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Cacodylic Acid

Publication Date: 9/93

TRADE OR OTHER NAMES

Ansar 138, Arsan, Bolls-Eye, Broadside, Check-Mate, Cotton Aide HC, Moncide, Montar, Phytar, Phytar 138, Phytar 600, Rad-E-Cate 25, Dilic, Silvisar 510, Sylvicor.

REGULATORY STATUS

Products containing cacodylic acid must bear the signal word "Caution" (3).

INTRODUCTION

Cacodylic acid is an arsenical non-selective contact herbicide which will defoliate or desiccate a wide variety of plant species (6). It is used as a cotton defoliant and for lawn renovation, for weed control in non-crop areas such as around buildings, near perennial ornamentals, along fence rows, and in forest management. Its phytotoxic properties are quickly inactivated upon contact with the soil (2). Cacodylic acid is available in concentrated solution formulations (3).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Cacodylic acid is toxic by inhalation and moderately toxic by ingestion. It is absorbed into the bloodstream more readily through inhalation than through ingestion or dermal exposure (4). Arsenate, from the metabolism of cacodylic acid, slows the production of energy by cells (glycosis).

The symptoms of subacute poisoning with arsenicals may include a salty taste, burning in the throat, colicky pains in the stomach and intestines, and garlicky odor of the breath, urine and sweat. In persons exposed to sufficient arsenical dust, the onset of illness is usually characterized by difficult or short breath, with pain in the chest, followed by nausea and diarrhea. Severe arsenic poisoning causes headache, dizziness, vomiting, profuse and watery diarrhea, followed by dehydration, electrolyte imbalance, gradual fall in blood pressure, stupor, convulsions, general paralysis, and possible death within 3 to 14 days (2, 4). Decreased peripheral circulation (blanching or flushing of the skin, especially of the fingers), cirrhosis of the liver, atrophy of the bone marrow, kidney damage, and loss of sensory and motor functions have also been reported. About six weeks after exposure, white bands may appear across the toe and finger nails (4, 5, 12).

Cacodylic acid is irritating to skin or eyes (4). Product formulations may be irritating, depending on their acidity or alkalinity. Blistering or conjunctivitis may occur (10, Grant. Tox. of the Eye 1974).

Breathing the spray mist is a common means of exposure to cacodylic acid (1). Fires may produce irritating and/or poisonous gases if cacodylic acid is burned (8).

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 cacodylic acid in rats is 644 to 830 mg/kg (2, 3, 4). 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 cacodylic acid in rats is 3900 mg/m3 (4).

CHRONIC TOXICITY

Signs of chronic arsenic poisoning include loss of appetite, weight loss, weakness, nausea, alternating diarrhea and constipation, colic, pain and tenderness in the limbs (usually starting in the fingers or toes), dermatitis, abnormal changes in skin color, loss of hair, giddiness and headache. Prolonged exposure may cause gradual mental and physical deterioration. There may be disturbances of sight, taste, smell and bladder function (4). Prolonged or repeated exposure of the skin to arsenicals may cause dermatitis. Prolonged eye contact may cause conjunctivitis and has caused eruptions of eyelids, conjunctiva and even the cornea. Repeated exposure to low levels of arsenic may produce increased tolerance for arsenic (4).

Reproductive Effects

Feeding lab animals large amounts of cacodylic acid for extended periods of time has decreased fertility. Male rats fed 226 mg/kg for 3 weeks showed reduced sperm production (2).

Teratogenic Effects

Oral doses to pregnant rats and mice have produced toxic effects and developmental changes in the embryos (4).

Mutagenic Effects

No information found. for mammals. Cacodylic acid does have an effect similar to colchicine, a chemical used to induce multiplication of the number of chromosomes in plants (6).

Carcinogenic Effects

Exposure to arsenic has been associated with increased incidence of skin and other cancers (4). It may cause lung carcinomas (cancer) (5). No information was found on carcinogenic effects of cacodylic acid.

Organ Toxicity

Cacodylic acid affects a variety of organ systems. The kidney, liver, heart, digestive tract, and central and peripheral nervous systems are all targets. Arsenic will accumulate in finger or toe nails, skin and hair (4, 5).

Fate in Humans and Animals

Most arsenicals including cacodylic acid are readily absorbed into the bloodstream when ingested. It is metabolized (broken down) in the liver. It accumulates in the skin, finger/toe nails and hair which also serves as a means of excretion (5).

ECOLOGICAL EFFECTS

Effects on Birds

No information found.

Effects on Aquatic Organisms

Cacodylic acid presents a low toxicity hazard to most fish (6). The LC50 for cacodylic acid in bluegill sunfish is 1000 ppm (0.1% of the water) (6).

Effects on Other Animals (Nontarget species)

Arsenic causes skin rashes in some animals, such as pigs and buffalo. Cacodylic acid is toxic to bees in the 100-1,000 ppm range (6). The lowest dose (LCLO) that will kill a mouse is 500 mg/kg. The LCLO in dogs is 1 g/kg (NIOSH RTECS Online File #83/8304).

