The Five Most Poisonous Substances: From Polonium to Mercury

Feared for a good reason. viperskin, CC BY-NC-SA
Feared for a good reason. viperskin, CC BY-NC-SA

With the announcement of an inquiry into the murder of Alexander Litvinenko, talk of poisons is back in the news. There are many articles with lists of the most poisonous substances, which are often gathered based on their acute toxicity as measured by something called LD50. But acute toxicity is only one factor that needs to be considered, and relying solely on LD50 or similar measures is overly simplistic.