References 1. Vohra, K. et al. Global mortality from outdoor ?ne particle pollution generated by fossil fuel combustion: results from GEOS-Chem. Environ. Res. 195, 110754 (2021). 2. Landrigan, P. J. et al. The Lancet Commission on pollution and health. Lancet 391, 462–512 (2018). 3. So?ev, M. et al. Cleaner fuels for ships provide public health bene?ts with climate tradeoffs. Nat. Commun. 9, 406 (2018). 4. Zhang, Y., Eastham, S. D., Lau, A. K., Fung, J. C. & Selin, N. E. Global air quality and health impacts of domestic and international shipping. Environ. Res. Lett. 16, 084055 (2021). 5. Liu, H. et al. Health and climate impacts of ocean-going vessels in East Asia. Nat. Clim. Change 6, 1037–1041 (2016). 6. Viana, M. et al. Estimated health impacts from maritime transport in the Mediterranean region and bene?ts from the use of cleaner fuels. Environ. Int. 138, 105670 (2020). 7. World Health Organization. Air Quality Guidelines: Global Update 2005: Particulate Matter, Ozone, Nitrogen Dioxide, and Sulfur Dioxide (World Health Organization, 2006). 8. IMO. Third IMO GHG Study 2014 Executive Summary and Final Report. www.imo.org (2015). 9. Corbett, J. J., Fischbeck, P. S. & Pandis, S. N. Global nitrogen and sulfur inventories for oceangoing ships. J. Geophys. Res. Atmos. 104, 3457–3470 (1999). 10. Corbett, J. J., Wang, C., Winebrake, J. J. & Green, E. Allocation and Forecasting of Global Ship Emissions ANNEX Allocation and Forecasting of Global Ship Emissions Prepared for the Clean Air Task Force. https://www.researchgate. net/publication/241579973 (2007). 11. Corbett, J. J. & Fischbeck, P. S. Emissions from ships. Science 278, 823–824 (1997). 12. Faber, J. et al. Fourth IMO GHG Study 2020 Full Report (2021). 13. Corbett, J. J. & Koehler, H. W. Updated emissions from ocean shipping. J. Geophys. Res. 108, 4650 (2003). 14. IMO. International Convention for the Prevention of Pollution from Ships 1973, as modi?ed by the Protocol of 1978 relating thereto (adopted 17 February 1978 (MARPOL), in force 2 October 1983) 1340 UNTS 61, as amended. International Maritime Organization. 15. Amendments to the Annex of the Protocol of 1997 to amend the International Convention for the Prevention of Pollution from Ships, 1973, as modi?ed by the Protocol of 1978 relating thereto (2021 Revised MARPOL Annex VI), Resolution MEPC.328(76), Entered into Force on 1 November 2022. 16. IMO. Status of IMO Treaties: Comprehensive Information on the Status of Multilateral Conventions and Instruments in Respect of Which the International Maritime Organization or Its Secretary-general Performs Depositary or Other Functions. https://www.imo.org/en/About/Conventions/ Pages/StatusOfConventions.aspx (2023). 17. MEPC. List of Special Areas, Emission Control Areas and Particularly Sensitive Sea Areas, Circular MEPC.1/Circ.778/Rev.3 of 2 July 2008. International Maritime Organization. 18. MEPC. Amendments to the Annex of the Protocol of 1997 to amend the International Convention for the Prevention of Pollution from Ships, 1973, as modi?ed by the Protocol of 1978 relating thereto. Amendments to MARPOL Annex VI (Designation of the Baltic Sea and the North Sea Emission Control Areas for NOx Tier III control), ResolutionMEPC.268(71), Adopted on 7 July 2017, Entered into Force on 1 January 2019. International Maritime Organization. 19. MEPC. Proposal to Designate the North Sea as an Emission Control Area for Nitrogen Oxides (submitted by Belgium et al.), Resolution MEPC.70/5/Rev.1. International Maritime Organization. 20. MEPC. Amendments to the Annex of the Protocol of 1997 to amend the International Convention for the prevention of pollution from ships, 1973, as modi?ed by the Protocol of 1978 relating thereto (Designation of the United States Caribbean Sea Emission Control Area and exemption of certain ships operating in the North American Emission Control Area and the United States Caribbean Sea Emission Control Area under regulations 13 and 14 and Appendix VII of MARPOL Annex VI), Resolution MEPC.202(62) Adopted on 15 July 2011. International Maritime Organization. 21. Fridell, E. et al. SCIPPER Project D5.5 Policy Recommendations Related to Regulations, Monitoring and Enforcement. https://www.scipper-project.eu/ library/ (2023). 22. Johansson, L., Jalkanen, J.-P. & Kukkonen, J. Global assessment of shipping emissions in 2015 on a high spatial and temporal resolution. Atmos. Environ. 167, 403–415 (2017). 23. Jalkanen, J.-P., Johansson, L. & Kukkonen, J. A comprehensive inventory of ship traf?c exhaust emissions in the European sea areas in 2011. Atmos. Chem. Phys. 16, 71–84 (2016). 24. Van Roy, W. et al. Assessment of the effect of international maritime regulations on air quality in the Southern North Sea. Atmosphere 14, 969 (2023). 25. Ship & Bunker. Bunker Fuel Prices for Rotterdam between 2015 and 2019 (2019). 