Abstract
The Critical Toxicity Reference (CTR) system is an approach for managing quantitative toxicity data. The essential components of this system include a thorough search of available literature, abstraction of information from selected references, entry of information into a computerized database, searching the database for specific types of studies, and reporting data in a form usable for direct analysis. The CTR system was developed in response to the need for quantitative use of data from animal studies in setting National Ambient Air Quality Standards (NAAQS), and the first application was the criteria pollutant ozone. Animal toxicity studies provide most information on health effects of ozone exposure. However, the data have been used only qualitatively for setting the NAAQS. A primary reason for this limited utilization is the lack of a method for combining results from different studies to present a comprehensive analysis of any given health effect observed upon ozone exposure. The CTR system deals with this problem and was specifically designed for retrieval on the basis of qualitative or quantitative comparisons. The method extends beyond conventional bibliographic methods by allowing integration with dosimetry and risk analysis modeling methods. This approach is generally applicable to any toxicant.