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Titanium dioxide (TiO2) is a metal oxide that occurs naturally when titanium reacts with airborne oxygen. It has various attractive and beneficial properties, such as thermal stability, photocatalysis potential, and resistance to ultraviolet radiation. As a result, it is widely used in industrial processes and commercial products. The physicochemical properties of TiO2 can vary depending on the material's primary particle size, crystallinity, and formulation. Different properties have been found to cause different toxicological responses. While most studies have focused on the effects of exposure to nano-TiO2, little attention has been given to other relevant TiO2 materials. In this review, we examine the toxicological profile of both titanium dioxide nanoparticles and pigmentary TiO2. This review aims to provide reliable information on titanium dioxide toxicity for public and private stakeholders to use in risk assessments.

Microplastics (MPs), in the form of fragments and fibers, were recently found in honey samples collected in Ecuador as well as in honey bees collected from Denmark and China. However, little is known about how MPs impact bee health. To fill this knowledge gap, we investigated the potential toxicity of irregularly shaped polystyrene (PS)-MP fragments on honey bee health. In the first experiment of its kind with honey bees, we chronically exposed bees with a well-established gut microbiome to small (27 ± 17 µm) or large (93 ± 25 µm) PS-MP fragments at varying concentrations (1, 10, 100 µg mL−1) for 14 days. Bee mortality, food consumption, and body weight were all studied. We found that chronic exposure to PS-MP fragments has no effect on honey bee survival, but reduced the feeding rate and body weight, particularly at 10 µg PS-MP fragments per mL, which may have long-term consequences for honey bee health. The findings of this study could assist in the risk assessment of MPs on pollinator health.