9 9 XA04NO320 Food and Drinking Water Safety: Can Help Us To Get Our Priorities Right? Dr. TV H. B. Denner Chief Scientist (Food), Ministry of Agriculture, Fisheries and Food 17 Smith Square, London SWIP 3JR UK

Introduction

Huge resources are devoted worldwide by governments and food producers to ensure that food and water are produced with due regard to the safety of consumers. This inevitably involves some form of risk assessment but in the field of food safety a formalised process of risk assessment has been slow to develop. An ad hoc mosaic of approaches has evolved which varies not only between countries but sometimes within countries as well. This may not be unexpected considering the vast variety of kinds of food (Table 1).

Table 1. Examples of food-related and drinking water-related hazards

Potential hazards iherent in food:

Inherent plant toxins Nutritional imbalances Malnutrition Over-nutrition Novel foods

Potential hazards related to food production and processing:

Food processing contaminants Products of biotechnology Novel food processes Veterinary drug residues Pesticide residues Water treatment agents Processing aids

Potential hazards accidentally associated with food:

Algal toxins in water Food spoilage microorganisms Diseases transmissible through food and water Marine biotoxins Environmental contaminants Mycotoxins Food contact materials Radioisotopes

Potential hazards added to food:

Colours Preservatives Flavourings Sweeteners Malicious contamination

Not only do food-related hazards themselves vary widely, so do the effects which they can cause. For example microorganisms can cause mild stomach upsets or death within a few hours depending upon the organism involved. For chemical contaminants in food the potential effects are usually less acute although no less serious. Many of the chemicals of concern are believed

190 ...... 9 9 2 to be carcinogens whose effects might only be realised after many years of exposure. Nutritional imbalances may result in an increased risk from diseases, such as heart disease and cancer, which can also arise from other causes. In these latter examples it is often difficult to relate cause to effect even when extensive epidemiological evidence is available.

It is important to understand the enormous diversity in possible food-related hazards before describing the assessment of risks associated with them. This great diversity makes it unlikely that any single approach to risk assessment can suit all situations. This means that making comparisons between risks from different hazards is extremely difficult. In fact trying to allocate resources in a logical way between all the different kinds of food-related hazards is a major problem in itself. For with finite resources there is always the danger of finding that focusing on one area of concern results in a potential risk elsewhere being neglected.

The aim of this paper is to take a general look at some of the issues facing those with responsibility for controlling food-related risks today and to ask whether a more formalised approach to risk assessment could help to get priorities right. Food safety is not a new subject and it is worth examining history first before going on to look at some issues and then attempting to draw some more general conclusions.

Historical perspective

In human history, concern for food safety has always been apparent. In ancient Egypt, we know that the Pharaohs had professional "tasters" who were responsible for primitive "risk assessments" and the notion of poisons was well-established in antiquity. However, the ancients had no way of telling whether the was, for example, the rats themselves or the diseases they carried, or "natural" toxins or poisons added by their enemies.

Nevertheless, in many ancient societies there was an awareness of the importance of purity and cleanliness which was reflected in customs and religion. Some religious practices may well have been based upon specific experience of avoiding risky food and water supplies. Prohibition of pork and shellfish may reflect the fact that they were common sources of food poisoning. For example, Trichinellaspiralis carried by pork can form cysts in human muscle and shellfish can accumulate pathogenic microorganisms and toxins from water.

The writing of early food law was, however, largely driven by the need to protect consumers from fraud. In England, King John prohibited the adulteration of bread in 1202 and in 1266 a law was passed to protect against short and unsafe meat. Hence an erroneous connection may have been made by the public between freedom from adulteration and freedom from risk.

Risk assessment of foods

The practice of risk assessment, in the context of food and water, is currently conducted in different ways in different countries. The USA generally uses the standard definition of risk - that is the statistical probability of some adverse event occurring - widely in the practice of risk assessment for food. In practice most other countries use an approach which seeks to minimise the risks from food without actually quantifying what these are. Of course in the majority of cases the risks associated with food are so small that it would be virtually impossible to make any reasonable kind of estimate of risk.

