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Trifluralin
Pesticide Fact Sheet
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Prepared for the U.S. Department of Agriculture, Forest Service by
Information Ventures, Inc.
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This fact sheet is one of a series issued by the Forest Service, the
Bureau of Land Management, and the Bonneville Power Administration for
their workers and the general public. It provides information on
forest and land management uses, environmental and human health
effects, and safety precautions for the herbicide trifluralin and its
formulations. Unless otherwise stated, the toxicity data presented in
this fact sheet refer to the active ingredient, trifluralin. When
included, data on formulated products will be specifically identified.
A list of definitions is included in Section VIII of the fact sheet.
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I. Basic Information
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Common name: Trifluralin
Chemical name: a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine
Common Product names: Treflan® 5G, Treflan® E.C., Trifluralin® 4EC
Pesticide classification: herbicide
Registered Use Status: "General Use"
Formulations: Commercial trifluralin products generally contain one or
more inert ingredients. An inert ingredient is anything added to the
product other than an active ingredient. Because of concern for human
health and the environment, the U.S. Environmental Protection Agency
(EPA) announced its policy on toxic inert ingredients in the Federal
Register on April 22, 1987 (52 FR 13305). The intent of this policy is
the regulation of inert ingredients. EPA's strategy for the
implementation of this policy included the development of four lists
of inerts based on toxicological concerns. Inerts of toxicological
concern were placed on List 1. Potentially toxic inerts/high priority
for testing were placed on List 2. Inerts of unknown toxicity were
placed on List 3 and inerts of minimal concern were placed on List 4.
For pesticides containing List 1 inerts, the EPA has given the
pesticide registrant the opportunity to reformulate the product to
remove the List 1 inerts. If the registrant chooses not to reformulate
the product, then the List 1 inerts must be identified on the product
label. For List 2 inerts, the EPA is monitoring ongoing testing and
gathering existing information on the potential adverse effects of
these chemicals to determine if further regulatory action is required.
The EPA has no particular regulatory plans for List 3 and List 4
inerts. The Forest Service will incorporate new data on inerts into
updated fact sheets as it becomes available.
The contents of 3 trifluralin formulations are listed below.
Treflan® E.C.: trifluralin (5%) and inert ingredients (95%)
Treflan® E.C.: trifluralin (44.5%) and inert ingredients (55.5%)
including xylene, ethylbenzene and naphthalene
Trifluralin 4EC: trifluralin (44.5%) and inert ingredients (55.5%)
Residue assay methods: Gas chromatography with electron capture
detector is available for residue assay.
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II. Herbicide Uses
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Registered forestry, rangeland, right-of-way uses: for use on
ornamental trees, rights of way, domestic outdoor and industrial
sites.
Operational details:
Target Plants: Trifluralin is used to control annual grasses and
certain broadleaf weeds.
Mode of action: Trifluralin applied to the soil kills weed seeds as
they germinate. It does not control established weeds.
Method of application: Trifluralin is applied by low pressure ground
spraying equipment, subsurface layering equipment, irrigation systems,
aerial equipment, or granular applicators. Soil incorporation within 4
to 24 hours after application is recommended for most uses. For some
products, surface application followed by irrigation is recommended.
Do not apply to muck soils or to soils containing more than 10%
organic matter.
Use rates: Use at ˝ to 1 pound of active ingredient per acre
Special Precautions:
Always read all of the information on the product label before using
any pesticide. Read the label for application restrictions.
Timing Of Application: Apply before weed germination or to cultivated
weed-free areas. Do not apply when foliage is wet.
Drift Control: Do not allow careless application or spray drift. Do
not spray aerially when wind speed is greater than 4 mph.
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III. Environmental Effects/Fate
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Soil:
Residual Soil Activity: Trifluralin is active in the soil. Germination
of crops may be impacted for up to 1˝ years after soil treatment,
especially in arid conditions. It is not usually absorbed from the
soil by plants.
Adsorption: Trifluralin is strongly adsorbed by the soil.
