Figure 1.

Model template structure for PBPK models applicable to PFAS. Chemical is introduced into the plasma (IV) or the gut lumen (oral).The absorbed fraction of an oral dose enters the GI tract or the liver by a first-order absorption rate constant $k_{\text{abs}}$, and the unabsorbed fraction enters the fecal storage compartment by a first order rate constant $k_{\text{unabs}}$. Chemical can also pass to the fecal storage compartment from the GI tract by the first order rate constant $k_{\text{f}}$ or from the liver by the first order rate constant $k_{\text{bile}}$. The kidney is separated into the filtrate compartment and the tissue compartment. Chemical enters the filtrate from the plasma by a first order rate constant $R_{\text{fil}}$, and, once in the filtrate compartment, chemical can be reabsorbed by a saturable process with maximum transport rate $T_{\text{m}}$ and affinity constant $K_{\text{t}}$ or eliminated to the urinary storage compartment by a first order rate constant $k_{\text{ust}}$. *See the Discussion section for more information on the biology of kidney filtration and reabsorption. Chemical is eliminated from the fecal and urinary storage compartments by first order rate constants $k_{\text{fst}}$ and $k_{\text{u}}$, respectively. $Q_{\text{i}}$ is the plasma flow rate between plasma and tissue i. Tissue compartments 1–5 are basic tissue compartments without metabolism, facilitated transport, or saturable binding processes. Additional information and a listing of all parameters included in the template are available in the supplementary materials (DOI: 10.23719/1520081).