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An Introduction to the IMO International Convention for the Prevention of Pollution from Ships 73/78 (as amended) and its Provisions


The International Convention for the Prevention of Pollution from Ships (MARPOL Convention) is the main international convention covering prevention of pollution of the marine environment by ships from operational or accidental causes. The MARPOL Convention was adopted on November 2, 1973 at IMO. The Protocol of 1978 was adopted in response to a spate of tanker accidents in 1976-1977. 

The Convention includes regulations aimed at preventing and minimizing pollution from ships - both accidental pollution and that from routine operations - and currently includes six technical Annexes. Special Areas with strict controls on operational discharges are included in most Annexes.

As the 1973 MARPOL Convention had not yet entered into force, the 1978 MARPOL Protocol absorbed the parent Convention. The combined instrument entered into force on October 2, 1983. In 1997, a Protocol was adopted to amend the Convention and a new Annex VI was added which entered into force on May 19, 2005. MARPOL has been updated by amendments through the years.

The MARPOL Convention is dvided into Six Annexes and they cover pollution of the sea by oil, by noxious liquid substances in bulk, by harmful substances in packaged form, by sewage from ships, and by garbage from ships. Annex VI was adopted by a further Protocol in 1997 and covers air pollution from ships.


marpol ship

MARPOL 1973/78

Annex I - Regulations for the Prevention of Pollution by Oil

 Annex I (Oil) came into force on October 2, 1983 and contains conditions for discharge of mixtures containing oil and also requirements applicable to the construction and equipment of tankers larger than 150GRT and other ships larger than 400GRT. 

Shipboard oil pollution sources include engine room bilges, fuel tanks, bunkering operations, cargo operations (loading/discharging), tank washings, ballasting/de-ballasting and accidents.

Oil Pollution

  • Any discharge into the sea of oil or oily mixtures from ships of 400 gross tons and greater shall be prohibited except when a number of process conditions are satisfied.
  • Any discharge into the sea of oil or oily mixtures from the cargo area of a vessel shall be prohibited except when a number of conditions are satisfied.
  • All vessels should be fitted with a standard discharge connection for safe discharge of oil and oily mixtures to an approved reception facility.
  • If there is an oil spill, refer to your Shipboard Oil Pollution Emergency Plan (SOPEP) manual and VRP (Vessel Response Plan) to see how to handle it safely, and communicate effectively with proper parties.
  • Entries of such items as oil and oily waste discharges, internal transfers and bilge water processing are to be accurately recorded in the Oil Record Book.

Annex II - Regulations for the Control of Pollution by Noxious Liquid Substances in Bulk

Annex II came into force on April 6, 1987 and contains discharge conditions for four categories of noxious substances and requirements applicable to the construction and equipment of ships carrying such substances. Unlike oil, most chemicals or noxious liquids will mix with water and are not easily separated from it. 

Noxious Liquid Substances

  • 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. Be aware of how these substances are classified and what this means regarding how you should handle them.
    • Category X - Major hazard; do not discharge into the sea!
    • Category Y - Hazardous; only limited discharging is permitted
    • Category Z - Minor hazard; only minor restrictions on discharging
    • Category OS (Other Substances) - No hazard or restrictions
  • Every bulk liquid cargo must be stored properly and completely contained. In addition to the IBC book, your ship should also have a Procedures and Arrangements Manual that tells you how to load, discharge, and manage your cargo.
  • Record all information regarding cargo loading, discharge of liquids, internal transfer, and cargo tank washing and ballasting in the Cargo Record Book.

Annex III - Regulations for the Prevention of Pollution by Harmful Substances carried by Sea in Packaged Form

Roughly 15% of goods carried as cargo are dangerous goods. Annex III which came into force on July 1, 1992 contains requirements for safe handling of packaged substances that represent a serious risk to the environment, as well as guidelines for identification of harmful substances.

Packaged Substances

  • The carriage of harmful substances is prohibited, except in accordance with the provisions of this Annex.
  • To supplement the provisions of this Annex, the Government of each Party to the Convention shall issue, or cause to be issued, detailed requirements on packing, marking, labeling, documentation, stowage, quantity limitations and exceptions for preventing or minimizing pollution of the marine environment by harmful substances.
  • For the purposes of this Annex, empty packaging which have been used previously for the carriage of harmful substances shall themselves be treated as harmful substances unless adequate precautions have been taken to ensure that they contain no residue that is harmful to the marine environment.
  • The requirements of this Annex do not apply to ship's stores and equipment.

Annex IV - Regulations for the Prevention of Pollution by Sewage

The regulations contain requirements for surveys and certification of sewage systems and impose operational restrictions regarding sewage discharge. Annex IV entered into force on the September 27, 2003.


  • Ships over 400 gross tons, or less than 400 gross tons but certified to carry more than 15 passengers, shall be fitted with an approved sewage treatment system and/or holding tank.
  • Seagoing vessels must also be fitted with standard discharge connections to pump sewage or treated effluent to a shore side reception facility.
  • After being treated on the ship, comminuted and disinfected sewage using an approved system is permitted to be discharged at a distance of more than 3 nautical miles from the nearest land, and sewage which is not comminuted or disinfected is permitted to be discharged at a distance of more than 12 nautical miles from the nearest land, provided that the sewage is not be discharged instantaneously but at a moderate rate while the ship is underway. The discharge of sewage in the waters under the jurisdiction of a Coastal State may impose more stringent regulations, such as “No Discharge Zones” where all discharge of sewage (treated or untreated) is prohibited.
  • When the sewage is mixed with wastes or waste water having different discharge regulations, the more stringent regulations shall apply.

Annex V - Regulations for the Prevention of Pollution by Garbage

Annex V, which came into force on December 31, 1988 and contains requirements relating to the disposal of all types of food, household and operational waste that have accumulated aboard ships during operation.


  • Anywhere at sea, it is illegal to discharge:
    • Plastics and materials containing plastic
    • Synthetic lines and fishing nets
    • Ash from the incineration of garbage or sludge
    • Residues from the cargo section of an oil tanker
    • Residues from the cargo section of any vessel that are deemed dangerous or harmful to the environment.
    • Most materials except food waste
  • All vessels 100 gross registered tons (GRT) and larger must have a Garbage Management Plan.
  • Records of garbage incinerated, discharged into the sea, or sent to reception facilities ashore shall be accurately recorded in the ship’s Garbage Record Book aboard vessels 400GRT and larger.
  • Vessels 12 meters and greater must display a garbage placard.

Annex VI - Regulations for the Prevention of Air Pollution from Ships

Annex VI, which came into force on 19 May 2005, governs the control of the discharge of noxious substances from ship diesels. It is applicable to ship diesels with a power larger than 130kW built and installed since January 1, 2000. 

Air Pollution

  • Ships operating in designated Emission Control Areas (ECAs) are required to comply with more stringent fuel, sulfur, and engine nitrogen oxides (NOX) limits.
  • Chlorofluorocarbon (CFC) and Halon chemicals, which are found in common refrigerants and extinguishing agents shall not be released into the air. Records should be kept showing delivery, use and landing ashore of all CFC and Halon chemicals.
  • Most vessels now have International Air Pollution Prevention (IAPP) certificates. When engine parts are repaired or replaced, you should use only approved materials. Additionally, many engines are now being made that greatly reduce the release of sulfur, nitrogen, and other chemicals into the air.
  • PVC plastics may only be burned in specially approved shipboard incinerators.
  • Garbage and sludge may not be burned in ports, harbors, or estuaries.

Disclaimer: For general information purpose only - please check with IMO marpol Convention for the latest and accurate info

LAST UPDATED ON Feb 11, 2020