Number 134 November 1997
DIOXINS AND PCBS IN COWS' MILK FROM THE BOLSOVER AREA - OCTOBER 1997
Index to MAFF UK Food Surveillance Information
Sheets, 1997
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)
75:
MAFF UK - Dioxins in Cows' Milk from the Bolsover Area (November 1995)
100: MAFF UK - Dioxins in Cows' Milk from
farms close to Industrial Sites (January 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)
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)
145: MAFF UK - Dioxins and PCBs in Farmed
Trout in England and Wales (March 1998)
184: MAFF UK - Dioxins and PCBs in UK and
Imported Marine Fish (August 1999)
Summary
MAFF has monitored the levels of dioxins in cows' milk from farms in the
Bolsover area of Derbyshire each year since 19911-8
and of selected PCBs in samples of milk collected since 1994. Since 1991, the
concentrations of dioxins in milk from farms in the Bolsover area have generally
been declining, but increased in 1996 compared with previous years.
Concentrations of PCBs in the 1996 samples were also higher than those found in
the 1995 samples. Further cows' milk samples were collected in July 1997, in
collaboration with local Environmental Health Officers, from Farms B and F, one
other farm which does not produce milk for human consumption and from all 16
dairy farms in the area to investigate the 1996 findings and to ensure that
levels in milk entering the human food supply remain below the Maximum Tolerable
Concentration (MTC) of 16.6 ng TEQ/kg milk fat.
For the two farms sampled in 1996 (Farms B and F), the concentrations of
dioxins and PCBs, expressed as Toxic Equivalents (TEQs), in samples collected in
July 1997 were lower than in samples collected in October 1996. With the
exception of Farm B, dioxin concentrations in milk from all farms were within
the range expected from previous survey results for other parts of the UK and
combined levels of dioxins and PCBs were below the MTC for all samples. These
results do not indicate any public health risk from the consumption of milk and
milk products from these farms. The combined dioxins and PCBs concentration in
milk from Farm B continues to exceed the MTC, but this farm runs a suckler herd
and does not produce milk for human consumption.
Further samples will be collected this year from some of the farms to
investigate whether the increased concentrations observed in October 1996 could
be due to seasonal variations in dioxins and PCBs concentrations in milk.
Background
Dioxins and PCBs are very stable, ubiquitous chemicals in the environment
and are generally present in very low concentrations in foods, especially
fat-containing foods including cows' milk. Further background information on
dioxins and PCBs can be found in Food Surveillance Information Sheets numbers
105,
106 and
107.9,10,11
The results are expressed in terms of Toxic Equivalents (TEQs), which have
been explained in detail in the Food Surveillance Information Sheet number
105.9
This allows an assessment of the toxicological significance of the complex
mixtures of dioxin and PCB congeners in cows' milk.
The total TEQ concentrations of dioxins and PCBs found in milk are compared
with the Maximum Tolerable Concentration (MTC) of 16.6 ng TEQ/kg milk fat.1,11 The MTC is
an assessment by scientists in MAFF and the Department of Health of the highest
concentration of PCBs and dioxins that could be present in milk and yet not
result in a high level (97.5 percentile) consumer of milk exceeding the
Tolerable Daily Intake (TDI) of 10 pg TEQ/kg bodyweight/day.1,12,13
MAFF has been conducting surveys for dioxins in food since 1989, including
in milk samples from farms in urban/industrialised areas.1
All samples are analysed for the 17 dioxin congeners of toxicological
significance. Following recent developments in analytical methodology, it is
now also possible to quantify virtually every one of the possible 209 PCB
congeners. However, such analysis would be prohibitively costly so specific
congeners are selected for analysis, including those which are toxicologically
significant.9
In 1989-90, MAFF collected samples of cows' milk from farms in various rural
and urban/industrialised areas for dioxin analysis.1
One relatively industrialised area chosen was Bolsover in Derbyshire. That
study, and subsequent work, revealed that samples of milk taken from three farms
(Farms A, B and C) in the vicinity of a chemical waste incinerator and a
smokeless fuels plant exceeded the MTC for dioxins in cows milk. Levels of
dioxins in milk from the other farms sampled, from dairies and in retail milk
sold in the area were all below the MTC.
