Abstract: Shipping activities contribute to degraded air quality and premature mortalities worldwide, but previous assessments of their health impact have not yet differentiated contributions from domestic and international shipping at the global level. The impacts of domestic shipping can affect different populations, and domestic and international shipping emissions are governed under different regulatory systems. Thus, a consistent global analysis comparing the health impacts from domestic and international shipping could inform policy making in attempts to coordinate policies across multiple scales to address the health burden of shipping emissions.

In this study, we conduct an integrated analysis of global ship emissions and their PM_2.5-related health impacts, in which we differentiate the contributions from domestic and international shipping. We create bottom-up global ship emission inventories based on ship activity records from the Automatic Identification System (AIS), and then apply the GEOS-Chem model and Global Exposure Mortality Model to quanitfy shipping-related PM_2.5-concentrations and associated moralities. We also quantify the public health benefits under different control scenarios including the 2020 0.5% Sulphur Cap, a post-2020 0.1% Sulphur Cap, and a post-2020 Tier III NOx Standard.

We find that 94,200 (95% confidence interval: 84,800 - 103,000) premature deaths were associated with PM_2.5 exposure due to maritime shipping in 2015, of which 83% were associated with international shipping activities and 17% with domestic shipping. Although the global health burdens of ship emissions are dominated by international shipping, the fraction varies by region: 44% of shipping-related deaths in China come from domestic shipping activities. We estimate about 30,200 (27,200 - 33,000) avoided deaths per year under a scenario consistent with a 2020 0.5% Sulphur Cap. We additionally examine two post-2020 control scenarios: we find that a Tier III NOx Standard would have greater benefits than a 0.1% Sulphur Cap, with the two policies reducing annual shipping-attributable PM_2.5-related premature deaths by 33,300 (30,100 - 36,400) and 5,070 (4,560 - 5,540), respectively.