On November 1, 2006 former soviet spy Alexander Litvineko suddenly fell ill at a London hotel. His hair fell out and he was dead by November 23. He'd been poisoned with POLONIUM-210 . POLONIUM, the element 84 is one of the deadliest substance in the planet. Between 10 and 30 micro grams is enough to kill an average adult. That's smaller than the grain of salt.
It emits high energy alpha radiation. destroying organs and causing cancer. It can be absorbed through unbroken skin. It need to be ingested or inhaled. The scientist Mary curie discovered polonium in 1898. It is believed that a lab accident exposed her daughter to the element causing leukemia and eventually killing her.
It occurs naturally in incredibly small amounts. Trace levels in tobacco plants contribute to cancer causing smoke. The amount used to poison Litvineko indicates it was made in a nuclear reactor. In January of 2016, British authorities released a report saying the polonium came from Russia.