Toluene, formerly known as toluol, is a clear, water-insoluble volatile liquid with an aromatic odour (smells like paint thinners) and the molecular formula C6H5CH3. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1,2]

Toluene occurs naturally in crude oil and in the tolu tree. It is also produced in the process of making gasoline and other fuels from crude oil and making coke from coal. [3]


Uses [4]


The majority of toluene is used as a component of petrol. It is also used in paints, lacquers, inks, adhesives, rubber, and cleaning agents. It is used to manufacture benzene, urethane raw materials, and other organic chemicals. It is used in the production of pharmaceuticals, dyes, and cosmetic nail products. It is used against roundworms and hookworms.


Sources of Emission & Routes of Exposure


Sources of Emission [4]


  • Industry sources: The primary sources of toluene are the industries that manufacture it or use it in production. Some of the industries that manufacture it or use it in production are oil refiners, chemical industry, rubber manufacturers, pharmaceutical industry, metal degreasing, printing, manufacturers of paints, varnishes and lacquers. These emissions mainly are to the air, but are also to the soil and water.
  • Diffuse sources: Other possible emitters of toluene are vapours and spilling of petrol, commercial and household painting and paint, varnish and lacquer removal, tobacco smoke, and consumer products containing toluene. These emissions are to the air unless there is a spill.
  • Natural sources: Natural sources of toluene include volcanoes, forest and bush fires and crude oil.
  • Transport sources: Some toluene is found in vehicle exhaust.
  • Consumer products: Adhesives, Auto polish and cleaners, floor polish, hard surface cleaners, paints, inks, paint cleaners, paint and varnish removers and thinners, coatings, particleboard, leather dressings, lubricating oils, fingernail enamels and removers, shoe polish and cleaners, solvent thinned products (exterior stains, primers, interior stains, clear finish), colouring pens and markers, wood office furniture, vinyl flooring.


Routes of Exposure [2]


  • Air: Air pollution from motor vehicle exhaust is unquestionably a major source of exposure. Occupational subpopulations involved in toluene production or use are likely to be exposed to considerably higher levels than the general population. In addition, air levels in the vicinity of industrial sources and petrol stations are likely to represent an additional burden to both workers and local residents.
  • Smoking: Toluene is a major component of tobacco smoke and concentrations can vary greatly. The concentration per cigarette in sidestream smoke is typically higher than in mainstream smoke. The amount of toluene in mainstream smoke from an unfiltered cigarette was estimated to range from 100 to 200 mg with a sidestream/mainstream smoke ratio of 1.3, using samplers to adsorb toluene in the breathing zone of smokers and nonsmokers over a 24-hour period, found that active smokers were exposed to about four times the level for passive smokers. Cigarette smoking enhanced elimination of toluene and hippuric acid from the body. Smokers had significantly higher blood levels than nonsmokers with the level affected more by the length of time since the last cigarette was smoked than by the extent of smoking.
  • Drinking-water: Exposure via drinking-water is minor, except in cases of unusually heavy contamination. Levels indicated by surveys in the USA are generally less than 10 μg/l.
  • Food: Exposure via food is also considered to be insignificant. A daily contribution from fish was estimated to be between 0.1–0.2 mg/kg bw.
  • Inhalation is the predominant route of exposure.


Health Effects [5]


Acute Effects


  • The Central Nervous System (CNS) is the primary target organ for toluene toxicity in both humans and animals for acute and chronic exposures. CNS dysfunction (which is often reversible) and narcosis have been frequently observed in humans acutely exposed to low or moderate levels of toluene by inhalation; symptoms include fatigue, sleepiness, headaches, and nausea. CNS depression and death have occurred at higher levels of exposure.
  • Cardiac arrhythmia has also been reported in humans acutely exposed to toluene.
  • Following the ingestion of toluene a person died from a severe depression of the CNS. Constriction and necrosis of myocardial fibres, swollen liver, congestion and haemorrhage of the lungs, and tubular kidney necrosis were also reported. Acute exposure of animals to toluene has been reported to affect the CNS as well as to decrease resistance to respiratory infection.
  • Acute animal tests in rats and mice have demonstrated toluene to have low acute toxicity by inhalation or oral exposure.


Chronic Effects


  • CNS depression has been reported to occur in chronic abusers exposed to high levels of toluene. Symptoms include drowsiness, ataxia, tremors, cerebral atrophy, nystagmus (involuntary eye movements), and impaired speech, hearing, and vision. Neurobehavioral effects have been observed in occupationally exposed workers.
  • Effects on the CNS have also been observed in studies of animals chronically exposed by inhalation.
  • Chronic inhalation exposure of humans to toluene causes irritation of the upper respiratory tract and eyes, sore throat, dizziness, headache, and difficulty with sleep.
  • Inflammation and degeneration of the nasal and respiratory epithelium and pulmonary lesions have been observed in rats and mice chronically exposed to high levels of toluene by inhalation.
  • Mild effects on the kidneys and liver have been reported in solvent abusers chronically exposed to toluene vapour. However, these studies are confounded by probable exposure to multiple solvents.
  • Slight adverse effects on the liver, kidneys, and lung and high-frequency hearing loss have been reported in some chronic inhalation studies of rodents.
  • The Reference Concentration (RfC) for toluene is 5 milligrams per cubic metre (5 mg/m3) based on neurological effects in humans.
  • The Reference Dose (RfD) for toluene is 0.08 milligrams per kilogram body weight per day (0.08 mg/kg/d) based on increased kidney weight in rats.


