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expert reaction to Defra comments about the ‘hotspots’ of nerve agent undergoing decontamination in Salisbury

DEFRA has said that toxic nerve agent ‘hotspots’ could still be in the city of Salisbury following the novichok attack on an ex-Russian spy and his daughter.


Dr Chris Morris, Medical Toxicology Centre, Newcastle University, said:

“The Defra Chief Scientist is taking a sensible and precautionary approach here.  We don’t know a great deal about how this class of agents are broken down in the environment due to their relatively novel nature and so taking these steps until the specific areas can be checked and any contaminated areas cleaned is appropriate.

“These potential ‘hotspots’ are in the locations such as those where the Skripals had been before they became ill, and are currently cordoned off, and so the risk to the public remains very low because of the quarantine placed on these areas.  There may however be very little of the agent left in these areas in any case which is perhaps why no-one has become ill as a consequence.

“It’s likely that any hotspots, if they are present in the cordoned off areas, could be on hard surfaces such as the original bench the Skripals were found on, and this has already been removed.  For contamination of hard surfaces there would be reduced opportunity for breaking down the agent by microbial activity which is one way the agents might be degraded.  On soils or grass the agent may have already been degraded by microbial activity and these areas would pose a much lower risk as high concentrations of agent are no longer present.”


Dr Michelle Carlin, Senior lecturer in forensic & analytical chemistry, Northumbria University, said:

“Decontamination will use chemicals to break down the nerve agent into less harmful chemicals for safe removal.  Since the hotspot areas have been cordoned off, the general public will have no contact with these areas until decontamination has occurred and the hotspots have been deemed safe.  The nerve agent will self-decontaminate with time, with interaction with the environment, but in order to ensure the areas are completely safe, decontamination will be carried out by specialist teams, however, the risk to the public remains low.”


Prof Alastair Hay, Professor Emeritus of Environmental Toxicology, University of Leeds, said:

“We now know that the nerve agent used against the Skripals was both very pure and one that does not degrade as readily as most other nerve agents.  The agent in question was developed because it is so toxic with the high degree of purity helping to slow degradation.

“The fact that the OPCW inspectors were able to obtain blood samples from the Skripals, which were still strongly positive for the nerve agent so long after the two were exposed, indicates that this chemical is slow to break down.

“Given that no other people have been affected by the nerve agent in Salisbury suggests very clearly that the authorities have mapped the area very well to locate the so-called ‘hotspots’.  As long as these areas remain out-of-bounds to the public until decontamination is complete, people will be safe.

“The nerve agent will be quite firmly attached to all sorts of surfaces and is unlikely to present an airborne hazard given both its persistence, and the fact that no one else, other than DS Nick Bailey, was injured.  DS Nick Bailey’s contact with the agent appears more likely to have been through skin contact.

“A variety of procedures will be tested to find a suitable decontaminant to degrade the agent.  Household bleach is very effective for degrading many chemical weapons including most nerve agents and is likely to be tried with this Novichok agent.  If ineffective, there are now many other products available, with a range of properties, that will be tested to find the most suitable.  As different surfaces are affected this may take some time as DEFRA has indicated.

“The problems the use of a small quantity of nerve agent has caused indicate how serious and malicious this attack was.  These chemicals have only one purpose and that is to harm others.  The attack on the Skripals was a violation of international law prohibiting such use of these chemicals.  I hope the perpetrators will eventually be prosecuted.”


All our previous output on this subject can be seen at this weblink:


Declared interests

Dr Michelle Carlin: “I have no conflicts.”

Prof Alastair Hay: “No conflicts of interest.  I worked on UK government committees (from 1989 until 2015) and an EU committee (2005-14) that recommended standards for chemical exposure in the workplace.  Over the years I have investigated some 6 allegations of use of chemical weapons.”

None others received.

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