Food Standards Agency UK - Dioxins and PCBs in the UK Diet: 1997 Total Diet Study (Number 04/00)

• Dioxins and polychlorinated biphenyls (PCBs) were analysed in samples of the food groups which made up the 1997 UK Total Diet Study.
• The estimated exposure of adults and schoolchildren to dioxins and dioxin-like PCBs from the UK diet has fallen since 1992 and are within both the current UK safety guideline (Tolerable Daily Intake - TDI) and the proposed World Health Organization TDI.
• Exposures to dioxins and dioxin-like PCBs from the diets of toddlers have also fallen. The exposures of toddlers aged 1.5-2.5 years consuming above average amounts of food are at the current UK safety guideline; those of toddlers aged 2.5-4.5 years are within the current UK safety guideline. These toddler groups would exceed the TDI proposed by the World Health Organization (WHO), although this TDI has not yet been endorsed in the UK, and the extent to which it is particularly relevant to toddlers is not clear. For this reason, pending a detailed review of the WHO TDI, the Chief Medical Officer for England's advisory committee, the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) does not recommend any changes to the diets of toddlers.
• The COT has concluded that the results of the survey show that dioxins and dioxin-like PCBs in food are unlikely to pose a risk to health. Consumers of all age groups are therefore not recommended to alter their diets on the basis of these results.

The UK Total Diet Study (TDS) is used to provide information on dietary exposures of the general UK population to chemicals such as nutrients and contaminants. Previous Total Diet surveys carried out by the Ministry of Agriculture, Fisheries and Food (MAFF) showed that estimated dietary exposures of UK consumers to dioxins and dioxin-like polychlorinated biphenyls (PCBs) fell substantially between 1982 and 1992.¹ The current survey was carried out to produce new estimates of dietary exposure to these chemicals in the UK. This allows the Food Standards Agency to check that exposures to these chemicals do not give cause for health concern and to assess time trends in exposure.

For adults, the estimated average and high level (97.5th percentile) dietary exposures to dioxins and dioxin-like PCBs via the whole diet, expressed as World Health Organization Toxic Equivalents (WHO-TEQs), were respectively:

• 1.8 and 3.1 pg WHO-TEQ/kg bodyweight/day in 1997; compared with
• 2.5 and 4.3 pg WHO-TEQ/kg bodyweight/day in 1992; and
• 7.2 and 13 pg WHO-TEQ/kg bodyweight/day in 1982.

For schoolchildren, the estimated average and high level dietary exposures to dioxins and dioxin-like PCBs via the whole diet were respectively:

• 2.2 and 3.5 pg WHO-TEQ/kg bodyweight/day in 1997; compared with
• 3.0 and 4.7 pg WHO-TEQ/kg bodyweight/day in 1992; and
• 8.6 and 15 pg WHO-TEQ/kg bodyweight/day in 1982.

For toddlers (1.5-4.5 years), depending on the age range, the estimated combined average and high level dietary exposures to dioxins and dioxin-like PCBs via the whole diet were respectively:

• 4.0-5.1 and 6.9-10 pg WHO-TEQ/kg bodyweight/day in 1997; compared with
• 5.6-7.6 and 9.2-14 pg WHO-TEQ/kg bodyweight/day in 1992; and
• 17-23 and 33-49 pg WHO-TEQ/kg bodyweight/day in 1982.

(Some of the documents referred to on this Information Sheet can be found through a link in the see also box, top right of this page) The dietary exposures above were all estimated using consumption data from dietary surveys of individual consumers of different age groups, and show a further decline since 1992. Population dietary exposures are estimated using information on household food purchases. The estimated population average dietary exposures to dioxins and dioxin-like PCBs via the whole diet also show a decline and were respectively:

• 1.7 pg WHO-TEQ/kg bodyweight/day in 1997; compared with
• 2.4 pg WHO-TEQ/kg bodyweight/day in 1992; and
• 7.5 pg WHO-TEQ/kg bodyweight/day in 1982.

The estimated exposures of adults, schoolchildren and all but the youngest toddlers are within the UK Tolerable Daily Intake (TDI) of 10 pg WHO-TEQ/kg bodyweight/day recommended by the independent expert Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT). The estimated high level exposures of toddlers aged 1.5-2.5 years are at the UK TDI.

The estimated exposures of adults and schoolchildren are also within the upper end of the range of the TDI of 1-4 pg WHO-TEQ/kg bodyweight/day recommended by WHO. The available data suggest that approximately 50 per cent of toddlers will exceed the upper value of the WHO TDI.

