State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4
Benzene is a colourless liquid with a characteristic, sweet aromatic odour. It evaporates into the air very quickly.
Melting point: 5.5°C
Boiling point: 80.1°C
Specific gravity: 0.879
Vapour pressure: 75.02 mm Hg at @ 20°C
Vapour density: 2.8 (air = 1)
Flashpoint: -11°C (closed cup)
Benzene is very stable. It is miscible with organic solvents and is soluble in water. It is explosive and highly flammable.
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 and is a constituent in motor fuels.
Petroleum refineries and terminals, coal coking plants, chemical plants, aluminium refineries, fossil fuel burning power plants and landfills.
Diffuse sources, and point sources included in aggregated emissions data
Service stations, lawnmowers and other petrol-fuelled implements, solid fuel combustion, particularly wood-burning, crop residue and forest management burning, tobacco smoke.
Crude oil, coal and bushfires.
Vehicle exhaust, evaporation of vehicle fuels from motors and vehicle fuel tanks.
Consumer products that may contain benzene
Petrol (2.6–3.3%), tobacco smoke (0.3–0.5 mg/cigarette in sidestream smoke and 0–0.1 mg/cigarette in mainstream smoke).
How might I be exposed to benzene?
People are exposed by inhalation of contaminated air, particularly indoor air in buildings and moving vehicles.
By what pathways might benzene enter my body?
Benzene evaporates very quickly, so the most common exposure is from breathing air containing benzene. Ingestion is unlikely as foods and drinking water contain either no or negligible amounts of benzene. Benzene can enter through the skin, though the skin absorbs benzene poorly; contact with products such as petrol is potentially dangerous.
National Occupational Health and Safety Commission (NOHSC):
- TWA (eight-hour time weighted average) exposure limit in the workplace: 5 ppm (16 mg/m³).
Benzene is listed as a substance under review for carcinogenicity by the NOHSC. Industrial use of feedstock containing more than 50% benzene must be notified to the relevant public authority. Benzene is listed in Schedule 7 in the Australian Standard for the Uniform Scheduling of Drugs and Poisons and must not be possessed, sold or supplied for domestic purposes in concentrations exceeding 5% in petrol and 1.5% in other products.
Australian Drinking Water Guidelines (NHMRC and ARMCANZ 1996):
- Maximum of 0.001 mg/L (0.000001 g/L).
What effect might benzene have on my health?
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. Exposure can result in symptoms such as skin and eye irritations, drowsiness, dizziness, headaches, and vomiting. Benzene is carcinogenic; 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 been linked with birth defects in animals and humans. The International Agency for Research on Cancer classifies benzene as 'carcinogenic to humans'.
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 either break down or 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 in plant or animal tissues.
Benzene is carried in the air. If released to soil, it will usually break down 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.
Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC 1992):
- Maximum of 0.3 mg/L (0.0003 g/L).
What effect might benzene have on the environment?
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. Benzene can cause death in plants and roots and damage to the leaves of many agricultural crops.
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