There are nano-sized particles in your food. Does this make you nervous?

A new report from an environmental health group, As You Sow, raises concern about nanoparticles in some popular sweets. The group says it found particles of titanium dioxide less than 10 nanometers in size in the powdered sugar coating on donuts from Dunkin' and Hostess (now sadly defunct). The group argues that the nanoparticles have no business in any kind of food until safety testing is done; in this case, the tiny bits could make donuts even unhealthier.

Nano-sized particles, roughly one-billionth of a meter in diameter (much smaller than the width of a human hair), have been in food for decades at least, often an unintentional byproduct of processing techniques. But a whole range of novel nano-sized particles—ranging from tiny flakes of titanium dioxide to whiten powdered donuts to submicroscopic silver bits to kill microbes—are showing up today in food and food packaging on purpose.

The nanoparticles on the donuts may fall into the happenstance category and result from the milling processes used on the powdered sugar mixture. "Whether these TiO2 nanoparticles were engineered or a byproduct of manufacturing processes is not known," the report notes, and the point was backed up by As You Sow chief executive Andrew Behar, who added in an email that the nanoparticles "may or may not have been present for a while. We have two experts that disagree on this: one saying that you cannot mill to 10 [nanometers] and the other saying that it is a result of crystals being shattered."

The small size is worrisome regardless, health advocates argue, because it allows for unique properties not seen in larger particles. For example, the tininess of nanoparticles allows them to travel through the body more widely, and enter cells more readily, than larger particles do. So far, no one knows whether nanomaterials in food or food packaging pose a health risk and titanium dioxide nanoparticles are likely to be benign given their ubiquity in sunscreens, lotions and other personal care products. But scientists do know that certain nanoparticles can kill cells; in fact, silver nanoparticles are often employed specifically to kill bacteria.

Dunkin' Donuts is not the only company facing greater pressure to identify nanoparticles in its products and verify their safety. The European Union already requires disclosure on food packaging of any "nanomaterials" with one or more dimensions measuring less than 100 nanometers. The U.S. Food and Drug Administration has called for companies to submit studies of the human health safety of any nano-sized materials intended for use in food, even if larger particle sizes have already been approved as safe. Meanwhile, the Environmental Protection Agency has ongoing tests on the environmental toxicity of nanoparticles used in sunscreen, such as TiO2, which may inform research into human health impacts. Regardless, industry and government spend far more on research and development of new nanotechnology than on safety testing.

Many companies appear not to know if their products contain nanoparticles or may be reluctant to submit to scrutiny. As You Sow attempted to survey 2,500 in the food industry for the new report that revealed the nanoparticles in donuts. Only 26 responded and only two had specific policies regarding nanoparticles. Ten of the companies did not know whether they used nanoparticles or not and only two admitted to intentionally incorporating them—both use nanotechnology in packaging rather than the food product itself. "We plan to work with scientists to understand if they will leach into food," Behar says.

As a next step, As You Sow is attempting to crowdfund further testing of foods for the presence of nanoparticles, such as M&Ms, Pop-Tarts and Trident gum—all likely to employ the same TiO2 found in the donuts and equally likely to be unintentional and potentially long-standing. "What are the health implications of nanomaterials that we know are in our food supply?" Behar asks. "How do we set up a system to make sure that they are safe?"