MARPOL overview for beginners – 15 min summary

MARPOL overview for beginners – 15 min summary


MARPOL stands for Marine Pollution. It is the main international convention that addresses the different types of pollution from ships operating around the world. It also covers fixed and floating platforms to some extent.

In this article, we explore MARPOL to get a brief overview of its rules and regulations. But before we begin, let us first understand the scope of MARPOL.

International Convention for the Prevention of Pollution from Ships (MARPOL)

The International Convention for the Prevention of Pollution from Ships is the official name for Marpol. It is an instrument of the International Maritime Organization (IMO). The convention includes regulations aimed at eliminating or minimizing pollution of the marine environment from ships.

Pollution can happen as both accidental pollution or from routine operations. As a result, Marpol sets out clear guidelines and regulations to prevent pollutants such as oil, sewage, harmful cargo, garbage, etc. from ending up in water bodies.

The MARPOL regulations are in six separate annexes, each of which addresses a different pollutant. These annexes are as follows:

  • Annex I – Regulations for the Prevention of Pollution by Oil
  • Annex II – Regulations for the Control of  Pollution by Noxious Liquid Substances in Bulk
  • Annex III – Prevention of Pollution by Harmful Substances Carried by Sea in Packaged Form
  • Annex IV – Prevention of Pollution by Sewage from Ships
  • Annex V – Regulation for preventing pollution by Garbage from Ships
  • Annex VI – Prevention of Air Pollution from Ships
History of Marpol Annexes entering into force
History of Marpol Annexes entering into force

Annex I – Regulations for the Prevention of Pollution by Oil (entered into force 2 October 1983)

Oil constitutes the largest risk to marine environments. There have been many massive oil spills in history such as the Persian Gulf War oil spill of 1991 (Intentional and up to 520 million barrels) and BP’s Deepwater Horizon oil spill of 2010 (Accidental pollution up to 206 million gallons).

But the majority of incidents still occur through ships. By building immanent barriers in the loading, transportation, discharge, and use of oil, we can minimize pollution to a large extent. With this objective in mind, Annex I entered into force in 1983.

It consists of 39 regulations divided into seven chapters. These chapters are as follows.

Chapter 1 – General

The first chapter focuses on orientation topics such as definitions, applications, exceptions and exemptions to Annex I.

It also defines Special Areas for Annex I. Special areas are areas where the restrictions on oil discharge are stricter than other areas. This could be because of them being landlocked or other geological, ecological or traffic conditions.

Chapter 2 – Surveys and Certification

Chapter 2 focuses on providing instructions for surveys and certifications. The aim is to ensure that vessel specifications are in line with the requirements of this annex as applicable. Once the surveys are done, the vessel receives an International Oil Pollution Prevention Certificate (IOPP).

Chapter 3 – Requirements for machinery spaces of all ships

The third chapter lays down the regulations for the construction and equipment in machinery spaces with respect to this annex. It gives the details about sludge tanks, fuel oil tanks, their capacities, piping arrangement overboard as well as the standard flange requirements to connect to reception facilities.

The fuel oil tank design requirements have been recently added as regulation 12A to this chapter for tanks that have a capacity of more than 600 cubic metres.

It also explains how and what needs to be recorded when pumping out allowable concentrations of oil through approved oil filtering equipment.

The Chapter also explains the conditions when the discharge of oil into the sea is allowed and the use of Oil Record Book Part 1 to record the same.

Chapter 4 – Requirements for the cargo areas of oil tankers

Chapter four discusses similar regulations for the construction and equipment of cargo areas of oil tankers. It standardizes segregated ballast tanks, double hulls, double bottoms, pump rooms, slop tanks, pumping, piping and discharge arrangements.

It also discusses cargo equipment such as Oil Discharge and Monitoring Control System (ODMCS), Oil/water interface detector and Crude Oil Washing requirements (COW).

The chapter also expands on topics such as the oily mixture discharge procedure at sea, crude oil washing operations and the use of Oil Record Book Part – II.

Chapter 5 – Prevention of oil pollution arising from an oil pollution incident

Chapter 5 mandates the possession of a Shipboard Oil Pollution Emergency Plan (SOPEP) for all ships > 400 GT ( > 150 GT in the case of oil tankers)

It also states the IMO’s guidelines on how to develop it and, if required, how to merge it with the Shipboard Marine Pollution Emergency Plan (SMPEP).

