United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-94-020
EPA-738-R-94-023
September 1994
R.E.D. FACTS
Mevinphos
Pesticide
Reregistration
Use Profile
Regulatory
History
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 EPA reaches a decision regarding the eligibility of a pesticide
for reregistration, the Agency announces this and provides opportunity for
public comment. This fact sheet serves as and explains the Agency's
Reregistration Eligibility Decision (RED) for mevinphos.
Mevinphos is an insecticide used on vegetables and fruits,
predominantly lettuce and cole crops. It is a member of the
organophosphate family of chemicals. Mevinphos is formulated as a ready-
to-use liquid and concentrate. It is applied to foliage using aerial, boom
spray and air blast equipment.
Mevinphos was initially registered as a pesticide in 1957. EPA
became concerned about its safety because of the high rate of related
occupational poisonings during the 1970s. In 1978, EPA classified
mevinphos as a Restricted Use Pesticide. Agency concerns about safety
continued to grow through the 1980s.
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In December 1991, based on concern about the toxicity of the
pesticide parathion, EPA initiated the Acute Worker Risk Strategy (AWRS)
project to identify and find regulatory solutions for other pesticides posing
acute risks to agricultural workers. The information used to identify
pesticides for this project was primarily human incident data. Using a
methodology to rank the pesticides in terms of concerns, EPA identified
five pesticides which warranted accelerated action. Mevinphos was one of
the five. In May 1993, EPA representatives met with registrants of the five
pesticides to discuss risk concerns and set timelines for submission of
voluntary risk-reduction measures.
In November 1993, Amvac (the sole U.S. registrant of mevinphos)
submitted proposed risk-reduction measures. EPA determined these
measures to be inadequate to allay the Agency's concerns and met with
Amvac in June of 1994 to discuss its remaining concerns. EPA and Amvac
were unable to agree on a way to reduce risks.
On June 30, 1994, EPA was prepared to issue a Notice of Intent to
Suspend all mevinphos registrations when Amvac submitted a request for
voluntary cancellation. EPA accepted this request and on July 1, 1994,
issued a Cancellation Order for all mevinphos registrations, effective
immediately. The Agency subsequently published a Notice of Receipt of
Request for Cancellation, Announcement of Cancellation Order, and FIFRA
section 6 (g) Notification for Mevinphos in the Federal Register on August
1, 1994.
Human Health Toxicity
AsS6SSm6nt Regarding its mode of action, mevinphos is active by contact,
inhalation and ingestion. The generally accepted biochemical mechanism of
mevinphos's acute toxicity is through inhibition of the enzyme
acetylcholinesterase (AChE). AChE breaks down acetylcholine (ACh), a
compound that assists in transmitting signals through the nervous system.
Mevinphos inhibits the AChE activity in the body. When AChE is inhibited
at nerve endings, the inhibition prevents the ACh from being degraded and
results in prolonged stimulation followed by paralysis of the nerves. If the
dose is large enough, the nerves controlling breathing may be affected
sufficiently that death occurs.
Physical signs and symptoms of mevinphos poisoning include
headache, nausea, dizziness, blurred vision, excessive perspiration,
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salivation, secretion of tears, vomiting, diarrhea, aching muscles, and a
general feeling of severe malaise. Uncontrollable muscle twitching and
fasciculations can occur. Severe poisoning can lead to convulsions, coma,
pulmonary edema, muscle paralysis, and death by asphyxiation. Mevinphos
poisoning also may cause various psychological, neurological and cognitive
effects including confusion, anxiety, depression, irritability, mood swings,
difficulty concentrating, short-term memory loss, persistent fatigue, blurred
vision and, in severe poisoning cases, toxic psychosis resulting in bizarre
behavior. Some of the symptoms may persist for weeks or months after the
initial exposure and individuals who have been exposed may become more
sensitive to additional exposures. Exposure to mevinphos may result in
long-lasting neurotoxic effects in some individuals.
Mevinphos is extremely toxic to mammals by all routes of exposure
and has been placed in Toxicity Category I, indicating the greatest degree of
acute toxicity, for oral, dermal and inhalation effects. The lethal dose and
lethal concentration levels for these routes of exposure fall well within the
limits for Toxicity Category I, and are significantly lower than the lethal
doses for the likely alternatives to mevinphos. Mevinphos has a steep dose
response curve; that is, the difference between a nonlethal dose and a lethal
dose is small.
Mevinphos is not a known carcinogen. In a chronic feeding/
carcinogenicity study using rats, the No Observed Adverse Effect Level
(NOAEL) was 0.025 mg/kg/day, and the Lowest Effect Level (LEL) was
0.35 mg/kg/day for decreases in plasma and brain cholinesterase activity.
Clinical signs were limited to cholinergic effects and included protruding
eyes, tremors, anogenital staining, and excessive salivation.
