Toxic Hazards in Food

304 Pages·1983·8.99 MB·English

by  David M. Conning MB

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
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THE MASTERPIECE OF NATURE:
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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.