Property Estimation of Per‐ and Polyfluoroalkyl Substances: A Comparative Assessment of Estimation Methods

Abstract

To accurately predict the environmental fate of per‐ and polyfluoroalkyl substances (PFAS), high‐quality physicochemical property data are required. Because such data are often not available from experiments, assessment of the accuracy of existing property estimation models is essential. The quality of predicted physicochemical property data for a set of 25 PFAS was examined using COSMOtherm, EPI Suite, the estimation models accessible through the US Environmental Protection Agency's CompTox Chemicals Dashboard, and Linear Solvation Energy Relationships (LSERs) available through the UFZ‐LSER Database. The results showed that COSMOtherm made the most accurate acid dissociation constant and air–water partition ratio estimates compared with literature data. The OPEn structure‐activity/property Relationship App (OPERA; developed through the CompTox Chemicals Dashboard) estimates of vapor pressure and dry octanol–air partition ratios were the most accurate compared with other models of interest. Wet octanol–water partition ratios were comparably predicted by OPERA and EPI Suite, and the organic carbon soil coefficient and solubility were well predicted by OPERA and COSMOtherm. Acid dissociation of the perfluoroalkyl acids has a significant impact on their physicochemical properties, and corrections for ionization were included where applicable. Environ Toxicol Chem 2020;39:775–786. © 2020 SETAC

Characterizing the Air Emissions, Transport, and Deposition of Per- and Polyfluoroalkyl Substances from a Fluoropolymer Manufacturing Facility

“…The saturation vapor concentration, C *, , was used to predict condensation to the particulate organic phase. The predicted C * values ranged from 2.0 × 10 4 to 3.6 × 10 12 μg m –3 (Table S2), which can vary up to 7 orders of magnitude where measurements exist for comparison (Table S3), although OPERA was shown to most accurately predict C * for a series of PFASs compared to other common property estimation models . The enthalpy of vaporization (ACD/labs, ), used to adjust the volatility to atmospheric temperature, ranged from 17.2 to 56.8 kJ mol –1 .…”

“…The predicted C* values ranged from 2.0 × 10 4 to 3.6 × 10 12 μg m −3 (Table S2), which can vary up to 7 orders of magnitude where measurements exist for comparison (Table S3), although OPERA was shown to most accurately predict C* for a series of PFASs compared to other common property estimation models. 38 The enthalpy of vaporization (ACD/labs, http://www.chemspider.com/), used to adjust the volatility to atmospheric temperature, ranged from 17.2 to 56.8 kJ mol −1 . Henry's law constants were estimated with OPERA to model solubility-driven condensation to the aqueous phase of atmospheric particles, cloud liquid water, and aqueous ground surfaces (e.g., bodies of water, leaf stomata, etc.…”

Occurrence of per- and polyfluoroalkyl substances in water: a review

“…This is consistent with the finding from several studies demonstrating that both K d and organic carbon-water partition coefficient (K oc ) were higher in PFASs of longer chain length. [150][151][152][153] This partly has to do with increasing hydrophobicity with increasing PFAS chain length. 105,154 Furthermore, comparing PFHxA with PFHxS, and PFOA with PFOS, Fig.…”

Reliable Prediction of the Octanol–Air Partition Ratio

“…Lampic and Parnis ( 2020 ) compared the prediction performance of ppLFERs with estimated solute descriptors, OPERA, COSMOtherm, and EPISuite for various physical–chemical properties of per‐ and polyfluoroalkyl compounds at 25 °C. The OPERA model had the smallest reported RMSE and MAE for K OA (Lampic & Parnis, 2020 ). The experimental data set included multiple measurements for the same compound, which can bias the statistical calculations.…”