United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-96-018
August 1997
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Paraquat Dichloride
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.
Under the Food Quality Protection Act of 1996, EPA must consider
the increased susceptibility of infants and children to pesticide residues in
food, as well as aggregate exposure of the public to pesticide residues from
all sources, and the cumulative effects of pesticides and other compounds
with a common mechanism of toxicity in establishing and reassessing
tolerances.
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. 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 reregi strati on, EPA explains the basis
for its decision in a Reregi strati on Eligibility Decision (RED) document.
This fact sheet summarizes the information in the RED document for
reregi strati on case 0262, paraquat dichloride (commonly referred to as
paraquat).
Paraquat dichloride is a herbicide currently registered to control
weeds and grasses in many agricultural and non-agricultural areas. It is
used preplant or preemergence on vegetables, grains, cotton, grasses, sugar
cane, peanuts, potatoes, and tree plantation areas; postemergence around
fruit crops, vegetables, trees, vines, grains, soybeans, and sugar cane;
during the dormant season on clover and other legumes; as a desiccant or
harvest aid on cotton, dry beans, soybeans, potatoes, sunflowers, and sugar
cane; and as a post harvest desiccant on staked tomatoes. It also is applied
to pine trees to induce resin soaking. Paraquat dichloride is also used on
non-crop areas such as public airports, electric transformer stations and
around commercial buildings to control weeds.
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Regulatory
History
Paraquat dichloride is applied aerially, by groundboom, backpack
sprayer, and low pressure handwand.
A soluble concentrate/liquid (SC/L) is the sole paraquat formulation
type registered for all uses. This formulation may be applied to crops pre-
plant, at planting, pre-emergence (broadcast or band), post-emergence
(broadcast, band, split, directed, or spot), post-harvest (as a pre-harvest
desiccant or harvest aid), and for suckering and stripping of hops.
Paraquat dichloride was first registered as a pesticide in the U.S. in
1964. EPA issued a Registration Standard for paraquat dichloride in June
1987 (NTIS# PB88-217005). A December 1991 Data Call-In (DCI)
required additional ecological effects, environmental fate and residue
chemistry data.
Currently, 7 pesticide products are registered which contain the active
ingredient paraquat dichloride. All paraquat products are classified as
Restricted Use Pesticides.
Human Health
Assessment
Toxicity
In acute toxicity studies using laboratory animals, paraquat has been
shown to be highly toxic by the inhalation route and has been placed in
Toxicity Category I (the highest of four levels ) for acute inhalation effects.
However, the Agency has determined that particles used in agricultural
practices (400 to SOOum) are well beyond the respirable range and therefore
inhalation toxicity is not a toxicological endpoint of concern. Paraquat is
moderately toxic (Category II) by the oral route and slightly toxic (Category
III) by the dermal route. Paraquat will cause moderate to severe eye
irritation and minimal dermal irritation, and has been placed in Toxicity
Categories II and IV for these effects.
In a subchronic toxicity study using rats, paraquat caused changes in
the lungs. A dermal toxicity study using rabbits resulted in scabbing and
inflammation when tested at the two highest doses (2.6 mg cation/kg group
and 6.0 mg cation/kg group). In an inhalation toxicity study, rats were
exposed to respirable aerosols (particle size - less than 2 um in diameter) of
paraquat dichloride which resulted in lung changes and extensive sores and
swelling in the larynx.
A chronic toxicity study using dogs resulted in an increase in the
severity and extent of chronic pneumonitis in the mid dose and high dose
male and female dogs. Two chronic toxicity/carcinogenicity studies using
rats were conducted with paraquat. In the first chronic toxicity study,
paraquat did not appear to be carcinogenic in the lungs or the head region
(middle ear, hard palate, head tissue and skin) of the rat. In the second
study, paraquat resulted in non-tumor lesions in various organs and no
evidence of carcinogenicity. Two chronic toxicity/carcinogenicity studies
using mice were also conducted with paraquat. The first study resulted in
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decreased body weight gain, kidney changes and no evidence of
carcinogen!city. The second study using mice also resulted in no evidence
of carcinogenicity. Based on these studies, paraquat was classified as a
"Group E" chemical—one showing evidence of noncarcinogenicity for
humans.
