Biological and chemical hazards in water-mix metalworking fluids and mists

Background: Occupational exposure to used metalworking fluid (MWF) mists is a risk factor in the development of allergic and irritant respiratory disease. Respiratory disease "outbreaks" have prompted further investigation into possible causative factors. These might include sensitizing agents accumulating in used MWF. However, there is no clear evidence that shows whether levels of biologicals and chemicals detected within the sump are representative of what is found in the mist. Method: Samples of used MWF and mist samples were obtained from UK sites. Analysis of biological contaminants was conducted using a combination of 16S rRNA PCR-DGGE, qPCR, zymography, fluorescence based assays and NanoLC-ESI-MSe. Metals particulates and dissolved metals were analysed using ICP-MS. Results: Bacteria were detected in both used MWF sump and mist samples. These included Ochrobactrum and Proprionibacterium at site visit one, and Methylobacterium at site visit two. Other potentially pathogenic bacterium detected within the MWF sump sample included organisms from the Mycobacterium chelonae-Mycobacterium abscessus complex, and Wautersiella Falsenii. Bacterial toxins in the form of “serine-like” proteases were detected within 76% of the MWF samples and in two of the mist samples. Potentially sensitizing metals such as zinc, aluminium, manganese, chromium and nickel were detected at different levels within both the used MWF sumps and the mist samples taken. Conclusions: This study demonstrates that it is likely contaminants and constituents of MWF become airborne during machining processes. However, further research is required to determine the quantities of such contaminants in the mist to determine whether they would meet the threshold to initiate the development of allergic respiratory diseases seen in machine operators.