US foods are increasingly full of nano-scale additives, even as researchers raise alarm bells about their safety

France is clamping down on a common food additive that has been shown to be carcinogenic in animal studies. The ban of titanium dioxide, announced by the French government last month, follows a review that could not rule out human cancer risks.

The ban is just the latest chapter in a long-running debate on the safety of widespread food additives known as nanoparticles, which are largely unregulated in the US. This suite of ingredients, engineered to almost atomic scale, may have unintended effects on cells and organs, particularly the digestive tract. There are also indications that nanoparticles may get into the bloodstream and accumulate elsewhere in the body. They have been linked to inflammation, liver and kidney damage and even heart and brain damage.

Technological developments over the past two decades have meant that we can now engineer tiny particles much more easily – and their unusual properties make them useful in the food industry.