Exposure to ultrafine (.0.1 um) particles is widespread at various workplaces. Several studies have revealed associations between ultrafine particle exposures and adverse health effects, including respiratory problems, impairment of cardiovascular function, and others. Condensation particle counters (CPCs) are conventionally deployed to measure the ultrafine particle concentrations in real time. For example, the P-Trak (Model 3007, TSI Inc., Shoreview, Minn.) is the most commonly used CPC in occupational environments. However, commercially available CPCs are typically too bulky to serve as workers' personal exposure monitors; furthermore, their performance is generally affected by their orientation. Several attempts have been made recently to design a better instrument for real-time personal exposure assessment, including a novel ultrafine particle counter (prototype) developed at the University of Cincinnati (UC UFP counter. The operation principle of this device, like any CPC, involves condensation on nuclei; however, the novelty of this instrument is that the condensation takes place on nano-materials entering through the input channel. After passing a PM filter (cyclone), the particles enter a non-wetting, porous evaporation condensation tube. Enlarged due to condensation growth, they are detected with an optical laser counter. Capillary force spontaneously generated on the surface of the non-wetting tube prevents flooding regardless of orientation and movement. This makes the instrument particularly advantageous for field applications. In addition, its time of response to a change in aerosol concentration is as low as approximately 0.3 sec. The detection particle size range is 4.5 nm to >1.0 um that, in contrast to conventional CPCs, includes a low nano-scale. The present prototype of the UC UFP counter is portable; however, it is undergoing additional miniaturization to make the device wearable. In this study, we examined the feasibility of using the UC UFP counter for measuring the aerosol particle penetration through an elastomeric half-mask respirator donned on a breathing manikin.(6,7) Elastomeric respirators are commonly used by firefighters and first responders. The UC UFP counter was tested against the TSI Model 3007 CPC operating side by side. Combustion particles (generated by burning wood, paper, or plastic) were used as challenge aerosols. Exposures to combustion aerosols at various workplace environments have been associated with adverse health outcomes.(2,3) More than 70% (by number) of particles in a fire generated smoke are ultrafine.(8) The penetration values were obtained by measuring the aerosol concentrations inside and outside the respirator. The sampled airflow was split with 0.3 L/min directed to the UC UFP counter and 0.7 L/min to the TSI CPC. Measurements were conducted for four respirator sealing conditions (unsealed, sealed at the nose area, sealed at chin and nose, fully sealed) and for three cyclic breathing flow rates (mean inspiratory flow = 30, 85, and 135 L/min) and one constant flow rate (30 L/min).
Sergey Grinshpun, University of Cincinnati, Environmental Health, 3223 Eden Ave., P.O. 670056, Cincinnati, OH 45267