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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for 

Polycyclic Aromatic Hydrocarbons (PAHs). It is 

one in a series of Public Health Statements about 

hazardous substances and their health effects. A 

shorter version, the ToxFAQsTM, is also available. 

This information is important because this 

substance may harm you. The effects of exposure to 

any hazardous substance depend on the dose, the 

duration, how you are exposed, personal traits and 

habits, and whether other chemicals are present. For 

more information, call the ATSDR Information 

Center at 1-888-422-8737. 

This statement was prepared to give you 

information about polycyclic aromatic 

hydrocarbons (PAHs) and to emphasize the human 

health effects that may result from exposure to 

them. The Environmental Protection Agency (EPA) 

has identified 1,408 hazardous waste sites as the 

most serious in the nation. These sites make up the 

National Priorities List (NPL) and are the sites 

targeted for long-term federal clean-up activities. 

PAHs have been found in at least 600 of the sites on 

the NPL. However, the number of NPL sites 

evaluated for PAHs is not known. As EPA 

evaluates more sites, the number of sites at which 

PAHs are found may increase. This information is 

important because exposure to PAHs may cause 

harmful health effects and because these sites are 

potential or actual sources of human exposure to 

PAHs. 

When a substance is released from a large area, 

such as an industrial plant, or from a container, such 

as a drum or bottle, it enters the environment. This 

release does not always lead to exposure. You can 

be exposed to a substance only when you come in 

contact with it. You may be exposed by breathing, 

eating, or drinking substances containing the 

substance or by skin contact with it. 

If you are exposed to substances such as PAHs, 

many factors will determine whether harmful health 

effects will occur and what the type and severity of 

those health effects will be. These factors include 

the dose (how much), the duration (how long), the 

route or pathway by which you are exposed 

(breathing, eating, drinking, or skin contact), the 

other chemicals to which you are exposed, and your 

individual characteristics such as age, sex, 

nutritional status, family traits, lifestyle, and state of 

health. 

1.1 WHAT ARE PAHs? 

PAHs are a group of chemicals that are formed 

during the incomplete burning of coal, oil, gas, 

wood, garbage, or other organic substances, such as 

tobacco and charbroiled meat. There are more than 

100 different PAHs. PAHs generally occur as 

complex mixtures (for example, as part of 

combustion products such as soot), not as single 

compounds. PAHs usually occur naturally, but they 

can be manufactured as individual compounds for 

research purposes; however, not as the mixtures 

found in combustion products. As pure chemicals, 

PAHs generally exist as colorless, white, or pale 

yellow-green solids. They can have a faint, pleasant 

odor. A few PAHs are used in medicines and to 

make dyes, plastics, and pesticides. Others are 

contained in asphalt used in road construction. They 

can also be found in substances such as crude oil, 

coal, coal tar pitch, creosote, and roofing tar. They 

are found throughout the environment in the air, 

water, and soil. They can occur in the air, either 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

attached to dust particles or as solids in soil or 

sediment. 

Although the health effects of individual PAHs are 

not exactly alike, the following 17 PAHs are 

considered as a group in this profile: 

acenaphthene 

acenaphthylene 

anthracene 

benz[a]anthracene 

benzo[a]pyrene 

benzo[e]pyrene 

benzo[b]fluoranthene 

benzo[g,h,i]perylene 

benzo[j]fluoranthene 

benzo[k]fluoranthene 

chrysene 

dibenz[a,h]anthracene 

fluoranthene 

fluorene 

indeno[1,2,3-c,d]pyrene 

phenanthrene 

pyrene 

These 17 PAHs were chosen to be included in this 

profile because (1) more information is available on 

these than on the others; (2) they are suspected to be 

more harmful than some of the others, and they 

exhibit harmful effects that are representative of the 

PAHs; (3) there is a greater chance that you will be 

exposed to these PAHs than to the others; and (4) of 

all the PAHs analyzed, these were the PAHs 

identified at the highest concentrations at NPL 

hazardous waste sites. 

1.2 WHAT HAPPENS TO PAHs WHEN THEY 

ENTER THE ENVIRONMENT? 

PAHs enter the environment mostly as releases to 

air from volcanoes, forest fires, residential wood 

burning, and exhaust from automobiles and trucks. 

