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There are any number of reasons why we should be worried about the dirty bomb menace, says nuclear terrorism expert Graham Allison, director of the Belfer Center for Science and International Affairs at Harvard University and former Assistant Secretary of Defense under President Clinton. Among them: Radioactive substances are everywhere; anyone can build a dirty bomb; and Al Qaeda has sought to make or acquire one. There is also one reason why we shouldn't be so worried, Allison says, and that's because a far more threatening sword of Damocles hangs over our heads: a potential terrorist attack with a nuclear bomb. To better grasp the scope of these very different threats, NOVA interviewed Allison in his office at Harvard's John F. Kennedy School of Government in Harvard Square, across the Charles River from Boston.

How prepared are we?

NOVA: Do you think the U.S. is well prepared to deal with the dirty bomb threat?

Allison: No, but it is complicated because the supply side of the dirty bomb threat is so mammoth that it is virtually impossible to imagine coping with it adequately. The number of actors who might conduct such an attack is also extremely large. And while you might like to try to make people aware of the threat and the fact that it's got a heavy psychological as well as physical component, it is difficult to do so without also suggesting opportunities for people to do things, mischievous things that they might not have thought of. So in the array of threats, it's a particularly complicated one to try to deal with.

And while there have been some preparations in the U.S. government to try to be capable of decontaminating sites in the same way that buildings were decontaminated after the anthrax attacks, that part has not been overly publicized and probably needs to be more so.

NOVA: What kind of response would there be if a dirty bomb attack occurred, say, here in Boston?

Allison: There would be alarm, of course. I think we need to give people an idea of what constitutes a dirty bomb. A dirty bomb is a blast caused by some bomb, and then there is a dispersal of radioactive material that may be more or less toxic, more or less harmful. Then there are the psychological consequences among the people, who are terrified.

“The first-ever dirty bomb attack would be a dramatic event, I suspect, because people wouldn't know quite what to make of it.”

If the blast is very small, let's say a stick of dynamite, and the material is not highly radioactive, the impact would be relatively small. Say you and I were in this room, and one stick of dynamite went off under my chair. I probably would be blown up, and you probably would be harmed, and you would get some amount of rads. But you get a certain amount of rads everyday from walking around in the sun or from getting a medical procedure.

So I think the question would depend on the strength and intensity of the various items. The first-ever dirty bomb attack would be a dramatic event, I suspect, because people wouldn't know quite what to make of it. Lots of people are confused about what is a dirty bomb and what is a nuclear weapon. They might mistakenly think that a nuclear weapon had gone off.

But since the major action would be physical consequences—which for most people would be small, involving probabilities of diseases contracted at some future date—people's behavior in time, I think, would adapt in the manner that it adapts when people live near a place that has, say, pollutants or chemical effects. Given the choice, you and I would prefer not to live by Love Canal or some other place that has some additional degree of risk to ourselves or our families. We already live in a world that is full of enough risk.

NOVA: So if a fairly sizable dirty bomb went off in the center of Boston on a windy day, and a lot of people were exposed to its radiation, would people be at all equipped to deal with it?

Allison: I suspect not, because they probably haven't been well-informed. They would quickly go to a Web site to try to see what they could learn about it. Some people would go out and buy a book about nuclear terrorism, and other people would take sodium iodide, thinking, "I heard that that had something to do with this or that." But there would be general confusion, as unfortunately there would be for most counterterrorist acts at this stage, given on the one hand the absence of an effective education process for people, and on the other the desire not to know too much about this.

NOVA: Is there anything average citizens should or could do to prepare for a dirty bomb attack, or should they just be informed?

Allison: I think they should be informed and aware. It is not the greatest risk for life, and it is not the greatest risk for most people. Anybody who smokes should put the dirty bomb threat in perspective and say, "Wait a minute. I am already living dangerously." Anybody who drinks and drives, or anybody who drives recklessly—there are a lot of foolish behaviors that we human beings do.

