Chemical risk assessment based on in vitro and human biomonitoring data: A case study on thyroid toxicants

Today, detailed risk assessment can only be performed for a few percent of the total number of current-use chemicals because of lack of data. Toxicity data is, therefore, needed for a substantial number of untested chemicals, a task that requires improved and faster chemical risk assessment strategies that are cost-efficient, human relevant and ethically responsible. In this commentary, we use a case study on five known thyroid toxic chemicals (perfluorooctanesulfonic acid, triclosan, tetrabromobisphenol A, decabromodiphenyl ether and hexabromocyclododecane) to explore the use of in vitro data for hazard assessment together with human biomonitoring (HBM) data for exposure assessment when evaluating human risk. Based on the case study, we conclude that in vitro and HBM data can be used for risk ranking of chemicals. We envision that an in vitro/HBM approach can use data from studies such as the big European initiative Human Biomonitoring for Europe (HBM4EU) together with human-relevant in vitro data to make alternative risk assessment more valuable to finally be able to ‘stand-alone’.