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There is however a similarity in most risk assessments which are applied when considering hazards added to food. Essentially a three stranded approach is employed, although the terminology will vary in different systems (Figure 1).

Figure . General scheme for food and water risk assessments

Risk Assessment

Hazard Evaluation

Occurrence Assessment -fIntake Estimation ]--I Consumption Estimation

The three essential elements of the risk assessment process are the hazard evaluation, where all of the available toxicological or epidemiological data are considered, the occurrence assessment which seeks to establish the or incidence of the hazard of concern in foods and the consumption estimate which seeks to establish how much of the foods of concern consumers actually eat. The occurrence assessment and consumption estimate are brought together to estimate the intake of the hazardous agent by consumers of the foods in question. Finally the intake estimate and the hazard assessment are brought together to estimate the risk. The risk assessment is then applied in . In some circumstances the hazard evaluation will provide a dose-response relationship so that the estimated intake can be read off against the likely risk. In other cases the hazard evaluation will generate an acceptable level of intake against which the estimate of actual intake can be compared.

In the case of food chemicals which are intentionally added the actual level of risk is minimal because the assessment process is based upon a level of exposure at which no adverse effects are expected. It would be a mistake though to say that the level of risk is zero. Although safety factors are included to allow for scientific uncertainty there is always a residual risk which is due to uncertainties which cannot be fully accounted for in the hazard evaluation process. This is not the level of "acceptable risk" since the level of risk is not being assessed. The best we can say is that the level of risk at the ADI is negligible based on our experience of toxicology and food- related risks of this kind.

Of course very few consumers ever ave a level of intake which approaches the ADI and this provides an even greater margin of safety. However, presenting information to consumers on this level of risk is very difficult because of their expectation of zero risk. There is a great danger in referring to this level of risk as "zero" because there is always the possibility that new scientific evidence will emerge which will require a change in the regulatory position. Under these circumstances it is very confusing for consumers to be told that something which they were previously told was "safe" is now not safe and this leads to mis-trust in the system. It is therefore necessary to introduce consumers to the idea of minimal risk associated with food.

One small group of consumers who are already familiar with managing residual risks from foods are those who experience intolerance reactions. Although many more people believe that they are intolerant of certain foods than can actually be shown in clinical studies, people with genuine

192 ...... 1 9 V 2 food allergies need to take special care over what they eat. Most intolerance reactions seem to be related to natural constituents of foods. However a small proportion can be associated with food additives. These reactions are so idiosyncratic that it is impossible to take account of them in the risk assessment process. Instead, foods are clearly labelled with the ingredients they contain so that consumers with known intolerances can avoid eating them. In addition, in the UK there is a Food Intolerance Databank which provides advice to dietitians in planning suitable diets for their patients.

Development of analytical capabilities

As our understanding of chemisty, biology and the other sciences has developed over the past centuries, we have been able to establish even more links between cause and disease and have developed ever more sensitive methods for the detection of hazards in food and water. While this is a triumph for science it can present us with serious difficulty vhen we wish to present information on risks to consumers. For example, some of the techniques for analysis of chemical contaminants are now so exquisitely sensitive that scientists hav- difficulty in explaining to the lay public the meaning of their results.

Even having convinced consumers of the very small amo. its involved, psychological research has shown that consumers are unwilling to accept any kind of "contagion" or "contamination" of their food by alien substances. Therefore by reducing analytical detection limits ever lower we apparently reveal more and more previously unknown (and therefore uncared about) hazards. The public are not sufficiently knowledgeable about toxicology to understand that very small traces of contamination do not necessarily present a significant hazard. They assume that the merest presence of a contaminant indicates harm. Risk assessment can help to evaluate these hazards and put them into perspective against other every day risks. However it may not be so easy to overcome the psychological factors underlying public perception which dictate that no level of contamination is acceptable.

