Contaminants are undesirable substances that lead to contamination of another substance or mixture of substances. According to the EU Contaminants Regulation, contaminants are substances that have not been intentionally added to food. These substances may be present in food as a result of environmental factors or the production process. If the food has been environmentally contaminated, it is called an environmental contaminant. However, the contamination may also be a residue resulting from the extraction, production, processing, preparation, treatment, presentation, packaging, transport and storage of the product. Typical contaminants include heavy metals such as lead, cadmium and mercury, dioxins, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, mycotoxins and other environmental toxins. Remnants of insects, pet dander, pharmaceutical residues, pesticides and other impurities are not considered contaminants. The term residue is used for substances that are intentionally applied to food but whose maximum quantities are controlled.