E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Assessment Program.
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Pesticide
Information
Profile
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Temephos
Publication Date: 9/93
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TRADE OR OTHER NAMES
Trade names for products containing the compound include Abat, Abate,
Abathion, Biothion, Bithion, Difennthos, Ecopro, Nimitox, and Swebate. The
compound may also be found in mixed formulations with other insecticides
including trichlorfon.
INTRODUCTION
Temephos is an non-systemic organophosphorus insecticide used to
control mosquito, midge and black fly larvae. It is used in lakes, ponds and
wetlands. It also may be used to control fleas on dogs and cats and to
control lice on humans.
Temephos is a General Use Pesticide.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Temephos containing products are moderately toxic compounds that carry
the signal word WARNING on their labels despite the relatively high LD50 of
the technical compound. This is due to the high toxicity of xylene, one of the
components (or carriers) found in many of the trade products. This Pesticide
Information Profile is oriented to the toxicity of the technical product
temephos and not the different trade products unless specifically noted.
Typical of other organophosphate insecticides, temephos inhibits the
action of the group of enzymes called cholinesterases. Specific types of
these enzymes are found throughout the body including the nervous system, the
brain, and the blood stream. Symptoms of acute exposure are also similar to
other organophosphates and may include nausea, salivation, headache, loss of
muscle coordination, and difficulty breathing (1). However, humans ingested
256 mg/kg for five days and 64 mg/kg for four months without any symptoms or
detectable effects on blood enzyme activity (1). At the higher dose the
volunteers in the study all refused to take the dose any longer because of the
obnoxious taste.
In other mammals, temephos produces signs and symptoms typical of
cholinesterase inhibition at moderate levels of exposure (500 mg/kg). Death
does not occur unless very large doses of the compound are administered. The
LD50 of temephos ranges from 2,000 to 13,000 mg/kg for rats (2) and is 4,700
mg/kg for mice. The LD50 for a 2% powder formulation of temephos in dogs and
cats is greater than 5,000 mg/kg for both species.
Temephos is nearly four times more toxic when used in combination with
the insecticide malathion. Its toxicity is relatively unaffected when used in
combination with 23 other organophosphate insecticides (3).
CHRONIC TOXICITY
Rats fed temephos at low doses (below 12.5 mg/kg) for a month had no
compound induced changes in blood and brain cholinesterase activity. At the
next higher feeding level (25 mg/kg), the rats experienced some weight loss
and changes in the enzyme activity in the blood and the brain. When fed much
higher amounts of the compound for three months, all of the surviving rats
experienced a complete inhibition of blood cholinesterase activity (3). Rats
exposed to very low amounts of the compound for three months experienced a
depression in their cholinesterase activity at and above 0.3 mg/kg.
A similar pattern of toxic effects at lower concentrations over longer
periods of time have been observed in the dog as well. Thus, while the LD50
values for acute toxicity indicate that the compound is relatively non-toxic
or only slightly toxic, the compound has the potential to cause significant
toxic effects (depression of the activity of the enzyme cholinesterase in the
blood and the brain) to mammals at low concentrations over long periods of
time.
Temephos was used in cisterns and other potable water sources in some
locations in the United States and in the West Indies for the control of
mosquito larvae. Subsequent tests on the residents that had used the water
sources showed no observable effects in the exposed individuals. No
indication of the total dose or levels of exposure with time were available.
Reproductive Effects
Neither of two separate studies of rats fed small amounts of temephos
showed any reproductive difficulties in the test animals. The maximum dose
(25 mg/kg) had no effect on the number of litters, litter size, or variability
in the young and produced no congenital defects in the offspring. The
concentration of temephos in the diet of the test animals was, however,
sufficient to produce cholinesterase inhibition and some toxic symptoms (3).
Low oral doses of temephos of up to 2.5 mg/kg administered in feed over a
year and a half caused no reproductive effects in sheep or in their offspring
(3).
Teratogenic Effects
There were no birth defects noted in the offspring of pregnant rabbits
fed low doses of temephos (time interval not noted). The two separate studies
utilized different formulations of temephos, a 2% formulation and a 90%
formulation. In both studies, maternal toxicity and depression of
cholinesterase activity occurred during the study (7). These two tests,
though negative, do not provide enough information to assess the potential
teratogenic risk to humans at low levels of exposure to temephos.
Mutagenic Effects
The potential of the commercial product containing temephos (Abate) to
cause mutations was tested on several strains of bacteria. Though the
conclusion of the study was that the compound was not mutagenic, weakly
mutagenic effects were noted in one of the strains. Additional tests on
rabbits and on other strains of bacteria have shown the compound to be non-
mutagenic.
Carcinogenic Effects
Only one study of the carcinogenic potential of temephos has been
conducted with rats. The rats were fed small amounts of the compound over a
two year interval. No tumors or cancer related changes were noted in the test
animals at the highest dose used (15 mg/kg). During the study the rats
experienced a reduction in liver weight at the lowest dose of 0.5 mg/kg. More
information is needed to make firm conclusions about the carcinogenic
potential of temephos in humans.
Organ Toxicity
As noted under carcinogenicity, a reduction in liver weights was noted in
a study on rats fed very small amounts of temephos over a two-year period. In
another study some minor pathological changes were noted in the liver at a low
dose of 10 mg/kg. No adverse effects in the liver were noted at lower doses
of 1 mg/kg (3). No other effects on organs have been reported.
Fate in Humans and Animals
In general, organophosphate insecticides are readily absorbed through
the lungs, skin, and digestive tract (1). A single oral dose of temephos
reached peak concentration in the bloodstream of rats between five and ten
hours after it was administered. Some of the compound was also found in the
digestive tract and some in fat. In mammals, elimination of the compound is
mainly in feces and urine. Most of the eliminated compound is the unchanged
parent compound though other breakdown products have been detected in the
urine and feces. No studies of the absorption and breakdown of temephos in
humans were found.
