Dense Nonaqueous Phase Liquids (DNAPLs)

Multi-Component Waste

Creosotes

Human Health Toxicity

Coal tar creosote derived from the fractional distillation of coal tars is a brownish black or yellowish dark-green oily liquid. Some creosotes are derived from beech wood or other botanical sources, but only the toxicology of coal tar creosote is discussed here and the term "creosote" always refers to coal tar creosote. The chemical characteristics of coal tar creosotes vary to some extent due to the composition of the coal tar feedstock, which varies with the type of coal and distillation method used to produce it (e.g., coal coking for the steel industry versus manufactured gas plant processes). The chemical composition of creosote may be further complicated by the solvents and oils used to dilute it. Creosote usually contains six major classes of compounds: aromatic hydrocarbons including polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs; phenolics; nitrogen-containing heterocyclics; aromatic amines; sulfur-containing heterocyclics; and oxygen-containing heterocyclics, such as the dibenzofurans. However, more than a thousand compounds may be present in creosote. The toxicity of creosote is largely due to the toxicity of its major components, such as the PAHs, but since creosote is a mixture, it may behave in unexpected ways. Individual components or groups of compounds may potentiate or antagonize each other's actions.

The general population may be exposed to creosote in pressure-treated lumber that itself has a variety of uses, such as landscaping, playground equipment, log homes, fencing, railroad ties, freshwater and marine boat docks, and recycled treated timbers for housing. In addition, the public may be exposed to creosote by consuming contaminated drinking water, fish, and shellfish. Children may come into dermal contact with creosote-contaminated sand or soil when playing near newly installed treated timbers. Creosote-contaminated sand or soil also poses an ingestion hazard for children. Occupational exposure occurs in coal tar distilleries, facilities that produce pressure-treated timber, and during the application of creosote as an insecticide. Typical occupational exposure routes are inhalation and dermal contact.

Although no human or animal studies exist on the rate and extent of creosote uptake, absorption can be inferred from the presence of creosote-related metabolites in the urine of exposed volunteers or workers. The distribution of creosote in the bodies of humans or laboratory animals is unknown. Metabolized or unmetabolized PAHs derived from creosote are excreted in breast milk, bile, urine, and feces.

Laboratory animal studies exist mainly on the acute toxicity of creosote with only minimal information available on the effects of short-term exposure. However, loss in body weight after oral exposure has been recorded in sheep, calves, and rats. Studies in mice suggest that creosote may have carcinogenic activity. Following the topical application of creosote, skin carcinomas and papillomas were observed and tumors developed at sites, such as the lung, that were distant from the application. Recent, 78-week mouse studies have confirmed that creosote has carcinogenic potential with the induction of skin tumors. Non-cancer effects noted in this mouse study included skin ulceration and decreased life-span. Creosote appeared to be five times more potent in inducing tumors than pure benzo(a)pyrene, a known carcinogen frequently applied as a positive control in animal cancer investigations.

The reproductive and developmental toxicity of creosote is not well understood due to the lack of adequate studies. In vitro testing indicates creosote is genotoxic and cytotoxic and may be an endocrine disruptor. The genotoxic and cytotoxic effects of creosote are similar to those observed for PAHs.

Scant information exists on the effects of creosote on the general population. Creosote has caused the deaths of adults and children after ingestion of approximately 7 g (adult) and 1-2 g (children) quantities. It has been suggested that skin rashes may be more frequent in a population living close to an abandoned wood creosoting plant. One study inferred an increased incidence of breast and gastrointestinal cancer in women exposed to a creosote contaminated water supply. However, creosote could not be clearly implicated as the responsible agent in this study due to confounding risk factors.

Dermal and inhalation exposure to creosote in the work place has been widely studied. Non-cancer effects of exposure include irritation of the skin and eyes and phototoxic and photoallergic reactions accompanied by depression, weakness, vertigo, headache, slight confusion, increased salivation, and vomiting. In addition, sensitization of the skin to sunlight (UV wavelengths) has been reported. Studies of workers involved in producing pressure treated wood containing creosote have reported increased incidence of skin and lip cancers. Increased mortality from cancer of the scrotum has been reported for brick makers exposed to creosote. Epidemiological studies suggest a possible increased risk of cancers of the bladder, lung, and multiple myeloma after creosote exposure. An increased risk of brain tumors and neuroblastoma has been suggested for the children of men occupationally exposed to creosote. The EPA's Integrated Risk Information System summary for creosote concludes that the substance is a probable human carcinogen.

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Adapted from:

Concise International Chemical Assessment Document (#62) Coal Tar Creosote
International Programme on Chemical Safety (IPCS), 2004

Creosote (CASRN 8001-58-9)
Integrated Risk Information System (IRIS)
U.S. EPA, 1988

Ecological Toxicity

In contrast to the well documented toxicity of creosote in aquatic species, minimal information exists on its effects on terrestrial organisms. However, one study indicates that plant growth, as determined by root elongation, is inhibited by creosote. Creosote-contaminated soil caused the death of a test population of earthworms within a few days.

Fish are adversely affected by creosote in surface water. A median lethal concentration (LC₅₀) of 0.7 mg/L has been reported for fish, indicating acute toxicity. Lower concentrations of creosote have been reported to cause adverse reproductive and developmental effects in fish. Aquatic crustaceans and mollusks are sensitive to creosote, and oysters exposed to contaminated sediment are more susceptible to infection.

When crustaceans, such as Mysidopsis bahia, a small shrimp, are exposed to creosote, they exhibit decreased weight and a decrease in the proportion of gravid females in the population. Aquatic plants show both abnormal growth and stress in response to creosote, which also has been shown to be phototoxic to them.

Human Health References

Concise International Chemical Assessment Document (#62) Coal Tar Creosote
International Programme on Chemical Safety (IPCS), 2004

This document is a comprehensive review of the physical/chemistry properties, fate and transport, human and ecological health effects, and occurrence of coal tar creosote.

Creosote (CASRN 8001-58-9)
Integrated Risk Information System (IRIS)
U.S. EPA, 1988

An EPA developed and maintained database that contains toxicological data and discussions of effects for a variety of chemicals of regulatory interest.

Toxicological Profile for Wood Creosote, Coal Tar Creosote, Coal Tar, Coal Tar Pitch, and Coal Tar Pitch Volatiles
Agency for Toxic Substances and Disease Registry (ATSDR)
Department of Health and Human Services, Atlanta, GA, 2002

This profile provides information on human health effects, fate and transport, production, and uses of coal tar creosote.

Ecological References

Concise International Chemical Assessment Document (#62) Coal Tar Creosote
International Programme on Chemical Safety (IPCS), 2004

This document is a comprehensive review of the physical/chemistry properties, fate and transport, human and ecological health effects, and occurrence of coal tar creosote.

Creosote
Kegley, S.; B. Hill, and S. Orme
Pan Pesticide Database, Pesticide Action Network, San Francisco, CA, 2007

A web page that describes physical/chemical properties and provides information similar to a materials data safety sheet plus multiple links to other web sites that contain information on creosote.

Creosote toxicity to photosynthesis and plant growth in aquatic microcosms
Marwood, C.A.; et al.
Environ Toxicol Chem 22:1075 85, 2003