Fluoride (F-) and cadmium (Cd) are toxicants found ubiquitously in the human environment. The aim of this review was to identify and characterize studies that attempted to determine the combined toxicity of F- and Cd. The effects of F- and Cd on liver and kidney (with a special focus on chronic kidney disease of unknown etiology), bone, tooth enamel, dental caries, and brain were taken into consideration. Based on the results of the studies described in this review, various types of combined toxicity of F- and Cd might occur: additive, synergistic, or antagonistic, with the latter two being true interactions. However, the type of combined action occurring seems to depend on many factors, such as which toxic effect is considered, the dose levels of F- and Cd and their dose ratio, exposure duration, presence of other elements, etc. Moreover, when analyzing the combined toxic effects of F- and Cd, the possible interactions of these toxicants with other elements (e.g., fluoride with aluminum and arsenic; cadmium with lead, arsenic, zinc, selenium, and calcium) should also be taken into consideration. We also may not exclude the independent action of F- and Cd on some selected functions/health outcomes. Due to the huge gaps in knowledge, additional studies are required to address this important public health issue, i.e., the combined effects of exposure to these common environmental toxicants, especially among people with high exposure to these elements.