There was no evidence of any developmental effect on the rat or rabbit
fetus, even at doses that were toxic to the dams and does. Reproductive
effects are unknown as data submissions have not been reviewed. Evidence
suggests that mevinphos is a slight mutagen.
Dietary Exposure
The Agency's preliminary risk assessment for acute effects resulting
from dietary exposure to mevinphos indicates a concern, particularly for
infants and children. If better data are submitted to the Agency, the Agency
would reassess risk.
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Environmental
Assessment
Human Risk Assessment
Based on the above scientific determinations and other evaluations,
such as human incident data, EPA determined mevinphos to be unsafe for
any use. Because of this determination, the Agency was prepared to issue a
Notice of Intent to Suspend all mevinphos registrations on June 30, 1994.
Environmental Fate
The environmental fate database for mevinphos is incomplete.
Information is available on the persistence and mobility of the parent
compound but not for its degradates. Mevinphos primarily dissipates via
microbial metabolism, which occurs quite rapidly (the half-life is
approximately one day). Hydrolysis and photodegradation occur, but not as
rapidly as metabolism.
Mevinphos degrades rapidly by microbial action with a half-life of
about one day under aerobic conditions and about 12 days under anaerobic
conditions. The amounts and nature of the degradates are not well
characterized. Mevinphos is very mobile in soils, but is not expected to
reach ground water due to its short half life.
Ecological Effects
Mevinphos is very highly toxic to avian species by the oral route of
exposure, and slightly toxic to highly toxic by the dietary route. Available
reproduction data are unacceptable.
In acute toxicity studies, mevinphos is very highly toxic to fish and
aquatic invertebrates. Acceptable data on chronic effects are unavailable.
Acceptable data regarding marine and estuarine toxicity also are
unavailable.
Risks to Non-Target Species
In the late 1980s, the Fish and Wildlife Service's Office of
Endangered Species determined that certain mevinphos uses could
jeopardize the continued existence of endangered species or their critical
habitat. Before cancellation, the mevinphos reregistration database was
being completed. The information from that database would have been used
by EPA to develop a program to reduce or eliminate endangered species'
exposure to mevinphos to the point where use would not have jeopardized
their existence.
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Regulatory
Conclusion
Ecological Effects Risk Assessment
Although mevinphos's high toxicity has been known for some time
and has generated concern, an incomplete database prevented EPA from
further determining mevinphos's risk to wildlife.
Mevinphos is not eligible for reregistration because all registrations
have been canceled. However, because mevinphos is so acutely toxic that
even a small exposure, whether by mistake, accident, or through routine
activity, can cause serious poisonings, EPA would have found it ineligible
for reregistration.
The August 1, 1994, Federal Register Notice of Receipt of Request
for Cancellation, Announcement of Cancellation Order, and FIFRA section
6(g) Notification for Mevinphos, sets the last legal sale, distribution, and
use dates. No person may sell or distribute existing stocks of canceled
mevinphos products after December 31, 1994. Mevinphos may be applied,
in accordance with prior-approved labeling, through February 28, 1995
(including commercial applicators). No person may use existing stocks of
canceled pesticide products containing mevinphos after February 28, 1995.
According to Resource Conservation and Recovery Act (RCRA)
regulations, mevinphos products will be classified as "solid waste," and
potentially "hazardous waste," once a decision is made to discard them.
They are then subject to RCRA requirements, in addition to any state and
local requirements. Persons in possession of mevinphos waste are
encouraged to contact state, local and federal authorities. The
RCRA/Superfund Industrial Assistance Hotline is 800-424-9346.
Mevinphos products produced in the U.S., including existing stocks,
may be exported to countries which permit mevinphos use. These stocks
and products must comply with the labeling and purchaser acknowledgement
requirements for unregistered pesticides under FIFRA section 17 (a) (7
U.S.C. 136 o(a)) and the EPA's Export Policy and Procedures for
Exporting Unregistered Pesticides in 40 CFR part 168 subpart D.
For MOTG EPA is accepting public comments on this Reregistration Eligibility
Information Decision (RED) during a 60-day time period, as announced in a Notice of
Availability published in the Federal Register. To submit written
comments, please contact the Pesticide Docket, Public Response and
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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/fact sheet can be downloaded from the
Pesticide Special Review and Reregistration Information System at
703-308-7224, and can be reached on the Internet via FEDWORLD.GOV
and EPA's gopher server, EARTH1.EPA. GOV.
Following the comment period, the mevinphos RED 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 mevinphos RED, or the status of individual products containing
mevinphos, contact the Special Review Branch, Special Review and
Reregistration Division (7508W), OPP, US EPA, Washington, DC 20460,
telephone 703-308-8010.
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 800-858-7378, between 8:00 am and 6:00 pm Central Time, Monday
through Friday.
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