Toward improved in vitro models for human health risk assessment : mechanisms of short-chain per- and polyfluoroalkyl substances (PFAS) toxicity.


The global prevalence of manufactured chemicals lacking comprehensive toxicological profiles poses a significant challenge. This issue is exemplified by the widespread contamination of per- and polyfluoroalkyl substances (PFAS) worldwide. Despite their extensive use in various consumer products, the persistent and toxic nature of PFAS was not fully understood until after their global dissemination. As scientific knowledge advanced and regulatory bodies took action, short-chain alternatives were introduced to replace problematic precursors. However, these alternatives still lack sufficient toxicity data, emphasizing the need for robust chemical safety assessments. Initiatives to develop rapid and cost-effective solutions that utilize exposure-based strategies, hypothesis-driven tiered systems, and animal-free toxicological testing techniques have evolved in response to these issues. While in vitro high-throughput screening (HTS) methods have shown promise, their integration into the existing chemical risk assessment framework faces obstacles concerning physiological relevance. The overarching objective of this dissertation was to enhance our understanding of the mechanisms underlying the toxicity of short-chain PFAS and to develop improved in vitro models for human health risk assessment. The specific aims of this research are as follows: (1) comprehensively review the current state of in vitro methods employed in assessing human health risks associated with PFAS; (2) compare the cytotoxicity profiles of seven PFAS in six human cell lines; (3) investigate the impact of short-chain PFAS on oxidative stress biomarkers in human liver, kidney, muscle, and microglia cell lines; (4) examine the effects of short-chain PFAS on human cytochrome P450 (CYP450) enzymes; and (5) evaluate the influence of short-chain PFAS on gene expression profiles relevant to toxicity using a liver-on-a-chip model. The findings of this research have the potential to impact decision-making processes related to PFAS, the management of PFAS risks, and the development of alternative PFAS compounds. By shedding light on the toxicity mechanisms and enhancing in vitro models, this dissertation contributes to the advancement of human health risk assessment and aids in the development of safer alternatives to PFAS.