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SOURCES, FATES, AND EFFECTS OF SHIPBORNE GARBAGE 52 These types of studies suggest that the arbitrary Annex V disposal demarcations of 12 and even 25 miles from land may not protect coastal areas fully against pollution from vessel garbage. Initial research in the Gulf of Mexico indicates that floating plastic sheets (used by the offshore oil industry to cover materials in transit) persist and remain a nuisance as long as they remain anywhere in the water (Lecke-Mitchell and Mullin, 1992). ENVIRONMENTAL AND PHYSICAL EFFECTS OF MARINE DEBRIS Marine debris may accumulate on beaches, on the surface waters, and in the benthos. The potential environmental and physical effects13 of this debris, whether from vessel or land-based sources, include. â¢ aesthetic degradation of surface sea waters and beach areas; â¢ physical injuries to humans and life-threatening interference with their activities; â¢ ecological damage caused by the interference of plastics with gas exchange between overlying waters and those in the benthos; â¢ alterations in the composition of ecosystems caused by debris that provides habitats for opportunistic organisms; â¢ entanglements of birds, fish, turtles, and cetaceans in lost or discarded nets, fishing gear, and packing materials; and â¢ ingestion of plastic particles by marine animals. The aesthetic problems are obvious to anyone who has visited a debris- littered beach or observed garbage floating in the sea. Indeed, the aesthetic degradation that is evident when a beach is littered may be more compelling to the public and to policymakers than is any number of numerical analyses of debris levels, animal mortality, or other effects. Yet these other effects are significant. Following is a summary of what is known about the health and ecological effects of marine debris, including vessel garbage. Additional details concerning ecological effects may be found in Appendix F. Human Health Problems Aside from the potential for beach goers to step on or in some other way be injured by pieces of glass, metal, or other sharp objects, the most widely perceived threat has been from the fear of contamination by medical waste washed 13 Marine debris also has economic effects, as noted in Chapter 1 and implied in the forthcoming discussion of ghost fishing. The committee did not examine this aspect of the problem in detail.