Dense Nonaqueous Phase Liquids (DNAPLs)

Multi-Component Waste

Heavy Oils

Human Health Toxicity

Heavy fuel oils (HFO) are blended products derived from petroleum refinery distillation and cracking processes. Many different oils are blended with HFOs, which are all viscous liquids that require heating before they can be used or stored. HFOs are used in large industrial plants, power stations, and on ships as fuel for boilers, diesel engines, and furnaces. These oils are known by many names, such as fuel oil 6, bunker fuel, bunker C, marine fuel oil, and industrial fuel oil. HFOs are complex mixtures of high molecular weight compounds that include aromatic, aliphatic, and naphthalenic hydrocarbons; small quantities of heterocyclic compounds containing either oxygen, sulfur, or nitrogen; polycyclic aromatic hydrocarbons (PAHs); polar aromatic ashphaltenes; organometallic compounds; and metallic elements. The toxicity of the HFOs is due largely to the toxicity of its major components, but compounds in a mixture may behave in unexpected ways. Individual compounds or groups of chemicals may potentiate or antagonize each other's actions.

Exposure to HFOs is generally occupational. Workers may be exposed via the dermal route and via inhalation to mists and vapors from heated HFOs as these oils are handled at elevated temperatures. The public may be exposed to the residues of spills on beaches or other areas where HFO has washed inland from marine accidents that have resulted in the release of oil.

Few studies are available concerning the absorption, distribution in the body, metabolism, and excretion of HFOs. Existing information on the absorption of fuel oil comes from cases studies of incidents involving accidental poisoning with lighter oils, such as kerosene.

No studies are available on the human health effects of the HFOs. However, median lethal dose (LD₅₀) studies have shown that HFOs demonstrate low acute toxicity by either the oral or dermal exposure route. Dermal sub-chronic studies (a total of 10 treatment days) in the rabbit produced severe irritation at the application site, 25% mortality, dermal and hepatic toxicity, and proliferative changes in the epithelium of the bladder. Continuously inhaled marine diesel vapor for three months resulted in chronic necrosis of the kidney in male rats, but not in female rats or mice of either sex.

HFOs did not show 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. The effects of exposure included vaginal bleeding, decreased body weight gain, thymic atrophy, and altered serum chemistry. Fetal resorptions were increased and fewer viable offspring were produced. No viable offspring were produced by rats exposed to the highest doses of HFO. Abnormal development was noted in both living and dead fetuses. Among the principal effects were tail and paw abnormalities, diaphragmatic hernia, and cleft palate.

Two-year mouse skin-painting studies of HFO to determine whether the mixture showed carcinogenic activity produced tumors in the test animals. In vitro and in vivo genotoxicity studies showed both positive and negative results.

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Adapted from:

Toxicological Profile for Fuel Oils
Agency for Toxic Substances and Disease Registry (ATSDR)
Department of Health and Human Services, Atlanta, GA, 1995

Heavy Fuel Oils
Conservation of Clean Water and Air in Europe (CONCAWE)
CONCAWE Petroleum Products and Health Management Groups, Product Dossier No. 98/109, 1998

Ecological Toxicity

Aquatic toxicity to HFO is difficult to evaluate from existing studies as many different heavy oils were employed, and these oils were "cut" (diluted) with different types and quantities of cutter stock. Test protocols do not always give a clear indication of how much oil was employed in these studies. Values for the median lethal concentration (LC₅₀) in rainbow trout range from 200 mg/L to 2970 mg/L in 96-hr tests. Sub-lethal effects in rainbow trout were produced by bunker C after 96 hours of exposure. These effects included slight damage to gill morphology and depressed serum glucose levels. Sheepshead minnows showed depressed oxygen consumption when exposed to bunker C. Radioactively labeled bunker C appeared in the gills, kidney, liver, and muscles of exposed rainbow trout. Some studies suggest that HFOs may be retained in the tissues of mollusks for periods of one year after an oil spill.

Spilled HFOs have penetrated the cellular matrix of marsh plants in warm weather causing heavy mortality, but 5 years after the spill, normal population growth was observed. EC₅₀ values of 19.8 g/L and 8.7 g/L have been determined for tradescantia and garden cress.

Egg-painting studies performed on the eggs of mallard ducks showed that 5 µL of bunker C applied to the shell greatly reduced hatching success and survival. This effect has also been seen in the brown pelican following a spill of fuel oil 6. Quail eggs maternally contaminated with bunker C showed reduced viability, and egg production was also reduced in this species. Bunker C ingested by ducks caused increased mortality when the birds were challenged by a pathogen.

Ingestion of low levels of bunker oil C by the American mink resulted in altered hepatic metabolism, renal physiology, and blood.

Human Health References

Heavy Fuel Oils
Conservation of Clean Water and Air in Europe (CONCAWE)
CONCAWE Petroleum Products and Health Management Groups, Product Dossier No. 98/109, 1998

A 53-page document that briefly discusses the properties of heavy fuel oils and provides an extensive discussion of toxicity.

Toxicological Profile for Fuel Oils
Agency for Toxic Substances and Disease Registry (ATSDR)
Department of Health and Human Services, Atlanta, GA, 1995

This profile covers human health effects, chemical and physical properties, manufacturing volume data, potential for human exposure (environmental fate and transport), and analytical methods for fuel oils.

Ecological References

Chronic fuel oil toxicity in American mink (Mustela vison): systemic and hematological effects of ingestion of a low-concentration of bunker C fuel oil
Schwartz, J.A.; B. Aldridge, B. Lasley, et al.
Toxicol Appl Pharmacol 200:146-58, 2004

Comparative study on sensitivity of higher plants and fish to heavy fuel oil
Kazlauskiene, N; G. Svecevicius, M. Vosyliene, et al.
Environ Toxicol 19:449-51, 2004

Chronic fuel oil toxicity in American mink (Mustela vison): systemic and hematological effects of ingestion of a low-concentration of bunker C fuel oil
Schwartz, J.A., et al.
Toxicol Appl Pharmacol 200:146-58, 2004

Environmental Contaminants Encyclopedia
Irwin, R.J. et al.
National Park Service, Water Resources Division, Fort Collins, CO, 1998

This web page provides information on human health effects, fate and transport, production, and uses of many chemicals including fuel oils.

Reproductive responses of quail to Bunker C oil fractions
Wootton, T.A., et al.
Arch Environ Contam Toxicol 8:457-63, 1979