IMO pollution regulation

Updated 11 Oct 2019

Regulation 75j2mprb7

In modern times the shipping industry has been unfairly singled out as a major source of global pollution. It is often said that when it comes to CO2 emissions, shipping is a bigger contributor than all but a handful of nation states. That may be true but so are power production, agriculture and most other essential industrial operations. It also does not take into account that shipping is a service industry that exists only to move goods and people around the globe. In that respect it is recognised as being the most efficient of the various options that exist.

However, when it comes to other means of affecting the marine environment, shipping is generally among the most regulated of human activities. Shipping is not alone in having an effect on the marine environment. All around the globe vast amounts of waste of all types find their way to the sea. From farming runoff into rivers through garbage from fishing and leisure use of the sea and coastal lands to sewage outflows from cities and towns, it is likely that far more damage is done to the marine environment by non-shipping activities than anything commercial ships are responsible for.

The latest threat is plastic, which is being found in increasing quantities in the world’s oceans. Whether it comes from microbeads used by cosmetic manufacturers, plastic bags or other synthetic materials used for all manner of reasons, it is certainly not related just to shipping but, because plastic is found at sea, it is shipping that gets an unfair proportion of the blame.

Regulating shipping’s environmental impact is quite a modern development and fewer than 60 years have passed since the first global regulations became effective. Beforee that, there may have been local rules in individual ports but – as those who can remember visiting harbours before the clean-up began in earnest in the 1980s can testify – whatever rules may have been in place appeared to have been universally ignored.

Even before ships had engines, they had the potential to impact on the environment. As well as the alien species that hitched a ride on ships – whether in the ship, in the cargo or under the hull – there was the waste produced by the crew and passenger on board and occasionally a cargo that needed to be dumped at sea.

It is generally accepted that oils and greases are the most pervasive and polluting by-products of shipping activity. The advent of mechanically-propelled ships has increased the level of oily waste and with no regulation barring it, that waste was regularly dumped at sea. Although steam ships also produced waste oil in quantities, the problem was only recognised soon after the first diesel engine was used in 1912. But it was the increase in crude oil transport and the consequent disposal of tanks washings at sea that was the spur for the first regulations prohibiting disposal of oil.

That was not to be until The International Convention for the Prevention of Pollution of the Sea by Oil (OILPOL) was formulated in London in 1954. The 1954 convention came into force in 1958 and was amended in 1962, 1969 and 1971. It was eventually superseded by the International Convention for the Prevention of Pollution from Ships (MARPOL) and its measures are now included there.

OILPOL did not put a complete ban on disposal at sea; it merely prohibited the dumping of oily wastes within a certain distance from land and in ‘special areas’ where the danger to the environment was especially acute. It also imposed a requirement for contracting parties to provide reception facilities but, more than half a century on, the lack of facilities is still a bone of contention for the industry. OILPOL was mainly concerned with operational discharges as was the 1973 version of MARPOL drawn up by the IMO.

This was to be amended by the Protocol of 1978, which was adopted in response to a spate of tanker accidents in 1976-1977. As the 1973 MARPOL Convention had not then entered into force and thus could not be amended, the 1978 MARPOL Protocol absorbed the parent Convention. The combined instrument entered into force on 2 October 1983. In 1997, a Protocol was adopted to amend the convention and a new Annex VI – relating to air pollution – was added, which entered into force on 19 May 2005. MARPOL has been updated by amendments through the years and most of its measures are the province of the IMO’s Marine Environment Protection Committee (MEPC), which is also entrusted with the development of other environmental conventions.

Categories of marine pollution
IMO says of MARPOL that it includes regulations aimed at preventing and minimising pollution from ships – both accidental pollution and that from routine operations – and currently includes six technical Annexes, most of which include special areas with strict controls on operational discharges.

Oil & Grease
The Annex I Regulations for the Prevention of Pollution by Oil (entered into force 2 October 1983) covers prevention of pollution by oil from operational measures as well as from accidental discharges; the 1992 amendments to Annex I 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.

Noxious liquid substances
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; some 250 substances were evaluated and included in the list appended to the convention; the discharge of their residues is allowed only to reception facilities until certain concentrations and conditions (which vary with the category of substances) are complied with. In any case, no discharge of residues containing noxious substances is permitted within 12 miles of the nearest land.

