Adverse pulmonary effects and metallic characteristic of size-resolved welding fumes in human lung epithelial BEAS-2B cells

Welding produces complex metal fumes containing fine and ultrafine particles that can penetrate different regions of the respiratory tract and cause adverse health effects. Analyses based solely on total particulates overlook the size-dependent toxicity of these aerosols. This study employed human lung epithelial cells to elucidate the effects of different sizes (2.5–10 μm, 1.0–2.5 μm, and < 1.0 μm) of metallic fume particles (MFPs) in a stainless steel arc welding workplace. High concentrations of iron (106.09 μg/m³), chromium (40.94 μg/m³), and manganese (27.43 μg/m³), which are the main components of stainless steel welding materials, were detected in the MFPs. The total concentrations of 23 metal elements in the MFPs were in the order of MFP_1.0 (79.74 %) > MFP_2.5–10 (12.89 %) > MFP_1–2.5 (7.37 %). The total deposited MPS flux was highest in the nasal cavity (87.90 %), followed by the alveolar region (5.16 %) and the tracheobronchial region (1.17 %), using the International Commission on Radiological Protection model. Cell viability decreased with increasing metal concentration. Ultrafine MFPs (50 μg/cm²) increased intracellular reactive oxygen species (ROS) levels by more than 4.24-fold compared to control levels. Principal component analysis highlighted iron, molybdenum, barium, and lead as the primary contributors to ROS generation. In conclusion, fine particles (MFP_1–2.5) posed a greater risk of lung injury, and welding fumes induced cytotoxicity via ROS even in the absence of classical carcinogenic metals. These findings highlight the critical role of particle size and metal composition in driving pulmonary toxicity and emphasize the need for size-specific exposure limits to better protect welders’ respiratory health.