By combining paleoecology, geochemistry, and ecotoxicology, CABAC will provide a new understanding of the links between source – exposure – bioaccumulation in a context of legacy contamination in the contemporary environment, all made possible by implementing Pb-, C- & N-isotopes as geochemical tracers across environmental compartments and food-chain niches. The objective of CABAC is to use fish as dynamic biosensors of impending changes in contaminant exposure and to assess the utility of fish otoliths as (mobile) natural archives of contamination in high-altitude mountain ecosystems. Specifically, CABAC aims to develop a novel and innovative method that will couple Laser and MC-ICP-MS, and thus measure the isotopic signatures stored in otoliths of mountain fish (e.g. Pb, Sr), which will be combined with existing data from previous OHM studies on trace metals in soil, peat and lake sediment. This will allow us to reconstruct the contamination history of the area, the contaminant exposure over the lifetime of each individual, as well as decipher potential shifts in contaminant sources over time (including seasonal changes such as snowmelt or flooding). Such information is of paramount importance in order to successfully predict and protect future ecosystem health in frontier ecosystems (i.e. high-altitude mountain environments). The output of CABAC will also be made available to mountain stakeholders thus optimizing the risk assessment of contaminant exposure towards human health (i.e. risk of legacy contamination towards recreational anglers as well as mountain tourism in general).