E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
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University of California at Davis. Major support and funding was provided
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Pesticide
Information
Profile
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Trifluralin
Publication Date: 9/93
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TRADE OR OTHER NAMES
Some trade names include Flurene SE, Treflan, Tri-4, Trust, M.T.F.,
Trifluralina 600, Elancolan, Su Seguro Carpidor, Trefanocide, Treficon, Trim,
L-36352, Crisalin, TR-10, Triflurex and Ipersan.
REGULATORY STATUS
In August, 1979, trifluralin was brought under Special Review by the EPA
because of the presence of a N-nitrosamine contaminant which had been shown to
cause tumors and to have mutagenic effects in animals. The principle
manufacturer of trifluralin had already instituted manufacturing methods to
reduce N-nitrosamine contaminant levels. The Special Review was concluded in
1982, with the requirement that N-nitrosamine contaminant levels in
trifluralin not exceed 0.5 ppm, a level which EPA believes will have no toxic
effects (12, 13).
Products containing trifluralin must bear one of the signal words
"Caution" or "Warning," depending on the type of formulation (3).
INTRODUCTION
Trifluralin is a selective, preemergence dinitroaniline herbicide used to
control many annual grasses and broadleaf weeds in a large variety of tree
fruit, nut, vegetable, and grain crops. Preemergence herbicides are applied
before weed seedlings sprout. Trifluralin should be incorporated into the
soil by mechanical means within 24 hours of application. Granular
formulations may be incorporated by overhead irrigation. Trifluralin is
available in granular and emulsifiable concentrate formulations (2, 3, 8, 9).
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Trifluralin is not acutely toxic to test animals by oral, dermal or
inhalation routes of exposure (12). Pesticide products containing trifluralin
may be moderately toxic to relatively non-toxic, depending on the type of
formulation (3). Nausea and severe gastrointestinal discomfort may occur
after eating trifluralin.
Trifluralin does not cause skin irritation. When applied to the eyes of
rabbits, trifluralin produced slight irritation which cleared within 7 days
(7). Skin sensitization (allergies) may occur in some individuals (1, 9).
Inhalation may cause irritation of the lining of the mouth, throat or lungs
(7). The solvent in emulsifiable concentrates of trifluralin may cause
irritation to the skin. Most cases of poisoning result from the carrier or
solvent in formulated trifluralin products, rather than from the trifluralin
itself (NRC Drinking Water and Health. 1977).
The amount of a chemical that is lethal to one-half (50%) of experimental
animals fed the material is referred to as its acute oral lethal dose fifty,
or LD50. The oral LD50 for technical trifluralin in rats is greater than
10,000 mg/kg, in mice is greater than 5,000 mg/kg, and in dogs, rabbits and
chickens is greater than 2,000 mg/kg. However, certain formulated products
which contain trifluralin may be more toxic than the technical material
itself. For example, the oral LD50 for Treflan TR-10 in rats is >500 mg/kg.
The dermal LD50 for technical trifluralin in rabbits is >2,000 mg/kg.
The lethal concentration fifty, or LC50, is that concentration of a
chemical in air or water that kills half of the experimental animals exposed
to it for a set time period. The 1-hour LC50 for technical trifluralin in
rats is >2.8 mg/l (2, 3).
CHRONIC TOXICITY
Prolonged or repeated skin contact with trifluralin may cause allergic
dermatitis (7). The administration of 25 mg/kg to dogs for 2 years resulted
in no toxicological effects (2).
The EPA has established a Lifetime Health Advisory (LHA) level of 5
micrograms per liter (ug/l) for trifluralin in drinking water. This means
that EPA believes that water containing trifluralin at or below this level is
acceptable for drinking every day over the course of one's lifetime, and does
not pose any health concerns. However, consumption of trifluralin at high
levels well above the LHA level over a long period of time has been shown to
cause liver and kidney damage, decreased fetal weight and size, and increased
miscarriages in animal studies (11).
Reproductive Effects
The reproductive capacity of rats fed dietary concentrations of
trifluralin as high as 10 mg/kg was unimpaired through 4 successive
generations, and no abnormalities were detected in the parents or the
offspring. Trifluralin administered to pregnant rabbits at doses as high as
100 mg/kg, and to rats at doses as high as 225 mg/kg, produced no adverse
effect on either the mothers or offspring (2).
Loss of appetite and weight loss followed by miscarriages were observed
when pregnant rabbits were fed 224 or 500 mg/kg/day. Fetal weight decreased
and there was an increase in the number of fetal runts at the 500 mg/kg/day
dosage (7).
