietary exposure to
mepiquat chloride residues in foods is extremely low, as is the cancer risk
posed to the general population.
Also of low concern is the risk posed to mepiquat chloride handlers,
consisting of mixers/loaders/applicators, and field workers who come into
contact with treated foliage following application of this pesticide.
Exposure and risk to workers was estimated to be low based on the
chemical's low toxicity and low usage rate. The Re-entry Interval (REI) is
currently the minimum set by the WPS of 12 hours with minimal early-entry
PPE. Registrants wishing to apply for a 4-hour REI may do so by
satisfying the associated epidemiological and end-use product toxicity data
requirements.
Food Quality Protection Act Considerations
The FQPA of 1996 amended the FFDCA by setting a new safety
standard for the establishment of tolerances and directs EPA to consider
available information concerning the susceptibility of infants and children to
pesticide residues in food. Based on the review of available data and the
absence of incident or epidemiological data for mepiquat chloride, an
additional safety factor for the protection of infants and children is not
necessary. The Act also requires EPA to consider aggregate exposure to the
pesticide residue, including all anticipated dietary exposure and other
exposures for which there is reliable information, as well as cumulative
effects from the pesticide and other substances that have a common
mechanism of toxicity. For mepiquat chloride, aggregate exposure risks are
not considered significant since it has not been found in drinking water and
non-dietary exposures are not expected. In assessing the potential risk from
cumulative effects of mepiquat chloride with other pesticides and substances,
only difenzoquat appears to have a common mode/mechanism of toxicity,
namely similar neurotoxic effects. The Agency has concluded that the
cumulative effects from the combined dietary exposure to mepiquat chloride
and difenzoquat would be virtually nil. Based on these conclusions, the
Agency considers the tolerances in the RED to be reassessed with regard to
FQPA requirements.
Environmental Environmental Fate
AsSGSSmGnt Mepiquat chloride is stable to hydrolysis and photolysis. Soil and
aqueous photolysis are not routes of dissipation. Under aerobic conditions,
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Risk Mitigation
Additional Data
Required
mepiquat chloride appears to degrade rapidly to C02. Under anaerobic
conditions, it appears stable. Based on study results, mepiquat chloride is
considered to be relatively non-mobile, and is not expected to accumulate in
fish. Since the other metabolites also degrade rapidly to C02, parent
mepiquat chloride is the only residue of concern. There have been no
mepiquat chloride detections reported in monitoring wells and it is
considered to have limited potential for groundwater contamination.
Although there is potential for contamination of surface water because of the
low usage rate and its rapid degradation, significant surface water migration
is not expected.
Ecological Effects
Mepiquat chloride is practically non-toxic to birds on an acute oral
and subacute dietary basis. Mepiquat chloride is moderately toxic to small
mammals at high concentrations. It is practically non-toxic to honey bees
on an acute contact basis and to freshwater, estuarine and marine fish and
aquatic invertebrates on an acute basis. Adverse chronic effects to aquatic
organisms are also not expected. Mepiquat chloride is slightly to practically
nontoxic to estuarine and marine invertebrates on an acute basis, and
chronic effects are not expected. The Agency does not expect significant
effects on nontarget terrestrial plant seedling emergence, vegetative vigor,
or nontarget aquatic plant toxicity.
Ecological Effects Risk Assessment
Based on the overall low toxicity of mepiquat chloride, its low usage
rate, and its rapid aerobic degradation, no risks to animals or non-target
plants or endangered species were identified.
The Agency is requiring that all end use product labeling be amended
consistent with the basic producer labels including entry restrictions,
application restrictions, and user safety requirements and recommendations.
Also in conjunction with the Agency's efforts to develop the best spray drift
management practices, the Agency is requiring interim measures that must
be placed on product label/labeling as specified in the RED.
EPA has required field residue data for cotton gin byproducts and a
tolerance must be proposed for this commodity when adequate data have
been submitted and evaluated. Although a replacement rabbit teratogenicity
study must still be submitted, the generic data base supporting the
reregistration of mepiquat chloride is substantially complete.
The Agency is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregistration.
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Product Labeling
Changes
Required
All mepiquat chloride end-use products must comply with EPA's
current pesticide product labeling requirements and the following
requirements.