Risk assessment for drinking water

Nowhere is this problem of trace contamination more prevalent than in the risk assessment for drinking water. Consumers in the developed world have come to expect high standards of drinking water safety and quality and continue to demand higher standards. Such demands are based in part upon the improving capability for micro-pollutant analysis and also on expanding information about their toxicity. There is also much more public awareness, and in some quarters concern, about water quality issues today. It is, therefore, of great importance that standards for drinking water be set on a scientific and rational basis in order that the public can be given reassurance in clear and unambiguous terms. It is also imperative to have clear standards in order to avoid uncertainty about the significance of the standards and consequent inappropriate expenditure on regulation and control.

The current philosophy of many groups is that absolute safety is a desirable and attainable goal for drinking water. One approach to dealing with demands for zero risks associated with drinking water is to set a level of risk which is indistinguishable from background risks. The application of the USA Environmental Protection Agency's Surface Water Treatment Rule to giardia is a good example of this risk assessment approach. Under the Rule water suppliers would need to ensure that the maximum of giardiasis was one case per year per 10,000 of the population. To guarantee this level of risk additional water treatment would be required.

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Meanwhile in Europe there are concerns about the European Community's Drinking Water Directive regarding standards for pesticides which do not relate to health effects. Other standards in the Directive may also not adequately distinguish between health and aesthetic standards and such ambiguity can lead to unjustified consumer concern. The Directive does not have the transparent basis which is evident in the US EPA approach which I have just described. Without any rational basis to setting standards for drinking water, all standards tend to be regarded as "health" standards and consumers become concerned if any are breached. The concern is greater because, apart from two of te standards, the Directive requires total compliance in every sample taken. This is so for colour, and iron as it is for other aesthetic parameters. This presents particular problems for water suppliers since in the absence of risk-related standards the supplier is unable to make any judgement as to whether a breach represents a serious risk to health - which justifies immediate provision of an alternative supply - or whether water can continue to be supplied pending the completion of remedial measures. This is an example where there is clear evidence that standards based upon rigorous risk assessment could improve the management of risks.

Risk assessment of food chemicals

Food chemical products such as food additives and pesticides are presented for risk assessment by their manufacturers and the risk management strategy here is to either approve, restrict or prohibit their use. It is the responsibility of the company making the submission to provide information on toxicology and conditions of use and to demonstrate the safety of the product. Approval for use is granted by the regulatory authorities within established legislative frameworks. In such cases the risk assessment can be comprehensive and any risks carefully balanced against any potential benefits to consumers.

In addition to those chemicals which are intentionally added to food many chemicals can arise in food as a result of contamination through the food chain. Substances such as heavy metals and dioxins are ubiquitous environmental contaminants and as a result traces of these chemicals can be detected in many foods. Chemical contaminants in food present slightly different problems to food additives: The presence of trace levels cannot be said to bring any direct benefit to the consumer and so there is limited scope for balancing risks against benefits. Also in many cases no-one can be identified as being directly responsible for, or can be said to benefit from, the presence of these substances in food.

For chemical contaminants the most common approach to risk management is to reduce levels of contamination to the lowest levels practicable. Tolerable daily intakes can be set for contaminants which are not genotoxic carcinogens in the same way that acceptable daily intakes are set for additives. However it may not prove practicable to achieve such low levels of intake since the same mechanisms for control are not always available. One factor often called upon when determining levels for chemical contaminants in food is the analytical limit of determination. It is impracticable to set a maximum tolerable concentration of a chemical in food which cannot be monitored.

