LAUSR

For some years, the characterization of workers' exposure to airborne metallic ultrafine particles (UFP) has been an increasing issue. Many industrial processes may generate UFP, which are characterized by constituent particle diameter less than 100 nm, and refer to nanosized particles not intentionally produced (welding, thermal spraying, 3D-printing ...). Thus, determining the size distribution of such an aerosol together with its chemical composition provide a real contribution to the understanding of UFP exposures and associated health effects. In the framework of proposing characterization methods adapted to occupational situations, the optimization of metallic aerosol sampling using cascade impactors is studied in order to improve the reproducibility of these samplings. Cascade impactors represent a valuable help since both the size distribution of an aerosol and its chemical characterization can be obtained from the samples collected. A welding fume bench was used to generate a highly reproducible test aerosol of metallic UFP (mass median aerodynamic diameter MMAD = 430 nm, ρeff = 0.55 g.cm-3). Four different cascade impactors were involved (DLPI+, MARPLE, SIOUTAS and Minimoudi 135-8). Our investigations allowed the lubrificating procedure of the collection supports (membranes, filters) to be optimized by determining the nature and the quantity of grease, which is of significative influence in the collection efficiency. Furthermore, under optimized conditions, the Minimoudi 135-8 (intended for personal sampling) leads to results very close to those stemming from the reference low pressure cascade impactor, DLPI+, thanks to its high resolution in terms of number of stages (8) and lowest cutoff diameter (180 nm).