Number 145 March 1998
MAFF UK - DIOXINS AND PCBs IN FARMED TROUT IN ENGLAND AND WALES
Index to MAFF UK Food Surveillance Information
Sheets, 1998
See also:
19: MAFF, UK -
Dioxins in Cows' Milk (November 1993)
43: MAFF, UK - Dioxins in Cows' Milk
(October 1994)
44: MAFF, UK -
Contaminants in Cows' Milk from the Clitheroe Area (October 1994)
71: MAFF, UK - Dioxins in Food - UK
Dietary Intakes (July 1995)
75:
MAFF, UK - Dioxins in Cows' Milk from the Bolsover Area (November 1995)
88: MAFF, UK - Dioxins in Human Milk (May
1996)
89: MAFF, UK -
Polychlorinated Biphenyls in Food - UK (May 1996)
100: MAFF, UK - Dioxins in Cows' Milk from
farms close to Industrial Sites (January 1997)
105: MAFF, UK - Dioxins and
Polychlorinated Biphenyls in Foods and Human Milk (June 1997)
106: MAFF, UK - Dioxins and
Polychlorinated Biphenyls in Fish Oil Dietary Supplements and Licensed Medicines
(June 1997)
107: MAFF, UK -
Dioxins and PCBs in Cows Milk from Farms Close to Industrial Sites (June 1997)
120: MAFF, UK - Dioxins in Cows' Milk from
Northern Ireland (August 1997)
123:
MAFF, UK - Dioxins and PCBs in Cows' Milk from farms close to Industrial Sites:
1996 Survey Results (August 1997)
124: MAFF, UK - Dioxins and PCBs in Cows'
Milk from the Bolsover Area (August 1997)
133: MAFF, UK - Dioxins and PCBs in Cows'
Milk from farms close to Industrial Sites: Rotherham 1997 (November 1997)
134: MAFF, UK - Dioxins and PCBs in Cows'
Milk from the Bolsover Area - October 1997 (November 1997)
135: MAFF, UK - Dioxins and PCBs in Cows'
Milk from farms close to Industrial Sites: Huddersfield 1997 (November 1997)
136: MAFF, UK - Dioxins and PCBs in Retail
Cows' Milk in England (December 1997)
143: MAFF, UK - Dioxins and PCBs in Cows'
Milk from the Bolsover Area Collected in October and November 1997 (March 1998)
184: MAFF UK - Dioxins and PCBs in UK and
Imported Marine Fish (August 1999)
Summary
MAFF has completed a survey for dioxins and polychlorinated biphenyls (PCBs)
in samples of farmed trout obtained from various locations in England and Wales.
The consumption of fish in the UK is increasing and this survey was carried out
to determine the range of concentrations of dioxins and PCBs in farmed trout
and, thus, to estimate the dietary intakes of these chemicals from the
consumption of these fish.
The concentrations of dioxins and PCBs, expressed as Toxic Equivalents
(TEQs), were in the range 12-60 ng TEQ/kg fat. Average and high level dietary
intakes of dioxins and PCBs via the consumption of trout alone, estimated from
the mean concentrations of dioxins and PCBs in this survey, are 0.41 and 0.66 pg
TEQ/kg bodyweight/day respectively. Estimated average and high level dietary
intakes of dioxins and PCBs via the consumption of trout in combination with the
rest of diet are 2.4 and 4.3 pg TEQ/kg bodyweight/day respectively. These
intakes are well below the Tolerable Daily Intake of 10 pg TEQ/kg bodyweight/day
endorsed by the Committee on Toxicity of Chemicals in Food, Consumer Products
and the Environment (COT). These results do not indicate the existence of any
health risk from the consumption of trout produced in England and Wales.
Background
Dioxins and PCBs are very persistent chemicals which are ubiquitous in the
environment and so are generally present in low concentrations in foods,
especially fat-containing foods such as fish. Further background information on
dioxins and PCBs can be found in Food Surveillance Information Sheets Nos.
105,
106 and
1071,2,3.
Analytical results for dioxins and PCBs are expressed in terms of Toxic
Equivalents (TEQs), which are explained in detail in Food Surveillance
Information Sheet No. 1051. This allows an assessment of the toxicological
significance of the complex mixtures of dioxin and PCB congeners found in foods.
