Chemical Contaminants: Preparing for the Unexpected
By Rebeca López-García, Ph.D.
The world has certainly changed in the last few decades. It is now possible to source products and ingredients from around the globe without even thinking about it. However, with great change come complex problems. Now as never before, we must be aware of potential contamination incidents and sources of contamination that may affect the safety and quality of our products.
To further complicate matters, technology has continued to evolve, and we now have new materials, extraction processes, sanitizing compounds and alternative production methods that may also affect our products. Recently, we have heard about melamine in milk, oil spills in the Gulf of Mexico, a nuclear meltdown in Japan, plasticizers migrating from packaging materials and many other incidents that have put chemical contamination in the spotlight. Managing the risks posed by chemical hazards poses unique challenges that must be addressed to avoid public health incidents, regulatory actions and recalls, and to identify the steps to take to shield your products and company from chemical contamination.
Is Contamination Expected or Unexpected?
Chemical contaminants take many forms. Some are commonly expected due to the nature of the commodity or processing method, while others, such as adulterants, initially may be completely unexpected, such as Sudan red dyes and melamine in milk. Unexpected adulterants pose a challenge even for regulatory agencies that need to first identify them, assess the risk and potential exposure and then quickly make proper management decisions that may be affected by their analytical abilities. All this must be done without forgetting that proper risk communication at all levels is essential to help resolve the crisis and maintain consumers’ trust. In the context of foods, chemical contaminants can be broadly defined as any chemical not intentionally added to food but present from many potential sources, such as the following:
1. Environmental Contaminants
Certain chemicals are manufactured for industrial use, so they are very stable and do not break down easily; if released into the environment, they can enter the food chain. Other compounds may occur naturally in the environment, but industrial activity may increase either their mobility or the amount available to circulate. Examples include heavy metals, persistent organic pollutants such as long-known dioxins and furans and PCBs or recently identified brominated flame retardants. Some of these compounds have been banned for years but, due to their stability, remain in the food chain. Others may have been recently introduced into the environment due to accidental spills. Such is the case of potential contamination of seafood from the 2010 BP oil spill in the Gulf of Mexico and the dispersants used for cleanup.
2. Food Processing-induced Contamination
Undesirable chemicals can be formed during the processing of certain foods. In some cases, these chemicals are the result of a food additive interacting with other compounds in the food matrix. Contaminants of this type include acrylamide, benzene, chloropropanols, ethyl carbamate, furan, heterocyclic aromatic hydrocarbons, nitrosamines, polycyclic aromatic hydrocarbons and semicarbazide.
Another source of contaminants may be the interactions of cleaning and sanitizing agents with other naturally occurring compounds. For example, the carcinogen bromate forms in water when naturally occurring bromide reacts with ozone used for disinfection; haloacetic acids form when chlorine disinfectants react with organic acids.
3. Presence of Natural Toxins
Natural toxins are chemicals produced by living organisms. The most common examples include mycotoxins, which are produced by mold contamination of certain commodities that include cereals, nuts, fruit and dried fruit, cocoa, spices, oilseeds and milk. Commonly known mycotoxins include aflatoxins, ochratoxin A, ergot alkaloids, fumonisins, patulin, tricothecenes and zearalenone. Other natural toxins include phycotoxins or toxins naturally occurring in fish and seafood, for example, domoic acid, ciguatera toxins and paralytic shellfish toxins. Finally, certain plants can produce compounds that are toxic to humans. Examples of plant toxins include glycoalkaloids and cyanide in bitter apricot kernels.
4. Accidental Contamination at a “Point Source”
This type of contamination may occur during the production, preparation and packaging of foods. Typically, this type of contamination occurs during the production of raw food commodities, in the way they are grown (fertilizers and pesticides used during agricultural production) or, in the case of animal products, how they are raised or produced (veterinary drugs such as antibiotics and hormones).
5. Intentional Contamination
This type of contamination is perhaps the most difficult to handle since adulteration is unexpected and difficult to anticipate. Adulterants may be used to sell lower-value products as the original product, mask products that are already past their prime or add a cheaper compound to a food or ingredient and sell it for a higher value. Recent examples include the use of Sudan red in spices, melamine in milk and the use of inedible Japanese star anise (which contains sikimitoxin) instead of the closely related edible and innocuous Chinese star anise.
So how can a company protect itself from this wide array of chemicals?
First, it is important to follow the usual due diligence and work with trustworthy suppliers. The usual prevention programs are essential since, in most cases, chemical contaminants cannot be removed during processing. Thus, avoiding them at the source is essential to ensure the safety of processed products. Regardless, regulatory bodies have established maximum levels for many contaminants, so it is important to know these levels and generate proper specifications for raw materials. In cases where there is no regulatory reference, consider the nature and source of the material to ensure that you have as much information as possible. If analysis is needed, then several considerations must be taken into account.
Importance of Sampling and Sample Preparation
Sampling and sample preparation are crucial operations in the analytical determination of chemical contaminants. Proper sampling will give reliable analytical results representative of the whole lot. When the food matrix or the potential contaminants are homogeneously distributed (e.g., antibiotics in milk), sampling is much easier, and only proper sampling and handling techniques are required. However, if the contaminant is not homogeneously distributed (e.g., aflatoxin in grains or peanuts), then it is important to follow sampling procedures that will yield the most representative results possible. Usually, when sampling is challenging, regulatory bodies provide guidance on proper methods. If a third-party laboratory is hired, it will usually provide you with the best sampling protocol and procedures to submit samples.
