A new international study led by researchers at the National Centre for Atmospheric Science (NCAS) has confirmed that recent global regulations have significantly reduced sulphur emissions from ships, helping to improve air quality in coastal regions.
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 Organisation’s 2020 regulation, which capped sulphur content in marine fuel at 0.5 per cent.
Before the change, many ships exceeded the previous global limit of 3.5 per cent sulphur. After 2020, however, only a small number of ships were found to breach the new, stricter standard.
“I think it was generally expected that the regulations would be adhered to and this research shows evidence that this is the case. I’m not sure why some ships still exceed the limits – it could be that exhaust scrubbing systems are not working very well or that high sulphur fuel is still being used in some cases,” said Professor James Lee, an atmospheric chemist at NCAS and the University of York.
In the European Sulphur Emission Control Areas (SECAs), such as the English Channel, fuel sulphur levels were even lower – well below the stricter SECA-limit of 0.1 per cent. 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 global 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.
Link to the article: https://pubs.rsc.org/en/content/articlelanding/2025/ea/d5ea00089k
Source: NCAS News, 28 November 2025
