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MAFF UK - 1994 TOTAL DIET STUDY (PART 2) - DIETARY INTAKES OF METALS AND OTHER ELEMENTS

Index to MAFF UK Food Surveillance Information Sheets, 1998

Summary

The JFSSG carries out regular surveys of metals and other elements in food to estimate dietary intakes of contaminants and nutrients. Improvements in analytical methodology have resulted in increased sensitivity which has enabled the detection of those metals and other elements which are present at very low concentrations in food and have not previously been included in surveys carried out by MAFF and the JFSSG.

The Total Diet Study (TDS) is used to determine dietary intakes by the general population of chemicals (such as metals) in food. Samples from the 1994 TDS were analysed in 1996/97 for 30 metals and other elements. The results of these analyses were reported in Food Surveillance Information Sheet No. 131 which also included estimates of dietary intakes by adults for 18 of these elements¹. Estimates for the remaining 12 elements (i.e. antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium) are reported here. Only antimony and thallium have been included in previous TDSs and, with the other 10 elements, required evaluation by the Committee on Toxicity of Chemicals in Food, Consumer Products and Environment (COT) on the toxicological implications of these elements in food. This was necessary because dietary intakes of these elements had not been evaluated in recent years, if ever, by the COT. The need to consult the COT has delayed the publication of these dietary intake estimates.

The COT identified limitations in the data on the chemical forms of the elements in food, the estimates of intake, the toxicity of the elements, and the identification of susceptible groups, and noted that its evaluation applied only to healthy adults. The COT concluded that:

'Acknowledging these limitations, we have seen no evidence to suggest that any of the estimated intakes should be a cause for concern.'

Brand names are not identified as TDS samples are composites of a number of similar foods.

Background

The Ministry of Agriculture, Fisheries and Food (MAFF) has carried out the Total Diet Study (TDS) since the early 1960s to identify trends in estimates of dietary intakes of the general population of various constituents². In the TDS, the major items of the national diet are combined into 20 groups of similar foods for analysis, Table 1. Foods are grouped so that commodities known to be susceptible to contamination (e.g. offals) are separated, as are commodities which are consumed in large quantities (e.g. bread, potatoes and milk)³.

The TDS is carried out annually but the interval for analysis of metals and other elements was increased in 1988 from 1 to approximately every 3 years as little variation had been found in results from year to year. Samples for the next TDS of metals and other elements were taken in 1997 and will be analysed in 1998 and 1999.

The concentrations of 30 metals and other elements found in 1994 Total Diet Study samples have been reported separately¹. This was the first time that such a wide range and large number of elements had been included in the TDS and is the result of improvements in analytical methodology which have allowed both the detection of those elements present at very low concentrations in food (e.g. platinum, rhodium, germanium, gold) and lower detection limits for other elements (e.g. cadmium, arsenic, mercury). Analyses for 10 elements (i.e. barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium and strontium) were included for the first time in the 1994 TDS. As the implications for health of the presence of these elements in food had not previously been evaluated due to lack of data, it was necessary to consult the COT. Dietary intakes for these 10 elements plus those of antimony and thallium are reported here together with the conclusions of the COT's evaluations.

Method

Sample Preparation

Individual components of the TDS food groups were purchased from retail outlets in 20 representative towns in the UK and prepared as for consumption, and cooked where appropriate, before being combined into one of 20 food groups. The 400 individual TDS samples used in this study were prepared for analysis by the Institute of Food Research (Norwich).

Multi-Element Analysis

Multi-element analyses for 30 elements (i.e. lithium, boron, calcium, aluminium, chromium, manganese, iron, cobalt, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, tin, mercury, lead, antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium) were carried out by the CSL Food Science Laboratory using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Details of the methods of analysis and quality control procedures have been reported previously¹ and full details are given in the final report of this project which is available for public access in MAFF's library⁴.

The limits of detection (LOD) for the 12 elements reported here (i.e. antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium) are listed in Table 2.

