The "Cause-specific hospital admission" chart.

A research team led by Professor Wu Shaowei from the School of Public Health at Xi'an Jiaotong University (XJTU) has published a groundbreaking study in the prestigious journal Nature Medicine.

The article, titled "Hospital admissions attributable to reduced air pollution due to clean-air policies in China", provides a comprehensive evaluation of the health benefits brought by improved air quality following the implementation of China's Air Pollution Prevention and Control Action Plan. For the first time, it identifies black carbon as the primary component of PM_2.5 responsible for negatively affecting health.

Using hospitalization data from urban populations in 292 cities across China between 2013 and 2017, combined with a spatiotemporal deep forest model, the research team made several important discoveries.

They found that the health impact of the black carbon component within PM_2.5 on hospital admissions for various diseases was stronger than that of PM_2.5 as a whole, and this effect remained consistent across multiple models. Exposure to black carbon was significantly associated with hospital admission risks for ten major disease categories, including respiratory, cardiovascular, and mental or neurological conditions. The reduction in depression-related hospitalizations was the most prominent, with a relative decrease of 21.14 percent. Between 2014 and 2017, the reduction in PM_2.5 and black carbon concentrations notably decreased hospitalizations for lower respiratory infections, coronary heart disease, and strokes.

To achieve these findings, the team overcame three major technical challenges. They developed a high-precision exposure model covering six components of PM_2.5, including black carbon and sulfate. They employed a two-stage case-crossover study design to build the exposure-response relationship and created a multi-model validation system to quantify the spatial and temporal differences in health benefits. Their research shows that, within just five years, China's "Air Ten Measures" have achieved public health gains equivalent to what typically takes 20 to 30 years in Western countries, with the drop in black carbon levels playing a particularly important role.

This study holds significant scientific and social value, providing three breakthrough contributions to global air pollution control. Firstly, it offers the first empirical evidence that black carbon should be prioritized as a target component for PM_2.5 reduction. Secondly, it establishes a "China paradigm" for evaluating the health benefits of air quality policies. And lastly, it highlights the critical role of coordinated regional action in narrowing spatial disparities in health outcomes.

The findings have already contributed directly to the improvement of China's environmental policies. They have also encouraged the World Health Organization to consider setting component-specific limits for PM_2.5 and prompted the Ministry of Ecology and Environment to strengthen monitoring of key components like black carbon.

Liu Huimeng, a PhD student from the class of 2022, and Assistant Professor Lei Jian are co-lead authors, with Wu and Associate Professor Liu Yuewei from Sun Yat-sen University serving as co-corresponding authors.