Final answer:
Heavy metal substances are chemical agents that can have significant effects on human health. Examples of heavy metal substances include mercury, lead, and cadmium.
Step-by-step explanation:
Heavy metal substances are chemical agents that can have significant effects on human health. Examples of heavy metal substances include mercury, lead, and cadmium. These heavy metals are typically produced as by-products of mining and manufacturing processes. They can accumulate in tissues and may cause sickness or death when they enter the body.