The aim of this study was to identify, among selected environmental toxins, the substance with the highest in vitro toxicity to neurons combined with the most marked induction of calcium imbalance, oxidative stress and mitochondrial dysfunction. Exposure of primary cultures of rat cerebellar granule cells for 30 min to polychlorinated biphenyls (PCBs) or brominated flame retardants (BFRs) at concentrations of 10-50 μM identified tetrabromobisphenol A as the compound with the highest toxicity. At a concentration of 25 μM, apart from the moderate activation of ⁴⁵Ca uptake, this BFR induced the most pronounced increase in intracellular Ca²⁺ concentration, depolarization of mitochondria, and activation of ROS production.