Most experts consider the food supply of the United States to be unmatched in quality and safety. But in recent years a series of deadly food poisoning outbreaks has begun to shake the public's confidence in the safety of their diet. These events have sparked legislative concern, leading state and federal officials to propose major changes in a regulatory system that has safeguarded domestic and imported foods for almost a hundred years.
The latest and most publicized outbreaks have turned the rare serotype 4b strain of the bacteria Listeria monocytogenes into a virtual household name. Sara Lee hot dogs and deli meats contaminated with Listeria at the company's Zeeland, Michigan, plant have caused over 70 illnesses and 16 deaths in 14 states since August 1998. Outbreaks of other foodborne pathogens on a much greater scale have also been recorded. Malt-O-Meal breakfast cereals contaminated with Salmonella agona infected an estimated 18,000 people during the spring of 1998. As many as 38% of the cases reported to state health agencies required hospitalization, and there was one fatality. Estimates vary widely, but the Ames, Iowa-based Council for Agricultural Science and Technology, an organization composed of 36 scientific societies, suggests that anywhere from 6.5 million to 33 million illnesses and up to 9,000 deaths each year may be caused by foodborne hazards. Many of the victims are children, the elderly, or people whose immune systems are compromised by preexisting illnesses such as AIDs. Of these infections, the vast majority are due to microbial contamination, although potential health effects from chronic pesticide exposures in the diet, particularly among children, are also causing increasing concern.
Underscoring these statistics is a groundswell of opinion that the nation's food safety system is in need of a major overhaul. This viewpoint was the dominant theme of the National Academy of Science's (NAS) August 1998 report, Ensuring Safe Food: From Production to Consumption, which compared the U.S. food safety system to a "patchwork quilt . . . of fragmented and outdated safety laws . . . that are barriers to improving the safety of the food supply."
Evolving Risks
Among the NAS's chief concerns is that the current food safety system is not keeping pace with the social, economic, and demographic shifts that are changing both the food we eat and how we go about getting it. Farm stands and local grocery stores are giving way to national and global distributers and supermarket chains carrying an average of 30,000 items each. Michael Doyle, director of the Center for Food Safety and Quality Enhancement at the University of Georgia's Griffin Campus and an NAS food committee member, says that the nature of the U.S. diet is also changing. People are eating less beef and more chicken and fish. Higher-risk foods such as fresh fruits and vegetables, and raw or minimally processed foods such as premixed salads and unpasteurized juices are also becoming more popular. Fast-food restaurants and ready-to-eat meals have become staples of the mobile and time-stressed U.S. society. "We're eating out more," says Doyle. "This means that, with less control over our food preparation, we're putting our trust in safe food in the hands of others, often young people working for minimum wage without the best understanding of food handling practices."
Meanwhile, many new and emerging pathogens are slipping through cracks in the inspection process to find their way onto the dinner table. Donald Schaffner, an extension specialist with the Department of Food Sciences at Rutgers University in New Jersey, says some of these emerging strains have resulted from changes in the mass production of food. "Sometimes a change in food production processes optimizes proliferation of a rare strain and makes that strain more common," he says. "Other times, these unique strains have always been there, but we get to know them because new tools and techniques tell us they are there." For example, Campylobacter jejuni is a microbe that was long recognized as a pathogen in animals, but was not identified as a source of human disease until better detection methods identified it as such in the early 1980s. Campylobacter is now considered the leading cause of acute bacterial diarrhea in the world.
According to Doyle, an example of a potentially new species of microbe is Escherichia coli O157:H7. Most forms of E. coli are safe, and inhabit the mammalian gastrointestinal tract by the billions. But E. coli O157:H7 is a virulent exception that debilitates its victims with acute gastrointestinal illness, bloody diarrhea, and in some cases kidney failure. "E. coli O157:H7 may have evolved in cattle fed high doses of antibiotics," says Doyle. First recognized as a human pathogen in 1982, E. coli O157:H7 strikes an estimated 20,000 people and kills as many as 500 annually.
