Toxic effects of TiO₂ NPs on soil organisms

This constant high rate of ROS production leads rapidly to extreme macromolecular oxidation, here it is observed in the AOPP and MDA detected after 3 h in samples treated with bare P25TiO₂NPs (Fig. 6, Fig. 7). Macromolecular oxidation includes, among others, both protein and lipid oxidation. The ROS causes protein oxidation by direct reaction or indirect reactions with secondary by-products of oxidative stress. Protein fragmentation or cross-linkages could be produced after the oxidation of amino acid side chains and protein backbones. These and later dityrosine-containing protein products formed during excessive production of oxidants are known as advanced oxidation protein products (AOPP). They absorb at 340 nm and are used to estimate the damage to structural cell amino acids. Lipid oxidation is detected by the conjugation of oxidized polyunsaturated lipids with thiobarbituric acid, forming a molecule that absorbs light at 532 nm. Polyunsaturated lipids are oxidized as a result of a free-radical-mediated chain of reactions. The most exposed targets are usually membrane lipids. The macromolecular damage could represent a deadly danger if it is too extensive, and this might be the case. Moreover, it could be observed that cellular damage continues further and becomes irrevocable after 6 h and MDA could not be detected. This may be due to the fact that the lipids were completely degraded and cells were no longer viable. Lipids from the cell membrane are the most prone to oxidation. In fact, lipid peroxidation biomarkers are used to screen the oxidative body balance [51]. At the same time, AOPP values are up to 30 times higher for bare nanoparticles in comparison to the functionalized ones.

Titanium dioxide (TiO₂) is commonly applied to enhance the white colour and brightness of food products. TiO₂ is also used as white pigment in other products such as toothpaste. A small fraction of the pigment is known to be present as nanoparticles (NPs). Recent studies with TiO₂ NPs indicate that these particles can have toxic effects. In this paper, we aimed to estimate the oral intake of TiO₂ and its NPs from food, food supplements and toothpaste in the Dutch population aged 2 to over 70 years by combining data on food consumption and supplement intake with concentrations of Ti and TiO₂ NPs in food products and supplements. For children aged 2-6 years, additional intake via ingestion of toothpaste was estimated. The mean long-term intake to TiO₂ ranges from 0.06 mg/kg bw/day in elderly (70+), 0.17 mg/kg bw/day for 7-69-year-old people, to 0.67 mg/kg bw/day in children (2-6 year old). The estimated mean intake of TiO₂ NPs ranges from 0.19 μg/kg bw/day in elderly, 0.55 μg/kg bw/day for 7-69-year-old people, to 2.16 μg/kg bw/day in young children. Ninety-fifth percentile (P95) values are 0.74, 1.61 and 4.16 μg/kg bw/day, respectively. The products contributing most to the TiO₂ intake are toothpaste (in young children only), candy, coffee creamer, fine bakery wares and sauces. In a separate publication, the results are used to evaluate whether the presence of TiO₂ NPs in these products can pose a human health risk.

With its storied history and distinct properties, lithopone remains a subject of historical significance and contemporary relevance. While its applications and popularity have evolved, its role in the annals of pigment history is indisputable.

Titanium dioxide manufacturer: CHTI