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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Dicamba

Trade and Other Names: Trade names include Banfel, Banvel, Banvel CST, Banvel D, Banvel XG, Dianat, Dicazin, Fallowmaster, Mediben, Metambane, Tracker, and Trooper.

Regulatory Status: The EPA has classified this General Use Pesticide (GUP) as toxicity class III - slightly toxic. Products containing dicamba bear the Signal Word WARNING. This is because of its irritating, corrosive effect on skin and eyes.

Chemical Class: benzoic acid compound

Introduction: Dicamba is a benzoic acid herbicide. It can be applied to the leaves or to the soil. Dicamba controls annual and perennial broadleaf weeds in grain crops and grasslands, and it is used to control brush and bracken in pastures. It will kill broadleaf weeds before and after they sprout. Legumes will be killed by dicamba. In combination with a phenoxyalkanoic acid or other herbicide, dicamba is used in pastures, range land, and non-crop areas such as fence-rows and roadways to control weeds.

Formulation: Not Available

Toxicological Effects:

• Acute toxicity: Dicamba is slightly toxic by ingestion and slightly toxic by inhalation or dermal exposure [7]. The oral LD50 for dicamba is 757 to 1707 mg/kg in rats, 1190 mg/kg in mice, 2000 mg/kg in rabbits, and 566 to 3000 mg/kg in guinea pigs [1,6]. The dermal LD50 in rabbits is greater than 2000 mg/kg (7). The inhalation LC50 for dicamba in rats is greater than 200 mg/L [7]. Symptoms of poisoning with dicamba include loss of appetite (anorexia), vomiting, muscle weakness, slowed heart rate, shortness of breath, central nervous system effects (victim may become excited or depressed), benzoic acid in the urine, incontinence, cyanosis (bluing of the skin and gums), and exhaustion following repeated muscle spasms [1,5]. In addition to these symptoms, inhalation can cause irritation of the linings of the nasal passages and the lungs, and loss of voice [7]. Most individuals who have survived severe poisoning from dicamba have recovered within 2 to 3 days with no permanent effects [7]. Dicamba is very irritating and corrosive, and can cause severe and permanent damage to the eyes [7]. The eyelids may swell and the cornea may be cloudy for a week after dicamba is splashed in the eyes [1]. In some individuals, dicamba is a skin sensitizer and may cause skin burns [7]. There is no evidence that dicamba is absorbed into the body through the skin [1].
• Chronic toxicity: Doses of 25 mg/kg/day in the diet administered to rats for 2 years produced no observable effects on survival, body weight, food consumption, organ weight, blood chemistry, or tissue structure [1,5,11]. Consumption of dicamba at high levels over a long period of time has been shown to cause changes in the liver and a decrease in body weight in rats [1,5,11]. In mice, some enlargement of liver cells has occurred [1].
• Reproductive effects: In a three-generation study, dicamba did not affect the reproductive capacity of rats [1]. When rabbits were given doses of 0.5, 1, 3, 10, or 20 mg/kg/day of technical dicamba from days 6 through 18 of pregnancy, toxic effects on the mothers, slightly reduced fetal body weights, and increased loss of fetuses occurred at the 10 mg/kg dose [5,10]. These data suggest that dicamba is unlikely to cause reproductive effects in humans at expected exposure levels.
• Teratogenic effects: No teratogenic effects have been shown in lab animals such as rabbits and rats exposed to dicamba [36].
• Mutagenic effects: Dicamba has not been shown to be a mutagen [5,10].
• Carcinogenic effects: Rats fed up to 25 mg dicamba/kg/day for 2 years showed no increased incidence of tumors [5,10]. This evidence suggests that dicamba is not carcinogenic.
• Organ toxicity: Chronic exposure can lead to the development of the same symptoms as described for acute exposure.

