“Food contamination” is an expression that means many things to many different groups of people. Whether it refers to the undesired presence of microorganisms, heavy metals, pesticides, or any other forms of “natural” or “man-made” compounds, one could simply define a food contaminant as a chemical or biological agent present in food that may be detrimental to the health of consumers exposed to them.
Many chemical food contaminants (pesticides, for example) are regulated in the U.S., with very clear limits that must be monitored and followed. American regulatory agencies, such as the U.S. FDA, the USDA, and the U.S. EPA have established limits of exposure for known contaminants to safeguard consumers. These limits are set at levels that will not put the health of consumers at an undue risk.
The issue becomes complex when the link between exposure and any potential impact on public health is not clearly established, and hence no limits are set even when such contaminants can be found in food. Hexabromocyclododecane, popularly known as a HBCD, for instance, is a flame retardant commonly used in many non-food items (such as thermal insulation and electrical equipment), which is not regulated in food, but can be found in numerous food items, possibly from leakage into water. It is considered a “persistent chemical,” which means it accumulates over time in the fatty tissue of animals that have been exposed (including humans). The consumption of low levels of HBCD is not known to cause any hazard for humans. However, it has been found to be highly toxic to aquatic organisms and there is little evidence on the effects of its accumulation in the human body when consumed in food. Therefore, it is complicated to establish levels of “safe” exposure.
Traditional classes of contaminants in food ingredients are naturally-occurring contaminants (e.g. heavy metals from soil) and man-made materials (e.g. pesticides). Where there is a reasonable expectation of the presence of contaminants in a specific food item, regulatory agencies have established appropriate limits, but not all contaminants can possibly be regulated in all food matrices. Arsenic is a commonly used illustration. As many heavy metals, arsenic exists in organic and inorganic forms, with the inorganic form being a higher health risk to humans than the organic form, and the U.S. FDA monitors the level of arsenic in different types of foods accordingly. One of the foods where arsenic levels are monitored is rice, where the plant takes up diverse forms of this metalloid element from the soil and the water where it grows, making arsenic levels in rice and rice products expectedly higher. On the other hand, arsenic in apple juice is not typically found in quantities that would cause any public health concerns, and it was not until samples of apple and grape juice showed limits above what the FDA considers safe, that attention was dedicated to this food product in particular. Today, arsenic levels in foods are monitored on a case-by-case basis, with special attention to foods that are consumed by children.
In general, contaminants are regulated based on the highest intake observed, taking into consideration the whole diet of individuals of a certain age and living in certain regions. Food toxicologists are much more concerned about the total exposure of consumers to a certain contaminant and, thus, always consider the whole diet of populations, including water consumption. The limits are usually set based on reports of food consumption that reflect the eating habits of certain populations and the exposure risk for each food group. Some food groups may contain a higher level of contaminants but are much less consumed than other groups with lower levels of that contaminant with high consumption rates. It is a very complex task to establish limits for contaminants in foods, when it comes to heavy metals and pesticides, for example.
The work of food toxicologists can become even more complicated when they have to consider possible interactions among the various contaminants. Luckily a large body of data is available to help understand how the body metabolizes the various contaminants, so that safe limits can be set. However, it is also fair to say, that scientists are still learning to fully understand all the effects on how the body reacts to the simultaneous presence of a mixture of contaminants.
It should be noted that testing of suspect crops is extremely costly, thus stressing the need and value of preventative measures.
One Large Family of ‘Bad Guys’
It is reasonable to assume that there is no such thing as zero risk for food contaminants. Contaminants are a part of the food supply and when controlled and monitored properly, they do not represent an undue risk for public health. However, dioxins are contaminants that escape the “minimum limit” notion that can be applied to other food contaminants.
Dioxins are considered one of the most, if not the most toxic man-made substances. They may not necessarily cause acute health problems, but are harmful to health at very low levels. Dioxins are persistent organic compounds that once created, are extremely hard to eliminate. They are mostly fat soluble, accumulating in the fatty tissue of animals, including meat and dairy. Once consumed, these compounds do not degrade easily and will accumulate in the human body. Accumulation of dioxins has been linked to a number of health problems.