26. Van Roy, W. et al. Measurement of sulfur-dioxide emissions from ocean-going vessels in Belgium using novel techniques. Atmosphere 13, 1756 (2022). 27. Mellqvist, J., Conde, V., Beecken, J. & Ekholm, J. CompMon Report: Certi?cation of an Aircraft and Airborne Surveillance of Fuel Sulfur Content in Ships at the SECA Border (Chalmers University of Technology, 2017). 28. Van Roy, W. et al. Airborne monitoring of compliance to NOx emission regulations from ocean-going vessels in the Belgian North Sea. Atmos. Pollut. Res. 13, 101518 (2022). 29. Knudsen, B., Lallana, A. L. & Ledermann, L. NOx Emissions from Ships in Danish Waters Assessment of Current Emission Levels and Potential Enforcement Models (Danish Environmental Protection Agency, 2022). 30. Jalkanen, J.-P. et al. Extension of an assessment model of ship traf?c exhaust emissions for particulate matter and carbon monoxide. Atmos. Chem. Phys. 12, 2641–2659 (2012). 31. Jalkanen, J.-P. et al. A modelling system for the exhaust emissions of marine traf?c and its application in the Baltic Sea area. Atmos. Chem. Phys. 9, 9209–9223 (2009). 32. The SCIPPER Project. SCIPPER Project Finds High Nitrogen Oxides Emissions of Tier III Vessels from Remote Measurements in North European Seas. https:// www.scipper-project.eu/news/ (2023). 33. Frederickson, C. et al. In-use emission measurements from two high-speed passenger ferries operating in California with Tier 2 and Tier 3 marine diesel engines. Emiss. Control Sci. Technol. 8, 109–121 (2022). 34. Magnusson, M., Fridell, E. & Härelind, H. Improved low-temperature activity for marine selective catalytic reduction systems. Proc. Inst. Mech. Eng. M 230, 126–135 (2016). 35. The European Commission. Commission Implementing Decision (EU) 2015/ 253 of 16 February 2015 Laying Down the Rules Concerning the Sampling and Reporting under Council Directive 1999/32/ec as Regards the Sulphur Content of Marine Fuels, OJ L 41/55, 17.02.2015. References to the Repealed Directive 1999/32/EC Shall Be Construed as References to Directive 2016/802 (Art. 19 Directive 2016/802) (The European Commission, 2015). 36. Directive (EU) 2016/802 of the European Parliament and of the Council of 11 May 2016 relating to a reduction in the sulphur content of certain liquid fuels, 12.05.2016. O. J. L. 132, 58–78 (2016). 37. Riess, T. C. V. W. et al. To new heights by ?ying low: comparison of aircraft vertical NO2 pro?les to model simulations and implications for TROPOMI NO2 retrievals. Preprint at EGUsphere. https://doi.org/10.5194/egusphere- 2023-1059 (2023). 38. Van Roy, W. et al. The role of Belgian airborne sniffer measurements in the MARPOL Annex VI Enforcement Chain. Atmosphere 14, 623 (2023). 39. Majamäki, E. & Jalkanen, J.-P. SCIPPER Project D4.2 Updated Inventories on Regional Shipping Activity and Port Regions. https://www.scipper-project.eu/ library/ (2021). 40. Marine Environment Protection Committee. Assessment of Low-Load Performance of IMO NOX Tier III Technologies Submitted by Canada. MEPC.80/5/1 (MEPC, 2023). 41. BLG. Review of MARPOL Annex VI and the NOx Technical Code Compliance and testing issues for Tier III engines Submitted by the United States BLG 12/6/23 (Subcommittee on Bulk Liquid and Gasses, 2007). 42. IMO. IMO progress on revised GHG strategy, Mediterranean ECA adopted. https://www.imo.org/en/MediaCentre/PressBrie?ngs/pages/MEPC-79.aspx (2022). 43. The Bonn Agreement. Accession of Spain to the Bonn Agreement. https://www. bonnagreement.org/news/accession-spain/ (2022). 44. Schallier, R. & Van Roy, W. Oil pollution in and around the waters of Belgium. Oil Pollution in the North Sea, Vol. 41, 93–115 (Springer, 2014). 45. Lagring, R. et al. Twenty years of Belgian North Sea aerial surveillance: a quantitative analysis of results con?rms effectiveness of international oil pollution legislation. Mar. Pollut. Bull. 64, 644–652 (2012). 46. Bellefontaine, N. & Johansson, T. The role of the International Maritime Organization in the prevention of illegal oil pollution from ships: North Sea special status area. Oil Pollution in the North Sea, 49–67. https://doi.org/10. 1007/698_2014_294 (Springer, 2014). 47. The Bonn Agreement. Text of the Bonn Agreement, Agreement for cooperation in dealing with pollution of the North Sea by oil and other harmful substances. 1–29. https://www.bonnagreement.org/publications. (2022). 48. Explicit ApS. Airborne Monitoring of Sulphur Emissions from Ships in Danish Waters: 2019 Campaign Results. https://www2.mst.dk/Udgiv/publications/ (2020). 49. Explicit ApS. Airborne Monitoring of Sulphur Emissions from Ships in Danish Waters: 2020 Campaign Results. https://www2.mst.dk/Udgiv/publications/ (2021). COMMUNICATIONS EARTH & ENVIRONMENT | https://doi.org/10.1038/s43247-023-01050-7 ARTICLE COMMUNICATIONS EARTH & ENVIRONMENT | (2023) 4:391 | https://doi.org/10.1038/s43247-023-01050-7 | www.nature.com/commsenv 15