Urban Blue Space Quality Promotion and Health of Residents: Evidence from Qingdao, China

Urban blue spaces (UBSs) play a pivotal role in supporting ecological integrity and public health, yet the causal mechanisms connecting the magnitude of water quality improvements to specific health outcomes remain insufficiently explored. The objective of the study is to investigate the effects of two large-scale surface water quality initiatives on the health and physical activity patterns of residents in Qingdao, China: a river pollution clean-up program and a shoreline and estuary monitoring program. Employing a quasi-experimental difference-in-differences (DID) framework with repeated cross-sectional survey data (2017 and 2018; n = 735), we evaluate effects on self-rated health (SRH), happiness, physical activity levels, and body mass index (BMI). Results reveal that both programs significantly enhanced exercise frequency. River pollution clean-up could promote SRH by 0.319 points on the 5-point scale (β = 0.319, p < 0.05), while shoreline quality monitoring program boosted happiness by 0.233 points on the 5-point scale (β = 0.233, p < 0.05). In contrast, both interventions had no significant effect on BMI (p > 0.1). Subgroup analysis revealed that the health and well-being benefits of water quality improvements varied by gender, age, education, and income level. These findings emphasize the importance of prioritizing high-impact UBS interventions in degraded urban areas and integrating them with accessible infrastructure to optimize health gains in a more effective and equitable way.