Exposure Assessment During the Industrial Formulation and Application of Photocatalytic Mortars Based on Safer n-TiO2 Additives

Abstract

Titanium dioxide nanoparticles (n-TiO2) are added to photocatalytic mortars to improve urban air quality. Their activity can be increased by dispersing and binding them on natural sepiolite surface. Workers handling photocatalytic additives can be exposed to n-TiO2. However, the release of nanoparticles to the workplace can be different if the material used is raw n-TiO2 powders or if the nanoparticles are supported on sepiolite. In this work, we compare occupational exposure to n-TiO2 for raw n-TiO2 and a hybrid additive n-TiO2/sepiolite obtained by a proprietary process. Measurements were performed in two industrial sites that process 1 ton batches of mortars, formulated with the same quantity of n-TiO2, followed by their application outdoors. Direct reading instruments were used to monitor particle number concentration and size distribution. Simultaneously, filter-based samples were collected for mass concentration and microscopy analysis. Two tasks produced a significant release of particles, the addition of fillers during the mortar formulation, in site 1, and the mixing of mortar with water for its application in the second site. For the first task, particle concentration was significantly lower when the n-TiO2/sepiolite was added compared to the raw n-TiO2. For the second task, once the mortar is fully formulated, this metric does not identify differences among the batches. Titanium mass concentration was 3–10 times lower when handling the mortar formulated with the hybrid additive. These results suggest that supporting the n-TiO2 on the sepiolite network not only increases the photocatalytic activity, but is also a safer design that reduces exposure to nanoparticles.