Results

The concentrations of all 30 elements and dietary intake estimates of 18 elements were reported in Food Surveillance Information Sheet No. 131¹. This Information Sheet did not include dietary intake estimates of 12 of these elements (i.e. antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium) either because they had not previously been evaluated, or had not been evaluated in recent years, by the COT. The COT considered dietary intakes of these 12 elements in February 1998. Dietary intake estimates of antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium are reported here together with outcomes of the COT's considerations.

Dietary Intake Estimates

The quantities of foods that make up the Total Diet Study samples and the relative proportion of each food are largely based on data from the National Food Survey and are updated annually⁵. Applying these quantities to the mean concentration of each element gives an estimate of population average intake (covering both adults and children). Mean and upper range (97.5 percentile) intakes have also been estimated for adult consumers using the mean concentrations of each element and data on consumption of each food group from the Dietary and Nutritional Survey of British Adults⁶. For dietary intakes estimated from results less than the LODs, it has been assumed that the concentrations of these elements are at the appropriate LODs and are thus upper bound estimates. These intakes can be regarded as 'worst cases' as it is assumed that each element is present in food at concentrations equal to or greater than the LODs.

The concentrations of metals and other elements discussed in this report are the means of the concentrations found in each food group from the 20 towns included in the 1994 TDS.

Interpretation

Dietary Intakes

Only antimony and thallium have previously been included in TDSs of metals and other elements. Total average dietary intakes for these two elements are lower than those from previous years. This can be explained by improvements in analytical methodology resulting in lower LODs. The LODs for antimony and thallium were up to ten-fold lower in the 1994 TDS (Table 2) than in previous TDSs⁷.

Antimony

Concentrations of antimony were very low in all the food groups but were highest in the miscellaneous cereals and meat products groups which both contained 0.004 mg/kg. Antimony has only been included once before in a TDS. The average dietary intake in the 1976 TDS was estimated to be 0.029 mg/day⁷. In comparison, the average and mean dietary intakes in the 1994 TDS were both 0.003 mg/day (Table 3). The corresponding upper range (97.5 percentile) dietary intake estimate was 0.004 mg/day (Table 3). This apparent reduction in average intake is caused by the development of more sensitive analytical methodology and a lower LOD^1,4.

Thallium

Thallium concentrations were low in all food groups with only carcase meat, offal, poultry, green vegetables, and nuts having concentrations above the LOD of 0.001 mg/kg. The average dietary intake in the 1979 TDS was estimated to be 0.063 mg/day⁷. In comparison, the average and mean dietary intakes in the 1994 TDS were both 0.002 mg/day with the upper range (97.5 percentile) intake being 0.004 mg/day. (Table 3). This apparent reduction in average intake may be explained by the development of more sensitive analytical methodology and a lower LOD^1,4.

Platinum Group Elements

This is the first time that platinum group elements have been included in a TDS. Concentrations of the platinum group elements (i.e. ruthenium, rhodium, iridium, palladium and platinum) were very low with few food groups containing concentrations of these elements above their LODs. Those food groups which contained detectable concentrations of the platinum group elements were nuts (0.003 mg/kg palladium, 0.004 mg/kg rhodium); and oils and fats, offal, and bread which all had palladium concentrations of 0.002 mg/kg^1,4.

Dietary intake estimates of the platinum group elements for average, mean and upper range (97.5 percentile) consumers were very low (Table 3).

Other Elements

Concentrations of those elements not included in previous TDSs (i.e. barium, gold, bismuth, germanium and strontium) were low^1,4. Barium and strontium were present in all food groups above the LODs of 0.008 mg/kg and 0.003 mg/kg, respectively. The highest mean concentrations of barium and strontium were found in the nuts group which contained 56 mg/kg and 8.6 mg/kg, respectively. Bread made the greatest contributions to total average intakes of barium (0.58 mg/day) and strontium (1.3 mg/day) contributing 20 per cent and 31 per cent, respectively. Gold was also present in all food groups above the LOD of 0.0003 mg/kg with the highest concentrations found in miscellaneous cereals (0.002 mg/kg). Germanium and bismuth concentrations were very low in all food groups^1,4.

