To date, the majority of exposure limits set by OSHA or EPA have been for individual particulate agents or chemical compounds. However, modern industrial operations generate complex mixed aerosols, the components of which are often process dependent. For example, the chemical composition of welding fume varies with the type of shielding and electrode used, while microbial contamination of organic dusts or used metal working fluids can dramatically alter the biological response upon exposure to these materials. In addition, the types and amounts of organic chemicals adsorbed onto the carbon core of particles generated by diesel engines can depend on engine speed, load, and the type of fuel consumed. There is increasing awareness that the toxicity of a mixed exposure may not simply be the additive effects of its components. Indeed, synergistic effects, involving soluble metals, adsorbed organics, surface acidity, microbial contamination and particle size or surface area may occur. For this reason, NIOSH has listed 'mixed exposures' as a priority area in its National Occupational Research Agenda that must be addressed to allow appropriate and complete risk assessment in complex occupational settings. The objective of this symposium is to elucidate the various interactions among components of mixed exposures that are possible and to characterize the mechanisms involved in these interactions, using real-world occupational aerosols as examples.
The Toxicologist. Society of Toxicology 42nd Annual Meeting and ToxExpo, Cutting-Edge Science, Networking, New Perspectives, March 9-13, 2003, Salt Lake City, Utah