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
Trade names include Bladex, DW3418, Fortrol,and Payze. Cyanazine may
be used in combinbation with other herbicides.
Cyanazine is a triazine herbicide used as a pre and postemergent to
control annual grasses and broadleaf weeds. By 1985 ninety-six percent of
cyanazine was used on corn, three percent on cotton, and less than one
percent on grain sorghum and wheat fallow (7).
Cyanazine is classified by the EPA as a Restricted Use Pesticide (RUP)
because of its teratogenicity and because it has been found in groundwater
(9). Restricted Use Pesticides may be purchased and used only by certified
Cyanazine is moderately toxic to mammals. Wettable powder and liquid
formulations are labeled with a WARNING signal word while granular
formulations are labeled with a CAUTION signal word. The oral LD50 for
rats ranges from 182 mg/kg to 332 mg/day. The oral LD50 is 380 mg/kg for
mice and 141 mg/kg for rabbits (4). Poisoned animals have labored
breathing and blood in their saliva (4). The pesticide also causes
inactivity and depression in laboratory animals. The dermal LD50 in
rabbits treated with technical cyanazine is greater than 2,000 mg/kg, and
the dermal LD50 in rats is greater than 1,200 mg/kg (6).
Rats fed very low doses (1.25 mg/kg) for two years showed no
In a long-term study of rats fed cyanazine, moderate doses resulted in
decreased weight gain in the parents and increased brain weights and
decreased kidney weights in third generation offspring (6). Toxic effects
on the fetus were also observed in experiments on rabbits using comparable
Cyanazine can cause a wide range of birth defects in animals over a
wide range of doses. When female rats were fed cyanazine through a stomach
tube during the sensitive period of pregnancy, they ate less food and their
fetuses had incomplete bone development. At the higher doses, fetuses
showed cleft palates and the absence of, or underdeveloped eyeballs (6).
Other birth defects include abnormalities in diaphragm development and
changes in the brain. Birth defects have been observed in the offspring of
pregnant rats fed cyanazine during gestation at doses as low as 1 mg/kg.
Cyanazine is not mutagenic.
It is not likely that cyanazine poses a cancer threat to mammals. A
study evaluated the carcinogenicity of the compound in mice and found, up
to the maximum dose tested (50 mg/kg), no evidence of cancer in the
One effect of cyanazine in animals is the depression of the central
nervous system. In addition, several long term feeding studies in rats and
mice at moderate doses (up to 225 mg/kg) showed that cyanazine decreases
body weight gain and increases liver weights (6).
Fate in Humans and Animals
Low doses of cyanazine fed to rats, dogs, and cows are rapidly
absorbed from the gastro-intestinal tract. In a study on rats and dogs,
much of the cyanazine ingested was eliminated from animals within four days
(6). There is some tendency for the compound to accumulate in animal
tissue. Cyanazine can accumulate in the brain, liver, kidney, muscle, and
Cows fed very low amounts of cyanazine in their daily ration
eliminated up to 88 percent of the cyanazine in urine and feces within 21
days. The concentration in cows' milk was very low, 0.022 ppm (6).
Cyanazine is only slightly toxic to birds, fish and aquatic
invertebrates (4, 5). The LC50 for cyanazine in harlequin fish is 10 mg/l,
and 18 mg/l in sheepshead minnow (8). It is non-toxic to bees. Mallards
are only slightly affected by the compound. The LC50 in mallards is in
excess of 2,000 mg/kg. Cyanazine, however, is moderately toxic to quail
with an LC50 of 400 mg/kg.
When applied to the soil, cyanazine is absorbed by the roots and is
translocated up the plant into the leaves. This herbicide works by
Cyanazine can be transported in runoff, sediment and water, and it can
leach through the soil to the groundwater. Cyanazine has been found in
numerous groundwater samples at very low concentrations (1 - 80 ppb) (6).
The EPA does not consider cyanazine to have significant groundwater
contamination potential, but a groundwater advisory statement on cyanazine
product labels is required because of reported contamination.
Cyanazine quickly degrades in many soil types (7) mostly due to the
action of microbes. Applied at 5 to 10 ppm, cyanazine has a half-life of 2
to 4 weeks in an air-dried sandy clay loam, 7 to 10 weeks in a sandy loam
soil, 10 to 14 weeks in a clay soil, and 9 weeks in a fresh sandy clay
soil. In all four soils, three degradation products were identified (6).
This chemical undergoes slight decomposition by sunlight. The rate of
evaporation of cyanazine from soil is very slow.
PHYSICAL PROPERTIES AND GUIDELINES
Cyanazine is a member of the s-triazine chemical family. Its
molecular weight is 240.73. This odorless, white crystalline solid is
incompatible with metals.
|NOEL: ||1.25 mg/kg/day (6)
|ADI: ||0.0013 mg/kg/day (6)
|Drinking water |
|Drinking Water Equivalent Level (DWEL): 0.013 mg/L (child); 0.046 mg/L (adult) (6)
|CAS #: ||21725-46-2
|Solubility in water: ||171 mg/L at 25 degrees C (8)
|Solubility in solvents: ||soluble in benzene, chloroform, alcohol, and hexane. Slightly soluble (<10%) in xylene, ethanol, chlorobenzene. Soluble (21%) in chlorofor and methyl-cyclohexanone.
|Melting point: ||(167 degrees C) (4)
|Vapor pressure: ||1.6 X 10 to the minus 9 power mm Hg (8) to 7.5 x 10 to the minus 9 power mm Hg at 20 degrees C (6)
|Kow: ||2.24 (6)
Du Pont Agricultural Products
Walker's Mill, Barley Mill Plaza
P.O. Box 80038
Wilmington, Deleware 19880
Review by Basic Manufacturer:
Comments solicited: November, 1992
Comments received: November, 1992
Bucher, K.H., ed., and Holmwood, G.M. 1983. Chemistry of Pesticides.
John Wiley & Sons.
Environmental Protection Agency. Office of Pesticide Programs.
Pesticide Fact Sheet on Cyanazine. No. 41. Dec. 31, 1984.
Hance, R.J., ed. 1980. Interactions Between Herbicides and the Soil.
Occupational Health Services. Material Safety Data Sheet on Cyanazine.
3/17/87 OHS: NY.
Rao, K.S. and Dad, N.K. Studies of herbicide toxicity in some
freshwater fishes and ectoprocta. J. Fish. Bio. 14: 517-522, 1979.
U.S. Environmental Protection Agency. Office of Drinking Water.
"Cyanazine Health Advisory." Draft Report. August 1987.
U.S. Environmental Protection Agency. Office of Pesticides and Toxic
Substances. Cyanazine. Special Review Position. Document 1. Washington
DC, April 1985.
Windholz, M., et al., eds. Cyanazine. The Merck Index. 10th edition.
p.384. Rahway, NJ: Merck & Co., 1983.
Walker, M.M. and L.H. Keith. 1992. EPA's Pesticide Fact Sheet
Database. Lewis Publishers, Chelsea, MI.