Coal tars and cancer
Coal tars are complex mixtures derived from the distillation of bituminous coal, primarily composed of aromatic hydrocarbons. Recognized as a known human carcinogen since 1980, exposure to coal tars and coal tar pitches is associated with several types of cancer, including skin cancer, lung cancer, bladder cancer, kidney cancer, and various digestive tract cancers. Occupational exposure poses significant risks, particularly for workers in industries such as coal gasification and coke production, where inhalation of coal tar fumes is common. Additionally, therapeutic use of coal tar preparations may increase the risk of skin cancer.
The carcinogenic properties of coal tars are attributed to their content of harmful substances like benzene and naphthalene. Historical evidence links coal tar exposure to health hazards dating back to the late 18th century, specifically noting its connection to scrotal cancer in chimney sweeps. Despite regulatory restrictions in North America and Europe, coal tar remains prevalent in various applications, including roofing materials and personal care products, necessitating caution and awareness of its potential risks. Labels warning consumers about the dangers of coal tar products are required in some regions, highlighting the ongoing concern regarding its use and health implications.
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Subject Terms
Coal tars and cancer
ROC STATUS: Known human carcinogen since 1980
ALSO KNOWN AS: Coal tar pitch volatiles (CTPVs)
RELATED CANCERS: Skin cancer, scrotal cancer, lung cancer, bladder cancer, kidney cancer, leukemia, digestive tract cancers including the esophagus, and cancers of the oral cavity and larynx
DEFINITION: Coal tar is a product of bituminous coal distillation composed mainly of aromatic hydrocarbons. Coal tar pitch is the residue produced by coal tar's distillation or heat treatment. Continued distillation of the coal tar yields various products, including benzene, toluene, xylene, naphthalene, anthracene, acridine, benzopyrene, chrysene, pyrene, and phenanthrene. The many coal tar distillates are central to synthesizing dyes, drugs, explosives, flavorings, perfumes, preservatives, synthetic resins, paints, and stains. The remaining pitch left after distillation is found to be used in paving, roofing, waterproofing, and insulation materials.
Exposure routes: Inhalation, ingestion, skin contact
Where found: Pesticides, roofing materials, pipe coatings, enamels, plastics, dyestuffs, synthetic fibers, synthetic rubbers, varnishes, paints, electrodes, binders used in aluminum smelting, epoxy resins, denatured alcohol, carbon brushes, graphites, road-paving materials, naphthalene, pharmaceuticals, high-temperature-resistant materials
At risk: Those at risk include workers exposed to coal tars or tar pitches. Additionally, patients using therapeutic levels of coal tar preparations may be at risk for skin cancer. Workers are especially vulnerable to coal tar fumes in coal gasification and coke production.
Etiology and symptoms of associated cancers: Coal tars and coal tar pitches contain several carcinogens, including known offenders such as benzene and naphthalene. The resulting cancers include skin cancernotably scrotal cancerdigestive tract cancers, lung cancer, bladder and kidney cancers, and leukemia. The cancer type is often associated with occupational exposure. For example, millwrights and welders are prone to digestive tract cancers and leukemia. At the same time, workers exposed to tar distillates show an increased risk of bladder cancer, and rates of kidney cancer climb with exposure to petroleum or coal tar pitches.
History: Coal tar has been a recognized health hazard since 1775, when scrotal cancer was first linked to cleaning chimney sweeps. Since then, industrial exposure to coal tar has been identified for its carcinogenic potential. This risk now ranges from coal tar pitch volatiles in coke ovens to pharmaceuticals used in the home.
In the 2020s coal tars remained an important substance used in cosmetic and personal care products. Nonetheless, in both Europe and North America, coal tar has faced regulatory guidelines and restrictions. This is because when applied to skin over long periods of time, coal tar has been shown to cause cancer in animal tests. In states such as California, coal tar products must carry a label warning.
Bibliography
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