Number 120      August 1997

MAFF UK - DIOXINS IN COWS' MILK FROM NORTHERN IRELAND

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)
123: MAFF UK - Dioxins 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)
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)
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 carried out a survey for dioxins in cows' milk from individual farms in Northern Ireland and in retail cows' milk purchased in Northern Ireland. This survey was carried out as none of the milk samples included in earlier surveys had been obtained from Northern Ireland. For all the farms sampled, concentrations of dioxins were within or below the expected range (1.1-7.1 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 concentrations of dioxins in retail milk were similar to those found in retail milk from other areas of the UK in 1990. These results are well below the Maximum Tolerable Concentration (MTC) for dioxins and PCBs in cows' milk of 16.6 ng TEQ/kg milk fat agreed with the Department of Health. The dioxins concentrations in the milk samples tested do not therefore pose a risk to human health.

Background

'Dioxins' is the generic term given to polychlorinated dibenzo-p-dioxins and dibenzofurans. 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. The concentrations of dioxins are presented as 'Toxic Equivalents' (TEQs).¹ Further background information on dioxins has been included in earlier surveillance reports.²

MAFF began the first surveys of cows' milk for dioxins in 1989, analysing samples taken from individual farms in rural and in urban/industrial areas of the UK. 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 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. From these earlier 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 areas.⁵ Concentrations of dioxins in pooled samples of retail milk purchased in the summer and winter of 1990 from various areas of the UK were in the range 0.05-0.13 ng TEQ/kg whole milk (approximately 1.3-3.3 ng TEQ/kg milk fat, assuming 4 per cent fat content).⁵ Since 1993 MAFF has analysed samples of cows' milk from farms close to various types of industrial sites with the potential to release dioxins. With the exception of milk from three farms, the concentrations of dioxins were in the range 0.87-6.2 ng TEQ/kg milk fat.²

Cows' milk (40 samples) was obtained by the Department of Agriculture for Northern Ireland on four occasions - April/May, July and November 1993 and March 1994. Samples were taken prior to retail sale from dairies (20 samples) and from bulk tanks of individual farms (20 samples). The farms and dairies were selected to provide as wide a coverage of Northern Ireland as possible. Some came from areas which were partially industrialised, but none of the samples came from farms close to specific industrial sites with the potential to release dioxins as there are very few such sites in Northern Ireland. Samples were collected in polypropylene containers from the same farms and dairies on each occasion and transported to CSL Food Science Laboratory, Norwich. A list of the samples and the locations of the sampling sites is included in Table 1.

Methods

The analytical methodology for dioxins in the cows' milk surveys has already been reported.^2,6,7 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 in human milk and human blood organised by the World Health Organization and has recognised expertise in the analysis of foods for dioxins. The results complied with published acceptance criteria.⁸ Reference materials for dioxins analyses were not yet available for the survey reported here. However, based on other work, the coefficient of variation was approximately 10 per cent. The fat contents of the samples were measured at the former CSL Food Science Laboratory, Torry.

Results

The concentrations of dioxins found in the samples from the various sites are summarised in Table 1. The concentrations given are upper bound values, which are calculated assuming that each congener which was present at concentrations below the reporting limit (0.25 ng TEQ/kg milk fat) or the limit of detection (LOD), was present at the reporting limit or, where higher, the LOD. The concentrations of dioxins were in the ranges 0.74-2.7 (mean 1.2) ng TEQ/kg milk fat, or 0.03-0.08 (mean 0.04) ng TEQ/kg whole milk, in retail samples from dairies, and 0.84-3.0 (mean 1.2) ng TEQ/kg milk fat, or 0.03-0.09 (mean 0.05) ng TEQ/kg whole milk, in the samples from individual farms. For all samples analysed the concentrations of dioxins were well within, or were below, the expected ranges for retail milk and milk from individual farms previously established for the UK.³ Full congener specific results for all samples are available on request.

Interpretation

For some of the samples, an unusually large number of congeners were present at concentrations below the LOD, with two of the samples having unusually high LODs for 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD, possibly because of analytical problems associated with the use of polypropylene containers used to transport the milk. One of these two samples contained the highest upper bound concentrations found in the milk from individual farms. This sample came from a farm in a more industrialised area of Northern Ireland. The true concentrations will be lower in both cases. In other samples, the concentrations of individual congeners were so low as to challenge the capability of the analytical method.

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 and yet not result in an individual who regularly drinks a large amount of milk exceeding the internationally agreed safe level of dioxins intake.⁹ 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 concentrations of dioxins found in all samples in this survey were well below the MTC. There is therefore no risk to human health from consumption of any of the milk tested.

