Yup
Dirty bombs would have an effect FAR exceeding the real damage- as terror weapons go, they are the most cost effective... People's fear of radiation is extreme to the point of irrationality- here is a document I think You and others will find VERY interesting and educational...
http://www.llnl.gov/tid/lof/documents/pdf/246170.pdf
I read it all and found it fascinating- it is a must read....
