Estimating the global burden of infant mortality attributable to ambient particulate pollution: Analysis using a nonlinear exposure-response function that combines multinational linear effect estimates

Public summary

* Prenatal exposure to PM2.5 is significantly associated with infant mortality.

* Based on best-available evidence, the exposure-response function was monotonic and sublinear.

* In 2019, prenatal exposure to PM2.5 could contribute to 1.44 million infant deaths.

* During 1998–2019, total number of PM2.5-attributed infant deaths was reduced, but the fraction increased.

* The trend could be explained by improved child healthcare and worse air quality.

Abstract

Fine particulate matter (PM2.5) 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 PM2.5 concentrations. In this study, we systematically reviewed the literature on PM2.5 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 PM2.5-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 PM2.5 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 PM2.5 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 PM2.5 exposure remained a significant risk factor.