They can also enter surface water through 

discharges from industrial plants and waste water 

treatment plants, and they can be released to soils at 

hazardous waste sites if they escape from storage 

containers. The movement of PAHs in the 

environment depends on properties such as how 

easily they dissolve in water, and how easily they 

evaporate into the air. PAHs in general do not easily 

dissolve in water. They are present in air as vapors 

or stuck to the surfaces of small solid particles. 

They can travel long distances before they return to 

earth in rainfall or particle settling. Some PAHs 

evaporate into the atmosphere from surface waters, 

but most stick to solid particles and settle to the 

bottoms of rivers or lakes. In soils, PAHs are most 

likely to stick tightly to particles. Some PAHs 

evaporate from surface soils to air. Certain PAHs in 

soils also contaminate underground water. The PAH 

content of plants and animals living on the land or 

in water can be many times higher than the content 

of PAHs in soil or water. PAHs can break down to 

longer-lasting products by reacting with sunlight 

and other chemicals in the air, generally over a 

period of days to weeks. Breakdown in soil and 

water generally takes weeks to months and is 

caused primarily by the actions of microorganisms. 

1.3 HOW MIGHT I BE EXPOSED TO PAHs? 

PAHs are present throughout the environment, and 

you may be exposed to these substances at home, 

outside, or at the workplace. Typically, you will not 

be exposed to an individual PAH, but to a mixture 

of PAHs. 

In the environment, you are most likely to be 

exposed to PAH vapors or PAHs that are attached 

to dust and other particles in the air. Sources include 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

cigarette smoke, vehicle exhausts, asphalt roads, 

coal, coal tar, wildfires, agricultural burning, 

residential wood burning, municipal and industrial 

waste incineration, and hazardous waste sites. 

Background levels of some representative PAHs in 

the air are reported to be 0.02–1.2 nanograms per 

cubic meter (ng/m3; a nanogram is one-millionth of 

a milligram) in rural areas and 0.15–19.3 ng/m3 in 

urban areas. You may be exposed to PAHs in soil 

near areas where coal, wood, gasoline, or other 

products have been burned. You may be exposed to 

PAHs in the soil at or near hazardous waste sites, 

such as former manufactured-gas factory sites and 

wood-preserving facilities. PAHs have been found 

in some drinking water supplies in the United 

States. Background levels of PAHs in drinking 

water range from 4 to 24 nanograms per liter (ng/L; 

a liter is slightly more than a quart). 

In the home, PAHs are present in tobacco smoke, 

smoke from wood fires, creosote-treated wood 

products, cereals, grains, flour, bread, vegetables, 

fruits, meat, processed or pickled foods, and 

contaminated cow's milk or human breast milk. 

Food grown in contaminated soil or air may also 

contain PAHs. Cooking meat or other food at high 

temperatures, which happens during grilling or 

charring, increases the amount of PAHs in the food. 

The level of PAHs in the typical U.S. diet is less 

than 2 parts of total PAHs per billion parts of food 

(ppb), or less than 2 micrograms per kilogram of 

food (μg/kg; a microgram is one-thousandth of a 

milligram). 

The primary sources of exposure to PAHs for most 

of the U.S. population are inhalation of the 

compounds in tobacco smoke, wood smoke, and 

ambient air, and consumption of PAHs in foods. For 

some people, the primary exposure to PAHs occurs 

in the workplace. PAHs have been found in coal tar 

production plants, coking plants, bitumen and 

asphalt production plants, coal-gasification sites, 

smoke houses, aluminum production plants, coal 

tarring facilities, and municipal trash incinerators. 

Workers may be exposed to PAHs by inhaling 

engine exhaust and by using products that contain 

PAHs in a variety of industries such as mining, oil 

refining, metalworking, chemical production, 

transportation, and the electrical industry. PAHs 

have also been found in other facilities where 

petroleum, petroleum products, or coal are used or 

where wood, cellulose, corn, or oil are burned. 

People living near waste sites containing PAHs may 

be exposed through contact with contaminated air, 

water, and soil. 

1.4 HOW CAN PAHs ENTER AND LEAVE MY 

BODY? 

