You are here:
METHODS AND TECHNIQUES FOR DEALING WITH THE UNIDENTIFIED FRACTION OF COMPLEX MIXTURES
Citation:
Simmons, J E., L K. Teuschler, G Rice, R. C. Hertzberg, T F. Speth, C. Gennings, AND S. D. Richardson. METHODS AND TECHNIQUES FOR DEALING WITH THE UNIDENTIFIED FRACTION OF COMPLEX MIXTURES. Presented at Toxicology and Risk Assessment Conference, Fairborn, OH, April 28-May 1, 2003.
Description:
For the vast majority of highly complex environmental mixtures to which humans are exposed, significant portions of the mixture are unidentified. Although toxicological data on the mixture itself are desired for risk assessment, such data, even on a similar mixture, are rarely available. For mixtures, the most frequently collected toxicological data are on defined mixtures where a limited number of chemicals are combined and tested. Mixtures risk is most often assessed by component-based approaches using toxicological data on the individual chemicals identified in the mixture. When these toxicological and risk assessment methods are applied to the known (or a selected subset) of chemicals in a complex mixture, the risk may be incompletely characterized because the toxicity of the unidentified fraction is excluded along with any toxicologic interactions with the unidentified chemicals. This presentation will review current, newly developed, and proposed methods for dealing with the unidentified fraction of complex mixtures. These include techniques such as: improving methodology for concentration of complex environmental mixtures to conserve the chemicals contained in the mixture, reducing the unidentified fraction by improved chemical analysis, applying principal component analysis to combined toxicological and chemical information on complex mixtures, estimating the toxicity of the unidentified fraction as part of the complex mixture health risk estimate, and developing experimental design and analysis techniques from which observed toxicity can be apportioned between the known and unidentified chemicals in the mixture. (This abstract does not necessarily reflect EPA policy or guidance.)