Oil Spill at Sea

Chapter 6 – Reception facilities

This chapter specifies the location, distribution and capacity of shore reception facilities for oil residues. It also gives some additional regulations for shore reception in Special areas.

Chapter 7 – Special requirements for fixed or floating platforms

The last chapter provides guidelines for platforms such as drilling rigs, FPSOs, and FSUs for the storage of produced oil.

These platforms should also have sufficient sludge tanks and functional oil-filtering equipment. They must also maintain a record of all operations involving oil or oily discharge mixtures in an approved format.

Annex II – Regulations for the Control of  Pollution by Noxious Liquid Substances in Bulk  (entered into force 2 October 1983)

Marpol annex II came into force along with Annex I. The second annex focuses on noxious liquid substances carried on ships. Such substances pose a significant danger to the marine environment and need to be regulated to control pollution and ensure environmental protection.

Marpol annex II consists of 18 regulations divided into 8 chapters.

Chapter 1 – General

Similar to Chapter 1 in the previous annex I, this chapter discusses orientation topics such as definitions, applications, exception and exemptions related to Marpol annex II.

Chapter 2 – Categorization of noxious liquid substances

The proposed regulations had an appended list of about 250 noxious liquid substances that vessels could only dispose to reception facilities unless below a certain threshold of concentration and other conditions. The noxious substances have four categories: X, Y, Z, and other substances (OS).

Other substances are substances that do not fall into any of the previous categories as per the International Bulk Chemical Code (Chapter 18 – Pollution category column).

Chapter 3 – Surveys and certification

Chapter 3 informs that all chemical tankers are to be surveyed and certified periodically as per the International Bulk Chemical Code (IBC). Surveys include initial, renewal, intermediate, annual and additional surveys.

Upon a successful survey, the International Pollution Prevention Certificate for the Carriage of Noxious Liquid Substances in Bulk whose validity shall not exceed five years.

Chapter 4 – Design, Construction, Arrangement and Equipment

The fourth chapter provides provisions for the design, construction, arrangement and equipment of vessels certified to carry noxious liquid substances in bulk. These are meant to reduce the possibility of their uncontrolled discharge into the sea.

It also sets standards for how much residues of these substances can be retained in tanks and associated piping.

Chapter 5 – Operational discharges of residues of noxious liquid substances

Chapter 5 stipulates the provisions and standards for the discharge of noxious liquid substances into the sea. It also provides the arrangements and procedures onboard for correct cargo handling, tank cleaning, slops handling, cargo tank ballasting and deballasting.

And finally, the chapter also speaks about the Cargo Record Book and the importance and method of filling it in the correct format.

Chapter 6 – Measures of Control by port states

This chapter states the extent of control awarded to port states to ensure that vessels are adhering to the annex requirements.

Chapter 7 – Prevention of pollution arising from an incident involving noxious liquid substances

This chapter mandates that vessels that are certified to carry the substances in this annex must have onboard an approved Shipboard Marine Pollution Emergency Plan (SMPEP). The plan must give a detailed procedure on what to do in the case of a pollution incident.

It would also guide the ship staff with who to contact and what to tell them so that effective action can be taken to minimize pollution.

Chapter 8 – Reception facilities

The final chapter of the annex allocates the responsibility to member states of providing capable and adequate shore reception facilities at their cargo handling terminals/ports and ship repair ports for the safe discharge of these substances.

Annex III – Prevention of Pollution by Harmful Substances Carried by Sea in Packaged Form (entered into force 1 July 1992)

Marpol annex III covers harmful substances that are defined as marine pollutants in the IMDG code. IMDG stands for the International Maritime Dangerous Goods Code.

This annex consists of 8 regulations that cover the different aspects of a harmful substance from packing to stowage to how much can be carried at a time.

Regulation 1 – Application

Regulation 1 covers the application of this annex to the shipping industry. It prohibits the carriage of harmful substances except when the activity complies with the requirements of this annex.

The regulation also instructs the member states to provide exhaustive instructions on packing, marking, labelling, documentation, quantity limits and any exceptions.

