Wash Those Hands!

October 12, 2003

http://www.sciencenews.org/20031011/food.asp

Science News

Week of Oct. 11, 2003; Vol. 164, No. 15

Wash Those Hands!

Janet Raloff

When physicians talk about food poisoning, they're not usually referring to the

effects of natural toxins made by plants or animals. But some foods do carry

that danger. For instance, potatoes can develop pest-deterring agents in and

just under their skins that can sicken or, rarely, kill a person. And certain

fish—such as the infamous puffer—produce chemicals that have done in more than

one sushi eater.

In most instances, however, food poisoning can be blamed on bacteria or viruses

that originate in animal or human feces. In some instances, livestock become

infected in the barnyard. Other times, the germs spread from animal feces to

newly butchered meat in the slaughterhouse. They can even be transmitted within

the home or the food-service industry by people who don't thoroughly wash their

hands after using the restroom. When these people return to food preparation,

the germs on their hands can be transferred to kitchen surfaces or directly to

the foods we eat.

A dirty hand carrying just a few germs can cause big problems. According to the

Food and Drug Administration (FDA), among bacteria that reproduce by dividing

themselves every half hour, a single germ can—given ideal conditions—yield 17

million offspring within just 12 hours. High-temperature cooking and

refrigeration can kill bacteria and viruses or at least slow the rate at which

many grow. However, any remaining germs that are ingested by a person can

reproduce within the human gut and cause serious illness.

A Florida-based company is now developing a laser-based scanning technology to

scout for dirty hands. Installed in restaurant washrooms or daycare centers, it

could identify fecal traces—evidence that hand washing was incomplete. Indeed,

these sensors might even be coupled to a lock that allows workers back into a

kitchen after a restroom break, notes Richard Stroman, vice president of eMerge

Interactive, which is applying for a patent on the system. Kitchen or

food-processing-plant workers who don't pass the laser test would be forced to

go back and lather up again.

Sources of germs

Survey after survey finds that many people don't routinely wash their hands

well, if at all. A new study conducted in major airports, for instance, shows

that about 40 percent of air travelers in the United States don't wash their

hands before leaving the restroom. If this reflects their habit, these people

could be spreading fecal germs whenever they touch their own or someone else's

food.

However, many fecal germs taint foods even before they reach the kitchen. FDA

scientists have surveyed meats in grocery stores and found fecal bacteria on 67

percent of the sampled chicken, 34 percent of the surveyed cuts of turkey, and

66 percent of the beef. Moreover, at least some of the microbes in each

contaminated sample proved resistant to multiple antibiotics, which means that

if they were to cause human disease, some medicines would fail to kill the

infection (SN: 5/26/01, p. 325: Available to rs at

http://www.sciencenews.org/20010526/fob3.asp). Such findings reinforce the

importance of washing hands, as well as any surfaces and utensils that contact

raw meat.

Other studies have shown that even fruits and vegetables may come home from the

grocery store harboring germs that aren't easily washed off the items (SN:

5/30/98, p. 340:

http://www.sciencenews.org/sn_arc98/5_30_98/fob1.htm). Because these foods don't

usually get cooked before eating, they can serve as a source of germs on hands.

Although there are techniques for disinfecting produce (Science News Online,

9/28/96:

http://www.sciencenews.org/Sn_arch/9_28_96/Food.htm), most cooks don't employ

them.

What makes such data especially troubling is the fact that surveys by FDA's

Center for Food Safety and Applied Nutrition consistently find that U.S.

consumers fail to wash between handling such potentially contaminated foods and

then touching kitchen utensils or other menu items.

Laser finds new use

About 5 years ago, Iowa scientists working for the U.S. Department of

Agriculture (USDA) developed a scanning technology to reveal contamination on

carcasses passing through the slaughterhouse. Whenever laser light produced a

specific glow on the meat, it signaled the presence of feces.

Stroman's team licensed USDA's technology and last year applied to patent the

method. The technology is based on the presence of chlorophyll—a primary

constituent of the bovine diet and therefore a cow's feces (SN: 5/17/03, p. 317:

Available to rs at

http://www.sciencenews.org/20030517/note14.asp).

However, Stroman notes that chlorophyll won't reliably identify human waste

because, " the human diet is so variable that we can't count on a person having a

salad every day or two. " So, his team analyzed scores of human fecal samples for

a combination of chemicals that might together reveal contamination. Adding to

the challenge is that these compounds must be distinct from chemicals that can

get onto skin from other sources.

Recently, eMerge's scientists successfully tested laser-light wavelengths that

reveal a telltale suite of fecal markers. Test volunteers were 24 people who had

been assigned different diets for 3 days. One group had eaten foods typifying

the normal U.S. diet. The second group had eaten high-protein fare and no

vegetables. The final group followed a vegetarian regimen. The researchers found

that the laser screener revealed fecal-contaminated hands regardless of a

person's diet.

In the next 2 months, the company expects to expand its patent application to

include scanning at the new wavelengths. A prototype of the hand-scanning system

should be available next spring for field-testing.

Stroman expects the device to consist of a wall-mounted unit that turns on when

hands appear below it. After scanning one side of the hands, the machine would

tell a user to turn his or her hands over for a full screening.

The system could even ask an employee to key in an identification number.

Management could then identify workers needing a reminder about their training

on sanitation.

The machines might even be customized for educational settings, where children

could check their hands after each restroom break. A green smiley face might

signal hands are clean, and a red frown could mean that another trip to the sink

is called for. Not only would this help slow the transfer of germs around the

classroom, say the researchers, but it could also teach kids the difference

between running water over their hands and really cleaning up.

References and Sources

References:

2002. CDC releases new hand-hygiene guidelines. Centers for Disease Control and

Prevention press release. Oct. 25. Available at

http://www.cdc.gov/handhygiene/pressrelease.htm.

Ashby, K.D. . . . and J.W. Petrich. 2003. Fluorescence of dietary porphyrins as

a basis for real-time detection of fecal contamination on meat. Journal of

Agricultural and Food Chemistry 51(May 21):3502-3507.

Center for Food Safety and Applied Nutrition. 2002. Food Safety Survey: Summary

of Major Trends in Food Handling Practices and Consumption of Potentially Risky

Foods. Washington, D.C.: U.S. Food and Drug Administration. Available at

http://www.cfsan.fda.gov/~dms/fssurvey.html.

Centers for Disease Control and Prevention. 2002. Preliminary FoodNet data on

the incidence of foodborne illnesses—selected sites, United States, 2001.

Morbidity and Mortality Weekly Report 51(April 19):325-329. Available at

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5115a3.htm.

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