Persistence and Agents of Degradation: Trifluralin remains unchanged
in the soil for varying lengths of time but is generally persistent.
In the field, trifluralin degrades to half of its original
concentration in 2 to 4 months. Trifluralin is photodegraded but not
hydrolyzed in soil. Under laboratory conditions, degradation is faster
in soil where no air is present.
Metabolites/Degradation Products and Potential Environmental Effects:
Break-down products of trifluralin in the soil include
a,a,a-trifluoro-2,6-dinitro-p-toluidine (the major breakdown product);
a,a,a-trifluoro-2,6-dinitro-n-propyl-p-toluidine;
a,a,a-trifluoro-N,N-dipropyl-5-nitrotoluene-3,4-diamine;
a,a,a-trifluoro-N,N-dipropyltoluene-3,4,5-triamine. No information is
available on the environmental effects of these breakdown products.
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Water:
Solubility: Trifluralin does not dissolve easily in water.
Potential For Leaching Into Ground-Water: The potential for leaching
into the ground-water is very low. Trifluralin is strongly adsorbed to
soil particles and is not readily leached. The mobility of trifluralin
is greatest in fine sand and least in muck soils; it is relatively
immobile in sand, sandy loam, silt, loam and clay loam soils. No
information is available on the half-life of trifluralin in water.
Surface Waters: Trifluralin could enter surface waters through the
runoff of sediment; one study showed very little runoff, however. When
trifluralin is applied to ditch banks, irrigation water should not be
used on food or feed crops for 18 months after application or until
the water is free of trifluralin residues.
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Air:
Volatilization: Trifluralin does not evaporate easily.
Potential For By-Products From Burning of Treated Vegetation: No
information is available. However, trifluralin is applied directly to
soil and is therefore not present in great concentration in foliage.
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IV. Ecological Effects
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Non-Target Toxicity:
Soil Microorganisms: No information available.
Plants: Trifluralin did not accumulate in crops grown in silt loam
soil treated with 1 pound active ingredient per acre. Contact with
susceptible non-target plants may injure these plants.
Aquatic Animals: Trifluralin is highly toxic to cold- and warm-water
fish and to aquatic invertebrate animals. It is very highly toxic to
amphibians (tadpoles). It has not been tested for effects on estuarine
and marine animals. It may build up (bioaccumulate) in fish exposed to
trifluralin in water at low levels; but in one test it was eliminated
from edible fish tissues 7 days after exposure ended. Trifluralin
affected the survival of minnows at chronic exposures as low as 5.1
ppb; and affected the survival of water fleas at chronic exposures as
low as 7.2 ppb.
Acute toxic level:
species LC50 Source Table
rainbow trout 41 ppb (Table II, Aquatic)
fathead minnow 105 ppb (Table II, Aquatic)
channel catfish 2.2 ppm (Table II, Aquatic)
bluegill sunfish 58 ppb (Table II, Aquatic)
largemouth bass 75 ppb (Table II, Aquatic)
goldfish 145 ppb (Table II, Aquatic)
species TL50
(96 hour) Source Table
tadpole 0.1 ppm ---
species LC50 Source Table
water flea 0.56-0.9 ppm ---
stone fly 2.8 ppm ---
side swimmer 2.2 ppm ---
Terrestrial Animals: Trifluralin is practically nontoxic to birds when
fed the chemical on both an acute and a subacute basis. It did not
impair reproduction in birds at dietary exposures below 50 ppm.
Trifluralin is practically nontoxic to mammals. It is of low acute
toxicity to honeybees. Acute toxic level:
species LD50 Source Table
birds <2,000 mg/kg (Table II, Avian)
rats <5,000 mg/kg (Table II, Mammalian)
Threatened and Endangered Species: Use of trifluralin for certain
agricultural applications may be a hazard to endangered species if it
is applied to areas where they live. The endangered species of concern
are the slackwater darter, woundfin, solano grass, and several
freshwater mussel species. Rangeland and right-of-way uses are under
evaluation, but are probably of minimal risk to endangered species.