MAFF has been conducting surveys for dioxins in food since 19894 and for PCBs in food since the 1960s5. All samples are analysed for the 17 dioxin congeners
of toxicological significance. The concentrations of dioxins in a small number
of retail samples of marine fish purchased in Norwich in 1988 were in the range
1.9-34 ng TEQ/kg fat basis, or 0.15-1.8 ng TEQ/kg fresh weight4. Combined concentrations of dioxins and PCBs in
samples of the fish groups of the 1982 and 1992 Total Diet Study (TDS) were 17.3
and 8.0 ng TEQ/kg fat basis, or 1.3 and 0.63 ng TEQ/kg fresh weight,
respectively1. The TDS consists of composite
samples and the fish group includes contributions from both marine and
freshwater fish in quantities reflecting their consumption in the UK. Except
for a survey on eels reported in Food Surveillance Information Sheet No.
1051,
no previous survey for dioxins in freshwater fish has been carried out by MAFF.
The current survey and the eels survey also represent the first surveys of
freshwater fish for PCB congeners1 carried out
by MAFF using analytical methodology capable of quantifying individual PCB
congeners.
For the current survey 40 samples of edible trout flesh were obtained during
the period October-December 1995, from trout farms across England and Wales by
Fish Health Inspectors from CEFAS, Weymouth, with the co-operation of the
British Trout Association. Analysis of the samples was not completed until 1997
due to pressure on the analytical facilities. Each sample consisted of several
fillets of muscle taken from different fish of similar age and size at each
location. This survey was started before the policy of naming brands was
introduced.
Methods
The analytical methodology for determining dioxin and PCB concentrations in
food has been reported previously1. In the
current survey the 17 dioxin congeners of toxicological significance and the
following PCB congeners were analysed: PCBs 77, 126, 169, 18, 28, 31, 47, 49,
51, 52, 99, 101, 105, 114, 118, 123, 128, 138, 153, 156, 157, 167, 180 and 189.
All samples were analysed by high resolution gas chromatography-high
resolution mass spectrometry (GC-MS) at the CSL Food Science Laboratory,
Norwich. The laboratory has participated in inter-laboratory trials of
measurement of dioxins and PCBs in human milk and human blood organised by the
World Health Organization and has recognised expertise in the analysis of foods
for dioxins and PCBs. The reporting limits in this survey are 0.25 ng/kg fat
for dioxins, 0.3 ng/kg fat for non-ortho PCBs and 0.13 micrograms/kg of
fat for ortho-PCBs.
The coefficient of variation for the analytical data is a measure of the
difference that may be expected between individual analyses of the same sample.
Reference materials were available for this survey, and good agreement was
achieved between actual and measured concentrations for individual congeners.
Based on other work, the coefficients of variation for the analysis of trout
were approximately 10 per cent for dioxins and non-ortho-PCBs and up to
5 per cent for
ortho-PCBs.
Results
This report presents the individual and total combined results for dioxins
and PCBs in trout samples collected during October-December 1995, expressed as
TEQs. The upper bound concentrations of dioxins and PCBs found in the
samples from the various sites are summarised in Table 1.
In summary, the results were:
- Dioxins concentrations were in the range 2.1-13 (mean 5.1) ng TEQ/kg fat,
or 0.06-0.67 (mean 0.24) ng TEQ/kg fresh weight.
- PCBs concentrations were in the range 8.9-51 (mean 19) ng TEQ/kg fat, or
0.22-2.4 (mean 0.87) ng TEQ/kg fresh weight.
- The combined dioxins and PCBs concentrations were in the range 12-60 (mean
24) ng TEQ/kg fat, or 0.29-3.1(mean 1.1) ng TEQ/kg fresh weight.
Full congener specific data are available on request. Measured fat contents
of the samples were in the range 1.8-8.6 per cent.
Dietary intakes of dioxins and PCBs have been estimated from these
concentrations using consumption data from the British Adult Study11. The average and high level (97.5th percentile)
consumption figures for trout by UK adults are 0.37 and 0.59 g/kg bodyweight/day
respectively. Multiplying these figures by the mean fresh weight concentrations
of dioxins and PCBs found in the current survey give estimated mean values for
average and high level dietary intakes from the consumption of trout alone of
0.41 and 0.66 pg TEQ/kg bodyweight/day respectively.
