Things that go boom! Fears?

I have had a very quick (Thursday through Friday) first contact to phone interview with a DHS contractor that does Explosives Trace Detection. It went well and I expect a site visit in short order.

They were looking for a Chemist (which I am not); I might be able to fake being a physical or analytical chemist, but not an organic chemist. Organic molecules are the ones that typically go boom! So anyway I did research on my best guess of what they wanted to detect (and nailed it), but I am sure that I've gotten on an FBI watch list (or at least my IP has).

If I had to fear terrorist attacks, I would prioritize my fears thus:
1. Being in a big city that is a transportation hub (NY, Seville, London, as examples)
2. The device being used, will be portable and have high energy and deployed for maximum effect (say at subway (London) or train stations (Seville)).
I am not fond of big cities or crowds, so I think I am safe. Although I could envision living in a city like Oklahoma City (good old home-grown terrorists).

The explosive used:
1. Easily obtained and easily synthesized. This is a biggie. A very simple search can give you a frightening list -- You could even use flour! Although deployment would be problematical.
2. Foreign obtained RDX.
3. Radiological materials -- These are not necessarily kill-instantly devices, but are health-threatening and certainly economic terror weapons (A book by Harry Turtledove, the master of alternate fiction wrote The Man with the Iron Heart about an instance in his alternate history where the Nazis had post-war resistance a la Iraq [1].)
4. Low yield nuclear devices smuggled over the Mexican border, or the Port of Longbeach, and obtained (stolen/purchased) from a Russian Satellite state, or less likely an unstable nuclear power, such as North Korea (IMHO too incompetent), Iran (IHMO too smart), or Pakistan (IMHO the best candidate. Tribal areas not subject to governmental control -- WTF?

I hate to say that the best bang for the buck in terms of human safety is outlawing cigarettes.

I recently read Freakanomics and there are a number of studies that challenges our fears. One of them being that backyard pools are about a hundred times more dangerous than handguns in the house. Having recently had one of my cats drownd in a neighboors pool, I can certainly understand that.

I must say that I have neglected biological weapons -- this might be the biggest fear. An outbreak of a 1918 flu epidemic would be devistating.

[1] you might want to check out The Man With The Iron Heart
[2] Freakanomics