Douglas L. Park and Carolos E. Ayala
Food consumption plays two roles in human development: nutrition and disease prevention. Foods provide not only protein, fats, vitamins, minerals and other constituents essential for growth, but also components necessary for prevention of certain diseases. For proper growth and mental development, people must eat a balanced diet. Food is both abundant and generally recognized to be safe, but some human illnesses can be traced to foods. The causes of these illnesses may be natural constituents of foods, such as contaminating pathogenic bacteria, or chemicals in minute amounts that have been added for other purposes, such as pesticides for insect control before harvest or food additives for enhancing food quality and safety.
Illnesses associated with foods are rare. When they occur, however, the adverse effect on human health and the food supply availability can be significant. Studies conducted in research laboratories play an important role in identifying the sources of foodborne health risks and the development of procedures and products that reduce the magnitude and significance of foodborne hazards. These studies help provide the assurance of a safe, wholesome food supply. Industry, academia and public health agencies work hand-in-hand to reach this goal. Components of Foodborne Hazards
Foodborne hazards can be classified into pathogenic organisms, intrinsic components and chemicals. The primary categories of foodborne pathogenic organisms are bacteria, viruses and parasites. Problem pathogens that have been featured in the news in recent years include Escherichia coli (E. coli) O157:H7 in meat and apple juice, Salmonella in eggs and on vegetables, Cyclospora on fruit, Cryptosporidium in drinking water and hepatitis A virus in frozen strawberries. Numerous methods have been developed and are used to reduce risks posed by pathogenic microorganisms including pasteurization, cooking, addition of preservatives and proper storage conditions.
Intrinsic food components include nutritional factors and thousands of contaminant compounds naturally present in foods. The intrinsic component hazards in the food supply associated with nutritional factors can be either deficiencies or excesses. Pellagra, scurvy, goiter, rickets and beriberi are examples of the former, and toxicity from excessive fat-soluble vitamins and minerals illustrates the latter. On the other hand, natural contaminants include those occurring in foods of plant origin, such as the oxalates in spinach and the glycoalkaloids in potatoes. Eating a nutritious diet including mixed and varied components can minimize most of these problems.
Hazardous chemicals in foods include naturally occurring toxicants, agro-industrial contaminants and food additives. The naturally occurring toxicants pose the greatest risk, and food additives the least. Naturally occurring toxicants are chemicals from the natural environment that occur in foods and animal feeds, including mycotoxins and algal metabolites, aquatic biotoxins, phytoalexins, intrinsic components of plants, bacterial toxins, cyanobacterial toxins and food decomposition components. Food additives pose relatively little risk because of intensive testing required by public health agencies before approval for food or animal feed use. Food additive categories in the United States are classified as direct, indirect, generally recognized as safe (GRAS) substances, pesticide residues and animal drug residues. Major efforts are under way to identify the risks posed by these compounds, develop cost-effective measures to remove the risk and provide important information to consumers on the role they can play in promoting food safety. Risk Assessment
Risks associated with food hazards and chemical exposure, although not common, make the public more aware of foodborne hazards in their daily lives.
Once a specified hazard has been identified as causing a particular health effect, a risk assessment is conducted. The goal of the risk assessment is to estimate the risk to humans caused by the potential hazard. A risk assessment is conducted following three basic steps: hazard evaluation, human exposure evaluation and risk determination or estimation. Once these have been determined, a risk management strategy is developed to reduce the risk to the lowest practical level, while trying to maintain an adequate, wholesome food supply.
Using aflatoxin contamination in agricultural commodities as an example, the initial step collects the available information about the level and extent of the contamination as well as the toxicity potential. Since the aflatoxin dose will have an effect on the risk, nature and severity of toxicity, this step also includes a dose-response evaluation. For each determined form of toxicity caused by aflatoxin, the dose-response evaluation will help establish the quantitative relationship between dose and risk of toxicity in the range of doses that have been or might be experienced by consumers. The assembled data are critically evaluated to determine the forms of toxicity that may be caused by aflatoxin and to determine how vulnerable human beings may be to its toxic effects under certain conditions.
The second step, human exposure evaluation, identifies the susceptible commodity or product and contamination levels, the target population, the dose of aflatoxin received by individuals consuming the products and the duration of exposure. Since not all individuals in the population are exposed to the same doses, the dose ranges or number of people exposed to each of several different doses need to be determined.
The final step is the risk determination or estimation, which uses the toxicological and exposure information to estimate the likelihood that an adverse health effect will occur in the population. Despite its limitations, risk assessment is the best approach for addressing safety, health and environmental risks. It analyzes and evaluates limited information, while eliminating the guesswork in decision-making, and identifies priority areas for further research. Risk Management
Risk management is the process of using information obtained in the risk assessment procedure and weighing policy alternatives to select the most appropriate regulatory action. Unlike risk assessment, risk management is a highly subjective scheme, because it involves preferences and attitudes not part of the risk assessment process. Also, a high degree of public acceptance is essential for the success of risk management decisions.
In principle, risk management involves the identification and appraisal of available management alternatives, the selection of the best alternatives, and the implementation, monitoring and enforcement of the selected alternatives. Some practical risk management alternatives contributing to food safety include:
Food Safety Programs
- Establishment of regulatory limits.
- Monitoring of food products before and during harvest and processing.
- Screening and testing of products in commercial channels.
- Developing decontamination procedures.
- Diverting products to less risky uses.
Food safety programs are designed to limit exposure to foodborne risks. Where feasible, prevention is the best policy. For illustrative purposes, risks associated with aflatoxins will be used to demonstrate how effective food safety programs can reduce human exposure to those naturally occurring toxicants. Cottonseed, corn, peanuts and tree nuts are the commodities most adversely affected by aflatoxin contamination. Preharvest invasion of the toxin-producing organism Aspergillus sp. and its subsequent production of the toxin are unavoidable. Disallowing total availability or sale of products with potential contamination is not practical, particularly when the products are diet staples or have high nutritional value. If contamination occurs, the hazard associated with the toxin must be removed if the product is intended for human or animal consumption.
Before an effective food safety monitoring program can be set up, it is necessary to understand how the products become toxic and to have the analytical tool to identify high-risk products. An optimum food safety monitoring program for aflatoxins has three basic components: (1) monitoring agricultural commodities for aflatoxins before or during harvest, (2) establishing regulatory limits to exposure and (3) screening in commercial channels to identify and separate toxic commodities.
When regulations for aflatoxin were first established by the Food and Drug Administration (FDA), the toxicological knowledge available at that time confirmed an adverse health effect on livestock and a potential health risk for humans. A human food and animal feed safety program has been established to minimize human exposure to aflatoxin and its metabolites, protect animal health and provide an adequate food supply. This led to regulatory levels that vary according to the intended end-use of the product.
This Louisiana Agriculture issue provides a snapshot of research efforts under way in the LSU Agricultural Center to minimize risks associated with the consumption of foods. These include alternative food packaging to control the growth of pathogenic bacteria, the pasteurization of raw in-shell oysters to reduce risks posed by Vibrio species, the implementation of a rapid microbial detection laboratory to support enhanced food quality efforts and the mandated hazard analysis and critical control points (HACCP) program, the development of a bar code system for continuous monitoring of pathogenic bacteria in muscle foods and the evaluation of new techniques to reduce aflatoxin levels in corn.
(This article was published in the spring 2000 issue of Louisiana Agriculture.)