With ambitious donut shops like Donut Plant (NYC), Dynamo (San Francisco), and Voodoo (Portland) popping up around the country, the old-fashioned powered donut is becoming increasingly less common. As it turns out, that might be a good thing—according to a recent Scientific American article, the topping might not all sugar as you’d expect. 

The environmental health group As You Sow found “particles of titanium dioxide less than 10 nanometers in size in the powdered sugar coating on donuts from Dunkin’ [Donuts].”

Defined as one-billionth of a meter in diameter, nanoparticles “have been in food for decades at least, often an unintentional byproduct of procession techniques.” It is not completely clear the exact harm caused by nanoparticles, however, “scientists do know that certain nanoparticles can kill cells.”

So you’ve probably already been ingesting nano-particles unwittingly. Whether you want to knowingly eat them just for a powered donut is a different story.

[via Scientific American]