Estimating the global burden of infant mortality attributable to ambient particulate pollution: Analysis using a...

Fine particulate matter (PM_2.5) is a major contributor to infant mortality. However, the attributable global burden remains unclear due to the absence of a nonlinear exposure-response function that links all-cause infant mortality to various PM_2.5 concentrations. In this study, we systematically reviewed the literature on PM_2.5 exposure and under-five child mortality, then conducted multicenter epidemiological analyses using Demographic and Health Survey (DHS) data with fixed-effects logit regression. We integrated literature-derived estimates with local PM_2.5-mortality associations across multiple regions. Using meta-regression, we quantified per unit exposure effects to develop a nonlinear exposure-response function, subsequently extrapolated to 189 countries (1998-2019) to estimate the global infant mortality burden attributable to PM_2.5 exposure. The results showed that prenatal exposure was more strongly associated with increased infant mortality in both linear and nonlinear analyses. The local effect of prenatal exposure was higher at the low-concentration end (<20 μg/m³) than at the high-concentration end (>20 μg/m³). The attributable deaths declined from 2.22 to 1.44 million, yet the attributable fraction rose from 32.6% to 39.3%, indicating persistent PM_2.5 risks despite child health improvements. These findings suggest that, although the improved child health partially mitigated the adverse effects of worsening air quality between 1998 and 2019, prenatal PM_2.5 exposure remained a significant risk factor.