These substances, widely used in the more industrialized countries, are normally defined as non-nutritive substances which are intentionally added to food, generally in small quantities, to improve its appearance, flavour, texture or storage properties. Although not contaminants in the strict sense, they may give rise to harmful chemical changes and should be regarded as potentially toxic materials. For example, nitrates or nitrites have been widely used as preservatives, but have been found to cause methaemoglobinaemia, especially in young children, and may give rise to carcinogenic nitrosamines. Certain non-nutritive sweetening agents (such as cyclamates) have been widely used in recent years, but it has been found that bladder tumours develop in animals to which they are fed in relatively high doses. As a result, the use of these agents has been restricted or completely prohibited in a number of countries.
31 artificial colours and more than 2,000 artificial flavours are actually listed. A single strawberry flavour of ice cream can contain as many as 55 different additives. In all, 2,800 substances are intentionally added to food in the USA.