The main use of metallic arsenic is for strengthening alloys of copper and lead to use in car batteries. It is also used as an n-type dopant in semi conductive electronic devices. Arsenic is also used in numerous pesticides, herbicides and insecticides though this practice is becoming less common as more of these products are banned. It has been used as a wood preserver because of its toxicity to insects, bacteria and fungi. Arsenic is added to animal food to prevent disease and to promote growth. Arsenic is used in the medical treatment of cancers such as acute promyelocytic leukemia. It is also used in medical solutions such as Fowler’s solution for psoriasis Arsenic-74 an isotope is being used as a way to locate tumours within the body. It produces clearer pictures than that of iodine. Arsenic is added in small quantities to alpha-brass to make it resistant to leaching zinc. This grade of brass is used to make plumbing fittings or other items which are in constant contact with water.