Teratogenic Effects
No abnormalities were observed the offspring of rats fed doses as high as
10 mg/kg for 4-generations (2). Studies in the rat and rabbit show no
evidence that trifluralin is teratogenic. The highest doses tested in these
studies were 1,000 mg/kg/day in rats and 500 mg/kg/day in rabbits (12).
Mutagenic Effects
No evidence of mutagenicity was observed when trifluralin was tested in
live animals, and in assays using bacterial and mammalian cell cultures (12).
Carcinogenic Effects
EPA considers trifluralin to be a possible human carcinogen (11). This
classification is used when there is limited or uncertain information
indicating that a chemical may cause cancer in animals receiving high doses of
the chemical over the course of their lifetimes. In a 2-year study of rats
fed 325 mg/kg/day, the highest dose tested, malignant tumors developed in the
kidneys, bladder and thyroid (7, 12). Because there is a possible increase in
the risk of cancer to humans, EPA's Lifetime Health Advisory level for
trifluralin drinking water includes an additional safety margin (11).
Organ Toxicity
Consumption of trifluralin at high levels well above the EPA's Lifetime
Health Advisory level for drinking water (5 ug/l) over a long period of time
has been shown to cause liver and kidney damage, in animal studies (11).
Fate in Humans and Animals
Trifluralin is not readily absorbed into the bloodstream from the
gastrointestinal tract. 80% of single oral doses administered to rats and
dogs was excreted in the feces (7).
ECOLOGICAL EFFECTS
Effects on Birds
Trifluralin is not hazardous to birds (2, 4). The LD50 for bobwhite
quail was greater than 2000 mg/kg. The 5-day LC50 in both quail and ducks was
greater than 5,000 mg/kg (2).
Effects on Aquatic Organisms
Trifluralin is toxic to fish and other aquatic organisms. However, its
strong adsorption to soil and the usual practice of incorporating trifluralin
into the soil at the time of application may prevent exposure of fish to this
herbicide. Run-off from fields should be avoided. Contamination of open
waters during mixing and loading operations by rinseate from the cleaning of
application equipment or by accidental spills should be avoided (2).
Trifluralin is toxic to Daphnia, a small freshwater crustacean (Hdbk. Acute
Tox. Chem. Fish and Aqua. Invert. 1986).
Effects on Other Animals (Nontarget species)
At exposure levels well above permissible application rates (100 ppm),
trifluralin has been shown to be toxic to earthworms. However, permitted
application rates will result in soil residues of approximately 1 ppm
trifluralin, a level that had no adverse effects on earthworms. (10, Proc.
NZ. Weed Pest. Control Conf. 35th: 328. 1982). In general, trifluralin is
not very toxic to higher animals (except fish) (8). Birds are very resistant
to trifluralin (4, 8). It is non-toxic to bees (3, 8).
ENVIRONMENTAL FATE
Breakdown of Chemical in Soil and Groundwater
The substituted dinitroanilines do not move much in the soil, but remain
where they are placed at application (Casarett & Doull's Tox. 2nd Ed. 1980).
Trifluralin is strongly absorbed on soils (Koc = 7,000 g/ml) and nearly
insoluble in water (6). Therefore leaching and groundwater contamination by
trifluralin is not expected to occur. Because adsorption is highest in soils
high in organic matter or clay content and adsorbed herbicide is inactive,
higher application rates may be required for effective weed control on such
soils (5, 2).
Trifluralin is subject to degradation by soil microorganisms.
Trifluralin remaining on the soil surface after application may be decomposed
by UV light or may volatilize. Recommended application rates give season long
weed control, but fall-seeded grain crops planted in soil treated with
trifluralin during the preceding spring were not injured under warm, moist
conditions (2). The half-life of trifluralin in the soil is 45 to 60 days
(6) or about 6-8 months (2.5 kg/ha) (8). After six months to one year, 80-
90% of its activity will be gone (5).
Breakdown of Chemical in Water
Trifluralin is nearly insoluble in water (8). Contamination of lakes and
streams should be avoided because fish are sensitive to trifluralin.
Breakdown of Chemical in Vegetation
Trifluralin inhibits the growth of roots and shoots when it is absorbed
by the roots of newly germinated weed seedlings (2, 8, 12). There is no
significant absorption or translocation of trifluralin in crops grown in soil
treated with trifluralin. Trifluralin residues in crop plants will occur only
on root tissues which are in direct contact with contaminated soil.
Trifluralin is not translocated into the leaves, seeds or fruit of most
plants. On most crops, trifluralin applied to the leaves has no effect, but
on certain crops, such as tobacco and summer squash, leaf distortion may occur
(2).
