Atrazine - Herbicide Profile 3/90
CHEMICAL name: 2-chloro-4-ethylamino-6-isopropyl
TRADE name(S): AAtrex, Atranex (56)
FORMULATION(S): Atranex 50% and 80% wettable powder, 4 lb/gal
flowable, 4L liquid. Griffex 4L contains 4 pound flowable atrazine.
Drexel Atrazine 4L, Drexel Atrazine 5L (contains 5 pounds of flowable
atrazine/gal). Drexel Atrazine 80W, and Drexel Atrazine 90 DF. Farmco
Atrazine flowable contains 500 g/l. FBC Atrazine 80. AAtrex: 80%
wettable powder, 90% water dispersible granule, and liquified 4L (56).
TYPE: Triazine herbicide
BASIC PRODUCER(S): Shell Chemical Company
One Shell Plaza
P.O. Box 3871
Houston, TX 77001
STATUS: Restricted-use as of 9/1/90
In late 1988, an atrazine management program was proposed to the
U.S. Environmental Protection Agency (EPA) by CIBA-GEIGY and
other registrants (producers) of the herbicide. We are pleased to tell
you that on January 26, 1990, the EPA announced the approval of
the program (with modifications).
Adoption of the management program means that several voluntary
exposure reduction measures will be adopted through changes in the
labels of all atrazine products registered by the EPA.
The resulting benefits will be: a reduction in potential exposure to
the herbicide by farmers and farm workers, a reduction in the
potential for infiltration of the herbicide into groundwater and
surface water, and a general reduction of the volume of the product
released into the environment.
Revised labeling is to be adopted by September 1, 1990, for atrazine
(along with all atrazine-containing products) to be sold for the 1991
use season. There is no requirement that stocks of products
remaining in channels of trade be relabeled. Atrazine-containing
products will become Restricted Use Pesticides (for use only by
certified applicators or persons under their direct supervision)
because of groundwater concerns. Exempt from this would be lawn
care products containing 2% atrazine or less in the formulation.
In announcing acceptance of the program, the EPA said "We
commend the technical manufacturers for their consideration of the
need to reduce exposure to atrazine. The label amendments designed
to reduce groundwater contamination may certainly reduce the
point-source problem. In addition, restriction to use by certified
applicators has the potential to reduce the risk of groundwater
contamination due to mixing/loading, application, and disposal."
The label revisions (in addition to the restricted use classification)
included the following:
1 Users must wear long-sleeve shirts and long pants (or equivalent),
chemical resistant gloves, and water-proofed boots. In addition,
persons involved in mixing and loading operations are required to
use chemical resistant rubber or neoprene gloves and a face shield or
2 Groundwater contamination may be reduced by diking and flooring
of permanent liquid bulk storage sites with an impermeable
3 This product may not be mixed/loaded or used within 50 feet of all
wells, including abandoned wells, drainage wells and sink holes.
4 Postemergence applications to corn and sorghum must be made
before the crops reach 12 inches in height.
5 The maximum application rate for corn and sorghum is three
pounds of active ingredient per acre per calendar year. Applications
of the product for quackgrass suppression in corn and sorghum are
restricted to spring application only. No fall applications are
6 Applications for industrial weed control in noncrop areas may not
exceed a combined maximum of 10 pounds of active ingredient per
acre per calendar year.
7 Do not apply this product through any type of irrigation system.
The use changes adopted by the EPA are similar to those already
implemented under atrazine management programs in Wisconsin
Also, the September will include the deletion of the uses on
pineapples, proso millet and rangeland.
revised labeling that will be sent to the EPA in
1990 will not only reflect the above revisions, but
will include the deletion of the uses on pineapples,
proso millet and rangeland.
PRINCIPAL USES: Atrazine is a widely used selective herbicide for
control of broadleaf and grassy weeds in corn, sorghum,
sugarcane, macadamia orchards, and turf grass sod. It is
used also in some areas for selective weed control in conifer
reforestation and Christmas tree plantations as well as for nonselective
control of vegetation in chemical fallow. Atrazine also is used as a
nonselective herbicide for vegetation control in noncrop land. Sugar-
beets, tobacco, oats, and many vegetable crops are very sensitive to
APPLICATION METHOD(S): Depending upon the crop or intended use,
atrazine sprays may be applied preplant, preemergence, or postemergence,
but before weed seedlings are more than 3.8 cm (1.5 inches) high with
few exceptions. These exceptions include postemergent application for
yellow nutsedge and Canada thistle control. Preemergence use is
generally the preferred method of application where it can be used.
Under dry conditions, a shallow incorporation may increase the degree of
weed control. A single lay-by cultivation is sometimes useful to
prevent relatively tolerant late season grasses from developing. Aerial
applications have been very successful, especially when wet weather
prevents the use of ground equipment and in cases where rough terrain
such as in conifer reforestation makes ground application impractical.
