A03045: To identify chemicals that could migrate into foodstuffs from pigments and dyes, and measure the migration of these chemicals into food simulants

Study Duration: April 2003 to August 2005

Contractor: Pira International

Colorants are used in food contact plastics to make products more appealing to the consumer and to reinforce a product brand image. A range of colorants can be used either individually or in mixtures to obtain a particular effect or colour.

Colorants' producers are based in many countries throughout the world.

No migration limits are set for these substances in the European Commission Plastics Directive 2002/72/EC (EC 2002) as amended, nor does any other Directive specifically deal with this class of substance. However, there has been a Council of Europe Resolution, which is not legally binding but gives guidance on their use.

Little information was available regarding potential migrants that may be present in colorants used in food contact plastics. Several different grades of a colorant may be available, all of which can nominally be described using the same identifying name, for example Colour Index (CI) Pigment White 6.

In addition, to achieve a desired effect colorants can be blended with each other so that a particular plastic may contain several different colorants. The aim of this study was to provide data on compounds including impurities and intentionally added substances, such as surface treatment chemicals, that may be present in the most commonly-used colorants. Information obtained would be used to help inform decisions on how best to control these substances.

This project will (with collaboration from industry) select the most commonly-used pigments and dyestuffs intended for plastic food contact applications. By reference to industry and by chemical analysis, impurities and surface treatment chemicals in the colorants will be identified. Plastic samples will be obtained containing these colorants and migration of substances into suitable food simulants will be determined. The levels of the colorants and associated impurities in the plastic samples will be measured analytically and, using migration models based on Fickian diffusion principles, migration of the chemicals of interest will be calculated. These values will be compared to the measured values and the suitability of mathematical modelling for these materials will be established.

Industry input was obtained from two masterbatch manufacturers and Members of the British Colour Makers Association (BCMA). In total, 22 samples of 16 colorants were tested which covered the majority of the UK's colorant usage. Those selected included inorganic and organic pigments and organic dyestuffs, applicable to all plastics commonly used for food contact applications.

The first step of the work centred on attempting to identify potential migrants. Each of the colorants was extracted with dichloromethane, acetone and methanol. The extracts were analysed by gas chromatography-mass spectrometry, high temperature gas chromatography and high-pressure liquid chromatography.

Based on the determination of potential migrants in the extracts, or wide usage in the UK, some of the colorants were used in the preparation of test articles of compounded plastics. Migration tests were undertaken on these compounded samples using food simulants or fatty simulant substitutes under worst case test conditions.

Some migration of the substances identified in the extraction tests was found but in general at concentrations of less than 50 micrograms/kilogram. The limit of detection was 35 micrograms/kilogram or better for all substances identified. Such compounds included phthalimide, decamethylcyclopentasiloxane, trimethylolpropane and o-phenetidine.

Migration of 4-chloro-2,5-dimethoxyaniline, a primary aromatic amine (PAA), was found at a concentration of 109 micrograms/kg from one plastic test article (CO115/11) prepared using C.I. Pigment Yellow 83. This equates to a migration of 54 micrograms/kg of aniline. The specific migration limit for PAAs, expressed as aniline in 2002/72/EC, is non detectable with a limit of detection of 20 micrograms/kg. It must be noted that this work was undertaken on specially prepared plastics, not real-use articles, using worst case migration conditions. However, evidence of such migration demonstrates that care must be taken over the use of such colorants, the choice of plastics, the processing conditions and the possible migration issues, particularly with respect to compounds such as PAAs.

Some colour leaching was noted from one polyester test article into 95% ethanol simulant. However, this was not repeated when a colour leaching test was undertaken as described in the CoE Resolution AP (89) 1 using simulant D (olive oil) at 50°C.

To simulate wear on plastic articles the effect of abrasion on migration of substances was investigated for two plastic test samples. In general this effect was found to be minimal. However, migration of trimethylol propane (TMP) increased by 40% from a polypropylene test article containing a titanium dioxide colorant.

Finally, based on the initial concentrations of migrants in the test articles (determined experimentally or from information supplied by the colorant manufacturer) a model was used to predict levels of migration. Results were compared with those obtained from the migration into simulants. On the basis of the work carried out to date, which encompasses the range of colorants so far examined, the model considerably over-predicted migration. It is suggested that the cause of this was adsorption of the migrating substances (impurities and intentionally added substances) onto the colorants. The model is based on the principle that the substance is present as a free agent and not bound to another material.

Information has been obtained about substances that might migrate into food from a selection of colorants (pigments and dyes) that are commonly used in plastic packaging. Some migration of the substances identified in the extraction tests was found, but in general at low levels (less than 50 micrograms/kilogram). This research will be used to inform future European Union discussions on the use of colorants in food contact plastics.

The final report is available from the Agency's Information Centre.

To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@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