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
Assessment Program.
| |
Pesticide
Information
Profile
|
Dicamba
Publication Date: 9/93
|
|
TRADE OR OTHER NAMES
Metambane, Dianat, Banfel, Banvel, Banvel CST, Banvel D, Banvel XG,
Mediben.
REGULATORY STATUS
Products containing dicamba must bear the signal word "Warning"
(10).
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 (3, 5). In combination with
a phenoxyalkanoic acid or other herbicide, dicamba is used in pastures,
range land, and non-crop areas (fence-rows, roadways and wastage) to
control weeds (1).
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Dicamba is moderately toxic by ingestion and slightly toxic by
inhalation or dermal exposure (11). 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 (2, 3). In addition to these symptoms,
inhalation can cause irritation of the linings of the nasal passages and
the lungs, and loss of voice (11). Most individuals who have survived
severe poisoning from dicamba have recovered within 2 to 3 days with no
permanent effects (11).
Dicamba is very irritating and corrosive and can cause severe and
permanent damage to the eyes (11, 14). Running water should be flushed
through the eyes for at least 15 minutes if any dicamba is splashed into
them (5). The eyelids may swell and the cornea may be cloudy for a week
after dicamba is splashed in the eyes (3).
In some individuals, dicamba is a skin sensitizer (5). It may
cause skin burns (15). There is no evidence that dicamba is absorbed
into the body through the skin (3).
The amount of a chemical 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 dicamba in rats is 757 to
1,707 mg/kg, 1190 mg/kg in mice, 2000 mg/kg in rabbits, and 566 to 3,000
mg/kg in guinea pigs (3, 10). The dermal LD50 in rabbits is greater
than 2,000 mg/kg (10). 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
inhalation LC50 for dicamba in rats is greater than 200 mg/l (11).
CHRONIC TOXICITY
Chronic exposure can lead to the development of the same symptoms
as described for acute exposure.
Doses of 500 ppm (25 mg/kg) in the diet administered to rats for a
2-year interval produced no observable effects on survival, body weight,
food consumption, organ weight, blood chemistry, or tissue structure (3,
13). A 2-year chronic feeding study in rats at dietary doses up to 25
mg/kg/day did not affect survival (2).
The EPA has established a Lifetime Health Advisory (LHA) level of
200 micrograms per liter (ug/l) for dicamba in drinking water. This
means that EPA believes that water containing dicamba at or below this
level is acceptable for drinking every day over the course of one's
lifetime, and does not pose any health concerns. However, consumption
of dicamba at high levels well above the LHA level over a long period of
time has been shown to cause adverse health effects in animal studies,
including changes in the liver and a decrease in body weight (12).
Reproductive Effects
In a 3-generation study, dicamba did not affect the reproductive
capacity of rats (3). When rabbits were given doses of 0, 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.
EPA has set the NOAEL for this study at 3 mg/kg/day (11, 13).
Teratogenic Effects
Dicamba is suspected of being a human teratogen. No teratogenic
effects have been shown in lab animals such as rabbits and rats (14).
Mutagenic Effects
Dicamba has not been shown to be a mutagen (8, 13).
Carcinogenic Effects
Data from laboratory studies are inadequate for EPA to determine if
dicamba can increase the risk of cancer in humans (12). Rats fed up to
25 mg dicamba/kg/day for 2 years showed no increased incidence of tumors
(13).
Organ Toxicity
In mice, some enlargement of liver cells has occurred. A similar
effect has not been shown in man.
Fate in Humans and Animals
Dicamba was excreted rapidly by rats, mainly in the urine, when
administered orally or subcutaneously. One to 4% was excreted in the
feces (3). 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 (13). Like most organic
acids, dicamba is joined to glycine (8), or glucuronic acid (6) in the
liver.
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 (3). It is
therefore concluded that dicamba does not bioaccumulate in mammalian
tissues.
