A preliminary investigation into the in vivo kinetics of branched isomers of perfluoroalkyl carboxylic acids in human bile, urine, and cerebrospinal fluid: A comparison to linear isomers.

Perfluoroalkyl carboxylic acids (PFCAs) are persistent in the environment, and can enter the human body. This study aimed to investigate the in vivo kinetics of branched PFCAs with seven to fourteen carbon atoms (C₇ to C₁₄) using samples collected different individuals: bile (n = 5), urine (n = 10), and cerebrospinal fluid (CSF) (n = 7), with their corresponding serum. This study revealed that the clearance values of PFCAs were greatly affected by whether they were linear or branched. Furthermore, it demonstrated that C₇ and C₈ branched PFCAs had higher total (renal plus fecal) clearance values than their linear counterparts and that they were more easily excreted from the body via urine (higher renal clearances). However, when the chain length was C₉ or longer, the clearance value was almost the same as that of linear PFCAs because fecal clearance through the bile is the main route of clearance from C₉ onwards, and there is no significant difference in fecal clearance between branched and linear ones. The ratio of branched to linear PFCAs in the CSF was similar as that in the serum for all PFCAs (C₇ to C₁₄) measured, and there appeared to be no difference in blood-brain barrier permeability. This information will be useful for evaluating potential health risks related to branched PFCAs.