Aerosolization of fine particles increases due to microbial contamination of metalworking fluids

Aerosolization of microorganisms from metalworking fluids (MWFs) was studied using a laboratory-scale set-up simulating grinding operations. An optical particle counter (OPC), a condensation nucleus counter (CNC), an electrical low pressure impactor (ELPI), and a photometric aerosol mass monitor were used to measure the airborne particles and microorganisms aerosolized from MWFs. The tests were performed using a semi-synthetic MWF with and without bacterial contamination ( Pseudomonas fluorescens). Microbial contamination of the MWF increased the number and mass concentrations of aerosolized particles by a factor of 2 (as measured by the OPC and the photometric aerosol mass monitor, respectively). At the same time, there was an up to 50-fold increase in the concentration of fine particles ( 0.02 – 1 μ m ) , as measured by the CNC. The data collected with the ELPI showed that the peak of the fine particle number concentration was at 0.37 μ m . The results indicate that MWF mist may contain high concentrations of microbial fragments, which may not be detected by traditional microbial analysis methods, such as cultivation or microscopic counting.