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International maritime regulation decreases sulfur 
dioxide but increases nitrogen oxide emissions in 
the North and Baltic Sea 
Ward Van Roy@ Benjamin Van Roozendael@/, Laurence Vigin@/, Annelore Van Nieuwenhove!, 
Kobe Scheldeman’, Jean-Baptiste Merveillel, Andreas Weigelt?, Johan Mellqvist@ 3, Jasper Van Vliet@®“* 
Danielle van Dinther®, Jorg Beecken®©, Frederik Tack’, Nicolas Theys’ & Frank Maes® 
Sulfur dioxide and nitrogen oxide emissions from shipping have been regulated internationally 
for more than fifteen years. Emissions reduction from shipping provides benefits for human 
health and the environment, but the effectiveness of regulations in reducing ship emissions is 
less well understood. Here, we examine how the establishment of European Emission Control 
Areas and other international maritime regulations in the North and Baltic Seas affect sulfur 
dioxide and nitrogen oxide emissions in the region. We combine and analyze more than 
110,000 ship plume measurements, inspection results, and satellite data from 2018 to 2022. 
We find that compliance rates for sulfur emissions are higher near ports than in open waters. 
lowever, the regulations did not affect the concentration of nitrogen oxide emissions, which 
ıncreased in the past three years. These findings highlight the need for enhanced emission 
regulations that improve air quality. 
“Royal Belgian Institute of Natural Sciences, Vautierstraat 29, 1000 Brussels, Belgium. ? Federal Maritime and Hydrographic Agency, Bernhard-Nocht-Straße 
78, 20359 Hamburg, Germany. 3Chalmers University of Technology, Hörsalsvägen 11, 412 96 Gothenburg, Sweden. “ Human Environment and Transport 
aspectorate, Rijnstraat 8, 2500 The Hague, the Netherlands. >TNO Innovation for life, Westerduinweg 3, 1755 LE Petten, the Netherlands. 6 Explicit ApS, 
Teknikerbyen 5, 2830 Virum, Denmark. ’ Royal Belgian Institute for Space Aeronomy, Ringlaan 3, 1180 Brussels, Belgium. 5 Ghent University, Faculty of Law 
& Criminology, Universiteitstraat 4, 9000 Ghent, Belgium. email: wvanroy@naturalsciences,be 
ZOMMUNICATIONS EARTH & ENVIRONMEN | ‚2023)4:391 I https: //doi.o0rg /10.1038/s5s43247-023-01050-7 | www.nature.com/commsenv