Harmful packaged substances
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, labelling, documentation, stowage, quantity limitations, exceptions and notifications. For the purpose of this annex, “harmful substances” are those that are identified as marine pollutants in the International Maritime Dangerous Goods Code (IMDG Code) or which meet the criteria in the Appendix of Annex III.

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 comminuted and disinfected sewage using an approved system at a distance of more than three nautical miles from the nearest land. Sewage that is not comminuted or disinfected 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 entered into force on 1 January 2013. The amendments introduced 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 into the sea, except as provided otherwise, under specific circumstances.

Air pollution and exhaust gases
Annex VI Prevention of Air Pollution from Ships (entered into force 19 May 2005) sets limits on sulphur oxide and nitrogen oxide emissions from ship exhausts and prohibits deliberate emissions of ozone depleting substances. Designated emission control areas (ECAs) set more stringent standards for SOx, NOx and particulate matter. Currently, these are few in number and, while more are predicted, there are none in the pipeline that will impact on the major trade lanes.

Particulate matter, or ‘PM’ as it is often known, consists of solid particles that originate from many sources. They are mostly natural but also come from an extremely diverse range of human activities including cooking, cement production and burning of fossil fuels. Shipping’s main source is, of course, the combustion of fuels in diesel engines. PM has been cited as a major health problem with the smallest size measuring 2.5μm, often referred to as PM2.5, being seen as the most dangerous in this regard. PM from burning fuels include sulphates which are of course partially regulated under Annex VI because of the limitation on sulphur levels in fuels.

Carbon dioxide is not actually classed as a pollutant under MARPOL but there are rules aimed at reducing emissions and there is a goal set by the IMO to decarbonise shipping over the next 50 years.

Black carbon
Another substance that is not yet regulated but which is coming under increasing attention is black carbon, especially with regards to Arctic shipping. There are many who believe that the impact is insignificant but the IMO’s MEPC has decided to pursue the matter.

At MEPC 68 in May 2015, the IMO approved the 2013 ‘Bond et al.’ definition as proposed by the Pollution Prevention and Response Sub-Committee and noting the need for voluntary black carbon measurement studies to be conducted in order to gain experience with the application of the definition and measurement methods, agreed that protocols for such voluntary measurement studies are needed and invited interested parties to submit relevant proposals/information to the next meeting of its Pollution Prevention and Response Sub-Committee.

Following that decision, the IMO’s interpretation of what constitutes black carbon was that it is a distinct type of carbonaceous material, formed only in flames during combustion of carbon-based fuels. It is distinguishable from other forms of carbon and carbon compounds contained in atmospheric aerosol because it has a unique combination of physical properties. With respect to this issue, it was also noted that at this stage measures to reduce the impact on the Arctic of emissions of black carbon from international shipping is not possible.

MARPOL with its six annexes and SOLAS between them regulate many aspects of ship construction aimed at minimising the environmental aspects of ships. Similarly, MARPOL has influenced many operational practices onboard tankers and every other type of ship. These areas are not be covered by this guide, which is focussed on describing the technology and equipment designed to aid compliance with those areas of regulation that can only be met using equipment.

In the main these are regulated by Annexes I, IV, V and VI of MARPOL but there are other areas outside of these where shipping has to meet regulatory demands. As examples, the International Convention on the Control of Harmful Anti Fouling Substances on Ships, 2001 and the International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004 which entered into force in 2018 (although a five-year dispensation has been given by the IMO, meaning it will be 2024 before all ships are subject to its provisions) are being addressed by a new generation of coatings and a growing number of ballast water treatment systems. Ironically, the coatings convention was designed to reduce the impact of biocides on marine life but there are now discussions on imposing new controls on bio-fouling of ships in order to prevent the transfer of species into new areas.

Both ballast water treatment and coatings are the subject of other ShipInsight Guides, which deal with them more comprehensively than they are covered in this.

All of the regulation mentioned so far has been promulgated by the IMO but there are also local regulations in some parts of the world that affect the equipment installed on ships. Once again, ballast water treatment serves an example, with the US having adopted its own rules.