PHYSICAL PROPERTIES AND GUIDELINES
Trifluralin is an odorless, yellow-orange crystalline solid (2).
Trifluralin will decompose in both sunlight and artificial light (7).
Trifluralin is stable under normal temperatures and pressures, but it may pose
a slight fire hazard if exposed to heat or flame. It poses a fire and
explosion hazard in the presence of strong oxidizers. Thermal decomposition
of trifluralin will release corrosive fumes of hydrogen fluoride and toxic
oxides of nitrogen (7).
Technical trifluralin is not flammable, but emulsifiable concentrate
formulations containing trifluralin may be flammable. The product Treflan EC
is classified as a combustible liquid. Closed containers of this product may
explode if exposed to excessive heat or intense fire (2).
It is recommended that applicators wear full protective clothing when
spraying trifluralin. This gear should include neoprene gloves, rubber
workshoes, rubber apron, goggles to protect the eyes and a respirator to
prevent inhalation of fumes or mists (1).
Occupational Exposure Limits:
No occupational exposure limits have been established for trifluralin by
OSHA, NIOSH or ACGIH (7).
Physical Properties:
| CAS#: | 1582-09-8 |
| Specific gravity: | 1.294 at 25 degrees C (7) |
| Solubility in water: | practically insoluble; 0.0024% at 27 degrees C (7) |
| Solubility: |
readily soluble in organic solvents such as xylene, acetone and aromatic napthas (3).
| Solvent | Solubility at 25 degrees C |
| Acetone | > 50 g/100 ml (2) |
| Methanol | 2 g/100 ml (2) |
| Xylene | 81 g/100 ml (2) |
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| Boiling point: | 139-140 degrees C (282-284 degrees F) at 4.2 mm Hg (2, 15); 96-97 degrees C at 0.18 mm Hg (2) |
| Melting point: | 46-47 degrees C (115-117 degrees F) (7) |
| Flash point: | Technical material is not flammable. However, emulsifiable concentrate formulations may be flammable. |
| Vapor pressure: | 1.99 x 10 to the minus 4 mm Hg at 29.5 degrees C (2) |
| pH: | 7.0 (50% suspension) (7) |
| Koc: | 7000 g/ml (6) |
| Soil half-life: | 60 days (6) |
| ADI: | 0.1 mg/kg/day (14) |
BASIC MANUFACTURER
DowElanco
9002 Purdue Rd.
Indianapolis, IN 46268-1189
Review by Basic Manufacturer:
Comments solicited: November, 1992
Comments received: December, 1992
REFERENCES
Meister, R.T. (ed.). 1987. Farm Chemicals Handbook. Meister
Publishing Co., Willoughby, OH.
WSSA Herbicide Handbook Committee. Herbicide Handbook of the Weed
Science Society of America, 6th Ed. WSSA, Champaign, IL. 1989.
Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister
Publishing Company, Willoughby, OH.
Tucker, Richard. 1970. Handbook of Toxicity of Pesticides to
Wildlife. USDI Fish and Wildlife Service.
Worthing, C.R. (ed.). 1987. The Pesticide Manual. 8th Ed. British
Crop Protection Council.
U.S. Department of Agriculture, Soil Conservation Service. 1990
(Nov.). SCS/ARS/CES Pesticide Properties Database: Version 2.0 (Summary).
USDA - Soil Conservation Service, Syracuse, NY.
Occupational Health Services, Inc. 1991. MSDS for Trifluralin. OHS
Inc., Secaucus, NJ.
The Agrochemicals Handbook. 1983. The Royal Society of Chemistry.
Crop Protection Chemicals Reference. 1986. 2nd Ed. Chemical and
Pharmaceutical Press.
Barber, Daniel T., Manager, State Regulatory Affairs. Letter of Dec.
3, 1991. DowElanco, Indianapolis, IN.
US Environmental Protection Agency. 1989 (Jan.). Health Advisory
Summary: Trifluralin. US EPA, Washington, DC.
_____. 1987 (Aug.). Guidance for the reregistration of pesticide
products containing trifluralin as the active ingredient. Office of
Pesticides and Toxic Substances, US EPA, Washington, DC.
_____. 1982 (Aug. 4). Trifluralin; Determination concluding the
Rebuttable Presumption Against Registration; Notice of availability of
position documents. Federal Register 47 (150): 33777-84.
_____. 1982 (Feb. 10). Trifluralin: proposed tolerances. Federal
Register 47 (28): 6033-4.
Merck Index. 1976. 9th Ed.
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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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