738F04003
United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508C)
EPA-738-F-04-003
November 2004
R.E.D. FACTS
Pesticide
Reregistration
Oxadiazon
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 humans 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. 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 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 oxadiazon (Chemical Code No.
109001; Case No. 2485).
Use Profile Oxadiazon is a pre-emergent or early post-emergent oxadiazole herbicide
registered for commercial use on turf grown on golf courses (-77% of total use)
and in apartment/condominium complexes, parks, athletic fields, playgrounds, and
cemeteries (~12% of total use). In addition, oxadiazon is used on sod farms and
on conifer nurseries and landscapes (i.e. industrial sites, ornamental, roadside
plantings, woody, ornamental shrubs, vines and trees, and herbaceous
ornamentals). Annual usage is approximately 249,000 pounds on 52,000 acres.
Regulatory Oxadiazon was registered in 1978. A Phase Four generic data call-in (DCI)
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n ISTO ry was issued in May of 1991. Due to additional data required under FIFRA as
amended in 1988, the oxadiazon registrant decided to no longer support food uses
of oxadiazon. On June 3, 2002, the Agency considered the FQPA safety finding to
be met and counted the oxadiazon tolerances as reassessed. There are no
CODEX, Canadian, or Mexican tolerances for oxadiazon residues.
Human Health
Assessment
Toxicity
In humans, acute exposure to oxadiazon can cause irritation to the skin, eyes
and mucous membranes. In both subchronic and chronic studies, effects on the
liver were consistent among the species tested (rat, dog, mouse). Oxadiazon is
classified as "likely to be carcinogenic to humans" based on studies that showed an
increase in the incidence of liver tumors in two species (mice and rats) following
chronic exposure to oxadiazon.
Dietary Risks
There are no food or feed, or anticipated food or feed uses for oxadiazon.
The Registrant is not supporting any tolerances for oxadiazon in the United States.
Existing tolerances have been revoked. Likewise, there are no Canadian or
Mexican tolerances for oxadiazon.
Worker Risks
Cancer risks for occupational handlers of wettable-powder formulations of
oxadiazon are of concern. Exposure scenarios of concern include
mixing/loading/applying wettable powder formulations. To reduce these risks, the
wettable powder formulations will be packaged in water-soluble packaging (WSP)
only.
Residential and Other Nonoccupational Risks
The oxadiazon label indicates that the purchase, storage and application of
this pesticide is limited to commercial nursery, turf and landscape personnel, and the
product is not available to homeowners. Post-application residential exposure
scenarios include apartment complexes, golf courses, and playgrounds. The
Agency has concluded that residential exposure to oxadiazon is not of concern.
FQPA Considerations
Given that there are no remaining food/feed uses for oxadiazon, and given
that all food tolerances have been revoked, this pesticide no longer falls under the
scope of FQPA. As such, no quantitative aggregate assessment of risk from
dietary and residential was conducted. EPA has qualitatively evaluated the
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Environmental
Assessment
likelihood of concurrent exposures from different sources of oxadiazon for the
general population, including children. Because of the relatively low volume of
oxadiazon use on sites other than golf courses, its specialized use pattern, and its
relatively high cost, concurrent exposures are not expected.
In addition, oxadiazon was not assessed for the cumulative effects of
pesticides having a common mechanism of toxicity. The Agency does not have
sufficient information at this time concerning common mechanism issues to determine
whether or not oxadiazon shares a common mechanism of toxicity with other
substances, including other oxadiazoles. Therefore, for the purposes of this risk
assessment, the Agency has assumed that oxadiazon does not share a common
mechanism of toxicity with any other chemicals.
Ecological Risks
Environmental fate studies indicate that oxadiazon persists in the environment
bound to organic matter. In clear, shallow bodies of water, oxadiazon not bound to
organic matter may be degraded by sunlight. Alternatively, oxadiazon is defined as
a light-dependent peroxidizing herbicide (LDPH), which suggests that toxicity is
greater in the presence of light. Studies indicate that after application to soil,
oxadiazon remains near the surface, and can be transported via runoff to nearby
surface water bodies. Leaching from surface soils to groundwater is expected to
be low or negligible, unless the soil is very porous. Since this stable compound can
bind to particulate and organic matter, oxadiazon residues can accumulate in
sediments at the bottom of bodies of water.
To mitigate ecological risks the technical registrants has agreed to label
amendments which include reductions in application rates. In addition, the Agency
is requiring that the registrant submit data related to fish and invertebrate toxicity,
as well as data from toxicity studies with aquatic plants and sediment.
Summary Tn's ^act Sheet explains the Agency's decision regarding the reregistration
eligibility of the registered uses of oxadiazon. The Agency has found that the current
uses of oxadiazon are eligible for reregistration, provided the changes specified in the
RED are made to the packaging and labels.
Additional Data
Required
EPA is requiring the following confirmatory data requirements for oxadiazon:
870.3465: 28-day inhalation toxicity
850.1300: Early-Life Stage in Freshwater and Estuarine/Marine Fish
850.1350: Life Cycle in Freshwater and Estuarine/Marine Invertebrates
850.4100: Seedling Emergence (Tier 1)
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850.4150: Vegetative Vigor (Tier 1)
850.4225: Seedling Germination/Emergence
850.4250: Vegetative Vigor (Tier 2)
835.4300: Aerobic Aquatic Metabolism
Aquatic Phototoxicity Studies (Fathead minnow)
Acute and Chronic Sediment Toxicity Testing
Water Monitoring Study
Product Labeling
Changes Required
All oxadiazon end-use products must comply with EPA's current pesticide
product labeling requirements. For a comprehensive list of labeling requirements,
please see Section V of the oxadiazon RED document.
Regulatory EPA has determined that all products containing oxadiazon as the active
Conclusion ingredient are eligible for reregistration, provided changes specified in the oxadiazon
RED are incorporated into the label and additional data identified in Section V of the
RED confirm this conclusion.
For More
Information
EPA is requesting public comments on the Reregistration Eligibility Decision
(RED) document for oxadiazon during a 60-day time period, as announced in a
Notice of Availability published in the Federal Register, To obtain a copy of the
oxadiazon RED document, please contact the OPP Public Docket (7502C), US EPA,
Ariel Rios Building, 1200 Pennsylvania Avenue, NW, Washington, DC 20460-0001,
telephone: (703) 305-5805. Electronic copies of the oxadiazon RED and all
supporting documents are also available on the Agency's website at
http:/Avww. cfpub. epa.gov/oppref/rereg/status. cfm ?show=rereg.
For more information about EPA's pesticide reregistration program or the
oxadiazon RED, please contact the U.S. EPA, OPP, Special Review and
Reregistration Division (7508C), Washington, DC 20460-0001, telephone: (703) 308-
8000.
For more information about the health effects of pesticides, or for assistance in
recognizing and managing pesticide poisoning symptoms, please contact the National
Pesticide Information Center (NPIC). Call toll-free (800) 858-7378, from 6:30 am to
4:30 pm Pacific Time, or 9:30 am to 7:30 pm Eastern Standard Time, seven days a
week. Their internet address is http://www. noic. orst. edu.
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