Toxins and perfumes: the death of dissidents and spies

The ex-spy is dead. Alexander Litvinenko died like a spy, almost like in a movie. An obscure poison got the best of him...but how toxic are poisons? Paracelsus once said: "everything is poison, it depends on the dosage"...some toxins are very powerful some less. Lets list a few toxins and compare them...just to have an idea.

• Botulism toxin is an exotoxin produced by Clostridium botulinum. This toxin is the MOST toxic toxin known to man. Its lethal dose is known to be around 200 pg/kg (so a human could be killed by as little as 10 ng of this toxin)...used as Botox
  
• Tetanospasmin is another highly lethal bacterial toxin. It is produced by Clostridium tetani bacteria. Ten times less powerful than botulinum toxin, it would take a dosage of 100 ng to kill a human.
• Strychnine is a plant derived toxin (from Strychnos nux-vomica tree) and is considered very toxic although it would take around 50 mg to kill a human. A problem with this toxin, the taste can be detected at very low doses
• Ricin is a toxin extracted from castor beans (Ricinus communis). Its lethal dose is 0.2mg. This toxin was used to kill Georgi Markov in London in 1978. Markov was shot in the leg and the bullet was coated with ricin.
• Sarin is a very toxic substance also known as O-Isopropyl methylphosphonofluoridate. This poison was used in a japanese subway in Tokyo in 1995 by a religious sect; Aum. The lethal dosage for sarin is around 0.5 mg (humans).
• Cyanide is a well known poison. There are various forms of this toxin so the dosage varies. Was widely used in suicides by Nazi. As a comparison, Sarin is know to be around 500 times more toxic than cyanide derivatives
• Dioxin is also a well known toxin. It was found in agent orange used as a defoliant durins the Vietnam war. Recently Viktor Yushchenko was poisoned with dioxin. The lethal dose of dioxin is around 1 mg.
• Polonium killed the ex-spy Alexander Litvinenko. Although that, weight for weight, this radioactive element is more toxic than cyanide it will take micrograms to milligrams to kill a human.