The 5 second rule is just a myth according to the blog. There is no bacteria that just waits 5 seconds before jumping onto the object that was dropped. However, The article states that there are places that you could drop you r food and be deemed "safe" to eat. The bacteria that touches the food may actually benefit you. But, there are some places that you just shouldn't trust the 5 second rule.
I found this article interesting because I know people who really believe in the 5 second rule and will eat/ use the object that dropped on the floor regardless of their location. I find it disturbing. The article made me feel a little better about dropping something on the floor in a clean, dry place, and still using the item. This is something that more people should be educated on. Some places you can "get away with" other places, not so much.
http://blog.education.nationalgeographic.com/2016/03/24/should-you-break-the-5-second-rule/