Implementation of the Basic Hazard Index Screening for Health Risks Associated with Simultaneous Exposure to Multiple Chemicals Using a Standardized Target Organ and Systems Framework

Environmental health risk assessments often involve assessing the potential health effects of exposure to multiple chemicals at once (i.e., complex mixtures). Because the possible number of chemical combinations is very large, few controlled in vivo toxicological studies with chemical mixtures are relevant or practical. In lieu of specific mixture toxicity data, the segregated hazard index (HI) approach has been used to determine whether simultaneous exposures may warrant further investigation due to their combined adverse effects. Each chemical is assigned to one or more target organs based on critical effects; HIs for each target organ are generated by summing the individual hazard quotients for each of the chemicals assigned to that organ or organ system. To conduct this phased risk assessment approach in a consistent manner, a comprehensive, systematized list of toxicity targets for implementing this approach is needed. We present a comprehensive and standardized list of toxicity target organs and systems (TTOS), with example data sets, for consistent implementation of the segregated HI method. This method is designed to facilitate the standardization of the widespread use of the basic segregated HI approach. The basic hazard index mixtures screening (BHIMS) tool allows for rapid identification of exposure concerns that may warrant further and more sophisticated assessment. Published 2017.