Creosote – A Chemical Mixture Produced from Wildfires

Creosote, an oily residue that forms from unburned wood gases, is often known for its use in railroad ties and utility poles as a preservative. However, this is not the only place creosote can be found. The heat and low oxygen conditions in a wildfire cause the breakdown of lignin, a complex organic polymer found in wood, and other compounds in plants, leading to the formation of phenolic compounds and polycyclic aromatic hydrocarbons (PAHs) that make up creosote. Phenolic compounds contain a benzene ring attached to a hydroxyl group (OH-) and have the ability to transport into the cells of the liver, kidneys, and brain. PAHs are carcinogens that have also been linked to genotoxicity.¹ Both phenolic compounds and PAHs have been studied extensively and classified as persistent organic pollutants (POPs) due to their risk to human health and ecological safety. Creosote is known to adsorb easily on to soil due to its mostly hydrophobic chemical makeup.² However, rain can leach the more water-soluble phenolic compounds into nearby rivers, lakes, or groundwater.³ In light of recent wildfire events on the west coast of the United States, creosote contamination is of particular concern. Contaminated sediment has the ability to transfer quickly into water bodies,⁴ making groundwater sampling a valuable method for monitoring the levels of these compounds.

Since PAHs and phenolic compounds are classified semivolatile organic compounds (SVOCs), they are included in many target analyte lists for EPA 8270. UCT provides a specialized 8270 cartridge (EC82702M15) that allows for the extraction of 1-liter samples, achieving concentrations in the μg/L range and enabling the detection of even trace amounts of creosote constituents. For a detailed extraction procedure, refer to UCT’s application note, Implementation of EPA Method 8270E Using Solid-Phase Extraction and Hydrogen as Carrier Gas for GC/MS Analysis.

References:

• Ewa, B.; Danuta, M. Š. Polycyclic Aromatic Hydrocarbons and PAH-Related DNA Adducts. J. Appl. Genet. 2017, 58, 321–330. https://doi.org/10.1007/s13353-016-0380-3.
• Fernandez-Marcos, M.L. Potentially Toxic Substances and Associated Risks in Soils Affected by Wildfires: A Review. Toxics 2022, 10, 31. https://doi.org/10.3390/toxics10010031
• Santín, C.; Doerr, S. H.; Otero, X. L.; Chafer, C. J. Quantity, Composition, and Water Contamination Potential of Ash Produced Under Different Wildfire Severities. Environ. Res. 2015, 142, 297-308. https://doi.org/10.1016/j.envres.2015.06.041.
• Black, J. J. Movement and Identification of a Creosote-Derived PAH Complex Below a River Pollution Point Source. Arch. Environ. Contam. Toxicol. 1982, 11(2), 161-166. https://doi.org/10.1007/BF01054892.