Oil is a thick, viscous liquid composed of complex hydrocarbon molecules. It is produced by plants that have become fossilised under the sea. Oil is therefore naturally found in the sea, at deposits close to the earth’s surface which seep oil as a natural process. Oil is also mined extensively to fuel the world's economy, and oil pollution problems are largely due to the scale of this exploitation and the practices used in recovery, transport and disposal.

oily facts

• Estimates of oil derived pollution to the world’s oceans suggest about 2.5 million tonnes per year. Of this, 23% comes from accidents and practices associated with oil transport, 8% from fixed installations such as oil rigs and coastal refineries, 58% from manufactured waste and oil pollutants washed into the sea from land, and 11% from natural inputs like oil deposit seepage.
• Spills from ships such as the Braer (1993) off Shetland, and the Sea Empress (1996) off Milford Haven grab headlines, but oil tanker accidents actually account for just 5% of the total oil discharged to the sea. These shipping accidents can be very highly destructive to marine life within a limited geographic area, but of far greater impact are the steady discharges from land based sources such as storm drains, urban storm water run-off, and domestic and industrial waste discharge. Globally, these sources account for about 1.45 million tonnes of oil derived pollution to the sea each year.
• In the UK, virtually all the oil discharged into the sea as a result of offshore oil and gas exploration and production activities is contained in the water that is produced with the oil. In 2005, approximately 5000 tonnes of oil was discharged in these processes, including spills.
• Legislation to control oil pollution of the seas is broadly covered by the International Convention for the Prevention of Pollution From Ships, also known as MARPOL 73/78,  which came into force in 1983. Annex 1 governs deliberate discharges from ships of waste oils, prohibits oil discharge within special areas, and requires the provision of oil reception facilities at all ports. It was amended in 1992 to include requirements for safer ‘double hull’ oil tanker construction, and this amendment was adopted into European Union regulations following the Prestige tanker disaster off the coast of Galicia in 2002.
• MARPOL is supported in the UK by the Prevention of Oil Pollution Act (1971 ), the Offshore Petroleum Activities (Oil Pollution Prevention and Control) Regulations 2005, and the Merchant Shipping (Prevention of Oil Pollution) Regulations 1996 (amended 2005) governing the transport and discharge of oil from ships.
• The official offshore regulator in the UK is the Maritime & Coastguard Agency.

• In the UK, virtually all the oil discharged onto the seabed comes as a result of offshore oil and gas exploration. In 2005, approximately 5000 tonnes of oil was discharged in these processes, including spills. Oil adsorption into sediments can poison habitats for burrowing organisms such as annelids and echinoderms, or simply smother the seabed.
• Sea birds are probably the animal most vulnerable to oil spills. Poisoning may occur during attempts preen, but the most common causes of death are drowning, starvation and hypothermia as a result of oil coated feathers. The 1989 Exxon Valdez disaster in Alaska killed at least 30,000 sea birds.
• Bottom dwelling organisms such as mussels and barnacles feed by sifting food particles out of the water. Oil can coat both their feeding apparatus and gills eventually killing them.
• Marine mammals such as whales, dolphins and seals may be able to avoid oil slicks but suffer from prey depletion. Seals may be poisoned if oil is swallowed, or by the volatile oil fractions which cause eye irritations. Some oil fractions are carcinogenic.
• Non mobile organisms such are barnacles, limpets and sea urchins are coated and poisoned, both on the seabed and along the shoreline.
• Changes in biological communities resulting from impacts to key stone organisms - increased dominance of algae on shorelines following oil induced death of animals such as limpets and sea urchins which graze on algae.

what you can do

• Take personal responsibility for the disposal of oil and petro-chemical based products. Don’t, for example, tip engine oil down the drain, and clean up fuel spills.
• If you see serious oil pollution on the coast, ring the Maritime & Coastguard Agency (tel: 01326 317 575) or the Coastguard (tel: 999) with details of the location and incident.
• If you see oiled animals, contact the RSPCA (0870 5555 999) or SSPCA (0131 339 0222) with the number, species and location.
• If you see serious oil pollution on in-land waterways, ring the Environment Agency pollution hotline: 0800 80 70 60
• Email photos of oil pollution, or any pollution incidents, to MCS at info@mcsuk.org
• Take part in the MCS Adopt-A-Beach volunteer beach litter clean ups, and support our campaigns to prevent oil pollution at source.