More than 53,000 commercial vessels—tankers, bulk carriers, container ships, barges, and passenger ships—travel the oceans and other waters of the world, carrying cargo and passengers for commerce, transport, and recreation. Their activities are regulated and scrutinized in a number of respects by international protocols and U.S. domestic laws, including those designed to protect against discharges of pollutants that could harm marine resources, other parts of the ambient environment, and human health. However, there are overlaps of some requirements, gaps in other areas, geographic differences in jurisdiction based on differing definitions, and questions about the adequacy of enforcement. Public attention to the environmental impacts of the maritime industry has been especially focused on the cruise industry, in part because its ships are highly visible and in part because of the industry's desire to promote a positive image. It represents a relatively small fraction of the entire shipping industry worldwide. As of October 2010, passenger ships (which include cruise ships and ferries) composed about 13% of the world shipping fleet. The cruise industry is a significant and growing contributor to the U.S. economy, providing $40 billion in total benefits in 2009 and generating more than 357,000 U.S. jobs, but also making the environmental impacts of its activities an issue to many. Since 1990, the average annual growth rate in the number of cruise passengers worldwide has been 7.4%, and in 2010, cruises hosted an estimated 14.3 million passengers. The worldwide cruise ship fleet consists of more than 230 ships, and the majority are foreign-flagged, with Liberia and Panama being the most popular flag countries. Foreign-flag cruise vessels owned by six companies account for nearly 95% of passenger ships operating in U.S. waters. Each year, the industry adds new ships to the total fleet, vessels that are bigger, more elaborate and luxurious, and that carry larger numbers of passengers and crew. Over the past two decades, the average ship size has been increasing at the rate of roughly 90 feet every five years. The average ship entering the market from 2008 to 2011 will be more than 1,050 feet long and will weigh more than 130,000 tons. To the cruise ship industry, a key issue is demonstrating to the public that cruising is safe and healthy for passengers and the tourist communities that are visited by their ships. Cruise ships carrying several thousand passengers and crew have been compared to "floating cities," in part because the volume of wastes produced and requiring disposal is greater than that of many small cities on land. During a typical one-week voyage, a large cruise ship (with 3,000 passengers and crew) is estimated to generate 210,000 gallons of sewage; 1 million gallons of graywater (wastewater from sinks, showers, and laundries); more than 130 gallons of hazardous wastes; 8 tons of solid waste; and 25,000 gallons of oily bilge water. Those wastes, if not properly treated and disposed of, can pose risks to human health, welfare, and the environment. Environmental advocates have raised concerns about the adequacy of existing laws for managing these wastes, and suggest that enforcement of existing laws is weak. A 2000 General Accounting Office (GAO) report focused attention on problems of cruise vessel compliance with environmental requirements. GAO found that between 1993 and 1998, foreign-flag cruise ships were involved in 87 confirmed illegal discharge cases in U.S. waters. A few of the cases included multiple illegal discharge incidents occurring over the six-year period. GAO reviewed three major waste streams (solids, hazardous chemicals, and oily bilge water) and concluded that 83% of the cases involved discharges of oil or oil-based products, the volumes of which ranged from a few drops to hundreds of gallons. The balance of the cases involved discharges of plastic or garbage. GAO judged that 72% of the illegal discharges were accidental, 15% were intentional, and 13% could not be determined. The 87 cruise ship cases represented 4% of the 2,400 illegal discharge cases by foreign-flag ships (including tankers, cargo ships and other commercial vessels, as well as cruise ships) confirmed during the six years studied by GAO. Although cruise ships operating in U.S. waters have been involved in a relatively small number of pollution cases, GAO said, several have been widely publicized and have led to criminal prosecutions and multimillion-dollar fines. In 2000, a coalition of 53 environmental advocacy groups petitioned the Environmental Protection Agency (EPA) to take regulatory action to address pollution by cruise ships. The petition called for an investigation of wastewater, oil, and solid waste discharges from cruise ships. In response, EPA agreed to study cruise ship discharges and waste management approaches. As part of that effort, in 2000 EPA issued a background document with preliminary information and recommendations for further assessment through data collection and public information hearings. Subsequently, in December 2008, the agency released a cruise ship discharge assessment report as part of its response