Combining Chemical Analysis and In Vitro Bioassays to Characterize the Exposome of Organic Contaminants in Marine Mammals

Abstract

Marine mammals are exposed to a wide range of environmental pollutants. Considering the complex mixture of chemicals that marine mammals are (potentially) exposed to, monitoring the chemical burden is necessary to evaluate the risk to these animals. Within the framework of this thesis, an innovative sampling approach was developed and validated that captures a broad variety of hydrophobic organic contaminants (HOCs) in different organs from marine mammals. Hence, passive equilibrium sampling (PES) with silicone was used to study the mixtures of chemicals in four organs of marine mammals: liver, kidney, brain, and blubber. Silicone-based PES allowed the assessment of the exposome of marine mammals by using two analytical techniques: targeted instrumental analysis of legacy and emerging HOCs with gas chromatography-high resolution mass spectrometry (GC-HRMS) and bioanalytical characterization in in vitro cell-based reporter gene assays. The analytical results highlighted the complexity of the chemical mixtures that were found within these animals: 70 different HOCs were determined, such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polycyclic aromatic hydrocarbons (PAHs). Moreover, the extracts activated the xenobiotic metabolism (aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor gamma (PPARγ)), the Nrf2-depended oxidative stress response, and caused cytotoxic effects. The mixture effects measured with the in vitro assays were compared with the predicted effects based on the quantified chemical mixture, by ‘iceberg modeling’, and for most cases, only a minor fraction could be explained by the targeted chemicals. Combining chemical analysis with the evaluation of mixture effects of environmental pollutants in marine mammals is useful for the determination of thresholds of adverse effects and provide information for large-scale monitoring and conservation programs.