The influence of chemical degradation during dietary exposures to fish on biomagnification factors and bioaccumulation factors

The chemical dietary absorption efficiency (E_D) quantifies the amount of chemical absorbed by an organism relative to the amount of chemical an organism is exposed to following ingestion. In particular, E_D can influence the extent of bioaccumulation and biomagnification for hydrophobic chemicals. A new E_D model is developed to quantify chemical process rates in the gastrointestinal tract (GIT). The new model is calibrated with critically evaluated measured E_D values (n = 250) for 80 hydrophobic persistent chemicals. The new E_D model is subsequently used to estimate chemical reaction rate constants (k_R) assumed to occur in the lumen of the GIT from experimental dietary exposure tests (n = 255) for 165 chemicals. The new k_R estimates are corroborated with k_R estimates for the same chemicals from the same data derived previously by other methods. The roles of k_R and the biotransformation rate constant (k_B) on biomagnification factors (BMFs) determined under laboratory test conditions and on BMFs and bioaccumulation factors (BAFs) in the environment are examined with the new model. In this regard, differences in lab and field BMFs are highlighted. Recommendations to address uncertainty in E_D and k_R data are provided.