Report on Carcinogens, Fourteenth Edition

For Table of Contents, see home page:  http://ntp.niehs.nih.gov/go/roc

Coal Tars and Coal-Tar Pitches

Properties

CAS No. 8007-45-2 (Coal Tar)

Coal tars are by-products of the destructive distillation (carbonization) of coal to produce coke or gas. The composition and properties
of a coal tar depend primarily on the temperature of the carbonization and to a lesser extent on the nature (source) of the coal used
as feedstock. In general, coal tars are complex combinations of hydrocarbons, phenols, and hetero­cyclic oxygen, sulfur, and nitrogen
compounds. Over 400 compounds have been identified in coal tars,
and as many as 10,000 may actually be present. The PAH content of
coal tars increases with increasing carbonization temperature. Coal
tars typically are black or almost-black viscous liquids or semisolids
with a characteristic naphthalene-like odor (ATSDR 2002). They are
slightly soluble in water, partially soluble in acetone, carbon disulfide,
chloroform, diethyl ether, ethanol, methanol, petroleum ether, and
sodium hydroxide, and soluble in benzene and nitrobenzene. Lowtemperature coal tars (formed at temperatures below 700°C) are black,
viscous liquids that are denser than water and contain a lower percentage (40% to 50%) of aromatic compounds than high-temperature
coal tars (IARC 1985). Coal tars are highly flammable and corrosive,
and toxic gases may be released when they burn. Their vapors can
form explosive mixtures with air (HSDB 2009).
Coal-tar pitches are shiny, dark-brown to black residues produced
during the distillation of coal tars. They contain various PAHs, their
methyl and polymethyl derivatives, and heteronuclear compounds
(IARC 1985).

No separate CAS No. is assigned to coal-tar pitches
Known to be human carcinogens
First listed in the First Annual Report on Carcinogens (1980)

Carcinogenicity
Coal tars and coal-tar pitches are known to be human carcinogens
based on sufficient evidence of carcinogenicity from studies in humans.
Cancer Studies in Humans
Numerous studies, mostly case reports, have found that occupational
exposure to coal tars or coal-tar pitches (coal-tar distillates) is associated with skin cancer, including scrotal cancer; workers in these studies have included patent-fuel (coal-briquette) workers, pitch loaders,
workers in electrical trades, and optical-lens polishers (IARC 1985,
1987). A 1946 study in the United Kingdom found that patent-fuel
workers were 500 times as likely as other workers to die of scrotal
cancer. In addition, there have been many case reports of skin cancer
among patients using therapeutic coal-tar preparations. Occupational
exposure to coal tars or coal-tar pitches has also been associated with
cancer at other tissue sites, including the lung, bladder, kidney, and
digestive tract. Excesses of lung cancer were found in several epidemiological studies of workers exposed to coal-tar fumes in coal gasification and coke production, in studies of workers exposed to pitch
fumes in aluminum production and calcium carbide production, and
in a study of millwrights and welders exposed to coal-tar pitches and
coal tars. The millwrights and welders also showed increased risks of
digestive-tract cancer and leukemia. The risk of bladder cancer was
increased in tar distillers and patent-fuel workers exposed to coal tars
and coal-tar pitches and in aluminum production workers exposed
to coal-tar pitches. The risk of kidney (renal-pelvis) cancer was increased in workers exposed to “petroleum or tar or pitch.” Studies of
roofers, who are exposed to coal-tar pitches, have found increased
risks of cancer at other tissue sites in addition to skin, bladder, and
lung cancer and leukemia, including cancer of the oral cavity, larynx,
esophagus, and stomach; however, roofers are also exposed to other
potentially carcinogenic agents, such as asphalt.
Cancer Studies in Experimental Animals
Dermal exposure to coal tars (including pharmaceutical and hightemperature coal tars) or coal-tar extracts caused skin tumors in mice
and rabbits and lung cancer (but not skin tumors) in rats. Inhalation
exposure to coal tar from coke ovens caused skin tumors in mice and
lung tumors in mice and rats. An extract of a coal-tar fume condensate administered by intramuscular injection caused tumors at the
injection site (sarcoma) in mice. Dermal exposure to coal-tar pitches
or coal-tar pitch extracts caused benign and malignant skin tumors
in mice (IARC 1985, 1987).
Studies on Mechanisms of Carcinogenesis
Both coal tars and coal-tar pitches contain a number of known and
potential carcinogens, including benzene, naphthalene, and other
polycyclic aromatic hydrocarbons (PAHs). Coal-tar pitch extracts
showed both tumor-initiating and tumor-promoting activity in
mouse skin (IARC 1985, 1987).