to the petition. This report summarized information on cruise ship waste streams and findings of recent data collection activities (especially from cruise ships operating in Alaskan waters). It also identified options to address ship discharges. This report presents information on issues related to cruise ship pollution. It begins by describing the several types of waste streams and contaminants that cruise ships may generate and release. It identifies the complex body of international and domestic laws that address pollution from cruise ships, as there is no single law in this area. Some wastes are covered by international standards, some are subject to U.S. law, and for some there are gaps in law, regulation, or possibly both. The report then describes federal and state legislative activity concerning cruise ships in Alaskan waters and activities in a few other states. Cruise ship companies have taken a number of steps to prevent illegal waste discharges and have adopted waste management plans and practices to improve their environmental operations. Environmental critics acknowledge these initiatives, even as they have petitioned the federal government to strengthen existing regulation of cruise ship wastes. Environmental groups endorsed legislation in the 109 th and 110 th Congresses (the Clean Cruise Ship Act) that would require stricter standards to control wastewater and other discharges from cruise ships. Similar legislation was introduced in the 111 th Congress (the Clean Cruise Ship Act, H.R. 3888 and S. 1820 ), but no legislative action occurred. Cruise ships generate a number of waste streams that can result in discharges to the marine environment, including sewage, graywater, hazardous wastes, oily bilge water, ballast water, and solid waste. They also emit air pollutants to the air and water. These wastes, if not properly treated and disposed of, can be a significant source of pathogens, nutrients, and toxic substances with the potential to threaten human health and damage aquatic life. It is important, however, to keep these discharges in some perspective, because cruise ships represent a small—although highly visible—portion of the entire international shipping industry, and the waste streams described here are not unique to cruise ships. However, particular types of wastes, such as sewage, graywater, and solid waste, may be of greater concern for cruise ships relative to other seagoing vessels, because of the large numbers of passengers and crew that cruise ships carry and the large volumes of wastes that they produce. Further, because cruise ships tend to concentrate their activities in specific coastal areas and visit the same ports repeatedly (especially Florida, California, New York, Galveston, Seattle, and the waters of Alaska), their cumulative impact on a local scale could be significant, as can impacts of individual large-volume releases (either accidental or intentional). Blackwater is sewage, wastewater from toilets and medical facilities, which can contain harmful bacteria, pathogens, diseases, viruses, intestinal parasites, and harmful nutrients. Discharges of untreated or inadequately treated sewage can cause bacterial and viral contamination of fisheries and shellfish beds, producing risks to public health. Nutrients in sewage, such as nitrogen and phosphorous, promote excessive algal growth, which consumes oxygen in the water and can lead to fish kills and destruction of other aquatic life. Cruise ships generate, on average, 8.4 gallons/day/person of sewage, and a large cruise ship (3,000 passengers and crew) can generate an estimated 15,000 to 30,000 gallons per day of sewage. Graywater is wastewater from the sinks, showers, galleys, laundry, and cleaning activities aboard a ship. It can contain a variety of pollutant substances, including fecal coliform bacteria, detergents, oil and grease, metals, organics, petroleum hydrocarbons, nutrients, food waste, and medical and dental waste. Sampling done by EPA and the state of Alaska found that untreated graywater from cruise ships can contain pollutants at variable strengths, and that it can contain levels of fecal coliform bacteria one to three times greater than is typically found in untreated domestic wastewater. Cruise ships generate, on average, 67 gallons/day/person of graywater (or, approximately 200,000 gallons per day for a 3,000-person cruise ship); by comparison, residential graywater generation is estimated to be 51 gallons/person/day. Graywater has potential to cause adverse environmental effects because of concentrations of nutrients and other oxygen-demanding materials, in particular. Graywater is typically the largest source of liquid waste generated by cruise ships (90%-95% of the total). Solid waste generated on a ship includes glass, paper, cardboard, aluminum and steel cans, and plastics. It can be either non-hazardous or hazardous in nature. Solid waste that enters the ocean may become marine debris, and it can then pose a threat to marine organisms, humans, coastal communities, and industries that utilize marine waters. Cruise ships typically manage solid waste by a combination of source reduction, waste minimization, and recycling.