United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-94-009
June 1994
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Maleic Hydrazide
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 years ago 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. The Agency imposes
any regulatory controls that are needed to effectively manage 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 announces this and
explains why in a Reregistration Eligibility Decision (RED) document. This
fact sheet summarizes the information in the RED for Case 0381, technical
maleic hydrazide and maleic hydrazide potassium salt, referred to as maleic
hydrazide.
Maleic hydrazide is a plant growth regulator (sprout inhibitor) and
herbicide, that acts by inhibiting cell division in plants. It is used to control
sprouting of potatoes and onions, suckers in tobacco, and growth of weeds,
grasses and trees in/along lawns, turf, ornamental plants, non-bearing
citrus, utility and highway rights-of-way, airports and industrial land. Most
of the maleic hydrazide used in the U.S. is applied to tobacco (86-88%),
followed by potatoes (11-12%).
Formulations include an emulsifiable concentrate and soluble
concentrate/liquid and solid. Maleic hydrazide is applied by aircraft or
ground spray equipment. Current use practice limitations prohibit treating
crops within 7 days of harvest, and grazing or feeding forage or hay from
treated areas to livestock.
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Regulatory
History
Human Health
Assessment
Maleic hydrazide was first synthesized in 1895 but its ability to
regulate plant growth was not discovered until 1949. It was first registered
as a plant growth regulator in 1952. In October 1976, maleic hydrazide
went into Special Review (then called Rebuttable Presumption Against
Registration or RPAR) because it met the risk criteria for oncogenic,
mutagenic and reproductive effects.
A Data Call-In notice issued in August 1980 resulted in suspension of
the diethanolamine salt of maleic hydrazide (DEA-MH) when its
manufacturers did not submit the required data. All DEA-MH registrations
now are cancelled.
Based on other data submitted, EPA determined that the oncogenicity
and reproductive effects triggers were not supported, and that only weak
evidence supported the mutagenicity trigger. In concluding the RPAR in
June 1982, EPA allowed continued use of maleic hydrazide and its
potassium salt (K-MH), but established an upper limit of 15 ppm for the
contaminant hydrazine (associated with tumor induction) in technical grade
maleic hydrazide. At this level, lifetime cancer risks for both dietary and
worker exposure are not of concern.
The Registration Standard issued in June 1988 (NTIS #PB88-236849)
continued to limit hydrazine in the technical product to 15 ppm. A Data
Call-In issued in November 1992 required additional ecological effects and
environmental fate data. Currently, 26 maleic hydrazide products remain
registered including 4 technical grade/manufacturing-use product(s).
Toxicity
In acute toxicity studies using laboratory animals, maleic hydrazide is
practically non-toxic by the oral, dermal and inhalation routes and has been
placed in Toxicity Category IV (the lowest of four levels) for these effects.
It causes slight irritation to the eyes (Toxicity Category III) and skin
(Toxicity Category IV), and is not a skin sensitizer.
Maleic hydrazide does not appear to cause any adverse developmental
or reproductive effects of concern. The potassium salt (K-MH) was not
found to be carcinogenic and has been classified as a "Group E" carcinogen-
-a chemical that is not considered to be a human carcinogen.
Maleic hydrazide and its potassium salt appear to be genotoxic (that is,
they have the potential to affect DNA repair processes) at high doses in
some mutagenicity tests. However, when all the available mutagenicity
studies are considered together with the results of all the other toxicological
studies on maleic hydrazide and its potassium salt, especially the negative
cancer studies, the potential genotoxic hazard is considered negligible.
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Dietary Exposure
People may be exposed to residues of maleic hydrazide in the diet
when consuming potatoes, potato chips and other potato products made from
potato granules; onions; and meat, milk, poultry and eggs.
Tolerances or maximum residue limits are established, and have been
reassessed, for residues of maleic hydrazide in or on potatoes, potato chips,
potato granules, potato waste (from processing), onions and cranberries
(please see 40 CFR 180.175, 185.3900, and 186.3900). The potato and
onion tolerances are acceptable, but an increased tolerance is needed for
potato chips and new, food/feed additive tolerances are needed for potato
granules and potato waste. The cranberry use is not on any currently
registered product labels and is not supported for reregistration by its
manufacturer. Unless another party decides to support this use, the
tolerance should be revoked.
Tolerances are needed but have not yet been established for meat,
milk, poultry or eggs. Animal feeding studies are being required in order to
set these tolerances. Also, a confined rotational crop study is required to
determine whether tolerances are needed for winter wheat planted as a
rotational crop in fields treated with maleic hydrazide.
Compatible international Codex Maximum Residue Levels (MRLs) are
established for potatoes and onions.
Based on reassessed tolerance levels for cranberries, onions, potatoes,
potato chips, potato granules and potato waste, and based on upper bound
residue levels for meat, milk, poultry and eggs, EPA estimates that the
overall U.S. population is exposed to about 29.5% of the Reference Dose
(RfD), or amount believed not to cause adverse effects if consumed daily
over a 70-year lifetime. Most of this exposure (27.5% of the RfD) is
contributed by potatoes. For children age 1-6 and non-nursing infants, the
two most highly exposed subgroups, the TMRC represents about 60% of the
RfD. These TMRCs are overestimates, however; and actual chronic dietary
risk (of decreased body weight gain) posed by maleic hydrazide is minimal.
