creosotes

Creosotes are oily liquids derived from the distillation of coal tar or wood tar. They are used primarily as wood preservatives and have a long history in industrial applications. The term creosote also appears in reference to the resinous material produced by the creosote bush in the desert, though this plant-based resin is chemically distinct from industrial creosotes.

The two main commercial forms are coal-tar creosote and wood-tar creosote. Coal-tar creosote is rich in phenols and polycyclic aromatic hydrocarbons (PAHs) and is the more widely used preservative in outdoor timber. Wood-tar creosote is derived from wood tar and has a somewhat different chemical profile, with phenols and related compounds playing prominent roles. In both cases creosotes are complex mixtures, not single chemicals.

Uses and stewardship: Treated timber—such as utility poles, railroad ties, marine pilings, and fencing—benefits from creosote’s decay resistance and insect deterrence. Its use has declined in some regions due to health and environmental concerns, and many countries regulate or restrict its application. Exposure can occur through skin contact, inhalation of vapors, or contact with contaminated soil.

Health and environmental considerations: Components of creosotes, particularly PAHs, are associated with irritant effects and potential carcinogenic risks with long-term exposure. Handling creosote requires protective equipment, and improper disposal can lead to soil or groundwater contamination. Environmental persistence means leakage or improper disposal can have lasting impacts.

See also: Creosote bush.