INDUSTRIAL CHEMICALS – MULTIPLE CLASSIFICATIONS (IARC 2A, 2B)
Bitumens are products of petroleum refining that are thick, black liquids or solids. Bitumens may also be called asphalt or asphaltic bitumens. However, in this document, bitumens should not be confused with paving asphalt (which is a mixture of bitumen, sand, and stones). Oxidized or air/steam-refined bitumens have undergone a process where hot air is blown through the substance to produce desirable characteristics for industrial applications.[1,3] Bitumens also occur as natural deposits.
Bitumens are generally composed of non-volatile hydrocarbons and their derivatives.[1,4] The chemical composition of bitumens depends on both the crude petroleum source and the refining process.
The International Agency for Research on Cancer (IARC) classified bitumens by job types expected to work with bitumen variants. Occupational exposure to hard bitumens and their emissions during mastic asphalt work was classified by IARC as Group 2B, possibly carcinogenic to humans. IARC classified occupational exposure to oxidized bitumens and their emissions during roofing as Group 2A, probably carcinogenic to humans. IARC classified occupational exposure to straight-run bitumens and their emissions during road paving as Group 2B, possibly carcinogenic to humans. Although there is some indication of increased lung and skin cancer rates in animals and humans, epidemiological studies have been inconclusive due to concurrent exposure to coal tar pitches, polyaromatic hydrocarbons (PAHs), diesel engine exhaust, and other materials used in the occupations reviewed. Naturally occurring bitumens, such as those found in northern Alberta, were not evaluated by the IARC monograph for bitumens.
Non-cancer health effects following exposure to bitumens include eye, respiratory, and skin irritation.[3,4] Hot bitumens may also cause dermal burns.
Regulations and Guidelines
Occupational exposure limits (OEL) [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
|Canadian Jurisdictions||OEL (mg/m3)|
|Canada Labour Code||0.5 [i]*|
|BC, MB, NL, NB, NS, ON, PE||0.5 [i]*|
|NT, NU, SK||0.5 [i]*
|Other Jurisdiction||OEL (mg/m3)|
|ACGIH 2020 TLV||0.5 [i]*|
*for asphalt (bitumen) fume as benzene-soluble aerosol
**for asphalt (petroleum fumes)
mg/m3 = milligrams per cubic meter
i = inhalable fraction
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian Environmental Guidelines
|Health Canada||DSL – high priority substance with the greatest potential for exposure||2006|
DSL = domestic substance list
Bitumen was not included in other Canadian government guidelines, standards, or chemical listings reviewed.
Canadian Production and Trade
Canadian refineries produced approximately 2.6 million barrels per day of raw bitumen, which is equivalent to 150,878,955 m3 annually. The largest market for exported Canadian bitumen is the United States.
Production and trade
|Domestic production||2.6 million MMb/d||2016|
|Export||3,251,878 t (of ‘petroleum bitumen’)||2021|
|Import||178,796 t (of ‘petroleum bitumen’)||2021|
MMb/d = million barrels per day
t = tonne
Environmental Exposures Overview
There is limited data available on environmental bitumen concentrations in drinking water, food, and soil. It is more likely that the general public would be exposed to bitumen fumes, rather than bitumens in their liquid or solid form. Sources of environmental exposure include inhaling emissions from industrial production and use of bitumens, such as asphalt mixing plants and road paving. Runoff from roads paved with bitumens may also contain low levels of polycyclic aromatic hydrocarbons (PAHs), leading to potential exposure via dermal and ingestion routes.
Bitumen is not reportable to the National Pollutant Release Inventory (NPRI) in Canada. A search of the US Consumer Product Information Database (search term “bitumen”) yielded over 60 products containing bitumens as an ingredient – all were asphalt products.
Occupational Exposures Overview
Inhalation of bitumen fumes and dusts is the most important route of occupational exposure. For bitumens used in cooler temperatures, such as cutback bitumens, blended bitumens, and bitumen emulsions, regular skin contact may also occur.
CAREX Canada estimates that approximately 58,000 Canadians are exposed to bitumens in their workplaces. The largest industrial groups exposed are highway, bridge, and street construction, followed by contractors in foundation, structure, and building exterior, finishing, and equipment.
The largest occupational groups exposed are construction trades helpers and labourers, followed by heavy equipment operators and roofers and shinglers. Other occupations potentially exposed to bitumens include those employed in refineries, asphalt mixing plants, and roofing material manufacturing,[1,3] as well as workers involved in transporting and storing bitumens.
Strategies to reduce exposures include selecting the correct kettle type/size, using low fuming asphalt, and using temperature control devices to reduce asphalt fume emissions.
For more information, see the occupational exposure estimate for bitumens.
Photo: U.S. Air Force photo/Chris Willis
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