FOOD ADDITIVES This is the second category of foreign sub stances which are directly ingested. However, food additives are usually of low biological activity. Many different additives are now added to food to alter the flavour or colour. prevent spoilage, or in some other way change the nature of the foodstuff. There are also many potentially toxic substances which may be regarded as contaminants occurring naturally in food, resulting from cooking, or from other contamination, examples will be chapter. Veterinary drugs breakdown products may also be foodstuffs as indicated above. Most of these substances, both natural and artificial may be present in food in very small amounts t for the majority little is known of their toxicity. In many cases they are ingested daily for perhaps a lifetime and the numbers of people exposed very large. Although reliable is data are still scarce. there certainly seems to be evidence that at least some additives may be associated with adverse effects. Public aware ness of this has now begun to influence the preparation and manufacture of fond such that additive free foods are appearing on supermarket shelves.