The presence of harmful chemicals in food can cause its chemical contamination, potentially causing consumer illness.
The impact of chemical contaminants on consumer health and well-being is often apparent only after many years of processing and prolonged exposure at low levels (e.g., cancer). Unlike food-borne pathogens, chemical contaminants present in foods are often unaffected by thermal processing. Chemical contaminants can be classified according to the source of contamination and the mechanism by which they enter the food product.
Agrochemicals are chemicals used in agricultural practices and animal husbandry with the intent to increase crop yields. 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 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 and contaminants common to that vector include:
Air: radionuclides (caesium-137, strontium-90), polycyclic aromatic hydrocarbons (PAH)
Water: arsenic, mercury
Soil: cadmium, nitrates, perchlorates
Packaging materials: antimony, tin, lead, perfluorooctanoic acid (PFOA), semicarbazide, benzophenone, isopropylthioxanthone (ITX), bisphenol A
Processing/cooking equipment: copper or other metal chips, lubricants, cleaning and sanitizing agents
Naturally occurring toxins: mycotoxins, phytohemagglutinin, pyrrolizidine alkaloids, grayanotoxin, scombrotoxin (histamine), ciguatera, shellfish toxins (see shellfish poisoning), tetrodotoxin, among many others.
There are many cases of banned pesticides or carcinogens found in foods.
Greenpeace exposed in 2006 that 25% of surveyed supermarkets in China stocked agricultural products contaminated with banned pesticides.