Benzene is used in the manufacture of a large number of chemicals that contribute to the production of plastics (such as polystyrene) synthetic fibres, detergents, pharmaceuticals, and pesticides. It is used as a solvent for fats, oils, inks, paints, plastics, and rubbers, and as a degreasing agent. Benzene is also used to make some types of rubbers as well as being a constituent in motor fuels.
Substance name: Benzene
CASR number: 71-43-2
Molecular formula: C6H6
Synonyms: Benzol, Benzoline, Coal naphtha, Cyclohexatriene, Phene, Phenyl hydride, Pyrobenzol
Clear colourless to light-yellow liquid, Aromatic odour, Evaporates into the air very quickly
Melting Point: 5.5°C
Boiling Point: 80.1°C
Specific Gravity: 0.879
Vapour Density: 2.77
Dissolves slightly in water
The National Pollutant Inventory (NPI) holds data for all sources of benzene emissions in Australia.
This depends on how much benzene you have been exposed to, for how long, and your current state of health. In certain circumstances, even a brief exposure to very high levels of benzene can result in death. Worksafe Australia classifies benzene as a toxic health hazard, listing its concentration cut off level at 0.10% weight/weight. Exposure can result in symptoms such as skin and eye irritations, drowsiness, dizziness, headaches, and vomiting. Benzene is carcinogenic and long-term exposure at various levels can affect normal blood production and can be harmful to the immune system. It can cause Leukaemia (cancer of the tissues that form white blood cells) and has also been linked with birth defects in animals and humans.
Entering the body
Benzene evaporates very quickly and so the most common exposure is from breathing air containing benzene. Very small amounts are found in some foods such as canned beef and if drinking water has been contaminated. While benzene is poorly absorbed by the skin, it can enter the skin in this way, with potentially dangerous contact being with products such as petrol.
Most people are exposed outdoors to low levels of benzene from tobacco smoke and car exhaust. Smoking cigarettes and passive smoking, especially indoors, increases the intake of benzene to higher levels. People living near industries that produce or use benzene, or near freeways may also be exposed to higher levels in the surrounding air.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standard for benzene through the workplace exposure standards for airborne contaminants:
- Maximum eight hour time weighted average (TWA): 1 part per million (3.2 mg/m3)
These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
Drinking water guidelines
The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:
- Maximum of 0.001 milligrams per litre of water for health purposes
Benzene has a high acute toxic effect on aquatic life. Long-term effects on marine life can mean shortened lifespan, reproductive problems, lower fertility and changes in appearance or behaviour. It can cause death in plants and roots and damage to the leaves of many agricultural crops.
Entering the environment
Benzene is carried in the air. If released to soil, benzene will usually breakdown quickly. It can be mobile in soil, however, and may contaminate groundwater. Benzene is only slightly soluble in water, but is readily absorbed by the lipid phase (fatty parts) of aquatic organisms, which can result in transport in the environment.
Where it ends up
In the atmosphere, benzene can react with other chemicals to produce phenol, nitrophenol, nitrobenzene, formic acid and peroxyacetyl nitrate. It is a "precursor" hydrocarbon leading to the formation of photochemical smog. It will usually breakdown (decompose) over a few days, with the products eventually ending up in the air. It can be washed out of the air by rain, but will evaporate and continue to contaminate the air. It can attach to rain or snow and be carried back down to the ground. Benzene in soil or water will decompose with the presence of oxygen. It does not build up concentration levels in plant or animal tissues.
Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992):
Maximum of 0.3 mg/L (i.e. 0.0003 g/L)
Releases to air from industries producing, using or handling benzene eg. rubber industry, oil refineries, chemical plants, footwear manufacturing, petrol.
Diffuse sources, and industry sources included in diffuse emissions data
Present in crude oil; cigarette smoke (will affect both active and passive smokers). Releases to air from service stations; evaporation of fuels during petrol refilling; releases to groundwater from underground storage tanks that leak.
Occurs naturally in volcanoes, forest fires, some plants and animals. Is present in crude oil.
Vehicle exhaust, Evaporation of vehicle fuels from motors and vehicle fuel tanks.
Glues, adhesives, household cleaning products, paint strippers, some art supplies and petrol. These products may contain benzene as a contaminant rather than a deliberately added component (e.g. Shellite may contain 0.1% benzene by volume).
Sources used in preparing this information
- Agency for Toxic Substances and Disease Registry (1989), Public Health Statement (accessed December, 1998)
- Agency for Toxic Substances and Disease Registry (1997), ToxFAQS (accessed December, 1998)
- Australian and New Zealand Environment and Conservation Council (ANZECC) (1992), Australian Water Quality Guidelines for Fresh and Marine Waters.
- Environmental Defense Fund (1998), Benzene The Chemical Scorecard (accessed December, 1998)
- Meagher, D (1991), The Macmillan Dictionary of The Australian Environment, Macmillan Education Australia Pty Ltd.
- Micromedex (1995), Knowledge Bases for Healthcare, Safety and the Environment (accessed December, 1998)
- National Environment Protection Council (1998), National Environment Protection Measure for the National Pollutant Inventory. (accessed December, 1998)
- National Library of Medicine (1998), Fact Sheet: Toxic Chemical Release Inventory Facts (accessed December, 1998)
- New Jersey Department of Health, Right to Know Program (1988), TRIFacts (accessed December, 1998)
- Richardson, M (1992), Dictionary of Substances and their Effects, Royal Society of Chemistry, Clays Ltd, England.
- Sittig, M (1991), Handbook of Toxic and Hazardous Chemicals and Carcinogens, 3rd edition, Noyes Publications, USA.
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
- US Department of Health and Human Services (1990), NIOSH Pocket Guide to Chemical Hazards, Publication No. 90-117.
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed June 2021.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018