Reproductive/Developmental Effects


  • CNS dysfunction, attention deficits, minor craniofacial and limb anomalies, and developmental delay were observed in the children of pregnant women exposed to toluene or to mixed solvents during solvent abuse. Growth retardation and dysmorphism were reported in infants of another study. However, these studies were confounded by exposure to multiple chemicals. Children born to toluene abusers have exhibited temporary renal tubular acidosis.
  • Paternal exposure (in which the mothers had no occupational exposure to toluene but the fathers did) increased the odds ratio for spontaneous abortions; however, these observations cannot be clearly ascribed to toluene because of the small number of cases evaluated and the large number of confounding variables. An increased incidence of spontaneous abortions was also reported among occupationally exposed women. However, these studies are not conclusive due to many confounding variables.
  • Several inhalation studies have shown toluene to be a developmental toxicant, but not a reproductive toxicant, in rodents.


Cancer Risk


  • Available studies in workers have reported limited or no evidence of the carcinogenic potential of toluene. Similarly, the few available epidemiological studies have failed to demonstrate increased risk of cancer due to inhalation exposure to toluene. However, these studies were limited due to the size of the study population and lack of historical monitoring data.
  • Chronic inhalation exposure of rats did not produce an increased incidence of treatment-related neoplastic lesions.
  • Under the Guidelines for Carcinogen Risk Assessments (US. EPA, 2005), the EPA considers that there is inadequate information to assess the carcinogenic potential of toluene.


Safety [6]


First Aid Measures


  • Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Get medical attention.
  • Skin Contact: In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. WARNING: It may be hazardous to the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek medical attention.
  • Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.


Fires & Explosion Information


  • Toluene is flammable
  • Auto-ignition temperature is 480°C (896°F)
  • Flash points: Closed cup is 4.4444°C (40°F) and open cup is 16°C (60.8°F).
  • Toluene is flammable in presence of open flames and sparks, of heat.
  • Non-flammable in presence of shocks.
  • Use dry chemical powder to extinguish small fires and water spray or fog for large fires.
  • Toluene forms explosive reaction with 1,3-dichloro-5,5-dimethyl-2,4-imidazolididione; dinitrogen tetraoxide; concentrated nitric acid, sulfuric acid + nitric acid; N2O4; AgClO4; BrF3; Uranium hexafluoride; sulfur dichloride. Also forms an explosive mixture with tetranitromethane.


Exposure Controls & Personal Protection


Engineering Controls


  • Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value.
  • Ensure that eyewash stations and safety showers are proximal to the work-station location.


Personal Protective Equipment


The following personal protective equipment is recommended when handling toluene:

  • Splash goggles;
  • Lab coat;
  • Vapour respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves.


Personal Protective Equipment in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Vapour respirator;
  • Boots;
  • Gloves;
  • A self contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.


Regulation [3,4,7]


United States


Exposure Limit Limit Values HE Code Health Factors and Target Organs
OSHA Permissible Exposure Limit (PEL) – General Industry
See 29 CFR 1910.1000 Table Z-2
(See also ANSI Z37.12-1967)
200 ppm TWA

300 ppm Ceiling

500 ppm Peak
(10 minutes)

HE7 Central nervous system depression, causing fatigue, headache, confusion, paresthesia, dizziness, and muscular incoordination
HE15 Irritation of the eyes, mucous membranes, and upper respiratory tract
OSHA PEL – Construction Industry
See 29 CFR 1926.55 Appendix A
200 ppm (750 mg/m3) TWA HE7 Central nervous system depression, causing fatigue, headache, confusion, paresthesia, dizziness, and muscular incoordination
HE15 Irritation of the eyes, mucous membranes, and upper respiratory tract
OSHA PEL – Shipyard Employment
See 29 CFR 1915.1000 Table Z-Shipyards
200 ppm (750 mg/m3) TWA HE7 Central nervous system depression, causing fatigue, headache, confusion, paresthesia, dizziness, and muscular incoordination
HE15 Irritation of the eyes, mucous membranes, and upper respiratory tract
National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) 100 ppm (375 mg/m3) TWA

150 ppm (560 mg/m3) STEL

HE7 Fatigue, weakness, confusion, headache, dizziness, drowsiness
HE8 Unconsciousness
HE15 Irritation of the eyes, respiratory tract, and skin
American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) (2007) 20 ppm
(75 mg/m3) TWA


HE5 Female reproductive system damage and pregnancy loss
HE7 Central nervous system impairment and visual impairment
CAL/OSHA PELs 10 ppm
(37 mg/m3)

500 ppm Ceiling

150 ppm (560 mg/m3) STEL


HE5 Female reproductive toxicity, spontaneous abortion
HE7 Impaired colour vision, impaired hearing, decreased performance in neurobehavioral analysis, changes in motor and sensory nerve conduction velocity, headache, and dizziness


  • The United States Environmental Protection Agency (EPA) has set a limit of 1 milligram per litre of drinking water (1mg/L).
  • Discharges, releases, or spills of more than 1,000 pounds of toluene must be reported to the National Response Centre.




  • Safe Work Australia: Safe Work Australia has set an eight hour time weighted average (TWA) exposure limit for toluene of 100 parts per million and the short term exposure limit (STEL) is 150 parts per million.
  • Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996):
    • Health: Maximum of 0.8 mg/L (i.e. 0.0008 g/L)
    • Aesthetic: Maximum of 0.025 mg/L (i.e. 0.000025 g/L)