There was no discernible seasonal trend in the dioxins concentrations. As expected, the concentrations of dioxins in cows' milk from individual farms were lower than those in the ongoing survey of milk from farms close to industrial sites in the UK.² As new controls on dioxins emissions under Integrated Pollution Control make an increasing impact, it is reasonable to assume that concentrations of dioxins in cows' milk will fall in the future.¹¹

The concentrations of dioxins found were similar to those found in other countries. In a survey of milk from dairies supplied by farms in an urban/industrial area of Germany, concentrations of dioxins were in the range 0.76-2.6 (mean 1.4) ng TEQ/kg milk fat).¹² The concentrations of dioxins in retail milk from glass bottles in Finland, when recalculated using international Toxic Equivalency Factors and upper bound concentrations, averaged 0.04 ng TEQ/kg whole milk (approximately 1.2 ng TEQ/kg milk fat).¹³ The concentrations of dioxins in milk from individual farms in the current survey were similar to those (0.67-2.0 ng TEQ/kg milk fat) found in control samples (not close to industrial sites) in Spain. Concentrations of dioxins in retail milk in the same study in Spain were slightly higher (mean 3.8 ng TEQ/kg milk fat) than those found by MAFF in the current survey.¹⁴ The concentrations of dioxins in the current survey are lower than those found in various surveys of dioxins in cows' milk from farms close to industrial sites.^15,16,17 However, they are comparable with those found in milk from farms close to a newly operating incinerator in Germany which was required to meet newer emission standards,¹⁸ similar to those standards which the UK industry must now meet.

References

1. 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 Report Number 176, publ. Environmental Protection Agency, Washington D.C., USA.
2. Ministry of Agriculture, Fisheries and Food (1995) Dioxins in cows' milk from farms close to industrial sites. Food Surveillance Information Sheet No. 100, publ. Ministry of Agriculture, Fisheries and Food.
3. Department of the Environment (1989) Dioxins in the environment. Pollution Paper No. 27, publ. HMSO.
4. 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.
5. Ministry of Agriculture, Fisheries and Food (1992) Dioxins in Food. Food Surveillance Paper No. 31, publ. HMSO.
6. Ministry of Agriculture, Fisheries and Food (1995) Dioxins in Human Milk. Food Surveillance Information Sheet No. 88, publ. Ministry of Agriculture, Fisheries and Food.
7. Krokos, F., Creaser, C.S., Wright, C. and Startin, J.R. (1997) Congener-specific method for the determination of ortho- and non-ortho-chlorobiphenyls, 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.
8. 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 dibenzofurans. Chemosphere 21, 999-1006.
9. Ministry of Agriculture, Fisheries and Food (1992) Report of Studies on Dioxins in Derbyshire carried out by the Ministry of Agriculture, Fisheries and Food.
10. 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.
11. Her Majesty's Inspectorate of Pollution (1995) A review of dioxin emissions in the UK. Research Report No DoE/CPR2/41/1/38.
12. Fürst, P., Fürst, C. and Wilmers, K. (1992) Survey of dairy products for PCDDs, PCDFs, PCBs and HCB. Chemosphere 25, 1039-1048.
13. Vartiainen, T. and Hallikainen, A. (1994) Polychlorodibenzo-p-dioxin and polychlorodibenzofuran levels in cow milk samples, egg samples and meat in Finland. Fresenius J. Anal. Chem. 348, 150-153.
14. Ramos, L., Eljarrat, E., Hernández, L.M., Alonso, L., Rivera, J. and González, M.J. (1996) Levels of PCDDs and PCDFs in farm cow's milk located near potential contaminant sources in Asturias (Spain). Comparison with levels found in control points and commercial pasteurized cow's milks. Paper presented at the 16th Symposium on Chlorinated Dioxins and Related Compounds, Amsterdam, 12-16 August 1996.
15. 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 the Netherlands. Chemosphere 23, 1675-1684.
16. Lassek, E., Jahr, D., and Mayer, R. (1993) Polychlorinated dibenzo-p-dioxins and dibenzofurans in cows milk from Bavaria, FRG. Chemosphere 27, 519-534.
17. 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.
18. 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 cows' milk. Chemosphere 32, 1617-1622

Contact Point

For further information, please contact:

Dr Nigel Harrison
Food Contaminants Division
Ergon House, c/o Nobel House
17 Smith Square
London SW1P 3JR

Tel: +44 (0) 171 238 6235
Fax: +44 (0) 171 238 5331

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These pages were last updated on July 31st 1997