Another recently emerged pathogen is Cyclospora cayetanensis, a unicellular parasite first recorded in the medical literature in 1979. Fresh raspberries imported from Guatemala were behind a large multistate outbreak of cyclosporiasis in 1996. Other important pathogens commonly linked to food poisoning outbreaks include Clostridium botulinum, a bacterium that produces a potent neurotoxin, and Listeria monocytogenes, a common environmental bacterium that clings to drainpipes and plastic surfaces. As with E. coli, most forms of Listeria are safe. But the virulent 4b serotype can cause meningitis, encephalitis, and spontaneous abortion in pregnant women. Data collected by the Centers for Disease Control and Prevention (CDC) indicate that Listeria, which has been associated with practically all kinds of food, causes at least 1,850 illnesses and 425 deaths a year in the United States.
A major problem is how to tell whether a food is contaminated. Unfortunately, there is no easy answer. Contaminated foods often look, smell, and taste no different than uncontaminated foods, and microbes often survive low-temperature cooking. And because they tend not to be distributed evenly in foods, microbial pathogens may not make everyone who eats a particular product sick. Paul Mead, a medical epidemiologist with the CDC, says that, although safeguards implemented by the increasingly consolidated food industry have done much to reduce contamination levels, the trend toward national and global distribution of foods is leaving many more people at risk if something does go wrong. "Rather than the local outbreaks of the past with high levels of contamination, we're seeing huge outbreaks with low attack rates," he says. "This is hard to track epidemiologically. One or two [disease] cases in any one given area can easily get lost in the background rate [of that disease]."
Fortunately, some new technologies are enabling detection of outbreaks that otherwise might be missed. Foremost is a technique called pulse-field gel electrophoresis, which allows researchers to develop DNA "fingerprints" of microbial strains isolated from infected patients. These fingerprints can be entered into a nationally linked database called PulseNet, through which public health officials can identify and group related cases, regardless of their geographical location. PulseNet, which was launched in May 1998 by the CDC, enables epidemiologists to track foodborne contaminants five times faster than before the technology was available.
The Current System
The regulatory origins for the current food safety system date back to 1906, the year that Congress delegated responsibility for the nation's food safety to the U.S. Department of Agriculture (USDA). When the Food and Drug Administration (FDA) was moved out from under the USDA, it took responsibility for the safety of essentially all foods other than meat and poultry, which it left to the USDA's Food Service Inspection System (FSIS). Both agencies are also charged with making sure that pesticide residues in food are below the tolerances set by the EPA for safe exposures.
The USDA and the FDA carry out their mandates in very different ways. By law, the USDA bases its enforcement strategy on one of continuous inspection of every carcass that makes its way through a slaughterhouse, as well as daily inspections of plants that process meat and poultry products. The FDA relies on a force of 7,400 inspectors with jurisdiction over an estimated 62,000 production, processing, and food storage facilities. This huge responsibility swamps the FDA's abilities, and according to the NAS report, the agency is only able to perform site-specific inspections roughly once a year.
The FSIS is widely considered to be more thorough. This probably reflects a historical concern for sanitary meat, which has traditionally been seen as the greatest source of foodborne diseases. FSIS inspectors actually work in the facilities they monitor for compliance, checking carcasses and other meat products one by one as they make their way down the production line. This intensive approach is coming under increasing criticism by experts who feel that visual inspection of meats can't prevent passage of microbes like Salmonella, Campylobacter, and E. coli O157:H7. According to Michael Taylor, vice president for public policy at Monsanto Corporation, the USDA did not traditionally consider these pathogens to be food adulterants, assuming that they would be killed during cooking, but the agency abandoned that position in 1994 as it began stepping up its efforts to minimize contamination during processing.
Both the USDA and the FDA have oversight over imported foods, which are making up an increasing share of the U.S. diet. Again, protocols for inspection differ sharply between the two agencies. The USDA regulates imported meat and poultry products by verifying that the exporting country's inspection system is equivalent to its own, and by reinspecting at the border. The FDA, on the other hand, limits its oversight to random port-of-entry inspections of imported foods. But in the same way that the FDA has been unable to keep up with domestic production, it is overwhelmed by imported foods as well, and can only inspect around 2% of overseas shipments.
A New Paradigm?