Estimated exposures for all age groups have declined substantially since 1982 and are anticipated to decline further still in the future. The available data indicate that approximately 50 per cent of toddlers will exceed the WHO TDI. However, it is not clear to what extent the WHO TDI is particularly relevant to toddlers. Therefore, pending a detailed review of the WHO TDI, and despite the fact that toddlers may exceed the WHO TDI, the COT does not recommend any changes to the diets of toddlers. The COT has concluded that the current concentrations of dioxins and dioxin-like PCBs in food are unlikely to pose a risk to health. Consumers of all age groups are therefore not recommended to change their diets on the basis of the results of this survey.

The term "dioxins" refers to two groups of closely related compounds, individually referred to as congeners. There are 75 polychlorinated dibenzo-p-dioxins (PCDDs) and 135 polychlorinated dibenzofurans (PCDFs). Of these two groups, 17 have been shown to be toxic to certain species of laboratory animals..² One of the compounds, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), may also be cancer producing in humans, and dioxins have been implicated in disrupting the endocrine systems in humans and wildlife. They are produced in small amounts during most combustion processes, both industrial and domestic, and may be formed as unwanted by-products in the manufacture of certain chemicals. Strict controls on the emissions of dioxins and PCBs from industrial processes came into effect from 1992 under Integrated Pollution Control Regulations. Stringent regulation of these emissions will continue under the Pollution Prevention and Control Regulations 2000, which implement Council Directive 96/61/EC..³ The regulations came into force on 1 August 2000 for new processes and will be phased in by industry sector up to 2007 for existing processes.

PCBs are another group of closely related chemicals. A few exhibit toxicity similar to those of the toxic dioxins and are therefore described as being "dioxin-like". In the United Kingdom, PCBs have been used since the early 1930s. The manufacture and general use of PCBs ceased in the mid 1970s and was banned under The Control of Pollution (Supply and Use of Injurious Substances Regulations 1986) (S.I. 1986 No. 902), as amended. The only remaining use of PCBs in the UK is sealed inside some older electrical equipment but these PCBs must be phased out and destroyed by the end of 2000 under the UK PCB Regulations.⁴ PCBs must be disposed of in an environmentally sound manner and are generally destroyed by high temperature incineration or dechlorination processes.

Dioxins and PCBs do not degrade easily and so are widespread in the environment. They are generally present at low concentrations in most foods, especially fat-containing foods such as milk and meat. As a result of emissions and past usage, their persistence and their tendency to bioaccumulate, it is likely to take many years for the full effect of control measures to be realised.

Previous surveys
MAFF has carried out surveys for dioxins and PCBs in food since 1989.¹,⁵In particular, samples of the composite food groups from the 1982 and 1992 Total Diet Studies (TDS) were analysed at the same time. The design of the TDS is described more fully in the glossary, but involves the preparation of a number of food group samples, each representing a major category of food, e.g. carcase meat, milk, etc.

Analysis for dioxins and PCBs is expensive and time consuming. Consequently, in the 1982 and 1992 TDS surveys, analysis was restricted to the eleven food groups considered likely to contribute most significantly to the estimated dietary exposure to dioxins and PCBs.¹ These eleven groups were selected either because they have significant fat contents (e.g. milk, meat, fish), and/or because they are consumed in large amounts by the majority of the population (e.g. milk, bread). Dietary exposures from the remaining food groups (fruit, vegetables, sugar and nuts) were estimated by assuming that each dioxin and PCB was present in each of those food groups at its limit of determination on a fresh weight basis. As samples from the 1982 and 1992 TDS were analysed concurrently, the same limits of determination were used for both years. In practice, it is probable that the concentrations fell between 1982 and 1992, as was generally found for the food groups that were analysed. The estimated dietary exposures of all age groups fell sharply between 1982 and 1992.¹

The current study involves analysis of the 1997 TDS food group samples and gives a more up-to-date estimate of the dietary exposure to dioxins and PCBs of UK consumers. In contrast to the previous TDS surveys carried out by MAFF, all food groups with the exception of the beverage food group, 19 in total, were analysed in this survey. Brand names are not available, as TDS samples are composites of a number of different foods.⁶

Toxic Equivalents
Except in Table 1, analytical results for dioxins and dioxin-like PCBs in this report are expressed in terms of World Health Organization Toxic Equivalents (WHO-TEQs).⁷ The use of Toxic Equivalents allows an assessment of the toxicological significance of the complex mixtures of dioxin and dioxin-like PCB congeners found in foods. The concept of Toxic Equivalents is explained in detail in the glossary. Estimates of dietary exposures have also been made in other countries, and details of some comparative studies are given in Table 1. As the use of WHO-TEQs is relatively recent, dietary exposure estimates for dioxins and PCBs are still mostly being reported in the open literature in terms of the previously agreed International Toxic Equivalents (I-TEQs), as was the case when MAFF published the 1982 and 1992 TDS surveys.¹ Since the results for individual dioxins and PCBs are seldom included, the results cannot be re-expressed as WHO-TEQs. For this reason the estimated dietary exposures in Table 1 only of this report (including those of the current survey) are reported in terms of I-TEQs.

