A document offering guidance on handling titanium dioxide (TiO₂) recently released by the National Institute of Occupational Safety and Health (NIOSH) could have implications for occupational risk management that go beyond TiO₂.

Current Intelligence Bulletin 63: Occupational Exposure to Titanium Dioxide “may be the first document (originally released for external review as a draft in 2005) to recommend separate occupational exposure limits for the same material based on particle size,” according to Vladimir Murashov, Ph.D, Special Assistant for Nanotechnology to the NIOSH Director.

The high level of interest generated by that innovative approach “signifies increasing attention to evaluating and mitigating risks of emerging hazards in the workplace before adverse health effects occur in workers and could proactively be used for how other poorly soluble, low toxicity (PSLT) particles are controlled in the workplace,” said Murashov.

Distinct exposure limits for distinct size fractions.

TiO₂ is an insoluble white powder used extensively in many commercial products, including paint, cosmetics, plastics, paper, and food, as an anticaking or whitening agent. Respirable dust of this material was classified as a potential occupational carcinogen in 1988. In recent years new toxicity data on the adverse pulmonary effects of exposure to TiO₂ indicated the need for revised risk management recommendations including recommended exposure limits (RELs) for fine (defined as primary particle diameters >100 nm) and ultrafine or nanoscale (defined as primary particle diameters <100 nm) TiO₂.

Implications for industrial hygienists

Exposure assessment. The main difference in exposure assessment in workplaces handling TiO₂ is the need to differentiate not just by chemical composition but also by size. NIOSH recommends measuring personal exposure concentrations to fine and nanoscale TiO2 with NIOSH Method 0600. If respirable exposure levels to TiO₂ are higher than 0.3 mg/m3 (REL for nanoscale TiO₂), then additional characterization by electron microscopy is required to determine the particle size and the percentage of ultrafine and fine TiO₂ so that the appropriate RELs can be applied

Exposure mitigation. NIOSH estimates that the risk of lung cancer would be less than 1/1,000 at working lifetime exposures to the RELs, and that lower exposures would further reduce the risk. Therefore, NIOSH recommends controlling exposures to TiO₂ dust as low as possible, below the recommended exposure limits. Use of basic engineering control systems such as enclosures and local exhaust ventilation was shown to greatly reduce exposure levels for both fine and nanoscale particles, while filters used in HVAC systems and respirators were reported to capture fine and nanoscale particles with stated levels of efficiency. If engineering controls and work practices cannot reduce worker TiO2 exposures to below exposure limits then a respirator program should be implemented. In addition, in workplaces where there is potential worker exposure to TiO₂, employers should establish an occupational health surveillance program.

Click here to view: Current Intelligence Bulletin 63: Occupational Exposure to Titanium Dioxide