Number 189 November 1999
MAFF UK - TOTAL DIET STUDY: STYRENE
Index to MAFF UK Food Surveillance Information
Sheets, 1999
see also:
1: MAFF UK - Metallic Compounds
in Plastics (July 1993)
15: MAFF UK - Hydrocarbons
in Chocolate (October 1993)
25: MAFF UK - Composition of
Films Used to Wrap Food (February 1994)
26: MAFF UK - Formaldehyde in
Tea-Bags (May 1994)
35: MAFF UK - Survey of Benzene
in Food Contact Plastics (September 1994)
38: MAFF UK - Survey of Styrene
in Food (October 1994)
47: MAFF UK - Fluorescent
Whitening Agents (January 1995)
58: MAFF UK - Benzene and other
Aromatic Hydrocarbons in Food - Average UK Dietary Intakes (March
1995)
59: MAFF UK - Dioxins in
PVC Food Packaging (April 1995)
60: MAFF UK - Phthalates
in Paper and Board Packaging (May 1995)
66: MAFF UK - Grease Proofing
Agents in Paper and Board (June 1995)
72: MAFF UK - Curing Agents
in Carton-Board Food Packaging (July 1995)
90: MAFF UK - Survey of Paper
and Board Food Contact Materials for Residual Amine Monomers from
Wet Strength Agents (May 1996)
98: MAFF UK - Hydrocarbons
in Foods from Shops in Petrol Stations and Stalls or Shops in Busy
Roads (October 1996)
141: MAFF UK - Chlorobenzenes
in Foods (February 1998)
Summary
The latest MAFF/DH Joint Food Safety and Standards Group (JFSSG)
survey of chemical migration from packaging was carried out on styrene
in five sets of UK Total Diet Study samples. Styrene was detected
at low levels (14 micrograms/kg or less). It was found in samples
of food groups other than that of potatoes. Dietary exposure to
styrene was estimated at 0.03 to 0.05 micrograms/kg bodyweight per
day. This is three orders of magnitude less than the Provisional
Maximum Tolerable Daily Intake of 40 micrograms/kg bodyweight per
day set by Joint FAO/WHO Expert Committee on Food Additives. This
survey is being submitted to the EC’s Scientific Committee
for Food (SCF) to aid its review of styrene.
Background
Styrene is a monomeric starting material that is widely used in
the manufacture of plastics. For example it is used to produce polystyrene
and as a comonomer to make acrylonitrile-butadiene-styrene (ABS).
Foamed polystyrene trays are used to package some meats, fish, fruit
and vegetables, whilst ABS tubs are used for some dairy products,
margarines and low-fat spreads. Some residual styrene can remain
in the finished packaging material. This residual monomer can migrate
into foods.1,2
Styrene in food might also arise from other sources. For example
styrene may migrate from coatings for bulk storage containers and
from resin beds used in some industries to treat processing water.
There is also some evidence that styrene can occur naturally in
some foods since it is structurally similar to certain flavouring
substances and can be formed from them.3,4
For example, Steele et al.4
found approximately 40 mg/kg of styrene in cinnamon and attributed
this to the decarboxylation of cinnamic acid.
Styrene is scheduled for consideration by the EC Scientific Committee
for Food as part of its routine review of substances used in food
contact plastics. This survey was carried out to aid this review.
The use of styrene as a monomer in food contact plastics is currently
authorised under Directive 90/128/EEC without a specific migration
limit (although an overall migration limit of 60 mg/kg food applies).
Sources of styrene in the diet other than its migration from plastics
in contact with food are controlled in Great Britain under the general
provisions of the Food Safety Act 1990.
Styrene levels in individual samples of food and packaging have
been surveyed previously.5, 6
However, this is the first JFSSG survey of styrene in UK Total Diet
Study (TDS) samples. The TDS involves over 100 categories of food
combined into groups of composite samples of similar foods for analysis
such as to reflect their importance in the average UK household
diet.7 The quantities of foods that
make up the TDS, and the relative proportions of each food category
within a group, are based on data from the National Food Survey
(NFS)8 and are updated annually based
on an average of data from three previous years.
Analysis of chemical contaminants such as styrene in samples from
the TDS provides information about the general types of foods that
might be contaminated. In this case, where dietary exposure has
not been estimated recently, the TDS provides a general check on
how dietary exposure compares with exposure limits that have been
defined by independent expert committees.9
For styrene, a Provisional Maximum Tolerable Daily Intake (PMTDI)
of 40 micrograms/kg bodyweight/day has been set by the Joint FAO/WHO
Expert Committee on Food Additives (JECFA).10
Analytical work for this survey was carried out at the Central
Science Laboratory in Norwich on TDS samples supplied by the Institute
of Food Research in Norwich. This survey was carried out before
adoption of the Guidelines for Planning and Reporting JFSSG Surveys11
announced in the January 1999 issue of the DH/MAFF Food Safety
Information Bulletin. Nevertheless every effort has been made
to report this survey to the standards defined in the Guidelines.
