Do you know what Emission Control Areas (ECAs) are?

Ships are moving global trade around the world, but their exhaust releases sulfur, nitrogen, and fine particles that harm air quality, human health, and the environment. Luckily, Emission Control Areas (ECAs) are here to change that.

What are ECAs and what is their purpose?

Most vessels burn fuels that emit sulfur oxides (SOx), nitrogen oxides (NOx), and fine particulates. These pollutants travel long distances, causing acid rain, particulate air pollution, and health problems such as asthma and heart disease. To address this, the International Maritime Organization (IMO) created Emission Control Areas (ECAs), which are special sea zones with stricter exhaust limits for ships.

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Under IMO’s MARPOL Annex VI, an ECA is legally defined as

Areas where the adoption of special mandatory measures to regulate emissions from ships is required to prevent, reduce and control air pollution from NOx and/or SOx and/or particulate matter (PM) and their attendant adverse impacts on human health and the environment.

In practice, ECAs require ships in certain defined waters to use cleaner fuels or technology to keep pollution at lower levels than the global rules.

For example, ships in an ECA may only burn fuel with at most 0.10% sulfur (by mass), instead of the 0.50% allowed globally since 2020.

These zones initially targeted just sulfur and were called Sulphur Emission Control Areas (SECAs). However, the 2008 amendments to MARPOL Annex VI expanded the concept of SECAs into broader Emission Control Areas (ECAs), allowing regulation of SOx, NOx, and associated particulate emissions.

ECAs cover both international waters and exclusive economic zones. Each ECA’s exact boundaries are set by IMO resolutions and national declarations.

Origin and regulatory background

The concept of ECAs grew out of IMO’s MARPOL Annex VI on air pollution. Annex VI was adopted in 1997 to curb ship exhaust and set a global fuel sulfur cap, allowing special areas with tighter rules. The initial fuel limit in ECAs was 1.5% sulfur.

The Baltic Sea was the first SOx ECA, followed by the North Sea and English Channel. Over time, rules were tightened. In 2010, SECAs were renamed Emission Control Areas and began including particulate matter. In addition, fuel sulfur limits in ECAs were reduced to 0.10%, effective 2015, and a global fuel cap of 0.50% sulfur applied from 2020. IMO also applied Tier III engine standards within ECAs to control NOx.

ECAs are implemented via MARPOL Annex VI and national laws. Many began as regional regulations and were later submitted to IMO for formal adoption.

Existing ECAs: Regions and enforcement dates

The Baltic Sea and North Sea were among the first to be designated, with SOx limits taking effect between 2006 and 2007 and stricter NOx standards applying from 2021.

The North America ECA began enforcing SOx and PM controls in 2012 and NOx limits in 2016, followed by the United States Caribbean Sea in 2014 (with NOx from 2016).

More recently, the Mediterranean Sea was designated as a SECA, with stricter SOx rules coming into effect in May 2025. In addition, in late 2025, Mediterranean States gathered Malta to examine the possible designation of the entire Mediterranean Sea as a Nitrogen Oxides Emission Control Area.

Apart from international ECAs, there are also domestic control areas regulated by nations. For instance, China has established extensive ECAs covering its entire coastline and major inland waterways, requiring ships to use fuel with a maximum 0.5% sulfur content since January 1, 2019. Stricter 0.1% sulfur limits apply in specific inland rivers and the Hainan coastal area, alongside bans on open-loop scrubbers in key areas.

Proposed ECAs and upcoming plans

IMO designated the Canadian Arctic and Norwegian Sea as new Emission Control Areas under amendments to MARPOL Annex VI, officially adopted through Resolution MEPC.392(82) in October 2024.

These ECAs impose stricter limits on NOx, SOx, and Particulate Matter (PM) from ships. While the amendments take effect on 1 March 2026, a phased implementation applies, with a 12-month grace period from the entry into force to allow fuel supply adjustments. For SOx and PM, mandatory compliance begins 1 March 2027.

In addition, the North-East Atlantic ECA, the world’s largest when in force, will span from the Arctic to the Iberian Peninsula and enforce both Tier III NOx and the 0.10% S fuel limit. The ECA will include coastlines of Portugal, Spain, and France, through the British Isles, and up to Iceland and Greenland, and is scheduled to come into force in 2027.

Actions for compliance

ABS has presented the following key recommendations for ensuring compliance with ECAs:

Fuel compliance and changeover procedures: Use low-sulfur fuel (≤0.1% m/m) when operating in SOx ECAs. If using higher-sulfur fuels outside ECAs, ensure systems are flushed before entry and record fuel details, tank volumes, and the date, time, and position of fuel changeover completion.
Exhaust gas cleaning systems: Vessels that continue using higher-sulfur fuels may install scrubbers to reduce sulfur emissions, considering cost, feasibility, and operational impact.
NOx reduction technologies: Evaluate appropriate solutions such as Selective Catalytic Reduction (SCR), Exhaust Gas Recirculation (EGR), or dual-fuel engines depending on engine type and operations.
Alternative fuels: Consider lower-emission fuels like LNG, biofuels, or hydrogen, assessing fuel availability, infrastructure, and engine compatibility.
Engine compliance and certification: Ensure marine diesel engines over 130 kW meet IMO Tier III NOx standards where applicable. Keep EIAPP and IAPP Certificates and the NOx Technical File updated and aligned with the NOx Technical Code 2008.
Logbook and recordkeeping requirements: Record engine tier status when entering/exiting ECAs or when operational status changes, including date, time, and ship position, per MARPOL Annex VI Regulation 13/5.3.
Crew training and awareness: Provide training on emission regulations, fuel procedures, and emission-control technologies.

At a glance

ECAs represent one of the most important regulatory tools for reducing air pollution from the maritime sector.

By imposing stricter limits on sulfur oxides, nitrogen oxides, and particulate matter in designated sea regions, ECAs help protect coastal ecosystems, improve air quality, and reduce health risks for communities living near busy shipping routes.

Over time, these areas have expanded geographically and technologically, reflecting the growing global commitment to cleaner maritime operations.