Estimated bioconcentration factors (BCFs) for the C(4) through C(8) perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acid (PFCA) congeners.

Bioconcentration factors (BCFs) were estimated for all congeners in each of the C(4) through C(8) homologue groups for perfluorinated alkylsulfonic acids (PFSAs) and alkylcarboxylic acids (PFCAs). Predictive equations were developed between molecular areas and volumes using optimized gas-phase geometries from the AM1 and PM3 semiempirical computational basis sets and previously determined BCFs for representative straight-chain members of each contaminant class. Molecular area approaches for estimating PFSA and PFCA BCFs resulted in more variability both between and within homologue groups than the use of molecular volumes as proxies for hydrophobicity of the perfluoroalkyl chain. An increasing degree of perfluoroalkyl chain branching within each homologue group reduces the estimated BCF, suggesting that the more linear PFSA and PFCA congeners will display the highest BCFs in aquatic organisms.