International Convention for the Prevention of Pollution from Ships


The International Maritime Organization (IMO) has taken responsibility for pollution issues and has adopted a wide range of measures to prevent and control pollution caused by ships and to mitigate the effects of any damage that may occur because of maritime operations and accidents.  


Participants will:  

  • Identify specific MARPOL Annex regulation criteria  
  • Know where to find MARPOL Annex resources  

International Maritime Organization (IMO):  An agency of the United Nations responsible for the safety of life at sea and the protection of the marine environment. 

International Convention for the Prevention of Pollution from Ships: Covers the prevention of pollution of the marine environment by ships operational or accidental. Universally known as MARPOL


The International Convention for the Prevention of Pollution from Ships, now universally known as MARPOL, is an agreement from the IMO to control and prevent pollution from ships. Its objective is to preserve the marine environment by regulating the handling of oil, garbage, sewage, noxious liquids, harmful substances and air emissions abroad a vessel and to minimize damage from operational or accidental discharge of such substances into water.  

MARPOL applies to 99% of the world’s merchant tonnage and has greatly contributed to a significant decrease in pollution from international shipping. Reductions of pollution generated by ships have been achieved by addressing technical, operational and human element issues.  

Other IMO conventions address anti-fouling systems used on ships, the transfer of alien species by ships’ ballast water and the environmentally sound recycling of ships. New environmental topics arising on the IMO agenda include underwater noise, biofouling and black carbon.  

Dive Deeper

Expand each section to learn more about MARPOL and other IMO conventions. 

Shipboard sources of oil pollution include engine room bilges, fuel tanks, bunkering operations, cargo operations (loading/discharging) and tank washings. Generally, oil or oily mixtures should not be discharged into the water. When operationally necessary, these substances should only be discharged using special equipment and outside of prohibited areas.

IMO has categorized noxious liquid substances in different categories with corresponding discharge limits. A complete list of noxious liquid substances is listed in the International Bulk Chemical Code (IBC) book, which classifies various liquids in terms of what level of hazard they pose to marine life and people if discharged into the sea. Check the MARPOL rules before discharging anything into the water.

Standards exist for packing, labeling, documenting, stowing and limiting quantity of harmful substances. A list of substances that are classified as marine pollutants can be found in the International Maritime Dangerous Goods (IMDG) code. Accidental loss overboard of containers, especially those which are known to contain marine pollutants, must be always reported to shore authorities.

The regulations in Annex IV of MARPOL allow the discharge of sewage into the sea when the sewage has been treated by an approved sewage treatment plant (STP). Such plants collect the sewage and treat it (either chemically or biologically) so it can be discharged either at sea or in an onshore facility. Untreated sewage can only be discharged when certain conditions are met, including a certain distance from the nearest land.

It is illegal to discharge any solid materials other than certain types of food and animal waste anywhere at sea. Solid waste, including plastics, should be taken to a reception facility while the ship is in port. Review the MARPOL regulations, the vessel’s Garbage Management Plan or the placard in the garbage storage area of your ship for specific instructions.

In the last decades, IMO has been actively working at regulating the emission of polluting air substances by ships. The international air pollution requirements establish limits on nitrogen oxides (NOx) emissions and require the use of fuel with lower sulfur content or the use of scrubbers. More stringent requirements apply to vessels operating in Emission Control Areas (ECAs) such as the North American ECA that includes U.S. waters as well as ships operating within 200 nautical miles of the coast of North America. The IMO has developed a package of measures for reducing shipping’s CO2 emissions and aims to cut carbon dioxide emissions in half (compared to 2008) by 2050. 

The ‘International Convention on the Control of Harmful Anti-Fouling Systems on Ships’ prohibits the use of harmful organotin (organic compounds containing tin) in anti-fouling paints used on ships and creates a possibility to prevent the potential future use of other harmful substances in anti-fouling systems. 

The regulations for management of ships’ ballast water are described in the International Convention for the Control and Management of Ships’ Ballast Water and Sediments. The Convention requires all ships to carry out ballast water management procedures to avoid the transfer of invasive species. Procedures include ballast water exchange (a temporary measure) and ballast water treatment.

The IMO Convention on Safe and Environmentally Sound Ship Recycling contains guidelines for human and environmentally friendly recycling of ships. It was agreed upon in Hong Kong in May 2009 but has not entered into force yet. When in force, every ship must have a list of all materials present on board that may be hazardous to man and nature, including materials present in the ship’s structure, systems and equipment. Ship owners are responsible for maintaining and updating this IHM (Inventory of Hazardous Materials) throughout the life of the ship. 

Seafarers are especially entrusted with stewardship of the oceans. For regulations to be effective, the people working in the shipping are very important. Compliance with MARPOL regulations, when combined with accurate documentation, thorough training, and proper contingency planning will help marine organizations stay proactive in environmental preservation. The environmental performance of the shipping industry always depends on the professionalism and competence of its people, on ships and on shore.


The shipping industry is working on minimizing its impact on the environment. The International Maritime
Organization (IMO) has taken responsibility for pollution issues and has adopted a wide range of measures to
prevent and control pollution caused by ships and to mitigate the effects of any damage that may occur because
of maritime operations and accidents.

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