Sex, age, and species differences of perfluorooctanoic acid modeled by flow- versus permeability-limited physiologically-based pharmacokinetic models

Integrated PBPK Modelling for PFOA Exposure and Risk Assessment

Per- and polyfluoroalkyl substances (PFASs) pose significant public health concerns due to their environmental persistence, bioaccumulation, and ubiquitous presence in human biomonitoring (HBM) data, despite regulatory restrictions. This study establishes a deterministic pharmacokinetic model for perfluorooctanoic acid (PFOA), enabling the estimation of PFOA concentrations in major human organs, even at low doses. The model integrates accumulation and recirculation mechanisms of PFOA in hepatic and renal tissues, leveraging publicly available HBM datasets (e.g., HBM4EU, NHANES, literature) to reconstruct bodyweight-normalized intake levels. Importantly, due to the extremely low urinary excretion concentrations of PFOA, most datasets were derived from blood-based measurements, particularly serum while confirming urine as unreliable biomarker of exposure. The analysis underscores the effectiveness of regulatory efforts in reducing PFOA exposures, as evidenced by declining time-trends in estimated exposure levels in recent studies. Risk characterization ratios were calculated based on recommended limits set by the European Food Safety Authority (EFSA), the United States, and Australia. While EFSA's tolerable weekly intake (TWI) indicated a high risk, other regulatory limits suggested less concern about risk at these intake levels. These findings highlight the need for continuous re-evaluation of exposures and targeted studies to identify key determinants of PFOA exposure, informing future regulatory measures. The study emphasizes the critical role of physiologically based pharmacokinetic (PBPK) modeling, HBM data, and exposure reconstruction in advancing chemical risk assessment. These tools form a science-based framework integral to the Chemical Strategy for Sustainability (CSS), enabling accurate predictions of internal exposure levels, empirical validation of models, and robust assessments of real-world exposure scenarios. The integration of these approaches supports the CSS goals of minimizing chemical risks while promoting innovation, ultimately contributing to a sustainable and protective regulatory landscape for human health and the environment.

Predicting Pharmacokinetics of Active Constituents in Spatholobi caulis by Using Physiologically Based Pharmacokinetic Models

BACKGROUND/OBJECTIVES

Spatholobi Caulis (SPC) is a medicinal plant that mainly grows in China and Southeast Asian countries and commonly used in clinics; the pharmacokinetic characteristics in humans need to be determined. This study was to establish the physiologically based pharmacokinetic (PBPK) models of multiple active constituents from SPC in rats, and predict the pharmacokinetic properties of rats with different dosages and extrapolated to humans.

METHODS

The parameters were collected based on our previous study and by prediction using ADMET Predictor software predict. The PBPK models for 3'-methoxydadizein (1), 8-O-methylretusin (2), daidzin (3), and isolariciresinol (4) administered orally to rats were established using GastroPlus software. These models were employed to simulate the pharmacokinetic properties in rats across various dosages, and subsequently extrapolated to humans. The calculated parameters including Cmax, Tmax, and AUC were compared with observed values. The accuracy of the PBPK models was assessed using fold-error (FE) values.

RESULT

The FE values ranged from 1.03 to 1.52, meeting the PBPK model regulations where FE should be less than 2. The sensitivity analysis focusing on the absorption amount and AUC0→t of these four constituents in humans was also conducted. These results confirm the successful establishment of PBPK models of these four constituents from SPC in this study, and these models were applicable to predict pharmacokinetics across various doses and extrapolate across species.

CONCLUSIONS

The PBPK models of four constituents can be used to predict the pharmacokinetic characteristics in humans after oral administration of SPC and provide useful data for safe and rational medication in clinical practice.