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V. Toxicology Data
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Acute toxicity:
Acute oral toxicity: In tests in male and female rats exposed to
trifluralin, the acute oral LD50 was >5,000 mg/kg. (Toxicity Category
IV, Table I, Oral).
Acute dermal toxicity: The acute dermal (skin) LD50 was >2,000 mg/kg
in rabbits exposed to trifluralin. (Toxicity Category III, Table I,
Dermal). The Environmental Protection Agency is requiring information
on the dermal penetration potential of trifluralin.
Primary irritation score: In laboratory tests in rabbits, trifluralin
was not an irritant. (Toxicity Category IV, Table I, Skin irritation).
Trifluralin is a skin sensitizer in guinea pigs.
Primary eye irritation: In laboratory tests in rabbits, trifluralin
was a mild eye irritant. (Toxicity Category III, Table I, Eye
irritation).
Acute Inhalation: In tests in rats exposed to trifluralin, the acute
inhalation LC50 was >2.8 mg/L. (Toxicity Category III, Table I,
Inhalation).
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Chronic toxicity:
Carcinogenicity: A laboratory test in male and female mice fed up to
4,500 ppm trifluralin in their diet for up to 2 years showed no
evidence of carcinogenicity. However, laboratory testing in rats fed
up to 325 mg/kg per day trifluralin in their diet for up to 2 years
did show some evidence of carcinogenicity. In this study there were
increased malignant kidney tumors in male rats exposed to trifluralin
dietary levels greater than 41 mg/kg per day; there were increased
benign bladder tumors in female rats. A carcinogenic nitrosamine
contaminant of trifluralin was not detectable in either of these
studies; therefore the carcinogenic activity was due to the
trifluralin itself.
Developmental: Laboratory studies with trifluralin in pregnant rats
(at dose levels up to 1,000 mg/kg per day) and rabbits (at dose levels
up to 500 mg/kg per day) indicated no evidence of teratogenesis (birth
defects).
Reproduction: A two-generation reproduction study in rats did not show
any adverse effects on fertility or reproduction at doses up to 2,000
ppm trifluralin in the diet.
Mutagenicity: Trifluralin was negative in 4 tests for mutagenicity
(the ability to cause genetic damage). Additional tests for
mutagenicity are required by the EPA.
The data reported above are results of animal studies which the
Environmental Protection Agency has evaluated in support of the
registration of trifluralin. These data are used to make inferences
relative to human health.
HAZARD: Based on the results of animal studies, trifluralin does not
cause genetic damage or birth defects, and has no effect on fertility,
reproduction or development of offspring. There is no evidence in
humans that trifluralin causes cancer; however there are some animal
studies in which trifluralin was carcinogenic. Trifluralin is
considered by the EPA to be a "possible human carcinogen."
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VI. Human Health Effects
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Acute toxicity (poisoning):
Reported effects: Most incidents of trifluralin exposure reported in
humans have involved dermal and eye irritation and nausea. Dizziness
and headache, fever or chills, and muscle aches or weakness have also
been reported.
Chronic toxicity:
Reported effects: There are no reported cases of long term health
effects in humans due to trifluralin or its formulations.
Potential for adverse health effects from contacting or consuming
treated vegetation, water or animals: The exposure levels a person
could receive from these sources, as a result of routine operations,
are probably below levels shown to cause harmful effects in laboratory
studies.
Potential for adverse health effects from inert ingredients contained
in the formulated product: Inert ingredients found in the emulsifiable
concentrate (E.C.) of trifluralin include xylene, ethylbenzene and
naphthalene. The effects of these compounds include: corneal (eye)
damage, liver changes, fetotoxicity, and teratogenicity (xylene);
blistering of skin, and liver, kidney and testicular changes
(ethylbenzene); and cataracts and liver changes (naphthalene).
Health effects of exposure to formulated products: The Trifluralin
E.C. formulation may cause skin and eye irritation. No specific
effects of exposure to the granular formulation have been noted.