In May 1997, the Clinton Administration directed the secretary of agriculture, the secretary of health and human services, and the administrator of the EPA to come up with a plan for improving the nation's food supply. Following an exhaustive effort and considerable collaborations with stakeholders, the cabinet members published a series of recommendations in a May 1997 report entitled Food Safety, from Farm to Table: A National Food Safety Initiative. The Food Safety Initiative, as it is called, provides a blueprint for a revamped food safety system, emphasizing improved outbreak response, consumer education, and increased use of scientifically based intervention strategies and microbial risk assessments. These recommendations were endorsed by the NAS, which concluded in its August 1998 report that the biggest stumbling blocks to implementing the Food Safety Initiative are a fragmented federal structure and an unfocused research agenda. Ultimately, argued the NAS, the best way to achieve the goal of improved food safety would be through a centralized authority that would provide a "single point of leadership."
Not surprisingly, this radical proposal garnered mixed reviews. According to Sanford Miller, a prior director of the FDA's Center for Food Safety and Applied Nutrition, the move toward a centralized authority is fraught with political overtones. Says Miller, a strong proponent of centralization, "Does the USDA want to be regulated by the FDA? No. And vice versa as well. Right now there's just a lot of political knee-jerk reactions going on. If you speak with industry people, the official response [to the proposal] is negative. But privately, among most people I talk to . . . they would love a common central authority--they're just not prepared to come out and say it."
The NAS call for an expanded emphasis on the use of science, on the other hand, was roundly applauded by regulators and industry alike. At the heart of this initiative are plans for increased use of risk assessments, and expanded use of Hazard Analysis Critical Control Point (HACCP) programs that plant managers can adopt to ensure their products are safe. HACCP programs, which were first introduced in the early 1960s, represent a systematic and scientific way for industry to identify hazards and prevent or control them in production [see EHP 106(10):A475-A478 (1998)]. Many companies have been using HACCP programs for years. The government has taken note of the ease with which HACCP can be adopted into regulation, and the FDA issued its first set of HACCP regulations--over the seafood industry--in 1995. Unfortunately, inspections by the FDA indicate that HACCP compliance by the seafood industry is distressingly low. According to Caroline Smith DeWaal, director for food safety at the Center for Science in the Public Interest in Washington, DC, only 30% of plants inspected in 1998 were found to be compliant, although in public meetings the FDA has indicated its goal to increase the compliance record to 50% in 1999.
Both the USDA and the FDA are looking for ways to expand the use of HACCP regulatory programs. The FDA, for example, is currently reviewing comments on proposed HACCP regulations for unpasteurized juice, and has recently initiated a pilot program to see how HACCP programs might be applied in retail settings. According to Catherine Woteki, the undersecretary for food safety at the USDA, the department will have even the smallest meat and poultry plants under some measure of HAACP regulations by the year 2000. "We're part of the way there," she says. "In January 1998, all plants with 500 or more employees came under HACCP regulations. In January 1999, we'll implement HACCP in plants with fewer than 500 employees, and the remainder will be addressed the following year."
The Battle over Technology
Microbial threats notwithstanding, the public is in a heated debate over the technologies that are changing food. Perhaps the greatest concerns center on irradiation, the use of hormones in milk production, and genetic engineering, all of which have been sanctioned by the government as safe. But popular skepticism over these technologies abounds, and none has yet received wholehearted approval from the public. For example, Food and Water, a nonprofit advocacy organization based in Walden, Vermont, is unwavering in its criticism of corporate agribusiness for, as it claims, imposing high-tech foods on consumers for profit without sufficient regard for public health. On the other end of the spectrum, Bill Grierson, a professor emeritus at the University of Florida Citrus Research and Educational Center in Gainesville, writes in the March 1997 issue of Priorities that "fearmongering [over food technology] has become a boom industry for alarmists and a popularity prop for politicians."
Irradiation, which is approved for use in wheat and wheat flour, potatoes, spices, fruits, vegetables, poultry, and red meat, has found limited use since the late 1940s. It is often used in hospitals for foods consumed by patients who need the cleanest of foods--for example, those undergoing bone marrow transplants. The National Aeronautics and Space Administration has also used irradiation to treat foods for astronauts in space. The technique essentially pasteurizes food with short-wavelength gamma rays that pass through it much like ultraviolet light, or microwaves [see EHP 106(3):A129-A130 (1998)]. Gamma radiation doesn't emit neutrons, so foods aren't made radioactive by the procedure. Furthermore, irradiation kills bacteria without raising food temperature, so unlike with pasteurization, there is minimal loss of nutrients. The process has undergone more than 40 years of scientific testing before approval. In so doing, it has accumulated an impressive list of sponsors, including the American Medical Association, the United Nations Food and Agriculture Organization, and the World Health Organization, among others.
