worldwide effort, but in the United States the liability regime and the resulting financial risk involved in using substandard vessels have led to a redoubling of efforts to improve marine safety.
U.S. initiatives have, to date, been directed at the tanker industry. Passenger and dry cargo ships, however, are at equal risk, and carry significant quantities of fuel oil and, at times, potentially polluting hazardous cargoes. All vessels carry crew, and the protection of life at sea is of primary importance. Vessel construction and operational procedures in these domains have yet to undergo the type of rigorous review that the tanker industry has undergone.
Oil spills from vessels in distress can result in severe economic and environmental damage. Vessels that incur structural damage, are involved in collisions, or are stranded pose a risk of pollution due to loss of cargo or fuel oil. The discharge of potentially polluting cargoes such as oil, chemicals, and even otherwise nonhazardous materials, such as edible oils and other nutrients, can have adverse effects on the marine environment. These effects may vary widely from incident to incident. The nature of the substance spilled, the location of the accident, and weather conditions at the time are among the most important factors in determining the seriousness of the event (Engelhardt, 1994).
Among potentially polluting cargoes lost in shipping accidents, oil and its products are by far the most common. Over the past 20 years, extensive research has been directed at understanding the effects of oil spills and factors that govern the environmental consequences of a given incident (NRC, 1985). Certain refined products, such as diesel oil and gasoline, generally are more toxic than crude oils, on a volume-for-volume basis, in that they contain a higher concentration of lighter aromatic hydrocarbons. The aromatic components of oil pose the greatest potential of acute toxicity to both plants and animals and cause a variety of sublethal effects, including impairment of reproduction, physiological stress, and reduced growth rates. However, light products generally evaporate, dissolve, and otherwise disperse much more readily in the environment than do heavier oils, which have greater smothering potential and are more difficult to clean up.
A wide variety of chemical products other than oil are spilled every year in U.S. waters. Sulfuric acid and ammonia generally top the list because they are shipped in high volumes. Spills of these substances have been associated with major fish kills in localized areas. Less common, but more toxic and more persistent substances have caused prolonged restrictions on fishing and even lengthy closures of important waterways to ship traffic. Occasionally, spills of seemingly innocuous products, such as fertilizers, have upset the delicate nutrient balance in enclosed estuaries and bays, resulting in severe short-term damage.
Historically, spill response has not been very effective. Only 10 to 15 percent of oil typically is recovered following a spill (Office of Technology Assessment [OTA], 1990). Hazardous chemicals pose a particularly difficult challenge. The Chemical Manufacturers Association (CMA) recently concluded that the capability to respond to a chemical spill of any significant magnitude in the sea does not exist anywhere in the United States (CMA, 1992).
Salvage operations help prevent pollution by providing assistance to a damaged or stressed vessel. For example, salvors may be able to transfer cargo or fuel from a damaged vessel to a sound one (a procedure known as lightering), thereby reducing the threat of a spill from an unstable vessel, tow a damaged vessel to a safe harbor for repairs, or perhaps repair on site. The Exxon Valdez accident3 is a case in point.
All instances of salvage in U.S. waters that were reported to the committee are listed in Appendix E.