Metalliferous airborne particulate matter in urban and industrial sites

Mixtures of respirable, bioavailable metalliferous airborne particles (e.g., Fe, Mn, Sn, Zn, Ba, Ni, Pt, Pd, Rh, Ce) provide a potential health hazard for those living in urban and industrial environments. A study of airborne particulate matter, involving thousands of analyses of particles from different sites across the UK, is revealing significant differences in the metal content of respirable-particle cocktails. The study uses a high-volume collector, the first employed in Europe, to obtain relatively large amounts of PM10 and PM2.5 over short periods of time, and thus a rapid supply of enough fresh material for toxicological assays and particle characterization. The sampler uses a stack of three impact levels. The top level collects particles above 10 µm on a polyurethane foam (PUF, (H2N-C(=O)O-CH2CH3)) substrate. The middle level is designed to collect 10-2.5 µm particles on a PUF, and finally the lowest level collects particles smaller than 2.5 µm on a third PUF substrate. These substrates are chemically inert and have a porous texture, allowing maximum surface for collection and relative ease of characterization using SEM and FESEM. To date, PM10 and PM2.5 samples have been collected, for a month each, in three urban sites (Cardiff, London and Birmingham), two industrial locations (Port Talbot and Sheffield) and one rural location (Cornwall). Metalliferous particles are mainly derived from detrital, industrial, and traffic-related sources. Fe is ubiquitous, commonly occurring as millions of tiny (PM2.5) spherules of oxides emitted from industrial sources such as the Port Talbot steelworks. Detrital Fe, seen with quartz and clay-mineral particles, tends to be coarser and shows a higher % within the PM10 rather than PM2.5 fraction. The influence of local geology is clearly discernable in some cases, as seen for example in the high Mg content of aerosols collected above the Lizard ophiolite in Cornwall. Sites close to motorways and busy urban roads, such as in Westminster, central London, contain the highest contents of traffic-related metal particles, such as Zn, Pb, Ba, and PGE. All samples are currently under investigation for their potential bioreactivity, at King's College (antioxidant effects) and NHLI (human lung cell studies) in London and Cardiff Biosciences (oxidative potential, toxicogenomic studies)