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Q: Is the recent advice to stock up on duct tape and plastic sheeting of any real use in the event of a dirty bomb attack? Would this actually provide any real protection against radioactive dust?

Anonymous

A: Duct tape and plastic sheeting could provide some protection against radioactive dust depending on the source of the radiation and the circumstances of the event. However, there are more important things to consider initially. First, if you are very close to the blast, it would make sense to evacuate the area. In this case, listen for instructions from the authorities. Second, depending on the radioactive source, the radiation could pose an external hazard. For instance, gamma radiation could easily penetrate plastic sheeting. However, for alpha radiation, plastic sheeting could provide adequate blocking protection as long as there is a tight seal. Of course, you would not want to remain in a tightly sealed room for a long time (more than several hours or a day or two). But depending on the circumstance, a radioactive cloud would pass through an area quicker than that. The three principles of radiation protection are: time, distance, and shielding. Minimize the time of exposure. Maximize the distance between you and the radiation source. Maximize the amount of shielding between you and the source.

Q: I am a high school history teacher. My question is often brought up by many of my students. What steps have been taken by the United States to protect its population against the threat of a dirty bomb? Do you think that people living in metropolitan areas are at higher risk for a possible attack?

Anonymous

A: After September 11th, the U.S. government stepped up its efforts to secure highly radioactive materials. These efforts include issuing advisories to licensees of radioactive materials, sweeping up disused radioactive sources using a Department of Energy program, finding and securing "orphan" sources (those lost, stolen, or abandoned) using a program among the Nuclear Regulatory Commission, Department of Energy, and the Environmental Protection Agency, and increasing inspections of facilities containing radioactive materials. Nonetheless, more support of these programs is needed. In answer to the second part of your question, probably people in metropolitan areas are at higher risk. Because dirty bombs would be intended to frighten a lot of people and shut down parts of our economy, terrorists would tend to target highly populated areas such as cities.

Q: If the release of radioactive materials in a dirty bomb is so "silent," how do we know that it has not been done already? According to the NOVA special, a firecracker could contaminate D.C.'s metro.

Elizabeth
Washington, D.C.

A: In theory, there could already have been a terrorist release of radioactivity that went unnoticed because a radiological dispersal device (RDD) would not even require a bomb blast (even a firecracker) to disperse material. In principle, an RDD attack could be very silent. However, I would tend to discount that this has occurred. First, terrorists typically and traditionally have wanted a lot of people to know immediately of an attack. By definition, the terrorists want to instill terror and the best way to do that is to get immediate attention. Second, the government has been installing radiation detectors in critical areas, so unless the government has hidden the news from us (which would be difficult to do in our society), authorities would likely have detected such a silent RDD attack.

Q: What would be the results if a terrorist put radioactive material in a large city water supply?

Richard Fulton
Kincaid, IL

A: If you don't mind, I'll quote directly from the report on dirty bombs that I wrote with Tahseen Kazi and Judith Perera: "Because contaminating large water supplies to levels beyond acceptable health limits would require an enormous amount of radioactive material, this method is not likely to succeed. Moreover, certain radioisotopes, such as Pu-238 [plutonium-238], are not even water soluble and would tend to sink to the bottom of reservoirs, thereby presenting an essentially insignificant danger to human health." - "Commercial Radioactive Sources: Surveying the Security Risks," Occasional Paper No. 11, Center for Nonproliferation Studies, p. 19

Q: In the event that a dirty bomb does go off (understanding the volume of cesium released would be virtually unknown):

1. What proximity to the site of explosion would people need to be to warrant a valid medical concern, i.e., where you would recommend they seek medical testing?

2. Is there any reason to even test such areas for contamination if the radiation levels are, indeed, as low as this program suggested?

Carolyn Collins
Dallas, TX

A:

1. There are a lot of hypothetical situations to consider. I would not want to speculate as to proximity versus medical concern. I would advise listening to emergency response officials. It is likely that they would take prudent steps to ensure that people are being properly monitored.

2. Even if there are no immediate health concerns, there can be significant land contamination that could lead to long term health effects if the contamination is not identified and cleaned up. So, testing for contamination would take place even if the threat to public health in the near term would be small.

Q: I spend a great deal of time on the freeways of the Bay Area. What should my response be to a broadcast announcement of a dirty bomb released in a specific area that I was about to pass through in, say, the next 10 minutes?

Jim Quinn
Oakland, CA

A: If I were in your position, I'd not drive through that area. This is just a prudent response. There might not be an immediate health hazard. However, it is likely that once that announcement is broadcast, many people will try to flee that area, so the roads near there would be tied up, preventing you from going there anyway.

Q: In the event of an incident that involves the detonation of an explosive device of unknown nature somewhere in the country, are our local, state, and federal authorities prepared at this time with sufficient procedures, equipment, and personnel to determine whether, in fact, it was a dirty bomb that spread radioisotopes or simply a conventional explosive? Will there come a time when all explosions, accidental or otherwise, will be checked for radioactive material dispersal?

