Whole-body inhalation study of nanoparticle-enhanced vegetable oil metalworking fluids in mice for assessing occupational health risks.

The increasing demand for sustainable machining necessitates the development and toxicological evaluation of environmentally friendly alternatives to conventional metalworking fluids (MWFs). This study investigated the respiratory and systemic effects of a nanoparticle-enhanced vegetable oil-based MWF (NPVO-MWF) using a whole-body inhalation exposure model in male C57BL/6 mice. Both sub-acute (4-week) and sub-chronic (13-week) exposures were performed, followed by detailed bioanalytical and histopathological assessments. Cytokine analyses (IL-1β, TNF-α, IL-6) via ELISA and RT-PCR revealed no significant pro-inflammatory responses. Reactive oxygen species (ROS) levels in blood, bronchoalveolar lavage fluid, and lung homogenates remained unchanged, indicating an absence of oxidative stress. Histopathological analysis using hematoxylin and eosin staining showed mild epithelial hyperplasia in sub-chronic exposures. Sirius Red staining revealed minimal collagen deposition and slight reductions in pulmonary airspace. No substantial evidence of lung injury, pulmonary toxicity, or carcinogenicity was observed. This study represents one of the first applications of a whole-body inhalation model for evaluating NPVO-MWFs, addressing a critical gap in occupational health risk assessment. The findings indicate that NPVO-MWFs present low toxicological risk under the tested conditions and offer a viable, sustainable alternative to conventional MWFs. Additional chronic exposure studies are recommended to further establish their occupational safety.