What types of substances are categorized as heavy metals?

Heavy metals are primarily defined as metallic elements that exhibit toxic properties at low concentrations, which makes them harmful to organisms and the environment. The classification of these substances is based on their potential for toxicity and their tendency to accumulate in biological systems. Heavy metals include elements such as lead, mercury, cadmium, and arsenic, which can cause significant health issues, including neurological and kidney damage, among others.

The identification of heavy metals revolves around their poisonous nature, particularly when they enter biological systems through various pathways. This toxicity is often due to their capability to disrupt biological processes, leading to detrimental effects on health and ecological balance. This understanding is critical in fields such as forensic science, environmental monitoring, and public health.

Other options do not accurately characterize heavy metals: substances that promote health are typically benign and lack the toxic characteristics associated with heavy metals; inorganic substances that are benign would not fall under the heavy metal category because they lack the harmful potential; and the reference to only naturally occurring elements disregards synthetically produced metals which can also exhibit heavy metal characteristics.