A decision tree for assessing effects from exposures to multiple substances

A series of tools were created that include: a decision tree, a system for grouping exposures, and a graphical tool (the MCR-HI plot). The decision tree allows the division of combined exposures into different groups, exposures where one or more individual components are a concern, exposures that are of low concern, and exposures that are a concern for combined effects but not for the effects of individual chemicals. These tools efficiently use available data, identify critical data gaps for combined assessments, and prioritize which chemicals require detailed toxicity information. The tools can be used to address multiple human health endpoints and ecological effects.The tools provide a useful approach for assessing risks associated with combined exposures to multiple chemicals.Human and ecological receptors are continuously exposed to multiple chemicals; however, chemicals have traditionally been regulated on a chemical-by-chemical basis. As a result, there is a possibility that are instances where chemicals independently do not cause adverse effects, but in combination they could pose a risk to human health and the environment. A number of organizations have investigated the effect of combined exposures to multiple chemicals and provided guidance on how risks from these exposures could be assessed [1-5].The Mixtures Industry Ad-hoc Team (MIAT) was created by the European Chemical Industry Council (Conseil Européen des Fédérations de l'Industrie Chimique, Cefic) to help address the concerns associated with combined exposures to multiple chemicals. In 2010 the MIAT began development of a decision tree to guide the assessment of risks from combined exposures. This paper presents the results of this effort. The tree draws on concepts developed by the World Health Organization (WHO) [1,2], the European Commission Non Food Scientific Committees (SCs) [6], and industry-sponsored research on the use of the Maximum Cumulative Ratio (MCR) [7,8]. An earlier version of the t