Background: It is estimated that over 80% of respirable particulate matter (PM₁₀) in cities comes from road transport and that tire and brake wear are responsible for the 3–7% emission of it. Data on the indicators of environmental impact of tire debris (TD), originated from the tire abrasion on roads, are extremely scarce, even though TD contains chemicals (zinc and organic compounds) which can be released in the environment. Methods: TD particle morphology was analysed with SEM, TEM and FIB instruments. TD eluates and TD organic extracts were tested at dilution series on human cell lines and Xenopus laevis embryos. 50 and 100 g/L TD were used for the eluates obtained after 24 h at pH 3 and the quantity of zinc present was measured with a ICP-AES. Eluates diluted to 1%, 10%, 50% in culture media and undiluted were used on X. laevis embryos in the FETAX test. HepG2 cells were exposed for 24 h to 0.05 – 50 μg/ml of zinc salt while A549 cells were exposed for 24, 48 and 72 h to 10, 50, 60, or 75 μg/ml of TD extract. X. laevis embryos were exposed to 50, 80, 100, or 120 μg/ml TD extract. Results: The solution of undiluted 50 g/L TD produced 80.2% mortality (p < 0.01) in X. laevis embryos and this toxic effect was three times greater than that produced by 100 g/L TD. Zn accumulation in HepG2 cells was evident after 4 h exposure. A549 cells exposed to TD organic extract for 72 h presented a modified morphology, a decrease in cell proliferation and an increase in DNA damage as shown by comet assay. The dose 80 μg/ml of TD extract produced 14.6% mortality in X. laevis embryos and 15.9% mortality at 120 μg/ml. Treatment with 80, 100, or 120 μg/ml TD organic extract increased from 14.8% to 37.8% malformed larvae percentages compared to 5.6% in the control. Conclusion: Since the amount of Zn leached from TD is related to pH, aggregation of particles and elution process, the quantity of TD present in the environment has to be taken into account. Moreover the atmospheric conditions, which may deeply influence the particle properties, have to be considered. The TD organic fraction was toxic for cells and organisms. Thus, because of its chemical components, TD may have a potential environmental impact and has to be further investigated.

The antibacterial properties of nano-metal oxides (ZnO, CuO) are based on the formation of reactive oxygen species (ROS). This work reveals that the antibacterial properties of these nano-metal oxides are strongly dependent on their crystalline structure. The antibacterial activity of the nanooxides was tested against four types of bacteria that commonly cause nosocomial infections. The sonochemical method was applied not only for synthesis of nanooxides but also to their coating on textiles. The antibacterial properties of textiles coated with commercial and sonochemically prepared nano-metal oxides were evaluated and compared. The toxicity was evaluated on human lung cells and amphibian embryos, as representative models for inhalation and aquatic toxicology. The sonochemically prepared metal nanooxides are better antimicrobials than commercially available metal oxides with the same particle size range. It was found that the crystallites which have more defects and less organized structure are more toxic. The formation of ROS was studied by electron spin resonance (ESR) measurements for both the sonochemically prepared and commercial samples of ZnO/CuO nanoparticles. A significant increase in the production of radical species was found in the more defective, sonochemically prepared samples, as compared to the commercial ones. Since modulation of the nanoparticle defects influenced their toxicity, the possibility of engineering safer nano-antibacterials is indicated.