Fact sheet: Benzo pyrene

From: Public Services and Procurement Canada

Discover a list of a contaminant's important chemical properties, how it will react in the environment, main sources of contamination related, and a brief overview of health and safety issues.

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General information

CAS number

50-32-8

Molecular formula

C20H12

Formula weight

252.3 g/mol

Family

Polycyclic aromatic hydrocarbons (PAH)

Properties (at room temperature where applicable)

Compound properties list
ParameterValueComment
Melting/boiling point 179 °CSolid
Relative density1.35 g/cm3Sinks in water
Vapour pressure1 x 10 -7 mm HgVery low volatility
Vapour density8.7Much denser than air
Solubility in water0.002 mg/LVery low solubility
Henry's law constant4 x 10-7 atm·m3/molSlow volatilization when dissolved
log Koc (Depending on soil or sediment characteristics)6.0 - 7.4*Very strong adsorption to organic matter

Environmental behaviour

At 20 0C, benzo(a)pyrene is a solid with very low volatility. Characterized by its very low solubility, it will volatilize slowly once dissolved and adsorbs very strongly to organic matter. When present in soil, this compound will volatilize very lightly and solubilize very slowly. Once dissolved, it will either migrate into the water table or drain towards a waterway, where it will be diluted before volatilizing slowly. Fragments of benzo(a)pyrene can also be carried into and deposited at the bottom of waterways, where they will very slowly dissolve. Once the source has been removed, the adsorbed benzo(a)pyrene will take a very long time to disappear, being released in its gaseous or dissolved forms. The resulting plumes (gaseous or dissolved) will be relatively small in size.

Health and safety

Benzo(a)pyrene should be handled with care, as it is toxic.

Principal resources

Benzo(a)pyrene is a polycyclic aromatic hydrocarbon (PAH). PAHs are a group of organic compounds that contain two or more benzene rings in their structure. There are more than 100 different PAHs that generally occur as complex mixtures (example, combustion by-products such as soot). Incomplete combustion of fuels in engines, during coal coking, or when wood is burning (forest fires, wood stoves) produces PAHs. PAHs are also constituents of petroleum and coal, and they are more present in some of their derivatives like tars and asphalt. The wood preservative industry (example, creosote), aluminum smelters using Soderberg electrodes, and hazardous waste disposal sites are further contributors of anthropogenic PAHs to the environment.

Benzo(a)pyrene, like most individual PAHs, has very limited or no known uses, except as reagents in biochemical or cancer research. Benzo(a)pyrene is more likely to be found mixed with other PAHs in commercial products like coal tar, coal tar pitch, creosote, bitumen and asphalt. Coal tar is used as a fuel in the steel industry, distilled to give coal tar pitch and creosote, and has been used in the clinical treatment of skin disorders such as eczema and dermatitis. Coal tar pitch is used primarily as a binder for aluminum smelting electrodes, but is also used in roofing, surface coatings and a variety of other applications. Creosote is used to preserve wood for railroad ties, marine pilings and telephone poles. Some creosote products are also used as a fuel by steel production. Bitumen and asphalt are used for paving roads, for sound- and water-proofing, and coating pipes.

References

Agency for Toxic Substances and Disease Registry (ATSDR). 1995. Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). U.S. Department of Health and Human Services, Public Health Service, Georgia, USA. (Viewed December 2013)

Canadian Council of Ministers of the Environment. 1999. Canadian Water Quality Guidelines for the Protection of Aquatic Life: Polycyclic Aromatic Hydrocarbons (PAHs). In: Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, Manitoba, Canada. (Viewed December 2013).

Montgomery, John H. 2007. Groundwater Chemicals, Desk Reference, Fourth Edition, CRC Press, Taylor and Francis Group, Florida, USA.

National Toxicology Program. 2005. Report on Carcinogens, Twelfth Edition: Substance Profile of Polycyclic Aromatic Hydrocarbons. U.S. Department of Health and Human Services, Public Health Services, USA.(PDF, 256KB) (Viewed December 2013)

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