Modeling bioaccumulation in humans using poly-parameter linear free energy relationships (PPLFERS)

Chemical partition coefficients between environmental media and biological tissues are a key component of bioaccumulation models. The single-parameter linear free energy relationships (spLFERs) commonly used for predicting partitioning are often derived using apolar chemicals and may not accurately capture polar chemicals. In this study, a poly-parameter LFER (ppLFER) based model of organic chemical bioaccumulation in humans is presented. Chemical partitioning was described by an air–body partition coefficient that was a volume weighted average of ppLFER based partition coefficients for the major organs and tissues constituting the human body. This model was compared to a spLFER model treating the body as a mixture of lipid (≈ octanol) and water. Although model agreement was good for hydrophobic chemicals (average difference 15% for log KOW > 4 and log KOA > 8), the ppLFER model predicted ~ 90% lower body burdens for hydrophilic chemicals (log KOW < 0). This was mainly due to lower predictions of muscle and adipose tissue sorption capacity for these chemicals. A comparison of the predicted muscle and adipose tissue sorption capacities of hydrophilic chemicals with measurements indicated that the ppLFER and spLFER models' uncertainties were similar. Consequently, little benefit from the implementation of ppLFERs in this model was identified.

Research Highlights
► Implementation of ppLFERs resulted in on average 90% lower predicted body burdens.
► Uncertainties in spLFER and ppLFER predictions were similar.
► The benefit from implementation of ppLFERs in bioaccumulation models was limited.