| Aerosolization of Fine Particles and Microbial Contaminants from Metalworking Fluids Contaminated with Microorganisms | |||||||||||||
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| In this study, the aerosolization of microorganisms from metalworking fluids (MWFs) was studied in laboratory conditions. Furthermore, the aerosolization of particles and endotoxin from MWFs was investigated under three conditions: 1. MWFs inoculated with microorganisms were aerosolized with a laboratory-scale set-up (MWF simulator) in the laboratory, 2. MWF collected in the field were aerosolized with the MWF simulator in the laboratory, 3. MWFs were aerosolized during routine field operations. For the experiments under conditions 2 (MWF collected in the field were aerosolized with the MWF simulator in the laboratory) and 3 (MWFs were aerosolized during routine field operations), the airborne particle and endotoxin concentrations in different size fractions were measured using the ELPI. In addition, the culturable counts of microorganisms and total endotoxin concentrations in the air and in the MWFs were measured during the field sampling. The data of the mass and number concentrations of airborne particles was also recorded in the filed. The results show high concentrations of airborne fine particles in areas that were affected by MWFs. The particle concentrations decreased linearly with increasing particle size, except in the reference area. High endotoxin concentrations were measured at the particle sizes of ≤0.39 µm, which is below the size of intact bacterial cells (0.5 µm). This confirmed the finding under condition 1 (laboratory study with artificially contaminated MWFs) that the aerosolized fine particles contain microbial fragments. High airborne microbial (up to 3.1x105 CFU/m3) and endotoxin (up to 83.1± 12.4 EU/m3) concentrations were detected in the filed sit although the total particle mass was lower than the NIOSH recommended exposure limit (REL) for MWF mist (0.5 mg/m3). The results of study consistently showed both in laboratory and field conditions that the particles aerosolized from MWFs contaminated with microorganisms contain high concentrations of fine particles and endotoxin in submicrometer size range. The results show the importance of size-selective measurements in exposure assessment in MWF environments. | |||||||||||||
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