Samples were collected from two farms in the Bolsover area in October 1996,
Farm B and Farm F. The concentration of dioxins in milk from farms in the
Bolsover area had generally been declining since 1991, but increased in 1996
compared with previous years. Although the levels of dioxins and PCBs in these
milk samples did not raise a food safety concern, the rise in concentrations in
1996 was unexpected. MAFF met with representatives of the Environment Agency
and with the local authority to discuss possible reasons for the increase in the
concentration of dioxins in milk sampled from the Bolsover area in 1996. The
incinerator previously implicated in elevated levels of dioxins in the area has
been unused since 1991. It was concluded that there was no obvious explanation
and that further investigations were necessary.
Further cows' milk samples were collected in July 1997, in collaboration
with local Environmental Health Officers, to investigate further the 1996
findings and to ensure that levels in milk entering the human food supply remain
below the MTC. These samples were obtained from Farms B and F and from one
other farm in the area which does not produce milk for human consumption as well
as from 16 dairy farms in the area. These other farms included some not sampled
for some time and some which had not previously been sampled. Milk samples from
dairy farms were obtained from the bulk tanks after thorough mixing of the
contents.
Methods
The analytical methodology for determining dioxin and PCB concentrations in
cows' milk has already been reported.14 All
samples were analysed by high resolution gas chromatography-high resolution mass
spectrometry (GC-MS) at 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 Organisation and has
recognised expertise in the analysis of foods for dioxins and 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. Based on
other work, the coefficients of variation for the analysis of milk were
approximately 10 per cent for dioxins and non-ortho-PCBs and up to 5 per
cent for ortho-PCBs.
Results
The total concentrations of dioxins and PCBs found in the milk taken from
farms in the Bolsover area in 1997 are summarised in Table
1. Table 2 shows the variation of concentrations of
dioxins and PCBs in milk taken from 1990 onwards. Full congener-specific data
are available on request.
Interpretation
With the exception of Farm B, dioxins concentrations were within the range
expected from previous surveys and the combined concentrations of dioxins and
PCBs were all well below the MTC. These results do not indicate any public
health risk. For Farms B and F, concentrations of dioxins and PCBs were lower
in samples collected in July 1997 than in those collected in October 1996. The
combined dioxin and PCB concentration in milk from Farm B continues to be in
excess of the Maximum Tolerable Concentration (MTC), but this farm runs a
suckler herd and does not produce milk for human consumption. MAFF has informed
all interested parties of these results, including the farmers and the local
authority.
The reason for the increase in dioxins and PCBs concentrations in 1996 is
still unclear. Further milk samples will be taken from selected farms in the
area in 1997 to investigate further whether the increased concentrations in
October 1996 samples could be due to seasonal variation.
References
- Ministry of Agriculture, Fisheries and Food (1992) Dioxins
in Food. Food Surveillance Paper No. 31, publ. HMSO.
- Ministry of Agriculture, Fisheries and Food (1992) Report
of Studies on Dioxins in Derbyshire carried out by the Ministry of Agriculture,
Fisheries and Food.
- Ministry of Agriculture, Fisheries and Food (1992) Further
Report of Studies on Dioxins in Derbyshire carried out by the Ministry of
Agriculture, Fisheries and Food.
- Ministry of Agriculture, Fisheries and Food (1992) Third
Report of Studies on Dioxins in Derbyshire carried out by the Ministry of
Agriculture, Fisheries and Food.
- Ministry of Agriculture, Fisheries and Food (1993) Dioxins
in Cows' Milk.
Food Surveillance Information Sheet No. 19, MAFF, London
- Ministry of Agriculture, Fisheries and Food (1994) Dioxins
in Cows' Milk.. Food Surveillance Information Sheet No. 43,
MAFF, London.
- Ministry of Agriculture, Fisheries and Food (1995) Dioxins
in Cows' Milk from the Bolsover Area. Food Surveillance Information Sheet
No. 75, MAFF, London.
- Ministry of Agriculture, Fisheries and Food (1997) Dioxins
and PCBs in Cows' Milk from the Bolsover Area. Food Surveillance Information
Sheet No. 124, MAFF, London.
- 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. 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
- World Health Organisation, 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.
- 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).
- 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.
Contact
Dr Nigel Harrison
MAFF, Joint Food Safety and Standards Group
Food Contaminants Division
Room 234, Ergon House
17 Smith Square
London
SW1P 3JR
Tel: +44 (0)171 238 6235
Fax: +44 (0)171 238 5331
Spreadsheet Table
Table 2: Variation of dioxins and PCBs
concentrations (ng TEQ/kg milk fat) in milk from individual farms in the
Bolsover area (excluding farms sampled only in one year)
Click here to download the Excel version of Table 2
Shift-Click here to download the .csv version of Table 2
(if you have any other spreadsheet package)
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These pages were last updated on 31st October 1997
