United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508C)
EPA-738-F99-018
November 1999
R.E.D. FACTS
Pesticide
Reregistration
Description of
Chemical
Oxythioquinox
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. 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 decision for reregistration case 2495, oxythioquinox,
which consists of a voluntary cancellation.
Common Name: Oxythioquinox, Chinomethionate
Chemical Formula: 6-methyl-l,3-dithiolo(4,5-b)quinoxalin-2-one
Trade Name: Morestan
Chemical Code: 054101
C.A.S. Number: 2439-01-2
Pesticide Type: Miticide, Fungicide, Insecticide
Chemical Class: Dithiocarbonate
Registrant: Bayer Corporation
Regulatory Oxythioquinox was first registered in the U.S. in 1968 as an insecticide,
History miticide and fungicide used to control mites, mite eggs, and powdery mildew.
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Previously, most products were emulsifiable concentrates that were applied
either through low volume concentrated spray from aircraft, or high volume
diluted spray from ground equipment to a variety of agricultural and
ornamental crops. Active products now are confined only to use on non-food
crops such as landscape ornamentals, and in such places as nurseries and
greenhouses. Oxythioquinox is applied by conventional hand or machine
operated sprayers.
On October 17, 1996, Bayer, the sole registrant, requested voluntary
cancellation of all oxythioquinox food uses except citrus. Bayer submitted data
to support the continued reregi strati on of Morestan 25WP (3125-117) and
Morestan Solupak 25WP (3125-302) on citrus. They also requested
cancellation of their remaining FIFRA section 24(c), state special local needs
registrations.
Subsequently, on May 30,1997, Bayer requested the cancellation of the
remaining food-use products, (3125-117) and (3125-302). These cancellations
became final March 9, 1998. The existing stocks period, which ran for 18
months, began when the Agency received the request for cancellation on June
4, 1997. Only the technical product (3125-205) and two-non-food use
products, Morestan 4 Ornamental Miticide (3125-381) and Morestan 4
Nursery Miticide (3125-437), remained active.
On February 1, 1999, Bayer requested voluntary cancellation of all the
remaining Morestan products, contingent upon an 18-month existing stock
provision which would allow them to deplete their remaining product
inventory. EPA published a notice of receipt of Bayer's request for voluntary
termination of oxythioquinox registrations in the Federal Register on March
17,1999. The cancellation notice was published September 17, 1999. Per
Bayer's request, the registrant will be allowed to sell and distribute existing
stocks of these products for eighteen months after the effective date of
cancellation, or until March 17, 2001. End-users will be allowed an additional
year, until September 17, 2001 (for a total of 2 years beyond the registrant's
requested date), for the use of existing stocks.
Human Health Toxicity
AsS6SSm6nt In four of seven acute toxicity studies conducted, oxythioquinox was
classified as Toxicity Category III or IV. In the primary eye irritation study, it
was classified as Toxicity Category II. Oxythioquinox can cause irreversible
eye damage. Also, some bystanders may experience a skin reaction similar to
sun burn (UV light), particularly if wind is present during applications.
EPA has also concluded that oxythioquinox should be classified as a
Group B2 (probable human) carcinogen based on statistically significant
increases in lung tumors in male NMRI mice, heptaocelluar tumors in both
sexes of the F344 rat, and rare kidney tumors in female F344 rats. However,
EPA did not complete risk estimates for oxythioquinox since it is being taken
off the market.
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Environmental
Assessment
For More
Information
Dietary Exposure
There are no food uses associated with oxythioquinox. Bayer
corporation voluntarily cancelled all food uses in 1996 and 1997. Sale and
distribution of the last food use products were allowed by registrants until
December 4, 1998. Tolerances for the canceled food uses will be proposed for
revocation in the near future.
Occupational and Residential Exposure
Oxythioquinox was used by nursery and landscape professionals and is
not sold to homeowners. Occupational, handlers (mixers, loaders, and
applicators) may be exposed to oxythioquinox during and after normal
applications in greenhouses and outdoor settings.
Environmental Fate
EPA did not complete an environmental fate assessment for
oxythioquinox. Several data requirements are still outstanding.
Ecological Effects
Oxythioquinox is moderately toxic to birds and adversely affected egg
production, embryo survival (and perhaps fertility), hatch ability, offspring
body weight and survival of offspring in avian reproduction studies.
Oxythioquinox is also highly toxic to fish and other aquatic organisms.
Electronic copies of this RED fact sheet and others are available on the
Internet. See http://www.epa.gov/REDs .
For more information about EPA's pesticide reregi strati on program or
about oxythioquinox, please contact Jamil Mixon of the Special Review and
Reregistration Division (7508C), OPP, US EPA, Washington, DC 20460,
telephone 703-308-8032.
For information about the health effects of pesticides, or for assistance in
recognizing and managing pesticide poisoning symptoms, please contact the
National Pesticide Telecommunications Network (NPTN). Call toll-free 1-
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
www.ace.orst.edu/info/nptn .
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