When we eat food that we have grown or bought we are unwittingly consuming many substances other than the basic nutrients which we assume make up the food item. The same applies to the feed we provide for our domesticated animals. Many foreign substances are added by man to improve quality and prevent biological decay, these include insecticides, colourants, minerals, vitamins and preservatives. However, there are many materials that have a damaging effect and are not added by man, but are the result of infections by other organisms. For example, foods can contain bacteria that grow naturally on produce and which may lead to food poisoning if ingested. Other harmful substances may be picked up as a result of environmental pollution, such as undesirable pesticides and heavy metals. [...]