Computer recycling is the process of extracting valuable secondary raw materials from obsolete computers. The EPA estimates that 30 to 40 million personal computers are ready for recycling each year. But because of the source material used to make them, simply throwing away your old computer can be dangerous and harmful to the environment. Depending on their age, computers can contain such toxic materials as lead, mercury, cadmium, chromium, and radioactive isotopes. They also contain valuable materials worth recovering, such as gold, tin, aluminum, iron, silicon, copper, and an array of different plastics.