Titanium dioxide (E 171) and four new toxicity studies
What it found
Four new studies on titanium dioxide (E 171) reported various effects in rats and in lab tests, but the authors found the results uncertain and of limited relevance for judging the additive in food.
The authors say the studies do not justify reopening the earlier safety opinion.
What they found
Animal and lab studies
Rat colon study
In rats given E 171 in drinking water for 100 days, more aberrant crypts and large aberrant crypt foci were seen in the colon at 10 mg/kg body weight per day than in controls. A few rats given E 171 alone, without an initiator, also developed these lesions.
Immune changes in rats
Rats given E 171 or nano titanium dioxide by gavage for 7 days showed changes in immune cells in the Peyer's patches and spleen. The authors noted the biomarker changes were small, within 10 to 20 percent.
Lab tests on colon cells
In human colon cancer cells, E 171 and other titanium dioxide materials increased DNA damage in comet assays, and E 171 increased micronucleated cells in a dose-related way. The authors noted that overall negative results were seen in studies in live animals.
Nutrient absorption in cells
In a lab model of the small intestine, 4 hours and 5 days of exposure to titanium dioxide tiny particles increased reactive oxygen species and reduced iron and zinc transport. No transport of the particles across the cell layer was observed.
Other findings
Risk assessment review
The risk assessment by Heringa et al. used assumptions and did not include a weight of evidence analysis of the whole database. The authors found significant uncertainty in its conclusions.
What the authors conclude
“Altogether, the Panel concluded that the outcome of the four studies did not merit re-opening the existing opinion of EFSA related to the safety of TiO2 (E 171) as a food additive.”
Also in their conclusions
- They concluded that the outcome of the four studies did not merit re-opening the existing opinion of EFSA related to the safety of TiO2 (E 171) as a food additive.
- They recommended that biomarkers for putative preneoplastic lesions in the colon should be examined in the extended one-generation reproductive toxicity study.
- They recommended that further studies on TiO2 nanoparticles should include administration in a food matrix.
How it was done
The European Commission asked EFSA to check four studies published after its 2016 opinion on titanium dioxide (E 171) and to say whether they merit reopening that opinion.
The authors reviewed four studies: one in rats given E 171 by gavage or in drinking water, two in lab tests using human colon cells, and one risk assessment based on data from other publications. They also questioned the study authors at an open meeting.
What it can’t tell you
- The rat and lab test results cannot show what happens in people eating foods that contain E 171.
- The studies used forms of titanium dioxide and ways of giving it that may not match how the additive is used in food.
- The risk assessment is based on assumptions and data from other studies, so it cannot give a direct measurement of risk.
The paper
- Title
- Evaluation of four new studies on the potential toxicity of titanium dioxide used as a food additive (E 171)
- Type
- Scientific opinion of the European Food Safety Authority
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Licence
- CC BY-ND. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), Younes M, Aggett P, et al (2018). Evaluation of four new studies on the potential toxicity of titanium dioxide used as a food additive (E 171). EFSA journal. European Food Safety Authority. doi:10.2903/j.efsa.2018.5366Free full textPubMed 32625996DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error