Pesticides and toxic chemicals

‘Contamination’ is a comparative term. In Britain at least, contaminants are trace substances; in the context of food they are distinguished from additives by whether or not there is an intention that the substances should be present when the food is consumed or prepared for consumption. Contaminants may be of natural or of technological origin: and technological contaminants may be direct or indirectly derived from additives. Contaminants occurring naturally in food may include alkaloids and cyanogenic glycosides : they may also arise from the natural action of micro-organisms as with certain fungal toxins or they may come about by direct environmental cross-contamination as with certain trace metals, allergens and polynuclear aromatic hydrocarbons. Technological contaminants can arise from deliberate treatment during the course of production as with agricultural or veterinary pesticides or other biocides. They may also arise from incidental treatment during processing or distribution, as residues from extraction solvent, trace metals from processing equipment, extractives or additives from plastics packaging materials, or residues from detergent, sterilants or disinfectants. Or they may arise from trace substances deliberately added during the course of the preparation and processing of food food additives residues of solvents used for the dispersal of colours and flavours, or nitrosamine compounds from nitrites for example. What constitutes contamination is a matter of opinion-enlightened professional toxicological opinion for preference, although this may be crystallized in the law of the land to remove toxicological discretion and leave room only for legal opinion. Golberg (1971) has recently reviewed toxicological aspects of the potential harm of trace chemical contaminants in food ; organochlorine pesticides and human health in particular have been considered by Deichmann & MacDonald (1971). Both the toxicological and the legal areas of opinion fall back on the analytical chemist. In considering trace contaminants in foods, I will indicate briefly the analytical principles concerned and then outline some of the particular areas of interest in this field. All trace analyses are characterized by sensitivity and specificity, both of which broadly follow the indications and requirements of the toxicologist, Looking first at the general principles of trace analysis, we can accept that the sensitivity of the analytical method used should match the requirements of the toxicological considerations. The general pattern in fact has been for the development of methods sensitive either to about 0.1 mg/kg (0.1 parts/ro6) or, in more recent years, and where the circumstance called for greater sensitivity, to about 0.1 parts/log. T h e