Effects of particulate polycyclic aromatic hydrocarbons from traffic emissions on human lung epithelial cells

• Autor(a) principal: Soares, Marlene de Jesus Salvado
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/34462
• topic: PM; PAH; Exhaust; Non-exhaust; A549; Cytotoxicity

Air pollution consitutes the largest risk to health in Europe. Particulate matter (PM) is considered the most harmful pollutant for humans. Road traffic represent a major source of PM. Emissions from traffic can be subdivided in exhaust emissions (tailpipe) and non-exhaust emissions, which comprise particles from tyre and brake wear, as well as road dust ressuspension. Contrary to exhaust PM, non-exhaust PM has been much less studied. Despite their low contribution to the PM mass, polycyclic aromatic hydrocarbons (PAH) constitute a group of persistent organic pollutants with a high carcinogenic and mutagenic potential. In this work the A549 pulmonary epithelial cell line was used to study the toxic effects of PAH extracted from PM emitted by traffic, including exhaust samples obtained under different driving cycles, samples collected in a road tunnel and simultaneously in a nearby urban background atmosphere, and samples from the wear of distinct types of brakes. Tests to assess cell viability, cell cycle and reactive oxygen species (ROS) intracellular levels were performed. The PM-bound PAH extracts from the wear of low steel brake pads induced greater decreases in cell viability. It was observed that cytotoxicity was more dependent on the individual composition of PAH than on the global concentration. The results obtained for the exhaust PM samples from from heavy-duty vehicles reveladed that Euro V trucks produce more toxic particles. The Euro VI norm adopted a limit of PM emission that is ten times lower than the levels allowed in the previous norm, contributing to a significant decrease of particulate matter in the exhaust and of the corresponding toxicity. Among Euro V vehicles, the one powered with GTL was the most toxic to A549 cell line. The composite weekly sample of the urban background atmosphere of the School Valsassina showed to be extremely toxic,decreasing the cell viability to 2.66%, while the maximum reduction observed for the daily road tunnel samples was 83.6%. Retene and naphthalene, which were not detected or were present at trace levels in samples from the tunnel, were found in the particulate extracts of the school sample. Irrespective of the sample, although some changes were observed in the A549 cell cycle after 24 h exposure in all the phases, the differences in the mean values were not great enough to exclude the possibility of random variability. When the results from the three phases (G0/G1, S and G2/M) from the cells exposed to all PM extracts were compared to control, no statistically significant difference was detected. Regardless of the type of sample, significant increases in cellular ROS levels were observed in cells exposed to the PM extracts of some heavy-duty vehicles.