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Toxic Hazards in Food PDF

304 Pages·1983·8.99 MB·English
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Toxic Hazards in Food D.M.Conningand A.B.G.Lansdown CROOM HELM London and Canberra ©1983 D.M. Conning and A.B.G. Lansdown Sof'tcover reprint of the hardcover 1st edition 1983 Croom Helm Ltd, Provident House, Burrell Row, Beckenham, Kent BR3 lAT Croom Helm Australia, PO Box 391 Manuka, ACT 2603, Australia British Library Cataloguing in Publication Data Toxic hazards in foods. 1. Food poisoning I. Conning, David M. II. Lansdown, Alan B.G. 615.9'54 RC143 ISBN 978-1-4615-9771-1 ISBN 978-1-4615-9769-8 (eBook) DOl 10.1007/978-1-4615-9769-8 Typeset by Mayhew Typesetting, Bristol CONTENTS Foreword D. V. Parke Contributors 4 1. Systemic Toxicity Due to Foodstuffs D.M Conning 5 Introduction 5 Cardiovascular and Haematological Disease 5 Central Nervous System 7 Hepatotoxicity 12 Renal Toxicity 16 References 18 2. Intolerance and Allergy to Foods and Food Additives: Its Relevance to Toxicology W.E. Parish 22 Allergy, Tolerance and Pseudo-allergy (Idiosyncrasy) 22 Lymphocyte Stimulation and Antibody Formation 25 Mucosal (Gastro-intestinal) Immune Systems 31 Classification of Allergic Responses 35 Anaphylaxis 37 Arthus Reaction and Immune Complex Disorders 45 Delayed Hypersensitivity (Cell-mediated Immune Response) 50 Intolerance to Natural Food Chemicals and to Food Additives 57 Reduced Immunocompetence (Immunosuppression) 61 Immunological Tests to Predict Toxicological Allergic Hazards to Man 64 References 68 3. Teratogenicity and Reduced Fertility Resulting from Factors Present in FoodA.B.G. Lansdown 73 Introduction 73 Epidemiological and Experimental Aspects 75 Food Constituents 78 Minerals 84 Food Additives 96 Alcohol 100 Food Contaminants 102 Discussion 111 References 112 4. Carcinogens in FoodP. Grasso 122 Carcinogens in Edible Plants 122 Fungal Carcinogens 124 Carcinogens Introduced During Food Processing and Preservation 127 Polycyclic Aromatic Hydrocarbons 127 Nitrosamines 130 Food Additives 133 Pesticides 136 Food and Cancer 138 Conclusion 140 References 140 5. The Mutagenicity of FoodD. Anderson and l.F.H. Purchase 145 Introduction 145 Principles of Testing Food for Mutagenicity 146 Background to Mutagenicity Testing 147 Mutagenicity Testing 148 Testing Strategy 158 Mutagens in Food 158 Extrapolation of Results from Laboratory Assays to Man 165 Significance of Food-borne Mutagens to Man 166 References 168 6. The Gastrointestinal Tract in Food Toxicology l.R. Rowlands and R. Walker 183 Introduction 183 Role of Gut Microflora in Intestinal Metabolism 183 Role of Mammalian Enzymes in Intestinal Metabolism 208 Toxicological Aspects of Intestinal Metabolism 211 Pathology of the Gastrointestinal Tract in Safety Evaluation 246 References 250 7. Food Allergies: Clinical Aspects and Natural AlleIgens 1.R. Mansfield 275 Introduction 275 Historical Development 276 Clinical Ecology 279 Clinical Conditions Related to Clinical Ecology 279 Investigation of Food Allergy 280 General Discussion 286 Summary 290 Further Reading 290 References 291 Index 292 CROOM HELM APPLIED BIOLOGY SERIES Edited by Peter J. Baron, BSe. Hons, PhD NUTRITION AND DISEASE Edited by R.J. Jarrett THE NATURE OF ENZYMOLOGY R.L. Foster NUTRITION AND FOOD PROCESSING H.G. Muller and G. Tobin THE MASTERPIECE OF NATURE: The Evolution and Genetics of Sexuality G. Bell CELL LOCOMOTION IN VITRO C.A. Middleton and J .A. Sharp FOREWORD In the world of plentiful, cheap food that so many of us in the Western World have come to accept as our birthright, it takes sensational journalism and horrific television coverage to make us realise that not all of the world's population shares this abundance. Visits to the Soviet Bloc countries, to China, most African states and various other coun tries of the Third World make one quickly realise that widespread shortage of food is just over the horizon and would be common experi ence to all were it not for the advanced technologies of Western agricul ture, food production and food manufacture. Without doubt, pesticides and other agricultural chemicals have made enormous contributions to world food production - and indeed to world peace. The introduction of many food additives, especially antioxidants, has also contributed greatly to the amount and quality of food which is available, preventing early spoilage and waste, and possibly indirectly contributing to man's health, as these antioxidants have been shown to have beneficial proper ties in the prevention of experimental malignancy and cardiovascular disease. Nevertheless, despite the enormous benefits derived from the use of agrochemicals and food additives, it is essential to remember that these are all selectively toxic chemicals, with no absolute guarantee of safety, and where the benefit to risk ratio is always a compromise adjusted by the expediency of political and financial aspects of food production. The major hazards from toxic chemicals in food have been generally recognised to comprise: (1) bacterial contamination; (2) naturally occurring toxins and carcinogens; (3) accidental chemical contaminants; (4) pesticide contaminants and; (5) food additives, with the last two being regarded as carrying little or no real hazard. Nevertheless, at the interface of these two groups of chemicals, when pesticides are deli berately