UK Report on WMD Risk

More housecleaning:

In February the Chatham House (a UK think tank) published a report on the risk of chemical, biological, radiological, and nuclear (CBRN) terrorism. It's essentially a concise, well researched primer on these threats. First, a few notes on the overall CBRN threat:

It is appropriate to think of CBRN as a system, offering all that might be required for a range of terrorist groups from the largest to the smallest, from the almost casual to the most organized, and from the poorest to the best funded.

In the absence of the Cold War military imperative, not only has genuine interest mounted in the civilian applications of WMD-relevant technology, but the illegal proliferation of sensitive technology, materials and knowledge has proved both more tempting and more possible. In short, WMD technology has increasingly become something of a commodity since the end of the Cold War.

Next a few notes on each threat:

Chemical

First, the precursor chemicals for chemical weapons (CW) are widely distributed:

Many of the CW precursor chemicals are ‘dual use’ in that they have civil industrial applications: mustard gas requires ethyl alcohol, sodium sulphide and bleach; thiodiglycol is used for ball-point pen ink, but is also ‘only one chemical step removed’ from mustard gas; the chemical ingredients for tabun (GA) are used in pesticides, those for sarin (GB) in flame retardants, those for soman (GD) in dairy and food-processing equipment, and those for VX in pyrotechnics.

A so-called Improvised Nuclear Device (IND) could also be produced using much larger quantities of lower-grade, less enriched U-235. The device might then ‘fizzle’ rather than detonate its entire mass instantly and efficiently. But if the resulting explosion were to be equivalent to just one or a few kilotons of TNT rather than tens of kilotons, terrorists could still find this option attractive.But taking the next step - building a chemical-weapons capability and actually producing chemical weapons - is difficult, as demonstrated by the widely-cited example of Aum Shinrikyo, who launched the 1995 sarin gas attack in the Tokyo subway:

According to some estimates, Aum Shinrikyo’s attempts to synthesize sarin cost as much as $30 million, involved as many as 80 scientists and other people with advanced laboratory facilities, and took a year or more to achieve.

To produce CW in large-scale quantities is challenging scientifically and technologically, and the handling and weaponizing of CW are generally understood to be very hazardous.

Chemical attacks are made more complicated by environmental factors:

In general, CW are dependent for their effect on ambient weather conditions, and particularly on the temperature, the intensity of sunlight, the strength and direction of wind, and rain (especially, of course, for those agents soluble in water).

For a terrorist group, simplicity may be preferred:

A rather more straightforward option, of course, would be to buy or steal a supply of toxic industrial chemicals, for simple release in a crowded area.

That's what al Qaeda is doing with chlorine in Iraq - simply acquiring whatever they can get and using it to supplement a more conventional attack, usually a truck bomb.

Biological

Biological threats seem relatively simple. All you have to do is acquire the desired biological agent, grow it, package it, and release the biological weapon (BW) as desired - right? But it's not nearly that simple:

BW production involves four stages – acquisition, production, weaponization and delivery – the first three of which are progressively more difficult:

1. Acquisition. It would not be easy to acquire the seed stock of a pathogen or a toxin-producing organism, but it would not be impossible either.
2. Production. The manufacturing of BW agents is not straightforward. Bulk production, in particular, would be demanding and dangerous.
3. Weaponization. Weaponizing a BW agent is yet more challenging, for two reasons. First, the health and safety of those involved in BW production could scarcely be more at risk. Second, it would not be a simple matter to produce a stable device with a predictable effect. BW agents are, in general, vulnerable to environmental and weather conditions.
4. Delivery. Once the first three stages have been passed through successfully, the delivery of a BW device would be a relatively simple matter.

More generally, it should always be borne in mind that BW use would inevitably be a complex undertaking, drawing upon many branches of science and technology, including microbiology, pathology, aerosol physics, aerobiology and meteorology.

And even if the high hurdles were passed, the effects are somewhat unpredictable. In some previous instances of civilian exposure to biological agents, casualties have not been catastrophic:

In 1979 an accident at a Russian military site led to some 65,000 people being exposed to anthrax spores. Of these, only 70 were reported to have been infected with anthrax, of whom 68 died. The anthrax attacks in the United States in late 2001 also had a very limited medical effect, albeit with widespread social and political impact.

Regarding biological weapons, the bigger threat might actually be something that we don't even know about yet. The report quotes G.L. Epstein as saying:

The rapidly increasing capability, market penetration, and geographic dissemination of relevant biotechnical disciplines will inevitably bring weapons capabilities within the reach of those who may wish to use them to do harm. If it takes close to a decade to develop and license a new therapeutic vaccine, it is not today’s threat but the threat a decade from now that we need to counter. And given how much easier it is to pose a threat than to counter one, the threat ten years out may not even materialize until eight or nine years out.

Especially as biotechnology advances, this threat will become increasingly complex.

Radiological

There is a wide variance to the severity of this threat. While the lower end is not hard to imagine, the upper end of the radiological weapons (RW) threat is somewhat unknown:

The ‘maximum credible event’ could be a device (explosive or other) designed to distribute tens or even hundreds of thousands of Curies of radioactive material. Little work has been done to model the effect of such an attack.

But the motivation is there:

‘Some of the major international terror groups, including al-Qaeda, have not only the resources to carry out such an attack, but also the willing martyrs, whose participation would significantly reduce the cost and complexity of any protective systems needed to allow the perpetrator to survive long enough to carry out the attack.’