The analytical methodology for determining dioxins and PCBs concentrations in food has been reported previously.¹,⁸ In the current survey, the 17 dioxins congeners of toxicological significance and the following dioxin-like PCB congeners were analysed: PCBs 77, 81, 126 and 169 (non-ortho PCBs); and 105, 114, 118, 123, 156, 157, 167 and 189 (ortho PCBs). All of the 17 dioxins and the 12 dioxin-like PCBs congeners to which a WHO-TEF has been assigned.⁷ are included. The following additional PCBs congeners were also analysed: 18, 28, 31, 47, 49, 51, 52, 99, 101, 128, 138, 180 and 153. These were selected as they have other non-dioxin-like toxic effects, are routinely analysed by the International Committee for the Exploration of the Sea (sometimes referred to as the 'ICES' congeners), and/or are commonly reported to occur in food and/or in human milk.

All samples were analysed by high resolution gas chromatography coupled with high or low resolution mass spectrometry (GC-MS) at CSL. The laboratory has participated in inter-laboratory trials of measurement of dioxins and PCBs in human milk and human blood organised by the WHO and has recognised expertise in the analysis of foods for dioxins and PCBs. The reporting limit for ortho PCBs in this survey was set to 0.05 microgram/kg fat. Analytical difficulties led to variation in the limits of determination (LODs) for dioxins and non-ortho PCBs, on a fat basis. In these cases the reporting limit was the LOD that prevailed in that instance. All analytical data were assessed for compliance with published acceptance criteria.⁹ Unless otherwise stated, the concentrations reported for this survey and dietary exposures calculated from them are upper bound values. Upper bound concentrations assume that all individual dioxins and PCBs that are present at concentrations below the reporting limit are present at the reporting limit, and therefore may be an overestimate of the true concentrations. By contrast, lower bound concentrations assume that all individual dioxins and PCBs that are present at concentrations below the reporting limit are absent, and therefore underestimate the true concentrations. The true concentrations will lie somewhere between the lower and upper bound values. For most of the fat containing food groups in the current survey, there was little difference between the lower and upper bound values as most congeners were present at measurable concentrations. For the other food groups the lower bound concentrations were typically around 50 per cent of the upper bound values.

The coefficients of variation from analyses of reference materials, obtained by the laboratory over a long period of time, are approximately 10 per cent for dioxins and non-ortho PCBs and 5 per cent for ortho PCBs. The coefficients of variation for the analysis of the food group samples in the current study are likely to be of a similar order.

This report presents the results for dioxins and dioxin-like PCBs in food groups from the 1997 TDS survey, expressed as WHO-TEQs. The upper bound concentrations of dioxins and dioxin-like PCBs found in the samples are presented in Table 2. For comparison, the concentrations found in the 1982 and 1992 TDS survey food group samples,1 re-expressed as WHO-TEQ, are also shown. Full congener-specific fat basis concentrations, and fresh weight concentrations as WHO-TEQs, for the current survey are available in the contractor's final report.10

The concentrations of dioxins and dioxin-like PCBs in the fresh fruit and the fruit products food groups appear to be relatively high when expressed on a fat basis. However, these two food groups have very low fat contents (0.14 and 0.30 per cent respectively in the current survey). The concentrations of dioxins and dioxin-like PCBs in these food groups on a fresh weight basis are low (0.019 and 0.010 ng WHO-TEQ/kg fresh weight for total dioxins and dioxin-like PCBs respectively).¹⁰ It is the fresh weight and not the fat basis concentrations which are used to estimate dietary exposures (see below and glossary).

Comparisons of concentrations of dioxins and PCBs in 1997 with those found in 1992 and 1982 can only be made for those food groups in which most individual congeners were present at detectable levels. Concentrations of dioxins were generally lower in most food groups in 1997 than those found in the 1992 and 1982 TDS survey. This is most noticeable in the poultry, offals, milk and eggs food groups, especially for eggs. In the meat products, oils and fats, and milk products food groups there appeared to be slight increases in dioxins concentrations in 1997 compared with 1992, although they may not be significant. In the case of dioxin-like PCBs, there were increases in the concentrations between 1992 and 1997 in most of the food groups, especially in the carcase meat, poultry, meat products and milk products food groups, but there were decreases in those of the milk and eggs food groups. The reasons for the apparent increase in dioxin-like PCB concentrations in several food groups is not clear. The combined concentrations of dioxins and dioxin-like PCBs decreased in the offals, and especially in the milk food groups, increased in the meat products food group, but showed relatively little change in the remaining food groups. The general fall in concentrations of dioxins between 1992 and 1997 is in line with that found previously in retail cows' milk.¹¹

Two types of dietary exposures were estimated from the results of the analysis of the TDS samples:
(i) consumer exposure and
(ii) population exposure.

