Cadmium - Printed circuit boards, semiconductors. By 2005, a total of more than 2 million pounds will exist in discarded computers. Cadmium and cadmium compounds accumulate in the human body, in particular in kidneys it is adsorbed through respiration but is also taken up with food. Cadmium can easily be accumulated in amounts that cause symptoms of poisoning. Mercury - Batteries, switches.
Methylated mercury causes chronic damage to the brain.
Chromium - Used as corrosion protection in steel. By 2005, estimated 1.2 million pounds. Chromium VI can easily pass through membranes of cells and is easily absorbed producing various toxic effects within the cells. It causes strong allergic reactions even in small concentrations. Chromium VI may also cause DNA damage.