Description

Polycyclic aromatic hydrocarbons (PAHs) are a group of over 100 different chemicals that are formed as byproducts of combustion (burning) of coal, oil, gas, garbage, tobacco, foods and other organic substances. Benzo[a]pyrene (BaP) is the most toxic and best studied of the PAHs.  Naphthalene is a type of PAH used in mothballs and some cleaners.

PAHs are usually found in smoke and soot. They are also found in coal tar pitch, creosote (used to preserve wood), asphalt, shale oil, vehicle exhaust, wood smoke, and cigarette smoke. PAHs can attach to other particles, including dust.  Besides collecting in household dust, these particles can be carried in air, water and soil and onto food crops.  Indoors, PAHs can also react with nitrates and form more toxic compounds.

Most people are exposed to some PAHs through the food they eat, especially foods that have been grilled, barbecued or smoked.  Otherwise, children are most likely to be exposed to PAHs outdoors, especially in polluted or high traffic areas.  Indoors, children experience high exposure to PAHs in homes where someone smokes tobacco, even if they are not directly exposed to the smoke, or where a fireplace or woodstove is used frequently or without proper venting.

Pregnant women exposed to PAHs, including benzo[a]pyrene, can pass them on to their developing babies through the placenta.

Health Effects

Immediate Health Effects

• If SWALLOWED, polycyclic aromatic hydrocarbons (PAHs) is Not Available
• If ABSORBED THROUGH SKIN, polycyclic aromatic hydrocarbons (PAHs) is Not Available
• If INHALED (SNIFFED OR BREATHED IN), polycyclic aromatic hydrocarbons (PAHs) is Not Available

Longterm or Delayed Health Effects

• This chemical is likely to cause cancer.  It is considered a Probable Carcinogen by the World Health Organization, the U.S. Environmental Protection Agency, or another agency.
• Suspected Endocrine Disruptor = May interfere with, mimic or block hormones
• Development Toxicant = Can interfere with normal development of a fetus or child
• Reproductive Toxicant = Can harm reproductive system

Other

• Long-term exposure to benzo[a]pyrene in humans has resulted in skin rashes, sensitivity to sunlight, eye irritation and cataracts.
• Cancer. Epidemiological studies have found an increase in lung cancer rates in people exposed to coke oven emissions, roofing tar emissions and tobacco smoke; all of these compounds contain BaP and other polycyclic aromatic hydrocarbons. In test animals, BaP has caused respiratory tract tumors from inhalation and stomach tumors, leukemia, and lung tumors from ingesting BaP. Cancers of the larynx and the scrotum may also be associated with PAH exposure.
• Reproductive effects. In test animals, BaP has resulted in decreased fertility and reduced incidence of pregnancy, and has damaged sperm and reproductive organs in males.
• May damage the developing fetus. Fetal exposure to PAHs has been linked to the birth of babies that are small for their gestational age (SGA). Studies of women who smoke during pregnancy link PAH (along with carbon monoxide) to a 200-gram decrease in birth weight.  Pregnant women who were exposed to heavy doses of PAHs near the World Trade Center on 9/11 and after similarly gave birth to smaller babies.
  
  In test animals exposed during pregnancy, BaP has caused reduced viability of litters, decreased birth weight, and cancer and reduced fertility in offspring.
• Short-term exposure to high levels of benzo[a]pyrene may cause red blood cell damage, leading to anemia, and suppressed immune system.  In test animals, BaP has caused blood and liver damage when high doses are ingested, and immune system damage through contact with the skin.

 

How Exposures Occur

From Foods

• Children can ingest traces of benzo[a]pyrene in smoked, grilled, barbecued or burned foods, as cooking food at high temperatures or charring or burning of foods increases the amount of BaP in such foods.
  
  Foods grown in contaminated soil or air may also contain BaP. It has been detected in trace amounts in cereals, bread, vegetables, vegetable oils, margarines, roasted coffee, fruits, meats, milk, and processed or pickled foods.

Tobacco Smoke

• Children can inhale benzo[a]pyrene when they are exposed to secondhand tobacco smoke. BaP particles from cigarette smoke can cling to household dust (see below).

Wood Smoke

• Children can inhale benzo[a]pyrene in indoor and outdoor air when fireplaces or wood stoves are in use.

Outdoor Air Pollution

• Children can inhale benzo[a]pyrene in outdoor air. Sources include:
  - soot, smoke and dust from the burning of wood, coal, and agricultural waste
  - manufacturing source emissions from refineries, coal, coke and coal tar processing, and heat and power generation sources
  - incinerator emissions
  - fumes from asphalt roads and roofing, coal, coal tar, and hazardous waste sites.
  - exhaust fumes from motor vehicles and other gasoline and diesel engines
  - forest fires and volcanic releases
  

During Pregnancy

• PAHs can pass through the placenta of pregnant women to expose the fetus. Pregnant women who are exposed to PAHs through any of the exposure routes listed here risk exposing their babies.

House Dust and Soil

• Small children can ingest BaP from normal hand-to-mouth behavior after crawling or playing on floors and carpets that contains contaminated dust. Dust can become contaminated especially in homes where smoking is permitted and/or where fireplaces, woodburning stoves and gas appliances are used frequently or without proper ventilation. BaP could also be tracked indoors on shoes. Outdoors, children can ingest soil contaminated with traces of BaP from the sources mentioned above under outdoor air pollution.

