Methodologies for assessing exposure to metals: speciation, bioavailability of metals, and ecological host factors.

Host factors play a role in the bioavailability of metals, making it critical to understand their nature and how to measure them, as well as how to measure bioavailability with respect to host factors. The host factors that are critical to consider during all phases of bioavailability studies are age, gender, size, genetic characteristics, behavior (food chain considerations), and interactions between all of them. Some of these vulnerabilities are unique to individuals, populations, species, or communities. There are many interactions between and among metals, the species of metals, and the physical environment (pH, salinity). Some factors enhance uptake and absorption, whereas others moderate it. Moreover, some metals have greater effects on invertebrate organisms, whereas other metals (or species thereof) affect vertebrates more strongly. Fish and wildlife are useful as sentinel species and bioindicators because they can help us understand the risk to the organisms themselves, to the ecosystem, and to humans.