Four developmental/maternal toxicity studies were evaluated for
paraquat. Treatment-related effects were seen (i.e., delayed hardening
[ossification] in the forelimb and hindlimb digits, or retarded ossification of
the posterior portion of the skull) in the fetuses only at the same or higher
dose levels than effects in the mother. Therefore, the no-observed effect
dose levels (NOEL) for maternal toxicity are at least or more conservative
(protective) than the NOEL based on developmental toxicity.
There is no evidence that paraquat is associated with reproductive
effects. In a reproduction study using rats, paraquat had no effect on body
weight gain, food consumption/utilization, fertility or length of gestation.
Paraquat also shows no evidence of causing mutagenicity.
Dietary Exposure
People may be exposed to residues of paraquat through the diet.
Tolerances or maximum residue limits have been established for well over
80 raw agricultural commodities, processed foods and feed (please see 40
CFR 180.205(a), (b); 185.4700; 186.4700). EPA has reassessed the
paraquat tolerances and found that numerous revisions are necessary. Most
of these revisions will be handled administratively.
The available data support the established tolerances on all but
sorghum forage, ruminant kidney, oats, rye, soybeans and hops. The
tolerance for sorghum forage was reassessed from 0.05 to .1 ppm, while
kidney was reassessed from 0.3 ppm to 0.5 ppm, soybeans from 0.05 ppm
to 0.25 ppm, and hops from 0.2 ppm to 0.5 ppm. As there are presently no
registered uses of paraquat on rye, the tolerances for this commodity will be
revoked. Also the tolerance on oats will be revoked, as the registrant has
indicated that they do not wish to support this use. Additionally, the
tolerances for poultry (except for eggs) will be revoked. Finally, a
tolerance for popcorn (0.05 ppm) will be established (See Section IV,
Tolerance Reassessment Summary and Table in the paraquat RED for
further specifics).
Numerous international Codex maximum residue limits (MRLs) have
been established for paraquat. Harmonization of Codex MRLs and U.S.
tolerances for paraquat exists for many crops. However, at this time there
remain some incompatibilities between U.S. tolerances and Codex MRLs
on the following raw plant commodities because of differences in
agricultural practices: cottonseed, dry hops, maize, olives, potatoes, rice,
sorghum, and dry soya beans.
EPA has assessed the dietary risk posed by paraquat. The Theoretical
Maximum Residue Contribution (TMRC) for the overall U.S. population
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represents 10% of the Reference Dose (RfD), or amount believed not to
cause adverse effects if consumed daily over a 70-year lifetime. The
highest subgroup, non-nursing infants (<1 year old) occupies 31% of the
RfD. This 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 paraquat dichloride during and after normal
agricultural use. Ground, aerial and backpack application methods were
considered. All the dermal and inhalation Margins of Exposure (MOEs)
were acceptable (greater than 100) except backpack applicators and resin-
soaking uses. The registrant has agreed to reduce the concentration of
paraquat dichloride allowed when using a backpack sprayer and make label
changes for tree injection (resin soaking) use.
Human Risk Assessment
Paraquat generally is of moderate to high acute toxicity based on
inhalation toxicity (Toxicity Category I), oral toxicity, and moderate to
severe eye irritation (Toxicity Category II). It is a Group E chemical—one
showing no evidence of carcinogenicity.
Although people may be exposed to residues of paraquat in many
food commodities, the chronic dietary risk from all uses is considered
minimal.
