"Our mothers were right! Cleaning our hands before eating really works, especially after handling sand at the beach," said Dr. Richard Whitman, the lead author of the U.S. Geological Survey (USGS) study. "Simply rinsing hands may help reduce risk, but a good scrubbing is the best way to avoid illness."
For this study, scientists measured how many E. coli bacteria could be transferred to people's hands when they dug in sand.
They analyzed sand from the shores of Lake Michigan in Chicago. Using past findings on illness rates, scientists found that if individuals were to ingest all of the sand and the associated biological community retained on their fingertip, 11 individuals in 1000 would develop symptoms of gastrointestinal illness.
Ingestion of all material on the entire hand would result in 33 of 1000 individuals developing gastrointestinal illness.
In a further laboratory experiment, scientists determined that submerging one's hands four times in clean water removed more than 99 percent of the E. coli and associated viruses from the hands.