Key Exposure Components and Oxidative Stress-Driven Health Risks Assessment of Oil Mist Generated by Metalworking Fluids in Industrial Building Environment

Metalworking fluids (MWFs) comprise base oils, water, and additives and are widely used in machining. Oil mist generated during machining poses health risks, yet the transformations of MWFs components during inhalation exposure and component-related toxicity differences remain poorly understood. This study aims to identify key exposure components of oil mist and quantify component-related health risks using an evaporation model and oxidative potential (OP). The evaporation model showed that both water- and oil-based MWFs droplets rapidly (0.1-60 s) evolved into water-free oil droplets, indicating that base oils and additives dominated inhalation exposure. OP was measured for three MWFs containing different base oils or additives. OP was associated with both mass concentration and MWFs composition. Mineral oil-based MWFs exhibited relatively higher OP below 0.5 mg/m³ , whereas OP differences among the three MWFs narrowed at 2 mg/m³ . At approximately 5 mg/m³ , the additive-containing MWFs showed a sharp increase in OP, likely due to redox-active substances in additives. These findings demonstrate that MWFs composition significantly affects the oxidative stress-related health risks of oil mist, especially those associated with highly oxidizing additives. This study provides a basis for occupational exposure risk assessment of MWFs oil mist.