Creosote is an oily, dark liquid widely recognized for its effectiveness as a wood preservative. Used for over a century to protect materials like railroad ties and utility poles from decay and pests, it also builds up as a common residue inside chimneys. Understanding the nature of creosote and its potential effects is necessary for anyone who encounters it, whether in older infrastructure or a residential setting.
Composition and Types of Creosote
Creosote is a complex mixture of hundreds of compounds, with its precise composition depending on its origin. The two main types are coal-tar creosote and wood-tar creosote, which differ substantially in their chemical makeup and toxicity. Coal-tar creosote, derived from the high-temperature distillation of coal tar, is primarily used as a heavy-duty wood preservative. It is rich in Polycyclic Aromatic Hydrocarbons (PAHs), which can make up as much as 85% of the mixture.
Wood-tar creosote is a distinctly different product, originating from the distillation of wood like beech or maple and is often found as a residue in residential chimneys. This type contains a higher concentration of phenolic compounds, which are less toxic than the PAHs found in coal-tar creosote. The substantial PAH content in coal-tar creosote is what drives most severe health classifications and regulatory warnings.
Immediate and Long-Term Health Risks
Exposure to creosote can cause a range of immediate and delayed health effects, depending on the type and level of contact. Acute exposure often results in severe irritation of the skin and eyes, sometimes leading to chemical burns. Skin that has touched creosote can also exhibit phototoxicity, meaning it becomes highly sensitive to sunlight, resulting in exaggerated sunburn or rashes.
Inhaling creosote vapors or sawdust from treated wood can irritate the respiratory tract, causing symptoms like coughing and wheezing. Accidental ingestion could cause painful burning in the mouth, throat, and stomach. The primary concern lies in the chronic effects associated with the PAH content of coal-tar creosote.
Major health organizations have classified creosote as a probable human carcinogen due to its established link to cancer in human and animal studies. Prolonged exposure has been associated with an increased risk of several cancers, including those of the skin, lung, and bladder. Creosote chemicals can also affect internal organs, with studies linking extended exposure to damage in the liver and kidneys.
Common Routes of Human Exposure
Human exposure to creosote occurs through three main pathways: dermal contact, inhalation, and ingestion. Dermal exposure is common when individuals handle treated wood products like railroad ties, telephone poles, or fence posts without proper protection. The oily nature of creosote allows the chemical mixture to be readily absorbed through the skin.
Inhalation exposure happens when fumes or sawdust particles are breathed in, such as during the cutting of treated wood. Homeowners may also be exposed to wood-tar creosote by inhaling soot and smoke released from a fireplace or wood stove when chimneys are not cleaned regularly. This airborne exposure is relevant in poorly ventilated areas or during activities that disturb the creosote material.
Ingestion is a risk, especially for young children who might accidentally consume contaminated soil or touch treated materials. Exposure can also occur indirectly through contaminated groundwater near old wood treatment sites. The chemicals within creosote, particularly the PAHs, are absorbed rapidly through the lungs and gastrointestinal tract once exposure occurs.
Safe Handling and Remediation
Minimizing health risks requires careful attention to materials and employing protective measures when handling potentially contaminated items. Personal Protective Equipment (PPE) is an effective first line of defense when working with treated wood. This includes:
- Wearing long-sleeved shirts and long pants.
- Using chemical-resistant gloves, such as vinyl-coated types.
- Wearing eye protection during activities that generate sawdust or particles.
It is advised to avoid using creosote-treated lumber for residential projects like decks, playground equipment, or garden beds where frequent skin contact is likely. If treated wood is already in place, it should not be burned in residential fireplaces, stoves, or open fires, as this releases toxic fumes and ash. Disposal should follow local regulations for treated wood, typically through ordinary trash collection or burial.
If skin contact occurs, immediately wash the exposed area thoroughly with soap and water to remove the oily residue. Contaminated clothing should be washed separately before being worn again. In certain applications, sealing the treated wood with two coats of an effective sealant like urethane, epoxy, or shellac can help reduce the release of vapors.