Marpol 73/78 is the International Convention for the Prevention of Pollution From Ships, 1973 as modified by the Protocol of 1978. ("Marpol" is short for marine pollution and 73/78 short for the years 1973 and 1978.)
Marpol 73/78 is one of the most important international marine environmental conventions. It was designed to minimize pollution of the seas, including dumping, oil and exhaust pollution. Its stated object is: to preserve the marine environment through the complete elimination of pollution by oil and other harmful substances and the minimization of accidental discharge of such substances.
The original MARPOL Convention was signed on 17 February 1973, but did not come into force due to a lack. The current convention is a combination of 1973 Convention and the 1978 Protocol. It entered into force on 2 October 1983. As of May 2013, 152 states, representing 99.2 per cent of the world's shipping tonnage, are parties to the convention.
All ships flagged under countries that are signatories to MARPOL are subject to its requirements, regardless of where they sail and member nations are responsible for vessels registered under their respective nationalities.
Marpol contains 6 annexes, concerned with preventing different forms of marine pollution from ships:
- Annex I - Oil
- Annex II - Noxious Liquid Substances carried in Bulk
- Annex III - Harmful Substances carried in Packaged Form
- Annex IV - Sewage
- Annex V - Garbage
- Annex VI - Air Pollution
A State that becomes party to Marpol must accept Annex I and II. Annexes III-VI are voluntary annexes.
Annexe 6 April 1987. As of October 2009, 150 countries representing almost 99.14% of the world's tonnage had become party to Annexes I and II.
Annex III entered into force on 1 July 1992 and (as of October 2009) 133 countries representing over 95.76% of the world's tonnage had become party to it.
Annex IV entered into force on 27 September 2003 and (as of October 2009) 124 countries representing over 81.62% of the world's tonnage had become party to it.
Annex V entered into force on 31 December 1988 and (as of October 2009) 139 countries representing over 97.18% of the world's tonnage had become party to it.
Annex VI entered into force on 19 May 2005 and (as of October 2009) 56 countries representing over 46% of the world's tonnage had become party to it.
Marpol Annex VI amendments according with MEPC 176(58) came into force 1 July 2010.
Amended Regulations 12 concerns control and record keeping of Ozone Depleting Substances.
Implementation and enforcement 
In order for IMO standards to be binding, they must first be ratified by a total number of member countries whose combined gross tonnage represents at least 50% of the world’s gross tonnage, a process that can be lengthy. A system of tacit acceptance has therefore been put into place, whereby if no objections are heard from a member state after a certain period has elapsed, it is assumed they have assented to the treaty.
All six Annexes have been ratified by the requisite number of nations; the most recent is Annex VI, which took effect in May 2005. The country where a ship is registered (flag state) is responsible for certifying the ship’s compliance with MARPOL’s pollution prevention standards. Each signatory nation is responsible for enacting domestic laws to implement the convention and effectively pledges to comply with the convention, annexes, and related laws of other nations. In the United States, for example, the relevant implementation legislation is the Act to Prevent Pollution from Ships.
One of the difficulties in implementing MARPOL arises from the very international nature of maritime shipping. The country that the ship visits can conduct its own examination to verify a ship’s compliance with international standards and can detain the ship if it finds significant noncompliance. When incidents occur outside such country's jurisdiction or jurisdiction cannot be determined, the country refers cases to flag states, in accordance with MARPOL. A 2000 GAO report documented that even when referrals have been made, the response rate from flag states has been poor.
See also 
- Crude oil washing
- Marine energy management
- Marine fuel management
- Merchant Shipping (Pollution) Act 2006
- Ship pollution
- Copeland, Claudia. "Cruise Ship Pollution: Background, Laws and Regulations, and Key Issues" (Order Code RL32450). Congressional Research Service (Updated February 6, 2008). This article incorporates text from this source, which is in the public domain.
|Wikimedia Commons has media related to: MARPOL|
- International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating thereto (MARPOL 73/78
- Amendments to the Annex of the Protocol of 1978 relating to the International Convention for the Prevention of Pollution from Ships, Treaty available in ECOLEX-the gateway to environmental law (English)