The spectre of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs) being used against civilians was highlighted in Kuala Lumpur Airport, Malaysia, in 2017, and then again in 2018 in Salisbury, United Kingdom. No longer a far-fetched imaginary plot from a Tom Clancy novel, the threat of a hostile state or proxy actor using such unconventional weapons merits careful examination and attention. Although it is commonly thought that the worst-case scenario is unlikely to occur – since many low-probability events generally must occur for the worst to happen – given the chilling nature of these unconventional weapons even an event which is not worst-case could have huge psychological effect, significant public health impact and huge economic cost. Alan Miller briefly looks at this emerging threat and the potential detection techniques.

With thankfully only a few historical precedents, determining the current risk from past events is difficult and perhaps misleading. However, the trend is clear: traditional nerve agents have been used to attack civilians in recent years and, to compound the problem, a new and relatively unknown third-generation nerve agent called Novichok has recently appeared in a state actor-backed attack in the UK.

There are generally four well-known nerve agents. These are:

1. Tabun (GA) Ethyl N-dimethylphosphoramidocyanidate, developed in Germany as a pesticide in 1936;

2. Soman (GD) Pinacolyl methylphosphonofluoridate, developed in Germany in 1944 as an insecticide;

3. Sarin (GB) Isopropyl methylphosphonofluoridate, developed in 1938, again in Germany, as a pesticide. The variant Cyclohexyl Sarin (GF) was discovered in 1949. Sarin (GB) is very volatile, this means it will quickly evaporate causing an immediate but short-lived threat, and since Sarin (GB) vapour is heavier than air, it will sink to low-lying areas and thus create a greater exposure hazard in these areas.

4. V series (V for ‘Venom’), known as (VX, VXII), O-Ethyl S-2-diisopropylaminoethyl methylphosphonothioate, developed in the early 1950s in the UK in the course of pesticide research. Considered too dangerous for commercial use, they were subsequently designated as chemical weapons and mass produced from 1961. VX is considered the most toxic of these traditional nerve agents being approximately ten times more toxic than Sarin (GB). Much like Sarin (GB), the vapour from VX is heavier than air and sinks to low-lying areas and again creates a greater exposure risk in those areas. VX is technically more difficult to produce than Sarin (GB).

In short, ‘G-type’ agents pose an inhalation risk while ‘V-type’, due to their lower volatility, pose a contact risk.

The historical use of these weapons against civilians is well documented. On 16 March 1988, the Kurdish town of Halbaja was attacked with mustard gas and a host of other agents believed to be Sarin (GB), Tabun (GA) and possibly VX, killing over 5,000 civilians – mainly woman and children – and shocking the world. In June 1994, the doomsday cult Aum Shinrikyo, founded by Shoko Asahara in 1984, used Sarin (GB) to attack the Matsumoto dormitory killing eight and, it is believed, harming an additional 500 people. This attack was followed by another in March 1995 on the Tokyo subway, killing 13, seriously injuring 54, affecting 980 more and causing perhaps as many as 5,500 people to seek medical treatment. Since then, we have seen Sarin (GB) being used in Syria, killing hundreds of civilians: in 2013 in Ghouta near Damascus, and then in 2017 in Khan Sheikhoun.

In 2017, the nerve agent VX (O-Ethyl S-2-Diisopropylaminoethyl methylphosphonothiolate) was used to assassinate Kim Jong Nam, the estranged half-brother of Kim Jong-il. The alleged female assassins, one Vietnamese and one Indonesian, smeared his face with a liquid.

VX is an oily, odourless and tasteless liquid. It is slow to evaporate, hence its use in this particular attack, and it is the least volatile of the nerve agents, albeit considered much more toxic than Sarin (GB). Because it has the viscosity of oil, any surface contaminated with VX may have to be considered as a long-term exposure hazard.

Most recently, in March 2018, a newer, third-generation, publicly unheard-of nerve agent called Novichok (which means ‘newcomer’ in Russian) was used in the United Kingdom against Sergei and Yulia Skripal in Salisbury. The international condemnation and well publicised expulsion of 23 Russian diplomats from the UK highlighted the severity of the concern.

Sungbaek Seo holds paper litmus tests for the detection of nerve agents (Credit: University of Michigan)
Sungbaek Seo holds paper litmus tests for the detection of nerve agents (Credit: University of Michigan)

The UK Novichok attack and subsequent accidental mishandling of the discarded bottle used in the original attack resulted in the death of 44-year-old Dawn Sturgess. Three other people also became critically ill, 21 emergency service personnel required medical checks and 500 members of the public were advised to decontaminate themselves to prevent possible long-term exposure.

The Novichok series (odourless carbonimidic phosphorohalides, which are organophosphate acetycholinearterase – AchE – enzyme inhibitors if you want the technical description) are believed to be perhaps ten times more potent than VX series nerve agents. Novichok works by interrupting the correct behaviour of the neurotransmitter acetylcholine inside the nerve synaptic gap, which causes a nervous system functional overload at the cellular level leading to, amongst other things, acute respiratory failure, eventual cardiac arrest and death – possibly within minutes of exposure.