National Toxicology Program, Department of Health and Human Services

Use
Coal tars and coal-tar pitches have many uses in industry and in consumer products. Coal tars are used primarily for the production of
refined chemicals and coal-tar products, such as creosote, coal-tar
pitch, and crude naphthalene and anthracene oils from the distillation
of crude coal tar. Coal tar has been used as a fuel in open-hearth furnaces and blast furnaces in the steel industry, as a binder and filler in
surface-coating formulations, and as a modifier for epoxy-resin surface coatings. U.S. Pharmacopeia–grade coal tar is approved for use
in denatured alcohol (IARC 1985). Coal-tar preparations have been
used for many years to treat various skin conditions, such as eczema,
psoriasis, seborrheic dermatitis, and dandruff. Both prescription and
nonprescription preparations are available and include cleansing bars,
creams, gels, lotions, ointments, shampoos, and other topical solutions and suspensions (DermNet NZ 2010). Coal tar is also registered
as an active ingredient in pesticides with the U.S. Environmental Protection Agency (EPA 2003).
Coal-tar pitches are used primarily as the binder for aluminumsmelting electrodes (IARC 1984). They are also used in roofing materials, to impregnate and strengthen refractory brick (for lining
industrial furnaces), and in surface coatings, such as pipe-coating
enamels and black varnishes used as protective coatings for industrial
steelwork and as antifouling paints for boats. Hard pitch is used as a
binder for foundry cores. Coke-oven pitch is used to produce pitch
coke, which is used as the carbon component of electrodes, carbon
brushes, and carbon and graphite articles. Distillation fractions and
residues from high-temperature coal tars are used for road paving
and construction and in the production of naphthalene, recovery of
benzene, production of anthracene paste, briquetting of smokeless
solid fuel, impregnation of electrodes and fibers, and manufacture
of electrodes and graphite (IARC 1985).

Production
Coal tar was first produced in the United States in 1913, when over
1.0 billion pounds was produced as a by-product of coke production
(IARC 1985). Because the majority of coal tar is produced by the steel

 Report on Carcinogens, Fourteenth Edition
industry, its production depends on the demand for steel. U.S. coaltar production was 168.6 million gallons in 1986, 188.5 million gallons in 1987 (ATSDR 2002), and 1.8 billion pounds in 1994 (USITC
1995). In 2009, six U.S. suppliers of coal tar and one U.S. supplier of
coal-tar pitch were identified (ChemSources 2009).

