Atmospheric chlorinated polyfluorinated ether sulfonate and ionic perfluoroalkyl acids in 2006 to 2014 in Dalian, China

Chlorinated Polyfluorinated Ether Sulfonates Exhibit Higher Activity toward Peroxisome Proliferator-Activated Receptors Signaling Pathways than Perfluorooctanesulfonate

Chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are the alternative products of perfluorooctanesulfonate (PFOS) in the metal plating industry in China. The similarity in chemical structures between Cl-PFAESs and PFOS makes it reasonable to assume they possess similar biological activities. In the present study, we investigated whether Cl-PFAESs could induce cellular effects through peroxisome proliferator-activated receptors (PPARs) signaling pathways like PFOS. By using fluorescence competitive binding assay, we found two dominant Cl-PFAESs (6:2 Cl-PFAES and 8:2 Cl-PFAES) bound to PPARs with affinity higher than PFOS. Based on the luciferase reporter gene transcription assay, the two Cl-PFAESs also showed agonistic activity toward PPARs signaling pathways with potency similar to (6:2 Cl-PFAES) or higher than (8:2 Cl-PFAES) PFOS. Molecular docking simulation showed the two Cl-PFAESs fitted into the ligand binding pockets of PPARs with very similar binding mode as PFOS. The cell function results showed Cl-PFAESs promoted the process of adipogenesis in 3T3-L1 cells with potency higher than PFOS. Taken together, we found for the first time that Cl-PFAESs have the ability to interfere with PPARs signaling pathways, and current exposure level of 6:2 Cl-PFAES in occupational workers has exceeded the margin of safety. Our study highlights the potential health risks of Cl-PFAESs as PFOS alternatives.

Bioaccumulation and effects of novel chlorinated polyfluorinated ether sulfonate in freshwater alga Scenedesmus obliquus

Chlorinated polyfluorinated ether sulfonate (Cl-PFESA) is a novel alternative compound for perfluorooctane sulfonate (PFOS), with its environmental risk not well known. The bioaccumulation and toxic effects of Cl-PFESA in the freshwater alga is crucial for the understanding of its potential hazards to the aquatic environment. Scenedesmus obliquus was exposed to Cl-PFESA at ng L^-1 to mg L^-1, with the exposure regime beginning at the environmentally relevant level. The total log BAF of Cl-PFESA in S. obliquus was 4.66, higher than the reported log BAF of PFOS in the freshwater plankton (2.2-3.2). Cl-PFESA adsorbed to the cell surface accounted for 33.5-68.3% of the total concentrations. The IC50 of Cl-PFESA to algal growth was estimated to be 40.3 mg L^-1. Significant changes in algal growth rate and chlorophyll a/b contents were observed at 11.6 mg L^-1 and 13.4 mg L^-1 of Cl-PFESA, respectively. The sample cell membrane permeability, measured by the fluorescein diacetate hydrolyzation, was increased by Cl-PFESA at 5.42 mg L^-1. The mitochondrial membrane potential, measured by Rh123 staining, was also increased, indicating the hyperpolarization induced by Cl-PFESA. The increasing ROS and MDA contents, along with the enhanced SOD, CAT activity, and GSH contents, suggested that Cl-PFESA caused oxidative damage in the algal cells. It is less possible that current Cl-PFESA pollution in surface water posed obvious toxic effects on the green algae. However, the bioaccumulation of Cl-PFESA in algae would contribute to its biomagnification in the aquatic food chain and its effects on membrane property could potentially increase the accessibility and toxicity of other coexisting pollutants.