Rapid assessment of microbial hazards in metalworking fluids

Industries that use metalworking fluids require a test method that can rapidly estimate the total number of bacteria. Such a test method would improve the ability to manage the metal working fluid by allowing near real-time decision making. The ability to manage the fluid more consistently and make critical decisions as they arise would reduce occupational exposures to contaminated metalworking fluid and likely result in fewer worker complaints and/or work stoppages. In this study, a filtration-based rapid adenosine triphosphate bioluminescence assay, which takes less than 10 min to perform, was evaluated as a test method for estimating total bacteria populations in metalworking fluid. This evaluation used two types of metalworking fluid (soluble and semisynthetic) that were inoculated using Pseudomonas aeruginosa and spoiled metalworking fluid. Daily parallel testing was completed on metalworking fluid samples using the rapid adenosine triphosphate assay and the standard plate count methods. Daily test results were evaluated by calculating r2 values using statistical correlation and regression procedures for each fluid type. Study results indicate the rapid adenosine triphosphate assay is strongly correlated to the standard plate count method for soluble and semisynthetic fluids, producing results of r2 = 0.74 and r2 = 0.89, respectively.