An expert panel recently concluded that food coloring E171 (titanium dioxide) "can no longer be considered safe as a food additive," and as a result, the European Food Safety Authority (EFSA) has reclassified it. The ruling comes after years of research suggesting the additive may be unsafe. 

In 2016, the EFSA reevaluated the safety of E171 and concluded that there was no clear evidence confirming the additive was carcinogenic or genotoxic. At that point in time, research was beginning to indicate the possible health dangers of titanium dioxide may be amplified when it is ingested in the form of nanoparticles—particles less than 100 nm in diameter.

In 2015, under pressure from public advocacy groups, Dunkin' Donuts announced it would remove titanium dioxide from all of its food products in the United States. At the beginning of 2020, France became one of the first countries in the world to broadly ban the food additive. 

EFSA's 2016 assessment cited the need for more research into E171's health effects, and over the subsequent years a large number of studies were published. The new research focused on the health effects of nanoparticles.