Developmental Toxicity and Lethality of Structurally Diverse PFAS in Zebrafish

Abstract

Per-and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants that have been associated with adverse health effects in highly exposed populations. Manufacturers have taken steps to replace toxic long-chain perfluoroalkyl acids (PFAAs) with short-chain PFAAs and perfluoroether acids (PFEAs). There is little to no toxicity data for many of these chemicals. Most of the data that are available are taken from studies that do not account for the pH of highly concentrated PFAS solutions, resulting in highly acidic conditions that do not accurately reflect real-world exposures. The goal of this study was to evaluate the lethality and developmental toxicity of 17 structurally diverse PFAS in zebrafish in a pH-neutral environment. We then compared results to determine the impacts of chain length, head group, and ether linkages on toxicity. The potency of PFAS to induce mortality and developmental toxicity endpoints increased with chain length, and sulfonic acids were more potent than carboxylic acids. The inclusion of ether oxygens was associated with reduced potency relative to PFAAs with equal chain length and head group. Perfluorooctane sulfonic acid (PFOS) was the most potent compound, followed by perfluoroundecanoic acid (PFUnDA) and perfluorododecanoic acid (PFDoDA). Short-chain compounds perfluoro-2-methoxyacetic acid (PFMOAA) and perfluorobutanoic acid (PFBA) were the least potent. These data were used to construct a multiple linear regression model for PFAS potency. Failed swim bladder inflation was the most sensitive developmental toxicity endpoint for all assessed chemicals. Other common phenotypes included spinal curvature, edema, craniofacial malformations, and ocular malformations. Ocular malformations were more common in response to sulfonic acids. No other phenotypes exhibited significant structural specificity. Our study provides new toxicity data for a diverse set of PFAS under environmentally relevant conditions. Future studies should be expanded to include more branched structures and head groups not present in our testing set to allow for improved understanding of how other structural features impact toxicity.