PM2.5-bound heavy metals from the major cities in China: Spatiotemporal distribution, fuzzy exposure assessment and health risk management

In facing the challenge of PM2.5 pollution across China, an overall macro-evaluation of the spatiotemporal pollution distribution and health risk of PM2.5-bound heavy metals at a national level is urgently needed. This study involved a bibliometric analysis of 8 PM2.5-bound heavy metals (Cd, Cr, Hg, As, Pb, Cu, Zn, Ni) in the 27 major cities across China from 2013 to 2019 that was combined with valid data from the published scientific literature. Based on time weight vector, the spatiotemporal metal distributions and their integrated enrichment factors were analyzed, and then a fuzzy health risk assessment model was established to synthetically screen regional priority control regions/pollutants, and explore the pollution trend. The integrated concentrations of As (19.44 ng/m3) and Cd (4.12 ng/m3) in most cities exceeded the limits of the Chinese Ambient Air Quality Standards, while Hg (0.81 ng/m3) and Pb (137.10 ng/m3) did not. Spatially, PM2.5-bound heavy metal pollution generally increased from southern to northern China, with North and Northwest of China being relatively hot regions. For integrated health risks, children (3.31) faced higher non-carcinogenic risks than adults (1.69), with As, Cd, and Cr as the main contributors. The total carcinogenic risk varied from 4.86 × 10−6 to 1.3 × 10−3. The total carcinogenic risk of 77.78% of major cities has reached Grade V (moderate-high risk) or above, and the risk contributions of Cr and As accounted for the largest proportion. The temporal variations showed that the pollution had a recent declining trend in most cities. Finally, 10 major cities and their corresponding metals were determined as the priority control cities/metals. The targeted risk management policies were developed for the identified hierarchical hot cities and their priority pollutants to control were based on the regional pollution trend and source characteristics.