Despite the benefits, irradiation has not been widely adopted, although a number of pilot studies have indicated that, when informed of the benefits, the public will purchase irradiated foods. Some consumers remain concerned because irradiation causes the production of radiolytic compounds (free radicals), thought by many to be associated with a number of diseases, including cancer. Yet these same compounds are produced during cooking, according to a position paper published by the American Dietetic Association. Furthermore, according to Rosetta Newsome, senior food scientist with the Chicago, Illinois-based Institute of Food Technologists, extensive toxicological testing has produced no evidence that any of these radiolytic compounds pose a health hazard. The NAS has described irradiation as a safe and effective means of reducing foodborne pathogens, and has criticized the FDA and the USDA as slow to accept the technology. However, according to Thomas Billy, administrator of the FSIS, a plan for expanding the use of irradiation in red meat is being put into place in that service. "We are providing a framework by which irradiation can be used," he says. "It comes down to whether or not industry will accept the technology."
A more widely used practice is the use of recombinant bovine growth hormone (rBGH) to boost milk production in dairy cows. Developed by Monsanto under the trade name Posilac and approved for commercial use by the FDA in 1993, rBGH is a genetically engineered molecule identical to a protein secreted by the bovine pituitary gland. Estimates of the number of cows actually treated with rBGH in the United States are uncertain, although Monsanto puts the figure at close to 30%. During the approval process of rBGH, the FDA relied largely on an unpublished Monsanto study showing that no gastrointestinal absorption of the hormone occurred among rats treated for 90 days. Based on these results, Monsanto concluded that there would be no danger to humans consuming milk from cows given rBGH and that no further investigations of the hormone's effects in humans or animals were necessary, a position that was echoed by the FDA. But a review of the study by Health Canada found that absorption may have occurred in as many as 30% of the animals tested. Furthermore, some of the male rats in the high-dose group developed thyroid cysts and prostate problems. The discovery of these discrepancies led to sharp public criticism of the FDA in December 1998, and a demand from Vermont senators James Jeffords (R) and Patrick Leahy (D) that the agency investigate whether it had correctly appraised studies of the hormone's safety. In January 1999, Health Canada decided not to approve rBGH following an eight-year period of review, citing additional evidence from its veterinary experts that the hormone increases risk in dairy cows of mastitis by up to 25%, of infertility by 18%, and of lameness by up to 50%.
Michael Hansen, a research associate at the Washington, DC-based Consumers Union, says that milk from hormonally treated cows also contains significantly elevated levels of IGF-1, a naturally occurring hormone that is thought to be involved in the mediation of breast and prostate cancer. Whether or not elevated concentrations of IGF-1 in milk may contribute to cancer in humans is unknown. But Hansen adds that part of the reason for this data gap dates back to the FDA's initial decision to not carry out a complete battery of animal tests for carcinogenic, teratogenic, and reproductive effects of rBGH.
Both Monsanto and the FDA have vigorously defended rBGH, insisting that milk from treated cows has the same nutritional value and composition as milk from untreated cows. At this stage, the FDA is standing by its approval, and has no plans to halt production and use of the supplement. "The agency has concluded that absorption of rBGH is not biologically meaningful," says Lawrence Bachorik, the FDA's deputy associate commissioner for public affairs. Even so, Bachorik says that the FDA is always monitoring products, and will look carefully into any petitions resulting from Jeffords and Leahy's efforts.
