[Pollution characteristics and health risk assessment of heavy metals in PM(2.5) in Lanzhou].

Objective: To understand the pollution characteristics and assess the pollution health risks of heavy metals in atmospheric PM(2.5) in Lanzhou. Methods: According to the regional characteristics of air pollution and industrial distribution characteristics in Lanzhou, atmospheric PM(2.5) was sampled monthly in Chengguan and Xigu Districts from January, 2015 to December, 2016. Detected the concentration of PM(2.5) and 12 kinds of elements (Sb, Al, As, Be, Cd, Cr, Hg, Pb, Mn, Ni, Se and Tl) by weighing method and inductively coupled plasma mass spectrometry. Enrichment factor and geo-accumulation index were used to describe the pollution characteristics, while health risk assessment was conducted using the recommended United States Environmental Protection Agency (USA EPA) model. The health risks of non-carcinogens were evaluated by non-cancer hazard quotient (HQ), the non-carcinogenic risk was considered to be negligible when HQ<1, HQ>1 meant a health risk. With a single contaminant cancer Risk value to evaluate the health risks of carcinogens, when the Risk value between 10(-6) to10(-4) as an acceptable level. Results: The daily average concentrations of PM(2.5) was 83.0 μg/m(3), 77.0 μg/m(3) in Chengguan and Xigu Districts, respectively, during the sampling periods, and the concentration of PM(2.5) in winter/spring was higher than summer/fall in both districts. The concentration of Al in PM(2.5) was the highest and other elements in descending order: Pb, Mn, As, Sb/Cd, Tl in both districts. Enrichment factor results showed that Al and Mn were mainly affected by natural factors, the rest of five elements were all typical man-made pollution elements and according to geo-accumulation index pollution level of Cd was the strongest in the winter. The results of health risk assessment showed that Mn had the highest non-cancer risks (HQ>1) and affected the health of the children seriously. HQ reached up to 2.44 and 1.79 in Chengguan and Xigu Districts, respectively. Pb, As, Sb, Cd had slight health impact (HQ<1), could be negligible. The cancer risks range of As, Cr were 6.33×10(-6) to 6.46×10(-5) between the acceptable level of risk (10(-6) to 10(-4)), which indicated that As and Cd had potential cancer-risks. Conclusions: The pollution level of atmospheric PM(2.5) and the heavy metals in it was still grim;the non-cancer risks caused by multiple metals on children deserved attention. Although the cancer risks of As and Cd were between the acceptable level of risk, the potential cancer risk still shall not be ignored.