Quantifying the environmental and health benefits of ship emission control policies in Guangdong of China.

Ship emissions are the main source of air pollution in coastal areas, prompting China to progressively implement the Domestic Emission Control Area (DECA) policy since 2016. In order to evaluate the effectiveness of this policy, we established a comprehensive framework combining high-resolution emission inventories, air quality modeling (WRF-CMAQ), observation-fusion (SMAT-CE), and health benefit assessments (BenMAP-CE) to quantify its impacts on Guangdong Province in 2022. The policy reduced SO2, NOx, and PM2.5 emissions from ships operating in Guangdong and its adjacent waters by 77.8%, 36.7%, and 72.0%, respectively. These reductions decrease the provincial annual mean PM2.5 by 0.37 μg/m3, while localized reductions in core port cities like Zhuhai reached 1.12 μg/m3. These reductions also induced seasonal variations in O3: widespread summer mitigation (-0.28 μg/m3) was largely counterbalanced by winter increases (+0.34 μg/m3) in the VOC-limited coastal core. Driven by the air quality improvements, the policy avoided approximately 1984 premature deaths. Health benefits were unevenly distributed, heavily favoring cities like Shenzhen due to significant air quality improvements and massive exposed populations. The fuel sulfur limit universally drove health benefits across all cities. In contrast, while NOx Tier standards and shore power adoption benefited peripheral coastal cities, their concentrated deployment in the PRD core weakened the local NO titration effect, triggering localized O3 increases under VOC-limited conditions. The continued implementation of DECA, coupled with the synergistic land-sea management strategies, will ultimately promote the simultaneous reduction of PM2.5 and O3, securing comprehensive air quality and health benefits. This study provides a scientific foundation for optimizing control strategies for sustainable coastal development.