Novichok in a hotel room?
The ongoing investigation into an act of chemical terrorism in the United Kingdom has focused on two Russian nationals. This pair travelled to the UK under the names “Alexander Petrov” and “Ruslan Boshirov”, which are almost certainly pseudonyms. The travel itinerary of this pair of alleged assassins has been painstakingly reconstructed and released to the public by UK authorities. Significant research in open source and leaked documentation have linked the pair to the GRU, Russia’s military intelligence agency. The two Russians stayed in the City Stay Hotel, a property on Bow road in East London that could be most kindly described as ‘budget’. Authorities have also released a statement indicating that a trace amount of the same Novichok-series nerve agent used in Salisbury was recovered in forensic evidence from the hotel room.
This news has led to inevitable discussion by the usual crowd online. One strain of commentary can be best summarized as “If there was Novichok in the hotel room, someone would have got sick or died”. So, what is the deal?
Here’s what actually happened. On or about 4 May, 2 months after the initial attack in Salisbury, police took swab samples in the City Stay Hotel. The UK police’s anti-terror lead Neil Basu said:
“On 4 May, 2018, tests were carried out in the hotel room where the suspects had stayed. A number of samples were tested at DSTL at Porton Down. Two swabs showed contamination of Novichok at levels below that which would cause concern for public health. A decision was made to take further samples from the room as a precautionary measure, including in the same areas originally tested, and all results came back negative. We believe the first process of taking swabs removed the contamination, so low were the traces of Novichok in the room. Following these tests, experts deemed the room was safe and that it posed no risk to the public. In terms of those who stayed in the room between 4 March and 4 May: to-date, we have had no reports of any persons falling ill."
Let me unpack this statement and make some inferences based on professional experience. The evidence collection effort in this particular hotel room would have been quite thorough. A chemical forensics investigation to collect swab samples would have taken many hours. Every surface in the hotel room that could conceivably held traces of nerve agent (or other chemicals of interest, such as degradation products) would have been swabbed with sterile absorbent wipes, such as (but not necessarily) gauze pads. I do not know the exact methodology used, but if it were up to me, I would have divided the room into 10 cm by 10 cm squares. Larger or smaller sizes could have been used. Each square would have been wiped with at least one swab. It is quite possible that two or three swabs were used, a dry swab first, and then one or two wet swabs, wetted with sterile water and/or a solvent. These swabs would have been put into sterile bags or jars, numbered and logged, and taken to Porton Down for analysis. Every glove used in the operation, as well as the boots and tools, would have been analyzed as well. Numerous blank samples, as negative controls, would have been included as well. This means that a number of swabs that never came in contact with any surfaces, as well as empty jars and unused gloves, would have been forensically examined as evidence as well, as a safeguard. You can read detailed discussions of wipe-sampling techniques here and here. The techniques are also described in several standard textbooks on the subject.
A thorough evidence-collection effort for a single room can yield many hundreds or thousands of swabs. In the London example, these swabs were taken to the DSTL facility at Porton Down for analysis. The standard method for detecting nerve agents in wipe samples in a laboratory is usually a combination of gas chromatography and mass spectrometry (GC/MS), although some other methods may be used as well. In laboratory settings, very small quantities of nerve agents can be detected with mass spectrometry. How small? For the Novichok agent A-234, there is not much literature. But for the similar nerve agent VX, there is excellent literature, and there is little reason to expect that the results for A-234 are radically different. The US Environmental Protection Agency has published an excellent document on detecting VX. This document (in Table 1, page 46, pictured) shows the “Method Detection Limit” for wipes/swabs containing the nerve agent VX.
The Method Detection Limit is the minimum amount of VX that gives the laboratory 99% confidence that VX is present. In this case, it depends on the type of mass spectrometer used, but this document clearly shows that amounts as small as 0.00223 micrograms of VX in a single wipe can be detected. This is a very small amount of VX. A microgram is one millionth of a gram, and we are talking about one 400th of a microgram. A few nanograms. A quick look through the available scientific literature gives no reason to doubt this well-researched and thorough EPA document. Even if the detection limits were somewhat higher for A-234, these are very small numbers.
How do we apply this knowledge to the hotel investigation? In the course of a forensic investigation, hundreds or thousands of swabs were taken in a hotel room. Only 2 out of those swabs showed any nerve agent, and it might have been as little as a few nanograms. At most, two 10 cm by 10 cm square areas had a microscopic drop of material. The police have not said, but it is possible that both positive swabs came from the same exact surface area, as it is often the practice to use multiple swabs.
The amount of material recovered isn’t enough to kill anyone, even if there was a method for it to get into someone’s body. Even so, the area where the nerve agent was found was subject to further scrutiny, likely physically removing the material (wall, furniture, or whatever else it may have been) and taking it to the lab for similar analysis. This yielded no detectable Novichok. This means that the wipes that had the Novichok effectively wiped up the small amount of material, or that any remaining material was so small that even the state of the art detection methods could not tell it was there.
But this does prove that there was some Novichok in the hotel room. So, why did nobody get ill or die? Nobody was affected because there was not enough chemical agent there. Even assuming, and this is a big assumption just for discussion, that the dermal toxicity of Novichok was 10 times higher than that of VX, it would mean that a lethal dose would be about 1 milligram, absorbed through the skin. However, what was present was far less than that. If we were talking about VX, 1 milligram is enough to contaminate perhaps 400,000 swabs at the low end of the method detection limit. Two swabs were found to have agent. Even assuming the highest end of possible detection limits for A-234 and the highest possible toxicity for it, there simply wasn’t enough Novichok to do anyone any serious harm.
There’s also the matter of route of entry. The small amount of Novichok that was in the hotel room needed to get into someone’s body if it was going to do any harm. If it was on a floor tile, perhaps someone could have stood on it barefoot for long enough. This is at least theoretically plausible. But there wasn’t enough material for that to have been feasible. Or someone could have licked the wall or table or chair. That’s not likely.
The bottom line is that the amount of Novichok found in the London hotel room is a clue, and a damning one at that. But it was not a threat to public health, as there was simply not anything like enough nerve agent to hurt a human being.
No grounds for spinning conspiracy theories.