I think we all know that the “5 second rule” for eating food that has dropped on the floor may not be accurate. But what about the carrot sticks or lettuce leaves that tumble from the colander into the sink? Surely the sink, which is regularly doused with soap and water, must be cleaner than the floor?

Kelly Reynolds, Ph.D., an assistant professor of microbiology at the University of Arizona states that unfortunately that is far from the truth. While the floor may be crawling with 1,000 bacteria per square inch, the sink typically hosts around 500,000 bacteria per square inch — and she’s seen sinks that had millions more than that. “The sink is a ready source of bacteria just from washing off hands as well as food, which may carry fecal bacteria.” The number of bacteria it takes to make us sick depends on the type, but Reynolds says that it takes between 100 and 1,000 bacteria to transmit salmonella, which is the most frequently reported cause of foodborne illness.

Reynolds says our kitchen sinks are often dirtier than the toilets of public bathrooms, which may be regularly scrubbed with powerful disinfectants. “If you dropped something in the toilet at the gas station, would you rinse it off and eat it? Use the same mentality for your sink.”