The Eureka! Lab at Science for Students did an experiment on the 5 second rule - is food still cleaner if only dropped for 5 seconds rather than longer?
Part 1 sets out the experiment: https://www.sciencenewsforstudents.org/blog/eureka-lab/five-second-rule-designing-experiment
Part 2 describes the experimental setup: https://www.sciencenewsforstudents.org/blog/eureka-lab/five-second-rule-growing-germs-science
and Part 3 calculated the results: https://www.sciencenewsforstudents.org/blog/eureka-lab/five-second-rule-myth-busted
Results? basically busted - food dropped for 5 seconds collects microbes just like food dropped for 50 seconds. But basically most microbes you pick up are not that harmful anyway.
Clean floors are always better though!!