Exposure, Toxicity, Health Impacts, and Bioavailability of Heavy Metal Mixtures

Exposure to chemical mixtures is a common and important determinant of toxicity in human and environmental health issues. Although there is a wealth of information on single metal interactions, very few studies have been conducted on the effects of mixtures of heavy metals on environmental quality and human health. Current national regulatory guidelines for soils are based solely on individual metal and metalloids concentrations. However, heavy metals and metalloids do not exist in isolation at the majority of sites. Soil properties such as pH, Eh, clay minerals, and cation exchange capacity influence multiple metal interactions. There are numerous adverse health effects on human, animals, and the environment due to mixed metal exposure resulting from additive and synergistic interactions even when concentrations of the individual metals are below their ecotoxicological benchmark levels. Two key strategies currently recognized as suitable for predicting toxicity of a mixture are: first, concentration addition, also known as Loewe additivity and second, effect addition, also referred to as the Bliss model of independent action. In this review we draw attention to research illustrating the interactions of multiple metal contaminants and their potential health impacts.