Creosote is a complex chemical mixture primarily used as a wood preservative to protect against pests like termites and fungi. Derived from the distillation of wood or coal tar, it has been a common treatment for outdoor wood structures such as railroad ties and utility poles since the mid-1800s. This substance often raises concerns about its potential health effects, particularly regarding cancer.
Understanding Creosote and Its Forms
Creosote is a diverse group of compounds, with its composition varying by source. The two main types are coal-tar creosote and wood-tar creosote. Coal-tar creosote, commonly used as a wood preservative, is a complex mixture containing a high percentage of polycyclic aromatic hydrocarbons (PAHs), along with phenols, cresols, and other heterocyclic compounds. Wood-tar creosote, derived from burning wood, is often found as a sticky residue in chimneys and predominantly contains phenolic compounds. Many of its components, especially certain PAHs, are known to have biological activity, influencing its potential health effects.
The Scientific Link to Cancer
Scientific bodies have evaluated creosote’s carcinogenic potential. The International Agency for Research on Cancer (IARC) has classified creosotes as “probably carcinogenic to humans” (Group 2A), based on limited human and sufficient animal study evidence. Similarly, the U.S. Environmental Protection Agency (EPA) considers creosote a “probable human carcinogen” (Group B1).
The carcinogenic effects of creosote are largely attributed to its PAHs, which are mutagenic, meaning they can cause changes to DNA. Long-term exposure has been associated with an increased risk of cancer in various tissues. Skin cancer, including squamous cell and basal cell carcinomas, and scrotum cancer, are particularly noted among individuals with prolonged skin contact, such as chimney sweeps and wood treatment workers. Evidence also suggests a potential link to cancers of the lung, bladder, and kidney from inhalation or ingestion exposures in occupational settings.
How Human Exposure Occurs
Humans can encounter creosote through several pathways, including direct skin contact, inhalation, and, less commonly, accidental ingestion. Direct skin contact occurs when handling creosote-treated wood or chimney buildup, potentially causing skin irritation and sun sensitivity. Inhalation exposure occurs by breathing in vapors or dust particles from creosote-treated materials or from the smoke produced by burning creosote-laden wood. Workers in industries like wood preservation, construction, or railway maintenance may experience chronic inhalation. Residential exposure can also occur from chimney residue, a byproduct of burning wood. Accidental ingestion, though infrequent, can happen if contaminated hands are brought to the mouth or from contaminated water sources, potentially leading to gastrointestinal irritation.
Minimizing Risk and Safe Handling
Minimizing creosote exposure involves adopting specific safety practices. When handling creosote-treated wood, wear protective clothing like long-sleeved shirts, long pants, and chemical-resistant gloves to prevent skin contact. Also wear eye protection, such as goggles, especially during activities that might generate dust or splinters. If working indoors with treated wood, ensure good ventilation or perform tasks outdoors to reduce inhalation of vapors and dust.
Avoid burning creosote-treated wood in residential fireplaces, stoves, or open fires, as this releases toxic chemicals into the air and ash. For proper disposal, creosote-treated wood should generally be handled as municipal solid waste, though local regulations may vary. After any potential exposure, wash exposed skin thoroughly with soap and water before eating, drinking, or using tobacco products. Regular cleaning and inspection of chimneys by a certified professional is important to manage creosote buildup from wood burning, reducing fire hazards and potential exposure.