It urges that the packaging used for these substances themselves be considered harmful substances unless all traces of the substance can be removed.

Regulation 2 – Packing

This regulation only states that packaging choices should be made consciously to minimise the dangers to the environment.

Regulation 3 – Marking and Labelling

Regulation 3 expands on the requirements for packaging. It states that the packages be marked with the correct United Nations or UN number for universal identification. Stickers or graphics that indicate that the substance is a marine pollutant should also be present.

The packaging must also be durable enough to last at least three months of immersion in the sea. Small packages may be exempted from these requirements.

Regulation 4 – Documentation

Regulation 4 urges the vessels to carry comprehensive documentation for the harmful substances along with a signed declaration from suppliers that the packaging is suitable and that it is marked and labelled correctly.

Copies are to be held on the vessels as well as ashore of the final stowage plan showing the location of these harmful substances onboard.

Regulation 5 – Stowage

The stowage and security of these substances onboard must fulfil two conditions in order to be acceptable. These are:

  1. It must minimize the harm to the environment.
  2. It must not jeopardize the safety of the persons and the ship itself.

Regulation 6 – Quantity limitations

Certain materials cannot be transported or stowed in large quantities. It is important that these limitations are followed for the safety of crew, ships, terminals and the environment.

The Beirut port explosion of August 2020 is a prime example of how haphazard storage of dangerous cargo can lead to disastrous consequences.

Regulation 7 – Exceptions

The regulation details the conditions under which ships may be excused for not adhering to the annex. For example, it is allowed to drop cargo into the sea if doing so is necessary to secure the safety of a ship or persons onboard.

Regulation 8 – Port state control on operation requirements

This final regulation of Marpol annex III gives authority to port state control to inspect ships where they believe that the ship crew is not familiar with pollution prevention procedures. They may hold the vessel until the situation is rectified to acceptable levels.

Annex IV – Prevention of Pollution by Sewage from Ships  (entered into force 27 September 2003)

The fourth annex focuses on sewage from ships. Sewage can be a real problem, especially in closed water bodies such as river channels, lakes and internal seas.

To address this problem, Marpol annex IV prohibits the discharge of sewage into the sea unless it is through an approved sewage treatment plant or comminuted and disinfected to specified limits.

In any case, the sewage is not to be disposed less than three nautical miles from the nearest land and when it is not comminuted or disinfected, the distance requirement increases to 12 nautical miles.

Marpol annex IV consists of 12 regulations that form 4 chapters.

Chapter 1 – General

Like previous annexes, the first chapter gives basic information about the annex such as the definitions of the terms used, the application of the annex and exceptions if any.

Chapter 2 – Surveys and certification

This chapter enumerates the surveys necessary to ensure compliance with the annex. It also gives details about the certificates to be issued and their duration and validity requirements.

Chapter 3 – Equipment and control of discharge

The third chapter covers two topics.

The first topic is equipment. This regulation invokes that the sewage equipment such as the sewage treatment plant (STP), sewage holding tank, sewage comminuting and disinfecting system and the discharge connection is of an approved type.

The second topic is discharge controls. The regulation clarifies how the sewage is to be discharged at sea. Some of it relating to discharge distance from nearest land was already discussed at the beginning of this section.

It also gives other criteria such as the speed of the ship, that it should be enroute and the discharge rate. Also, the effluent should not produce discolouration or have visible solids.

Chapter 4 – Reception facilities

The last chapter stresses the need to provide quick and reliable shore reception facilities to the vessels at ports and anchorages.

Annex V – Regulation for preventing pollution by Garbage from Ships (entered into force 31 December 1998)

Garbage is a real menace at sea because it never really goes away. Plastics, in particular, not only degrade marine environment but are extremely harmful to marine organisms.

Annex V was brought into effect to prevent the unfettered discharge of garbage into the sea. It classifies garbage into multiple categories with instructions on how and where each category is to be disposed.

It consists of 9 regulations as follows:

Regulation 1 and 2 are pretty self explanatory by this point.

Regulation 3 – Disposal of garbage outside special areas

This regulation gives information on how we can dispose of the garbage outside special areas. It also gives us a list of garbage types which we cannot discharge at all at sea.

It goes on to specify the types of garbage we can dispose of and beyond what distance to the nearest land. Regulation 4 follows up with special requirements for the same.