In the dirty bomb arena, I would say that one should be aware of anyone who is seeking radioactive materials in a medical facility or a food-processing facility or nuclear power plant. Generally we're aware of people who are seeking dynamite or hand grenades or other explosives. I think this is part of the general "Be aware."

If there were a dirty bomb blast, you would obviously hope not to be hurt by the blast, and then you would hope not to be in the immediate vicinity. The more distant you are from the site, the better off you will be for some period of time, depending again on how radioactive the material is that is dispersed.

All together, I think for most of us it's a smaller risk in the spectrum of things that we have to be concerned about.

Prospects for an attack

NOVA: You and others have argued that acquiring the materials for a dirty bomb and building and detonating one is, relatively speaking, not a difficult prospect. With this in mind, why do you think a dirty bomb attack has not yet occurred?

Allison: Great question. I think it is a puzzle, because it's a simple fact that people don't have to look very far on the Web to find information that would give them a reasonable picture of the issue. That's just there. I don't want to give anybody bad ideas, but at the same time you don't want citizens to be unaware of what exists. I prefer that it wasn't there, but it is there, that's a fact.

How then given such availability has there not been such an event? If you try to think, well, how hard was it to blow up the Federal Office Building in Oklahoma City? Not very. Timothy McVeigh takes a van and fills it with fertilizer-based explosive. How hard is it to get fertilizer and a trigger? Not very. And there it happened. Fortunately, there are fewer nuts of that sort than one might imagine, or they don't think of doing such horrible things.

“I think it is a great puzzle—and a happy fact—that we haven't had such attacks.”

We've been very blessed in not having lots of people actually doing terrorist acts within the U.S., which they are not prohibited by any physical encumbrance from doing. If you had come into this building today with a gun in your briefcase and decided to shoot up 50 people in a classroom or a dorm, there would not have been a guard to stop you. Similarly, if you had a small dirty bomb in your briefcase, and you decided to set it off here at the Kennedy School or in Harvard Square or in a building downtown... There are a few buildings where you have to pass through a guard, but mostly you don't. Anybody can get on the subway; there aren't too many people inspecting. And so on.

So I think it is a great puzzle—and a happy fact—that we haven't had such attacks. In the case of Israel, it becomes even more puzzling, because there you have people carrying out suicidal attacks. They clearly have the bombs and for whatever reason haven't gone to this next stage. I would suspect that is just a matter of time.

NOVA: What do you think is a likely scenario for a dirty bomb attack in the United States or Israel?

Allison: A plausible scenario would be simply the explosion of a bomb that you are already seeing used in terror attacks but that happens to get wrapped in some radioactive material.

NOVA: I've read that the Nuclear Regulatory Commission receives nearly 300 reports a year that radioactive materials have gone missing. Where do you think they've ended up?

Allison: I suspect most of them have just been lost. It is interesting to think of the Iraqis, who are ostensibly trying to give an account of everything they have (though I do believe they have weapons of mass destruction and are trying to hide them), and then to think of the U.S., which doesn't give a very good account of everything it has. It is not because we're hiding it. It is because in large, complex systems a lot of stuff goes missing. Whether some people have taken some of this material home, imagining that they're going to do something mischievous with it—well, it would seem implausible that that wouldn't have happened in some cases.

NOVA: You mentioned Timothy McVeigh. Is it just as likely a domestic terrorist could pull off a dirty bomb attack as, say, Al Qaeda?

Allison: I think, unfortunately, that if somebody wants to do a terrorist act, and if they are trying to make a splash in order to impact people, they might simply just shoot somebody, or they might have a bomb and blow up a building, or they might decide to wrap the bomb in something that would have further consequences. So, yes, I could imagine that could happen.

Nothing like nuclear

NOVA: You believe that we have a much more serious threat to worry about than a dirty bomb—namely, the possibility of a nuclear weapon attack.

Allison: Well, if you look at 9/11, and you look at Al Qaeda and their M.O., and you look at what they said, you know that they like big, spectacular events that kill large numbers of people. The press spokesman for Mr. bin Laden put out a rather chilling statement which said that they're required to kill four million Americans, including women and children, in order to balance the scale of the atrocities that we and the Israelis have visited upon the Arab population. If you are trying to kill a lot of people at one time, you're at the high end of violence, which is nuclear. There is something almost like the moth to the flame with respect to the nuclear threat.

