Food and Industrial Grade Titanium Dioxide Impacts Gut Microbiota

Titanium dioxide (TiO2), frequently used in foods, coatings, pigments, and paints, accounts for a major fraction of engineered nanomaterials released from products during usage. Impacts of food and industrial grade TiO2 on the composition and phenotype of a human gut microbiota, representing an upstream anthropogenic system, were studied to elucidate systemic perturbations to the microbial community. Findings show an inhibition of an expected, natural shift in microbial composition observed during control conditions from Proteobacteria to Firmicutes phyla in the presence of both types of TiO2 particles, with food grade exposures having a greater effect. Additionally, both TiO2 exposures resulted in lower values of the colonic pH (<5) as compared to the control (>5), with food grade exposures recording the largest reduction (approximate to pH 4). Similar trends in microbial community hydrophobicity and electrophoretic mobility between baseline, food, and industrial grade exposures indicate TiO2 exposures may have little effect on microbial stability. Results of this study indicate that inherent physical and chemical properties of the two TiO2 forms may indeed produce different microbial responses, which is significant when considering environmental exposure and risk, and the design of environmental fate and toxicity studies.