Evaluation of a personal air sampler for twenty-four hour collection of fine particles and semivolatile organics¹

Abstract

The U.S. EPA has conducted an evaluation of a commercially available lightweight fine particle personal sampler for use in human exposure and biomarker studies involving 24-h collections of particulate matter, particle-bound organics such as polycyclic aromatic hydrocarbons (PAHs), and semivolatile organics (PAHs). Independent laboratory evaluation of the prototype design, intended to produce a 2.5-μm aerodynamic diameter cut-point at a flow between 1.5 and 1.7 lpm (liters per minute), indicated that at a challenge flow rate of 1.5 lpm, the sampler provided an aerodynamic cut-point (dp₅₀) of only 1.7 μm. The variance between expected size selection resulted from the prototype's jet diameter dimension being inadvertently based upon a flow rate of 2.0 lpm rather than an intended 1.5–1.7 lpm. Other aerodynamic factors not presently accounted for may also have played an influence. Extrapolated cut-points for flow rates at 1 and 3 lpm for the prototype were determined to be 2.1 and 1.2 μm, respectively. Total losses attributed to unwanted particle retention within the sampler ranged from 10% for 0.91 μm size particles to essentially zero approaching diameters greater than 2.0 μm. The ambient concentration of particles (<1.7 μm) needed for acceptable gravimetric filter measurements involving 24-h sample collection was determined to be 10 μg/m³. Investigation of the sampler to retain and recover PAHs using XAD-2 resin, often of importance in human exposure biomarker studies, indicated that corrected recoveries between 94% and 108% could be obtained for 16 priority pollutant PAH species. Overall evaluation of the personal monitor indicates that it has research utility due to its modular features and size but reconfiguration should be performed that would permit true PM_2.5 size selection. The current configuration collects particles less than 2.5 μm at approximately 95% collection efficiency.