The management of chemical contaminants is often aimed at targeting the main sources contributing to intakes and reducing to the lowest levels practicable. Of course there is a need for risk assessment and management techniques in deciding what concentrations are the lowest practicable. Often it is valid to estimate what the background level is in the diet and then to consider whether any particular source makes a significant contribution over and

194 ...... 9 9 2 above this. Another possible approach to determining tolerable levels in food is to seek to identify the point at which a small decrease in adverse health effects no longer justifies the additional cost of control. However establishing tolerable concentrations of chemical contaminants in food is likely to be a very delicate process because both the very small health consequences at low levels of contamination and the true costs are extremely difficult to determine. Once against formal procedures of risk assessment and management will need to be developed if this is to be successfully accomplished.

In addition to chemicals which are alien in food there are thousands of substances which can arise quite naturally. Chemical compounds which occur naturally in food, however, are rarely given formal risk assessments unless safety concerns arise through food poisoning incidents or are identified by research. One subject which has received close attention is the production of mycotoxins by fungal contaminants in food. Stored food is very prone to attack by fungi although the presence of the organism may not be obvious to the naked eye. Sophisticated chemical analyses are therefore often required to detect the presence of mycotoxins.

The problems of mycotoxins have been recognised for many years and many countries have introduced legislation to control concentrations to parts per billion levels. In Asia, sub-tropical Africa and certain other parts of the world, fungal contamination of stored foods is widespread because the climatic conditions encourage fungal growth. If all food contaminated with mycotoxins above parts per billion levels were to be prohibited in these countries then food shortages could be the result. In this example it is clear that a risk assessment carried out under one set of conditions may not be relevant if applied elsewhere.

It is interesting to note that there is a "folklore" amongst some consumers that "natural equals good". It seems logical to them to assume that foods which we have been eating for generations should be intrinsically safe. This notion is appealed to over and over again in food advertising and so the idea is continually reinforced in peoples' minds. This belief in the "goodness" of natural things and suspicions about anything altered or synthetic perhaps underlies our heavy emphasis on te regulation of substances added to, or contaminating food. However there are many chemicals of toxicological concern present naturally in our everyday diet. A typical menu of everyday foods can illustrate this (Figure 2 This includes only a few of the natural toxicants which have been identified and there may well be many others present in these foods.

One group of compounds of particular interest are the heterocyclic amines. These compounds are produced during high charring of proteinaceous foods and are therefore found at high concentrations in grilled, fried and roast meats. This class of chemicals is related to some of the most carcinogenic known.

Many scientists now question the relative priorities assigned to "synthetic" and "natural" chemicals in food and water in our present approach to risk assessments. In the USA, Ames has estimated that 99.99% by weight of pesticides in the diet are "natural" - in that they are produced by plants as natural defences against insect attack - and he adds that only a small proportion of these natural pesticides has received any toxicological evaluation. However the evaluation of all natural food chemicals for toxic hazard by traditional animal-based methods would be an enormous task since there are many thousands of natural plant substances. It is also questioned whether the traditional methods of hazard evaluation would be even relevant since many naturally occurring toxicants occur with protective agents like the anti-oxidant vitamins

195 ...... 9 9 2 which could limit the toxic effects. Toxicological assessment of inherent plant toxins therefore needs to take place in the context of the foods in which they occur.

Protective agents in the diet may prove to be a very important factor in the risk assessment of naturally occurring toxicants. For example naturally occurring carcinogens appear to be so common in the diet that one would expect a much higher incidence of cancers of the digestive tract than is actually observed. The nutritional status of individuals may also have a significant impact upon their susceptibility to natural toxicants and risk assessment methodologies will need to take all of these factors into account. Ultimately it will only be through epidemiological studies that the hazards of natural toxicants will be linked with any adverse health effects. One major problem - of assessing the exposure of individual consumers to natural toxicants in their diets - may be overcome by the use of biomarkers wich provide an indication of the level of a marker compound in a bodily tissue or fluid.

The risk assessment of inherent toxicants is therefore an area where there is vast scope for development of new testing methodologies and management strategies. Only through the application of appropriate technologies can we hope to make sense of the many potential toxicants which occur naturally in the diet.

