Creosote is a coal tar-based pesticide used as a wood preservative. Unlike most pesticides it is applied in a controlled and limited setting under closed process conditions. Railroad ties, utility poles and pilings are the wood products treated with creosote. It is these treated wood products that are released into the chain of commerce, as opposed to most pesticides which are applied directly to the open environment under a variety of climate and weather conditions. Most exposure to creosote is to the wood treatment worker, but such exposure is also controlled to a larger degree than the typical pesticide applicator.

Creosote is a highly complex mixture containing hundreds of individual compounds. Although the actual composition of creosote may vary somewhat due to differences in the source material, coal, coal tar creosote (CAS# 8001-58-9) when used as a pesticide to preserve wood can only be manufactured by the distillation of tar obtained from coal and must conform to standards established by the American Wood Preservers Association (AWPA, 1995), P1/P13 or P2. These standards identify the source material for pesticide creosote as well as the physical-chemical characteristics of the pesticide product. AWPA defines the P1/P13 and P2 (creosote) fractions for use as heavy duty wood preservatives as “a pure coal tar product, derived entirely from tar produced by carbonization of bituminous coal.” Carbonization of coal is accomplished by distilling coal and the coal tar fraction is collected. The coal tar fraction itself consists of: light oil, middle oil and heavy (oil) anthracene. It is the middle oil fraction that is further distilled and various fractions from this distillation are collected between the temperatures of 210o and 355o C. The creosote mixture is further defined by its physical/chemical characteristics (i.e., xylene insolubles, specific gravity, water content, etc.). The fraction of coal tar isolated as creosote is a heterogeneous mixture of primarily polycyclic aromatic hydrocarbons and other heteronuclear aromatic compounds. Compositionally, there is a clear qualitative and quantitative difference in the make-up of creosote and other coal tar products. These differences manifest as differences in chemical and physical properties. Just as the compositional differences among coal tar, pitch and creosote manifest as differences chemical properties, so to are there differences in toxicological activities among these materials.

Since 1992, the Creosote Council III has engaged in health effects research on creosote. To date, 12 acute mammalian toxicity studies, 4 mammalian developmental or reproductive function toxicity studies, 4 subchronic studies, two in vivo mammalian genetic toxicity studies, a mammalian cancer bioassay, a wood treating worker exposure study and a protective clothing permeability study have been completed. In addition, the Creosote Council has supported several field and laboratory marine and estuarine ecological studies of creosote and creosote-treated wood.

The results of these studies are summarized in the HEALTH SECTION of the Creosote Council Website.