Trace element fractionation between PM10 and PM2.5 in coal mine dust: Implications for occupational respiratory health

Abstract

Investigations into the respiratory health impacts of coal mine particulate matter (PM) face the challenge of understanding its chemical complexity. This includes highly variable concentrations of trace metals and metalloids such as Fe, Ti, Mn, Zn, Ni, V, Cr, Cu, Pb, Cd, Sb, As and Sn, which may be capable of inducing cell damage. Analysis of PM10 and PM2.5 samples size-separated from deposited coal mine dusts collected on PVC flat surfaces at a height of 1.5-2 m inside the second level in the Velenje lignite mine, Slovenia, demonstrates that some of these metallic elements (in this case Cu, Sb, Sn, Pb, Zn, As, Ni) can be concentrated in PM2.5, the most deeply inhalable and therefore potentially most bioreactive size fraction. These elements are likely to be mainly present in silicates, oxides, and perhaps antimonides and arsenides, rather than in the calcareous, carbonaceous or sulphide components which show no obvious affinity for PM2.5. Whereas in the Velenje lignites concentrations of these metallic elements are low and so do not present any obvious extra health risk to the miners, this is unlikely to be the case in mines where unusually metal-enriched coals are being excavated. We therefore recommend that levels of potentially toxic elements in PM2.5 should be assessed where metal- and metalloid-rich coals are being mined worldwide, especially given uncertainties relating to the efficiency of current dust suppression and respiratory protective equipment for such fine particle sizes.