One interesting approach to food chemical risk assessment which Ames has proposed is the Human Exposure/Rodent Potency (HERP) index for assessing cancer risks. This is a measure of the ratio of the estimated human exposure to a toxin to the results of toxicological studies on rodents (Figure 3.

Figure 3 Calculation of the HERP index

HERP = Human exposure index Rat Potency index

The higher the HERP value, the greater the risk. Ames regards the index as a means for rationally setting priorities although the HERP has been the subject of criticism amongst toxicologists. Nevertheless, the approach provides some interesting comparisons between some natural and synthetic cancer risks (Table 2.

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Table 2 HERP Index for Possible Carcinogenic Potency

Average or Reasonable Carcinogen and Dose Daily Human Exposure per 150-Pound Person HERP Substance Amount Carcinogen Dose 4.7 Wine 8 oz Alcohol 30 ml 2.8 Beer 12 oz Alcohol 18 ml 0.1 Basil I g dry leaf Estragol 8.8 mg 0.1 Mushroom 0.5 oz Hydrazines 0.06 Saccharin One diet cola Saccharin 95 mg 0.03 Comfrey tea I cup Symphytine 38 ug 0.03 Peanut butter One sandwich Aflatoxin 2 ppb 0.003 Baconcooked 100 grammes Nitrosamine 0.04 ug 0.001 Chlorinated tap water I litre Chloroform 8 ug 0.0004 Grain products Daily intake EDB 0.42 ug 0.0002 PCBs Daily intake OCBs 0.2 ug EDB = Ethylene dibromide PCB = polychlorinated biphenyl

(From "Food Safety" by J. M. Jones, Eagan Press, 1992.) Microbiological risk assessment

In spite of the importance of microbiological risks associated with food, formalised risk assessment has not been applied to decision-making in tis field. This is largely attributable to the unique problems posed by te assessment of the risk of microbiological disease. Estimating risks from microbiological azards is complicated by the wide variability of the virulence of strains of organisms, the foods in which contamination can occur and the susceptibility of the populus. It is therefore very difficult to make any numerical estimate of the degree of risk. The degree of hazard may also change dramatically as a food passes through the food chain so that a satisfactory assessment at one point in the chain is only meaningful if appropriate measures to maintain microbiological quality are taken at all stages later in the chain. Many experts rate the risks from microbiological hazards in foods to be just as important as those from chemical hazards, but allocation of regulatory resources is only just beginning to reflect this. Radioactivity in food

The risk assessment of radioactive contamination of food, by contrast, is a relatively well developed science. It occupies a unique place in our considerations, because te risks to the consumer of a wide variety of natural and man-made contaminants can be related in terms of the single concept of radiation dose. Radioactivity also has a high profile in public and media concern, much higher than it merits in terms of any objective assessment of risks. Although the assessment of risk is the subject of a wide degree of international agreement there remain small areas of disagreement within the scientific community. These disagreements, however, are in matters of detail that are minute compared to the uncertainties regarding many other forms of contamination.

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This is one area where risk assessment is used in a direct, quantitative way in the control of contamination of food and drink. Because exposure to radiation can be expressed in a single dose and the relation between dose and effect is well established, it is possible to make probabilistic estimates of risk which are reflected in the regulatory system used in the United Kingdom to control man-made radioactivity in the environment and the food-chain. Both the control of radioactive discharges by nuclear sites and the limits on contamination following a nuclear accident are based on the concept of acceptable or tolerable radiation dose, which is in turn derived from the risk per unit dose calculated by the International Commission for Radiological Protection and interpreted for us in the UK by the National Radiological Protection Board. As with other forms of contamination, the debate on what level of risk is acceptable or tolerable is a matter of widespread concern, but it can at least be based on a reasonably solid scientific foundation.

