Underappreciated roles of soil nitrogen oxide emissions on global acute health burden.

The recognized importance of ambient fine particulate matter (PM), ozone (O), and nitrogen dioxide (NO) on human health has prompted the world to enact increasingly strict regulations on anthropogenic nitrogen oxides (NO) emissions. However, the health concerns from soil NO, potentially driven by fertilizer input but conventionally categorized as natural sources, remain less studied. Here, we emphasize the underappreciated roles of soil NO emissions on health burden attributable to short-term PM, O, and NO exposure. Globally, we quantify acute health effects using machine-learning-based daily exposure estimates and identify influences of soil NO emissions based on chemical transport model simulations. We find that 72.3% of the globe is affected by soil NO emissions, whose contributions to short-term PM, O, and NO pollution lead to 13.9 (95% Confidence Interval [CI]: 9.1-18.8), 26.0 (18.2-34.2), and 13.9 (10.3-17.5) thousand premature mortality, respectively, in 2019. With distinct variations in regions, seasons, and pollutants, soil NO-originated air pollution poses a global health concern, particularly for developing regions and intensively agricultural areas. In response to the intensive fertilizer use, South Asia, Southern Sub-Saharan Africa, and Central Europe witness the largest soil NO-related health burden of up to 1.6 (95% CI: 1.1-2.1) mortality per 100k population. The overall health risk peaks in May, with O pollution typically dominating the soil NO-attributable health burden during warm seasons and NO or PM during cold months. Our study highlights the necessity of dynamically adapted agricultural strategies for health-oriented multi-pollutant control, among which the improved use of synthetic fertilizers deserves priority under the ever-changing climate.