Number 100 January 1997
MAFF UK - DIOXINS IN COWS' MILK FROM FARMS CLOSE TO INDUSTRIAL SITES
Index to MAFF UK Food Surveillance Information
19: MAFF, UK: Dioxins in Cows' Milk
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)
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)
MAFF UK - Dioxins and PCBs in Cows' Milk from Farms Close to Industrial Sites:
1996 Survey Results (August 1997)
124: MAFF UK - Dioxins in Cows Milk from
the Bolsover Area (August 1997)
MAFF, UK- Dioxins and PCBs in Cows' Milk from farms close to Industrial Sites:
Rotherham 1997 (November 1997)
MAFF, UK- Dioxins and PCBs in Cows' Milk from the Bolsover Area - October 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)
MAFF is carrying out a survey of dioxins in samples of cows' milk from
individual farms in the vicinity of potential sources of dioxins in the UK.
This survey is in response to a recommendation by the Committee on Toxicity of
Chemicals in Food, Consumer Products and the Environment that food from around
known emission sources should be monitored. A progress report on this survey
was published in the Food Safety Information Bulletin in October 1996. This
report presents the results for all samples taken during the period 1993-1995.
Further samples were taken from around other industrial sites in 1996, and the
results are expected later this year. For all but two of the farms sampled
during 1993-1995, concentrations of dioxins were within the normal range
(1.7-7.1 ng TEQ/kg milk fat, or 0.04-0.27 ng TEQ/kg whole milk) previously
established for cows' milk from individual farms in the UK. The two farms were
in the Huddersfield area in 1995 and contained concentrations of dioxins of 9.2
and 11 ng TEQ/kg milk fat, or 0.36 and 0.38 ng TEQ/kg whole milk respectively.
Further samples were taken from these two farms and additional farms in this
area in October 1996. Milk from one farm has now fallen from 9.2 ng TEQ/kg milk
fat (0.35 ng TEQ/kg whole milk) to 4.6 ng TEQ/kg milk fat (0.20 ng TEQ/kg whole
milk) (within the normal range), while that from the other has fallen only
slightly (now 8.6 ng TEQ/kg milk fat, or 0.37 ng TEQ/kg whole milk). The
concentrations of dioxins in milk from a third farm not previously sampled was
slightly outside the normal range (7.8 ng TEQ/kg milk fat, or 0.30 ng TEQ/kg
whole milk). The results from these and all other farms included in the survey
are well below the Maximum Tolerable Concentration (MTC) of 0.7 ng TEQ/kg whole
milk (17.5 ng TEQ/kg milk fat) agreed with the Department of Health. The
dioxins levels in the milk from the farms tested do not therefore pose a risk to
'Dioxins' is the generic term given to polychlorinated dibenzo-p-dioxins
and dibenzofurans. Concern over dioxins arose initially because one particular
dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), was found to produce
clinical effects (chloracne) in workers exposed to it through industrial
accidents. It is also very toxic to some species of laboratory animals. The
sixteen other dioxins which also contain chlorine at positions 2, 3, 7 and 8 of
the molecule are considered to be less toxic and concentrations of these
compounds are multiplied by a weighting factor reflecting their relative
toxicities to give a total dioxins content in terms of 'Toxic Equivalents'
(TEQs).1 The vast majority of dioxins do not
contain chlorine at positions 2, 3, 7 and 8 of the molecule and are thought to
have no significant biological activity.
Dioxins are produced during various combustion and incineration processes
and are also unwanted by-products in the manufacture of certain chemicals.
Dioxins are chemically very stable and so are ubiquitous in the environment and
are generally present at very low concentrations in all foods, especially fatty
foods including cows' milk.
