Chlorobenzene, also called monochlorobenzene, is a monocyclic aromatic compound. It is a colorless liquid with an aromatic almond-like odor and is manufactured for use as a solvent, is used in the production of other chemicals (pesticides), and in making certain other chemicals, rubber, dyes and grease solvents. It is used as a feedstock to produce ortho- and para- nitrochlorobenzenes, and aniline; as a solvent for paints; and as a heat transfer medium. In the past, chlorobenzene was used as an intermediate in phenol and DDT production. Only one pesticide in Canada under temporary registration contains chlorobenzene.
Chlorobenzene enters the environment from industrial and municipal discharges. Another potential source is the formation and emission of chlorobenzene as a product of incomplete combustion in waste incinerators.
Occupational exposure occurs primarily through breathing the chemical. Personnel engaged in the production and handling of chlorobenzene would be at greatest risk.
Daily maximum concentrations in air in Canada range between 0.15 to 1.74 g/m3. Chlorobenzene concentrations in surface, raw and treated drinking water in Canada are generally below 1.0 g/L although a concentration of 5 g/l was detected in treated water. In contaminated effluents or groundwater, concentrations of up to 5,31 mg/L have been found in Ontario.
Chlorobenzene is moderately soluble in water; up to 1,000 milligrams will mix with a litre of water. Chlorobenzene is slightly persistent in water, with a half-life of between 2 to 20 days. Chlorobenzene persists in soil (several months), in air (3.5 days), and water (less than 1 day). About 99.25% of chlorobenzene will eventually end up in air; the rest will end up in the water.
Chlorobenzene is a flammable liquid and a fire hazard. It is unreactive towards water and decomposes only at high temperatures. When heated to decomposition this compound emits toxic fumes of hydrogen chloride gas, CO and CO2.
| BENCHMARKS | |
Canadian Water Quality Guidelines (Monochlorene) | |
| Drinking water guideline | 0.08 mg/L; 0.03mg/L (aesthetic objective) |
| Protection of freshwater aquatic life | 0.015 mg/L (under review) |
Ontario Water Quality Objectives | |
| PWQO | 0.015 mg/L |
U.S.EPA | |
| Reference Concentration (RfC) | 0.02 mg/kg/d |
| Proposed Maximum Level (drinking water) | 0.1 ppm |
| Short-term exposures drinking water levels | <2 ppm for up to 10 days |
OSHA | |
| Legal airborne permissible exposure limit (PEL) | 75 ppm
averaged over an 8-hour work-shift 40-hour workweek. |
ACGIH | |
| Recommended airborne exposure limit | 75 ppm averaged over an 8-hour workshift. |
Odor Threshold |
0.68 ppm |
Toxicity Values | |
| LC 50 - Male rats | 13 490 mg/m3 air |
| LC 50 - Female mice | 8 581 mg/m3 air |
| LD 50 - Rats | 4000 mg/kg |
| LD 50 - Male Mice | 1000 mg/kg |
| LD 50 - Female Mice | 2000 mg/kg |
| LC 50 - Daphnia magna | 5.8 - 25.8 mg/L (48 hr)
3.9 mg/L (16 day) |
| LC 50 - Rainbow trout | 4.7 - 7.46 mg/L (96 hr) |
| LC 50 - Rainbow trout (early stage) | 0.11 mg/L from fertilization until 4 days after hatching (average: 27 days) |
| LC 50 - Largemouth bass | 0.05 mg/L
from fertilization until 4 days after hatching average: 7 days) |
HUMAN HEALTH
There is potential for humans to be exposed to chlorobenzene by breathing contaminated air, by
drinking water or eating food contaminated with chlorobenzene, or by getting chlorobenzene -contaminated soil on the skin. These exposures are most likely to occur in the workplace or in the vicinity of hazardous waste sites.
Exposure to chlorobenzene occurs most commonly through inhalation and skin contact. It is readily absorbed through the lungs and gastrointestinal tract and likely to be absorbed through skin because of its lipophilic characteristic. Once absorbed, it is rapidly distributed throughout the body and concentrates readily in fat tissues. It is metabolized in the kidney and liver. Chlorobenzene is excreted through exhalation and urine.
Vapor or mist is irritating to the eyes, mucous membranes and upper respiratory tract.
Chlorobenzene may cause severe irritation and redness of the eyes, and pain to the cornea.
Skin contact with the liquid may irritate the skin, cause a rash or a burning feeling. The liquid can cause severe skin burns if held in place by clothing or shoes. Overexposure may occur as a result of skin contact, even though air levels are less than the limits.
Exposure to high concentrations can cause dizziness, lightheadedness, and loss of consciousness.
Chlorobenzene exposure may cause neurotoxicity. Signs of neurotoxicity include numbness, cyanosis, hyperesthesia (increased sensation), and muscle spasms.
Headaches and irritation of the mucosa of the upper respiratory tract and eyes have also been reported in humans chronically exposed via inhalation.
Exposure to chlorobenzene may cause lung, kidney and/or liver damage.
Mild to severe depression of functions of parts of the nervous system is a common response to exposure to a wide variety of industrial solvents.
Ingestion of cholorobenzene may cause abdominal pain, headache, nausea and vomiting. These symptoms may be followed by paleness, cyanosis, and coma, which may be delayed several hours. Ingested chlorobenzene may disturb digestion.
MEDICAL TESTS
Exposure to chlorobenzene can be determined by measuring the chemical or its metabolite in urine, exhaled air, blood, and body fat. Liver, lung and kidney function tests can also be useful in determining impacts of chlorobenzene exposure.
Interview for brain effects, including recent memory, mood (irritability, withdrawal), concentration, headaches, malaise and altered sleep patterns.
Consider cerebellar, autonomic and peripheral nervous system evaluation. Positive and borderline individuals should be referred for neuropsychological testing.
ANIMAL HEALTH
In animals, exposure to chlorobenzene affects the brain, central nervous system, liver, and kidneys. It is acutely toxic to mammals through dermal and oral exposure.
Unconsciousness, tremors and restlessness have been observed in cases of exposure to high concentrations.
Studies in animals have shown that chlorobenzene can produce liver nodules, providing some but not clear evidence of cancer risk.
Chlorobenzene metabolites are suspected to cause necrosis of the kidneys and liver in rodents.
Acute inhalation exposure of cats to chlorobenzene produced narcosis, restlessness, tremors, and muscle spasms.
In a study of rats and mice exposed to chlorobenzene via gavage (experimentally placing the chemical in the stomach), an increased incidence of neoplastic nodules of the liver in male rats was observed, but not in mice or female rats.
Chlorobenzene has moderately acute and chronic toxicity to aquatic life.
The concentration of chlorobenzene found in fish tissues is expected to be only somewhat higher than the average concentration of chlorobenzene in the water from which the fish was taken as it has not been found to bioconcentrate significantly.
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