PAHs can enter your body through your lungs when 

you breathe air that contains them (usually stuck to 

particles or dust). Cigarette smoke, wood smoke, 

coal smoke, and smoke from many industrial sites 

may contain PAHs. People living near hazardous 

waste sites can also be exposed by breathing air 

containing PAHs. However, it is not known how 

rapidly or completely your lungs absorb PAHs. 

Drinking water and swallowing food, soil, or dust 

particles that contain PAHs are other routes for 

these chemicals to enter your body, but absorption 

is generally slow when PAHs are swallowed. Under 

normal conditions of environmental exposure, 

PAHs could enter your body if your skin comes into 

contact with soil that contains high levels of PAHs 

(this could occur near a hazardous waste site) or 

with used crankcase oil or other products (such as 

creosote) that contain PAHs. The rate at which 

PAHs enter your body by eating, drinking, or 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

through the skin can be influenced by the presence 

of other compounds that you may be exposed to at 

the same time with PAHs. PAHs can enter all the 

tissues of your body that contain fat. They tend to 

be stored mostly in your kidneys, liver, and fat. 

Smaller amounts are stored in your spleen, adrenal 

glands, and ovaries. PAHs are changed by all 

tissues in the body into many different substances. 

Some of these substances are more harmful and 

some are less harmful than the original PAHs. 

Results from animal studies show that PAHs do not 

tend to be stored in your body for a long time. Most 

PAHs that enter the body leave within a few days, 

primarily in the feces and urine. 

1.5 HOW CAN PAHs AFFECT MY HEALTH? 

PAHs can be harmful to your health under some 

circumstances. Several of the PAHs, including 

benz[a]anthracene, benzo[a]pyrene, 

benzo[b]fluoranthene, benzo[j]fluoranthene, 

benzo[k]fluoranthene, chrysene, 

dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene, 

have caused tumors in laboratory animals when 

they breathed these substances in the air, when they 

ate them, or when they had long periods of skin 

contact with them. Studies of people show that 

individuals exposed by breathing or skin contact for 

long periods to mixtures that contain PAHs and 

other compounds can also develop cancer. 

Mice fed high levels of benzo[a]pyrene during 

pregnancy had difficulty reproducing and so did 

their offspring. The offspring of pregnant mice fed 

benzo[a]pyrene also showed other harmful effects, 

such as birth defects and decreased body weight. 

Similar effects could occur in people, but we have 

no information to show that these effects do occur. 

Studies in animals have also shown that PAHs can 

cause harmful effects on skin, body fluids, and the 

body's system for fighting disease after both shortand long-term exposure. These effects have not 

been reported in people. 

The Department of Health and Human Services 

(DHHS) has determined that benz[a]anthracene, 

benzo[b]fluoranthene, benzo[j]fluoranthene, 

benzo[k]fluoranthene, benzo[a]pyrene, 

dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene 

are known animal carcinogens. The International 

Agency for Research on Cancer (IARC) has 

determined the following: benz[a]anthracene and 

benzo[a]pyrene are probably carcinogenic to 

humans; benzo[b]fluoranthene, 

benzo[j]fluoranthene, benzo[k]fluoranthene, and 

indeno[1,2,3-c,d]pyrene are possibly carcinogenic 

to humans; and anthracene, benzo[g,h,i]perylene, 

benzo[e]pyrene, chrysene, fluoranthene, fluorene, 

phenanthrene, and pyrene are not classifiable as to 

their carcinogenicity to humans. EPA has 

determined that benz[a]anthracene, benzo[a]pyrene, 

benzo[b]fluoranthene, benzo[k]fluoranthene, 

chrysene, dibenz[a,h]anthracene, and indeno[1,2,3­

c,d]pyrene are probable human carcinogens and that 

acenaphthylene, anthracene, benzo[g,h,i]perylene, 

fluoranthene, fluorene, phenanthrene, and pyrene 

are not classifiable as to human carcinogenicity. 

Acenaphthene has not been classified for 

carcinogenic effects by the DHHS, IARC, or EPA. 

1.6 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO PAHs? 

In your body, PAHs are changed into chemicals that 

can attach to substances within the body. The 

presence of PAHs attached to these substances can 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

then be measured in body tissues or blood after 

exposure to PAHs. PAHs or their metabolites can 

also be measured in urine, blood, or body tissues. 

