Spills of crude oil and refined products from tankers have declined markedly since the 1970s, despite a pronounced increase in tanker trade, according to the International Association of Independent Tanker Owners (Intertanko)
Using statistics compiled by International Tanker Owners Pollution Federation Ltd. (ITOPF), Intertanko said that an average of 24 spills in excess of 700 tonnes occurred every year in the 1970s. In the 1980s, ITOPF-compiled statistics indicate that an average of 8.9 spills of more than 700 tonnes occurred each year during that period. And of the 1990s, Intertanko said, "Notwithstanding the two heavy fuel oil spills from Erika and Volgoneft 248 during the last few days of 1999, the past decade has been one of further steady improvements in the accidental tanker spill record."
The association attributes the decline in spill numbers and volumes chiefly to stepped-up safety efforts by industry itself as well as by various governments.
Bunker spill woes
Medium-sized spills from tankers have also declined, said Intertanko.
The association reported that data compiled by Oil Spill Intelligence Report (OSIR), Boston, show that about 12,050 tonnes of oil-involving spills of more than 34 tonnes-was spilled from tankers during 1998. OSIR said that this was the lowest recorded level for this category since 1968, the year it began gathering spill data.
"As the oil lost from tankers declines," Intertanko explained, "the relative significance of bunker spills from other types of ships is increasing. Of the total number of oil spills attended by ITOPF experts over the past 15 years, 28% have been incidents involving the loss of bunker fuel from ships other than tankers.
"As experience has shown, spills of heavy marine fuel oil, although usually smaller in volume than tanker cargo spills, can cause clean-up problems as well as damage to coastal resources," said Intertanko.
Using data from an ITOPF-maintained database of accidental oil spills in excess of 7 tonnes from tankers, combination carriers, and barges since 1974, Intertanko notes two trends of the spills' causes over two consecutive 6-year periods, namely 1987-92 and 1993-98:
- During the second time period, the number of spills due to hull failure showed a 51% decrease from the level for the first time period.
- Comparing the same respective periods of time, the number of oil spills resulting from groundings increased by 37%.
Reasons behind the reduction of spills due to structural failure, says Intertanko, could include the now relatively commonplace practice of scrapping older tankers. Also, the institution of more-thorough ship inspection programs has helped fuel this reduction.
Intertanko has a more difficult time explaining the increased number of groundings but says that ITOPF notes that factors could include deficiencies in passage planning and pilotage. Also, difficulties with the correct measurement of water depths also could play a part.
