The NCBI (National Center for Biotechnology Information) USA has performed research to study the Factors Influencing Microbial Composition of Metalworking Fluids and Potential Implications for Machine Operator's Lung. They simply divided used metalworking fluid samples in two categories: Non-Automotive Industry and Automotive Industry.  The results are scary.  Machine Operators Lungs from Automotive Industry are at risk.  It’s not just metalworking fluid formulations that are potential at fault.  Machined metals like chromium, nickel and even iron aggravate the risk. Refer article link for detailed report