Bunker fuel is the generic term given to any fuel poured into a ship’s bunkers to power its engines. Deepsea cargo ships typically burn the heavy, residual oil left over after gasoline, diesel and other light hydrocarbons are extracted from crude oil during the refining process.

• Industry material safety sheets for marine fuel oil classify it as hazardous and very toxic to aquatic life, with long-lasting effects.

• Bunker fuel is graded A, B or C, with C being the thickest and most viscous, often requiring heating or blending in order to make it flow. Mixed with up to 10 per cent of a lighter fuel, such as diesel, it becomes a cheap fuel for use in shipping.

• Characterized as persistent oil, it is likely to spread large distances because it does not easily evaporate.

• It is a brown to black liquid, with a characteristic odour.

• Vapours are harmful if inhaled, exposure can cause eye or skin irritation.

• Suspected of damaging fertility, may cause organ damage through prolonged exposure.

• Harmful to fish, toxic to crustaceans and shellfish, very toxic to aquatic plants with potentially long-term adverse effects.

• Contains constituent parts with the potential to bioaccumulate.

• Left stagnant in storage tanks, deadly hydrogen sulphide gas can form.

Source: Marine engineer Brian Norohnha, BCIT; Shell Marine Fuel Oil Safety Data Sheet, Chevron Marine Products Material Safety Data Sheet and U.S. Office of Response and Restoration of the National Oceanic and Atmospheric Administration.

Shell marine fuel oil safety data sheet