Of greater concern is the risk posed to paraquat handlers, particularly
mixers/loaders/applicators. A dermal endpoint—based on maternal toxicity
effects— was used to assess risks to handlers. Margins of Exposure
(MOEs) for dermal effects to paraquat are adequate (greater than 100) for
all exposure scenarios considered except for backpack sprayer applicators
(non-spot treatment) and low pressure sprayer (resin soaking) for
mixer/loader/applicators. Even with gloves, the margin of exposure for
handlers using a backpack sprayer was too low. Exposure and risk to
workers will be mitigated by reducing the concentration of paraquat in
backpack sprayers, and through the use of Personal Protective Equipment
(PPE) required by the WPS, supplemented by gloves, a chemical-resistant
apron and face shield for all occupational uses of paraquat end-use
products, as required by this RED. PPE requirements for applicators and
other handlers (other than mixers and loaders) include a long-sleeved shirt
and long pants, chemical-resistant gloves and shoes plus socks. Based on a
biological monitoring study, post-application reentry workers will be
required to observe a 12-hour Restricted Entry Interval for the uses of
paraquat for preemergent or early-season weed control and weed control for
orchard and vegetable crops where the spray is directed solely at the weeds
(not broadcast over the entire crop area). A 24-hour Restricted Entry
Interval is required for desiccation and harvest aid applications of paraquat
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Environmental
Assessment
since the Agency concludes such uses result in a greater degree of exposure
to workers.
Food Quality Protection Act Considerations
In establishing or reassessing tolerances, FQPA requires the Agency to
consider 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 Act
further directs EPA to consider the potential for increased susceptibly of
infants and children to the toxic effects of pesticide residue.
The Agency considered the appropriateness of an additional
uncertainty factor to account for situations where available data indicate
increased sensitivity of infants and children and concluded that it is not
warranted based on an evaluation of the toxicology database. Regarding
aggregate exposure, the Agency only considered dietary exposure because
there are no residential or other non-occupational uses of paraquat, and
exposure to paraquat in drinking water is not expected. The EPA estimates
that paraquat residues in the diet of the general U.S. population account for
10% of the RfD, 24% of the RFD for children aged 1-6 years and 31% of
the RfD for non-nursing infants (less than 1 year). Therefore, the Agency
has determined that there is a reasonable certainty that no harm will result
to infants and children or to the general population from aggregate exposure
to paraquat dichloride residues. Further, based on the available data, the
Agency does not believe that the effects produced by paraquat would be
cumulative with those of other structurally related compounds. Therefore,
based on these conclusions, the Agency considers the tolerances in the RED
to be reassessed with regard to FQPA requirements.
Environmental Fate
Paraquat dichloride was shown to be very immobile in soil. Paraquat
does not hydrolyze, does not photodegrade in aqueous solutions, and is
resistant to microbial degradation under aerobic and anaerobic conditions.
The primary route of environmental dissipation of paraquat is adsorption to
biological materials and soil clay particles. Due to the apparent adsorption
strength of paraquat for soil clays, these bound residues do not appear to be
environmentally available. Nevertheless, since paraquat is persistent, it
could potentially be found in surface water systems associated with soil
particles carried by erosion. However, detections would not be considered
to be representative of normal paraquat use (since it binds so strongly to soil
clay particles and becomes environmentally inactive). Therefore, paraquat
is not expected or considered to be a groundwater concern from normal
paraquat dichloride use patterns.
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Ecological Effects
Paraquat is practically non-toxic to honey bees and slightly toxic to
fish on an acute basis. Paraquat is moderately toxic to non-endangered and
endangered terrestrial animals (birds and mammals), non-target terrestrial
and semi-aquatic plants. Acute toxicity to terrestrial animals (birds) and
mammals only exists immediately after application.
Ecological Effects Risk Assessment
Paraquat exposure to birds, mammals, non-target terrestrial and semi-
aquatic plants including endangered species may result from paraquat spray
drift during application.
The Agency levels of concern (LOCs) have been exceeded for acute
effects for birds and small (herbivorous and insectivorous) mammals and
for acute effects on semi-aquatic and terrestrial plants. However, the risk
for birds and small mammals only exists shortly after application. Once the
applied paraquat has dried (or becomes bound) its risk is greatly reduced.
Therefore, the Agency concludes the registered uses of paraquat are not
expected to pose significant risk to birds or mammals. The Agency LOCs
have also been exceeded for non-endangered and endangered non-target
terrestrial and semi-aquatic plants. Depending on the application method
and application rate, the risk quotients ranged from acceptable to acute
effects. To mitigate these risks, the registrant has agreed to lower the
maximum use rate, amend all paraquat labels to include a warning about
possible adverse effects to non-target and semi-aquatic plants due to drift
and include spray drift language.
Risk Mitigation To lessen the occupational and ecological risks posed by paraquat,
EPA is requiring the following risk mitigation measures.
