What makes Metals Substances different?
Metal substances are naturally occurring substances that are present in our environment. Everybody is in some way, and in some form exposed to metal substances. On the earth, there are natural background levels of metal substances (as they are part of nature), and levels that have been added through human activities, as anthropogenic sources. A distinction between both is necessary when assessing risks from metal exposures.
One of the most important points is that many metal substances are essential to life (human, animal and/or plants). This means that for these metal substances there is a concentration at which the organism functions optimally. If the concentration of the metal is too high, toxicity will occur. If the concentration is too low, deficiency will also cause adverse effects. A common everyday example is iron deficiency, in which an inadequate amount of iron intake can lead to anaemia and other potential health issues.
Many organisms have developed a tolerance to some non-essential metal substances, due to the natural exposure to such metal substances in their environment. For essential metal substances, organisms have developed specific mechanisms to absorb these metal substances. The absorption, distribution, transformation, and excretion of a metal (toxicokinetics) within an organism depends on:
- The metal substance (whether it is essential or not for that particular organism)
- The chemical and physical form and properties of the metal substance
- The organism’s ability to regulate and/or store the metal
- The natural concentration of the metal substance in the environment of the organism
Living organisms have to maintain appropriate concentrations of essential metal substances in order to support biological function. Too little or too much of the metal can result in adverse effects. This is a fundamental principle that needs to be considered in hazard and risk assessment for metal substances.