The Energy Efficiency Design Index

In recent years, the issue of climate change, supposedly caused by the emission of greenhouse gases most notably carbon dioxide (CO2), has had an impact on many areas of industrial and social activity around the globe. There are other gases which are considered as causes of global warming but for some reason attention of regulators and politicians has been almost solely focussed on CO2.

It is an inevitable product of the combustion of any fuel containing carbon, which is most fossil fuels including LNG. The air used to support combustion contains oxygen and this will combine with the carbon in the fuel to produce CO2 and other compounds. Any nitrogen in the fuel will be converted to NOx, hydrogen to H2O and sulphur to SOx. Effectively, the only means of reducing CO2 while still burning fuel oil is to burn less, which is the intention of the efficiency regulations developed by the IMO.

In 2011, after extensive work and debate, IMO adopted these mandatory technical and operational energy efficiency measures: The energy efficiency design index (EEDI); ship energy efficiency management plans (SEEMPs) and the energy efficiency operational index (EEOI). They were included in MARPOL Annex VI and entered into force on 1 January 2013.

These measures are aimed at reducing the amount of CO2 produced per unit of work done which is crudely measured as moving one tonne of cargo over a distance of one kilometre. As introduced, the EEDI mandated a regular reduction for new ships at five-yearly intervals with the current framework due to cease in 2025 when ship emissions should be around 30% below those of vessels in service when the regulation began.

At MEPC72 in April 2018, the IMO announced an ambitious (some might say impossible) target for decarbonising the shipping industry. In particular, it set out the following programme of ambitions:

  • Carbon intensity of the ship to decline through implementation of further phases of the energy efficiency design index (EEDI) for new ships;
  • Review with the aim to strengthen the energy efficiency design requirements for ships with the percentage improvement for each phase to be determined for each ship type, as appropriate;
  • Carbon intensity of international shipping to decline;
  • To reduce CO2 emissions per transport work, as an average across international shipping, by at least 40% by 2030, pursuing efforts towards 70% by 2050, compared to 2008; and
  • GHG emissions from international shipping to peak and decline;
  • To peak GHG emissions from international shipping as soon as possible and to reduce the total annual GHG emissions by at least 50% by 2050 compared to 2008 whilst pursuing efforts towards phasing them out, as called for in IMO’s Vision, as a point on a pathway of CO2 emissions reduction consistent with the Paris Agreement temperature goals.

As things stand, it is impossible to completely decarbonise shipping as even the cleanest of fuels presently available do produce some CO2 and in some cases, the benefit compared to oil fuels is actually quite negligible. For the short- to mid-term future, these fuels may provide a bridge towards a lower carbon future but not much more. In the long-term, other technologies will need to be developed.

In 2019, the MEPC decided that some categories of ships were having little difficulty in meeting the scheduled EEDI targets and decided that the 2025 date for Phase 3 could be brought forward by three years. It was also felt that consideration should be given to adding a fourth phase and possibly extending that even further in future. As can be seen from the table of new EEDI limits shown below, the largest container ships will be obliged to be 50% more efficient by 2022 which is well in advance of the targets set as recently as 2018.

Accelerated EEDI Phase 3 Dates and Reductions

Ship type

Starting year

Reduction rate

Gas Carriers

2022 (≥15,000dwt)


2025 (10,000 – 15,000dwt)


2025 (2,000 – 10,000dwt)

0 – 30%**

Container Ships

2022 (200,000dwt and above)


2022 (120,000 – 200,000dwt)


2022 (80,000 – 120,000dwt)


2022 (40,000 – 80,000dwt)


2022 (15,000 – 40,000dwt)


2022 (10,000 – 15,000dwt)

15% – 30% **

General Cargo

2022 (15,000dwt and above)


2022 (3.000 – 15,000dwt)

0 – 30%**


2025 (5,000dwt and above)


2025 (3,000 – 5,000dwt)

0 – 30%**

Combination Carriers

2025 (20,000dwt and above)


2025 (4,000 – 20,000dwt)

0 – 30%**

LNG Carriers

2022 (10,000dwt and above)


Cruise ships having non-conventional propulsion

2022 (85,000 GT and above)


2022 (25,000 – 85,000GT)

0 – 30%**

Entries in bold italics indicate changed requirement
**actual percentage to be extrapolated depending upon dwt

US Pollution laws beyond MARPOL

In general, the US follows the requirements of international regulations such as MARPOL but it is also very active in producing additional regulations or even making alternative laws that may be similar but not identical to IMO rules.

