PMEP Home Page --> Pesticide Active Ingredient Information --> EXTOXNET: The Extension Toxicology Network --> Carbaryl to Dicrotophos --> Chlorobenzilate

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
Chlorobenzilate

Publication Date: 5/94

TRADE OR OTHER NAMES

Acaraben, Akar 338, Folbex, Kop-mite, Benzilan, ECB, Geigy 338, Benz- o-chlor.

REGULATORY STATUS

Chlorobenzilate has been cancelled and is no longer available in the United States (20). Previously, the U. S. Environmental Protection Agency (EPA) had classified all formulations containing chlorobenzilate as Restricted Use Pesticides (RUPs). RUPs may be purchased and used only by certified applicators. The criteria used for this classification was its ability to cause tumors in mice, and its effects on the testes of rats (18). Aerial and ground foliar sprays were restricted to citrus use in the states of Arizona, California, Florida and Texas for the control of mites (13).

INTRODUCTION

Chlorobenzilate was introduced in 1952. It is used for mite control on citrus crops and in beehives (8). It is nonsystemic, meaning that it is not absorbed or transported throughout a plant. It has little insecticidal action, killing only ticks and mites (2, 17).

Chlorobenzilate is available as emulsifiable concentrate and as wettable powder formulations (8).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Chlorobenzilate is slightly to moderately toxic to humans. Symptoms of acute poisoning from ingestion of chlorobenzilate include incoordination, nausea, vomiting, fever, apprehension, confusion, muscle weakness or pain, disturbed sense of balance, dizziness, weight loss, wheezing and coma. Symptoms may occur within several hours after exposure. Death may result from discontinued breathing or irregular heartbeats (9, 19).

Chlorobenzilate is a mild skin and eye irritant (19).

The oral LD50 for chlorobenzilate in rats and hamsters is 700 mg/kg, and 729 mg/kg in mice (2, 19).

CHRONIC TOXICITY

Prolonged or repeated exposure to chlorobenzilate may cause the same effects as acute exposure (19). After continuous exposure to chlorobenzilate, 16 out of 73 workmen tested had abnormal electroencephalograms, or EEGs. EEGs are recordings of electrical activity of the brain. The most severe brain activity changes were seen in those persons exposed to the herbicide for one to two years (11) . Chronic skin exposure to chlorobenzilate may cause inflamed skin or rashes, also known as dermatitis. Chronic eye exposure to this material may cause conjunctivitis (9).

The use of chlorobenzilate has been restricted in the U.S. because the compound is tumor-forming (oncogenic) in rats and mice (3). Atrophy of the testes was observed in a two-year study of male rats (19). Symptoms of poisoning in test animals included depression, salivation, tearing, diarrhea and deep, rapid breathing (11).

Reproductive Effects

In 1979, the EPA recommended that sperm counts be examined in a selected population of chlorobenzilate applicators (2). A three-generation rat reproduction study resulted in reduced testicular weights, but did not affect reproduction. The results of another study indicate that chlorobenzilate does not adversely affect reproductive performance nor produce testicular atrophy at dosage levels up to 100 mg/kg per day (15).

Teratogenic Effects

Information is incomplete on the potential for chlorobenzilate to cause birth defects (14).

Mutagenic Effects

No information is available.

Carcinogenic Effects

Chlorobenzilate is a suspected carcinogen in animals and a possible human carcinogen. It has produced liver tumors in mice, but the evidence for carcinogenicity in rats is uncertain (2).

Organ Toxicity

Poisoning may effect the central nervous system, the kidneys and the liver (19). Autopsies revealed intestinal irritation and bleeding in the lungs of rats poisoned by dietary doses of 25 mg/kg of chlorobenzilate (11). Liver damage may be caused by repeated or prolonged contact with this material (9).

Fate in Humans and Animals

Chlorobenzilate is rapidly excreted by humans, usually within 3 to 4 days (19). After daily doses of 12.8 mg/kg to dogs, for 5 days/week for 35 weeks, about 40% of the dose was excreted unchanged or as urinary metabolites. No significant storage in fat of dogs or rats was reported (2).

Chlorobenzilate has a slight tendency to accumulate in fatty tissues (3). Intense activity or starvation may mobilize the stored pesticide and cause the reappearance of toxic symptoms (19). In a study funded by the National Pesticide Hazard Assessment Program of EPA, detectable traces of chlorobenzilate were found in urine collected from Texas and Florida citrus-grove growers and workers. The collected information showed a range of exposure: from low levels in harvest season pickers, exposed to little or no chlorobenzilate exposure, to higher levels among permanent or semi- permanent workers employed during the spraying season. Among all workers, urinary values ranged from zero to 63.6 ppm (4). This acaricide has not been found in human milk in the United States (11) .

ECOLOGICAL EFFECTS

Effects on Birds

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 seven-day LC50 for chlorobenzilate was 3,375 ppm in bobwhite quail. Its five-day LC50 in mallard ducks was greater than 8000 ppm (14).

Effects on Fish

Chlorobenzilate is not expected to bioconcentrate in aquatic organisms (12). Its LC50 is 0.7 mg/l for 95 hours in rainbow trout (14, 11).

Effects on Other Animals (Nontarget Species)

Chlorobenzilate is believed to be non-toxic to beneficial insects (10). Chlorobenzilate is non-toxic to honey bees (8).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Because chlorobenzilate is practically insoluble in water and it adsorbs strongly to soil particles (Koc = 1,065) in the upper soil layers, it is expected to exhibit low mobility in soils, and to therefore be unlikely to leach to groundwater (12). Its soil half-life in fine sandy soils was 1.5 to 5 weeks after application of 0.5-1.0 ppm, with the removal probably due to microbial degradation (12). Due to its strong adsorption to soil particles and low vapor pressure, chlorobenzilate is not expected to volatilize from soil surfaces (12, 5).

