Flame retardants are compounds widely used in industry. They are added to all kinds of products, such as clothing, electronics, furniture, or upholstery, in order to reduce their flammability. Over time, they have been shown to be very persistent environmental pollutants, which accumulate in organisms and can have harmful effects on both organisms and people. In the study, researchers demonstrate that three species of cetaceans—the common dolphin, the pilot whale, and the bottlenose dolphin—with different distribution areas and feeding habits, accumulate and biomagnify flame retardants. The study shows that cetaceans at the highest level of the food chain accumulate greater levels of these pollutants. Biomagnification means that the concentration of pollutants is higher in organisms at higher levels of the trophic chain because they ingest and accumulate in their bodies the pollutants from their prey. This work demonstrates a direct relationship between higher trophic levels and greater concentrations of flame retardants. Most interestingly, biomagnification occurs both for the classic and now prohibited PBDEs, and for their substitutes, the dechloranes. The dolphins analyzed in this study occupy different positions in the trophic chain. The bottlenose dolphin, in the most elevated position, is precisely the one with the highest concentrations of these pollutants. In nearly 20% of the samples analyzed, values were found to be greater than the established limits—for example, for seals—above which endocrine disruption effects are observed, specifically in the thyroid hormone. This indicates that these pollutants pose a serious problem for animals at the upper levels of the food chains, such as dolphins and humans. The study also demonstrates that, despite their prohibition in Europe in 2004, the old flame retardants are still present in the environment, and that the alternatives, the dechloranes, are just as persistent as the former. Furthermore, although their toxicological effects are not yet known, some studies suggest that dechloranes could also be endocrine disruptors and genotoxic