FTIR spectroscopy as a convenient tool for detection and identification of airborne Cr(VI) compounds arising from arc welding fumes

Given the significant presence of the carcinogenic Cr(VI) in arc welding fumes from stainless steels, it is also important, in addition to estimating the Cr(VI) levels, to identify Cr(VI) compounds, as it throws light on the mechanistic pathways towards fume formation. FTIR data is presented in this paper for arc welding fumes collected from Manual Metal Arc Welding (MMA), Flux Cored Arc Welding (FCAW) and Solid Wire Welding (Metal Inert/ Active Gas Welding [MIG/ MAG]). For MMA and FCAW samples, clear spectra corresponding to Na, K, dichromates was observed at wave number of around 725-740 cm^-1 and at 890-900 cm^-1. Chromate species were also observed at around 850-855 cm^-1, as was evidence of CrO₃ (chromium trioxide) too (950-970 cm^-1). The identification of these compounds was done by carefully identifying the Cr-O-Cr anti-symmetric vibrations, the symmetric stretching of the CrO₄ tetrahedra, and the stretching vibrations of the planar CrO₃ structure for the chromium trioxide. All the above compounds were volatile, and present as nanoparticles in welding fumes, thereby potentially causing significant harm to the welders. Additionally, crystalline phases (Fe-Mn spinels) were also observed through powder XRD, and the data was compared with ion chromatography estimates for Cr(VI) and found to be consistent.