Nanomaterials in food and packaging: what's there, what's regulated, what nobody knows

For decades the bright white shell on a sugar-coated chocolate, the opaque white of some icings and the clean look of certain chewing gums came partly from the same ingredient: titanium dioxide, listed in Europe as E171. In August 2022 the European Union stopped allowing it in food. Most shoppers never noticed, and the confectioners mostly reformulated without fuss.

The reason for the ban had little to do with titanium dioxide as such. It had to do with size. A share of the particles in food-grade titanium dioxide are small enough to count as nanoparticles, and European regulators concluded they could no longer rule out that those particles might damage DNA.

That story is a good entry point into a wider and more muddled subject. Engineered nanomaterials have been marketed for food and packaging since the early 2000s, and nano-sized particles have sat inside some familiar additives for much longer, as a side effect of how the powders are made. The rules covering them vary widely by country, labelling is close to invisible, and some of the most basic questions about exposure still lack good answers.

What counts as "nano"?

A nanometer is a millionth of a millimeter. The usual working boundary for nanomaterials is 1 to 100 nanometers, a size range at which particles can behave differently from the same substance in bulk. They have far more surface area per gram, they can be more chemically reactive, and they may cross biological barriers that larger particles cannot.

The European Commission's definition, updated in a 2022 recommendation, calls a material "nano" if at least half of its particles, counted by number, have one or more external dimensions in that range. Counting by number rather than weight matters a great deal. A powder can be mostly nanoparticles by count while those particles make up a small share of its mass.

Food law adds another wrinkle. EU rules on novel foods and food labelling use the narrower term engineered nanomaterial: something intentionally produced with properties characteristic of the nanoscale. That word "intentionally" carries a lot of weight, as we'll see.

It is also worth remembering that food is full of natural structures at this scale. The protein clusters in milk, for instance, fall around this size range. "Nano" is not a synonym for "artificial" or "dangerous". The regulatory question is narrower: whether particles engineered or processed to this size behave in ways that existing safety assessments miss.

Where nanomaterials turn up

There are three main routes into the food chain.

Additives. Titanium dioxide was the best known, used for whiteness and opacity. Synthetic amorphous silica (E551), an anti-caking agent in salt, spices and powdered foods, is made of tiny primary particles fused into larger clusters. Some nutrients, such as vitamins and omega-3 oils, are packaged in nano-sized carriers to make them disperse in drinks or survive digestion.

Packaging and food-contact materials. This is where much of the deliberate engineering happens. Plate-like clay particles a nanometer or so thick can be dispersed through plastics to slow the movement of oxygen and carbon dioxide, which helps keep drinks and packaged foods fresh. Silver nanoparticles, which release antimicrobial silver ions, have been built into storage containers, refrigerator liners and kitchen tools. Titanium nitride nanoparticles are used in some PET bottles. Researchers have also worked on "smart" packaging with nanoscale sensors that change color as food spoils.

Farming inputs. Nano-formulated pesticides and fertilizers are an active research area. Their regulatory status is a separate story, and most remain at an early stage, so this piece concentrates on food and packaging.

The E171 case, step by step

The titanium dioxide ban is the clearest example of how nano concerns move through a regulatory system.

In 2017 a rat study by French government researchers reported precancerous changes in the colons of some animals exposed to E171 through drinking water. The study had limits, as rodent studies do, but it prompted France to suspend E171 in food from January 2020.

The European Food Safety Authority then re-examined the evidence. In May 2021 it concluded that E171 could no longer be considered safe as a food additive. EFSA did not say it had proof of harm. It said that concerns about genotoxicity, meaning damage to genetic material, could not be ruled out, particularly for the nano fraction, and that without being able to exclude that, it could not set a safe daily intake. The European Commission adopted a ban in January 2022, which took full effect in August 2022 after a six-month phase-out. Medicines were exempted for the time being, because replacing titanium dioxide in tablet coatings is technically harder.

