Toxic and inflammatory effects of filters frequently used for the collection of airborne particulate matter

Epidemiological studies indicate that exacerbations of airway diseases and cardio-respiratory mortality hate been associated with high levels of parti culate air pollution. in the search for explanatory mechanisms, there is a need to collect particulate matter (such as PM10/PM2.5) Onto filters for bi ological analysis. The removal of airborne particulate matter from a filter into solution involves agitation of the samples to release the particles a nd this is done by such methods as high-speed vortexing, Since it is possib le that components of filters could contaminate the preparation and interfe re with biological investigations it is necessary to find an inert filter s uitable for both particulate collection and biological analysis. Extracts o f the following six filters were assessed for toxicological activity both i n vivo and in vitro:-Millipore AP20, Whatman GF/A, Whatman WCN, Gelman TF10 00, Gelman DM800 and polycarbonate (PC), Treatment with the extract of eith er Whatman GF/A, Gelman DM800 or Millipore AP20 filters for 24 h significan tly (p < 0.001) decreased the metabolic competence of A549 cells, as measur ed by MTT (3-(4,5-dimetholthiazol-2,5-diphenyl tetrazolium bromide) reducti on. In addition instillation of filter extracts into rat lungs was carried out to investigate their ability to cause inflammation. The cellular compon ents of the bronchoalveolar lavage fluid (BALF) were analysed for the numbe r of neutrophils, as markers of inflammation. After 24 h the filter extract of the Millipore AP20, polycarbonate LPC), Whatman WCN and Whatman GF/A in duced a significant (P < 0.001) influx of neutrophils into the rat lung. Fi nally the ability of each filter to absorb phosphate buffer solution (PBS) was assessed. The Whatman GF/A increased in weight 13 fold and the Millipor e AP20 8 fold. In comparison the polycarbonate and the Gelman TF1000 were h ydrophobic, These results suggest that of the six filters tested, the Teflo n Gelman TF1000 filter was the most suitable for the collection and subsequ ent biological analysis of airborne particulate matter, as it releases litt le in the way of toxic material. (C) 2000 Elsevier Science Ltd. All rights reserved.