HEAVY-METAL IONS IN GLASS AND RELATED LEGISLATION

Within the framework of the measures taken to regulate the use of toxi c heavy metals the recent EC Directive 94\62, of environmental concern , and the revision of the International Standard ISO 7086, of more spe cific food safety concern, are playing a very significant role. The co mpositional limits for heavy metals set up by the Directive on packagi ng and packaging waste are not really relevant to the aim of preventin g feachingfrom glass because of the inherent inertness of the glass as a material. On the other hand it may discourage recycling which is a main objective of the Directive. An overview on the typical contaminat ion occurring for glass bottles available on the market is given, toge ther with the corresponding migration levels. The new limit values pro posed by ISO 7086 for the migration of lead and cadmium from food arti cles can easily be fulfilled by lead bearing glasses providing there i s careful control over the chemical composition. A regression analysis carried out on a large set of lead crystal glasses enables us to pred ict the chemical durability of a glass related to the required viscosi ty and workability.