Nano Titanium Dioxide

NICNAS Nanomaterial health hazard review: health effects of titanium dioxide nanoparticles

Industrial nanomaterials (also called nanoparticles) are defined as substances that are intentionally produced, manufactured or engineered to have specific properties and one or more dimensions typically between 1 and 100 nanometres. Most industrial nanomaterials come in varying sizes, shapes, and in some cases surface coatings. 

Titanium dioxide (TiO2) nanoparticles exist in three forms: rutile, anatase and brookite.

Industrial uses

TiO2 nanoparticles are widely reported to be used in cosmetics, sunscreens, household products, surface coatings (e.g. paint and printing ink) and plastics. Reported uses in Australia are in cosmetics, sunscreens and surface coatings.

Health effects

Note: The following information is based on published reviews and journal articles (to July 2012). They are based predominantly on information from studies in rodents using various particle sizes and types. Therefore, available data may not represent human health effects of all TiO2 nanoparticles.

Ingestion

The available data indicate that TiO2 nanoparticles do not cause adverse effects if accidentally ingested (swallowed). Ingestion of very high amounts may cause toxic effects.

Two studies showed that, after repeated administration into the stomach, some TiO2 nanoparticles were absorbed through the gastrointestinal tract and caused some adverse effects to the liver and brain. However, in these studies large doses of TiO2 nanoparticles were delivered directly into the stomach of mice, therefore the relevance of such exposure to humans is questionable.

Skin contact

The current evidence indicates that TiO2 nanoparticles do not penetrate through the outer layers of the skin to reach viable skin cells and do not cause skin irritation or allergies. Skin contact with TiO2 is not likely to cause harm due to minimal penetration through the skin under normal use conditions. However, information on long-term use of sunscreens containing nanoparticles on hairy, damaged, flexed or aged skin is limited.

Inhalation

Small-sized TiO2 nanoparticles show low toxicity after inhalation. Large-sized nanoparticles are deposited in the lung of rats with a small fraction transported to other areas such as lymph nodes. There is some evidence that breathing in large quantities of TiO2 nanoparticles over a long period of time may cause toxic effects due to impairment of normal lung clearance mechanisms.

Eye irritation

TiO2 nanoparticles caused mild eye irritation.

Reproductive effects

Reported effects on reproductive organs are limited and inconclusive.

Potential to cause cancer

Based on reports in some rodent studies of increased lung tumours after inhalation, the International Agency for Research on Cancer (IARC) has classified TiO2 as possibly carcinogenic to humans (Group 2B). Current studies do not provide sufficient evidence to conclude that TiO2 causes lung tumours in humans.

Health effects from specific uses
Cosmetics and sunscreens

Skin contact with TiO2 nanoparticles is possible through the use of cosmetic and sunscreen products (e.g. face/body lotions). Current evidence suggests there is limited absorption into the skin because nanoparticles remain on the outer layer of the skin.

Breathing in small amounts of TiO2 nanoparticles during normal use of cosmetic powders is not expected to cause harmful effects because of anticipated low exposures. Also, nanoparticles in cosmetic powders may present as clumps (not as single nanoparticles) and may not reach the lung, but only reach the upper airways.

Accidentally swallowing TiO2 nanoparticles during normal use of cosmetics is not expected to cause harmful effects because of the small amounts ingested and low toxicity through the oral route.

Based on the information available, there are no significant health concerns from normal consumer use of TiO2 nanoparticles in cosmetics and sunscreens.

Surface coatings

TiO2 nanoparticles may be inhaled during normal spray application of surface coatings, but this is not expected to pose a concern due to the film-forming nature of paints when applied on surfaces. In occupational settings, all spray applications need to be carried out in accordance with SafeWork Australia's National Guidance Material for Spray Painting. Workplaces are required to maintain airborne concentrations of TiO2 below the exposure standard (10 mg/m3 over an eight hour period).

Based on available health information and the use of workplace controls, TiO2 nanoparticles in surface coatings are not expected to cause harmful effects to workers.

Current regulatory status in Australia

There are no nanoparticle-specific regulatory requirements in place for TiO2. However, regulatory requirements applying to regular/bulk TiO2 will apply to its nano-forms.

July 2013

Last update 1 July 2013