IARC Monograph Vol. 82, 2002 and Vol. 60, 1994 (Group 2B and 2A)
Both styrene and styrene-7,8-oxide are sweet-smelling liquids that appear colourless or yellow in colour. Produced since the 1920's, styrene is one of the most important monomers worldwide. Styrene-7,8-oxide is a major metabolite of styrene in humans as well as an industrial chemical.[4,5] Styrene may also be referred to as vinylbenzene or ethenylbenzene. Styrene-7,8-oxide may be referred to as phenyloxirane or styrene oxide.[2,6] There are numerous other synonyms and product names for both styrene and styrene-7,8-oxide; see the Hazardous Substances Data Bank (HSDB) for more information.
Styrene has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans, based on limited evidence in animals and humans. Styrene caused lung tumours in one inhalation study in mice, but other studies did not provide reliable evidence on carcinogenicity. In occupational studies, exposure to styrene has been linked to lymphatic and hematopoietic cancers, but the excess risk is generally small and statistically unstable.
Styrene-7,8-oxide has been classified by IARC as Group 2A, probably carcinogenic to humans, based on animal and mechanistic evidence. Styrene-7,8-oxide caused forestomach cancer in rats and mice, as well as liver tumours in male mice. There is speculation that styrene-7,8-oxide is the cause of positive results in the study of styrene exposure and lung tumours in mice.
In addition, styrene exposure can lead to central and peripheral nervous system effects, decreased colour discrimination (reversible), and hearing problems. It can also irritate eyes and throat, and cause dermatitis and a syndrome called "styrene sickness" characterized by feelings of unsteadiness, headache, weakness, and decreased nerve conduction. Exposure to styrene-7,8-oxide causes skin irritation and sensitization.
stel = short term exposure limit (15 min. maximum)
sk = easily absorbed through the skin
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value (8 hour maximum)
No occupational exposure limits are available for styrene-7,8-oxide in Canada or from the ACGIH.
Canadian Environmental Guidelines
Manitoba Ambient Air Quality Guideline
24 hour: 400 µg/m3 MALC
Alberta Ambient Air Quality Objectives & Guidelines
1 hour: 215 µg/m3
Ontario Ambient Air Quality Criteria
24 hour: 400 µg/m3
BC's Contaminated Sites Regulation, BC Reg 375/96
Sets soil standards for styrene for: Agricultural soil: 0.1 μg/g Urban park and residential soil: 5 μg/g Commercial and industrial soil: 50 μg/g
µg/m3 = micrograms per cubic metre
µg/g = micrograms per gram
MALC = maximum allowable concentration level
Styrene and styrene-7,8-oxide are not included in Canadian environmental guidelines reviewed.[11,12,13,14,15,16,17]
DSL - low priority substance with risks already managed (styrene)
National Classification System for Contaminated Sites
Rank = "High hazard"
Agreement Respecting the Great Lakes Basin Ecosystem
Listed as a "Hazardous Polluting Substance
Styrene-7,8-oxide was removed from the domestic substances list (DSL) in 2013. Styrene and styrene-7,8-oxide were not found in any other Canadian chemical listings reviewed.[22,23]
Styrene is used primarily in manufacturing:[5,24]
Polystyrene resins for plastic packaging, disposable cups, containers, and insulation
Copolymers with acrylonitrile and/or 1,3-butadiene for synthetic rubber and latex (usually referred to as ABS – acrylonitrile, butadiene, styrene)
These products may then be used to manufacture pipes, automobile parts, food containers, and carpet backing
Styrene is also used to manufacture styrene-butadiene (SB) latex and styrene-butadiene rubbers. SB rubber is primarily used in tire manufacture, while SB latex is used in the foam underlay of carpets and as a paper coating.
An additional use for styrene is in producing glass-reinforced plastics.
Styrene-7,8-oxide is used as a chemical intermediate in producing styrene glycol, cosmetics, surface coatings, treatment of fibres and textiles, as well as agricultural and biological chemicals.[6,24] It is also used to produce epoxy resins and the perfume chemical 2-phenylethanol.[6,24]
Canadian Production and Trade
Production and Trade
517,782 t of 'styrene'
69,377 t 'polymers of styrene'
7,492 t of 'styrene'
208,811 t of 'polymers of styrene'
t = tonne
Canadian production and trade information was not available for styrene-7,8-oxide in the industry databases reviewed.[26,27]
Inhalation is the most important route of occupational exposure to styrene.
CAREX Canada estimates that approximately 89,000 Canadians are likely exposed to styrene in their workplaces. The two largest industrial groups exposed to styrene are automotive repair and maintenance, followed by plastic products manufacturing. The largest occupational groups exposed include automotive service technicians, plastics processing machine operators, and furniture finishers and refinishers.
For workers involved in manufacturing polystyrene, styrene-butadiene (SB) rubber, acrylonitrile butadiene styrene (ABS) resins, and glass-reinforced plastic, exposure levels can be higher (generally <100 ppm, but higher levels have been reported). Reinforced plastics are used in to make boats, automobile parts, shower stalls, tanks, and tubs. In other styrene exposure scenarios, exposure levels are rarely reported above 20 ppm.
Occupational exposure to styrene-7,8-oxide is primarily due to indirect exposure to styrene. This is because styrene is primarily metabolized via the styrene-7,8-oxide pathway in humans. Styrene-7,8-oxide is also formed when styrene reacts with oxygen in air, or with other oxidizing agents in industrial processes.[4,23] Direct occupational exposure to styrene-7,8-oxide may also occur in workers involved in rubber product and paint manufacturing.
The general population is most commonly exposed to styrene via indoor air. Styrene can enter the air from industrial releases, vehicle exhaust, incineration emissions, and tobacco smoke.[2,5,26] Between 2009 and 2011, over 3,000 homes were sampled for styrene in Canada; average levels were 1.13 µg/m3, an increase compared to the average levels found in a similar study conducted in 1992 (0.30 µg/m3). Indoor sources contributed to indoor styrene concentrations to a greater extent than outdoor sources.
Environmental exposure to styrene-7,8-oxide may occur by inhaling contaminated air and consuming contaminated water and foods. However, general public exposure is expected to be low as environmental releases of styrene-7,8-oxide from industrial sites are low in both Canada and the US.[23,29]
Low levels of naturally occurring styrene have been found in a number of foods including fruits, vegetables, nuts, beverages, and meats. Small amounts of styrene and styrene-7,8-oxide may also migrate to different foods from styrene-based plastic food packaging.[24,25,30] A typical amount of styrene migration from packaging into food ranges from 5-30 parts per billion (ppb). One UK study estimated that the migration of styrene-7,8-oxide into food is in the range of 0.002-0.15 ppb.In the 2007 Canadian Total Diet Study, styrene was found in 133 of 153 composite samples. Styrene levels in most of these samples were low, but higher levels were found in herbs and spices, in which styrene naturally forms upon degradation.
Searches of Environment Canada's National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to styrene in Canada:
NPRI and US Household Products Database
Released into Environment
Manufacturing of plastics, glass, transportation equipment, resin, rubber, synthetic fibres, and filaments
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to styrene in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at email@example.com.