There are no tolerance levels of dioxins established by the FDA, but the agency is working in conjunction with the European Union and the EPA and USDA to address the issue of dioxins and other persistent organic compounds (such as PCBs) in animal feed.
In 1997, “ball clay,” a mined clay product used as an anti-caking agent in animal feed was found to be the source of high concentrations of dioxins in chicken, eggs, and catfish. After the findings, the FDA’s Center for Veterinary Medicine worked with industry to test feed samples for other sources of dioxins in mined feed ingredients. Today, the risk of dioxin contamination from clay is minimal as it is very well understood how to avoid the use of clays containing larger amounts of dioxins. In 2008, USDA’s Food Safety and Inspection Services (FSIS) completed a survey of 510 domestic beef, pork, and poultry samples for dioxins. The results of the survey showed very low levels of no toxicological concern, with turkey and beef presenting the higher concentrations.
There is not much consumers can do once dioxins are present in the food supply chain, but consumers can and should contribute to the reduction of dioxins creation. While dioxins cannot be generated in the home environment (temperatures needed to create dioxins are extremely high), one of the ways dioxins are created is through incineration of waste. Recycling metal materials, in particular copper – which catalyzes dioxin formation and is present in many household items, such as batteries – is a way to contribute to the reduction of dioxins in the environment.
Not All Harmful Contaminants are Man-Made
These contaminants are byproducts of fungi (mold) that essentially can grow on all foods provided that enough moisture is present. Not all molds produce mycotoxins, but once produced, they can get into the food chain and are extremely hard to eliminate. Preventing mold growth through good agricultural practices pre- and post-harvest are the only effective measures to limit the amount of mycotoxins in food. It should be noted that testing of suspect crops is extremely costly, thus stressing the need and value of preventative measures.
One of the most common mycotoxins found in foods are aflatoxins, of which Aflatoxin B1, is the most toxic and a potent carcinogen. Aflatoxins contamination is prevalent in cotton, peanuts, spices, pistachios, and maize produced in tropical and subtropical regions, which could be conducive to molds. Other mycotoxins that make it into the food supply are ochratoxins (mostly found in beer and wine); citrinins (associated with yellow rice disease in Japan, acting as a nephrotoxin in all animal species tested); ergot alkaloids (found in contaminated flours and cereals, even though modern methods of grain cleaning have significantly reduced the risk); patulins (associated with moldy fruits and vegetables, and connected to immune system damage in animals); and fusarium toxins, of which trichothecenes are most strongly associated with toxic effects in animals and humans and can more commonly be found in wheat and maize grains.
A careful evaluation of what to test and the impact of such testing on public health are within a risk-based approach.
Addressing Food Contaminants
As a standard setting organization for which public health is the core of its mission, USP has typically set limits for contaminants in food ingredients contained in the Food Chemicals Codex (FCC), a source of quality standards for food ingredients that industry uses as a tool to establish food integrity in the U.S. and abroad.
USP desires to strengthen and increase the role of the FCC to help limit the exposure of the consumer to contaminants through food. One of the efforts USP is engaged in is promoting risk-based approaches to food contaminants. Contaminants testing have costs associated that ultimately trickle down to the consumer and a careful evaluation of what to test and the impact of such testing on public health are within a risk-based approach.
Reasonable sources of specific contaminants, testing resources for quantifying contaminants, and determining whether certain risks are acceptable are topics that should be addressed to help guide questions on how to better predict hazard exposure and how to prevent it.
USP is holding an open workshop entitled “Chemical Contaminants in Foods—Risk-Based Approaches to Protect Public Health” on November 20 to 21, 2014 at its headquarters in Rockville, Md., for experts, regulators, and industry to gather information and gauge the needs of stakeholders around the globe with the objective of setting or improving standards for contaminants in food. When a limit is known, compliance is easy to determine; however, many of the limits for food contaminants are yet to be established. When there are no limits for a contaminant, compliance becomes a more complex question and, therefore, more difficult to answer. It’s expected that some of the interactions in this workshop will result in actions and guidelines on what to do when there is no regulatory limit for a specific contaminant in a specific food.
Dr. Lipp is the senior director of food standards at USP. Reach him at [email protected]. Dr. Mejia is a senior scientific liaison for USP. Other USP staff contributors are Gabriel Giancaspro, PhD, and Claudia Costabile, MA.
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