Risk assessment in developed and developing countries

In developing countries, microbiological hazards are often of greater importance than other kinds of food-related hazards. A supply of drinking water which is free from pathogenic micro- organisms is often jeopardised by natural conditions and there may be arguments for accepting risks associated with the chemicals used to treat water in order to control acute microbiological hazards. For example, a decision made on the best of intentions by Peruvian officials not to chlorinate much of the country's drinking water seems to have led to a cholera epidemic of major proportions. The decision appears to have been based upon studies by the US EPA which showed that the chlorination of organic matter in water may create a cancer risk from the formation of trihalomethanes. Studies had shown that, at 100 ppb levels, these compounds could pose a cancer risk of in 10,000 lifetimes.

It would be very difficult to justify the introduction of alternative treatment methods in the USA to reduce such a small risk since it is doubtful that the benefits could in any way outweigh the immense costs involved. However in the South American situation - where there was no possibility of replacing chlorination with other forms of treatment - the risks from cholera were far in excess of the risks from cancer due to chlorination. A risk assessment of the removal of chlorine from South American water supplies would probably have resulted in a very different decision being made. Managing uncertainty in food risk assessments

Risk assessment and risk management of foods and water are often complicated because there are a large number of factors contributing to variability in the human population (Table 3. Table 3 Factors contributing to variability in the human population

Genetic diversity of man Age-related differences in response Medical conditions Regional and ethnic variations in diet Overall nutritional status.

In addition to these factors is the wide variety in traditional diets and in what individuals choose to eat from the foods available to them.

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Toxicological testing procedures also introduce uncertainties into the risk assessment process. In particular the interpretation of animal studies and the extrapolation of animal data to man are great sources of uncertainty. In order to allow for these uncertainties two approaches are adopted: Firstly only data from the most susceptible animal species are considered; secondly safety factors are introduced to allow for the uncertainty.

In some systems further conservative measures are used especially when quantitative risk assessment (QRA) computer models are used to extrapolate from high doses in animals to low doses in humans. It is impossible to select a model which accurately represents the underlying biological cancer induction mechanism while this mechanism remains unknown. Therefore many systems adopt a "worst case model" approach. Furthermore, in some systems the risk estimate is based on te upper confidence limit of the dose-response curve selected. Where the quality of data is poor this can introduce a very large element of systematic error. Overall, whilst QRA techniques appear to offer great potential for improving risk assessments their validity seems limited until they can be sown to reliably model the underlying biological mechanism.

A conservative approach is also adopted when making estimates of the likely intakes of consumers. Here worst case estimates are often employed to estimate the occurrence of a hazardous agent in the food supply when the true occurrence is not known. Also food consumption estimates are designed to ensure that the diet of even the most extreme consumer is considered. It is furthermore assumed that high level consumers will maintain this level of consumption throughout their lifetime.

The problem with such a conservative approach is that the margins of error which are quite properly introduced to allow for uncertainties in the data are compounded at each stage in the risk assessment process. The final effect can be to produce a margin of safety which far exceeds the realms of possibility. The reason for this is that although each correction for uncertainty is valid, it is most unlikely that unpredicted events associated with all of the sources of uncertainty would arise in any one incident. This phenomenon has been called "creeping conservatism" and its effect is to over-estimate the true degree of risk associated with food hazards. This in turn leads to sub-optimal risk management decisions so that the cost of control far outweighs any benefit that might be gained from the action. This is an area of food risk assessment where considerable further development is needed.

Nevertheless it is important not to under-estimate the need for a conservative approach and any strategy adopted for dealing with uncertainty in a rational way must make adequate allowance. For example the wide variety in perfectly normal dietary patterns means that it is not valid to estimate the average risk on a population basis from exposure to a hazard through food. It is not sufficient just to estimate societal risks - the risks to actual consumers must be assessed.

