Types of Oil
Characterization of crude oils and refined petroleum products in a release situation is one of the earliest response tasks that must be undertaken. Proper classification and an understanding of the chemical and physical properties of these substances helps determine:
- The hazard to personnel and wildlife;
- The effects that may be observed on adjacent shorelines or estuaries (for spills into water); and
- The form a response should take.
Non-petroleum-based oils also pose a potential threat to human health and the environment. This discussion focuses only on crude oils and refined products; there are also non-petroleum oils such as synthetic oils and animal fats and vegetable oils.
Chemical Composition
Crude oils and refined petroleum products consist largely of hydrocarbons, which are chemicals composed solely of hydrogen and carbon in various molecular arrangements. Crude oils contain hundreds of different hydrocarbons and other organic and inorganic substances including atoms of sulfur, nitrogen, and oxygen, as well as metals such as iron, vanadium, nickel, and chromium.
Upon release, the hydrocarbons that are composed of fewer carbon and hydrogen atoms vaporize, leaving behind a heavier, less volatile fraction. Gasolines contain relatively high proportions of toxic and volatile hydrocarbons, such as benzene, which is known to cause cancer in humans, and hexane, which can affect the nervous system. Gasoline and kerosene releases are exceptionally hazardous due to their high flammability. Crude oils and semi-refined products, such as diesel and bunkering oils, may contain cancer-causing polycyclic aromatic hydrocarbons and other toxic substances.