Other regulators read the same literature differently. In the United States, the Food and Drug Administration permits titanium dioxide as a color additive at up to 1 percent of a food's weight. When California lawmakers debated banning several additives in 2023, titanium dioxide was in early versions of the bill but was removed before it passed. Consumer and environmental groups petitioned the FDA in 2023 to revoke its approval; as of September 2024 the agency had not done so. Health Canada reviewed the evidence in 2022 and decided not to restrict it. Great Britain has kept it permitted, while Northern Ireland, which follows EU food additive rules, applies the ban.

That divergence is not necessarily a sign that one side is reckless. It reflects different thresholds for acting under uncertainty, which is ultimately a political choice as much as a scientific one.

Status at a glance

Labelling: a rule you rarely see

Since December 2014, EU food labelling law has required any ingredient present as an engineered nanomaterial to appear in the ingredients list followed by "(nano)". In practice shoppers almost never see it.

Part of the reason is the definition. Food-grade titanium dioxide was not deliberately engineered to be nano; its nano fraction is a byproduct of how the pigment is made. Whether such materials count as "engineered nanomaterials" has been argued over for years, and the food-specific definition has been under revision to bring it into line with the 2022 recommendation. Part of the reason is measurement: detecting and counting nanoparticles inside a chocolate bar or a sauce is much harder than doing it in a clean powder.

Packaging is a separate patchwork. EU rules on plastic food-contact materials say nanoforms of a substance may be used only if they have been explicitly authorized as nanoforms; approval of the bulk substance does not cover them. The EU's biocides regulation requires treated articles containing nanomaterials, such as an antimicrobial container, to name them with "nano" in brackets on the label. In the United States, by contrast, there is no nano-specific labelling for food or packaging. The FDA's 2014 guidance said it does not treat nanotechnology products as inherently safe or harmful, but expects companies to consider whether size changes a product's properties.

What is genuinely unknown

Do nanoparticles migrate out of packaging into food? Studies of nanoclay and nanosilver packaging generally report low migration, and some detect silver mostly as dissolved ions rather than intact particles. But results depend heavily on the food, temperature, storage time and test method, and many studies were small. A container reused for years, scratched and microwaved, is a different case from a freshly made test sample.

What happens in the gut? This is the core uncertainty behind the E171 decision. Animal studies suggest some nanoparticles can interact with the gut lining, the immune cells beneath it and possibly the gut microbiome. Human data are thin, and extrapolating from rodents given high doses to people eating small amounts over decades is difficult in both directions.

How much are people actually exposed? Exposure estimates rely on assumptions about which foods contain which particles in which form. EFSA's work on E171 found that children, who eat more sweets per kilogram of body weight, had higher estimated exposure than adults. For many other materials, nobody has good figures.

Can regulators measure what they regulate? Rules that depend on particle counts need reliable methods for counting particles in complex foods. EFSA published updated guidance on nanomaterial risk assessment in 2021, but routine enforcement testing remains limited.

What happens at end of life? Packaging with embedded nanoparticles goes to landfills, incinerators and recycling streams. How those particles behave in recycled plastic or in the environment is an open research question.

Why this is a governance story, not just a chemistry one

The nanotechnology debate of the mid-2000s asked whether "nano" as a category needed its own rules. The answer that emerged, at least in Europe, was a compromise: no single nano law, but nano-specific clauses inserted into existing laws on food additives, novel foods, plastics and biocides. That approach works when regulators know a nanomaterial is present and have methods to assess it. It struggles when particles arrive as an unplanned fraction of a familiar additive.

It also shows how much depends on who is asked to prove what. Under EU food law a company has to show an additive is safe; when EFSA could not close the genotoxicity question, the burden fell on the additive. Elsewhere, regulators generally need evidence of harm before withdrawing an approval. Neither stance is neutral.

There is a family resemblance here with other new technologies. Early synthetic biology tried to settle its risks through self-governance, and the EU's recent fight over whether gene-edited plants should carry GMO labels turned on similar questions about definitions and disclosure. In each case the technical definition of a category ends up deciding what consumers are told.

The modest lesson of E171 is that regulators can act on unresolved evidence, and that industry can adapt when they do. The less comfortable lesson is that titanium dioxide had been in food for decades before its nano fraction got a close look, and that for most other nanomaterials in the kitchen, nobody has looked that closely yet.