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With metalworking processes such as sanding, lathe work and drilling the application of metalworking fluids is an absolute necessity. More or less direct or indirect skin contact with such lubricants is a virtually unavoidable work hazard for those involved with such processes. In addition, inhaling the vapors of metalworking fluids applied in aerosol form must be considered. Until recently, evaluation of the hygienic character of such lubricants was generally performed through a rather crude calculation of aggregate microbe levels.In the following study, a newly developed method is presented which allows the concentration of Endotoxins in metalworking fluids to be determined. The technique involves the separation of the oilin-water emulsions of tested lubricants into their respective oil and water states. This then permits a Limulus-Amoebocyte-Lysate test to e performed to measure the level of Endotoxins which gather in the water state of the separated emulsions.Through the determination of Endotoxin concentration we may draw valuable conclusions concerning bacteria colonies present in metalworking fluids containing gramnegative bacteria. This is also true for lubricants reated with preservative processes such that no viable bacteria are present. Conclusions to be drawn are based on the Endotoxin activity resulting from dying bacteria cells. The Endotoxin parameter thus represents a significant addition to the hygienic evaluation of metalworking fluids, especially in the evaluation of lubricants with negative bacterial traces.Furthermore, the presence of Endotoxins in metalworking fluids holds special meaning in the evaluation of Endotoxins suspended in the air of workplaces. From the medical standpoint airborne Endotoxins play a significant role in the contraction of various respiratory diseases.Preliminary results of studies measuring the concentration of airborne Endotoxins in various workplaces of the metalworking industry bear this out. Such studies have lead to the currently proposed facilities management guideline of air purity levels of 50 EU/m³ to maintain a tolerable workplace for an average eight-hour work shift. Studies related to this guideline were performed using the standard measuring processes of the Industrial Workers Institute for Job Safety.