Regulation 5 – Disposal of garbage within special areas

Garbage disposal within special areas has more stringent requirements than outside special areas. This regulation informs about those requirements and which special areas have even stricter conditions.

Garbage on Body of Water
Garbage on Body of Water

Regulation 6 and 7 – Exceptions and Reception facilities

These regulations note the exceptions to this annex and the need for reception facilities.

Regulation 8 – Port state control on operational requirements

The Port state control has the authority to inspect and detain any vessel that is not familiar with essential shipboard procedures. Article 5 of the present Convention tells us about these procedures.

Regulation 9 – Placards, garbage management plans and garbage record-keeping

This regulation instructs the ship staff to maintain placards, follow the garbage management plan and keep records diligently.

For all vessels greater than 12 m in length, placards are to be displayed in the working language of the ship. If these ships operate in international waters, the placards must also be in either English, French or Spanish.

The vessel must also have a written garbage management plan if the vessel is certified to carry more than 15 passengers or is greater than 400 gross tonnage in size. It must have detailed procedures for the collection, storage, processing and disposal of garbage.

The same vessels are also required to carry a garbage record book which gives sufficient details about incineration or discharge of garbage such as the time, position, garbage type and amount.

Annex VI – Prevention of Air Pollution from Ships (entered into force 19 May 2005)

Air pollution from ships has come increasingly into focus in the past two decades. It emits green house gases and ozone depleting substances that are causing climate change as well as damage to humans and marine environment.

To prevent this, the Organization has enforced many measures. Many others are in development by the Marine Environment Protection Committee of the IMO.

Marpol Annex VI covers air pollution from ships. It consists of 19 regulations in three chapters. The three chapters are as follows:

Chapter 1 – General

This chapter consists of orientation topics such as Definitions, Annex VI applications and exceptions.

Chapter 2 – Survey, certification and means of control

This chapter details the different surveys and certifications required to ensure that vessels comply with this annex.

When a vessel complies and passes relevant surveys as mentioned in Regulation 5 of this annex, it receives an International Air Pollution Prevention Certificate (IAPP).

The chapter also states that the vessels are subject to inspections to ensure compliance. If a violation is found, the inspecting Party will forward the inspection report along with the evidence to the Administration.

The Administration will verify the claim and, if required, ask for more or better evidence. Once the violation is clear, the Administration will take action according to its laws and inform the former Party as well as the Organization of the action taken.

Chapter 3 – Requirements for control of emissions from ships

This chapter covers the various air pollutants that ships operating in different parts of the world emit.

The list includes pollutants such as ozone-depleting substances, Nitrogen oxides (NOx), Sulphur oxides (SOx), carbon dioxide and volatile organic compounds.

Smoke billowing from a ship's funnel
Smoke billowing from a ship’s funnel

Most of these compounds originate from marine fuels through marine diesel engines. Therefore, one of the most important reforms of this annex has been to improve the fuel oil quality.

The introduction of operational measures (CII) and technical regulatory measures (EEDI/EEXI) have helped set goals for emission reduction.

Exhaust gas cleaning systems have also seen many advances. These systems capture pollutants such as particulate matter before their release into the atmosphere through the exhaust gas. These systems allow the use of heavy fuel oil without restriction as the exhaust gas no longer contains pollutants as before.

Shipboard incinerators also release problematic compounds. Regulation 16 has standardized them to prevent pollution from operational or accidental causes.

The final regulation speaks about exemptions for drilling rigs and platforms in complying with this annex.


  1. How many technical annexes are there in MARPOL?

Marpol consists of six separate annexes. Each one is for a different pollutant. These are oil, noxious liquid substances in bulk, harmful substances in packaged form, sewage, garbage, and air pollution.

  1. Can we throw incinerator ash overboard?

We cannot throw incinerator ash overboard. We discharge it to an approved shore reception facility and record the quantity and other details in the Garbage Record Book.

  1. For how long do vessels maintain Oil Record Book onboard?

Vessels maintain old Oil Record Books onboard for three years after the date of last entry.

  1. For how long do vessels maintain the Garbage Record Book onboard?

Vessels maintain old Garbage Record Books onboard for two years after the date of last entry.



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