Occupational and Residential Exposure
Pesticide handlers (mixers, loaders and applicators) may be exposed to
maleic hydrazide via the inhalation and dermal route. However, based on
the lack of toxicological concerns with maleic hydrazide, the risk is
considered minimal for all workers.
Smokers and others near them may be exposed to maleic hydrazide
and the contaminant hydrazine as pyrolysis products from tobacco.
However, increased levels of hydrazine are not expected, so the risk is no
greater than that already associated with the use of tobacco.
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Environmental
Assessment
Human Risk Assessment
Maleic hydrazide is of low acute toxicity. It has been shown to cause
genotoxic effects in some mutagenicity studies. However, in view of
several negative cancer studies, its genotoxic hazard is considered
negligible. The contaminant hydrazine has been shown to induce tumors.
However, EPA has set an upper limit of < 15 ppm hydrazine in technical
grade maleic hydrazide products. This level alleviates any concern of
lifetime cancer risk to humans considering both dietary and worker
exposure.
Environmental Fate
Maleic hydrazide is mobile, especially in sandy soils, but not
persistent in the environment. It therefore is not likely to impact
groundwater quality. It could contaminate surface waters, however, if it is
washed into anaerobic soil zones by rainfall soon after application. EPA is
requiring a surface water label advisory to address this concern.
When maleic hydrazide is aerially or air-blast sprayed, drift from use
sites could affect non-target crops or endangered plant species.
Ecological Effects
In acute toxicity studies, maleic hydrazide is "practically nontoxic" to
birds, fish, invertebrates and honey bees. It is considered to pose minimal
risks to birds, mammals, aquatic organisms, non-target insects and aquatic
plants.
Maleic hydrazide may pose risks of concern to non-target terrestrial
and semi-aquatic plants as a result of runoff from ground application, and
runoff and drift from aerial and air-blast applications.
Ecological Effects Risk Assessment
Maleic hydrazide does not pose risks to ground water but it has the
potential to contaminate surface water. It also may drift from target use
sites when it is aerially or air-blast applied. EPA is requiring that a surface
water advisory statement and spray drift management information be added
to maleic hydrazide end-use product labels to address these concerns.
Maleic hydrazide poses minimal acute risks to birds, mammals,
aquatic species, insects and non-target aquatic plants, but exceeds levels of
concern for non-target semi-aquatic and terrestrial plants. To mitigate
exposure to non-target plants, EPA is requiring that the number of
applications to fallow land, rights-of-way, turf and lawns be limited to one
per year.
EPA has concerns about the exposure of endangered plant species to
maleic hydrazide. These concerns will be addressed through
implementation of the Endangered Species Protection Program.
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Additional Data
Required
Product Labeling
Changes Required
EPA is requiring the following additional generic data for maleic
hydrazide to confirm its regulatory assessments and conclusions:
Nature of the residue in animals;
Analytical method for residue in animals;
Magnitude of the residue in animal commodities;
Confined rotational crop;
Droplet size spectrum; and
Drift field evaluation.
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSF) and revised labeling for reregistration.
All maleic hydrazide end-use products must comply with EPA's
current pesticide product labeling requirements, and with the following:
Worker Protection Standard (WPS) - All maleic hydrazide products
within the scope of the Worker Protection Standard (WPS) for Agricultural
Pesticides (see PR Notice 93-7) must, within the timeframes listed in PR
Notices 93-7 and 93-11, revise their labeling to be consistent with the WPS,
as directed in those notices and the requirements of the RED.
Surface Water Advisory - All end-use labels must be revised to bear the
following statement:
"Under some conditions, maleic hydrazide may have a significant
potential for runoff into surface water (primarily via dissolution in
runoff water), for several days post-application. Conditions favoring
runoff include poorly draining soils or wet soils with readily visible
slopes, frequently flooded areas, areas where an intense or sustained
rainfall is forecast to occur within 48 hours, areas overlying extremely
shallow ground water, and areas overlying tile drainage systems that
flow to surface water."
Application Rates - Application rates must be provided for all uses. In
instances where labels indicate to spray to "drip-point," labels must clearly
state the maximum application rate per acre. For fallow land, lawns, turf
and rights of way uses, labels must indicate that the number of applications
is limited to one per year.
Regulatory
Conclusion
The use of currently registered pesticide products containing maleic
hydrazide and the potassium salt of maleic hydrazide in accordance with
approved labeling will not pose unreasonable risks or adverse effects to
humans or the environment. Therefore, all uses of these currently
registered products are eligible for reregistration. (The cranberry use of
maleic hydrazide, which is not on any currently registered product labels, is
not among the uses eligible for reregistration.)
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For More
Information
Eligible maleic hydrazide products will be reregistered once the
required confirmatory generic data, product specific data, Confidential
Statements of Formula and revised labeling are received and accepted by
EPA.
Products which contain active ingredients in addition to maleic
hydrazide will be reregistered when all of their other active ingredients also
are eligible for reregistration.
EPA is requesting public comments on the Reregistration Eligibility
Decision (RED) document for maleic hydrazide 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.
Following the comment period, the maleic hydrazide RED document
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 maleic hydrazide RED, or reregistration of individual products
containing maleic hydrazide, 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, from 8:00 am to 6:00 pm Central Time, Monday
through Friday.
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