In the last decade, Circular Economy has gained importance as a way to minimize emissions and consumption of raw materials. It is strongly based on sharing, reusing, repairing, and recycling. Indeed, it represents a key value for Sustainable Transition since our planet can count on finite resources and circularity implies that materials can undergo the same processes many times (e.g. production, disposal, triage). However, some harmful compounds may accumulate in the soil, in the hydrosphere, or even in human bodies during these cycles. In literature, this issue has never been developed with a complex network approach. The aim of this thesis is to investigate how this could be done.