MARPOL Convention Complete Guide 2026

Annex I — Oil

The oldest and most heavily enforced Annex covers discharge of oil and oily mixtures. The core rule is a 15 parts-per-million discharge limit outside special areas, monitored through an Oil Discharge Monitoring and Control system on tankers and an Oily Water Separator on the engine room bilge system elsewhere. Every transfer of oil, and every discharge or disposal, has to be logged in the Oil Record Book — and because these entries are the primary evidence in any pollution investigation, falsifying them is treated as a serious offence in its own right, separate from the pollution event itself. Several of the largest MARPOL fines on record, including multi-million dollar cases in US ports, were driven not by the original discharge but by a falsified ORB found during a subsequent inspection.

Annex II — Noxious liquid substances

Covers chemical tankers carrying noxious liquid substances in bulk, categorizing chemicals by hazard level (X, Y, Z, and Other) and setting discharge and tank-washing procedures specific to each category. A Cargo Record Book tracks every loading, transfer, and cleaning operation involving these substances.

Annex III — Harmful substances in packaged form

Applies to harmful substances carried in packaged form — drums, containers, portable tanks — and works alongside the IMDG (International Maritime Dangerous Goods) Code to govern packaging, marking, labelling, documentation, and stowage so that hazardous cargo is identifiable and handled correctly at every stage.

Annex IV — Sewage

Regulates sewage discharge, requiring an approved sewage treatment plant or holding tank on most vessels and setting minimum distances from land for discharge of untreated versus treated sewage. Special Areas impose stricter limits.

Annex V — Garbage

Sets out what can and cannot go over the side, and it’s stricter than most crew initially expect. Plastics of any kind are completely banned from sea disposal in all circumstances, no exceptions. Food waste can be discharged beyond 12 nautical miles from the nearest land under normal rules (3nm if passed through an approved comminuter or grinder in permitted areas), and other cargo residues and cleaning agents have their own distance and concentration rules. Special Areas — the Mediterranean, Baltic, Black Sea, Antarctic, and others — impose tighter or zero-discharge requirements, and the Garbage Record Book has to reflect exactly what was disposed of, how, and where.

Annex VI — Air pollution

The newest Annex, and the one that’s changed the most in the last decade. It caps sulphur content in fuel oil — the global limit dropped to 0.50% in January 2020 (from 3.5% previously), with Emission Control Areas enforcing an even stricter 0.10% limit. Ships either burn compliant low-sulphur fuel, install an exhaust gas cleaning system (a “scrubber”), or in some cases switch to alternative fuels. Annex VI also regulates NOx emissions from marine diesel engines and governs shipboard incineration.

Why the Annexes matter as a set, not individually

A single vessel is typically subject to several Annexes simultaneously — a tanker deals with Annex I, V, and VI at minimum, a chemical carrier adds Annex II — and inspectors during PSC or flag state audits check compliance and record-keeping against each applicable Annex separately. Treating MARPOL as one undifferentiated rule, rather than knowing which specific Annexes and record books apply to the ship’s actual trade, is how genuine gaps in compliance get missed until an inspection finds them.

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