Ship pollution
Ship pollution is the pollution of air and water by shipping. It is a problem that has been accelerating as trade has become increasingly globalized, posing an increasing threat to the worlds oceans and waterways as globalization continues. It is expected that, ...shipping traffic to and from the USA is projected to double by 2020." Because of increased traffic in ocean ports, pollution from ships also directly affects coastal areas. The pollution produced affects biodiversity, climate, food, and human health. However, the degree to which humans are polluting and how it affects the world is highly debated and has been a hot international topic for the past 30 years.

# Sources and causes
Ships can pollute the waterways and oceans in many ways. For instance, spills from oil tankers and chemical tankers, and ejection of sulfur dioxide, nitrogen dioxide and carbon dioxide gases into the atmosphere from exhaust fumes. Discharge of cargo residues from bulk carriers can pollute ports, waterways and oceans. Ships create noise pollution that disturbs natural wildlife, and water from ballast tanks can spread harmful algae and other invasive species. In many instances vessels due to a variety of reasons intentionally discharge illegal wastes despite foreign and domestic regulation prohibiting such actions.
This section describes how ships pollute the ocean; for the Protocol of 1978 Relating to the International Convention for the Prevention of Pollution From Ships of 1973, sometimes abbreviated as Ship Pollution, refer to MARPOL 73/78.

## Ballast water
When a larger vessel, such as a container ship or an oil tanker unloads cargo, sea-water is pumped into compartments in the hull. Similarly, when a larger vessel is being loaded it discharges sea-water from these compartments. The sea water is meant to help stabilize and balance a ship. Ballast discharges from ships are responsible for tar balls in the open oceans and seas, and can cause problems navigating tanker routes. Nevertheless, the discharge of ballast water only accounts for a small percentage of oil pollution in the marine environment.
Ships are also responsible for transporting harmful organisms in their ballast water. Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless jellyfish. Mnemiopsis leidyi, a species of comb jellyfish that inhabits estuaries from the United States to the Valdes peninsula in Argentina along the Atlantic coast, has caused notable damage in the Black Sea. It was first introduced in 1982, and thought to have been transported to the Black Sea in a ships ballast water. The population of the jellyfish shot up exponentially and, by 1988, it was wreaking havoc upon the local fishing industry. The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993; sprat from 24,600 tons in 1984 to 12,000 tons in 1993; horse mackerel from 4,000 tons in 1984 to zero in 1993. Now that the jellyfish have exhausted the zooplankton, including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the ecosystem. Recently the jellyfish have been discovered in the Caspian Sea. Invasive species can take over once occupied areas, facilitate the spread of new diseases, introduce new genetic material, alter landscapes and jeopardize the ability of native species to obtain food. On land and in the sea, invasive species are responsible for about 137 billion dollars in lost revenue and management costs in the U.S. each year.
In addition to introducing non native species into new environments, ballast and bilge discharge from ships can spread human pathogens and other harmful diseases and toxins potentially causing health issues for humans and marine life alike. Discharges into coastal waters along with other sources of marine pollution have the potential to be toxic to marine plants, animals, and microorganisms causing alterations such as changes in growth, disruption of hormone cycles, birth defects, suppression of the immune system, and disorders resulting in cancer, tumors, and genetic abnormalities or even death. They may also have the opposite affect upon some marine life stimulating growth and providing a source of food. Sources of seafood can become contaminated and unhealthy for consumption. Not surprisingly, cholera outbreaks have been attributed to ship operations. Current research indicates that the bacterium responsible for causing cholera, Vibrio cholerae can spread through attachment to marine organisms in ship ballast water. Shellfish and drinking water can then be contaminated when the ship discharges its ballast water.

## Exhaust emissions
Exhaust emissions from ships are considered to be a significant source of air pollution. Seagoing vessels are responsible for an estimated 14 percent of emissions of nitrogen from fossil fuels and 16 percent of the emissions of sulfur from petroleum uses into the atmosphere. In Europe ships make up a large percentage of the sulfur introduced to the air, ...as much sulfur as all the cars, lorries and factories in Europe put together. By 2010, up to 40% of air pollution over land could come from ships. Sulfur in the air creates acid rain which damages crops and buildings. When inhaled the sulfur is known to cause respiratory problems and even increase the risk of a heart attack. According to Irene Blooming, a spokeswoman for the European environmental coalition Seas at Risk, the fuel used in oil tankers and container ships is high in sulfur and cheaper to buy compared to the fuel used for domestic land use. A ship lets out around 50 times more sulfur than a lorry per metric tonne of cargo carried. Cities in the U.S. like Long Beach, Los Angeles, Houston, Galveston, and Pittsburgh see some of the heaviest shipping traffic in the nation and have left local officials desperately trying to clean up the air. Increasing trade between the U.S. and China is helping to increase the number of vessels navigating the Pacific and exacerbating many of the environmental problems. To maintain the level of growth China is currently experiencing, large amounts of grain are being shipped to China by the boat load. The number of voyages are expected to continue increasing.

## Oil spills
Most commonly associated with ship pollution are oil spills. While less frequent than the pollution that occurs from daily operations, oil spills have devastating effects. While being toxic to marine life, polycyclic aromatic hydrocarbons (PAHs), the components in crude oil, are very difficult to clean up, and last for years in the sediment and marine environment. Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles. One of the more widely known spills was the Exxon Valdez incident in Alaska. The ship ran aground and dumped a massive amount of oil into the ocean in March of 1989. Despite efforts of scientists, managers, and volunteers over 400,000 seabirds, about 1,000 sea otters, and immense numbers of fish were killed.

## Cruise ships
Along with global trade the tourism industry has also seen growth in recent years. The cruise ship industry has seen 8 percent annual growth and continues to increase demand. With some cruise ships holding upwards of 5000 people, passengers and crew combined, these ships are likened to floating cities. In one week, a typical cruise ship generates 210,000 gallons of black water (sewage), 1,000,000 gallons of gray water (shower, sink, dishwashing water), 37,000 gallons of oily bilge water, more than eight tons of solid waste, millions of gallons of ballast water containing potential invasive species, and toxic wastes from dry cleaning and photo processing laboratories. This is also compounded with fuel emissions to have detrimental effects on the environment. From 1993 to 1998, cruise ships were involved in 104 confirmed cases of illegal discharge of oil, garbage, and hazardous wastes. One of the worst reported cases was by Royal Caribbean Cruises Ltd. Over several years, while in U.S. waters, they had been routinely and deliberately dumping waste oil, photo processing, dry cleaning, and print shop chemicals into coastal waters. Their ships were even fitted with concealed piping that would bypass pollution treatment equipment.

# Regulation
Some of the major international efforts in the form of treaties are the Marine Pollution Treaty, Honolulu, which deals with regulating marine pollution from ships, and the UN Convention on Law of the Sea, which deals with marine species and pollution. While plenty of local and international regulations have been introduced throughout maritime history, much of the current regulations are considered inadequate. In general, the treaties tend to emphasize the technical features of safety and pollution control measures without going to the root causes of sub-standard shipping, the absence of incentives for compliance and the lack of enforceability of measures. Cruise ships for example are exempt from regulation under the Clean Water Act of 1972 (CWA) point source permitting system that requires compliance with U.S. federal standards through technological requirements. In the Caribbean, many ports lack proper waste disposal facilities, and many ships dump their waste at sea.