A03023: Strategy for assessing risk and assigning priorities to chemicals used to make food contact materials - a tiered approach with progressive refinement to calculate exposure levels

Study Duration: October 1999 to November 2003

Contractor: Central Science Laboratory

There are many hundreds if not thousands of chemicals used for the manufacture of materials and articles intended to come into contact with foodstuffs. Although underway for more than two decades now, work by the Commission of the European Union acting in conjunction with Member States is still in its infancy and detailed rulemaking applies to plastics only. Decisions on other materials, including paper, coatings, ion exchange resins, rubber, silicones, metals, wood and textiles, are still pending.

Even for plastics materials, there are a number of rather crude and imprecise assumptions that are conventionally applied to move from a tolerable daily intake value to risk management using a specific migration limit or a limit on composition. Some of these assumptions are currently under review, for example the possible application of food type factors and packaging usage factors. There are other assumptions made within the Commission and the Scientific Committee on Food (SCF) (and now by the European Food Safety Authority, subject to confirmation) that require similar examination. For example when moving from a specific petition to giving general approval for a substance, the assumption is made that all applications will use the maximum formulation level and that all migration to foods is equal to that determined by the petitioner under the worst-case conditions of use.

The purpose of this project is to assess the feasibility of a structured, tiered approach to estimating potential exposure to chemicals that may migrate from food contact materials.

The approach uses progressively refined assumptions, calculations and, finally, actual migration, usage and food consumption data where available. The utility of the approach is tested for six substances for which some exposure information was available. The substances, chosen to cover a variety of technological roles, were: bisphenol A, benzophenone, di(2-ethylhexyl) adipate, styrene, polyethyleneglycol 2,4,7,9-tetramethyl-5-decyn-4,7-diol ether, and crotonic acid.

For all the case studies considered, it was difficult to evaluate fully the factors that will affect the intake of a substance. One critical issue was a due consideration of the 'high consumer'.

The case study for bisphenol A brought-out the fact that food consumption by infants and small children is much higher, on a body weight basis, than for the conventional adult model of 1 kilogram (kg) food/60 kg body mass. For an infant of 0-4 months of age, food consumption can be up to 155 grams (g)/kg bodyweight (bw)/day. For a small child, aged 4-6 years, food consumption can be up to 58 g/kg bw/day. For the conventional exposure model, the factor used is 17 g/kg bw/day. Thus, in order to provide the same level of protection and ensure that any respective Tolerable Daily Intake is not exceeded, special rules should be considered to reduce the Specific Migration Limit (SML) values for substances used to make food contact materials and articles intended specifically for the foodstuffs of infants and small children. The case studies for bisphenol A and for styrene demonstrated that, in some food contact applications, the plastic could in principle depolymerise to form additional monomer that might migrate. These special circumstances would need to be taken into account if migration levels and exposure levels were estimated using empirical composition-migration relationships or using mathematical diffusion modelling.

In all of the six case studies, examples are given where the estimation of exposure can use statistics on the market share of different types of food contact materials. This information came from the results of market research. However, this information is not available for the UK in any general sense, and it has not been fully explored how these market averages can be used to estimate the packaging usage of different sections of the population.

The last two of the six case studies presented, illustrate how, if the scope of application of a substances is restricted, then simple calculations of consumer exposure can be made quickly based on usage or residual levels alone. In those two cases, for the migration of polyethyleneglycol 2,4,7,9-tetramethyl-5-decyn-4,7-diol ether from non-stick coatings and for the migration of crotonic acid from PVC, the calculations illustrated that the potential for consumer exposure was very low.

Such restrictions in scope are increasing for plastics and for coatings and for non-plastics they may prove to be the norm rather than the exception. However, in the absence of detailed and validated usage information, the conservative assumptions that are presently made on packaging usage are justified when establishing SML values. It is not possible to prioritise in any general way, those chemicals that are used widely and so require a full risk assessment compared with any chemicals that are perhaps used so little that an abbreviated risk assessment could be made.

At present, and for important monomers and additives used to make plastics, there is no generally acceptable alternative when assessing consumer exposure than conducting food surveys to obtain concentration data and coupling this information with detailed statistics on dietary habits to calculate reliable estimates of intake.

Final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr. Elsie Widdowson Library and Information Services, Food Standards Agency (020 7276 8181/8182 or at library&info@foodstandards.gsi.gov.uk).

Contact: For any enquiries concerning this research project, please contact the relevant Programme contact or email science@foodstandards.gsi.gov.uk