° For all risk concerns:
Reduce the maximum rate of application from 1.6 Ib cation/A to 1.0
Ib cation/A and maintain the Restricted Use Classification.
o To protect workers:
Additional PPE are being required for mixers and loaders: gloves,
chemical-resistant apron and face shield. PPE requirements for applicators
and other handlers (other than mixers and loaders) include: long-sleeved
shirt and long pants, chemical-resistant gloves, and shoes plus socks.
Further, the concentration of paraquat in backpack sprayers will be reduced
and the resin soaking sections on the paraquat labels amended (i.e., delete
plastic acid bottle use) to lessen the exposure and risk to applicators.
° To protect non-target terrestrial and semi-aquatic plants from drift:
Aerial applications will include the most current spray drift language
and all paraquat products must place a statement in the "Environmental
Hazard"section of the label that warns the user about possible adverse
effects to non-target and semi-aquatic plants due to drift.
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Additional Data
Required
EPA is requiring data to establish tolerances for paraquat dichloride
on taro foliage, corn and soybean aspirated grain fractions, wheat and hay,
cotton and gin byproducts and processed grapes. The Agency is also
requiring data to confirm that the existing tolerances for field corn is
adequate to cover the specialized use of paraquat as a harvest aid.
Additionally, the Agency 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.
Product Labeling All paraquat dichloride end-use products must comply with EPA's
Changes current pesticide product labeling requirements and with the following. For
Reauired a comPrenensive list of labeling requirements, please see the paraquat
dichloride RED document.
Application Rates and Label Deletions for End-Use Products
In cooperation with the Agency the registrant has agreed to the following
application rates and label deletions:
O The maximum paraquat dichloride application rate for all products will
be lowered from 1.6 Ib cation/A to 1.0 Ib cation/A.
• For broadcast applications of paraquat with backpack
sprayers, non-spot, the application rate should not exceed 0.625
Ib cation/A and the application volume should be no less than
20 gallons per acre.
• The maximum application rate for spot spraying on all
paraquat labels will be no more than 0.0195 Ibs cation/gallon.
O Delete the plastic acid bottle and the tree injection directions for use
from the resin soaking sections of all paraquat dichloride labels.
Hazard Statement
The following hazard statement must be placed in the "Environmental
Hazard" section of all paraquat labels to warn the user about possible
adverse effects to non-target terrestrial and semi-aquatic plants due to drift:
"Paraquat dichloride is toxic to nontarget crops and plants if off-
target movement occurs. Extreme care must be taken to ensure
that off-target drift is minimized to the greatest extent possible."
PPE/Engineering Control Requirements for Pesticide Handlers
For sole-active-ingredient end-use products that contain paraquat,
the product labeling must be revised to adopt the handler personal
protective equipment/engineering control requirements set forth in this
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section. Any conflicting PPE requirements on the current labeling must be
removed.
For multiple-active-ingredient end-use products that contain
paraquat, the handler personal protective equipment/engineering control
requirements set forth in this section must be compared to the requirements
on the current labeling and the more protective must be retained. For
guidance on which requirements are considered more protective, see PR
Notice 93-7.
Products Intended Primarily for Occupational Use (WPS and
nonWPS)
Minimum (Baseline) PPE/Engineering Control Requirements
Although the MOE's were greater than 100 for all but two scenarios
(backpack applicators and resin-soaking uses) without personal protective
equipment requirements beyond long-sleeve shirt, long pants, shoes and
socks, the Agency notes the relatively significant epidemiological evidence
of poisonings from intentional/accidental swallowing and numerous non-
systemic skin and eye effects in California (see OREB J. Blondell memo,
12/5/95). These considerations have led to the Agency establishing the
following minimum (baseline) PPE is required for all occupational uses of
paraquat end-use products:
"Mixers and loaders must wear:
—long-sleeved shirt and long pants,
—chemical-resistant gloves*,
—shoes plus socks,
—chemical-resistant apron,
—face shield"
Although there is no direct evidence that occupational handlers have
ever ingested a lethal amount of paraquat from a splash or spill, the
requirement for a face shield for all mixers and loaders reflects the
Agency's particular concern about accidental swallowing in case of a spill
or splash back.
