Estimating under-five mortality attributable to fine particulate matter brought by wind-blown dust in 100 low- and...

Wind-blown dust (dust PM_2.5) is a major contributor to fine particulate matter (PM_2.5) in low- and middle-income countries (LMICs), yet its impact on under-five mortality (U5M) remains underexplored. In particular, due to the lack of an exposure-response function (ERF) focusing on dust PM_2.5, the relevant burden is evaluated based on pre-established ERFs for total PM_2.5 mass. Our study aimed to evaluate the association between long-term dust PM_2.5 exposure and U5M, estimating the attributable mortality burden in LMICs. Using high-resolution PM_2.5 mass-maps, well-validated dust ratio data, and 125 demographic and health surveys, we applied a fixed-effects Cox model to examine the association between life-course dust PM_2.5 exposure and the survival status of 1 411 851 children from 53 LMICs. Subsequently, we developed a nonlinear ERF by integrating the marginal effects of within-strata exposure variation, and extrapolated this function to estimate the U5M burden attributable to dust PM_2.5 across 100 LMICs, comparing results with two existing ERFs for total PM_2.5. Each 10-μg/m³ increase in dust PM_2.5 exposure was associated with a 7.13% (95% confidence interval [CI]: 4.54-9.78) increase in U5M risk. The ERF indicated no threshold effect at low concentrations and a steeper slope at higher levels. Based on this function, we estimated that dust PM_2.5 contributed to ∼1.74 million, 1.30 million, and 1.07 million U5Ms in 2000, 2010, and 2017, respectively. Notably, these estimates exceeded those derived from pre-established ERFs for total PM_2.5 mass in most countries. Our findings underscore the significant contribution of dust PM_2.5 to the U5M burden and emphasize the importance of early-warning systems to effectively safeguard child health.