On the evaluation of fibrous particles in remote ambient air

Abstract

Nuclepore filters were used for sampling fibrous particles in ambient air. The fiber counting and fiber size measurements were done by means of SEM-methods. One square mm of the filter surface containing ambient air particles was photographed and all fiber-like particles on this surface were counted and measured. The number of fibers, distribution of fiber lengths and diameters and the estimated fiber aerodynamic diameters were plotted. The specific identification of asbestos fibers was made by electron microprobe analysis. Certain elements such as Si, Fe, Mg, Al, Mn, Ca, and Na as well as ratios such as Fe/Si, Mg/Si proved to be approximative identification factors for ambient asbestos. Many other inorganic fibrous particles were found in the urban atmosphere as well as in the atmosphere of remote regions. Fibrous gypsum, fibrous ammonium sulfates, fibrous aluminium silicates, fibrious mica, and quartz were identified among these particles. Even in remote ambient air, relatively high concentrations of fibrous particles (10 3−10 4 m −3; nanogram region) could be measured, although the concentrations of asbestos fibers were usually smaller than 10 2 m −3 (picogram region).