Ocean health is inextricably linked to human health. Connections between the health of humans, animals, and the environments in which they live are recognized within the One Health paradigm. Our interdisciplinary research examines cetacean health in the context of marine mammals as sentinel species. Such sentinels are used to gain early warnings about current or potential negative impacts on individual- and population-level animal health. Marine mammals are described as prime sentinels because many species have long life spans, are long-term coastal residents, feed at a high trophic level, and have large blubber stores that can serve as depots for anthropogenic chemicals and toxins. Many of our studies examine legacy toxins including PCBs, DDTs and trace elements through to emerging contaminants including PFAs, BFRs and microplastics. Additionally, we examine wider human impacts affecting marine mammal populations including vessel impacts and climate change.