Gerba: Sometimes It’s Better Not to Clean
According to Dr. Charles Gerba, famed microbiologist with the University of Arizona and a well-known researcher on disease and germ transmission, in some cases “it may be better not to clean a surface than to clean it with soiled cleaning tools … [because] it can spread microorganisms around without your realizing it.”
Gerba says that as some cleaning tools, such as sponges, mops, microfiber cloths and mop heads, as well as conventional cloths, are used, “they actually become micropile compost heaps. In many cases, [the cleaning worker] is just laying down a thin layer of E. coli over the surface as they clean.”
This was made clear in a series of soil removal tests that compared conventional cleaning methods and products with high-flow fluid extraction technologies such as spray-and-vac cleaning systems.
To test the surfaces and determine whether contaminants were present, an ATP monitoring system was used.
ATP, or adenosine triphosphate, is a molecule found in all animal, plant, bacterial, yeast, and mold cells. Its existence on surfaces is usually considered a “red flag” that potential disease-causing germs and bacteria are present.
Testing Procedure … and Surprises
In one test, a floor was thoroughly cleaned and then tested for ATP. A low reading of 25 was measured, which was used as a benchmark.
Then a grape, which contains very high levels of ATP, was spread over the tile floor. The ATP jumped to a very high concentration level of 7267.
The same area was then mopped with a new microfiber mop head soaked in a hospital-grade disinfectant. After cleaning the surface, ATP levels dropped to 1479.
“But surprisingly, surrounding tile areas saw their ATP reading jump from 25 to nearly 700—over 27 times greater than initial readings,” says John Richter, a presenter at last year’s Cleaning Industry Research Institute (CIRI) symposium and an engineer and researcher with Kaivac, Inc.
According to Richter, soils and contaminants can become entangled in mop fibers and are redistributed in the cleaning process. “This means the microfiber mop head, as it became soiled, actually spread contaminants to nearby tiles, causing cross contamination,” he says.
The second part of the test involved using a high-flow fluid extraction/spray-and-vac system. Again a grape was spread over a clean surface with an initial ATP measurement of 25. After the grape was applied, the reading jumped to nearly 8000.
“We cleaned the floor using the same disinfectant but with the high-flow fluid extractor, but this time the ATP level dropped to 27,” says Richter. “What’s more, the ATP level on the surrounding floor areas dropped even further to about 20, indicating no evidence of cross contamination.”
Similar tests were conducted on student desktops using microfiber cleaning cloths and a new flat-surface cleaning system (FSC). Here again, the contamination levels as measured by presence of ATP were improved only somewhat with the microfiber, but dramatically with the FSC.
“Many cleaning professionals don’t realize that the cleaning tools they use [can give] germs a free ride around a facility,” says Gerba. “The professional cleaning industry must recognize that they are really in the health-care business. Preventing cross contamination and effectively removing soils and contaminants reduces illness and helps keep people healthy.”
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