Although these tests can show that you have been 

exposed to PAHs, these tests cannot be used to 

predict whether any health effects will occur or to 

determine the extent or source of your exposure to 

the PAHs. It is not known how effective or 

informative the tests are after exposure is 

discontinued. These tests to identify PAHs or their 

products are not routinely available at a doctor's 

office because special equipment is required to 

detect these chemicals. 

1.7 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government has set regulations to 

protect people from the possible health effects of 

eating, drinking, or breathing PAHs. EPA has 

suggested that taking into your body each day the 

following amounts of individual PAHs is not likely 

to cause any harmful health effects: 0.3 milligrams 

(mg) of anthracene, 0.06 mg of acenaphthene, 0.04 

mg of fluoranthene, 0.04 mg of fluorene, and 0.03 

mg of pyrene per kilogram (kg) of your body 

weight (one kilogram is equal to 2.2 pounds). 

Actual exposure for most of the United States 

population occurs from active or passive inhalation 

of the compounds in tobacco smoke, wood smoke, 

and contaminated air, and from eating the 

compounds in foods. Skin contact with 

contaminated water, soot, tar, and soil may also 

occur. Estimates for total exposure in the United 

States population have been listed as 3 mg/day. 

From what is currently known about 

benzo[a]pyrene, the federal government has 

developed regulatory standards and guidelines to 

protect people from the potential health effects of 

PAHs in drinking water. EPA has provided 

estimates of levels of total cancer-causing PAHs in 

lakes and streams associated with a risk of human 

cancer development. If the following amounts of 

individual PAHs are released to the environment 

within a 24-hour period, EPA must be notified: 1 

pound of benzo[b]fluoranthene, benzo[a]pyrene, or 

dibenz[a,h]anthracene; 10 pounds of 

benz[a]anthracene; 100 pounds of acenaphthene, 

chrysene, fluoranthene, or indeno[1,2,3-c,d]pyrene; 

or 5,000 pounds of acenaphthylene, anthracene, 

benzo[k]fluoranthene, benzo[g,h,i]perylene, 

fluorene, phenanthrene, or pyrene. 

PAHs are generally not produced commercially in 

the United States except as research chemicals. 

However, PAHs are found in coal, coal tar, and in 

the creosote oils, oil mists, and pitches formed from 

the distillation of coal tars. The National Institute 

for Occupational Safety and Health (NIOSH) 

concluded that occupational exposure to coal 

products can increase the risk of lung and skin 

cancer in workers. NIOSH established a 

recommended occupational exposure limit, timeweighted average (REL-TWA) for coal tar products 

of 0.1 milligram of PAHs per cubic meter of air (0.1 

mg/m3) for a 10-hour workday, within a 40-hour 

workweek. The American Conference of 

Governmental Industrial Hygienists (ACGIH) 

recommends an occupational exposure limit for coal 

tar products of 0.2 mg/m3 for an 8-hour workday, 

within a 40-hour workweek. The Occupational 

Safety and Health Administration (OSHA) has 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) 

Division of Toxicology August 1995 

established a legally enforceable limit of 0.2 mg/m3 

averaged over an 8-hour exposure period. 

Mineral oil mists have been given an IARC 

classification of 1 (sufficient evidence of 

carcinogenicity). The OSHA Permissible Exposure 

Limit (PEL) for mineral oil mist is 5 mg/m3 

averaged over an 8-hour exposure period. NIOSH 

has concurred with this limit, and has established a 

recommended occupational exposure limit (RELTWA) for mineral oil mists of 5 mg/m3 for a 10­

hour work day, 40-hour work week, with a 10 

mg/m3 Short Term Exposure Limit (STEL). 

1.8 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, please 

contact your community or state health or 

environmental quality department or: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology 

1600 Clifton Road NE, Mailstop F-32 

Atlanta, GA 30333 

Information line and technical assistance: 

Phone: 888-422-8737 

FAX: (770)-488-4178 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses resulting from exposure to 

hazardous substances. 

To order toxicological profiles, contact: 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 800-553-6847 or 703-605-6000 

Reference 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1995. Toxicological profile for 

polycyclic aromatic hydrocarbons (PAHs). Atlanta, 

GA: U.S. Department of Health and Human 

Services, Public Health Service. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov