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Forensic Science

Novichok compound poisoned Navalny

German government reports toxicology findings on samples from poisoned Russian politician

by Laura Howes
September 8, 2020 | A version of this story appeared in Volume 98, Issue 35


Opposition activist Alexei Navalny holds a microphone in his hand.
Credit: Sergei Bobylev/TASS/Sipa USA/Newscom
Alexei Navalny

On Sept. 2, the German government announced that toxicological tests had provided “unequivocal proof” that Russian opposition leader Alexei Navalny was poisoned with a Novichok nerve agent. “It is therefore clear that Alexei Navalny is the victim of a crime,” said German Chancellor Angela Merkel at a press conference the same day. “The aim was to silence him.”

Navalny is a politician and outspoken critic of Russian president Vladimir Putin. He became ill on Aug. 20 while on a flight in Russia, and German doctors have been treating him at the Charité hospital in Berlin since Aug 22. According to a Sep. 7 statement from the hospital, Navalny is no longer in a medically induced coma and he is responding to verbal stimuli. Doctors are unsure about the poisoning’s long-term effects.

Novichok nerve agents include these organophosporus compounds.
Chemical structures of organophosphorus nerve agents A-230, A232, and A-234.
Novichok nerve agents include these organophosporus compounds.

Novichok agents were originally developed in the Soviet Union and made headlines in 2018 after a former Russian spy was poisoned by one of the compounds in the UK. The German government did not disclose the specific agent used against Navalny, so it is unclear if it is the same compound as the one used in 2018, but the mechanism of poisoning would be the same.

Novichoks are organophosphorus compounds that inhibit acetylcholinesterase enzymes in the body. These enzymes continually break down the neurotransmitter acetylcholine. When the agents block the enzymes, levels of the neurotransmitter build up, which can cause muscles to misfire or stop working all together, disrupting breathing and heart function.

Scientists at the Bundeswehr Institute of Pharmacology and Toxicology performed the tests on samples from Navalny. According to Marc-Michael Blum, an expert in chemical weapons testing who used to work for the Organisation for the Prohibition of Chemical Weapons (OPCW), these tests are likely to be similar to those used to identify Sarin poisoning (Forensic Toxicol. 2018, DOI: 10.1007/s11419-017-0376-7). These include using mass spectrometry to look for the poison bound to proteins found in the blood.

But Blum points out that these biomedical tests can’t be used to determine the source of the poison. “The concentrations (ppb levels) are just too low to do things like stable isotope ratios,” which can be a fingerprint for nerve agents, he explains in an email sent to C&EN. Also, impurities and by-products, which can help investigators determine how the compounds were made, get lost between when a person is poisoned and when tests are performed, as those compounds get metabolized or cleared from the body. However, he says “the tests show that biomedical analytical methods are mature and robust.”

At a press conference after a NATO meeting on Sept. 4, NATO Secretary General Jens Stoltenberg said, “the Russian government must fully cooperate with the Organisation for the Prohibition of Chemical Weapons on an impartial, international investigation.” Stoltenberg also called on Russia “to provide complete disclosure of the Novichok program to the OPCW.” Novichok chemicals are subject to the most stringent controls outlined in the Chemical Weapons Convention, an international treaty that prohibits the use of the weapons.

“Under the Chemical Weapons Convention, any poisoning of an individual through the use of a nerve agent is considered a use of chemical weapons,” said OPCW Director-General Fernando Arias in a Sept. 3 statement. “The OPCW continues to monitor the situation and stands ready to engage with and to assist any States Parties that may request its assistance.”


This story was updated on Sept. 16, 2020, to correct "ppd levels" to "ppb levels" in a quote supplied to C&EN.


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