When unknown chemical contamination is suspected, then laboratories usually ask for a precise description of the taste and smell (if available) of the suspected food or beverage to provide useful clues to the identity of the contaminant. Likewise, if illness or injury has already occurred, then a full description of the onset time, symptoms and any medical diagnosis can also provide important information to determine the appropriate analytical procedure.
If investigation of the nature of the contaminant is needed, then the analytical laboratory will also need control samples to run many tests. A control sample is a food that is identical or close to identical to the suspect food and very likely to be free of contamination. Controls are essential due to the chemical complexity of foods and beverages. Test results will be compared with the control to determine differences and provide evidence that any unusual findings in the suspect sample are not due to the analyst’s misinterpretation or instrumental error but are, in fact, true findings.
Once samples are obtained, then selection of an extraction and analytical method will help you get proper information. If the compound is a known food contaminant, then an analytical method will likely be available and can be used to analyze the suspect sample. If this is the case, it is important to note whether the method is validated for the particular food matrix in question and whether the limit of detection will provide information that is appropriate to make an informed decision.
When contaminants are unexpected, then the very first step will likely be to develop a new method. This involves a thorough literature search of the “unknown” compound to narrow down a method suitable for extracting the contaminant from the particular food matrix and quantifying it with sufficient certainty to make appropriate decisions.
Sample extraction will also play a vital role in the quantification of the contaminant since it is important to obtain the compound from the matrix to quantify it. If the extraction is flawed, the potential for false-negative results increases. Extraction techniques include liquid-solid extraction and liquid-liquid extraction; the selection of the method will depend on the type of product and the nature of the suspected contaminant. If immunoaffinity columns are used, it is essential to handle and store them properly since many systems require refrigerated storage of the columns to maintain their functionality.
Seeking Laboratory Assistance
In many cases, the internal laboratory will not have the analytical capabilities to look for an unknown, suspected contaminant. If the contamination is related to a single incident, the investment in analytical capacity probably is not worthwhile. In this case, it is important to find a laboratory that is willing to work with you and help you work through the sampling issues and identification of the unknown compound. When selecting a laboratory, the first question should be whether it has ever analyzed samples of the food and the contaminant in question. Obviously, if the laboratory is accredited for that particular analysis, then the process will be easier. ISO/IEC 17025 accreditation specifically addresses a laboratory’s ability to produce precise and accurate analytical results. Accreditation processes have specific criteria to determine not only the laboratory’s competence in a particular analysis but also the overall management and quality control processes that include the technical competency of personnel, validity and appropriateness of the methods, the traceability of measurements to national standards, the suitability, calibration and maintenance of equipment, the appropriateness of the testing environment and the adequacy of quality assurance and quality control procedures. An accredited laboratory will be able to help you identify and quantify the contaminant even without prior experience in analyzing the unknown compound.
If the contaminant is regulated and a maximum limit has been established, it is important to consider the regulatory requirements for testing. For products bound for the export market, laboratories that produce results with international recognition may be needed.
Currently available analytical techniques and instrumentation will be able to detect contaminants at very low levels. This is the so-called case of the shrinking zero, in which contaminants can be detected sometimes at even the parts-per-trillion level. All contamination incidents occur against a background of consumer outrage and demands for products with an “absolute absence of contamination.” We now know this may not be possible. Thus, it is important to keep a level head and consider the toxicological implications of the compound in question. Toxicological criteria will always take into account a safety margin large enough to ensure public health. Obviously, when uncertainty is involved, it is better to err on the more conservative side. However, some compounds have a level of toxicity at the parts-per-million range; if the compound is found at the parts-per-trillion range and the sampling, extraction and analytical procedures were appropriate, then the finding may not be toxicologically relevant and no further action will be required. In this case, risk communication will be essential to address consumers’ concerns and quell their outrage.
Prepare for the Unexpected!
Chemical contamination poses unique challenges and, judging from recent incidents, will keep food processors on their toes. However, in times of crisis, the most important reaction is to stay calm and design an analytical process with proper sampling, controls and instrumentation that will yield sufficient information to make proper risk management decisions. Obviously, in many cases, you will be unable to address it on your own, and you will need help from appropriate partners, such as accredited laboratories, regulatory agencies and industry associations. When developing a crisis management system, it is essential to identify these resources and include their contact information in the manual prior to the crisis. In addition, you can identify proper sampling techniques for the raw materials handled in your facility as well as traceability issues for products that represent particular challenges, such as materials received and stored in bulk. Change-control procedures in your facility should include a risk assessment process of any new ingredients, sourcing and processing methods and new sanitizing compounds to help identify new potential sources of chemical contamination. Although there is no way to predict the source of the next incident, having this information will help you navigate the uncertain waters of chemical contamination.
Rebeca López-García, Ph.D., is the Principal at Logre International Food Science Consulting, based in Mexico City. Her work involves the implementation of food safety programs and international standards in multicultural environments, regulatory compliance for exporting companies, mycotoxin control programs, auditing and development of suppliers and creation of bilingual education programs and materials. She is actively involved in teaching workshops on Hazard Analysis and Critical Control Points, basic sanitation and food legislation to the food processing, retail and foodservice industries as well as at universities in several countries.