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.
LD50 is a measure of the dose of a substance needed to kill half of a given population, usually of mice. It is usually measured in dosage needed per unit weight of the animal.
This seems a cruel but objective way to quantify how deadly a given substance is, but overall toxicity is more complex than that.Toxicologists are aware of the limitations of LD50,
and for technical, ethical, and legal reasons, measuring that values in animals is increasingly less common. So here is a list of substances that are more poisonous than their LD50 values might indicate.
1. Botulinum toxins
Even though some of them are used in the cosmetic industry (including in botox), the botulinum family of neurotoxins includes the most toxic substances known to man.
The LD50 values reported for these seven proteins are about 5 ng/kg (ng stands for nanogram, which is a billionth of a gram).