Health effects associated with contaminants: Trifluralin contains the
contaminant N-nitroso-di-n-propylamine (NDPA). This contaminant is an
N-nitrosamine class chemical; these chemicals have a known potential
for causing cancer. However, the Environmental Protection Agency (EPA)
requires that manufacturers of trifluralin certify that technical
trifluralin products contain a total N-nitrosamine concentration of no
greater than 0.5 ppm. The EPA concluded that the benefits of
trifluralin outweighed the identified risks. They also conclude that
exposure to NDPA in trifluralin is not of toxicological significance
in evaluating the risk of exposure to trifluralin.
Health effects associated with other formulations: Some formulations
of trifluralin also contain other herbicides such as alachlor. The
information in this fact sheet only applies to trifluralin. Consult
other fact sheets for information on the other herbicides.
Health risk management procedures: The Forest Service has evaluated
health effects data in the development of both pesticide background
statement documents and environmental impact statements for pesticide
use on forest lands. These health effects evaluations have taken into
consideration the potential for both worker and public exposure from
Forest Service operations. This information has been used in assessing
health risks and consequently in formulating protective measures to
reduce risk to forest workers and to the public. Section VII of this
fact sheet, Safety Precautions, provides guidance for the safe
handling and use of trifluralin.
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VII. Safety precautions:
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Signal word and definition:
Treflan® 5G: CAUTION - CAUSES EYE IRRITATION. HARMFUL IF SWALLOWED,
INHALED, OR ABSORBED THROUGH THE SKIN.
Treflan® E.C.: WARNING - CAUSES SUBSTANTIAL BUT TEMPORARY EYE INJURY.
CAUSES SKIN IRRITATION. HARMFUL IF SWALLOWED, INHALED, OR ABSORBED
THROUGH THE SKIN. MAY CAUSE SKIN SENSITIZATION REACTIONS IN CERTAIN
INDIVIDUALS.
Trifluralin® 4EC: WARNING - CAUSES EYE AND SKIN IRRITATION. HARMFUL IF
SWALLOWED OR ABSORBED THROUGH THE SKIN.
Protective Precautions for Workers: Avoid contact with eyes, skin or
clothing. Avoid breathing vapors or spray mist. Wear goggles, face
shield or safety glasses, and protective clothing, such as coveralls,
a long-sleeved shirt, and impermeable gloves when handling. Wash
thoroughly with soap and water after handling. Remove contaminated
clothing and wash before reuse. Do not allow children or pets on
treated areas until ˝ inch of water has been applied and the water has
dried or until 24 hours have passed.
Medical Treatment Procedures (Antidotes): For exposure to the eyes,
hold eyelids open and flush with a steady, gentle stream of water for
15 minutes. Get medical attention. For exposure to the skin,
immediately wash with plenty of soap and water. If granular
formulation is swallowed, drink one or two glasses of water (if
conscious) and induce vomiting. If E.C. formulation is swallowed,
administer activated charcoal (6-8 heaping teaspoons) with water. If
inhaled, move individual to fresh air and get medical attention if
breathing difficulty occurs. If not breathing, provide cardiopulmonary
resuscitation assistance. In case of emergency, call your local poison
control center for advice.
Handling, Storage, And Disposal: Do not apply directly to water or
wetlands (swamps, bogs, or marshes). Drift or runoff from treatment
areas may be hazardous to aquatic organisms in neighboring aquatic
sites. Do not discharge water containing trifluralin into lakes,
streams, ponds estuaries, oceans, or public water unless disposal is
specifically permitted. Do not discharge into sewer systems without
first notifying the sewage treatment plant authority. Wastes resulting
from use of trifluralin may be disposed of on site or at an approved
waste disposal facility.
Emergency (Spill) Hazards And Procedures: Use absorbent materials to
contain and clean up small spills and dispose of as waste. Prohibit
use of hot or sparking equipment in area of spill of E.C.
formulations. Prevent runoff. Do not contaminate water, food, animal
feeds or seed by storage or disposal. In case of a large spill, call
CHEMTREC at 1-800-424-9300 for advice.
