Advances in Dielectrophoretic Mineral Fiber Classification

LEONID TURKEVICH, Greg Deye

NIOSH

     Abstract Number: 603
     Last modified: April 4, 2011

Abstract
Fiber length has long been suspected (Stanton hypothesis) as being a crucial parameter which determines various toxicological responses (fibrosis, lung cancer, mesothelioma) to the presence of asbestos in the lung. Direct toxicological testing has been hampered by the inability to prepare significant quantities of length-classified asbestos samples. We report on recent work at NIOSH to classify mineral fibers by length in order to prepare asbestos samples of well-defined length for subsequent toxicological study. The Baron aerodynamic fiber classifier can successfully analyze fibers in the desired length scale (L ~ 15 micron) regime. We report on our work to increase the throughput of this instrument in order to separate fibers in quantities sufficient for subsequent toxicological study. We now have a better understanding of the role that humidity plays in the operation of this instrument, especially at the aerosol generation stage; at low humidity, tribo-charging can give rise to a ‘piggy-back’ effect, whereby short fibers can accompany the correctly separated fibers, thereby contaminating the length segregated sample. The instrument performance is quite robust as the aerosol generation concentration is increased. We present fiber length distributions of both classified fibers and fibers separated in the low pass filter mode. Techniques have also been developed to monitor (real-time) the quality of the separated product.