For example, exports to the U.S. from the Middle East grew by nearly a factor of three to 346,900 tonnes/day in 1999. For the world as a whole, the growth in exports from the Middle East increased by a factor of two (API, 2001).

Databases. Since the NRC 1985 report, significant new databases that contain more accurate information have been generated by public, governmental, and private agencies. These databases have become much more accessible with the advent of the worldwide web. In the present report, data bases existed that allowed a) dividing oil and gas operations into four categories (platforms, outer continental shelf (OCS) pipelines, coastal pipelines, and produced waters), b) estimating atmospheric deposition of petroleum hydrocarbons, and c) estimating recreational/small craft inputs. In general, the international databases for spills are neither as comprehensive nor as carefully maintained as those for U.S. and Canadian waters, and therefore the worldwide estimates have a greater uncertainty.

Regulations. Since 1981, a number of regulations intended to reduce petroleum hydrocarbon inputs into the oceans have been implemented. The 1978 Protocol of the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) was implemented in the U.S. in June 1981, and went into effect worldwide in 1983. These regulations mandate segregated ballast tanks (SBT) for new tankers and set limits on the oil content of overboard discharges. The Oil Pollution Act of 1990 (OPA 90; Appendix K) and the 1992 amendments to MARPOL 73/78 mandate double-hull requirements or equivalent protection for all new tankers, and establish phase-out schedules for existing single-hull tankers. Other relevant regulations include restrictions on produced water discharges into coastal waters of the United States, the elimination of oil-based drilling cutting into the North Sea, and limits on the average oil and grease content of produced water discharge. These and other regulatory changes have contributed to a significant reduction in both operational discharges and accidental spills.

Identification of geographic distribution of inputs. In 1985, data did not exist to accurately pinpoint the geographic area of the major sources of input of hydrocarbons to the oceans. Since then, new reporting databases contain the location of major spills, and it is now possible to subdivide the input of hydrocarbons to relatively small geographic zones in North American waters. Although similar databases exist for only a few other worldwide areas, they are still not refined enough to allow specific allocation of inputs by geographic zones.

Increase in urban population. In the fifteen years since the last NRC report, there has been a significant increase in urban population, particularly in the coastal zone. Current trends indicate that by the year 2010, 60 percent of the U.S. population will live along the coast. This is consistent with the worldwide profile in which two-thirds of the urban centers, defined as cities with populations of 2.5 million or more, are near tidal estuaries. This increased population has resulted in a considerable increase in land-based runoff of petroleum hydrocarbons.

Increase in number of two- and four-stroke engines. In 1985, the NRC report Oil in the Sea did not discuss petroleum hydrocarbon inputs from operation of recreational marine vehicles. In 1990, heightened awareness about the large number and design inefficiencies of these engines led the US EPA to begin regulating the “non-road engine” population under the authority of the Clean Air Act. The average hours of use nationwide for two-stroke personal watercraft engines is 77.3 hours per year and for outboard engines is 34.8 hours per year (EPA, in preparation). This increased use of two-stroke engines has proven to be a major contribution to discharge of petroleum hydrocarbons to marine waters, especially in coastal waters from recreational marine vehicles.

In the 1985 NRC report, inputs were categorized into five major sources: Natural, Offshore Production, Transportation, Atmospheric, and Municipal and Industrial. Subcategories were delineated within several of these major input areas (Table 3.1). In the present report, inputs were organized into four major sources, with subcategories within each of the major sources (Table 3-1).

Although the categories are organized slightly differently in the two reports, the major input sources are the same. In

TABLE 3-1 Input Sources in 1985 and Present Report

1985 Report

Present Report

Natural Sources

Marine seeps

Sediment erosion

Offshore production


Tanker operations


Marine terminals

Bilge and fuel oils

Tanker accidents

Non-tanker accidents


Municipal & Industrial wastes

Municipal wastes


Non-refining industrial wastes

Urban runoff

River runoff

Ocean dumping

Natural seeps

Extraction of Petroleum


Atmospheric deposition

Produced waters

Transportation of Petroleum

Pipeline spills

Spills (tank vessels)

Operational discharges (cargo oil)

Coastal facility spills

Atmospheric deposition (tanker VOC)

Consumption of Petroleum

Land-based (river and runoff)

Recreational vessel discharge

Spills (commercial vessels ≥100 GT)

Operational discharges (vessels ≥100 GT)

Operational discharges (vessels <100 GT)

Atmospheric deposition

Aircraft dumping


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