The association of birthweight with fine particle exposure is modifiable by source sector: Findings from a cross-sectional study of 17 low- and middle-income countries.

Background: Low birthweight attributable to fine particulate matter (PM) exposure is a global issue affecting infant health, especially in low- and middle-income countries (LMICs). However, large-population studies of multiple LMICs are lacking, and little is known about whether the source of PM is a determinant of the toxic effect on birthweight.

Objective: We examined the effect on birthweight of long-term exposure to PM from different sources in LMICs.

Methods: The birthweights of 53,449 infants born between September 16, 2017 and September 15, 2018 in 17 LMICs were collected from demographic and health surveys. Long-term exposure to PM in 2017 produced by 20 different sources was estimated by combining chemical transport model simulations with satellite-based concentrations of total mass. Generalized linear regression models were used to investigate the associations between birthweight and each source-specific PM exposure. A multiple-pollutant model with a ridge penalty on the coefficients of all 20-source-specific components was employed to develop a joint exposure-response function (JERF) of the PM mixtures. The estimated JERF was then used to quantify the global burden of birthweight reduction attributable to PM mixtures and to PM from specific sources.

Results: The fully adjusted single-pollutant model indicated that exposure to a 10 μg/m increase in total PM was significantly associated with a -6.6 g (95% CI -11.0 to -2.3) reduction in birthweight. In single- and multiple-pollutant models, significant birthweight changes were associated with exposure to PM produced by international shipping (SHP), solvents (SLV), agricultural waste burning (GFEDagburn), road transportation (ROAD), waste handling and disposal (WST), and windblown dust (WDUST). Based on the global average exposure to PM mixtures, the JERF showed that the overall change in birthweight could mostly be attributed to PM produced by ROAD (-37.7 g [95% CI -49.2 to -24.4] for a global average exposure of 2.2 μg/m), followed by WST (-27.5 g [95% CI -42.6 to -10.7] for a 1.6-μg/m exposure), WDUST (-19.5 g [95% CI -26.7 to -12.6] for a 8.6-μg/m exposure), and SHP (-19.0 g [95% CI -32.3 to -5.7] for a 0.2-μg/m exposure), which, with the exception of WDUST, are anthropogenic sources. The changes in birthweight varied geographically and were co-determined by the concentration as well as the source profile of the PM mixture.

Conclusion: PM exposure is associated with a reduction in birthweight, but our study shows that the magnitude of the association differs depending on the PM source. A source-targeted emission-control strategy that considers local features is therefore critical to maximize the health benefits of air quality improvement, especially with respect to promoting maternal and child health.