8 Ways Cruise Ships Can Cause Marine Pollution

No road travelled is without problems. At sea, when talking about marine transport, there are no clear-cut roads, but issues in the form of pollution exist and persist, threatening our marine environment badly.

The shipping industry that fulfils more than 90 per cent of trade across the world with the help of around 90,000 marine vessels contributes heavily to global pollution and climate change.

The studies indicate that the shipping industry is responsible for large quantities of pollutants being omitted, including over three per cent of global carbon dioxide emissions, apart from deadly emissions of nitrogen oxide and sulfur oxides. Being one of the world’s most polluting sectors, the increase in marine transport in huge magnitudes these days also increase ship pollution substantially. Hence, the International Maritime Organization, a branch of the United Nations, has established regulations to check the shipping industry’s emissions.

Related Read: How Are Cruise Ships Powered?

Within the shipping industry, the cruise lines make no difference. Though representing a small fraction of the industry, cruise liners, as much as the entertainment they provide, are also a source of significant pollution in the oceanic and marine areas like commercial vessels. A luxury cruise ship releases ten times more carbon emissions than all of Europe’s cars.

A 3000-capacity cruise ship generates 150,000 gallons of sewage and graywater, enough to fill 10 swimming pools. Many other hazardous wastes such as oily bilge water and bio-waste containing viruses are generated on a cruise trip.

In 2019, Carnival Cruise Lines was fined 60 million US dollars for obstructing justice and illegally dumping vast quantities of oil, plastics and garbage into the sea.

In 2018, the cruise industry offered service to more than 26 million customers. It is expected the industry will continue to grow in the coming years. Environmental groups state that the passenger’s carbon footprint triples when one opts for a cruise journey as these ‘floating cities’ produce around 15 gallons of hazardous chemical waste every single day.

Though maritime environmental protection agencies and marine organisations are working to resolve issues, a lot still needs to be done.

cruise ship

Here are the significant ways cruise ships threaten the marine environment and contribute to global pollution.

Ballast Water Pollution

Cruise ships, like other big vessels, use a huge amount of ballast water to stabilise the boat while travelling. As these vessels travel longer, the Ballast water is often filled from one region and discharged in another whenever required. The amount of ballast water released typically is around 1,000 metric tons. This discharge of the ballast water from the cruise ships is a significant cause of cruise pollution.

Since the ballast water contains microbes and micro-organisms in addition to vegetation and other sea animals, the pollution is mainly caused by the local species and marine life. One example of such ecological damage would be the massive swell of jellyfish in the Black Sea.

Related reading:

How ballast water treatment system works?

Air Pollution

As we are all aware, poor air quality is one of the major global health hazards as, according to the World Health Organisation, 4.2 million people die due to air pollution. Just as vehicle exhaust tanks emit waste fumes and toxic air, cruise ships’ engines also emit such unwanted air.

Related reading:

What are NOx emissions from ships?

What are SOx emissions from ships?

The scope of the gases emitted from the vehicular emissions on the road and the cruise ship emissions on the sea differs hugely, leading to the pollution of immense proportions in the marine areas. Similarly, recent research also found that the air on the aft areas of cruise ships, particulate matter pollution in detail, is as polluted as the air in significant cities, such as Beijing.

Related reading:

10 Technologies for controlling NOx and SOx emissions from Ships?

Noise pollution

The noise the passing ships produce badly affects the environment as it disturbs the marine ecosystem. Unlike other ships, Cruise ships contribute heavily to marine noise pollution as the windows of noise pollution are high in cruise ships.

In addition to the noise pollution from the ship’s machinery, cruise ships produce more noise thanks to the entertainment activities on board. These noises disturb the marine animals and mammals, including killer whales and dolphins, whose sensitive hearing gets harmed and debilitated, often leading to their unwanted death and an overall loss to the ecosystem.

Grey Water Pollution

Unlike other vessels, cruise ships dump more wastewater offshore (after passing through a treatment plant), mainly Grey water from sinks, laundries, showers and galleys abroad the vessel. Thus, even the most regular activity onboard the cruise ship, such as cleaning utensils and doing the laundry, causes cruise ship pollution.

Classified under the head of the greywater, this water accumulation contains not just harmful chemicals but sometimes even metals and minerals. The potency of greywater harming the marine environment is greater because of its high concentration in oceanic waters. Studies show that a large cruise ship releases around one million gallons of grey water during a single week’s voyage.

Blackwater/ Sewage Pollution

What happens when someone flushes the loo on a cruise ship? The answer is straightforward. The ship dumps human waste into our oceans (after passing through sewage treatment plants). And, we have larger cruise ships that can accommodate up to 6680 passengers and 2200 crew members.  Yes, the next colossal cruise pollution cause is sewage.

Classified as Blackwater, cruise ships deposit around 210,000 gallons of human sewage into the ocean during a week’s voyage. Sewage includes waste from the toilets and the health facilities on the cruise ship. Such wastewater is rich in bacteria and algae, adversely affecting the oceanic life-forms and the entire marine ecosystem.

