Benzene, an aromatic hydrocarbon, is a clear, usually colourless liquid with a gasoline-like odour. Benzene occurs naturally as a constituent of crude oil and has been synthesized from coal since 1849 and from petroleum sources since 1941. Trace amounts of benzene are produced from the incomplete combustion of organic materials. Benzene may also be referred to as, benzol or coal naphtha. There are numerous other synonyms and product names; see HSDB for more information.
Benzene has been classified by IARC as Group 1, carcinogenic to humans.[2,6] A recent review of Group 1 agents by IARC reaffirmed this classification, citing sufficient evidence for human carcinogenicity for acute non-lymphocytic leukaemia, and limited evidence of carcinogenicity in acute lymphocytic leukaemia, chronic lymphocytic leukaemia, multiple myeloma and non-Hodgkin lymphoma. Benzene is considered a 'non-threshold toxicant,' where adverse effects may occur at any level of exposure.
Although the hematopoietic system is the main target for benzene toxicity, the immune, lymph and nervous systems are also adversely affected. Short-term exposure can cause drowsiness, headaches, and unconsciousness. The effects of long-term exposure include anaemia, neuropathies, and memory loss. Benzene is also a skin irritant.
Benzene in Gasoline Regulations: 1.0% max. benzene (by volume) in supplied gasoline (Exceptions: aircraft use, vehicle competitions, scientific research)
Benzene was not included in other Canadian government chemical listings reviewed.
Benzene is used primarily as a raw material in the production of chemicals including ethylbenzene, for styrene; cumene, for phenol and acetone; and cyclohexane, for nylon and synthetic fibres.[2,7]
Benzene was formerly added to gasoline as an octane enhancer and anti-knock agent (along with toluene and xylene). Benzene is not generally not used as a gasoline additive any more in Canada, but it does occur naturally in crude oil and gasoline. Benzene has also been used in manufacturing of rubbers, lubricants, dyes, detergents, drugs and pesticides.
Canadian Production and Trade
In 2002 there were 7 facilities producing benzene – 4 in Ontario, 2 in Alberta and 1 in Quebec – with a production capacity of 1,142 kilotonnes.
Production and Trade
Export: Mainly to US
175,747 t of 'benzene'
Import: Mainly from US
40,189 t of 'benzene'
kt = kilotonne
t = tonne
The major route of occupational exposure to benzene is inhalation, but dermal exposure can also occur.[5,7]
Industries where exposure to benzene is likely to occur include benzene production in petrochemical plants, petroleum refining, and coke and coal chemical manufacturing; rubber tire manufacturing; and storage or transport of benzene and petroleum products containing benzene.
Occupations at risk of benzene exposure include steel workers, printers, rubber workers, shoe makers, laboratory technicians, firefighters, and gas station employees. Workers who spend significant time in motor vehicles in areas of congested traffic may also be exposed to benzene.[5,7]
The primary source of environmental benzene exposure is indoor air.[18,21] Benzene is emitted by a number of indoor sources, including glues, paints, furniture wax, and some detergents. Combustion sources such as fireplaces, gas furnaces, vehicle in attached garages and cigarette smoke may also contribute to concentrations of benzene indoors. A recent Canadian survey of homes in Regina, Saskatchewan found indoor concentrations of benzene ranging from 0.18 to 32.33 µg/m3, with average concentrations of 2.72 µg/m3 in the summer and 2.06 µg/m3 in the winter.
Outdoor concentrations of benzene are generally lower than indoor concentrations. Major sources of benzene in outdoor air include vehicular combustion of gasoline and diesel fuels, residential fuel combustion, iron and steel production, chemical manufacturing, as well as petroleum and coal products manufacturing.[3,21] Natural sources of benzene in the environment include forest fires, volcanos, petroleum seepage, and emissions from vegetation.
Ambient air benzene levels in different locations in Canada have been monitored since 1989 by the National Air Pollution Surveillance (NAPS) network. A 2003 NAPS update indicated that the concentrations of benzene at eighteen urban sites decreased by 65% between 1990 and 2002. Annual mean levels at these urban sites were below 2 µg/m3 from 1999 to 2003. Average concentrations of benzene in rural sites were generally around 0.5 µg/m3.
Low levels of benzene are found in some soft drinks and a number of other food and beverages.
Benzene contamination in soils and groundwater can arise from oil and gas spills, underground storage tanks, and seepage from waste disposal sites.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to benzene in Canada:
NPRI and US Household Products Database
Search term: 'benzene'
Released into Environment
Steelworks, petroleum refineries, mines, power plants (204 companies)
Sent to off-site recycling
US Household Products 2010
Interior paints (2), wood finish (1), adhesive remover (1), auto part cleaner/degreaser (1)