Jonathan F. Kotas
Moorpark, CA

A: Federal, state, and local officials are still far from being fully prepared to know how to respond effectively to such an attack. Nonetheless, at the federal level, the Nuclear Emergency Search Team (NEST) can make the types of determinations you're talking about. NEST can reportedly deploy to anywhere in the U.S. within a short time period. More and more local emergency responders are equipping themselves with radiation detection gear. However, my concern is that these responders should be getting adequate training for operating the equipment. There is some coordination among federal and local officials to provide the equipment and training, but based on what I've seen, there is not enough coordination between local and federal officials.

Q: How serious is the threat of this happening in our country? Should we really be worried, or is this threat far beyond the realm of possibility? We have yet to see it used anywhere.

Anonymous

A: Other than the incident reported in the NOVA program "Dirty Bomb," when Chechen rebels placed unreleased radioactive cesium in a Moscow park, there have not been any dirty bomb events or explosions. However, we now find ourselves in a heightened state of alert about all sorts of threats. Although I cannot quantify how likely it is that there would be a dirty bomb event in this country, I feel that even if there were such an event, it would typically not lead to many deaths from radiation. The conventional bomb blast might kill a lot of people. The use of radiation would tend to scare people. I would encourage our government to do a better job at conveying the message not to panic in the case of a dirty bomb attack.

Q: Our legislature is studying the possibility of allowing Envirocare of Utah to bring millions of tons of Class B and C radioactive nuclear waste to Utah by way of the nation's railroads. I worry that this may provide a real opportunity for terrorists to use rail cars as low-tech dirty bombs. A van filled with explosives under a rail overpass could spread deadly radioactive material over a huge area. A derailment caused by terrorists over a major river could spread for hundreds of miles. What do you think? Seems extremely dangerous to me.

Michael Ernsten
West Valley City, Utah

A: I understand your concern. However, based on what I've heard about the security of the transports, I feel reasonably confident that this does not pose a significant danger. I'm more concerned about the radiation safety and security risks of people holding on to their disused radioactive sources rather than properly disposing of them in facilities such as Envirocare. Our nation has to do a better job at securing and properly disposing of disused sources.

Q: Would firefighters' personal protective equipment (bunking gear and SCBA or APR) protect them from beta radiation? Both low and high energy?

What types of instrumentation would you recommend, and with what sort of dose range capability, for first response and initial surveying at an R.D.D. incident?

At what point, in mR or R, would you establish a "nobody goes beyond here, even for rescues" line?

Edwin J. Peterson
Seattle, WA

A:At the mRem/hour (1/1000 of a Rem per hour) level, there is really not much of a concern for emergency responders. This is a low level. At the Rem/hour level, precautions should be taken. But emergency workers can still operate in that area for a reasonable period of time, say an hour or so without exceeding regulatory limits for radiation workers. Not until the radiation level goes up to tens or hundreds of R would emergency responders have to significantly shorten their time in the area to a very short period, perhaps a few minutes depending on the radiation level. However, it is very unlikely that the typical dirty bomb would generate radiation levels this high.

Q: The NOVA program makes it seem that all cesium chloride (CsCl) is radioactive. Could you confirm that this is not true and that CsCl does indeed come in a stable, non-radioactive form?

Anonymous

A: You're correct. Only the CsCl containing radioactive cesium, such as the isotope cesium-137, would be radioactive. CsCl can also come in non-radioactive forms.

Q: Is it possible to wear some sort of over-the-counter mask to protect yourself in the event of a dirty bomb that contained cesium-137? Probably not since it can be absorbed through the skin, right?

Anonymous

A: There has been a lot of talk about the over-the-counter N95 masks, which are designed to be 95 percent effective at blocking 0.3 micron and larger sized particulates. In the case of Cs-137, an N95 mask might be able to provide some protection against inhalation of the matter; however, Cs-137, because it emits gamma radiation, is also an external health hazard. It also tends to bind to materials such as concrete. So, better advice would be to stay away from the immediate area of a dirty bomb blast. Minimize the time near the area. Maximize the distance between you and the source of the radiation. Place as much shielding, such as dense buildings, as possible between you and the contaminated area.

Q: What would happen if someone tried mixing different sources of radiation to make one huge dirty bomb? Would it be possible to mix cesium-137 with other radioactive material?

Anonymous

A: Yes, this is possible. I could imagine someone trying to maximize both internal and external health risks, so they might combine alpha-emitting and gamma-emitting sources of radiation.

Q: After viewing the NOVA program I am thinking about purchasing a general purpose Geiger counter for home protection. Since I know nothing about this subject, I was wondering if you could suggest a particular product, something easy to use that does not require frequent calibration. I presume calibration requires sending the product back to the manufacturer. Products I have viewed on the net have capability to measure alpha, beta, gamma, and x-radiation, and I wonder if this is sufficient for my protection, should something happen in my area.

Bob
Santa Clara, CA

A: If you and your family would feel safer with the purchase of a Geiger counter, then by all means buy one. However, I'd strongly recommend taking the time to learn how much background radiation is in your area. I would not want you to become overly concerned if you hear clicking when you first turn on the device. As you saw on the NOVA show, when my colleague Andrew Karam turned on a Geiger counter, it registered radiation. This is just normal background radiation. Since I work for a non-profit educational institute and because I have not studied particular product lines, I would not feel comfortable advising which product to buy.

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