Metals such as cadmium, lead and mercury are natural occurring chemical compounds that vary tremendously. All these elements can appear in a lot of different kinds of compounds. The behavior and the risk depend strongly according to the environmental conditions. They can be present at various levels in the environment, e.g. soil, water and atmosphere. Metals can also occur as residues in food because of their presence in the environment, as a result of human activities such as farming, industry or car exhausts or from contamination during food processing and storage. People can be exposed to these metals from the environment or by ingesting contaminated food or water. Their accumulation in the body can lead to harmful effects over time.