Harmful Elements
Some elements should be avoided completely. These foes include metals, such as lead and mercury, and the metalloid arsenic. Harmful elements may enter the body in water, air, or food. Inside the body, nonessential elements may compete with essential elements and disrupt cell functions. Large amounts of harmful elements can stress the body's normal methods for eliminating toxins. Harmful elements can build up in body tissues.
For decades lead was used in paint and in gasoline to improve engine performance. These products are now lead free. The use of mercury in thermometers has been reduced and arsenic compounds are no longer used in pesticides.
Many trace elements are only helpful if ingested in the small recommended amounts. Larger quantities of most trace elements can be harmful, as can larger-than-required amounts of lesser elements, such as sodium.