What are polycyclic aromatic hydrocarbons (PAHs)?

Polycyclic aromatic hydrocarbons (PAHs) are a group of more than 100 different chemicals that are released from burning coal, oil, gasoline, trash, tobacco, wood, or other organic substances such as charcoal-broiled meat. They are also called polynuclear aromatic hydrocarbons. They can occur naturally when they are released from forest fires and volcanoes, and can be manufactured. Other activities that release PAHs include driving, agricultural burning, roofing or working with coal tar products, sound- and water-proofing, coating pipes, steelmaking, and paving with asphalt. PAHs are persistent organic pollutants (POPs).

Manufactured PAHs are colorless, white, or pale yellow solids. Some can take the form of needles, plates, crystals, or prisms.

PAHs are found in the asphalt that covers roads and parking lots, and in smoke and soot. They are also found in coal tar, coal tar pitch, and creosotes, which are by-products of distilling and heating coal and some woods. Coal tar products are used in medicines for skin diseases such as psoriasis, and in insecticides, fungicides, and pesticides. Coal tar creosote is widely used for wood preservation. Coal tar and coal tar pitch are used for roofing, road paving, aluminum smelting, and production of coke, a coal residue used as fuel.

Some PAHs are used to make medicines, dyes, plastics, and pesticides.

You can be exposed to PAHs primarily by breathing polluted air, wood smoke, vehicle exhaust, or cigarette smoke; eating contaminated food; or drinking contaminated water. You can breathe PAHs outside when they are attached to dust and other particles in the air. Outdoor sources of PAHs include soot, smoke, cigarette smoke, vehicle exhaust, asphalt roads, wildfires, volcanoes, agricultural or wood burning, municipal and industrial waste incineration, and releases from hazardous waste sites. You can also be exposed to PAHs in the soil near areas where coal, wood, gasoline, or other products have been burned, or in the soil at hazardous waste sites, former manufactured gas factory sites, and wood-preserving facilities.

At home, you can be exposed to PAHs if you breathe cigarette smoke, burn wood, eat grilled or charred meats, drink contaminated water or milk, eat contaminated foods, use medicines made with PAHs, use pesticides, or use wood products treated with creosote. You may be exposed to creosote if you eat herbal dietary supplements which contain the leaves of the creosote bush, called chaparral.

At work, you can be exposed to PAHs if you work at a coal tar, aluminum, or asphalt production plant; smokehouse; foundry; engine repair shop; trash incinerator; coal gasification site; or farm where agricultural burning and pesticide application takes place. You can be exposed if you work in coking, mining, gas or oil refining, metalworking, chemical production, iron or steel production, wood preserving, coal tarring, roofing, transportation, cooking or catering, and the electrical industry. You can be exposed if you work as a roof tarrer, asphalt applicator, or chimney sweep, or use creosote-treated wood.

Of the more than 100 forms of PAHs, 15 are listed as "reasonably anticipated to be human carcinogens" in the Twelfth Report on Carcinogens published by the National Toxicology Program because exposure to these PAHs is linked to lung, liver, and skin cancers.

Exposure to large amounts of coal tar creosote may result in convulsions, unconsciousness, and even death. Breathing vapors of coal tar, coal tar pitch, and creosote can irritate the respiratory tract. Eating large amounts of herbal supplements that contain creosote leaves may cause liver damage.

If you think your health has been affected by exposure to PAHs, contact your health care professional.

For poison emergencies or questions about possible poisons, contact your local poison control center at 1-800-222-1222.

This description is based on the information found in the Web links listed with this topic.

Locations where PAHs may be found: more neighborhoods >>
City	Farm	Town
Brownfield Construction Drinking Water Factory Food Services Homes Hospital Indoor Air Offices and Stores Outdoor Air Park Pharmacy River School School Bus Vehicles	Agricultural Runoff Barn and Silo Crop Fields Drinking Water Farm Pond Homes Indoor Air Landfill Off-road Vehicles Outdoor Air Shed Tree Farm and Logging Vehicles	Drinking Water Factory Homes Indoor Air Offices and Stores Outdoor Air Park River School School Bus Vehicles
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US Border Regions	Port	US Southwest
Auto Shop Border Crossing Crop Fields Drinking Water Homes Illegal Dumps and Tire Piles Indoor Air Maquiladora Outdoor Air Park River Stormwater and Sewage Tienda Trash Burning Vehicles Wildfires	Coastal Brownfield Cruise Ship Drinking Water Homes Indoor Air Marina and Boats Offices and Stores Outdoor Air River Shipping Shipyard Stormwater and Sewage Urban and Industrial Runoff Vehicles	Agricultural Runoff Coal-Fired Power Plants Crop Fields Drinking Water Homes Illegal Dumps and Tire Piles Indoor Air Off-road Vehicles Outdoor Air River Trash Burning Vehicles Wildfires

Last Updated: October 9, 2012