Concurrent with the development of MARPOL before emissions to air were included, the US was introducing its own regulations in the form of the Clean Water Act (CWA) passed by the US Congress in 1972 and covering cleaning up the territorial waters of the US. This was done through the National Pollutant Discharge Elimination System (NPDES) permit programme which controls water pollution by regulating sources that discharge pollutants into the nation’s waters.

In most cases, the NPDES permit programme is administered by individual states but for matters extending beyond individual states, the Environmental Protection Agency (EPA) is the governing body.

Section 301(a) of the CWA prohibits the discharge of any ‘pollutant’ unless authorised by an NPDES permit. Shortly after the enactment of the CWA, the EPA issued a regulation that exempted from NPDES permitting “any discharge of sewage from vessels, effluent from properly functioning marine engines, laundry, shower, and galley sink wastes, or any other discharge incidental to the normal operation of a vessel.”

After the turn of the century, environmentalists began legal actions in some states demanding ships should not be exempted from the regulations. In December 2003, the California federal district and appeals courts ruled that the EPA had exceeded its authority when it excluded ships’ discharges from the NPDES permitting system.

As a consequence, EPA had to implement a permit system for a wide variety of vessel discharges which would affect all US-flagged vessel and foreign-flagged vessels trading to the US. This resulted in the introduction in 2008 of the Vessel General Permit (VGP) that would apply to all affected vessels whose owners filed a Notice of Intent. A VGP provides “NPDES permit coverage nationwide for discharges incidental to the normal operation of commercial vessels greater than 79 feet (24m) in length.”

The initial VGP did not cover ballast water and in the fact sheet that it issued as a guide to the VGP, the EPA emphasises that it fought efforts to require incidental discharges to be permitted, not because it dismissed the significance of aquatic invasive species or other environmental hazards resulting from these discharges, but because, in its view, permitting was not the best or most efficient way of addressing the problem. The EPA notes that Congress has already enacted legislation that directed the US Coast Guard, rather than the EPA, to address and come up with a regulatory programme for the discharge of ballast water and other discharges, and that nothing in the CWA prevented individual states from coming up with regulations to control ballast water discharges under state law.

In 2013, a new version of the VGP was introduced which should have run until 2018 but has since been extended.

This permit regulates 27 specific discharge categories and also provides for improvements to the efficiency of the permit process and clarifies discharge requirements.

For the first time, the final 2013 VGP contains numeric ballast water discharge limits for most vessels and generally aligns with requirements contained within the 2012 US Coast Guard ballast water rulemaking. Additionally, the VGP contains requirements to ensure ballast water treatment systems are functioning correctly. The final permit also provides additional environmental protection for certain vessels. For example, certain high-risk vessels entering the Great Lakes must conduct additional management measures to reduce the risk of introducing new invasive species to US waters. More details of the US rules pertaining to ballast water can be found in the dedicated ShipInsight ballast water guide.

Of far more interest to this guide, the final VGP also contains more stringent effluent limits for oil-to-sea interfaces such as propeller shaft seals, along with exhaust gas scrubber washwater. These will be detailed in relevant chapters of this guide. EPA has also amended several of the VGP’s administrative requirements, including allowing electronic recordkeeping, requiring an annual report in lieu of the one-time report and annual non-compliance report, allowing combined annual reports for some vessel operators.

In September 2018 it was recognised by the US authorities that the renewal of the VGP regulations would not be completed in time to introduce on schedule. Thus, the existing rules were extended to ships already covered by a VGP and those without one were recommended to apply before the end of the year or risk being excluded from US waters.

On 4 December 2018, the US signed into law the Vessel Incidental Discharge Act (VIDA) (Title IX of the Frank LoBiondo Coast Guard Authorization Act of 2018). VIDA requires EPA to develop new national standards of performance for commercial vessel incidental discharges and the USCG to develop corresponding implementing regulations. Pursuant to VIDA, the 2013 VGP rules continue to apply until EPA publishes future standards and the USCG publishes corresponding implementing regulations under VIDA. Currently this is anticipated in 2022.

