WHAT ARE POLYCYCLICWHAT ARE POLYCYCLICAROMATIC AROMATIC

HYDROCARBONS?HYDROCARBONS?

PAHsPAHs

Polycyclic Aromatic Hydrocarbons, or Polycyclic Aromatic Hydrocarbons, or PAHs, are a group of chemicals that are PAHs, are a group of chemicals that are formed during the burning of coal, oil, formed during the burning of coal, oil, gas, garbage, tobacco or charbroiled gas, garbage, tobacco or charbroiled meat.meat.

PAHs occur naturally or can be man-PAHs occur naturally or can be man-made.made.

Properties of PAHsProperties of PAHs

Colorless, white, or paleColorless, white, or pale

yellow-green solidyellow-green solid Evaporate quickly into Evaporate quickly into

the air when heatedthe air when heated Attach strongly to soil Attach strongly to soil

and other particlesand other particles Break down slowlyBreak down slowly Do not dissolve easily in Do not dissolve easily in

waterwater Do not burn easilyDo not burn easily

Common PAHsCommon PAHs

AnthraceneAnthracene Benzo(a)pyreneBenzo(a)pyrene ChryseneChrysene FluoreneFluorene PyrenePyrene

DISTRIBUTION OFDISTRIBUTION OFPOLYCYCLICPOLYCYCLICAROMATIC AROMATIC

HYDROCARBONSHYDROCARBONS

How do PAHs get in the How do PAHs get in the Environment?Environment?

PAHs are released to the environment PAHs are released to the environment through natural and man made processes. through natural and man made processes. Man-made sources contribute far more Man-made sources contribute far more PAHs to the environment than natural PAHs to the environment than natural sources.sources.

Man-made SourcesMan-made Sources

Burning of woodBurning of wood Vehicle exhaustVehicle exhaust Grilled/smoked foodsGrilled/smoked foods Cigarette smokeCigarette smoke Asphalt roads/Parking lotsAsphalt roads/Parking lots Roofing/coal tar productsRoofing/coal tar products Agricultural burningAgricultural burning

Natural SourcesNatural Sources

• • Forest fireForest fire

• • VolcanoesVolcanoes

PAHs in the EnvironmentPAHs in the Environment

PAHs stick tightly to soil particles.PAHs stick tightly to soil particles. Some PAHs evaporate into the air from soil or Some PAHs evaporate into the air from soil or

surface waters.surface waters. PAHs in air settle to the ground where they are PAHs in air settle to the ground where they are

deposited on soil, plants, or in lakes and deposited on soil, plants, or in lakes and streams.streams.

PAHs stay very close to the surface of the PAHs stay very close to the surface of the ground or move to lakes and streams by a ground or move to lakes and streams by a process called erosion.process called erosion.

PAHs that enter lakes or streams settle to the PAHs that enter lakes or streams settle to the bottom and are buried in sediments.bottom and are buried in sediments.

EFFECTS OF PAHsEFFECTS OF PAHs

PAHs IN THE BODYPAHs IN THE BODYKNOWN HUMAN EFFECTSKNOWN HUMAN EFFECTS

Breathing ambient airBreathing ambient air Cigarette smokeCigarette smoke Eating food Eating food

containign PAHs or containign PAHs or grilled meatgrilled meat

Drinking water or milk Drinking water or milk containig PAHscontainig PAHs

Breathing air at work Breathing air at work sitessites

EFFECTS ONEFFECTS ONLABORATORYLABORATORY

ANIMALSANIMALS Tumors occur in some Tumors occur in some

animals exposed for animals exposed for long periods of time.long periods of time.

PAHs have been shown PAHs have been shown to have an effect on the to have an effect on the immune system of some immune system of some animals.animals.

EPA considers PAHs to EPA considers PAHs to be probable human be probable human carcinogens (cancer-carcinogens (cancer-causing substances).causing substances).

KNOWN HUMAN EFFECTSKNOWN HUMAN EFFECTS

Individuals breathing or Individuals breathing or having skin contact with having skin contact with PAHs combined with PAHs combined with other chemicals over a other chemicals over a long period of time, have long period of time, have developed cancer.developed cancer.

There are no known There are no known studies to indicate that studies to indicate that PAHs alone can cause PAHs alone can cause cancer in people.cancer in people.

There are no other known There are no other known health effects of PAHs.health effects of PAHs.