The International Convention for the Prevention of Pollution from Ships (MARPOL) is the main international convention covering prevention of pollution of the marine environment by ships from operational or accidental causes.
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.
Annex I: Regulations for the Prevention of Pollution by Oil (entered into force 2 October 1983) details the prevention of pollution by oil from operational measures as well as from accidental discharges.
The 1992 amendments to Annex I also made it mandatory for new oil tankers to have double hulls and brought in a phase-in schedule for existing tankers to fit double hulls, which was subsequently revised in 2001 and 2003.
Annex II: Regulations for the Control of Pollution by Noxious Liquid Substances in Bulk (entered into force 2 October 1983) details the discharge criteria and measures for the control of pollution by noxious liquid substances carried in bulk.
Today no discharge of residues containing noxious substances is permitted within 12 miles of the nearest land and the discharge of cargo residue is only allowed into port reception facilities.
Annex III: Prevention of Pollution by Harmful Substances Carried by Sea in Packaged Form (entered into force 1 July 1992) contains general requirements for the issuing of detailed standards on packing, marking, labeling, documentation, stowage, quantity limitations, exceptions and notifications.
Annex IV: Prevention of Pollution by Sewage from Ships (entered into force 27 September 2003) contains requirements to control pollution of the sea by sewage; the discharge of sewage into the sea is prohibited, except when the ship has in operation an approved sewage treatment plant or when the ship is discharging treated sewage using an approved system at a distance of more than three nautical miles from the nearest land; sewage which is not treated has to be discharged at a distance of more than 12 nautical miles from the nearest land.
In July 2011, IMO adopted the most recent amendments to MARPOL Annex IV which came into force on 1 January 2013. The amendments introduce the Baltic Sea as a special area under Annex IV and add new discharge requirements for passenger ships while in a special area.
Annex V: Prevention of Pollution by Garbage from Ships (entered into force 31 December 1988) deals with different types of garbage and specifies the distances from land and the manner in which they may be disposed of; the most important feature of the Annex is the complete ban imposed on the disposal into the sea of all forms of plastics.
In July 2011, IMO adopted extensive amendments to Annex V which entered into force on 1 January 2013. The revised Annex V prohibits the discharge of all garbage and harmful cargo hold washings into the sea, except as provided for under specific circumstances.
Annex VI: Prevention of Air Pollution from Ships (entered into force 19 May 2005) sets limits on sulfur oxide and nitrogen oxide emissions from ship exhausts and prohibits deliberate emissions of ozone depleting substances; designated emission control areas set more stringent standards for SOx, NOx and particulate matter.
In 2011, after extensive work and debate, IMO adopted ground breaking mandatory technical and operational energy efficiency measures which will significantly reduce the amount of greenhouse gas emissions from ships; these measures were included in Annex VI and entered into force on 1 January 2013.