Labeling Requirements for Manufacturing-Use Products
To remain in compliance with FIFRA, manufacturing use product
(MP) labeling must be revised to comply with all current EPA regulations,
PR Notices and applicable policies. The MP labeling must bear the
following statement under Directions for Use:
"Only for formulation into an [fill blank with Insecticide, Herbicide
or the applicable term which describes the type of pesticide use(s)] for
the following use(s) [fill blank only with those uses that are being
supported by MP registrant."
An MP registrant may, at his/her discretion, add one of the following
statements to an MP label under "Directions for Use" to permit the
reformulation of the product for a specific use or all additional uses
supported by a formulator or user group:
"This product may be used to formulate products for specific
use(s) not listed on the MP label if the formulator, user group,
or grower has complied with U.S. EPA submission requirements
regarding support of such use(s)."
"This product may be used to formulate products for any
additional use(s) not listed on the MP label if the formulator,
user group, or grower has complied with U.S. EPA submission
requirements regarding support of such use(s)."
Labeling Requirements for End-Use Products
When end-use product DCIs are developed (e.g., at issuance of the
RED), the Agency will require that all end-use product labels (e.g., MAI
labels, SLNs, and products subject to the generic data exemption) be
amended such that they are consistent with the basic producer labels.
PPE/Engineering Control Requirements for Pesticide Handlers:
For sole-active-ingredient end-use products that contain mepiquat
chloride, the handler personal protective equipment requirements set forth in
the RED must be incorporated on all mepiquat chloride product labels. Any
conflicting PPE requirements on current labeling must be removed. There
are currently no multiple-active-ingredient end-use products that contain
mepiquat chloride.
Actual End-use Product PPE Requirements: PPE for handlers is to be
established based on the acute toxicity of each end-use product, using the
instructions in PR Notice 93-7. The personal protective equipment must be
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placed on the end-use product labeling in the location specified in PR Notice
93-7 and the format and language of the PPE requirements must be the same
as is specified in that PR Notice.
a. Entry Restrictions
For sole-active-ingredient end-use products that contain
mepiquat chloride, product labels must be revised to adopt the entry
restrictions set forth in this section. Any conflicting entry restrictions
on current labeling must be removed. There are currently no
multiple-active-ingredient end-use products that contain mepiquat
chloride.
The REI and early-entry PPE must be inserted into the
standardized REI and early-entry PPE statements required by
Supplement Three of PR Notice 93-7.
Restricted-entry interval: A 12-hour restricted entry interval (REI) is
required for uses within the scope of the WPS (see tests in PR Notices
93-7 and 93-11) on all end-use products.
Early-entry personal protective equipment (PPE): The PPE required
for early entry is:
— coveralls,
— chemical-resistant gloves, and
— shoes plus socks.
Other Label Requirements
The Agency is requiring the following labeling statements to be
located on all end-use products containing mepiquat chloride:
i. 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."
"Do not plant another crop within 75 days after last
treatment."
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ii. User Safety Requirements
"Follow manufacturer's instructions for
cleaning/maintaining PPE. If no such instructions for
washables, use detergent and hot water. Keep and
wash PPE separately from other laundry."
iii. 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."
"Users should remove PPE immediately after handling this
product. Wash the outside of gloves before removing. As
soon as possible, wash thoroughly and change into clean
clothing."
iv. Spray Drift Labeling
The following language must be placed on the label each
product that can be applied aerially:
"Avoiding spray drift at the application site is the
responsibility of the applicator. The interaction of many
equipment-and-weather-related factors determine the
potential for spray drift. The applicator and the grower are
responsible for considering all these factors when making
decisions."
The following drift management requirements must be
followed to avoid off-target drift movement from aerial
applications to agricultural field crops. These requirements do
not apply to forestry applications, public health uses or to
applications using dry formulations.
• The distance of the outer most nozzles on the boom must
not exceed 3/4 the length of the wingspan or rotor.
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• Nozzles must always point backward parallel with the air
stream and never be pointed downwards more than 45
degrees.
Where states have more stringent regulations, they should
be observed.
The applicator should be familiar with and take into account
the information covered in the Aerial Drift Reduction Advisory
Information.
