Titanium dioxide is produced or imported into the EU for over one million tons/year. The International Agency for Research on Cancer (IARC) classification is 2B, a possible inhalation carcinogen for humans. This study evaluates urinary biomarkers of oxidative stress in workers of a plant producing TiO₂ pigment powder, having 0.25 µm average particle size and an ultrafine fraction, compared to unexposed subjects. Urine samples were collected from forty workers before and after the shift, from six employees of the same company and eighteen volunteers from the same geographical area. Titanium and other metals concentrations were measured by ICP-MS, while DNA, RNA, and protein oxidation products by HPLC/MS-MS. A statistically significant increase was found for the urinary concentration of Al, Cd, Cr, Cu, Fe, Mn, Pb, Ti, and Zr, and for all biomarkers of oxidative stress in post-shift workers’ urine samples. Urinary concentrations after the working shift were higher than for employees and volunteers pooled together for Cd, Mn, and Zr, and for the oxidative stress biomarkers 8-oxoGuo, 8-oxodGuo, and 3NO₂Tyr. Biomonitoring studies on dose and effect biomarkers for TiO₂ occupational exposure provide information useful for protecting workers’ health even in conditions that comply with health and safety standards, highlighting reversible effects of chronic exposure at very low doses.

It is well known that genetic and environmental factors jointly influence the risk of developing human diseases. The interplay between genes and the environment is mediated by epigenetic changes of the genome consisting in modifications of DNA (e.g., by methylation) or of proteins that intimately associate with DNA, without altering the underlying DNA sequence. One of the main focuses of epigenetic research is the study of cancer, that traditionally was viewed as a genetic disease but it is now clear that its onset is preceded by epigenetic abnormalities while the genetic modifications occur later. The study of epigenetic alterations has also a particular relevance in understanding the effect of occupational exposures to pollutants and new materials, such as titanium dioxide (TiO2) nanoparticles (NPs) and nanofibers (NF), which are promising candidates for numerous applications in consumer products, but with potential toxic effects.The aim of this project is to investigate whether TiO2 represents a risk to human health.To this purpose, we have chosen to investigate the possible presence of circulating DNA in the plasma showing methylation alterations identified by our research group as tumor biomarkers, in subjects exposed to TiO2, compared to the plasma of cancer patients. We enrolled 40 workers employed in TiO2 production, 5 office workers, 18 external controls and 19 patients affected by colorectal cancer. Circulating DNA was extracted from the plasma of each subject, then converted by sodium bisulfite to interrogate the methylation levels of a particularly informative tumor biomarker using the qPCR technique called MethyLight. Preliminary results show, as expected, high methylation levels in cancer patients, low or negligible levels in control subjects and, quite surprisingly, intermediate levels in exposed subjects, with values very similar to those of cancer patients for some categories of workers. More in-depth multivariate analyses, taking into account possible confounding factors such as smoking habits, diet, comorbidities, will be conducted, as well as extending the series as much as possible.These results, although preliminary, seem to confirm a potential risk conferred by TiO2 exposure on human health. To date, the European Food Safety Authority has stated that a potential genotoxicity of titanium dioxide as a food additive (E171) cannot be excluded. However, its use in cosmetics and medicines has not yet been banned.