Is It Safe To Eat Something Dropped On The Floor As Long As You Pick It Up Within 5-Seconds?

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Updated on Jun 17, 2013

Grade Level: 4th-6th; Type: Microbiology


To discover whether the “five-second rule” is effective in determining if food is still safe to eat after being dropped on the ground.

Research Questions:

Shoes harbor bacteria and help transfer dirt and germs from one location to another, which means we probably shouldn't eat food that's been dropped on the floor. However, people have come up with a “five-second rule,” which says that if food has been dropped on the ground for five seconds or less, it can still be consumed safely. But is this true?


  • Chunks of bread
  • Microscope
  • Well slide
  • Pen and paper for notes

Experimental Procedure

  1. Put a piece of fresh, untouched bread under a well slide and view it under a microscope. Look for bacteria and record what you see.
  2. Drop another piece of bread on the floor for one minute. Pick it up and put it under a well slide, again for viewing under a microscope. Record the amount of bacteria that you see.
  3. Now drop a third piece of bread and leave it on the ground for 30 seconds. Once again, record the amount of bacteria.
  4. Finally, drop a piece of bread for less than 5 seconds and view it under the microscope. What do you see?
  5. Compare the four pieces of bread and how much bacteria you saw on each one.

Terms: bacteria; dirt; germ transfer; timer

References: Bacteria: Life History and Ecology; Fundamentals of Microbiology, by IE Alcamo (Jones and Bartlett, 2001)

Sofia PC is currently a college student with a deep interest in science who is aspiring to become a writer. She writes about all sorts of things across all subjects including, but not limited to; science, crafts, and fashion. She hopes to become a good writer so she can share her thoughts and experiences with the world and future generations.

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