Titanium dioxide (TiO 2 ) is commonly applied to enhance the white colour and brightness of food products. TiO 2 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 TiO 2 NPs indicate that these particles can have toxic effects. In this paper, we aimed to estimate the oral intake of TiO 2 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 TiO 2 NPs in food products and supplements. For children aged 2-6 years, additional intake via ingestion of toothpaste was estimated. The mean longterm intake to TiO 2 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 TiO 2 NPs ranges from 0.19 mg/kg bw/day in elderly, 0.55 mg/kg bw/day for 7-69-yearold people, to 2.16 mg/kg bw/day in young children. Ninety-fifth percentile (P95) values are 0.74, 1.61 and 4.16 mg/kg bw/day, respectively. The products contributing most to the TiO 2 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 TiO 2 NPs in these products can pose a human health risk.

ABSTRACT:Metabolism and transport from intestinal cells back into the lumen by ATP-binding cassette (ABC) transporters is believed to limit the bioavailability of flavonoids. We studied metabolism and transport of the citrus flavonoid hesperetin, the aglycone of hesperidin, using a two-compartment transwell Caco-2 cell monolayer system, simulating the intestinal barrier. The role of apically located ABC (3.7) and 2.1 (0.8) pmol/min/monolayer, respectively. Hesperetin aglycone also permeated to the basolateral side, and this process was unaffected by the inhibitors used, possibly implying a passive diffusion process. Inhibition studies, however, showed that efflux of hesperetin conjugates to the apical side involved active transport, which from the pattern of inhibition appeared to involve mainly BCRP. Upon inhibition by the BCRP inhibitor Ko143 (5 M), the apical efflux of hesperetin conjugates was 1.9-fold reduced (p < 0.01), and transport to the basolateral side was 3.1-fold increased (p < 0.001). These findings elucidate a novel pathway of hesperetin metabolism and transport and show that BCRPmediated transport could be a limiting step for hesperetin bioavailability.

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