Styrene and Styrene-7,8-Oxide Profile

INDUSTRIAL CHEMICALS  PROBABLE CARCINOGEN (IARC 2A)

CAS No. 100-42-5 and 96-09-3
IARC Monograph Vol. 82, 2002 and Vol. 60, 1994 (Group 2B and 2A)
IARC Monograph Vol. 121, 2018 (Group 2A) – in prep.

Styrene and Styrene-7,8-Oxide Profile

General Information

Both styrene and styrene-7,8-oxide are sweet-smelling liquids that appear colourless or yellow in colour.[1] Produced since the 1920’s, styrene is one of the most important monomers worldwide.[2] Styrene-7,8-oxide is a major metabolite of styrene in humans as well as an industrial chemical.[3,4] Styrene may also be referred to as vinylbenzene or ethenylbenzene.[1] Styrene-7,8-oxide may be referred to as phenyloxirane or styrene oxide.[1,5] 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.[5]

Styrene has been classified by the International Agency for Research on Cancer (IARC) as Group 2A, probably carcinogenic to humans, based on limited human and sufficient animal evidence.[4] Elevated incidence or mortality of lymphohematopoietic cancers was observed in large occupational cohorts of workers in the reinforced plastics industry from Europe, the UK, Denmark, and the United States. In particular, there was greater consistency in evidence for myeloid leukaemia; one study found increasing incidence of myeloid leukaemia with increasing cumulative exposure, and another found increased mortality associated with the highest cumulative styrene exposure group. In multiple studies of mice, increased incidence of lung cancers was observed in male and females. Other studies found increased incidence of mammary tumours and liver cancers in females. In addition to the animal and human evidence, there was strong mechanistic evidence that supported the decision.

Styrene-7,8-oxide has been classified by IARC as Group 2A, probably carcinogenic to humans, based on sufficient animal and strong mechanistic evidence.[4] Styrene-7,8-oxide caused forestomach cancer in rats and mice, as well as mammary tumours in rats, and liver tumours in male mice.[4]

In addition, styrene exposure can lead to central and peripheral nervous system effects, decreased colour discrimination (reversible), and hearing problems.[4] 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.[5] Exposure to styrene-7,8-oxide causes skin irritation and sensitization.[5]

Regulations and Guidelines

Occupational Exposure Limits (OEL)[6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

Styrene  
Canadian Jurisdictions OEL (ppm)
Canada Labour Code 20
40 [stel]
AB, MB, NB, NL, NS, PE, SK, NU, NT 20
40 [stel]
BC 50
75 [stel]
ON 35
100 [stel]
QC 50 [sk]
100 [stel]
YT 100
125 [stel]
Other Jurisdictions OEL (ppm)
ACGIH 2018 TLV 20
40 [stel]
ppm = parts per million
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

Jurisdiction Limit Year
Manitoba Ambient Air Quality Guideline 24 hour: 400 µg/m3 MALC 2005[21]
Alberta Ambient Air Quality Objectives & Guidelines 1 hour: 215 µg/m3 2017[22]
Ontario Ambient Air Quality Criteria 24 hour: 400 µg/m3 2016[23]
BC’s Contaminated Sites Regulation, BC Reg 375/96 Sets soil standards for the protection of human health:
Agricultural and low density residential sites: 8,500 μg/g
Urban park and high density residential sites: 15,000 μg/g
Commercial sites: 50,000 μg/g
Industrial sites: >1,000 mg/g
Drinking water: 800 µg/L

 

 

Sets vapour standards for the protection of human health:
Agricultural, urban park, residential use standard: 1,000 μg/m3
Commercial use standard: 3,000 μg/m3
Industrial use standard: 9,000 μg/m3
Parkade use standard: 8,000 μg/m3
(Vapours derived from soil, sediment, or water)

2017[24]
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.[25,26,27,28,29,30,31]

Canadian Agencies/Organizations

Agency Designation/Position Year
Health Canada DSL – low priority substance with risks already managed (styrene) 2006[32]
National Classification System for Contaminated Sites Rank = “High hazard” 2008[33]
Agreement Respecting the Great Lakes Basin Ecosystem Listed as a “Hazardous Polluting Substance 1987[34]
Environment Canada’s National Pollutant Release Inventory NPRI Part (Threshold Category): 1A, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes; 5, Reportable to NPRI if released at quantities greater than: 1 tonne of 10-tonne total VOC air release 2016[35]
 

Styrene-7,8-oxide was removed from the domestic substances list (DSL) in 2013.[36] Styrene and styrene-7,8-oxide were not found in any other Canadian chemical listings reviewed.[37,38]

Main Uses

Styrene is used primarily in manufacturing:[4,39]

  • 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.[39] 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.[40]

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.[5,39] It is also used to produce epoxy resins and the perfume chemical 2-phenylethanol.[5,39]

