Which heavy metal is considered toxic and poses a burden to human health?

Lead is recognized as a highly toxic heavy metal that poses significant health risks to humans. It can be absorbed through various routes, including ingestion and inhalation, and once in the body, lead interferes with multiple biological processes. It is known to affect the nervous system, particularly in children, leading to developmental delays, cognitive deficits, and learning difficulties. Lead exposure can also result in kidney damage, hypertension, and reproductive issues in adults.

In contrast to lead, other metals listed, like copper and zinc, are essential trace elements necessary for various physiological functions in the body, although they can also be toxic at high levels. Arsenic is toxic as well, but lead's historical prevalence in environmental contamination and its well-documented health impacts highlight its particular concern in the realm of human health. Thus, lead is more prominently recognized as a heavy metal that poses a serious burden to health compared to the others listed.