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)

Styrene (ethenylbenzene)

Substance name: Styrene (ethenylbenzene)
CASR number: 100-42-5
Molecular formula: C8H8
Synonyms: Ethenylbenzene, ethenyl benzene, cinnamene, cinnamenol, NCI-C02200, phenylethene, phenylethylene, styrene monomer, styrol, styrole, styrolene, vinylbenzol, and vinylbenzene

Physical and chemical properties

Pure styrene is a colourless to yellowish oily liquid that evaporates easily and has a sweet smell. It is often mixed with other substances that give it a sharp smell. It is flammable.

Melting point: -31 to -30.6°C
Boiling point: 145°C
Specific gravity: 0.905
Vapour pressure: 4.3 mm Hg @ 15°C; 10 mm Hg @ 35°C

Styrene dissolves in some liquids, but dissolves only slightly in water. It is soluble in alcohol, ether, acetone, and carbon disulfide; it is incompatible with oxidisers, catalysts for vinyl polymers, peroxides, strong acids, and aluminium chloride. Styrene is dangerous when exposed to flame, heat or oxidants; it reacts violently with chlorosulfonic acid, oleum, and alkali metal-graphite, and reacts vigorously with oxidising materials. It may polymerise if contaminated or subjected to heat; on decomposition, it emits acrid fumes. It usually contains an inhibitor such as tert-butylcatechol.

Common uses

When it is linked together in long chains, or polymerised, styrene is used predominantly in the production of polystyrene plastics and resins, such as in insulation or in the fabrication of fibreglass boats; most styrene products contain a residue of unlinked styrene. Styrene is also used to make rubber, as an intermediate in the synthesis of materials used for ion exchange resins and to produce copolymers such as styrene-acrylonitrile, acrylonitrile-butadiene-styrene, and styrene-butadiene rubber.

Sources of emissions

Point sources

Styrene will be emitted to air from industrial processes that either use or manufacture the material or where it is formed as a byproduct.

Diffuse sources, and point sources included in aggregated emissions data

Styrene is present in combustion products such as cigarette smoke.

Natural sources

Low levels of styrene occur naturally in a variety of foods, such as fruits, vegetables, nuts, beverages, and meats.

Mobile sources

Styrene is present in car exhaust.

Consumer products that may contain styrene (ethenylbenzene)

Products produced from styrene include packaging, electrical and thermal insulation, fibreglass, pipes, car parts, drinking cups and other food-use items, and carpet backing.

Health effects

How might I be exposed to styrene?

Exposure to styrene can be by breathing the vapours, contact with pure styrene or substances containing styrene or by eating or drinking foods containing or contaminated by styrene.

By what pathways might styrene enter my body?

Styrene can enter the body by absorption into the blood through the lungs, stomach, skin or eyes. Populations with potentially high exposures to styrene include people working in various styrene industries, smokers, and those eating a high proportion of foods packaged in polystyrene.

Health guidelines

National Occupational Health and Safety Commission (NOHSC):

Australian Drinking Water Guidelines (NHMRC and ARMCANZ 1996):

What effect might styrene have on my health?

Styrene affects the central nervous and respiratory systems, and may cause depression, concentration problems, muscle weakness, fatigue, unsteadiness, narcosis, defatting dermatitis and nausea. Exposure may also irritate the nose, throat, and eyes, including causing severe eye injuries. Styrene is classified by the NOHSC as harmful by inhalation and also as a skin irritant. The International Association for Research on Cancer (IARC) classifies styrene as 'possibly carcinogenic to humans' (Group 2B).

Environmental effects

Environmental fate

Styrene is quickly broken down in the air, usually within one to two days; it evaporates from shallow soils and surface water. Styrene that remains in soil or water may be broken down by bacteria. Styrene monomer is nonpersistent in water, with a half-life of less than two days. About 99% of styrene monomer will eventually end up in air; about 0.85% will end up in water; the rest will end up in terrestrial soils and aquatic sediments.

Environmental transport

Styrene will be transported as a vapour in air, in water and in contaminated soils. Styrene has a slight tendency to bioaccumulate.

Environmental guidelines

There are no national guidelines.

What effect might styrene have on the environment?

Styrene is moderately toxic to aquatic organisms. Styrene is expected to have low toxicity towards terrestrial animals. Styrene contributes to the formation of photochemical smog due to indirect photochemical reactions.

Key

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