Figures compiled by International Tanker Owners Pollution Federation Ltd., London, dispel the commonly held belief that tanker groundings are more significant than collisions in terms of oil pollution.
During the past 21 years, the number of spills and volumes released after collisions and groundings were almost the same, said Catherine Grey, the federation's database manager.
The federation said efforts to design environmentally safer tankers, such as those with double hulls, to minimize oil spills following accidents should take full account of the causes of major spills.
"Analysis also reveals that a considerable number of major oil spills in recent years were due primarily to hull failure or fires and explosions, which suggests that no single tanker design is likely to offer a panacea," Grey said.
An analysis of spills of more than 50 bbl during 1970-90 shows that of 531 incidents, 264 were caused by collisions and 267 by groundings. The total volume of oil spilled in collisions was 6.9 million bbl, or 44% of the total, with 8.7 million bbl spilled in groundings.
The federation said the number of major oil spills by tankers has fallen sharply since the end of the 1970s. In 1970-79 there were 252 spills of more than 5,000 bbl, compared with 91 spills in this category in the 10 years ending in 1989.
Ian White, federation managing director, said the trend confirmed the findings of a 1990 United Nations report on the health of the marine environment. The U.N. expressed more concern about the harm from coastal development, pollution from onshore industries, and river discharge of oil, chemicals, and other contaminants rather than the release of oil from shipping operations.
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