Thallium is the element used as rat poison and in the electro-technical and chemical industries. The element was discovered by Sir William Crookes in 1861 and appears as No. 81 on the periodic table.
Thallium is toxic to rats and also has negative effects on plants, such as leaf color changes and growth decline. The human body does absorb the substance effectively through the skin and lungs, with most thallium poisoning is due to the accidental intake of rat poison. In humans, accumulation may lead to side effects that include tiredness or fatigue, headaches, depression, loss of appetite, leg pain, hair loss and loss of vision.