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Colorless liquid with a gasoline- or kerosene-like odor. A mixture of paraffins (C5 to C13). May contain a small amount of aromatic hydrocarbons. Flash point ranges from -40° F to -86° F

Highly flammable. Insoluble in water.

Saturated aliphatic hydrocarbons, which are contained in Lubricant base, may be incompatible with strong oxidizing agents like nitric acid. Charring of the hydrocarbon may occur followed by ignition of unreacted hydrocarbon and other nearby combustibles. In other settings, aliphatic saturated hydrocarbons are mostly unreactive. They are not affected by aqueous solutions of acids, alkalis, most oxidizing agents, and most reducing agents. When heated sufficiently or when ignited in the presence of air, oxygen or strong oxidizing agents, they burn exothermically to produce carbon dioxide and water. May be ignited by strong oxidizers.

Vapor irritates respiratory tract, causes coughing and mild depression. Aspiration causes severe lung irritation with coughing, gagging, and rapidly developing pulmonary edema. Ingestion irritates mouth and stomach, causes nausea, vomiting, swelling of abdomen, cardiac arrhythmias.

Crude oil is a complex mixture of chemicals. The relative composition of these chemicals is different in crude oil from different sources. However, the overall composition remains fairly consistent between sources. The chemical classes present in crude oil include paraffinic hydrocarbons, long-chain straight or branched carbon-based chemicals and naphthenic hydrocarbons, multiple-ringed carbon-based chemicals. Crude oil contains more than 30 parent polycyclic aromatic hydrocarbons (PAHs). The United States Environmental Protection Agency has designated 16 of them as priority pollutants and classified 7 of them as probable human carcinogens. Low percentages of sulfur, nitrogen, and oxygen compounds, and trace quantities of many other elements such as metals (cadmium, mercury, lead, vanadium, nickel) are also present. The petroleum crude category contains only CAS Number 8002059 to identify all conventional crude oils and those derived from tar sands, regardless of source or hydrocarbon distribution.
Regulatory agencies have classified crude oil into categories (summarized in Table 1) that are useful to help understand how the oil will behave if released into the environment. However, weather conditions and water temperature greatly influence the behavior of oil in the environment and a Class B oil may become a Class C oil as volatiles evaporate, whereas a Class C oil may solidify and resemble a Class D oil at low temperatures (e.g., upon going deeper in the sea).

Rubber solvent is a clear, colorless, and flammable liquid, somewhat less volatile than petroleum ether.

Rubber solvent is used as a solvent in the manufacture of adhesives, brake linings, rubber cements, tires, intaglio inks, paints, and lacquers, and in degreasing operations.

The world production of crude oil per year is of the order of 3–4 billion tons per year, of which about half is transported by sea. The separation of the components of crude oil into useable products is known as refining. Each of the crude oil fractions finds its way into consumer products. A typical list of fractions is gasoline, kerosene and fuel oil, gas oil, wax distillate, and bottoms or asphaltics. Refineries must be designed to handle the type of crude oil they are going to process. For example, if a crude oil is highly paraffinic in nature, it will yield a lower amount of gasoline fuel by distillation. Highly paraffinic oils may be processed into lubricating stock. The chemical fraction consisting of chemicals with the largest carbon numbers, the asphaltic fraction, is used as roof or road tar.

Lubricant base is a complex combination of hydrocarbons. It consists predominantly of aliphatic, alicyclic and aromatic hydrocarbons. It may also contain small amounts of nitrogen, oxygen and sulfur compounds. This category encompasses light, medium, and heavy petroleums, as well as the oils extracted from tar sands. Hydrocarbonaceous materials requiring major chemical changes for their recovery or conversion to petroleum refinery feedstocks such as crude shale oils, upgraded shale oils and liquid coal fuels are not included in this definition.

