Benzene

(USAN, rINN)
Benzene Chemical formula
Synonyms: Benceno; Benzen; Phenyl Hydride.
Cyrillic synonym: Бензол.

💊 Chemical information

Chemical formula: C6H6 = 78.11.
CAS — 71-43-2.

Description.

Benzene is a clear colourless flammable liquid with a characteristic aromatic odour. Wt per mL about 0.88 g. B.p. about 80°. Store in airtight containers.

💊 Adverse Effects, Treatment, and Precautions

Symptoms of acute poisoning after inhalation or ingestion of benzene include initial excitement or euphoria followed by CNS depression with headache, dizziness, blurred vision, and ataxia, which in severe cases may progress to coma (accompanied by hyperactive reflexes), convulsions, and death from respiratory failure. Other symptoms include nausea and irritation of the mucous membranes; ventricular arrhythmias may occur. Direct skin contact with liquid benzene may result in marked irritation, and dermatitis may develop on prolonged or repeated exposure. Prolonged industrial exposure to benzene vapour has been associated with adverse effects on the gastrointestinal tract and the CNS but in particular with marked effects on the bone marrow and blood. Decreases in the numbers of red or white blood cells or of platelets may occur, producing symptoms of headache, fatigue, anorexia, pallor, and petechiae. In severe cases pancytopenia or aplastic anaemia may develop. Leukaemia, particularly acute myeloid leukaemia, has also developed, often many years after exposure to benzene has ceased. These effects have been reported in workers exposed to relatively high concentrations of the vapour (around 200 ppm or more) but reduced red blood cell counts and anaemia have also been reported at lower concentrations. Chromosome abnormalities have been observed after prolonged exposure to benzene, particularly at the higher concentrations associated with blood dyscrasias; however, the significance of these abnormalities in the development of leukaemia is unclear. Treatment of poisoning consists of symptomatic and supportive measures. The UK National Poisons Information Service considers that gut decontamination (gastric lavage) is contra-indicated because it may increase the risk of aspiration. In chronic poisoning, repeated blood transfusions may be necessary. Adrenaline and other sympathomimetics should be avoided because of the risk of precipitating cardiac arrhythmias.
1. Health and Safety Executive. Benzene. Toxicity Revie
4. London: HMSO, 1982
2. WHO. Benzene. Environmental Health Criteria 150. Geneva: WHO, 1993. Available at: http://www.inchem.org/documents/ ehc/ehc/ehc150.htm (accessed 29/06/04)

Malignant neoplasms.

Epidemiological data support an association between benzene exposure and acute myeloid leukaemia, but the risk after low levels of exposure (1 to 10 ppm) is less clear.1 However, a large cohort study2 suggested that there is an increased risk of acute myeloid leukaemia and of non-Hodgkin’s lymphoma with benzene exposure at levels below 10 ppm.
1. Austin H, et al. Benzene and leukemia: a review of the literature and a risk assessment. Am J Epidemiol 1988; 127: 419–39
2. Hayes RB, et al. Benzene and the dose-related incidence of hematologic neoplasms in China. J Natl Cancer Inst 1997; 89: 1065–71.

Pregnancy.

An evaluation of the USA National Natality and Fetal Mortality Survey noted that maternal or paternal occupational exposure to agents such as benzene was associated with an increased risk of still-birth and that paternal exposure to benzene increased the risk of low-birth-weight infants.1
1. Savitz DA, et al. Effect of parents’ occupational exposures on risk of stillbirth, preterm delivery, and small-for-gestational-age infants. Am J Epidemiol 1989; 129: 1201–18.

💊 Pharmacokinetics

Benzene is absorbed after inhalation and ingestion, but is not significantly absorbed through the skin. Some is excreted unchanged from the lungs. Oxidation to phenol and related quinol compounds occurs, the metabolites being excreted in the urine as conjugates of sulfuric or glucuronic acid.

💊 Uses

Benzene was formerly applied as a pediculicide. Its use as an industrial solvent is decreasing.
Published October 10, 2018.