Consumer exposure
Dietary exposures of UK consumers to dioxins and dioxin-like PCBs were estimated from the fresh weight concentrations using consumption data from the Dietary and Nutritional Survey of British Adults¹² and the Diets of British Schoolchildren.¹³ Food consumption data for toddlers from the National Diet and Nutrition Survey (NDNS) of children aged 1.5-4.5 years were used,¹⁴ but the consumption data for foods produced specifically for toddlers cannot yet be taken into account in exposure estimates generated from Total Diet Study surveys. When the results of the 1982 and 1992 TDS surveys were published, provisional estimates of toddlers exposures were made on the assumption that the variety and proportions of foods eaten by toddlers were the same as those of the foods eaten by adults.1 However, the use of consumption data from the Toddlers survey provides a more robust estimate of dietary exposure and this revised method of estimation has been supported by the COT (Annex 1 ). Accordingly, these consumption data have been used to estimate all the dietary exposures of toddlers in this report. For comparison, dietary exposures of toddlers in 1982 and 1992 have also been similarly re-estimated.

Consumer dietary exposure estimates via individual food groups are given for 1982, 1992 and 1997 in Tables 3a and 3b for adults, and in Tables 4a and 4b for schoolchildren. A summary of total dietary exposures of all age groups including toddlers is presented in Tables 5a and 5b. For comparison, the dietary exposures estimated from the 1982 and 1992 TDS surveys¹ have also been re-expressed as WHO-TEQs. To assist with following time trends in the data, the total average adult dietary exposures to dioxins and dioxin-like PCBs are plotted in Figure 1.

The estimated dietary exposures reflect the concentrations of dioxins and dioxin-like PCBs found in the individual food groups. Concentrations as measured may change both as a result of 'real' concentration changes and of changes in composition of the food groups with changes in household consumption patterns. The composition of the TDS samples is based on the National Food Survey (NFS) and is updated annually.¹⁵ The NFS provides information on household food purchases and takes no account of consumption by individuals within a household. However, it should be noted that the adults, schoolchildren and toddler surveys¹² have each only been carried out once, although the National Diet and Nutrition Survey (NDNS) of young people aged 4-18 years has been published since the calculations for the current survey were carried out.¹⁸ This means that the same consumption data have been used to estimate the dietary exposures from each of the three years TDS surveys. Exposures estimated using the dietary surveys do not therefore fully take account of changes in individual dietary habits which have occurred during the period 1982-1997.

The estimated upper bound average and high level (97.5th percentile) combined dietary exposures to dioxins and dioxin-like PCBs through the total diet in 1997 are as follows:

• 1.8 and 3.1 pg WHO-TEQ/kg body weight/day respectively for adult consumers;
• 2.2 and 3.5 pg WHO-TEQ/kg body weight/day respectively for schoolchild consumers;
• and 4.0-5.1 and 6.9-10 pg WHO-TEQ/kg body weight/day respectively for toddler consumers, decreasing with increasing age range.
• The lower bound dietary exposures are approximately 85 per cent of the corresponding upper bound values.

The estimated dietary exposures of all age groups to dioxins have fallen between 1992 and 1997. For example, the estimated average dietary exposures of adults to dioxins have fallen from 1.6 to 0.9 pg WHO-TEQ/kg bodyweight/day. However, the estimated average dietary exposures of adults to dioxin-like PCBs are unchanged at 0.9 pg WHO-TEQ/kg bodyweight/day in both years. A survey in Canada of market basket food samples for PCBs obtained from Toronto showed that the estimated dietary exposure to PCBs (measured as the sum of individual PCBs) fell by only a small amount between 1992 and 1996 (from 6.05 to 5.71 ng/kg bodyweight/day).¹⁹ Dioxins were not analysed in that survey.

Data from the NFS ^16,17 (see below) indicate that the contributions of saturated fat from the eleven food groups analysed in the 1992 TDS fell from 32 g in 1992 to 28 g in 1997. Dioxins and PCBs are primarily found in the fat component of the diet, especially in the saturated fat in foods derived from animals. This is because animals can accumulate dioxins and PCBs as a result of their environmental exposure. The fall in the amount of saturated fat in the diet may have contributed to the observed decrease in average dietary exposures from the meat products and carcase meat food groups. The general switch towards eating more poultry and less red meats has probably also contributed to the decrease in dietary exposures. Red meat is represented by the carcase meat food group, which has higher fresh weight concentrations of total dioxins and dioxin-like PCBs than the poultry food group.

