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Human Health Risk Assessment of Perfluorinated Chemicals
Published in David M. Kempisty, Yun Xing, LeeAnn Racz, Perfluoroalkyl Substances in the Environment, 2018
The broad category of poly- and perfluoroalkyl substances (PFAS) substances may be grouped into various subclasses of PFAS based on two factors: the number of carbons in the perfluoroalkyl chain and the functional group attached to this chain. Perfluorinated carboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) are subsets of perfluorinated acids that consist of a nonpolar perfluorinated alkyl chain and a polar carboxylic acid (PFCA) or sulfonate (PFSA) end group (Buck et al., 2011). Long-chain PFAS (LC-PFAS) are defined as those PFAS that contain an extended perfluoroalkyl chain of eight carbons (C8) or longer for PFCAs and their precursors or six carbons (C6) for PFSAs and their precursors. Several concerns have been identified for LC-PFAS, including persistence in the environment and human tissues, potent reproductive and developmental toxicity, and carcinogenicity (USEPA, 2009). PFCAs and PFSAs with perfluorinated chain lengths shorter than those of LC-PFAS do not accumulate in mammalian tissues (Chengelis et al., 2009), although they are still persistent in the environment.
The Influence of Microfluidic Channel Wettability on PEM Carbon Paper Fuel Cell
Published in Sushanta K. Mitra, Suman Chakraborty, Fabrication, Implementation, and Applications, 2016
S. AlShakhshir, X. Li, P. Chen
Perfluorosulfonic acid is the most commonly used membrane material for PEM fuel cell (Larmine and Dicks, 2003). When the membrane gets hydrated, the hydrogen ions (H+) become mobile by bonding to the water molecules to form hydronium ions; these ions move between the sulfonic acid sites. The water content of the polymer electrolyte is essential for proton conduction; if the membrane becomes dehydrated, it will no longer be protonically conductive. Nation 112,115, and 117 from DuPont are commonly used membranes in PEM fuel cells. The CL is a thin layer (several microns to several tens of microns thick) on either side of the membrane. It usually consists of microscale carbon particles. Each particle can support nanoscale platinum (Pt) catalyst particles, which are loosely embedded in a matrix of an ionomer. HOR occurs in the anode CL, and ORR occurs in the cathode CL. The electrochemical reaction is not evenly distributed over the CL; therefore, the Pt particles must be properly distributed in the CL to maximize the reaction efficiency and minimize the cost (Mehta et al, 2003).
Recent Research Trends in Polymer Nanocomposite Proton Exchange Membranes for Electrochemical Energy Conversion and Storage Devices
Published in Sundergopal Sridhar, Membrane Technology, 2018
A. Muthumeenal, M. Sri Abirami Saraswathi, D. Rana, A. Nagendran
Although Nafion membranes find extensive applications in fuel cells and VRFB environments, they do have limitations. One of the major problems with the perfluorosulfonic acid membranes has been, and still is, their high cost. Thus, for a PEMFC operating at the desired power density of about 0.6 Wcm−2, the cost of membrane alone will be about US$ 120 kW−1. The glass transition temperature of Nafion limits the upper temperature ranges to about 100°C. The useful operating temperature is closer to 80°C because the membrane loses water, and hence the ionic conductivity reduces at a high temperature. It functions as proton conductors only in a highly hydrated state, so humidification is necessary (Sridhar et al., 2001).
The transplacental transfer efficiency of per- and polyfluoroalkyl substances (PFAS): a first meta-analysis
Published in Journal of Toxicology and Environmental Health, Part B, 2022
Mareike Appel, Martin Forsthuber, Romualdo Ramos, Raimund Widhalm, Sebastian Granitzer, Maria Uhl, Markus Hengstschläger, Tanja Stamm, Claudia Gundacker
Transplacental transfer efficiency (TTE) of PFAS seems to depend upon carbon chain length and functional groups (PFCAs and perfluorosulfonic acids (PFSAs)). Several studies reported a U-shaped trend relating TTEs to carbon chain length and functional group (Cai et al. 2020; Eryasa et al. 2019; Gao et al. 2019; Kato et al. 2014; Li et al. 2020a; Liu et al. 2011; Pan et al. 2017; Wang et al. 2019; Zhang et al. 2021, 2013). Short- and long-chain compounds appear to be transported across the placental barrier more efficiently than medium-chain compounds. For PFCAs and PFSAs with different functional groups, a different rate of transfer efficiency was suggested by Cai et al. (2020) and Eryasa et al. (2019). Thus far, however, no attempt has yet been made to synthesize the empirical findings into a common picture through meta-analysis. The aim of the present study was to (1) provide meta-analytic evidence on the TTE of different PFAS and (2) test the hypothesis of a U-shaped trend in TTEs of 10 PFCAs (C4-C14) and 3 PFSAs (C6-C8). Valid data on maternal-to-infant transmission rates of legacy PFAS and less well studied PFAS (often referred to as ‘emerging’ or ‘new’ PFAS) are needed as these are critical to assessing fetal exposure.