Surveys like the TDS which analyse composite samples of several
brands of foodstuffs are excluded from JFSSG arrangements to release
information on the identity of individual samples.11
Methodology
Sampling
Samples of individual foods in the various categories comprising
the 20 TDS food groups were purchased at five different locations
on different dates during 1997 from retail outlets in different
parts of the UK. These samples were prepared as for consumption
(including cooking where appropriate) and combined into the 100
composite samples analysed in this study. Each composite sample
was homogenised before being stored, by the Institute of Food Research
in Norwich, at –20oC until required for analysis.
The samples were supplied for analysis in screw cap, 150 ml polypropylene
bottles.
Analysis
The method of analysis12 involved
a Likens-Nickerson extraction of styrene from a portion of the food
(10 plus or minus 0.5 g), using deuterated styrene as an internal
standard, followed by GC-MS analysis. Quantification was based on
comparison of chromatographic peak areas for styrene at m/z 103
and 104 and deuterated styrene at m/z 110 and 112, and the construction
of a calibration graph of peak area ratio at m/z 104 to m/z 112.
Values were corrected for recovery, using the recoveries for in-batch
‘spiked’ samples. Results were also corrected for the
batch blank value. The detection limit was 0.3 micrograms/kg. This
limit of detection (LoD) was derived from the maximum styrene levels
in the method blanks which were between 0 and 0.3 micrograms/kg.
The limit of quantification (LoQ) was 1.0 micrograms/kg (3.3 x the
LoD).
Quality assurance
Analysis of the five sets of TDS samples was carried out in batches,
with samples of the same food group analysed in a batch. Each batch
consisted of 20 samples including one reagent blank, one ‘spiked’
sample selected at random from the batch, one calibration standard
and a sub-sample of an appropriate in-house reference material.
For ‘spiking’ two portions of a sample were weighed out
and one portion ‘spiked’ with styrene at 10 micrograms/kg
using 100 microlitres of 1 microgram/ml working standard of styrene.
For the ‘in-batch’ calibration standard, 10 plus or minus
0.5 g deionised water was ‘spiked’ with 100 microlitres
of 1 microgram/ml working standard and then subjected to steam distillation.
The reagent blank was water. The mean values of styrene in yoghurt
and margarine in-house reference materials were respectively 5.7
plus or minus 0.4 (n=7) and 6.0 plus or minus 0.6 (n=3) micrograms/kg.
The average value for cooked chicken in-house reference material
was 4.3 micrograms/kg (n=2). Within-batch recovery was 107 to 139
per cent.
For styrene to be considered to be present in samples all of the
following criteria had to be met for each analytical run:
- less than or equal to 0.02 minutes difference between the retention
times for m/z 110 and 112 and between m/z 103 and 104;
- less than or equal to 0.02 minutes difference in the retention
time for m/z 112 between standards and samples;
- less than or equal to 0.02 minutes difference in the retention
time for m/z 104 between standards and samples; and
- ion ratios m/z 104/103 and 112/110 for samples to be within
plus or minus 20 per cent of the mean of these ratios for standards.
Checks were made to ensure that there had been no accidental contamination
with styrene during the preparation of TDS samples. A range of samples
was purchased from retail outlets by Central Science Laboratory
(CSL) staff and each sample was divided in two. One half of the
sample was then prepared at CSL, taking all possible precautions
to avoid contact with styrene. The other half of the sample was
prepared at the Institute of Food Research (IFR) using the usual
procedures for preparing TDS samples. All samples were then analysed
as described above. There was no significant difference in styrene
levels between the samples prepared at IFR and those prepared at
CSL. This indicated that any styrene detected in TDS samples was
not introduced by the preparation procedures used at the IFR.
Dietary Exposure Estimates
The dietary exposure estimates were carried out using the published
methodology.7 Thus multiplying the
amounts of foods consumed (based on average consumption data from
the 1997 National Food Survey) by the corresponding mean levels
of styrene detected in each TDS food group gave an estimate of average
dietary exposure (for an average household) for that year. The consumption
data (from the National Food Survey) used to estimate dietary exposure
of styrene are shown in Table 1.
Upper and lower bounds were calculated for the mean levels of styrene
and hence for the estimate of dietary exposure. For the upper bound,
levels which were reported as less than the limit of detection (LoD)
were taken as being equal to the LoD, and levels which were reported
as between the LoD and the limit of quantification (LoQ) were taken
as equal to the LoQ. For the lower bound, levels which were reported
as less than the LoD were taken as equal to zero, and levels which
were reported as between the LoD and the LoQ were taken as equal
to the LoD.
Results
Styrene levels in the TDS food samples and the mean styrene levels
for the sets of samples of each food group are shown in Table
2. Styrene was detected at up to 14 micrograms/kg in food groups
other than ‘potatoes’. Levels were highest in the ‘oils
and fats’ and ‘nuts’ food groups. Migration may have
contributed to styrene in the ‘oils and fats’ group, and
in the offal, poultry, dairy products, carcass meat and fish groups
as samples of food in these groups had been packaged in material
made from styrene. But the other food groups, including ‘nuts’,
had apparently not been in contact with packaging made from styrene.
