Is titanium dioxide dangerous to health?

It is well established that nano-TiO₂ are more toxic than the micrometric form. Indeed, nano-TiO₂ particles can be inhaled when present in spray or aerosol products, such as certain sprays, although their use in these formulations has been prohibited since 2009 by EU Cosmetics Regulation (EC) No. 1223/2009. Inhalation of these particles may cause respiratory irritation and pulmonary inflammation, which over time may lead to impaired lung function, fibrosis and cancer risk, depending on their nanometric properties (size, shape, crystallinity, etc.). The risks are mainly associated with occupational exposure or aerosol cosmetic products.

However, these cases are rare in domestic use, and prolonged or high-dose exposure appears more problematic. For short-term inhalation, a threshold of 3.5 mg/m³ is estimated for spray applications, and a threshold of 17 mg/m³ is suggested for repeated inhalations over an eight-hour working day. Studies show that inhalation concentrations up to 35 mg/m³ do not cause chronic pulmonary overload.

In recent years, concerns have emerged over the use of titanium dioxide after its ban as a food additive (E171) in some countries. It is essential to distinguish its use in foods from its use in topical formulations, where exposure levels and contexts differ.

Studies available to date using models in vitro and in animals have reported that gastrointestinal absorption of titanium dioxide, whether nano or non-nano, after oral exposure is negligible or nonexistent. The amounts of TiO₂ used in these experimental studies exceed those to which people may be exposed through accidental ingestion, for example when using lip products such as lipsticks. Current data do not show clear evidence of carcinogenic or genotoxic activity associated with oral ingestion of titanium dioxide.

Distinguishing the exposure contexts assessed by different regulatory agencies is important. The CSSC assesses the risks of titanium dioxide in topical products not designed for ingestion, where any ingestion is accidental and involves negligible quantities. By contrast, the European Food Safety Authority (EFSA) assesses titanium dioxide as a food additive, where exposure levels are much higher due to deliberate consumption in foods.

To summarise, although uncertainties remain, current data do not indicate significant concern over accidental ingestion of titanium dioxide in cosmetics, given the low amounts involved and the absence of clear evidence of toxicity. However, further research is needed to clarify long-term effects and reassure consumers.

It is important to note that the nano-TiO₂ form presents a greater potential risk than the micrometre form, due to its increased penetration into tissues and cells.

To date, there is no specific ban or warning on the use of skincare products containing titanium dioxide by pregnant or breastfeeding individuals, including lip products. Regulatory authorities consider the levels of titanium dioxide in these products safe for consumers, including in cases of accidental ingestion.

However, some experimental studies have examined the effects of titanium dioxide on pregnancy and postnatal development. For example, one study administered 100 mg/kg/day of nano-TiO₂ orally to pregnant rats during gestation. Although this dose exceeds human exposure from cosmetic use, where incidental ingestion is minimal, the results showed minor physiological disturbances in the mothers, such as altered antioxidant enzyme levels and metabolic markers. Titanium dioxide also accumulated in organs including the liver, brain, and placenta.

In the offspring, effects on postnatal development were observed, including variations in body weight, delays in sensorimotor maturation, and changes in motor reflexes. These observations suggest a potential effect on the central nervous system, although no major malformation or structural anomaly was detected in the foetuses.

It is crucial to note that these findings come from animal studies using doses exceeding those encountered in everyday life.

For example, accidental ingestion of titanium dioxide from lip products is minimal and represents only a tiny fraction of the dose tested in these studies. Moreover, human data on this topic are limited and show no conclusive evidence of risk for pregnant or breastfeeding individuals.