ARTICLE 
COMMUNICATIONS EARTH & ENVIRONMENT | https://doi.org/10.1038/s43247-023-01050-7 
ith a death toll of up to 8.8 million premature deaths 
We: year, anthropogenic air pollution has been iden- 
tified as the global leading cause of death! Air pol- 
lution from ocean-going vessels (OGVs) is one of the main 
sources of air pollution. Sofiev et al. have calculated that up to 
800,000 of these premature deaths can be attributed to OGVSs?. 
These are mainly caused by fine particulate matter known as 
PM‚„5.This PM, can be generated during the combustion pro- 
cess; however, a substantial amount of secondary PM„25 is also 
formed from other pollutants like sulfur oxides (SO,), nitrogen 
oxides (NO,) and Volatile Organic Compounds (VOCs)?7. Air 
pollutants from OGVs—S$SO,, NO, Ozone (Os) and VOCs—a also 
have direct adverse effects on human health and the environment. 
In 2014, OGVs were responsible for 13% and 14% of global 
anthropogenic emissions of SO, and NO,, respectively®-15. 
The regulations put in place to reduce emissions from OGVs 
fall under the MARPOL Convention of the IMO!*, Annex VI of 
the revised MARPOL Convention aims for a gradual decrease of 
global air pollution by SO, and NO, from OGVs!5 (Supple- 
mentary Notes 1). In addition, MARPOL Annex VI introduced 
ECAs with tighter emissions standards (Supplementary 
Fig. 1A-C) and is ratified by 105 countries representing 96.81% of 
the gross tonnage of the world merchant fleet!°-20 
According to the International Maritime Organization (IMO), 
thanks to the establishment of Emission Control Areas (ECAs) 
and the stricter SO, emission limits in 2015, SO, emissions fell by 
28.6% between 2014 and 2017, while NO, reported a 1.2% 
increase over the same period!?. Sofiev et al. have estimated that 
before the strengthening of the global sulfur emission regulations 
for OGVs in 2020, SO, and sulfur-related particles in OGV 
emissions were responsible for up to 403,300 premature deaths a 
year and 14 million cases of childhood asthma®. With the 
introduction of global emission regulations for OGVs, it was 
estimated that 263,300 premature deaths (—-33%) and 7.6 million 
cases of childhood asthma (—54%) could be avoided?*, When 
concerning NO,, the health benefits of introducing NO, 
emission regulations are not immediately observed as new 
emission abatement technology needs to be introduced to be 
compliant with the defined emission limits of the regulations. The 
compliance rate is therefore linked to the scrapping rate, ie., the 
rate at which old OGVs are scrapped and replaced by new OGVs 
as well as the engine overhaul rate, i.e., the rate at which old 
engines are replaced by new engines with lower emission limits®. 
Zhang et al. have estimated that the application of the latest 
introduced Tier III NO, emission standards is the most advan- 
tageous approach to further reduce the detrimental impact of 
shipping on human health, as it would reduce up to 36,400 
premature deaths per year‘. The recently completed EU-funded 
Shipping Contributions to Inland Pollution Push for the Enfor- 
cement of Regulations (SCIPPER) project also recommended the 
establishment of further NO, Emission Control Areas 
(NECAs)?!. It should be highlighted that in order to attain the 
afore-mentioned health benefits a high compliance rate of 
international emission standards for OGVs needs to be reached. 
Despite the fact that the abovementioned publications pro- 
jected important health benefits from the implementation of 
international maritime emission regulations and that emissions 
models predict a decrease in air pollution from shipping??23, 
there still remains a research gap regarding the effectiveness of 
che established international regulations in reducing real-world 
emissions from OGVs in the wider ECAs. At the national level, 
Van Roy et al. showed varying results of the success of interna- 
tional regulations to improve air quality in Belgium? 
The main objective of this article is therefore to examine the 
effects of the implementation of the European ECAs and other 
international maritime regulations in the wider North Sea and the 
Baltic Sea on OGVs’ emissions. This is accomplished in a three- 
step approach. As a first step, the effects of international emis- 
sions regulations in the Bonn Agreement (BA) area (North Sea 
and North-East Atlantic area) (Supplementary Fig. 2) are exam- 
ined. This was done by analyzing compliance rates based on more 
:han 100,000 remote OGV emission measurements (Supple- 
mentary Table 2) collected by the BA Contracting Parties (CPs) 
asing in-situ air quality (sniffer) sensors (Supplementary Meth- 
ods 1). In the second step, data on (1) emission violations and 
venalties for the BA; and (2) overall port inspection results for the 
entire EU were examined. In the third step, satellite data for the 
years 2018-2022 was used to assess any changes in the atmo- 
spheric concentrations of SO, and NO, in the European ECAs. 
The presented work reveals that international regulations on fuel 
sulfur content (FSC) are well enforced by the BA Parties and by 
extension by the entire EU. Compliance rates are well under 
control and the results of this study show that SO, non- 
compliance has reduced substantially since the introduction of 
che global sulfur cap. The number of recorded infringements in 
BA and EU ports follows a similar trend. Based on satellite data it 
was found that atmospheric SO, concentrations inside the ECA 
nave decreased since the introduction of the global sulfur cap. In 
contrast, this article demonstrates that NO, emission regulations 
are less successful, with NO, emissions from OGVs even 
increasing. 
Results 
Regionwide analysis of the remote monitoring data. Non- 
zompliance data from all remote measurement stations and 
deployments was collected based on three different cutoff levels. 
This allows the assessment of the severity of the non-compliance 
sehavior in addition to a temporal and spatial non-compliance 
trend analysis. For the main results, the 0.15% FSC cutoff level 
was used. 
Temporal sulfur compliance trends. A decreasing trend in FSC 
non-compliance rates was observed across all measurement 
‘ocations within the European Sulfur Emission Control Area 
‘SECA) regions. The non-compliance rate decreased from 7.1 to 
0.7%, with an average non-compliance rate of 1.5% when a 0.15% 
FSC cutoff level is used (Fig. 1). The pattern is similar for the 
ather cutoff levels (Supplementary Fig. 3A, B). Following the 
‘mplementation of the global sulfur cap in 2020, the non- 
compliance rates reached their lowest point, with an average non- 
compliance rate of 0.6%. It is important to acknowledge that the 
‚mplementation of the sulfur cap in 2020 coincided with the 
global COVID-19 pandemic, which led to reduced fuel prices?>26, 
Additionally, several monitoring operations observed a slight 
‚.ncrease in non-compliance, starting in 2022. This increase can be 
attributed to the rise in marine fuel prices resulting from the 
Russian invasion of Ukraine and the subsequent global price 
inflation?®. 
Among the different remote measurement operations applied 
5y the SECA countries, the French measurements with the 
:emote piloted airborne systems (RPAS) exhibited the highest 
a0on-compliance rates. The average non-compliance rate was 
9.4% and therefore substantially higher than the non-compliance 
observed by the other remote measurement operations, which 
varied between 0.1 and 3.7% for the same period. When 
considering the remote monitoring locations that conducted 
measurements throughout the entire 2015-2022 period, the 
Belgian airborne measurements recorded the highest non- 
compliance rate for the 0.15% FSC cutoff level (5.2%). However, 
che Danish helicopter measurements displayed the highest non- 
compliance rate for the 0.13% FSC cutoff level (8.5%). This 
COMMUNICATIONS EARTH & ENVIRONMENT | (2023)4:391 | https: //dol.0rg /10.1038/s43247-023-01050-7 | www.nature.com/cammsenv