Assessment of heavy metal pollution characteristics and human health risk of exposure to ambient PM2.5 in Tianjin, China

To examine the features of heavy metal pollution of PM2.5 (particulate matter less than 2.5 mu m) in Tianjin, China, as well as the exposure risk of PM2.5 to human health, we analyzed ambient PM2.5 samples collected from a campus of Nankai University in June, August, and October 2012. The concentrations of PM2.5 and heavy metals (Ni, Cu, Pb, Zn, Cr, Cd, Hg, As and Mn) in PM2.5 were analyzed by gravimetric analysis and inductively coupled plasma-mass spectrometry, respectively. The results show that the heavy metals contained in PM2.5 were, in descending order, Cu, Zn, Pb, Mn, Cr, Ni, Cd, As, and Hg. The proportion of Cd exceeded the secondary level of National Ambient Air Quality Standard of China (GB 3095-2012) by 1.3 times, while others were within the limit. Enrichment factor analysis indicated that Cu, Zn, Cd, Pb, and Hg are mainly from anthropogenic sources. Principal component analysis indicated that the main sources of the heavy metals are vehicle exhaust, chemical waste, and coal-burning activities. The nine heavy metals which may cause health issues by exposure through the human respiratory system and should be further examined are Cr, Cd, As, Ni, Cu, Pb, Mn, Zn, and Hg, in the order of decreasing risk levels. With reference to the U.S. EPA standard the risk levels of all nine metals were below the acceptable level (10(-6)/year). (c) 2014 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.