Exposure
The primary routes of potential human exposure to coal tars and
coal-tar products are inhalation, ingestion, and dermal contact. The
general population may be exposed to coal tar through its use in
treating skin disorders. It has been estimated that nearly 2% of the
United States population is affected by psoriasis, one of the conditions for which coal-tar ointments (containing 1% to 10% coal tar) are
prescribed (IARC 1985). Others may be exposed through the use of
coal-tar shampoos to treat dandruff or coal-tar ointments to treat eczema. The general population may also be exposed to coal tars present as environmental contaminants (ATSDR 2002).
Occupational exposure to coal tars and coal-tar pitches may occur at foundries and during coke production, coal gasification, and
aluminum production. Coal gasification and iron and steel foundry
workers potentially are also exposed to coal-tar pitch volatiles, including a variety of PAHs (IARC 1984). Coke ovens are the primary
source of coal tar (NIOSH 1977). In 1970, the United States had 64
coking plants operating more than 13,000 coke ovens, with about
10,000 workers (NIOSH 1973). The numbers of plants and ovens remained essentially the same through 1975 but by 1998 had declined
to 23 coking plants operating about 3,800 ovens (EPA 2001). In the
early 1970s, an estimated 145,000 workers were directly or indirectly
involved with coal-tar products (NIOSH 1977). The National Occupational Hazard Survey (conducted from 1972 to 1974) estimated
that 1,354 workers potentially were exposed to coal-tar pitch (NIOSH
1976). The National Occupational Exposure Survey (conducted from
1981 to 1983) estimated that 7,274 workers (including 42 women)
potentially were exposed to coal tar, 19,021 workers (including 98
women) to coal-tar pitch, and 7,677 workers (including 78 women)
to coal-tar-pitch volatiles (NIOSH 1990). No more recent occupational exposure surveys were found.
Workers potentially exposed to coal-tar pitches include those producing or using pavement tar, roofing tar, coal-tar pitch, coal-tar
paints, coal-tar enamels, other coal-tar coatings, or refractory bricks.
The concentrations of PAHs in ambient air ranged from 0 to 200 μg/
m3 near roof-tarring operations and from 0 to 3,700 μg/m3 near pavement-tarring operations. Another study found that coal-tar pitch
workers at a U.S. roofing site inhaled up to 53 μg of benzo[a]pyrene
in seven hours (Hammond et al. 1976). The potential for skin exposure may be considerable; because of the heat, workers often wear little clothing, thereby exposing large portions of the body to coal tars
or coal-tar pitches. In the skin oil of nine roofing workers (potentially
exposed to coal-tar pitch and bitumen), 0.000048 to 0.036 μg of PAHs
were detected in a 36‑cm2 area of the forehead (Wolff et al. 1982).

Regulations
Coast Guard, Department of Homeland Security
Minimum requirements have been established for safe transport of coal-tar pitches on ships and
barges.
Department of Transportation (DOT)
Flammable coal-tar distillates are considered a hazardous material, and special requirements have
been set for marking, labeling, and transporting these materials.
Environmental Protection Agency (EPA)
Clean Air Act
National Emission Standards for Hazardous Air Pollutants: Air emissions of hazardous air pollutants from
the handling of coal tar are regulated under certain source categories.

National Toxicology Program, Department of Health and Human Services

Resource Conservation and Recovery Act
Listed Hazardous Waste: Waste codes for which the listing is based wholly or partly on the presence of
certain coal-tar residues = K141, K142, K147, K148.
Coal-tar creosote is listed as a hazardous constituent of waste.
Food and Drug Administration (FDA)
Any drug products containing coal tar (alone or in combination with external analgesic active
ingredients) at levels of 0.5% to 5% must contain a label specifying the identity and
concentration of the coal tar.
Any hair dye containing coal tar must display a warning label stating that the product contains an
ingredient that has been determined to cause cancer in laboratory animals.
Certain dermal products containing coal tar must provide warning labels of specific precautions for
that product.
The use of coal tar in several over-the-counter drugs is no longer recognized as safe and effective for
the specified uses.
Occupational Safety and Health Administration (OSHA)
While this section accurately identifies OSHA’s legally enforceable PELs for this substance in 2010,
specific PELs may not reflect the more current studies and may not adequately protect workers.
Permissible exposure limit = 0.2 mg/m3 for coal-tar-pitch volatiles – benzene-soluble fraction.

Guidelines
American Conference of Governmental Industrial Hygienists (ACGIH)
Threshold limit value – time-weighted average (TLV-TWA) = 0.2 mg/m3 for coal-tar-pitch volatiles as
benzene-soluble aerosol.
National Institute for Occupational Safety and Health (NIOSH)
Recommended exposure limit (time-weighted-average workday) = 0.1 mg/m3 for coal-tar-pitch
volatiles and coal-tar products – cyclohexane-extractable fraction.
Immediately dangerous to life and health (IDLH) limit = 80 mg/m3 for coal-tar-pitch volatiles.
Coal-tar-pitch volatiles are listed as potential occupational carcinogens.
A comprehensive set of guidelines has been established to prevent occupational exposures to
hazardous drugs in health-care settings.
Occupational Safety and Health Administration (OSHA)
A comprehensive set of guidelines has been established to prevent occupational exposures to
hazardous drugs in health-care settings.

