honestly, i would be much more worried about an india/pakistan conflict, probably the most likely modern day scenario in which we might witness a massive nuclear exchange. there was a great documentary made by vice for their new hbo series that went into a bit of detail about the conflict. it covered the some of the politics regarding the disputed kashmir region, and discussed the provocateur attempts by pakistan to destabelize india, and how close the somewhat recent mumbai terror attacks were in pushing an all out war between the 2 countries. apparently, it was stated that if 100 nuclear warheads(depending on kilotons) were detonated in rapid succession, it very well might be the end game for all of us!