Comparing the worst oil spills

The biggest spill was off Brittany in 1978

Environmentalists are warning that if all 70,000 metric tons of fuel oil escape from the Prestige which broke up off the Spanish coast it could rank as one of the worst environmental disasters.

Greenpeace spokesman Dr David Santillo says that making comparisons can be difficult as the impact depends on the type of oil spilled, the weather conditions and the sensitivity of the region.

The Exxon Valdez spilled 38,800 tons of crude oil into Prince William Sound in Alaska in 1989 and it took many years for the area to recover.

Change of law

Dr Santillo, who works for the Greenpeace research laboratory at Exeter University in the UK, explained that a combination of shallow water and a poor flush of water through the Sound magnified the impact of the spill on a particularly sensitive region.

Many seabirds have been affected by the Prestige disaster

More recently, in 1999, the Erika spilled 13,000 tons of heavy diesel oil off the coast of Brittany - a disaster which led to a change in the laws governing the shipment of oil by tanker.

The Prestige was carrying fuel oil.

Some of the lighter, more volatile oils can evaporate and dissolve before they get ashore - though wildlife at sea will still be affected.

Although some thick deposits have already come ashore it is not yet clear how the rest of the cargo from the Prestige will behave or if the weather will aid in the dispersion.

Dr Santillo said: "The total quantity of oil is very much larger than the Erika and this is a very sensitive coastline and a very important area for fishing."

In 1993 the Braer grounded south of the Shetland Island, off the north coast of Scotland, spilling 85,000 tons of oil.

Deliberate release

Dr Santillo said that although it was a large-scale spill, the impact was lessened by the severe weather which broke up and dispersed the slick at sea.

Pipeline spills have also had devastating results.

Two years ago a ruptured pipeline spewed about 340,000 gallons of heavy oil into Guanabara Bay, Rio de Janeiro, in Brazil.

And in January 1991 during the Gulf War, the Iraqi army deliberately released an estimated 460 million gallons of crude oil into the Persian Gulf.

There have been dozens of oil spills during the last 35 years. Some of the worst include:

• January 2000: A ruptured pipeline spewed about 340,000 gallons of heavy oil into Guanabara Bay, Rio de Janeiro, in Brazil.
  
• December 1999: The Erika spilled 13,000 tons of heavy diesel oil off the coast of Brittany.
  
• February 1996: The Sea Empress spilled about 72,000 tons of crude oil near the port of Milford Haven in Wales.
  
• January 1993: The Braer grounded off the Shetland Islands spilling 85,000 tons.
  
• December 1992: A ship called the Aegean Sea spilled 80,000 tons of crude near the port of La Coruna in Spain.
  
• May 1991: The ABT Summer leaked oil after an explosion off Angola spilling 260,000 tonnes.
  
  
• April 1991: The Haven spilled more than 50,000 tons of oil off Genoa in Italy.
  
• January 1991: Iraq released about 460 million gallons of crude oil into the Persian Gulf during the Gulf War.
  
• March 1989: The Exxon Valdez is grounded and spilled 38,800 tons of crude oil into Prince William Sound in Alaska - the worst spill in US history.
  
• August 1983: Fire broke out on the the Castillo de Bellver and its cargo of 252,000 tonnes of oil burnt.
  
• 1979: The Atlantic Empress spilled 160,000 tons off Tobago.
  
• 1978: Wrecked tanker Amoco Cadiz spilled 220,000 tons gallons off the Brittany coast.
  
• March 1967: The Torrey Canyon spilled 119,000 tons of crude off the Isles of Scilly in the UK.

Various sources. All figures approximates