At a time when both Congress and the Obama administration are calling for reforms to the nation's fractured food-safety system, it seems fair to ask: Can we trust what we eat and drink?
Five SPH experts weigh in with answers:
With fish, as with so many public health issues, it’s a matter of balancing the benefits and the risks. Fish are one of greatest sources of protein and nutrition available, but they’re also one of the major routes by which we’re exposed to mercury.
Nearly seven thousand tons of mercury are released into the environment every year, most of it from coal-fired power plants, and those levels are increasing. Once mercury is released into the air, it falls with the rain into bodies of water where it accumulates in fish. Nearly 40 percent of the lakes and rivers in the United States have a fish-consumption advisory because of mercury pollution, including almost every single river and lake in Michigan.
Fetal exposure to mercury through maternal consumption of contaminated fish can cause mental retardation and brain damage, cerebral palsy, and other impairments, while exposure during early childhood can reduce IQ and result in learning disabilities and attention deficit disorders. Even small levels of mercury can cause problems.
But we only really need to be concerned about those species that live longer, are predatory, and eat at a high level of the food chain. The Environmental Protection Agency recommends we restrict our intake of these four fish: tilefish, swordfish, shark, and king mackerel. Women of childbearing age should also limit their exposure to albacore (“white”) tuna, which contains more mercury than canned light tuna.
Hundreds of other fish species, including salmon, trout, sardines, and many varieties of shellfish, are extremely good for your health. There is ample evidence that fish consumption results in higher infant health and more refined neurological systems. The omega-3 fatty acids found in fish—which few other food sources provide—are important for brain development. Several recent large-scale assessments have concluded that the potential benefits of fish consumption outweigh the risks associated with mercury. So yes, we need to avoid certain kinds of fish, and women of childbearing age and pregnant women should be especially careful, but targeted fish consumption should be promoted. An ecological toxicologist, Nil Basu studies the paths by which mercury moves through the environment. Basu is interested in those species of fish that build up high levels of mercury, and in wildlife, such as bald eagles and polar bears, that consume high levels of fish. He is also working to understand how humans metabolize and rid themselves of mercury. “My goal,” he says, “is to determine why we differ in our abilities to process mercury, and to use this knowledge to better inform risk assessment and to better understand the true risks and benefits of fish consumption.” Learn more: https://www.epa.gov/fish-tech
In the U.S., the risk of contaminated drinking water is low, but it exists. A recent surveillance study by the CDC shows that disease outbreaks related to drinking water sicken thousands of Americans yearly.
Although our drinking water-treatment systems do a pretty good job of removing microorganisms, water-borne pathogens can develop resistance to the disinfectants used in our treatment systems, and water pipes can develop biofilms that foster the regrowth of microorganisms. Because the EPA only regulates the quality of the water in pipes that run from treatment plants to individual buildings—and not the quality of water in pipes that run inside individual buildings—consumers need to be vigilant. If you notice that the color or taste of the water in your home has changed, you should contact your local water authority, because the pipes may have deteriorated. The water authority can test your water in a certified lab.
And it’s a bad idea to ingest hot tap water. Chemicals and metals are more likely to leach from pipes into hot water, and hot water promotes the growth of pathogens such as Legionella and Mycobacterium. Water-borne pathogens can also enter our food chain through irrigation and food processing. Scientists are working to develop new methods for the fast and sensitive detection of water-borne pathogens, and engineers are developing new methods of water-treatment technology that can remove more of these pathogens from our drinking water and limit their regrowth.
A growing threat is the presence of pharmaceuticals and personal-care products in our water. At their current levels these are mostly of concern for wildlife, but they may pose a slight risk for humans. We can all contribute to the safety of our drinking water by properly disposing of prescription drugs. The federal government has posted guidelines for the safe disposal of pharmaceuticals at https://www.whitehouse.gov/ondcp.
How worried should we be about the safety of our water in the U.S.? I would say that healthy adults have little reason for concern. But immuno-compromised people and those with other serious health issues should be careful and may want to get a physician’s advice. Chuanwu Xi, an assistant professor of environmental health sciences, studies how biofilms in drinking-water systems contribute to the survival of water-borne pathogens and the spread of antibiotic resistance in the urban water cycle. Biofilms attach themselves to the surface of water pipes, he says, and protect microorganisms in the water system “by providing a kind of shield that lets pathogens survive.” Learn more: www.cdc.gov/healthywater/ or http://www.ns.umich.edu/htdocs/releases/story.php?id=7144
When it comes to producing and consuming goods, we’re all connected. Take T-shirts, for example. They may be consumed in the U.S. or Europe, but they’re produced in countries like India or China, where emissions standards are often less rigorous.
People in those countries breathe in the persistent organic pollutants, such as dioxins or heavy metals, that are emitted into the air from the T-shirt factory. Some of these pollutants also fall into the soil and are absorbed by plants that then enter the food chain, either as basic agricultural products, such as wheat, or through animals, or through processed foods, such as bread. And when those foods products are exported, the pollutant goes with it.