MAFF began the first surveys of cows' milk for dioxins in 1989, analysing
samples taken from farms in rural and in urban/industrial areas of the UK. From
these surveys it was found that concentrations of dioxins were usually in the
range 1.1-1.5 ng TEQ/kg milk fat (0.04-0.06 ng TEQ/kg whole milk) in milk from
farms in rural areas and 3.0-7.1 ng TEQ/kg milk fat (0.09-0.27 ng TEQ/kg whole
milk) in milk from farms in urban/industrial area.2
This sampling was undertaken in response to a recommendation from the Committee
on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT)
that samples of foods known to accumulate dioxins, taken from around known
emission sources, should be investigated.3 In
1995 the COT recommended that continuing major sources of dioxins should be
identified with a view to reducing further inputs of dioxins to the environment.4
Although the concentrations of dioxins in most of the samples analysed were
within the expected range established from samples taken in 1989 and 1990, in
1991 it was found that the concentrations of dioxins in milk from three farms in
the Bolsover area of Derbyshire were above the current Maximum Tolerable
Concentration (MTC),2 although with the
exception of one farm the concentrations have now fallen to within the normal
range.5-9 This farm kept a suckler herd and
did not supply milk for human consumption. In the case of the two other farms,
the former Milk Marketing Board stopped accepting their milk as it did not meet
the standard conditions for sale because the levels of dioxins exceeded the MTC
of 0.7 ng TEQ/kg whole milk5 (17.5 ng TEQ/kg
milk fat). The mtc is an expert assessment by scientists and advisors in MAFF
and the Department of Health of the highest level of dioxins that could be
present in milk without an individual who drinks even a large amount of milk
exceeding the internationally agreed safe level of dioxins intake. It is based
on the Tolerable Daily Intake of 10 pg 2,3,7,8-TCDD/kg bodyweight/day set by the
World Health Organization in 199010 and
endorsed by the COT in 1992 as 10 pg TEQ/kg bodyweight/day for mixtures of
dioxins. The upper limit of the normal range of dioxins concentrations in milk
in the UK is about one-third of this MTC. Concentrations of dioxins in retail
milk purchased in 1988 from various areas of the UK were at the lower end of the
normal range. This is expected as milk from a number of farms is blended in the
dairy prior to sale. Concentrations of dioxins in milk from dairies supplied by
farms in the Bolsover area were also very low.2
Following the findings of elevated concentrations of dioxins in milk from
farms in the Bolsover area, and in line the recommendation of the COT, samples
of milk have been collected during the period 1993-1995 from 93 farms in the
vicinity of 29 industrial sites throughout England which are potential sources
of dioxins. Additional samples were taken from 12 farms in the Huddersfield
area in 1996. These sites included municipal, clinical and chemical waste
incinerators, coal-fired power stations, landfill sites, a secondary metal
refiner, a manufacturer of chlorinated chemicals and a cement kiln. A list of
the sites included in the monitoring programme is included in
Table 1. Cows' milk was chosen for investigation
because cows graze relatively large areas and any dioxins present on grass eaten
by the cows would concentrate in the milk fat. Milk is also an important food
and a significant source of dioxins in the diet and is a relatively easy matrix
to analyse for dioxins.
Under the Environmental Protection Act 1990 (EPA), all prescribed processes
require authorisations from the regulatory authorities before operations can
start. Regulations made under the Act, The Environmental Protection (Prescribed
Processes and Substances) Regulations 1991, SI 472 (as amended) describe the
processes and substances that require control. Under these Regulations
processes are divided into Part A and Part B. Part A processes are those that
have the greatest potential for pollution to the three (air, land and water)
environmental media and are controlled under Integrated Pollution Control (IPC)
of the Act. Part B processes have less serious potential to pollute and are
controlled by local authorities for air pollution. The Act and Regulations do
not place numerical limits on pollutants that can be emitted. However they do
require that in operating a process, an operator uses Best Available Techniques
Not Entailing Excessive Costs to prevent or minimise the release of prescribed
substances and to render harmless any such substances which are released.
Municipal waste incinerators have been the major source of dioxins emissions
in the UK. These plants came under IPC control in August 1992 and were required
to meet new plant standards defined in the Community Directive (89/429/EEC) by 1
December 1996. The Directive did not set a dioxins limit but a limit of 1 ng/m3 was set by the Environment Agency. The same
limit was also applied to other types of incinerators, e.g. clinical waste,
chemical waste, sewage sludge. A practical effect of this limit, which became
binding from 1 December 1996, is that municipal waste incinerators will no
longer be the major source of dioxins. Her Majesty's Inspectorate of Pollution
estimated in 1995 that these incinerators produced 460-580 g/year. This will
reduce to less than 10 g/year from now on. Other sources of dioxins emissions
which are projected to fall significantly by the year 2000 are clinical waste
incineration, sewage sludge incineration, iron, steel and non-ferrous metal
processes, and chemical waste incineration.11
As a statutory consultee, the Ministry receives copies of all Integrated
Pollution Control applications submitted to the Environment Agency. These
applications contain details of dioxins emissions and this information was used
to select industrial sites for inclusion in the current survey where there were
dairy farms within 7 km of the site. Using dispersion models it is possible to
predict the area of maximum deposition of dioxins and milk from dairy farms
which lay within such an area was selected for analysis.