In Drinking Water

• BaP has been detected in some water supplies. It is regulated by the U.S. Safe Drinking Water Act, which requires public water facilities to regular test water supplies and report high levels of this substance.
  
  Polycyclic aromatic hydrocarbons primarily enter tap water by leaching from coal tar and asphalt linings in water storage tanks and distribution lines. It is possible, though rare, that children could be exposed to BaP from drinking water that has been contaminated on route to your home.

Skin Contact

• Exposure to BaP and other PAHs may also occur through skin contact with products that contain PAHs, such as creosote-treated wood.

 

Significant Statistics

Each day, the average urban infant will ingest 110 nanograms of benzo[a]pyrene by ingesting house dust through typical hand-to-mouth behavior after crawling on floors and carpets. This amount is equal to what an infant would inhale by smoking three cigarettes.

Ninety-six percent of the benzo[a]pyrene released into the environment comes from coal refuse piles, outcrops, abandoned coal mines, coke manufacture, and residential external combustion of coal.

“Polycyclic Aromatic Hydrocarbons, 15 Listings.” Tenth Report on Carcinogens. U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, December 2002.http://ehp.niehs.nih.gov/roc/tenth/profiles/s150pah.pdf

Typically, levels of PAHs in indoor air are 2-5 times higher than in outdoor air.  In smokers’ homes, PAH levels are 130-300% higher than outdoors.

Toxicological Profile for Polycyclic Aromatic Hydrocarbons (PAHs). Agency for Toxic Substances and Disease Registry, August 1995.http://www.atsdr.cdc.gov/toxprofiles/tp69.html

The general population ingests 1-9 micrograms of PAHs per day through consumption of food, making food the primary route of exposure.

 

Solutions

How to detect polycyclic aromatic hydrocarbons (PAHs)

• Benzo[a]pyrene is found in tobacco smoke and wood smoke, which can both be detected by their odor.
  
  Otherwise, except for professional testing, there is no way for us to detect how much benzo[a]pyrene is entering our homes.
• Benzo[a]pyrene is regulated under the Safe Drinking Water Act. This law requires that community water systems monitor benzo[a]pyrene levels, and make public when levels exceed the set Maximum Contamination Level (MCL). The MCL for benzo[a]pyrene has been set at 0.2 parts per billion.
  
  Community water systems are required to produce annual consumer confidence reports and mail them to every water customer.
  
  If your water source is a well, your water is not monitored for contaminants as is required for public water supplies by the Safe Drinking Water Act. Private testing of the water is necessary.
  
  Even if your water comes from a community water system, contaminant levels can vary from house to house. You can have your water tested by sending samples to a certified laboratory.
  
  You can search for water quality reports from your water provider, obtain information on well water testing and find a list of state-certified drinking water laboratories at the U.S. Environmental Protection Agency’s Office of Water website or call the EPA’s Safe Drinking Water Hotline, 800-426-4791.
• Install and properly maintain a carbon monoxide monitor.  Carbon monoxide and PAHs are simultaneously emitted by combustion appliances such as furnaces and gas stoves.

How to minimize exposure to polycyclic aromatic hydrocarbons (PAHs)

• Minimize your children�s exposure to secondhand tobacco smoke. If you live with children, do not smoke inside your home or permit others to do so. Any smoking should be done outdoors. Do not smoke where children, particularly infants and toddlers, tend to play, especially in day care centers, nurseries, or other settings where they spend long hours.
  
  Do not smoke in the car: The high concentration of smoke in a small, closed compartment substantially increases the exposure to other passengers. If smoking in the home cannot be avoided, open windows and increase ventilation with box or exhaust fans.
• Reduce consumption of smoked, barbecued, or charcoal-grilled foods.
• Use fireplaces and wood stoves properly. For tips, see Burning Clean: Wood Stoves and Fireplaces and How to Build a Safer Fire.
• Maintain and operate gas appliances appropriately. See Gas Appliances Can Be Source of Unhealthy Indoor Air.
• Don�t leave a car or lawnmower engine running in a shed or garage or in other enclosed spaces. Even if the garage door to the outside is open, fumes can build up very quickly in the garage and living area of your home. Also, don�t operate gasoline-powered appliances, engines or tools (mowers, weed trimmers, snow blowers, chain saws, small engines or generators) in enclosed or partly-enclosed spaces.

Alternatives

• Fresh or lightly-cooked foods should contain lower levels of BaP and other PAHs than grilled, barbecued or smoked foods.
• Heating systems powered by electricity and electrical appliances (as opposed to gas) don’t release BaP and other combustion pollutants into indoor air. However, some power plants release combustion byproducts like PAHs into the environment. Choose clean and environmental energy sources, if you have a choice.

 

For More information

Books, articles, factsheets and reports

Other government agencies

Agency of Toxic Substances and Disease Registry

Division of Toxicology
1600 Clifton Road E-29
Atlanta, GA 30333
800-447-1544, 888-422-8737

http://www.atsdr.cdc.gov

U.S. Environmental Protection Agency

Office of Ground Water and Drinking Water
Ariel Rios Building
1200 Pennsylvania Avenue, NW
Washington DC 20460-0003

http://www.epa.gov/safewater

Nonprofit organizations

Burning Issues (A Project of Clean Air Revival, Inc.)

Box 1045
Point Arena, CA 95468
707-882-3601

http://www.burningissues.org

Other websites

Environmental Defense Chemical Scorecard

http://www.scorecard.org

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