Total dietary intakes of dioxins and PCBs have previously been estimated to
be 2.4 and 4.2 pg TEQ/kg bodyweight/day respectively for average and high level
consumers, based on the concentrations of these chemicals found in 1992 Total
Diet Study (TDS) samples1. The 1992 TDS fish
group, as analysed, was a composite of different species purchased from each of
24 locations in the UK, and cannot therefore reflect localised contamination.
The dietary intakes of dioxins and PCBs by people who consistently consume trout
caught from the same location could potentially be elevated if that location was
affected by localised sources of dioxins and PCBs. Using the maximum
concentrations found in trout during the current survey and the concentrations
of dioxins and PCBs in the 1992 TDS fish group (8.0 ng TEQ/kg fat basis)1 for the other fish species, the mean and high level
dietary intakes of dioxins and PCBs via the consumption of trout sourced from a
single location, in combination with the rest of the diet, are estimated to be
up to 2.4 and 4.3 pg TEQ/kg bodyweight/day respectively.
Interpretation
Estimated dietary intakes of dioxins and PCBs are assessed against the
Tolerable Daily Intake (TDI) of 10 pg 2,3,7,8-TCDD/kg bodyweight/day set by the
World Health Organization Regional Office for Europe12.
The Committee on Toxicity of Chemicals in Food, Consumer Products and the
Environment (COT) has recommended that this TDI can be regarded as 10 pg TEQ/kg
bodyweight/day for mixtures of dioxins and PCBs4,9,13,14.
The estimated dietary intakes of dioxins and PCBs by mean and high level UK
consumers from trout alone (and in combination with the rest of the diet) are
all well below this TDI. In addition, the estimated intakes of dioxins and PCBs
from the consumption of trout and the rest of the diet are not significantly
higher for those who consume only trout taken from a single location even when
the trout is assumed to contain the maximum concentrations of dioxins and PCBs
recorded in this survey. The concentrations of dioxins and PCBs in the current
survey do not therefore constitute a health risk.
Statistical analysis of the individual results (Table
1) indicates that for many of the samples the concentrations of dioxins and
PCBs fell within relatively well defined ranges. One sample (2459) had the
highest concentrations of both dioxins (13 ng TEQ/kg fat) and ortho-PCBs
(11 ng TEQ/kg fat), and the second highest concentrations of non-ortho-PCBs
(36 ng TEQ/kg fat). Several individual dioxins and PCB congeners were also
present at elevated concentrations compared with other samples in this survey.
This sample is statistically different from the other samples for concentrations
of both dioxins and PCBs, expressed as TEQs, and for the concentrations of many
of the individual congeners. The estimated intake of dioxins and PCBs from
consumption of this sample would not give cause for health concern but the
possible reasons for this difference are being investigated.
The concentrations of dioxins in these samples are lower than those found in
the 1989 retail fish survey4, and this is in
line with the general fall in concentrations of dioxins in food between 1982 and
19921. However it should be noted that only a
small number of samples were analysed in the 1989 survey, and their ages and
sizes were not recorded. The concentrations of dioxins and PCBs in the farmed
trout are higher than those found in the 1992 TDS fish group. This may reflect
the fact that the TDS fish group is a mixture of several fish species. The TDS
fish group also contains fish products which may include other ingredients (e.g.
breadcrumbs) which may be expected to have lower concentrations of dioxins and
PCBs.
The concentrations of dioxins in trout found in the current survey are lower
than those (44 ng TEQ/kg fat basis) found for brown trout taken in 1993 in a
survey of five freshwater fish species in UK lakes by other workers15. None of these lakes were in the vicinity of
potential sources of dioxins and PCBs. However the surveys are not directly
comparable. The ages of the trout are not specified in that survey, and whole
fish (including the possibility of sediment in the gut) were analysed as opposed
to just the edible portions as in the MAFF survey.