"Applicators and other handlers (other than mixers and loaders) must
wear:
—long-sleeved shirt and long pants,
—chemical-resistant gloves*,
—shoes plus socks"
* For the glove statement, use the statement established for
paraquat through the instructions in Supplement Three of PR
Notice 93-7.
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Determining PPE Requirements for End-use Product Labels
The PPE that would be established on the basis of the acute toxicity
category of the end-use product must be compared to the active-ingredient-
based minimum (baseline) personal protective equipment specified above.
The more protective PPE must be placed on the product labeling. For
guidance on which PPE is considered more protective, see PR Notice 93-7.
Placement in Labeling
The personal protective equipment requirements must be 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 PR Notice 93-7.
Products Intended Primarily for Occupational Use
There are no registered homeowner-use products.
Entry Restrictions
For sole-active-ingredient end-use products that contain paraquat the
product labeling must be revised to adopt the entry restrictions set forth in
this section. Any conflicting entry restrictions on the current labeling must
be removed.
For multiple-active-ingredient end-use products that contain
paraquat the entry restrictions set forth in this section must be compared to
the entry restrictions on the current labeling and the more protective must
be retained. A specific time period in hours or days is considered more
protective than "sprays have dried" or "dusts have settled."
Products Intended Primarily for Occupational Use - Entry Restrictions
and Labeling
WPS Uses
Restricted-entry interval:
"For preplant or preemergence (broadcast or banded) applications,
post-emergence directed-spray applications, dormant-season
applications, and "between cutting" alfalfa applications: Do not enter
or allow worker entry into treated areas during the restricted entry
interval (REI) of 12 hours."
"For harvest-aid and desiccation applications: Do not enter or allow
worker entry into treated areas during the restricted entry interval
(REI) of 24 hours."
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Early-entry personal protective equipment (PPE):
The PPE required for early entry is:
— coveralls,
— chemical-resistant gloves*,
— shoes plus socks,
— protective eyewear.
* For the glove statement, use the statement established for
paraquat through the instructions in Supplement Three of PR Notice
93-7.
WPS Notification Statement:
Not required on label.
NonWPS uses
Entry restrictions:
The Agency is establishing the following entry restrictions for
nonWPS occupational uses of paraquat end-use products:
"Do not enter or allow others to enter the treated area until
sprays have dried."
Placement in labeling:
If WPS uses are also on label — Follow the instructions in PR Notice
93-7 for establishing a Non-Agricultural Use Requirements box, and
place the appropriate nonWPS entry restrictions in that box.
If no WPS uses are on the label — Place the appropriate nonWPS
entry restrictions in the Directions for Use, under the heading "Entry
Restrictions."
Products Intended Primarily for Homeowner Use
Entry restrictions:
There are no registered homeowner-use products.
Other Labeling Requirements
Products Intended Primarily for Occupational Use
The Agency is requiring the following labeling statements to be
located on all end-use products containing paraquat that are intended
primarily for occupational use.
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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."
User Safety Requirements
"Discard clothing or other absorbent materials that have been
drenched or heavily contaminated with this product's concentrate. Do
not reuse them."
"Follow manufacturer's instructions for cleaning/maintaining PPE. If
no such instructions for washable, use detergent and hot water. Keep
and wash PPE separately from other laundry."
"DO NOT USE AROUND HOMES, SCHOOLS, RECREATIONAL
PARKS, GOLF COURSES, OR PLAYGROUNDS"
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."
Spray Drift Labeling
Please see the paraquat dichloride RED document for the text of this
Advisory, which must be contained on each paraquat product label that can
be applied aerially.
The use of currently registered products containing paraquat
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Conclusion
dichloride 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.
Paraquat products will be reregistered once the required product-
specific data, revised Confidential Statements of Formula, and revised
labeling are received and accepted by EPA.
For More
Information
EPA is requesting public comments on the Reregi strati on Eligibility
Decision (RED) document for paraquat dichloride 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 paraquat dichloride 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 paraquat dichloride RED, or reregi strati on of individual products
containing paraquat dichloride, please contact the Special Review and
Reregi strati on 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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