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Household and Worksite Germs - Where are They Hiding?
Edited by: Mary Schroeder, M.S., R.D. & Pat Kendall, Ph.D., R.D., Colorado State - Summer 2005
In a series of studies, Dr. Charles Gerba (a.k.a. Dr. Germ) and colleagues at the University of Arizona have investigated key transfer points for illness-causing bacteria in the home and at the worksite. Here are the highlights of their findings:
Kitchen Hot Zones
In a 7½ month study of 15 households, the Gerba team identified five "bacterial hot zones." In descending order by highest bacterial count, these are:
- Sponges and dishcloths
- Sink drain area
- Faucet handles
- Cutting boards
- Refrigerator handles
How high is high?
The numbers were staggering. Sponges and dishcloths topped the list with a count of more than 7 billion bacteria per average-sized sponge/cloth. Frequently touched kitchen faucet handles netted an average of 229,000 germs per square inch. Cutting boards registered an average of 62,000 bacteria per square inch. Since the number of bacteria it takes to make people sick can range from as few as 10 up to millions, the goal is to reduce the number of illness-causing microorganisms in the home.
Attacking the "Hot Zones."
As an alternative to tossing those dirty sponges, Gerba recommends the following simple steps to create a healthier kitchen environment:
- Dip sponges after every use in dilute sanitizer water (1 teaspoon bleach per quart of water); boil them for 3 minutes on a weekly basis.
- Change dish cloths daily, especially after wiping up raw meat juices.
- Avoid rinsing raw meats. It contaminates the sink.
- Wash sinks with hot soapy water prior to food preparation and before washing dishes.
- Wipe down refrigerator handles daily with dilute sanitizer water.
- Choose non-porous cutting boards that are easy to clean.
Gerba has also checked out the bathroom. His big discovery? Always flush with the lid down. According to Gerba, when flushing with the lid up, a polluted plume of bacteria and water vapor erupts out of the flushing toilet bowl. It can take several hours for these particles to finally settle, not to mention where. Surprisingly, of all household samples collected, toilet seats had the lowest bacterial counts. Go figure?! Although no one really knows why, one possible reason is that toilet seats are too dry to provide a good home for growing bacteria.
In a 2001 study, Gerba and colleagues sampled 12 worksite surfaces in four different offices three times a day for 5 days looking for 5 types of bacteria (E. coli, Klebsiella pneumonia, Streptococcus, Salmonella and Staphylococcus aureus). To see the effect of cleaning, one group of employees used disinfecting wipes to clean the surfaces they worked with, while the other group did not. Gerba's team discovered the four "most germy" worksite surfaces to be the:
- Phone receiver (probably because many people share the same phone),
- Computer keyboard, and
- Computer mouse. The good news is that where office workers who were told to clean their desks with disinfecting wipes, bacterial levels were reduced by 99%.
While it is impossible to completely eliminate germs in our surroundings, we can minimize the risk of contamination by washing our hands on a regular basis and using alcoholic wipes on surfaces exposed to lots of people contact. These studies reinforce the need for good hygienic practices both at work and in the home. Pass the wipes please!Sources:
- Gerba, C., Are your kitchen sinks cleaner than your toilets? Cleaning Management
- Flushing Out the truth. Great Moments in Science. http://www.abc.net.au/science/k2/moments
- Terrazas, A.L., Yeech! The word from Gr. Germ. University of Arizona Alumnus Magazine, Winter, 2005.
- Cancer Experts Reissue Warning About Grilling. American Institute for Cancer Research Press Release. May 23, 2005. http://www.aicr.org.
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