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
Publication Date: 9/93
TRADE OR OTHER NAMES
G-30027, Aatrex, Aktikon, Alazine, Atred, Atranex, Atrataf,
Atratol, Azinotox, Crisazina, Farmco Atrazine, Gesaprim, Giffex 4L,
Malermais, Primatol, Simazat, Zeaphos (25).
Atrazine has been classified as a Restricted Use Pesticide (RUP),
due to its potential for groundwater contamination (32). RUPs may be
purchased and used only by certified applicators. Products containing
atra-zine must bear the signal word "Caution" (25).
Atrazine is a selective triazine herbicide used to control
broadleaf and grassy weeds in corn, sorghum, sugarcane, pineapple,
Christmas trees and other crops, and in conifer reforestation plantings.
It is also used as a non-selective herbicide on non-cropped industrial
lands and on fallow lands. It is available as dry flowable, flowable
liquid, liquid, water dispersible granular, and wettable powder
formulations (25, 28).
Atrazine is slightly to moderately toxic to humans and other
animals. It can be ab-sorbed into the bloodstream through oral, dermal
and inhalation exposure. Symptoms of poisoning include abdominal pain,
diarrhea and vomiting, eye irritation, irritation of mucous membranes,
and possible skin reactions (14). At very high doses, rats showed
excitation followed by depression, slowed breathing, incoordination,
muscle spasms, and hypothermia (24). After consuming a large oral dose,
rats exhibited muscular weakness, hypoactivity, breathing difficulty,
prostration, convulsions and death (33).
Atrazine is a mild skin irritant. Rashes associated with exposure
have been reported. Moderate to severe eye irritation can occur.
Exposure to large concentrations of airborne particles or droplets may
cause irritation of the mucous membranes (24, 30).
The amount of atrazine 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 atrazine in rats is 672
to 3,000 mg/kg, in mice is 850 to 1,750 mg/kg, in rabbits is 750 mg/kg,
and in hamsters is 1,000 mg/kg. The dermal LD50 in rabbits is 7,500
mg/kg, and in rats is greater than 3,000 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 one-hour inhalation LC50 in
rats is greater than 700 mg/m3. The 4-hour inhalation LC50 in rats is
5,200 mg/m3 (24, 25, 33, NIOSH RTECS Online File # 85/8408).
Forty percent of rats receiving oral doses of 20 mg/kg/day for 6
months died with signs of respiratory distress and paralysis of the
limbs. Morphological and biochemical changes in the brain, heart,
liver, lungs, kidney, ovaries and endocrine organs were observed (30).
Rats fed 5 or 25 mg/kg/day of atrazine for 6 months exhibited growth
retardation. Examination of these rats revealed no lesions (24). In a
2-year study with dogs fed 0, 0.75. 7.5 or 75 mg/kg/day, the NOAEL was
0.75 mg/kg. At 7.5 mg/kg, decreased food intake and increased heart and
liver weights were observed. At 75 mg/kg, there were decreases in food
intake and body weight gain, increased adrenal weight, lowered blood
cell counts, and occasional tremors or stiffness in the rear limbs (29).
The EPA has established a Lifetime Health Advisory level for
atrazine in drinking water of 3 micrograms per liter (ug/l). Water
containing atrazine at or below this level is acceptable for drinking
every day over the course of one's lifetime, and does not pose any
health risk. Long-term consumption of high levels of atrazine has
caused adverse health effects in animals, including tremors, changes in
organ weights and damage to the liver and heart (29).
Subcutaneous injection of atrazine of near lethal doses of 800
mg/kg/day on days 3, 6 and 9 of gestation resulted in the death and
resorption of some or all the pups in each litter of rats. Dosages as
high as 200 mg/kg/day by this route did not affect the number of pups
per litter or their weight at weaning. Dietary levels up to 1,000 ppm
(about 50 mg/kg/day) caused no adverse effects (24).
In mice, atrazine did not cause abnormalities in fetuses whose dams
were given doses of 46.4 mg/kg/day during days 6 through 14 of gestation
The weight of evidence from more than 50 studies reported in the
literature indicates that atrazine is not mutagenic (24). In tests with
mice, atrazine induced dominant lethal mutations and increased the
frequency of chromatid breaks in bone marrow (29).
Atrazine did not cause tumors when mice were given oral doses of
21.5 mg/kg/day from age 1 to 4 weeks followed by dietary doses of 82
mg/kg for an additional 17 months. Mammary tumors were observed in rats
after lifetime administration of atrazine (24). EPA has classified
atrazine as a possible human carcinogen because it has caused cancer in
rats receiving high doses over the course of their lifetimes (29).
Lethal doses in test animals have caused severe damage, in the form
of congestion and/or hemorrhaging, to the lungs, kidneys, liver, spleen,
brain and heart (29).
Fate in Humans and Animals
Ingested atrazine is readily absorbed into the body through the
gastrointestinal tract. When a single dose of 0.53 mg atrazine was
administered to rats by gavage, 20% of the dose was excreted in the
feces within 72 hours. The other 80% was absorbed across the lining of
the gastrointestinal tract into the bloodstream. After 72 hours, 65%
was eliminated in the urine and 15% was retained in body tissues, mainly
in the liver, kidneys and lungs (24).
Effects on Birds
Atrazine is only slightly toxic to birds. The LD50 in mallard
ducks is greater than 2,000 mg/kg. The NOELs for bobwhite quail and
ring-necked pheasants fed atrazine were both greater than 5,000 ppm.