Genetically engineered foods are also the subject of considerable public debate, particularly in Europe, where sales of many of these products are either banned or highly regulated. With the rapid expansion of this technology, foods are now being engineered to exhibit a host of traits including adaptability to harsh growing environments, herbicide tolerance, enhanced nutritional content, and increased crop yields. Perhaps the most controversial of the genetically engineered crops are those that have been bred to express pesticidal substances, an attribute that proponents say could help to significantly reduce the use of chemical pesticides in agriculture [see EHP 106(9):A432-A437 (1998)]. The only such crops approved thus far contain an endotoxin produced by the microbe Bacillus thuringiensis (Bt), which is toxic only to insects. Recently, the EPA finalized a proposed rule to regulate the substances produced by these plants as pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act. This move was heavily criticized by a consortium of 11 separate scientific societies who claim emphatically that genetically engineered plants, including those made with Bt, are no more dangerous than conventionally bred plants, and that it is scientifically indefensible to regulate plants as pesticides. But in regulating these substances, the EPA has countered that it is merely attempting to protect consumers from the potentially toxic effects of unknown "novel" proteins that may prove to be allergenic or have other unforeseen implications for human and ecological health.
Along with irradiated and genetically engineered foods, the use of soils treated with sewage sludge (also called biosolids) is a growing agricultural practice that proponents say provides an effective and environmentally friendly way to dispose of wastes while simultaneously improving soil quality. Biosolids not only improve soil structure and water holding capacity, they also feed essential soil microorganisms, says Robert Brobst, biosolids program coordinator for the EPA's Region 8. Furthermore, he adds, biosolids are preferable to chemical fertilizers because they feed both the soil and the plant. But these reassurances do little to allay the fears of a somewhat skeptical public, many of whom remain wary of odors and the presence of heavy metals, toxic organic compounds, or pathogens.
These fears are largely unsubstantiated by science, however. According to the EPA, the threat of both microbial and chemical pollutants can be significantly reduced by using proper land management practices. The National Research Council (NRC) agrees with this position, and has stated that, "while no disposal or reuse option can guarantee complete safety, the use of biosolids in the production of crops for human consumption, when practiced in accordance with federal guidelines and regulations, presents negligible risk to the consumer, to crop production, or to the environment." It is important to note, however, that the microbial safety of biosolid-treated crop soils was endorsed by the NRC largely because no outbreaks had ever been linked to sludge in the past.
Back to the Land
The fear of the unknown effects of these technologies has driven some consumers to seek out organically grown foods, for which they are willing to pay a premium. But whether or not organic foods actually pose a healthier alternative is not entirely certain.
Organic farmers who hope to sell their products are held to strict state guidelines that govern their production. The use of chemical pesticides and fungicides is prohibited, as is the use of synthetic fertilizers, which have recently come under scrutiny for their potential contamination with heavy metals [see "Fertilizing or Contaminating?" p. A136, this issue]. The USDA is also planning to issue national guidelines under its National Organics Program, which is currently still under review. [see "Organic: What's in a Name?" p. A150, this issue].
Not just simple groceries. Food safety issues are becoming more complex with the development of new and controversial technologies including irradiation, genetic engineering, growth hormones, and the use of biosolids and industrial waste-derived fertilizers.
The risk of microbial contamination of organic foods is not necessarily less than that associated with conventionally grown foods, however. Linda Harris, an extension specialist in microbial food safety at the University of California at Davis, says that microbial contamination could occur just as easily on an organic farm as on a conventional one. "If an organic farmer is applying manure incorrectly, definitely you could have an increased risk from a microbial perspective. Conventional farmers applying manure run the same risk," she says.
But because organic farmers don't use pesticides and other synthetic chemicals on their crops, the risks from these substances is reduced--although the net benefit of this reduction to one's health is a matter of great debate. Says Miller, "Problems with chemicals in food are low compared to microbiologicals. The biggest problem is improper use of chemicals. Properly used, chemical risks are relatively minor." Many agency and industry stakeholders contend that EPA pesticide tolerances are set with a large enough margin of safety that even fairly substantial exceedences are unlikely to cause any adverse health risks.
On the other hand, a growing difference of opinion holds that some segments of society, particularly children, may be at elevated risk for typical dietary exposures to pesticides. This is especially true if those exposures are to various pesticides with a common mechanism of toxicity, such as the now highly controversial organophosphate insecticides. Organophosphates, which act by inhibiting acetylcholinesterase in the nervous system, are associated with a wide spectrum of toxic effects that include nausea, blurred vision, irregular heartbeat, and possibly cancer. Children are thought to be at higher risk than adults primarily for two reasons. First, they eat many more high-risk foods such as fresh fruits and vegetables, which tend to have more pesticides applied during cultivation. A typical one-year-old child drinks 21 times more apple juice and 11 times more grape juice, and eats 2-7 times more grapes, bananas, pears, carrots, and broccoli than the average adult, according to Edward Groth, director of technical policy and public service at the Consumers Union. Second, the rapid growth and development of children make them physiologically more sensitive to pesticide toxicity. Recent evidence suggests that fetal and neonatal animals may be especially sensitive to the toxic effects of organophosphates, and that infant exposures to pesticides during critical periods of central nervous system development may lead to long-lasting effects on brain function and behavior.