“A single nuclear weapon would have more explosive power than all the bombs dropped in all the wars in all of history.”

Technically, nuclear weapons are not like any other weapons. A single nuclear weapon—that is, any one of many weapons in the U.S. arsenal—would have more explosive power than all the bombs dropped in all the wars in all of history. So you're not on the same scale. It is so quantitatively different that it becomes a qualitative difference. I have compared the difference between a dirty bomb and a nuclear bomb to the difference between a lightning bug and lightning. They are both kind of similar, but the difference is obviously enormous.

If terrorists, God forbid, had had a weapon of a size that would have fit in the mini-van that Mr. Youssef parked in the World Trade Center when he tried to blow it up in 1993, but had had in it not the fertilizer kind of explosives that McVeigh had in Oklahoma City but a small nuclear weapon, the blast of that would have destroyed everything within a mile's radius. So if such a bomb had gone off at the World Trade Center in 1993, you would have seen not just the World Trade Center crumble but the whole southern tip of Manhattan disappear. You wouldn't have seen anything there; it would have vaporized. And you would have seen buildings up to Gramercy Park—that is, up to 30th Street or so in New York City—looking like the Federal Office Building.

Here in Boston, if you imagine such a relatively small nuclear bomb going off at City Hall, basically Boston would cease to exist as a modern city.

NOVA: What do you mean by small?

Allison: Small would have a 15-kiloton explosion. In terms of size, this is a weapon that fits into a van.

Your question then is: Is anyone motivated to do such a horrible thing? That was an academic debate before 9/11. After 9/11, that debate is kind of over. Secondly, if they are so motivated, could anyone acquire a nuclear weapon or the materials with which to make a nuclear weapon? Well, where could they get a nuclear weapon? How many nuclear weapons are in Russia?

NOVA: Tens of thousands.

Allison: Tens of thousands. Has anything been lost or stolen in Russia? Why not? Would it be possible for some guards, who are guarding these weapons, to decide to enrich themselves by becoming thieves? It would be possible. If they stole the weapon, could they transport it out of Russia? Russian borders are fairly porous. You don't even need a visa to go to Kazakhstan; just walk across the border or get in a plane and go. Same with many other territories of the former Soviet Union. And if you are in Kazakhstan, it is easy enough to go to Iran or Iraq.

So could they get it out of Russia? Yes. Could they sell it to bin Laden or Saddam or to some other terrorist group? Why not? If they were able to do that, could they bring it into the U.S.? Well, what percentage of the containers that come on container ships are opened? The answer is fewer than two percent.

And how much of our own border is nobody guarding? I mean, there was this fellow from Canada who recently drove into Maine to buy some gasoline on his way to go hunting in Canada. He had the gun in the back of his car, and he drove across the border, the way all Canadians living near Maine evidently do. He was arrested as a terrorist, because he had a gun in his car for hunting. The borders provide lots of opportunities for people to come in.

“I would not say it's inevitable that there will be a nuclear terror act. But I would say it is highly likely.”

Once a terrorist is in the city, say here in Boston, is there a magic shield that would go up that would set off a buzzer so we would know about it? I wish there were, but of course the answer is no. So I would say that this could happen.

NOVA: If it's so possible, why hasn't it happened already?

Allison: Again, that's absolutely the right question. Why didn't 9/11 happen before 9/11? The answer is we were fortunate. I would not say it's inevitable that there will be a nuclear terror act (though, interestingly, Warren Buffet, who's a pretty good judge of risk, at least when it comes to investing, says he thinks it's essentially inevitable). But I would say it is highly likely.

Taking action

NOVA: Are there things the U.S. could do that would substantially reduce the risk of a nuclear terrorist attack?

