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Heavy metal is a broad term that describes a group of naturally occurring metallic elements of high molecular weight and density compared to water.[1] At low concentrations, certain heavy metals, such as iron, zinc, copper, and manganese, are essential for human survival but can become toxic agents at higher concentrations. Other heavy metals, such as arsenic, cadmium, lead, thallium, and mercury, serve no biological role. However, they will inevitably enter the human body due to their presence in the environment. Similarly to essential metals, they induce toxicity once specific concentrations are reached.[2] Confirming the diagnosis of elemental toxicity is challenging as signs and symptoms are similar to those of many non-element-dependent diseases. Diagnosis of elemental toxicity requires demonstration of all of the following factors: (1) a source of elemental exposure must be evident, (2) the patient must demonstrate signs and report symptoms typical of the element, and (3) abnormal element concentration in the appropriate tissue must be evident. If one of these features is absent, one cannot make a conclusive diagnosis of elemental toxicity. The laboratory plays a vital role in this process, and appropriate specimen collection coupled with accurate analysis can aid in correct diagnosis.[3] In clinical practice, analysis of toxic elements should always be considered in the clinical work-up of the patient with (1) renal disease of unexplained origin, (2) bilateral peripheral neuropathy, (3) acute changes in mental function, (4) acute inflammation of the nasal or laryngeal epithelium, or (5) a history of elemental exposure.[4]

The general mechanism of heavy metal toxicity disrupts metabolic homeostasis at a cellular level. This results from excess heavy metal in the body, leading to deposition and accumulation in various tissues. The metallic deposits hinder biological function via enzymatic, metabolic, and mitochondrial interference.[17] The extent of this dysfunction and subsequent damage depends on the pharmacokinetics of each metal and the route of exposure.

Heavy metal toxicity can present as general symptoms and, therefore, make diagnosis difficult. A thorough history is needed to determine if any environmental metal sources are present, especially for children, due to the long-term neurological effects that can occur. Routine heavy metal tests should be performed when a patient has occupational exposure. Clinicians should consult their local poison control center or toxicologist if heavy metal toxicity is suspected. Working closely with public health officials can also provide insight into local regulation violations leading to above-average metal concentrations in patients. Nurses and laboratory technologists should be trained in proper technique and handling of vials to minimize trace elemental contamination that can potentially interfere with results.