The Los Angeles Police Department (L.A.P.D.) has recently procured—using some of the $3 million in funding from the Department of Homeland Security (DHS)—devices capable of detecting so-called dirty bombs or radiological dispersion devices (RDDs). One of the detectors will be deployed onboard a helicopter and supposedly is capable of detecting a radiation signature from an altitude of 800 feet. Six other devices are hand-held units for use by police officers on the ground (and presumably have a much shorter detection range, probably only a few feet). According to Chief of Police William Bratton, “Terrorism is all about getting them before they get us.” But how likely are such radiation detection devices to “get them”?

If we assume that the helicopter-mounted device is 100 percent effective (and nothing ever is) and that it can detect small quantities of radioactive material within an 800-foot detection radius, its effective surface area of detection is about 2 million square feet or less than one-tenth of a square mile. If a dirty bomb could be anywhere inside the city limits of Los Angeles (468 square miles) and the helicopter could be flying anywhere within that airspace, the probability that a single helicopter would detect the dirty bomb is less than two one-hundredths of one percent. In other words, not very good odds. The odds are even worse for six police officers carrying handheld detectors with a range of only a few feet, each responsible for covering nearly 80 square miles.

Moreover, there are many legitimate sources of radiation—by definition, a dirty bomb is explosives laced with radioactive material, not a nuclear device—that could set off detectors, which could result in countless false alarms. According to the U.S. Nuclear Regulatory Commission, radioactive materials are routinely used at hospitals, research facilities, and industrial and construction sites for such purposes as diagnosing and treating illnesses, sterilizing equipment, and inspecting welding seams. And there are many naturally occurring sources of radiation, such as fertilizers, ceramics, bananas, kitty litter, and smoke detectors—all of which could be carried in sufficient quantities by trucks traveling on the 6,800 miles of roadways, including 27 intertwining freeways—in Los Angeles to trigger detectors.

Beyond being able to detect the relatively small amount of radioactive material used in a dirty bomb, there is the question of how real such a threat is. There are only two known cases—in Russia and Chechnya—of attempted terrorism using a radiological dispersion device. In May, 2002, Jose Padilla was arrested on suspicion that he was an al Qaeda terrorist intending to detonate a dirty bomb in the United States. But when he was finally indicted—after being held for 3 years as an enemy combatant—the dirty-bomb charges were dropped (Padilla was convicted in August on charges of aiding terrorist organizations abroad).

The truth is that although a dirty bomb is a relatively simple device compared to a nuclear weapon, it is also a “high tech” weapon—which makes it more difficult for terrorists to construct and use (indeed, if it was easy and simple to build a dirty bomb, one would think they would be as prolific as improvised explosive devices in Iraq). And despite rhetorical sensationalism about dirty bombs—announcing Jose Padilla’s arrest, former Attorney General John Ashcroft claimed that a dirty bomb “can cause mass death and injury”—they are hardly weapons of mass destruction. The actual physical damage caused by a dirty bomb would likely be no more than if it were a conventional bomb using the same amount of explosives.

So the dirty-bomb threat to Los Angeles is probably overstated. But that should come as no surprise, since Chief Braddock doesn’t understand the larger terrorist threat. According to Braddock, Los Angeles is at risk to terrorism—and presumably a dirty bomb attack—because it is “the symbolism of so much of what they hate. In their rush to get back into the 7th century again, 21st century Hollywood is not exactly where they want to be.” The reality is that—as the 9/11 Commission concluded and as numerous polls conducted throughout the Islamic world show—they do not hate us for our freedoms, way of life, culture, accomplishments, or values. Rather, the growing tide of Muslim anti-American hatred—the basis for the radical Islamists to cultivate terrorism—is fueled more by what we do, i.e., U.S. policies, than who we are.

With more than one billion Muslims in the world, we cannot continue to ignore the reality of why so many of them possess a growing hatred of the United States—largely U.S. foreign policy. Otherwise, getting them before they get us will be as elusive as trying to find a dirty bomb in Los Angeles.