Weight of Evidence: Criteria and Applications

Toxicologists and authorities evaluate substances that in the traditional way refer to data and knowledge on the toxic mechanism. Non-testing methods (NTMs) proved to be a valuable resource for risk assessment of chemical substances. Indeed, they can be particularly useful when the information provided by different sources is integrated to increase confidence in the result. In this chapter, we will address data obtained from NTM, including in silico models and read-across. Typically, these two approaches are used separately, but in this way, we lose some information. The integration of different results can be sometimes difficult because different methods can lead to conflicting results and because a clear guideline for integrating information from different sources was not available in the recent past. In this chapter, we present and discuss the recently published guideline from EFSA for integrating and weighting evidence for scientific assessment, and how to proceed, manually or through novel integrated tool, SWAN. Moreover, practical examples of the application of these integration principles on evidence from different in silico models are shown. These examples represent a demonstration of the suitability and effectiveness of in silico methods for risk assessment, as well as a practical guide to end users to perform similar analyses on likely hazardous chemicals.