Complements, Not Substitutes? Health Systems, Institutional Quality, and the PM2.5–NCD Mortality Nexus—A Global Panel Analysis

This study investigates whether Universal Health Coverage (UHC) and institutional quality—proxied by the Corruption Perceptions Index (CPI)—moderate the association between ambient PM2.5 exposure and adult non-communicable disease (NCD) mortality. Using a country-year panel of 157 countries over 2012–2021, we estimated two-way fixed-effects panel regressions with Driscoll–Kraay standard errors. A consistency check confirmed the expected positive association between PM2.5 and air-pollution-attributable mortality (β = 0.247, p = 0.002). However, the direct effect of PM2.5 on NCD mortality was not significant in any specification. Critically, the interaction terms PM2.5 × UHC (β = 0.000485, p = 0.215) and PM2.5 × CPI (β = 0.000838, p = 0.067) were not statistically significant, indicating that neither health-system capacity nor institutional quality significantly moderates the PM2.5–NCD mortality relationship at the global level. These findings contrast with prior studies documenting moderating effects in specific contexts—under-five mortality and West Africa—suggesting that such effects may be context-dependent rather than universally applicable. While UHC showed a positive association with NCD mortality (β = 0.056, p < 0.001) likely reflecting improved diagnosis, reporting, and broader development processes, CPI was negatively associated (β = −0.033, p = 0.029), suggesting that higher institutional quality is associated with lower NCD mortality. Our findings are consistent with the view that emissions reduction and health-system strengthening should be pursued as complements rather than substitutes, implying a dual strategy for low- and middle-income countries: invest in health systems and institutional quality while simultaneously pursuing cleaner energy, transport, and industrial policies.