The presence of potentially toxic cations and anions in the environment has become a global problem, mainly due to their high toxicity and ability to bioaccumulate/biomagnify. Although elements considered toxic may occur naturally, human activities contribute significantly to increasing the concentration of these substances in ecosystems. In this context, this review addresses details of the disposition of mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr), selenium (Se) and copper (Cu) ions in soils and water bodies, as well as the consequences of the presence of these ions to human health and the environment. In small amounts, part of these elements are considered essential and with established and significant functions in several biological processes, but in high concentrations they can cause serious damage to human health.