Metalworking Fluid—The Toxicity of a Complex Mixture

Various chemicals are used in the manufacture of cooling and lubricating fluids and fall into the classes of straight, soluble, semisynthetic, and synthetic metalworking fluids. The diversity of chemicals and in-use contaminants makes the risk assessment of metalworking fluids quite difficult. Toxicologists have used a number of methods to evaluate the component(s) responsible for the adverse pulmonary effects of metal working fluid aerosols encountered in the workplace. Although investigators have studied the adverse effects of metalworking fluid chemicals alone and in combination, the majority of evidence strongly suggests that the microbial changes that occur in fluid composition, during use and storage in the workplace, are responsible for the pulmonary effects reported for workers exposed to metalworking fluid aerosols. This review discusses the methodologies used to examine the toxicity of the complex nature of modern metalworking fluids and the findings that point toward bacterial endotoxin as a major contributor to their adverse effects.