Toluene

(BAN, USAN, rINN)
Toluene Chemical formula
Synonyms: Methylbenzene; Phenylmethane; Toluen; Tolueno; Toluol; To l uo l e.
Cyrillic synonym: Толуол.

💊 Chemical information

Chemical formula: C7H8 = 92.14.
CAS — 108-88-3.

Description.

Toluene is a colourless, volatile, flammable liquid with a characteristic odour. Wt per mL about 0.87 g. B.p. about 111°. Store in airtight containers.

💊 Adverse Effects, Treatment, and Precautions

Toluene has similar acute toxicity to benzene but is a less serious industrial hazard. Adverse effects are treated similarly to benzene. It is a common constituent of adhesives and is frequently implicated in volatile substance abuse. Commercial toluene may contain benzene, and this may perhaps influence the pattern of adverse effects. In addition to acute toxic effects, toluene abuse has been associated with damage to the nervous system, kidneys, liver, heart, and lungs (see below). Chronic poisoning caused by occupational exposure to toluene has resulted mainly in nervous system disorders.
1. WHO. Recommended health-based limits in occupational exposure to selected organic solvents. WHO Tech Rep Ser 664 1981. Available at: http://libdoc.who.int/trs/WHO_TRS_664.pdf (accessed 03/09/08
2. WHO. Toluene. Environmental Health Criteri
52. Geneva: WHO, 1985. Available at: http://www.inchem.org/documents/ ehc/ehc/ehc52.htm (accessed 30/06/04
3. Health and Safety Executive. Toluene. Toxicity Revie
20. London: HMSO, 1989.
Chronic toluene abuse may result in damage to the kidneys; renal tubular acidosis and glomerulonephritis have been described, although evidence for the latter is only circumstantial. Renal tubular acidosis has been regarded as reversible; however, there are reports suggesting that damage to renal tubules is permanent. The few reports linking chronic toluene abuse with liver damage cover hepatomegaly and hepatorenal failure. Effects on the heart are usually acute; sudden death has resulted from ventricular arrhythmias. Chronic myocarditis with fibrosis has been reported. Chronic toluene inhalation can cause damage to the lungs. Autopsies in a few patients have shown changes indicative of emphysema. Nervous system toxicity has also been reviewed.2,3 Cerebellar dysfunction has occurred after toluene abuse; an acute intoxication phase, which usually subsides within weeks of abstinence, is followed by a chronic phase which may be permanent. Diffuse CNS disease such as encephalopathy, dementia, and multifocal brain injury may also develop. An association between toluene abuse and peripheral neuropathy has not been confirmed; muscle weakness may be a result of electrolyte and fluid disturbances. Choreoathetosis, epilepsy, and optic atrophy with anosmia and deafness have been reported after toluene abuse. Some of these neurological effects, particularly cerebellar effects and diffuse CNS disease have also occurred after occupational exposure to toluene. Some studies have noted an excess mortality from motor neurone diseases among leather workers,4 although this has not been confirmed by others.5 Occupational exposure to solvents has been postulated as the cause.4 Of the many agents currently used in leather work, those with known or probable neurotoxic effects are n-hexane, methyl butyl ketone, toluene, and methyl ethyl ketone. Ethyl acetate is commonly used but has no recognised neurological adverse effects.4 A Swedish study of workers in a range of occupations has found some support for an increased risk of amyotrophic lateral sclerosis after occupational exposure to solvents, probably toluene and petrol.6 Another Swedish study found an association between multiple sclerosis and occupational exposure to solvents, especially white spirit and petrol.6
1. Marjot R, McLeod AA. Chronic non-neurological toxicity from volatile substance abuse. Hum Toxicol 1989; 8: 301–6
2. Lolin Y. Chronic neurological toxicity associated with exposure to volatile substances. Hum Toxicol 1989; 8: 293–300
3. Filley CM, et al. The effects of toluene on the central nervous system. J Neuropathol Exp Neurol 2004; 63: 1–12
4. Hawkes CH, et al. Motoneuron disease: a disorder secondary to solvent exposure? Lancet 1989; i: 73–6
5. Martyn CN. Motoneuron disease and exposure to solvents. Lancet 1989; i: 394
6. Gunnarsson L-G, Lindberg G. Amyotrophic lateral sclerosis in Sweden 1970-83 and solvent exposure. Lancet 1989; i: 958.

Handling.

Suitable precautions should be taken to avoid skin contact with toluene as it can penetrate skin and produce systemic toxicity.

Pregnancy.

Retrospective surveys of pregnancies in mothers with a history of solvent abuse suggested that toluene abuse during pregnancy can cause preterm delivery and perinatal death. It was suggested that toluene may be teratogenic as intra-uterine exposure was associated with prenatal and postnatal growth retardation, microcephaly, impairment of mental development, and facial dysmorphia.1-3 It is uncertain if these results can be extrapolated to cover occupational exposure. Although some studies of occupational exposure to solvents during pregnancy have suggested an association,4,5 exposure is usually to a number of solvents5 and there is little consistent evidence to link exposure to any particular one with spontaneous abortion, retarded fetal development, still-birth, or congenital malformation.6
1. Wilkins-Haug L, Gabow PA. Toluene abuse during pregnancy: obstetric complications and perinatal outcomes. Obstet Gynecol 1991; 77: 504–9
2. Pearson MA, et al. Toluene embryopathy: delineation of the phenotype and comparison with fetal alcohol syndrome. Pediatrics 1994; 93: 211–15
3. Arnold GL, et al. Toluene embryopathy: clinical delineation and developmental follow-up. Pediatrics 1994; 93: 216–20
4. McDonald JC, et al. Chemical exposures at work in early pregnancy and congenital defect: a case-referent study. Br J Ind Med 1987; 44: 527–33
5. Khattak S, et al. Pregnancy outcome following gestational exposure to organic solvents: a prospective controlled study. JAMA 1999; 281: 1106–9
6. Scott A. BMJ 1992; 304: 369.

💊 Pharmacokinetics

Toluene is absorbed after inhalation and ingestion, and to some extent through the skin. It is rapidly metabolised mainly by oxidation to benzoic acid which is excreted in the urine largely as the glycine conjugate hippuric acid; o-, m-, and p-cresol are minor urinary metabolites. Some unchanged toluene is excreted through the lungs.

💊 Uses

Toluene is widely used as an industrial solvent.
Published November 30, 2018.