Public perceptions of food-related risks

While regulatory authorities go to great lengths to accurately estimate the risks to consumers the public's perceptions of the relative risks associated with food and water have often been found to differ markedly from those of the experts on food safety. This is not a unique phenomenon but is of particular importance in food safety because people are naturally very sensitive about an issue as intimate as what they put in their mouths to eat. It is no use saying that consumers are irrational about the decisions they make and therefore need educating because consumers ultimately have the right to demand food of the nature and quality they expect. Instead it

199 ...... 1 9 9 2 is necessary to begin to understand the factors which consumers take into account when making decisions about food. Once these factors are understood then it will be possible to take them into account when framing information for consumers and even in some cases in the risk assessment process itself.

As part of the risk management process it is necessary to allocate resources rationally between the many competing demands for risk assessment for the various food hazards listed in Table . There is also a need to understand the systems which governments currently adopt to do this. The balance seems to be about right most of the time but it is apparent that the allocation is not strictly based upon the scientific data alone. For example regulatory authorities will need to consider whether they can take any action about a problem. It is far easier to control pesticide residues through the centralised process of product approvals than it is to improve food hygiene in millions of domestic kitchens. But what is also important is that the public feel that they are able to control hazards which might occur in their own homes. In contrast they rely upon governments to control hidden hazards such as pesticides. The public is also concerned about hazards which affect vulnerable groups like children and are concerned that the costs of a particular hazard might not be borne by those who reap the benefit.

These kinds of factors, in addition to scientific judgements about the likely risks have driven our priorities in the past and there is a need to develop more formal ways in future. The scientific process of risk assessment should be undertaken within a social context if it is to be successfully accomplished.

Food irradiation

An example of the public's perception of risk sometimes differing from that of the scientific community is that of the risk associated with food irradiation. Over the last 40 years food irradiation has been studied more than any other food preservation process. The risk has been assessed by a number of international organisations such as the WHO and FAO, including consideration by an independent UK Safety Committee (the Advisory Committee on Irradiated and Novel Foods). Yet despite reassurances that the process is without identifiable risk consumers are still reluctant to accept irradiated food and the potential benefits of the process.

Regulations have recently been introduced in the UK to allow the controlled use of the process under a strict licensing system. To date only a single licence has been issued for a range of herbs and spices. This to some extent reflects the hesitancy of food retailers and their perception of the public's attitude to irradiated food. Nevertheless, other applications may follow and food irradiation will no doubt find its niche amongst the armoury of preservation methods developed over the centuries to enhance food safety.

In this case the Government's decision was to permit the use of food irradiation provided that the final product was appropriately labelled. This gives the final decision on whether to consume irradiated food or not to the consumer. In other circumstances this would not be so easy. For example there are frequently calls to label foods with the pesticides used in their production. This would be an impossible task when you consider imported foods which may have been mixed and blended and passed through several suppliers and the problem of composite foods is even more daunting. Consumers are however able to select "organically produced" food and thus make a choice about the use of agricultural chemicals in that way. Even though consumers express high levels of concern about pesticides in their food the level of take-up of organically

200 ...... 1 9 9 2 grown foods is surprisingly small. This may be due to the high prices charged for organic food but is probably also because consumers are against the principle of the use of agro-chemicals and their potential environmental effects rather than being concerned about specific adverse health effects. In this case no amount of revision of the risk assessment process would make the use of pesticides on food crops more acceptable to consumers.

Biotechnology

In the UK guidelines have been published on labelling requirements for products of biotechnology. The US Food and Drug Administration, on the other hand, has recently decided to treat foods created through plant biotechnology just like any other foods derived from plant breeding. The merit of labelling is that it enables the consumer to make an informed choice where there has been material alteration to the final food. However, this should not be used as a primary education tool. In order to avoid conveying over-simplistic and potentially misleading messages a wider public information campaign would be required. For this to be effective there is a need to understand better the factors which underlie consumers' concerns about the products of biotechnology.

