Physicochemical characterization of welding and grinding fine particulates at a machinery plant: A comprehensive case study of workers’ health risk assessment

Electric welding is a well-developed technology and an indispensable process in today's metal processing-related manufacturing industries. However, high-temperature operation could easily expose welding personnel to metal fume containing particle matters (PM) with aerodynamic diameters (d_p) ranging from sub-microns to microns. This investigation focused on a high-pressure vessel manufacturing factory in southern Taiwan, and workers in the same indoor factory building were divided into five similar exposure groups (SEGs), including design, layout/assembling, arc welding, grinding and pickling/painting, to implement personal sampling. According to the monitoring data on-site, high concentrations of PM are mainly found in the areas within 0.5 m of welding operations; the fume produced from ilmenite electrodes has the highest concentration of PM, and followed by those using high-fiber electrodes and high-tensile steel electrodes. Especially when welding with ilmenite electrodes at the current of 150 A, the concentrations of PM_2.5 and PM₁₀ reached the highest 1716 and 3024 μg/m³, respectively. The SEG of welding, who manually welded carbon steel and stainless steel, even exposed to submicron particles with d_p = 151–170 nm. Metal analysis of PM using inductively coupled plasma optical emission spectroscopy (ICP-OES) found that the cancer risk of cadmium (Cd) and chromium (Cr(VI)) in the SEG of pickling and painting was significantly the highest among all SEGs; the non-cancer risk (hazard index) of manganese (Mn) was high among all SEGs.