April 2021 EMM Editor's Choice

The April 2021 EMM Editor's Choice article is “Biomonitoring of workers employed in a titanium dioxide production plant: Use of buccal micronucleus cytome assay as noninvasive biomarker to evaluate genotoxic and cytotoxic effects” (https://onlinelibrary.wiley.com/doi/10.1002/em.22431) by Cinzia Lucia Ursini, Marco Di Basilio, Aureliano Ciervo, Anna Maria Fresegna, Raffaele Maiello, Giuliana Buresti, Antonella Campopiano, Federica Angelosanto, Maddalena Papacchini, Sergio Iavicoli, and Delia Cavallo.

Titanium dioxide (TiO2) has been used in a wide range of applications, due to the ability to confer whiteness and opacity on various products. Despite the promising commercial opportunities, many studies have shown that TiO2 nanoparticles can induce oxidative stress, inflammation, and genotoxic damage. The International Agency for Research on Cancer (IARC) classified TiO2 as a Group 2B carcinogen (possibly carcinogenic to humans) and the National Institute for Occupational Safety and Health (NIOSH) assigned ultrafine TiO2 as a potential occupational carcinogen via inhalation. Inhalation exposure to TiO2 particles can naturally occur in occupational settings during TiO2 production, packing, milling, or site cleaning. Therefore, the potential exposure to TiO2 in the workplace may cause adverse health effects to workers. Ursini and colleagues reported a useful and suitable method for assessing the cyto–genotoxic risk of TiO2 occupational exposure. They enrolled 40 workers employed in a TiO2 production plant (13 maintainers, 5 industrial cleaners, 9 mobile operators, 9 technicians, 4 bagging operators), 5 office workers, and 18 external controls (healthy subjects). TiO2 exposure was characterized by measuring inhalable and respirable particles via personal monitoring. The exfoliated buccal cells were collected and used for evaluating chromosomal instability, cytokinesis defect or arrest, cell death, and apoptosis using the buccal micronucleus cytome assay (BMCyt assay). The results showed that workers employed in TiO2 production process had higher frequency of micronucleus (MN) and other cellular anomalies such as nuclear buds (NB), binucleated cells (BIN), and condensed chromatin (CC) than the external controls, demonstrating the induction of genotoxic and cytotoxic effects. The highest percentage of MN positive subjects were found in the group of maintainers (76.9%), followed by industrial cleaners (60.0%). Unexpectedly, the bagging operators, which were reputed more at risk of occupational exposure to TiO2, showed lower percentage of MN positive (25%) than office workers (40%). This could be due to the more precautionary organizational procedures for the bagging operators. These findings are important in suggesting that TiO2 production process is capable of inducing genotoxic and cytotoxic effects on buccal cells of exposed workers, and that wearing the protective masks and other personal protective equipment may significantly reduce the risk. The buccal cells are the specific target organ of inhalation or oral exposure and the samples can be easily collected through a mouth rinse or simple swab. The BMCyt assay could be used by other researchers as a sensitive and noninvasive biomarker of cyto-genotoxicity for biomonitoring of TiO2 exposed workers.

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