ARCHIVE - FOOD SURVEILLANCE INFORMATION SHEETS

	\| Help \| Site map \| Search \| Text links \|
	Archive - MAFF

Home

MAFF UK - DIOXINS AND PCBS IN COWS' MILK FROM FARMS CLOSE TO INDUSTRIAL SITES

Index to MAFF UK Food Surveillance Information Sheets, 1997

Summary

MAFF has carried out a survey of polychlorinated biphenyls (PCBs) and dioxins in samples of cows' milk from individual farms in the vicinity of potential industrial sources of dioxins and PCBs emissions. Samples of milk for this survey were collected from 1993-1996. Information on the concentration of dioxins in samples collected from 1993-1995 and those results available for 1996 have already been published.¹ All samples collected from 1994-1996 have been subsequently analysed for polychlorinated biphenyls (PCBs).

The concentrations of both dioxins and PCBs in milk samples collected in 1994, 1995 and the available data for 1996 are reported here. Also reported are the concentrations of dioxins in samples of milk taken from farms in 1993¹ to give a more complete picture of the results from this survey. The remaining results for samples taken in 1996 will be published later this year.

The combined concentrations of PCBs and dioxins in milk samples were found to be below the Maximum Tolerable Concentration (MTC) set by MAFF and the Department of Health of 0.66 ng TEQ/kg whole milk (16.6 ng TEQ/kg milk fat - assuming a 4 per cent fat content in cows' milk). These results are therefore not considered to give any cause for concern.

Background

Dioxins and PCBs are very stable, ubiquitous chemicals in the environment and are generally present in very low concentrations in all foods, especially fatty foods including cows' milk. For further background on dioxins and PCBs, see Food Surveillance Information Sheets Nos. 19, 43, 44, 75, 100, 105 and 106.

The results presented here are expressed in terms of Toxic Equivalents (TEQs), which have been explained in detail in the Food Surveillance Information Sheet No. 105.² The Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) has tentatively accepted³ that the Toxic Equivalency Factors (TEFs) proposed by the 1994 WHO-ECEH/IPCS task force can be assigned to PCBs⁴ as a pragmatic approach to the evaluation of these compounds. The COT has also agreed that the Tolerable Daily Intake (TDI) of 10 pg 2,3,7,8-TCDD/kg bodyweight/day set by the World Health Organisation in 1990⁵, and endorsed by the COT in 1992⁶ (a position re-affirmed in 1995⁷) for dioxins can now be applied to mixtures of dioxins and PCBs.³ This allows an assessment of the toxicological significance of the complex mixtures of dioxin and PCB congeners in cows' milk.

The total concentrations of dioxins and PCBs found in milk are compared with the Maximum Tolerable Concentration (MTC)⁶. 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 without a high level (97.5 percentile) consumer of milk exceeding the Tolerable Daily Intake (TDI). The MTC was originally set in 1992 for dioxins only at 0.7 ng TEQ/kg whole milk⁸ (approximately 17.5 ng TEQ/kg for milk fat). However this value has been revised to take account of both dioxins and PCBs. A new MTC of 0.66 ng TEQ/kg whole milk (approximately 16.6 ng TEQ/kg milk fat) has therefore been agreed with the Department of Health for mixtures of dioxins and PCBs.

Data on the concentrations of PCBs in UK milk are limited and the COT has recommended that milk from farms in the vicinity of industrial locations, such as landfill sites, be monitored for these contaminants.⁹ In 1995, the COT recommended that major sources of dioxins should be identified with a view to reducing further inputs of dioxins to the environment.⁷

The first MAFF survey of cows' milk for dioxins was in 1989, analysing samples taken from farms in rural and in urban/industrial areas of the UK.⁶ Following the detection of concentrations of dioxins above the MTC in milk samples from three farms in the Bolsover area of Derbyshire in 1991,^{8, 10-14} and in line with the recommendation of the COT, samples of milk were collected during the period 1993-1995 from 93 farms in the vicinity of 29 industrial sites throughout England.¹ The sites selected (see Table 1) were potential sources of dioxins and PCBs¹ and 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.

Cows' milk was chosen for investigation because cows graze relatively large areas and any PCBs or dioxins present on grass eaten by the cows would concentrate in the milk fat. Milk and milk products are an important source of nutrients for a large part of the population and are a significant source of PCBs and dioxins in the diet. Milk is also a relatively easy matrix to analyse for these chemicals. All cows' milk samples were collected between 1993-1996 and were analysed for dioxins. Those collected from 1994-1996 (73 farms around 23 sites) were subsequently analysed for polychlorinated biphenyls (PCBs). The PCB congeners analysed were those regarded as 'dioxin-like', those with reported toxicological effects and some of those reported to occur in food or human milk.²

Methods

The analytical methodology for dioxins and PCBs in cows' milk has already been reported.¹⁵ 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

This report presents the individual and combined results for dioxins and PCBs in the 1994-96 samples. Also reported are the concentrations of dioxins in samples of milk taken from farms in 1993 to give a more complete picture of the results from this survey. The concentrations of PCBs and dioxins found in the samples from the various sites are summarised in Table 1. The concentration of dioxins in these samples have already been published.¹

Dioxin concentrations (1993-1996) were in the range 0.87-11 (mean 2.8) ng TEQ/kg milk fat, or 0.03-0.38 (mean 0.11) ng TEQ/kg whole milk. PCB concentrations (1994-1996) were in the range of 0.6-9.3 (mean 2.7) ng TEQ/kg milk fat, or 0.02-0.36 (mean 0.10) ng/kg TEQ/kg in whole milk. Full congener specific data is available on request.

