dards have contributed to the decline in oil spills and operational discharges and should be continued and further strengthened where appropriate.

Worldwide, operational discharges of cargo oil from tankers have declined dramatically over the last two decades, principally due to regulatory changes mandating segregated ballast tankers and double-hull tankers. The current best estimate is only 5 percent of the best estimate in the NRC 1985 report. Estimated operational discharges of bilge oil and sludge from vessels remain very significant inputs. Over 99 percent of the volume of operational discharges are related to estimates of non-compliance, as existing regulations restrict operational discharge of oil or limit them to not more than 15 ppm. The extent of non-compliance is difficult to assess, and therefore these estimates have a high level of uncertainty. Federal agencies, especially the U.S. Coast Guard, should work with the transportation industry to undertake a systematic assessment of the extent of non-compliance. If estimates of non-compliance assumed in this report are essentially correct, more rigorous monitoring and enforcement policies should be developed and implemented.

Gasoline and lube oil inputs from older, inefficient, two-stroke recreational vessels are a large marine source of petroleum hydrocarbons. These discharges are primarily gasoline and lube oil, which have high evaporation rates and low PAH

PHOTO 14 The use of recreational marine vessels, including personal watercraft (e.g., jet skis), have increased dramatically in the last few decades as leisure time and access to coastal waters has increased. Unfortunately, the older, less efficient two-stroke engines powering many of these craft can contribute significantly to the total load of petroleum entering the marine environments where they are operated. (Photo courtesy of Christine Henderson.)

levels. These inputs frequently occur near ecologically sensitive areas (estuaries, mangroves) during vulnerable stages in the life cycle of organisms. Federal agencies, especially the EPA, should continue efforts to regulate and encourage the phase-out of inefficient two-stroke engines, and a coordinated enforcement policy should be established.

Large quantities of VOC are discharged into the atmosphere from tank vessels and oil and gas operations. The VOC are mostly comprised of methane and ethane, which tend to oxidize rather than deposit into the oceans. These emissions may represent a “greenhouse gas” concern, but the atmospheric deposition of these hydrocarbons into North American waters is less than 0.5 percent of all inputs, and inputs of VOC into the oceans worldwide are less than 4 percent of the estimated total inputs. The U.S. Coast Guard should work with the International Maritime Organization to assess the overall impact of VOC on air quality from tank vessels, and establish design and/or operational standards on VOC emissions where appropriate.

On the basis of controlled data, aircraft inputs from deliberate dumping to jet fuel in the sea appear to be locally significant. Federal agencies, especially the FAA, should work with industry to determine more rigorously the amounts of fuel dumping by aircraft and to formulate appropriate actions to limit this potential threat to the marine environment.

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