Summary of COT statement on the results of multielement surveys

'We have considered estimates of intakes by adults in the UK of: antimony, barium, bismuth, germanium, gold, iridium, palladium, platinum, rhodium, ruthenium, strontium and thallium in the diet.

We have been provided with the available information on the toxicology of these elements relevant to their oral administration or ingestion. In evaluating the implications for human health, we note the following assumptions and limitations:

a) the chemical forms of the elements in food are not known. The relevance of the available toxicity data is therefore uncertain;

b) the estimates of intake assume that, where an element has not been detected, it is present at the limit of detection. Intakes in these cases are therefore dependent on the limit of detection or other limit assigned and can be regarded as overestimates, possibly by a considerable margin;

c) the toxicity data available to us are inadequate for a complete evaluation of any of these elements in the diet, particularly germanium, gold, iridium, palladium, platinum, rhodium and ruthenium;

d) the data are insufficient to allow the identification of groups of individuals who might be particularly susceptible to any adverse health effects from dietary intakes of these elements. Consequently our evaluation applies only to healthy adults.

Acknowledging these limitations, we have seen no evidence to suggest that any of the estimated intakes should be a cause for concern.'

References

Ministry of Agriculture, Fisheries and Food (1997). 1994 Total Diet Study: Metals and Other Elements. Food Surveillance Information Sheet No. 131.
Ministry of Agriculture, Fisheries and Food (1994). Steering Group on Chemical Aspects of Food Surveillance. The British Diet: Finding the Facts 1989-1993. Food Surveillance Paper No. 40. HMSO
Peattie, M.E., Buss, D.H., Lindsay, D.G. and Smart, G.A. (1983). Reorganization of the British Total Diet Study for monitoring food constituents from 1981. Fd. Chem. Toxic. 21(4), 503-507.
CSL Food Science Laboratory (1997). The Multi-Element Analysis of 1994 Total Diet Survey Samples. Final Report. Report No. FD96/109.
Ministry of Agriculture, Fisheries and Food. (1995). National Food Survey 1994: annual report on household food consumption and expenditure. HMSO.
Gregory, J., Foster, K., Tyler, H. and Wiseman, M (1990). The Dietary and Nutritional Survey of British Adults. HMSO.
Ministry of Agriculture, Fisheries and Food (1985). Steering Group on Chemical Aspects of Food Surveillance. Survey of Aluminium, Antimony, Chromium, Cobalt, Indium, Nickel, Thallium and Tin in Food. Food Surveillance Paper No. 15. HMSO.

Contact Points

Further information on this survey can be obtained from:

Dr Gillian Ysart
MAFF, Joint Food Safety and Standards Group
Food Contaminants Division
Room 238, Ergon House, c/o Nobel House
17 Smith Square
London, SW1P 3JR.
Tel: +44 (0)20 7238 6756
Fax: +44 (0)20 7238 5331

Further copies of this Information Sheet can be obtained from:

MAFF, Publicity and Information Section
Room 303B, Ergon House, c/o Nobel House
17 Smith Square
London, SW1P 3JR.
Tel: +44 (0)20 7238 6244/5 or 6150
Fax: +44 (0)20 7238 6330
E-mail: s.h.fssginfo@fssg.maff.gov.uk

Copies of the full COT statement on the results of multielement surveys can be obtained from:

Mr Jonathan Lighthill
COT Secretariat
Room 652C, Skipton House
80 London Road
London SE1 6LW.
Tel: +44 (0)20 7972 5007
Fax: +44 (0)20 7972 5134
E-mail: jlighthill@hefm.demon.co.uk

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These pages were last updated on 30th April 1998