And the materials are out there:

Radiological materials are used in a wide variety of circumstances: general industry, agriculture, medicine, communications and navigation. But not all radioactive isotopes would be suitable for RW use. Among the candidates, ‘only a few stand out as being highly suitable for radiological terror’: cobalt-60; strontium-90; yttrium-90; caesium-137, iridium-192, radium-226, plutonium-238, americium-241 and californium-252.

The US Nuclear Regulatory Commission has estimated that one licensed US radioactive source is lost every day.

While the phrase "dirty bomb" has entered the lexicon, an explosive might not be the most attractive means for dispersing radioactive material:

Radioactive material can be distributed in a variety of ways; some isotopes can be dissolved in a solvent and poured or sprayed, others can be burned or vaporized. From the point of view of a terrorist group, non-explosive delivery might offer an advantage in that authorities might be slow to suspect and detect radiological release. In the delay, radioactive material might be ingested or inhaled by yet more people, and radioactive pollution allowed to spread still further.

The main effect of a radiological weapon would probably be economic (assuming that the radioactive materials contaminated an area of economic importance, such as the business district of a major city):

There appears to be a reasonably firm consensus in the literature that while the political and economic effects of a RW attack could be extreme, only the largest conceivable RW device could kill more than scores or hundreds of people.

Thus, a recent US Department of Defense study estimated that a 100 lb (45 kg) RW device carried in a backpack, containing radioactive material used for cancer treatment, detonated in a city centre, would kill no one through radiation. However, a truck-borne device using a similar amount of explosive but with about 100 lb (45 kg) of spent nuclear fuel rods could cause lethal doses of radiation within a half-mile radius.

Nuclear

This is the ultimate nightmare, of course. Fortunately, there are only two possible materials suitable for making a nuclear weapon:

Although various nuclear isotopes are used in the construction of a nuclear weapon, at the core of any device must be a mass of sub-critical fissile material – either highly enriched uranium-235 (HEU) or separated, ‘weapons-grade’ plutonium (Pu-239).

And while a terrorist group would need specialized knowledge and plenty of resources, it's not impossible to imagine that they could build a weapon:

Graham Allison, writing in late 2003, claimed that ‘given the right materials – a grapefruit- or soccer ball-sized amount of fissionable material is sufficient – several masters-level engineering students … with several hundred thousand dollars and the type of equipment you could purchase off the shelf at Radio Shack could make a device that would explode. The last time I checked, researchers at Los Alamos, trying to develop strategies to combat this threat, had come up with sixty-nine different workable designs for a nuclear device.’ Barnaby makes a similar point: ‘The difficulty of designing and fabricating a nuclear weapon … is often exaggerated. A competent group of nuclear physicists, and electronics and explosives engineers, given adequate resources and access to the literature, would have little difficulty in designing and constructing such a weapon from scratch. They would not need access to any classified literature.’

If that's not possible, another option exists:

Another alternative might be to eschew nuclear weapons development and delivery altogether, and instead ‘deliver’ an attack on a nuclear power station, using conventional means (such as a large proximate explosion or the direct impact of an aircraft)...

In 1981 a US study estimated that such an attack carried out with an explosive-laden aircraft could cause 130,000 deaths.

Perhaps most ominously, the study points out that, in the eyes of a terrorist group such as al Qaeda, the risk of destruction is not a limiting factor - though it may be a factor in the response of their target:

But the difficulty arises, of course, when traditional terrorism gives way to so-called ‘expressive terrorism’, and when the object of nuclear weapon use would be not to negotiate but simply to destroy. For terrorist individuals and groups driven by some religious, millennial or apocalyptic vision, the massive and hugely symbolic impact of a unilateral, ‘spectacular’ nuclear strike could be precisely their goal. Furthermore, the destruction of themselves and everything associated with them in the retaliatory attack which followed their nuclear attack might be a prospect to be accepted, if not welcomed. What, then, would be the point of launching a nuclear counterattack against such perpetrators, other than to provide for them the martyrdom they seek?

Quite apart from the massive human cost of such an attack, the rationale for a punitive nuclear response falls away when account is taken of the likely size and scale of the organization carrying out the attack; would a group of a few hundred people dispersed across a wide area, and perhaps even among several countries, really be a suitable target for a retaliatory nuclear strike? If not, and if the decision is taken instead to pursue the terrorists with conventional military means, then the terrorists will have gained whatever benefit they envisage from a nuclear attack, without a substantial change in their circumstances, since they would have expected to be pursued by conventional military forces in any case.

The prospect now begins to loom of a nuclear weapon state being self-deterred when contemplating the wisdom of a nuclear response to a limited nuclear attack. ... Surprisingly perhaps, the ‘post-modern’ terrorist begins to assume a good deal of initiative in this scenario; the rewards of nuclear use might be perceived as maximal, with the attendant risks minimal (or, at least, unchanged).

While this threat may be improbable, the risk is so great that it cannot be ignored:

[I]t might be improbable that a terrorist organization could either design and manufacture, or acquire a nuclear weapon, and then deliver it, but even the slightest possibility that this could happen would entail massively disproportionate consequences. In other words, the risk of terrorist use of nuclear weapons, as traditionally calculated, could scarcely be higher. For Western governments the risk is of such a magnitude that worst-case analysis seems not only unavoidable but also appropriate.