Answer to Question #4778 Submitted to "Ask the Experts"

How thick should lead shielding be to protect against "low yield" radiation that might come from a terroristic weapon? I am considering redoing part of my house to address possible scenarios.

There is really no good answer to your question because there are so many variables to consider— the yield of the device, the distance at which it explodes, whether or not you are in the "line of sight" (i.e., can you see the explosion directly or are you in a valley, or is there a hill or mountain between you and the explosion, etc.), and the local terrain are all important factors. Even the weather can be a factor—dry air provides less radiation shielding than wet or humid air. For example, you may be exposed to almost no radiation at one mile from a low-yield device that explodes behind a hill, but might get significantly higher doses from the same device that has a clear line of sight.
 
Another factor to consider is the likelihood that your city will be attacked. Unless you live in a likely "target" city, you are not likely to have to worry about an attack at all. In fact, unless you live within five miles or so (for a large device) of the central part of the city or large cargo ports, you're not likely to experience significant radiation levels.
 
So, to be honest with you, I really don't think I could advise putting up any lead shielding on your home for these reasons:

• There are too many variables that we just don't have the answer to, so you would either put up too much or too little lead.
   
• The money you would spend on lead shielding can be better used for other things that have a greater chance of really helping your family.
   
• Lead is a toxic heavy metal, so you would place yourself and your family at certain risk from using it, versus possible risk from not having it.
   
• The risk of a nuclear attack, unless you are in a very likely target city, is very small.
   
• The presence of lead paint can be a major detractor in the sale of a house. The presence of lead shielding, which I'm assuming you would have to report, would probably be equally likely to reduce the house's resale value.
   
• I'm not aware of any radiation safety or nuclear professionals who have installed lead shielding in their homes. This suggests that those who know the most about radiation and nuclear effects don't consider it worth the cost and trouble to install.
   

Andy Karam, CHP, PhD