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Hand Washing and Drying to Reduce Microbial Contamination

November 07, 2012
Hand Washing and Drying

Everybody’s hands are frequently contaminated with enteric microorganisms, and food workers are no exception. These workers may be even more exposed because of their work with raw food ingredients and their frequent contact with fellow workers and the public.


Unlike hand contamination with staphylococci from the nasopharynx, the enteric bacteria that contaminate the hands of food workers more often are associated with raw foods of animal origin rather than poor personal hygiene after visiting the toilet.


Hand hygiene compliance at the retail food service level is known to be inadequate. Hand hygiene practices of food workers are dependent on the type of work involved and the type and nature of the soil on their hands. Compliance begins with a commitment by management to designate safety as the number 1 concern in the establishment and to introduce regular training programs for safe production of food, as well as when and how to wash hands effectively.


Many people, workers included, feel that their hygiene routines are sufficient because no adverse consequences have been experienced over many years of performing the same procedures. Gross hygiene errors may be in place for a long time in foodservice operations and not be identified until associated illnesses are reported. For instance, two United Kingdom catering facilities (in Scotland and Wales) were thoroughly investigated in public inquiries following large outbreaks with illnesses and deaths. Workers with management acceptance had contaminated cooked meat products.




Hand washing times of 15 to 30 seconds have been recommended by different agencies around the world. For many years sanitarians have specified that the hands of food service workers should be washed and rinsed in hot water to reduce the risk of cross-contamination and disease transmission. However, the use of water at these temperatures has not been supported by research. Hand washing with water at high temperatures may contribute to skin damage when frequent hand washing is required, and insistence on hot water usage may be a deterrent to hand washing compliance.


To reduce the potential for bacterial transfer, food workers may need to wash their hands for longer than 15 seconds or may need to wash more often. Thorough rinsing is important because this action also removes potential skin irritants and contact sensitizers originating in food, soaps, metals, and facility disinfectants that could lead to dermatitis. Triclosan, triclocarban-trichlorocarbamide, and parachlorometaxylenol-chloroxylenol are commonly used antibacterial hand cleaning agents, however Gillespy and Thorpe found that germicidal soaps were not remarkably more effective than ordinary soap for reducing the numbers of bacteria transferable from the skin to handled objects. Infectious disease outbreaks have also been linked to workers with long or artificial fingernails. Without the regular use of a nail brush, they are very difficult to clean even with appropriate soaps, hand rubs, or gels.




Hand drying has two effects: removal of moisture through absorption and removal of microorganisms through friction. The friction generated during hand drying is even more important than that generated during washing because the soaping stage has loosened the microorganisms from the skin. The drying stage physically removes microorganisms in a film of water from the skin by wiping and depositing them on a towel. Thus, hand hygiene efficiency is a combination of washing efficiency (soap, water, rubbing, and rinsing) and hand drying.


Although cloth towels are popular because of their rapid drying, they become contaminated through multiple usages, and once pathogens are deposited on towels, they can survive long enough to contaminate the hands of other users.  Cellulose fiber is the main material in institutional paper towels, which are usually made of rougher paper than used for domestic paper towels. The coarser the grain of paper used, the more efficient the friction effect will be for organism removal, although harsh, non-absorbent paper towels could discourage their use compared to softer paper. Also, hand-operated paper towel dispensers have their limitations.


In a survey of 12 food processing or food service facilities, researchers found coliforms, E. coli, and S. aureus on paper towel dispenser equipment. Air driers that are used in many communal washrooms allow one user at a time, and that take up to 1 minute to dry the hands, have not been convenient and lead to avoidance or incomplete drying. In several studies, on average people spent 22.5 seconds drying hands, and 41% wiped their hands unhygienically on clothes. Newer fast air flow driers are becoming more widespread, but have yet to be completely evaluated for their sanitary qualities.


Because of the uncertain or limited effectiveness of hand hygiene, multiple hurdles to reduce pathogen contamination and reduce their spread are better than one or two hurdles. When coupled with glove use and proper handwashing, these steps should minimize the opportunities for pathogens to reach the food being prepared.


Ewen ToddProf. Todd is an Adjunct Professor with the Food Science and Human Nutrition Department at Michigan State University.  As a scientist with over 45 years in food safety, in particular relating to foodborne outbreaks, Prof. Todd has written many publications and spoken at national and international meetings. He is currently working on Listeria transfer coefficient and modeling projects, hygiene in child care centers, avoidance of norovirus in elder care facilities, and rapid recall and traceability research in multidisciplinary projects with colleagues at MSU and other universities.

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