• Fate in humans and animals: Dicamba was excreted rapidly by rats, mainly in the urine, when administered orally or subcutaneously; 1 to 4% was excreted in the feces [1]. Mice, rats, rabbits, and dogs excreted 85% of an oral dose as unmetabolized dicamba in the urine within 48 hours of dosing. Eventually, between 90 and 99% of the dose was excreted unmetabolized in the urine. This indicates that dicamba is rapidly absorbed into the bloodstream from the gastrointestinal tract [10]. When dicamba was ingested daily in the feed, the concentrations in different organs reached a steady state within 2 weeks. When daily intake stopped, storage in the organs declined rapidly [1]. It is therefore concluded that dicamba does not bioaccumulate in mammalian tissues.

Ecological Effects:

• Effects on birds: Dicamba is practically nontoxic to birds. The LD50 for technical dicamba in mallard ducks is 2009 mg/kg. The 8-day dietary LC50 in mallards and in bobwhite quail is greater than 10,000 ppm [5,7].

• Effects on aquatic organisms: Dicamba is of low toxicity to fish [5,7]. The LC50 (96-hour) for technical dicamba is 135 mg/L in rainbow trout and bluegill sunfish, greater than 100 mg/L in grass shrimp, and greater than 180 mg/L in fiddler crab and sheepshead minnow [5]. The LC50 (48-hour) for dicamba is 35 mg/L in rainbow trout, 40 mg/L in bluegill, 465 mg/L in carp, and 110 mg/L in Daphnia magna, a small freshwater crustacean [5,7].
• Effects on other organisms: Dicamba poses little threat to wildlife. Dicamba is not toxic to bees [7].

Environmental Fate:

• Breakdown in soil and groundwater: Dicamba is moderately persistent in soil. The half-life of dicamba in soil is typically 1 to 4 weeks [21]. Under conditions suitable for rapid metabolism, the half-life is less than 2 weeks [20]. Metabolism by soil microorganisms is the major pathway of loss under most soil conditions. The rate of biodegradation increases with temperature and increasing soil moisture, and tends to be faster when soil is slightly acidic. When soil moisture increases above 50%, the rate of biodegradation declines [5]. Dicamba slowly breaks down in sunlight [5]. Volatilization from soil surfaces is probably not significant, but some volatilization may occur from plant surfaces [20]. It is stable to water and other chemicals in the soil [6]. Dicamba does not bind to soil particles and is highly soluble in water. It is therefore highly mobile in the soil and may contaminate groundwater [21]. In humid areas, dicamba will be leached from the soil in 3-12 weeks [20].
• Breakdown in water: In water, microbial degradation is the main route of dicamba disappearance. Photolysis may also occur. Aquatic hydrolysis, volatilization, adsorption to sediments, and bioconcentration are not expected to be significant [20].
• Breakdown in vegetation: Dicamba is rapidly taken up by the leaves and roots of plants, and it is readily translocated to other plant parts. It some plant species, dicamba accumulates in the tips of mature leaves [5]. Desirable broadleaf plants such as fruit trees and tomatoes may be harmed during their growth and development stages [5]. Residues of dicamba on treated plants can disappear through exudation from the roots into the surrounding soil, metabolism within the plant, or by loss from leaf surfaces [5].

Physical Properties:

• Appearance: Pure dicamba is an odorless, white crystalline solid. The technical acid is a pale buff crystalline solid [6].
• Chemical Name: 3,6-dichloro-O-anisic acid [6]
• CAS Number: 1918-00-9
• Molecular Weight: 221.04
• Water Solubility: 6500 mg/L @ 25 C [6]
• Solubility in Other Solvents: acetone s.; dichloromethane s.; dioxane v.s.; ethanol s.; toluene s.; xylene s. [6]
• Melting Point: 114-116 C [6]
• Vapor Pressure: 4.5 mPa @ 25 C [6]
• Partition Coefficient: -0.5376 [5]
• Adsorption Coefficient: 2 (salt) [21]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.03 mg/kg/day [31]
• PEL: Not Available
• HA: 0.2 mg/L [10]
• TLV: Not Available

Basic Manufacturer:

Sanex, Inc.
5300 Harvester Road
Burlington, Ontario
L7L 5N5 Canada

• Phone: 905-639-7535
• Emergency: Not Available
  

References:

References for the information in this PIP can be found in Reference List Number 7

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.