A liquified formulation containing 0.48 kg/l (4 lb ai/gal) has been
developed and is registered for weed control in conifers, corn,
chemical fallow, rangeland, sugarcane, and sorghum. A 90% water
dispersible granular formulation has been registered bearing the full
AAtrex label. Future registration of the 4L formulation is planned on
other crops. Postemergent application of the wettable powder, the
water dispersible granule or liquified formulation of atrazine is usually
made in combination with a nonphytotoxic crop oil, crop oil concentrate
or surfactant. These additions enhance the uptake of atrazine and hence
its activity (58). May be applied to corn in solution with liquid
Important Weeds Controlled:
1. Crop areas - Barnyardgrass, mustards, chickweed, cocklebur,
crabgrass, downy brome, foxtail, jimsonweed, lambsquarters, nutgrass,
quackgrass, purslane, ragweed, velvetleaf, wild oats, and many others.
2. Total vegetation control - The above weeds plus bindweed, dock,
horsetail, milkweed, mullein, orchardgrass, plantain, quackgrass,
leafy spurge, Canada thistle, and many others (8b).
Moisture activates the chemical. Usually considered more toxic
than the other triazines. Will not control Johnsongrass or Bermudagrass.
Corn completely metabolizes it, not being injured. Effective on most
annual broadleaves for about three months. Resembles simazine, but is
faster acting under low rainfall conditions. Proven and used in all
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C8 H14 Cl N5 (62)
MOLECULAR WEIGHT: 215.7 (62)
PHYSICAL STATE: Colorless powder (pure compound) (62)
MELTING POINT: 175-177 C (pure compound) (62); 173-175 C (pure
VAPOR PRESSURE: 3.0 x 10-7 mmHg at 20 C (pure compound) (58)
SOLUBILITY: 30 mg/l water at 20 C (pure compound) (62)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: TWA (Time Weighted Average) = 5 mg/m3 (15c)
A. ACUTE TOXICITY
DERMAL: LD50 = >3100 mg/kg (rat, technical material);
>10,200 mg/kg, mild skin irritation (rabbit,
AAtrex 4L); 9300 mg/kg, minimal skin
irritation (rabbit, AAtrex 80W); >10,200
mg/kg, minimal skin irritation (rabbit, AAtrex
ORAL: LD50 = 1869 mg/kg (rat, technical material); 3800
mg/kg (rat, AAtrex 4L); 5100 mg/kg (rat, AAtrex
80W); 1600 mg/kg (rat, AAtrex Nine-O) (56).
INHALATION: LC50 = >6.8 mg/l for 4 hours (rat, AAtrex 4L);
>2 mg/l for 4 hours (rat, AAtrex 80W);
5.2 mg/l for 4 hours (rat, AAtrex Nine-O) (56).
EYES: Non-irritating (rabbit, technical material); mild
eye irritation (rabbit, AAtrex 4L, AAtrex 80W);
minimal eye irritation (rabbit, AAtrex Nine-O) (56).
B. SUBACUTE AND CHRONIC TOXICITY:
No observable ill effects were detected in cattle, dogs, horses or
rats fed a diet which included more than 25 ppm atrazine over extended
Two-year feeding studies in which male and female rats were given
daily dosages of atrazine at various levels, showed no gross or
microscopic signs of toxicity due to ingestion of levels as high as 100
ppm in the total diet (58).
IV. ENVIRONMENTAL CONSIDERATIONS
Behavior In or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Atrazine is more readily adsorbed on muck or clay soils than on
soils of low clay and organic matter content. The downward
movement or leaching is limited by its adsorption to certain soil
constituents. Adsorption is not irreversible and desorption often
occurs readily, depending on such factors as temperature,
moisture, and pH. Atrazine normally is not found below the upper
foot of soil in detectable quantities, even after years of
2. Microbial breakdown: Microbial activity possibly accounts for
decomposition of a significant portion of atrazine in the soil. A
range of soil microorganisms can utilize it as a source of energy
and nitrogen. The effect of atrazine on these and other organisms
appears to be small.
3. Loss from photodecomposition and/or volatilization: The
significance of photodecomposition and/or volatilization of
atrazine from soil is not fully understood. Available data
indicate that both occur to some extent if high temperatures and
prolonged sunlight follow application before precipitation, but
that these factors are of little significance in atrazine
dissipation under most field conditions. Atrazine is more subject
to UV and volatility losses than simazine, but probably about
equal or less subject to these losses compared to the commercial
methylmercapto- or methoxytriazines.
4. Resultant average persistence at recommended rates: The residual
activity of atrazine in soil at selective rates for specific soil
types is such that most rotational crops can be planted 1 year
after applications, except under an arid or semiarid climate.
Atrazine will persist longer under dry and cold conditions or
conditions not conducive to maximum chemical or biological
activity. Broadcast rates needed in some of the finer and
relatively higher organic matter soils of the north central states
result in enough residue carryover, under some conditions, to
injure small grains, alfalfa, and soybeans planted 12 months
later. Plant removal and chemical alteration are also factors in
Toxicological investigations conducted with bobwhite quail,
mallard ducks, goldfish, rainbow trout, and bluegill sunfish have shown
atrazine to have a very low toxicity to these species (58).
