Bioaccumulation Behavior of Pharmaceuticals and Personal Care Products in Adult Zebrafish (<i>Danio rerio</i>): Influence of Physical-Chemical Properties and Biotransformation

Abstract

The factors influencing bioaccumulation of pharmaceuticals and personal care products (PPCPs) in aquatic organisms are not well understood. The present study involved a comprehensive laboratory investigation to assess the bioaccumulation behavior of several PPCPs in adult zebrafish (<i>Danio rerio</i>). The studied PPCPs included several ionogenic organic compounds (IOCs) such as weak acids and weak bases. Experiments involved two exposure groups (high and low) and a control group, with a 6 day aqueous exposure, followed by a 7 day depuration phase under flow-through conditions. Uptake rate constants (<i>k</i>_u) ranged between 0.19 and 8610 L·kg^–1·d^–1, while depuration rate constants (<i>k</i>_d) ranged between 0.14 and 5.14 d^–1 in different fish tissues. Steady-state bioconcentration factor (BCF_ss) values varied widely among the studied PPCPs, ranging from 0.09 to 6,460. In many cases, BCF_ss values of individual PPCPs differed substantially among different fish tissues. Positive linear relationships were observed between log BCF_ss values and physical-chemical properties such as octanol–water distribution coefficients (log <i>D</i>_ow), membrane–water distribution coefficients (log <i>D</i>_mw), albumin–water distribution coefficients (log <i>D</i>_BSAw), and muscle protein–water distribution coefficients (log <i>D</i>_mpw), indicating the importance of lipid–, phospholipid–, and protein–water partitioning. The results also showed that for many PPCPs, the estimated whole-body metabolism rate constant (<i>k</i>_m) values were comparable to the observed depuration rate (<i>k</i>_d), indicating that metabolism plays a major role in the overall elimination of these compounds in zebrafish. An exception was sertraline, which exhibited a <i>k</i>_d value (0.4–0.5 d^–1) that was much higher than the estimated whole-body <i>k</i>_m (0.03 d^–1). Overall, the results help to better understand the influence of physical-chemical properties and biotransformation on bioaccumulation behavior of these contaminants of concern in aquatic organisms