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DIOXINS AND PCBs IN RETAIL COWS' MILK IN ENGLAND

Index to MAFF UK Food Surveillance Information Sheets, 1997

Summary

The Ministry of Agriculture, Fisheries and Food (MAFF) has carried out a survey of dioxins and polychlorinated biphenyls (PCBs) in samples of retail cows' milk purchased from 12 locations in England. This survey was carried out to determine whether the levels of dioxins had changed since a comparable survey in 1990 in the light of actions taken by the Environment Agency and others to reduce emissions of dioxins from industries.

The concentrations of dioxins, expressed as Toxic Equivalents (TEQs), in the pooled samples from each area were lower than those found in a previous survey of retail cows' milk purchased in 1990. The combined concentrations of dioxins and PCBs in all the milk samples were well below the Maximum Tolerable Concentration (MTC) for dioxins and PCBs in cows' milk set by MAFF and the Department of Health of 16.6 ng TEQ/kg milk fat. These results do not indicate the existence of any health risk.

Background

Dioxins and PCBs are very persistent chemicals which are ubiquitous in the environment and so 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.^1,^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 Number 105.² 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) of 16.6 ng TEQ/kg milk fat, or 0.66 ng TEQ/kg whole milk^1,⁴

MAFF has been conducting surveys for dioxins in food since 1989, including samples of retail milk, milk from farms in urban/industrialised areas,⁴ and milk from farms close to industrial sites. All samples are analysed for the 17 dioxin congeners of toxicological significance. The concentrations of dioxins found in the survey of retail milk samples purchased in summer and winter 1990 were in the range 0.05-0.13 (mean 0.08) ng TEQ/kg whole milk (approximately 1.3-3.3 (mean 1.9) ng TEQ/kg milk fat, assuming 4 per cent fat content). The current survey was carried out to determine whether the levels had changed since 1990 in the light of actions taken by the Environment Agency and others to reduce emissions of dioxins to reduce emissions of dioxins from industries.

The results of previous analysis of retail milk for PCBs by MAFF were expressed as 'total PCBs' quantified against a commercial mixture of PCBs. Individual congeners could not be analysed by this methodology. The high limits of detection for this method meant that PCBs were seldom detected.⁵ 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.² The current survey represents the first survey of retail milk for PCB congeners carried out by MAFF using the new analytical methodology.

Samples were collected by MAFF staff in 1995 from 12 locations in England, corresponding where possible to those locations sampled in 1990. A total of 105 pints of full fat ('silver top') milk in glass bottles were purchased at various shops in each region, and the samples from each region were pooled prior to analysis. As in 1990, the actual locations were chosen to represent different regions of England rather than because of any expectation that levels of dioxins and PCBs would be elevated in these locations. Milk in glass bottles was selected in 1990 to allow comparison with retail cartoned milk, and milk in glass bottles was selected again in the current survey to ensure results would be comparable. As the retail samples were pooled prior to analysis, no brand details are provided. A list of the locations is included in Table 1.

Methods

The analytical methodology for determining dioxin and PCB concentrations in cows' milk has been reported previously.⁶

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 reporting limits in this survey are 0.10 ng/kg for dioxins and non-ortho PCBs and 0.10 micrograms/kg for ortho-PCBs, all in milk fat. These are lower than were achieved with the other MAFF surveys of dioxins and PCBs in cows' milk and demonstrate an improvement in the analytical methodology.

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 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 pooled retail cows' milk samples collected in 1995. The concentrations of dioxins and PCBs found in the samples from the various sites are summarised in Table 1.

In summary, the results were:

Dioxin concentrations were in the range 0.67-1.4 ng TEQ/kg milk fat, or 0.02-0.05 ng TEQ/kg whole milk.
PCB concentrations were in the range 0.75-2.3 ng TEQ/kg milk fat, or 0.03-0.08 ng TEQ/kg whole milk.
The combined dioxin and PCB concentrations were in the range 1.4-3.5 ng TEQ/kg milk fat, or 0.05-0.12 ng TEQ/kg whole milk.

Full congener specific data are available on request.

Interpretation

The combined concentrations of dioxins and PCBs in the pooled retail samples of milk tested were all well below the Maximum Tolerable Concentration (MTC) set by MAFF and the Department of Health of 16.6 ng TEQ/kg milk fat. The MTC is an assessment by scientists in MAFF and the Department of Health of the highest concentration of dioxins and PCBs 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) for these chemicals of 10 pg 2,3,7,8-TCDD/kg bodyweight/day,⁷ or 10 pg TEQ/kg bodyweight/day for mixtures of dioxins and PCBs.^4,⁸ These results do not indicate the existence of any health risk.

The concentrations of dioxins found in the 1995 samples are lower than those found in the 1990 pooled retail samples. The concentrations of dioxins found in the 1995 samples are also similar to those found in samples of milk from individual farms in rural areas of the UK in 1989, and to those found in a survey of milk from dairies in Northern Ireland [0.74-2.7 (mean 1.2) ng TEQ/kg milk fat, or 0.03-0.08 ng TEQ/kg whole milk].⁹

The concentrations of dioxins found in the current MAFF survey are generally comparable with those found in other countries. In a survey of milk from dairies supplied by farms in an urban/industrial area of Germany in 1990, concentrations of dioxins were in the range 0.76-2.6 (mean 1.4) ng TEQ/kg milk fat).¹⁰ The upper bound concentrations of dioxins in retail milk in Finland obtained in 1991, when recalculated with International Toxic Equivalency Factors (I-TEFs) as used for this and other MAFF surveys, averaged 0.04 ng TEQ/kg whole milk (approximately 1.2 ng TEQ/kg milk fat).¹¹ Concentrations of dioxins in retail milk in Spain purchased in 1995 were slightly higher (mean 3.8 ng TEQ/kg milk fat) than those found by MAFF in the current survey.¹² In a survey of PCBs in pooled retail milk (year not specified) in Finland, PCB congeners were not found at a limit of detection of 0.05 micrograms/kg whole milk (approximately 1.3 micrograms/kg milk fat) which is higher than the reporting limit of 0.10 micrograms/kg milk fat achieved for the current MAFF study.¹³ However the concentrations of PCBs in the current MAFF survey are similar to those found in milk collected from cows on farms in rural and urban areas in the north west of England in 1996, which analysed for PCB 77, 105, 118, 126, 156, 169, 170 and 180.¹⁴ Based on this limited congener set 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).

References

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 (1997) Dioxins and Polychlorinated Biphenyls and 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 (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.
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.
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).
Ministry of Agriculture, Fisheries and Food (1997) Dioxins in Cows' Milk from Northern Ireland. Food Surveillance Information Sheet No. 120, MAFF, London.
Fürst, P., Fürst, C. and Wilmers, K. (1992) Survey of dairy products for PCDDs, PCDFs, PCBs and HCB. Chemosphere 25, 1039-1048.
Vartiainen, T. and Hallikainen, A. (1994) Polychlorodibenzo-p-dioxin and polychloro-dibenzofuran levels in cow milk samples, egg samples and meat in Finland. Fresenius J. Anal. Chem. 348, 150-153.
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.
Hietaniemi, V. and Kumpulainen, J. (1994) Isomer specific analysis of PCBs and organochlorine pesticides in Finnish diet samples and selected individual foodstuffs. Food Additives and Contaminants 11, 685-694.
Sewart, A. and Jones, K. C. (1996) A Survey of PCB Congeners in U.K. Cows' Milk. Chemosphere 32, 12, 2481-2492.

Contact Points

Further information on this survey can be obtained from:

Mr Martin Gem
MAFF, 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

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These pages were last updated on 30th November 1997