Characterization of occupational inhalation exposures to particulate and gaseous straight and water-based metalworking fluids (MWF)

Exposure to aerosols from metalworking fluids (MWF) has been associated with several adverse health outcomes. This inconsistency in health effects might be related to the lack of exposure assessments considering the complex nature of MWF aerosols. This study describes a comprehensive exposure assessment to straight and water-based MWFs. Method. A cohort of 65 workers from 20 workshops, exposed to either straight or water-based MWFs, participated in the study. Comprehensive characterizations of new and used MWF included the analysis of metal and organic carbon (OC) content in new and used MWF fluids. Full-shift air samples of both inhalable particulate and gaseous fraction were collected and analysed using gravimetric or other quantification methods for metals, OC, and aldehydes. Exposure determinants were ascertained through observations and interviews with company workers. Determinants associated with personal inhalable particulate and gaseous fractions were systematically identified using mixed models. Results. Similar inhalable particle exposure was observed for straight and water-based MWFs (64-386 g/m3). The gaseous fraction was the most important contributor to the mass fraction for both straight (322-2 344 g/m3) and water-based MWFs (101-699 g/m3). The aerosolized particles exhibited low metal content irrespective of the MWF type; however, notable concentrations were observed in the sumps potentially reaching hazardous concentrations. Job activities were clustered, and these clusters were important determinants for both exposure to particulate and gaseous fractions from straight MWF. Conclusion. Current machine enclosures remain an efficient determinant to reduce particulate MWF but were inefficient for the gaseous fraction. Properly managed water based MWF meaning no recycling and no contamination from hydraulic fluids minimizes gaseous exposure. Finally, the mass fraction was also influenced by the workshop temperature. These findings suggest that exposures may be improved with control measures that reduce the gaseous fraction and proper management of MWF.