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Creosote

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Introduction

Creosote is a complex mixture of many chemicals. There are three kinds of creosote. One type results from high-temperature treatment of coal (coaltar creosote), one results from high-temperature treatment of beech and other woods (beechwood creosote), and one comes from the resin of the creosote bush (creosote bush resin). Coal-tar creosote is the most widely used wood preservative in the United States. Coal-tar products are also ingredients in medicines that are used to treat skin diseases. About 300 chemicals have been identified in coal-tar creosote, and there may be 10,000 other chemicals present in the mixture. The major chemicals in coal-tar creosote that can cause harmful health effects are polycyclic aromatic hydrocarbons (PAHs), phenol, and cresols. Beechwood creosote was at one time used as a disinfectant and as a treatment for coughs, but it is rarely used today. The major chemicals present in beechwood creosote are phenol, cresols, and guaiacol. Because coal-tar creosote is the only type found in the environment and at hazardous waste sites, its effects on human health will be emphasized. Furthermore, because the creosote mixture is specifically addressed, effects on health from exposure to the individual major chemicals in creosote, namely, the PAHs or phenol, will not be discussed in any great detail.

Coal-tar creosote is usually a heavy, oily, liquid that is typically amber to brown in color. Mixtures of creosote and other coal-tar products are black. The creosote found at hazardous waste sites is most often a black, heavy liquid. It has a sharp smoky odor, and a burning taste. It burns easily, but does not dissolve readily in water.

Fate & Transport

Creosote does not occur naturally in the environment but it can be released to water and soil through its use as a wood preservative. However, there are many known natural sources for components of the creosote mixture, such as PAHs. Some parts of the creosote mixture can enter groundwater or change into other substances while other parts persist in treated wood products for decades.

Exposure Pathways

The major sources of human exposure to coal-tar creosote are contaminated hazardous waste sites, wood treatment facilities, and wood products treated with creosote. You cannot buy coal-tar creosote for treating wood products in your home. Wood products that are typically treated with creosote are railroad ties used by the railroads and landscapers, telephone poles, marine pilings, and fence posts. You can also be exposed to creosote through contact with soil, water, or air contaminated as the result of releases from waste disposal sites and wood treatment facilities and the burning of treated scrap wood. Exposure of the general population to creosote from currently operating wood treatment facilities should be minimal because all of these facilities are subject to strict controls by the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA). However, exposure to creosote from abandoned wood treatment facilities is possible. There should be very little exposure of the average homeowner to creosote solutions used for wood treatment because it can only be sold to certified applicators; however, you can still be exposed to creosote treated products.

There is no information on background levels of creosote in air or food. Background levels of certain parts of the creosote mixture such as PAHs can be found in some city soils and foods, but it is not known if these substances came from creosote.

Metabolism

Creosote can enter your body through the lungs as a contaminant of air, through the stomach and intestines after eating contaminated food or drinking contaminated water, or through the skin. Although there is no information on how fast or how much of the creosote mixture is absorbed, many of the parts of the creosote mixture (for example, PAHs) are rapidly absorbed through the lungs and the stomach and the intestines.

The most common routes of exposure around hazardous waste sites are likely to be through the skin, and drinking water contaminated with creosote. Although it is not known how rapidly creosote can enter the body through the skin, creosote can cause reddening just from skin contact. Eating soil contaminated with coal-tar creosote can also provide a source of exposure. Chemicals in coal-tar creosote appear to accumulate in the body, particularly in fat tissue. Most of the chemicals in creosote that are taken into the body and are not stored in the body tissues, leave in the feces within a few days.

Health Effects

Reports describing coal-tar creosote poisoning in workers or accidental or intentional ingestion of coal-tar creosote indicate that brief exposures to large amounts of coal-tar creosote can cause harmful effects on your skin, eyes, nervous system, and kidneys and can result in death. Longer-term exposure to lower levels of coal-tar creosote can also result in damage to your skin, such as reddening, blistering or peeling.

The major organs or systems affected by longer-term exposure to lower levels of coal-tar creosote in animals are the skin and lungs, whereas only the skin has been observed to be affected in humans under these exposure conditions. All of these effects worsen as the level of coal-tar creosote exposure increases.

An increased risk for cancer has been demonstrated in animals exposed to coal-tar creosote. Birth defects have been seen in livestock exposed to coal-tar creosote-treated wood. Since these effects were seen in animals, it is also possible that they could occur in humans. The International Agency for Research on Cancer has determined that creosote is probably carcinogenic to humans.

Information excerpted from:

Toxicological Profile for Creosote December 1990

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services