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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 Assessment Program.


Publication Date: 9/93


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 applicators.



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 toxicological effects.

Reproductive Effects

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 doses.

Teratogenic Effects

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.

Mutagenic Effects

Cyanazine is not mutagenic.

Carcinogenic Effects

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 animals.

Organ Toxicity

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 fat (6).

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 inhibiting photosynthesis.

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.


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.

Exposure Guidelines:

NOEL: 1.25 mg/kg/day (6)
ADI: 0.0013 mg/kg/day (6)
Drinking water
health advisory:
Drinking Water Equivalent Level (DWEL): 0.013 mg/L (child); 0.046 mg/L (adult) (6)

Physical Properties:

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)
Koc: 190


Du Pont Agricultural Products
Walker's Mill, Barley Mill Plaza
P.O. Box 80038
Wilmington, Deleware 19880
Telephone 800-441-7515

Review by Basic Manufacturer:

Comments solicited: November, 1992
Comments received: November, 1992


  1. Bucher, K.H., ed., and Holmwood, G.M. 1983. Chemistry of Pesticides. John Wiley & Sons.
  2. Environmental Protection Agency. Office of Pesticide Programs. Pesticide Fact Sheet on Cyanazine. No. 41. Dec. 31, 1984.
  3. Hance, R.J., ed. 1980. Interactions Between Herbicides and the Soil. Academic Press.
  4. Occupational Health Services. Material Safety Data Sheet on Cyanazine. 3/17/87 OHS: NY.
  5. Rao, K.S. and Dad, N.K. Studies of herbicide toxicity in some freshwater fishes and ectoprocta. J. Fish. Bio. 14: 517-522, 1979.
  6. U.S. Environmental Protection Agency. Office of Drinking Water. "Cyanazine Health Advisory." Draft Report. August 1987.
  7. U.S. Environmental Protection Agency. Office of Pesticides and Toxic Substances. Cyanazine. Special Review Position. Document 1. Washington DC, April 1985.
  8. Windholz, M., et al., eds. Cyanazine. The Merck Index. 10th edition. p.384. Rahway, NJ: Merck & Co., 1983.
  9. Walker, M.M. and L.H. Keith. 1992. EPA's Pesticide Fact Sheet Database. Lewis Publishers, Chelsea, MI.