Impacts of discriminated PM on global under-five and maternal mortality.

Globally, it was estimated that maternal and under-five deaths were high in low-income countries than that of high-income countries. Most studies, however, have focused only on the clinical causes of maternal and under-five deaths, and yet there could be other factors such as ambient particulate matter (PM). The current global estimates indicate that exposure to ambient PM (with ≤ 2.5 microns aerodynamic diameter) has caused about 7 million deaths and over 100 million disability-adjusted life-years. There are also several health risks that have been linked PM, including mortality, both regionally and globally; however, PM is a mixture of many compounds from various sources. Globally, there is little evidence of the health effects of various types of PM which may uniquely contribute to the global burden of disease. Currently, only two studies had estimated the effects of discriminated ambient PM, that is, anthropogenic, biomass and dust, on under-five and maternal mortality using satellite measurements, and this study found a positive association in Africa and Asia. However, the study area was conducted in only one region and may not reflect the spatial variations throughout the world. Therefore, in this study, we discriminated different ambient PM and estimated the effects on a global scale. Using the generalized linear mixed-effects model (GLMM) with a random-effects model, we found that biomass PM was associated with an 8.9% (95% confidence interval [CI] 4.1-13.9%) increased risk of under-five deaths, while dust PM was marginally associated with 9.5% of under-five deaths. Nevertheless, our study found no association between PM type and global maternal deaths. This result may be because the majority of maternal deaths could be associated with preventable deaths that would require clinical interventions. Identification of the mortality-related types of ambient PM can enable the development of a focused intervention strategy of placing appropriate preventive measures for reducing the generation of source-specific PM and subsequently diminishing PM-related mortality.