Ambient and personal PM2.5 exposure assessment in the Chinese megacity of Guangzhou

Introduction: Due to the rapid economic development and the associated increase of transportation, agricultural and industrial activities, the densely populated Pearl River Delta, China has significant problems with air pollution. With a population of almost 13 million residents, the megacity of Guangzhou is of particular interest with respect to environmental health due to its large population and numerous anthropogenic and industrial sources of fine airborne particulate matter (< 2.5 mu m in aerodynamic diameter [PM2.5). Material and methods: During the winter months of November and December 2011, extensive ambient PM2.5 monitoring was simultaneously conducted within nine of 12 districts of Guangzhou. In addition, personal PM2.5 monitoring was carried out within eight of the 12 districts to determine the levels of PM2.5 to which individuals were exposed to over 24-h periods. Results: Results of the ambient monitoring showed average PM2.5 mass concentrations ranging from 52.4 +/- 24.1 (SD, standard deviation) mu g m(-3) (Median: 53.7) in the Conghua District to 106.6 +/- 31.7 mu g m(-3) (Median: 108.1) in the Yuexiu District. Results of the personal monitoring showed average concentrations ranging from 45.4 +/- 21.2 mu g m(-3) (Median: 53.1) in the Conghua District to 92.5 +/- 33.2 mu g m(-3) (Median: 102.4) in the Luogang District. Three of the districts showed moderate to high correlations between ambient and personal PM2.5 (Yuexiu: Spearman's Rho [r(s)] = 0.77, p = 0.072; Panyu: r(s) = 0.59, p = 0.033; Luogang: r(s) = 0.79, p = 0.021). Five of the seven districts had ambient PM2.5 concentrations higher than personal PM2.5 concentrations. An overall correlation analysis of all ambient and personal data shows a high and significant correlation (r(s) = 0.7, p = 0.01). Discussion: This study revealed elevated PM2.5 mass concentrations throughout all of Guangzhou's districts, with ambient PM2.5 levels that consistently exceeded the 24-h standards of both the World Health Organization and the United States Environmental Protection Agency. Results from the PM2.5 personal monitoring program also revealed elevated concentrations. Conclusions: Firstly, based on findings from previous epidemiological studies, one can conclude that this level of PM2.5 burden has strong adverse effects on the inhabitants' health. Secondly, as only three of the districts showed moderate to high correlations between ambient and personal PM2.5 (with two of them being statistically significant), it is likely that the personal monitoring results were greatly influenced by indoor sources of PM2.5. The weak correlations between the ambient PM mass and personal exposure levels underline the demand for future studies measuring personal exposure in different environments with high temporal and spatial resolution, while taking into account detailed activity analyses. (C) 2013 Elsevier Ltd. All rights reserved.