Study: Major drop in ship sulphur emissions confirmed following IMO regulations

Recent global regulations have significantly reduced sulphur emissions from ships, helping to improve air quality in coastal regions – confirmed by a recent international study led by researchers at the National Centre for Atmospheric Science. 

The research, published in Environmental Science: Atmospheres, used aircraft and ground-based instruments to measure sulphur dioxide and nitrogen oxides emitted by ships in the North-East Atlantic and European coastal waters between 2019 and 2023.

The team found that the average sulphur content in ship fuel dropped nearly tenfold in open ocean areas following the International Maritime Organization’s 2020 regulation, which capped sulphur content in marine fuel at 0.5%. 

Before the change, many ships exceeded the previous 3.5% limit. After 2020, only a small number of ships were found to breach the new standard.

In European sulphur Emission Control Areas (SECAs), such as the English Channel and the Port of Tyne, sulphur levels were even lower – well below the stricter 0.1% limit. Interestingly, ports outside these zones, like Valencia in Spain, also showed low sulphur levels, likely due to EU rules requiring cleaner fuel when ships are docked for extended periods.

This is the first study to use aircraft-based measurements and predictions from the Ship Traffic Emission Assessment Model (STEAM3) to assess ship emissions outside of sulphur control zones since the 2020 regulation came into effect. The findings support the widely held view that ships now emit around seven times less sulphur than before the rule change – an important step toward cleaner air and healthier coastal environments.

Note: The research, titled ‘SO2 and NOx emissions from ships in North-East Atlantic waters: in situ measurements and comparison with an emission model’ can be found here. 

Photo credit: shraga kopstein on Unsplash
Published: 8 December, 2025