The NFS ^16,17 also shows that there has been a fall between 1992 and 1997 in total fat (the sum of saturated, monounsaturated and polyunsaturated fats) from the eleven food groups analysed in both years in the diet from 79 to 69 g. The increase in the proportion of dietary fat that is of vegetable rather than animal origin, may also have contributed to the observed decrease in overall dietary exposure. Polyunsaturated fats are derived mainly from plants, and since uptake of dioxins and PCBs by plants from soil is known to be very low, this type of fat would be expected to accumulate less dioxins and PCBs than saturated fat.²⁰ Another change which may have resulted in decreasing dietary exposure to dioxins and dioxin-like PCBs is the increasing popularity of vegetarian and vegan foods. The NFS shows that household purchases of novel protein foods (e.g. soya bean curd) more than doubled between 1992 and 1997.

On the other hand, the NFS shows that household purchases of oily fish (other than herring) rose by 44 per cent between 1992 and 1997.^16,17 Oily fish are rich sources of certain long chain polyunsaturated fatty acids (PUFAs), which are beneficial in reducing mortality from heart disease. The Committee on Medical Aspects of Food Policy (COMA), has advised that individuals should eat at least two portions of fish, one of which should be oily fish, per week as part of a balanced diet.²¹ The concentrations of dioxins and especially of PCBs in the fish group are higher than those in the various meat (except dioxins in offals) and fruit and vegetable food groups. Fish may be a significant source of these chemicals in the diet. However, the COT advised that consumers should continue to follow the COMA advice regarding fish consumption because of the demonstrated health benefits.^22,23

Dietary exposures from the food groups which were not analysed in the 1982 and 1992 TDS surveys (fruit, vegetables, sugar and nuts) were estimated by assuming that each dioxin and PCB was present in each of those food groups at its limit of determination on a fresh weight basis. As samples from the 1982 and 1992 TDS were analysed concurrently, the same limits of determination were used for both years. Because of improvements in the analytical methodology since the 1982 and 1992 TDS samples were analysed, lower LODs were generally achieved in the current survey, and the reporting limit for ortho PCBs could be set at a lower level. The concentrations of dioxins and PCBs which could be measured in the current survey were generally lower in most of the food groups not analysed in the 1982 and 1992 surveys than the previously assumed concentrations used to estimate dietary exposures from those groups. The main exceptions to this were for the sugar and preserves and the nuts food groups, which contained higher concentrations in 1997 than those assumed for the 1982 and 1992 surveys.

Population exposure
One way of further testing the possible influence of changes in dietary habits on dietary exposure estimates is to compare dietary exposures as estimated from the NFS. Multiplying the amounts of foods consumed (based on consumption data from the appropriate years of the NFS) by the corresponding mean concentrations of dioxins and dioxin-like PCBs detected in each TDS food group gives an estimate of population average exposure (covering both adults and children) for that year. These estimates can be used to follow trends in exposure as they take into account changes in both consumption of the various foods making up the general UK diet and in concentrations of dioxins and PCBs in these foods. However, the NFS does not provide information on who within a household actually eats the food purchased, and estimates of high level dietary exposure cannot be made using the NFS. It is the dietary exposures of consumers, as estimated from the dietary surveys (Tables 3a-5a, 3b-5b), rather than those of households as estimated from the NFS, which are compared with safety guidelines when assessing any possible risk to human health. The population average dietary exposures to dioxins and dioxin-like PCBs, estimated using the NFS, are shown in Table 5a. The estimated upper bound population average dietary exposures to dioxins and dioxin-like PCBs through the total diet were 1.7 pg WHO-TEQ/kg bodyweight/day in 1997, compared to 2.4 pg WHO-TEQ/kg bodyweight/day in 1992 and 7.5 pg WHO-TEQ/kg bodyweight/day in 1982. The estimated dietary exposures to dioxins and PCBs in the current survey are broadly similar to those found in other countries (Table 1). It should be noted that the designs of these surveys and the consumption data used vary from one country to another, and therefore some caution must be exercised in making comparisons.

The UK Tolerable Daily Intake (TDI) for mixtures of dioxins and dioxin-like PCBs is 10 pg WHO-TEQ/kg bodyweight per day. This TDI was recommended in 1997 by the COT.^24-27A WHO-European Centre for Environment and Health/International Programme on Chemical Safety (ECEH/IPCS) consultation has proposed a TDI of 1-4 pg TEQ/kg body weight per day for dioxins and dioxin-like PCBs.²⁸ The COT will undertake a review of the data used to derive this recently proposed TDI now that a full report of the consultation is available.²⁹ In the interim, the COT has considered the results of this survey against both TDIs. The COT statement on the current survey is included in Annex 1 of this report.