In January 1998, the Environmental Working Group (EWG), a Washington, DC-based nonprofit organization, released a controversial report entitled Overexposed: Organophosphate Insecticides in Children's Food, in which they concluded that 1 million children a day are being exposed to "unsafe levels of toxic pesticides in fruit, vegetables, and baby food." The EWG based its conclusions on the results of a risk assessment that estimated exposures to children using pesticide residue data from three separate sources: the USDA Pesticide Data Program, the FDA Pesticide Surveillance and Monitoring Program, and the FDA Total Diet Study. These programs all monitor chemical residues in commercially bought foods. Food- and age-specific consumption rates for children under five years old were obtained from the USDA Continuing Survey of Food Intakes by Individuals. The analysis normalized all organophosphate exposures to chlorpyrifos (the most widely used and best toxicologically characterized of all the organophosphate insecticides) by applying a toxic equivalency scheme similar to that used by the NRC in its landmark 1993 report, Pesticides in the Diets of Infants and Children. This approach--which assigns each pesticide a toxicity value relative to that of chlorpyrifos--is consistent with the concept of the "risk cup" developed under the 1996 Food Quality Protection Act. The risk cup quantifies all routes of exposure to multiple chemicals with a common mechanism of toxicity, and adds them up to arrive at a more representative estimate of the daily dose.
According to the EWG, the foods posing the most risk to children are peaches, apples, pears, and grapes, all of which tend to have higher residue levels than other foods listed in the USDA and FDA databases. The analysis also suggested that aggregate exposures to pesticides in prepared baby foods might exceed the reference doses set by the EPA for safe exposures, leading the EWG to demand that the EPA prohibit the use of organophosphate compounds in foods destined for infant diets. Over 90% of the risk was found to derive from just five pesticides: methyl parathion, dimethoate, chlorpyrifos, pirimiphos methyl, and azinphos methyl. Organophosphate residues on these products were, for the most part, below EPA tolerances, and were therefore acceptable under FDA regulations.
Carl Winter, an extension food toxicologist and director of the FoodSafe Program at the University of California at Davis, is highly skeptical of the EWG's assessment. "It's easy to create risks on paper. Whether they exist in the real world is a different story," he says. He explains, "Pesticide risk assessors generally take into account a 100-fold safety factor when assessing risks, which assumes that humans are 10 times more sensitive than the most sensitive laboratory animals tested, and that some humans are 10 times more sensitive than the average person. These conservative estimates provide us with a very large margin of safety. For any noticeable effects to be observed, animals generally need to be exposed to 10,000 times our daily dose." Currently, the EPA is exploring whether or not to apply an additional 10-fold safety factor to some pesticide tolerances that are deemed to have been set with insufficient consideration of children's health. This measure, dictated by the Food Quality Protection Act, has caused tremendous upheaval in industry.
But Groth says that of the 1 million children described in the EWG's report, as many as 40,000-50,000 may ingest pesticides at levels 10 times higher than EPA reference doses. Says Groth, "You can make a sound argument that these exposures may result in some damage. Can you prove this? No. But the EPA's social contract with the public holds that exposures above the reference dose are, by definition, not safe."
Nonetheless, says Steven Johnson, deputy director of the EPA's Office of Pesticide Programs, the results of risk assessments are dependent on the numerical toxicity values and exposure assumptions used, and the selection of these parameters can be biased. Furthermore, he adds, most of the fruits and vegetables monitored by the FDA and the USDA contain no pesticide residues whatsoever. "Right now, we're not aware of any imminent hazards to children from pesticides in food, and if we were, we'd take action," he says. The EPA is now conducting risk assessments on the most toxic of the organophosphate and carbamate insecticides, and will be evaluating cumulative exposures to these chemicals during the summer of 1999. "If risks are found to be unacceptable, then we'll propose some level of mitigation," says Johnson. "These measures could range from changes in labeling, to restricting uses, all the way to removing the chemical [from commerce]."