However contact may have occurred earlier in the production chain
and there may possibly have been contamination from environmental
sources. Natural production of styrene cannot be discounted, although
for such a biologically-diverse group of food sources in this case
(animals, vegetables and fruit) a common natural source of styrene
would appear to be very unlikely.
Exposure of styrene was estimated to be 0.03 to 0.05 micrograms/kg
bodyweight/day for a 60 kg person. This is three orders of magnitude
less than the Provisional Maximum Tolerable Daily Intake (PMTDI)
of 40 micrograms/kg bodyweight/day set by Joint FAO/WHO Expert Committee
on Food Additives (JECFA).10
Conclusions
Exposure to styrene from the diet in the UK is well below the PMTDI.
This survey provides information that will be of use when the EC’s
Scientific Committee for Food considers styrene as part of its routine
review of substances used in food contact plastics.
References
- Gilbert, J. and Startin, J.R. (1983) A survey
of styrene monomer levels in foods and plastic packaging by coupled
mass spectrometry-headspace analysis. Journal of Chromatography
34, 647-652.
- Varner, S.L., Breder, C.V. and Fazio, T. (1983)
Determination of styrene migration from food contact materials
into margarine using azeotropic distillation and headspace gas
chromatography. Journal of the Association of Official Analytical
Chemists 66, 1067-1072.
- Woller, R. (1991) Styrene in wines. International
Vigne et de Vin, Group of Experts on Nutrition and Health.
Document T944/91/VH/504-1x.
- Steele, D.H., Thorburg, M.J., Stanley, J.S.,
Miller, R.R., Brooke, R., Cushman, J.R. and Cruzan, G. (1994)
Determination of styrene in selected foods. Journal of Agricultural
and Food Chemistry 42, 1661-1665.
- Ministry of Agriculture, Fisheries and Food
(1983) Survey of styrene levels in food contact materials and
in foods. Food Surveillance Paper Number 11, HMSO.
- Ministry of Agriculture, Fisheries and Food
(1994) Survey of styrene in food. Food
Surveillance Information Sheet, Number 38, HMSO.
- Peattie, M.E., Buss, D.H., Lindsay, D.G. and
Smart, G.A. (1983) Reorganisation of the British Total Diet Study
for monitoring food constituents from 1981. Food and Chemical
Toxicology 21, 503-507.
- Ministry of Agriculture, Fisheries and Food
(1997) National Food Survey 1996. HMSO.
- Ministry of Agriculture, Fisheries and Food
(1994) The British Diet: Finding the Facts 1989-1993. Food
Surveillance Paper, Number 40. HMSO.
- World Health Organisation (1984) Toxicological
Evaluation of Certain Food Additives and Food Contaminants. 28th
Report of the Joint FAO/WHO Expert Committee on Food Additives.
WHO Food Additives Series No. 19. World Health Organisation,
Geneva.
- MAFF/DH Joint Food Safety and Standards Group
(1999) Guidelines for planning and reporting JFSSG surveys (announced
in JFSSG Food Safety Information Bulletin Number 104,
January 1999).
- Gramshaw, J.W and Vandenburgh, H.J (1995).
Compositional analysis of samples of thermoset polyester and migration
of ethylbenzene and styrene from thermoset polyester into pork
during cooking. Food Additives and Contaminants. 12,
223-234.
Further information
Units of measurement
1 microgram = 10-6 g
1 milligram (mg) = 10-3 g
1 kilogram (kg) = 103 g
The report of the survey is held in the MAFF Library at Nobel House,
17 Smith Square, London SW1P 3JR (Tel: +44 (0) 20 7238-6573). If
you wish to consult a copy please contact the library for an appointment
giving at least 24 hours notice or, alternatively, copies can be
obtained from the library: a charge will be made to cover photocopying
and postage.
Further enquiries should be addressed to:
Mr Patrice Mongelard
JFSSG (MAFF)
Food Contact Materials Unit
Branch B
Additives and Novel Foods Division
Room 213, Ergon House
17 Smith Square
London SW1P 3JR
Tel: +44 (0) 20 7238 6225
Fax: +44 (0) 20 7238 6124
e-mail: p.mongelard@fssg.maff.gov.uk
Spreadsheet tables
| Table 1: |
Consumption data from the National Food Survey used to
estimate dietary exposure in the 1997 Total Diet Study used
in this survey of styrene |
| Table 2: |
Styrene in 1997 Total Diet Study (TDS) samples and mean
levels |
Click here to download the Excel 5.0 version
of Tables 1 and 2
Click here to view the .pdf version of Tables
1 and 2 (if you have any other spreadsheet package)
This material is Crown Copyright but may be reproduced without
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Crown Copyright 1999.
These pages were last updated on 29 October 1999.