In various freshwater species in Lake Ontario (from an area in the vicinity
of potential sources of dioxins) concentrations of 2,3,7,8-TCDD (the only
congener reported) exceeding 5 ng/kg were found in 30 out of 98 samples of
edible tissues16 compared with the highest
measured concentration of 0.09 ng/kg in the MAFF survey, assuming the US data
are fresh weight concentrations. The age of the fish is unclear and no further
comparison is possible due to the high limit of detection in the US survey. In
a survey of various species of freshwater fish in Taiwan, concentrations of
dioxins and PCBs were in the range 0.12-0.65 ng TEQ/kg dry weight, or
approximately 0.5-2.5 ng TEQ/kg fresh weight. Most of these samples were taken
from the vicinity of an incinerator and were either of single fish or composites
of a number of smaller fish17.
References
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and Polychlorinated Biphenyls in
Foods and Human Milk. Food Surveillance Information Sheet No. 105,
MAFF, London.
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and Polychlorinated Biphenyls in
Fish Oil Dietary Supplements and Licensed Medicines. Food Surveillance
Information Sheet No. 106, MAFF, London.
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and PCBs in Cows' Milk from Farms
Close to Industrial Sites. Food Surveillance Information Sheet No. 107,
MAFF, London.
- Ministry of Agriculture, Fisheries and Food (1992) Dioxins
in Food. Food Surveillance Paper No. 31, publ. HMSO.
- Ministry of Agriculture, Fisheries and Food (1983)
Polychlorinated biphenyl (PCBs) residues in food and human tissues. Food
Surveillance Paper No. 13, publ. HMSO.
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and PCBs in Cows' Milk from Farms
Close to Industrial Sites: 1996 survey results. Food Surveillance
Information Sheet No. 123, MAFF, London.
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and PCBs in cows' milk from farms
close to industrial sites: Rotherham 1997.
Food Surveillance Information Sheet No. 133, MAFF, London.
- Ministry of
Agriculture, Fisheries and Food (1997) Dioxins and PCBs in cows' milk from farms
close to industrial sites: Huddersfield 1997.
Food Surveillance Information Sheet No. 135, MAFF, London.
- Statement by the Committee on Toxicity of Chemicals in
Food, Consumer Products and the Environment on the health hazards of
polychlorinated biphenyls (1997).
- Krokos, F., Creaser, C.S., Wright, C. and Startin, J.R.
(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.
- Gregory, J., Foster, K., Tyler, H. and Wiseman, M. (1990)
Dietary and nutritional survey of British adults, publ. HMSO, London.
- 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, publ. 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, publ. US Environmental Protection Agency, Washington DC.
- Statement by the Committee on Toxicity of Chemicals in
Food, Consumer Products and the Environment on the US EPA draft health
assessment document for 2,3,7,8-tetrachlorodibenzo-p-dioxin and related
compounds (1995).
- Rose, C.L. and McKay, W.A. (1996) PCDDs (dioxins) and
PCDFs (furans) in selected UK lake and reservoir sites - concentrations and TEQs
in sediment and fish samples. The Science of the Total Environment 177,
43-56.
- Firestone, D., Fehringer, N.V., Walters, S.M., Kozara,
R.J., Ayres, R.J., Ogger, J.D., Schneider, L.F., Glidden, R.M., Ahlrep, J.R.,
Brown, P.J., Ford, S.E., Davy, R.A., Gulick, D.J., McCullough, B.H., Sittig,
R.A., Smith, P.V., Syvertson, C.N. and Barber, M.R. (1996) TCDD residues in fish
and shellfish from US waterways. Journal of AOAC International 79
1174-1183.
- Ling, Y.C., Soong, D.K. and Lee, M.K. (1995) PCDD/DFs and
Coplanar PCBs in Sediment and Fish Samples From the Er-Jen River in Taiwan.
Chemosphere
31, 2863-2872.
Contact Points
Further information on this survey can be obtained from:
Mr Martin Gem
MAFF, Joint Food Safety and Standards Group
Food
Contaminants Division
Room 238, Ergon House, c/o Nobel House
17 Smith
Square
London SW1P 3JR
Tel: +44 (0) 171 238 6219
Fax: +44 (0) 171
238 5331
Further copies of this and other Food Surveillance Information Sheets can be
obtained from:
Publicity and Information Section
MAFF
Room 303b,
Ergon House, c/o Nobel House
17 Smith Square
London SW1P 3JR
Tel:
+44 (0) 171 238 6244/5 or 6150
Fax: +44 (0) 171 238 6330
E-mail:
s.h.fssginfo@fssg.maff.gov.uk
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These pages were last updated on 27th February 1998