Bioaccumulation is unlikely because cacodylic acid is not persistent in the environment.

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Cacodylic acid is quickly inactivated upon contact with the soil by adsorption to soil particles and ion exchange (2, 7). Soil microorganisms degrade most of the cacodylic acid in the soil (6, 11). Cacodylic acid is practically non-volatile and is not decomposed by UV light (2).

Arsenic competes with phosphorus in the soil. It forms insoluble salts with chromium, silver nitrate or other metals. 15-80% of the cacodylic acid in the soil will disappear in 8 months.

Breakdown of Chemical in Water

Run-off from fire control or dilution water may cause pollution of surface waters (8). However, contamination of streams and lakes from proper use of cacodylic acid is unlikely (11). Contamination of forest streams is unlikely when cacodylic acid is used to thin forests (Bull. Environ. Contam. Tox. 30 (3):309- 16.1983). Information on groundwater contamination was not found.

Breakdown of Chemical in Vegetation

Arsenic, from the metabolism of cacodylic acid, is tightly bound in the foliage (leaves) of plants (6, Bull. Environ. Contam. Tox. 30 (3):309-16.1983). The arsenicals are poisons to cell division in plants (6).

Phosphorous can affect the phytotoxicity (ability to harm plants) of arsenic. Phosphorous can free the arsenic from the soil, but also will compete with the arsenic for uptake into the plant (6).

PHYSICAL PROPERTIES AND GUIDELINES

Cacodylic acid is a colorless crystalline solid with an offensive odor (2, 4). It is not flammable and is stable under normal temperatures and pressures. It will not ignite, but may burn if exposed to heat or flame. Thermal decomposition may release toxic oxides of arsenic and carbon (4). Since cacodylic acid is hygroscopic (it can pull moisture out of the atmosphere), it should only be stored in airtight containers which are kept closed and away from moisture (4). Cacodylic acid is mildly corrosive and will cause damage to zinc, tin and aluminum (2, 7). It is very dangerous to mix cacodylic acid with active metals such as iron, aluminum, or zinc (11). Do not store cacodylic acid near fertilizers, seeds, insecticides or fungicides (1).

Occupational Exposure Limits:

0.5 mg (as) /m3 OSHA TWA (2)
0.2 mg (as) /m3 ACGIH TWA (2)

Physical Properties:

CAS #: 75-60-5
Specific gravity: >1.1 (4)
Solubility in water: 66.7g/100 ml. Forms water soluble sodium and potassium salts (2); 83% at 22 degrees C (4)
Solubility: cacodylic acid is insoluble in ethyl ether. At 20 degrees C, its solubility in alcohol is 20.6g/100g (2). It is soluble in ethanol and acetic acid (4).
Boiling point: >392 degrees F (>200 degrees C) (4)
Melting point: 378 degrees F (192 degrees C) (4)
Flash point: nonflammable
Chemical class/use: organo-arsenical herbicide

BASIC MANUFACTURER

Drexel Chemical Co.
PO Box 9306
2487 Pennsylvania St.
Memphis, TN 38109

Review by Basic Manufacturer:

Comments solicited: October, 1992
Comments received:

REFERENCES

  1. Meister, R.T. (ed.) 1987. Farm Chemicals Handbook. Willoughby, OH: Meister Publishing Co.
  2. WSSA Herbicide Handbook Committee. 1983. Herbicide Handbook of the Weed Science Society of America. 5th Ed. WSSA, Champaign, IL.
  3. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, Ohio. 4 Occupational Health Services, Inc. 1991 (Feb. 25). MSDS for Cacodylic Acid. OHS Inc., Secaucus, NJ.
  4. Occupational Health Services, Inc. 1991 (Feb. 25). MSDS for Cacodylic Acid. OHS Inc., Secaucus, NJ.
  5. Hayes, Wayland, Jr. 1982. Pesticides studied in man. Baltimore, MD: Williams & Wilkins.
  6. Herbicides. 2nd Ed. Vols. 1,2. Kearney. 1975.
  7. Crop Protection Chemicals Reference. 2nd Ed. Chemical and Pharmaceutical Press. 1986.
  8. Department of Transportation. 1984. Emergency Response Guidebook: Guidebook for hazardous materials incidents. Washington, DC: U.S. DOT.
  9. Hallenbeck, W.H. & K.M. Cunningham-Burns. 1985. Pesticides and human health. New York: Springer-Verlag.
  10. Lef'evre, M.J. 1980. First aid manual for chemical accidents. New York: Van Nostrand Reinhold.
  11. Sax, N.I. 1975. Dangerous properties of industrial materials. 4th Ed. New York: Van Nostrand Reinhold Co.
  12. Gosselin, R.E. 1984. Clinical toxicology of commercial products. 5th Ed. Baltimore, MD: Williams & Wilkins.