A specific, credible but unconfirmed terrorist threat to residents of New York City and Washington, D.C., was brought to the public's attention Thursday evening, just three days before the 10th anniversary of the September 11 attacks on those two cities. In the past decade such alerts from government and public safety officials have been all too common as home-grown and international terrorists alike have attempted to use a variety of methods to inflict widespread damage on the U.S. and its residents. So the question remaining these days is: What's likely to be next among all the possible threats?

The CIA notes the annual U.S. death rate is 8.38 fatalities per 1,000 citizens, below that of a country like Nigeria but above other places, such as Uzbekistan. The leading causes of death in the U.S. are heart disease, cancer and car accidents, which killed roughly 1.2 million Americans in 2007, according to the U.S. Centers for Disease Control—more than half of all fatalities in the country. For comparison, terrorists killed no one in the U.S. that year.

But, judging by previous assaults and interviews with experts, the following covers a short-list of real and perceived terrorist threats in order of likelihood, from most to least.

1. CHEMICAL EXPLOSIVES
On December 22, 2001, Richard Reid attempted to light his shoe on fire on American Airlines Flight 63. His shoe sole contained a chemical explosive—and ignited a security regulation for removing shoes at U.S. airport security checkpoints that persists to this day.

But Reid is hardly the first to attempt to use chemical explosives to terrorize the population. Favorite compounds for such efforts include pentaerythritol tetranitrate (PETN), triacetone triperoxide (TATP) and nitroglycerin, among others. The ingredients for some such explosives can be found at the local pharmacy and are hard to identify individually by current airport security technology, hence the prohibition against bringing anything but very small quantities of liquids on board an aircraft.

In the 1990s terrorists succeeded in smuggling liquid chemical explosives onto an aircraft from the Philippines in the type of saline solution bottle typically carried by contact lens wearers, detonated it and killed a fellow passenger. Subsequently, terrorists have tried everything from sewing bombs into underwear to smuggling explosives onto flights in packages bearing printer cartridges.

Such incendiaries have been used time and time again to attack transportation, from car bombs, like the one that fizzled in New York City's Times Square in May 2010, to bombing planes. In 2006 terrorists plotted to blow up 10 planes simultaneously, and failed thanks to covert intelligence efforts by the U.K., U.S. and other countries. In Russia, terrorists did detonate bombs on board two planes in 2004, killing all 89 passengers and crew. In 1988 a bomb destroyed Pan Am Flight 103, which fell from the sky above Lockerbie, Scotland, taking 259 lives on the plane as well as 11 on the ground.

Urban mass transit also attracts terrorist bomb efforts, such as the suicide bombings on London trains and buses on July 7, 2005. The files seized after Osama bin Laden's assassination revealed plots to attack U.S. railways and detonate car bombs in similar fashion.

2 Comments

1. 1. janeskid 03:27 PM 9/10/11

   Why was Oklahoma City not mentioned?

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2. 2. hanmeng 06:22 PM 9/10/11

   7. The terrorists scare us into building a huge security apparatus with so many regulations it actually ends up hurting us.

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