Estimation and Spatiotemporal Analysis of NO<sub>2</sub> Pollution in East Asia During 2001–2016
Mingyun Hu, Yiang Chen, Dehao Yuan, Rui Yu, Xingcheng Lu, Jimmy Chi Hung Fung, Wanying Chen, Yeqi Huang, Alexis K.H. Lau
Abstract
Abstract Ambient nitrogen dioxide (NO 2 ) not only has adverse health effects on humans but also contributes to the production of two major secondary atmospheric pollutants, ozone (O 3 ) and fine particulate matter (PM 2.5 ). In this study, surface NO 2 concentrations in East Asia from 2001 to 2016 were estimated by combining an ensemble backpropagation neural network method, satellite NO 2 column data, and reanalysis data. The estimated monthly and annual mean NO 2 concentrations were well‐correlated with the observations, with R (correlation coefficient) values of 0.89 and 0.91, respectively. Our results indicate that the NO 2 concentrations in most areas of East Asia peaked during 2011–2013. The NO 2 concentrations in autumn and winter, especially in the eastern and northern parts of China, were much higher than those in summer. In terms of population NO 2 exposure, over 25 million South Korea residents (∼45% of the population) were exposed to NO 2 concentrations higher than the 2005 World Health Organization's annual standard (40 μg/m 3 , ∼22 ppbv at 25°C) in 2015. In contrast, the entire populations of some developing countries, such as Vietnam, Cambodia, Myanmar, the Philippines, and Lao PDR, were exposed to NO 2 concentrations less than 14 ppbv. Based on the estimation, NO 2 ‐related asthma cases in East Asia increased by 1.37% annually from 2001 to 2015, reaching 139,000 cases (95% confidence interval: 37,400–263,400) in 2015. NO x emission inventories vary from country to country in East Asia; thus, more targeted NO x emission‐control policies are urgently required.