A small fraction of the petroleum products is released to land, either accidentally or intentionally. Release of refined oils, particularly gasoline, from leaking underground storage tanks is the most widely recognized source of petroleum contamination of soils and groundwater. In contrast, over 2 million tons of oil per year enter the marine environment from all sources. Anthropogenic sources (~85%) include chronic discharges (storage facilities, refineries, tankers), accidental oil spills and to a lesser extent, river-borne discharges, and diffuse discharges (industry, offshore oil platforms, atmosphere). The main source of chronic discharges offshore is produced water, the maximum permitted concentration of crude oil in discharged produced water being 30 mg l^-1.
Following release to the environment, petroleum products may accumulate in soils and sediments where they undergo dispersal and weathering (changes in physical and chemical properties). Crude oil spilled on water also undergoes weathering.
Weathering affects the composition and toxicity of the hydrocarbon mixtures, occurs by abiotic (volatilization and oxidation) and biotic processes (including biodegradation), and begins immediately after crude oil is released into the environment. Its chemical-specific properties will determine how an individual compound of crude oil fares during weathering. Small volatile compounds are lost first from both land and water releases whereas large paraffinic compounds are more persistent and asphaltic compounds are the residual material. Heavy fractions with high density may adsorb to suspended solids and sink into the sediment. This happens after the initial removal of the smaller and more volatile chemicals by either dissolution or volatilization. Persistence depends on the type of oil, the season, the geomorphology of the coast and the degree of exposure, and goes from some few to many decades. After 20 years, most of the oil spilled by Exxon Valdez was eliminated due to natural weathering although some subsurface oil residues, sequestered and slowly affected by natural weathering, remained.
Although controversial due to the well-known side effects and toxicity, the judicious and proper application of chemical dispersants may accelerate the dispersion of crude oil from the sea surface into the water column, which in turn helps to accelerate its dilution, weathering, and biodegradation.
Biodegradation is a major process that removes hydrocarbons released into both soil and aquatic environments. However, the biodegradation of crude oil is only efficient when crude oil concentrations are low. It may last for decades and requires the simultaneous action of different microbial populations, including fungi and bacteria. Biodegradation rates for crude oils will vary considerably, but in standard 28-day studies, none would be expected to be readily biodegradable. Most of the nonvolatile constituents of crude oil are inherently biodegradable but some of the highest molecular weight components are persistent in water. n-Alkanes are utilized as food by many marine microbes and readily biodegraded in seawater. Branched-chain or iso-alkanes are less biodegradable but they do ultimately biodegrade. Cycloalkanes and aromatic hydrocarbons are resistant to biodegradation, but a few microorganisms are able to utilize them. High molecular weight compounds, the tars and asphaltenes are practically reluctant to ultimate biodegradation and persist in the environment. In soils, 25% total PAHs of spilled crude oil can be naturally removed by soil microorganisms within a period of 9 months under optimal conditions, but the time needed to eliminate the remaining PAHs may also extend to decades. Biodegradation can be enhanced by the presence or earthworms and other soil invertebrates that contribute to optimize microbial habitats and by artificially adding nutrients to stimulate microbial action.

The concern for both dermal and inhalation exposures is the site of contact and effects on that tissue. The mechanism of crude oil toxicity is mediated through its irritant effects which after sufficient exposure duration and concentration result in tissue hyperplasia. Chronic hyperplasia leads to subsequent loss of tissue integrity and damage and in someanimalmodels of cancer. It has been suggested that at exposures below levels that cause chronic irritation, other long-termeffects would not be expected.
Although studies on the mechanisms of toxicity of crude oils are relatively few, there is a substantial body of data on products derived from crude oils, such as gasoline, diesel fuels, kerosene and jet fuels, lubricating oils, and white oils. Extrapolation from these studies provides insight into biologically active components of crude oils. Crude oil contains many chemicals considered toxic and the effects of these individual chemicals should be evaluated if exposure is possible. Although polar- and nonpolar compounds contribute to the toxicity of (weathered) crude oil, the water-soluble fraction (WSF) is dominated by polar compounds, which accounts for a large portion of the toxicity.
Crude oil toxicity can vary depending on environmental factors. For instance, exposure of crude oil to sunlight enhances the toxicity of its WSF because this contains some hydrocarbon compounds that are phototoxic or exhibit at least photoenhanced toxicity.