Following a five-day application of chlorobenzilate to several different citrus groves employing various tillage treatments, chlorobenzilate was not found in subsurface drainage waters, nor in surface runoff waters (5).

Breakdown of Chemical in Water

Chlorobenzilate adsorbs to sediment and suspended particulate material in water. It is practically insoluble in water (12, 11) . It is not expected to volatilize or to bioconcentrate in aquatic organisms, but may be subject to biodegradation (12).

Breakdown of Chemical in Vegetation

Chlorobenzilate is fairly persistent on plant foliage and may be phytotoxic, or poisonous, to some plants (6).

Chlorobenzilate residues have been found in the peel of citrus fruit. Its half-life in lemon and orange peels was from 60 to over 160 days (11). The spraying of 200, 1,000 and 5,000 ppm chlorobenzilate (in emulsions or suspensions) caused browning of the edges or the veins of leaves on most treated crops (11) . When chlorobenzilate was applied to the surface of soybean leaves, the miticide was quite stable and very little was absorbed and moved, or translocated, from one part of the plant to another (7).

PHYSICAL PROPERTIES AND GUIDELINES

Technical chlorobenzilate contains approximately 90% active compound (11). It is a brownish liquid. Pure chlorobenzilate is a yellow solid (1, 8, 11).

Chlorobenzilate is stable under normal temperatures and pressures. It may burn, but does not ignite readily. Breakdown of chlorobenzilate by heat may create corrosive fumes of hydrogen chloride and toxic oxides of carbon. Exposure to alkalis or strong acids may cause hydrolysis (19, 9, 14).

Occupational Exposure Limits:

No occupational exposure limits have been established by ACGIH, NIOSH or OSHA (19).

Physical Properties:

CAS #: 510-15-6
H2O solubility: practically insoluble in water (8, 13)
Solubility in other solvents: soluble in most organic solvents including benzene, acetone, methyl alcohol, toluene, hexane, octan-1-ol, alcohol, ethanol, and petroleum oils (8, 19, 11, 17)
Melting point: 35-37 degrees C (95-99 degrees F) for pure chlorobenzilate (13, 17)
Boiling point: 313-316 degrees F (156-158 degrees C) (19)
Flash point: 104 degrees F (40 degrees C) (19)
Specific gravity: 1.2816 (19)
Koc: 1065 (12)
Vapor pressure: 2.2 x 10 to the minus 6 mm Hg at 20 degrees C (12)
Chemical Class/Use: Chlorinated hydrocarbon; organochlorine miticide

BASIC MANUFACTURER

Ciba-Geigy Corporation
CIBA Plant Protection
P.O. Box 18300
Greensboro, NC 27419-8300
Telephone: 919-632-6000

Review by Basic Manufacturer:

Comments solicited: November, 1992
Comments received: January, 1994

REFERENCES

  1. Berg, G. L., ed. 1986. Farm chemicals handbook. Willoughby, OH: Meister Publishing Company.
  2. Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of Pesticide Toxicology, Vol. 3, Classes of Pesticides. Academic Press, Inc., NY.
  3. Gosselin, R. E., et al. 1984. Clinical toxicology of commercial products. Fifth edition. Baltimore, MD: Williams and Wilkins.
  4. Griffeth, J. and R. C. Duncan. 1985. Urinary chlorobenzilate residues in citrus fieldworkers. Bulletin of Environmental Contamination and Toxicology 35: 496-499. New York: Springer-Verlag, Inc.
  5. Lyman, W. J., et al. 1983. Handbook of chemical property estimation methods. Environmental behavior of organic compounds. NY: McGraw-Hill.
  6. McEwen, F. L. and G. R. Stephenson. 1979. The use and significance of pesticides in the environment. NY: John Wiley and Sons, Inc.
  7. Menzie, C. M. 1974. Metabolism of pesticides. U.S. Department of the Interior. Fish and Wildlife Service Special Scientific Report: Wildlife. Washington, DC: U. S. Government Printing Office.
  8. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, Ohio.
  9. Occupational Health Services, Inc. 1986. Material safety data sheet. Secaucus, NJ: OHS, Inc.
  10. Thomson, W. T. 1985. nsecticides. Agricultural Chemicals, Book I. Fresno, CA: Thomson Publications.
  11. TOXNET. 1975-1986. National library of medicine's toxicology data network. Hazardous Substances Databank. Public Health Service. National Institute of Health, U. S. Department of Health and Human Services. Bethesda, MD: NLM.
  12. Howard, P.H. (ed.). 1989. Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Vol. III: Pesticides. Lewis Publishers, Chelsea, MI.
  13. U. S. Environmental Protection Agency. 1986. Memorandum from Ferial S. Bishop. List of federally restricted products. Registration Support and Emergency Response Branch (TS-767). Washington, DC.
  14. _____. 1984. Fact sheet for chlorobenzilate. Fact sheet no 15. Office of Pesticide Programs. Washington, DC.
  15. _____. 1983. Guidance for the reregistration of pesticide products containing chlorobenzilate as the active ingredient. Office of Pesticide Programs. Registration Division. Washington, DC.
  16. Worthing, C. R., ed. 1983. The pesticide manual: A world compendium. Croydon, England: The British Crop Protection Council.
  17. US Environmental Protection Agency. 1990 (Feb.). Suspended, Canceled, and Restricted Pesticides. Pesticides and Toxic Substances, US EPA, Washington, DC.
  18. Occupational Health Services, Inc. 1991 (Sept. 16). MSDS for Chlorobenzilate. OHS Inc., Secaucus, NJ.
  19. Review by Ciba-Geigy Corporation. January 18, 1994.
  20. Pesticide Chemical News Guide. CRC Press. Washington DC.