Source: IMO and Flanders Marine Institute (VLIZ), Belgium; (2020). Emission Control Areas (ECAs) designated under regulation 13 of MARPOL Annex VI (NOx emission control).
The International Convention for the Prevention of Pollution from Ships (MARPOL) established a protocol titled “Prevention of air pollution from ships” that became effective in 2005. Under this protocol, member nations of the International Maritime Organization agree to abide by fuel emission standards that are (about three times) more stringent within selected emission control areas (ECA). Emissions are measured by the sulfur content of bunker fuel as a percentage of its mass (% m/m). While SOx standards were 4.5% m/m outside ECAs and 1.5% m/m inside ECAs in the early 2010s, by 2020, they reached 0.5% and 0.1%, respectively.
Since May 2025, the Mediterranean Sea has joined the list of existing ECAs (i.e., the Baltic Sea, the North Sea, the North American ECA, and the United States Caribbean Sea ECA) for sulfur oxides (SOx) under MARPOL Annex VI Regulation 14. In the future, additional SOx ECAs may be designated, such as the North-East Atlantic Ocean ECA, which would connect the existing ECAs in the Baltic Sea and North Sea with the Mediterranean ECA
ECA impacts maritime shipping in two dimensions related to port access and shipping lanes. About 23% of the global port container throughput is within one of the three ECAs. Even if this share is relatively small, the ports within ECAs serve the wealthiest markets of Europe and North America, such as the Hamburg-Le Havre range and the East and West coasts of the United States. Therefore, shipping lines calling at these ports must use lower sulfur bunker fuel, impacting their service network with other ports that have less stringent emission standards. This substantially impacted bunker fuel sales, such as for Singapore, the world’s largest.
The second dimension is more limited since the existing ECAs are not extensive enough to impact shipping lanes. Traffic going through the English Channel or the North Sea is already bound to the Hamburg-Le Havre range ports and thus subject to ECA regulations. Great circle distance traffic passing by the American West Coast ECA, such as Asia-South America lanes, can be avoided through a deviation.
The impact of ECAs on shipping lanes has become significant since the Mediterranean became an ECA, as a large volume of shipping transits through the region. This may incentivize using the Cape Route, particularly since the Suez Route has become less reliable since 2023 with the Red Sea crisis.