MARPOL

MARPOL is the International Convention for the Prevention of Pollution from Ships, adopted in 1973 and entered into force in 1983. It is the primary international agreement governing how ships must manage waste, ballast water, and emissions at sea. Compliance is enforced through port state control: any vessel that violates MARPOL regulations can be detained, fined, and prohibited from trading until violations are remedied.

The convention is organized into six annexes, each addressing a different pollution source. Annex I covers oil; Annex II covers hazardous liquids in bulk; Annexes III and IV cover packaged harmful substances and sewage respectively; Annex V covers garbage; and Annex VI addresses air pollution from ships, including sulfur oxide and nitrogen oxide emissions. Not all annexes are ratified by every nation, which means a ship's compliance obligations depend partly on where it operates and which flag state registers it.

Practical compliance at sea

Ships must carry an International Oil Pollution Prevention Certificate, an International Sewage Pollution Prevention Certificate, or equivalent documentation depending on their size and type. They must maintain Oil Record Books or equivalent logs documenting operations that generate regulated waste. Ballast water must either be treated with approved systems or exchanged in open ocean beyond 200 nautical miles from land. Fuel oil used aboard must meet sulfur content limits, currently capped at 0.5 percent by mass for most vessels, though ships with approved scrubber systems can burn higher-sulfur fuel.

The rules create real friction in shipboard operations. Mariners must coordinate with authorized reception facilities ashore to discharge oily sludge, bilge water, and sewage. Timing transfers around port calls requires planning. Bunker fuel testing and recordkeeping add administrative overhead. Large container ships and tankers employ dedicated environmental officers to manage compliance documentation and oversee procedures. Violations can result in fines exceeding USD 100,000 and criminal prosecution of responsible crew members in some jurisdictions.

MARPOL's name preserves the convention's original acronym from 1973, before the 1978 Protocol substantially expanded its scope. The protocol was prompted by the Torrey Canyon and other major oil spills; subsequent amendments reflected emerging knowledge about ballast water bioinvasion, greenhouse gas emissions, and air quality impacts. The convention now covers roughly 99 percent of merchant shipping by tonnage, though enforcement remains uneven in poorly resourced ports.