Associations of residential green and blue space with risk of esophageal squamous cell carcinoma and gastric cancer: Mediating roles of air pollution

Introduction Residential natural environments are increasingly recognized as important determinants of human health. However, few studies focus on their associations with risk of esophageal squamous cell carcinoma and gastric cancer (GC). We examined the associations of exposure to green and blue space with gastroesophageal cancer (GEC) risks, and explored the interaction and mediating roles of ambient PM 2.5 and NO 2 . Methods This population-based case-control study in Taixing included 2,200 GEC cases (1332 ESCC and 868 GC cases) and 1711 controls. The 30 m resolution Normalized Difference Vegetation Index (NDVI) and China Land Cover Dataset were used to estimate NDVI values and the proportions of green space (vegetation) and blue space (water bodies) within 300-, 1,000-, and 3,000-m buffers around residential addresses. PM 2.5 and NO 2 concentrations were derived from satellite-based estimates. Long-term exposure was defined as the 3-year average before recruitment. Logistic regression models were used to estimate the associations. The interaction and causal mediation analyses were further conducted. Results Within the 3,000-m buffer, higher NDVI (odds ratio (OR) = 0.81 per standard deviation increase; 95% confidence intervals (CIs), 0.75-0.87) and green space proportion (OR = 0.89; 95% CI, 0.83-0.96) were associated with lower GEC risks, while higher blue space proportion was associated with increased risks, particularly for GC (OR = 1.20; 95% CI, 1.11-1.31). Long-term exposure to PM 2.5 and NO 2 was positively associated with GEC risks, and mediated 24.9%-33.8% of the protective associations of green space, and 26.9%-42.0% of the adverse associations of blue space. Conclusions Green and blue spaces were heterogeneously associated with GEC risk, partially mediated by PM 2.5 and NO 2 , highlighting the importance of integrating space planning with quality management to promote public health.