whatever volatile components it had and its density approached that of sea- 

 water, the remaining fractions were rapidly dispersed through the water 

 column. A similar observation was made after the wreck of the Atvow in 

 Chedabucto Bay, Nova Scotia, with particles of oil found in the water column 

 at substantial distances from the wreck. 



Using the worldwide accident data published by Lloyds of London, Keith 

 and Porricelli (1973) published an analysis of 1,416 tanker accidents that 

 occurred in 1969 and 1970. Of these accidents, 266 reported measurable out- 

 flows of oil, and an analysis of these documented cases presents some picture 

 of the causes of accident-related oil pollution. Keith and Porricelli found 

 that this accident-related input of oil to the sea during 1969 and 1970 was 

 somewhere between 427,000 and 447,000 metric tons, or about 218,000 metric 

 tons (1,526,000 barrels) per year. This compares well with the NAS Workshop 

 estimate of 300, 000 metric tons per year which includes pollution from non- 

 tanker accidents (100,000 metric tons per year) as well as tanker accidents 

 (200,000 metric tons per year). Table 1-1 summarizes the magnitude of oil 

 pollution for each class of accident during the 2-year period. 



Table 1-1. 



Vessel-related oil pollution worldwide by accident type, 

 1969-70 (from Keith and Porricelli, 1973) 



Type of casualty 



Structural failure 



Grounding 



Collision (ship-to-ship) 



Explosion 



Breakdown* 



Ramming (ship-to-object) 



Fire 



Other 



Totals 



*Mechanical breakdown that led to eventual grounding and breakup of the 

 tanker . 



