Navalny poisoningNovichok: How Are Victims Surviving Poisoning?

Russian opposition leader Alexei Navalny is likely to survive a suspected poisoning with the nerve agent Novichok, according to the hospital treating him. There have now been at least six known cases of serious Novichok poisoning in the past two years. But only one victim tragically died from it.

Why is that? Is the substance less lethal than previously thought? Or could it be that the stockpile of the nerve agent is degrading?

Nerve agents were discovered through pesticide research. They belong to a group of substances known as organophosphorus chemicals, or “OPs” for short. There are literally thousands of OP substances, many of which can damage the body by inhibiting a family of enzymes known as “cholinesterases” that are critical to regulating the activity of the central nervous system in animals.

OP pesticides are much less toxic to humans than nerve agents because they have been designed to specifically inhibit insect cholinesterases. In contrast, nerve agents target human cholinesterases.

By disrupting the nervous system, Novichok and other nerve agents can kill people through asphyxiation or cardiac arrest. We know they are deadly. The nerve agent Sarin caused multiple casualties in 1995 when it was released in the Tokyo subway.

The nerve agent VX is thought to have killed Kim Jong-nam, the half brother of North Korea’s leader Kim Jong-un, in just 20 minutes after it was allegedly smeared across his face. But all types of nerve agent poisoning can be treated with standard antidotes such as atropine and diazepam.

Little is known about the types of Novichok that have been synthesised or deployed in assassination attempts, other than that they tend to be liquids or powders.

The Dose Makes the Poison
One of the fundamental principles of toxicology was first proposed by a 16th century alchemist, known as Paracelsus, who is often credited with the statement “sola dosis facit venenum”, or “the dose makes the poison”. It means that all substances are capable of being toxic if administered in a sufficient dose. This applies to normally innocuous chemicals such as water, as well as highly toxic materials such as nerve agents.

So have the recent Novichok victims somehow got smaller doses than intended? In the case of the poisoning of Sergei and Yulia Skripal in Salisbury, UK, in 2018, it appears that the poison was initially applied to a door knob.