Using catalytic converters is one of the most effective methods to control vehicle emissions. A washcoat of cerium oxide-zirconia (CeO2–ZrO2) has been used to enhance the performance of the catalytic converter device. To date, the prevalence of this material in the environment has not been assessed. In this study, we present evidence of the existence of inhalable zirconia in urban dust. Samples of the washcoat, exhaust pipe, topsoil, and road dust were analyzed by X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) spectroscopy, and thermally stimulated luminescence (TSL). The results showed a CeO2–ZrO2 phase separation after sintering. This causes the emission of ZrO2, CeO2, and CeZrOx particles smaller than 1 μm, which can likely reach the alveolar macrophages in the lungs. The Ce-Zr content in road dust exceeds geogenic levels, and a significant correlation of 0.87 (p < 0.05) reflects a common anthropic source. Chronic exposure to such refractory particles may result in the development of non-occupational respiratory diseases. The inhalable crystalline compounds emitted by vehicles are a significant environmental health hazard, revealing the need for further investigation and assessment of zirconia levels generated by automobiles in urban areas worldwide.
Bibliographical noteFunding Information:
National Council for Science and Technology in Mexico ( CONACyT ) Grant A1-S-29697 to Diana Meza-Figueroa. Results of this paper are part of a PhD dissertation by S. Navarro-Espinoza with D. Meza-Figueroa and M. Pedroza-Montero as advisors. Benedetto Schiavo was funded by a post-doctoral (supervised by Prof. Meza-Figueroa) and Sofía Navarro-Espinoza by a doctoral scholarship (Advisors Prof. Meza-Figueroa and Prof. Pedroza-Montero) from CONACyT .
© 2020 Elsevier B.V.
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- Catalytic converters
- CeO–ZrO washcoat
- Inhalable particles
- Refractory microcrystals
- Vehicle emissions