Comparative analysis of metal concentrations in respirable particles and nanoparticulate matter (NPM) from mild steel, aluminum, and stainless steel welding fumes.

Welding fumes contain metal-rich particles whose health effects depend on particle size and metal composition, which determine lung deposition and toxicity, respectively. Because metal profiles vary by welding materials, identifying dominant metals is important for exposure and risk assessment. This study conducted field sampling at welding stations in manufacturing facilities using respirable and nanoparticle respiratory deposition (NRD) samplers placed in the breathing zones of 61 participants (38 welders, 12 factory controls, and 11 office controls) and compared the metal composition of respirable particles and nanoparticulate matter (NPM) generated during mild steel (MS), aluminum (Al), and stainless steel (SS) welding. Manganese (Mn), iron (Fe), chromium (Cr), nickel (Ni), copper (Cu), and Al were quantified in respirable particles and NPM using inductively coupled plasma-optical emission spectrometry. Particle morphology and elemental composition were characterized using transmission electron microscopy and energy-dispersive X-ray spectroscopy. Metal concentrations differed among welding departments (p < 0.01), although comparisons involving Al and SS welding were limited by small sample size. MS welding fumes (N = 31) were dominated by Mn and Fe, SS welding fumes (N = 3) contained elevated Cr and Ni, and Al welding fumes (N = 4) primarily contained Al. On average, the six measured metals in NPM accounted for 48.3% of the corresponding respirable metal concentrations. Substantial fractions of Mn, Cr, and Ni were present in NPM. These findings suggest that respirable-based assessments may underestimate health risks and that particle size and metal composition should be considered in workplace exposure and risk assessment.