Elemental metals are commonly measured in clinical samples and account for a large percentage of routine clinical chemistry testing. Recall that the majority of elements are metals. Thus, common measurements of analytes like serum sodium, magnesium, calcium, iron, and potassium are, in fact, heavy metal testing. In this course, however, we will focus not on these common elements but instead will cover heavy metals found in lower concentrations within the body. These are sometimes referred to as trace elements. Trace elements usually refer to elements present in the body in amounts less than one microgram per gram of tissue.
Some essential trace elements have had a recommended daily allowance (RDA) established. These include zinc, iodine (which is not a metal), selenium, copper, and molybdenum.
Other trace elements are essential for human life but don’t have established RDAs. These include chromium, cobalt, and manganese. An Adequate Intake (AI) level is recommended for these elements, but there is no RDA. An AI is the level assumed to ensure nutritional adequacy and is used when evidence is insufficient to develop an RDA.
Some elements have no known biological function in humans and are associated with toxicity. These include aluminum, beryllium, cadmium, mercury, lead, and arsenic. We will review most of these elements in this course. In addition to these, other elements appear to have no physiologic role and may also be toxic. Still, since quantities of these elements are extremely low in the environment and exposures are exceedingly rare, they are not discussed in clinical contexts. Examples in this group include cesium, iridium, thallium, gadolinium, and a few other rare earth metals.
This course will cover the most significant trace, heavy metal elements: zinc, copper, chromium, cobalt, manganese, lead, arsenic, aluminum, cadmium, and mercury.
