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Polycyclic Aromatic
Hydrocarbons (PAHs) Polycyclic aromatic hydrocarbons (PAHs) are a class of
chemicals that occur naturally in coal, crude oil, and gasoline.
They also are produced when
coal, oil, gas, wood, garbage, and tobacco are burned.
PAHs generated from these
sources can bind to or form small particles in the air. High-temperature
cooking will form PAHs in meat and in other foods.
Naphthalene is a PAH that is
produced commercially in the United States to make other chemicals and
mothballs.
Cigarette smoke contains
many PAHs.
How People Are Exposed to
PAHs
People are usually exposed
to mixtures of PAHs. Breathing air contaminated with motor vehicle exhaust,
cigarette smoke, wood smoke, or fumes from asphalt roads are common ways
exposure occurs.
People take in PAHs when they
eat grilled or charred meats or foods or foods on which PAH particles have
settled from the air.
After PAHs are swallowed,
breathed in, or in some cases, passed through the skin, the body converts PAHs
into breakdown products called metabolites that pass out of the body in the
urine and feces.
How PAHs Affect People's
Health Human health effects from environmental exposure to low levels of PAHs
are unknown.
Large amounts of naphthalene
in air can irritate eyes and breathing passages. Workers who have been exposed
to large amounts of naphthalene from skin contact with the liquid form and from
breathing naphthalene vapor have developed blood and liver abnormalities.
Several of the PAHs and some
specific mixtures of PAHs are considered to be cancer-causing chemicals.
Levels of PAH Metabolites in
the U.S. Population In the Fourth National Report on Human Exposure to
Environmental Chemicals (Fourth Report), CDC scientists measured ten different
PAH metabolites in the urine of 2,504 or more participants aged six years and
older who took part in the National Health and Nutrition Examination Survey
(NHANES) during 2003–2004.
The Fourth Report includes
results from the earlier survey period of 2001–2002 for several PAH
metabolites. By measuring PAH metabolites in urine, scientists can estimate the
amounts of PAHs that have entered people’s bodies.
PAHs were measured in most
participants, indicating widespread exposure in the U.S. population. Research
has found that urinary PAH metabolites are higher in adults who smoke than in
nonsmoking adults. Finding a measurable amount of one or more PAH metabolites
in the urine does not mean that the levels of one or more PAH metabolites or
PAHs cause an adverse health effect.
Biomonitoring studies on
levels of PAH metabolites provide physicians and public health officials with
reference values so that they can determine whether people have been exposed to
higher levels of these chemicals than are found in the general population.
Biomonitoring data can also
help scientists plan and conduct research on exposure and health effects. For
More Information §
Agency for Toxic Substances and Disease Registry ToxFAQs for Polycyclic
Aromatic Hydrocarbons (PAHs) http://www.atsdr.cdc.gov/tfacts69.html
§
Environmental Protection Agency Consumer Factsheet on: BENZO(A)PYRENE http://www.epa.gov/ogwdw000/contaminants/dw_contamfs/benzopyr.html
§
United States Geological Survey Definition Page for Polynuclear Aromatic
Hydrocarbons http://toxics.usgs.gov/definitions/pah.html
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