The document discusses health and environmental effects of heavy metals, focusing on major elements like mercury, cadmium, chromium, and lead, which are toxic even at low concentrations. It outlines historical disasters caused by heavy metal pollution, such as the Minamata tragedy and the Sandoz incident, and details the health impacts on humans, including nervous system disruption and reproductive harm. Additionally, the document highlights how these metals can bioaccumulate in ecosystems, posing risks to wildlife and human health through contaminated food and water sources.