A chemical thermodynamics-based approach to quantifying contaminant exposure

点击翻译按钮获取中文摘要

This grant will support a unique program of basic research that builds on the principles of chemical thermodynamics to advance chemical exposure assessment in general and the understanding of contaminant biomagnification in particular. Biomagnification is the process through which organisms can have higher lipid-normalized concentrations of contaminants in their bodies than are prevalent in the food they eat. It is arguably the most potent contaminant amplification process; even small emissions and relatively low environmental concentrations can lead to high internal exposure to biomagnifying contaminants. Because ethical considerations limit the type of investigations that can be conducted, a solid mechanistic understanding of biomagnification in humans and wildlife species has been elusive. Adopting innovative approaches that combine non-invasive or minimally invasive analytical chemistry methods with kinetic modelling, we will conduct a series of studies to elucidate how factors related to diet, digestion and contaminants influence biomagnification. We will use silicone-based equilibrium devices to quantify the capacity of paired food and feces samples for contaminants, which allows for an estimation of biomagnification potential in wildlife species and humans. We will compare the biomagnification potential of different carnivores being fed the same diet, investigate seasonal changes in the biomagnification of polar bears during catabolic and anabolic phases, and quantify the decrease in the biomagnification potential for contaminants caused by the ingestion of non-digestible fat substitutes and microplastics. Relying on human volunteers we will further study interindividual differences in biomagnification potential caused by different digestion efficiencies, e.g. influenced by the gut microbiome, and the differences in biomagnification caused by variable diet composition. By integrating the experimental findings into food chain bioaccumulation models and linking those models with global scale environmental fate and transport calculations, we will identify the terrestrial and marine wildlife populations that are in danger of experiencing the highest exposure to particular organic contaminants, i.e. the global canaries in the goldmine for biomagnifying substances. We will further use models to estimate the influence of the variability in human food digestion and assimilation capabilities on the measured variability in biomarkers of exposure (e.g. concentrations of biomagnifying contaminants in blood) within a population. Whereas bioaccumulation assessment is central to effective chemical management, the empirical basis for judging biomagnification has been heavily biased towards fish and lab animals. By studying biomagnification non-invasively in ways that had never been possible before, we will greatly enhance bioaccumulation assessment through generating information on those organisms most at risk from biomagnifying substances.