This incident as well as train bombing in Madrid and the World Trade Center attack on 9/11 have all made me consider the following items in my EDC. By EDC I mean actually "on my person" rather than in a vehicle or a desk drawer etc.

Leatherman Wave
N95/N100 Masks
Duct Tape for sealing the masks (I tend to be a little scruffy in the facial hair dept)
Surefire Flashlight

None of these items have been added to my EDC but like I said, I have "considered" adding all of them as a result of each of the above-mentioned situations.

The Leatherman Wave, N95 Masks and Duct Tape still sit in my vehicle (which would render them useless to me if I were involved in any of the above-mentioned incidents) and I don't even own a Surefire Flashlight.

My current EDC is a Large Regular Sebenza, a Photon II LED light and a Mini Bic Lighter, none of which would probably be nearly as useful in such situations.