References
ATSDR. 2002. Toxicological Profile for Wood Creosote, Coal Tar Creosote, Coal Tar, Coal Tar Pitch, and Coal Tar
Pitch Volatiles. Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/toxprofiles/
tp85.pdf. 354 pp.
ChemSources. 2009. Chem Sources - Chemical Search. Chemical Sources International. http://www.
chemsources.com/chemonline.html and search on coal tar and coal tar pitch. Last accessed: 10/22/09.
DermNet NZ. 2010. Coal Tar. New Zealand Dermatological Society. Last updated: 8?27/10. http://www.
dermnetnz.org/treatments/coaltar.html.
EPA. 2001. National Emissions Standards for Hazardous Air Pollutants (NESHAP) for Coke Ovens: Pushing
Quenching, and Battery Stacks – Background Information for Proposed Standards. EPA-453/R-01-006.
Research Triangle Park, NC: U.S. Environmental Protection Agency.
EPA. 2003. Pesticide reregistration performance measures and goals. Fed Regist 68(146): 44767-44776.
Hammond EC, Selikoff IJ, Lawther PL, Seidman H. 1976. Inhalation of benzpyrene and cancer in man.
Ann N Y Acad Sci 271: 116-124.
HSDB. 2009. Hazardous Substances Data Bank. National Library of Medicine. http://toxnet.nlm.nih.gov/
cgi-bin/sis/htmlgen?HSDB and search on CAS number. Last accessed: 10/22/09.
IARC. 1984. Polynuclear Aromatic Compounds, Part 3. Industrial Exposures in Aluminum Production,
Coal Gasification, Coke Production, and Iron and Steel Founding. IARC Monographs on the Evaluation of
Carcinogenic Risk of Chemicals to Humans, vol. 34. Lyon, France: International Agency for Research on
Cancer. 219 pp.
IARC. 1985. Coal-tars and derived products. In Polynuclear Aromatic Compounds, Part 4, Bitumens, Coaltars and Derived Products, Shale-oils and Soots. IARC Monographs on the Evaluation of Carcinogenic Risk
of Chemicals to Humans, vol. 35. Lyon, France: International Agency for Research on Cancer. pp. 83-159.
IARC. 1987. Coal-tar pitches and coal-tars. In Overall Evaluations of Carcinogenicity. IARC Monographs on
the Evaluation of Carcinogenic Risk of Chemicals to Humans, suppl 7. Lyon, France: International Agency
for Research on Cancer. pp. 174-176.
NIOSH. 1973. Criteria for a Recommended Standard: Occupational Exposure to Coke Oven Emissions. DHEW
(NIOSH) Publication No. 73-11016. National Institute for Occupational Safety and Health. http://www.
cdc.gov/niosh/73-11016.html.
NIOSH. 1976. National Occupational Hazard Survey (1972-74). DHEW (NIOSH) Publication No. 78-114.
Cincinnati, OH: National Institute for Occupational Safety and Health.
NIOSH. 1977. Criteria for a Recommended Standard: Occupational Exposure to Coal Tar Products. DHEW
(NIOSH) Publication No. 78-107. National Institute for Occupational Safety and Health. http://www.cdc.
gov/niosh/78-107.html.

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 Report on Carcinogens, Fourteenth Edition
NIOSH. 1990. National Occupational Exposure Survey (1981-83). National Institute for Occupational Safety
and Health. Last updated: 7/1/90. http://www.cdc.gov/noes/noes1/90610sic.html, http://www.cdc.gov/
noes/noes1/90620sic.html, http://www.cdc.gov/noes/noes1/t0535sic.html.
USITC. 1995. Synthetic Organic Chemicals, United States Production and Sales, 1994. USITC Publication No
2933. Washington, DC: U.S. Government Printing Office.
Wolff MS, Taffe B, Boesch R, Selikoff I. 1982. Detection of polycyclic aromatic hydrocarbons in skin oil
obtained from roofing workers. Chemosphere 11(6): 595-599.

National Toxicology Program, Department of Health and Human Services

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