Cadmium is a toxic heavy metal that accumulates in the body, primarily affecting the liver and kidneys, with increasing levels in humans typically peaking around age 50. It has no known biological function and competes with zinc, potentially inhibiting enzyme reactions and increasing the risk of kidney damage, hypertension, heart diseases, and certain cancers. Cadmium is primarily sourced from cigarette smoke, refined foods, and industrial processes, and its toxic levels vary with exposure and environmental factors.