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Nanomaterials

Silver in antimicrobial plastic packaging leaches into foods

Toxicity of the metal nanoparticles is unclear, but findings could play a role in future policy decisions

by Prachi Patel
January 21, 2025

New study raises concerns about the possibility of adding silver nanoparticles to antimicrobial packaging
Credit: Shutterstock
A new study raises concerns about antimicrobial packaging containing silver nanoparticles.

Antimicrobial packaging could help extend the shelf life of food, prevent illnesses, and reduce food waste. While there has been commercial interest in plastic food packaging containing antimicrobial silver nanoparticles, it is not approved in the US or Europe.

That caution might be warranted, according to new research that shows that silver escapes from nanoparticle-containing plastic packaging to the food it holds (ACS Food Sci. Technol. 2025, DOI: 10.1021/acsfoodscitech.4c00813).

Humans have used silver for disinfection and medical treatment for centuries. But advocacy groups have raised concerns about the use of engineered nanosilver in health-care and consumer products in recent decades because scientists don’t fully understand the effect of its exposure on humans and other organisms.

These concerns are why US Food and Drug Administration research scientist Timothy Duncan and colleagues wanted to analyze whether silver nanoparticles stay put in food packaging. They have previously studied the leakage of silver into beverages and into liquid foods such as yogurt (ACS Appl. Mater. Interfaces 2021, DOI: 10.1021/acsami.0c17867). Silver is expected to seep into liquids because they are homogeneous and come into close contact with plastic packaging. But with solid foods, “you have a lot of air gaps between the food particles and the polymer, so the expectation was you wouldn’t see any migration at all,” Duncan says.

The researchers set out to test that hypothesis. They made their own nanoparticle-embedded polyethylene films to wrap four food items—cheese slices, wheat flour, spinach leaves, and ground rice—and stored the packaged items at various simulated storage conditions. For instance, they stored cheese at 25 °C for 10 days to simulate long-term refrigeration and spinach at 4 °C for 5 days for short-term refrigeration. “We expected to see nothing. We thought this was going to be a quick one and done,” Duncan says.

To the researchers’ surprise, when they analyzed the foods using inductively coupled plasma mass spectrometry, they found that silver contaminated all the items. The amount depended on food particle size and the level of contact between food surface and packaging. Silver concentration was higher in finely ground rice than in coarsely ground rice, for instance, and higher in cheese than in flour because more of the relative flat cheese surface contacted the plastic. The silver stays mostly on the food’s surface, Duncan says, “which means that you can wash some of it off. We found that washing removes a lot of the silver, but not all of it.”

The released silver concentration is low, and any related risk will need further studies, says Katrin Löschner, an analytical food chemist at the Technical University of Denmark. She says the study adds important new knowledge to the field. While the European Food Safety Authority has identified no safety concerns for plastic packaging containing up to 0.025% by weight of nanosilver, she says, long-term exposure to higher levels could still bring risks. “I believe that it has its place in health applications but not in food contact materials despite not being toxic for consumers,” she says.

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