The Risks of Titanium Dioxide Exposure

Titanium Dioxide (TiO2) was deemed a class 2 carcinogen by the European Union if inhaled, triggering an update to its regulations on February 18, 2020. The update addresses the classification, labelling and packaging of substances and mixtures containing titanium dioxide. It has also been classified as a group 2b carcinogen by the International Agency for Research on Cancer (IARC).

Titanium dioxide is often used as a pigment and additive to several commercial products, including sunscreen, paints, varnishes, cosmetics, plastics, paper and food. The size of its powder molecules can vary depending on the use of the product and ranges from fine (respirable) to ultrafine (nanoparticles). When a product contains more than 1% of titanium dioxide particles in powder form with an aerodynamic diameter of ≤ 10 μm, the product needs to be labelled as a hazardous substance.

Titanium Dioxide Occupational Exposure Hazards

In a production facility, titanium dioxide can create an occupational hazard through inhalation, as well as through eye and skin contact, when it enters the air and contaminates surfaces. At high concentrations, particles can irritate the nose and throat, creating an unsafe environment for facility workers. Long-term exposure may even cause bronchitis, resulting in symptoms such as coughing, phlegm, and/or shortness of breath.

The following recommended exposure limits have been classified:

• OSHA TWA – 15 mg/m³ as total dust
• NIOSH TWA – 2.4 mg/m³ for fine titanium dioxide particles and 0.3 mg/m³ for ultrafine particles
• ACGIH TLV-TWA – 2.5 mg/m³ for fine titanium dioxide particles and 0.2 mg/m³ for ultrafine particles – sampled as a respirable fraction

Titanium Dioxide Sample Collection

Active airborne sample collection techniques involve using pumps and filters. It is recommended that a mixed cellulose ester (MCE) filter be used if total dust determination is not required. A pre-weighed polyvinyl chloride (PVC) filter should be used if total or respirable dust determination is necessary.

For our proprietary method’s analysis, airborne samples should be collected using a 37 mm 0.8 µm MCE filter, a 37 mm 0.5 µm pre-weighed PVC filter, or a laboratory provided IOM sampler containing a 25 mm MCE filter. Disposable IOM samplers are not recommended for collection, as the cellulose capsule is usually adhered to the filter and must be digested in addition to the filter.

Titanium Dioxide Analysis and Chemistry

Titanium dioxide is analyzed using Ion Coupled Plasma Optical Emission Spectroscopy (ICP-OES) or Ion Coupled Plasma Mass Spectroscopy (ICP-MS). Due to the nature of how titanium dioxide is bonded, typical mineral acid digestion methods such as hydrochloric and nitric acids cannot successfully break it down. This negatively impacts analysis results. More aggressive acid schemes or digestion equipment are required to fully free all the titanium present.

Bureau Veritas uses an internally developed digestion method capable of ascertaining the total amount of titanium from the titanium dioxide structure. In contrast to other laboratories, the Bureau Veritas method specifically targets elemental titanium. This is a far better technique than using a nonspecific gravimetric procedure that overstates the titanium dioxide, especially in dusty areas. It can detect titanium dioxide at levels up to 0.0036 mg/m³ for an eight hour sample with a minimum flow rate of 1L/minute and a STEL detection level of 0.12mg/m³. This is one of the lowest reporting limits in the industry. Samples for titanium dioxide are analyzed using an ICP-OES and can be shipped to our laboratory under ambient conditions.