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Assessing chlorine gas bombs: a chlorine gas attack requires perfect conditions and a poor emergency response if it is to result in a high death toll.

CHLORINE GAS has added a new twist to bombs being detonated by insurgents in Iraq. The question now is whether that tactic will be adopted by terrorists elsewhere.

Chlorine gas is an indiscriminate weapon. Heavier than air, it hugs the ground and disperses downwind immediately upon release. While small doses only irritate the eyes, skin, and respiratory tract, large concentrations of chlorine gas will "immediately overcome a person and kill within minutes," says Rose Ann G. Soloway, a clinical toxicologist at the National Capital Poison Center.

The chemical causes pulmonary edema, or fluid in the lungs, and the victims essentially drown to death in their own fluids.

It was first used by Germany at the Second Battle of Ypres during World War I. Due to the horror it caused, chlorine gas, along with other chemical agents, was outlawed by the 1925 Geneva Protocols and that was reinforced by the Chemical Weapons Convention of 1992.

Those international accords have not always deterred nations, and they, of course, hold no meaning for terrorists. The fear that chlorine gas provokes may be why terrorists have added it to their arsenal.

As for whether this chemical could become a weapon of choice for terrorists today, one question is how easy would it be to obtain? The answer is that it is widely available because it has a number of legitimate commercial uses. For example, chlorine gas is the most common chemical used to purify water at wastewater treatment plants. It is also used heavily in paper manufacturing as a bleaching agent.

Tankers of chlorine gas are carried daily by rail and truck through heavily populated areas; they are eventually stored at thousands of facilities across the nation.

On 9-11, three chlorine rail cars holding 90 tons of liquidized chlorine each, with a fourth being unloaded, sat at the Blue Plains Water Treatment Facility in Washington, D.C., says Aklile Tesfaye, manager of Blue Plains Wastewater Branch. The treatment plant is located about 4 miles from the Capitol Building. (The facility has since switched to a safer alternative, sodium hypochlorite, because of chlorine's potential as a target for terrorism.)

The next question is can chlorine gas give terrorists the deadly outcome they seek? That is less certain.

If properly released in a well-populated area, chlorine gas has the potential to cause tens of thousands of casualties. The Homeland Security Council, in partnership with the U.S. Department of Homeland Security (DHS) estimates that a terrorist attack on a chlorine tank would kill 17,500, severely injure 10,000, and cause 100,000 hospitalizations in a high-density population area; 700,000 people would have to be evacuated, thus causing more panic and accident related deaths.

Another study done by the Naval Research Laboratory estimates that a railroad tank car accident near the National Mall in the District of Columbia could release enough contaminant to kill or seriously harm 100,000 people in half an hour. The release could disperse a lethal plume of contaminant over several square miles of the city.

But theses estimates are worst-case scenarios.

Some experts are skeptical that the necessary set of circumstances would converge to create that worst-case event. They note that even if terrorists successfully breached a tanker and dispersed chlorine gas, they would be heavily dependent on nature and poor emergency response for a successful attack.


"The conditions would have to be perfect," says Mackenzie Eaglen, a senior policy analyst at the Heritage Foundation. "For example, if it were vehicle borne, the car would have to be stationary. It has to be an ideal temperature. There has to be wind to spread the gas."

And that's not all. "There has to be no alerts or evacuations after the incident. The terrorists would have to know exactly when and where to attack," she says. And they have to be able to breach the container with exactly the right amount of explosives to ensure a quick release of the contents without the gas being consumed in the explosion. (At high temperatures, chlorine oxidizes, which reduces its toxicity.) "[A]ll this has to happen in perfect order," explains Eaglen.

The chlorine bombs in Iraq have not been more deadly than nonchemical attacks. In the nine attacks where terrorists detonated trucks carrying chlorine cylinders, an estimated 56 people have been killed and about 620 have been injured.

By contrast, on March 27, an al Qaeda truck bomb exploded in Tal Afar, a Shia town 90 miles from the Syria border. This bombing, the worst of the war, killed 152 and wounded 347 people. The explosion created a 75-foot-wide crater and destroyed 100 homes. That attack killed almost three times as many people as had nine previous separate chlorine-bomb blasts.

Nevertheless, using chemical gas adds another layer of fear onto what is already psychological warfare. "A Chlorine truck bomb is something that is extremely effective as a terror weapon," said Brian Jackson, who serves as associate director of the RAND Corporation's Homeland Security Department.

While a devastating chemical attack might be hard for terrorists to achieve, underestimating their ability to climb the learning curve could be fatal. That's why, in 2004, the Homeland Security Council included a chlorine tank explosion detonated by terrorists among its list of possible risk scenarios worth planning for.

More recently, in late December, the Department of Transportation and the Transportation Security Administration issued notices proposing new regulations for transporting poisonous-by-inhalation (PIH) materials, such as chlorine gas.

One regulation requires railroad personnel to inspect rail cars for improvised explosive devices (IEDs) while providing for a strict chain of custody as rail cars move from point to point. The TSA will issue the final rules for rail transportation security late this year.

Jackson advises that we take chlorine bombs seriously, but keep the risk in the proper perspective. "It is certainly something that needs to be included in our risk management efforts," he said, but "we have to make sure we keep in mind the spectrum of possible outcomes so we don't expend our resources in ways that end up dissipating them and not addressing risks that are more likely."

By Matthew Harwood, staff editor
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Title Annotation:Intelligence
Author:Harwood, Matthew
Publication:Security Management
Article Type:Editorial
Geographic Code:1USA
Date:Jun 1, 2007
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