Canadian Production and Trade

Production and Trade

Activity Quantity Year
Export 517,782 t of ‘styrene’ 2015[41]
Export 69,377 t ‘polymers of styrene’ 2015[41]
Import 7,492 t of ‘styrene’ 2015[41]
Import 208,811 t of ‘polymers of styrene’ 2015[41]
t = tonne

Canadian production and trade information was not available for styrene-7,8-oxide in the industry databases reviewed.[41]

Environmental Exposures Overview

The general population is most commonly exposed to styrene via indoor air.[1] Styrene can enter the air from industrial releases, vehicle exhaust, incineration emissions, and tobacco smoke.[1,4,41] 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.[42]

Environmental exposure to styrene-7,8-oxide may occur by inhaling contaminated air and consuming contaminated water and foods.[38] 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.[38,43]

Low levels of naturally occurring styrene have been found in a number of foods including fruits, vegetables, nuts, beverages, and meats.[44] Small amounts of styrene and styrene-7,8-oxide may also migrate to different foods from styrene-based plastic food packaging.[39,40,44] A typical amount of styrene migration from packaging into food ranges from 5-30 parts per billion (ppb).[44] One UK study estimated that the migration of styrene-7,8-oxide into food is in the range of 0.002-0.15 ppb.[39] 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.[45]

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

NPRI 2015[43]
Search Term: ‘styrene’
Results 89 facilities
Category Quantity Industry
Released into Environment 1,450 t Manufacturing of plastics, glass, transportation equipment, resin, rubber, synthetic fibres, and filaments
Disposed of 278 t
Sent to off-site recycling 2.4 t
t = tonne
US Household Products 2016[46]
Search Term Quantity Product Type
‘styrene’ 14 Automotive paints (2), adhesives (2), wood fillers (3),
cements (3), and sealants (4)

Occupational Exposures

Inhalation is the most important route of occupational exposure to styrene.[1]

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).[1] Reinforced plastics are used in to make boats, automobile parts, shower stalls, tanks, and tubs.[1] In other styrene exposure scenarios, exposure levels are rarely reported above 20 ppm.[1]

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.[4] Styrene-7,8-oxide is also formed when styrene reacts with oxygen in air, or with other oxidizing agents in industrial processes.[3,38] Direct occupational exposure to styrene-7,8-oxide may also occur in workers involved in rubber product and paint manufacturing.[38]

For more information, see the occupational exposure estimate for styrene.

Sources

1. National Toxicology Program (NTP). Final Report on Carcinogens, Background Document for Styrene (2008) (PDF)
3. International Agency for Research on Cancer (IARC). Monograph summary, Volume 60 (1994) (PDF)
4. International Agency for Research on Cancer Monograph Working Group. “Carcinogenicity of quinoline, styrene, and styrene-7,8-oxide.” The Lancet Oncol 2018.
5. US National Library of Medicine. Hazardous Substances Data Bank (Search term: ‘styrene’)
11. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2012)
12. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2016) (PDF)
14. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
16. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
18. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
19. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2012) (PDF)
20. Occupational Safety and Health Administration (OSHA). Annotated PELs (2018)
21. Government of Manitoba. Ambient Air Quality Guideline (2005)
22. Alberta Environment and Parks. Ambient Air Quality Objectives (2017)
23. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2016)
24. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2017)
27. Health Canada. Cosmetic Ingredient Hotlist (2014)
30. The Canadian Legal Information Institute (CanLII). Ontario Drinking Water Quality Standards, O Reg 169/03 (2017)
31. The Canadian Legal Information Institute (CanLII). Regulation respecting the quality of drinking water, CQLR c Q-2, r 40 (2014)
33. Canadian Council of Ministers of the Environment (CCME). National Classification System for Contaminated Sites (2008) (PDF)
34. International Joint Commission. Revised Great Lakes Water Quality Agreement of 1978 (1978) (PDF)
37. Environment and Climate Change Canada. Toxic Substances List -CEPA Schedule 1 (2010)
39. National Toxicology Program (NTP). 14th report on carcinogens for Styrene (2016) (PDF)
40. Government of Canada, Environment Canada & Health Canada. Priority Substances List Assessment Report Styrene (1993) (PDF)
41. International Trade Centre. TradeMap (Free subscription required)
42. Xu J,Szyszkowicz B, Cakmak S, Austin CC, Zhu J.“Estimation of indoor and outdoor ratios of selected volatile organic compounds in Canada.” Atmos Environ 2016;141:523-531.
43. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (Substance name: ‘styrene-7,8-oxide’)
44. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Styrene (2007) (PDF)
45. Cao X-L, Sparling M, Dabeka R.“Occurrence of 13 volatile organic compounds in foods from the Canadian total diet study.”Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2016;33(2):373-82.
46. US Household Products Database (HPD). Household Products (Search term: ‘Styrene’)

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