Abstract
Tungsten inert gas welding (TIG) represents one of the most widely used metal joining processes in industry. Its propensity to generate a greater portion of welding fume particles at the nanoscale poses a potential occupational health hazard for workers. However, current literature lacks comprehensive characterization of TIG welding fume particles. Even less is known about welding fumes generated by welding apprentices with little experience in welding. We characterized TIG welding fume generated by apprentice welders (N = 20) in a ventilated exposure cabin. Exposure assessment was conducted for each apprentice welder at the breathing zone (BZ) inside of the welding helmet and at a near-field (NF) location, 60cm away from the welding task. We characterized particulate matter (PM4), particle number concentration and particle size, particle morphology, chemical composition, reactive oxygen species (ROS) production potential, and gaseous components. The mean particle number concentration at the BZ was 1.69E+06 particles cm−3, with a mean geometric mean diameter of 45nm. On average across all subjects, 92% of the particle counts at the BZ were below 100nm. We observed elevated concentrations of tungsten, which was most likely due to electrode consumption. Mean ROS production potential of TIG welding fumes at the BZ exceeded average concentrations previously found in traffic-polluted air. Furthermore, ROS production potential was significantly higher for apprentices that burned their metal during their welding task. We recommend that future exposure assessments take into consideration welding performance as a potential exposure modifier for apprentice welders or welders with minimal training.
Highlights
Worldwide, ~2 million employees work full-time in welding processes, in addition to numerous other workers who perform welding tasks as part of their occupation (Cena et al, 2014)
As polarity and shielding gas was correctly established for all welders in our study, our findings suggest that composition of the welding fume particles was influenced in part by the ability of the welder to avoid contacting the electrode to the welding puddle
We showed that apprentice welders are exposed to high concentrations of welding fume particles that consist almost exclusively of particles with geometric mean diameter (GMD)
Summary
Worldwide, ~2 million employees work full-time in welding processes, in addition to numerous other workers who perform welding tasks as part of their occupation (Cena et al, 2014). Workers that participate in welding tasks are exposed to a complex and heterogeneous mixture of welding fumes that consist of metals, metal oxides, gases, and vapours Metal oxide nanoparticles (NPs) in welding fumes have gained increased attention due to their potential for triggering oxidative stress reactions and contribution to adverse respiratory and cardiovascular outcomes (Antonini et al, 2005). ROS can react quickly with surrounding tissue, damage cell components, and launch a cascade of local and systemic responses (Riediker, 2007). Such oxidative stress response is an important contributor to acute and chronic vascular and pulmonary diseases (Newby et al, 2014)
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