Effects on Aquatic Organisms
Atrazine is only slightly toxic to fish and other pond or stream
life. In whitefish, atrazine accumulates in the brain, gall bladder,
liver and gut (Arch. Hydrobiol. Suppl. 59(2-3):252-87. 1981). Fish may
bioaccumulate atrazine to levels of 11 times the concentration in
surrounding water. This is a low level of bioaccumulation. Atrazine is
easily broken down.
Effects on Other Animals (Nontarget species)
Atrazine is not toxic to bees (25).
Breakdown of the Chemical in Soil and Groundwater
Atrazine is moderately to highly mobile in soils, especially where
soils have low clay or organic matter content. Because it does not
absorb strongly to soil particles (Koc = 100 g/ml) and it has a lengthy
soil half-life (60 to 100+ days), it is expected to have a high
potential for groundwater contamination, even though it is only
moderately soluble in water (33 ug/ml) (26, 29).
Atrazine is not normally found below the first foot of soil, even
after years of continuous use.
Chemical hydrolysis, followed by degradation by soil microorganisms
probably account for most of the breakdown of atrazine in soil.
Hydrolysis is rapid in acidic or basic environments, but is slower at
neutral pHs. Addition of humic material increased the rate of
hydrolysis. Atrazine is also subject to photo-decomposition and
volatilization when high temperatures and prolonged sunlight occur after
precipitation, but these effects are small under normal field
conditions. Atrazine can persist for longer than one year under
conditions which are not conducive to chemical or biological activity,
such as dry or cold climates (27, 28). Atrazine usually lasts about 4
months at the surface and 2 months at deeper sites (Agro-Ecosystems
Breakdown of the Chemical in Water
Atrazine is not very water soluble. Chemical hydrolysis, followed
by bio-degradation, may be the most important route of disappearance
from aquatic environments. Hydrolysis is rapid under acidic or basic
conditions, but is slower at neutral pHs. Addition of humic material
increased the rate of hydrolysis. Atrazine is not expected to strongly
adsorb to sediments. Bioconcentration and volatilization of atrazine
are not environmentally important (27).
Trace amounts of atrazine have been found in drinking water samples
from Louisiana and Iowa and in groundwater samples from Pennsylvania,
Iowa, Nebraska, Wisconsin and Maryland (27, 29, NRC Drinking Water and
Health 1977). Atrazine has been detected in each of 146 water samples
collected at 8 locations from the Mississippi, Ohio and Missouri Rivers
and their tributaries. For several weeks, 27% of these samples
contained atrazine at concentrations above the EPA's maximum
concentration level (MCL) for atrazine of 3 ppb. The MCL is the
maximum permissible level of a contaminant in water delivered to any
user of a public water system (30). A five year survey of drinking
water wells detected trace amounts of atrazine in an estimated 1.7% of
community water systems and 0.7% of rural domestic wells nationwide.
Levels detected in rural domestic wells sometimes exceeded the MCL (31).
Breakdown of the Chemical in Vegetation
Atrazine is absorbed by plants mainly through the roots, but also
through the foliage. Once absorbed, atrazine is translocated upward and
accumulates in the growing tips and the new leaves of the plant. In
susceptible plant species, atrazine inhibits photosynthesis. In
tolerant plants, it is metabolized (28).
Most crops can be planted one year after application of atrazine.
Atrazine blocks the plant's ability to carry on photosynthesis (Hartley.
Agrochem Hdbk 1983). Atrazine increases the uptake of arsenic by
treated plants (such as grapes) (7).
PHYSICAL PROPERTIES AND GUIDELINES
Atrazine is a white, crystalline solid (25). It is stable under
normal temperatures and pressures, but may burn if exposed to heat or
flame. Excessive heating of atrazine may cause the production of toxic
and corrosive fumes of chlorides and of toxic fumes of nitrogen.
Atrazine is stable in neutral, slightly acidic, or basic material, but
it is hydrolyzed by alkali or mineral acids at higher temperatures (24,
Occupational Exposure Limits:
|5 mg/m3 OSHA TWA
|5 mg/m3 ACGIH TWA
|5 mg/m3 NIOSH recommended TWA
|2 mg/m3 DFG MAK TWA (total dust)
|CAS #: ||1912-24-9
|Specific gravity: ||1.187 g/cubic cm (7, 33)
|H20 solubility: ||33 ppm at 25 degrees C (25, 26). 0.007% at 25 degrees C (33)
|Solubility in other solvents:
|Solvent||T (degrees C)||Solubility
|Chloroform ||25 ||52,000 ppm (22)
|Diethyl ether ||27 ||1.2% (2)
|Dimethyl sulfoxide ||27 ||18.3% (2)
|Ether ||25 ||12,000 ppm (22)
|Ethyl acetate ||27 ||2.8% (2)
|Methanol ||25 ||18,000 ppm (22)
|N-pentane ||27 ||360 ppm (2)
|Melting point: ||173-175 degrees C (25).
|Vapor pressure: ||3.0 x 10 to the minus 7th power mm Hg at 20 degrees C (2, 28). Atrazine is slightly volatile.
|Koc: ||100 g/ml (26): 0.6 on sandy loam; 1.8 on gravelly sand; 5.6 on silty clay; 7.9 on clay loam; 8.7 on sandy loam, 11.6 on silty clay loam; and greater than 21 on peat (29)
|Chemical Class/Use: ||triazine herbicide
PO Box 18300
Greensboro, NC 27419-8300
Review by Basic Manufacturer:
Comments solicited: January, 1992
Comments received: April, 1992
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