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Food contaminants

Food contamination refers to the presence in food of harmful chemicals and microorganisms which can cause consumer illness. This article addresses the chemical contamination of foods, as opposed to microbiological contamination, which can be found under Foodborne illness. A separate issue is Genetically modified food, or the presence in foods of ingredients from Genetically modified organisms, also referred to as a form of food contamination.^[1]

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Impact

The impact of chemical contaminants on consumer health and well-being is often apparent only after many years of prolonged exposure at low levels (e.g. cancer). Chemical contaminants present in foods are often unaffected by thermal processing (unlike most microbiological agents). Chemical contaminants can be classified according to the source of contamination and the mechanism by which they enter the food product.

Agrochemicals

Agrochemicals are chemicals used in agricultural practices and animal husbandry with the intent to increase crops and reduce costs. Such agents include pesticides (e.g. insecticides, herbicides, rodenticides), plant growth regulators, veterinary drugs (e.g. nitrofuran, fluoroquinolones, malachite green, chloramphenicol), and bovine somatotropin (rBST).

Environmental contaminants

Environmental contaminants are chemicals that are present in the environment in which the food is grown, harvested, transported, stored, packaged, processed, and consumed. The physical contact of the food with its environment results in its contamination. Possible sources of contamination are:

-Air: radionuclides (¹³⁷Caesium, ⁹⁰Strontium), polycyclic aromatic hydrocarbons (PAH).

-Water: arsenic, mercury.

-Soil: cadmium, nitrate, perchlorate.

Polychlorinated biphenyls (PCB) , dioxins, and polybrominated diphenyl ether (PBDE) are ubiquitous chemicals, which are present in air, water, soil, and the entire biosphere.

-Packaging materials: antimony, tin, lead, perfluorooctanoic acid (PFOA), semicarbazide, benzophenone, isopropylthioxanthone (ITX), bisphenol A.

-Processing/cooking equipment: copper, lubricants, cleaning and sanitizing agents.

-Naturally occurring toxins: mycotoxins, phytohaemagglutinin, pyrrolizidine alkaloids, grayanotoxin, mushroom toxins, scombrotoxin (histamine), ciguatera, shellfish toxins (see shellfish poisoning), tetrodotoxin, among many others.

Food additives

Food additives are chemicals intentionally added to foods during processing. Most food additives play important technological roles in the food product and their use is justified from an economical, nutritional, or safety point of view. However, the employment of food additives in a manner inconsistent with their intended use may result in undesirable levels in the finished product (e.g. nitrate, nitrite). In such cases, food additives may become contaminants and may exert unfavorable effects on consumer health and/or the food product. Similarly, unapproved food additives (e.g. Sudan Red dyes, melamine), or food additives which have been withdrawn because of safety concerns (e.g. Butter Yellow) should be regarded as food contaminants.

Processing contaminants

Processing contaminants are generated during the processing of foods (e.g. heating, fermentation). They are absent in the raw materials, and are formed by chemical reactions between natural and/or added food constituents during processing. The presence of these contaminants in processed foods can not be entirely avoided. However, technological processes can be adjusted and/or optimized in order to reduce the levels of formation of processing contaminants. Examples are: nitrosamines, polycyclic aromatic hydrocarbons (PAH), heterocyclic amines, histamine, acrylamide, furan, benzene, trans fat, monochloropropanediol (MCPD), semicarbazide, 4-hydroxynonenal (4-HNE), and ethyl carbamate.

Emerging food contaminants

While many food contaminants have been known for decades, the formation and presence of certain chemicals in foods has been discovered relatively recently. These are the so-called emerging food contaminants, e.g. acrylamide, furan, benzene, perchlorate, perfluorooctanoic acid (PFOA) ,monochloropropanediol (MCPD) ,4-hydroxynonenal (4-HNE), and trans fat. The list is likely to grow in the future.

Safety and regulation

Acceptable Daily Intake (ADI) levels and tolerable concentrations of contaminants in individual foods are determined on the basis of the "No Observed Adverse Effect Level" (NOAEL) in animal experiments, by using a safety factor (usually 100). The maximum concentrations of contaminants allowed by legislation are often well below toxicological tolerance levels, because such levels can often be reasonably achieved by using good agricultural and manufacturing practices.

The establishment of ADIs for certain emerging food contaminants is currently an active area of research and regulatory debate.

References

^ [1] Briefing on GM Food Contamination