All samples, together with appropriate analytical blanks, were analysed at
the CSL Food Science Laboratory, Norwich. Milk was freeze-dried, spiked with
13C12 labelled internal standards and extracted with
dichloromethane/cyclohexane. The extract was passed through beds of silica gel
and base-modified silica, then fractionated using a column containing activated
carbon dispersed on glass fibres. Details of the fractionation process have
been published.12 The fraction containing
dioxins was recovered by eluting the column by reversed flow with toluene, and
purified by chromatography on acid-modified and base-modified silicas and on
Florisil. Dioxins were determined by high resolution gas chromatography/high
resolution mass spectrometry at 7000 resolution.
The analysis of the very low concentrations of dioxins found in foods is
exceptionally demanding and involves a chain of steps, most of which have to
operate at the limit of performance. 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 previous work, the coefficient
of variation for the analysis of dioxins in milk was approximately 10 percent.2
The results complied with published acceptance criteria.13
These criteria lay down general conditions for use of internal standards and
specification of limits of detection. They also cover the following more
- Validation: extraction efficiency; average and repeatability for blanks
and recovery; selection of appropriate GC column and MS resolution;
repeatability of relative response factors and isotope ratios; and absence of
- Quality control: adequate blanks; check sample extraction; recovery of
internal standards; chromatographic separation; MS calibration, tuning and
- Data acceptance: validated and quality controlled procedures; criteria for
identification as a dioxin or furan; criteria for assignment as specific isomer;
and criteria for acceptance of quantification.
For Quality Control purposes a reference sample with known concentrations of
dioxins congeners was included in the batches of samples analysed. The sample
was of powdered milk, and the dioxins content had been analysed by several
laboratories in an interlaboratory study carried out by BCR. The concentrations
found in the current survey were within the confidence interval of the
concentrations accepted by BCR.
The concentrations of dioxins found in the samples from the various sites
are summarised in Table 1. The concentrations of
dioxins were in the range 0.87-11 (mean 2.7) ng TEQ/kg milk fat, or 0.03-0.38
(mean 0.10) ng TEQ/kg whole product.
In all but two of the samples taken during the period 1993-1995, the
concentrations of dioxins were within or below the normal range of 1.1-7.1 ng
TEQ/kg milk fat previously established for milk from individual farms in the UK
in 1989. The two samples of milk which had slightly elevated
concentrations of dioxins were both taken in 1995 from farms in the Huddersfield
area. The largest potential source of dioxins in this area at that time was
probably the Vine Street Municipal Waste Incinerator which closed down on 1
December 1996 as it did not meet the new plant emission standards (i.e. dioxins
emissions limit of 1 ng TEQ/m3). As with any
urban/industrial area, there are also other potential sources of dioxins.
MAFF had previously given a commitment to undertake further investigations
if the surveillance uncovered concentrations of dioxins outside the normal
range. Accordingly, a total of 12 further samples were taken from these and
additional farms in the Huddersfield area in October 1996. The results show
that milk from one farm has fallen from 9.2 ng TEQ/kg milk fat (0.35 ng TEQ/kg
whole milk) to 4.6 ng TEQ/kg milk fat (0.20 ng TEQ/kg whole milk) and is now
within the normal range, while that from the other has not fallen to such a
large extent (now 8.6 ng TEQ/kg, or 0.37 ng TEQ/kg whole milk). The
concentration of dioxins in milk from a third farm not previously sampled (7.8
ng TEQ/kg milk fat, or 0.30 ng TEQ/kg whole milk) is slightly outside the normal
range. MAFF is discussing these results with the local authority for the area.
The concentrations of dioxins in milk from the other farms (1.9-5.5 ng TEQ/kg
milk fat, or 0.08-0.24 ng TEQ/kg whole product) are all within the normal range.
The results from all the farms in Huddersfield and all other areas included in
the survey are well below the Maximum Tolerable Concentration of 0.7 ng TEQ/kg
whole milk (17.5 ng TEQ/kg milk fat), and there is no risk to human health from
consumption of milk from any of the farms.