Few environmental health threats strike a chord in the public as deeply as contaminated foods. Foodborne hazards bring the specter of environmental disease into our homes and kitchens, to the meals we feed to our families and children. In spite of its flaws, the U.S. food safety system is still one of the best in the world. Current reforms and research programs at the agencies responsible for food safety are working to ensure that this system continues to be updated and improved. Even so, foods continue to pose a certain degree of risk. While federal and state environmental agencies continue their attempts to reduce environmental contaminants in water, soil, and air, naturally occurring foodborne mutagens are a daily component of the human diet. "We have to recognize that it is virtually impossible to have risk-free food," says Doyle, "but we must continue to work to make the risk as low as possible."
Foodborne Pathogens in the United States
Campylobacter jejuni
Leading cause of bacterial diarrheal illness in the United States
Infective dose: 400-500 bacteria or more
Incidence: Estimated 2-4 million cases per year
Sources: Raw and undercooked poultry and beef, raw milk, and untreated water
Clostridium botulinum
Produces a toxin that causes a severe form of food poisoning with muscle paralysis
Infective dose: A few nanograms of toxin can cause illness
Incidence: Low (10-30 outbreaks per year) but mortality is high if not treated immediately
Sources: Inadequately processed home-canned foods and herbal oils, sausages, meat products, and seafood
Escherichia coli O157:H7
Produces a toxin that causes severe damage to the lining of the intestine, resulting in diarrhea and potential loss of kidney function and death
Infective dose: Unknown but estimated at 10 organisms
Incidence: Increased by over 500 cases between 1994 and 1995 with over 2,000 cases in 1995
Sources: Meat, especially undercooked or raw hamburger, and raw milk
Hepatitis A
Causes illness characterized by sudden fever, malaise, abdominal cramps, anorexia, and jaundice
Infective dose: 10-100 virus particles
Incidence: 22,700 cases per year but only an estimated 7% are foodborne or waterborne
Sources: Food contaminated by human feces, most often in food processing plants and restaurants
Listeria monocytogenes
Causes listeriosis, characterized by septicemia, meningitis, encephalitis, and intrauterine and cervical infections in pregnant woman that may result in spontaneous abortion and stillbirths
Infective dose: Varies, but may be as low as 1,000 organisms
Incidence: 1,850 cases of listeriosis and 425 deaths per year
Sources: Raw milk, soft cheeses, ice cream, raw vegetables, raw undercooked meat, poultry, and seafood
Salmonella
Causes salmonellosis, characterized by nausea, vomiting, abdominal cramps, fever, and headache
Infective dose: As few as 15-20 cells
Incidence: 2-4 million cases of salmonellosis per year; second most common cause of foodborne illness
Sources: Raw and undercooked eggs, poultry, and meat, dairy products, seafood, fruits, and vegetables
Staphylococcus aureus
Produces an enterotoxin that causes nausea, vomiting, abdominal cramps, and prostration
Infective dose: Less than 1.0 microgram
Incidence: Estimated 1,200 cases per year although true incidence is unknown
Sources: Cooked foods high in protein (e.g., cooked ham, tuna, chicken, macaroni, and potato salads, cream-filled bakery products, dairy products)
Shigella
Causes shigellosis, characterized by diarrheal illnesses, fever, vomiting, and tenesmus
Infective dose: As few as 10 cells
Incidence: An estimated 300,000 cases
Sources: Potato, tuna, macaroni, and shrimp salads, milk and dairy products, poultry, raw vegetables
Vibrio vulnificus
Causes wound infections, gastroenteritis, and primary septicemia
Infective dose: Unknown for healthy persons but can cause septicemia in predisposed persons with doses of less than 100 organisms
Incidence: Rare but underreported. The CDC received 300 reports between 1988 and 1995
Sources: Raw or undercooked seafood, including oysters, crabs, and clams
Source: CFSAN. Foodborne pathogenic microorganisms and natural toxins handbook. Washington, DC:U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 1992.
Photo credit: Partnership for Food Safety Education, http://www.fightbac.org/.
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Charles W. Schmidt
Last Updated: March 1 , 1999