The estimated mean consumer dietary exposures of adults, children and toddlers to dioxins and dioxin-like PCBs via the total diet in 1997 are all below the UK TDI. The estimated high level consumer dietary exposures of adults, children and of most toddlers to dioxins and dioxin-like PCBs are also below the UK TDI. The estimated high level dietary exposure of toddlers in the youngest age range (1.5-2.5 years) is at the UK TDI. The estimated average and high level dietary exposures of adults and schoolchildren via the total diet in 1997 are also estimated to be within the recently recommended WHO TDI, but the estimated dietary exposures of toddlers are all at or above the upper end of the range of the recently recommended WHO TDI. For the youngest age group, average consumption is estimated to exceed the WHO TDI by 28 per cent, and high level toddler consumption to exceed it approximately two-fold. However, despite the fact that toddlers may exceed the WHO TDI, estimated exposures for all age groups have declined substantially since 1982 and are anticipated to decline further still in the future. The COT has concluded that the current concentrations of dioxins and dioxin-like PCBs in food are unlikely to pose a risk to health. Consumers of all age groups are therefore not recommended to change their diets on the basis of the results of this survey.

Dietary exposure
Dietary exposures (also referred to as dietary intakes) are estimates of the amount of a contaminant which is present in a given food(s) eaten during a given time period, usually a day. These estimates are then compared with the Tolerable Daily Intake (TDI - see below). Dietary exposures may be given per person, or more usually as in this report, on a body weight basis. This is done by dividing the per person exposures by an appropriate body weight. When expressed in this way it is easier to compare dietary exposures across the different age groups.

Dietary survey
In dietary surveys, the amounts of all foods eaten by each of a number of individual consumers during a given time period are recorded. From these surveys, the consumer average and the high level consumptions of a food or combination of foods can be estimated. These consumption data are used to estimate dietary exposures to contaminants. The dietary surveys used in this report are the adults survey (age 16-64),¹² the schoolchildren survey (ages 10-11 and 14-15)¹³ and the toddlers survey (age 1.5-4.5).¹⁴

Fat basis concentration
The amount of a contaminant which is present in a given weight of the fat of a food. For chemicals such as dioxins and PCBs, which tend to be found mainly in the fat of foods, it is common practice in the UK and other countries to express concentrations in this way. It is easier to compare such concentrations in a given food in different surveys and to follow time trends. If the fat content of a food is very low, as with the fresh fruit and fruit products food groups in the current survey, the fat basis concentrations may appear to be rather high. The amount of contaminant in the whole food as actually eaten (the fresh weight concentration - see below) may be relatively low.

Fresh weight concentration
The amount of a contaminant which is present in a given weight of the whole food as it is actually eaten. It is the fresh weight concentrations and not fat basis concentrations given in Table 2 which are used to estimate the dietary exposures to dioxins and dioxin-like PCBs.

Limit of determination (LOD)
The lowest concentration of a chemical that is measurable with confidence by the analytical method used. For compounds such as dioxins which are present at very low levels and require very sensitive analysis, the LOD achieved can vary between the individual compounds due to analytical difficulties.

National Food Survey (NFS)
This is a continuous survey which provides information on the types and quantities of food purchased by households on an annual basis. Since 1994, the NFS has also reported on food consumed outside the home.

Tolerable Daily Intake
The maximum amount of a contaminant which can be eaten every day over a whole lifetime without incurring appreciable risk to health. Tolerable Daily Intakes (TDIs) may be given per person, or more usually as in this report, on a body weight basis. For example, the UK TDI for dioxins and dioxin-like PCBs is 10 pg WHO-TEQ/kg bodyweight/day.²³

Total Diet Study
The Total Diet Study is a model of the average domestic diet in the UK.^30,31A total of 121 categories of food and drink are specified for inclusion in the Total Diet. These are assigned to one of twenty broad food groups. Foods are grouped so that commodities known to be susceptible to contamination (e.g. offals and fish) are kept separate, as are foods which are consumed in large quantities, e.g. bread, potatoes, milk. The quantities and relative proportions of each food that make up the Total Diet are largely based on data from the National Food Survey and are updated annually. Food samples are purchased fortnightly from 24 randomly selected locations representative of the UK as a whole. The food samples are prepared and cooked according to normal consumer practice. The constituents of each food group are then homogenised and frozen. Samples can be analysed for a range of food constituents.