The concentrations of dioxins (all on a fat basis) are similar to those
found in the Netherlands (up to 13.5 ng TEQ/kg) in milk from cows grazing close
to incinerators in the Lickebaert area and to those found in the Tyrol region of
Austria (up to 8.6 ng TEQ/kg milk fat) in milk from cows grazing close to a
metal reclamation plant,14 and cows grazing
near potential sources in Bavaria (up to 5.6 ng TEQ/kg milk fat).15 Higher concentrations (13.5-37.0 ng TEQ/kg milk
fat, using German TEF system) have been reported in milk from cows grazing in
the vicinity of a metal reclamation plant in Germany.16
The results of a more recent survey in Germany confirm expectations that
dioxins emissions from newer incinerators are lower: concentrations of dioxins
in milk from farms close to an incinerator built in 1993 were up to 0.8 ng
TEQ/kg milk fat.17 All the incinerators
targeted in the MAFF survey were built well before this time and the existence
of IPC controls, so it is reasonable to expect that concentrations of dioxins in
milk in the UK will fall further.
In September 1996, the survey was extended to include samples of cows' milk
taken from the vicinity of other potential sources of dioxins (steel and
non-ferrous metals plants). These samples are currently being analysed, and the
results will be published in the Food Safety Information Bulletin when
- NATO/Committee on the Challenges of Modern Society (1988)
International Toxicity Equivalency Factor (I-TEF) method of risk assessment for
complex mixtures of dioxins and related compounds. Pilot study on
international information exchange on dioxins and related compounds. CCMS
176, publ. Environmental Protection Agency, Washington D.C., USA.
- Ministry of Agriculture, Fisheries and Food (1992)
Dioxins in Food. Food Surveillance Paper No. 31, publ. HMSO.
- Department of the Environment (1989) Dioxins in the
environment. Pollution Paper No. 27, publ. HMSO.
- Department of Health (1995) 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, publ. Department of Health, London.
- 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
- Ministry of Agriculture, Fisheries and Food (1994) Dioxins in cows milk.
Food Surveillance Information Sheet 43.
- Ministry of Agriculture, Fisheries and Food (1995) Dioxins in cows' milk
from the Bolsover area. Food Surveillance Information Sheet 75.
- 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.
- Her Majesty's Inspectorate of Pollution (1995) A review
of dioxin emissions in the UK. Research Report No DoE/CPR2/41/1/38.
- Krokos, F., Creaser, C.S., Startin, J.R. and Wright, C.
(1996) Congener-specific method for the determination of ortho-chlorobiphenyls,
non-ortho-chlorobiphenyls, PCDDs and PCDFs in foods by carbon-column
fractionation and gas chromatography-isotope dilution mass spectrometry. Fresenius
Journal of Analytical Chemistry (in press).
- Ambidge, P.F., Cox, E.A., Creaser, C.S., Greenberg,
M., Gem, M.G. de M., Gilbert, J., Jones, P.W., Kibblewhite, M.G., Levey,
J., Lisseter, S.G., Meredith, T.J., Smith, L., Smith, P., Startin, J.R.,
Stenhouse, I. and Whitworth, M. (1990) Acceptance criteria for analytical
data on polychlorinated dibenzo-p-dioxins and polychlorinated
- Liem, A.K.D., Hoogerbrugge, R., Kootstra, P.R., van der
Velde, E.G. and de Jong, A.P.J.M. (1991) Occurrence of dioxins in cow's milk in
the vicinity of municipal waste incinerators and a metal reclamation plant in
Chemosphere 23, 1675-1684.
- Lassek, E., Jahr, D., and Mayer, R. (1993)
Polychlorinated dibenzo-p-dioxins and dibenzofurans in cows milk from
Bavaria, FRG. Chemosphere 27, 519-534.
- Riss, A. and Hagenmaier, H. (1989) Environmental
monitoring of PCDD/PCDF in the vicinity of a metal reclamation plant in
Tyrol/Austria. Paper presented at the 9th International Symposium on
Chlorinated Dioxins in the Environment, Ontario, Canada, 17-22 September 1989.
- Hippelein, M., Kaupp, H., Dörr, G. and Hutzinger, O.
(1996) Baseline contamination assessment for a new resource recovery facility
in Germany. Part III: PCDD/Fs, HCB and PCBs in cow's milk. Chemosphere
For further information, please contact:
Dr Nigel Harrison
Food Safety and Science Group
Food Contaminants Division
17 Smith Square
London SW1P 3JR
Tel: +44 (0) 171 238 6235
Fax: +44 (0) 171 238 5331
Return to Index to Surveillance Information Sheets, 1997 page
Go to top of page
These pages were last updated on 31 January 1996