Figure 2-2 shows the amount of crude oil transported by sea annually for the past few years, with projections for future years. The past data agrees with other estimates of oil transported (). At the present time, about 1.5 billion metric tons of oil are transported by sea each year. As shown in Table 1-1, approximately 250,000 tons of oil per year are spilled due to tanker casualties. It is likely that this is an underestimate, because some spills due to tanker casualties far from land are not reported. Even so, pollution due to tanker casualties is frequently in the public eye because of the large amounts of oil that are sometimes spilled. Porricelli () provides a comprehensive analysis of tanker casualties for 1969 and 1970 covering 1,416 of them, including 269 that caused pollution. Figure 2-3 shows a breakdown of the polluting incidents in terms of the type of casualties. Two hundred nine of the 269 polluting incidents occurred in harbors, harbor entrances, coastal zones, and at piers. Except for a few casualties at unknown locations, most of the remaining sixty casualties occurred

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