Acute toxicity to fish and wildlife - AAtrex 80W
Fish species 96-hr LC50 (ppm)
Rainbow trout 4.5
Bluegill sunfish >24
Bird species 8-day Dietary LC50 (ppm)
Bobwhite quail 5,760
Mallard duck 19,650 (58)
V. EMERGENCY AND FIRST AID PROCEDURES
The chemical information provided below has been condensed
from original source documents, primarily from "Recognition and
Management of Pesticide Poisonings", 3rd ed. by Donald P. Morgan,
which have been footnoted. This information has been provided in
this form for your convenience and general guidance only. In
specific cases, further consultation and reference may be required
and is recommended. This information is not intended as a sub-
stitute for a more exhaustive review of the literature nor for the
judgement of a physician or other trained professional.
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
KNOWN OR SUSPECTED ADVERSE EFFECTS: Some triazines are mildly
irritating to skin, eyes, and upper respiratory tract. Systemic
toxicity is unlikely unless very large amounts have been ingested (25).
SKIN CONTACT: Wash contaminated skin with soap and water (25).
INGESTION: Ingestions of small amounts (less than 10 mg/kg
body weight) occurring less than an hour before treatment, are probably
best treated by: Syrup of Ipecac, followed by 1-2 glasses of water.
Dose for adults and children over 12 years: 30 ml. Dose for children
under 12 years: 15 ml (25).
EYE CONTACT: Flush contaminated eyes with copious amounts of
fresh water for 15 minutes (25).
NOTES TO PHYSICIAN:
INGESTIONS of LARGE amounts (more than 10 mg/kg) occurring less than an
hour before treatment, should probably be treated by gastric lavage:
A. INTUBATE stomach and ASPIRATE contents.
B. LAVAGE stomach with slurry of ACTIVATED CHARCOAL in 0.9% saline.
Leave 30-50 gm activated charcoal in the stomach before
C. SODIUM SULFATE, 0.25 mg/kg in tap water, as a cathartic.
CAUTION: Hydrocarbons (kerosene, petroleum distillates) are
included in some formulations of these chemicals.
Ingestion of very LARGE AMOUNTS may cause CNS
depression. In this case, IPECAC IS CONTRAINDICATED.
Also, gastric intubation incurs a risk of HYDROCARBON
PNEUMONITIS. For this reason observe the following
(1) If the victim is unconscious or obtunded and
facilities are at hand, insert an ENDOTRACHEAL TUBE
(cuffed, if available) prior to gastric intubation.
(2) Keep victim's head BELOW LEVEL OF STOMACH during
intubation adn lavage (Trendelenburg, or left
lateral decubitus, with head of table tipped
downward). Keep victim's head turned to the left.
(3) ASPIRATE PHARYNX as regularly as possible to remove
gagged or vomited stomach contents.
INGESTIONS occurring MORE THAN an HOUR before treatment are probably
best treated only by ACTIVATED CHARCOAL, 30-50 gm and SODIUM or
MAGNESIUM SULFATE, 0.25 gm/kg, as described above.
There are no specific antidotes for these chemicals. Because
manifestations of toxicity do occasionally occur in peculiarly
predisposed individuals, MAINTAIN CONTACT with victim for at least 72
hours so that unexpected adverse effects can be treated promptly (25).
VI. FIRE AND EXPLOSION INFORMATION
Compatible with most other pesticides and fertilizers when used at
normal rates. Noncorrosive under normal use conditions (58).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Harmful if swallowed. Avoid contact with eyes,
prolonged contact with skin, inhalation of dust. Use with adequate
ventilation. Do not contaminate food, feed, or water supplies (56).
Very stable over several years of shelf life, with only slight
sensitivity to natural light and extreme temperatures which would occur
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
8b. Thomson, W.T. 1981. Agricultural chemicals - book 2:
herbicides. Revised ed. Thomson Publications, Fresno, CA.
15c. American Conference of Governmental Industrial Hygienists. 1984.
TLVs: threshold limit values for chemical substances and
physical agents in the work environment and biological exposure
indices with intended changes for 1984-85. Cincinnati, OH.
25. Morgan, D.P. 1982. Recognition and management of pesticide
poisonings, 3rd ed. U.S. Environmental Protection Agency,
Washington, DC. 120 pp.
56. Farm Chemicals Handbook, 70th ed. 1984. R. T. Meister, G. L.
Berg, C. Sine, S. Meister, and J. Poplyk, eds. Meister
Publishing Co., Willoughby, OH.
58. Weed Science Society of America, Herbicide Handbook Committee.
1983. Herbicide handbook of the weed science society of
America, 5th ed. Weed Science Society of America, Champaign,
IL. 515 pp.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.