Following an attempted suicide with a mixture of dicamba and 2,4-D,
dicamba levels in the blood serum and urine of the victim became
undetectable within 2 weeks (3).
ECOLOGICAL EFFECTS
Effects on Birds
Dicamba is only slightly toxic to birds. The LD50 for technical
dicamba in mallard ducks is 2,009 mg/kg. The 8-day dietary LC50 in
mallards and in bobwhite quail is greater than 10,000 ppm (2).
Effects on Aquatic Organisms
Dicamba is of low toxicity to fish (2, 5). 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 96-hour LC50 for technical dicamba in rainbow trout is
135.4 mg/l, 135.3 mg/l in bluegill sunfish, greater than 100.0 mg/l in
grass shrimp, and greater than 180.0 mg/l in fiddler crab and sheepshead
minnow (2). The 48-hour LC50 for dicamba in rainbow trout is 35 mg/l,
40 mg/l in bluegill, 465 mg/l in carp (10), and 110.7 mg/l in Daphnia
magna, a small freshwater crustacean (2).
Effects on Other Animals (Nontarget species)
When used according to the instructions, dicamba poses little
threat to wildlife. Dicamba is not toxic to bees (10).
ENVIRONMENTAL FATE
Breakdown of Chemical in Soil and Groundwater
Dicamba does not bind to soil particles (Koc = 2 g/ml) (4) and is
highly soluble in water. It is therefore highly mobile in the soil and
may contaminate groundwater. Its leaching potential increases with
precipitation and the volume applied.
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 (2).
Dicamba slowly breaks down in sunlight (2). Volatilization from
soil surfaces is probably not significant, but some volatilization may
occur from plant surfaces (7). It is stable to water and other
chemicals in the soil (8). In humid areas, dicamba will be leached from
the soil in 3-12 weeks. The half-life if dicamba in soil has varied
from 4 to 555 days with the typical half-life being 1 to 4 weeks. Under
conditions suitable to rapid metabolism, the half-life is less than 2
weeks (7). At an application rate of 6.7 kg/HA, no dicamba remained in
the soil after one year.
Breakdown of Chemical 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 (7).
Breakdown of Chemical 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 (2, 3, 8). Desirable
broadleaf plants (such as fruit trees, tomatoes, etc.) may be harmed
during their growth and development stages (9).
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 (2).
PHYSICAL PROPERTIES AND GUIDELINES
Pure dicamba is an odorless, white crystalline solid. The
technical acid is a pale buff crystalline solid. The technical material
is stable and resistant to hydrolysis and oxidation under normal
conditions (2, 3).
Dicamba is stable under normal temperatures and pressures, but it
may pose a slight fire hazard if exposed to heat or flame. It poses a
fire and explosion hazard in the presence of strong oxidizers. Thermal
decomposition of dicamba will release toxic and corrosive fumes of
chlorides and toxic oxides of carbon (11).
Spills or other releases of 1,000 pounds (454 kg) or more of
dicamba must be reported to the National Response Center: (800) 424-8802.
Dicamba is volatile and presents a drift hazard.
Occupational Exposure Limits:
No occupational exposure limits have been established for dicamba
by OSHA, NIOSH or ACGIH (11).
Physical Properties
| CAS #: | 1918-00-9 |
| Specific gravity: | 1.57 at 25 degrees C (11) |
| Solubility in water: | Highly soluble; 500,000 ug/ml (4) |
| Solubility in other solvents: |
| Solvent | Solubility at 25 degrees C |
| Acetone | 810 g/L (5) |
| Dichloromethane | 260 g/L (5) |
| Dioxane | 1.18 kg/L (5) |
| Ethanol | 922 g/L (5) |
| Toluene | 130 g/L (5) |
| Xylene | 8 g/L (5) |
|
| Dicamba is an acid that forms water soluble salts: | Sodium salts - 360 g.a.e./L; Potassium salts - 480 g.a.e./L; Dimethylammonium - 720 g.a.e./L. |
| Melting point: | 114-116 degrees C (237-241 degrees F) (10). |
| Flash point: | 390 degrees F (199 degrees C) (11) |
| Decomposition temperature: | decomposes at approx. 392 degrees F (200 degrees C) (11) |
| Vapor pressure: | 3.75 x 10 to the minus 3 power mm Hg at 100 degrees C (5); Zero (4) |
| Oil: | water partition coefficient: |
| Koc: | 2 g/ml (4) |
| Odor threshold: | 250.8 ppm (6) |
| Chemical class/use: | phenoxy herbicide; benzoic acid derivative; carboxylic acid |
BASIC MANUFACTURER
Sandoz Crop Protection Corp.
