U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)


Multi-Component Waste

Human Health Toxicity

Coal tar creosote; coal tar; and heavy fuel oil (HFO), such as bunker oil, heavy fuel oil 6, and marine oil, are complex mixtures that vary due to the type of feedstock and manufacturing method used to produce them. Nevertheless, they all contain some common groups of compounds, such as polycyclic aromatic hydrocarbons (PAHs) and other heterocyclic ring compounds that contain elements, such as oxygen, sulfur, or nitrogen. The proportions of each class of compound vary, with creosote containing greater proportions of the lighter phenols, cresols, and PAHs than coal tar and HFO. Coal tar and HFOs contain greater proportions of 5- and 6-ring PAHs and other more complex, polar, ring structures. Due to the variability of these complex mixtures, their toxicology is difficult to study. The toxicology of an individual component of the mixture may be potentiated or antagonized by other components of the same mixture, making it difficult to predict the behavior of a particular compound in a mixture even when the toxicology of that compound is well known.

Occupational exposure to creosote, coal tar, and HFOs is likely to occur from dermal exposure or possibly inhalation pathways when heated mixtures vaporize. As the use of HFOs is limited to heavy industry and marine applications, there is little expectation that the general population will be exposed, other than in the case of dermal exposure to HFOs washed onto beaches after an oil spill. Coal tar and creosote are more widely used, and the general population might be exposed to them by contact with some pharmaceutical products or freshly creosoted landscaping timbers or other creosote-preserved timber. In addition, the public may be exposed to coal tars and creosotes through the ingestion of contaminated ground water (when used for drinking water purposes) and contaminated fish or shellfish. There is some evidence to suggest that PAHs, present in coal tars, creosote, and HFOs, can bioaccumulate. The presence of these compounds in the breast milk of lactating mothers provides a route of exposure to nursing infants.

No studies are available on the human health effects of the HFOs. However, short-term animal studies (dermal route of exposure) indicate dermal and hepatic toxicity, plus proliferative changes in the epithelium of the bladder. Chronic (2-year) animal studies have shown that HFOs induce tumors in test animals. Numerous studies of occupational exposure to coal tars are available, leading to the conclusion that coal tars are known human carcinogens. Epidemiological studies link creosote exposure to an increased incidence of cancers of the bladder, lung, and multiple myeloma. This mixture also is considered to be a probable human carcinogen.

HFOs have not shown an effect on the fertility of male or female rats. However, dermal exposure of pregnant rats to HFOs resulted in maternal toxicity even at low doses. Furthermore, fetal resorptions were increased and fewer viable offspring were produced. Abnormal development was noted in both living and dead fetuses. In general, it may be concluded that coal tar exerts developmental toxicity in rats and mice by all routes of exposure. These effects are severe and include an increased incidence of abnormalities and prenatal mortality. By contrast, the reproductive and developmental toxicity of creosote is not well understood due to the lack of adequate studies.

Ecological Toxicity

There is no informaton on the ecological toxicity of the coal tars for either the terrestrial or aquatic environments. Although the toxicity of creosote to aquatic organisms is well documented, minimal information exists on its effects on terrestrial organisms. Fish are adversely affected by creosote in surface water and adverse reproductive and developmental effects have been reported. Aquatic crustaceans and mollusks are also sensitive to creosote. The mixture also exhibits toxicity towards aquatic plants. Some studies indicate that HFOs are toxic to fish. Among ecological receptors, HFOs have been observed to penetrate the cellular matrix of marsh plants causing heavy mortality, but after a few years, normal growth was re-established. Studies performed on the eggs of mallard ducks showed that HFO applied to the shell greatly reduced hatching success and survival. However, minimal information exists on the effects of HFOs on terrestrial receptors.

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