Mortality burden due to ambient nitrogen dioxide pollution in China: Application of high-resolution models.

BACKGROUND

A large gap exists between the latest Global Air Quality Guidelines (AQG 2021) and Chinese air quality standards for NO. Assessing whether and to what extent air quality standards for NO should be tightened in China requires a comprehensive understanding of the spatiotemporal characteristics of population exposure to ambient NO and related health risks, which have not been studied to date.

OBJECTIVE

We predicted ground NO concentrations with high resolution in mainland China, explored exposure characteristics to NO pollution, and assessed the mortality burden attributable to NO exposure.

METHODS

Daily NO concentrations in 2019 were predicted at 1-km spatial resolution in mainland China using random forest models incorporating multiple predictors. From these high-resolution predictions, we explored the spatiotemporal distribution of NO, population and area percentages with NO exposure exceeding criterion levels, and premature deaths attributable to long- and short-term NO exposure in China.

RESULTS

The cross-validation Rand root mean squared error of the NO predicting model were 0.80 and 7.78 μg/m, respectively,at the daily level in 2019.The percentage of people (population number) with annual NO exposure over 40 μg/m in mainland China in 2019 was 10.40 % (145,605,200), and it reached 99.68 % (1,395,569,840) with the AQG guideline value of 10 μg/m. NO levels and population exposure risk were elevated in urban areas than in rural. Long- and short-term exposures to NO were associated with 285,036 and 121,263 non-accidental deaths, respectively, in China in 2019. Tightening standards in steps gradually would increase the potential health benefit.

CONCLUSION

In China, NO pollution is associated with significant mortality burden. Spatial disparities exist in NO pollution and exposure risks. China's current air quality standards may no longer objectively reflect the severity of NO pollution and exposure risk. Tightening the national standards for NO is needed and will lead to significant health benefits.