ECOLOGICAL EFFECTS
Tests with various wildlife species indicate that the compound is highly
toxic to some organisms and moderately toxic to other species. The LD50 of
temephos ranges from 18.9 mg/kg for the California quail to 240 mg/kg for the
chukar partridge. Most of the bird species had an LD50 within the 35 mg/kg to
85 mg/kg range indicating a compound that is moderately to highly toxic to
avian species. Species tested include the house sparrow, mallard ducks, red-
winged blackbird and rock doves. Mallards fed diets containing moderate
amounts of temephos showed no changes in reproduction except in the frequency
of egg laying (4).
Temephos shows a wide range of toxicity to aquatic organisms. The most
sensitive species of fish is the rainbow trout with a temephos LD50 ranging
from 0.16 to 3.49 mg/kg (1). Other LD50 values for temephos are coho salmon
(0.35 mg/kg), largemouth bass (1.44 mg/kg), channel catfish (3.23 to 10
mg/kg), bluegill sunfish (1.44 to 21.8 mg/kg), and Atlantic salmon (6.7 mg/kg
to 21 mg/kg).
Freshwater aquatic invertebrates such as amphipods are very highly
susceptible to temephos as are some marine invertebrates such as mysids
(8). The LD50 of temephos for Gammarus lacustris is 0.08 mg/kg. Because
the compound is an insecticide and is used effectively to control the
aquatic larval stages of mosquitos, black flies and midges, its highly toxic
nature to these organisms is not surprising. The product Abate 4E is highly
toxic to the saltwater species, the pink shrimp (LD50 0.005 mg/l) and the
Eastern oyster (LD50 0.019 mg/l) (6). The compound is nearly non-toxic to
the bull frog with an LD50 of greater than 2000 mg/kg. Temephos is highly
toxic to bees.
Temephos has the potential to accumulate in aquatic organisms. The
bluegill sunfish accumulated 2,300 times the concentration present in the
water. Nearly 75% of the compound was eliminated from the fish after exposure
ended (6).
ENVIRONMENTAL FATE
There is only a minimal amount of information available about the fate
and behavior of temephos in the environment. Current evidence suggests that
the compound has a low persistence in the environment. Weekly application of
temephos at twice the normal application rates on pond water resulted in the
rapid disappearance of the compound from the water and from the sediments
(2). At even higher application rates to pond water there were still only
traces of the compound detected one week after application.
Temephos was sprayed over an intertidal mangrove community in Florida.
Between 15% and 70% of the sprayed amount reaching the leaf surface entered
the water below the trees. Additional amounts were washed into the water
during rainfall. Pesticide residues were detected in the water two hours but
not four hours after application, indicating a very short persistence in the
water. However, in simulated tide pools the compound persisted for up to four
days. It also persisted in oysters for two days after application (8).
PHYSICAL PROPERTIES AND GUIDELINES
Exposure Guidelines:
| NOEL (rat): | 0.3 mg/kg (cholinesterase inhibitions) |
| RfD: | NA |
| ADI: | NA |
| MCL: | NA |
| HA: | NA |
| TLV: | 10 mg/m3 |
Physical Properties:
| Common Name: | temephos |
| CAS #: | 3383-96-8 |
| Chemical name: | O,O'-(thiodi-4,1-phenylene)O,O,O'O'-tetramethylphosphorothioate |
| Chemical class: | organophosphate |
| Solubility in water: | 0.03 mg/l at 25 degrees C |
| Solubility in solvents: | Soluble in common organic solvents. Insoluble in hexane and methylcyclohexane |
| Melting point: | 30 - 30.5 degrees C |
| Vapor pressure: | NA |
| Partition coefficient: | NA |
BASIC MANUFACTURER
American Cyanamid Co.
One Cyanamid Plaza
Wayne, New Jersey 07470
Telephone: 210-831-2000
Emergency: 210-831-2000
Review by Basic Manufacturer:
Comments solicited: June, 1993
Comments received:
REFERENCES
Hazardous Substance Data Base. 1993. TOXNET. National Library of
Medicine. Bathesda, MD.
Smith, G.J. 1993. Toxicology and Pesticide Use in relation to
Wildlife: Organophosphorous and Carbamate Compounds. U.S. Department of
the Interior. C.K. Smoley. Boca Raton, FL.
Gallo, M.A. and N.J. Lawryk. 1991. Organic Phosphorous Pesticides.
In Handbook of Pesticide Toxicology, Volume 2, Classes of Pesticides.
Wayland J. Hayes and Edward R. Laws (eds.). Academic Press Inc., NY.
Franson, J.C. and J.W. Spann. 1983. Effects of Dietary ABATE on
Reproductive Success, Duckling Survival, Behavior, and Clinical Pathology
in Game-Farm Mallards <Temephos>. Archives of Environmental Contamination
and Toxicology 12:529-534.
Farm Chemicals Handbook. 1992. Meister Publishing Co. Willoughby,
OH.
Communication between American Cyanamid and US EPA Office of Pesticide
Programs. Re: Temephos. July 2, 1986.
US Environmental Protection Agency. Office of Pesticides/HED/SACB.
Tox. Oneliners. 6/18/85. Temephos #845.
Pierce, R.H., R.B. Brown, K.R. Hardman, M.S. Henry, C.L. Palmer, T.W.
Miller and G. Witcherman. 1989. Fate and Toxicity of Temephos Applied
to an Intertidal mangrove Community. Journal of the American Mosquito
Control Association. December 5 (4): 569-578.
Disclaimer: Please read
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site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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