ToxMixtures: A package to explore toxicity due to chemical mixtures

The ToxMixtures R-package includes a set of functions to analyze, visualize, and organize measured chemical concentration data as it relates to chemical mixtures. ToxMixtures combines outputs from the R-package toxEval with
open access sources on molecular biology to provide information on potential biological effects of chemicals detected in environmental matrices. To use ToxMixtures, the user will need to become familiar with toxEval as the ToxMixtures package was designed to further investigate chemical mixtures after ToxCast-based hazard ratios (Exposure Activity Ratios, or EARs) have been computed using routines within toxEval. ToxMixtures assumes additivity of biological effects for common modes of action by summing EAR values for chemicals with common ToxCast assay endpoints, gene targets, or Adverse Outcome Pathways (AOPs). Mixtures exceeding user-defined EAR thresholds for a specified number of study sites are tabulated and linked with gene ontology databases. Additionally, ToxCast assay endpoints and genes are referenced in biological pathways databases, such as AOPs to provide additional context of the potential effects of chemical mixtures. These biological functions, gene ontologies, and pathways are provided to offer guidance as to how chemicals may interact biochemically at the concentrations detected in environmental samples. These techniques are intended to serve as screening methods to estimate potential for chemical mixture effects rather than definitive evaluations of the modifications to cellular and organismal processes.