Web edition: October 8, 2003
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 subscribers 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 subscribers 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.
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