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VIII. Definitions
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adsorption - the process of attaching to a surface
avian - of, or related to, birds
carcinogenicity - ability to cause cancer
dermal - of, or related to, the skin
ecotoxicology - the study of the effects of environmental toxicants on
populations of organisms originating, being produced, growing, or
living naturally in a particular region or environment.
ecotoxicological - related to the study of the effects of
environmental toxicants on populations of organisms originating, being
produced, growing, or living naturally in a particular region or
environment.
formulation - the form in which the pesticide is supplied by the
manufacturer for use
half-life - the time required for half the amount of substance to be
reduced by natural processes
herbicide - a substance used to destroy plants or to slow down their
growth
LC50 - the concentration in air, water, or food which will kill
approximately 50% of the subjects
LD50 - the dose which will kill approximately 50% of the subjects
leach - to dissolve out by the action of water
mg/kg - milligrams of the substance per kilogram of body weight
microorganisms - living things too small to be seen without a
micro-scope
mutagenicity - ability to cause genetic changes
non-target - animals or plants other than the ones which the pesticide
is intended to kill
persistence - tendency of a pesticide to remain active after it is
applied
ppb - parts per billion
ppm - parts per million
TL50 - the concentration in water which will kill approximately 50% of
the subjects during a specific exposure period
residual activity - the remaining amount of activity as a pesticide
volatility - the tendency to become a vapor at relatively low
temperature
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IX. Additional Reading
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Final Environmental Impact Statement for Managing Competing and
Unwanted Vegetation. Pacific Northwest Region. Forest Service, U.S.
Department of Agriculture, Portland, Oregon. 1988.
Final Environmental Impact Statement. Vegetation Management in the
Coastal Plain/Piedmont. Forest Service, U.S. Department of
Agriculture, Atlanta, Georgia. Management Bulletin R8-MB-23, 1989.
Registration Standard for Pesticide Products Containing Trifluralin as
the Active Ingredient. Office of Pesticides and Toxic Substances, U.S.
Environmental Protection Agency, Washington, DC. EPA Publication No.
540/RS-87-195, 1987.
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X. Toxicity Categories
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Tables of Categories of Toxicity
Table I: Human Hazards Route of Administration Hazard
Category Signal word Oral
(mg/kg) Dermal
(mg/kg) Inhalation
(mg/L) Eye Irritation Skin Irritation
I DANGER
Poison 0-50 0-200 0-0.2 corrosive: corneal opacity not reversible
within 7 days corrosive
II WARNING >50-500 >200-2000 >0.2-20 corneal opacity reversible within
7 days; irritation persisting for 7 days severe irritation at 72 hours
III CAUTION >500-5000 >2000-20,000 >2.0-20 no corneal opacity;
irritation reversible within 7 days moderate irritation at 72 hours
IV none >5000 >20,000 >20 no irritation mild or slight irritation at
72 hours
40 CFR 162.10 (h) (1), July 3, 1975
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Table II: Ecotoxicological Categories Toxicity
Category Mammalian
(Acute Oral)*
mg/kg Avian
(Acute Oral)*
mg/kg Avian
(Dietary)_
ppm Aquatic
Organisms‡
ppm
very highly toxic <10 <10 <50 <0.1
highly toxic 10-50 10-50 50-500 0.1-1
moderately toxic 51-500 51-500 501-1000 >1-10
slightly toxic 501-2000 501-2000 1000-5000 >10-100
practically non-toxic >2000 >2000 >5000 >100
* Reflects dose given to test animals and is based on body weight of
the test animal.
_Concentration in the diet. Unrelated to body weight of the test
animal. Measure of environmental exposure.
‡Concentration in water. Unrelated to body weight of test animal.
Measure of environmental exposure.
Adapted from Insecticides, Brooks, H.L. et al. (1973) Cooperative
Extension, Kansas State University, Manhattan, Kansas
For more information on Trifluralin contact your local Forest Service,
Bureau of Land Management, or Bonneville Power Administration office.
Prepared by Information Ventures, Inc. under U.S. Forest Service
Contract. November 1995 |