Toxic Equivalent
Dioxins and dioxin-like PCBs in food occur as mixtures of a number of different individual chemicals which have different degrees of dioxin-like toxicity. The concentration of each individual dioxin and dioxin-like PCB is multiplied by a weighting factor (referred to as a Toxic Equivalency Factor - TEF) which reflects its toxicity relative to that of the most toxic dioxin. The weighted concentrations are then added together to give the Toxic Equivalent (TEQ). The system of TEFs set by the World Health Organization in 1997 (WHO-TEFs) is used in this report.⁷ However, most results in the published literature, including the report of the MAFF survey of 1982 and 1992 TDS samples,¹ are still in terms of the previous widely used International Toxic Equivalency Factors (I-TEFS) set in 1988 for dioxins and the TEFs recommended in 1994 for dioxin-like PCBs. Compared to concentrations expressed as I-TEQs, those expressed as WHO-TEQs are typically about 15 per cent higher for dioxins and marginally lower for dioxin-like PCBs, resulting in a net increase for combined concentrations. The actual difference depends on the distribution of individual dioxins and PCBs in the sample.

microgram: a microgram is one millionth of a gram (g)
kg: a kilogram (kg) is one thousand grams (g).
ng: a nanogram (ng) is one thousand millionth of a gram (g).
pg: a picogram (pg) is one million millionth of a gram (g).
ng WHO-TEQ/kg: nanograms of WHO Toxic Equivalents per kilogram; equivalent to parts per million million (parts per trillion) by weight
pg WHO-TEQ/kg: picograms of WHO Toxic Equivalents per kilogram; equivalent to parts per thousand million million (parts per quadrillion) by weight.
pg I-TEQ/kg bw/day: picograms of International Toxic Equivalents per kilogram of bodyweight per day; equivalent to parts per thousand million million (parts per quadrillion) by weight.

1. Ministry of Agriculture, Fisheries and Food. (1997). Dioxins and polychlorinated biphenyls and foods and human milk. Food Surveillance Information Sheet, 105. MAFF.
2. Ministry of Agriculture, Fisheries and Food. (1992). Dioxins in food. Food Surveillance Paper,31. HMSO.
3. European Commission. (1996). Council Directive 96/61/EC on Integrated Pollution Prevention and Control. Official Journal of the European Communities,L 257, 10 October 1996, 26.
4. Department of the Environment. (2000). The Environmental Protection (Disposal of Polychlorinated Biphenyls and other Dangerous Substances) (England and Wales) Regulations 2000. Statutory Instrument, 1043. Stationery Office.
5. Ministry of Agriculture, Fisheries and Food. (1983). Polychlorinated biphenyl (PCB) residues in food and human tissues. Food Surveillance Paper, 16. HMSO.
6. Ministry of Agriculture, Fisheries and Food/Department of Health. (1997). Food Safety Information Bulletin, 88. MAFF.
7. Van den Berg, M. et al. (1998). Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives. 106, 775-792.
8. Krokos, F. et al. (1997). Congener-specific method for the determination of ortho- and non-ortho polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in foods by carbon-column fractionation and gas chromatography-isotope dilution mass spectrometry. Fresenius Journal of Analytical Chemistry. 357, 732-742.
9. Ambidge, P.F. et al. (1990). Acceptance criteria for analytical data on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. Chemosphere. 21, 999-1006.
10. Central Science Laboratory. (1999). PCDDs, PCDFs and PCBs in 1997 Total Diet samples. CSL Report, FD98/119. Central Science Laboratory.
11. Ministry of Agriculture, Fisheries and Food. (1997). Dioxins and PCBs in retail cows' milk in England. Food Surveillance Information Sheet, 136. MAFF.
12. Gregory, J. et al. (1990). Dietary and Nutritional survey of British adults. HMSO.
13. Department of Health. (1989). The Diets of British schoolchildren. Report on Health and Social Subjects, 36. HMSO.
14. Gregory, J. et al. (1995). National Diet and Nutrition Survey: children aged 1.5 to 4.5 years. Volume 1: report of the diet and nutrition survey. HMSO.
15. Ministry of Agriculture, Fisheries and Food. (1984). Household Food Consumption and Expenditure 1982 - Annual Report of the National Food Survey Committee. HMSO.
16. Ministry of Agriculture, Fisheries and Food. (1994). National Food Survey 1992. HMSO.
17. Ministry of Agriculture, Fisheries and Food. (1998). National Food Survey 1997. HMSO.
18. Gregory J. et al. (2000). National Diet and Nutrition Survey: young people aged 4-18 years. Volume 1: report of the diet and nutrition survey. The Stationery Office.
19. Newsome, W.H., Davies, D.J. and Sun, W.F. (1998). Residues of polychlorinated biphenyl (PCB) in fatty foods of the Canadian diet. Food Additives and Contaminants. 15, 19-29.
20. Kew, G.A. et al. (1989). Review of plant uptake of 2,3,7,8-TCDD from soil and potential influences of bioavailability. Chemosphere, 18, 1313-1318.
21. Department of Health. (1994). Nutritional Aspects of Cardiovascular Disease. Report on Health and Social Subjects, 49. HMSO.
22. Ministry of Agriculture, Fisheries and Food. (1999). Dioxins and PCBs in UK and imported marine fish. Food Surveillance Information Sheet, 184. MAFF.
23. Department of Health. (1999). Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Statement on surveillance for PCDDs, PCDFs and PCBs marine fish and fish products. Department of Health.
24. World Health Organization, Regional Office for Europe. (1991). Summary Report. Consultation on Tolerable Daily Intake from food of PCDDs and PCDFs. Bilthoven, Netherlands, 4-7 December 1990. EUR/ICP/PCS 030(S) 0369n. WHO Regional Office for Europe, Copenhagen.
25. US Environmental Protection Agency. (1994). Health assessment document for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. US Environmental Protection Agency, Washington DC.
26. Department of Health. (1995). Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Statement on the US EPA draft health assessment document for 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds. Department of Health.
27. Department of Health. (1997). Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Statement on the health hazards of polychlorinated biphenyls. Department of Health.
28. van Leeuwen, F.X.R. et al. (2000). Dioxins: WHO's Tolerable Daily Intake (TDI) revisited. Chemosphere. 40, 1095-1101.
29. Van Leeuwen, F.X.R and Younes, M.M. eds. (2000). Assessment of the health risk of dioxins: re-evaluation of the tolerable daily intake (TDI). Organized by WHO European Centre for Enviornment and Health and International Programme on Chemical Safety. Food Additives and Contaminants. 17, 233-369.
30. Ministry of Agriculture, Fisheries and Food. (1994). The British Diet: finding the facts. Food Surveillance Paper, 40. HMSO.
31. Peattie, M.E. et al. (1983). Reorganisation of the British Total Diet Study for monitoring food constituents from 1981. Food and Chemical Toxicology. 21, 503-507.
32. Zanotto, E. et al. (1999). PCDD/Fs in Venetian foods and a quantitative assessment of dietary intake. Organohalogen Compounds. 44,13-17.
33. Becher, G. et al. (1998). Dietary exposure and human body burden of dioxins and dioxin-like PCBs in Norway. Organohalogen Compounds. 38, 79-82.
34. Jimenez, B. et al. (1996). Estimated intake of PCDDs, PCDFs and co-planar PCBs in individuals from Madrid (Spain) eating an average diet. Chemosphere. 33, 1465-1474.
35. Domingo, J.L. et al. (1999). PCDDs and PCDFs in food samples from Catelonia, Spain. An assessment of dietary intake. Chemosphere. 38, 3517-3528.
36. Schecter, A. and Li, L. (1997). Dioxins, dibenzofurans, dioxin-like PCBs, and DDE in U.S. fast food, 1995. Chemosphere. 34, 1449-1557.
37. Buckland, S.J. et al. (1998). Concentrations of PCDDs, PCDFs, and PCBs in New Zealand retail foods and an assessment of dietary exposure. Organohalogen Compounds. 38, 71-74.
38. Wittsiepe, J., Schrey, P. and Wilhelm, M. (1999). Dietary intake of PCDD/F by small children with different food consumption measured by the duplicate method. Organohalogen Compounds. 44, 289-294.
39. Schrey, P. et al. (1995). Dietary intake of PCDD/F by small children measured by the duplicate method. Organohalogen Compounds. 30, 166-171.

Further information on this survey can be obtained from:
Dr Nigel Harrison
Food Standards Agency
Contaminants Division
Room 703 Aviation House
125 Kingsway
London WC2B 6NH

Tel: +44 (0) 20 7276 8708
Fax: +44 (0) 20 7276 8477

Further copies of this Information Sheet can be obtained from:
Library & Information Services
Food Standards Agency
Ground Floor, Aviation House
125 Kingsway
London WC2B 6NH

Tel: +44 (0) 20 7276 8181
Fax: +44 (0) 20 7276 8069

Email:library&info@foodstandards.gsi.gov.uk
Copies of the full COT statement on the results of this survey can be obtained from: Ms Akosua Adjei COT Secretariat
E-mail: akousa.adjei@foodstandards.gsi.gov.uk

A copy of the full report of this survey has been placed in the Library & Information service, Aviation House, 125 Kingsway, London, WC2B 6NH. Tel. No. + 44 (0) 20 7276 8181. If you wish to consult it please contact the library for an appointment giving at least 24 hours notice or alternatively copies can be obtained from the library: a charge will be made to cover photocopying and postage.