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Recommended occupational exposure limits for titanium dioxide nanoparticles

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News of 04/03/2021

With 17,000 tonnes produced or imported each year in France, titanium dioxide in nanoparticle form or TiO2-NP is one of the most widely used nanomaterials in various industrial sectors. It is therefore a major source of potential exposure in the workplace. Following on from the work carried out for the general population, ANSES is now recommending occupational exposure limits (OELs) to strengthen risk prevention for workers.

TiO2-NP: used since the 1990s for its anti-UV and photocatalytic properties

Titanium dioxide in nanoparticle form or TiO2-NP has been used for the past thirty years primarily for its ultraviolet radiation absorption and photocatalytic properties, which degrade certain pollutants through chemical decomposition and are used for example in "self-cleaning" glass.

In people exposed by the respiratory route, it can cause lung inflammation, which may in some cases lead to carcinogenesis.

Several physico-chemical characteristics of TiO2-NP – size, shape, whether or not there is a surface coating, crystallinity – can influence its toxicity, making it a highly complex substance.

An OEL based on the prevention of lung inflammation

Following on from the expert appraisal carried out to set a toxicity reference value (TRV) for the general population, ANSES is now recommending an occupational exposure limit (8h-OEL) of 0.80 microgram per cubic metre. Compliance with this value should help prevent lung inflammation, an effect that occurs at the lowest exposure concentrations.

In addition, due to the lack of available data on the immediate or short-term effects of TiO2-NP and in accordance with its methodological guide, ANSES also recommends not exceeding the concentration of 4 micrograms per cubic metre over a 15-minute period. Compliance with this value should help limit the size and number of exposure peaks over the working day.

An expert appraisal on the assessment of methods for measuring TiO2-NP in air is currently under way. This will determine which method(s) to use to measure TiO2-NP concentrations in air in view of the OELs recommended by the Agency. In addition, the studies requested by ANSES when assessing TiO2 under the REACh Regulation should enable these values to be further refined.