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SOURCES, FATES, AND EFFECTS OF SHIPBORNE GARBAGE 53 up on beaches 14. Public health officials believe the risk of contracting blood- home diseases from exposure to medical wastes found on beaches is low, but the EPA has asserted that "inadvertent exposure is publicly unacceptable and should be prevented" (U.S. Environmental Protection Agency, 1989). A similar threat is posed by debris items containing hazardous waste. At Padre Island National Seashore in Texas, hazardous wastes such as acids have been found in bottles and other containers washed up on beaches. Although no serious incidents have occurred, National Park Service employees consider themselves lucky (John Miller, National Park Service, personal communication to member of the Committee on Shipborne Wastes, November 1, 1993). Marine debris also has been known to disable divers and vessels, with potentially life-threatening results. Divers sometimes become entangled in pieces of monofilament fishing line that have snagged on reefs or other underwater structures. Fishing has been banned from some oil platforms in the North Sea because of related problems experienced by divers (Borne, 1990). In addition, large debris items have caused boat collisions, while smaller items have been reported to wrap around propellers or clog cooling water intakes, causing engine failure. These problems have not been studied in detail. To improve understanding of the magnitude of the problem, incidents involving debris could be coded and recorded in the Coast Guard's accident database; insurance agencies might be another source of information. Ecological Effects Little scientific information is available concerning how debris may affect marine invertebrate species, plant life, or marine habitats in general, aside from observations that debris damages coral reefs, is ingested by squid (Array, 1983; Machida, 1983), and may offer a new habitat niche for encrusting marine species (Winston, 1982). Concern has been expressed about the biological uptake of minute suspended particles possibly contaminated with heavy metals or other toxic substances. Such particles may result from the degradation of large plastic items, cosmetic additives (minute plastics are added as abrasives), and aeroblasting (use of plastic "sand" to remove paint from ship hulls) (Gregory, 1994). Also, concern has been expressed that floating plastics may facilitate the 14 During the summers of 1987 and 1988, medical wastes appearing on beaches in the Northeast raised concerns over the potential threat of exposure to diseases such as Acquired Immune Deficiency Syndrome (AIDS). In fact, several syringes, needles, and blood vials that were found tested positive for the AIDS antibodies and the hepatitis B virus, and there were reports of persons being punctured by these items. But the majority of the items reported were syringes generated by land-based sources, not ships (ICF, 1989).