European and Chinese pollution regulations

In other areas of the globe beyond the US, either individual states or regional groupings also make regulations that affect shipping and result in new technology being needed onboard.

Arguably, the area with the most regulation is the EU which frequently seeks to impose requirements in excess of those covered under IMO rules or earlier than the IMO deadlines. This is despite the fact that individual member states of the EU are signatories to IMO conventions and codes.

One area where this is best exemplified is in connection with sulphur levels in fuels. The basic EU legislation for regulating sulphur emissions from ships was Directive 1999/32/EC. This was amended by Directive 2005/33/EC, which designated the Baltic Sea, the North Sea and the English Channel as sulphur emission control areas (SECAs) which were approved and adopted by the IMO and limited the maximum sulphur content of the fuels used by ships operating in these sea areas to 1.5%. The fuel standards also applied to passenger ships operating on regular service outside the controlled areas.

From 1 January 2010 when the 2005 directive came into force, as well as reinforcing the limits of sulphur for vessels operating in SECAs and limiting the sulphur content of fuels used ashore in the EU, it also introduced legislation governing the maximum sulphur content of fuels used by inland waterway vessels and ships at berth in ports which are part of the European Community. The limit for ships in ports was set at 0.1% sulphur, which is the maximum sulphur content of gas oil under ISO standards.

The rules permit some leeway in that they allow ‘sufficient time’ for the crew to complete any necessary fuel changeover operation as soon as possible after arrival at the berth and as late as possible before departure. Ships in port for periods of less than one hour or those that connect to shore electricity supplies are exempt from the requirement.

Considering the IMO timeline for cutting sulphur levels, the EU is now only out of step in applying the 0.1% limit to ports outside of the two SECA zones.

Away from the EU, China’s Air Pollution Control (Marine Light Diesel) Regulation 01/04/2014 introduced a new sulphur content cap of 0.05% for the locally-supplied marine light diesel (MLD). Hong Kong’s Environmental Protection Department has required all ocean-going vessels to use low sulphur fuel, defined in the new legislation as fuel with sulphur content not exceeding 0.5% by weight, when at berth in Hong Kong waters. All such ships must initiate fuel switch upon arrival at berth, complete the switch to low-sulphur fuel within one hour, then use low-sulphur fuel throughout the berthing period and until one hour after departure.

On 4 December 2015, China announced the establishment of further ship ECAs in the Pearl River Delta, the Yangtze River Delta and the Bohai Bay rim area. The regulation applies to all merchant ships navigating, anchored or under operation in the waters of the control areas. With effect from 1 January 2016, ships were required to follow the requirements current international conventions or local laws/regulations (whichever is stricter) on the emission control of SOx, particulates and NOx. If the port condition allows, ports within control areas may implement stricter requirements than current conventions, regulations such as requiring use of fuel with 0.5% m/m sulphur content or below. The implementation schedule for the new Chinese requirements was:

  • From 1 January 2016, some ports (if the port condition allows) within the control areas may implement the requirement for use of fuel with 0.5% m/m sulphur content or below when ships are alongside or at anchor. Note that this is for any port within the control area, not just the key/core ports;
  • From 1 January 2017, key/core ports of control areas shall implement the requirements for use of fuel with 0.5% m/m sulphur content or below when ships are alongside or at anchor;
  • From 1 January 2018, all ports within control areas shall implement requirements for use of fuel with 0.5% m/m sulphur content or below when ships are alongside or at anchor; and
  • From 1 January 2019, ships entering into control areas shall use fuel with 0.5% m/m sulphur content or below.

It should be noted that following an assessment of the effects of the above actions China will possibly implement requirements for use of fuel with 0.1% m/m Sulphur content or below after 31 December 2019. The requirements for ships at berth or at anchor are applicable from one hour after ships are berthed to one hour before departure. Ships may use other alternative measures to reduce emissions, such as shore power, clean energy systems or scrubbers.

More regulations, including restrictions on use of scrubbers, have been announced in 2019 by Singapore, Norway and Fujairah some with immediate effect.

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