What are heavy metals?

Heavy metals are defined as metallic elements that possess a high density and are known to be toxic even at low concentrations. This characteristic is significant because it differentiates them from other elements and materials that may not pose the same health risks. Heavy metals, such as lead, mercury, cadmium, and arsenic, can accumulate in the environment and in living organisms, leading to various detrimental effects on health and ecosystems. Their toxicity at low levels makes them a focal point in discussions surrounding pollution, especially aquatic pollution, where they can enter water bodies through industrial runoff, waste disposal, and other human activities.

The other answer choices do not accurately describe heavy metals. They either present incorrect characterizations, such as describing them as lightweight and non-toxic, or they define elements or compounds unrelated to the typical understanding of heavy metals and their impact on the environment. Understanding the specific qualities of heavy metals is crucial for environmental science, public health, and addressing pollution challenges.