Migration of silver from commercial plastic food containers and implications for consumer exposure assessment

Abstract

Food storage containers with embedded silver as an antibacterial agent promise longer durability of food. For risk assessment the release of this silver into the stored food and resulting human exposure need to be known. For the purpose of exposure assessment, silver migration from commercial plastic containers with declared content of ‘nano-’ or ‘micro-silver’ into different food simulants (water, 10% ethanol, 3% acetic acid, olive oil) was quantitatively determined by ICP-MS and the form of the released silver was investigated. The highest migration of silver was observed for the acidic food simulant with 30 ng silver cm⁻² contact surface within 10 days at 20°C. In a second and third use cycle, migration dropped by a factor of up to 10, so that the maximum cumulated release over three use cycles was 34 ng cm⁻². The silver release over time was described using a power function and a numerical model that simulates Fickian diffusion through the plastic material. The released silver was found to be in ionic form, but also in the form of silver nanoparticles (around 12%). Consumer exposure to the total amount of silver released from the food containers is low in comparison with the background silver exposure of the general population, but since natural background concentrations are only known for ionic silver, the exposure to silver nanoparticles is not directly comparable with a safe background level.

Keywords:

• silver
• nanoparticles
• food container
• migration
• food simulant

Acknowledgement

The authors thank Christiane Lorenz for valuable advice, Frank Krumeich for SEM and TEM analyses, Akshata Rao for AFM analyses, Sabrina Gschwind for conducting the SP-ICP-MS experiment, and Claude Rerat for parameter optimisation. For helpful discussions they thank Ralf Kaegi, Martin Scheringer and Pawel Sikorski.