Estimation and Spatiotemporal Analysis of NO2 Pollution in East Asia During 2001–2016. Issue 2 (24th January 2022)

• Record Type: Journal Article
• Authors: Hu, Mingyun; Chen, Yiang; Yuan, Dehao; Yu, Rui; Lu, Xingcheng; Fung, Jimmy C. H.; Chen, Wanying; Huang, Yeqi; Lau, Alexis K. H.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-24
• Subjects: NO2 -- East Asia -- machine learning -- exposure -- asthma; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD035129
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Ambient nitrogen dioxide (NO2 ) not only has adverse health effects on humans but also contributes to the production of two major secondary atmospheric pollutants, ozone (O3 ) and fine particulate matter (PM2.5 ). In this study, surface NO2 concentrations in East Asia from 2001 to 2016 were estimated by combining an ensemble backpropagation neural network method, satellite NO2 column data, and reanalysis data. The estimated monthly and annual mean NO2 concentrations were well‐correlated with the observations, with R (correlation coefficient) values of 0.89 and 0.91, respectively. Our results indicate that the NO2 concentrations in most areas of East Asia peaked during 2011–2013. The NO2 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 NO2 exposure, over 25 million South Korea residents (∼45% of the population) were exposed to NO2 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 NO2 concentrations less than 14 ppbv. Based on the estimation, NO2 ‐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. NOx emission inventories vary from country to country in East Asia; thus, more targeted NOx emission‐control policies are urgently required. Plain Language Summary: As one of the major atmospheric pollutants, NO2 contributes to the formation of several secondary atmospheric pollutants and the development of respiratory diseases. Satellite NO2 data and meteorological factors are commonly used to retrieve surface NO2 concentrations. Several regression methods have been adopted to construct models to estimate NO2 pollution concentrations; however, limitations such as low resolution and relatively large bias hinder the performance of these simulations. In this study, we applied a machine learning method to estimate surface NO2 concentrations over East Asia, improving the estimation accuracy and resolution compared with previous models. The spatial distribution pattern revealed that NO2 concentrations were relatively high in most territories in South Korea and the North China Plain. Based on the estimated NO2 concentrations, population NO2 exposure and NO2 ‐related asthma incidence were analyzed for each country. Residents of South Korea and China were exposed to higher NO2 concentrations than those in other countries, and NO2 ‐related asthma incidence increased by 1.37% annually in East Asia from 2001 to 2015. Therefore, more stringent NOx emission‐control policies are urgently needed in East Asian countries. Key Points: An ensemble machine learning method with satellite NO2 and reanalysis data was adopted to estimate surface NO2 concentration in East Asia The populations of South Korea and North China were exposed to the highest NO2 levels, which peaked in 2010 and decreased slightly in 2015 NO2 ‐related asthma incidence increased by 1.37% annually from 2001 to 2015 in East Asia, reaching 139, 000 cases in 2015