Versatile aerosol concentration enrichment system (VACES) for simultaneousin vivo and in vitro evaluation of toxic effects of ultrafine, fine and coarse ambient particles - Part II: Field evaluation

This study presents results from a field evaluation of a mobile versatile a erosol concentration enrichment system (VACES), designed to enhance the amb ient concentrations of ultrafine (less than 0.18 mum), fine (0-2.5 mum), an d coarse particles (2.5-10 mum) for in vivo and in vitro toxicity studies. The VACES may be coupled to an exposure chamber system to assess exposure-d ose effects of any one, or all, of ambient aerosol on either human subjects and/or animals. Alternatively, concentrated ultrafine, fine and coarse par ticles can be directly collected by impaction onto a medium suitable for ap plication to cell cultures for in vitro evaluation of their toxic effects. The enrichment and preservation of ambient ultrafine, fine and coarse parti cles by size and chemical composition was determined by comparisons made be tween the VACES and a co-located multistage MOUDI impactor, used as a refer ence sampler. Furthermore, preservation of the ultrafine fraction is measur ed by the enrichment based on ultrafine particle numbers, morphological cha racteristics as well as their elemental carbon (EC) content. The results suggest that the concentration enrichment process of the VACES does not differentially affect the particle size or chemical composition of ambient PM. The following fractions: (1) mass (coarse and fine PM); (2) nu mber (ultrafine PM); (3) sulfate (fine PM); (4) nitrate (fine PM, after cor recting for nitrate losses within the MOUDI); (5) EC (ultrafine PM); and (6 ) selected trace elements and metals (coarse and fine PM), are concentrated very close to the "ideal" enrichment value of 22-thereby indicating a near 100% concentration efficiency for the VACES. Furthermore, ultrafine partic les are concentrated without substantial changes in their compactness or de nseness, as measured by the fractal dimension analysis. (C) 2001 Elsevier S cience Ltd. All rights reserved.