Why Preparing Against Terrorist Chlorine Attacks Is Imperative

Chlorine is a nasty substance (E-Plan). It has many characteristics desirable for terrorists, since it:

  • Is lethal in small quantities (100 ppm)
  • Is readily available as it is used widely in water treatment and plastics production
  • Is processed, transported and stored with little or no security
  • Becomes airborne by simply puncturing the container
  • Doesn’t dissipate easily as gas, since it is heavier than air

Unlike conventional explosives exploiting its lethal force doesn’t require complex or expensive preparation – just puncturing the vessel or blowing a hole in it is enough to release a lethal chlorine cloud. And unlike specialized chemical or biological weapons, a terrorist doesn’t need to manufacture it as they can go directly to locations where it is used.

A worst-case scenario is created below to further highlight the need for immediate action, and to prevent and prepare for a chlorine terrorist attack. While knowing the threat level is important, it is also important to know how one can protect against such an attack, and to not overreact over the slim possibility of being affected.

Chlorine trucks and containers have already been used successfully as a terrorist weapon in Iraq on several occasions, killing tens of people (WMD Insights). Fortunately the attacks have used relatively small amounts of chlorine – the largest has been a 200-gallon tank. For comparison, a railcar containing 90 tons of chlorine released 60 tons in a massive cloud in an accident in Macdona, Texas in 2004 (NTSB). It was sheer luck that only three people were killed.

To determine the threat posed by chlorine, a realistic worst-case scenario is built. According to a Center for American Progress (CfAP) – a non-profit, non-partisan “progressive think-tank dedicated to improving the lives of Americans through ideas and action” – survey chlorine transportation by rail is still quite common in the United States (CfAP report). The map shows that Dallas, Texas has seven facilities receiving chlorine by rail. Therefore Dallas, Texas is chosen for the scenario. One of the likely sites is Bachman Water Treatment Plant only 10km north-east of downtown Dallas.

Dallas, TexasThe adjacent image (also Google Earth kml) shows the path of a potential chlorine cloud if the contents of entire railcar full of chlorine is released into the air. A chlorine cloud can travel up to 40km, but this scenario is conservative at 30km. Please note that the cloud pictured here is only the lethal portion, and that such a massive (delibarate) spill will most likely be much wider than the 1km.

Dallas, Texas population densityA population density map of Dallas is then superimposed. This reveals that approximately 80,000 people live within the potentially lethal cloud. While this number is significantly lower than the 2 million submitted to the EPA (CfAP report), this is a more realistic figure, as the EPA figure includes the entire population within the vicinity of the facility. Nevertheless, casualties in the tens of thousands and serious injuries an order of magnitude higher are possible in a worst-case scenario. Even a conservative assessment for such a downtown attack yields thousands of casualties.

In light of the above analysis, it is clear that public entities need to take immediate action to secure chlorine transports and facilities processing and using it. Some nations, such as the Netherlands, have stopped rail transportation of chlorine altogether. But many nations still transport massive amounts of chlorine. Unlike most of the security theater – phrase coined by Bruce Schneier in the book Beyond Fear – initiatives since 9/11, protecting people against chlorine terrorism is cost-effective, prudent and doesn’t involve unnecessary breaches of civil liberties. And perhaps most importantly, taking action now would prepare us for one of the next likely attack vectors, instead of fighting the “previous war.”

Eliminating chlorine tranportation or using safer alternative processes is always the most desirable solution. Where that is not possible, physically securing facilities and tranportation using traditional security measures is the next step. Also, population in the potential hazard areas needs to be informed and trained in proper precautions and what to do in case of such an attack. Emergency face masks are cheap. And knowing that chlorine is heavier than air, and getting to higher ground, closing air conditioners, windows and doors is a huge step towards creating an informed populace much less vulnerable to an actual attack.

The imperative is alleviating the “terror” aspect of the threat of such an attack, and avoiding creating yet another terrorism boogey man.


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