The following aerial drift reduction advisory information
must be contained in the product labeling:
[This section is advisory in nature and does not supersede the
mandatory label requirements.]
INFORMATION ON DROPLET SIZE: The most effective
way to reduce drift potential is to apply large droplets. The best
drift management strategy is to apply the largest droplets that
provide sufficient coverage and control. Applying larger
droplets reduces drift potential, but will not prevent drift if
applications are made improperly, or under unfavorable
environmental conditions (see Wind, Temperature and
Humidity, and Temperature Inversions).
CONTROLLING DROPLET SIZE:
• Volume - Use high flow rate nozzles to apply the highest
practical spray volume. Nozzles with higher rated flows
produce larger droplets.
• Pressure - Do not exceed the nozzle manufacturer's
recommended pressures. For many nozzle types lower pressure
produces larger droplets. When higher flow rates are needed,
use higher flow rate nozzles instead of increasing pressure.
• Number of nozzles - Use the minimum number of nozzles
that provide uniform coverage.
• Nozzle Orientation - Orienting nozzles so that the spray is
released parallel to the airstream produces larger droplets than
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other orientations and is the recommended practice. Significant
deflection from horizontal will reduce droplet size and increase
drift potential.
• Nozzle Type - Use a nozzle type that is designed for the
intended application. With most nozzle types, narrower spray
angles produce larger droplets. Consider using low-drift
nozzles. Solid stream nozzles oriented straight back produce the
largest droplets and the lowest drift.
BOOM LENGTH: For some use patterns, reducing the
effective boom length to less than 3/4 of the wingspan or rotor
length may further reduce drift without reducing swath width.
APPLICATION HEIGHT: Applications should not be made at
a height greater than 10 feet above the top of the largest plants
unless a greater height is required for aircraft safety. Making
applications at the lowest height that is safe reduces exposure of
droplets to evaporation and wind.
SWATH ADJUSTMENT: When applications are made with a
crosswind, the swath will be displaced downward. Therefore,
on the up and downwind edges of the field, the applicator must
compensate for this displacement by adjusting the path of the
aircraft upwind. Swath adjustment distance should increase,
with increasing drift potential (higher wind, smaller drops, etc.)
WIND: Drift potential is lowest between wind speeds of 2-10
mph. However, many factors, including droplet size and
equipment type determine drift potential at any given speed.
Application should be avoided below 2 mph due to variable wind
direction and high inversion potential. NOTE: Local terrain
can influence wind patterns. Every applicator should be familiar
with local wind patterns and how they affect spray drift.
TEMPERATURE AND HUMIDITY: When making
applications in low relative humidity, set up equipment to
produce larger droplets to compensate for evaporation. Droplet
evaporation is most severe when conditions are both hot and
dry.
TEMPERATURE INVERSIONS: Applications should not
occur during a temperature inversion because drift potential is
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high. Temperature inversions restrict vertical air mixing, which
causes small suspended droplets to remain in a concentrated
cloud. This cloud can move in unpredictable directions due to
the light variable winds common during inversions. They begin
to form as the sun sets and often continue into the morning.
Their presence can be indicated by ground fog; however, if fog
is not present, inversions can also be identified by the movement
of smoke from a ground source or an aircraft smoke generator.
Smoke that layers and moves laterally in a concentrated cloud
(under low wind conditions) indicates an inversion, while smoke
that moves upward and rapidly dissipates indicates good vertical
air mixing.
Regulatory
Conclusion
For More
Information
SENSITIVE AREAS: The pesticide should only be applied
when the potential for drift to adjacent sensitive areas (e.g.
residential areas, bodies of water, known habitat for threatened
or endangered species, non-target crops) is minimal (e.g. when
wind is blowing away from the sensitive areas).
The use of currently registered products containing mepiquat chloride
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 reregistration.
Mepiquat chloride 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 Reregistration Eligibility
Decision (RED) document for mepiquat chloride 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 Reregistration 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 45242-0419, telephone
513-489-8190, fax 513-489-8695.
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Following the comment period, the mepiquat chloride 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 reregistration program,
the mepiquat chloride RED, or reregistration of individual products
containing mepiquat chloride, please contact the Special Review and
Reregistration Division (7508W), OPP, US EPA, Washington, DC 20460,
telephone
703-308-8000.
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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