“…the Novichok series (odourless carbonimidic phosphorohalides, which are organophosphate acetycholinearterase enzyme inhibitors if you want the technical description) is believed to be perhaps ten times more potent than VX nerve agent…”

The Novichok series were developed secretly in the Soviet Union in the 1980s (and in Russia in the 1990s), and are all third-generation nerve agents. In particular, Novichok-5 and Novichok-7 are binary weapons, created when two non-lethal compounds are added together. This third-generation nerve agent was specifically designed to defeat traditional chemical protective gear and to be undetectable using standard chemical detection equipment (especially that used by NATO). In all likelihood it was perfected in an attempt to circumvent the Chemical Weapons Convention by using precursors that were not specifically and clearly defined by the convention, although naturally Russia has denied this. Unsurprisingly, being secret, little was known about Novichok in the medical community; in fact, a check on the CDC’s website for Emergency Preparedness and Response ( shows that (at the time of writing) it is not even listed! Other nerve agents are very well documented to help aid medical treatment. Generally, nerve agents are treated with atropine, and pralidoxime chloride (protopam chloride) also known as (2-PAM) with some Diazepam.

Novichok can be deployed in various forms; as a fluid or as a spray, but also as a fine powder, which can be weaponised using 5-micron nanoglass spheres, causing the substance to remain suspended in the air and therefore resulting in an exceptionally dangerous weapon whose lethality can be measured in years. This is of particular concern in crowded airports as well as low-pressure environments such as inside an aircraft where aerosol dispersion efficiency is greatly amplified.

The lethality of this unconventional weapon class presents unique challenges to safe detection. In particular, it poses an obvious moral dilemma – we can either acquire a physical sample of the substance, which can then be analysed using a greater range of accurate detection options but risks potential exposure to staff, or we can analyse the substance remotely, which is safer but presents greater technical and cost challenges. The costs of such remote analysis are, however, rapidly declining, thanks in part to the development of explosive detection technologies, which share similar core principles.

“…particular concern in crowded airports as well as low-pressure environments such as inside an aircraft where aerosol dispersion efficiency is greatly amplified…”

Detection by Obtaining a Physical Sample

There are several technologies that can be used to analyse a physical sample. Access to a lab allows all the usual gas chromatography, ion trap mobility spectrometry, chemiluminescence techniques, and flame photometry options, but the nature of the threat and the airport environment demand more practical and immediate onsite solutions. By far the most promising techniques being developed are chemiluminescence, amplifying florescent polymers and similar visual marker assay techniques.

There have been a few groups progressing in this area but one of particular note is a team at Michigan University College of Engineering, headed by Prof. Jinsang Kim, who have developed a working model of such a visual marker – a piece of paper that changes colour within 30 seconds in the presence of a nerve agent. It works by a very novel and clever combination of ‘stimuli sensitive conjugate polymers’ and parts of a nerve agent antidote called Pralidoxime (2-PAM). This technique would work as a sprayed chemical test or even as an additive to paint or ink, opening up numerous future practical deployment options.

The 1988 attack in Halabja was an early indicator of the threat posed by chemical weapons.
The 1988 attack in Halabja was an early indicator of the threat posed by chemical weapons.

The original idea came from previous work by the group, which used bacteria that glows in the presence of explosives and is used to detect landmines. Similar techniques now allow for printing of biosensors on paper for multiple simultaneous tests, resulting in an inexpensive assay. Colour metric sensors are exceptionally cheap at only a few cents and open up possibilities for practical mass screening use as well as a practical instant detection for unknown substances. Although cheap and very practical, a high degree of caution would still be needed to minimise the risk of staff exposure.

Detection Remotely (Standoff)

At the other end of the moral dilemma is remote detection for which we do not need a physical sample but, instead, try and identify the substance in question from a safe distance. As we move away from the usual lab techniques available for physical samples, we enter an area of technology which although established is still relatively expensive. Recent advances however are making these technologies cheaper.

Each object absorbs light frequencies differently, resulting in different colours. At night however less light makes it harder for the eye to distinguish colour. The solution? A torch! It is exactly the same for detecting chemicals at a distance, except we shine an infrared tuneable laser rather than a torch. By looking at the spectrum we can identify any substance by looking up its signature in a known database. This technique is generally called spectroscopy with related variants: non-dispersive infrared, IR absorption and Fourier transform infrared (FTIR) spectroscopy. These emerging techniques are already capable of scanning large public areas automatically. Although they are still expensive and bordering on military, some commercial solutions are starting to appear in the market. The present state-of-the-art can detect toxic clouds at between 1-5 kms range in about 10 seconds, but they have to be clouds. Smaller units for car and truck screening at borders have started to appear using Quantum Cascade Laser and FTIR techniques; although initially expensive, it is a good start. The most promising developments are in the hand-held laser scanning techniques, which will be able to scan a local area up to about 30m. Much like the temperature probes used today, these handheld units are becoming so accurate that the latest devices can detect the type of bacteria present in a pond. It will only be a matter of time before we have devices cheap and accurate enough to be practical for staff to use safely.


Although the risk of unconventional weapons will increase over time, we have to offset that concern with the advancements being made in detection technology. Over the past few years we have seen many advancements in chemical detection, and certainly some of those techniques will become increasingly capable of detecting more complex chemicals such as nerve agents and even biological threats. Although we have limited practical options presently, these techniques are rapidly developing into reliable, unified solutions for deployment in airports, helping to tackle yet another concern facing the industry.

Dr. Alan G. Miller is a professional chartered engineer and senior executive who has specialised in the practical application of disruptive technology. With over 20 years industrial experience he has worked on a multitude of projects across several dozen countries and several industries including the aviation, defence and biomedical sectors. He can be contacted at: