INFORMATION SHEET
Number 4/00 September
2000
Food Standards Agency UK - DIOXINS AND PCBs
IN THE UK DIET: 1997 TOTAL DIET STUDY SAMPLES
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Key Facts
Summary
Background
Methodology
Results
Interpretation
References
Further Information
Spreadsheet Tables
- 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 2.54.5 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
Englands 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.
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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.
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.
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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.3The 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 1989.1,5
In 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.
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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 assigned7
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
7 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.
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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 contractors 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 1½-4½ 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.15-17
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 surveys12-14
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 NFS16,17 (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 NFS16,17 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.
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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.24-27
A 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.
Glossary of Terms
| 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.30,31
A 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.
|
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Summary of Units
| 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. |
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- Ministry of Agriculture,
Fisheries and Food. (1997). Dioxins and polychlorinated biphenyls
and foods and human milk. Food Surveillance
Information Sheet, 105. MAFF.
- Ministry of Agriculture,
Fisheries and Food. (1992). Dioxins in food. Food Surveillance
Paper, 31. HMSO.
- 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.
- 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.
- Ministry of Agriculture,
Fisheries and Food. (1983). Polychlorinated biphenyl (PCB) residues
in food and human tissues. Food Surveillance Paper, 16.
HMSO.
- Ministry of Agriculture,
Fisheries and Food/Department of Health. (1997). Food Safety
Information Bulletin, 88. MAFF.
- 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.
- 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.
- Ambidge, P.F. et al.
(1990). Acceptance criteria for analytical data on polychlorinated
dibenzo-p-dioxins and polychlorinated dibenzofurans. Chemosphere.
21, 999-1006.
- Central Science Laboratory.
(1999). PCDDs, PCDFs and PCBs in 1997 Total Diet samples. CSL
Report, FD98/119. Central Science Laboratory.
- Ministry of Agriculture,
Fisheries and Food. (1997). Dioxins and PCBs in retail cows' milk
in England. Food Surveillance
Information Sheet, 136. MAFF.
- Gregory, J. et al.
(1990). Dietary and Nutritional survey of British adults. HMSO.
- Department of Health. (1989).
The Diets of British schoolchildren. Report on Health and Social
Subjects, 36. HMSO.
- Gregory, J. et al.
(1995). National Diet and Nutrition Survey: children aged 1½
to 4½ years. Volume 1: report of the diet and nutrition survey.
HMSO.
- Ministry of Agriculture,
Fisheries and Food. (1984). Household Food Consumption and Expenditure
1982 Annual Report of the National Food Survey Committee.
HMSO.
- Ministry of Agriculture,
Fisheries and Food. (1994). National Food Survey 1992. HMSO.
- Ministry of Agriculture,
Fisheries and Food. (1998). National Food Survey 1997. HMSO.
- 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.
- 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.
- 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.
- Department of Health. (1994).
Nutritional Aspects of Cardiovascular Disease. Report on Health
and Social Subjects, 49. HMSO.
- Ministry of Agriculture,
Fisheries and Food. (1999). Dioxins and PCBs in UK and imported
marine fish. Food Surveillance
Information Sheet, 184. MAFF.
- 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.
- 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.
- 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.
- 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.
- 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.
- van Leeuwen, F.X.R. et
al. (2000). Dioxins: WHOs Tolerable Daily Intake (TDI)
revisited. Chemosphere. 40, 1095-1101.
- 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.
- Ministry of Agriculture,
Fisheries and Food. (1994). The British Diet: finding the facts.
Food Surveillance Paper, 40. HMSO.
- 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.
- Zanotto, E. et al.
(1999). PCDD/Fs in Venetian foods and a quantitative assessment
of dietary intake. Organohalogen Compounds. 44,13-17.
- Becher, G. et al.
(1998). Dietary exposure and human body burden of dioxins and
dioxin-like PCBs in Norway. Organohalogen Compounds. 38,
79-82.
- Jimènez, 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.
- Domingo, J.L. et al.
(1999). PCDDs and PCDFs in food samples from Catelonia, Spain.
An assessment of dietary intake. Chemosphere. 38,
3517-3528.
- Schecter, A. and Li, L.
(1997). Dioxins, dibenzofurans, dioxin-like PCBs, and DDE in U.S.
fast food, 1995. Chemosphere. 34, 1449-1557.
- 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.
- 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.
- Schrey, P. et al.
(1995). Dietary intake of PCDD/F by small children measured by
the duplicate method. Organohalogen Compounds. 30,
166-171.
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Further information on this survey can be obtained
from:
Dr Nigel Harrison
Food Standards Agency
Contaminants Division
PO Box 31037
Room 238, Ergon House
17 Smith Square
London SW1P 3WG
Tel: +44 (0) 20 7238 6235
Fax: +44 (0) 20 7238 5331
E-mail: nigel.harrison@foodstandards.gsi.gov.uk
Further copies of this Information Sheet can
be obtained from:
Information Centre
Food Standards Agency
PO Box 31037
Room 303b, Ergon House
17 Smith Square
London SW1P 3WG
Tel: +44 (0) 20 7238 6223
Fax: +44 (0) 20 7238 6330
E-mail: information.centre@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
Food Standards Agency
PO Box 30077
Room 651C, Skipton House
80 London Road
London SE1 6XZ
Tel: +44 (0) 20 7972 5023
Fax: +44 (0) 20 7972 5134
E-mail: akosua.adjei@foodstandards.gsi.gov.uk
A copy of the full report of this survey has
been placed in the Library, Nobel House, 17 Smith Square, London,
SW1P 3JR Tel. No. + 44 (0) 20 7238 6575. 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.
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Table 1: Estimated dietary
exposures to dioxins and dioxin-like PCBs estimated in other countries
Click here to download the
Excel 5.0 version of Table1
Click here to download the .csv version of Table
1 (if you have any other spreadsheet package)
Table 2: Concentrations
of dioxins and dioxin-like PCBs in TDS food group samples in 1982,
1992 and 1997.
Click here to download the
Excel 5.0 version of Table 2
Click here to download the .csv version of Table
2 (if you have any other spreadsheet package)
Table 3a: Estimated
upper bound mean dietary exposure of adults to dioxins and dioxin-like
PCBs in 1982, 1992 and 1997 (pg WHO-TEQ/kg bodyweight/day)
Click here to download
the Excel 5.0 version of Table 3a
Click here to download the .csv version of
Table 3a (if you have any other spreadsheet package)
Table 3b: Estimated
upper bound high level dietary exposure of adults to dioxins and
dioxin-like PCBs in 1982, 1992 and 1997 (pg WHO-TEQ/kg bodyweight/day)
Click here to download
the Excel 5.0 version of Table 3b
Click here to download the .csv version of
Table 3b (if you have any other spreadsheet package)
Table 4a: Estimated
upper bound mean dietary exposure of schoolchildren aged 10-15 years
to dioxins and dioxin-like PCBs in 1982, 1992 and 1997 (pg WHO-TEQ/kg
bodyweight/day)
Click here to download
the Excel 5.0 version of Table 4a
Click here to download the .csv version of
Table 4a (if you have any other spreadsheet package)
Table 4b: Estimated
upper bound high level dietary exposure of schoolchildren aged 10-15
years to dioxins and dioxin-like PCBs in 1982, 1992 and 1997 (pg
WHO-TEQ/kg bodyweight/day)
Click here to download
the Excel 5.0 version of Table 4b
Click here to download the .csv version of
Table 4b (if you have any other spreadsheet package)
Table 5a: Summary of
estimated upper bound mean dietary exposures of all age groups to
dioxins and dioxin-like PCBs in 1982, 1992 and 1997 (pg WHO-TEQ/kg
bodyweight/day)
Click here to download
the Excel 5.0 version of Table 5a
Click here to download the .csv version of
Table 5a (if you have any other spreadsheet package)
Table 5b: Summary of
estimated upper bound high level dietary exposure of all age groups
to dioxins and dioxin-like PCBs in 1982, 1992 and 1997 (pg WHO-TEQ/kg
bodyweight/day)
Click here to download
the Excel 5.0 version of Table 5b
Click here to download the .csv version of
Table 5b (if you have any other spreadsheet package)
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These pages were last updated 31 August 2000