However, the use of titanium dioxide has also raised concerns about its potential impact on human health and the environment. Some studies have suggested that titanium dioxide nanoparticles may have harmful effects when inhaled or ingested. Manufacturers of titanium dioxide are therefore taking steps to minimize the risk of exposure and develop safer products.

In a study published in the journal Food and Chemical Toxicology in 2016, researchers investigated whether titanium dioxide exposure led to an increase in colorectal tumor creation in mice by using a colitis associated cancer model. By measuring tumor progression markers, the researchers found that mice given titanium dioxide experienced enhanced tumor formation in the distal colon.  There was also a decrease of cells that act as a protective barrier in the colon. The researchers wrote: “These results suggest that E171 could worsen pre-existent intestinal diseases.”

Titanium dioxide in sunscreen