Chemical Pollution

The entry of chemicals from the cruise ships to the oceans through the grey water or the black water channels is another threat the cruise ships make to the marine ecosystem.

Cruise ships emit toxic chemicals from batteries, dry cleaning and industrial products, chemicals for daily operations, and several other substances past their expiry, polluting the waters the ships travel. Environmentalists argue that these chemicals pose a huge threat to the lives of marine creatures and life forms.

Oil Pollution/ Bilge Oil Pollution

Oil pollution from the shipping industry is the main reason for the increased marine pollution. Cruise ships, huge compared to other vessels, end up burning more heavy fuel oil, one of the dirtiest fossil fuels on the market. This oil contains dangerous levels of sulfur and heavy metals etc.

It is estimated that cruise ships use, on average, 150 tons of heavy fuel oil every day. With the bilge oil mixing with oceanic water, the use of this oil causes marine pollution. Faulty engine systems and improper repair work are two areas where oil could leak and mix with the oceanic water. Collisions and accidents also act as a reason for such oil pollution.

Related Reading10 methods for oil spill cleanup at sea

Solid Waste Pollution

It is estimated that cruise ships contribute 24% to the total solid waste generated by maritime traffic across the world as one of such luxury vessels can produce seven tons of garbage and solid waste in a single day.

A cruise ship’s solid waste materials include paper, cardboard, aluminium, etc. Such materials form unwanted debris on our oceans’ surface, posing large-scale threats to marine plants and creatures.

Related ReadingTips for reducing and recycling waste at sea

Destruction of Coral Reefs

Cruise ships are a severe threat to coral reefs and their related organisms. As tourist vessels, the entry and anchoring of cruise ships on disturbed and undisturbed areas of coral reefs across the world have resulted in several incidents that involve the destruction of these natural wonders.

These accidents also affect these coral reefs’ rich ecological integrity and biodiversity.  In 2017, the British cruise ship MS Caledonian crashed onto the pristine coral reefs of Indonesia, destroying 17,222 square feet of coral reefs and causing more than $19 million in irreparable damage.

Physical damages to marine life

In addition to the air and water pollution these cruise ships cause, Whales and Dolphins are also victims of the increasing traffic of these ships. These massive ships are responsible for injuring, often killing, marine lives, particularly fin whales, killer whales and humpback whales.

Considering the risks and the damages caused to the marine environment, countries have laid proper resolutions to protect the oceanic surroundings.

Slowly and steadily, even cruise shipping conglomerates have begun to understand the importance and necessity of preserving the marine ecosystem. For the time being, a better cruise shipping experience with the necessary caution and care for the aquatic life remains a dream to be realized and attained.  Hopefully, it will be in the days and years to come.

Frequently Asked Questions

1. How much pollution is caused by a cruise ship?

As per the Bureau of Transportation Statistics, a 3000-passenger cruise ship generates one million gallons of gray water, 210,000 gallons of sewage and 25,000 gallons of oily bilge water in just 7 days.

2. How are cruise ships harmful to our environment?

Cruise ships utilise enormous amounts of fuel. They also generate vast quantities of solid and liquid waste, often dumped into oceans and seas, affecting marine flora and fauna. The carbon emissions released into the atmosphere pollute the air.

3. How toxic are cruise ships?

Some waste is incinerated onboard, so cruise ships generate ash and smoke containing toxic substances. Due to this waste treatment, toxic materials like polychorate biphenyls or PCBs, dioxins, and furans have been found in fuel from burning fuel.

4. How much emissions does a cruise ship generate?

A medium-sized cruise ship uses about 150 tonnes of fuel daily, emitting as much particulate as one million cars. The quantity is far greater for large-sized cruise ships.

5. Are there any eco-friendly cruise ships?

With technological progress and innovation, there have been efforts to curtail the emissions of the shipping industry. Cruise ships are usually associated with waste generation and pollution. However, some eco-friendly ones are being built. One such is the MSC Europa which will run on LNG.

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Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.
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About Author

Zahra is an alumna of Miranda House, University of Delhi. She is an avid writer, possessing immaculate research and editing skills. Author of several academic papers, she has also worked as a freelance writer, producing many technical, creative and marketing pieces. A true aesthete at heart, she loves books a little more than anything else.


  1. Friends of mine who have taken holidays on cruiseships have said they have seen garbage loads tipped overboard at night, weighted down so that ‘no-one knows’. Plastics, non-recyclables, poisonous materials, food etc go to the bottom of the ocean and gradually rise to the surface once the ships have long passed. She tells me she has seen this happening on several occasions.
    If the ships have to carry their rubbish to port and pay fees to dispose of it, then of course they’ll do this. There needs to be free rubbish disposal at port, built into the harbour fees, and some big-time prosecutions for those who are caught.
    Or just don’t bother, and kill the oceans……

  2. I have never been on a cruise ship but, I’m sure that there would be loads of waste, oil spills and pollution in the water/ocean/sea. it is very sad to see all the rubbish in the water and that the mammals/se animals have to swim in it and also die from it being caught around their neck, or from them accidentally eating it.

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