An upper bound is estimated for the magnitude of potential exposure to nano-TiO2 with the purpose of enabling exposure assessment and, ultimately, risk assessment Knowledge of the existing bulk TiO2 market is combined with available nano-TiO2 production data to estimate current nano-TiO2 sources as a baseline. The evolution of nano-TiO2 production as a percentage of the total TiO2 market is then projected based on material and market information along with a method that combines observations from scientific articles and patents as predictive indicators of the rate of innovative transformation.