1300 E. Touhy Ave.
Des Plaines, IL 60018
Review by Basic Manufacturer
Comments solicited: October, 1992
Comments received:
REFERENCES
Meister, R.T. (ed.) 1987. Farm Chemicals Handbook. Willoughby,
OH: Meister Publishing Co.
WSSA Herbicide Handbook Committee. 1989. Herbicide Handbook of
the Weed Science Society of America, 6th Ed. WSSA, Champaign, IL.
Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of Pesticide
Toxicology, Vol. 3, Classes of Pesticides. Academic Press, Inc., NY.
U. S. Department of Agriculture, Soil Conservation Service. 1990
(Nov.). SCS/ARS/CES Pesticide Properties Database: Version 2.0
(Summary). USDA - Soil Conservation Service, Syracuse, NY.
Worthing, C.R. (ed.). 1987. The pesticide manual: A world
compendium. 8th Ed. British Crop Protection Council. Croydon,
England.
Hayes, Wayland, Jr. 1982. Pesticides Studies in Man. Baltimore,
MD: Williams & Wilkins.
Howard, P.H. (ed.). 1989. Handbook of Environmental Fate and
Exposure Data for Organic Chemicals, Vol. III: Pesticides. Lewis
Publishers, Chelsea, MI.
Hartley, D. and H. Kidd, (eds.) 1983. The agrochemicals handbook.
Nottingham, England: Royal Society of Chemistry.
Crop Protection Chemicals Reference. 1986. 2nd Ed. New York:
Chemical and Pharmaceutical Pub. Corp.
Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister
Publishing Company, Willoughby, OH.
Occupational Health Services, Inc. 1991 (Feb. 21). MSDS for
Dicamba. OHS Inc., Secaucus, NJ.
U.S. Environmental Protection Agency. 1989 (Jan.). Health
Advisory Summary: Dicamba. US EPA, Washington, DC.
_____. 1988 (Aug.). Dicamba: Health Advisory. Office of
Drinking Water, US EPA, Washington, DC.
Hallenbeck, W.H. & K.M. Cunningham-Burns. 1985. Pesticides and
Human Health. New York: Springer-Verlag.
Department of Transportation. 1984. Emergency Response
Guidebook: Guidebook for hazardous materials incidents. Washington,
DC: U.S. DOT.
TOXNET. 1985. National library of medicine's toxicology data
network. Hazardous Substances Databank. Public Health Service.
National Institute of Healtyh. U.S. Department of Health and Human
Services. Bethesda, MD: NLM.
Gosselin, R.E. 1984. Clinical Toxicology of Commercial Products.
5th Ed. Baltimore, MD: Williams & Wilkins.
Disclaimer: Please read
the pesticide label prior to use. The information contained at this web
site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
To Top
For more information relative to pesticides and their use, please contact the PMEP staff at:
Pesticide Safety Education Pgm.
5123 Comstock Hall
Cornell University
Ithaca, NY 14853-0901
(607) 255-1866 |
Pesticide Sales & Use Reporting Database Grp.
Cornell University
20 Thornwood Dr. #106
Ithaca, NY 14850
(607) 257-5706 |
|
 |
This site is supported, in part, by funding from the
 |
Questions regarding the development of this web site should be directed to the
PMEP Webmaster
