Creosote is a family of complex chemical mixtures whose association with serious health conditions, particularly cancer, is a long-standing public concern. Whether creosote poses a cancer risk depends heavily on the specific type and context of exposure. Scientific and regulatory bodies have evaluated the evidence, linking certain forms of this substance to carcinogenic activity in humans and animals.
Defining Creosote and Its Uses
Creosote is a category of oily liquids derived from the high-temperature treatment of organic materials, primarily coal or wood. The distinction between the two main types, coal-tar creosote and wood-tar creosote, is essential for understanding the associated health risks. Coal-tar creosote is a byproduct of coal gasification and is a complex mixture containing hundreds of chemical compounds. This form is the one of greatest concern, as it is composed of up to 85% Polycyclic Aromatic Hydrocarbons (PAHs), which are known to be potent toxins.
Wood-tar creosote, derived from the distillation of wood like beechwood, has a very different chemical profile, consisting mainly of phenols, cresols, and guaiacols. Historically, wood creosote had limited medicinal uses as an antiseptic, though this is rare today. The primary industrial use, and therefore the main source of public exposure, is coal-tar creosote, which serves as a restricted-use wood preservative. This product protects materials such as railroad ties, utility poles, and marine pilings from fungal decay and insect damage.
The Scientific Classification of Carcinogenicity
The scientific consensus consistently identifies coal-tar creosote as a substance that can cause cancer. This determination is based on decades of occupational health studies and laboratory evidence linking exposure to its chemical components with tumor formation. The cancer-causing potential is largely attributed to the high concentration of PAHs within the coal-tar product. These chemicals are known mutagens, meaning they can cause changes to cellular DNA that lead to uncontrolled cell growth.
The International Agency for Research on Cancer (IARC) classifies creosotes as “probably carcinogenic to humans,” placing them in Group 2A. This classification is based on limited evidence of cancer in humans and sufficient evidence from animal studies. IARC classifies related substances like coal tar and coal-tar pitch, which contain the same PAHs, as “carcinogenic to humans” (Group 1), citing sufficient evidence in humans for cancers like skin cancer.
The U.S. Environmental Protection Agency (EPA) classifies creosote as a “probable human carcinogen,” or Group B1, based on similar evidence in human and animal studies. The U.S. Department of Health and Human Services (HHS), through the National Toxicology Program (NTP), lists coal tars and coal-tar pitches as “known to be human carcinogens.” This regulatory classification reflects the understanding that long-term, repeated exposure carries a health risk, particularly occupational exposure in the wood-treating industry, which has been linked to higher rates of skin and scrotal cancer.
Routes of Exposure and Immediate Health Risks
Exposure to creosote occurs through three main routes: skin contact, inhalation, and ingestion. Dermal contact is the most common route, especially for individuals working with freshly treated wood or handling older, recycled materials like railroad ties used in landscaping. The skin readily absorbs the oily components of coal-tar creosote, allowing the PAHs to enter the bloodstream.
Inhalation exposure occurs from breathing creosote vapors, which are particularly strong near heated or freshly treated wood, or from chimney soot buildup. Ingestion is less common but can occur accidentally, such as through contaminated drinking water or when children put contaminated hands into their mouths. Even small amounts of contamination, such as from soil near wood treatment sites, can be absorbed.
Beyond the long-term cancer risk, acute exposure can result in several immediate health effects. Direct skin contact can cause severe irritation, burning, redness, and chemical burns. A notable effect of dermal exposure is phototoxicity, a heightened sensitivity to sunlight that results in severe blistering or sunburn-like reactions. Inhaling creosote vapors can irritate the respiratory tract, leading to symptoms like coughing and wheezing. Ingesting high levels of creosote can cause burning in the mouth and throat, stomach pain, and, in severe cases, damage to the liver and kidneys, potentially leading to convulsions or unconsciousness.
Protecting Yourself from Creosote Exposure
Because coal-tar creosote is a restricted-use pesticide, the general public cannot purchase it, but exposure still occurs through existing treated wood. The most direct preventive measure is to avoid contact with materials like old railroad ties and utility poles, especially where the oily residue or characteristic odor is present. Do not use creosote-treated wood for residential purposes like picnic tables, cutting boards, or children’s play structures.
If handling old creosote-treated material is necessary, minimize skin exposure by wearing appropriate Personal Protective Equipment (PPE). This includes using chemical-resistant gloves, long-sleeved shirts, and long pants to create a barrier against the oily substance. Work in well-ventilated areas to avoid inhaling the vapors and dust created by cutting or sanding the wood.
It is advised never to burn creosote-treated wood in residential fireplaces, stoves, or open pits, as this releases toxic PAHs into the air, smoke, and ash. Regular professional cleaning of home chimneys is necessary to remove creosote buildup, which is a highly flammable fire hazard and a source of potential inhalation exposure. If you live near a former wood treatment facility, check with local health authorities regarding potential soil or water contamination.