Interpretation

The combined concentrations of dioxins and PCBs in all samples of milk tested were found to be below the Maximum Tolerable Concentration (MTC) set by MAFF and the Department of Health of 0.66 ng TEQ/kg whole milk (16.6 ng TEQ/kg milk fat). These results are therefore not considered to give any cause for concern.

In all but two of the samples taken during the period 1993-1995, the concentrations of dioxins were within or below the expected range of 1.1-7.1 ng TEQ/kg milk fat previously established for milk from individual farms in the UK in 1989.⁶ The two samples of milk which contained slightly elevated concentrations of dioxins were both taken in 1995 from farms in the Huddersfield area, though these concentrations were below the MTC. The largest potential source of dioxins in this area at that time was 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).¹ As with any urban/industrial area, there are also other potential sources of dioxins and PCBs. No survey for the presence of PCBs in milk from individual farms comparable to that on dioxins has been carried out so no background range has been established.

MAFF has previously given a commitment to undertake further investigations if a survey uncovered concentrations of dioxins outside the normal range. Accordingly, a total of 12 further samples were taken from the original and additional farms in the Huddersfield area in October 1996. The results indicate that the concentration of dioxins in milk samples 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 in the area (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. PCB concentrations in the milk from farms sampled in the Huddersfield area ranged from 1.9-9.3 ng TEQ/kg milk fat (0.06-0.36 ng TEQ/kg whole milk) in 1995, whereas for the samples taken in 1996, PCB concentrations fell to 1.2-3.4 ng TEQ/kg milk fat (0.05-0.15 ng TEQ/kg whole milk). In no case did the combined concentrations of dioxins and PCBs exceed the revised MTC.

The concentrations of dioxins in cows' milk reported here are consistent with data produced by similar surveys in Europe,¹ but few data exist on PCBs in cows' milk.

The concentrations of PCBs in milk collected from cows on farms in rural and urban areas in the north west of England were measured in a Lancaster University survey in 1996, which analysed for PCB 77, 105, 118, 126, 156, 169, 170 and 180.¹⁶ The range was 0.048-0.085 ng TEQ/kg fresh milk (approximately 1.2-2.1 ng TEQ/kg milk fat, assuming a 4 per cent fat content). The range of concentrations of PCBs (0.6-3.8 ng TEQ/kg milk fat) in MAFF's 1994-95 survey of cows' milk from farms close to disposal sites is similar to the range found in the Lancaster University survey. This suggests that any leaching of PCBs from the refuse disposal sites chosen by MAFF appears to have little influence on the concentration of PCBs in the milk sampled. However, the corresponding range for farms in the vicinity of all types of selected incinerator and coal fired power stations is 1.1-9.3 ng TEQ/kg milk fat (see Table 1) and, generally, is slightly higher than the Lancaster University survey. It should be noted that the Lancaster University survey sampled farms in rural and urban areas while the MAFF survey covered farms around specific industrial sites with the potential to release PCBs. In addition, the calculated TEQ concentration of PCBs for the MAFF survey includes a greater number of PCB congeners than reported in the Lancaster University study. Therefore, some elevation of PCB concentrations might be expected in the MAFF survey.

References

Ministry of Agriculture, Fisheries and Food (1997) Dioxins in Cows' Milk from Farms Close to Industrial Sites. Food Surveillance Information Sheet No. 100, MAFF, London.
Ministry of Agriculture, Fisheries and Food (1997) Polychlorinated Biphenyls and Dioxins in Foods and Human Milk - UK Dietary Intakes. Food Surveillance Information Sheet No. 105, 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).
Ahlborg, U.G., Becking, G.C., Birnbaum, L.S., Brouwer, A., Derks, H.J.G.M., Feeley, M., Golor, G., Hanberg, A., Larsen, J.C., Liem, A.K.D., Safe, S.H., Schlatter, C., Wærn, F., Younes, M. and Yrjänheikki, E. (1994) Toxic equivalency factors for dioxin-like PCBs: report on a WHO-ECEH and IPCS consultation, December 1993. Chemosphere 28, 1049-1067.
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.
Ministry of Agriculture, Fisheries and Food (1992) Dioxins in Food. Food Surveillance Paper No. 31, publ. HMSO.
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).
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 (1983) Polychlorinated biphenyl (PCB) residues in food and human tissues. Food Surveillance Paper No.13, publ. HMSO.
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.
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.
Sewart, A. and Jones, K. C. (1996) A Survey of PCB Congeners in U.K. Cows' Milk. Chemosphere 32, 12, 2481-2492.

Contact Point

For further information, please contact:

Dr Nigel Harrison
MAFF, Food Safety and Science Group
Food Contaminants Division
Room 234 Ergon House, c/o Nobel House
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 13 May 1997