Allison: Absolutely. We know what those things are. We know how to do them. We're just not doing them. If I compared and contrasted with the dirty bomb case, I'd also agree that there are a number of important things we can be doing to take better care of dangerous material. We can learn to do it for radioactive material, and we can learn to do it for biological agents.

But we are not going to learn to do it until we get smarter, and it will probably take two or three more instances of terrorists beating us over the head before we wake up and say, "This is crazy to allow such material into the hands of people who might want to do horrible things."

In the nuclear weapons case, there is only a finite amount of fissile material, either highly enriched uranium or plutonium, and it is almost impossible for anyone to make plutonium or highly enriched uranium unless they are a state that has a big, visible, complicated technical production process. What's needed is a concerted effort to contain the spread of existing material, in which the U.S. takes the initiative by leading the rest of the world. This material and these weapons are too dangerous for the rest of us to be left to the individual predilections of whoever happens to have them.

Securing all such weapons and materials would be a vast undertaking, because, oh my God, that means securing 70,000 to 80,000 real or potential nuclear weapons in Russia. And you'd have to do the same in Pakistan and elsewhere. And then there are research reactors. In Belgrade, Yugoslavia, despite the fact that we were bombing that city in the war, there had been left a research reactor with enough highly enriched uranium to make three nuclear weapons. That was only extracted by a joint Russian-American initiative in August of last year. That's nuts. And there are plenty of other places where such things exist.

So I would say if we had a nuclear terrorist event tomorrow, God forbid, we would all wake up and say, "Well, this makes no sense. We shouldn't leave nuclear materials unsecured." Let's simply say now, "This is not going to happen," and go about doing it now. If I could have my chief wish, it would be that President Bush would say, "Wait a minute, the real threat is terrorists getting their hands on the worst, most destructive mechanisms. We can do something about that. We can cause it not to happen."

“The extent to which nuclear danger has somehow fallen off of the radar is remarkable.”

I think if President Bush would take this up as a cause he would have President Putin as his ally in a heartbeat, so that part's easy. China is easy. France and Britain are easy. Pakistan is hard but if China supports it, they'd go with it in Pakistan. And then going and rounding up the rest, I think it becomes a vast, complicated, and expensive but quite doable job.

The forgotten threat

NOVA: With all this talk of terrorism, it is easy to forget that Russia and the U.S. have ICBMs trained on each other. Is there is a danger of an accidental launch on either side?

Allison: Absolutely. We've all kind of tuned out about that. The extent to which nuclear danger has somehow fallen off of the radar—either because people are saying "Oh, that was the Cold War" or "That's over"—is remarkable.

I was in Washington last week with Senator Sam Nunn and my colleague Andrei Kokoshin, and we were making the point that if you were a Martian nuclear strategist, and you only got pictures, you didn't get any words, you'd never know the Cold War is over. The arsenals look almost the same, except that the situation is such that neither side means to threaten the other. It is a fantastic anachronism. It's just this dead hand of the past.

But you would think something funny had happened in the former Soviet Union. Because clearly there's a lot more activity in the capitals of these places that used to be part of the Soviet Union. You'd see, for example, borders with guard houses appearing with Latvia, and in Poland, all the troops from the Soviet Union that used to be there have left. If you looked at the nuclear arsenal of Russia and the U.S.—the number and status of the ICBMs, the activities of the submarines—you the Martian strategist would say, "Well, I guess something is happening in Russia. They look to be poorer or something, because they have fewer satellites than they used to have for command-and-control."

And the truth is some of the Russians' early-warning and command/control systems have degraded. So therefore you would say yes, the chances of accidents happening in most complex mechanical processes there have become greater. And that's an unsettling thought to say the least. [For more on this issue, see Russia's Nuclear Warriors.]

Preparing for Terrorism Graham Allison discusses both radiological and nuclear terrorism. Ask the Expert Charles Ferguson of the Center for Nonproliferation Studies answers your questions. Chronology of Events Review incidents involving unprotected radioactive materials. Sources of Radiation Explore radioactive sources both harmful and beneficial, natural and manmade.

Interview conducted and edited by Peter Tyson, editor in chief of NOVA online.