The problem exists within the U.S., as well. Pollutants can be deposited in crops that are then transported to the rest of the country. If there is an emission in California or Florida, we’ll get it through our food, not the air.
Some of the most persistent and dangerous contaminants—lead, cadmium, chromium, PCBs, dioxin—are bioconcentrated in the food chain. If you look at the intake fraction—meaning the fraction of an emission that is taken in by the human population—you’ll see that the highest fraction transferred to populations comes from the food chain. This is as significant a health issue as the global transfer of pollutants through the air. We know our habits are con-tributing to the spread of contaminants, so it’s important to quantify the impact we’re having. It’s a matter of environmental justice as well as health. Olivier Jolliet’s research group has created an environmental model that shows how persistent organic pollutants move through the world. By coupling this model with an economic model showing where food is produced and how it’s consumed, they’ve been able to quantify the impact the global food chain is having on the spread of pollutant matter. Jolliet is an associate professor in the Department of Environmental Health Sciences and an associate director of the UM Risk Science Center.
Bisphenol A, or BPA, is a high-volume industrial chemical that can be found in a variety of food-container applications, including polycarbonate plastics used as storage or beverage containers (including some baby bottles), epoxy resins used in the linings of some canned foods, and many plastic consumer products, including toys. A number of recent animal and in vitro studies suggest that at low doses, BPA disrupts endocrine function. Some animal studies show serious effects, including reproductive and fertility problems, reproductive-related cancers (breast, testicular, prostate), inhibited brain development, and metabolic disorders that could lead to diabetes or obesity. Very few human studies of BPA have been conducted, and more are needed.
Evidence of exposure to BPA has been measured in a majority of the U.S. population. (Few BPA exposure studies have been conducted in the developing world.) A recent survey by the CDC detected BPA in 93 percent of the urine samples from a representative sample of the population that included 2,500 participants six years old and older.
BPA is metabolized quickly by the body and doesn’t bioaccumulate like dioxins and other substances. But that doesn’t mean it’s harmless, especially since people are continuously exposed to BPA through multiple sources and pathways. Scientists are especially concerned about the health effects that BPA exposures may have on fetuses and infants, because these populations are more developmentally susceptible and may experience especially high exposure levels. BPA can pass from mother to fetus in utero and through breast milk, and it can leach into milk or formula through polycarbonate baby bottles. In addition, heating products that contain BPA can accelerate its ability to leach into food and liquids.
While food and drink are thought to be the primary route by which BPA enters humans,
preliminary studies also suggest that environmental pathways, such as house dust,
may be important. We need further human data if we are to fully understand the health
risks associated with this compound. John Meeker, an assistant professor of environmental health sciences, is involved in ongoing
studies of the human-health effects of BPA. He also studies phthalates and brominated
flame retardants, chemical compounds found in plastics and other consumer goods, which
can affect endocrine activity. Meeker is espe-cially interested in the impact of these
compounds on the human reproductive system.
Learn more: http://www.journals.elsevier.com/reproductive-toxicology/; and Meeker’s contribution to a special issue of Philosophical Transactions of the Royal Society B on plastics and the environment. Last fall, SPH Professor and Associate Dean Martin Philbert chaired an FDA subcommittee on BPA.
In the past two years, the number of reported food-borne outbreaks at the national level has increased. The reason is twofold: the growing centralization of food production in the U.S. and the globalization of our food supply. Also, public health’s capacity for detecting outbreaks has been greatly enhanced with the advent of highly sophisticated electronic surveillance systems for the detection of communicable diseases.
Food-borne pathogens are ubiquitous—a study a few years ago showed that roughly one-third of all poultry in the U.S. was infected with salmonella, for example. And the massive use of antibiotics to enhance growth in food animals has likely contributed to the development of new antibiotic-resistant pathogens.
The transmission of pathogens can occur at home (through the consumption of uncooked meat or eggs), in restaurants (from infected food handlers), or person to person. You see it in aggregate settings, especially daycare centers, where kids are in diapers, and fecal-oral contamination can occur. Our food supply is also vulnerable to bioterrorism and the intentional introduction of pathogens.
Those at greatest risk of significant morbidity from food-borne pathogens are the very young, the very old, and the immunocompromised. Certain food-borne pathogens, such as listeria, are associated with spontaneous abortion or miscarriage, so pregnant women are advised to avoid non-pasteurized products that can harbor these pathogens.
Once there’s an outbreak of a food-borne illness, public health officials work with the U.S. Department of Agriculture to try to quickly identify the sources, or suspected sources, of contamination, issue warnings, and hopefully interrupt the transmission of disease. But it’s equally important that consumers take measures to reduce their risk. Cook meat thoroughly and wash your hands. Just doing those two things would greatly reduce the incidence of food-borne pathogens nationally. That’s got to be a big part of the public health prevention message. While serving as the State of Michigan Epidemiologist from 1997 to 2005, Matthew Boulton oversaw the response to dozens of statewide and national food-borne outbreaks and was instrumental in developing a statewide electronic disease-surveillance system. He has subsequently participated in several research projects on salmonella, many of them focused on Michigan. Boulton is an associate professor of epidemiology and associate dean for practice at SPH.