MARPOL explained for ship operators and compliance teams
MARPOL covers six types of ship pollution. Annexes, special areas, ECAs and garbage placards are separate tests, not a single discharge permit.
MARPOL is the International Convention for the Prevention of Pollution from Ships, covering pollution from routine operations and accidents. Its six annexes address oil, bulk noxious liquids, packaged harmful substances, sewage, garbage and air pollution. The International Maritime Organization (IMO) describes it as the main international convention for preventing ship-source marine pollution.
Which rules apply depends on the ship, the cargo and the voyage. An annex summary is not permission to discharge.
What MARPOL 73/78 means
IMO adopted the convention on 2 November 1973. The 1978 Protocol absorbed the original convention, which had not yet entered into force. The combined instrument entered into force on 2 October 1983. This explains the familiar name "MARPOL 73/78".
The name is shorthand.
A 1997 Protocol added Annex VI. The six annexes did not enter into force together. Annexes I and II entered into force on 2 October 1983. But Annex II's provisions took effect on 6 April 1987. Annex V entered into force on 31 December 1988, Annex III on 1 July 1992, Annex IV on 27 September 2003, and Annex VI on 19 May 2005, so the 73/78 label does not freeze today's text. These dates are on IMO's convention page.
The six MARPOL annexes
Each annex addresses a different pollution category. The table follows IMO's overview of the convention.
| Annex | Pollution category | Main controls |
|---|---|---|
| I | Oil | Pollution from routine operations and accidents, including tanker construction and discharge controls. |
| II | Noxious liquid substances carried in bulk | Discharge criteria and pollution-control measures for bulk liquid cargoes. |
| III | Harmful substances carried in packaged form | Packing, marking, labelling, documentation, stowage, quantity limits, exceptions and notifications. |
| IV | Sewage | Treatment and conditional discharge controls. |
| V | Garbage | A general discharge prohibition, subject to specific exceptions. |
| VI | Air pollution | Sulphur oxides, nitrogen oxides, ozone-depleting substances, emission control areas and energy-efficiency measures related to greenhouse-gas emissions. |
MARPOL Annex I (Annex 1) is the oil annex. Treating the convention as only an oil-spill instrument misses the other five. Annex IV (Annex 4) is sewage: treatment and conditional discharge. A distance-from-shore shorthand is not a discharge clearance. IMO's annex summaries are the starting point, not the operating rule.
Bulk cargo and packaged cargo are different annexes. Annex II addresses noxious liquids in bulk. Annex III addresses harmful substances in packaged form: substances identified as marine pollutants in the IMDG Code, or substances that meet the criteria in the appendix to Annex III. And a supply label doesn't settle that test. The IMO convention page states the packaged-form test.
The convention overview still calls the plastics ban the most important feature of Annex V. That line is incomplete. IMO's garbage page says Annex V generally prohibits the discharge of all garbage into the sea, except as regulations 4, 5 and 6 provide. Those regulations relate to food waste, cargo residues, cleaning agents and additives, and animal carcasses. The exception topics are not a permit. Read the conditions before anything goes overboard.
Special areas and emission control areas
A special area and an emission control area are different legal categories. IMO identifies special areas under Annexes I, II, IV and V, where particular marine discharges receive stricter controls. Annex VI uses emission control areas, or ECAs, for air emissions. IMO's special-area page separates them: SOx emission control areas set more stringent sulphur controls, and NOx emission control areas apply Tier III nitrogen-oxide standards. A sulphur figure does not answer a nitrogen-oxide question.
Designation, entry into force and the date a requirement takes effect are separate points. Some special-area discharge requirements depend on notifications of adequate reception facilities. IMO's special-area table separates these stages. A place name on that table is not, by itself, the date every control applies. And the table is not a complete current list of areas.
For sulphur, IMO's sulphur page gives 0.50% m/m outside SOx ECAs and 0.10% m/m within applicable SOx ECAs. The 0.50% limit replaced the previous 3.5% cap. Flag States can accept exhaust gas cleaning systems, also called scrubbers, as an alternative means to meet the sulphur limit. Scrubbers do not settle the nitrogen-oxide rules.
MARPOL garbage placards, plans and record books
Annex V splits placards, garbage management plans and the Garbage Record Book. The triggers differ.
Garbage placards
Every ship 12 metres in length or over, and every fixed or floating platform, must display garbage-discharge placards. IMO's garbage page says regulation 10.1 requires those placards to notify passengers and crew of the Annex's disposal requirements.
The same page says the placards should be written in the crew's working language, and also in English, French or Spanish for ships travelling to other States' ports or offshore terminals. English is one of those three additional languages.
Garbage management plans
A garbage management plan is required for ships of 100 GT and above, ships certified to carry 15 persons or more, and every fixed or floating platform. It includes written procedures for minimising, collecting, storing, processing and disposing of garbage, including the use of equipment on board. The plan designates the responsible person and is written in the crew's working language. These points are Annex V regulation 10.2.
The record book's voyage wording is not part of this plan rule.
Garbage Record Books
For the Garbage Record Book, IMO's current Annex V page says regulation 10.3 requires:
all ships of 100 gross tonnage and above and every ship which is certified to carry 15 persons or more engaged in voyages to ports and offshore terminals under the jurisdiction of another Party to the Convention and every fixed or floating platform to be provided with a Garbage Record Book and to record all disposal and incineration operations
Check the quoted voyage qualification when assessing whether your ship needs a Garbage Record Book. "Certified to carry" means capacity, not how many people are aboard that day. The book is kept for two years after the date of the last entry, as the IMO guidance states.
US garbage placards use different thresholds
US placards need their own check. Under 33 CFR 151.51(e), the placard rule in section 151.59 applies to:
- A manned US ship of 26 feet or more in length, other than a fixed or floating drilling rig or other platform.
- A manned floating drilling rig or other platform in transit that is subject to US jurisdiction.
- A manned ship of 40 feet or more in length, operated under the authority of a country other than the United States, while in US navigable waters or the US exclusive economic zone.
The 26-foot figure is a US rule. It is not the international 12-metre threshold.
Under 33 CFR 151.59, placards must be displayed in prominent locations and in sufficient numbers so crew and passengers can read them. Each placard must be at least 20 cm (8 inches) wide by 12½ cm (5 inches) high, made of a durable material, and legible.
The same section says each placard must notify the reader of the operating requirements in 33 CFR 151.67 through 151.73 as they apply to that ship. It also calls for prominent statements on the garbage-discharge prohibition and its exceptions, the ban on all forms of plastic, possible civil or criminal penalties, and regional, state and local restrictions that may apply. Those size and message rules are US requirements, not a universal MARPOL placard specification.
Applying the overview to a ship
Match the pollution to the annex, then the ship, the voyage and the location, before anyone treats a summary as a discharge permission. Placard length, plan tonnage and record-book wording stay separate checks.
See the RegAffairs AI explanation of MARPOL for the convention overview and garbage-placard source links. For the ship in front of you, the applicable annex text controls, not this overview.