In 2011, titanium dioxide (TiO2) was added to California’s Proposition 65 list after the International Agency for Research on Cancer (IARC) classified it as a group 2B agent, indicating it is possibly carcinogenic when present as “airborne, unbound particles of respirable size.”

According to the Office of Environmental Health Hazard Assessment (OEHHA), Proposition 65, the Safe Drinking Water and Toxic Enforcement Act of 1986, mandates that businesses provide a clear warning before intentionally exposing individuals to any chemical listed as a carcinogen or reproductive toxicant.

During the drafting of a regulatory proposal by OEHHA, the industry pushed back, requesting a preliminary injunction to halt enforcement due to the lack of a defined ‘safe harbor’ level for titanium dioxide. This absence created uncertainty about when a warning would be necessary.

In response, OEHHA proposed a ‘No Significant Risk Level’ (NSRL) for titanium dioxide (airborne, unbound particles of respirable size). The suggested NSRL would apply if the daily average exposure does not exceed:

  1. 440 micrograms (µg) for airborne, unbound particles with diameters of 10 micrometers (µm) or less, and
  2. 44 micrograms (µg) for airborne, unbound particles with diameters of 0.8 micrometers (µm) or less.

Both parts of the NSRL must be met before it applies.

The notice initiated a 45-day public comment period that was scheduled to close on June 24, 2024. OEHHA has extended the public comment period on amending the California Code of Regulations to incorporate the proposed NSRL for TiO2. Comments on the proposed regulation will now be accepted until July 1, 2024.

OEHHA strongly recommends that comments be submitted electronically through their website at