added to food, as in the treatment of cereal grains for the control of insect pests, it is essential that the pesticides added should be rigorously examined for their safety and health hazards. Recent developments in this area have seen the introduction of a very wide range of new chemicals for use in grain silos and these developments have to be watched carefully. Constant vigil is necessary to ensure that imported food conforms with the accepted stringent standards for the absence of contaminant 2 Foreword chemicals, such as aflatoxins and other mycotoxins and preformed nitrosamines. Food imported into North America and Western Europe from tropical countries generally contains only the smallest traces of these potent natural carcinogens, even though the same products on sale in the market places of the countries of origin may be several orders of magnitude greater in their contents of mycotoxins and nitros amines. It is tempting to speculate that before the introduction of the rigorous chemical analyses, much imported tropical food was heavily contaminated with these natural toxic chemicals, and may have been responsible for as much human cancer in our Western civilisation as still occurs today in the tropical areas of production. Similarly, there is a real international need to prevent the accidental contamination offood with dangerous industrial chemicals, such as occurred in the Michigan disaster involving the polybromobiphenyl mixture, 'Firemaster'. The final chapters of this catastrophe have still to be written, but the persistence of this industrial chemical produced a magnitude of con tamination that has never before been seen, and involved food produc tion imd manufacture on a world-wide scale. The safety evaluation of food chemicals depends very largely on toxicity studies and the use of animal models. These widely accepted practices of toxicology are of value only provided that the animal data can be suitably translated to predict safety for man. More for convenience than for scientific reasons, small rodents are generally used in these toxicological studies, and in many cases there is little attempt to ascertain to what extent these animals are suitable models for man, for the specific chemicals under study. Carcinogenicity studies on pesticides, food additives and even natural food constituents, are generally conducted at extremely high dosage, and the smallest increase in occurrence of tumours has indicted as carcinogens such widely occurring food components as caffeine and saccharin. This empirical testing of chemicals, often with scant regard for any scientific basis, and the use of unsuitable small animal species as models for man, will frequently grossly magnify the toxic and carcino genic risks of many chemicals, and may generate spurious toxicity data that could lead tOXicology into disrepute and ridicule. Politicians often prefer to use commonsense to the pseudo-science of some of their toxicology advisors, and international regulatory bodies such as the WHO and F AO, find it expedient not to pay too much attention to carcinogenicity data which indicate positive findings only in the mouse. There is an urgent need for more logical and scientific approaches to the choice of animal species for toxicity testing, to the selection of dose Foreword 3 levels, and the consideration of species differences in the toxicokinetics, metabolism, and mechanisms of toxicity of chemicals. Several inter national bodies are now coming to grips with these problems and inter national experts are re-evaluating the most suitable techniques for determining and monitoring toxic hazards of chemicals, and the most appropriate scientific methods for interpreting the data generated. Nevertheless, adulterant practices are still rife in many countries; lead chromate and carcinogenic yellow azo dyes are sometimes added illegally to curry pastes and powders in India, and well-meaning persons may send samples of these to relatives abroad. Of the numerous natural xenobiotics present in our food only a very few have been examined for safety, and of these perhaps too great a percentage has been found to be undesirably toxic (e.g. gossypol and ipomeanol) or potently car cinogenic (mycotoxins). The continuous and extended study of these natural components is well merited, but rarely funded. The safety evaluation of new pesticides and agrochemicals, and the re-evaluation of existing ones, is obviously a continuing and expanding need, and ways must be found to ensure prevention of gross contamination of food by industrial chemicals. Recent developments have again highlighted the the widespread occurrence of food allergies, which sometimes result in severely debilitating and incapacitating diseases. These and several facets of the toxic hzards of food are now reviewed in this most impor tant new publication, by acknowledged experts in these many and diverse fields of study. Dennis V. Parke Department of Biochemistry, University of Surrey, Guildford.

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In the world of plentiful, cheap food that so many of us in the Western World have come to accept as our birthright, it takes sensational journalism and horrific television coverage to make us realise that not all of the world's population shares this abundance. Visits to the Soviet Bloc countries,
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