The Washington Post reports today that ISIS has potentially had the ingredients of a dirty bomb available to them; at this time, apparently they did not have the skills to retrieve them. But radioactive materials are widely available, and a dirty bomb is the scariest weaponry that may become available to terrorist organizations in the future. (Nuclear weapons are very difficult to obtain and build; biological weapons are currently difficult, although that might change in the future; chemical weapons are very difficult to deliver to a target.)
The following is a discussion about how you should feel, and what you should do, about dirty bomb attacks. I am not an expert; this may be amended after expert colleagues have read and commented on it.
What is a dirty bomb?
A dirty bomb is a conventional explosive encased in or containing radioactive material. When the bomb explodes, this radioactive material is dispersed over an area as large as, or slightly larger than, the blast radius.
A dirty bomb is not a nuclear bomb. Nuclear bombs are immensely powerful and widely devastating. The radioactive material in a dirty bomb does not contribute to its explosive power; the bomb is no more powerful than the conventional explosive would be without the radioactive materials. As a result, the area which is irradiated by a dirty bomb is likewise constrained. There is no fallout. There is very little chance that radioactive materials will be carried by wind, and if it is, there is so little of it that it poses a small risk. Nuclear bombs create fallout because they create a large amount of airborne debris which is highly radioactive; dirty bombs do not create airborne debris (or very little), hence no fallout extending the radioactive radius.
A dirty bomb can kill you with radiation if you are within the blast radius. However, if you’re inside the blast radius, the conventional explosion will already turn you into pudding. Dirty bombs are only really an additional concern for those people within an injury but not lethal zone, or perhaps for people who feel the blast but are not injured; these people may have radioactive health impacts beyond the conventional blast.
If you are outside the blast radius, you are not at risk from radiation. You will not be at risk from radiation in the future.
The Washington Post article mentions the possibility of a dirty bomb going off and irradiating a large area. To the best of my knowledge, this is only possible with particular kinds of explosives in an airburst; such weaponry is not available to terrorist organizations, so the article should have noted that this becomes a concern only if we’re at war with a nation-state.
What you should do
Summary: stay in place, as long as you can, unless you are evacuated. Tell your family to do likewise. Do not try to reunite, not yet.
Most people have no idea that there is a difference between dirty bombs and nuclear bombs, and will be terrified. They will likewise be terrified of radiation (which, to be fair, is terrifying in large doses). Expect a mass migration away from what is perceived as the affected area (much larger than the actual affected area). Expect gridlock as families try to reunite. Expect civil law enforcement and authorities to fail at first in containing panic; even if they’re well-trained, they’re going to be overwhelmed.
This may also happen in case of conventional attack, if a disinformation terrorist broadcast announces radiation where there is none, or if an irresponsible media or government report does likewise. This happened briefly after 9/11. It may happen again. Act on your best information; listen for better.
Stay where you are, as long as you can.
The greatest danger to you and your loved ones is not from the bomb, but from your panicking fellow citizens. (This is also the case with biological, chemical, and nuclear attacks if you’re outside the much larger affected area, but in those cases, panic may very well be justified. “Stay in place” is not necessarily the right thing to do in those cases.) If your fellow citizens are well-armed, there will probably be bloodshed. Even if everyone remains non-violent, there will be gridlock on local streets and highways leaving the city. Fleeing is likely futile; furthermore, it’s unnecessary.
Eventually there will be an all-clear alert from the authorities, or you may notice the traffic and panic is lessening in your area. It’s probably a good idea to wait longer until you can be certain, but that’s when you can reunite with your family and—if you wish—get the hell out of Dodge.
Cell phones will likely be unable to place calls; your phone Internet may still work, but will be very slow. Due to this, it is an excellent idea to buy a portable radio now, especially one which is hand-powered. Landline Internet and phone connections should still work. Use these to contact your family if they’re available.
If you are evacuated, it is entirely likely that the beat cop or firefighter who is doing so has no more understanding of dirty bombs than you do. But they know enough to get you away from the dangerous blast radius, which will remain radioactive. Conventional civil emergency procedures are appropriate here, and we have good training programs in place in urban areas for police and firefighters. This may be less true in exurban and rural areas.
Finally, the last thing you should do. Share this with your friends, neighbors, and coworkers. (If they are nearby during an emergency, their best interests are also your best interests; reducing panic is crucial. Sharing this information during an emergency is unlikely to do that.)
Also: contact your local and national politicians and express your concerns with them. We’ve had 16 years since 9/11 for a widespread campaign to inform the public, similar to what was done in England during the Blitz. We have not done so. Rather we have often increased fear and the likelihood of panic; I have also never seen a general media story containing the above information. This is civic negligence. Ask for better.