Silicon dioxide and titanium dioxide particles found in human tissues

Abstract

Silicon dioxide (silica, SiO 2 , SAS) and titanium dioxide (TiO 2) are produced in high volumes and applied in many consumer and food products. As a consequence, there is a potential human exposure and subsequent systemic uptake of these particles. In this study we show the characterization and quantification of both total silicon (Si) and titanium (Ti), and particulate SiO 2 and TiO 2 in postmortem tissue samples from 15 deceased persons. Included tissues are liver, spleen, kidney and the intestinal tissues jejunum and ileum. Low-level analysis was enabled by the use of fully validated sample digestion methods combined with (single particle) inductively coupled plasma high resolution mass spectrometry techniques (spICP-HRMS). The results show a total-Si concentration ranging from <2 to 191 mg Si/kg (median values of 5.8 (liver), 9.5 (spleen), 7.7 (kidney), 6.8 (jejunum), 7.6 (ileum) mg Si/kg) while the particulate SiO 2 ranged from <0.2 to 25 mg Si/kg (median values of 0.4 (liver), 1.0 (spleen), 0.4 (kidney), 0.7 (jejunum, 0.6 (ileum) mg Si/kg), explaining about 10% of the total-Si concentration. Particle sizes ranged from 150 to 850 nm with a mode of 270 nm. For total-Ti the results show concentrations ranging from <0.01 to 2.0 mg Ti/kg (median values of 0.02 (liver), 0.04 (spleen), 0.05 (kidney), 0.13 (jejunum), 0.26 (ileum) mg Ti/kg) while particulate TiO 2 concentrations ranged from 0.01 to 1.8 mg Ti/kg (median values of 0.02 (liver), 0.02 (spleen), 0.03 (kidney), 0.08 (jejunum), 0.25 (ileum) mg Ti/kg). In general, the particulate TiO 2 explained 80% of the total-Ti concentration. This indicates that most Ti in these organ tissues is particulate material. The detected particles comprise primary particles, aggregates and agglomerates, and were in the range of 50-500 nm with a mode in the range of 100-160 nm. About 17% of the detected TiO 2 particles had a size <100 nm. The presence of SiO 2 and TiO 2 particles in liver tissue was confirmed by scanning electron microscopy with energy dispersive X-ray spectrometry.

Possible effects of titanium dioxide particles on human liver, intestinal tissue, spleen and kidney after oral exposure

“…The quantified Ti content in the human postmortem tissues from 15 individuals have been reported in a separate publication (Peters et al 2020). The findings confirmed the results from our previous study with human postmortem liver and spleen from 15 (other) individuals (Heringa et al 2018).…”

“…In biological matrices, the concentration of TiO 2 is usually determined by quantifying the level of titanium (Ti). As is argued in Heringa et al (2018) and Peters et al (2020), it can be assumed that the Ti found in human tissues almost exclusively originate from oral exposure to TiO 2 particles. A potentially alternative source of Ti in organs (at least for internal organs) could come from corrosion of titanium implants, however, in the study by Heringa et al (2018) two donors with such implants did not have elevated Ti or Ti-particle levels in the internal organs analyzed (i.e.…”

“…In human Ti determined in human organs and tissues is believed to be predominately caused by the presence of TiO 2 particles, which, in individuals without an occupational inhalatory exposure to TiO 2 , almost exclusively originates from oral exposure to TiO 2 particles. Still, potentially a limited part could be caused by other Ti compounds (Rompelberg et al 2016, Locci et al 2019, Peters et al 2020. Quantified Ti content (as well as Ti-particle content) in several human postmortem tissues have been reported separately (Heringa et al 2018, Peters et al 2020.…”

“…Still, potentially a limited part could be caused by other Ti compounds (Rompelberg et al 2016, Locci et al 2019, Peters et al 2020. Quantified Ti content (as well as Ti-particle content) in several human postmortem tissues have been reported separately (Heringa et al 2018, Peters et al 2020. The tissues included liver and spleen (Heringa et al 2018, Peters et al 2020, and kidney and two sections of intestinal tissue (Peters et al 2020).…”

“…Quantified Ti content (as well as Ti-particle content) in several human postmortem tissues have been reported separately (Heringa et al 2018, Peters et al 2020. The tissues included liver and spleen (Heringa et al 2018, Peters et al 2020, and kidney and two sections of intestinal tissue (Peters et al 2020). Liver, spleen, kidney and specific parts of the intestine are among the organs to which NPs, including TiO 2 , are known to distribute to and/ or accumulate in (Kreyling et al 2017, EFSA Scientific Committee et al 2018.…”