More on the different types of isotopes you may encounter in a post-apocalyptic scenario next time.
For now, it's important to add that fallout isn't just of the radioactive variety. Here's Phil:
You can get fallout from any light particulate floating through the air. Volcanic ash, fuel smoke coming up the stack from cargo ships, forest fires. If you've ever parked a car near Port Elizabeth and had to clear grime off it after parking overnight, congratulations, you've encountered fallout.
And mushroom clouds aren't just caused by nuclear bombs either. Volcanoes have been known to erupt into great pyrocumulus clouds, and in the late 1780s, a mushroom cloud was featured in a French painting of the Siege of Gibraltar.