Nutritional hazards

In many parts of the world food shortages and nutrient deficiency diseases are still major problems. In such regions sophisticated risk assessments are not required to show that what is needed is simply more or better food. In western countries the supply of food is not a problem and here the main diet-related diseases are due to over-nutrition and the inappropriate choice of food. It has been found that many people seem not to be willing to change their diets in the light of information provided to help consumers adopt a more healthy diet. It is thus apparent that we need to provide better quality information about the major food-related risks to consumers if we are to have any significant impact on dietary change and improvements in health. Risk assessment can help in the development of policies on the issues and in presenting information to consumers in a clear and consistent manner.

Conclusions

Given the enormous diversity of food and drinking water-related hazards no single approach can address all of the problems encountered and this means that it will probably always be difficult to directly compare the results of one risk assessment with another. This in turn makes it very difficult to prioritise risks and thus allocate resources in a rational way between them. We will probably therefore always have to rely upon expert assessment of the available information in order to judge between different risks and get our priorities right.

This does not mean, however, that there is no role for formalised risk assessment and no need for improvements in risk assessment methodologies. There are many examples where risk assessment can help us to identify and evaluate the factors involved in food-related risks. Tere is also vast scope for improving commonality between different procedures. For example, a common language of risk is vital if we are to be able to make any judgement about the results of different risk assessments. There is also a place for a common philosophy - for instance the expression "as low as reasonably practicable" has been well defined in the context of occupational health and this approach might find application in food risk assessments. Furthermore it should be possible to develop consistent standards so that the meanings of

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acceptable and tolerable risk when associated with food are well defined. This does not necessarily mean that they will always reflect the same probability of harm since what is acceptable in one set of circumstances may not be acceptable in another. What it should mean is that a common strategy has been applied to determine the acceptable risk in any particular context.

In conclusion it should be said that risk assessment is a management tool and its value should therefore be assessed in the terms of the results that are achieved with it. Food safety should always command a high priority above other considerations but there will always come a point at which the additional benefit to be achieved from providing an extra degree of freedom from risk is far outweighed by the sacrifices required to achieve it. We must always aim for the optimum and carry public opinion with us. Risk assessment can help us to achieve this. If risk assessment procedures take account of the context in which they are to be applied, if they use clear and unambiguous language and if they adopt a conservative approach without exceeding the limits of probability then they will provide a valuable tool for the management of food-related hazards and ultimately help us to get our priorities right.

It is important that those carrying out risk assessments of food hazards should make them accurate and consistent and use methodologies which are open to public scrutiny so that the public can understand the decisions taken. In turn consumer lobby groups must be sensible and rational in their demands for safety standards. Otherwise we might as well adopt a strategy where we ban everything which looks remotely hazardous, aim for the impossibly absurd standard of absolute safety and starve as a result!

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Figure2 Naturally occurring toxicants in food

DINNER MENU

Fresh Orange Juice Methanol

Mushroom Soup Agaritine and other mushroom hydrazines

Seafood Cocktail ParalyticshelUish poisoning Diarrhreticshellsh poisoning

Roast Beef Heterocyclic amines or Devilled (Pig) Kidneys Ochratoxin A, heterocyclic amines

Horseradish sauce or mustard Glucosinolates

Broccoli Glucosinolates, allyl isothiocyanategoitrin

Broad Beans Vici.ne, convicine, leclins

Potatoes Glycoalkaloids,phytoestrogens or a vegetarian alternative

Vegetarian Lasagne Deoxynivenol,fumontsins ohratoxin A tomatine, gycoalkaloids, apsacins, safrole, estragole, aflatoxin MI

Lemon Sorbet Psoralens

Plums in Brandy Ethyl carbamate, yanogenetic glycosides

Pistachio Nut Ice-cream Aflatoxins

Bread Rolls Ethyl carbarnate

Red Wine Alcohol, ethyl carbamate, tyramine

Coffee Caffeine

Herbal (Comfrey) Tea Pyrrolizidinealkaloids

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