Trace elements pollution and toxicity of airborne PM10 in a coal industrial city

Trace elements in particulate matter associated with coal industries hold high risk to human health. Understanding the contents and occurrences of modes of these elements as well as their contribution to particulate toxicity is significant both environmentally and pathologically. A total of 24 PM10 samples were collected in Pingdingshan City, a coal industrial city in North China, in both winter and summer of 2008. An inductively coupled plasma mass spectrometry (ICP–MS) was used to determine the concentrations of 12 trace elements associated with coal industries (Cr, Ni, Cu, Zn, As, Mo, Cd, Sn, Sb, Tl, Pb, and Bi) in PM10 samples. The results indicated that the trace element concentrations were higher in winter than in summer; due mainly to more coal combustion during winter and to the different meteorological conditions of these two seasons. The soluble proportions of these trace elements compared with total values of intact whole samples were higher in winter than in summer, and this difference was attributed mainly to more SO2 reacting with pre–existing particles to form soluble particles in winter. Of all the analyzed elements, Ni, Tl, Sb, Mo, and Cd occurred mainly in the soluble state (>50% in the soluble fraction), Cr, Cu, Zn, and As occurred in both the soluble and insoluble state (20% to 50% in the soluble fraction), and Sn, Pb, and Bi occurred mainly in the insoluble state (<20% in the soluble fraction). A plasmid DNA assay indicated that winter samples had higher toxicity than summer samples. The correlation of PM10 toxicity (TD50 value) with the contribution of various trace elements to DNA damage (trace element concentration) was further analyzed, and the results indicated that PM10 toxicity was caused mainly by the soluble fractions of trace elements, including those of Ni, Pb, Cu, Cd, As, Zn, Cr, and Tl, which were the major toxic trace elements in Pingdingshan PM10.