Atmosphere

Air toxics and indoor air quality in Australia

State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4

Part C: Factsheets (continued)

Benzene

Substance name: Benzene
CASR number: 71-43-2
Molecular formula C6H6
Synonyms: None

Physical and chemical properties

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.

Common uses

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.

Sources of emissions

Point sources

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.

Natural sources

Crude oil, coal and bushfires.

Mobile sources

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).

Health effects

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.

Health guidelines

National Occupational Health and Safety Commission (NOHSC):

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):

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'.

Environmental effects

Environmental fate

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.

Environmental transport

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.

Environmental guidelines

Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC 1992):

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.

Key

   Links to another web site
   Opens a pop-up window