This document discusses using ontologies to model exposure events, adverse outcome pathways, and phenotypes in order to support predictive toxicology. It describes existing ontologies like the Environment, Conditions, and Treatments Ontology (ECTO) and Gene Ontology Causal Activity Models (GO-CAMs) that can be used to represent exposure mechanisms and adverse outcomes. The document also presents challenges for developing an open predictive toxicology framework that leverages ontologies and linked data to make toxicology data more findable, accessible, interoperable, and reusable.