Tuesday, October 25, 2011

Germs - The 7 dirtiest objects

Jack Dikian
October 2011

According to a new study from Kimberly-Clark Professional, the Dallas Health-care products maker, much of the everyday germs we pick up may be less to do with sharing our workplace our sniffily colleagues and more to do with objects we come in contact with on our commute.

The study was designed with help from Environmental Microbiologist Charles Gerba, a professor at the University of Arizona. Measurements of contamination levels were taken with repeated swabs of the everyday items using the same methods as in the food and other industries to monitor sanitary conditions.

These included high-traffic locations petrol pumps, mail box handles, parking meters, traffic light buttons, escalator handles and vending machine buttons in six cities; Atlanta, Chicago, Dallas, Los Angeles, Miami and Philadelphia.

Swabs were taken and measured for levels of Adenosine Triphosphate (ATP). ATP is the universal energy molecule found in animal, plant, bacterial, yeast and mould cells. Residues, particularly food or organic residue, contain large amounts of ATP. Microbial contamination contains ATP, but in smaller amounts. So ATP measurements represents dirt that otherwise may be invisible to the human eye. So the amount of ATP serves as a good indicator health risk. The greater the levels of ATP, the greater the health risk.

ATP is easily and accurately measured by treating an ATP-containing sample with a reagent that reacts with ATP and produces light that can be measured in a luminometer. The amount of light produced (relative light units) is proportional to the amount of ATP in the sample. As an aside, this reaction occurs naturally in fireflies to produce their characteristic light. ATP readings of 300 or higher indicated a higher risk for illness transmissions when the items are touched.

The results:

  • Petrol pump handles had the highest levels of contamination with 71% of those tested having ATP levels of 300 or more.

  • Mailbox handles were a close second with 68% having high ATP levels.

  • Escalator rails came in third with 43% of tested showed contamination.

  • ATM buttons tested poorly with 41% of those tested were contaminated.

  • Parking meters (41%) were found to be breeding grounds for germs.

  • Traffic light buttons (35%) and 35% of the snake vending machine buttons tested had higher than accepted ATP levels.

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