Styrene (ethenylbenzene)

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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 *Physical 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. Boiling Point: 145 (°C) Specific Gravity: 0.905 Melting Point (°C): -31 to -30.6 (°C) Boiling Point (°C): 145-146 (°C) Vapour pressure: 4.3 mm Hg @ 15 (°C); 9.5 mm Hg @ 30 (°C); 10 mm Hg @ 35 (°C). *Chemical properties:* 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, and 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 process that use or manufacture the material or where it is formed as a by-product. 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 which 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 (ethenylbenzene)? 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 (ethenylbenzene) enter my 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. Relative health hazard On a health hazard spectrum of 0 - 3 Styrene (ethenylbenzene) registers 1.5. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the evaluation of its tendency to cause, or not cause cancer and/or birth defects. It does not take into account exposure to the substance. Human exposure is reflected in the NPI rank given to this substance (see comparative data below). A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0. Health guidelines Worksafe Australia: standards are eight hour time weighted average (TWA) exposure limit: 50 ppm (213 mg/m³), short term exposure limit (STEL): 100 ppm (426 mg/m³) Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996): Health Maximum of 0.03 mg/L (i.e. 0.00003 g/L) Aesthetic Maximum of 0.004 mg/L (i.e. 0.000004 g/L) See the Additional Information page for current health information. The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information. Note that the emissions data in the NPI database is not directly comparable with these guidelines. What effect might Styrene (ethenylbenzene) have on my health? Styrene affects the central nervous and respiratory systems, including depression, concentration problems, muscle weakness, fatigue, unsteadiness, narcosis, defatting dermatitis, and nausea. Exposure may also irritate the nose, throat, and eyes, including severe eye injuries. The International Association for Research into 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 non-persistent in water, with a half-life of less than 2 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. Relative hazard to the environment On an environmental spectrum of 0 - 3 Styrene (ethenylbenzene) registers 1. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. Environmental guidelines See the Additional Information page for current environmental guidelines. No national guidelines. What effect might Styrene (ethenylbenzene) 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.
Comparative data NPI Rank Approximately 400 substances were considered for inclusion on the NPI reporting list. A risk ranking was given based on health and environmental hazard identification and human and environmental exposure to the substance. Some substances were grouped together at the same rank with 208 ranks in total. Styrene (ethenylbenzene) was ranked as 51 out of the 208 ranks. Total hazard score (human health + environmental criteria) = 2.5.
Sources of information used in preparing this fact sheet ChemFinder Searching (accessed, May, 1999) Environmental Chemicals Data and Information Network (accessed, May, 1999) Environmental Writer (accessed, May, 1999) International Association for Research into Cancer: Styrene (accessed, May, 1999) National Environment Protection Council (1998a), National Environment Protection Measure for the National Pollutant Inventory (accessed, May, 1999) National Health and Medical Research Council (NHMRC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (1996), Australian Drinking Water Guidelines. New Jersey Dept of Health, Right to Know, TRIFacts (accessed, May, 1999) Technical Advisory Panel (1999), Final Report to the National Environment Protection Council. University of Cornell Material Safety Data Sheets (accessed, May, 1999) US EPA Chemical Summaries (accessed, May, 1999) US National Toxicology Program (accessed, May, 1999) USEPA Integrated risk Information System (accessed, May, 1999) Worksafe Australia (30 April 1999) Exposure Standard: Styrene Monomer (accessed, May, 1999)

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